randomdev.c revision 83976 
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/randomdev.c 83976 2001-09-26 20:15:42Z rwatson $
27 */
28
29#include <sys/param.h>
30#include <sys/systm.h>
31#include <sys/bus.h>
32#include <sys/conf.h>
33#include <sys/fcntl.h>
34#include <sys/filio.h>
35#include <sys/kernel.h>
36#include <sys/kthread.h>
37#include <sys/lock.h>
38#include <sys/malloc.h>
39#include <sys/module.h>
40#include <sys/mutex.h>
41#include <sys/poll.h>
42#include <sys/proc.h>
43#include <sys/queue.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#include <machine/resource.h>
54
55#include <dev/random/randomdev.h>
56
57static d_open_t		random_open;
58static d_close_t	random_close;
59static d_read_t		random_read;
60static d_write_t	random_write;
61static d_ioctl_t	random_ioctl;
62static d_poll_t		random_poll;
63
64#define CDEV_MAJOR	2
65#define RANDOM_MINOR	3
66
67static struct cdevsw random_cdevsw = {
68	/* open */	random_open,
69	/* close */	random_close,
70	/* read */	random_read,
71	/* write */	random_write,
72	/* ioctl */	random_ioctl,
73	/* poll */	random_poll,
74	/* mmap */	nommap,
75	/* strategy */	nostrategy,
76	/* name */	"random",
77	/* maj */	CDEV_MAJOR,
78	/* dump */	nodump,
79	/* psize */	nopsize,
80	/* flags */	0,
81};
82
83static void random_kthread(void *);
84static void random_harvest_internal(u_int64_t, void *, u_int, u_int, u_int, enum esource);
85static void random_write_internal(void *, u_int);
86
87/* Ring buffer holding harvested entropy */
88static struct harvestring {
89	volatile u_int	head;
90	volatile u_int	tail;
91	struct harvest	data[HARVEST_RING_SIZE];
92} harvestring;
93
94static struct random_systat {
95	u_int		seeded;	/* 0 causes blocking 1 allows normal output */
96	u_int		burst;	/* number of events to do before sleeping */
97	struct selinfo	rsel;	/* For poll(2) */
98} random_systat;
99
100/* <0 to end the kthread, 0 to let it run */
101static int random_kthread_control = 0;
102
103static struct proc *random_kthread_proc;
104
105/* For use with make_dev(9)/destroy_dev(9). */
106static dev_t	random_dev;
107static dev_t	urandom_dev;
108
109static int
110random_check_boolean(SYSCTL_HANDLER_ARGS)
111{
112	if (oidp->oid_arg1 != NULL && *(u_int *)(oidp->oid_arg1) != 0)
113		*(u_int *)(oidp->oid_arg1) = 1;
114        return sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
115}
116
117RANDOM_CHECK_UINT(burst, 0, 20);
118
119SYSCTL_NODE(_kern, OID_AUTO, random, CTLFLAG_RW,
120	0, "Random Number Generator");
121SYSCTL_NODE(_kern_random, OID_AUTO, sys, CTLFLAG_RW,
122	0, "Entropy Device Parameters");
123SYSCTL_PROC(_kern_random_sys, OID_AUTO, seeded,
124	CTLTYPE_INT|CTLFLAG_RW, &random_systat.seeded, 1,
125	random_check_boolean, "I", "Seeded State");
126SYSCTL_PROC(_kern_random_sys, OID_AUTO, burst,
127	CTLTYPE_INT|CTLFLAG_RW, &random_systat.burst, 20,
128	random_check_uint_burst, "I", "Harvest Burst Size");
129SYSCTL_NODE(_kern_random_sys, OID_AUTO, harvest, CTLFLAG_RW,
130	0, "Entropy Sources");
131SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, ethernet,
132	CTLTYPE_INT|CTLFLAG_RW, &harvest.ethernet, 0,
133	random_check_boolean, "I", "Harvest NIC entropy");
134SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, point_to_point,
135	CTLTYPE_INT|CTLFLAG_RW, &harvest.point_to_point, 0,
136	random_check_boolean, "I", "Harvest serial net entropy");
137SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, interrupt,
138	CTLTYPE_INT|CTLFLAG_RW, &harvest.interrupt, 0,
139	random_check_boolean, "I", "Harvest IRQ entropy");
140
141static int
142random_open(dev_t dev, int flags, int fmt, struct thread *td)
143{
144	int error;
145
146	if (flags & FWRITE) {
147		error = suser(td->td_proc);
148		if (error)
149			return (error);
150		error = securelevel_gt(td->td_proc->p_ucred, 0);
151		if (error)
152			return (error);
153	}
154	return 0;
155}
156
157static int
158random_close(dev_t dev, int flags, int fmt, struct thread *td)
159{
160	if (flags & FWRITE) {
161		if (!(suser(td->td_proc) ||
162		    securelevel_gt(td->td_proc->p_ucred, 0)))
163			random_reseed();
164	}
165	return 0;
166}
167
168static int
169random_read(dev_t dev, struct uio *uio, int flag)
170{
171	u_int	c, ret;
172	int	error = 0;
173	void	*random_buf;
174
175	while (!random_systat.seeded) {
176		if (flag & IO_NDELAY)
177			error =  EWOULDBLOCK;
178		else
179			error = tsleep(&random_systat, PUSER|PCATCH,
180				"block", 0);
181		if (error != 0)
182			return error;
183	}
184	c = min(uio->uio_resid, PAGE_SIZE);
185	random_buf = (void *)malloc(c, M_TEMP, M_WAITOK);
186	while (uio->uio_resid > 0 && error == 0) {
187		ret = read_random_real(random_buf, c);
188		error = uiomove(random_buf, ret, uio);
189	}
190	free(random_buf, M_TEMP);
191	return error;
192}
193
194static int
195random_write(dev_t dev, struct uio *uio, int flag)
196{
197	u_int	c;
198	int	error;
199	void	*random_buf;
200
201	error = 0;
202	random_buf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK);
203	while (uio->uio_resid > 0) {
204		c = min(uio->uio_resid, PAGE_SIZE);
205		error = uiomove(random_buf, c, uio);
206		if (error)
207			break;
208		random_write_internal(random_buf, c);
209	}
210	free(random_buf, M_TEMP);
211	return error;
212}
213
214static int
215random_ioctl(dev_t dev, u_long cmd, caddr_t addr, int flags, struct thread *td)
216{
217	switch (cmd) {
218	/* Really handled in upper layer */
219	case FIOASYNC:
220	case FIONBIO:
221		return 0;
222	default:
223		return ENOTTY;
224	}
225}
226
227static int
228random_poll(dev_t dev, int events, struct thread *td)
229{
230	int	revents;
231
232	revents = 0;
233	if (events & (POLLIN | POLLRDNORM)) {
234		if (random_systat.seeded)
235			revents = events & (POLLIN | POLLRDNORM);
236		else
237			selrecord(td, &random_systat.rsel);
238	}
239	return revents;
240}
241
242static int
243random_modevent(module_t mod, int type, void *data)
244{
245	int	error;
246
247	switch(type) {
248	case MOD_LOAD:
249		random_init();
250
251		/* This can be turned off by the very paranoid
252		 * a reseed will turn it back on.
253		 */
254		random_systat.seeded = 1;
255
256		/* Number of envents to process off the harvest
257		 * queue before giving it a break and sleeping
258		 */
259		random_systat.burst = 20;
260
261		/* Initialise the harvest ringbuffer */
262		harvestring.head = 0;
263		harvestring.tail = 0;
264
265		if (bootverbose)
266			printf("random: <entropy source>\n");
267		random_dev = make_dev(&random_cdevsw, RANDOM_MINOR, UID_ROOT,
268			GID_WHEEL, 0666, "random");
269		urandom_dev = make_dev_alias(random_dev, "urandom");
270
271		/* Start the hash/reseed thread */
272		error = kthread_create(random_kthread, NULL,
273			&random_kthread_proc, RFHIGHPID, "random");
274		if (error != 0)
275			return error;
276
277		/* Register the randomness harvesting routine */
278		random_init_harvester(random_harvest_internal,
279			read_random_real);
280
281		return 0;
282
283	case MOD_UNLOAD:
284		/* Deregister the randomness harvesting routine */
285		random_deinit_harvester();
286
287		/* Command the hash/reseed thread to end and
288		 * wait for it to finish
289		 */
290		random_kthread_control = -1;
291		tsleep((void *)&random_kthread_control, PUSER, "term", 0);
292
293		random_deinit();
294
295		destroy_dev(random_dev);
296		destroy_dev(urandom_dev);
297		return 0;
298
299	case MOD_SHUTDOWN:
300		return 0;
301
302	default:
303		return EOPNOTSUPP;
304	}
305}
306
307DEV_MODULE(random, random_modevent, NULL);
308
309static void
310random_kthread(void *arg /* NOTUSED */)
311{
312	struct harvest	*event;
313	int		newtail, burst;
314
315	/* Drain the harvest queue (in 'burst' size chunks,
316	 * if 'burst' > 0. If 'burst' == 0, then completely
317	 * drain the queue.
318	 */
319	for (burst = 0; ; burst++) {
320
321		if ((harvestring.tail == harvestring.head) ||
322			(random_systat.burst && burst == random_systat.burst)) {
323				tsleep(&harvestring, PUSER, "sleep", hz/10);
324				burst = 0;
325
326		}
327		else {
328
329			/* Suck a harvested entropy event out of the queue and
330			 * hand it to the event processor
331			 */
332
333			newtail = (harvestring.tail + 1) & HARVEST_RING_MASK;
334			event = &harvestring.data[harvestring.tail];
335
336			/* Bump the ring counter. This action is assumed
337			 * to be atomic.
338			 */
339			harvestring.tail = newtail;
340
341			random_process_event(event);
342
343		}
344
345		/* Is the thread scheduled for a shutdown? */
346		if (random_kthread_control != 0) {
347#ifdef DEBUG
348			mtx_lock(&Giant);
349			printf("Random kthread setting terminate\n");
350			mtx_unlock(&Giant);
351#endif
352			random_set_wakeup_exit(&random_kthread_control);
353			/* NOTREACHED */
354			break;
355		}
356
357	}
358
359}
360
361/* Entropy harvesting routine. This is supposed to be fast; do
362 * not do anything slow in here!
363 */
364static void
365random_harvest_internal(u_int64_t somecounter, void *entropy, u_int count,
366	u_int bits, u_int frac, enum esource origin)
367{
368	struct harvest	*harvest;
369	int		newhead;
370
371	newhead = (harvestring.head + 1) & HARVEST_RING_MASK;
372
373	if (newhead != harvestring.tail) {
374
375		/* Add the harvested data to the ring buffer */
376
377		harvest = &harvestring.data[harvestring.head];
378
379		/* Stuff the harvested data into the ring */
380		harvest->somecounter = somecounter;
381		count = count > HARVESTSIZE ? HARVESTSIZE : count;
382		memcpy(harvest->entropy, entropy, count);
383		harvest->size = count;
384		harvest->bits = bits;
385		harvest->frac = frac;
386		harvest->source = origin < ENTROPYSOURCE ? origin : 0;
387
388		/* Bump the ring counter. This action is assumed
389		 * to be atomic.
390		 */
391		harvestring.head = newhead;
392
393	}
394
395}
396
397static void
398random_write_internal(void *buf, u_int count)
399{
400	u_int	i;
401
402	/* Break the input up into HARVESTSIZE chunks.
403	 * The writer has too much control here, so "estimate" the
404	 * the entropy as zero.
405	 */
406	for (i = 0; i < count; i += HARVESTSIZE) {
407		random_harvest_internal(get_cyclecount(), (char *)buf + i,
408			HARVESTSIZE, 0, 0, RANDOM_WRITE);
409	}
410
411	/* Maybe the loop iterated at least once */
412	if (i > count)
413		i -= HARVESTSIZE;
414
415	/* Get the last bytes even if the input length is not
416	 * a multiple of HARVESTSIZE.
417	 */
418	count %= HARVESTSIZE;
419	if (count) {
420		random_harvest_internal(get_cyclecount(), (char *)buf + i,
421			count, 0, 0, RANDOM_WRITE);
422	}
423}
424
425void
426random_unblock(void)
427{
428	if (!random_systat.seeded) {
429		random_systat.seeded = 1;
430		selwakeup(&random_systat.rsel);
431		wakeup(&random_systat);
432	}
433}
434