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The Cisco ASA must be configured to implement replay-resistant authentication mechanisms for network access to privileged accounts.


Finding ID Version Rule ID IA Controls Severity
V-239913 CASA-ND-000470 SV-239913r666102_rule Medium
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.
Cisco ASA NDM Security Technical Implementation Guide 2021-03-15


Check Text ( C-43146r666100_chk )
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.
Fix Text (F-43105r666101_fix)
Step 1: Enable FIPS mode via the fips enable command.

Step 2: Configure SSH to only use FIPS-compliant ciphers and Diffie-Hellman Group 14 for the key exchange.

ASA(config)# ssh cipher encryption fips
ASA(config)# ssh key-exchange group dh-group14-sha