RHEL 9 must implement DOD-approved encryption ciphers to protect the confidentiality of SSH connections.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-257988 | RHEL-09-255060 | SV-257988r1051234_rule | Medium |
| Description |
| 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 9 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/opensshserver.config file. |
| STIG | Date |
| Red Hat Enterprise Linux 9 Security Technical Implementation Guide | 2024-12-04 |
Details
| Check Text (C-61729r1051232_chk) |
| Verify that RHEL 9 implements DOD-approved encryption ciphers for SSH connections. Verify that the SSH configuration files include the path to the systemwide policy with the following command: $ sudo grep -R Include /etc/ssh/sshd_config /etc/ssh/sshd_config.d/ /etc/ssh/sshd_config:Include /etc/ssh/sshd_config.d/*.conf /etc/ssh/sshd_config.d/50-redhat.conf:Include /etc/crypto-policies/back-ends/opensshserver.config If "Include /etc/ssh/sshd_config.d/*.conf" or "Include /etc/crypto-policies/back-ends/opensshserver.config" are not included in the system sshd config or if the file "/etc/ssh/sshd_config.d/50-redhat.conf" is missing, this is a finding. |
| Fix Text (F-61653r1051233_fix) |
| Configure the RHEL 9 SSH daemon to use systemwide crypto policies. Reinstall OpenSSH client package contents with the following command: $ sudo dnf -y reinstall openssh |