randomdev.c revision 119418 
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 */
27
28#include <sys/cdefs.h>
29__FBSDID("$FreeBSD: head/sys/dev/random/randomdev.c 119418 2003-08-24 17:55:58Z obrien $");
30
31#include <sys/param.h>
32#include <sys/systm.h>
33#include <sys/bus.h>
34#include <sys/conf.h>
35#include <sys/fcntl.h>
36#include <sys/filio.h>
37#include <sys/kernel.h>
38#include <sys/kthread.h>
39#include <sys/lock.h>
40#include <sys/malloc.h>
41#include <sys/mutex.h>
42#include <sys/poll.h>
43#include <sys/proc.h>
44#include <sys/random.h>
45#include <sys/selinfo.h>
46#include <sys/sysctl.h>
47#include <sys/uio.h>
48#include <sys/unistd.h>
49#include <sys/vnode.h>
50
51#include <machine/bus.h>
52#include <machine/cpu.h>
53
54#include <dev/random/randomdev.h>
55
56static d_open_t		random_open;
57static d_close_t	random_close;
58static d_read_t		random_read;
59static d_write_t	random_write;
60static d_ioctl_t	random_ioctl;
61static d_poll_t		random_poll;
62
63#define CDEV_MAJOR	2
64#define RANDOM_MINOR	3
65
66static struct cdevsw random_cdevsw = {
67	.d_open =	random_open,
68	.d_close =	random_close,
69	.d_read =	random_read,
70	.d_write =	random_write,
71	.d_ioctl =	random_ioctl,
72	.d_poll =	random_poll,
73	.d_name =	"random",
74	.d_maj =	CDEV_MAJOR,
75};
76
77static void random_kthread(void *);
78static void random_harvest_internal(u_int64_t, void *, u_int, u_int, u_int, enum esource);
79static void random_write_internal(void *, int);
80
81/* Ring buffer holding harvested entropy */
82static struct harvestring {
83	volatile u_int	head;
84	volatile u_int	tail;
85	struct harvest	data[HARVEST_RING_SIZE];
86} harvestring;
87
88static struct random_systat {
89	u_int		seeded;	/* 0 causes blocking 1 allows normal output */
90	u_int		burst;	/* number of events to do before sleeping */
91	struct selinfo	rsel;	/* For poll(2) */
92} random_systat;
93
94/* <0 to end the kthread, 0 to let it run */
95static int random_kthread_control = 0;
96
97static struct proc *random_kthread_proc;
98
99/* For use with make_dev(9)/destroy_dev(9). */
100static dev_t	random_dev;
101static dev_t	urandom_dev;
102
103/* ARGSUSED */
104static int
105random_check_boolean(SYSCTL_HANDLER_ARGS)
106{
107	if (oidp->oid_arg1 != NULL && *(u_int *)(oidp->oid_arg1) != 0)
108		*(u_int *)(oidp->oid_arg1) = 1;
109        return sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
110}
111
112RANDOM_CHECK_UINT(burst, 0, 20);
113
114SYSCTL_NODE(_kern, OID_AUTO, random, CTLFLAG_RW,
115	0, "Random Number Generator");
116SYSCTL_NODE(_kern_random, OID_AUTO, sys, CTLFLAG_RW,
117	0, "Entropy Device Parameters");
118SYSCTL_PROC(_kern_random_sys, OID_AUTO, seeded,
119	CTLTYPE_INT|CTLFLAG_RW, &random_systat.seeded, 1,
120	random_check_boolean, "I", "Seeded State");
121SYSCTL_PROC(_kern_random_sys, OID_AUTO, burst,
122	CTLTYPE_INT|CTLFLAG_RW, &random_systat.burst, 20,
123	random_check_uint_burst, "I", "Harvest Burst Size");
124SYSCTL_NODE(_kern_random_sys, OID_AUTO, harvest, CTLFLAG_RW,
125	0, "Entropy Sources");
126SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, ethernet,
127	CTLTYPE_INT|CTLFLAG_RW, &harvest.ethernet, 0,
128	random_check_boolean, "I", "Harvest NIC entropy");
129SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, point_to_point,
130	CTLTYPE_INT|CTLFLAG_RW, &harvest.point_to_point, 0,
131	random_check_boolean, "I", "Harvest serial net entropy");
132SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, interrupt,
133	CTLTYPE_INT|CTLFLAG_RW, &harvest.interrupt, 0,
134	random_check_boolean, "I", "Harvest IRQ entropy");
135SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, swi,
136	CTLTYPE_INT|CTLFLAG_RW, &harvest.swi, 0,
137	random_check_boolean, "I", "Harvest SWI entropy");
138
139/* ARGSUSED */
140static int
141random_open(dev_t dev __unused, int flags, int fmt __unused, struct thread *td)
142{
143	int error;
144
145	if (flags & FWRITE) {
146		error = suser(td);
147		if (error)
148			return (error);
149		error = securelevel_gt(td->td_ucred, 0);
150		if (error)
151			return (error);
152	}
153	return 0;
154}
155
156/* ARGSUSED */
157static int
158random_close(dev_t dev __unused, int flags, int fmt __unused, struct thread *td)
159{
160	if (flags & FWRITE) {
161		if (!(suser(td) ||
162		    securelevel_gt(td->td_ucred, 0)))
163			random_reseed();
164	}
165	return 0;
166}
167
168/* ARGSUSED */
169static int
170random_read(dev_t dev __unused, struct uio *uio, int flag)
171{
172	int	c, ret;
173	int	error = 0;
174	void	*random_buf;
175
176	while (!random_systat.seeded) {
177		if (flag & IO_NDELAY)
178			error =  EWOULDBLOCK;
179		else
180			error = tsleep(&random_systat, PUSER|PCATCH,
181				"block", 0);
182		if (error != 0)
183			return error;
184	}
185	c = uio->uio_resid < PAGE_SIZE ? uio->uio_resid : PAGE_SIZE;
186	random_buf = (void *)malloc((u_long)c, M_TEMP, M_WAITOK);
187	while (uio->uio_resid > 0 && error == 0) {
188		ret = read_random_real(random_buf, c);
189		error = uiomove(random_buf, ret, uio);
190	}
191	free(random_buf, M_TEMP);
192	return error;
193}
194
195/* ARGSUSED */
196static int
197random_write(dev_t dev __unused, struct uio *uio, int flag __unused)
198{
199	int	c;
200	int	error;
201	void	*random_buf;
202
203	error = 0;
204	random_buf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK);
205	while (uio->uio_resid > 0) {
206		c = (int)(uio->uio_resid < PAGE_SIZE
207		    ? uio->uio_resid
208		    : PAGE_SIZE);
209		error = uiomove(random_buf, c, uio);
210		if (error)
211			break;
212		random_write_internal(random_buf, c);
213	}
214	free(random_buf, M_TEMP);
215	return error;
216}
217
218/* ARGSUSED */
219static int
220random_ioctl(dev_t dev __unused, u_long cmd, caddr_t addr __unused,
221    int flags __unused, struct thread *td __unused)
222{
223	switch (cmd) {
224	/* Really handled in upper layer */
225	case FIOASYNC:
226	case FIONBIO:
227		return 0;
228	default:
229		return ENOTTY;
230	}
231}
232
233/* ARGSUSED */
234static int
235random_poll(dev_t dev __unused, int events, struct thread *td)
236{
237	int	revents;
238
239	revents = 0;
240	if (events & (POLLIN | POLLRDNORM)) {
241		if (random_systat.seeded)
242			revents = events & (POLLIN | POLLRDNORM);
243		else
244			selrecord(td, &random_systat.rsel);
245	}
246	return revents;
247}
248
249/* ARGSUSED */
250static int
251random_modevent(module_t mod __unused, int type, void *data __unused)
252{
253	int	error;
254
255	switch(type) {
256	case MOD_LOAD:
257		random_init();
258
259		/* This can be turned off by the very paranoid
260		 * a reseed will turn it back on.
261		 */
262		random_systat.seeded = 1;
263
264		/* Number of envents to process off the harvest
265		 * queue before giving it a break and sleeping
266		 */
267		random_systat.burst = 20;
268
269		/* Initialise the harvest ringbuffer */
270		harvestring.head = 0;
271		harvestring.tail = 0;
272
273		if (bootverbose)
274			printf("random: <entropy source>\n");
275		random_dev = make_dev(&random_cdevsw, RANDOM_MINOR, UID_ROOT,
276			GID_WHEEL, 0666, "random");
277		urandom_dev = make_dev_alias(random_dev, "urandom");
278
279		/* Start the hash/reseed thread */
280		error = kthread_create(random_kthread, NULL,
281			&random_kthread_proc, RFHIGHPID, 0, "random");
282		if (error != 0)
283			return error;
284
285		/* Register the randomness harvesting routine */
286		random_init_harvester(random_harvest_internal,
287			read_random_real);
288
289		return 0;
290
291	case MOD_UNLOAD:
292		/* Deregister the randomness harvesting routine */
293		random_deinit_harvester();
294
295		/* Command the hash/reseed thread to end and
296		 * wait for it to finish
297		 */
298		random_kthread_control = -1;
299		tsleep((void *)&random_kthread_control, PUSER, "term", 0);
300
301		random_deinit();
302
303		destroy_dev(random_dev);
304		destroy_dev(urandom_dev);
305		return 0;
306
307	case MOD_SHUTDOWN:
308		return 0;
309
310	default:
311		return EOPNOTSUPP;
312	}
313}
314
315DEV_MODULE(random, random_modevent, NULL);
316
317/* ARGSUSED */
318static void
319random_kthread(void *arg __unused)
320{
321	struct harvest	*event;
322	u_int		newtail, burst;
323
324	/* Drain the harvest queue (in 'burst' size chunks,
325	 * if 'burst' > 0. If 'burst' == 0, then completely
326	 * drain the queue.
327	 */
328	for (burst = 0; ; burst++) {
329
330		if ((harvestring.tail == harvestring.head) ||
331			(random_systat.burst && burst == random_systat.burst)) {
332				tsleep(&harvestring, PUSER, "-", hz/10);
333				burst = 0;
334
335		}
336		else {
337
338			/* Suck a harvested entropy event out of the queue and
339			 * hand it to the event processor
340			 */
341
342			newtail = (harvestring.tail + 1) & HARVEST_RING_MASK;
343			event = &harvestring.data[harvestring.tail];
344
345			/* Bump the ring counter. This action is assumed
346			 * to be atomic.
347			 */
348			harvestring.tail = newtail;
349
350			random_process_event(event);
351
352		}
353
354		/* Is the thread scheduled for a shutdown? */
355		if (random_kthread_control != 0) {
356#ifdef DEBUG
357			printf("Random kthread setting terminate\n");
358#endif
359			random_set_wakeup_exit(&random_kthread_control);
360			/* NOTREACHED */
361			break;
362		}
363
364	}
365
366}
367
368/* Entropy harvesting routine. This is supposed to be fast; do
369 * not do anything slow in here!
370 */
371static void
372random_harvest_internal(u_int64_t somecounter, void *entropy, u_int count,
373	u_int bits, u_int frac, enum esource origin)
374{
375	struct harvest	*pharvest;
376	u_int		newhead;
377
378	newhead = (harvestring.head + 1) & HARVEST_RING_MASK;
379
380	if (newhead != harvestring.tail) {
381
382		/* Add the harvested data to the ring buffer */
383
384		pharvest = &harvestring.data[harvestring.head];
385
386		/* Stuff the harvested data into the ring */
387		pharvest->somecounter = somecounter;
388		count = count > HARVESTSIZE ? HARVESTSIZE : count;
389		memcpy(pharvest->entropy, entropy, count);
390		pharvest->size = count;
391		pharvest->bits = bits;
392		pharvest->frac = frac;
393		pharvest->source =
394		    origin < ENTROPYSOURCE ? origin : RANDOM_START;
395
396		/* Bump the ring counter. This action is assumed
397		 * to be atomic.
398		 */
399		harvestring.head = newhead;
400
401	}
402
403}
404
405static void
406random_write_internal(void *buf, int count)
407{
408	int	i;
409
410	/* Break the input up into HARVESTSIZE chunks.
411	 * The writer has too much control here, so "estimate" the
412	 * the entropy as zero.
413	 */
414	for (i = 0; i < count; i += HARVESTSIZE) {
415		random_harvest_internal(get_cyclecount(), (char *)buf + i,
416			HARVESTSIZE, 0, 0, RANDOM_WRITE);
417	}
418
419	/* Maybe the loop iterated at least once */
420	if (i > count)
421		i -= HARVESTSIZE;
422
423	/* Get the last bytes even if the input length is not
424	 * a multiple of HARVESTSIZE.
425	 */
426	count %= HARVESTSIZE;
427	if (count) {
428		random_harvest_internal(get_cyclecount(), (char *)buf + i,
429			(u_int)count, 0, 0, RANDOM_WRITE);
430	}
431}
432
433void
434random_unblock(void)
435{
436	if (!random_systat.seeded) {
437		random_systat.seeded = 1;
438		selwakeup(&random_systat.rsel);
439		wakeup(&random_systat);
440	}
441}
442