Hi,
I understand why for a client comunicating with a server the server will garantee its idientity with TLS, while the client will have to respond to a challange. My question concerns two proxies. where each proxy want's to verify the other side by using TLS. As I understood it it is premissable to require client authentication for incoming connections (infact RFC3261/ 26.3.1 mandates that capability).


I understand that certificate are associated to entities but I still think that the commonName filed and the altDns fileds still needs to be checked so the server that was presented with the certificate knows that the certificate was indeed issued to the presenting server (again RFC3261/ 26.3.1).






From: [EMAIL PROTECTED]
To: "Eron Stein" <[EMAIL PROTECTED]>
CC: [EMAIL PROTECTED]
Subject: Re: [Sipping] TLS and sip messages
Date: Wed, 12 Mar 2003 10:36:45 +0530



Hi Eron,

For the server, TLS is more for the data transport security than client
authentication.

Client authentication is done at application layer by challenging the user
(this happens if the SIP message didnt contain correct credentials).

I think the certificates can-not be associated with an IP address.
certificates are assigned to an entity by a trusted CA.

When we verify the certificate, we'll have to verify if the certificate
presented by the peer is signed by the trusted CA. It need not be
verified against any IP address. B'cause certificates are not assigned for
IP address but to some functional entities.

regards,
Shetti





"Eron Stein" <[EMAIL PROTECTED]> on 03/11/2003 06:37:32 PM

To:   [EMAIL PROTECTED], [EMAIL PROTECTED]
cc:    (bcc: Shrinivas Shetti/HSSBLR)

Subject: [Sipping] TLS and sip messages




Hi, I want to implement sip over TLS and I have encountered a problematic question: The question concerns a situation where an incoming connection has to be authenticated with TLS, that is TLS handshake with client certificates. (That might be the situation between two proxies).

As I understand it the side that initiated the connection has no problem
authenticating the certificate since it knows the connection's desired
destination, and can compare that destination address to the addresses
found
in the certificate.

The problem is with the side that receives the connection (the server).
What
domain-name/ip should that proxy use to check if the certificate matches
the
connection address.

One possibility is to check the certificate against the source address of
the incoming connection, that option might be problematic if the
certificate
contains a FQDN rather than a specific IP address.

Another possibility is to wait for the first message on the connection and
compare the host field from the VIA header the the common name in the
certificate.

I would appreciate any comments, ideas or real world implementation data on
the matter.

Regards,
Eron Stein.

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