Guide to the Secure Configuration of Red Hat Enterprise Linux CoreOS 4
with profile DRAFT - ANSSI-BP-028 (minimal)This profile contains configurations that align to ANSSI-BP-028 at the minimal 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
https://www.open-scap.org/security-policies/scap-security-guide
This guide presents a catalog of security-relevant
configuration settings for Red Hat Enterprise Linux CoreOS 4. 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
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.
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 | DRAFT - ANSSI-BP-028 (minimal) |
|---|---|
| Profile ID | xccdf_org.ssgproject.content_profile_anssi_bp28_minimal |
CPE Platforms
- cpe:/o:redhat:enterprise_linux_coreos:4
Revision History
Current version: 0.1.76
- draft (as of 2024-11-29)
Table of Contents
Checklist
| Group Guide to the Secure Configuration of Red Hat Enterprise Linux CoreOS 4 Group contains 15 groups and 9 rules | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Group System Settings Group contains 10 groups and 7 rules | ||||||||||||||||||||||||||||||||||||||||||||||||||
[ref]
Contains rules that check correct system settings. | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Group Installing and Maintaining Software Group contains 1 group and 1 rule | ||||||||||||||||||||||||||||||||||||||||||||||||||
[ref]
The following sections contain information on
security-relevant choices during the initial operating system
installation process and the setup of software
updates. | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Group Updating Software Group contains 1 rule | ||||||||||||||||||||||||||||||||||||||||||||||||||
[ref]
The dnf command line tool is used to install and
update software packages. The system also provides a graphical
software update tool in the System menu, in the Administration submenu,
called Software Update.
Red Hat Enterprise Linux CoreOS 4 systems contain an installed software catalog called the RPM database, which records metadata of installed packages. Consistently using dnf or the graphical Software Update for all software installation
allows for insight into the current inventory of installed software on the system.
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| Group Account and Access Control Group contains 5 groups and 4 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
Red Hat Enterprise Linux CoreOS 4. | ||||||||||||||||||||||||||||||||||||||||||||||||||
| 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 = 3The arguments can be modified to ensure compliance with your organization's security policy. Discussion of each parameter follows. | ||||||||||||||||||||||||||||||||||||||||||||||||||
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| Group Protect Accounts by Restricting Password-Based Login Group contains 1 group 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 2 rules | ||||||||||||||||||||||||||||||||||||||||||||||||||
[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 | ||||||||||||||||||||||||||||||||||||||||||||||||||
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| Group File Permissions and Masks Group contains 1 group and 2 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 Red Hat Enterprise Linux CoreOS 4 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 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. | ||||||||||||||||||||||||||||||||||||||||||||||||||
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| Group Services Group contains 3 groups and 2 rules | ||||||||||||||||||||||||||||||||||||||||||||||||||
[ref]
The best protection against vulnerable software is running less software. This section describes how to review
the software which Red Hat Enterprise Linux CoreOS 4 installs on a system and disable software which is not needed. It
then enumerates the software packages installed on a default Red Hat Enterprise Linux CoreOS 4 system and provides guidance about which
ones can be safely disabled.
Red Hat Enterprise Linux CoreOS 4 provides a convenient minimal install option that essentially installs the bare necessities for a functional system. When building Red Hat Enterprise Linux CoreOS 4 systems, it is highly recommended to select the minimal packages and then build up the system from there. | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Group DHCP Group contains 1 group and 1 rule | ||||||||||||||||||||||||||||||||||||||||||||||||||
[ref]
The Dynamic Host Configuration Protocol (DHCP) allows
systems to request and obtain an IP address and other configuration
parameters from a server.
This guide recommends configuring networking on clients by manually editing the appropriate files under /etc/sysconfig. Use of DHCP can make client
systems vulnerable to compromise by rogue DHCP servers, and should be avoided
unless necessary. If using DHCP is necessary, however, there are best practices
that should be followed to minimize security risk. | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Group Disable DHCP Server Group contains 1 rule | ||||||||||||||||||||||||||||||||||||||||||||||||||
[ref]
The DHCP server dhcpd is not installed or activated by
default. If the software was installed and activated, but the
system does not need to act as a DHCP server, it should be disabled
and removed. | ||||||||||||||||||||||||||||||||||||||||||||||||||
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| Group Mail Server Software Group contains 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 Red Hat Enterprise Linux CoreOS 4 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. | ||||||||||||||||||||||||||||||||||||||||||||||||||
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