Line data Source code
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 0 : rand_source_init(void) {
80 0 : if (dev_random_fdes >= 0) {
81 : /* already open */
82 0 : 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 0 : fprintf(stderr, "WARNING: no real random source present!\n");
94 0 : dev_random_fdes = RAND_SOURCE_READY;
95 : #endif
96 0 : return err_status_ok;
97 : }
98 :
99 : err_status_t
100 0 : 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 0 : uint8_t *dst = (uint8_t *)dest;
134 0 : while (len)
135 : {
136 0 : 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 0 : *dst++ = val & 0xff;
141 0 : len--;
142 : }
143 : #endif
144 0 : return err_status_ok;
145 : }
146 :
147 : err_status_t
148 0 : rand_source_deinit(void) {
149 0 : if (dev_random_fdes < 0)
150 0 : 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 0 : dev_random_fdes = RAND_SOURCE_NOT_READY;
156 :
157 0 : return err_status_ok;
158 : }
|
