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/* Test the exposed interface of get_random_bytes.
Written by Zack Weinberg <zackw at panix.com> in 2018.
To the extent possible under law, Zack Weinberg has waived all
copyright and related or neighboring rights to this work.
See https://creativecommons.org/publicdomain/zero/1.0/ for further
details. */
#include "crypt-port.h"
#include <errno.h>
#include <setjmp.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <sys/mman.h>
static bool error_occurred;
/* Note: both of the following test functions expect PAGE to point to
PAGESIZE bytes of read-write memory followed by another PAGESIZE
bytes of unwritable memory. Both functions also assume that
PAGESIZE is greater than or equal to 256. */
static void
test_basic (char *page, size_t pagesize)
{
printf ("Testing basic functionality...\n");
// A request for zero bytes should succeed, and should not touch the
// output buffer.
if (!get_random_bytes (page + pagesize, 0))
{
printf ("ERROR: get_random_bytes(0) = %s\n", strerror (errno));
error_occurred = 1;
}
else
printf ("ok: get_random_bytes(0)\n");
// A request for 257 bytes should fail, and should not touch the
// output buffer.
if (get_random_bytes (page + pagesize, 257))
{
printf ("ERROR: get_random_bytes(257) succeeded\n");
error_occurred = 1;
}
else if (errno != EIO)
{
printf ("ERROR: get_random_bytes(257) = %s (expected: %s)\n",
strerror (errno), strerror (EIO));
error_occurred = 1;
}
else
printf ("ok: get_random_bytes(257)\n");
// A request for five bytes should succeed, and should not write
// past the end of the buffer. (We use an odd, prime number here to
// catch implementations that might write e.g. four or eight bytes
// at once.)
if (!get_random_bytes (page + pagesize - 5, 5))
{
printf ("ERROR: get_random_bytes(5) = %s\n", strerror (errno));
error_occurred = 1;
}
else
printf ("ok: get_random_bytes(5)\n");
// It's extremely difficult to say whether any output of a random
// number generator is or is not "good", but the odds that 251 bytes
// of RNG output are all zero is one in 2**2008, and the odds that
// the first 251 bytes of RNG output are equal to the second 251
// bytes of RNG output is also one in 2**2008. (Again, we use an
// odd, prime number to trip up implementations that do wide writes.)
char prev[251];
memset (prev, 0, 251);
if (!get_random_bytes (page + pagesize - 251, 251))
{
printf ("ERROR: get_random_bytes(251)/1 = %s\n", strerror (errno));
error_occurred = 1;
return;
}
if (!memcmp (prev, page + pagesize - 251, 251))
{
printf ("ERROR: get_random_bytes(251)/1 produced all zeroes\n");
error_occurred = 1;
return;
}
memcpy (prev, page + pagesize - 251, 251);
if (!get_random_bytes (page + pagesize - 251, 251))
{
printf ("ERROR: get_random_bytes(251)/2 = %s\n", strerror (errno));
error_occurred = 1;
return;
}
if (!memcmp (prev, page + pagesize - 251, 251))
{
printf ("ERROR: get_random_bytes(251)/2 produced same output "
"as /1\n");
error_occurred = 1;
return;
}
printf ("ok: get_random_bytes(251) smoke test of output\n");
}
static void
test_fault (char *page, size_t pagesize)
{
printf ("Testing partially inaccessible output buffer...\n");
bool rv = get_random_bytes (page + pagesize - 64, 128);
/* shouldn't ever get here */
error_occurred = 1;
if (rv)
printf ("ERROR: success (should have faulted)\n");
else
printf ("ERROR: failed with %s (should have faulted)\n",
strerror (errno));
}
/* In one of the tests above, a segmentation fault is the expected result. */
static sigjmp_buf env;
static void
segv_handler (int sig)
{
siglongjmp (env, sig);
}
static void
expect_no_fault (char *page, size_t pagesize,
void (*testfn) (char *, size_t))
{
int rv = sigsetjmp (env, 1);
if (!rv)
testfn (page, pagesize);
else
{
printf ("ERROR: Unexpected %s\n", strsignal (rv));
error_occurred = 1;
}
}
static void
expect_a_fault (char *page, size_t pagesize,
void (*testfn) (char *, size_t))
{
int rv = sigsetjmp (env, 1);
if (!rv)
{
testfn (page, pagesize);
printf ("ERROR: No signal occurred\n");
error_occurred = 1;
}
else
{
printf ("ok: %s (as expected)\n", strsignal (rv));
}
}
int
main (void)
{
/* Set up a two-page region whose first page is read-write and
whose second page is inaccessible. */
long pagesize_l = sysconf (_SC_PAGESIZE);
if (pagesize_l < 256)
{
printf ("ERROR: pagesize of %ld is too small\n", pagesize_l);
return 99;
}
size_t pagesize = (size_t) pagesize_l;
char *page = mmap (0, pagesize * 2, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANON, -1, 0);
if (page == MAP_FAILED)
{
perror ("mmap");
return 1;
}
memset (page, 'x', pagesize * 2);
if (mprotect (page + pagesize, pagesize, PROT_NONE))
{
perror ("mprotect");
return 1;
}
struct sigaction sa, os, ob;
sigfillset (&sa.sa_mask);
sa.sa_flags = SA_RESTART;
sa.sa_handler = segv_handler;
if (sigaction (SIGBUS, &sa, &ob) || sigaction (SIGSEGV, &sa, &os))
{
perror ("sigaction");
return 1;
}
expect_no_fault (page, pagesize, test_basic);
expect_a_fault (page, pagesize, test_fault);
sigaction (SIGBUS, &ob, 0);
sigaction (SIGSEGV, &os, 0);
return error_occurred;
}
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