The Cisco ASA remote access VPN server must be configured to use SHA-2 at 384 bits or greater for hashing to protect the integrity of IPsec remote access sessions.

Without strong cryptographic integrity protections, information can be altered by unauthorized users without detection.

SHA-1 is considered a compromised hashing standard and is being phased out of use by industry and Government standards. DOD systems must not be configured to use SHA-1 for integrity of remote access sessions.

The remote access VPN provides access to DOD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network.

Verify that the ASA uses SHA-2 at 384 bits or greater for hashing to protect the integrity of IPsec remote access sessions as shown in the example below.

Step 1: Verify that SHA-2 at 384 bits or greater is used for IKE Phase 1 as shown in the example below.

crypto ikev2 policy 1 … … … integrity sha384

Step 2: Verify that SHA-2 at 384 bits or greater is used for the IPsec Security Association.

crypto ipsec ikev2 ipsec-proposal IPSEC_TRANS protocol esp integrity sha-384

If the ASA does not use SHA-2 at 384 bits or greater for hashing to protect the integrity of IPsec remote access sessions, this is a finding.

Configure the ASA to use SHA-2 at 384 bits or greater for hashing to protect the integrity of IPsec remote access sessions as shown in the example below.

ASA1(config)# crypto ikev2 policy 1 ASA1(config-ikev2-policy)# integrity sha384 ASA1(config-ikev2-policy)# exit ASA1(config)# crypto ipsec ikev2 ipsec-proposal IPSEC_TRANS ASA1(config-ipsec-proposal)# protocol esp integrity sha-384 ASA1(config-ikev2-policy)# end