/*

 * Copyright (C) 2005-2012 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/>

 *

 */

#include "gnutls_int.h"

#ifdef ENABLE_PSK

#include "errors.h"

#include "auth.h"

#include "debug.h"

#include "num.h"

#include "auth/psk.h"

#include "auth/psk_passwd.h"

#include "str.h"

#include "datum.h"

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

static int _gnutls_proc_psk_server_kx(gnutls_session_t session, uint8_t *data,

              size_t data_size);

const mod_auth_st psk_auth_struct = { "PSK",

              NULL,

              NULL,

              _gnutls_gen_psk_server_kx,

              _gnutls_gen_psk_client_kx,

              NULL,

              NULL,

              NULL,

              NULL, /* certificate */

              _gnutls_proc_psk_server_kx,

              _gnutls_proc_psk_client_kx,

              NULL,

              NULL };

/* Set the PSK premaster secret.

 */

int _gnutls_set_psk_session_key(gnutls_session_t session,

        gnutls_datum_t *ppsk /* key */,

        gnutls_datum_t *dh_secret)

{

  gnutls_datum_t pwd_psk = { NULL, 0 };

  size_t dh_secret_size;

  uint8_t *p;

  int ret;

  if (dh_secret == NULL)

    dh_secret_size = ppsk->size;

  else

    dh_secret_size = dh_secret->size;

  /* set the session key

   */

  session->key.key.size = 4 + dh_secret_size + 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) psk_size

   * psk_size bytes of (0)s

   * (uint16_t) psk_size

   * the psk

   */

  p = session->key.key.data;

  _gnutls_write_uint16(dh_secret_size, p);

  p += 2;

  if (dh_secret == NULL)

    memset(p, 0, dh_secret_size);

  else

    memcpy(p, dh_secret->data, dh_secret->size);

  p += dh_secret_size;

  _gnutls_write_uint16(ppsk->size, p);

  if (ppsk->data != NULL)

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

  ret = 0;

error:

  _gnutls_free_key_datum(&pwd_psk);

  return ret;

}

/* Generates the PSK client key exchange

 *

 * 

 * struct {

 *    select (KeyExchangeAlgorithm) {

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

 *    } exchange_keys;

 * } ClientKeyExchange;

 *

 */

int _gnutls_gen_psk_client_kx(gnutls_session_t session, gnutls_buffer_st *data)

{

  int ret, free;

  gnutls_datum_t username = { NULL, 0 };

  gnutls_datum_t key;

  gnutls_psk_client_credentials_t cred;

  psk_auth_info_t info;

  cred = (gnutls_psk_client_credentials_t)_gnutls_get_cred(

    session, GNUTLS_CRD_PSK);

  if (cred == NULL) {

    gnutls_assert();

    return GNUTLS_E_INSUFFICIENT_CREDENTIALS;

  }

  info = _gnutls_get_auth_info(session, GNUTLS_CRD_PSK);

  if (info == NULL) {

    gnutls_assert();

    return GNUTLS_E_INTERNAL_ERROR;

  }

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

  if (ret < 0)

    return gnutls_assert_val(ret);

  ret = _gnutls_set_psk_session_key(session, &key, NULL);

  if (ret < 0) {

    gnutls_assert();

    goto cleanup;

  }

  ret = _gnutls_buffer_append_data_prefix16(data, username.data,

              username.size);

  if (ret < 0) {

    gnutls_assert();

  }

  if (username.size > MAX_USERNAME_SIZE) {

    gnutls_assert();

    ret = GNUTLS_E_ILLEGAL_SRP_USERNAME;

    goto cleanup;

  }

  assert(username.data != NULL);

  ret = _gnutls_copy_psk_username(info, username);

  if (ret < 0) {

    gnutls_assert();

    goto cleanup;

  }

cleanup:

  if (free) {

    gnutls_free(username.data);

    _gnutls_free_key_datum(&key);

  }

  return ret;

}

/* just read the username from the client key exchange.

 */

static int _gnutls_proc_psk_client_kx(gnutls_session_t session, uint8_t *data,

              size_t data_size)

{

  int ret;

  gnutls_datum_t username, psk_key;

  gnutls_psk_server_credentials_t cred;

  psk_auth_info_t info;

  cred = (gnutls_psk_server_credentials_t)_gnutls_get_cred(

    session, GNUTLS_CRD_PSK);

  if (cred == NULL) {

    gnutls_assert();

    return GNUTLS_E_INSUFFICIENT_CREDENTIALS;

  }

  if ((ret = _gnutls_auth_info_init(session, GNUTLS_CRD_PSK,

            sizeof(psk_auth_info_st), 1)) < 0) {

    gnutls_assert();

    return ret;

  }

  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)

    return gnutls_assert_val(ret);

  ret = _gnutls_psk_pwd_find_entry(session, info->username,

           info->username_len, &psk_key, NULL);

  if (ret < 0)

    return gnutls_assert_val(ret);

  ret = _gnutls_set_psk_session_key(session, &psk_key, NULL);

  if (ret < 0) {

    gnutls_assert();

    goto error;

  }

  ret = 0;

error:

  _gnutls_free_key_datum(&psk_key);

  return ret;

}

/* Generates the PSK server key exchange

 *

 * struct {

 *     select (KeyExchangeAlgorithm) {

 *   // other cases for rsa, diffie_hellman, etc.

 *   case psk:  // NEW

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

 *     };

 * } ServerKeyExchange;

 *

 */

int _gnutls_gen_psk_server_kx(gnutls_session_t session, gnutls_buffer_st *data)

{

  gnutls_psk_server_credentials_t cred;

  gnutls_datum_t hint;

  cred = (gnutls_psk_server_credentials_t)_gnutls_get_cred(

    session, GNUTLS_CRD_PSK);

  if (cred == NULL) {

    gnutls_assert();

    return GNUTLS_E_INSUFFICIENT_CREDENTIALS;

  }

  /* Abort sending this message if there is no PSK identity hint. */

  if (cred->hint == NULL) {

    gnutls_assert();

    return GNUTLS_E_INT_RET_0;

  }

  hint.data = (uint8_t *)cred->hint;

  hint.size = strlen(cred->hint);

  return _gnutls_buffer_append_data_prefix16(data, hint.data, hint.size);

}

/* Read the hint from the server key exchange */

static int _gnutls_proc_psk_server_kx(gnutls_session_t session, uint8_t *data,

              size_t data_size)

{

  int ret;

  gnutls_psk_client_credentials_t cred;

  psk_auth_info_t info;

  gnutls_datum_t hint;

  cred = (gnutls_psk_client_credentials_t)_gnutls_get_cred(

    session, GNUTLS_CRD_PSK);

  if (cred == NULL)

    return gnutls_assert_val(GNUTLS_E_INSUFFICIENT_CREDENTIALS);

  ret = _gnutls_auth_info_init(session, GNUTLS_CRD_PSK,

             sizeof(psk_auth_info_st), 1);

  if (ret < 0)

    return gnutls_assert_val(ret);

  DECR_LENGTH_RET(data_size, 2, 0);

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

  DECR_LEN(data_size, hint.size);

  hint.data = &data[2];

  info = _gnutls_get_auth_info(session, GNUTLS_CRD_PSK);

  if (info == NULL)

    return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

  if (hint.size > MAX_USERNAME_SIZE)

    return gnutls_assert_val(GNUTLS_E_ILLEGAL_SRP_USERNAME);

  ret = _gnutls_copy_psk_hint(info, hint);

  return ret;

}

#endif /* ENABLE_PSK */