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Breaking and Fixing Public-Key Kerberos

2007; Springer Science+Business Media; Linguagem: Inglês

10.1007/978-3-540-77505-8_13

1611-3349

Iliano Cervesato, Aaron D. Jaggard, Andre Scedrov, Joe-Kai Tsay, Christopher Walstad,

Cryptography and Data Security

We report on a man-in-the-middle attack on PKINIT, the public key extension of the widely deployed Kerberos 5 authentication protocol. This flaw allows an attacker to impersonate Kerberos administrative principals (KDC) and end-servers to a client, hence breaching the authentication guarantees of Kerberos. It also gives the attacker the keys that the KDC would normally generate to encrypt the service requests of this client, hence defeating confidentiality as well. The discovery of this attack caused the IETF to change the specification of PKINIT and Microsoft to release a security update for some Windows operating systems. We discovered this attack as part of an ongoing formal analysis of the Kerberos protocol suite, and we have formally verified several possible fixes to PKINIT—including the one adopted by the IETF—that prevent our attack.