Re: [TLS] Re: when is it ok to resume a cached SSL/TLS session

> RFC 4346 S 7.3.
>
>   If a match is found, and the server is willing to 
> re-establish the
>   connection under the specified session state, it will 
> send a
>   ServerHello with the same Session ID value.  At this 
> point, both
>   client and server MUST send change cipher spec messages 
> and proceed
>   directly to finished messages.  Once the 
> re-establishment is
>   complete, the client and server MAY begin to exchange 
> application
>   layer data.  (See flow chart below.)  If a Session ID 
> match is not
>   found, the server generates a new session ID and the TLS 
> client and
>   server perform a full handshake.
>
> In other words, refused session resumptions are totally 
> normal
> behavior. Clients which treat them as anomalous are 
> confused.
>
> Yes, a client can terminate the connection at any time and 
> for
> any reason, including that it doesn't like the phase of 
> the moon,
> but that doesn't make the assumption that a server will 
> always
> resume a session---presenting an error to the user if it
> doesn't---any less insane. No such error occurred.

This only partly reflects the case in question. I agree its 
the defining technical paragraph, tho (*).

The server in Martin's case didn't find a match: that was 
the whole point. So, the last phrase controls. And, there is 
not a MUST in there.

Ok. Lets conclude this, procedurally. Who agrees that TLS 
1.2 shall be changed to:-

"If a Session ID match is not found, the server generates a 
new session ID and the TLS client and server MUST perform a 
full handshake."

With that settled, the next implementer get a nice, simple 
conformance case to test. No more interpretive arguments.

------
(*) I think THE FOLLOWING WAS BETTER WRITTEN personally

"   Sessions cannot be resumed unless both the client and 
server agree.
   If either party suspects that the session may have been
   compromised, or that certificates may have expired or 
been revoked,
   it should force a full handshake. "

and lets not forget that maintaining a session resumption 
cache is OPTIONAL for a client in SSLv3.

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