stdlib/tst-getrandom.c

   1 /* Tests for the getentropy, getrandom functions.
   2    Copyright (C) 2016-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <stdbool.h>
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <sys/random.h>
  24
  25 /* Set to true if any errors are encountered.  */
  26 static bool errors;
  27
  28 /* Test getrandom with a single buffer length.  NB: The passed-in
  29    buffer must have room for four extra bytes after the specified
  30    length, which are used to test that getrandom leaves those bytes
  31    unchanged.  */
  32 static void
  33 test_length (char *buffer, size_t length, unsigned int flags)
  34 {
  35   memset (buffer, 0, length);
  36   strcpy (buffer + length, "123");
  37   ssize_t ret = getrandom (buffer, length, flags);
  38   if (ret < 0)
  39     {
  40       /* EAGAIN is an expected error with GRND_RANDOM and
  41          GRND_NONBLOCK.  */
  42       if ((flags & GRND_RANDOM)
  43           && (flags & GRND_NONBLOCK)
  44           && errno == EAGAIN)
  45         return;
  46       printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);
  47       errors = true;
  48       return;
  49     }
  50  if (ret != length)
  51     {
  52       if (flags & GRND_RANDOM)
  53         {
  54           if (ret == 0 || ret > length)
  55             {
  56               printf ("error: getrandom (%zu, 0x%x) returned %zd\n",
  57                       length, flags, ret);
  58               errors = true;
  59             }
  60         }
  61       else
  62         {
  63           printf ("error: getrandom (%zu, 0x%x) returned %zd\n",
  64                   length, flags, ret);
  65           errors = true;
  66         }
  67     }
  68   if (length >= 7)
  69     {
  70       /* One spurious test failure in 2**56 is sufficiently
  71          unlikely.  */
  72       int non_null = 0;
  73       for (int i = 0; i < length; ++i)
  74         non_null += buffer[i] != 0;
  75       if (non_null == 0)
  76         {
  77           printf ("error: getrandom (%zu, 0x%x) returned all-zero bytes\n",
  78                   length, flags);
  79           errors = true;
  80         }
  81     }
  82   if (memcmp (buffer + length, "123", 4) != 0)
  83     {
  84       printf ("error: getrandom (%zu, 0x%x) wrote spurious bytes\n",
  85               length, flags);
  86       errors = true;
  87     }
  88 }
  89
  90 /* Call getrandom repeatedly to fill the buffer.  */
  91 static bool
  92 getrandom_full (char *buffer, size_t length, unsigned int flags)
  93 {
  94   char *end = buffer + length;
  95   while (buffer < end)
  96     {
  97       ssize_t ret = getrandom (buffer, end - buffer, flags);
  98       if (ret < 0)
  99         {
 100           printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);
 101           errors = true;
 102           return false;
 103         }
 104       buffer += ret;
 105     }
 106
 107   return true;
 108 }
 109
 110 static void
 111 test_flags (unsigned int flags)
 112 {
 113   /* Test various lengths, but only for !GRND_RANDOM, to conserve
 114      entropy.  */
 115   {
 116     enum { max_length = 300 };
 117     char buffer[max_length + 4];
 118     if (flags & GRND_RANDOM)
 119       test_length (buffer, 0, flags);
 120     else
 121       {
 122         for (int length = 0; length <= 9; ++length)
 123           test_length (buffer, length, flags);
 124         test_length (buffer, 16, flags);
 125         test_length (buffer, max_length, flags);
 126       }
 127   }
 128
 129   /* Test that getrandom returns different data.  */
 130   if (!(flags & GRND_NONBLOCK))
 131     {
 132       char buffer1[8];
 133       memset (buffer1, 0, sizeof (buffer1));
 134
 135       char buffer2[8];
 136       memset (buffer2, 0, sizeof (buffer2));
 137
 138       if (getrandom_full (buffer1, sizeof (buffer1), flags)
 139           && getrandom_full (buffer2, sizeof (buffer2), flags))
 140         {
 141           /* The probability that these two 8-byte buffers are equal
 142              is very small (assuming that two subsequent calls to
 143              getrandom result are independent, uniformly distributed
 144              random variables).  */
 145           if (memcmp (buffer1, buffer2, sizeof (buffer1)) == 0)
 146             {
 147               printf ("error: getrandom returns constant value\n");
 148               errors = true;
 149             }
 150         }
 151     }
 152 }
 153
 154 static void
 155 test_getentropy (void)
 156 {
 157   char buf[16];
 158   memset (buf, '@', sizeof (buf));
 159   if (getentropy (buf, 0) != 0)
 160     {
 161       printf ("error: getentropy zero length: %m\n");
 162       errors = true;
 163       return;
 164     }
 165   for (size_t i = 0; i < sizeof (buf); ++i)
 166     if (buf[i] != '@')
 167       {
 168         printf ("error: getentropy modified zero-length buffer\n");
 169         errors = true;
 170         return;
 171       }
 172
 173   if (getentropy (buf, sizeof (buf)) != 0)
 174     {
 175       printf ("error: getentropy buf: %m\n");
 176       errors = true;
 177       return;
 178     }
 179
 180   char buf2[256];
 181   _Static_assert (sizeof (buf) < sizeof (buf2), "buf and buf2 compatible");
 182   memset (buf2, '@', sizeof (buf2));
 183   if (getentropy (buf2, sizeof (buf)) != 0)
 184     {
 185       printf ("error: getentropy buf2: %m\n");
 186       errors = true;
 187       return;
 188     }
 189
 190   /* The probability that these two buffers are equal is very
 191      small. */
 192   if (memcmp (buf, buf2, sizeof (buf)) == 0)
 193     {
 194       printf ("error: getentropy appears to return constant bytes\n");
 195       errors = true;
 196       return;
 197     }
 198
 199   for (size_t i = sizeof (buf); i < sizeof (buf2); ++i)
 200     if (buf2[i] != '@')
 201       {
 202         printf ("error: getentropy wrote beyond the end of the buffer\n");
 203         errors = true;
 204         return;
 205       }
 206
 207   char buf3[257];
 208   if (getentropy (buf3, sizeof (buf3)) == 0)
 209     {
 210       printf ("error: getentropy successful for 257 byte buffer\n");
 211       errors = true;
 212       return;
 213     }
 214   if (errno != EIO)
 215     {
 216       printf ("error: getentropy wrong error for 257 byte buffer: %m\n");
 217       errors = true;
 218       return;
 219     }
 220 }
 221
 222 static int
 223 do_test (void)
 224 {
 225   /* Check if getrandom is not supported by this system.  */
 226   if (getrandom (NULL, 0, 0) == -1 && errno == ENOSYS)
 227     return 77;
 228
 229   for (int use_random = 0; use_random < 2; ++use_random)
 230     for (int use_nonblock = 0; use_nonblock < 2; ++use_nonblock)
 231       {
 232         unsigned int flags = 0;
 233         if (use_random)
 234           flags |= GRND_RANDOM;
 235         if (use_nonblock)
 236           flags |= GRND_NONBLOCK;
 237         test_flags (flags);
 238       }
 239
 240   test_getentropy ();
 241
 242   return errors;
 243 }
 244
 245 #include <support/test-driver.c>