Title: IKE Aggressive Mode Shared Secret Hash Leakage Weakness
Severity: HIGH
Description:
IKE is the Internet Key Exchange protocol. It is used for the negotiation of authentication and encryption methods and keys during VPN session initiation. During key negotiation, IKE supports two modes: main mode and aggressive mode. Aggressive mode is the fastest but least secure means of IKE key negotiation.
When a VPN is configured to use a pre-shared master secret and a client attempts to negotiate keys in aggressive mode, a hash of the secret is transmitted across the network in clear-text. This can result in the hash being exposed to eavesdroppers or malicious peers. An offline brute-force attack on this hash may then be performed to obtain the clear-text secret. As pre-shared secrets are often set as though they are passwords, dictionary-based attacks are feasible.
This weakness in the protocol is well documented. This attack was originally published in 1999 and code to perform the brute-force attack on hashes has been available for some time.
Administrators are advised to disable support for aggressive mode whenever possible. It should be noted that some devices may switch to aggressive mode at client request despite being configured not to (see BID 5920).
Affected Products:
- Check Point Software Firewall-1 [ VPN + DES + STRONG ] 4.1.0 Build 41439
- Check Point Software Firewall-1 [ VPN + DES + STRONG ] 4.1.0 SP2 Build 41716
- Check Point Software Firewall-1 [ VPN + DES ] 4.1.0
- Check Point Software VPN-1 4.1.0
- Check Point Software VPN-1 4.1.0 SP1
- Check Point Software VPN-1 4.1.0 SP2
- Check Point Software VPN-1 4.1.0 SP3
- Check Point Software VPN-1 4.1.0 SP4
- Cisco VPN 3000 Concentrator 2.0.0
- Cisco VPN 3000 Concentrator 2.5.2(A)
- Cisco VPN 3000 Concentrator 2.5.2(B)
- Cisco VPN 3000 Concentrator 2.5.2(C)
- Cisco VPN 3000 Concentrator 2.5.2(D)
- Cisco VPN 3000 Concentrator 2.5.2(F)
- Cisco VPN 3000 Concentrator 3.0.0
- Cisco VPN 3000 Concentrator 3.0.0
- Cisco VPN 3000 Concentrator 3.0.3(A)
- Cisco VPN 3000 Concentrator 3.0.3(B)
- Cisco VPN 3000 Concentrator 3.0.4
- Cisco VPN 3000 Concentrator 3.1.0
- Cisco VPN 3000 Concentrator 3.1.0(Rel)
- Cisco VPN 3000 Concentrator 3.1.1
- Cisco VPN 3000 Concentrator 3.1.2
- Cisco VPN 3000 Concentrator 3.1.4
- Cisco VPN 3000 Concentrator 3.5.0(Rel)
- Cisco VPN 3000 Concentrator 3.5.1
- Cisco VPN 3000 Concentrator 3.5.2
- Cisco VPN 3000 Concentrator 3.5.3
- Cisco VPN 3000 Concentrator 3.5.4
- Cisco VPN 3000 Concentrator 3.5.5
- Cisco VPN 3000 Concentrator 3.6.0
- Cisco VPN 3000 Concentrator 3.6.1
- Cisco VPN 3002 Hardware Client 0.0.0
- IETF RFC 2409: The Internet Key Exchange (IKE) 0.0.0
References:
- Check Point Software: IKE Aggressive Mode
- IETF: RFC 2409: The Internet Key Exchange (IKE)
- John Pliam <pliam@ima.umn.edu>: Authentication Vulnerabilities in IKE and Xauth with Weak Pre-Shared Secrets
- SecurityFocus: Bugtraq ID 5920: Check Point VPN-1 IKE Aggressive Mode Forcing Vulnerability
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