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1// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
2/*
3 * Copyright (C) 2017-2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
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. Prior to initialization, some of that
19 * data is then "credited" as having a certain number of bits of entropy.
20 * When enough bits of entropy are available, the hash is finalized and
21 * handed as a key to a stream cipher that expands it indefinitely for
22 * various consumers. This key is periodically refreshed as the various
23 * entropy collectors, described below, add data to the input pool.
24 */
25
26#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
27
28#include <linux/utsname.h>
29#include <linux/module.h>
30#include <linux/kernel.h>
31#include <linux/major.h>
32#include <linux/string.h>
33#include <linux/fcntl.h>
34#include <linux/slab.h>
35#include <linux/random.h>
36#include <linux/poll.h>
37#include <linux/init.h>
38#include <linux/fs.h>
39#include <linux/blkdev.h>
40#include <linux/interrupt.h>
41#include <linux/mm.h>
42#include <linux/nodemask.h>
43#include <linux/spinlock.h>
44#include <linux/kthread.h>
45#include <linux/percpu.h>
46#include <linux/ptrace.h>
47#include <linux/workqueue.h>
48#include <linux/irq.h>
49#include <linux/ratelimit.h>
50#include <linux/syscalls.h>
51#include <linux/completion.h>
52#include <linux/uuid.h>
53#include <linux/uaccess.h>
54#include <linux/suspend.h>
55#include <linux/siphash.h>
56#include <linux/sched/isolation.h>
57#include <crypto/chacha.h>
58#include <crypto/blake2s.h>
59#include <asm/archrandom.h>
60#include <asm/processor.h>
61#include <asm/irq.h>
62#include <asm/irq_regs.h>
63#include <asm/io.h>
64
65/*********************************************************************
66 *
67 * Initialization and readiness waiting.
68 *
69 * Much of the RNG infrastructure is devoted to various dependencies
70 * being able to wait until the RNG has collected enough entropy and
71 * is ready for safe consumption.
72 *
73 *********************************************************************/
74
75/*
76 * crng_init is protected by base_crng->lock, and only increases
77 * its value (from empty->early->ready).
78 */
79static enum {
80 CRNG_EMPTY = 0, /* Little to no entropy collected */
81 CRNG_EARLY = 1, /* At least POOL_EARLY_BITS collected */
82 CRNG_READY = 2 /* Fully initialized with POOL_READY_BITS collected */
83} crng_init __read_mostly = CRNG_EMPTY;
84static DEFINE_STATIC_KEY_FALSE(crng_is_ready);
85#define crng_ready() (static_branch_likely(&crng_is_ready) || crng_init >= CRNG_READY)
86/* Various types of waiters for crng_init->CRNG_READY transition. */
87static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
88static struct fasync_struct *fasync;
89static ATOMIC_NOTIFIER_HEAD(random_ready_notifier);
90
91/* Control how we warn userspace. */
92static struct ratelimit_state urandom_warning =
93 RATELIMIT_STATE_INIT_FLAGS("urandom_warning", HZ, 3, RATELIMIT_MSG_ON_RELEASE);
94static int ratelimit_disable __read_mostly =
95 IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM);
96module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
97MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
98
99/*
100 * Returns whether or not the input pool has been seeded and thus guaranteed
101 * to supply cryptographically secure random numbers. This applies to: the
102 * /dev/urandom device, the get_random_bytes function, and the get_random_{u8,
103 * u16,u32,u64,long} family of functions.
104 *
105 * Returns: true if the input pool has been seeded.
106 * false if the input pool has not been seeded.
107 */
108bool rng_is_initialized(void)
109{
110 return crng_ready();
111}
112EXPORT_SYMBOL(rng_is_initialized);
113
114static void __cold crng_set_ready(struct work_struct *work)
115{
116 static_branch_enable(&crng_is_ready);
117}
118
119/* Used by wait_for_random_bytes(), and considered an entropy collector, below. */
120static void try_to_generate_entropy(void);
121
122/*
123 * Wait for the input pool to be seeded and thus guaranteed to supply
124 * cryptographically secure random numbers. This applies to: the /dev/urandom
125 * device, the get_random_bytes function, and the get_random_{u8,u16,u32,u64,
126 * long} family of functions. Using any of these functions without first
127 * calling this function forfeits the guarantee of security.
128 *
129 * Returns: 0 if the input pool has been seeded.
130 * -ERESTARTSYS if the function was interrupted by a signal.
131 */
132int wait_for_random_bytes(void)
133{
134 while (!crng_ready()) {
135 int ret;
136
137 try_to_generate_entropy();
138 ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
139 if (ret)
140 return ret > 0 ? 0 : ret;
141 }
142 return 0;
143}
144EXPORT_SYMBOL(wait_for_random_bytes);
145
146/*
147 * Add a callback function that will be invoked when the crng is initialised,
148 * or immediately if it already has been. Only use this is you are absolutely
149 * sure it is required. Most users should instead be able to test
150 * `rng_is_initialized()` on demand, or make use of `get_random_bytes_wait()`.
151 */
152int __cold execute_with_initialized_rng(struct notifier_block *nb)
153{
154 unsigned long flags;
155 int ret = 0;
156
157 spin_lock_irqsave(&random_ready_notifier.lock, flags);
158 if (crng_ready())
159 nb->notifier_call(nb, 0, NULL);
160 else
161 ret = raw_notifier_chain_register((struct raw_notifier_head *)&random_ready_notifier.head, nb);
162 spin_unlock_irqrestore(&random_ready_notifier.lock, flags);
163 return ret;
164}
165
166#define warn_unseeded_randomness() \
167 if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \
168 printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \
169 __func__, (void *)_RET_IP_, crng_init)
170
171
172/*********************************************************************
173 *
174 * Fast key erasure RNG, the "crng".
175 *
176 * These functions expand entropy from the entropy extractor into
177 * long streams for external consumption using the "fast key erasure"
178 * RNG described at <https://blog.cr.yp.to/20170723-random.html>.
179 *
180 * There are a few exported interfaces for use by other drivers:
181 *
182 * void get_random_bytes(void *buf, size_t len)
183 * u8 get_random_u8()
184 * u16 get_random_u16()
185 * u32 get_random_u32()
186 * u32 get_random_u32_below(u32 ceil)
187 * u32 get_random_u32_above(u32 floor)
188 * u32 get_random_u32_inclusive(u32 floor, u32 ceil)
189 * u64 get_random_u64()
190 * unsigned long get_random_long()
191 *
192 * These interfaces will return the requested number of random bytes
193 * into the given buffer or as a return value. This is equivalent to
194 * a read from /dev/urandom. The u8, u16, u32, u64, long family of
195 * functions may be higher performance for one-off random integers,
196 * because they do a bit of buffering and do not invoke reseeding
197 * until the buffer is emptied.
198 *
199 *********************************************************************/
200
201enum {
202 CRNG_RESEED_START_INTERVAL = HZ,
203 CRNG_RESEED_INTERVAL = 60 * HZ
204};
205
206static struct {
207 u8 key[CHACHA_KEY_SIZE] __aligned(__alignof__(long));
208 unsigned long generation;
209 spinlock_t lock;
210} base_crng = {
211 .lock = __SPIN_LOCK_UNLOCKED(base_crng.lock)
212};
213
214struct crng {
215 u8 key[CHACHA_KEY_SIZE];
216 unsigned long generation;
217 local_lock_t lock;
218};
219
220static DEFINE_PER_CPU(struct crng, crngs) = {
221 .generation = ULONG_MAX,
222 .lock = INIT_LOCAL_LOCK(crngs.lock),
223};
224
225/*
226 * Return the interval until the next reseeding, which is normally
227 * CRNG_RESEED_INTERVAL, but during early boot, it is at an interval
228 * proportional to the uptime.
229 */
230static unsigned int crng_reseed_interval(void)
231{
232 static bool early_boot = true;
233
234 if (unlikely(READ_ONCE(early_boot))) {
235 time64_t uptime = ktime_get_seconds();
236 if (uptime >= CRNG_RESEED_INTERVAL / HZ * 2)
237 WRITE_ONCE(early_boot, false);
238 else
239 return max_t(unsigned int, CRNG_RESEED_START_INTERVAL,
240 (unsigned int)uptime / 2 * HZ);
241 }
242 return CRNG_RESEED_INTERVAL;
243}
244
245/* Used by crng_reseed() and crng_make_state() to extract a new seed from the input pool. */
246static void extract_entropy(void *buf, size_t len);
247
248/* This extracts a new crng key from the input pool. */
249static void crng_reseed(struct work_struct *work)
250{
251 static DECLARE_DELAYED_WORK(next_reseed, crng_reseed);
252 unsigned long flags;
253 unsigned long next_gen;
254 u8 key[CHACHA_KEY_SIZE];
255
256 /* Immediately schedule the next reseeding, so that it fires sooner rather than later. */
257 if (likely(system_unbound_wq))
258 queue_delayed_work(system_unbound_wq, &next_reseed, crng_reseed_interval());
259
260 extract_entropy(key, sizeof(key));
261
262 /*
263 * We copy the new key into the base_crng, overwriting the old one,
264 * and update the generation counter. We avoid hitting ULONG_MAX,
265 * because the per-cpu crngs are initialized to ULONG_MAX, so this
266 * forces new CPUs that come online to always initialize.
267 */
268 spin_lock_irqsave(&base_crng.lock, flags);
269 memcpy(base_crng.key, key, sizeof(base_crng.key));
270 next_gen = base_crng.generation + 1;
271 if (next_gen == ULONG_MAX)
272 ++next_gen;
273 WRITE_ONCE(base_crng.generation, next_gen);
274 if (!static_branch_likely(&crng_is_ready))
275 crng_init = CRNG_READY;
276 spin_unlock_irqrestore(&base_crng.lock, flags);
277 memzero_explicit(key, sizeof(key));
278}
279
280/*
281 * This generates a ChaCha block using the provided key, and then
282 * immediately overwrites that key with half the block. It returns
283 * the resultant ChaCha state to the user, along with the second
284 * half of the block containing 32 bytes of random data that may
285 * be used; random_data_len may not be greater than 32.
286 *
287 * The returned ChaCha state contains within it a copy of the old
288 * key value, at index 4, so the state should always be zeroed out
289 * immediately after using in order to maintain forward secrecy.
290 * If the state cannot be erased in a timely manner, then it is
291 * safer to set the random_data parameter to &chacha_state[4] so
292 * that this function overwrites it before returning.
293 */
294static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE],
295 u32 chacha_state[CHACHA_STATE_WORDS],
296 u8 *random_data, size_t random_data_len)
297{
298 u8 first_block[CHACHA_BLOCK_SIZE];
299
300 BUG_ON(random_data_len > 32);
301
302 chacha_init_consts(chacha_state);
303 memcpy(&chacha_state[4], key, CHACHA_KEY_SIZE);
304 memset(&chacha_state[12], 0, sizeof(u32) * 4);
305 chacha20_block(chacha_state, first_block);
306
307 memcpy(key, first_block, CHACHA_KEY_SIZE);
308 memcpy(random_data, first_block + CHACHA_KEY_SIZE, random_data_len);
309 memzero_explicit(first_block, sizeof(first_block));
310}
311
312/*
313 * This function returns a ChaCha state that you may use for generating
314 * random data. It also returns up to 32 bytes on its own of random data
315 * that may be used; random_data_len may not be greater than 32.
316 */
317static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS],
318 u8 *random_data, size_t random_data_len)
319{
320 unsigned long flags;
321 struct crng *crng;
322
323 BUG_ON(random_data_len > 32);
324
325 /*
326 * For the fast path, we check whether we're ready, unlocked first, and
327 * then re-check once locked later. In the case where we're really not
328 * ready, we do fast key erasure with the base_crng directly, extracting
329 * when crng_init is CRNG_EMPTY.
330 */
331 if (!crng_ready()) {
332 bool ready;
333
334 spin_lock_irqsave(&base_crng.lock, flags);
335 ready = crng_ready();
336 if (!ready) {
337 if (crng_init == CRNG_EMPTY)
338 extract_entropy(base_crng.key, sizeof(base_crng.key));
339 crng_fast_key_erasure(base_crng.key, chacha_state,
340 random_data, random_data_len);
341 }
342 spin_unlock_irqrestore(&base_crng.lock, flags);
343 if (!ready)
344 return;
345 }
346
347 local_lock_irqsave(&crngs.lock, flags);
348 crng = raw_cpu_ptr(&crngs);
349
350 /*
351 * If our per-cpu crng is older than the base_crng, then it means
352 * somebody reseeded the base_crng. In that case, we do fast key
353 * erasure on the base_crng, and use its output as the new key
354 * for our per-cpu crng. This brings us up to date with base_crng.
355 */
356 if (unlikely(crng->generation != READ_ONCE(base_crng.generation))) {
357 spin_lock(&base_crng.lock);
358 crng_fast_key_erasure(base_crng.key, chacha_state,
359 crng->key, sizeof(crng->key));
360 crng->generation = base_crng.generation;
361 spin_unlock(&base_crng.lock);
362 }
363
364 /*
365 * Finally, when we've made it this far, our per-cpu crng has an up
366 * to date key, and we can do fast key erasure with it to produce
367 * some random data and a ChaCha state for the caller. All other
368 * branches of this function are "unlikely", so most of the time we
369 * should wind up here immediately.
370 */
371 crng_fast_key_erasure(crng->key, chacha_state, random_data, random_data_len);
372 local_unlock_irqrestore(&crngs.lock, flags);
373}
374
375static void _get_random_bytes(void *buf, size_t len)
376{
377 u32 chacha_state[CHACHA_STATE_WORDS];
378 u8 tmp[CHACHA_BLOCK_SIZE];
379 size_t first_block_len;
380
381 if (!len)
382 return;
383
384 first_block_len = min_t(size_t, 32, len);
385 crng_make_state(chacha_state, buf, first_block_len);
386 len -= first_block_len;
387 buf += first_block_len;
388
389 while (len) {
390 if (len < CHACHA_BLOCK_SIZE) {
391 chacha20_block(chacha_state, tmp);
392 memcpy(buf, tmp, len);
393 memzero_explicit(tmp, sizeof(tmp));
394 break;
395 }
396
397 chacha20_block(chacha_state, buf);
398 if (unlikely(chacha_state[12] == 0))
399 ++chacha_state[13];
400 len -= CHACHA_BLOCK_SIZE;
401 buf += CHACHA_BLOCK_SIZE;
402 }
403
404 memzero_explicit(chacha_state, sizeof(chacha_state));
405}
406
407/*
408 * This returns random bytes in arbitrary quantities. The quality of the
409 * random bytes is good as /dev/urandom. In order to ensure that the
410 * randomness provided by this function is okay, the function
411 * wait_for_random_bytes() should be called and return 0 at least once
412 * at any point prior.
413 */
414void get_random_bytes(void *buf, size_t len)
415{
416 warn_unseeded_randomness();
417 _get_random_bytes(buf, len);
418}
419EXPORT_SYMBOL(get_random_bytes);
420
421static ssize_t get_random_bytes_user(struct iov_iter *iter)
422{
423 u32 chacha_state[CHACHA_STATE_WORDS];
424 u8 block[CHACHA_BLOCK_SIZE];
425 size_t ret = 0, copied;
426
427 if (unlikely(!iov_iter_count(iter)))
428 return 0;
429
430 /*
431 * Immediately overwrite the ChaCha key at index 4 with random
432 * bytes, in case userspace causes copy_to_iter() below to sleep
433 * forever, so that we still retain forward secrecy in that case.
434 */
435 crng_make_state(chacha_state, (u8 *)&chacha_state[4], CHACHA_KEY_SIZE);
436 /*
437 * However, if we're doing a read of len <= 32, we don't need to
438 * use chacha_state after, so we can simply return those bytes to
439 * the user directly.
440 */
441 if (iov_iter_count(iter) <= CHACHA_KEY_SIZE) {
442 ret = copy_to_iter(&chacha_state[4], CHACHA_KEY_SIZE, iter);
443 goto out_zero_chacha;
444 }
445
446 for (;;) {
447 chacha20_block(chacha_state, block);
448 if (unlikely(chacha_state[12] == 0))
449 ++chacha_state[13];
450
451 copied = copy_to_iter(block, sizeof(block), iter);
452 ret += copied;
453 if (!iov_iter_count(iter) || copied != sizeof(block))
454 break;
455
456 BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0);
457 if (ret % PAGE_SIZE == 0) {
458 if (signal_pending(current))
459 break;
460 cond_resched();
461 }
462 }
463
464 memzero_explicit(block, sizeof(block));
465out_zero_chacha:
466 memzero_explicit(chacha_state, sizeof(chacha_state));
467 return ret ? ret : -EFAULT;
468}
469
470/*
471 * Batched entropy returns random integers. The quality of the random
472 * number is good as /dev/urandom. In order to ensure that the randomness
473 * provided by this function is okay, the function wait_for_random_bytes()
474 * should be called and return 0 at least once at any point prior.
475 */
476
477#define DEFINE_BATCHED_ENTROPY(type) \
478struct batch_ ##type { \
479 /* \
480 * We make this 1.5x a ChaCha block, so that we get the \
481 * remaining 32 bytes from fast key erasure, plus one full \
482 * block from the detached ChaCha state. We can increase \
483 * the size of this later if needed so long as we keep the \
484 * formula of (integer_blocks + 0.5) * CHACHA_BLOCK_SIZE. \
485 */ \
486 type entropy[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(type))]; \
487 local_lock_t lock; \
488 unsigned long generation; \
489 unsigned int position; \
490}; \
491 \
492static DEFINE_PER_CPU(struct batch_ ##type, batched_entropy_ ##type) = { \
493 .lock = INIT_LOCAL_LOCK(batched_entropy_ ##type.lock), \
494 .position = UINT_MAX \
495}; \
496 \
497type get_random_ ##type(void) \
498{ \
499 type ret; \
500 unsigned long flags; \
501 struct batch_ ##type *batch; \
502 unsigned long next_gen; \
503 \
504 warn_unseeded_randomness(); \
505 \
506 if (!crng_ready()) { \
507 _get_random_bytes(&ret, sizeof(ret)); \
508 return ret; \
509 } \
510 \
511 local_lock_irqsave(&batched_entropy_ ##type.lock, flags); \
512 batch = raw_cpu_ptr(&batched_entropy_##type); \
513 \
514 next_gen = READ_ONCE(base_crng.generation); \
515 if (batch->position >= ARRAY_SIZE(batch->entropy) || \
516 next_gen != batch->generation) { \
517 _get_random_bytes(batch->entropy, sizeof(batch->entropy)); \
518 batch->position = 0; \
519 batch->generation = next_gen; \
520 } \
521 \
522 ret = batch->entropy[batch->position]; \
523 batch->entropy[batch->position] = 0; \
524 ++batch->position; \
525 local_unlock_irqrestore(&batched_entropy_ ##type.lock, flags); \
526 return ret; \
527} \
528EXPORT_SYMBOL(get_random_ ##type);
529
530DEFINE_BATCHED_ENTROPY(u8)
531DEFINE_BATCHED_ENTROPY(u16)
532DEFINE_BATCHED_ENTROPY(u32)
533DEFINE_BATCHED_ENTROPY(u64)
534
535u32 __get_random_u32_below(u32 ceil)
536{
537 /*
538 * This is the slow path for variable ceil. It is still fast, most of
539 * the time, by doing traditional reciprocal multiplication and
540 * opportunistically comparing the lower half to ceil itself, before
541 * falling back to computing a larger bound, and then rejecting samples
542 * whose lower half would indicate a range indivisible by ceil. The use
543 * of `-ceil % ceil` is analogous to `2^32 % ceil`, but is computable
544 * in 32-bits.
545 */
546 u32 rand = get_random_u32();
547 u64 mult;
548
549 /*
550 * This function is technically undefined for ceil == 0, and in fact
551 * for the non-underscored constant version in the header, we build bug
552 * on that. But for the non-constant case, it's convenient to have that
553 * evaluate to being a straight call to get_random_u32(), so that
554 * get_random_u32_inclusive() can work over its whole range without
555 * undefined behavior.
556 */
557 if (unlikely(!ceil))
558 return rand;
559
560 mult = (u64)ceil * rand;
561 if (unlikely((u32)mult < ceil)) {
562 u32 bound = -ceil % ceil;
563 while (unlikely((u32)mult < bound))
564 mult = (u64)ceil * get_random_u32();
565 }
566 return mult >> 32;
567}
568EXPORT_SYMBOL(__get_random_u32_below);
569
570#ifdef CONFIG_SMP
571/*
572 * This function is called when the CPU is coming up, with entry
573 * CPUHP_RANDOM_PREPARE, which comes before CPUHP_WORKQUEUE_PREP.
574 */
575int __cold random_prepare_cpu(unsigned int cpu)
576{
577 /*
578 * When the cpu comes back online, immediately invalidate both
579 * the per-cpu crng and all batches, so that we serve fresh
580 * randomness.
581 */
582 per_cpu_ptr(&crngs, cpu)->generation = ULONG_MAX;
583 per_cpu_ptr(&batched_entropy_u8, cpu)->position = UINT_MAX;
584 per_cpu_ptr(&batched_entropy_u16, cpu)->position = UINT_MAX;
585 per_cpu_ptr(&batched_entropy_u32, cpu)->position = UINT_MAX;
586 per_cpu_ptr(&batched_entropy_u64, cpu)->position = UINT_MAX;
587 return 0;
588}
589#endif
590
591
592/**********************************************************************
593 *
594 * Entropy accumulation and extraction routines.
595 *
596 * Callers may add entropy via:
597 *
598 * static void mix_pool_bytes(const void *buf, size_t len)
599 *
600 * After which, if added entropy should be credited:
601 *
602 * static void credit_init_bits(size_t bits)
603 *
604 * Finally, extract entropy via:
605 *
606 * static void extract_entropy(void *buf, size_t len)
607 *
608 **********************************************************************/
609
610enum {
611 POOL_BITS = BLAKE2S_HASH_SIZE * 8,
612 POOL_READY_BITS = POOL_BITS, /* When crng_init->CRNG_READY */
613 POOL_EARLY_BITS = POOL_READY_BITS / 2 /* When crng_init->CRNG_EARLY */
614};
615
616static struct {
617 struct blake2s_state hash;
618 spinlock_t lock;
619 unsigned int init_bits;
620} input_pool = {
621 .hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE),
622 BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4,
623 BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 },
624 .hash.outlen = BLAKE2S_HASH_SIZE,
625 .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
626};
627
628static void _mix_pool_bytes(const void *buf, size_t len)
629{
630 blake2s_update(&input_pool.hash, buf, len);
631}
632
633/*
634 * This function adds bytes into the input pool. It does not
635 * update the initialization bit counter; the caller should call
636 * credit_init_bits if this is appropriate.
637 */
638static void mix_pool_bytes(const void *buf, size_t len)
639{
640 unsigned long flags;
641
642 spin_lock_irqsave(&input_pool.lock, flags);
643 _mix_pool_bytes(buf, len);
644 spin_unlock_irqrestore(&input_pool.lock, flags);
645}
646
647/*
648 * This is an HKDF-like construction for using the hashed collected entropy
649 * as a PRF key, that's then expanded block-by-block.
650 */
651static void extract_entropy(void *buf, size_t len)
652{
653 unsigned long flags;
654 u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE];
655 struct {
656 unsigned long rdseed[32 / sizeof(long)];
657 size_t counter;
658 } block;
659 size_t i, longs;
660
661 for (i = 0; i < ARRAY_SIZE(block.rdseed);) {
662 longs = arch_get_random_seed_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
663 if (longs) {
664 i += longs;
665 continue;
666 }
667 longs = arch_get_random_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
668 if (longs) {
669 i += longs;
670 continue;
671 }
672 block.rdseed[i++] = random_get_entropy();
673 }
674
675 spin_lock_irqsave(&input_pool.lock, flags);
676
677 /* seed = HASHPRF(last_key, entropy_input) */
678 blake2s_final(&input_pool.hash, seed);
679
680 /* next_key = HASHPRF(seed, RDSEED || 0) */
681 block.counter = 0;
682 blake2s(next_key, (u8 *)&block, seed, sizeof(next_key), sizeof(block), sizeof(seed));
683 blake2s_init_key(&input_pool.hash, BLAKE2S_HASH_SIZE, next_key, sizeof(next_key));
684
685 spin_unlock_irqrestore(&input_pool.lock, flags);
686 memzero_explicit(next_key, sizeof(next_key));
687
688 while (len) {
689 i = min_t(size_t, len, BLAKE2S_HASH_SIZE);
690 /* output = HASHPRF(seed, RDSEED || ++counter) */
691 ++block.counter;
692 blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed));
693 len -= i;
694 buf += i;
695 }
696
697 memzero_explicit(seed, sizeof(seed));
698 memzero_explicit(&block, sizeof(block));
699}
700
701#define credit_init_bits(bits) if (!crng_ready()) _credit_init_bits(bits)
702
703static void __cold _credit_init_bits(size_t bits)
704{
705 static struct execute_work set_ready;
706 unsigned int new, orig, add;
707 unsigned long flags;
708
709 if (!bits)
710 return;
711
712 add = min_t(size_t, bits, POOL_BITS);
713
714 orig = READ_ONCE(input_pool.init_bits);
715 do {
716 new = min_t(unsigned int, POOL_BITS, orig + add);
717 } while (!try_cmpxchg(&input_pool.init_bits, &orig, new));
718
719 if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) {
720 crng_reseed(NULL); /* Sets crng_init to CRNG_READY under base_crng.lock. */
721 if (static_key_initialized)
722 execute_in_process_context(crng_set_ready, &set_ready);
723 atomic_notifier_call_chain(&random_ready_notifier, 0, NULL);
724 wake_up_interruptible(&crng_init_wait);
725 kill_fasync(&fasync, SIGIO, POLL_IN);
726 pr_notice("crng init done\n");
727 if (urandom_warning.missed)
728 pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
729 urandom_warning.missed);
730 } else if (orig < POOL_EARLY_BITS && new >= POOL_EARLY_BITS) {
731 spin_lock_irqsave(&base_crng.lock, flags);
732 /* Check if crng_init is CRNG_EMPTY, to avoid race with crng_reseed(). */
733 if (crng_init == CRNG_EMPTY) {
734 extract_entropy(base_crng.key, sizeof(base_crng.key));
735 crng_init = CRNG_EARLY;
736 }
737 spin_unlock_irqrestore(&base_crng.lock, flags);
738 }
739}
740
741
742/**********************************************************************
743 *
744 * Entropy collection routines.
745 *
746 * The following exported functions are used for pushing entropy into
747 * the above entropy accumulation routines:
748 *
749 * void add_device_randomness(const void *buf, size_t len);
750 * void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after);
751 * void add_bootloader_randomness(const void *buf, size_t len);
752 * void add_vmfork_randomness(const void *unique_vm_id, size_t len);
753 * void add_interrupt_randomness(int irq);
754 * void add_input_randomness(unsigned int type, unsigned int code, unsigned int value);
755 * void add_disk_randomness(struct gendisk *disk);
756 *
757 * add_device_randomness() adds data to the input pool that
758 * is likely to differ between two devices (or possibly even per boot).
759 * This would be things like MAC addresses or serial numbers, or the
760 * read-out of the RTC. This does *not* credit any actual entropy to
761 * the pool, but it initializes the pool to different values for devices
762 * that might otherwise be identical and have very little entropy
763 * available to them (particularly common in the embedded world).
764 *
765 * add_hwgenerator_randomness() is for true hardware RNGs, and will credit
766 * entropy as specified by the caller. If the entropy pool is full it will
767 * block until more entropy is needed.
768 *
769 * add_bootloader_randomness() is called by bootloader drivers, such as EFI
770 * and device tree, and credits its input depending on whether or not the
771 * command line option 'random.trust_bootloader'.
772 *
773 * add_vmfork_randomness() adds a unique (but not necessarily secret) ID
774 * representing the current instance of a VM to the pool, without crediting,
775 * and then force-reseeds the crng so that it takes effect immediately.
776 *
777 * add_interrupt_randomness() uses the interrupt timing as random
778 * inputs to the entropy pool. Using the cycle counters and the irq source
779 * as inputs, it feeds the input pool roughly once a second or after 64
780 * interrupts, crediting 1 bit of entropy for whichever comes first.
781 *
782 * add_input_randomness() uses the input layer interrupt timing, as well
783 * as the event type information from the hardware.
784 *
785 * add_disk_randomness() uses what amounts to the seek time of block
786 * layer request events, on a per-disk_devt basis, as input to the
787 * entropy pool. Note that high-speed solid state drives with very low
788 * seek times do not make for good sources of entropy, as their seek
789 * times are usually fairly consistent.
790 *
791 * The last two routines try to estimate how many bits of entropy
792 * to credit. They do this by keeping track of the first and second
793 * order deltas of the event timings.
794 *
795 **********************************************************************/
796
797static bool trust_cpu __initdata = true;
798static bool trust_bootloader __initdata = true;
799static int __init parse_trust_cpu(char *arg)
800{
801 return kstrtobool(arg, &trust_cpu);
802}
803static int __init parse_trust_bootloader(char *arg)
804{
805 return kstrtobool(arg, &trust_bootloader);
806}
807early_param("random.trust_cpu", parse_trust_cpu);
808early_param("random.trust_bootloader", parse_trust_bootloader);
809
810static int random_pm_notification(struct notifier_block *nb, unsigned long action, void *data)
811{
812 unsigned long flags, entropy = random_get_entropy();
813
814 /*
815 * Encode a representation of how long the system has been suspended,
816 * in a way that is distinct from prior system suspends.
817 */
818 ktime_t stamps[] = { ktime_get(), ktime_get_boottime(), ktime_get_real() };
819
820 spin_lock_irqsave(&input_pool.lock, flags);
821 _mix_pool_bytes(&action, sizeof(action));
822 _mix_pool_bytes(stamps, sizeof(stamps));
823 _mix_pool_bytes(&entropy, sizeof(entropy));
824 spin_unlock_irqrestore(&input_pool.lock, flags);
825
826 if (crng_ready() && (action == PM_RESTORE_PREPARE ||
827 (action == PM_POST_SUSPEND && !IS_ENABLED(CONFIG_PM_AUTOSLEEP) &&
828 !IS_ENABLED(CONFIG_PM_USERSPACE_AUTOSLEEP)))) {
829 crng_reseed(NULL);
830 pr_notice("crng reseeded on system resumption\n");
831 }
832 return 0;
833}
834
835static struct notifier_block pm_notifier = { .notifier_call = random_pm_notification };
836
837/*
838 * This is called extremely early, before time keeping functionality is
839 * available, but arch randomness is. Interrupts are not yet enabled.
840 */
841void __init random_init_early(const char *command_line)
842{
843 unsigned long entropy[BLAKE2S_BLOCK_SIZE / sizeof(long)];
844 size_t i, longs, arch_bits;
845
846#if defined(LATENT_ENTROPY_PLUGIN)
847 static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy;
848 _mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed));
849#endif
850
851 for (i = 0, arch_bits = sizeof(entropy) * 8; i < ARRAY_SIZE(entropy);) {
852 longs = arch_get_random_seed_longs(entropy, ARRAY_SIZE(entropy) - i);
853 if (longs) {
854 _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
855 i += longs;
856 continue;
857 }
858 longs = arch_get_random_longs(entropy, ARRAY_SIZE(entropy) - i);
859 if (longs) {
860 _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
861 i += longs;
862 continue;
863 }
864 arch_bits -= sizeof(*entropy) * 8;
865 ++i;
866 }
867
868 _mix_pool_bytes(init_utsname(), sizeof(*(init_utsname())));
869 _mix_pool_bytes(command_line, strlen(command_line));
870
871 /* Reseed if already seeded by earlier phases. */
872 if (crng_ready())
873 crng_reseed(NULL);
874 else if (trust_cpu)
875 _credit_init_bits(arch_bits);
876}
877
878/*
879 * This is called a little bit after the prior function, and now there is
880 * access to timestamps counters. Interrupts are not yet enabled.
881 */
882void __init random_init(void)
883{
884 unsigned long entropy = random_get_entropy();
885 ktime_t now = ktime_get_real();
886
887 _mix_pool_bytes(&now, sizeof(now));
888 _mix_pool_bytes(&entropy, sizeof(entropy));
889 add_latent_entropy();
890
891 /*
892 * If we were initialized by the cpu or bootloader before jump labels
893 * are initialized, then we should enable the static branch here, where
894 * it's guaranteed that jump labels have been initialized.
895 */
896 if (!static_branch_likely(&crng_is_ready) && crng_init >= CRNG_READY)
897 crng_set_ready(NULL);
898
899 /* Reseed if already seeded by earlier phases. */
900 if (crng_ready())
901 crng_reseed(NULL);
902
903 WARN_ON(register_pm_notifier(&pm_notifier));
904
905 WARN(!entropy, "Missing cycle counter and fallback timer; RNG "
906 "entropy collection will consequently suffer.");
907}
908
909/*
910 * Add device- or boot-specific data to the input pool to help
911 * initialize it.
912 *
913 * None of this adds any entropy; it is meant to avoid the problem of
914 * the entropy pool having similar initial state across largely
915 * identical devices.
916 */
917void add_device_randomness(const void *buf, size_t len)
918{
919 unsigned long entropy = random_get_entropy();
920 unsigned long flags;
921
922 spin_lock_irqsave(&input_pool.lock, flags);
923 _mix_pool_bytes(&entropy, sizeof(entropy));
924 _mix_pool_bytes(buf, len);
925 spin_unlock_irqrestore(&input_pool.lock, flags);
926}
927EXPORT_SYMBOL(add_device_randomness);
928
929/*
930 * Interface for in-kernel drivers of true hardware RNGs. Those devices
931 * may produce endless random bits, so this function will sleep for
932 * some amount of time after, if the sleep_after parameter is true.
933 */
934void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after)
935{
936 mix_pool_bytes(buf, len);
937 credit_init_bits(entropy);
938
939 /*
940 * Throttle writing to once every reseed interval, unless we're not yet
941 * initialized or no entropy is credited.
942 */
943 if (sleep_after && !kthread_should_stop() && (crng_ready() || !entropy))
944 schedule_timeout_interruptible(crng_reseed_interval());
945}
946EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
947
948/*
949 * Handle random seed passed by bootloader, and credit it depending
950 * on the command line option 'random.trust_bootloader'.
951 */
952void __init add_bootloader_randomness(const void *buf, size_t len)
953{
954 mix_pool_bytes(buf, len);
955 if (trust_bootloader)
956 credit_init_bits(len * 8);
957}
958
959#if IS_ENABLED(CONFIG_VMGENID)
960static BLOCKING_NOTIFIER_HEAD(vmfork_chain);
961
962/*
963 * Handle a new unique VM ID, which is unique, not secret, so we
964 * don't credit it, but we do immediately force a reseed after so
965 * that it's used by the crng posthaste.
966 */
967void __cold add_vmfork_randomness(const void *unique_vm_id, size_t len)
968{
969 add_device_randomness(unique_vm_id, len);
970 if (crng_ready()) {
971 crng_reseed(NULL);
972 pr_notice("crng reseeded due to virtual machine fork\n");
973 }
974 blocking_notifier_call_chain(&vmfork_chain, 0, NULL);
975}
976#if IS_MODULE(CONFIG_VMGENID)
977EXPORT_SYMBOL_GPL(add_vmfork_randomness);
978#endif
979
980int __cold register_random_vmfork_notifier(struct notifier_block *nb)
981{
982 return blocking_notifier_chain_register(&vmfork_chain, nb);
983}
984EXPORT_SYMBOL_GPL(register_random_vmfork_notifier);
985
986int __cold unregister_random_vmfork_notifier(struct notifier_block *nb)
987{
988 return blocking_notifier_chain_unregister(&vmfork_chain, nb);
989}
990EXPORT_SYMBOL_GPL(unregister_random_vmfork_notifier);
991#endif
992
993struct fast_pool {
994 unsigned long pool[4];
995 unsigned long last;
996 unsigned int count;
997 struct timer_list mix;
998};
999
1000static void mix_interrupt_randomness(struct timer_list *work);
1001
1002static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {
1003#ifdef CONFIG_64BIT
1004#define FASTMIX_PERM SIPHASH_PERMUTATION
1005 .pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 },
1006#else
1007#define FASTMIX_PERM HSIPHASH_PERMUTATION
1008 .pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 },
1009#endif
1010 .mix = __TIMER_INITIALIZER(mix_interrupt_randomness, 0)
1011};
1012
1013/*
1014 * This is [Half]SipHash-1-x, starting from an empty key. Because
1015 * the key is fixed, it assumes that its inputs are non-malicious,
1016 * and therefore this has no security on its own. s represents the
1017 * four-word SipHash state, while v represents a two-word input.
1018 */
1019static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2)
1020{
1021 s[3] ^= v1;
1022 FASTMIX_PERM(s[0], s[1], s[2], s[3]);
1023 s[0] ^= v1;
1024 s[3] ^= v2;
1025 FASTMIX_PERM(s[0], s[1], s[2], s[3]);
1026 s[0] ^= v2;
1027}
1028
1029#ifdef CONFIG_SMP
1030/*
1031 * This function is called when the CPU has just come online, with
1032 * entry CPUHP_AP_RANDOM_ONLINE, just after CPUHP_AP_WORKQUEUE_ONLINE.
1033 */
1034int __cold random_online_cpu(unsigned int cpu)
1035{
1036 /*
1037 * During CPU shutdown and before CPU onlining, add_interrupt_
1038 * randomness() may schedule mix_interrupt_randomness(), and
1039 * set the MIX_INFLIGHT flag. However, because the worker can
1040 * be scheduled on a different CPU during this period, that
1041 * flag will never be cleared. For that reason, we zero out
1042 * the flag here, which runs just after workqueues are onlined
1043 * for the CPU again. This also has the effect of setting the
1044 * irq randomness count to zero so that new accumulated irqs
1045 * are fresh.
1046 */
1047 per_cpu_ptr(&irq_randomness, cpu)->count = 0;
1048 return 0;
1049}
1050#endif
1051
1052static void mix_interrupt_randomness(struct timer_list *work)
1053{
1054 struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix);
1055 /*
1056 * The size of the copied stack pool is explicitly 2 longs so that we
1057 * only ever ingest half of the siphash output each time, retaining
1058 * the other half as the next "key" that carries over. The entropy is
1059 * supposed to be sufficiently dispersed between bits so on average
1060 * we don't wind up "losing" some.
1061 */
1062 unsigned long pool[2];
1063 unsigned int count;
1064
1065 /* Check to see if we're running on the wrong CPU due to hotplug. */
1066 local_irq_disable();
1067 if (fast_pool != this_cpu_ptr(&irq_randomness)) {
1068 local_irq_enable();
1069 return;
1070 }
1071
1072 /*
1073 * Copy the pool to the stack so that the mixer always has a
1074 * consistent view, before we reenable irqs again.
1075 */
1076 memcpy(pool, fast_pool->pool, sizeof(pool));
1077 count = fast_pool->count;
1078 fast_pool->count = 0;
1079 fast_pool->last = jiffies;
1080 local_irq_enable();
1081
1082 mix_pool_bytes(pool, sizeof(pool));
1083 credit_init_bits(clamp_t(unsigned int, (count & U16_MAX) / 64, 1, sizeof(pool) * 8));
1084
1085 memzero_explicit(pool, sizeof(pool));
1086}
1087
1088void add_interrupt_randomness(int irq)
1089{
1090 enum { MIX_INFLIGHT = 1U << 31 };
1091 unsigned long entropy = random_get_entropy();
1092 struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
1093 struct pt_regs *regs = get_irq_regs();
1094 unsigned int new_count;
1095
1096 fast_mix(fast_pool->pool, entropy,
1097 (regs ? instruction_pointer(regs) : _RET_IP_) ^ swab(irq));
1098 new_count = ++fast_pool->count;
1099
1100 if (new_count & MIX_INFLIGHT)
1101 return;
1102
1103 if (new_count < 1024 && !time_is_before_jiffies(fast_pool->last + HZ))
1104 return;
1105
1106 fast_pool->count |= MIX_INFLIGHT;
1107 if (!timer_pending(&fast_pool->mix)) {
1108 fast_pool->mix.expires = jiffies;
1109 add_timer_on(&fast_pool->mix, raw_smp_processor_id());
1110 }
1111}
1112EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1113
1114/* There is one of these per entropy source */
1115struct timer_rand_state {
1116 unsigned long last_time;
1117 long last_delta, last_delta2;
1118};
1119
1120/*
1121 * This function adds entropy to the entropy "pool" by using timing
1122 * delays. It uses the timer_rand_state structure to make an estimate
1123 * of how many bits of entropy this call has added to the pool. The
1124 * value "num" is also added to the pool; it should somehow describe
1125 * the type of event that just happened.
1126 */
1127static void add_timer_randomness(struct timer_rand_state *state, unsigned int num)
1128{
1129 unsigned long entropy = random_get_entropy(), now = jiffies, flags;
1130 long delta, delta2, delta3;
1131 unsigned int bits;
1132
1133 /*
1134 * If we're in a hard IRQ, add_interrupt_randomness() will be called
1135 * sometime after, so mix into the fast pool.
1136 */
1137 if (in_hardirq()) {
1138 fast_mix(this_cpu_ptr(&irq_randomness)->pool, entropy, num);
1139 } else {
1140 spin_lock_irqsave(&input_pool.lock, flags);
1141 _mix_pool_bytes(&entropy, sizeof(entropy));
1142 _mix_pool_bytes(&num, sizeof(num));
1143 spin_unlock_irqrestore(&input_pool.lock, flags);
1144 }
1145
1146 if (crng_ready())
1147 return;
1148
1149 /*
1150 * Calculate number of bits of randomness we probably added.
1151 * We take into account the first, second and third-order deltas
1152 * in order to make our estimate.
1153 */
1154 delta = now - READ_ONCE(state->last_time);
1155 WRITE_ONCE(state->last_time, now);
1156
1157 delta2 = delta - READ_ONCE(state->last_delta);
1158 WRITE_ONCE(state->last_delta, delta);
1159
1160 delta3 = delta2 - READ_ONCE(state->last_delta2);
1161 WRITE_ONCE(state->last_delta2, delta2);
1162
1163 if (delta < 0)
1164 delta = -delta;
1165 if (delta2 < 0)
1166 delta2 = -delta2;
1167 if (delta3 < 0)
1168 delta3 = -delta3;
1169 if (delta > delta2)
1170 delta = delta2;
1171 if (delta > delta3)
1172 delta = delta3;
1173
1174 /*
1175 * delta is now minimum absolute delta. Round down by 1 bit
1176 * on general principles, and limit entropy estimate to 11 bits.
1177 */
1178 bits = min(fls(delta >> 1), 11);
1179
1180 /*
1181 * As mentioned above, if we're in a hard IRQ, add_interrupt_randomness()
1182 * will run after this, which uses a different crediting scheme of 1 bit
1183 * per every 64 interrupts. In order to let that function do accounting
1184 * close to the one in this function, we credit a full 64/64 bit per bit,
1185 * and then subtract one to account for the extra one added.
1186 */
1187 if (in_hardirq())
1188 this_cpu_ptr(&irq_randomness)->count += max(1u, bits * 64) - 1;
1189 else
1190 _credit_init_bits(bits);
1191}
1192
1193void add_input_randomness(unsigned int type, unsigned int code, unsigned int value)
1194{
1195 static unsigned char last_value;
1196 static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES };
1197
1198 /* Ignore autorepeat and the like. */
1199 if (value == last_value)
1200 return;
1201
1202 last_value = value;
1203 add_timer_randomness(&input_timer_state,
1204 (type << 4) ^ code ^ (code >> 4) ^ value);
1205}
1206EXPORT_SYMBOL_GPL(add_input_randomness);
1207
1208#ifdef CONFIG_BLOCK
1209void add_disk_randomness(struct gendisk *disk)
1210{
1211 if (!disk || !disk->random)
1212 return;
1213 /* First major is 1, so we get >= 0x200 here. */
1214 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1215}
1216EXPORT_SYMBOL_GPL(add_disk_randomness);
1217
1218void __cold rand_initialize_disk(struct gendisk *disk)
1219{
1220 struct timer_rand_state *state;
1221
1222 /*
1223 * If kzalloc returns null, we just won't use that entropy
1224 * source.
1225 */
1226 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1227 if (state) {
1228 state->last_time = INITIAL_JIFFIES;
1229 disk->random = state;
1230 }
1231}
1232#endif
1233
1234struct entropy_timer_state {
1235 unsigned long entropy;
1236 struct timer_list timer;
1237 atomic_t samples;
1238 unsigned int samples_per_bit;
1239};
1240
1241/*
1242 * Each time the timer fires, we expect that we got an unpredictable jump in
1243 * the cycle counter. Even if the timer is running on another CPU, the timer
1244 * activity will be touching the stack of the CPU that is generating entropy.
1245 *
1246 * Note that we don't re-arm the timer in the timer itself - we are happy to be
1247 * scheduled away, since that just makes the load more complex, but we do not
1248 * want the timer to keep ticking unless the entropy loop is running.
1249 *
1250 * So the re-arming always happens in the entropy loop itself.
1251 */
1252static void __cold entropy_timer(struct timer_list *timer)
1253{
1254 struct entropy_timer_state *state = container_of(timer, struct entropy_timer_state, timer);
1255 unsigned long entropy = random_get_entropy();
1256
1257 mix_pool_bytes(&entropy, sizeof(entropy));
1258 if (atomic_inc_return(&state->samples) % state->samples_per_bit == 0)
1259 credit_init_bits(1);
1260}
1261
1262/*
1263 * If we have an actual cycle counter, see if we can generate enough entropy
1264 * with timing noise.
1265 */
1266static void __cold try_to_generate_entropy(void)
1267{
1268 enum { NUM_TRIAL_SAMPLES = 8192, MAX_SAMPLES_PER_BIT = HZ / 15 };
1269 u8 stack_bytes[sizeof(struct entropy_timer_state) + SMP_CACHE_BYTES - 1];
1270 struct entropy_timer_state *stack = PTR_ALIGN((void *)stack_bytes, SMP_CACHE_BYTES);
1271 unsigned int i, num_different = 0;
1272 unsigned long last = random_get_entropy();
1273 int cpu = -1;
1274
1275 for (i = 0; i < NUM_TRIAL_SAMPLES - 1; ++i) {
1276 stack->entropy = random_get_entropy();
1277 if (stack->entropy != last)
1278 ++num_different;
1279 last = stack->entropy;
1280 }
1281 stack->samples_per_bit = DIV_ROUND_UP(NUM_TRIAL_SAMPLES, num_different + 1);
1282 if (stack->samples_per_bit > MAX_SAMPLES_PER_BIT)
1283 return;
1284
1285 atomic_set(&stack->samples, 0);
1286 timer_setup_on_stack(&stack->timer, entropy_timer, 0);
1287 while (!crng_ready() && !signal_pending(current)) {
1288 /*
1289 * Check !timer_pending() and then ensure that any previous callback has finished
1290 * executing by checking try_to_del_timer_sync(), before queueing the next one.
1291 */
1292 if (!timer_pending(&stack->timer) && try_to_del_timer_sync(&stack->timer) >= 0) {
1293 struct cpumask timer_cpus;
1294 unsigned int num_cpus;
1295
1296 /*
1297 * Preemption must be disabled here, both to read the current CPU number
1298 * and to avoid scheduling a timer on a dead CPU.
1299 */
1300 preempt_disable();
1301
1302 /* Only schedule callbacks on timer CPUs that are online. */
1303 cpumask_and(&timer_cpus, housekeeping_cpumask(HK_TYPE_TIMER), cpu_online_mask);
1304 num_cpus = cpumask_weight(&timer_cpus);
1305 /* In very bizarre case of misconfiguration, fallback to all online. */
1306 if (unlikely(num_cpus == 0)) {
1307 timer_cpus = *cpu_online_mask;
1308 num_cpus = cpumask_weight(&timer_cpus);
1309 }
1310
1311 /* Basic CPU round-robin, which avoids the current CPU. */
1312 do {
1313 cpu = cpumask_next(cpu, &timer_cpus);
1314 if (cpu >= nr_cpu_ids)
1315 cpu = cpumask_first(&timer_cpus);
1316 } while (cpu == smp_processor_id() && num_cpus > 1);
1317
1318 /* Expiring the timer at `jiffies` means it's the next tick. */
1319 stack->timer.expires = jiffies;
1320
1321 add_timer_on(&stack->timer, cpu);
1322
1323 preempt_enable();
1324 }
1325 mix_pool_bytes(&stack->entropy, sizeof(stack->entropy));
1326 schedule();
1327 stack->entropy = random_get_entropy();
1328 }
1329 mix_pool_bytes(&stack->entropy, sizeof(stack->entropy));
1330
1331 del_timer_sync(&stack->timer);
1332 destroy_timer_on_stack(&stack->timer);
1333}
1334
1335
1336/**********************************************************************
1337 *
1338 * Userspace reader/writer interfaces.
1339 *
1340 * getrandom(2) is the primary modern interface into the RNG and should
1341 * be used in preference to anything else.
1342 *
1343 * Reading from /dev/random has the same functionality as calling
1344 * getrandom(2) with flags=0. In earlier versions, however, it had
1345 * vastly different semantics and should therefore be avoided, to
1346 * prevent backwards compatibility issues.
1347 *
1348 * Reading from /dev/urandom has the same functionality as calling
1349 * getrandom(2) with flags=GRND_INSECURE. Because it does not block
1350 * waiting for the RNG to be ready, it should not be used.
1351 *
1352 * Writing to either /dev/random or /dev/urandom adds entropy to
1353 * the input pool but does not credit it.
1354 *
1355 * Polling on /dev/random indicates when the RNG is initialized, on
1356 * the read side, and when it wants new entropy, on the write side.
1357 *
1358 * Both /dev/random and /dev/urandom have the same set of ioctls for
1359 * adding entropy, getting the entropy count, zeroing the count, and
1360 * reseeding the crng.
1361 *
1362 **********************************************************************/
1363
1364SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags)
1365{
1366 struct iov_iter iter;
1367 int ret;
1368
1369 if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE))
1370 return -EINVAL;
1371
1372 /*
1373 * Requesting insecure and blocking randomness at the same time makes
1374 * no sense.
1375 */
1376 if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM))
1377 return -EINVAL;
1378
1379 if (!crng_ready() && !(flags & GRND_INSECURE)) {
1380 if (flags & GRND_NONBLOCK)
1381 return -EAGAIN;
1382 ret = wait_for_random_bytes();
1383 if (unlikely(ret))
1384 return ret;
1385 }
1386
1387 ret = import_ubuf(ITER_DEST, ubuf, len, &iter);
1388 if (unlikely(ret))
1389 return ret;
1390 return get_random_bytes_user(&iter);
1391}
1392
1393static __poll_t random_poll(struct file *file, poll_table *wait)
1394{
1395 poll_wait(file, &crng_init_wait, wait);
1396 return crng_ready() ? EPOLLIN | EPOLLRDNORM : EPOLLOUT | EPOLLWRNORM;
1397}
1398
1399static ssize_t write_pool_user(struct iov_iter *iter)
1400{
1401 u8 block[BLAKE2S_BLOCK_SIZE];
1402 ssize_t ret = 0;
1403 size_t copied;
1404
1405 if (unlikely(!iov_iter_count(iter)))
1406 return 0;
1407
1408 for (;;) {
1409 copied = copy_from_iter(block, sizeof(block), iter);
1410 ret += copied;
1411 mix_pool_bytes(block, copied);
1412 if (!iov_iter_count(iter) || copied != sizeof(block))
1413 break;
1414
1415 BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0);
1416 if (ret % PAGE_SIZE == 0) {
1417 if (signal_pending(current))
1418 break;
1419 cond_resched();
1420 }
1421 }
1422
1423 memzero_explicit(block, sizeof(block));
1424 return ret ? ret : -EFAULT;
1425}
1426
1427static ssize_t random_write_iter(struct kiocb *kiocb, struct iov_iter *iter)
1428{
1429 return write_pool_user(iter);
1430}
1431
1432static ssize_t urandom_read_iter(struct kiocb *kiocb, struct iov_iter *iter)
1433{
1434 static int maxwarn = 10;
1435
1436 /*
1437 * Opportunistically attempt to initialize the RNG on platforms that
1438 * have fast cycle counters, but don't (for now) require it to succeed.
1439 */
1440 if (!crng_ready())
1441 try_to_generate_entropy();
1442
1443 if (!crng_ready()) {
1444 if (!ratelimit_disable && maxwarn <= 0)
1445 ++urandom_warning.missed;
1446 else if (ratelimit_disable || __ratelimit(&urandom_warning)) {
1447 --maxwarn;
1448 pr_notice("%s: uninitialized urandom read (%zu bytes read)\n",
1449 current->comm, iov_iter_count(iter));
1450 }
1451 }
1452
1453 return get_random_bytes_user(iter);
1454}
1455
1456static ssize_t random_read_iter(struct kiocb *kiocb, struct iov_iter *iter)
1457{
1458 int ret;
1459
1460 if (!crng_ready() &&
1461 ((kiocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) ||
1462 (kiocb->ki_filp->f_flags & O_NONBLOCK)))
1463 return -EAGAIN;
1464
1465 ret = wait_for_random_bytes();
1466 if (ret != 0)
1467 return ret;
1468 return get_random_bytes_user(iter);
1469}
1470
1471static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1472{
1473 int __user *p = (int __user *)arg;
1474 int ent_count;
1475
1476 switch (cmd) {
1477 case RNDGETENTCNT:
1478 /* Inherently racy, no point locking. */
1479 if (put_user(input_pool.init_bits, p))
1480 return -EFAULT;
1481 return 0;
1482 case RNDADDTOENTCNT:
1483 if (!capable(CAP_SYS_ADMIN))
1484 return -EPERM;
1485 if (get_user(ent_count, p))
1486 return -EFAULT;
1487 if (ent_count < 0)
1488 return -EINVAL;
1489 credit_init_bits(ent_count);
1490 return 0;
1491 case RNDADDENTROPY: {
1492 struct iov_iter iter;
1493 ssize_t ret;
1494 int len;
1495
1496 if (!capable(CAP_SYS_ADMIN))
1497 return -EPERM;
1498 if (get_user(ent_count, p++))
1499 return -EFAULT;
1500 if (ent_count < 0)
1501 return -EINVAL;
1502 if (get_user(len, p++))
1503 return -EFAULT;
1504 ret = import_ubuf(ITER_SOURCE, p, len, &iter);
1505 if (unlikely(ret))
1506 return ret;
1507 ret = write_pool_user(&iter);
1508 if (unlikely(ret < 0))
1509 return ret;
1510 /* Since we're crediting, enforce that it was all written into the pool. */
1511 if (unlikely(ret != len))
1512 return -EFAULT;
1513 credit_init_bits(ent_count);
1514 return 0;
1515 }
1516 case RNDZAPENTCNT:
1517 case RNDCLEARPOOL:
1518 /* No longer has any effect. */
1519 if (!capable(CAP_SYS_ADMIN))
1520 return -EPERM;
1521 return 0;
1522 case RNDRESEEDCRNG:
1523 if (!capable(CAP_SYS_ADMIN))
1524 return -EPERM;
1525 if (!crng_ready())
1526 return -ENODATA;
1527 crng_reseed(NULL);
1528 return 0;
1529 default:
1530 return -EINVAL;
1531 }
1532}
1533
1534static int random_fasync(int fd, struct file *filp, int on)
1535{
1536 return fasync_helper(fd, filp, on, &fasync);
1537}
1538
1539const struct file_operations random_fops = {
1540 .read_iter = random_read_iter,
1541 .write_iter = random_write_iter,
1542 .poll = random_poll,
1543 .unlocked_ioctl = random_ioctl,
1544 .compat_ioctl = compat_ptr_ioctl,
1545 .fasync = random_fasync,
1546 .llseek = noop_llseek,
1547 .splice_read = copy_splice_read,
1548 .splice_write = iter_file_splice_write,
1549};
1550
1551const struct file_operations urandom_fops = {
1552 .read_iter = urandom_read_iter,
1553 .write_iter = random_write_iter,
1554 .unlocked_ioctl = random_ioctl,
1555 .compat_ioctl = compat_ptr_ioctl,
1556 .fasync = random_fasync,
1557 .llseek = noop_llseek,
1558 .splice_read = copy_splice_read,
1559 .splice_write = iter_file_splice_write,
1560};
1561
1562
1563/********************************************************************
1564 *
1565 * Sysctl interface.
1566 *
1567 * These are partly unused legacy knobs with dummy values to not break
1568 * userspace and partly still useful things. They are usually accessible
1569 * in /proc/sys/kernel/random/ and are as follows:
1570 *
1571 * - boot_id - a UUID representing the current boot.
1572 *
1573 * - uuid - a random UUID, different each time the file is read.
1574 *
1575 * - poolsize - the number of bits of entropy that the input pool can
1576 * hold, tied to the POOL_BITS constant.
1577 *
1578 * - entropy_avail - the number of bits of entropy currently in the
1579 * input pool. Always <= poolsize.
1580 *
1581 * - write_wakeup_threshold - the amount of entropy in the input pool
1582 * below which write polls to /dev/random will unblock, requesting
1583 * more entropy, tied to the POOL_READY_BITS constant. It is writable
1584 * to avoid breaking old userspaces, but writing to it does not
1585 * change any behavior of the RNG.
1586 *
1587 * - urandom_min_reseed_secs - fixed to the value CRNG_RESEED_INTERVAL.
1588 * It is writable to avoid breaking old userspaces, but writing
1589 * to it does not change any behavior of the RNG.
1590 *
1591 ********************************************************************/
1592
1593#ifdef CONFIG_SYSCTL
1594
1595#include <linux/sysctl.h>
1596
1597static int sysctl_random_min_urandom_seed = CRNG_RESEED_INTERVAL / HZ;
1598static int sysctl_random_write_wakeup_bits = POOL_READY_BITS;
1599static int sysctl_poolsize = POOL_BITS;
1600static u8 sysctl_bootid[UUID_SIZE];
1601
1602/*
1603 * This function is used to return both the bootid UUID, and random
1604 * UUID. The difference is in whether table->data is NULL; if it is,
1605 * then a new UUID is generated and returned to the user.
1606 */
1607static int proc_do_uuid(struct ctl_table *table, int write, void *buf,
1608 size_t *lenp, loff_t *ppos)
1609{
1610 u8 tmp_uuid[UUID_SIZE], *uuid;
1611 char uuid_string[UUID_STRING_LEN + 1];
1612 struct ctl_table fake_table = {
1613 .data = uuid_string,
1614 .maxlen = UUID_STRING_LEN
1615 };
1616
1617 if (write)
1618 return -EPERM;
1619
1620 uuid = table->data;
1621 if (!uuid) {
1622 uuid = tmp_uuid;
1623 generate_random_uuid(uuid);
1624 } else {
1625 static DEFINE_SPINLOCK(bootid_spinlock);
1626
1627 spin_lock(&bootid_spinlock);
1628 if (!uuid[8])
1629 generate_random_uuid(uuid);
1630 spin_unlock(&bootid_spinlock);
1631 }
1632
1633 snprintf(uuid_string, sizeof(uuid_string), "%pU", uuid);
1634 return proc_dostring(&fake_table, 0, buf, lenp, ppos);
1635}
1636
1637/* The same as proc_dointvec, but writes don't change anything. */
1638static int proc_do_rointvec(struct ctl_table *table, int write, void *buf,
1639 size_t *lenp, loff_t *ppos)
1640{
1641 return write ? 0 : proc_dointvec(table, 0, buf, lenp, ppos);
1642}
1643
1644static struct ctl_table random_table[] = {
1645 {
1646 .procname = "poolsize",
1647 .data = &sysctl_poolsize,
1648 .maxlen = sizeof(int),
1649 .mode = 0444,
1650 .proc_handler = proc_dointvec,
1651 },
1652 {
1653 .procname = "entropy_avail",
1654 .data = &input_pool.init_bits,
1655 .maxlen = sizeof(int),
1656 .mode = 0444,
1657 .proc_handler = proc_dointvec,
1658 },
1659 {
1660 .procname = "write_wakeup_threshold",
1661 .data = &sysctl_random_write_wakeup_bits,
1662 .maxlen = sizeof(int),
1663 .mode = 0644,
1664 .proc_handler = proc_do_rointvec,
1665 },
1666 {
1667 .procname = "urandom_min_reseed_secs",
1668 .data = &sysctl_random_min_urandom_seed,
1669 .maxlen = sizeof(int),
1670 .mode = 0644,
1671 .proc_handler = proc_do_rointvec,
1672 },
1673 {
1674 .procname = "boot_id",
1675 .data = &sysctl_bootid,
1676 .mode = 0444,
1677 .proc_handler = proc_do_uuid,
1678 },
1679 {
1680 .procname = "uuid",
1681 .mode = 0444,
1682 .proc_handler = proc_do_uuid,
1683 },
1684};
1685
1686/*
1687 * random_init() is called before sysctl_init(),
1688 * so we cannot call register_sysctl_init() in random_init()
1689 */
1690static int __init random_sysctls_init(void)
1691{
1692 register_sysctl_init("kernel/random", random_table);
1693 return 0;
1694}
1695device_initcall(random_sysctls_init);
1696#endif
1/*
2 * random.c -- A strong random number generator
3 *
4 * Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All
5 * Rights Reserved.
6 *
7 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
8 *
9 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
10 * rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, and the entire permission notice in its entirety,
17 * including the disclaimer of warranties.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. The name of the author may not be used to endorse or promote
22 * products derived from this software without specific prior
23 * written permission.
24 *
25 * ALTERNATIVELY, this product may be distributed under the terms of
26 * the GNU General Public License, in which case the provisions of the GPL are
27 * required INSTEAD OF the above restrictions. (This clause is
28 * necessary due to a potential bad interaction between the GPL and
29 * the restrictions contained in a BSD-style copyright.)
30 *
31 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
32 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
33 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
34 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
35 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
36 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
37 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
38 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
39 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
41 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
42 * DAMAGE.
43 */
44
45/*
46 * (now, with legal B.S. out of the way.....)
47 *
48 * This routine gathers environmental noise from device drivers, etc.,
49 * and returns good random numbers, suitable for cryptographic use.
50 * Besides the obvious cryptographic uses, these numbers are also good
51 * for seeding TCP sequence numbers, and other places where it is
52 * desirable to have numbers which are not only random, but hard to
53 * predict by an attacker.
54 *
55 * Theory of operation
56 * ===================
57 *
58 * Computers are very predictable devices. Hence it is extremely hard
59 * to produce truly random numbers on a computer --- as opposed to
60 * pseudo-random numbers, which can easily generated by using a
61 * algorithm. Unfortunately, it is very easy for attackers to guess
62 * the sequence of pseudo-random number generators, and for some
63 * applications this is not acceptable. So instead, we must try to
64 * gather "environmental noise" from the computer's environment, which
65 * must be hard for outside attackers to observe, and use that to
66 * generate random numbers. In a Unix environment, this is best done
67 * from inside the kernel.
68 *
69 * Sources of randomness from the environment include inter-keyboard
70 * timings, inter-interrupt timings from some interrupts, and other
71 * events which are both (a) non-deterministic and (b) hard for an
72 * outside observer to measure. Randomness from these sources are
73 * added to an "entropy pool", which is mixed using a CRC-like function.
74 * This is not cryptographically strong, but it is adequate assuming
75 * the randomness is not chosen maliciously, and it is fast enough that
76 * the overhead of doing it on every interrupt is very reasonable.
77 * As random bytes are mixed into the entropy pool, the routines keep
78 * an *estimate* of how many bits of randomness have been stored into
79 * the random number generator's internal state.
80 *
81 * When random bytes are desired, they are obtained by taking the SHA
82 * hash of the contents of the "entropy pool". The SHA hash avoids
83 * exposing the internal state of the entropy pool. It is believed to
84 * be computationally infeasible to derive any useful information
85 * about the input of SHA from its output. Even if it is possible to
86 * analyze SHA in some clever way, as long as the amount of data
87 * returned from the generator is less than the inherent entropy in
88 * the pool, the output data is totally unpredictable. For this
89 * reason, the routine decreases its internal estimate of how many
90 * bits of "true randomness" are contained in the entropy pool as it
91 * outputs random numbers.
92 *
93 * If this estimate goes to zero, the routine can still generate
94 * random numbers; however, an attacker may (at least in theory) be
95 * able to infer the future output of the generator from prior
96 * outputs. This requires successful cryptanalysis of SHA, which is
97 * not believed to be feasible, but there is a remote possibility.
98 * Nonetheless, these numbers should be useful for the vast majority
99 * of purposes.
100 *
101 * Exported interfaces ---- output
102 * ===============================
103 *
104 * There are four exported interfaces; two for use within the kernel,
105 * and two or use from userspace.
106 *
107 * Exported interfaces ---- userspace output
108 * -----------------------------------------
109 *
110 * The userspace interfaces are two character devices /dev/random and
111 * /dev/urandom. /dev/random is suitable for use when very high
112 * quality randomness is desired (for example, for key generation or
113 * one-time pads), as it will only return a maximum of the number of
114 * bits of randomness (as estimated by the random number generator)
115 * contained in the entropy pool.
116 *
117 * The /dev/urandom device does not have this limit, and will return
118 * as many bytes as are requested. As more and more random bytes are
119 * requested without giving time for the entropy pool to recharge,
120 * this will result in random numbers that are merely cryptographically
121 * strong. For many applications, however, this is acceptable.
122 *
123 * Exported interfaces ---- kernel output
124 * --------------------------------------
125 *
126 * The primary kernel interface is
127 *
128 * void get_random_bytes(void *buf, int nbytes);
129 *
130 * This interface will return the requested number of random bytes,
131 * and place it in the requested buffer. This is equivalent to a
132 * read from /dev/urandom.
133 *
134 * For less critical applications, there are the functions:
135 *
136 * u32 get_random_u32()
137 * u64 get_random_u64()
138 * unsigned int get_random_int()
139 * unsigned long get_random_long()
140 *
141 * These are produced by a cryptographic RNG seeded from get_random_bytes,
142 * and so do not deplete the entropy pool as much. These are recommended
143 * for most in-kernel operations *if the result is going to be stored in
144 * the kernel*.
145 *
146 * Specifically, the get_random_int() family do not attempt to do
147 * "anti-backtracking". If you capture the state of the kernel (e.g.
148 * by snapshotting the VM), you can figure out previous get_random_int()
149 * return values. But if the value is stored in the kernel anyway,
150 * this is not a problem.
151 *
152 * It *is* safe to expose get_random_int() output to attackers (e.g. as
153 * network cookies); given outputs 1..n, it's not feasible to predict
154 * outputs 0 or n+1. The only concern is an attacker who breaks into
155 * the kernel later; the get_random_int() engine is not reseeded as
156 * often as the get_random_bytes() one.
157 *
158 * get_random_bytes() is needed for keys that need to stay secret after
159 * they are erased from the kernel. For example, any key that will
160 * be wrapped and stored encrypted. And session encryption keys: we'd
161 * like to know that after the session is closed and the keys erased,
162 * the plaintext is unrecoverable to someone who recorded the ciphertext.
163 *
164 * But for network ports/cookies, stack canaries, PRNG seeds, address
165 * space layout randomization, session *authentication* keys, or other
166 * applications where the sensitive data is stored in the kernel in
167 * plaintext for as long as it's sensitive, the get_random_int() family
168 * is just fine.
169 *
170 * Consider ASLR. We want to keep the address space secret from an
171 * outside attacker while the process is running, but once the address
172 * space is torn down, it's of no use to an attacker any more. And it's
173 * stored in kernel data structures as long as it's alive, so worrying
174 * about an attacker's ability to extrapolate it from the get_random_int()
175 * CRNG is silly.
176 *
177 * Even some cryptographic keys are safe to generate with get_random_int().
178 * In particular, keys for SipHash are generally fine. Here, knowledge
179 * of the key authorizes you to do something to a kernel object (inject
180 * packets to a network connection, or flood a hash table), and the
181 * key is stored with the object being protected. Once it goes away,
182 * we no longer care if anyone knows the key.
183 *
184 * prandom_u32()
185 * -------------
186 *
187 * For even weaker applications, see the pseudorandom generator
188 * prandom_u32(), prandom_max(), and prandom_bytes(). If the random
189 * numbers aren't security-critical at all, these are *far* cheaper.
190 * Useful for self-tests, random error simulation, randomized backoffs,
191 * and any other application where you trust that nobody is trying to
192 * maliciously mess with you by guessing the "random" numbers.
193 *
194 * Exported interfaces ---- input
195 * ==============================
196 *
197 * The current exported interfaces for gathering environmental noise
198 * from the devices are:
199 *
200 * void add_device_randomness(const void *buf, unsigned int size);
201 * void add_input_randomness(unsigned int type, unsigned int code,
202 * unsigned int value);
203 * void add_interrupt_randomness(int irq, int irq_flags);
204 * void add_disk_randomness(struct gendisk *disk);
205 *
206 * add_device_randomness() is for adding data to the random pool that
207 * is likely to differ between two devices (or possibly even per boot).
208 * This would be things like MAC addresses or serial numbers, or the
209 * read-out of the RTC. This does *not* add any actual entropy to the
210 * pool, but it initializes the pool to different values for devices
211 * that might otherwise be identical and have very little entropy
212 * available to them (particularly common in the embedded world).
213 *
214 * add_input_randomness() uses the input layer interrupt timing, as well as
215 * the event type information from the hardware.
216 *
217 * add_interrupt_randomness() uses the interrupt timing as random
218 * inputs to the entropy pool. Using the cycle counters and the irq source
219 * as inputs, it feeds the randomness roughly once a second.
220 *
221 * add_disk_randomness() uses what amounts to the seek time of block
222 * layer request events, on a per-disk_devt basis, as input to the
223 * entropy pool. Note that high-speed solid state drives with very low
224 * seek times do not make for good sources of entropy, as their seek
225 * times are usually fairly consistent.
226 *
227 * All of these routines try to estimate how many bits of randomness a
228 * particular randomness source. They do this by keeping track of the
229 * first and second order deltas of the event timings.
230 *
231 * Ensuring unpredictability at system startup
232 * ============================================
233 *
234 * When any operating system starts up, it will go through a sequence
235 * of actions that are fairly predictable by an adversary, especially
236 * if the start-up does not involve interaction with a human operator.
237 * This reduces the actual number of bits of unpredictability in the
238 * entropy pool below the value in entropy_count. In order to
239 * counteract this effect, it helps to carry information in the
240 * entropy pool across shut-downs and start-ups. To do this, put the
241 * following lines an appropriate script which is run during the boot
242 * sequence:
243 *
244 * echo "Initializing random number generator..."
245 * random_seed=/var/run/random-seed
246 * # Carry a random seed from start-up to start-up
247 * # Load and then save the whole entropy pool
248 * if [ -f $random_seed ]; then
249 * cat $random_seed >/dev/urandom
250 * else
251 * touch $random_seed
252 * fi
253 * chmod 600 $random_seed
254 * dd if=/dev/urandom of=$random_seed count=1 bs=512
255 *
256 * and the following lines in an appropriate script which is run as
257 * the system is shutdown:
258 *
259 * # Carry a random seed from shut-down to start-up
260 * # Save the whole entropy pool
261 * echo "Saving random seed..."
262 * random_seed=/var/run/random-seed
263 * touch $random_seed
264 * chmod 600 $random_seed
265 * dd if=/dev/urandom of=$random_seed count=1 bs=512
266 *
267 * For example, on most modern systems using the System V init
268 * scripts, such code fragments would be found in
269 * /etc/rc.d/init.d/random. On older Linux systems, the correct script
270 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
271 *
272 * Effectively, these commands cause the contents of the entropy pool
273 * to be saved at shut-down time and reloaded into the entropy pool at
274 * start-up. (The 'dd' in the addition to the bootup script is to
275 * make sure that /etc/random-seed is different for every start-up,
276 * even if the system crashes without executing rc.0.) Even with
277 * complete knowledge of the start-up activities, predicting the state
278 * of the entropy pool requires knowledge of the previous history of
279 * the system.
280 *
281 * Configuring the /dev/random driver under Linux
282 * ==============================================
283 *
284 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
285 * the /dev/mem major number (#1). So if your system does not have
286 * /dev/random and /dev/urandom created already, they can be created
287 * by using the commands:
288 *
289 * mknod /dev/random c 1 8
290 * mknod /dev/urandom c 1 9
291 *
292 * Acknowledgements:
293 * =================
294 *
295 * Ideas for constructing this random number generator were derived
296 * from Pretty Good Privacy's random number generator, and from private
297 * discussions with Phil Karn. Colin Plumb provided a faster random
298 * number generator, which speed up the mixing function of the entropy
299 * pool, taken from PGPfone. Dale Worley has also contributed many
300 * useful ideas and suggestions to improve this driver.
301 *
302 * Any flaws in the design are solely my responsibility, and should
303 * not be attributed to the Phil, Colin, or any of authors of PGP.
304 *
305 * Further background information on this topic may be obtained from
306 * RFC 1750, "Randomness Recommendations for Security", by Donald
307 * Eastlake, Steve Crocker, and Jeff Schiller.
308 */
309
310#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
311
312#include <linux/utsname.h>
313#include <linux/module.h>
314#include <linux/kernel.h>
315#include <linux/major.h>
316#include <linux/string.h>
317#include <linux/fcntl.h>
318#include <linux/slab.h>
319#include <linux/random.h>
320#include <linux/poll.h>
321#include <linux/init.h>
322#include <linux/fs.h>
323#include <linux/genhd.h>
324#include <linux/interrupt.h>
325#include <linux/mm.h>
326#include <linux/nodemask.h>
327#include <linux/spinlock.h>
328#include <linux/kthread.h>
329#include <linux/percpu.h>
330#include <linux/fips.h>
331#include <linux/ptrace.h>
332#include <linux/workqueue.h>
333#include <linux/irq.h>
334#include <linux/ratelimit.h>
335#include <linux/syscalls.h>
336#include <linux/completion.h>
337#include <linux/uuid.h>
338#include <crypto/chacha.h>
339#include <crypto/sha1.h>
340
341#include <asm/processor.h>
342#include <linux/uaccess.h>
343#include <asm/irq.h>
344#include <asm/irq_regs.h>
345#include <asm/io.h>
346
347#define CREATE_TRACE_POINTS
348#include <trace/events/random.h>
349
350/* #define ADD_INTERRUPT_BENCH */
351
352/*
353 * Configuration information
354 */
355#define INPUT_POOL_SHIFT 12
356#define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
357#define OUTPUT_POOL_SHIFT 10
358#define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
359#define EXTRACT_SIZE 10
360
361
362#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
363
364/*
365 * To allow fractional bits to be tracked, the entropy_count field is
366 * denominated in units of 1/8th bits.
367 *
368 * 2*(ENTROPY_SHIFT + poolbitshift) must <= 31, or the multiply in
369 * credit_entropy_bits() needs to be 64 bits wide.
370 */
371#define ENTROPY_SHIFT 3
372#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
373
374/*
375 * If the entropy count falls under this number of bits, then we
376 * should wake up processes which are selecting or polling on write
377 * access to /dev/random.
378 */
379static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
380
381/*
382 * Originally, we used a primitive polynomial of degree .poolwords
383 * over GF(2). The taps for various sizes are defined below. They
384 * were chosen to be evenly spaced except for the last tap, which is 1
385 * to get the twisting happening as fast as possible.
386 *
387 * For the purposes of better mixing, we use the CRC-32 polynomial as
388 * well to make a (modified) twisted Generalized Feedback Shift
389 * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
390 * generators. ACM Transactions on Modeling and Computer Simulation
391 * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
392 * GFSR generators II. ACM Transactions on Modeling and Computer
393 * Simulation 4:254-266)
394 *
395 * Thanks to Colin Plumb for suggesting this.
396 *
397 * The mixing operation is much less sensitive than the output hash,
398 * where we use SHA-1. All that we want of mixing operation is that
399 * it be a good non-cryptographic hash; i.e. it not produce collisions
400 * when fed "random" data of the sort we expect to see. As long as
401 * the pool state differs for different inputs, we have preserved the
402 * input entropy and done a good job. The fact that an intelligent
403 * attacker can construct inputs that will produce controlled
404 * alterations to the pool's state is not important because we don't
405 * consider such inputs to contribute any randomness. The only
406 * property we need with respect to them is that the attacker can't
407 * increase his/her knowledge of the pool's state. Since all
408 * additions are reversible (knowing the final state and the input,
409 * you can reconstruct the initial state), if an attacker has any
410 * uncertainty about the initial state, he/she can only shuffle that
411 * uncertainty about, but never cause any collisions (which would
412 * decrease the uncertainty).
413 *
414 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
415 * Videau in their paper, "The Linux Pseudorandom Number Generator
416 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
417 * paper, they point out that we are not using a true Twisted GFSR,
418 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
419 * is, with only three taps, instead of the six that we are using).
420 * As a result, the resulting polynomial is neither primitive nor
421 * irreducible, and hence does not have a maximal period over
422 * GF(2**32). They suggest a slight change to the generator
423 * polynomial which improves the resulting TGFSR polynomial to be
424 * irreducible, which we have made here.
425 */
426static const struct poolinfo {
427 int poolbitshift, poolwords, poolbytes, poolfracbits;
428#define S(x) ilog2(x)+5, (x), (x)*4, (x) << (ENTROPY_SHIFT+5)
429 int tap1, tap2, tap3, tap4, tap5;
430} poolinfo_table[] = {
431 /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
432 /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
433 { S(128), 104, 76, 51, 25, 1 },
434};
435
436/*
437 * Static global variables
438 */
439static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
440static struct fasync_struct *fasync;
441
442static DEFINE_SPINLOCK(random_ready_list_lock);
443static LIST_HEAD(random_ready_list);
444
445struct crng_state {
446 __u32 state[16];
447 unsigned long init_time;
448 spinlock_t lock;
449};
450
451static struct crng_state primary_crng = {
452 .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
453};
454
455/*
456 * crng_init = 0 --> Uninitialized
457 * 1 --> Initialized
458 * 2 --> Initialized from input_pool
459 *
460 * crng_init is protected by primary_crng->lock, and only increases
461 * its value (from 0->1->2).
462 */
463static int crng_init = 0;
464#define crng_ready() (likely(crng_init > 1))
465static int crng_init_cnt = 0;
466static unsigned long crng_global_init_time = 0;
467#define CRNG_INIT_CNT_THRESH (2*CHACHA_KEY_SIZE)
468static void _extract_crng(struct crng_state *crng, __u8 out[CHACHA_BLOCK_SIZE]);
469static void _crng_backtrack_protect(struct crng_state *crng,
470 __u8 tmp[CHACHA_BLOCK_SIZE], int used);
471static void process_random_ready_list(void);
472static void _get_random_bytes(void *buf, int nbytes);
473
474static struct ratelimit_state unseeded_warning =
475 RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
476static struct ratelimit_state urandom_warning =
477 RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
478
479static int ratelimit_disable __read_mostly;
480
481module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
482MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
483
484/**********************************************************************
485 *
486 * OS independent entropy store. Here are the functions which handle
487 * storing entropy in an entropy pool.
488 *
489 **********************************************************************/
490
491struct entropy_store;
492struct entropy_store {
493 /* read-only data: */
494 const struct poolinfo *poolinfo;
495 __u32 *pool;
496 const char *name;
497
498 /* read-write data: */
499 spinlock_t lock;
500 unsigned short add_ptr;
501 unsigned short input_rotate;
502 int entropy_count;
503 unsigned int last_data_init:1;
504 __u8 last_data[EXTRACT_SIZE];
505};
506
507static ssize_t extract_entropy(struct entropy_store *r, void *buf,
508 size_t nbytes, int min, int rsvd);
509static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
510 size_t nbytes, int fips);
511
512static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
513static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy;
514
515static struct entropy_store input_pool = {
516 .poolinfo = &poolinfo_table[0],
517 .name = "input",
518 .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
519 .pool = input_pool_data
520};
521
522static __u32 const twist_table[8] = {
523 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
524 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
525
526/*
527 * This function adds bytes into the entropy "pool". It does not
528 * update the entropy estimate. The caller should call
529 * credit_entropy_bits if this is appropriate.
530 *
531 * The pool is stirred with a primitive polynomial of the appropriate
532 * degree, and then twisted. We twist by three bits at a time because
533 * it's cheap to do so and helps slightly in the expected case where
534 * the entropy is concentrated in the low-order bits.
535 */
536static void _mix_pool_bytes(struct entropy_store *r, const void *in,
537 int nbytes)
538{
539 unsigned long i, tap1, tap2, tap3, tap4, tap5;
540 int input_rotate;
541 int wordmask = r->poolinfo->poolwords - 1;
542 const char *bytes = in;
543 __u32 w;
544
545 tap1 = r->poolinfo->tap1;
546 tap2 = r->poolinfo->tap2;
547 tap3 = r->poolinfo->tap3;
548 tap4 = r->poolinfo->tap4;
549 tap5 = r->poolinfo->tap5;
550
551 input_rotate = r->input_rotate;
552 i = r->add_ptr;
553
554 /* mix one byte at a time to simplify size handling and churn faster */
555 while (nbytes--) {
556 w = rol32(*bytes++, input_rotate);
557 i = (i - 1) & wordmask;
558
559 /* XOR in the various taps */
560 w ^= r->pool[i];
561 w ^= r->pool[(i + tap1) & wordmask];
562 w ^= r->pool[(i + tap2) & wordmask];
563 w ^= r->pool[(i + tap3) & wordmask];
564 w ^= r->pool[(i + tap4) & wordmask];
565 w ^= r->pool[(i + tap5) & wordmask];
566
567 /* Mix the result back in with a twist */
568 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
569
570 /*
571 * Normally, we add 7 bits of rotation to the pool.
572 * At the beginning of the pool, add an extra 7 bits
573 * rotation, so that successive passes spread the
574 * input bits across the pool evenly.
575 */
576 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
577 }
578
579 r->input_rotate = input_rotate;
580 r->add_ptr = i;
581}
582
583static void __mix_pool_bytes(struct entropy_store *r, const void *in,
584 int nbytes)
585{
586 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
587 _mix_pool_bytes(r, in, nbytes);
588}
589
590static void mix_pool_bytes(struct entropy_store *r, const void *in,
591 int nbytes)
592{
593 unsigned long flags;
594
595 trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
596 spin_lock_irqsave(&r->lock, flags);
597 _mix_pool_bytes(r, in, nbytes);
598 spin_unlock_irqrestore(&r->lock, flags);
599}
600
601struct fast_pool {
602 __u32 pool[4];
603 unsigned long last;
604 unsigned short reg_idx;
605 unsigned char count;
606};
607
608/*
609 * This is a fast mixing routine used by the interrupt randomness
610 * collector. It's hardcoded for an 128 bit pool and assumes that any
611 * locks that might be needed are taken by the caller.
612 */
613static void fast_mix(struct fast_pool *f)
614{
615 __u32 a = f->pool[0], b = f->pool[1];
616 __u32 c = f->pool[2], d = f->pool[3];
617
618 a += b; c += d;
619 b = rol32(b, 6); d = rol32(d, 27);
620 d ^= a; b ^= c;
621
622 a += b; c += d;
623 b = rol32(b, 16); d = rol32(d, 14);
624 d ^= a; b ^= c;
625
626 a += b; c += d;
627 b = rol32(b, 6); d = rol32(d, 27);
628 d ^= a; b ^= c;
629
630 a += b; c += d;
631 b = rol32(b, 16); d = rol32(d, 14);
632 d ^= a; b ^= c;
633
634 f->pool[0] = a; f->pool[1] = b;
635 f->pool[2] = c; f->pool[3] = d;
636 f->count++;
637}
638
639static void process_random_ready_list(void)
640{
641 unsigned long flags;
642 struct random_ready_callback *rdy, *tmp;
643
644 spin_lock_irqsave(&random_ready_list_lock, flags);
645 list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
646 struct module *owner = rdy->owner;
647
648 list_del_init(&rdy->list);
649 rdy->func(rdy);
650 module_put(owner);
651 }
652 spin_unlock_irqrestore(&random_ready_list_lock, flags);
653}
654
655/*
656 * Credit (or debit) the entropy store with n bits of entropy.
657 * Use credit_entropy_bits_safe() if the value comes from userspace
658 * or otherwise should be checked for extreme values.
659 */
660static void credit_entropy_bits(struct entropy_store *r, int nbits)
661{
662 int entropy_count, orig;
663 const int pool_size = r->poolinfo->poolfracbits;
664 int nfrac = nbits << ENTROPY_SHIFT;
665
666 if (!nbits)
667 return;
668
669retry:
670 entropy_count = orig = READ_ONCE(r->entropy_count);
671 if (nfrac < 0) {
672 /* Debit */
673 entropy_count += nfrac;
674 } else {
675 /*
676 * Credit: we have to account for the possibility of
677 * overwriting already present entropy. Even in the
678 * ideal case of pure Shannon entropy, new contributions
679 * approach the full value asymptotically:
680 *
681 * entropy <- entropy + (pool_size - entropy) *
682 * (1 - exp(-add_entropy/pool_size))
683 *
684 * For add_entropy <= pool_size/2 then
685 * (1 - exp(-add_entropy/pool_size)) >=
686 * (add_entropy/pool_size)*0.7869...
687 * so we can approximate the exponential with
688 * 3/4*add_entropy/pool_size and still be on the
689 * safe side by adding at most pool_size/2 at a time.
690 *
691 * The use of pool_size-2 in the while statement is to
692 * prevent rounding artifacts from making the loop
693 * arbitrarily long; this limits the loop to log2(pool_size)*2
694 * turns no matter how large nbits is.
695 */
696 int pnfrac = nfrac;
697 const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
698 /* The +2 corresponds to the /4 in the denominator */
699
700 do {
701 unsigned int anfrac = min(pnfrac, pool_size/2);
702 unsigned int add =
703 ((pool_size - entropy_count)*anfrac*3) >> s;
704
705 entropy_count += add;
706 pnfrac -= anfrac;
707 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
708 }
709
710 if (WARN_ON(entropy_count < 0)) {
711 pr_warn("negative entropy/overflow: pool %s count %d\n",
712 r->name, entropy_count);
713 entropy_count = 0;
714 } else if (entropy_count > pool_size)
715 entropy_count = pool_size;
716 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
717 goto retry;
718
719 trace_credit_entropy_bits(r->name, nbits,
720 entropy_count >> ENTROPY_SHIFT, _RET_IP_);
721
722 if (r == &input_pool) {
723 int entropy_bits = entropy_count >> ENTROPY_SHIFT;
724
725 if (crng_init < 2 && entropy_bits >= 128)
726 crng_reseed(&primary_crng, r);
727 }
728}
729
730static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
731{
732 const int nbits_max = r->poolinfo->poolwords * 32;
733
734 if (nbits < 0)
735 return -EINVAL;
736
737 /* Cap the value to avoid overflows */
738 nbits = min(nbits, nbits_max);
739
740 credit_entropy_bits(r, nbits);
741 return 0;
742}
743
744/*********************************************************************
745 *
746 * CRNG using CHACHA20
747 *
748 *********************************************************************/
749
750#define CRNG_RESEED_INTERVAL (300*HZ)
751
752static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
753
754#ifdef CONFIG_NUMA
755/*
756 * Hack to deal with crazy userspace progams when they are all trying
757 * to access /dev/urandom in parallel. The programs are almost
758 * certainly doing something terribly wrong, but we'll work around
759 * their brain damage.
760 */
761static struct crng_state **crng_node_pool __read_mostly;
762#endif
763
764static void invalidate_batched_entropy(void);
765static void numa_crng_init(void);
766
767static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
768static int __init parse_trust_cpu(char *arg)
769{
770 return kstrtobool(arg, &trust_cpu);
771}
772early_param("random.trust_cpu", parse_trust_cpu);
773
774static bool crng_init_try_arch(struct crng_state *crng)
775{
776 int i;
777 bool arch_init = true;
778 unsigned long rv;
779
780 for (i = 4; i < 16; i++) {
781 if (!arch_get_random_seed_long(&rv) &&
782 !arch_get_random_long(&rv)) {
783 rv = random_get_entropy();
784 arch_init = false;
785 }
786 crng->state[i] ^= rv;
787 }
788
789 return arch_init;
790}
791
792static bool __init crng_init_try_arch_early(struct crng_state *crng)
793{
794 int i;
795 bool arch_init = true;
796 unsigned long rv;
797
798 for (i = 4; i < 16; i++) {
799 if (!arch_get_random_seed_long_early(&rv) &&
800 !arch_get_random_long_early(&rv)) {
801 rv = random_get_entropy();
802 arch_init = false;
803 }
804 crng->state[i] ^= rv;
805 }
806
807 return arch_init;
808}
809
810static void __maybe_unused crng_initialize_secondary(struct crng_state *crng)
811{
812 chacha_init_consts(crng->state);
813 _get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
814 crng_init_try_arch(crng);
815 crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
816}
817
818static void __init crng_initialize_primary(struct crng_state *crng)
819{
820 chacha_init_consts(crng->state);
821 _extract_entropy(&input_pool, &crng->state[4], sizeof(__u32) * 12, 0);
822 if (crng_init_try_arch_early(crng) && trust_cpu) {
823 invalidate_batched_entropy();
824 numa_crng_init();
825 crng_init = 2;
826 pr_notice("crng done (trusting CPU's manufacturer)\n");
827 }
828 crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
829}
830
831#ifdef CONFIG_NUMA
832static void do_numa_crng_init(struct work_struct *work)
833{
834 int i;
835 struct crng_state *crng;
836 struct crng_state **pool;
837
838 pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
839 for_each_online_node(i) {
840 crng = kmalloc_node(sizeof(struct crng_state),
841 GFP_KERNEL | __GFP_NOFAIL, i);
842 spin_lock_init(&crng->lock);
843 crng_initialize_secondary(crng);
844 pool[i] = crng;
845 }
846 mb();
847 if (cmpxchg(&crng_node_pool, NULL, pool)) {
848 for_each_node(i)
849 kfree(pool[i]);
850 kfree(pool);
851 }
852}
853
854static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init);
855
856static void numa_crng_init(void)
857{
858 schedule_work(&numa_crng_init_work);
859}
860#else
861static void numa_crng_init(void) {}
862#endif
863
864/*
865 * crng_fast_load() can be called by code in the interrupt service
866 * path. So we can't afford to dilly-dally.
867 */
868static int crng_fast_load(const char *cp, size_t len)
869{
870 unsigned long flags;
871 char *p;
872
873 if (!spin_trylock_irqsave(&primary_crng.lock, flags))
874 return 0;
875 if (crng_init != 0) {
876 spin_unlock_irqrestore(&primary_crng.lock, flags);
877 return 0;
878 }
879 p = (unsigned char *) &primary_crng.state[4];
880 while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
881 p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp;
882 cp++; crng_init_cnt++; len--;
883 }
884 spin_unlock_irqrestore(&primary_crng.lock, flags);
885 if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
886 invalidate_batched_entropy();
887 crng_init = 1;
888 pr_notice("fast init done\n");
889 }
890 return 1;
891}
892
893/*
894 * crng_slow_load() is called by add_device_randomness, which has two
895 * attributes. (1) We can't trust the buffer passed to it is
896 * guaranteed to be unpredictable (so it might not have any entropy at
897 * all), and (2) it doesn't have the performance constraints of
898 * crng_fast_load().
899 *
900 * So we do something more comprehensive which is guaranteed to touch
901 * all of the primary_crng's state, and which uses a LFSR with a
902 * period of 255 as part of the mixing algorithm. Finally, we do
903 * *not* advance crng_init_cnt since buffer we may get may be something
904 * like a fixed DMI table (for example), which might very well be
905 * unique to the machine, but is otherwise unvarying.
906 */
907static int crng_slow_load(const char *cp, size_t len)
908{
909 unsigned long flags;
910 static unsigned char lfsr = 1;
911 unsigned char tmp;
912 unsigned i, max = CHACHA_KEY_SIZE;
913 const char * src_buf = cp;
914 char * dest_buf = (char *) &primary_crng.state[4];
915
916 if (!spin_trylock_irqsave(&primary_crng.lock, flags))
917 return 0;
918 if (crng_init != 0) {
919 spin_unlock_irqrestore(&primary_crng.lock, flags);
920 return 0;
921 }
922 if (len > max)
923 max = len;
924
925 for (i = 0; i < max ; i++) {
926 tmp = lfsr;
927 lfsr >>= 1;
928 if (tmp & 1)
929 lfsr ^= 0xE1;
930 tmp = dest_buf[i % CHACHA_KEY_SIZE];
931 dest_buf[i % CHACHA_KEY_SIZE] ^= src_buf[i % len] ^ lfsr;
932 lfsr += (tmp << 3) | (tmp >> 5);
933 }
934 spin_unlock_irqrestore(&primary_crng.lock, flags);
935 return 1;
936}
937
938static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
939{
940 unsigned long flags;
941 int i, num;
942 union {
943 __u8 block[CHACHA_BLOCK_SIZE];
944 __u32 key[8];
945 } buf;
946
947 if (r) {
948 num = extract_entropy(r, &buf, 32, 16, 0);
949 if (num == 0)
950 return;
951 } else {
952 _extract_crng(&primary_crng, buf.block);
953 _crng_backtrack_protect(&primary_crng, buf.block,
954 CHACHA_KEY_SIZE);
955 }
956 spin_lock_irqsave(&crng->lock, flags);
957 for (i = 0; i < 8; i++) {
958 unsigned long rv;
959 if (!arch_get_random_seed_long(&rv) &&
960 !arch_get_random_long(&rv))
961 rv = random_get_entropy();
962 crng->state[i+4] ^= buf.key[i] ^ rv;
963 }
964 memzero_explicit(&buf, sizeof(buf));
965 crng->init_time = jiffies;
966 spin_unlock_irqrestore(&crng->lock, flags);
967 if (crng == &primary_crng && crng_init < 2) {
968 invalidate_batched_entropy();
969 numa_crng_init();
970 crng_init = 2;
971 process_random_ready_list();
972 wake_up_interruptible(&crng_init_wait);
973 kill_fasync(&fasync, SIGIO, POLL_IN);
974 pr_notice("crng init done\n");
975 if (unseeded_warning.missed) {
976 pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n",
977 unseeded_warning.missed);
978 unseeded_warning.missed = 0;
979 }
980 if (urandom_warning.missed) {
981 pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
982 urandom_warning.missed);
983 urandom_warning.missed = 0;
984 }
985 }
986}
987
988static void _extract_crng(struct crng_state *crng,
989 __u8 out[CHACHA_BLOCK_SIZE])
990{
991 unsigned long v, flags;
992
993 if (crng_ready() &&
994 (time_after(crng_global_init_time, crng->init_time) ||
995 time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
996 crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
997 spin_lock_irqsave(&crng->lock, flags);
998 if (arch_get_random_long(&v))
999 crng->state[14] ^= v;
1000 chacha20_block(&crng->state[0], out);
1001 if (crng->state[12] == 0)
1002 crng->state[13]++;
1003 spin_unlock_irqrestore(&crng->lock, flags);
1004}
1005
1006static void extract_crng(__u8 out[CHACHA_BLOCK_SIZE])
1007{
1008 struct crng_state *crng = NULL;
1009
1010#ifdef CONFIG_NUMA
1011 if (crng_node_pool)
1012 crng = crng_node_pool[numa_node_id()];
1013 if (crng == NULL)
1014#endif
1015 crng = &primary_crng;
1016 _extract_crng(crng, out);
1017}
1018
1019/*
1020 * Use the leftover bytes from the CRNG block output (if there is
1021 * enough) to mutate the CRNG key to provide backtracking protection.
1022 */
1023static void _crng_backtrack_protect(struct crng_state *crng,
1024 __u8 tmp[CHACHA_BLOCK_SIZE], int used)
1025{
1026 unsigned long flags;
1027 __u32 *s, *d;
1028 int i;
1029
1030 used = round_up(used, sizeof(__u32));
1031 if (used + CHACHA_KEY_SIZE > CHACHA_BLOCK_SIZE) {
1032 extract_crng(tmp);
1033 used = 0;
1034 }
1035 spin_lock_irqsave(&crng->lock, flags);
1036 s = (__u32 *) &tmp[used];
1037 d = &crng->state[4];
1038 for (i=0; i < 8; i++)
1039 *d++ ^= *s++;
1040 spin_unlock_irqrestore(&crng->lock, flags);
1041}
1042
1043static void crng_backtrack_protect(__u8 tmp[CHACHA_BLOCK_SIZE], int used)
1044{
1045 struct crng_state *crng = NULL;
1046
1047#ifdef CONFIG_NUMA
1048 if (crng_node_pool)
1049 crng = crng_node_pool[numa_node_id()];
1050 if (crng == NULL)
1051#endif
1052 crng = &primary_crng;
1053 _crng_backtrack_protect(crng, tmp, used);
1054}
1055
1056static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
1057{
1058 ssize_t ret = 0, i = CHACHA_BLOCK_SIZE;
1059 __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1060 int large_request = (nbytes > 256);
1061
1062 while (nbytes) {
1063 if (large_request && need_resched()) {
1064 if (signal_pending(current)) {
1065 if (ret == 0)
1066 ret = -ERESTARTSYS;
1067 break;
1068 }
1069 schedule();
1070 }
1071
1072 extract_crng(tmp);
1073 i = min_t(int, nbytes, CHACHA_BLOCK_SIZE);
1074 if (copy_to_user(buf, tmp, i)) {
1075 ret = -EFAULT;
1076 break;
1077 }
1078
1079 nbytes -= i;
1080 buf += i;
1081 ret += i;
1082 }
1083 crng_backtrack_protect(tmp, i);
1084
1085 /* Wipe data just written to memory */
1086 memzero_explicit(tmp, sizeof(tmp));
1087
1088 return ret;
1089}
1090
1091
1092/*********************************************************************
1093 *
1094 * Entropy input management
1095 *
1096 *********************************************************************/
1097
1098/* There is one of these per entropy source */
1099struct timer_rand_state {
1100 cycles_t last_time;
1101 long last_delta, last_delta2;
1102};
1103
1104#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
1105
1106/*
1107 * Add device- or boot-specific data to the input pool to help
1108 * initialize it.
1109 *
1110 * None of this adds any entropy; it is meant to avoid the problem of
1111 * the entropy pool having similar initial state across largely
1112 * identical devices.
1113 */
1114void add_device_randomness(const void *buf, unsigned int size)
1115{
1116 unsigned long time = random_get_entropy() ^ jiffies;
1117 unsigned long flags;
1118
1119 if (!crng_ready() && size)
1120 crng_slow_load(buf, size);
1121
1122 trace_add_device_randomness(size, _RET_IP_);
1123 spin_lock_irqsave(&input_pool.lock, flags);
1124 _mix_pool_bytes(&input_pool, buf, size);
1125 _mix_pool_bytes(&input_pool, &time, sizeof(time));
1126 spin_unlock_irqrestore(&input_pool.lock, flags);
1127}
1128EXPORT_SYMBOL(add_device_randomness);
1129
1130static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
1131
1132/*
1133 * This function adds entropy to the entropy "pool" by using timing
1134 * delays. It uses the timer_rand_state structure to make an estimate
1135 * of how many bits of entropy this call has added to the pool.
1136 *
1137 * The number "num" is also added to the pool - it should somehow describe
1138 * the type of event which just happened. This is currently 0-255 for
1139 * keyboard scan codes, and 256 upwards for interrupts.
1140 *
1141 */
1142static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
1143{
1144 struct entropy_store *r;
1145 struct {
1146 long jiffies;
1147 unsigned cycles;
1148 unsigned num;
1149 } sample;
1150 long delta, delta2, delta3;
1151
1152 sample.jiffies = jiffies;
1153 sample.cycles = random_get_entropy();
1154 sample.num = num;
1155 r = &input_pool;
1156 mix_pool_bytes(r, &sample, sizeof(sample));
1157
1158 /*
1159 * Calculate number of bits of randomness we probably added.
1160 * We take into account the first, second and third-order deltas
1161 * in order to make our estimate.
1162 */
1163 delta = sample.jiffies - READ_ONCE(state->last_time);
1164 WRITE_ONCE(state->last_time, sample.jiffies);
1165
1166 delta2 = delta - READ_ONCE(state->last_delta);
1167 WRITE_ONCE(state->last_delta, delta);
1168
1169 delta3 = delta2 - READ_ONCE(state->last_delta2);
1170 WRITE_ONCE(state->last_delta2, delta2);
1171
1172 if (delta < 0)
1173 delta = -delta;
1174 if (delta2 < 0)
1175 delta2 = -delta2;
1176 if (delta3 < 0)
1177 delta3 = -delta3;
1178 if (delta > delta2)
1179 delta = delta2;
1180 if (delta > delta3)
1181 delta = delta3;
1182
1183 /*
1184 * delta is now minimum absolute delta.
1185 * Round down by 1 bit on general principles,
1186 * and limit entropy estimate to 12 bits.
1187 */
1188 credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1189}
1190
1191void add_input_randomness(unsigned int type, unsigned int code,
1192 unsigned int value)
1193{
1194 static unsigned char last_value;
1195
1196 /* ignore autorepeat and the like */
1197 if (value == last_value)
1198 return;
1199
1200 last_value = value;
1201 add_timer_randomness(&input_timer_state,
1202 (type << 4) ^ code ^ (code >> 4) ^ value);
1203 trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1204}
1205EXPORT_SYMBOL_GPL(add_input_randomness);
1206
1207static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
1208
1209#ifdef ADD_INTERRUPT_BENCH
1210static unsigned long avg_cycles, avg_deviation;
1211
1212#define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
1213#define FIXED_1_2 (1 << (AVG_SHIFT-1))
1214
1215static void add_interrupt_bench(cycles_t start)
1216{
1217 long delta = random_get_entropy() - start;
1218
1219 /* Use a weighted moving average */
1220 delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
1221 avg_cycles += delta;
1222 /* And average deviation */
1223 delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
1224 avg_deviation += delta;
1225}
1226#else
1227#define add_interrupt_bench(x)
1228#endif
1229
1230static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
1231{
1232 __u32 *ptr = (__u32 *) regs;
1233 unsigned int idx;
1234
1235 if (regs == NULL)
1236 return 0;
1237 idx = READ_ONCE(f->reg_idx);
1238 if (idx >= sizeof(struct pt_regs) / sizeof(__u32))
1239 idx = 0;
1240 ptr += idx++;
1241 WRITE_ONCE(f->reg_idx, idx);
1242 return *ptr;
1243}
1244
1245void add_interrupt_randomness(int irq, int irq_flags)
1246{
1247 struct entropy_store *r;
1248 struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
1249 struct pt_regs *regs = get_irq_regs();
1250 unsigned long now = jiffies;
1251 cycles_t cycles = random_get_entropy();
1252 __u32 c_high, j_high;
1253 __u64 ip;
1254
1255 if (cycles == 0)
1256 cycles = get_reg(fast_pool, regs);
1257 c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
1258 j_high = (sizeof(now) > 4) ? now >> 32 : 0;
1259 fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
1260 fast_pool->pool[1] ^= now ^ c_high;
1261 ip = regs ? instruction_pointer(regs) : _RET_IP_;
1262 fast_pool->pool[2] ^= ip;
1263 fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
1264 get_reg(fast_pool, regs);
1265
1266 fast_mix(fast_pool);
1267 add_interrupt_bench(cycles);
1268
1269 if (unlikely(crng_init == 0)) {
1270 if ((fast_pool->count >= 64) &&
1271 crng_fast_load((char *) fast_pool->pool,
1272 sizeof(fast_pool->pool))) {
1273 fast_pool->count = 0;
1274 fast_pool->last = now;
1275 }
1276 return;
1277 }
1278
1279 if ((fast_pool->count < 64) &&
1280 !time_after(now, fast_pool->last + HZ))
1281 return;
1282
1283 r = &input_pool;
1284 if (!spin_trylock(&r->lock))
1285 return;
1286
1287 fast_pool->last = now;
1288 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
1289 spin_unlock(&r->lock);
1290
1291 fast_pool->count = 0;
1292
1293 /* award one bit for the contents of the fast pool */
1294 credit_entropy_bits(r, 1);
1295}
1296EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1297
1298#ifdef CONFIG_BLOCK
1299void add_disk_randomness(struct gendisk *disk)
1300{
1301 if (!disk || !disk->random)
1302 return;
1303 /* first major is 1, so we get >= 0x200 here */
1304 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1305 trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1306}
1307EXPORT_SYMBOL_GPL(add_disk_randomness);
1308#endif
1309
1310/*********************************************************************
1311 *
1312 * Entropy extraction routines
1313 *
1314 *********************************************************************/
1315
1316/*
1317 * This function decides how many bytes to actually take from the
1318 * given pool, and also debits the entropy count accordingly.
1319 */
1320static size_t account(struct entropy_store *r, size_t nbytes, int min,
1321 int reserved)
1322{
1323 int entropy_count, orig, have_bytes;
1324 size_t ibytes, nfrac;
1325
1326 BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1327
1328 /* Can we pull enough? */
1329retry:
1330 entropy_count = orig = READ_ONCE(r->entropy_count);
1331 ibytes = nbytes;
1332 /* never pull more than available */
1333 have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1334
1335 if ((have_bytes -= reserved) < 0)
1336 have_bytes = 0;
1337 ibytes = min_t(size_t, ibytes, have_bytes);
1338 if (ibytes < min)
1339 ibytes = 0;
1340
1341 if (WARN_ON(entropy_count < 0)) {
1342 pr_warn("negative entropy count: pool %s count %d\n",
1343 r->name, entropy_count);
1344 entropy_count = 0;
1345 }
1346 nfrac = ibytes << (ENTROPY_SHIFT + 3);
1347 if ((size_t) entropy_count > nfrac)
1348 entropy_count -= nfrac;
1349 else
1350 entropy_count = 0;
1351
1352 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1353 goto retry;
1354
1355 trace_debit_entropy(r->name, 8 * ibytes);
1356 if (ibytes && ENTROPY_BITS(r) < random_write_wakeup_bits) {
1357 wake_up_interruptible(&random_write_wait);
1358 kill_fasync(&fasync, SIGIO, POLL_OUT);
1359 }
1360
1361 return ibytes;
1362}
1363
1364/*
1365 * This function does the actual extraction for extract_entropy.
1366 *
1367 * Note: we assume that .poolwords is a multiple of 16 words.
1368 */
1369static void extract_buf(struct entropy_store *r, __u8 *out)
1370{
1371 int i;
1372 union {
1373 __u32 w[5];
1374 unsigned long l[LONGS(20)];
1375 } hash;
1376 __u32 workspace[SHA1_WORKSPACE_WORDS];
1377 unsigned long flags;
1378
1379 /*
1380 * If we have an architectural hardware random number
1381 * generator, use it for SHA's initial vector
1382 */
1383 sha1_init(hash.w);
1384 for (i = 0; i < LONGS(20); i++) {
1385 unsigned long v;
1386 if (!arch_get_random_long(&v))
1387 break;
1388 hash.l[i] = v;
1389 }
1390
1391 /* Generate a hash across the pool, 16 words (512 bits) at a time */
1392 spin_lock_irqsave(&r->lock, flags);
1393 for (i = 0; i < r->poolinfo->poolwords; i += 16)
1394 sha1_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1395
1396 /*
1397 * We mix the hash back into the pool to prevent backtracking
1398 * attacks (where the attacker knows the state of the pool
1399 * plus the current outputs, and attempts to find previous
1400 * ouputs), unless the hash function can be inverted. By
1401 * mixing at least a SHA1 worth of hash data back, we make
1402 * brute-forcing the feedback as hard as brute-forcing the
1403 * hash.
1404 */
1405 __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1406 spin_unlock_irqrestore(&r->lock, flags);
1407
1408 memzero_explicit(workspace, sizeof(workspace));
1409
1410 /*
1411 * In case the hash function has some recognizable output
1412 * pattern, we fold it in half. Thus, we always feed back
1413 * twice as much data as we output.
1414 */
1415 hash.w[0] ^= hash.w[3];
1416 hash.w[1] ^= hash.w[4];
1417 hash.w[2] ^= rol32(hash.w[2], 16);
1418
1419 memcpy(out, &hash, EXTRACT_SIZE);
1420 memzero_explicit(&hash, sizeof(hash));
1421}
1422
1423static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
1424 size_t nbytes, int fips)
1425{
1426 ssize_t ret = 0, i;
1427 __u8 tmp[EXTRACT_SIZE];
1428 unsigned long flags;
1429
1430 while (nbytes) {
1431 extract_buf(r, tmp);
1432
1433 if (fips) {
1434 spin_lock_irqsave(&r->lock, flags);
1435 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1436 panic("Hardware RNG duplicated output!\n");
1437 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1438 spin_unlock_irqrestore(&r->lock, flags);
1439 }
1440 i = min_t(int, nbytes, EXTRACT_SIZE);
1441 memcpy(buf, tmp, i);
1442 nbytes -= i;
1443 buf += i;
1444 ret += i;
1445 }
1446
1447 /* Wipe data just returned from memory */
1448 memzero_explicit(tmp, sizeof(tmp));
1449
1450 return ret;
1451}
1452
1453/*
1454 * This function extracts randomness from the "entropy pool", and
1455 * returns it in a buffer.
1456 *
1457 * The min parameter specifies the minimum amount we can pull before
1458 * failing to avoid races that defeat catastrophic reseeding while the
1459 * reserved parameter indicates how much entropy we must leave in the
1460 * pool after each pull to avoid starving other readers.
1461 */
1462static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1463 size_t nbytes, int min, int reserved)
1464{
1465 __u8 tmp[EXTRACT_SIZE];
1466 unsigned long flags;
1467
1468 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1469 if (fips_enabled) {
1470 spin_lock_irqsave(&r->lock, flags);
1471 if (!r->last_data_init) {
1472 r->last_data_init = 1;
1473 spin_unlock_irqrestore(&r->lock, flags);
1474 trace_extract_entropy(r->name, EXTRACT_SIZE,
1475 ENTROPY_BITS(r), _RET_IP_);
1476 extract_buf(r, tmp);
1477 spin_lock_irqsave(&r->lock, flags);
1478 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1479 }
1480 spin_unlock_irqrestore(&r->lock, flags);
1481 }
1482
1483 trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1484 nbytes = account(r, nbytes, min, reserved);
1485
1486 return _extract_entropy(r, buf, nbytes, fips_enabled);
1487}
1488
1489#define warn_unseeded_randomness(previous) \
1490 _warn_unseeded_randomness(__func__, (void *) _RET_IP_, (previous))
1491
1492static void _warn_unseeded_randomness(const char *func_name, void *caller,
1493 void **previous)
1494{
1495#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1496 const bool print_once = false;
1497#else
1498 static bool print_once __read_mostly;
1499#endif
1500
1501 if (print_once ||
1502 crng_ready() ||
1503 (previous && (caller == READ_ONCE(*previous))))
1504 return;
1505 WRITE_ONCE(*previous, caller);
1506#ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1507 print_once = true;
1508#endif
1509 if (__ratelimit(&unseeded_warning))
1510 printk_deferred(KERN_NOTICE "random: %s called from %pS "
1511 "with crng_init=%d\n", func_name, caller,
1512 crng_init);
1513}
1514
1515/*
1516 * This function is the exported kernel interface. It returns some
1517 * number of good random numbers, suitable for key generation, seeding
1518 * TCP sequence numbers, etc. It does not rely on the hardware random
1519 * number generator. For random bytes direct from the hardware RNG
1520 * (when available), use get_random_bytes_arch(). In order to ensure
1521 * that the randomness provided by this function is okay, the function
1522 * wait_for_random_bytes() should be called and return 0 at least once
1523 * at any point prior.
1524 */
1525static void _get_random_bytes(void *buf, int nbytes)
1526{
1527 __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1528
1529 trace_get_random_bytes(nbytes, _RET_IP_);
1530
1531 while (nbytes >= CHACHA_BLOCK_SIZE) {
1532 extract_crng(buf);
1533 buf += CHACHA_BLOCK_SIZE;
1534 nbytes -= CHACHA_BLOCK_SIZE;
1535 }
1536
1537 if (nbytes > 0) {
1538 extract_crng(tmp);
1539 memcpy(buf, tmp, nbytes);
1540 crng_backtrack_protect(tmp, nbytes);
1541 } else
1542 crng_backtrack_protect(tmp, CHACHA_BLOCK_SIZE);
1543 memzero_explicit(tmp, sizeof(tmp));
1544}
1545
1546void get_random_bytes(void *buf, int nbytes)
1547{
1548 static void *previous;
1549
1550 warn_unseeded_randomness(&previous);
1551 _get_random_bytes(buf, nbytes);
1552}
1553EXPORT_SYMBOL(get_random_bytes);
1554
1555
1556/*
1557 * Each time the timer fires, we expect that we got an unpredictable
1558 * jump in the cycle counter. Even if the timer is running on another
1559 * CPU, the timer activity will be touching the stack of the CPU that is
1560 * generating entropy..
1561 *
1562 * Note that we don't re-arm the timer in the timer itself - we are
1563 * happy to be scheduled away, since that just makes the load more
1564 * complex, but we do not want the timer to keep ticking unless the
1565 * entropy loop is running.
1566 *
1567 * So the re-arming always happens in the entropy loop itself.
1568 */
1569static void entropy_timer(struct timer_list *t)
1570{
1571 credit_entropy_bits(&input_pool, 1);
1572}
1573
1574/*
1575 * If we have an actual cycle counter, see if we can
1576 * generate enough entropy with timing noise
1577 */
1578static void try_to_generate_entropy(void)
1579{
1580 struct {
1581 unsigned long now;
1582 struct timer_list timer;
1583 } stack;
1584
1585 stack.now = random_get_entropy();
1586
1587 /* Slow counter - or none. Don't even bother */
1588 if (stack.now == random_get_entropy())
1589 return;
1590
1591 timer_setup_on_stack(&stack.timer, entropy_timer, 0);
1592 while (!crng_ready()) {
1593 if (!timer_pending(&stack.timer))
1594 mod_timer(&stack.timer, jiffies+1);
1595 mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
1596 schedule();
1597 stack.now = random_get_entropy();
1598 }
1599
1600 del_timer_sync(&stack.timer);
1601 destroy_timer_on_stack(&stack.timer);
1602 mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
1603}
1604
1605/*
1606 * Wait for the urandom pool to be seeded and thus guaranteed to supply
1607 * cryptographically secure random numbers. This applies to: the /dev/urandom
1608 * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
1609 * family of functions. Using any of these functions without first calling
1610 * this function forfeits the guarantee of security.
1611 *
1612 * Returns: 0 if the urandom pool has been seeded.
1613 * -ERESTARTSYS if the function was interrupted by a signal.
1614 */
1615int wait_for_random_bytes(void)
1616{
1617 if (likely(crng_ready()))
1618 return 0;
1619
1620 do {
1621 int ret;
1622 ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
1623 if (ret)
1624 return ret > 0 ? 0 : ret;
1625
1626 try_to_generate_entropy();
1627 } while (!crng_ready());
1628
1629 return 0;
1630}
1631EXPORT_SYMBOL(wait_for_random_bytes);
1632
1633/*
1634 * Returns whether or not the urandom pool has been seeded and thus guaranteed
1635 * to supply cryptographically secure random numbers. This applies to: the
1636 * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
1637 * ,u64,int,long} family of functions.
1638 *
1639 * Returns: true if the urandom pool has been seeded.
1640 * false if the urandom pool has not been seeded.
1641 */
1642bool rng_is_initialized(void)
1643{
1644 return crng_ready();
1645}
1646EXPORT_SYMBOL(rng_is_initialized);
1647
1648/*
1649 * Add a callback function that will be invoked when the nonblocking
1650 * pool is initialised.
1651 *
1652 * returns: 0 if callback is successfully added
1653 * -EALREADY if pool is already initialised (callback not called)
1654 * -ENOENT if module for callback is not alive
1655 */
1656int add_random_ready_callback(struct random_ready_callback *rdy)
1657{
1658 struct module *owner;
1659 unsigned long flags;
1660 int err = -EALREADY;
1661
1662 if (crng_ready())
1663 return err;
1664
1665 owner = rdy->owner;
1666 if (!try_module_get(owner))
1667 return -ENOENT;
1668
1669 spin_lock_irqsave(&random_ready_list_lock, flags);
1670 if (crng_ready())
1671 goto out;
1672
1673 owner = NULL;
1674
1675 list_add(&rdy->list, &random_ready_list);
1676 err = 0;
1677
1678out:
1679 spin_unlock_irqrestore(&random_ready_list_lock, flags);
1680
1681 module_put(owner);
1682
1683 return err;
1684}
1685EXPORT_SYMBOL(add_random_ready_callback);
1686
1687/*
1688 * Delete a previously registered readiness callback function.
1689 */
1690void del_random_ready_callback(struct random_ready_callback *rdy)
1691{
1692 unsigned long flags;
1693 struct module *owner = NULL;
1694
1695 spin_lock_irqsave(&random_ready_list_lock, flags);
1696 if (!list_empty(&rdy->list)) {
1697 list_del_init(&rdy->list);
1698 owner = rdy->owner;
1699 }
1700 spin_unlock_irqrestore(&random_ready_list_lock, flags);
1701
1702 module_put(owner);
1703}
1704EXPORT_SYMBOL(del_random_ready_callback);
1705
1706/*
1707 * This function will use the architecture-specific hardware random
1708 * number generator if it is available. The arch-specific hw RNG will
1709 * almost certainly be faster than what we can do in software, but it
1710 * is impossible to verify that it is implemented securely (as
1711 * opposed, to, say, the AES encryption of a sequence number using a
1712 * key known by the NSA). So it's useful if we need the speed, but
1713 * only if we're willing to trust the hardware manufacturer not to
1714 * have put in a back door.
1715 *
1716 * Return number of bytes filled in.
1717 */
1718int __must_check get_random_bytes_arch(void *buf, int nbytes)
1719{
1720 int left = nbytes;
1721 char *p = buf;
1722
1723 trace_get_random_bytes_arch(left, _RET_IP_);
1724 while (left) {
1725 unsigned long v;
1726 int chunk = min_t(int, left, sizeof(unsigned long));
1727
1728 if (!arch_get_random_long(&v))
1729 break;
1730
1731 memcpy(p, &v, chunk);
1732 p += chunk;
1733 left -= chunk;
1734 }
1735
1736 return nbytes - left;
1737}
1738EXPORT_SYMBOL(get_random_bytes_arch);
1739
1740/*
1741 * init_std_data - initialize pool with system data
1742 *
1743 * @r: pool to initialize
1744 *
1745 * This function clears the pool's entropy count and mixes some system
1746 * data into the pool to prepare it for use. The pool is not cleared
1747 * as that can only decrease the entropy in the pool.
1748 */
1749static void __init init_std_data(struct entropy_store *r)
1750{
1751 int i;
1752 ktime_t now = ktime_get_real();
1753 unsigned long rv;
1754
1755 mix_pool_bytes(r, &now, sizeof(now));
1756 for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1757 if (!arch_get_random_seed_long(&rv) &&
1758 !arch_get_random_long(&rv))
1759 rv = random_get_entropy();
1760 mix_pool_bytes(r, &rv, sizeof(rv));
1761 }
1762 mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1763}
1764
1765/*
1766 * Note that setup_arch() may call add_device_randomness()
1767 * long before we get here. This allows seeding of the pools
1768 * with some platform dependent data very early in the boot
1769 * process. But it limits our options here. We must use
1770 * statically allocated structures that already have all
1771 * initializations complete at compile time. We should also
1772 * take care not to overwrite the precious per platform data
1773 * we were given.
1774 */
1775int __init rand_initialize(void)
1776{
1777 init_std_data(&input_pool);
1778 crng_initialize_primary(&primary_crng);
1779 crng_global_init_time = jiffies;
1780 if (ratelimit_disable) {
1781 urandom_warning.interval = 0;
1782 unseeded_warning.interval = 0;
1783 }
1784 return 0;
1785}
1786
1787#ifdef CONFIG_BLOCK
1788void rand_initialize_disk(struct gendisk *disk)
1789{
1790 struct timer_rand_state *state;
1791
1792 /*
1793 * If kzalloc returns null, we just won't use that entropy
1794 * source.
1795 */
1796 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1797 if (state) {
1798 state->last_time = INITIAL_JIFFIES;
1799 disk->random = state;
1800 }
1801}
1802#endif
1803
1804static ssize_t
1805urandom_read_nowarn(struct file *file, char __user *buf, size_t nbytes,
1806 loff_t *ppos)
1807{
1808 int ret;
1809
1810 nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1811 ret = extract_crng_user(buf, nbytes);
1812 trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
1813 return ret;
1814}
1815
1816static ssize_t
1817urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1818{
1819 unsigned long flags;
1820 static int maxwarn = 10;
1821
1822 if (!crng_ready() && maxwarn > 0) {
1823 maxwarn--;
1824 if (__ratelimit(&urandom_warning))
1825 pr_notice("%s: uninitialized urandom read (%zd bytes read)\n",
1826 current->comm, nbytes);
1827 spin_lock_irqsave(&primary_crng.lock, flags);
1828 crng_init_cnt = 0;
1829 spin_unlock_irqrestore(&primary_crng.lock, flags);
1830 }
1831
1832 return urandom_read_nowarn(file, buf, nbytes, ppos);
1833}
1834
1835static ssize_t
1836random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1837{
1838 int ret;
1839
1840 ret = wait_for_random_bytes();
1841 if (ret != 0)
1842 return ret;
1843 return urandom_read_nowarn(file, buf, nbytes, ppos);
1844}
1845
1846static __poll_t
1847random_poll(struct file *file, poll_table * wait)
1848{
1849 __poll_t mask;
1850
1851 poll_wait(file, &crng_init_wait, wait);
1852 poll_wait(file, &random_write_wait, wait);
1853 mask = 0;
1854 if (crng_ready())
1855 mask |= EPOLLIN | EPOLLRDNORM;
1856 if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1857 mask |= EPOLLOUT | EPOLLWRNORM;
1858 return mask;
1859}
1860
1861static int
1862write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1863{
1864 size_t bytes;
1865 __u32 t, buf[16];
1866 const char __user *p = buffer;
1867
1868 while (count > 0) {
1869 int b, i = 0;
1870
1871 bytes = min(count, sizeof(buf));
1872 if (copy_from_user(&buf, p, bytes))
1873 return -EFAULT;
1874
1875 for (b = bytes ; b > 0 ; b -= sizeof(__u32), i++) {
1876 if (!arch_get_random_int(&t))
1877 break;
1878 buf[i] ^= t;
1879 }
1880
1881 count -= bytes;
1882 p += bytes;
1883
1884 mix_pool_bytes(r, buf, bytes);
1885 cond_resched();
1886 }
1887
1888 return 0;
1889}
1890
1891static ssize_t random_write(struct file *file, const char __user *buffer,
1892 size_t count, loff_t *ppos)
1893{
1894 size_t ret;
1895
1896 ret = write_pool(&input_pool, buffer, count);
1897 if (ret)
1898 return ret;
1899
1900 return (ssize_t)count;
1901}
1902
1903static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1904{
1905 int size, ent_count;
1906 int __user *p = (int __user *)arg;
1907 int retval;
1908
1909 switch (cmd) {
1910 case RNDGETENTCNT:
1911 /* inherently racy, no point locking */
1912 ent_count = ENTROPY_BITS(&input_pool);
1913 if (put_user(ent_count, p))
1914 return -EFAULT;
1915 return 0;
1916 case RNDADDTOENTCNT:
1917 if (!capable(CAP_SYS_ADMIN))
1918 return -EPERM;
1919 if (get_user(ent_count, p))
1920 return -EFAULT;
1921 return credit_entropy_bits_safe(&input_pool, ent_count);
1922 case RNDADDENTROPY:
1923 if (!capable(CAP_SYS_ADMIN))
1924 return -EPERM;
1925 if (get_user(ent_count, p++))
1926 return -EFAULT;
1927 if (ent_count < 0)
1928 return -EINVAL;
1929 if (get_user(size, p++))
1930 return -EFAULT;
1931 retval = write_pool(&input_pool, (const char __user *)p,
1932 size);
1933 if (retval < 0)
1934 return retval;
1935 return credit_entropy_bits_safe(&input_pool, ent_count);
1936 case RNDZAPENTCNT:
1937 case RNDCLEARPOOL:
1938 /*
1939 * Clear the entropy pool counters. We no longer clear
1940 * the entropy pool, as that's silly.
1941 */
1942 if (!capable(CAP_SYS_ADMIN))
1943 return -EPERM;
1944 input_pool.entropy_count = 0;
1945 return 0;
1946 case RNDRESEEDCRNG:
1947 if (!capable(CAP_SYS_ADMIN))
1948 return -EPERM;
1949 if (crng_init < 2)
1950 return -ENODATA;
1951 crng_reseed(&primary_crng, &input_pool);
1952 crng_global_init_time = jiffies - 1;
1953 return 0;
1954 default:
1955 return -EINVAL;
1956 }
1957}
1958
1959static int random_fasync(int fd, struct file *filp, int on)
1960{
1961 return fasync_helper(fd, filp, on, &fasync);
1962}
1963
1964const struct file_operations random_fops = {
1965 .read = random_read,
1966 .write = random_write,
1967 .poll = random_poll,
1968 .unlocked_ioctl = random_ioctl,
1969 .compat_ioctl = compat_ptr_ioctl,
1970 .fasync = random_fasync,
1971 .llseek = noop_llseek,
1972};
1973
1974const struct file_operations urandom_fops = {
1975 .read = urandom_read,
1976 .write = random_write,
1977 .unlocked_ioctl = random_ioctl,
1978 .compat_ioctl = compat_ptr_ioctl,
1979 .fasync = random_fasync,
1980 .llseek = noop_llseek,
1981};
1982
1983SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1984 unsigned int, flags)
1985{
1986 int ret;
1987
1988 if (flags & ~(GRND_NONBLOCK|GRND_RANDOM|GRND_INSECURE))
1989 return -EINVAL;
1990
1991 /*
1992 * Requesting insecure and blocking randomness at the same time makes
1993 * no sense.
1994 */
1995 if ((flags & (GRND_INSECURE|GRND_RANDOM)) == (GRND_INSECURE|GRND_RANDOM))
1996 return -EINVAL;
1997
1998 if (count > INT_MAX)
1999 count = INT_MAX;
2000
2001 if (!(flags & GRND_INSECURE) && !crng_ready()) {
2002 if (flags & GRND_NONBLOCK)
2003 return -EAGAIN;
2004 ret = wait_for_random_bytes();
2005 if (unlikely(ret))
2006 return ret;
2007 }
2008 return urandom_read_nowarn(NULL, buf, count, NULL);
2009}
2010
2011/********************************************************************
2012 *
2013 * Sysctl interface
2014 *
2015 ********************************************************************/
2016
2017#ifdef CONFIG_SYSCTL
2018
2019#include <linux/sysctl.h>
2020
2021static int min_write_thresh;
2022static int max_write_thresh = INPUT_POOL_WORDS * 32;
2023static int random_min_urandom_seed = 60;
2024static char sysctl_bootid[16];
2025
2026/*
2027 * This function is used to return both the bootid UUID, and random
2028 * UUID. The difference is in whether table->data is NULL; if it is,
2029 * then a new UUID is generated and returned to the user.
2030 *
2031 * If the user accesses this via the proc interface, the UUID will be
2032 * returned as an ASCII string in the standard UUID format; if via the
2033 * sysctl system call, as 16 bytes of binary data.
2034 */
2035static int proc_do_uuid(struct ctl_table *table, int write,
2036 void *buffer, size_t *lenp, loff_t *ppos)
2037{
2038 struct ctl_table fake_table;
2039 unsigned char buf[64], tmp_uuid[16], *uuid;
2040
2041 uuid = table->data;
2042 if (!uuid) {
2043 uuid = tmp_uuid;
2044 generate_random_uuid(uuid);
2045 } else {
2046 static DEFINE_SPINLOCK(bootid_spinlock);
2047
2048 spin_lock(&bootid_spinlock);
2049 if (!uuid[8])
2050 generate_random_uuid(uuid);
2051 spin_unlock(&bootid_spinlock);
2052 }
2053
2054 sprintf(buf, "%pU", uuid);
2055
2056 fake_table.data = buf;
2057 fake_table.maxlen = sizeof(buf);
2058
2059 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
2060}
2061
2062/*
2063 * Return entropy available scaled to integral bits
2064 */
2065static int proc_do_entropy(struct ctl_table *table, int write,
2066 void *buffer, size_t *lenp, loff_t *ppos)
2067{
2068 struct ctl_table fake_table;
2069 int entropy_count;
2070
2071 entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
2072
2073 fake_table.data = &entropy_count;
2074 fake_table.maxlen = sizeof(entropy_count);
2075
2076 return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
2077}
2078
2079static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
2080extern struct ctl_table random_table[];
2081struct ctl_table random_table[] = {
2082 {
2083 .procname = "poolsize",
2084 .data = &sysctl_poolsize,
2085 .maxlen = sizeof(int),
2086 .mode = 0444,
2087 .proc_handler = proc_dointvec,
2088 },
2089 {
2090 .procname = "entropy_avail",
2091 .maxlen = sizeof(int),
2092 .mode = 0444,
2093 .proc_handler = proc_do_entropy,
2094 .data = &input_pool.entropy_count,
2095 },
2096 {
2097 .procname = "write_wakeup_threshold",
2098 .data = &random_write_wakeup_bits,
2099 .maxlen = sizeof(int),
2100 .mode = 0644,
2101 .proc_handler = proc_dointvec_minmax,
2102 .extra1 = &min_write_thresh,
2103 .extra2 = &max_write_thresh,
2104 },
2105 {
2106 .procname = "urandom_min_reseed_secs",
2107 .data = &random_min_urandom_seed,
2108 .maxlen = sizeof(int),
2109 .mode = 0644,
2110 .proc_handler = proc_dointvec,
2111 },
2112 {
2113 .procname = "boot_id",
2114 .data = &sysctl_bootid,
2115 .maxlen = 16,
2116 .mode = 0444,
2117 .proc_handler = proc_do_uuid,
2118 },
2119 {
2120 .procname = "uuid",
2121 .maxlen = 16,
2122 .mode = 0444,
2123 .proc_handler = proc_do_uuid,
2124 },
2125#ifdef ADD_INTERRUPT_BENCH
2126 {
2127 .procname = "add_interrupt_avg_cycles",
2128 .data = &avg_cycles,
2129 .maxlen = sizeof(avg_cycles),
2130 .mode = 0444,
2131 .proc_handler = proc_doulongvec_minmax,
2132 },
2133 {
2134 .procname = "add_interrupt_avg_deviation",
2135 .data = &avg_deviation,
2136 .maxlen = sizeof(avg_deviation),
2137 .mode = 0444,
2138 .proc_handler = proc_doulongvec_minmax,
2139 },
2140#endif
2141 { }
2142};
2143#endif /* CONFIG_SYSCTL */
2144
2145struct batched_entropy {
2146 union {
2147 u64 entropy_u64[CHACHA_BLOCK_SIZE / sizeof(u64)];
2148 u32 entropy_u32[CHACHA_BLOCK_SIZE / sizeof(u32)];
2149 };
2150 unsigned int position;
2151 spinlock_t batch_lock;
2152};
2153
2154/*
2155 * Get a random word for internal kernel use only. The quality of the random
2156 * number is good as /dev/urandom, but there is no backtrack protection, with
2157 * the goal of being quite fast and not depleting entropy. In order to ensure
2158 * that the randomness provided by this function is okay, the function
2159 * wait_for_random_bytes() should be called and return 0 at least once at any
2160 * point prior.
2161 */
2162static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = {
2163 .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u64.lock),
2164};
2165
2166u64 get_random_u64(void)
2167{
2168 u64 ret;
2169 unsigned long flags;
2170 struct batched_entropy *batch;
2171 static void *previous;
2172
2173 warn_unseeded_randomness(&previous);
2174
2175 batch = raw_cpu_ptr(&batched_entropy_u64);
2176 spin_lock_irqsave(&batch->batch_lock, flags);
2177 if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
2178 extract_crng((u8 *)batch->entropy_u64);
2179 batch->position = 0;
2180 }
2181 ret = batch->entropy_u64[batch->position++];
2182 spin_unlock_irqrestore(&batch->batch_lock, flags);
2183 return ret;
2184}
2185EXPORT_SYMBOL(get_random_u64);
2186
2187static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = {
2188 .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u32.lock),
2189};
2190u32 get_random_u32(void)
2191{
2192 u32 ret;
2193 unsigned long flags;
2194 struct batched_entropy *batch;
2195 static void *previous;
2196
2197 warn_unseeded_randomness(&previous);
2198
2199 batch = raw_cpu_ptr(&batched_entropy_u32);
2200 spin_lock_irqsave(&batch->batch_lock, flags);
2201 if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
2202 extract_crng((u8 *)batch->entropy_u32);
2203 batch->position = 0;
2204 }
2205 ret = batch->entropy_u32[batch->position++];
2206 spin_unlock_irqrestore(&batch->batch_lock, flags);
2207 return ret;
2208}
2209EXPORT_SYMBOL(get_random_u32);
2210
2211/* It's important to invalidate all potential batched entropy that might
2212 * be stored before the crng is initialized, which we can do lazily by
2213 * simply resetting the counter to zero so that it's re-extracted on the
2214 * next usage. */
2215static void invalidate_batched_entropy(void)
2216{
2217 int cpu;
2218 unsigned long flags;
2219
2220 for_each_possible_cpu (cpu) {
2221 struct batched_entropy *batched_entropy;
2222
2223 batched_entropy = per_cpu_ptr(&batched_entropy_u32, cpu);
2224 spin_lock_irqsave(&batched_entropy->batch_lock, flags);
2225 batched_entropy->position = 0;
2226 spin_unlock(&batched_entropy->batch_lock);
2227
2228 batched_entropy = per_cpu_ptr(&batched_entropy_u64, cpu);
2229 spin_lock(&batched_entropy->batch_lock);
2230 batched_entropy->position = 0;
2231 spin_unlock_irqrestore(&batched_entropy->batch_lock, flags);
2232 }
2233}
2234
2235/**
2236 * randomize_page - Generate a random, page aligned address
2237 * @start: The smallest acceptable address the caller will take.
2238 * @range: The size of the area, starting at @start, within which the
2239 * random address must fall.
2240 *
2241 * If @start + @range would overflow, @range is capped.
2242 *
2243 * NOTE: Historical use of randomize_range, which this replaces, presumed that
2244 * @start was already page aligned. We now align it regardless.
2245 *
2246 * Return: A page aligned address within [start, start + range). On error,
2247 * @start is returned.
2248 */
2249unsigned long
2250randomize_page(unsigned long start, unsigned long range)
2251{
2252 if (!PAGE_ALIGNED(start)) {
2253 range -= PAGE_ALIGN(start) - start;
2254 start = PAGE_ALIGN(start);
2255 }
2256
2257 if (start > ULONG_MAX - range)
2258 range = ULONG_MAX - start;
2259
2260 range >>= PAGE_SHIFT;
2261
2262 if (range == 0)
2263 return start;
2264
2265 return start + (get_random_long() % range << PAGE_SHIFT);
2266}
2267
2268/* Interface for in-kernel drivers of true hardware RNGs.
2269 * Those devices may produce endless random bits and will be throttled
2270 * when our pool is full.
2271 */
2272void add_hwgenerator_randomness(const char *buffer, size_t count,
2273 size_t entropy)
2274{
2275 struct entropy_store *poolp = &input_pool;
2276
2277 if (unlikely(crng_init == 0)) {
2278 crng_fast_load(buffer, count);
2279 return;
2280 }
2281
2282 /* Suspend writing if we're above the trickle threshold.
2283 * We'll be woken up again once below random_write_wakeup_thresh,
2284 * or when the calling thread is about to terminate.
2285 */
2286 wait_event_interruptible(random_write_wait, kthread_should_stop() ||
2287 ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
2288 mix_pool_bytes(poolp, buffer, count);
2289 credit_entropy_bits(poolp, entropy);
2290}
2291EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
2292
2293/* Handle random seed passed by bootloader.
2294 * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise
2295 * it would be regarded as device data.
2296 * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER.
2297 */
2298void add_bootloader_randomness(const void *buf, unsigned int size)
2299{
2300 if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
2301 add_hwgenerator_randomness(buf, size, size * 8);
2302 else
2303 add_device_randomness(buf, size);
2304}
2305EXPORT_SYMBOL_GPL(add_bootloader_randomness);