1// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
   2/*
   3 * Copyright (C) 2017-2024 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#ifdef CONFIG_VDSO_GETRANDOM
  60#include <vdso/getrandom.h>
  61#include <vdso/datapage.h>
  62#include <vdso/vsyscall.h>
  63#endif
  64#include <asm/archrandom.h>
  65#include <asm/processor.h>
 
  66#include <asm/irq.h>
  67#include <asm/irq_regs.h>
  68#include <asm/io.h>
  69
  70/*********************************************************************
  71 *
  72 * Initialization and readiness waiting.
  73 *
  74 * Much of the RNG infrastructure is devoted to various dependencies
  75 * being able to wait until the RNG has collected enough entropy and
  76 * is ready for safe consumption.
  77 *
  78 *********************************************************************/
  79
  80/*
  81 * crng_init is protected by base_crng->lock, and only increases
  82 * its value (from empty->early->ready).
  83 */
  84static enum {
  85	CRNG_EMPTY = 0, /* Little to no entropy collected */
  86	CRNG_EARLY = 1, /* At least POOL_EARLY_BITS collected */
  87	CRNG_READY = 2  /* Fully initialized with POOL_READY_BITS collected */
  88} crng_init __read_mostly = CRNG_EMPTY;
  89static DEFINE_STATIC_KEY_FALSE(crng_is_ready);
  90#define crng_ready() (static_branch_likely(&crng_is_ready) || crng_init >= CRNG_READY)
  91/* Various types of waiters for crng_init->CRNG_READY transition. */
  92static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
  93static struct fasync_struct *fasync;
  94static ATOMIC_NOTIFIER_HEAD(random_ready_notifier);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  95
  96/* Control how we warn userspace. */
  97static struct ratelimit_state urandom_warning =
  98	RATELIMIT_STATE_INIT_FLAGS("urandom_warning", HZ, 3, RATELIMIT_MSG_ON_RELEASE);
  99static int ratelimit_disable __read_mostly =
 100	IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM);
 101module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
 102MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
 103
 104/*
 105 * Returns whether or not the input pool has been seeded and thus guaranteed
 106 * to supply cryptographically secure random numbers. This applies to: the
 107 * /dev/urandom device, the get_random_bytes function, and the get_random_{u8,
 108 * u16,u32,u64,long} family of functions.
 109 *
 110 * Returns: true if the input pool has been seeded.
 111 *          false if the input pool has not been seeded.
 112 */
 113bool rng_is_initialized(void)
 114{
 115	return crng_ready();
 116}
 117EXPORT_SYMBOL(rng_is_initialized);
 118
 119static void __cold crng_set_ready(struct work_struct *work)
 120{
 121	static_branch_enable(&crng_is_ready);
 122}
 123
 124/* Used by wait_for_random_bytes(), and considered an entropy collector, below. */
 125static void try_to_generate_entropy(void);
 126
 127/*
 128 * Wait for the input pool to be seeded and thus guaranteed to supply
 129 * cryptographically secure random numbers. This applies to: the /dev/urandom
 130 * device, the get_random_bytes function, and the get_random_{u8,u16,u32,u64,
 131 * long} family of functions. Using any of these functions without first
 132 * calling this function forfeits the guarantee of security.
 133 *
 134 * Returns: 0 if the input pool has been seeded.
 135 *          -ERESTARTSYS if the function was interrupted by a signal.
 136 */
 137int wait_for_random_bytes(void)
 138{
 139	while (!crng_ready()) {
 140		int ret;
 141
 142		try_to_generate_entropy();
 143		ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
 144		if (ret)
 145			return ret > 0 ? 0 : ret;
 146	}
 147	return 0;
 148}
 149EXPORT_SYMBOL(wait_for_random_bytes);
 150
 151/*
 152 * Add a callback function that will be invoked when the crng is initialised,
 153 * or immediately if it already has been. Only use this is you are absolutely
 154 * sure it is required. Most users should instead be able to test
 155 * `rng_is_initialized()` on demand, or make use of `get_random_bytes_wait()`.
 156 */
 157int __cold execute_with_initialized_rng(struct notifier_block *nb)
 158{
 159	unsigned long flags;
 160	int ret = 0;
 161
 162	spin_lock_irqsave(&random_ready_notifier.lock, flags);
 163	if (crng_ready())
 164		nb->notifier_call(nb, 0, NULL);
 165	else
 166		ret = raw_notifier_chain_register((struct raw_notifier_head *)&random_ready_notifier.head, nb);
 167	spin_unlock_irqrestore(&random_ready_notifier.lock, flags);
 168	return ret;
 169}
 170
 171#define warn_unseeded_randomness() \
 172	if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \
 173		printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \
 174				__func__, (void *)_RET_IP_, crng_init)
 175
 176
 177/*********************************************************************
 178 *
 179 * Fast key erasure RNG, the "crng".
 180 *
 181 * These functions expand entropy from the entropy extractor into
 182 * long streams for external consumption using the "fast key erasure"
 183 * RNG described at <https://blog.cr.yp.to/20170723-random.html>.
 184 *
 185 * There are a few exported interfaces for use by other drivers:
 186 *
 187 *	void get_random_bytes(void *buf, size_t len)
 188 *	u8 get_random_u8()
 189 *	u16 get_random_u16()
 190 *	u32 get_random_u32()
 191 *	u32 get_random_u32_below(u32 ceil)
 192 *	u32 get_random_u32_above(u32 floor)
 193 *	u32 get_random_u32_inclusive(u32 floor, u32 ceil)
 194 *	u64 get_random_u64()
 195 *	unsigned long get_random_long()
 196 *
 197 * These interfaces will return the requested number of random bytes
 198 * into the given buffer or as a return value. This is equivalent to
 199 * a read from /dev/urandom. The u8, u16, u32, u64, long family of
 200 * functions may be higher performance for one-off random integers,
 201 * because they do a bit of buffering and do not invoke reseeding
 202 * until the buffer is emptied.
 203 *
 204 *********************************************************************/
 205
 206enum {
 207	CRNG_RESEED_START_INTERVAL = HZ,
 208	CRNG_RESEED_INTERVAL = 60 * HZ
 209};
 
 
 
 
 210
 211static struct {
 212	u8 key[CHACHA_KEY_SIZE] __aligned(__alignof__(long));
 213	unsigned long generation;
 214	spinlock_t lock;
 215} base_crng = {
 216	.lock = __SPIN_LOCK_UNLOCKED(base_crng.lock)
 
 
 
 
 
 
 217};
 218
 219struct crng {
 220	u8 key[CHACHA_KEY_SIZE];
 221	unsigned long generation;
 222	local_lock_t lock;
 
 
 
 
 
 
 
 223};
 224
 225static DEFINE_PER_CPU(struct crng, crngs) = {
 226	.generation = ULONG_MAX,
 227	.lock = INIT_LOCAL_LOCK(crngs.lock),
 
 
 
 
 
 
 228};
 229
 230/*
 231 * Return the interval until the next reseeding, which is normally
 232 * CRNG_RESEED_INTERVAL, but during early boot, it is at an interval
 233 * proportional to the uptime.
 234 */
 235static unsigned int crng_reseed_interval(void)
 236{
 237	static bool early_boot = true;
 238
 239	if (unlikely(READ_ONCE(early_boot))) {
 240		time64_t uptime = ktime_get_seconds();
 241		if (uptime >= CRNG_RESEED_INTERVAL / HZ * 2)
 242			WRITE_ONCE(early_boot, false);
 243		else
 244			return max_t(unsigned int, CRNG_RESEED_START_INTERVAL,
 245				     (unsigned int)uptime / 2 * HZ);
 246	}
 247	return CRNG_RESEED_INTERVAL;
 248}
 249
 250/* Used by crng_reseed() and crng_make_state() to extract a new seed from the input pool. */
 251static void extract_entropy(void *buf, size_t len);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 252
 253/* This extracts a new crng key from the input pool. */
 254static void crng_reseed(struct work_struct *work)
 255{
 256	static DECLARE_DELAYED_WORK(next_reseed, crng_reseed);
 257	unsigned long flags;
 258	unsigned long next_gen;
 259	u8 key[CHACHA_KEY_SIZE];
 260
 261	/* Immediately schedule the next reseeding, so that it fires sooner rather than later. */
 262	if (likely(system_unbound_wq))
 263		queue_delayed_work(system_unbound_wq, &next_reseed, crng_reseed_interval());
 
 
 
 
 
 264
 265	extract_entropy(key, sizeof(key));
 
 
 266
 267	/*
 268	 * We copy the new key into the base_crng, overwriting the old one,
 269	 * and update the generation counter. We avoid hitting ULONG_MAX,
 270	 * because the per-cpu crngs are initialized to ULONG_MAX, so this
 271	 * forces new CPUs that come online to always initialize.
 272	 */
 273	spin_lock_irqsave(&base_crng.lock, flags);
 274	memcpy(base_crng.key, key, sizeof(base_crng.key));
 275	next_gen = base_crng.generation + 1;
 276	if (next_gen == ULONG_MAX)
 277		++next_gen;
 278	WRITE_ONCE(base_crng.generation, next_gen);
 279#ifdef CONFIG_VDSO_GETRANDOM
 280	/* base_crng.generation's invalid value is ULONG_MAX, while
 281	 * _vdso_rng_data.generation's invalid value is 0, so add one to the
 282	 * former to arrive at the latter. Use smp_store_release so that this
 283	 * is ordered with the write above to base_crng.generation. Pairs with
 284	 * the smp_rmb() before the syscall in the vDSO code.
 285	 *
 286	 * Cast to unsigned long for 32-bit architectures, since atomic 64-bit
 287	 * operations are not supported on those architectures. This is safe
 288	 * because base_crng.generation is a 32-bit value. On big-endian
 289	 * architectures it will be stored in the upper 32 bits, but that's okay
 290	 * because the vDSO side only checks whether the value changed, without
 291	 * actually using or interpreting the value.
 292	 */
 293	smp_store_release((unsigned long *)&__arch_get_k_vdso_rng_data()->generation, next_gen + 1);
 294#endif
 295	if (!static_branch_likely(&crng_is_ready))
 296		crng_init = CRNG_READY;
 297	spin_unlock_irqrestore(&base_crng.lock, flags);
 298	memzero_explicit(key, sizeof(key));
 299}
 300
 301/*
 302 * This generates a ChaCha block using the provided key, and then
 303 * immediately overwrites that key with half the block. It returns
 304 * the resultant ChaCha state to the user, along with the second
 305 * half of the block containing 32 bytes of random data that may
 306 * be used; random_data_len may not be greater than 32.
 307 *
 308 * The returned ChaCha state contains within it a copy of the old
 309 * key value, at index 4, so the state should always be zeroed out
 310 * immediately after using in order to maintain forward secrecy.
 311 * If the state cannot be erased in a timely manner, then it is
 312 * safer to set the random_data parameter to &chacha_state[4] so
 313 * that this function overwrites it before returning.
 314 */
 315static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE],
 316				  u32 chacha_state[CHACHA_STATE_WORDS],
 317				  u8 *random_data, size_t random_data_len)
 318{
 319	u8 first_block[CHACHA_BLOCK_SIZE];
 320
 321	BUG_ON(random_data_len > 32);
 322
 323	chacha_init_consts(chacha_state);
 324	memcpy(&chacha_state[4], key, CHACHA_KEY_SIZE);
 325	memset(&chacha_state[12], 0, sizeof(u32) * 4);
 326	chacha20_block(chacha_state, first_block);
 327
 328	memcpy(key, first_block, CHACHA_KEY_SIZE);
 329	memcpy(random_data, first_block + CHACHA_KEY_SIZE, random_data_len);
 330	memzero_explicit(first_block, sizeof(first_block));
 331}
 332
 333/*
 334 * This function returns a ChaCha state that you may use for generating
 335 * random data. It also returns up to 32 bytes on its own of random data
 336 * that may be used; random_data_len may not be greater than 32.
 337 */
 338static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS],
 339			    u8 *random_data, size_t random_data_len)
 340{
 341	unsigned long flags;
 342	struct crng *crng;
 343
 344	BUG_ON(random_data_len > 32);
 345
 346	/*
 347	 * For the fast path, we check whether we're ready, unlocked first, and
 348	 * then re-check once locked later. In the case where we're really not
 349	 * ready, we do fast key erasure with the base_crng directly, extracting
 350	 * when crng_init is CRNG_EMPTY.
 351	 */
 352	if (!crng_ready()) {
 353		bool ready;
 354
 355		spin_lock_irqsave(&base_crng.lock, flags);
 356		ready = crng_ready();
 357		if (!ready) {
 358			if (crng_init == CRNG_EMPTY)
 359				extract_entropy(base_crng.key, sizeof(base_crng.key));
 360			crng_fast_key_erasure(base_crng.key, chacha_state,
 361					      random_data, random_data_len);
 362		}
 363		spin_unlock_irqrestore(&base_crng.lock, flags);
 364		if (!ready)
 365			return;
 366	}
 367
 368	local_lock_irqsave(&crngs.lock, flags);
 369	crng = raw_cpu_ptr(&crngs);
 370
 371	/*
 372	 * If our per-cpu crng is older than the base_crng, then it means
 373	 * somebody reseeded the base_crng. In that case, we do fast key
 374	 * erasure on the base_crng, and use its output as the new key
 375	 * for our per-cpu crng. This brings us up to date with base_crng.
 376	 */
 377	if (unlikely(crng->generation != READ_ONCE(base_crng.generation))) {
 378		spin_lock(&base_crng.lock);
 379		crng_fast_key_erasure(base_crng.key, chacha_state,
 380				      crng->key, sizeof(crng->key));
 381		crng->generation = base_crng.generation;
 382		spin_unlock(&base_crng.lock);
 383	}
 384
 385	/*
 386	 * Finally, when we've made it this far, our per-cpu crng has an up
 387	 * to date key, and we can do fast key erasure with it to produce
 388	 * some random data and a ChaCha state for the caller. All other
 389	 * branches of this function are "unlikely", so most of the time we
 390	 * should wind up here immediately.
 391	 */
 392	crng_fast_key_erasure(crng->key, chacha_state, random_data, random_data_len);
 393	local_unlock_irqrestore(&crngs.lock, flags);
 394}
 395
 396static void _get_random_bytes(void *buf, size_t len)
 397{
 398	u32 chacha_state[CHACHA_STATE_WORDS];
 399	u8 tmp[CHACHA_BLOCK_SIZE];
 400	size_t first_block_len;
 401
 402	if (!len)
 403		return;
 404
 405	first_block_len = min_t(size_t, 32, len);
 406	crng_make_state(chacha_state, buf, first_block_len);
 407	len -= first_block_len;
 408	buf += first_block_len;
 409
 410	while (len) {
 411		if (len < CHACHA_BLOCK_SIZE) {
 412			chacha20_block(chacha_state, tmp);
 413			memcpy(buf, tmp, len);
 414			memzero_explicit(tmp, sizeof(tmp));
 415			break;
 416		}
 417
 418		chacha20_block(chacha_state, buf);
 419		if (unlikely(chacha_state[12] == 0))
 420			++chacha_state[13];
 421		len -= CHACHA_BLOCK_SIZE;
 422		buf += CHACHA_BLOCK_SIZE;
 423	}
 
 
 
 
 
 
 424
 425	memzero_explicit(chacha_state, sizeof(chacha_state));
 
 426}
 427
 428/*
 429 * This returns random bytes in arbitrary quantities. The quality of the
 430 * random bytes is good as /dev/urandom. In order to ensure that the
 431 * randomness provided by this function is okay, the function
 432 * wait_for_random_bytes() should be called and return 0 at least once
 433 * at any point prior.
 434 */
 435void get_random_bytes(void *buf, size_t len)
 436{
 437	warn_unseeded_randomness();
 438	_get_random_bytes(buf, len);
 439}
 440EXPORT_SYMBOL(get_random_bytes);
 441
 442static ssize_t get_random_bytes_user(struct iov_iter *iter)
 443{
 444	u32 chacha_state[CHACHA_STATE_WORDS];
 445	u8 block[CHACHA_BLOCK_SIZE];
 446	size_t ret = 0, copied;
 447
 448	if (unlikely(!iov_iter_count(iter)))
 449		return 0;
 450
 451	/*
 452	 * Immediately overwrite the ChaCha key at index 4 with random
 453	 * bytes, in case userspace causes copy_to_iter() below to sleep
 454	 * forever, so that we still retain forward secrecy in that case.
 455	 */
 456	crng_make_state(chacha_state, (u8 *)&chacha_state[4], CHACHA_KEY_SIZE);
 457	/*
 458	 * However, if we're doing a read of len <= 32, we don't need to
 459	 * use chacha_state after, so we can simply return those bytes to
 460	 * the user directly.
 461	 */
 462	if (iov_iter_count(iter) <= CHACHA_KEY_SIZE) {
 463		ret = copy_to_iter(&chacha_state[4], CHACHA_KEY_SIZE, iter);
 464		goto out_zero_chacha;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 465	}
 466
 467	for (;;) {
 468		chacha20_block(chacha_state, block);
 469		if (unlikely(chacha_state[12] == 0))
 470			++chacha_state[13];
 471
 472		copied = copy_to_iter(block, sizeof(block), iter);
 473		ret += copied;
 474		if (!iov_iter_count(iter) || copied != sizeof(block))
 475			break;
 476
 477		BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0);
 478		if (ret % PAGE_SIZE == 0) {
 479			if (signal_pending(current))
 480				break;
 481			cond_resched();
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 482		}
 483	}
 
 484
 485	memzero_explicit(block, sizeof(block));
 486out_zero_chacha:
 487	memzero_explicit(chacha_state, sizeof(chacha_state));
 488	return ret ? ret : -EFAULT;
 489}
 490
 491/*
 492 * Batched entropy returns random integers. The quality of the random
 493 * number is good as /dev/urandom. In order to ensure that the randomness
 494 * provided by this function is okay, the function wait_for_random_bytes()
 495 * should be called and return 0 at least once at any point prior.
 496 */
 497
 498#define DEFINE_BATCHED_ENTROPY(type)						\
 499struct batch_ ##type {								\
 500	/*									\
 501	 * We make this 1.5x a ChaCha block, so that we get the			\
 502	 * remaining 32 bytes from fast key erasure, plus one full		\
 503	 * block from the detached ChaCha state. We can increase		\
 504	 * the size of this later if needed so long as we keep the		\
 505	 * formula of (integer_blocks + 0.5) * CHACHA_BLOCK_SIZE.		\
 506	 */									\
 507	type entropy[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(type))];		\
 508	local_lock_t lock;							\
 509	unsigned long generation;						\
 510	unsigned int position;							\
 511};										\
 512										\
 513static DEFINE_PER_CPU(struct batch_ ##type, batched_entropy_ ##type) = {	\
 514	.lock = INIT_LOCAL_LOCK(batched_entropy_ ##type.lock),			\
 515	.position = UINT_MAX							\
 516};										\
 517										\
 518type get_random_ ##type(void)							\
 519{										\
 520	type ret;								\
 521	unsigned long flags;							\
 522	struct batch_ ##type *batch;						\
 523	unsigned long next_gen;							\
 524										\
 525	warn_unseeded_randomness();						\
 526										\
 527	if  (!crng_ready()) {							\
 528		_get_random_bytes(&ret, sizeof(ret));				\
 529		return ret;							\
 530	}									\
 531										\
 532	local_lock_irqsave(&batched_entropy_ ##type.lock, flags);		\
 533	batch = raw_cpu_ptr(&batched_entropy_##type);				\
 534										\
 535	next_gen = READ_ONCE(base_crng.generation);				\
 536	if (batch->position >= ARRAY_SIZE(batch->entropy) ||			\
 537	    next_gen != batch->generation) {					\
 538		_get_random_bytes(batch->entropy, sizeof(batch->entropy));	\
 539		batch->position = 0;						\
 540		batch->generation = next_gen;					\
 541	}									\
 542										\
 543	ret = batch->entropy[batch->position];					\
 544	batch->entropy[batch->position] = 0;					\
 545	++batch->position;							\
 546	local_unlock_irqrestore(&batched_entropy_ ##type.lock, flags);		\
 547	return ret;								\
 548}										\
 549EXPORT_SYMBOL(get_random_ ##type);
 550
 551DEFINE_BATCHED_ENTROPY(u8)
 552DEFINE_BATCHED_ENTROPY(u16)
 553DEFINE_BATCHED_ENTROPY(u32)
 554DEFINE_BATCHED_ENTROPY(u64)
 555
 556u32 __get_random_u32_below(u32 ceil)
 557{
 558	/*
 559	 * This is the slow path for variable ceil. It is still fast, most of
 560	 * the time, by doing traditional reciprocal multiplication and
 561	 * opportunistically comparing the lower half to ceil itself, before
 562	 * falling back to computing a larger bound, and then rejecting samples
 563	 * whose lower half would indicate a range indivisible by ceil. The use
 564	 * of `-ceil % ceil` is analogous to `2^32 % ceil`, but is computable
 565	 * in 32-bits.
 566	 */
 567	u32 rand = get_random_u32();
 568	u64 mult;
 569
 570	/*
 571	 * This function is technically undefined for ceil == 0, and in fact
 572	 * for the non-underscored constant version in the header, we build bug
 573	 * on that. But for the non-constant case, it's convenient to have that
 574	 * evaluate to being a straight call to get_random_u32(), so that
 575	 * get_random_u32_inclusive() can work over its whole range without
 576	 * undefined behavior.
 577	 */
 578	if (unlikely(!ceil))
 579		return rand;
 580
 581	mult = (u64)ceil * rand;
 582	if (unlikely((u32)mult < ceil)) {
 583		u32 bound = -ceil % ceil;
 584		while (unlikely((u32)mult < bound))
 585			mult = (u64)ceil * get_random_u32();
 586	}
 587	return mult >> 32;
 588}
 589EXPORT_SYMBOL(__get_random_u32_below);
 590
 591#ifdef CONFIG_SMP
 592/*
 593 * This function is called when the CPU is coming up, with entry
 594 * CPUHP_RANDOM_PREPARE, which comes before CPUHP_WORKQUEUE_PREP.
 595 */
 596int __cold random_prepare_cpu(unsigned int cpu)
 597{
 598	/*
 599	 * When the cpu comes back online, immediately invalidate both
 600	 * the per-cpu crng and all batches, so that we serve fresh
 601	 * randomness.
 602	 */
 603	per_cpu_ptr(&crngs, cpu)->generation = ULONG_MAX;
 604	per_cpu_ptr(&batched_entropy_u8, cpu)->position = UINT_MAX;
 605	per_cpu_ptr(&batched_entropy_u16, cpu)->position = UINT_MAX;
 606	per_cpu_ptr(&batched_entropy_u32, cpu)->position = UINT_MAX;
 607	per_cpu_ptr(&batched_entropy_u64, cpu)->position = UINT_MAX;
 608	return 0;
 609}
 610#endif
 611
 612
 613/**********************************************************************
 614 *
 615 * Entropy accumulation and extraction routines.
 616 *
 617 * Callers may add entropy via:
 618 *
 619 *     static void mix_pool_bytes(const void *buf, size_t len)
 620 *
 621 * After which, if added entropy should be credited:
 622 *
 623 *     static void credit_init_bits(size_t bits)
 624 *
 625 * Finally, extract entropy via:
 626 *
 627 *     static void extract_entropy(void *buf, size_t len)
 628 *
 629 **********************************************************************/
 630
 631enum {
 632	POOL_BITS = BLAKE2S_HASH_SIZE * 8,
 633	POOL_READY_BITS = POOL_BITS, /* When crng_init->CRNG_READY */
 634	POOL_EARLY_BITS = POOL_READY_BITS / 2 /* When crng_init->CRNG_EARLY */
 635};
 636
 637static struct {
 638	struct blake2s_state hash;
 639	spinlock_t lock;
 640	unsigned int init_bits;
 641} input_pool = {
 642	.hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE),
 643		    BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4,
 644		    BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 },
 645	.hash.outlen = BLAKE2S_HASH_SIZE,
 646	.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
 647};
 648
 649static void _mix_pool_bytes(const void *buf, size_t len)
 650{
 651	blake2s_update(&input_pool.hash, buf, len);
 652}
 653
 654/*
 655 * This function adds bytes into the input pool. It does not
 656 * update the initialization bit counter; the caller should call
 657 * credit_init_bits if this is appropriate.
 
 
 
 658 */
 659static void mix_pool_bytes(const void *buf, size_t len)
 660{
 
 661	unsigned long flags;
 662
 
 663	spin_lock_irqsave(&input_pool.lock, flags);
 664	_mix_pool_bytes(buf, len);
 
 665	spin_unlock_irqrestore(&input_pool.lock, flags);
 
 
 
 
 
 666}
 
 
 
 667
 668/*
 669 * This is an HKDF-like construction for using the hashed collected entropy
 670 * as a PRF key, that's then expanded block-by-block.
 
 
 
 
 
 
 671 */
 672static void extract_entropy(void *buf, size_t len)
 673{
 674	unsigned long flags;
 675	u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE];
 676	struct {
 677		unsigned long rdseed[32 / sizeof(long)];
 678		size_t counter;
 679	} block;
 680	size_t i, longs;
 681
 682	for (i = 0; i < ARRAY_SIZE(block.rdseed);) {
 683		longs = arch_get_random_seed_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
 684		if (longs) {
 685			i += longs;
 686			continue;
 687		}
 688		longs = arch_get_random_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
 689		if (longs) {
 690			i += longs;
 691			continue;
 692		}
 693		block.rdseed[i++] = random_get_entropy();
 694	}
 695
 696	spin_lock_irqsave(&input_pool.lock, flags);
 697
 698	/* seed = HASHPRF(last_key, entropy_input) */
 699	blake2s_final(&input_pool.hash, seed);
 
 
 
 700
 701	/* next_key = HASHPRF(seed, RDSEED || 0) */
 702	block.counter = 0;
 703	blake2s(next_key, (u8 *)&block, seed, sizeof(next_key), sizeof(block), sizeof(seed));
 704	blake2s_init_key(&input_pool.hash, BLAKE2S_HASH_SIZE, next_key, sizeof(next_key));
 
 705
 706	spin_unlock_irqrestore(&input_pool.lock, flags);
 707	memzero_explicit(next_key, sizeof(next_key));
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 708
 709	while (len) {
 710		i = min_t(size_t, len, BLAKE2S_HASH_SIZE);
 711		/* output = HASHPRF(seed, RDSEED || ++counter) */
 712		++block.counter;
 713		blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed));
 714		len -= i;
 715		buf += i;
 716	}
 717
 718	memzero_explicit(seed, sizeof(seed));
 719	memzero_explicit(&block, sizeof(block));
 720}
 721
 722#define credit_init_bits(bits) if (!crng_ready()) _credit_init_bits(bits)
 723
 724static void __cold _credit_init_bits(size_t bits)
 725{
 726	static DECLARE_WORK(set_ready, crng_set_ready);
 727	unsigned int new, orig, add;
 728	unsigned long flags;
 729
 730	if (!bits)
 
 731		return;
 732
 733	add = min_t(size_t, bits, POOL_BITS);
 734
 735	orig = READ_ONCE(input_pool.init_bits);
 736	do {
 737		new = min_t(unsigned int, POOL_BITS, orig + add);
 738	} while (!try_cmpxchg(&input_pool.init_bits, &orig, new));
 739
 740	if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) {
 741		crng_reseed(NULL); /* Sets crng_init to CRNG_READY under base_crng.lock. */
 742		if (static_key_initialized && system_unbound_wq)
 743			queue_work(system_unbound_wq, &set_ready);
 744		atomic_notifier_call_chain(&random_ready_notifier, 0, NULL);
 745#ifdef CONFIG_VDSO_GETRANDOM
 746		WRITE_ONCE(__arch_get_k_vdso_rng_data()->is_ready, true);
 747#endif
 748		wake_up_interruptible(&crng_init_wait);
 749		kill_fasync(&fasync, SIGIO, POLL_IN);
 750		pr_notice("crng init done\n");
 751		if (urandom_warning.missed)
 752			pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
 753				  urandom_warning.missed);
 754	} else if (orig < POOL_EARLY_BITS && new >= POOL_EARLY_BITS) {
 755		spin_lock_irqsave(&base_crng.lock, flags);
 756		/* Check if crng_init is CRNG_EMPTY, to avoid race with crng_reseed(). */
 757		if (crng_init == CRNG_EMPTY) {
 758			extract_entropy(base_crng.key, sizeof(base_crng.key));
 759			crng_init = CRNG_EARLY;
 760		}
 761		spin_unlock_irqrestore(&base_crng.lock, flags);
 762	}
 763}
 
 764
 
 765
 766/**********************************************************************
 767 *
 768 * Entropy collection routines.
 769 *
 770 * The following exported functions are used for pushing entropy into
 771 * the above entropy accumulation routines:
 772 *
 773 *	void add_device_randomness(const void *buf, size_t len);
 774 *	void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after);
 775 *	void add_bootloader_randomness(const void *buf, size_t len);
 776 *	void add_vmfork_randomness(const void *unique_vm_id, size_t len);
 777 *	void add_interrupt_randomness(int irq);
 778 *	void add_input_randomness(unsigned int type, unsigned int code, unsigned int value);
 779 *	void add_disk_randomness(struct gendisk *disk);
 780 *
 781 * add_device_randomness() adds data to the input pool that
 782 * is likely to differ between two devices (or possibly even per boot).
 783 * This would be things like MAC addresses or serial numbers, or the
 784 * read-out of the RTC. This does *not* credit any actual entropy to
 785 * the pool, but it initializes the pool to different values for devices
 786 * that might otherwise be identical and have very little entropy
 787 * available to them (particularly common in the embedded world).
 788 *
 789 * add_hwgenerator_randomness() is for true hardware RNGs, and will credit
 790 * entropy as specified by the caller. If the entropy pool is full it will
 791 * block until more entropy is needed.
 792 *
 793 * add_bootloader_randomness() is called by bootloader drivers, such as EFI
 794 * and device tree, and credits its input depending on whether or not the
 795 * command line option 'random.trust_bootloader'.
 796 *
 797 * add_vmfork_randomness() adds a unique (but not necessarily secret) ID
 798 * representing the current instance of a VM to the pool, without crediting,
 799 * and then force-reseeds the crng so that it takes effect immediately.
 800 *
 801 * add_interrupt_randomness() uses the interrupt timing as random
 802 * inputs to the entropy pool. Using the cycle counters and the irq source
 803 * as inputs, it feeds the input pool roughly once a second or after 64
 804 * interrupts, crediting 1 bit of entropy for whichever comes first.
 805 *
 806 * add_input_randomness() uses the input layer interrupt timing, as well
 807 * as the event type information from the hardware.
 808 *
 809 * add_disk_randomness() uses what amounts to the seek time of block
 810 * layer request events, on a per-disk_devt basis, as input to the
 811 * entropy pool. Note that high-speed solid state drives with very low
 812 * seek times do not make for good sources of entropy, as their seek
 813 * times are usually fairly consistent.
 814 *
 815 * The last two routines try to estimate how many bits of entropy
 816 * to credit. They do this by keeping track of the first and second
 817 * order deltas of the event timings.
 818 *
 819 **********************************************************************/
 820
 821static bool trust_cpu __initdata = true;
 822static bool trust_bootloader __initdata = true;
 823static int __init parse_trust_cpu(char *arg)
 824{
 825	return kstrtobool(arg, &trust_cpu);
 826}
 827static int __init parse_trust_bootloader(char *arg)
 828{
 829	return kstrtobool(arg, &trust_bootloader);
 830}
 831early_param("random.trust_cpu", parse_trust_cpu);
 832early_param("random.trust_bootloader", parse_trust_bootloader);
 
 
 
 
 
 
 
 
 
 
 
 
 
 833
 834static int random_pm_notification(struct notifier_block *nb, unsigned long action, void *data)
 835{
 836	unsigned long flags, entropy = random_get_entropy();
 
 
 
 
 
 
 837
 838	/*
 839	 * Encode a representation of how long the system has been suspended,
 840	 * in a way that is distinct from prior system suspends.
 
 841	 */
 842	ktime_t stamps[] = { ktime_get(), ktime_get_boottime(), ktime_get_real() };
 843
 844	spin_lock_irqsave(&input_pool.lock, flags);
 845	_mix_pool_bytes(&action, sizeof(action));
 846	_mix_pool_bytes(stamps, sizeof(stamps));
 847	_mix_pool_bytes(&entropy, sizeof(entropy));
 848	spin_unlock_irqrestore(&input_pool.lock, flags);
 
 
 849
 850	if (crng_ready() && (action == PM_RESTORE_PREPARE ||
 851	    (action == PM_POST_SUSPEND && !IS_ENABLED(CONFIG_PM_AUTOSLEEP) &&
 852	     !IS_ENABLED(CONFIG_PM_USERSPACE_AUTOSLEEP)))) {
 853		crng_reseed(NULL);
 854		pr_notice("crng reseeded on system resumption\n");
 
 
 
 855	}
 856	return 0;
 857}
 858
 859static struct notifier_block pm_notifier = { .notifier_call = random_pm_notification };
 
 860
 861/*
 862 * This is called extremely early, before time keeping functionality is
 863 * available, but arch randomness is. Interrupts are not yet enabled.
 864 */
 865void __init random_init_early(const char *command_line)
 866{
 867	unsigned long entropy[BLAKE2S_BLOCK_SIZE / sizeof(long)];
 868	size_t i, longs, arch_bits;
 869
 870#if defined(LATENT_ENTROPY_PLUGIN)
 871	static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy;
 872	_mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed));
 873#endif
 874
 875	for (i = 0, arch_bits = sizeof(entropy) * 8; i < ARRAY_SIZE(entropy);) {
 876		longs = arch_get_random_seed_longs(entropy, ARRAY_SIZE(entropy) - i);
 877		if (longs) {
 878			_mix_pool_bytes(entropy, sizeof(*entropy) * longs);
 879			i += longs;
 880			continue;
 881		}
 882		longs = arch_get_random_longs(entropy, ARRAY_SIZE(entropy) - i);
 883		if (longs) {
 884			_mix_pool_bytes(entropy, sizeof(*entropy) * longs);
 885			i += longs;
 886			continue;
 887		}
 888		arch_bits -= sizeof(*entropy) * 8;
 889		++i;
 890	}
 891
 892	_mix_pool_bytes(init_utsname(), sizeof(*(init_utsname())));
 893	_mix_pool_bytes(command_line, strlen(command_line));
 894
 895	/* Reseed if already seeded by earlier phases. */
 896	if (crng_ready())
 897		crng_reseed(NULL);
 898	else if (trust_cpu)
 899		_credit_init_bits(arch_bits);
 900}
 901
 902/*
 903 * This is called a little bit after the prior function, and now there is
 904 * access to timestamps counters. Interrupts are not yet enabled.
 
 905 */
 906void __init random_init(void)
 
 907{
 908	unsigned long entropy = random_get_entropy();
 909	ktime_t now = ktime_get_real();
 910
 911	_mix_pool_bytes(&now, sizeof(now));
 912	_mix_pool_bytes(&entropy, sizeof(entropy));
 913	add_latent_entropy();
 914
 915	/*
 916	 * If we were initialized by the cpu or bootloader before jump labels
 917	 * or workqueues are initialized, then we should enable the static
 918	 * branch here, where it's guaranteed that these have been initialized.
 919	 */
 920	if (!static_branch_likely(&crng_is_ready) && crng_init >= CRNG_READY)
 921		crng_set_ready(NULL);
 922
 923	/* Reseed if already seeded by earlier phases. */
 924	if (crng_ready())
 925		crng_reseed(NULL);
 926
 927	WARN_ON(register_pm_notifier(&pm_notifier));
 928
 929	WARN(!entropy, "Missing cycle counter and fallback timer; RNG "
 930		       "entropy collection will consequently suffer.");
 931}
 932
 933/*
 934 * Add device- or boot-specific data to the input pool to help
 935 * initialize it.
 936 *
 937 * None of this adds any entropy; it is meant to avoid the problem of
 938 * the entropy pool having similar initial state across largely
 939 * identical devices.
 940 */
 941void add_device_randomness(const void *buf, size_t len)
 942{
 943	unsigned long entropy = random_get_entropy();
 944	unsigned long flags;
 945
 946	spin_lock_irqsave(&input_pool.lock, flags);
 947	_mix_pool_bytes(&entropy, sizeof(entropy));
 948	_mix_pool_bytes(buf, len);
 949	spin_unlock_irqrestore(&input_pool.lock, flags);
 950}
 951EXPORT_SYMBOL(add_device_randomness);
 952
 953/*
 954 * Interface for in-kernel drivers of true hardware RNGs. Those devices
 955 * may produce endless random bits, so this function will sleep for
 956 * some amount of time after, if the sleep_after parameter is true.
 957 */
 958void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after)
 959{
 960	mix_pool_bytes(buf, len);
 961	credit_init_bits(entropy);
 962
 963	/*
 964	 * Throttle writing to once every reseed interval, unless we're not yet
 965	 * initialized or no entropy is credited.
 966	 */
 967	if (sleep_after && !kthread_should_stop() && (crng_ready() || !entropy))
 968		schedule_timeout_interruptible(crng_reseed_interval());
 969}
 970EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
 971
 972/*
 973 * Handle random seed passed by bootloader, and credit it depending
 974 * on the command line option 'random.trust_bootloader'.
 
 
 975 */
 976void __init add_bootloader_randomness(const void *buf, size_t len)
 977{
 978	mix_pool_bytes(buf, len);
 979	if (trust_bootloader)
 980		credit_init_bits(len * 8);
 
 
 
 981}
 982
 983#if IS_ENABLED(CONFIG_VMGENID)
 984static BLOCKING_NOTIFIER_HEAD(vmfork_chain);
 985
 986/*
 987 * Handle a new unique VM ID, which is unique, not secret, so we
 988 * don't credit it, but we do immediately force a reseed after so
 989 * that it's used by the crng posthaste.
 990 */
 991void __cold add_vmfork_randomness(const void *unique_vm_id, size_t len)
 
 992{
 993	add_device_randomness(unique_vm_id, len);
 994	if (crng_ready()) {
 995		crng_reseed(NULL);
 996		pr_notice("crng reseeded due to virtual machine fork\n");
 997	}
 998	blocking_notifier_call_chain(&vmfork_chain, 0, NULL);
 999}
1000#if IS_MODULE(CONFIG_VMGENID)
1001EXPORT_SYMBOL_GPL(add_vmfork_randomness);
1002#endif
1003
1004int __cold register_random_vmfork_notifier(struct notifier_block *nb)
1005{
1006	return blocking_notifier_chain_register(&vmfork_chain, nb);
1007}
1008EXPORT_SYMBOL_GPL(register_random_vmfork_notifier);
1009
1010int __cold unregister_random_vmfork_notifier(struct notifier_block *nb)
1011{
1012	return blocking_notifier_chain_unregister(&vmfork_chain, nb);
1013}
1014EXPORT_SYMBOL_GPL(unregister_random_vmfork_notifier);
1015#endif
1016
1017struct fast_pool {
1018	unsigned long pool[4];
1019	unsigned long last;
1020	unsigned int count;
1021	struct timer_list mix;
1022};
 
 
 
 
 
 
 
 
1023
1024static void mix_interrupt_randomness(struct timer_list *work);
 
1025
1026static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {
1027#ifdef CONFIG_64BIT
1028#define FASTMIX_PERM SIPHASH_PERMUTATION
1029	.pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 },
1030#else
1031#define FASTMIX_PERM HSIPHASH_PERMUTATION
1032	.pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 },
1033#endif
1034	.mix = __TIMER_INITIALIZER(mix_interrupt_randomness, 0)
1035};
1036
1037/*
1038 * This is [Half]SipHash-1-x, starting from an empty key. Because
1039 * the key is fixed, it assumes that its inputs are non-malicious,
1040 * and therefore this has no security on its own. s represents the
1041 * four-word SipHash state, while v represents a two-word input.
1042 */
1043static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2)
1044{
1045	s[3] ^= v1;
1046	FASTMIX_PERM(s[0], s[1], s[2], s[3]);
1047	s[0] ^= v1;
1048	s[3] ^= v2;
1049	FASTMIX_PERM(s[0], s[1], s[2], s[3]);
1050	s[0] ^= v2;
1051}
1052
1053#ifdef CONFIG_SMP
1054/*
1055 * This function is called when the CPU has just come online, with
1056 * entry CPUHP_AP_RANDOM_ONLINE, just after CPUHP_AP_WORKQUEUE_ONLINE.
 
 
1057 */
1058int __cold random_online_cpu(unsigned int cpu)
1059{
 
 
 
 
 
 
 
 
 
1060	/*
1061	 * During CPU shutdown and before CPU onlining, add_interrupt_
1062	 * randomness() may schedule mix_interrupt_randomness(), and
1063	 * set the MIX_INFLIGHT flag. However, because the worker can
1064	 * be scheduled on a different CPU during this period, that
1065	 * flag will never be cleared. For that reason, we zero out
1066	 * the flag here, which runs just after workqueues are onlined
1067	 * for the CPU again. This also has the effect of setting the
1068	 * irq randomness count to zero so that new accumulated irqs
1069	 * are fresh.
1070	 */
1071	per_cpu_ptr(&irq_randomness, cpu)->count = 0;
1072	return 0;
1073}
1074#endif
 
 
 
 
 
 
 
 
1075
1076static void mix_interrupt_randomness(struct timer_list *work)
1077{
1078	struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix);
1079	/*
1080	 * The size of the copied stack pool is explicitly 2 longs so that we
1081	 * only ever ingest half of the siphash output each time, retaining
1082	 * the other half as the next "key" that carries over. The entropy is
1083	 * supposed to be sufficiently dispersed between bits so on average
1084	 * we don't wind up "losing" some.
 
 
1085	 */
1086	unsigned long pool[2];
1087	unsigned int count;
1088
1089	/* Check to see if we're running on the wrong CPU due to hotplug. */
1090	local_irq_disable();
1091	if (fast_pool != this_cpu_ptr(&irq_randomness)) {
1092		local_irq_enable();
1093		return;
1094	}
1095
1096	/*
1097	 * Copy the pool to the stack so that the mixer always has a
1098	 * consistent view, before we reenable irqs again.
1099	 */
1100	memcpy(pool, fast_pool->pool, sizeof(pool));
1101	count = fast_pool->count;
1102	fast_pool->count = 0;
1103	fast_pool->last = jiffies;
1104	local_irq_enable();
1105
1106	mix_pool_bytes(pool, sizeof(pool));
1107	credit_init_bits(clamp_t(unsigned int, (count & U16_MAX) / 64, 1, sizeof(pool) * 8));
 
 
 
 
 
 
1108
1109	memzero_explicit(pool, sizeof(pool));
 
1110}
1111
1112void add_interrupt_randomness(int irq)
 
 
 
 
 
 
 
 
 
 
1113{
1114	enum { MIX_INFLIGHT = 1U << 31 };
1115	unsigned long entropy = random_get_entropy();
1116	struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
1117	struct pt_regs *regs = get_irq_regs();
1118	unsigned int new_count;
1119
1120	fast_mix(fast_pool->pool, entropy,
1121		 (regs ? instruction_pointer(regs) : _RET_IP_) ^ swab(irq));
1122	new_count = ++fast_pool->count;
 
 
 
 
 
 
 
 
 
 
 
 
1123
1124	if (new_count & MIX_INFLIGHT)
1125		return;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1126
1127	if (new_count < 1024 && !time_is_before_jiffies(fast_pool->last + HZ))
1128		return;
1129
1130	fast_pool->count |= MIX_INFLIGHT;
1131	if (!timer_pending(&fast_pool->mix)) {
1132		fast_pool->mix.expires = jiffies;
1133		add_timer_on(&fast_pool->mix, raw_smp_processor_id());
1134	}
1135}
1136EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1137
1138/* There is one of these per entropy source */
1139struct timer_rand_state {
1140	unsigned long last_time;
1141	long last_delta, last_delta2;
1142};
1143
1144/*
1145 * This function adds entropy to the entropy "pool" by using timing
1146 * delays. It uses the timer_rand_state structure to make an estimate
1147 * of how many bits of entropy this call has added to the pool. The
1148 * value "num" is also added to the pool; it should somehow describe
1149 * the type of event that just happened.
1150 */
1151static void add_timer_randomness(struct timer_rand_state *state, unsigned int num)
 
1152{
1153	unsigned long entropy = random_get_entropy(), now = jiffies, flags;
1154	long delta, delta2, delta3;
1155	unsigned int bits;
1156
1157	/*
1158	 * If we're in a hard IRQ, add_interrupt_randomness() will be called
1159	 * sometime after, so mix into the fast pool.
1160	 */
1161	if (in_hardirq()) {
1162		fast_mix(this_cpu_ptr(&irq_randomness)->pool, entropy, num);
1163	} else {
1164		spin_lock_irqsave(&input_pool.lock, flags);
1165		_mix_pool_bytes(&entropy, sizeof(entropy));
1166		_mix_pool_bytes(&num, sizeof(num));
1167		spin_unlock_irqrestore(&input_pool.lock, flags);
1168	}
 
1169
1170	if (crng_ready())
1171		return;
 
 
 
 
1172
1173	/*
1174	 * Calculate number of bits of randomness we probably added.
1175	 * We take into account the first, second and third-order deltas
1176	 * in order to make our estimate.
1177	 */
1178	delta = now - READ_ONCE(state->last_time);
1179	WRITE_ONCE(state->last_time, now);
1180
1181	delta2 = delta - READ_ONCE(state->last_delta);
1182	WRITE_ONCE(state->last_delta, delta);
1183
1184	delta3 = delta2 - READ_ONCE(state->last_delta2);
1185	WRITE_ONCE(state->last_delta2, delta2);
1186
1187	if (delta < 0)
1188		delta = -delta;
1189	if (delta2 < 0)
1190		delta2 = -delta2;
1191	if (delta3 < 0)
1192		delta3 = -delta3;
1193	if (delta > delta2)
1194		delta = delta2;
1195	if (delta > delta3)
1196		delta = delta3;
 
 
 
 
 
 
 
 
 
 
1197
1198	/*
1199	 * delta is now minimum absolute delta. Round down by 1 bit
1200	 * on general principles, and limit entropy estimate to 11 bits.
1201	 */
1202	bits = min(fls(delta >> 1), 11);
 
 
 
 
 
 
 
 
 
 
 
 
 
1203
1204	/*
1205	 * As mentioned above, if we're in a hard IRQ, add_interrupt_randomness()
1206	 * will run after this, which uses a different crediting scheme of 1 bit
1207	 * per every 64 interrupts. In order to let that function do accounting
1208	 * close to the one in this function, we credit a full 64/64 bit per bit,
1209	 * and then subtract one to account for the extra one added.
1210	 */
1211	if (in_hardirq())
1212		this_cpu_ptr(&irq_randomness)->count += max(1u, bits * 64) - 1;
1213	else
1214		_credit_init_bits(bits);
1215}
 
1216
1217void add_input_randomness(unsigned int type, unsigned int code, unsigned int value)
1218{
1219	static unsigned char last_value;
1220	static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES };
1221
1222	/* Ignore autorepeat and the like. */
1223	if (value == last_value)
1224		return;
 
 
 
 
 
 
 
 
 
 
 
1225
1226	last_value = value;
1227	add_timer_randomness(&input_timer_state,
1228			     (type << 4) ^ code ^ (code >> 4) ^ value);
 
 
 
 
 
 
1229}
1230EXPORT_SYMBOL_GPL(add_input_randomness);
1231
1232#ifdef CONFIG_BLOCK
1233void add_disk_randomness(struct gendisk *disk)
1234{
1235	if (!disk || !disk->random)
1236		return;
1237	/* First major is 1, so we get >= 0x200 here. */
1238	add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
 
 
 
 
 
 
 
 
 
1239}
1240EXPORT_SYMBOL_GPL(add_disk_randomness);
1241
1242void __cold rand_initialize_disk(struct gendisk *disk)
 
1243{
1244	struct timer_rand_state *state;
1245
1246	/*
1247	 * If kzalloc returns null, we just won't use that entropy
1248	 * source.
1249	 */
1250	state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1251	if (state) {
1252		state->last_time = INITIAL_JIFFIES;
1253		disk->random = state;
1254	}
1255}
1256#endif
1257
1258struct entropy_timer_state {
1259	unsigned long entropy;
1260	struct timer_list timer;
1261	atomic_t samples;
1262	unsigned int samples_per_bit;
1263};
1264
1265/*
1266 * Each time the timer fires, we expect that we got an unpredictable jump in
1267 * the cycle counter. Even if the timer is running on another CPU, the timer
1268 * activity will be touching the stack of the CPU that is generating entropy.
1269 *
1270 * Note that we don't re-arm the timer in the timer itself - we are happy to be
1271 * scheduled away, since that just makes the load more complex, but we do not
1272 * want the timer to keep ticking unless the entropy loop is running.
1273 *
1274 * So the re-arming always happens in the entropy loop itself.
 
1275 */
1276static void __cold entropy_timer(struct timer_list *timer)
1277{
1278	struct entropy_timer_state *state = container_of(timer, struct entropy_timer_state, timer);
1279	unsigned long entropy = random_get_entropy();
1280
1281	mix_pool_bytes(&entropy, sizeof(entropy));
1282	if (atomic_inc_return(&state->samples) % state->samples_per_bit == 0)
1283		credit_init_bits(1);
1284}
1285
1286/*
1287 * If we have an actual cycle counter, see if we can generate enough entropy
1288 * with timing noise.
1289 */
1290static void __cold try_to_generate_entropy(void)
1291{
1292	enum { NUM_TRIAL_SAMPLES = 8192, MAX_SAMPLES_PER_BIT = HZ / 15 };
1293	u8 stack_bytes[sizeof(struct entropy_timer_state) + SMP_CACHE_BYTES - 1];
1294	struct entropy_timer_state *stack = PTR_ALIGN((void *)stack_bytes, SMP_CACHE_BYTES);
1295	unsigned int i, num_different = 0;
1296	unsigned long last = random_get_entropy();
1297	int cpu = -1;
1298
1299	for (i = 0; i < NUM_TRIAL_SAMPLES - 1; ++i) {
1300		stack->entropy = random_get_entropy();
1301		if (stack->entropy != last)
1302			++num_different;
1303		last = stack->entropy;
1304	}
1305	stack->samples_per_bit = DIV_ROUND_UP(NUM_TRIAL_SAMPLES, num_different + 1);
1306	if (stack->samples_per_bit > MAX_SAMPLES_PER_BIT)
1307		return;
1308
1309	atomic_set(&stack->samples, 0);
1310	timer_setup_on_stack(&stack->timer, entropy_timer, 0);
1311	while (!crng_ready() && !signal_pending(current)) {
1312		/*
1313		 * Check !timer_pending() and then ensure that any previous callback has finished
1314		 * executing by checking try_to_del_timer_sync(), before queueing the next one.
1315		 */
1316		if (!timer_pending(&stack->timer) && try_to_del_timer_sync(&stack->timer) >= 0) {
1317			struct cpumask timer_cpus;
1318			unsigned int num_cpus;
1319
1320			/*
1321			 * Preemption must be disabled here, both to read the current CPU number
1322			 * and to avoid scheduling a timer on a dead CPU.
1323			 */
1324			preempt_disable();
1325
1326			/* Only schedule callbacks on timer CPUs that are online. */
1327			cpumask_and(&timer_cpus, housekeeping_cpumask(HK_TYPE_TIMER), cpu_online_mask);
1328			num_cpus = cpumask_weight(&timer_cpus);
1329			/* In very bizarre case of misconfiguration, fallback to all online. */
1330			if (unlikely(num_cpus == 0)) {
1331				timer_cpus = *cpu_online_mask;
1332				num_cpus = cpumask_weight(&timer_cpus);
1333			}
1334
1335			/* Basic CPU round-robin, which avoids the current CPU. */
1336			do {
1337				cpu = cpumask_next(cpu, &timer_cpus);
1338				if (cpu >= nr_cpu_ids)
1339					cpu = cpumask_first(&timer_cpus);
1340			} while (cpu == smp_processor_id() && num_cpus > 1);
1341
1342			/* Expiring the timer at `jiffies` means it's the next tick. */
1343			stack->timer.expires = jiffies;
1344
1345			add_timer_on(&stack->timer, cpu);
1346
1347			preempt_enable();
1348		}
1349		mix_pool_bytes(&stack->entropy, sizeof(stack->entropy));
1350		schedule();
1351		stack->entropy = random_get_entropy();
1352	}
1353	mix_pool_bytes(&stack->entropy, sizeof(stack->entropy));
1354
1355	del_timer_sync(&stack->timer);
1356	destroy_timer_on_stack(&stack->timer);
1357}
1358
 
 
 
 
1359
1360/**********************************************************************
1361 *
1362 * Userspace reader/writer interfaces.
1363 *
1364 * getrandom(2) is the primary modern interface into the RNG and should
1365 * be used in preference to anything else.
1366 *
1367 * Reading from /dev/random has the same functionality as calling
1368 * getrandom(2) with flags=0. In earlier versions, however, it had
1369 * vastly different semantics and should therefore be avoided, to
1370 * prevent backwards compatibility issues.
1371 *
1372 * Reading from /dev/urandom has the same functionality as calling
1373 * getrandom(2) with flags=GRND_INSECURE. Because it does not block
1374 * waiting for the RNG to be ready, it should not be used.
1375 *
1376 * Writing to either /dev/random or /dev/urandom adds entropy to
1377 * the input pool but does not credit it.
1378 *
1379 * Polling on /dev/random indicates when the RNG is initialized, on
1380 * the read side, and when it wants new entropy, on the write side.
1381 *
1382 * Both /dev/random and /dev/urandom have the same set of ioctls for
1383 * adding entropy, getting the entropy count, zeroing the count, and
1384 * reseeding the crng.
1385 *
1386 **********************************************************************/
1387
1388SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags)
1389{
1390	struct iov_iter iter;
1391	int ret;
 
 
 
 
 
 
1392
1393	if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE))
1394		return -EINVAL;
1395
1396	/*
1397	 * Requesting insecure and blocking randomness at the same time makes
1398	 * no sense.
1399	 */
1400	if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM))
1401		return -EINVAL;
1402
1403	if (!crng_ready() && !(flags & GRND_INSECURE)) {
1404		if (flags & GRND_NONBLOCK)
1405			return -EAGAIN;
1406		ret = wait_for_random_bytes();
1407		if (unlikely(ret))
1408			return ret;
1409	}
1410
1411	ret = import_ubuf(ITER_DEST, ubuf, len, &iter);
1412	if (unlikely(ret))
1413		return ret;
1414	return get_random_bytes_user(&iter);
1415}
1416
1417static __poll_t random_poll(struct file *file, poll_table *wait)
1418{
1419	poll_wait(file, &crng_init_wait, wait);
1420	return crng_ready() ? EPOLLIN | EPOLLRDNORM : EPOLLOUT | EPOLLWRNORM;
1421}
1422
1423static ssize_t write_pool_user(struct iov_iter *iter)
 
1424{
1425	u8 block[BLAKE2S_BLOCK_SIZE];
1426	ssize_t ret = 0;
1427	size_t copied;
1428
1429	if (unlikely(!iov_iter_count(iter)))
1430		return 0;
1431
1432	for (;;) {
1433		copied = copy_from_iter(block, sizeof(block), iter);
1434		ret += copied;
1435		mix_pool_bytes(block, copied);
1436		if (!iov_iter_count(iter) || copied != sizeof(block))
1437			break;
1438
1439		BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0);
1440		if (ret % PAGE_SIZE == 0) {
1441			if (signal_pending(current))
1442				break;
1443			cond_resched();
1444		}
1445	}
1446
1447	memzero_explicit(block, sizeof(block));
1448	return ret ? ret : -EFAULT;
 
1449}
1450
1451static ssize_t random_write_iter(struct kiocb *kiocb, struct iov_iter *iter)
 
1452{
1453	return write_pool_user(iter);
1454}
1455
1456static ssize_t urandom_read_iter(struct kiocb *kiocb, struct iov_iter *iter)
1457{
1458	static int maxwarn = 10;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1459
1460	/*
1461	 * Opportunistically attempt to initialize the RNG on platforms that
1462	 * have fast cycle counters, but don't (for now) require it to succeed.
1463	 */
1464	if (!crng_ready())
1465		try_to_generate_entropy();
1466
1467	if (!crng_ready()) {
1468		if (!ratelimit_disable && maxwarn <= 0)
1469			++urandom_warning.missed;
1470		else if (ratelimit_disable || __ratelimit(&urandom_warning)) {
1471			--maxwarn;
1472			pr_notice("%s: uninitialized urandom read (%zu bytes read)\n",
1473				  current->comm, iov_iter_count(iter));
1474		}
1475	}
1476
1477	return get_random_bytes_user(iter);
1478}
1479
1480static ssize_t random_read_iter(struct kiocb *kiocb, struct iov_iter *iter)
 
1481{
1482	int ret;
1483
1484	if (!crng_ready() &&
1485	    ((kiocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) ||
1486	     (kiocb->ki_filp->f_flags & O_NONBLOCK)))
1487		return -EAGAIN;
1488
1489	ret = wait_for_random_bytes();
1490	if (ret != 0)
1491		return ret;
1492	return get_random_bytes_user(iter);
 
 
 
 
1493}
1494
1495static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1496{
 
1497	int __user *p = (int __user *)arg;
1498	int ent_count;
1499
1500	switch (cmd) {
1501	case RNDGETENTCNT:
1502		/* Inherently racy, no point locking. */
1503		if (put_user(input_pool.init_bits, p))
 
1504			return -EFAULT;
1505		return 0;
1506	case RNDADDTOENTCNT:
1507		if (!capable(CAP_SYS_ADMIN))
1508			return -EPERM;
1509		if (get_user(ent_count, p))
1510			return -EFAULT;
1511		if (ent_count < 0)
1512			return -EINVAL;
1513		credit_init_bits(ent_count);
1514		return 0;
1515	case RNDADDENTROPY: {
1516		struct iov_iter iter;
1517		ssize_t ret;
1518		int len;
1519
1520		if (!capable(CAP_SYS_ADMIN))
1521			return -EPERM;
1522		if (get_user(ent_count, p++))
1523			return -EFAULT;
1524		if (ent_count < 0)
1525			return -EINVAL;
1526		if (get_user(len, p++))
1527			return -EFAULT;
1528		ret = import_ubuf(ITER_SOURCE, p, len, &iter);
1529		if (unlikely(ret))
1530			return ret;
1531		ret = write_pool_user(&iter);
1532		if (unlikely(ret < 0))
1533			return ret;
1534		/* Since we're crediting, enforce that it was all written into the pool. */
1535		if (unlikely(ret != len))
1536			return -EFAULT;
1537		credit_init_bits(ent_count);
 
 
 
 
1538		return 0;
1539	}
1540	case RNDZAPENTCNT:
1541	case RNDCLEARPOOL:
1542		/* No longer has any effect. */
1543		if (!capable(CAP_SYS_ADMIN))
1544			return -EPERM;
1545		return 0;
1546	case RNDRESEEDCRNG:
1547		if (!capable(CAP_SYS_ADMIN))
1548			return -EPERM;
1549		if (!crng_ready())
1550			return -ENODATA;
1551		crng_reseed(NULL);
1552		return 0;
1553	default:
1554		return -EINVAL;
1555	}
1556}
1557
1558static int random_fasync(int fd, struct file *filp, int on)
1559{
1560	return fasync_helper(fd, filp, on, &fasync);
1561}
1562
1563const struct file_operations random_fops = {
1564	.read_iter = random_read_iter,
1565	.write_iter = random_write_iter,
1566	.poll = random_poll,
1567	.unlocked_ioctl = random_ioctl,
1568	.compat_ioctl = compat_ptr_ioctl,
1569	.fasync = random_fasync,
1570	.llseek = noop_llseek,
1571	.splice_read = copy_splice_read,
1572	.splice_write = iter_file_splice_write,
1573};
1574
1575const struct file_operations urandom_fops = {
1576	.read_iter = urandom_read_iter,
1577	.write_iter = random_write_iter,
1578	.unlocked_ioctl = random_ioctl,
1579	.compat_ioctl = compat_ptr_ioctl,
1580	.fasync = random_fasync,
1581	.llseek = noop_llseek,
1582	.splice_read = copy_splice_read,
1583	.splice_write = iter_file_splice_write,
1584};
1585
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1586
1587/********************************************************************
1588 *
1589 * Sysctl interface.
1590 *
1591 * These are partly unused legacy knobs with dummy values to not break
1592 * userspace and partly still useful things. They are usually accessible
1593 * in /proc/sys/kernel/random/ and are as follows:
1594 *
1595 * - boot_id - a UUID representing the current boot.
1596 *
1597 * - uuid - a random UUID, different each time the file is read.
1598 *
1599 * - poolsize - the number of bits of entropy that the input pool can
1600 *   hold, tied to the POOL_BITS constant.
1601 *
1602 * - entropy_avail - the number of bits of entropy currently in the
1603 *   input pool. Always <= poolsize.
1604 *
1605 * - write_wakeup_threshold - the amount of entropy in the input pool
1606 *   below which write polls to /dev/random will unblock, requesting
1607 *   more entropy, tied to the POOL_READY_BITS constant. It is writable
1608 *   to avoid breaking old userspaces, but writing to it does not
1609 *   change any behavior of the RNG.
1610 *
1611 * - urandom_min_reseed_secs - fixed to the value CRNG_RESEED_INTERVAL.
1612 *   It is writable to avoid breaking old userspaces, but writing
1613 *   to it does not change any behavior of the RNG.
1614 *
1615 ********************************************************************/
1616
1617#ifdef CONFIG_SYSCTL
1618
1619#include <linux/sysctl.h>
1620
1621static int sysctl_random_min_urandom_seed = CRNG_RESEED_INTERVAL / HZ;
1622static int sysctl_random_write_wakeup_bits = POOL_READY_BITS;
1623static int sysctl_poolsize = POOL_BITS;
1624static u8 sysctl_bootid[UUID_SIZE];
1625
1626/*
1627 * This function is used to return both the bootid UUID, and random
1628 * UUID. The difference is in whether table->data is NULL; if it is,
1629 * then a new UUID is generated and returned to the user.
 
 
 
 
1630 */
1631static int proc_do_uuid(const struct ctl_table *table, int write, void *buf,
1632			size_t *lenp, loff_t *ppos)
1633{
1634	u8 tmp_uuid[UUID_SIZE], *uuid;
1635	char uuid_string[UUID_STRING_LEN + 1];
1636	struct ctl_table fake_table = {
1637		.data = uuid_string,
1638		.maxlen = UUID_STRING_LEN
1639	};
1640
1641	if (write)
1642		return -EPERM;
1643
1644	uuid = table->data;
1645	if (!uuid) {
1646		uuid = tmp_uuid;
1647		generate_random_uuid(uuid);
1648	} else {
1649		static DEFINE_SPINLOCK(bootid_spinlock);
1650
1651		spin_lock(&bootid_spinlock);
1652		if (!uuid[8])
1653			generate_random_uuid(uuid);
1654		spin_unlock(&bootid_spinlock);
1655	}
1656
1657	snprintf(uuid_string, sizeof(uuid_string), "%pU", uuid);
1658	return proc_dostring(&fake_table, 0, buf, lenp, ppos);
 
 
 
 
1659}
1660
1661/* The same as proc_dointvec, but writes don't change anything. */
1662static int proc_do_rointvec(const struct ctl_table *table, int write, void *buf,
1663			    size_t *lenp, loff_t *ppos)
 
 
1664{
1665	return write ? 0 : proc_dointvec(table, 0, buf, lenp, ppos);
 
 
 
 
 
 
 
 
1666}
1667
1668static struct ctl_table random_table[] = {
 
 
1669	{
1670		.procname	= "poolsize",
1671		.data		= &sysctl_poolsize,
1672		.maxlen		= sizeof(int),
1673		.mode		= 0444,
1674		.proc_handler	= proc_dointvec,
1675	},
1676	{
1677		.procname	= "entropy_avail",
1678		.data		= &input_pool.init_bits,
1679		.maxlen		= sizeof(int),
1680		.mode		= 0444,
1681		.proc_handler	= proc_dointvec,
 
 
 
 
 
 
 
 
 
 
1682	},
1683	{
1684		.procname	= "write_wakeup_threshold",
1685		.data		= &sysctl_random_write_wakeup_bits,
1686		.maxlen		= sizeof(int),
1687		.mode		= 0644,
1688		.proc_handler	= proc_do_rointvec,
 
 
1689	},
1690	{
1691		.procname	= "urandom_min_reseed_secs",
1692		.data		= &sysctl_random_min_urandom_seed,
1693		.maxlen		= sizeof(int),
1694		.mode		= 0644,
1695		.proc_handler	= proc_do_rointvec,
1696	},
1697	{
1698		.procname	= "boot_id",
1699		.data		= &sysctl_bootid,
 
1700		.mode		= 0444,
1701		.proc_handler	= proc_do_uuid,
1702	},
1703	{
1704		.procname	= "uuid",
 
1705		.mode		= 0444,
1706		.proc_handler	= proc_do_uuid,
1707	},
 
1708};
 
 
 
 
 
 
 
 
 
1709
1710/*
1711 * random_init() is called before sysctl_init(),
1712 * so we cannot call register_sysctl_init() in random_init()
 
 
1713 */
1714static int __init random_sysctls_init(void)
 
1715{
1716	register_sysctl_init("kernel/random", random_table);
1717	return 0;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1718}
1719device_initcall(random_sysctls_init);
1720#endif