gnutls-cli fails to handshake with Exchange server that uses DES-CBC3-SHA cipher

Nikos Mavrogiannopoulos nmav at
Sat Mar 31 19:32:16 CEST 2012

On 03/30/2012 02:02 PM, Ted Zlatanov wrote:

> On Thu, 29 Mar 2012 20:22:31 -0400 Thomas Fitzsimmons <fitzsim at> wrote: 
> TF> Emacs allows overriding the default GnuTLS priority string using a
> TF> variable (gnutls-algorithm-priority) so I set it to "performance" to
> TF> work around this server-side issue.  In cases where Emacs would
> TF> otherwise fail to connect to a server because of a weak ciphersuite
> TF> maybe the UI should warn the user and ask them whether or not to
> TF> proceed.  Anyway, thanks for analyzing the logs.
> I don't think currently Emacs can distinguish this case from a normal
> negotiation failure.  The best we can do is to generally suggest a
> weaker priority string, which seems to be a bad idea.  Is there a way to
> determine that this case has occurred?

You cannot in general distinguish a negotiation with a broken server and
negotiation failure. What (I think) browsers do is if negotiation fails
they fallback to the most compatible mode (SSL 3.0 or so).


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