/src/gnutls/lib/hello_ext.c

Source
/*
 * 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_assert(GNUTLS_EXTENSION_MAX < GNUTLS_EXTENSION_MAX_VALUE);
static_assert(GNUTLS_EXTENSION_MAX < MAX_EXT_TYPES);

/* we must provide at least 16 extensions for users to register;
 * increase GNUTLS_EXTENSION_MAX_VALUE, MAX_EXT_TYPES and used_exts
 * type if this fails
 */
static_assert(GNUTLS_EXTENSION_MAX_VALUE - GNUTLS_EXTENSION_MAX >= 16);

/* MAX_EXT_TYPES must fit in a single byte, to generate random
 * permutation at once.
 */
static_assert(MAX_EXT_TYPES <= UINT8_MAX);

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;
}

static inline void swap_exts(extensions_t *exts, size_t index1, size_t index2)
{
  extensions_t temp = exts[index1];
  exts[index1] = exts[index2];
  exts[index2] = temp;
}

static int shuffle_exts(extensions_t *exts, size_t size)
{
  uint8_t permutation[MAX_EXT_TYPES];
  size_t i;
  int ret;

  assert(size <= MAX_EXT_TYPES);

  if (unlikely(size == 0))
    return 0;

  /* Generate random permutation, assuming MAX_EXT_TYPES <=
   * UINT8_MAX.
   */
  ret = gnutls_rnd(GNUTLS_RND_RANDOM, permutation, size);
  if (ret < 0)
    return gnutls_assert_val(ret);

  for (i = size - 1; i > 0; i--) {
    extensions_t j = permutation[i] % (i + 1);
    swap_exts(exts, i, j);
  }

  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);
  }

  if (msg & GNUTLS_EXT_FLAG_CLIENT_HELLO &&
      !session->internals.client_hello_exts_set) {
    /* Initializing extensions array */
    for (i = 0; i < MAX_EXT_TYPES; i++) {
      session->internals.client_hello_exts[i] = i;
    }

    if (!session->internals.priorities->no_shuffle_extensions) {
      /* Ordering padding and pre_shared_key as last extensions */
      swap_exts(session->internals.client_hello_exts,
          MAX_EXT_TYPES - 2, GNUTLS_EXTENSION_DUMBFW);
      swap_exts(session->internals.client_hello_exts,
          MAX_EXT_TYPES - 1,
          GNUTLS_EXTENSION_PRE_SHARED_KEY);

      ret = shuffle_exts(session->internals.client_hello_exts,
             MAX_EXT_TYPES - 2);
      if (ret < 0)
        return gnutls_assert_val(ret);
    }
    session->internals.client_hello_exts_set = true;
  }

  /* hello_ext_send() ensures we don't send duplicates, in case
   * of overridden extensions */
  for (i = 0; i < MAX_EXT_TYPES; i++) {
    size_t ii;

    if (msg & GNUTLS_EXT_FLAG_CLIENT_HELLO)
      ii = session->internals.client_hello_exts[i];
    else
      ii = i;

    if (!extfunc[ii])
      continue;

    ctx.ext = extfunc[ii];
    ret = _gnutls_extv_append(buf, extfunc[ii]->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);
  if (tmp_mod->name == NULL) {
    gnutls_free(tmp_mod);
    return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);
  }

  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(
          GNUTLS_E_ALREADY_REGISTERED);
      }
      break;
    }

    if (extfunc[i]->gid >= gid)
      gid = extfunc[i]->gid + 1;
  }

  for (i = 0; i < session->internals.rexts_size; i++) {
    if (session->internals.rexts[i].tls_id == id) {
      return gnutls_assert_val(GNUTLS_E_ALREADY_REGISTERED);
    }

    if (session->internals.rexts[i].gid >= gid)
      gid = session->internals.rexts[i].gid + 1;
  }

  if (gid > GNUTLS_EXTENSION_MAX_VALUE)
    return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

  memset(&tmp_mod, 0, sizeof(hello_ext_entry_st));
  tmp_mod.name = gnutls_strdup(name);
  if (tmp_mod.name == NULL)
    return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

  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 = flags;

  if ((tmp_mod.validity & VALIDITY_MASK) == 0) {
    tmp_mod.validity = GNUTLS_EXT_FLAG_CLIENT_HELLO |
           GNUTLS_EXT_FLAG_TLS12_SERVER_HELLO |
           GNUTLS_EXT_FLAG_EE;
  }

  if ((tmp_mod.validity & (GNUTLS_EXT_FLAG_DTLS | GNUTLS_EXT_FLAG_TLS)) ==
      0) {
    if (IS_DTLS(session))
      tmp_mod.validity |= GNUTLS_EXT_FLAG_DTLS;
    else
      tmp_mod.validity |= GNUTLS_EXT_FLAG_TLS;
  }

  if (unlikely(INT_ADD_OVERFLOW(session->internals.rexts_size, 1))) {
    gnutls_free(tmp_mod.name);
    return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);
  }

  exts = _gnutls_reallocarray(session->internals.rexts,
            session->internals.rexts_size + 1,
            sizeof(*exts));
  if (exts == NULL) {
    gnutls_free(tmp_mod.name);
    return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);
  }

  session->internals.rexts = exts;

  memcpy(&session->internals.rexts[session->internals.rexts_size],
         &tmp_mod, sizeof(hello_ext_entry_st));
  session->internals.rexts_size++;

  return 0;
}

/**
 * gnutls_ext_set_data:
 * @session: a #gnutls_session_t opaque pointer
 * @tls_id: the numeric id of the extension
 * @data: the private data to set
 *
 * This function allows an extension handler to store data in the current session
 * and retrieve them later on. The set data will be deallocated using
 * the gnutls_ext_deinit_data_func.
 *
 * Since: 3.4.0
 **/
void gnutls_ext_set_data(gnutls_session_t session, unsigned tls_id,
       gnutls_ext_priv_data_t data)
{
  unsigned id = tls_id_to_gid(session, tls_id);
  if (id == GNUTLS_EXTENSION_INVALID)
    return;

  _gnutls_hello_ext_set_priv(session, id, data);
}

/**
 * gnutls_ext_get_data:
 * @session: a #gnutls_session_t opaque pointer
 * @tls_id: the numeric id of the extension
 * @data: a pointer to the private data to retrieve
 *
 * This function retrieves any data previously stored with gnutls_ext_set_data().
 *
 * Returns: %GNUTLS_E_SUCCESS on success, otherwise a negative error code.
 *
 * Since: 3.4.0
 **/
int gnutls_ext_get_data(gnutls_session_t session, unsigned tls_id,
      gnutls_ext_priv_data_t *data)
{
  unsigned id = tls_id_to_gid(session, tls_id);
  if (id == GNUTLS_EXTENSION_INVALID)
    return gnutls_assert_val(GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE);

  return _gnutls_hello_ext_get_priv(session, id, data);
}

/**
 * gnutls_ext_get_current_msg:
 * @session: a #gnutls_session_t opaque pointer
 *
 * This function allows an extension handler to obtain the message
 * this extension is being called from. The returned value is a single
 * entry of the %gnutls_ext_flags_t enumeration. That is, if an
 * extension was registered with the %GNUTLS_EXT_FLAG_HRR and
 * %GNUTLS_EXT_FLAG_EE flags, the value when called during parsing of the
 * encrypted extensions message will be %GNUTLS_EXT_FLAG_EE.
 *
 * If not called under an extension handler, its value is undefined.
 *
 * Since: 3.6.3
 **/
unsigned gnutls_ext_get_current_msg(gnutls_session_t session)
{
  return _gnutls_ext_get_msg(session);
}

/**
 * gnutls_ext_get_name2:
 * @session: a #gnutls_session_t opaque pointer
 * @tls_id: is a TLS extension numeric ID
 * @parse_point: the parse type of the extension
 *
 * 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_name2(gnutls_session_t session, unsigned int tls_id,
         gnutls_ext_parse_type_t parse_point)
{
  const struct hello_ext_entry_st *ext;

  ext = tls_id_to_ext_entry(session, tls_id, parse_point);
  if (ext)
    return ext->name;

  return NULL;
}

Coverage Report

Created: 2026-05-16 06:55