Title

NixOS must prevent all software from executing at higher privilege levels than users executing the software. (Cat II impact)

Discussion

In certain situations, software applications/programs need to execute with elevated privileges to perform required functions. However, if the privileges required for execution are at a higher level than the privileges assigned to organizational users invoking such applications/programs, those users are indirectly provided with greater privileges than assigned by the organizations. Some programs and processes are required to operate at a higher privilege level and therefore should be excluded from the organization-defined software list after review.

Check Content

Verify NixOS audits and provides alerts of audit failures by running the following command: $grep A -15 security.auditd /etc/nixos/configuration.nix /etc/nixos/configuration.nix: security.auditd.enable = true; security.audit.enable = true; security.audit.rules = [ '' <audit_rules> '' ]; security.audit.rules = [ "-a always,exit -F arch=b32 -S execve -C uid!=euid -F euid=0 -k execpriv" "-a always,exit -F arch=b64 -S execve -C uid!=euid -F euid=0 -k execpriv" "-a always,exit -F arch=b32 -S execve -C gid!=egid -F egid=0 -k execpriv" "-a always,exit -F arch=b64 -S execve -C gid!=egid -F egid=0 -k execpriv" ]; If "security.auditd", "security.audit" and the additional modifications do not equal true, are missing, or are commented out, this is a finding.

Fix Text

Configure the audit service to produce audit records. Add the following Nix code to the NixOS Configuration, usually located in /etc/nixos/configuration.nix or /etc/nixos/flake.nix: security.auditd.enable = true; security.audit.enable = true; Add the following audit rules: security.audit.rules = [ "-a always,exit -F arch=b32 -S execve -C uid!=euid -F euid=0 -k execpriv" "-a always,exit -F arch=b64 -S execve -C uid!=euid -F euid=0 -k execpriv" "-a always,exit -F arch=b32 -S execve -C gid!=egid -F egid=0 -k execpriv" "-a always,exit -F arch=b64 -S execve -C gid!=egid -F egid=0 -k execpriv" ]; Rebuild and switch to the new NixOS configuration: $ sudo nixos-rebuild switch

Additional Identifiers

Rule ID: SV-268148r1131097_rule

Vulnerability ID: V-268148

Group Title: SRG-OS-000326-GPOS-00126

Expert Comments

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