NixOS must implement cryptographic mechanisms to protect the integrity of nonlocal maintenance and diagnostic communications, when used for nonlocal maintenance sessions.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
high	V-268157	SRG-OS-000393-GPOS-00173	ANIX-00-001550	SV-268157r1039359_rule	2024-10-25	1

Description
Privileged access contains control and configuration information and is particularly sensitive, so additional protections are necessary. This is maintained by using cryptographic mechanisms, such as a hash function or digital signature, to protect integrity. Nonlocal maintenance and diagnostic activities are those activities conducted by individuals communicating through a network, either an external network (e.g., the internet) or an internal network. Local maintenance and diagnostic activities are those activities carried out by individuals physically present at the information system or information system component and not communicating across a network connection. The operating system can meet this requirement through leveraging a cryptographic module. This requirement does not cover hardware/software components that may support information system maintenance, yet are a part of the system (e.g., the software implementing "ping," "ls," "ipconfig," or the hardware and software implementing the monitoring port of an Ethernet switch).

Description

Privileged access contains control and configuration information and is particularly sensitive, so additional protections are necessary. This is maintained by using cryptographic mechanisms, such as a hash function or digital signature, to protect integrity. Nonlocal maintenance and diagnostic activities are those activities conducted by individuals communicating through a network, either an external network (e.g., the internet) or an internal network. Local maintenance and diagnostic activities are those activities carried out by individuals physically present at the information system or information system component and not communicating across a network connection. The operating system can meet this requirement through leveraging a cryptographic module. This requirement does not cover hardware/software components that may support information system maintenance, yet are a part of the system (e.g., the software implementing "ping," "ls," "ipconfig," or the hardware and software implementing the monitoring port of an Ethernet switch).

ℹ️ Check
Verify NixOS uses the following FIPS 140-3 approved MAC codes in openssh with the following command: $grep services.openssh.macs -A 3 /etc/nixos/configuration.nix services.openssh.macs = [ "hmac-sha2-512" "hmac-sha2-256" ]; If "services.openssh.macs" contains any ciphers other than "hmac-sha2-512" or "hmac-sha2-256", this is a finding.

✔️ Fix
Configure /etc/nixos/configuration.nix to use the following FIPS 140-3 approved MAC codes in openssh by adding the following configuration settings: services.openssh.macs = [ "hmac-sha2-512" "hmac-sha2-256" ]; Then, rebuild the system with the following command: $ sudo nixos-rebuild switch