5.2.26 Ensure only FIPS 140-2 MACs are used for SSH

Information

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

Rationale:

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

Solution

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):
Example: vim /etc/ssh/sshd_config
Add, uncomment or update the following line.

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

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

# systemctl restart sshd.service

Notes:

This Benchmark recommendation maps to:

Red Hat Enterprise Linux 7 Security Technical Implementation Guide:

Version 2, Release: 3 Benchmark Date: 26 Apr 2019



Vul ID: V-72253

Rule ID: SV-86877r3_rule

STIG ID: RHEL-07-040400

Severity: CAT II

See Also

https://workbench.cisecurity.org/files/2688

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-13

Plugin: Unix

Control ID: ffcacd1570aba4b2fdf50aa479ef63554271027fa0eb277276fdad3a7fa5e4f6