Trustwave SpiderLabs Security Advisory TWSL2013-004: Group Name Enumeration Vulnerability in Cisco IKE Implementation https://www.trustwave.com/spiderlabs/advisories/TWSL2013-004.txt Published: 04/18/13 Version: 1.0 Vendor: Cisco (www.cisco.com) Product: ASA (Adaptive Security Appliance) Versions affected: 8.4(2), 8.4(5), 9.1(1) Product description: The Cisco ASA 5505 Adaptive Security Appliance is a next-generation, full-featured security appliance for small business, branch office, and enterprise teleworker environments. The Cisco ASA 5505 delivers high-performance firewall, SSL and IPsec VPN, and rich networking services in a modular, "plug-and-play" appliance. Finding 1: Group Name Enumeration **** Credit: Daniel Turner of Trustwave SpiderLabs CVE: CVE-2013-1194 CWE: CWE-206 Each VPN configuration is assigned a group name, which is used to manage separate Security Associations. Previous advisories have found that when a VPN endpoint is configured to allow Aggressive Mode IKE negotiations using PSK, a hash of the PSK can be captured and potentially cracked offline. In order to successfully crack this hash a correct group name is required. The above product versions are susceptible to a group name enumeration vulnerability, because of a difference in the way the device responds to correct and incorrect group names sent in the initial exchange packet. Similar to CSCeg00323 and CSCtj96108 where this was possible because of no response and a response with a DPD payload respectively. It has been found that it remains possible to distinguish a correct group name by the number of response packets sent by the device. A correct group name elicits three attempts to continue the handshake and an additional encrypted phase 2 packet, while the device will only respond twice to an incorrect group. Enumeration is slow because of the requirement to wait for the responding packets, but this has been successfully accomplished. Below are examples of the different responses: Example 1: #Request using invalid group name ike-scan 10.70.70.25 -M -A --id=incorrectgroup #Response using invalid group name 13:22:59.929273 IP 10.70.70.204.isakmp > 10.70.70.25.isakmp: isakmp: phase 1 I agg 13:22:59.932624 IP 10.70.70.25.isakmp > 10.70.70.204.isakmp: isakmp: phase 1 R agg 13:23:05.696571 IP 10.70.70.25.isakmp > 10.70.70.204.isakmp: isakmp: phase 1 R agg Example 2: #Request using valid group name ike-scan 10.70.70.25 -M -A --id=correctgroup #Response using valid group name 13:23:05.693673 IP 10.70.70.204.isakmp > 10.70.70.25.isakmp: isakmp: phase 1 I agg 13:23:13.690392 IP 10.70.70.25.isakmp > 10.70.70.204.isakmp: isakmp: phase 1 R agg 13:23:21.690464 IP 10.70.70.25.isakmp > 10.70.70.204.isakmp: isakmp: phase 1 R agg 13:23:29.690528 IP 10.70.70.25.isakmp > 10.70.70.204.isakmp: isakmp: phase 1 R agg 13:23:37.691275 IP 10.70.70.25.isakmp > 10.70.70.204.isakmp: isakmp: phase 2/others R inf[E] This information can be used to capture and crack a weak PSK if Aggressive Mode is enabled. Remediation Steps: The vendor will be releasing security fixes to the above issues and affected versions can be patched by installing the 8.4(6) firmware or the 9.1(2) firmware for the Cisco ASA platform. Administrators with other affected firmware versions should be aware that this information could be potentially be revealed and it is recommended that factory default group or easily guessable group names are not used. Additional Credits: Jonathan Claudius of Trustwave SpiderLabs: Confirmation of Vulnerability/Behavior on Cisco ASA 8.4(5) and 9.1(1) Revision History: 02/21/13 - Vulnerability disclosed 03/14/13 - Vendor acknowledges security issue 04/17/13 - Vendor releases security alert 04/18/13 - Advisory published References 1. http://www.cisco.com/warp/public/707/cisco-sn-20050624-vpn-grpname.shtml 2. http://www.cisco.com/en/US/products/csr/cisco-sr-20101124-vpn-grpname.html 3. http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2013-1194 About Trustwave: Trustwave is the leading provider of on-demand and subscription-based information security and payment card industry compliance management solutions to businesses and government entities throughout the world. For organizations faced with today's challenging data security and compliance environment, Trustwave provides a unique approach with comprehensive solutions that include its flagship TrustKeeper compliance management software and other proprietary security solutions. Trustwave has helped thousands of organizations--ranging from Fortune 500 businesses and large financial institutions to small and medium-sized retailers--manage compliance and secure their network infrastructure, data communications and critical information assets. Trustwave is headquartered in Chicago with offices throughout North America, South America, Europe, Africa, China and Australia. For more information, visit https://www.trustwave.com About Trustwave SpiderLabs: SpiderLabs(R) is the advanced security team at Trustwave focused on application security, incident response, penetration testing, physical security and security research. The team has performed over a thousand incident investigations, thousands of penetration tests and hundreds of application security tests globally. In addition, the SpiderLabs Research team provides intelligence through bleeding-edge research and proof of concept tool development to enhance Trustwave's products and services. https://www.trustwave.com/spiderlabs Disclaimer: The information provided in this advisory is provided "as is" without warranty of any kind. Trustwave disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Trustwave or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Trustwave or its suppliers have been advised of the possibility of such damages. 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