1/*-
2 * Copyright (c) 2017 Oliver Pinter
3 * Copyright (c) 2000-2015 Mark R V Murray
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer
11 *    in this position and unchanged.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
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/module.h>
39#include <sys/malloc.h>
40#include <sys/poll.h>
41#include <sys/proc.h>
42#include <sys/random.h>
43#include <sys/sbuf.h>
44#include <sys/selinfo.h>
45#include <sys/sysctl.h>
46#include <sys/systm.h>
47#include <sys/uio.h>
48#include <sys/unistd.h>
49
50#include <crypto/rijndael/rijndael-api-fst.h>
51#include <crypto/sha2/sha256.h>
52
53#include <dev/random/hash.h>
54#include <dev/random/randomdev.h>
55#include <dev/random/random_harvestq.h>
56
57#define	RANDOM_UNIT	0
58
59/*
60 * In loadable random, the core randomdev.c / random(9) routines have static
61 * visibility and an alternative name to avoid conflicting with the function
62 * pointers of the real names in the core kernel.  random_alg_context_init
63 * installs pointers to the loadable static names into the core kernel's
64 * function pointers at SI_SUB_RANDOM:SI_ORDER_SECOND.
65 */
66#if defined(RANDOM_LOADABLE)
67static int (read_random_uio)(struct uio *, bool);
68static void (read_random)(void *, u_int);
69static bool (is_random_seeded)(void);
70#endif
71
72static d_read_t randomdev_read;
73static d_write_t randomdev_write;
74static d_poll_t randomdev_poll;
75static d_ioctl_t randomdev_ioctl;
76
77static struct cdevsw random_cdevsw = {
78	.d_name = "random",
79	.d_version = D_VERSION,
80	.d_read = randomdev_read,
81	.d_write = randomdev_write,
82	.d_poll = randomdev_poll,
83	.d_ioctl = randomdev_ioctl,
84};
85
86/* For use with make_dev(9)/destroy_dev(9). */
87static struct cdev *random_dev;
88
89#if defined(RANDOM_LOADABLE)
90static void
91random_alg_context_init(void *dummy __unused)
92{
93	_read_random_uio = (read_random_uio);
94	_read_random = (read_random);
95	_is_random_seeded = (is_random_seeded);
96}
97SYSINIT(random_device, SI_SUB_RANDOM, SI_ORDER_SECOND, random_alg_context_init,
98    NULL);
99#endif
100
101static struct selinfo rsel;
102
103/*
104 * This is the read uio(9) interface for random(4).
105 */
106/* ARGSUSED */
107static int
108randomdev_read(struct cdev *dev __unused, struct uio *uio, int flags)
109{
110
111	return ((read_random_uio)(uio, (flags & O_NONBLOCK) != 0));
112}
113
114/*
115 * If the random device is not seeded, blocks until it is seeded.
116 *
117 * Returns zero when the random device is seeded.
118 *
119 * If the 'interruptible' parameter is true, and the device is unseeded, this
120 * routine may be interrupted.  If interrupted, it will return either ERESTART
121 * or EINTR.
122 */
123#define SEEDWAIT_INTERRUPTIBLE		true
124#define SEEDWAIT_UNINTERRUPTIBLE	false
125static int
126randomdev_wait_until_seeded(bool interruptible)
127{
128	int error, spamcount, slpflags;
129
130	slpflags = interruptible ? PCATCH : 0;
131
132	error = 0;
133	spamcount = 0;
134	while (!p_random_alg_context->ra_seeded()) {
135		/* keep tapping away at the pre-read until we seed/unblock. */
136		p_random_alg_context->ra_pre_read();
137		/* Only bother the console every 10 seconds or so */
138		if (spamcount == 0)
139			printf("random: %s unblock wait\n", __func__);
140		spamcount = (spamcount + 1) % 100;
141		error = tsleep(p_random_alg_context, slpflags, "randseed",
142		    hz / 10);
143		if (error == ERESTART || error == EINTR) {
144			KASSERT(interruptible,
145			    ("unexpected wake of non-interruptible sleep"));
146			break;
147		}
148		/* Squash tsleep timeout condition */
149		if (error == EWOULDBLOCK)
150			error = 0;
151		KASSERT(error == 0, ("unexpected tsleep error %d", error));
152	}
153	return (error);
154}
155
156int
157(read_random_uio)(struct uio *uio, bool nonblock)
158{
159	/* 16 MiB takes about 0.08 s CPU time on my 2017 AMD Zen CPU */
160#define SIGCHK_PERIOD (16 * 1024 * 1024)
161	const size_t sigchk_period = SIGCHK_PERIOD;
162	CTASSERT(SIGCHK_PERIOD % PAGE_SIZE == 0);
163#undef SIGCHK_PERIOD
164
165	uint8_t *random_buf;
166	size_t total_read, read_len;
167	ssize_t bufsize;
168	int error;
169
170
171	KASSERT(uio->uio_rw == UIO_READ, ("%s: bogus write", __func__));
172	KASSERT(uio->uio_resid >= 0, ("%s: bogus negative resid", __func__));
173
174	p_random_alg_context->ra_pre_read();
175	error = 0;
176	/* (Un)Blocking logic */
177	if (!p_random_alg_context->ra_seeded()) {
178		if (nonblock)
179			error = EWOULDBLOCK;
180		else
181			error = randomdev_wait_until_seeded(
182			    SEEDWAIT_INTERRUPTIBLE);
183	}
184	if (error != 0)
185		return (error);
186
187	total_read = 0;
188
189	/* Easy to deal with the trivial 0 byte case. */
190	if (__predict_false(uio->uio_resid == 0))
191		return (0);
192
193	/*
194	 * If memory is plentiful, use maximally sized requests to avoid
195	 * per-call algorithm overhead.  But fall back to a single page
196	 * allocation if the full request isn't immediately available.
197	 */
198	bufsize = MIN(sigchk_period, (size_t)uio->uio_resid);
199	random_buf = malloc(bufsize, M_ENTROPY, M_NOWAIT);
200	if (random_buf == NULL) {
201		bufsize = PAGE_SIZE;
202		random_buf = malloc(bufsize, M_ENTROPY, M_WAITOK);
203	}
204
205	error = 0;
206	while (uio->uio_resid > 0 && error == 0) {
207		read_len = MIN((size_t)uio->uio_resid, bufsize);
208
209		p_random_alg_context->ra_read(random_buf, read_len);
210
211		/*
212		 * uiomove() may yield the CPU before each 'read_len' bytes (up
213		 * to bufsize) are copied out.
214		 */
215		error = uiomove(random_buf, read_len, uio);
216		total_read += read_len;
217
218		/*
219		 * Poll for signals every few MBs to avoid very long
220		 * uninterruptible syscalls.
221		 */
222		if (error == 0 && uio->uio_resid != 0 &&
223		    total_read % sigchk_period == 0) {
224			error = tsleep_sbt(p_random_alg_context, PCATCH,
225			    "randrd", SBT_1NS, 0, C_HARDCLOCK);
226			/* Squash tsleep timeout condition */
227			if (error == EWOULDBLOCK)
228				error = 0;
229		}
230	}
231
232	/*
233	 * Short reads due to signal interrupt should not indicate error.
234	 * Instead, the uio will reflect that the read was shorter than
235	 * requested.
236	 */
237	if (error == ERESTART || error == EINTR)
238		error = 0;
239
240	zfree(random_buf, M_ENTROPY);
241	return (error);
242}
243
244/*-
245 * Kernel API version of read_random().  This is similar to read_random_uio(),
246 * except it doesn't interface with uio(9).  It cannot assumed that random_buf
247 * is a multiple of RANDOM_BLOCKSIZE bytes.
248 *
249 * If the tunable 'kern.random.initial_seeding.bypass_before_seeding' is set
250 * non-zero, silently fail to emit random data (matching the pre-r346250
251 * behavior).  If read_random is called prior to seeding and bypassed because
252 * of this tunable, the condition is reported in the read-only sysctl
253 * 'kern.random.initial_seeding.read_random_bypassed_before_seeding'.
254 */
255void
256(read_random)(void *random_buf, u_int len)
257{
258
259	KASSERT(random_buf != NULL, ("No suitable random buffer in %s", __func__));
260	p_random_alg_context->ra_pre_read();
261
262	if (len == 0)
263		return;
264
265	/* (Un)Blocking logic */
266	if (__predict_false(!p_random_alg_context->ra_seeded())) {
267		if (random_bypass_before_seeding) {
268			if (!read_random_bypassed_before_seeding) {
269				if (!random_bypass_disable_warnings)
270					printf("read_random: WARNING: bypassing"
271					    " request for random data because "
272					    "the random device is not yet "
273					    "seeded and the knob "
274					    "'bypass_before_seeding' was "
275					    "enabled.\n");
276				read_random_bypassed_before_seeding = true;
277			}
278			/* Avoid potentially leaking stack garbage */
279			memset(random_buf, 0, len);
280			return;
281		}
282
283		(void)randomdev_wait_until_seeded(SEEDWAIT_UNINTERRUPTIBLE);
284	}
285	p_random_alg_context->ra_read(random_buf, len);
286}
287
288bool
289(is_random_seeded)(void)
290{
291	return (p_random_alg_context->ra_seeded());
292}
293
294static __inline void
295randomdev_accumulate(uint8_t *buf, u_int count)
296{
297	static u_int destination = 0;
298	static struct harvest_event event;
299	static struct randomdev_hash hash;
300	static uint32_t entropy_data[RANDOM_KEYSIZE_WORDS];
301	uint32_t timestamp;
302	int i;
303
304	/* Extra timing here is helpful to scrape scheduler jitter entropy */
305	randomdev_hash_init(&hash);
306	timestamp = (uint32_t)get_cyclecount();
307	randomdev_hash_iterate(&hash, &timestamp, sizeof(timestamp));
308	randomdev_hash_iterate(&hash, buf, count);
309	timestamp = (uint32_t)get_cyclecount();
310	randomdev_hash_iterate(&hash, &timestamp, sizeof(timestamp));
311	randomdev_hash_finish(&hash, entropy_data);
312	for (i = 0; i < RANDOM_KEYSIZE_WORDS; i += sizeof(event.he_entropy)/sizeof(event.he_entropy[0])) {
313		event.he_somecounter = (uint32_t)get_cyclecount();
314		event.he_size = sizeof(event.he_entropy);
315		event.he_source = RANDOM_CACHED;
316		event.he_destination = destination++; /* Harmless cheating */
317		memcpy(event.he_entropy, entropy_data + i, sizeof(event.he_entropy));
318		p_random_alg_context->ra_event_processor(&event);
319	}
320	explicit_bzero(&event, sizeof(event));
321	explicit_bzero(entropy_data, sizeof(entropy_data));
322}
323
324/* ARGSUSED */
325static int
326randomdev_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
327{
328	uint8_t *random_buf;
329	int c, error = 0;
330	ssize_t nbytes;
331
332	random_buf = malloc(PAGE_SIZE, M_ENTROPY, M_WAITOK);
333	nbytes = uio->uio_resid;
334	while (uio->uio_resid > 0 && error == 0) {
335		c = MIN(uio->uio_resid, PAGE_SIZE);
336		error = uiomove(random_buf, c, uio);
337		if (error)
338			break;
339		randomdev_accumulate(random_buf, c);
340	}
341	if (nbytes != uio->uio_resid && (error == ERESTART || error == EINTR))
342		/* Partial write, not error. */
343		error = 0;
344	free(random_buf, M_ENTROPY);
345	return (error);
346}
347
348/* ARGSUSED */
349static int
350randomdev_poll(struct cdev *dev __unused, int events, struct thread *td __unused)
351{
352
353	if (events & (POLLIN | POLLRDNORM)) {
354		if (p_random_alg_context->ra_seeded())
355			events &= (POLLIN | POLLRDNORM);
356		else
357			selrecord(td, &rsel);
358	}
359	return (events);
360}
361
362/* This will be called by the entropy processor when it seeds itself and becomes secure */
363void
364randomdev_unblock(void)
365{
366
367	selwakeuppri(&rsel, PUSER);
368	wakeup(p_random_alg_context);
369	printf("random: unblocking device.\n");
370#ifndef RANDOM_FENESTRASX
371	/* Do random(9) a favour while we are about it. */
372	(void)atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_NONE, ARC4_ENTR_HAVE);
373#endif
374}
375
376/* ARGSUSED */
377static int
378randomdev_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t addr __unused,
379    int flags __unused, struct thread *td __unused)
380{
381	int error = 0;
382
383	switch (cmd) {
384		/* Really handled in upper layer */
385	case FIOASYNC:
386	case FIONBIO:
387		break;
388	default:
389		error = ENOTTY;
390	}
391
392	return (error);
393}
394
395/* ARGSUSED */
396static int
397randomdev_modevent(module_t mod __unused, int type, void *data __unused)
398{
399	int error = 0;
400
401	switch (type) {
402	case MOD_LOAD:
403		printf("random: entropy device external interface\n");
404		random_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &random_cdevsw,
405		    RANDOM_UNIT, NULL, UID_ROOT, GID_WHEEL, 0644, "random");
406		make_dev_alias(random_dev, "urandom"); /* compatibility */
407		break;
408	case MOD_UNLOAD:
409		error = EBUSY;
410		break;
411	case MOD_SHUTDOWN:
412		break;
413	default:
414		error = EOPNOTSUPP;
415		break;
416	}
417	return (error);
418}
419
420static moduledata_t randomdev_mod = {
421	"random_device",
422	randomdev_modevent,
423	0
424};
425
426DECLARE_MODULE(random_device, randomdev_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST);
427MODULE_VERSION(random_device, 1);
428MODULE_DEPEND(random_device, crypto, 1, 1, 1);
429MODULE_DEPEND(random_device, random_harvestq, 1, 1, 1);
430