[Help-gnutls] GNUTLS in handshake procedure

[Lennart Koopmann]

Hello John,

thank you very much! That seems to be what i planned to do. Good to hear
that it should make no problems. I will try it today.

The MITM attack should be no problem, because the client is forced to
use GNUTLS when the user specified it. There is no possibilty to send
unencrypted data after the handshaking procedure if useGNUTLS is set to
true. :)

Thank you!

So long
Lennart

Am Sonntag, den 14.09.2008, 10:40 -0600 schrieb John Brooks:
> As long as the handshake is called in the proper order (client must
> speak first, which means client must initiate the handshake), it
> doesn't matter when that happens during a connection's lifetime. The
> server does need to be expecting it, or it would try to handle the
> data normally instead of passing it to gnutls for handshaking.
> Provided both ends are expecting it when it happens, and the client
> goes first, you won't have any problems.
> 
> This is generally referred to as 'starttls'; it's a great way to
> support both SSL and non-SSL connections, but care needs to be taken
> to avoid MITM attacks stripping the SSL (for example, an attacker
> faking a response from the server stating that SSL is not supported,
> to force your connection to remain unencrypted), and to ensure that
> nothing private is sent before the SSL connection starts.
> 
> - John Brooks