/*

 * Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2009, 2010

 * Free Software Foundation, Inc.

 *

 * Copyright (C) 2011

 * Bardenheuer GmbH, Munich and Bundesdruckerei GmbH, Berlin

 *

 * Copyright (C) 2013 Frank Morgner

 * Copyright (C) 2013 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 library.  If not, see <https://www.gnu.org/licenses/>.

 *

 */

#include "gnutls_int.h"

#ifdef ENABLE_PSK

# include "auth.h"

# include "dh.h"

# include "errors.h"

# include "mpi.h"

# include "num.h"

# include "gnutls_int.h"

# include "pk.h"

# include "random.h"

# include <abstract_int.h>

# include <algorithms.h>

# include <auth/dh_common.h>

# include <auth/psk.h>

# include <auth/psk_passwd.h>

# include <auth/rsa_common.h>

# include <cert.h>

# include <datum.h>

# include <state.h>

static int _gnutls_gen_rsa_psk_client_kx(gnutls_session_t session,

           gnutls_buffer_st * data);

static int _gnutls_proc_rsa_psk_client_kx(gnutls_session_t, uint8_t *, size_t);

static int

_gnutls_proc_rsa_psk_server_kx(gnutls_session_t session, uint8_t * data,

             size_t _data_size);

const mod_auth_st rsa_psk_auth_struct = {

  "RSA PSK",

  _gnutls_gen_cert_server_crt,

  NULL,     /* generate_client_certificate */

  _gnutls_gen_psk_server_kx,

  _gnutls_gen_rsa_psk_client_kx,

  NULL,     /* generate_client_cert_vrfy */

  NULL,     /* generate_server_certificate_request */

  _gnutls_proc_crt,

  NULL,     /* process_client_certificate */

  _gnutls_proc_rsa_psk_server_kx,

  _gnutls_proc_rsa_psk_client_kx,

  NULL,     /* process_client_cert_vrfy */

  NULL      /* process_server_certificate_reuqest */

};

/* Set the PSK premaster secret.

 */

static int

set_rsa_psk_session_key(gnutls_session_t session,

      gnutls_datum_t * ppsk, gnutls_datum_t * rsa_secret)

{

  unsigned char *p;

  size_t rsa_secret_size;

  int ret;

  rsa_secret_size = rsa_secret->size;

  /* set the session key

   */

  session->key.key.size = 2 + rsa_secret_size + 2 + ppsk->size;

  session->key.key.data = gnutls_malloc(session->key.key.size);

  if (session->key.key.data == NULL) {

    gnutls_assert();

    ret = GNUTLS_E_MEMORY_ERROR;

    goto error;

  }

  /* format of the premaster secret:

   * (uint16_t) other_secret size (48)

   * other_secret: 2 byte version + 46 byte random

   * (uint16_t) psk_size

   * the psk

   */

  _gnutls_write_uint16(rsa_secret_size, session->key.key.data);

  memcpy(&session->key.key.data[2], rsa_secret->data, rsa_secret->size);

  p = &session->key.key.data[rsa_secret_size + 2];

  _gnutls_write_uint16(ppsk->size, p);

  if (ppsk->data != NULL)

    memcpy(p + 2, ppsk->data, ppsk->size);

  ret = 0;

 error:

  return ret;

}

/* Generate client key exchange message

 *

 *

 * struct {

 *    select (KeyExchangeAlgorithm) {

 *       uint8_t psk_identity<0..2^16-1>;

 *       EncryptedPreMasterSecret;

 *    } exchange_keys;

 * } ClientKeyExchange;

 */

static int

_gnutls_gen_rsa_psk_client_kx(gnutls_session_t session, gnutls_buffer_st * data)

{

  cert_auth_info_t auth = session->key.auth_info;

  gnutls_datum_t sdata; /* data to send */

  gnutls_pk_params_st params;

  gnutls_psk_client_credentials_t cred;

  gnutls_datum_t username, key;

  int ret, free;

  unsigned init_pos;

  if (auth == NULL) {

    /* this shouldn't have happened. The proc_certificate

     * function should have detected that.

     */

    gnutls_assert();

    return GNUTLS_E_INSUFFICIENT_CREDENTIALS;

  }

  gnutls_datum_t premaster_secret;

  premaster_secret.size = GNUTLS_MASTER_SIZE;

  premaster_secret.data = gnutls_malloc(premaster_secret.size);

  if (premaster_secret.data == NULL) {

    gnutls_assert();

    return GNUTLS_E_MEMORY_ERROR;

  }

  /* Generate random */

  ret = gnutls_rnd(GNUTLS_RND_RANDOM, premaster_secret.data,

       premaster_secret.size);

  if (ret < 0) {

    gnutls_assert();

    return ret;

  }

  /* Set version */

  if (session->internals.rsa_pms_version[0] == 0) {

    premaster_secret.data[0] =

        _gnutls_get_adv_version_major(session);

    premaster_secret.data[1] =

        _gnutls_get_adv_version_minor(session);

  } else {   /* use the version provided */

    premaster_secret.data[0] =

        session->internals.rsa_pms_version[0];

    premaster_secret.data[1] =

        session->internals.rsa_pms_version[1];

  }

  /* move RSA parameters to key (session).

   */

  if ((ret = _gnutls_get_public_rsa_params(session, &params)) < 0) {

    gnutls_assert();

    return ret;

  }

  /* Encrypt premaster secret */

  if ((ret =

       _gnutls_pk_encrypt(GNUTLS_PK_RSA, &sdata, &premaster_secret,

        &params)) < 0) {

    gnutls_assert();

    return ret;

  }

  gnutls_pk_params_release(&params);

  cred = (gnutls_psk_client_credentials_t)

      _gnutls_get_cred(session, GNUTLS_CRD_PSK);

  if (cred == NULL) {

    gnutls_assert();

    return GNUTLS_E_INSUFFICIENT_CREDENTIALS;

  }

  ret = _gnutls_find_psk_key(session, cred, &username, &key, &free);

  if (ret < 0)

    return gnutls_assert_val(ret);

  /* Here we set the PSK key */

  ret = set_rsa_psk_session_key(session, &key, &premaster_secret);

  if (ret < 0) {

    gnutls_assert();

    goto cleanup;

  }

  /* Create message for client key exchange

   *

   * struct {

   *   uint8_t psk_identity<0..2^16-1>;

   *   EncryptedPreMasterSecret;

   * }

   */

  init_pos = data->length;

  /* Write psk_identity and EncryptedPreMasterSecret into data stream

   */

  ret =

      _gnutls_buffer_append_data_prefix(data, 16,

                username.data, username.size);

  if (ret < 0) {

    gnutls_assert();

    goto cleanup;

  }

  ret =

      _gnutls_buffer_append_data_prefix(data, 16, sdata.data, sdata.size);

  if (ret < 0) {

    gnutls_assert();

    goto cleanup;

  }

  ret = data->length - init_pos;

 cleanup:

  _gnutls_free_datum(&sdata);

  _gnutls_free_temp_key_datum(&premaster_secret);

  if (free) {

    _gnutls_free_temp_key_datum(&key);

    gnutls_free(username.data);

  }

  return ret;

}

/*

  Process the client key exchange message

*/

static int

_gnutls_proc_rsa_psk_client_kx(gnutls_session_t session, uint8_t * data,

             size_t _data_size)

{

  gnutls_datum_t username;

  psk_auth_info_t info;

  gnutls_datum_t plaintext;

  gnutls_datum_t ciphertext;

  gnutls_datum_t pwd_psk = { NULL, 0 };

  int ret, dsize;

  int randomize_key = 0;

  ssize_t data_size = _data_size;

  gnutls_psk_server_credentials_t cred;

  gnutls_datum_t premaster_secret = { NULL, 0 };

  cred = (gnutls_psk_server_credentials_t)

      _gnutls_get_cred(session, GNUTLS_CRD_PSK);

  if (cred == NULL) {

    gnutls_assert();

    return GNUTLS_E_INSUFFICIENT_CREDENTIALS;

  }

  ret = _gnutls_auth_info_init(session, GNUTLS_CRD_PSK,

             sizeof(psk_auth_info_st), 1);

  if (ret < 0) {

    gnutls_assert();

    return ret;

  }

  /*** 1. Extract user psk_identity ***/

  DECR_LEN(data_size, 2);

  username.size = _gnutls_read_uint16(&data[0]);

  DECR_LEN(data_size, username.size);

  username.data = &data[2];

  /* copy the username to the auth info structures

   */

  info = _gnutls_get_auth_info(session, GNUTLS_CRD_PSK);

  if (info == NULL) {

    gnutls_assert();

    return GNUTLS_E_INTERNAL_ERROR;

  }

  if (username.size > MAX_USERNAME_SIZE) {

    gnutls_assert();

    return GNUTLS_E_ILLEGAL_SRP_USERNAME;

  }

  ret = _gnutls_copy_psk_username(info, username);

  if (ret < 0)

    gnutls_assert_val(ret);

  /* Adjust data so it points to EncryptedPreMasterSecret */

  data += username.size + 2;

  /*** 2. Decrypt and extract EncryptedPreMasterSecret ***/

  DECR_LEN(data_size, 2);

  ciphertext.data = &data[2];

  dsize = _gnutls_read_uint16(data);

  if (dsize != data_size) {

    gnutls_assert();

    return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;

  }

  ciphertext.size = dsize;

  ret =

      gnutls_privkey_decrypt_data(session->internals.selected_key, 0,

          &ciphertext, &plaintext);

  if (ret < 0 || plaintext.size != GNUTLS_MASTER_SIZE) {

    /* In case decryption fails then don't inform

     * the peer. Just use a random key. (in order to avoid

     * attack against pkcs-1 formatting).

     */

    gnutls_assert();

    _gnutls_debug_log

        ("auth_rsa_psk: Possible PKCS #1 format attack\n");

    if (ret >= 0) {

      gnutls_free(plaintext.data);

    }

    randomize_key = 1;

  } else {

    /* If the secret was properly formatted, then

     * check the version number.

     */

    if (_gnutls_get_adv_version_major(session) != plaintext.data[0]

        || (session->internals.allow_wrong_pms == 0

      && _gnutls_get_adv_version_minor(session) !=

      plaintext.data[1])) {

      /* No error is returned here, if the version number check

       * fails. We proceed normally.

       * That is to defend against the attack described in the paper

       * "Attacking RSA-based sessions in SSL/TLS" by Vlastimil Klima,

       * Ondej Pokorny and Tomas Rosa.

       */

      gnutls_assert();

      _gnutls_debug_log

          ("auth_rsa: Possible PKCS #1 version check format attack\n");

    }

  }

  if (randomize_key != 0) {

    premaster_secret.size = GNUTLS_MASTER_SIZE;

    premaster_secret.data = gnutls_malloc(premaster_secret.size);

    if (premaster_secret.data == NULL) {

      gnutls_assert();

      return GNUTLS_E_MEMORY_ERROR;

    }

    /* we do not need strong random numbers here.

     */

    ret = gnutls_rnd(GNUTLS_RND_NONCE, premaster_secret.data,

         premaster_secret.size);

    if (ret < 0) {

      gnutls_assert();

      goto cleanup;

    }

  } else {

    premaster_secret.data = plaintext.data;

    premaster_secret.size = plaintext.size;

  }

  /* This is here to avoid the version check attack

   * discussed above.

   */

  premaster_secret.data[0] = _gnutls_get_adv_version_major(session);

  premaster_secret.data[1] = _gnutls_get_adv_version_minor(session);

  /* find the key of this username

   */

  ret =

      _gnutls_psk_pwd_find_entry(session, info->username,

               strlen(info->username), &pwd_psk);

  if (ret < 0) {

    gnutls_assert();

    goto cleanup;

  }

  ret = set_rsa_psk_session_key(session, &pwd_psk, &premaster_secret);

  if (ret < 0) {

    gnutls_assert();

    goto cleanup;

  }

  ret = 0;

 cleanup:

  _gnutls_free_key_datum(&pwd_psk);

  _gnutls_free_temp_key_datum(&premaster_secret);

  return ret;

}

static int

_gnutls_proc_rsa_psk_server_kx(gnutls_session_t session, uint8_t * data,

             size_t _data_size)

{

  /* In RSA-PSK the key is calculated elsewhere.

   * Moreover, since we only keep a single auth info structure, we cannot

   * store the hint (as we store certificate auth info).

   * Ideally we need to handle that by multiple auth info

   * structures or something similar.

   */

  return 0;

}

#endif        /* ENABLE_PSK */