Disconnect hostapd from building in base
[dragonfly.git] / contrib / hostapd / src / crypto / random.c
CommitLineData
4781064b
JM
1/*
2 * Random number generator
3 * Copyright (c) 2010-2011, Jouni Malinen <j@w1.fi>
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 *
8 * This random number generator is used to provide additional entropy to the
9 * one provided by the operating system (os_get_random()) for session key
10 * generation. The os_get_random() output is expected to be secure and the
11 * implementation here is expected to provide only limited protection against
12 * cases where os_get_random() cannot provide strong randomness. This
13 * implementation shall not be assumed to be secure as the sole source of
14 * randomness. The random_get_bytes() function mixes in randomness from
15 * os_get_random() and as such, calls to os_get_random() can be replaced with
16 * calls to random_get_bytes() without reducing security.
17 *
18 * The design here follows partially the design used in the Linux
19 * drivers/char/random.c, but the implementation here is simpler and not as
20 * strong. This is a compromise to reduce duplicated CPU effort and to avoid
21 * extra code/memory size. As pointed out above, os_get_random() needs to be
22 * guaranteed to be secure for any of the security assumptions to hold.
23 */
24
25#include "utils/includes.h"
26#ifdef __linux__
27#include <fcntl.h>
28#endif /* __linux__ */
29
30#include "utils/common.h"
31#include "utils/eloop.h"
32#include "crypto/crypto.h"
33#include "sha1.h"
34#include "random.h"
35
36#define POOL_WORDS 32
37#define POOL_WORDS_MASK (POOL_WORDS - 1)
38#define POOL_TAP1 26
39#define POOL_TAP2 20
40#define POOL_TAP3 14
41#define POOL_TAP4 7
42#define POOL_TAP5 1
43#define EXTRACT_LEN 16
44#define MIN_READY_MARK 2
45
46static u32 pool[POOL_WORDS];
47static unsigned int input_rotate = 0;
48static unsigned int pool_pos = 0;
49static u8 dummy_key[20];
50#ifdef __linux__
51static size_t dummy_key_avail = 0;
52static int random_fd = -1;
53#endif /* __linux__ */
54static unsigned int own_pool_ready = 0;
55#define RANDOM_ENTROPY_SIZE 20
56static char *random_entropy_file = NULL;
57static int random_entropy_file_read = 0;
58
59#define MIN_COLLECT_ENTROPY 1000
60static unsigned int entropy = 0;
61static unsigned int total_collected = 0;
62
63
64static void random_write_entropy(void);
65
66
67static u32 __ROL32(u32 x, u32 y)
68{
69 return (x << (y & 31)) | (x >> (32 - (y & 31)));
70}
71
72
73static void random_mix_pool(const void *buf, size_t len)
74{
75 static const u32 twist[8] = {
76 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
77 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278
78 };
79 const u8 *pos = buf;
80 u32 w;
81
82 wpa_hexdump_key(MSG_EXCESSIVE, "random_mix_pool", buf, len);
83
84 while (len--) {
85 w = __ROL32(*pos++, input_rotate & 31);
86 input_rotate += pool_pos ? 7 : 14;
87 pool_pos = (pool_pos - 1) & POOL_WORDS_MASK;
88 w ^= pool[pool_pos];
89 w ^= pool[(pool_pos + POOL_TAP1) & POOL_WORDS_MASK];
90 w ^= pool[(pool_pos + POOL_TAP2) & POOL_WORDS_MASK];
91 w ^= pool[(pool_pos + POOL_TAP3) & POOL_WORDS_MASK];
92 w ^= pool[(pool_pos + POOL_TAP4) & POOL_WORDS_MASK];
93 w ^= pool[(pool_pos + POOL_TAP5) & POOL_WORDS_MASK];
94 pool[pool_pos] = (w >> 3) ^ twist[w & 7];
95 }
96}
97
98
99static void random_extract(u8 *out)
100{
101 unsigned int i;
102 u8 hash[SHA1_MAC_LEN];
103 u32 *hash_ptr;
104 u32 buf[POOL_WORDS / 2];
105
106 /* First, add hash back to pool to make backtracking more difficult. */
107 hmac_sha1(dummy_key, sizeof(dummy_key), (const u8 *) pool,
108 sizeof(pool), hash);
109 random_mix_pool(hash, sizeof(hash));
110 /* Hash half the pool to extra data */
111 for (i = 0; i < POOL_WORDS / 2; i++)
112 buf[i] = pool[(pool_pos - i) & POOL_WORDS_MASK];
113 hmac_sha1(dummy_key, sizeof(dummy_key), (const u8 *) buf,
114 sizeof(buf), hash);
115 /*
116 * Fold the hash to further reduce any potential output pattern.
117 * Though, compromise this to reduce CPU use for the most common output
118 * length (32) and return 16 bytes from instead of only half.
119 */
120 hash_ptr = (u32 *) hash;
121 hash_ptr[0] ^= hash_ptr[4];
122 os_memcpy(out, hash, EXTRACT_LEN);
123}
124
125
126void random_add_randomness(const void *buf, size_t len)
127{
128 struct os_time t;
129 static unsigned int count = 0;
130
131 count++;
132 if (entropy > MIN_COLLECT_ENTROPY && (count & 0x3ff) != 0) {
133 /*
134 * No need to add more entropy at this point, so save CPU and
135 * skip the update.
136 */
137 return;
138 }
139 wpa_printf(MSG_EXCESSIVE, "Add randomness: count=%u entropy=%u",
140 count, entropy);
141
142 os_get_time(&t);
143 wpa_hexdump_key(MSG_EXCESSIVE, "random pool",
144 (const u8 *) pool, sizeof(pool));
145 random_mix_pool(&t, sizeof(t));
146 random_mix_pool(buf, len);
147 wpa_hexdump_key(MSG_EXCESSIVE, "random pool",
148 (const u8 *) pool, sizeof(pool));
149 entropy++;
150 total_collected++;
151}
152
153
154int random_get_bytes(void *buf, size_t len)
155{
156 int ret;
157 u8 *bytes = buf;
158 size_t left;
159
160 wpa_printf(MSG_MSGDUMP, "Get randomness: len=%u entropy=%u",
161 (unsigned int) len, entropy);
162
163 /* Start with assumed strong randomness from OS */
164 ret = os_get_random(buf, len);
165 wpa_hexdump_key(MSG_EXCESSIVE, "random from os_get_random",
166 buf, len);
167
168 /* Mix in additional entropy extracted from the internal pool */
169 left = len;
170 while (left) {
171 size_t siz, i;
172 u8 tmp[EXTRACT_LEN];
173 random_extract(tmp);
174 wpa_hexdump_key(MSG_EXCESSIVE, "random from internal pool",
175 tmp, sizeof(tmp));
176 siz = left > EXTRACT_LEN ? EXTRACT_LEN : left;
177 for (i = 0; i < siz; i++)
178 *bytes++ ^= tmp[i];
179 left -= siz;
180 }
181
182#ifdef CONFIG_FIPS
183 /* Mix in additional entropy from the crypto module */
184 left = len;
185 while (left) {
186 size_t siz, i;
187 u8 tmp[EXTRACT_LEN];
188 if (crypto_get_random(tmp, sizeof(tmp)) < 0) {
189 wpa_printf(MSG_ERROR, "random: No entropy available "
190 "for generating strong random bytes");
191 return -1;
192 }
193 wpa_hexdump_key(MSG_EXCESSIVE, "random from crypto module",
194 tmp, sizeof(tmp));
195 siz = left > EXTRACT_LEN ? EXTRACT_LEN : left;
196 for (i = 0; i < siz; i++)
197 *bytes++ ^= tmp[i];
198 left -= siz;
199 }
200#endif /* CONFIG_FIPS */
201
202 wpa_hexdump_key(MSG_EXCESSIVE, "mixed random", buf, len);
203
204 if (entropy < len)
205 entropy = 0;
206 else
207 entropy -= len;
208
209 return ret;
210}
211
212
213int random_pool_ready(void)
214{
215#ifdef __linux__
216 int fd;
217 ssize_t res;
218
219 /*
220 * Make sure that there is reasonable entropy available before allowing
221 * some key derivation operations to proceed.
222 */
223
224 if (dummy_key_avail == sizeof(dummy_key))
225 return 1; /* Already initialized - good to continue */
226
227 /*
228 * Try to fetch some more data from the kernel high quality
229 * /dev/random. There may not be enough data available at this point,
230 * so use non-blocking read to avoid blocking the application
231 * completely.
232 */
233 fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
234 if (fd < 0) {
235#ifndef CONFIG_NO_STDOUT_DEBUG
236 int error = errno;
237 perror("open(/dev/random)");
238 wpa_printf(MSG_ERROR, "random: Cannot open /dev/random: %s",
239 strerror(error));
240#endif /* CONFIG_NO_STDOUT_DEBUG */
241 return -1;
242 }
243
244 res = read(fd, dummy_key + dummy_key_avail,
245 sizeof(dummy_key) - dummy_key_avail);
246 if (res < 0) {
247 wpa_printf(MSG_ERROR, "random: Cannot read from /dev/random: "
248 "%s", strerror(errno));
249 res = 0;
250 }
251 wpa_printf(MSG_DEBUG, "random: Got %u/%u bytes from "
252 "/dev/random", (unsigned) res,
253 (unsigned) (sizeof(dummy_key) - dummy_key_avail));
254 dummy_key_avail += res;
255 close(fd);
256
257 if (dummy_key_avail == sizeof(dummy_key)) {
258 if (own_pool_ready < MIN_READY_MARK)
259 own_pool_ready = MIN_READY_MARK;
260 random_write_entropy();
261 return 1;
262 }
263
264 wpa_printf(MSG_INFO, "random: Only %u/%u bytes of strong "
265 "random data available from /dev/random",
266 (unsigned) dummy_key_avail, (unsigned) sizeof(dummy_key));
267
268 if (own_pool_ready >= MIN_READY_MARK ||
269 total_collected + 10 * own_pool_ready > MIN_COLLECT_ENTROPY) {
270 wpa_printf(MSG_INFO, "random: Allow operation to proceed "
271 "based on internal entropy");
272 return 1;
273 }
274
275 wpa_printf(MSG_INFO, "random: Not enough entropy pool available for "
276 "secure operations");
277 return 0;
278#else /* __linux__ */
279 /* TODO: could do similar checks on non-Linux platforms */
280 return 1;
281#endif /* __linux__ */
282}
283
284
285void random_mark_pool_ready(void)
286{
287 own_pool_ready++;
288 wpa_printf(MSG_DEBUG, "random: Mark internal entropy pool to be "
289 "ready (count=%u/%u)", own_pool_ready, MIN_READY_MARK);
290 random_write_entropy();
291}
292
293
294#ifdef __linux__
295
296static void random_close_fd(void)
297{
298 if (random_fd >= 0) {
299 eloop_unregister_read_sock(random_fd);
300 close(random_fd);
301 random_fd = -1;
302 }
303}
304
305
306static void random_read_fd(int sock, void *eloop_ctx, void *sock_ctx)
307{
308 ssize_t res;
309
310 if (dummy_key_avail == sizeof(dummy_key)) {
311 random_close_fd();
312 return;
313 }
314
315 res = read(sock, dummy_key + dummy_key_avail,
316 sizeof(dummy_key) - dummy_key_avail);
317 if (res < 0) {
318 wpa_printf(MSG_ERROR, "random: Cannot read from /dev/random: "
319 "%s", strerror(errno));
320 return;
321 }
322
323 wpa_printf(MSG_DEBUG, "random: Got %u/%u bytes from /dev/random",
324 (unsigned) res,
325 (unsigned) (sizeof(dummy_key) - dummy_key_avail));
326 dummy_key_avail += res;
327
328 if (dummy_key_avail == sizeof(dummy_key)) {
329 random_close_fd();
330 if (own_pool_ready < MIN_READY_MARK)
331 own_pool_ready = MIN_READY_MARK;
332 random_write_entropy();
333 }
334}
335
336#endif /* __linux__ */
337
338
339static void random_read_entropy(void)
340{
341 char *buf;
342 size_t len;
343
344 if (!random_entropy_file)
345 return;
346
347 buf = os_readfile(random_entropy_file, &len);
348 if (buf == NULL)
349 return; /* entropy file not yet available */
350
351 if (len != 1 + RANDOM_ENTROPY_SIZE) {
352 wpa_printf(MSG_DEBUG, "random: Invalid entropy file %s",
353 random_entropy_file);
354 os_free(buf);
355 return;
356 }
357
358 own_pool_ready = (u8) buf[0];
359 random_add_randomness(buf + 1, RANDOM_ENTROPY_SIZE);
360 random_entropy_file_read = 1;
361 os_free(buf);
362 wpa_printf(MSG_DEBUG, "random: Added entropy from %s "
363 "(own_pool_ready=%u)",
364 random_entropy_file, own_pool_ready);
365}
366
367
368static void random_write_entropy(void)
369{
370 char buf[RANDOM_ENTROPY_SIZE];
371 FILE *f;
372 u8 opr;
373 int fail = 0;
374
375 if (!random_entropy_file)
376 return;
377
378 if (random_get_bytes(buf, RANDOM_ENTROPY_SIZE) < 0)
379 return;
380
381 f = fopen(random_entropy_file, "wb");
382 if (f == NULL) {
383 wpa_printf(MSG_ERROR, "random: Could not open entropy file %s "
384 "for writing", random_entropy_file);
385 return;
386 }
387
388 opr = own_pool_ready > 0xff ? 0xff : own_pool_ready;
389 if (fwrite(&opr, 1, 1, f) != 1 ||
390 fwrite(buf, RANDOM_ENTROPY_SIZE, 1, f) != 1)
391 fail = 1;
392 fclose(f);
393 if (fail) {
394 wpa_printf(MSG_ERROR, "random: Could not write entropy data "
395 "to %s", random_entropy_file);
396 return;
397 }
398
399 wpa_printf(MSG_DEBUG, "random: Updated entropy file %s "
400 "(own_pool_ready=%u)",
401 random_entropy_file, own_pool_ready);
402}
403
404
405void random_init(const char *entropy_file)
406{
407 os_free(random_entropy_file);
408 if (entropy_file)
409 random_entropy_file = os_strdup(entropy_file);
410 else
411 random_entropy_file = NULL;
412 random_read_entropy();
413
414#ifdef __linux__
415 if (random_fd >= 0)
416 return;
417
418 random_fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
419 if (random_fd < 0) {
420#ifndef CONFIG_NO_STDOUT_DEBUG
421 int error = errno;
422 perror("open(/dev/random)");
423 wpa_printf(MSG_ERROR, "random: Cannot open /dev/random: %s",
424 strerror(error));
425#endif /* CONFIG_NO_STDOUT_DEBUG */
426 return;
427 }
428 wpa_printf(MSG_DEBUG, "random: Trying to read entropy from "
429 "/dev/random");
430
431 eloop_register_read_sock(random_fd, random_read_fd, NULL, NULL);
432#endif /* __linux__ */
433
434 random_write_entropy();
435}
436
437
438void random_deinit(void)
439{
440#ifdef __linux__
441 random_close_fd();
442#endif /* __linux__ */
443 random_write_entropy();
444 os_free(random_entropy_file);
445 random_entropy_file = NULL;
446}