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AZLX-23-001210 - Amazon Linux 2023 SSH server must be configured to use only Message Authentication Codes (MACs) employing FIPS 140-2/140-3 validated cryptographic hash algorithms to protect the confidentiality of SSH server connections.

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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.

Amazon Linux 2023 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.

Solution

Configure Amazon Linux 2023 so that the SSH server uses only MACs employing FIPS 140-2/140-3 approved algorithms.

Reinstall crypto-policies with the following command:

$ sudo dnf -y reinstall crypto-policies

Set the crypto-policy to FIPS with the following command:

$ sudo update-crypto-policies --set FIPS
Setting system policy to FIPS

Note: Systemwide crypto policies are applied on application startup. It is recommended to restart the system for the change of policies to fully take place.

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Amazon_Linux_2023_V1R3_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-17(2), CAT|I, CCI|CCI-001453, Rule-ID|SV-274043r1184014_rule, STIG-ID|AZLX-23-001210, Vuln-ID|V-274043

Plugin: Unix

Control ID: 6d016e1f571a08f2866532e3962fe51c06ec7c3290421a83c16c203562940d5a