Emacs and TLS support

Simon Josefsson simon at josefsson.org
Thu Sep 30 12:18:26 CEST 2010

Ted Zlatanov <tzz at lifelogs.com> writes:

> On Sun, 26 Sep 2010 23:06:46 +0200 Lars Magne Ingebrigtsen <larsi at gnus.org> wrote: 
> LMI> Ted Zlatanov <tzz at lifelogs.com> writes:
>>> I stepped through the GnuTLS function calls and couldn't find a problem
>>> with the credential structures.  It's frustrating that the exact same
>>> code works for the example client in GnuTLS but breaks in Emacs (most of
>>> my time debugging this was spent double-checking that the same functions
>>> are called with the same parameters in both cases).
> LMI> I know nothing about tls, but have you confirmed that the library calls
> LMI> really work in non-blocking mode?  It's not uncommon to write libraries
> LMI> that assume that socket connections are blocking...
> It would be great if the GnuTLS developers could comment.  But these
> references seem to specifically confirm that non-blocking sockets should
> work the way I'm doing it:
> http://lists.gnupg.org/pipermail/gnutls-dev/2005-March/000839.html
> http://www.gnu.org/software/gnutls/manual/html_node/The-transport-layer.html

Yes, it should work both in blocking and non-blocking.

> I tried setting the low water value to 0 in `Fgnutls_handshake' after
> `gnutls_transport_set_ptr2' but it didn't make a difference:
>     gnutls_transport_set_lowat (state, 0);
> So I removed it in the patch.  I sort of suspect right now that
> recv/send are not working correctly so I need to provide custom versions
> with `gnutls_transport_set_pull_function' and
> `gnutls_transport_set_push_function'.  But I don't know enough about the
> Emacs internals that set up processes, which are ridiculously
> complicated because of all the supported platforms.  And Simon Josefsson
> said his patch worked when he first wrote it, so I assumed that this
> kind of deep surgery would not be required.

I don't know Emacs internals well enough, but it may be that replacing
the send/recv functions could make things more reliable...

I don't have a lot of time to help here alas, and when I tried building
Emacs from CVS the other day it just crashed...  maybe you could provide
simple step-by-step instructions to get something building that I can
test?  With some specific CVS revision that is known working.


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