diff options
Diffstat (limited to 'drivers/char/random.c')
| -rw-r--r-- | drivers/char/random.c | 3038 |
1 files changed, 1266 insertions, 1772 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 68613f0b6887..bab03c7c4194 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1,320 +1,26 @@ +// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) /* - * random.c -- A strong random number generator - * - * Copyright (C) 2017-2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. - * + * Copyright (C) 2017-2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005 - * - * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All - * rights reserved. - * - * Redistribution and use in source and binary forms, with or without - * modification, are permitted provided that the following conditions - * are met: - * 1. Redistributions of source code must retain the above copyright - * notice, and the entire permission notice in its entirety, - * including the disclaimer of warranties. - * 2. Redistributions in binary form must reproduce the above copyright - * notice, this list of conditions and the following disclaimer in the - * documentation and/or other materials provided with the distribution. - * 3. The name of the author may not be used to endorse or promote - * products derived from this software without specific prior - * written permission. - * - * ALTERNATIVELY, this product may be distributed under the terms of - * the GNU General Public License, in which case the provisions of the GPL are - * required INSTEAD OF the above restrictions. (This clause is - * necessary due to a potential bad interaction between the GPL and - * the restrictions contained in a BSD-style copyright.) - * - * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED - * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES - * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF - * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE - * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR - * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT - * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR - * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF - * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT - * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE - * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH - * DAMAGE. - */ - -/* - * (now, with legal B.S. out of the way.....) - * - * This routine gathers environmental noise from device drivers, etc., - * and returns good random numbers, suitable for cryptographic use. - * Besides the obvious cryptographic uses, these numbers are also good - * for seeding TCP sequence numbers, and other places where it is - * desirable to have numbers which are not only random, but hard to - * predict by an attacker. - * - * Theory of operation - * =================== - * - * Computers are very predictable devices. Hence it is extremely hard - * to produce truly random numbers on a computer --- as opposed to - * pseudo-random numbers, which can easily generated by using a - * algorithm. Unfortunately, it is very easy for attackers to guess - * the sequence of pseudo-random number generators, and for some - * applications this is not acceptable. So instead, we must try to - * gather "environmental noise" from the computer's environment, which - * must be hard for outside attackers to observe, and use that to - * generate random numbers. In a Unix environment, this is best done - * from inside the kernel. - * - * Sources of randomness from the environment include inter-keyboard - * timings, inter-interrupt timings from some interrupts, and other - * events which are both (a) non-deterministic and (b) hard for an - * outside observer to measure. Randomness from these sources are - * added to an "entropy pool", which is mixed using a CRC-like function. - * This is not cryptographically strong, but it is adequate assuming - * the randomness is not chosen maliciously, and it is fast enough that - * the overhead of doing it on every interrupt is very reasonable. - * As random bytes are mixed into the entropy pool, the routines keep - * an *estimate* of how many bits of randomness have been stored into - * the random number generator's internal state. - * - * When random bytes are desired, they are obtained by taking the BLAKE2s - * hash of the contents of the "entropy pool". The BLAKE2s hash avoids - * exposing the internal state of the entropy pool. It is believed to - * be computationally infeasible to derive any useful information - * about the input of BLAKE2s from its output. Even if it is possible to - * analyze BLAKE2s in some clever way, as long as the amount of data - * returned from the generator is less than the inherent entropy in - * the pool, the output data is totally unpredictable. For this - * reason, the routine decreases its internal estimate of how many - * bits of "true randomness" are contained in the entropy pool as it - * outputs random numbers. - * - * If this estimate goes to zero, the routine can still generate - * random numbers; however, an attacker may (at least in theory) be - * able to infer the future output of the generator from prior - * outputs. This requires successful cryptanalysis of BLAKE2s, which is - * not believed to be feasible, but there is a remote possibility. - * Nonetheless, these numbers should be useful for the vast majority - * of purposes. - * - * Exported interfaces ---- output - * =============================== - * - * There are four exported interfaces; two for use within the kernel, - * and two for use from userspace. - * - * Exported interfaces ---- userspace output - * ----------------------------------------- - * - * The userspace interfaces are two character devices /dev/random and - * /dev/urandom. /dev/random is suitable for use when very high - * quality randomness is desired (for example, for key generation or - * one-time pads), as it will only return a maximum of the number of - * bits of randomness (as estimated by the random number generator) - * contained in the entropy pool. - * - * The /dev/urandom device does not have this limit, and will return - * as many bytes as are requested. As more and more random bytes are - * requested without giving time for the entropy pool to recharge, - * this will result in random numbers that are merely cryptographically - * strong. For many applications, however, this is acceptable. - * - * Exported interfaces ---- kernel output - * -------------------------------------- - * - * The primary kernel interface is - * - * void get_random_bytes(void *buf, int nbytes); - * - * This interface will return the requested number of random bytes, - * and place it in the requested buffer. This is equivalent to a - * read from /dev/urandom. - * - * For less critical applications, there are the functions: - * - * u32 get_random_u32() - * u64 get_random_u64() - * unsigned int get_random_int() - * unsigned long get_random_long() - * - * These are produced by a cryptographic RNG seeded from get_random_bytes, - * and so do not deplete the entropy pool as much. These are recommended - * for most in-kernel operations *if the result is going to be stored in - * the kernel*. - * - * Specifically, the get_random_int() family do not attempt to do - * "anti-backtracking". If you capture the state of the kernel (e.g. - * by snapshotting the VM), you can figure out previous get_random_int() - * return values. But if the value is stored in the kernel anyway, - * this is not a problem. - * - * It *is* safe to expose get_random_int() output to attackers (e.g. as - * network cookies); given outputs 1..n, it's not feasible to predict - * outputs 0 or n+1. The only concern is an attacker who breaks into - * the kernel later; the get_random_int() engine is not reseeded as - * often as the get_random_bytes() one. - * - * get_random_bytes() is needed for keys that need to stay secret after - * they are erased from the kernel. For example, any key that will - * be wrapped and stored encrypted. And session encryption keys: we'd - * like to know that after the session is closed and the keys erased, - * the plaintext is unrecoverable to someone who recorded the ciphertext. - * - * But for network ports/cookies, stack canaries, PRNG seeds, address - * space layout randomization, session *authentication* keys, or other - * applications where the sensitive data is stored in the kernel in - * plaintext for as long as it's sensitive, the get_random_int() family - * is just fine. - * - * Consider ASLR. We want to keep the address space secret from an - * outside attacker while the process is running, but once the address - * space is torn down, it's of no use to an attacker any more. And it's - * stored in kernel data structures as long as it's alive, so worrying - * about an attacker's ability to extrapolate it from the get_random_int() - * CRNG is silly. - * - * Even some cryptographic keys are safe to generate with get_random_int(). - * In particular, keys for SipHash are generally fine. Here, knowledge - * of the key authorizes you to do something to a kernel object (inject - * packets to a network connection, or flood a hash table), and the - * key is stored with the object being protected. Once it goes away, - * we no longer care if anyone knows the key. - * - * prandom_u32() - * ------------- - * - * For even weaker applications, see the pseudorandom generator - * prandom_u32(), prandom_max(), and prandom_bytes(). If the random - * numbers aren't security-critical at all, these are *far* cheaper. - * Useful for self-tests, random error simulation, randomized backoffs, - * and any other application where you trust that nobody is trying to - * maliciously mess with you by guessing the "random" numbers. - * - * Exported interfaces ---- input - * ============================== - * - * The current exported interfaces for gathering environmental noise - * from the devices are: - * - * void add_device_randomness(const void *buf, unsigned int size); - * void add_input_randomness(unsigned int type, unsigned int code, - * unsigned int value); - * void add_interrupt_randomness(int irq); - * void add_disk_randomness(struct gendisk *disk); - * void add_hwgenerator_randomness(const char *buffer, size_t count, - * size_t entropy); - * void add_bootloader_randomness(const void *buf, unsigned int size); - * - * add_device_randomness() is for adding data to the random pool that - * is likely to differ between two devices (or possibly even per boot). - * This would be things like MAC addresses or serial numbers, or the - * read-out of the RTC. This does *not* add any actual entropy to the - * pool, but it initializes the pool to different values for devices - * that might otherwise be identical and have very little entropy - * available to them (particularly common in the embedded world). - * - * add_input_randomness() uses the input layer interrupt timing, as well as - * the event type information from the hardware. - * - * add_interrupt_randomness() uses the interrupt timing as random - * inputs to the entropy pool. Using the cycle counters and the irq source - * as inputs, it feeds the randomness roughly once a second. - * - * add_disk_randomness() uses what amounts to the seek time of block - * layer request events, on a per-disk_devt basis, as input to the - * entropy pool. Note that high-speed solid state drives with very low - * seek times do not make for good sources of entropy, as their seek - * times are usually fairly consistent. - * - * All of these routines try to estimate how many bits of randomness a - * particular randomness source. They do this by keeping track of the - * first and second order deltas of the event timings. - * - * add_hwgenerator_randomness() is for true hardware RNGs, and will credit - * entropy as specified by the caller. If the entropy pool is full it will - * block until more entropy is needed. - * - * add_bootloader_randomness() is the same as add_hwgenerator_randomness() or - * add_device_randomness(), depending on whether or not the configuration - * option CONFIG_RANDOM_TRUST_BOOTLOADER is set. - * - * Ensuring unpredictability at system startup - * ============================================ - * - * When any operating system starts up, it will go through a sequence - * of actions that are fairly predictable by an adversary, especially - * if the start-up does not involve interaction with a human operator. - * This reduces the actual number of bits of unpredictability in the - * entropy pool below the value in entropy_count. In order to - * counteract this effect, it helps to carry information in the - * entropy pool across shut-downs and start-ups. To do this, put the - * following lines an appropriate script which is run during the boot - * sequence: - * - * echo "Initializing random number generator..." - * random_seed=/var/run/random-seed - * # Carry a random seed from start-up to start-up - * # Load and then save the whole entropy pool - * if [ -f $random_seed ]; then - * cat $random_seed >/dev/urandom - * else - * touch $random_seed - * fi - * chmod 600 $random_seed - * dd if=/dev/urandom of=$random_seed count=1 bs=512 - * - * and the following lines in an appropriate script which is run as - * the system is shutdown: - * - * # Carry a random seed from shut-down to start-up - * # Save the whole entropy pool - * echo "Saving random seed..." - * random_seed=/var/run/random-seed - * touch $random_seed - * chmod 600 $random_seed - * dd if=/dev/urandom of=$random_seed count=1 bs=512 - * - * For example, on most modern systems using the System V init - * scripts, such code fragments would be found in - * /etc/rc.d/init.d/random. On older Linux systems, the correct script - * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0. - * - * Effectively, these commands cause the contents of the entropy pool - * to be saved at shut-down time and reloaded into the entropy pool at - * start-up. (The 'dd' in the addition to the bootup script is to - * make sure that /etc/random-seed is different for every start-up, - * even if the system crashes without executing rc.0.) Even with - * complete knowledge of the start-up activities, predicting the state - * of the entropy pool requires knowledge of the previous history of - * the system. - * - * Configuring the /dev/random driver under Linux - * ============================================== - * - * The /dev/random driver under Linux uses minor numbers 8 and 9 of - * the /dev/mem major number (#1). So if your system does not have - * /dev/random and /dev/urandom created already, they can be created - * by using the commands: - * - * mknod /dev/random c 1 8 - * mknod /dev/urandom c 1 9 - * - * Acknowledgements: - * ================= - * - * Ideas for constructing this random number generator were derived - * from Pretty Good Privacy's random number generator, and from private - * discussions with Phil Karn. Colin Plumb provided a faster random - * number generator, which speed up the mixing function of the entropy - * pool, taken from PGPfone. Dale Worley has also contributed many - * useful ideas and suggestions to improve this driver. - * - * Any flaws in the design are solely my responsibility, and should - * not be attributed to the Phil, Colin, or any of authors of PGP. - * - * Further background information on this topic may be obtained from - * RFC 1750, "Randomness Recommendations for Security", by Donald - * Eastlake, Steve Crocker, and Jeff Schiller. + * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All rights reserved. + * + * This driver produces cryptographically secure pseudorandom data. It is divided + * into roughly six sections, each with a section header: + * + * - Initialization and readiness waiting. + * - Fast key erasure RNG, the "crng". + * - Entropy accumulation and extraction routines. + * - Entropy collection routines. + * - Userspace reader/writer interfaces. + * - Sysctl interface. + * + * The high level overview is that there is one input pool, into which + * various pieces of data are hashed. Prior to initialization, some of that + * data is then "credited" as having a certain number of bits of entropy. + * When enough bits of entropy are available, the hash is finalized and + * handed as a key to a stream cipher that expands it indefinitely for + * various consumers. This key is periodically refreshed as the various + * entropy collectors, described below, add data to the input pool. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt @@ -330,7 +36,7 @@ #include <linux/poll.h> #include <linux/init.h> #include <linux/fs.h> -#include <linux/genhd.h> +#include <linux/blkdev.h> #include <linux/interrupt.h> #include <linux/mm.h> #include <linux/nodemask.h> @@ -344,1371 +50,1197 @@ #include <linux/syscalls.h> #include <linux/completion.h> #include <linux/uuid.h> +#include <linux/uaccess.h> +#include <linux/suspend.h> +#include <linux/siphash.h> +#include <linux/sched/isolation.h> #include <crypto/chacha.h> #include <crypto/blake2s.h> - +#ifdef CONFIG_VDSO_GETRANDOM +#include <vdso/getrandom.h> +#include <vdso/datapage.h> +#include <vdso/vsyscall.h> +#endif +#include <asm/archrandom.h> #include <asm/processor.h> -#include <linux/uaccess.h> #include <asm/irq.h> #include <asm/irq_regs.h> #include <asm/io.h> -#define CREATE_TRACE_POINTS -#include <trace/events/random.h> - -/* #define ADD_INTERRUPT_BENCH */ - -/* - * If the entropy count falls under this number of bits, then we - * should wake up processes which are selecting or polling on write - * access to /dev/random. - */ -static int random_write_wakeup_bits = 28 * (1 << 5); - -/* - * Originally, we used a primitive polynomial of degree .poolwords - * over GF(2). The taps for various sizes are defined below. They - * were chosen to be evenly spaced except for the last tap, which is 1 - * to get the twisting happening as fast as possible. - * - * For the purposes of better mixing, we use the CRC-32 polynomial as - * well to make a (modified) twisted Generalized Feedback Shift - * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR - * generators. ACM Transactions on Modeling and Computer Simulation - * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted - * GFSR generators II. ACM Transactions on Modeling and Computer - * Simulation 4:254-266) +/********************************************************************* * - * Thanks to Colin Plumb for suggesting this. + * Initialization and readiness waiting. * - * The mixing operation is much less sensitive than the output hash, - * where we use BLAKE2s. All that we want of mixing operation is that - * it be a good non-cryptographic hash; i.e. it not produce collisions - * when fed "random" data of the sort we expect to see. As long as - * the pool state differs for different inputs, we have preserved the - * input entropy and done a good job. The fact that an intelligent - * attacker can construct inputs that will produce controlled - * alterations to the pool's state is not important because we don't - * consider such inputs to contribute any randomness. The only - * property we need with respect to them is that the attacker can't - * increase his/her knowledge of the pool's state. Since all - * additions are reversible (knowing the final state and the input, - * you can reconstruct the initial state), if an attacker has any - * uncertainty about the initial state, he/she can only shuffle that - * uncertainty about, but never cause any collisions (which would - * decrease the uncertainty). + * Much of the RNG infrastructure is devoted to various dependencies + * being able to wait until the RNG has collected enough entropy and + * is ready for safe consumption. * - * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and - * Videau in their paper, "The Linux Pseudorandom Number Generator - * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their - * paper, they point out that we are not using a true Twisted GFSR, - * since Matsumoto & Kurita used a trinomial feedback polynomial (that - * is, with only three taps, instead of the six that we are using). - * As a result, the resulting polynomial is neither primitive nor - * irreducible, and hence does not have a maximal period over - * GF(2**32). They suggest a slight change to the generator - * polynomial which improves the resulting TGFSR polynomial to be - * irreducible, which we have made here. - */ -enum poolinfo { - POOL_WORDS = 128, - POOL_WORDMASK = POOL_WORDS - 1, - POOL_BYTES = POOL_WORDS * sizeof(u32), - POOL_BITS = POOL_BYTES * 8, - POOL_BITSHIFT = ilog2(POOL_BITS), - - /* To allow fractional bits to be tracked, the entropy_count field is - * denominated in units of 1/8th bits. */ - POOL_ENTROPY_SHIFT = 3, -#define POOL_ENTROPY_BITS() (input_pool.entropy_count >> POOL_ENTROPY_SHIFT) - POOL_FRACBITS = POOL_BITS << POOL_ENTROPY_SHIFT, - - /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */ - POOL_TAP1 = 104, - POOL_TAP2 = 76, - POOL_TAP3 = 51, - POOL_TAP4 = 25, - POOL_TAP5 = 1, - - EXTRACT_SIZE = BLAKE2S_HASH_SIZE / 2 -}; + *********************************************************************/ /* - * Static global variables + * crng_init is protected by base_crng->lock, and only increases + * its value (from empty->early->ready). */ -static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); +static enum { + CRNG_EMPTY = 0, /* Little to no entropy collected */ + CRNG_EARLY = 1, /* At least POOL_EARLY_BITS collected */ + CRNG_READY = 2 /* Fully initialized with POOL_READY_BITS collected */ +} crng_init __read_mostly = CRNG_EMPTY; +static DEFINE_STATIC_KEY_FALSE(crng_is_ready); +#define crng_ready() (static_branch_likely(&crng_is_ready) || crng_init >= CRNG_READY) +/* Various types of waiters for crng_init->CRNG_READY transition. */ +static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); static struct fasync_struct *fasync; +static ATOMIC_NOTIFIER_HEAD(random_ready_notifier); -static DEFINE_SPINLOCK(random_ready_list_lock); -static LIST_HEAD(random_ready_list); - -struct crng_state { - u32 state[16]; - unsigned long init_time; - spinlock_t lock; -}; - -static struct crng_state primary_crng = { - .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock), - .state[0] = CHACHA_CONSTANT_EXPA, - .state[1] = CHACHA_CONSTANT_ND_3, - .state[2] = CHACHA_CONSTANT_2_BY, - .state[3] = CHACHA_CONSTANT_TE_K, -}; - -/* - * crng_init = 0 --> Uninitialized - * 1 --> Initialized - * 2 --> Initialized from input_pool - * - * crng_init is protected by primary_crng->lock, and only increases - * its value (from 0->1->2). - */ -static int crng_init = 0; -static bool crng_need_final_init = false; -#define crng_ready() (likely(crng_init > 1)) -static int crng_init_cnt = 0; -static unsigned long crng_global_init_time = 0; -#define CRNG_INIT_CNT_THRESH (2 * CHACHA_KEY_SIZE) -static void _extract_crng(struct crng_state *crng, u8 out[CHACHA_BLOCK_SIZE]); -static void _crng_backtrack_protect(struct crng_state *crng, - u8 tmp[CHACHA_BLOCK_SIZE], int used); -static void process_random_ready_list(void); -static void _get_random_bytes(void *buf, int nbytes); - -static struct ratelimit_state unseeded_warning = - RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3); +/* Control how we warn userspace. */ static struct ratelimit_state urandom_warning = - RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3); - -static int ratelimit_disable __read_mostly; - + RATELIMIT_STATE_INIT_FLAGS("urandom_warning", HZ, 3, RATELIMIT_MSG_ON_RELEASE); +static int ratelimit_disable __read_mostly = + IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM); module_param_named(ratelimit_disable, ratelimit_disable, int, 0644); MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression"); -/********************************************************************** - * - * OS independent entropy store. Here are the functions which handle - * storing entropy in an entropy pool. - * - **********************************************************************/ - -static u32 input_pool_data[POOL_WORDS] __latent_entropy; - -static struct { - spinlock_t lock; - u16 add_ptr; - u16 input_rotate; - int entropy_count; -} input_pool = { - .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), -}; - -static ssize_t extract_entropy(void *buf, size_t nbytes, int min); -static ssize_t _extract_entropy(void *buf, size_t nbytes); - -static void crng_reseed(struct crng_state *crng, bool use_input_pool); - -static const u32 twist_table[8] = { - 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158, - 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; - /* - * 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. + * Returns whether or not the input pool has been seeded and thus guaranteed + * to supply cryptographically secure random numbers. This applies to: the + * /dev/urandom device, the get_random_bytes function, and the get_random_{u8, + * u16,u32,u64,long} family of functions. * - * The pool is stirred with a primitive polynomial of the appropriate - * degree, and then twisted. We twist by three bits at a time because - * it's cheap to do so and helps slightly in the expected case where - * the entropy is concentrated in the low-order bits. + * Returns: true if the input pool has been seeded. + * false if the input pool has not been seeded. */ -static void _mix_pool_bytes(const void *in, int nbytes) +bool rng_is_initialized(void) { - unsigned long i; - int input_rotate; - const u8 *bytes = in; - u32 w; - - input_rotate = input_pool.input_rotate; - i = input_pool.add_ptr; - - /* mix one byte at a time to simplify size handling and churn faster */ - while (nbytes--) { - w = rol32(*bytes++, input_rotate); - i = (i - 1) & POOL_WORDMASK; - - /* XOR in the various taps */ - w ^= input_pool_data[i]; - w ^= input_pool_data[(i + POOL_TAP1) & POOL_WORDMASK]; - w ^= input_pool_data[(i + POOL_TAP2) & POOL_WORDMASK]; - w ^= input_pool_data[(i + POOL_TAP3) & POOL_WORDMASK]; - w ^= input_pool_data[(i + POOL_TAP4) & POOL_WORDMASK]; - w ^= input_pool_data[(i + POOL_TAP5) & POOL_WORDMASK]; - - /* Mix the result back in with a twist */ - input_pool_data[i] = (w >> 3) ^ twist_table[w & 7]; - - /* - * Normally, we add 7 bits of rotation to the pool. - * At the beginning of the pool, add an extra 7 bits - * rotation, so that successive passes spread the - * input bits across the pool evenly. - */ - input_rotate = (input_rotate + (i ? 7 : 14)) & 31; - } - - input_pool.input_rotate = input_rotate; - input_pool.add_ptr = i; + return crng_ready(); } +EXPORT_SYMBOL(rng_is_initialized); -static void __mix_pool_bytes(const void *in, int nbytes) +static void __cold crng_set_ready(struct work_struct *work) { - trace_mix_pool_bytes_nolock(nbytes, _RET_IP_); - _mix_pool_bytes(in, nbytes); + static_branch_enable(&crng_is_ready); } -static void mix_pool_bytes(const void *in, int nbytes) +/* Used by wait_for_random_bytes(), and considered an entropy collector, below. */ +static void try_to_generate_entropy(void); + +/* + * Wait for the input pool to be seeded and thus guaranteed to supply + * cryptographically secure random numbers. This applies to: the /dev/urandom + * device, the get_random_bytes function, and the get_random_{u8,u16,u32,u64, + * long} family of functions. Using any of these functions without first + * calling this function forfeits the guarantee of security. + * + * Returns: 0 if the input pool has been seeded. + * -ERESTARTSYS if the function was interrupted by a signal. + */ +int wait_for_random_bytes(void) { - unsigned long flags; + while (!crng_ready()) { + int ret; - trace_mix_pool_bytes(nbytes, _RET_IP_); - spin_lock_irqsave(&input_pool.lock, flags); - _mix_pool_bytes(in, nbytes); - spin_unlock_irqrestore(&input_pool.lock, flags); + try_to_generate_entropy(); + ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ); + if (ret) + return ret > 0 ? 0 : ret; + } + return 0; } - -struct fast_pool { - u32 pool[4]; - unsigned long last; - u16 reg_idx; - u8 count; -}; +EXPORT_SYMBOL(wait_for_random_bytes); /* - * This is a fast mixing routine used by the interrupt randomness - * collector. It's hardcoded for an 128 bit pool and assumes that any - * locks that might be needed are taken by the caller. + * Add a callback function that will be invoked when the crng is initialised, + * or immediately if it already has been. Only use this is you are absolutely + * sure it is required. Most users should instead be able to test + * `rng_is_initialized()` on demand, or make use of `get_random_bytes_wait()`. */ -static void fast_mix(struct fast_pool *f) +int __cold execute_with_initialized_rng(struct notifier_block *nb) { - u32 a = f->pool[0], b = f->pool[1]; - u32 c = f->pool[2], d = f->pool[3]; + unsigned long flags; + int ret = 0; - a += b; c += d; - b = rol32(b, 6); d = rol32(d, 27); - d ^= a; b ^= c; + spin_lock_irqsave(&random_ready_notifier.lock, flags); + if (crng_ready()) + nb->notifier_call(nb, 0, NULL); + else + ret = raw_notifier_chain_register((struct raw_notifier_head *)&random_ready_notifier.head, nb); + spin_unlock_irqrestore(&random_ready_notifier.lock, flags); + return ret; +} - a += b; c += d; - b = rol32(b, 16); d = rol32(d, 14); - d ^= a; b ^= c; +#define warn_unseeded_randomness() \ + if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \ + printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \ + __func__, (void *)_RET_IP_, crng_init) - a += b; c += d; - b = rol32(b, 6); d = rol32(d, 27); - d ^= a; b ^= c; - a += b; c += d; - b = rol32(b, 16); d = rol32(d, 14); - d ^= a; b ^= c; +/********************************************************************* + * + * Fast key erasure RNG, the "crng". + * + * These functions expand entropy from the entropy extractor into + * long streams for external consumption using the "fast key erasure" + * RNG described at <https://blog.cr.yp.to/20170723-random.html>. + * + * There are a few exported interfaces for use by other drivers: + * + * void get_random_bytes(void *buf, size_t len) + * u8 get_random_u8() + * u16 get_random_u16() + * u32 get_random_u32() + * u32 get_random_u32_below(u32 ceil) + * u32 get_random_u32_above(u32 floor) + * u32 get_random_u32_inclusive(u32 floor, u32 ceil) + * u64 get_random_u64() + * unsigned long get_random_long() + * + * These interfaces will return the requested number of random bytes + * into the given buffer or as a return value. This is equivalent to + * a read from /dev/urandom. The u8, u16, u32, u64, long family of + * functions may be higher performance for one-off random integers, + * because they do a bit of buffering and do not invoke reseeding + * until the buffer is emptied. + * + *********************************************************************/ - f->pool[0] = a; f->pool[1] = b; - f->pool[2] = c; f->pool[3] = d; - f->count++; -} +enum { + CRNG_RESEED_START_INTERVAL = HZ, + CRNG_RESEED_INTERVAL = 60 * HZ +}; -static void process_random_ready_list(void) -{ - unsigned long flags; - struct random_ready_callback *rdy, *tmp; +static struct { + u8 key[CHACHA_KEY_SIZE] __aligned(__alignof__(long)); + unsigned long generation; + spinlock_t lock; +} base_crng = { + .lock = __SPIN_LOCK_UNLOCKED(base_crng.lock) +}; - spin_lock_irqsave(&random_ready_list_lock, flags); - list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) { - struct module *owner = rdy->owner; +struct crng { + u8 key[CHACHA_KEY_SIZE]; + unsigned long generation; + local_lock_t lock; +}; - list_del_init(&rdy->list); - rdy->func(rdy); - module_put(owner); - } - spin_unlock_irqrestore(&random_ready_list_lock, flags); -} +static DEFINE_PER_CPU(struct crng, crngs) = { + .generation = ULONG_MAX, + .lock = INIT_LOCAL_LOCK(crngs.lock), +}; /* - * Credit (or debit) the entropy store with n bits of entropy. - * Use credit_entropy_bits_safe() if the value comes from userspace - * or otherwise should be checked for extreme values. + * Return the interval until the next reseeding, which is normally + * CRNG_RESEED_INTERVAL, but during early boot, it is at an interval + * proportional to the uptime. */ -static void credit_entropy_bits(int nbits) +static unsigned int crng_reseed_interval(void) { - int entropy_count, entropy_bits, orig; - int nfrac = nbits << POOL_ENTROPY_SHIFT; + static bool early_boot = true; - /* Ensure that the multiplication can avoid being 64 bits wide. */ - BUILD_BUG_ON(2 * (POOL_ENTROPY_SHIFT + POOL_BITSHIFT) > 31); + if (unlikely(READ_ONCE(early_boot))) { + time64_t uptime = ktime_get_seconds(); + if (uptime >= CRNG_RESEED_INTERVAL / HZ * 2) + WRITE_ONCE(early_boot, false); + else + return max_t(unsigned int, CRNG_RESEED_START_INTERVAL, + (unsigned int)uptime / 2 * HZ); + } + return CRNG_RESEED_INTERVAL; +} - if (!nbits) - return; +/* Used by crng_reseed() and crng_make_state() to extract a new seed from the input pool. */ +static void extract_entropy(void *buf, size_t len); -retry: - entropy_count = orig = READ_ONCE(input_pool.entropy_count); - if (nfrac < 0) { - /* Debit */ - entropy_count += nfrac; - } else { - /* - * Credit: we have to account for the possibility of - * overwriting already present entropy. Even in the - * ideal case of pure Shannon entropy, new contributions - * approach the full value asymptotically: - * - * entropy <- entropy + (pool_size - entropy) * - * (1 - exp(-add_entropy/pool_size)) - * - * For add_entropy <= pool_size/2 then - * (1 - exp(-add_entropy/pool_size)) >= - * (add_entropy/pool_size)*0.7869... - * so we can approximate the exponential with - * 3/4*add_entropy/pool_size and still be on the - * safe side by adding at most pool_size/2 at a time. - * - * The use of pool_size-2 in the while statement is to - * prevent rounding artifacts from making the loop - * arbitrarily long; this limits the loop to log2(pool_size)*2 - * turns no matter how large nbits is. - */ - int pnfrac = nfrac; - const int s = POOL_BITSHIFT + POOL_ENTROPY_SHIFT + 2; - /* The +2 corresponds to the /4 in the denominator */ - - do { - unsigned int anfrac = min(pnfrac, POOL_FRACBITS / 2); - unsigned int add = - ((POOL_FRACBITS - entropy_count) * anfrac * 3) >> s; - - entropy_count += add; - pnfrac -= anfrac; - } while (unlikely(entropy_count < POOL_FRACBITS - 2 && pnfrac)); - } +/* This extracts a new crng key from the input pool. */ +static void crng_reseed(struct work_struct *work) +{ + static DECLARE_DELAYED_WORK(next_reseed, crng_reseed); + unsigned long flags; + unsigned long next_gen; + u8 key[CHACHA_KEY_SIZE]; - if (WARN_ON(entropy_count < 0)) { - pr_warn("negative entropy/overflow: count %d\n", entropy_count); - entropy_count = 0; - } else if (entropy_count > POOL_FRACBITS) - entropy_count = POOL_FRACBITS; - if (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig) - goto retry; + /* Immediately schedule the next reseeding, so that it fires sooner rather than later. */ + if (likely(system_dfl_wq)) + queue_delayed_work(system_dfl_wq, &next_reseed, crng_reseed_interval()); - trace_credit_entropy_bits(nbits, entropy_count >> POOL_ENTROPY_SHIFT, _RET_IP_); + extract_entropy(key, sizeof(key)); - entropy_bits = entropy_count >> POOL_ENTROPY_SHIFT; - if (crng_init < 2 && entropy_bits >= 128) - crng_reseed(&primary_crng, true); + /* + * We copy the new key into the base_crng, overwriting the old one, + * and update the generation counter. We avoid hitting ULONG_MAX, + * because the per-cpu crngs are initialized to ULONG_MAX, so this + * forces new CPUs that come online to always initialize. + */ + spin_lock_irqsave(&base_crng.lock, flags); + memcpy(base_crng.key, key, sizeof(base_crng.key)); + next_gen = base_crng.generation + 1; + if (next_gen == ULONG_MAX) + ++next_gen; + WRITE_ONCE(base_crng.generation, next_gen); +#ifdef CONFIG_VDSO_GETRANDOM + /* base_crng.generation's invalid value is ULONG_MAX, while + * vdso_k_rng_data->generation's invalid value is 0, so add one to the + * former to arrive at the latter. Use smp_store_release so that this + * is ordered with the write above to base_crng.generation. Pairs with + * the smp_rmb() before the syscall in the vDSO code. + * + * Cast to unsigned long for 32-bit architectures, since atomic 64-bit + * operations are not supported on those architectures. This is safe + * because base_crng.generation is a 32-bit value. On big-endian + * architectures it will be stored in the upper 32 bits, but that's okay + * because the vDSO side only checks whether the value changed, without + * actually using or interpreting the value. + */ + smp_store_release((unsigned long *)&vdso_k_rng_data->generation, next_gen + 1); +#endif + if (!static_branch_likely(&crng_is_ready)) + crng_init = CRNG_READY; + spin_unlock_irqrestore(&base_crng.lock, flags); + memzero_explicit(key, sizeof(key)); } -static int credit_entropy_bits_safe(int nbits) +/* + * This generates a ChaCha block using the provided key, and then + * immediately overwrites that key with half the block. It returns + * the resultant ChaCha state to the user, along with the second + * half of the block containing 32 bytes of random data that may + * be used; random_data_len may not be greater than 32. + * + * The returned ChaCha state contains within it a copy of the old + * key value, at index 4, so the state should always be zeroed out + * immediately after using in order to maintain forward secrecy. + * If the state cannot be erased in a timely manner, then it is + * safer to set the random_data parameter to &chacha_state->x[4] + * so that this function overwrites it before returning. + */ +static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE], + struct chacha_state *chacha_state, + u8 *random_data, size_t random_data_len) { - if (nbits < 0) - return -EINVAL; - - /* Cap the value to avoid overflows */ - nbits = min(nbits, POOL_BITS); + u8 first_block[CHACHA_BLOCK_SIZE]; - credit_entropy_bits(nbits); - return 0; -} - -/********************************************************************* - * - * CRNG using CHACHA20 - * - *********************************************************************/ + BUG_ON(random_data_len > 32); -#define CRNG_RESEED_INTERVAL (300 * HZ) + chacha_init_consts(chacha_state); + memcpy(&chacha_state->x[4], key, CHACHA_KEY_SIZE); + memset(&chacha_state->x[12], 0, sizeof(u32) * 4); + chacha20_block(chacha_state, first_block); -static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); + memcpy(key, first_block, CHACHA_KEY_SIZE); + memcpy(random_data, first_block + CHACHA_KEY_SIZE, random_data_len); + memzero_explicit(first_block, sizeof(first_block)); +} /* - * Hack to deal with crazy userspace progams when they are all trying - * to access /dev/urandom in parallel. The programs are almost - * certainly doing something terribly wrong, but we'll work around - * their brain damage. + * This function returns a ChaCha state that you may use for generating + * random data. It also returns up to 32 bytes on its own of random data + * that may be used; random_data_len may not be greater than 32. */ -static struct crng_state **crng_node_pool __read_mostly; - -static void invalidate_batched_entropy(void); -static void numa_crng_init(void); - -static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); -static int __init parse_trust_cpu(char *arg) +static void crng_make_state(struct chacha_state *chacha_state, + u8 *random_data, size_t random_data_len) { - return kstrtobool(arg, &trust_cpu); -} -early_param("random.trust_cpu", parse_trust_cpu); + unsigned long flags; + struct crng *crng; -static bool crng_init_try_arch(struct crng_state *crng) -{ - int i; - bool arch_init = true; - unsigned long rv; - - for (i = 4; i < 16; i++) { - if (!arch_get_random_seed_long(&rv) && - !arch_get_random_long(&rv)) { - rv = random_get_entropy(); - arch_init = false; + BUG_ON(random_data_len > 32); + + /* + * For the fast path, we check whether we're ready, unlocked first, and + * then re-check once locked later. In the case where we're really not + * ready, we do fast key erasure with the base_crng directly, extracting + * when crng_init is CRNG_EMPTY. + */ + if (!crng_ready()) { + bool ready; + + spin_lock_irqsave(&base_crng.lock, flags); + ready = crng_ready(); + if (!ready) { + if (crng_init == CRNG_EMPTY) + extract_entropy(base_crng.key, sizeof(base_crng.key)); + crng_fast_key_erasure(base_crng.key, chacha_state, + random_data, random_data_len); } - crng->state[i] ^= rv; + spin_unlock_irqrestore(&base_crng.lock, flags); + if (!ready) + return; } - return arch_init; -} + local_lock_irqsave(&crngs.lock, flags); + crng = raw_cpu_ptr(&crngs); -static bool __init crng_init_try_arch_early(struct crng_state *crng) -{ - int i; - bool arch_init = true; - unsigned long rv; - - for (i = 4; i < 16; i++) { - if (!arch_get_random_seed_long_early(&rv) && - !arch_get_random_long_early(&rv)) { - rv = random_get_entropy(); - arch_init = false; - } - crng->state[i] ^= rv; + /* + * If our per-cpu crng is older than the base_crng, then it means + * somebody reseeded the base_crng. In that case, we do fast key + * erasure on the base_crng, and use its output as the new key + * for our per-cpu crng. This brings us up to date with base_crng. + */ + if (unlikely(crng->generation != READ_ONCE(base_crng.generation))) { + spin_lock(&base_crng.lock); + crng_fast_key_erasure(base_crng.key, chacha_state, + crng->key, sizeof(crng->key)); + crng->generation = base_crng.generation; + spin_unlock(&base_crng.lock); } - return arch_init; -} - -static void crng_initialize_secondary(struct crng_state *crng) -{ - chacha_init_consts(crng->state); - _get_random_bytes(&crng->state[4], sizeof(u32) * 12); - crng_init_try_arch(crng); - crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1; + /* + * Finally, when we've made it this far, our per-cpu crng has an up + * to date key, and we can do fast key erasure with it to produce + * some random data and a ChaCha state for the caller. All other + * branches of this function are "unlikely", so most of the time we + * should wind up here immediately. + */ + crng_fast_key_erasure(crng->key, chacha_state, random_data, random_data_len); + local_unlock_irqrestore(&crngs.lock, flags); } -static void __init crng_initialize_primary(struct crng_state *crng) +static void _get_random_bytes(void *buf, size_t len) { - _extract_entropy(&crng->state[4], sizeof(u32) * 12); - if (crng_init_try_arch_early(crng) && trust_cpu && crng_init < 2) { - invalidate_batched_entropy(); - numa_crng_init(); - crng_init = 2; - pr_notice("crng init done (trusting CPU's manufacturer)\n"); - } - crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1; -} + struct chacha_state chacha_state; + u8 tmp[CHACHA_BLOCK_SIZE]; + size_t first_block_len; -static void crng_finalize_init(struct crng_state *crng) -{ - if (crng != &primary_crng || crng_init >= 2) + if (!len) return; - if (!system_wq) { - /* We can't call numa_crng_init until we have workqueues, - * so mark this for processing later. */ - crng_need_final_init = true; - return; - } - invalidate_batched_entropy(); - numa_crng_init(); - crng_init = 2; - process_random_ready_list(); - wake_up_interruptible(&crng_init_wait); - kill_fasync(&fasync, SIGIO, POLL_IN); - pr_notice("crng init done\n"); - if (unseeded_warning.missed) { - pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n", - unseeded_warning.missed); - unseeded_warning.missed = 0; - } - if (urandom_warning.missed) { - pr_notice("%d urandom warning(s) missed due to ratelimiting\n", - urandom_warning.missed); - urandom_warning.missed = 0; - } -} + first_block_len = min_t(size_t, 32, len); + crng_make_state(&chacha_state, buf, first_block_len); + len -= first_block_len; + buf += first_block_len; -static void do_numa_crng_init(struct work_struct *work) -{ - int i; - struct crng_state *crng; - struct crng_state **pool; - - pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL | __GFP_NOFAIL); - for_each_online_node(i) { - crng = kmalloc_node(sizeof(struct crng_state), - GFP_KERNEL | __GFP_NOFAIL, i); - spin_lock_init(&crng->lock); - crng_initialize_secondary(crng); - pool[i] = crng; - } - /* pairs with READ_ONCE() in select_crng() */ - if (cmpxchg_release(&crng_node_pool, NULL, pool) != NULL) { - for_each_node(i) - kfree(pool[i]); - kfree(pool); - } -} - -static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init); - -static void numa_crng_init(void) -{ - if (IS_ENABLED(CONFIG_NUMA)) - schedule_work(&numa_crng_init_work); -} + while (len) { + if (len < CHACHA_BLOCK_SIZE) { + chacha20_block(&chacha_state, tmp); + memcpy(buf, tmp, len); + memzero_explicit(tmp, sizeof(tmp)); + break; + } -static struct crng_state *select_crng(void) -{ - if (IS_ENABLED(CONFIG_NUMA)) { - struct crng_state **pool; - int nid = numa_node_id(); - - /* pairs with cmpxchg_release() in do_numa_crng_init() */ - pool = READ_ONCE(crng_node_pool); - if (pool && pool[nid]) - return pool[nid]; + chacha20_block(&chacha_state, buf); + if (unlikely(chacha_state.x[12] == 0)) + ++chacha_state.x[13]; + len -= CHACHA_BLOCK_SIZE; + buf += CHACHA_BLOCK_SIZE; } - return &primary_crng; + chacha_zeroize_state(&chacha_state); } /* - * crng_fast_load() can be called by code in the interrupt service - * path. So we can't afford to dilly-dally. Returns the number of - * bytes processed from cp. + * This returns random bytes in arbitrary quantities. The quality of the + * random bytes is as good as /dev/urandom. In order to ensure that the + * randomness provided by this function is okay, the function + * wait_for_random_bytes() should be called and return 0 at least once + * at any point prior. */ -static size_t crng_fast_load(const u8 *cp, size_t len) +void get_random_bytes(void *buf, size_t len) { - unsigned long flags; - u8 *p; - size_t ret = 0; - - if (!spin_trylock_irqsave(&primary_crng.lock, flags)) - return 0; - if (crng_init != 0) { - spin_unlock_irqrestore(&primary_crng.lock, flags); - return 0; - } - p = (u8 *)&primary_crng.state[4]; - while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) { - p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp; - cp++; crng_init_cnt++; len--; ret++; - } - spin_unlock_irqrestore(&primary_crng.lock, flags); - if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { - invalidate_batched_entropy(); - crng_init = 1; - pr_notice("fast init done\n"); - } - return ret; + warn_unseeded_randomness(); + _get_random_bytes(buf, len); } +EXPORT_SYMBOL(get_random_bytes); -/* - * crng_slow_load() is called by add_device_randomness, which has two - * attributes. (1) We can't trust the buffer passed to it is - * guaranteed to be unpredictable (so it might not have any entropy at - * all), and (2) it doesn't have the performance constraints of - * crng_fast_load(). - * - * So we do something more comprehensive which is guaranteed to touch - * all of the primary_crng's state, and which uses a LFSR with a - * period of 255 as part of the mixing algorithm. Finally, we do - * *not* advance crng_init_cnt since buffer we may get may be something - * like a fixed DMI table (for example), which might very well be - * unique to the machine, but is otherwise unvarying. - */ -static int crng_slow_load(const u8 *cp, size_t len) +static ssize_t get_random_bytes_user(struct iov_iter *iter) { - unsigned long flags; - static u8 lfsr = 1; - u8 tmp; - unsigned int i, max = CHACHA_KEY_SIZE; - const u8 *src_buf = cp; - u8 *dest_buf = (u8 *)&primary_crng.state[4]; + struct chacha_state chacha_state; + u8 block[CHACHA_BLOCK_SIZE]; + size_t ret = 0, copied; - if (!spin_trylock_irqsave(&primary_crng.lock, flags)) - return 0; - if (crng_init != 0) { - spin_unlock_irqrestore(&primary_crng.lock, flags); + if (unlikely(!iov_iter_count(iter))) return 0; - } - if (len > max) - max = len; - - for (i = 0; i < max; i++) { - tmp = lfsr; - lfsr >>= 1; - if (tmp & 1) - lfsr ^= 0xE1; - tmp = dest_buf[i % CHACHA_KEY_SIZE]; - dest_buf[i % CHACHA_KEY_SIZE] ^= src_buf[i % len] ^ lfsr; - lfsr += (tmp << 3) | (tmp >> 5); - } - spin_unlock_irqrestore(&primary_crng.lock, flags); - return 1; -} -static void crng_reseed(struct crng_state *crng, bool use_input_pool) -{ - unsigned long flags; - int i, num; - union { - u8 block[CHACHA_BLOCK_SIZE]; - u32 key[8]; - } buf; - - if (use_input_pool) { - num = extract_entropy(&buf, 32, 16); - if (num == 0) - return; - } else { - _extract_crng(&primary_crng, buf.block); - _crng_backtrack_protect(&primary_crng, buf.block, - CHACHA_KEY_SIZE); - } - spin_lock_irqsave(&crng->lock, flags); - for (i = 0; i < 8; i++) { - unsigned long rv; - if (!arch_get_random_seed_long(&rv) && - !arch_get_random_long(&rv)) - rv = random_get_entropy(); - crng->state[i + 4] ^= buf.key[i] ^ rv; + /* + * Immediately overwrite the ChaCha key at index 4 with random + * bytes, in case userspace causes copy_to_iter() below to sleep + * forever, so that we still retain forward secrecy in that case. + */ + crng_make_state(&chacha_state, (u8 *)&chacha_state.x[4], + CHACHA_KEY_SIZE); + /* + * However, if we're doing a read of len <= 32, we don't need to + * use chacha_state after, so we can simply return those bytes to + * the user directly. + */ + if (iov_iter_count(iter) <= CHACHA_KEY_SIZE) { + ret = copy_to_iter(&chacha_state.x[4], CHACHA_KEY_SIZE, iter); + goto out_zero_chacha; } - memzero_explicit(&buf, sizeof(buf)); - WRITE_ONCE(crng->init_time, jiffies); - spin_unlock_irqrestore(&crng->lock, flags); - crng_finalize_init(crng); -} -static void _extract_crng(struct crng_state *crng, u8 out[CHACHA_BLOCK_SIZE]) -{ - unsigned long flags, init_time; + for (;;) { + chacha20_block(&chacha_state, block); + if (unlikely(chacha_state.x[12] == 0)) + ++chacha_state.x[13]; - if (crng_ready()) { - init_time = READ_ONCE(crng->init_time); - if (time_after(READ_ONCE(crng_global_init_time), init_time) || - time_after(jiffies, init_time + CRNG_RESEED_INTERVAL)) - crng_reseed(crng, crng == &primary_crng); + copied = copy_to_iter(block, sizeof(block), iter); + ret += copied; + if (!iov_iter_count(iter) || copied != sizeof(block)) + break; + + BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0); + if (ret % PAGE_SIZE == 0) { + if (signal_pending(current)) + break; + cond_resched(); + } } - spin_lock_irqsave(&crng->lock, flags); - chacha20_block(&crng->state[0], out); - if (crng->state[12] == 0) - crng->state[13]++; - spin_unlock_irqrestore(&crng->lock, flags); -} -static void extract_crng(u8 out[CHACHA_BLOCK_SIZE]) -{ - _extract_crng(select_crng(), out); + memzero_explicit(block, sizeof(block)); +out_zero_chacha: + chacha_zeroize_state(&chacha_state); + return ret ? ret : -EFAULT; } /* - * Use the leftover bytes from the CRNG block output (if there is - * enough) to mutate the CRNG key to provide backtracking protection. + * Batched entropy returns random integers. The quality of the random + * number is as good as /dev/urandom. In order to ensure that the randomness + * provided by this function is okay, the function wait_for_random_bytes() + * should be called and return 0 at least once at any point prior. */ -static void _crng_backtrack_protect(struct crng_state *crng, - u8 tmp[CHACHA_BLOCK_SIZE], int used) + +#define DEFINE_BATCHED_ENTROPY(type) \ +struct batch_ ##type { \ + /* \ + * We make this 1.5x a ChaCha block, so that we get the \ + * remaining 32 bytes from fast key erasure, plus one full \ + * block from the detached ChaCha state. We can increase \ + * the size of this later if needed so long as we keep the \ + * formula of (integer_blocks + 0.5) * CHACHA_BLOCK_SIZE. \ + */ \ + type entropy[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(type))]; \ + local_lock_t lock; \ + unsigned long generation; \ + unsigned int position; \ +}; \ + \ +static DEFINE_PER_CPU(struct batch_ ##type, batched_entropy_ ##type) = { \ + .lock = INIT_LOCAL_LOCK(batched_entropy_ ##type.lock), \ + .position = UINT_MAX \ +}; \ + \ +type get_random_ ##type(void) \ +{ \ + type ret; \ + unsigned long flags; \ + struct batch_ ##type *batch; \ + unsigned long next_gen; \ + \ + 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(u8) +DEFINE_BATCHED_ENTROPY(u16) +DEFINE_BATCHED_ENTROPY(u32) +DEFINE_BATCHED_ENTROPY(u64) + +u32 __get_random_u32_below(u32 ceil) { - unsigned long flags; - u32 *s, *d; - int i; + /* + * This is the slow path for variable ceil. It is still fast, most of + * the time, by doing traditional reciprocal multiplication and + * opportunistically comparing the lower half to ceil itself, before + * falling back to computing a larger bound, and then rejecting samples + * whose lower half would indicate a range indivisible by ceil. The use + * of `-ceil % ceil` is analogous to `2^32 % ceil`, but is computable + * in 32-bits. + */ + u32 rand = get_random_u32(); + u64 mult; - used = round_up(used, sizeof(u32)); - if (used + CHACHA_KEY_SIZE > CHACHA_BLOCK_SIZE) { - extract_crng(tmp); - used = 0; + /* + * This function is technically undefined for ceil == 0, and in fact + * for the non-underscored constant version in the header, we build bug + * on that. But for the non-constant case, it's convenient to have that + * evaluate to being a straight call to get_random_u32(), so that + * get_random_u32_inclusive() can work over its whole range without + * undefined behavior. + */ + if (unlikely(!ceil)) + return rand; + + mult = (u64)ceil * rand; + if (unlikely((u32)mult < ceil)) { + u32 bound = -ceil % ceil; + while (unlikely((u32)mult < bound)) + mult = (u64)ceil * get_random_u32(); } - spin_lock_irqsave(&crng->lock, flags); - s = (u32 *)&tmp[used]; - d = &crng->state[4]; - for (i = 0; i < 8; i++) - *d++ ^= *s++; - spin_unlock_irqrestore(&crng->lock, flags); + return mult >> 32; } +EXPORT_SYMBOL(__get_random_u32_below); -static void crng_backtrack_protect(u8 tmp[CHACHA_BLOCK_SIZE], int used) +#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) { - _crng_backtrack_protect(select_crng(), tmp, used); + /* + * When the cpu comes back online, immediately invalidate both + * the per-cpu crng and all batches, so that we serve fresh + * randomness. + */ + per_cpu_ptr(&crngs, cpu)->generation = ULONG_MAX; + per_cpu_ptr(&batched_entropy_u8, cpu)->position = UINT_MAX; + per_cpu_ptr(&batched_entropy_u16, cpu)->position = UINT_MAX; + per_cpu_ptr(&batched_entropy_u32, cpu)->position = UINT_MAX; + per_cpu_ptr(&batched_entropy_u64, cpu)->position = UINT_MAX; + return 0; } +#endif -static ssize_t extract_crng_user(void __user *buf, size_t nbytes) -{ - ssize_t ret = 0, i = CHACHA_BLOCK_SIZE; - u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4); - int large_request = (nbytes > 256); - - while (nbytes) { - if (large_request && need_resched()) { - if (signal_pending(current)) { - if (ret == 0) - ret = -ERESTARTSYS; - break; - } - schedule(); - } - - extract_crng(tmp); - i = min_t(int, nbytes, CHACHA_BLOCK_SIZE); - if (copy_to_user(buf, tmp, i)) { - ret = -EFAULT; - break; - } - - nbytes -= i; - buf += i; - ret += i; - } - crng_backtrack_protect(tmp, i); - - /* Wipe data just written to memory */ - memzero_explicit(tmp, sizeof(tmp)); - return ret; -} - -/********************************************************************* +/********************************************************************** * - * Entropy input management + * 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) + * + **********************************************************************/ -/* There is one of these per entropy source */ -struct timer_rand_state { - cycles_t last_time; - long last_delta, last_delta2; +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 */ }; -#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, }; +static struct { + struct blake2s_ctx hash; + spinlock_t lock; + unsigned int init_bits; +} input_pool = { + .hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE), + BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4, + BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 }, + .hash.outlen = BLAKE2S_HASH_SIZE, + .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), +}; + +static void _mix_pool_bytes(const void *buf, size_t len) +{ + blake2s_update(&input_pool.hash, buf, len); +} /* - * 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. + * 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. */ -void add_device_randomness(const void *buf, unsigned int size) +static void mix_pool_bytes(const void *buf, size_t len) { - unsigned long time = random_get_entropy() ^ jiffies; unsigned long flags; - if (!crng_ready() && size) - crng_slow_load(buf, size); - - trace_add_device_randomness(size, _RET_IP_); spin_lock_irqsave(&input_pool.lock, flags); - _mix_pool_bytes(buf, size); - _mix_pool_bytes(&time, sizeof(time)); + _mix_pool_bytes(buf, len); spin_unlock_irqrestore(&input_pool.lock, flags); } -EXPORT_SYMBOL(add_device_randomness); - -static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE; /* - * 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. - * + * 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 add_timer_randomness(struct timer_rand_state *state, unsigned num) +static void extract_entropy(void *buf, size_t len) { + unsigned long flags; + u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE]; struct { - long jiffies; - unsigned int cycles; - unsigned int num; - } sample; - long delta, delta2, delta3; - - sample.jiffies = jiffies; - sample.cycles = random_get_entropy(); - sample.num = num; - mix_pool_bytes(&sample, sizeof(sample)); + unsigned long rdseed[32 / sizeof(long)]; + size_t counter; + } block; + size_t i, longs; + + for (i = 0; i < ARRAY_SIZE(block.rdseed);) { + longs = arch_get_random_seed_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); + if (longs) { + i += longs; + continue; + } + longs = arch_get_random_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); + if (longs) { + i += longs; + continue; + } + block.rdseed[i++] = random_get_entropy(); + } - /* - * Calculate number of bits of randomness we probably added. - * We take into account the first, second and third-order deltas - * in order to make our estimate. - */ - delta = sample.jiffies - READ_ONCE(state->last_time); - WRITE_ONCE(state->last_time, sample.jiffies); + spin_lock_irqsave(&input_pool.lock, flags); - delta2 = delta - READ_ONCE(state->last_delta); - WRITE_ONCE(state->last_delta, delta); + /* seed = HASHPRF(last_key, entropy_input) */ + blake2s_final(&input_pool.hash, seed); - delta3 = delta2 - READ_ONCE(state->last_delta2); - WRITE_ONCE(state->last_delta2, delta2); + /* next_key = HASHPRF(seed, RDSEED || 0) */ + block.counter = 0; + blake2s(seed, sizeof(seed), (const u8 *)&block, sizeof(block), next_key, sizeof(next_key)); + blake2s_init_key(&input_pool.hash, BLAKE2S_HASH_SIZE, next_key, sizeof(next_key)); - 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; + spin_unlock_irqrestore(&input_pool.lock, flags); + memzero_explicit(next_key, sizeof(next_key)); + + while (len) { + i = min_t(size_t, len, BLAKE2S_HASH_SIZE); + /* output = HASHPRF(seed, RDSEED || ++counter) */ + ++block.counter; + blake2s(seed, sizeof(seed), (const u8 *)&block, sizeof(block), buf, i); + len -= i; + buf += i; + } - /* - * 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(int, fls(delta >> 1), 11)); + memzero_explicit(seed, sizeof(seed)); + memzero_explicit(&block, sizeof(block)); } -void add_input_randomness(unsigned int type, unsigned int code, - unsigned int value) +#define credit_init_bits(bits) if (!crng_ready()) _credit_init_bits(bits) + +static void __cold _credit_init_bits(size_t bits) { - static unsigned char last_value; + static DECLARE_WORK(set_ready, crng_set_ready); + unsigned int new, orig, add; + unsigned long flags; + int m; - /* ignore autorepeat and the like */ - if (value == last_value) + if (!bits) return; - last_value = value; - add_timer_randomness(&input_timer_state, - (type << 4) ^ code ^ (code >> 4) ^ value); - trace_add_input_randomness(POOL_ENTROPY_BITS()); -} -EXPORT_SYMBOL_GPL(add_input_randomness); + add = min_t(size_t, bits, POOL_BITS); -static DEFINE_PER_CPU(struct fast_pool, irq_randomness); + orig = READ_ONCE(input_pool.init_bits); + do { + new = min_t(unsigned int, POOL_BITS, orig + add); + } while (!try_cmpxchg(&input_pool.init_bits, &orig, new)); + + if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) { + crng_reseed(NULL); /* Sets crng_init to CRNG_READY under base_crng.lock. */ + if (system_dfl_wq) + queue_work(system_dfl_wq, &set_ready); + atomic_notifier_call_chain(&random_ready_notifier, 0, NULL); +#ifdef CONFIG_VDSO_GETRANDOM + WRITE_ONCE(vdso_k_rng_data->is_ready, true); +#endif + wake_up_interruptible(&crng_init_wait); + kill_fasync(&fasync, SIGIO, POLL_IN); + pr_notice("crng init done\n"); + m = ratelimit_state_get_miss(&urandom_warning); + if (m) + pr_notice("%d urandom warning(s) missed due to ratelimiting\n", m); + } else if (orig < POOL_EARLY_BITS && new >= POOL_EARLY_BITS) { + spin_lock_irqsave(&base_crng.lock, flags); + /* Check if crng_init is CRNG_EMPTY, to avoid race with crng_reseed(). */ + if (crng_init == CRNG_EMPTY) { + extract_entropy(base_crng.key, sizeof(base_crng.key)); + crng_init = CRNG_EARLY; + } + spin_unlock_irqrestore(&base_crng.lock, flags); + } +} -#ifdef ADD_INTERRUPT_BENCH -static unsigned long avg_cycles, avg_deviation; -#define AVG_SHIFT 8 /* Exponential average factor k=1/256 */ -#define FIXED_1_2 (1 << (AVG_SHIFT - 1)) +/********************************************************************** + * + * Entropy collection routines. + * + * The following exported functions are used for pushing entropy into + * the above entropy accumulation routines: + * + * void add_device_randomness(const void *buf, size_t len); + * void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after); + * void add_bootloader_randomness(const void *buf, size_t len); + * void add_vmfork_randomness(const void *unique_vm_id, size_t len); + * void add_interrupt_randomness(int irq); + * void add_input_randomness(unsigned int type, unsigned int code, unsigned int value); + * void add_disk_randomness(struct gendisk *disk); + * + * add_device_randomness() adds data to the input pool that + * is likely to differ between two devices (or possibly even per boot). + * This would be things like MAC addresses or serial numbers, or the + * read-out of the RTC. This does *not* credit any actual entropy to + * the pool, but it initializes the pool to different values for devices + * that might otherwise be identical and have very little entropy + * available to them (particularly common in the embedded world). + * + * add_hwgenerator_randomness() is for true hardware RNGs, and will credit + * entropy as specified by the caller. If the entropy pool is full it will + * block until more entropy is needed. + * + * add_bootloader_randomness() is called by bootloader drivers, such as EFI + * and device tree, and credits its input depending on whether or not the + * command line option 'random.trust_bootloader' is set. + * + * add_vmfork_randomness() adds a unique (but not necessarily secret) ID + * representing the current instance of a VM to the pool, without crediting, + * and then force-reseeds the crng so that it takes effect immediately. + * + * add_interrupt_randomness() uses the interrupt timing as random + * inputs to the entropy pool. Using the cycle counters and the irq source + * as inputs, it feeds the input pool roughly once a second or after 64 + * interrupts, crediting 1 bit of entropy for whichever comes first. + * + * add_input_randomness() uses the input layer interrupt timing, as well + * as the event type information from the hardware. + * + * add_disk_randomness() uses what amounts to the seek time of block + * layer request events, on a per-disk_devt basis, as input to the + * entropy pool. Note that high-speed solid state drives with very low + * seek times do not make for good sources of entropy, as their seek + * times are usually fairly consistent. + * + * The last two routines try to estimate how many bits of entropy + * to credit. They do this by keeping track of the first and second + * order deltas of the event timings. + * + **********************************************************************/ -static void add_interrupt_bench(cycles_t start) +static bool trust_cpu __initdata = true; +static bool trust_bootloader __initdata = true; +static int __init parse_trust_cpu(char *arg) { - long delta = random_get_entropy() - start; - - /* Use a weighted moving average */ - delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT); - avg_cycles += delta; - /* And average deviation */ - delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT); - avg_deviation += delta; + return kstrtobool(arg, &trust_cpu); } -#else -#define add_interrupt_bench(x) -#endif - -static u32 get_reg(struct fast_pool *f, struct pt_regs *regs) +static int __init parse_trust_bootloader(char *arg) { - u32 *ptr = (u32 *)regs; - unsigned int idx; - - if (regs == NULL) - return 0; - idx = READ_ONCE(f->reg_idx); - if (idx >= sizeof(struct pt_regs) / sizeof(u32)) - idx = 0; - ptr += idx++; - WRITE_ONCE(f->reg_idx, idx); - return *ptr; + return kstrtobool(arg, &trust_bootloader); } +early_param("random.trust_cpu", parse_trust_cpu); +early_param("random.trust_bootloader", parse_trust_bootloader); -void add_interrupt_randomness(int irq) +static int random_pm_notification(struct notifier_block *nb, unsigned long action, void *data) { - struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness); - struct pt_regs *regs = get_irq_regs(); - unsigned long now = jiffies; - cycles_t cycles = random_get_entropy(); - u32 c_high, j_high; - u64 ip; - - if (cycles == 0) - cycles = get_reg(fast_pool, regs); - c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0; - j_high = (sizeof(now) > 4) ? now >> 32 : 0; - fast_pool->pool[0] ^= cycles ^ j_high ^ irq; - fast_pool->pool[1] ^= now ^ c_high; - ip = regs ? instruction_pointer(regs) : _RET_IP_; - fast_pool->pool[2] ^= ip; - fast_pool->pool[3] ^= - (sizeof(ip) > 4) ? ip >> 32 : get_reg(fast_pool, regs); - - fast_mix(fast_pool); - add_interrupt_bench(cycles); - - if (unlikely(crng_init == 0)) { - if ((fast_pool->count >= 64) && - crng_fast_load((u8 *)fast_pool->pool, sizeof(fast_pool->pool)) > 0) { - fast_pool->count = 0; - fast_pool->last = now; - } - return; - } - - if ((fast_pool->count < 64) && !time_after(now, fast_pool->last + HZ)) - return; + unsigned long flags, entropy = random_get_entropy(); - if (!spin_trylock(&input_pool.lock)) - return; - - fast_pool->last = now; - __mix_pool_bytes(&fast_pool->pool, sizeof(fast_pool->pool)); - spin_unlock(&input_pool.lock); - - fast_pool->count = 0; + /* + * 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() }; - /* award one bit for the contents of the fast pool */ - credit_entropy_bits(1); -} -EXPORT_SYMBOL_GPL(add_interrupt_randomness); + 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); -#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)); - trace_add_disk_randomness(disk_devt(disk), POOL_ENTROPY_BITS()); + if (crng_ready() && (action == PM_RESTORE_PREPARE || + (action == PM_POST_SUSPEND && !IS_ENABLED(CONFIG_PM_AUTOSLEEP) && + !IS_ENABLED(CONFIG_PM_USERSPACE_AUTOSLEEP)))) { + crng_reseed(NULL); + pr_notice("crng reseeded on system resumption\n"); + } + return 0; } -EXPORT_SYMBOL_GPL(add_disk_randomness); -#endif -/********************************************************************* - * - * Entropy extraction routines - * - *********************************************************************/ +static struct notifier_block pm_notifier = { .notifier_call = random_pm_notification }; /* - * This function decides how many bytes to actually take from the - * given pool, and also debits the entropy count accordingly. + * This is called extremely early, before time keeping functionality is + * available, but arch randomness is. Interrupts are not yet enabled. */ -static size_t account(size_t nbytes, int min) +void __init random_init_early(const char *command_line) { - int entropy_count, orig; - size_t ibytes, nfrac; + unsigned long entropy[BLAKE2S_BLOCK_SIZE / sizeof(long)]; + size_t i, longs, arch_bits; - BUG_ON(input_pool.entropy_count > POOL_FRACBITS); +#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 - /* Can we pull enough? */ -retry: - entropy_count = orig = READ_ONCE(input_pool.entropy_count); - if (WARN_ON(entropy_count < 0)) { - pr_warn("negative entropy count: count %d\n", entropy_count); - entropy_count = 0; + for (i = 0, arch_bits = sizeof(entropy) * 8; i < ARRAY_SIZE(entropy);) { + longs = arch_get_random_seed_longs(entropy, ARRAY_SIZE(entropy) - i); + if (longs) { + _mix_pool_bytes(entropy, sizeof(*entropy) * longs); + i += longs; + continue; + } + longs = arch_get_random_longs(entropy, ARRAY_SIZE(entropy) - i); + if (longs) { + _mix_pool_bytes(entropy, sizeof(*entropy) * longs); + i += longs; + continue; + } + arch_bits -= sizeof(*entropy) * 8; + ++i; } - /* never pull more than available */ - ibytes = min_t(size_t, nbytes, entropy_count >> (POOL_ENTROPY_SHIFT + 3)); - if (ibytes < min) - ibytes = 0; - nfrac = ibytes << (POOL_ENTROPY_SHIFT + 3); - if ((size_t)entropy_count > nfrac) - entropy_count -= nfrac; - else - entropy_count = 0; - - if (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig) - goto retry; - - trace_debit_entropy(8 * ibytes); - if (ibytes && POOL_ENTROPY_BITS() < random_write_wakeup_bits) { - wake_up_interruptible(&random_write_wait); - kill_fasync(&fasync, SIGIO, POLL_OUT); - } + _mix_pool_bytes(init_utsname(), sizeof(*(init_utsname()))); + _mix_pool_bytes(command_line, strlen(command_line)); - return ibytes; + /* Reseed if already seeded by earlier phases. */ + if (crng_ready()) + crng_reseed(NULL); + else if (trust_cpu) + _credit_init_bits(arch_bits); } /* - * This function does the actual extraction for extract_entropy. - * - * Note: we assume that .poolwords is a multiple of 16 words. + * This is called a little bit after the prior function, and now there is + * access to timestamps counters. Interrupts are not yet enabled. */ -static void extract_buf(u8 *out) +void __init random_init(void) { - struct blake2s_state state __aligned(__alignof__(unsigned long)); - u8 hash[BLAKE2S_HASH_SIZE]; - unsigned long *salt; - unsigned long flags; - - blake2s_init(&state, sizeof(hash)); - - /* - * If we have an architectural hardware random number - * generator, use it for BLAKE2's salt & personal fields. - */ - for (salt = (unsigned long *)&state.h[4]; - salt < (unsigned long *)&state.h[8]; ++salt) { - unsigned long v; - if (!arch_get_random_long(&v)) - break; - *salt ^= v; - } + unsigned long entropy = random_get_entropy(); + ktime_t now = ktime_get_real(); - /* Generate a hash across the pool */ - spin_lock_irqsave(&input_pool.lock, flags); - blake2s_update(&state, (const u8 *)input_pool_data, POOL_BYTES); - blake2s_final(&state, hash); /* final zeros out state */ + _mix_pool_bytes(&now, sizeof(now)); + _mix_pool_bytes(&entropy, sizeof(entropy)); + add_latent_entropy(); /* - * We mix the hash back into the pool to prevent backtracking - * attacks (where the attacker knows the state of the pool - * plus the current outputs, and attempts to find previous - * outputs), unless the hash function can be inverted. By - * mixing at least a hash worth of hash data back, we make - * brute-forcing the feedback as hard as brute-forcing the - * hash. + * If we were initialized by the cpu or bootloader before workqueues + * are initialized, then we should enable the static branch here. */ - __mix_pool_bytes(hash, sizeof(hash)); - spin_unlock_irqrestore(&input_pool.lock, flags); + if (!static_branch_likely(&crng_is_ready) && crng_init >= CRNG_READY) + crng_set_ready(NULL); - /* Note that EXTRACT_SIZE is half of hash size here, because above - * we've dumped the full length back into mixer. By reducing the - * amount that we emit, we retain a level of forward secrecy. - */ - memcpy(out, hash, EXTRACT_SIZE); - memzero_explicit(hash, sizeof(hash)); -} - -static ssize_t _extract_entropy(void *buf, size_t nbytes) -{ - ssize_t ret = 0, i; - u8 tmp[EXTRACT_SIZE]; - - while (nbytes) { - extract_buf(tmp); - i = min_t(int, nbytes, EXTRACT_SIZE); - memcpy(buf, tmp, i); - nbytes -= i; - buf += i; - ret += i; - } + /* Reseed if already seeded by earlier phases. */ + if (crng_ready()) + crng_reseed(NULL); - /* Wipe data just returned from memory */ - memzero_explicit(tmp, sizeof(tmp)); + WARN_ON(register_pm_notifier(&pm_notifier)); - return ret; + WARN(!entropy, "Missing cycle counter and fallback timer; RNG " + "entropy collection will consequently suffer."); } /* - * This function extracts randomness from the "entropy pool", and - * returns it in a buffer. + * Add device- or boot-specific data to the input pool to help + * initialize it. * - * The min parameter specifies the minimum amount we can pull before - * failing to avoid races that defeat catastrophic reseeding. + * 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. */ -static ssize_t extract_entropy(void *buf, size_t nbytes, int min) -{ - trace_extract_entropy(nbytes, POOL_ENTROPY_BITS(), _RET_IP_); - nbytes = account(nbytes, min); - return _extract_entropy(buf, nbytes); -} - -#define warn_unseeded_randomness(previous) \ - _warn_unseeded_randomness(__func__, (void *)_RET_IP_, (previous)) - -static void _warn_unseeded_randomness(const char *func_name, void *caller, void **previous) +void add_device_randomness(const void *buf, size_t len) { -#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM - const bool print_once = false; -#else - static bool print_once __read_mostly; -#endif + unsigned long entropy = random_get_entropy(); + unsigned long flags; - if (print_once || crng_ready() || - (previous && (caller == READ_ONCE(*previous)))) - return; - WRITE_ONCE(*previous, caller); -#ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM - print_once = true; -#endif - if (__ratelimit(&unseeded_warning)) - printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", - func_name, caller, crng_init); + 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); /* - * This function is the exported kernel interface. It returns some - * number of good random numbers, suitable for key generation, seeding - * TCP sequence numbers, etc. It does not rely on the hardware random - * number generator. For random bytes direct from the hardware RNG - * (when available), use get_random_bytes_arch(). In order to ensure - * that the randomness provided by this function is okay, the function - * wait_for_random_bytes() should be called and return 0 at least once - * at any point prior. + * Interface for in-kernel drivers of true hardware RNGs. Those devices + * may produce endless random bits, so this function will sleep for + * some amount of time after, if the sleep_after parameter is true. */ -static void _get_random_bytes(void *buf, int nbytes) -{ - u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4); - - trace_get_random_bytes(nbytes, _RET_IP_); - - while (nbytes >= CHACHA_BLOCK_SIZE) { - extract_crng(buf); - buf += CHACHA_BLOCK_SIZE; - nbytes -= CHACHA_BLOCK_SIZE; - } - - if (nbytes > 0) { - extract_crng(tmp); - memcpy(buf, tmp, nbytes); - crng_backtrack_protect(tmp, nbytes); - } else - crng_backtrack_protect(tmp, CHACHA_BLOCK_SIZE); - memzero_explicit(tmp, sizeof(tmp)); -} - -void get_random_bytes(void *buf, int nbytes) +void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after) { - static void *previous; + mix_pool_bytes(buf, len); + credit_init_bits(entropy); - warn_unseeded_randomness(&previous); - _get_random_bytes(buf, nbytes); + /* + * Throttle writing to once every reseed interval, unless we're not yet + * initialized or no entropy is credited. + */ + if (sleep_after && !kthread_should_stop() && (crng_ready() || !entropy)) + schedule_timeout_interruptible(crng_reseed_interval()); } -EXPORT_SYMBOL(get_random_bytes); +EXPORT_SYMBOL_GPL(add_hwgenerator_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. + * Handle random seed passed by bootloader, and credit it depending + * on the command line option 'random.trust_bootloader'. */ -static void entropy_timer(struct timer_list *t) +void __init add_bootloader_randomness(const void *buf, size_t len) { - credit_entropy_bits(1); + mix_pool_bytes(buf, len); + if (trust_bootloader) + credit_init_bits(len * 8); } +#if IS_ENABLED(CONFIG_VMGENID) +static BLOCKING_NOTIFIER_HEAD(vmfork_chain); + /* - * If we have an actual cycle counter, see if we can - * generate enough entropy with timing noise + * 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. */ -static void try_to_generate_entropy(void) +void __cold add_vmfork_randomness(const void *unique_vm_id, size_t len) { - struct { - unsigned long now; - struct timer_list timer; - } stack; - - stack.now = random_get_entropy(); - - /* Slow counter - or none. Don't even bother */ - if (stack.now == random_get_entropy()) - return; - - timer_setup_on_stack(&stack.timer, entropy_timer, 0); - while (!crng_ready()) { - if (!timer_pending(&stack.timer)) - mod_timer(&stack.timer, jiffies + 1); - mix_pool_bytes(&stack.now, sizeof(stack.now)); - schedule(); - stack.now = random_get_entropy(); + add_device_randomness(unique_vm_id, len); + if (crng_ready()) { + crng_reseed(NULL); + pr_notice("crng reseeded due to virtual machine fork\n"); } + blocking_notifier_call_chain(&vmfork_chain, 0, NULL); +} +#if IS_MODULE(CONFIG_VMGENID) +EXPORT_SYMBOL_GPL(add_vmfork_randomness); +#endif - del_timer_sync(&stack.timer); - destroy_timer_on_stack(&stack.timer); - mix_pool_bytes(&stack.now, sizeof(stack.now)); +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); -/* - * Wait for the urandom pool to be seeded and thus guaranteed to supply - * cryptographically secure random numbers. This applies to: the /dev/urandom - * device, the get_random_bytes function, and the get_random_{u32,u64,int,long} - * family of functions. Using any of these functions without first calling - * this function forfeits the guarantee of security. - * - * Returns: 0 if the urandom pool has been seeded. - * -ERESTARTSYS if the function was interrupted by a signal. - */ -int wait_for_random_bytes(void) +int __cold unregister_random_vmfork_notifier(struct notifier_block *nb) { - if (likely(crng_ready())) - return 0; + return blocking_notifier_chain_unregister(&vmfork_chain, nb); +} +EXPORT_SYMBOL_GPL(unregister_random_vmfork_notifier); +#endif - do { - int ret; - ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ); - if (ret) - return ret > 0 ? 0 : ret; +struct fast_pool { + unsigned long pool[4]; + unsigned long last; + unsigned int count; + struct timer_list mix; +}; - try_to_generate_entropy(); - } while (!crng_ready()); +static void mix_interrupt_randomness(struct timer_list *work); - return 0; -} -EXPORT_SYMBOL(wait_for_random_bytes); +static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = { +#ifdef CONFIG_64BIT +#define FASTMIX_PERM SIPHASH_PERMUTATION + .pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 }, +#else +#define FASTMIX_PERM HSIPHASH_PERMUTATION + .pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 }, +#endif + .mix = __TIMER_INITIALIZER(mix_interrupt_randomness, 0) +}; /* - * Returns whether or not the urandom pool has been seeded and thus guaranteed - * to supply cryptographically secure random numbers. This applies to: the - * /dev/urandom device, the get_random_bytes function, and the get_random_{u32, - * ,u64,int,long} family of functions. - * - * Returns: true if the urandom pool has been seeded. - * false if the urandom pool has not been seeded. + * 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. */ -bool rng_is_initialized(void) +static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2) { - return crng_ready(); + 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; } -EXPORT_SYMBOL(rng_is_initialized); +#ifdef CONFIG_SMP /* - * Add a callback function that will be invoked when the nonblocking - * pool is initialised. - * - * returns: 0 if callback is successfully added - * -EALREADY if pool is already initialised (callback not called) - * -ENOENT if module for callback is not alive + * This function is called when the CPU has just come online, with + * entry CPUHP_AP_RANDOM_ONLINE, just after CPUHP_AP_WORKQUEUE_ONLINE. */ -int add_random_ready_callback(struct random_ready_callback *rdy) +int __cold random_online_cpu(unsigned int cpu) { - struct module *owner; - unsigned long flags; - int err = -EALREADY; + /* + * 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 - if (crng_ready()) - return err; +static void mix_interrupt_randomness(struct timer_list *work) +{ + struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix); + /* + * The size of the copied stack pool is explicitly 2 longs so that we + * only ever ingest half of the siphash output each time, retaining + * the other half as the next "key" that carries over. The entropy is + * supposed to be sufficiently dispersed between bits so on average + * we don't wind up "losing" some. + */ + unsigned long pool[2]; + unsigned int count; - owner = rdy->owner; - if (!try_module_get(owner)) - return -ENOENT; + /* 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; + } - spin_lock_irqsave(&random_ready_list_lock, flags); - if (crng_ready()) - goto out; + /* + * 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(); - owner = NULL; + mix_pool_bytes(pool, sizeof(pool)); + credit_init_bits(clamp_t(unsigned int, (count & U16_MAX) / 64, 1, sizeof(pool) * 8)); - list_add(&rdy->list, &random_ready_list); - err = 0; + memzero_explicit(pool, sizeof(pool)); +} -out: - spin_unlock_irqrestore(&random_ready_list_lock, flags); +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; - module_put(owner); + fast_mix(fast_pool->pool, entropy, + (regs ? instruction_pointer(regs) : _RET_IP_) ^ swab(irq)); + new_count = ++fast_pool->count; - return err; + if (new_count & MIX_INFLIGHT) + return; + + if (new_count < 1024 && !time_is_before_jiffies(fast_pool->last + HZ)) + return; + + fast_pool->count |= MIX_INFLIGHT; + if (!timer_pending(&fast_pool->mix)) { + fast_pool->mix.expires = jiffies; + add_timer_on(&fast_pool->mix, raw_smp_processor_id()); + } } -EXPORT_SYMBOL(add_random_ready_callback); +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; +}; /* - * Delete a previously registered readiness callback function. + * 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. */ -void del_random_ready_callback(struct random_ready_callback *rdy) +static void add_timer_randomness(struct timer_rand_state *state, unsigned int num) { - unsigned long flags; - struct module *owner = NULL; + unsigned long entropy = random_get_entropy(), now = jiffies, flags; + long delta, delta2, delta3; + unsigned int bits; - spin_lock_irqsave(&random_ready_list_lock, flags); - if (!list_empty(&rdy->list)) { - list_del_init(&rdy->list); - owner = rdy->owner; + /* + * 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); } - spin_unlock_irqrestore(&random_ready_list_lock, flags); - module_put(owner); -} -EXPORT_SYMBOL(del_random_ready_callback); + if (crng_ready()) + return; -/* - * This function will use the architecture-specific hardware random - * number generator if it is available. The arch-specific hw RNG will - * almost certainly be faster than what we can do in software, but it - * is impossible to verify that it is implemented securely (as - * opposed, to, say, the AES encryption of a sequence number using a - * key known by the NSA). So it's useful if we need the speed, but - * only if we're willing to trust the hardware manufacturer not to - * have put in a back door. - * - * Return number of bytes filled in. - */ -int __must_check get_random_bytes_arch(void *buf, int nbytes) -{ - int left = nbytes; - u8 *p = buf; + /* + * 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); - trace_get_random_bytes_arch(left, _RET_IP_); - while (left) { - unsigned long v; - int chunk = min_t(int, left, sizeof(unsigned long)); + delta2 = delta - READ_ONCE(state->last_delta); + WRITE_ONCE(state->last_delta, delta); - if (!arch_get_random_long(&v)) - break; + delta3 = delta2 - READ_ONCE(state->last_delta2); + WRITE_ONCE(state->last_delta2, delta2); - memcpy(p, &v, chunk); - p += chunk; - left -= chunk; - } + 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; - return nbytes - left; + /* + * 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); } -EXPORT_SYMBOL(get_random_bytes_arch); -/* - * init_std_data - initialize pool with system data - * - * This function clears the pool's entropy count and mixes some system - * data into the pool to prepare it for use. The pool is not cleared - * as that can only decrease the entropy in the pool. - */ -static void __init init_std_data(void) +void add_input_randomness(unsigned int type, unsigned int code, unsigned int value) { - int i; - ktime_t now = ktime_get_real(); - unsigned long rv; - - mix_pool_bytes(&now, sizeof(now)); - for (i = POOL_BYTES; i > 0; i -= sizeof(rv)) { - if (!arch_get_random_seed_long(&rv) && - !arch_get_random_long(&rv)) - rv = random_get_entropy(); - mix_pool_bytes(&rv, sizeof(rv)); - } - mix_pool_bytes(utsname(), sizeof(*(utsname()))); + 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); -/* - * Note that setup_arch() may call add_device_randomness() - * long before we get here. This allows seeding of the pools - * with some platform dependent data very early in the boot - * process. But it limits our options here. We must use - * statically allocated structures that already have all - * initializations complete at compile time. We should also - * take care not to overwrite the precious per platform data - * we were given. - */ -int __init rand_initialize(void) +#ifdef CONFIG_BLOCK +void add_disk_randomness(struct gendisk *disk) { - init_std_data(); - if (crng_need_final_init) - crng_finalize_init(&primary_crng); - crng_initialize_primary(&primary_crng); - crng_global_init_time = jiffies; - if (ratelimit_disable) { - urandom_warning.interval = 0; - unseeded_warning.interval = 0; - } - return 0; + 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); -#ifdef CONFIG_BLOCK -void rand_initialize_disk(struct gendisk *disk) +void __cold rand_initialize_disk(struct gendisk *disk) { struct timer_rand_state *state; @@ -1724,109 +1256,257 @@ void rand_initialize_disk(struct gendisk *disk) } #endif -static ssize_t urandom_read_nowarn(struct file *file, char __user *buf, - size_t nbytes, loff_t *ppos) +struct entropy_timer_state { + unsigned long entropy; + struct timer_list timer; + atomic_t samples; + unsigned int samples_per_bit; +}; + +/* + * Each time the timer fires, we expect that we got an unpredictable jump in + * the cycle counter. Even if the timer is running on another CPU, the timer + * activity will be touching the stack of the CPU that is generating entropy. + * + * Note that we don't re-arm the timer in the timer itself - we are happy to be + * scheduled away, since that just makes the load more complex, but we do not + * want the timer to keep ticking unless the entropy loop is running. + * + * So the re-arming always happens in the entropy loop itself. + */ +static void __cold entropy_timer(struct timer_list *timer) { - int ret; + struct entropy_timer_state *state = container_of(timer, struct entropy_timer_state, timer); + unsigned long entropy = random_get_entropy(); - nbytes = min_t(size_t, nbytes, INT_MAX >> (POOL_ENTROPY_SHIFT + 3)); - ret = extract_crng_user(buf, nbytes); - trace_urandom_read(8 * nbytes, 0, POOL_ENTROPY_BITS()); - return ret; + mix_pool_bytes(&entropy, sizeof(entropy)); + if (atomic_inc_return(&state->samples) % state->samples_per_bit == 0) + credit_init_bits(1); } -static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, - loff_t *ppos) -{ - static int maxwarn = 10; +/* + * If we have an actual cycle counter, see if we can generate enough entropy + * with timing noise. + */ +static void __cold try_to_generate_entropy(void) +{ + enum { NUM_TRIAL_SAMPLES = 8192, MAX_SAMPLES_PER_BIT = HZ / 15 }; + u8 stack_bytes[sizeof(struct entropy_timer_state) + SMP_CACHE_BYTES - 1]; + struct entropy_timer_state *stack = PTR_ALIGN((void *)stack_bytes, SMP_CACHE_BYTES); + unsigned int i, num_different = 0; + unsigned long last = random_get_entropy(); + cpumask_var_t timer_cpus; + int cpu = -1; + + for (i = 0; i < NUM_TRIAL_SAMPLES - 1; ++i) { + stack->entropy = random_get_entropy(); + if (stack->entropy != last) + ++num_different; + last = stack->entropy; + } + stack->samples_per_bit = DIV_ROUND_UP(NUM_TRIAL_SAMPLES, num_different + 1); + if (stack->samples_per_bit > MAX_SAMPLES_PER_BIT) + return; + + atomic_set(&stack->samples, 0); + timer_setup_on_stack(&stack->timer, entropy_timer, 0); + if (!alloc_cpumask_var(&timer_cpus, GFP_KERNEL)) + goto out; + + while (!crng_ready() && !signal_pending(current)) { + /* + * Check !timer_pending() and then ensure that any previous callback has finished + * executing by checking timer_delete_sync_try(), before queueing the next one. + */ + if (!timer_pending(&stack->timer) && timer_delete_sync_try(&stack->timer) >= 0) { + unsigned int num_cpus; + + /* + * Preemption must be disabled here, both to read the current CPU number + * and to avoid scheduling a timer on a dead CPU. + */ + preempt_disable(); + + /* Only schedule callbacks on timer CPUs that are online. */ + cpumask_and(timer_cpus, housekeeping_cpumask(HK_TYPE_TIMER), cpu_online_mask); + num_cpus = cpumask_weight(timer_cpus); + /* In very bizarre case of misconfiguration, fallback to all online. */ + if (unlikely(num_cpus == 0)) { + *timer_cpus = *cpu_online_mask; + num_cpus = cpumask_weight(timer_cpus); + } - if (!crng_ready() && maxwarn > 0) { - maxwarn--; - if (__ratelimit(&urandom_warning)) - pr_notice("%s: uninitialized urandom read (%zd bytes read)\n", - current->comm, nbytes); + /* Basic CPU round-robin, which avoids the current CPU. */ + do { + cpu = cpumask_next(cpu, timer_cpus); + if (cpu >= nr_cpu_ids) + cpu = cpumask_first(timer_cpus); + } while (cpu == smp_processor_id() && num_cpus > 1); + + /* Expiring the timer at `jiffies` means it's the next tick. */ + stack->timer.expires = jiffies; + + add_timer_on(&stack->timer, cpu); + + preempt_enable(); + } + mix_pool_bytes(&stack->entropy, sizeof(stack->entropy)); + schedule(); + stack->entropy = random_get_entropy(); } + mix_pool_bytes(&stack->entropy, sizeof(stack->entropy)); - return urandom_read_nowarn(file, buf, nbytes, ppos); + free_cpumask_var(timer_cpus); +out: + timer_delete_sync(&stack->timer); + timer_destroy_on_stack(&stack->timer); } -static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, - loff_t *ppos) + +/********************************************************************** + * + * Userspace reader/writer interfaces. + * + * getrandom(2) is the primary modern interface into the RNG and should + * be used in preference to anything else. + * + * Reading from /dev/random has the same functionality as calling + * getrandom(2) with flags=0. In earlier versions, however, it had + * vastly different semantics and should therefore be avoided, to + * prevent backwards compatibility issues. + * + * Reading from /dev/urandom has the same functionality as calling + * getrandom(2) with flags=GRND_INSECURE. Because it does not block + * waiting for the RNG to be ready, it should not be used. + * + * Writing to either /dev/random or /dev/urandom adds entropy to + * the input pool but does not credit it. + * + * Polling on /dev/random indicates when the RNG is initialized, on + * the read side, and when it wants new entropy, on the write side. + * + * Both /dev/random and /dev/urandom have the same set of ioctls for + * adding entropy, getting the entropy count, zeroing the count, and + * reseeding the crng. + * + **********************************************************************/ + +SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags) { + struct iov_iter iter; int ret; - ret = wait_for_random_bytes(); - if (ret != 0) + if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE)) + return -EINVAL; + + /* + * Requesting insecure and blocking randomness at the same time makes + * no sense. + */ + if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM)) + return -EINVAL; + + if (!crng_ready() && !(flags & GRND_INSECURE)) { + if (flags & GRND_NONBLOCK) + return -EAGAIN; + ret = wait_for_random_bytes(); + if (unlikely(ret)) + return ret; + } + + ret = import_ubuf(ITER_DEST, ubuf, len, &iter); + if (unlikely(ret)) return ret; - return urandom_read_nowarn(file, buf, nbytes, ppos); + return get_random_bytes_user(&iter); } 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 (POOL_ENTROPY_BITS() < random_write_wakeup_bits) - mask |= EPOLLOUT | EPOLLWRNORM; - return mask; + return crng_ready() ? EPOLLIN | EPOLLRDNORM : EPOLLOUT | EPOLLWRNORM; } -static int write_pool(const char __user *buffer, size_t count) +static ssize_t write_pool_user(struct iov_iter *iter) { - size_t bytes; - u32 t, buf[16]; - const char __user *p = buffer; + u8 block[BLAKE2S_BLOCK_SIZE]; + ssize_t ret = 0; + size_t copied; - while (count > 0) { - int b, i = 0; + if (unlikely(!iov_iter_count(iter))) + return 0; - bytes = min(count, sizeof(buf)); - if (copy_from_user(&buf, p, bytes)) - return -EFAULT; + 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; - for (b = bytes; b > 0; b -= sizeof(u32), i++) { - if (!arch_get_random_int(&t)) + BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0); + if (ret % PAGE_SIZE == 0) { + if (signal_pending(current)) break; - buf[i] ^= t; + 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; - count -= bytes; - p += bytes; + /* + * 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(); - mix_pool_bytes(buf, bytes); - cond_resched(); + if (!crng_ready()) { + if (!ratelimit_disable && maxwarn <= 0) + ratelimit_state_inc_miss(&urandom_warning); + else if (ratelimit_disable || __ratelimit(&urandom_warning)) { + --maxwarn; + pr_notice("%s: uninitialized urandom read (%zu bytes read)\n", + current->comm, iov_iter_count(iter)); + } } - return 0; + return get_random_bytes_user(iter); } -static ssize_t random_write(struct file *file, const char __user *buffer, - size_t count, loff_t *ppos) +static ssize_t random_read_iter(struct kiocb *kiocb, struct iov_iter *iter) { - size_t ret; + int ret; - ret = write_pool(buffer, count); - if (ret) - return ret; + if (!crng_ready() && + ((kiocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) || + (kiocb->ki_filp->f_flags & O_NONBLOCK))) + return -EAGAIN; - return (ssize_t)count; + 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 size, ent_count; int __user *p = (int __user *)arg; - int retval; + int ent_count; switch (cmd) { case RNDGETENTCNT: - /* inherently racy, no point locking */ - ent_count = POOL_ENTROPY_BITS(); - if (put_user(ent_count, p)) + /* Inherently racy, no point locking. */ + if (put_user(input_pool.init_bits, p)) return -EFAULT; return 0; case RNDADDTOENTCNT: @@ -1834,37 +1514,47 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) return -EPERM; if (get_user(ent_count, p)) return -EFAULT; - return credit_entropy_bits_safe(ent_count); - case RNDADDENTROPY: + if (ent_count < 0) + return -EINVAL; + credit_init_bits(ent_count); + return 0; + case RNDADDENTROPY: { + struct iov_iter iter; + ssize_t ret; + int len; + if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (get_user(ent_count, p++)) return -EFAULT; if (ent_count < 0) return -EINVAL; - if (get_user(size, p++)) + if (get_user(len, p++)) return -EFAULT; - retval = write_pool((const char __user *)p, size); - if (retval < 0) - return retval; - return credit_entropy_bits_safe(ent_count); + ret = import_ubuf(ITER_SOURCE, p, len, &iter); + if (unlikely(ret)) + return ret; + ret = write_pool_user(&iter); + if (unlikely(ret < 0)) + return ret; + /* Since we're crediting, enforce that it was all written into the pool. */ + if (unlikely(ret != len)) + return -EFAULT; + credit_init_bits(ent_count); + return 0; + } case RNDZAPENTCNT: case RNDCLEARPOOL: - /* - * Clear the entropy pool counters. We no longer clear - * the entropy pool, as that's silly. - */ + /* No longer has any effect. */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; - input_pool.entropy_count = 0; return 0; case RNDRESEEDCRNG: if (!capable(CAP_SYS_ADMIN)) return -EPERM; - if (crng_init < 2) + if (!crng_ready()) return -ENODATA; - crng_reseed(&primary_crng, true); - WRITE_ONCE(crng_global_init_time, jiffies - 1); + crng_reseed(NULL); return 0; default: return -EINVAL; @@ -1877,55 +1567,56 @@ static int random_fasync(int fd, struct file *filp, int on) } const struct file_operations random_fops = { - .read = random_read, - .write = random_write, + .read_iter = random_read_iter, + .write_iter = random_write_iter, .poll = random_poll, .unlocked_ioctl = random_ioctl, .compat_ioctl = compat_ptr_ioctl, .fasync = random_fasync, .llseek = noop_llseek, + .splice_read = copy_splice_read, + .splice_write = iter_file_splice_write, }; const struct file_operations urandom_fops = { - .read = urandom_read, - .write = random_write, + .read_iter = urandom_read_iter, + .write_iter = random_write_iter, .unlocked_ioctl = random_ioctl, .compat_ioctl = compat_ptr_ioctl, .fasync = random_fasync, .llseek = noop_llseek, + .splice_read = copy_splice_read, + .splice_write = iter_file_splice_write, }; -SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, - flags) -{ - 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 (count > INT_MAX) - count = INT_MAX; - - if (!(flags & GRND_INSECURE) && !crng_ready()) { - if (flags & GRND_NONBLOCK) - return -EAGAIN; - ret = wait_for_random_bytes(); - if (unlikely(ret)) - return ret; - } - return urandom_read_nowarn(NULL, buf, count, NULL); -} /******************************************************************** * - * Sysctl interface + * 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. * ********************************************************************/ @@ -1933,25 +1624,28 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, #include <linux/sysctl.h> -static int min_write_thresh; -static int max_write_thresh = POOL_BITS; -static int random_min_urandom_seed = 60; -static char sysctl_bootid[16]; +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, + * UUID. The difference is in whether table->data is NULL; if it is, * then a new UUID is generated and returned to the user. - * - * If the user accesses this via the proc interface, the UUID will be - * returned as an ASCII string in the standard UUID format; if via the - * sysctl system call, as 16 bytes of binary data. */ -static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, +static int proc_do_uuid(const struct ctl_table *table, int write, void *buf, size_t *lenp, loff_t *ppos) { - struct ctl_table fake_table; - unsigned char buf[64], tmp_uuid[16], *uuid; + 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) { @@ -1966,33 +1660,18 @@ static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, spin_unlock(&bootid_spinlock); } - sprintf(buf, "%pU", uuid); - - fake_table.data = buf; - fake_table.maxlen = sizeof(buf); - - return proc_dostring(&fake_table, write, buffer, lenp, ppos); + snprintf(uuid_string, sizeof(uuid_string), "%pU", uuid); + return proc_dostring(&fake_table, 0, buf, lenp, ppos); } -/* - * Return entropy available scaled to integral bits - */ -static int proc_do_entropy(struct ctl_table *table, int write, void *buffer, - size_t *lenp, loff_t *ppos) +/* The same as proc_dointvec, but writes don't change anything. */ +static int proc_do_rointvec(const struct ctl_table *table, int write, void *buf, + size_t *lenp, loff_t *ppos) { - struct ctl_table fake_table; - int entropy_count; - - entropy_count = *(int *)table->data >> POOL_ENTROPY_SHIFT; - - fake_table.data = &entropy_count; - fake_table.maxlen = sizeof(entropy_count); - - return proc_dointvec(&fake_table, write, buffer, lenp, ppos); + return write ? 0 : proc_dointvec(table, 0, buf, lenp, ppos); } -static int sysctl_poolsize = POOL_BITS; -static struct ctl_table random_table[] = { +static const struct ctl_table random_table[] = { { .procname = "poolsize", .data = &sysctl_poolsize, @@ -2002,62 +1681,41 @@ static struct ctl_table random_table[] = { }, { .procname = "entropy_avail", + .data = &input_pool.init_bits, .maxlen = sizeof(int), .mode = 0444, - .proc_handler = proc_do_entropy, - .data = &input_pool.entropy_count, + .proc_handler = proc_dointvec, }, { .procname = "write_wakeup_threshold", - .data = &random_write_wakeup_bits, + .data = &sysctl_random_write_wakeup_bits, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec_minmax, - .extra1 = &min_write_thresh, - .extra2 = &max_write_thresh, + .proc_handler = proc_do_rointvec, }, { .procname = "urandom_min_reseed_secs", - .data = &random_min_urandom_seed, + .data = &sysctl_random_min_urandom_seed, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec, + .proc_handler = proc_do_rointvec, }, { .procname = "boot_id", .data = &sysctl_bootid, - .maxlen = 16, .mode = 0444, .proc_handler = proc_do_uuid, }, { .procname = "uuid", - .maxlen = 16, .mode = 0444, .proc_handler = proc_do_uuid, }, -#ifdef ADD_INTERRUPT_BENCH - { - .procname = "add_interrupt_avg_cycles", - .data = &avg_cycles, - .maxlen = sizeof(avg_cycles), - .mode = 0444, - .proc_handler = proc_doulongvec_minmax, - }, - { - .procname = "add_interrupt_avg_deviation", - .data = &avg_deviation, - .maxlen = sizeof(avg_deviation), - .mode = 0444, - .proc_handler = proc_doulongvec_minmax, - }, -#endif - { } }; /* - * rand_initialize() is called before sysctl_init(), - * so we cannot call register_sysctl_init() in rand_initialize() + * random_init() is called before sysctl_init(), + * so we cannot call register_sysctl_init() in random_init() */ static int __init random_sysctls_init(void) { @@ -2065,168 +1723,4 @@ static int __init random_sysctls_init(void) return 0; } device_initcall(random_sysctls_init); -#endif /* CONFIG_SYSCTL */ - -struct batched_entropy { - union { - u64 entropy_u64[CHACHA_BLOCK_SIZE / sizeof(u64)]; - u32 entropy_u32[CHACHA_BLOCK_SIZE / sizeof(u32)]; - }; - unsigned int position; - spinlock_t batch_lock; -}; - -/* - * Get a random word for internal kernel use only. The quality of the random - * number is good as /dev/urandom, but there is no backtrack protection, with - * the goal of being quite fast and not depleting entropy. 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. - */ -static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = { - .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u64.lock), -}; - -u64 get_random_u64(void) -{ - u64 ret; - unsigned long flags; - struct batched_entropy *batch; - static void *previous; - - warn_unseeded_randomness(&previous); - - batch = raw_cpu_ptr(&batched_entropy_u64); - spin_lock_irqsave(&batch->batch_lock, flags); - if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) { - extract_crng((u8 *)batch->entropy_u64); - batch->position = 0; - } - ret = batch->entropy_u64[batch->position++]; - spin_unlock_irqrestore(&batch->batch_lock, flags); - return ret; -} -EXPORT_SYMBOL(get_random_u64); - -static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = { - .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u32.lock), -}; -u32 get_random_u32(void) -{ - u32 ret; - unsigned long flags; - struct batched_entropy *batch; - static void *previous; - - warn_unseeded_randomness(&previous); - - batch = raw_cpu_ptr(&batched_entropy_u32); - spin_lock_irqsave(&batch->batch_lock, flags); - if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) { - extract_crng((u8 *)batch->entropy_u32); - batch->position = 0; - } - ret = batch->entropy_u32[batch->position++]; - spin_unlock_irqrestore(&batch->batch_lock, flags); - return ret; -} -EXPORT_SYMBOL(get_random_u32); - -/* It's important to invalidate all potential batched entropy that might - * be stored before the crng is initialized, which we can do lazily by - * simply resetting the counter to zero so that it's re-extracted on the - * next usage. */ -static void invalidate_batched_entropy(void) -{ - int cpu; - unsigned long flags; - - for_each_possible_cpu(cpu) { - struct batched_entropy *batched_entropy; - - batched_entropy = per_cpu_ptr(&batched_entropy_u32, cpu); - spin_lock_irqsave(&batched_entropy->batch_lock, flags); - batched_entropy->position = 0; - spin_unlock(&batched_entropy->batch_lock); - - batched_entropy = per_cpu_ptr(&batched_entropy_u64, cpu); - spin_lock(&batched_entropy->batch_lock); - batched_entropy->position = 0; - spin_unlock_irqrestore(&batched_entropy->batch_lock, flags); - } -} - -/** - * 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); -} - -/* 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 char *buffer, size_t count, - size_t entropy) -{ - if (unlikely(crng_init == 0)) { - size_t ret = crng_fast_load(buffer, count); - mix_pool_bytes(buffer, ret); - count -= ret; - buffer += ret; - if (!count || crng_init == 0) - return; - } - - /* Suspend writing if we're above the trickle threshold. - * We'll be woken up again once below random_write_wakeup_thresh, - * or when the calling thread is about to terminate. - */ - wait_event_interruptible(random_write_wait, - !system_wq || kthread_should_stop() || - POOL_ENTROPY_BITS() <= random_write_wakeup_bits); - 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, unsigned int size) -{ - if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER)) - add_hwgenerator_randomness(buf, size, size * 8); - else - add_device_randomness(buf, size); -} -EXPORT_SYMBOL_GPL(add_bootloader_randomness); +#endif |