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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)/* * Copyright (C) 2017-2024 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 <vdso/datapage.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 = 0;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;}
/********************************************************************* * * 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_dfl_wq)) queue_delayed_work(system_dfl_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);
/* base_crng.generation's invalid value is ULONG_MAX, while * vdso_k_rng_data->generation's invalid value is 0, so add one to the * former to arrive at the latter. Use smp_store_release so that this * is ordered with the write above to base_crng.generation. Pairs with * the smp_rmb() before the syscall in the vDSO code. * * Cast to unsigned long for 32-bit architectures, since atomic 64-bit * operations are not supported on those architectures. This is safe * because base_crng.generation is a 32-bit value. On big-endian * architectures it will be stored in the upper 32 bits, but that's okay * because the vDSO side only checks whether the value changed, without * actually using or interpreting the value. */ if (IS_ENABLED(CONFIG_VDSO_GETRANDOM)) smp_store_release((unsigned long *)&vdso_k_rng_data->generation, next_gen + 1);
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->x[4] * so that this function overwrites it before returning. */static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE], struct chacha_state *chacha_state, 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->x[4], key, CHACHA_KEY_SIZE); memset(&chacha_state->x[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(struct chacha_state *chacha_state, 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){ struct chacha_state chacha_state; 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.x[12] == 0)) ++chacha_state.x[13]; len -= CHACHA_BLOCK_SIZE; buf += CHACHA_BLOCK_SIZE; }
chacha_zeroize_state(&chacha_state);}
/* * This returns random bytes in arbitrary quantities. The quality of the * random bytes is as 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){ _get_random_bytes(buf, len);}EXPORT_SYMBOL(get_random_bytes);
static ssize_t get_random_bytes_user(struct iov_iter *iter){ struct chacha_state chacha_state; 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.x[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.x[4], CHACHA_KEY_SIZE, iter); goto out_zero_chacha; }
for (;;) { chacha20_block(&chacha_state, block); if (unlikely(chacha_state.x[12] == 0)) ++chacha_state.x[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: chacha_zeroize_state(&chacha_state); return ret ? ret : -EFAULT;}
/* * Batched entropy returns random integers. The quality of the random * number is as 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; \ \ 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_ctx 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(seed, sizeof(seed), (const u8 *)&block, sizeof(block), next_key, sizeof(next_key)); 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(seed, sizeof(seed), (const u8 *)&block, sizeof(block), buf, i); 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 DECLARE_WORK(set_ready, crng_set_ready); unsigned int new, orig, add; unsigned long flags; int m;
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 (system_dfl_wq) queue_work(system_dfl_wq, &set_ready); atomic_notifier_call_chain(&random_ready_notifier, 0, NULL); if (IS_ENABLED(CONFIG_VDSO_GETRANDOM)) WRITE_ONCE(vdso_k_rng_data->is_ready, true); wake_up_interruptible(&crng_init_wait); kill_fasync(&fasync, SIGIO, POLL_IN); pr_notice("crng init done\n"); m = ratelimit_state_get_miss(&urandom_warning); if (m) pr_notice("%d urandom warning(s) missed due to ratelimiting\n", m); } 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' is set. * * 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 workqueues * are initialized, then we should enable the static branch here. */ 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_BLOCKvoid 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_obj(struct timer_rand_state); 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(); cpumask_var_t timer_cpus; 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); if (!alloc_cpumask_var(&timer_cpus, GFP_KERNEL)) goto out;
while (!crng_ready() && !signal_pending(current)) { /* * Check !timer_pending() and then ensure that any previous callback has finished * executing by checking timer_delete_sync_try(), before queueing the next one. */ if (!timer_pending(&stack->timer) && timer_delete_sync_try(&stack->timer) >= 0) { 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));
free_cpumask_var(timer_cpus);out: timer_delete_sync(&stack->timer); timer_destroy_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; 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_ubuf(ITER_DEST, ubuf, len, &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) ratelimit_state_inc_miss(&urandom_warning); 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; 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_ubuf(ITER_SOURCE, p, len, &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(const 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(const 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 const 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