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/*
* rand_source.c
*
* implements a random source based on /dev/random
*
* David A. McGrew
* Cisco Systems, Inc.
*/
/*
*
* Copyright(c) 2001-2006 Cisco Systems, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* Neither the name of the Cisco Systems, Inc. nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS 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
* COPYRIGHT HOLDERS OR 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.
*
*/
#include "config.h"
#ifdef DEV_URANDOM
# include <fcntl.h> /* for open() */
# include <unistd.h> /* for close() */
#elif defined(HAVE_RAND_S)
# define _CRT_RAND_S
# include <stdlib.h>
#else
# include <stdio.h>
#endif
#include "rand_source.h"
/*
* global dev_rand_fdes is file descriptor for /dev/random
*
* This variable is also used to indicate that the random source has
* been initialized. When this variable is set to the value of the
* #define RAND_SOURCE_NOT_READY, it indicates that the random source
* is not ready to be used. The value of the #define
* RAND_SOURCE_READY is for use whenever that variable is used as an
* indicator of the state of the random source, but not as a file
* descriptor.
*/
#define RAND_SOURCE_NOT_READY (-1)
#define RAND_SOURCE_READY (17)
static int dev_random_fdes = RAND_SOURCE_NOT_READY;
err_status_t
rand_source_init(void) {
if (dev_random_fdes >= 0) {
/* already open */
return err_status_ok;
}
#ifdef DEV_URANDOM
/* open random source for reading */
dev_random_fdes = open(DEV_URANDOM, O_RDONLY);
if (dev_random_fdes < 0)
return err_status_init_fail;
#elif defined(HAVE_RAND_S)
dev_random_fdes = RAND_SOURCE_READY;
#else
/* no random source available; let the user know */
fprintf(stderr, "WARNING: no real random source present!\n");
dev_random_fdes = RAND_SOURCE_READY;
#endif
return err_status_ok;
}
err_status_t
rand_source_get_octet_string(void *dest, uint32_t len) {
/*
* read len octets from /dev/random to dest, and
* check return value to make sure enough octets were
* written
*/
#ifdef DEV_URANDOM
uint8_t *dst = (uint8_t *)dest;
while (len)
{
ssize_t num_read = read(dev_random_fdes, dst, len);
if (num_read <= 0 || num_read > len)
return err_status_fail;
len -= num_read;
dst += num_read;
}
#elif defined(HAVE_RAND_S)
uint8_t *dst = (uint8_t *)dest;
while (len)
{
unsigned int val;
errno_t err = rand_s(&val);
if (err != 0)
return err_status_fail;
*dst++ = val & 0xff;
len--;
}
#else
/* Generic C-library (rand()) version */
/* This is a random source of last resort */
uint8_t *dst = (uint8_t *)dest;
while (len)
{
int val = rand();
/* rand() returns 0-32767 (ugh) */
/* Is this a good enough way to get random bytes?
It is if it passes FIPS-140... */
*dst++ = val & 0xff;
len--;
}
#endif
return err_status_ok;
}
err_status_t
rand_source_deinit(void) {
if (dev_random_fdes < 0)
return err_status_dealloc_fail; /* well, we haven't really failed, *
* but there is something wrong */
#ifdef DEV_URANDOM
close(dev_random_fdes);
#endif
dev_random_fdes = RAND_SOURCE_NOT_READY;
return err_status_ok;
}
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