119 lines
3.4 KiB
C
119 lines
3.4 KiB
C
/*
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* rand_source.c
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*
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* implements a random source based on /dev/random
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*
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* David A. McGrew
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* Cisco Systems, Inc.
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*/
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/*
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*
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* Copyright(c) 2001-2005 Cisco Systems, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* Neither the name of the Cisco Systems, Inc. nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#include "config.h"
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#include "rand_source.h"
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#ifdef DEV_URANDOM
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# include <fcntl.h> /* for open() */
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# include <unistd.h> /* for close() */
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#else
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# include <stdio.h>
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#endif
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/* global dev_rand_fdes is file descriptor for /dev/random */
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static int dev_random_fdes = -1;
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err_status_t
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rand_source_init(void) {
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if (dev_random_fdes >= 0) {
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/* already open */
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return err_status_ok;
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}
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#ifdef DEV_URANDOM
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/* open random source for reading */
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dev_random_fdes = open(DEV_URANDOM, O_RDONLY);
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if (dev_random_fdes < 0)
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return err_status_init_fail;
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#else
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/* no random source available; let the user know */
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fprintf(stderr, "WARNING: no real random source present!\n");
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dev_random_fdes = 17;
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#endif
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return err_status_ok;
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}
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err_status_t
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rand_source_get_octet_string(void *dest, uint32_t len) {
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/*
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* read len octets from /dev/random to dest, and
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* check return value to make sure enough octets were
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* written
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*/
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#ifdef DEV_URANDOM
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if (read(dev_random_fdes, dest, len) != len)
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return err_status_fail;
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#else
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/* Generic C-library (rand()) version */
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/* This is a random source of last resort */
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uint8_t *dst = dest;
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while (len)
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{
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int val = rand();
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/* rand() returns 0-32767 (ugh) */
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/* Is this a good enough way to get random bytes?
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It is if it passes FIPS-140... */
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*dst++ = (uint8_t)(val & 0xff);
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len--;
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}
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#endif
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return err_status_ok;
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}
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err_status_t
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rand_source_deinit(void) {
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if (dev_random_fdes < 0)
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return err_status_dealloc_fail; /* well, we haven't really failed, *
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* but there is something wrong */
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#ifdef DEV_URANDOM
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close(dev_random_fdes);
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#endif
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dev_random_fdes = -1;
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return err_status_ok;
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}
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