path: root/lib/gnutls_cert.c

/*
 * Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation
 *
 * Author: Nikos Mavroyanopoulos
 *
 * This file is part of GNUTLS.
 *
 * The GNUTLS 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
 *
 */

/* Some of the stuff needed for Certificate authentication is contained
 * in this file.
 */

#include <gnutls_int.h>
#include <gnutls_errors.h>
#include <auth_cert.h>
#include <gnutls_cert.h>
#include <libtasn1.h>
#include <gnutls_datum.h>
#include <gnutls_mpi.h>
#include <gnutls_global.h>
#include <gnutls_algorithms.h>
#include <gnutls_dh.h>
#include <gnutls_str.h>
#include <gnutls_state.h>
#include <gnutls_auth_int.h>
#include <gnutls_x509.h>
#include <gnutls_extra_hooks.h>
#include "x509/x509.h"
#include "x509/mpi.h"

/**
  * gnutls_certificate_free_keys - Used to free all the keys from a gnutls_certificate_credentials_t structure
  * @sc: is an #gnutls_certificate_credentials_t structure.
  *
  * This function will delete all the keys and the certificates associated
  * with the given credentials. This function must not be called when a
  * TLS negotiation that uses the credentials is in progress.
  *
  **/
void
gnutls_certificate_free_keys (gnutls_certificate_credentials_t sc)
{
  unsigned i, j;

  for (i = 0; i < sc->ncerts; i++)
    {
      for (j = 0; j < sc->cert_list_length[i]; j++)
	{
	  _gnutls_gcert_deinit (&sc->cert_list[i][j]);
	}
      gnutls_free (sc->cert_list[i]);
    }

  gnutls_free (sc->cert_list_length);
  sc->cert_list_length = NULL;

  gnutls_free (sc->cert_list);
  sc->cert_list = NULL;

  for (i = 0; i < sc->ncerts; i++)
    {
      _gnutls_gkey_deinit (&sc->pkey[i]);
    }

  gnutls_free (sc->pkey);
  sc->pkey = NULL;

  sc->ncerts = 0;

}

/**
  * gnutls_certificate_free_cas - Used to free all the CAs from a gnutls_certificate_credentials_t structure
  * @sc: is an #gnutls_certificate_credentials_t structure.
  *
  * This function will delete all the CAs associated
  * with the given credentials. Servers that do not use
  * gnutls_certificate_verify_peers2() may call this to
  * save some memory.
  *
  **/
void
gnutls_certificate_free_cas (gnutls_certificate_credentials_t sc)
{
  unsigned j;

  for (j = 0; j < sc->x509_ncas; j++)
    {
      gnutls_x509_crt_deinit (sc->x509_ca_list[j]);
    }

  sc->x509_ncas = 0;

  gnutls_free (sc->x509_ca_list);
  sc->x509_ca_list = NULL;

}

/**
  * gnutls_certificate_free_ca_names - Used to free all the CA names from a gnutls_certificate_credentials_t structure
  * @sc: is an #gnutls_certificate_credentials_t structure.
  *
  * This function will delete all the CA name in the
  * given credentials. Clients may call this to save some memory
  * since in client side the CA names are not used.
  *
  * CA names are used by servers to advertize the CAs they
  * support to clients.
  *
  **/
void
gnutls_certificate_free_ca_names (gnutls_certificate_credentials_t sc)
{
  _gnutls_free_datum (&sc->x509_rdn_sequence);
}

/*-
  * _gnutls_certificate_get_rsa_params - Returns the RSA parameters pointer
  * @rsa_params: holds the RSA parameters or NULL.
  * @func: function to retrieve the parameters or NULL.
  * @session: The session.
  *
  * This function will return the rsa parameters pointer.
  *
  -*/
gnutls_rsa_params_t
_gnutls_certificate_get_rsa_params (gnutls_rsa_params_t rsa_params,
				    gnutls_params_function * func,
				    gnutls_session_t session)
{
  gnutls_params_st params;
  int ret;

  if (session->internals.params.rsa_params)
    {
      return session->internals.params.rsa_params;
    }

  if (rsa_params)
    {
      session->internals.params.rsa_params = rsa_params;
    }
  else if (func)
    {
      ret = func (session, GNUTLS_PARAMS_RSA_EXPORT, &params);
      if (ret == 0 && params.type == GNUTLS_PARAMS_RSA_EXPORT)
	{
	  session->internals.params.rsa_params = params.params.rsa_export;
	  session->internals.params.free_rsa_params = params.deinit;
	}
    }

  return session->internals.params.rsa_params;
}


/**
  * gnutls_certificate_free_credentials - Used to free an allocated gnutls_certificate_credentials_t structure
  * @sc: is an #gnutls_certificate_credentials_t structure.
  *
  * This structure is complex enough to manipulate directly thus
  * this helper function is provided in order to free (deallocate) it.
  *
  * This function does not free any temporary parameters associated
  * with this structure (ie RSA and DH parameters are not freed by
  * this function).
  **/
void
gnutls_certificate_free_credentials (gnutls_certificate_credentials_t sc)
{
  gnutls_certificate_free_keys (sc);
  gnutls_certificate_free_cas (sc);
  gnutls_certificate_free_ca_names (sc);
#ifdef ENABLE_PKI
  gnutls_certificate_free_crls (sc);
#endif
  if (_E_gnutls_openpgp_keyring_deinit)
    _E_gnutls_openpgp_keyring_deinit( sc->keyring);

  gnutls_free (sc);
}


/**
  * gnutls_certificate_allocate_credentials - Used to allocate a gnutls_certificate_credentials_t structure
  * @res: is a pointer to an #gnutls_certificate_credentials_t structure.
  *
  * This structure is complex enough to manipulate directly thus
  * this helper function is provided in order to allocate it.
  *
  * Returns 0 on success.
  **/
int
gnutls_certificate_allocate_credentials (gnutls_certificate_credentials_t *
					 res)
{
  *res = gnutls_calloc (1, sizeof (certificate_credentials_st));

  if (*res == NULL)
    return GNUTLS_E_MEMORY_ERROR;

  (*res)->verify_bits = DEFAULT_VERIFY_BITS;
  (*res)->verify_depth = DEFAULT_VERIFY_DEPTH;

  return 0;
}


/* returns the KX algorithms that are supported by a
 * certificate. (Eg a certificate with RSA params, supports
 * GNUTLS_KX_RSA algorithm).
 * This function also uses the KeyUsage field of the certificate
 * extensions in order to disable unneded algorithms.
 */
int
_gnutls_selected_cert_supported_kx (gnutls_session_t session,
				    gnutls_kx_algorithm_t ** alg,
				    int *alg_size)
{
  gnutls_kx_algorithm_t kx;
  gnutls_pk_algorithm_t pk;
  gnutls_kx_algorithm_t kxlist[MAX_ALGOS];
  gnutls_cert *cert;
  int i;

  if (session->internals.selected_cert_list_length == 0)
    {
      *alg_size = 0;
      *alg = NULL;
      return 0;
    }

  cert = &session->internals.selected_cert_list[0];
  i = 0;

  for (kx = 0; kx < MAX_ALGOS; kx++)
    {
      pk = _gnutls_map_pk_get_pk (kx);
      if (pk == cert->subject_pk_algorithm)
	{
	  /* then check key usage */
	  if (_gnutls_check_key_usage (cert, kx) == 0)
	    {
	      kxlist[i] = kx;
	      i++;
	    }
	}
    }

  if (i == 0)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  *alg = gnutls_calloc (1, sizeof (gnutls_kx_algorithm_t) * i);
  if (*alg == NULL)
    return GNUTLS_E_MEMORY_ERROR;

  *alg_size = i;

  memcpy (*alg, kxlist, i * sizeof (gnutls_kx_algorithm_t));

  return 0;
}


/**
  * gnutls_certificate_server_set_request - Used to set whether to request a client certificate
  * @session: is an #gnutls_session_t structure.
  * @req: is one of GNUTLS_CERT_REQUEST, GNUTLS_CERT_REQUIRE
  *
  * This function specifies if we (in case of a server) are going
  * to send a certificate request message to the client. If @req
  * is GNUTLS_CERT_REQUIRE then the server will return an error if
  * the peer does not provide a certificate. If you do not
  * call this function then the client will not be asked to
  * send a certificate.
  **/
void
gnutls_certificate_server_set_request (gnutls_session_t session,
				       gnutls_certificate_request_t req)
{
  session->internals.send_cert_req = req;
}

/**
  * gnutls_certificate_client_set_retrieve_function - Used to set a callback to retrieve the certificate
  * @cred: is a #gnutls_certificate_credentials_t structure.
  * @func: is the callback function
  *
  * This function sets a callback to be called in order to retrieve the certificate
  * to be used in the handshake.
  * The callback's function prototype is:
  * int (*callback)(gnutls_session_t, const gnutls_datum_t* req_ca_dn, int nreqs, 
  * gnutls_pk_algorithm_t* pk_algos, int pk_algos_length, gnutls_retr_st* st);
  *
  * @st should contain the certificates and private keys.
  *
  * @req_ca_cert, is only used in X.509 certificates. 
  * Contains a list with the CA names that the server considers trusted. 
  * Normally we should send a certificate that is signed
  * by one of these CAs. These names are DER encoded. To get a more
  * meaningful value use the function gnutls_x509_rdn_get().
  *
  * @pk_algos, contains a list with server's acceptable signature algorithms.
  * The certificate returned should support the server's given algorithms.
  *
  * If the callback function is provided then gnutls will call it, in the
  * handshake, after the certificate request message has been received.
  *
  * The callback function should set the certificate list to be sent, and
  * return 0 on success. If no certificate was selected then the number of certificates
  * should be set to zero. The value (-1) indicates error and the handshake
  * will be terminated.
  **/
void gnutls_certificate_client_set_retrieve_function
  (gnutls_certificate_credentials_t cred,
   gnutls_certificate_client_retrieve_function * func)
{
  cred->client_get_cert_callback = func;
}

/**
  * gnutls_certificate_server_set_retrieve_function - Used to set a callback to retrieve the certificate
  * @cred: is a #gnutls_certificate_credentials_t structure.
  * @func: is the callback function
  *
  * This function sets a callback to be called in order to retrieve the certificate
  * to be used in the handshake.
  * The callback's function prototype is:
  * int (*callback)(gnutls_session_t, gnutls_retr_st* st);
  *
  * @st should contain the certificates and private keys.
  *
  * If the callback function is provided then gnutls will call it, in the
  * handshake, after the certificate request message has been received.
  *
  * The callback function should set the certificate list to be sent, and
  * return 0 on success.  The value (-1) indicates error and the handshake
  * will be terminated.
  **/
void gnutls_certificate_server_set_retrieve_function
  (gnutls_certificate_credentials_t cred,
   gnutls_certificate_server_retrieve_function * func)
{
  cred->server_get_cert_callback = func;
}

/*-
 * _gnutls_x509_extract_certificate_activation_time - This function returns the peer's certificate activation time
 * @cert: should contain an X.509 DER encoded certificate
 *
 * This function will return the certificate's activation time in UNIX time
 * (ie seconds since 00:00:00 UTC January 1, 1970).
 *
 * Returns a (time_t) -1 in case of an error.
 *
 -*/
static time_t
_gnutls_x509_get_raw_crt_activation_time (const gnutls_datum_t * cert)
{
  gnutls_x509_crt_t xcert;
  time_t result;

  result = gnutls_x509_crt_init (&xcert);
  if (result < 0)
    return (time_t) - 1;

  result = gnutls_x509_crt_import (xcert, cert, GNUTLS_X509_FMT_DER);
  if (result < 0)
    {
      gnutls_x509_crt_deinit (xcert);
      return (time_t) - 1;
    }

  result = gnutls_x509_crt_get_activation_time (xcert);

  gnutls_x509_crt_deinit (xcert);

  return result;
}

/*-
 * gnutls_x509_extract_certificate_expiration_time - This function returns the certificate's expiration time
 * @cert: should contain an X.509 DER encoded certificate
 *
 * This function will return the certificate's expiration time in UNIX
 * time (ie seconds since 00:00:00 UTC January 1, 1970).  Returns a
 *
 * (time_t) -1 in case of an error.
 *
 -*/
static time_t
_gnutls_x509_get_raw_crt_expiration_time (const gnutls_datum_t * cert)
{
  gnutls_x509_crt_t xcert;
  time_t result;

  result = gnutls_x509_crt_init (&xcert);
  if (result < 0)
    return (time_t) - 1;

  result = gnutls_x509_crt_import (xcert, cert, GNUTLS_X509_FMT_DER);
  if (result < 0)
    {
      gnutls_x509_crt_deinit (xcert);
      return (time_t) - 1;
    }

  result = gnutls_x509_crt_get_expiration_time (xcert);

  gnutls_x509_crt_deinit (xcert);

  return result;
}

/*-
  * _gnutls_openpgp_crt_verify_peers - This function returns the peer's certificate status
  * @session: is a gnutls session
  *
  * This function will try to verify the peer's certificate and return its status (TRUSTED, INVALID etc.). 
  * Returns a negative error code in case of an error, or GNUTLS_E_NO_CERTIFICATE_FOUND if no certificate was sent.
  *
  -*/
int
_gnutls_openpgp_crt_verify_peers (gnutls_session_t session,
				   unsigned int *status)
{
  cert_auth_info_t info;
  gnutls_certificate_credentials_t cred;
  int peer_certificate_list_size, ret;

  CHECK_AUTH (GNUTLS_CRD_CERTIFICATE, GNUTLS_E_INVALID_REQUEST);

  info = _gnutls_get_auth_info (session);
  if (info == NULL)
    return GNUTLS_E_INVALID_REQUEST;

  cred = (gnutls_certificate_credentials_t)
    _gnutls_get_cred (session->key, GNUTLS_CRD_CERTIFICATE, NULL);
  if (cred == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
    }

  if (info->raw_certificate_list == NULL || info->ncerts == 0)
    {
      gnutls_assert ();
      return GNUTLS_E_NO_CERTIFICATE_FOUND;
    }

  /* generate a list of gnutls_certs based on the auth info
   * raw certs.
   */
  peer_certificate_list_size = info->ncerts;

  if (peer_certificate_list_size != 1)
    {
      gnutls_assert ();
      return GNUTLS_E_INTERNAL_ERROR;
    }

  /* Verify certificate 
   */
  if (_E_gnutls_openpgp_verify_key == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_INIT_LIBEXTRA;
    }
  ret =
    _E_gnutls_openpgp_verify_key (cred, &info->raw_certificate_list[0],
				  peer_certificate_list_size, status);

  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  return 0;
}


/**
  * gnutls_certificate_verify_peers2 - This function returns the peer's certificate verification status
  * @session: is a gnutls session
  * @status: is the output of the verification
  *
  * This function will try to verify the peer's certificate and return
  * its status (trusted, invalid etc.).  The value of @status should
  * be one or more of the gnutls_certificate_status_t enumerated
  * elements bitwise or'd. To avoid denial of service attacks some
  * default upper limits regarding the certificate key size and chain
  * size are set. To override them use
  * gnutls_certificate_set_verify_limits().
  *
  * Note that you must also check the peer's name in order to check if
  * the verified certificate belongs to the actual peer.
  *
  * Returns a negative error code on error and zero on success.
  *
  * This is the same as gnutls_x509_verify_certificate() and uses the
  * loaded CAs in the credentials as trusted CAs.
  *
  * Note that some commonly used X.509 Certificate Authorities are
  * still using Version 1 certificates.  If you want to accept them,
  * you need to call gnutls_certificate_set_verify_flags() with, e.g.,
  * %GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT parameter.
  **/
int
gnutls_certificate_verify_peers2 (gnutls_session_t session,
				  unsigned int *status)
{
  cert_auth_info_t info;

  CHECK_AUTH (GNUTLS_CRD_CERTIFICATE, GNUTLS_E_INVALID_REQUEST);

  info = _gnutls_get_auth_info (session);
  if (info == NULL)
    {
      return GNUTLS_E_NO_CERTIFICATE_FOUND;
    }

  if (info->raw_certificate_list == NULL || info->ncerts == 0)
    return GNUTLS_E_NO_CERTIFICATE_FOUND;

  switch (gnutls_certificate_type_get (session))
    {
    case GNUTLS_CRT_X509:
      return _gnutls_x509_cert_verify_peers (session, status);
    case GNUTLS_CRT_OPENPGP:
      return _gnutls_openpgp_crt_verify_peers (session, status);
    default:
      return GNUTLS_E_INVALID_REQUEST;
    }
}

/**
  * gnutls_certificate_verify_peers - This function returns the peer's certificate verification status
  * @session: is a gnutls session
  *
  * This function will try to verify the peer's certificate and return
  * its status (trusted, invalid etc.).  However you must also check
  * the peer's name in order to check if the verified certificate
  * belongs to the actual peer.
  *
  * The return value should be one or more of the
  * gnutls_certificate_status_t enumerated elements bitwise or'd, or a
  * negative value on error.
  *
  * This is the same as gnutls_x509_verify_certificate().
  *
  * Deprecated: Use gnutls_certificate_verify_peers2() instead.
  *
  **/
int
gnutls_certificate_verify_peers (gnutls_session_t session)
{
  unsigned int status;
  int ret;

  ret = gnutls_certificate_verify_peers2 (session, &status);

  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  return status;
}

/**
  * gnutls_certificate_expiration_time_peers - This function returns the peer's certificate expiration time
  * @session: is a gnutls session
  *
  * This function will return the peer's certificate expiration time.
  *
  * Returns (time_t) -1 on error.
  *
  **/
time_t
gnutls_certificate_expiration_time_peers (gnutls_session_t session)
{
  cert_auth_info_t info;

  CHECK_AUTH (GNUTLS_CRD_CERTIFICATE, GNUTLS_E_INVALID_REQUEST);

  info = _gnutls_get_auth_info (session);
  if (info == NULL)
    {
      return (time_t) - 1;
    }

  if (info->raw_certificate_list == NULL || info->ncerts == 0)
    {
      gnutls_assert ();
      return (time_t) - 1;
    }

  switch (gnutls_certificate_type_get (session))
    {
    case GNUTLS_CRT_X509:
      return _gnutls_x509_get_raw_crt_expiration_time (&info->
						       raw_certificate_list
						       [0]);
    case GNUTLS_CRT_OPENPGP:
      if (_E_gnutls_openpgp_get_raw_key_expiration_time == NULL)
	return (time_t) - 1;
      return _E_gnutls_openpgp_get_raw_key_expiration_time (&info->
							    raw_certificate_list
							    [0]);
    default:
      return (time_t) - 1;
    }
}

/**
  * gnutls_certificate_activation_time_peers - This function returns the peer's certificate activation time
  * @session: is a gnutls session
  *
  * This function will return the peer's certificate activation time.
  * This is the creation time for openpgp keys.
  *
  * Returns (time_t) -1 on error.
  *
  **/
time_t
gnutls_certificate_activation_time_peers (gnutls_session_t session)
{
  cert_auth_info_t info;

  CHECK_AUTH (GNUTLS_CRD_CERTIFICATE, GNUTLS_E_INVALID_REQUEST);

  info = _gnutls_get_auth_info (session);
  if (info == NULL)
    {
      return (time_t) - 1;
    }

  if (info->raw_certificate_list == NULL || info->ncerts == 0)
    {
      gnutls_assert ();
      return (time_t) - 1;
    }

  switch (gnutls_certificate_type_get (session))
    {
    case GNUTLS_CRT_X509:
      return _gnutls_x509_get_raw_crt_activation_time (&info->
						       raw_certificate_list
						       [0]);
    case GNUTLS_CRT_OPENPGP:
      if (_E_gnutls_openpgp_get_raw_key_creation_time == NULL)
	return (time_t) - 1;
      return _E_gnutls_openpgp_get_raw_key_creation_time (&info->
							  raw_certificate_list
							  [0]);
    default:
      return (time_t) - 1;
    }
}

int
_gnutls_raw_cert_to_gcert (gnutls_cert * gcert,
			   gnutls_certificate_type_t type,
			   const gnutls_datum_t * raw_cert,
			   int flags /* OR of ConvFlags */ )
{
  switch (type)
    {
    case GNUTLS_CRT_X509:
      return _gnutls_x509_raw_cert_to_gcert (gcert, raw_cert, flags);
    case GNUTLS_CRT_OPENPGP:
      if (_E_gnutls_openpgp_raw_key_to_gcert == NULL)
	{
	  gnutls_assert ();
	  return GNUTLS_E_INIT_LIBEXTRA;
	}
      return _E_gnutls_openpgp_raw_key_to_gcert (gcert, raw_cert);
    default:
      gnutls_assert ();
      return GNUTLS_E_INTERNAL_ERROR;
    }
}

int
_gnutls_raw_privkey_to_gkey (gnutls_privkey * key,
			     gnutls_certificate_type_t type,
			     const gnutls_datum_t * raw_key,
			     int key_enc /* DER or PEM */ )
{
  switch (type)
    {
    case GNUTLS_CRT_X509:
      return _gnutls_x509_raw_privkey_to_gkey (key, raw_key, key_enc);
    case GNUTLS_CRT_OPENPGP:
      if (_E_gnutls_openpgp_raw_privkey_to_gkey == NULL)
	{
	  gnutls_assert ();
	  return GNUTLS_E_INIT_LIBEXTRA;
	}
      return _E_gnutls_openpgp_raw_privkey_to_gkey (key, raw_key,
						    (gnutls_openpgp_crt_fmt_t)
						    key_enc);
    default:
      gnutls_assert ();
      return GNUTLS_E_INTERNAL_ERROR;
    }
}


/* This function will convert a der certificate to a format
 * (structure) that gnutls can understand and use. Actually the
 * important thing on this function is that it extracts the 
 * certificate's (public key) parameters.
 *
 * The noext flag is used to complete the handshake even if the
 * extensions found in the certificate are unsupported and critical. 
 * The critical extensions will be catched by the verification functions.
 */
int
_gnutls_x509_raw_cert_to_gcert (gnutls_cert * gcert,
				const gnutls_datum_t * derCert,
				int flags /* OR of ConvFlags */ )
{
  int ret;
  gnutls_x509_crt_t cert;

  ret = gnutls_x509_crt_init (&cert);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  ret = gnutls_x509_crt_import (cert, derCert, GNUTLS_X509_FMT_DER);
  if (ret < 0)
    {
      gnutls_assert ();
      gnutls_x509_crt_deinit (cert);
      return ret;
    }

  ret = _gnutls_x509_crt_to_gcert (gcert, cert, flags);
  gnutls_x509_crt_deinit (cert);

  return ret;
}

/* Like above but it accepts a parsed certificate instead.
 */
int
_gnutls_x509_crt_to_gcert (gnutls_cert * gcert,
			   gnutls_x509_crt_t cert, unsigned int flags)
{
  int ret = 0;

  memset (gcert, 0, sizeof (gnutls_cert));
  gcert->cert_type = GNUTLS_CRT_X509;

  if (!(flags & CERT_NO_COPY))
    {
#define SMALL_DER 512
      opaque *der;
      size_t der_size = SMALL_DER;

      /* initially allocate a bogus size, just in case the certificate
       * fits in it. That way we minimize the DER encodings performed.
       */
      der = gnutls_malloc (SMALL_DER);
      if (der == NULL)
	{
	  gnutls_assert ();
	  return GNUTLS_E_MEMORY_ERROR;
	}

      ret =
	gnutls_x509_crt_export (cert, GNUTLS_X509_FMT_DER, der, &der_size);
      if (ret < 0 && ret != GNUTLS_E_SHORT_MEMORY_BUFFER)
	{
	  gnutls_assert ();
	  gnutls_free (der);
	  return ret;
	}

      if (ret == GNUTLS_E_SHORT_MEMORY_BUFFER)
	{
	  der = gnutls_realloc (der, der_size);
	  if (der == NULL)
	    {
	      gnutls_assert ();
	      return GNUTLS_E_MEMORY_ERROR;
	    }

	  ret =
	    gnutls_x509_crt_export (cert, GNUTLS_X509_FMT_DER, der,
				    &der_size);
	  if (ret < 0)
	    {
	      gnutls_assert ();
	      gnutls_free (der);
	      return ret;
	    }
	}

      gcert->raw.data = der;
      gcert->raw.size = der_size;
    }
  else
    /* now we have 0 or a bitwise or of things to decode */
    flags ^= CERT_NO_COPY;


  if (flags & CERT_ONLY_EXTENSIONS || flags == 0)
    {
      gnutls_x509_crt_get_key_usage (cert, &gcert->key_usage, NULL);
      gcert->version = gnutls_x509_crt_get_version (cert);
    }
  gcert->subject_pk_algorithm = gnutls_x509_crt_get_pk_algorithm (cert, NULL);

  if (flags & CERT_ONLY_PUBKEY || flags == 0)
    {
      gcert->params_size = MAX_PUBLIC_PARAMS_SIZE;
      ret =
	_gnutls_x509_crt_get_mpis (cert, gcert->params, &gcert->params_size);
      if (ret < 0)
	{
	  gnutls_assert ();
	  return ret;
	}
    }

  return 0;

}

void
_gnutls_gcert_deinit (gnutls_cert * cert)
{
  int i;

  if (cert == NULL)
    return;

  for (i = 0; i < cert->params_size; i++)
    {
      _gnutls_mpi_release (&cert->params[i]);
    }

  _gnutls_free_datum (&cert->raw);
}

/**
 * gnutls_sign_callback_set:
 * @session: is a gnutls session
 * @sign_func: function pointer to application's sign callback.
 * @userdata: void pointer that will be passed to sign callback.
 *
 * Set the callback function.  The function must have this prototype:
 *
 * typedef int (*gnutls_sign_func) (gnutls_session_t session,
 *                                  void *userdata,
 *                                  gnutls_certificate_type_t cert_type,
 *                                  const gnutls_datum_t * cert,
 *                                  const gnutls_datum_t * hash,
 *                                  gnutls_datum_t * signature);
 *
 * The @userdata parameter is passed to the @sign_func verbatim, and
 * can be used to store application-specific data needed in the
 * callback function.  See also gnutls_sign_callback_get().
 **/
void
gnutls_sign_callback_set (gnutls_session_t session,
			  gnutls_sign_func sign_func,
			  void *userdata)
{
  session->internals.sign_func = sign_func;
  session->internals.sign_func_userdata = userdata;
}

/**
 * gnutls_sign_callback_get:
 * @session: is a gnutls session
 * @userdata: if non-%NULL, will be set to abstract callback pointer.
 *
 * Retrieve the callback function, and its userdata pointer.
 *
 * Return value: The function pointer set by
 *   gnutls_sign_callback_set(), or if not set, %NULL.
 **/
gnutls_sign_func
gnutls_sign_callback_get (gnutls_session_t session,
			  void **userdata)
{
  if (userdata)
    *userdata = session->internals.sign_func_userdata;
  return session->internals.sign_func;
}