Dr Stephen Henson wrote:
>
> Adrian Peck wrote:
> >
> > The basic problem is that IE4 or 5 will issue a client hello message
> > immediately after receiving the server hello and server certificate if it
> > finds that this certificate was a Server Gated Crypto ( SGC ) certificate.
> > The 'point' of this is to change the cipher suites that are offered to the
> > server without starting a new SSL session. My code peeks at the client
> > message to check for a client hello and resets the SSL state to
> > SSL_ST_ACCEPT if it spots one. The code is only visited if the SSL mode
> > SSL_MODE_NCIPHER_SGC_HACK is set.
> >
>
>
> I'm not sure what the MSIE logic of not starting a new session is
> though. At this point no cryptographic operations have been performed so
> there isn't much overhead.
>
Ah I see the point now. The server doesn't have to generate the RSA
temporary key and more importantly sign it with the certified key: this
is likely to be an expensive operation.
The next problem is how can the server in general determine whether to
expect the second client hello?
I can think of lots of possible solutions.
One simple way is for it to accept the client hello after it has sent
the server done message and then restart. This will however mean that it
must perform the expensive private key operations on the initial
handshake. This will at least work and is I believe what the patch does
when a memory BIO is present. I'll look into checking in a fix that
works in all circumstances.
Trickier solutions might involve attempting to read the second client
hello if we have an SGC certificate and timing out otherwise. Getting
this going cross platform could be nasty.
What I suspect is going on is that somehow the server can determine that
it is an MSIE client and that it can do SGC. Maybe something naughty in
the client hello message?
Steve.
--
Dr Stephen N. Henson. http://www.drh-consultancy.demon.co.uk/
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