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V-268093

CAT II (Medium)

NixOS must allocate an audit_backlog_limit of sufficient size to capture processes that start prior to the audit daemon.

Rule ID

SV-268093r1130988_rule

STIG

Anduril NixOS Security Technical Implementation Guide

Version

V1R2

CCIs

CCI-000135, CCI-001849

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:

$ sudo auditctl -s | grep backlog_limit

backlog_limit 8192 

If the "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 the following Nix code to the NixOS Configuration, usually located in /etc/nixos/configuration.nix or /etc/nixos/flake.nix:

 boot.kernelParams = [
  "audit_backlog_limit=8192"
 ];
security.audit.backlogLimit = 8192;

Rebuild and switch to the new NixOS configuration:
$ sudo nixos-rebuild switch