// 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.
*/
/*
* Exported interfaces ---- output
* ===============================
*
* There are four exported interfaces; two for use within the kernel,
* and two for use from userspace.
*
* Exported interfaces ---- userspace output
* -----------------------------------------
*
* The userspace interfaces are two character devices /dev/random and
* /dev/urandom. /dev/random is suitable for use when very high
* quality randomness is desired (for example, for key generation or
* one-time pads), as it will only return a maximum of the number of
* bits of randomness (as estimated by the random number generator)
* contained in the entropy pool.
*
* The /dev/urandom device does not have this limit, and will return
* as many bytes as are requested. As more and more random bytes are
* requested without giving time for the entropy pool to recharge,
* this will result in random numbers that are merely cryptographically
* strong. For many applications, however, this is acceptable.
*
* Exported interfaces ---- kernel output
* --------------------------------------
*
* The primary kernel interfaces are:
*
* void get_random_bytes(void *buf, size_t nbytes);
* u32 get_random_u32()
* u64 get_random_u64()
* unsigned int get_random_int()
* 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 get_random_{u32,u64,int,long}() family
* of functions may be higher performance for one-off random integers,
* because they do a bit of buffering.
*
* prandom_u32()
* -------------
*
* For even weaker applications, see the pseudorandom generator
* prandom_u32(), prandom_max(), and prandom_bytes(). If the random
* numbers aren't security-critical at all, these are *far* cheaper.
* Useful for self-tests, random error simulation, randomized backoffs,
* and any other application where you trust that nobody is trying to
* maliciously mess with you by guessing the "random" numbers.
*
* Exported interfaces ---- input
* ==============================
*
* The current exported interfaces for gathering environmental noise
* from the devices are:
*
* void add_device_randomness(const void *buf, size_t size);
* void add_input_randomness(unsigned int type, unsigned int code,
* unsigned int value);
* void add_interrupt_randomness(int irq);
* void add_disk_randomness(struct gendisk *disk);
* void add_hwgenerator_randomness(const void *buffer, size_t count,
* size_t entropy);
* void add_bootloader_randomness(const void *buf, size_t size);
*
* add_device_randomness() is for adding data to the random 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* add 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_input_randomness() uses the input layer interrupt timing, as well as
* the event type information from the hardware.
*
* 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 randomness roughly once a second.
*
* 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.
*
* All of these routines try to estimate how many bits of randomness a
* particular randomness source. They do this by keeping track of the
* first and second order deltas of the event timings.
*
* 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 the same as add_hwgenerator_randomness() or
* add_device_randomness(), depending on whether or not the configuration
* option CONFIG_RANDOM_TRUST_BOOTLOADER is set.
*
* Ensuring unpredictability at system startup
* ============================================
*
* When any operating system starts up, it will go through a sequence
* of actions that are fairly predictable by an adversary, especially
* if the start-up does not involve interaction with a human operator.
* This reduces the actual number of bits of unpredictability in the
* entropy pool below the value in entropy_count. In order to
* counteract this effect, it helps to carry information in the
* entropy pool across shut-downs and start-ups. To do this, put the
* following lines an appropriate script which is run during the boot
* sequence:
*
* echo "Initializing random number generator..."
* random_seed=/var/run/random-seed
* # Carry a random seed from start-up to start-up
* # Load and then save the whole entropy pool
* if [ -f $random_seed ]; then
* cat $random_seed >/dev/urandom
* else
* touch $random_seed
* fi
* chmod 600 $random_seed
* dd if=/dev/urandom of=$random_seed count=1 bs=512
*
* and the following lines in an appropriate script which is run as
* the system is shutdown:
*
* # Carry a random seed from shut-down to start-up
* # Save the whole entropy pool
* echo "Saving random seed..."
* random_seed=/var/run/random-seed
* touch $random_seed
* chmod 600 $random_seed
* dd if=/dev/urandom of=$random_seed count=1 bs=512
*
* For example, on most modern systems using the System V init
* scripts, such code fragments would be found in
* /etc/rc.d/init.d/random. On older Linux systems, the correct script
* location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
*
* Effectively, these commands cause the contents of the entropy pool
* to be saved at shut-down time and reloaded into the entropy pool at
* start-up. (The 'dd' in the addition to the bootup script is to
* make sure that /etc/random-seed is different for every start-up,
* even if the system crashes without executing rc.0.) Even with
* complete knowledge of the start-up activities, predicting the state
* of the entropy pool requires knowledge of the previous history of
* the system.
*
* Configuring the /dev/random driver under Linux
* ==============================================
*
* The /dev/random driver under Linux uses minor numbers 8 and 9 of
* the /dev/mem major number (#1). So if your system does not have
* /dev/random and /dev/urandom created already, they can be created
* by using the commands:
*
* mknod /dev/random c 1 8
* mknod /dev/urandom c 1 9
*/
#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/genhd.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 <crypto/chacha.h>
#include <crypto/blake2s.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 = 0 --> Uninitialized
* 1 --> Initialized
* 2 --> Initialized from input_pool
*
* crng_init is protected by base_crng->lock, and only increases
* its value (from 0->1->2).
*/
static int crng_init = 0;
#define crng_ready() (likely(crng_init > 1))
/* Various types of waiters for crng_init->2 transition. */
static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
static struct fasync_struct *fasync;
static DEFINE_SPINLOCK(random_ready_list_lock);
static LIST_HEAD(random_ready_list);
/* Control how we warn userspace. */
static struct ratelimit_state unseeded_warning =
RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
static struct ratelimit_state urandom_warning =
RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
static int ratelimit_disable __read_mostly;
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_{u32,
* ,u64,int,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);
/* 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_{u32,u64,int,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)
{
if (likely(crng_ready()))
return 0;
do {
int ret;
ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
if (ret)
return ret > 0 ? 0 : ret;
try_to_generate_entropy();
} while (!crng_ready());
return 0;
}
EXPORT_SYMBOL(wait_for_random_bytes);
/*
* Add a callback function that will be invoked when the input
* pool is initialised.
*
* returns: 0 if callback is successfully added
* -EALREADY if pool is already initialised (callback not called)
* -ENOENT if module for callback is not alive
*/
int add_random_ready_callback(struct random_ready_callback *rdy)
{
struct module *owner;
unsigned long flags;
int err = -EALREADY;
if (crng_ready())
return err;
owner = rdy->owner;
if (!try_module_get(owner))
return -ENOENT;
spin_lock_irqsave(&random_ready_list_lock, flags);
if (crng_ready())
goto out;
owner = NULL;
list_add(&rdy->list, &random_ready_list);
err = 0;
out:
spin_unlock_irqrestore(&random_ready_list_lock, flags);
module_put(owner);
return err;
}
EXPORT_SYMBOL(add_random_ready_callback);
/*
* Delete a previously registered readiness callback function.
*/
void del_random_ready_callback(struct random_ready_callback *rdy)
{
unsigned long flags;
struct module *owner = NULL;
spin_lock_irqsave(&random_ready_list_lock, flags);
if (!list_empty(&rdy->list)) {
list_del_init(&rdy->list);
owner = rdy->owner;
}
spin_unlock_irqrestore(&random_ready_list_lock, flags);
module_put(owner);
}
EXPORT_SYMBOL(del_random_ready_callback);
static void process_random_ready_list(void)
{
unsigned long flags;
struct random_ready_callback *rdy, *tmp;
spin_lock_irqsave(&random_ready_list_lock, flags);
list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
struct module *owner = rdy->owner;
list_del_init(&rdy->list);
rdy->func(rdy);
module_put(owner);
}
spin_unlock_irqrestore(&random_ready_list_lock, flags);
}
#define warn_unseeded_randomness(previous) \
_warn_unseeded_randomness(__func__, (void *)_RET_IP_, (previous))
static void _warn_unseeded_randomness(const char *func_name, void *caller, void **previous)
{
#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
const bool print_once = false;
#else
static bool print_once __read_mostly;
#endif
if (print_once || crng_ready() ||
(previous && (caller == READ_ONCE(*previous))))
return;
WRITE_ONCE(*previous, caller);
#ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
print_once = true;
#endif
if (__ratelimit(&unseeded_warning))
printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n",
func_name, caller, 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 nbytes)
* u32 get_random_u32()
* u64 get_random_u64()
* unsigned int get_random_int()
* 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 integer family of functions may be
* higher performance for one-off random integers, because they do a
* bit of buffering.
*
*********************************************************************/
enum {
CRNG_RESEED_INTERVAL = 300 * HZ,
CRNG_INIT_CNT_THRESH = 2 * CHACHA_KEY_SIZE
};
static struct {
u8 key[CHACHA_KEY_SIZE] __aligned(__alignof__(long));
unsigned long birth;
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),
};
/* Used by crng_reseed() to extract a new seed from the input pool. */
static bool drain_entropy(void *buf, size_t nbytes);
/*
* This extracts a new crng key from the input pool, but only if there is a
* sufficient amount of entropy available, in order to mitigate bruteforcing
* of newly added bits.
*/
static void crng_reseed(void)
{
unsigned long flags;
unsigned long next_gen;
u8 key[CHACHA_KEY_SIZE];
bool finalize_init = false;
/* Only reseed if we can, to prevent brute forcing a small amount of new bits. */
if (!drain_entropy(key, sizeof(key)))
return;
/*
* 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);
WRITE_ONCE(base_crng.birth, jiffies);
if (crng_init < 2) {
crng_init = 2;
finalize_init = true;
}
spin_unlock_irqrestore(&base_crng.lock, flags);
memzero_explicit(key, sizeof(key));
if (finalize_init) {
process_random_ready_list();
wake_up_interruptible(&crng_init_wait);
kill_fasync(&fasync, SIGIO, POLL_IN);
pr_notice("crng init done\n");
if (unseeded_warning.missed) {
pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n",
unseeded_warning.missed);
unseeded_warning.missed = 0;
}
if (urandom_warning.missed) {
pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
urandom_warning.missed);
urandom_warning.missed = 0;
}
}
}
/*
* This generates a ChaCha block using the provided key, and then
* immediately overwites 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.
*/
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, because
* this is what crng_{fast,slow}_load mutate during early init.
*/
if (unlikely(!crng_ready())) {
bool ready;
spin_lock_irqsave(&base_crng.lock, flags);
ready = crng_ready();
if (!ready)
crng_fast_key_erasure(base_crng.key, chacha_state,
random_data, random_data_len);
spin_unlock_irqrestore(&base_crng.lock, flags);
if (!ready)
return;
}
/*
* If the base_crng is more than 5 minutes old, we reseed, which
* in turn bumps the generation counter that we check below.
*/
if (unlikely(time_after(jiffies, READ_ONCE(base_crng.birth) + CRNG_RESEED_INTERVAL)))
crng_reseed();
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);
}
/*
* This function is for crng_init == 0 only.
*
* crng_fast_load() can be called by code in the interrupt service
* path. So we can't afford to dilly-dally. Returns the number of
* bytes processed from cp.
*/
static size_t crng_fast_load(const void *cp, size_t len)
{
static int crng_init_cnt = 0;
unsigned long flags;
const u8 *src = (const u8 *)cp;
size_t ret = 0;
if (!spin_trylock_irqsave(&base_crng.lock, flags))
return 0;
if (crng_init != 0) {
spin_unlock_irqrestore(&base_crng.lock, flags);
return 0;
}
while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
base_crng.key[crng_init_cnt % sizeof(base_crng.key)] ^= *src;
src++; crng_init_cnt++; len--; ret++;
}
if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
++base_crng.generation;
crng_init = 1;
}
spin_unlock_irqrestore(&base_crng.lock, flags);
if (crng_init == 1)
pr_notice("fast init done\n");
return ret;
}
/*
* This function is for crng_init == 0 only.
*
* crng_slow_load() is called by add_device_randomness, which has two
* attributes. (1) We can't trust the buffer passed to it is
* guaranteed to be unpredictable (so it might not have any entropy at
* all), and (2) it doesn't have the performance constraints of
* crng_fast_load().
*
* So, we simply hash the contents in with the current key. Finally,
* we do *not* advance crng_init_cnt since buffer we may get may be
* something like a fixed DMI table (for example), which might very
* well be unique to the machine, but is otherwise unvarying.
*/
static void crng_slow_load(const void *cp, size_t len)
{
unsigned long flags;
struct blake2s_state hash;
blake2s_init(&hash, sizeof(base_crng.key));
if (!spin_trylock_irqsave(&base_crng.lock, flags))
return;
if (crng_init != 0) {
spin_unlock_irqrestore(&base_crng.lock, flags);
return;
}
blake2s_update(&hash, base_crng.key, sizeof(base_crng.key));
blake2s_update(&hash, cp, len);
blake2s_final(&hash, base_crng.key);
spin_unlock_irqrestore(&base_crng.lock, flags);
}
static void _get_random_bytes(void *buf, size_t nbytes)
{
u32 chacha_state[CHACHA_STATE_WORDS];
u8 tmp[CHACHA_BLOCK_SIZE];
size_t len;
if (!nbytes)
return;
len = min_t(size_t, 32, nbytes);
crng_make_state(chacha_state, buf, len);
nbytes -= len;
buf += len;
while (nbytes) {
if (nbytes < CHACHA_BLOCK_SIZE) {
chacha20_block(chacha_state, tmp);
memcpy(buf, tmp, nbytes);
memzero_explicit(tmp, sizeof(tmp));
break;
}
chacha20_block(chacha_state, buf);
if (unlikely(chacha_state[12] == 0))
++chacha_state[13];
nbytes -= CHACHA_BLOCK_SIZE;
buf += CHACHA_BLOCK_SIZE;
}
memzero_explicit(chacha_state, sizeof(chacha_state));
}
/*
* This function is the exported kernel interface. It returns some
* number of good random numbers, suitable for key generation, seeding
* TCP sequence numbers, etc. It does not rely on the hardware random
* number generator. For random bytes direct from the hardware RNG
* (when available), use get_random_bytes_arch(). 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 nbytes)
{
static void *previous;
warn_unseeded_randomness(&previous);
_get_random_bytes(buf, nbytes);
}
EXPORT_SYMBOL(get_random_bytes);
static ssize_t get_random_bytes_user(void __user *buf, size_t nbytes)
{
bool large_request = nbytes > 256;
ssize_t ret = 0;
size_t len;
u32 chacha_state[CHACHA_STATE_WORDS];
u8 output[CHACHA_BLOCK_SIZE];
if (!nbytes)
return 0;
len = min_t(size_t, 32, nbytes);
crng_make_state(chacha_state, output, len);
if (copy_to_user(buf, output, len))
return -EFAULT;
nbytes -= len;
buf += len;
ret += len;
while (nbytes) {
if (large_request && need_resched()) {
if (signal_pending(current))
break;
schedule();
}
chacha20_block(chacha_state, output);
if (unlikely(chacha_state[12] == 0))
++chacha_state[13];
len = min_t(size_t, nbytes, CHACHA_BLOCK_SIZE);
if (copy_to_user(buf, output, len)) {
ret = -EFAULT;
break;
}
nbytes -= len;
buf += len;
ret += len;
}
memzero_explicit(chacha_state, sizeof(chacha_state));
memzero_explicit(output, sizeof(output));
return ret;
}
/*
* 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.
*/
struct batched_entropy {
union {
/*
* 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.
*/
u64 entropy_u64[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(u64))];
u32 entropy_u32[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(u32))];
};
local_lock_t lock;
unsigned long generation;
unsigned int position;
};
static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = {
.lock = INIT_LOCAL_LOCK(batched_entropy_u64.lock),
.position = UINT_MAX
};
u64 get_random_u64(void)
{
u64 ret;
unsigned long flags;
struct batched_entropy *batch;
static void *previous;
unsigned long next_gen;
warn_unseeded_randomness(&previous);
local_lock_irqsave(&batched_entropy_u64.lock, flags);
batch = raw_cpu_ptr(&batched_entropy_u64);
next_gen = READ_ONCE(base_crng.generation);
if (batch->position >= ARRAY_SIZE(batch->entropy_u64) ||
next_gen != batch->generation) {
_get_random_bytes(batch->entropy_u64, sizeof(batch->entropy_u64));
batch->position = 0;
batch->generation = next_gen;
}
ret = batch->entropy_u64[batch->position];
batch->entropy_u64[batch->position] = 0;
++batch->position;
local_unlock_irqrestore(&batched_entropy_u64.lock, flags);
return ret;
}
EXPORT_SYMBOL(get_random_u64);
static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = {
.lock = INIT_LOCAL_LOCK(batched_entropy_u32.lock),
.position = UINT_MAX
};
u32 get_random_u32(void)
{
u32 ret;
unsigned long flags;
struct batched_entropy *batch;
static void *previous;
unsigned long next_gen;
warn_unseeded_randomness(&previous);
local_lock_irqsave(&batched_entropy_u32.lock, flags);
batch = raw_cpu_ptr(&batched_entropy_u32);
next_gen = READ_ONCE(base_crng.generation);
if (batch->position >= ARRAY_SIZE(batch->entropy_u32) ||
next_gen != batch->generation) {
_get_random_bytes(batch->entropy_u32, sizeof(batch->entropy_u32));
batch->position = 0;
batch->generation = next_gen;
}
ret = batch->entropy_u32[batch->position];
batch->entropy_u32[batch->position] = 0;
++batch->position;
local_unlock_irqrestore(&batched_entropy_u32.lock, flags);
return ret;
}
EXPORT_SYMBOL(get_random_u32);
/**
* randomize_page - Generate a random, page aligned address
* @start: The smallest acceptable address the caller will take.
* @range: The size of the area, starting at @start, within which the
* random address must fall.
*
* If @start + @range would overflow, @range is capped.
*
* NOTE: Historical use of randomize_range, which this replaces, presumed that
* @start was already page aligned. We now align it regardless.
*
* Return: A page aligned address within [start, start + range). On error,
* @start is returned.
*/
unsigned long randomize_page(unsigned long start, unsigned long range)
{
if (!PAGE_ALIGNED(start)) {
range -= PAGE_ALIGN(start) - start;
start = PAGE_ALIGN(start);
}
if (start > ULONG_MAX - range)
range = ULONG_MAX - start;
range >>= PAGE_SHIFT;
if (range == 0)
return start;
return start + (get_random_long() % range << PAGE_SHIFT);
}
/*
* This function will use the architecture-specific hardware random
* number generator if it is available. It is not recommended for
* use. Use get_random_bytes() instead. It returns the number of
* bytes filled in.
*/
size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes)
{
size_t left = nbytes;
u8 *p = buf;
while (left) {
unsigned long v;
size_t chunk = min_t(size_t, left, sizeof(unsigned long));
if (!arch_get_random_long(&v))
break;
memcpy(p, &v, chunk);
p += chunk;
left -= chunk;
}
return nbytes - left;
}
EXPORT_SYMBOL(get_random_bytes_arch);
/**********************************************************************
*
* Entropy accumulation and extraction routines.
*
* Callers may add entropy via:
*
* static void mix_pool_bytes(const void *in, size_t nbytes)
*
* After which, if added entropy should be credited:
*
* static void credit_entropy_bits(size_t nbits)
*
* Finally, extract entropy via these two, with the latter one
* setting the entropy count to zero and extracting only if there
* is POOL_MIN_BITS entropy credited prior:
*
* static void extract_entropy(void *buf, size_t nbytes)
* static bool drain_entropy(void *buf, size_t nbytes)
*
**********************************************************************/
enum {
POOL_BITS = BLAKE2S_HASH_SIZE * 8,
POOL_MIN_BITS = POOL_BITS /* No point in settling for less. */
};
/* For notifying userspace should write into /dev/random. */
static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
static struct {
struct blake2s_state hash;
spinlock_t lock;
unsigned int entropy_count;
} 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 *in, size_t nbytes)
{
blake2s_update(&input_pool.hash, in, nbytes);
}
/*
* This function adds bytes into the entropy "pool". It does not
* update the entropy estimate. The caller should call
* credit_entropy_bits if this is appropriate.
*/
static void mix_pool_bytes(const void *in, size_t nbytes)
{
unsigned long flags;
spin_lock_irqsave(&input_pool.lock, flags);
_mix_pool_bytes(in, nbytes);
spin_unlock_irqrestore(&input_pool.lock, flags);
}
static void credit_entropy_bits(size_t nbits)
{
unsigned int entropy_count, orig, add;
if (!nbits)
return;
add = min_t(size_t, nbits, POOL_BITS);
do {
orig = READ_ONCE(input_pool.entropy_count);
entropy_count = min_t(unsigned int, POOL_BITS, orig + add);
} while (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig);
if (crng_init < 2 && entropy_count >= POOL_MIN_BITS)
crng_reseed();
}
/*
* 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 nbytes)
{
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;
for (i = 0; i < ARRAY_SIZE(block.rdseed); ++i) {
if (!arch_get_random_seed_long(&block.rdseed[i]) &&
!arch_get_random_long(&block.rdseed[i]))
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 (nbytes) {
i = min_t(size_t, nbytes, BLAKE2S_HASH_SIZE);
/* output = HASHPRF(seed, RDSEED || ++counter) */
++block.counter;
blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed));
nbytes -= i;
buf += i;
}
memzero_explicit(seed, sizeof(seed));
memzero_explicit(&block, sizeof(block));
}
/*
* First we make sure we have POOL_MIN_BITS of entropy in the pool, and then we
* set the entropy count to zero (but don't actually touch any data). Only then
* can we extract a new key with extract_entropy().
*/
static bool drain_entropy(void *buf, size_t nbytes)
{
unsigned int entropy_count;
do {
entropy_count = READ_ONCE(input_pool.entropy_count);
if (entropy_count < POOL_MIN_BITS)
return false;
} while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count);
extract_entropy(buf, nbytes);
wake_up_interruptible(&random_write_wait);
kill_fasync(&fasync, SIGIO, POLL_OUT);
return true;
}
/**********************************************************************
*
* 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 size);
* void add_input_randomness(unsigned int type, unsigned int code,
* unsigned int value);
* void add_disk_randomness(struct gendisk *disk);
* void add_hwgenerator_randomness(const void *buffer, size_t count,
* size_t entropy);
* void add_bootloader_randomness(const void *buf, size_t size);
* void add_interrupt_randomness(int irq);
*
* 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_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 above 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.
*
* 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 the same as add_hwgenerator_randomness() or
* add_device_randomness(), depending on whether or not the configuration
* option CONFIG_RANDOM_TRUST_BOOTLOADER is set.
*
* 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.
*
**********************************************************************/
static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
static int __init parse_trust_cpu(char *arg)
{
return kstrtobool(arg, &trust_cpu);
}
early_param("random.trust_cpu", parse_trust_cpu);
/*
* The first collection of entropy occurs at system boot while interrupts
* are still turned off. Here we push in RDSEED, a timestamp, and utsname().
* Depending on the above configuration knob, RDSEED may be considered
* sufficient for initialization. Note that much earlier setup may already
* have pushed entropy into the input pool by the time we get here.
*/
int __init rand_initialize(void)
{
size_t i;
ktime_t now = ktime_get_real();
bool arch_init = true;
unsigned long rv;
for (i = 0; i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) {
if (!arch_get_random_seed_long_early(&rv) &&
!arch_get_random_long_early(&rv)) {
rv = random_get_entropy();
arch_init = false;
}
mix_pool_bytes(&rv, sizeof(rv));
}
mix_pool_bytes(&now, sizeof(now));
mix_pool_bytes(utsname(), sizeof(*(utsname())));
extract_entropy(base_crng.key, sizeof(base_crng.key));
++base_crng.generation;
if (arch_init && trust_cpu && crng_init < 2) {
crng_init = 2;
pr_notice("crng init done (trusting CPU's manufacturer)\n");
}
if (ratelimit_disable) {
urandom_warning.interval = 0;
unseeded_warning.interval = 0;
}
return 0;
}
/* There is one of these per entropy source */
struct timer_rand_state {
cycles_t last_time;
long last_delta, last_delta2;
};
/*
* 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 size)
{
unsigned long time = random_get_entropy() ^ jiffies;
unsigned long flags;
if (!crng_ready() && size)
crng_slow_load(buf, size);
spin_lock_irqsave(&input_pool.lock, flags);
_mix_pool_bytes(buf, size);
_mix_pool_bytes(&time, sizeof(time));
spin_unlock_irqrestore(&input_pool.lock, flags);
}
EXPORT_SYMBOL(add_device_randomness);
/*
* 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 number "num" is also added to the pool - it should somehow describe
* the type of event which just happened. This is currently 0-255 for
* keyboard scan codes, and 256 upwards for interrupts.
*
*/
static void add_timer_randomness(struct timer_rand_state *state, unsigned int num)
{
struct {
long jiffies;
unsigned int cycles;
unsigned int num;
} sample;
long delta, delta2, delta3;
sample.jiffies = jiffies;
sample.cycles = random_get_entropy();
sample.num = num;
mix_pool_bytes(&sample, sizeof(sample));
/*
* 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 = sample.jiffies - READ_ONCE(state->last_time);
WRITE_ONCE(state->last_time, sample.jiffies);
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 12 bits.
*/
credit_entropy_bits(min_t(unsigned int, fls(delta >> 1), 11));
}
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 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
/*
* Interface for in-kernel drivers of true hardware RNGs.
* Those devices may produce endless random bits and will be throttled
* when our pool is full.
*/
void add_hwgenerator_randomness(const void *buffer, size_t count,
size_t entropy)
{
if (unlikely(crng_init == 0)) {
size_t ret = crng_fast_load(buffer, count);
mix_pool_bytes(buffer, ret);
count -= ret;
buffer += ret;
if (!count || crng_init == 0)
return;
}
/*
* Throttle writing if we're above the trickle threshold.
* We'll be woken up again once below POOL_MIN_BITS, when
* the calling thread is about to terminate, or once
* CRNG_RESEED_INTERVAL has elapsed.
*/
wait_event_interruptible_timeout(random_write_wait,
!system_wq || kthread_should_stop() ||
input_pool.entropy_count < POOL_MIN_BITS,
CRNG_RESEED_INTERVAL);
mix_pool_bytes(buffer, count);
credit_entropy_bits(entropy);
}
EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
/*
* Handle random seed passed by bootloader.
* If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise
* it would be regarded as device data.
* The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER.
*/
void add_bootloader_randomness(const void *buf, size_t size)
{
if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
add_hwgenerator_randomness(buf, size, size * 8);
else
add_device_randomness(buf, size);
}
EXPORT_SYMBOL_GPL(add_bootloader_randomness);
struct fast_pool {
union {
u32 pool32[4];
u64 pool64[2];
};
unsigned long last;
u16 reg_idx;
u8 count;
};
/*
* This is a fast mixing routine used by the interrupt randomness
* collector. It's hardcoded for an 128 bit pool and assumes that any
* locks that might be needed are taken by the caller.
*/
static void fast_mix(u32 pool[4])
{
u32 a = pool[0], b = pool[1];
u32 c = pool[2], d = pool[3];
a += b; c += d;
b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
a += b; c += d;
b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
a += b; c += d;
b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
a += b; c += d;
b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
pool[0] = a; pool[1] = b;
pool[2] = c; pool[3] = d;
}
static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
static u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
{
u32 *ptr = (u32 *)regs;
unsigned int idx;
if (regs == NULL)
return 0;
idx = READ_ONCE(f->reg_idx);
if (idx >= sizeof(struct pt_regs) / sizeof(u32))
idx = 0;
ptr += idx++;
WRITE_ONCE(f->reg_idx, idx);
return *ptr;
}
void add_interrupt_randomness(int irq)
{
struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
struct pt_regs *regs = get_irq_regs();
unsigned long now = jiffies;
cycles_t cycles = random_get_entropy();
if (cycles == 0)
cycles = get_reg(fast_pool, regs);
if (sizeof(cycles) == 8)
fast_pool->pool64[0] ^= cycles ^ rol64(now, 32) ^ irq;
else {
fast_pool->pool32[0] ^= cycles ^ irq;
fast_pool->pool32[1] ^= now;
}
if (sizeof(unsigned long) == 8)
fast_pool->pool64[1] ^= regs ? instruction_pointer(regs) : _RET_IP_;
else {
fast_pool->pool32[2] ^= regs ? instruction_pointer(regs) : _RET_IP_;
fast_pool->pool32[3] ^= get_reg(fast_pool, regs);
}
fast_mix(fast_pool->pool32);
++fast_pool->count;
if (unlikely(crng_init == 0)) {
if (fast_pool->count >= 64 &&
crng_fast_load(fast_pool->pool32, sizeof(fast_pool->pool32)) > 0) {
fast_pool->count = 0;
fast_pool->last = now;
if (spin_trylock(&input_pool.lock)) {
_mix_pool_bytes(&fast_pool->pool32, sizeof(fast_pool->pool32));
spin_unlock(&input_pool.lock);
}
}
return;
}
if ((fast_pool->count < 64) && !time_after(now, fast_pool->last + HZ))
return;
if (!spin_trylock(&input_pool.lock))
return;
fast_pool->last = now;
_mix_pool_bytes(&fast_pool->pool32, sizeof(fast_pool->pool32));
spin_unlock(&input_pool.lock);
fast_pool->count = 0;
/* Award one bit for the contents of the fast pool. */
credit_entropy_bits(1);
}
EXPORT_SYMBOL_GPL(add_interrupt_randomness);
/*
* 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 entropy_timer(struct timer_list *t)
{
credit_entropy_bits(1);
}
/*
* If we have an actual cycle counter, see if we can
* generate enough entropy with timing noise
*/
static void try_to_generate_entropy(void)
{
struct {
unsigned long now;
struct timer_list timer;
} stack;
stack.now = random_get_entropy();
/* Slow counter - or none. Don't even bother */
if (stack.now == random_get_entropy())
return;
timer_setup_on_stack(&stack.timer, entropy_timer, 0);
while (!crng_ready()) {
if (!timer_pending(&stack.timer))
mod_timer(&stack.timer, jiffies + 1);
mix_pool_bytes(&stack.now, sizeof(stack.now));
schedule();
stack.now = random_get_entropy();
}
del_timer_sync(&stack.timer);
destroy_timer_on_stack(&stack.timer);
mix_pool_bytes(&stack.now, sizeof(stack.now));
}
/**********************************************************************
*
* 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 *, buf, size_t, count, unsigned int,
flags)
{
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 (count > INT_MAX)
count = INT_MAX;
if (!(flags & GRND_INSECURE) && !crng_ready()) {
int ret;
if (flags & GRND_NONBLOCK)
return -EAGAIN;
ret = wait_for_random_bytes();
if (unlikely(ret))
return ret;
}
return get_random_bytes_user(buf, count);
}
static __poll_t random_poll(struct file *file, poll_table *wait)
{
__poll_t mask;
poll_wait(file, &crng_init_wait, wait);
poll_wait(file, &random_write_wait, wait);
mask = 0;
if (crng_ready())
mask |= EPOLLIN | EPOLLRDNORM;
if (input_pool.entropy_count < POOL_MIN_BITS)
mask |= EPOLLOUT | EPOLLWRNORM;
return mask;
}
static int write_pool(const char __user *ubuf, size_t count)
{
size_t len;
int ret = 0;
u8 block[BLAKE2S_BLOCK_SIZE];
while (count) {
len = min(count, sizeof(block));
if (copy_from_user(block, ubuf, len)) {
ret = -EFAULT;
goto out;
}
count -= len;
ubuf += len;
mix_pool_bytes(block, len);
cond_resched();
}
out:
memzero_explicit(block, sizeof(block));
return ret;
}
static ssize_t random_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
int ret;
ret = write_pool(buffer, count);
if (ret)
return ret;
return (ssize_t)count;
}
static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes,
loff_t *ppos)
{
static int maxwarn = 10;
if (!crng_ready() && maxwarn > 0) {
maxwarn--;
if (__ratelimit(&urandom_warning))
pr_notice("%s: uninitialized urandom read (%zd bytes read)\n",
current->comm, nbytes);
}
return get_random_bytes_user(buf, nbytes);
}
static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes,
loff_t *ppos)
{
int ret;
ret = wait_for_random_bytes();
if (ret != 0)
return ret;
return get_random_bytes_user(buf, nbytes);
}
static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
{
int size, ent_count;
int __user *p = (int __user *)arg;
int retval;
switch (cmd) {
case RNDGETENTCNT:
/* Inherently racy, no point locking. */
if (put_user(input_pool.entropy_count, 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_entropy_bits(ent_count);
return 0;
case RNDADDENTROPY:
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (get_user(ent_count, p++))
return -EFAULT;
if (ent_count < 0)
return -EINVAL;
if (get_user(size, p++))
return -EFAULT;
retval = write_pool((const char __user *)p, size);
if (retval < 0)
return retval;
credit_entropy_bits(ent_count);
return 0;
case RNDZAPENTCNT:
case RNDCLEARPOOL:
/*
* Clear the entropy pool counters. We no longer clear
* the entropy pool, as that's silly.
*/
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (xchg(&input_pool.entropy_count, 0)) {
wake_up_interruptible(&random_write_wait);
kill_fasync(&fasync, SIGIO, POLL_OUT);
}
return 0;
case RNDRESEEDCRNG:
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (crng_init < 2)
return -ENODATA;
crng_reseed();
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 = random_read,
.write = random_write,
.poll = random_poll,
.unlocked_ioctl = random_ioctl,
.compat_ioctl = compat_ptr_ioctl,
.fasync = random_fasync,
.llseek = noop_llseek,
};
const struct file_operations urandom_fops = {
.read = urandom_read,
.write = random_write,
.unlocked_ioctl = random_ioctl,
.compat_ioctl = compat_ptr_ioctl,
.fasync = random_fasync,
.llseek = noop_llseek,
};
/********************************************************************
*
* 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_MIN_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 meaningless value "60".
* 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 = 60;
static int sysctl_random_write_wakeup_bits = POOL_MIN_BITS;
static int sysctl_poolsize = POOL_BITS;
static char sysctl_bootid[16];
/*
* 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.
*
* If the user accesses this via the proc interface, the UUID will be
* returned as an ASCII string in the standard UUID format; if via the
* sysctl system call, as 16 bytes of binary data.
*/
static int proc_do_uuid(struct ctl_table *table, int write, void *buffer,
size_t *lenp, loff_t *ppos)
{
struct ctl_table fake_table;
unsigned char buf[64], tmp_uuid[16], *uuid;
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);
}
sprintf(buf, "%pU", uuid);
fake_table.data = buf;
fake_table.maxlen = sizeof(buf);
return proc_dostring(&fake_table, write, buffer, 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.entropy_count,
.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_dointvec,
},
{
.procname = "urandom_min_reseed_secs",
.data = &sysctl_random_min_urandom_seed,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "boot_id",
.data = &sysctl_bootid,
.maxlen = 16,
.mode = 0444,
.proc_handler = proc_do_uuid,
},
{
.procname = "uuid",
.maxlen = 16,
.mode = 0444,
.proc_handler = proc_do_uuid,
},
{ }
};
/*
* rand_initialize() is called before sysctl_init(),
* so we cannot call register_sysctl_init() in rand_initialize()
*/
static int __init random_sysctls_init(void)
{
register_sysctl_init("kernel/random", random_table);
return 0;
}
device_initcall(random_sysctls_init);
#endif
