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
 259#ifdef CONFIG_GENERIC_HARDIRQS
 260# include <linux/irq.h>
 261#endif
 262
 263#include <asm/processor.h>
 264#include <asm/uaccess.h>
 265#include <asm/irq.h>
 266#include <asm/irq_regs.h>
 267#include <asm/io.h>
 268
 269#define CREATE_TRACE_POINTS
 270#include <trace/events/random.h>
 271
 272/*
 273 * Configuration information
 274 */
 275#define INPUT_POOL_WORDS 128
 276#define OUTPUT_POOL_WORDS 32
 277#define SEC_XFER_SIZE 512
 278#define EXTRACT_SIZE 10
 279
 280#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
 281
 282/*
 283 * The minimum number of bits of entropy before we wake up a read on
 284 * /dev/random.  Should be enough to do a significant reseed.
 285 */
 286static int random_read_wakeup_thresh = 64;
 287
 288/*
 289 * If the entropy count falls under this number of bits, then we
 290 * should wake up processes which are selecting or polling on write
 291 * access to /dev/random.
 292 */
 293static int random_write_wakeup_thresh = 128;
 294
 295/*
 296 * When the input pool goes over trickle_thresh, start dropping most
 297 * samples to avoid wasting CPU time and reduce lock contention.
 298 */
 299
 300static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
 301
 302static DEFINE_PER_CPU(int, trickle_count);
 303
 304/*
 305 * A pool of size .poolwords is stirred with a primitive polynomial
 306 * of degree .poolwords over GF(2).  The taps for various sizes are
 307 * defined below.  They are chosen to be evenly spaced (minimum RMS
 308 * distance from evenly spaced; the numbers in the comments are a
 309 * scaled squared error sum) except for the last tap, which is 1 to
 310 * get the twisting happening as fast as possible.
 311 */
 312static struct poolinfo {
 313        int poolwords;
 314        int tap1, tap2, tap3, tap4, tap5;
 315} poolinfo_table[] = {
 316        /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
 317        { 128,  103,    76,     51,     25,     1 },
 318        /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
 319        { 32,   26,     20,     14,     7,      1 },
 320#if 0
 321        /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
 322        { 2048, 1638,   1231,   819,    411,    1 },
 323
 324        /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
 325        { 1024, 817,    615,    412,    204,    1 },
 326
 327        /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
 328        { 1024, 819,    616,    410,    207,    2 },
 329
 330        /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
 331        { 512,  411,    308,    208,    104,    1 },
 332
 333        /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
 334        { 512,  409,    307,    206,    102,    2 },
 335        /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
 336        { 512,  409,    309,    205,    103,    2 },
 337
 338        /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
 339        { 256,  205,    155,    101,    52,     1 },
 340
 341        /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
 342        { 128,  103,    78,     51,     27,     2 },
 343
 344        /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
 345        { 64,   52,     39,     26,     14,     1 },
 346#endif
 347};
 348
 349#define POOLBITS        poolwords*32
 350#define POOLBYTES       poolwords*4
 351
 352/*
 353 * For the purposes of better mixing, we use the CRC-32 polynomial as
 354 * well to make a twisted Generalized Feedback Shift Reigster
 355 *
 356 * (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR generators.  ACM
 357 * Transactions on Modeling and Computer Simulation 2(3):179-194.
 358 * Also see M. Matsumoto & Y. Kurita, 1994.  Twisted GFSR generators
 359 * II.  ACM Transactions on Mdeling and Computer Simulation 4:254-266)
 360 *
 361 * Thanks to Colin Plumb for suggesting this.
 362 *
 363 * We have not analyzed the resultant polynomial to prove it primitive;
 364 * in fact it almost certainly isn't.  Nonetheless, the irreducible factors
 365 * of a random large-degree polynomial over GF(2) are more than large enough
 366 * that periodicity is not a concern.
 367 *
 368 * The input hash is much less sensitive than the output hash.  All
 369 * that we want of it is that it be a good non-cryptographic hash;
 370 * i.e. it not produce collisions when fed "random" data of the sort
 371 * we expect to see.  As long as the pool state differs for different
 372 * inputs, we have preserved the input entropy and done a good job.
 373 * The fact that an intelligent attacker can construct inputs that
 374 * will produce controlled alterations to the pool's state is not
 375 * important because we don't consider such inputs to contribute any
 376 * randomness.  The only property we need with respect to them is that
 377 * the attacker can't increase his/her knowledge of the pool's state.
 378 * Since all additions are reversible (knowing the final state and the
 379 * input, you can reconstruct the initial state), if an attacker has
 380 * any uncertainty about the initial state, he/she can only shuffle
 381 * that uncertainty about, but never cause any collisions (which would
 382 * decrease the uncertainty).
 383 *
 384 * The chosen system lets the state of the pool be (essentially) the input
 385 * modulo the generator polymnomial.  Now, for random primitive polynomials,
 386 * this is a universal class of hash functions, meaning that the chance
 387 * of a collision is limited by the attacker's knowledge of the generator
 388 * polynomail, so if it is chosen at random, an attacker can never force
 389 * a collision.  Here, we use a fixed polynomial, but we *can* assume that
 390 * ###--> it is unknown to the processes generating the input entropy. <-###
 391 * Because of this important property, this is a good, collision-resistant
 392 * hash; hash collisions will occur no more often than chance.
 393 */
 394
 395/*
 396 * Static global variables
 397 */
 398static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 399static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
 400static struct fasync_struct *fasync;
 401
 402static bool debug;
 403module_param(debug, bool, 0644);
 404#define DEBUG_ENT(fmt, arg...) do { \
 405        if (debug) \
 406                printk(KERN_DEBUG "random %04d %04d %04d: " \
 407                fmt,\
 408                input_pool.entropy_count,\
 409                blocking_pool.entropy_count,\
 410                nonblocking_pool.entropy_count,\
 411                ## arg); } while (0)
 412
 413/**********************************************************************
 414 *
 415 * OS independent entropy store.   Here are the functions which handle
 416 * storing entropy in an entropy pool.
 417 *
 418 **********************************************************************/
 419
 420struct entropy_store;
 421struct entropy_store {
 422        /* read-only data: */
 423        struct poolinfo *poolinfo;
 424        __u32 *pool;
 425        const char *name;
 426        struct entropy_store *pull;
 427        int limit;
 428
 429        /* read-write data: */
 430        spinlock_t lock;
 431        unsigned add_ptr;
 432        unsigned input_rotate;
 433        int entropy_count;
 434        int entropy_total;
 435        unsigned int initialized:1;
 436        bool last_data_init;
 437        __u8 last_data[EXTRACT_SIZE];
 438};
 439
 440static __u32 input_pool_data[INPUT_POOL_WORDS];
 441static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
 442static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
 443
 444static struct entropy_store input_pool = {
 445        .poolinfo = &poolinfo_table[0],
 446        .name = "input",
 447        .limit = 1,
 448        .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
 449        .pool = input_pool_data
 450};
 451
 452static struct entropy_store blocking_pool = {
 453        .poolinfo = &poolinfo_table[1],
 454        .name = "blocking",
 455        .limit = 1,
 456        .pull = &input_pool,
 457        .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
 458        .pool = blocking_pool_data
 459};
 460
 461static struct entropy_store nonblocking_pool = {
 462        .poolinfo = &poolinfo_table[1],
 463        .name = "nonblocking",
 464        .pull = &input_pool,
 465        .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
 466        .pool = nonblocking_pool_data
 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 & 31);
 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 += i ? 7 : 14;
 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, const void *in, int nbytes)
 568{
 569        const char      *bytes = in;
 570        __u32           w;
 571        unsigned        i = f->count;
 572        unsigned        input_rotate = f->rotate;
 573
 574        while (nbytes--) {
 575                w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
 576                        f->pool[(i + 1) & 3];
 577                f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
 578                input_rotate += (i++ & 3) ? 7 : 14;
 579        }
 580        f->count = i;
 581        f->rotate = input_rotate;
 582}
 583
 584/*
 585 * Credit (or debit) the entropy store with n bits of entropy
 586 */
 587static void credit_entropy_bits(struct entropy_store *r, int nbits)
 588{
 589        int entropy_count, orig;
 590
 591        if (!nbits)
 592                return;
 593
 594        DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
 595retry:
 596        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
 597        entropy_count += nbits;
 598
 599        if (entropy_count < 0) {
 600                DEBUG_ENT("negative entropy/overflow\n");
 601                entropy_count = 0;
 602        } else if (entropy_count > r->poolinfo->POOLBITS)
 603                entropy_count = r->poolinfo->POOLBITS;
 604        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 605                goto retry;
 606
 607        if (!r->initialized && nbits > 0) {
 608                r->entropy_total += nbits;
 609                if (r->entropy_total > 128)
 610                        r->initialized = 1;
 611        }
 612
 613        trace_credit_entropy_bits(r->name, nbits, entropy_count,
 614                                  r->entropy_total, _RET_IP_);
 615
 616        /* should we wake readers? */
 617        if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
 618                wake_up_interruptible(&random_read_wait);
 619                kill_fasync(&fasync, SIGIO, POLL_IN);
 620        }
 621}
 622
 623/*********************************************************************
 624 *
 625 * Entropy input management
 626 *
 627 *********************************************************************/
 628
 629/* There is one of these per entropy source */
 630struct timer_rand_state {
 631        cycles_t last_time;
 632        long last_delta, last_delta2;
 633        unsigned dont_count_entropy:1;
 634};
 635
 636/*
 637 * Add device- or boot-specific data to the input and nonblocking
 638 * pools to help initialize them to unique values.
 639 *
 640 * None of this adds any entropy, it is meant to avoid the
 641 * problem of the nonblocking pool having similar initial state
 642 * across largely identical devices.
 643 */
 644void add_device_randomness(const void *buf, unsigned int size)
 645{
 646        unsigned long time = get_cycles() ^ jiffies;
 647
 648        mix_pool_bytes(&input_pool, buf, size, NULL);
 649        mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
 650        mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
 651        mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
 652}
 653EXPORT_SYMBOL(add_device_randomness);
 654
 655static struct timer_rand_state input_timer_state;
 656
 657/*
 658 * This function adds entropy to the entropy "pool" by using timing
 659 * delays.  It uses the timer_rand_state structure to make an estimate
 660 * of how many bits of entropy this call has added to the pool.
 661 *
 662 * The number "num" is also added to the pool - it should somehow describe
 663 * the type of event which just happened.  This is currently 0-255 for
 664 * keyboard scan codes, and 256 upwards for interrupts.
 665 *
 666 */
 667static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
 668{
 669        struct {
 670                long jiffies;
 671                unsigned cycles;
 672                unsigned num;
 673        } sample;
 674        long delta, delta2, delta3;
 675
 676        preempt_disable();
 677        /* if over the trickle threshold, use only 1 in 4096 samples */
 678        if (input_pool.entropy_count > trickle_thresh &&
 679            ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
 680                goto out;
 681
 682        sample.jiffies = jiffies;
 683        sample.cycles = get_cycles();
 684        sample.num = num;
 685        mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
 686
 687        /*
 688         * Calculate number of bits of randomness we probably added.
 689         * We take into account the first, second and third-order deltas
 690         * in order to make our estimate.
 691         */
 692
 693        if (!state->dont_count_entropy) {
 694                delta = sample.jiffies - state->last_time;
 695                state->last_time = sample.jiffies;
 696
 697                delta2 = delta - state->last_delta;
 698                state->last_delta = delta;
 699
 700                delta3 = delta2 - state->last_delta2;
 701                state->last_delta2 = delta2;
 702
 703                if (delta < 0)
 704                        delta = -delta;
 705                if (delta2 < 0)
 706                        delta2 = -delta2;
 707                if (delta3 < 0)
 708                        delta3 = -delta3;
 709                if (delta > delta2)
 710                        delta = delta2;
 711                if (delta > delta3)
 712                        delta = delta3;
 713
 714                /*
 715                 * delta is now minimum absolute delta.
 716                 * Round down by 1 bit on general principles,
 717                 * and limit entropy entimate to 12 bits.
 718                 */
 719                credit_entropy_bits(&input_pool,
 720                                    min_t(int, fls(delta>>1), 11));
 721        }
 722out:
 723        preempt_enable();
 724}
 725
 726void add_input_randomness(unsigned int type, unsigned int code,
 727                                 unsigned int value)
 728{
 729        static unsigned char last_value;
 730
 731        /* ignore autorepeat and the like */
 732        if (value == last_value)
 733                return;
 734
 735        DEBUG_ENT("input event\n");
 736        last_value = value;
 737        add_timer_randomness(&input_timer_state,
 738                             (type << 4) ^ code ^ (code >> 4) ^ value);
 739}
 740EXPORT_SYMBOL_GPL(add_input_randomness);
 741
 742static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
 743
 744void add_interrupt_randomness(int irq, int irq_flags)
 745{
 746        struct entropy_store    *r;
 747        struct fast_pool        *fast_pool = &__get_cpu_var(irq_randomness);
 748        struct pt_regs          *regs = get_irq_regs();
 749        unsigned long           now = jiffies;
 750        __u32                   input[4], cycles = get_cycles();
 751
 752        input[0] = cycles ^ jiffies;
 753        input[1] = irq;
 754        if (regs) {
 755                __u64 ip = instruction_pointer(regs);
 756                input[2] = ip;
 757                input[3] = ip >> 32;
 758        }
 759
 760        fast_mix(fast_pool, input, sizeof(input));
 761
 762        if ((fast_pool->count & 1023) &&
 763            !time_after(now, fast_pool->last + HZ))
 764                return;
 765
 766        fast_pool->last = now;
 767
 768        r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 769        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
 770        /*
 771         * If we don't have a valid cycle counter, and we see
 772         * back-to-back timer interrupts, then skip giving credit for
 773         * any entropy.
 774         */
 775        if (cycles == 0) {
 776                if (irq_flags & __IRQF_TIMER) {
 777                        if (fast_pool->last_timer_intr)
 778                                return;
 779                        fast_pool->last_timer_intr = 1;
 780                } else
 781                        fast_pool->last_timer_intr = 0;
 782        }
 783        credit_entropy_bits(r, 1);
 784}
 785
 786#ifdef CONFIG_BLOCK
 787void add_disk_randomness(struct gendisk *disk)
 788{
 789        if (!disk || !disk->random)
 790                return;
 791        /* first major is 1, so we get >= 0x200 here */
 792        DEBUG_ENT("disk event %d:%d\n",
 793                  MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
 794
 795        add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
 796}
 797#endif
 798
 799/*********************************************************************
 800 *
 801 * Entropy extraction routines
 802 *
 803 *********************************************************************/
 804
 805static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 806                               size_t nbytes, int min, int rsvd);
 807
 808/*
 809 * This utility inline function is responsible for transferring entropy
 810 * from the primary pool to the secondary extraction pool. We make
 811 * sure we pull enough for a 'catastrophic reseed'.
 812 */
 813static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 814{
 815        __u32   tmp[OUTPUT_POOL_WORDS];
 816
 817        if (r->pull && r->entropy_count < nbytes * 8 &&
 818            r->entropy_count < r->poolinfo->POOLBITS) {
 819                /* If we're limited, always leave two wakeup worth's BITS */
 820                int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
 821                int bytes = nbytes;
 822
 823                /* pull at least as many as BYTES as wakeup BITS */
 824                bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
 825                /* but never more than the buffer size */
 826                bytes = min_t(int, bytes, sizeof(tmp));
 827
 828                DEBUG_ENT("going to reseed %s with %d bits "
 829                          "(%zu of %d requested)\n",
 830                          r->name, bytes * 8, nbytes * 8, r->entropy_count);
 831
 832                bytes = extract_entropy(r->pull, tmp, bytes,
 833                                        random_read_wakeup_thresh / 8, rsvd);
 834                mix_pool_bytes(r, tmp, bytes, NULL);
 835                credit_entropy_bits(r, bytes*8);
 836        }
 837}
 838
 839/*
 840 * These functions extracts randomness from the "entropy pool", and
 841 * returns it in a buffer.
 842 *
 843 * The min parameter specifies the minimum amount we can pull before
 844 * failing to avoid races that defeat catastrophic reseeding while the
 845 * reserved parameter indicates how much entropy we must leave in the
 846 * pool after each pull to avoid starving other readers.
 847 *
 848 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
 849 */
 850
 851static size_t account(struct entropy_store *r, size_t nbytes, int min,
 852                      int reserved)
 853{
 854        unsigned long flags;
 855        int wakeup_write = 0;
 856
 857        /* Hold lock while accounting */
 858        spin_lock_irqsave(&r->lock, flags);
 859
 860        BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
 861        DEBUG_ENT("trying to extract %zu bits from %s\n",
 862                  nbytes * 8, r->name);
 863
 864        /* Can we pull enough? */
 865        if (r->entropy_count / 8 < min + reserved) {
 866                nbytes = 0;
 867        } else {
 868                int entropy_count, orig;
 869retry:
 870                entropy_count = orig = ACCESS_ONCE(r->entropy_count);
 871                /* If limited, never pull more than available */
 872                if (r->limit && nbytes + reserved >= entropy_count / 8)
 873                        nbytes = entropy_count/8 - reserved;
 874
 875                if (entropy_count / 8 >= nbytes + reserved) {
 876                        entropy_count -= nbytes*8;
 877                        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 878                                goto retry;
 879                } else {
 880                        entropy_count = reserved;
 881                        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 882                                goto retry;
 883                }
 884
 885                if (entropy_count < random_write_wakeup_thresh)
 886                        wakeup_write = 1;
 887        }
 888
 889        DEBUG_ENT("debiting %zu entropy credits from %s%s\n",
 890                  nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
 891
 892        spin_unlock_irqrestore(&r->lock, flags);
 893
 894        if (wakeup_write) {
 895                wake_up_interruptible(&random_write_wait);
 896                kill_fasync(&fasync, SIGIO, POLL_OUT);
 897        }
 898
 899        return nbytes;
 900}
 901
 902static void extract_buf(struct entropy_store *r, __u8 *out)
 903{
 904        int i;
 905        union {
 906                __u32 w[5];
 907                unsigned long l[LONGS(EXTRACT_SIZE)];
 908        } hash;
 909        __u32 workspace[SHA_WORKSPACE_WORDS];
 910        __u8 extract[64];
 911        unsigned long flags;
 912
 913        /* Generate a hash across the pool, 16 words (512 bits) at a time */
 914        sha_init(hash.w);
 915        spin_lock_irqsave(&r->lock, flags);
 916        for (i = 0; i < r->poolinfo->poolwords; i += 16)
 917                sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
 918
 919        /*
 920         * We mix the hash back into the pool to prevent backtracking
 921         * attacks (where the attacker knows the state of the pool
 922         * plus the current outputs, and attempts to find previous
 923         * ouputs), unless the hash function can be inverted. By
 924         * mixing at least a SHA1 worth of hash data back, we make
 925         * brute-forcing the feedback as hard as brute-forcing the
 926         * hash.
 927         */
 928        __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
 929        spin_unlock_irqrestore(&r->lock, flags);
 930
 931        /*
 932         * To avoid duplicates, we atomically extract a portion of the
 933         * pool while mixing, and hash one final time.
 934         */
 935        sha_transform(hash.w, extract, workspace);
 936        memset(extract, 0, sizeof(extract));
 937        memset(workspace, 0, sizeof(workspace));
 938
 939        /*
 940         * In case the hash function has some recognizable output
 941         * pattern, we fold it in half. Thus, we always feed back
 942         * twice as much data as we output.
 943         */
 944        hash.w[0] ^= hash.w[3];
 945        hash.w[1] ^= hash.w[4];
 946        hash.w[2] ^= rol32(hash.w[2], 16);
 947
 948        /*
 949         * If we have a architectural hardware random number
 950         * generator, mix that in, too.
 951         */
 952        for (i = 0; i < LONGS(EXTRACT_SIZE); i++) {
 953                unsigned long v;
 954                if (!arch_get_random_long(&v))
 955                        break;
 956                hash.l[i] ^= v;
 957        }
 958
 959        memcpy(out, &hash, EXTRACT_SIZE);
 960        memset(&hash, 0, sizeof(hash));
 961}
 962
 963static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 964                                 size_t nbytes, int min, int reserved)
 965{
 966        ssize_t ret = 0, i;
 967        __u8 tmp[EXTRACT_SIZE];
 968        unsigned long flags;
 969
 970        /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
 971        if (fips_enabled) {
 972                spin_lock_irqsave(&r->lock, flags);
 973                if (!r->last_data_init) {
 974                        r->last_data_init = true;
 975                        spin_unlock_irqrestore(&r->lock, flags);
 976                        trace_extract_entropy(r->name, EXTRACT_SIZE,
 977                                              r->entropy_count, _RET_IP_);
 978                        xfer_secondary_pool(r, EXTRACT_SIZE);
 979                        extract_buf(r, tmp);
 980                        spin_lock_irqsave(&r->lock, flags);
 981                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
 982                }
 983                spin_unlock_irqrestore(&r->lock, flags);
 984        }
 985
 986        trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
 987        xfer_secondary_pool(r, nbytes);
 988        nbytes = account(r, nbytes, min, reserved);
 989
 990        while (nbytes) {
 991                extract_buf(r, tmp);
 992
 993                if (fips_enabled) {
 994                        spin_lock_irqsave(&r->lock, flags);
 995                        if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
 996                                panic("Hardware RNG duplicated output!\n");
 997                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
 998                        spin_unlock_irqrestore(&r->lock, flags);
 999                }
1000                i = min_t(int, nbytes, EXTRACT_SIZE);
1001                memcpy(buf, tmp, i);
1002                nbytes -= i;
1003                buf += i;
1004                ret += i;
1005        }
1006
1007        /* Wipe data just returned from memory */
1008        memset(tmp, 0, sizeof(tmp));
1009
1010        return ret;
1011}
1012
1013static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1014                                    size_t nbytes)
1015{
1016        ssize_t ret = 0, i;
1017        __u8 tmp[EXTRACT_SIZE];
1018
1019        trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
1020        xfer_secondary_pool(r, nbytes);
1021        nbytes = account(r, nbytes, 0, 0);
1022
1023        while (nbytes) {
1024                if (need_resched()) {
1025                        if (signal_pending(current)) {
1026                                if (ret == 0)
1027                                        ret = -ERESTARTSYS;
1028                                break;
1029                        }
1030                        schedule();
1031                }
1032
1033                extract_buf(r, tmp);
1034                i = min_t(int, nbytes, EXTRACT_SIZE);
1035                if (copy_to_user(buf, tmp, i)) {
1036                        ret = -EFAULT;
1037                        break;
1038                }
1039
1040                nbytes -= i;
1041                buf += i;
1042                ret += i;
1043        }
1044
1045        /* Wipe data just returned from memory */
1046        memset(tmp, 0, sizeof(tmp));
1047
1048        return ret;
1049}
1050
1051/*
1052 * This function is the exported kernel interface.  It returns some
1053 * number of good random numbers, suitable for key generation, seeding
1054 * TCP sequence numbers, etc.  It does not use the hw random number
1055 * generator, if available; use get_random_bytes_arch() for that.
1056 */
1057void get_random_bytes(void *buf, int nbytes)
1058{
1059        extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1060}
1061EXPORT_SYMBOL(get_random_bytes);
1062
1063/*
1064 * This function will use the architecture-specific hardware random
1065 * number generator if it is available.  The arch-specific hw RNG will
1066 * almost certainly be faster than what we can do in software, but it
1067 * is impossible to verify that it is implemented securely (as
1068 * opposed, to, say, the AES encryption of a sequence number using a
1069 * key known by the NSA).  So it's useful if we need the speed, but
1070 * only if we're willing to trust the hardware manufacturer not to
1071 * have put in a back door.
1072 */
1073void get_random_bytes_arch(void *buf, int nbytes)
1074{
1075        char *p = buf;
1076
1077        trace_get_random_bytes(nbytes, _RET_IP_);
1078        while (nbytes) {
1079                unsigned long v;
1080                int chunk = min(nbytes, (int)sizeof(unsigned long));
1081
1082                if (!arch_get_random_long(&v))
1083                        break;
1084                
1085                memcpy(p, &v, chunk);
1086                p += chunk;
1087                nbytes -= chunk;
1088        }
1089
1090        if (nbytes)
1091                extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1092}
1093EXPORT_SYMBOL(get_random_bytes_arch);
1094
1095
1096/*
1097 * init_std_data - initialize pool with system data
1098 *
1099 * @r: pool to initialize
1100 *
1101 * This function clears the pool's entropy count and mixes some system
1102 * data into the pool to prepare it for use. The pool is not cleared
1103 * as that can only decrease the entropy in the pool.
1104 */
1105static void init_std_data(struct entropy_store *r)
1106{
1107        int i;
1108        ktime_t now = ktime_get_real();
1109        unsigned long rv;
1110
1111        r->entropy_count = 0;
1112        r->entropy_total = 0;
1113        r->last_data_init = false;
1114        mix_pool_bytes(r, &now, sizeof(now), NULL);
1115        for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) {
1116                if (!arch_get_random_long(&rv))
1117                        break;
1118                mix_pool_bytes(r, &rv, sizeof(rv), NULL);
1119        }
1120        mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
1121}
1122
1123/*
1124 * Note that setup_arch() may call add_device_randomness()
1125 * long before we get here. This allows seeding of the pools
1126 * with some platform dependent data very early in the boot
1127 * process. But it limits our options here. We must use
1128 * statically allocated structures that already have all
1129 * initializations complete at compile time. We should also
1130 * take care not to overwrite the precious per platform data
1131 * we were given.
1132 */
1133static int rand_initialize(void)
1134{
1135        init_std_data(&input_pool);
1136        init_std_data(&blocking_pool);
1137        init_std_data(&nonblocking_pool);
1138        return 0;
1139}
1140module_init(rand_initialize);
1141
1142#ifdef CONFIG_BLOCK
1143void rand_initialize_disk(struct gendisk *disk)
1144{
1145        struct timer_rand_state *state;
1146
1147        /*
1148         * If kzalloc returns null, we just won't use that entropy
1149         * source.
1150         */
1151        state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1152        if (state)
1153                disk->random = state;
1154}
1155#endif
1156
1157static ssize_t
1158random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1159{
1160        ssize_t n, retval = 0, count = 0;
1161
1162        if (nbytes == 0)
1163                return 0;
1164
1165        while (nbytes > 0) {
1166                n = nbytes;
1167                if (n > SEC_XFER_SIZE)
1168                        n = SEC_XFER_SIZE;
1169
1170                DEBUG_ENT("reading %zu bits\n", n*8);
1171
1172                n = extract_entropy_user(&blocking_pool, buf, n);
1173
1174                if (n < 0) {
1175                        retval = n;
1176                        break;
1177                }
1178
1179                DEBUG_ENT("read got %zd bits (%zd still needed)\n",
1180                          n*8, (nbytes-n)*8);
1181
1182                if (n == 0) {
1183                        if (file->f_flags & O_NONBLOCK) {
1184                                retval = -EAGAIN;
1185                                break;
1186                        }
1187
1188                        DEBUG_ENT("sleeping?\n");
1189
1190                        wait_event_interruptible(random_read_wait,
1191                                input_pool.entropy_count >=
1192                                                 random_read_wakeup_thresh);
1193
1194                        DEBUG_ENT("awake\n");
1195
1196                        if (signal_pending(current)) {
1197                                retval = -ERESTARTSYS;
1198                                break;
1199                        }
1200
1201                        continue;
1202                }
1203
1204                count += n;
1205                buf += n;
1206                nbytes -= n;
1207                break;          /* This break makes the device work */
1208                                /* like a named pipe */
1209        }
1210
1211        return (count ? count : retval);
1212}
1213
1214static ssize_t
1215urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1216{
1217        return extract_entropy_user(&nonblocking_pool, buf, nbytes);
1218}
1219
1220static unsigned int
1221random_poll(struct file *file, poll_table * wait)
1222{
1223        unsigned int mask;
1224
1225        poll_wait(file, &random_read_wait, wait);
1226        poll_wait(file, &random_write_wait, wait);
1227        mask = 0;
1228        if (input_pool.entropy_count >= random_read_wakeup_thresh)
1229                mask |= POLLIN | POLLRDNORM;
1230        if (input_pool.entropy_count < random_write_wakeup_thresh)
1231                mask |= POLLOUT | POLLWRNORM;
1232        return mask;
1233}
1234
1235static int
1236write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1237{
1238        size_t bytes;
1239        __u32 buf[16];
1240        const char __user *p = buffer;
1241
1242        while (count > 0) {
1243                bytes = min(count, sizeof(buf));
1244                if (copy_from_user(&buf, p, bytes))
1245                        return -EFAULT;
1246
1247                count -= bytes;
1248                p += bytes;
1249
1250                mix_pool_bytes(r, buf, bytes, NULL);
1251                cond_resched();
1252        }
1253
1254        return 0;
1255}
1256
1257static ssize_t random_write(struct file *file, const char __user *buffer,
1258                            size_t count, loff_t *ppos)
1259{
1260        size_t ret;
1261
1262        ret = write_pool(&blocking_pool, buffer, count);
1263        if (ret)
1264                return ret;
1265        ret = write_pool(&nonblocking_pool, buffer, count);
1266        if (ret)
1267                return ret;
1268
1269        return (ssize_t)count;
1270}
1271
1272static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1273{
1274        int size, ent_count;
1275        int __user *p = (int __user *)arg;
1276        int retval;
1277
1278        switch (cmd) {
1279        case RNDGETENTCNT:
1280                /* inherently racy, no point locking */
1281                if (put_user(input_pool.entropy_count, p))
1282                        return -EFAULT;
1283                return 0;
1284        case RNDADDTOENTCNT:
1285                if (!capable(CAP_SYS_ADMIN))
1286                        return -EPERM;
1287                if (get_user(ent_count, p))
1288                        return -EFAULT;
1289                credit_entropy_bits(&input_pool, ent_count);
1290                return 0;
1291        case RNDADDENTROPY:
1292                if (!capable(CAP_SYS_ADMIN))
1293                        return -EPERM;
1294                if (get_user(ent_count, p++))
1295                        return -EFAULT;
1296                if (ent_count < 0)
1297                        return -EINVAL;
1298                if (get_user(size, p++))
1299                        return -EFAULT;
1300                retval = write_pool(&input_pool, (const char __user *)p,
1301                                    size);
1302                if (retval < 0)
1303                        return retval;
1304                credit_entropy_bits(&input_pool, ent_count);
1305                return 0;
1306        case RNDZAPENTCNT:
1307        case RNDCLEARPOOL:
1308                /* Clear the entropy pool counters. */
1309                if (!capable(CAP_SYS_ADMIN))
1310                        return -EPERM;
1311                rand_initialize();
1312                return 0;
1313        default:
1314                return -EINVAL;
1315        }
1316}
1317
1318static int random_fasync(int fd, struct file *filp, int on)
1319{
1320        return fasync_helper(fd, filp, on, &fasync);
1321}
1322
1323const struct file_operations random_fops = {
1324        .read  = random_read,
1325        .write = random_write,
1326        .poll  = random_poll,
1327        .unlocked_ioctl = random_ioctl,
1328        .fasync = random_fasync,
1329        .llseek = noop_llseek,
1330};
1331
1332const struct file_operations urandom_fops = {
1333        .read  = urandom_read,
1334        .write = random_write,
1335        .unlocked_ioctl = random_ioctl,
1336        .fasync = random_fasync,
1337        .llseek = noop_llseek,
1338};
1339
1340/***************************************************************
1341 * Random UUID interface
1342 *
1343 * Used here for a Boot ID, but can be useful for other kernel
1344 * drivers.
1345 ***************************************************************/
1346
1347/*
1348 * Generate random UUID
1349 */
1350void generate_random_uuid(unsigned char uuid_out[16])
1351{
1352        get_random_bytes(uuid_out, 16);
1353        /* Set UUID version to 4 --- truly random generation */
1354        uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1355        /* Set the UUID variant to DCE */
1356        uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1357}
1358EXPORT_SYMBOL(generate_random_uuid);
1359
1360/********************************************************************
1361 *
1362 * Sysctl interface
1363 *
1364 ********************************************************************/
1365
1366#ifdef CONFIG_SYSCTL
1367
1368#include <linux/sysctl.h>
1369
1370static int min_read_thresh = 8, min_write_thresh;
1371static int max_read_thresh = INPUT_POOL_WORDS * 32;
1372static int max_write_thresh = INPUT_POOL_WORDS * 32;
1373static char sysctl_bootid[16];
1374
1375/*
1376 * These functions is used to return both the bootid UUID, and random
1377 * UUID.  The difference is in whether table->data is NULL; if it is,
1378 * then a new UUID is generated and returned to the user.
1379 *
1380 * If the user accesses this via the proc interface, it will be returned
1381 * as an ASCII string in the standard UUID format.  If accesses via the
1382 * sysctl system call, it is returned as 16 bytes of binary data.
1383 */
1384static int proc_do_uuid(ctl_table *table, int write,
1385                        void __user *buffer, size_t *lenp, loff_t *ppos)
1386{
1387        ctl_table fake_table;
1388        unsigned char buf[64], tmp_uuid[16], *uuid;
1389
1390        uuid = table->data;
1391        if (!uuid) {
1392                uuid = tmp_uuid;
1393                generate_random_uuid(uuid);
1394        } else {
1395                static DEFINE_SPINLOCK(bootid_spinlock);
1396
1397                spin_lock(&bootid_spinlock);
1398                if (!uuid[8])
1399                        generate_random_uuid(uuid);
1400                spin_unlock(&bootid_spinlock);
1401        }
1402
1403        sprintf(buf, "%pU", uuid);
1404
1405        fake_table.data = buf;
1406        fake_table.maxlen = sizeof(buf);
1407
1408        return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1409}
1410
1411static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1412extern ctl_table random_table[];
1413ctl_table random_table[] = {
1414        {
1415                .procname       = "poolsize",
1416                .data           = &sysctl_poolsize,
1417                .maxlen         = sizeof(int),
1418                .mode           = 0444,
1419                .proc_handler   = proc_dointvec,
1420        },
1421        {
1422                .procname       = "entropy_avail",
1423                .maxlen         = sizeof(int),
1424                .mode           = 0444,
1425                .proc_handler   = proc_dointvec,
1426                .data           = &input_pool.entropy_count,
1427        },
1428        {
1429                .procname       = "read_wakeup_threshold",
1430                .data           = &random_read_wakeup_thresh,
1431                .maxlen         = sizeof(int),
1432                .mode           = 0644,
1433                .proc_handler   = proc_dointvec_minmax,
1434                .extra1         = &min_read_thresh,
1435                .extra2         = &max_read_thresh,
1436        },
1437        {
1438                .procname       = "write_wakeup_threshold",
1439                .data           = &random_write_wakeup_thresh,
1440                .maxlen         = sizeof(int),
1441                .mode           = 0644,
1442                .proc_handler   = proc_dointvec_minmax,
1443                .extra1         = &min_write_thresh,
1444                .extra2         = &max_write_thresh,
1445        },
1446        {
1447                .procname       = "boot_id",
1448                .data           = &sysctl_bootid,
1449                .maxlen         = 16,
1450                .mode           = 0444,
1451                .proc_handler   = proc_do_uuid,
1452        },
1453        {
1454                .procname       = "uuid",
1455                .maxlen         = 16,
1456                .mode           = 0444,
1457                .proc_handler   = proc_do_uuid,
1458        },
1459        { }
1460};
1461#endif  /* CONFIG_SYSCTL */
1462
1463static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1464
1465static int __init random_int_secret_init(void)
1466{
1467        get_random_bytes(random_int_secret, sizeof(random_int_secret));
1468        return 0;
1469}
1470late_initcall(random_int_secret_init);
1471
1472/*
1473 * Get a random word for internal kernel use only. Similar to urandom but
1474 * with the goal of minimal entropy pool depletion. As a result, the random
1475 * value is not cryptographically secure but for several uses the cost of
1476 * depleting entropy is too high
1477 */
1478static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1479unsigned int get_random_int(void)
1480{
1481        __u32 *hash;
1482        unsigned int ret;
1483
1484        if (arch_get_random_int(&ret))
1485                return ret;
1486
1487        hash = get_cpu_var(get_random_int_hash);
1488
1489        hash[0] += current->pid + jiffies + get_cycles();
1490        md5_transform(hash, random_int_secret);
1491        ret = hash[0];
1492        put_cpu_var(get_random_int_hash);
1493
1494        return ret;
1495}
1496EXPORT_SYMBOL(get_random_int);
1497
1498/*
1499 * randomize_range() returns a start address such that
1500 *
1501 *    [...... <range> .....]
1502 *  start                  end
1503 *
1504 * a <range> with size "len" starting at the return value is inside in the
1505 * area defined by [start, end], but is otherwise randomized.
1506 */
1507unsigned long
1508randomize_range(unsigned long start, unsigned long end, unsigned long len)
1509{
1510        unsigned long range = end - len - start;
1511
1512        if (end <= start + len)
1513                return 0;
1514        return PAGE_ALIGN(get_random_int() % range + start);
1515}
1516
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