At Thu, 06 Nov 2008 01:02:10 -0500, Thierry Moreau wrote: > Eric Rescorla wrote: > > This is a classic single sided authentication situation. If > > Alice calls Bob and the attacker mounts a MITM attack, then > > it will not be able to impersonate Alice to Bob because it > > can't generate the correct RFC 4474 signature. Thus, either > > the attacker won't provide a valid signature (being anonymous > > from Bob's perspective) or it will produce a valid signature > > with its own identity. In either case, this isn't really a > > useful MITM attack since Bob thinks he's talking to the > > attacker, not to Alice. > > If the certificate is self-signed and nonetheless accepted in the > DTLS handshake, then anybody can forge a signature pretending it > comes from Alice, including the MITM attacker (auto-issued > certificates would have the same property). Or did I miss > something?
Yes. The fingerprints in the SIP messages preclude certificate substitution. > > Note the analagous situation with SSL/TLS, where the attacker > > can mount an MITM attack, but only with an identity that doesn't > > match the identity that the client expects, so it's not > > useful. > > > > This is because neither self-signed certificates (at least those that do > not acquire the "trust anchor" status by "some other means") nor > auto-issued certificates are allowed in SSL/TLS. Otherwise, > impersonation is possible. Or did I miss something? But in DTLS-SRTP the fingerprints in the SIP messages (signed via RFC 4474) substitute for the certificate chain. > I guess the draft document might proceed only if the man-in-the-middle > attack is referred to in the security considerations for self-signed > certificates. I think you misunderstand the security issues, as discussed above. -Ekr _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
