Title

NixOS audit system must protect login UIDs from unauthorized change. (Cat II impact)

Discussion

If audit information were to become compromised, then forensic analysis and discovery of the true source of potentially malicious system activity is impossible to achieve. Audit information includes all information (e.g., audit records, audit settings, audit reports) needed to successfully audit system activity. In immutable mode, unauthorized users cannot execute changes to the audit system to potentially hide malicious activity and then put the audit rules back. A system reboot would be noticeable and a system administrator could then investigate the unauthorized changes. Satisfies: SRG-OS-000058-GPOS-00028, SRG-OS-000059-GPOS-00029

Check Content

Verify the audit system prevents unauthorized changes to login UIDs with the following command: $ sudo auditctl -s | grep -i immutable loginuid_immutable 1 locked If the command does not return "loginuid_immutable 1 locked", this is a finding.

Fix Text

Configure NixOS to prevent unauthorized changes to login UIDs. Add or update the "security.audit.rules" configuration in /etc/nixos/configuration.nix to include the following rule: security.audit.rules = [ "--loginuid-immutable" ]; Rebuild the NixOS configuration with the following command: $ sudo nixos-rebuild switch

Additional Identifiers

Rule ID: SV-268119r1039577_rule

Vulnerability ID: V-268119

Group Title: SRG-OS-000058-GPOS-00028

Expert Comments

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