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The 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-72253 RHEL-07-040400 SV-86877r2_rule Medium
Description
DoD information systems are required to use FIPS 140-2 approved cryptographic hash functions. The only SSHv2 hash algorithm meeting this requirement is SHA.
STIG Date
Red Hat Enterprise Linux 7 Security Technical Implementation Guide 2017-12-14

Details

Check Text ( C-72487r4_chk )
Verify the SSH daemon is configured to only use MACs employing FIPS 140-2-approved ciphers.

Note: If RHEL-07-021350 is a finding, this is automatically a finding as the system cannot implement FIPS 140-2-approved cryptographic algorithms and hashes.

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

# grep -i macs /etc/ssh/sshd_config
MACs hmac-sha2-256,hmac-sha2-512

If any ciphers other than "hmac-sha2-256" or "hmac-sha2-512" are listed or the retuned line is commented out, this is a finding.
Fix Text (F-78607r2_fix)
Edit the "/etc/ssh/sshd_config" file to uncomment or add the line for the "MACs" keyword and set its value to "hmac-sha2-256" and/or "hmac-sha2-512" (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor):

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

The SSH service must be restarted for changes to take effect.