/* Tests for the getentropy, getrandom functions.

   Copyright (C) 2016-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library 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.

   The GNU C 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 the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <errno.h>

#include <stdbool.h>

#include <stdio.h>

#include <string.h>

#include <sys/random.h>

/* Set to true if any errors are encountered.  */

static bool errors;

/* Test getrandom with a single buffer length.  NB: The passed-in

   buffer must have room for four extra bytes after the specified

   length, which are used to test that getrandom leaves those bytes

   unchanged.  */

static void

test_length (char *buffer, size_t length, unsigned int flags)

{

  memset (buffer, 0, length);

  strcpy (buffer + length, "123");

  ssize_t ret = getrandom (buffer, length, flags);

  if (ret < 0)

    {

      /* EAGAIN is an expected error with GRND_RANDOM and

         GRND_NONBLOCK.  */

      if ((flags & GRND_RANDOM)

          && (flags & GRND_NONBLOCK)

          && errno == EAGAIN)

        return;

      printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);

      errors = true;

      return;

    }

 if (ret != length)

    {

      if (flags & GRND_RANDOM)

        {

          if (ret == 0 || ret > length)

            {

              printf ("error: getrandom (%zu, 0x%x) returned %zd\n",

                      length, flags, ret);

              errors = true;

            }

        }

      else

        {

          printf ("error: getrandom (%zu, 0x%x) returned %zd\n",

                  length, flags, ret);

          errors = true;

        }

    }

  if (length >= 7)

    {

      /* One spurious test failure in 2**56 is sufficiently

         unlikely.  */

      int non_null = 0;

      for (int i = 0; i < length; ++i)

        non_null += buffer[i] != 0;

      if (non_null == 0)

        {

          printf ("error: getrandom (%zu, 0x%x) returned all-zero bytes\n",

                  length, flags);

          errors = true;

        }

    }

  if (memcmp (buffer + length, "123", 4) != 0)

    {

      printf ("error: getrandom (%zu, 0x%x) wrote spurious bytes\n",

              length, flags);

      errors = true;

    }

}

/* Call getrandom repeatedly to fill the buffer.  */

static bool

getrandom_full (char *buffer, size_t length, unsigned int flags)

{

  char *end = buffer + length;

  while (buffer < end)

    {

      ssize_t ret = getrandom (buffer, end - buffer, flags);

      if (ret < 0)

        {

          printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);

          errors = true;

          return false;

        }

      buffer += ret;

    }

  return true;

}

static void

test_flags (unsigned int flags)

{

  /* Test various lengths, but only for !GRND_RANDOM, to conserve

     entropy.  */

  {

    enum { max_length = 300 };

    char buffer[max_length + 4];

    if (flags & GRND_RANDOM)

      test_length (buffer, 0, flags);

    else

      {

        for (int length = 0; length <= 9; ++length)

          test_length (buffer, length, flags);

        test_length (buffer, 16, flags);

        test_length (buffer, max_length, flags);

      }

  }

  /* Test that getrandom returns different data.  */

  if (!(flags & GRND_NONBLOCK))

    {

      char buffer1[8];

      memset (buffer1, 0, sizeof (buffer1));

      char buffer2[8];

      memset (buffer2, 0, sizeof (buffer2));

      if (getrandom_full (buffer1, sizeof (buffer1), flags)

          && getrandom_full (buffer2, sizeof (buffer2), flags))

        {

          /* The probability that these two 8-byte buffers are equal

             is very small (assuming that two subsequent calls to

             getrandom result are independent, uniformly distributed

             random variables).  */

          if (memcmp (buffer1, buffer2, sizeof (buffer1)) == 0)

            {

              printf ("error: getrandom returns constant value\n");

              errors = true;

            }

        }

    }

}

static void

test_getentropy (void)

{

  char buf[16];

  memset (buf, '@', sizeof (buf));

  if (getentropy (buf, 0) != 0)

    {

      printf ("error: getentropy zero length: %m\n");

      errors = true;

      return;

    }

  for (size_t i = 0; i < sizeof (buf); ++i)

    if (buf[i] != '@')

      {

        printf ("error: getentropy modified zero-length buffer\n");

        errors = true;

        return;

      }

  if (getentropy (buf, sizeof (buf)) != 0)

    {

      printf ("error: getentropy buf: %m\n");

      errors = true;

      return;

    }

  char buf2[256];

  _Static_assert (sizeof (buf) < sizeof (buf2), "buf and buf2 compatible");

  memset (buf2, '@', sizeof (buf2));

  if (getentropy (buf2, sizeof (buf)) != 0)

    {

      printf ("error: getentropy buf2: %m\n");

      errors = true;

      return;

    }

  /* The probability that these two buffers are equal is very

     small. */

  if (memcmp (buf, buf2, sizeof (buf) == 0))

    {

      printf ("error: getentropy appears to return constant bytes\n");

      errors = true;

      return;

    }

  for (size_t i = sizeof (buf); i < sizeof (buf2); ++i)

    if (buf2[i] != '@')

      {

        printf ("error: getentropy wrote beyond the end of the buffer\n");

        errors = true;

        return;

      }

  char buf3[257];

  if (getentropy (buf3, sizeof (buf3)) == 0)

    {

      printf ("error: getentropy successful for 257 byte buffer\n");

      errors = true;

      return;

    }

  if (errno != EIO)

    {

      printf ("error: getentropy wrong error for 257 byte buffer: %m\n");

      errors = true;

      return;

    }

}

static int

do_test (void)

{

  /* Check if getrandom is not supported by this system.  */

  if (getrandom (NULL, 0, 0) == -1 && errno == ENOSYS)

    return 77;

  for (int use_random = 0; use_random < 2; ++use_random)

    for (int use_nonblock = 0; use_nonblock < 2; ++use_nonblock)

      {

        unsigned int flags = 0;

        if (use_random)

          flags |= GRND_RANDOM;

        if (use_nonblock)

          flags |= GRND_NONBLOCK;

        test_flags (flags);

      }

  test_getentropy ();

  return errors;

}

#include <support/test-driver.c>