path: root/lib/ext/ecc.c

/*
 * Copyright (C) 2002, 2003, 2004, 2005, 2010 Free Software Foundation,
 * Inc.
 *
 * Author: 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 * USA
 *
 */

/* This file contains the code the Certificate Type TLS extension.
 * This extension is currently gnutls specific.
 */

#include "gnutls_int.h"
#include "gnutls_errors.h"
#include "gnutls_num.h"
#include <ext/ecc.h>
#include <gnutls_state.h>
#include <gnutls_num.h>
#include <algorithms.h>

/* Maps record size to numbers according to the
 * extensions draft.
 */

static int _gnutls_supported_ecc_recv_params (gnutls_session_t session,
                                          const opaque * data,
                                          size_t data_size);
static int _gnutls_supported_ecc_send_params (gnutls_session_t session,
                                          gnutls_buffer_st * extdata);

static int _gnutls_supported_ecc_pf_recv_params (gnutls_session_t session,
                                          const opaque * data,
                                          size_t data_size);
static int _gnutls_supported_ecc_pf_send_params (gnutls_session_t session,
                                          gnutls_buffer_st * extdata);

extension_entry_st ext_mod_supported_ecc = {
  .name = "SUPPORTED ECC",
  .type = GNUTLS_EXTENSION_SUPPORTED_ECC,
  .parse_type = GNUTLS_EXT_TLS,

  .recv_func = _gnutls_supported_ecc_recv_params,
  .send_func = _gnutls_supported_ecc_send_params,
  .pack_func = NULL,
  .unpack_func = NULL,
  .deinit_func = NULL
};

extension_entry_st ext_mod_supported_ecc_pf = {
  .name = "SUPPORTED ECC POINT FORMATS",
  .type = GNUTLS_EXTENSION_SUPPORTED_ECC_PF,
  .parse_type = GNUTLS_EXT_TLS,

  .recv_func = _gnutls_supported_ecc_pf_recv_params,
  .send_func = _gnutls_supported_ecc_pf_send_params,
  .pack_func = NULL,
  .unpack_func = NULL,
  .deinit_func = NULL
};

/* 
 * In case of a server: if a SUPPORTED_ECC extension type is received then it stores
 * into the session security parameters the new value. The server may use gnutls_session_certificate_type_get(),
 * to access it.
 *
 * In case of a client: If a supported_eccs have been specified then we send the extension.
 *
 */
static int
_gnutls_supported_ecc_recv_params (gnutls_session_t session,
                               const opaque * data, size_t _data_size)
{
  int new_type = -1, ret, i;
  ssize_t data_size = _data_size;
  uint16_t len;
  const opaque* p = data;

  if (session->security_parameters.entity == GNUTLS_CLIENT)
    {
      /* A client shouldn't receive this extension */
      return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);
    }
  else
    { /* SERVER SIDE - we must check if the sent supported ecc type is the right one 
       */
      if (data_size < 2)
        return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);

      DECR_LEN (data_size, 2);
      len = _gnutls_read_uint16(p);
      p += 2;

      DECR_LEN (data_size, len);

      for (i = 0; i < len; i+=2)
        {
          new_type = _gnutls_tls_id_to_ecc_curve (_gnutls_read_uint16(&p[i]));
          if (new_type < 0)
            continue;

          /* Check if we support this supported_ecc */
          if ((ret =
               _gnutls_session_supports_ecc_curve (session, new_type)) < 0)
            {
              gnutls_assert ();
              continue;
            }
          else
            break;
          /* new_type is ok */
        }

      if (new_type < 0)
        {
          gnutls_assert ();
          return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
        }

      if ((ret =
           _gnutls_session_supports_ecc_curve (session, new_type)) < 0)
        {
              /* The peer has requested unsupported ecc
               * types. Instead of failing, procceed normally.
               * (the ciphersuite selection would fail, or a
               * non certificate ciphersuite will be selected).
               */
          return gnutls_assert_val(0);
        }

      _gnutls_session_ecc_curve_set (session, new_type);
    }

  return 0;
}


/* returns data_size or a negative number on failure
 */
static int
_gnutls_supported_ecc_send_params (gnutls_session_t session, gnutls_buffer_st* extdata)
{
  unsigned len, i;
  int ret;
  uint16_t p;
  
  /* this extension is only being sent on client side */
  if (session->security_parameters.entity == GNUTLS_CLIENT)
    {

      if (session->internals.priorities.supported_ecc.algorithms > 0)
        {

          len = session->internals.priorities.supported_ecc.algorithms;

          /* this is a vector!
           */
          ret = _gnutls_buffer_append_prefix(extdata, 16, len*2);
          if (ret < 0)
            return gnutls_assert_val(ret);

          for (i = 0; i < len; i++)
            {
              p =
                _gnutls_ecc_curve_get_tls_id (session->internals.priorities.
                                       supported_ecc.priority[i]);
              ret = _gnutls_buffer_append_prefix(extdata, 16, p);
              if (ret < 0)
                return gnutls_assert_val(ret);
            }
          return (len + 1)*2;
        }

    }

  return 0;
}

/* 
 * In case of a server: if a SUPPORTED_ECC extension type is received then it stores
 * into the session security parameters the new value. The server may use gnutls_session_certificate_type_get(),
 * to access it.
 *
 * In case of a client: If a supported_eccs have been specified then we send the extension.
 *
 */
static int
_gnutls_supported_ecc_pf_recv_params (gnutls_session_t session,
                               const opaque * data, size_t _data_size)
{
int len, i;
int uncompressed = 0;
int data_size = _data_size;

  if (session->security_parameters.entity == GNUTLS_CLIENT)
    {
      if (data_size < 1)
        return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);
      
      len = data[0];
      DECR_LEN (data_size, len+1);

      for (i=0;i<len;i++)
        if (data[1+i] == 0) /* uncompressed */
          uncompressed = 1;
      
      if (uncompressed == 0)
        return gnutls_assert_val(GNUTLS_E_UNKNOWN_PK_ALGORITHM);
    }
  else
    {
      /* only sanity check here. We only support uncompressed points
       * and a client must support it thus nothing to check.
       */
      if (_data_size < 1)
        return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);
    }

  return 0;
}

/* returns data_size or a negative number on failure
 */
static int
_gnutls_supported_ecc_pf_send_params (gnutls_session_t session, gnutls_buffer_st* extdata)
{
  const opaque p[2] = {0x01, 0x00}; /* only support uncompressed point format */
  
  /* this extension is only being sent on client and server side */
  _gnutls_buffer_append_data(extdata, p, 2);
  return 2;
}


/* Returns 0 if the given ECC curve is allowed in the current
 * session. A negative error value is returned otherwise.
 */
int
_gnutls_session_supports_ecc_curve (gnutls_session_t session, int ecc_type)
{
  unsigned i;
  
  if (session->internals.priorities.supported_ecc.algorithms > 0)
    {
      for (i = 0; i < session->internals.priorities.supported_ecc.algorithms; i++)
        {
          if (session->internals.priorities.supported_ecc.priority[i] == ecc_type)
            return 0;
        }
    }

  return GNUTLS_E_ECC_NO_SUPPORTED_CURVES;
}