Re: Emacs core TLS support

[Ted Zlatanov <tzz@lifelogs.com>]

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On Mon, 13 Sep 2010 09:49:30 +0200 Nikos Mavrogiannopoulos <nmav@gnutls.org> wrote: 

NM> I cannot look at the patch but the example you are looking for is:
NM> http://www.gnu.org/software/gnutls/manual/html_node/Simple-client-example-with-X_002e509-certificate-support.html#Simple-client-example-with-X_002e509-certificate-support
NM> to do the connection, and this one to verify the certificate:
NM> http://www.gnu.org/software/gnutls/manual/html_node/Verifying-peer_0027s-certificate.html#Verifying-peer_0027s-certificate

Thanks for your help.  I am still a little lost though :)

Can you give a specific command line that would start gnutls-serv so the
simple client (ex-client2.c) you reference will connect to it?  If
that's not possible, is there a way to augment ex-client2.c so it
connects to an invocation of gnutls-serv without building all the
gnutls-cli (cli.c, etc.) infrastructure?

I can do a test connection with gnutls-cli but that's a much more
complicated program and I'm trying to get the simple connection working,
even without verification.  If I can get the bare minimum SSL and TLS
working I can drop the patch into Emacs and get more eyes on it.  I'm
tempted to do so now so I can stop sending this patch out :)

It would be wonderful, incidentally, if there was a way to configure all
the file options with a single string, similar to the priority string,
and just get back a session.  A config file would also work if a single
string is too hard to parse.  I don't see any options that couldn't work
like this and it would make setting up a GnuTLS connection much easier.

On Tue, 14 Sep 2010 20:55:51 +0200 Nikos Mavrogiannopoulos <nmav@gnutls.org> wrote: 

NM> GNUTLS_E_AGAIN is returned only if the transport layer function
NM> (recv/send) return -1 and EAGAIN. Usually this is normal behavior and is
NM> enough to loop around them. Do you use non-blocking IO?

Ah, thanks for the hint.  All the GnuTLS source code (e.g. the
do_handshake() function in cli.c) keeps looping forever as long as
GNUTLS_E_AGAIN is returned.  That seems dangerous regardless of the
underlying mechanism because we don't want to lock up Emacs waiting for
a connection, but OTOH there's no other way to know if the handshake is
done.  I limited it to 25000 times (used to be 25) in my patch.  Is that
a reasonable limit?  Should I base it on time elapsed?

With a limit of 25K and by checking `gnutls-error-fatalp' which calls
`gnutls_error_is_fatal', the handshake succeeds after 1250 tries against
a remote SSL server.  So now against that server I get:

-24 (Decryption has failed.)

and against "gnutls-serv --priority NORMAL --http" I get

-12 (A TLS fatal alert has been received.)

(the server side says "Error in handshake
Error: Could not negotiate a supported cipher suite.")

which is a lot better: at least the handshake is no longer the problem
and it tells us the transport FDs are set correctly.  So we can progress
to figuring out the bare minimum I mentioned above.

Latest patch attached, as usual.

Thanks again...
Ted


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=== modified file 'configure.in'
--- configure.in	2010-09-13 19:50:30 +0000
+++ configure.in	2010-09-15 09:13:07 +0000
@@ -171,6 +171,7 @@
 OPTION_DEFAULT_ON([dbus],[don't compile with D-Bus support])
 OPTION_DEFAULT_ON([gconf],[don't compile with GConf support])
 OPTION_DEFAULT_ON([selinux],[don't compile with SELinux support])
+OPTION_DEFAULT_ON([gnutls],[don't use -lgnutls for SSL/TLS support])
 
 ## For the times when you want to build Emacs but don't have
 ## a suitable makeinfo, and can live without the manuals.
@@ -1999,6 +2000,13 @@
 fi
 AC_SUBST(LIBSELINUX_LIBS)
 
+HAVE_GNUTLS=no
+if test "${with_gnutls}" = "yes" ; then
+  PKG_CHECK_MODULES([LIBGNUTLS], [gnutls >= 2.2.4])
+  AC_DEFINE(HAVE_GNUTLS)
+  HAVE_GNUTLS=yes
+fi
+
 dnl Do not put whitespace before the #include statements below.
 dnl Older compilers (eg sunos4 cc) choke on it.
 HAVE_XAW3D=no
@@ -3701,6 +3709,7 @@
 echo "  Does Emacs use -ldbus?                                  ${HAVE_DBUS}"
 echo "  Does Emacs use -lgconf?                                 ${HAVE_GCONF}"
 echo "  Does Emacs use -lselinux?                               ${HAVE_LIBSELINUX}"
+echo "  Does Emacs use -lgnutls?                                ${HAVE_GNUTLS}"
 
 echo "  Does Emacs use -lfreetype?                              ${HAVE_FREETYPE}"
 echo "  Does Emacs use -lm17n-flt?                              ${HAVE_M17N_FLT}"

=== added file 'lisp/net/gnutls.el'
--- lisp/net/gnutls.el	1970-01-01 00:00:00 +0000
+++ lisp/net/gnutls.el	2010-09-15 10:38:20 +0000
@@ -0,0 +1,131 @@
+;;; gnutls.el --- Support SSL and TLS connections through GnuTLS
+;; Copyright (C) 2010 Free Software Foundation, Inc.
+
+;; Author: Ted Zlatanov <tzz@lifelogs.com>
+;; Keywords: comm, tls, ssl, encryption
+;; Originally-By: Simon Josefsson (See http://josefsson.org/emacs-security/)
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This package provides language bindings for the GnuTLS library
+;; using the corresponding core functions in gnutls.c.
+
+;; Simple test:
+;;
+;; (setq jas (open-ssl-stream "ssl" (current-buffer) "www.pdc.kth.se" 443))
+;; (process-send-string jas "GET /\r\n\r\n")
+
+;;; Code:
+
+(defconst gnutls-version "0.3.1")
+
+(defun open-ssl-stream (name buffer host service)
+  "Open a SSL connection for a service to a host.
+Returns a subprocess-object to represent the connection.
+Input and output work as for subprocesses; `delete-process' closes it.
+Args are NAME BUFFER HOST SERVICE.
+NAME is name for process.  It is modified if necessary to make it unique.
+BUFFER is the buffer (or `buffer-name') to associate with the process.
+ Process output goes at end of that buffer, unless you specify
+ an output stream or filter function to handle the output.
+ BUFFER may be also nil, meaning that this process is not associated
+ with any buffer
+Third arg is name of the host to connect to, or its IP address.
+Fourth arg SERVICE is name of the service desired, or an integer
+specifying a port number to connect to."
+  (let ((proc (open-network-stream name buffer host service)))
+    (starttls-negotiate proc nil 'gnutls-x509pki)))
+
+;; (open-ssl-stream "tls" "tls-buffer" "yourserver.com" "https")
+(defun starttls-negotiate (proc &optional priority-string
+                                credentials credentials-file)
+  "Negotiate a SSL or TLS connection.
+PROC is the process returned by `starttls-open-stream'.
+PRIORITY-STRING is as per the GnuTLS docs.
+CREDENTIALS is `gnutls-x509pki' or `gnutls-anon'.
+CREDENTIALS-FILE is a filename with meaning dependent on CREDENTIALS."
+  (let* ((credentials (or credentials 'gnutls-x509pki))
+         (credentials-file (or credentials-file
+                               ;"/etc/ssl/certs/ca-certificates.crt"
+                               ;"/etc/ssl/certs/ca.pem"
+                               "/tmp/ca.pem"
+                               ))
+
+         (priority-string (or priority-string
+                              (cond
+                               ((eq credentials 'gnutls-anon)
+                                "PERFORMANCE:+ANON-DH:!ARCFOUR-128")
+                               ((eq credentials 'gnutls-x509pki)
+                                "PERFORMANCE"))))
+         ret)
+
+    (gnutls-message-maybe
+     (setq ret (gnutls-boot proc priority-string credentials credentials-file))
+     "boot: %s")
+
+    (when (gnutls-errorp ret)
+      (error "Could not boot GnuTLS for this process"));
+
+    (let ((ret 'gnutls-e-again)
+          (n 25000))
+      (while (and (not (gnutls-error-fatalp ret))
+                  (> n 0))
+        (decf n)
+        (gnutls-message-maybe
+         (setq ret (gnutls-handshake proc))
+         "handshake: %s")
+        ;(debug "handshake ret" ret (gnutls-error-string ret)))
+        )
+      (if (gnutls-errorp ret)
+          (progn
+            (message "Ouch, error return %s (%s)"
+                     ret (gnutls-error-string ret))
+            (setq proc nil))
+        (message "Handshake complete %s." ret)))
+     proc))
+
+(defun starttls-open-stream (name buffer host service)
+  "Open a TLS connection for a service to a host.
+Returns a subprocess-object to represent the connection.
+Input and output work as for subprocesses; `delete-process' closes it.
+Args are NAME BUFFER HOST SERVICE.
+NAME is name for process.  It is modified if necessary to make it unique.
+BUFFER is the buffer (or `buffer-name') to associate with the process.
+ Process output goes at end of that buffer, unless you specify
+ an output stream or filter function to handle the output.
+ BUFFER may be also nil, meaning that this process is not associated
+ with any buffer
+Third arg is name of the host to connect to, or its IP address.
+Fourth arg SERVICE is name of the service desired, or an integer
+specifying a port number to connect to."
+  (open-network-stream name buffer host service))
+
+(defun gnutls-message-maybe (doit format &rest params)
+  "When DOIT, message with the caller name followed by FORMAT on PARAMS."
+  ;; (apply 'debug format (or params '(nil)))
+  (when (gnutls-errorp doit)
+    (message "%s: (err=[%s] %s) %s"
+             "gnutls.el"
+             doit (gnutls-error-string doit)
+             (apply 'format format (or params '(nil))))))
+
+(provide 'ssl)
+(provide 'gnutls)
+(provide 'starttls)
+
+;;; gnutls.el ends here

=== modified file 'src/Makefile.in'
--- src/Makefile.in	2010-09-10 16:44:35 +0000
+++ src/Makefile.in	2010-09-15 09:13:07 +0000
@@ -287,6 +287,9 @@
 
 LIBSELINUX_LIBS = @LIBSELINUX_LIBS@
 
+LIBGNUTLS_LIBS = @LIBGNUTLS_LIBS@
+LIBGNUTLS_CFLAGS = @LIBGNUTLS_CFLAGS@
+
 INTERVALS_H = dispextern.h intervals.h composite.h
 
 GETLOADAVG_LIBS = @GETLOADAVG_LIBS@
@@ -326,6 +329,7 @@
   ${LIBXML2_CFLAGS} ${DBUS_CFLAGS} \
   ${GCONF_CFLAGS} ${FREETYPE_CFLAGS} ${FONTCONFIG_CFLAGS} \
   ${LIBOTF_CFLAGS} ${M17N_FLT_CFLAGS} ${DEPFLAGS} ${PROFILING_CFLAGS} \
+  $(LIBGNUTLS_CFLAGS) \
   ${C_WARNINGS_SWITCH} ${CFLAGS}
 ALL_OBJC_CFLAGS=$(ALL_CFLAGS) $(GNU_OBJC_CFLAGS)
 
@@ -350,7 +354,7 @@
 	alloc.o data.o doc.o editfns.o callint.o \
 	eval.o floatfns.o fns.o font.o print.o lread.o \
 	syntax.o $(UNEXEC_OBJ) bytecode.o \
-	process.o callproc.o \
+	process.o gnutls.o callproc.o \
 	region-cache.o sound.o atimer.o \
 	doprnt.o strftime.o intervals.o textprop.o composite.o md5.o xml.o \
 	$(MSDOS_OBJ) $(MSDOS_X_OBJ) $(NS_OBJ) $(CYGWIN_OBJ) $(FONT_OBJ)
@@ -602,6 +606,7 @@
    ${LIBXML2_LIBS} $(LIBGPM) $(LIBRESOLV) $(LIBS_SYSTEM) \
    $(LIBS_TERMCAP) $(GETLOADAVG_LIBS) ${GCONF_LIBS} ${LIBSELINUX_LIBS} \
    $(FREETYPE_LIBS) $(FONTCONFIG_LIBS) $(LIBOTF_LIBS) $(M17N_FLT_LIBS) \
+   $(LIBGNUTLS_LIBS) \
    $(LIB_GCC) $(LIB_MATH) $(LIB_STANDARD) $(LIB_GCC)
 
 all: emacs${EXEEXT} $(OTHER_FILES)

=== modified file 'src/config.in'
--- src/config.in	2010-09-10 16:44:35 +0000
+++ src/config.in	2010-09-15 09:13:07 +0000
@@ -255,6 +255,9 @@
 /* Define to 1 if you have a gif (or ungif) library. */
 #undef HAVE_GIF
 
+/* Define if we have the GNU TLS library.  */
+#undef HAVE_GNUTLS
+
 /* Define to 1 if you have the gpm library (-lgpm). */
 #undef HAVE_GPM
 
@@ -1094,6 +1097,12 @@
 #include config_opsysfile
 #include config_machfile
 
+#if HAVE_GNUTLS
+#define LIBGNUTLS $(LIBGNUTLS_LIBS)
+#else /* not HAVE_GNUTLS */
+#define LIBGNUTLS
+#endif /* not HAVE_GNUTLS */
+
 /* Set up some defines, C and LD flags for NeXTstep interface on GNUstep.
   (There is probably a better place to do this, but right now the Cocoa
    side does this in s/darwin.h and we cannot

=== modified file 'src/emacs.c'
--- src/emacs.c	2010-09-10 16:44:35 +0000
+++ src/emacs.c	2010-09-15 09:13:07 +0000
@@ -63,6 +63,10 @@
 #include "keyboard.h"
 #include "keymap.h"
 
+#ifdef HAVE_GNUTLS
+#include "gnutls.h"
+#endif
+
 #ifdef HAVE_NS
 #include "nsterm.h"
 #endif
@@ -1573,6 +1577,10 @@
       syms_of_fontset ();
 #endif /* HAVE_NS */
 
+#ifdef HAVE_GNUTLS
+      syms_of_gnutls ();
+#endif
+
 #ifdef HAVE_DBUS
       syms_of_dbusbind ();
 #endif /* HAVE_DBUS */

=== added file 'src/gnutls.c'
--- src/gnutls.c	1970-01-01 00:00:00 +0000
+++ src/gnutls.c	2010-09-15 10:29:28 +0000
@@ -0,0 +1,546 @@
+/* GnuTLS glue for GNU Emacs.
+   Copyright (C) 2010  Free Software Foundation, Inc.
+
+This file is part of GNU Emacs.
+
+GNU Emacs is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+GNU Emacs is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+#include <errno.h>
+#include <setjmp.h>
+
+#include "lisp.h"
+#include "process.h"
+
+#ifdef HAVE_GNUTLS
+#include <gnutls/gnutls.h>
+
+Lisp_Object Qgnutls_code;
+Lisp_Object Qgnutls_anon, Qgnutls_x509pki;
+Lisp_Object Qgnutls_e_interrupted, Qgnutls_e_again,
+  Qgnutls_e_invalid_session, Qgnutls_e_not_ready_for_handshake;
+int global_initialized;
+
+int
+emacs_gnutls_write (int fildes, gnutls_session_t state, char *buf,
+                    unsigned int nbyte)
+{
+  register int rtnval, bytes_written;
+
+  bytes_written = 0;
+
+  while (nbyte > 0)
+    {
+      rtnval = gnutls_write (state, buf, nbyte);
+
+      if (rtnval == -1)
+        {
+          if (errno == EINTR)
+            continue;
+          else
+            return (bytes_written ? bytes_written : -1);
+        }
+
+      buf += rtnval;
+      nbyte -= rtnval;
+      bytes_written += rtnval;
+    }
+  fsync (STDOUT_FILENO);
+
+  return (bytes_written);
+}
+
+int
+emacs_gnutls_read (int fildes, gnutls_session_t state, char *buf,
+                   unsigned int nbyte)
+{
+  register int rtnval;
+
+  do {
+    rtnval = gnutls_read (state, buf, nbyte);
+  } while (rtnval == GNUTLS_E_INTERRUPTED || rtnval == GNUTLS_E_AGAIN);
+  fsync (STDOUT_FILENO);
+
+  return (rtnval);
+}
+
+/* convert an integer error to a Lisp_Object; it will be either a
+   known symbol like `gnutls_e_interrupted' and `gnutls_e_again' or
+   simply the integer value of the error.  GNUTLS_E_SUCCESS is mapped
+   to Qt.  */
+Lisp_Object gnutls_make_error (int error)
+{
+  switch (error)
+  {
+  case GNUTLS_E_SUCCESS:
+    return Qt;
+  case GNUTLS_E_AGAIN:
+    return Qgnutls_e_again;
+  case GNUTLS_E_INTERRUPTED:
+    return Qgnutls_e_interrupted;
+  case GNUTLS_E_INVALID_SESSION:
+    return Qgnutls_e_invalid_session;
+  }
+
+  return make_number (error);
+}
+
+DEFUN ("gnutls-get-initstage", Fgnutls_get_initstage, Sgnutls_get_initstage, 1, 1, 0,
+       doc: /* Return the GnuTLS init stage of PROCESS.
+See also `gnutls-boot'.  */)
+    (Lisp_Object proc)
+{
+  CHECK_PROCESS (proc);
+
+  return make_number (GNUTLS_INITSTAGE (proc));
+}
+
+DEFUN ("gnutls-errorp", Fgnutls_errorp, Sgnutls_errorp, 1, 1, 0,
+       doc: /* Returns t if ERROR (as generated by gnutls_make_error)
+indicates a GnuTLS problem.  */)
+    (Lisp_Object error)
+{
+  if (EQ (error, Qt)) return Qnil;
+
+  return Qt;
+}
+
+DEFUN ("gnutls-error-fatalp", Fgnutls_error_fatalp, Sgnutls_error_fatalp, 1, 1, 0,
+       doc: /* Checks if ERROR is fatal.
+ERROR is an integer or a symbol with an integer `gnutls-code' property.  */)
+    (Lisp_Object err)
+{
+  Lisp_Object code;
+
+  if (EQ (err, Qt)) return Qnil;
+
+  if (SYMBOLP (err))
+  {
+    code = Fget (err, Qgnutls_code);
+    if (NUMBERP (code))
+    {
+      err = code;
+    }
+    else
+    {
+      error ("Symbol has no numeric gnutls-code property");
+    }
+  }
+
+  if (!NUMBERP (err))
+    error ("Not an error symbol or code");
+
+  if (0 == gnutls_error_is_fatal (XINT (err)))
+    return Qnil;
+
+  return Qt;
+}
+
+DEFUN ("gnutls-error-string", Fgnutls_error_string, Sgnutls_error_string, 1, 1, 0,
+       doc: /* Returns a description of ERROR.
+ERROR is an integer or a symbol with an integer `gnutls-code' property.  */)
+    (Lisp_Object err)
+{
+  Lisp_Object code;
+
+  if (EQ (err, Qt)) return build_string ("Not an error");
+
+  if (SYMBOLP (err))
+  {
+    code = Fget (err, Qgnutls_code);
+    if (NUMBERP (code))
+    {
+      err = code;
+    }
+    else
+    {
+      return build_string ("Symbol has no numeric gnutls-code property");
+    }
+  }
+
+  if (!NUMBERP (err))
+    return build_string ("Not an error symbol or code");
+
+  return build_string (gnutls_strerror (XINT (err)));
+}
+
+DEFUN ("gnutls-deinit", Fgnutls_deinit, Sgnutls_deinit, 1, 1, 0,
+       doc: /* Deallocate GNU TLS resources associated with PROCESS.
+See also `gnutls-init'.  */)
+    (Lisp_Object proc)
+{
+  gnutls_session_t state;
+
+  CHECK_PROCESS (proc);
+  state = XPROCESS (proc)->gnutls_state;
+
+  if (GNUTLS_INITSTAGE (proc) >= GNUTLS_STAGE_INIT)
+  {
+      gnutls_deinit (state);
+      GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_INIT - 1;
+  }
+
+  return Qt;
+}
+
+DEFUN ("gnutls-global-init", Fgnutls_global_init,
+       Sgnutls_global_init, 0, 0, 0,
+       doc: /* Initializes global GNU TLS state to defaults.
+Call `gnutls-global-deinit' when GNU TLS usage is no longer needed.
+Returns zero on success.  */)
+     (void)
+{
+  int ret = GNUTLS_E_SUCCESS;
+
+  if (!global_initialized)
+    ret = gnutls_global_init ();
+
+  global_initialized = 1;
+
+  return gnutls_make_error (ret);
+}
+
+DEFUN ("gnutls-global-deinit", Fgnutls_global_deinit,
+       Sgnutls_global_deinit, 0, 0, 0,
+       doc: /* Deinitializes global GNU TLS state.
+See also `gnutls-global-init'.  */)
+     (void)
+{
+  if (global_initialized)
+    gnutls_global_deinit ();
+
+  global_initialized = 0;
+
+  return gnutls_make_error (GNUTLS_E_SUCCESS);
+}
+
+DEFUN ("gnutls-boot", Fgnutls_boot, Sgnutls_boot, 3, 6, 0,
+       doc: /* Initializes client-mode GnuTLS for process PROC.
+Currently only client mode is supported.  Returns a success/failure
+value you can check with `gnutls-errorp'.
+
+PRIORITY_STRING is a string describing the priority.
+TYPE is either `gnutls-anon' or `gnutls-x509pki'.
+TRUSTFILE is a PEM encoded trust file for `gnutls-x509pki'.
+KEYFILE is ... for `gnutls-x509pki' (TODO).
+CALLBACK is ... for `gnutls-x509pki' (TODO).
+
+Note that the priority is set on the client.  The server does not use
+the protocols's priority except for disabling protocols that were not
+specified.
+
+Processes must be initialized with this function before other GNU TLS
+functions are used.  This function allocates resources which can only
+be deallocated by calling `gnutls-deinit' or by calling it again.
+
+Each authentication type may need additional information in order to
+work.  For X.509 PKI (`gnutls-x509pki'), you need TRUSTFILE and
+KEYFILE and optionally CALLBACK.  */)
+    (Lisp_Object proc, Lisp_Object priority_string, Lisp_Object type,
+     Lisp_Object trustfile, Lisp_Object keyfile, Lisp_Object callback)
+{
+  int ret = GNUTLS_E_SUCCESS;
+
+  /* TODO: GNUTLS_X509_FMT_DER is also an option.  */
+  int file_format = GNUTLS_X509_FMT_PEM;
+
+  gnutls_session_t state;
+  gnutls_certificate_credentials_t x509_cred;
+  gnutls_anon_client_credentials_t anon_cred;
+  gnutls_srp_client_credentials_t srp_cred;
+  gnutls_datum_t data;
+  Lisp_Object global_init;
+
+  CHECK_PROCESS (proc);
+  CHECK_SYMBOL (type);
+  CHECK_STRING (priority_string);
+
+  state = XPROCESS (proc)->gnutls_state;
+
+  /* always initialize globals.  */
+  global_init = Fgnutls_global_init ();
+  if (! NILP (Fgnutls_errorp (global_init)))
+    return global_init;
+
+  /* deinit and free resources.  */
+  if (GNUTLS_INITSTAGE (proc) >= GNUTLS_STAGE_CRED_ALLOC)
+  {
+      message ("gnutls: deallocating certificates");
+
+      if (EQ (type, Qgnutls_x509pki))
+      {
+          message ("gnutls: deallocating x509 certificates");
+
+          x509_cred = XPROCESS (proc)->x509_cred;
+          gnutls_certificate_free_credentials (x509_cred);
+      }
+      else if (EQ (type, Qgnutls_anon))
+      {
+          message ("gnutls: deallocating anon certificates");
+
+          anon_cred = XPROCESS (proc)->anon_cred;
+          gnutls_anon_free_client_credentials (anon_cred);
+      }
+      else
+      {
+          error ("unknown credential type");
+          ret = GNUTLS_EMACS_ERROR_INVALID_TYPE;
+      }
+
+      if (GNUTLS_INITSTAGE (proc) >= GNUTLS_STAGE_INIT)
+      {
+          message ("gnutls: deinitializing");
+
+          Fgnutls_deinit (proc);
+      }
+  }
+
+  GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_EMPTY;
+
+  message ("gnutls: allocating credentials");
+
+  if (EQ (type, Qgnutls_x509pki))
+  {
+      message ("gnutls: allocating x509 credentials");
+
+      x509_cred = XPROCESS (proc)->x509_cred;
+      if (gnutls_certificate_allocate_credentials (&x509_cred) < 0)
+        memory_full ();
+  }
+  else if (EQ (type, Qgnutls_anon))
+  {
+      message ("gnutls: allocating anon credentials");
+
+      anon_cred = XPROCESS (proc)->anon_cred;
+      if (gnutls_anon_allocate_client_credentials (&anon_cred) < 0)
+        memory_full ();
+  }
+  else
+  {
+      error ("unknown credential type");
+      ret = GNUTLS_EMACS_ERROR_INVALID_TYPE;
+  }
+
+  if (ret < GNUTLS_E_SUCCESS)
+      return gnutls_make_error (ret);
+
+  GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_CRED_ALLOC;
+
+  message ("gnutls: setting the trustfile");
+
+  if (EQ (type, Qgnutls_x509pki))
+  {
+      if (STRINGP (trustfile))
+      {
+          ret = gnutls_certificate_set_x509_trust_file
+            (x509_cred,
+             XSTRING (trustfile)->data,
+             file_format);
+
+          if (ret < GNUTLS_E_SUCCESS)
+            return gnutls_make_error (ret);
+
+          message ("gnutls: processed %d CA certificates", ret);
+      }
+
+      message ("gnutls: setting the keyfile");
+
+      if (STRINGP (keyfile))
+      {
+          ret = gnutls_certificate_set_x509_crl_file
+            (x509_cred,
+             XSTRING (keyfile)->data,
+             file_format);
+
+          if (ret < GNUTLS_E_SUCCESS)
+            return gnutls_make_error (ret);
+
+          message ("gnutls: processed %d CRL(s)", ret);
+      }
+  }
+
+  GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_FILES;
+
+  message ("gnutls: gnutls_init");
+
+  ret = gnutls_init (&state, GNUTLS_CLIENT);
+
+  if (ret < GNUTLS_E_SUCCESS)
+      return gnutls_make_error (ret);
+
+  XPROCESS (proc)->gnutls_state = state;
+
+  GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_INIT;
+
+  message ("gnutls: setting the priority string");
+
+  ret = gnutls_priority_set_direct(state,
+                                   (char*) SDATA (priority_string),
+                                   NULL);
+
+  if (ret < GNUTLS_E_SUCCESS)
+      return gnutls_make_error (ret);
+
+  GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_PRIORITY;
+
+  message ("gnutls: setting the credentials");
+
+  if (EQ (type, Qgnutls_x509pki))
+  {
+      message ("gnutls: setting the x509 credentials");
+
+      ret = gnutls_cred_set (state, GNUTLS_CRD_CERTIFICATE, x509_cred);
+  }
+  else if (EQ (type, Qgnutls_anon))
+  {
+      message ("gnutls: setting the anon credentials");
+
+      ret = gnutls_cred_set (state, GNUTLS_CRD_ANON, anon_cred);
+  }
+  else
+  {
+      error ("unknown credential type");
+      ret = GNUTLS_EMACS_ERROR_INVALID_TYPE;
+  }
+
+  if (ret < GNUTLS_E_SUCCESS)
+      return gnutls_make_error (ret);
+
+  XPROCESS (proc)->anon_cred = anon_cred;
+  XPROCESS (proc)->x509_cred = x509_cred;
+  XPROCESS (proc)->gnutls_cred_type = type;
+
+  GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_CRED_SET;
+
+  return gnutls_make_error (GNUTLS_E_SUCCESS);
+}
+
+DEFUN ("gnutls-bye", Fgnutls_bye,
+       Sgnutls_bye, 2, 2, 0,
+       doc: /* Terminate current GNU TLS connection for PROCESS.
+The connection should have been initiated using `gnutls-handshake'.
+
+If CONT is not nil the TLS connection gets terminated and further
+receives and sends will be disallowed. If the return value is zero you
+may continue using the connection.  If CONT is nil, GnuTLS actually
+sends an alert containing a close request and waits for the peer to
+reply with the same message.  In order to reuse the connection you
+should wait for an EOF from the peer.
+
+This function may also return `gnutls-e-again', or
+`gnutls-e-interrupted'.  */)
+    (Lisp_Object proc, Lisp_Object cont)
+{
+  gnutls_session_t state;
+  int ret;
+
+  CHECK_PROCESS (proc);
+
+  state = XPROCESS (proc)->gnutls_state;
+
+  ret = gnutls_bye (state,
+                    NILP (cont) ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
+
+  return gnutls_make_error (ret);
+}
+
+DEFUN ("gnutls-handshake", Fgnutls_handshake,
+       Sgnutls_handshake, 1, 1, 0,
+       doc: /* Perform GNU TLS handshake for PROCESS.
+The identity of the peer is checked automatically.  This function will
+fail if any problem is encountered, and will return a negative error
+code. In case of a client, if it has been asked to resume a session,
+but the server didn't, then a full handshake will be performed.
+
+If the error `gnutls-e-not-ready-for-handshake' is returned, you
+didn't call `gnutls-boot' first.
+
+This function may also return the non-fatal errors `gnutls-e-again',
+or `gnutls-e-interrupted'. In that case you may resume the handshake
+(by calling this function again).  */)
+    (Lisp_Object proc)
+{
+  gnutls_session_t state;
+  int ret;
+
+  CHECK_PROCESS (proc);
+  state = XPROCESS (proc)->gnutls_state;
+
+  if (GNUTLS_INITSTAGE (proc) < GNUTLS_STAGE_HANDSHAKE_CANDO)
+    return Qgnutls_e_not_ready_for_handshake;
+
+  /* for a network process in Emacs infd and outfd are the same
+     but this shows our intent more clearly.  */
+  gnutls_transport_set_ptr2 (state, XPROCESS (proc)->infd,
+                             XPROCESS (proc)->outfd);
+  ret = gnutls_handshake (state);
+
+  GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_HANDSHAKE_DONE;
+
+  if (GNUTLS_E_SUCCESS == ret)
+  {
+    /* here we're finally done.  */
+    GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_READY;
+  }
+
+  return gnutls_make_error (ret);
+}
+
+void
+syms_of_gnutls (void)
+{
+  global_initialized = 0;
+
+  Qgnutls_code = intern_c_string ("gnutls-code");
+  staticpro (&Qgnutls_code);
+
+  Qgnutls_anon = intern_c_string ("gnutls-anon");
+  staticpro (&Qgnutls_anon);
+
+  Qgnutls_x509pki = intern_c_string ("gnutls-x509pki");
+  staticpro (&Qgnutls_x509pki);
+
+  Qgnutls_e_interrupted = intern_c_string ("gnutls-e-interrupted");
+  staticpro (&Qgnutls_e_interrupted);
+  Fput (Qgnutls_e_interrupted, Qgnutls_code,
+        make_number (GNUTLS_E_INTERRUPTED));
+
+  Qgnutls_e_again = intern_c_string ("gnutls-e-again");
+  staticpro (&Qgnutls_e_again);
+  Fput (Qgnutls_e_again, Qgnutls_code,
+        make_number (GNUTLS_E_AGAIN));
+
+  Qgnutls_e_invalid_session = intern_c_string ("gnutls-e-invalid-session");
+  staticpro (&Qgnutls_e_invalid_session);
+  Fput (Qgnutls_e_invalid_session, Qgnutls_code,
+        make_number (GNUTLS_E_INVALID_SESSION));
+
+  Qgnutls_e_not_ready_for_handshake =
+    intern_c_string ("gnutls-e-not-ready-for-handshake");
+  staticpro (&Qgnutls_e_not_ready_for_handshake);
+  Fput (Qgnutls_e_not_ready_for_handshake, Qgnutls_code,
+        make_number (GNUTLS_E_APPLICATION_ERROR_MIN));
+
+  defsubr (&Sgnutls_get_initstage);
+  defsubr (&Sgnutls_errorp);
+  defsubr (&Sgnutls_error_fatalp);
+  defsubr (&Sgnutls_error_string);
+  defsubr (&Sgnutls_global_init);
+  defsubr (&Sgnutls_global_deinit);
+  defsubr (&Sgnutls_boot);
+  defsubr (&Sgnutls_deinit);
+  defsubr (&Sgnutls_handshake);
+  defsubr (&Sgnutls_bye);
+}
+#endif

=== added file 'src/gnutls.h'
--- src/gnutls.h	1970-01-01 00:00:00 +0000
+++ src/gnutls.h	2010-09-15 01:29:34 +0000
@@ -0,0 +1,57 @@
+/* GnuTLS glue for GNU Emacs.
+   Copyright (C) 2010  Free Software Foundation, Inc.
+
+This file is part of GNU Emacs.
+
+GNU Emacs is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+GNU Emacs is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef EMACS_GNUTLS_DEFINED
+#define EMACS_GNUTLS_DEFINED
+
+#ifdef HAVE_GNUTLS
+#include <gnutls/gnutls.h>
+
+typedef enum
+{
+  GNUTLS_STAGE_EMPTY = 0,
+  GNUTLS_STAGE_CRED_ALLOC,
+  GNUTLS_STAGE_FILES,
+  GNUTLS_STAGE_INIT,
+  GNUTLS_STAGE_PRIORITY,
+  GNUTLS_STAGE_CRED_SET,
+
+  GNUTLS_STAGE_HANDSHAKE_CANDO = GNUTLS_STAGE_CRED_SET,
+  GNUTLS_STAGE_HANDSHAKE_DONE,
+
+  GNUTLS_STAGE_READY,
+} gnutls_initstage_t;
+
+#define GNUTLS_EMACS_ERROR_INVALID_TYPE GNUTLS_E_APPLICATION_ERROR_MIN
+
+#define GNUTLS_INITSTAGE(proc) (XPROCESS (proc)->gnutls_initstage)
+
+#define GNUTLS_PROCESS_USABLE(proc) (GNUTLS_INITSTAGE(proc) >= GNUTLS_STAGE_READY)
+
+int
+emacs_gnutls_write (int fildes, gnutls_session_t state, char *buf,
+                    unsigned int nbyte);
+int
+emacs_gnutls_read (int fildes, gnutls_session_t state, char *buf,
+                   unsigned int nbyte);
+
+extern void syms_of_gnutls (void);
+
+#endif 
+
+#endif

=== modified file 'src/process.c'
--- src/process.c	2010-08-22 15:14:37 +0000
+++ src/process.c	2010-09-15 01:29:34 +0000
@@ -105,6 +105,9 @@
 #include "sysselect.h"
 #include "syssignal.h"
 #include "syswait.h"
+#ifdef HAVE_GNUTLS
+#include "gnutls.h"
+#endif
 
 #if defined (USE_GTK) || defined (HAVE_GCONF)
 #include "xgselect.h"
@@ -583,6 +586,10 @@
   p->read_output_skip = 0;
 #endif
 
+#ifdef HAVE_GNUTLS
+  p->gnutls_initstage = GNUTLS_STAGE_EMPTY;
+#endif
+
   /* If name is already in use, modify it until it is unused.  */
 
   name1 = name;
@@ -1526,6 +1533,12 @@
   XPROCESS (proc)->filter = Qnil;
   XPROCESS (proc)->command = Flist (nargs - 2, args + 2);
 
+#ifdef HAVE_GNUTLS
+  /* AKA GNUTLS_INITSTAGE(proc).  */
+  XPROCESS (proc)->gnutls_initstage = GNUTLS_STAGE_EMPTY;
+  XPROCESS (proc)->gnutls_cred_type = Qnil;
+#endif
+
 #ifdef ADAPTIVE_READ_BUFFERING
   XPROCESS (proc)->adaptive_read_buffering
     = (NILP (Vprocess_adaptive_read_buffering) ? 0
@@ -5097,7 +5110,13 @@
 #endif
   if (proc_buffered_char[channel] < 0)
     {
-      nbytes = emacs_read (channel, chars + carryover, readmax);
+#ifdef HAVE_GNUTLS
+      if (NETCONN_P(proc) && GNUTLS_PROCESS_USABLE (proc))
+	nbytes = emacs_gnutls_read (channel, XPROCESS (proc)->gnutls_state,
+                                    chars + carryover, readmax);
+      else
+#endif
+	nbytes = emacs_read (channel, chars + carryover, readmax);
 #ifdef ADAPTIVE_READ_BUFFERING
       if (nbytes > 0 && p->adaptive_read_buffering)
 	{
@@ -5130,7 +5149,13 @@
     {
       chars[carryover] = proc_buffered_char[channel];
       proc_buffered_char[channel] = -1;
-      nbytes = emacs_read (channel, chars + carryover + 1,  readmax - 1);
+#ifdef HAVE_GNUTLS
+      if (NETCONN_P(proc) && GNUTLS_PROCESS_USABLE (proc))
+	nbytes = emacs_gnutls_read (channel, XPROCESS (proc)->gnutls_state,
+                                    chars + carryover + 1, readmax - 1);
+      else
+#endif
+	nbytes = emacs_read (channel, chars + carryover + 1,  readmax - 1);
       if (nbytes < 0)
 	nbytes = 1;
       else
@@ -5540,7 +5565,14 @@
 	      else
 #endif
 		{
-		  rv = emacs_write (outfd, (char *) buf, this);
+#ifdef HAVE_GNUTLS
+		  if (NETCONN_P(proc) && GNUTLS_PROCESS_USABLE (proc))
+		    rv = emacs_gnutls_write (outfd,
+					     XPROCESS (proc)->gnutls_state, 
+					     (char *) buf, this);
+		  else
+#endif
+		    rv = emacs_write (outfd, (char *) buf, this);
 #ifdef ADAPTIVE_READ_BUFFERING
 		  if (p->read_output_delay > 0
 		      && p->adaptive_read_buffering == 1)

=== modified file 'src/process.h'
--- src/process.h	2010-08-11 12:34:46 +0000
+++ src/process.h	2010-09-15 01:29:34 +0000
@@ -24,6 +24,10 @@
 #include <unistd.h>
 #endif
 
+#ifdef HAVE_GNUTLS
+#include "gnutls.h"
+#endif
+
 /* This structure records information about a subprocess
    or network connection.
 
@@ -76,6 +80,10 @@
     /* Working buffer for encoding.  */
     Lisp_Object encoding_buf;
 
+#ifdef HAVE_GNUTLS
+    Lisp_Object gnutls_cred_type;
+#endif
+
     /* After this point, there are no Lisp_Objects any more.  */
     /* alloc.c assumes that `pid' is the first such non-Lisp slot.  */
 
@@ -121,6 +129,13 @@
        needs to be synced to `status'.  */
     unsigned int raw_status_new : 1;
     int raw_status;
+
+#ifdef HAVE_GNUTLS
+    gnutls_initstage_t gnutls_initstage;
+    gnutls_session_t gnutls_state;
+    gnutls_certificate_client_credentials x509_cred;
+    gnutls_anon_client_credentials_t anon_cred;
+#endif
 };
 
 /* Every field in the preceding structure except for the first two


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