CAPEC-459: Creating a Rogue Certification Authority Certificate
Description
An adversary exploits a weakness resulting from using a hashing algorithm with weak collision resistance to generate certificate signing requests (CSR) that contain collision blocks in their to be signed parts. The adversary submits one CSR to be signed by a trusted certificate authority then uses the signed blob to make a second certificate appear signed by said certificate authority. Due to the hash collision, both certificates, though different, hash to the same value and so the signed blob works just as well in the second certificate. The net effect is that the adversary's second X.509 certificate, which the Certification Authority has never seen, is now signed and validated by that Certification Authority.
- Likelihood of attack
- Medium
- Typical severity
- Very High
- Abstraction
- DetailedA low-level, detailed pattern, often for a particular technology.
Mechanism of attack: Engage in Deceptive Interactions
Prerequisites
- Certification Authority is using a hash function with insufficient collision resistance to generate the certificate hash to be signed
Skills required
- HighUnderstanding of how to force a hash collision in X.509 certificates
- HighAn attacker must be able to craft two X.509 certificates that produce the same hash value
- MediumKnowledge needed to set up a certification authority
Consequences
- Access ControlAuthentication
Gain Privileges
Mitigations
- Certification Authorities need to stop using deprecated or cryptographically insecure hashing algorithms to hash the certificates that they are about to sign. Instead they should be using stronger hashing functions such as SHA-256 or SHA-512.