1572 строки
47 KiB
C
1572 строки
47 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. Prior to initialization, some of that
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* data is then "credited" as having a certain number of bits of entropy.
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* When enough bits of entropy are available, the hash is finalized and
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* handed as a key to a stream cipher that expands it indefinitely for
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* various consumers. This key is periodically refreshed as the various
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* entropy collectors, described below, add data to the input pool.
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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 <linux/suspend.h>
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#include <linux/siphash.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 is protected by base_crng->lock, and only increases
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* its value (from empty->early->ready).
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*/
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static enum {
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CRNG_EMPTY = 0, /* Little to no entropy collected */
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CRNG_EARLY = 1, /* At least POOL_EARLY_BITS collected */
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CRNG_READY = 2 /* Fully initialized with POOL_READY_BITS collected */
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} crng_init __read_mostly = CRNG_EMPTY;
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static DEFINE_STATIC_KEY_FALSE(crng_is_ready);
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#define crng_ready() (static_branch_likely(&crng_is_ready) || crng_init >= CRNG_READY)
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/* Various types of waiters for crng_init->CRNG_READY 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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/* Control how we warn userspace. */
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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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IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM);
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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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static void __cold crng_set_ready(struct work_struct *work)
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{
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static_branch_enable(&crng_is_ready);
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}
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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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#define warn_unseeded_randomness() \
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if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \
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printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \
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__func__, (void *)_RET_IP_, crng_init)
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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 len)
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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_START_INTERVAL = HZ,
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CRNG_RESEED_INTERVAL = 60 * HZ
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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() and crng_make_state() to extract a new seed from the input pool. */
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static void extract_entropy(void *buf, size_t len);
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/* This extracts a new crng key from the input pool. */
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static void crng_reseed(void)
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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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extract_entropy(key, sizeof(key));
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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 (!static_branch_likely(&crng_is_ready))
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crng_init = CRNG_READY;
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spin_unlock_irqrestore(&base_crng.lock, flags);
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memzero_explicit(key, sizeof(key));
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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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* The returned ChaCha state contains within it a copy of the old
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* key value, at index 4, so the state should always be zeroed out
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* immediately after using in order to maintain forward secrecy.
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* If the state cannot be erased in a timely manner, then it is
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* safer to set the random_data parameter to &chacha_state[4] so
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* that this function overwrites it before returning.
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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 old
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* that a reseeding is needed. This happens if the last reseeding
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* was CRNG_RESEED_INTERVAL ago, or during early boot, at an interval
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* 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, CRNG_RESEED_START_INTERVAL,
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(unsigned int)uptime / 2 * HZ);
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}
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return time_is_before_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, extracting
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* when crng_init is CRNG_EMPTY.
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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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if (crng_init == CRNG_EMPTY)
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extract_entropy(base_crng.key, sizeof(base_crng.key));
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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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}
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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 reseed, which in turn bumps the
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* 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();
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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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static void _get_random_bytes(void *buf, size_t len)
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{
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u32 chacha_state[CHACHA_STATE_WORDS];
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u8 tmp[CHACHA_BLOCK_SIZE];
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size_t first_block_len;
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if (!len)
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return;
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first_block_len = min_t(size_t, 32, len);
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crng_make_state(chacha_state, buf, first_block_len);
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len -= first_block_len;
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buf += first_block_len;
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while (len) {
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if (len < CHACHA_BLOCK_SIZE) {
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chacha20_block(chacha_state, tmp);
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memcpy(buf, tmp, len);
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memzero_explicit(tmp, sizeof(tmp));
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break;
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}
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chacha20_block(chacha_state, buf);
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if (unlikely(chacha_state[12] == 0))
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++chacha_state[13];
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len -= CHACHA_BLOCK_SIZE;
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buf += CHACHA_BLOCK_SIZE;
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}
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memzero_explicit(chacha_state, sizeof(chacha_state));
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}
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/*
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* This function is the exported kernel interface. It returns some
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* number of good random numbers, suitable for key generation, seeding
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* TCP sequence numbers, etc. In order to ensure that the randomness
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* by this function is okay, the function wait_for_random_bytes()
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* should be called and return 0 at least once at any point prior.
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*/
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void get_random_bytes(void *buf, size_t len)
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{
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warn_unseeded_randomness();
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_get_random_bytes(buf, len);
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}
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EXPORT_SYMBOL(get_random_bytes);
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static ssize_t get_random_bytes_user(struct iov_iter *iter)
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{
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u32 chacha_state[CHACHA_STATE_WORDS];
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u8 block[CHACHA_BLOCK_SIZE];
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size_t ret = 0, copied;
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if (unlikely(!iov_iter_count(iter)))
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return 0;
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/*
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* Immediately overwrite the ChaCha key at index 4 with random
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* bytes, in case userspace causes copy_to_user() below to sleep
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* forever, so that we still retain forward secrecy in that case.
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*/
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crng_make_state(chacha_state, (u8 *)&chacha_state[4], CHACHA_KEY_SIZE);
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/*
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* However, if we're doing a read of len <= 32, we don't need to
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* use chacha_state after, so we can simply return those bytes to
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* the user directly.
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*/
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if (iov_iter_count(iter) <= CHACHA_KEY_SIZE) {
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ret = copy_to_iter(&chacha_state[4], CHACHA_KEY_SIZE, iter);
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goto out_zero_chacha;
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}
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for (;;) {
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chacha20_block(chacha_state, block);
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if (unlikely(chacha_state[12] == 0))
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++chacha_state[13];
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copied = copy_to_iter(block, sizeof(block), iter);
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ret += copied;
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if (!iov_iter_count(iter) || copied != sizeof(block))
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break;
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BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0);
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if (ret % PAGE_SIZE == 0) {
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if (signal_pending(current))
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break;
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cond_resched();
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}
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}
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memzero_explicit(block, sizeof(block));
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out_zero_chacha:
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memzero_explicit(chacha_state, sizeof(chacha_state));
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return ret ? ret : -EFAULT;
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}
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/*
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* Batched entropy returns random integers. The quality of the random
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* number is good as /dev/urandom. In order to ensure that the randomness
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* provided by this function is okay, the function wait_for_random_bytes()
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* should be called and return 0 at least once at any point prior.
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*/
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#define DEFINE_BATCHED_ENTROPY(type) \
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struct batch_ ##type { \
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/* \
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* We make this 1.5x a ChaCha block, so that we get the \
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* remaining 32 bytes from fast key erasure, plus one full \
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* block from the detached ChaCha state. We can increase \
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* the size of this later if needed so long as we keep the \
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* formula of (integer_blocks + 0.5) * CHACHA_BLOCK_SIZE. \
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*/ \
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type entropy[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(type))]; \
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local_lock_t lock; \
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unsigned long generation; \
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unsigned int position; \
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}; \
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\
|
|
static DEFINE_PER_CPU(struct batch_ ##type, batched_entropy_ ##type) = { \
|
|
.lock = INIT_LOCAL_LOCK(batched_entropy_ ##type.lock), \
|
|
.position = UINT_MAX \
|
|
}; \
|
|
\
|
|
type get_random_ ##type(void) \
|
|
{ \
|
|
type ret; \
|
|
unsigned long flags; \
|
|
struct batch_ ##type *batch; \
|
|
unsigned long next_gen; \
|
|
\
|
|
warn_unseeded_randomness(); \
|
|
\
|
|
if (!crng_ready()) { \
|
|
_get_random_bytes(&ret, sizeof(ret)); \
|
|
return ret; \
|
|
} \
|
|
\
|
|
local_lock_irqsave(&batched_entropy_ ##type.lock, flags); \
|
|
batch = raw_cpu_ptr(&batched_entropy_##type); \
|
|
\
|
|
next_gen = READ_ONCE(base_crng.generation); \
|
|
if (batch->position >= ARRAY_SIZE(batch->entropy) || \
|
|
next_gen != batch->generation) { \
|
|
_get_random_bytes(batch->entropy, sizeof(batch->entropy)); \
|
|
batch->position = 0; \
|
|
batch->generation = next_gen; \
|
|
} \
|
|
\
|
|
ret = batch->entropy[batch->position]; \
|
|
batch->entropy[batch->position] = 0; \
|
|
++batch->position; \
|
|
local_unlock_irqrestore(&batched_entropy_ ##type.lock, flags); \
|
|
return ret; \
|
|
} \
|
|
EXPORT_SYMBOL(get_random_ ##type);
|
|
|
|
DEFINE_BATCHED_ENTROPY(u64)
|
|
DEFINE_BATCHED_ENTROPY(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 __cold random_prepare_cpu(unsigned int cpu)
|
|
{
|
|
/*
|
|
* When the cpu comes back online, immediately invalidate both
|
|
* the per-cpu crng and all batches, so that we serve fresh
|
|
* randomness.
|
|
*/
|
|
per_cpu_ptr(&crngs, cpu)->generation = ULONG_MAX;
|
|
per_cpu_ptr(&batched_entropy_u32, cpu)->position = UINT_MAX;
|
|
per_cpu_ptr(&batched_entropy_u64, cpu)->position = UINT_MAX;
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
|
|
/**********************************************************************
|
|
*
|
|
* Entropy accumulation and extraction routines.
|
|
*
|
|
* Callers may add entropy via:
|
|
*
|
|
* static void mix_pool_bytes(const void *buf, size_t len)
|
|
*
|
|
* After which, if added entropy should be credited:
|
|
*
|
|
* static void credit_init_bits(size_t bits)
|
|
*
|
|
* Finally, extract entropy via:
|
|
*
|
|
* static void extract_entropy(void *buf, size_t len)
|
|
*
|
|
**********************************************************************/
|
|
|
|
enum {
|
|
POOL_BITS = BLAKE2S_HASH_SIZE * 8,
|
|
POOL_READY_BITS = POOL_BITS, /* When crng_init->CRNG_READY */
|
|
POOL_EARLY_BITS = POOL_READY_BITS / 2 /* When crng_init->CRNG_EARLY */
|
|
};
|
|
|
|
static struct {
|
|
struct blake2s_state hash;
|
|
spinlock_t lock;
|
|
unsigned int init_bits;
|
|
} input_pool = {
|
|
.hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE),
|
|
BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4,
|
|
BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 },
|
|
.hash.outlen = BLAKE2S_HASH_SIZE,
|
|
.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
|
|
};
|
|
|
|
static void _mix_pool_bytes(const void *buf, size_t len)
|
|
{
|
|
blake2s_update(&input_pool.hash, buf, len);
|
|
}
|
|
|
|
/*
|
|
* This function adds bytes into the input pool. It does not
|
|
* update the initialization bit counter; the caller should call
|
|
* credit_init_bits if this is appropriate.
|
|
*/
|
|
static void mix_pool_bytes(const void *buf, size_t len)
|
|
{
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&input_pool.lock, flags);
|
|
_mix_pool_bytes(buf, len);
|
|
spin_unlock_irqrestore(&input_pool.lock, flags);
|
|
}
|
|
|
|
/*
|
|
* This is an HKDF-like construction for using the hashed collected entropy
|
|
* as a PRF key, that's then expanded block-by-block.
|
|
*/
|
|
static void extract_entropy(void *buf, size_t len)
|
|
{
|
|
unsigned long flags;
|
|
u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE];
|
|
struct {
|
|
unsigned long rdseed[32 / sizeof(long)];
|
|
size_t counter;
|
|
} block;
|
|
size_t i;
|
|
|
|
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 (len) {
|
|
i = min_t(size_t, len, BLAKE2S_HASH_SIZE);
|
|
/* output = HASHPRF(seed, RDSEED || ++counter) */
|
|
++block.counter;
|
|
blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed));
|
|
len -= i;
|
|
buf += i;
|
|
}
|
|
|
|
memzero_explicit(seed, sizeof(seed));
|
|
memzero_explicit(&block, sizeof(block));
|
|
}
|
|
|
|
#define credit_init_bits(bits) if (!crng_ready()) _credit_init_bits(bits)
|
|
|
|
static void __cold _credit_init_bits(size_t bits)
|
|
{
|
|
static struct execute_work set_ready;
|
|
unsigned int new, orig, add;
|
|
unsigned long flags;
|
|
|
|
if (!bits)
|
|
return;
|
|
|
|
add = min_t(size_t, bits, POOL_BITS);
|
|
|
|
do {
|
|
orig = READ_ONCE(input_pool.init_bits);
|
|
new = min_t(unsigned int, POOL_BITS, orig + add);
|
|
} while (cmpxchg(&input_pool.init_bits, orig, new) != orig);
|
|
|
|
if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) {
|
|
crng_reseed(); /* Sets crng_init to CRNG_READY under base_crng.lock. */
|
|
execute_in_process_context(crng_set_ready, &set_ready);
|
|
wake_up_interruptible(&crng_init_wait);
|
|
kill_fasync(&fasync, SIGIO, POLL_IN);
|
|
pr_notice("crng init done\n");
|
|
if (urandom_warning.missed)
|
|
pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
|
|
urandom_warning.missed);
|
|
} else if (orig < POOL_EARLY_BITS && new >= POOL_EARLY_BITS) {
|
|
spin_lock_irqsave(&base_crng.lock, flags);
|
|
/* Check if crng_init is CRNG_EMPTY, to avoid race with crng_reseed(). */
|
|
if (crng_init == CRNG_EMPTY) {
|
|
extract_entropy(base_crng.key, sizeof(base_crng.key));
|
|
crng_init = CRNG_EARLY;
|
|
}
|
|
spin_unlock_irqrestore(&base_crng.lock, flags);
|
|
}
|
|
}
|
|
|
|
|
|
/**********************************************************************
|
|
*
|
|
* Entropy collection routines.
|
|
*
|
|
* The following exported functions are used for pushing entropy into
|
|
* the above entropy accumulation routines:
|
|
*
|
|
* void add_device_randomness(const void *buf, size_t len);
|
|
* void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy);
|
|
* void add_bootloader_randomness(const void *buf, size_t len);
|
|
* void add_vmfork_randomness(const void *unique_vm_id, size_t len);
|
|
* void add_interrupt_randomness(int irq);
|
|
* void add_input_randomness(unsigned int type, unsigned int code, unsigned int value);
|
|
* void add_disk_randomness(struct gendisk *disk);
|
|
*
|
|
* add_device_randomness() adds data to the input pool that
|
|
* is likely to differ between two devices (or possibly even per boot).
|
|
* This would be things like MAC addresses or serial numbers, or the
|
|
* read-out of the RTC. This does *not* credit any actual entropy to
|
|
* the pool, but it initializes the pool to different values for devices
|
|
* that might otherwise be identical and have very little entropy
|
|
* available to them (particularly common in the embedded world).
|
|
*
|
|
* add_hwgenerator_randomness() is for true hardware RNGs, and will credit
|
|
* entropy as specified by the caller. If the entropy pool is full it will
|
|
* block until more entropy is needed.
|
|
*
|
|
* add_bootloader_randomness() is called by bootloader drivers, such as EFI
|
|
* and device tree, and credits its input depending on whether or not the
|
|
* 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.
|
|
*
|
|
* add_input_randomness() uses the input layer interrupt timing, as well
|
|
* as the event type information from the hardware.
|
|
*
|
|
* add_disk_randomness() uses what amounts to the seek time of block
|
|
* layer request events, on a per-disk_devt basis, as input to the
|
|
* entropy pool. Note that high-speed solid state drives with very low
|
|
* seek times do not make for good sources of entropy, as their seek
|
|
* times are usually fairly consistent.
|
|
*
|
|
* The last two routines try to estimate how many bits of entropy
|
|
* to credit. They do this by keeping track of the first and second
|
|
* order deltas of the event timings.
|
|
*
|
|
**********************************************************************/
|
|
|
|
static bool used_arch_random;
|
|
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);
|
|
|
|
static int random_pm_notification(struct notifier_block *nb, unsigned long action, void *data)
|
|
{
|
|
unsigned long flags, entropy = random_get_entropy();
|
|
|
|
/*
|
|
* Encode a representation of how long the system has been suspended,
|
|
* in a way that is distinct from prior system suspends.
|
|
*/
|
|
ktime_t stamps[] = { ktime_get(), ktime_get_boottime(), ktime_get_real() };
|
|
|
|
spin_lock_irqsave(&input_pool.lock, flags);
|
|
_mix_pool_bytes(&action, sizeof(action));
|
|
_mix_pool_bytes(stamps, sizeof(stamps));
|
|
_mix_pool_bytes(&entropy, sizeof(entropy));
|
|
spin_unlock_irqrestore(&input_pool.lock, flags);
|
|
|
|
if (crng_ready() && (action == PM_RESTORE_PREPARE ||
|
|
(action == PM_POST_SUSPEND &&
|
|
!IS_ENABLED(CONFIG_PM_AUTOSLEEP) && !IS_ENABLED(CONFIG_ANDROID)))) {
|
|
crng_reseed();
|
|
pr_notice("crng reseeded on system resumption\n");
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static struct notifier_block pm_notifier = { .notifier_call = random_pm_notification };
|
|
|
|
/*
|
|
* The first collection of entropy occurs at system boot while interrupts
|
|
* are still turned off. Here we push in latent entropy, RDSEED, a timestamp,
|
|
* utsname(), and the command line. 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 random_init(const char *command_line)
|
|
{
|
|
ktime_t now = ktime_get_real();
|
|
unsigned int i, arch_bytes;
|
|
unsigned long entropy;
|
|
|
|
#if defined(LATENT_ENTROPY_PLUGIN)
|
|
static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy;
|
|
_mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed));
|
|
#endif
|
|
|
|
for (i = 0, arch_bytes = BLAKE2S_BLOCK_SIZE;
|
|
i < BLAKE2S_BLOCK_SIZE; i += sizeof(entropy)) {
|
|
if (!arch_get_random_seed_long_early(&entropy) &&
|
|
!arch_get_random_long_early(&entropy)) {
|
|
entropy = random_get_entropy();
|
|
arch_bytes -= sizeof(entropy);
|
|
}
|
|
_mix_pool_bytes(&entropy, sizeof(entropy));
|
|
}
|
|
_mix_pool_bytes(&now, sizeof(now));
|
|
_mix_pool_bytes(utsname(), sizeof(*(utsname())));
|
|
_mix_pool_bytes(command_line, strlen(command_line));
|
|
add_latent_entropy();
|
|
|
|
if (crng_ready())
|
|
crng_reseed();
|
|
else if (trust_cpu)
|
|
credit_init_bits(arch_bytes * 8);
|
|
used_arch_random = arch_bytes * 8 >= POOL_READY_BITS;
|
|
|
|
WARN_ON(register_pm_notifier(&pm_notifier));
|
|
|
|
WARN(!random_get_entropy(), "Missing cycle counter and fallback timer; RNG "
|
|
"entropy collection will consequently suffer.");
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Returns whether arch randomness has been mixed into the initial
|
|
* state of the RNG, regardless of whether or not that randomness
|
|
* was credited. Knowing this is only good for a very limited set
|
|
* of uses, such as early init printk pointer obfuscation.
|
|
*/
|
|
bool rng_has_arch_random(void)
|
|
{
|
|
return used_arch_random;
|
|
}
|
|
|
|
/*
|
|
* Add device- or boot-specific data to the input pool to help
|
|
* initialize it.
|
|
*
|
|
* None of this adds any entropy; it is meant to avoid the problem of
|
|
* the entropy pool having similar initial state across largely
|
|
* identical devices.
|
|
*/
|
|
void add_device_randomness(const void *buf, size_t len)
|
|
{
|
|
unsigned long entropy = random_get_entropy();
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&input_pool.lock, flags);
|
|
_mix_pool_bytes(&entropy, sizeof(entropy));
|
|
_mix_pool_bytes(buf, len);
|
|
spin_unlock_irqrestore(&input_pool.lock, flags);
|
|
}
|
|
EXPORT_SYMBOL(add_device_randomness);
|
|
|
|
/*
|
|
* Interface for in-kernel drivers of true hardware RNGs.
|
|
* Those devices may produce endless random bits and will be throttled
|
|
* when our pool is full.
|
|
*/
|
|
void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy)
|
|
{
|
|
mix_pool_bytes(buf, len);
|
|
credit_init_bits(entropy);
|
|
|
|
/*
|
|
* Throttle writing to once every CRNG_RESEED_INTERVAL, unless
|
|
* we're not yet initialized.
|
|
*/
|
|
if (!kthread_should_stop() && crng_ready())
|
|
schedule_timeout_interruptible(CRNG_RESEED_INTERVAL);
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
|
|
|
|
/*
|
|
* Handle random seed passed by bootloader, and credit it if
|
|
* CONFIG_RANDOM_TRUST_BOOTLOADER is set.
|
|
*/
|
|
void __cold add_bootloader_randomness(const void *buf, size_t len)
|
|
{
|
|
mix_pool_bytes(buf, len);
|
|
if (trust_bootloader)
|
|
credit_init_bits(len * 8);
|
|
}
|
|
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 __cold add_vmfork_randomness(const void *unique_vm_id, size_t len)
|
|
{
|
|
add_device_randomness(unique_vm_id, len);
|
|
if (crng_ready()) {
|
|
crng_reseed();
|
|
pr_notice("crng reseeded due to virtual machine fork\n");
|
|
}
|
|
blocking_notifier_call_chain(&vmfork_chain, 0, NULL);
|
|
}
|
|
#if IS_MODULE(CONFIG_VMGENID)
|
|
EXPORT_SYMBOL_GPL(add_vmfork_randomness);
|
|
#endif
|
|
|
|
int __cold register_random_vmfork_notifier(struct notifier_block *nb)
|
|
{
|
|
return blocking_notifier_chain_register(&vmfork_chain, nb);
|
|
}
|
|
EXPORT_SYMBOL_GPL(register_random_vmfork_notifier);
|
|
|
|
int __cold unregister_random_vmfork_notifier(struct notifier_block *nb)
|
|
{
|
|
return blocking_notifier_chain_unregister(&vmfork_chain, nb);
|
|
}
|
|
EXPORT_SYMBOL_GPL(unregister_random_vmfork_notifier);
|
|
#endif
|
|
|
|
struct fast_pool {
|
|
struct work_struct mix;
|
|
unsigned long pool[4];
|
|
unsigned long last;
|
|
unsigned int count;
|
|
};
|
|
|
|
static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {
|
|
#ifdef CONFIG_64BIT
|
|
#define FASTMIX_PERM SIPHASH_PERMUTATION
|
|
.pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 }
|
|
#else
|
|
#define FASTMIX_PERM HSIPHASH_PERMUTATION
|
|
.pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 }
|
|
#endif
|
|
};
|
|
|
|
/*
|
|
* This is [Half]SipHash-1-x, starting from an empty key. Because
|
|
* the key is fixed, it assumes that its inputs are non-malicious,
|
|
* and therefore this has no security on its own. s represents the
|
|
* four-word SipHash state, while v represents a two-word input.
|
|
*/
|
|
static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2)
|
|
{
|
|
s[3] ^= v1;
|
|
FASTMIX_PERM(s[0], s[1], s[2], s[3]);
|
|
s[0] ^= v1;
|
|
s[3] ^= v2;
|
|
FASTMIX_PERM(s[0], s[1], s[2], s[3]);
|
|
s[0] ^= v2;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* This function is called when the CPU has just come online, with
|
|
* entry CPUHP_AP_RANDOM_ONLINE, just after CPUHP_AP_WORKQUEUE_ONLINE.
|
|
*/
|
|
int __cold random_online_cpu(unsigned int cpu)
|
|
{
|
|
/*
|
|
* During CPU shutdown and before CPU onlining, add_interrupt_
|
|
* randomness() may schedule mix_interrupt_randomness(), and
|
|
* set the MIX_INFLIGHT flag. However, because the worker can
|
|
* be scheduled on a different CPU during this period, that
|
|
* flag will never be cleared. For that reason, we zero out
|
|
* the flag here, which runs just after workqueues are onlined
|
|
* for the CPU again. This also has the effect of setting the
|
|
* irq randomness count to zero so that new accumulated irqs
|
|
* are fresh.
|
|
*/
|
|
per_cpu_ptr(&irq_randomness, cpu)->count = 0;
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
static void mix_interrupt_randomness(struct work_struct *work)
|
|
{
|
|
struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix);
|
|
/*
|
|
* The size of the copied stack pool is explicitly 2 longs so that we
|
|
* only ever ingest half of the siphash output each time, retaining
|
|
* the other half as the next "key" that carries over. The entropy is
|
|
* supposed to be sufficiently dispersed between bits so on average
|
|
* we don't wind up "losing" some.
|
|
*/
|
|
unsigned long pool[2];
|
|
unsigned int count;
|
|
|
|
/* Check to see if we're running on the wrong CPU due to hotplug. */
|
|
local_irq_disable();
|
|
if (fast_pool != this_cpu_ptr(&irq_randomness)) {
|
|
local_irq_enable();
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Copy the pool to the stack so that the mixer always has a
|
|
* consistent view, before we reenable irqs again.
|
|
*/
|
|
memcpy(pool, fast_pool->pool, sizeof(pool));
|
|
count = fast_pool->count;
|
|
fast_pool->count = 0;
|
|
fast_pool->last = jiffies;
|
|
local_irq_enable();
|
|
|
|
mix_pool_bytes(pool, sizeof(pool));
|
|
credit_init_bits(max(1u, (count & U16_MAX) / 64));
|
|
|
|
memzero_explicit(pool, sizeof(pool));
|
|
}
|
|
|
|
void add_interrupt_randomness(int irq)
|
|
{
|
|
enum { MIX_INFLIGHT = 1U << 31 };
|
|
unsigned long entropy = random_get_entropy();
|
|
struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
|
|
struct pt_regs *regs = get_irq_regs();
|
|
unsigned int new_count;
|
|
|
|
fast_mix(fast_pool->pool, entropy,
|
|
(regs ? instruction_pointer(regs) : _RET_IP_) ^ swab(irq));
|
|
new_count = ++fast_pool->count;
|
|
|
|
if (new_count & MIX_INFLIGHT)
|
|
return;
|
|
|
|
if (new_count < 64 && !time_is_before_jiffies(fast_pool->last + HZ))
|
|
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);
|
|
|
|
/* There is one of these per entropy source */
|
|
struct timer_rand_state {
|
|
unsigned long last_time;
|
|
long last_delta, last_delta2;
|
|
};
|
|
|
|
/*
|
|
* This function adds entropy to the entropy "pool" by using timing
|
|
* delays. It uses the timer_rand_state structure to make an estimate
|
|
* of how many bits of entropy this call has added to the pool. The
|
|
* value "num" is also added to the pool; it should somehow describe
|
|
* the type of event that just happened.
|
|
*/
|
|
static void add_timer_randomness(struct timer_rand_state *state, unsigned int num)
|
|
{
|
|
unsigned long entropy = random_get_entropy(), now = jiffies, flags;
|
|
long delta, delta2, delta3;
|
|
unsigned int bits;
|
|
|
|
/*
|
|
* If we're in a hard IRQ, add_interrupt_randomness() will be called
|
|
* sometime after, so mix into the fast pool.
|
|
*/
|
|
if (in_hardirq()) {
|
|
fast_mix(this_cpu_ptr(&irq_randomness)->pool, entropy, num);
|
|
} else {
|
|
spin_lock_irqsave(&input_pool.lock, flags);
|
|
_mix_pool_bytes(&entropy, sizeof(entropy));
|
|
_mix_pool_bytes(&num, sizeof(num));
|
|
spin_unlock_irqrestore(&input_pool.lock, flags);
|
|
}
|
|
|
|
if (crng_ready())
|
|
return;
|
|
|
|
/*
|
|
* Calculate number of bits of randomness we probably added.
|
|
* We take into account the first, second and third-order deltas
|
|
* in order to make our estimate.
|
|
*/
|
|
delta = now - READ_ONCE(state->last_time);
|
|
WRITE_ONCE(state->last_time, now);
|
|
|
|
delta2 = delta - READ_ONCE(state->last_delta);
|
|
WRITE_ONCE(state->last_delta, delta);
|
|
|
|
delta3 = delta2 - READ_ONCE(state->last_delta2);
|
|
WRITE_ONCE(state->last_delta2, delta2);
|
|
|
|
if (delta < 0)
|
|
delta = -delta;
|
|
if (delta2 < 0)
|
|
delta2 = -delta2;
|
|
if (delta3 < 0)
|
|
delta3 = -delta3;
|
|
if (delta > delta2)
|
|
delta = delta2;
|
|
if (delta > delta3)
|
|
delta = delta3;
|
|
|
|
/*
|
|
* delta is now minimum absolute delta. Round down by 1 bit
|
|
* on general principles, and limit entropy estimate to 11 bits.
|
|
*/
|
|
bits = min(fls(delta >> 1), 11);
|
|
|
|
/*
|
|
* As mentioned above, if we're in a hard IRQ, add_interrupt_randomness()
|
|
* will run after this, which uses a different crediting scheme of 1 bit
|
|
* per every 64 interrupts. In order to let that function do accounting
|
|
* close to the one in this function, we credit a full 64/64 bit per bit,
|
|
* and then subtract one to account for the extra one added.
|
|
*/
|
|
if (in_hardirq())
|
|
this_cpu_ptr(&irq_randomness)->count += max(1u, bits * 64) - 1;
|
|
else
|
|
_credit_init_bits(bits);
|
|
}
|
|
|
|
void add_input_randomness(unsigned int type, unsigned int code, unsigned int value)
|
|
{
|
|
static unsigned char last_value;
|
|
static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES };
|
|
|
|
/* Ignore autorepeat and the like. */
|
|
if (value == last_value)
|
|
return;
|
|
|
|
last_value = value;
|
|
add_timer_randomness(&input_timer_state,
|
|
(type << 4) ^ code ^ (code >> 4) ^ value);
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_input_randomness);
|
|
|
|
#ifdef CONFIG_BLOCK
|
|
void add_disk_randomness(struct gendisk *disk)
|
|
{
|
|
if (!disk || !disk->random)
|
|
return;
|
|
/* First major is 1, so we get >= 0x200 here. */
|
|
add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_disk_randomness);
|
|
|
|
void __cold rand_initialize_disk(struct gendisk *disk)
|
|
{
|
|
struct timer_rand_state *state;
|
|
|
|
/*
|
|
* If kzalloc returns null, we just won't use that entropy
|
|
* source.
|
|
*/
|
|
state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
|
|
if (state) {
|
|
state->last_time = INITIAL_JIFFIES;
|
|
disk->random = state;
|
|
}
|
|
}
|
|
#endif
|
|
|
|
struct entropy_timer_state {
|
|
unsigned long entropy;
|
|
struct timer_list timer;
|
|
unsigned int samples, samples_per_bit;
|
|
};
|
|
|
|
/*
|
|
* Each time the timer fires, we expect that we got an unpredictable
|
|
* jump in the cycle counter. Even if the timer is running on another
|
|
* CPU, the timer activity will be touching the stack of the CPU that is
|
|
* generating entropy..
|
|
*
|
|
* Note that we don't re-arm the timer in the timer itself - we are
|
|
* happy to be scheduled away, since that just makes the load more
|
|
* complex, but we do not want the timer to keep ticking unless the
|
|
* entropy loop is running.
|
|
*
|
|
* So the re-arming always happens in the entropy loop itself.
|
|
*/
|
|
static void __cold entropy_timer(struct timer_list *timer)
|
|
{
|
|
struct entropy_timer_state *state = container_of(timer, struct entropy_timer_state, timer);
|
|
|
|
if (++state->samples == state->samples_per_bit) {
|
|
credit_init_bits(1);
|
|
state->samples = 0;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If we have an actual cycle counter, see if we can
|
|
* generate enough entropy with timing noise
|
|
*/
|
|
static void __cold try_to_generate_entropy(void)
|
|
{
|
|
enum { NUM_TRIAL_SAMPLES = 8192, MAX_SAMPLES_PER_BIT = 32 };
|
|
struct entropy_timer_state stack;
|
|
unsigned int i, num_different = 0;
|
|
unsigned long last = random_get_entropy();
|
|
|
|
for (i = 0; i < NUM_TRIAL_SAMPLES - 1; ++i) {
|
|
stack.entropy = random_get_entropy();
|
|
if (stack.entropy != last)
|
|
++num_different;
|
|
last = stack.entropy;
|
|
}
|
|
stack.samples_per_bit = DIV_ROUND_UP(NUM_TRIAL_SAMPLES, num_different + 1);
|
|
if (stack.samples_per_bit > MAX_SAMPLES_PER_BIT)
|
|
return;
|
|
|
|
stack.samples = 0;
|
|
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.entropy, sizeof(stack.entropy));
|
|
schedule();
|
|
stack.entropy = random_get_entropy();
|
|
}
|
|
|
|
del_timer_sync(&stack.timer);
|
|
destroy_timer_on_stack(&stack.timer);
|
|
mix_pool_bytes(&stack.entropy, sizeof(stack.entropy));
|
|
}
|
|
|
|
|
|
/**********************************************************************
|
|
*
|
|
* Userspace reader/writer interfaces.
|
|
*
|
|
* getrandom(2) is the primary modern interface into the RNG and should
|
|
* be used in preference to anything else.
|
|
*
|
|
* Reading from /dev/random has the same functionality as calling
|
|
* getrandom(2) with flags=0. In earlier versions, however, it had
|
|
* vastly different semantics and should therefore be avoided, to
|
|
* prevent backwards compatibility issues.
|
|
*
|
|
* Reading from /dev/urandom has the same functionality as calling
|
|
* getrandom(2) with flags=GRND_INSECURE. Because it does not block
|
|
* waiting for the RNG to be ready, it should not be used.
|
|
*
|
|
* Writing to either /dev/random or /dev/urandom adds entropy to
|
|
* the input pool but does not credit it.
|
|
*
|
|
* Polling on /dev/random indicates when the RNG is initialized, on
|
|
* the read side, and when it wants new entropy, on the write side.
|
|
*
|
|
* Both /dev/random and /dev/urandom have the same set of ioctls for
|
|
* adding entropy, getting the entropy count, zeroing the count, and
|
|
* reseeding the crng.
|
|
*
|
|
**********************************************************************/
|
|
|
|
SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags)
|
|
{
|
|
struct iov_iter iter;
|
|
struct iovec iov;
|
|
int ret;
|
|
|
|
if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE))
|
|
return -EINVAL;
|
|
|
|
/*
|
|
* Requesting insecure and blocking randomness at the same time makes
|
|
* no sense.
|
|
*/
|
|
if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM))
|
|
return -EINVAL;
|
|
|
|
if (!crng_ready() && !(flags & GRND_INSECURE)) {
|
|
if (flags & GRND_NONBLOCK)
|
|
return -EAGAIN;
|
|
ret = wait_for_random_bytes();
|
|
if (unlikely(ret))
|
|
return ret;
|
|
}
|
|
|
|
ret = import_single_range(READ, ubuf, len, &iov, &iter);
|
|
if (unlikely(ret))
|
|
return ret;
|
|
return get_random_bytes_user(&iter);
|
|
}
|
|
|
|
static __poll_t random_poll(struct file *file, poll_table *wait)
|
|
{
|
|
poll_wait(file, &crng_init_wait, wait);
|
|
return crng_ready() ? EPOLLIN | EPOLLRDNORM : EPOLLOUT | EPOLLWRNORM;
|
|
}
|
|
|
|
static ssize_t write_pool_user(struct iov_iter *iter)
|
|
{
|
|
u8 block[BLAKE2S_BLOCK_SIZE];
|
|
ssize_t ret = 0;
|
|
size_t copied;
|
|
|
|
if (unlikely(!iov_iter_count(iter)))
|
|
return 0;
|
|
|
|
for (;;) {
|
|
copied = copy_from_iter(block, sizeof(block), iter);
|
|
ret += copied;
|
|
mix_pool_bytes(block, copied);
|
|
if (!iov_iter_count(iter) || copied != sizeof(block))
|
|
break;
|
|
|
|
BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0);
|
|
if (ret % PAGE_SIZE == 0) {
|
|
if (signal_pending(current))
|
|
break;
|
|
cond_resched();
|
|
}
|
|
}
|
|
|
|
memzero_explicit(block, sizeof(block));
|
|
return ret ? ret : -EFAULT;
|
|
}
|
|
|
|
static ssize_t random_write_iter(struct kiocb *kiocb, struct iov_iter *iter)
|
|
{
|
|
return write_pool_user(iter);
|
|
}
|
|
|
|
static ssize_t urandom_read_iter(struct kiocb *kiocb, struct iov_iter *iter)
|
|
{
|
|
static int maxwarn = 10;
|
|
|
|
/*
|
|
* Opportunistically attempt to initialize the RNG on platforms that
|
|
* have fast cycle counters, but don't (for now) require it to succeed.
|
|
*/
|
|
if (!crng_ready())
|
|
try_to_generate_entropy();
|
|
|
|
if (!crng_ready()) {
|
|
if (!ratelimit_disable && maxwarn <= 0)
|
|
++urandom_warning.missed;
|
|
else if (ratelimit_disable || __ratelimit(&urandom_warning)) {
|
|
--maxwarn;
|
|
pr_notice("%s: uninitialized urandom read (%zu bytes read)\n",
|
|
current->comm, iov_iter_count(iter));
|
|
}
|
|
}
|
|
|
|
return get_random_bytes_user(iter);
|
|
}
|
|
|
|
static ssize_t random_read_iter(struct kiocb *kiocb, struct iov_iter *iter)
|
|
{
|
|
int ret;
|
|
|
|
ret = wait_for_random_bytes();
|
|
if (ret != 0)
|
|
return ret;
|
|
return get_random_bytes_user(iter);
|
|
}
|
|
|
|
static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
|
|
{
|
|
int __user *p = (int __user *)arg;
|
|
int ent_count;
|
|
|
|
switch (cmd) {
|
|
case RNDGETENTCNT:
|
|
/* Inherently racy, no point locking. */
|
|
if (put_user(input_pool.init_bits, p))
|
|
return -EFAULT;
|
|
return 0;
|
|
case RNDADDTOENTCNT:
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
if (get_user(ent_count, p))
|
|
return -EFAULT;
|
|
if (ent_count < 0)
|
|
return -EINVAL;
|
|
credit_init_bits(ent_count);
|
|
return 0;
|
|
case RNDADDENTROPY: {
|
|
struct iov_iter iter;
|
|
struct iovec iov;
|
|
ssize_t ret;
|
|
int len;
|
|
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
if (get_user(ent_count, p++))
|
|
return -EFAULT;
|
|
if (ent_count < 0)
|
|
return -EINVAL;
|
|
if (get_user(len, p++))
|
|
return -EFAULT;
|
|
ret = import_single_range(WRITE, p, len, &iov, &iter);
|
|
if (unlikely(ret))
|
|
return ret;
|
|
ret = write_pool_user(&iter);
|
|
if (unlikely(ret < 0))
|
|
return ret;
|
|
/* Since we're crediting, enforce that it was all written into the pool. */
|
|
if (unlikely(ret != len))
|
|
return -EFAULT;
|
|
credit_init_bits(ent_count);
|
|
return 0;
|
|
}
|
|
case RNDZAPENTCNT:
|
|
case RNDCLEARPOOL:
|
|
/* No longer has any effect. */
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
case RNDRESEEDCRNG:
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
if (!crng_ready())
|
|
return -ENODATA;
|
|
crng_reseed();
|
|
return 0;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
static int random_fasync(int fd, struct file *filp, int on)
|
|
{
|
|
return fasync_helper(fd, filp, on, &fasync);
|
|
}
|
|
|
|
const struct file_operations random_fops = {
|
|
.read_iter = random_read_iter,
|
|
.write_iter = random_write_iter,
|
|
.poll = random_poll,
|
|
.unlocked_ioctl = random_ioctl,
|
|
.compat_ioctl = compat_ptr_ioctl,
|
|
.fasync = random_fasync,
|
|
.llseek = noop_llseek,
|
|
.splice_read = generic_file_splice_read,
|
|
.splice_write = iter_file_splice_write,
|
|
};
|
|
|
|
const struct file_operations urandom_fops = {
|
|
.read_iter = urandom_read_iter,
|
|
.write_iter = random_write_iter,
|
|
.unlocked_ioctl = random_ioctl,
|
|
.compat_ioctl = compat_ptr_ioctl,
|
|
.fasync = random_fasync,
|
|
.llseek = noop_llseek,
|
|
.splice_read = generic_file_splice_read,
|
|
.splice_write = iter_file_splice_write,
|
|
};
|
|
|
|
|
|
/********************************************************************
|
|
*
|
|
* Sysctl interface.
|
|
*
|
|
* These are partly unused legacy knobs with dummy values to not break
|
|
* userspace and partly still useful things. They are usually accessible
|
|
* in /proc/sys/kernel/random/ and are as follows:
|
|
*
|
|
* - boot_id - a UUID representing the current boot.
|
|
*
|
|
* - uuid - a random UUID, different each time the file is read.
|
|
*
|
|
* - poolsize - the number of bits of entropy that the input pool can
|
|
* hold, tied to the POOL_BITS constant.
|
|
*
|
|
* - entropy_avail - the number of bits of entropy currently in the
|
|
* input pool. Always <= poolsize.
|
|
*
|
|
* - write_wakeup_threshold - the amount of entropy in the input pool
|
|
* below which write polls to /dev/random will unblock, requesting
|
|
* more entropy, tied to the POOL_READY_BITS constant. It is writable
|
|
* to avoid breaking old userspaces, but writing to it does not
|
|
* change any behavior of the RNG.
|
|
*
|
|
* - urandom_min_reseed_secs - fixed to the value CRNG_RESEED_INTERVAL.
|
|
* It is writable to avoid breaking old userspaces, but writing
|
|
* to it does not change any behavior of the RNG.
|
|
*
|
|
********************************************************************/
|
|
|
|
#ifdef CONFIG_SYSCTL
|
|
|
|
#include <linux/sysctl.h>
|
|
|
|
static int sysctl_random_min_urandom_seed = CRNG_RESEED_INTERVAL / HZ;
|
|
static int sysctl_random_write_wakeup_bits = POOL_READY_BITS;
|
|
static int sysctl_poolsize = POOL_BITS;
|
|
static u8 sysctl_bootid[UUID_SIZE];
|
|
|
|
/*
|
|
* This function is used to return both the bootid UUID, and random
|
|
* UUID. The difference is in whether table->data is NULL; if it is,
|
|
* then a new UUID is generated and returned to the user.
|
|
*/
|
|
static int proc_do_uuid(struct ctl_table *table, int write, void *buf,
|
|
size_t *lenp, loff_t *ppos)
|
|
{
|
|
u8 tmp_uuid[UUID_SIZE], *uuid;
|
|
char uuid_string[UUID_STRING_LEN + 1];
|
|
struct ctl_table fake_table = {
|
|
.data = uuid_string,
|
|
.maxlen = UUID_STRING_LEN
|
|
};
|
|
|
|
if (write)
|
|
return -EPERM;
|
|
|
|
uuid = table->data;
|
|
if (!uuid) {
|
|
uuid = tmp_uuid;
|
|
generate_random_uuid(uuid);
|
|
} else {
|
|
static DEFINE_SPINLOCK(bootid_spinlock);
|
|
|
|
spin_lock(&bootid_spinlock);
|
|
if (!uuid[8])
|
|
generate_random_uuid(uuid);
|
|
spin_unlock(&bootid_spinlock);
|
|
}
|
|
|
|
snprintf(uuid_string, sizeof(uuid_string), "%pU", uuid);
|
|
return proc_dostring(&fake_table, 0, buf, lenp, ppos);
|
|
}
|
|
|
|
/* The same as proc_dointvec, but writes don't change anything. */
|
|
static int proc_do_rointvec(struct ctl_table *table, int write, void *buf,
|
|
size_t *lenp, loff_t *ppos)
|
|
{
|
|
return write ? 0 : proc_dointvec(table, 0, buf, lenp, ppos);
|
|
}
|
|
|
|
static struct ctl_table random_table[] = {
|
|
{
|
|
.procname = "poolsize",
|
|
.data = &sysctl_poolsize,
|
|
.maxlen = sizeof(int),
|
|
.mode = 0444,
|
|
.proc_handler = proc_dointvec,
|
|
},
|
|
{
|
|
.procname = "entropy_avail",
|
|
.data = &input_pool.init_bits,
|
|
.maxlen = sizeof(int),
|
|
.mode = 0444,
|
|
.proc_handler = proc_dointvec,
|
|
},
|
|
{
|
|
.procname = "write_wakeup_threshold",
|
|
.data = &sysctl_random_write_wakeup_bits,
|
|
.maxlen = sizeof(int),
|
|
.mode = 0644,
|
|
.proc_handler = proc_do_rointvec,
|
|
},
|
|
{
|
|
.procname = "urandom_min_reseed_secs",
|
|
.data = &sysctl_random_min_urandom_seed,
|
|
.maxlen = sizeof(int),
|
|
.mode = 0644,
|
|
.proc_handler = proc_do_rointvec,
|
|
},
|
|
{
|
|
.procname = "boot_id",
|
|
.data = &sysctl_bootid,
|
|
.mode = 0444,
|
|
.proc_handler = proc_do_uuid,
|
|
},
|
|
{
|
|
.procname = "uuid",
|
|
.mode = 0444,
|
|
.proc_handler = proc_do_uuid,
|
|
},
|
|
{ }
|
|
};
|
|
|
|
/*
|
|
* random_init() is called before sysctl_init(),
|
|
* so we cannot call register_sysctl_init() in random_init()
|
|
*/
|
|
static int __init random_sysctls_init(void)
|
|
{
|
|
register_sysctl_init("kernel/random", random_table);
|
|
return 0;
|
|
}
|
|
device_initcall(random_sysctls_init);
|
|
#endif
|