Guide to the Secure Configuration of Debian 12

with profile ANSSI-BP-028 (intermediary)
This profile contains configurations that align to ANSSI-BP-028 v2.0 at the intermediary hardening level. ANSSI is the French National Information Security Agency, and stands for Agence nationale de la sécurité des systèmes d'information. ANSSI-BP-028 is a configuration recommendation for GNU/Linux systems. A copy of the ANSSI-BP-028 can be found at the ANSSI website: https://www.ssi.gouv.fr/administration/guide/recommandations-de-securite-relatives-a-un-systeme-gnulinux/

The SCAP Security Guide Project
https://www.open-scap.org/security-policies/scap-security-guide

This guide presents a catalog of security-relevant configuration settings for Debian 12. It is a rendering of content structured in the eXtensible Configuration Checklist Description Format (XCCDF) in order to support security automation. The SCAP content is is available in the scap-security-guide package which is developed at https://www.open-scap.org/security-policies/scap-security-guide.

Providing system administrators with such guidance informs them how to securely configure systems under their control in a variety of network roles. Policy makers and baseline creators can use this catalog of settings, with its associated references to higher-level security control catalogs, in order to assist them in security baseline creation. This guide is a catalog, not a checklist, and satisfaction of every item is not likely to be possible or sensible in many operational scenarios. However, the XCCDF format enables granular selection and adjustment of settings, and their association with OVAL and OCIL content provides an automated checking capability. Transformations of this document, and its associated automated checking content, are capable of providing baselines that meet a diverse set of policy objectives. Some example XCCDF Profiles, which are selections of items that form checklists and can be used as baselines, are available with this guide. They can be processed, in an automated fashion, with tools that support the Security Content Automation Protocol (SCAP). The DISA STIG, which provides required settings for US Department of Defense systems, is one example of a baseline created from this guidance.

Do not attempt to implement any of the settings in this guide without first testing them in a non-operational environment. The creators of this guidance assume no responsibility whatsoever for its use by other parties, and makes no guarantees, expressed or implied, about its quality, reliability, or any other characteristic.

Profile Information

Profile Title	ANSSI-BP-028 (intermediary)
Profile ID	xccdf_org.ssgproject.content_profile_anssi_bp28_intermediary

CPE Platforms

cpe:/o:debian:debian_linux:12

Revision History

Current version: 0.1.73

draft (as of 2024-05-08)

System Settings
Services
System Accounting with auditd

Checklist

Group Guide to the Secure Configuration of Debian 12 Group contains 38 groups and 113 rules

Group System Settings Group contains 30 groups and 97 rules

[ref] Contains rules that check correct system settings.

Group Installing and Maintaining Software Group contains 5 groups and 19 rules

[ref] The following sections contain information on security-relevant choices during the initial operating system installation process and the setup of software updates.

Group System and Software Integrity Group contains 2 groups and 2 rules

[ref] System and software integrity can be gained by installing antivirus, increasing system encryption strength with FIPS, verifying installed software, enabling SELinux, installing an Intrusion Prevention System, etc. However, installing or enabling integrity checking tools cannot prevent intrusions, but they can detect that an intrusion may have occurred. Requirements for integrity checking may be highly dependent on the environment in which the system will be used. Snapshot-based approaches such as AIDE may induce considerable overhead in the presence of frequent software updates.

Group Software Integrity Checking Group contains 1 group and 2 rules

[ref] Both the AIDE (Advanced Intrusion Detection Environment) software and the RPM package management system provide mechanisms for verifying the integrity of installed software. AIDE uses snapshots of file metadata (such as hashes) and compares these to current system files in order to detect changes.

The RPM package management system can conduct integrity checks by comparing information in its metadata database with files installed on the system.

Group Verify Integrity with AIDE Group contains 2 rules

[ref] AIDE conducts integrity checks by comparing information about files with previously-gathered information. Ideally, the AIDE database is created immediately after initial system configuration, and then again after any software update. AIDE is highly configurable, with further configuration information located in

/usr/share/doc/aide-VERSION

Rule Install AIDE [ref]

The aide package can be installed with the following command:

$ apt-get install aide

Rationale:

The AIDE package must be installed if it is to be available for integrity checking.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_package_aide_installed

References:

cis-csc	1, 11, 12, 13, 14, 15, 16, 2, 3, 5, 7, 8, 9
cjis	5.10.1.3
cobit5	APO01.06, BAI01.06, BAI02.01, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS04.07, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.02, DSS06.06
disa	CCI-002696, CCI-002699, CCI-001744
isa-62443-2009	4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4
isa-62443-2013	SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 4.1, SR 6.2, SR 7.6
ism	1034, 1288, 1341, 1417
iso27001-2013	A.11.2.4, A.12.1.2, A.12.2.1, A.12.4.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.14.2.7, A.15.2.1, A.8.2.3
nist	CM-6(a)
nist-csf	DE.CM-1, DE.CM-7, PR.DS-1, PR.DS-6, PR.DS-8, PR.IP-1, PR.IP-3
pcidss	Req-11.5
os-srg	SRG-OS-000445-GPOS-00199
anssi	R76, R79
pcidss4	11.5.2

Remediation OSBuild Blueprint snippet ⇲


[[packages]]
name = "aide"
version = "*"

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

- name: Ensure aide is installed
  package:
    name: aide
    state: present
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - CJIS-5.10.1.3
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-11.5
  - PCI-DSSv4-11.5.2
  - enable_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - package_aide_installed

Remediation Puppet snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

include install_aide

class install_aide {
  package { 'aide':
    ensure => 'installed',
  }
}

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

DEBIAN_FRONTEND=noninteractive apt-get install -y "aide"

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Build and Test AIDE Database [ref]

Run the following command to generate a new database:

$ sudo aideinit

By default, the database will be written to the file /var/lib/aide/aide.db.new. Storing the database, the configuration file /etc/aide.conf, and the binary /usr/sbin/aide (or hashes of these files), in a secure location (such as on read-only media) provides additional assurance about their integrity. The newly-generated database can be installed as follows:

$ sudo cp /var/lib/aide/aide.db.new /var/lib/aide/aide.db

To initiate a manual check, run the following command:

$ sudo /usr/sbin/aide --check

If this check produces any unexpected output, investigate.

Rationale:

For AIDE to be effective, an initial database of "known-good" information about files must be captured and it should be able to be verified against the installed files.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_aide_build_database

References:

cis-csc	1, 11, 12, 13, 14, 15, 16, 2, 3, 5, 7, 8, 9
cjis	5.10.1.3
cobit5	APO01.06, BAI01.06, BAI02.01, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS04.07, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.02, DSS06.06
isa-62443-2009	4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4
isa-62443-2013	SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 4.1, SR 6.2, SR 7.6
iso27001-2013	A.11.2.4, A.12.1.2, A.12.2.1, A.12.4.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.14.2.7, A.15.2.1, A.8.2.3
nist	CM-6(a)
nist-csf	DE.CM-1, DE.CM-7, PR.DS-1, PR.DS-6, PR.DS-8, PR.IP-1, PR.IP-3
pcidss	Req-11.5
os-srg	SRG-OS-000445-GPOS-00199
anssi	R76, R79
pcidss4	11.5.2

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Build and Test AIDE Database - Ensure AIDE Is Installed
  ansible.builtin.apt:
    name: aide
    state: present
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - CJIS-5.10.1.3
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-11.5
  - PCI-DSSv4-11.5.2
  - aide_build_database
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Build and Test AIDE Database - Check if DB Path in /etc/aide/aide.conf Is
    Already Set
  ansible.builtin.lineinfile:
    path: /etc/aide/aide.conf
    regexp: ^#?(\s*)(database=)(.*)$
    state: absent
  check_mode: true
  changed_when: false
  register: database_replace
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - CJIS-5.10.1.3
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-11.5
  - PCI-DSSv4-11.5.2
  - aide_build_database
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Build and Test AIDE Database - Check if DB Out Path in /etc/aide/aide.conf
    Is Already Set
  ansible.builtin.lineinfile:
    path: /etc/aide/aide.conf
    regexp: ^#?(\s*)(database_out=)(.*)$
    state: absent
  check_mode: true
  changed_when: false
  register: database_out_replace
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - CJIS-5.10.1.3
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-11.5
  - PCI-DSSv4-11.5.2
  - aide_build_database
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Build and Test AIDE Database - Fix DB Path in Config File if Necessary
  ansible.builtin.lineinfile:
    path: /etc/aide/aide.conf
    regexp: ^#?(\s*)(database)(\s*)=(\s*)(.*)$
    line: \2\3=\4file:/var/lib/aide/aide.db
    backrefs: true
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - database_replace.found > 0
  tags:
  - CJIS-5.10.1.3
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-11.5
  - PCI-DSSv4-11.5.2
  - aide_build_database
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Build and Test AIDE Database - Fix DB Out Path in Config File if Necessary
  ansible.builtin.lineinfile:
    path: /etc/aide/aide.conf
    regexp: ^#?(\s*)(database_out)(\s*)=(\s*)(.*)$
    line: \2\3=\4file:/var/lib/aide/aide.db.new
    backrefs: true
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - database_out_replace.found > 0
  tags:
  - CJIS-5.10.1.3
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-11.5
  - PCI-DSSv4-11.5.2
  - aide_build_database
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Build and Test AIDE Database - Ensure the Default DB Path is Added
  ansible.builtin.lineinfile:
    path: /etc/aide/aide.conf
    line: database=file:/var/lib/aide/aide.db
    create: true
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - database_replace.found == 0
  tags:
  - CJIS-5.10.1.3
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-11.5
  - PCI-DSSv4-11.5.2
  - aide_build_database
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Build and Test AIDE Database - Ensure the Default Out Path is Added
  ansible.builtin.lineinfile:
    path: /etc/aide/aide.conf
    line: database_out=file:/var/lib/aide/aide.db.new
    create: true
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - database_out_replace.found == 0
  tags:
  - CJIS-5.10.1.3
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-11.5
  - PCI-DSSv4-11.5.2
  - aide_build_database
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Build and Test AIDE Database - Build and Test AIDE Database
  ansible.builtin.command: /usr/sbin/aideinit -y -f
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - CJIS-5.10.1.3
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-11.5
  - PCI-DSSv4-11.5.2
  - aide_build_database
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

DEBIAN_FRONTEND=noninteractive apt-get install -y "aide"

AIDE_CONFIG=/etc/aide/aide.conf
DEFAULT_DB_PATH=/var/lib/aide/aide.db

# Fix db path in the config file, if necessary
if ! grep -q '^database=file:' ${AIDE_CONFIG}; then
    # replace_or_append gets confused by 'database=file' as a key, so should not be used.
    #replace_or_append "${AIDE_CONFIG}" '^database=file' "${DEFAULT_DB_PATH}" '@CCENUM@' '%s:%s'
    echo "database=file:${DEFAULT_DB_PATH}" >> ${AIDE_CONFIG}
fi

# Fix db out path in the config file, if necessary
if ! grep -q '^database_out=file:' ${AIDE_CONFIG}; then
    echo "database_out=file:${DEFAULT_DB_PATH}.new" >> ${AIDE_CONFIG}
fi

/usr/sbin/aideinit -y -f

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Disk Partitioning Group contains 5 rules

[ref] To ensure separation and protection of data, there are top-level system directories which should be placed on their own physical partition or logical volume. The installer's default partitioning scheme creates separate logical volumes for /, /boot, and swap.

If starting with any of the default layouts, check the box to \"Review and modify partitioning.\" This allows for the easy creation of additional logical volumes inside the volume group already created, though it may require making /'s logical volume smaller to create space. In general, using logical volumes is preferable to using partitions because they can be more easily adjusted later.
If creating a custom layout, create the partitions mentioned in the previous paragraph (which the installer will require anyway), as well as separate ones described in the following sections.

If a system has already been installed, and the default partitioning scheme was used, it is possible but nontrivial to modify it to create separate logical volumes for the directories listed above. The Logical Volume Manager (LVM) makes this possible. See the LVM HOWTO at http://tldp.org/HOWTO/LVM-HOWTO/ for more detailed information on LVM.

Rule Ensure /home Located On Separate Partition [ref]

If user home directories will be stored locally, create a separate partition for /home at installation time (or migrate it later using LVM). If /home will be mounted from another system such as an NFS server, then creating a separate partition is not necessary at installation time, and the mountpoint can instead be configured later.

Rationale:

Ensuring that /home is mounted on its own partition enables the setting of more restrictive mount options, and also helps ensure that users cannot trivially fill partitions used for log or audit data storage.

Severity:

low

Rule ID: xccdf_org.ssgproject.content_rule_partition_for_home

References:

cis-csc	12, 15, 8
cobit5	APO13.01, DSS05.02
disa	CCI-000366, CCI-001208
isa-62443-2013	SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013	A.13.1.1, A.13.2.1, A.14.1.3
nist	CM-6(a), SC-5(2)
nist-csf	PR.PT-4
os-srg	SRG-OS-000480-GPOS-00227
anssi	R28

Rule Ensure /srv Located On Separate Partition [ref]

If a file server (FTP, TFTP...) is hosted locally, create a separate partition for /srv at installation time (or migrate it later using LVM). If /srv will be mounted from another system such as an NFS server, then creating a separate partition is not necessary at installation time, and the mountpoint can instead be configured later.

Rationale:

Srv deserves files for local network file server such as FTP. Ensuring that /srv is mounted on its own partition enables the setting of more restrictive mount options, and also helps ensure that users cannot trivially fill partitions used for log or audit data storage.

Severity:

unknown

Rule ID: xccdf_org.ssgproject.content_rule_partition_for_srv

References:

anssi	R28

Rule Ensure /var Located On Separate Partition [ref]

The /var directory is used by daemons and other system services to store frequently-changing data. Ensure that /var has its own partition or logical volume at installation time, or migrate it using LVM.

Rationale:

Ensuring that /var is mounted on its own partition enables the setting of more restrictive mount options. This helps protect system services such as daemons or other programs which use it. It is not uncommon for the /var directory to contain world-writable directories installed by other software packages.

Severity:

low

Rule ID: xccdf_org.ssgproject.content_rule_partition_for_var

References:

cis-csc	12, 15, 8
cobit5	APO13.01, DSS05.02
disa	CCI-000366
isa-62443-2013	SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013	A.13.1.1, A.13.2.1, A.14.1.3
nist	CM-6(a), SC-5(2)
nist-csf	PR.PT-4
os-srg	SRG-OS-000480-GPOS-00227
anssi	R28

Rule Ensure /var/log Located On Separate Partition [ref]

System logs are stored in the /var/log directory. Ensure that /var/log has its own partition or logical volume at installation time, or migrate it using LVM.

Rationale:

Placing /var/log in its own partition enables better separation between log files and other files in /var/.

Severity:

low

Rule ID: xccdf_org.ssgproject.content_rule_partition_for_var_log

References:

cis-csc	1, 12, 14, 15, 16, 3, 5, 6, 8
cobit5	APO11.04, APO13.01, BAI03.05, DSS05.02, DSS05.04, DSS05.07, MEA02.01
disa	CCI-000366
isa-62443-2009	4.3.3.3.9, 4.3.3.5.8, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4
isa-62443-2013	SR 2.10, SR 2.11, SR 2.12, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013	A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3
nerc-cip	CIP-007-3 R6.5
nist	CM-6(a), AU-4, SC-5(2)
nist-csf	PR.PT-1, PR.PT-4
os-srg	SRG-OS-000480-GPOS-00227
anssi	R28

Rule Ensure tmp.mount Unit Us Enabled [ref]

The /tmp directory is a world-writable directory used for temporary file storage. This directory is managed by systemd-tmpfiles. Ensure that the tmp.mount systemd unit is enabled.

Rationale:

The /tmp directory is used as temporary storage by many programs. Placing /tmp in a tmpfs filesystem enables the setting of more restrictive mount options, which can help protect programs which use it. The tmp.mount unit configures the tmpfs filesystem and ensures the /tmp directory is wiped during reboot.

Severity:

low

Rule ID: xccdf_org.ssgproject.content_rule_systemd_tmp_mount_enabled

References:

anssi	R28

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

- name: Enable mount tmp
  ansible.builtin.systemd:
    name: tmp.mount
    enabled: 'yes'
    state: started
    masked: 'false'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - enable_strategy
  - low_complexity
  - low_disruption
  - low_severity
  - no_reboot_needed
  - systemd_tmp_mount_enabled

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

SYSTEMCTL_EXEC='/usr/bin/systemctl'
"$SYSTEMCTL_EXEC" unmask 'tmp.mount'
"$SYSTEMCTL_EXEC" start 'tmp.mount'
"$SYSTEMCTL_EXEC" enable 'tmp.mount'

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Sudo Group contains 12 rules

[ref] Sudo, which stands for "su 'do'", provides the ability to delegate authority to certain users, groups of users, or system administrators. When configured for system users and/or groups, Sudo can allow a user or group to execute privileged commands that normally only root is allowed to execute.

For more information on Sudo and addition Sudo configuration options, see https://www.sudo.ws.

Rule Verify Group Who Owns /etc/sudoers.d Directory [ref]

To properly set the group owner of /etc/sudoers.d, run the command:

$ sudo chgrp root /etc/sudoers.d

Rationale:

The ownership of the /etc/sudoers.d directory by the root group is important because this directory hosts sudo configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the sudo configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_groupowner_etc_sudoersd

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Ensure group owner on /etc/sudoers.d/
  file:
    path: /etc/sudoers.d/
    state: directory
    group: root
  tags:
  - configure_strategy
  - directory_groupowner_etc_sudoersd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

find -H /etc/sudoers.d/ -maxdepth 1 -type d -exec chgrp root {} \;

Rule Verify User Who Owns /etc/sudoers.d Directory [ref]

To properly set the owner of /etc/sudoers.d, run the command:

$ sudo chown root /etc/sudoers.d

Rationale:

The ownership of the /etc/sudoers.d directory by the root user is important because this directory hosts sudo configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the sudo configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_owner_etc_sudoersd

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Ensure owner on directory /etc/sudoers.d/
  file:
    path: /etc/sudoers.d/
    state: directory
    owner: '0'
  tags:
  - configure_strategy
  - directory_owner_etc_sudoersd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

find -H /etc/sudoers.d/ -maxdepth 1 -type d -exec chown 0 {} \;

Rule Verify Permissions On /etc/sudoers.d Directory [ref]

To properly set the permissions of /etc/sudoers.d, run the command:

$ sudo chmod 0750 /etc/sudoers.d

Rationale:

Setting correct permissions on the /etc/sudoers.d directory is important because this directory hosts sudo configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the sudo configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_permissions_etc_sudoersd

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Find /etc/sudoers.d/ file(s)
  command: 'find -H /etc/sudoers.d/ -maxdepth 1 -perm /u+s,g+ws,o+xwrt  -type d '
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  tags:
  - configure_strategy
  - directory_permissions_etc_sudoersd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set permissions for /etc/sudoers.d/ file(s)
  file:
    path: '{{ item }}'
    mode: u-s,g-ws,o-xwrt
    state: directory
  with_items:
  - '{{ files_found.stdout_lines }}'
  tags:
  - configure_strategy
  - directory_permissions_etc_sudoersd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure






find -H /etc/sudoers.d/ -maxdepth 1 -perm /u+s,g+ws,o+xwrt -type d -exec chmod u-s,g-ws,o-xwrt {} \;

Rule Verify Group Who Owns /etc/sudoers File [ref]

To properly set the group owner of /etc/sudoers, run the command:

$ sudo chgrp root /etc/sudoers

Rationale:

The ownership of the /etc/sudoers file by the root group is important because this file hosts sudo configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the sudo configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_sudoers

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/sudoers
  stat:
    path: /etc/sudoers
  register: file_exists
  tags:
  - configure_strategy
  - file_groupowner_etc_sudoers
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner root on /etc/sudoers
  file:
    path: /etc/sudoers
    group: root
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_groupowner_etc_sudoers
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chgrp root /etc/sudoers

Rule Verify User Who Owns /etc/sudoers File [ref]

To properly set the owner of /etc/sudoers, run the command:

$ sudo chown root /etc/sudoers

Rationale:

The ownership of the /etc/sudoers file by the root user is important because this file hosts sudo configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the sudo configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_sudoers

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/sudoers
  stat:
    path: /etc/sudoers
  register: file_exists
  tags:
  - configure_strategy
  - file_owner_etc_sudoers
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/sudoers
  file:
    path: /etc/sudoers
    owner: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_owner_etc_sudoers
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chown 0 /etc/sudoers

Rule Verify Permissions On /etc/sudoers File [ref]

To properly set the permissions of /etc/sudoers, run the command:

$ sudo chmod 0440 /etc/sudoers

Rationale:

Setting correct permissions on the /etc/sudoers file is important because this file hosts sudo configuration. Protection of this file is critical for system security. Restricting the permissions ensures exclusive control of the sudo configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_sudoers

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/sudoers
  stat:
    path: /etc/sudoers
  register: file_exists
  tags:
  - configure_strategy
  - file_permissions_etc_sudoers
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xws,g-xws,o-xwrt on /etc/sudoers
  file:
    path: /etc/sudoers
    mode: u-xws,g-xws,o-xwrt
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_permissions_etc_sudoers
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure






chmod u-xws,g-xws,o-xwrt /etc/sudoers

Rule Ensure Privileged Escalated Commands Cannot Execute Other Commands - sudo NOEXEC [ref]

The sudo NOEXEC tag, when specified, prevents user executed commands from executing other commands, like a shell for example. This should be enabled by making sure that the NOEXEC tag exists in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/.

Rationale:

Restricting the capability of sudo allowed commands to execute sub-commands prevents users from running programs with privileges they wouldn't have otherwise.

Severity:

high

Rule ID: xccdf_org.ssgproject.content_rule_sudo_add_noexec

References:

anssi	R39

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Ensure noexec is enabled in /etc/sudoers
  lineinfile:
    path: /etc/sudoers
    regexp: ^[\s]*Defaults.*\bnoexec\b.*$
    line: Defaults noexec
    validate: /usr/sbin/visudo -cf %s
  tags:
  - high_severity
  - low_complexity
  - low_disruption
  - no_reboot_needed
  - restrict_strategy
  - sudo_add_noexec

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict


if /usr/sbin/visudo -qcf /etc/sudoers; then
    cp /etc/sudoers /etc/sudoers.bak
    if ! grep -P '^[\s]*Defaults[\s]*\bnoexec\b.*$' /etc/sudoers; then
        # sudoers file doesn't define Option noexec
        echo "Defaults noexec" >> /etc/sudoers
    fi
    
    # Check validity of sudoers and cleanup bak
    if /usr/sbin/visudo -qcf /etc/sudoers; then
        rm -f /etc/sudoers.bak
    else
        echo "Fail to validate remediated /etc/sudoers, reverting to original file."
        mv /etc/sudoers.bak /etc/sudoers
        false
    fi
else
    echo "Skipping remediation, /etc/sudoers failed to validate"
    false
fi

Rule Ensure Only Users Logged In To Real tty Can Execute Sudo - sudo requiretty [ref]

The sudo requiretty tag, when specified, will only execute sudo commands from users logged in to a real tty. This should be enabled by making sure that the requiretty tag exists in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/.

Rationale:

Restricting the use cases in which a user is allowed to execute sudo commands reduces the attack surface.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sudo_add_requiretty

References:

anssi	R39

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Ensure requiretty is enabled in /etc/sudoers
  lineinfile:
    path: /etc/sudoers
    regexp: ^[\s]*Defaults.*\brequiretty\b.*$
    line: Defaults requiretty
    validate: /usr/sbin/visudo -cf %s
  tags:
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
  - sudo_add_requiretty

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict


if /usr/sbin/visudo -qcf /etc/sudoers; then
    cp /etc/sudoers /etc/sudoers.bak
    if ! grep -P '^[\s]*Defaults[\s]*\brequiretty\b.*$' /etc/sudoers; then
        # sudoers file doesn't define Option requiretty
        echo "Defaults requiretty" >> /etc/sudoers
    fi
    
    # Check validity of sudoers and cleanup bak
    if /usr/sbin/visudo -qcf /etc/sudoers; then
        rm -f /etc/sudoers.bak
    else
        echo "Fail to validate remediated /etc/sudoers, reverting to original file."
        mv /etc/sudoers.bak /etc/sudoers
        false
    fi
else
    echo "Skipping remediation, /etc/sudoers failed to validate"
    false
fi

Rule Ensure Only Users Logged In To Real tty Can Execute Sudo - sudo use_pty [ref]

The sudo use_pty tag, when specified, will only execute sudo commands from users logged in to a real tty. This should be enabled by making sure that the use_pty tag exists in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/.

Rationale:

Requiring that sudo commands be run in a pseudo-terminal can prevent an attacker from retaining access to the user's terminal after the main program has finished executing.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sudo_add_use_pty

References:

pcidss	Req-10.2.5
anssi	R39
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - PCI-DSS-Req-10.2.5
  - PCI-DSSv4-2.2.6
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
  - sudo_add_use_pty

- name: Ensure use_pty is enabled in /etc/sudoers
  lineinfile:
    path: /etc/sudoers
    regexp: ^[\s]*Defaults.*\buse_pty\b.*$
    line: Defaults use_pty
    validate: /usr/sbin/visudo -cf %s
  when: '"sudo" in ansible_facts.packages'
  tags:
  - PCI-DSS-Req-10.2.5
  - PCI-DSSv4-2.2.6
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
  - sudo_add_use_pty

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'sudo' 2>/dev/null | grep -q installed; then

if /usr/sbin/visudo -qcf /etc/sudoers; then
    cp /etc/sudoers /etc/sudoers.bak
    if ! grep -P '^[\s]*Defaults[\s]*\buse_pty\b.*$' /etc/sudoers; then
        # sudoers file doesn't define Option use_pty
        echo "Defaults use_pty" >> /etc/sudoers
    fi
    
    # Check validity of sudoers and cleanup bak
    if /usr/sbin/visudo -qcf /etc/sudoers; then
        rm -f /etc/sudoers.bak
    else
        echo "Fail to validate remediated /etc/sudoers, reverting to original file."
        mv /etc/sudoers.bak /etc/sudoers
        false
    fi
else
    echo "Skipping remediation, /etc/sudoers failed to validate"
    false
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Explicit arguments in sudo specifications [ref]

All commands in the sudoers file must strictly specify the arguments allowed to be used for a given user. If the command is supposed to be executed only without arguments, pass "" as an argument in the corresponding user specification.

Warning: This rule doesn't come with a remediation, as absence of arguments in the user spec doesn't mean that the command is intended to be executed with no arguments.

Warning: The rule can produce false findings when an argument contains a comma - sudoers syntax allows comma escaping using backslash, but the check doesn't support that. For example, root ALL=(ALL) echo 1\,2 allows root to execute echo 1,2, but the check would interpret it as two commands echo 1\ and 2.

Rationale:

Any argument can modify quite significantly the behavior of a program, whether regarding the realized operation (read, write, delete, etc.) or accessed resources (path in a file system tree). To avoid any possibility of misuse of a command by a user, the ambiguities must be removed at the level of its specification. For example, on some systems, the kernel messages are only accessible by root. If a user nevertheless must have the privileges to read them, the argument of the dmesg command has to be restricted in order to prevent the user from flushing the buffer through the -c option:

user ALL = dmesg ""

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sudoers_explicit_command_args

References:

anssi	R43

Rule Don't define allowed commands in sudoers by means of exclusion [ref]

Policies applied by sudo through the sudoers file should not involve negation. Each user specification in the sudoers file contains a comma-delimited list of command specifications. The definition can make use glob patterns, as well as of negations. Indirect definition of those commands by means of exclusion of a set of commands is trivial to bypass, so it is not allowed to use such constructs.

Warning: This rule doesn't come with a remediation, as negations indicate design issues with the sudoers user specifications design. Just removing negations doesn't increase the security - you typically have to rethink the definition of allowed commands to fix the issue.

Rationale:

Specifying access right using negation is inefficient and can be easily circumvented. For example, it is expected that a specification like

# To avoid absolutely , this rule can be easily circumvented!
user ALL = ALL ,!/ bin/sh

prevents the execution of the shell but that’s not the case: just copy the binary /bin/sh to a different name to make it executable again through the rule keyword ALL.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sudoers_no_command_negation

References:

anssi	R42

Rule Don't target root user in the sudoers file [ref]

The targeted users of a user specification should be, as much as possible, non privileged users (i.e.: non-root). User specifications have to explicitly list the runas spec (i.e. the list of target users that can be impersonated), and ALL or root should not be used.

Warning: This rule doesn't come with a remediation, as the exact requirement allows exceptions, and removing lines from the sudoers file can make the system non-administrable.

Rationale:

It is common that the command to be executed does not require superuser rights (editing a file whose the owner is not root, sending a signal to an unprivileged process,etc.). In order to limit any attempt of privilege escalation through a command, it is better to apply normal user rights.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sudoers_no_root_target

References:

anssi	R40

Group Account and Access Control Group contains 8 groups and 11 rules

[ref] In traditional Unix security, if an attacker gains shell access to a certain login account, they can perform any action or access any file to which that account has access. Therefore, making it more difficult for unauthorized people to gain shell access to accounts, particularly to privileged accounts, is a necessary part of securing a system. This section introduces mechanisms for restricting access to accounts under Debian 12.

Group Protect Accounts by Configuring PAM Group contains 2 groups and 2 rules

[ref] PAM, or Pluggable Authentication Modules, is a system which implements modular authentication for Linux programs. PAM provides a flexible and configurable architecture for authentication, and it should be configured to minimize exposure to unnecessary risk. This section contains guidance on how to accomplish that.

PAM is implemented as a set of shared objects which are loaded and invoked whenever an application wishes to authenticate a user. Typically, the application must be running as root in order to take advantage of PAM, because PAM's modules often need to be able to access sensitive stores of account information, such as /etc/shadow. Traditional privileged network listeners (e.g. sshd) or SUID programs (e.g. sudo) already meet this requirement. An SUID root application, userhelper, is provided so that programs which are not SUID or privileged themselves can still take advantage of PAM.

PAM looks in the directory /etc/pam.d for application-specific configuration information. For instance, if the program login attempts to authenticate a user, then PAM's libraries follow the instructions in the file /etc/pam.d/login to determine what actions should be taken.

One very important file in /etc/pam.d is /etc/pam.d/system-auth. This file, which is included by many other PAM configuration files, defines 'default' system authentication measures. Modifying this file is a good way to make far-reaching authentication changes, for instance when implementing a centralized authentication service.

Warning: Be careful when making changes to PAM's configuration files. The syntax for these files is complex, and modifications can have unexpected consequences. The default configurations shipped with applications should be sufficient for most users.

Warning: Running authconfig or system-config-authentication will re-write the PAM configuration files, destroying any manually made changes and replacing them with a series of system defaults. One reference to the configuration file syntax can be found at https://fossies.org/linux/Linux-PAM-docs/doc/sag/Linux-PAM_SAG.pdf.

Group Set Password Quality Requirements Group contains 1 group and 2 rules

[ref] The default pam_pwquality PAM module provides strength checking for passwords. It performs a number of checks, such as making sure passwords are not similar to dictionary words, are of at least a certain length, are not the previous password reversed, and are not simply a change of case from the previous password. It can also require passwords to be in certain character classes. The pam_pwquality module is the preferred way of configuring password requirements.

The man pages pam_pwquality(8) provide information on the capabilities and configuration of each.

Group Set Password Quality Requirements with pam_pwquality Group contains 2 rules

[ref] The pam_pwquality PAM module can be configured to meet requirements for a variety of policies.

For example, to configure pam_pwquality to require at least one uppercase character, lowercase character, digit, and other (special) character, make sure that pam_pwquality exists in /etc/pam.d/system-auth:

password    requisite     pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type=

If no such line exists, add one as the first line of the password section in /etc/pam.d/system-auth. Next, modify the settings in /etc/security/pwquality.conf to match the following:

difok = 4
minlen = 14
dcredit = -1
ucredit = -1
lcredit = -1
ocredit = -1
maxrepeat = 3

The arguments can be modified to ensure compliance with your organization's security policy. Discussion of each parameter follows.

Rule Ensure PAM Enforces Password Requirements - Minimum Different Categories [ref]

The pam_pwquality module's minclass parameter controls requirements for usage of different character classes, or types, of character that must exist in a password before it is considered valid. For example, setting this value to three (3) requires that any password must have characters from at least three different categories in order to be approved. The default value is zero (0), meaning there are no required classes. There are four categories available:

* Upper-case characters
* Lower-case characters
* Digits
* Special characters (for example, punctuation)

Modify the minclass setting in /etc/security/pwquality.conf entry to require 4 differing categories of characters when changing passwords.

Rationale:

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

Requiring a minimum number of character categories makes password guessing attacks more difficult by ensuring a larger search space.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_accounts_password_pam_minclass

References:

cis-csc	1, 12, 15, 16, 5
cobit5	DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa	CCI-000195
isa-62443-2009	4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013	SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
ism	0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561
iso27001-2013	A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist	IA-5(c), IA-5(1)(a), CM-6(a), IA-5(4)
nist-csf	PR.AC-1, PR.AC-6, PR.AC-7
os-srg	SRG-OS-000072-GPOS-00040
anssi	R68

Rule Ensure PAM Enforces Password Requirements - Authentication Retry Prompts Permitted Per-Session [ref]

To configure the number of retry prompts that are permitted per-session: Edit the pam_pwquality.so statement in /etc/pam.d/system-auth to show

retry=3

, or a lower value if site policy is more restrictive. The DoD requirement is a maximum of 3 prompts per session.

Rationale:

Setting the password retry prompts that are permitted on a per-session basis to a low value requires some software, such as SSH, to re-connect. This can slow down and draw additional attention to some types of password-guessing attacks. Note that this is different from account lockout, which is provided by the pam_faillock module.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_accounts_password_pam_retry

References:

cis-csc	1, 11, 12, 15, 16, 3, 5, 9
cjis	5.5.3
cobit5	BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa	CCI-000192, CCI-000366
isa-62443-2009	4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013	SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 7.6
iso27001-2013	A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist	CM-6(a), AC-7(a), IA-5(4)
nist-csf	PR.AC-1, PR.AC-6, PR.AC-7, PR.IP-1
ospp	FMT_MOF_EXT.1
os-srg	SRG-OS-000069-GPOS-00037, SRG-OS-000480-GPOS-00227
anssi	R68

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q installed; then

var_password_pam_retry='3'



	
		if [ -e "/etc/pam.d/system-auth" ] ; then
    PAM_FILE_PATH="/etc/pam.d/system-auth"
    if [ -f /usr/bin/authselect ]; then
        
        if ! authselect check; then
        echo "
        authselect integrity check failed. Remediation aborted!
        This remediation could not be applied because an authselect profile was not selected or the selected profile is not intact.
        It is not recommended to manually edit the PAM files when authselect tool is available.
        In cases where the default authselect profile does not cover a specific demand, a custom authselect profile is recommended."
        exit 1
        fi

        CURRENT_PROFILE=$(authselect current -r | awk '{ print $1 }')
        # If not already in use, a custom profile is created preserving the enabled features.
        if [[ ! $CURRENT_PROFILE == custom/* ]]; then
            ENABLED_FEATURES=$(authselect current | tail -n+3 | awk '{ print $2 }')
            authselect create-profile hardening -b $CURRENT_PROFILE
            CURRENT_PROFILE="custom/hardening"
            
            authselect apply-changes -b --backup=before-hardening-custom-profile
            authselect select $CURRENT_PROFILE
            for feature in $ENABLED_FEATURES; do
                authselect enable-feature $feature;
            done
            
            authselect apply-changes -b --backup=after-hardening-custom-profile
        fi
        PAM_FILE_NAME=$(basename "/etc/pam.d/system-auth")
        PAM_FILE_PATH="/etc/authselect/$CURRENT_PROFILE/$PAM_FILE_NAME"

        authselect apply-changes -b
    fi
    if ! grep -qP '^\s*password\s+'"requisite"'\s+pam_pwquality.so\s*.*' "$PAM_FILE_PATH"; then
            # Line matching group + control + module was not found. Check group + module.
            if [ "$(grep -cP '^\s*password\s+.*\s+pam_pwquality.so\s*' "$PAM_FILE_PATH")" -eq 1 ]; then
                # The control is updated only if one single line matches.
                sed -i -E --follow-symlinks 's/^(\s*password\s+).*(\bpam_pwquality.so.*)/\1'"requisite"' \2/' "$PAM_FILE_PATH"
            else
                LAST_MATCH_LINE=$(grep -nP "^\s*account" "$PAM_FILE_PATH" | tail -n 1 | cut -d: -f 1)
                if [ ! -z $LAST_MATCH_LINE ]; then
                    sed -i --follow-symlinks $LAST_MATCH_LINE' a password     '"requisite"'    pam_pwquality.so' "$PAM_FILE_PATH"
                else
                    echo 'password    '"requisite"'    pam_pwquality.so' >> "$PAM_FILE_PATH"
                fi
            fi
        fi
        # Check the option
        if ! grep -qP '^\s*password\s+'"requisite"'\s+pam_pwquality.so\s*.*\sretry\b' "$PAM_FILE_PATH"; then
            sed -i -E --follow-symlinks '/\s*password\s+'"requisite"'\s+pam_pwquality.so.*/ s/$/ retry='"$var_password_pam_retry"'/' "$PAM_FILE_PATH"
        else
            sed -i -E --follow-symlinks 's/(\s*password\s+'"requisite"'\s+pam_pwquality.so\s+.*)('"retry"'=)[[:alnum:]]+\s*(.*)/\1\2'"$var_password_pam_retry"' \3/' "$PAM_FILE_PATH"
        fi
    if [ -f /usr/bin/authselect ]; then
        
        authselect apply-changes -b
    fi
else
    echo "/etc/pam.d/system-auth was not found" >&2
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Protect Physical Console Access Group contains 1 rule

[ref] It is impossible to fully protect a system from an attacker with physical access, so securing the space in which the system is located should be considered a necessary step. However, there are some steps which, if taken, make it more difficult for an attacker to quickly or undetectably modify a system from its console.

Rule Configure Logind to terminate idle sessions after certain time of inactivity [ref]

To configure logind service to terminate inactive user sessions after 600 seconds, edit the file /etc/systemd/logind.conf. Ensure that there is a section

[Login]

which contains the configuration

StopIdleSessionSec=600

Rationale:

Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been let unattended.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_logind_session_timeout

References:

cis-csc	1, 12, 13, 14, 15, 16, 18, 3, 5, 7, 8
cjis	5.5.6
cobit5	APO13.01, BAI03.01, BAI03.02, BAI03.03, DSS01.03, DSS03.05, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui	3.1.11
isa-62443-2009	4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.3
isa-62443-2013	SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 6.2
iso27001-2013	A.12.4.1, A.12.4.3, A.14.1.1, A.14.2.1, A.14.2.5, A.18.1.4, A.6.1.2, A.6.1.5, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nerc-cip	CIP-004-6 R2.2.3, CIP-007-3 R5.1, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist	CM-6(a), AC-17(a), AC-2(5), AC-12, AC-17(a), SC-10, CM-6(a)
nist-csf	DE.CM-1, DE.CM-3, PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.IP-2
ospp	FMT_SMF_EXT.1.1
pcidss	Req-8.1.8
os-srg	SRG-OS-000163-GPOS-00072
anssi	R32

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	true
Strategy:	restrict

- name: XCCDF Value var_logind_session_timeout # promote to variable
  set_fact:
    var_logind_session_timeout: !!str 600
  tags:
    - always

- name: Set 'StopIdleSessionSec' to '{{ var_logind_session_timeout }}' in the [Login]
    section of '/etc/systemd/logind.conf'
  ini_file:
    path: /etc/systemd/logind.conf
    section: Login
    option: StopIdleSessionSec
    value: '{{ var_logind_session_timeout }}'
    create: true
    mode: 420
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - ( ansible_distribution == 'RedHat' and ansible_distribution_version is version('8.7',
    '>=') and ansible_distribution == 'RedHat' and ansible_distribution_version is
    version('9.0', '!=') ) or ansible_distribution == 'OracleLinux' and ansible_distribution_version
    is version('8.7', '>=')
  tags:
  - CJIS-5.5.6
  - NIST-800-171-3.1.11
  - NIST-800-53-AC-12
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-2(5)
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-6(a)
  - NIST-800-53-SC-10
  - PCI-DSS-Req-8.1.8
  - logind_session_timeout
  - low_complexity
  - low_disruption
  - medium_severity
  - reboot_required
  - restrict_strategy

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ] && { ( grep -qP "^ID=[\"']?rhel[\"']?$" "/etc/os-release" && { real="$(grep -P "^VERSION_ID=[\"']?[\w.]+[\"']?$" /etc/os-release | sed "s/^VERSION_ID=[\"']\?\([^\"']\+\)[\"']\?$/\1/")"; expected="8.7"; printf "%s\n%s" "$expected" "$real" | sort -VC; } && grep -qP "^ID=[\"']?rhel[\"']?$" "/etc/os-release" && { real="$(grep -P "^VERSION_ID=[\"']?[\w.]+[\"']?$" /etc/os-release | sed "s/^VERSION_ID=[\"']\?\([^\"']\+\)[\"']\?$/\1/")"; expected="9.0"; [[ "$real" != "$expected" ]]; } ) || grep -qP "^ID=[\"']?ol[\"']?$" "/etc/os-release" && { real="$(grep -P "^VERSION_ID=[\"']?[\w.]+[\"']?$" /etc/os-release | sed "s/^VERSION_ID=[\"']\?\([^\"']\+\)[\"']\?$/\1/")"; expected="8.7"; printf "%s\n%s" "$expected" "$real" | sort -VC; }; }; then

var_logind_session_timeout='600'



# Try find '[Login]' and 'StopIdleSessionSec' in '/etc/systemd/logind.conf', if it exists, set
# to '$var_logind_session_timeout', if it isn't here, add it, if '[Login]' doesn't exist, add it there
if grep -qzosP '[[:space:]]*\[Login]([^\n\[]*\n+)+?[[:space:]]*StopIdleSessionSec' '/etc/systemd/logind.conf'; then
    
    sed -i "s/StopIdleSessionSec[^(\n)]*/StopIdleSessionSec=$var_logind_session_timeout/" '/etc/systemd/logind.conf'
elif grep -qs '[[:space:]]*\[Login]' '/etc/systemd/logind.conf'; then
    sed -i "/[[:space:]]*\[Login]/a StopIdleSessionSec=$var_logind_session_timeout" '/etc/systemd/logind.conf'
else
    if test -d "/etc/systemd"; then
        printf '%s\n' '[Login]' "StopIdleSessionSec=$var_logind_session_timeout" >> '/etc/systemd/logind.conf'
    else
        echo "Config file directory '/etc/systemd' doesnt exist, not remediating, assuming non-applicability." >&2
    fi
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Protect Accounts by Restricting Password-Based Login Group contains 2 groups and 2 rules

[ref] Conventionally, Unix shell accounts are accessed by providing a username and password to a login program, which tests these values for correctness using the /etc/passwd and /etc/shadow files. Password-based login is vulnerable to guessing of weak passwords, and to sniffing and man-in-the-middle attacks against passwords entered over a network or at an insecure console. Therefore, mechanisms for accessing accounts by entering usernames and passwords should be restricted to those which are operationally necessary.

Group Set Password Expiration Parameters Group contains 1 rule

[ref] The file /etc/login.defs controls several password-related settings. Programs such as passwd, su, and login consult /etc/login.defs to determine behavior with regard to password aging, expiration warnings, and length. See the man page login.defs(5) for more information.

Users should be forced to change their passwords, in order to decrease the utility of compromised passwords. However, the need to change passwords often should be balanced against the risk that users will reuse or write down passwords if forced to change them too often. Forcing password changes every 90-360 days, depending on the environment, is recommended. Set the appropriate value as PASS_MAX_DAYS and apply it to existing accounts with the -M flag.

The PASS_MIN_DAYS (-m) setting prevents password changes for 7 days after the first change, to discourage password cycling. If you use this setting, train users to contact an administrator for an emergency password change in case a new password becomes compromised. The PASS_WARN_AGE (-W) setting gives users 7 days of warnings at login time that their passwords are about to expire.

For example, for each existing human user USER, expiration parameters could be adjusted to a 180 day maximum password age, 7 day minimum password age, and 7 day warning period with the following command:

$ sudo chage -M 180 -m 7 -W 7 USER

Rule Set Root Account Password Maximum Age [ref]

Configure the root account to enforce a 365-day maximum password lifetime restriction by running the following command:

$ sudo chage -M 365 root

Rationale:

Any password, no matter how complex, can eventually be cracked. Therefore, passwords need to be changed periodically. If the operating system does not limit the lifetime of passwords and force users to change their passwords, there is the risk that the operating system passwords could be compromised.

Severity:

medium

Rule ID:

xccdf_org.ssgproject.content_rule_accounts_password_set_max_life_root

References:

anssi	R31

Group Restrict Root Logins Group contains 1 rule

[ref] Direct root logins should be allowed only for emergency use. In normal situations, the administrator should access the system via a unique unprivileged account, and then use su or sudo to execute privileged commands. Discouraging administrators from accessing the root account directly ensures an audit trail in organizations with multiple administrators. Locking down the channels through which root can connect directly also reduces opportunities for password-guessing against the root account. The login program uses the file /etc/securetty to determine which interfaces should allow root logins. The virtual devices /dev/console and /dev/tty* represent the system consoles (accessible via the Ctrl-Alt-F1 through Ctrl-Alt-F6 keyboard sequences on a default installation). The default securetty file also contains /dev/vc/*. These are likely to be deprecated in most environments, but may be retained for compatibility. Root should also be prohibited from connecting via network protocols. Other sections of this document include guidance describing how to prevent root from logging in via SSH.

Rule Direct root Logins Not Allowed [ref]

To further limit access to the root account, administrators can disable root logins at the console by editing the /etc/securetty file. This file lists all devices the root user is allowed to login to. If the file does not exist at all, the root user can login through any communication device on the system, whether via the console or via a raw network interface. This is dangerous as user can login to the system as root via Telnet, which sends the password in plain text over the network. By default, Debian 12's /etc/securetty file only allows the root user to login at the console physically attached to the system. To prevent root from logging in, remove the contents of this file. To prevent direct root logins, remove the contents of this file by typing the following command:

$ sudo echo > /etc/securetty

Warning: This rule only checks the /etc/securetty file existence and its content. If you need to restrict user access using the /etc/securetty file, make sure the pam_securetty.so PAM module is properly enabled in relevant PAM files.

Rationale:

Disabling direct root logins ensures proper accountability and multifactor authentication to privileged accounts. Users will first login, then escalate to privileged (root) access via su / sudo. This is required for FISMA Low and FISMA Moderate systems.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_no_direct_root_logins

References:

cis-csc	1, 12, 15, 16, 5
cobit5	DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui	3.1.1, 3.1.6
hipaa	164.308(a)(1)(ii)(B), 164.308(a)(7)(i), 164.308(a)(7)(ii)(A), 164.310(a)(1), 164.310(a)(2)(i), 164.310(a)(2)(ii), 164.310(a)(2)(iii), 164.310(b), 164.310(c), 164.310(d)(1), 164.310(d)(2)(iii)
isa-62443-2009	4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013	SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
iso27001-2013	A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.2.3, CIP-004-6 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist	IA-2, CM-6(a)
nist-csf	PR.AC-1, PR.AC-6, PR.AC-7
anssi	R33
pcidss4	8.6.1

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Direct root Logins Not Allowed
  copy:
    dest: /etc/securetty
    content: ''
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.1
  - NIST-800-171-3.1.6
  - NIST-800-53-CM-6(a)
  - NIST-800-53-IA-2
  - PCI-DSSv4-8.6.1
  - low_complexity
  - low_disruption
  - medium_severity
  - no_direct_root_logins
  - no_reboot_needed
  - restrict_strategy

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

echo > /etc/securetty

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Secure Session Configuration Files for Login Accounts Group contains 6 rules

[ref] When a user logs into a Unix account, the system configures the user's session by reading a number of files. Many of these files are located in the user's home directory, and may have weak permissions as a result of user error or misconfiguration. If an attacker can modify or even read certain types of account configuration information, they can often gain full access to the affected user's account. Therefore, it is important to test and correct configuration file permissions for interactive accounts, particularly those of privileged users such as root or system administrators.

Rule User Initialization Files Must Be Group-Owned By The Primary Group [ref]

Change the group owner of interactive users files to the group found in

/etc/passwd

for the user. To change the group owner of a local interactive user home directory, use the following command:

$ sudo chgrp USER_GROUP /home/USER/.INIT_FILE

This rule ensures every initialization file related to an interactive user is group-owned by an interactive user.

Warning: Due to OVAL limitation, this rule can report a false negative in a specific situation where two interactive users swap the group-ownership of their respective initialization files.

Rationale:

Local initialization files for interactive users are used to configure the user's shell environment upon logon. Malicious modification of these files could compromise accounts upon logon.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_accounts_user_dot_group_ownership

References:

disa	CCI-000366
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Ensure interactive local users are the group-owners of their respective initialization
    files
  ansible.builtin.command:
    cmd: awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chgrp -f " $4" "$6"/.[^\.]?*")
      }' /etc/passwd
  tags:
  - accounts_user_dot_group_ownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict


awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chgrp -f " $4" "$6"/.[^\.]?*") }' /etc/passwd

Rule User Initialization Files Must Be Owned By the Primary User [ref]

Set the owner of the user initialization files for interactive users to the primary owner with the following command:

$ sudo chown USER /home/USER/.*

This rule ensures every initialization file related to an interactive user is owned by an interactive user.

Warning: Due to OVAL limitation, this rule can report a false negative in a specific situation where two interactive users swap the ownership of their respective initialization files.

Rationale:

Local initialization files are used to configure the user's shell environment upon logon. Malicious modification of these files could compromise accounts upon logon.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_accounts_user_dot_user_ownership

References:

disa	CCI-000366
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Ensure interactive local users are the owners of their respective initialization
    files
  ansible.builtin.command:
    cmd: awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chown -f " $3" "$6"/.[^\.]?*")
      }' /etc/passwd
  tags:
  - accounts_user_dot_user_ownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict


awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chown -f " $3" "$6"/.[^\.]?*") }' /etc/passwd

Rule All User Files and Directories In The Home Directory Must Be Group-Owned By The Primary Group [ref]

Change the group of a local interactive users files and directories to a group that the interactive user is a member of. To change the group owner of a local interactive users files and directories, use the following command:

$ sudo chgrp USER_GROUP /home/USER/FILE_DIR

This rule ensures every file or directory under the home directory related to an interactive user is group-owned by an interactive user.

Warning: Due to OVAL limitation, this rule can report a false negative in a specific situation where two interactive users swap the group-ownership of folders or files in their respective home directories.

Rationale:

If a local interactive users files are group-owned by a group of which the user is not a member, unintended users may be able to access them.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_accounts_users_home_files_groupownership

References:

disa	CCI-000366
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Get all local users from /etc/passwd
  ansible.builtin.getent:
    database: passwd
    split: ':'
  tags:
  - accounts_users_home_files_groupownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Create local_users variable from the getent output
  ansible.builtin.set_fact:
    local_users: '{{ ansible_facts.getent_passwd|dict2items }}'
  tags:
  - accounts_users_home_files_groupownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Test for existence of home directories to avoid creating them, but only fixing
    ownership
  ansible.builtin.stat:
    path: '{{ item.value[4] }}'
  register: path_exists
  loop: '{{ local_users }}'
  when:
  - item.value[1]|int >= 1000
  - item.value[1]|int != 65534
  tags:
  - accounts_users_home_files_groupownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Ensure interactive local users are the owners of their respective home directories
  ansible.builtin.file:
    path: '{{ item.0.value[4] }}'
    group: '{{ item.0.value[2] }}'
    recurse: true
  loop: '{{ local_users|zip(path_exists.results)|list }}'
  when: item.1.stat is defined and item.1.stat.exists
  tags:
  - accounts_users_home_files_groupownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict


for user in $(awk -F':' '{ if ($3 >= 1000 && $3 != 65534) print $1 }' /etc/passwd); do
    home_dir=$(getent passwd $user | cut -d: -f6)
    group=$(getent passwd $user | cut -d: -f4)
    # Only update the group-ownership when necessary. This will avoid changing the inode timestamp
    # when the group is already defined as expected, therefore not impacting in possible integrity
    # check systems that also check inodes timestamps.
    find $home_dir -not -group $group -exec chgrp -f $group {} \;
done

Rule All User Files and Directories In The Home Directory Must Have a Valid Owner [ref]

Either remove all files and directories from the system that do not have a valid user, or assign a valid user to all unowned files and directories. To assign a valid owner to a local interactive user's files and directories, use the following command:

$ sudo chown -R USER /home/USER

This rule ensures every file or directory under the home directory related to an interactive user is owned by an interactive user.

Warning: Due to OVAL limitation, this rule can report a false negative in a specific situation where two interactive users swap the ownership of folders or files in their respective home directories.

Rationale:

If local interactive users do not own the files in their directories, unauthorized users may be able to access them. Additionally, if files are not owned by the user, this could be an indication of system compromise.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_accounts_users_home_files_ownership

References:

disa	CCI-000366
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Get all local users from /etc/passwd
  ansible.builtin.getent:
    database: passwd
    split: ':'
  tags:
  - accounts_users_home_files_ownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Create local_users variable from the getent output
  ansible.builtin.set_fact:
    local_users: '{{ ansible_facts.getent_passwd|dict2items }}'
  tags:
  - accounts_users_home_files_ownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Test for existence of home directories to avoid creating them, but only fixing
    ownership
  ansible.builtin.stat:
    path: '{{ item.value[4] }}'
  register: path_exists
  loop: '{{ local_users }}'
  when:
  - item.value[1]|int >= 1000
  - item.value[1]|int != 65534
  tags:
  - accounts_users_home_files_ownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Ensure interactive local users are the owners of their respective home directories
  ansible.builtin.file:
    path: '{{ item.0.value[4] }}'
    owner: '{{ item.0.value[1] }}'
    recurse: true
  loop: '{{ local_users|zip(path_exists.results)|list }}'
  when: item.1.stat is defined and item.1.stat.exists
  tags:
  - accounts_users_home_files_ownership
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict


for user in $(awk -F':' '{ if ($3 >= 1000 && $3 != 65534) print $1 }' /etc/passwd); do
    home_dir=$(getent passwd $user | cut -d: -f6)
    # Only update the ownership when necessary. This will avoid changing the inode timestamp
    # when the owner is already defined as expected, therefore not impacting in possible integrity
    # check systems that also check inodes timestamps.
    find $home_dir -not -user $user -exec chown -f $user {} \;
done

Rule All User Files and Directories In The Home Directory Must Have Mode 0750 Or Less Permissive [ref]

Set the mode on files and directories in the local interactive user home directory with the following command:

$ sudo chmod 0750 /home/USER/FILE_DIR

Files that begin with a "." are excluded from this requirement.

Rationale:

If a local interactive user files have excessive permissions, unintended users may be able to access or modify them.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_accounts_users_home_files_permissions

References:

disa	CCI-000366
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Get all local users from /etc/passwd
  ansible.builtin.getent:
    database: passwd
    split: ':'
  tags:
  - accounts_users_home_files_permissions
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Create local_users variable from the getent output
  ansible.builtin.set_fact:
    local_users: '{{ ansible_facts.getent_passwd|dict2items }}'
  tags:
  - accounts_users_home_files_permissions
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Test for existence home directories to avoid creating them.
  ansible.builtin.stat:
    path: '{{ item.value[4] }}'
  register: path_exists
  loop: '{{ local_users }}'
  when:
  - item.value[1]|int >= 1000
  - item.value[1]|int != 65534
  tags:
  - accounts_users_home_files_permissions
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Ensure interactive local users have proper permissions on their respective
    home directories
  ansible.builtin.file:
    path: '{{ item.0.value[4] }}'
    mode: u-s,g-w-s,o=-
    follow: false
    recurse: true
  loop: '{{ local_users|zip(path_exists.results)|list }}'
  when: item.1.stat is defined and item.1.stat.exists
  tags:
  - accounts_users_home_files_permissions
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict


for home_dir in $(awk -F':' '{ if ($3 >= 1000 && $3 != 65534) print $6 }' /etc/passwd); do
    # Only update the permissions when necessary. This will avoid changing the inode timestamp when
    # the permission is already defined as expected, therefore not impacting in possible integrity
    # check systems that also check inodes timestamps.
    find "$home_dir" -perm /7027 -exec chmod u-s,g-w-s,o=- {} \;
done

Rule Ensure All User Initialization Files Have Mode 0740 Or Less Permissive [ref]

Set the mode of the user initialization files to 0740 with the following command:

$ sudo chmod 0740 /home/USER/.INIT_FILE

Rationale:

Local initialization files are used to configure the user's shell environment upon logon. Malicious modification of these files could compromise accounts upon logon.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permission_user_init_files

References:

disa	CCI-000366
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: XCCDF Value var_user_initialization_files_regex # promote to variable
  set_fact:
    var_user_initialization_files_regex: !!str ^(\.bashrc|\.zshrc|\.cshrc|\.profile|\.bash_login|\.bash_profile)$
  tags:
    - always

- name: Ensure All User Initialization Files Have Mode 0740 Or Less Permissive - Gather
    User Info
  ansible.builtin.getent:
    database: passwd
  tags:
  - file_permission_user_init_files
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Ensure All User Initialization Files Have Mode 0740 Or Less Permissive - Find
    Init Files
  ansible.builtin.find:
    paths: '{{ item.value[4] }}'
    pattern: '{{ var_user_initialization_files_regex }}'
    hidden: true
    use_regex: true
  with_dict: '{{ ansible_facts.getent_passwd }}'
  when:
  - item.value[4] != "/sbin/nologin"
  - item.key not in ["nobody", "nfsnobody"]
  - item.value[1] | int >= 1000
  register: found_init_files
  tags:
  - file_permission_user_init_files
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Ensure All User Initialization Files Have Mode 0740 Or Less Permissive - Fix
    Init Files Permissions
  ansible.builtin.file:
    path: '{{ item.1.path }}'
    mode: u-s,g-wxs,o=
  loop: '{{ q(''ansible.builtin.subelements'', found_init_files.results, ''files'',
    {''skip_missing'': True}) }}'
  tags:
  - file_permission_user_init_files
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict


var_user_initialization_files_regex='^(\.bashrc|\.zshrc|\.cshrc|\.profile|\.bash_login|\.bash_profile)$'


readarray -t interactive_users < <(awk -F: '$3>=1000   {print $1}' /etc/passwd)
readarray -t interactive_users_home < <(awk -F: '$3>=1000   {print $6}' /etc/passwd)
readarray -t interactive_users_shell < <(awk -F: '$3>=1000   {print $7}' /etc/passwd)

USERS_IGNORED_REGEX='nobody|nfsnobody'

for (( i=0; i<"${#interactive_users[@]}"; i++ )); do
    if ! grep -qP "$USERS_IGNORED_REGEX" <<< "${interactive_users[$i]}" && \
        [ "${interactive_users_shell[$i]}" != "/sbin/nologin" ]; then
        
        readarray -t init_files < <(find "${interactive_users_home[$i]}" -maxdepth 1 \
            -exec basename {} \; | grep -P "$var_user_initialization_files_regex")
        for file in "${init_files[@]}"; do
            chmod u-s,g-wxs,o= "${interactive_users_home[$i]}/$file"
        done
    fi
done

Group GRUB2 bootloader configuration Group contains 6 rules

[ref] During the boot process, the boot loader is responsible for starting the execution of the kernel and passing options to it. The boot loader allows for the selection of different kernels - possibly on different partitions or media. The default Debian 12 boot loader for x86 systems is called GRUB2. Options it can pass to the kernel include single-user mode, which provides root access without any authentication, and the ability to disable SELinux. To prevent local users from modifying the boot parameters and endangering security, protect the boot loader configuration with a password and ensure its configuration file's permissions are set properly.

Rule Configure L1 Terminal Fault mitigations [ref]

L1 Terminal Fault (L1TF) is a hardware vulnerability which allows unprivileged speculative access to data which is available in the Level 1 Data Cache when the page table entry isn't present. Select the appropriate mitigation by adding the argument

l1tf=full,force

to the default GRUB 2 command line for the Linux operating system. Configure the default Grub2 kernel command line to contain l1tf=full,force as follows:

# grub2-editenv - set "$(grub2-editenv - list | grep kernelopts) l1tf=full,force"

Since Linux Kernel 4.19 you can check the L1TF vulnerability state with the following command: cat /sys/devices/system/cpu/vulnerabilities/l1tf

Warning: Enabling L1TF mitigations may impact performance of the system.

Rationale:

The L1TF vulnerability allows an attacker to bypass memory access security controls imposed by the system or hypervisor. The L1TF vulnerability allows read access to any physical memory location that is cached in the L1 Data Cache.

Severity:

high

Rule ID: xccdf_org.ssgproject.content_rule_grub2_l1tf_argument

References:

anssi	R8

Remediation Ansible snippet ⇲

Complexity:	medium
Disruption:	low
Reboot:	true
Strategy:	restrict

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - grub2_l1tf_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy
- name: XCCDF Value var_l1tf_options # promote to variable
  set_fact:
    var_l1tf_options: !!str full,force
  tags:
    - always

- name: Check l1tf argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=.*l1tf=' /etc/default/grub
  failed_when: false
  register: argcheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_l1tf_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Check l1tf argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=' /etc/default/grub
  failed_when: false
  register: linecheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_l1tf_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Add l1tf argument
  ansible.builtin.lineinfile:
    line: GRUB_CMDLINE_LINUX="l1tf={{ var_l1tf_options }} "
    state: present
    dest: /etc/default/grub
    create: true
    mode: '0644'
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc != 0
  tags:
  - grub2_l1tf_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Replace existing l1tf argument
  replace:
    path: /etc/default/grub
    regexp: l1tf=[a-zA-Z0-9,]+
    replace: l1tf={{ var_l1tf_options }}
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc == 0 and
    linecheck.rc == 0
  tags:
  - grub2_l1tf_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Add l1tf argument
  replace:
    path: /etc/default/grub
    regexp: (^\s*GRUB_CMDLINE_LINUX=.*)"
    replace: \1 l1tf={{ var_l1tf_options }}"
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc == 0
  tags:
  - grub2_l1tf_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Update grub defaults and the bootloader menu
  command: /usr/sbin/update-grub
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_l1tf_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'grub2-common' 2>/dev/null | grep -q installed && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

var_l1tf_options='full,force'




# Correct the form of default kernel command line in GRUB
if grep -q '^\s*GRUB_CMDLINE_LINUX=.*l1tf=.*"'  '/etc/default/grub' ; then
       # modify the GRUB command-line if an l1tf= arg already exists
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)l1tf=[^[:space:]]\+\(.*\"\)/\1l1tf=$var_l1tf_options\2/"  '/etc/default/grub'
# Add to already existing GRUB_CMDLINE_LINUX parameters
elif grep -q '^\s*GRUB_CMDLINE_LINUX='  '/etc/default/grub' ; then
       # no l1tf=arg is present, append it
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)\"/\1 l1tf=$var_l1tf_options\"/"  '/etc/default/grub'
# Add GRUB_CMDLINE_LINUX parameters line
else
       echo "GRUB_CMDLINE_LINUX=\"l1tf=$var_l1tf_options\"" >> '/etc/default/grub'
fi
update-grub

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Force kernel panic on uncorrected MCEs [ref]

A Machine Check Exception is an error generated by the CPU itdetects an error in itself, memory or I/O devices. These errors may be corrected and generate a check log entry, if an error cannot be corrected the kernel may panic or SIGBUS. To force the kernel to panic on any uncorrected error reported by Machine Check set the MCE tolerance to zero by adding mce=0 to the default GRUB 2 command line for the Linux operating system. Configure the default Grub2 kernel command line to contain mce=0 as follows:

# grub2-editenv - set "$(grub2-editenv - list | grep kernelopts) mce=0"

Rationale:

Allowing uncorrected errors to result on a SIGBUS may allow an attacker to continue trying to exploit a vulnerability such as Rowhammer.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_grub2_mce_argument

References:

anssi	R8

Remediation Ansible snippet ⇲

Complexity:	medium
Disruption:	low
Reboot:	true
Strategy:	restrict

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - grub2_mce_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Check mce argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=.*mce=' /etc/default/grub
  failed_when: false
  register: argcheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_mce_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Check mce argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=' /etc/default/grub
  failed_when: false
  register: linecheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_mce_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Add mce argument
  ansible.builtin.lineinfile:
    line: GRUB_CMDLINE_LINUX="mce=0 "
    state: present
    dest: /etc/default/grub
    create: true
    mode: '0644'
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc != 0
  tags:
  - grub2_mce_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Replace existing mce argument
  replace:
    path: /etc/default/grub
    regexp: mce=[a-zA-Z0-9,]+
    replace: mce=0
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc == 0 and
    linecheck.rc == 0
  tags:
  - grub2_mce_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Add mce argument
  replace:
    path: /etc/default/grub
    regexp: (^\s*GRUB_CMDLINE_LINUX=.*)"
    replace: \1 mce=0"
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc == 0
  tags:
  - grub2_mce_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Update grub defaults and the bootloader menu
  command: /usr/sbin/update-grub
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_mce_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'grub2-common' 2>/dev/null | grep -q installed && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

# Correct the form of default kernel command line in GRUB
if grep -q '^\s*GRUB_CMDLINE_LINUX=.*mce=.*"'  '/etc/default/grub' ; then
       # modify the GRUB command-line if an mce= arg already exists
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)mce=[^[:space:]]\+\(.*\"\)/\1mce=0\2/"  '/etc/default/grub'
# Add to already existing GRUB_CMDLINE_LINUX parameters
elif grep -q '^\s*GRUB_CMDLINE_LINUX='  '/etc/default/grub' ; then
       # no mce=arg is present, append it
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)\"/\1 mce=0\"/"  '/etc/default/grub'
# Add GRUB_CMDLINE_LINUX parameters line
else
       echo "GRUB_CMDLINE_LINUX=\"mce=0\"" >> '/etc/default/grub'
fi
update-grub

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Configure the confidence in TPM for entropy [ref]

The TPM security chip that is available in most modern systems has a hardware RNG. It is also used to feed the entropy pool, but generally not credited entropy. Use rng_core.default_quality in the kernel command line to set the trust level on the hardware generators. The trust level defines the amount of entropy to credit. A value of 0 tells the system not to trust the hardware random number generators available, and doesn't credit any entropy to the pool. A value of 1000 assigns full confidence in the generators, and credits all the entropy it provides to the pool. Note that the value of rng_core.default_quality is global, affecting the trust on all hardware random number generators. Select the appropriate confidence by adding the argument

rng_core.default_quality=500

to the default GRUB 2 command line for the Linux operating system. Configure the default Grub2 kernel command line to contain rng_core.default_quality=500 as follows:

# grub2-editenv - set "$(grub2-editenv - list | grep kernelopts) rng_core.default_quality=500"

Rationale:

A system may struggle to initialize its entropy pool and end up starving. Crediting entropy from the hardware number generators available in the system helps fill up the entropy pool.

Severity:

low

Rule ID: xccdf_org.ssgproject.content_rule_grub2_rng_core_default_quality_argument

References:

anssi	R8

Remediation Ansible snippet ⇲

Complexity:	medium
Disruption:	low
Reboot:	true
Strategy:	restrict

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - grub2_rng_core_default_quality_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy
- name: XCCDF Value var_rng_core_default_quality # promote to variable
  set_fact:
    var_rng_core_default_quality: !!str 500
  tags:
    - always

- name: Check rng_core.default_quality argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=.*rng_core.default_quality=' /etc/default/grub
  failed_when: false
  register: argcheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_rng_core_default_quality_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Check rng_core.default_quality argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=' /etc/default/grub
  failed_when: false
  register: linecheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_rng_core_default_quality_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Add rng_core.default_quality argument
  ansible.builtin.lineinfile:
    line: GRUB_CMDLINE_LINUX="rng_core.default_quality={{ var_rng_core_default_quality
      }} "
    state: present
    dest: /etc/default/grub
    create: true
    mode: '0644'
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc != 0
  tags:
  - grub2_rng_core_default_quality_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Replace existing rng_core.default_quality argument
  replace:
    path: /etc/default/grub
    regexp: rng_core.default_quality=[a-zA-Z0-9,]+
    replace: rng_core.default_quality={{ var_rng_core_default_quality }}
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc == 0 and
    linecheck.rc == 0
  tags:
  - grub2_rng_core_default_quality_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Add rng_core.default_quality argument
  replace:
    path: /etc/default/grub
    regexp: (^\s*GRUB_CMDLINE_LINUX=.*)"
    replace: \1 rng_core.default_quality={{ var_rng_core_default_quality }}"
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc == 0
  tags:
  - grub2_rng_core_default_quality_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Update grub defaults and the bootloader menu
  command: /usr/sbin/update-grub
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_rng_core_default_quality_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'grub2-common' 2>/dev/null | grep -q installed && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

var_rng_core_default_quality='500'




# Correct the form of default kernel command line in GRUB
if grep -q '^\s*GRUB_CMDLINE_LINUX=.*rng_core.default_quality=.*"'  '/etc/default/grub' ; then
       # modify the GRUB command-line if an rng_core.default_quality= arg already exists
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)rng_core.default_quality=[^[:space:]]\+\(.*\"\)/\1rng_core.default_quality=$var_rng_core_default_quality\2/"  '/etc/default/grub'
# Add to already existing GRUB_CMDLINE_LINUX parameters
elif grep -q '^\s*GRUB_CMDLINE_LINUX='  '/etc/default/grub' ; then
       # no rng_core.default_quality=arg is present, append it
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)\"/\1 rng_core.default_quality=$var_rng_core_default_quality\"/"  '/etc/default/grub'
# Add GRUB_CMDLINE_LINUX parameters line
else
       echo "GRUB_CMDLINE_LINUX=\"rng_core.default_quality=$var_rng_core_default_quality\"" >> '/etc/default/grub'
fi
update-grub

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Disable merging of slabs with similar size [ref]

The kernel may merge similar slabs together to reduce overhead and increase cache hotness of objects. Disabling merging of slabs keeps the slabs separate and reduces the risk of kernel heap overflows overwriting objects in merged caches. To disable merging of slabs in the Kernel add the argument slab_nomerge=yes to the default GRUB 2 command line for the Linux operating system. Configure the default Grub2 kernel command line to contain slab_nomerge=yes as follows:

# grub2-editenv - set "$(grub2-editenv - list | grep kernelopts) slab_nomerge=yes"

Warning: Disabling merge of slabs will slightly increase kernel memory utilization.

Rationale:

Disabling the merge of slabs of similar sizes prevents the kernel from merging a seemingly useless but vulnerable slab with a useful and valuable slab. This increase the risk that a heap overflow could overwrite objects from merged caches, with unmerged caches the heap overflow would only affect the objects in the same cache. Overall, this reduces the kernel attack surface area by isolating slabs from each other.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_grub2_slab_nomerge_argument

References:

anssi	R8

Remediation Ansible snippet ⇲

Complexity:	medium
Disruption:	low
Reboot:	true
Strategy:	restrict

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - grub2_slab_nomerge_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Check slab_nomerge argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=.*slab_nomerge=' /etc/default/grub
  failed_when: false
  register: argcheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_slab_nomerge_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Check slab_nomerge argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=' /etc/default/grub
  failed_when: false
  register: linecheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_slab_nomerge_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Add slab_nomerge argument
  ansible.builtin.lineinfile:
    line: GRUB_CMDLINE_LINUX="slab_nomerge=yes "
    state: present
    dest: /etc/default/grub
    create: true
    mode: '0644'
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc != 0
  tags:
  - grub2_slab_nomerge_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Replace existing slab_nomerge argument
  replace:
    path: /etc/default/grub
    regexp: slab_nomerge=[a-zA-Z0-9,]+
    replace: slab_nomerge=yes
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc == 0 and
    linecheck.rc == 0
  tags:
  - grub2_slab_nomerge_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Add slab_nomerge argument
  replace:
    path: /etc/default/grub
    regexp: (^\s*GRUB_CMDLINE_LINUX=.*)"
    replace: \1 slab_nomerge=yes"
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc == 0
  tags:
  - grub2_slab_nomerge_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Update grub defaults and the bootloader menu
  command: /usr/sbin/update-grub
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_slab_nomerge_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'grub2-common' 2>/dev/null | grep -q installed && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

# Correct the form of default kernel command line in GRUB
if grep -q '^\s*GRUB_CMDLINE_LINUX=.*slab_nomerge=.*"'  '/etc/default/grub' ; then
       # modify the GRUB command-line if an slab_nomerge= arg already exists
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)slab_nomerge=[^[:space:]]\+\(.*\"\)/\1slab_nomerge=yes\2/"  '/etc/default/grub'
# Add to already existing GRUB_CMDLINE_LINUX parameters
elif grep -q '^\s*GRUB_CMDLINE_LINUX='  '/etc/default/grub' ; then
       # no slab_nomerge=arg is present, append it
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)\"/\1 slab_nomerge=yes\"/"  '/etc/default/grub'
# Add GRUB_CMDLINE_LINUX parameters line
else
       echo "GRUB_CMDLINE_LINUX=\"slab_nomerge=yes\"" >> '/etc/default/grub'
fi
update-grub

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Configure Speculative Store Bypass Mitigation [ref]

Certain CPUs are vulnerable to an exploit against a common wide industry wide performance optimization known as Speculative Store Bypass (SSB). In such cases, recent stores to the same memory location cannot always be observed by later loads during speculative execution. However, such stores are unlikely and thus they can be detected prior to instruction retirement at the end of a particular speculation execution window. Since Linux Kernel 4.17 you can check the SSB mitigation state with the following command: cat /sys/devices/system/cpu/vulnerabilities/spec_store_bypass Select the appropriate SSB state by adding the argument

spec_store_bypass_disable=seccomp

to the default GRUB 2 command line for the Linux operating system. Configure the default Grub2 kernel command line to contain spec_store_bypass_disable=seccomp as follows:

# grub2-editenv - set "$(grub2-editenv - list | grep kernelopts) spec_store_bypass_disable=seccomp"

Warning: Disabling Speculative Store Bypass may impact performance of the system.

Rationale:

In vulnerable processsors, the speculatively forwarded store can be used in a cache side channel attack. An example of this is reading memory to which the attacker does not directly have access, for example inside the sandboxed code.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_grub2_spec_store_bypass_disable_argument

References:

anssi	R8

Remediation Ansible snippet ⇲

Complexity:	medium
Disruption:	low
Reboot:	true
Strategy:	restrict

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - grub2_spec_store_bypass_disable_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy
- name: XCCDF Value var_spec_store_bypass_disable_options # promote to variable
  set_fact:
    var_spec_store_bypass_disable_options: !!str seccomp
  tags:
    - always

- name: Check spec_store_bypass_disable argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=.*spec_store_bypass_disable=' /etc/default/grub
  failed_when: false
  register: argcheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_spec_store_bypass_disable_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Check spec_store_bypass_disable argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=' /etc/default/grub
  failed_when: false
  register: linecheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_spec_store_bypass_disable_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Add spec_store_bypass_disable argument
  ansible.builtin.lineinfile:
    line: GRUB_CMDLINE_LINUX="spec_store_bypass_disable={{ var_spec_store_bypass_disable_options
      }} "
    state: present
    dest: /etc/default/grub
    create: true
    mode: '0644'
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc != 0
  tags:
  - grub2_spec_store_bypass_disable_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Replace existing spec_store_bypass_disable argument
  replace:
    path: /etc/default/grub
    regexp: spec_store_bypass_disable=[a-zA-Z0-9,]+
    replace: spec_store_bypass_disable={{ var_spec_store_bypass_disable_options }}
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc == 0 and
    linecheck.rc == 0
  tags:
  - grub2_spec_store_bypass_disable_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Add spec_store_bypass_disable argument
  replace:
    path: /etc/default/grub
    regexp: (^\s*GRUB_CMDLINE_LINUX=.*)"
    replace: \1 spec_store_bypass_disable={{ var_spec_store_bypass_disable_options
      }}"
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc == 0
  tags:
  - grub2_spec_store_bypass_disable_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

- name: Update grub defaults and the bootloader menu
  command: /usr/sbin/update-grub
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_spec_store_bypass_disable_argument
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - restrict_strategy

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'grub2-common' 2>/dev/null | grep -q installed && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

var_spec_store_bypass_disable_options='seccomp'




# Correct the form of default kernel command line in GRUB
if grep -q '^\s*GRUB_CMDLINE_LINUX=.*spec_store_bypass_disable=.*"'  '/etc/default/grub' ; then
       # modify the GRUB command-line if an spec_store_bypass_disable= arg already exists
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)spec_store_bypass_disable=[^[:space:]]\+\(.*\"\)/\1spec_store_bypass_disable=$var_spec_store_bypass_disable_options\2/"  '/etc/default/grub'
# Add to already existing GRUB_CMDLINE_LINUX parameters
elif grep -q '^\s*GRUB_CMDLINE_LINUX='  '/etc/default/grub' ; then
       # no spec_store_bypass_disable=arg is present, append it
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)\"/\1 spec_store_bypass_disable=$var_spec_store_bypass_disable_options\"/"  '/etc/default/grub'
# Add GRUB_CMDLINE_LINUX parameters line
else
       echo "GRUB_CMDLINE_LINUX=\"spec_store_bypass_disable=$var_spec_store_bypass_disable_options\"" >> '/etc/default/grub'
fi
update-grub

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Enforce Spectre v2 mitigation [ref]

Spectre V2 is an indirect branch poisoning attack that can lead to data leakage. An exploit for Spectre V2 tricks the indirect branch predictor into executing code from a future indirect branch chosen by the attacker, even if the privilege level is different. Since Linux Kernel 4.15 you can check the Spectre V2 mitigation state with the following command: cat /sys/devices/system/cpu/vulnerabilities/spectre_v2 Enforce the Spectre V2 mitigation by adding the argument spectre_v2=on to the default GRUB 2 command line for the Linux operating system. Configure the default Grub2 kernel command line to contain spectre_v2=on as follows:

# grub2-editenv - set "$(grub2-editenv - list | grep kernelopts) spectre_v2=on"

Rationale:

The Spectre V2 vulnerability allows an attacker to read memory that he should not have access to.

Severity:

high

Rule ID: xccdf_org.ssgproject.content_rule_grub2_spectre_v2_argument

References:

anssi	R8

Remediation Ansible snippet ⇲

Complexity:	medium
Disruption:	low
Reboot:	true
Strategy:	restrict

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - grub2_spectre_v2_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Check spectre_v2 argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=.*spectre_v2=' /etc/default/grub
  failed_when: false
  register: argcheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_spectre_v2_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Check spectre_v2 argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=' /etc/default/grub
  failed_when: false
  register: linecheck
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_spectre_v2_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Add spectre_v2 argument
  ansible.builtin.lineinfile:
    line: GRUB_CMDLINE_LINUX="spectre_v2=on "
    state: present
    dest: /etc/default/grub
    create: true
    mode: '0644'
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc != 0
  tags:
  - grub2_spectre_v2_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Replace existing spectre_v2 argument
  replace:
    path: /etc/default/grub
    regexp: spectre_v2=[a-zA-Z0-9,]+
    replace: spectre_v2=on
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc == 0 and
    linecheck.rc == 0
  tags:
  - grub2_spectre_v2_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Add spectre_v2 argument
  replace:
    path: /etc/default/grub
    regexp: (^\s*GRUB_CMDLINE_LINUX=.*)"
    replace: \1 spectre_v2=on"
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc == 0
  tags:
  - grub2_spectre_v2_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Update grub defaults and the bootloader menu
  command: /usr/sbin/update-grub
  when:
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - grub2_spectre_v2_argument
  - high_severity
  - low_disruption
  - medium_complexity
  - reboot_required
  - restrict_strategy

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'grub2-common' 2>/dev/null | grep -q installed && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

# Correct the form of default kernel command line in GRUB
if grep -q '^\s*GRUB_CMDLINE_LINUX=.*spectre_v2=.*"'  '/etc/default/grub' ; then
       # modify the GRUB command-line if an spectre_v2= arg already exists
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)spectre_v2=[^[:space:]]\+\(.*\"\)/\1spectre_v2=on\2/"  '/etc/default/grub'
# Add to already existing GRUB_CMDLINE_LINUX parameters
elif grep -q '^\s*GRUB_CMDLINE_LINUX='  '/etc/default/grub' ; then
       # no spectre_v2=arg is present, append it
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)\"/\1 spectre_v2=on\"/"  '/etc/default/grub'
# Add GRUB_CMDLINE_LINUX parameters line
else
       echo "GRUB_CMDLINE_LINUX=\"spectre_v2=on\"" >> '/etc/default/grub'
fi
update-grub

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Network Configuration and Firewalls Group contains 5 groups and 21 rules

[ref] Most systems must be connected to a network of some sort, and this brings with it the substantial risk of network attack. This section discusses the security impact of decisions about networking which must be made when configuring a system.

This section also discusses firewalls, network access controls, and other network security frameworks, which allow system-level rules to be written that can limit an attackers' ability to connect to your system. These rules can specify that network traffic should be allowed or denied from certain IP addresses, hosts, and networks. The rules can also specify which of the system's network services are available to particular hosts or networks.

Group IPSec Support Group contains 9 rules

[ref] Support for Internet Protocol Security (IPsec) is provided with Libreswan.

Rule Verify Group Who Owns /etc/ipsec.d Directory [ref]

To properly set the group owner of /etc/ipsec.d, run the command:

$ sudo chgrp root /etc/ipsec.d

Rationale:

The ownership of the /etc/ipsec.d directory by the root group is important because this directory hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_groupowner_etc_ipsecd

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - directory_groupowner_etc_ipsecd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner on /etc/ipsec.d/
  file:
    path: /etc/ipsec.d/
    state: directory
    group: root
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_groupowner_etc_ipsecd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libreswan' 2>/dev/null | grep -q installed; then

find -H /etc/ipsec.d/ -maxdepth 1 -type d -exec chgrp root {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify User Who Owns /etc/ipsec.d Directory [ref]

To properly set the owner of /etc/ipsec.d, run the command:

$ sudo chown root /etc/ipsec.d

Rationale:

The ownership of the /etc/ipsec.d directory by the root user is important because this directory hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_owner_etc_ipsecd

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - directory_owner_etc_ipsecd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner on directory /etc/ipsec.d/
  file:
    path: /etc/ipsec.d/
    state: directory
    owner: '0'
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_owner_etc_ipsecd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libreswan' 2>/dev/null | grep -q installed; then

find -H /etc/ipsec.d/ -maxdepth 1 -type d -exec chown 0 {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions On /etc/ipsec.d Directory [ref]

To properly set the permissions of /etc/ipsec.d, run the command:

$ sudo chmod 0700 /etc/ipsec.d

Rationale:

Setting correct permissions on the /etc/ipsec.d directory is important because this directory hosts Libreswan configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the Libreswan configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_permissions_etc_ipsecd

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - directory_permissions_etc_ipsecd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Find /etc/ipsec.d/ file(s)
  command: 'find -H /etc/ipsec.d/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt  -type d '
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_permissions_etc_ipsecd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set permissions for /etc/ipsec.d/ file(s)
  file:
    path: '{{ item }}'
    mode: u-s,g-xwrs,o-xwrt
    state: directory
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_permissions_etc_ipsecd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libreswan' 2>/dev/null | grep -q installed; then

find -H /etc/ipsec.d/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt -type d -exec chmod u-s,g-xwrs,o-xwrt {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Group Who Owns /etc/ipsec.conf File [ref]

To properly set the group owner of /etc/ipsec.conf, run the command:

$ sudo chgrp root /etc/ipsec.conf

Rationale:

The ownership of the /etc/ipsec.conf file by the root group is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_ipsec_conf

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - file_groupowner_etc_ipsec_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Test for existence /etc/ipsec.conf
  stat:
    path: /etc/ipsec.conf
  register: file_exists
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - file_groupowner_etc_ipsec_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner root on /etc/ipsec.conf
  file:
    path: /etc/ipsec.conf
    group: root
  when:
  - '"libreswan" in ansible_facts.packages'
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_groupowner_etc_ipsec_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libreswan' 2>/dev/null | grep -q installed; then

chgrp root /etc/ipsec.conf

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Group Who Owns /etc/ipsec.secrets File [ref]

To properly set the group owner of /etc/ipsec.secrets, run the command:

$ sudo chgrp root /etc/ipsec.secrets

Rationale:

The ownership of the /etc/ipsec.secrets file by the root group is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_ipsec_secrets

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - file_groupowner_etc_ipsec_secrets
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Test for existence /etc/ipsec.secrets
  stat:
    path: /etc/ipsec.secrets
  register: file_exists
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - file_groupowner_etc_ipsec_secrets
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner root on /etc/ipsec.secrets
  file:
    path: /etc/ipsec.secrets
    group: root
  when:
  - '"libreswan" in ansible_facts.packages'
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_groupowner_etc_ipsec_secrets
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libreswan' 2>/dev/null | grep -q installed; then

chgrp root /etc/ipsec.secrets

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify User Who Owns /etc/ipsec.conf File [ref]

To properly set the owner of /etc/ipsec.conf, run the command:

$ sudo chown root /etc/ipsec.conf

Rationale:

The ownership of the /etc/ipsec.conf file by the root user is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_ipsec_conf

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - file_owner_etc_ipsec_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Test for existence /etc/ipsec.conf
  stat:
    path: /etc/ipsec.conf
  register: file_exists
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - file_owner_etc_ipsec_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/ipsec.conf
  file:
    path: /etc/ipsec.conf
    owner: '0'
  when:
  - '"libreswan" in ansible_facts.packages'
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_owner_etc_ipsec_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libreswan' 2>/dev/null | grep -q installed; then

chown 0 /etc/ipsec.conf

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify User Who Owns /etc/ipsec.secrets File [ref]

To properly set the owner of /etc/ipsec.secrets, run the command:

$ sudo chown root /etc/ipsec.secrets

Rationale:

The ownership of the /etc/ipsec.secrets file by the root user is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_ipsec_secrets

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - file_owner_etc_ipsec_secrets
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Test for existence /etc/ipsec.secrets
  stat:
    path: /etc/ipsec.secrets
  register: file_exists
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - file_owner_etc_ipsec_secrets
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/ipsec.secrets
  file:
    path: /etc/ipsec.secrets
    owner: '0'
  when:
  - '"libreswan" in ansible_facts.packages'
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_owner_etc_ipsec_secrets
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libreswan' 2>/dev/null | grep -q installed; then

chown 0 /etc/ipsec.secrets

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions On /etc/ipsec.conf File [ref]

To properly set the permissions of /etc/ipsec.conf, run the command:

$ sudo chmod 0644 /etc/ipsec.conf

Rationale:

Setting correct permissions on the /etc/ipsec.conf file is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Restricting the permissions ensures exclusive control of the Libreswan configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_ipsec_conf

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - file_permissions_etc_ipsec_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Test for existence /etc/ipsec.conf
  stat:
    path: /etc/ipsec.conf
  register: file_exists
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - file_permissions_etc_ipsec_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xws,o-xwt on /etc/ipsec.conf
  file:
    path: /etc/ipsec.conf
    mode: u-xs,g-xws,o-xwt
  when:
  - '"libreswan" in ansible_facts.packages'
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_permissions_etc_ipsec_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libreswan' 2>/dev/null | grep -q installed; then

chmod u-xs,g-xws,o-xwt /etc/ipsec.conf

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions On /etc/ipsec.secrets File [ref]

To properly set the permissions of /etc/ipsec.secrets, run the command:

$ sudo chmod 0644 /etc/ipsec.secrets

Rationale:

Setting correct permissions on the /etc/ipsec.secrets file is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Restricting the permissions ensures exclusive control of the Libreswan configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_ipsec_secrets

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - file_permissions_etc_ipsec_secrets
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Test for existence /etc/ipsec.secrets
  stat:
    path: /etc/ipsec.secrets
  register: file_exists
  when: '"libreswan" in ansible_facts.packages'
  tags:
  - configure_strategy
  - file_permissions_etc_ipsec_secrets
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xws,o-xwt on /etc/ipsec.secrets
  file:
    path: /etc/ipsec.secrets
    mode: u-xs,g-xws,o-xwt
  when:
  - '"libreswan" in ansible_facts.packages'
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_permissions_etc_ipsec_secrets
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libreswan' 2>/dev/null | grep -q installed; then

chmod u-xs,g-xws,o-xwt /etc/ipsec.secrets

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group iptables and ip6tables Group contains 3 rules

[ref] A host-based firewall called netfilter is included as part of the Linux kernel distributed with the system. It is activated by default. This firewall is controlled by the program iptables, and the entire capability is frequently referred to by this name. An analogous program called ip6tables handles filtering for IPv6.

Unlike TCP Wrappers, which depends on the network server program to support and respect the rules written, netfilter filtering occurs at the kernel level, before a program can even process the data from the network packet. As such, any program on the system is affected by the rules written.

This section provides basic information about strengthening the iptables and ip6tables configurations included with the system. For more complete information that may allow the construction of a sophisticated ruleset tailored to your environment, please consult the references at the end of this section.

Rule Verify Group Who Owns /etc/iptables Directory [ref]

To properly set the group owner of /etc/iptables, run the command:

$ sudo chgrp root /etc/iptables

Rationale:

The ownership of the /etc/iptables directory by the root group is important because this directory hosts iptables configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the iptables configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_groupowner_etc_iptables

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - directory_groupowner_etc_iptables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner on /etc/iptables/
  file:
    path: /etc/iptables/
    state: directory
    group: root
  when: '"iptables" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_groupowner_etc_iptables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q installed; then

find -H /etc/iptables/ -maxdepth 1 -type d -exec chgrp root {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify User Who Owns /etc/iptables Directory [ref]

To properly set the owner of /etc/iptables, run the command:

$ sudo chown root /etc/iptables

Rationale:

The ownership of the /etc/iptables directory by the root user is important because this directory hosts iptables configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the iptables configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_owner_etc_iptables

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - directory_owner_etc_iptables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner on directory /etc/iptables/
  file:
    path: /etc/iptables/
    state: directory
    owner: '0'
  when: '"iptables" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_owner_etc_iptables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q installed; then

find -H /etc/iptables/ -maxdepth 1 -type d -exec chown 0 {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions On /etc/iptables Directory [ref]

To properly set the permissions of /etc/iptables, run the command:

$ sudo chmod 0600 /etc/iptables

Rationale:

Setting correct permissions on the /etc/iptables directory is important because this directory hosts iptables configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the iptables configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_permissions_etc_iptables

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - directory_permissions_etc_iptables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Find /etc/iptables/ file(s)
  command: 'find -H /etc/iptables/ -maxdepth 1 -perm /u+xs,g+xwrs,o+xwrt  -type d '
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: '"iptables" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_permissions_etc_iptables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set permissions for /etc/iptables/ file(s)
  file:
    path: '{{ item }}'
    mode: u-xs,g-xwrs,o-xwrt
    state: directory
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: '"iptables" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_permissions_etc_iptables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q installed; then

find -H /etc/iptables/ -maxdepth 1 -perm /u+xs,g+xwrs,o+xwrt -type d -exec chmod u-xs,g-xwrs,o-xwrt {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Kernel Parameters Which Affect Networking Group contains 1 group and 6 rules

[ref] The sysctl utility is used to set parameters which affect the operation of the Linux kernel. Kernel parameters which affect networking and have security implications are described here.

Group Network Related Kernel Runtime Parameters for Hosts and Routers Group contains 6 rules

[ref] Certain kernel parameters should be set for systems which are acting as either hosts or routers to improve the system's ability defend against certain types of IPv4 protocol attacks.

Rule Disable Accepting Packets Routed Between Local Interfaces [ref]

To set the runtime status of the net.ipv4.conf.all.accept_local kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.all.accept_local=0

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

net.ipv4.conf.all.accept_local = 0

Rationale:

Configure net.ipv4.conf.all.accept_local=0 to consider as invalid the packets received from outside whose source is the 127.0.0.0/8 address block. In combination with suitable routing, this can be used to direct packets between two local interfaces over the wire and have them accepted properly.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_accept_local

References:

anssi	R12

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*net.ipv4.conf.all.accept_local.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_accept_local

- name: Comment out any occurrences of net.ipv4.conf.all.accept_local from config
    files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*net.ipv4.conf.all.accept_local
    replace: '#net.ipv4.conf.all.accept_local'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_accept_local

- name: Ensure sysctl net.ipv4.conf.all.accept_local is set to 0
  sysctl:
    name: net.ipv4.conf.all.accept_local
    value: '0'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_accept_local

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of net.ipv4.conf.all.accept_local from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.accept_local.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "net.ipv4.conf.all.accept_local" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"


#
# Set runtime for net.ipv4.conf.all.accept_local
#
/sbin/sysctl -q -n -w net.ipv4.conf.all.accept_local="0"

#
# If net.ipv4.conf.all.accept_local present in /etc/sysctl.conf, change value to "0"
#	else, add "net.ipv4.conf.all.accept_local = 0" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.accept_local")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "0"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.accept_local\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.accept_local\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Configure ARP filtering for All IPv4 Interfaces [ref]

To set the runtime status of the net.ipv4.conf.all.arp_filter kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.all.arp_filter=0

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

net.ipv4.conf.all.arp_filter = 0

Warning: This behaviour may cause problems to system on a high availability or load balancing configuration.

Rationale:

Prevents the Linux Kernel from handling the ARP table globally. By default, the kernel may respond to an ARP request from a certain interface with information from another interface.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_arp_filter

References:

anssi	R12

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*net.ipv4.conf.all.arp_filter.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_arp_filter

- name: Comment out any occurrences of net.ipv4.conf.all.arp_filter from config files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*net.ipv4.conf.all.arp_filter
    replace: '#net.ipv4.conf.all.arp_filter'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_arp_filter
- name: XCCDF Value sysctl_net_ipv4_conf_all_arp_filter_value # promote to variable
  set_fact:
    sysctl_net_ipv4_conf_all_arp_filter_value: !!str 0
  tags:
    - always

- name: Ensure sysctl net.ipv4.conf.all.arp_filter is set
  sysctl:
    name: net.ipv4.conf.all.arp_filter
    value: '{{ sysctl_net_ipv4_conf_all_arp_filter_value }}'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_arp_filter

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of net.ipv4.conf.all.arp_filter from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.arp_filter.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "net.ipv4.conf.all.arp_filter" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"

sysctl_net_ipv4_conf_all_arp_filter_value='0'


#
# Set runtime for net.ipv4.conf.all.arp_filter
#
/sbin/sysctl -q -n -w net.ipv4.conf.all.arp_filter="$sysctl_net_ipv4_conf_all_arp_filter_value"

#
# If net.ipv4.conf.all.arp_filter present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv4.conf.all.arp_filter = value" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.arp_filter")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_all_arp_filter_value"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.arp_filter\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.arp_filter\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Configure Response Mode of ARP Requests for All IPv4 Interfaces [ref]

To set the runtime status of the net.ipv4.conf.all.arp_ignore kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.all.arp_ignore=2

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

net.ipv4.conf.all.arp_ignore = 2

Warning: The ARP response mode may impact behaviour of workloads and firewalls on the system.

Rationale:

Avoids ARP Flux on system that have more than one interface on the same subnet.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_arp_ignore

References:

anssi	R12

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*net.ipv4.conf.all.arp_ignore.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_arp_ignore

- name: Comment out any occurrences of net.ipv4.conf.all.arp_ignore from config files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*net.ipv4.conf.all.arp_ignore
    replace: '#net.ipv4.conf.all.arp_ignore'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_arp_ignore
- name: XCCDF Value sysctl_net_ipv4_conf_all_arp_ignore_value # promote to variable
  set_fact:
    sysctl_net_ipv4_conf_all_arp_ignore_value: !!str 2
  tags:
    - always

- name: Ensure sysctl net.ipv4.conf.all.arp_ignore is set
  sysctl:
    name: net.ipv4.conf.all.arp_ignore
    value: '{{ sysctl_net_ipv4_conf_all_arp_ignore_value }}'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_arp_ignore

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of net.ipv4.conf.all.arp_ignore from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.arp_ignore.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "net.ipv4.conf.all.arp_ignore" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"

sysctl_net_ipv4_conf_all_arp_ignore_value='2'


#
# Set runtime for net.ipv4.conf.all.arp_ignore
#
/sbin/sysctl -q -n -w net.ipv4.conf.all.arp_ignore="$sysctl_net_ipv4_conf_all_arp_ignore_value"

#
# If net.ipv4.conf.all.arp_ignore present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv4.conf.all.arp_ignore = value" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.arp_ignore")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_all_arp_ignore_value"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.arp_ignore\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.arp_ignore\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Prevent Routing External Traffic to Local Loopback on All IPv4 Interfaces [ref]

To set the runtime status of the net.ipv4.conf.all.route_localnet kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.all.route_localnet=0

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

net.ipv4.conf.all.route_localnet = 0

Rationale:

Refuse the routing of packets whose source or destination address is the local loopback. This prohibits the use of network 127/8 for local routing purposes. Enabling route_localnet can expose applications listening on localhost to external traffic.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_route_localnet

References:

anssi	R12

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*net.ipv4.conf.all.route_localnet.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_route_localnet

- name: Comment out any occurrences of net.ipv4.conf.all.route_localnet from config
    files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*net.ipv4.conf.all.route_localnet
    replace: '#net.ipv4.conf.all.route_localnet'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_route_localnet

- name: Ensure sysctl net.ipv4.conf.all.route_localnet is set to 0
  sysctl:
    name: net.ipv4.conf.all.route_localnet
    value: '0'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_route_localnet

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of net.ipv4.conf.all.route_localnet from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.route_localnet.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "net.ipv4.conf.all.route_localnet" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"


#
# Set runtime for net.ipv4.conf.all.route_localnet
#
/sbin/sysctl -q -n -w net.ipv4.conf.all.route_localnet="0"

#
# If net.ipv4.conf.all.route_localnet present in /etc/sysctl.conf, change value to "0"
#	else, add "net.ipv4.conf.all.route_localnet = 0" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.route_localnet")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "0"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.route_localnet\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.route_localnet\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Configure Sending and Accepting Shared Media Redirects for All IPv4 Interfaces [ref]

To set the runtime status of the net.ipv4.conf.all.shared_media kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.all.shared_media=0

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

net.ipv4.conf.all.shared_media = 0

Rationale:

This setting should be aligned with net.ipv4.conf.all.secure_redirects because it overrides it. If shared_media is enabled for an interface secure_redirects will be enabled too.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_shared_media

References:

anssi	R12

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*net.ipv4.conf.all.shared_media.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_shared_media

- name: Comment out any occurrences of net.ipv4.conf.all.shared_media from config
    files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*net.ipv4.conf.all.shared_media
    replace: '#net.ipv4.conf.all.shared_media'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_shared_media
- name: XCCDF Value sysctl_net_ipv4_conf_all_shared_media_value # promote to variable
  set_fact:
    sysctl_net_ipv4_conf_all_shared_media_value: !!str 0
  tags:
    - always

- name: Ensure sysctl net.ipv4.conf.all.shared_media is set
  sysctl:
    name: net.ipv4.conf.all.shared_media
    value: '{{ sysctl_net_ipv4_conf_all_shared_media_value }}'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_all_shared_media

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of net.ipv4.conf.all.shared_media from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.shared_media.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "net.ipv4.conf.all.shared_media" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"

sysctl_net_ipv4_conf_all_shared_media_value='0'


#
# Set runtime for net.ipv4.conf.all.shared_media
#
/sbin/sysctl -q -n -w net.ipv4.conf.all.shared_media="$sysctl_net_ipv4_conf_all_shared_media_value"

#
# If net.ipv4.conf.all.shared_media present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv4.conf.all.shared_media = value" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.shared_media")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_all_shared_media_value"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.shared_media\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.shared_media\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Configure Sending and Accepting Shared Media Redirects by Default [ref]

To set the runtime status of the net.ipv4.conf.default.shared_media kernel parameter, run the following command:

$ sudo sysctl -w net.ipv4.conf.default.shared_media=0

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

net.ipv4.conf.default.shared_media = 0

Rationale:

This setting should be aligned with net.ipv4.conf.default.secure_redirects because it overrides it. If shared_media is enabled for an interface secure_redirects will be enabled too.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_default_shared_media

References:

anssi	R12

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*net.ipv4.conf.default.shared_media.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_default_shared_media

- name: Comment out any occurrences of net.ipv4.conf.default.shared_media from config
    files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*net.ipv4.conf.default.shared_media
    replace: '#net.ipv4.conf.default.shared_media'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_default_shared_media
- name: XCCDF Value sysctl_net_ipv4_conf_default_shared_media_value # promote to variable
  set_fact:
    sysctl_net_ipv4_conf_default_shared_media_value: !!str 0
  tags:
    - always

- name: Ensure sysctl net.ipv4.conf.default.shared_media is set
  sysctl:
    name: net.ipv4.conf.default.shared_media
    value: '{{ sysctl_net_ipv4_conf_default_shared_media_value }}'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_net_ipv4_conf_default_shared_media

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of net.ipv4.conf.default.shared_media from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.default.shared_media.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "net.ipv4.conf.default.shared_media" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"

sysctl_net_ipv4_conf_default_shared_media_value='0'


#
# Set runtime for net.ipv4.conf.default.shared_media
#
/sbin/sysctl -q -n -w net.ipv4.conf.default.shared_media="$sysctl_net_ipv4_conf_default_shared_media_value"

#
# If net.ipv4.conf.default.shared_media present in /etc/sysctl.conf, change value to appropriate value
#	else, add "net.ipv4.conf.default.shared_media = value" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.default.shared_media")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_default_shared_media_value"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.default.shared_media\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.default.shared_media\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group nftables Group contains 3 rules

[ref]

If firewalld or iptables are being used in your environment, please follow the guidance in their
respective section and pass-over the guidance in this section.

nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames and is the successor to iptables. The biggest change with the successor nftables is its simplicity. With iptables, we have to configure every single rule and use the syntax which can be compared with normal commands. With nftables, the simpler syntax, much like BPF (Berkely Packet Filter) means shorter lines and less repetition. Support for nftables should also be compiled into the kernel, together with the related nftables modules.

It is available in Linux kernels >= 3.13. Please ensure that your kernel supports nftables before choosing this option.

Rule Verify Group Who Owns /etc/nftables Directory [ref]

To properly set the group owner of /etc/nftables, run the command:

$ sudo chgrp root /etc/nftables

Rationale:

The ownership of the /etc/nftables directory by the root group is important because this directory hosts nftables configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the nftables configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_groupowner_etc_nftables

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - directory_groupowner_etc_nftables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner on /etc/nftables/
  file:
    path: /etc/nftables/
    state: directory
    group: root
  when: '"nftables" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_groupowner_etc_nftables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q installed; then

find -H /etc/nftables/ -maxdepth 1 -type d -exec chgrp root {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify User Who Owns /etc/nftables Directory [ref]

To properly set the owner of /etc/nftables, run the command:

$ sudo chown root /etc/nftables

Rationale:

The ownership of the /etc/nftables directory by the root user is important because this directory hosts nftables configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the nftables configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_owner_etc_nftables

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - directory_owner_etc_nftables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner on directory /etc/nftables/
  file:
    path: /etc/nftables/
    state: directory
    owner: '0'
  when: '"nftables" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_owner_etc_nftables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q installed; then

find -H /etc/nftables/ -maxdepth 1 -type d -exec chown 0 {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions On /etc/nftables Directory [ref]

To properly set the permissions of /etc/nftables, run the command:

$ sudo chmod 0700 /etc/nftables

Rationale:

Setting correct permissions on the /etc/nftables directory is important because this directory hosts nftables configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the nftables configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_permissions_etc_nftables

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - configure_strategy
  - directory_permissions_etc_nftables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Find /etc/nftables/ file(s)
  command: 'find -H /etc/nftables/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt  -type d '
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: '"nftables" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_permissions_etc_nftables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set permissions for /etc/nftables/ file(s)
  file:
    path: '{{ item }}'
    mode: u-s,g-xwrs,o-xwrt
    state: directory
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: '"nftables" in ansible_facts.packages'
  tags:
  - configure_strategy
  - directory_permissions_etc_nftables
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q installed; then

find -H /etc/nftables/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt -type d -exec chmod u-s,g-xwrs,o-xwrt {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group File Permissions and Masks Group contains 6 groups and 34 rules

[ref] Traditional Unix security relies heavily on file and directory permissions to prevent unauthorized users from reading or modifying files to which they should not have access.

Several of the commands in this section search filesystems for files or directories with certain characteristics, and are intended to be run on every local partition on a given system. When the variable PART appears in one of the commands below, it means that the command is intended to be run repeatedly, with the name of each local partition substituted for PART in turn.

The following command prints a list of all xfs partitions on the local system, which is the default filesystem for Debian 12 installations:

$ mount -t xfs | awk '{print $3}'

For any systems that use a different local filesystem type, modify this command as appropriate.

Group Verify Permissions on Important Files and Directories Group contains 2 groups and 30 rules

[ref] Permissions for many files on a system must be set restrictively to ensure sensitive information is properly protected. This section discusses important permission restrictions which can be verified to ensure that no harmful discrepancies have arisen.

Group Verify Permissions on Files with Local Account Information and Credentials Group contains 15 rules

[ref] The default restrictive permissions for files which act as important security databases such as passwd, shadow, group, and gshadow files must be maintained. Many utilities need read access to the passwd file in order to function properly, but read access to the shadow file allows malicious attacks against system passwords, and should never be enabled.

Rule Verify Group Who Owns group File [ref]

To properly set the group owner of /etc/group, run the command:

$ sudo chgrp root /etc/group

Rationale:

The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_group

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.2.2
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-8.7.c
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/group
  stat:
    path: /etc/group
  register: file_exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_groupowner_etc_group
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner 0 on /etc/group
  file:
    path: /etc/group
    group: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_groupowner_etc_group
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chgrp 0 /etc/group

Rule Verify Group Who Owns gshadow File [ref]

To properly set the group owner of /etc/gshadow, run the command:

$ sudo chgrp shadow /etc/gshadow

Rationale:

The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_gshadow

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/gshadow
  stat:
    path: /etc/gshadow
  register: file_exists
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_groupowner_etc_gshadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner 42 on /etc/gshadow
  file:
    path: /etc/gshadow
    group: '42'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_groupowner_etc_gshadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chgrp 42 /etc/gshadow

Rule Verify Group Who Owns passwd File [ref]

To properly set the group owner of /etc/passwd, run the command:

$ sudo chgrp root /etc/passwd

Rationale:

The /etc/passwd file contains information about the users that are configured on the system. Protection of this file is critical for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_passwd

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.2.2
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-8.7.c
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/passwd
  stat:
    path: /etc/passwd
  register: file_exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_groupowner_etc_passwd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner 0 on /etc/passwd
  file:
    path: /etc/passwd
    group: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_groupowner_etc_passwd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chgrp 0 /etc/passwd

Rule Verify Group Who Owns shadow File [ref]

To properly set the group owner of /etc/shadow, run the command:

$ sudo chgrp shadow /etc/shadow

Rationale:

The /etc/shadow file stores password hashes. Protection of this file is critical for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_shadow

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.2.2
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-8.7.c
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/shadow
  stat:
    path: /etc/shadow
  register: file_exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_groupowner_etc_shadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner 42 on /etc/shadow
  file:
    path: /etc/shadow
    group: '42'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_groupowner_etc_shadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chgrp 42 /etc/shadow

Rule Verify Group Who Owns /etc/shells File [ref]

To properly set the group owner of /etc/shells, run the command:

$ sudo chgrp root /etc/shells

Rationale:

The /etc/shells file contains the list of full pathnames to shells on the system. Since this file is used by many system programs this file should be protected.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_shells

References:

nist	AC-3, MP-2
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/shells
  stat:
    path: /etc/shells
  register: file_exists
  tags:
  - NIST-800-53-AC-3
  - NIST-800-53-MP-2
  - configure_strategy
  - file_groupowner_etc_shells
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner 0 on /etc/shells
  file:
    path: /etc/shells
    group: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-3
  - NIST-800-53-MP-2
  - configure_strategy
  - file_groupowner_etc_shells
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chgrp 0 /etc/shells

Rule Verify User Who Owns group File [ref]

To properly set the owner of /etc/group, run the command:

$ sudo chown root /etc/group

Rationale:

The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_group

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.2.2
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-002223
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-8.7.c
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/group
  stat:
    path: /etc/group
  register: file_exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_owner_etc_group
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/group
  file:
    path: /etc/group
    owner: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_owner_etc_group
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chown 0 /etc/group

Rule Verify User Who Owns gshadow File [ref]

To properly set the owner of /etc/gshadow, run the command:

$ sudo chown root /etc/gshadow

Rationale:

The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_gshadow

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-002223
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/gshadow
  stat:
    path: /etc/gshadow
  register: file_exists
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_owner_etc_gshadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/gshadow
  file:
    path: /etc/gshadow
    owner: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_owner_etc_gshadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chown 0 /etc/gshadow

Rule Verify User Who Owns passwd File [ref]

To properly set the owner of /etc/passwd, run the command:

$ sudo chown root /etc/passwd

Rationale:

The /etc/passwd file contains information about the users that are configured on the system. Protection of this file is critical for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_passwd

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.2.2
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-002223
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-8.7.c
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/passwd
  stat:
    path: /etc/passwd
  register: file_exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_owner_etc_passwd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/passwd
  file:
    path: /etc/passwd
    owner: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_owner_etc_passwd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chown 0 /etc/passwd

Rule Verify User Who Owns shadow File [ref]

To properly set the owner of /etc/shadow, run the command:

$ sudo chown root /etc/shadow

Rationale:

The /etc/shadow file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_shadow

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.2.2
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-002223
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-8.7.c
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/shadow
  stat:
    path: /etc/shadow
  register: file_exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_owner_etc_shadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/shadow
  file:
    path: /etc/shadow
    owner: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_owner_etc_shadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chown 0 /etc/shadow

Rule Verify Who Owns /etc/shells File [ref]

To properly set the owner of /etc/shells, run the command:

$ sudo chown root /etc/shells

Rationale:

The /etc/shells file contains the list of full pathnames to shells on the system. Since this file is used by many system programs this file should be protected.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_shells

References:

nist	AC-3, MP-2
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/shells
  stat:
    path: /etc/shells
  register: file_exists
  tags:
  - NIST-800-53-AC-3
  - NIST-800-53-MP-2
  - configure_strategy
  - file_owner_etc_shells
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/shells
  file:
    path: /etc/shells
    owner: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-3
  - NIST-800-53-MP-2
  - configure_strategy
  - file_owner_etc_shells
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chown 0 /etc/shells

Rule Verify Permissions on group File [ref]

To properly set the permissions of /etc/group, run the command:

$ sudo chmod 0644 /etc/group

Rationale:

The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_group

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.2.2
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-002223
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-8.7.c
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/group
  stat:
    path: /etc/group
  register: file_exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_etc_group
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xws,o-xwt on /etc/group
  file:
    path: /etc/group
    mode: u-xs,g-xws,o-xwt
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_etc_group
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure






chmod u-xs,g-xws,o-xwt /etc/group

Rule Verify Permissions on gshadow File [ref]

To properly set the permissions of /etc/gshadow, run the command:

$ sudo chmod 0640 /etc/gshadow

Rationale:

The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_gshadow

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-002223
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/gshadow
  stat:
    path: /etc/gshadow
  register: file_exists
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_permissions_etc_gshadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xws,o-xwrt on /etc/gshadow
  file:
    path: /etc/gshadow
    mode: u-xs,g-xws,o-xwrt
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_permissions_etc_gshadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure






chmod u-xs,g-xws,o-xwrt /etc/gshadow

Rule Verify Permissions on passwd File [ref]

To properly set the permissions of /etc/passwd, run the command:

$ sudo chmod 0644 /etc/passwd

Rationale:

If the /etc/passwd file is writable by a group-owner or the world the risk of its compromise is increased. The file contains the list of accounts on the system and associated information, and protection of this file is critical for system security.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_passwd

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.2.2
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-002223
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-8.7.c
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/passwd
  stat:
    path: /etc/passwd
  register: file_exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_etc_passwd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xws,o-xwt on /etc/passwd
  file:
    path: /etc/passwd
    mode: u-xs,g-xws,o-xwt
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_etc_passwd
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure






chmod u-xs,g-xws,o-xwt /etc/passwd

Rule Verify Permissions on shadow File [ref]

To properly set the permissions of /etc/shadow, run the command:

$ sudo chmod 0640 /etc/shadow

Rationale:

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_shadow

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.2.2
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-002223
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-8.7.c
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/shadow
  stat:
    path: /etc/shadow
  register: file_exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_etc_shadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xws,o-xwrt on /etc/shadow
  file:
    path: /etc/shadow
    mode: u-xs,g-xws,o-xwrt
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CJIS-5.5.2.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-8.7.c
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_etc_shadow
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure






chmod u-xs,g-xws,o-xwrt /etc/shadow

Rule Verify Permissions on /etc/shells File [ref]

To properly set the permissions of /etc/shells, run the command:

$ sudo chmod 0644 /etc/shells

Rationale:

The /etc/shells file contains the list of full pathnames to shells on the system. Since this file is used by many system programs this file should be protected.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_shells

References:

nist	AC-3, MP-2
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/shells
  stat:
    path: /etc/shells
  register: file_exists
  tags:
  - NIST-800-53-AC-3
  - NIST-800-53-MP-2
  - configure_strategy
  - file_permissions_etc_shells
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xws,o-xwt on /etc/shells
  file:
    path: /etc/shells
    mode: u-xs,g-xws,o-xwt
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-3
  - NIST-800-53-MP-2
  - configure_strategy
  - file_permissions_etc_shells
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure






chmod u-xs,g-xws,o-xwt /etc/shells

Group Verify File Permissions Within Some Important Directories Group contains 6 rules

[ref] Some directories contain files whose confidentiality or integrity is notably important and may also be susceptible to misconfiguration over time, particularly if unpackaged software is installed. As such, an argument exists to verify that files' permissions within these directories remain configured correctly and restrictively.

Rule Verify Group Who Owns /etc/sysctl.d Directory [ref]

To properly set the group owner of /etc/sysctl.d, run the command:

$ sudo chgrp root /etc/sysctl.d

Rationale:

The ownership of the /etc/sysctl.d directory by the root group is important because this directory hosts kernel configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the kernel configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_groupowner_etc_sysctld

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Ensure group owner on /etc/sysctl.d/
  file:
    path: /etc/sysctl.d/
    state: directory
    group: root
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - directory_groupowner_etc_sysctld
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find -H /etc/sysctl.d/ -maxdepth 1 -type d -exec chgrp root {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify User Who Owns /etc/sysctl.d Directory [ref]

To properly set the owner of /etc/sysctl.d, run the command:

$ sudo chown root /etc/sysctl.d

Rationale:

The ownership of the /etc/sysctl.d directory by the root user is important because this directory hosts kernel configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the kernel configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_owner_etc_sysctld

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Ensure owner on directory /etc/sysctl.d/
  file:
    path: /etc/sysctl.d/
    state: directory
    owner: '0'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - directory_owner_etc_sysctld
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find -H /etc/sysctl.d/ -maxdepth 1 -type d -exec chown 0 {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions On /etc/sysctl.d Directory [ref]

To properly set the permissions of /etc/sysctl.d, run the command:

$ sudo chmod 0755 /etc/sysctl.d

Rationale:

Setting correct permissions on the /etc/sysctl.d directory is important because this directory hosts kernel configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the kernel configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_permissions_etc_sysctld

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Find /etc/sysctl.d/ file(s)
  command: 'find -H /etc/sysctl.d/ -maxdepth 1 -perm /u+s,g+ws,o+wt  -type d '
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - directory_permissions_etc_sysctld
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set permissions for /etc/sysctl.d/ file(s)
  file:
    path: '{{ item }}'
    mode: u-s,g-ws,o-wt
    state: directory
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - directory_permissions_etc_sysctld
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find -H /etc/sysctl.d/ -maxdepth 1 -perm /u+s,g+ws,o+wt -type d -exec chmod u-s,g-ws,o-wt {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify that system commands files are group owned by root or a system account [ref]

System commands files are stored in the following directories by default:

/bin
/sbin
/usr/bin
/usr/sbin
/usr/local/bin
/usr/local/sbin

All files in these directories should be owned by the root group, or a system account. If the directory, or any file in these directories, is found to be owned by a group other than root or a a system account correct its ownership with the following command:

$ sudo chgrp root FILE

Rationale:

If the operating system allows any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process. This requirement applies to operating systems with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs which execute with escalated privileges. Only qualified and authorized individuals must be allowed to obtain access to information system components for purposes of initiating changes, including upgrades and modifications.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupownership_system_commands_dirs

References:

disa	CCI-001499
nist	CM-5(6), CM-5(6).1
os-srg	SRG-OS-000259-GPOS-00100
anssi	R50

Rule Verify that System Executables Have Root Ownership [ref]

System executables are stored in the following directories by default:

/bin
/sbin
/usr/bin
/usr/libexec
/usr/local/bin
/usr/local/sbin
/usr/sbin

All files in these directories should be owned by the root user. If any file FILE in these directories is found to be owned by a user other than root, correct its ownership with the following command:

$ sudo chown root FILE

Rationale:

System binaries are executed by privileged users as well as system services, and restrictive permissions are necessary to ensure that their execution of these programs cannot be co-opted.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_ownership_binary_dirs

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-001499
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-5(6), CM-5(6).1, CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
os-srg	SRG-OS-000259-GPOS-00100
anssi	R50

Rule Verify that System Executables Have Restrictive Permissions [ref]

System executables are stored in the following directories by default:

/bin
/sbin
/usr/bin
/usr/libexec
/usr/local/bin
/usr/local/sbin
/usr/sbin

All files in these directories should not be group-writable or world-writable. If any file FILE in these directories is found to be group-writable or world-writable, correct its permission with the following command:

$ sudo chmod go-w FILE

Rationale:

System binaries are executed by privileged users, as well as system services, and restrictive permissions are necessary to ensure execution of these programs cannot be co-opted.

Severity:

medium

Rule ID:

xccdf_org.ssgproject.content_rule_file_permissions_binary_dirs

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-001499
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-5(6), CM-5(6).1, CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
os-srg	SRG-OS-000259-GPOS-00100
anssi	R50

Rule Verify that All World-Writable Directories Have Sticky Bits Set [ref]

When the so-called 'sticky bit' is set on a directory, only the owner of a given file may remove that file from the directory. Without the sticky bit, any user with write access to a directory may remove any file in the directory. Setting the sticky bit prevents users from removing each other's files. In cases where there is no reason for a directory to be world-writable, a better solution is to remove that permission rather than to set the sticky bit. However, if a directory is used by a particular application, consult that application's documentation instead of blindly changing modes.
To set the sticky bit on a world-writable directory DIR, run the following command:

$ sudo chmod +t DIR

Warning: This rule can take a long time to perform the check and might consume a considerable amount of resources depending on the number of directories present on the system. It is not a problem in most cases, but especially systems with a large number of directories can be affected. See https://access.redhat.com/articles/6999111.

Rationale:

Failing to set the sticky bit on public directories allows unauthorized users to delete files in the directory structure.

The only authorized public directories are those temporary directories supplied with the system, or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system, by users for temporary file storage (such as /tmp), and for directories requiring global read/write access.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_dir_perms_world_writable_sticky_bits

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
disa	CCI-001090
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
os-srg	SRG-OS-000138-GPOS-00069
anssi	R54
pcidss4	2.2.6

Rule Verify that system commands directories have root as a group owner [ref]

System commands are stored in the following directories: by default:

/bin 
/sbin 
/usr/bin 
/usr/sbin 
/usr/local/bin 
/usr/local/sbin

All these directories should have root user as a group owner. If any system command directory is not group owned by a user other than root correct its ownership with the following command:

$ sudo chgrp root DIR

Rationale:

If the operating system were to allow any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process. This requirement applies to operating systems with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs which execute with escalated privileges. Only qualified and authorized individuals must be allowed to obtain access to information system components for purposes of initiating changes, including upgrades and modifications.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_dir_system_commands_group_root_owned

References:

disa	CCI-001499
nist	CM-5(6), CM-5(6).1
os-srg	SRG-OS-000259-GPOS-00100
anssi	R50

Rule Verify that system commands directories have root ownership [ref]

System commands are stored in the following directories by default:

/bin 
/sbin 
/usr/bin 
/usr/sbin 
/usr/local/bin 
/usr/local/sbin

All these directories should be owned by the root user. If any system command directory is not owned by a user other than root correct its ownership with the following command:

$ sudo chown root DIR

Rationale:

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_dir_system_commands_root_owned

References:

disa	CCI-001499
nist	CM-5(6), CM-5(6).1
os-srg	SRG-OS-000259-GPOS-00100
anssi	R50

Rule Verify Group Who Owns /etc/crypttab File [ref]

To properly set the group owner of /etc/crypttab, run the command:

$ sudo chgrp root /etc/crypttab

Rationale:

The ownership of the /etc/crypttab file by the root group is important because this file hosts encrypted block devices configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the encrypted block devices configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_crypttab

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/crypttab
  stat:
    path: /etc/crypttab
  register: file_exists
  tags:
  - configure_strategy
  - file_groupowner_etc_crypttab
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner root on /etc/crypttab
  file:
    path: /etc/crypttab
    group: root
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_groupowner_etc_crypttab
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chgrp root /etc/crypttab

Rule Verify User Who Owns /etc/crypttab File [ref]

To properly set the owner of /etc/crypttab, run the command:

$ sudo chown root /etc/crypttab

Rationale:

The ownership of the /etc/crypttab file by the root user is important because this file hosts encrypted block devices configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the encrypted block devices configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_crypttab

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/crypttab
  stat:
    path: /etc/crypttab
  register: file_exists
  tags:
  - configure_strategy
  - file_owner_etc_crypttab
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/crypttab
  file:
    path: /etc/crypttab
    owner: '0'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_owner_etc_crypttab
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

chown 0 /etc/crypttab

Rule Verify Permissions On /etc/crypttab File [ref]

To properly set the permissions of /etc/crypttab, run the command:

$ sudo chmod 0600 /etc/crypttab

Rationale:

Setting correct permissions on the /etc/crypttab file is important because this file hosts encrypted block devices configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the encrypted block devices configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_crypttab

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/crypttab
  stat:
    path: /etc/crypttab
  register: file_exists
  tags:
  - configure_strategy
  - file_permissions_etc_crypttab
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xwrs,o-xwrt on /etc/crypttab
  file:
    path: /etc/crypttab
    mode: u-xs,g-xwrs,o-xwrt
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_permissions_etc_crypttab
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure






chmod u-xs,g-xwrs,o-xwrt /etc/crypttab

Rule Ensure No World-Writable Files Exist [ref]

It is generally a good idea to remove global (other) write access to a file when it is discovered. However, check with documentation for specific applications before making changes. Also, monitor for recurring world-writable files, as these may be symptoms of a misconfigured application or user account. Finally, this applies to real files and not virtual files that are a part of pseudo file systems such as sysfs or procfs.

Warning: This rule can take a long time to perform the check and might consume a considerable amount of resources depending on the number of files present on the system. It is not a problem in most cases, but especially systems with a large number of files can be affected. See https://access.redhat.com/articles/6999111.

Rationale:

Data in world-writable files can be modified by any user on the system. In almost all circumstances, files can be configured using a combination of user and group permissions to support whatever legitimate access is needed without the risk caused by world-writable files.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_unauthorized_world_writable

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
anssi	R54
pcidss4	2.2.6

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure


FILTER_NODEV=$(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,)
PARTITIONS=$(findmnt -n -l -k -it $FILTER_NODEV | awk '{ print $1 }')
for PARTITION in $PARTITIONS; do
  find "${PARTITION}" -xdev -type f -perm -002 -exec chmod o-w {} \; 2>/dev/null
done

# Ensure /tmp is also fixed whem tmpfs is used.
if grep "^tmpfs /tmp" /proc/mounts; then
  find /tmp -xdev -type f -perm -002 -exec chmod o-w {} \; 2>/dev/null
fi

Rule Enable Kernel Parameter to Enforce DAC on Hardlinks [ref]

To set the runtime status of the fs.protected_hardlinks kernel parameter, run the following command:

$ sudo sysctl -w fs.protected_hardlinks=1

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

fs.protected_hardlinks = 1

Rationale:

By enabling this kernel parameter, users can no longer create soft or hard links to files which they do not own. Disallowing such hardlinks mitigate vulnerabilities based on insecure file system accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat().

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_fs_protected_hardlinks

References:

disa	CCI-002165
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
os-srg	SRG-OS-000312-GPOS-00122, SRG-OS-000312-GPOS-00123, SRG-OS-000324-GPOS-00125
anssi	R14

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*fs.protected_hardlinks.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_fs_protected_hardlinks

- name: Comment out any occurrences of fs.protected_hardlinks from config files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*fs.protected_hardlinks
    replace: '#fs.protected_hardlinks'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_fs_protected_hardlinks

- name: Ensure sysctl fs.protected_hardlinks is set to 1
  sysctl:
    name: fs.protected_hardlinks
    value: '1'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_fs_protected_hardlinks

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of fs.protected_hardlinks from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*fs.protected_hardlinks.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "fs.protected_hardlinks" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"


#
# Set runtime for fs.protected_hardlinks
#
/sbin/sysctl -q -n -w fs.protected_hardlinks="1"

#
# If fs.protected_hardlinks present in /etc/sysctl.conf, change value to "1"
#	else, add "fs.protected_hardlinks = 1" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^fs.protected_hardlinks")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "1"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^fs.protected_hardlinks\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^fs.protected_hardlinks\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Enable Kernel Parameter to Enforce DAC on Symlinks [ref]

To set the runtime status of the fs.protected_symlinks kernel parameter, run the following command:

$ sudo sysctl -w fs.protected_symlinks=1

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

fs.protected_symlinks = 1

Rationale:

By enabling this kernel parameter, symbolic links are permitted to be followed only when outside a sticky world-writable directory, or when the UID of the link and follower match, or when the directory owner matches the symlink's owner. Disallowing such symlinks helps mitigate vulnerabilities based on insecure file system accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat().

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_fs_protected_symlinks

References:

disa	CCI-002165
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	CM-6(a), AC-6(1)
os-srg	SRG-OS-000312-GPOS-00122, SRG-OS-000312-GPOS-00123, SRG-OS-000324-GPOS-00125
anssi	R14

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*fs.protected_symlinks.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_fs_protected_symlinks

- name: Comment out any occurrences of fs.protected_symlinks from config files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*fs.protected_symlinks
    replace: '#fs.protected_symlinks'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_fs_protected_symlinks

- name: Ensure sysctl fs.protected_symlinks is set to 1
  sysctl:
    name: fs.protected_symlinks
    value: '1'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_fs_protected_symlinks

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of fs.protected_symlinks from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*fs.protected_symlinks.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "fs.protected_symlinks" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"


#
# Set runtime for fs.protected_symlinks
#
/sbin/sysctl -q -n -w fs.protected_symlinks="1"

#
# If fs.protected_symlinks present in /etc/sysctl.conf, change value to "1"
#	else, add "fs.protected_symlinks = 1" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^fs.protected_symlinks")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "1"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^fs.protected_symlinks\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^fs.protected_symlinks\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Restrict Programs from Dangerous Execution Patterns Group contains 2 groups and 4 rules

[ref] The recommendations in this section are designed to ensure that the system's features to protect against potentially dangerous program execution are activated. These protections are applied at the system initialization or kernel level, and defend against certain types of badly-configured or compromised programs.

Group Disable Core Dumps Group contains 1 rule

[ref] A core dump file is the memory image of an executable program when it was terminated by the operating system due to errant behavior. In most cases, only software developers legitimately need to access these files. The core dump files may also contain sensitive information, or unnecessarily occupy large amounts of disk space.

Once a hard limit is set in /etc/security/limits.conf, or to a file within the /etc/security/limits.d/ directory, a user cannot increase that limit within his or her own session. If access to core dumps is required, consider restricting them to only certain users or groups. See the limits.conf man page for more information.

The core dumps of setuid programs are further protected. The sysctl variable fs.suid_dumpable controls whether the kernel allows core dumps from these programs at all. The default value of 0 is recommended.

Rule Disable Core Dumps for SUID programs [ref]

To set the runtime status of the fs.suid_dumpable kernel parameter, run the following command:

$ sudo sysctl -w fs.suid_dumpable=0

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

fs.suid_dumpable = 0

Rationale:

The core dump of a setuid program is more likely to contain sensitive data, as the program itself runs with greater privileges than the user who initiated execution of the program. Disabling the ability for any setuid program to write a core file decreases the risk of unauthorized access of such data.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_fs_suid_dumpable

References:

hipaa	164.308(a)(1)(ii)(D), 164.308(a)(3), 164.308(a)(4), 164.310(b), 164.310(c), 164.312(a), 164.312(e)
nist	SI-11(a), SI-11(b)
anssi	R14
pcidss4	3.3.1.1

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*fs.suid_dumpable.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-SI-11(a)
  - NIST-800-53-SI-11(b)
  - PCI-DSSv4-3.3.1.1
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_fs_suid_dumpable

- name: Comment out any occurrences of fs.suid_dumpable from config files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*fs.suid_dumpable
    replace: '#fs.suid_dumpable'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-SI-11(a)
  - NIST-800-53-SI-11(b)
  - PCI-DSSv4-3.3.1.1
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_fs_suid_dumpable

- name: Ensure sysctl fs.suid_dumpable is set to 0
  sysctl:
    name: fs.suid_dumpable
    value: '0'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-SI-11(a)
  - NIST-800-53-SI-11(b)
  - PCI-DSSv4-3.3.1.1
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_fs_suid_dumpable

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of fs.suid_dumpable from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*fs.suid_dumpable.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "fs.suid_dumpable" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"


#
# Set runtime for fs.suid_dumpable
#
/sbin/sysctl -q -n -w fs.suid_dumpable="0"

#
# If fs.suid_dumpable present in /etc/sysctl.conf, change value to "0"
#	else, add "fs.suid_dumpable = 0" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^fs.suid_dumpable")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "0"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^fs.suid_dumpable\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^fs.suid_dumpable\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Enable ExecShield Group contains 2 rules

[ref] ExecShield describes kernel features that provide protection against exploitation of memory corruption errors such as buffer overflows. These features include random placement of the stack and other memory regions, prevention of execution in memory that should only hold data, and special handling of text buffers. These protections are enabled by default on 32-bit systems and controlled through sysctl variables kernel.exec-shield and kernel.randomize_va_space. On the latest 64-bit systems, kernel.exec-shield cannot be enabled or disabled with sysctl.

Rule Restrict Exposed Kernel Pointer Addresses Access [ref]

To set the runtime status of the kernel.kptr_restrict kernel parameter, run the following command:

$ sudo sysctl -w kernel.kptr_restrict=2

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

kernel.kptr_restrict = 2

Rationale:

Exposing kernel pointers (through procfs or seq_printf()) exposes kernel writeable structures which may contain functions pointers. If a write vulnerability occurs in the kernel, allowing write access to any of this structure, the kernel can be compromised. This option disallow any program without the CAP_SYSLOG capability to get the addresses of kernel pointers by replacing them with 0.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_kernel_kptr_restrict

References:

disa	CCI-002824, CCI-000366
nerc-cip	CIP-002-5 R1.1, CIP-002-5 R1.2, CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 4.1, CIP-004-6 4.2, CIP-004-6 R2.2.3, CIP-004-6 R2.2.4, CIP-004-6 R2.3, CIP-004-6 R4, CIP-005-6 R1, CIP-005-6 R1.1, CIP-005-6 R1.2, CIP-007-3 R3, CIP-007-3 R3.1, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.1.3, CIP-007-3 R5.2.1, CIP-007-3 R5.2.3, CIP-007-3 R8.4, CIP-009-6 R.1.1, CIP-009-6 R4
nist	SC-30, SC-30(2), SC-30(5), CM-6(a)
os-srg	SRG-OS-000132-GPOS-00067, SRG-OS-000433-GPOS-00192, SRG-OS-000480-GPOS-00227
anssi	R9

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*kernel.kptr_restrict.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-CM-6(a)
  - NIST-800-53-SC-30
  - NIST-800-53-SC-30(2)
  - NIST-800-53-SC-30(5)
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_kernel_kptr_restrict

- name: Comment out any occurrences of kernel.kptr_restrict from config files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*kernel.kptr_restrict
    replace: '#kernel.kptr_restrict'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-CM-6(a)
  - NIST-800-53-SC-30
  - NIST-800-53-SC-30(2)
  - NIST-800-53-SC-30(5)
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_kernel_kptr_restrict
- name: XCCDF Value sysctl_kernel_kptr_restrict_value # promote to variable
  set_fact:
    sysctl_kernel_kptr_restrict_value: !!str 2
  tags:
    - always

- name: Ensure sysctl kernel.kptr_restrict is set
  sysctl:
    name: kernel.kptr_restrict
    value: '{{ sysctl_kernel_kptr_restrict_value }}'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-CM-6(a)
  - NIST-800-53-SC-30
  - NIST-800-53-SC-30(2)
  - NIST-800-53-SC-30(5)
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_kernel_kptr_restrict

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of kernel.kptr_restrict from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*kernel.kptr_restrict.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "kernel.kptr_restrict" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"

sysctl_kernel_kptr_restrict_value='2'


#
# Set runtime for kernel.kptr_restrict
#
/sbin/sysctl -q -n -w kernel.kptr_restrict="$sysctl_kernel_kptr_restrict_value"

#
# If kernel.kptr_restrict present in /etc/sysctl.conf, change value to appropriate value
#	else, add "kernel.kptr_restrict = value" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^kernel.kptr_restrict")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_kernel_kptr_restrict_value"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^kernel.kptr_restrict\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^kernel.kptr_restrict\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Enable Randomized Layout of Virtual Address Space [ref]

To set the runtime status of the kernel.randomize_va_space kernel parameter, run the following command:

$ sudo sysctl -w kernel.randomize_va_space=2

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

kernel.randomize_va_space = 2

Rationale:

Address space layout randomization (ASLR) makes it more difficult for an attacker to predict the location of attack code they have introduced into a process's address space during an attempt at exploitation. Additionally, ASLR makes it more difficult for an attacker to know the location of existing code in order to re-purpose it using return oriented programming (ROP) techniques.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_kernel_randomize_va_space

References:

cui	3.1.7
disa	CCI-000366, CCI-002824
hipaa	164.308(a)(1)(ii)(D), 164.308(a)(3), 164.308(a)(4), 164.310(b), 164.310(c), 164.312(a), 164.312(e)
nerc-cip	CIP-002-5 R1.1, CIP-002-5 R1.2, CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 4.1, CIP-004-6 4.2, CIP-004-6 R2.2.3, CIP-004-6 R2.2.4, CIP-004-6 R2.3, CIP-004-6 R4, CIP-005-6 R1, CIP-005-6 R1.1, CIP-005-6 R1.2, CIP-007-3 R3, CIP-007-3 R3.1, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.1.3, CIP-007-3 R5.2.1, CIP-007-3 R5.2.3, CIP-007-3 R8.4, CIP-009-6 R.1.1, CIP-009-6 R4
nist	SC-30, SC-30(2), CM-6(a)
pcidss	Req-2.2.1
os-srg	SRG-OS-000433-GPOS-00193, SRG-OS-000480-GPOS-00227
app-srg-ctr	SRG-APP-000450-CTR-001105
anssi	R9
pcidss4	3.3.1.1

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*kernel.randomize_va_space.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.7
  - NIST-800-53-CM-6(a)
  - NIST-800-53-SC-30
  - NIST-800-53-SC-30(2)
  - PCI-DSS-Req-2.2.1
  - PCI-DSSv4-3.3.1.1
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_kernel_randomize_va_space

- name: Comment out any occurrences of kernel.randomize_va_space from config files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*kernel.randomize_va_space
    replace: '#kernel.randomize_va_space'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.7
  - NIST-800-53-CM-6(a)
  - NIST-800-53-SC-30
  - NIST-800-53-SC-30(2)
  - PCI-DSS-Req-2.2.1
  - PCI-DSSv4-3.3.1.1
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_kernel_randomize_va_space

- name: Ensure sysctl kernel.randomize_va_space is set to 2
  sysctl:
    name: kernel.randomize_va_space
    value: '2'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.7
  - NIST-800-53-CM-6(a)
  - NIST-800-53-SC-30
  - NIST-800-53-SC-30(2)
  - PCI-DSS-Req-2.2.1
  - PCI-DSSv4-3.3.1.1
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_kernel_randomize_va_space

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of kernel.randomize_va_space from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*kernel.randomize_va_space.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "kernel.randomize_va_space" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"


#
# Set runtime for kernel.randomize_va_space
#
/sbin/sysctl -q -n -w kernel.randomize_va_space="2"

#
# If kernel.randomize_va_space present in /etc/sysctl.conf, change value to "2"
#	else, add "kernel.randomize_va_space = 2" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^kernel.randomize_va_space")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "2"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^kernel.randomize_va_space\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^kernel.randomize_va_space\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Kernel panic on oops [ref]

To set the runtime status of the kernel.panic_on_oops kernel parameter, run the following command:

$ sudo sysctl -w kernel.panic_on_oops=1

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

kernel.panic_on_oops = 1

Warning: The system may start to panic when it normally wouldn't. A non-catastrophic error that would have allowed the system to continue operating will now result in a panic.

Rationale:

An attacker trying to exploit the kernel may trigger kernel OOPSes, panicking the system will impede them from continuing.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sysctl_kernel_panic_on_oops

References:

anssi	R9

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/
    - /usr/lib/sysctl.d/
    contains: ^[\s]*kernel.panic_on_oops.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_kernel_panic_on_oops

- name: Comment out any occurrences of kernel.panic_on_oops from config files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*kernel.panic_on_oops
    replace: '#kernel.panic_on_oops'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_kernel_panic_on_oops

- name: Ensure sysctl kernel.panic_on_oops is set to 1
  sysctl:
    name: kernel.panic_on_oops
    value: '1'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - disable_strategy
  - low_complexity
  - medium_disruption
  - medium_severity
  - reboot_required
  - sysctl_kernel_panic_on_oops

Remediation Shell script ⇲

Complexity:	low
Disruption:	medium
Reboot:	true
Strategy:	disable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

# Comment out any occurrences of kernel.panic_on_oops from /etc/sysctl.d/*.conf files

for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf; do


  # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
  if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

  matching_list=$(grep -P '^(?!#).*[\s]*kernel.panic_on_oops.*$' $f | uniq )
  if ! test -z "$matching_list"; then
    while IFS= read -r entry; do
      escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
      # comment out "kernel.panic_on_oops" matches to preserve user data
      sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
    done <<< "$matching_list"
  fi
done

#
# Set sysctl config file which to save the desired value
#

SYSCONFIG_FILE="/etc/sysctl.conf"


#
# Set runtime for kernel.panic_on_oops
#
/sbin/sysctl -q -n -w kernel.panic_on_oops="1"

#
# If kernel.panic_on_oops present in /etc/sysctl.conf, change value to "1"
#	else, add "kernel.panic_on_oops = 1" to /etc/sysctl.conf
#

# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^kernel.panic_on_oops")

# shellcheck disable=SC2059
printf -v formatted_output "%s = %s" "$stripped_key" "1"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^kernel.panic_on_oops\\>" "${SYSCONFIG_FILE}"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^kernel.panic_on_oops\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
else
    if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
    fi
    printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group SELinux Group contains 6 rules

[ref] SELinux is a feature of the Linux kernel which can be used to guard against misconfigured or compromised programs. SELinux enforces the idea that programs should be limited in what files they can access and what actions they can take.

The default SELinux policy, as configured on Debian 12, has been sufficiently developed and debugged that it should be usable on almost any system with minimal configuration and a small amount of system administrator training. This policy prevents system services - including most of the common network-visible services such as mail servers, FTP servers, and DNS servers - from accessing files which those services have no valid reason to access. This action alone prevents a huge amount of possible damage from network attacks against services, from trojaned software, and so forth.

This guide recommends that SELinux be enabled using the default (targeted) policy on every Debian 12 system, unless that system has unusual requirements which make a stronger policy appropriate.

Rule Verify Group Who Owns /etc/selinux Directory [ref]

To properly set the group owner of /etc/selinux, run the command:

$ sudo chgrp root /etc/selinux

Rationale:

The ownership of the /etc/selinux directory by the root group is important because this directory hosts SELinux configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the SELinux configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_groupowner_etc_selinux

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Ensure group owner on /etc/selinux/
  file:
    path: /etc/selinux/
    state: directory
    group: root
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - directory_groupowner_etc_selinux
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find -H /etc/selinux/ -maxdepth 1 -type d -exec chgrp root {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify User Who Owns /etc/selinux Directory [ref]

To properly set the owner of /etc/selinux, run the command:

$ sudo chown root /etc/selinux

Rationale:

The ownership of the /etc/selinux directory by the root user is important because this directory hosts SELinux configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the SELinux configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_owner_etc_selinux

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Ensure owner on directory /etc/selinux/
  file:
    path: /etc/selinux/
    state: directory
    owner: '0'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - directory_owner_etc_selinux
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find -H /etc/selinux/ -maxdepth 1 -type d -exec chown 0 {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions On /etc/selinux Directory [ref]

To properly set the permissions of /etc/selinux, run the command:

$ sudo chmod 0755 /etc/selinux

Rationale:

Setting correct permissions on the /etc/selinux directory is important because this directory hosts SELinux configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the SELinux configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_directory_permissions_etc_selinux

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Find /etc/selinux/ file(s)
  command: 'find -H /etc/selinux/ -maxdepth 1 -perm /u+s,g+ws,o+wt  -type d '
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - directory_permissions_etc_selinux
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set permissions for /etc/selinux/ file(s)
  file:
    path: '{{ item }}'
    mode: u-s,g-ws,o-wt
    state: directory
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - directory_permissions_etc_selinux
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find -H /etc/selinux/ -maxdepth 1 -perm /u+s,g+ws,o+wt -type d -exec chmod u-s,g-ws,o-wt {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Group Who Owns /etc/sestatus.conf File [ref]

To properly set the group owner of /etc/sestatus.conf, run the command:

$ sudo chgrp root /etc/sestatus.conf

Rationale:

The ownership of the /etc/sestatus.conf file by the root group is important because this file hosts SELinux configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the SELinux configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_sestatus_conf

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/sestatus.conf
  stat:
    path: /etc/sestatus.conf
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_groupowner_etc_sestatus_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner root on /etc/sestatus.conf
  file:
    path: /etc/sestatus.conf
    group: root
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_groupowner_etc_sestatus_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chgrp root /etc/sestatus.conf

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify User Who Owns /etc/sestatus.conf File [ref]

To properly set the owner of /etc/sestatus.conf, run the command:

$ sudo chown root /etc/sestatus.conf

Rationale:

The ownership of the /etc/sestatus.conf file by the root user is important because this file hosts SELinux configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the SELinux configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_sestatus_conf

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/sestatus.conf
  stat:
    path: /etc/sestatus.conf
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_owner_etc_sestatus_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/sestatus.conf
  file:
    path: /etc/sestatus.conf
    owner: '0'
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_owner_etc_sestatus_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chown 0 /etc/sestatus.conf

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions On /etc/sestatus.conf File [ref]

To properly set the permissions of /etc/sestatus.conf, run the command:

$ sudo chmod 0644 /etc/sestatus.conf

Rationale:

Setting correct permissions on the /etc/sestatus.conf file is important because this file hosts SELinux configuration. Protection of this file is critical for system security. Restricting the permissions ensures exclusive control of the SELinux configuration.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_sestatus_conf

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/sestatus.conf
  stat:
    path: /etc/sestatus.conf
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_permissions_etc_sestatus_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xws,o-xwt on /etc/sestatus.conf
  file:
    path: /etc/sestatus.conf
    mode: u-xs,g-xws,o-xwt
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_permissions_etc_sestatus_conf
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chmod u-xs,g-xws,o-xwt /etc/sestatus.conf

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Services Group contains 5 groups and 14 rules

[ref] The best protection against vulnerable software is running less software. This section describes how to review the software which Debian 12 installs on a system and disable software which is not needed. It then enumerates the software packages installed on a default Debian 12 system and provides guidance about which ones can be safely disabled.

Debian 12 provides a convenient minimal install option that essentially installs the bare necessities for a functional system. When building Debian 12 systems, it is highly recommended to select the minimal packages and then build up the system from there.

Group Mail Server Software Group contains 1 group and 1 rule

[ref] Mail servers are used to send and receive email over the network. Mail is a very common service, and Mail Transfer Agents (MTAs) are obvious targets of network attack. Ensure that systems are not running MTAs unnecessarily, and configure needed MTAs as defensively as possible.

Very few systems at any site should be configured to directly receive email over the network. Users should instead use mail client programs to retrieve email from a central server that supports protocols such as IMAP or POP3. However, it is normal for most systems to be independently capable of sending email, for instance so that cron jobs can report output to an administrator. Most MTAs, including Postfix, support a submission-only mode in which mail can be sent from the local system to a central site MTA (or directly delivered to a local account), but the system still cannot receive mail directly over a network.

The alternatives program in Debian 12 permits selection of other mail server software (such as Sendmail), but Postfix is the default and is preferred. Postfix was coded with security in mind and can also be more effectively contained by SELinux as its modular design has resulted in separate processes performing specific actions. More information is available on its website, http://www.postfix.org.

Group Configure SMTP For Mail Clients Group contains 1 rule

[ref] This section discusses settings for Postfix in a submission-only e-mail configuration.

Rule Configure System to Forward All Mail For The Root Account [ref]

Make sure that mails delivered to root user are forwarded to a monitored email address. Make sure that the address change_me@localhost is a valid email address reachable from the system in question. Use the following command to configure the alias:

$ sudo echo "root: change_me@localhost" >> /etc/aliases
$ sudo newaliases

Rationale:

A number of system services utilize email messages sent to the root user to notify system administrators of active or impending issues. These messages must be forwarded to at least one monitored email address.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_postfix_client_configure_mail_alias

References:

disa	CCI-000139, CCI-000366
nist	CM-6(a)
os-srg	SRG-OS-000046-GPOS-00022
anssi	R75

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: XCCDF Value var_postfix_root_mail_alias # promote to variable
  set_fact:
    var_postfix_root_mail_alias: !!str change_me@localhost
  tags:
    - always

- name: Make sure that "/etc/aliases" has a defined value for root
  lineinfile:
    path: /etc/aliases
    line: 'root: {{ var_postfix_root_mail_alias }}'
    regexp: ^(?:[rR][oO][oO][tT]|"[rR][oO][oO][tT]")\s*:\s*(.+)$
    create: true
    state: present
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - postfix_client_configure_mail_alias

- name: Check if newaliases command is available
  ansible.builtin.stat:
    path: /usr/bin/newaliases
  register: result_newaliases_present
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - postfix_client_configure_mail_alias

- name: Update postfix aliases
  ansible.builtin.command:
    cmd: newaliases
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - result_newaliases_present.stat.exists
  tags:
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - postfix_client_configure_mail_alias

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

var_postfix_root_mail_alias='change_me@localhost'


# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^root")

# shellcheck disable=SC2059
printf -v formatted_output "%s: %s" "$stripped_key" "$var_postfix_root_mail_alias"

# If the key exists, change it. Otherwise, add it to the config_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC_ALL=C grep -q -m 1 -i -e "^root\\>" "/etc/aliases"; then
    escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
    LC_ALL=C sed -i --follow-symlinks "s/^root\\>.*/$escaped_formatted_output/gi" "/etc/aliases"
else
    if [[ -s "/etc/aliases" ]] && [[ -n "$(tail -c 1 -- "/etc/aliases" || true)" ]]; then
        LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/aliases"
    fi
    printf '%s\n' "$formatted_output" >> "/etc/aliases"
fi

if [ -f /usr/bin/newaliases ]; then
    newaliases
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group Network Time Protocol Group contains 3 rules

[ref] The Network Time Protocol is used to manage the system clock over a network. Computer clocks are not very accurate, so time will drift unpredictably on unmanaged systems. Central time protocols can be used both to ensure that time is consistent among a network of systems, and that their time is consistent with the outside world.

If every system on a network reliably reports the same time, then it is much easier to correlate log messages in case of an attack. In addition, a number of cryptographic protocols (such as Kerberos) use timestamps to prevent certain types of attacks. If your network does not have synchronized time, these protocols may be unreliable or even unusable.

Depending on the specifics of the network, global time accuracy may be just as important as local synchronization, or not very important at all. If your network is connected to the Internet, using a public timeserver (or one provided by your enterprise) provides globally accurate timestamps which may be essential in investigating or responding to an attack which originated outside of your network.

A typical network setup involves a small number of internal systems operating as NTP servers, and the remainder obtaining time information from those internal servers.

There is a choice between the daemons ntpd and chronyd, which are available from the repositories in the ntp and chrony packages respectively.

The default chronyd daemon can work well when external time references are only intermittently accesible, can perform well even when the network is congested for longer periods of time, can usually synchronize the clock faster and with better time accuracy, and quickly adapts to sudden changes in the rate of the clock, for example, due to changes in the temperature of the crystal oscillator. Chronyd should be considered for all systems which are frequently suspended or otherwise intermittently disconnected and reconnected to a network. Mobile and virtual systems for example.

The ntpd NTP daemon fully supports NTP protocol version 4 (RFC 5905), including broadcast, multicast, manycast clients and servers, and the orphan mode. It also supports extra authentication schemes based on public-key cryptography (RFC 5906). The NTP daemon (ntpd) should be considered for systems which are normally kept permanently on. Systems which are required to use broadcast or multicast IP, or to perform authentication of packets with the Autokey protocol, should consider using ntpd.

Refer to https://wiki.debian.org/NTP for more detailed comparison of features of chronyd and ntpd daemon features respectively, and for further guidance how to choose between the two NTP daemons.

The upstream manual pages at https://chrony-project.org/documentation.html for chronyd and http://www.ntp.org for ntpd provide additional information on the capabilities and configuration of each of the NTP daemons.

Rule Verify Group Who Owns /etc/chrony.keys File [ref]

To properly set the group owner of /etc/chrony.keys, run the command:

$ sudo chgrp root /etc/chrony.keys

Rationale:

The ownership of the /etc/chrony.keys file by the root group is important because this file hosts chrony cryptographic keys. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the chrony cryptography keys.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_etc_chrony_keys

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/chrony.keys
  stat:
    path: /etc/chrony.keys
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_groupowner_etc_chrony_keys
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner root on /etc/chrony.keys
  file:
    path: /etc/chrony.keys
    group: root
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_groupowner_etc_chrony_keys
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chgrp root /etc/chrony.keys

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify User Who Owns /etc/chrony.keys File [ref]

To properly set the owner of /etc/chrony.keys, run the command:

$ sudo chown root /etc/chrony.keys

Rationale:

The ownership of the /etc/chrony.keys file by the root user is important because this file hosts chrony cryptographic keys. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the chrony cryptographic keys.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_etc_chrony_keys

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/chrony.keys
  stat:
    path: /etc/chrony.keys
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_owner_etc_chrony_keys
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/chrony.keys
  file:
    path: /etc/chrony.keys
    owner: '0'
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_owner_etc_chrony_keys
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chown 0 /etc/chrony.keys

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions On /etc/chrony.keys File [ref]

To properly set the permissions of /etc/chrony.keys, run the command:

$ sudo chmod 0600 /etc/chrony.keys

Rationale:

Setting correct permissions on the /etc/chrony.keys file is important because this file hosts chrony cryptographic keys. Protection of this file is critical for system security. Assigning the correct mode ensures exclusive control of the chrony cryptographic keys.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_etc_chrony_keys

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/chrony.keys
  stat:
    path: /etc/chrony.keys
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_permissions_etc_chrony_keys
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xwrs,o-xwrt on /etc/chrony.keys
  file:
    path: /etc/chrony.keys
    mode: u-xs,g-xwrs,o-xwrt
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_permissions_etc_chrony_keys
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chmod u-xs,g-xwrs,o-xwrt /etc/chrony.keys

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group SSH Server Group contains 1 group and 10 rules

[ref] The SSH protocol is recommended for remote login and remote file transfer. SSH provides confidentiality and integrity for data exchanged between two systems, as well as server authentication, through the use of public key cryptography. The implementation included with the system is called OpenSSH, and more detailed documentation is available from its website, https://www.openssh.com. Its server program is called sshd and provided by the RPM package openssh-server.

Group Configure OpenSSH Server if Necessary Group contains 1 rule

[ref] If the system needs to act as an SSH server, then certain changes should be made to the OpenSSH daemon configuration file /etc/ssh/sshd_config. The following recommendations can be applied to this file. See the sshd_config(5) man page for more detailed information.

Rule Disable SSH Root Login [ref]

The root user should never be allowed to login to a system directly over a network. To disable root login via SSH, add or correct the following line in /etc/ssh/sshd_config:

PermitRootLogin no

Rationale:

Even though the communications channel may be encrypted, an additional layer of security is gained by extending the policy of not logging directly on as root. In addition, logging in with a user-specific account provides individual accountability of actions performed on the system and also helps to minimize direct attack attempts on root's password.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_sshd_disable_root_login

References:

cis-csc	1, 11, 12, 13, 14, 15, 16, 18, 3, 5
cjis	5.5.6
cobit5	APO01.06, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.02, DSS06.03, DSS06.06, DSS06.10
cui	3.1.1, 3.1.5
disa	CCI-000366, CCI-000770
hipaa	164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009	4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013	SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.18.1.4, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.2.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist	AC-6(2), AC-17(a), IA-2, IA-2(5), CM-7(a), CM-7(b), CM-6(a)
nist-csf	PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.DS-5, PR.PT-3
ospp	FAU_GEN.1
pcidss	Req-2.2.4
os-srg	SRG-OS-000109-GPOS-00056, SRG-OS-000480-GPOS-00227
app-srg-ctr	SRG-APP-000148-CTR-000335, SRG-APP-000190-CTR-000500
anssi	R33
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

- name: Disable SSH Root Login
  block:

  - name: Check for duplicate values
    lineinfile:
      path: /etc/ssh/sshd_config
      create: true
      regexp: (?i)^\s*PermitRootLogin\s+
      state: absent
    check_mode: true
    changed_when: false
    register: dupes

  - name: Deduplicate values from /etc/ssh/sshd_config
    lineinfile:
      path: /etc/ssh/sshd_config
      create: true
      regexp: (?i)^\s*PermitRootLogin\s+
      state: absent
    when: dupes.found is defined and dupes.found > 1

  - name: Insert correct line to /etc/ssh/sshd_config
    lineinfile:
      path: /etc/ssh/sshd_config
      create: true
      regexp: (?i)^\s*PermitRootLogin\s+
      line: PermitRootLogin no
      state: present
      insertbefore: BOF
      validate: /usr/sbin/sshd -t -f %s
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - CJIS-5.5.6
  - NIST-800-171-3.1.1
  - NIST-800-171-3.1.5
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(2)
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - NIST-800-53-IA-2
  - NIST-800-53-IA-2(5)
  - PCI-DSS-Req-2.2.4
  - PCI-DSSv4-2.2.6
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
  - sshd_disable_root_login

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	restrict

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

if [ -e "/etc/ssh/sshd_config" ] ; then
    
    LC_ALL=C sed -i "/^\s*PermitRootLogin\s\+/Id" "/etc/ssh/sshd_config"
else
    touch "/etc/ssh/sshd_config"
fi
# make sure file has newline at the end
sed -i -e '$a\' "/etc/ssh/sshd_config"

cp "/etc/ssh/sshd_config" "/etc/ssh/sshd_config.bak"
# Insert at the beginning of the file
printf '%s\n' "PermitRootLogin no" > "/etc/ssh/sshd_config"
cat "/etc/ssh/sshd_config.bak" >> "/etc/ssh/sshd_config"
# Clean up after ourselves.
rm "/etc/ssh/sshd_config.bak"

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Group Who Owns SSH Server config file [ref]

To properly set the group owner of /etc/ssh/sshd_config, run the command:

$ sudo chgrp root /etc/ssh/sshd_config

Rationale:

Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupowner_sshd_config

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	AC-17(a), CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/ssh/sshd_config
  stat:
    path: /etc/ssh/sshd_config
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_groupowner_sshd_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner 0 on /etc/ssh/sshd_config
  file:
    path: /etc/ssh/sshd_config
    group: '0'
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_groupowner_sshd_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chgrp 0 /etc/ssh/sshd_config

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Group Ownership on SSH Server Private *_key Key Files [ref]

SSH server private keys, files that match the /etc/ssh/*_key glob, must be group-owned by root group.

Rationale:

If an unauthorized user obtains the private SSH host key file, the host could be impersonated.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupownership_sshd_private_key

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Find /etc/ssh/ file(s) matching ^.*_key$
  command: find -H /etc/ssh/ -maxdepth 1 -type f ! -group 0 -regex "^.*_key$"
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_groupownership_sshd_private_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner on /etc/ssh/ file(s) matching ^.*_key$
  file:
    path: '{{ item }}'
    group: '0'
    state: file
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_groupownership_sshd_private_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find /etc/ssh/ -maxdepth 1 -type f ! -group 0 -regex '^.*_key$' -exec chgrp 0 {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Group Ownership on SSH Server Public *.pub Key Files [ref]

SSH server public keys, files that match the /etc/ssh/*.pub glob, must be group-owned by root group.

Rationale:

If a public host key file is modified by an unauthorized user, the SSH service may be compromised.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_groupownership_sshd_pub_key

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Find /etc/ssh/ file(s) matching ^.*\.pub$
  command: find -H /etc/ssh/ -maxdepth 1 -type f ! -group 0 -regex "^.*\.pub$"
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_groupownership_sshd_pub_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner on /etc/ssh/ file(s) matching ^.*\.pub$
  file:
    path: '{{ item }}'
    group: '0'
    state: file
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_groupownership_sshd_pub_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find /etc/ssh/ -maxdepth 1 -type f ! -group 0 -regex '^.*\.pub$' -exec chgrp 0 {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Owner on SSH Server config file [ref]

To properly set the owner of /etc/ssh/sshd_config, run the command:

$ sudo chown root /etc/ssh/sshd_config

Rationale:

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_owner_sshd_config

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	AC-17(a), CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/ssh/sshd_config
  stat:
    path: /etc/ssh/sshd_config
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_owner_sshd_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /etc/ssh/sshd_config
  file:
    path: /etc/ssh/sshd_config
    owner: '0'
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - configure_strategy
  - file_owner_sshd_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chown 0 /etc/ssh/sshd_config

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Ownership on SSH Server Private *_key Key Files [ref]

SSH server private keys, files that match the /etc/ssh/*_key glob, must be owned by root user.

Rationale:

If an unauthorized user obtains the private SSH host key file, the host could be impersonated.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_ownership_sshd_private_key

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Find /etc/ssh/ file(s) matching ^.*_key$
  command: find -H /etc/ssh/ -maxdepth 1 -type f ! -uid 0 -regex "^.*_key$"
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_ownership_sshd_private_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner on /etc/ssh/ file(s) matching ^.*_key$
  file:
    path: '{{ item }}'
    owner: '0'
    state: file
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_ownership_sshd_private_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find /etc/ssh/ -maxdepth 1 -type f ! -uid 0 -regex '^.*_key$' -exec chown 0 {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Ownership on SSH Server Public *.pub Key Files [ref]

SSH server public keys, files that match the /etc/ssh/*.pub glob, must be owned by root user.

Rationale:

If a public host key file is modified by an unauthorized user, the SSH service may be compromised.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_ownership_sshd_pub_key

References:

anssi	R50

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Find /etc/ssh/ file(s) matching ^.*\.pub$
  command: find -H /etc/ssh/ -maxdepth 1 -type f ! -uid 0 -regex "^.*\.pub$"
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_ownership_sshd_pub_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner on /etc/ssh/ file(s) matching ^.*\.pub$
  file:
    path: '{{ item }}'
    owner: '0'
    state: file
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - file_ownership_sshd_pub_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find /etc/ssh/ -maxdepth 1 -type f ! -uid 0 -regex '^.*\.pub$' -exec chown 0 {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions on SSH Server config file [ref]

To properly set the permissions of /etc/ssh/sshd_config, run the command:

$ sudo chmod 0600 /etc/ssh/sshd_config

Rationale:

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_sshd_config

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	AC-17(a), CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Test for existence /etc/ssh/sshd_config
  stat:
    path: /etc/ssh/sshd_config
  register: file_exists
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_sshd_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure permission u-xs,g-xwrs,o-xwrt on /etc/ssh/sshd_config
  file:
    path: /etc/ssh/sshd_config
    mode: u-xs,g-xwrs,o-xwrt
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_sshd_config
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

chmod u-xs,g-xwrs,o-xwrt /etc/ssh/sshd_config

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions on SSH Server Private *_key Key Files [ref]

SSH server private keys - files that match the /etc/ssh/*_key glob, have to have restricted permissions. If those files are owned by the root user and the root group, they have to have the 0600 permission or stricter.

Rationale:

If an unauthorized user obtains the private SSH host key file, the host could be impersonated.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_sshd_private_key

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
cui	3.1.13, 3.13.10
disa	CCI-000366
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	AC-17(a), CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-2.2.4
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Find root:root-owned keys
  ansible.builtin.command: find -H /etc/ssh/ -maxdepth 1 -user root -regex ".*_key$"
    -type f -group root -perm /u+xs,g+xwrs,o+xwrt
  register: root_owned_keys
  changed_when: false
  failed_when: false
  check_mode: false
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.13
  - NIST-800-171-3.13.10
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-2.2.4
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_sshd_private_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set permissions for root:root-owned keys
  ansible.builtin.file:
    path: '{{ item }}'
    mode: u-xs,g-xwrs,o-xwrt
    state: file
  with_items:
  - '{{ root_owned_keys.stdout_lines }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.13
  - NIST-800-171-3.13.10
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-2.2.4
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_sshd_private_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Puppet snippet ⇲

include ssh_private_key_perms

class ssh_private_key_perms {
  exec { 'sshd_priv_key':
    command => "chmod 0640 /etc/ssh/*_key",
    path    => '/bin:/usr/bin'
  }
}

Remediation Shell script ⇲

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

for keyfile in /etc/ssh/*_key; do
    test -f "$keyfile" || continue
    if test root:root = "$(stat -c "%U:%G" "$keyfile")"; then
    
	chmod u-xs,g-xwrs,o-xwrt "$keyfile"
    
    
    else
        echo "Key-like file '$keyfile' is owned by an unexpected user:group combination"
    fi
done

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Verify Permissions on SSH Server Public *.pub Key Files [ref]

To properly set the permissions of /etc/ssh/*.pub, run the command:

$ sudo chmod 0644 /etc/ssh/*.pub

Rationale:

If a public host key file is modified by an unauthorized user, the SSH service may be compromised.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_file_permissions_sshd_pub_key

References:

cis-csc	12, 13, 14, 15, 16, 18, 3, 5
cobit5	APO01.06, DSS05.04, DSS05.07, DSS06.02
cui	3.1.13, 3.13.10
disa	CCI-000366
isa-62443-2009	4.3.3.7.3
isa-62443-2013	SR 2.1, SR 5.2
iso27001-2013	A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip	CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist	AC-17(a), CM-6(a), AC-6(1)
nist-csf	PR.AC-4, PR.DS-5
pcidss	Req-2.2.4
os-srg	SRG-OS-000480-GPOS-00227
anssi	R50
pcidss4	2.2.6

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

- name: Find /etc/ssh/ file(s)
  command: find -H /etc/ssh/ -maxdepth 1 -perm /u+xs,g+xws,o+xwt  -type f -regex "^.*\.pub$"
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.13
  - NIST-800-171-3.13.10
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-2.2.4
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_sshd_pub_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set permissions for /etc/ssh/ file(s)
  file:
    path: '{{ item }}'
    mode: u-xs,g-xws,o-xwt
    state: file
  with_items:
  - '{{ files_found.stdout_lines }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.13
  - NIST-800-171-3.13.10
  - NIST-800-53-AC-17(a)
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-2.2.4
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_permissions_sshd_pub_key
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

Remediation Puppet snippet ⇲

include ssh_public_key_perms

class ssh_public_key_perms {
  exec { 'sshd_pub_key':
    command => "chmod 0644 /etc/ssh/*.pub",
    path    => '/bin:/usr/bin'
  }
}

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	configure

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

find -H /etc/ssh/ -maxdepth 1 -perm /u+xs,g+xws,o+xwt  -type f -regex '^.*\.pub$' -exec chmod u-xs,g-xws,o-xwt {} \;

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Group System Accounting with auditd Group contains 2 rules

[ref] The audit service provides substantial capabilities for recording system activities. By default, the service audits about SELinux AVC denials and certain types of security-relevant events such as system logins, account modifications, and authentication events performed by programs such as sudo. Under its default configuration, auditd has modest disk space requirements, and should not noticeably impact system performance.

NOTE: The Linux Audit daemon auditd can be configured to use the augenrules program to read audit rules files (*.rules) located in /etc/audit/rules.d location and compile them to create the resulting form of the /etc/audit/audit.rules configuration file during the daemon startup (default configuration). Alternatively, the auditd daemon can use the auditctl utility to read audit rules from the /etc/audit/audit.rules configuration file during daemon startup, and load them into the kernel. The expected behavior is configured via the appropriate ExecStartPost directive setting in the /usr/lib/systemd/system/auditd.service configuration file. To instruct the auditd daemon to use the augenrules program to read audit rules (default configuration), use the following setting:

ExecStartPost=-/sbin/augenrules --load

in the /usr/lib/systemd/system/auditd.service configuration file. In order to instruct the auditd daemon to use the auditctl utility to read audit rules, use the following setting:

ExecStartPost=-/sbin/auditctl -R /etc/audit/audit.rules

in the /usr/lib/systemd/system/auditd.service configuration file. Refer to [Service] section of the /usr/lib/systemd/system/auditd.service configuration file for further details.

Government networks often have substantial auditing requirements and auditd can be configured to meet these requirements. Examining some example audit records demonstrates how the Linux audit system satisfies common requirements. The following example from Red Hat Enterprise Linux 7 Documentation available at

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html-single/selinux_users_and_administrators_guide/index#sect-Security-Enhanced_Linux-Fixing_Problems-Raw_Audit_Messages

shows the substantial amount of information captured in a two typical "raw" audit messages, followed by a breakdown of the most important fields. In this example the message is SELinux-related and reports an AVC denial (and the associated system call) that occurred when the Apache HTTP Server attempted to access the /var/www/html/file1 file (labeled with the samba_share_t type):

type=AVC msg=audit(1226874073.147:96): avc:  denied  { getattr } for pid=2465 comm="httpd"
path="/var/www/html/file1" dev=dm-0 ino=284133 scontext=unconfined_u:system_r:httpd_t:s0
tcontext=unconfined_u:object_r:samba_share_t:s0 tclass=file

type=SYSCALL msg=audit(1226874073.147:96): arch=40000003 syscall=196 success=no exit=-13
a0=b98df198 a1=bfec85dc a2=54dff4 a3=2008171 items=0 ppid=2463 pid=2465 auid=502 uid=48
gid=48 euid=48 suid=48 fsuid=48 egid=48 sgid=48 fsgid=48 tty=(none) ses=6 comm="httpd"
exe="/usr/sbin/httpd" subj=unconfined_u:system_r:httpd_t:s0 key=(null)

msg=audit(1226874073.147:96)
- The number in parentheses is the unformatted time stamp (Epoch time) for the event, which can be converted to standard time by using the date command.
{ getattr }
- The item in braces indicates the permission that was denied. getattr indicates the source process was trying to read the target file's status information. This occurs before reading files. This action is denied due to the file being accessed having the wrong label. Commonly seen permissions include getattr, read, and write.
comm="httpd"
- The executable that launched the process. The full path of the executable is found in the exe= section of the system call (SYSCALL) message, which in this case, is exe="/usr/sbin/httpd".
path="/var/www/html/file1"
- The path to the object (target) the process attempted to access.
scontext="unconfined_u:system_r:httpd_t:s0"
- The SELinux context of the process that attempted the denied action. In this case, it is the SELinux context of the Apache HTTP Server, which is running in the httpd_t domain.
tcontext="unconfined_u:object_r:samba_share_t:s0"
- The SELinux context of the object (target) the process attempted to access. In this case, it is the SELinux context of file1. Note: the samba_share_t type is not accessible to processes running in the httpd_t domain.
From the system call (SYSCALL) message, two items are of interest:
- success=no: indicates whether the denial (AVC) was enforced or not. success=no indicates the system call was not successful (SELinux denied access). success=yes indicates the system call was successful - this can be seen for permissive domains or unconfined domains, such as initrc_t and kernel_t.
- exe="/usr/sbin/httpd": the full path to the executable that launched the process, which in this case, is exe="/usr/sbin/httpd".

Rule Ensure the audit Subsystem is Installed [ref]

The audit package should be installed.

Rationale:

The auditd service is an access monitoring and accounting daemon, watching system calls to audit any access, in comparison with potential local access control policy such as SELinux policy.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_package_audit_installed

References:

disa	CCI-000130, CCI-000131, CCI-000132, CCI-000133, CCI-000134, CCI-000135, CCI-000154, CCI-000158, CCI-000172, CCI-001464, CCI-001487, CCI-001814, CCI-001875, CCI-001876, CCI-001877, CCI-001878, CCI-001879, CCI-001880, CCI-001881, CCI-001882, CCI-001889, CCI-001914, CCI-002884, CCI-000169
hipaa	164.308(a)(1)(ii)(D), 164.308(a)(5)(ii)(C), 164.310(a)(2)(iv), 164.310(d)(2)(iii), 164.312(b)
nerc-cip	CIP-004-6 R3.3, CIP-007-3 R6.5
nist	AC-7(a), AU-7(1), AU-7(2), AU-14, AU-12(2), AU-2(a), CM-6(a)
ospp	FAU_GEN.1
pcidss	Req-10.1
os-srg	SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000038-GPOS-00016, SRG-OS-000039-GPOS-00017, SRG-OS-000040-GPOS-00018, SRG-OS-000041-GPOS-00019, SRG-OS-000042-GPOS-00021, SRG-OS-000051-GPOS-00024, SRG-OS-000054-GPOS-00025, SRG-OS-000122-GPOS-00063, SRG-OS-000254-GPOS-00095, SRG-OS-000255-GPOS-00096, SRG-OS-000337-GPOS-00129, SRG-OS-000348-GPOS-00136, SRG-OS-000349-GPOS-00137, SRG-OS-000350-GPOS-00138, SRG-OS-000351-GPOS-00139, SRG-OS-000352-GPOS-00140, SRG-OS-000353-GPOS-00141, SRG-OS-000354-GPOS-00142, SRG-OS-000358-GPOS-00145, SRG-OS-000365-GPOS-00152, SRG-OS-000392-GPOS-00172, SRG-OS-000475-GPOS-00220
anssi	R33, R73
pcidss4	10.2.1

Remediation OSBuild Blueprint snippet ⇲


[[packages]]
name = "auditd"
version = "*"

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

- name: Ensure auditd is installed
  package:
    name: auditd
    state: present
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-7(a)
  - NIST-800-53-AU-12(2)
  - NIST-800-53-AU-14
  - NIST-800-53-AU-2(a)
  - NIST-800-53-AU-7(1)
  - NIST-800-53-AU-7(2)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-10.1
  - PCI-DSSv4-10.2.1
  - enable_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - package_audit_installed

Remediation Puppet snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

include install_auditd

class install_auditd {
  package { 'auditd':
    ensure => 'installed',
  }
}

Remediation Shell script ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

DEBIAN_FRONTEND=noninteractive apt-get install -y "auditd"

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Rule Enable auditd Service [ref]

The auditd service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The auditd service can be enabled with the following command:

$ sudo systemctl enable auditd.service

Rationale:

Without establishing what type of events occurred, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack. Ensuring the auditd service is active ensures audit records generated by the kernel are appropriately recorded.

Additionally, a properly configured audit subsystem ensures that actions of individual system users can be uniquely traced to those users so they can be held accountable for their actions.

Severity:

medium

Rule ID: xccdf_org.ssgproject.content_rule_service_auditd_enabled

References:

cis-csc	1, 11, 12, 13, 14, 15, 16, 19, 2, 3, 4, 5, 6, 7, 8, 9
cjis	5.4.1.1
cobit5	APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO12.06, APO13.01, BAI03.05, BAI08.02, DSS01.03, DSS01.04, DSS02.02, DSS02.04, DSS02.07, DSS03.01, DSS03.05, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01
cui	3.3.1, 3.3.2, 3.3.6
disa	CCI-000126, CCI-000130, CCI-000131, CCI-000132, CCI-000133, CCI-000134, CCI-000135, CCI-000154, CCI-000158, CCI-000172, CCI-000366, CCI-001464, CCI-001487, CCI-001814, CCI-001875, CCI-001876, CCI-001877, CCI-002884, CCI-001878, CCI-001879, CCI-001880, CCI-001881, CCI-001882, CCI-001889, CCI-001914, CCI-000169
hipaa	164.308(a)(1)(ii)(D), 164.308(a)(5)(ii)(C), 164.310(a)(2)(iv), 164.310(d)(2)(iii), 164.312(b)
isa-62443-2009	4.2.3.10, 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.3.6.6, 4.3.4.4.7, 4.3.4.5.6, 4.3.4.5.7, 4.3.4.5.8, 4.4.2.1, 4.4.2.2, 4.4.2.4
isa-62443-2013	SR 1.13, SR 2.10, SR 2.11, SR 2.12, SR 2.6, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.1, SR 6.2, SR 7.1, SR 7.6
iso27001-2013	A.11.2.6, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.7, A.15.2.1, A.15.2.2, A.16.1.4, A.16.1.5, A.16.1.7, A.6.2.1, A.6.2.2
nerc-cip	CIP-004-6 R3.3, CIP-007-3 R6.5
nist	AC-2(g), AU-3, AU-10, AU-2(d), AU-12(c), AU-14(1), AC-6(9), CM-6(a), SI-4(23)
nist-csf	DE.AE-3, DE.AE-5, DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.AC-3, PR.PT-1, PR.PT-4, RS.AN-1, RS.AN-4
ospp	FAU_GEN.1
pcidss	Req-10.1
os-srg	SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000038-GPOS-00016, SRG-OS-000039-GPOS-00017, SRG-OS-000040-GPOS-00018, SRG-OS-000041-GPOS-00019, SRG-OS-000042-GPOS-00021, SRG-OS-000051-GPOS-00024, SRG-OS-000054-GPOS-00025, SRG-OS-000122-GPOS-00063, SRG-OS-000254-GPOS-00095, SRG-OS-000255-GPOS-00096, SRG-OS-000337-GPOS-00129, SRG-OS-000348-GPOS-00136, SRG-OS-000349-GPOS-00137, SRG-OS-000350-GPOS-00138, SRG-OS-000351-GPOS-00139, SRG-OS-000352-GPOS-00140, SRG-OS-000353-GPOS-00141, SRG-OS-000354-GPOS-00142, SRG-OS-000358-GPOS-00145, SRG-OS-000365-GPOS-00152, SRG-OS-000392-GPOS-00172, SRG-OS-000475-GPOS-00220
app-srg-ctr	SRG-APP-000095-CTR-000170, SRG-APP-000409-CTR-000990, SRG-APP-000508-CTR-001300, SRG-APP-000510-CTR-001310
anssi	R33, R73
pcidss4	10.2.1

Remediation OSBuild Blueprint snippet ⇲


[customizations.services]
enabled = ["auditd"]

Remediation Ansible snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - CJIS-5.4.1.1
  - NIST-800-171-3.3.1
  - NIST-800-171-3.3.2
  - NIST-800-171-3.3.6
  - NIST-800-53-AC-2(g)
  - NIST-800-53-AC-6(9)
  - NIST-800-53-AU-10
  - NIST-800-53-AU-12(c)
  - NIST-800-53-AU-14(1)
  - NIST-800-53-AU-2(d)
  - NIST-800-53-AU-3
  - NIST-800-53-CM-6(a)
  - NIST-800-53-SI-4(23)
  - PCI-DSS-Req-10.1
  - PCI-DSSv4-10.2.1
  - enable_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - service_auditd_enabled

- name: Enable auditd Service - Enable service auditd
  block:

  - name: Gather the package facts
    package_facts:
      manager: auto

  - name: Enable auditd Service - Enable Service auditd
    ansible.builtin.systemd:
      name: auditd
      enabled: true
      state: started
      masked: false
    when:
    - '"auditd" in ansible_facts.packages'
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - '"auditd" in ansible_facts.packages'
  tags:
  - CJIS-5.4.1.1
  - NIST-800-171-3.3.1
  - NIST-800-171-3.3.2
  - NIST-800-171-3.3.6
  - NIST-800-53-AC-2(g)
  - NIST-800-53-AC-6(9)
  - NIST-800-53-AU-10
  - NIST-800-53-AU-12(c)
  - NIST-800-53-AU-14(1)
  - NIST-800-53-AU-2(d)
  - NIST-800-53-AU-3
  - NIST-800-53-CM-6(a)
  - NIST-800-53-SI-4(23)
  - PCI-DSS-Req-10.1
  - PCI-DSSv4-10.2.1
  - enable_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - service_auditd_enabled

Remediation Puppet snippet ⇲

Complexity:	low
Disruption:	low
Reboot:	false
Strategy:	enable

include enable_auditd

class enable_auditd {
  service {'auditd':
    enable => true,
    ensure => 'running',
  }
}

Red Hat and Red Hat Enterprise Linux are either registered trademarks or trademarks of Red Hat, Inc. in the United States and other countries. All other names are registered trademarks or trademarks of their respective companies.