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. Install the audit service (if the audit service is not already installed) and ensure the audit service is enabled by adding or updating the following configurations in /etc/nixos/configuration.nix: security.auditd.enable = true; security.audit.enable = true; Additionally, 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" ]; Then, rebuild the NixOS configuration with the following command: $ sudo nixos-rebuild switch

Additional Identifiers

Rule ID: SV-268148r1039332_rule

Vulnerability ID: V-268148

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

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