On Thu, Feb 21, 2008 at 12:58:03PM -0800, Justin Karneges wrote: > On Thursday 21 February 2008 9:49 am, Peter Saint-Andre wrote: > > First let's take Shumon's example of upenn.edu, which resolves via SRV > > to jabber.upenn.edu. In this case, the certificate would include an > > SRVName of _xmpp.jabber.upenn.edu, which would help the connecting > > client (or server) to know that jabber.upenn.edu is the authorized > > domain for connecting to the canonical XMPP service at upenn.edu (e.g., > > thus knowing that the DNS SRV lookup did not return poisoned results). > > This is not my understanding. > > If I resolve SRV for _xmpp-client._tcp.upenn.edu and receive > jabber.attacker.com as a result, and then I connect to jabber.attacker.com > and receive a certificate containing SRVName of > _xmpp-client.jabber.attacker.com, then I don't see the security improvement.
No, you'd be expecting to see SRVName of _xmpp-client.upenn.edu. Presumably the operator of jabber.attacker.com would not be able to persuade a reputable CA to issue him a certificate with _xmpp-client.upenn.edu populated in the SRVName field. --Shumon.
