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1795 lines
52 KiB
1795 lines
52 KiB
// 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 <[email protected]>. All Rights Reserved. |
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* Copyright Matt Mackall <[email protected]>, 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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|
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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|
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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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* |
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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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/* |
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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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|
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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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/* |
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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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|
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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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/* |
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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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|
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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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/* |
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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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|
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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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/* |
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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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|
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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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|
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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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|
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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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|
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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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|
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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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/* |
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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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|
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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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/* |
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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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|
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BUG_ON(random_data_len > 32); |
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|
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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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|
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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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/* |
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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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|
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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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/* |
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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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|
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BUG_ON(random_data_len > 32); |
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|
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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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|
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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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/* |
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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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|
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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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/* |
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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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/* |
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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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/* |
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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 |
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* boot time when it's better to have something there rather than |
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* nothing. |
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* |
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* If account is set, then the crng_init_cnt counter is incremented. |
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* This shouldn't be set by functions like add_device_randomness(), |
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* where we can't trust the buffer passed to it is guaranteed to be |
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* unpredictable (so it might not have any entropy at all). |
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*/ |
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static void crng_pre_init_inject(const void *input, size_t len, bool account) |
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{ |
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static int crng_init_cnt = 0; |
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struct blake2s_state hash; |
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unsigned long flags; |
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|
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blake2s_init(&hash, sizeof(base_crng.key)); |
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|
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spin_lock_irqsave(&base_crng.lock, flags); |
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if (crng_init != 0) { |
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spin_unlock_irqrestore(&base_crng.lock, flags); |
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return; |
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} |
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|
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blake2s_update(&hash, base_crng.key, sizeof(base_crng.key)); |
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blake2s_update(&hash, input, len); |
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blake2s_final(&hash, base_crng.key); |
|
|
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if (account) { |
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crng_init_cnt += min_t(size_t, len, CRNG_INIT_CNT_THRESH - crng_init_cnt); |
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if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { |
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++base_crng.generation; |
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crng_init = 1; |
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} |
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} |
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|
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spin_unlock_irqrestore(&base_crng.lock, flags); |
|
|
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if (crng_init == 1) |
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pr_notice("fast init done\n"); |
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} |
|
|
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static void _get_random_bytes(void *buf, size_t nbytes) |
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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 len; |
|
|
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if (!nbytes) |
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return; |
|
|
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len = min_t(size_t, 32, nbytes); |
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crng_make_state(chacha_state, buf, len); |
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nbytes -= len; |
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buf += len; |
|
|
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while (nbytes) { |
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if (nbytes < CHACHA_BLOCK_SIZE) { |
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chacha20_block(chacha_state, tmp); |
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memcpy(buf, tmp, nbytes); |
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memzero_explicit(tmp, sizeof(tmp)); |
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break; |
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} |
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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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nbytes -= CHACHA_BLOCK_SIZE; |
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buf += CHACHA_BLOCK_SIZE; |
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} |
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|
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memzero_explicit(chacha_state, sizeof(chacha_state)); |
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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 |
|
* 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. |
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*/ |
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void get_random_bytes(void *buf, size_t nbytes) |
|
{ |
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static void *previous; |
|
|
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warn_unseeded_randomness(&previous); |
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_get_random_bytes(buf, nbytes); |
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} |
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EXPORT_SYMBOL(get_random_bytes); |
|
|
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static ssize_t get_random_bytes_user(void __user *buf, size_t nbytes) |
|
{ |
|
size_t len, left, ret = 0; |
|
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 = nbytes - copy_to_user(buf, &chacha_state[4], nbytes); |
|
goto out_zero_chacha; |
|
} |
|
|
|
for (;;) { |
|
chacha20_block(chacha_state, output); |
|
if (unlikely(chacha_state[12] == 0)) |
|
++chacha_state[13]; |
|
|
|
len = min_t(size_t, nbytes, CHACHA_BLOCK_SIZE); |
|
left = copy_to_user(buf, output, len); |
|
if (left) { |
|
ret += len - left; |
|
break; |
|
} |
|
|
|
buf += len; |
|
ret += len; |
|
nbytes -= len; |
|
if (!nbytes) |
|
break; |
|
|
|
BUILD_BUG_ON(PAGE_SIZE % CHACHA_BLOCK_SIZE != 0); |
|
if (ret % PAGE_SIZE == 0) { |
|
if (signal_pending(current)) |
|
break; |
|
cond_resched(); |
|
} |
|
} |
|
|
|
memzero_explicit(output, sizeof(output)); |
|
out_zero_chacha: |
|
memzero_explicit(chacha_state, sizeof(chacha_state)); |
|
return ret ? ret : -EFAULT; |
|
} |
|
|
|
/* |
|
* Batched entropy returns random integers. The quality of the random |
|
* number is good as /dev/urandom. In order to ensure that the randomness |
|
* provided by this function is okay, the function wait_for_random_bytes() |
|
* should be called and return 0 at least once at any point prior. |
|
*/ |
|
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) |
|
{ |
|
unsigned long 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) |
|
{ |
|
unsigned long cycles = random_get_entropy(), now = jiffies, flags; |
|
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 }; |
|
unsigned long cycles = random_get_entropy(), 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(unsigned long) == 8) { |
|
irq_data.u64[0] = cycles ^ rol64(now, 32) ^ irq; |
|
irq_data.u64[1] = regs ? instruction_pointer(regs) : _RET_IP_; |
|
} else { |
|
irq_data.u32[0] = cycles ^ irq; |
|
irq_data.u32[1] = now; |
|
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 { |
|
unsigned long 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
|
|
|