yarrow.c revision 100082 
1/*-
2 * Copyright (c) 2000 Mark R V Murray
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer
10 *    in this position and unchanged.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
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 * $FreeBSD: head/sys/dev/random/yarrow.c 100082 2002-07-15 13:58:35Z markm $
27 */
28
29#include <sys/param.h>
30#include <sys/systm.h>
31#include <sys/kernel.h>
32#include <sys/lock.h>
33#include <sys/mutex.h>
34#include <sys/random.h>
35#include <sys/sysctl.h>
36
37#include <crypto/rijndael/rijndael.h>
38#include <crypto/sha2/sha2.h>
39
40#include <dev/random/hash.h>
41#include <dev/random/randomdev.h>
42#include <dev/random/yarrow.h>
43
44/* #define DEBUG */
45
46RANDOM_CHECK_UINT(gengateinterval, 4, 64);
47RANDOM_CHECK_UINT(bins, 2, 16);
48RANDOM_CHECK_UINT(fastthresh, BLOCKSIZE/4, BLOCKSIZE);
49RANDOM_CHECK_UINT(slowthresh, BLOCKSIZE/4, BLOCKSIZE);
50RANDOM_CHECK_UINT(slowoverthresh, 1, 5);
51
52/* Structure holding the entropy state */
53static struct random_state random_state;
54
55SYSCTL_NODE(_kern_random, OID_AUTO, yarrow, CTLFLAG_RW, 0, "Yarrow Parameters");
56SYSCTL_PROC(_kern_random_yarrow, OID_AUTO, gengateinterval,
57	CTLTYPE_INT|CTLFLAG_RW, &random_state.gengateinterval, 10,
58	random_check_uint_gengateinterval, "I", "Generator Gate Interval");
59SYSCTL_PROC(_kern_random_yarrow, OID_AUTO, bins,
60	CTLTYPE_INT|CTLFLAG_RW, &random_state.bins, 10,
61	random_check_uint_bins, "I", "Execution time tuner");
62SYSCTL_PROC(_kern_random_yarrow, OID_AUTO, fastthresh,
63	CTLTYPE_INT|CTLFLAG_RW, &random_state.pool[0].thresh, (3*BLOCKSIZE)/4,
64	random_check_uint_fastthresh, "I", "Fast reseed threshold");
65SYSCTL_PROC(_kern_random_yarrow, OID_AUTO, slowthresh,
66	CTLTYPE_INT|CTLFLAG_RW, &random_state.pool[1].thresh, BLOCKSIZE,
67	random_check_uint_slowthresh, "I", "Slow reseed threshold");
68SYSCTL_PROC(_kern_random_yarrow, OID_AUTO, slowoverthresh,
69	CTLTYPE_INT|CTLFLAG_RW, &random_state.slowoverthresh, 2,
70	random_check_uint_slowoverthresh, "I", "Slow over-threshold reseed");
71
72static void generator_gate(void);
73static void reseed(u_int);
74
75/* The reseed thread mutex */
76static struct mtx random_reseed_mtx;
77
78/* Process a single stochastic event off the harvest queue */
79void
80random_process_event(struct harvest *event)
81{
82	u_int pl, overthreshhold[2];
83	struct source *source;
84	enum esource src;
85
86	/* Unpack the event into the appropriate source accumulator */
87	pl = random_state.which;
88	source = &random_state.pool[pl].source[event->source];
89	yarrow_hash_iterate(&random_state.pool[pl].hash, event->entropy,
90		sizeof(event->entropy));
91	yarrow_hash_iterate(&random_state.pool[pl].hash, &event->somecounter,
92		sizeof(event->somecounter));
93	source->frac += event->frac;
94	source->bits += event->bits + source->frac/1024;
95	source->frac %= 1024;
96
97	/* Count the over-threshold sources in each pool */
98	for (pl = 0; pl < 2; pl++) {
99		overthreshhold[pl] = 0;
100		for (src = RANDOM_START; src < ENTROPYSOURCE; src++) {
101			if (random_state.pool[pl].source[src].bits
102				> random_state.pool[pl].thresh)
103				overthreshhold[pl]++;
104		}
105	}
106
107	/* if any fast source over threshhold, reseed */
108	if (overthreshhold[FAST])
109		reseed(FAST);
110
111	/* if enough slow sources are over threshhold, reseed */
112	if (overthreshhold[SLOW] >= random_state.slowoverthresh)
113		reseed(SLOW);
114
115	/* Invert the fast/slow pool selector bit */
116	random_state.which = !random_state.which;
117}
118
119void
120random_init(void)
121{
122	int i;
123
124	/* Yarrow parameters. Do not adjust these unless you have
125	 * have a very good clue about what they do!
126	 */
127	random_state.gengateinterval = 10;
128	random_state.bins = 10;
129	random_state.pool[0].thresh = (3*BLOCKSIZE)/4;
130	random_state.pool[1].thresh = BLOCKSIZE;
131	random_state.slowoverthresh = 2;
132	random_state.which = FAST;
133
134	/* Initialise the fast and slow entropy pools */
135	for (i = 0; i < 2; i++)
136		yarrow_hash_init(&random_state.pool[i].hash);
137
138	/* Clear the counter */
139	for (i = 0; i < 4; i++)
140		random_state.counter[i] = 0;
141
142	/* Set up a lock for the reseed process */
143	mtx_init(&random_reseed_mtx, "random reseed", NULL, MTX_DEF);
144}
145
146void
147random_deinit(void)
148{
149	mtx_destroy(&random_reseed_mtx);
150}
151
152static void
153reseed(u_int fastslow)
154{
155	/* Interrupt-context stack is a limited resource; make large
156	 * structures static.
157	 */
158	static u_char v[TIMEBIN][KEYSIZE];	/* v[i] */
159	static struct yarrowhash context;
160	u_char hash[KEYSIZE];			/* h' */
161	u_char temp[KEYSIZE];
162	u_int i;
163	enum esource j;
164
165#ifdef DEBUG
166	mtx_lock(&Giant);
167	printf("Reseed type %d\n", fastslow);
168	mtx_unlock(&Giant);
169#endif
170
171	/* The reseed task must not be jumped on */
172	mtx_lock(&random_reseed_mtx);
173
174	/* 1. Hash the accumulated entropy into v[0] */
175
176	yarrow_hash_init(&context);
177	/* Feed the slow pool hash in if slow */
178	if (fastslow == SLOW)
179		yarrow_hash_iterate(&context,
180			&random_state.pool[SLOW].hash,
181			sizeof(struct yarrowhash));
182	yarrow_hash_iterate(&context,
183		&random_state.pool[FAST].hash, sizeof(struct yarrowhash));
184	yarrow_hash_finish(&context, v[0]);
185
186	/* 2. Compute hash values for all v. _Supposed_ to be computationally
187	 *    intensive.
188	 */
189
190	if (random_state.bins > TIMEBIN)
191		random_state.bins = TIMEBIN;
192	for (i = 1; i < random_state.bins; i++) {
193		yarrow_hash_init(&context);
194		/* v[i] #= h(v[i - 1]) */
195		yarrow_hash_iterate(&context, v[i - 1], KEYSIZE);
196		/* v[i] #= h(v[0]) */
197		yarrow_hash_iterate(&context, v[0], KEYSIZE);
198		/* v[i] #= h(i) */
199		yarrow_hash_iterate(&context, &i, sizeof(u_int));
200		/* Return the hashval */
201		yarrow_hash_finish(&context, v[i]);
202	}
203
204	/* 3. Compute a new key; h' is the identity function here;
205	 *    it is not being ignored!
206	 */
207
208	yarrow_hash_init(&context);
209	yarrow_hash_iterate(&context, &random_state.key, KEYSIZE);
210	for (i = 1; i < random_state.bins; i++)
211		yarrow_hash_iterate(&context, &v[i], KEYSIZE);
212	yarrow_hash_finish(&context, temp);
213	yarrow_encrypt_init(&random_state.key, temp);
214
215	/* 4. Recompute the counter */
216
217	for (i = 0; i < 4; i++)
218		random_state.counter[i] = 0;
219	yarrow_encrypt(&random_state.key, random_state.counter, temp);
220	memcpy(random_state.counter, temp, sizeof(random_state.counter));
221
222	/* 5. Reset entropy estimate accumulators to zero */
223
224	for (i = 0; i <= fastslow; i++) {
225		for (j = RANDOM_START; j < ENTROPYSOURCE; j++) {
226			random_state.pool[i].source[j].bits = 0;
227			random_state.pool[i].source[j].frac = 0;
228		}
229	}
230
231	/* 6. Wipe memory of intermediate values */
232
233	memset((void *)v, 0, sizeof(v));
234	memset((void *)temp, 0, sizeof(temp));
235	memset((void *)hash, 0, sizeof(hash));
236
237	/* 7. Dump to seed file */
238	/* XXX Not done here yet */
239
240	/* Release the reseed mutex */
241	mtx_unlock(&random_reseed_mtx);
242
243#ifdef DEBUG
244	mtx_lock(&Giant);
245	printf("Reseed finish\n");
246	mtx_unlock(&Giant);
247#endif
248
249	/* Unblock the device if it was blocked due to being unseeded */
250	random_unblock();
251}
252
253/* Internal function to return processed entropy from the PRNG */
254int
255read_random_real(void *buf, int count)
256{
257	static int cur = 0;
258	static int gate = 1;
259	static u_char genval[KEYSIZE];
260	int i;
261	int retval;
262
263	/* The reseed task must not be jumped on */
264	mtx_lock(&random_reseed_mtx);
265
266	if (gate) {
267		generator_gate();
268		random_state.outputblocks = 0;
269		gate = 0;
270	}
271	if (count > 0 && (size_t)count >= sizeof(random_state.counter)) {
272		retval = 0;
273		for (i = 0; i < count; i += (int)sizeof(random_state.counter)) {
274			random_state.counter[0]++;
275			yarrow_encrypt(&random_state.key, random_state.counter,
276				genval);
277			memcpy((char *)buf + i, genval,
278				sizeof(random_state.counter));
279			if (++random_state.outputblocks >=
280				random_state.gengateinterval) {
281				generator_gate();
282				random_state.outputblocks = 0;
283			}
284			retval += (int)sizeof(random_state.counter);
285		}
286	}
287	else {
288		if (!cur) {
289			random_state.counter[0]++;
290			yarrow_encrypt(&random_state.key, random_state.counter,
291				genval);
292			memcpy(buf, genval, (size_t)count);
293			cur = (int)sizeof(random_state.counter) - count;
294			if (++random_state.outputblocks >=
295				random_state.gengateinterval) {
296				generator_gate();
297				random_state.outputblocks = 0;
298			}
299			retval = count;
300		}
301		else {
302			retval = cur < count ? cur : count;
303			memcpy(buf,
304			    &genval[(int)sizeof(random_state.counter) - cur],
305			    (size_t)retval);
306			cur -= retval;
307		}
308	}
309	mtx_unlock(&random_reseed_mtx);
310	return retval;
311}
312
313static void
314generator_gate(void)
315{
316	u_int i;
317	u_char temp[KEYSIZE];
318
319#ifdef DEBUG
320	mtx_lock(&Giant);
321	printf("Generator gate\n");
322	mtx_unlock(&Giant);
323#endif
324
325	for (i = 0; i < KEYSIZE; i += sizeof(random_state.counter)) {
326		random_state.counter[0]++;
327		yarrow_encrypt(&random_state.key, random_state.counter,
328			&(temp[i]));
329	}
330
331	yarrow_encrypt_init(&random_state.key, temp);
332	memset((void *)temp, 0, KEYSIZE);
333
334#ifdef DEBUG
335	mtx_lock(&Giant);
336	printf("Generator gate finish\n");
337	mtx_unlock(&Giant);
338#endif
339}
340
341/* Helper routine to perform explicit reseeds */
342void
343random_reseed(void)
344{
345	reseed(SLOW);
346}
347