1 /* 2 * rand_source.c 3 * 4 * implements a random source based on /dev/random 5 * 6 * David A. McGrew 7 * Cisco Systems, Inc. 8 */ 9 /* 10 * 11 * Copyright(c) 2001-2006 Cisco Systems, Inc. 12 * All rights reserved. 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 18 * Redistributions of source code must retain the above copyright 19 * notice, this list of conditions and the following disclaimer. 20 * 21 * Redistributions in binary form must reproduce the above 22 * copyright notice, this list of conditions and the following 23 * disclaimer in the documentation and/or other materials provided 24 * with the distribution. 25 * 26 * Neither the name of the Cisco Systems, Inc. nor the names of its 27 * contributors may be used to endorse or promote products derived 28 * from this software without specific prior written permission. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 31 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 32 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 33 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 34 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 35 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 36 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 37 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 41 * OF THE POSSIBILITY OF SUCH DAMAGE. 42 * 43 */ 44 45 #include "config.h" 46 47 #ifdef DEV_URANDOM 48 # include <fcntl.h> /* for open() */ 49 # include <unistd.h> /* for close() */ 50 #elif defined(HAVE_RAND_S) 51 # define _CRT_RAND_S 52 # include <stdlib.h> 53 #else 54 # include <stdio.h> 55 #endif 56 57 #include "rand_source.h" 58 59 60 /* 61 * global dev_rand_fdes is file descriptor for /dev/random 62 * 63 * This variable is also used to indicate that the random source has 64 * been initialized. When this variable is set to the value of the 65 * #define RAND_SOURCE_NOT_READY, it indicates that the random source 66 * is not ready to be used. The value of the #define 67 * RAND_SOURCE_READY is for use whenever that variable is used as an 68 * indicator of the state of the random source, but not as a file 69 * descriptor. 70 */ 71 72 #define RAND_SOURCE_NOT_READY (-1) 73 #define RAND_SOURCE_READY (17) 74 75 static int dev_random_fdes = RAND_SOURCE_NOT_READY; 76 77 78 err_status_t 79 rand_source_init(void) { 80 if (dev_random_fdes >= 0) { 81 /* already open */ 82 return err_status_ok; 83 } 84 #ifdef DEV_URANDOM 85 /* open random source for reading */ 86 dev_random_fdes = open(DEV_URANDOM, O_RDONLY); 87 if (dev_random_fdes < 0) 88 return err_status_init_fail; 89 #elif defined(HAVE_RAND_S) 90 dev_random_fdes = RAND_SOURCE_READY; 91 #else 92 /* no random source available; let the user know */ 93 fprintf(stderr, "WARNING: no real random source present!\n"); 94 dev_random_fdes = RAND_SOURCE_READY; 95 #endif 96 return err_status_ok; 97 } 98 99 err_status_t 100 rand_source_get_octet_string(void *dest, uint32_t len) { 101 102 /* 103 * read len octets from /dev/random to dest, and 104 * check return value to make sure enough octets were 105 * written 106 */ 107 #ifdef DEV_URANDOM 108 uint8_t *dst = (uint8_t *)dest; 109 while (len) 110 { 111 ssize_t num_read = read(dev_random_fdes, dst, len); 112 if (num_read <= 0 || num_read > len) 113 return err_status_fail; 114 len -= num_read; 115 dst += num_read; 116 } 117 #elif defined(HAVE_RAND_S) 118 uint8_t *dst = (uint8_t *)dest; 119 while (len) 120 { 121 unsigned int val; 122 errno_t err = rand_s(&val); 123 124 if (err != 0) 125 return err_status_fail; 126 127 *dst++ = val & 0xff; 128 len--; 129 } 130 #else 131 /* Generic C-library (rand()) version */ 132 /* This is a random source of last resort */ 133 uint8_t *dst = (uint8_t *)dest; 134 while (len) 135 { 136 int val = rand(); 137 /* rand() returns 0-32767 (ugh) */ 138 /* Is this a good enough way to get random bytes? 139 It is if it passes FIPS-140... */ 140 *dst++ = val & 0xff; 141 len--; 142 } 143 #endif 144 return err_status_ok; 145 } 146 147 err_status_t 148 rand_source_deinit(void) { 149 if (dev_random_fdes < 0) 150 return err_status_dealloc_fail; /* well, we haven't really failed, * 151 * but there is something wrong */ 152 #ifdef DEV_URANDOM 153 close(dev_random_fdes); 154 #endif 155 dev_random_fdes = RAND_SOURCE_NOT_READY; 156 157 return err_status_ok; 158 } 159
