Title

NixOS must allocate an audit_backlog_limit of sufficient size to capture processes that start prior to the audit daemon. (Cat II impact)

Discussion

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. If auditing is enabled late in the startup process, the actions of some startup processes may not be audited. Some audit systems also maintain state information only available if auditing is enabled before a given process is created. Audit records can be generated from various components within the information system (e.g., module or policy filter). Allocating an audit_backlog_limit of sufficient size is critical in maintaining a stable boot process. With an insufficient limit allocated, the system is susceptible to boot failures and crashes. Satisfies: SRG-OS-000042-GPOS-00020, SRG-OS-000341-GPOS-00132

Check Content

Verify NixOS allocates a sufficient audit_backlog_limit to capture processes that start prior to the audit daemon with the following command: $ grep backlog_limit /proc/cmdline BOOT_IMAGE=(hd0,msdos1)/nix/store/glc0midc78caq9sc7pzciymx4c3in7kn-linux-6.1.64/bzImage init=/nix/store/grl4baymr9q60mbcz3sidm4agckn3bx5-nixos-system-nixos-23.1.1.20231129.057f9ae/init audit=1 audit_backlog_limit=8192 loglevel=4 If the "audit_backlog_limit" entry does not equal "8192" or greater or is missing, this is a finding.

Fix Text

Configure NixOS to allocate sufficient audit_backlog_limit to capture processes that start prior to the audit daemon. Add or update the "boot.kernelParams" configuration in /etc/nixos/configuration.nix to include the following rule: boot.kernelParams = [ "audit_backlog_limit=8192" ]; Rebuild the NixOS configuration with the following command: $ sudo nixos-rebuild switch

Additional Identifiers

Rule ID: SV-268093r1039167_rule

Vulnerability ID: V-268093

Group Title: SRG-OS-000042-GPOS-00020

Expert Comments

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