/*
 * rpc_misc.c
 * ----------
 * RPC interface to TRNG and PIN functions
 *
 * Authors: Rob Austein
 * Copyright (c) 2015, NORDUnet A/S All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of the NORDUnet nor the names of its contributors may
 *   be used to endorse or promote products derived from this software
 *   without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <assert.h>

#include "hal.h"
#include "hal_internal.h"

static hal_error_t get_random(void *buffer, const size_t length)
{
  assert(buffer != NULL && length > 0);

  return hal_get_random(NULL, buffer, length);
}

/*
 * PINs, salt, and iteration count live in the keystore.
 *
 * We also need a client table in conventional memory (here, probably)
 * to record login status.
 *
 * The USER and SO PINs correspond to PKCS #11.
 *
 * The WHEEL PIN is the one that's allowed to change the SO PIN.
 *
 * It's a bit unclear how we should manage changes to the WHEEL PIN.
 * Implementing a factory default would be easy enough (just
 * pre-compute and compile in a const hal_ks_pin_t), question is
 * whether doing so provides anything useful.  Certainly adds no real
 * security, question is whether it would help prevent accidently
 * bricking the HSM right out of the shrink wrap.
 *
 * More interesting question is whether we should ever allow the WHEEL
 * PIN to be changed a second time without toasting the keystore.
 *
 * We also need a function which the rest of the library can use to
 * check current login status for a particular hal_client_t.  Don't
 * know yet whether we need anything else.
 */

#warning PIN code not yet fully implemented

#ifndef HAL_PIN_MINIMUM_ITERATIONS
#define HAL_PIN_MINIMUM_ITERATIONS 10000
#endif

#ifndef HAL_PIN_DEFAULT_ITERATIONS
#define HAL_PIN_DEFAULT_ITERATIONS 20000
#endif

static hal_error_t set_pin(const hal_user_t user,
                           const char * const newpin, const size_t newpin_len)
{
  assert(newpin != NULL && newpin_len != 0);

#warning Need access control to decide who is allowed to set this PIN
#warning Need length checks on supplied PIN

  const hal_ks_pin_t *pp;
  hal_error_t err;

  if ((err = hal_ks_get_pin(user, &pp)) != HAL_OK)
    return err;

  hal_ks_pin_t p = *pp;

  if (p.iterations == 0)
    p.iterations = HAL_PIN_DEFAULT_ITERATIONS;

  if ((err = hal_get_random(NULL, p.salt, sizeof(p.salt)))      != HAL_OK ||
      (err = hal_pbkdf2(NULL, hal_hash_sha256,
                        (const uint8_t *) newpin, newpin_len,
                        p.salt, sizeof(p.salt),
                        p.pin,  sizeof(p.pin), p.iterations))   != HAL_OK ||
      (err = hal_ks_set_pin(user, &p))                          != HAL_OK)
    return err;

  return HAL_OK;
}

static hal_error_t login(const hal_client_handle_t client,
                         const hal_user_t user,
                         const char * const pin, const size_t pin_len)
{
  assert(pin != NULL && pin_len != 0);
  assert(user == HAL_USER_NORMAL || user == HAL_USER_SO || user == HAL_USER_WHEEL);

  const hal_ks_pin_t *p;
  hal_error_t err;

  if ((err = hal_ks_get_pin(user, &p)) != HAL_OK)
    return err;

  uint8_t buf[sizeof(p->pin)];

  if ((err = hal_pbkdf2(NULL, hal_hash_sha256, (const uint8_t *) pin, pin_len,
                        p->salt, sizeof(p->salt), buf, sizeof(buf), p->iterations)) != HAL_OK)
    return err;

  unsigned diff = 0;
  for (int i = 0; i < sizeof(buf); i++)
    diff |= buf[i] ^ p->pin[i];

  if (diff != 0)
    return HAL_ERROR_PIN_INCORRECT;

#warning Do something with client table here

  return HAL_OK;
}

static hal_error_t logout(const hal_client_handle_t client)
{
#warning And do something else with client table here
  return HAL_ERROR_IMPOSSIBLE;
}

const hal_rpc_misc_dispatch_t hal_rpc_remote_misc_dispatch = {
  set_pin, login, logout, get_random
};

/*
 * Local variables:
 * indent-tabs-mode: nil
 * End:
 */