SLES-15-010160 - The SUSE operating system must implement DoD-approved encryption to protect the confidentiality of SSH remote connections.

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Information

Without confidentiality protection mechanisms, unauthorized individuals may gain access to sensitive information via a remote access session.

Remote access is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

Encryption provides a means to secure the remote connection to prevent unauthorized access to the data traversing the remote access connection (e.g., RDP), thereby providing a degree of confidentiality. The encryption strength of a mechanism is selected based on the security categorization of the information.

By specifying a cipher list with the order of ciphers being in a 'strongest to weakest' orientation, the system will automatically attempt to use the strongest cipher for securing SSH connections.

Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000125-GPOS-00065, SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173

Solution

Edit the SSH daemon configuration (/etc/ssh/sshd_config) and remove any ciphers not starting with 'aes' and remove any ciphers ending with 'cbc'. If necessary, add a 'Ciphers' line:

Ciphers aes256-ctr,aes192-ctr,aes128-ctr

Restart the SSH daemon:

> sudo systemctl restart sshd.service

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_SLES_15_V1R1_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-13, CAT|II, CCI|CCI-000068, Rule-ID|SV-234816r622137_rule, STIG-ID|SLES-15-010160, STIG-Legacy|SV-92151, STIG-Legacy|V-77455, Vuln-ID|V-234816

Plugin: Unix

Control ID: 082177bde72a10612f14f3d423227d3b8fee287b28c51452c31d6651681bfc47