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Diffstat (limited to '')
| -rw-r--r-- | drivers/char/random.c | 1699 |
1 files changed, 1699 insertions, 0 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c new file mode 100644 index 0000000000..3cb37760df --- /dev/null +++ b/drivers/char/random.c @@ -0,0 +1,1699 @@ +// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) +/* + * Copyright (C) 2017-2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. + * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005 + * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All rights reserved. + * + * This driver produces cryptographically secure pseudorandom data. It is divided + * into roughly six sections, each with a section header: + * + * - Initialization and readiness waiting. + * - Fast key erasure RNG, the "crng". + * - Entropy accumulation and extraction routines. + * - Entropy collection routines. + * - Userspace reader/writer interfaces. + * - Sysctl interface. + * + * The high level overview is that there is one input pool, into which + * various pieces of data are hashed. Prior to initialization, some of that + * data is then "credited" as having a certain number of bits of entropy. + * When enough bits of entropy are available, the hash is finalized and + * handed as a key to a stream cipher that expands it indefinitely for + * various consumers. This key is periodically refreshed as the various + * entropy collectors, described below, add data to the input pool. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/utsname.h> +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/major.h> +#include <linux/string.h> +#include <linux/fcntl.h> +#include <linux/slab.h> +#include <linux/random.h> +#include <linux/poll.h> +#include <linux/init.h> +#include <linux/fs.h> +#include <linux/blkdev.h> +#include <linux/interrupt.h> +#include <linux/mm.h> +#include <linux/nodemask.h> +#include <linux/spinlock.h> +#include <linux/kthread.h> +#include <linux/percpu.h> +#include <linux/ptrace.h> +#include <linux/workqueue.h> +#include <linux/irq.h> +#include <linux/ratelimit.h> +#include <linux/syscalls.h> +#include <linux/completion.h> +#include <linux/uuid.h> +#include <linux/uaccess.h> +#include <linux/suspend.h> +#include <linux/siphash.h> +#include <linux/sched/isolation.h> +#include <crypto/chacha.h> +#include <crypto/blake2s.h> +#include <asm/archrandom.h> +#include <asm/processor.h> +#include <asm/irq.h> +#include <asm/irq_regs.h> +#include <asm/io.h> + +/********************************************************************* + * + * Initialization and readiness waiting. + * + * Much of the RNG infrastructure is devoted to various dependencies + * being able to wait until the RNG has collected enough entropy and + * is ready for safe consumption. + * + *********************************************************************/ + +/* + * crng_init is protected by base_crng->lock, and only increases + * its value (from empty->early->ready). + */ +static enum { + CRNG_EMPTY = 0, /* Little to no entropy collected */ + CRNG_EARLY = 1, /* At least POOL_EARLY_BITS collected */ + CRNG_READY = 2 /* Fully initialized with POOL_READY_BITS collected */ +} crng_init __read_mostly = CRNG_EMPTY; +static DEFINE_STATIC_KEY_FALSE(crng_is_ready); +#define crng_ready() (static_branch_likely(&crng_is_ready) || crng_init >= CRNG_READY) +/* Various types of waiters for crng_init->CRNG_READY transition. */ +static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); +static struct fasync_struct *fasync; +static ATOMIC_NOTIFIER_HEAD(random_ready_notifier); + +/* Control how we warn userspace. */ +static struct ratelimit_state urandom_warning = + RATELIMIT_STATE_INIT_FLAGS("urandom_warning", HZ, 3, RATELIMIT_MSG_ON_RELEASE); +static int ratelimit_disable __read_mostly = + IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM); +module_param_named(ratelimit_disable, ratelimit_disable, int, 0644); +MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression"); + +/* + * Returns whether or not the input pool has been seeded and thus guaranteed + * to supply cryptographically secure random numbers. This applies to: the + * /dev/urandom device, the get_random_bytes function, and the get_random_{u8, + * u16,u32,u64,long} family of functions. + * + * Returns: true if the input pool has been seeded. + * false if the input pool has not been seeded. + */ +bool rng_is_initialized(void) +{ + return crng_ready(); +} +EXPORT_SYMBOL(rng_is_initialized); + +static void __cold crng_set_ready(struct work_struct *work) +{ + static_branch_enable(&crng_is_ready); +} + +/* Used by wait_for_random_bytes(), and considered an entropy collector, below. */ +static void try_to_generate_entropy(void); + +/* + * Wait for the input pool to be seeded and thus guaranteed to supply + * cryptographically secure random numbers. This applies to: the /dev/urandom + * device, the get_random_bytes function, and the get_random_{u8,u16,u32,u64, + * long} family of functions. Using any of these functions without first + * calling this function forfeits the guarantee of security. + * + * Returns: 0 if the input pool has been seeded. + * -ERESTARTSYS if the function was interrupted by a signal. + */ +int wait_for_random_bytes(void) +{ + while (!crng_ready()) { + int ret; + + try_to_generate_entropy(); + ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ); + if (ret) + return ret > 0 ? 0 : ret; + } + return 0; +} +EXPORT_SYMBOL(wait_for_random_bytes); + +/* + * Add a callback function that will be invoked when the crng is initialised, + * or immediately if it already has been. Only use this is you are absolutely + * sure it is required. Most users should instead be able to test + * `rng_is_initialized()` on demand, or make use of `get_random_bytes_wait()`. + */ +int __cold execute_with_initialized_rng(struct notifier_block *nb) +{ + unsigned long flags; + int ret = 0; + + spin_lock_irqsave(&random_ready_notifier.lock, flags); + if (crng_ready()) + nb->notifier_call(nb, 0, NULL); + else + ret = raw_notifier_chain_register((struct raw_notifier_head *)&random_ready_notifier.head, nb); + spin_unlock_irqrestore(&random_ready_notifier.lock, flags); + return ret; +} + +#define warn_unseeded_randomness() \ + if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \ + printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \ + __func__, (void *)_RET_IP_, crng_init) + + +/********************************************************************* + * + * Fast key erasure RNG, the "crng". + * + * These functions expand entropy from the entropy extractor into + * long streams for external consumption using the "fast key erasure" + * RNG described at <https://blog.cr.yp.to/20170723-random.html>. + * + * There are a few exported interfaces for use by other drivers: + * + * void get_random_bytes(void *buf, size_t len) + * u8 get_random_u8() + * u16 get_random_u16() + * u32 get_random_u32() + * u32 get_random_u32_below(u32 ceil) + * u32 get_random_u32_above(u32 floor) + * u32 get_random_u32_inclusive(u32 floor, u32 ceil) + * u64 get_random_u64() + * unsigned long get_random_long() + * + * These interfaces will return the requested number of random bytes + * into the given buffer or as a return value. This is equivalent to + * a read from /dev/urandom. The u8, u16, u32, u64, long family of + * functions may be higher performance for one-off random integers, + * because they do a bit of buffering and do not invoke reseeding + * until the buffer is emptied. + * + *********************************************************************/ + +enum { + CRNG_RESEED_START_INTERVAL = HZ, + CRNG_RESEED_INTERVAL = 60 * HZ +}; + +static struct { + u8 key[CHACHA_KEY_SIZE] __aligned(__alignof__(long)); + unsigned long generation; + spinlock_t lock; +} base_crng = { + .lock = __SPIN_LOCK_UNLOCKED(base_crng.lock) +}; + +struct crng { + u8 key[CHACHA_KEY_SIZE]; + unsigned long generation; + local_lock_t lock; +}; + +static DEFINE_PER_CPU(struct crng, crngs) = { + .generation = ULONG_MAX, + .lock = INIT_LOCAL_LOCK(crngs.lock), +}; + +/* + * Return the interval until the next reseeding, which is normally + * CRNG_RESEED_INTERVAL, but during early boot, it is at an interval + * proportional to the uptime. + */ +static unsigned int crng_reseed_interval(void) +{ + static bool early_boot = true; + + if (unlikely(READ_ONCE(early_boot))) { + time64_t uptime = ktime_get_seconds(); + if (uptime >= CRNG_RESEED_INTERVAL / HZ * 2) + WRITE_ONCE(early_boot, false); + else + return max_t(unsigned int, CRNG_RESEED_START_INTERVAL, + (unsigned int)uptime / 2 * HZ); + } + return CRNG_RESEED_INTERVAL; +} + +/* Used by crng_reseed() and crng_make_state() to extract a new seed from the input pool. */ +static void extract_entropy(void *buf, size_t len); + +/* This extracts a new crng key from the input pool. */ +static void crng_reseed(struct work_struct *work) +{ + static DECLARE_DELAYED_WORK(next_reseed, crng_reseed); + unsigned long flags; + unsigned long next_gen; + u8 key[CHACHA_KEY_SIZE]; + + /* Immediately schedule the next reseeding, so that it fires sooner rather than later. */ + if (likely(system_unbound_wq)) + queue_delayed_work(system_unbound_wq, &next_reseed, crng_reseed_interval()); + + extract_entropy(key, sizeof(key)); + + /* + * We copy the new key into the base_crng, overwriting the old one, + * and update the generation counter. We avoid hitting ULONG_MAX, + * because the per-cpu crngs are initialized to ULONG_MAX, so this + * forces new CPUs that come online to always initialize. + */ + spin_lock_irqsave(&base_crng.lock, flags); + memcpy(base_crng.key, key, sizeof(base_crng.key)); + next_gen = base_crng.generation + 1; + if (next_gen == ULONG_MAX) + ++next_gen; + WRITE_ONCE(base_crng.generation, next_gen); + if (!static_branch_likely(&crng_is_ready)) + crng_init = CRNG_READY; + spin_unlock_irqrestore(&base_crng.lock, flags); + memzero_explicit(key, sizeof(key)); +} + +/* + * This generates a ChaCha block using the provided key, and then + * immediately overwrites that key with half the block. It returns + * the resultant ChaCha state to the user, along with the second + * half of the block containing 32 bytes of random data that may + * be used; random_data_len may not be greater than 32. + * + * The returned ChaCha state contains within it a copy of the old + * key value, at index 4, so the state should always be zeroed out + * immediately after using in order to maintain forward secrecy. + * If the state cannot be erased in a timely manner, then it is + * safer to set the random_data parameter to &chacha_state[4] so + * that this function overwrites it before returning. + */ +static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE], + u32 chacha_state[CHACHA_STATE_WORDS], + u8 *random_data, size_t random_data_len) +{ + u8 first_block[CHACHA_BLOCK_SIZE]; + + BUG_ON(random_data_len > 32); + + chacha_init_consts(chacha_state); + memcpy(&chacha_state[4], key, CHACHA_KEY_SIZE); + memset(&chacha_state[12], 0, sizeof(u32) * 4); + chacha20_block(chacha_state, first_block); + + memcpy(key, first_block, CHACHA_KEY_SIZE); + memcpy(random_data, first_block + CHACHA_KEY_SIZE, random_data_len); + memzero_explicit(first_block, sizeof(first_block)); +} + +/* + * This function returns a ChaCha state that you may use for generating + * random data. It also returns up to 32 bytes on its own of random data + * that may be used; random_data_len may not be greater than 32. + */ +static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS], + u8 *random_data, size_t random_data_len) +{ + unsigned long flags; + struct crng *crng; + + BUG_ON(random_data_len > 32); + + /* + * For the fast path, we check whether we're ready, unlocked first, and + * then re-check once locked later. In the case where we're really not + * ready, we do fast key erasure with the base_crng directly, extracting + * when crng_init is CRNG_EMPTY. + */ + if (!crng_ready()) { + bool ready; + + spin_lock_irqsave(&base_crng.lock, flags); + ready = crng_ready(); + if (!ready) { + if (crng_init == CRNG_EMPTY) + extract_entropy(base_crng.key, sizeof(base_crng.key)); + crng_fast_key_erasure(base_crng.key, chacha_state, + random_data, random_data_len); + } + spin_unlock_irqrestore(&base_crng.lock, flags); + if (!ready) + return; + } + + local_lock_irqsave(&crngs.lock, flags); + crng = raw_cpu_ptr(&crngs); + + /* + * If our per-cpu crng is older than the base_crng, then it means + * somebody reseeded the base_crng. In that case, we do fast key + * erasure on the base_crng, and use its output as the new key + * for our per-cpu crng. This brings us up to date with base_crng. + */ + if (unlikely(crng->generation != READ_ONCE(base_crng.generation))) { + spin_lock(&base_crng.lock); + crng_fast_key_erasure(base_crng.key, chacha_state, + crng->key, sizeof(crng->key)); + crng->generation = base_crng.generation; + spin_unlock(&base_crng.lock); + } + + /* + * Finally, when we've made it this far, our per-cpu crng has an up + * to date key, and we can do fast key erasure with it to produce + * some random data and a ChaCha state for the caller. All other + * branches of this function are "unlikely", so most of the time we + * should wind up here immediately. + */ + crng_fast_key_erasure(crng->key, chacha_state, random_data, random_data_len); + local_unlock_irqrestore(&crngs.lock, flags); +} + +static void _get_random_bytes(void *buf, size_t len) +{ + u32 chacha_state[CHACHA_STATE_WORDS]; + u8 tmp[CHACHA_BLOCK_SIZE]; + size_t first_block_len; + + if (!len) + return; + + first_block_len = min_t(size_t, 32, len); + crng_make_state(chacha_state, buf, first_block_len); + len -= first_block_len; + buf += first_block_len; + + while (len) { + if (len < CHACHA_BLOCK_SIZE) { + chacha20_block(chacha_state, tmp); + memcpy(buf, tmp, len); + memzero_explicit(tmp, sizeof(tmp)); + break; + } + + chacha20_block(chacha_state, buf); + if (unlikely(chacha_state[12] == 0)) + ++chacha_state[13]; + len -= CHACHA_BLOCK_SIZE; + buf += CHACHA_BLOCK_SIZE; + } + + memzero_explicit(chacha_state, sizeof(chacha_state)); +} + +/* + * This returns random bytes in arbitrary quantities. The quality of the + * random bytes is good as /dev/urandom. In order to ensure that the + * randomness provided by this function is okay, the function + * wait_for_random_bytes() should be called and return 0 at least once + * at any point prior. + */ +void get_random_bytes(void *buf, size_t len) +{ + warn_unseeded_randomness(); + _get_random_bytes(buf, len); +} +EXPORT_SYMBOL(get_random_bytes); + +static ssize_t get_random_bytes_user(struct iov_iter *iter) +{ + u32 chacha_state[CHACHA_STATE_WORDS]; + u8 block[CHACHA_BLOCK_SIZE]; + size_t ret = 0, copied; + + if (unlikely(!iov_iter_count(iter))) + return 0; + + /* + * Immediately overwrite the ChaCha key at index 4 with random + * bytes, in case userspace causes copy_to_iter() below to sleep + * forever, so that we still retain forward secrecy in that case. + */ + crng_make_state(chacha_state, (u8 *)&chacha_state[4], CHACHA_KEY_SIZE); + /* + * However, if we're doing a read of len <= 32, we don't need to + * use chacha_state after, so we can simply return those bytes to + * the user directly. + */ + if (iov_iter_count(iter) <= CHACHA_KEY_SIZE) { + ret = copy_to_iter(&chacha_state[4], CHACHA_KEY_SIZE, iter); + goto out_zero_chacha; + } + + for (;;) { + chacha20_block(chacha_state, block); + if (unlikely(chacha_state[12] == 0)) + ++chacha_state[13]; + + copied = copy_to_iter(block, sizeof(block), iter); + ret += copied; + if (!iov_iter_count(iter) || copied != sizeof(block)) + break; + + BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0); + if (ret % PAGE_SIZE == 0) { + if (signal_pending(current)) + break; + cond_resched(); + } + } + + memzero_explicit(block, sizeof(block)); +out_zero_chacha: + memzero_explicit(chacha_state, sizeof(chacha_state)); + return ret ? ret : -EFAULT; +} + +/* + * Batched entropy returns random integers. The quality of the random + * number is good as /dev/urandom. In order to ensure that the randomness + * provided by this function is okay, the function wait_for_random_bytes() + * should be called and return 0 at least once at any point prior. + */ + +#define DEFINE_BATCHED_ENTROPY(type) \ +struct batch_ ##type { \ + /* \ + * We make this 1.5x a ChaCha block, so that we get the \ + * remaining 32 bytes from fast key erasure, plus one full \ + * block from the detached ChaCha state. We can increase \ + * the size of this later if needed so long as we keep the \ + * formula of (integer_blocks + 0.5) * CHACHA_BLOCK_SIZE. \ + */ \ + type entropy[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(type))]; \ + local_lock_t lock; \ + unsigned long generation; \ + unsigned int position; \ +}; \ + \ +static DEFINE_PER_CPU(struct batch_ ##type, batched_entropy_ ##type) = { \ + .lock = INIT_LOCAL_LOCK(batched_entropy_ ##type.lock), \ + .position = UINT_MAX \ +}; \ + \ +type get_random_ ##type(void) \ +{ \ + type ret; \ + unsigned long flags; \ + struct batch_ ##type *batch; \ + unsigned long next_gen; \ + \ + warn_unseeded_randomness(); \ + \ + if (!crng_ready()) { \ + _get_random_bytes(&ret, sizeof(ret)); \ + return ret; \ + } \ + \ + local_lock_irqsave(&batched_entropy_ ##type.lock, flags); \ + batch = raw_cpu_ptr(&batched_entropy_##type); \ + \ + next_gen = READ_ONCE(base_crng.generation); \ + if (batch->position >= ARRAY_SIZE(batch->entropy) || \ + next_gen != batch->generation) { \ + _get_random_bytes(batch->entropy, sizeof(batch->entropy)); \ + batch->position = 0; \ + batch->generation = next_gen; \ + } \ + \ + ret = batch->entropy[batch->position]; \ + batch->entropy[batch->position] = 0; \ + ++batch->position; \ + local_unlock_irqrestore(&batched_entropy_ ##type.lock, flags); \ + return ret; \ +} \ +EXPORT_SYMBOL(get_random_ ##type); + +DEFINE_BATCHED_ENTROPY(u8) +DEFINE_BATCHED_ENTROPY(u16) +DEFINE_BATCHED_ENTROPY(u32) +DEFINE_BATCHED_ENTROPY(u64) + +u32 __get_random_u32_below(u32 ceil) +{ + /* + * This is the slow path for variable ceil. It is still fast, most of + * the time, by doing traditional reciprocal multiplication and + * opportunistically comparing the lower half to ceil itself, before + * falling back to computing a larger bound, and then rejecting samples + * whose lower half would indicate a range indivisible by ceil. The use + * of `-ceil % ceil` is analogous to `2^32 % ceil`, but is computable + * in 32-bits. + */ + u32 rand = get_random_u32(); + u64 mult; + + /* + * This function is technically undefined for ceil == 0, and in fact + * for the non-underscored constant version in the header, we build bug + * on that. But for the non-constant case, it's convenient to have that + * evaluate to being a straight call to get_random_u32(), so that + * get_random_u32_inclusive() can work over its whole range without + * undefined behavior. + */ + if (unlikely(!ceil)) + return rand; + + mult = (u64)ceil * rand; + if (unlikely((u32)mult < ceil)) { + u32 bound = -ceil % ceil; + while (unlikely((u32)mult < bound)) + mult = (u64)ceil * get_random_u32(); + } + return mult >> 32; +} +EXPORT_SYMBOL(__get_random_u32_below); + +#ifdef CONFIG_SMP +/* + * This function is called when the CPU is coming up, with entry + * CPUHP_RANDOM_PREPARE, which comes before CPUHP_WORKQUEUE_PREP. + */ +int __cold random_prepare_cpu(unsigned int cpu) +{ + /* + * When the cpu comes back online, immediately invalidate both + * the per-cpu crng and all batches, so that we serve fresh + * randomness. + */ + per_cpu_ptr(&crngs, cpu)->generation = ULONG_MAX; + per_cpu_ptr(&batched_entropy_u8, cpu)->position = UINT_MAX; + per_cpu_ptr(&batched_entropy_u16, cpu)->position = UINT_MAX; + per_cpu_ptr(&batched_entropy_u32, cpu)->position = UINT_MAX; + per_cpu_ptr(&batched_entropy_u64, cpu)->position = UINT_MAX; + return 0; +} +#endif + + +/********************************************************************** + * + * Entropy accumulation and extraction routines. + * + * Callers may add entropy via: + * + * static void mix_pool_bytes(const void *buf, size_t len) + * + * After which, if added entropy should be credited: + * + * static void credit_init_bits(size_t bits) + * + * Finally, extract entropy via: + * + * static void extract_entropy(void *buf, size_t len) + * + **********************************************************************/ + +enum { + POOL_BITS = BLAKE2S_HASH_SIZE * 8, + POOL_READY_BITS = POOL_BITS, /* When crng_init->CRNG_READY */ + POOL_EARLY_BITS = POOL_READY_BITS / 2 /* When crng_init->CRNG_EARLY */ +}; + +static struct { + struct blake2s_state hash; + spinlock_t lock; + unsigned int init_bits; +} input_pool = { + .hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE), + BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4, + BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 }, + .hash.outlen = BLAKE2S_HASH_SIZE, + .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), +}; + +static void _mix_pool_bytes(const void *buf, size_t len) +{ + blake2s_update(&input_pool.hash, buf, len); +} + +/* + * This function adds bytes into the input pool. It does not + * update the initialization bit counter; the caller should call + * credit_init_bits if this is appropriate. + */ +static void mix_pool_bytes(const void *buf, size_t len) +{ + unsigned long flags; + + spin_lock_irqsave(&input_pool.lock, flags); + _mix_pool_bytes(buf, len); + spin_unlock_irqrestore(&input_pool.lock, flags); +} + +/* + * This is an HKDF-like construction for using the hashed collected entropy + * as a PRF key, that's then expanded block-by-block. + */ +static void extract_entropy(void *buf, size_t len) +{ + unsigned long flags; + u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE]; + struct { + unsigned long rdseed[32 / sizeof(long)]; + size_t counter; + } block; + size_t i, longs; + + for (i = 0; i < ARRAY_SIZE(block.rdseed);) { + longs = arch_get_random_seed_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); + if (longs) { + i += longs; + continue; + } + longs = arch_get_random_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); + if (longs) { + i += longs; + continue; + } + block.rdseed[i++] = random_get_entropy(); + } + + spin_lock_irqsave(&input_pool.lock, flags); + + /* seed = HASHPRF(last_key, entropy_input) */ + blake2s_final(&input_pool.hash, seed); + + /* next_key = HASHPRF(seed, RDSEED || 0) */ + block.counter = 0; + blake2s(next_key, (u8 *)&block, seed, sizeof(next_key), sizeof(block), sizeof(seed)); + blake2s_init_key(&input_pool.hash, BLAKE2S_HASH_SIZE, next_key, sizeof(next_key)); + + spin_unlock_irqrestore(&input_pool.lock, flags); + memzero_explicit(next_key, sizeof(next_key)); + + while (len) { + i = min_t(size_t, len, BLAKE2S_HASH_SIZE); + /* output = HASHPRF(seed, RDSEED || ++counter) */ + ++block.counter; + blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed)); + len -= i; + buf += i; + } + + memzero_explicit(seed, sizeof(seed)); + memzero_explicit(&block, sizeof(block)); +} + +#define credit_init_bits(bits) if (!crng_ready()) _credit_init_bits(bits) + +static void __cold _credit_init_bits(size_t bits) +{ + static struct execute_work set_ready; + unsigned int new, orig, add; + unsigned long flags; + + if (!bits) + return; + + add = min_t(size_t, bits, POOL_BITS); + + orig = READ_ONCE(input_pool.init_bits); + do { + new = min_t(unsigned int, POOL_BITS, orig + add); + } while (!try_cmpxchg(&input_pool.init_bits, &orig, new)); + + if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) { + crng_reseed(NULL); /* Sets crng_init to CRNG_READY under base_crng.lock. */ + if (static_key_initialized) + execute_in_process_context(crng_set_ready, &set_ready); + atomic_notifier_call_chain(&random_ready_notifier, 0, NULL); + wake_up_interruptible(&crng_init_wait); + kill_fasync(&fasync, SIGIO, POLL_IN); + pr_notice("crng init done\n"); + if (urandom_warning.missed) + pr_notice("%d urandom warning(s) missed due to ratelimiting\n", + urandom_warning.missed); + } else if (orig < POOL_EARLY_BITS && new >= POOL_EARLY_BITS) { + spin_lock_irqsave(&base_crng.lock, flags); + /* Check if crng_init is CRNG_EMPTY, to avoid race with crng_reseed(). */ + if (crng_init == CRNG_EMPTY) { + extract_entropy(base_crng.key, sizeof(base_crng.key)); + crng_init = CRNG_EARLY; + } + spin_unlock_irqrestore(&base_crng.lock, flags); + } +} + + +/********************************************************************** + * + * Entropy collection routines. + * + * The following exported functions are used for pushing entropy into + * the above entropy accumulation routines: + * + * void add_device_randomness(const void *buf, size_t len); + * void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after); + * void add_bootloader_randomness(const void *buf, size_t len); + * void add_vmfork_randomness(const void *unique_vm_id, size_t len); + * void add_interrupt_randomness(int irq); + * void add_input_randomness(unsigned int type, unsigned int code, unsigned int value); + * void add_disk_randomness(struct gendisk *disk); + * + * add_device_randomness() adds data to the input pool that + * is likely to differ between two devices (or possibly even per boot). + * This would be things like MAC addresses or serial numbers, or the + * read-out of the RTC. This does *not* credit any actual entropy to + * the pool, but it initializes the pool to different values for devices + * that might otherwise be identical and have very little entropy + * available to them (particularly common in the embedded world). + * + * add_hwgenerator_randomness() is for true hardware RNGs, and will credit + * entropy as specified by the caller. If the entropy pool is full it will + * block until more entropy is needed. + * + * add_bootloader_randomness() is called by bootloader drivers, such as EFI + * and device tree, and credits its input depending on whether or not the + * command line option 'random.trust_bootloader'. + * + * add_vmfork_randomness() adds a unique (but not necessarily secret) ID + * representing the current instance of a VM to the pool, without crediting, + * and then force-reseeds the crng so that it takes effect immediately. + * + * add_interrupt_randomness() uses the interrupt timing as random + * inputs to the entropy pool. Using the cycle counters and the irq source + * as inputs, it feeds the input pool roughly once a second or after 64 + * interrupts, crediting 1 bit of entropy for whichever comes first. + * + * add_input_randomness() uses the input layer interrupt timing, as well + * as the event type information from the hardware. + * + * add_disk_randomness() uses what amounts to the seek time of block + * layer request events, on a per-disk_devt basis, as input to the + * entropy pool. Note that high-speed solid state drives with very low + * seek times do not make for good sources of entropy, as their seek + * times are usually fairly consistent. + * + * The last two routines try to estimate how many bits of entropy + * to credit. They do this by keeping track of the first and second + * order deltas of the event timings. + * + **********************************************************************/ + +static bool trust_cpu __initdata = true; +static bool trust_bootloader __initdata = true; +static int __init parse_trust_cpu(char *arg) +{ + return kstrtobool(arg, &trust_cpu); +} +static int __init parse_trust_bootloader(char *arg) +{ + return kstrtobool(arg, &trust_bootloader); +} +early_param("random.trust_cpu", parse_trust_cpu); +early_param("random.trust_bootloader", parse_trust_bootloader); + +static int random_pm_notification(struct notifier_block *nb, unsigned long action, void *data) +{ + unsigned long flags, entropy = random_get_entropy(); + + /* + * Encode a representation of how long the system has been suspended, + * in a way that is distinct from prior system suspends. + */ + ktime_t stamps[] = { ktime_get(), ktime_get_boottime(), ktime_get_real() }; + + spin_lock_irqsave(&input_pool.lock, flags); + _mix_pool_bytes(&action, sizeof(action)); + _mix_pool_bytes(stamps, sizeof(stamps)); + _mix_pool_bytes(&entropy, sizeof(entropy)); + spin_unlock_irqrestore(&input_pool.lock, flags); + + if (crng_ready() && (action == PM_RESTORE_PREPARE || + (action == PM_POST_SUSPEND && !IS_ENABLED(CONFIG_PM_AUTOSLEEP) && + !IS_ENABLED(CONFIG_PM_USERSPACE_AUTOSLEEP)))) { + crng_reseed(NULL); + pr_notice("crng reseeded on system resumption\n"); + } + return 0; +} + +static struct notifier_block pm_notifier = { .notifier_call = random_pm_notification }; + +/* + * This is called extremely early, before time keeping functionality is + * available, but arch randomness is. Interrupts are not yet enabled. + */ +void __init random_init_early(const char *command_line) +{ + unsigned long entropy[BLAKE2S_BLOCK_SIZE / sizeof(long)]; + size_t i, longs, arch_bits; + +#if defined(LATENT_ENTROPY_PLUGIN) + static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy; + _mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed)); +#endif + + for (i = 0, arch_bits = sizeof(entropy) * 8; i < ARRAY_SIZE(entropy);) { + longs = arch_get_random_seed_longs(entropy, ARRAY_SIZE(entropy) - i); + if (longs) { + _mix_pool_bytes(entropy, sizeof(*entropy) * longs); + i += longs; + continue; + } + longs = arch_get_random_longs(entropy, ARRAY_SIZE(entropy) - i); + if (longs) { + _mix_pool_bytes(entropy, sizeof(*entropy) * longs); + i += longs; + continue; + } + arch_bits -= sizeof(*entropy) * 8; + ++i; + } + + _mix_pool_bytes(init_utsname(), sizeof(*(init_utsname()))); + _mix_pool_bytes(command_line, strlen(command_line)); + + /* Reseed if already seeded by earlier phases. */ + if (crng_ready()) + crng_reseed(NULL); + else if (trust_cpu) + _credit_init_bits(arch_bits); +} + +/* + * This is called a little bit after the prior function, and now there is + * access to timestamps counters. Interrupts are not yet enabled. + */ +void __init random_init(void) +{ + unsigned long entropy = random_get_entropy(); + ktime_t now = ktime_get_real(); + + _mix_pool_bytes(&now, sizeof(now)); + _mix_pool_bytes(&entropy, sizeof(entropy)); + add_latent_entropy(); + + /* + * If we were initialized by the cpu or bootloader before jump labels + * are initialized, then we should enable the static branch here, where + * it's guaranteed that jump labels have been initialized. + */ + if (!static_branch_likely(&crng_is_ready) && crng_init >= CRNG_READY) + crng_set_ready(NULL); + + /* Reseed if already seeded by earlier phases. */ + if (crng_ready()) + crng_reseed(NULL); + + WARN_ON(register_pm_notifier(&pm_notifier)); + + WARN(!entropy, "Missing cycle counter and fallback timer; RNG " + "entropy collection will consequently suffer."); +} + +/* + * Add device- or boot-specific data to the input pool to help + * initialize it. + * + * None of this adds any entropy; it is meant to avoid the problem of + * the entropy pool having similar initial state across largely + * identical devices. + */ +void add_device_randomness(const void *buf, size_t len) +{ + unsigned long entropy = random_get_entropy(); + unsigned long flags; + + spin_lock_irqsave(&input_pool.lock, flags); + _mix_pool_bytes(&entropy, sizeof(entropy)); + _mix_pool_bytes(buf, len); + spin_unlock_irqrestore(&input_pool.lock, flags); +} +EXPORT_SYMBOL(add_device_randomness); + +/* + * Interface for in-kernel drivers of true hardware RNGs. Those devices + * may produce endless random bits, so this function will sleep for + * some amount of time after, if the sleep_after parameter is true. + */ +void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after) +{ + mix_pool_bytes(buf, len); + credit_init_bits(entropy); + + /* + * Throttle writing to once every reseed interval, unless we're not yet + * initialized or no entropy is credited. + */ + if (sleep_after && !kthread_should_stop() && (crng_ready() || !entropy)) + schedule_timeout_interruptible(crng_reseed_interval()); +} +EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); + +/* + * Handle random seed passed by bootloader, and credit it depending + * on the command line option 'random.trust_bootloader'. + */ +void __init add_bootloader_randomness(const void *buf, size_t len) +{ + mix_pool_bytes(buf, len); + if (trust_bootloader) + credit_init_bits(len * 8); +} + +#if IS_ENABLED(CONFIG_VMGENID) +static BLOCKING_NOTIFIER_HEAD(vmfork_chain); + +/* + * Handle a new unique VM ID, which is unique, not secret, so we + * don't credit it, but we do immediately force a reseed after so + * that it's used by the crng posthaste. + */ +void __cold add_vmfork_randomness(const void *unique_vm_id, size_t len) +{ + add_device_randomness(unique_vm_id, len); + if (crng_ready()) { + crng_reseed(NULL); + pr_notice("crng reseeded due to virtual machine fork\n"); + } + blocking_notifier_call_chain(&vmfork_chain, 0, NULL); +} +#if IS_MODULE(CONFIG_VMGENID) +EXPORT_SYMBOL_GPL(add_vmfork_randomness); +#endif + +int __cold register_random_vmfork_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_register(&vmfork_chain, nb); +} +EXPORT_SYMBOL_GPL(register_random_vmfork_notifier); + +int __cold unregister_random_vmfork_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_unregister(&vmfork_chain, nb); +} +EXPORT_SYMBOL_GPL(unregister_random_vmfork_notifier); +#endif + +struct fast_pool { + unsigned long pool[4]; + unsigned long last; + unsigned int count; + struct timer_list mix; +}; + +static void mix_interrupt_randomness(struct timer_list *work); + +static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = { +#ifdef CONFIG_64BIT +#define FASTMIX_PERM SIPHASH_PERMUTATION + .pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 }, +#else +#define FASTMIX_PERM HSIPHASH_PERMUTATION + .pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 }, +#endif + .mix = __TIMER_INITIALIZER(mix_interrupt_randomness, 0) +}; + +/* + * This is [Half]SipHash-1-x, starting from an empty key. Because + * the key is fixed, it assumes that its inputs are non-malicious, + * and therefore this has no security on its own. s represents the + * four-word SipHash state, while v represents a two-word input. + */ +static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2) +{ + s[3] ^= v1; + FASTMIX_PERM(s[0], s[1], s[2], s[3]); + s[0] ^= v1; + s[3] ^= v2; + FASTMIX_PERM(s[0], s[1], s[2], s[3]); + s[0] ^= v2; +} + +#ifdef CONFIG_SMP +/* + * This function is called when the CPU has just come online, with + * entry CPUHP_AP_RANDOM_ONLINE, just after CPUHP_AP_WORKQUEUE_ONLINE. + */ +int __cold random_online_cpu(unsigned int cpu) +{ + /* + * During CPU shutdown and before CPU onlining, add_interrupt_ + * randomness() may schedule mix_interrupt_randomness(), and + * set the MIX_INFLIGHT flag. However, because the worker can + * be scheduled on a different CPU during this period, that + * flag will never be cleared. For that reason, we zero out + * the flag here, which runs just after workqueues are onlined + * for the CPU again. This also has the effect of setting the + * irq randomness count to zero so that new accumulated irqs + * are fresh. + */ + per_cpu_ptr(&irq_randomness, cpu)->count = 0; + return 0; +} +#endif + +static void mix_interrupt_randomness(struct timer_list *work) +{ + struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix); + /* + * The size of the copied stack pool is explicitly 2 longs so that we + * only ever ingest half of the siphash output each time, retaining + * the other half as the next "key" that carries over. The entropy is + * supposed to be sufficiently dispersed between bits so on average + * we don't wind up "losing" some. + */ + unsigned long pool[2]; + unsigned int count; + + /* Check to see if we're running on the wrong CPU due to hotplug. */ + local_irq_disable(); + if (fast_pool != this_cpu_ptr(&irq_randomness)) { + local_irq_enable(); + return; + } + + /* + * Copy the pool to the stack so that the mixer always has a + * consistent view, before we reenable irqs again. + */ + memcpy(pool, fast_pool->pool, sizeof(pool)); + count = fast_pool->count; + fast_pool->count = 0; + fast_pool->last = jiffies; + local_irq_enable(); + + mix_pool_bytes(pool, sizeof(pool)); + credit_init_bits(clamp_t(unsigned int, (count & U16_MAX) / 64, 1, sizeof(pool) * 8)); + + memzero_explicit(pool, sizeof(pool)); +} + +void add_interrupt_randomness(int irq) +{ + enum { MIX_INFLIGHT = 1U << 31 }; + unsigned long entropy = random_get_entropy(); + struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness); + struct pt_regs *regs = get_irq_regs(); + unsigned int new_count; + + fast_mix(fast_pool->pool, entropy, + (regs ? instruction_pointer(regs) : _RET_IP_) ^ swab(irq)); + new_count = ++fast_pool->count; + + if (new_count & MIX_INFLIGHT) + return; + + if (new_count < 1024 && !time_is_before_jiffies(fast_pool->last + HZ)) + return; + + fast_pool->count |= MIX_INFLIGHT; + if (!timer_pending(&fast_pool->mix)) { + fast_pool->mix.expires = jiffies; + add_timer_on(&fast_pool->mix, raw_smp_processor_id()); + } +} +EXPORT_SYMBOL_GPL(add_interrupt_randomness); + +/* There is one of these per entropy source */ +struct timer_rand_state { + unsigned long last_time; + long last_delta, last_delta2; +}; + +/* + * This function adds entropy to the entropy "pool" by using timing + * delays. It uses the timer_rand_state structure to make an estimate + * of how many bits of entropy this call has added to the pool. The + * value "num" is also added to the pool; it should somehow describe + * the type of event that just happened. + */ +static void add_timer_randomness(struct timer_rand_state *state, unsigned int num) +{ + unsigned long entropy = random_get_entropy(), now = jiffies, flags; + long delta, delta2, delta3; + unsigned int bits; + + /* + * If we're in a hard IRQ, add_interrupt_randomness() will be called + * sometime after, so mix into the fast pool. + */ + if (in_hardirq()) { + fast_mix(this_cpu_ptr(&irq_randomness)->pool, entropy, num); + } else { + spin_lock_irqsave(&input_pool.lock, flags); + _mix_pool_bytes(&entropy, sizeof(entropy)); + _mix_pool_bytes(&num, sizeof(num)); + spin_unlock_irqrestore(&input_pool.lock, flags); + } + + if (crng_ready()) + return; + + /* + * Calculate number of bits of randomness we probably added. + * We take into account the first, second and third-order deltas + * in order to make our estimate. + */ + delta = now - READ_ONCE(state->last_time); + WRITE_ONCE(state->last_time, now); + + delta2 = delta - READ_ONCE(state->last_delta); + WRITE_ONCE(state->last_delta, delta); + + delta3 = delta2 - READ_ONCE(state->last_delta2); + WRITE_ONCE(state->last_delta2, delta2); + + if (delta < 0) + delta = -delta; + if (delta2 < 0) + delta2 = -delta2; + if (delta3 < 0) + delta3 = -delta3; + if (delta > delta2) + delta = delta2; + if (delta > delta3) + delta = delta3; + + /* + * delta is now minimum absolute delta. Round down by 1 bit + * on general principles, and limit entropy estimate to 11 bits. + */ + bits = min(fls(delta >> 1), 11); + + /* + * As mentioned above, if we're in a hard IRQ, add_interrupt_randomness() + * will run after this, which uses a different crediting scheme of 1 bit + * per every 64 interrupts. In order to let that function do accounting + * close to the one in this function, we credit a full 64/64 bit per bit, + * and then subtract one to account for the extra one added. + */ + if (in_hardirq()) + this_cpu_ptr(&irq_randomness)->count += max(1u, bits * 64) - 1; + else + _credit_init_bits(bits); +} + +void add_input_randomness(unsigned int type, unsigned int code, unsigned int value) +{ + static unsigned char last_value; + static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES }; + + /* Ignore autorepeat and the like. */ + if (value == last_value) + return; + + last_value = value; + add_timer_randomness(&input_timer_state, + (type << 4) ^ code ^ (code >> 4) ^ value); +} +EXPORT_SYMBOL_GPL(add_input_randomness); + +#ifdef CONFIG_BLOCK +void add_disk_randomness(struct gendisk *disk) +{ + if (!disk || !disk->random) + return; + /* First major is 1, so we get >= 0x200 here. */ + add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); +} +EXPORT_SYMBOL_GPL(add_disk_randomness); + +void __cold rand_initialize_disk(struct gendisk *disk) +{ + struct timer_rand_state *state; + + /* + * If kzalloc returns null, we just won't use that entropy + * source. + */ + state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); + if (state) { + state->last_time = INITIAL_JIFFIES; + disk->random = state; + } +} +#endif + +struct entropy_timer_state { + unsigned long entropy; + struct timer_list timer; + atomic_t samples; + unsigned int samples_per_bit; +}; + +/* + * Each time the timer fires, we expect that we got an unpredictable jump in + * the cycle counter. Even if the timer is running on another CPU, the timer + * activity will be touching the stack of the CPU that is generating entropy. + * + * Note that we don't re-arm the timer in the timer itself - we are happy to be + * scheduled away, since that just makes the load more complex, but we do not + * want the timer to keep ticking unless the entropy loop is running. + * + * So the re-arming always happens in the entropy loop itself. + */ +static void __cold entropy_timer(struct timer_list *timer) +{ + struct entropy_timer_state *state = container_of(timer, struct entropy_timer_state, timer); + unsigned long entropy = random_get_entropy(); + + mix_pool_bytes(&entropy, sizeof(entropy)); + if (atomic_inc_return(&state->samples) % state->samples_per_bit == 0) + credit_init_bits(1); +} + +/* + * If we have an actual cycle counter, see if we can generate enough entropy + * with timing noise. + */ +static void __cold try_to_generate_entropy(void) +{ + enum { NUM_TRIAL_SAMPLES = 8192, MAX_SAMPLES_PER_BIT = HZ / 15 }; + u8 stack_bytes[sizeof(struct entropy_timer_state) + SMP_CACHE_BYTES - 1]; + struct entropy_timer_state *stack = PTR_ALIGN((void *)stack_bytes, SMP_CACHE_BYTES); + unsigned int i, num_different = 0; + unsigned long last = random_get_entropy(); + int cpu = -1; + + for (i = 0; i < NUM_TRIAL_SAMPLES - 1; ++i) { + stack->entropy = random_get_entropy(); + if (stack->entropy != last) + ++num_different; + last = stack->entropy; + } + stack->samples_per_bit = DIV_ROUND_UP(NUM_TRIAL_SAMPLES, num_different + 1); + if (stack->samples_per_bit > MAX_SAMPLES_PER_BIT) + return; + + atomic_set(&stack->samples, 0); + timer_setup_on_stack(&stack->timer, entropy_timer, 0); + while (!crng_ready() && !signal_pending(current)) { + /* + * Check !timer_pending() and then ensure that any previous callback has finished + * executing by checking try_to_del_timer_sync(), before queueing the next one. + */ + if (!timer_pending(&stack->timer) && try_to_del_timer_sync(&stack->timer) >= 0) { + struct cpumask timer_cpus; + unsigned int num_cpus; + + /* + * Preemption must be disabled here, both to read the current CPU number + * and to avoid scheduling a timer on a dead CPU. + */ + preempt_disable(); + + /* Only schedule callbacks on timer CPUs that are online. */ + cpumask_and(&timer_cpus, housekeeping_cpumask(HK_TYPE_TIMER), cpu_online_mask); + num_cpus = cpumask_weight(&timer_cpus); + /* In very bizarre case of misconfiguration, fallback to all online. */ + if (unlikely(num_cpus == 0)) { + timer_cpus = *cpu_online_mask; + num_cpus = cpumask_weight(&timer_cpus); + } + + /* Basic CPU round-robin, which avoids the current CPU. */ + do { + cpu = cpumask_next(cpu, &timer_cpus); + if (cpu >= nr_cpu_ids) + cpu = cpumask_first(&timer_cpus); + } while (cpu == smp_processor_id() && num_cpus > 1); + + /* Expiring the timer at `jiffies` means it's the next tick. */ + stack->timer.expires = jiffies; + + add_timer_on(&stack->timer, cpu); + + preempt_enable(); + } + mix_pool_bytes(&stack->entropy, sizeof(stack->entropy)); + schedule(); + stack->entropy = random_get_entropy(); + } + mix_pool_bytes(&stack->entropy, sizeof(stack->entropy)); + + del_timer_sync(&stack->timer); + destroy_timer_on_stack(&stack->timer); +} + + +/********************************************************************** + * + * Userspace reader/writer interfaces. + * + * getrandom(2) is the primary modern interface into the RNG and should + * be used in preference to anything else. + * + * Reading from /dev/random has the same functionality as calling + * getrandom(2) with flags=0. In earlier versions, however, it had + * vastly different semantics and should therefore be avoided, to + * prevent backwards compatibility issues. + * + * Reading from /dev/urandom has the same functionality as calling + * getrandom(2) with flags=GRND_INSECURE. Because it does not block + * waiting for the RNG to be ready, it should not be used. + * + * Writing to either /dev/random or /dev/urandom adds entropy to + * the input pool but does not credit it. + * + * Polling on /dev/random indicates when the RNG is initialized, on + * the read side, and when it wants new entropy, on the write side. + * + * Both /dev/random and /dev/urandom have the same set of ioctls for + * adding entropy, getting the entropy count, zeroing the count, and + * reseeding the crng. + * + **********************************************************************/ + +SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags) +{ + struct iov_iter iter; + struct iovec iov; + int ret; + + if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE)) + return -EINVAL; + + /* + * Requesting insecure and blocking randomness at the same time makes + * no sense. + */ + if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM)) + return -EINVAL; + + if (!crng_ready() && !(flags & GRND_INSECURE)) { + if (flags & GRND_NONBLOCK) + return -EAGAIN; + ret = wait_for_random_bytes(); + if (unlikely(ret)) + return ret; + } + + ret = import_single_range(ITER_DEST, ubuf, len, &iov, &iter); + if (unlikely(ret)) + return ret; + return get_random_bytes_user(&iter); +} + +static __poll_t random_poll(struct file *file, poll_table *wait) +{ + poll_wait(file, &crng_init_wait, wait); + return crng_ready() ? EPOLLIN | EPOLLRDNORM : EPOLLOUT | EPOLLWRNORM; +} + +static ssize_t write_pool_user(struct iov_iter *iter) +{ + u8 block[BLAKE2S_BLOCK_SIZE]; + ssize_t ret = 0; + size_t copied; + + if (unlikely(!iov_iter_count(iter))) + return 0; + + for (;;) { + copied = copy_from_iter(block, sizeof(block), iter); + ret += copied; + mix_pool_bytes(block, copied); + if (!iov_iter_count(iter) || copied != sizeof(block)) + break; + + BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0); + if (ret % PAGE_SIZE == 0) { + if (signal_pending(current)) + break; + cond_resched(); + } + } + + memzero_explicit(block, sizeof(block)); + return ret ? ret : -EFAULT; +} + +static ssize_t random_write_iter(struct kiocb *kiocb, struct iov_iter *iter) +{ + return write_pool_user(iter); +} + +static ssize_t urandom_read_iter(struct kiocb *kiocb, struct iov_iter *iter) +{ + static int maxwarn = 10; + + /* + * Opportunistically attempt to initialize the RNG on platforms that + * have fast cycle counters, but don't (for now) require it to succeed. + */ + if (!crng_ready()) + try_to_generate_entropy(); + + if (!crng_ready()) { + if (!ratelimit_disable && maxwarn <= 0) + ++urandom_warning.missed; + else if (ratelimit_disable || __ratelimit(&urandom_warning)) { + --maxwarn; + pr_notice("%s: uninitialized urandom read (%zu bytes read)\n", + current->comm, iov_iter_count(iter)); + } + } + + return get_random_bytes_user(iter); +} + +static ssize_t random_read_iter(struct kiocb *kiocb, struct iov_iter *iter) +{ + int ret; + + if (!crng_ready() && + ((kiocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) || + (kiocb->ki_filp->f_flags & O_NONBLOCK))) + return -EAGAIN; + + ret = wait_for_random_bytes(); + if (ret != 0) + return ret; + return get_random_bytes_user(iter); +} + +static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) +{ + int __user *p = (int __user *)arg; + int ent_count; + + switch (cmd) { + case RNDGETENTCNT: + /* Inherently racy, no point locking. */ + if (put_user(input_pool.init_bits, p)) + return -EFAULT; + return 0; + case RNDADDTOENTCNT: + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + if (get_user(ent_count, p)) + return -EFAULT; + if (ent_count < 0) + return -EINVAL; + credit_init_bits(ent_count); + return 0; + case RNDADDENTROPY: { + struct iov_iter iter; + struct iovec iov; + ssize_t ret; + int len; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + if (get_user(ent_count, p++)) + return -EFAULT; + if (ent_count < 0) + return -EINVAL; + if (get_user(len, p++)) + return -EFAULT; + ret = import_single_range(ITER_SOURCE, p, len, &iov, &iter); + if (unlikely(ret)) + return ret; + ret = write_pool_user(&iter); + if (unlikely(ret < 0)) + return ret; + /* Since we're crediting, enforce that it was all written into the pool. */ + if (unlikely(ret != len)) + return -EFAULT; + credit_init_bits(ent_count); + return 0; + } + case RNDZAPENTCNT: + case RNDCLEARPOOL: + /* No longer has any effect. */ + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + return 0; + case RNDRESEEDCRNG: + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + if (!crng_ready()) + return -ENODATA; + crng_reseed(NULL); + return 0; + default: + return -EINVAL; + } +} + +static int random_fasync(int fd, struct file *filp, int on) +{ + return fasync_helper(fd, filp, on, &fasync); +} + +const struct file_operations random_fops = { + .read_iter = random_read_iter, + .write_iter = random_write_iter, + .poll = random_poll, + .unlocked_ioctl = random_ioctl, + .compat_ioctl = compat_ptr_ioctl, + .fasync = random_fasync, + .llseek = noop_llseek, + .splice_read = copy_splice_read, + .splice_write = iter_file_splice_write, +}; + +const struct file_operations urandom_fops = { + .read_iter = urandom_read_iter, + .write_iter = random_write_iter, + .unlocked_ioctl = random_ioctl, + .compat_ioctl = compat_ptr_ioctl, + .fasync = random_fasync, + .llseek = noop_llseek, + .splice_read = copy_splice_read, + .splice_write = iter_file_splice_write, +}; + + +/******************************************************************** + * + * Sysctl interface. + * + * These are partly unused legacy knobs with dummy values to not break + * userspace and partly still useful things. They are usually accessible + * in /proc/sys/kernel/random/ and are as follows: + * + * - boot_id - a UUID representing the current boot. + * + * - uuid - a random UUID, different each time the file is read. + * + * - poolsize - the number of bits of entropy that the input pool can + * hold, tied to the POOL_BITS constant. + * + * - entropy_avail - the number of bits of entropy currently in the + * input pool. Always <= poolsize. + * + * - write_wakeup_threshold - the amount of entropy in the input pool + * below which write polls to /dev/random will unblock, requesting + * more entropy, tied to the POOL_READY_BITS constant. It is writable + * to avoid breaking old userspaces, but writing to it does not + * change any behavior of the RNG. + * + * - urandom_min_reseed_secs - fixed to the value CRNG_RESEED_INTERVAL. + * It is writable to avoid breaking old userspaces, but writing + * to it does not change any behavior of the RNG. + * + ********************************************************************/ + +#ifdef CONFIG_SYSCTL + +#include <linux/sysctl.h> + +static int sysctl_random_min_urandom_seed = CRNG_RESEED_INTERVAL / HZ; +static int sysctl_random_write_wakeup_bits = POOL_READY_BITS; +static int sysctl_poolsize = POOL_BITS; +static u8 sysctl_bootid[UUID_SIZE]; + +/* + * This function is used to return both the bootid UUID, and random + * UUID. The difference is in whether table->data is NULL; if it is, + * then a new UUID is generated and returned to the user. + */ +static int proc_do_uuid(struct ctl_table *table, int write, void *buf, + size_t *lenp, loff_t *ppos) +{ + u8 tmp_uuid[UUID_SIZE], *uuid; + char uuid_string[UUID_STRING_LEN + 1]; + struct ctl_table fake_table = { + .data = uuid_string, + .maxlen = UUID_STRING_LEN + }; + + if (write) + return -EPERM; + + uuid = table->data; + if (!uuid) { + uuid = tmp_uuid; + generate_random_uuid(uuid); + } else { + static DEFINE_SPINLOCK(bootid_spinlock); + + spin_lock(&bootid_spinlock); + if (!uuid[8]) + generate_random_uuid(uuid); + spin_unlock(&bootid_spinlock); + } + + snprintf(uuid_string, sizeof(uuid_string), "%pU", uuid); + return proc_dostring(&fake_table, 0, buf, lenp, ppos); +} + +/* The same as proc_dointvec, but writes don't change anything. */ +static int proc_do_rointvec(struct ctl_table *table, int write, void *buf, + size_t *lenp, loff_t *ppos) +{ + return write ? 0 : proc_dointvec(table, 0, buf, lenp, ppos); +} + +static struct ctl_table random_table[] = { + { + .procname = "poolsize", + .data = &sysctl_poolsize, + .maxlen = sizeof(int), + .mode = 0444, + .proc_handler = proc_dointvec, + }, + { + .procname = "entropy_avail", + .data = &input_pool.init_bits, + .maxlen = sizeof(int), + .mode = 0444, + .proc_handler = proc_dointvec, + }, + { + .procname = "write_wakeup_threshold", + .data = &sysctl_random_write_wakeup_bits, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_do_rointvec, + }, + { + .procname = "urandom_min_reseed_secs", + .data = &sysctl_random_min_urandom_seed, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_do_rointvec, + }, + { + .procname = "boot_id", + .data = &sysctl_bootid, + .mode = 0444, + .proc_handler = proc_do_uuid, + }, + { + .procname = "uuid", + .mode = 0444, + .proc_handler = proc_do_uuid, + }, + { } +}; + +/* + * random_init() is called before sysctl_init(), + * so we cannot call register_sysctl_init() in random_init() + */ +static int __init random_sysctls_init(void) +{ + register_sysctl_init("kernel/random", random_table); + return 0; +} +device_initcall(random_sysctls_init); +#endif |