Vulnerability 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, 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.

AlmaLinux OS 9 incorporates systemwide crypto policies by default. Configuration files in /etc/ssh/ have no effect on the ciphers, MACs, or algorithms used by the operating system. The employed ssh client algorithms can be viewed in the /etc/crypto-policies/back-ends/openssh.config file.

Check

Verify the SSH client is configured to use only ciphers employing FIPS 140-3-approved algorithms with the following command:

$ grep -i Ciphers /etc/crypto-policies/back-ends/openssh.config

Ciphers [email protected],[email protected],aes256-ctr,aes128-ctr

If the cipher entries in the "openssh.config" file have any ciphers other than "[email protected],[email protected],aes256-ctr,aes128-ctr", they are missing, or commented out, this is a finding.

Fix

Configure the AlmaLinux OS 9 SSH client to use only ciphers employing FIPS 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