The SUSE operating system SSH daemon must be configured to only use Message Authentication Codes (MACs) employing FIPS 140-2 approved cryptographic hash algorithms.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-234826	SLES-15-010270	SV-234826r958510_rule		Medium

Description
Without cryptographic integrity protections, information can be altered by unauthorized users without detection. Remote access (e.g., RDP) is access to DOD nonpublic information systems by an authorized user (or an information system) communicating through an external, nonorganization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless. Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions using asymmetric cryptography enabling distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash. The system will attempt to use the first hash presented by the client that matches the server list. Listing the values "strongest to weakest" is a method to ensure the use of the strongest hash available to secure the SSH connection. Satisfies: SRG-OS-000125-GPOS-00065, SRG-OS-000394-GPOS-00174

Description

Without cryptographic integrity protections, information can be altered by unauthorized users without detection. Remote access (e.g., RDP) is access to DOD nonpublic information systems by an authorized user (or an information system) communicating through an external, nonorganization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless. Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions using asymmetric cryptography enabling distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash. The system will attempt to use the first hash presented by the client that matches the server list. Listing the values "strongest to weakest" is a method to ensure the use of the strongest hash available to secure the SSH connection. Satisfies: SRG-OS-000125-GPOS-00065, SRG-OS-000394-GPOS-00174

STIG	Date
SUSE Linux Enterprise Server 15 Security Technical Implementation Guide	2024-05-30

Details

Check Text ( C-38014r951631_chk )
Verify the SUSE operating system SSH daemon is configured to only use MACs that employ FIPS 140-2 approved hashes. Check that the SSH daemon is configured to only use MACs that employ FIPS 140-2 approved hashes with the following command: > sudo /usr/sbin/sshd -dd 2>&1 \| awk '/filename/ {print $4}' \| tr -d '\r' \| tr '\n' ' ' \| xargs sudo grep -iH '^\s*macs' MACs hmac-sha2-512,hmac-sha2-256 If any ciphers other than "hmac-sha2-512" or "hmac-sha2-256" are listed, the order differs from the example above, they are missing, or the returned line is commented out, this is a finding.

Check Text ( C-38014r951631_chk )

Verify the SUSE operating system SSH daemon is configured to only use MACs that employ FIPS 140-2 approved hashes.

Check that the SSH daemon is configured to only use MACs that employ FIPS 140-2 approved hashes with the following command:

> sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*macs'

MACs hmac-sha2-512,hmac-sha2-256

If any ciphers other than "hmac-sha2-512" or "hmac-sha2-256" are listed, the order differs from the example above, they are missing, or the returned line is commented out, this is a finding.

Fix Text (F-37977r618748_fix)
Configure the SUSE operating system SSH daemon to only use MACs that employ FIPS 140-2 approved hashes. Edit the "/etc/ssh/sshd_config" file to uncomment or add the line for the "MACs" keyword and set its value to "hmac-sha2-512" and/or "hmac-sha2-256" (The file might be named differently or be in a different location): MACs hmac-sha2-512,hmac-sha2-256