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

<home_pw@msn.com> writes:

>>> > You say choked, I say graceful fail.
>>>
>>> No, I don't agree with this analysis. The server being unwilling
>>> to resume a session is normal behavior. The TLS state machine
>>> explicitly handles such cases. Implementations which choke
>>> rather than doing a full handshake are broken.
>>
>> I fully agree with Eric that a client MUST deal gracefully with
>> a server that does not resume a proposes SSL session (ID) for
>> whatever reason.
>
>
> Show me the text in the standard that says MUST (or even half hints
> MUST from the English wording). Tell me it MUST apply to EAP-TLS,
> too. More importantly, tell me what "appropriate" and "graceful" then
> mean, for packets on the wire. Tell me what the server MUST do, if the
> client does not comply. Your both making this out to be security- or
> interoperability- critical (it's a MUST, Peter!!)
>
> Eric is clear that this is not a new concept (for novel discussion);
> but an ancient one. It must be pretty obviously disclosed, or have
> been improved (by now) due to the years of text review.
>
> Now, for my part, I already pointed out text that says, I the
> implementer have 100% control over open and closing
> connections. NOTHING IN THIS STANDARD SHALL ...

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.

-Ekr

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