path: root/lib/openpgp/pgp.c

/*
 * Copyright (C) 2002-2012 Free Software Foundation, Inc.
 *
 * Author: Timo Schulz, Nikos Mavrogiannopoulos
 *
 * This file is part of GnuTLS.
 *
 * The GnuTLS 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 program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

/* Functions on OpenPGP key parsing
 */

#include <gnutls_int.h>
#include <gnutls_datum.h>
#include <gnutls_global.h>
#include <gnutls_errors.h>
#include <openpgp_int.h>
#include <gnutls_str.h>
#include <gnutls_num.h>
#include <x509/common.h>

/**
 * gnutls_openpgp_crt_init:
 * @key: The structure to be initialized
 *
 * This function will initialize an OpenPGP key structure.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.
 **/
int
gnutls_openpgp_crt_init (gnutls_openpgp_crt_t * key)
{
  *key = gnutls_calloc (1, sizeof (gnutls_openpgp_crt_int));

  if (*key)
    return 0;                   /* success */
  return GNUTLS_E_MEMORY_ERROR;
}

/**
 * gnutls_openpgp_crt_deinit:
 * @key: The structure to be initialized
 *
 * This function will deinitialize a key structure.
 **/
void
gnutls_openpgp_crt_deinit (gnutls_openpgp_crt_t key)
{
  if (!key)
    return;

  if (key->knode)
    {
      cdk_kbnode_release (key->knode);
      key->knode = NULL;
    }

  gnutls_free (key);
}

/**
 * gnutls_openpgp_crt_import:
 * @key: The structure to store the parsed key.
 * @data: The RAW or BASE64 encoded key.
 * @format: One of gnutls_openpgp_crt_fmt_t elements.
 *
 * This function will convert the given RAW or Base64 encoded key to
 * the native #gnutls_openpgp_crt_t format. The output will be stored
 * in 'key'.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.
 **/
int
gnutls_openpgp_crt_import (gnutls_openpgp_crt_t key,
                           const gnutls_datum_t * data,
                           gnutls_openpgp_crt_fmt_t format)
{
  cdk_packet_t pkt;
  int rc, armor;

  if (data->data == NULL || data->size == 0)
    {
      gnutls_assert ();
      return GNUTLS_E_OPENPGP_GETKEY_FAILED;
    }

  if (format == GNUTLS_OPENPGP_FMT_RAW) armor = 0;
  else armor = 1;

  rc = cdk_kbnode_read_from_mem (&key->knode, armor, data->data, data->size);
  if (rc)
    {
      rc = _gnutls_map_cdk_rc (rc);
      gnutls_assert ();
      return rc;
    }

  /* Test if the import was successful. */
  pkt = cdk_kbnode_find_packet (key->knode, CDK_PKT_PUBLIC_KEY);
  if (pkt == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_OPENPGP_GETKEY_FAILED;
    }

  return 0;
}

int _gnutls_openpgp_export2 (cdk_kbnode_t node,
                             gnutls_openpgp_crt_fmt_t format,
                             gnutls_datum_t* out, int priv)
{
int ret;
size_t size = 0;

  ret = _gnutls_openpgp_export(node, format, NULL, &size, priv);
  if (ret == GNUTLS_E_SHORT_MEMORY_BUFFER)
    {
      out->data = gnutls_malloc(size);
    
      ret = _gnutls_openpgp_export(node, format, out->data, &size, priv);
      if (ret < 0)
        {
          gnutls_free(out->data);
          return gnutls_assert_val(ret);
        }
      out->size = size;
    }
  else if (ret < 0)
    return gnutls_assert_val(ret);
    
  return 0;
}

/* internal version of export
 */
int
_gnutls_openpgp_export (cdk_kbnode_t node,
                        gnutls_openpgp_crt_fmt_t format,
                        void *output_data,
                        size_t * output_data_size, int priv)
{
  size_t input_data_size = *output_data_size;
  size_t calc_size;
  int rc;

  rc = cdk_kbnode_write_to_mem (node, output_data, output_data_size);
  if (rc)
    {
      rc = _gnutls_map_cdk_rc (rc);
      gnutls_assert ();
      return rc;
    }

  /* If the caller uses output_data == NULL then return what he expects.
   */
  if (!output_data && format != GNUTLS_OPENPGP_FMT_BASE64)
    {
      gnutls_assert ();
      return GNUTLS_E_SHORT_MEMORY_BUFFER;
    }

  if (format == GNUTLS_OPENPGP_FMT_BASE64)
    {
      unsigned char *in = gnutls_calloc (1, *output_data_size);
      memcpy (in, output_data, *output_data_size);

      /* Calculate the size of the encoded data and check if the provided
         buffer is large enough. */
      rc = cdk_armor_encode_buffer (in, *output_data_size,
                                    NULL, 0, &calc_size,
                                    priv ? CDK_ARMOR_SECKEY :
                                    CDK_ARMOR_PUBKEY);
      if (rc || calc_size > input_data_size)
        {
          gnutls_free (in);
          *output_data_size = calc_size;
          gnutls_assert ();
          return GNUTLS_E_SHORT_MEMORY_BUFFER;
        }

      rc = cdk_armor_encode_buffer (in, *output_data_size,
                                    output_data, input_data_size, &calc_size,
                                    priv ? CDK_ARMOR_SECKEY :
                                    CDK_ARMOR_PUBKEY);
      gnutls_free (in);
      *output_data_size = calc_size;

      if (rc)
        {
          rc = _gnutls_map_cdk_rc (rc);
          gnutls_assert ();
          return rc;
        }
    }

  return 0;

}

/**
 * gnutls_openpgp_crt_export:
 * @key: Holds the key.
 * @format: One of gnutls_openpgp_crt_fmt_t elements.
 * @output_data: will contain the raw or base64 encoded key
 * @output_data_size: holds the size of output_data (and will
 *   be replaced by the actual size of parameters)
 *
 * This function will convert the given key to RAW or Base64 format.
 * If the buffer provided is not long enough to hold the output, then
 * %GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.
 **/
int
gnutls_openpgp_crt_export (gnutls_openpgp_crt_t key,
                           gnutls_openpgp_crt_fmt_t format,
                           void *output_data, size_t * output_data_size)
{
  return _gnutls_openpgp_export (key->knode, format, output_data,
                                 output_data_size, 0);
}

/**
 * gnutls_openpgp_crt_export2:
 * @key: Holds the key.
 * @format: One of gnutls_openpgp_crt_fmt_t elements.
 * @out: will contain the raw or base64 encoded key
 *
 * This function will convert the given key to RAW or Base64 format.
 * The output buffer is allocated using gnutls_malloc().
 *
 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.
 *
 * Since: 3.1.3
 **/
int
gnutls_openpgp_crt_export2 (gnutls_openpgp_crt_t key,
                            gnutls_openpgp_crt_fmt_t format,
                            gnutls_datum_t *out)
{
  return _gnutls_openpgp_export2 (key->knode, format, out, 0);
}

/**
 * gnutls_openpgp_crt_get_fingerprint:
 * @key: the raw data that contains the OpenPGP public key.
 * @fpr: the buffer to save the fingerprint, must hold at least 20 bytes.
 * @fprlen: the integer to save the length of the fingerprint.
 *
 * Get key fingerprint.  Depending on the algorithm, the fingerprint
 * can be 16 or 20 bytes.
 *
 * Returns: On success, 0 is returned.  Otherwise, an error code.
 **/
int
gnutls_openpgp_crt_get_fingerprint (gnutls_openpgp_crt_t key,
                                    void *fpr, size_t * fprlen)
{
  cdk_packet_t pkt;
  cdk_pkt_pubkey_t pk = NULL;

  if (!fpr || !fprlen)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  *fprlen = 0;

  pkt = cdk_kbnode_find_packet (key->knode, CDK_PKT_PUBLIC_KEY);
  if (!pkt)
    return GNUTLS_E_OPENPGP_GETKEY_FAILED;

  pk = pkt->pkt.public_key;
  *fprlen = 20;

  /* FIXME: Check if the draft allows old PGP keys. */
  if (is_RSA (pk->pubkey_algo) && pk->version < 4)
    *fprlen = 16;
  cdk_pk_get_fingerprint (pk, fpr);

  return 0;
}

static int
_gnutls_openpgp_count_key_names (gnutls_openpgp_crt_t key)
{
  cdk_kbnode_t p, ctx;
  cdk_packet_t pkt;
  int nuids;

  if (key == NULL)
    {
      gnutls_assert ();
      return 0;
    }

  ctx = NULL;
  nuids = 0;
  while ((p = cdk_kbnode_walk (key->knode, &ctx, 0)))
    {
      pkt = cdk_kbnode_get_packet (p);
      if (pkt->pkttype == CDK_PKT_USER_ID)
        nuids++;
    }

  return nuids;
}


/**
 * gnutls_openpgp_crt_get_name:
 * @key: the structure that contains the OpenPGP public key.
 * @idx: the index of the ID to extract
 * @buf: a pointer to a structure to hold the name, may be %NULL
 *       to only get the @sizeof_buf.
 * @sizeof_buf: holds the maximum size of @buf, on return hold the
 *   actual/required size of @buf.
 *
 * Extracts the userID from the parsed OpenPGP key.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, and if the index of the ID
 *   does not exist %GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE, or an
 *   error code.
 **/
int
gnutls_openpgp_crt_get_name (gnutls_openpgp_crt_t key,
                             int idx, char *buf, size_t * sizeof_buf)
{
  cdk_kbnode_t ctx = NULL, p;
  cdk_packet_t pkt = NULL;
  cdk_pkt_userid_t uid = NULL;
  int pos = 0;

  if (!key)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  if (idx < 0 || idx >= _gnutls_openpgp_count_key_names (key))
    return GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE;

  pos = 0;
  while ((p = cdk_kbnode_walk (key->knode, &ctx, 0)))
    {
      pkt = cdk_kbnode_get_packet (p);
      if (pkt->pkttype == CDK_PKT_USER_ID)
        {
          if (pos == idx)
            break;
          pos++;
        }
    }

  if (!pkt)
    {
      gnutls_assert ();
      return GNUTLS_E_INTERNAL_ERROR;
    }

  uid = pkt->pkt.user_id;
  if (uid->len >= *sizeof_buf)
    {
      gnutls_assert ();
      *sizeof_buf = uid->len + 1;
      return GNUTLS_E_SHORT_MEMORY_BUFFER;
    }

  if (buf)
    {
      memcpy (buf, uid->name, uid->len);
      buf[uid->len] = '\0';     /* make sure it's a string */
    }
  *sizeof_buf = uid->len + 1;

  if (uid->is_revoked)
    return GNUTLS_E_OPENPGP_UID_REVOKED;

  return 0;
}

/**
 * gnutls_openpgp_crt_get_pk_algorithm:
 * @key: is an OpenPGP key
 * @bits: if bits is non null it will hold the size of the parameters' in bits
 *
 * This function will return the public key algorithm of an OpenPGP
 * certificate.
 *
 * If bits is non null, it should have enough size to hold the parameters
 * size in bits. For RSA the bits returned is the modulus.
 * For DSA the bits returned are of the public exponent.
 *
 * Returns: a member of the #gnutls_pk_algorithm_t enumeration on
 *   success, or GNUTLS_PK_UNKNOWN on error.
 **/
gnutls_pk_algorithm_t
gnutls_openpgp_crt_get_pk_algorithm (gnutls_openpgp_crt_t key,
                                     unsigned int *bits)
{
  cdk_packet_t pkt;
  int algo = 0, ret;
  uint8_t keyid[GNUTLS_OPENPGP_KEYID_SIZE];

  if (!key)
    {
      gnutls_assert ();
      return GNUTLS_PK_UNKNOWN;
    }

  ret = gnutls_openpgp_crt_get_preferred_key_id (key, keyid);
  if (ret == 0)
    {
      int idx;

      idx = gnutls_openpgp_crt_get_subkey_idx (key, keyid);
      if (idx != GNUTLS_OPENPGP_MASTER_KEYID_IDX)
        {
          algo =
            gnutls_openpgp_crt_get_subkey_pk_algorithm (key, idx, bits);
          return algo;
        }
    }

  pkt = cdk_kbnode_find_packet (key->knode, CDK_PKT_PUBLIC_KEY);
  if (pkt)
    {
      if (bits)
        *bits = cdk_pk_get_nbits (pkt->pkt.public_key);
      algo = _gnutls_openpgp_get_algo (pkt->pkt.public_key->pubkey_algo);
    }

  return algo;
}


/**
 * gnutls_openpgp_crt_get_version:
 * @key: the structure that contains the OpenPGP public key.
 *
 * Extract the version of the OpenPGP key.
 *
 * Returns: the version number is returned, or a negative error code on errors.
 **/
int
gnutls_openpgp_crt_get_version (gnutls_openpgp_crt_t key)
{
  cdk_packet_t pkt;
  int version;

  if (!key)
    return -1;

  pkt = cdk_kbnode_find_packet (key->knode, CDK_PKT_PUBLIC_KEY);
  if (pkt)
    version = pkt->pkt.public_key->version;
  else
    version = 0;

  return version;
}


/**
 * gnutls_openpgp_crt_get_creation_time:
 * @key: the structure that contains the OpenPGP public key.
 *
 * Get key creation time.
 *
 * Returns: the timestamp when the OpenPGP key was created.
 **/
time_t
gnutls_openpgp_crt_get_creation_time (gnutls_openpgp_crt_t key)
{
  cdk_packet_t pkt;
  time_t timestamp;

  if (!key)
    return (time_t) - 1;

  pkt = cdk_kbnode_find_packet (key->knode, CDK_PKT_PUBLIC_KEY);
  if (pkt)
    timestamp = pkt->pkt.public_key->timestamp;
  else
    timestamp = 0;

  return timestamp;
}


/**
 * gnutls_openpgp_crt_get_expiration_time:
 * @key: the structure that contains the OpenPGP public key.
 *
 * Get key expiration time.  A value of '0' means that the key doesn't
 * expire at all.
 *
 * Returns: the time when the OpenPGP key expires.
 **/
time_t
gnutls_openpgp_crt_get_expiration_time (gnutls_openpgp_crt_t key)
{
  cdk_packet_t pkt;
  time_t expiredate;

  if (!key)
    return (time_t) - 1;

  pkt = cdk_kbnode_find_packet (key->knode, CDK_PKT_PUBLIC_KEY);
  if (pkt)
    expiredate = pkt->pkt.public_key->expiredate;
  else
    expiredate = 0;

  return expiredate;
}

/**
 * gnutls_openpgp_crt_get_key_id:
 * @key: the structure that contains the OpenPGP public key.
 * @keyid: the buffer to save the keyid.
 *
 * Get key id string.
 *
 * Returns: the 64-bit keyID of the OpenPGP key.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_key_id (gnutls_openpgp_crt_t key,
                               gnutls_openpgp_keyid_t keyid)
{
  cdk_packet_t pkt;
  uint32_t kid[2];

  if (!key || !keyid)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  pkt = cdk_kbnode_find_packet (key->knode, CDK_PKT_PUBLIC_KEY);
  if (!pkt)
    return GNUTLS_E_OPENPGP_GETKEY_FAILED;

  cdk_pk_get_keyid (pkt->pkt.public_key, kid);
  _gnutls_write_uint32 (kid[0], keyid);
  _gnutls_write_uint32 (kid[1], keyid + 4);

  return 0;
}

/**
 * gnutls_openpgp_crt_get_revoked_status:
 * @key: the structure that contains the OpenPGP public key.
 *
 * Get revocation status of key.
 *
 * Returns: true (1) if the key has been revoked, or false (0) if it
 *   has not.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_revoked_status (gnutls_openpgp_crt_t key)
{
  cdk_packet_t pkt;

  if (!key)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  pkt = cdk_kbnode_find_packet (key->knode, CDK_PKT_PUBLIC_KEY);
  if (!pkt)
    return GNUTLS_E_OPENPGP_GETKEY_FAILED;

  if (pkt->pkt.public_key->is_revoked != 0)
    return 1;
  return 0;
}

/**
 * gnutls_openpgp_crt_check_hostname:
 * @key: should contain a #gnutls_openpgp_crt_t structure
 * @hostname: A null terminated string that contains a DNS name
 *
 * This function will check if the given key's owner matches the
 * given hostname. This is a basic implementation of the matching
 * described in RFC2818 (HTTPS), which takes into account wildcards.
 *
 * Returns: non-zero for a successful match, and zero on failure.
 **/
int
gnutls_openpgp_crt_check_hostname (gnutls_openpgp_crt_t key,
                                   const char *hostname)
{
  char dnsname[MAX_CN];
  size_t dnsnamesize;
  int ret = 0;
  int i;

  /* Check through all included names. */
  for (i = 0; !(ret < 0); i++)
    {
      dnsnamesize = sizeof (dnsname);
      ret = gnutls_openpgp_crt_get_name (key, i, dnsname, &dnsnamesize);

      if (ret == 0)
        {
          /* Length returned by gnutls_openpgp_crt_get_name includes
             the terminating (0). */
          dnsnamesize--;

          if (_gnutls_hostname_compare (dnsname, dnsnamesize, hostname, 0))
            return 1;
        }
    }

  /* not found a matching name */
  return 0;
}

unsigned int
_gnutls_get_pgp_key_usage (unsigned int cdk_usage)
{
  unsigned int usage = 0;

  if (cdk_usage & CDK_KEY_USG_CERT_SIGN)
    usage |= GNUTLS_KEY_KEY_CERT_SIGN;
  if (cdk_usage & CDK_KEY_USG_DATA_SIGN)
    usage |= GNUTLS_KEY_DIGITAL_SIGNATURE;
  if (cdk_usage & CDK_KEY_USG_COMM_ENCR)
    usage |= GNUTLS_KEY_KEY_ENCIPHERMENT;
  if (cdk_usage & CDK_KEY_USG_STORAGE_ENCR)
    usage |= GNUTLS_KEY_DATA_ENCIPHERMENT;
  if (cdk_usage & CDK_KEY_USG_AUTH)
    usage |= GNUTLS_KEY_KEY_AGREEMENT;

  return usage;
}

/**
 * gnutls_openpgp_crt_get_key_usage:
 * @key: should contain a gnutls_openpgp_crt_t structure
 * @key_usage: where the key usage bits will be stored
 *
 * This function will return certificate's key usage, by checking the
 * key algorithm. The key usage value will ORed values of the:
 * %GNUTLS_KEY_DIGITAL_SIGNATURE, %GNUTLS_KEY_KEY_ENCIPHERMENT.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.
 */
int
gnutls_openpgp_crt_get_key_usage (gnutls_openpgp_crt_t key,
                                  unsigned int *key_usage)
{
  cdk_packet_t pkt;

  if (!key)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  pkt = cdk_kbnode_find_packet (key->knode, CDK_PKT_PUBLIC_KEY);
  if (!pkt)
    return GNUTLS_E_OPENPGP_GETKEY_FAILED;

  *key_usage = _gnutls_get_pgp_key_usage (pkt->pkt.public_key->pubkey_usage);

  return 0;
}

/**
 * gnutls_openpgp_crt_get_subkey_count:
 * @key: is an OpenPGP key
 *
 * This function will return the number of subkeys present in the
 * given OpenPGP certificate.
 *
 * Returns: the number of subkeys, or a negative error code on error.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_subkey_count (gnutls_openpgp_crt_t key)
{
  cdk_kbnode_t p, ctx;
  cdk_packet_t pkt;
  int subkeys;

  if (key == NULL)
    {
      gnutls_assert ();
      return 0;
    }

  ctx = NULL;
  subkeys = 0;
  while ((p = cdk_kbnode_walk (key->knode, &ctx, 0)))
    {
      pkt = cdk_kbnode_get_packet (p);
      if (pkt->pkttype == CDK_PKT_PUBLIC_SUBKEY)
        subkeys++;
    }

  return subkeys;
}

/* returns the subkey with the given index */
static cdk_packet_t
_get_public_subkey (gnutls_openpgp_crt_t key, unsigned int indx)
{
  cdk_kbnode_t p, ctx;
  cdk_packet_t pkt;
  unsigned int subkeys;

  if (key == NULL)
    {
      gnutls_assert ();
      return NULL;
    }

  ctx = NULL;
  subkeys = 0;
  while ((p = cdk_kbnode_walk (key->knode, &ctx, 0)))
    {
      pkt = cdk_kbnode_get_packet (p);
      if (pkt->pkttype == CDK_PKT_PUBLIC_SUBKEY && indx == subkeys++)
        return pkt;
    }

  return NULL;
}

/* returns the key with the given keyid. It can be either key or subkey.
 * depending on what requested:
 *   pkt->pkt.secret_key;
 *   pkt->pkt.public_key;
 */
cdk_packet_t
_gnutls_openpgp_find_key (cdk_kbnode_t knode, uint32_t keyid[2],
                          unsigned int priv)
{
  cdk_kbnode_t p, ctx;
  cdk_packet_t pkt;
  uint32_t local_keyid[2];

  ctx = NULL;
  while ((p = cdk_kbnode_walk (knode, &ctx, 0)))
    {
      pkt = cdk_kbnode_get_packet (p);

      if ((priv == 0
           && (pkt->pkttype == CDK_PKT_PUBLIC_SUBKEY
               || pkt->pkttype == CDK_PKT_PUBLIC_KEY)) || (priv != 0
                                                           && (pkt->pkttype ==
                                                               CDK_PKT_SECRET_SUBKEY
                                                               || pkt->pkttype
                                                               ==
                                                               CDK_PKT_SECRET_KEY)))
        {
          if (priv == 0)
            cdk_pk_get_keyid (pkt->pkt.public_key, local_keyid);
          else
            cdk_pk_get_keyid (pkt->pkt.secret_key->pk, local_keyid);

          if (local_keyid[0] == keyid[0] && local_keyid[1] == keyid[1])
            {
              return pkt;
            }
        }
    }

  gnutls_assert ();
  return NULL;
}

/* returns the key with the given keyid
 * depending on what requested:
 *   pkt->pkt.secret_key;
 *   pkt->pkt.public_key;
 */
int
_gnutls_openpgp_find_subkey_idx (cdk_kbnode_t knode, uint32_t keyid[2],
                                 unsigned int priv)
{
  cdk_kbnode_t p, ctx;
  cdk_packet_t pkt;
  int i = 0;
  uint32_t local_keyid[2];

  _gnutls_hard_log ("Looking keyid: %x.%x\n", keyid[0], keyid[1]);

  ctx = NULL;
  while ((p = cdk_kbnode_walk (knode, &ctx, 0)))
    {
      pkt = cdk_kbnode_get_packet (p);

      if ((priv == 0 && (pkt->pkttype == CDK_PKT_PUBLIC_SUBKEY)) ||
          (priv != 0 && (pkt->pkttype == CDK_PKT_SECRET_SUBKEY)))
        {
          if (priv == 0)
            cdk_pk_get_keyid (pkt->pkt.public_key, local_keyid);
          else
            cdk_pk_get_keyid (pkt->pkt.secret_key->pk, local_keyid);

          _gnutls_hard_log ("Found keyid: %x.%x\n", local_keyid[0],
                            local_keyid[1]);
          if (local_keyid[0] == keyid[0] && local_keyid[1] == keyid[1])
            {
              return i;
            }
          i++;
        }
    }

  gnutls_assert ();
  return GNUTLS_E_OPENPGP_SUBKEY_ERROR;
}

/**
 * gnutls_openpgp_crt_get_subkey_revoked_status:
 * @key: the structure that contains the OpenPGP public key.
 * @idx: is the subkey index
 *
 * Get subkey revocation status.  A negative error code indicates an error.
 *
 * Returns: true (1) if the key has been revoked, or false (0) if it
 *   has not.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_subkey_revoked_status (gnutls_openpgp_crt_t key,
                                              unsigned int idx)
{
  cdk_packet_t pkt;

  if (!key)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  if (idx == GNUTLS_OPENPGP_MASTER_KEYID_IDX)
    return gnutls_openpgp_crt_get_revoked_status(key);

  pkt = _get_public_subkey (key, idx);
  if (!pkt)
    return GNUTLS_E_OPENPGP_GETKEY_FAILED;

  if (pkt->pkt.public_key->is_revoked != 0)
    return 1;
  return 0;
}

/**
 * gnutls_openpgp_crt_get_subkey_pk_algorithm:
 * @key: is an OpenPGP key
 * @idx: is the subkey index
 * @bits: if bits is non null it will hold the size of the parameters' in bits
 *
 * This function will return the public key algorithm of a subkey of an OpenPGP
 * certificate.
 *
 * If bits is non null, it should have enough size to hold the
 * parameters size in bits.  For RSA the bits returned is the modulus.
 * For DSA the bits returned are of the public exponent.
 *
 * Returns: a member of the #gnutls_pk_algorithm_t enumeration on
 *   success, or GNUTLS_PK_UNKNOWN on error.
 *
 * Since: 2.4.0
 **/
gnutls_pk_algorithm_t
gnutls_openpgp_crt_get_subkey_pk_algorithm (gnutls_openpgp_crt_t key,
                                            unsigned int idx,
                                            unsigned int *bits)
{
  cdk_packet_t pkt;
  int algo;

  if (!key)
    {
      gnutls_assert ();
      return GNUTLS_PK_UNKNOWN;
    }

  if (idx == GNUTLS_OPENPGP_MASTER_KEYID_IDX)
    return gnutls_openpgp_crt_get_pk_algorithm(key, bits);

  pkt = _get_public_subkey (key, idx);

  algo = 0;
  if (pkt)
    {
      if (bits)
        *bits = cdk_pk_get_nbits (pkt->pkt.public_key);
      algo = _gnutls_openpgp_get_algo (pkt->pkt.public_key->pubkey_algo);
    }

  return algo;
}

/**
 * gnutls_openpgp_crt_get_subkey_creation_time:
 * @key: the structure that contains the OpenPGP public key.
 * @idx: the subkey index
 *
 * Get subkey creation time.
 *
 * Returns: the timestamp when the OpenPGP sub-key was created.
 *
 * Since: 2.4.0
 **/
time_t
gnutls_openpgp_crt_get_subkey_creation_time (gnutls_openpgp_crt_t key,
                                             unsigned int idx)
{
  cdk_packet_t pkt;
  time_t timestamp;

  if (!key)
    return (time_t) - 1;

  if (idx == GNUTLS_OPENPGP_MASTER_KEYID_IDX)
    return gnutls_openpgp_crt_get_creation_time(key);

  pkt = _get_public_subkey (key, idx);
  if (pkt)
    timestamp = pkt->pkt.public_key->timestamp;
  else
    timestamp = 0;

  return timestamp;
}


/**
 * gnutls_openpgp_crt_get_subkey_expiration_time:
 * @key: the structure that contains the OpenPGP public key.
 * @idx: the subkey index
 *
 * Get subkey expiration time.  A value of '0' means that the key
 * doesn't expire at all.
 *
 * Returns: the time when the OpenPGP key expires.
 *
 * Since: 2.4.0
 **/
time_t
gnutls_openpgp_crt_get_subkey_expiration_time (gnutls_openpgp_crt_t key,
                                               unsigned int idx)
{
  cdk_packet_t pkt;
  time_t expiredate;

  if (!key)
    return (time_t) - 1;

  if (idx == GNUTLS_OPENPGP_MASTER_KEYID_IDX)
    return gnutls_openpgp_crt_get_expiration_time(key);

  pkt = _get_public_subkey (key, idx);
  if (pkt)
    expiredate = pkt->pkt.public_key->expiredate;
  else
    expiredate = 0;

  return expiredate;
}

/**
 * gnutls_openpgp_crt_get_subkey_id:
 * @key: the structure that contains the OpenPGP public key.
 * @idx: the subkey index
 * @keyid: the buffer to save the keyid.
 *
 * Get the subkey's key-id.
 *
 * Returns: the 64-bit keyID of the OpenPGP key.
 **/
int
gnutls_openpgp_crt_get_subkey_id (gnutls_openpgp_crt_t key,
                                  unsigned int idx,
                                  gnutls_openpgp_keyid_t keyid)
{
  cdk_packet_t pkt;
  uint32_t kid[2];

  if (!key || !keyid)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }
  
  if (idx == GNUTLS_OPENPGP_MASTER_KEYID_IDX)
    return gnutls_openpgp_crt_get_key_id(key, keyid);

  pkt = _get_public_subkey (key, idx);
  if (!pkt)
    return GNUTLS_E_OPENPGP_GETKEY_FAILED;

  cdk_pk_get_keyid (pkt->pkt.public_key, kid);
  _gnutls_write_uint32 (kid[0], keyid);
  _gnutls_write_uint32 (kid[1], keyid + 4);

  return 0;
}

/**
 * gnutls_openpgp_crt_get_subkey_fingerprint:
 * @key: the raw data that contains the OpenPGP public key.
 * @idx: the subkey index
 * @fpr: the buffer to save the fingerprint, must hold at least 20 bytes.
 * @fprlen: the integer to save the length of the fingerprint.
 *
 * Get key fingerprint of a subkey.  Depending on the algorithm, the
 * fingerprint can be 16 or 20 bytes.
 *
 * Returns: On success, 0 is returned.  Otherwise, an error code.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_subkey_fingerprint (gnutls_openpgp_crt_t key,
                                           unsigned int idx,
                                           void *fpr, size_t * fprlen)
{
  cdk_packet_t pkt;
  cdk_pkt_pubkey_t pk = NULL;

  if (!fpr || !fprlen)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }
  
  if (idx == GNUTLS_OPENPGP_MASTER_KEYID_IDX)
    return gnutls_openpgp_crt_get_fingerprint(key, fpr, fprlen);

  *fprlen = 0;

  pkt = _get_public_subkey (key, idx);
  if (!pkt)
    return GNUTLS_E_OPENPGP_GETKEY_FAILED;

  pk = pkt->pkt.public_key;
  *fprlen = 20;

  /* FIXME: Check if the draft allows old PGP keys. */
  if (is_RSA (pk->pubkey_algo) && pk->version < 4)
    *fprlen = 16;
  cdk_pk_get_fingerprint (pk, fpr);

  return 0;
}

/**
 * gnutls_openpgp_crt_get_subkey_idx:
 * @key: the structure that contains the OpenPGP public key.
 * @keyid: the keyid.
 *
 * Get subkey's index.
 *
 * Returns: the index of the subkey or a negative error value.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_subkey_idx (gnutls_openpgp_crt_t key,
                                   const gnutls_openpgp_keyid_t keyid)
{
  int ret;
  uint32_t kid[2];
  uint8_t master_id[GNUTLS_OPENPGP_KEYID_SIZE];

  if (!key)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  ret = gnutls_openpgp_crt_get_key_id (key, master_id);
  if (ret < 0)
    return gnutls_assert_val(ret);  
  if (memcmp(master_id, keyid, GNUTLS_OPENPGP_KEYID_SIZE)==0)
    return GNUTLS_OPENPGP_MASTER_KEYID_IDX;

  KEYID_IMPORT (kid, keyid);
  ret = _gnutls_openpgp_find_subkey_idx (key->knode, kid, 0);

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

  return ret;
}

/**
 * gnutls_openpgp_crt_get_subkey_usage:
 * @key: should contain a gnutls_openpgp_crt_t structure
 * @idx: the subkey index
 * @key_usage: where the key usage bits will be stored
 *
 * This function will return certificate's key usage, by checking the
 * key algorithm.  The key usage value will ORed values of
 * %GNUTLS_KEY_DIGITAL_SIGNATURE or %GNUTLS_KEY_KEY_ENCIPHERMENT.
 *
 * A negative error code may be returned in case of parsing error.
 *
 * Returns: key usage value.
 *
 * Since: 2.4.0
 */
int
gnutls_openpgp_crt_get_subkey_usage (gnutls_openpgp_crt_t key,
                                     unsigned int idx,
                                     unsigned int *key_usage)
{
  cdk_packet_t pkt;

  if (!key)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  if (idx == GNUTLS_OPENPGP_MASTER_KEYID_IDX)
    return gnutls_openpgp_crt_get_key_usage(key, key_usage);

  pkt = _get_public_subkey (key, idx);
  if (!pkt)
    return GNUTLS_E_OPENPGP_SUBKEY_ERROR;

  *key_usage = _gnutls_get_pgp_key_usage (pkt->pkt.public_key->pubkey_usage);

  return 0;
}

int
_gnutls_read_pgp_mpi (cdk_packet_t pkt, unsigned int priv, size_t idx,
                      bigint_t * m)
{
  size_t buf_size = 512;
  uint8_t *buf = gnutls_malloc (buf_size);
  int err;
  unsigned int max_pub_params = 0;

  if (priv != 0)
    max_pub_params = cdk_pk_get_npkey (pkt->pkt.secret_key->pk->pubkey_algo);

  if (buf == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_MEMORY_ERROR;
    }

  /* FIXME: Note that opencdk doesn't like the buf to be NULL.
   */
  if (priv == 0)
    err =
      cdk_pk_get_mpi (pkt->pkt.public_key, idx, buf, buf_size, &buf_size,
                      NULL);
  else
    {
      if (idx < max_pub_params)
        err =
          cdk_pk_get_mpi (pkt->pkt.secret_key->pk, idx, buf, buf_size,
                          &buf_size, NULL);
      else
        {
          err =
            cdk_sk_get_mpi (pkt->pkt.secret_key, idx - max_pub_params, buf,
                            buf_size, &buf_size, NULL);
        }
    }

  if (err == CDK_Too_Short)
    {
      buf = gnutls_realloc_fast (buf, buf_size);
      if (buf == NULL)
        {
          gnutls_assert ();
          return GNUTLS_E_MEMORY_ERROR;
        }

      if (priv == 0)
        err =
          cdk_pk_get_mpi (pkt->pkt.public_key, idx, buf, buf_size, &buf_size,
                          NULL);
      else
        {
          if (idx < max_pub_params)
            err =
              cdk_pk_get_mpi (pkt->pkt.secret_key->pk, idx, buf, buf_size,
                              &buf_size, NULL);
          else
            {
              err =
                cdk_sk_get_mpi (pkt->pkt.secret_key, idx - max_pub_params,
                                buf, buf_size, &buf_size, NULL);
            }
        }
    }

  if (err != CDK_Success)
    {
      gnutls_assert ();
      gnutls_free (buf);
      return _gnutls_map_cdk_rc (err);
    }

  err = _gnutls_mpi_scan (m, buf, buf_size);
  gnutls_free (buf);

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

  return 0;
}


/* Extracts DSA and RSA parameters from a certificate.
 */
int
_gnutls_openpgp_crt_get_mpis (gnutls_openpgp_crt_t cert,
                              uint32_t * keyid /* [2] */ ,
                              gnutls_pk_params_st * params)
{
  int result, i;
  int pk_algorithm, local_params;
  cdk_packet_t pkt;

  if (keyid == NULL)
    pkt = cdk_kbnode_find_packet (cert->knode, CDK_PKT_PUBLIC_KEY);
  else
    pkt = _gnutls_openpgp_find_key (cert->knode, keyid, 0);

  if (pkt == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_OPENPGP_GETKEY_FAILED;
    }

  pk_algorithm = _gnutls_openpgp_get_algo (pkt->pkt.public_key->pubkey_algo);

  switch (pk_algorithm)
    {
    case GNUTLS_PK_RSA:
      local_params = RSA_PUBLIC_PARAMS;
      break;
    case GNUTLS_PK_DSA:
      local_params = DSA_PUBLIC_PARAMS;
      break;
    default:
      gnutls_assert ();
      return GNUTLS_E_UNSUPPORTED_CERTIFICATE_TYPE;
    }

  gnutls_pk_params_init(params);

  for (i = 0; i < local_params; i++)
    {
      result = _gnutls_read_pgp_mpi (pkt, 0, i, &params->params[i]);
      if (result < 0)
        {
          gnutls_assert ();
          goto error;
        }
      params->params_nr++;
    }

  return 0;

error:
  gnutls_pk_params_release(params);

  return result;
}

/* The internal version of export
 */
static int
_get_pk_rsa_raw (gnutls_openpgp_crt_t crt, gnutls_openpgp_keyid_t keyid,
                 gnutls_datum_t * m, gnutls_datum_t * e)
{
  int pk_algorithm, ret;
  cdk_packet_t pkt;
  uint32_t kid32[2];
  gnutls_pk_params_st params;

  gnutls_pk_params_init(&params);

  if (crt == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  KEYID_IMPORT (kid32, keyid);

  pkt = _gnutls_openpgp_find_key (crt->knode, kid32, 0);
  if (pkt == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_OPENPGP_GETKEY_FAILED;
    }

  pk_algorithm = _gnutls_openpgp_get_algo (pkt->pkt.public_key->pubkey_algo);

  if (pk_algorithm != GNUTLS_PK_RSA)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  ret = _gnutls_openpgp_crt_get_mpis (crt, kid32, &params);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  ret = _gnutls_mpi_dprint (params.params[0], m);
  if (ret < 0)
    {
      gnutls_assert ();
      goto cleanup;
    }

  ret = _gnutls_mpi_dprint (params.params[1], e);
  if (ret < 0)
    {
      gnutls_assert ();
      _gnutls_free_datum (m);
      goto cleanup;
    }

  ret = 0;

cleanup:
  gnutls_pk_params_release(&params);
  return ret;
}

static int
_get_pk_dsa_raw (gnutls_openpgp_crt_t crt, gnutls_openpgp_keyid_t keyid,
                 gnutls_datum_t * p, gnutls_datum_t * q,
                 gnutls_datum_t * g, gnutls_datum_t * y)
{
  int pk_algorithm, ret;
  cdk_packet_t pkt;
  uint32_t kid32[2];
  gnutls_pk_params_st params;
  
  gnutls_pk_params_init(&params);

  if (crt == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  KEYID_IMPORT (kid32, keyid);

  pkt = _gnutls_openpgp_find_key (crt->knode, kid32, 0);
  if (pkt == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_OPENPGP_GETKEY_FAILED;
    }

  pk_algorithm = _gnutls_openpgp_get_algo (pkt->pkt.public_key->pubkey_algo);

  if (pk_algorithm != GNUTLS_PK_DSA)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  ret = _gnutls_openpgp_crt_get_mpis (crt, kid32, &params);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  /* P */
  ret = _gnutls_mpi_dprint (params.params[0], p);
  if (ret < 0)
    {
      gnutls_assert ();
      goto cleanup;
    }

  /* Q */
  ret = _gnutls_mpi_dprint (params.params[1], q);
  if (ret < 0)
    {
      gnutls_assert ();
      _gnutls_free_datum (p);
      goto cleanup;
    }


  /* G */
  ret = _gnutls_mpi_dprint (params.params[2], g);
  if (ret < 0)
    {
      gnutls_assert ();
      _gnutls_free_datum (p);
      _gnutls_free_datum (q);
      goto cleanup;
    }


  /* Y */
  ret = _gnutls_mpi_dprint (params.params[3], y);
  if (ret < 0)
    {
      gnutls_assert ();
      _gnutls_free_datum (p);
      _gnutls_free_datum (g);
      _gnutls_free_datum (q);
      goto cleanup;
    }

  ret = 0;

cleanup:
  gnutls_pk_params_release(&params);
  return ret;
}


/**
 * gnutls_openpgp_crt_get_pk_rsa_raw:
 * @crt: Holds the certificate
 * @m: will hold the modulus
 * @e: will hold the public exponent
 *
 * This function will export the RSA public key's parameters found in
 * the given structure.  The new parameters will be allocated using
 * gnutls_malloc() and will be stored in the appropriate datum.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, otherwise a negative error code.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_pk_rsa_raw (gnutls_openpgp_crt_t crt,
                                   gnutls_datum_t * m, gnutls_datum_t * e)
{
  uint8_t keyid[GNUTLS_OPENPGP_KEYID_SIZE];
  int ret;

  ret = gnutls_openpgp_crt_get_key_id (crt, keyid);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  return _get_pk_rsa_raw (crt, keyid, m, e);
}

/**
 * gnutls_openpgp_crt_get_pk_dsa_raw:
 * @crt: Holds the certificate
 * @p: will hold the p
 * @q: will hold the q
 * @g: will hold the g
 * @y: will hold the y
 *
 * This function will export the DSA public key's parameters found in
 * the given certificate.  The new parameters will be allocated using
 * gnutls_malloc() and will be stored in the appropriate datum.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, otherwise a negative error code.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_pk_dsa_raw (gnutls_openpgp_crt_t crt,
                                   gnutls_datum_t * p, gnutls_datum_t * q,
                                   gnutls_datum_t * g, gnutls_datum_t * y)
{
  uint8_t keyid[GNUTLS_OPENPGP_KEYID_SIZE];
  int ret;

  ret = gnutls_openpgp_crt_get_key_id (crt, keyid);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  return _get_pk_dsa_raw (crt, keyid, p, q, g, y);
}

/**
 * gnutls_openpgp_crt_get_subkey_pk_rsa_raw:
 * @crt: Holds the certificate
 * @idx: Is the subkey index
 * @m: will hold the modulus
 * @e: will hold the public exponent
 *
 * This function will export the RSA public key's parameters found in
 * the given structure.  The new parameters will be allocated using
 * gnutls_malloc() and will be stored in the appropriate datum.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, otherwise a negative error code.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_subkey_pk_rsa_raw (gnutls_openpgp_crt_t crt,
                                          unsigned int idx,
                                          gnutls_datum_t * m,
                                          gnutls_datum_t * e)
{
  uint8_t keyid[GNUTLS_OPENPGP_KEYID_SIZE];
  int ret;

  if (idx == GNUTLS_OPENPGP_MASTER_KEYID_IDX)
    return gnutls_openpgp_crt_get_pk_rsa_raw(crt, m, e);

  ret = gnutls_openpgp_crt_get_subkey_id (crt, idx, keyid);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  return _get_pk_rsa_raw (crt, keyid, m, e);
}

/**
 * gnutls_openpgp_crt_get_subkey_pk_dsa_raw:
 * @crt: Holds the certificate
 * @idx: Is the subkey index
 * @p: will hold the p
 * @q: will hold the q
 * @g: will hold the g
 * @y: will hold the y
 *
 * This function will export the DSA public key's parameters found in
 * the given certificate.  The new parameters will be allocated using
 * gnutls_malloc() and will be stored in the appropriate datum.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, otherwise a negative error code.
 *
 * Since: 2.4.0
 **/
int
gnutls_openpgp_crt_get_subkey_pk_dsa_raw (gnutls_openpgp_crt_t crt,
                                          unsigned int idx,
                                          gnutls_datum_t * p,
                                          gnutls_datum_t * q,
                                          gnutls_datum_t * g,
                                          gnutls_datum_t * y)
{
  uint8_t keyid[GNUTLS_OPENPGP_KEYID_SIZE];
  int ret;

  if (idx == GNUTLS_OPENPGP_MASTER_KEYID_IDX)
    return gnutls_openpgp_crt_get_pk_dsa_raw(crt, p,q, g, y);

  ret = gnutls_openpgp_crt_get_subkey_id (crt, idx, keyid);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  return _get_pk_dsa_raw (crt, keyid, p, q, g, y);
}

/**
 * gnutls_openpgp_crt_get_preferred_key_id:
 * @key: the structure that contains the OpenPGP public key.
 * @keyid: the struct to save the keyid.
 *
 * Get preferred key id.  If it hasn't been set it returns
 * %GNUTLS_E_INVALID_REQUEST.
 *
 * Returns: the 64-bit preferred keyID of the OpenPGP key.
 **/
int
gnutls_openpgp_crt_get_preferred_key_id (gnutls_openpgp_crt_t key,
                                         gnutls_openpgp_keyid_t keyid)
{
  if (!key->preferred_set)
    return gnutls_assert_val(GNUTLS_E_OPENPGP_PREFERRED_KEY_ERROR);

  if (!key || !keyid)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  memcpy (keyid, key->preferred_keyid, GNUTLS_OPENPGP_KEYID_SIZE);

  return 0;
}

/**
 * gnutls_openpgp_crt_set_preferred_key_id:
 * @key: the structure that contains the OpenPGP public key.
 * @keyid: the selected keyid
 *
 * This allows setting a preferred key id for the given certificate.
 * This key will be used by functions that involve key handling.
 *
 * If the provided @keyid is %NULL then the master key is
 * set as preferred.
 *
 * Returns: On success, %GNUTLS_E_SUCCESS (0) is returned,
 *   otherwise a negative error code is returned.
 **/
int
gnutls_openpgp_crt_set_preferred_key_id (gnutls_openpgp_crt_t key,
                                         const gnutls_openpgp_keyid_t keyid)
{
  int ret;

  if (!key)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }
    
  if (keyid == NULL) /* set the master as preferred */
    {
      uint8_t tmp[GNUTLS_OPENPGP_KEYID_SIZE];
      
      ret = gnutls_openpgp_crt_get_key_id (key, tmp);
      if (ret < 0)
        return gnutls_assert_val(ret);
        
      key->preferred_set = 1;
      memcpy (key->preferred_keyid, tmp, GNUTLS_OPENPGP_KEYID_SIZE);

      return 0;
    }

  /* check if the id is valid */
  ret = gnutls_openpgp_crt_get_subkey_idx (key, keyid);
  if (ret < 0)
    {
      _gnutls_debug_log ("the requested subkey does not exist\n");
      gnutls_assert ();
      return ret;
    }

  key->preferred_set = 1;
  memcpy (key->preferred_keyid, keyid, GNUTLS_OPENPGP_KEYID_SIZE);

  return 0;
}

/**
 * gnutls_openpgp_crt_get_auth_subkey:
 * @crt: the structure that contains the OpenPGP public key.
 * @keyid: the struct to save the keyid.
 * @flag: Non-zero indicates that a valid subkey is always returned.
 *
 * Returns the 64-bit keyID of the first valid OpenPGP subkey marked
 * for authentication.  If flag is non-zero and no authentication
 * subkey exists, then a valid subkey will be returned even if it is
 * not marked for authentication.
 *
 * Returns: %GNUTLS_E_SUCCESS on success, or an error code.
 **/
int
gnutls_openpgp_crt_get_auth_subkey (gnutls_openpgp_crt_t crt,
                                    gnutls_openpgp_keyid_t keyid,
                                    unsigned int flag)
{
  int ret, subkeys, i;
  unsigned int usage;
  unsigned int keyid_init = 0;

  subkeys = gnutls_openpgp_crt_get_subkey_count (crt);
  if (subkeys <= 0)
    {
      gnutls_assert ();
      return GNUTLS_E_OPENPGP_SUBKEY_ERROR;
    }

  /* Try to find a subkey with the authentication flag set.
   * if none exists use the last one found
   */
  for (i = 0; i < subkeys; i++)
    {
      ret = gnutls_openpgp_crt_get_subkey_pk_algorithm(crt, i, NULL);
      if (ret == GNUTLS_PK_UNKNOWN)
        continue;
      
      ret = gnutls_openpgp_crt_get_subkey_revoked_status (crt, i);
      if (ret != 0)             /* it is revoked. ignore it */
        continue;

      if (keyid_init == 0)
        {                       /* keep the first valid subkey */
          ret = gnutls_openpgp_crt_get_subkey_id (crt, i, keyid);
          if (ret < 0)
            {
              gnutls_assert ();
              return ret;
            }

          keyid_init = 1;
        }

      ret = gnutls_openpgp_crt_get_subkey_usage (crt, i, &usage);
      if (ret < 0)
        {
          gnutls_assert ();
          return ret;
        }

      if (usage & GNUTLS_KEY_KEY_AGREEMENT)
        {
          ret = gnutls_openpgp_crt_get_subkey_id (crt, i, keyid);
          if (ret < 0)
            {
              gnutls_assert ();
              return ret;
            }
          return 0;
        }
    }

  if (flag && keyid_init)
    return 0;
  else
    return GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE;
}