1 /* $NetBSD: crypto-rand.c,v 1.2 2017/01/28 21:31:49 christos 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 #undef HEIMDAL_WARN_UNUSED_RESULT_ATTRIBUTE
39 #define HEIMDAL_WARN_UNUSED_RESULT_ATTRIBUTE
40
41 #define ENTROPY_NEEDED 128
42
43 static HEIMDAL_MUTEX crypto_mutex = HEIMDAL_MUTEX_INITIALIZER;
44
45 static int
seed_something(void)46 seed_something(void)
47 {
48 #ifndef NO_RANDFILE
49 char buf[1024], seedfile[256];
50
51 /* If there is a seed file, load it. But such a file cannot be trusted,
52 so use 0 for the entropy estimate */
53 if (RAND_file_name(seedfile, sizeof(seedfile))) {
54 int fd;
55 fd = open(seedfile, O_RDONLY | O_BINARY | O_CLOEXEC);
56 if (fd >= 0) {
57 ssize_t ret;
58 rk_cloexec(fd);
59 ret = read(fd, buf, sizeof(buf));
60 if (ret > 0)
61 RAND_add(buf, ret, 0.0);
62 close(fd);
63 } else
64 seedfile[0] = '\0';
65 } else
66 seedfile[0] = '\0';
67 #endif
68
69 /* Calling RAND_status() will try to use /dev/urandom if it exists so
70 we do not have to deal with it. */
71 if (RAND_status() != 1) {
72 /* TODO: Once a Windows CryptoAPI RAND method is defined, we
73 can use that and failover to another method. */
74 }
75
76 if (RAND_status() == 1) {
77 #ifndef NO_RANDFILE
78 /* Update the seed file */
79 if (seedfile[0])
80 RAND_write_file(seedfile);
81 #endif
82
83 return 0;
84 } else
85 return -1;
86 }
87
88 /**
89 * Fill buffer buf with len bytes of PRNG randomness that is ok to use
90 * for key generation, padding and public diclosing the randomness w/o
91 * disclosing the randomness source.
92 *
93 * This function can fail, and callers must check the return value.
94 *
95 * @param buf a buffer to fill with randomness
96 * @param len length of memory that buf points to.
97 *
98 * @return return 0 on success or HEIM_ERR_RANDOM_OFFLINE if the
99 * funcation failed to initialize the randomness source.
100 *
101 * @ingroup krb5_crypto
102 */
103
104 HEIMDAL_WARN_UNUSED_RESULT_ATTRIBUTE
105 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_generate_random(void * buf,size_t len)106 krb5_generate_random(void *buf, size_t len)
107 {
108 static int rng_initialized = 0;
109 int ret;
110
111 HEIMDAL_MUTEX_lock(&crypto_mutex);
112 if (!rng_initialized) {
113 if (seed_something()) {
114 HEIMDAL_MUTEX_unlock(&crypto_mutex);
115 return HEIM_ERR_RANDOM_OFFLINE;
116 }
117 rng_initialized = 1;
118 }
119 if (RAND_bytes(buf, len) <= 0)
120 ret = HEIM_ERR_RANDOM_OFFLINE;
121 else
122 ret = 0;
123 HEIMDAL_MUTEX_unlock(&crypto_mutex);
124
125 return ret;
126 }
127
128 /**
129 * Fill buffer buf with len bytes of PRNG randomness that is ok to use
130 * for key generation, padding and public diclosing the randomness w/o
131 * disclosing the randomness source.
132 *
133 * This function can NOT fail, instead it will abort() and program will crash.
134 *
135 * If this function is called after a successful krb5_init_context(),
136 * the chance of it failing is low due to that krb5_init_context()
137 * pulls out some random, and quite commonly the randomness sources
138 * will not fail once it have started to produce good output,
139 * /dev/urandom behavies that way.
140 *
141 * @param buf a buffer to fill with randomness
142 * @param len length of memory that buf points to.
143 *
144 * @ingroup krb5_crypto
145 */
146
147
148 KRB5_LIB_FUNCTION void KRB5_LIB_CALL
krb5_generate_random_block(void * buf,size_t len)149 krb5_generate_random_block(void *buf, size_t len)
150 {
151 int ret = krb5_generate_random(buf, len);
152 if (ret)
153 krb5_abortx(NULL, "Failed to generate random block");
154 }
155