/*

 * 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, &params.spki)) < 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, NULL, &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_prefix16(data, username.data,

              username.size);

  if (ret < 0) {

    gnutls_assert();

    goto cleanup;

  }

  ret = _gnutls_buffer_append_data_prefix16(data, sdata.data, sdata.size);

  if (ret < 0) {

    gnutls_assert();

    goto cleanup;

  }

  ret = data->length - init_pos;

cleanup:

  _gnutls_free_datum(&sdata);

  _gnutls_free_key_datum(&premaster_secret);

  if (free) {

    _gnutls_free_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 ciphertext;

  gnutls_datum_t pwd_psk = { NULL, 0 };

  int ret;

  gnutls_psk_server_credentials_t cred;

  volatile uint8_t ver_maj, ver_min;

  unsigned int rsa_key_bits;

  size_t dsize;

  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;

  gnutls_privkey_get_pk_algorithm(session->internals.selected_key,

          &rsa_key_bits);

  if (ciphertext.size != (rsa_key_bits + 7) / 8)

    return gnutls_assert_val(GNUTLS_E_DECRYPTION_FAILED);

  ver_maj = _gnutls_get_adv_version_major(session);

  ver_min = _gnutls_get_adv_version_minor(session);

  /* Find the key of this username. A random value will be

   * filled in if the key is not found.

   */

  ret = _gnutls_psk_pwd_find_entry(session, info->username,

           info->username_len, &pwd_psk, NULL);

  if (ret < 0)

    return gnutls_assert_val(ret);

  /* Allocate memory for premaster secret, and fill in the

   * fields except the decryption result.

   */

  session->key.key.size = 2 + GNUTLS_MASTER_SIZE + 2 + pwd_psk.size;

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

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

    gnutls_assert();

    _gnutls_free_key_datum(&pwd_psk);

    /* No need to zeroize, as the secret is not copied in yet */

    _gnutls_free_datum(&session->key.key);

    return GNUTLS_E_MEMORY_ERROR;

  }

  /* Fallback value when decryption fails. Needs to be unpredictable. */

  ret = gnutls_rnd(GNUTLS_RND_NONCE, session->key.key.data + 2,

       GNUTLS_MASTER_SIZE);

  if (ret < 0) {

    gnutls_assert();

    _gnutls_free_key_datum(&pwd_psk);

    /* No need to zeroize, as the secret is not copied in yet */

    _gnutls_free_datum(&session->key.key);

    return ret;

  }

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

  _gnutls_write_uint16(pwd_psk.size,

           &session->key.key.data[2 + GNUTLS_MASTER_SIZE]);

  memcpy(&session->key.key.data[2 + GNUTLS_MASTER_SIZE + 2], pwd_psk.data,

         pwd_psk.size);

  _gnutls_free_key_datum(&pwd_psk);

  gnutls_privkey_decrypt_data2(session->internals.selected_key, 0,

             &ciphertext, session->key.key.data + 2,

             GNUTLS_MASTER_SIZE);

  /* After this point, any conditional on failure that cause differences

   * in execution may create a timing or cache access pattern side

   * channel that can be used as an oracle, so tread carefully */

  /* Error handling logic:

   * In case decryption fails then don't inform the peer. Just use the

   * random key previously generated. (in order to avoid attack against

   * pkcs-1 formatting).

   *

   * If we get version mismatches no error is returned either. We

   * proceed normally. This 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.

   */

  /* This is here to avoid the version check attack

   * discussed above.

   */

  session->key.key.data[2] = ver_maj;

  session->key.key.data[3] = ver_min;

  return 0;

}

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 */