Re: Identity Checking in Application Protocols

["tom.petch" <cfinss at dial.pipex.com>]

----- Original Message ----- 
From: "Peter Saint-Andre" <stpeter at stpeter.im>
Sent: Tuesday, October 27, 2009 10:28 PM
 
> On 10/27/09 4:28 AM, Alexey Melnikov wrote:
> > Hi Peter,
> > 
> > Peter Saint-Andre wrote:
> >> I had hoped to update draft-saintandre-tls-server-id-check before the
> >> submission cutoff today, but it's not going to happen because there's
> >> quite a bit of feedback to sift through (ideally I would have followed
> >> the list discussions more closely the first time around).  However, I
> >> shall work to update it in the next few days, at which time I will also
> >> rename it to remove the strings "tls" and "server" since the scope of
> >> the spec has widened to include non-TLS interactions as well as client
> >> identity checking. My apologies for the delay.
> >>   
> > Without my AD hat: I don't think the document should cover client
> > identity checking. I found Kurt's arguments to be convincing.
> 
> I think that the distinction between application roles and security
> roles causes some confusion here. This I-D talks about security roles,
> not application roles. Thus, for example, when two XMPP servers wish to
> establish a TLS-encrypted connection, from the security point of view
> the server that initiates the connection is a TLS client whereas the
> server that receives the connection is a TLS server (despite the fact
> that from an application point of view both of them are XMPP servers).
> 
> My understanding of Kurt's argument is that we can't say much that's
> helpful about how a TLS server checks the identity of a TLS client
> because the problem is application-specific and the TLS server doesn't
> really have a "reference identity" (an idea of what identity the client
> will assert). At some level, the TLS server knows that it expects the
> TLS client to assert a kind of identity (domain name, email address,
> XMPP address, etc.) but not necessarily a particular instance of that
> kind ("example.com", "foo at example.com", or whatever).
> 
> I need to think about this further. I'm sure that re-reading Kurt's
> messages will help...

My take is that the only difference is one of number.

A client is 'configured' with a single reference identity, eg by the user
keying it into a window, which is then used in a comparison with what 
is returned in an X.509 certificate.

A server may support more than one client and so may be configured
with more than one reference identity and use any or all of them in a 
comparison with what is received in an X.509 certificate eg with SIP, 
Netconf, syslog,
....

Of course, a server may not care to check, may not be configured with 
anything, in which case the procedures in this I-D are irrelevant

Tom Petch
> 
> Peter
> 
> - --
> Peter Saint-Andre
> https://stpeter.im/
>