Re: [Bug-wget] please remove SSLv3 from being used until explicitly specified

[Tim Rühsen]

Am Sonntag, 19. Oktober 2014, 21:11:01 schrieb Ángel González:
> Tim Rühsen wrote:
> > Hi Ángel,
> > 
> > thanks for your testing.
> > 
> > I would like to reproduce it - can you tell me what you did exactly ?
> 
> I used a simple server that printed the TLS Client Hello and closed the
> connection.
> Browsers automatically retried with lower SSL versions.
> wget aborted with an «Unable to establish SSL connection.» message
> 
> > The original paper talks about 'client renegotiation dance'.
> > What about renegotiation at protocol level ? Isn't it possible that a TLS
> > connection goes down to SSLv3 intransparent to the client/server code ?
> 
> AFAIK no. That is protected by the HMAC. The problem is the version
> downgrading
> on a network error, which can be inserted by a MiTM (and without
> TLS_FALLBACK_SCSV the server won't be able to that the client downgraded its
> version thinking the server didn't support a greater one).
> 
> > I am not that deep into the TLS/SSL libraries to answer that question
> > myself right now. The paper talks about 'proper protocol version
> > negotiation' - that seems to need some clarification.
> 
> That's the server replying with a lower protocol version in the same
> connection.
> The downgrade was a hack for broken servers not properly supporting SSL.
> And
> we are paying it now.

Thank you !

Tim