Check: UBTU-16-030240
Canonical Ubuntu STIG:
UBTU-16-030240
(in version v1 r2)
Title
The SSH daemon must be configured to only use Message Authentication Codes (MACs) employing FIPS 140-2 approved cryptographic hash algorithms. (Cat II impact)
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, non-organization-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. Satisfies: SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174
Check Content
Verify the SSH daemon is configured to only use Message Authentication Codes (MACs) that employ FIPS 140-2 approved ciphers. Check that the SSH daemon is configured to only use MACs that employ FIPS 140-2 approved ciphers with the following command: # sudo grep -i macs /etc/ssh/sshd_config MACs hmac-sha2-256,hmac-sha2-512 If any ciphers other than "hmac-sha2-256" or "hmac-sha2-512" are listed, or the retuned line is commented out, this is a finding.
Fix Text
Configure the Ubuntu operating system to allow the SSH daemon to only use Message Authentication Codes (MACs) that employ FIPS 140-2 approved ciphers. Edit the "/etc/ssh/sshd_config" file to uncomment or add the line for the "MACs" keyword and set its value to "hmac-sha2-256" and/or "hmac-sha2-512": MACs hmac-sha2-256,hmac-sha2-512 The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command: # sudo systemctl restart sshd.service
Additional Identifiers
Rule ID: SV-90511r2_rule
Vulnerability ID: V-75831
Group Title:
Expert Comments
CCIs
| Number | Definition |
|---|---|
| CCI-001453 |
The information system implements cryptographic mechanisms to protect the integrity of remote access sessions. |
| CCI-002890 |
The information system implements cryptographic mechanisms to protect the integrity of nonlocal maintenance and diagnostic communications. |
| CCI-003123 |
The information system implements cryptographic mechanisms to protect the confidentiality of nonlocal maintenance and diagnostic communications. |