linux/drivers/char/random.c
<<
>>
Prefs
   1/*
   2 * random.c -- A strong random number generator
   3 *
   4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
   5 *
   6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.  All
   7 * rights reserved.
   8 *
   9 * Redistribution and use in source and binary forms, with or without
  10 * modification, are permitted provided that the following conditions
  11 * are met:
  12 * 1. Redistributions of source code must retain the above copyright
  13 *    notice, and the entire permission notice in its entirety,
  14 *    including the disclaimer of warranties.
  15 * 2. Redistributions in binary form must reproduce the above copyright
  16 *    notice, this list of conditions and the following disclaimer in the
  17 *    documentation and/or other materials provided with the distribution.
  18 * 3. The name of the author may not be used to endorse or promote
  19 *    products derived from this software without specific prior
  20 *    written permission.
  21 *
  22 * ALTERNATIVELY, this product may be distributed under the terms of
  23 * the GNU General Public License, in which case the provisions of the GPL are
  24 * required INSTEAD OF the above restrictions.  (This clause is
  25 * necessary due to a potential bad interaction between the GPL and
  26 * the restrictions contained in a BSD-style copyright.)
  27 *
  28 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
  31 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
  32 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
  34 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  35 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  36 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  38 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
  39 * DAMAGE.
  40 */
  41
  42/*
  43 * (now, with legal B.S. out of the way.....)
  44 *
  45 * This routine gathers environmental noise from device drivers, etc.,
  46 * and returns good random numbers, suitable for cryptographic use.
  47 * Besides the obvious cryptographic uses, these numbers are also good
  48 * for seeding TCP sequence numbers, and other places where it is
  49 * desirable to have numbers which are not only random, but hard to
  50 * predict by an attacker.
  51 *
  52 * Theory of operation
  53 * ===================
  54 *
  55 * Computers are very predictable devices.  Hence it is extremely hard
  56 * to produce truly random numbers on a computer --- as opposed to
  57 * pseudo-random numbers, which can easily generated by using a
  58 * algorithm.  Unfortunately, it is very easy for attackers to guess
  59 * the sequence of pseudo-random number generators, and for some
  60 * applications this is not acceptable.  So instead, we must try to
  61 * gather "environmental noise" from the computer's environment, which
  62 * must be hard for outside attackers to observe, and use that to
  63 * generate random numbers.  In a Unix environment, this is best done
  64 * from inside the kernel.
  65 *
  66 * Sources of randomness from the environment include inter-keyboard
  67 * timings, inter-interrupt timings from some interrupts, and other
  68 * events which are both (a) non-deterministic and (b) hard for an
  69 * outside observer to measure.  Randomness from these sources are
  70 * added to an "entropy pool", which is mixed using a CRC-like function.
  71 * This is not cryptographically strong, but it is adequate assuming
  72 * the randomness is not chosen maliciously, and it is fast enough that
  73 * the overhead of doing it on every interrupt is very reasonable.
  74 * As random bytes are mixed into the entropy pool, the routines keep
  75 * an *estimate* of how many bits of randomness have been stored into
  76 * the random number generator's internal state.
  77 *
  78 * When random bytes are desired, they are obtained by taking the SHA
  79 * hash of the contents of the "entropy pool".  The SHA hash avoids
  80 * exposing the internal state of the entropy pool.  It is believed to
  81 * be computationally infeasible to derive any useful information
  82 * about the input of SHA from its output.  Even if it is possible to
  83 * analyze SHA in some clever way, as long as the amount of data
  84 * returned from the generator is less than the inherent entropy in
  85 * the pool, the output data is totally unpredictable.  For this
  86 * reason, the routine decreases its internal estimate of how many
  87 * bits of "true randomness" are contained in the entropy pool as it
  88 * outputs random numbers.
  89 *
  90 * If this estimate goes to zero, the routine can still generate
  91 * random numbers; however, an attacker may (at least in theory) be
  92 * able to infer the future output of the generator from prior
  93 * outputs.  This requires successful cryptanalysis of SHA, which is
  94 * not believed to be feasible, but there is a remote possibility.
  95 * Nonetheless, these numbers should be useful for the vast majority
  96 * of purposes.
  97 *
  98 * Exported interfaces ---- output
  99 * ===============================
 100 *
 101 * There are three exported interfaces; the first is one designed to
 102 * be used from within the kernel:
 103 *
 104 *      void get_random_bytes(void *buf, int nbytes);
 105 *
 106 * This interface will return the requested number of random bytes,
 107 * and place it in the requested buffer.
 108 *
 109 * The two other interfaces are two character devices /dev/random and
 110 * /dev/urandom.  /dev/random is suitable for use when very high
 111 * quality randomness is desired (for example, for key generation or
 112 * one-time pads), as it will only return a maximum of the number of
 113 * bits of randomness (as estimated by the random number generator)
 114 * contained in the entropy pool.
 115 *
 116 * The /dev/urandom device does not have this limit, and will return
 117 * as many bytes as are requested.  As more and more random bytes are
 118 * requested without giving time for the entropy pool to recharge,
 119 * this will result in random numbers that are merely cryptographically
 120 * strong.  For many applications, however, this is acceptable.
 121 *
 122 * Exported interfaces ---- input
 123 * ==============================
 124 *
 125 * The current exported interfaces for gathering environmental noise
 126 * from the devices are:
 127 *
 128 *      void add_device_randomness(const void *buf, unsigned int size);
 129 *      void add_input_randomness(unsigned int type, unsigned int code,
 130 *                                unsigned int value);
 131 *      void add_interrupt_randomness(int irq, int irq_flags);
 132 *      void add_disk_randomness(struct gendisk *disk);
 133 *
 134 * add_device_randomness() is for adding data to the random pool that
 135 * is likely to differ between two devices (or possibly even per boot).
 136 * This would be things like MAC addresses or serial numbers, or the
 137 * read-out of the RTC. This does *not* add any actual entropy to the
 138 * pool, but it initializes the pool to different values for devices
 139 * that might otherwise be identical and have very little entropy
 140 * available to them (particularly common in the embedded world).
 141 *
 142 * add_input_randomness() uses the input layer interrupt timing, as well as
 143 * the event type information from the hardware.
 144 *
 145 * add_interrupt_randomness() uses the interrupt timing as random
 146 * inputs to the entropy pool. Using the cycle counters and the irq source
 147 * as inputs, it feeds the randomness roughly once a second.
 148 *
 149 * add_disk_randomness() uses what amounts to the seek time of block
 150 * layer request events, on a per-disk_devt basis, as input to the
 151 * entropy pool. Note that high-speed solid state drives with very low
 152 * seek times do not make for good sources of entropy, as their seek
 153 * times are usually fairly consistent.
 154 *
 155 * All of these routines try to estimate how many bits of randomness a
 156 * particular randomness source.  They do this by keeping track of the
 157 * first and second order deltas of the event timings.
 158 *
 159 * Ensuring unpredictability at system startup
 160 * ============================================
 161 *
 162 * When any operating system starts up, it will go through a sequence
 163 * of actions that are fairly predictable by an adversary, especially
 164 * if the start-up does not involve interaction with a human operator.
 165 * This reduces the actual number of bits of unpredictability in the
 166 * entropy pool below the value in entropy_count.  In order to
 167 * counteract this effect, it helps to carry information in the
 168 * entropy pool across shut-downs and start-ups.  To do this, put the
 169 * following lines an appropriate script which is run during the boot
 170 * sequence:
 171 *
 172 *      echo "Initializing random number generator..."
 173 *      random_seed=/var/run/random-seed
 174 *      # Carry a random seed from start-up to start-up
 175 *      # Load and then save the whole entropy pool
 176 *      if [ -f $random_seed ]; then
 177 *              cat $random_seed >/dev/urandom
 178 *      else
 179 *              touch $random_seed
 180 *      fi
 181 *      chmod 600 $random_seed
 182 *      dd if=/dev/urandom of=$random_seed count=1 bs=512
 183 *
 184 * and the following lines in an appropriate script which is run as
 185 * the system is shutdown:
 186 *
 187 *      # Carry a random seed from shut-down to start-up
 188 *      # Save the whole entropy pool
 189 *      echo "Saving random seed..."
 190 *      random_seed=/var/run/random-seed
 191 *      touch $random_seed
 192 *      chmod 600 $random_seed
 193 *      dd if=/dev/urandom of=$random_seed count=1 bs=512
 194 *
 195 * For example, on most modern systems using the System V init
 196 * scripts, such code fragments would be found in
 197 * /etc/rc.d/init.d/random.  On older Linux systems, the correct script
 198 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
 199 *
 200 * Effectively, these commands cause the contents of the entropy pool
 201 * to be saved at shut-down time and reloaded into the entropy pool at
 202 * start-up.  (The 'dd' in the addition to the bootup script is to
 203 * make sure that /etc/random-seed is different for every start-up,
 204 * even if the system crashes without executing rc.0.)  Even with
 205 * complete knowledge of the start-up activities, predicting the state
 206 * of the entropy pool requires knowledge of the previous history of
 207 * the system.
 208 *
 209 * Configuring the /dev/random driver under Linux
 210 * ==============================================
 211 *
 212 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
 213 * the /dev/mem major number (#1).  So if your system does not have
 214 * /dev/random and /dev/urandom created already, they can be created
 215 * by using the commands:
 216 *
 217 *      mknod /dev/random c 1 8
 218 *      mknod /dev/urandom c 1 9
 219 *
 220 * Acknowledgements:
 221 * =================
 222 *
 223 * Ideas for constructing this random number generator were derived
 224 * from Pretty Good Privacy's random number generator, and from private
 225 * discussions with Phil Karn.  Colin Plumb provided a faster random
 226 * number generator, which speed up the mixing function of the entropy
 227 * pool, taken from PGPfone.  Dale Worley has also contributed many
 228 * useful ideas and suggestions to improve this driver.
 229 *
 230 * Any flaws in the design are solely my responsibility, and should
 231 * not be attributed to the Phil, Colin, or any of authors of PGP.
 232 *
 233 * Further background information on this topic may be obtained from
 234 * RFC 1750, "Randomness Recommendations for Security", by Donald
 235 * Eastlake, Steve Crocker, and Jeff Schiller.
 236 */
 237
 238#include <linux/utsname.h>
 239#include <linux/module.h>
 240#include <linux/kernel.h>
 241#include <linux/major.h>
 242#include <linux/string.h>
 243#include <linux/fcntl.h>
 244#include <linux/slab.h>
 245#include <linux/random.h>
 246#include <linux/poll.h>
 247#include <linux/init.h>
 248#include <linux/fs.h>
 249#include <linux/genhd.h>
 250#include <linux/interrupt.h>
 251#include <linux/mm.h>
 252#include <linux/nodemask.h>
 253#include <linux/spinlock.h>
 254#include <linux/kthread.h>
 255#include <linux/percpu.h>
 256#include <linux/cryptohash.h>
 257#include <linux/fips.h>
 258#include <linux/ptrace.h>
 259#include <linux/kmemcheck.h>
 260#include <linux/workqueue.h>
 261#include <linux/irq.h>
 262#include <linux/syscalls.h>
 263#include <linux/completion.h>
 264#include <linux/uuid.h>
 265#include <crypto/chacha20.h>
 266
 267#include <asm/processor.h>
 268#include <asm/uaccess.h>
 269#include <asm/irq.h>
 270#include <asm/irq_regs.h>
 271#include <asm/io.h>
 272
 273#define CREATE_TRACE_POINTS
 274#include <trace/events/random.h>
 275
 276/* #define ADD_INTERRUPT_BENCH */
 277
 278/*
 279 * Configuration information
 280 */
 281#define INPUT_POOL_SHIFT        12
 282#define INPUT_POOL_WORDS        (1 << (INPUT_POOL_SHIFT-5))
 283#define OUTPUT_POOL_SHIFT       10
 284#define OUTPUT_POOL_WORDS       (1 << (OUTPUT_POOL_SHIFT-5))
 285#define SEC_XFER_SIZE           512
 286#define EXTRACT_SIZE            10
 287
 288#define DEBUG_RANDOM_BOOT 0
 289
 290#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
 291
 292/*
 293 * To allow fractional bits to be tracked, the entropy_count field is
 294 * denominated in units of 1/8th bits.
 295 *
 296 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
 297 * credit_entropy_bits() needs to be 64 bits wide.
 298 */
 299#define ENTROPY_SHIFT 3
 300#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
 301
 302/*
 303 * The minimum number of bits of entropy before we wake up a read on
 304 * /dev/random.  Should be enough to do a significant reseed.
 305 */
 306static int random_read_wakeup_bits = 64;
 307
 308/*
 309 * If the entropy count falls under this number of bits, then we
 310 * should wake up processes which are selecting or polling on write
 311 * access to /dev/random.
 312 */
 313static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
 314
 315/*
 316 * The minimum number of seconds between urandom pool reseeding.  We
 317 * do this to limit the amount of entropy that can be drained from the
 318 * input pool even if there are heavy demands on /dev/urandom.
 319 */
 320static int random_min_urandom_seed = 60;
 321
 322/*
 323 * Originally, we used a primitive polynomial of degree .poolwords
 324 * over GF(2).  The taps for various sizes are defined below.  They
 325 * were chosen to be evenly spaced except for the last tap, which is 1
 326 * to get the twisting happening as fast as possible.
 327 *
 328 * For the purposes of better mixing, we use the CRC-32 polynomial as
 329 * well to make a (modified) twisted Generalized Feedback Shift
 330 * Register.  (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR
 331 * generators.  ACM Transactions on Modeling and Computer Simulation
 332 * 2(3):179-194.  Also see M. Matsumoto & Y. Kurita, 1994.  Twisted
 333 * GFSR generators II.  ACM Transactions on Modeling and Computer
 334 * Simulation 4:254-266)
 335 *
 336 * Thanks to Colin Plumb for suggesting this.
 337 *
 338 * The mixing operation is much less sensitive than the output hash,
 339 * where we use SHA-1.  All that we want of mixing operation is that
 340 * it be a good non-cryptographic hash; i.e. it not produce collisions
 341 * when fed "random" data of the sort we expect to see.  As long as
 342 * the pool state differs for different inputs, we have preserved the
 343 * input entropy and done a good job.  The fact that an intelligent
 344 * attacker can construct inputs that will produce controlled
 345 * alterations to the pool's state is not important because we don't
 346 * consider such inputs to contribute any randomness.  The only
 347 * property we need with respect to them is that the attacker can't
 348 * increase his/her knowledge of the pool's state.  Since all
 349 * additions are reversible (knowing the final state and the input,
 350 * you can reconstruct the initial state), if an attacker has any
 351 * uncertainty about the initial state, he/she can only shuffle that
 352 * uncertainty about, but never cause any collisions (which would
 353 * decrease the uncertainty).
 354 *
 355 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
 356 * Videau in their paper, "The Linux Pseudorandom Number Generator
 357 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf).  In their
 358 * paper, they point out that we are not using a true Twisted GFSR,
 359 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
 360 * is, with only three taps, instead of the six that we are using).
 361 * As a result, the resulting polynomial is neither primitive nor
 362 * irreducible, and hence does not have a maximal period over
 363 * GF(2**32).  They suggest a slight change to the generator
 364 * polynomial which improves the resulting TGFSR polynomial to be
 365 * irreducible, which we have made here.
 366 */
 367static struct poolinfo {
 368        int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
 369#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
 370        int tap1, tap2, tap3, tap4, tap5;
 371} poolinfo_table[] = {
 372        /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
 373        /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
 374        { S(128),       104,    76,     51,     25,     1 },
 375        /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
 376        /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
 377        { S(32),        26,     19,     14,     7,      1 },
 378#if 0
 379        /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
 380        { S(2048),      1638,   1231,   819,    411,    1 },
 381
 382        /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
 383        { S(1024),      817,    615,    412,    204,    1 },
 384
 385        /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
 386        { S(1024),      819,    616,    410,    207,    2 },
 387
 388        /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
 389        { S(512),       411,    308,    208,    104,    1 },
 390
 391        /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
 392        { S(512),       409,    307,    206,    102,    2 },
 393        /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
 394        { S(512),       409,    309,    205,    103,    2 },
 395
 396        /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
 397        { S(256),       205,    155,    101,    52,     1 },
 398
 399        /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
 400        { S(128),       103,    78,     51,     27,     2 },
 401
 402        /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
 403        { S(64),        52,     39,     26,     14,     1 },
 404#endif
 405};
 406
 407/*
 408 * Static global variables
 409 */
 410static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 411static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
 412static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
 413static struct fasync_struct *fasync;
 414
 415static DEFINE_SPINLOCK(random_ready_list_lock);
 416static LIST_HEAD(random_ready_list);
 417
 418struct crng_state {
 419        __u32           state[16];
 420        unsigned long   init_time;
 421        spinlock_t      lock;
 422};
 423
 424struct crng_state primary_crng = {
 425        .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
 426};
 427
 428/*
 429 * crng_init =  0 --> Uninitialized
 430 *              1 --> Initialized
 431 *              2 --> Initialized from input_pool
 432 *
 433 * crng_init is protected by primary_crng->lock, and only increases
 434 * its value (from 0->1->2).
 435 */
 436static int crng_init = 0;
 437#define crng_ready() (likely(crng_init > 0))
 438static int crng_init_cnt = 0;
 439#define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
 440static void _extract_crng(struct crng_state *crng,
 441                          __u8 out[CHACHA20_BLOCK_SIZE]);
 442static void _crng_backtrack_protect(struct crng_state *crng,
 443                                    __u8 tmp[CHACHA20_BLOCK_SIZE], int used);
 444static void process_random_ready_list(void);
 445
 446/**********************************************************************
 447 *
 448 * OS independent entropy store.   Here are the functions which handle
 449 * storing entropy in an entropy pool.
 450 *
 451 **********************************************************************/
 452
 453struct entropy_store;
 454struct entropy_store {
 455        /* read-only data: */
 456        const struct poolinfo *poolinfo;
 457        __u32 *pool;
 458        const char *name;
 459        struct entropy_store *pull;
 460        struct work_struct push_work;
 461
 462        /* read-write data: */
 463        unsigned long last_pulled;
 464        spinlock_t lock;
 465        unsigned short add_ptr;
 466        unsigned short input_rotate;
 467        int entropy_count;
 468        int entropy_total;
 469        unsigned int initialized:1;
 470        unsigned int limit:1;
 471        unsigned int last_data_init:1;
 472        __u8 last_data[EXTRACT_SIZE];
 473};
 474
 475static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 476                               size_t nbytes, int min, int rsvd);
 477static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
 478                                size_t nbytes, int fips);
 479
 480static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
 481static void push_to_pool(struct work_struct *work);
 482static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy;
 483static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy;
 484
 485static struct entropy_store input_pool = {
 486        .poolinfo = &poolinfo_table[0],
 487        .name = "input",
 488        .limit = 1,
 489        .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
 490        .pool = input_pool_data
 491};
 492
 493static struct entropy_store blocking_pool = {
 494        .poolinfo = &poolinfo_table[1],
 495        .name = "blocking",
 496        .limit = 1,
 497        .pull = &input_pool,
 498        .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
 499        .pool = blocking_pool_data,
 500        .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
 501                                        push_to_pool),
 502};
 503
 504static __u32 const twist_table[8] = {
 505        0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
 506        0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
 507
 508/*
 509 * This function adds bytes into the entropy "pool".  It does not
 510 * update the entropy estimate.  The caller should call
 511 * credit_entropy_bits if this is appropriate.
 512 *
 513 * The pool is stirred with a primitive polynomial of the appropriate
 514 * degree, and then twisted.  We twist by three bits at a time because
 515 * it's cheap to do so and helps slightly in the expected case where
 516 * the entropy is concentrated in the low-order bits.
 517 */
 518static void _mix_pool_bytes(struct entropy_store *r, const void *in,
 519                            int nbytes)
 520{
 521        unsigned long i, tap1, tap2, tap3, tap4, tap5;
 522        int input_rotate;
 523        int wordmask = r->poolinfo->poolwords - 1;
 524        const char *bytes = in;
 525        __u32 w;
 526
 527        tap1 = r->poolinfo->tap1;
 528        tap2 = r->poolinfo->tap2;
 529        tap3 = r->poolinfo->tap3;
 530        tap4 = r->poolinfo->tap4;
 531        tap5 = r->poolinfo->tap5;
 532
 533        input_rotate = r->input_rotate;
 534        i = r->add_ptr;
 535
 536        /* mix one byte at a time to simplify size handling and churn faster */
 537        while (nbytes--) {
 538                w = rol32(*bytes++, input_rotate);
 539                i = (i - 1) & wordmask;
 540
 541                /* XOR in the various taps */
 542                w ^= r->pool[i];
 543                w ^= r->pool[(i + tap1) & wordmask];
 544                w ^= r->pool[(i + tap2) & wordmask];
 545                w ^= r->pool[(i + tap3) & wordmask];
 546                w ^= r->pool[(i + tap4) & wordmask];
 547                w ^= r->pool[(i + tap5) & wordmask];
 548
 549                /* Mix the result back in with a twist */
 550                r->pool[i] = (w >> 3) ^ twist_table[w & 7];
 551
 552                /*
 553                 * Normally, we add 7 bits of rotation to the pool.
 554                 * At the beginning of the pool, add an extra 7 bits
 555                 * rotation, so that successive passes spread the
 556                 * input bits across the pool evenly.
 557                 */
 558                input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
 559        }
 560
 561        r->input_rotate = input_rotate;
 562        r->add_ptr = i;
 563}
 564
 565static void __mix_pool_bytes(struct entropy_store *r, const void *in,
 566                             int nbytes)
 567{
 568        trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
 569        _mix_pool_bytes(r, in, nbytes);
 570}
 571
 572static void mix_pool_bytes(struct entropy_store *r, const void *in,
 573                           int nbytes)
 574{
 575        unsigned long flags;
 576
 577        trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
 578        spin_lock_irqsave(&r->lock, flags);
 579        _mix_pool_bytes(r, in, nbytes);
 580        spin_unlock_irqrestore(&r->lock, flags);
 581}
 582
 583struct fast_pool {
 584        __u32           pool[4];
 585        unsigned long   last;
 586        unsigned short  reg_idx;
 587        unsigned char   count;
 588};
 589
 590/*
 591 * This is a fast mixing routine used by the interrupt randomness
 592 * collector.  It's hardcoded for an 128 bit pool and assumes that any
 593 * locks that might be needed are taken by the caller.
 594 */
 595static void fast_mix(struct fast_pool *f)
 596{
 597        __u32 a = f->pool[0],   b = f->pool[1];
 598        __u32 c = f->pool[2],   d = f->pool[3];
 599
 600        a += b;                 c += d;
 601        b = rol32(b, 6);        d = rol32(d, 27);
 602        d ^= a;                 b ^= c;
 603
 604        a += b;                 c += d;
 605        b = rol32(b, 16);       d = rol32(d, 14);
 606        d ^= a;                 b ^= c;
 607
 608        a += b;                 c += d;
 609        b = rol32(b, 6);        d = rol32(d, 27);
 610        d ^= a;                 b ^= c;
 611
 612        a += b;                 c += d;
 613        b = rol32(b, 16);       d = rol32(d, 14);
 614        d ^= a;                 b ^= c;
 615
 616        f->pool[0] = a;  f->pool[1] = b;
 617        f->pool[2] = c;  f->pool[3] = d;
 618        f->count++;
 619}
 620
 621static void process_random_ready_list(void)
 622{
 623        unsigned long flags;
 624        struct random_ready_callback *rdy, *tmp;
 625
 626        spin_lock_irqsave(&random_ready_list_lock, flags);
 627        list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
 628                struct module *owner = rdy->owner;
 629
 630                list_del_init(&rdy->list);
 631                rdy->func(rdy);
 632                module_put(owner);
 633        }
 634        spin_unlock_irqrestore(&random_ready_list_lock, flags);
 635}
 636
 637/*
 638 * Credit (or debit) the entropy store with n bits of entropy.
 639 * Use credit_entropy_bits_safe() if the value comes from userspace
 640 * or otherwise should be checked for extreme values.
 641 */
 642static void credit_entropy_bits(struct entropy_store *r, int nbits)
 643{
 644        int entropy_count, orig;
 645        const int pool_size = r->poolinfo->poolfracbits;
 646        int nfrac = nbits << ENTROPY_SHIFT;
 647
 648        if (!nbits)
 649                return;
 650
 651retry:
 652        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
 653        if (nfrac < 0) {
 654                /* Debit */
 655                entropy_count += nfrac;
 656        } else {
 657                /*
 658                 * Credit: we have to account for the possibility of
 659                 * overwriting already present entropy.  Even in the
 660                 * ideal case of pure Shannon entropy, new contributions
 661                 * approach the full value asymptotically:
 662                 *
 663                 * entropy <- entropy + (pool_size - entropy) *
 664                 *      (1 - exp(-add_entropy/pool_size))
 665                 *
 666                 * For add_entropy <= pool_size/2 then
 667                 * (1 - exp(-add_entropy/pool_size)) >=
 668                 *    (add_entropy/pool_size)*0.7869...
 669                 * so we can approximate the exponential with
 670                 * 3/4*add_entropy/pool_size and still be on the
 671                 * safe side by adding at most pool_size/2 at a time.
 672                 *
 673                 * The use of pool_size-2 in the while statement is to
 674                 * prevent rounding artifacts from making the loop
 675                 * arbitrarily long; this limits the loop to log2(pool_size)*2
 676                 * turns no matter how large nbits is.
 677                 */
 678                int pnfrac = nfrac;
 679                const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
 680                /* The +2 corresponds to the /4 in the denominator */
 681
 682                do {
 683                        unsigned int anfrac = min(pnfrac, pool_size/2);
 684                        unsigned int add =
 685                                ((pool_size - entropy_count)*anfrac*3) >> s;
 686
 687                        entropy_count += add;
 688                        pnfrac -= anfrac;
 689                } while (unlikely(entropy_count < pool_size-2 && pnfrac));
 690        }
 691
 692        if (unlikely(entropy_count < 0)) {
 693                pr_warn("random: negative entropy/overflow: pool %s count %d\n",
 694                        r->name, entropy_count);
 695                WARN_ON(1);
 696                entropy_count = 0;
 697        } else if (entropy_count > pool_size)
 698                entropy_count = pool_size;
 699        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 700                goto retry;
 701
 702        r->entropy_total += nbits;
 703        if (!r->initialized && r->entropy_total > 128) {
 704                r->initialized = 1;
 705                r->entropy_total = 0;
 706        }
 707
 708        trace_credit_entropy_bits(r->name, nbits,
 709                                  entropy_count >> ENTROPY_SHIFT,
 710                                  r->entropy_total, _RET_IP_);
 711
 712        if (r == &input_pool) {
 713                int entropy_bits = entropy_count >> ENTROPY_SHIFT;
 714
 715                if (crng_init < 2 && entropy_bits >= 128) {
 716                        crng_reseed(&primary_crng, r);
 717                        entropy_bits = r->entropy_count >> ENTROPY_SHIFT;
 718                }
 719
 720                /* should we wake readers? */
 721                if (entropy_bits >= random_read_wakeup_bits) {
 722                        wake_up_interruptible(&random_read_wait);
 723                        kill_fasync(&fasync, SIGIO, POLL_IN);
 724                }
 725                /* If the input pool is getting full, send some
 726                 * entropy to the blocking pool until it is 75% full.
 727                 */
 728                if (entropy_bits > random_write_wakeup_bits &&
 729                    r->initialized &&
 730                    r->entropy_total >= 2*random_read_wakeup_bits) {
 731                        struct entropy_store *other = &blocking_pool;
 732
 733                        if (other->entropy_count <=
 734                            3 * other->poolinfo->poolfracbits / 4) {
 735                                schedule_work(&other->push_work);
 736                                r->entropy_total = 0;
 737                        }
 738                }
 739        }
 740}
 741
 742static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
 743{
 744        const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
 745
 746        if (nbits < 0)
 747                return -EINVAL;
 748
 749        /* Cap the value to avoid overflows */
 750        nbits = min(nbits,  nbits_max);
 751
 752        credit_entropy_bits(r, nbits);
 753        return 0;
 754}
 755
 756/*********************************************************************
 757 *
 758 * CRNG using CHACHA20
 759 *
 760 *********************************************************************/
 761
 762#define CRNG_RESEED_INTERVAL (300*HZ)
 763
 764static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
 765
 766#ifdef CONFIG_NUMA
 767/*
 768 * Hack to deal with crazy userspace progams when they are all trying
 769 * to access /dev/urandom in parallel.  The programs are almost
 770 * certainly doing something terribly wrong, but we'll work around
 771 * their brain damage.
 772 */
 773static struct crng_state **crng_node_pool __read_mostly;
 774#endif
 775
 776static void crng_initialize(struct crng_state *crng)
 777{
 778        int             i;
 779        unsigned long   rv;
 780
 781        memcpy(&crng->state[0], "expand 32-byte k", 16);
 782        if (crng == &primary_crng)
 783                _extract_entropy(&input_pool, &crng->state[4],
 784                                 sizeof(__u32) * 12, 0);
 785        else
 786                get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
 787        for (i = 4; i < 16; i++) {
 788                if (!arch_get_random_seed_long(&rv) &&
 789                    !arch_get_random_long(&rv))
 790                        rv = random_get_entropy();
 791                crng->state[i] ^= rv;
 792        }
 793        crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
 794}
 795
 796static int crng_fast_load(const char *cp, size_t len)
 797{
 798        unsigned long flags;
 799        char *p;
 800
 801        if (!spin_trylock_irqsave(&primary_crng.lock, flags))
 802                return 0;
 803        if (crng_ready()) {
 804                spin_unlock_irqrestore(&primary_crng.lock, flags);
 805                return 0;
 806        }
 807        p = (unsigned char *) &primary_crng.state[4];
 808        while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
 809                p[crng_init_cnt % CHACHA20_KEY_SIZE] ^= *cp;
 810                cp++; crng_init_cnt++; len--;
 811        }
 812        if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
 813                crng_init = 1;
 814                wake_up_interruptible(&crng_init_wait);
 815                pr_notice("random: fast init done\n");
 816        }
 817        spin_unlock_irqrestore(&primary_crng.lock, flags);
 818        return 1;
 819}
 820
 821static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
 822{
 823        unsigned long   flags;
 824        int             i, num;
 825        union {
 826                __u8    block[CHACHA20_BLOCK_SIZE];
 827                __u32   key[8];
 828        } buf;
 829
 830        if (r) {
 831                num = extract_entropy(r, &buf, 32, 16, 0);
 832                if (num == 0)
 833                        return;
 834        } else {
 835                _extract_crng(&primary_crng, buf.block);
 836                _crng_backtrack_protect(&primary_crng, buf.block,
 837                                        CHACHA20_KEY_SIZE);
 838        }
 839        spin_lock_irqsave(&primary_crng.lock, flags);
 840        for (i = 0; i < 8; i++) {
 841                unsigned long   rv;
 842                if (!arch_get_random_seed_long(&rv) &&
 843                    !arch_get_random_long(&rv))
 844                        rv = random_get_entropy();
 845                crng->state[i+4] ^= buf.key[i] ^ rv;
 846        }
 847        memzero_explicit(&buf, sizeof(buf));
 848        crng->init_time = jiffies;
 849        if (crng == &primary_crng && crng_init < 2) {
 850                crng_init = 2;
 851                process_random_ready_list();
 852                wake_up_interruptible(&crng_init_wait);
 853                pr_notice("random: crng init done\n");
 854        }
 855        spin_unlock_irqrestore(&primary_crng.lock, flags);
 856}
 857
 858static inline void maybe_reseed_primary_crng(void)
 859{
 860        if (crng_init > 2 &&
 861            time_after(jiffies, primary_crng.init_time + CRNG_RESEED_INTERVAL))
 862                crng_reseed(&primary_crng, &input_pool);
 863}
 864
 865static inline void crng_wait_ready(void)
 866{
 867        wait_event_interruptible(crng_init_wait, crng_ready());
 868}
 869
 870static void _extract_crng(struct crng_state *crng,
 871                          __u8 out[CHACHA20_BLOCK_SIZE])
 872{
 873        unsigned long v, flags;
 874
 875        if (crng_init > 1 &&
 876            time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL))
 877                crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
 878        spin_lock_irqsave(&crng->lock, flags);
 879        if (arch_get_random_long(&v))
 880                crng->state[14] ^= v;
 881        chacha20_block(&crng->state[0], out);
 882        if (crng->state[12] == 0)
 883                crng->state[13]++;
 884        spin_unlock_irqrestore(&crng->lock, flags);
 885}
 886
 887static void extract_crng(__u8 out[CHACHA20_BLOCK_SIZE])
 888{
 889        struct crng_state *crng = NULL;
 890
 891#ifdef CONFIG_NUMA
 892        if (crng_node_pool)
 893                crng = crng_node_pool[numa_node_id()];
 894        if (crng == NULL)
 895#endif
 896                crng = &primary_crng;
 897        _extract_crng(crng, out);
 898}
 899
 900/*
 901 * Use the leftover bytes from the CRNG block output (if there is
 902 * enough) to mutate the CRNG key to provide backtracking protection.
 903 */
 904static void _crng_backtrack_protect(struct crng_state *crng,
 905                                    __u8 tmp[CHACHA20_BLOCK_SIZE], int used)
 906{
 907        unsigned long   flags;
 908        __u32           *s, *d;
 909        int             i;
 910
 911        used = round_up(used, sizeof(__u32));
 912        if (used + CHACHA20_KEY_SIZE > CHACHA20_BLOCK_SIZE) {
 913                extract_crng(tmp);
 914                used = 0;
 915        }
 916        spin_lock_irqsave(&crng->lock, flags);
 917        s = (__u32 *) &tmp[used];
 918        d = &crng->state[4];
 919        for (i=0; i < 8; i++)
 920                *d++ ^= *s++;
 921        spin_unlock_irqrestore(&crng->lock, flags);
 922}
 923
 924static void crng_backtrack_protect(__u8 tmp[CHACHA20_BLOCK_SIZE], int used)
 925{
 926        struct crng_state *crng = NULL;
 927
 928#ifdef CONFIG_NUMA
 929        if (crng_node_pool)
 930                crng = crng_node_pool[numa_node_id()];
 931        if (crng == NULL)
 932#endif
 933                crng = &primary_crng;
 934        _crng_backtrack_protect(crng, tmp, used);
 935}
 936
 937static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
 938{
 939        ssize_t ret = 0, i = CHACHA20_BLOCK_SIZE;
 940        __u8 tmp[CHACHA20_BLOCK_SIZE];
 941        int large_request = (nbytes > 256);
 942
 943        while (nbytes) {
 944                if (large_request && need_resched()) {
 945                        if (signal_pending(current)) {
 946                                if (ret == 0)
 947                                        ret = -ERESTARTSYS;
 948                                break;
 949                        }
 950                        schedule();
 951                }
 952
 953                extract_crng(tmp);
 954                i = min_t(int, nbytes, CHACHA20_BLOCK_SIZE);
 955                if (copy_to_user(buf, tmp, i)) {
 956                        ret = -EFAULT;
 957                        break;
 958                }
 959
 960                nbytes -= i;
 961                buf += i;
 962                ret += i;
 963        }
 964        crng_backtrack_protect(tmp, i);
 965
 966        /* Wipe data just written to memory */
 967        memzero_explicit(tmp, sizeof(tmp));
 968
 969        return ret;
 970}
 971
 972
 973/*********************************************************************
 974 *
 975 * Entropy input management
 976 *
 977 *********************************************************************/
 978
 979/* There is one of these per entropy source */
 980struct timer_rand_state {
 981        cycles_t last_time;
 982        long last_delta, last_delta2;
 983        unsigned dont_count_entropy:1;
 984};
 985
 986#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
 987
 988/*
 989 * Add device- or boot-specific data to the input pool to help
 990 * initialize it.
 991 *
 992 * None of this adds any entropy; it is meant to avoid the problem of
 993 * the entropy pool having similar initial state across largely
 994 * identical devices.
 995 */
 996void add_device_randomness(const void *buf, unsigned int size)
 997{
 998        unsigned long time = random_get_entropy() ^ jiffies;
 999        unsigned long flags;
1000
1001        trace_add_device_randomness(size, _RET_IP_);
1002        spin_lock_irqsave(&input_pool.lock, flags);
1003        _mix_pool_bytes(&input_pool, buf, size);
1004        _mix_pool_bytes(&input_pool, &time, sizeof(time));
1005        spin_unlock_irqrestore(&input_pool.lock, flags);
1006}
1007EXPORT_SYMBOL(add_device_randomness);
1008
1009static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
1010
1011/*
1012 * This function adds entropy to the entropy "pool" by using timing
1013 * delays.  It uses the timer_rand_state structure to make an estimate
1014 * of how many bits of entropy this call has added to the pool.
1015 *
1016 * The number "num" is also added to the pool - it should somehow describe
1017 * the type of event which just happened.  This is currently 0-255 for
1018 * keyboard scan codes, and 256 upwards for interrupts.
1019 *
1020 */
1021static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
1022{
1023        struct entropy_store    *r;
1024        struct {
1025                long jiffies;
1026                unsigned cycles;
1027                unsigned num;
1028        } sample;
1029        long delta, delta2, delta3;
1030
1031        preempt_disable();
1032
1033        sample.jiffies = jiffies;
1034        sample.cycles = random_get_entropy();
1035        sample.num = num;
1036        r = &input_pool;
1037        mix_pool_bytes(r, &sample, sizeof(sample));
1038
1039        /*
1040         * Calculate number of bits of randomness we probably added.
1041         * We take into account the first, second and third-order deltas
1042         * in order to make our estimate.
1043         */
1044
1045        if (!state->dont_count_entropy) {
1046                delta = sample.jiffies - state->last_time;
1047                state->last_time = sample.jiffies;
1048
1049                delta2 = delta - state->last_delta;
1050                state->last_delta = delta;
1051
1052                delta3 = delta2 - state->last_delta2;
1053                state->last_delta2 = delta2;
1054
1055                if (delta < 0)
1056                        delta = -delta;
1057                if (delta2 < 0)
1058                        delta2 = -delta2;
1059                if (delta3 < 0)
1060                        delta3 = -delta3;
1061                if (delta > delta2)
1062                        delta = delta2;
1063                if (delta > delta3)
1064                        delta = delta3;
1065
1066                /*
1067                 * delta is now minimum absolute delta.
1068                 * Round down by 1 bit on general principles,
1069                 * and limit entropy entimate to 12 bits.
1070                 */
1071                credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1072        }
1073        preempt_enable();
1074}
1075
1076void add_input_randomness(unsigned int type, unsigned int code,
1077                                 unsigned int value)
1078{
1079        static unsigned char last_value;
1080
1081        /* ignore autorepeat and the like */
1082        if (value == last_value)
1083                return;
1084
1085        last_value = value;
1086        add_timer_randomness(&input_timer_state,
1087                             (type << 4) ^ code ^ (code >> 4) ^ value);
1088        trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1089}
1090EXPORT_SYMBOL_GPL(add_input_randomness);
1091
1092static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
1093
1094#ifdef ADD_INTERRUPT_BENCH
1095static unsigned long avg_cycles, avg_deviation;
1096
1097#define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
1098#define FIXED_1_2 (1 << (AVG_SHIFT-1))
1099
1100static void add_interrupt_bench(cycles_t start)
1101{
1102        long delta = random_get_entropy() - start;
1103
1104        /* Use a weighted moving average */
1105        delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
1106        avg_cycles += delta;
1107        /* And average deviation */
1108        delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
1109        avg_deviation += delta;
1110}
1111#else
1112#define add_interrupt_bench(x)
1113#endif
1114
1115static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
1116{
1117        __u32 *ptr = (__u32 *) regs;
1118
1119        if (regs == NULL)
1120                return 0;
1121        if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
1122                f->reg_idx = 0;
1123        return *(ptr + f->reg_idx++);
1124}
1125
1126void add_interrupt_randomness(int irq, int irq_flags)
1127{
1128        struct entropy_store    *r;
1129        struct fast_pool        *fast_pool = this_cpu_ptr(&irq_randomness);
1130        struct pt_regs          *regs = get_irq_regs();
1131        unsigned long           now = jiffies;
1132        cycles_t                cycles = random_get_entropy();
1133        __u32                   c_high, j_high;
1134        __u64                   ip;
1135        unsigned long           seed;
1136        int                     credit = 0;
1137
1138        if (cycles == 0)
1139                cycles = get_reg(fast_pool, regs);
1140        c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
1141        j_high = (sizeof(now) > 4) ? now >> 32 : 0;
1142        fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
1143        fast_pool->pool[1] ^= now ^ c_high;
1144        ip = regs ? instruction_pointer(regs) : _RET_IP_;
1145        fast_pool->pool[2] ^= ip;
1146        fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
1147                get_reg(fast_pool, regs);
1148
1149        fast_mix(fast_pool);
1150        add_interrupt_bench(cycles);
1151
1152        if (!crng_ready()) {
1153                if ((fast_pool->count >= 64) &&
1154                    crng_fast_load((char *) fast_pool->pool,
1155                                   sizeof(fast_pool->pool))) {
1156                        fast_pool->count = 0;
1157                        fast_pool->last = now;
1158                }
1159                return;
1160        }
1161
1162        if ((fast_pool->count < 64) &&
1163            !time_after(now, fast_pool->last + HZ))
1164                return;
1165
1166        r = &input_pool;
1167        if (!spin_trylock(&r->lock))
1168                return;
1169
1170        fast_pool->last = now;
1171        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
1172
1173        /*
1174         * If we have architectural seed generator, produce a seed and
1175         * add it to the pool.  For the sake of paranoia don't let the
1176         * architectural seed generator dominate the input from the
1177         * interrupt noise.
1178         */
1179        if (arch_get_random_seed_long(&seed)) {
1180                __mix_pool_bytes(r, &seed, sizeof(seed));
1181                credit = 1;
1182        }
1183        spin_unlock(&r->lock);
1184
1185        fast_pool->count = 0;
1186
1187        /* award one bit for the contents of the fast pool */
1188        credit_entropy_bits(r, credit + 1);
1189}
1190EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1191
1192#ifdef CONFIG_BLOCK
1193void add_disk_randomness(struct gendisk *disk)
1194{
1195        if (!disk || !disk->random)
1196                return;
1197        /* first major is 1, so we get >= 0x200 here */
1198        add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1199        trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1200}
1201EXPORT_SYMBOL_GPL(add_disk_randomness);
1202#endif
1203
1204/*********************************************************************
1205 *
1206 * Entropy extraction routines
1207 *
1208 *********************************************************************/
1209
1210/*
1211 * This utility inline function is responsible for transferring entropy
1212 * from the primary pool to the secondary extraction pool. We make
1213 * sure we pull enough for a 'catastrophic reseed'.
1214 */
1215static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
1216static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1217{
1218        if (!r->pull ||
1219            r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
1220            r->entropy_count > r->poolinfo->poolfracbits)
1221                return;
1222
1223        if (r->limit == 0 && random_min_urandom_seed) {
1224                unsigned long now = jiffies;
1225
1226                if (time_before(now,
1227                                r->last_pulled + random_min_urandom_seed * HZ))
1228                        return;
1229                r->last_pulled = now;
1230        }
1231
1232        _xfer_secondary_pool(r, nbytes);
1233}
1234
1235static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1236{
1237        __u32   tmp[OUTPUT_POOL_WORDS];
1238
1239        /* For /dev/random's pool, always leave two wakeups' worth */
1240        int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
1241        int bytes = nbytes;
1242
1243        /* pull at least as much as a wakeup */
1244        bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
1245        /* but never more than the buffer size */
1246        bytes = min_t(int, bytes, sizeof(tmp));
1247
1248        trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
1249                                  ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
1250        bytes = extract_entropy(r->pull, tmp, bytes,
1251                                random_read_wakeup_bits / 8, rsvd_bytes);
1252        mix_pool_bytes(r, tmp, bytes);
1253        credit_entropy_bits(r, bytes*8);
1254}
1255
1256/*
1257 * Used as a workqueue function so that when the input pool is getting
1258 * full, we can "spill over" some entropy to the output pools.  That
1259 * way the output pools can store some of the excess entropy instead
1260 * of letting it go to waste.
1261 */
1262static void push_to_pool(struct work_struct *work)
1263{
1264        struct entropy_store *r = container_of(work, struct entropy_store,
1265                                              push_work);
1266        BUG_ON(!r);
1267        _xfer_secondary_pool(r, random_read_wakeup_bits/8);
1268        trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1269                           r->pull->entropy_count >> ENTROPY_SHIFT);
1270}
1271
1272/*
1273 * This function decides how many bytes to actually take from the
1274 * given pool, and also debits the entropy count accordingly.
1275 */
1276static size_t account(struct entropy_store *r, size_t nbytes, int min,
1277                      int reserved)
1278{
1279        int entropy_count, orig;
1280        size_t ibytes, nfrac;
1281
1282        BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1283
1284        /* Can we pull enough? */
1285retry:
1286        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
1287        ibytes = nbytes;
1288        /* If limited, never pull more than available */
1289        if (r->limit) {
1290                int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1291
1292                if ((have_bytes -= reserved) < 0)
1293                        have_bytes = 0;
1294                ibytes = min_t(size_t, ibytes, have_bytes);
1295        }
1296        if (ibytes < min)
1297                ibytes = 0;
1298
1299        if (unlikely(entropy_count < 0)) {
1300                pr_warn("random: negative entropy count: pool %s count %d\n",
1301                        r->name, entropy_count);
1302                WARN_ON(1);
1303                entropy_count = 0;
1304        }
1305        nfrac = ibytes << (ENTROPY_SHIFT + 3);
1306        if ((size_t) entropy_count > nfrac)
1307                entropy_count -= nfrac;
1308        else
1309                entropy_count = 0;
1310
1311        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1312                goto retry;
1313
1314        trace_debit_entropy(r->name, 8 * ibytes);
1315        if (ibytes &&
1316            (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1317                wake_up_interruptible(&random_write_wait);
1318                kill_fasync(&fasync, SIGIO, POLL_OUT);
1319        }
1320
1321        return ibytes;
1322}
1323
1324/*
1325 * This function does the actual extraction for extract_entropy and
1326 * extract_entropy_user.
1327 *
1328 * Note: we assume that .poolwords is a multiple of 16 words.
1329 */
1330static void extract_buf(struct entropy_store *r, __u8 *out)
1331{
1332        int i;
1333        union {
1334                __u32 w[5];
1335                unsigned long l[LONGS(20)];
1336        } hash;
1337        __u32 workspace[SHA_WORKSPACE_WORDS];
1338        unsigned long flags;
1339
1340        /*
1341         * If we have an architectural hardware random number
1342         * generator, use it for SHA's initial vector
1343         */
1344        sha_init(hash.w);
1345        for (i = 0; i < LONGS(20); i++) {
1346                unsigned long v;
1347                if (!arch_get_random_long(&v))
1348                        break;
1349                hash.l[i] = v;
1350        }
1351
1352        /* Generate a hash across the pool, 16 words (512 bits) at a time */
1353        spin_lock_irqsave(&r->lock, flags);
1354        for (i = 0; i < r->poolinfo->poolwords; i += 16)
1355                sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1356
1357        /*
1358         * We mix the hash back into the pool to prevent backtracking
1359         * attacks (where the attacker knows the state of the pool
1360         * plus the current outputs, and attempts to find previous
1361         * ouputs), unless the hash function can be inverted. By
1362         * mixing at least a SHA1 worth of hash data back, we make
1363         * brute-forcing the feedback as hard as brute-forcing the
1364         * hash.
1365         */
1366        __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1367        spin_unlock_irqrestore(&r->lock, flags);
1368
1369        memzero_explicit(workspace, sizeof(workspace));
1370
1371        /*
1372         * In case the hash function has some recognizable output
1373         * pattern, we fold it in half. Thus, we always feed back
1374         * twice as much data as we output.
1375         */
1376        hash.w[0] ^= hash.w[3];
1377        hash.w[1] ^= hash.w[4];
1378        hash.w[2] ^= rol32(hash.w[2], 16);
1379
1380        memcpy(out, &hash, EXTRACT_SIZE);
1381        memzero_explicit(&hash, sizeof(hash));
1382}
1383
1384static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
1385                                size_t nbytes, int fips)
1386{
1387        ssize_t ret = 0, i;
1388        __u8 tmp[EXTRACT_SIZE];
1389        unsigned long flags;
1390
1391        while (nbytes) {
1392                extract_buf(r, tmp);
1393
1394                if (fips) {
1395                        spin_lock_irqsave(&r->lock, flags);
1396                        if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1397                                panic("Hardware RNG duplicated output!\n");
1398                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
1399                        spin_unlock_irqrestore(&r->lock, flags);
1400                }
1401                i = min_t(int, nbytes, EXTRACT_SIZE);
1402                memcpy(buf, tmp, i);
1403                nbytes -= i;
1404                buf += i;
1405                ret += i;
1406        }
1407
1408        /* Wipe data just returned from memory */
1409        memzero_explicit(tmp, sizeof(tmp));
1410
1411        return ret;
1412}
1413
1414/*
1415 * This function extracts randomness from the "entropy pool", and
1416 * returns it in a buffer.
1417 *
1418 * The min parameter specifies the minimum amount we can pull before
1419 * failing to avoid races that defeat catastrophic reseeding while the
1420 * reserved parameter indicates how much entropy we must leave in the
1421 * pool after each pull to avoid starving other readers.
1422 */
1423static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1424                                 size_t nbytes, int min, int reserved)
1425{
1426        __u8 tmp[EXTRACT_SIZE];
1427        unsigned long flags;
1428
1429        /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1430        if (fips_enabled) {
1431                spin_lock_irqsave(&r->lock, flags);
1432                if (!r->last_data_init) {
1433                        r->last_data_init = 1;
1434                        spin_unlock_irqrestore(&r->lock, flags);
1435                        trace_extract_entropy(r->name, EXTRACT_SIZE,
1436                                              ENTROPY_BITS(r), _RET_IP_);
1437                        xfer_secondary_pool(r, EXTRACT_SIZE);
1438                        extract_buf(r, tmp);
1439                        spin_lock_irqsave(&r->lock, flags);
1440                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
1441                }
1442                spin_unlock_irqrestore(&r->lock, flags);
1443        }
1444
1445        trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1446        xfer_secondary_pool(r, nbytes);
1447        nbytes = account(r, nbytes, min, reserved);
1448
1449        return _extract_entropy(r, buf, nbytes, fips_enabled);
1450}
1451
1452/*
1453 * This function extracts randomness from the "entropy pool", and
1454 * returns it in a userspace buffer.
1455 */
1456static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1457                                    size_t nbytes)
1458{
1459        ssize_t ret = 0, i;
1460        __u8 tmp[EXTRACT_SIZE];
1461        int large_request = (nbytes > 256);
1462
1463        trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1464        xfer_secondary_pool(r, nbytes);
1465        nbytes = account(r, nbytes, 0, 0);
1466
1467        while (nbytes) {
1468                if (large_request && need_resched()) {
1469                        if (signal_pending(current)) {
1470                                if (ret == 0)
1471                                        ret = -ERESTARTSYS;
1472                                break;
1473                        }
1474                        schedule();
1475                }
1476
1477                extract_buf(r, tmp);
1478                i = min_t(int, nbytes, EXTRACT_SIZE);
1479                if (copy_to_user(buf, tmp, i)) {
1480                        ret = -EFAULT;
1481                        break;
1482                }
1483
1484                nbytes -= i;
1485                buf += i;
1486                ret += i;
1487        }
1488
1489        /* Wipe data just returned from memory */
1490        memzero_explicit(tmp, sizeof(tmp));
1491
1492        return ret;
1493}
1494
1495/*
1496 * This function is the exported kernel interface.  It returns some
1497 * number of good random numbers, suitable for key generation, seeding
1498 * TCP sequence numbers, etc.  It does not rely on the hardware random
1499 * number generator.  For random bytes direct from the hardware RNG
1500 * (when available), use get_random_bytes_arch().
1501 */
1502void get_random_bytes(void *buf, int nbytes)
1503{
1504        __u8 tmp[CHACHA20_BLOCK_SIZE];
1505
1506#if DEBUG_RANDOM_BOOT > 0
1507        if (!crng_ready())
1508                printk(KERN_NOTICE "random: %pF get_random_bytes called "
1509                       "with crng_init = %d\n", (void *) _RET_IP_, crng_init);
1510#endif
1511        trace_get_random_bytes(nbytes, _RET_IP_);
1512
1513        while (nbytes >= CHACHA20_BLOCK_SIZE) {
1514                extract_crng(buf);
1515                buf += CHACHA20_BLOCK_SIZE;
1516                nbytes -= CHACHA20_BLOCK_SIZE;
1517        }
1518
1519        if (nbytes > 0) {
1520                extract_crng(tmp);
1521                memcpy(buf, tmp, nbytes);
1522                crng_backtrack_protect(tmp, nbytes);
1523        } else
1524                crng_backtrack_protect(tmp, CHACHA20_BLOCK_SIZE);
1525        memzero_explicit(tmp, sizeof(tmp));
1526}
1527EXPORT_SYMBOL(get_random_bytes);
1528
1529/*
1530 * Add a callback function that will be invoked when the nonblocking
1531 * pool is initialised.
1532 *
1533 * returns: 0 if callback is successfully added
1534 *          -EALREADY if pool is already initialised (callback not called)
1535 *          -ENOENT if module for callback is not alive
1536 */
1537int add_random_ready_callback(struct random_ready_callback *rdy)
1538{
1539        struct module *owner;
1540        unsigned long flags;
1541        int err = -EALREADY;
1542
1543        if (crng_ready())
1544                return err;
1545
1546        owner = rdy->owner;
1547        if (!try_module_get(owner))
1548                return -ENOENT;
1549
1550        spin_lock_irqsave(&random_ready_list_lock, flags);
1551        if (crng_ready())
1552                goto out;
1553
1554        owner = NULL;
1555
1556        list_add(&rdy->list, &random_ready_list);
1557        err = 0;
1558
1559out:
1560        spin_unlock_irqrestore(&random_ready_list_lock, flags);
1561
1562        module_put(owner);
1563
1564        return err;
1565}
1566EXPORT_SYMBOL(add_random_ready_callback);
1567
1568/*
1569 * Delete a previously registered readiness callback function.
1570 */
1571void del_random_ready_callback(struct random_ready_callback *rdy)
1572{
1573        unsigned long flags;
1574        struct module *owner = NULL;
1575
1576        spin_lock_irqsave(&random_ready_list_lock, flags);
1577        if (!list_empty(&rdy->list)) {
1578                list_del_init(&rdy->list);
1579                owner = rdy->owner;
1580        }
1581        spin_unlock_irqrestore(&random_ready_list_lock, flags);
1582
1583        module_put(owner);
1584}
1585EXPORT_SYMBOL(del_random_ready_callback);
1586
1587/*
1588 * This function will use the architecture-specific hardware random
1589 * number generator if it is available.  The arch-specific hw RNG will
1590 * almost certainly be faster than what we can do in software, but it
1591 * is impossible to verify that it is implemented securely (as
1592 * opposed, to, say, the AES encryption of a sequence number using a
1593 * key known by the NSA).  So it's useful if we need the speed, but
1594 * only if we're willing to trust the hardware manufacturer not to
1595 * have put in a back door.
1596 */
1597void get_random_bytes_arch(void *buf, int nbytes)
1598{
1599        char *p = buf;
1600
1601        trace_get_random_bytes_arch(nbytes, _RET_IP_);
1602        while (nbytes) {
1603                unsigned long v;
1604                int chunk = min(nbytes, (int)sizeof(unsigned long));
1605
1606                if (!arch_get_random_long(&v))
1607                        break;
1608                
1609                memcpy(p, &v, chunk);
1610                p += chunk;
1611                nbytes -= chunk;
1612        }
1613
1614        if (nbytes)
1615                get_random_bytes(p, nbytes);
1616}
1617EXPORT_SYMBOL(get_random_bytes_arch);
1618
1619
1620/*
1621 * init_std_data - initialize pool with system data
1622 *
1623 * @r: pool to initialize
1624 *
1625 * This function clears the pool's entropy count and mixes some system
1626 * data into the pool to prepare it for use. The pool is not cleared
1627 * as that can only decrease the entropy in the pool.
1628 */
1629static void init_std_data(struct entropy_store *r)
1630{
1631        int i;
1632        ktime_t now = ktime_get_real();
1633        unsigned long rv;
1634
1635        r->last_pulled = jiffies;
1636        mix_pool_bytes(r, &now, sizeof(now));
1637        for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1638                if (!arch_get_random_seed_long(&rv) &&
1639                    !arch_get_random_long(&rv))
1640                        rv = random_get_entropy();
1641                mix_pool_bytes(r, &rv, sizeof(rv));
1642        }
1643        mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1644}
1645
1646/*
1647 * Note that setup_arch() may call add_device_randomness()
1648 * long before we get here. This allows seeding of the pools
1649 * with some platform dependent data very early in the boot
1650 * process. But it limits our options here. We must use
1651 * statically allocated structures that already have all
1652 * initializations complete at compile time. We should also
1653 * take care not to overwrite the precious per platform data
1654 * we were given.
1655 */
1656static int rand_initialize(void)
1657{
1658#ifdef CONFIG_NUMA
1659        int i;
1660        struct crng_state *crng;
1661        struct crng_state **pool;
1662#endif
1663
1664        init_std_data(&input_pool);
1665        init_std_data(&blocking_pool);
1666        crng_initialize(&primary_crng);
1667
1668#ifdef CONFIG_NUMA
1669        pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
1670        for_each_online_node(i) {
1671                crng = kmalloc_node(sizeof(struct crng_state),
1672                                    GFP_KERNEL | __GFP_NOFAIL, i);
1673                spin_lock_init(&crng->lock);
1674                crng_initialize(crng);
1675                pool[i] = crng;
1676        }
1677        mb();
1678        crng_node_pool = pool;
1679#endif
1680        return 0;
1681}
1682early_initcall(rand_initialize);
1683
1684#ifdef CONFIG_BLOCK
1685void rand_initialize_disk(struct gendisk *disk)
1686{
1687        struct timer_rand_state *state;
1688
1689        /*
1690         * If kzalloc returns null, we just won't use that entropy
1691         * source.
1692         */
1693        state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1694        if (state) {
1695                state->last_time = INITIAL_JIFFIES;
1696                disk->random = state;
1697        }
1698}
1699#endif
1700
1701static ssize_t
1702_random_read(int nonblock, char __user *buf, size_t nbytes)
1703{
1704        ssize_t n;
1705
1706        if (nbytes == 0)
1707                return 0;
1708
1709        nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1710        while (1) {
1711                n = extract_entropy_user(&blocking_pool, buf, nbytes);
1712                if (n < 0)
1713                        return n;
1714                trace_random_read(n*8, (nbytes-n)*8,
1715                                  ENTROPY_BITS(&blocking_pool),
1716                                  ENTROPY_BITS(&input_pool));
1717                if (n > 0)
1718                        return n;
1719
1720                /* Pool is (near) empty.  Maybe wait and retry. */
1721                if (nonblock)
1722                        return -EAGAIN;
1723
1724                wait_event_interruptible(random_read_wait,
1725                        ENTROPY_BITS(&input_pool) >=
1726                        random_read_wakeup_bits);
1727                if (signal_pending(current))
1728                        return -ERESTARTSYS;
1729        }
1730}
1731
1732static ssize_t
1733random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1734{
1735        return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1736}
1737
1738static ssize_t
1739urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1740{
1741        unsigned long flags;
1742        static int maxwarn = 10;
1743        int ret;
1744
1745        if (!crng_ready() && maxwarn > 0) {
1746                maxwarn--;
1747                printk(KERN_NOTICE "random: %s: uninitialized urandom read "
1748                       "(%zd bytes read)\n",
1749                       current->comm, nbytes);
1750                spin_lock_irqsave(&primary_crng.lock, flags);
1751                crng_init_cnt = 0;
1752                spin_unlock_irqrestore(&primary_crng.lock, flags);
1753        }
1754        nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1755        ret = extract_crng_user(buf, nbytes);
1756        trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
1757        return ret;
1758}
1759
1760static unsigned int
1761random_poll(struct file *file, poll_table * wait)
1762{
1763        unsigned int mask;
1764
1765        poll_wait(file, &random_read_wait, wait);
1766        poll_wait(file, &random_write_wait, wait);
1767        mask = 0;
1768        if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1769                mask |= POLLIN | POLLRDNORM;
1770        if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1771                mask |= POLLOUT | POLLWRNORM;
1772        return mask;
1773}
1774
1775static int
1776write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1777{
1778        size_t bytes;
1779        __u32 buf[16];
1780        const char __user *p = buffer;
1781
1782        while (count > 0) {
1783                bytes = min(count, sizeof(buf));
1784                if (copy_from_user(&buf, p, bytes))
1785                        return -EFAULT;
1786
1787                count -= bytes;
1788                p += bytes;
1789
1790                mix_pool_bytes(r, buf, bytes);
1791                cond_resched();
1792        }
1793
1794        return 0;
1795}
1796
1797static ssize_t random_write(struct file *file, const char __user *buffer,
1798                            size_t count, loff_t *ppos)
1799{
1800        size_t ret;
1801
1802        ret = write_pool(&input_pool, buffer, count);
1803        if (ret)
1804                return ret;
1805
1806        return (ssize_t)count;
1807}
1808
1809static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1810{
1811        int size, ent_count;
1812        int __user *p = (int __user *)arg;
1813        int retval;
1814
1815        switch (cmd) {
1816        case RNDGETENTCNT:
1817                /* inherently racy, no point locking */
1818                ent_count = ENTROPY_BITS(&input_pool);
1819                if (put_user(ent_count, p))
1820                        return -EFAULT;
1821                return 0;
1822        case RNDADDTOENTCNT:
1823                if (!capable(CAP_SYS_ADMIN))
1824                        return -EPERM;
1825                if (get_user(ent_count, p))
1826                        return -EFAULT;
1827                return credit_entropy_bits_safe(&input_pool, ent_count);
1828        case RNDADDENTROPY:
1829                if (!capable(CAP_SYS_ADMIN))
1830                        return -EPERM;
1831                if (get_user(ent_count, p++))
1832                        return -EFAULT;
1833                if (ent_count < 0)
1834                        return -EINVAL;
1835                if (get_user(size, p++))
1836                        return -EFAULT;
1837                retval = write_pool(&input_pool, (const char __user *)p,
1838                                    size);
1839                if (retval < 0)
1840                        return retval;
1841                return credit_entropy_bits_safe(&input_pool, ent_count);
1842        case RNDZAPENTCNT:
1843        case RNDCLEARPOOL:
1844                /*
1845                 * Clear the entropy pool counters. We no longer clear
1846                 * the entropy pool, as that's silly.
1847                 */
1848                if (!capable(CAP_SYS_ADMIN))
1849                        return -EPERM;
1850                input_pool.entropy_count = 0;
1851                blocking_pool.entropy_count = 0;
1852                return 0;
1853        default:
1854                return -EINVAL;
1855        }
1856}
1857
1858static int random_fasync(int fd, struct file *filp, int on)
1859{
1860        return fasync_helper(fd, filp, on, &fasync);
1861}
1862
1863const struct file_operations random_fops = {
1864        .read  = random_read,
1865        .write = random_write,
1866        .poll  = random_poll,
1867        .unlocked_ioctl = random_ioctl,
1868        .fasync = random_fasync,
1869        .llseek = noop_llseek,
1870};
1871
1872const struct file_operations urandom_fops = {
1873        .read  = urandom_read,
1874        .write = random_write,
1875        .unlocked_ioctl = random_ioctl,
1876        .fasync = random_fasync,
1877        .llseek = noop_llseek,
1878};
1879
1880SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1881                unsigned int, flags)
1882{
1883        if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
1884                return -EINVAL;
1885
1886        if (count > INT_MAX)
1887                count = INT_MAX;
1888
1889        if (flags & GRND_RANDOM)
1890                return _random_read(flags & GRND_NONBLOCK, buf, count);
1891
1892        if (!crng_ready()) {
1893                if (flags & GRND_NONBLOCK)
1894                        return -EAGAIN;
1895                crng_wait_ready();
1896                if (signal_pending(current))
1897                        return -ERESTARTSYS;
1898        }
1899        return urandom_read(NULL, buf, count, NULL);
1900}
1901
1902/********************************************************************
1903 *
1904 * Sysctl interface
1905 *
1906 ********************************************************************/
1907
1908#ifdef CONFIG_SYSCTL
1909
1910#include <linux/sysctl.h>
1911
1912static int min_read_thresh = 8, min_write_thresh;
1913static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1914static int max_write_thresh = INPUT_POOL_WORDS * 32;
1915static char sysctl_bootid[16];
1916
1917/*
1918 * This function is used to return both the bootid UUID, and random
1919 * UUID.  The difference is in whether table->data is NULL; if it is,
1920 * then a new UUID is generated and returned to the user.
1921 *
1922 * If the user accesses this via the proc interface, the UUID will be
1923 * returned as an ASCII string in the standard UUID format; if via the
1924 * sysctl system call, as 16 bytes of binary data.
1925 */
1926static int proc_do_uuid(struct ctl_table *table, int write,
1927                        void __user *buffer, size_t *lenp, loff_t *ppos)
1928{
1929        struct ctl_table fake_table;
1930        unsigned char buf[64], tmp_uuid[16], *uuid;
1931
1932        uuid = table->data;
1933        if (!uuid) {
1934                uuid = tmp_uuid;
1935                generate_random_uuid(uuid);
1936        } else {
1937                static DEFINE_SPINLOCK(bootid_spinlock);
1938
1939                spin_lock(&bootid_spinlock);
1940                if (!uuid[8])
1941                        generate_random_uuid(uuid);
1942                spin_unlock(&bootid_spinlock);
1943        }
1944
1945        sprintf(buf, "%pU", uuid);
1946
1947        fake_table.data = buf;
1948        fake_table.maxlen = sizeof(buf);
1949
1950        return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1951}
1952
1953/*
1954 * Return entropy available scaled to integral bits
1955 */
1956static int proc_do_entropy(struct ctl_table *table, int write,
1957                           void __user *buffer, size_t *lenp, loff_t *ppos)
1958{
1959        struct ctl_table fake_table;
1960        int entropy_count;
1961
1962        entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1963
1964        fake_table.data = &entropy_count;
1965        fake_table.maxlen = sizeof(entropy_count);
1966
1967        return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1968}
1969
1970static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1971extern struct ctl_table random_table[];
1972struct ctl_table random_table[] = {
1973        {
1974                .procname       = "poolsize",
1975                .data           = &sysctl_poolsize,
1976                .maxlen         = sizeof(int),
1977                .mode           = 0444,
1978                .proc_handler   = proc_dointvec,
1979        },
1980        {
1981                .procname       = "entropy_avail",
1982                .maxlen         = sizeof(int),
1983                .mode           = 0444,
1984                .proc_handler   = proc_do_entropy,
1985                .data           = &input_pool.entropy_count,
1986        },
1987        {
1988                .procname       = "read_wakeup_threshold",
1989                .data           = &random_read_wakeup_bits,
1990                .maxlen         = sizeof(int),
1991                .mode           = 0644,
1992                .proc_handler   = proc_dointvec_minmax,
1993                .extra1         = &min_read_thresh,
1994                .extra2         = &max_read_thresh,
1995        },
1996        {
1997                .procname       = "write_wakeup_threshold",
1998                .data           = &random_write_wakeup_bits,
1999                .maxlen         = sizeof(int),
2000                .mode           = 0644,
2001                .proc_handler   = proc_dointvec_minmax,
2002                .extra1         = &min_write_thresh,
2003                .extra2         = &max_write_thresh,
2004        },
2005        {
2006                .procname       = "urandom_min_reseed_secs",
2007                .data           = &random_min_urandom_seed,
2008                .maxlen         = sizeof(int),
2009                .mode           = 0644,
2010                .proc_handler   = proc_dointvec,
2011        },
2012        {
2013                .procname       = "boot_id",
2014                .data           = &sysctl_bootid,
2015                .maxlen         = 16,
2016                .mode           = 0444,
2017                .proc_handler   = proc_do_uuid,
2018        },
2019        {
2020                .procname       = "uuid",
2021                .maxlen         = 16,
2022                .mode           = 0444,
2023                .proc_handler   = proc_do_uuid,
2024        },
2025#ifdef ADD_INTERRUPT_BENCH
2026        {
2027                .procname       = "add_interrupt_avg_cycles",
2028                .data           = &avg_cycles,
2029                .maxlen         = sizeof(avg_cycles),
2030                .mode           = 0444,
2031                .proc_handler   = proc_doulongvec_minmax,
2032        },
2033        {
2034                .procname       = "add_interrupt_avg_deviation",
2035                .data           = &avg_deviation,
2036                .maxlen         = sizeof(avg_deviation),
2037                .mode           = 0444,
2038                .proc_handler   = proc_doulongvec_minmax,
2039        },
2040#endif
2041        { }
2042};
2043#endif  /* CONFIG_SYSCTL */
2044
2045static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
2046
2047int random_int_secret_init(void)
2048{
2049        get_random_bytes(random_int_secret, sizeof(random_int_secret));
2050        return 0;
2051}
2052
2053static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash)
2054                __aligned(sizeof(unsigned long));
2055
2056/*
2057 * Get a random word for internal kernel use only. Similar to urandom but
2058 * with the goal of minimal entropy pool depletion. As a result, the random
2059 * value is not cryptographically secure but for several uses the cost of
2060 * depleting entropy is too high
2061 */
2062unsigned int get_random_int(void)
2063{
2064        __u32 *hash;
2065        unsigned int ret;
2066
2067        if (arch_get_random_int(&ret))
2068                return ret;
2069
2070        hash = get_cpu_var(get_random_int_hash);
2071
2072        hash[0] += current->pid + jiffies + random_get_entropy();
2073        md5_transform(hash, random_int_secret);
2074        ret = hash[0];
2075        put_cpu_var(get_random_int_hash);
2076
2077        return ret;
2078}
2079EXPORT_SYMBOL(get_random_int);
2080
2081/*
2082 * Same as get_random_int(), but returns unsigned long.
2083 */
2084unsigned long get_random_long(void)
2085{
2086        __u32 *hash;
2087        unsigned long ret;
2088
2089        if (arch_get_random_long(&ret))
2090                return ret;
2091
2092        hash = get_cpu_var(get_random_int_hash);
2093
2094        hash[0] += current->pid + jiffies + random_get_entropy();
2095        md5_transform(hash, random_int_secret);
2096        ret = *(unsigned long *)hash;
2097        put_cpu_var(get_random_int_hash);
2098
2099        return ret;
2100}
2101EXPORT_SYMBOL(get_random_long);
2102
2103/**
2104 * randomize_page - Generate a random, page aligned address
2105 * @start:      The smallest acceptable address the caller will take.
2106 * @range:      The size of the area, starting at @start, within which the
2107 *              random address must fall.
2108 *
2109 * If @start + @range would overflow, @range is capped.
2110 *
2111 * NOTE: Historical use of randomize_range, which this replaces, presumed that
2112 * @start was already page aligned.  We now align it regardless.
2113 *
2114 * Return: A page aligned address within [start, start + range).  On error,
2115 * @start is returned.
2116 */
2117unsigned long
2118randomize_page(unsigned long start, unsigned long range)
2119{
2120        if (!PAGE_ALIGNED(start)) {
2121                range -= PAGE_ALIGN(start) - start;
2122                start = PAGE_ALIGN(start);
2123        }
2124
2125        if (start > ULONG_MAX - range)
2126                range = ULONG_MAX - start;
2127
2128        range >>= PAGE_SHIFT;
2129
2130        if (range == 0)
2131                return start;
2132
2133        return start + (get_random_long() % range << PAGE_SHIFT);
2134}
2135
2136/* Interface for in-kernel drivers of true hardware RNGs.
2137 * Those devices may produce endless random bits and will be throttled
2138 * when our pool is full.
2139 */
2140void add_hwgenerator_randomness(const char *buffer, size_t count,
2141                                size_t entropy)
2142{
2143        struct entropy_store *poolp = &input_pool;
2144
2145        if (!crng_ready()) {
2146                crng_fast_load(buffer, count);
2147                return;
2148        }
2149
2150        /* Suspend writing if we're above the trickle threshold.
2151         * We'll be woken up again once below random_write_wakeup_thresh,
2152         * or when the calling thread is about to terminate.
2153         */
2154        wait_event_interruptible(random_write_wait, kthread_should_stop() ||
2155                        ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
2156        mix_pool_bytes(poolp, buffer, count);
2157        credit_entropy_bits(poolp, entropy);
2158}
2159EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
2160
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.