/* GIO - GLib Input, Output and Streaming Library
 *
 * Copyright 2009 Red Hat, Inc
 *
 * 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 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, see
 * <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include <string.h>

#include "gtlscertificate-gnutls.h"
#include <glib/gi18n-lib.h>

static void     g_tls_certificate_gnutls_initable_iface_init (GInitableIface  *iface);

G_DEFINE_TYPE_WITH_CODE (GTlsCertificateGnutls, g_tls_certificate_gnutls, G_TYPE_TLS_CERTIFICATE,
			 G_IMPLEMENT_INTERFACE (G_TYPE_INITABLE,
						g_tls_certificate_gnutls_initable_iface_init);)

enum
{
  PROP_0,

  PROP_CERTIFICATE,
  PROP_CERTIFICATE_PEM,
  PROP_PRIVATE_KEY,
  PROP_PRIVATE_KEY_PEM,
  PROP_ISSUER
};

struct _GTlsCertificateGnutlsPrivate
{
  gnutls_x509_crt_t cert;
  gnutls_x509_privkey_t key;

  GTlsCertificateGnutls *issuer;

  GError *construct_error;

  guint have_cert : 1;
  guint have_key  : 1;
};

static void
g_tls_certificate_gnutls_finalize (GObject *object)
{
  GTlsCertificateGnutls *gnutls = G_TLS_CERTIFICATE_GNUTLS (object);

  gnutls_x509_crt_deinit (gnutls->priv->cert);
  if (gnutls->priv->key)
    gnutls_x509_privkey_deinit (gnutls->priv->key);

  if (gnutls->priv->issuer)
    g_object_unref (gnutls->priv->issuer);

  g_clear_error (&gnutls->priv->construct_error);

  G_OBJECT_CLASS (g_tls_certificate_gnutls_parent_class)->finalize (object);
}

static void
g_tls_certificate_gnutls_get_property (GObject    *object,
				       guint       prop_id,
				       GValue     *value,
				       GParamSpec *pspec)
{
  GTlsCertificateGnutls *gnutls = G_TLS_CERTIFICATE_GNUTLS (object);
  GByteArray *certificate;
  char *certificate_pem;
  int status;
  size_t size;

  switch (prop_id)
    {
    case PROP_CERTIFICATE:
      size = 0;
      status = gnutls_x509_crt_export (gnutls->priv->cert,
				       GNUTLS_X509_FMT_DER,
				       NULL, &size);
      if (status != GNUTLS_E_SHORT_MEMORY_BUFFER)
	certificate = NULL;
      else
	{
	  certificate = g_byte_array_sized_new (size);
	  certificate->len = size;
	  status = gnutls_x509_crt_export (gnutls->priv->cert,
					   GNUTLS_X509_FMT_DER,
					   certificate->data, &size);
	  if (status != 0)
	    {
	      g_byte_array_free (certificate, TRUE);
	      certificate = NULL;
	    }
	}
      g_value_take_boxed (value, certificate);
      break;

    case PROP_CERTIFICATE_PEM:
      size = 0;
      status = gnutls_x509_crt_export (gnutls->priv->cert,
				       GNUTLS_X509_FMT_PEM,
				       NULL, &size);
      if (status != GNUTLS_E_SHORT_MEMORY_BUFFER)
	certificate_pem = NULL;
      else
	{
	  certificate_pem = g_malloc (size);
	  status = gnutls_x509_crt_export (gnutls->priv->cert,
					   GNUTLS_X509_FMT_PEM,
					   certificate_pem, &size);
	  if (status != 0)
	    {
	      g_free (certificate_pem);
	      certificate_pem = NULL;
	    }
	}
      g_value_take_string (value, certificate_pem);
      break;

    case PROP_ISSUER:
      g_value_set_object (value, gnutls->priv->issuer);
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
    }
}

static void
g_tls_certificate_gnutls_set_property (GObject      *object,
				       guint         prop_id,
				       const GValue *value,
				       GParamSpec   *pspec)
{
  GTlsCertificateGnutls *gnutls = G_TLS_CERTIFICATE_GNUTLS (object);
  GByteArray *bytes;
  const char *string;
  gnutls_datum_t data;
  int status;

  switch (prop_id)
    {
    case PROP_CERTIFICATE:
      bytes = g_value_get_boxed (value);
      if (!bytes)
	break;
      g_return_if_fail (gnutls->priv->have_cert == FALSE);
      data.data = bytes->data;
      data.size = bytes->len;
      status = gnutls_x509_crt_import (gnutls->priv->cert, &data,
				       GNUTLS_X509_FMT_DER);
      if (status == 0)
	gnutls->priv->have_cert = TRUE;
      else if (!gnutls->priv->construct_error)
	{
	  gnutls->priv->construct_error =
	    g_error_new (G_TLS_ERROR, G_TLS_ERROR_BAD_CERTIFICATE,
			 _("Could not parse DER certificate: %s"),
			 gnutls_strerror (status));
	}

      break;

    case PROP_CERTIFICATE_PEM:
      string = g_value_get_string (value);
      if (!string)
	break;
      g_return_if_fail (gnutls->priv->have_cert == FALSE);
      data.data = (void *)string;
      data.size = strlen (string);
      status = gnutls_x509_crt_import (gnutls->priv->cert, &data,
				       GNUTLS_X509_FMT_PEM);
      if (status == 0)
	gnutls->priv->have_cert = TRUE;
      else if (!gnutls->priv->construct_error)
	{
	  gnutls->priv->construct_error =
	    g_error_new (G_TLS_ERROR, G_TLS_ERROR_BAD_CERTIFICATE,
			 _("Could not parse PEM certificate: %s"),
			 gnutls_strerror (status));
	}
      break;

    case PROP_PRIVATE_KEY:
      bytes = g_value_get_boxed (value);
      if (!bytes)
	break;
      g_return_if_fail (gnutls->priv->have_key == FALSE);
      data.data = bytes->data;
      data.size = bytes->len;
      if (!gnutls->priv->key)
        gnutls_x509_privkey_init (&gnutls->priv->key);
      status = gnutls_x509_privkey_import (gnutls->priv->key, &data,
					   GNUTLS_X509_FMT_DER);
      if (status != 0)
	{
	  int pkcs8_status =
	    gnutls_x509_privkey_import_pkcs8 (gnutls->priv->key, &data,
					      GNUTLS_X509_FMT_DER, NULL,
					      GNUTLS_PKCS_PLAIN);
	  if (pkcs8_status == 0)
	    status = 0;
	}
      if (status == 0)
	gnutls->priv->have_key = TRUE;
      else if (!gnutls->priv->construct_error)
	{
	  gnutls->priv->construct_error =
	    g_error_new (G_TLS_ERROR, G_TLS_ERROR_BAD_CERTIFICATE,
			 _("Could not parse DER private key: %s"),
			 gnutls_strerror (status));
	}
      break;

    case PROP_PRIVATE_KEY_PEM:
      string = g_value_get_string (value);
      if (!string)
	break;
      g_return_if_fail (gnutls->priv->have_key == FALSE);
      data.data = (void *)string;
      data.size = strlen (string);
      if (!gnutls->priv->key)
        gnutls_x509_privkey_init (&gnutls->priv->key);
      status = gnutls_x509_privkey_import (gnutls->priv->key, &data,
					   GNUTLS_X509_FMT_PEM);
      if (status != 0)
	{
	  int pkcs8_status =
	    gnutls_x509_privkey_import_pkcs8 (gnutls->priv->key, &data,
					      GNUTLS_X509_FMT_PEM, NULL,
					      GNUTLS_PKCS_PLAIN);
	  if (pkcs8_status == 0)
	    status = 0;
	}
      if (status == 0)
	gnutls->priv->have_key = TRUE;
      else if (!gnutls->priv->construct_error)
	{
	  gnutls->priv->construct_error =
	    g_error_new (G_TLS_ERROR, G_TLS_ERROR_BAD_CERTIFICATE,
			 _("Could not parse PEM private key: %s"),
			 gnutls_strerror (status));
	}
      break;

    case PROP_ISSUER:
      gnutls->priv->issuer = g_value_dup_object (value);
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
    }
}

static void
g_tls_certificate_gnutls_init (GTlsCertificateGnutls *gnutls)
{
  gnutls->priv = G_TYPE_INSTANCE_GET_PRIVATE (gnutls,
					      G_TYPE_TLS_CERTIFICATE_GNUTLS,
					      GTlsCertificateGnutlsPrivate);

  gnutls_x509_crt_init (&gnutls->priv->cert);
}

static gboolean
g_tls_certificate_gnutls_initable_init (GInitable       *initable,
					GCancellable    *cancellable,
					GError         **error)
{
  GTlsCertificateGnutls *gnutls = G_TLS_CERTIFICATE_GNUTLS (initable);

  if (gnutls->priv->construct_error)
    {
      g_propagate_error (error, gnutls->priv->construct_error);
      gnutls->priv->construct_error = NULL;
      return FALSE;
    }
  else if (!gnutls->priv->have_cert)
    {
      g_set_error_literal (error, G_TLS_ERROR, G_TLS_ERROR_BAD_CERTIFICATE,
			   _("No certificate data provided"));
      return FALSE;
    }
  else
    return TRUE;
}

static GTlsCertificateFlags
g_tls_certificate_gnutls_verify (GTlsCertificate     *cert,
				 GSocketConnectable  *identity,
				 GTlsCertificate     *trusted_ca)
{
  GTlsCertificateGnutls *cert_gnutls;
  guint num_certs, i;
  gnutls_x509_crt_t *chain;
  GTlsCertificateFlags gtls_flags;
  time_t t, now;

  cert_gnutls = G_TLS_CERTIFICATE_GNUTLS (cert);
  for (num_certs = 0; cert_gnutls; cert_gnutls = cert_gnutls->priv->issuer)
    num_certs++;
  chain = g_new (gnutls_x509_crt_t, num_certs);
  cert_gnutls = G_TLS_CERTIFICATE_GNUTLS (cert);
  for (i = 0; cert_gnutls; cert_gnutls = cert_gnutls->priv->issuer, i++)
    chain[i] = cert_gnutls->priv->cert;

  if (trusted_ca)
    {
      gnutls_x509_crt_t ca;
      guint gnutls_flags;
      int status;

      ca = G_TLS_CERTIFICATE_GNUTLS (trusted_ca)->priv->cert;
      status = gnutls_x509_crt_list_verify (chain, num_certs,
					    &ca, 1,
					    NULL, 0,
					    GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT,
					    &gnutls_flags);
      if (status != 0)
	{
	  g_free (chain);
	  return G_TLS_CERTIFICATE_GENERIC_ERROR;
	}

      gtls_flags = g_tls_certificate_gnutls_convert_flags (gnutls_flags);
    }
  else
    gtls_flags = 0;

  /* We have to check these ourselves since gnutls_x509_crt_list_verify
   * won't bother if it gets an UNKNOWN_CA.
   */
  now = time (NULL);
  for (i = 0; i < num_certs; i++)
    {
      t = gnutls_x509_crt_get_activation_time (chain[i]);
      if (t == (time_t) -1 || t > now)
	gtls_flags |= G_TLS_CERTIFICATE_NOT_ACTIVATED;

      t = gnutls_x509_crt_get_expiration_time (chain[i]);
      if (t == (time_t) -1 || t < now)
	gtls_flags |= G_TLS_CERTIFICATE_EXPIRED;
    }

  g_free (chain);

  if (identity)
    gtls_flags |= g_tls_certificate_gnutls_verify_identity (G_TLS_CERTIFICATE_GNUTLS (cert), identity);

  return gtls_flags;
}

static void
g_tls_certificate_gnutls_real_copy (GTlsCertificateGnutls    *gnutls,
                                    const gchar              *interaction_id,
                                    gnutls_retr2_st          *st)
{
  GTlsCertificateGnutls *chain;
  gnutls_x509_crt_t cert;
  gnutls_datum_t data;
  guint num_certs = 0;
  size_t size = 0;

  /* We will do this loop twice. It's probably more efficient than
   * re-allocating memory.
   */
  chain = gnutls;
  while (chain != NULL)
    {
      num_certs++;
      chain = chain->priv->issuer;
    }

  st->ncerts = 0;
  st->cert.x509 = gnutls_malloc (sizeof (gnutls_x509_crt_t) * num_certs);

  /* Now do the actual copy of the whole chain. */
  chain = gnutls;
  while (chain != NULL)
    {
      gnutls_x509_crt_export (chain->priv->cert, GNUTLS_X509_FMT_DER,
                              NULL, &size);
      data.data = g_malloc (size);
      data.size = size;
      gnutls_x509_crt_export (chain->priv->cert, GNUTLS_X509_FMT_DER,
                              data.data, &size);

      gnutls_x509_crt_init (&cert);
      gnutls_x509_crt_import (cert, &data, GNUTLS_X509_FMT_DER);
      g_free (data.data);

      st->cert.x509[st->ncerts] = cert;
      st->ncerts++;

      chain = chain->priv->issuer;
    }

  if (gnutls->priv->key != NULL)
    {
      gnutls_x509_privkey_init (&st->key.x509);
      gnutls_x509_privkey_cpy (st->key.x509, gnutls->priv->key);
      st->key_type = GNUTLS_PRIVKEY_X509;
    }

  st->deinit_all = TRUE;
}

static void
g_tls_certificate_gnutls_class_init (GTlsCertificateGnutlsClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  GTlsCertificateClass *certificate_class = G_TLS_CERTIFICATE_CLASS (klass);

  g_type_class_add_private (klass, sizeof (GTlsCertificateGnutlsPrivate));

  gobject_class->get_property = g_tls_certificate_gnutls_get_property;
  gobject_class->set_property = g_tls_certificate_gnutls_set_property;
  gobject_class->finalize     = g_tls_certificate_gnutls_finalize;

  certificate_class->verify = g_tls_certificate_gnutls_verify;

  klass->copy = g_tls_certificate_gnutls_real_copy;

  g_object_class_override_property (gobject_class, PROP_CERTIFICATE, "certificate");
  g_object_class_override_property (gobject_class, PROP_CERTIFICATE_PEM, "certificate-pem");
  g_object_class_override_property (gobject_class, PROP_PRIVATE_KEY, "private-key");
  g_object_class_override_property (gobject_class, PROP_PRIVATE_KEY_PEM, "private-key-pem");
  g_object_class_override_property (gobject_class, PROP_ISSUER, "issuer");
}

static void
g_tls_certificate_gnutls_initable_iface_init (GInitableIface  *iface)
{
  iface->init = g_tls_certificate_gnutls_initable_init;
}

GTlsCertificate *
g_tls_certificate_gnutls_new (const gnutls_datum_t *datum,
			      GTlsCertificate      *issuer)
{
  GTlsCertificateGnutls *gnutls;

  gnutls = g_object_new (G_TYPE_TLS_CERTIFICATE_GNUTLS,
			 "issuer", issuer,
			 NULL);
  g_tls_certificate_gnutls_set_data (gnutls, datum);

  return G_TLS_CERTIFICATE (gnutls);
}

void
g_tls_certificate_gnutls_set_data (GTlsCertificateGnutls *gnutls,
                                   const gnutls_datum_t  *datum)
{
  g_return_if_fail (G_IS_TLS_CERTIFICATE_GNUTLS (gnutls));
  g_return_if_fail (!gnutls->priv->have_cert);

  if (gnutls_x509_crt_import (gnutls->priv->cert, datum,
                              GNUTLS_X509_FMT_DER) == 0)
    gnutls->priv->have_cert = TRUE;
}

const gnutls_x509_crt_t
g_tls_certificate_gnutls_get_cert (GTlsCertificateGnutls *gnutls)
{
  return gnutls->priv->cert;
}

gboolean
g_tls_certificate_gnutls_has_key (GTlsCertificateGnutls *gnutls)
{
  return gnutls->priv->have_key;
}

void
g_tls_certificate_gnutls_copy  (GTlsCertificateGnutls *gnutls,
                                const gchar           *interaction_id,
                                gnutls_retr2_st       *st)
{
  g_return_if_fail (G_IS_TLS_CERTIFICATE_GNUTLS (gnutls));
  g_return_if_fail (st != NULL);
  g_return_if_fail (G_TLS_CERTIFICATE_GNUTLS_GET_CLASS (gnutls)->copy);
  G_TLS_CERTIFICATE_GNUTLS_GET_CLASS (gnutls)->copy (gnutls, interaction_id, st);
}

static const struct {
  int gnutls_flag;
  GTlsCertificateFlags gtls_flag;
} flags_map[] = {
  { GNUTLS_CERT_SIGNER_NOT_FOUND | GNUTLS_CERT_SIGNER_NOT_CA, G_TLS_CERTIFICATE_UNKNOWN_CA },
  { GNUTLS_CERT_NOT_ACTIVATED, G_TLS_CERTIFICATE_NOT_ACTIVATED },
  { GNUTLS_CERT_EXPIRED, G_TLS_CERTIFICATE_EXPIRED },
  { GNUTLS_CERT_REVOKED, G_TLS_CERTIFICATE_REVOKED },
  { GNUTLS_CERT_INSECURE_ALGORITHM, G_TLS_CERTIFICATE_INSECURE }
};
static const int flags_map_size = G_N_ELEMENTS (flags_map);

GTlsCertificateFlags
g_tls_certificate_gnutls_convert_flags (guint gnutls_flags)
{
  int i;
  GTlsCertificateFlags gtls_flags;

  /* Convert GNUTLS status to GTlsCertificateFlags. GNUTLS sets
   * GNUTLS_CERT_INVALID if it sets any other flag, so we want to
   * strip that out unless it's the only flag set. Then we convert
   * specific flags we recognize, and if there are any flags left over
   * at the end, we add G_TLS_CERTIFICATE_GENERIC_ERROR.
   */
  gtls_flags = 0;

  if (gnutls_flags != GNUTLS_CERT_INVALID)
    gnutls_flags = gnutls_flags & ~GNUTLS_CERT_INVALID;
  for (i = 0; i < flags_map_size && gnutls_flags != 0; i++)
    {
      if (gnutls_flags & flags_map[i].gnutls_flag)
	{
	  gnutls_flags &= ~flags_map[i].gnutls_flag;
	  gtls_flags |= flags_map[i].gtls_flag;
	}
    }
  if (gnutls_flags)
    gtls_flags |= G_TLS_CERTIFICATE_GENERIC_ERROR;

  return gtls_flags;
}

static gboolean
verify_identity_hostname (GTlsCertificateGnutls *gnutls,
			  GSocketConnectable    *identity)
{
  const char *hostname;

  if (G_IS_NETWORK_ADDRESS (identity))
    hostname = g_network_address_get_hostname (G_NETWORK_ADDRESS (identity));
  else if (G_IS_NETWORK_SERVICE (identity))
    hostname = g_network_service_get_domain (G_NETWORK_SERVICE (identity));
  else
    return FALSE;

  return gnutls_x509_crt_check_hostname (gnutls->priv->cert, hostname);
}

static gboolean
verify_identity_ip (GTlsCertificateGnutls *gnutls,
		    GSocketConnectable    *identity)
{
  GInetAddress *addr;
  int i, ret = 0;
  gsize addr_size;
  const guint8 *addr_bytes;

  if (G_IS_INET_SOCKET_ADDRESS (identity))
    addr = g_object_ref (g_inet_socket_address_get_address (G_INET_SOCKET_ADDRESS (identity)));
  else {
    const char *hostname;

    if (G_IS_NETWORK_ADDRESS (identity))
      hostname = g_network_address_get_hostname (G_NETWORK_ADDRESS (identity));
    else if (G_IS_NETWORK_SERVICE (identity))
      hostname = g_network_service_get_domain (G_NETWORK_SERVICE (identity));
    else
      return FALSE;

    addr = g_inet_address_new_from_string (hostname);
    if (!addr)
      return FALSE;
  }

  addr_bytes = g_inet_address_to_bytes (addr);
  addr_size = g_inet_address_get_native_size (addr);

  for (i = 0; ret >= 0; i++)
    {
      char san[500];
      size_t san_size;

      san_size = sizeof (san);
      ret = gnutls_x509_crt_get_subject_alt_name (gnutls->priv->cert, i,
						  san, &san_size, NULL);

      if ((ret == GNUTLS_SAN_IPADDRESS) && (addr_size == san_size))
	{
	  if (memcmp (addr_bytes, san, addr_size) == 0)
	    {
	      g_object_unref (addr);
	      return TRUE;
	    }
	}
    }

  g_object_unref (addr);
  return FALSE;
}

GTlsCertificateFlags
g_tls_certificate_gnutls_verify_identity (GTlsCertificateGnutls *gnutls,
					  GSocketConnectable    *identity)
{
  if (verify_identity_hostname (gnutls, identity))
    return 0;
  else if (verify_identity_ip (gnutls, identity))
    return 0;

  /* FIXME: check sRVName and uniformResourceIdentifier
   * subjectAltNames, if appropriate for @identity.
   */

  return G_TLS_CERTIFICATE_BAD_IDENTITY;
}

void
g_tls_certificate_gnutls_set_issuer (GTlsCertificateGnutls *gnutls,
                                     GTlsCertificateGnutls *issuer)
{
  g_return_if_fail (G_IS_TLS_CERTIFICATE_GNUTLS (gnutls));
  g_return_if_fail (!issuer || G_IS_TLS_CERTIFICATE_GNUTLS (issuer));

  if (issuer)
    g_object_ref (issuer);
  if (gnutls->priv->issuer)
    g_object_unref (gnutls->priv->issuer);
  gnutls->priv->issuer = issuer;
  g_object_notify (G_OBJECT (gnutls), "issuer");
}

GBytes *
g_tls_certificate_gnutls_get_bytes (GTlsCertificateGnutls *gnutls)
{
  GByteArray *array;

  g_return_val_if_fail (G_IS_TLS_CERTIFICATE_GNUTLS (gnutls), NULL);

  g_object_get (gnutls, "certificate", &array, NULL);
  return g_byte_array_free_to_bytes (array);
}

static gnutls_x509_crt_t *
convert_data_to_gnutls_certs (const gnutls_datum_t  *certs,
                              guint                  num_certs,
                              gnutls_x509_crt_fmt_t  format)
{
  gnutls_x509_crt_t *gnutls_certs;
  guint i;

  gnutls_certs = g_new (gnutls_x509_crt_t, num_certs);

  for (i = 0; i < num_certs; i++)
    {
      if (gnutls_x509_crt_init (&gnutls_certs[i]) < 0)
        {
          i--;
          goto error;
        }
    }

  for (i = 0; i < num_certs; i++)
    {
      if (gnutls_x509_crt_import (gnutls_certs[i], &certs[i], format) < 0)
        {
          i = num_certs - 1;
          goto error;
        }
    }

  return gnutls_certs;

error:
  for (; i != G_MAXUINT; i--)
    gnutls_x509_crt_deinit (gnutls_certs[i]);
  g_free (gnutls_certs);
  return NULL;
}

GTlsCertificateGnutls *
g_tls_certificate_gnutls_build_chain (const gnutls_datum_t  *certs,
                                      guint                  num_certs,
                                      gnutls_x509_crt_fmt_t  format)
{
  GPtrArray *glib_certs;
  gnutls_x509_crt_t *gnutls_certs;
  GTlsCertificateGnutls *issuer;
  GTlsCertificateGnutls *result;
  guint i, j;

  g_return_val_if_fail (certs, NULL);

  gnutls_certs = convert_data_to_gnutls_certs (certs, num_certs, format);
  if (!gnutls_certs)
    return NULL;

  glib_certs = g_ptr_array_new_full (num_certs, g_object_unref);
  for (i = 0; i < num_certs; i++)
    g_ptr_array_add (glib_certs, g_tls_certificate_gnutls_new (&certs[i], NULL));

  /* Some servers send certs out of order, or will send duplicate
   * certs, so we need to be careful when assigning the issuer of
   * our new GTlsCertificateGnutls.
   */
  for (i = 0; i < num_certs; i++)
    {
      issuer = NULL;

      if (i < num_certs - 1 &&
          gnutls_x509_crt_check_issuer (gnutls_certs[i], gnutls_certs[i + 1]))
        {
          issuer = glib_certs->pdata[i + 1];
        }
      else
        {
          for (j = 0; j < num_certs; j++)
            {
              if (j != i &&
                  gnutls_x509_crt_check_issuer (gnutls_certs[i], gnutls_certs[j]))
                {
                  issuer = glib_certs->pdata[j];
                  break;
                }
            }
        }

      if (issuer)
        g_tls_certificate_gnutls_set_issuer (glib_certs->pdata[i], issuer);
    }

  result = g_object_ref (glib_certs->pdata[0]);
  g_ptr_array_unref (glib_certs);

  for (i = 0; i < num_certs; i++)
    gnutls_x509_crt_deinit (gnutls_certs[i]);
  g_free (gnutls_certs);

  return result;
}
