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
 402#if 0
 403static bool debug;
 404module_param(debug, bool, 0644);
 405#define DEBUG_ENT(fmt, arg...) do { \
 406        if (debug) \
 407                printk(KERN_DEBUG "random %04d %04d %04d: " \
 408                fmt,\
 409                input_pool.entropy_count,\
 410                blocking_pool.entropy_count,\
 411                nonblocking_pool.entropy_count,\
 412                ## arg); } while (0)
 413#else
 414#define DEBUG_ENT(fmt, arg...) do {} while (0)
 415#endif
 416
 417/**********************************************************************
 418 *
 419 * OS independent entropy store.   Here are the functions which handle
 420 * storing entropy in an entropy pool.
 421 *
 422 **********************************************************************/
 423
 424struct entropy_store;
 425struct entropy_store {
 426        /* read-only data: */
 427        struct poolinfo *poolinfo;
 428        __u32 *pool;
 429        const char *name;
 430        struct entropy_store *pull;
 431        int limit;
 432
 433        /* read-write data: */
 434        spinlock_t lock;
 435        unsigned add_ptr;
 436        unsigned input_rotate;
 437        int entropy_count;
 438        int entropy_total;
 439        unsigned int initialized:1;
 440        __u8 last_data[EXTRACT_SIZE];
 441};
 442
 443static __u32 input_pool_data[INPUT_POOL_WORDS];
 444static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
 445static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
 446
 447static struct entropy_store input_pool = {
 448        .poolinfo = &poolinfo_table[0],
 449        .name = "input",
 450        .limit = 1,
 451        .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock),
 452        .pool = input_pool_data
 453};
 454
 455static struct entropy_store blocking_pool = {
 456        .poolinfo = &poolinfo_table[1],
 457        .name = "blocking",
 458        .limit = 1,
 459        .pull = &input_pool,
 460        .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock),
 461        .pool = blocking_pool_data
 462};
 463
 464static struct entropy_store nonblocking_pool = {
 465        .poolinfo = &poolinfo_table[1],
 466        .name = "nonblocking",
 467        .pull = &input_pool,
 468        .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock),
 469        .pool = nonblocking_pool_data
 470};
 471
 472static __u32 const twist_table[8] = {
 473        0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
 474        0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
 475
 476/*
 477 * This function adds bytes into the entropy "pool".  It does not
 478 * update the entropy estimate.  The caller should call
 479 * credit_entropy_bits if this is appropriate.
 480 *
 481 * The pool is stirred with a primitive polynomial of the appropriate
 482 * degree, and then twisted.  We twist by three bits at a time because
 483 * it's cheap to do so and helps slightly in the expected case where
 484 * the entropy is concentrated in the low-order bits.
 485 */
 486static void _mix_pool_bytes(struct entropy_store *r, const void *in,
 487                            int nbytes, __u8 out[64])
 488{
 489        unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
 490        int input_rotate;
 491        int wordmask = r->poolinfo->poolwords - 1;
 492        const char *bytes = in;
 493        __u32 w;
 494
 495        tap1 = r->poolinfo->tap1;
 496        tap2 = r->poolinfo->tap2;
 497        tap3 = r->poolinfo->tap3;
 498        tap4 = r->poolinfo->tap4;
 499        tap5 = r->poolinfo->tap5;
 500
 501        smp_rmb();
 502        input_rotate = ACCESS_ONCE(r->input_rotate);
 503        i = ACCESS_ONCE(r->add_ptr);
 504
 505        /* mix one byte at a time to simplify size handling and churn faster */
 506        while (nbytes--) {
 507                w = rol32(*bytes++, input_rotate & 31);
 508                i = (i - 1) & wordmask;
 509
 510                /* XOR in the various taps */
 511                w ^= r->pool[i];
 512                w ^= r->pool[(i + tap1) & wordmask];
 513                w ^= r->pool[(i + tap2) & wordmask];
 514                w ^= r->pool[(i + tap3) & wordmask];
 515                w ^= r->pool[(i + tap4) & wordmask];
 516                w ^= r->pool[(i + tap5) & wordmask];
 517
 518                /* Mix the result back in with a twist */
 519                r->pool[i] = (w >> 3) ^ twist_table[w & 7];
 520
 521                /*
 522                 * Normally, we add 7 bits of rotation to the pool.
 523                 * At the beginning of the pool, add an extra 7 bits
 524                 * rotation, so that successive passes spread the
 525                 * input bits across the pool evenly.
 526                 */
 527                input_rotate += i ? 7 : 14;
 528        }
 529
 530        ACCESS_ONCE(r->input_rotate) = input_rotate;
 531        ACCESS_ONCE(r->add_ptr) = i;
 532        smp_wmb();
 533
 534        if (out)
 535                for (j = 0; j < 16; j++)
 536                        ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
 537}
 538
 539static void __mix_pool_bytes(struct entropy_store *r, const void *in,
 540                             int nbytes, __u8 out[64])
 541{
 542        trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
 543        _mix_pool_bytes(r, in, nbytes, out);
 544}
 545
 546static void mix_pool_bytes(struct entropy_store *r, const void *in,
 547                           int nbytes, __u8 out[64])
 548{
 549        unsigned long flags;
 550
 551        trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
 552        spin_lock_irqsave(&r->lock, flags);
 553        _mix_pool_bytes(r, in, nbytes, out);
 554        spin_unlock_irqrestore(&r->lock, flags);
 555}
 556
 557struct fast_pool {
 558        __u32           pool[4];
 559        unsigned long   last;
 560        unsigned short  count;
 561        unsigned char   rotate;
 562        unsigned char   last_timer_intr;
 563};
 564
 565/*
 566 * This is a fast mixing routine used by the interrupt randomness
 567 * collector.  It's hardcoded for an 128 bit pool and assumes that any
 568 * locks that might be needed are taken by the caller.
 569 */
 570static void fast_mix(struct fast_pool *f, const void *in, int nbytes)
 571{
 572        const char      *bytes = in;
 573        __u32           w;
 574        unsigned        i = f->count;
 575        unsigned        input_rotate = f->rotate;
 576
 577        while (nbytes--) {
 578                w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
 579                        f->pool[(i + 1) & 3];
 580                f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
 581                input_rotate += (i++ & 3) ? 7 : 14;
 582        }
 583        f->count = i;
 584        f->rotate = input_rotate;
 585}
 586
 587/*
 588 * Credit (or debit) the entropy store with n bits of entropy
 589 */
 590static void credit_entropy_bits(struct entropy_store *r, int nbits)
 591{
 592        int entropy_count, orig;
 593
 594        if (!nbits)
 595                return;
 596
 597        DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
 598retry:
 599        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
 600        entropy_count += nbits;
 601
 602        if (entropy_count < 0) {
 603                DEBUG_ENT("negative entropy/overflow\n");
 604                entropy_count = 0;
 605        } else if (entropy_count > r->poolinfo->POOLBITS)
 606                entropy_count = r->poolinfo->POOLBITS;
 607        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 608                goto retry;
 609
 610        if (!r->initialized && nbits > 0) {
 611                r->entropy_total += nbits;
 612                if (r->entropy_total > 128)
 613                        r->initialized = 1;
 614        }
 615
 616        trace_credit_entropy_bits(r->name, nbits, entropy_count,
 617                                  r->entropy_total, _RET_IP_);
 618
 619        /* should we wake readers? */
 620        if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
 621                wake_up_interruptible(&random_read_wait);
 622                kill_fasync(&fasync, SIGIO, POLL_IN);
 623        }
 624}
 625
 626/*********************************************************************
 627 *
 628 * Entropy input management
 629 *
 630 *********************************************************************/
 631
 632/* There is one of these per entropy source */
 633struct timer_rand_state {
 634        cycles_t last_time;
 635        long last_delta, last_delta2;
 636        unsigned dont_count_entropy:1;
 637};
 638
 639/*
 640 * Add device- or boot-specific data to the input and nonblocking
 641 * pools to help initialize them to unique values.
 642 *
 643 * None of this adds any entropy, it is meant to avoid the
 644 * problem of the nonblocking pool having similar initial state
 645 * across largely identical devices.
 646 */
 647void add_device_randomness(const void *buf, unsigned int size)
 648{
 649        unsigned long time = get_cycles() ^ jiffies;
 650
 651        mix_pool_bytes(&input_pool, buf, size, NULL);
 652        mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
 653        mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
 654        mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
 655}
 656EXPORT_SYMBOL(add_device_randomness);
 657
 658static struct timer_rand_state input_timer_state;
 659
 660/*
 661 * This function adds entropy to the entropy "pool" by using timing
 662 * delays.  It uses the timer_rand_state structure to make an estimate
 663 * of how many bits of entropy this call has added to the pool.
 664 *
 665 * The number "num" is also added to the pool - it should somehow describe
 666 * the type of event which just happened.  This is currently 0-255 for
 667 * keyboard scan codes, and 256 upwards for interrupts.
 668 *
 669 */
 670static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
 671{
 672        struct {
 673                long jiffies;
 674                unsigned cycles;
 675                unsigned num;
 676        } sample;
 677        long delta, delta2, delta3;
 678
 679        preempt_disable();
 680        /* if over the trickle threshold, use only 1 in 4096 samples */
 681        if (input_pool.entropy_count > trickle_thresh &&
 682            ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
 683                goto out;
 684
 685        sample.jiffies = jiffies;
 686        sample.cycles = get_cycles();
 687        sample.num = num;
 688        mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
 689
 690        /*
 691         * Calculate number of bits of randomness we probably added.
 692         * We take into account the first, second and third-order deltas
 693         * in order to make our estimate.
 694         */
 695
 696        if (!state->dont_count_entropy) {
 697                delta = sample.jiffies - state->last_time;
 698                state->last_time = sample.jiffies;
 699
 700                delta2 = delta - state->last_delta;
 701                state->last_delta = delta;
 702
 703                delta3 = delta2 - state->last_delta2;
 704                state->last_delta2 = delta2;
 705
 706                if (delta < 0)
 707                        delta = -delta;
 708                if (delta2 < 0)
 709                        delta2 = -delta2;
 710                if (delta3 < 0)
 711                        delta3 = -delta3;
 712                if (delta > delta2)
 713                        delta = delta2;
 714                if (delta > delta3)
 715                        delta = delta3;
 716
 717                /*
 718                 * delta is now minimum absolute delta.
 719                 * Round down by 1 bit on general principles,
 720                 * and limit entropy entimate to 12 bits.
 721                 */
 722                credit_entropy_bits(&input_pool,
 723                                    min_t(int, fls(delta>>1), 11));
 724        }
 725out:
 726        preempt_enable();
 727}
 728
 729void add_input_randomness(unsigned int type, unsigned int code,
 730                                 unsigned int value)
 731{
 732        static unsigned char last_value;
 733
 734        /* ignore autorepeat and the like */
 735        if (value == last_value)
 736                return;
 737
 738        DEBUG_ENT("input event\n");
 739        last_value = value;
 740        add_timer_randomness(&input_timer_state,
 741                             (type << 4) ^ code ^ (code >> 4) ^ value);
 742}
 743EXPORT_SYMBOL_GPL(add_input_randomness);
 744
 745static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
 746
 747void add_interrupt_randomness(int irq, int irq_flags)
 748{
 749        struct entropy_store    *r;
 750        struct fast_pool        *fast_pool = &__get_cpu_var(irq_randomness);
 751        struct pt_regs          *regs = get_irq_regs();
 752        unsigned long           now = jiffies;
 753        __u32                   input[4], cycles = get_cycles();
 754
 755        input[0] = cycles ^ jiffies;
 756        input[1] = irq;
 757        if (regs) {
 758                __u64 ip = instruction_pointer(regs);
 759                input[2] = ip;
 760                input[3] = ip >> 32;
 761        }
 762
 763        fast_mix(fast_pool, input, sizeof(input));
 764
 765        if ((fast_pool->count & 1023) &&
 766            !time_after(now, fast_pool->last + HZ))
 767                return;
 768
 769        fast_pool->last = now;
 770
 771        r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 772        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
 773        /*
 774         * If we don't have a valid cycle counter, and we see
 775         * back-to-back timer interrupts, then skip giving credit for
 776         * any entropy.
 777         */
 778        if (cycles == 0) {
 779                if (irq_flags & __IRQF_TIMER) {
 780                        if (fast_pool->last_timer_intr)
 781                                return;
 782                        fast_pool->last_timer_intr = 1;
 783                } else
 784                        fast_pool->last_timer_intr = 0;
 785        }
 786        credit_entropy_bits(r, 1);
 787}
 788
 789#ifdef CONFIG_BLOCK
 790void add_disk_randomness(struct gendisk *disk)
 791{
 792        if (!disk || !disk->random)
 793                return;
 794        /* first major is 1, so we get >= 0x200 here */
 795        DEBUG_ENT("disk event %d:%d\n",
 796                  MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
 797
 798        add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
 799}
 800#endif
 801
 802/*********************************************************************
 803 *
 804 * Entropy extraction routines
 805 *
 806 *********************************************************************/
 807
 808static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 809                               size_t nbytes, int min, int rsvd);
 810
 811/*
 812 * This utility inline function is responsible for transferring entropy
 813 * from the primary pool to the secondary extraction pool. We make
 814 * sure we pull enough for a 'catastrophic reseed'.
 815 */
 816static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 817{
 818        __u32   tmp[OUTPUT_POOL_WORDS];
 819
 820        if (r->pull && r->entropy_count < nbytes * 8 &&
 821            r->entropy_count < r->poolinfo->POOLBITS) {
 822                /* If we're limited, always leave two wakeup worth's BITS */
 823                int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
 824                int bytes = nbytes;
 825
 826                /* pull at least as many as BYTES as wakeup BITS */
 827                bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
 828                /* but never more than the buffer size */
 829                bytes = min_t(int, bytes, sizeof(tmp));
 830
 831                DEBUG_ENT("going to reseed %s with %d bits "
 832                          "(%d of %d requested)\n",
 833                          r->name, bytes * 8, nbytes * 8, r->entropy_count);
 834
 835                bytes = extract_entropy(r->pull, tmp, bytes,
 836                                        random_read_wakeup_thresh / 8, rsvd);
 837                mix_pool_bytes(r, tmp, bytes, NULL);
 838                credit_entropy_bits(r, bytes*8);
 839        }
 840}
 841
 842/*
 843 * These functions extracts randomness from the "entropy pool", and
 844 * returns it in a buffer.
 845 *
 846 * The min parameter specifies the minimum amount we can pull before
 847 * failing to avoid races that defeat catastrophic reseeding while the
 848 * reserved parameter indicates how much entropy we must leave in the
 849 * pool after each pull to avoid starving other readers.
 850 *
 851 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
 852 */
 853
 854static size_t account(struct entropy_store *r, size_t nbytes, int min,
 855                      int reserved)
 856{
 857        unsigned long flags;
 858
 859        /* Hold lock while accounting */
 860        spin_lock_irqsave(&r->lock, flags);
 861
 862        BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
 863        DEBUG_ENT("trying to extract %d bits from %s\n",
 864                  nbytes * 8, r->name);
 865
 866        /* Can we pull enough? */
 867        if (r->entropy_count / 8 < min + reserved) {
 868                nbytes = 0;
 869        } else {
 870                /* If limited, never pull more than available */
 871                if (r->limit && nbytes + reserved >= r->entropy_count / 8)
 872                        nbytes = r->entropy_count/8 - reserved;
 873
 874                if (r->entropy_count / 8 >= nbytes + reserved)
 875                        r->entropy_count -= nbytes*8;
 876                else
 877                        r->entropy_count = reserved;
 878
 879                if (r->entropy_count < random_write_wakeup_thresh) {
 880                        wake_up_interruptible(&random_write_wait);
 881                        kill_fasync(&fasync, SIGIO, POLL_OUT);
 882                }
 883        }
 884
 885        DEBUG_ENT("debiting %d entropy credits from %s%s\n",
 886                  nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
 887
 888        spin_unlock_irqrestore(&r->lock, flags);
 889
 890        return nbytes;
 891}
 892
 893static void extract_buf(struct entropy_store *r, __u8 *out)
 894{
 895        int i;
 896        union {
 897                __u32 w[5];
 898                unsigned long l[LONGS(EXTRACT_SIZE)];
 899        } hash;
 900        __u32 workspace[SHA_WORKSPACE_WORDS];
 901        __u8 extract[64];
 902        unsigned long flags;
 903
 904        /* Generate a hash across the pool, 16 words (512 bits) at a time */
 905        sha_init(hash.w);
 906        spin_lock_irqsave(&r->lock, flags);
 907        for (i = 0; i < r->poolinfo->poolwords; i += 16)
 908                sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
 909
 910        /*
 911         * We mix the hash back into the pool to prevent backtracking
 912         * attacks (where the attacker knows the state of the pool
 913         * plus the current outputs, and attempts to find previous
 914         * ouputs), unless the hash function can be inverted. By
 915         * mixing at least a SHA1 worth of hash data back, we make
 916         * brute-forcing the feedback as hard as brute-forcing the
 917         * hash.
 918         */
 919        __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
 920        spin_unlock_irqrestore(&r->lock, flags);
 921
 922        /*
 923         * To avoid duplicates, we atomically extract a portion of the
 924         * pool while mixing, and hash one final time.
 925         */
 926        sha_transform(hash.w, extract, workspace);
 927        memset(extract, 0, sizeof(extract));
 928        memset(workspace, 0, sizeof(workspace));
 929
 930        /*
 931         * In case the hash function has some recognizable output
 932         * pattern, we fold it in half. Thus, we always feed back
 933         * twice as much data as we output.
 934         */
 935        hash.w[0] ^= hash.w[3];
 936        hash.w[1] ^= hash.w[4];
 937        hash.w[2] ^= rol32(hash.w[2], 16);
 938
 939        /*
 940         * If we have a architectural hardware random number
 941         * generator, mix that in, too.
 942         */
 943        for (i = 0; i < LONGS(EXTRACT_SIZE); i++) {
 944                unsigned long v;
 945                if (!arch_get_random_long(&v))
 946                        break;
 947                hash.l[i] ^= v;
 948        }
 949
 950        memcpy(out, &hash, EXTRACT_SIZE);
 951        memset(&hash, 0, sizeof(hash));
 952}
 953
 954static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 955                                 size_t nbytes, int min, int reserved)
 956{
 957        ssize_t ret = 0, i;
 958        __u8 tmp[EXTRACT_SIZE];
 959
 960        trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
 961        xfer_secondary_pool(r, nbytes);
 962        nbytes = account(r, nbytes, min, reserved);
 963
 964        while (nbytes) {
 965                extract_buf(r, tmp);
 966
 967                if (fips_enabled) {
 968                        unsigned long flags;
 969
 970                        spin_lock_irqsave(&r->lock, flags);
 971                        if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
 972                                panic("Hardware RNG duplicated output!\n");
 973                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
 974                        spin_unlock_irqrestore(&r->lock, flags);
 975                }
 976                i = min_t(int, nbytes, EXTRACT_SIZE);
 977                memcpy(buf, tmp, i);
 978                nbytes -= i;
 979                buf += i;
 980                ret += i;
 981        }
 982
 983        /* Wipe data just returned from memory */
 984        memset(tmp, 0, sizeof(tmp));
 985
 986        return ret;
 987}
 988
 989static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
 990                                    size_t nbytes)
 991{
 992        ssize_t ret = 0, i;
 993        __u8 tmp[EXTRACT_SIZE];
 994
 995        trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
 996        xfer_secondary_pool(r, nbytes);
 997        nbytes = account(r, nbytes, 0, 0);
 998
 999        while (nbytes) {
1000                if (need_resched()) {
1001                        if (signal_pending(current)) {
1002                                if (ret == 0)
1003                                        ret = -ERESTARTSYS;
1004                                break;
1005                        }
1006                        schedule();
1007                }
1008
1009                extract_buf(r, tmp);
1010                i = min_t(int, nbytes, EXTRACT_SIZE);
1011                if (copy_to_user(buf, tmp, i)) {
1012                        ret = -EFAULT;
1013                        break;
1014                }
1015
1016                nbytes -= i;
1017                buf += i;
1018                ret += i;
1019        }
1020
1021        /* Wipe data just returned from memory */
1022        memset(tmp, 0, sizeof(tmp));
1023
1024        return ret;
1025}
1026
1027/*
1028 * This function is the exported kernel interface.  It returns some
1029 * number of good random numbers, suitable for key generation, seeding
1030 * TCP sequence numbers, etc.  It does not use the hw random number
1031 * generator, if available; use get_random_bytes_arch() for that.
1032 */
1033void get_random_bytes(void *buf, int nbytes)
1034{
1035        extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1036}
1037EXPORT_SYMBOL(get_random_bytes);
1038
1039/*
1040 * This function will use the architecture-specific hardware random
1041 * number generator if it is available.  The arch-specific hw RNG will
1042 * almost certainly be faster than what we can do in software, but it
1043 * is impossible to verify that it is implemented securely (as
1044 * opposed, to, say, the AES encryption of a sequence number using a
1045 * key known by the NSA).  So it's useful if we need the speed, but
1046 * only if we're willing to trust the hardware manufacturer not to
1047 * have put in a back door.
1048 */
1049void get_random_bytes_arch(void *buf, int nbytes)
1050{
1051        char *p = buf;
1052
1053        trace_get_random_bytes(nbytes, _RET_IP_);
1054        while (nbytes) {
1055                unsigned long v;
1056                int chunk = min(nbytes, (int)sizeof(unsigned long));
1057
1058                if (!arch_get_random_long(&v))
1059                        break;
1060                
1061                memcpy(p, &v, chunk);
1062                p += chunk;
1063                nbytes -= chunk;
1064        }
1065
1066        if (nbytes)
1067                extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1068}
1069EXPORT_SYMBOL(get_random_bytes_arch);
1070
1071
1072/*
1073 * init_std_data - initialize pool with system data
1074 *
1075 * @r: pool to initialize
1076 *
1077 * This function clears the pool's entropy count and mixes some system
1078 * data into the pool to prepare it for use. The pool is not cleared
1079 * as that can only decrease the entropy in the pool.
1080 */
1081static void init_std_data(struct entropy_store *r)
1082{
1083        int i;
1084        ktime_t now = ktime_get_real();
1085        unsigned long rv;
1086
1087        r->entropy_count = 0;
1088        r->entropy_total = 0;
1089        mix_pool_bytes(r, &now, sizeof(now), NULL);
1090        for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) {
1091                if (!arch_get_random_long(&rv))
1092                        break;
1093                mix_pool_bytes(r, &rv, sizeof(rv), NULL);
1094        }
1095        mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
1096}
1097
1098/*
1099 * Note that setup_arch() may call add_device_randomness()
1100 * long before we get here. This allows seeding of the pools
1101 * with some platform dependent data very early in the boot
1102 * process. But it limits our options here. We must use
1103 * statically allocated structures that already have all
1104 * initializations complete at compile time. We should also
1105 * take care not to overwrite the precious per platform data
1106 * we were given.
1107 */
1108static int rand_initialize(void)
1109{
1110        init_std_data(&input_pool);
1111        init_std_data(&blocking_pool);
1112        init_std_data(&nonblocking_pool);
1113        return 0;
1114}
1115module_init(rand_initialize);
1116
1117#ifdef CONFIG_BLOCK
1118void rand_initialize_disk(struct gendisk *disk)
1119{
1120        struct timer_rand_state *state;
1121
1122        /*
1123         * If kzalloc returns null, we just won't use that entropy
1124         * source.
1125         */
1126        state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1127        if (state)
1128                disk->random = state;
1129}
1130#endif
1131
1132static ssize_t
1133random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1134{
1135        ssize_t n, retval = 0, count = 0;
1136
1137        if (nbytes == 0)
1138                return 0;
1139
1140        while (nbytes > 0) {
1141                n = nbytes;
1142                if (n > SEC_XFER_SIZE)
1143                        n = SEC_XFER_SIZE;
1144
1145                DEBUG_ENT("reading %d bits\n", n*8);
1146
1147                n = extract_entropy_user(&blocking_pool, buf, n);
1148
1149                DEBUG_ENT("read got %d bits (%d still needed)\n",
1150                          n*8, (nbytes-n)*8);
1151
1152                if (n == 0) {
1153                        if (file->f_flags & O_NONBLOCK) {
1154                                retval = -EAGAIN;
1155                                break;
1156                        }
1157
1158                        DEBUG_ENT("sleeping?\n");
1159
1160                        wait_event_interruptible(random_read_wait,
1161                                input_pool.entropy_count >=
1162                                                 random_read_wakeup_thresh);
1163
1164                        DEBUG_ENT("awake\n");
1165
1166                        if (signal_pending(current)) {
1167                                retval = -ERESTARTSYS;
1168                                break;
1169                        }
1170
1171                        continue;
1172                }
1173
1174                if (n < 0) {
1175                        retval = n;
1176                        break;
1177                }
1178                count += n;
1179                buf += n;
1180                nbytes -= n;
1181                break;          /* This break makes the device work */
1182                                /* like a named pipe */
1183        }
1184
1185        return (count ? count : retval);
1186}
1187
1188static ssize_t
1189urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1190{
1191        return extract_entropy_user(&nonblocking_pool, buf, nbytes);
1192}
1193
1194static unsigned int
1195random_poll(struct file *file, poll_table * wait)
1196{
1197        unsigned int mask;
1198
1199        poll_wait(file, &random_read_wait, wait);
1200        poll_wait(file, &random_write_wait, wait);
1201        mask = 0;
1202        if (input_pool.entropy_count >= random_read_wakeup_thresh)
1203                mask |= POLLIN | POLLRDNORM;
1204        if (input_pool.entropy_count < random_write_wakeup_thresh)
1205                mask |= POLLOUT | POLLWRNORM;
1206        return mask;
1207}
1208
1209static int
1210write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1211{
1212        size_t bytes;
1213        __u32 buf[16];
1214        const char __user *p = buffer;
1215
1216        while (count > 0) {
1217                bytes = min(count, sizeof(buf));
1218                if (copy_from_user(&buf, p, bytes))
1219                        return -EFAULT;
1220
1221                count -= bytes;
1222                p += bytes;
1223
1224                mix_pool_bytes(r, buf, bytes, NULL);
1225                cond_resched();
1226        }
1227
1228        return 0;
1229}
1230
1231static ssize_t random_write(struct file *file, const char __user *buffer,
1232                            size_t count, loff_t *ppos)
1233{
1234        size_t ret;
1235
1236        ret = write_pool(&blocking_pool, buffer, count);
1237        if (ret)
1238                return ret;
1239        ret = write_pool(&nonblocking_pool, buffer, count);
1240        if (ret)
1241                return ret;
1242
1243        return (ssize_t)count;
1244}
1245
1246static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1247{
1248        int size, ent_count;
1249        int __user *p = (int __user *)arg;
1250        int retval;
1251
1252        switch (cmd) {
1253        case RNDGETENTCNT:
1254                /* inherently racy, no point locking */
1255                if (put_user(input_pool.entropy_count, p))
1256                        return -EFAULT;
1257                return 0;
1258        case RNDADDTOENTCNT:
1259                if (!capable(CAP_SYS_ADMIN))
1260                        return -EPERM;
1261                if (get_user(ent_count, p))
1262                        return -EFAULT;
1263                credit_entropy_bits(&input_pool, ent_count);
1264                return 0;
1265        case RNDADDENTROPY:
1266                if (!capable(CAP_SYS_ADMIN))
1267                        return -EPERM;
1268                if (get_user(ent_count, p++))
1269                        return -EFAULT;
1270                if (ent_count < 0)
1271                        return -EINVAL;
1272                if (get_user(size, p++))
1273                        return -EFAULT;
1274                retval = write_pool(&input_pool, (const char __user *)p,
1275                                    size);
1276                if (retval < 0)
1277                        return retval;
1278                credit_entropy_bits(&input_pool, ent_count);
1279                return 0;
1280        case RNDZAPENTCNT:
1281        case RNDCLEARPOOL:
1282                /* Clear the entropy pool counters. */
1283                if (!capable(CAP_SYS_ADMIN))
1284                        return -EPERM;
1285                rand_initialize();
1286                return 0;
1287        default:
1288                return -EINVAL;
1289        }
1290}
1291
1292static int random_fasync(int fd, struct file *filp, int on)
1293{
1294        return fasync_helper(fd, filp, on, &fasync);
1295}
1296
1297const struct file_operations random_fops = {
1298        .read  = random_read,
1299        .write = random_write,
1300        .poll  = random_poll,
1301        .unlocked_ioctl = random_ioctl,
1302        .fasync = random_fasync,
1303        .llseek = noop_llseek,
1304};
1305
1306const struct file_operations urandom_fops = {
1307        .read  = urandom_read,
1308        .write = random_write,
1309        .unlocked_ioctl = random_ioctl,
1310        .fasync = random_fasync,
1311        .llseek = noop_llseek,
1312};
1313
1314/***************************************************************
1315 * Random UUID interface
1316 *
1317 * Used here for a Boot ID, but can be useful for other kernel
1318 * drivers.
1319 ***************************************************************/
1320
1321/*
1322 * Generate random UUID
1323 */
1324void generate_random_uuid(unsigned char uuid_out[16])
1325{
1326        get_random_bytes(uuid_out, 16);
1327        /* Set UUID version to 4 --- truly random generation */
1328        uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1329        /* Set the UUID variant to DCE */
1330        uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1331}
1332EXPORT_SYMBOL(generate_random_uuid);
1333
1334/********************************************************************
1335 *
1336 * Sysctl interface
1337 *
1338 ********************************************************************/
1339
1340#ifdef CONFIG_SYSCTL
1341
1342#include <linux/sysctl.h>
1343
1344static int min_read_thresh = 8, min_write_thresh;
1345static int max_read_thresh = INPUT_POOL_WORDS * 32;
1346static int max_write_thresh = INPUT_POOL_WORDS * 32;
1347static char sysctl_bootid[16];
1348
1349/*
1350 * These functions is used to return both the bootid UUID, and random
1351 * UUID.  The difference is in whether table->data is NULL; if it is,
1352 * then a new UUID is generated and returned to the user.
1353 *
1354 * If the user accesses this via the proc interface, it will be returned
1355 * as an ASCII string in the standard UUID format.  If accesses via the
1356 * sysctl system call, it is returned as 16 bytes of binary data.
1357 */
1358static int proc_do_uuid(ctl_table *table, int write,
1359                        void __user *buffer, size_t *lenp, loff_t *ppos)
1360{
1361        ctl_table fake_table;
1362        unsigned char buf[64], tmp_uuid[16], *uuid;
1363
1364        uuid = table->data;
1365        if (!uuid) {
1366                uuid = tmp_uuid;
1367                generate_random_uuid(uuid);
1368        } else {
1369                static DEFINE_SPINLOCK(bootid_spinlock);
1370
1371                spin_lock(&bootid_spinlock);
1372                if (!uuid[8])
1373                        generate_random_uuid(uuid);
1374                spin_unlock(&bootid_spinlock);
1375        }
1376
1377        sprintf(buf, "%pU", uuid);
1378
1379        fake_table.data = buf;
1380        fake_table.maxlen = sizeof(buf);
1381
1382        return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1383}
1384
1385static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1386extern ctl_table random_table[];
1387ctl_table random_table[] = {
1388        {
1389                .procname       = "poolsize",
1390                .data           = &sysctl_poolsize,
1391                .maxlen         = sizeof(int),
1392                .mode           = 0444,
1393                .proc_handler   = proc_dointvec,
1394        },
1395        {
1396                .procname       = "entropy_avail",
1397                .maxlen         = sizeof(int),
1398                .mode           = 0444,
1399                .proc_handler   = proc_dointvec,
1400                .data           = &input_pool.entropy_count,
1401        },
1402        {
1403                .procname       = "read_wakeup_threshold",
1404                .data           = &random_read_wakeup_thresh,
1405                .maxlen         = sizeof(int),
1406                .mode           = 0644,
1407                .proc_handler   = proc_dointvec_minmax,
1408                .extra1         = &min_read_thresh,
1409                .extra2         = &max_read_thresh,
1410        },
1411        {
1412                .procname       = "write_wakeup_threshold",
1413                .data           = &random_write_wakeup_thresh,
1414                .maxlen         = sizeof(int),
1415                .mode           = 0644,
1416                .proc_handler   = proc_dointvec_minmax,
1417                .extra1         = &min_write_thresh,
1418                .extra2         = &max_write_thresh,
1419        },
1420        {
1421                .procname       = "boot_id",
1422                .data           = &sysctl_bootid,
1423                .maxlen         = 16,
1424                .mode           = 0444,
1425                .proc_handler   = proc_do_uuid,
1426        },
1427        {
1428                .procname       = "uuid",
1429                .maxlen         = 16,
1430                .mode           = 0444,
1431                .proc_handler   = proc_do_uuid,
1432        },
1433        { }
1434};
1435#endif  /* CONFIG_SYSCTL */
1436
1437static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1438
1439static int __init random_int_secret_init(void)
1440{
1441        get_random_bytes(random_int_secret, sizeof(random_int_secret));
1442        return 0;
1443}
1444late_initcall(random_int_secret_init);
1445
1446/*
1447 * Get a random word for internal kernel use only. Similar to urandom but
1448 * with the goal of minimal entropy pool depletion. As a result, the random
1449 * value is not cryptographically secure but for several uses the cost of
1450 * depleting entropy is too high
1451 */
1452static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1453unsigned int get_random_int(void)
1454{
1455        __u32 *hash;
1456        unsigned int ret;
1457
1458        if (arch_get_random_int(&ret))
1459                return ret;
1460
1461        hash = get_cpu_var(get_random_int_hash);
1462
1463        hash[0] += current->pid + jiffies + get_cycles();
1464        md5_transform(hash, random_int_secret);
1465        ret = hash[0];
1466        put_cpu_var(get_random_int_hash);
1467
1468        return ret;
1469}
1470
1471/*
1472 * randomize_range() returns a start address such that
1473 *
1474 *    [...... <range> .....]
1475 *  start                  end
1476 *
1477 * a <range> with size "len" starting at the return value is inside in the
1478 * area defined by [start, end], but is otherwise randomized.
1479 */
1480unsigned long
1481randomize_range(unsigned long start, unsigned long end, unsigned long len)
1482{
1483        unsigned long range = end - len - start;
1484
1485        if (end <= start + len)
1486                return 0;
1487        return PAGE_ALIGN(get_random_int() % range + start);
1488}
1489
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