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a07fdae3 | 1 | // SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) |
1da177e4 | 2 | /* |
9f9eff85 | 3 | * Copyright (C) 2017-2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. |
9e95ce27 | 4 | * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005 |
5f75d9f3 JD |
5 | * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All rights reserved. |
6 | * | |
7 | * This driver produces cryptographically secure pseudorandom data. It is divided | |
8 | * into roughly six sections, each with a section header: | |
9 | * | |
10 | * - Initialization and readiness waiting. | |
11 | * - Fast key erasure RNG, the "crng". | |
12 | * - Entropy accumulation and extraction routines. | |
13 | * - Entropy collection routines. | |
14 | * - Userspace reader/writer interfaces. | |
15 | * - Sysctl interface. | |
16 | * | |
17 | * The high level overview is that there is one input pool, into which | |
18 | * various pieces of data are hashed. Some of that data is then "credited" as | |
19 | * having a certain number of bits of entropy. When enough bits of entropy are | |
20 | * available, the hash is finalized and handed as a key to a stream cipher that | |
21 | * expands it indefinitely for various consumers. This key is periodically | |
22 | * refreshed as the various entropy collectors, described below, add data to the | |
23 | * input pool and credit it. There is currently no Fortuna-like scheduler | |
24 | * involved, which can lead to malicious entropy sources causing a premature | |
25 | * reseed, and the entropy estimates are, at best, conservative guesses. | |
1da177e4 LT |
26 | */ |
27 | ||
12cd53af YL |
28 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
29 | ||
1da177e4 | 30 | #include <linux/utsname.h> |
1da177e4 LT |
31 | #include <linux/module.h> |
32 | #include <linux/kernel.h> | |
33 | #include <linux/major.h> | |
34 | #include <linux/string.h> | |
35 | #include <linux/fcntl.h> | |
36 | #include <linux/slab.h> | |
37 | #include <linux/random.h> | |
38 | #include <linux/poll.h> | |
39 | #include <linux/init.h> | |
40 | #include <linux/fs.h> | |
41 | #include <linux/genhd.h> | |
42 | #include <linux/interrupt.h> | |
27ac792c | 43 | #include <linux/mm.h> |
dd0f0cf5 | 44 | #include <linux/nodemask.h> |
1da177e4 | 45 | #include <linux/spinlock.h> |
c84dbf61 | 46 | #include <linux/kthread.h> |
1da177e4 | 47 | #include <linux/percpu.h> |
775f4b29 | 48 | #include <linux/ptrace.h> |
6265e169 | 49 | #include <linux/workqueue.h> |
0244ad00 | 50 | #include <linux/irq.h> |
4e00b339 | 51 | #include <linux/ratelimit.h> |
c6e9d6f3 TT |
52 | #include <linux/syscalls.h> |
53 | #include <linux/completion.h> | |
8da4b8c4 | 54 | #include <linux/uuid.h> |
87e7d5ab | 55 | #include <linux/uaccess.h> |
1ca1b917 | 56 | #include <crypto/chacha.h> |
9f9eff85 | 57 | #include <crypto/blake2s.h> |
1da177e4 | 58 | #include <asm/processor.h> |
1da177e4 | 59 | #include <asm/irq.h> |
775f4b29 | 60 | #include <asm/irq_regs.h> |
1da177e4 LT |
61 | #include <asm/io.h> |
62 | ||
5f1bb112 JD |
63 | /********************************************************************* |
64 | * | |
65 | * Initialization and readiness waiting. | |
66 | * | |
67 | * Much of the RNG infrastructure is devoted to various dependencies | |
68 | * being able to wait until the RNG has collected enough entropy and | |
69 | * is ready for safe consumption. | |
70 | * | |
71 | *********************************************************************/ | |
205a525c | 72 | |
e192be9d TT |
73 | /* |
74 | * crng_init = 0 --> Uninitialized | |
75 | * 1 --> Initialized | |
76 | * 2 --> Initialized from input_pool | |
77 | * | |
5f1bb112 | 78 | * crng_init is protected by base_crng->lock, and only increases |
e192be9d TT |
79 | * its value (from 0->1->2). |
80 | */ | |
81 | static int crng_init = 0; | |
43838a23 | 82 | #define crng_ready() (likely(crng_init > 1)) |
5f1bb112 JD |
83 | /* Various types of waiters for crng_init->2 transition. */ |
84 | static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); | |
85 | static struct fasync_struct *fasync; | |
86 | static DEFINE_SPINLOCK(random_ready_list_lock); | |
87 | static LIST_HEAD(random_ready_list); | |
e192be9d | 88 | |
5f1bb112 | 89 | /* Control how we warn userspace. */ |
4e00b339 TT |
90 | static struct ratelimit_state unseeded_warning = |
91 | RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3); | |
92 | static struct ratelimit_state urandom_warning = | |
93 | RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3); | |
4e00b339 | 94 | static int ratelimit_disable __read_mostly; |
4e00b339 TT |
95 | module_param_named(ratelimit_disable, ratelimit_disable, int, 0644); |
96 | MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression"); | |
97 | ||
5f1bb112 JD |
98 | /* |
99 | * Returns whether or not the input pool has been seeded and thus guaranteed | |
100 | * to supply cryptographically secure random numbers. This applies to: the | |
101 | * /dev/urandom device, the get_random_bytes function, and the get_random_{u32, | |
102 | * ,u64,int,long} family of functions. | |
103 | * | |
104 | * Returns: true if the input pool has been seeded. | |
105 | * false if the input pool has not been seeded. | |
106 | */ | |
107 | bool rng_is_initialized(void) | |
108 | { | |
109 | return crng_ready(); | |
110 | } | |
111 | EXPORT_SYMBOL(rng_is_initialized); | |
112 | ||
113 | /* Used by wait_for_random_bytes(), and considered an entropy collector, below. */ | |
114 | static void try_to_generate_entropy(void); | |
115 | ||
116 | /* | |
117 | * Wait for the input pool to be seeded and thus guaranteed to supply | |
118 | * cryptographically secure random numbers. This applies to: the /dev/urandom | |
119 | * device, the get_random_bytes function, and the get_random_{u32,u64,int,long} | |
120 | * family of functions. Using any of these functions without first calling | |
121 | * this function forfeits the guarantee of security. | |
122 | * | |
123 | * Returns: 0 if the input pool has been seeded. | |
124 | * -ERESTARTSYS if the function was interrupted by a signal. | |
125 | */ | |
126 | int wait_for_random_bytes(void) | |
127 | { | |
128 | if (likely(crng_ready())) | |
129 | return 0; | |
130 | ||
131 | do { | |
132 | int ret; | |
133 | ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ); | |
134 | if (ret) | |
135 | return ret > 0 ? 0 : ret; | |
136 | ||
137 | try_to_generate_entropy(); | |
138 | } while (!crng_ready()); | |
139 | ||
140 | return 0; | |
141 | } | |
142 | EXPORT_SYMBOL(wait_for_random_bytes); | |
143 | ||
144 | /* | |
145 | * Add a callback function that will be invoked when the input | |
146 | * pool is initialised. | |
147 | * | |
148 | * returns: 0 if callback is successfully added | |
149 | * -EALREADY if pool is already initialised (callback not called) | |
150 | * -ENOENT if module for callback is not alive | |
151 | */ | |
152 | int add_random_ready_callback(struct random_ready_callback *rdy) | |
153 | { | |
154 | struct module *owner; | |
155 | unsigned long flags; | |
156 | int err = -EALREADY; | |
157 | ||
158 | if (crng_ready()) | |
159 | return err; | |
160 | ||
161 | owner = rdy->owner; | |
162 | if (!try_module_get(owner)) | |
163 | return -ENOENT; | |
164 | ||
165 | spin_lock_irqsave(&random_ready_list_lock, flags); | |
166 | if (crng_ready()) | |
167 | goto out; | |
168 | ||
169 | owner = NULL; | |
170 | ||
171 | list_add(&rdy->list, &random_ready_list); | |
172 | err = 0; | |
173 | ||
174 | out: | |
175 | spin_unlock_irqrestore(&random_ready_list_lock, flags); | |
176 | ||
177 | module_put(owner); | |
178 | ||
179 | return err; | |
180 | } | |
181 | EXPORT_SYMBOL(add_random_ready_callback); | |
182 | ||
183 | /* | |
184 | * Delete a previously registered readiness callback function. | |
185 | */ | |
186 | void del_random_ready_callback(struct random_ready_callback *rdy) | |
187 | { | |
188 | unsigned long flags; | |
189 | struct module *owner = NULL; | |
190 | ||
191 | spin_lock_irqsave(&random_ready_list_lock, flags); | |
192 | if (!list_empty(&rdy->list)) { | |
193 | list_del_init(&rdy->list); | |
194 | owner = rdy->owner; | |
195 | } | |
196 | spin_unlock_irqrestore(&random_ready_list_lock, flags); | |
197 | ||
198 | module_put(owner); | |
199 | } | |
200 | EXPORT_SYMBOL(del_random_ready_callback); | |
201 | ||
202 | static void process_random_ready_list(void) | |
203 | { | |
204 | unsigned long flags; | |
205 | struct random_ready_callback *rdy, *tmp; | |
206 | ||
207 | spin_lock_irqsave(&random_ready_list_lock, flags); | |
208 | list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) { | |
209 | struct module *owner = rdy->owner; | |
210 | ||
211 | list_del_init(&rdy->list); | |
212 | rdy->func(rdy); | |
213 | module_put(owner); | |
214 | } | |
215 | spin_unlock_irqrestore(&random_ready_list_lock, flags); | |
216 | } | |
217 | ||
218 | #define warn_unseeded_randomness(previous) \ | |
219 | _warn_unseeded_randomness(__func__, (void *)_RET_IP_, (previous)) | |
220 | ||
221 | static void _warn_unseeded_randomness(const char *func_name, void *caller, void **previous) | |
222 | { | |
223 | #ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM | |
224 | const bool print_once = false; | |
225 | #else | |
226 | static bool print_once __read_mostly; | |
227 | #endif | |
228 | ||
229 | if (print_once || crng_ready() || | |
230 | (previous && (caller == READ_ONCE(*previous)))) | |
231 | return; | |
232 | WRITE_ONCE(*previous, caller); | |
233 | #ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM | |
234 | print_once = true; | |
235 | #endif | |
236 | if (__ratelimit(&unseeded_warning)) | |
237 | printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", | |
238 | func_name, caller, crng_init); | |
239 | } | |
240 | ||
241 | ||
3655adc7 | 242 | /********************************************************************* |
1da177e4 | 243 | * |
3655adc7 | 244 | * Fast key erasure RNG, the "crng". |
1da177e4 | 245 | * |
3655adc7 JD |
246 | * These functions expand entropy from the entropy extractor into |
247 | * long streams for external consumption using the "fast key erasure" | |
248 | * RNG described at <https://blog.cr.yp.to/20170723-random.html>. | |
e192be9d | 249 | * |
3655adc7 JD |
250 | * There are a few exported interfaces for use by other drivers: |
251 | * | |
252 | * void get_random_bytes(void *buf, size_t nbytes) | |
253 | * u32 get_random_u32() | |
254 | * u64 get_random_u64() | |
255 | * unsigned int get_random_int() | |
256 | * unsigned long get_random_long() | |
257 | * | |
258 | * These interfaces will return the requested number of random bytes | |
259 | * into the given buffer or as a return value. This is equivalent to | |
260 | * a read from /dev/urandom. The integer family of functions may be | |
261 | * higher performance for one-off random integers, because they do a | |
262 | * bit of buffering. | |
e192be9d TT |
263 | * |
264 | *********************************************************************/ | |
265 | ||
186873c5 JD |
266 | enum { |
267 | CRNG_RESEED_INTERVAL = 300 * HZ, | |
268 | CRNG_INIT_CNT_THRESH = 2 * CHACHA_KEY_SIZE | |
269 | }; | |
270 | ||
271 | static struct { | |
272 | u8 key[CHACHA_KEY_SIZE] __aligned(__alignof__(long)); | |
273 | unsigned long birth; | |
274 | unsigned long generation; | |
275 | spinlock_t lock; | |
276 | } base_crng = { | |
277 | .lock = __SPIN_LOCK_UNLOCKED(base_crng.lock) | |
278 | }; | |
279 | ||
280 | struct crng { | |
281 | u8 key[CHACHA_KEY_SIZE]; | |
282 | unsigned long generation; | |
283 | local_lock_t lock; | |
284 | }; | |
285 | ||
286 | static DEFINE_PER_CPU(struct crng, crngs) = { | |
287 | .generation = ULONG_MAX, | |
288 | .lock = INIT_LOCAL_LOCK(crngs.lock), | |
289 | }; | |
e192be9d | 290 | |
3655adc7 JD |
291 | /* Used by crng_reseed() to extract a new seed from the input pool. */ |
292 | static bool drain_entropy(void *buf, size_t nbytes); | |
e192be9d | 293 | |
dc12baac | 294 | /* |
3655adc7 JD |
295 | * This extracts a new crng key from the input pool, but only if there is a |
296 | * sufficient amount of entropy available, in order to mitigate bruteforcing | |
297 | * of newly added bits. | |
dc12baac | 298 | */ |
a9412d51 | 299 | static void crng_reseed(void) |
e192be9d | 300 | { |
248045b8 | 301 | unsigned long flags; |
186873c5 JD |
302 | unsigned long next_gen; |
303 | u8 key[CHACHA_KEY_SIZE]; | |
7191c628 | 304 | bool finalize_init = false; |
e192be9d | 305 | |
246c03dd JD |
306 | /* Only reseed if we can, to prevent brute forcing a small amount of new bits. */ |
307 | if (!drain_entropy(key, sizeof(key))) | |
308 | return; | |
a9412d51 | 309 | |
186873c5 JD |
310 | /* |
311 | * We copy the new key into the base_crng, overwriting the old one, | |
312 | * and update the generation counter. We avoid hitting ULONG_MAX, | |
313 | * because the per-cpu crngs are initialized to ULONG_MAX, so this | |
314 | * forces new CPUs that come online to always initialize. | |
315 | */ | |
316 | spin_lock_irqsave(&base_crng.lock, flags); | |
317 | memcpy(base_crng.key, key, sizeof(base_crng.key)); | |
318 | next_gen = base_crng.generation + 1; | |
319 | if (next_gen == ULONG_MAX) | |
320 | ++next_gen; | |
321 | WRITE_ONCE(base_crng.generation, next_gen); | |
322 | WRITE_ONCE(base_crng.birth, jiffies); | |
a9412d51 | 323 | if (crng_init < 2) { |
a9412d51 | 324 | crng_init = 2; |
7191c628 DB |
325 | finalize_init = true; |
326 | } | |
327 | spin_unlock_irqrestore(&base_crng.lock, flags); | |
328 | memzero_explicit(key, sizeof(key)); | |
329 | if (finalize_init) { | |
a9412d51 JD |
330 | process_random_ready_list(); |
331 | wake_up_interruptible(&crng_init_wait); | |
332 | kill_fasync(&fasync, SIGIO, POLL_IN); | |
333 | pr_notice("crng init done\n"); | |
334 | if (unseeded_warning.missed) { | |
335 | pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n", | |
336 | unseeded_warning.missed); | |
337 | unseeded_warning.missed = 0; | |
338 | } | |
339 | if (urandom_warning.missed) { | |
340 | pr_notice("%d urandom warning(s) missed due to ratelimiting\n", | |
341 | urandom_warning.missed); | |
342 | urandom_warning.missed = 0; | |
343 | } | |
344 | } | |
e192be9d TT |
345 | } |
346 | ||
186873c5 | 347 | /* |
3655adc7 JD |
348 | * This generates a ChaCha block using the provided key, and then |
349 | * immediately overwites that key with half the block. It returns | |
350 | * the resultant ChaCha state to the user, along with the second | |
351 | * half of the block containing 32 bytes of random data that may | |
352 | * be used; random_data_len may not be greater than 32. | |
186873c5 JD |
353 | */ |
354 | static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE], | |
355 | u32 chacha_state[CHACHA_STATE_WORDS], | |
356 | u8 *random_data, size_t random_data_len) | |
e192be9d | 357 | { |
186873c5 | 358 | u8 first_block[CHACHA_BLOCK_SIZE]; |
009ba856 | 359 | |
186873c5 JD |
360 | BUG_ON(random_data_len > 32); |
361 | ||
362 | chacha_init_consts(chacha_state); | |
363 | memcpy(&chacha_state[4], key, CHACHA_KEY_SIZE); | |
364 | memset(&chacha_state[12], 0, sizeof(u32) * 4); | |
365 | chacha20_block(chacha_state, first_block); | |
366 | ||
367 | memcpy(key, first_block, CHACHA_KEY_SIZE); | |
368 | memcpy(random_data, first_block + CHACHA_KEY_SIZE, random_data_len); | |
369 | memzero_explicit(first_block, sizeof(first_block)); | |
1e7f583a TT |
370 | } |
371 | ||
c92e040d | 372 | /* |
186873c5 JD |
373 | * This function returns a ChaCha state that you may use for generating |
374 | * random data. It also returns up to 32 bytes on its own of random data | |
375 | * that may be used; random_data_len may not be greater than 32. | |
c92e040d | 376 | */ |
186873c5 JD |
377 | static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS], |
378 | u8 *random_data, size_t random_data_len) | |
c92e040d | 379 | { |
248045b8 | 380 | unsigned long flags; |
186873c5 | 381 | struct crng *crng; |
c92e040d | 382 | |
186873c5 JD |
383 | BUG_ON(random_data_len > 32); |
384 | ||
385 | /* | |
386 | * For the fast path, we check whether we're ready, unlocked first, and | |
387 | * then re-check once locked later. In the case where we're really not | |
388 | * ready, we do fast key erasure with the base_crng directly, because | |
389 | * this is what crng_{fast,slow}_load mutate during early init. | |
390 | */ | |
391 | if (unlikely(!crng_ready())) { | |
392 | bool ready; | |
393 | ||
394 | spin_lock_irqsave(&base_crng.lock, flags); | |
395 | ready = crng_ready(); | |
396 | if (!ready) | |
397 | crng_fast_key_erasure(base_crng.key, chacha_state, | |
398 | random_data, random_data_len); | |
399 | spin_unlock_irqrestore(&base_crng.lock, flags); | |
400 | if (!ready) | |
401 | return; | |
c92e040d | 402 | } |
186873c5 JD |
403 | |
404 | /* | |
405 | * If the base_crng is more than 5 minutes old, we reseed, which | |
406 | * in turn bumps the generation counter that we check below. | |
407 | */ | |
408 | if (unlikely(time_after(jiffies, READ_ONCE(base_crng.birth) + CRNG_RESEED_INTERVAL))) | |
409 | crng_reseed(); | |
410 | ||
411 | local_lock_irqsave(&crngs.lock, flags); | |
412 | crng = raw_cpu_ptr(&crngs); | |
413 | ||
414 | /* | |
415 | * If our per-cpu crng is older than the base_crng, then it means | |
416 | * somebody reseeded the base_crng. In that case, we do fast key | |
417 | * erasure on the base_crng, and use its output as the new key | |
418 | * for our per-cpu crng. This brings us up to date with base_crng. | |
419 | */ | |
420 | if (unlikely(crng->generation != READ_ONCE(base_crng.generation))) { | |
421 | spin_lock(&base_crng.lock); | |
422 | crng_fast_key_erasure(base_crng.key, chacha_state, | |
423 | crng->key, sizeof(crng->key)); | |
424 | crng->generation = base_crng.generation; | |
425 | spin_unlock(&base_crng.lock); | |
426 | } | |
427 | ||
428 | /* | |
429 | * Finally, when we've made it this far, our per-cpu crng has an up | |
430 | * to date key, and we can do fast key erasure with it to produce | |
431 | * some random data and a ChaCha state for the caller. All other | |
432 | * branches of this function are "unlikely", so most of the time we | |
433 | * should wind up here immediately. | |
434 | */ | |
435 | crng_fast_key_erasure(crng->key, chacha_state, random_data, random_data_len); | |
436 | local_unlock_irqrestore(&crngs.lock, flags); | |
c92e040d TT |
437 | } |
438 | ||
3655adc7 JD |
439 | /* |
440 | * This function is for crng_init == 0 only. | |
441 | * | |
442 | * crng_fast_load() can be called by code in the interrupt service | |
443 | * path. So we can't afford to dilly-dally. Returns the number of | |
444 | * bytes processed from cp. | |
445 | */ | |
446 | static size_t crng_fast_load(const void *cp, size_t len) | |
447 | { | |
448 | static int crng_init_cnt = 0; | |
449 | unsigned long flags; | |
450 | const u8 *src = (const u8 *)cp; | |
451 | size_t ret = 0; | |
452 | ||
453 | if (!spin_trylock_irqsave(&base_crng.lock, flags)) | |
454 | return 0; | |
455 | if (crng_init != 0) { | |
456 | spin_unlock_irqrestore(&base_crng.lock, flags); | |
457 | return 0; | |
458 | } | |
459 | while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) { | |
460 | base_crng.key[crng_init_cnt % sizeof(base_crng.key)] ^= *src; | |
461 | src++; crng_init_cnt++; len--; ret++; | |
462 | } | |
463 | if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { | |
464 | ++base_crng.generation; | |
465 | crng_init = 1; | |
466 | } | |
467 | spin_unlock_irqrestore(&base_crng.lock, flags); | |
468 | if (crng_init == 1) | |
469 | pr_notice("fast init done\n"); | |
470 | return ret; | |
471 | } | |
472 | ||
473 | /* | |
474 | * This function is for crng_init == 0 only. | |
475 | * | |
476 | * crng_slow_load() is called by add_device_randomness, which has two | |
477 | * attributes. (1) We can't trust the buffer passed to it is | |
478 | * guaranteed to be unpredictable (so it might not have any entropy at | |
479 | * all), and (2) it doesn't have the performance constraints of | |
480 | * crng_fast_load(). | |
481 | * | |
482 | * So, we simply hash the contents in with the current key. Finally, | |
483 | * we do *not* advance crng_init_cnt since buffer we may get may be | |
484 | * something like a fixed DMI table (for example), which might very | |
485 | * well be unique to the machine, but is otherwise unvarying. | |
486 | */ | |
487 | static void crng_slow_load(const void *cp, size_t len) | |
488 | { | |
489 | unsigned long flags; | |
490 | struct blake2s_state hash; | |
491 | ||
492 | blake2s_init(&hash, sizeof(base_crng.key)); | |
493 | ||
494 | if (!spin_trylock_irqsave(&base_crng.lock, flags)) | |
495 | return; | |
496 | if (crng_init != 0) { | |
497 | spin_unlock_irqrestore(&base_crng.lock, flags); | |
498 | return; | |
499 | } | |
500 | ||
501 | blake2s_update(&hash, base_crng.key, sizeof(base_crng.key)); | |
502 | blake2s_update(&hash, cp, len); | |
503 | blake2s_final(&hash, base_crng.key); | |
504 | ||
505 | spin_unlock_irqrestore(&base_crng.lock, flags); | |
506 | } | |
507 | ||
508 | static void _get_random_bytes(void *buf, size_t nbytes) | |
e192be9d | 509 | { |
186873c5 | 510 | u32 chacha_state[CHACHA_STATE_WORDS]; |
3655adc7 JD |
511 | u8 tmp[CHACHA_BLOCK_SIZE]; |
512 | size_t len; | |
513 | ||
514 | if (!nbytes) | |
515 | return; | |
516 | ||
517 | len = min_t(size_t, 32, nbytes); | |
518 | crng_make_state(chacha_state, buf, len); | |
519 | nbytes -= len; | |
520 | buf += len; | |
521 | ||
522 | while (nbytes) { | |
523 | if (nbytes < CHACHA_BLOCK_SIZE) { | |
524 | chacha20_block(chacha_state, tmp); | |
525 | memcpy(buf, tmp, nbytes); | |
526 | memzero_explicit(tmp, sizeof(tmp)); | |
527 | break; | |
528 | } | |
529 | ||
530 | chacha20_block(chacha_state, buf); | |
531 | if (unlikely(chacha_state[12] == 0)) | |
532 | ++chacha_state[13]; | |
533 | nbytes -= CHACHA_BLOCK_SIZE; | |
534 | buf += CHACHA_BLOCK_SIZE; | |
535 | } | |
536 | ||
537 | memzero_explicit(chacha_state, sizeof(chacha_state)); | |
538 | } | |
539 | ||
540 | /* | |
541 | * This function is the exported kernel interface. It returns some | |
542 | * number of good random numbers, suitable for key generation, seeding | |
543 | * TCP sequence numbers, etc. It does not rely on the hardware random | |
544 | * number generator. For random bytes direct from the hardware RNG | |
545 | * (when available), use get_random_bytes_arch(). In order to ensure | |
546 | * that the randomness provided by this function is okay, the function | |
547 | * wait_for_random_bytes() should be called and return 0 at least once | |
548 | * at any point prior. | |
549 | */ | |
550 | void get_random_bytes(void *buf, size_t nbytes) | |
551 | { | |
552 | static void *previous; | |
553 | ||
554 | warn_unseeded_randomness(&previous); | |
555 | _get_random_bytes(buf, nbytes); | |
556 | } | |
557 | EXPORT_SYMBOL(get_random_bytes); | |
558 | ||
559 | static ssize_t get_random_bytes_user(void __user *buf, size_t nbytes) | |
560 | { | |
561 | bool large_request = nbytes > 256; | |
562 | ssize_t ret = 0; | |
563 | size_t len; | |
564 | u32 chacha_state[CHACHA_STATE_WORDS]; | |
565 | u8 output[CHACHA_BLOCK_SIZE]; | |
566 | ||
567 | if (!nbytes) | |
568 | return 0; | |
569 | ||
570 | len = min_t(size_t, 32, nbytes); | |
571 | crng_make_state(chacha_state, output, len); | |
572 | ||
573 | if (copy_to_user(buf, output, len)) | |
574 | return -EFAULT; | |
575 | nbytes -= len; | |
576 | buf += len; | |
577 | ret += len; | |
578 | ||
579 | while (nbytes) { | |
580 | if (large_request && need_resched()) { | |
581 | if (signal_pending(current)) | |
582 | break; | |
583 | schedule(); | |
584 | } | |
585 | ||
586 | chacha20_block(chacha_state, output); | |
587 | if (unlikely(chacha_state[12] == 0)) | |
588 | ++chacha_state[13]; | |
589 | ||
590 | len = min_t(size_t, nbytes, CHACHA_BLOCK_SIZE); | |
591 | if (copy_to_user(buf, output, len)) { | |
592 | ret = -EFAULT; | |
593 | break; | |
594 | } | |
595 | ||
596 | nbytes -= len; | |
597 | buf += len; | |
598 | ret += len; | |
599 | } | |
600 | ||
601 | memzero_explicit(chacha_state, sizeof(chacha_state)); | |
602 | memzero_explicit(output, sizeof(output)); | |
603 | return ret; | |
604 | } | |
605 | ||
606 | /* | |
607 | * Batched entropy returns random integers. The quality of the random | |
608 | * number is good as /dev/urandom. In order to ensure that the randomness | |
609 | * provided by this function is okay, the function wait_for_random_bytes() | |
610 | * should be called and return 0 at least once at any point prior. | |
611 | */ | |
612 | struct batched_entropy { | |
613 | union { | |
614 | /* | |
615 | * We make this 1.5x a ChaCha block, so that we get the | |
616 | * remaining 32 bytes from fast key erasure, plus one full | |
617 | * block from the detached ChaCha state. We can increase | |
618 | * the size of this later if needed so long as we keep the | |
619 | * formula of (integer_blocks + 0.5) * CHACHA_BLOCK_SIZE. | |
620 | */ | |
621 | u64 entropy_u64[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(u64))]; | |
622 | u32 entropy_u32[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(u32))]; | |
623 | }; | |
624 | local_lock_t lock; | |
625 | unsigned long generation; | |
626 | unsigned int position; | |
627 | }; | |
628 | ||
629 | ||
630 | static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = { | |
631 | .lock = INIT_LOCAL_LOCK(batched_entropy_u64.lock), | |
632 | .position = UINT_MAX | |
633 | }; | |
634 | ||
635 | u64 get_random_u64(void) | |
636 | { | |
637 | u64 ret; | |
638 | unsigned long flags; | |
639 | struct batched_entropy *batch; | |
640 | static void *previous; | |
641 | unsigned long next_gen; | |
642 | ||
643 | warn_unseeded_randomness(&previous); | |
644 | ||
645 | local_lock_irqsave(&batched_entropy_u64.lock, flags); | |
646 | batch = raw_cpu_ptr(&batched_entropy_u64); | |
647 | ||
648 | next_gen = READ_ONCE(base_crng.generation); | |
649 | if (batch->position >= ARRAY_SIZE(batch->entropy_u64) || | |
650 | next_gen != batch->generation) { | |
651 | _get_random_bytes(batch->entropy_u64, sizeof(batch->entropy_u64)); | |
652 | batch->position = 0; | |
653 | batch->generation = next_gen; | |
654 | } | |
655 | ||
656 | ret = batch->entropy_u64[batch->position]; | |
657 | batch->entropy_u64[batch->position] = 0; | |
658 | ++batch->position; | |
659 | local_unlock_irqrestore(&batched_entropy_u64.lock, flags); | |
660 | return ret; | |
661 | } | |
662 | EXPORT_SYMBOL(get_random_u64); | |
663 | ||
664 | static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = { | |
665 | .lock = INIT_LOCAL_LOCK(batched_entropy_u32.lock), | |
666 | .position = UINT_MAX | |
667 | }; | |
668 | ||
669 | u32 get_random_u32(void) | |
670 | { | |
671 | u32 ret; | |
672 | unsigned long flags; | |
673 | struct batched_entropy *batch; | |
674 | static void *previous; | |
675 | unsigned long next_gen; | |
676 | ||
677 | warn_unseeded_randomness(&previous); | |
678 | ||
679 | local_lock_irqsave(&batched_entropy_u32.lock, flags); | |
680 | batch = raw_cpu_ptr(&batched_entropy_u32); | |
681 | ||
682 | next_gen = READ_ONCE(base_crng.generation); | |
683 | if (batch->position >= ARRAY_SIZE(batch->entropy_u32) || | |
684 | next_gen != batch->generation) { | |
685 | _get_random_bytes(batch->entropy_u32, sizeof(batch->entropy_u32)); | |
686 | batch->position = 0; | |
687 | batch->generation = next_gen; | |
688 | } | |
689 | ||
690 | ret = batch->entropy_u32[batch->position]; | |
691 | batch->entropy_u32[batch->position] = 0; | |
692 | ++batch->position; | |
693 | local_unlock_irqrestore(&batched_entropy_u32.lock, flags); | |
694 | return ret; | |
695 | } | |
696 | EXPORT_SYMBOL(get_random_u32); | |
697 | ||
698 | /** | |
699 | * randomize_page - Generate a random, page aligned address | |
700 | * @start: The smallest acceptable address the caller will take. | |
701 | * @range: The size of the area, starting at @start, within which the | |
702 | * random address must fall. | |
703 | * | |
704 | * If @start + @range would overflow, @range is capped. | |
705 | * | |
706 | * NOTE: Historical use of randomize_range, which this replaces, presumed that | |
707 | * @start was already page aligned. We now align it regardless. | |
708 | * | |
709 | * Return: A page aligned address within [start, start + range). On error, | |
710 | * @start is returned. | |
711 | */ | |
712 | unsigned long randomize_page(unsigned long start, unsigned long range) | |
713 | { | |
714 | if (!PAGE_ALIGNED(start)) { | |
715 | range -= PAGE_ALIGN(start) - start; | |
716 | start = PAGE_ALIGN(start); | |
717 | } | |
718 | ||
719 | if (start > ULONG_MAX - range) | |
720 | range = ULONG_MAX - start; | |
721 | ||
722 | range >>= PAGE_SHIFT; | |
723 | ||
724 | if (range == 0) | |
725 | return start; | |
726 | ||
727 | return start + (get_random_long() % range << PAGE_SHIFT); | |
728 | } | |
729 | ||
730 | /* | |
731 | * This function will use the architecture-specific hardware random | |
732 | * number generator if it is available. It is not recommended for | |
733 | * use. Use get_random_bytes() instead. It returns the number of | |
734 | * bytes filled in. | |
735 | */ | |
736 | size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes) | |
737 | { | |
738 | size_t left = nbytes; | |
739 | u8 *p = buf; | |
740 | ||
741 | while (left) { | |
742 | unsigned long v; | |
743 | size_t chunk = min_t(size_t, left, sizeof(unsigned long)); | |
744 | ||
745 | if (!arch_get_random_long(&v)) | |
746 | break; | |
747 | ||
748 | memcpy(p, &v, chunk); | |
749 | p += chunk; | |
750 | left -= chunk; | |
751 | } | |
752 | ||
753 | return nbytes - left; | |
754 | } | |
755 | EXPORT_SYMBOL(get_random_bytes_arch); | |
756 | ||
a5ed7cb1 JD |
757 | |
758 | /********************************************************************** | |
759 | * | |
760 | * Entropy accumulation and extraction routines. | |
761 | * | |
762 | * Callers may add entropy via: | |
763 | * | |
764 | * static void mix_pool_bytes(const void *in, size_t nbytes) | |
765 | * | |
766 | * After which, if added entropy should be credited: | |
767 | * | |
768 | * static void credit_entropy_bits(size_t nbits) | |
769 | * | |
770 | * Finally, extract entropy via these two, with the latter one | |
771 | * setting the entropy count to zero and extracting only if there | |
772 | * is POOL_MIN_BITS entropy credited prior: | |
773 | * | |
774 | * static void extract_entropy(void *buf, size_t nbytes) | |
775 | * static bool drain_entropy(void *buf, size_t nbytes) | |
776 | * | |
777 | **********************************************************************/ | |
778 | ||
3655adc7 JD |
779 | enum { |
780 | POOL_BITS = BLAKE2S_HASH_SIZE * 8, | |
781 | POOL_MIN_BITS = POOL_BITS /* No point in settling for less. */ | |
782 | }; | |
783 | ||
a5ed7cb1 | 784 | /* For notifying userspace should write into /dev/random. */ |
3655adc7 JD |
785 | static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); |
786 | ||
3655adc7 JD |
787 | static struct { |
788 | struct blake2s_state hash; | |
789 | spinlock_t lock; | |
790 | unsigned int entropy_count; | |
791 | } input_pool = { | |
792 | .hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE), | |
793 | BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4, | |
794 | BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 }, | |
795 | .hash.outlen = BLAKE2S_HASH_SIZE, | |
796 | .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), | |
797 | }; | |
798 | ||
a5ed7cb1 JD |
799 | static void _mix_pool_bytes(const void *in, size_t nbytes) |
800 | { | |
801 | blake2s_update(&input_pool.hash, in, nbytes); | |
802 | } | |
3655adc7 JD |
803 | |
804 | /* | |
805 | * This function adds bytes into the entropy "pool". It does not | |
806 | * update the entropy estimate. The caller should call | |
807 | * credit_entropy_bits if this is appropriate. | |
808 | */ | |
a5ed7cb1 | 809 | static void mix_pool_bytes(const void *in, size_t nbytes) |
3655adc7 | 810 | { |
a5ed7cb1 JD |
811 | unsigned long flags; |
812 | ||
813 | spin_lock_irqsave(&input_pool.lock, flags); | |
814 | _mix_pool_bytes(in, nbytes); | |
815 | spin_unlock_irqrestore(&input_pool.lock, flags); | |
3655adc7 JD |
816 | } |
817 | ||
a5ed7cb1 JD |
818 | static void credit_entropy_bits(size_t nbits) |
819 | { | |
820 | unsigned int entropy_count, orig, add; | |
821 | ||
822 | if (!nbits) | |
823 | return; | |
824 | ||
825 | add = min_t(size_t, nbits, POOL_BITS); | |
826 | ||
827 | do { | |
828 | orig = READ_ONCE(input_pool.entropy_count); | |
829 | entropy_count = min_t(unsigned int, POOL_BITS, orig + add); | |
830 | } while (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig); | |
831 | ||
832 | if (crng_init < 2 && entropy_count >= POOL_MIN_BITS) | |
833 | crng_reseed(); | |
834 | } | |
835 | ||
836 | /* | |
837 | * This is an HKDF-like construction for using the hashed collected entropy | |
838 | * as a PRF key, that's then expanded block-by-block. | |
839 | */ | |
840 | static void extract_entropy(void *buf, size_t nbytes) | |
3655adc7 JD |
841 | { |
842 | unsigned long flags; | |
a5ed7cb1 JD |
843 | u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE]; |
844 | struct { | |
845 | unsigned long rdseed[32 / sizeof(long)]; | |
846 | size_t counter; | |
847 | } block; | |
848 | size_t i; | |
849 | ||
850 | for (i = 0; i < ARRAY_SIZE(block.rdseed); ++i) { | |
851 | if (!arch_get_random_seed_long(&block.rdseed[i]) && | |
852 | !arch_get_random_long(&block.rdseed[i])) | |
853 | block.rdseed[i] = random_get_entropy(); | |
854 | } | |
3655adc7 JD |
855 | |
856 | spin_lock_irqsave(&input_pool.lock, flags); | |
a5ed7cb1 JD |
857 | |
858 | /* seed = HASHPRF(last_key, entropy_input) */ | |
859 | blake2s_final(&input_pool.hash, seed); | |
860 | ||
861 | /* next_key = HASHPRF(seed, RDSEED || 0) */ | |
862 | block.counter = 0; | |
863 | blake2s(next_key, (u8 *)&block, seed, sizeof(next_key), sizeof(block), sizeof(seed)); | |
864 | blake2s_init_key(&input_pool.hash, BLAKE2S_HASH_SIZE, next_key, sizeof(next_key)); | |
865 | ||
3655adc7 | 866 | spin_unlock_irqrestore(&input_pool.lock, flags); |
a5ed7cb1 JD |
867 | memzero_explicit(next_key, sizeof(next_key)); |
868 | ||
869 | while (nbytes) { | |
870 | i = min_t(size_t, nbytes, BLAKE2S_HASH_SIZE); | |
871 | /* output = HASHPRF(seed, RDSEED || ++counter) */ | |
872 | ++block.counter; | |
873 | blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed)); | |
874 | nbytes -= i; | |
875 | buf += i; | |
876 | } | |
877 | ||
878 | memzero_explicit(seed, sizeof(seed)); | |
879 | memzero_explicit(&block, sizeof(block)); | |
880 | } | |
881 | ||
882 | /* | |
883 | * First we make sure we have POOL_MIN_BITS of entropy in the pool, and then we | |
884 | * set the entropy count to zero (but don't actually touch any data). Only then | |
885 | * can we extract a new key with extract_entropy(). | |
886 | */ | |
887 | static bool drain_entropy(void *buf, size_t nbytes) | |
888 | { | |
889 | unsigned int entropy_count; | |
890 | do { | |
891 | entropy_count = READ_ONCE(input_pool.entropy_count); | |
892 | if (entropy_count < POOL_MIN_BITS) | |
893 | return false; | |
894 | } while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count); | |
895 | extract_entropy(buf, nbytes); | |
896 | wake_up_interruptible(&random_write_wait); | |
897 | kill_fasync(&fasync, SIGIO, POLL_OUT); | |
898 | return true; | |
3655adc7 JD |
899 | } |
900 | ||
92c653cf JD |
901 | |
902 | /********************************************************************** | |
903 | * | |
904 | * Entropy collection routines. | |
905 | * | |
906 | * The following exported functions are used for pushing entropy into | |
907 | * the above entropy accumulation routines: | |
908 | * | |
909 | * void add_device_randomness(const void *buf, size_t size); | |
910 | * void add_input_randomness(unsigned int type, unsigned int code, | |
911 | * unsigned int value); | |
912 | * void add_disk_randomness(struct gendisk *disk); | |
913 | * void add_hwgenerator_randomness(const void *buffer, size_t count, | |
914 | * size_t entropy); | |
915 | * void add_bootloader_randomness(const void *buf, size_t size); | |
916 | * void add_interrupt_randomness(int irq); | |
917 | * | |
918 | * add_device_randomness() adds data to the input pool that | |
919 | * is likely to differ between two devices (or possibly even per boot). | |
920 | * This would be things like MAC addresses or serial numbers, or the | |
921 | * read-out of the RTC. This does *not* credit any actual entropy to | |
922 | * the pool, but it initializes the pool to different values for devices | |
923 | * that might otherwise be identical and have very little entropy | |
924 | * available to them (particularly common in the embedded world). | |
925 | * | |
926 | * add_input_randomness() uses the input layer interrupt timing, as well | |
927 | * as the event type information from the hardware. | |
928 | * | |
929 | * add_disk_randomness() uses what amounts to the seek time of block | |
930 | * layer request events, on a per-disk_devt basis, as input to the | |
931 | * entropy pool. Note that high-speed solid state drives with very low | |
932 | * seek times do not make for good sources of entropy, as their seek | |
933 | * times are usually fairly consistent. | |
934 | * | |
935 | * The above two routines try to estimate how many bits of entropy | |
936 | * to credit. They do this by keeping track of the first and second | |
937 | * order deltas of the event timings. | |
938 | * | |
939 | * add_hwgenerator_randomness() is for true hardware RNGs, and will credit | |
940 | * entropy as specified by the caller. If the entropy pool is full it will | |
941 | * block until more entropy is needed. | |
942 | * | |
943 | * add_bootloader_randomness() is the same as add_hwgenerator_randomness() or | |
944 | * add_device_randomness(), depending on whether or not the configuration | |
945 | * option CONFIG_RANDOM_TRUST_BOOTLOADER is set. | |
946 | * | |
947 | * add_interrupt_randomness() uses the interrupt timing as random | |
948 | * inputs to the entropy pool. Using the cycle counters and the irq source | |
949 | * as inputs, it feeds the input pool roughly once a second or after 64 | |
950 | * interrupts, crediting 1 bit of entropy for whichever comes first. | |
951 | * | |
952 | **********************************************************************/ | |
953 | ||
954 | static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); | |
955 | static int __init parse_trust_cpu(char *arg) | |
956 | { | |
957 | return kstrtobool(arg, &trust_cpu); | |
958 | } | |
959 | early_param("random.trust_cpu", parse_trust_cpu); | |
3655adc7 JD |
960 | |
961 | /* | |
92c653cf JD |
962 | * The first collection of entropy occurs at system boot while interrupts |
963 | * are still turned off. Here we push in RDSEED, a timestamp, and utsname(). | |
964 | * Depending on the above configuration knob, RDSEED may be considered | |
965 | * sufficient for initialization. Note that much earlier setup may already | |
966 | * have pushed entropy into the input pool by the time we get here. | |
3655adc7 | 967 | */ |
92c653cf | 968 | int __init rand_initialize(void) |
3655adc7 | 969 | { |
92c653cf JD |
970 | size_t i; |
971 | ktime_t now = ktime_get_real(); | |
972 | bool arch_init = true; | |
973 | unsigned long rv; | |
186873c5 | 974 | |
92c653cf JD |
975 | for (i = 0; i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) { |
976 | if (!arch_get_random_seed_long_early(&rv) && | |
977 | !arch_get_random_long_early(&rv)) { | |
978 | rv = random_get_entropy(); | |
979 | arch_init = false; | |
980 | } | |
981 | mix_pool_bytes(&rv, sizeof(rv)); | |
982 | } | |
983 | mix_pool_bytes(&now, sizeof(now)); | |
984 | mix_pool_bytes(utsname(), sizeof(*(utsname()))); | |
186873c5 | 985 | |
92c653cf JD |
986 | extract_entropy(base_crng.key, sizeof(base_crng.key)); |
987 | ++base_crng.generation; | |
186873c5 | 988 | |
92c653cf JD |
989 | if (arch_init && trust_cpu && crng_init < 2) { |
990 | crng_init = 2; | |
991 | pr_notice("crng init done (trusting CPU's manufacturer)\n"); | |
992 | } | |
e192be9d | 993 | |
92c653cf JD |
994 | if (ratelimit_disable) { |
995 | urandom_warning.interval = 0; | |
996 | unseeded_warning.interval = 0; | |
997 | } | |
998 | return 0; | |
3655adc7 | 999 | } |
e192be9d | 1000 | |
1da177e4 LT |
1001 | /* There is one of these per entropy source */ |
1002 | struct timer_rand_state { | |
1003 | cycles_t last_time; | |
90b75ee5 | 1004 | long last_delta, last_delta2; |
1da177e4 LT |
1005 | }; |
1006 | ||
a2080a67 | 1007 | /* |
e192be9d TT |
1008 | * Add device- or boot-specific data to the input pool to help |
1009 | * initialize it. | |
a2080a67 | 1010 | * |
e192be9d TT |
1011 | * None of this adds any entropy; it is meant to avoid the problem of |
1012 | * the entropy pool having similar initial state across largely | |
1013 | * identical devices. | |
a2080a67 | 1014 | */ |
04ec96b7 | 1015 | void add_device_randomness(const void *buf, size_t size) |
a2080a67 | 1016 | { |
61875f30 | 1017 | unsigned long time = random_get_entropy() ^ jiffies; |
3ef4cb2d | 1018 | unsigned long flags; |
a2080a67 | 1019 | |
dc12baac TT |
1020 | if (!crng_ready() && size) |
1021 | crng_slow_load(buf, size); | |
ee7998c5 | 1022 | |
3ef4cb2d | 1023 | spin_lock_irqsave(&input_pool.lock, flags); |
90ed1e67 JD |
1024 | _mix_pool_bytes(buf, size); |
1025 | _mix_pool_bytes(&time, sizeof(time)); | |
3ef4cb2d | 1026 | spin_unlock_irqrestore(&input_pool.lock, flags); |
a2080a67 LT |
1027 | } |
1028 | EXPORT_SYMBOL(add_device_randomness); | |
1029 | ||
1da177e4 LT |
1030 | /* |
1031 | * This function adds entropy to the entropy "pool" by using timing | |
1032 | * delays. It uses the timer_rand_state structure to make an estimate | |
1033 | * of how many bits of entropy this call has added to the pool. | |
1034 | * | |
1035 | * The number "num" is also added to the pool - it should somehow describe | |
1036 | * the type of event which just happened. This is currently 0-255 for | |
1037 | * keyboard scan codes, and 256 upwards for interrupts. | |
1038 | * | |
1039 | */ | |
04ec96b7 | 1040 | static void add_timer_randomness(struct timer_rand_state *state, unsigned int num) |
1da177e4 LT |
1041 | { |
1042 | struct { | |
1da177e4 | 1043 | long jiffies; |
d38bb085 JD |
1044 | unsigned int cycles; |
1045 | unsigned int num; | |
1da177e4 LT |
1046 | } sample; |
1047 | long delta, delta2, delta3; | |
1048 | ||
1da177e4 | 1049 | sample.jiffies = jiffies; |
61875f30 | 1050 | sample.cycles = random_get_entropy(); |
1da177e4 | 1051 | sample.num = num; |
90ed1e67 | 1052 | mix_pool_bytes(&sample, sizeof(sample)); |
1da177e4 LT |
1053 | |
1054 | /* | |
1055 | * Calculate number of bits of randomness we probably added. | |
1056 | * We take into account the first, second and third-order deltas | |
1057 | * in order to make our estimate. | |
1058 | */ | |
e00d996a QC |
1059 | delta = sample.jiffies - READ_ONCE(state->last_time); |
1060 | WRITE_ONCE(state->last_time, sample.jiffies); | |
5e747dd9 | 1061 | |
e00d996a QC |
1062 | delta2 = delta - READ_ONCE(state->last_delta); |
1063 | WRITE_ONCE(state->last_delta, delta); | |
5e747dd9 | 1064 | |
e00d996a QC |
1065 | delta3 = delta2 - READ_ONCE(state->last_delta2); |
1066 | WRITE_ONCE(state->last_delta2, delta2); | |
5e747dd9 RV |
1067 | |
1068 | if (delta < 0) | |
1069 | delta = -delta; | |
1070 | if (delta2 < 0) | |
1071 | delta2 = -delta2; | |
1072 | if (delta3 < 0) | |
1073 | delta3 = -delta3; | |
1074 | if (delta > delta2) | |
1075 | delta = delta2; | |
1076 | if (delta > delta3) | |
1077 | delta = delta3; | |
1da177e4 | 1078 | |
5e747dd9 RV |
1079 | /* |
1080 | * delta is now minimum absolute delta. | |
1081 | * Round down by 1 bit on general principles, | |
727d499a | 1082 | * and limit entropy estimate to 12 bits. |
5e747dd9 | 1083 | */ |
04ec96b7 | 1084 | credit_entropy_bits(min_t(unsigned int, fls(delta >> 1), 11)); |
1da177e4 LT |
1085 | } |
1086 | ||
d251575a | 1087 | void add_input_randomness(unsigned int type, unsigned int code, |
248045b8 | 1088 | unsigned int value) |
1da177e4 LT |
1089 | { |
1090 | static unsigned char last_value; | |
92c653cf | 1091 | static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES }; |
1da177e4 | 1092 | |
92c653cf | 1093 | /* Ignore autorepeat and the like. */ |
1da177e4 LT |
1094 | if (value == last_value) |
1095 | return; | |
1096 | ||
1da177e4 LT |
1097 | last_value = value; |
1098 | add_timer_randomness(&input_timer_state, | |
1099 | (type << 4) ^ code ^ (code >> 4) ^ value); | |
1100 | } | |
80fc9f53 | 1101 | EXPORT_SYMBOL_GPL(add_input_randomness); |
1da177e4 | 1102 | |
92c653cf JD |
1103 | #ifdef CONFIG_BLOCK |
1104 | void add_disk_randomness(struct gendisk *disk) | |
1105 | { | |
1106 | if (!disk || !disk->random) | |
1107 | return; | |
1108 | /* First major is 1, so we get >= 0x200 here. */ | |
1109 | add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); | |
1110 | } | |
1111 | EXPORT_SYMBOL_GPL(add_disk_randomness); | |
1112 | ||
1113 | void rand_initialize_disk(struct gendisk *disk) | |
1114 | { | |
1115 | struct timer_rand_state *state; | |
1116 | ||
1117 | /* | |
1118 | * If kzalloc returns null, we just won't use that entropy | |
1119 | * source. | |
1120 | */ | |
1121 | state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); | |
1122 | if (state) { | |
1123 | state->last_time = INITIAL_JIFFIES; | |
1124 | disk->random = state; | |
1125 | } | |
1126 | } | |
1127 | #endif | |
1128 | ||
1129 | /* | |
1130 | * Interface for in-kernel drivers of true hardware RNGs. | |
1131 | * Those devices may produce endless random bits and will be throttled | |
1132 | * when our pool is full. | |
1133 | */ | |
1134 | void add_hwgenerator_randomness(const void *buffer, size_t count, | |
1135 | size_t entropy) | |
1136 | { | |
1137 | if (unlikely(crng_init == 0)) { | |
1138 | size_t ret = crng_fast_load(buffer, count); | |
1139 | mix_pool_bytes(buffer, ret); | |
1140 | count -= ret; | |
1141 | buffer += ret; | |
1142 | if (!count || crng_init == 0) | |
1143 | return; | |
1144 | } | |
1145 | ||
1146 | /* | |
1147 | * Throttle writing if we're above the trickle threshold. | |
1148 | * We'll be woken up again once below POOL_MIN_BITS, when | |
1149 | * the calling thread is about to terminate, or once | |
1150 | * CRNG_RESEED_INTERVAL has elapsed. | |
1151 | */ | |
1152 | wait_event_interruptible_timeout(random_write_wait, | |
1153 | !system_wq || kthread_should_stop() || | |
1154 | input_pool.entropy_count < POOL_MIN_BITS, | |
1155 | CRNG_RESEED_INTERVAL); | |
1156 | mix_pool_bytes(buffer, count); | |
1157 | credit_entropy_bits(entropy); | |
1158 | } | |
1159 | EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); | |
1160 | ||
1161 | /* | |
1162 | * Handle random seed passed by bootloader. | |
1163 | * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise | |
1164 | * it would be regarded as device data. | |
1165 | * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER. | |
1166 | */ | |
1167 | void add_bootloader_randomness(const void *buf, size_t size) | |
1168 | { | |
1169 | if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER)) | |
1170 | add_hwgenerator_randomness(buf, size, size * 8); | |
1171 | else | |
1172 | add_device_randomness(buf, size); | |
1173 | } | |
1174 | EXPORT_SYMBOL_GPL(add_bootloader_randomness); | |
1175 | ||
1176 | struct fast_pool { | |
1177 | union { | |
1178 | u32 pool32[4]; | |
1179 | u64 pool64[2]; | |
1180 | }; | |
1181 | unsigned long last; | |
1182 | u16 reg_idx; | |
1183 | u8 count; | |
1184 | }; | |
1185 | ||
1186 | /* | |
1187 | * This is a fast mixing routine used by the interrupt randomness | |
1188 | * collector. It's hardcoded for an 128 bit pool and assumes that any | |
1189 | * locks that might be needed are taken by the caller. | |
1190 | */ | |
1191 | static void fast_mix(u32 pool[4]) | |
1192 | { | |
1193 | u32 a = pool[0], b = pool[1]; | |
1194 | u32 c = pool[2], d = pool[3]; | |
1195 | ||
1196 | a += b; c += d; | |
1197 | b = rol32(b, 6); d = rol32(d, 27); | |
1198 | d ^= a; b ^= c; | |
1199 | ||
1200 | a += b; c += d; | |
1201 | b = rol32(b, 16); d = rol32(d, 14); | |
1202 | d ^= a; b ^= c; | |
1203 | ||
1204 | a += b; c += d; | |
1205 | b = rol32(b, 6); d = rol32(d, 27); | |
1206 | d ^= a; b ^= c; | |
1207 | ||
1208 | a += b; c += d; | |
1209 | b = rol32(b, 16); d = rol32(d, 14); | |
1210 | d ^= a; b ^= c; | |
1211 | ||
1212 | pool[0] = a; pool[1] = b; | |
1213 | pool[2] = c; pool[3] = d; | |
1214 | } | |
1215 | ||
775f4b29 TT |
1216 | static DEFINE_PER_CPU(struct fast_pool, irq_randomness); |
1217 | ||
d38bb085 | 1218 | static u32 get_reg(struct fast_pool *f, struct pt_regs *regs) |
ee3e00e9 | 1219 | { |
248045b8 | 1220 | u32 *ptr = (u32 *)regs; |
92e75428 | 1221 | unsigned int idx; |
ee3e00e9 TT |
1222 | |
1223 | if (regs == NULL) | |
1224 | return 0; | |
92e75428 | 1225 | idx = READ_ONCE(f->reg_idx); |
d38bb085 | 1226 | if (idx >= sizeof(struct pt_regs) / sizeof(u32)) |
92e75428 TT |
1227 | idx = 0; |
1228 | ptr += idx++; | |
1229 | WRITE_ONCE(f->reg_idx, idx); | |
9dfa7bba | 1230 | return *ptr; |
ee3e00e9 TT |
1231 | } |
1232 | ||
703f7066 | 1233 | void add_interrupt_randomness(int irq) |
1da177e4 | 1234 | { |
248045b8 JD |
1235 | struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness); |
1236 | struct pt_regs *regs = get_irq_regs(); | |
1237 | unsigned long now = jiffies; | |
1238 | cycles_t cycles = random_get_entropy(); | |
3060d6fe | 1239 | |
ee3e00e9 TT |
1240 | if (cycles == 0) |
1241 | cycles = get_reg(fast_pool, regs); | |
3060d6fe | 1242 | |
b2f408fe JD |
1243 | if (sizeof(cycles) == 8) |
1244 | fast_pool->pool64[0] ^= cycles ^ rol64(now, 32) ^ irq; | |
1245 | else { | |
1246 | fast_pool->pool32[0] ^= cycles ^ irq; | |
1247 | fast_pool->pool32[1] ^= now; | |
1248 | } | |
1249 | ||
1250 | if (sizeof(unsigned long) == 8) | |
1251 | fast_pool->pool64[1] ^= regs ? instruction_pointer(regs) : _RET_IP_; | |
1252 | else { | |
1253 | fast_pool->pool32[2] ^= regs ? instruction_pointer(regs) : _RET_IP_; | |
1254 | fast_pool->pool32[3] ^= get_reg(fast_pool, regs); | |
1255 | } | |
1256 | ||
1257 | fast_mix(fast_pool->pool32); | |
1258 | ++fast_pool->count; | |
3060d6fe | 1259 | |
43838a23 | 1260 | if (unlikely(crng_init == 0)) { |
04ec96b7 | 1261 | if (fast_pool->count >= 64 && |
b2f408fe | 1262 | crng_fast_load(fast_pool->pool32, sizeof(fast_pool->pool32)) > 0) { |
e192be9d TT |
1263 | fast_pool->count = 0; |
1264 | fast_pool->last = now; | |
c30c575d | 1265 | if (spin_trylock(&input_pool.lock)) { |
b2f408fe | 1266 | _mix_pool_bytes(&fast_pool->pool32, sizeof(fast_pool->pool32)); |
c30c575d JD |
1267 | spin_unlock(&input_pool.lock); |
1268 | } | |
e192be9d TT |
1269 | } |
1270 | return; | |
1271 | } | |
1272 | ||
248045b8 | 1273 | if ((fast_pool->count < 64) && !time_after(now, fast_pool->last + HZ)) |
1da177e4 LT |
1274 | return; |
1275 | ||
90ed1e67 | 1276 | if (!spin_trylock(&input_pool.lock)) |
91fcb532 | 1277 | return; |
83664a69 | 1278 | |
91fcb532 | 1279 | fast_pool->last = now; |
b2f408fe | 1280 | _mix_pool_bytes(&fast_pool->pool32, sizeof(fast_pool->pool32)); |
90ed1e67 | 1281 | spin_unlock(&input_pool.lock); |
83664a69 | 1282 | |
ee3e00e9 | 1283 | fast_pool->count = 0; |
83664a69 | 1284 | |
92c653cf | 1285 | /* Award one bit for the contents of the fast pool. */ |
90ed1e67 | 1286 | credit_entropy_bits(1); |
1da177e4 | 1287 | } |
4b44f2d1 | 1288 | EXPORT_SYMBOL_GPL(add_interrupt_randomness); |
1da177e4 | 1289 | |
50ee7529 LT |
1290 | /* |
1291 | * Each time the timer fires, we expect that we got an unpredictable | |
1292 | * jump in the cycle counter. Even if the timer is running on another | |
1293 | * CPU, the timer activity will be touching the stack of the CPU that is | |
1294 | * generating entropy.. | |
1295 | * | |
1296 | * Note that we don't re-arm the timer in the timer itself - we are | |
1297 | * happy to be scheduled away, since that just makes the load more | |
1298 | * complex, but we do not want the timer to keep ticking unless the | |
1299 | * entropy loop is running. | |
1300 | * | |
1301 | * So the re-arming always happens in the entropy loop itself. | |
1302 | */ | |
1303 | static void entropy_timer(struct timer_list *t) | |
1304 | { | |
90ed1e67 | 1305 | credit_entropy_bits(1); |
50ee7529 LT |
1306 | } |
1307 | ||
1308 | /* | |
1309 | * If we have an actual cycle counter, see if we can | |
1310 | * generate enough entropy with timing noise | |
1311 | */ | |
1312 | static void try_to_generate_entropy(void) | |
1313 | { | |
1314 | struct { | |
1315 | unsigned long now; | |
1316 | struct timer_list timer; | |
1317 | } stack; | |
1318 | ||
1319 | stack.now = random_get_entropy(); | |
1320 | ||
1321 | /* Slow counter - or none. Don't even bother */ | |
1322 | if (stack.now == random_get_entropy()) | |
1323 | return; | |
1324 | ||
1325 | timer_setup_on_stack(&stack.timer, entropy_timer, 0); | |
1326 | while (!crng_ready()) { | |
1327 | if (!timer_pending(&stack.timer)) | |
248045b8 | 1328 | mod_timer(&stack.timer, jiffies + 1); |
90ed1e67 | 1329 | mix_pool_bytes(&stack.now, sizeof(stack.now)); |
50ee7529 LT |
1330 | schedule(); |
1331 | stack.now = random_get_entropy(); | |
1332 | } | |
1333 | ||
1334 | del_timer_sync(&stack.timer); | |
1335 | destroy_timer_on_stack(&stack.timer); | |
90ed1e67 | 1336 | mix_pool_bytes(&stack.now, sizeof(stack.now)); |
50ee7529 LT |
1337 | } |
1338 | ||
a6adf8e7 JD |
1339 | |
1340 | /********************************************************************** | |
1341 | * | |
1342 | * Userspace reader/writer interfaces. | |
1343 | * | |
1344 | * getrandom(2) is the primary modern interface into the RNG and should | |
1345 | * be used in preference to anything else. | |
1346 | * | |
1347 | * Reading from /dev/random has the same functionality as calling | |
1348 | * getrandom(2) with flags=0. In earlier versions, however, it had | |
1349 | * vastly different semantics and should therefore be avoided, to | |
1350 | * prevent backwards compatibility issues. | |
1351 | * | |
1352 | * Reading from /dev/urandom has the same functionality as calling | |
1353 | * getrandom(2) with flags=GRND_INSECURE. Because it does not block | |
1354 | * waiting for the RNG to be ready, it should not be used. | |
1355 | * | |
1356 | * Writing to either /dev/random or /dev/urandom adds entropy to | |
1357 | * the input pool but does not credit it. | |
1358 | * | |
1359 | * Polling on /dev/random indicates when the RNG is initialized, on | |
1360 | * the read side, and when it wants new entropy, on the write side. | |
1361 | * | |
1362 | * Both /dev/random and /dev/urandom have the same set of ioctls for | |
1363 | * adding entropy, getting the entropy count, zeroing the count, and | |
1364 | * reseeding the crng. | |
1365 | * | |
1366 | **********************************************************************/ | |
1367 | ||
1368 | SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, | |
1369 | flags) | |
1da177e4 | 1370 | { |
a6adf8e7 JD |
1371 | if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE)) |
1372 | return -EINVAL; | |
301f0595 | 1373 | |
a6adf8e7 JD |
1374 | /* |
1375 | * Requesting insecure and blocking randomness at the same time makes | |
1376 | * no sense. | |
1377 | */ | |
1378 | if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM)) | |
1379 | return -EINVAL; | |
c6f1deb1 | 1380 | |
a6adf8e7 JD |
1381 | if (count > INT_MAX) |
1382 | count = INT_MAX; | |
1da177e4 | 1383 | |
a6adf8e7 JD |
1384 | if (!(flags & GRND_INSECURE) && !crng_ready()) { |
1385 | int ret; | |
30c08efe | 1386 | |
a6adf8e7 JD |
1387 | if (flags & GRND_NONBLOCK) |
1388 | return -EAGAIN; | |
1389 | ret = wait_for_random_bytes(); | |
1390 | if (unlikely(ret)) | |
1391 | return ret; | |
1392 | } | |
1393 | return get_random_bytes_user(buf, count); | |
30c08efe AL |
1394 | } |
1395 | ||
248045b8 | 1396 | static __poll_t random_poll(struct file *file, poll_table *wait) |
1da177e4 | 1397 | { |
a11e1d43 | 1398 | __poll_t mask; |
1da177e4 | 1399 | |
30c08efe | 1400 | poll_wait(file, &crng_init_wait, wait); |
a11e1d43 LT |
1401 | poll_wait(file, &random_write_wait, wait); |
1402 | mask = 0; | |
30c08efe | 1403 | if (crng_ready()) |
a9a08845 | 1404 | mask |= EPOLLIN | EPOLLRDNORM; |
489c7fc4 | 1405 | if (input_pool.entropy_count < POOL_MIN_BITS) |
a9a08845 | 1406 | mask |= EPOLLOUT | EPOLLWRNORM; |
1da177e4 LT |
1407 | return mask; |
1408 | } | |
1409 | ||
04ec96b7 | 1410 | static int write_pool(const char __user *ubuf, size_t count) |
1da177e4 | 1411 | { |
04ec96b7 | 1412 | size_t len; |
7b5164fb | 1413 | int ret = 0; |
04ec96b7 | 1414 | u8 block[BLAKE2S_BLOCK_SIZE]; |
1da177e4 | 1415 | |
04ec96b7 JD |
1416 | while (count) { |
1417 | len = min(count, sizeof(block)); | |
7b5164fb JD |
1418 | if (copy_from_user(block, ubuf, len)) { |
1419 | ret = -EFAULT; | |
1420 | goto out; | |
1421 | } | |
04ec96b7 JD |
1422 | count -= len; |
1423 | ubuf += len; | |
1424 | mix_pool_bytes(block, len); | |
91f3f1e3 | 1425 | cond_resched(); |
1da177e4 | 1426 | } |
7f397dcd | 1427 | |
7b5164fb JD |
1428 | out: |
1429 | memzero_explicit(block, sizeof(block)); | |
1430 | return ret; | |
7f397dcd MM |
1431 | } |
1432 | ||
90b75ee5 MM |
1433 | static ssize_t random_write(struct file *file, const char __user *buffer, |
1434 | size_t count, loff_t *ppos) | |
7f397dcd | 1435 | { |
04ec96b7 | 1436 | int ret; |
7f397dcd | 1437 | |
90ed1e67 | 1438 | ret = write_pool(buffer, count); |
7f397dcd MM |
1439 | if (ret) |
1440 | return ret; | |
1441 | ||
7f397dcd | 1442 | return (ssize_t)count; |
1da177e4 LT |
1443 | } |
1444 | ||
a6adf8e7 JD |
1445 | static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, |
1446 | loff_t *ppos) | |
1447 | { | |
1448 | static int maxwarn = 10; | |
1449 | ||
1450 | if (!crng_ready() && maxwarn > 0) { | |
1451 | maxwarn--; | |
1452 | if (__ratelimit(&urandom_warning)) | |
1453 | pr_notice("%s: uninitialized urandom read (%zd bytes read)\n", | |
1454 | current->comm, nbytes); | |
1455 | } | |
1456 | ||
1457 | return get_random_bytes_user(buf, nbytes); | |
1458 | } | |
1459 | ||
1460 | static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, | |
1461 | loff_t *ppos) | |
1462 | { | |
1463 | int ret; | |
1464 | ||
1465 | ret = wait_for_random_bytes(); | |
1466 | if (ret != 0) | |
1467 | return ret; | |
1468 | return get_random_bytes_user(buf, nbytes); | |
1469 | } | |
1470 | ||
43ae4860 | 1471 | static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) |
1da177e4 LT |
1472 | { |
1473 | int size, ent_count; | |
1474 | int __user *p = (int __user *)arg; | |
1475 | int retval; | |
1476 | ||
1477 | switch (cmd) { | |
1478 | case RNDGETENTCNT: | |
a6adf8e7 | 1479 | /* Inherently racy, no point locking. */ |
c5704490 | 1480 | if (put_user(input_pool.entropy_count, p)) |
1da177e4 LT |
1481 | return -EFAULT; |
1482 | return 0; | |
1483 | case RNDADDTOENTCNT: | |
1484 | if (!capable(CAP_SYS_ADMIN)) | |
1485 | return -EPERM; | |
1486 | if (get_user(ent_count, p)) | |
1487 | return -EFAULT; | |
a49c010e JD |
1488 | if (ent_count < 0) |
1489 | return -EINVAL; | |
1490 | credit_entropy_bits(ent_count); | |
1491 | return 0; | |
1da177e4 LT |
1492 | case RNDADDENTROPY: |
1493 | if (!capable(CAP_SYS_ADMIN)) | |
1494 | return -EPERM; | |
1495 | if (get_user(ent_count, p++)) | |
1496 | return -EFAULT; | |
1497 | if (ent_count < 0) | |
1498 | return -EINVAL; | |
1499 | if (get_user(size, p++)) | |
1500 | return -EFAULT; | |
90ed1e67 | 1501 | retval = write_pool((const char __user *)p, size); |
1da177e4 LT |
1502 | if (retval < 0) |
1503 | return retval; | |
a49c010e JD |
1504 | credit_entropy_bits(ent_count); |
1505 | return 0; | |
1da177e4 LT |
1506 | case RNDZAPENTCNT: |
1507 | case RNDCLEARPOOL: | |
ae9ecd92 TT |
1508 | /* |
1509 | * Clear the entropy pool counters. We no longer clear | |
1510 | * the entropy pool, as that's silly. | |
1511 | */ | |
1da177e4 LT |
1512 | if (!capable(CAP_SYS_ADMIN)) |
1513 | return -EPERM; | |
489c7fc4 | 1514 | if (xchg(&input_pool.entropy_count, 0)) { |
042e293e JD |
1515 | wake_up_interruptible(&random_write_wait); |
1516 | kill_fasync(&fasync, SIGIO, POLL_OUT); | |
1517 | } | |
1da177e4 | 1518 | return 0; |
d848e5f8 TT |
1519 | case RNDRESEEDCRNG: |
1520 | if (!capable(CAP_SYS_ADMIN)) | |
1521 | return -EPERM; | |
1522 | if (crng_init < 2) | |
1523 | return -ENODATA; | |
a9412d51 | 1524 | crng_reseed(); |
d848e5f8 | 1525 | return 0; |
1da177e4 LT |
1526 | default: |
1527 | return -EINVAL; | |
1528 | } | |
1529 | } | |
1530 | ||
9a6f70bb JD |
1531 | static int random_fasync(int fd, struct file *filp, int on) |
1532 | { | |
1533 | return fasync_helper(fd, filp, on, &fasync); | |
1534 | } | |
1535 | ||
2b8693c0 | 1536 | const struct file_operations random_fops = { |
248045b8 | 1537 | .read = random_read, |
1da177e4 | 1538 | .write = random_write, |
248045b8 | 1539 | .poll = random_poll, |
43ae4860 | 1540 | .unlocked_ioctl = random_ioctl, |
507e4e2b | 1541 | .compat_ioctl = compat_ptr_ioctl, |
9a6f70bb | 1542 | .fasync = random_fasync, |
6038f373 | 1543 | .llseek = noop_llseek, |
1da177e4 LT |
1544 | }; |
1545 | ||
2b8693c0 | 1546 | const struct file_operations urandom_fops = { |
248045b8 | 1547 | .read = urandom_read, |
1da177e4 | 1548 | .write = random_write, |
43ae4860 | 1549 | .unlocked_ioctl = random_ioctl, |
4aa37c46 | 1550 | .compat_ioctl = compat_ptr_ioctl, |
9a6f70bb | 1551 | .fasync = random_fasync, |
6038f373 | 1552 | .llseek = noop_llseek, |
1da177e4 LT |
1553 | }; |
1554 | ||
0deff3c4 | 1555 | |
1da177e4 LT |
1556 | /******************************************************************** |
1557 | * | |
0deff3c4 JD |
1558 | * Sysctl interface. |
1559 | * | |
1560 | * These are partly unused legacy knobs with dummy values to not break | |
1561 | * userspace and partly still useful things. They are usually accessible | |
1562 | * in /proc/sys/kernel/random/ and are as follows: | |
1563 | * | |
1564 | * - boot_id - a UUID representing the current boot. | |
1565 | * | |
1566 | * - uuid - a random UUID, different each time the file is read. | |
1567 | * | |
1568 | * - poolsize - the number of bits of entropy that the input pool can | |
1569 | * hold, tied to the POOL_BITS constant. | |
1570 | * | |
1571 | * - entropy_avail - the number of bits of entropy currently in the | |
1572 | * input pool. Always <= poolsize. | |
1573 | * | |
1574 | * - write_wakeup_threshold - the amount of entropy in the input pool | |
1575 | * below which write polls to /dev/random will unblock, requesting | |
1576 | * more entropy, tied to the POOL_MIN_BITS constant. It is writable | |
1577 | * to avoid breaking old userspaces, but writing to it does not | |
1578 | * change any behavior of the RNG. | |
1579 | * | |
1580 | * - urandom_min_reseed_secs - fixed to the meaningless value "60". | |
1581 | * It is writable to avoid breaking old userspaces, but writing | |
1582 | * to it does not change any behavior of the RNG. | |
1da177e4 LT |
1583 | * |
1584 | ********************************************************************/ | |
1585 | ||
1586 | #ifdef CONFIG_SYSCTL | |
1587 | ||
1588 | #include <linux/sysctl.h> | |
1589 | ||
0deff3c4 JD |
1590 | static int sysctl_random_min_urandom_seed = 60; |
1591 | static int sysctl_random_write_wakeup_bits = POOL_MIN_BITS; | |
489c7fc4 | 1592 | static int sysctl_poolsize = POOL_BITS; |
1da177e4 LT |
1593 | static char sysctl_bootid[16]; |
1594 | ||
1595 | /* | |
f22052b2 | 1596 | * This function is used to return both the bootid UUID, and random |
1da177e4 LT |
1597 | * UUID. The difference is in whether table->data is NULL; if it is, |
1598 | * then a new UUID is generated and returned to the user. | |
1599 | * | |
f22052b2 GP |
1600 | * If the user accesses this via the proc interface, the UUID will be |
1601 | * returned as an ASCII string in the standard UUID format; if via the | |
1602 | * sysctl system call, as 16 bytes of binary data. | |
1da177e4 | 1603 | */ |
248045b8 JD |
1604 | static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, |
1605 | size_t *lenp, loff_t *ppos) | |
1da177e4 | 1606 | { |
a151427e | 1607 | struct ctl_table fake_table; |
1da177e4 LT |
1608 | unsigned char buf[64], tmp_uuid[16], *uuid; |
1609 | ||
1610 | uuid = table->data; | |
1611 | if (!uuid) { | |
1612 | uuid = tmp_uuid; | |
1da177e4 | 1613 | generate_random_uuid(uuid); |
44e4360f MD |
1614 | } else { |
1615 | static DEFINE_SPINLOCK(bootid_spinlock); | |
1616 | ||
1617 | spin_lock(&bootid_spinlock); | |
1618 | if (!uuid[8]) | |
1619 | generate_random_uuid(uuid); | |
1620 | spin_unlock(&bootid_spinlock); | |
1621 | } | |
1da177e4 | 1622 | |
35900771 JP |
1623 | sprintf(buf, "%pU", uuid); |
1624 | ||
1da177e4 LT |
1625 | fake_table.data = buf; |
1626 | fake_table.maxlen = sizeof(buf); | |
1627 | ||
8d65af78 | 1628 | return proc_dostring(&fake_table, write, buffer, lenp, ppos); |
1da177e4 LT |
1629 | } |
1630 | ||
5475e8f0 | 1631 | static struct ctl_table random_table[] = { |
1da177e4 | 1632 | { |
1da177e4 LT |
1633 | .procname = "poolsize", |
1634 | .data = &sysctl_poolsize, | |
1635 | .maxlen = sizeof(int), | |
1636 | .mode = 0444, | |
6d456111 | 1637 | .proc_handler = proc_dointvec, |
1da177e4 LT |
1638 | }, |
1639 | { | |
1da177e4 | 1640 | .procname = "entropy_avail", |
c5704490 | 1641 | .data = &input_pool.entropy_count, |
1da177e4 LT |
1642 | .maxlen = sizeof(int), |
1643 | .mode = 0444, | |
c5704490 | 1644 | .proc_handler = proc_dointvec, |
1da177e4 | 1645 | }, |
1da177e4 | 1646 | { |
1da177e4 | 1647 | .procname = "write_wakeup_threshold", |
0deff3c4 | 1648 | .data = &sysctl_random_write_wakeup_bits, |
1da177e4 LT |
1649 | .maxlen = sizeof(int), |
1650 | .mode = 0644, | |
489c7fc4 | 1651 | .proc_handler = proc_dointvec, |
1da177e4 | 1652 | }, |
f5c2742c TT |
1653 | { |
1654 | .procname = "urandom_min_reseed_secs", | |
0deff3c4 | 1655 | .data = &sysctl_random_min_urandom_seed, |
f5c2742c TT |
1656 | .maxlen = sizeof(int), |
1657 | .mode = 0644, | |
1658 | .proc_handler = proc_dointvec, | |
1659 | }, | |
1da177e4 | 1660 | { |
1da177e4 LT |
1661 | .procname = "boot_id", |
1662 | .data = &sysctl_bootid, | |
1663 | .maxlen = 16, | |
1664 | .mode = 0444, | |
6d456111 | 1665 | .proc_handler = proc_do_uuid, |
1da177e4 LT |
1666 | }, |
1667 | { | |
1da177e4 LT |
1668 | .procname = "uuid", |
1669 | .maxlen = 16, | |
1670 | .mode = 0444, | |
6d456111 | 1671 | .proc_handler = proc_do_uuid, |
1da177e4 | 1672 | }, |
894d2491 | 1673 | { } |
1da177e4 | 1674 | }; |
5475e8f0 XN |
1675 | |
1676 | /* | |
1677 | * rand_initialize() is called before sysctl_init(), | |
1678 | * so we cannot call register_sysctl_init() in rand_initialize() | |
1679 | */ | |
1680 | static int __init random_sysctls_init(void) | |
1681 | { | |
1682 | register_sysctl_init("kernel/random", random_table); | |
1683 | return 0; | |
1684 | } | |
1685 | device_initcall(random_sysctls_init); | |
0deff3c4 | 1686 | #endif |