V-272482

Discussion

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. RHEL 8 incorporates systemwide crypto policies by default. The SSH configuration file has no effect on the ciphers, MACs, or algorithms unless specifically defined in the /etc/sysconfig/sshd file. The employed algorithms can be viewed in the /etc/crypto-policies/back-ends/openssh.config file.

Check Content

Verify the RHEL 8 SSH client is configured to use only MACs employing FIPS 140-3-approved algorithms.

To verify the MACs in the systemwide SSH configuration file, use the following command:

$ grep -i MACs /etc/crypto-policies/back-ends/openssh.config

MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512,hmac-sha2-256

If the MACs entries in the "openssh.config" file have any hashes other than "hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512,hmac-sha2-2562", or they are missing or commented out, this is a finding.