STIGQter: STIG Summary: Canonical Ubuntu 20.04 LTS Security Technical Implementation Guide Version: 1 Release: 1 Benchmark Date: 10 Mar 2021:

The Ubuntu operating system must configure the SSH daemon to use Message Authentication Codes (MACs) employing FIPS 140-2 approved cryptographic hashes to prevent the unauthorized disclosure of information and/or detect changes to information during transmission.

DISA Rule

SV-238216r654316_rule

Vulnerability Number

V-238216

Group Title

SRG-OS-000424-GPOS-00188

Rule Version

UBTU-20-010043

Severity

CAT II

CCI(s)

• CCI-001453 - The information system implements cryptographic mechanisms to protect the integrity of remote access sessions.
• CCI-002421 - The information system implements cryptographic mechanisms to prevent unauthorized disclosure of information and/or detect changes to information during transmission unless otherwise protected by organization-defined alternative physical safeguards.
• CCI-002890 - The information system implements cryptographic mechanisms to protect the integrity of nonlocal maintenance and diagnostic communications.

Weight

10

Fix Recommendation

Configure the Ubuntu operating system to allow the SSH daemon to only use MACs that employ FIPS 140-2 approved ciphers.

Add the following line (or modify the line to have the required value) to the "/etc/ssh/sshd_config" file (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor):

MACs hmac-sha2-512,hmac-sha2-256

Restart the SSH daemon for the changes to take effect:

$ sudo systemctl reload sshd.service

Check Contents

Verify the SSH daemon is configured to only use MACs that employ FIPS 140-2 approved ciphers with the following command:

$ grep -i macs /etc/ssh/sshd_config

MACs hmac-sha2-512,hmac-sha2-256

If any ciphers other than "hmac-sha2-512" or "hmac-sha2-256" are listed, the order differs from the example above, or the returned line is commented out, this is a finding.

Vulnerability Number

V-238216

Documentable

False

Rule Version

UBTU-20-010043

Severity Override Guidance

Verify the SSH daemon is configured to only use MACs that employ FIPS 140-2 approved ciphers with the following command:

$ grep -i macs /etc/ssh/sshd_config

MACs hmac-sha2-512,hmac-sha2-256

If any ciphers other than "hmac-sha2-512" or "hmac-sha2-256" are listed, the order differs from the example above, or the returned line is commented out, this is a finding.

Check Content Reference

M

Target Key

5318

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