/*
 * Copyright (C) 2001-2012 Free Software Foundation, Inc.
 *
 * Author: Nikos Mavrogiannopoulos, Simon Josefsson
 *
 * 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 3 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 that relate to the TLS hello extension parsing.
 * Hello extensions are packets appended in the TLS hello packet, and
 * allow for extra functionality.
 */

#include "gnutls_int.h"
#include "gnutls_extensions.h"
#include "gnutls_errors.h"
#include "ext/max_record.h"
#include <ext/cert_type.h>
#include <ext/server_name.h>
#include <ext/srp.h>
#include <ext/session_ticket.h>
#include <ext/safe_renegotiation.h>
#include <ext/signature.h>
#include <ext/safe_renegotiation.h>
#include <ext/ecc.h>
#include <ext/status_request.h>
#include <gnutls_num.h>


static void _gnutls_ext_unset_resumed_session_data (gnutls_session_t session,
                                                    uint16_t type);


static size_t extfunc_size = 0;
static extension_entry_st *extfunc = NULL;

static gnutls_ext_parse_type_t
_gnutls_ext_parse_type (uint16_t type)
{
  size_t i;

  for (i = 0; i < extfunc_size; i++)
    {
      if (extfunc[i].type == type)
        return extfunc[i].parse_type;
    }

  return GNUTLS_EXT_NONE;
}

static gnutls_ext_recv_func
_gnutls_ext_func_recv (uint16_t type, gnutls_ext_parse_type_t parse_type)
{
  size_t i;

  for (i = 0; i < extfunc_size; i++)
    if (extfunc[i].type == type)
      if (parse_type == GNUTLS_EXT_ANY || extfunc[i].parse_type == parse_type)
        return extfunc[i].recv_func;

  return NULL;
}

static gnutls_ext_deinit_data_func
_gnutls_ext_func_deinit (uint16_t type)
{
  size_t i;

  for (i = 0; i < extfunc_size; i++)
    if (extfunc[i].type == type)
      return extfunc[i].deinit_func;

  return NULL;
}

static gnutls_ext_unpack_func
_gnutls_ext_func_unpack (uint16_t type)
{
  size_t i;

  for (i = 0; i < extfunc_size; i++)
    if (extfunc[i].type == type)
      return extfunc[i].unpack_func;

  return NULL;
}


static const char *
_gnutls_extension_get_name (uint16_t type)
{
  size_t i;

  for (i = 0; i < extfunc_size; i++)
    if (extfunc[i].type == type)
      return extfunc[i].name;

  return NULL;
}

/* Checks if the extension we just received is one of the 
 * requested ones. Otherwise it's a fatal error.
 */
static int
_gnutls_extension_list_check (gnutls_session_t session, uint16_t type)
{
  if (session->security_parameters.entity == GNUTLS_CLIENT)
    {
      int i;

      for (i = 0; i < session->internals.extensions_sent_size; i++)
        {
          if (type == session->internals.extensions_sent[i])
            return 0;           /* ok found */
        }

      return GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION;
    }

  return 0;
}

int
_gnutls_parse_extensions (gnutls_session_t session,
                          gnutls_ext_parse_type_t parse_type,
                          const uint8_t * data, int data_size)
{
  int next, ret;
  int pos = 0;
  uint16_t type;
  const uint8_t *sdata;
  gnutls_ext_recv_func ext_recv;
  uint16_t size;

#ifdef DEBUG
  int i;

  if (session->security_parameters.entity == GNUTLS_CLIENT)
    for (i = 0; i < session->internals.extensions_sent_size; i++)
      {
        _gnutls_handshake_log ("EXT[%d]: expecting extension '%s'\n",
                           session,
                           _gnutls_extension_get_name
                           (session->internals.extensions_sent[i]));
      }
#endif

  DECR_LENGTH_RET (data_size, 2, 0);
  next = _gnutls_read_uint16 (data);
  pos += 2;

  DECR_LENGTH_RET (data_size, next, 0);

  do
    {
      DECR_LENGTH_RET (next, 2, 0);
      type = _gnutls_read_uint16 (&data[pos]);
      pos += 2;

#if 0
      _gnutls_handshake_log ("EXT[%p]: Found extension '%s/%d'\n", session,
                         _gnutls_extension_get_name (type), type);
#endif

      if ((ret = _gnutls_extension_list_check (session, type)) < 0)
        {
          gnutls_assert ();
          return ret;
        }

      DECR_LENGTH_RET (next, 2, 0);
      size = _gnutls_read_uint16 (&data[pos]);
      pos += 2;

      DECR_LENGTH_RET (next, size, 0);
      sdata = &data[pos];
      pos += size;

      ext_recv = _gnutls_ext_func_recv (type, parse_type);
      if (ext_recv == NULL)
        continue;

      _gnutls_handshake_log ("EXT[%p]: Parsing extension '%s/%d' (%d bytes)\n",
                         session, _gnutls_extension_get_name (type), type,
                         size);

      if ((ret = ext_recv (session, sdata, size)) < 0)
        {
          gnutls_assert ();
          return ret;
        }

    }
  while (next > 2);

  return 0;

}

/* Adds the extension we want to send in the extensions list.
 * This list is used to check whether the (later) received
 * extensions are the ones we requested.
 */
void
_gnutls_extension_list_add (gnutls_session_t session, uint16_t type)
{

  if (session->security_parameters.entity == GNUTLS_CLIENT)
    {
      if (session->internals.extensions_sent_size < MAX_EXT_TYPES)
        {
          session->internals.extensions_sent[session->internals.
                                             extensions_sent_size] = type;
          session->internals.extensions_sent_size++;
        }
      else
        {
          _gnutls_handshake_log ("extensions: Increase MAX_EXT_TYPES\n");
        }
    }
}

int
_gnutls_gen_extensions (gnutls_session_t session, gnutls_buffer_st * extdata,
                        gnutls_ext_parse_type_t parse_type)
{
  int size;
  int pos, size_pos, ret;
  size_t i, init_size = extdata->length;

  pos = extdata->length; /* we will store length later on */
  _gnutls_buffer_append_prefix( extdata, 16, 0);

  for (i = 0; i < extfunc_size; i++)
    {
      extension_entry_st *p = &extfunc[i];

      if (p->send_func == NULL)
        continue;

      if (parse_type != GNUTLS_EXT_ANY && p->parse_type != parse_type)
        continue;

      ret = _gnutls_buffer_append_prefix( extdata, 16, p->type);
      if (ret < 0)
        return gnutls_assert_val(ret); 

      size_pos = extdata->length;
      ret = _gnutls_buffer_append_prefix (extdata, 16, 0);
      if (ret < 0)
        return gnutls_assert_val(ret); 

      size = p->send_func (session, extdata);
      /* returning GNUTLS_E_INT_RET_0 means to send an empty
       * extension of this type.
       */
      if (size > 0 || size == GNUTLS_E_INT_RET_0)
        {
          if (size == GNUTLS_E_INT_RET_0)
            size = 0;
            
          /* write the real size */
          _gnutls_write_uint16(size, &extdata->data[size_pos]);
          
          /* add this extension to the extension list
           */
          _gnutls_extension_list_add (session, p->type);

          _gnutls_handshake_log ("EXT[%p]: Sending extension %s (%d bytes)\n",
                             session, p->name, size);
        }
      else if (size < 0)
        {
          gnutls_assert ();
          return size;
        }
      else if (size == 0)
        extdata->length -= 4; /* reset type and size */
    }

  /* remove any initial data, and the size of the header */
  size = extdata->length - init_size - 2;
  
  if ( size > 0)
    _gnutls_write_uint16(size, &extdata->data[pos]);
  else if (size == 0) extdata->length -= 2; /* the length bytes */

  return size;
}

int
_gnutls_ext_init (void)
{
  int ret;

  ret = _gnutls_ext_register (&ext_mod_max_record_size);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;

  ret = _gnutls_ext_register (&ext_mod_status_request);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;

  ret = _gnutls_ext_register (&ext_mod_cert_type);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;

  ret = _gnutls_ext_register (&ext_mod_server_name);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;

  ret = _gnutls_ext_register (&ext_mod_sr);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;

#ifdef ENABLE_SRP
  ret = _gnutls_ext_register (&ext_mod_srp);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;
#endif

  ret = _gnutls_ext_register (&ext_mod_session_ticket);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;

  ret = _gnutls_ext_register (&ext_mod_supported_ecc);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;

  ret = _gnutls_ext_register (&ext_mod_supported_ecc_pf);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;

  ret = _gnutls_ext_register (&ext_mod_sig);
  if (ret != GNUTLS_E_SUCCESS)
    return ret;

  return GNUTLS_E_SUCCESS;
}

void
_gnutls_ext_deinit (void)
{
  gnutls_free (extfunc);
  extfunc = NULL;
  extfunc_size = 0;
}

int
_gnutls_ext_register (extension_entry_st * mod)
{
  extension_entry_st *p;

  p = gnutls_realloc (extfunc, sizeof (*extfunc) * (extfunc_size + 1));
  if (!p)
    {
      gnutls_assert ();
      return GNUTLS_E_MEMORY_ERROR;
    }

  extfunc = p;

  memcpy (&extfunc[extfunc_size], mod, sizeof (*mod));

  extfunc_size++;

  return GNUTLS_E_SUCCESS;
}

int
_gnutls_ext_pack (gnutls_session_t session, gnutls_buffer_st * packed)
{
  unsigned int i;
  int ret;
  extension_priv_data_t data;
  int cur_size;
  int size_offset;
  int total_exts_pos;
  int exts = 0;

  total_exts_pos = packed->length;
  BUFFER_APPEND_NUM (packed, 0);

  for (i = 0; i < extfunc_size; i++)
    {
      ret = _gnutls_ext_get_session_data (session, extfunc[i].type, &data);
      if (ret >= 0 && extfunc[i].pack_func != NULL)
        {
          BUFFER_APPEND_NUM (packed, extfunc[i].type);

          size_offset = packed->length;
          BUFFER_APPEND_NUM (packed, 0);

          cur_size = packed->length;

          ret = extfunc[i].pack_func (data, packed);
          if (ret < 0)
            {
              gnutls_assert ();
              return ret;
            }

          exts++;
          /* write the actual size */
          _gnutls_write_uint32 (packed->length - cur_size,
                                packed->data + size_offset);
        }
    }

  _gnutls_write_uint32 (exts, packed->data + total_exts_pos);

  return 0;

}

void
_gnutls_ext_restore_resumed_session (gnutls_session_t session)
{
  int i;


  /* clear everything except MANDATORY extensions */
  for (i = 0; i < MAX_EXT_TYPES; i++)
    {
      if (session->internals.extension_int_data[i].set != 0 &&
          _gnutls_ext_parse_type (session->internals.
                                  extension_int_data[i].type) !=
          GNUTLS_EXT_MANDATORY)
        {
          _gnutls_ext_unset_session_data (session,
                                          session->
                                          internals.extension_int_data[i].
                                          type);
        }
    }

  /* copy resumed to main */
  for (i = 0; i < MAX_EXT_TYPES; i++)
    {
      if (session->internals.resumed_extension_int_data[i].set != 0 &&
          _gnutls_ext_parse_type (session->
                                  internals.resumed_extension_int_data[i].
                                  type) != GNUTLS_EXT_MANDATORY)
        {
          _gnutls_ext_set_session_data (session,
                                        session->
                                        internals.resumed_extension_int_data
                                        [i].type,
                                        session->
                                        internals.resumed_extension_int_data
                                        [i].priv);
          session->internals.resumed_extension_int_data[i].set = 0;
        }
    }

}


static void
_gnutls_ext_set_resumed_session_data (gnutls_session_t session, uint16_t type,
                                      extension_priv_data_t data)
{
  int i;

  for (i = 0; i < MAX_EXT_TYPES; i++)
    {
      if (session->internals.resumed_extension_int_data[i].type == type
          || session->internals.resumed_extension_int_data[i].set == 0)
        {

          if (session->internals.resumed_extension_int_data[i].set != 0)
            _gnutls_ext_unset_resumed_session_data (session, type);

          session->internals.resumed_extension_int_data[i].type = type;
          session->internals.resumed_extension_int_data[i].priv = data;
          session->internals.resumed_extension_int_data[i].set = 1;
          return;
        }
    }
}

int
_gnutls_ext_unpack (gnutls_session_t session, gnutls_buffer_st * packed)
{
  int i, ret;
  extension_priv_data_t data;
  gnutls_ext_unpack_func unpack;
  int max_exts = 0;
  uint16_t type;
  int size_for_type, cur_pos;


  BUFFER_POP_NUM (packed, max_exts);
  for (i = 0; i < max_exts; i++)
    {
      BUFFER_POP_NUM (packed, type);
      BUFFER_POP_NUM (packed, size_for_type);

      cur_pos = packed->length;

      unpack = _gnutls_ext_func_unpack (type);
      if (unpack == NULL)
        {
          gnutls_assert ();
          return GNUTLS_E_PARSING_ERROR;
        }

      ret = unpack (packed, &data);
      if (ret < 0)
        {
          gnutls_assert ();
          return ret;
        }

      /* verify that unpack read the correct bytes */
      cur_pos = cur_pos - packed->length;
      if (cur_pos /* read length */  != size_for_type)
        {
          gnutls_assert ();
          return GNUTLS_E_PARSING_ERROR;
        }

      _gnutls_ext_set_resumed_session_data (session, type, data);
    }

  return 0;

error:
  return ret;
}

void
_gnutls_ext_unset_session_data (gnutls_session_t session, uint16_t type)
{
  gnutls_ext_deinit_data_func deinit;
  extension_priv_data_t data;
  int ret, i;

  deinit = _gnutls_ext_func_deinit (type);
  ret = _gnutls_ext_get_session_data (session, type, &data);

  if (ret >= 0 && deinit != NULL)
    {
      deinit (data);
    }

  for (i = 0; i < MAX_EXT_TYPES; i++)
    {
      if (session->internals.extension_int_data[i].type == type)
        {
          session->internals.extension_int_data[i].set = 0;
          return;
        }
    }

}

static void
_gnutls_ext_unset_resumed_session_data (gnutls_session_t session,
                                        uint16_t type)
{
  gnutls_ext_deinit_data_func deinit;
  extension_priv_data_t data;
  int ret, i;

  deinit = _gnutls_ext_func_deinit (type);
  ret = _gnutls_ext_get_resumed_session_data (session, type, &data);

  if (ret >= 0 && deinit != NULL)
    {
      deinit (data);
    }

  for (i = 0; i < MAX_EXT_TYPES; i++)
    {
      if (session->internals.resumed_extension_int_data[i].type == type)
        {
          session->internals.resumed_extension_int_data[i].set = 0;
          return;
        }
    }

}

/* Deinitializes all data that are associated with TLS extensions.
 */
void
_gnutls_ext_free_session_data (gnutls_session_t session)
{
  unsigned int i;

  for (i = 0; i < extfunc_size; i++)
    {
      _gnutls_ext_unset_session_data (session, extfunc[i].type);
    }

  for (i = 0; i < extfunc_size; i++)
    {
      _gnutls_ext_unset_resumed_session_data (session, extfunc[i].type);
    }

}

/* This function allows and extension to store data in the current session
 * and retrieve them later on. We use functions instead of a pointer to a
 * private pointer, to allow API additions by individual extensions.
 */
void
_gnutls_ext_set_session_data (gnutls_session_t session, uint16_t type,
                              extension_priv_data_t data)
{
  unsigned int i;
  gnutls_ext_deinit_data_func deinit;

  deinit = _gnutls_ext_func_deinit (type);

  for (i = 0; i < MAX_EXT_TYPES; i++)
    {
      if (session->internals.extension_int_data[i].type == type
          || session->internals.extension_int_data[i].set == 0)
        {
          if (session->internals.extension_int_data[i].set != 0)
            {
              if (deinit)
                deinit (session->internals.extension_int_data[i].priv);
            }
          session->internals.extension_int_data[i].type = type;
          session->internals.extension_int_data[i].priv = data;
          session->internals.extension_int_data[i].set = 1;
          return;
        }
    }
}

int
_gnutls_ext_get_session_data (gnutls_session_t session,
                              uint16_t type, extension_priv_data_t * data)
{
  int i;

  for (i = 0; i < MAX_EXT_TYPES; i++)
    {
      if (session->internals.extension_int_data[i].set != 0 &&
          session->internals.extension_int_data[i].type == type)
        {
          *data = session->internals.extension_int_data[i].priv;
          return 0;
        }
    }
  return GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE;
}

int
_gnutls_ext_get_resumed_session_data (gnutls_session_t session,
                                      uint16_t type,
                                      extension_priv_data_t * data)
{
  int i;

  for (i = 0; i < MAX_EXT_TYPES; i++)
    {
      if (session->internals.resumed_extension_int_data[i].set != 0 &&
          session->internals.resumed_extension_int_data[i].type == type)
        {
          *data = session->internals.resumed_extension_int_data[i].priv;
          return 0;
        }
    }
  return GNUTLS_E_INVALID_REQUEST;
}