V-239913

Discussion

A replay attack may enable an unauthorized user to gain access to the application. Authentication sessions between the authenticator and the application validating the user credentials must not be vulnerable to a replay attack. An authentication process resists replay attacks if it is impractical to achieve a successful authentication by recording and replaying a previous authentication message. Techniques used to address this include protocols using nonces (e.g., numbers generated for a specific one-time use) or challenges (e.g., TLS, WS_Security). Additional techniques include time-synchronous or challenge-response one-time authenticators.

Check Content

Step 1: Verify that FIPS mode is enabled as shown in the example.

fips enable

Step 2: Verify only SSH is configured to only use FIPS-compliant ciphers and that Diffie-Hellman Group 14  is used for the key exchange as shown in the example below.

ssh version 2
ssh cipher encryption fips
ssh key-exchange group dh-group14-sha1

Note: The ASA only supports SSHv2.

If the ASA is not configured to implement replay-resistant authentication mechanisms for network access, this is a finding.