linux/drivers/char/random.c
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   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/spinlock.h>
 253#include <linux/percpu.h>
 254#include <linux/cryptohash.h>
 255#include <linux/fips.h>
 256#include <linux/ptrace.h>
 257#include <linux/kmemcheck.h>
 258#include <linux/workqueue.h>
 259#include <linux/irq.h>
 260
 261#include <asm/processor.h>
 262#include <asm/uaccess.h>
 263#include <asm/irq.h>
 264#include <asm/irq_regs.h>
 265#include <asm/io.h>
 266
 267#define CREATE_TRACE_POINTS
 268#include <trace/events/random.h>
 269
 270/*
 271 * Configuration information
 272 */
 273#define INPUT_POOL_SHIFT        12
 274#define INPUT_POOL_WORDS        (1 << (INPUT_POOL_SHIFT-5))
 275#define OUTPUT_POOL_SHIFT       10
 276#define OUTPUT_POOL_WORDS       (1 << (OUTPUT_POOL_SHIFT-5))
 277#define SEC_XFER_SIZE           512
 278#define EXTRACT_SIZE            10
 279
 280#define DEBUG_RANDOM_BOOT 0
 281
 282#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
 283
 284/*
 285 * To allow fractional bits to be tracked, the entropy_count field is
 286 * denominated in units of 1/8th bits.
 287 *
 288 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
 289 * credit_entropy_bits() needs to be 64 bits wide.
 290 */
 291#define ENTROPY_SHIFT 3
 292#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
 293
 294/*
 295 * The minimum number of bits of entropy before we wake up a read on
 296 * /dev/random.  Should be enough to do a significant reseed.
 297 */
 298static int random_read_wakeup_bits = 64;
 299
 300/*
 301 * If the entropy count falls under this number of bits, then we
 302 * should wake up processes which are selecting or polling on write
 303 * access to /dev/random.
 304 */
 305static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
 306
 307/*
 308 * The minimum number of seconds between urandom pool reseeding.  We
 309 * do this to limit the amount of entropy that can be drained from the
 310 * input pool even if there are heavy demands on /dev/urandom.
 311 */
 312static int random_min_urandom_seed = 60;
 313
 314/*
 315 * Originally, we used a primitive polynomial of degree .poolwords
 316 * over GF(2).  The taps for various sizes are defined below.  They
 317 * were chosen to be evenly spaced except for the last tap, which is 1
 318 * to get the twisting happening as fast as possible.
 319 *
 320 * For the purposes of better mixing, we use the CRC-32 polynomial as
 321 * well to make a (modified) twisted Generalized Feedback Shift
 322 * Register.  (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR
 323 * generators.  ACM Transactions on Modeling and Computer Simulation
 324 * 2(3):179-194.  Also see M. Matsumoto & Y. Kurita, 1994.  Twisted
 325 * GFSR generators II.  ACM Transactions on Modeling and Computer
 326 * Simulation 4:254-266)
 327 *
 328 * Thanks to Colin Plumb for suggesting this.
 329 *
 330 * The mixing operation is much less sensitive than the output hash,
 331 * where we use SHA-1.  All that we want of mixing operation is that
 332 * it be a good non-cryptographic hash; i.e. it not produce collisions
 333 * when fed "random" data of the sort we expect to see.  As long as
 334 * the pool state differs for different inputs, we have preserved the
 335 * input entropy and done a good job.  The fact that an intelligent
 336 * attacker can construct inputs that will produce controlled
 337 * alterations to the pool's state is not important because we don't
 338 * consider such inputs to contribute any randomness.  The only
 339 * property we need with respect to them is that the attacker can't
 340 * increase his/her knowledge of the pool's state.  Since all
 341 * additions are reversible (knowing the final state and the input,
 342 * you can reconstruct the initial state), if an attacker has any
 343 * uncertainty about the initial state, he/she can only shuffle that
 344 * uncertainty about, but never cause any collisions (which would
 345 * decrease the uncertainty).
 346 *
 347 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
 348 * Videau in their paper, "The Linux Pseudorandom Number Generator
 349 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf).  In their
 350 * paper, they point out that we are not using a true Twisted GFSR,
 351 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
 352 * is, with only three taps, instead of the six that we are using).
 353 * As a result, the resulting polynomial is neither primitive nor
 354 * irreducible, and hence does not have a maximal period over
 355 * GF(2**32).  They suggest a slight change to the generator
 356 * polynomial which improves the resulting TGFSR polynomial to be
 357 * irreducible, which we have made here.
 358 */
 359static struct poolinfo {
 360        int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
 361#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
 362        int tap1, tap2, tap3, tap4, tap5;
 363} poolinfo_table[] = {
 364        /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
 365        /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
 366        { S(128),       104,    76,     51,     25,     1 },
 367        /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
 368        /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
 369        { S(32),        26,     19,     14,     7,      1 },
 370#if 0
 371        /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
 372        { S(2048),      1638,   1231,   819,    411,    1 },
 373
 374        /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
 375        { S(1024),      817,    615,    412,    204,    1 },
 376
 377        /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
 378        { S(1024),      819,    616,    410,    207,    2 },
 379
 380        /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
 381        { S(512),       411,    308,    208,    104,    1 },
 382
 383        /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
 384        { S(512),       409,    307,    206,    102,    2 },
 385        /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
 386        { S(512),       409,    309,    205,    103,    2 },
 387
 388        /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
 389        { S(256),       205,    155,    101,    52,     1 },
 390
 391        /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
 392        { S(128),       103,    78,     51,     27,     2 },
 393
 394        /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
 395        { S(64),        52,     39,     26,     14,     1 },
 396#endif
 397};
 398
 399/*
 400 * Static global variables
 401 */
 402static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 403static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
 404static struct fasync_struct *fasync;
 405
 406/**********************************************************************
 407 *
 408 * OS independent entropy store.   Here are the functions which handle
 409 * storing entropy in an entropy pool.
 410 *
 411 **********************************************************************/
 412
 413struct entropy_store;
 414struct entropy_store {
 415        /* read-only data: */
 416        const struct poolinfo *poolinfo;
 417        __u32 *pool;
 418        const char *name;
 419        struct entropy_store *pull;
 420        struct work_struct push_work;
 421
 422        /* read-write data: */
 423        unsigned long last_pulled;
 424        spinlock_t lock;
 425        unsigned short add_ptr;
 426        unsigned short input_rotate;
 427        int entropy_count;
 428        int entropy_total;
 429        unsigned int initialized:1;
 430        unsigned int limit:1;
 431        unsigned int last_data_init:1;
 432        __u8 last_data[EXTRACT_SIZE];
 433};
 434
 435static void push_to_pool(struct work_struct *work);
 436static __u32 input_pool_data[INPUT_POOL_WORDS];
 437static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
 438static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
 439
 440static struct entropy_store input_pool = {
 441        .poolinfo = &poolinfo_table[0],
 442        .name = "input",
 443        .limit = 1,
 444        .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
 445        .pool = input_pool_data
 446};
 447
 448static struct entropy_store blocking_pool = {
 449        .poolinfo = &poolinfo_table[1],
 450        .name = "blocking",
 451        .limit = 1,
 452        .pull = &input_pool,
 453        .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
 454        .pool = blocking_pool_data,
 455        .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
 456                                        push_to_pool),
 457};
 458
 459static struct entropy_store nonblocking_pool = {
 460        .poolinfo = &poolinfo_table[1],
 461        .name = "nonblocking",
 462        .pull = &input_pool,
 463        .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
 464        .pool = nonblocking_pool_data,
 465        .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
 466                                        push_to_pool),
 467};
 468
 469static __u32 const twist_table[8] = {
 470        0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
 471        0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
 472
 473/*
 474 * This function adds bytes into the entropy "pool".  It does not
 475 * update the entropy estimate.  The caller should call
 476 * credit_entropy_bits if this is appropriate.
 477 *
 478 * The pool is stirred with a primitive polynomial of the appropriate
 479 * degree, and then twisted.  We twist by three bits at a time because
 480 * it's cheap to do so and helps slightly in the expected case where
 481 * the entropy is concentrated in the low-order bits.
 482 */
 483static void _mix_pool_bytes(struct entropy_store *r, const void *in,
 484                            int nbytes, __u8 out[64])
 485{
 486        unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
 487        int input_rotate;
 488        int wordmask = r->poolinfo->poolwords - 1;
 489        const char *bytes = in;
 490        __u32 w;
 491
 492        tap1 = r->poolinfo->tap1;
 493        tap2 = r->poolinfo->tap2;
 494        tap3 = r->poolinfo->tap3;
 495        tap4 = r->poolinfo->tap4;
 496        tap5 = r->poolinfo->tap5;
 497
 498        smp_rmb();
 499        input_rotate = ACCESS_ONCE(r->input_rotate);
 500        i = ACCESS_ONCE(r->add_ptr);
 501
 502        /* mix one byte at a time to simplify size handling and churn faster */
 503        while (nbytes--) {
 504                w = rol32(*bytes++, input_rotate);
 505                i = (i - 1) & wordmask;
 506
 507                /* XOR in the various taps */
 508                w ^= r->pool[i];
 509                w ^= r->pool[(i + tap1) & wordmask];
 510                w ^= r->pool[(i + tap2) & wordmask];
 511                w ^= r->pool[(i + tap3) & wordmask];
 512                w ^= r->pool[(i + tap4) & wordmask];
 513                w ^= r->pool[(i + tap5) & wordmask];
 514
 515                /* Mix the result back in with a twist */
 516                r->pool[i] = (w >> 3) ^ twist_table[w & 7];
 517
 518                /*
 519                 * Normally, we add 7 bits of rotation to the pool.
 520                 * At the beginning of the pool, add an extra 7 bits
 521                 * rotation, so that successive passes spread the
 522                 * input bits across the pool evenly.
 523                 */
 524                input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
 525        }
 526
 527        ACCESS_ONCE(r->input_rotate) = input_rotate;
 528        ACCESS_ONCE(r->add_ptr) = i;
 529        smp_wmb();
 530
 531        if (out)
 532                for (j = 0; j < 16; j++)
 533                        ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
 534}
 535
 536static void __mix_pool_bytes(struct entropy_store *r, const void *in,
 537                             int nbytes, __u8 out[64])
 538{
 539        trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
 540        _mix_pool_bytes(r, in, nbytes, out);
 541}
 542
 543static void mix_pool_bytes(struct entropy_store *r, const void *in,
 544                           int nbytes, __u8 out[64])
 545{
 546        unsigned long flags;
 547
 548        trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
 549        spin_lock_irqsave(&r->lock, flags);
 550        _mix_pool_bytes(r, in, nbytes, out);
 551        spin_unlock_irqrestore(&r->lock, flags);
 552}
 553
 554struct fast_pool {
 555        __u32           pool[4];
 556        unsigned long   last;
 557        unsigned short  count;
 558        unsigned char   rotate;
 559        unsigned char   last_timer_intr;
 560};
 561
 562/*
 563 * This is a fast mixing routine used by the interrupt randomness
 564 * collector.  It's hardcoded for an 128 bit pool and assumes that any
 565 * locks that might be needed are taken by the caller.
 566 */
 567static void fast_mix(struct fast_pool *f, __u32 input[4])
 568{
 569        __u32           w;
 570        unsigned        input_rotate = f->rotate;
 571
 572        w = rol32(input[0], input_rotate) ^ f->pool[0] ^ f->pool[3];
 573        f->pool[0] = (w >> 3) ^ twist_table[w & 7];
 574        input_rotate = (input_rotate + 14) & 31;
 575        w = rol32(input[1], input_rotate) ^ f->pool[1] ^ f->pool[0];
 576        f->pool[1] = (w >> 3) ^ twist_table[w & 7];
 577        input_rotate = (input_rotate + 7) & 31;
 578        w = rol32(input[2], input_rotate) ^ f->pool[2] ^ f->pool[1];
 579        f->pool[2] = (w >> 3) ^ twist_table[w & 7];
 580        input_rotate = (input_rotate + 7) & 31;
 581        w = rol32(input[3], input_rotate) ^ f->pool[3] ^ f->pool[2];
 582        f->pool[3] = (w >> 3) ^ twist_table[w & 7];
 583        input_rotate = (input_rotate + 7) & 31;
 584
 585        f->rotate = input_rotate;
 586        f->count++;
 587}
 588
 589/*
 590 * Credit (or debit) the entropy store with n bits of entropy.
 591 * Use credit_entropy_bits_safe() if the value comes from userspace
 592 * or otherwise should be checked for extreme values.
 593 */
 594static void credit_entropy_bits(struct entropy_store *r, int nbits)
 595{
 596        int entropy_count, orig;
 597        const int pool_size = r->poolinfo->poolfracbits;
 598        int nfrac = nbits << ENTROPY_SHIFT;
 599
 600        if (!nbits)
 601                return;
 602
 603retry:
 604        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
 605        if (nfrac < 0) {
 606                /* Debit */
 607                entropy_count += nfrac;
 608        } else {
 609                /*
 610                 * Credit: we have to account for the possibility of
 611                 * overwriting already present entropy.  Even in the
 612                 * ideal case of pure Shannon entropy, new contributions
 613                 * approach the full value asymptotically:
 614                 *
 615                 * entropy <- entropy + (pool_size - entropy) *
 616                 *      (1 - exp(-add_entropy/pool_size))
 617                 *
 618                 * For add_entropy <= pool_size/2 then
 619                 * (1 - exp(-add_entropy/pool_size)) >=
 620                 *    (add_entropy/pool_size)*0.7869...
 621                 * so we can approximate the exponential with
 622                 * 3/4*add_entropy/pool_size and still be on the
 623                 * safe side by adding at most pool_size/2 at a time.
 624                 *
 625                 * The use of pool_size-2 in the while statement is to
 626                 * prevent rounding artifacts from making the loop
 627                 * arbitrarily long; this limits the loop to log2(pool_size)*2
 628                 * turns no matter how large nbits is.
 629                 */
 630                int pnfrac = nfrac;
 631                const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
 632                /* The +2 corresponds to the /4 in the denominator */
 633
 634                do {
 635                        unsigned int anfrac = min(pnfrac, pool_size/2);
 636                        unsigned int add =
 637                                ((pool_size - entropy_count)*anfrac*3) >> s;
 638
 639                        entropy_count += add;
 640                        pnfrac -= anfrac;
 641                } while (unlikely(entropy_count < pool_size-2 && pnfrac));
 642        }
 643
 644        if (unlikely(entropy_count < 0)) {
 645                pr_warn("random: negative entropy/overflow: pool %s count %d\n",
 646                        r->name, entropy_count);
 647                WARN_ON(1);
 648                entropy_count = 0;
 649        } else if (entropy_count > pool_size)
 650                entropy_count = pool_size;
 651        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 652                goto retry;
 653
 654        r->entropy_total += nbits;
 655        if (!r->initialized && r->entropy_total > 128) {
 656                r->initialized = 1;
 657                r->entropy_total = 0;
 658                if (r == &nonblocking_pool) {
 659                        prandom_reseed_late();
 660                        pr_notice("random: %s pool is initialized\n", r->name);
 661                }
 662        }
 663
 664        trace_credit_entropy_bits(r->name, nbits,
 665                                  entropy_count >> ENTROPY_SHIFT,
 666                                  r->entropy_total, _RET_IP_);
 667
 668        if (r == &input_pool) {
 669                int entropy_bits = entropy_count >> ENTROPY_SHIFT;
 670
 671                /* should we wake readers? */
 672                if (entropy_bits >= random_read_wakeup_bits) {
 673                        wake_up_interruptible(&random_read_wait);
 674                        kill_fasync(&fasync, SIGIO, POLL_IN);
 675                }
 676                /* If the input pool is getting full, send some
 677                 * entropy to the two output pools, flipping back and
 678                 * forth between them, until the output pools are 75%
 679                 * full.
 680                 */
 681                if (entropy_bits > random_write_wakeup_bits &&
 682                    r->initialized &&
 683                    r->entropy_total >= 2*random_read_wakeup_bits) {
 684                        static struct entropy_store *last = &blocking_pool;
 685                        struct entropy_store *other = &blocking_pool;
 686
 687                        if (last == &blocking_pool)
 688                                other = &nonblocking_pool;
 689                        if (other->entropy_count <=
 690                            3 * other->poolinfo->poolfracbits / 4)
 691                                last = other;
 692                        if (last->entropy_count <=
 693                            3 * last->poolinfo->poolfracbits / 4) {
 694                                schedule_work(&last->push_work);
 695                                r->entropy_total = 0;
 696                        }
 697                }
 698        }
 699}
 700
 701static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
 702{
 703        const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
 704
 705        /* Cap the value to avoid overflows */
 706        nbits = min(nbits,  nbits_max);
 707        nbits = max(nbits, -nbits_max);
 708
 709        credit_entropy_bits(r, nbits);
 710}
 711
 712/*********************************************************************
 713 *
 714 * Entropy input management
 715 *
 716 *********************************************************************/
 717
 718/* There is one of these per entropy source */
 719struct timer_rand_state {
 720        cycles_t last_time;
 721        long last_delta, last_delta2;
 722        unsigned dont_count_entropy:1;
 723};
 724
 725#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
 726
 727/*
 728 * Add device- or boot-specific data to the input and nonblocking
 729 * pools to help initialize them to unique values.
 730 *
 731 * None of this adds any entropy, it is meant to avoid the
 732 * problem of the nonblocking pool having similar initial state
 733 * across largely identical devices.
 734 */
 735void add_device_randomness(const void *buf, unsigned int size)
 736{
 737        unsigned long time = random_get_entropy() ^ jiffies;
 738        unsigned long flags;
 739
 740        trace_add_device_randomness(size, _RET_IP_);
 741        spin_lock_irqsave(&input_pool.lock, flags);
 742        _mix_pool_bytes(&input_pool, buf, size, NULL);
 743        _mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
 744        spin_unlock_irqrestore(&input_pool.lock, flags);
 745
 746        spin_lock_irqsave(&nonblocking_pool.lock, flags);
 747        _mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
 748        _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
 749        spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
 750}
 751EXPORT_SYMBOL(add_device_randomness);
 752
 753static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
 754
 755/*
 756 * This function adds entropy to the entropy "pool" by using timing
 757 * delays.  It uses the timer_rand_state structure to make an estimate
 758 * of how many bits of entropy this call has added to the pool.
 759 *
 760 * The number "num" is also added to the pool - it should somehow describe
 761 * the type of event which just happened.  This is currently 0-255 for
 762 * keyboard scan codes, and 256 upwards for interrupts.
 763 *
 764 */
 765static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
 766{
 767        struct entropy_store    *r;
 768        struct {
 769                long jiffies;
 770                unsigned cycles;
 771                unsigned num;
 772        } sample;
 773        long delta, delta2, delta3;
 774
 775        preempt_disable();
 776
 777        sample.jiffies = jiffies;
 778        sample.cycles = random_get_entropy();
 779        sample.num = num;
 780        r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 781        mix_pool_bytes(r, &sample, sizeof(sample), NULL);
 782
 783        /*
 784         * Calculate number of bits of randomness we probably added.
 785         * We take into account the first, second and third-order deltas
 786         * in order to make our estimate.
 787         */
 788
 789        if (!state->dont_count_entropy) {
 790                delta = sample.jiffies - state->last_time;
 791                state->last_time = sample.jiffies;
 792
 793                delta2 = delta - state->last_delta;
 794                state->last_delta = delta;
 795
 796                delta3 = delta2 - state->last_delta2;
 797                state->last_delta2 = delta2;
 798
 799                if (delta < 0)
 800                        delta = -delta;
 801                if (delta2 < 0)
 802                        delta2 = -delta2;
 803                if (delta3 < 0)
 804                        delta3 = -delta3;
 805                if (delta > delta2)
 806                        delta = delta2;
 807                if (delta > delta3)
 808                        delta = delta3;
 809
 810                /*
 811                 * delta is now minimum absolute delta.
 812                 * Round down by 1 bit on general principles,
 813                 * and limit entropy entimate to 12 bits.
 814                 */
 815                credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
 816        }
 817        preempt_enable();
 818}
 819
 820void add_input_randomness(unsigned int type, unsigned int code,
 821                                 unsigned int value)
 822{
 823        static unsigned char last_value;
 824
 825        /* ignore autorepeat and the like */
 826        if (value == last_value)
 827                return;
 828
 829        last_value = value;
 830        add_timer_randomness(&input_timer_state,
 831                             (type << 4) ^ code ^ (code >> 4) ^ value);
 832        trace_add_input_randomness(ENTROPY_BITS(&input_pool));
 833}
 834EXPORT_SYMBOL_GPL(add_input_randomness);
 835
 836static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
 837
 838void add_interrupt_randomness(int irq, int irq_flags)
 839{
 840        struct entropy_store    *r;
 841        struct fast_pool        *fast_pool = &__get_cpu_var(irq_randomness);
 842        struct pt_regs          *regs = get_irq_regs();
 843        unsigned long           now = jiffies;
 844        cycles_t                cycles = random_get_entropy();
 845        __u32                   input[4], c_high, j_high;
 846        __u64                   ip;
 847        unsigned long           seed;
 848        int                     credit;
 849
 850        c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
 851        j_high = (sizeof(now) > 4) ? now >> 32 : 0;
 852        input[0] = cycles ^ j_high ^ irq;
 853        input[1] = now ^ c_high;
 854        ip = regs ? instruction_pointer(regs) : _RET_IP_;
 855        input[2] = ip;
 856        input[3] = ip >> 32;
 857
 858        fast_mix(fast_pool, input);
 859
 860        if ((fast_pool->count & 63) && !time_after(now, fast_pool->last + HZ))
 861                return;
 862
 863        fast_pool->last = now;
 864
 865        r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 866        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
 867
 868        /*
 869         * If we don't have a valid cycle counter, and we see
 870         * back-to-back timer interrupts, then skip giving credit for
 871         * any entropy, otherwise credit 1 bit.
 872         */
 873        credit = 1;
 874        if (cycles == 0) {
 875                if (irq_flags & __IRQF_TIMER) {
 876                        if (fast_pool->last_timer_intr)
 877                                credit = 0;
 878                        fast_pool->last_timer_intr = 1;
 879                } else
 880                        fast_pool->last_timer_intr = 0;
 881        }
 882
 883        /*
 884         * If we have architectural seed generator, produce a seed and
 885         * add it to the pool.  For the sake of paranoia count it as
 886         * 50% entropic.
 887         */
 888        if (arch_get_random_seed_long(&seed)) {
 889                __mix_pool_bytes(r, &seed, sizeof(seed), NULL);
 890                credit += sizeof(seed) * 4;
 891        }
 892
 893        credit_entropy_bits(r, credit);
 894}
 895
 896#ifdef CONFIG_BLOCK
 897void add_disk_randomness(struct gendisk *disk)
 898{
 899        if (!disk || !disk->random)
 900                return;
 901        /* first major is 1, so we get >= 0x200 here */
 902        add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
 903        trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
 904}
 905EXPORT_SYMBOL_GPL(add_disk_randomness);
 906#endif
 907
 908/*********************************************************************
 909 *
 910 * Entropy extraction routines
 911 *
 912 *********************************************************************/
 913
 914static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 915                               size_t nbytes, int min, int rsvd);
 916
 917/*
 918 * This utility inline function is responsible for transferring entropy
 919 * from the primary pool to the secondary extraction pool. We make
 920 * sure we pull enough for a 'catastrophic reseed'.
 921 */
 922static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
 923static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 924{
 925        if (r->limit == 0 && random_min_urandom_seed) {
 926                unsigned long now = jiffies;
 927
 928                if (time_before(now,
 929                                r->last_pulled + random_min_urandom_seed * HZ))
 930                        return;
 931                r->last_pulled = now;
 932        }
 933        if (r->pull &&
 934            r->entropy_count < (nbytes << (ENTROPY_SHIFT + 3)) &&
 935            r->entropy_count < r->poolinfo->poolfracbits)
 936                _xfer_secondary_pool(r, nbytes);
 937}
 938
 939static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 940{
 941        __u32   tmp[OUTPUT_POOL_WORDS];
 942
 943        /* For /dev/random's pool, always leave two wakeups' worth */
 944        int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
 945        int bytes = nbytes;
 946
 947        /* pull at least as much as a wakeup */
 948        bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
 949        /* but never more than the buffer size */
 950        bytes = min_t(int, bytes, sizeof(tmp));
 951
 952        trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
 953                                  ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
 954        bytes = extract_entropy(r->pull, tmp, bytes,
 955                                random_read_wakeup_bits / 8, rsvd_bytes);
 956        mix_pool_bytes(r, tmp, bytes, NULL);
 957        credit_entropy_bits(r, bytes*8);
 958}
 959
 960/*
 961 * Used as a workqueue function so that when the input pool is getting
 962 * full, we can "spill over" some entropy to the output pools.  That
 963 * way the output pools can store some of the excess entropy instead
 964 * of letting it go to waste.
 965 */
 966static void push_to_pool(struct work_struct *work)
 967{
 968        struct entropy_store *r = container_of(work, struct entropy_store,
 969                                              push_work);
 970        BUG_ON(!r);
 971        _xfer_secondary_pool(r, random_read_wakeup_bits/8);
 972        trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
 973                           r->pull->entropy_count >> ENTROPY_SHIFT);
 974}
 975
 976/*
 977 * This function decides how many bytes to actually take from the
 978 * given pool, and also debits the entropy count accordingly.
 979 */
 980static size_t account(struct entropy_store *r, size_t nbytes, int min,
 981                      int reserved)
 982{
 983        int entropy_count, orig;
 984        size_t ibytes, nfrac;
 985
 986        BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
 987
 988        /* Can we pull enough? */
 989retry:
 990        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
 991        ibytes = nbytes;
 992        /* If limited, never pull more than available */
 993        if (r->limit) {
 994                int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
 995
 996                if ((have_bytes -= reserved) < 0)
 997                        have_bytes = 0;
 998                ibytes = min_t(size_t, ibytes, have_bytes);
 999        }
1000        if (ibytes < min)
1001                ibytes = 0;
1002
1003        if (unlikely(entropy_count < 0)) {
1004                pr_warn("random: negative entropy count: pool %s count %d\n",
1005                        r->name, entropy_count);
1006                WARN_ON(1);
1007                entropy_count = 0;
1008        }
1009        nfrac = ibytes << (ENTROPY_SHIFT + 3);
1010        if ((size_t) entropy_count > nfrac)
1011                entropy_count -= nfrac;
1012        else
1013                entropy_count = 0;
1014
1015        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1016                goto retry;
1017
1018        trace_debit_entropy(r->name, 8 * ibytes);
1019        if (ibytes &&
1020            (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1021                wake_up_interruptible(&random_write_wait);
1022                kill_fasync(&fasync, SIGIO, POLL_OUT);
1023        }
1024
1025        return ibytes;
1026}
1027
1028/*
1029 * This function does the actual extraction for extract_entropy and
1030 * extract_entropy_user.
1031 *
1032 * Note: we assume that .poolwords is a multiple of 16 words.
1033 */
1034static void extract_buf(struct entropy_store *r, __u8 *out)
1035{
1036        int i;
1037        union {
1038                __u32 w[5];
1039                unsigned long l[LONGS(20)];
1040        } hash;
1041        __u32 workspace[SHA_WORKSPACE_WORDS];
1042        __u8 extract[64];
1043        unsigned long flags;
1044
1045        /*
1046         * If we have an architectural hardware random number
1047         * generator, use it for SHA's initial vector
1048         */
1049        sha_init(hash.w);
1050        for (i = 0; i < LONGS(20); i++) {
1051                unsigned long v;
1052                if (!arch_get_random_long(&v))
1053                        break;
1054                hash.l[i] = v;
1055        }
1056
1057        /* Generate a hash across the pool, 16 words (512 bits) at a time */
1058        spin_lock_irqsave(&r->lock, flags);
1059        for (i = 0; i < r->poolinfo->poolwords; i += 16)
1060                sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1061
1062        /*
1063         * We mix the hash back into the pool to prevent backtracking
1064         * attacks (where the attacker knows the state of the pool
1065         * plus the current outputs, and attempts to find previous
1066         * ouputs), unless the hash function can be inverted. By
1067         * mixing at least a SHA1 worth of hash data back, we make
1068         * brute-forcing the feedback as hard as brute-forcing the
1069         * hash.
1070         */
1071        __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
1072        spin_unlock_irqrestore(&r->lock, flags);
1073
1074        /*
1075         * To avoid duplicates, we atomically extract a portion of the
1076         * pool while mixing, and hash one final time.
1077         */
1078        sha_transform(hash.w, extract, workspace);
1079        memset(extract, 0, sizeof(extract));
1080        memset(workspace, 0, sizeof(workspace));
1081
1082        /*
1083         * In case the hash function has some recognizable output
1084         * pattern, we fold it in half. Thus, we always feed back
1085         * twice as much data as we output.
1086         */
1087        hash.w[0] ^= hash.w[3];
1088        hash.w[1] ^= hash.w[4];
1089        hash.w[2] ^= rol32(hash.w[2], 16);
1090
1091        memcpy(out, &hash, EXTRACT_SIZE);
1092        memset(&hash, 0, sizeof(hash));
1093}
1094
1095/*
1096 * This function extracts randomness from the "entropy pool", and
1097 * returns it in a buffer.
1098 *
1099 * The min parameter specifies the minimum amount we can pull before
1100 * failing to avoid races that defeat catastrophic reseeding while the
1101 * reserved parameter indicates how much entropy we must leave in the
1102 * pool after each pull to avoid starving other readers.
1103 */
1104static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1105                                 size_t nbytes, int min, int reserved)
1106{
1107        ssize_t ret = 0, i;
1108        __u8 tmp[EXTRACT_SIZE];
1109        unsigned long flags;
1110
1111        /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1112        if (fips_enabled) {
1113                spin_lock_irqsave(&r->lock, flags);
1114                if (!r->last_data_init) {
1115                        r->last_data_init = 1;
1116                        spin_unlock_irqrestore(&r->lock, flags);
1117                        trace_extract_entropy(r->name, EXTRACT_SIZE,
1118                                              ENTROPY_BITS(r), _RET_IP_);
1119                        xfer_secondary_pool(r, EXTRACT_SIZE);
1120                        extract_buf(r, tmp);
1121                        spin_lock_irqsave(&r->lock, flags);
1122                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
1123                }
1124                spin_unlock_irqrestore(&r->lock, flags);
1125        }
1126
1127        trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1128        xfer_secondary_pool(r, nbytes);
1129        nbytes = account(r, nbytes, min, reserved);
1130
1131        while (nbytes) {
1132                extract_buf(r, tmp);
1133
1134                if (fips_enabled) {
1135                        spin_lock_irqsave(&r->lock, flags);
1136                        if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1137                                panic("Hardware RNG duplicated output!\n");
1138                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
1139                        spin_unlock_irqrestore(&r->lock, flags);
1140                }
1141                i = min_t(int, nbytes, EXTRACT_SIZE);
1142                memcpy(buf, tmp, i);
1143                nbytes -= i;
1144                buf += i;
1145                ret += i;
1146        }
1147
1148        /* Wipe data just returned from memory */
1149        memset(tmp, 0, sizeof(tmp));
1150
1151        return ret;
1152}
1153
1154/*
1155 * This function extracts randomness from the "entropy pool", and
1156 * returns it in a userspace buffer.
1157 */
1158static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1159                                    size_t nbytes)
1160{
1161        ssize_t ret = 0, i;
1162        __u8 tmp[EXTRACT_SIZE];
1163
1164        trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1165        xfer_secondary_pool(r, nbytes);
1166        nbytes = account(r, nbytes, 0, 0);
1167
1168        while (nbytes) {
1169                if (need_resched()) {
1170                        if (signal_pending(current)) {
1171                                if (ret == 0)
1172                                        ret = -ERESTARTSYS;
1173                                break;
1174                        }
1175                        schedule();
1176                }
1177
1178                extract_buf(r, tmp);
1179                i = min_t(int, nbytes, EXTRACT_SIZE);
1180                if (copy_to_user(buf, tmp, i)) {
1181                        ret = -EFAULT;
1182                        break;
1183                }
1184
1185                nbytes -= i;
1186                buf += i;
1187                ret += i;
1188        }
1189
1190        /* Wipe data just returned from memory */
1191        memset(tmp, 0, sizeof(tmp));
1192
1193        return ret;
1194}
1195
1196/*
1197 * This function is the exported kernel interface.  It returns some
1198 * number of good random numbers, suitable for key generation, seeding
1199 * TCP sequence numbers, etc.  It does not rely on the hardware random
1200 * number generator.  For random bytes direct from the hardware RNG
1201 * (when available), use get_random_bytes_arch().
1202 */
1203void get_random_bytes(void *buf, int nbytes)
1204{
1205#if DEBUG_RANDOM_BOOT > 0
1206        if (unlikely(nonblocking_pool.initialized == 0))
1207                printk(KERN_NOTICE "random: %pF get_random_bytes called "
1208                       "with %d bits of entropy available\n",
1209                       (void *) _RET_IP_,
1210                       nonblocking_pool.entropy_total);
1211#endif
1212        trace_get_random_bytes(nbytes, _RET_IP_);
1213        extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1214}
1215EXPORT_SYMBOL(get_random_bytes);
1216
1217/*
1218 * This function will use the architecture-specific hardware random
1219 * number generator if it is available.  The arch-specific hw RNG will
1220 * almost certainly be faster than what we can do in software, but it
1221 * is impossible to verify that it is implemented securely (as
1222 * opposed, to, say, the AES encryption of a sequence number using a
1223 * key known by the NSA).  So it's useful if we need the speed, but
1224 * only if we're willing to trust the hardware manufacturer not to
1225 * have put in a back door.
1226 */
1227void get_random_bytes_arch(void *buf, int nbytes)
1228{
1229        char *p = buf;
1230
1231        trace_get_random_bytes_arch(nbytes, _RET_IP_);
1232        while (nbytes) {
1233                unsigned long v;
1234                int chunk = min(nbytes, (int)sizeof(unsigned long));
1235
1236                if (!arch_get_random_long(&v))
1237                        break;
1238                
1239                memcpy(p, &v, chunk);
1240                p += chunk;
1241                nbytes -= chunk;
1242        }
1243
1244        if (nbytes)
1245                extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1246}
1247EXPORT_SYMBOL(get_random_bytes_arch);
1248
1249
1250/*
1251 * init_std_data - initialize pool with system data
1252 *
1253 * @r: pool to initialize
1254 *
1255 * This function clears the pool's entropy count and mixes some system
1256 * data into the pool to prepare it for use. The pool is not cleared
1257 * as that can only decrease the entropy in the pool.
1258 */
1259static void init_std_data(struct entropy_store *r)
1260{
1261        int i;
1262        ktime_t now = ktime_get_real();
1263        unsigned long rv;
1264
1265        r->last_pulled = jiffies;
1266        mix_pool_bytes(r, &now, sizeof(now), NULL);
1267        for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1268                if (!arch_get_random_seed_long(&rv) &&
1269                    !arch_get_random_long(&rv))
1270                        rv = random_get_entropy();
1271                mix_pool_bytes(r, &rv, sizeof(rv), NULL);
1272        }
1273        mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
1274}
1275
1276/*
1277 * Note that setup_arch() may call add_device_randomness()
1278 * long before we get here. This allows seeding of the pools
1279 * with some platform dependent data very early in the boot
1280 * process. But it limits our options here. We must use
1281 * statically allocated structures that already have all
1282 * initializations complete at compile time. We should also
1283 * take care not to overwrite the precious per platform data
1284 * we were given.
1285 */
1286static int rand_initialize(void)
1287{
1288        init_std_data(&input_pool);
1289        init_std_data(&blocking_pool);
1290        init_std_data(&nonblocking_pool);
1291        return 0;
1292}
1293early_initcall(rand_initialize);
1294
1295#ifdef CONFIG_BLOCK
1296void rand_initialize_disk(struct gendisk *disk)
1297{
1298        struct timer_rand_state *state;
1299
1300        /*
1301         * If kzalloc returns null, we just won't use that entropy
1302         * source.
1303         */
1304        state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1305        if (state) {
1306                state->last_time = INITIAL_JIFFIES;
1307                disk->random = state;
1308        }
1309}
1310#endif
1311
1312/*
1313 * Attempt an emergency refill using arch_get_random_seed_long().
1314 *
1315 * As with add_interrupt_randomness() be paranoid and only
1316 * credit the output as 50% entropic.
1317 */
1318static int arch_random_refill(void)
1319{
1320        const unsigned int nlongs = 64; /* Arbitrary number */
1321        unsigned int n = 0;
1322        unsigned int i;
1323        unsigned long buf[nlongs];
1324
1325        if (!arch_has_random_seed())
1326                return 0;
1327
1328        for (i = 0; i < nlongs; i++) {
1329                if (arch_get_random_seed_long(&buf[n]))
1330                        n++;
1331        }
1332
1333        if (n) {
1334                unsigned int rand_bytes = n * sizeof(unsigned long);
1335
1336                mix_pool_bytes(&input_pool, buf, rand_bytes, NULL);
1337                credit_entropy_bits(&input_pool, rand_bytes*4);
1338        }
1339
1340        return n;
1341}
1342
1343static ssize_t
1344random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1345{
1346        ssize_t n;
1347
1348        if (nbytes == 0)
1349                return 0;
1350
1351        nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1352        while (1) {
1353                n = extract_entropy_user(&blocking_pool, buf, nbytes);
1354                if (n < 0)
1355                        return n;
1356                trace_random_read(n*8, (nbytes-n)*8,
1357                                  ENTROPY_BITS(&blocking_pool),
1358                                  ENTROPY_BITS(&input_pool));
1359                if (n > 0)
1360                        return n;
1361
1362                /* Pool is (near) empty.  Maybe wait and retry. */
1363
1364                /* First try an emergency refill */
1365                if (arch_random_refill())
1366                        continue;
1367
1368                if (file->f_flags & O_NONBLOCK)
1369                        return -EAGAIN;
1370
1371                wait_event_interruptible(random_read_wait,
1372                        ENTROPY_BITS(&input_pool) >=
1373                        random_read_wakeup_bits);
1374                if (signal_pending(current))
1375                        return -ERESTARTSYS;
1376        }
1377}
1378
1379static ssize_t
1380urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1381{
1382        int ret;
1383
1384        if (unlikely(nonblocking_pool.initialized == 0))
1385                printk_once(KERN_NOTICE "random: %s urandom read "
1386                            "with %d bits of entropy available\n",
1387                            current->comm, nonblocking_pool.entropy_total);
1388
1389        nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1390        ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
1391
1392        trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
1393                           ENTROPY_BITS(&input_pool));
1394        return ret;
1395}
1396
1397static unsigned int
1398random_poll(struct file *file, poll_table * wait)
1399{
1400        unsigned int mask;
1401
1402        poll_wait(file, &random_read_wait, wait);
1403        poll_wait(file, &random_write_wait, wait);
1404        mask = 0;
1405        if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1406                mask |= POLLIN | POLLRDNORM;
1407        if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1408                mask |= POLLOUT | POLLWRNORM;
1409        return mask;
1410}
1411
1412static int
1413write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1414{
1415        size_t bytes;
1416        __u32 buf[16];
1417        const char __user *p = buffer;
1418
1419        while (count > 0) {
1420                bytes = min(count, sizeof(buf));
1421                if (copy_from_user(&buf, p, bytes))
1422                        return -EFAULT;
1423
1424                count -= bytes;
1425                p += bytes;
1426
1427                mix_pool_bytes(r, buf, bytes, NULL);
1428                cond_resched();
1429        }
1430
1431        return 0;
1432}
1433
1434static ssize_t random_write(struct file *file, const char __user *buffer,
1435                            size_t count, loff_t *ppos)
1436{
1437        size_t ret;
1438
1439        ret = write_pool(&blocking_pool, buffer, count);
1440        if (ret)
1441                return ret;
1442        ret = write_pool(&nonblocking_pool, buffer, count);
1443        if (ret)
1444                return ret;
1445
1446        return (ssize_t)count;
1447}
1448
1449static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1450{
1451        int size, ent_count;
1452        int __user *p = (int __user *)arg;
1453        int retval;
1454
1455        switch (cmd) {
1456        case RNDGETENTCNT:
1457                /* inherently racy, no point locking */
1458                ent_count = ENTROPY_BITS(&input_pool);
1459                if (put_user(ent_count, p))
1460                        return -EFAULT;
1461                return 0;
1462        case RNDADDTOENTCNT:
1463                if (!capable(CAP_SYS_ADMIN))
1464                        return -EPERM;
1465                if (get_user(ent_count, p))
1466                        return -EFAULT;
1467                credit_entropy_bits_safe(&input_pool, ent_count);
1468                return 0;
1469        case RNDADDENTROPY:
1470                if (!capable(CAP_SYS_ADMIN))
1471                        return -EPERM;
1472                if (get_user(ent_count, p++))
1473                        return -EFAULT;
1474                if (ent_count < 0)
1475                        return -EINVAL;
1476                if (get_user(size, p++))
1477                        return -EFAULT;
1478                retval = write_pool(&input_pool, (const char __user *)p,
1479                                    size);
1480                if (retval < 0)
1481                        return retval;
1482                credit_entropy_bits_safe(&input_pool, ent_count);
1483                return 0;
1484        case RNDZAPENTCNT:
1485        case RNDCLEARPOOL:
1486                /*
1487                 * Clear the entropy pool counters. We no longer clear
1488                 * the entropy pool, as that's silly.
1489                 */
1490                if (!capable(CAP_SYS_ADMIN))
1491                        return -EPERM;
1492                input_pool.entropy_count = 0;
1493                nonblocking_pool.entropy_count = 0;
1494                blocking_pool.entropy_count = 0;
1495                return 0;
1496        default:
1497                return -EINVAL;
1498        }
1499}
1500
1501static int random_fasync(int fd, struct file *filp, int on)
1502{
1503        return fasync_helper(fd, filp, on, &fasync);
1504}
1505
1506const struct file_operations random_fops = {
1507        .read  = random_read,
1508        .write = random_write,
1509        .poll  = random_poll,
1510        .unlocked_ioctl = random_ioctl,
1511        .fasync = random_fasync,
1512        .llseek = noop_llseek,
1513};
1514
1515const struct file_operations urandom_fops = {
1516        .read  = urandom_read,
1517        .write = random_write,
1518        .unlocked_ioctl = random_ioctl,
1519        .fasync = random_fasync,
1520        .llseek = noop_llseek,
1521};
1522
1523/***************************************************************
1524 * Random UUID interface
1525 *
1526 * Used here for a Boot ID, but can be useful for other kernel
1527 * drivers.
1528 ***************************************************************/
1529
1530/*
1531 * Generate random UUID
1532 */
1533void generate_random_uuid(unsigned char uuid_out[16])
1534{
1535        get_random_bytes(uuid_out, 16);
1536        /* Set UUID version to 4 --- truly random generation */
1537        uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1538        /* Set the UUID variant to DCE */
1539        uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1540}
1541EXPORT_SYMBOL(generate_random_uuid);
1542
1543/********************************************************************
1544 *
1545 * Sysctl interface
1546 *
1547 ********************************************************************/
1548
1549#ifdef CONFIG_SYSCTL
1550
1551#include <linux/sysctl.h>
1552
1553static int min_read_thresh = 8, min_write_thresh;
1554static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1555static int max_write_thresh = INPUT_POOL_WORDS * 32;
1556static char sysctl_bootid[16];
1557
1558/*
1559 * This function is used to return both the bootid UUID, and random
1560 * UUID.  The difference is in whether table->data is NULL; if it is,
1561 * then a new UUID is generated and returned to the user.
1562 *
1563 * If the user accesses this via the proc interface, the UUID will be
1564 * returned as an ASCII string in the standard UUID format; if via the
1565 * sysctl system call, as 16 bytes of binary data.
1566 */
1567static int proc_do_uuid(struct ctl_table *table, int write,
1568                        void __user *buffer, size_t *lenp, loff_t *ppos)
1569{
1570        struct ctl_table fake_table;
1571        unsigned char buf[64], tmp_uuid[16], *uuid;
1572
1573        uuid = table->data;
1574        if (!uuid) {
1575                uuid = tmp_uuid;
1576                generate_random_uuid(uuid);
1577        } else {
1578                static DEFINE_SPINLOCK(bootid_spinlock);
1579
1580                spin_lock(&bootid_spinlock);
1581                if (!uuid[8])
1582                        generate_random_uuid(uuid);
1583                spin_unlock(&bootid_spinlock);
1584        }
1585
1586        sprintf(buf, "%pU", uuid);
1587
1588        fake_table.data = buf;
1589        fake_table.maxlen = sizeof(buf);
1590
1591        return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1592}
1593
1594/*
1595 * Return entropy available scaled to integral bits
1596 */
1597static int proc_do_entropy(struct ctl_table *table, int write,
1598                           void __user *buffer, size_t *lenp, loff_t *ppos)
1599{
1600        struct ctl_table fake_table;
1601        int entropy_count;
1602
1603        entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1604
1605        fake_table.data = &entropy_count;
1606        fake_table.maxlen = sizeof(entropy_count);
1607
1608        return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1609}
1610
1611static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1612extern struct ctl_table random_table[];
1613struct ctl_table random_table[] = {
1614        {
1615                .procname       = "poolsize",
1616                .data           = &sysctl_poolsize,
1617                .maxlen         = sizeof(int),
1618                .mode           = 0444,
1619                .proc_handler   = proc_dointvec,
1620        },
1621        {
1622                .procname       = "entropy_avail",
1623                .maxlen         = sizeof(int),
1624                .mode           = 0444,
1625                .proc_handler   = proc_do_entropy,
1626                .data           = &input_pool.entropy_count,
1627        },
1628        {
1629                .procname       = "read_wakeup_threshold",
1630                .data           = &random_read_wakeup_bits,
1631                .maxlen         = sizeof(int),
1632                .mode           = 0644,
1633                .proc_handler   = proc_dointvec_minmax,
1634                .extra1         = &min_read_thresh,
1635                .extra2         = &max_read_thresh,
1636        },
1637        {
1638                .procname       = "write_wakeup_threshold",
1639                .data           = &random_write_wakeup_bits,
1640                .maxlen         = sizeof(int),
1641                .mode           = 0644,
1642                .proc_handler   = proc_dointvec_minmax,
1643                .extra1         = &min_write_thresh,
1644                .extra2         = &max_write_thresh,
1645        },
1646        {
1647                .procname       = "urandom_min_reseed_secs",
1648                .data           = &random_min_urandom_seed,
1649                .maxlen         = sizeof(int),
1650                .mode           = 0644,
1651                .proc_handler   = proc_dointvec,
1652        },
1653        {
1654                .procname       = "boot_id",
1655                .data           = &sysctl_bootid,
1656                .maxlen         = 16,
1657                .mode           = 0444,
1658                .proc_handler   = proc_do_uuid,
1659        },
1660        {
1661                .procname       = "uuid",
1662                .maxlen         = 16,
1663                .mode           = 0444,
1664                .proc_handler   = proc_do_uuid,
1665        },
1666        { }
1667};
1668#endif  /* CONFIG_SYSCTL */
1669
1670static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1671
1672int random_int_secret_init(void)
1673{
1674        get_random_bytes(random_int_secret, sizeof(random_int_secret));
1675        return 0;
1676}
1677
1678/*
1679 * Get a random word for internal kernel use only. Similar to urandom but
1680 * with the goal of minimal entropy pool depletion. As a result, the random
1681 * value is not cryptographically secure but for several uses the cost of
1682 * depleting entropy is too high
1683 */
1684static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1685unsigned int get_random_int(void)
1686{
1687        __u32 *hash;
1688        unsigned int ret;
1689
1690        if (arch_get_random_int(&ret))
1691                return ret;
1692
1693        hash = get_cpu_var(get_random_int_hash);
1694
1695        hash[0] += current->pid + jiffies + random_get_entropy();
1696        md5_transform(hash, random_int_secret);
1697        ret = hash[0];
1698        put_cpu_var(get_random_int_hash);
1699
1700        return ret;
1701}
1702EXPORT_SYMBOL(get_random_int);
1703
1704/*
1705 * randomize_range() returns a start address such that
1706 *
1707 *    [...... <range> .....]
1708 *  start                  end
1709 *
1710 * a <range> with size "len" starting at the return value is inside in the
1711 * area defined by [start, end], but is otherwise randomized.
1712 */
1713unsigned long
1714randomize_range(unsigned long start, unsigned long end, unsigned long len)
1715{
1716        unsigned long range = end - len - start;
1717
1718        if (end <= start + len)
1719                return 0;
1720        return PAGE_ALIGN(get_random_int() % range + start);
1721}
1722
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