Trustwave's SpiderLabs Security Advisory TWSL2011-007: iOS SSL Implementation Does Not Validate Certificate Chain https://www.trustwave.com/spiderlabs/advisories/TWSL2011-007.txt Published: 2011-07-25 Version: 1.0 Vendor: Apple (http://www.apple.com) Product: iOS Version affected: Versions Prior to 5.0b4, 4.3.5, and 4.2.10 Product description: iOS is Apple's mobile operating system for the iPhone, iPod Touch, and iPad hardware platforms. Credit: Paul Kehrer of Trustwave Finding: iOS SSL Implementation Does Not Validate Certificate Chain CVE: CVE-2011-0228 iOS's SSL certificate parsing contains a flaw where it fails to check the basicConstraints parameter of certificates in the chain. By signing a new certificate using a legitimate end entity certificate, an attacker can obtain a "valid" certificate for any domain. For example: -TrustedCA --somedomain.com (legitimate certificate) ---api.someotherdomain.com (signed by somedomain.com) Using this technique any SSL traffic using the api.someotherdomain.com certificate can be intercepted and decrypted by the issuer. No notification of the invalid nature of the certificate is presented to the iOS user. This method allows for transparent man-in-the-middle attacks against encrypted iOS communications. Remediation Steps: Users should update to the latest version of iOS in order to address this issue. This vulnerability has been corrected in versions 5.0b4, 4.3.5, and 4.2.10. Revision History: 07/15/11 - Vulnerability Disclosed 07/25/11 - Patch Released 07/25/11 - Advisory Published References: 1. http://support.apple.com/kb/HT4824 2. http://support.apple.com/kb/HT4825 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's 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. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply. This transmission may contain information that is privileged, confidential, and/or exempt from disclosure under applicable law. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, or use of the information contained herein (including any reliance thereon) is STRICTLY PROHIBITED. If you received this transmission in error, please immediately contact the sender and destroy the material in its entirety, whether in electronic or hard copy format.