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![Jason A. Donenfeld](/assets/img/avatar_default.png)
In 1448769c9c
("random: check for signal_pending() outside of
need_resched() check"), Jann pointed out that we previously were only
checking the TIF_NOTIFY_SIGNAL and TIF_SIGPENDING flags if the process
had TIF_NEED_RESCHED set, which meant in practice, super long reads to
/dev/[u]random would delay signal handling by a long time. I tried this
using the below program, and indeed I wasn't able to interrupt a
/dev/urandom read until after several megabytes had been read. The bug
he fixed has always been there, and so code that reads from /dev/urandom
without checking the return value of read() has mostly worked for a long
time, for most sizes, not just for <= 256.
Maybe it makes sense to keep that code working. The reason it was so
small prior, ignoring the fact that it didn't work anyway, was likely
because /dev/random used to block, and that could happen for pretty
large lengths of time while entropy was gathered. But now, it's just a
chacha20 call, which is extremely fast and is just operating on pure
data, without having to wait for some external event. In that sense,
/dev/[u]random is a lot more like /dev/zero.
Taking a page out of /dev/zero's read_zero() function, it always returns
at least one chunk, and then checks for signals after each chunk. Chunk
sizes there are of length PAGE_SIZE. Let's just copy the same thing for
/dev/[u]random, and check for signals and cond_resched() for every
PAGE_SIZE amount of data. This makes the behavior more consistent with
expectations, and should mitigate the impact of Jann's fix for the
age-old signal check bug.
---- test program ----
#include <unistd.h>
#include <signal.h>
#include <stdio.h>
#include <sys/random.h>
static unsigned char x[~0U];
static void handle(int) { }
int main(int argc, char *argv[])
{
pid_t pid = getpid(), child;
signal(SIGUSR1, handle);
if (!(child = fork())) {
for (;;)
kill(pid, SIGUSR1);
}
pause();
printf("interrupted after reading %zd bytes\n", getrandom(x, sizeof(x), 0));
kill(child, SIGTERM);
return 0;
}
Cc: Jann Horn <jannh@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
1792 lines
52 KiB
C
1792 lines
52 KiB
C
// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
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/*
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* Copyright (C) 2017-2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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* Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
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* Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All rights reserved.
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*
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* This driver produces cryptographically secure pseudorandom data. It is divided
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* into roughly six sections, each with a section header:
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*
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* - Initialization and readiness waiting.
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* - Fast key erasure RNG, the "crng".
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* - Entropy accumulation and extraction routines.
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* - Entropy collection routines.
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* - Userspace reader/writer interfaces.
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* - Sysctl interface.
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*
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* The high level overview is that there is one input pool, into which
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* various pieces of data are hashed. Some of that data is then "credited" as
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* having a certain number of bits of entropy. When enough bits of entropy are
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* available, the hash is finalized and handed as a key to a stream cipher that
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* expands it indefinitely for various consumers. This key is periodically
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* refreshed as the various entropy collectors, described below, add data to the
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* input pool and credit it. There is currently no Fortuna-like scheduler
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* involved, which can lead to malicious entropy sources causing a premature
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* reseed, and the entropy estimates are, at best, conservative guesses.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/utsname.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/major.h>
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#include <linux/string.h>
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#include <linux/fcntl.h>
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#include <linux/slab.h>
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#include <linux/random.h>
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#include <linux/poll.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/blkdev.h>
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#include <linux/interrupt.h>
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#include <linux/mm.h>
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#include <linux/nodemask.h>
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#include <linux/spinlock.h>
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#include <linux/kthread.h>
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#include <linux/percpu.h>
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#include <linux/ptrace.h>
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#include <linux/workqueue.h>
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#include <linux/irq.h>
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#include <linux/ratelimit.h>
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#include <linux/syscalls.h>
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#include <linux/completion.h>
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#include <linux/uuid.h>
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#include <linux/uaccess.h>
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#include <crypto/chacha.h>
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#include <crypto/blake2s.h>
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#include <asm/processor.h>
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#include <asm/irq.h>
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#include <asm/irq_regs.h>
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#include <asm/io.h>
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/*********************************************************************
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*
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* Initialization and readiness waiting.
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*
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* Much of the RNG infrastructure is devoted to various dependencies
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* being able to wait until the RNG has collected enough entropy and
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* is ready for safe consumption.
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*
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*********************************************************************/
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/*
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* crng_init = 0 --> Uninitialized
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* 1 --> Initialized
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* 2 --> Initialized from input_pool
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*
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* crng_init is protected by base_crng->lock, and only increases
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* its value (from 0->1->2).
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*/
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static int crng_init = 0;
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#define crng_ready() (likely(crng_init > 1))
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/* Various types of waiters for crng_init->2 transition. */
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static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
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static struct fasync_struct *fasync;
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static DEFINE_SPINLOCK(random_ready_chain_lock);
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static RAW_NOTIFIER_HEAD(random_ready_chain);
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/* Control how we warn userspace. */
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static struct ratelimit_state unseeded_warning =
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RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
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static struct ratelimit_state urandom_warning =
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RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
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static int ratelimit_disable __read_mostly;
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module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
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MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
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/*
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* Returns whether or not the input pool has been seeded and thus guaranteed
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* to supply cryptographically secure random numbers. This applies to: the
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* /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
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* ,u64,int,long} family of functions.
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*
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* Returns: true if the input pool has been seeded.
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* false if the input pool has not been seeded.
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*/
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bool rng_is_initialized(void)
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{
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return crng_ready();
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}
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EXPORT_SYMBOL(rng_is_initialized);
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/* Used by wait_for_random_bytes(), and considered an entropy collector, below. */
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static void try_to_generate_entropy(void);
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/*
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* Wait for the input pool to be seeded and thus guaranteed to supply
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* cryptographically secure random numbers. This applies to: the /dev/urandom
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* device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
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* family of functions. Using any of these functions without first calling
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* this function forfeits the guarantee of security.
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*
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* Returns: 0 if the input pool has been seeded.
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* -ERESTARTSYS if the function was interrupted by a signal.
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*/
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int wait_for_random_bytes(void)
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{
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while (!crng_ready()) {
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int ret;
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try_to_generate_entropy();
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ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
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if (ret)
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return ret > 0 ? 0 : ret;
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}
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return 0;
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}
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EXPORT_SYMBOL(wait_for_random_bytes);
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/*
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* Add a callback function that will be invoked when the input
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* pool is initialised.
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*
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* returns: 0 if callback is successfully added
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* -EALREADY if pool is already initialised (callback not called)
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*/
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int register_random_ready_notifier(struct notifier_block *nb)
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{
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unsigned long flags;
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int ret = -EALREADY;
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if (crng_ready())
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return ret;
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spin_lock_irqsave(&random_ready_chain_lock, flags);
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if (!crng_ready())
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ret = raw_notifier_chain_register(&random_ready_chain, nb);
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spin_unlock_irqrestore(&random_ready_chain_lock, flags);
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return ret;
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}
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/*
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* Delete a previously registered readiness callback function.
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*/
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int unregister_random_ready_notifier(struct notifier_block *nb)
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{
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unsigned long flags;
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int ret;
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spin_lock_irqsave(&random_ready_chain_lock, flags);
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ret = raw_notifier_chain_unregister(&random_ready_chain, nb);
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spin_unlock_irqrestore(&random_ready_chain_lock, flags);
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return ret;
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}
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static void process_random_ready_list(void)
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{
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unsigned long flags;
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spin_lock_irqsave(&random_ready_chain_lock, flags);
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raw_notifier_call_chain(&random_ready_chain, 0, NULL);
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spin_unlock_irqrestore(&random_ready_chain_lock, flags);
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}
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#define warn_unseeded_randomness(previous) \
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_warn_unseeded_randomness(__func__, (void *)_RET_IP_, (previous))
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static void _warn_unseeded_randomness(const char *func_name, void *caller, void **previous)
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{
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#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
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const bool print_once = false;
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#else
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static bool print_once __read_mostly;
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#endif
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if (print_once || crng_ready() ||
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(previous && (caller == READ_ONCE(*previous))))
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return;
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WRITE_ONCE(*previous, caller);
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#ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
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print_once = true;
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#endif
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if (__ratelimit(&unseeded_warning))
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printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n",
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func_name, caller, crng_init);
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}
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/*********************************************************************
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*
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* Fast key erasure RNG, the "crng".
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*
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* These functions expand entropy from the entropy extractor into
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* long streams for external consumption using the "fast key erasure"
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* RNG described at <https://blog.cr.yp.to/20170723-random.html>.
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*
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* There are a few exported interfaces for use by other drivers:
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*
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* void get_random_bytes(void *buf, size_t nbytes)
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* u32 get_random_u32()
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* u64 get_random_u64()
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* unsigned int get_random_int()
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* unsigned long get_random_long()
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*
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* These interfaces will return the requested number of random bytes
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* into the given buffer or as a return value. This is equivalent to
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* a read from /dev/urandom. The u32, u64, int, and long family of
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* functions may be higher performance for one-off random integers,
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* because they do a bit of buffering and do not invoke reseeding
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* until the buffer is emptied.
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*
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*********************************************************************/
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enum {
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CRNG_RESEED_INTERVAL = 300 * HZ,
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CRNG_INIT_CNT_THRESH = 2 * CHACHA_KEY_SIZE
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};
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static struct {
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u8 key[CHACHA_KEY_SIZE] __aligned(__alignof__(long));
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unsigned long birth;
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unsigned long generation;
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spinlock_t lock;
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} base_crng = {
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.lock = __SPIN_LOCK_UNLOCKED(base_crng.lock)
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};
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struct crng {
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u8 key[CHACHA_KEY_SIZE];
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unsigned long generation;
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local_lock_t lock;
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};
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static DEFINE_PER_CPU(struct crng, crngs) = {
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.generation = ULONG_MAX,
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.lock = INIT_LOCAL_LOCK(crngs.lock),
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};
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/* Used by crng_reseed() to extract a new seed from the input pool. */
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static bool drain_entropy(void *buf, size_t nbytes, bool force);
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/*
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* This extracts a new crng key from the input pool, but only if there is a
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* sufficient amount of entropy available or force is true, in order to
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* mitigate bruteforcing of newly added bits.
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*/
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static void crng_reseed(bool force)
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{
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unsigned long flags;
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unsigned long next_gen;
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u8 key[CHACHA_KEY_SIZE];
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bool finalize_init = false;
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/* Only reseed if we can, to prevent brute forcing a small amount of new bits. */
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if (!drain_entropy(key, sizeof(key), force))
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return;
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/*
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* We copy the new key into the base_crng, overwriting the old one,
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* and update the generation counter. We avoid hitting ULONG_MAX,
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* because the per-cpu crngs are initialized to ULONG_MAX, so this
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* forces new CPUs that come online to always initialize.
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*/
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spin_lock_irqsave(&base_crng.lock, flags);
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memcpy(base_crng.key, key, sizeof(base_crng.key));
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next_gen = base_crng.generation + 1;
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if (next_gen == ULONG_MAX)
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++next_gen;
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WRITE_ONCE(base_crng.generation, next_gen);
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WRITE_ONCE(base_crng.birth, jiffies);
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if (!crng_ready()) {
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crng_init = 2;
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finalize_init = true;
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}
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spin_unlock_irqrestore(&base_crng.lock, flags);
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memzero_explicit(key, sizeof(key));
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if (finalize_init) {
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process_random_ready_list();
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wake_up_interruptible(&crng_init_wait);
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kill_fasync(&fasync, SIGIO, POLL_IN);
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pr_notice("crng init done\n");
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if (unseeded_warning.missed) {
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pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n",
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unseeded_warning.missed);
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unseeded_warning.missed = 0;
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}
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if (urandom_warning.missed) {
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pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
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urandom_warning.missed);
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urandom_warning.missed = 0;
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}
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}
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}
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/*
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* This generates a ChaCha block using the provided key, and then
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* immediately overwites that key with half the block. It returns
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* the resultant ChaCha state to the user, along with the second
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* half of the block containing 32 bytes of random data that may
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* be used; random_data_len may not be greater than 32.
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*/
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static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE],
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u32 chacha_state[CHACHA_STATE_WORDS],
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u8 *random_data, size_t random_data_len)
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{
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u8 first_block[CHACHA_BLOCK_SIZE];
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BUG_ON(random_data_len > 32);
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chacha_init_consts(chacha_state);
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memcpy(&chacha_state[4], key, CHACHA_KEY_SIZE);
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memset(&chacha_state[12], 0, sizeof(u32) * 4);
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chacha20_block(chacha_state, first_block);
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memcpy(key, first_block, CHACHA_KEY_SIZE);
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memcpy(random_data, first_block + CHACHA_KEY_SIZE, random_data_len);
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memzero_explicit(first_block, sizeof(first_block));
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}
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/*
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* Return whether the crng seed is considered to be sufficiently
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* old that a reseeding might be attempted. This happens if the last
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* reseeding was CRNG_RESEED_INTERVAL ago, or during early boot, at
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* an interval proportional to the uptime.
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*/
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static bool crng_has_old_seed(void)
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{
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static bool early_boot = true;
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unsigned long interval = CRNG_RESEED_INTERVAL;
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if (unlikely(READ_ONCE(early_boot))) {
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time64_t uptime = ktime_get_seconds();
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if (uptime >= CRNG_RESEED_INTERVAL / HZ * 2)
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WRITE_ONCE(early_boot, false);
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else
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interval = max_t(unsigned int, 5 * HZ,
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(unsigned int)uptime / 2 * HZ);
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}
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return time_after(jiffies, READ_ONCE(base_crng.birth) + interval);
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}
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/*
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* This function returns a ChaCha state that you may use for generating
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* random data. It also returns up to 32 bytes on its own of random data
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* that may be used; random_data_len may not be greater than 32.
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*/
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static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS],
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u8 *random_data, size_t random_data_len)
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{
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unsigned long flags;
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struct crng *crng;
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BUG_ON(random_data_len > 32);
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/*
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* For the fast path, we check whether we're ready, unlocked first, and
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* then re-check once locked later. In the case where we're really not
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* ready, we do fast key erasure with the base_crng directly, because
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* this is what crng_pre_init_inject() mutates during early init.
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*/
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if (!crng_ready()) {
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bool ready;
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spin_lock_irqsave(&base_crng.lock, flags);
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ready = crng_ready();
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if (!ready)
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crng_fast_key_erasure(base_crng.key, chacha_state,
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random_data, random_data_len);
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spin_unlock_irqrestore(&base_crng.lock, flags);
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if (!ready)
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return;
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}
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/*
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* If the base_crng is old enough, we try to reseed, which in turn
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* bumps the generation counter that we check below.
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*/
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if (unlikely(crng_has_old_seed()))
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crng_reseed(false);
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local_lock_irqsave(&crngs.lock, flags);
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crng = raw_cpu_ptr(&crngs);
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/*
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* If our per-cpu crng is older than the base_crng, then it means
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* somebody reseeded the base_crng. In that case, we do fast key
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* erasure on the base_crng, and use its output as the new key
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* for our per-cpu crng. This brings us up to date with base_crng.
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*/
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if (unlikely(crng->generation != READ_ONCE(base_crng.generation))) {
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spin_lock(&base_crng.lock);
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crng_fast_key_erasure(base_crng.key, chacha_state,
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crng->key, sizeof(crng->key));
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crng->generation = base_crng.generation;
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spin_unlock(&base_crng.lock);
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}
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/*
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* Finally, when we've made it this far, our per-cpu crng has an up
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* to date key, and we can do fast key erasure with it to produce
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* some random data and a ChaCha state for the caller. All other
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* branches of this function are "unlikely", so most of the time we
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* should wind up here immediately.
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*/
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crng_fast_key_erasure(crng->key, chacha_state, random_data, random_data_len);
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local_unlock_irqrestore(&crngs.lock, flags);
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}
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/*
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* This function is for crng_init == 0 only. It loads entropy directly
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* into the crng's key, without going through the input pool. It is,
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* generally speaking, not very safe, but we use this only at early
|
|
* boot time when it's better to have something there rather than
|
|
* nothing.
|
|
*
|
|
* If account is set, then the crng_init_cnt counter is incremented.
|
|
* This shouldn't be set by functions like add_device_randomness(),
|
|
* where we can't trust the buffer passed to it is guaranteed to be
|
|
* unpredictable (so it might not have any entropy at all).
|
|
*/
|
|
static void crng_pre_init_inject(const void *input, size_t len, bool account)
|
|
{
|
|
static int crng_init_cnt = 0;
|
|
struct blake2s_state hash;
|
|
unsigned long flags;
|
|
|
|
blake2s_init(&hash, sizeof(base_crng.key));
|
|
|
|
spin_lock_irqsave(&base_crng.lock, flags);
|
|
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, input, len);
|
|
blake2s_final(&hash, base_crng.key);
|
|
|
|
if (account) {
|
|
crng_init_cnt += min_t(size_t, len, CRNG_INIT_CNT_THRESH - crng_init_cnt);
|
|
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");
|
|
}
|
|
|
|
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)
|
|
{
|
|
ssize_t ret = 0;
|
|
size_t len;
|
|
u32 chacha_state[CHACHA_STATE_WORDS];
|
|
u8 output[CHACHA_BLOCK_SIZE];
|
|
|
|
if (!nbytes)
|
|
return 0;
|
|
|
|
/*
|
|
* Immediately overwrite the ChaCha key at index 4 with random
|
|
* bytes, in case userspace causes copy_to_user() below to sleep
|
|
* forever, so that we still retain forward secrecy in that case.
|
|
*/
|
|
crng_make_state(chacha_state, (u8 *)&chacha_state[4], CHACHA_KEY_SIZE);
|
|
/*
|
|
* However, if we're doing a read of len <= 32, we don't need to
|
|
* use chacha_state after, so we can simply return those bytes to
|
|
* the user directly.
|
|
*/
|
|
if (nbytes <= CHACHA_KEY_SIZE) {
|
|
ret = copy_to_user(buf, &chacha_state[4], nbytes) ? -EFAULT : nbytes;
|
|
goto out_zero_chacha;
|
|
}
|
|
|
|
do {
|
|
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;
|
|
|
|
BUILD_BUG_ON(PAGE_SIZE % CHACHA_BLOCK_SIZE != 0);
|
|
if (!(ret % PAGE_SIZE) && nbytes) {
|
|
if (signal_pending(current))
|
|
break;
|
|
cond_resched();
|
|
}
|
|
} while (nbytes);
|
|
|
|
memzero_explicit(output, sizeof(output));
|
|
out_zero_chacha:
|
|
memzero_explicit(chacha_state, sizeof(chacha_state));
|
|
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);
|
|
|
|
#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 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_u32, cpu)->position = UINT_MAX;
|
|
per_cpu_ptr(&batched_entropy_u64, cpu)->position = UINT_MAX;
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
/**
|
|
* 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 or force is true:
|
|
*
|
|
* static void extract_entropy(void *buf, size_t nbytes)
|
|
* static bool drain_entropy(void *buf, size_t nbytes, bool force)
|
|
*
|
|
**********************************************************************/
|
|
|
|
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_ready() && entropy_count >= POOL_MIN_BITS)
|
|
crng_reseed(false);
|
|
}
|
|
|
|
/*
|
|
* 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 unless force
|
|
* is true, 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, bool force)
|
|
{
|
|
unsigned int entropy_count;
|
|
do {
|
|
entropy_count = READ_ONCE(input_pool.entropy_count);
|
|
if (!force && 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_vmfork_randomness(const void *unique_vm_id, 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_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.
|
|
*
|
|
**********************************************************************/
|
|
|
|
static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
|
|
static bool trust_bootloader __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER);
|
|
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);
|
|
|
|
/*
|
|
* 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;
|
|
|
|
#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; 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_ready()) {
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
cycles_t cycles = random_get_entropy();
|
|
unsigned long flags, now = jiffies;
|
|
|
|
if (crng_init == 0 && size)
|
|
crng_pre_init_inject(buf, size, false);
|
|
|
|
spin_lock_irqsave(&input_pool.lock, flags);
|
|
_mix_pool_bytes(&cycles, sizeof(cycles));
|
|
_mix_pool_bytes(&now, sizeof(now));
|
|
_mix_pool_bytes(buf, size);
|
|
spin_unlock_irqrestore(&input_pool.lock, flags);
|
|
}
|
|
EXPORT_SYMBOL(add_device_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 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)
|
|
{
|
|
cycles_t cycles = random_get_entropy();
|
|
unsigned long flags, now = jiffies;
|
|
long delta, delta2, delta3;
|
|
|
|
spin_lock_irqsave(&input_pool.lock, flags);
|
|
_mix_pool_bytes(&cycles, sizeof(cycles));
|
|
_mix_pool_bytes(&now, sizeof(now));
|
|
_mix_pool_bytes(&num, sizeof(num));
|
|
spin_unlock_irqrestore(&input_pool.lock, flags);
|
|
|
|
/*
|
|
* 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 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 && entropy < POOL_MIN_BITS)) {
|
|
crng_pre_init_inject(buffer, count, true);
|
|
mix_pool_bytes(buffer, count);
|
|
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 (trust_bootloader)
|
|
add_hwgenerator_randomness(buf, size, size * 8);
|
|
else
|
|
add_device_randomness(buf, size);
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_bootloader_randomness);
|
|
|
|
#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 add_vmfork_randomness(const void *unique_vm_id, size_t size)
|
|
{
|
|
add_device_randomness(unique_vm_id, size);
|
|
if (crng_ready()) {
|
|
crng_reseed(true);
|
|
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 register_random_vmfork_notifier(struct notifier_block *nb)
|
|
{
|
|
return blocking_notifier_chain_register(&vmfork_chain, nb);
|
|
}
|
|
EXPORT_SYMBOL_GPL(register_random_vmfork_notifier);
|
|
|
|
int 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 {
|
|
struct work_struct mix;
|
|
unsigned long pool[4];
|
|
unsigned long last;
|
|
unsigned int count;
|
|
u16 reg_idx;
|
|
};
|
|
|
|
static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {
|
|
#ifdef CONFIG_64BIT
|
|
/* SipHash constants */
|
|
.pool = { 0x736f6d6570736575UL, 0x646f72616e646f6dUL,
|
|
0x6c7967656e657261UL, 0x7465646279746573UL }
|
|
#else
|
|
/* HalfSipHash constants */
|
|
.pool = { 0, 0, 0x6c796765U, 0x74656462U }
|
|
#endif
|
|
};
|
|
|
|
/*
|
|
* 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
|
|
* 128 or 256-bit SipHash state, while v represents a 128-bit input.
|
|
*/
|
|
static void fast_mix(unsigned long s[4], const unsigned long *v)
|
|
{
|
|
size_t i;
|
|
|
|
for (i = 0; i < 16 / sizeof(long); ++i) {
|
|
s[3] ^= v[i];
|
|
#ifdef CONFIG_64BIT
|
|
s[0] += s[1]; s[1] = rol64(s[1], 13); s[1] ^= s[0]; s[0] = rol64(s[0], 32);
|
|
s[2] += s[3]; s[3] = rol64(s[3], 16); s[3] ^= s[2];
|
|
s[0] += s[3]; s[3] = rol64(s[3], 21); s[3] ^= s[0];
|
|
s[2] += s[1]; s[1] = rol64(s[1], 17); s[1] ^= s[2]; s[2] = rol64(s[2], 32);
|
|
#else
|
|
s[0] += s[1]; s[1] = rol32(s[1], 5); s[1] ^= s[0]; s[0] = rol32(s[0], 16);
|
|
s[2] += s[3]; s[3] = rol32(s[3], 8); s[3] ^= s[2];
|
|
s[0] += s[3]; s[3] = rol32(s[3], 7); s[3] ^= s[0];
|
|
s[2] += s[1]; s[1] = rol32(s[1], 13); s[1] ^= s[2]; s[2] = rol32(s[2], 16);
|
|
#endif
|
|
s[0] ^= v[i];
|
|
}
|
|
}
|
|
|
|
#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 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 unsigned long get_reg(struct fast_pool *f, struct pt_regs *regs)
|
|
{
|
|
unsigned long *ptr = (unsigned long *)regs;
|
|
unsigned int idx;
|
|
|
|
if (regs == NULL)
|
|
return 0;
|
|
idx = READ_ONCE(f->reg_idx);
|
|
if (idx >= sizeof(struct pt_regs) / sizeof(unsigned long))
|
|
idx = 0;
|
|
ptr += idx++;
|
|
WRITE_ONCE(f->reg_idx, idx);
|
|
return *ptr;
|
|
}
|
|
|
|
static void mix_interrupt_randomness(struct work_struct *work)
|
|
{
|
|
struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix);
|
|
/*
|
|
* The size of the copied stack pool is explicitly 16 bytes so that we
|
|
* tax mix_pool_byte()'s compression function the same amount on all
|
|
* platforms. This means on 64-bit we copy half the pool into this,
|
|
* while on 32-bit we copy all of it. The entropy is supposed to be
|
|
* sufficiently dispersed between bits that in the sponge-like
|
|
* half case, on average we don't wind up "losing" some.
|
|
*/
|
|
u8 pool[16];
|
|
|
|
/* 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));
|
|
fast_pool->count = 0;
|
|
fast_pool->last = jiffies;
|
|
local_irq_enable();
|
|
|
|
if (unlikely(crng_init == 0)) {
|
|
crng_pre_init_inject(pool, sizeof(pool), true);
|
|
mix_pool_bytes(pool, sizeof(pool));
|
|
} else {
|
|
mix_pool_bytes(pool, sizeof(pool));
|
|
credit_entropy_bits(1);
|
|
}
|
|
|
|
memzero_explicit(pool, sizeof(pool));
|
|
}
|
|
|
|
void add_interrupt_randomness(int irq)
|
|
{
|
|
enum { MIX_INFLIGHT = 1U << 31 };
|
|
cycles_t cycles = random_get_entropy();
|
|
unsigned long now = jiffies;
|
|
struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
|
|
struct pt_regs *regs = get_irq_regs();
|
|
unsigned int new_count;
|
|
union {
|
|
u32 u32[4];
|
|
u64 u64[2];
|
|
unsigned long longs[16 / sizeof(long)];
|
|
} irq_data;
|
|
|
|
if (cycles == 0)
|
|
cycles = get_reg(fast_pool, regs);
|
|
|
|
if (sizeof(cycles) == 8)
|
|
irq_data.u64[0] = cycles ^ rol64(now, 32) ^ irq;
|
|
else {
|
|
irq_data.u32[0] = cycles ^ irq;
|
|
irq_data.u32[1] = now;
|
|
}
|
|
|
|
if (sizeof(unsigned long) == 8)
|
|
irq_data.u64[1] = regs ? instruction_pointer(regs) : _RET_IP_;
|
|
else {
|
|
irq_data.u32[2] = regs ? instruction_pointer(regs) : _RET_IP_;
|
|
irq_data.u32[3] = get_reg(fast_pool, regs);
|
|
}
|
|
|
|
fast_mix(fast_pool->pool, irq_data.longs);
|
|
new_count = ++fast_pool->count;
|
|
|
|
if (new_count & MIX_INFLIGHT)
|
|
return;
|
|
|
|
if (new_count < 64 && (!time_after(now, fast_pool->last + HZ) ||
|
|
unlikely(crng_init == 0)))
|
|
return;
|
|
|
|
if (unlikely(!fast_pool->mix.func))
|
|
INIT_WORK(&fast_pool->mix, mix_interrupt_randomness);
|
|
fast_pool->count |= MIX_INFLIGHT;
|
|
queue_work_on(raw_smp_processor_id(), system_highpri_wq, &fast_pool->mix);
|
|
}
|
|
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 {
|
|
cycles_t cycles;
|
|
struct timer_list timer;
|
|
} stack;
|
|
|
|
stack.cycles = random_get_entropy();
|
|
|
|
/* Slow counter - or none. Don't even bother */
|
|
if (stack.cycles == random_get_entropy())
|
|
return;
|
|
|
|
timer_setup_on_stack(&stack.timer, entropy_timer, 0);
|
|
while (!crng_ready() && !signal_pending(current)) {
|
|
if (!timer_pending(&stack.timer))
|
|
mod_timer(&stack.timer, jiffies + 1);
|
|
mix_pool_bytes(&stack.cycles, sizeof(stack.cycles));
|
|
schedule();
|
|
stack.cycles = random_get_entropy();
|
|
}
|
|
|
|
del_timer_sync(&stack.timer);
|
|
destroy_timer_on_stack(&stack.timer);
|
|
mix_pool_bytes(&stack.cycles, sizeof(stack.cycles));
|
|
}
|
|
|
|
|
|
/**********************************************************************
|
|
*
|
|
* 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;
|
|
|
|
/*
|
|
* 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() && 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) >= POOL_MIN_BITS) {
|
|
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_ready())
|
|
return -ENODATA;
|
|
crng_reseed(false);
|
|
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 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_MIN_BITS;
|
|
static int sysctl_poolsize = POOL_BITS;
|
|
static u8 sysctl_bootid[UUID_SIZE];
|
|
|
|
/*
|
|
* This function is used to return both the bootid UUID, and random
|
|
* UUID. The difference is in whether table->data is NULL; if it is,
|
|
* then a new UUID is generated and returned to the user.
|
|
*/
|
|
static int proc_do_uuid(struct ctl_table *table, int write, void *buffer,
|
|
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, buffer, lenp, ppos);
|
|
}
|
|
|
|
/* The same as proc_dointvec, but writes don't change anything. */
|
|
static int proc_do_rointvec(struct ctl_table *table, int write, void *buffer,
|
|
size_t *lenp, loff_t *ppos)
|
|
{
|
|
return write ? 0 : proc_dointvec(table, 0, 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_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,
|
|
},
|
|
{ }
|
|
};
|
|
|
|
/*
|
|
* 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
|