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comparison: ipc/chromium/src/third_party/libevent/arc4random.c

ipc/chromium/src/third_party/libevent/arc4random.c

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-1:000000000000 0:6d6827c7aa46
1 /* Portable arc4random.c based on arc4random.c from OpenBSD.
2 * Portable version by Chris Davis, adapted for Libevent by Nick Mathewson
3 * Copyright (c) 2010 Chris Davis, Niels Provos, and Nick Mathewson
4 * Copyright (c) 2010-2012 Niels Provos and Nick Mathewson
5 *
6 * Note that in Libevent, this file isn't compiled directly. Instead,
7 * it's included from evutil_rand.c
8 */
9
10 /*
11 * Copyright (c) 1996, David Mazieres <dm@uun.org>
12 * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
13 *
14 * Permission to use, copy, modify, and distribute this software for any
15 * purpose with or without fee is hereby granted, provided that the above
16 * copyright notice and this permission notice appear in all copies.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
19 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
20 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
21 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
22 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
23 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
24 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
25 */
26
27 /*
28 * Arc4 random number generator for OpenBSD.
29 *
30 * This code is derived from section 17.1 of Applied Cryptography,
31 * second edition, which describes a stream cipher allegedly
32 * compatible with RSA Labs "RC4" cipher (the actual description of
33 * which is a trade secret). The same algorithm is used as a stream
34 * cipher called "arcfour" in Tatu Ylonen's ssh package.
35 *
36 * Here the stream cipher has been modified always to include the time
37 * when initializing the state. That makes it impossible to
38 * regenerate the same random sequence twice, so this can't be used
39 * for encryption, but will generate good random numbers.
40 *
41 * RC4 is a registered trademark of RSA Laboratories.
42 */
43
44 #ifndef ARC4RANDOM_EXPORT
45 #define ARC4RANDOM_EXPORT
46 #endif
47
48 #ifndef ARC4RANDOM_UINT32
49 #define ARC4RANDOM_UINT32 uint32_t
50 #endif
51
52 #ifndef ARC4RANDOM_NO_INCLUDES
53 #ifdef WIN32
54 #include <wincrypt.h>
55 #include <process.h>
56 #else
57 #include <fcntl.h>
58 #include <unistd.h>
59 #include <sys/param.h>
60 #include <sys/time.h>
61 #ifdef _EVENT_HAVE_SYS_SYSCTL_H
62 #include <sys/sysctl.h>
63 #endif
64 #endif
65 #include <limits.h>
66 #include <stdlib.h>
67 #include <string.h>
68 #endif
69
70 /* Add platform entropy 32 bytes (256 bits) at a time. */
71 #define ADD_ENTROPY 32
72
73 /* Re-seed from the platform RNG after generating this many bytes. */
74 #define BYTES_BEFORE_RESEED 1600000
75
76 struct arc4_stream {
77 unsigned char i;
78 unsigned char j;
79 unsigned char s[256];
80 };
81
82 #ifdef WIN32
83 #define getpid _getpid
84 #define pid_t int
85 #endif
86
87 static int rs_initialized;
88 static struct arc4_stream rs;
89 static pid_t arc4_stir_pid;
90 static int arc4_count;
91 static int arc4_seeded_ok;
92
93 static inline unsigned char arc4_getbyte(void);
94
95 static inline void
96 arc4_init(void)
97 {
98 int n;
99
100 for (n = 0; n < 256; n++)
101 rs.s[n] = n;
102 rs.i = 0;
103 rs.j = 0;
104 }
105
106 static inline void
107 arc4_addrandom(const unsigned char *dat, int datlen)
108 {
109 int n;
110 unsigned char si;
111
112 rs.i--;
113 for (n = 0; n < 256; n++) {
114 rs.i = (rs.i + 1);
115 si = rs.s[rs.i];
116 rs.j = (rs.j + si + dat[n % datlen]);
117 rs.s[rs.i] = rs.s[rs.j];
118 rs.s[rs.j] = si;
119 }
120 rs.j = rs.i;
121 }
122
123 #ifndef WIN32
124 static ssize_t
125 read_all(int fd, unsigned char *buf, size_t count)
126 {
127 size_t numread = 0;
128 ssize_t result;
129
130 while (numread < count) {
131 result = read(fd, buf+numread, count-numread);
132 if (result<0)
133 return -1;
134 else if (result == 0)
135 break;
136 numread += result;
137 }
138
139 return (ssize_t)numread;
140 }
141 #endif
142
143 #ifdef WIN32
144 #define TRY_SEED_WIN32
145 static int
146 arc4_seed_win32(void)
147 {
148 /* This is adapted from Tor's crypto_seed_rng() */
149 static int provider_set = 0;
150 static HCRYPTPROV provider;
151 unsigned char buf[ADD_ENTROPY];
152
153 if (!provider_set) {
154 if (!CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
155 CRYPT_VERIFYCONTEXT)) {
156 if (GetLastError() != (DWORD)NTE_BAD_KEYSET)
157 return -1;
158 }
159 provider_set = 1;
160 }
161 if (!CryptGenRandom(provider, sizeof(buf), buf))
162 return -1;
163 arc4_addrandom(buf, sizeof(buf));
164 memset(buf, 0, sizeof(buf));
165 arc4_seeded_ok = 1;
166 return 0;
167 }
168 #endif
169
170 #if defined(_EVENT_HAVE_SYS_SYSCTL_H) && defined(_EVENT_HAVE_SYSCTL)
171 #if _EVENT_HAVE_DECL_CTL_KERN && _EVENT_HAVE_DECL_KERN_RANDOM && _EVENT_HAVE_DECL_RANDOM_UUID
172 #define TRY_SEED_SYSCTL_LINUX
173 static int
174 arc4_seed_sysctl_linux(void)
175 {
176 /* Based on code by William Ahern, this function tries to use the
177 * RANDOM_UUID sysctl to get entropy from the kernel. This can work
178 * even if /dev/urandom is inaccessible for some reason (e.g., we're
179 * running in a chroot). */
180 int mib[] = { CTL_KERN, KERN_RANDOM, RANDOM_UUID };
181 unsigned char buf[ADD_ENTROPY];
182 size_t len, n;
183 unsigned i;
184 int any_set;
185
186 memset(buf, 0, sizeof(buf));
187
188 for (len = 0; len < sizeof(buf); len += n) {
189 n = sizeof(buf) - len;
190
191 if (0 != sysctl(mib, 3, &buf[len], &n, NULL, 0))
192 return -1;
193 }
194 /* make sure that the buffer actually got set. */
195 for (i=0,any_set=0; i<sizeof(buf); ++i) {
196 any_set |= buf[i];
197 }
198 if (!any_set)
199 return -1;
200
201 arc4_addrandom(buf, sizeof(buf));
202 memset(buf, 0, sizeof(buf));
203 arc4_seeded_ok = 1;
204 return 0;
205 }
206 #endif
207
208 #if _EVENT_HAVE_DECL_CTL_KERN && _EVENT_HAVE_DECL_KERN_ARND
209 #define TRY_SEED_SYSCTL_BSD
210 static int
211 arc4_seed_sysctl_bsd(void)
212 {
213 /* Based on code from William Ahern and from OpenBSD, this function
214 * tries to use the KERN_ARND syscall to get entropy from the kernel.
215 * This can work even if /dev/urandom is inaccessible for some reason
216 * (e.g., we're running in a chroot). */
217 int mib[] = { CTL_KERN, KERN_ARND };
218 unsigned char buf[ADD_ENTROPY];
219 size_t len, n;
220 int i, any_set;
221
222 memset(buf, 0, sizeof(buf));
223
224 len = sizeof(buf);
225 if (sysctl(mib, 2, buf, &len, NULL, 0) == -1) {
226 for (len = 0; len < sizeof(buf); len += sizeof(unsigned)) {
227 n = sizeof(unsigned);
228 if (n + len > sizeof(buf))
229 n = len - sizeof(buf);
230 if (sysctl(mib, 2, &buf[len], &n, NULL, 0) == -1)
231 return -1;
232 }
233 }
234 /* make sure that the buffer actually got set. */
235 for (i=any_set=0; i<sizeof(buf); ++i) {
236 any_set |= buf[i];
237 }
238 if (!any_set)
239 return -1;
240
241 arc4_addrandom(buf, sizeof(buf));
242 memset(buf, 0, sizeof(buf));
243 arc4_seeded_ok = 1;
244 return 0;
245 }
246 #endif
247 #endif /* defined(_EVENT_HAVE_SYS_SYSCTL_H) */
248
249 #ifdef __linux__
250 #define TRY_SEED_PROC_SYS_KERNEL_RANDOM_UUID
251 static int
252 arc4_seed_proc_sys_kernel_random_uuid(void)
253 {
254 /* Occasionally, somebody will make /proc/sys accessible in a chroot,
255 * but not /dev/urandom. Let's try /proc/sys/kernel/random/uuid.
256 * Its format is stupid, so we need to decode it from hex.
257 */
258 int fd;
259 char buf[128];
260 unsigned char entropy[64];
261 int bytes, n, i, nybbles;
262 for (bytes = 0; bytes<ADD_ENTROPY; ) {
263 fd = evutil_open_closeonexec("/proc/sys/kernel/random/uuid", O_RDONLY, 0);
264 if (fd < 0)
265 return -1;
266 n = read(fd, buf, sizeof(buf));
267 close(fd);
268 if (n<=0)
269 return -1;
270 memset(entropy, 0, sizeof(entropy));
271 for (i=nybbles=0; i<n; ++i) {
272 if (EVUTIL_ISXDIGIT(buf[i])) {
273 int nyb = evutil_hex_char_to_int(buf[i]);
274 if (nybbles & 1) {
275 entropy[nybbles/2] |= nyb;
276 } else {
277 entropy[nybbles/2] |= nyb<<4;
278 }
279 ++nybbles;
280 }
281 }
282 if (nybbles < 2)
283 return -1;
284 arc4_addrandom(entropy, nybbles/2);
285 bytes += nybbles/2;
286 }
287 memset(entropy, 0, sizeof(entropy));
288 memset(buf, 0, sizeof(buf));
289 return 0;
290 }
291 #endif
292
293 #ifndef WIN32
294 #define TRY_SEED_URANDOM
295 static int
296 arc4_seed_urandom(void)
297 {
298 /* This is adapted from Tor's crypto_seed_rng() */
299 static const char *filenames[] = {
300 "/dev/srandom", "/dev/urandom", "/dev/random", NULL
301 };
302 unsigned char buf[ADD_ENTROPY];
303 int fd, i;
304 size_t n;
305
306 for (i = 0; filenames[i]; ++i) {
307 fd = evutil_open_closeonexec(filenames[i], O_RDONLY, 0);
308 if (fd<0)
309 continue;
310 n = read_all(fd, buf, sizeof(buf));
311 close(fd);
312 if (n != sizeof(buf))
313 return -1;
314 arc4_addrandom(buf, sizeof(buf));
315 memset(buf, 0, sizeof(buf));
316 arc4_seeded_ok = 1;
317 return 0;
318 }
319
320 return -1;
321 }
322 #endif
323
324 static int
325 arc4_seed(void)
326 {
327 int ok = 0;
328 /* We try every method that might work, and don't give up even if one
329 * does seem to work. There's no real harm in over-seeding, and if
330 * one of these sources turns out to be broken, that would be bad. */
331 #ifdef TRY_SEED_WIN32
332 if (0 == arc4_seed_win32())
333 ok = 1;
334 #endif
335 #ifdef TRY_SEED_URANDOM
336 if (0 == arc4_seed_urandom())
337 ok = 1;
338 #endif
339 #ifdef TRY_SEED_PROC_SYS_KERNEL_RANDOM_UUID
340 if (0 == arc4_seed_proc_sys_kernel_random_uuid())
341 ok = 1;
342 #endif
343 #ifdef TRY_SEED_SYSCTL_LINUX
344 /* Apparently Linux is deprecating sysctl, and spewing warning
345 * messages when you try to use it. */
346 if (!ok && 0 == arc4_seed_sysctl_linux())
347 ok = 1;
348 #endif
349 #ifdef TRY_SEED_SYSCTL_BSD
350 if (0 == arc4_seed_sysctl_bsd())
351 ok = 1;
352 #endif
353 return ok ? 0 : -1;
354 }
355
356 static int
357 arc4_stir(void)
358 {
359 int i;
360
361 if (!rs_initialized) {
362 arc4_init();
363 rs_initialized = 1;
364 }
365
366 arc4_seed();
367 if (!arc4_seeded_ok)
368 return -1;
369
370 /*
371 * Discard early keystream, as per recommendations in
372 * "Weaknesses in the Key Scheduling Algorithm of RC4" by
373 * Scott Fluhrer, Itsik Mantin, and Adi Shamir.
374 * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
375 *
376 * Ilya Mironov's "(Not So) Random Shuffles of RC4" suggests that
377 * we drop at least 2*256 bytes, with 12*256 as a conservative
378 * value.
379 *
380 * RFC4345 says to drop 6*256.
381 *
382 * At least some versions of this code drop 4*256, in a mistaken
383 * belief that "words" in the Fluhrer/Mantin/Shamir paper refers
384 * to processor words.
385 *
386 * We add another sect to the cargo cult, and choose 12*256.
387 */
388 for (i = 0; i < 12*256; i++)
389 (void)arc4_getbyte();
390 arc4_count = BYTES_BEFORE_RESEED;
391
392 return 0;
393 }
394
395
396 static void
397 arc4_stir_if_needed(void)
398 {
399 pid_t pid = getpid();
400
401 if (arc4_count <= 0 || !rs_initialized || arc4_stir_pid != pid)
402 {
403 arc4_stir_pid = pid;
404 arc4_stir();
405 }
406 }
407
408 static inline unsigned char
409 arc4_getbyte(void)
410 {
411 unsigned char si, sj;
412
413 rs.i = (rs.i + 1);
414 si = rs.s[rs.i];
415 rs.j = (rs.j + si);
416 sj = rs.s[rs.j];
417 rs.s[rs.i] = sj;
418 rs.s[rs.j] = si;
419 return (rs.s[(si + sj) & 0xff]);
420 }
421
422 static inline unsigned int
423 arc4_getword(void)
424 {
425 unsigned int val;
426
427 val = arc4_getbyte() << 24;
428 val |= arc4_getbyte() << 16;
429 val |= arc4_getbyte() << 8;
430 val |= arc4_getbyte();
431
432 return val;
433 }
434
435 #ifndef ARC4RANDOM_NOSTIR
436 ARC4RANDOM_EXPORT int
437 arc4random_stir(void)
438 {
439 int val;
440 _ARC4_LOCK();
441 val = arc4_stir();
442 _ARC4_UNLOCK();
443 return val;
444 }
445 #endif
446
447 #ifndef ARC4RANDOM_NOADDRANDOM
448 ARC4RANDOM_EXPORT void
449 arc4random_addrandom(const unsigned char *dat, int datlen)
450 {
451 int j;
452 _ARC4_LOCK();
453 if (!rs_initialized)
454 arc4_stir();
455 for (j = 0; j < datlen; j += 256) {
456 /* arc4_addrandom() ignores all but the first 256 bytes of
457 * its input. We want to make sure to look at ALL the
458 * data in 'dat', just in case the user is doing something
459 * crazy like passing us all the files in /var/log. */
460 arc4_addrandom(dat + j, datlen - j);
461 }
462 _ARC4_UNLOCK();
463 }
464 #endif
465
466 #ifndef ARC4RANDOM_NORANDOM
467 ARC4RANDOM_EXPORT ARC4RANDOM_UINT32
468 arc4random(void)
469 {
470 ARC4RANDOM_UINT32 val;
471 _ARC4_LOCK();
472 arc4_count -= 4;
473 arc4_stir_if_needed();
474 val = arc4_getword();
475 _ARC4_UNLOCK();
476 return val;
477 }
478 #endif
479
480 ARC4RANDOM_EXPORT void
481 arc4random_buf(void *_buf, size_t n)
482 {
483 unsigned char *buf = _buf;
484 _ARC4_LOCK();
485 arc4_stir_if_needed();
486 while (n--) {
487 if (--arc4_count <= 0)
488 arc4_stir();
489 buf[n] = arc4_getbyte();
490 }
491 _ARC4_UNLOCK();
492 }
493
494 #ifndef ARC4RANDOM_NOUNIFORM
495 /*
496 * Calculate a uniformly distributed random number less than upper_bound
497 * avoiding "modulo bias".
498 *
499 * Uniformity is achieved by generating new random numbers until the one
500 * returned is outside the range [0, 2**32 % upper_bound). This
501 * guarantees the selected random number will be inside
502 * [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
503 * after reduction modulo upper_bound.
504 */
505 ARC4RANDOM_EXPORT unsigned int
506 arc4random_uniform(unsigned int upper_bound)
507 {
508 ARC4RANDOM_UINT32 r, min;
509
510 if (upper_bound < 2)
511 return 0;
512
513 #if (UINT_MAX > 0xffffffffUL)
514 min = 0x100000000UL % upper_bound;
515 #else
516 /* Calculate (2**32 % upper_bound) avoiding 64-bit math */
517 if (upper_bound > 0x80000000)
518 min = 1 + ~upper_bound; /* 2**32 - upper_bound */
519 else {
520 /* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */
521 min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound;
522 }
523 #endif
524
525 /*
526 * This could theoretically loop forever but each retry has
527 * p > 0.5 (worst case, usually far better) of selecting a
528 * number inside the range we need, so it should rarely need
529 * to re-roll.
530 */
531 for (;;) {
532 r = arc4random();
533 if (r >= min)
534 break;
535 }
536
537 return r % upper_bound;
538 }
539 #endif

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