ALMA-09-003320 - AlmaLinux OS 9 must implement DOD-approved encryption ciphers to protect the confidentiality of SSH server connections.

Information

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.

Solution

Configure the AlmaLinux OS 9 SSH server to use only ciphers employing FIPS 140-3 approved algorithms by updating the "/etc/crypto-policies/back-ends/opensshserver.config" file with the following commands:

Note: Before enabling FIPS mode, ensure that the dracut-fips package is installed on the system.

Enable FIPS mode by updating the system's crypto policy with the following command:
$ sudo update-crypto-policies --set FIPS

Note: If FIPS mode has never been enabled on the system, additional steps will need to be conducted. Refer to vendor documentation.

To manually update the Ciphers in the systemwide SSH configuration, use the following command:

$ sudo sed -i -E '/^Ciphers/s/.*/Ciphers [email protected],[email protected],aes256-ctr,aes128-ctr/' "$(readlink -f /etc/crypto-policies/back-ends/opensshserver.config)"

A reboot is required for the changes to take effect.

See Also

https://workbench.cisecurity.org/benchmarks/0

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-17(2), CAT|II, CCI|CCI-001453, Rule-ID|SV-269116r1050608_rule, STIG-ID|ALMA-09-003320, Vuln-ID|V-269116

Plugin: Unix

Control ID: 4f55c1a2f5c2b28afa3fd31256090819bbef79b9a6641c54c302df938fde1bf4