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Add getentropy, getrandom, <sys/random.h> [BZ #17252]
This commit is contained in:
Florian Weimer
245
stdlib/tst-getrandom.c
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245
stdlib/tst-getrandom.c
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/* Tests for the getentropy, getrandom functions.
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Copyright (C) 2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/random.h>
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/* Set to true if any errors are encountered. */
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static bool errors;
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/* Test getrandom with a single buffer length. NB: The passed-in
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buffer must have room for four extra bytes after the specified
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length, which are used to test that getrandom leaves those bytes
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unchanged. */
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static void
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test_length (char *buffer, size_t length, unsigned int flags)
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{
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memset (buffer, 0, length);
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strcpy (buffer + length, "123");
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ssize_t ret = getrandom (buffer, length, flags);
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if (ret < 0)
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{
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/* EAGAIN is an expected error with GRND_RANDOM and
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GRND_NONBLOCK. */
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if ((flags & GRND_RANDOM)
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&& (flags & GRND_NONBLOCK)
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&& errno == EAGAIN)
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return;
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printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);
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errors = true;
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return;
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}
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if (ret != length)
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{
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if (flags & GRND_RANDOM)
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{
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if (ret == 0 || ret > length)
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{
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printf ("error: getrandom (%zu, 0x%x) returned %zd\n",
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length, flags, ret);
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errors = true;
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}
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}
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else
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{
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printf ("error: getrandom (%zu, 0x%x) returned %zd\n",
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length, flags, ret);
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errors = true;
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}
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}
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if (length >= 7)
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{
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/* One spurious test failure in 2**56 is sufficiently
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unlikely. */
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int non_null = 0;
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for (int i = 0; i < length; ++i)
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non_null += buffer[i] != 0;
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if (non_null == 0)
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{
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printf ("error: getrandom (%zu, 0x%x) returned all-zero bytes\n",
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length, flags);
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errors = true;
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}
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}
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if (memcmp (buffer + length, "123", 4) != 0)
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{
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printf ("error: getrandom (%zu, 0x%x) wrote spurious bytes\n",
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length, flags);
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errors = true;
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}
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}
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/* Call getrandom repeatedly to fill the buffer. */
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static bool
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getrandom_full (char *buffer, size_t length, unsigned int flags)
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{
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char *end = buffer + length;
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while (buffer < end)
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{
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ssize_t ret = getrandom (buffer, end - buffer, flags);
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if (ret < 0)
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{
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printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);
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errors = true;
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return false;
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}
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buffer += ret;
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}
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return true;
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}
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static void
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test_flags (unsigned int flags)
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{
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/* Test various lengths, but only for !GRND_RANDOM, to conserve
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entropy. */
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{
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enum { max_length = 300 };
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char buffer[max_length + 4];
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if (flags & GRND_RANDOM)
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test_length (buffer, 0, flags);
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else
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{
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for (int length = 0; length <= 9; ++length)
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test_length (buffer, length, flags);
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test_length (buffer, 16, flags);
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test_length (buffer, max_length, flags);
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}
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}
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/* Test that getrandom returns different data. */
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if (!(flags & GRND_NONBLOCK))
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{
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char buffer1[8];
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memset (buffer1, 0, sizeof (buffer1));
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char buffer2[8];
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memset (buffer2, 0, sizeof (buffer2));
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if (getrandom_full (buffer1, sizeof (buffer1), flags)
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&& getrandom_full (buffer2, sizeof (buffer2), flags))
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{
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/* The probability that these two 8-byte buffers are equal
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is very small (assuming that two subsequent calls to
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getrandom result are independent, uniformly distributed
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random variables). */
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if (memcmp (buffer1, buffer2, sizeof (buffer1)) == 0)
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{
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printf ("error: getrandom returns constant value\n");
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errors = true;
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}
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}
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}
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}
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static void
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test_getentropy (void)
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{
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char buf[16];
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memset (buf, '@', sizeof (buf));
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if (getentropy (buf, 0) != 0)
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{
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printf ("error: getentropy zero length: %m\n");
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errors = true;
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return;
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}
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for (size_t i = 0; i < sizeof (buf); ++i)
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if (buf[i] != '@')
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{
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printf ("error: getentropy modified zero-length buffer\n");
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errors = true;
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return;
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}
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if (getentropy (buf, sizeof (buf)) != 0)
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{
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printf ("error: getentropy buf: %m\n");
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errors = true;
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return;
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}
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char buf2[256];
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_Static_assert (sizeof (buf) < sizeof (buf2), "buf and buf2 compatible");
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memset (buf2, '@', sizeof (buf2));
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if (getentropy (buf2, sizeof (buf)) != 0)
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{
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printf ("error: getentropy buf2: %m\n");
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errors = true;
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return;
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}
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/* The probability that these two buffers are equal is very
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small. */
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if (memcmp (buf, buf2, sizeof (buf) == 0))
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{
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printf ("error: getentropy appears to return constant bytes\n");
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errors = true;
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return;
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}
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for (size_t i = sizeof (buf); i < sizeof (buf2); ++i)
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if (buf2[i] != '@')
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{
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printf ("error: getentropy wrote beyond the end of the buffer\n");
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errors = true;
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return;
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}
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char buf3[257];
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if (getentropy (buf3, sizeof (buf3)) == 0)
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{
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printf ("error: getentropy successful for 257 byte buffer\n");
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errors = true;
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return;
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}
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if (errno != EIO)
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{
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printf ("error: getentropy wrong error for 257 byte buffer: %m\n");
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errors = true;
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return;
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}
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}
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static int
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do_test (void)
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{
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/* Check if getrandom is not supported by this system. */
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if (getrandom (NULL, 0, 0) == -1 && errno == ENOSYS)
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return 77;
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for (int use_random = 0; use_random < 2; ++use_random)
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for (int use_nonblock = 0; use_nonblock < 2; ++use_nonblock)
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{
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unsigned int flags = 0;
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if (use_random)
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flags |= GRND_RANDOM;
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if (use_nonblock)
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flags |= GRND_NONBLOCK;
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test_flags (flags);
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}
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test_getentropy ();
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return errors;
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}
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#include <support/test-driver.c>
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