/*

 * Copyright (C) 2001-2018 Free Software Foundation, Inc.

 * Copyright (C) 2015-2018 Red Hat, 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 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/>

 *

 */

/* 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 "hello_ext.h"

#include "errors.h"

#include "ext/max_record.h"

#include <ext/server_name.h>

#include <ext/srp.h>

#include <ext/heartbeat.h>

#include <ext/session_ticket.h>

#include <ext/safe_renegotiation.h>

#include <ext/signature.h>

#include <ext/safe_renegotiation.h>

#include "ext/supported_groups.h"

#include "ext/ec_point_formats.h"

#include <ext/status_request.h>

#include <ext/ext_master_secret.h>

#include <ext/supported_versions.h>

#include <ext/post_handshake.h>

#include <ext/srtp.h>

#include <ext/alpn.h>

#include <ext/dumbfw.h>

#include <ext/key_share.h>

#include <ext/pre_shared_key.h>

#include <ext/psk_ke_modes.h>

#include <ext/etm.h>

#include <ext/cookie.h>

#include <ext/early_data.h>

#include <ext/record_size_limit.h>

#include "extv.h"

#include <num.h>

#include <ext/client_cert_type.h>

#include <ext/server_cert_type.h>

#include <ext/compress_certificate.h>

#include "intprops.h"

static void

unset_ext_data(gnutls_session_t session, const struct hello_ext_entry_st *,

         unsigned idx);

static void unset_resumed_ext_data(gnutls_session_t session,

           const struct hello_ext_entry_st *,

           unsigned idx);

static hello_ext_entry_st const *extfunc[MAX_EXT_TYPES + 1] = {

  [GNUTLS_EXTENSION_EXT_MASTER_SECRET] = &ext_mod_ext_master_secret,

  [GNUTLS_EXTENSION_SUPPORTED_VERSIONS] = &ext_mod_supported_versions,

  [GNUTLS_EXTENSION_POST_HANDSHAKE] = &ext_mod_post_handshake,

  [GNUTLS_EXTENSION_ETM] = &ext_mod_etm,

#ifdef ENABLE_OCSP

  [GNUTLS_EXTENSION_STATUS_REQUEST] = &ext_mod_status_request,

#endif

  [GNUTLS_EXTENSION_SERVER_NAME] = &ext_mod_server_name,

  [GNUTLS_EXTENSION_SAFE_RENEGOTIATION] = &ext_mod_sr,

#ifdef ENABLE_SRP

  [GNUTLS_EXTENSION_SRP] = &ext_mod_srp,

#endif

#ifdef ENABLE_HEARTBEAT

  [GNUTLS_EXTENSION_HEARTBEAT] = &ext_mod_heartbeat,

#endif

  [GNUTLS_EXTENSION_SESSION_TICKET] = &ext_mod_session_ticket,

  [GNUTLS_EXTENSION_CLIENT_CERT_TYPE] = &ext_mod_client_cert_type,

  [GNUTLS_EXTENSION_SERVER_CERT_TYPE] = &ext_mod_server_cert_type,

  [GNUTLS_EXTENSION_SUPPORTED_GROUPS] = &ext_mod_supported_groups,

  [GNUTLS_EXTENSION_SUPPORTED_EC_POINT_FORMATS] =

      &ext_mod_supported_ec_point_formats,

  [GNUTLS_EXTENSION_SIGNATURE_ALGORITHMS] = &ext_mod_sig,

  [GNUTLS_EXTENSION_KEY_SHARE] = &ext_mod_key_share,

  [GNUTLS_EXTENSION_COOKIE] = &ext_mod_cookie,

  [GNUTLS_EXTENSION_EARLY_DATA] = &ext_mod_early_data,

#ifdef ENABLE_DTLS_SRTP

  [GNUTLS_EXTENSION_SRTP] = &ext_mod_srtp,

#endif

#ifdef ENABLE_ALPN

  [GNUTLS_EXTENSION_ALPN] = &ext_mod_alpn,

#endif

  [GNUTLS_EXTENSION_RECORD_SIZE_LIMIT] = &ext_mod_record_size_limit,

  [GNUTLS_EXTENSION_MAX_RECORD_SIZE] = &ext_mod_max_record_size,

  [GNUTLS_EXTENSION_PSK_KE_MODES] = &ext_mod_psk_ke_modes,

  [GNUTLS_EXTENSION_COMPRESS_CERTIFICATE] = &ext_mod_compress_certificate,

  [GNUTLS_EXTENSION_PRE_SHARED_KEY] = &ext_mod_pre_shared_key,

  /* This must be the last extension registered.

   */

  [GNUTLS_EXTENSION_DUMBFW] = &ext_mod_dumbfw,

};

static const hello_ext_entry_st *gid_to_ext_entry(gnutls_session_t session,

              extensions_t id)

{

  unsigned i;

  assert(id < MAX_EXT_TYPES);

  for (i = 0; i < session->internals.rexts_size; i++) {

    if (session->internals.rexts[i].gid == id) {

      return &session->internals.rexts[i];

    }

  }

  return extfunc[id];

}

static const hello_ext_entry_st *tls_id_to_ext_entry(gnutls_session_t session,

                 uint16_t tls_id,

                 gnutls_ext_parse_type_t

                 parse_point)

{

  unsigned i;

  const hello_ext_entry_st *e;

  for (i = 0; i < session->internals.rexts_size; i++) {

    if (session->internals.rexts[i].tls_id == tls_id) {

      e = &session->internals.rexts[i];

      goto done;

    }

  }

  for (i = 0; i < MAX_EXT_TYPES; i++) {

    if (!extfunc[i])

      continue;

    if (extfunc[i]->tls_id == tls_id) {

      e = extfunc[i];

      goto done;

    }

  }

  return NULL;

 done:

  if (parse_point == GNUTLS_EXT_ANY

      || (IS_SERVER(session) && e->server_parse_point == parse_point)

      || (!IS_SERVER(session) && e->client_parse_point == parse_point)) {

    return e;

  } else {

    return NULL;

  }

}

/**

 * gnutls_ext_get_name:

 * @ext: is a TLS extension numeric ID

 *

 * Convert a TLS extension numeric ID to a printable string.

 *

 * Returns: a pointer to a string that contains the name of the

 *   specified cipher, or %NULL.

 **/

const char *gnutls_ext_get_name(unsigned int ext)

{

  size_t i;

  for (i = 0; i < MAX_EXT_TYPES; i++) {

    if (!extfunc[i])

      continue;

    if (extfunc[i]->tls_id == ext)

      return extfunc[i]->name;

  }

  return NULL;

}

/* Returns %GNUTLS_EXTENSION_INVALID on error

 */

static unsigned tls_id_to_gid(gnutls_session_t session, unsigned tls_id)

{

  unsigned i;

  for (i = 0; i < session->internals.rexts_size; i++) {

    if (session->internals.rexts[i].tls_id == tls_id)

      return session->internals.rexts[i].gid;

  }

  for (i = 0; i < MAX_EXT_TYPES; i++) {

    if (!extfunc[i])

      continue;

    if (extfunc[i]->tls_id == tls_id)

      return extfunc[i]->gid;

  }

  return GNUTLS_EXTENSION_INVALID;

}

typedef struct hello_ext_ctx_st {

  gnutls_session_t session;

  gnutls_ext_flags_t msg;

  gnutls_ext_parse_type_t parse_point;

  const hello_ext_entry_st *ext;  /* used during send */

  unsigned seen_pre_shared_key;

} hello_ext_ctx_st;

static

int hello_ext_parse(void *_ctx, unsigned tls_id, const uint8_t * data,

        unsigned data_size)

{

  hello_ext_ctx_st *ctx = _ctx;

  gnutls_session_t session = ctx->session;

  const hello_ext_entry_st *ext;

  int ret;

  if (tls_id == PRE_SHARED_KEY_TLS_ID) {

    ctx->seen_pre_shared_key = 1;

  } else if (ctx->seen_pre_shared_key

       && session->security_parameters.entity == GNUTLS_SERVER) {

    /* the pre-shared key extension must always be the last one,

     * draft-ietf-tls-tls13-28: 4.2.11 */

    return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);

  }

  ext = tls_id_to_ext_entry(session, tls_id, ctx->parse_point);

  if (ext == NULL || ext->recv_func == NULL) {

    goto ignore;

  }

  /* we do not hard fail when extensions defined for TLS are used for

   * DTLS and vice-versa. They may extend their role in the future. */

  if (IS_DTLS(session)) {

    if (!(ext->validity & GNUTLS_EXT_FLAG_DTLS)) {

      gnutls_assert();

      goto ignore;

    }

  } else {

    if (!(ext->validity & GNUTLS_EXT_FLAG_TLS)) {

      gnutls_assert();

      goto ignore;

    }

  }

  if (session->security_parameters.entity == GNUTLS_CLIENT) {

    if (!(ext->validity & GNUTLS_EXT_FLAG_IGNORE_CLIENT_REQUEST) &&

        !_gnutls_hello_ext_is_present(session, ext->gid)) {

      _gnutls_debug_log

          ("EXT[%p]: Received unexpected extension '%s/%d'\n",

           session, ext->name, (int)tls_id);

      return

          gnutls_assert_val

          (GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);

    }

  }

  if ((ext->validity & ctx->msg) == 0) {

    _gnutls_debug_log

        ("EXT[%p]: Received unexpected extension (%s/%d) for '%s'\n",

         session, ext->name, (int)tls_id,

         ext_msg_validity_to_str(ctx->msg));

    return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);

  }

  if (session->security_parameters.entity == GNUTLS_SERVER) {

    ret = _gnutls_hello_ext_save(session, ext->gid, 1);

    if (ret == 0)

      return

          gnutls_assert_val

          (GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);

  }

  _gnutls_handshake_log

      ("EXT[%p]: Parsing extension '%s/%d' (%d bytes)\n",

       session, ext->name, (int)tls_id, data_size);

  _gnutls_ext_set_msg(session, ctx->msg);

  if ((ret = ext->recv_func(session, data, data_size)) < 0) {

    gnutls_assert();

    return ret;

  }

  return 0;

 ignore:

  if (ext) {

    _gnutls_handshake_log

        ("EXT[%p]: Ignoring extension '%s/%d'\n", session,

         ext->name, (int)tls_id);

  }

  return 0;

}

int

_gnutls_parse_hello_extensions(gnutls_session_t session,

             gnutls_ext_flags_t msg,

             gnutls_ext_parse_type_t parse_point,

             const uint8_t * data, int data_size)

{

  int ret;

  hello_ext_ctx_st ctx;

  msg &= GNUTLS_EXT_FLAG_SET_ONLY_FLAGS_MASK;

  ctx.session = session;

  ctx.msg = msg;

  ctx.parse_point = parse_point;

  ctx.seen_pre_shared_key = 0;

  ret = _gnutls_extv_parse(&ctx, hello_ext_parse, data, data_size);

  if (ret < 0)

    return gnutls_assert_val(ret);

  return 0;

}

static

int hello_ext_send(void *_ctx, gnutls_buffer_st * buf)

{

  hello_ext_ctx_st *ctx = _ctx;

  int ret;

  const hello_ext_entry_st *p = ctx->ext;

  gnutls_session_t session = ctx->session;

  int appended;

  size_t size_prev;

  if (unlikely(p->send_func == NULL))

    return 0;

  if (ctx->parse_point != GNUTLS_EXT_ANY &&

      ((IS_SERVER(session) && p->server_parse_point != ctx->parse_point)

       || (!IS_SERVER(session)

     && p->client_parse_point != ctx->parse_point))) {

    return 0;

  }

  if (IS_DTLS(session)) {

    if (!(p->validity & GNUTLS_EXT_FLAG_DTLS)) {

      gnutls_assert();

      goto skip;

    }

  } else {

    if (!(p->validity & GNUTLS_EXT_FLAG_TLS)) {

      gnutls_assert();

      goto skip;

    }

  }

  if ((ctx->msg & p->validity) == 0) {

    goto skip;

  } else {

    _gnutls_handshake_log

        ("EXT[%p]: Preparing extension (%s/%d) for '%s'\n", session,

         p->name, (int)p->tls_id,

         ext_msg_validity_to_str(ctx->msg));

  }

  /* ensure we don't send something twice (i.e, overridden extensions in

   * client), and ensure we are sending only what we received in server. */

  ret = _gnutls_hello_ext_is_present(session, p->gid);

  if (session->security_parameters.entity == GNUTLS_SERVER) {

    /* if client didn't advertise and the override flag is not present */

    if (!(p->validity & GNUTLS_EXT_FLAG_IGNORE_CLIENT_REQUEST)

        && ret == 0)

      return 0;

  } else {

    if (ret != 0) /* already sent */

      return 0;

  }

  size_prev = buf->length;

  _gnutls_ext_set_msg(session, ctx->msg);

  ret = p->send_func(session, buf);

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

    return gnutls_assert_val(ret);

  }

  appended = buf->length - size_prev;

  /* add this extension to the extension list, to know which extensions

   * to expect.

   */

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

      session->security_parameters.entity == GNUTLS_CLIENT) {

    _gnutls_hello_ext_save(session, p->gid, 0);

  }

  return ret;

 skip:

  _gnutls_handshake_log

      ("EXT[%p]: Not sending extension (%s/%d) for '%s'\n", session,

       p->name, (int)p->tls_id, ext_msg_validity_to_str(ctx->msg));

  return 0;

}

int

_gnutls_gen_hello_extensions(gnutls_session_t session,

           gnutls_buffer_st * buf,

           gnutls_ext_flags_t msg,

           gnutls_ext_parse_type_t parse_point)

{

  int pos, ret;

  size_t i;

  hello_ext_ctx_st ctx;

  msg &= GNUTLS_EXT_FLAG_SET_ONLY_FLAGS_MASK;

  ctx.session = session;

  ctx.msg = msg;

  ctx.parse_point = parse_point;

  ret = _gnutls_extv_append_init(buf);

  if (ret < 0)

    return gnutls_assert_val(ret);

  pos = ret;

  _gnutls_ext_set_extensions_offset(session, pos);

  for (i = 0; i < session->internals.rexts_size; i++) {

    ctx.ext = &session->internals.rexts[i];

    ret =

        _gnutls_extv_append(buf, session->internals.rexts[i].tls_id,

          &ctx, hello_ext_send);

    if (ret < 0)

      return gnutls_assert_val(ret);

    if (ret > 0)

      _gnutls_handshake_log

          ("EXT[%p]: Sending extension %s/%d (%d bytes)\n",

           session, ctx.ext->name, (int)ctx.ext->tls_id,

           ret - 4);

  }

  /* hello_ext_send() ensures we don't send duplicates, in case

   * of overridden extensions */

  for (i = 0; i < MAX_EXT_TYPES; i++) {

    if (!extfunc[i])

      continue;

    ctx.ext = extfunc[i];

    ret = _gnutls_extv_append(buf, extfunc[i]->tls_id,

            &ctx, hello_ext_send);

    if (ret < 0)

      return gnutls_assert_val(ret);

    if (ret > 0)

      _gnutls_handshake_log

          ("EXT[%p]: Sending extension %s/%d (%d bytes)\n",

           session, ctx.ext->name, (int)ctx.ext->tls_id,

           ret - 4);

  }

  ret = _gnutls_extv_append_final(buf, pos, !(msg & GNUTLS_EXT_FLAG_EE));

  if (ret < 0)

    return gnutls_assert_val(ret);

  return 0;

}

/* Global deinit and init of global extensions */

int _gnutls_hello_ext_init(void)

{

  return GNUTLS_E_SUCCESS;

}

void _gnutls_hello_ext_deinit(void)

{

  unsigned i;

  for (i = 0; i < MAX_EXT_TYPES; i++) {

    if (!extfunc[i])

      continue;

    if (extfunc[i]->free_struct != 0) {

      gnutls_free(((hello_ext_entry_st *) extfunc[i])->name);

      gnutls_free(extfunc[i]);

    }

  }

}

/* Packing of extension data (for use in resumption) */

static int pack_extension(gnutls_session_t session,

        const hello_ext_entry_st * extp,

        gnutls_buffer_st * packed)

{

  int ret;

  int size_offset;

  int cur_size;

  gnutls_ext_priv_data_t data;

  int rval = 0;

  ret = _gnutls_hello_ext_get_priv(session, extp->gid, &data);

  if (ret >= 0 && extp->pack_func != NULL) {

    BUFFER_APPEND_NUM(packed, extp->gid);

    size_offset = packed->length;

    BUFFER_APPEND_NUM(packed, 0);

    cur_size = packed->length;

    ret = extp->pack_func(data, packed);

    if (ret < 0) {

      gnutls_assert();

      return ret;

    }

    rval = 1;

    /* write the actual size */

    _gnutls_write_uint32(packed->length - cur_size,

             packed->data + size_offset);

  }

  return rval;

}

int _gnutls_hello_ext_pack(gnutls_session_t session, gnutls_buffer_st * packed)

{

  unsigned int i;

  int ret;

  int total_exts_pos;

  int n_exts = 0;

  const struct hello_ext_entry_st *ext;

  total_exts_pos = packed->length;

  BUFFER_APPEND_NUM(packed, 0);

  for (i = 0; i <= GNUTLS_EXTENSION_MAX_VALUE; i++) {

    if (session->internals.used_exts & ((ext_track_t) 1 << i)) {

      ext = gid_to_ext_entry(session, i);

      if (ext == NULL)

        continue;

      ret = pack_extension(session, ext, packed);

      if (ret < 0)

        return gnutls_assert_val(ret);

      if (ret > 0)

        n_exts++;

    }

  }

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

  return 0;

}

int _gnutls_ext_set_full_client_hello(gnutls_session_t session,

              handshake_buffer_st * recv_buf)

{

  int ret;

  gnutls_buffer_st *buf = &session->internals.full_client_hello;

  _gnutls_buffer_clear(buf);

  if ((ret = _gnutls_buffer_append_prefix(buf, 8, recv_buf->htype)) < 0)

    return gnutls_assert_val(ret);

  if ((ret =

       _gnutls_buffer_append_prefix(buf, 24, recv_buf->data.length)) < 0)

    return gnutls_assert_val(ret);

  if ((ret =

       _gnutls_buffer_append_data(buf, recv_buf->data.data,

          recv_buf->data.length)) < 0)

    return gnutls_assert_val(ret);

  return 0;

}

unsigned _gnutls_ext_get_full_client_hello(gnutls_session_t session,

             gnutls_datum_t * d)

{

  gnutls_buffer_st *buf = &session->internals.full_client_hello;

  if (!buf->length)

    return 0;

  d->data = buf->data;

  d->size = buf->length;

  return 1;

}

static void

_gnutls_ext_set_resumed_session_data(gnutls_session_t session,

             extensions_t id,

             gnutls_ext_priv_data_t data)

{

  const struct hello_ext_entry_st *ext;

  /* If this happens we need to increase the max */

  assert(id < MAX_EXT_TYPES);

  ext = gid_to_ext_entry(session, id);

  assert(ext != NULL);

  if (session->internals.ext_data[id].resumed_set != 0)

    unset_resumed_ext_data(session, ext, id);

  session->internals.ext_data[id].resumed_priv = data;

  session->internals.ext_data[id].resumed_set = 1;

  return;

}

int _gnutls_hello_ext_unpack(gnutls_session_t session,

           gnutls_buffer_st * packed)

{

  int i, ret;

  gnutls_ext_priv_data_t data;

  int max_exts = 0;

  extensions_t id;

  int size_for_id, cur_pos;

  const struct hello_ext_entry_st *ext;

  BUFFER_POP_NUM(packed, max_exts);

  for (i = 0; i < max_exts; i++) {

    BUFFER_POP_NUM(packed, id);

    BUFFER_POP_NUM(packed, size_for_id);

    cur_pos = packed->length;

    ext = gid_to_ext_entry(session, id);

    if (ext == NULL || ext->unpack_func == NULL) {

      gnutls_assert();

      return GNUTLS_E_PARSING_ERROR;

    }

    ret = ext->unpack_func(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_id) {

      gnutls_assert();

      return GNUTLS_E_PARSING_ERROR;

    }

    _gnutls_ext_set_resumed_session_data(session, id, data);

  }

  return 0;

 error:

  return ret;

}

static void

unset_ext_data(gnutls_session_t session, const struct hello_ext_entry_st *ext,

         unsigned idx)

{

  if (session->internals.ext_data[idx].set == 0)

    return;

  if (ext && ext->deinit_func

      && session->internals.ext_data[idx].priv != NULL)

    ext->deinit_func(session->internals.ext_data[idx].priv);

  session->internals.ext_data[idx].set = 0;

}

void _gnutls_hello_ext_unset_priv(gnutls_session_t session, extensions_t id)

{

  const struct hello_ext_entry_st *ext;

  ext = gid_to_ext_entry(session, id);

  if (ext)

    unset_ext_data(session, ext, id);

}

static void unset_resumed_ext_data(gnutls_session_t session,

           const struct hello_ext_entry_st *ext,

           unsigned idx)

{

  if (session->internals.ext_data[idx].resumed_set == 0)

    return;

  if (ext && ext->deinit_func

      && session->internals.ext_data[idx].resumed_priv) {

    ext->deinit_func(session->internals.ext_data[idx].resumed_priv);

  }

  session->internals.ext_data[idx].resumed_set = 0;

}

/* Deinitializes all data that are associated with TLS extensions.

 */

void _gnutls_hello_ext_priv_deinit(gnutls_session_t session)

{

  unsigned int i;

  const struct hello_ext_entry_st *ext;

  for (i = 0; i < MAX_EXT_TYPES; i++) {

    if (!session->internals.ext_data[i].set

        && !session->internals.ext_data[i].resumed_set)

      continue;

    ext = gid_to_ext_entry(session, i);

    if (ext) {

      unset_ext_data(session, ext, i);

      unset_resumed_ext_data(session, ext, i);

    }

  }

}

/* This function allows an 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_hello_ext_set_priv(gnutls_session_t session, extensions_t id,

         gnutls_ext_priv_data_t data)

{

  const struct hello_ext_entry_st *ext;

  assert(id < MAX_EXT_TYPES);

  ext = gid_to_ext_entry(session, id);

  assert(ext != NULL);

  if (session->internals.ext_data[id].set != 0) {

    unset_ext_data(session, ext, id);

  }

  session->internals.ext_data[id].priv = data;

  session->internals.ext_data[id].set = 1;

  return;

}

int

_gnutls_hello_ext_get_priv(gnutls_session_t session,

         extensions_t id, gnutls_ext_priv_data_t * data)

{

  if (session->internals.ext_data[id].set != 0) {

    *data = session->internals.ext_data[id].priv;

    return 0;

  }

  return GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE;

}

int

_gnutls_hello_ext_get_resumed_priv(gnutls_session_t session,

           extensions_t id,

           gnutls_ext_priv_data_t * data)

{

  if (session->internals.ext_data[id].resumed_set != 0) {

    *data = session->internals.ext_data[id].resumed_priv;

    return 0;

  }

  return GNUTLS_E_INVALID_REQUEST;

}

/**

 * gnutls_ext_register:

 * @name: the name of the extension to register

 * @id: the numeric TLS id of the extension

 * @parse_point: the parse type of the extension (see gnutls_ext_parse_type_t)

 * @recv_func: a function to receive the data

 * @send_func: a function to send the data

 * @deinit_func: a function deinitialize any private data

 * @pack_func: a function which serializes the extension's private data (used on session packing for resumption)

 * @unpack_func: a function which will deserialize the extension's private data

 *

 * This function will register a new extension type. The extension will remain

 * registered until gnutls_global_deinit() is called. If the extension type

 * is already registered then %GNUTLS_E_ALREADY_REGISTERED will be returned.

 *

 * Each registered extension can store temporary data into the gnutls_session_t

 * structure using gnutls_ext_set_data(), and they can be retrieved using

 * gnutls_ext_get_data().

 *

 * Any extensions registered with this function are valid for the client

 * and TLS1.2 server hello (or encrypted extensions for TLS1.3).

 *

 * This function is not thread safe.

 *

 * Returns: %GNUTLS_E_SUCCESS on success, otherwise a negative error code.

 *

 * Since: 3.4.0

 **/

int

gnutls_ext_register(const char *name, int id,

        gnutls_ext_parse_type_t parse_point,

        gnutls_ext_recv_func recv_func,

        gnutls_ext_send_func send_func,

        gnutls_ext_deinit_data_func deinit_func,

        gnutls_ext_pack_func pack_func,

        gnutls_ext_unpack_func unpack_func)

{

  hello_ext_entry_st *tmp_mod;

  unsigned i;

  unsigned gid = GNUTLS_EXTENSION_MAX + 1;

  for (i = 0; i < MAX_EXT_TYPES; i++) {

    if (!extfunc[i])

      continue;

    if (extfunc[i]->tls_id == id)

      return gnutls_assert_val(GNUTLS_E_ALREADY_REGISTERED);

    if (extfunc[i]->gid >= gid)

      gid = extfunc[i]->gid + 1;

  }

  assert(gid < sizeof(extfunc) / sizeof(extfunc[0]));

  if (gid > GNUTLS_EXTENSION_MAX_VALUE)

    return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

  tmp_mod = gnutls_calloc(1, sizeof(*tmp_mod));

  if (tmp_mod == NULL)

    return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

  tmp_mod->name = gnutls_strdup(name);

  tmp_mod->free_struct = 1;

  tmp_mod->tls_id = id;

  tmp_mod->gid = gid;

  tmp_mod->client_parse_point = parse_point;

  tmp_mod->server_parse_point = parse_point;

  tmp_mod->recv_func = recv_func;

  tmp_mod->send_func = send_func;

  tmp_mod->deinit_func = deinit_func;

  tmp_mod->pack_func = pack_func;

  tmp_mod->unpack_func = unpack_func;

  tmp_mod->validity =

      GNUTLS_EXT_FLAG_CLIENT_HELLO | GNUTLS_EXT_FLAG_TLS12_SERVER_HELLO |

      GNUTLS_EXT_FLAG_EE | GNUTLS_EXT_FLAG_DTLS | GNUTLS_EXT_FLAG_TLS;

  assert(extfunc[gid] == NULL);

  extfunc[gid] = tmp_mod;

  return 0;

}

#define VALIDITY_MASK (GNUTLS_EXT_FLAG_CLIENT_HELLO | GNUTLS_EXT_FLAG_TLS12_SERVER_HELLO | \

      GNUTLS_EXT_FLAG_TLS13_SERVER_HELLO | \

      GNUTLS_EXT_FLAG_EE | GNUTLS_EXT_FLAG_HRR)

/**

 * gnutls_session_ext_register:

 * @session: the session for which this extension will be set

 * @name: the name of the extension to register

 * @id: the numeric id of the extension

 * @parse_point: the parse type of the extension (see gnutls_ext_parse_type_t)

 * @recv_func: a function to receive the data

 * @send_func: a function to send the data

 * @deinit_func: a function deinitialize any private data

 * @pack_func: a function which serializes the extension's private data (used on session packing for resumption)

 * @unpack_func: a function which will deserialize the extension's private data

 * @flags: must be zero or flags from %gnutls_ext_flags_t

 *

 * This function will register a new extension type. The extension will be

 * only usable within the registered session. If the extension type

 * is already registered then %GNUTLS_E_ALREADY_REGISTERED will be returned,

 * unless the flag %GNUTLS_EXT_FLAG_OVERRIDE_INTERNAL is specified. The latter

 * flag when specified can be used to override certain extensions introduced

 * after 3.6.0. It is expected to be used by applications which handle

 * custom extensions that are not currently supported in GnuTLS, but direct

 * support for them may be added in the future.

 *

 * Each registered extension can store temporary data into the gnutls_session_t

 * structure using gnutls_ext_set_data(), and they can be retrieved using

 * gnutls_ext_get_data().

 *

 * The validity of the extension registered can be given by the appropriate flags

 * of %gnutls_ext_flags_t. If no validity is given, then the registered extension

 * will be valid for client and TLS1.2 server hello (or encrypted extensions for TLS1.3).

 *

 * Returns: %GNUTLS_E_SUCCESS on success, otherwise a negative error code.

 *

 * Since: 3.5.5

 **/

int

gnutls_session_ext_register(gnutls_session_t session,

          const char *name, int id,

          gnutls_ext_parse_type_t parse_point,

          gnutls_ext_recv_func recv_func,

          gnutls_ext_send_func send_func,

          gnutls_ext_deinit_data_func deinit_func,

          gnutls_ext_pack_func pack_func,

          gnutls_ext_unpack_func unpack_func, unsigned flags)

{

  hello_ext_entry_st tmp_mod;

  hello_ext_entry_st *exts;

  unsigned i;

  unsigned gid = GNUTLS_EXTENSION_MAX + 1;

  /* reject handling any extensions which modify the TLS handshake

   * in any way, or are mapped to an exported API. */

  for (i = 0; i < GNUTLS_EXTENSION_MAX; i++) {

    if (!extfunc[i])

      continue;

    if (extfunc[i]->tls_id == id) {

      if (!(flags & GNUTLS_EXT_FLAG_OVERRIDE_INTERNAL)) {

        return

            gnutls_assert_val

            (GNUTLS_E_ALREADY_REGISTERED);

      } else if (extfunc[i]->cannot_be_overriden) {

        return

            gnutls_assert_val