Off-Path Attacks Against PKI
summary
An off path attacker forges a CA-signed certificate by forcing DNS responses to fragment, guessing the IP ID and UDP checksum, and injecting a spoofed second fragment so a resolver caches attacker-controlled mail and NS records, causing the CA to accept a validation code sent to the attacker. The team demonstrates IP fragmentation cache poisoning, targets email-based domain validation, and finds 5 of 17 CAs vulnerable. Mitigations: suppress fragmentation, use DNS over TCP or DANE, or deploy distributed DV++ agents that vote over HTTPS with out-of-PKS certificates.
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chapters (11)
- 0:00Introduction
- 0:39Objectives and background
- 2:21DNS and cache poisoning
- 4:55IP fragmentation attack
- 7:57Attack procedure
- 11:08Demonstration
- 13:50Exploiting validation
- 15:14Impact analysis
- 16:18Mitigation approaches
- 18:57Proposed solution: DV++
- 20:30Conclusion and Q&A
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