ossp-pkg/uuid/uuid_prng.c
1.21
/*
** OSSP uuid - Universally Unique Identifier
** Copyright (c) 2004-2008 Ralf S. Engelschall <rse@engelschall.com>
** Copyright (c) 2004-2008 The OSSP Project <http://www.ossp.org/>
**
** This file is part of OSSP uuid, a library for the generation
** of UUIDs which can found at http://www.ossp.org/pkg/lib/uuid/
**
** Permission to use, copy, modify, and distribute this software for
** any purpose with or without fee is hereby granted, provided that
** the above copyright notice and this permission notice appear in all
** copies.
**
** THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
** WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
** IN NO EVENT SHALL THE AUTHORS AND COPYRIGHT HOLDERS AND THEIR
** CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
** USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
** ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
** OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
** OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
** SUCH DAMAGE.
**
** uuid_prng.c: PRNG API implementation
*/
/* own headers (part 1/2) */
#include "uuid_ac.h"
/* system headers */
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>
#include <fcntl.h>
#if defined(WIN32)
#define WINVER 0x0500
#include <windows.h>
#include <wincrypt.h>
#endif
/* own headers (part 2/2) */
#include "uuid_time.h"
#include "uuid_prng.h"
#include "uuid_md5.h"
struct prng_st {
int dev; /* system PRNG device */
md5_t *md5; /* local MD5 PRNG engine */
long cnt; /* time resolution compensation counter */
};
prng_rc_t prng_create(prng_t **prng)
{
#if !defined(WIN32)
int fd = -1;
#endif
struct timeval tv;
pid_t pid;
unsigned int i;
/* sanity check argument(s) */
if (prng == NULL)
return PRNG_RC_ARG;
/* allocate object */
if ((*prng = (prng_t *)malloc(sizeof(prng_t))) == NULL)
return PRNG_RC_MEM;
/* try to open the system PRNG device */
(*prng)->dev = -1;
#if !defined(WIN32)
if ((fd = open("/dev/urandom", O_RDONLY)) == -1)
fd = open("/dev/random", O_RDONLY|O_NONBLOCK);
if (fd != -1) {
(void)fcntl(fd, F_SETFD, FD_CLOEXEC);
(*prng)->dev = fd;
}
#endif
/* initialize MD5 engine */
if (md5_create(&((*prng)->md5)) != MD5_RC_OK) {
free(*prng);
return PRNG_RC_INT;
}
/* initialize time resolution compensation counter */
(*prng)->cnt = 0;
/* seed the C library PRNG once */
(void)time_gettimeofday(&tv);
pid = getpid();
srand((unsigned int)(
((unsigned int)pid << 16)
^ (unsigned int)pid
^ (unsigned int)tv.tv_sec
^ (unsigned int)tv.tv_usec));
for (i = (unsigned int)((tv.tv_sec ^ tv.tv_usec) & 0x1F); i > 0; i--)
(void)rand();
return PRNG_RC_OK;
}
prng_rc_t prng_data(prng_t *prng, void *data_ptr, size_t data_len)
{
size_t n;
unsigned char *p;
struct {
struct timeval tv;
long cnt;
int rnd;
} entropy;
unsigned char md5_buf[MD5_LEN_BIN];
unsigned char *md5_ptr;
size_t md5_len;
int retries;
int i;
#if defined(WIN32)
HCRYPTPROV hProv;
#endif
/* sanity check argument(s) */
if (prng == NULL || data_len == 0)
return PRNG_RC_ARG;
/* prepare for generation */
p = (unsigned char *)data_ptr;
n = data_len;
/* approach 1: try to gather data via stronger system PRNG device */
if (prng->dev != -1) {
retries = 0;
while (n > 0) {
i = (int)read(prng->dev, (void *)p, n);
if (i <= 0) {
if (retries++ > 16)
break;
continue;
}
retries = 0;
n -= (unsigned int)i;
p += (unsigned int)i;
}
}
#if defined(WIN32)
else {
if (CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, 0))
CryptGenRandom(hProv, n, p);
}
#endif
/* approach 2: try to gather data via weaker libc PRNG API. */
while (n > 0) {
/* gather new entropy */
(void)time_gettimeofday(&(entropy.tv)); /* source: libc time */
entropy.rnd = rand(); /* source: libc PRNG */
entropy.cnt = prng->cnt++; /* source: local counter */
/* pass entropy into MD5 engine */
if (md5_update(prng->md5, (void *)&entropy, sizeof(entropy)) != MD5_RC_OK)
return PRNG_RC_INT;
/* store MD5 engine state as PRN output */
md5_ptr = md5_buf;
md5_len = sizeof(md5_buf);
if (md5_store(prng->md5, (void **)(void *)&md5_ptr, &md5_len) != MD5_RC_OK)
return PRNG_RC_INT;
for (i = 0; i < MD5_LEN_BIN && n > 0; i++, n--)
*p++ ^= md5_buf[i]; /* intentionally no assignment because arbitrary
caller buffer content is leveraged, too */
}
return PRNG_RC_OK;
}
prng_rc_t prng_destroy(prng_t *prng)
{
/* sanity check argument(s) */
if (prng == NULL)
return PRNG_RC_ARG;
/* close PRNG device */
if (prng->dev != -1)
(void)close(prng->dev);
/* destroy MD5 engine */
(void)md5_destroy(prng->md5);
/* free object */
free(prng);
return PRNG_RC_OK;
}
