/src/gnutls/lib/kx.c

Source
/*
 * Copyright (C) 2000-2012 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 program.  If not, see <https://www.gnu.org/licenses/>
 *
 */

/* This file contains functions which are wrappers for the key exchange
 * part of TLS. They are called by the handshake functions (gnutls_handshake)
 */

#include "gnutls_int.h"
#include "handshake.h"
#include "kx.h"
#include "dh.h"
#include "errors.h"
#include "algorithms.h"
#include "debug.h"
#include "locks.h"
#include "mpi.h"
#include "state.h"
#include "datum.h"
#include "mbuffers.h"

/* This file contains important thing for the TLS handshake procedure.
 */

#define MASTER_SECRET "master secret"
#define MASTER_SECRET_SIZE (sizeof(MASTER_SECRET) - 1)

#define EXT_MASTER_SECRET "extended master secret"
#define EXT_MASTER_SECRET_SIZE (sizeof(EXT_MASTER_SECRET) - 1)

GNUTLS_STATIC_MUTEX(keylog_mutex);
static FILE *keylog;

static int generate_normal_master(gnutls_session_t session, gnutls_datum_t *,
          int);

int _gnutls_generate_master(gnutls_session_t session, int keep_premaster)
{
  if (!session->internals.resumed)
    return generate_normal_master(session, &session->key.key,
                keep_premaster);
  else if (session->internals.premaster_set) {
    gnutls_datum_t premaster;
    premaster.size =
      sizeof(session->internals.resumed_security_parameters
               .master_secret);
    premaster.data = session->internals.resumed_security_parameters
           .master_secret;
    return generate_normal_master(session, &premaster, 1);
  }
  return 0;
}

/**
 * gnutls_session_get_keylog_function:
 * @session: is #gnutls_session_t type
 *
 * This function will return the callback function set using
 * gnutls_session_set_keylog_function().
 *
 * Returns: The function set or %NULL otherwise.
 *
 * Since: 3.6.13
 */
gnutls_keylog_func
gnutls_session_get_keylog_function(const gnutls_session_t session)
{
  return session->internals.keylog_func;
}

/**
 * gnutls_session_set_keylog_function:
 * @session: is #gnutls_session_t type
 * @func: is the function to be called
 *
 * This function will set a callback to be called when a new secret is
 * derived and installed during handshake.
 *
 * Since: 3.6.13
 */
void gnutls_session_set_keylog_function(gnutls_session_t session,
          gnutls_keylog_func func)
{
  session->internals.keylog_func = func;
}

int _gnutls_call_keylog_func(gnutls_session_t session, const char *label,
           const uint8_t *data, unsigned size)
{
  if (session->internals.keylog_func) {
    gnutls_datum_t secret = { (void *)data, size };
    return session->internals.keylog_func(session, label, &secret);
  }
  return 0;
}

int _gnutls_nss_keylog_func(gnutls_session_t session, const char *label,
          const gnutls_datum_t *secret)
{
  /* ignore subsequent traffic secrets that are calculated from
   * the previous traffic secret
   */
  if (!session->internals.handshake_in_progress)
    return 0;

  _gnutls_nss_keylog_write(session, label, secret->data, secret->size);
  return 0;
}

/* GCC analyzer doesn't like static FILE pointer */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wanalyzer-file-leak"

GNUTLS_ONCE(keylog_once);

static void keylog_once_init(void)
{
  const char *keylogfile;

  keylogfile = secure_getenv("SSLKEYLOGFILE");
  if (keylogfile != NULL && *keylogfile != '\0') {
    keylog = fopen(keylogfile, "ae");
    _gnutls_debug_log("unable to open keylog file %s\n",
          keylogfile);
  }
}

void _gnutls_nss_keylog_write(gnutls_session_t session, const char *label,
            const uint8_t *secret, size_t secret_size)
{
  (void)gnutls_once(&keylog_once, keylog_once_init);

  if (keylog) {
    char client_random_hex[2 * GNUTLS_RANDOM_SIZE + 1];
    char secret_hex[2 * MAX_HASH_SIZE + 1];

    if (gnutls_static_mutex_lock(&keylog_mutex) < 0) {
      return;
    }
    fprintf(keylog, "%s %s %s\n", label,
      _gnutls_bin2hex(
        session->security_parameters.client_random,
        GNUTLS_RANDOM_SIZE, client_random_hex,
        sizeof(client_random_hex), NULL),
      _gnutls_bin2hex(secret, secret_size, secret_hex,
          sizeof(secret_hex), NULL));
    fflush(keylog);
    (void)gnutls_static_mutex_unlock(&keylog_mutex);
  }
}

void _gnutls_nss_keylog_deinit(void)
{
  if (keylog) {
    fclose(keylog);
    keylog = NULL;
  }
}

#pragma GCC diagnostic pop

/* here we generate the TLS Master secret.
 */
static int generate_normal_master(gnutls_session_t session,
          gnutls_datum_t *premaster, int keep_premaster)
{
  int ret = 0;
  char buf[512];

  _gnutls_hard_log("INT: PREMASTER SECRET[%d]: %s\n", premaster->size,
       _gnutls_bin2hex(premaster->data, premaster->size, buf,
           sizeof(buf), NULL));
  _gnutls_hard_log(
    "INT: CLIENT RANDOM[%d]: %s\n", 32,
    _gnutls_bin2hex(session->security_parameters.client_random, 32,
        buf, sizeof(buf), NULL));
  _gnutls_hard_log(
    "INT: SERVER RANDOM[%d]: %s\n", 32,
    _gnutls_bin2hex(session->security_parameters.server_random, 32,
        buf, sizeof(buf), NULL));

  if (session->security_parameters.ext_master_secret == 0) {
    uint8_t rnd[2 * GNUTLS_RANDOM_SIZE + 1];
    memcpy(rnd, session->security_parameters.client_random,
           GNUTLS_RANDOM_SIZE);
    memcpy(&rnd[GNUTLS_RANDOM_SIZE],
           session->security_parameters.server_random,
           GNUTLS_RANDOM_SIZE);

    _gnutls_memory_mark_defined(
      session->security_parameters.master_secret,
      GNUTLS_MASTER_SIZE);
#ifdef ENABLE_SSL3
    if (get_num_version(session) == GNUTLS_SSL3) {
      ret = _gnutls_ssl3_generate_random(
        premaster->data, premaster->size, rnd,
        2 * GNUTLS_RANDOM_SIZE, GNUTLS_MASTER_SIZE,
        session->security_parameters.master_secret);
    } else
#endif
      ret = _gnutls_PRF(
        session, premaster->data, premaster->size,
        MASTER_SECRET, MASTER_SECRET_SIZE, rnd,
        2 * GNUTLS_RANDOM_SIZE, GNUTLS_MASTER_SIZE,
        session->security_parameters.master_secret);
    if (ret < 0)
      _gnutls_memory_mark_undefined(
        session->security_parameters.master_secret,
        GNUTLS_MASTER_SIZE);
  } else {
    gnutls_datum_t shash = { NULL, 0 };

    /* draft-ietf-tls-session-hash-02 */
    ret = _gnutls_handshake_get_session_hash(session, &shash);
    if (ret < 0)
      return gnutls_assert_val(ret);
#ifdef ENABLE_SSL3
    if (get_num_version(session) == GNUTLS_SSL3)
      return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
#endif

    _gnutls_memory_mark_defined(
      session->security_parameters.master_secret,
      GNUTLS_MASTER_SIZE);
    ret = _gnutls_PRF(session, premaster->data, premaster->size,
          EXT_MASTER_SECRET, EXT_MASTER_SECRET_SIZE,
          shash.data, shash.size, GNUTLS_MASTER_SIZE,
          session->security_parameters.master_secret);
    if (ret < 0)
      _gnutls_memory_mark_undefined(
        session->security_parameters.master_secret,
        GNUTLS_MASTER_SIZE);

    gnutls_free(shash.data);
  }

  if (!keep_premaster)
    _gnutls_free_key_datum(premaster);

  if (ret < 0)
    return ret;

  ret = _gnutls_call_keylog_func(
    session, "CLIENT_RANDOM",
    session->security_parameters.master_secret, GNUTLS_MASTER_SIZE);
  if (ret < 0)
    return gnutls_assert_val(ret);

  _gnutls_hard_log(
    "INT: MASTER SECRET[%d]: %s\n", GNUTLS_MASTER_SIZE,
    _gnutls_bin2hex(session->security_parameters.master_secret,
        GNUTLS_MASTER_SIZE, buf, sizeof(buf), NULL));

  return ret;
}

/* This is called when we want to receive the key exchange message of the
 * server. It does nothing if this type of message is not required
 * by the selected ciphersuite. 
 */
int _gnutls_send_server_kx_message(gnutls_session_t session, int again)
{
  gnutls_buffer_st buf;
  int ret = 0;
  mbuffer_st *bufel = NULL;

  if (session->internals.auth_struct->gnutls_generate_server_kx == NULL)
    return 0;

  if (again == 0) {
    ret = _gnutls_buffer_init_handshake_mbuffer(&buf);
    if (ret < 0)
      return gnutls_assert_val(ret);

    ret = session->internals.auth_struct->gnutls_generate_server_kx(
      session, &buf);

    if (ret == GNUTLS_E_INT_RET_0) {
      gnutls_assert();
      ret = 0;
      goto cleanup;
    }

    if (ret < 0) {
      gnutls_assert();
      goto cleanup;
    }

    bufel = _gnutls_buffer_to_mbuffer(&buf);
  }

  return _gnutls_send_handshake(session, bufel,
              GNUTLS_HANDSHAKE_SERVER_KEY_EXCHANGE);

cleanup:
  _gnutls_buffer_clear(&buf);
  return ret;
}

/* This function sends a certificate request message to the
 * client.
 */
int _gnutls_send_server_crt_request(gnutls_session_t session, int again)
{
  gnutls_buffer_st buf;
  int ret = 0;
  mbuffer_st *bufel = NULL;

  if (session->internals.auth_struct->gnutls_generate_server_crt_request ==
      NULL)
    return 0;

  if (session->internals.send_cert_req <= 0)
    return 0;

  if (again == 0) {
    ret = _gnutls_buffer_init_handshake_mbuffer(&buf);
    if (ret < 0)
      return gnutls_assert_val(ret);

    ret = session->internals.auth_struct
            ->gnutls_generate_server_crt_request(session,
                   &buf);

    if (ret < 0) {
      gnutls_assert();
      goto cleanup;
    }

    bufel = _gnutls_buffer_to_mbuffer(&buf);
  }

  return _gnutls_send_handshake(session, bufel,
              GNUTLS_HANDSHAKE_CERTIFICATE_REQUEST);

cleanup:
  _gnutls_buffer_clear(&buf);
  return ret;
}

/* This is the function for the client to send the key
 * exchange message 
 */
int _gnutls_send_client_kx_message(gnutls_session_t session, int again)
{
  gnutls_buffer_st buf;
  int ret = 0;
  mbuffer_st *bufel = NULL;

  if (session->internals.auth_struct->gnutls_generate_client_kx == NULL)
    return 0;

  if (again == 0) {
    ret = _gnutls_buffer_init_handshake_mbuffer(&buf);
    if (ret < 0)
      return gnutls_assert_val(ret);

    ret = session->internals.auth_struct->gnutls_generate_client_kx(
      session, &buf);
    if (ret < 0) {
      gnutls_assert();
      goto cleanup;
    }

    bufel = _gnutls_buffer_to_mbuffer(&buf);
  }

  return _gnutls_send_handshake(session, bufel,
              GNUTLS_HANDSHAKE_CLIENT_KEY_EXCHANGE);

cleanup:
  _gnutls_buffer_clear(&buf);
  return ret;
}

/* This is the function for the client to send the certificate
 * verify message
 */
int _gnutls_send_client_certificate_verify(gnutls_session_t session, int again)
{
  gnutls_buffer_st buf;
  int ret = 0;
  mbuffer_st *bufel = NULL;

  /* This is a packet that is only sent by the client
   */
  if (session->security_parameters.entity == GNUTLS_SERVER)
    return 0;

  /* if certificate verify is not needed just exit 
   */
  if (!(session->internals.hsk_flags & HSK_CRT_ASKED))
    return 0;

  if (session->internals.auth_struct->gnutls_generate_client_crt_vrfy ==
      NULL) {
    gnutls_assert();
    return 0; /* this algorithm does not support cli_crt_vrfy 
         */
  }

  if (again == 0) {
    ret = _gnutls_buffer_init_handshake_mbuffer(&buf);
    if (ret < 0)
      return gnutls_assert_val(ret);

    ret = session->internals.auth_struct
            ->gnutls_generate_client_crt_vrfy(session, &buf);
    if (ret < 0) {
      gnutls_assert();
      goto cleanup;
    }

    if (ret == 0)
      goto cleanup;

    bufel = _gnutls_buffer_to_mbuffer(&buf);
  }

  return _gnutls_send_handshake(session, bufel,
              GNUTLS_HANDSHAKE_CERTIFICATE_VERIFY);

cleanup:
  _gnutls_buffer_clear(&buf);
  return ret;
}

/* This is called when we want send our certificate
 */
int _gnutls_send_client_certificate(gnutls_session_t session, int again)
{
  gnutls_buffer_st buf;
  int ret = 0;
  mbuffer_st *bufel = NULL;

  if (!(session->internals.hsk_flags & HSK_CRT_ASKED))
    return 0;

  if (session->internals.auth_struct->gnutls_generate_client_certificate ==
      NULL)
    return 0;

  if (again == 0) {
    ret = _gnutls_buffer_init_handshake_mbuffer(&buf);
    if (ret < 0)
      return gnutls_assert_val(ret);

#ifdef ENABLE_SSL3
    if (get_num_version(session) != GNUTLS_SSL3 ||
        session->internals.selected_cert_list_length > 0)
#endif
    {
      /* TLS 1.x or SSL 3.0 with a valid certificate 
       */
      ret = session->internals.auth_struct
              ->gnutls_generate_client_certificate(
                session, &buf);

      if (ret < 0) {
        gnutls_assert();
        goto cleanup;
      }
    }

    bufel = _gnutls_buffer_to_mbuffer(&buf);
  }
#ifdef ENABLE_SSL3
  /* In the SSL 3.0 protocol we need to send a
   * no certificate alert instead of an
   * empty certificate.
   */
  if (get_num_version(session) == GNUTLS_SSL3 &&
      session->internals.selected_cert_list_length == 0) {
    _mbuffer_xfree(&bufel);
    return gnutls_alert_send(session, GNUTLS_AL_WARNING,
           GNUTLS_A_SSL3_NO_CERTIFICATE);

  } else /* TLS 1.0 or SSL 3.0 with a valid certificate 
         */
#endif
    return _gnutls_send_handshake(session, bufel,
                GNUTLS_HANDSHAKE_CERTIFICATE_PKT);

cleanup:
  _gnutls_buffer_clear(&buf);
  return ret;
}

/* This is called when we want send our certificate
 */
int _gnutls_send_server_certificate(gnutls_session_t session, int again)
{
  gnutls_buffer_st buf;
  int ret = 0;
  mbuffer_st *bufel = NULL;

  if (session->internals.auth_struct->gnutls_generate_server_certificate ==
      NULL)
    return 0;

  if (again == 0) {
    ret = _gnutls_buffer_init_handshake_mbuffer(&buf);
    if (ret < 0)
      return gnutls_assert_val(ret);

    ret = session->internals.auth_struct
            ->gnutls_generate_server_certificate(session,
                   &buf);

    if (ret < 0) {
      gnutls_assert();
      goto cleanup;
    }

    bufel = _gnutls_buffer_to_mbuffer(&buf);
  }

  return _gnutls_send_handshake(session, bufel,
              GNUTLS_HANDSHAKE_CERTIFICATE_PKT);

cleanup:
  _gnutls_buffer_clear(&buf);
  return ret;
}

int _gnutls_recv_server_kx_message(gnutls_session_t session)
{
  gnutls_buffer_st buf;
  int ret = 0;
  unsigned int optflag = 0;

  if (session->internals.auth_struct->gnutls_process_server_kx != NULL) {
    /* Server key exchange packet is optional for PSK. */
    if (_gnutls_session_is_psk(session))
      optflag = 1;

    ret = _gnutls_recv_handshake(
      session, GNUTLS_HANDSHAKE_SERVER_KEY_EXCHANGE, optflag,
      &buf);
    if (ret < 0) {
      gnutls_assert();
      return ret;
    }

    ret = session->internals.auth_struct->gnutls_process_server_kx(
      session, buf.data, buf.length);
    _gnutls_buffer_clear(&buf);

    if (ret < 0) {
      gnutls_assert();
      return ret;
    }
  }
  return ret;
}

int _gnutls_recv_server_crt_request(gnutls_session_t session)
{
  gnutls_buffer_st buf;
  int ret = 0;

  if (session->internals.auth_struct->gnutls_process_server_crt_request !=
      NULL) {
    ret = _gnutls_recv_handshake(
      session, GNUTLS_HANDSHAKE_CERTIFICATE_REQUEST, 1, &buf);
    if (ret < 0)
      return ret;

    if (ret == 0 && buf.length == 0) {
      _gnutls_buffer_clear(&buf);
      return 0; /* ignored */
    }

    ret = session->internals.auth_struct
            ->gnutls_process_server_crt_request(
              session, buf.data, buf.length);
    _gnutls_buffer_clear(&buf);
    if (ret < 0)
      return ret;
  }
  return ret;
}

int _gnutls_recv_client_kx_message(gnutls_session_t session)
{
  gnutls_buffer_st buf;
  int ret = 0;

  /* Do key exchange only if the algorithm permits it */
  if (session->internals.auth_struct->gnutls_process_client_kx != NULL) {
    ret = _gnutls_recv_handshake(
      session, GNUTLS_HANDSHAKE_CLIENT_KEY_EXCHANGE, 0, &buf);
    if (ret < 0)
      return ret;

    ret = session->internals.auth_struct->gnutls_process_client_kx(
      session, buf.data, buf.length);
    _gnutls_buffer_clear(&buf);
    if (ret < 0)
      return ret;
  }

  return ret;
}

int _gnutls_recv_client_certificate(gnutls_session_t session)
{
  gnutls_buffer_st buf;
  int ret = 0;
  int optional;

  if (session->internals.auth_struct->gnutls_process_client_certificate ==
      NULL)
    return 0;

  /* if we have not requested a certificate then just return
   */
  if (session->internals.send_cert_req == 0) {
    return 0;
  }

  if (session->internals.send_cert_req == GNUTLS_CERT_REQUIRE)
    optional = 0;
  else
    optional = 1;

  ret = _gnutls_recv_handshake(session, GNUTLS_HANDSHAKE_CERTIFICATE_PKT,
             optional, &buf);

  if (ret < 0) {
    /* Handle the case of old SSL3 clients who send
     * a warning alert instead of an empty certificate to indicate
     * no certificate.
     */
#ifdef ENABLE_SSL3
    if (optional != 0 && ret == GNUTLS_E_WARNING_ALERT_RECEIVED &&
        get_num_version(session) == GNUTLS_SSL3 &&
        gnutls_alert_get(session) == GNUTLS_A_SSL3_NO_CERTIFICATE) {
      /* SSL3 does not send an empty certificate,
       * but this alert. So we just ignore it.
       */
      gnutls_assert();
      return 0;
    }
#endif

    /* certificate was required 
     */
    if ((ret == GNUTLS_E_WARNING_ALERT_RECEIVED ||
         ret == GNUTLS_E_FATAL_ALERT_RECEIVED) &&
        optional == 0) {
      gnutls_assert();
      return GNUTLS_E_NO_CERTIFICATE_FOUND;
    }

    return ret;
  }

  if (ret == 0 && buf.length == 0 && optional != 0) {
    /* Client has not sent the certificate message.
     * well I'm not sure we should accept this
     * behaviour.
     */
    gnutls_assert();
    ret = 0;
    goto cleanup;
  }
  ret = session->internals.auth_struct->gnutls_process_client_certificate(
    session, buf.data, buf.length);

  if (ret < 0 && ret != GNUTLS_E_NO_CERTIFICATE_FOUND) {
    gnutls_assert();
    goto cleanup;
  }

  /* ok we should expect a certificate verify message now 
   */
  if (ret == GNUTLS_E_NO_CERTIFICATE_FOUND && optional != 0)
    ret = 0;
  else
    session->internals.hsk_flags |= HSK_CRT_VRFY_EXPECTED;

cleanup:
  _gnutls_buffer_clear(&buf);
  return ret;
}

int _gnutls_recv_server_certificate(gnutls_session_t session)
{
  gnutls_buffer_st buf;
  int ret = 0;

  if (session->internals.auth_struct->gnutls_process_server_certificate !=
      NULL) {
    ret = _gnutls_recv_handshake(
      session, GNUTLS_HANDSHAKE_CERTIFICATE_PKT, 0, &buf);
    if (ret < 0) {
      gnutls_assert();
      return ret;
    }

    ret = session->internals.auth_struct
            ->gnutls_process_server_certificate(
              session, buf.data, buf.length);
    _gnutls_buffer_clear(&buf);
    if (ret < 0) {
      gnutls_assert();
      return ret;
    }
  }

  return ret;
}

/* Recv the client certificate verify. This packet may not
 * arrive if the peer did not send us a certificate.
 */
int _gnutls_recv_client_certificate_verify_message(gnutls_session_t session)
{
  gnutls_buffer_st buf;
  int ret = 0;

  if (session->internals.auth_struct->gnutls_process_client_crt_vrfy ==
      NULL)
    return 0;

  if (session->internals.send_cert_req == 0 ||
      (!(session->internals.hsk_flags & HSK_CRT_VRFY_EXPECTED))) {
    return 0;
  }

  ret = _gnutls_recv_handshake(
    session, GNUTLS_HANDSHAKE_CERTIFICATE_VERIFY, 1, &buf);
  if (ret < 0)
    return ret;

  if (ret == 0 && buf.length == 0 &&
      session->internals.send_cert_req == GNUTLS_CERT_REQUIRE) {
    /* certificate was required */
    gnutls_assert();
    ret = GNUTLS_E_NO_CERTIFICATE_FOUND;
    goto cleanup;
  }

  ret = session->internals.auth_struct->gnutls_process_client_crt_vrfy(
    session, buf.data, buf.length);

cleanup:
  _gnutls_buffer_clear(&buf);
  return ret;
}

Coverage Report

Created: 2025-11-16 06:46