1 | /* $NetBSD: rndpseudo.c,v 1.35 2015/08/20 14:40:17 christos Exp $ */ |
2 | |
3 | /*- |
4 | * Copyright (c) 1997-2013 The NetBSD Foundation, Inc. |
5 | * All rights reserved. |
6 | * |
7 | * This code is derived from software contributed to The NetBSD Foundation |
8 | * by Michael Graff <explorer@flame.org>, Thor Lancelot Simon, and |
9 | * Taylor R. Campbell. |
10 | * |
11 | * Redistribution and use in source and binary forms, with or without |
12 | * modification, are permitted provided that the following conditions |
13 | * are met: |
14 | * 1. Redistributions of source code must retain the above copyright |
15 | * notice, this list of conditions and the following disclaimer. |
16 | * 2. Redistributions in binary form must reproduce the above copyright |
17 | * notice, this list of conditions and the following disclaimer in the |
18 | * documentation and/or other materials provided with the distribution. |
19 | * |
20 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
21 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
22 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
23 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
24 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
25 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
26 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
27 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
28 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
29 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
30 | * POSSIBILITY OF SUCH DAMAGE. |
31 | */ |
32 | |
33 | #include <sys/cdefs.h> |
34 | __KERNEL_RCSID(0, "$NetBSD: rndpseudo.c,v 1.35 2015/08/20 14:40:17 christos Exp $" ); |
35 | |
36 | #if defined(_KERNEL_OPT) |
37 | #include "opt_compat_netbsd.h" |
38 | #endif |
39 | |
40 | #include <sys/param.h> |
41 | #include <sys/atomic.h> |
42 | #include <sys/conf.h> |
43 | #include <sys/cprng.h> |
44 | #include <sys/cpu.h> |
45 | #include <sys/evcnt.h> |
46 | #include <sys/fcntl.h> |
47 | #include <sys/file.h> |
48 | #include <sys/filedesc.h> |
49 | #include <sys/ioctl.h> |
50 | #include <sys/kauth.h> |
51 | #include <sys/kernel.h> |
52 | #include <sys/kmem.h> |
53 | #include <sys/mutex.h> |
54 | #include <sys/percpu.h> |
55 | #include <sys/poll.h> |
56 | #include <sys/pool.h> |
57 | #include <sys/proc.h> |
58 | #include <sys/rnd.h> |
59 | #include <sys/rndpool.h> |
60 | #include <sys/rndsource.h> |
61 | #include <sys/select.h> |
62 | #include <sys/stat.h> |
63 | #include <sys/systm.h> |
64 | #include <sys/vnode.h> |
65 | |
66 | #include <dev/rnd_private.h> |
67 | |
68 | #include "ioconf.h" |
69 | |
70 | #if defined(__HAVE_CPU_COUNTER) |
71 | #include <machine/cpu_counter.h> |
72 | #endif |
73 | |
74 | #ifdef RND_DEBUG |
75 | #define DPRINTF(l,x) if (rnd_debug & (l)) printf x |
76 | #else |
77 | #define DPRINTF(l,x) |
78 | #endif |
79 | |
80 | /* |
81 | * list devices attached |
82 | */ |
83 | #if 0 |
84 | #define RND_VERBOSE |
85 | #endif |
86 | |
87 | /* |
88 | * The size of a temporary buffer for reading and writing entropy. |
89 | */ |
90 | #define RND_TEMP_BUFFER_SIZE 512 |
91 | |
92 | static pool_cache_t rnd_temp_buffer_cache __read_mostly; |
93 | |
94 | /* |
95 | * Per-open state -- a lazily initialized CPRNG. |
96 | */ |
97 | struct rnd_ctx { |
98 | struct cprng_strong *rc_cprng; |
99 | bool rc_hard; |
100 | }; |
101 | |
102 | static pool_cache_t rnd_ctx_cache __read_mostly; |
103 | |
104 | /* |
105 | * The per-CPU RNGs used for short requests |
106 | */ |
107 | static percpu_t *percpu_urandom_cprng __read_mostly; |
108 | |
109 | |
110 | dev_type_open(rndopen); |
111 | |
112 | const struct cdevsw rnd_cdevsw = { |
113 | .d_open = rndopen, |
114 | .d_close = noclose, |
115 | .d_read = noread, |
116 | .d_write = nowrite, |
117 | .d_ioctl = noioctl, |
118 | .d_stop = nostop, |
119 | .d_tty = notty, |
120 | .d_poll = nopoll, |
121 | .d_mmap = nommap, |
122 | .d_kqfilter = nokqfilter, |
123 | .d_discard = nodiscard, |
124 | .d_flag = D_OTHER | D_MPSAFE |
125 | }; |
126 | |
127 | static int rnd_read(struct file *, off_t *, struct uio *, kauth_cred_t, int); |
128 | static int rnd_write(struct file *, off_t *, struct uio *, kauth_cred_t, int); |
129 | static int rnd_ioctl(struct file *, u_long, void *); |
130 | static int rnd_poll(struct file *, int); |
131 | static int rnd_stat(struct file *, struct stat *); |
132 | static int rnd_close(struct file *); |
133 | static int rnd_kqfilter(struct file *, struct knote *); |
134 | |
135 | const struct fileops rnd_fileops = { |
136 | .fo_read = rnd_read, |
137 | .fo_write = rnd_write, |
138 | .fo_ioctl = rnd_ioctl, |
139 | .fo_fcntl = fnullop_fcntl, |
140 | .fo_poll = rnd_poll, |
141 | .fo_stat = rnd_stat, |
142 | .fo_close = rnd_close, |
143 | .fo_kqfilter = rnd_kqfilter, |
144 | .fo_restart = fnullop_restart |
145 | }; |
146 | |
147 | static struct evcnt rndpseudo_soft = EVCNT_INITIALIZER(EVCNT_TYPE_MISC, |
148 | NULL, "rndpseudo" , "open soft" ); |
149 | static struct evcnt rndpseudo_hard = EVCNT_INITIALIZER(EVCNT_TYPE_MISC, |
150 | NULL, "rndpseudo" , "open hard" ); |
151 | EVCNT_ATTACH_STATIC(rndpseudo_soft); |
152 | EVCNT_ATTACH_STATIC(rndpseudo_hard); |
153 | |
154 | /* |
155 | * Generate a 32-bit counter. |
156 | */ |
157 | static inline uint32_t |
158 | rndpseudo_counter(void) |
159 | { |
160 | struct bintime bt; |
161 | uint32_t ret; |
162 | |
163 | #if defined(__HAVE_CPU_COUNTER) |
164 | if (cpu_hascounter()) |
165 | return (cpu_counter32()); |
166 | #endif |
167 | |
168 | binuptime(&bt); |
169 | ret = bt.sec; |
170 | ret ^= bt.sec >> 32; |
171 | ret ^= bt.frac; |
172 | ret ^= bt.frac >> 32; |
173 | |
174 | return ret; |
175 | } |
176 | |
177 | /* |
178 | * Used by ioconf.c to attach the rnd pseudo-device. |
179 | * `Attach' the random device. We use the timing of this event as |
180 | * another potential source of initial entropy. |
181 | */ |
182 | void |
183 | rndattach(int num) |
184 | { |
185 | uint32_t c; |
186 | |
187 | /* Trap unwary players who don't call rnd_init() early. */ |
188 | KASSERT(rnd_ready); |
189 | |
190 | rnd_temp_buffer_cache = pool_cache_init(RND_TEMP_BUFFER_SIZE, 0, 0, 0, |
191 | "rndtemp" , NULL, IPL_NONE, NULL, NULL, NULL); |
192 | rnd_ctx_cache = pool_cache_init(sizeof(struct rnd_ctx), 0, 0, 0, |
193 | "rndctx" , NULL, IPL_NONE, NULL, NULL, NULL); |
194 | percpu_urandom_cprng = percpu_alloc(sizeof(struct cprng_strong *)); |
195 | |
196 | /* Mix in another counter. */ |
197 | c = rndpseudo_counter(); |
198 | rnd_add_data(NULL, &c, sizeof(c), 1); |
199 | } |
200 | |
201 | int |
202 | rndopen(dev_t dev, int flags, int fmt, struct lwp *l) |
203 | { |
204 | bool hard; |
205 | struct file *fp; |
206 | int fd; |
207 | int error; |
208 | |
209 | switch (minor(dev)) { |
210 | case RND_DEV_URANDOM: |
211 | hard = false; |
212 | rndpseudo_soft.ev_count++; |
213 | break; |
214 | |
215 | case RND_DEV_RANDOM: |
216 | hard = true; |
217 | rndpseudo_hard.ev_count++; |
218 | break; |
219 | |
220 | default: |
221 | return ENXIO; |
222 | } |
223 | |
224 | error = fd_allocfile(&fp, &fd); |
225 | if (error) |
226 | return error; |
227 | |
228 | /* |
229 | * Allocate a context, but don't create a CPRNG yet -- do that |
230 | * lazily because it consumes entropy from the system entropy |
231 | * pool, which (currently) has the effect of depleting it and |
232 | * causing readers from /dev/random to block. If this is |
233 | * /dev/urandom and the process is about to send only short |
234 | * reads to it, then we will be using a per-CPU CPRNG anyway. |
235 | */ |
236 | struct rnd_ctx *const ctx = pool_cache_get(rnd_ctx_cache, PR_WAITOK); |
237 | ctx->rc_cprng = NULL; |
238 | ctx->rc_hard = hard; |
239 | |
240 | error = fd_clone(fp, fd, flags, &rnd_fileops, ctx); |
241 | KASSERT(error == EMOVEFD); |
242 | |
243 | return error; |
244 | } |
245 | |
246 | /* |
247 | * Fetch a /dev/u?random context's CPRNG, or create and save one if |
248 | * necessary. |
249 | */ |
250 | static struct cprng_strong * |
251 | rnd_ctx_cprng(struct rnd_ctx *ctx) |
252 | { |
253 | struct cprng_strong *cprng, *tmp = NULL; |
254 | |
255 | /* Fast path: if someone has already allocated a CPRNG, use it. */ |
256 | cprng = ctx->rc_cprng; |
257 | if (__predict_true(cprng != NULL)) { |
258 | /* Make sure the CPU hasn't prefetched cprng's guts. */ |
259 | membar_consumer(); |
260 | goto out; |
261 | } |
262 | |
263 | /* Slow path: create a CPRNG. Allocate before taking locks. */ |
264 | char name[64]; |
265 | struct lwp *const l = curlwp; |
266 | (void)snprintf(name, sizeof(name), "%d %" PRIu64" %u" , |
267 | (int)l->l_proc->p_pid, l->l_ncsw, l->l_cpticks); |
268 | const int flags = (ctx->rc_hard? (CPRNG_USE_CV | CPRNG_HARD) : |
269 | (CPRNG_INIT_ANY | CPRNG_REKEY_ANY)); |
270 | tmp = cprng_strong_create(name, IPL_NONE, flags); |
271 | |
272 | /* Publish cprng's guts before the pointer to them. */ |
273 | membar_producer(); |
274 | |
275 | /* Attempt to publish tmp, unless someone beat us. */ |
276 | cprng = atomic_cas_ptr(&ctx->rc_cprng, NULL, tmp); |
277 | if (__predict_false(cprng != NULL)) { |
278 | /* Make sure the CPU hasn't prefetched cprng's guts. */ |
279 | membar_consumer(); |
280 | goto out; |
281 | } |
282 | |
283 | /* Published. Commit tmp. */ |
284 | cprng = tmp; |
285 | tmp = NULL; |
286 | |
287 | out: if (tmp != NULL) |
288 | cprng_strong_destroy(tmp); |
289 | KASSERT(cprng != NULL); |
290 | return cprng; |
291 | } |
292 | |
293 | /* |
294 | * Fetch a per-CPU CPRNG, or create and save one if necessary. |
295 | */ |
296 | static struct cprng_strong * |
297 | rnd_percpu_cprng(void) |
298 | { |
299 | struct cprng_strong **cprngp, *cprng, *tmp = NULL; |
300 | |
301 | /* Fast path: if there already is a CPRNG for this CPU, use it. */ |
302 | cprngp = percpu_getref(percpu_urandom_cprng); |
303 | cprng = *cprngp; |
304 | if (__predict_true(cprng != NULL)) |
305 | goto out; |
306 | percpu_putref(percpu_urandom_cprng); |
307 | |
308 | /* |
309 | * Slow path: create a CPRNG named by this CPU. |
310 | * |
311 | * XXX The CPU of the name may be different from the CPU to |
312 | * which it is assigned, because we need to choose a name and |
313 | * allocate a cprng while preemption is enabled. This could be |
314 | * fixed by changing the cprng_strong API (e.g., by adding a |
315 | * cprng_strong_setname or by separating allocation from |
316 | * initialization), but it's not clear that's worth the |
317 | * trouble. |
318 | */ |
319 | char name[32]; |
320 | (void)snprintf(name, sizeof(name), "urandom%u" , cpu_index(curcpu())); |
321 | tmp = cprng_strong_create(name, IPL_NONE, |
322 | (CPRNG_INIT_ANY | CPRNG_REKEY_ANY)); |
323 | |
324 | /* Try again, but we may have been preempted and lost a race. */ |
325 | cprngp = percpu_getref(percpu_urandom_cprng); |
326 | cprng = *cprngp; |
327 | if (__predict_false(cprng != NULL)) |
328 | goto out; |
329 | |
330 | /* Commit the CPRNG we just created. */ |
331 | cprng = tmp; |
332 | tmp = NULL; |
333 | *cprngp = cprng; |
334 | |
335 | out: percpu_putref(percpu_urandom_cprng); |
336 | if (tmp != NULL) |
337 | cprng_strong_destroy(tmp); |
338 | KASSERT(cprng != NULL); |
339 | return cprng; |
340 | } |
341 | |
342 | static int |
343 | rnd_read(struct file *fp, off_t *offp, struct uio *uio, kauth_cred_t cred, |
344 | int flags) |
345 | { |
346 | int error = 0; |
347 | |
348 | DPRINTF(RND_DEBUG_READ, |
349 | ("Random: Read of %zu requested, flags 0x%08x\n" , |
350 | uio->uio_resid, flags)); |
351 | |
352 | if (uio->uio_resid == 0) |
353 | return 0; |
354 | |
355 | struct rnd_ctx *const ctx = fp->f_rndctx; |
356 | uint8_t *const buf = pool_cache_get(rnd_temp_buffer_cache, PR_WAITOK); |
357 | |
358 | /* |
359 | * Choose a CPRNG to use -- either the per-open CPRNG, if this |
360 | * is /dev/random or a long read, or the per-CPU one otherwise. |
361 | * |
362 | * XXX NIST_BLOCK_KEYLEN_BYTES is a detail of the cprng(9) |
363 | * implementation and as such should not be mentioned here. |
364 | */ |
365 | struct cprng_strong *const cprng = |
366 | ((ctx->rc_hard || (uio->uio_resid > NIST_BLOCK_KEYLEN_BYTES))? |
367 | rnd_ctx_cprng(ctx) : rnd_percpu_cprng()); |
368 | |
369 | /* |
370 | * Generate the data in RND_TEMP_BUFFER_SIZE chunks. |
371 | */ |
372 | while (uio->uio_resid > 0) { |
373 | const size_t n_req = MIN(uio->uio_resid, RND_TEMP_BUFFER_SIZE); |
374 | |
375 | CTASSERT(RND_TEMP_BUFFER_SIZE <= CPRNG_MAX_LEN); |
376 | const size_t n_read = cprng_strong(cprng, buf, n_req, |
377 | ((ctx->rc_hard && ISSET(fp->f_flag, FNONBLOCK))? |
378 | FNONBLOCK : 0)); |
379 | |
380 | /* |
381 | * Equality will hold unless this is /dev/random, in |
382 | * which case we get only as many bytes as are left |
383 | * from the CPRNG's `information-theoretic strength' |
384 | * since the last rekey. |
385 | */ |
386 | KASSERT(n_read <= n_req); |
387 | KASSERT(ctx->rc_hard || (n_read == n_req)); |
388 | |
389 | error = uiomove(buf, n_read, uio); |
390 | if (error) |
391 | goto out; |
392 | |
393 | /* |
394 | * For /dev/urandom: Reads always succeed in full, no |
395 | * matter how many iterations that takes. (XXX But |
396 | * this means the computation can't be interrupted, |
397 | * wihch seems suboptimal.) |
398 | * |
399 | * For /dev/random, nonblocking: Reads succeed with as |
400 | * many bytes as a single request can return without |
401 | * blocking, or fail with EAGAIN if a request would |
402 | * block. (There is no sense in trying multiple |
403 | * requests because if the first one didn't fill the |
404 | * buffer, the second one would almost certainly |
405 | * block.) |
406 | * |
407 | * For /dev/random, blocking: Reads succeed with as |
408 | * many bytes as a single request -- which may block -- |
409 | * can return if uninterrupted, or fail with EINTR if |
410 | * the request is interrupted. |
411 | */ |
412 | KASSERT((0 < n_read) || ctx->rc_hard); |
413 | if (ctx->rc_hard) { |
414 | if (0 < n_read) |
415 | error = 0; |
416 | else if (ISSET(fp->f_flag, FNONBLOCK)) |
417 | error = EAGAIN; |
418 | else |
419 | error = EINTR; |
420 | goto out; |
421 | } |
422 | } |
423 | |
424 | out: pool_cache_put(rnd_temp_buffer_cache, buf); |
425 | return error; |
426 | } |
427 | |
428 | static int |
429 | rnd_write(struct file *fp, off_t *offp, struct uio *uio, |
430 | kauth_cred_t cred, int flags) |
431 | { |
432 | uint8_t *bf; |
433 | int n, ret = 0, estimate_ok = 0, estimate = 0, added = 0; |
434 | |
435 | ret = kauth_authorize_device(cred, |
436 | KAUTH_DEVICE_RND_ADDDATA, NULL, NULL, NULL, NULL); |
437 | if (ret) { |
438 | return (ret); |
439 | } |
440 | estimate_ok = !kauth_authorize_device(cred, |
441 | KAUTH_DEVICE_RND_ADDDATA_ESTIMATE, NULL, NULL, NULL, NULL); |
442 | |
443 | DPRINTF(RND_DEBUG_WRITE, |
444 | ("Random: Write of %zu requested\n" , uio->uio_resid)); |
445 | |
446 | if (uio->uio_resid == 0) |
447 | return (0); |
448 | ret = 0; |
449 | bf = pool_cache_get(rnd_temp_buffer_cache, PR_WAITOK); |
450 | while (uio->uio_resid > 0) { |
451 | /* |
452 | * Don't flood the pool. |
453 | */ |
454 | if (added > RND_POOLWORDS * sizeof(int)) { |
455 | #ifdef RND_VERBOSE |
456 | printf("rnd: added %d already, adding no more.\n" , |
457 | added); |
458 | #endif |
459 | break; |
460 | } |
461 | n = min(RND_TEMP_BUFFER_SIZE, uio->uio_resid); |
462 | |
463 | ret = uiomove((void *)bf, n, uio); |
464 | if (ret != 0) |
465 | break; |
466 | |
467 | if (estimate_ok) { |
468 | /* |
469 | * Don't cause samples to be discarded by taking |
470 | * the pool's entropy estimate to the max. |
471 | */ |
472 | if (added > RND_POOLWORDS / 2) |
473 | estimate = 0; |
474 | else |
475 | estimate = n * NBBY / 2; |
476 | #ifdef RND_VERBOSE |
477 | printf("rnd: adding on write, %d bytes, estimate %d\n" , |
478 | n, estimate); |
479 | #endif |
480 | } else { |
481 | #ifdef RND_VERBOSE |
482 | printf("rnd: kauth says no entropy.\n" ); |
483 | #endif |
484 | } |
485 | |
486 | /* |
487 | * Mix in the bytes. |
488 | */ |
489 | rnd_add_data(NULL, bf, n, estimate); |
490 | |
491 | added += n; |
492 | DPRINTF(RND_DEBUG_WRITE, ("Random: Copied in %d bytes\n" , n)); |
493 | } |
494 | pool_cache_put(rnd_temp_buffer_cache, bf); |
495 | return (ret); |
496 | } |
497 | |
498 | int |
499 | rnd_ioctl(struct file *fp, u_long cmd, void *addr) |
500 | { |
501 | |
502 | switch (cmd) { |
503 | case FIONBIO: |
504 | case FIOASYNC: |
505 | return 0; |
506 | default: |
507 | return rnd_system_ioctl(fp, cmd, addr); |
508 | } |
509 | } |
510 | |
511 | static int |
512 | rnd_poll(struct file *fp, int events) |
513 | { |
514 | struct rnd_ctx *const ctx = fp->f_rndctx; |
515 | int revents; |
516 | |
517 | /* |
518 | * We are always writable. |
519 | */ |
520 | revents = events & (POLLOUT | POLLWRNORM); |
521 | |
522 | /* |
523 | * Save some work if not checking for reads. |
524 | */ |
525 | if ((events & (POLLIN | POLLRDNORM)) == 0) |
526 | return revents; |
527 | |
528 | /* |
529 | * For /dev/random, ask the CPRNG, which may require creating |
530 | * one. For /dev/urandom, we're always readable. |
531 | */ |
532 | if (ctx->rc_hard) |
533 | revents |= cprng_strong_poll(rnd_ctx_cprng(ctx), events); |
534 | else |
535 | revents |= (events & (POLLIN | POLLRDNORM)); |
536 | |
537 | return revents; |
538 | } |
539 | |
540 | static int |
541 | rnd_stat(struct file *fp, struct stat *st) |
542 | { |
543 | struct rnd_ctx *const ctx = fp->f_rndctx; |
544 | |
545 | /* XXX lock, if cprng allocated? why? */ |
546 | memset(st, 0, sizeof(*st)); |
547 | st->st_dev = makedev(cdevsw_lookup_major(&rnd_cdevsw), |
548 | (ctx->rc_hard? RND_DEV_RANDOM : RND_DEV_URANDOM)); |
549 | /* XXX leave atimespect, mtimespec, ctimespec = 0? */ |
550 | |
551 | st->st_uid = kauth_cred_geteuid(fp->f_cred); |
552 | st->st_gid = kauth_cred_getegid(fp->f_cred); |
553 | st->st_mode = S_IFCHR; |
554 | return 0; |
555 | } |
556 | |
557 | static int |
558 | rnd_close(struct file *fp) |
559 | { |
560 | struct rnd_ctx *const ctx = fp->f_rndctx; |
561 | |
562 | if (ctx->rc_cprng != NULL) |
563 | cprng_strong_destroy(ctx->rc_cprng); |
564 | fp->f_rndctx = NULL; |
565 | pool_cache_put(rnd_ctx_cache, ctx); |
566 | |
567 | return 0; |
568 | } |
569 | |
570 | static int |
571 | rnd_kqfilter(struct file *fp, struct knote *kn) |
572 | { |
573 | struct rnd_ctx *const ctx = fp->f_rndctx; |
574 | |
575 | return cprng_strong_kqfilter(rnd_ctx_cprng(ctx), kn); |
576 | } |
577 | |