OL07-00-040400 - The Oracle Linux 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 - MACs employing FIPS 140-2 approved cryptographic hash algorithms.

Information

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

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.

Solution

Edit the '/etc/ssh/sshd_config' file to uncomment or add the line for the 'MACs' keyword and set its value to 'hmac-sha2-512' and/or 'hmac-sha2-256' (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-sha2-512,hmac-sha2-256

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

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Oracle_Linux_7_V2R5_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-13, CAT|II, CCI|CCI-001453, Rule-ID|SV-221857r744091_rule, STIG-ID|OL07-00-040400, STIG-Legacy|SV-108557, STIG-Legacy|V-99453, Vuln-ID|V-221857

Plugin: Unix

Control ID: 7f269f2df4fbf866173bdd3099fba50ae78a6af84e10c2c16162756621995ede