The SSH daemon must be configured to use only FIPS 140-2 approved ciphers.

From Red Hat Enterprise Linux 6 Security Technical Implementation Guide

Associated with: CCI-001144

SV-50418r1_rule The SSH daemon must be configured to use only FIPS 140-2 approved ciphers.

Vulnerability discussion

Approved algorithms should impart some level of confidence in their implementation. These are also required for compliance.

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Only FIPS-approved ciphers should be used. To verify that only FIPS-approved ciphers are in use, run the following command: # grep Ciphers /etc/ssh/sshd_config The output should contain only those ciphers which are FIPS-approved, namely, the AES and 3DES ciphers. If that is not the case, this is a finding.

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Limit the ciphers to those algorithms which are FIPS-approved. Counter (CTR) mode is also preferred over cipher-block chaining (CBC) mode. The following line in "/etc/ssh/sshd_config" demonstrates use of FIPS-approved ciphers: Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc The man page "sshd_config(5)" contains a list of supported ciphers.

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