Re: [gnutls-dev] External signing API

[Simon Josefsson]

The entire patch for the external sign callback, now applied to the
trunk, is as follows.  It is not very large, so I'd thought I'd post it.
It include a self-test.  Please review.

/Simon

commit 4431c4369db575dc8ecd8ec3622bc2dfc9bee725
Author: Simon Josefsson <address@hidden>
Date:   Fri Aug 10 15:20:40 2007 +0200

    External signing callback interface.
        * includes/gnutls/gnutls.h.in (gnutls_sign_func): New type.
        (gnutls_sign_callback_set): New function.
    
        * includes/gnutls/x509.h (gnutls_x509_privkey_sign_hash): New
        function.
    
        * lib/gnutls_x509.c (gnutls_certificate_set_x509_key_mem): Handle
        NULL key.  Doc fix.
    
        * lib/gnutls_sig.c (_gnutls_tls_sign_hdata): Pass session to
        _gnutls_tls_sign.
        (_gnutls_tls_sign_params): Likewise.
        (_gnutls_tls_sign): Add new parameter 'session'.  Call sign
        callback if appropriate.
        (gnutls_sign_callback_set): New function.
    
        * lib/gnutls_x509.c (read_key_mem): Support a NULL key.
    
        * lib/gnutls_int.h (internals_st): Add sign_func,
        sign_func_userdata.
    
        * lib/auth_dhe.c (gen_dhe_server_kx): Use length of certificate
        list to decide wheter to sign, not presence of private key.
        * lib/auth_cert.c (_gnutls_gen_cert_client_cert_vrfy): Likewise.
    
        * lib/auth_rsa_export.c (gen_rsa_export_server_kx): Likewise.
    
        * lib/auth_cert.c(_gnutls_get_selected_cert): Don't require that
        private key is present.
    
        * lib/auth_rsa_export.c (gen_rsa_export_server_kx): Don't check
        key size when key is not present, assume it is > 512 bits.
    
        * lib/x509/privkey.c (gnutls_x509_privkey_sign_hash): New
        function.
    
        * tests/Makefile.am: Add x509signself.

diff --git a/NEWS b/NEWS
index 908da11..9f39fd1 100644
--- a/NEWS
+++ b/NEWS
@@ -5,8 +5,14 @@ See the end for copying conditions.
 
 * Version 1.7.17 (unreleased)
 
+** New functions to perform external signing.
+Set the signing callback function (of the gnutls_sign_func prototype)
+using gnutls_sign_callback_set.  In the callback, you may find the new
+function gnutls_x509_privkey_sign_hash useful.
+
 ** New self test of client and server authenticated X.509 TLS sessions.
-See tests/x509self.c.
+See tests/x509self.c and tests/x509signself.c.  The latter also tests
+the new external signing callback interface.
 
 ** gnutls_set_default_priority now disable TLS 1.2 by default.
 The RFC is not released yet, and we're approaching a major release so
@@ -24,7 +30,9 @@ Thanks to Jakub Bogusz <address@hidden> and Daniel Nylander
 <address@hidden>.
 
 ** API and ABI modifications:
-No changes since last version.
+gnutls_sign_func: ADD, new type for sign callback.
+gnutls_sign_callback_set: ADD, new function to set sign callback.
+gnutls_x509_privkey_sign_hash: ADD, new function useful in sign callback.
 
 * Version 1.7.16 (released 2007-08-07)
 
diff --git a/includes/gnutls/gnutls.h.in b/includes/gnutls/gnutls.h.in
index 4071a10..8f1e364 100644
--- a/includes/gnutls/gnutls.h.in
+++ b/includes/gnutls/gnutls.h.in
@@ -703,7 +703,6 @@ extern "C"
                                       gnutls_x509_crl_t * crl_list,
                                       int crl_list_size);
 
-
 /* global state functions
  */
   int gnutls_global_init (void);
@@ -1048,6 +1047,18 @@ extern "C"
 
   /* X509PKI */
 
+  /* External signing callback.  Experimental. */
+  typedef int (*gnutls_sign_func) (gnutls_session_t session,
+                                  void *userdata,
+                                  gnutls_certificate_type_t cert_type,
+                                  gnutls_datum_t cert,
+                                  const gnutls_datum_t hash,
+                                  gnutls_datum_t * signature);
+
+  void gnutls_sign_callback_set (gnutls_session_t session,
+                                gnutls_sign_func sign_func,
+                                void *userdata);
+
   /* These are set on the credentials structure.
    */
   void gnutls_certificate_client_set_retrieve_function
diff --git a/includes/gnutls/x509.h b/includes/gnutls/x509.h
index 8f570df..8357dc2 100644
--- a/includes/gnutls/x509.h
+++ b/includes/gnutls/x509.h
@@ -605,6 +605,10 @@ extern "C"
                                   const gnutls_datum_t * data,
                                   const gnutls_datum_t * signature);
 
+  int gnutls_x509_privkey_sign_hash (gnutls_x509_privkey_t key,
+                                    const gnutls_datum_t hash,
+                                    gnutls_datum_t *signature);
+
 
 /* Certificate request stuff.
  */
diff --git a/lib/auth_cert.c b/lib/auth_cert.c
index f0cb427..54b4a50 100644
--- a/lib/auth_cert.c
+++ b/lib/auth_cert.c
@@ -1307,7 +1307,7 @@ _gnutls_gen_cert_client_cert_vrfy (gnutls_session_t 
session, opaque ** data)
       return ret;
     }
 
-  if (apr_pkey != NULL)
+  if (apr_cert_list_length > 0)
     {
       if ((ret =
           _gnutls_tls_sign_hdata (session,
@@ -1483,8 +1483,7 @@ _gnutls_get_selected_cert (gnutls_session_t session,
       *apr_pkey = session->internals.selected_key;
       *apr_cert_list_length = session->internals.selected_cert_list_length;
 
-      if (*apr_cert_list_length == 0 || *apr_pkey == NULL ||
-         *apr_cert_list == NULL)
+      if (*apr_cert_list_length == 0 || *apr_cert_list == NULL)
        {
          gnutls_assert ();
          return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
diff --git a/lib/auth_dhe.c b/lib/auth_dhe.c
index c9ff9f5..6cf658a 100644
--- a/lib/auth_dhe.c
+++ b/lib/auth_dhe.c
@@ -145,7 +145,7 @@ gen_dhe_server_kx (gnutls_session_t session, opaque ** data)
   ddata.data = *data;
   ddata.size = data_size;
 
-  if (apr_pkey != NULL)
+  if (apr_cert_list_length > 0)
     {
       if ((ret =
           _gnutls_tls_sign_params (session, &apr_cert_list[0],
diff --git a/lib/auth_rsa_export.c b/lib/auth_rsa_export.c
index a16ed17..a1b867a 100644
--- a/lib/auth_rsa_export.c
+++ b/lib/auth_rsa_export.c
@@ -100,7 +100,7 @@ gen_rsa_export_server_kx (gnutls_session_t session, opaque 
** data)
   /* abort sending this message if we have a certificate
    * of 512 bits or less.
    */
-  if (_gnutls_mpi_get_nbits (apr_pkey->params[0]) <= 512)
+  if (apr_pkey && _gnutls_mpi_get_nbits (apr_pkey->params[0]) <= 512)
     {
       gnutls_assert ();
       return GNUTLS_E_INT_RET_0;
@@ -153,7 +153,7 @@ gen_rsa_export_server_kx (gnutls_session_t session, opaque 
** data)
   ddata.data = *data;
   ddata.size = data_size;
 
-  if (apr_pkey != NULL)
+  if (apr_cert_list_length > 0)
     {
       if ((ret =
           _gnutls_tls_sign_params (session, &apr_cert_list[0],
diff --git a/lib/gnutls_int.h b/lib/gnutls_int.h
index b9a9dcd..6f01c96 100644
--- a/lib/gnutls_int.h
+++ b/lib/gnutls_int.h
@@ -627,6 +627,12 @@ typedef struct
    */
   int errnum;
 
+  /* Function used to perform public-key signing operation during
+     handshake.  Used by gnutls_sig.c:_gnutls_tls_sign(), see also
+     gnutls_sign_callback_set(). */
+  gnutls_sign_func sign_func;
+  void *sign_func_userdata;
+
   /* If you add anything here, check _gnutls_handshake_internal_state_clear().
    */
 } internals_st;
diff --git a/lib/gnutls_sig.c b/lib/gnutls_sig.c
index 31c845c..31db1cf 100644
--- a/lib/gnutls_sig.c
+++ b/lib/gnutls_sig.c
@@ -37,10 +37,11 @@
 #include <gnutls_sig.h>
 #include <gnutls_kx.h>
 
-static
-  int _gnutls_tls_sign (gnutls_cert * cert, gnutls_privkey * pkey,
-                       const gnutls_datum_t * hash_concat,
-                       gnutls_datum_t * signature);
+static int
+_gnutls_tls_sign (gnutls_session_t session,
+                 gnutls_cert * cert, gnutls_privkey * pkey,
+                 const gnutls_datum_t * hash_concat,
+                 gnutls_datum_t * signature);
 
 
 /* Generates a signature of all the previous sent packets in the 
@@ -111,7 +112,7 @@ _gnutls_tls_sign_hdata (gnutls_session_t session,
       gnutls_assert ();
       return GNUTLS_E_INTERNAL_ERROR;
     }
-  ret = _gnutls_tls_sign (cert, pkey, &dconcat, signature);
+  ret = _gnutls_tls_sign (session, cert, pkey, &dconcat, signature);
   if (ret < 0)
     {
       gnutls_assert ();
@@ -202,7 +203,7 @@ _gnutls_tls_sign_params (gnutls_session_t session, 
gnutls_cert * cert,
       _gnutls_hash_deinit (td_sha, NULL);
       return GNUTLS_E_INTERNAL_ERROR;
     }
-  ret = _gnutls_tls_sign (cert, pkey, &dconcat, signature);
+  ret = _gnutls_tls_sign (session, cert, pkey, &dconcat, signature);
   if (ret < 0)
     {
       gnutls_assert ();
@@ -257,7 +258,8 @@ _gnutls_sign (gnutls_pk_algorithm_t algo, mpi_t * params,
  * it supports signing.
  */
 static int
-_gnutls_tls_sign (gnutls_cert * cert, gnutls_privkey * pkey,
+_gnutls_tls_sign (gnutls_session_t session,
+                 gnutls_cert * cert, gnutls_privkey * pkey,
                  const gnutls_datum_t * hash_concat,
                  gnutls_datum_t * signature)
 {
@@ -273,11 +275,49 @@ _gnutls_tls_sign (gnutls_cert * cert, gnutls_privkey * 
pkey,
          return GNUTLS_E_KEY_USAGE_VIOLATION;
        }
 
+  /* External signing. */
+  if (!pkey || pkey->params_size == 0)
+    {
+      if (!session->internals.sign_func)
+       return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
+
+      return (*session->internals.sign_func)
+       (session, session->internals.sign_func_userdata,
+        cert->cert_type, cert->raw,
+        *hash_concat, signature);
+    }
+
   return _gnutls_sign (pkey->pk_algorithm, pkey->params,
                       pkey->params_size, hash_concat, signature);
-
 }
 
+/**
+ * gnutls_sign_callback_set:
+ * @session:
+ * @sign_func:
+ * @userdata:
+ *
+ * Set the callback function.  The function must have this prototype:
+ *
+ * typedef int (*gnutls_sign_func) (gnutls_session_t session,
+ *                                  void *userdata,
+ *                                  gnutls_certificate_type_t cert_type,
+ *                                  gnutls_datum_t cert,
+ *                                  const gnutls_datum_t hash,
+ *                                  gnutls_datum_t * signature);
+ *
+ * The @userdata parameter is passed to the @sign_func verbatim, and
+ * can be used to store application-specific data needed in the
+ * callback function.
+ **/
+void
+gnutls_sign_callback_set (gnutls_session_t session,
+                         gnutls_sign_func sign_func,
+                         void *userdata)
+{
+  session->internals.sign_func = sign_func;
+  session->internals.sign_func_userdata = userdata;
+}
 
 static int
 _gnutls_verify_sig (gnutls_cert * cert,
diff --git a/lib/gnutls_x509.c b/lib/gnutls_x509.c
index d4b66ac..352f002 100644
--- a/lib/gnutls_x509.c
+++ b/lib/gnutls_x509.c
@@ -702,9 +702,9 @@ _gnutls_x509_raw_privkey_to_gkey (gnutls_privkey * privkey,
   return 0;
 }
 
-/* Reads a PEM encoded PKCS-1 RSA private key from memory
- * 2002-01-26: Added ability to read DSA keys.
- * type indicates the certificate format.
+/* Reads a PEM encoded PKCS-1 RSA/DSA private key from memory.  Type
+ * indicates the certificate format.  KEY can be NULL, to indicate
+ * that GnuTLS doesn't know the private key.
  */
 static int
 read_key_mem (gnutls_certificate_credentials_t res,
@@ -724,16 +724,21 @@ read_key_mem (gnutls_certificate_credentials_t res,
       return GNUTLS_E_MEMORY_ERROR;
     }
 
-  tmp.data = (opaque *) key;
-  tmp.size = key_size;
-
-  ret =
-    _gnutls_x509_raw_privkey_to_gkey (&res->pkey[res->ncerts], &tmp, type);
-  if (ret < 0)
+  if (key)
     {
-      gnutls_assert ();
-      return ret;
+      tmp.data = (opaque *) key;
+      tmp.size = key_size;
+
+      ret =
+       _gnutls_x509_raw_privkey_to_gkey (&res->pkey[res->ncerts], &tmp, type);
+      if (ret < 0)
+       {
+         gnutls_assert ();
+         return ret;
+       }
     }
+  else
+    memset (&res->pkey[res->ncerts], 0, sizeof (gnutls_privkey));
 
   return 0;
 }
@@ -790,7 +795,7 @@ read_key_file (gnutls_certificate_credentials_t res,
   * gnutls_certificate_set_x509_key_mem - Used to set keys in a 
gnutls_certificate_credentials_t structure
   * @res: is an #gnutls_certificate_credentials_t structure.
   * @cert: contains a certificate list (path) for the specified private key
-  * @key: is the private key
+  * @key: is the private key, or %NULL
   * @type: is PEM or DER
   *
   * This function sets a certificate/private key pair in the 
@@ -811,6 +816,9 @@ read_key_file (gnutls_certificate_credentials_t res,
   * If the certificate and the private key are given in PEM encoding
   * then the strings that hold their values must be null terminated.
   *
+  * The @key may be %NULL if you are using a sign callback, see
+  * gnutls_sign_callback_set().
+  *
   **/
 int
 gnutls_certificate_set_x509_key_mem (gnutls_certificate_credentials_t
@@ -822,7 +830,8 @@ gnutls_certificate_set_x509_key_mem 
(gnutls_certificate_credentials_t
 
   /* this should be first 
    */
-  if ((ret = read_key_mem (res, key->data, key->size, type)) < 0)
+  if ((ret = read_key_mem (res, key ? key->data : NULL,
+                          key ? key->size : 0, type)) < 0)
     return ret;
 
   if ((ret = read_cert_mem (res, cert->data, cert->size, type)) < 0)
@@ -830,7 +839,7 @@ gnutls_certificate_set_x509_key_mem 
(gnutls_certificate_credentials_t
 
   res->ncerts++;
 
-  if ((ret = _gnutls_check_key_cert_match (res)) < 0)
+  if (key && (ret = _gnutls_check_key_cert_match (res)) < 0)
     {
       gnutls_assert ();
       return ret;
diff --git a/lib/x509/privkey.c b/lib/x509/privkey.c
index dd29e89..5044828 100644
--- a/lib/x509/privkey.c
+++ b/lib/x509/privkey.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2003, 2004, 2005 Free Software Foundation
+ * Copyright (C) 2003, 2004, 2005, 2007 Free Software Foundation
  *
  * Author: Nikos Mavroyanopoulos
  *
@@ -27,6 +27,7 @@
 #include <gnutls_global.h>
 #include <gnutls_errors.h>
 #include <gnutls_rsa_export.h>
+#include <gnutls_sig.h>
 #include <common.h>
 #include <gnutls_x509.h>
 #include <x509_b64.h>
@@ -1555,6 +1556,41 @@ gnutls_x509_privkey_sign_data (gnutls_x509_privkey_t key,
 }
 
 /**
+ * gnutls_x509_privkey_sign_hash - This function will sign the given data 
using the private key params
+ * @key: Holds the key
+ * @hash: holds the data to be signed
+ * @signature: will contain newly allocated signature
+ *
+ * This function will sign the given hash using the private key.
+ *
+ * Return value: In case of failure a negative value will be returned,
+ * and 0 on success.
+ **/
+int
+gnutls_x509_privkey_sign_hash (gnutls_x509_privkey_t key,
+                              const gnutls_datum_t hash,
+                              gnutls_datum_t *signature)
+{
+  int result;
+
+  if (key == NULL)
+    {
+      gnutls_assert ();
+      return GNUTLS_E_INVALID_REQUEST;
+    }
+
+  result = _gnutls_sign (key->pk_algorithm, key->params,
+                        key->params_size, &hash, signature);
+  if (result < 0)
+    {
+      gnutls_assert ();
+      return result;
+    }
+
+  return 0;
+}
+
+/**
   * gnutls_x509_privkey_verify_data - This function will verify the given 
signed data.
   * @key: Holds the key
   * @flags: should be 0 for now
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 15c63e5..209f343 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -40,7 +40,7 @@ ctests = simple openssl gc set_pkcs12_cred certder    \
        certificate_set_x509_crl dn parse_ca
 openssl_LDADD = $(LDADD) ../libextra/libgnutls-openssl.la
 if HAVE_FORK
-ctests +=  x509self anonself pskself dhepskself tlsia resume
+ctests +=  x509self x509signself anonself pskself dhepskself tlsia resume
 tlsia_LDADD = ../libextra/libgnutls-extra.la $(LDADD) @LTLIBREADLINE@
 endif
 gc_LDADD = $(LDADD) $(LIBGCRYPT_LIBS)
diff --git a/tests/x509signself.c b/tests/x509signself.c
new file mode 100644
index 0000000..2a0a44c
--- /dev/null
+++ b/tests/x509signself.c
@@ -0,0 +1,527 @@
+/*
+ * Copyright (C) 2004, 2005, 2006, 2007 Free Software Foundation
+ *
+ * Author: Simon Josefsson
+ *
+ * This file is part of GNUTLS.
+ *
+ * GNUTLS 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * GNUTLS 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 GNUTLS; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+/* Parts copied from GnuTLS example programs. */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+#include <gnutls/gnutls.h>
+#include <gnutls/x509.h>
+
+#include "utils.h"
+
+pid_t child;
+
+static void
+tls_log_func (int level, const char *str)
+{
+  fprintf (stderr, "%s |<%d>| %s", child ? "server" : "client", level, str);
+}
+
+/* A very basic TLS client, with anonymous authentication.
+ */
+
+#define MAX_BUF 1024
+#define MSG "Hello TLS"
+
+/* Connects to the peer and returns a socket
+ * descriptor.
+ */
+int
+tcp_connect (void)
+{
+  const char *PORT = "5556";
+  const char *SERVER = "127.0.0.1";
+  int err, sd;
+  struct sockaddr_in sa;
+
+  /* connects to server
+   */
+  sd = socket (AF_INET, SOCK_STREAM, 0);
+
+  memset (&sa, '\0', sizeof (sa));
+  sa.sin_family = AF_INET;
+  sa.sin_port = htons (atoi (PORT));
+  inet_pton (AF_INET, SERVER, &sa.sin_addr);
+
+  err = connect (sd, (struct sockaddr *) &sa, sizeof (sa));
+  if (err < 0)
+    {
+      fprintf (stderr, "Connect error\n");
+      exit (1);
+    }
+
+  return sd;
+}
+
+/* closes the given socket descriptor.
+ */
+void
+tcp_close (int sd)
+{
+  shutdown (sd, SHUT_RDWR);    /* no more receptions */
+  close (sd);
+}
+
+const char ca_pem[] =
+  "-----BEGIN CERTIFICATE-----\n"
+  "MIIB5zCCAVKgAwIBAgIERiYdJzALBgkqhkiG9w0BAQUwGTEXMBUGA1UEAxMOR251\n"
+  "VExTIHRlc3QgQ0EwHhcNMDcwNDE4MTMyOTExWhcNMDgwNDE3MTMyOTExWjAZMRcw\n"
+  "FQYDVQQDEw5HbnVUTFMgdGVzdCBDQTCBnDALBgkqhkiG9w0BAQEDgYwAMIGIAoGA\n"
+  "vuyYeh1vfmslnuggeEKgZAVmQ5ltSdUY7H25WGSygKMUYZ0KT74v8C780qtcNt9T\n"
+  "7EPH/N6RvB4BprdssgcQLsthR3XKA84jbjjxNCcaGs33lvOz8A1nf8p3hD+cKfRi\n"
+  "kfYSW2JazLrtCC4yRCas/SPOUxu78of+3HiTfFm/oXUCAwEAAaNDMEEwDwYDVR0T\n"
+  "AQH/BAUwAwEB/zAPBgNVHQ8BAf8EBQMDBwQAMB0GA1UdDgQWBBTpPBz7rZJu5gak\n"
+  "Viyi4cBTJ8jylTALBgkqhkiG9w0BAQUDgYEAiaIRqGfp1jPpNeVhABK60SU0KIAy\n"
+  "njuu7kHq5peUgYn8Jd9zNzExBOEp1VOipGsf6G66oQAhDFp2o8zkz7ZH71zR4HEW\n"
+  "KoX6n5Emn6DvcEH/9pAhnGxNHJAoS7czTKv/JDZJhkqHxyrE1fuLsg5Qv25DTw7+\n"
+  "PfqUpIhz5Bbm7J4=\n"
+  "-----END CERTIFICATE-----\n";
+const gnutls_datum_t ca = { ca_pem, sizeof (ca_pem) };
+
+const char cert_pem[] =
+  "-----BEGIN CERTIFICATE-----\n"
+  "MIICHjCCAYmgAwIBAgIERiYdNzALBgkqhkiG9w0BAQUwGTEXMBUGA1UEAxMOR251\n"
+  "VExTIHRlc3QgQ0EwHhcNMDcwNDE4MTMyOTI3WhcNMDgwNDE3MTMyOTI3WjAdMRsw\n"
+  "GQYDVQQDExJHbnVUTFMgdGVzdCBjbGllbnQwgZwwCwYJKoZIhvcNAQEBA4GMADCB\n"
+  "iAKBgLtmQ/Xyxde2jMzF3/WIO7HJS2oOoa0gUEAIgKFPXKPQ+GzP5jz37AR2ExeL\n"
+  "ZIkiW8DdU3w77XwEu4C5KL6Om8aOoKUSy/VXHqLnu7czSZ/ju0quak1o/8kR4jKN\n"
+  "zj2AC41179gAgY8oBAOgIo1hBAf6tjd9IQdJ0glhaZiQo1ipAgMBAAGjdjB0MAwG\n"
+  "A1UdEwEB/wQCMAAwEwYDVR0lBAwwCgYIKwYBBQUHAwIwDwYDVR0PAQH/BAUDAweg\n"
+  "ADAdBgNVHQ4EFgQUTLkKm/odNON+3svSBxX+odrLaJEwHwYDVR0jBBgwFoAU6Twc\n"
+  "+62SbuYGpFYsouHAUyfI8pUwCwYJKoZIhvcNAQEFA4GBALujmBJVZnvaTXr9cFRJ\n"
+  "jpfc/3X7sLUsMvumcDE01ls/cG5mIatmiyEU9qI3jbgUf82z23ON/acwJf875D3/\n"
+  "U7jyOsBJ44SEQITbin2yUeJMIm1tievvdNXBDfW95AM507ShzP12sfiJkJfjjdhy\n"
+  "dc8Siq5JojruiMizAf0pA7in\n"
+  "-----END CERTIFICATE-----\n";
+const gnutls_datum_t cert = { cert_pem, sizeof (cert_pem) };
+
+int
+sign_func (gnutls_session_t session,
+          void *userdata,
+          gnutls_certificate_type_t cert_type,
+          gnutls_datum_t cert,
+          const gnutls_datum_t hash,
+          gnutls_datum_t * signature)
+{
+  gnutls_x509_privkey_t key;
+  const char key_pem[] =
+    "-----BEGIN RSA PRIVATE KEY-----\n"
+    "MIICXAIBAAKBgQC7ZkP18sXXtozMxd/1iDuxyUtqDqGtIFBACIChT1yj0Phsz+Y8\n"
+    "9+wEdhMXi2SJIlvA3VN8O+18BLuAuSi+jpvGjqClEsv1Vx6i57u3M0mf47tKrmpN\n"
+    "aP/JEeIyjc49gAuNde/YAIGPKAQDoCKNYQQH+rY3fSEHSdIJYWmYkKNYqQIDAQAB\n"
+    "AoGADpmARG5CQxS+AesNkGmpauepiCz1JBF/JwnyiX6vEzUh0Ypd39SZztwrDxvF\n"
+    "PJjQaKVljml1zkJpIDVsqvHdyVdse8M+Qn6hw4x2p5rogdvhhIL1mdWo7jWeVJTF\n"
+    "RKB7zLdMPs3ySdtcIQaF9nUAQ2KJEvldkO3m/bRJFEp54k0CQQDYy+RlTmwRD6hy\n"
+    "7UtMjR0H3CSZJeQ8svMCxHLmOluG9H1UKk55ZBYfRTsXniqUkJBZ5wuV1L+pR9EK\n"
+    "ca89a+1VAkEA3UmBelwEv2u9cAU1QjKjmwju1JgXbrjEohK+3B5y0ESEXPAwNQT9\n"
+    "TrDM1m9AyxYTWLxX93dI5QwNFJtmbtjeBQJARSCWXhsoaDRG8QZrCSjBxfzTCqZD\n"
+    "ZXtl807ymCipgJm60LiAt0JLr4LiucAsMZz6+j+quQbSakbFCACB8SLV1QJBAKZQ\n"
+    "YKf+EPNtnmta/rRKKvySsi3GQZZN+Dt3q0r094XgeTsAqrqujVNfPhTMeP4qEVBX\n"
+    "/iVX2cmMTSh3w3z8MaECQEp0XJWDVKOwcTW6Ajp9SowtmiZ3YDYo1LF9igb4iaLv\n"
+    "sWZGfbnU3ryjvkb6YuFjgtzbZDZHWQCo8/cOtOBmPdk=\n"
+    "-----END RSA PRIVATE KEY-----\n";
+  const gnutls_datum_t key_dat = { key_pem, sizeof (key_pem) };
+  int ret;
+
+  ret = gnutls_x509_privkey_init (&key);
+  if (ret < 0)
+    return ret;
+
+  ret = gnutls_x509_privkey_import (key, &key_dat, GNUTLS_X509_FMT_PEM);
+  if (ret < 0)
+    goto done;
+
+  ret = gnutls_x509_privkey_sign_hash (key, hash, signature);
+  if (ret < 0)
+    goto done;
+
+  ret = 0;
+
+ done:
+  gnutls_x509_privkey_deinit (key);
+  return ret;
+}
+
+void
+client (void)
+{
+  int ret, sd, ii;
+  gnutls_session_t session;
+  char buffer[MAX_BUF + 1];
+  gnutls_certificate_credentials_t xcred;
+
+  gnutls_global_init ();
+
+  gnutls_global_set_log_function (tls_log_func);
+  gnutls_global_set_log_level (4711);
+
+  gnutls_certificate_allocate_credentials (&xcred);
+
+  /* sets the trusted cas file
+   */
+  gnutls_certificate_set_x509_trust_mem (xcred, &ca, GNUTLS_X509_FMT_PEM);
+  gnutls_certificate_set_x509_key_mem (xcred, &cert, NULL,
+                                      GNUTLS_X509_FMT_PEM);
+
+  /* Initialize TLS session
+   */
+  gnutls_init (&session, GNUTLS_CLIENT);
+
+  /* Set sign callback. */
+  gnutls_sign_callback_set (session, sign_func, NULL);
+
+  /* Use default priorities */
+  gnutls_set_default_priority (session);
+
+  /* put the x509 credentials to the current session
+   */
+  gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred);
+
+  /* connect to the peer
+   */
+  sd = tcp_connect ();
+
+  gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd);
+
+  /* Perform the TLS handshake
+   */
+  ret = gnutls_handshake (session);
+
+  if (ret < 0)
+    {
+      fail ("client: Handshake failed\n");
+      gnutls_perror (ret);
+      goto end;
+    }
+  else
+    {
+      success ("client: Handshake was completed\n");
+    }
+
+  success ("client: TLS version is: %s\n",
+          gnutls_protocol_get_name (gnutls_protocol_get_version (session)));
+
+  /* see the Getting peer's information example */
+  print_info(session);
+
+  gnutls_record_send (session, MSG, strlen (MSG));
+
+  ret = gnutls_record_recv (session, buffer, MAX_BUF);
+  if (ret == 0)
+    {
+      success ("client: Peer has closed the TLS connection\n");
+      goto end;
+    }
+  else if (ret < 0)
+    {
+      fail ("client: Error: %s\n", gnutls_strerror (ret));
+      goto end;
+    }
+
+  printf ("- Received %d bytes: ", ret);
+  for (ii = 0; ii < ret; ii++)
+    {
+      fputc (buffer[ii], stdout);
+    }
+  fputs ("\n", stdout);
+
+  gnutls_bye (session, GNUTLS_SHUT_RDWR);
+
+end:
+
+  tcp_close (sd);
+
+  gnutls_deinit (session);
+
+  gnutls_certificate_free_credentials (xcred);
+
+  gnutls_global_deinit ();
+}
+
+/* This is a sample TLS 1.0 echo server, using X.509 authentication.
+ */
+
+#define SA struct sockaddr
+#define MAX_BUF 1024
+#define PORT 5556              /* listen to 5556 port */
+#define DH_BITS 1024
+
+/* These are global */
+gnutls_certificate_credentials_t x509_cred;
+
+gnutls_session_t
+initialize_tls_session (void)
+{
+  gnutls_session_t session;
+
+  gnutls_init (&session, GNUTLS_SERVER);
+
+  /* avoid calling all the priority functions, since the defaults
+   * are adequate.
+   */
+  gnutls_set_default_priority (session);
+
+  gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, x509_cred);
+
+  /* request client certificate if any.
+   */
+  gnutls_certificate_server_set_request (session, GNUTLS_CERT_REQUEST);
+
+  gnutls_dh_set_prime_bits (session, DH_BITS);
+
+  return session;
+}
+
+static gnutls_dh_params_t dh_params;
+
+static int
+generate_dh_params (void)
+{
+  const gnutls_datum_t p3 = { pkcs3, strlen (pkcs3) };
+  /* Generate Diffie Hellman parameters - for use with DHE
+   * kx algorithms. These should be discarded and regenerated
+   * once a day, once a week or once a month. Depending on the
+   * security requirements.
+   */
+  gnutls_dh_params_init (&dh_params);
+  return gnutls_dh_params_import_pkcs3 (dh_params, &p3, GNUTLS_X509_FMT_PEM);
+}
+
+int err, listen_sd, i;
+int sd, ret;
+struct sockaddr_in sa_serv;
+struct sockaddr_in sa_cli;
+int client_len;
+char topbuf[512];
+gnutls_session_t session;
+char buffer[MAX_BUF + 1];
+int optval = 1;
+
+
+const char server_cert_pem[] =
+  "-----BEGIN CERTIFICATE-----\n"
+  "MIICVjCCAcGgAwIBAgIERiYdMTALBgkqhkiG9w0BAQUwGTEXMBUGA1UEAxMOR251\n"
+  "VExTIHRlc3QgQ0EwHhcNMDcwNDE4MTMyOTIxWhcNMDgwNDE3MTMyOTIxWjA3MRsw\n"
+  "GQYDVQQKExJHbnVUTFMgdGVzdCBzZXJ2ZXIxGDAWBgNVBAMTD3Rlc3QuZ251dGxz\n"
+  "Lm9yZzCBnDALBgkqhkiG9w0BAQEDgYwAMIGIAoGA17pcr6MM8C6pJ1aqU46o63+B\n"
+  "dUxrmL5K6rce+EvDasTaDQC46kwTHzYWk95y78akXrJutsoKiFV1kJbtple8DDt2\n"
+  "DZcevensf9Op7PuFZKBroEjOd35znDET/z3IrqVgbtm2jFqab7a+n2q9p/CgMyf1\n"
+  "tx2S5Zacc1LWn9bIjrECAwEAAaOBkzCBkDAMBgNVHRMBAf8EAjAAMBoGA1UdEQQT\n"
+  "MBGCD3Rlc3QuZ251dGxzLm9yZzATBgNVHSUEDDAKBggrBgEFBQcDATAPBgNVHQ8B\n"
+  "Af8EBQMDB6AAMB0GA1UdDgQWBBTrx0Vu5fglyoyNgw106YbU3VW0dTAfBgNVHSME\n"
+  "GDAWgBTpPBz7rZJu5gakViyi4cBTJ8jylTALBgkqhkiG9w0BAQUDgYEAaFEPTt+7\n"
+  "bzvBuOf7+QmeQcn29kT6Bsyh1RHJXf8KTk5QRfwp6ogbp94JQWcNQ/S7YDFHglD1\n"
+  "AwUNBRXwd3riUsMnsxgeSDxYBfJYbDLeohNBsqaPDJb7XailWbMQKfAbFQ8cnOxg\n"
+  "rOKLUQRWJ0K3HyXRMhbqjdLIaQiCvQLuizo=\n"
+  "-----END CERTIFICATE-----\n";
+
+const gnutls_datum_t server_cert = { server_cert_pem,
+                                    sizeof (server_cert_pem) };
+
+const char server_key_pem[] =
+  "-----BEGIN RSA PRIVATE KEY-----\n"
+  "MIICXAIBAAKBgQDXulyvowzwLqknVqpTjqjrf4F1TGuYvkrqtx74S8NqxNoNALjq\n"
+  "TBMfNhaT3nLvxqResm62ygqIVXWQlu2mV7wMO3YNlx696ex/06ns+4VkoGugSM53\n"
+  "fnOcMRP/PciupWBu2baMWppvtr6far2n8KAzJ/W3HZLllpxzUtaf1siOsQIDAQAB\n"
+  "AoGAYAFyKkAYC/PYF8e7+X+tsVCHXppp8AoP8TEZuUqOZz/AArVlle/ROrypg5kl\n"
+  "8YunrvUdzH9R/KZ7saNZlAPLjZyFG9beL/am6Ai7q7Ma5HMqjGU8kTEGwD7K+lbG\n"
+  "iomokKMOl+kkbY/2sI5Czmbm+/PqLXOjtVc5RAsdbgvtmvkCQQDdV5QuU8jap8Hs\n"
+  "Eodv/tLJ2z4+SKCV2k/7FXSKWe0vlrq0cl2qZfoTUYRnKRBcWxc9o92DxK44wgPi\n"
+  "oMQS+O7fAkEA+YG+K9e60sj1K4NYbMPAbYILbZxORDecvP8lcphvwkOVUqbmxOGh\n"
+  "XRmTZUuhBrJhJKKf6u7gf3KWlPl6ShKEbwJASC118cF6nurTjuLf7YKARDjNTEws\n"
+  "qZEeQbdWYINAmCMj0RH2P0mvybrsXSOD5UoDAyO7aWuqkHGcCLv6FGG+qwJAOVqq\n"
+  "tXdUucl6GjOKKw5geIvRRrQMhb/m5scb+5iw8A4LEEHPgGiBaF5NtJZLALgWfo5n\n"
+  "hmC8+G8F0F78znQtPwJBANexu+Tg5KfOnzSILJMo3oXiXhf5PqXIDmbN0BKyCKAQ\n"
+  "LfkcEcUbVfmDaHpvzwY9VEaoMOKVLitETXdNSxVpvWM=\n"
+  "-----END RSA PRIVATE KEY-----\n";
+
+const gnutls_datum_t server_key = { server_key_pem,
+                                   sizeof (server_key_pem) };
+
+void
+server_start (void)
+{
+  /* this must be called once in the program
+   */
+  gnutls_global_init ();
+
+  gnutls_global_set_log_function (tls_log_func);
+  gnutls_global_set_log_level (4711);
+
+  gnutls_certificate_allocate_credentials (&x509_cred);
+  gnutls_certificate_set_x509_trust_mem (x509_cred, &ca, GNUTLS_X509_FMT_PEM);
+
+  gnutls_certificate_set_x509_key_mem (x509_cred, &server_cert, &server_key,
+                                      GNUTLS_X509_FMT_PEM);
+
+  success ("Launched, generating DH parameters...\n");
+
+  generate_dh_params ();
+
+  gnutls_certificate_set_dh_params (x509_cred, dh_params);
+
+  /* Socket operations
+   */
+  listen_sd = socket (AF_INET, SOCK_STREAM, 0);
+  if (err == -1)
+    {
+      perror ("socket");
+      fail ("server: socket failed\n");
+      return;
+    }
+
+  memset (&sa_serv, '\0', sizeof (sa_serv));
+  sa_serv.sin_family = AF_INET;
+  sa_serv.sin_addr.s_addr = INADDR_ANY;
+  sa_serv.sin_port = htons (PORT);     /* Server Port number */
+
+  setsockopt (listen_sd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof (int));
+
+  err = bind (listen_sd, (SA *) & sa_serv, sizeof (sa_serv));
+  if (err == -1)
+    {
+      perror ("bind");
+      fail ("server: bind failed\n");
+      return;
+    }
+
+  err = listen (listen_sd, 1024);
+  if (err == -1)
+    {
+      perror ("listen");
+      fail ("server: listen failed\n");
+      return;
+    }
+
+  success ("server: ready. Listening to port '%d'.\n", PORT);
+}
+
+#include "ex-session-info.c"
+#include "ex-x509-info.c"
+
+void
+server (void)
+{
+  client_len = sizeof (sa_cli);
+
+  session = initialize_tls_session ();
+
+  sd = accept (listen_sd, (SA *) & sa_cli, &client_len);
+
+  success ("server: connection from %s, port %d\n",
+          inet_ntop (AF_INET, &sa_cli.sin_addr, topbuf,
+                     sizeof (topbuf)), ntohs (sa_cli.sin_port));
+
+  gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd);
+  ret = gnutls_handshake (session);
+  if (ret < 0)
+    {
+      close (sd);
+      gnutls_deinit (session);
+      fail ("server: Handshake has failed (%s)\n\n", gnutls_strerror (ret));
+      return;
+    }
+  success ("server: Handshake was completed\n");
+
+  success ("server: TLS version is: %s\n",
+          gnutls_protocol_get_name (gnutls_protocol_get_version (session)));
+
+  /* see the Getting peer's information example */
+  print_info(session);
+
+  i = 0;
+  for (;;)
+    {
+      bzero (buffer, MAX_BUF + 1);
+      ret = gnutls_record_recv (session, buffer, MAX_BUF);
+
+      if (ret == 0)
+       {
+         success ("server: Peer has closed the GNUTLS connection\n");
+         break;
+       }
+      else if (ret < 0)
+       {
+         fail ("server: Received corrupted data(%d). Closing...\n", ret);
+         break;
+       }
+      else if (ret > 0)
+       {
+         /* echo data back to the client
+          */
+         gnutls_record_send (session, buffer, strlen (buffer));
+       }
+    }
+  /* do not wait for the peer to close the connection.
+   */
+  gnutls_bye (session, GNUTLS_SHUT_WR);
+
+  close (sd);
+  gnutls_deinit (session);
+
+  close (listen_sd);
+
+  gnutls_certificate_free_credentials (x509_cred);
+
+  gnutls_global_deinit ();
+
+  success ("server: finished\n");
+}
+
+
+void
+doit (void)
+{
+  server_start ();
+  if (error_count)
+    return;
+
+  child = fork ();
+  if (child < 0)
+    {
+      perror ("fork");
+      fail ("fork");
+      return;
+    }
+
+  if (child)
+    {
+      int status;
+      /* parent */
+      server ();
+      wait (&status);
+    }
+  else
+    client ();
+}