Successful/unsuccessful uses of the init_module, finit_module, and delete_module system calls in NixOS must generate an audit record.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-268096	SRG-OS-000042-GPOS-00020	ANIX-00-000290	SV-268096r1039563_rule	2024-10-25	1

Description
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). The "init_module" and "finit_module" system calls are used to load a kernel module, and the "delete_module" is used to unload a kernel module. When a user logs in, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way. The system call rules are loaded into a matching engine that intercepts each syscall made by all programs on the system. Therefore, it is very important to use syscall rules only when absolutely necessary since these affect performance. The more rules, the bigger the performance hit. The performance can be helped, however, by combining syscalls into one rule whenever possible. Satisfies: SRG-OS-000042-GPOS-00020, SRG-OS-000471-GPOS-00216

Description

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). The "init_module" and "finit_module" system calls are used to load a kernel module, and the "delete_module" is used to unload a kernel module. When a user logs in, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way. The system call rules are loaded into a matching engine that intercepts each syscall made by all programs on the system. Therefore, it is very important to use syscall rules only when absolutely necessary since these affect performance. The more rules, the bigger the performance hit. The performance can be helped, however, by combining syscalls into one rule whenever possible. Satisfies: SRG-OS-000042-GPOS-00020, SRG-OS-000471-GPOS-00216

ℹ️ Check
Verify NixOS generates an audit record upon successful/unsuccessful attempts to use the "init_module", "finit_module", and "delete_module" system calls. Check the auditing rules currently loaded into the audit daemon with the following command: $ sudo auditctl -l \| grep -w init_module -a always,exit -F arch=b32 -S init_module,finit_module,delete_module -F auid>=1000 -F auid!=-1 -k module_chng -a always,exit -F arch=b64 -S init_module,finit_module,delete_module -F auid>=1000 -F auid!=-1 -k module_chng If the command does not return an audit rule for "init_module", "finit_module", and "delete_module", 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.

ℹ️ Check

Verify NixOS generates an audit record upon successful/unsuccessful attempts to use the "init_module", "finit_module", and "delete_module" system calls. Check the auditing rules currently loaded into the audit daemon with the following command: $ sudo auditctl -l | grep -w init_module -a always,exit -F arch=b32 -S init_module,finit_module,delete_module -F auid>=1000 -F auid!=-1 -k module_chng -a always,exit -F arch=b64 -S init_module,finit_module,delete_module -F auid>=1000 -F auid!=-1 -k module_chng If the command does not return an audit rule for "init_module", "finit_module", and "delete_module", 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
Configure /etc/nixos/configuration.nix to log successful/unsuccessful attempts to use the "init_module", "finit_module", and "delete_module" 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 init_module,finit_module,delete_module -F auid>=1000 -F auid!=unset -k module_chng" "-a always,exit -F arch=b64 -S init_module,finit_module,delete_module -F auid>=1000 -F auid!=unset -k module_chng" ]; Rebuild the NixOS configuration with the following command: $ sudo nixos-rebuild switch

✔️ Fix

Configure /etc/nixos/configuration.nix to log successful/unsuccessful attempts to use the "init_module", "finit_module", and "delete_module" 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 init_module,finit_module,delete_module -F auid>=1000 -F auid!=unset -k module_chng" "-a always,exit -F arch=b64 -S init_module,finit_module,delete_module -F auid>=1000 -F auid!=unset -k module_chng" ]; Rebuild the NixOS configuration with the following command: $ sudo nixos-rebuild switch