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lib: random utilities

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Add a random number(s) generator specific file. The intial functions are based
on what libuuid provide. I did some modifications like avoid WIN32 checks - this
is util-LINUX.

[kzak@redhat.com: - move jrand_seed to lib/randutils.c
                  - use TLS for jrand_seed (like original code from libuuid)
                  - use size_t for buffer sizes
                  - add close() to random_get_bytes]

Signed-off-by: Davidlohr Bueso <dave@gnu.org>
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Davidlohr Bueso 2012-04-05 23:52:04 +02:00 • committed by Karel Zak
parent c344350948
commit fe72459e41
3 changed files with 134 additions and 0 deletions
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lib/randutils.c Normal file
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/*
* General purpose random utilities
*/
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/syscall.h>
#include "randutils.h"
#ifdef HAVE_TLS
#define THREAD_LOCAL static __thread
#else
#define THREAD_LOCAL static
#endif
#if defined(__linux__) && defined(__NR_gettid) && defined(HAVE_JRAND48)
#define DO_JRAND_MIX
THREAD_LOCAL unsigned short ul_jrand_seed[3];
#endif
int random_get_fd(void)
{
int i, fd;
struct timeval tv;
gettimeofday(&tv, 0);
fd = open("/dev/urandom", O_RDONLY);
if (fd == -1)
fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
if (fd >= 0) {
i = fcntl(fd, F_GETFD);
if (i >= 0)
fcntl(fd, F_SETFD, i | FD_CLOEXEC);
}
srand((getpid() << 16) ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
#ifdef DO_JRAND_MIX
ul_jrand_seed[0] = getpid() ^ (tv.tv_sec & 0xFFFF);
ul_jrand_seed[1] = getppid() ^ (tv.tv_usec & 0xFFFF);
ul_jrand_seed[2] = (tv.tv_sec ^ tv.tv_usec) >> 16;
#endif
/* Crank the random number generator a few times */
gettimeofday(&tv, 0);
for (i = (tv.tv_sec ^ tv.tv_usec) & 0x1F; i > 0; i--)
rand();
return fd;
}
/*
* Generate a stream of random nbytes into buf.
* Use /dev/urandom if possible, and if not,
* use glibc pseudo-random functions.
*/
void random_get_bytes(void *buf, size_t nbytes)
{
size_t i, n = nbytes;
int fd = random_get_fd();
int lose_counter = 0;
unsigned char *cp = (unsigned char *) buf;
if (fd >= 0) {
while (n > 0) {
ssize_t x = read(fd, cp, n);
if (x <= 0) {
if (lose_counter++ > 16)
break;
continue;
}
n -= x;
cp += x;
lose_counter = 0;
}
close(fd);
}
/*
* We do this all the time, but this is the only source of
* randomness if /dev/random/urandom is out to lunch.
*/
for (cp = buf, i = 0; i < nbytes; i++)
*cp++ ^= (rand() >> 7) & 0xFF;
#ifdef DO_JRAND_MIX
{
unsigned short tmp_seed[3];
memcpy(tmp_seed, ul_jrand_seed, sizeof(tmp_seed));
ul_jrand_seed[2] = ul_jrand_seed[2] ^ syscall(__NR_gettid);
for (cp = buf, i = 0; i < nbytes; i++)
*cp++ ^= (jrand48(tmp_seed) >> 7) & 0xFF;
memcpy(ul_jrand_seed, tmp_seed,
sizeof(ul_jrand_seed)-sizeof(unsigned short));
}
#endif
return;
}
#ifdef TEST_PROGRAM
int main(int argc, char *argv[])
{
unsigned int v, i;
/* generate and print 10 random numbers */
for (i = 0; i < 10; i++) {
random_get_bytes(&v, sizeof(v));
printf("%d\n", v);
}
return EXIT_SUCCESS;
}
#endif /* TEST_PROGRAM */