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

From Red Hat Enterprise Linux 7 Security Technical Implementation Guide

Associated with: CCI-001453

SV-86877r2_rule The SSH daemon must be configured to only use Message Authentication Codes (MACs) employing FIPS 140-2 approved cryptographic hash algorithms.

Vulnerability discussion

DoD information systems are required to use FIPS 140-2 approved cryptographic hash functions. The only SSHv2 hash algorithm meeting this requirement is SHA.

Check content

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

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.

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