GNU bug report logs - #16253
24.3.50; Irrelevant warnings from gnutls

Previous Next

Full log

View this message in rfc822 format

From: Ted Zlatanov <tzz <at> lifelogs.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: Nikos Mavrogiannopoulos <n.mavrogiannopoulos <at> gmail.com>, Roland Winkler <winkler <at> gnu.org>, 15057 <at> debbugs.gnu.org, 16253 <at> debbugs.gnu.org, 11267 <at> debbugs.gnu.org, Tassilo Horn <tsdh <at> gnu.org>
Subject: bug#16253: bug#11267: bug#15057: 24.3.50; TLS error with reasonably high gnutls-min-prime-bits, bug#11267: 24.0.95; gnutls.c: [0] (Emacs) fatal error: The Diffie-Hellman prime sent by the server is not acceptable (not long enough).
Date: Tue, 11 Feb 2014 09:21:58 -0500

On Mon, 10 Feb 2014 21:09:25 -0800 Lars Ingebrigtsen <larsi <at> gnus.org> wrote: 

LI> (Emacs, being Emacs, might offer as an option a way to restrict all TLS
LI> connections to a smaller set of algorithms/levels, but that should not
LI> be the default.)

I think it should, as long as we make it easy to drop down the security,
as I described:

>> * how to try allowing the less-secure connection (perhaps a simple
>> command to automate this, or even a clickable button, would be nicer
>> than asking the user to `customize-variable').  The original discussion
>> sort of settled on magically reopening the connection with less security
>> but I think that might be a disservice to the users.

LI> We would always try to get the most secure TLS connection possible, so I
LI> don't quite understand "reconnect"...

So my proposal is simply to provide two buttons "allow host X to connect
with lower DHE security [temporarily] [permanently]" and when the button
is clicked, customize `gnutls-algorithm-priority' to allow DHE to that
specific host.

`gnutls-negotiate' has to be changed slightly and the connection
rejection from insecure hosts will need to be handled in gnutls.c and
gnutls.el.

I think that's as seamless as we can make it, especially noting that
`gnutls-min-prime-bits' is deprecated since GnuTLS 3.1.7 (see
http://www.gnutls.org/manual/gnutls.html#index-gnutls_005fdh_005fset_005fprime_005fbits).

If we provide that simple UI, plus some help messaging, I think we can
disable DHE by default.  Based on Nikos' explanation, it seems to be the
best way forward.

Ted

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.