/*

 * Copyright (C) 2017-2018 Red Hat, 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 program.  If not, see <https://www.gnu.org/licenses/>

 *

 */

#include "gnutls_int.h"

#include "hello_ext.h"

#include "errors.h"

#include "extv.h"

/* Iterates through all extensions found, and calls the cb()

 * function with their data */

int _gnutls_extv_parse(void *ctx, gnutls_ext_raw_process_func cb,

           const uint8_t *data, int data_size)

{

  int next, ret;

  int pos = 0;

  uint16_t tls_id;

  const uint8_t *sdata;

  uint16_t size;

  if (data_size == 0)

    return 0;

  DECR_LENGTH_RET(data_size, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);

  next = _gnutls_read_uint16(data);

  pos += 2;

  DECR_LENGTH_RET(data_size, next, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);

  if (next == 0 &&

      data_size ==

        0) /* field is present, but has zero length? Ignore it. */

    return 0;

  else if (data_size > 0) /* forbid unaccounted data */

    return gnutls_assert_val(GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);

  do {

    DECR_LENGTH_RET(next, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);

    tls_id = _gnutls_read_uint16(&data[pos]);

    pos += 2;

    DECR_LENGTH_RET(next, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);

    size = _gnutls_read_uint16(&data[pos]);

    pos += 2;

    DECR_LENGTH_RET(next, size,

        GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);

    sdata = &data[pos];

    pos += size;

    ret = cb(ctx, tls_id, sdata, size);

    if (ret < 0)

      return gnutls_assert_val(ret);

  } while (next > 2);

  /* forbid leftovers */

  if (next > 0)

    return gnutls_assert_val(GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);

  return 0;

}

#define HANDSHAKE_SESSION_ID_POS (34)

/**

 * gnutls_ext_raw_parse:

 * @ctx: a pointer to pass to callback function

 * @cb: callback function to process each extension found

 * @data: TLS extension data

 * @flags: should be zero or %GNUTLS_EXT_RAW_FLAG_TLS_CLIENT_HELLO or %GNUTLS_EXT_RAW_FLAG_DTLS_CLIENT_HELLO

 *

 * This function iterates through the TLS extensions as passed in

 * @data, passing the individual extension data to callback. The

 * @data must conform to Extension extensions<0..2^16-1> format.

 *

 * If flags is %GNUTLS_EXT_RAW_TLS_FLAG_CLIENT_HELLO then this function

 * will parse the extension data from the position, as if the packet in

 * @data is a client hello (without record or handshake headers) -

 * as provided by gnutls_handshake_set_hook_function().

 *

 * The return value of the callback will be propagated.

 *

 * Returns: %GNUTLS_E_SUCCESS on success, or an error code. On unknown

 *   flags it returns %GNUTLS_E_INVALID_REQUEST.

 *

 * Since: 3.6.3

 **/

int gnutls_ext_raw_parse(void *ctx, gnutls_ext_raw_process_func cb,

       const gnutls_datum_t *data, unsigned int flags)

{

  if (flags & GNUTLS_EXT_RAW_FLAG_TLS_CLIENT_HELLO) {

    size_t size = data->size;

    size_t len;

    uint8_t *p = data->data;

    DECR_LEN(size, HANDSHAKE_SESSION_ID_POS);

    if (p[0] != 0x03)

      return gnutls_assert_val(

        GNUTLS_E_UNSUPPORTED_VERSION_PACKET);

    p += HANDSHAKE_SESSION_ID_POS;

    /* skip session id */

    DECR_LEN(size, 1);

    len = p[0];

    p++;

    DECR_LEN(size, len);

    p += len;

    /* CipherSuites */

    DECR_LEN(size, 2);

    len = _gnutls_read_uint16(p);

    p += 2;

    DECR_LEN(size, len);

    p += len;

    /* legacy_compression_methods */

    DECR_LEN(size, 1);

    len = p[0];

    p++;

    DECR_LEN(size, len);

    p += len;

    if (size == 0)

      return gnutls_assert_val(

        GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE);

    return _gnutls_extv_parse(ctx, cb, p, size);

  } else if (flags & GNUTLS_EXT_RAW_FLAG_DTLS_CLIENT_HELLO) {

    size_t size = data->size;

    size_t len;

    uint8_t *p = data->data;

    DECR_LEN(size, HANDSHAKE_SESSION_ID_POS);

    if (p[0] != 254)

      return gnutls_assert_val(

        GNUTLS_E_UNSUPPORTED_VERSION_PACKET);

    p += HANDSHAKE_SESSION_ID_POS;

    /* skip session id */

    DECR_LEN(size, 1);

    len = p[0];

    p++;

    DECR_LEN(size, len);

    p += len;

    /* skip cookie */

    DECR_LEN(size, 1);

    len = p[0];

    p++;

    DECR_LEN(size, len);

    p += len;

    /* CipherSuites */

    DECR_LEN(size, 2);

    len = _gnutls_read_uint16(p);

    p += 2;

    DECR_LEN(size, len);

    p += len;

    /* legacy_compression_methods */

    DECR_LEN(size, 1);

    len = p[0];

    p++;

    DECR_LEN(size, len);

    p += len;

    if (size == 0)

      return gnutls_assert_val(

        GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE);

    return _gnutls_extv_parse(ctx, cb, p, size);

  }

  if (flags != 0)

    return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

  return _gnutls_extv_parse(ctx, cb, data->data, data->size);

}

/* Returns:

 *  * On success the number of bytes appended (always positive), or zero if not sent

 *  * On failure, a negative error code.

 */

int _gnutls_extv_append(gnutls_buffer_st *buf, uint16_t tls_id, void *ctx,

      int (*cb)(void *ctx, gnutls_buffer_st *buf))

{

  int size_pos, appended, ret;

  size_t size_prev;

  ret = _gnutls_buffer_append_prefix(buf, 16, tls_id);

  if (ret < 0)

    return gnutls_assert_val(ret);

  size_pos = buf->length;

  ret = _gnutls_buffer_append_prefix(buf, 16, 0);

  if (ret < 0)

    return gnutls_assert_val(ret);

  size_prev = buf->length;

  ret = cb(ctx, buf);

  if (ret < 0 && ret != GNUTLS_E_INT_RET_0) {

    return gnutls_assert_val(ret);

  }

  /* returning GNUTLS_E_INT_RET_0 means to send an empty

   * extension of this type.

   */

  appended = buf->length - size_prev;

  if (appended > 0 || ret == GNUTLS_E_INT_RET_0) {

    if (ret == GNUTLS_E_INT_RET_0)

      appended = 0;

    /* write the real size */

    _gnutls_write_uint16(appended, &buf->data[size_pos]);

  } else if (appended == 0) {

    buf->length -= 4; /* reset type and size */

    return 0;

  }

  return appended + 4;

}