path: root/csprng.c

/*
 * csprng.c
 * --------
 * HAL interface to Cryptech CSPRNG.
 *
 * Authors: Joachim Strömbergson, Paul Selkirk, Rob Austein
 * Copyright (c) 2014-2015, 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 <stdint.h>

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

#ifndef WAIT_FOR_CSPRNG_VALID
#define WAIT_FOR_CSPRNG_VALID   1
#endif

hal_error_t hal_get_random(hal_core_t *core, void *buffer, const size_t length)
{
  uint8_t temp[4], ior = 0, * const buf = buffer;
  const int free_core = core == NULL;
  hal_error_t err = HAL_OK;

  if (free_core && (err = hal_core_alloc(CSPRNG_NAME, &core, NULL)) != HAL_OK)
    return err;

  for (size_t i = 0; i < length; i += 4) {
    const int last = (length - i) < 4;

    if (WAIT_FOR_CSPRNG_VALID && (err = hal_io_wait_valid(core)) != HAL_OK)
      break;

    if ((err = hal_io_read(core, CSPRNG_ADDR_RANDOM, (last ? temp : &buf[i]), 4)) != HAL_OK)
      break;

    if (last)
      for (; i < length; i++)
        buf[i] = temp[i&3];
  }

  if (err == HAL_OK) {
    for (size_t i = 0; i < length; i++)
      ior |= buf[i];

    if (ior == 0 && length > 0)
      err = HAL_ERROR_CSPRNG_BROKEN;
  }

  if (free_core)
    hal_core_free(core);
  return err;
}

/*
 * "Any programmer who fails to comply with the standard naming, formatting,
 *  or commenting conventions should be shot.  If it so happens that it is
 *  inconvenient to shoot him, then he is to be politely requested to recode
 *  his program in adherence to the above standard."
 *                      -- Michael Spier, Digital Equipment Corporation
 *
 * Local variables:
 * indent-tabs-mode: nil
 * End:
 */