evutil_rand.c revision 290001 
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>
46int
47evutil_secure_rng_set_urandom_device_file(char *fname)
48{
49	(void) fname;
50	return -1;
51}
52int
53evutil_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
60int
61evutil_secure_rng_global_setup_locks_(const int enable_locks)
62{
63	return 0;
64}
65#endif
66static void
67evutil_free_secure_rng_globals_locks(void)
68{
69}
70
71static void
72ev_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
126static 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
137int
138evutil_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
145static void
146evutil_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
157int
158evutil_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
168int
169evutil_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
181static void
182ev_arc4random_buf(void *buf, size_t n)
183{
184	arc4random_buf(buf, n);
185}
186
187#endif /* } !EVENT__HAVE_ARC4RANDOM */
188
189void
190evutil_secure_rng_get_bytes(void *buf, size_t n)
191{
192	ev_arc4random_buf(buf, n);
193}
194
195void
196evutil_secure_rng_add_bytes(const char *buf, size_t n)
197{
198	arc4random_addrandom((unsigned char*)buf,
199	    n>(size_t)INT_MAX ? INT_MAX : (int)n);
200}
201
202void
203evutil_free_secure_rng_globals_(void)
204{
205    evutil_free_secure_rng_globals_locks();
206}
207