diff options
Diffstat (limited to 'drivers/char/random.c')
-rw-r--r-- | drivers/char/random.c | 3150 |
1 files changed, 1071 insertions, 2079 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 19bfbaf13598..364dd5eaebda 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1,311 +1,29 @@ +// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) /* - * random.c -- A strong random number generator - * - * Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All - * Rights Reserved. - * + * Copyright (C) 2017-2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005 - * - * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All - * rights reserved. - * - * 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. + * 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. */ -/* - * (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 SHA - * hash of the contents of the "entropy pool". The SHA 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 SHA from its output. Even if it is possible to - * analyze SHA 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 SHA, 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 or 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, int irq_flags); - * void add_disk_randomness(struct gendisk *disk); - * - * 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. - * - * 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. - */ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/utsname.h> #include <linux/module.h> @@ -325,8 +43,6 @@ #include <linux/spinlock.h> #include <linux/kthread.h> #include <linux/percpu.h> -#include <linux/cryptohash.h> -#include <linux/fips.h> #include <linux/ptrace.h> #include <linux/workqueue.h> #include <linux/irq.h> @@ -334,1425 +50,1085 @@ #include <linux/syscalls.h> #include <linux/completion.h> #include <linux/uuid.h> +#include <linux/uaccess.h> +#include <linux/siphash.h> +#include <linux/uio.h> #include <crypto/chacha.h> - +#include <crypto/blake2s.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 */ +/********************************************************************* + * + * Initialization and readiness waiting. + * + * Much of the RNG infrastructure is devoted to various dependencies + * being able to wait until the RNG has collected enough entropy and + * is ready for safe consumption. + * + *********************************************************************/ /* - * Configuration information + * crng_init is protected by base_crng->lock, and only increases + * its value (from empty->early->ready). */ -#define INPUT_POOL_SHIFT 12 -#define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5)) -#define OUTPUT_POOL_SHIFT 10 -#define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5)) -#define SEC_XFER_SIZE 512 -#define EXTRACT_SIZE 10 - +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; +#define crng_ready() (likely(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 DEFINE_SPINLOCK(random_ready_chain_lock); +static RAW_NOTIFIER_HEAD(random_ready_chain); -#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long)) +/* Control how we warn userspace. */ +static struct ratelimit_state urandom_warning = + 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"); /* - * To allow fractional bits to be tracked, the entropy_count field is - * denominated in units of 1/8th bits. + * Returns whether or not the input pool has been seeded and thus guaranteed + * to supply cryptographically secure random numbers. This applies to: the + * /dev/urandom device, the get_random_bytes function, and the get_random_{u32, + * ,u64,int,long} family of functions. * - * 2*(ENTROPY_SHIFT + poolbitshift) must <= 31, or the multiply in - * credit_entropy_bits() needs to be 64 bits wide. + * Returns: true if the input pool has been seeded. + * false if the input pool has not been seeded. */ -#define ENTROPY_SHIFT 3 -#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT) +bool rng_is_initialized(void) +{ + return crng_ready(); +} +EXPORT_SYMBOL(rng_is_initialized); -/* - * The minimum number of bits of entropy before we wake up a read on - * /dev/random. Should be enough to do a significant reseed. - */ -static int random_read_wakeup_bits = 64; +/* Used by wait_for_random_bytes(), and considered an entropy collector, below. */ +static void try_to_generate_entropy(void); /* - * 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. + * Wait for the input pool to be seeded and thus guaranteed to supply + * cryptographically secure random numbers. This applies to: the /dev/urandom + * device, the get_random_bytes function, and the get_random_{u32,u64,int,long} + * family of functions. Using any of these functions without first calling + * this function forfeits the guarantee of security. + * + * Returns: 0 if the input pool has been seeded. + * -ERESTARTSYS if the function was interrupted by a signal. */ -static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS; +int wait_for_random_bytes(void) +{ + while (!crng_ready()) { + int ret; + + try_to_generate_entropy(); + ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ); + if (ret) + return ret > 0 ? 0 : ret; + } + return 0; +} +EXPORT_SYMBOL(wait_for_random_bytes); /* - * 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. - * - * The mixing operation is much less sensitive than the output hash, - * where we use SHA-1. 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). + * Add a callback function that will be invoked when the input + * pool is initialised. * - * 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. + * returns: 0 if callback is successfully added + * -EALREADY if pool is already initialised (callback not called) */ -static const struct poolinfo { - int poolbitshift, poolwords, poolbytes, poolfracbits; -#define S(x) ilog2(x)+5, (x), (x)*4, (x) << (ENTROPY_SHIFT+5) - int tap1, tap2, tap3, tap4, tap5; -} poolinfo_table[] = { - /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */ - /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */ - { S(128), 104, 76, 51, 25, 1 }, - /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */ - /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */ - { S(32), 26, 19, 14, 7, 1 }, -#if 0 - /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */ - { S(2048), 1638, 1231, 819, 411, 1 }, - - /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */ - { S(1024), 817, 615, 412, 204, 1 }, - - /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */ - { S(1024), 819, 616, 410, 207, 2 }, - - /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */ - { S(512), 411, 308, 208, 104, 1 }, - - /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */ - { S(512), 409, 307, 206, 102, 2 }, - /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */ - { S(512), 409, 309, 205, 103, 2 }, - - /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */ - { S(256), 205, 155, 101, 52, 1 }, - - /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */ - { S(128), 103, 78, 51, 27, 2 }, - - /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */ - { S(64), 52, 39, 26, 14, 1 }, -#endif -}; +int __cold register_random_ready_notifier(struct notifier_block *nb) +{ + unsigned long flags; + int ret = -EALREADY; + + if (crng_ready()) + return ret; + + spin_lock_irqsave(&random_ready_chain_lock, flags); + if (!crng_ready()) + ret = raw_notifier_chain_register(&random_ready_chain, nb); + spin_unlock_irqrestore(&random_ready_chain_lock, flags); + return ret; +} /* - * Static global variables + * Delete a previously registered readiness callback function. */ -static DECLARE_WAIT_QUEUE_HEAD(random_read_wait); -static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); -static struct fasync_struct *fasync; - -static DEFINE_SPINLOCK(random_ready_list_lock); -static LIST_HEAD(random_ready_list); +int __cold unregister_random_ready_notifier(struct notifier_block *nb) +{ + unsigned long flags; + int ret; -struct crng_state { - __u32 state[16]; - unsigned long init_time; - spinlock_t lock; -}; + spin_lock_irqsave(&random_ready_chain_lock, flags); + ret = raw_notifier_chain_unregister(&random_ready_chain, nb); + spin_unlock_irqrestore(&random_ready_chain_lock, flags); + return ret; +} -static struct crng_state primary_crng = { - .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock), -}; +static void __cold process_random_ready_list(void) +{ + unsigned long flags; -/* - * 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); -static struct ratelimit_state urandom_warning = - RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3); + spin_lock_irqsave(&random_ready_chain_lock, flags); + raw_notifier_call_chain(&random_ready_chain, 0, NULL); + spin_unlock_irqrestore(&random_ready_chain_lock, flags); +} -static int ratelimit_disable __read_mostly; +#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) -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. + * 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) + * u32 get_random_u32() + * u64 get_random_u64() + * unsigned int get_random_int() + * unsigned long get_random_long() + * + * These interfaces will return the requested number of random bytes + * into the given buffer or as a return value. This is equivalent to + * a read from /dev/urandom. The u32, u64, int, and 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. + * + *********************************************************************/ -struct entropy_store; -struct entropy_store { - /* read-only data: */ - const struct poolinfo *poolinfo; - __u32 *pool; - const char *name; - struct entropy_store *pull; - struct work_struct push_work; - - /* read-write data: */ - unsigned long last_pulled; - spinlock_t lock; - unsigned short add_ptr; - unsigned short input_rotate; - int entropy_count; - unsigned int initialized:1; - unsigned int last_data_init:1; - __u8 last_data[EXTRACT_SIZE]; +enum { + CRNG_RESEED_START_INTERVAL = HZ, + CRNG_RESEED_INTERVAL = 60 * HZ }; -static ssize_t extract_entropy(struct entropy_store *r, void *buf, - size_t nbytes, int min, int rsvd); -static ssize_t _extract_entropy(struct entropy_store *r, void *buf, - size_t nbytes, int fips); - -static void crng_reseed(struct crng_state *crng, struct entropy_store *r); -static void push_to_pool(struct work_struct *work); -static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy; -static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy; - -static struct entropy_store input_pool = { - .poolinfo = &poolinfo_table[0], - .name = "input", - .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), - .pool = input_pool_data +static struct { + u8 key[CHACHA_KEY_SIZE] __aligned(__alignof__(long)); + unsigned long birth; + unsigned long generation; + spinlock_t lock; +} base_crng = { + .lock = __SPIN_LOCK_UNLOCKED(base_crng.lock) }; -static struct entropy_store blocking_pool = { - .poolinfo = &poolinfo_table[1], - .name = "blocking", - .pull = &input_pool, - .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock), - .pool = blocking_pool_data, - .push_work = __WORK_INITIALIZER(blocking_pool.push_work, - push_to_pool), +struct crng { + u8 key[CHACHA_KEY_SIZE]; + unsigned long generation; }; -static __u32 const 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. - * - * 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. - */ -static void _mix_pool_bytes(struct entropy_store *r, const void *in, - int nbytes) -{ - unsigned long i, tap1, tap2, tap3, tap4, tap5; - int input_rotate; - int wordmask = r->poolinfo->poolwords - 1; - const char *bytes = in; - __u32 w; - - tap1 = r->poolinfo->tap1; - tap2 = r->poolinfo->tap2; - tap3 = r->poolinfo->tap3; - tap4 = r->poolinfo->tap4; - tap5 = r->poolinfo->tap5; - - input_rotate = r->input_rotate; - i = r->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) & wordmask; - - /* XOR in the various taps */ - w ^= r->pool[i]; - w ^= r->pool[(i + tap1) & wordmask]; - w ^= r->pool[(i + tap2) & wordmask]; - w ^= r->pool[(i + tap3) & wordmask]; - w ^= r->pool[(i + tap4) & wordmask]; - w ^= r->pool[(i + tap5) & wordmask]; - - /* Mix the result back in with a twist */ - r->pool[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; - } - - r->input_rotate = input_rotate; - r->add_ptr = i; -} +static DEFINE_PER_CPU(struct crng, crngs) = { + .generation = ULONG_MAX +}; -static void __mix_pool_bytes(struct entropy_store *r, const void *in, - int nbytes) -{ - trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_); - _mix_pool_bytes(r, in, nbytes); -} +/* 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); -static void mix_pool_bytes(struct entropy_store *r, const void *in, - int nbytes) +/* This extracts a new crng key from the input pool. */ +static void crng_reseed(void) { unsigned long flags; + unsigned long next_gen; + u8 key[CHACHA_KEY_SIZE]; - trace_mix_pool_bytes(r->name, nbytes, _RET_IP_); - spin_lock_irqsave(&r->lock, flags); - _mix_pool_bytes(r, in, nbytes); - spin_unlock_irqrestore(&r->lock, flags); -} + extract_entropy(key, sizeof(key)); -struct fast_pool { - __u32 pool[4]; - unsigned long last; - unsigned short reg_idx; - unsigned char count; -}; + /* + * We copy the new key into the base_crng, overwriting the old one, + * and update the generation counter. We avoid hitting ULONG_MAX, + * because the per-cpu crngs are initialized to ULONG_MAX, so this + * forces new CPUs that come online to always initialize. + */ + spin_lock_irqsave(&base_crng.lock, flags); + memcpy(base_crng.key, key, sizeof(base_crng.key)); + next_gen = base_crng.generation + 1; + if (next_gen == ULONG_MAX) + ++next_gen; + WRITE_ONCE(base_crng.generation, next_gen); + WRITE_ONCE(base_crng.birth, jiffies); + if (!crng_ready()) + crng_init = CRNG_READY; + spin_unlock_irqrestore(&base_crng.lock, flags); + memzero_explicit(key, sizeof(key)); +} /* - * 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. + * This generates a ChaCha block using the provided key, and then + * immediately overwites that key with half the block. It returns + * the resultant ChaCha state to the user, along with the second + * half of the block containing 32 bytes of random data that may + * be used; random_data_len may not be greater than 32. + * + * 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[4] so + * that this function overwrites it before returning. */ -static void fast_mix(struct fast_pool *f) +static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE], + u32 chacha_state[CHACHA_BLOCK_SIZE / sizeof(u32)], + u8 *random_data, size_t random_data_len) { - __u32 a = f->pool[0], b = f->pool[1]; - __u32 c = f->pool[2], d = f->pool[3]; - - a += b; c += d; - b = rol32(b, 6); d = rol32(d, 27); - d ^= a; b ^= c; + u8 first_block[CHACHA_BLOCK_SIZE]; - a += b; c += d; - b = rol32(b, 16); d = rol32(d, 14); - d ^= a; b ^= c; + BUG_ON(random_data_len > 32); - a += b; c += d; - b = rol32(b, 6); d = rol32(d, 27); - d ^= a; b ^= c; + chacha_init_consts(chacha_state); + memcpy(&chacha_state[4], key, CHACHA_KEY_SIZE); + memset(&chacha_state[12], 0, sizeof(u32) * 4); + chacha20_block(chacha_state, first_block); - a += b; c += d; - b = rol32(b, 16); d = rol32(d, 14); - d ^= a; b ^= c; - - f->pool[0] = a; f->pool[1] = b; - f->pool[2] = c; f->pool[3] = d; - f->count++; + 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)); } -static void process_random_ready_list(void) -{ - unsigned long flags; - struct random_ready_callback *rdy, *tmp; - - spin_lock_irqsave(&random_ready_list_lock, flags); - list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) { - struct module *owner = rdy->owner; - - list_del_init(&rdy->list); - rdy->func(rdy); - module_put(owner); +/* + * Return whether the crng seed is considered to be sufficiently old + * that a reseeding is needed. This happens if the last reseeding + * was CRNG_RESEED_INTERVAL ago, or during early boot, at an interval + * proportional to the uptime. + */ +static bool crng_has_old_seed(void) +{ + static bool early_boot = true; + unsigned long interval = CRNG_RESEED_INTERVAL; + + 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 + interval = max_t(unsigned int, CRNG_RESEED_START_INTERVAL, + (unsigned int)uptime / 2 * HZ); } - spin_unlock_irqrestore(&random_ready_list_lock, flags); + return time_is_before_jiffies(READ_ONCE(base_crng.birth) + interval); } /* - * 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. + * This function returns a ChaCha state that you may use for generating + * random data. It also returns up to 32 bytes on its own of random data + * that may be used; random_data_len may not be greater than 32. */ -static void credit_entropy_bits(struct entropy_store *r, int nbits) +static void crng_make_state(u32 chacha_state[CHACHA_BLOCK_SIZE / sizeof(u32)], + u8 *random_data, size_t random_data_len) { - int entropy_count, orig, has_initialized = 0; - const int pool_size = r->poolinfo->poolfracbits; - int nfrac = nbits << ENTROPY_SHIFT; - - if (!nbits) - return; - -retry: - entropy_count = orig = READ_ONCE(r->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 = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2; - /* The +2 corresponds to the /4 in the denominator */ - - do { - unsigned int anfrac = min(pnfrac, pool_size/2); - unsigned int add = - ((pool_size - entropy_count)*anfrac*3) >> s; - - entropy_count += add; - pnfrac -= anfrac; - } while (unlikely(entropy_count < pool_size-2 && pnfrac)); - } - - if (unlikely(entropy_count < 0)) { - pr_warn("random: negative entropy/overflow: pool %s count %d\n", - r->name, entropy_count); - WARN_ON(1); - entropy_count = 0; - } else if (entropy_count > pool_size) - entropy_count = pool_size; - if ((r == &blocking_pool) && !r->initialized && - (entropy_count >> ENTROPY_SHIFT) > 128) - has_initialized = 1; - if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) - goto retry; - - if (has_initialized) { - r->initialized = 1; - wake_up_interruptible(&random_read_wait); - kill_fasync(&fasync, SIGIO, POLL_IN); - } - - trace_credit_entropy_bits(r->name, nbits, - entropy_count >> ENTROPY_SHIFT, _RET_IP_); + unsigned long flags; + struct crng *crng; - if (r == &input_pool) { - int entropy_bits = entropy_count >> ENTROPY_SHIFT; - struct entropy_store *other = &blocking_pool; + BUG_ON(random_data_len > 32); - if (crng_init < 2) { - if (entropy_bits < 128) - return; - crng_reseed(&primary_crng, r); - entropy_bits = r->entropy_count >> ENTROPY_SHIFT; + /* + * 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); } - - /* initialize the blocking pool if necessary */ - if (entropy_bits >= random_read_wakeup_bits && - !other->initialized) { - schedule_work(&other->push_work); + spin_unlock_irqrestore(&base_crng.lock, flags); + if (!ready) return; - } - - /* should we wake readers? */ - if (entropy_bits >= random_read_wakeup_bits && - wq_has_sleeper(&random_read_wait)) { - wake_up_interruptible(&random_read_wait); - kill_fasync(&fasync, SIGIO, POLL_IN); - } - /* If the input pool is getting full, and the blocking - * pool has room, send some entropy to the blocking - * pool. - */ - if (!work_pending(&other->push_work) && - (ENTROPY_BITS(r) > 6 * r->poolinfo->poolbytes) && - (ENTROPY_BITS(other) <= 6 * other->poolinfo->poolbytes)) - schedule_work(&other->push_work); } -} -static int credit_entropy_bits_safe(struct entropy_store *r, int nbits) -{ - const int nbits_max = r->poolinfo->poolwords * 32; + /* + * If the base_crng is old enough, we reseed, which in turn bumps the + * generation counter that we check below. + */ + if (unlikely(crng_has_old_seed())) + crng_reseed(); - if (nbits < 0) - return -EINVAL; + local_irq_save(flags); + crng = raw_cpu_ptr(&crngs); - /* Cap the value to avoid overflows */ - nbits = min(nbits, nbits_max); + /* + * 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); + } - credit_entropy_bits(r, nbits); - return 0; + /* + * 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_irq_restore(flags); } -/********************************************************************* - * - * CRNG using CHACHA20 - * - *********************************************************************/ +static void _get_random_bytes(void *buf, size_t len) +{ + u32 chacha_state[CHACHA_BLOCK_SIZE / sizeof(u32)]; + u8 tmp[CHACHA_BLOCK_SIZE]; + size_t first_block_len; -#define CRNG_RESEED_INTERVAL (300*HZ) + if (!len) + return; -static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); + 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; -#ifdef CONFIG_NUMA -/* - * 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. - */ -static struct crng_state **crng_node_pool __read_mostly; -#endif + while (len) { + if (len < CHACHA_BLOCK_SIZE) { + chacha20_block(chacha_state, tmp); + memcpy(buf, tmp, len); + memzero_explicit(tmp, sizeof(tmp)); + break; + } -static void invalidate_batched_entropy(void); -static void numa_crng_init(void); + chacha20_block(chacha_state, buf); + if (unlikely(chacha_state[12] == 0)) + ++chacha_state[13]; + len -= CHACHA_BLOCK_SIZE; + buf += CHACHA_BLOCK_SIZE; + } -static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); -static int __init parse_trust_cpu(char *arg) -{ - return kstrtobool(arg, &trust_cpu); + memzero_explicit(chacha_state, sizeof(chacha_state)); } -early_param("random.trust_cpu", parse_trust_cpu); -static void crng_initialize(struct crng_state *crng) +/* + * This function is the exported kernel interface. It returns some + * number of good random numbers, suitable for key generation, seeding + * TCP sequence numbers, etc. It does not rely on the hardware random + * number generator. For random bytes direct from the hardware RNG + * (when available), use get_random_bytes_arch(). In order to ensure + * that the randomness provided by this function is okay, the function + * wait_for_random_bytes() should be called and return 0 at least once + * at any point prior. + */ +void get_random_bytes(void *buf, size_t len) { - int i; - int arch_init = 1; - unsigned long rv; - - memcpy(&crng->state[0], "expand 32-byte k", 16); - if (crng == &primary_crng) - _extract_entropy(&input_pool, &crng->state[4], - sizeof(__u32) * 12, 0); - else - _get_random_bytes(&crng->state[4], sizeof(__u32) * 12); - for (i = 4; i < 16; i++) { - if (!arch_get_random_seed_long(&rv) && - !arch_get_random_long(&rv)) { - rv = random_get_entropy(); - arch_init = 0; - } - crng->state[i] ^= rv; - } - if (trust_cpu && arch_init && crng == &primary_crng) { - invalidate_batched_entropy(); - numa_crng_init(); - crng_init = 2; - pr_notice("random: crng done (trusting CPU's manufacturer)\n"); - } - crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1; + warn_unseeded_randomness(); + _get_random_bytes(buf, len); } +EXPORT_SYMBOL(get_random_bytes); -static void crng_finalize_init(struct crng_state *crng) +static ssize_t get_random_bytes_user(struct iov_iter *iter) { - if (crng != &primary_crng || crng_init >= 2) - 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; - } + u32 chacha_state[CHACHA_BLOCK_SIZE / sizeof(u32)]; + u8 block[CHACHA_BLOCK_SIZE]; + size_t ret = 0, copied; - 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("random: %d get_random_xx warning(s) missed " - "due to ratelimiting\n", - unseeded_warning.missed); - unseeded_warning.missed = 0; - } - if (urandom_warning.missed) { - pr_notice("random: %d urandom warning(s) missed " - "due to ratelimiting\n", - urandom_warning.missed); - urandom_warning.missed = 0; - } -} + if (unlikely(!iov_iter_count(iter))) + return 0; -#ifdef CONFIG_NUMA -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(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); + /* + * 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[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[4], CHACHA_KEY_SIZE, iter); + goto out_zero_chacha; } -} -static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init); + for (;;) { + chacha20_block(chacha_state, block); + if (unlikely(chacha_state[12] == 0)) + ++chacha_state[13]; -static void numa_crng_init(void) -{ - schedule_work(&numa_crng_init_work); -} - -static struct crng_state *select_crng(void) -{ - struct crng_state **pool; - int nid = numa_node_id(); + copied = copy_to_iter(block, sizeof(block), iter); + ret += copied; + if (!iov_iter_count(iter) || copied != sizeof(block)) + break; - /* pairs with cmpxchg_release() in do_numa_crng_init() */ - pool = READ_ONCE(crng_node_pool); - if (pool && pool[nid]) - return pool[nid]; + BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0); + if (ret % PAGE_SIZE == 0) { + if (signal_pending(current)) + break; + cond_resched(); + } + } - return &primary_crng; + memzero_explicit(block, sizeof(block)); +out_zero_chacha: + memzero_explicit(chacha_state, sizeof(chacha_state)); + return ret ? ret : -EFAULT; } -#else -static void numa_crng_init(void) {} - -static struct crng_state *select_crng(void) -{ - return &primary_crng; -} -#endif /* - * 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. + * Batched entropy returns random integers. The quality of the random + * number is good as /dev/urandom. In order to ensure that the randomness + * provided by this function is okay, the function wait_for_random_bytes() + * should be called and return 0 at least once at any point prior. */ -static size_t crng_fast_load(const char *cp, size_t len) -{ - unsigned long flags; - char *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 = (unsigned char *) &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; - wake_up_interruptible(&crng_init_wait); - pr_notice("random: fast init done\n"); - } - return ret; -} +#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))]; \ + unsigned long generation; \ + unsigned int position; \ +}; \ + \ +static DEFINE_PER_CPU(struct batch_ ##type, batched_entropy_ ##type) = { \ + .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_irq_save(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_irq_restore(flags); \ + return ret; \ +} \ +EXPORT_SYMBOL(get_random_ ##type); + +DEFINE_BATCHED_ENTROPY(u64) +DEFINE_BATCHED_ENTROPY(u32) + +#ifdef CONFIG_SMP /* - * 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. + * This function is called when the CPU is coming up, with entry + * CPUHP_RANDOM_PREPARE, which comes before CPUHP_WORKQUEUE_PREP. */ -static int crng_slow_load(const char *cp, size_t len) -{ - unsigned long flags; - static unsigned char lfsr = 1; - unsigned char tmp; - unsigned i, max = CHACHA_KEY_SIZE; - const char * src_buf = cp; - char * dest_buf = (char *) &primary_crng.state[4]; - - if (!spin_trylock_irqsave(&primary_crng.lock, flags)) - return 0; - if (crng_init != 0) { - spin_unlock_irqrestore(&primary_crng.lock, flags); - 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, struct entropy_store *r) -{ - unsigned long flags; - int i, num; - union { - __u8 block[CHACHA_BLOCK_SIZE]; - __u32 key[8]; - } buf; - - if (r) { - num = extract_entropy(r, &buf, 32, 16, 0); - 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; - } - 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]) +int __cold random_prepare_cpu(unsigned int cpu) { - unsigned long v, flags, init_time; - - 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 ? - &input_pool : NULL); - } - spin_lock_irqsave(&crng->lock, flags); - if (arch_get_random_long(&v)) - crng->state[14] ^= v; - 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); + /* + * When the cpu comes back online, immediately invalidate both + * the per-cpu crng and all batches, so that we serve fresh + * randomness. + */ + per_cpu_ptr(&crngs, cpu)->generation = ULONG_MAX; + per_cpu_ptr(&batched_entropy_u32, cpu)->position = UINT_MAX; + per_cpu_ptr(&batched_entropy_u64, cpu)->position = UINT_MAX; + return 0; } +#endif /* - * Use the leftover bytes from the CRNG block output (if there is - * enough) to mutate the CRNG key to provide backtracking protection. + * This function will use the architecture-specific hardware random + * number generator if it is available. It is not recommended for + * use. Use get_random_bytes() instead. It returns the number of + * bytes filled in. */ -static void _crng_backtrack_protect(struct crng_state *crng, - __u8 tmp[CHACHA_BLOCK_SIZE], int used) -{ - unsigned long flags; - __u32 *s, *d; - int i; - - used = round_up(used, sizeof(__u32)); - if (used + CHACHA_KEY_SIZE > CHACHA_BLOCK_SIZE) { - extract_crng(tmp); - used = 0; - } - 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); -} - -static void crng_backtrack_protect(__u8 tmp[CHACHA_BLOCK_SIZE], int used) +size_t __must_check get_random_bytes_arch(void *buf, size_t len) { - _crng_backtrack_protect(select_crng(), tmp, used); -} + size_t left = len; + u8 *p = buf; -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(); - } + while (left) { + unsigned long v; + size_t block_len = min_t(size_t, left, sizeof(unsigned long)); - extract_crng(tmp); - i = min_t(int, nbytes, CHACHA_BLOCK_SIZE); - if (copy_to_user(buf, tmp, i)) { - ret = -EFAULT; + if (!arch_get_random_long(&v)) break; - } - nbytes -= i; - buf += i; - ret += i; + memcpy(p, &v, block_len); + p += block_len; + left -= block_len; } - crng_backtrack_protect(tmp, i); - /* Wipe data just written to memory */ - memzero_explicit(tmp, sizeof(tmp)); - - return ret; + return len - left; } +EXPORT_SYMBOL(get_random_bytes_arch); -/********************************************************************* +/********************************************************************** * - * 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 */ +}; + +static struct { + struct blake2s_state hash; + spinlock_t lock; + unsigned int init_bits; +} input_pool = { + .hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE), + BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4, + BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 }, + .hash.outlen = BLAKE2S_HASH_SIZE, + .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), }; -#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, }; +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(&input_pool, buf, size); - _mix_pool_bytes(&input_pool, &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) { - struct entropy_store *r; + unsigned long flags; + u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE]; struct { - long jiffies; - unsigned cycles; - unsigned num; - } sample; - long delta, delta2, delta3; - - sample.jiffies = jiffies; - sample.cycles = random_get_entropy(); - sample.num = num; - r = &input_pool; - mix_pool_bytes(r, &sample, sizeof(sample)); + unsigned long rdseed[32 / sizeof(long)]; + size_t counter; + } block; + size_t i; + + for (i = 0; i < ARRAY_SIZE(block.rdseed); ++i) { + if (!arch_get_random_seed_long(&block.rdseed[i]) && + !arch_get_random_long(&block.rdseed[i])) + block.rdseed[i] = random_get_entropy(); + } - /* - * 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(next_key, (u8 *)&block, seed, sizeof(next_key), sizeof(block), sizeof(seed)); + blake2s_init_key(&input_pool.hash, BLAKE2S_HASH_SIZE, next_key, sizeof(next_key)); - 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(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed)); + len -= i; + buf += i; + } - /* - * delta is now minimum absolute delta. - * Round down by 1 bit on general principles, - * and limit entropy entimate to 12 bits. - */ - credit_entropy_bits(r, 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; + unsigned int new, orig, add; + unsigned long flags; - /* 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(ENTROPY_BITS(&input_pool)); -} -EXPORT_SYMBOL_GPL(add_input_randomness); + add = min_t(size_t, bits, POOL_BITS); -static DEFINE_PER_CPU(struct fast_pool, irq_randomness); + do { + orig = READ_ONCE(input_pool.init_bits); + new = min_t(unsigned int, POOL_BITS, orig + add); + } while (cmpxchg(&input_pool.init_bits, orig, new) != orig); -#ifdef ADD_INTERRUPT_BENCH -static unsigned long avg_cycles, avg_deviation; + if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) { + crng_reseed(); /* Sets crng_init to CRNG_READY under base_crng.lock. */ + process_random_ready_list(); + wake_up_interruptible(&crng_init_wait); + kill_fasync(&fasync, SIGIO, POLL_IN); + pr_notice("crng init done\n"); + if (urandom_warning.missed) + pr_notice("%d urandom warning(s) missed due to ratelimiting\n", + urandom_warning.missed); + } else if (orig < POOL_EARLY_BITS && new >= POOL_EARLY_BITS) { + spin_lock_irqsave(&base_crng.lock, flags); + /* Check if crng_init is CRNG_EMPTY, to avoid race with crng_reseed(). */ + if (crng_init == CRNG_EMPTY) { + extract_entropy(base_crng.key, sizeof(base_crng.key)); + crng_init = CRNG_EARLY; + } + spin_unlock_irqrestore(&base_crng.lock, flags); + } +} -#define AVG_SHIFT 8 /* Exponential average factor k=1/256 */ -#define FIXED_1_2 (1 << (AVG_SHIFT-1)) -static void add_interrupt_bench(cycles_t start) +/********************************************************************** + * + * Entropy collection routines. + * + * The following exported functions are used for pushing entropy into + * the above entropy accumulation routines: + * + * void add_device_randomness(const void *buf, size_t len); + * void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy); + * void add_bootloader_randomness(const void *buf, size_t len); + * void add_interrupt_randomness(int irq); + * void add_input_randomness(unsigned int type, unsigned int code, unsigned int value); + * void add_disk_randomness(struct gendisk *disk); + * + * add_device_randomness() adds data to the input pool that + * is likely to differ between two devices (or possibly even per boot). + * This would be things like MAC addresses or serial numbers, or the + * read-out of the RTC. This does *not* credit any actual entropy to + * the pool, but it initializes the pool to different values for devices + * that might otherwise be identical and have very little entropy + * available to them (particularly common in the embedded world). + * + * add_hwgenerator_randomness() is for true hardware RNGs, and will credit + * entropy as specified by the caller. If the entropy pool is full it will + * block until more entropy is needed. + * + * add_bootloader_randomness() is called by bootloader drivers, such as EFI + * and device tree, and credits its input depending on whether or not the + * configuration option CONFIG_RANDOM_TRUST_BOOTLOADER is set. + * + * add_interrupt_randomness() uses the interrupt timing as random + * inputs to the entropy pool. Using the cycle counters and the irq source + * as inputs, it feeds the input pool roughly once a second or after 64 + * interrupts, crediting 1 bit of entropy for whichever comes first. + * + * add_input_randomness() uses the input layer interrupt timing, as well + * as the event type information from the hardware. + * + * add_disk_randomness() uses what amounts to the seek time of block + * layer request events, on a per-disk_devt basis, as input to the + * entropy pool. Note that high-speed solid state drives with very low + * seek times do not make for good sources of entropy, as their seek + * times are usually fairly consistent. + * + * The last two routines try to estimate how many bits of entropy + * to credit. They do this by keeping track of the first and second + * order deltas of the event timings. + * + **********************************************************************/ + +static bool trust_cpu __initdata = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); +static bool trust_bootloader __initdata = IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER); +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, int irq_flags) +/* + * The first collection of entropy occurs at system boot while interrupts + * are still turned off. Here we push in latent entropy, RDSEED, a timestamp, + * utsname(), and the command line. Depending on the above configuration knob, + * RDSEED may be considered sufficient for initialization. Note that much + * earlier setup may already have pushed entropy into the input pool by the + * time we get here. + */ +int __init random_init(const char *command_line) { - struct entropy_store *r; - 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; - unsigned long seed; - int credit = 0; - - 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((char *) 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; - - r = &input_pool; - if (!spin_trylock(&r->lock)) - return; + ktime_t now = ktime_get_real(); + unsigned int i, arch_bits; + unsigned long entropy; - fast_pool->last = now; - __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool)); +#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 - /* - * If we have architectural seed generator, produce a seed and - * add it to the pool. For the sake of paranoia don't let the - * architectural seed generator dominate the input from the - * interrupt noise. - */ - if (arch_get_random_seed_long(&seed)) { - __mix_pool_bytes(r, &seed, sizeof(seed)); - credit = 1; + for (i = 0, arch_bits = BLAKE2S_BLOCK_SIZE * 8; + i < BLAKE2S_BLOCK_SIZE; i += sizeof(entropy)) { + if (!arch_get_random_seed_long_early(&entropy) && + !arch_get_random_long_early(&entropy)) { + entropy = random_get_entropy(); + arch_bits -= sizeof(entropy) * 8; + } + _mix_pool_bytes(&entropy, sizeof(entropy)); } - spin_unlock(&r->lock); + _mix_pool_bytes(&now, sizeof(now)); + _mix_pool_bytes(utsname(), sizeof(*(utsname()))); + _mix_pool_bytes(command_line, strlen(command_line)); + add_latent_entropy(); - fast_pool->count = 0; - - /* award one bit for the contents of the fast pool */ - credit_entropy_bits(r, credit + 1); -} -EXPORT_SYMBOL_GPL(add_interrupt_randomness); + if (crng_ready()) + crng_reseed(); + else if (trust_cpu) + _credit_init_bits(arch_bits); -#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), ENTROPY_BITS(&input_pool)); + return 0; } -EXPORT_SYMBOL_GPL(add_disk_randomness); -#endif - -/********************************************************************* - * - * Entropy extraction routines - * - *********************************************************************/ /* - * This utility inline function is responsible for transferring entropy - * from the primary pool to the secondary extraction pool. We make - * sure we pull enough for a 'catastrophic reseed'. + * 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. */ -static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes); -static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes) +void add_device_randomness(const void *buf, size_t len) { - if (!r->pull || - r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) || - r->entropy_count > r->poolinfo->poolfracbits) - return; + unsigned long entropy = random_get_entropy(); + unsigned long flags; - _xfer_secondary_pool(r, nbytes); + 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); -static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes) +/* + * Interface for in-kernel drivers of true hardware RNGs. + * Those devices may produce endless random bits and will be throttled + * when our pool is full. + */ +void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy) { - __u32 tmp[OUTPUT_POOL_WORDS]; - - int bytes = nbytes; + mix_pool_bytes(buf, len); + credit_init_bits(entropy); - /* pull at least as much as a wakeup */ - bytes = max_t(int, bytes, random_read_wakeup_bits / 8); - /* but never more than the buffer size */ - bytes = min_t(int, bytes, sizeof(tmp)); - - trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8, - ENTROPY_BITS(r), ENTROPY_BITS(r->pull)); - bytes = extract_entropy(r->pull, tmp, bytes, - random_read_wakeup_bits / 8, 0); - mix_pool_bytes(r, tmp, bytes); - credit_entropy_bits(r, bytes*8); + /* + * Throttle writing to once every CRNG_RESEED_INTERVAL, unless + * we're not yet initialized. + */ + if (!kthread_should_stop() && crng_ready()) + schedule_timeout_interruptible(CRNG_RESEED_INTERVAL); } +EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); /* - * Used as a workqueue function so that when the input pool is getting - * full, we can "spill over" some entropy to the output pools. That - * way the output pools can store some of the excess entropy instead - * of letting it go to waste. + * Handle random seed passed by bootloader, and credit it if + * CONFIG_RANDOM_TRUST_BOOTLOADER is set. */ -static void push_to_pool(struct work_struct *work) +void __init add_bootloader_randomness(const void *buf, size_t len) { - struct entropy_store *r = container_of(work, struct entropy_store, - push_work); - BUG_ON(!r); - _xfer_secondary_pool(r, random_read_wakeup_bits/8); - trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT, - r->pull->entropy_count >> ENTROPY_SHIFT); + mix_pool_bytes(buf, len); + if (trust_bootloader) + credit_init_bits(len * 8); } -/* - * This function decides how many bytes to actually take from the - * given pool, and also debits the entropy count accordingly. - */ -static size_t account(struct entropy_store *r, size_t nbytes, int min, - int reserved) -{ - int entropy_count, orig, have_bytes; - size_t ibytes, nfrac; - - BUG_ON(r->entropy_count > r->poolinfo->poolfracbits); - - /* Can we pull enough? */ -retry: - entropy_count = orig = READ_ONCE(r->entropy_count); - ibytes = nbytes; - /* never pull more than available */ - have_bytes = entropy_count >> (ENTROPY_SHIFT + 3); - - if ((have_bytes -= reserved) < 0) - have_bytes = 0; - ibytes = min_t(size_t, ibytes, have_bytes); - if (ibytes < min) - ibytes = 0; - - if (unlikely(entropy_count < 0)) { - pr_warn("random: negative entropy count: pool %s count %d\n", - r->name, entropy_count); - WARN_ON(1); - entropy_count = 0; - } - nfrac = ibytes << (ENTROPY_SHIFT + 3); - if ((size_t) entropy_count > nfrac) - entropy_count -= nfrac; - else - entropy_count = 0; +struct fast_pool { + unsigned long pool[4]; + unsigned long last; + unsigned int count; + struct timer_list mix; +}; - if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) - goto retry; +static void mix_interrupt_randomness(struct timer_list *work); - trace_debit_entropy(r->name, 8 * ibytes); - if (ibytes && - (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) { - wake_up_interruptible(&random_write_wait); - kill_fasync(&fasync, SIGIO, POLL_OUT); - } +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) +}; - return ibytes; +/* + * This is [Half]SipHash-1-x, starting from an empty key. Because + * the key is fixed, it assumes that its inputs are non-malicious, + * and therefore this has no security on its own. s represents the + * four-word SipHash state, while v represents a two-word input. + */ +static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2) +{ + s[3] ^= v1; + FASTMIX_PERM(s[0], s[1], s[2], s[3]); + s[0] ^= v1; + s[3] ^= v2; + FASTMIX_PERM(s[0], s[1], s[2], s[3]); + s[0] ^= v2; } +#ifdef CONFIG_SMP /* - * This function does the actual extraction for extract_entropy and - * extract_entropy_user. - * - * Note: we assume that .poolwords is a multiple of 16 words. + * This function is called when the CPU has just come online, with + * entry CPUHP_AP_RANDOM_ONLINE, just after CPUHP_AP_WORKQUEUE_ONLINE. */ -static void extract_buf(struct entropy_store *r, __u8 *out) +int __cold random_online_cpu(unsigned int cpu) { - int i; - union { - __u32 w[5]; - unsigned long l[LONGS(20)]; - } hash; - __u32 workspace[SHA_WORKSPACE_WORDS]; - unsigned long flags; - /* - * If we have an architectural hardware random number - * generator, use it for SHA's initial vector + * 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. */ - sha_init(hash.w); - for (i = 0; i < LONGS(20); i++) { - unsigned long v; - if (!arch_get_random_long(&v)) - break; - hash.l[i] = v; - } - - /* Generate a hash across the pool, 16 words (512 bits) at a time */ - spin_lock_irqsave(&r->lock, flags); - for (i = 0; i < r->poolinfo->poolwords; i += 16) - sha_transform(hash.w, (__u8 *)(r->pool + i), workspace); + per_cpu_ptr(&irq_randomness, cpu)->count = 0; + return 0; +} +#endif +static void mix_interrupt_randomness(struct timer_list *work) +{ + struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix); /* - * 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 - * ouputs), unless the hash function can be inverted. By - * mixing at least a SHA1 worth of hash data back, we make - * brute-forcing the feedback as hard as brute-forcing the - * hash. + * 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. */ - __mix_pool_bytes(r, hash.w, sizeof(hash.w)); - spin_unlock_irqrestore(&r->lock, flags); + unsigned long pool[2]; + unsigned int count; - memzero_explicit(workspace, sizeof(workspace)); + /* 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; + } /* - * In case the hash function has some recognizable output - * pattern, we fold it in half. Thus, we always feed back - * twice as much data as we output. + * Copy the pool to the stack so that the mixer always has a + * consistent view, before we reenable irqs again. */ - hash.w[0] ^= hash.w[3]; - hash.w[1] ^= hash.w[4]; - hash.w[2] ^= rol32(hash.w[2], 16); + memcpy(pool, fast_pool->pool, sizeof(pool)); + count = fast_pool->count; + fast_pool->count = 0; + fast_pool->last = jiffies; + local_irq_enable(); - memcpy(out, &hash, EXTRACT_SIZE); - memzero_explicit(&hash, sizeof(hash)); + mix_pool_bytes(pool, sizeof(pool)); + credit_init_bits(clamp_t(unsigned int, (count & U16_MAX) / 64, 1, sizeof(pool) * 8)); + + memzero_explicit(pool, sizeof(pool)); } -static ssize_t _extract_entropy(struct entropy_store *r, void *buf, - size_t nbytes, int fips) +void add_interrupt_randomness(int irq) { - ssize_t ret = 0, i; - __u8 tmp[EXTRACT_SIZE]; - unsigned long flags; + 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; - while (nbytes) { - extract_buf(r, tmp); + fast_mix(fast_pool->pool, entropy, + (regs ? instruction_pointer(regs) : _RET_IP_) ^ swab(irq)); + new_count = ++fast_pool->count; - if (fips) { - spin_lock_irqsave(&r->lock, flags); - if (!memcmp(tmp, r->last_data, EXTRACT_SIZE)) - panic("Hardware RNG duplicated output!\n"); - memcpy(r->last_data, tmp, EXTRACT_SIZE); - spin_unlock_irqrestore(&r->lock, flags); - } - i = min_t(int, nbytes, EXTRACT_SIZE); - memcpy(buf, tmp, i); - nbytes -= i; - buf += i; - ret += i; - } + if (new_count & MIX_INFLIGHT) + return; - /* Wipe data just returned from memory */ - memzero_explicit(tmp, sizeof(tmp)); + if (new_count < 1024 && !time_is_before_jiffies(fast_pool->last + HZ)) + return; - return ret; + 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_GPL(add_interrupt_randomness); + +/* There is one of these per entropy source */ +struct timer_rand_state { + unsigned long last_time; + long last_delta, last_delta2; +}; /* - * This function extracts randomness from the "entropy pool", and - * returns it in a buffer. - * - * The min parameter specifies the minimum amount we can pull before - * failing to avoid races that defeat catastrophic reseeding while the - * reserved parameter indicates how much entropy we must leave in the - * pool after each pull to avoid starving other readers. + * This function adds entropy to the entropy "pool" by using timing + * delays. It uses the timer_rand_state structure to make an estimate + * of how many bits of entropy this call has added to the pool. The + * value "num" is also added to the pool; it should somehow describe + * the type of event that just happened. */ -static ssize_t extract_entropy(struct entropy_store *r, void *buf, - size_t nbytes, int min, int reserved) +static void add_timer_randomness(struct timer_rand_state *state, unsigned int num) { - __u8 tmp[EXTRACT_SIZE]; - unsigned long flags; + unsigned long entropy = random_get_entropy(), now = jiffies, flags; + long delta, delta2, delta3; + unsigned int bits; - /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */ - if (fips_enabled) { - spin_lock_irqsave(&r->lock, flags); - if (!r->last_data_init) { - r->last_data_init = 1; - spin_unlock_irqrestore(&r->lock, flags); - trace_extract_entropy(r->name, EXTRACT_SIZE, - ENTROPY_BITS(r), _RET_IP_); - xfer_secondary_pool(r, EXTRACT_SIZE); - extract_buf(r, tmp); - spin_lock_irqsave(&r->lock, flags); - memcpy(r->last_data, tmp, EXTRACT_SIZE); - } - spin_unlock_irqrestore(&r->lock, flags); + /* + * If we're in a hard IRQ, add_interrupt_randomness() will be called + * sometime after, so mix into the fast pool. + */ + if (in_irq()) { + 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); } - trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_); - xfer_secondary_pool(r, nbytes); - nbytes = account(r, nbytes, min, reserved); + if (crng_ready()) + return; - return _extract_entropy(r, buf, nbytes, fips_enabled); -} + /* + * 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); -/* - * This function extracts randomness from the "entropy pool", and - * returns it in a userspace buffer. - */ -static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, - size_t nbytes) -{ - ssize_t ret = 0, i; - __u8 tmp[EXTRACT_SIZE]; - int large_request = (nbytes > 256); - - trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_); - if (!r->initialized && r->pull) { - xfer_secondary_pool(r, ENTROPY_BITS(r->pull)/8); - if (!r->initialized) - return 0; - } - xfer_secondary_pool(r, nbytes); - nbytes = account(r, nbytes, 0, 0); - - while (nbytes) { - if (large_request && need_resched()) { - if (signal_pending(current)) { - if (ret == 0) - ret = -ERESTARTSYS; - break; - } - schedule(); - } + delta2 = delta - READ_ONCE(state->last_delta); + WRITE_ONCE(state->last_delta, delta); - extract_buf(r, tmp); - i = min_t(int, nbytes, EXTRACT_SIZE); - if (copy_to_user(buf, tmp, i)) { - ret = -EFAULT; - break; - } + delta3 = delta2 - READ_ONCE(state->last_delta2); + WRITE_ONCE(state->last_delta2, delta2); - nbytes -= i; - buf += i; - ret += i; - } + 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; - /* Wipe data just returned from memory */ - memzero_explicit(tmp, sizeof(tmp)); + /* + * 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); - return ret; + /* + * 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_irq()) + this_cpu_ptr(&irq_randomness)->count += max(1u, bits * 64) - 1; + else + _credit_init_bits(bits); } -#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_input_randomness(unsigned int type, unsigned int code, unsigned int value) { -#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM - const bool print_once = false; -#else - static bool print_once __read_mostly; -#endif + static unsigned char last_value; + static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES }; - if (print_once || - crng_ready() || - (previous && (caller == READ_ONCE(*previous)))) + /* Ignore autorepeat and the like. */ + if (value == last_value) 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); + + last_value = value; + add_timer_randomness(&input_timer_state, + (type << 4) ^ code ^ (code >> 4) ^ value); } +EXPORT_SYMBOL_GPL(add_input_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. - */ -static void _get_random_bytes(void *buf, int nbytes) +#ifdef CONFIG_BLOCK +void add_disk_randomness(struct gendisk *disk) { - __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)); + if (!disk || !disk->random) + return; + /* First major is 1, so we get >= 0x200 here. */ + add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); } +EXPORT_SYMBOL_GPL(add_disk_randomness); -void get_random_bytes(void *buf, int nbytes) +void __cold rand_initialize_disk(struct gendisk *disk) { - static void *previous; + struct timer_rand_state *state; - warn_unseeded_randomness(&previous); - _get_random_bytes(buf, nbytes); + /* + * If kzalloc returns null, we just won't use that entropy + * source. + */ + state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); + if (state) { + state->last_time = INITIAL_JIFFIES; + disk->random = state; + } } -EXPORT_SYMBOL(get_random_bytes); - +#endif /* * Each time the timer fires, we expect that we got an unpredictable @@ -1767,373 +1143,181 @@ EXPORT_SYMBOL(get_random_bytes); * * So the re-arming always happens in the entropy loop itself. */ -static void entropy_timer(struct timer_list *t) +static void __cold entropy_timer(struct timer_list *t) { - credit_entropy_bits(&input_pool, 1); + credit_init_bits(1); } /* * If we have an actual cycle counter, see if we can * generate enough entropy with timing noise */ -static void try_to_generate_entropy(void) +static void __cold try_to_generate_entropy(void) { struct { - unsigned long now; + unsigned long entropy; struct timer_list timer; } stack; - stack.now = random_get_entropy(); + stack.entropy = random_get_entropy(); /* Slow counter - or none. Don't even bother */ - if (stack.now == random_get_entropy()) + if (stack.entropy == random_get_entropy()) return; timer_setup_on_stack(&stack.timer, entropy_timer, 0); - while (!crng_ready()) { + while (!crng_ready() && !signal_pending(current)) { if (!timer_pending(&stack.timer)) - mod_timer(&stack.timer, jiffies+1); - mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now)); + mod_timer(&stack.timer, jiffies + 1); + mix_pool_bytes(&stack.entropy, sizeof(stack.entropy)); schedule(); - stack.now = random_get_entropy(); + stack.entropy = random_get_entropy(); } del_timer_sync(&stack.timer); destroy_timer_on_stack(&stack.timer); - mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now)); + mix_pool_bytes(&stack.entropy, sizeof(stack.entropy)); } -/* - * 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) -{ - if (likely(crng_ready())) - return 0; - do { - int ret; - ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ); - if (ret) - return ret > 0 ? 0 : ret; - - try_to_generate_entropy(); - } while (!crng_ready()); - - return 0; -} -EXPORT_SYMBOL(wait_for_random_bytes); - -/* - * 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. - */ -bool rng_is_initialized(void) -{ - return crng_ready(); -} -EXPORT_SYMBOL(rng_is_initialized); - -/* - * Add a callback function that will be invoked when the nonblocking - * pool is initialised. + * Userspace reader/writer interfaces. * - * returns: 0 if callback is successfully added - * -EALREADY if pool is already initialised (callback not called) - * -ENOENT if module for callback is not alive - */ -int add_random_ready_callback(struct random_ready_callback *rdy) -{ - struct module *owner; - unsigned long flags; - int err = -EALREADY; - - if (crng_ready()) - return err; - - owner = rdy->owner; - if (!try_module_get(owner)) - return -ENOENT; - - spin_lock_irqsave(&random_ready_list_lock, flags); - if (crng_ready()) - goto out; - - owner = NULL; - - list_add(&rdy->list, &random_ready_list); - err = 0; - -out: - spin_unlock_irqrestore(&random_ready_list_lock, flags); - - module_put(owner); - - return err; -} -EXPORT_SYMBOL(add_random_ready_callback); - -/* - * Delete a previously registered readiness callback function. - */ -void del_random_ready_callback(struct random_ready_callback *rdy) -{ - unsigned long flags; - struct module *owner = NULL; - - spin_lock_irqsave(&random_ready_list_lock, flags); - if (!list_empty(&rdy->list)) { - list_del_init(&rdy->list); - owner = rdy->owner; - } - spin_unlock_irqrestore(&random_ready_list_lock, flags); - - module_put(owner); -} -EXPORT_SYMBOL(del_random_ready_callback); - -/* - * 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. + * getrandom(2) is the primary modern interface into the RNG and should + * be used in preference to anything else. * - * Return number of bytes filled in. - */ -int __must_check get_random_bytes_arch(void *buf, int nbytes) -{ - int left = nbytes; - char *p = buf; - - trace_get_random_bytes_arch(left, _RET_IP_); - while (left) { - unsigned long v; - int chunk = min_t(int, left, sizeof(unsigned long)); - - if (!arch_get_random_long(&v)) - break; - - memcpy(p, &v, chunk); - p += chunk; - left -= chunk; - } - - return nbytes - left; -} -EXPORT_SYMBOL(get_random_bytes_arch); - -/* - * init_std_data - initialize pool with system data + * 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. * - * @r: pool to initialize + * 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. * - * 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(struct entropy_store *r) -{ - int i; - ktime_t now = ktime_get_real(); - unsigned long rv; - - r->last_pulled = jiffies; - mix_pool_bytes(r, &now, sizeof(now)); - for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) { - if (!arch_get_random_seed_long(&rv) && - !arch_get_random_long(&rv)) - rv = random_get_entropy(); - mix_pool_bytes(r, &rv, sizeof(rv)); - } - mix_pool_bytes(r, utsname(), sizeof(*(utsname()))); -} + * 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. + * + **********************************************************************/ -/* - * 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) +SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags) { - init_std_data(&input_pool); - init_std_data(&blocking_pool); - if (crng_need_final_init) - crng_finalize_init(&primary_crng); - crng_initialize(&primary_crng); - crng_global_init_time = jiffies; - if (ratelimit_disable) { - urandom_warning.interval = 0; - unseeded_warning.interval = 0; - } - return 0; -} + struct iov_iter iter; + struct iovec iov; + int ret; -#ifdef CONFIG_BLOCK -void rand_initialize_disk(struct gendisk *disk) -{ - struct timer_rand_state *state; + if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE)) + return -EINVAL; /* - * If kzalloc returns null, we just won't use that entropy - * source. + * Requesting insecure and blocking randomness at the same time makes + * no sense. */ - state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); - if (state) { - state->last_time = INITIAL_JIFFIES; - disk->random = state; - } -} -#endif - -static ssize_t -_random_read(int nonblock, char __user *buf, size_t nbytes) -{ - ssize_t n; - - if (nbytes == 0) - return 0; + if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM)) + return -EINVAL; - nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE); - while (1) { - n = extract_entropy_user(&blocking_pool, buf, nbytes); - if (n < 0) - return n; - trace_random_read(n*8, (nbytes-n)*8, - ENTROPY_BITS(&blocking_pool), - ENTROPY_BITS(&input_pool)); - if (n > 0) - return n; - - /* Pool is (near) empty. Maybe wait and retry. */ - if (nonblock) + if (!crng_ready() && !(flags & GRND_INSECURE)) { + if (flags & GRND_NONBLOCK) return -EAGAIN; - - wait_event_interruptible(random_read_wait, - blocking_pool.initialized && - (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)); - if (signal_pending(current)) - return -ERESTARTSYS; + ret = wait_for_random_bytes(); + if (unlikely(ret)) + return ret; } + + ret = import_single_range(READ, ubuf, len, &iov, &iter); + if (unlikely(ret)) + return ret; + return get_random_bytes_user(&iter); } -static ssize_t -random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) +static __poll_t random_poll(struct file *file, poll_table *wait) { - return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes); + poll_wait(file, &crng_init_wait, wait); + return crng_ready() ? EPOLLIN | EPOLLRDNORM : EPOLLOUT | EPOLLWRNORM; } -static ssize_t -urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) +static ssize_t write_pool_user(struct iov_iter *iter) { - unsigned long flags; - static int maxwarn = 10; - int ret; + u8 block[BLAKE2S_BLOCK_SIZE]; + ssize_t ret = 0; + size_t copied; - if (!crng_ready() && maxwarn > 0) { - maxwarn--; - if (__ratelimit(&urandom_warning)) - printk(KERN_NOTICE "random: %s: uninitialized " - "urandom read (%zd bytes read)\n", - current->comm, nbytes); - spin_lock_irqsave(&primary_crng.lock, flags); - crng_init_cnt = 0; - spin_unlock_irqrestore(&primary_crng.lock, flags); + if (unlikely(!iov_iter_count(iter))) + return 0; + + for (;;) { + copied = copy_from_iter(block, sizeof(block), iter); + ret += copied; + mix_pool_bytes(block, copied); + if (!iov_iter_count(iter) || copied != sizeof(block)) + break; + + BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0); + if (ret % PAGE_SIZE == 0) { + if (signal_pending(current)) + break; + cond_resched(); + } } - nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3)); - ret = extract_crng_user(buf, nbytes); - trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool)); - return ret; + + memzero_explicit(block, sizeof(block)); + return ret ? ret : -EFAULT; } -static __poll_t -random_poll(struct file *file, poll_table * wait) +static ssize_t random_write_iter(struct kiocb *kiocb, struct iov_iter *iter) { - __poll_t mask; - - poll_wait(file, &random_read_wait, wait); - poll_wait(file, &random_write_wait, wait); - mask = 0; - if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits) - mask |= EPOLLIN | EPOLLRDNORM; - if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits) - mask |= EPOLLOUT | EPOLLWRNORM; - return mask; + return write_pool_user(iter); } -static int -write_pool(struct entropy_store *r, const char __user *buffer, size_t count) +static ssize_t urandom_read_iter(struct kiocb *kiocb, struct iov_iter *iter) { - size_t bytes; - __u32 t, buf[16]; - const char __user *p = buffer; - - while (count > 0) { - int b, i = 0; - - bytes = min(count, sizeof(buf)); - if (copy_from_user(&buf, p, bytes)) - return -EFAULT; + static int maxwarn = 10; - for (b = bytes ; b > 0 ; b -= sizeof(__u32), i++) { - if (!arch_get_random_int(&t)) - break; - buf[i] ^= t; + if (!crng_ready()) { + if (!ratelimit_disable && maxwarn <= 0) + ++urandom_warning.missed; + else if (ratelimit_disable || __ratelimit(&urandom_warning)) { + --maxwarn; + pr_notice("%s: uninitialized urandom read (%zu bytes read)\n", + current->comm, iov_iter_count(iter)); } - - count -= bytes; - p += bytes; - - mix_pool_bytes(r, buf, bytes); - cond_resched(); } - 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(&input_pool, buffer, count); - if (ret) - return ret; + if (!crng_ready() && + ((kiocb->ki_flags & IOCB_NOWAIT) || + (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 = ENTROPY_BITS(&input_pool); - 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: @@ -2141,39 +1325,48 @@ 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(&input_pool, ent_count); - case RNDADDENTROPY: + if (ent_count < 0) + return -EINVAL; + credit_init_bits(ent_count); + return 0; + case RNDADDENTROPY: { + struct iov_iter iter; + struct iovec iov; + ssize_t ret; + int len; + if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (get_user(ent_count, p++)) return -EFAULT; if (ent_count < 0) return -EINVAL; - if (get_user(size, p++)) + if (get_user(len, p++)) + return -EFAULT; + ret = import_single_range(WRITE, p, len, &iov, &iter); + if (unlikely(ret)) + return ret; + ret = write_pool_user(&iter); + if (unlikely(ret < 0)) + return ret; + /* Since we're crediting, enforce that it was all written into the pool. */ + if (unlikely(ret != len)) return -EFAULT; - retval = write_pool(&input_pool, (const char __user *)p, - size); - if (retval < 0) - return retval; - return credit_entropy_bits_safe(&input_pool, ent_count); + 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; - blocking_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, &input_pool); - WRITE_ONCE(crng_global_init_time, jiffies - 1); + crng_reseed(); return 0; default: return -EINVAL; @@ -2186,49 +1379,56 @@ static int random_fasync(int fd, struct file *filp, int on) } const struct file_operations random_fops = { - .read = random_read, - .write = random_write, - .poll = random_poll, + .read_iter = random_read_iter, + .write_iter = random_write_iter, + .poll = random_poll, .unlocked_ioctl = random_ioctl, + .compat_ioctl = compat_ptr_ioctl, .fasync = random_fasync, .llseek = noop_llseek, + .splice_read = generic_file_splice_read, + .splice_write = iter_file_splice_write, }; const struct file_operations urandom_fops = { - .read = 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 = generic_file_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)) - return -EINVAL; - - if (count > INT_MAX) - count = INT_MAX; - - if (flags & GRND_RANDOM) - return _random_read(flags & GRND_NONBLOCK, buf, count); - - if (!crng_ready()) { - if (flags & GRND_NONBLOCK) - return -EAGAIN; - ret = wait_for_random_bytes(); - if (unlikely(ret)) - return ret; - } - return urandom_read(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. * ********************************************************************/ @@ -2236,26 +1436,28 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, #include <linux/sysctl.h> -static int min_read_thresh = 8, min_write_thresh; -static int max_read_thresh = OUTPUT_POOL_WORDS * 32; -static int max_write_thresh = INPUT_POOL_WORDS * 32; -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 __user *buffer, size_t *lenp, loff_t *ppos) -{ - struct ctl_table fake_table; - unsigned char buf[64], tmp_uuid[16], *uuid; +static int proc_do_uuid(struct ctl_table *table, int write, void __user *buf, + size_t *lenp, loff_t *ppos) +{ + u8 tmp_uuid[UUID_SIZE], *uuid; + char uuid_string[UUID_STRING_LEN + 1]; + struct ctl_table fake_table = { + .data = uuid_string, + .maxlen = UUID_STRING_LEN + }; + + if (write) + return -EPERM; uuid = table->data; if (!uuid) { @@ -2270,32 +1472,17 @@ static int proc_do_uuid(struct ctl_table *table, int write, 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 __user *buffer, size_t *lenp, loff_t *ppos) +/* The same as proc_dointvec, but writes don't change anything. */ +static int proc_do_rointvec(struct ctl_table *table, int write, void __user *buf, + size_t *lenp, loff_t *ppos) { - struct ctl_table fake_table; - int entropy_count; - - entropy_count = *(int *)table->data >> 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 = INPUT_POOL_WORDS * 32; extern struct ctl_table random_table[]; struct ctl_table random_table[] = { { @@ -2307,231 +1494,36 @@ 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, - }, - { - .procname = "read_wakeup_threshold", - .data = &random_read_wakeup_bits, - .maxlen = sizeof(int), - .mode = 0644, - .proc_handler = proc_dointvec_minmax, - .extra1 = &min_read_thresh, - .extra2 = &max_read_thresh, + .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 { } }; -#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) -{ - struct entropy_store *poolp = &input_pool; - - if (unlikely(crng_init == 0)) { - size_t ret = crng_fast_load(buffer, count); - 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() || - ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits); - mix_pool_bytes(poolp, buffer, count); - credit_entropy_bits(poolp, 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 /* CONFIG_SYSCTL */ |