bug#13877: 24.3; gnutls.el: Enable Certificate Checks

[Moritz Ulrich <moritz@tarn-vedra.de>]

Currently, gnutls.el doesn't check certificate signatures when used via
`open-network-stream' with :type 'tls or `open-gnutls-stream'.

This is caused by the following code from `open-gnutls-stream'
(gnutls.el:110):

--8<---------------cut here---------------start------------->8---
(gnutls-negotiate :process (open-network-stream name buffer host service)
                  :type 'gnutls-x509pki
                  :hostname host)
--8<---------------cut here---------------end--------------->8---

There is NO way to set :verify-host, :verify-flags, etc. for this call
to `gnutls-negotiate' when using gnutls via high-level functions like
`open-network-stream'.

I consider this a bug, as Emacs won't check any certificates and
therefore allow man in the middle attacks without even documenting this.

It should at least be possible to pass :verify-* from
`open-network-stream' down to `gnutls-negotiate'. That would be a simple
yet effective solution.


In GNU Emacs 24.3.1 (x86_64-apple-darwin11.4.2, NS apple-appkit-1138.51)
 of 2013-03-05 on Moritzs-MacBook-Air
Windowing system distributor `Apple', version 10.3.1138
Configured using:
 `configure '--prefix=/usr/local/Cellar/emacs/24.3-rc1' '--without-dbus'
 '--enable-locallisppath=/usr/local/share/emacs/site-lisp'
 '--infodir=/usr/local/Cellar/emacs/24.3-rc1/share/info/emacs'
 '--with-ns' '--disable-ns-self-contained' '--with-gnutls' '--with-jpeg'
 '--with-xml2' '--with-imagemagick' 'CC=cc''

<#secure method=pgpmime mode=sign>

-- 
Moritz Ulrich