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← Back to Anduril NixOS Security Technical Implementation Guide

V-268099

CAT II (Medium)

Successful/unsuccessful uses of the chown, fchown, fchownat, and lchown system calls in NixOS must generate an audit record.

Rule ID

SV-268099r1131000_rule

STIG

Anduril NixOS Security Technical Implementation Guide

Version

V1R2

CCIs

CCI-000135

Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter).

Check Content

Verify NixOS generates an audit record upon attempts to use the "chown", "fchown", "fchownat", and "lchown" system calls.

Check the auditing rules currently loaded into the audit daemon with the following command:

$ sudo auditctl -l | grep chown

-a always,exit -F arch=b32 -S lchown,fchown,chown,fchownat -F auid>=1000 -F auid!=-1 -F key=perm_mod
-a always,exit -F arch=b64 -S chown,fchown,lchown,fchownat -F auid>=1000 -F auid!=-1 -F key=perm_mod

If the command does not return an audit rule for "chown", "fchown", "fchownat", and "lchown", this is a finding.

Note: The "-k" allows for specifying an arbitrary identifier. The string following "-k" does not need to match the example output above.

Fix Text

Configure NixOS to generate audit records for any attempts to use the "chown", "fchown", "fchownat", and "lchown" system calls.

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

 security.audit.rules = [
  "-a always,exit -F arch=b32 -S lchown,fchown,chown,fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod"
  "-a always,exit -F arch=b64 -S chown,fchown,lchown,fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod"
 ];

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