GnuTLS 2.12.3

UNIX

Simon Josefsson Datakonsult
Hagagatan 24
113 47 Stockholm
Sweden

E-mail: simon@josefsson.org

     #include <gnutls.h>

     gnutls_rsa_params_t rsa_params;
     gnutls_dh_params_t dh_params;

     /* This function will be called once a session requests DH
      * or RSA parameters. The parameters returned (if any) will
      * be used for the first handshake only.
      */
     static int get_params( gnutls_session_t session,
             gnutls_params_type_t type,
             gnutls_params_st *st)
     {
        if (type == GNUTLS_PARAMS_RSA_EXPORT)
           st->params.rsa_export = rsa_params;
        else if (type == GNUTLS_PARAMS_DH)
           st->params.dh = dh_params;
        else return -1;

        st->type = type;
        /* do not deinitialize those parameters.
         */
        st->deinit = 0;

        return 0;
     }

     int main()
     {
        gnutls_certificate_credentials_t cert_cred;

        initialize_params();

        /* ...
         */

        gnutls_certificate_set_params_function( cert_cred, get_params);
     }

load=/usr/lib/opensc-pkcs11.so
load=/usr/lib/gnome-keyring/gnome-keyring-pkcs11.so

     pkcs11:token=Nikos;serial=307521161601031;model=PKCS%2315; \
     manufacturer=EnterSafe;object=test1;objecttype=public;\
     id=32:f1:53:f3:e3:79:90:b0:86:24:14:10:77:ca:5d:ec:2d:15:fa:ed

     pkcs11:token=Nikos;serial=307521161601031;model=PKCS%2315;manufacturer=EnterSafe

int i;
char* url;

gnutls_global_init();

for (i=0;;i++) {
	ret = gnutls_pkcs11_token_get_url(i, &url);
	if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
		break;

	if (ret < 0)
		exit(1);

	fprintf(stdout, "Token[%d]: URL: %s\n", i, url);
	gnutls_free(url);
}
gnutls_global_deinit();

gnutls_pkcs11_obj_t *obj_list;
unsigned int obj_list_size = 0;
gnutls_datum_t cinfo;
int i;

obj_list_size = 0;
ret = gnutls_pkcs11_obj_list_import_url( obj_list, NULL, url, \
			GNUTLS_PKCS11_OBJ_ATTR_CRT_WITH_PRIVKEY);
if (ret < 0 && ret != GNUTLS_E_SHORT_MEMORY_BUFFER)
	exit(1);

/* no error checking from now on */
obj_list = malloc(sizeof(*obj_list)*obj_list_size);

gnutls_pkcs11_obj_list_import_url( obj_list, &obj_list_size, url, flags);

/* now all certificates are in obj_list */
for (i=0;i<obj_list_size;i++) {

	gnutls_x509_crt_init(&xcrt);

	gnutls_x509_crt_import_pkcs11(xcrt, obj_list[i]);

	gnutls_x509_crt_print (xcrt, GNUTLS_CRT_PRINT_FULL, &cinfo);

	fprintf(stdout, "cert[%d]:\n %s\n\n", cinfo.data);

	gnutls_free(cinfo.data);
	gnutls_x509_crt_deinit(&xcrt);
}

#inlude <gnutls/abstract.h>
#inlude <gnutls/pkcs11.h>

void sign_cert( gnutls_x509_crt_t to_be_signed)
{
gnutls_pkcs11_privkey_t ca_key;
gnutls_x509_crt_t ca_cert;
gnutls_privkey_t abs_key;

	/* load the PKCS #11 key and certificates */
	gnutls_pkcs11_privkey_init(&ca_key);
	gnutls_pkcs11_privkey_import_url(ca_key, key_url);

	gnutls_x509_crt_init(&ca_cert);
	gnutls_x509_crt_import_pkcs11_url(&ca_cert, cert_url);

	/* initialize the abstract key */
	gnutls_privkey_init(&abs_key);
	gnutls_privkey_import_pkcs11(abs_key, ca_key);

	/* sign the certificate to be signed */
	gnutls_x509_crt_privkey_sign(to_be_signed, ca_cert, ca_key, GNUTLS_DIG_SHA1, 0);
}

       gnutls_certificate_set_verify_flags (x509cred,
                                            GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5);

     gcc -c foo.c `pkg-config gnutls --cflags`

     gcc -o foo foo.o `pkg-config gnutls --libs`

     gcc -o foo foo.c `pkg-config gnutls --cflags --libs`

          #include <gnutls.h>
          #include <errno.h>
          #include <pthread.h>

          int main()
          {
             gnutls_global_init();
          }

          int main()
          {
             gnutls_global_mutex_set (mutex_init, mutex_deinit, mutex_lock, mutex_unlock);
             gnutls_global_init();
          }

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <gnutls/gnutls.h>

/* A very basic TLS client, with anonymous authentication.
 */

#define MAX_BUF 1024
#define MSG "GET / HTTP/1.0\r\n\r\n"

extern int tcp_connect (void);
extern void tcp_close (int sd);

int
main (void)
{
  int ret, sd, ii;
  gnutls_session_t session;
  char buffer[MAX_BUF + 1];
  gnutls_anon_client_credentials_t anoncred;
  /* Need to enable anonymous KX specifically. */

  gnutls_global_init ();

  gnutls_anon_allocate_client_credentials (&anoncred);

  /* Initialize TLS session 
   */
  gnutls_init (&session, GNUTLS_CLIENT);

  /* Use default priorities */
  gnutls_priority_set_direct (session, "PERFORMANCE:+ANON-DH:!ARCFOUR-128",
                              NULL);

  /* put the anonymous credentials to the current session
   */
  gnutls_credentials_set (session, GNUTLS_CRD_ANON, anoncred);

  /* 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)
    {
      fprintf (stderr, "*** Handshake failed\n");
      gnutls_perror (ret);
      goto end;
    }
  else
    {
      printf ("- Handshake was completed\n");
    }

  gnutls_record_send (session, MSG, strlen (MSG));

  ret = gnutls_record_recv (session, buffer, MAX_BUF);
  if (ret == 0)
    {
      printf ("- Peer has closed the TLS connection\n");
      goto end;
    }
  else if (ret < 0)
    {
      fprintf (stderr, "*** 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_anon_free_client_credentials (anoncred);

  gnutls_global_deinit ();

  return 0;
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <gnutls/gnutls.h>

/* A very basic TLS client, with X.509 authentication.
 */

#define MAX_BUF 1024
#define CAFILE "ca.pem"
#define MSG "GET / HTTP/1.0\r\n\r\n"

extern int tcp_connect (void);
extern void tcp_close (int sd);

int
main (void)
{
  int ret, sd, ii;
  gnutls_session_t session;
  char buffer[MAX_BUF + 1];
  const char *err;
  gnutls_certificate_credentials_t xcred;

  gnutls_global_init ();

  /* X509 stuff */
  gnutls_certificate_allocate_credentials (&xcred);

  /* sets the trusted cas file
   */
  gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM);

  /* Initialize TLS session 
   */
  gnutls_init (&session, GNUTLS_CLIENT);

  /* Use default priorities */
  ret = gnutls_priority_set_direct (session, "PERFORMANCE", &err);
  if (ret < 0)
    {
      if (ret == GNUTLS_E_INVALID_REQUEST)
        {
          fprintf (stderr, "Syntax error at: %s\n", err);
        }
      exit (1);
    }

  /* 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)
    {
      fprintf (stderr, "*** Handshake failed\n");
      gnutls_perror (ret);
      goto end;
    }
  else
    {
      printf ("- Handshake was completed\n");
    }

  gnutls_record_send (session, MSG, strlen (MSG));

  ret = gnutls_record_recv (session, buffer, MAX_BUF);
  if (ret == 0)
    {
      printf ("- Peer has closed the TLS connection\n");
      goto end;
    }
  else if (ret < 0)
    {
      fprintf (stderr, "*** 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 ();

  return 0;
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>

#include "examples.h"

/* This function will print some details of the
 * given session.
 */
int
print_info (gnutls_session_t session)
{
  const char *tmp;
  gnutls_credentials_type_t cred;
  gnutls_kx_algorithm_t kx;

  /* print the key exchange's algorithm name
   */
  kx = gnutls_kx_get (session);
  tmp = gnutls_kx_get_name (kx);
  printf ("- Key Exchange: %s\n", tmp);

  /* Check the authentication type used and switch
   * to the appropriate.
   */
  cred = gnutls_auth_get_type (session);
  switch (cred)
    {
    case GNUTLS_CRD_IA:
      printf ("- TLS/IA session\n");
      break;

#ifdef ENABLE_SRP
    case GNUTLS_CRD_SRP:
      printf ("- SRP session with username %s\n",
              gnutls_srp_server_get_username (session));
      break;
#endif

    case GNUTLS_CRD_PSK:
      /* This returns NULL in server side.
       */
      if (gnutls_psk_client_get_hint (session) != NULL)
        printf ("- PSK authentication. PSK hint '%s'\n",
                gnutls_psk_client_get_hint (session));
      /* This returns NULL in client side.
       */
      if (gnutls_psk_server_get_username (session) != NULL)
        printf ("- PSK authentication. Connected as '%s'\n",
                gnutls_psk_server_get_username (session));
      break;

    case GNUTLS_CRD_ANON:      /* anonymous authentication */

      printf ("- Anonymous DH using prime of %d bits\n",
              gnutls_dh_get_prime_bits (session));
      break;

    case GNUTLS_CRD_CERTIFICATE:       /* certificate authentication */

      /* Check if we have been using ephemeral Diffie-Hellman.
       */
      if (kx == GNUTLS_KX_DHE_RSA || kx == GNUTLS_KX_DHE_DSS)
        {
          printf ("\n- Ephemeral DH using prime of %d bits\n",
                  gnutls_dh_get_prime_bits (session));
        }

      /* if the certificate list is available, then
       * print some information about it.
       */
      print_x509_certificate_info (session);

    }                           /* switch */

  /* print the protocol's name (ie TLS 1.0) 
   */
  tmp = gnutls_protocol_get_name (gnutls_protocol_get_version (session));
  printf ("- Protocol: %s\n", tmp);

  /* print the certificate type of the peer.
   * ie X.509
   */
  tmp =
    gnutls_certificate_type_get_name (gnutls_certificate_type_get (session));

  printf ("- Certificate Type: %s\n", tmp);

  /* print the compression algorithm (if any)
   */
  tmp = gnutls_compression_get_name (gnutls_compression_get (session));
  printf ("- Compression: %s\n", tmp);

  /* print the name of the cipher used.
   * ie 3DES.
   */
  tmp = gnutls_cipher_get_name (gnutls_cipher_get (session));
  printf ("- Cipher: %s\n", tmp);

  /* Print the MAC algorithms name.
   * ie SHA1
   */
  tmp = gnutls_mac_get_name (gnutls_mac_get (session));
  printf ("- MAC: %s\n", tmp);

  return 0;
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include "examples.h"

/* A very basic TLS client, with X.509 authentication and server certificate
 * verification.
 */

#define MAX_BUF 1024
#define CAFILE "ca.pem"
#define MSG "GET / HTTP/1.0\r\n\r\n"

extern int tcp_connect (void);
extern void tcp_close (int sd);

/* This function will try to verify the peer's certificate, and
 * also check if the hostname matches, and the activation, expiration dates.
 */
static int
verify_certificate_callback (gnutls_session_t session)
{
  unsigned int status;
  const gnutls_datum_t *cert_list;
  unsigned int cert_list_size;
  int ret;
  gnutls_x509_crt_t cert;
  const char *hostname;

  /* read hostname */
  hostname = gnutls_session_get_ptr (session);

  /* This verification function uses the trusted CAs in the credentials
   * structure. So you must have installed one or more CA certificates.
   */
  ret = gnutls_certificate_verify_peers2 (session, &status);
  if (ret < 0)
    {
      printf ("Error\n");
      return GNUTLS_E_CERTIFICATE_ERROR;
    }

  if (status & GNUTLS_CERT_INVALID)
    printf ("The certificate is not trusted.\n");

  if (status & GNUTLS_CERT_SIGNER_NOT_FOUND)
    printf ("The certificate hasn't got a known issuer.\n");

  if (status & GNUTLS_CERT_REVOKED)
    printf ("The certificate has been revoked.\n");

  if (status & GNUTLS_CERT_EXPIRED)
    printf ("The certificate has expired\n");

  if (status & GNUTLS_CERT_NOT_ACTIVATED)
    printf ("The certificate is not yet activated\n");

  /* Up to here the process is the same for X.509 certificates and
   * OpenPGP keys. From now on X.509 certificates are assumed. This can
   * be easily extended to work with openpgp keys as well.
   */
  if (gnutls_certificate_type_get (session) != GNUTLS_CRT_X509)
    return GNUTLS_E_CERTIFICATE_ERROR;

  if (gnutls_x509_crt_init (&cert) < 0)
    {
      printf ("error in initialization\n");
      return GNUTLS_E_CERTIFICATE_ERROR;
    }

  cert_list = gnutls_certificate_get_peers (session, &cert_list_size);
  if (cert_list == NULL)
    {
      printf ("No certificate was found!\n");
      return GNUTLS_E_CERTIFICATE_ERROR;
    }

  /* This is not a real world example, since we only check the first 
   * certificate in the given chain.
   */
  if (gnutls_x509_crt_import (cert, &cert_list[0], GNUTLS_X509_FMT_DER) < 0)
    {
      printf ("error parsing certificate\n");
      return GNUTLS_E_CERTIFICATE_ERROR;
    }

  if (!gnutls_x509_crt_check_hostname (cert, hostname))
    {
      printf ("The certificate's owner does not match hostname '%s'\n",
              hostname);
      return GNUTLS_E_CERTIFICATE_ERROR;
    }

  gnutls_x509_crt_deinit (cert);

  /* notify gnutls to continue handshake normally */
  return 0;
}

int
main (void)
{
  int ret, sd, ii;
  gnutls_session_t session;
  char buffer[MAX_BUF + 1];
  const char *err;
  gnutls_certificate_credentials_t xcred;

  gnutls_global_init ();

  /* X509 stuff */
  gnutls_certificate_allocate_credentials (&xcred);

  /* sets the trusted cas file
   */
  gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM);
  gnutls_certificate_set_verify_function (xcred, verify_certificate_callback);
  gnutls_certificate_set_verify_flags (xcred,
                                       GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT);

  /* Initialize TLS session 
   */
  gnutls_init (&session, GNUTLS_CLIENT);

  gnutls_session_set_ptr (session, (void *) "my_host_name");

  /* Use default priorities */
  ret = gnutls_priority_set_direct (session, "PERFORMANCE", &err);
  if (ret < 0)
    {
      if (ret == GNUTLS_E_INVALID_REQUEST)
        {
          fprintf (stderr, "Syntax error at: %s\n", err);
        }
      exit (1);
    }

  /* 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)
    {
      fprintf (stderr, "*** Handshake failed\n");
      gnutls_perror (ret);
      goto end;
    }
  else
    {
      printf ("- Handshake was completed\n");
    }

  gnutls_record_send (session, MSG, strlen (MSG));

  ret = gnutls_record_recv (session, buffer, MAX_BUF);
  if (ret == 0)
    {
      printf ("- Peer has closed the TLS connection\n");
      goto end;
    }
  else if (ret < 0)
    {
      fprintf (stderr, "*** 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 ();

  return 0;
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>

#include "examples.h"

/* All the available CRLs
 */
gnutls_x509_crl_t *crl_list;
int crl_list_size;

/* All the available trusted CAs
 */
gnutls_x509_crt_t *ca_list;
int ca_list_size;

static void verify_cert2 (gnutls_x509_crt_t crt,
                          gnutls_x509_crt_t issuer,
                          gnutls_x509_crl_t * crl_list, int crl_list_size);
static void verify_last_cert (gnutls_x509_crt_t crt,
                              gnutls_x509_crt_t * ca_list, int ca_list_size,
                              gnutls_x509_crl_t * crl_list,
                              int crl_list_size);

/* This function will try to verify the peer's certificate chain, and
 * also check if the hostname matches, and the activation, expiration dates.
 */
void
verify_certificate_chain (gnutls_session_t session,
                          const char *hostname,
                          const gnutls_datum_t * cert_chain,
                          int cert_chain_length)
{
  int i;
  gnutls_x509_crt_t *cert;

  cert = malloc (sizeof (*cert) * cert_chain_length);

  /* Import all the certificates in the chain to
   * native certificate format.
   */
  for (i = 0; i < cert_chain_length; i++)
    {
      gnutls_x509_crt_init (&cert[i]);
      gnutls_x509_crt_import (cert[i], &cert_chain[i], GNUTLS_X509_FMT_DER);
    }

  /* If the last certificate in the chain is self signed ignore it.
   * That is because we want to check against our trusted certificate
   * list.
   */
  if (gnutls_x509_crt_check_issuer (cert[cert_chain_length - 1],
                                    cert[cert_chain_length - 1]) > 0
      && cert_chain_length > 0)
    {
      cert_chain_length--;
    }

  /* Now verify the certificates against their issuers
   * in the chain.
   */
  for (i = 1; i < cert_chain_length; i++)
    {
      verify_cert2 (cert[i - 1], cert[i], crl_list, crl_list_size);
    }

  /* Here we must verify the last certificate in the chain against
   * our trusted CA list.
   */
  verify_last_cert (cert[cert_chain_length - 1],
                    ca_list, ca_list_size, crl_list, crl_list_size);

  /* Check if the name in the first certificate matches our destination!
   */
  if (!gnutls_x509_crt_check_hostname (cert[0], hostname))
    {
      printf ("The certificate's owner does not match hostname '%s'\n",
              hostname);
    }

  for (i = 0; i < cert_chain_length; i++)
    gnutls_x509_crt_deinit (cert[i]);

  return;
}

/* Verifies a certificate against an other certificate
 * which is supposed to be it's issuer. Also checks the
 * crl_list if the certificate is revoked.
 */
static void
verify_cert2 (gnutls_x509_crt_t crt, gnutls_x509_crt_t issuer,
              gnutls_x509_crl_t * crl_list, int crl_list_size)
{
  unsigned int output;
  int ret;
  size_t name_size;
  char name[64];

  /* Print information about the certificates to
   * be checked.
   */
  name_size = sizeof (name);
  gnutls_x509_crt_get_dn (crt, name, &name_size);

  fprintf (stderr, "\nCertificate: %s\n", name);

  name_size = sizeof (name);
  gnutls_x509_crt_get_issuer_dn (crt, name, &name_size);

  fprintf (stderr, "Issued by: %s\n", name);

  /* Get the DN of the issuer cert.
   */
  name_size = sizeof (name);
  gnutls_x509_crt_get_dn (issuer, name, &name_size);

  fprintf (stderr, "Checking against: %s\n", name);

  /* Do the actual verification.
   */
  gnutls_x509_crt_verify (crt, &issuer, 1, 0, &output);

  if (output & GNUTLS_CERT_INVALID)
    {
      fprintf (stderr, "Not trusted");

      if (output & GNUTLS_CERT_SIGNER_NOT_FOUND)
        fprintf (stderr, ": no issuer was found");
      if (output & GNUTLS_CERT_SIGNER_NOT_CA)
        fprintf (stderr, ": issuer is not a CA");
      if (output & GNUTLS_CERT_NOT_ACTIVATED)
        fprintf (stderr, ": not yet activated\n");
      if (output & GNUTLS_CERT_EXPIRED)
        fprintf (stderr, ": expired\n");

      fprintf (stderr, "\n");
    }
  else
    fprintf (stderr, "Trusted\n");

  /* Check if the certificate is revoked.
   */
  ret = gnutls_x509_crt_check_revocation (crt, crl_list, crl_list_size);
  if (ret == 1)
    {                           /* revoked */
      fprintf (stderr, "Revoked\n");
    }
}

/* Verifies a certificate against our trusted CA list.
 * Also checks the crl_list if the certificate is revoked.
 */
static void
verify_last_cert (gnutls_x509_crt_t crt,
                  gnutls_x509_crt_t * ca_list, int ca_list_size,
                  gnutls_x509_crl_t * crl_list, int crl_list_size)
{
  unsigned int output;
  int ret;
  size_t name_size;
  char name[64];

  /* Print information about the certificates to
   * be checked.
   */
  name_size = sizeof (name);
  gnutls_x509_crt_get_dn (crt, name, &name_size);

  fprintf (stderr, "\nCertificate: %s\n", name);

  name_size = sizeof (name);
  gnutls_x509_crt_get_issuer_dn (crt, name, &name_size);

  fprintf (stderr, "Issued by: %s\n", name);

  /* Do the actual verification.
   */
  gnutls_x509_crt_verify (crt, ca_list, ca_list_size,
                          GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT, &output);

  if (output & GNUTLS_CERT_INVALID)
    {
      fprintf (stderr, "Not trusted");

      if (output & GNUTLS_CERT_SIGNER_NOT_CA)
        fprintf (stderr, ": Issuer is not a CA\n");
      if (output & GNUTLS_CERT_NOT_ACTIVATED)
        fprintf (stderr, ": Not yet activated\n");
      if (output & GNUTLS_CERT_EXPIRED)
        fprintf (stderr, ": Expired\n");
      fprintf (stderr, "\n");
    }
  else
    fprintf (stderr, "Trusted\n");

  /* Check if the certificate is revoked.
   */
  ret = gnutls_x509_crt_check_revocation (crt, crl_list, crl_list_size);
  if (ret == 1)
    {                           /* revoked */
      fprintf (stderr, "Revoked\n");
    }
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

/* A TLS client that loads the certificate and key.
 */

#define MAX_BUF 1024
#define MSG "GET / HTTP/1.0\r\n\r\n"

#define CERT_FILE "cert.pem"
#define KEY_FILE "key.pem"
#define CAFILE "ca.pem"

extern int tcp_connect (void);
extern void tcp_close (int sd);

static int cert_callback (gnutls_session_t session,
                          const gnutls_datum_t * req_ca_rdn, int nreqs,
                          const gnutls_pk_algorithm_t * sign_algos,
                          int sign_algos_length, gnutls_retr2_st * st);

gnutls_x509_crt_t crt;
gnutls_x509_privkey_t key;

/* Helper functions to load a certificate and key
 * files into memory.
 */
static gnutls_datum_t
load_file (const char *file)
{
  FILE *f;
  gnutls_datum_t loaded_file = { NULL, 0 };
  long filelen;
  void *ptr;

  if (!(f = fopen (file, "r"))
      || fseek (f, 0, SEEK_END) != 0
      || (filelen = ftell (f)) < 0
      || fseek (f, 0, SEEK_SET) != 0
      || !(ptr = malloc ((size_t) filelen))
      || fread (ptr, 1, (size_t) filelen, f) < (size_t) filelen)
    {
      return loaded_file;
    }

  loaded_file.data = ptr;
  loaded_file.size = (unsigned int) filelen;
  return loaded_file;
}

static void
unload_file (gnutls_datum_t data)
{
  free (data.data);
}

/* Load the certificate and the private key.
 */
static void
load_keys (void)
{
  int ret;
  gnutls_datum_t data;

  data = load_file (CERT_FILE);
  if (data.data == NULL)
    {
      fprintf (stderr, "*** Error loading cert file.\n");
      exit (1);
    }
  gnutls_x509_crt_init (&crt);

  ret = gnutls_x509_crt_import (crt, &data, GNUTLS_X509_FMT_PEM);
  if (ret < 0)
    {
      fprintf (stderr, "*** Error loading key file: %s\n",
               gnutls_strerror (ret));
      exit (1);
    }

  unload_file (data);

  data = load_file (KEY_FILE);
  if (data.data == NULL)
    {
      fprintf (stderr, "*** Error loading key file.\n");
      exit (1);
    }

  gnutls_x509_privkey_init (&key);

  ret = gnutls_x509_privkey_import (key, &data, GNUTLS_X509_FMT_PEM);
  if (ret < 0)
    {
      fprintf (stderr, "*** Error loading key file: %s\n",
               gnutls_strerror (ret));
      exit (1);
    }

  unload_file (data);

}

int
main (void)
{
  int ret, sd, ii;
  gnutls_session_t session;
  gnutls_priority_t priorities_cache;
  char buffer[MAX_BUF + 1];
  gnutls_certificate_credentials_t xcred;
  /* Allow connections to servers that have OpenPGP keys as well.
   */

  gnutls_global_init ();

  load_keys ();

  /* X509 stuff */
  gnutls_certificate_allocate_credentials (&xcred);

  /* priorities */
  gnutls_priority_init (&priorities_cache, "NORMAL", NULL);

  /* sets the trusted cas file
   */
  gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM);

  gnutls_certificate_set_retrieve_function (xcred, cert_callback);

  /* Initialize TLS session 
   */
  gnutls_init (&session, GNUTLS_CLIENT);

  /* Use default priorities */
  gnutls_priority_set (session, priorities_cache);

  /* 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)
    {
      fprintf (stderr, "*** Handshake failed\n");
      gnutls_perror (ret);
      goto end;
    }
  else
    {
      printf ("- Handshake was completed\n");
    }

  gnutls_record_send (session, MSG, strlen (MSG));

  ret = gnutls_record_recv (session, buffer, MAX_BUF);
  if (ret == 0)
    {
      printf ("- Peer has closed the TLS connection\n");
      goto end;
    }
  else if (ret < 0)
    {
      fprintf (stderr, "*** 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_priority_deinit (priorities_cache);

  gnutls_global_deinit ();

  return 0;
}

/* This callback should be associated with a session by calling
 * gnutls_certificate_client_set_retrieve_function( session, cert_callback),
 * before a handshake.
 */

static int
cert_callback (gnutls_session_t session,
               const gnutls_datum_t * req_ca_rdn, int nreqs,
               const gnutls_pk_algorithm_t * sign_algos,
               int sign_algos_length, gnutls_retr2_st * st)
{
  char issuer_dn[256];
  int i, ret;
  size_t len;
  gnutls_certificate_type_t type;

  /* Print the server's trusted CAs
   */
  if (nreqs > 0)
    printf ("- Server's trusted authorities:\n");
  else
    printf ("- Server did not send us any trusted authorities names.\n");

  /* print the names (if any) */
  for (i = 0; i < nreqs; i++)
    {
      len = sizeof (issuer_dn);
      ret = gnutls_x509_rdn_get (&req_ca_rdn[i], issuer_dn, &len);
      if (ret >= 0)
        {
          printf ("   [%d]: ", i);
          printf ("%s\n", issuer_dn);
        }
    }

  /* Select a certificate and return it.
   * The certificate must be of any of the "sign algorithms"
   * supported by the server.
   */

  type = gnutls_certificate_type_get (session);
  if (type == GNUTLS_CRT_X509)
    {
      /* check if the certificate we are sending is signed
       * with an algorithm that the server accepts */
      gnutls_sign_algorithm_t cert_algo, req_algo;
      int i, match = 0;

      ret = gnutls_x509_crt_get_signature_algorithm (crt);
      if (ret < 0)
        {
          /* error reading signature algorithm 
           */
          return -1;
        }
      cert_algo = ret;

      i = 0;
      do
        {
          ret = gnutls_sign_algorithm_get_requested (session, i, &req_algo);
          if (ret >= 0 && cert_algo == req_algo)
            {
              match = 1;
              break;
            }

          /* server has not requested anything specific */
          if (i == 0 && ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
            {
              match = 1;
              break;
            }
          i++;
        }
      while (ret >= 0);

      if (match == 0)
        {
          printf
            ("- Could not find a suitable certificate to send to server\n");
          return -1;
        }

      st->cert_type = type;
      st->ncerts = 1;

      st->cert.x509 = &crt;
      st->key.x509 = key;
      st->key_type = GNUTLS_PRIVKEY_X509;

      st->deinit_all = 0;
    }
  else
    {
      return -1;
    }

  return 0;

}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <getpass.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include <gnutls/pkcs11.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

/* A TLS client that loads the certificate and key.
 */

#define MAX_BUF 1024
#define MSG "GET / HTTP/1.0\r\n\r\n"
#define MIN(x,y) (((x)<(y))?(x):(y))

#define CAFILE "ca.pem"
#define KEY_URL "pkcs11:manufacturer=SomeManufacturer;object=Private%20Key" \
  ";objecttype=private;id=db:5b:3e:b5:72:33"
#define CERT_URL "pkcs11:manufacturer=SomeManufacturer;object=Certificate;" \
  "objecttype=cert;id=db:5b:3e:b5:72:33"

extern int tcp_connect (void);
extern void tcp_close (int sd);

static int cert_callback (gnutls_session_t session,
                          const gnutls_datum_t * req_ca_rdn, int nreqs,
                          const gnutls_pk_algorithm_t * sign_algos,
                          int sign_algos_length, gnutls_retr2_st * st);

gnutls_x509_crt_t crt;
gnutls_pkcs11_privkey_t key;

/* Load the certificate and the private key.
 */
static void
load_keys (void)
{
  int ret;

  gnutls_x509_crt_init (&crt);

  ret = gnutls_x509_crt_import_pkcs11_url (crt, CERT_URL, 0);

  /* some tokens require login to read data */
  if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
    ret = gnutls_x509_crt_import_pkcs11_url (crt, CERT_URL,
                                             GNUTLS_PKCS11_OBJ_FLAG_LOGIN);

  if (ret < 0)
    {
      fprintf (stderr, "*** Error loading key file: %s\n",
               gnutls_strerror (ret));
      exit (1);
    }

  gnutls_pkcs11_privkey_init (&key);

  ret = gnutls_pkcs11_privkey_import_url (key, KEY_URL, 0);
  if (ret < 0)
    {
      fprintf (stderr, "*** Error loading key file: %s\n",
               gnutls_strerror (ret));
      exit (1);
    }

}

static int
pin_callback (void *user, int attempt, const char *token_url,
              const char *token_label, unsigned int flags, char *pin,
              size_t pin_max)
{
  const char *password;
  int len;

  printf ("PIN required for token '%s' with URL '%s'\n", token_label,
          token_url);
  if (flags & GNUTLS_PKCS11_PIN_FINAL_TRY)
    printf ("*** This is the final try before locking!\n");
  if (flags & GNUTLS_PKCS11_PIN_COUNT_LOW)
    printf ("*** Only few tries left before locking!\n");

  password = getpass ("Enter pin: ");
  if (password == NULL || password[0] == 0)
    {
      fprintf (stderr, "No password given\n");
      exit (1);
    }

  len = MIN (pin_max, strlen (password));
  memcpy (pin, password, len);
  pin[len] = 0;

  return 0;
}

int
main (void)
{
  int ret, sd, ii;
  gnutls_session_t session;
  gnutls_priority_t priorities_cache;
  char buffer[MAX_BUF + 1];
  gnutls_certificate_credentials_t xcred;
  /* Allow connections to servers that have OpenPGP keys as well.
   */

  gnutls_global_init ();
  /* PKCS11 private key operations might require PIN.
   * Register a callback.
   */
  gnutls_pkcs11_set_pin_function (pin_callback, NULL);

  load_keys ();

  /* X509 stuff */
  gnutls_certificate_allocate_credentials (&xcred);

  /* priorities */
  gnutls_priority_init (&priorities_cache, "NORMAL", NULL);

  /* sets the trusted cas file
   */
  gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM);

  gnutls_certificate_set_retrieve_function (xcred, cert_callback);

  /* Initialize TLS session
   */
  gnutls_init (&session, GNUTLS_CLIENT);

  /* Use default priorities */
  gnutls_priority_set (session, priorities_cache);

  /* 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)
    {
      fprintf (stderr, "*** Handshake failed\n");
      gnutls_perror (ret);
      goto end;
    }
  else
    {
      printf ("- Handshake was completed\n");
    }

  gnutls_record_send (session, MSG, strlen (MSG));

  ret = gnutls_record_recv (session, buffer, MAX_BUF);
  if (ret == 0)
    {
      printf ("- Peer has closed the TLS connection\n");
      goto end;
    }
  else if (ret < 0)
    {
      fprintf (stderr, "*** 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_priority_deinit (priorities_cache);

  gnutls_global_deinit ();

  return 0;
}

/* This callback should be associated with a session by calling
 * gnutls_certificate_client_set_retrieve_function( session, cert_callback),
 * before a handshake.
 */

static int
cert_callback (gnutls_session_t session,
               const gnutls_datum_t * req_ca_rdn, int nreqs,
               const gnutls_pk_algorithm_t * sign_algos,
               int sign_algos_length, gnutls_retr2_st * st)
{
  char issuer_dn[256];
  int i, ret;
  size_t len;
  gnutls_certificate_type_t type;

  /* Print the server's trusted CAs
   */
  if (nreqs > 0)
    printf ("- Server's trusted authorities:\n");
  else
    printf ("- Server did not send us any trusted authorities names.\n");

  /* print the names (if any) */
  for (i = 0; i < nreqs; i++)
    {
      len = sizeof (issuer_dn);
      ret = gnutls_x509_rdn_get (&req_ca_rdn[i], issuer_dn, &len);
      if (ret >= 0)
        {
          printf ("   [%d]: ", i);
          printf ("%s\n", issuer_dn);
        }
    }

  /* Select a certificate and return it.
   * The certificate must be of any of the "sign algorithms"
   * supported by the server.
   */

  type = gnutls_certificate_type_get (session);
  if (type == GNUTLS_CRT_X509)
    {
      /* check if the certificate we are sending is signed
       * with an algorithm that the server accepts */
      gnutls_sign_algorithm_t cert_algo, req_algo;
      int i, match = 0;

      ret = gnutls_x509_crt_get_signature_algorithm (crt);
      if (ret < 0)
        {
          /* error reading signature algorithm
           */
          return -1;
        }
      cert_algo = ret;

      i = 0;
      do
        {
          ret = gnutls_sign_algorithm_get_requested (session, i, &req_algo);
          if (ret >= 0 && cert_algo == req_algo)
            {
              match = 1;
              break;
            }

          /* server has not requested anything specific */
          if (i == 0 && ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
            {
              match = 1;
              break;
            }
          i++;
        }
      while (ret >= 0);

      if (match == 0)
        {
          printf
            ("- Could not find a suitable certificate to send to server\n");
          return -1;
        }

      st->cert_type = type;
      st->ncerts = 1;

      st->cert.x509 = &crt;
      st->key.pkcs11 = key;
      st->key_type = GNUTLS_PRIVKEY_PKCS11;

      st->deinit_all = 0;
    }
  else
    {
      return -1;
    }

  return 0;

}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>

/* Those functions are defined in other examples.
 */
extern void check_alert (gnutls_session_t session, int ret);
extern int tcp_connect (void);
extern void tcp_close (int sd);

#define MAX_BUF 1024
#define CAFILE "ca.pem"
#define MSG "GET / HTTP/1.0\r\n\r\n"

int
main (void)
{
  int ret;
  int sd, ii;
  gnutls_session_t session;
  char buffer[MAX_BUF + 1];
  gnutls_certificate_credentials_t xcred;

  /* variables used in session resuming 
   */
  int t;
  char *session_data = NULL;
  size_t session_data_size = 0;

  gnutls_global_init ();

  /* X509 stuff */
  gnutls_certificate_allocate_credentials (&xcred);

  gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM);

  for (t = 0; t < 2; t++)
    {                           /* connect 2 times to the server */

      sd = tcp_connect ();

      gnutls_init (&session, GNUTLS_CLIENT);

      gnutls_priority_set_direct (session, "PERFORMANCE:!ARCFOUR-128", NULL);

      gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred);

      if (t > 0)
        {
          /* if this is not the first time we connect */
          gnutls_session_set_data (session, session_data, session_data_size);
          free (session_data);
        }

      gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd);

      /* Perform the TLS handshake
       */
      ret = gnutls_handshake (session);

      if (ret < 0)
        {
          fprintf (stderr, "*** Handshake failed\n");
          gnutls_perror (ret);
          goto end;
        }
      else
        {
          printf ("- Handshake was completed\n");
        }

      if (t == 0)
        {                       /* the first time we connect */
          /* get the session data size */
          gnutls_session_get_data (session, NULL, &session_data_size);
          session_data = malloc (session_data_size);

          /* put session data to the session variable */
          gnutls_session_get_data (session, session_data, &session_data_size);

        }
      else
        {                       /* the second time we connect */

          /* check if we actually resumed the previous session */
          if (gnutls_session_is_resumed (session) != 0)
            {
              printf ("- Previous session was resumed\n");
            }
          else
            {
              fprintf (stderr, "*** Previous session was NOT resumed\n");
            }
        }

      /* This function was defined in a previous example
       */
      /* print_info(session); */

      gnutls_record_send (session, MSG, strlen (MSG));

      ret = gnutls_record_recv (session, buffer, MAX_BUF);
      if (ret == 0)
        {
          printf ("- Peer has closed the TLS connection\n");
          goto end;
        }
      else if (ret < 0)
        {
          fprintf (stderr, "*** 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);

    }                           /* for() */

  gnutls_certificate_free_credentials (xcred);

  gnutls_global_deinit ();

  return 0;
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gnutls/gnutls.h>
#include <gnutls/extra.h>

/* Those functions are defined in other examples.
 */
extern void check_alert (gnutls_session_t session, int ret);
extern int tcp_connect (void);
extern void tcp_close (int sd);

#define MAX_BUF 1024
#define USERNAME "user"
#define PASSWORD "pass"
#define CAFILE "ca.pem"
#define MSG "GET / HTTP/1.0\r\n\r\n"

int
main (void)
{
  int ret;
  int sd, ii;
  gnutls_session_t session;
  char buffer[MAX_BUF + 1];
  gnutls_srp_client_credentials_t srp_cred;
  gnutls_certificate_credentials_t cert_cred;

  gnutls_global_init ();

  /* now enable the gnutls-extra library which contains the
   * SRP stuff.
   */
  gnutls_global_init_extra ();

  gnutls_srp_allocate_client_credentials (&srp_cred);
  gnutls_certificate_allocate_credentials (&cert_cred);

  gnutls_certificate_set_x509_trust_file (cert_cred, CAFILE,
                                          GNUTLS_X509_FMT_PEM);
  gnutls_srp_set_client_credentials (srp_cred, USERNAME, PASSWORD);

  /* connects to server
   */
  sd = tcp_connect ();

  /* Initialize TLS session
   */
  gnutls_init (&session, GNUTLS_CLIENT);

  /* Set the priorities.
   */
  gnutls_priority_set_direct (session, "NORMAL:+SRP:+SRP-RSA:+SRP-DSS", NULL);

  /* put the SRP credentials to the current session
   */
  gnutls_credentials_set (session, GNUTLS_CRD_SRP, srp_cred);
  gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, cert_cred);

  gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd);

  /* Perform the TLS handshake
   */
  ret = gnutls_handshake (session);

  if (ret < 0)
    {
      fprintf (stderr, "*** Handshake failed\n");
      gnutls_perror (ret);
      goto end;
    }
  else
    {
      printf ("- Handshake was completed\n");
    }

  gnutls_record_send (session, MSG, strlen (MSG));

  ret = gnutls_record_recv (session, buffer, MAX_BUF);
  if (gnutls_error_is_fatal (ret) == 1 || ret == 0)
    {
      if (ret == 0)
        {
          printf ("- Peer has closed the GnuTLS connection\n");
          goto end;
        }
      else
        {
          fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret));
          goto end;
        }
    }
  else
    check_alert (session, ret);

  if (ret > 0)
    {
      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_srp_free_client_credentials (srp_cred);
  gnutls_certificate_free_credentials (cert_cred);

  gnutls_global_deinit ();

  return 0;
}

#include <iostream>
#include <stdexcept>
#include <gnutls/gnutls.h>
#include <gnutls/gnutlsxx.h>
#include <cstring> /* for strlen */

/* A very basic TLS client, with anonymous authentication.
 * written by Eduardo Villanueva Che.
 */

#define MAX_BUF 1024
#define SA struct sockaddr

#define CAFILE "ca.pem"
#define MSG "GET / HTTP/1.0\r\n\r\n"

extern "C"
{
    int tcp_connect(void);
    void tcp_close(int sd);
}

int main(void)
{
    int sd = -1;
    gnutls_global_init();

    try
    {

        /* Allow connections to servers that have OpenPGP keys as well.
         */
        gnutls::client_session session;

        /* X509 stuff */
        gnutls::certificate_credentials credentials;

        /* sets the trusted cas file
         */
        credentials.set_x509_trust_file(CAFILE, GNUTLS_X509_FMT_PEM);
        /* put the x509 credentials to the current session
         */
        session.set_credentials(credentials);

        /* Use default priorities */
        session.set_priority ("NORMAL", NULL);

        /* connect to the peer
         */
        sd = tcp_connect();
        session.set_transport_ptr((gnutls_transport_ptr_t) sd);

        /* Perform the TLS handshake
         */
        int ret = session.handshake();
        if (ret < 0)
        {
            throw std::runtime_error("Handshake failed");
        }
        else
        {
            std::cout << "- Handshake was completed" << std::endl;
        }

        session.send(MSG, strlen(MSG));
        char buffer[MAX_BUF + 1];
        ret = session.recv(buffer, MAX_BUF);
        if (ret == 0)
        {
            throw std::runtime_error("Peer has closed the TLS connection");
        }
        else if (ret < 0)
        {
            throw std::runtime_error(gnutls_strerror(ret));
        }

        std::cout << "- Received " << ret << " bytes:" << std::endl;
        std::cout.write(buffer, ret);
        std::cout << std::endl;

        session.bye(GNUTLS_SHUT_RDWR);
    }
    catch (std::exception &ex)
    {
        std::cerr << "Exception caught: " << ex.what() << std::endl;
    }

    if (sd != -1)
        tcp_close(sd);

    gnutls_global_deinit();

    return 0;
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <unistd.h>

#define SA struct sockaddr

/* tcp.c */
int tcp_connect (void);
void tcp_close (int sd);

/* Connects to the peer and returns a socket
 * descriptor.
 */
extern 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, (SA *) & sa, sizeof (sa));
  if (err < 0)
    {
      fprintf (stderr, "Connect error\n");
      exit (1);
    }

  return sd;
}

/* closes the given socket descriptor.
 */
extern void
tcp_close (int sd)
{
  shutdown (sd, SHUT_RDWR);     /* no more receptions */
  close (sd);
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>

#define KEYFILE "key.pem"
#define CERTFILE "cert.pem"
#define CAFILE "ca.pem"
#define CRLFILE "crl.pem"

/* This is a sample TLS 1.0 echo server, using X.509 authentication.
 */

#define SA struct sockaddr
#define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);}
#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_priority_t priority_cache;

static gnutls_session_t
initialize_tls_session (void)
{
  gnutls_session_t session;

  gnutls_init (&session, GNUTLS_SERVER);

  gnutls_priority_set (session, priority_cache);

  gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, x509_cred);

  /* request client certificate if any.
   */
  gnutls_certificate_server_set_request (session, GNUTLS_CERT_REQUEST);

  /* Set maximum compatibility mode. This is only suggested on public webservers
   * that need to trade security for compatibility
   */
  gnutls_session_enable_compatibility_mode (session);

  return session;
}

static gnutls_dh_params_t dh_params;

static int
generate_dh_params (void)
{

  /* Generate Diffie-Hellman parameters - for use with DHE
   * kx algorithms. When short bit length is used, it might
   * be wise to regenerate parameters.
   *
   * Check the ex-serv-export.c example for using static
   * parameters.
   */
  gnutls_dh_params_init (&dh_params);
  gnutls_dh_params_generate2 (dh_params, DH_BITS);

  return 0;
}

int
main (void)
{
  int err, listen_sd;
  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;

  /* this must be called once in the program
   */
  gnutls_global_init ();

  gnutls_certificate_allocate_credentials (&x509_cred);
  gnutls_certificate_set_x509_trust_file (x509_cred, CAFILE,
                                          GNUTLS_X509_FMT_PEM);

  gnutls_certificate_set_x509_crl_file (x509_cred, CRLFILE,
                                        GNUTLS_X509_FMT_PEM);

  gnutls_certificate_set_x509_key_file (x509_cred, CERTFILE, KEYFILE,
                                        GNUTLS_X509_FMT_PEM);

  generate_dh_params ();

  gnutls_priority_init (&priority_cache, "NORMAL", NULL);

  gnutls_certificate_set_dh_params (x509_cred, dh_params);

  /* Socket operations
   */
  listen_sd = socket (AF_INET, SOCK_STREAM, 0);
  SOCKET_ERR (listen_sd, "socket");

  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, (void *) &optval,
              sizeof (int));

  err = bind (listen_sd, (SA *) & sa_serv, sizeof (sa_serv));
  SOCKET_ERR (err, "bind");
  err = listen (listen_sd, 1024);
  SOCKET_ERR (err, "listen");

  printf ("Server ready. Listening to port '%d'.\n\n", PORT);

  client_len = sizeof (sa_cli);
  for (;;)
    {
      session = initialize_tls_session ();

      sd = accept (listen_sd, (SA *) & sa_cli, &client_len);

      printf ("- 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);
          fprintf (stderr, "*** Handshake has failed (%s)\n\n",
                   gnutls_strerror (ret));
          continue;
        }
      printf ("- Handshake was completed\n");

      /* see the Getting peer's information example */
      /* print_info(session); */

      for (;;)
        {
          memset (buffer, 0, MAX_BUF + 1);
          ret = gnutls_record_recv (session, buffer, MAX_BUF);

          if (ret == 0)
            {
              printf ("\n- Peer has closed the GnuTLS connection\n");
              break;
            }
          else if (ret < 0)
            {
              fprintf (stderr, "\n*** Received corrupted "
                       "data(%d). Closing the connection.\n\n", ret);
              break;
            }
          else if (ret > 0)
            {
              /* echo data back to the client
               */
              gnutls_record_send (session, buffer, strlen (buffer));
            }
        }
      printf ("\n");
      /* 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_priority_deinit (priority_cache);

  gnutls_global_deinit ();

  return 0;

}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
#include <gnutls/openpgp.h>

#define KEYFILE "secret.asc"
#define CERTFILE "public.asc"
#define RINGFILE "ring.gpg"

/* This is a sample TLS 1.0-OpenPGP echo server.
 */

#define SA struct sockaddr
#define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);}
#define MAX_BUF 1024
#define PORT 5556               /* listen to 5556 port */
#define DH_BITS 1024

/* These are global */
gnutls_certificate_credentials_t cred;
gnutls_dh_params_t dh_params;

static int
generate_dh_params (void)
{

  /* 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);
  gnutls_dh_params_generate2 (dh_params, DH_BITS);

  return 0;
}

static gnutls_session_t
initialize_tls_session (void)
{
  gnutls_session_t session;

  gnutls_init (&session, GNUTLS_SERVER);

  gnutls_priority_set_direct (session, "NORMAL", NULL);

  /* request client certificate if any.
   */
  gnutls_certificate_server_set_request (session, GNUTLS_CERT_REQUEST);

  gnutls_dh_set_prime_bits (session, DH_BITS);

  return session;
}

int
main (void)
{
  int err, listen_sd;
  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;
  char name[256];

  strcpy (name, "Echo Server");

  /* this must be called once in the program
   */
  gnutls_global_init ();

  gnutls_certificate_allocate_credentials (&cred);
  gnutls_certificate_set_openpgp_keyring_file (cred, RINGFILE,
                                               GNUTLS_OPENPGP_FMT_BASE64);

  gnutls_certificate_set_openpgp_key_file (cred, CERTFILE, KEYFILE,
                                           GNUTLS_OPENPGP_FMT_BASE64);

  generate_dh_params ();

  gnutls_certificate_set_dh_params (cred, dh_params);

  /* Socket operations
   */
  listen_sd = socket (AF_INET, SOCK_STREAM, 0);
  SOCKET_ERR (listen_sd, "socket");

  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, (void *) &optval,
              sizeof (int));

  err = bind (listen_sd, (SA *) & sa_serv, sizeof (sa_serv));
  SOCKET_ERR (err, "bind");
  err = listen (listen_sd, 1024);
  SOCKET_ERR (err, "listen");

  printf ("%s ready. Listening to port '%d'.\n\n", name, PORT);

  client_len = sizeof (sa_cli);
  for (;;)
    {
      session = initialize_tls_session ();

      sd = accept (listen_sd, (SA *) & sa_cli, &client_len);

      printf ("- 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);
          fprintf (stderr, "*** Handshake has failed (%s)\n\n",
                   gnutls_strerror (ret));
          continue;
        }
      printf ("- Handshake was completed\n");

      /* see the Getting peer's information example */
      /* print_info(session); */

      for (;;)
        {
          memset (buffer, 0, MAX_BUF + 1);
          ret = gnutls_record_recv (session, buffer, MAX_BUF);

          if (ret == 0)
            {
              printf ("\n- Peer has closed the GnuTLS connection\n");
              break;
            }
          else if (ret < 0)
            {
              fprintf (stderr, "\n*** Received corrupted "
                       "data(%d). Closing the connection.\n\n", ret);
              break;
            }
          else if (ret > 0)
            {
              /* echo data back to the client
               */
              gnutls_record_send (session, buffer, strlen (buffer));
            }
        }
      printf ("\n");
      /* 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 (cred);

  gnutls_global_deinit ();

  return 0;

}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
#include <gnutls/extra.h>

#define SRP_PASSWD "tpasswd"
#define SRP_PASSWD_CONF "tpasswd.conf"

#define KEYFILE "key.pem"
#define CERTFILE "cert.pem"
#define CAFILE "ca.pem"

/* This is a sample TLS-SRP echo server.
 */

#define SA struct sockaddr
#define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);}
#define MAX_BUF 1024
#define PORT 5556               /* listen to 5556 port */

/* These are global */
gnutls_srp_server_credentials_t srp_cred;
gnutls_certificate_credentials_t cert_cred;

static gnutls_session_t
initialize_tls_session (void)
{
  gnutls_session_t session;

  gnutls_init (&session, GNUTLS_SERVER);

  gnutls_priority_set_direct (session, "NORMAL:+SRP:+SRP-DSS:+SRP-RSA", NULL);

  gnutls_credentials_set (session, GNUTLS_CRD_SRP, srp_cred);
  /* for the certificate authenticated ciphersuites.
   */
  gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, cert_cred);

  /* request client certificate if any.
   */
  gnutls_certificate_server_set_request (session, GNUTLS_CERT_IGNORE);

  return session;
}

int
main (void)
{
  int err, listen_sd;
  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;
  char name[256];

  strcpy (name, "Echo Server");

  /* these must be called once in the program
   */
  gnutls_global_init ();
  gnutls_global_init_extra ();  /* for SRP */

  /* SRP_PASSWD a password file (created with the included srptool utility) 
   */
  gnutls_srp_allocate_server_credentials (&srp_cred);
  gnutls_srp_set_server_credentials_file (srp_cred, SRP_PASSWD,
                                          SRP_PASSWD_CONF);

  gnutls_certificate_allocate_credentials (&cert_cred);
  gnutls_certificate_set_x509_trust_file (cert_cred, CAFILE,
                                          GNUTLS_X509_FMT_PEM);
  gnutls_certificate_set_x509_key_file (cert_cred, CERTFILE, KEYFILE,
                                        GNUTLS_X509_FMT_PEM);

  /* TCP socket operations
   */
  listen_sd = socket (AF_INET, SOCK_STREAM, 0);
  SOCKET_ERR (listen_sd, "socket");

  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, (void *) &optval,
              sizeof (int));

  err = bind (listen_sd, (SA *) & sa_serv, sizeof (sa_serv));
  SOCKET_ERR (err, "bind");
  err = listen (listen_sd, 1024);
  SOCKET_ERR (err, "listen");

  printf ("%s ready. Listening to port '%d'.\n\n", name, PORT);

  client_len = sizeof (sa_cli);
  for (;;)
    {
      session = initialize_tls_session ();

      sd = accept (listen_sd, (SA *) & sa_cli, &client_len);

      printf ("- 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);
          fprintf (stderr, "*** Handshake has failed (%s)\n\n",
                   gnutls_strerror (ret));
          continue;
        }
      printf ("- Handshake was completed\n");

      /* print_info(session); */

      for (;;)
        {
          memset (buffer, 0, MAX_BUF + 1);
          ret = gnutls_record_recv (session, buffer, MAX_BUF);

          if (ret == 0)
            {
              printf ("\n- Peer has closed the GnuTLS connection\n");
              break;
            }
          else if (ret < 0)
            {
              fprintf (stderr, "\n*** Received corrupted "
                       "data(%d). Closing the connection.\n\n", ret);
              break;
            }
          else if (ret > 0)
            {
              /* echo data back to the client
               */
              gnutls_record_send (session, buffer, strlen (buffer));
            }
        }
      printf ("\n");
      /* 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_srp_free_server_credentials (srp_cred);
  gnutls_certificate_free_credentials (cert_cred);

  gnutls_global_deinit ();

  return 0;

}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>

/* This is a sample TLS 1.0 echo server, for anonymous authentication only.
 */

#define SA struct sockaddr
#define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);}
#define MAX_BUF 1024
#define PORT 5556               /* listen to 5556 port */
#define DH_BITS 1024

/* These are global */
gnutls_anon_server_credentials_t anoncred;

static gnutls_session_t
initialize_tls_session (void)
{
  gnutls_session_t session;

  gnutls_init (&session, GNUTLS_SERVER);

  gnutls_priority_set_direct (session, "NORMAL:+ANON-DH", NULL);

  gnutls_credentials_set (session, GNUTLS_CRD_ANON, anoncred);

  gnutls_dh_set_prime_bits (session, DH_BITS);

  return session;
}

static gnutls_dh_params_t dh_params;

static int
generate_dh_params (void)
{

  /* 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);
  gnutls_dh_params_generate2 (dh_params, DH_BITS);

  return 0;
}

int
main (void)
{
  int err, listen_sd;
  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;

  /* this must be called once in the program
   */
  gnutls_global_init ();

  gnutls_anon_allocate_server_credentials (&anoncred);

  generate_dh_params ();

  gnutls_anon_set_server_dh_params (anoncred, dh_params);

  /* Socket operations
   */
  listen_sd = socket (AF_INET, SOCK_STREAM, 0);
  SOCKET_ERR (listen_sd, "socket");

  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, (void *) &optval,
              sizeof (int));

  err = bind (listen_sd, (SA *) & sa_serv, sizeof (sa_serv));
  SOCKET_ERR (err, "bind");
  err = listen (listen_sd, 1024);
  SOCKET_ERR (err, "listen");

  printf ("Server ready. Listening to port '%d'.\n\n", PORT);

  client_len = sizeof (sa_cli);
  for (;;)
    {
      session = initialize_tls_session ();

      sd = accept (listen_sd, (SA *) & sa_cli, &client_len);

      printf ("- 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);
          fprintf (stderr, "*** Handshake has failed (%s)\n\n",
                   gnutls_strerror (ret));
          continue;
        }
      printf ("- Handshake was completed\n");

      /* see the Getting peer's information example */
      /* print_info(session); */

      for (;;)
        {
          memset (buffer, 0, MAX_BUF + 1);
          ret = gnutls_record_recv (session, buffer, MAX_BUF);

          if (ret == 0)
            {
              printf ("\n- Peer has closed the GnuTLS connection\n");
              break;
            }
          else if (ret < 0)
            {
              fprintf (stderr, "\n*** Received corrupted "
                       "data(%d). Closing the connection.\n\n", ret);
              break;
            }
          else if (ret > 0)
            {
              /* echo data back to the client
               */
              gnutls_record_send (session, buffer, strlen (buffer));
            }
        }
      printf ("\n");
      /* 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_anon_free_server_credentials (anoncred);

  gnutls_global_deinit ();

  return 0;

}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>

#include "examples.h"

/* This function will check whether the given return code from
 * a gnutls function (recv/send), is an alert, and will print
 * that alert.
 */
void
check_alert (gnutls_session_t session, int ret)
{
  int last_alert;

  if (ret == GNUTLS_E_WARNING_ALERT_RECEIVED
      || ret == GNUTLS_E_FATAL_ALERT_RECEIVED)
    {
      last_alert = gnutls_alert_get (session);

      /* The check for renegotiation is only useful if we are 
       * a server, and we had requested a rehandshake.
       */
      if (last_alert == GNUTLS_A_NO_RENEGOTIATION &&
          ret == GNUTLS_E_WARNING_ALERT_RECEIVED)
        printf ("* Received NO_RENEGOTIATION alert. "
                "Client Does not support renegotiation.\n");
      else
        printf ("* Received alert '%d': %s.\n", last_alert,
                gnutls_alert_get_name (last_alert));
    }
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>

#include "examples.h"

static const char *
bin2hex (const void *bin, size_t bin_size)
{
  static char printable[110];
  const unsigned char *_bin = bin;
  char *print;
  size_t i;

  if (bin_size > 50)
    bin_size = 50;

  print = printable;
  for (i = 0; i < bin_size; i++)
    {
      sprintf (print, "%.2x ", _bin[i]);
      print += 2;
    }

  return printable;
}

/* This function will print information about this session's peer
 * certificate.
 */
void
print_x509_certificate_info (gnutls_session_t session)
{
  char serial[40];
  char dn[256];
  size_t size;
  unsigned int algo, bits;
  time_t expiration_time, activation_time;
  const gnutls_datum_t *cert_list;
  unsigned int cert_list_size = 0;
  gnutls_x509_crt_t cert;
  gnutls_datum_t cinfo;

  /* This function only works for X.509 certificates.
   */
  if (gnutls_certificate_type_get (session) != GNUTLS_CRT_X509)
    return;

  cert_list = gnutls_certificate_get_peers (session, &cert_list_size);

  printf ("Peer provided %d certificates.\n", cert_list_size);

  if (cert_list_size > 0)
    {
      int ret;

      /* we only print information about the first certificate.
       */
      gnutls_x509_crt_init (&cert);

      gnutls_x509_crt_import (cert, &cert_list[0], GNUTLS_X509_FMT_DER);

      printf ("Certificate info:\n");

      /* This is the preferred way of printing short information about
         a certificate. */

      ret = gnutls_x509_crt_print (cert, GNUTLS_CRT_PRINT_ONELINE, &cinfo);
      if (ret == 0)
        {
          printf ("\t%s\n", cinfo.data);
          gnutls_free (cinfo.data);
        }

      /* If you want to extract fields manually for some other reason,
         below are popular example calls. */

      expiration_time = gnutls_x509_crt_get_expiration_time (cert);
      activation_time = gnutls_x509_crt_get_activation_time (cert);

      printf ("\tCertificate is valid since: %s", ctime (&activation_time));
      printf ("\tCertificate expires: %s", ctime (&expiration_time));

      /* Print the serial number of the certificate.
       */
      size = sizeof (serial);
      gnutls_x509_crt_get_serial (cert, serial, &size);

      printf ("\tCertificate serial number: %s\n", bin2hex (serial, size));

      /* Extract some of the public key algorithm's parameters
       */
      algo = gnutls_x509_crt_get_pk_algorithm (cert, &bits);

      printf ("Certificate public key: %s",
              gnutls_pk_algorithm_get_name (algo));

      /* Print the version of the X.509
       * certificate.
       */
      printf ("\tCertificate version: #%d\n",
              gnutls_x509_crt_get_version (cert));

      size = sizeof (dn);
      gnutls_x509_crt_get_dn (cert, dn, &size);
      printf ("\tDN: %s\n", dn);

      size = sizeof (dn);
      gnutls_x509_crt_get_issuer_dn (cert, dn, &size);
      printf ("\tIssuer's DN: %s\n", dn);

      gnutls_x509_crt_deinit (cert);

    }
}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include <gnutls/abstract.h>
#include <time.h>

/* This example will generate a private key and a certificate
 * request.
 */

int
main (void)
{
  gnutls_x509_crq_t crq;
  gnutls_x509_privkey_t key;
  gnutls_privkey_t pkey; /* object used for signing */
  unsigned char buffer[10 * 1024];
  size_t buffer_size = sizeof (buffer);
  unsigned int bits;

  gnutls_global_init ();

  /* Initialize an empty certificate request, and
   * an empty private key.
   */
  gnutls_x509_crq_init (&crq);

  gnutls_x509_privkey_init (&key);
  gnutls_privkey_init (&pkey);

  /* Generate an RSA key of moderate security.
   */
  bits = gnutls_sec_param_to_pk_bits (GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_NORMAL);
  gnutls_x509_privkey_generate (key, GNUTLS_PK_RSA, bits, 0);

  /* Add stuff to the distinguished name
   */
  gnutls_x509_crq_set_dn_by_oid (crq, GNUTLS_OID_X520_COUNTRY_NAME,
                                 0, "GR", 2);

  gnutls_x509_crq_set_dn_by_oid (crq, GNUTLS_OID_X520_COMMON_NAME,
                                 0, "Nikos", strlen ("Nikos"));

  /* Set the request version.
   */
  gnutls_x509_crq_set_version (crq, 1);

  /* Set a challenge password.
   */
  gnutls_x509_crq_set_challenge_password (crq, "something to remember here");

  /* Associate the request with the private key
   */
  gnutls_x509_crq_set_key (crq, key);

  /* Self sign the certificate request.
   */
  gnutls_privkey_import_x509( pkey, key, 0);
  gnutls_x509_crq_privkey_sign (crq, pkey, GNUTLS_DIG_SHA1, 0);

  /* Export the PEM encoded certificate request, and
   * display it.
   */
  gnutls_x509_crq_export (crq, GNUTLS_X509_FMT_PEM, buffer, &buffer_size);

  printf ("Certificate Request: \n%s", buffer);

  /* Export the PEM encoded private key, and
   * display it.
   */
  buffer_size = sizeof (buffer);
  gnutls_x509_privkey_export (key, GNUTLS_X509_FMT_PEM, buffer, &buffer_size);

  printf ("\n\nPrivate key: \n%s", buffer);

  gnutls_x509_crq_deinit (crq);
  gnutls_x509_privkey_deinit (key);

  return 0;

}

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/pkcs12.h>

#include "examples.h"

#define OUTFILE "out.p12"

/* This function will write a pkcs12 structure into a file.
 * cert: is a DER encoded certificate
 * pkcs8_key: is a PKCS #8 encrypted key (note that this must be
 *  encrypted using a PKCS #12 cipher, or some browsers will crash)
 * password: is the password used to encrypt the PKCS #12 packet.
 */
int
write_pkcs12 (const gnutls_datum_t * cert,
              const gnutls_datum_t * pkcs8_key, const char *password)
{
  gnutls_pkcs12_t pkcs12;
  int ret, bag_index;
  gnutls_pkcs12_bag_t bag, key_bag;
  char pkcs12_struct[10 * 1024];
  size_t pkcs12_struct_size;
  FILE *fd;

  /* A good idea might be to use gnutls_x509_privkey_get_key_id()
   * to obtain a unique ID.
   */
  gnutls_datum_t key_id = { (char *) "\x00\x00\x07", 3 };

  gnutls_global_init ();

  /* Firstly we create two helper bags, which hold the certificate,
   * and the (encrypted) key.
   */

  gnutls_pkcs12_bag_init (&bag);
  gnutls_pkcs12_bag_init (&key_bag);

  ret = gnutls_pkcs12_bag_set_data (bag, GNUTLS_BAG_CERTIFICATE, cert);
  if (ret < 0)
    {
      fprintf (stderr, "ret: %s\n", gnutls_strerror (ret));
      return 1;
    }

  /* ret now holds the bag's index.
   */
  bag_index = ret;

  /* Associate a friendly name with the given certificate. Used
   * by browsers.
   */
  gnutls_pkcs12_bag_set_friendly_name (bag, bag_index, "My name");

  /* Associate the certificate with the key using a unique key
   * ID.
   */
  gnutls_pkcs12_bag_set_key_id (bag, bag_index, &key_id);

  /* use weak encryption for the certificate. 
   */
  gnutls_pkcs12_bag_encrypt (bag, password, GNUTLS_PKCS_USE_PKCS12_RC2_40);

  /* Now the key.
   */

  ret = gnutls_pkcs12_bag_set_data (key_bag,
                                    GNUTLS_BAG_PKCS8_ENCRYPTED_KEY,
                                    pkcs8_key);
  if (ret < 0)
    {
      fprintf (stderr, "ret: %s\n", gnutls_strerror (ret));
      return 1;
    }

  /* Note that since the PKCS #8 key is already encrypted we don't
   * bother encrypting that bag.
   */
  bag_index = ret;

  gnutls_pkcs12_bag_set_friendly_name (key_bag, bag_index, "My name");

  gnutls_pkcs12_bag_set_key_id (key_bag, bag_index, &key_id);

  /* The bags were filled. Now create the PKCS #12 structure.
   */
  gnutls_pkcs12_init (&pkcs12);

  /* Insert the two bags in the PKCS #12 structure.
   */

  gnutls_pkcs12_set_bag (pkcs12, bag);
  gnutls_pkcs12_set_bag (pkcs12, key_bag);

  /* Generate a message authentication code for the PKCS #12
   * structure.
   */
  gnutls_pkcs12_generate_mac (pkcs12, password);

  pkcs12_struct_size = sizeof (pkcs12_struct);
  ret =
    gnutls_pkcs12_export (pkcs12, GNUTLS_X509_FMT_DER, pkcs12_struct,
                          &pkcs12_struct_size);
  if (ret < 0)
    {
      fprintf (stderr, "ret: %s\n", gnutls_strerror (ret));
      return 1;
    }

  fd = fopen (OUTFILE, "w");
  if (fd == NULL)
    {
      fprintf (stderr, "cannot open file\n");
      return 1;
    }
  fwrite (pkcs12_struct, 1, pkcs12_struct_size, fd);
  fclose (fd);

  gnutls_pkcs12_bag_deinit (bag);
  gnutls_pkcs12_bag_deinit (key_bag);
  gnutls_pkcs12_deinit (pkcs12);

  return 0;
}

     #define MYLABEL "EXPORTER-FOO"
     #define MYCONTEXT "some context data"
     char out[32];
     rc = gnutls_prf (session, strlen (MYLABEL), MYLABEL, 0,
                      strlen (MYCONTEXT), MYCONTEXT, 32, out);

     {
       gnutls_datum cb;
       int rc;

       rc = gnutls_session_channel_binding (session,
                                            GNUTLS_CB_TLS_UNIQUE,
                                            &cb);
       if (rc)
         fprintf (stderr, "Channel binding error: %s\n",
                  gnutls_strerror (rc));
       else
         {
           size_t i;
           printf ("- Channel binding 'tls-unique': ");
           for (i = 0; i < cb.size; i++)
             printf ("%02x", cb.data[i]);
           printf ("\n");
         }
     }

Certtool help
Usage: certtool [options]
     -s, --generate-self-signed
                              Generate a self-signed certificate.
     -c, --generate-certificate
                              Generate a signed certificate.
     --generate-proxy         Generate a proxy certificate.
     --generate-crl           Generate a CRL.
     -u, --update-certificate
                              Update a signed certificate.
     -p, --generate-privkey   Generate a private key.
     -q, --generate-request   Generate a PKCS #10 certificate
                              request.
     -e, --verify-chain       Verify a PEM encoded certificate chain.
                              The last certificate in the chain must
                              be a self signed one.
     --verify-crl             Verify a CRL.
     --generate-dh-params     Generate PKCS #3 encoded Diffie-Hellman
                              parameters.
     --get-dh-params          Get the included PKCS #3 encoded Diffie
                              Hellman parameters.
     --load-privkey FILE      Private key file to use.
     --load-request FILE      Certificate request file to use.
     --load-certificate FILE
                              Certificate file to use.
     --load-ca-privkey FILE   Certificate authority's private key
                              file to use.
     --load-ca-certificate FILE
                              Certificate authority's certificate
                              file to use.
     --password PASSWORD      Password to use.
     -i, --certificate-info   Print information on a certificate.
     -l, --crl-info           Print information on a CRL.
     --p12-info               Print information on a PKCS #12
                              structure.
     --p7-info                Print information on a PKCS #7
                              structure.
     --smime-to-p7            Convert S/MIME to PKCS #7 structure.
     -k, --key-info           Print information on a private key.
     --fix-key                Regenerate the parameters in a private
                              key.
     --to-p12                 Generate a PKCS #12 structure.
     -8, --pkcs8              Use PKCS #8 format for private keys.
     --dsa                    Use DSA keys.
     --hash STR               Hash algorithm to use for signing
                              (MD5,SHA1,RMD160).
     --export-ciphers         Use weak encryption algorithms.
     --inder                  Use DER format for input certificates
                              and private keys.
     --outder                 Use DER format for output certificates
                              and private keys.
     --bits BITS              specify the number of bits for key
                              generation.
     --outfile FILE           Output file.
     --infile FILE            Input file.
     --template FILE          Template file to use for non
                              interactive operation.
     -d, --debug LEVEL        specify the debug level. Default is 1.
     -h, --help               shows this help text
     -v, --version            shows the program's version

          $ certtool --generate-dh-params --outfile dh.pem

          $ certtool --generate-privkey --bits 512 --outfile rsa.pem

          $ certtool --generate-privkey --outfile ca-key.pem
          $ certtool --generate-self-signed --load-privkey ca-key.pem \
             --outfile ca-cert.pem

          $ certtool --generate-privkey --outfile key.pem

          $ certtool --dsa --generate-privkey --outfile key-dsa.pem

          $ certtool --generate-certificate --load-privkey key.pem \
             --outfile cert.pem --load-ca-certificate ca-cert.pem \
             --load-ca-privkey ca-key.pem

          $ certtool --generate-request --load-privkey key.pem \
            --outfile request.pem

          $ certtool --generate-certificate --load-request request.pem \
             --outfile cert.pem \
             --load-ca-certificate ca-cert.pem --load-ca-privkey ca-key.pem

          $ certtool --certificate-info --infile cert.pem

          $ certtool --load-certificate cert.pem --load-privkey key.pem \
            --to-p12 --outder --outfile key.p12

          $ certtool --load-ca-certificate ca.pem \
            --load-certificate cert.pem --load-privkey key.pem \
            --to-p12 --outder --outfile key.p12

          $ certtool --generate-privkey > proxy-key.pem
          $ certtool --generate-proxy --load-ca-privkey key.pem \
            --load-privkey proxy-key.pem --load-certificate cert.pem \
            --outfile proxy-cert.pem

          $ certtool --generate-crl --load-ca-privkey x509-ca-key.pem --load-ca-certificate x509-ca.pem

          $ certtool --generate-crl --load-ca-privkey x509-ca-key.pem --load-ca-certificate x509-ca.pem --load-certificate revoked-certs.pem

          $ certtool --verify-crl --load-ca-certificate x509-ca.pem < crl.pem

          $ certtool --generate-certificate cert.pem --load-privkey key.pem  \
             --template cert.cfg \
             --load-ca-certificate ca-cert.pem --load-ca-privkey ca-key.pem

     # X.509 Certificate options
     #
     # DN options

     # The organization of the subject.
     organization = "Koko inc."

     # The organizational unit of the subject.
     unit = "sleeping dept."

     # The locality of the subject.
     # locality =

     # The state of the certificate owner.
     state = "Attiki"

     # The country of the subject. Two letter code.
     country = GR

     # The common name of the certificate owner.
     cn = "Cindy Lauper"

     # A user id of the certificate owner.
     #uid = "clauper"

     # If the supported DN OIDs are not adequate you can set
     # any OID here.
     # For example set the X.520 Title and the X.520 Pseudonym
     # by using OID and string pairs.
     #dn_oid = "2.5.4.12" "Dr." "2.5.4.65" "jackal"

     # This is deprecated and should not be used in new
     # certificates.
     # pkcs9_email = "none@none.org"

     # The serial number of the certificate
     serial = 007

     # In how many days, counting from today, this certificate will expire.
     expiration_days = 700

     # X.509 v3 extensions

     # A dnsname in case of a WWW server.
     #dns_name = "www.none.org"
     #dns_name = "www.morethanone.org"

     # An IP address in case of a server.
     #ip_address = "192.168.1.1"

     # An email in case of a person
     email = "none@none.org"

     # An URL that has CRLs (certificate revocation lists)
     # available. Needed in CA certificates.
     #crl_dist_points = "http://www.getcrl.crl/getcrl/"

     # Whether this is a CA certificate or not
     #ca

     # Whether this certificate will be used for a TLS client
     #tls_www_client

     # Whether this certificate will be used for a TLS server
     #tls_www_server

     # Whether this certificate will be used to sign data (needed
     # in TLS DHE ciphersuites).
     signing_key

     # Whether this certificate will be used to encrypt data (needed
     # in TLS RSA ciphersuites). Note that it is preferred to use different
     # keys for encryption and signing.
     #encryption_key

     # Whether this key will be used to sign other certificates.
     #cert_signing_key

     # Whether this key will be used to sign CRLs.
     #crl_signing_key

     # Whether this key will be used to sign code.
     #code_signing_key

     # Whether this key will be used to sign OCSP data.
     #ocsp_signing_key

     # Whether this key will be used for time stamping.
     #time_stamping_key

     # Whether this key will be used for IPsec IKE operations.
     #ipsec_ike_key

GnuTLS test client
Usage:  gnutls-cli [options] hostname

     -d, --debug integer      Enable debugging
     -r, --resume             Connect, establish a session. Connect
                              again and resume this session.
     -s, --starttls           Connect, establish a plain session and
                              start TLS when EOF or a SIGALRM is
                              received.
     --crlf                   Send CR LF instead of LF.
     --x509fmtder             Use DER format for certificates to read
                              from.
     -f, --fingerprint        Send the openpgp fingerprint, instead
                              of the key.
     --disable-extensions     Disable all the TLS extensions.
     --print-cert             Print the certificate in PEM format.
     --recordsize integer     The maximum record size to advertize.
     -V, --verbose            More verbose output.
     --ciphers cipher1 cipher2...
                              Ciphers to enable.
     --protocols protocol1 protocol2...
                              Protocols to enable.
     --comp comp1 comp2...    Compression methods to enable.
     --macs mac1 mac2...      MACs to enable.
     --kx kx1 kx2...          Key exchange methods to enable.
     --ctypes certType1 certType2...
                              Certificate types to enable.
     --priority PRIORITY STRING
                              Priorities string.
     --x509cafile FILE        Certificate file to use.
     --x509crlfile FILE       CRL file to use.
     --pgpkeyfile FILE        PGP Key file to use.
     --pgpkeyring FILE        PGP Key ring file to use.
     --pgpcertfile FILE       PGP Public Key (certificate) file to
                              use.
     --pgpsubkey HEX|auto     PGP subkey to use.
     --x509keyfile FILE       X.509 key file to use.
     --x509certfile FILE      X.509 Certificate file to use.
     --srpusername NAME       SRP username to use.
     --srppasswd PASSWD       SRP password to use.
     --pskusername NAME       PSK username to use.
     --pskkey KEY             PSK key (in hex) to use.
     --opaque-prf-input DATA
                              Use Opaque PRF Input DATA.
     -p, --port PORT          The port to connect to.
     --insecure               Don't abort program if server
                              certificate can't be validated.
     -l, --list               Print a list of the supported
                              algorithms and modes.
     -h, --help               prints this help
     -v, --version            prints the program's version number

     $ gnutls-cli -p 5556 test.gnutls.org --pskusername jas --pskkey 9e32cf7786321a828ef7668f09fb35db --priority NORMAL:+PSK:-RSA:-DHE-RSA -d 4711

     $ ./gnutls-cli -p 5556 localhost
     Resolving 'localhost'...
     Connecting to '127.0.0.1:5556'...
     - PSK client callback. PSK hint 'psk_identity_hint'
     Enter PSK identity: psk_identity
     Enter password:
     - PSK authentication. PSK hint 'psk_identity_hint'
     - Version: TLS1.1
     - Key Exchange: PSK
     - Cipher: AES-128-CBC
     - MAC: SHA1
     - Compression: NULL
     - Handshake was completed

     - Simple Client Mode:

     $ ./gnutls-cli -p 5556 localhost --pskusername psk_identity --pskkey 88f3824b3e5659f52d00e959bacab954b6540344
     Resolving 'localhost'...
     Connecting to '127.0.0.1:5556'...
     - PSK authentication. PSK hint 'psk_identity_hint'
     - Version: TLS1.1
     - Key Exchange: PSK
     - Cipher: AES-128-CBC
     - MAC: SHA1
     - Compression: NULL
     - Handshake was completed

     - Simple Client Mode:

     crystal:/cvs/gnutls/src$ ./gnutls-cli-debug localhost -p 5556
     Resolving 'localhost'...
     Connecting to '127.0.0.1:5556'...
     Checking for TLS 1.1 support... yes
     Checking fallback from TLS 1.1 to... N/A
     Checking for TLS 1.0 support... yes
     Checking for SSL 3.0 support... yes
     Checking for version rollback bug in RSA PMS... no
     Checking for version rollback bug in Client Hello... no
     Checking whether we need to disable TLS 1.0... N/A
     Checking whether the server ignores the RSA PMS version... no
     Checking whether the server can accept Hello Extensions... yes
     Checking whether the server can accept cipher suites not in SSL 3.0 spec... yes
     Checking whether the server can accept a bogus TLS record version in the client hello... yes
     Checking for certificate information... N/A
     Checking for trusted CAs... N/A
     Checking whether the server understands TLS closure alerts... yes
     Checking whether the server supports session resumption... yes
     Checking for export-grade ciphersuite support... no
     Checking RSA-export ciphersuite info... N/A
     Checking for anonymous authentication support... no
     Checking anonymous Diffie-Hellman group info... N/A
     Checking for ephemeral Diffie-Hellman support... no
     Checking ephemeral Diffie-Hellman group info... N/A
     Checking for AES cipher support (TLS extension)... yes
     Checking for 3DES cipher support... yes
     Checking for ARCFOUR 128 cipher support... yes
     Checking for ARCFOUR 40 cipher support... no
     Checking for MD5 MAC support... yes
     Checking for SHA1 MAC support... yes
     Checking for ZLIB compression support (TLS extension)... yes
     Checking for LZO compression support (GnuTLS extension)... yes
     Checking for max record size (TLS extension)... yes
     Checking for SRP authentication support (TLS extension)... yes
     Checking for OpenPGP authentication support (TLS extension)... no

GnuTLS test server
Usage: gnutls-serv [options]

     -d, --debug integer      Enable debugging
     -g, --generate           Generate Diffie-Hellman Parameters.
     -p, --port integer       The port to connect to.
     -q, --quiet              Suppress some messages.
     --nodb                   Does not use the resume database.
     --http                   Act as an HTTP Server.
     --echo                   Act as an Echo Server.
     --dhparams FILE          DH params file to use.
     --x509fmtder             Use DER format for certificates
     --x509cafile FILE        Certificate file to use.
     --x509crlfile FILE       CRL file to use.
     --pgpkeyring FILE        PGP Key ring file to use.
     --pgpkeyfile FILE        PGP Key file to use.
     --pgpcertfile FILE       PGP Public Key (certificate) file to
                              use.
     --pgpsubkey HEX|auto     PGP subkey to use.
     --x509keyfile FILE       X.509 key file to use.
     --x509certfile FILE      X.509 Certificate file to use.
     --x509dsakeyfile FILE    Alternative X.509 key file to use.
     --x509dsacertfile FILE   Alternative X.509 certificate file to
                              use.
     -r, --require-cert       Require a valid certificate.
     -a, --disable-client-cert
                              Disable request for a client
                              certificate.
     --pskpasswd FILE         PSK password file to use.
     --pskhint HINT           PSK identity hint to use.
     --srppasswd FILE         SRP password file to use.
     --srppasswdconf FILE     SRP password conf file to use.
     --opaque-prf-input DATA
                              Use Opaque PRF Input DATA.
     --ciphers cipher1 cipher2...
                              Ciphers to enable.
     --protocols protocol1 protocol2...
                              Protocols to enable.
     --comp comp1 comp2...    Compression methods to enable.
     --macs mac1 mac2...      MACs to enable.
     --kx kx1 kx2...          Key exchange methods to enable.
     --ctypes certType1 certType2...
                              Certificate types to enable.
     --priority PRIORITY STRING
                              Priorities string.
     -l, --list               Print a list of the supported
                              algorithms  and modes.
     -h, --help               prints this help
     -v, --version            prints the program's version number

     gnutls-serv --http

     certtool --generate-privkey > x509-ca-key.pem
     echo 'cn = GnuTLS test CA' > ca.tmpl
     echo 'ca' >> ca.tmpl
     echo 'cert_signing_key' >> ca.tmpl
     certtool --generate-self-signed --load-privkey x509-ca-key.pem \
       --template ca.tmpl --outfile x509-ca.pem
     ...

     certtool --generate-privkey > x509-server-key.pem
     echo 'organization = GnuTLS test server' > server.tmpl
     echo 'cn = test.gnutls.org' >> server.tmpl
     echo 'tls_www_server' >> server.tmpl
     echo 'encryption_key' >> server.tmpl
     echo 'signing_key' >> server.tmpl
     echo 'dns_name = test.gnutls.org' >> server.tmpl
     certtool --generate-certificate --load-privkey x509-server-key.pem \
       --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem \
       --template server.tmpl --outfile x509-server.pem
     ...

     certtool --generate-privkey > x509-client-key.pem
     echo 'cn = GnuTLS test client' > client.tmpl
     echo 'tls_www_client' >> client.tmpl
     echo 'encryption_key' >> client.tmpl
     echo 'signing_key' >> client.tmpl
     certtool --generate-certificate --load-privkey x509-client-key.pem \
       --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem \
       --template client.tmpl --outfile x509-client.pem
     ...

     certtool --to-p12 --load-ca-certificate x509-ca.pem --load-privkey x509-client-key.pem --load-certificate x509-client.pem --outder --outfile x509-client.p12

     certtool --generate-privkey > x509-proxy-key.pem
     echo 'cn = GnuTLS test client proxy' > proxy.tmpl
     certtool --generate-proxy --load-privkey x509-proxy-key.pem \
       --load-ca-certificate x509-client.pem --load-ca-privkey x509-client-key.pem \
       --load-certificate x509-client.pem --template proxy.tmpl \
       --outfile x509-proxy.pem
     ...

     gnutls-serv --http \
                 --x509cafile x509-ca.pem \
                 --x509keyfile x509-server-key.pem \
                 --x509certfile x509-server.pem

     certtool --generate-privkey --dsa > x509-server-key-dsa.pem
     certtool --generate-certificate --load-privkey x509-server-key-dsa.pem \
       --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem \
       --template server.tmpl --outfile x509-server-dsa.pem
     ...

     gpg --gen-key
     ...enter whatever details you want, use 'test.gnutls.org' as name...

     gpg -a --export 5D1D14D8 > openpgp-server.txt
     gpg --export 5D1D14D8 > openpgp-server.bin
     gpg --export-secret-keys 5D1D14D8 > openpgp-server-key.bin
     gpg -a --export-secret-keys 5D1D14D8 > openpgp-server-key.txt

     gnutls-serv --http \
                 --pgpkeyfile openpgp-server-key.txt \
                 --pgpcertfile openpgp-server.txt

     srptool --create-conf srp-tpasswd.conf
     srptool --passwd-conf srp-tpasswd.conf --username jas --passwd srp-passwd.txt
     Enter password: [TYPE "foo"]

     gnutls-serv --http \
                 --srppasswdconf srp-tpasswd.conf \
                 --srppasswd srp-passwd.txt

     $ psktool --passwd psk-passwd.txt

     gnutls-serv --http \
                 --pskpasswd psk-passwd.txt

     gnutls-serv --http \
                 --x509cafile x509-ca.pem \
                 --x509keyfile x509-server-key.pem \
                 --x509certfile x509-server.pem \
                 --x509dsakeyfile x509-server-key-dsa.pem \
                 --x509dsacertfile x509-server-dsa.pem \
                 --pgpkeyfile openpgp-server-key.txt \
                 --pgpcertfile openpgp-server.txt \
                 --srppasswdconf srp-tpasswd.conf \
                 --srppasswd srp-passwd.txt \
                 --pskpasswd psk-passwd.txt

     $ ./psktool -u psk_identity -p psks.txt -n psk_identity_hint
     Enter password:
     Key stored to psks.txt
     $ cat psks.txt
     psk_identity:88f3824b3e5659f52d00e959bacab954b6540344
     $

     $ ./gnutls-serv --pskpasswd psks.txt  --pskhint psk_identity_hint --priority NORMAL:-DHE-PSK
     Set static Diffie-Hellman parameters, consider --dhparams.
     Echo Server ready. Listening to port '5556'.

PSKtool help
Usage : psktool [options]
     -u, --username username
                              specify username.
     -p, --passwd FILE        specify a password file.
     -n, --netconf-hint HINT
                              derive key from Netconf password, using 
                              HINT as the psk_identity_hint.
     -s, --keysize SIZE       specify the key size in bytes.
     -v, --version            prints the program's version number
     -h, --help               shows this help text

          $ srptool --create-conf /etc/tpasswd.conf

          $ srptool --passwd /etc/tpasswd \
              --passwd-conf /etc/tpasswd.conf -u test

          $ srptool --passwd /etc/tpasswd \
              --passwd-conf /etc/tpasswd.conf --verify -u test

p11tool help
Usage: p11tool [options]

     --export URL             Export an object specified by a pkcs11 
                              URL
     --list-tokens            List all available tokens
     --list-mechanisms URL    List all available mechanisms in token.
     --list-all               List all objects specified by a PKCS#11 
                              URL
     --list-all-certs         List all certificates specified by a 
                              PKCS#11 URL
     --list-certs             List certificates that have a private 
                              key specified by a PKCS#11 URL
     --list-privkeys          List private keys specified by a 
                              PKCS#11 URL
     --list-trusted           List certificates marked as trusted, 
                              specified by a PKCS#11 URL
     --initialize URL         Initializes a PKCS11 token.
     --write URL              Writes loaded certificates, private or 
                              secret keys to a PKCS11 token.
     --delete URL             Deletes objects matching the URL.
     --label label            Sets a label for the write operation.
     --trusted                Marks the certificate to be imported as 
                              trusted.
     --login                  Force login to token
     --detailed-url           Export detailed URLs.
     --no-detailed-url        Export less detailed URLs.
     --secret-key HEX_KEY     Provide a hex encoded secret key.
     --load-privkey FILE      Private key file to use.
     --load-pubkey FILE       Private key file to use.
     --load-certificate FILE  
                              Certificate file to use.
     -8, --pkcs8              Use PKCS #8 format for private keys.
     --inder                  Use DER format for input certificates 
                              and private keys.
     --inraw                  Use RAW/DER format for input 
                              certificates and private keys.
     --provider Library       Specify the pkcs11 provider library
     --outfile FILE           Output file.
     -d, --debug LEVEL        specify the debug level. Default is 1.
     -h, --help               shows this help text

          $ p11tool --list-tokens

          $ p11tool --login --list-all

          $ p11tool --login --export pkcs11:(OBJECT URL)

          $ p11tool --login --write pkcs11:(TOKEN URL) --load-certificate (certificate file) --label "my_cert"

     int client_avp (gnuls_session_t *session, void *ptr,
                     const char *last, size_t lastlen,
     		char **new, size_t *newlen)
     {
     ...
     }
     ...
     int main ()
     {
       gnutls_ia_client_credentials_t iacred;
     ...
       gnutls_init (&session, GNUTLS_CLIENT);
     ...
       /* Enable TLS/IA. */
       gnutls_ia_allocate_client_credentials(&iacred);
       gnutls_ia_set_client_avp_function(iacred, client_avp);
       gnutls_credentials_set (session, GNUTLS_CRD_IA, iacred);
     ...
       ret = gnutls_handshake (session);
       // Error handling...
     ...
       if (gnutls_ia_handshake_p (session))
         {
           ret = gnutls_ia_handshake (session);
           // Error handling...
     ...

     $ guile
     guile> (use-modules (gnutls))
     <unnamed port>: no code for module (gnutls)
     guile>

     $ ./configure --with-guile-site-dir=no

     $ ./configure --prefix=/usr

     $ ./configure --with-guile-site-dir=/opt/guile/share/guile/site

     $ GUILE_LOAD_PATH="/usr/local/share/guile/site:$GUILE_LOAD_PATH" guile
     guile> (use-modules (gnutls))
     guile>

     gnutls.scm:361:1: In procedure dynamic-link in expression (load-extension "libguile-gnutls-v-0" "scm_init_gnutls"):
     gnutls.scm:361:1: file: "libguile-gnutls-v-0", message: "libguile-gnutls-v-0.so: cannot open shared object file: No such file or directory"

     $ LD_LIBRARY_PATH=/usr/local/lib GUILE_LOAD_PATH=/usr/local/share/guile/site guile
     guile> (use-modules (gnutls))
     guile>

     $ guile
     guile> (use-modules (gnutls))
     guile> (gnutls-version)
     "2.12.3"
     guile>

     typedef enum
     {
       GNUTLS_CRD_CERTIFICATE = 1,
       GNUTLS_CRD_ANON,
       GNUTLS_CRD_SRP,
       GNUTLS_CRD_PSK,
       GNUTLS_CRD_IA
     } gnutls_credentials_type_t;

     credentials/certificate
     credentials/anonymous
     credentials/srp
     credentials/psk
     credentials/ia

     (let ((session (make-session connection-end/client)))

       ;;
       ;; ...
       ;;

       ;; Check the ciphering algorithm currently used by SESSION.
       (if (eq? cipher/arcfour (session-cipher session))
           (format #t "We're using the ARCFOUR algorithm")))

     (let* ((rsa-params (make-rsa-parameters 1024))
            (raw-data
             (pkcs1-export-rsa-parameters rsa-params
                                          x509-certificate-format/pem)))
       (uniform-vector-write raw-data (open-output-file "some-file.pem")))

     (let ((socket (socket PF_INET SOCK_STREAM 0))
           (session (make-session connection-end/client)))

       ;;
       ;; Establish a TCP connection...
       ;;

       ;; Use the file descriptor that underlies SOCKET.
       (set-session-transport-fd! session (fileno socket)))

     (let ((session (make-session connection-end/client)))

       ;;
       ;; Initialize the various parameters of SESSION, set up
       ;; a network connection, etc...
       ;;

       (let ((i/o (session-record-port session)))
         (write "Hello peer!" i/o)
         (let ((greetings (read i/o)))

           ;; ...

           (bye session close-request/rdwr))))

     (let ((session (make-session connection-end/server)))

       ;;
       ;; ...
       ;;

       (catch 'gnutls-error
         (lambda ()
           (handshake session))
         (lambda (key err function . currently-unused)
           (format (current-error-port)
                   "a GnuTLS error was raised by `~a': ~a~%"
                   function (error->string err)))))

         ;; `gnutls-error' handler.
         (lambda (key err function . currently-unused)
           (if (eq? err error/fatal-alert-received)
               (format (current-error-port)
                       "a fatal alert was caught!~%")
               (format (current-error-port)
                       "something bad happened: ~a~%"
                       (error->string err))))

     ;; Client-side.

     (let ((client (make-session connection-end/client)))
       ;; Use the default settings.
       (set-session-default-priority! client)

       ;; Don't use certificate-based authentication.
       (set-session-certificate-type-priority! client '())

       ;; Request the "anonymous Diffie-Hellman" key exchange method.
       (set-session-kx-priority! client (list kx/anon-dh))

       ;; Specify the underlying socket.
       (set-session-transport-fd! client (fileno some-socket))

       ;; Create anonymous credentials.
       (set-session-credentials! client
                                 (make-anonymous-client-credentials))

       ;; Perform the TLS handshake with the server.
       (handshake client)

       ;; Send data over the TLS record layer.
       (write "hello, world!" (session-record-port client))

       ;; Terminate the TLS session.
       (bye client close-request/rdwr))

     ;; Server-side.

     (let ((server (make-session connection-end/server)))
       (set-session-default-priority! server)
       (set-session-certificate-type-priority! server '())
       (set-session-kx-priority! server (list kx/anon-dh))

       ;; Specify the underlying transport socket.
       (set-session-transport-fd! server (fileno some-socket))

       ;; Create anonymous credentials.
       (let ((cred (make-anonymous-server-credentials))
             (dh-params (make-dh-parameters 1024)))
         ;; Note: DH parameter generation can take some time.
         (set-anonymous-server-dh-parameters! cred dh-params)
         (set-session-credentials! server cred))

       ;; Perform the TLS handshake with the client.
       (handshake server)

       ;; Receive data over the TLS record layer.
       (let ((message (read (session-record-port server))))
         (format #t "received the following message: ~a~%"
                 message)

         (bye server close-request/rdwr)))

     ;; Client-side.

     (define %certs (list certificate-type/openpgp))

     (let ((client (make-session connection-end/client))
           (cred   (make-certificate-credentials)))
       (set-session-default-priority! client)

       ;; Choose OpenPGP certificates.
       (set-session-certificate-type-priority! client %certs)

       ;; Prepare appropriate client credentials.
       (set-certificate-credentials-openpgp-keys! cred pub sec)
       (set-session-credentials! client cred)

       ;; Specify the underlying transport socket.
       (set-session-transport-fd! client (fileno some-socket))

       (handshake client)
       (write "hello, world!" (session-record-port client))
       (bye client close-request/rdwr))

     ;; Server-side.

     (define %certs (list certificate-type/openpgp))

     (let ((server (make-session connection-end/server))
           (rsa    (make-rsa-parameters 1024))
           (dh     (make-dh-parameters 1024)))
       (set-session-default-priority! server)

       ;; Choose OpenPGP certificates.
       (set-session-certificate-type-priority! server %certs)

       (let ((cred (make-certificate-credentials)))
         ;; Prepare credentials with RSA and Diffie-Hellman parameters.
         (set-certificate-credentials-dh-parameters! cred dh)
         (set-certificate-credentials-rsa-export-parameters! cred rsa)
         (set-certificate-credentials-openpgp-keys! cred pub sec)
         (set-session-credentials! server cred))

       (set-session-transport-fd! server (fileno some-socket))

       (handshake server)
       (let ((msg (read (session-record-port server))))
         (format #t "received: ~a~%" msg)

         (bye server close-request/rdwr)))

     (use-modules (srfi srfi-4)
                  (gnutls extra))

     (define (import-key-from-file import-proc file)
       ;; Import OpenPGP key from FILE using IMPORT-PROC.

       ;; Prepare a u8vector large enough to hold the raw
       ;; key contents.
       (let* ((size (stat:size (stat path)))
              (raw  (make-u8vector size)))

         ;; Fill in the u8vector with the contents of FILE.
         (uniform-vector-read! raw (open-input-file file))

         ;; Pass the u8vector to the import procedure.
         (import-proc raw openpgp-certificate-format/base64)))

     (define (import-public-key-from-file file)
       (import-key-from-file import-openpgp-certificate file))

     (define (import-private-key-from-file file)
       (import-key-from-file import-openpgp-private-key file))

          AC_MSG_CHECKING([whether to disable foobar support])
          AC_ARG_ENABLE(foobar,
          	AS_HELP_STRING([--disable-foobar],
          		[disable foobar support]),
          	ac_enable_foobar=no)
          if test x$ac_enable_foobar != xno; then
           AC_MSG_RESULT(no)
           AC_DEFINE(ENABLE_FOOBAR, 1, [enable foobar])
          else
           ac_full=0
           AC_MSG_RESULT(yes)
          fi
          AM_CONDITIONAL(ENABLE_FOOBAR, test "$ac_enable_foobar" != "no")

            int ret;

            /* ...
             */

          #if ENABLE_FOOBAR

            ret = _gnutls_ext_register (&foobar_ext);
            if (ret != GNUTLS_E_SUCCESS)
              return ret;
          #endif

            extension_entry_st foobar_ext = {
              .name = "FOOBAR",
              .type = GNUTLS_EXTENSION_FOOBAR,
              .parse_type = GNUTLS_EXT_TLS,
              .recv_func = _foobar_recv_params,
              .send_func = _foobar_send_params,
              .pack_func = _foobar_pack,
              .unpack_func = _foobar_unpack,
              .deinit_func = NULL
            }

          int
          _foobar_recv_params (gnutls_session_t session,
                                      const opaque * data,
                                      size_t data_size)
          {
            return 0;
          }

          int
          _foobar_send_params (gnutls_session_t session,
                                      opaque * data,
                                      size_t _data_size)
          {
            return 0;
          }

          int
          _foobar_pack (extension_priv_data_t epriv, gnutls_buffer_st * ps)
          {
             /* Append the extension's internal state to buffer */
             return 0;
          }

          int
          _foobar_unpack (gnutls_buffer_st * ps, extension_priv_data_t * epriv)
          {
             /* Read the internal state from buffer */
             return 0;
          }

          int
          _gnutls_foobar_recv_params (gnutls_session_t session,
                                      const opaque * data,
                                      size_t data_size)
          {
            if (session->security_parameters.entity == GNUTLS_CLIENT)
              return foobar_recv_client (session, data, data_size);
            else
              return foobar_recv_server (session, data, data_size);
          }

          int
          _gnutls_foobar_send_params (gnutls_session_t session,
                                      opaque * data,
                                      size_t data_size)
          {
            if (session->security_parameters.entity == GNUTLS_CLIENT)
              return foobar_send_client (session, data, data_size);
            else
              return foobar_send_server (session, data, data_size);
          }

          if ENABLE_FOOBAR
          COBJECTS += ext_foobar.c
          HFILES += ext_foobar.h
          endif

     Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
     http://fsf.org/

     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

       Copyright (C)  year  your name.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.3
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

         with the Invariant Sections being list their titles, with
         the Front-Cover Texts being list, and with the Back-Cover Texts
         being list.

     Copyright © 1991, 1999 Free Software Foundation, Inc.
     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA

     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

     [This is the first released version of the Lesser GPL.  It also counts
     as the successor of the GNU Library Public License, version 2, hence the
     version number 2.1.]

     one line to give the library's name and an idea of what it does.
     Copyright (C) year  name of author

     This library is free software; you can redistribute it and/or modify it
     under the terms of the GNU Lesser General Public License as published by
     the Free Software Foundation; either version 2.1 of the License, or (at
     your option) any later version.

     This library 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
     Lesser General Public License for more details.

     You should have received a copy of the GNU Lesser General Public
     License along with this library; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
     USA.

     Yoyodyne, Inc., hereby disclaims all copyright interest in the library
     `Frob' (a library for tweaking knobs) written by James Random Hacker.

     signature of Ty Coon, 1 April 1990
     Ty Coon, President of Vice

     Copyright © 2007 Free Software Foundation, Inc. http://fsf.org/

     Everyone is permitted to copy and distribute verbatim copies of this
     license document, but changing it is not allowed.

     one line to give the program's name and a brief idea of what it does.
     Copyright (C) year name of author

     This program 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.

     This program 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 this program.  If not, see http://www.gnu.org/licenses/.

     program Copyright (C) year name of author
     This program comes with ABSOLUTELY NO WARRANTY; for details type ‘show w’.
     This is free software, and you are welcome to redistribute it
     under certain conditions; type ‘show c’ for details.

Security bits	RSA, DH and SRP parameter size	ECC key size	`gnutls_sec_param_t`	Description
64	816	128	`WEAK`	Very short term protection against small organizations
80	1248	160	`LOW`	Very short term protection against agencies
112	2432	224	`NORMAL`	Medium-term protection
128	3248	256	`HIGH`	Long term protection
256	15424	512	`ULTRA`	Foreseeable future

Key exchange	Client credentials	Server credentials
`KX_RSA`
`KX_DHE_RSA`
`KX_DHE_DSS`
`KX_RSA_EXPORT`	`CRD_CERTIFICATE`	`CRD_CERTIFICATE`
`KX_SRP_RSA`	`CRD_SRP`	`CRD_SRP`
`KX_SRP_DSS`		`CRD_CERTIFICATE`
`KX_SRP`	`CRD_SRP`	`CRD_SRP`
`KX_ANON_DH`	`CRD_ANON`	`CRD_ANON`
`KX_PSK`	`CRD_PSK`	`CRD_PSK`

TLS_ANON_DH_ARCFOUR_MD5	0x00 0x18	SSL3.0
TLS_ANON_DH_3DES_EDE_CBC_SHA1	0x00 0x1b	SSL3.0
TLS_ANON_DH_AES_128_CBC_SHA1	0x00 0x34	SSL3.0
TLS_ANON_DH_AES_256_CBC_SHA1	0x00 0x3a	SSL3.0
TLS_ANON_DH_CAMELLIA_128_CBC_SHA1	0x00 0x46	TLS1.0
TLS_ANON_DH_CAMELLIA_256_CBC_SHA1	0x00 0x89	TLS1.0
TLS_ANON_DH_AES_128_CBC_SHA256	0x00 0x6c	TLS1.2
TLS_ANON_DH_AES_256_CBC_SHA256	0x00 0x6d	TLS1.2
TLS_PSK_SHA_ARCFOUR_SHA1	0x00 0x8a	TLS1.0
TLS_PSK_SHA_3DES_EDE_CBC_SHA1	0x00 0x8b	TLS1.0
TLS_PSK_SHA_AES_128_CBC_SHA1	0x00 0x8c	TLS1.0
TLS_PSK_SHA_AES_256_CBC_SHA1	0x00 0x8d	TLS1.0
TLS_DHE_PSK_SHA_ARCFOUR_SHA1	0x00 0x8e	TLS1.0
TLS_DHE_PSK_SHA_3DES_EDE_CBC_SHA1	0x00 0x8f	TLS1.0
TLS_DHE_PSK_SHA_AES_128_CBC_SHA1	0x00 0x90	TLS1.0
TLS_DHE_PSK_SHA_AES_256_CBC_SHA1	0x00 0x91	TLS1.0
TLS_SRP_SHA_3DES_EDE_CBC_SHA1	0xc0 0x1a	TLS1.0
TLS_SRP_SHA_AES_128_CBC_SHA1	0xc0 0x1d	TLS1.0
TLS_SRP_SHA_AES_256_CBC_SHA1	0xc0 0x20	TLS1.0
TLS_SRP_SHA_DSS_3DES_EDE_CBC_SHA1	0xc0 0x1c	TLS1.0
TLS_SRP_SHA_RSA_3DES_EDE_CBC_SHA1	0xc0 0x1b	TLS1.0
TLS_SRP_SHA_DSS_AES_128_CBC_SHA1	0xc0 0x1f	TLS1.0
TLS_SRP_SHA_RSA_AES_128_CBC_SHA1	0xc0 0x1e	TLS1.0
TLS_SRP_SHA_DSS_AES_256_CBC_SHA1	0xc0 0x22	TLS1.0
TLS_SRP_SHA_RSA_AES_256_CBC_SHA1	0xc0 0x21	TLS1.0
TLS_DHE_DSS_ARCFOUR_SHA1	0x00 0x66	TLS1.0
TLS_DHE_DSS_3DES_EDE_CBC_SHA1	0x00 0x13	SSL3.0
TLS_DHE_DSS_AES_128_CBC_SHA1	0x00 0x32	SSL3.0
TLS_DHE_DSS_AES_256_CBC_SHA1	0x00 0x38	SSL3.0
TLS_DHE_DSS_CAMELLIA_128_CBC_SHA1	0x00 0x44	TLS1.0
TLS_DHE_DSS_CAMELLIA_256_CBC_SHA1	0x00 0x87	TLS1.0
TLS_DHE_DSS_AES_128_CBC_SHA256	0x00 0x40	TLS1.2
TLS_DHE_DSS_AES_256_CBC_SHA256	0x00 0x6a	TLS1.2
TLS_DHE_RSA_3DES_EDE_CBC_SHA1	0x00 0x16	SSL3.0
TLS_DHE_RSA_AES_128_CBC_SHA1	0x00 0x33	SSL3.0
TLS_DHE_RSA_AES_256_CBC_SHA1	0x00 0x39	SSL3.0
TLS_DHE_RSA_CAMELLIA_128_CBC_SHA1	0x00 0x45	TLS1.0
TLS_DHE_RSA_CAMELLIA_256_CBC_SHA1	0x00 0x88	TLS1.0
TLS_DHE_RSA_AES_128_CBC_SHA256	0x00 0x67	TLS1.2
TLS_DHE_RSA_AES_256_CBC_SHA256	0x00 0x6b	TLS1.2
TLS_RSA_NULL_MD5	0x00 0x01	SSL3.0
TLS_RSA_NULL_SHA1	0x00 0x02	SSL3.0
TLS_RSA_NULL_SHA256	0x00 0x3b	TLS1.2
TLS_RSA_EXPORT_ARCFOUR_40_MD5	0x00 0x03	SSL3.0
TLS_RSA_ARCFOUR_SHA1	0x00 0x05	SSL3.0
TLS_RSA_ARCFOUR_MD5	0x00 0x04	SSL3.0
TLS_RSA_3DES_EDE_CBC_SHA1	0x00 0x0a	SSL3.0
TLS_RSA_AES_128_CBC_SHA1	0x00 0x2f	SSL3.0
TLS_RSA_AES_256_CBC_SHA1	0x00 0x35	SSL3.0
TLS_RSA_CAMELLIA_128_CBC_SHA1	0x00 0x41	TLS1.0
TLS_RSA_CAMELLIA_256_CBC_SHA1	0x00 0x84	TLS1.0
TLS_RSA_AES_128_CBC_SHA256	0x00 0x3c	TLS1.2
TLS_RSA_AES_256_CBC_SHA256	0x00 0x3d	TLS1.2

GnuTLS 2.12.3

Table of Contents

GnuTLS

1 Preface

1.1 Getting Help

1.2 Commercial Support

1.3 Downloading and Installing

1.4 Bug Reports

1.5 Contributing

2 The Library

2.1 General Idea

2.2 Error Handling

2.3 Memory Handling

2.4 Callback Functions

3 Introduction to TLS

3.1 TLS Layers

3.2 The Transport Layer

3.3 The TLS Record Protocol

3.3.1 Encryption Algorithms Used in the Record Layer

3.3.2 Compression Algorithms Used in the Record Layer

3.3.3 Weaknesses and Countermeasures

3.3.4 On Record Padding

3.4 The TLS Alert Protocol

3.5 The TLS Handshake Protocol

3.5.1 TLS Cipher Suites

3.5.2 Priority strings

3.5.3 Client Authentication

3.5.4 Resuming Sessions

3.5.5 Resuming Internals

3.6 TLS Extensions

3.6.1 Maximum Fragment Length Negotiation

3.6.2 Server Name Indication

3.6.3 Session Tickets

3.6.4 Safe Renegotiation

3.7 Selecting Cryptographic Key Sizes

3.8 On SSL 2 and Older Protocols

4 Authentication Methods

4.1 Certificate Authentication

4.1.1 Authentication Using X.509 Certificates

4.1.2 Authentication Using OpenPGP Keys

4.1.3 Using Certificate Authentication

4.2 Anonymous Authentication

4.3 Authentication using SRP

4.4 Authentication using PSK

4.5 Authentication and Credentials

4.6 Parameters Stored in Credentials

5 More on Certificate Authentication

5.1 The X.509 Trust Model

5.1.1 X.509 Certificates

5.1.2 Verifying X.509 Certificate Paths

5.1.3 PKCS #10 Certificate Requests

5.1.4 PKCS #12 Structures

5.2 The OpenPGP Trust Model

5.2.1 OpenPGP Keys

5.2.2 Verifying an OpenPGP Key

5.3 PKCS #11 tokens

5.3.1 Introduction

5.3.2 Initialization

5.3.3 Reading Objects

5.3.4 Writing Objects

5.3.5 Using a PKCS #11 token with TLS

5.4 Abstract data types

5.5 Digital Signatures

5.5.1 Trading Security for Interoperability

6 How To Use TLS in Application Protocols

6.1 Separate Ports

6.2 Upward Negotiation

7 How To Use GnuTLS in Applications

7.1 Preparation

7.1.1 Headers

7.1.2 Initialization

7.1.3 Version Check

7.1.4 Debugging

7.1.5 Building the Source

7.2 Multi-Threaded Applications

7.3 Client Examples

7.3.1 Simple Client Example with Anonymous Authentication

7.3.2 Simple Client Example with X.509 Certificate Support

7.3.3 Obtaining Session Information

7.3.4 Verifying Peer's Certificate