Title

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

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 or update the "security.audit.rules" configuration in /etc/nixos/configuration.nix to include the following rule: 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 the NixOS configuration with the following command: $ sudo nixos-rebuild switch

Additional Identifiers

Rule ID: SV-268099r1039185_rule

Vulnerability ID: V-268099

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

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.