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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_secure_rng_add_bytes(const char * buf,size_t n)196 evutil_secure_rng_add_bytes(const char *buf, size_t n)
197 {
198 #if !defined(__BIONIC__) /* bionic and OpenBSD removed this; it's a no-op in their current implementation. */
199 	arc4random_addrandom((unsigned char*)buf,
200 	    n>(size_t)INT_MAX ? INT_MAX : (int)n);
201 #endif
202 }
203 
204 void
evutil_free_secure_rng_globals_(void)205 evutil_free_secure_rng_globals_(void)
206 {
207     evutil_free_secure_rng_globals_locks();
208 }
209