The macOS system must implement approved ciphers within the SSH client configuration to protect the confidentiality of SSH connections.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-257773	APPL-12-000057	SV-257773r922864_rule		High

Description
Operating systems using encryption are required to use FIPS-compliant mechanisms for authenticating to macOS. For OpenSSH to utilize the Apple Corecrypto FIPS-validated algorithms, a specific configuration is required to leverage the shim implemented by macOS to bypass the non-FIPS validated LibreSSL crypto module packaged with OpenSSH. Information regarding this configuration can be found in the manual page "apple_ssh_and_fips". Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000120-GPOS-00061, SRG-OS-000125-GPOS-00065, SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174

Description

Operating systems using encryption are required to use FIPS-compliant mechanisms for authenticating to macOS. For OpenSSH to utilize the Apple Corecrypto FIPS-validated algorithms, a specific configuration is required to leverage the shim implemented by macOS to bypass the non-FIPS validated LibreSSL crypto module packaged with OpenSSH. Information regarding this configuration can be found in the manual page "apple_ssh_and_fips". Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000120-GPOS-00061, SRG-OS-000125-GPOS-00065, SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174

STIG	Date
Apple macOS 12 (Monterey) Security Technical Implementation Guide	2023-08-28

Details

Check Text ( C-61514r922862_chk )
Verify the macOS system is configured to use approved SSH ciphers within the SSH client configuration with the following command: /usr/bin/sudo /usr/bin/grep -ir "ciphers" /etc/ssh/ssh_config* /etc/ssh/ssh_config.d/fips_ssh_config:Ciphers aes128-gcm@openssh.com If any ciphers other than "aes128-gcm@openssh.com" are listed, or the "ciphers" keyword is missing, this is a finding.

Fix Text (F-61438r922863_fix)
Configure the macOS system to use approved SSH ciphers by creating a plain text file in the /private/etc/ssh/ssh_config.d/ directory containing the following: Ciphers aes128-gcm@openssh.com The SSH service must be restarted for changes to take effect.