randomdev.c revision 76166 
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 76166 2001-05-01 08:13:21Z markm $
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/queue.h>
43#include <sys/random.h>
44#include <sys/selinfo.h>
45#include <sys/sysctl.h>
46#include <sys/uio.h>
47#include <sys/unistd.h>
48#include <sys/vnode.h>
49
50#include <machine/bus.h>
51#include <machine/cpu.h>
52#include <machine/resource.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	/* open */	random_open,
68	/* close */	random_close,
69	/* read */	random_read,
70	/* write */	random_write,
71	/* ioctl */	random_ioctl,
72	/* poll */	random_poll,
73	/* mmap */	nommap,
74	/* strategy */	nostrategy,
75	/* name */	"random",
76	/* maj */	CDEV_MAJOR,
77	/* dump */	nodump,
78	/* psize */	nopsize,
79	/* flags */	0,
80};
81
82static void random_kthread(void *);
83static void random_harvest_internal(u_int64_t, void *, u_int, u_int, u_int, enum esource);
84static void random_write_internal(void *, u_int);
85
86/* Ring buffer holding harvested entropy */
87static struct harvestring {
88	volatile u_int	head;
89	volatile u_int	tail;
90	struct harvest	data[HARVEST_RING_SIZE];
91} harvestring;
92
93static struct random_systat {
94	u_int		seeded;	/* 0 causes blocking 1 allows normal output */
95	u_int		burst;	/* number of events to do before sleeping */
96	struct selinfo	rsel;	/* For poll(2) */
97} random_systat;
98
99/* <0 to end the kthread, 0 to let it run */
100static int random_kthread_control = 0;
101
102static struct proc *random_kthread_proc;
103
104/* For use with make_dev(9)/destroy_dev(9). */
105static dev_t	random_dev;
106static dev_t	urandom_dev;
107
108static int
109random_check_boolean(SYSCTL_HANDLER_ARGS)
110{
111	if (oidp->oid_arg1 != NULL && *(u_int *)(oidp->oid_arg1) != 0)
112		*(u_int *)(oidp->oid_arg1) = 1;
113        return sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
114}
115
116RANDOM_CHECK_UINT(burst, 0, 20);
117
118SYSCTL_NODE(_kern, OID_AUTO, random, CTLFLAG_RW,
119	0, "Random Number Generator");
120SYSCTL_NODE(_kern_random, OID_AUTO, sys, CTLFLAG_RW,
121	0, "Entropy Device Parameters");
122SYSCTL_PROC(_kern_random_sys, OID_AUTO, seeded,
123	CTLTYPE_INT|CTLFLAG_RW, &random_systat.seeded, 1,
124	random_check_boolean, "I", "Seeded State");
125SYSCTL_PROC(_kern_random_sys, OID_AUTO, burst,
126	CTLTYPE_INT|CTLFLAG_RW, &random_systat.burst, 20,
127	random_check_uint_burst, "I", "Harvest Burst Size");
128SYSCTL_NODE(_kern_random_sys, OID_AUTO, harvest, CTLFLAG_RW,
129	0, "Entropy Sources");
130SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, ethernet,
131	CTLTYPE_INT|CTLFLAG_RW, &harvest.ethernet, 0,
132	random_check_boolean, "I", "Harvest NIC entropy");
133SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, point_to_point,
134	CTLTYPE_INT|CTLFLAG_RW, &harvest.point_to_point, 0,
135	random_check_boolean, "I", "Harvest serial net entropy");
136SYSCTL_PROC(_kern_random_sys_harvest, OID_AUTO, interrupt,
137	CTLTYPE_INT|CTLFLAG_RW, &harvest.interrupt, 0,
138	random_check_boolean, "I", "Harvest IRQ entropy");
139
140static int
141random_open(dev_t dev, int flags, int fmt, struct proc *p)
142{
143	if ((flags & FWRITE) && (securelevel > 0 || suser(p)))
144		return EPERM;
145	else
146		return 0;
147}
148
149static int
150random_close(dev_t dev, int flags, int fmt, struct proc *p)
151{
152	if ((flags & FWRITE) && !(securelevel > 0 || suser(p)))
153		random_reseed();
154	return 0;
155}
156
157static int
158random_read(dev_t dev, struct uio *uio, int flag)
159{
160	u_int	c, ret;
161	int	error = 0;
162	void	*random_buf;
163
164	while (!random_systat.seeded) {
165		if (flag & IO_NDELAY)
166			error =  EWOULDBLOCK;
167		else
168			error = tsleep(&random_systat, PUSER|PCATCH,
169				"block", 0);
170		if (error != 0)
171			return error;
172	}
173	c = min(uio->uio_resid, PAGE_SIZE);
174	random_buf = (void *)malloc(c, M_TEMP, M_WAITOK);
175	while (uio->uio_resid > 0 && error == 0) {
176		ret = read_random_real(random_buf, c);
177		error = uiomove(random_buf, ret, uio);
178	}
179	free(random_buf, M_TEMP);
180	return error;
181}
182
183static int
184random_write(dev_t dev, struct uio *uio, int flag)
185{
186	u_int	c;
187	int	error;
188	void	*random_buf;
189
190	error = 0;
191	random_buf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK);
192	while (uio->uio_resid > 0) {
193		c = min(uio->uio_resid, PAGE_SIZE);
194		error = uiomove(random_buf, c, uio);
195		if (error)
196			break;
197		random_write_internal(random_buf, c);
198	}
199	free(random_buf, M_TEMP);
200	return error;
201}
202
203static int
204random_ioctl(dev_t dev, u_long cmd, caddr_t addr, int flags, struct proc *p)
205{
206	switch (cmd) {
207	/* Really handled in upper layer */
208	case FIOASYNC:
209	case FIONBIO:
210		return 0;
211	default:
212		return ENOTTY;
213	}
214}
215
216static int
217random_poll(dev_t dev, int events, struct proc *p)
218{
219	int	revents;
220
221	revents = 0;
222	if (events & (POLLIN | POLLRDNORM)) {
223		if (random_systat.seeded)
224			revents = events & (POLLIN | POLLRDNORM);
225		else
226			selrecord(p, &random_systat.rsel);
227	}
228	return revents;
229}
230
231static int
232random_modevent(module_t mod, int type, void *data)
233{
234	int	error;
235
236	switch(type) {
237	case MOD_LOAD:
238		random_init();
239
240		/* This can be turned off by the very paranoid
241		 * a reseed will turn it back on.
242		 */
243		random_systat.seeded = 1;
244
245		/* Number of envents to process off the harvest
246		 * queue before giving it a break and sleeping
247		 */
248		random_systat.burst = 20;
249
250		/* Initialise the harvest ringbuffer */
251		harvestring.head = 0;
252		harvestring.tail = 0;
253
254		if (bootverbose)
255			printf("random: <entropy source>\n");
256		random_dev = make_dev(&random_cdevsw, RANDOM_MINOR, UID_ROOT,
257			GID_WHEEL, 0666, "random");
258		urandom_dev = make_dev_alias(random_dev, "urandom");
259
260		/* Start the hash/reseed thread */
261		error = kthread_create(random_kthread, NULL,
262			&random_kthread_proc, RFHIGHPID, "random");
263		if (error != 0)
264			return error;
265
266		/* Register the randomness harvesting routine */
267		random_init_harvester(random_harvest_internal,
268			read_random_real);
269
270		return 0;
271
272	case MOD_UNLOAD:
273		/* Deregister the randomness harvesting routine */
274		random_deinit_harvester();
275
276		/* Command the hash/reseed thread to end and
277		 * wait for it to finish
278		 */
279		random_kthread_control = -1;
280		tsleep((void *)&random_kthread_control, PUSER, "term", 0);
281
282		random_deinit();
283
284		destroy_dev(random_dev);
285		destroy_dev(urandom_dev);
286		return 0;
287
288	case MOD_SHUTDOWN:
289		return 0;
290
291	default:
292		return EOPNOTSUPP;
293	}
294}
295
296DEV_MODULE(random, random_modevent, NULL);
297
298static void
299random_kthread(void *arg /* NOTUSED */)
300{
301	struct harvest	*event;
302	int		newtail, burst;
303
304	/* Drain the harvest queue (in 'burst' size chunks,
305	 * if 'burst' > 0. If 'burst' == 0, then completely
306	 * drain the queue.
307	 */
308	for (burst = 0; ; burst++) {
309
310		if ((harvestring.tail == harvestring.head) ||
311			(random_systat.burst && burst == random_systat.burst)) {
312				tsleep(&harvestring, PUSER, "sleep", hz/10);
313				burst = 0;
314
315		}
316		else {
317
318			/* Suck a harvested entropy event out of the queue and
319			 * hand it to the event processor
320			 */
321
322			newtail = (harvestring.tail + 1) & HARVEST_RING_MASK;
323			event = &harvestring.data[harvestring.tail];
324
325			/* Bump the ring counter. This action is assumed
326			 * to be atomic.
327			 */
328			harvestring.tail = newtail;
329
330			random_process_event(event);
331
332		}
333
334		/* Is the thread scheduled for a shutdown? */
335		if (random_kthread_control != 0) {
336#ifdef DEBUG
337			mtx_lock(&Giant);
338			printf("Random kthread setting terminate\n");
339			mtx_unlock(&Giant);
340#endif
341			random_set_wakeup_exit(&random_kthread_control);
342			/* NOTREACHED */
343			break;
344		}
345
346	}
347
348}
349
350/* Entropy harvesting routine. This is supposed to be fast; do
351 * not do anything slow in here!
352 */
353static void
354random_harvest_internal(u_int64_t somecounter, void *entropy, u_int count,
355	u_int bits, u_int frac, enum esource origin)
356{
357	struct harvest	*harvest;
358	int		newhead;
359
360	newhead = (harvestring.head + 1) & HARVEST_RING_MASK;
361
362	if (newhead != harvestring.tail) {
363
364		/* Add the harvested data to the ring buffer */
365
366		harvest = &harvestring.data[harvestring.head];
367
368		/* Stuff the harvested data into the ring */
369		harvest->somecounter = somecounter;
370		count = count > HARVESTSIZE ? HARVESTSIZE : count;
371		memcpy(harvest->entropy, entropy, count);
372		harvest->size = count;
373		harvest->bits = bits;
374		harvest->frac = frac;
375		harvest->source = origin < ENTROPYSOURCE ? origin : 0;
376
377		/* Bump the ring counter. This action is assumed
378		 * to be atomic.
379		 */
380		harvestring.head = newhead;
381
382	}
383
384}
385
386static void
387random_write_internal(void *buf, u_int count)
388{
389	u_int	i;
390
391	/* Break the input up into HARVESTSIZE chunks.
392	 * The writer has too much control here, so "estimate" the
393	 * the entropy as zero.
394	 */
395	for (i = 0; i < count; i += HARVESTSIZE) {
396		random_harvest_internal(get_cyclecount(), (char *)buf + i,
397			HARVESTSIZE, 0, 0, RANDOM_WRITE);
398	}
399
400	/* Maybe the loop iterated at least once */
401	if (i > count)
402		i -= HARVESTSIZE;
403
404	/* Get the last bytes even if the input length is not
405	 * a multiple of HARVESTSIZE.
406	 */
407	count %= HARVESTSIZE;
408	if (count) {
409		random_harvest_internal(get_cyclecount(), (char *)buf + i,
410			count, 0, 0, RANDOM_WRITE);
411	}
412}
413
414void
415random_unblock(void)
416{
417	if (!random_systat.seeded) {
418		random_systat.seeded = 1;
419		selwakeup(&random_systat.rsel);
420		wakeup(&random_systat);
421	}
422}
423