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
37 #include <limits.h>
38
39 #include "util-internal.h"
40 #include "evthread-internal.h"
41
42 #ifdef _EVENT_HAVE_ARC4RANDOM
43 #include <stdlib.h>
44 #include <string.h>
45 int
evutil_secure_rng_set_urandom_device_file(char * fname)46 evutil_secure_rng_set_urandom_device_file(char *fname)
47 {
48 (void) fname;
49 return -1;
50 }
51 int
evutil_secure_rng_init(void)52 evutil_secure_rng_init(void)
53 {
54 /* call arc4random() now to force it to self-initialize */
55 (void) arc4random();
56 return 0;
57 }
58 int
evutil_secure_rng_global_setup_locks_(const int enable_locks)59 evutil_secure_rng_global_setup_locks_(const int enable_locks)
60 {
61 return 0;
62 }
63
64 static void
ev_arc4random_buf(void * buf,size_t n)65 ev_arc4random_buf(void *buf, size_t n)
66 {
67 #if defined(_EVENT_HAVE_ARC4RANDOM_BUF) && !defined(__APPLE__)
68 return arc4random_buf(buf, n);
69 #else
70 unsigned char *b = buf;
71
72 #if defined(_EVENT_HAVE_ARC4RANDOM_BUF)
73 /* OSX 10.7 introducd arc4random_buf, so if you build your program
74 * there, you'll get surprised when older versions of OSX fail to run.
75 * To solve this, we can check whether the function pointer is set,
76 * and fall back otherwise. (OSX does this using some linker
77 * trickery.)
78 */
79 {
80 void (*tptr)(void *,size_t) =
81 (void (*)(void*,size_t))arc4random_buf;
82 if (tptr != NULL) {
83 return arc4random_buf(buf, n);
84 }
85 }
86 #endif
87 /* Make sure that we start out with b at a 4-byte alignment; plenty
88 * of CPUs care about this for 32-bit access. */
89 if (n >= 4 && ((ev_uintptr_t)b) & 3) {
90 ev_uint32_t u = arc4random();
91 int n_bytes = 4 - (((ev_uintptr_t)b) & 3);
92 memcpy(b, &u, n_bytes);
93 b += n_bytes;
94 n -= n_bytes;
95 }
96 while (n >= 4) {
97 *(ev_uint32_t*)b = arc4random();
98 b += 4;
99 n -= 4;
100 }
101 if (n) {
102 ev_uint32_t u = arc4random();
103 memcpy(b, &u, n);
104 }
105 #endif
106 }
107
108 #else /* !_EVENT_HAVE_ARC4RANDOM { */
109
110 #ifdef _EVENT_ssize_t
111 #define ssize_t _EVENT_SSIZE_t
112 #endif
113 #define ARC4RANDOM_EXPORT static
114 #define _ARC4_LOCK() EVLOCK_LOCK(arc4rand_lock, 0)
115 #define _ARC4_UNLOCK() EVLOCK_UNLOCK(arc4rand_lock, 0)
116 #ifndef _EVENT_DISABLE_THREAD_SUPPORT
117 static void *arc4rand_lock;
118 #endif
119
120 #define ARC4RANDOM_UINT32 ev_uint32_t
121 #define ARC4RANDOM_NOSTIR
122 #define ARC4RANDOM_NORANDOM
123 #define ARC4RANDOM_NOUNIFORM
124
125 #include "./arc4random.c"
126
127 #ifndef _EVENT_DISABLE_THREAD_SUPPORT
128 int
evutil_secure_rng_global_setup_locks_(const int enable_locks)129 evutil_secure_rng_global_setup_locks_(const int enable_locks)
130 {
131 EVTHREAD_SETUP_GLOBAL_LOCK(arc4rand_lock, 0);
132 return 0;
133 }
134 #endif
135
136 int
evutil_secure_rng_set_urandom_device_file(char * fname)137 evutil_secure_rng_set_urandom_device_file(char *fname)
138 {
139 #ifdef TRY_SEED_URANDOM
140 _ARC4_LOCK();
141 arc4random_urandom_filename = fname;
142 _ARC4_UNLOCK();
143 #endif
144 return 0;
145 }
146
147 int
evutil_secure_rng_init(void)148 evutil_secure_rng_init(void)
149 {
150 int val;
151
152 _ARC4_LOCK();
153 if (!arc4_seeded_ok)
154 arc4_stir();
155 val = arc4_seeded_ok ? 0 : -1;
156 _ARC4_UNLOCK();
157 return val;
158 }
159
160 static void
ev_arc4random_buf(void * buf,size_t n)161 ev_arc4random_buf(void *buf, size_t n)
162 {
163 arc4random_buf(buf, n);
164 }
165
166 #endif /* } !_EVENT_HAVE_ARC4RANDOM */
167
168 void
evutil_secure_rng_get_bytes(void * buf,size_t n)169 evutil_secure_rng_get_bytes(void *buf, size_t n)
170 {
171 ev_arc4random_buf(buf, n);
172 }
173
174 void
evutil_secure_rng_add_bytes(const char * buf,size_t n)175 evutil_secure_rng_add_bytes(const char *buf, size_t n)
176 {
177 #if !defined(__BIONIC__) /* bionic and OpenBSD removed this; it's a no-op in their current implementation. */
178 arc4random_addrandom((unsigned char*)buf,
179 n>(size_t)INT_MAX ? INT_MAX : (int)n);
180 #endif
181 }
182
183