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ConfigProof

All controls

ASA-SEC-023HighCisco ASA

Weak IKE policy

At a glance

Base severity

High

Area

IPSec VPN

Platform

Cisco ASA

Evidence level

Fact1.00

Benchmark reference

Reads the export, not the device

ConfigProof reads a configuration export. This control is evaluated against the objects in that file, and it reports what the file says. It does not connect to the device and sees no traffic, so a finding here describes the configuration, not what the firewall is doing right now.

Why it matters

DES, 3DES, MD5, SHA-1 and Diffie-Hellman groups 1, 2, 5 and 24 are deprecated; a peer that negotiates them protects the tunnel's keys with breakable cryptography.

How to fix it

Web interface

The steps below are written for the web interface. A finding raised on your own export carries the same steps with your object names filled in.

  1. In ASDM: Configuration > Site-to-Site VPN > Advanced > IKE Policies, edit the policy (or delete it) so it offers AES-GCM or AES-256 with SHA-256 or better and DH group 19, 20, 21 or 14. Apply and save.
  2. On the CLI: no crypto ikev1 policy <n> (or crypto isakmp policy <n> before 9.0), and crypto ikev2 policy <n> with encryption aes-gcm-256, integrity null, group 20 19, prf sha384; write memory.

Command line

Cisco ASA CLI

configure terminalno crypto ikev1 policy <priority>crypto ikev2 policy <priority>encryption aes-gcm-256integrity nullgroup 20 19prf sha384endwrite memory

An example. Values in angle brackets are yours to supply; a finding on your own export fills in the names it read. Typed in configuration mode; write memory saves it, with no separate commit. Read every line first.

Read it back

show running-config crypto ikev2show crypto ikev2 sa detail
Values to fill in1
<priority>
The IKE policy's priority number
Before you type it3
  • Written from the ASA 9.x command reference and not run on a device: read each line before you paste it.
  • In multiple context mode, type it in the context it applies to (changeto context <name>).
  • The far end has to offer the same proposal, so coordinate the change with whoever runs it.

How to confirm the fix

  • Run show crypto ikev2 sa detail and confirm the tunnels use the new algorithms.

Limits

  • Both peers must agree before the old proposal is removed.

Compliance references

No benchmark recommendation is mapped to this control in this version.

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