1 /* $NetBSD: crypto-rand.c,v 1.1.1.1 2011/04/13 18:15:32 elric Exp $ */
2
3 /*
4 * Copyright (c) 1997 - 2008 Kungliga Tekniska Högskolan
5 * (Royal Institute of Technology, Stockholm, Sweden).
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * 3. Neither the name of the Institute nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #include "krb5_locl.h"
37
38 #define ENTROPY_NEEDED 128
39
40 static HEIMDAL_MUTEX crypto_mutex = HEIMDAL_MUTEX_INITIALIZER;
41
42 static int
seed_something(void)43 seed_something(void)
44 {
45 char buf[1024], seedfile[256];
46
47 /* If there is a seed file, load it. But such a file cannot be trusted,
48 so use 0 for the entropy estimate */
49 if (RAND_file_name(seedfile, sizeof(seedfile))) {
50 int fd;
51 fd = open(seedfile, O_RDONLY | O_BINARY | O_CLOEXEC);
52 if (fd >= 0) {
53 ssize_t ret;
54 rk_cloexec(fd);
55 ret = read(fd, buf, sizeof(buf));
56 if (ret > 0)
57 RAND_add(buf, ret, 0.0);
58 close(fd);
59 } else
60 seedfile[0] = '\0';
61 } else
62 seedfile[0] = '\0';
63
64 /* Calling RAND_status() will try to use /dev/urandom if it exists so
65 we do not have to deal with it. */
66 if (RAND_status() != 1) {
67 #ifndef _WIN32
68 krb5_context context;
69 const char *p;
70
71 /* Try using egd */
72 if (!krb5_init_context(&context)) {
73 p = krb5_config_get_string(context, NULL, "libdefaults",
74 "egd_socket", NULL);
75 if (p != NULL)
76 RAND_egd_bytes(p, ENTROPY_NEEDED);
77 krb5_free_context(context);
78 }
79 #else
80 /* TODO: Once a Windows CryptoAPI RAND method is defined, we
81 can use that and failover to another method. */
82 #endif
83 }
84
85 if (RAND_status() == 1) {
86 /* Update the seed file */
87 if (seedfile[0])
88 RAND_write_file(seedfile);
89
90 return 0;
91 } else
92 return -1;
93 }
94
95 KRB5_LIB_FUNCTION void KRB5_LIB_CALL
krb5_generate_random_block(void * buf,size_t len)96 krb5_generate_random_block(void *buf, size_t len)
97 {
98 static int rng_initialized = 0;
99
100 HEIMDAL_MUTEX_lock(&crypto_mutex);
101 if (!rng_initialized) {
102 if (seed_something())
103 krb5_abortx(NULL, "Fatal: could not seed the "
104 "random number generator");
105
106 rng_initialized = 1;
107 }
108 HEIMDAL_MUTEX_unlock(&crypto_mutex);
109 if (RAND_bytes(buf, len) <= 0)
110 krb5_abortx(NULL, "Failed to generate random block");
111 }
112