1 /*
2 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. The name of the author may not be used to endorse or promote products
13 * derived from this software without specific prior written permission.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 /* This file has our secure PRNG code. On platforms that have arc4random(),
28 * we just use that. Otherwise, we include arc4random.c as a bunch of static
29 * functions, and wrap it lightly. We don't expose the arc4random*() APIs
30 * because A) they aren't in our namespace, and B) it's not nice to name your
31 * APIs after their implementations. We keep them in a separate file
32 * so that other people can rip it out and use it for whatever.
33 */
34
35 #include "event2/event-config.h"
36 #include "evconfig-private.h"
37
38 #include <limits.h>
39
40 #include "util-internal.h"
41 #include "evthread-internal.h"
42
43 #ifdef EVENT__HAVE_ARC4RANDOM
44 #include <stdlib.h>
45 #include <string.h>
46 int
evutil_secure_rng_set_urandom_device_file(char * fname)47 evutil_secure_rng_set_urandom_device_file(char *fname)
48 {
49 (void) fname;
50 return -1;
51 }
52 int
evutil_secure_rng_init(void)53 evutil_secure_rng_init(void)
54 {
55 /* call arc4random() now to force it to self-initialize */
56 (void) arc4random();
57 return 0;
58 }
59 #ifndef EVENT__DISABLE_THREAD_SUPPORT
60 int
evutil_secure_rng_global_setup_locks_(const int enable_locks)61 evutil_secure_rng_global_setup_locks_(const int enable_locks)
62 {
63 return 0;
64 }
65 #endif
66 static void
evutil_free_secure_rng_globals_locks(void)67 evutil_free_secure_rng_globals_locks(void)
68 {
69 }
70
71 static void
ev_arc4random_buf(void * buf,size_t n)72 ev_arc4random_buf(void *buf, size_t n)
73 {
74 #if defined(EVENT__HAVE_ARC4RANDOM_BUF) && !defined(__APPLE__)
75 arc4random_buf(buf, n);
76 return;
77 #else
78 unsigned char *b = buf;
79
80 #if defined(EVENT__HAVE_ARC4RANDOM_BUF)
81 /* OSX 10.7 introducd arc4random_buf, so if you build your program
82 * there, you'll get surprised when older versions of OSX fail to run.
83 * To solve this, we can check whether the function pointer is set,
84 * and fall back otherwise. (OSX does this using some linker
85 * trickery.)
86 */
87 {
88 void (*tptr)(void *,size_t) =
89 (void (*)(void*,size_t))arc4random_buf;
90 if (tptr != NULL) {
91 arc4random_buf(buf, n);
92 return;
93 }
94 }
95 #endif
96 /* Make sure that we start out with b at a 4-byte alignment; plenty
97 * of CPUs care about this for 32-bit access. */
98 if (n >= 4 && ((ev_uintptr_t)b) & 3) {
99 ev_uint32_t u = arc4random();
100 int n_bytes = 4 - (((ev_uintptr_t)b) & 3);
101 memcpy(b, &u, n_bytes);
102 b += n_bytes;
103 n -= n_bytes;
104 }
105 while (n >= 4) {
106 *(ev_uint32_t*)b = arc4random();
107 b += 4;
108 n -= 4;
109 }
110 if (n) {
111 ev_uint32_t u = arc4random();
112 memcpy(b, &u, n);
113 }
114 #endif
115 }
116
117 #else /* !EVENT__HAVE_ARC4RANDOM { */
118
119 #ifdef EVENT__ssize_t
120 #define ssize_t EVENT__ssize_t
121 #endif
122 #define ARC4RANDOM_EXPORT static
123 #define ARC4_LOCK_() EVLOCK_LOCK(arc4rand_lock, 0)
124 #define ARC4_UNLOCK_() EVLOCK_UNLOCK(arc4rand_lock, 0)
125 #ifndef EVENT__DISABLE_THREAD_SUPPORT
126 static void *arc4rand_lock;
127 #endif
128
129 #define ARC4RANDOM_UINT32 ev_uint32_t
130 #define ARC4RANDOM_NOSTIR
131 #define ARC4RANDOM_NORANDOM
132 #define ARC4RANDOM_NOUNIFORM
133
134 #include "./arc4random.c"
135
136 #ifndef EVENT__DISABLE_THREAD_SUPPORT
137 int
evutil_secure_rng_global_setup_locks_(const int enable_locks)138 evutil_secure_rng_global_setup_locks_(const int enable_locks)
139 {
140 EVTHREAD_SETUP_GLOBAL_LOCK(arc4rand_lock, 0);
141 return 0;
142 }
143 #endif
144
145 static void
evutil_free_secure_rng_globals_locks(void)146 evutil_free_secure_rng_globals_locks(void)
147 {
148 #ifndef EVENT__DISABLE_THREAD_SUPPORT
149 if (arc4rand_lock != NULL) {
150 EVTHREAD_FREE_LOCK(arc4rand_lock, 0);
151 arc4rand_lock = NULL;
152 }
153 #endif
154 return;
155 }
156
157 int
evutil_secure_rng_set_urandom_device_file(char * fname)158 evutil_secure_rng_set_urandom_device_file(char *fname)
159 {
160 #ifdef TRY_SEED_URANDOM
161 ARC4_LOCK_();
162 arc4random_urandom_filename = fname;
163 ARC4_UNLOCK_();
164 #endif
165 return 0;
166 }
167
168 int
evutil_secure_rng_init(void)169 evutil_secure_rng_init(void)
170 {
171 int val;
172
173 ARC4_LOCK_();
174 if (!arc4_seeded_ok)
175 arc4_stir();
176 val = arc4_seeded_ok ? 0 : -1;
177 ARC4_UNLOCK_();
178 return val;
179 }
180
181 static void
ev_arc4random_buf(void * buf,size_t n)182 ev_arc4random_buf(void *buf, size_t n)
183 {
184 arc4random_buf(buf, n);
185 }
186
187 #endif /* } !EVENT__HAVE_ARC4RANDOM */
188
189 void
evutil_secure_rng_get_bytes(void * buf,size_t n)190 evutil_secure_rng_get_bytes(void *buf, size_t n)
191 {
192 ev_arc4random_buf(buf, n);
193 }
194
195 void
evutil_free_secure_rng_globals_(void)196 evutil_free_secure_rng_globals_(void)
197 {
198 evutil_free_secure_rng_globals_locks();
199 }
200