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/* Tests for the getentropy, getrandom functions.
Copyright (C) 2016-2024 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
<https://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>
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