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)
67 static int (read_random_uio)(struct uio *, bool);
68 static void (read_random)(void *, u_int);
69 static bool (is_random_seeded)(void);
70 #endif
71
72 static d_read_t randomdev_read;
73 static d_write_t randomdev_write;
74 static d_poll_t randomdev_poll;
75 static d_ioctl_t randomdev_ioctl;
76
77 static 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). */
87 static struct cdev *random_dev;
88
89 #if defined(RANDOM_LOADABLE)
90 static void
random_alg_context_init(void * dummy __unused)91 random_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 }
97 SYSINIT(random_device, SI_SUB_RANDOM, SI_ORDER_SECOND, random_alg_context_init,
98 NULL);
99 #endif
100
101 static struct selinfo rsel;
102
103 /*
104 * This is the read uio(9) interface for random(4).
105 */
106 /* ARGSUSED */
107 static int
randomdev_read(struct cdev * dev __unused,struct uio * uio,int flags)108 randomdev_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
125 static int
randomdev_wait_until_seeded(bool interruptible)126 randomdev_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
156 int
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 */
255 void
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
288 bool
289 (is_random_seeded)(void)
290 {
291 return (p_random_alg_context->ra_seeded());
292 }
293
294 static __inline void
randomdev_accumulate(uint8_t * buf,u_int count)295 randomdev_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, ×tamp, sizeof(timestamp));
308 randomdev_hash_iterate(&hash, buf, count);
309 timestamp = (uint32_t)get_cyclecount();
310 randomdev_hash_iterate(&hash, ×tamp, 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 */
325 static int
randomdev_write(struct cdev * dev __unused,struct uio * uio,int flags __unused)326 randomdev_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 */
349 static int
randomdev_poll(struct cdev * dev __unused,int events,struct thread * td __unused)350 randomdev_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 */
363 void
randomdev_unblock(void)364 randomdev_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 */
377 static int
randomdev_ioctl(struct cdev * dev __unused,u_long cmd,caddr_t addr __unused,int flags __unused,struct thread * td __unused)378 randomdev_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 */
396 static int
randomdev_modevent(module_t mod __unused,int type,void * data __unused)397 randomdev_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
420 static moduledata_t randomdev_mod = {
421 "random_device",
422 randomdev_modevent,
423 0
424 };
425
426 DECLARE_MODULE(random_device, randomdev_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST);
427 MODULE_VERSION(random_device, 1);
428 MODULE_DEPEND(random_device, crypto, 1, 1, 1);
429 MODULE_DEPEND(random_device, random_harvestq, 1, 1, 1);
430