UCF STIG Viewer Logo

The Oracle Linux operating system SSH server must be configured to use only FIPS-validated key exchange algorithms.


Overview

Finding ID Version Rule ID IA Controls Severity
V-255899 OL07-00-040712 SV-255899r880582_rule Medium
Description
The use of FIPS-validated cryptographic algorithms is enforced by enabling kernel FIPS mode. In the event that kernel FIPS mode is disabled, the use of nonvalidated cryptographic algorithms will be permitted systemwide. The SSH server configuration must manually define only FIPS-validated key exchange algorithms to prevent the use of nonvalidated algorithms.
STIG Date
Oracle Linux 7 Security Technical Implementation Guide 2022-12-06

Details

Check Text ( C-59576r880580_chk )
Verify that the SSH server is configured to use only FIPS-validated key exchange algorithms:

$ sudo grep -i kexalgorithms /etc/ssh/sshd_config
KexAlgorithms ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256

If "KexAlgorithms" is not configured, is commented out, or does not contain only the algorithms "ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256" in exact order, this is a finding.
Fix Text (F-59519r880581_fix)
Configure the SSH server to use only FIPS-validated key exchange algorithms by adding or modifying the following line in "/etc/ssh/sshd_config":

KexAlgorithms ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256

Restart the "sshd" service for changes to take effect:

$ sudo systemctl restart sshd