[Mod_nss-list] TLS MITM issues CVE-2009-3555 vs. mod_nss

[Rob Crittenden]

Tomas Hoger wrote:
> Hi Rob!
> 
> On Tue, 10 Nov 2009 14:07:06 -0500 Rob Crittenden <rcritten at redhat.com>
> wrote:
> 
>>> Are there any plans for mod_nss modifications to address / mitigate
>>> this issue?
>> Yes, I'm looking into this. I'm not sure I can take the same approach
>> as mod_ssl since I have much less visibility into the SSL handshake
>> with NSS than with OpenSSL.
> 
> So do you think SSL_HandshakeCallback-registered callbacks should be
> insufficient?  I do see HandshakeDone callback is already used during
> the server-initiated rehandshake to track its progress.  It is then
> unregistered when rehandshake is done.
> 
> What about registering another function instead of the NULL callback?
> The function that will trigger connection abort when called.  Can that
> be a way or is unlikely to work and is not work more effort?
> 
> Thank you!

Very clever idea!

I think this can be extended a bit too. We really should set the 
handshake callback to something that returns SECFailure in all cases 
except where we do a server-initiated renegotiation. So once the initial 
handshake is completed we shouldn't allow any further handshaking 
(unless initiated using existing mechanism). I need to check with the 
NSS guys on a few things but this seems like a very simple way of fixing it.

thanks

rob
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