Guide to the Secure Configuration of Debian 12
with profile ANSSI-BP-028 (minimal)This profile contains configurations that align to ANSSI-BP-028 v2.0 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 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
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 | ANSSI-BP-028 (minimal) |
|---|---|
| Profile ID | xccdf_org.ssgproject.content_profile_anssi_bp28_minimal |
CPE Platforms
- cpe:/o:debian:debian_linux:12
Revision History
Current version: 0.1.73
- draft (as of 2024-05-09)
Table of Contents
Checklist
| Group Guide to the Secure Configuration of Debian 12 Group contains 9 groups and 5 rules | ||||||||||||||||||||||||||||||||||||||||||
| Group System Settings Group contains 8 groups and 5 rules | ||||||||||||||||||||||||||||||||||||||||||
[ref]
Contains rules that check correct system settings. | ||||||||||||||||||||||||||||||||||||||||||
| Group Account and Access Control Group contains 5 groups and 3 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 = 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 1 rule | ||||||||||||||||||||||||||||||||||||||||||
[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 | ||||||||||||||||||||||||||||||||||||||||||
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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 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 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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