Tristan Matthews | 0a329cc | 2013-07-17 13:20:14 -0400 | [diff] [blame] | 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 "srtp_config.h" |
| 46 | |
| 47 | #if defined(DEV_URANDOM) || defined(PJ_DEV_URANDOM) |
| 48 | # include <fcntl.h> /* for open() */ |
| 49 | # include <unistd.h> /* for close() */ |
| 50 | #elif (_MSC_VER >= 1400) |
| 51 | #define _CRT_RAND_S |
| 52 | # include <stdlib.h> |
| 53 | # include <stdio.h> |
| 54 | #else |
| 55 | # include <stdio.h> |
| 56 | #endif |
| 57 | |
| 58 | #include "rand_source.h" |
| 59 | |
| 60 | |
| 61 | /* |
| 62 | * global dev_rand_fdes is file descriptor for /dev/random |
| 63 | * |
| 64 | * This variable is also used to indicate that the random source has |
| 65 | * been initialized. When this variable is set to the value of the |
| 66 | * #define RAND_SOURCE_NOT_READY, it indicates that the random source |
| 67 | * is not ready to be used. The value of the #define |
| 68 | * RAND_SOURCE_READY is for use whenever that variable is used as an |
| 69 | * indicator of the state of the random source, but not as a file |
| 70 | * descriptor. |
| 71 | */ |
| 72 | |
| 73 | #define RAND_SOURCE_NOT_READY (-1) |
| 74 | #define RAND_SOURCE_READY (17) |
| 75 | |
| 76 | static int dev_random_fdes = RAND_SOURCE_NOT_READY; |
| 77 | |
| 78 | |
| 79 | err_status_t |
| 80 | rand_source_init(void) { |
| 81 | if (dev_random_fdes >= 0) { |
| 82 | /* already open */ |
| 83 | return err_status_ok; |
| 84 | } |
| 85 | #ifdef DEV_URANDOM |
| 86 | /* open random source for reading */ |
| 87 | dev_random_fdes = open(DEV_URANDOM, O_RDONLY); |
| 88 | if (dev_random_fdes < 0) |
| 89 | return err_status_init_fail; |
| 90 | #elif defined(PJ_DEV_URANDOM) |
| 91 | /* open random source for reading */ |
| 92 | dev_random_fdes = open(PJ_DEV_URANDOM, O_RDONLY); |
| 93 | if (dev_random_fdes < 0) { |
| 94 | err_report(3,"Ugh: /dev/urandom not present, using rand() instead"); |
| 95 | return err_status_ok; /* it's ok, it'll fallback to using rand() */ |
| 96 | } |
| 97 | #elif (_MSC_VER >= 1400) |
| 98 | dev_random_fdes = RAND_SOURCE_READY; |
| 99 | #else |
| 100 | /* no random source available; let the user know */
|
| 101 | err_report(err_level_info, "WARNING: no real random source present!\n"); |
| 102 | dev_random_fdes = RAND_SOURCE_READY; |
| 103 | #endif |
| 104 | return err_status_ok; |
| 105 | } |
| 106 | |
| 107 | err_status_t |
| 108 | rand_source_get_octet_string(void *dest, uint32_t len) { |
| 109 | |
| 110 | /* |
| 111 | * read len octets from /dev/random to dest, and |
| 112 | * check return value to make sure enough octets were |
| 113 | * written |
| 114 | */ |
| 115 | #ifdef DEV_URANDOM |
| 116 | if (read(dev_random_fdes, dest, len) != len) |
| 117 | return err_status_fail; |
| 118 | #elif 0 && (_MSC_VER >= 1400) /* disabled rand_s, causing assertion 'rand_s not supported' in vs8 */ |
| 119 | unsigned int *dst = dest; |
| 120 | while (len) |
| 121 | { |
| 122 | unsigned int val = 0; |
| 123 | errno_t err = rand_s(&val); |
| 124 | if (err != 0) |
| 125 | { |
| 126 | return err_status_fail; |
| 127 | } |
| 128 | |
| 129 | *dst++ = val; |
| 130 | len--; |
| 131 | } |
| 132 | #else |
| 133 | uint8_t *dst = (uint8_t *)dest; |
| 134 |
|
| 135 | #ifdef PJ_DEV_URANDOM |
| 136 | /* First try with /dev/urandom, if it's opened */ |
| 137 | if (dev_random_fdes >= 0) { |
| 138 | if (read(dev_random_fdes, dest, len) == len) |
| 139 | return err_status_ok; /* success */ |
| 140 | }
|
| 141 | #endif |
| 142 | |
| 143 | /* Generic C-library (rand()) version */ |
| 144 | /* This is a random source of last resort */ |
| 145 | while (len) |
| 146 | { |
| 147 | int val = rand(); |
| 148 | /* rand() returns 0-32767 (ugh) */ |
| 149 | /* Is this a good enough way to get random bytes? |
| 150 | It is if it passes FIPS-140... */ |
| 151 | *dst++ = val & 0xff; |
| 152 | len--; |
| 153 | } |
| 154 | #endif |
| 155 | return err_status_ok; |
| 156 | } |
| 157 | |
| 158 | err_status_t |
| 159 | rand_source_deinit(void) { |
| 160 | #ifndef PJ_DEV_URANDOM |
| 161 | if (dev_random_fdes < 0) |
| 162 | return err_status_dealloc_fail; /* well, we haven't really failed, * |
| 163 | * but there is something wrong */ |
| 164 | #endif |
| 165 |
|
| 166 | #if defined(DEV_URANDOM) || defined(PJ_DEV_URANDOM) |
| 167 | if (dev_random_fdes >= 0) |
| 168 | close(dev_random_fdes); |
| 169 | |
| 170 | dev_random_fdes = RAND_SOURCE_NOT_READY;
|
| 171 | #endif |
| 172 | |
| 173 | return err_status_ok; |
| 174 | } |
| 175 | |