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/kthread.h>
 254#include <linux/percpu.h>
 255#include <linux/cryptohash.h>
 256#include <linux/fips.h>
 257#include <linux/ptrace.h>
 258#include <linux/kmemcheck.h>
 259#include <linux/workqueue.h>
 260#include <linux/irq.h>
 261#include <linux/syscalls.h>
 262#include <linux/completion.h>
 263
 264#include <asm/processor.h>
 265#include <asm/uaccess.h>
 266#include <asm/irq.h>
 267#include <asm/irq_regs.h>
 268#include <asm/io.h>
 269
 270#define CREATE_TRACE_POINTS
 271#include <trace/events/random.h>
 272
 273/* #define ADD_INTERRUPT_BENCH */
 274
 275/*
 276 * Configuration information
 277 */
 278#define INPUT_POOL_SHIFT        12
 279#define INPUT_POOL_WORDS        (1 << (INPUT_POOL_SHIFT-5))
 280#define OUTPUT_POOL_SHIFT       10
 281#define OUTPUT_POOL_WORDS       (1 << (OUTPUT_POOL_SHIFT-5))
 282#define SEC_XFER_SIZE           512
 283#define EXTRACT_SIZE            10
 284
 285#define DEBUG_RANDOM_BOOT 0
 286
 287#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
 288
 289/*
 290 * To allow fractional bits to be tracked, the entropy_count field is
 291 * denominated in units of 1/8th bits.
 292 *
 293 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
 294 * credit_entropy_bits() needs to be 64 bits wide.
 295 */
 296#define ENTROPY_SHIFT 3
 297#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
 298
 299/*
 300 * The minimum number of bits of entropy before we wake up a read on
 301 * /dev/random.  Should be enough to do a significant reseed.
 302 */
 303static int random_read_wakeup_bits = 64;
 304
 305/*
 306 * If the entropy count falls under this number of bits, then we
 307 * should wake up processes which are selecting or polling on write
 308 * access to /dev/random.
 309 */
 310static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
 311
 312/*
 313 * The minimum number of seconds between urandom pool reseeding.  We
 314 * do this to limit the amount of entropy that can be drained from the
 315 * input pool even if there are heavy demands on /dev/urandom.
 316 */
 317static int random_min_urandom_seed = 60;
 318
 319/*
 320 * Originally, we used a primitive polynomial of degree .poolwords
 321 * over GF(2).  The taps for various sizes are defined below.  They
 322 * were chosen to be evenly spaced except for the last tap, which is 1
 323 * to get the twisting happening as fast as possible.
 324 *
 325 * For the purposes of better mixing, we use the CRC-32 polynomial as
 326 * well to make a (modified) twisted Generalized Feedback Shift
 327 * Register.  (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR
 328 * generators.  ACM Transactions on Modeling and Computer Simulation
 329 * 2(3):179-194.  Also see M. Matsumoto & Y. Kurita, 1994.  Twisted
 330 * GFSR generators II.  ACM Transactions on Modeling and Computer
 331 * Simulation 4:254-266)
 332 *
 333 * Thanks to Colin Plumb for suggesting this.
 334 *
 335 * The mixing operation is much less sensitive than the output hash,
 336 * where we use SHA-1.  All that we want of mixing operation is that
 337 * it be a good non-cryptographic hash; i.e. it not produce collisions
 338 * when fed "random" data of the sort we expect to see.  As long as
 339 * the pool state differs for different inputs, we have preserved the
 340 * input entropy and done a good job.  The fact that an intelligent
 341 * attacker can construct inputs that will produce controlled
 342 * alterations to the pool's state is not important because we don't
 343 * consider such inputs to contribute any randomness.  The only
 344 * property we need with respect to them is that the attacker can't
 345 * increase his/her knowledge of the pool's state.  Since all
 346 * additions are reversible (knowing the final state and the input,
 347 * you can reconstruct the initial state), if an attacker has any
 348 * uncertainty about the initial state, he/she can only shuffle that
 349 * uncertainty about, but never cause any collisions (which would
 350 * decrease the uncertainty).
 351 *
 352 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
 353 * Videau in their paper, "The Linux Pseudorandom Number Generator
 354 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf).  In their
 355 * paper, they point out that we are not using a true Twisted GFSR,
 356 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
 357 * is, with only three taps, instead of the six that we are using).
 358 * As a result, the resulting polynomial is neither primitive nor
 359 * irreducible, and hence does not have a maximal period over
 360 * GF(2**32).  They suggest a slight change to the generator
 361 * polynomial which improves the resulting TGFSR polynomial to be
 362 * irreducible, which we have made here.
 363 */
 364static struct poolinfo {
 365        int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
 366#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
 367        int tap1, tap2, tap3, tap4, tap5;
 368} poolinfo_table[] = {
 369        /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
 370        /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
 371        { S(128),       104,    76,     51,     25,     1 },
 372        /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
 373        /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
 374        { S(32),        26,     19,     14,     7,      1 },
 375#if 0
 376        /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
 377        { S(2048),      1638,   1231,   819,    411,    1 },
 378
 379        /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
 380        { S(1024),      817,    615,    412,    204,    1 },
 381
 382        /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
 383        { S(1024),      819,    616,    410,    207,    2 },
 384
 385        /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
 386        { S(512),       411,    308,    208,    104,    1 },
 387
 388        /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
 389        { S(512),       409,    307,    206,    102,    2 },
 390        /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
 391        { S(512),       409,    309,    205,    103,    2 },
 392
 393        /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
 394        { S(256),       205,    155,    101,    52,     1 },
 395
 396        /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
 397        { S(128),       103,    78,     51,     27,     2 },
 398
 399        /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
 400        { S(64),        52,     39,     26,     14,     1 },
 401#endif
 402};
 403
 404/*
 405 * Static global variables
 406 */
 407static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 408static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
 409static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
 410static struct fasync_struct *fasync;
 411
 412/**********************************************************************
 413 *
 414 * OS independent entropy store.   Here are the functions which handle
 415 * storing entropy in an entropy pool.
 416 *
 417 **********************************************************************/
 418
 419struct entropy_store;
 420struct entropy_store {
 421        /* read-only data: */
 422        const struct poolinfo *poolinfo;
 423        __u32 *pool;
 424        const char *name;
 425        struct entropy_store *pull;
 426        struct work_struct push_work;
 427
 428        /* read-write data: */
 429        unsigned long last_pulled;
 430        spinlock_t lock;
 431        unsigned short add_ptr;
 432        unsigned short input_rotate;
 433        int entropy_count;
 434        int entropy_total;
 435        unsigned int initialized:1;
 436        unsigned int limit:1;
 437        unsigned int last_data_init:1;
 438        __u8 last_data[EXTRACT_SIZE];
 439};
 440
 441static void push_to_pool(struct work_struct *work);
 442static __u32 input_pool_data[INPUT_POOL_WORDS];
 443static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
 444static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
 445
 446static struct entropy_store input_pool = {
 447        .poolinfo = &poolinfo_table[0],
 448        .name = "input",
 449        .limit = 1,
 450        .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
 451        .pool = input_pool_data
 452};
 453
 454static struct entropy_store blocking_pool = {
 455        .poolinfo = &poolinfo_table[1],
 456        .name = "blocking",
 457        .limit = 1,
 458        .pull = &input_pool,
 459        .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
 460        .pool = blocking_pool_data,
 461        .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
 462                                        push_to_pool),
 463};
 464
 465static struct entropy_store nonblocking_pool = {
 466        .poolinfo = &poolinfo_table[1],
 467        .name = "nonblocking",
 468        .pull = &input_pool,
 469        .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
 470        .pool = nonblocking_pool_data,
 471        .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
 472                                        push_to_pool),
 473};
 474
 475static __u32 const twist_table[8] = {
 476        0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
 477        0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
 478
 479/*
 480 * This function adds bytes into the entropy "pool".  It does not
 481 * update the entropy estimate.  The caller should call
 482 * credit_entropy_bits if this is appropriate.
 483 *
 484 * The pool is stirred with a primitive polynomial of the appropriate
 485 * degree, and then twisted.  We twist by three bits at a time because
 486 * it's cheap to do so and helps slightly in the expected case where
 487 * the entropy is concentrated in the low-order bits.
 488 */
 489static void _mix_pool_bytes(struct entropy_store *r, const void *in,
 490                            int nbytes)
 491{
 492        unsigned long i, tap1, tap2, tap3, tap4, tap5;
 493        int input_rotate;
 494        int wordmask = r->poolinfo->poolwords - 1;
 495        const char *bytes = in;
 496        __u32 w;
 497
 498        tap1 = r->poolinfo->tap1;
 499        tap2 = r->poolinfo->tap2;
 500        tap3 = r->poolinfo->tap3;
 501        tap4 = r->poolinfo->tap4;
 502        tap5 = r->poolinfo->tap5;
 503
 504        input_rotate = r->input_rotate;
 505        i = r->add_ptr;
 506
 507        /* mix one byte at a time to simplify size handling and churn faster */
 508        while (nbytes--) {
 509                w = rol32(*bytes++, input_rotate);
 510                i = (i - 1) & wordmask;
 511
 512                /* XOR in the various taps */
 513                w ^= r->pool[i];
 514                w ^= r->pool[(i + tap1) & wordmask];
 515                w ^= r->pool[(i + tap2) & wordmask];
 516                w ^= r->pool[(i + tap3) & wordmask];
 517                w ^= r->pool[(i + tap4) & wordmask];
 518                w ^= r->pool[(i + tap5) & wordmask];
 519
 520                /* Mix the result back in with a twist */
 521                r->pool[i] = (w >> 3) ^ twist_table[w & 7];
 522
 523                /*
 524                 * Normally, we add 7 bits of rotation to the pool.
 525                 * At the beginning of the pool, add an extra 7 bits
 526                 * rotation, so that successive passes spread the
 527                 * input bits across the pool evenly.
 528                 */
 529                input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
 530        }
 531
 532        r->input_rotate = input_rotate;
 533        r->add_ptr = i;
 534}
 535
 536static void __mix_pool_bytes(struct entropy_store *r, const void *in,
 537                             int nbytes)
 538{
 539        trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
 540        _mix_pool_bytes(r, in, nbytes);
 541}
 542
 543static void mix_pool_bytes(struct entropy_store *r, const void *in,
 544                           int nbytes)
 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);
 551        spin_unlock_irqrestore(&r->lock, flags);
 552}
 553
 554struct fast_pool {
 555        __u32           pool[4];
 556        unsigned long   last;
 557        unsigned short  reg_idx;
 558        unsigned char   count;
 559};
 560
 561/*
 562 * This is a fast mixing routine used by the interrupt randomness
 563 * collector.  It's hardcoded for an 128 bit pool and assumes that any
 564 * locks that might be needed are taken by the caller.
 565 */
 566static void fast_mix(struct fast_pool *f)
 567{
 568        __u32 a = f->pool[0],   b = f->pool[1];
 569        __u32 c = f->pool[2],   d = f->pool[3];
 570
 571        a += b;                 c += d;
 572        b = rol32(b, 6);        d = rol32(d, 27);
 573        d ^= a;                 b ^= c;
 574
 575        a += b;                 c += d;
 576        b = rol32(b, 16);       d = rol32(d, 14);
 577        d ^= a;                 b ^= c;
 578
 579        a += b;                 c += d;
 580        b = rol32(b, 6);        d = rol32(d, 27);
 581        d ^= a;                 b ^= c;
 582
 583        a += b;                 c += d;
 584        b = rol32(b, 16);       d = rol32(d, 14);
 585        d ^= a;                 b ^= c;
 586
 587        f->pool[0] = a;  f->pool[1] = b;
 588        f->pool[2] = c;  f->pool[3] = d;
 589        f->count++;
 590}
 591
 592/*
 593 * Credit (or debit) the entropy store with n bits of entropy.
 594 * Use credit_entropy_bits_safe() if the value comes from userspace
 595 * or otherwise should be checked for extreme values.
 596 */
 597static void credit_entropy_bits(struct entropy_store *r, int nbits)
 598{
 599        int entropy_count, orig;
 600        const int pool_size = r->poolinfo->poolfracbits;
 601        int nfrac = nbits << ENTROPY_SHIFT;
 602
 603        if (!nbits)
 604                return;
 605
 606retry:
 607        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
 608        if (nfrac < 0) {
 609                /* Debit */
 610                entropy_count += nfrac;
 611        } else {
 612                /*
 613                 * Credit: we have to account for the possibility of
 614                 * overwriting already present entropy.  Even in the
 615                 * ideal case of pure Shannon entropy, new contributions
 616                 * approach the full value asymptotically:
 617                 *
 618                 * entropy <- entropy + (pool_size - entropy) *
 619                 *      (1 - exp(-add_entropy/pool_size))
 620                 *
 621                 * For add_entropy <= pool_size/2 then
 622                 * (1 - exp(-add_entropy/pool_size)) >=
 623                 *    (add_entropy/pool_size)*0.7869...
 624                 * so we can approximate the exponential with
 625                 * 3/4*add_entropy/pool_size and still be on the
 626                 * safe side by adding at most pool_size/2 at a time.
 627                 *
 628                 * The use of pool_size-2 in the while statement is to
 629                 * prevent rounding artifacts from making the loop
 630                 * arbitrarily long; this limits the loop to log2(pool_size)*2
 631                 * turns no matter how large nbits is.
 632                 */
 633                int pnfrac = nfrac;
 634                const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
 635                /* The +2 corresponds to the /4 in the denominator */
 636
 637                do {
 638                        unsigned int anfrac = min(pnfrac, pool_size/2);
 639                        unsigned int add =
 640                                ((pool_size - entropy_count)*anfrac*3) >> s;
 641
 642                        entropy_count += add;
 643                        pnfrac -= anfrac;
 644                } while (unlikely(entropy_count < pool_size-2 && pnfrac));
 645        }
 646
 647        if (unlikely(entropy_count < 0)) {
 648                pr_warn("random: negative entropy/overflow: pool %s count %d\n",
 649                        r->name, entropy_count);
 650                WARN_ON(1);
 651                entropy_count = 0;
 652        } else if (entropy_count > pool_size)
 653                entropy_count = pool_size;
 654        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 655                goto retry;
 656
 657        r->entropy_total += nbits;
 658        if (!r->initialized && r->entropy_total > 128) {
 659                r->initialized = 1;
 660                r->entropy_total = 0;
 661                if (r == &nonblocking_pool) {
 662                        prandom_reseed_late();
 663                        wake_up_interruptible(&urandom_init_wait);
 664                        pr_notice("random: %s pool is initialized\n", r->name);
 665                }
 666        }
 667
 668        trace_credit_entropy_bits(r->name, nbits,
 669                                  entropy_count >> ENTROPY_SHIFT,
 670                                  r->entropy_total, _RET_IP_);
 671
 672        if (r == &input_pool) {
 673                int entropy_bits = entropy_count >> ENTROPY_SHIFT;
 674
 675                /* should we wake readers? */
 676                if (entropy_bits >= random_read_wakeup_bits) {
 677                        wake_up_interruptible(&random_read_wait);
 678                        kill_fasync(&fasync, SIGIO, POLL_IN);
 679                }
 680                /* If the input pool is getting full, send some
 681                 * entropy to the two output pools, flipping back and
 682                 * forth between them, until the output pools are 75%
 683                 * full.
 684                 */
 685                if (entropy_bits > random_write_wakeup_bits &&
 686                    r->initialized &&
 687                    r->entropy_total >= 2*random_read_wakeup_bits) {
 688                        static struct entropy_store *last = &blocking_pool;
 689                        struct entropy_store *other = &blocking_pool;
 690
 691                        if (last == &blocking_pool)
 692                                other = &nonblocking_pool;
 693                        if (other->entropy_count <=
 694                            3 * other->poolinfo->poolfracbits / 4)
 695                                last = other;
 696                        if (last->entropy_count <=
 697                            3 * last->poolinfo->poolfracbits / 4) {
 698                                schedule_work(&last->push_work);
 699                                r->entropy_total = 0;
 700                        }
 701                }
 702        }
 703}
 704
 705static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
 706{
 707        const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
 708
 709        /* Cap the value to avoid overflows */
 710        nbits = min(nbits,  nbits_max);
 711        nbits = max(nbits, -nbits_max);
 712
 713        credit_entropy_bits(r, nbits);
 714}
 715
 716/*********************************************************************
 717 *
 718 * Entropy input management
 719 *
 720 *********************************************************************/
 721
 722/* There is one of these per entropy source */
 723struct timer_rand_state {
 724        cycles_t last_time;
 725        long last_delta, last_delta2;
 726        unsigned dont_count_entropy:1;
 727};
 728
 729#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
 730
 731/*
 732 * Add device- or boot-specific data to the input and nonblocking
 733 * pools to help initialize them to unique values.
 734 *
 735 * None of this adds any entropy, it is meant to avoid the
 736 * problem of the nonblocking pool having similar initial state
 737 * across largely identical devices.
 738 */
 739void add_device_randomness(const void *buf, unsigned int size)
 740{
 741        unsigned long time = random_get_entropy() ^ jiffies;
 742        unsigned long flags;
 743
 744        trace_add_device_randomness(size, _RET_IP_);
 745        spin_lock_irqsave(&input_pool.lock, flags);
 746        _mix_pool_bytes(&input_pool, buf, size);
 747        _mix_pool_bytes(&input_pool, &time, sizeof(time));
 748        spin_unlock_irqrestore(&input_pool.lock, flags);
 749
 750        spin_lock_irqsave(&nonblocking_pool.lock, flags);
 751        _mix_pool_bytes(&nonblocking_pool, buf, size);
 752        _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
 753        spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
 754}
 755EXPORT_SYMBOL(add_device_randomness);
 756
 757static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
 758
 759/*
 760 * This function adds entropy to the entropy "pool" by using timing
 761 * delays.  It uses the timer_rand_state structure to make an estimate
 762 * of how many bits of entropy this call has added to the pool.
 763 *
 764 * The number "num" is also added to the pool - it should somehow describe
 765 * the type of event which just happened.  This is currently 0-255 for
 766 * keyboard scan codes, and 256 upwards for interrupts.
 767 *
 768 */
 769static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
 770{
 771        struct entropy_store    *r;
 772        struct {
 773                long jiffies;
 774                unsigned cycles;
 775                unsigned num;
 776        } sample;
 777        long delta, delta2, delta3;
 778
 779        preempt_disable();
 780
 781        sample.jiffies = jiffies;
 782        sample.cycles = random_get_entropy();
 783        sample.num = num;
 784        r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 785        mix_pool_bytes(r, &sample, sizeof(sample));
 786
 787        /*
 788         * Calculate number of bits of randomness we probably added.
 789         * We take into account the first, second and third-order deltas
 790         * in order to make our estimate.
 791         */
 792
 793        if (!state->dont_count_entropy) {
 794                delta = sample.jiffies - state->last_time;
 795                state->last_time = sample.jiffies;
 796
 797                delta2 = delta - state->last_delta;
 798                state->last_delta = delta;
 799
 800                delta3 = delta2 - state->last_delta2;
 801                state->last_delta2 = delta2;
 802
 803                if (delta < 0)
 804                        delta = -delta;
 805                if (delta2 < 0)
 806                        delta2 = -delta2;
 807                if (delta3 < 0)
 808                        delta3 = -delta3;
 809                if (delta > delta2)
 810                        delta = delta2;
 811                if (delta > delta3)
 812                        delta = delta3;
 813
 814                /*
 815                 * delta is now minimum absolute delta.
 816                 * Round down by 1 bit on general principles,
 817                 * and limit entropy entimate to 12 bits.
 818                 */
 819                credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
 820        }
 821        preempt_enable();
 822}
 823
 824void add_input_randomness(unsigned int type, unsigned int code,
 825                                 unsigned int value)
 826{
 827        static unsigned char last_value;
 828
 829        /* ignore autorepeat and the like */
 830        if (value == last_value)
 831                return;
 832
 833        last_value = value;
 834        add_timer_randomness(&input_timer_state,
 835                             (type << 4) ^ code ^ (code >> 4) ^ value);
 836        trace_add_input_randomness(ENTROPY_BITS(&input_pool));
 837}
 838EXPORT_SYMBOL_GPL(add_input_randomness);
 839
 840static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
 841
 842#ifdef ADD_INTERRUPT_BENCH
 843static unsigned long avg_cycles, avg_deviation;
 844
 845#define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
 846#define FIXED_1_2 (1 << (AVG_SHIFT-1))
 847
 848static void add_interrupt_bench(cycles_t start)
 849{
 850        long delta = random_get_entropy() - start;
 851
 852        /* Use a weighted moving average */
 853        delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
 854        avg_cycles += delta;
 855        /* And average deviation */
 856        delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
 857        avg_deviation += delta;
 858}
 859#else
 860#define add_interrupt_bench(x)
 861#endif
 862
 863static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
 864{
 865        __u32 *ptr = (__u32 *) regs;
 866
 867        if (regs == NULL)
 868                return 0;
 869        if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
 870                f->reg_idx = 0;
 871        return *(ptr + f->reg_idx++);
 872}
 873
 874void add_interrupt_randomness(int irq, int irq_flags)
 875{
 876        struct entropy_store    *r;
 877        struct fast_pool        *fast_pool = this_cpu_ptr(&irq_randomness);
 878        struct pt_regs          *regs = get_irq_regs();
 879        unsigned long           now = jiffies;
 880        cycles_t                cycles = random_get_entropy();
 881        __u32                   c_high, j_high;
 882        __u64                   ip;
 883        unsigned long           seed;
 884        int                     credit = 0;
 885
 886        if (cycles == 0)
 887                cycles = get_reg(fast_pool, regs);
 888        c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
 889        j_high = (sizeof(now) > 4) ? now >> 32 : 0;
 890        fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
 891        fast_pool->pool[1] ^= now ^ c_high;
 892        ip = regs ? instruction_pointer(regs) : _RET_IP_;
 893        fast_pool->pool[2] ^= ip;
 894        fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
 895                get_reg(fast_pool, regs);
 896
 897        fast_mix(fast_pool);
 898        add_interrupt_bench(cycles);
 899
 900        if ((fast_pool->count < 64) &&
 901            !time_after(now, fast_pool->last + HZ))
 902                return;
 903
 904        r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 905        if (!spin_trylock(&r->lock))
 906                return;
 907
 908        fast_pool->last = now;
 909        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
 910
 911        /*
 912         * If we have architectural seed generator, produce a seed and
 913         * add it to the pool.  For the sake of paranoia don't let the
 914         * architectural seed generator dominate the input from the
 915         * interrupt noise.
 916         */
 917        if (arch_get_random_seed_long(&seed)) {
 918                __mix_pool_bytes(r, &seed, sizeof(seed));
 919                credit = 1;
 920        }
 921        spin_unlock(&r->lock);
 922
 923        fast_pool->count = 0;
 924
 925        /* award one bit for the contents of the fast pool */
 926        credit_entropy_bits(r, credit + 1);
 927}
 928
 929#ifdef CONFIG_BLOCK
 930void add_disk_randomness(struct gendisk *disk)
 931{
 932        if (!disk || !disk->random)
 933                return;
 934        /* first major is 1, so we get >= 0x200 here */
 935        add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
 936        trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
 937}
 938EXPORT_SYMBOL_GPL(add_disk_randomness);
 939#endif
 940
 941/*********************************************************************
 942 *
 943 * Entropy extraction routines
 944 *
 945 *********************************************************************/
 946
 947static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 948                               size_t nbytes, int min, int rsvd);
 949
 950/*
 951 * This utility inline function is responsible for transferring entropy
 952 * from the primary pool to the secondary extraction pool. We make
 953 * sure we pull enough for a 'catastrophic reseed'.
 954 */
 955static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
 956static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 957{
 958        if (!r->pull ||
 959            r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
 960            r->entropy_count > r->poolinfo->poolfracbits)
 961                return;
 962
 963        if (r->limit == 0 && random_min_urandom_seed) {
 964                unsigned long now = jiffies;
 965
 966                if (time_before(now,
 967                                r->last_pulled + random_min_urandom_seed * HZ))
 968                        return;
 969                r->last_pulled = now;
 970        }
 971
 972        _xfer_secondary_pool(r, nbytes);
 973}
 974
 975static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 976{
 977        __u32   tmp[OUTPUT_POOL_WORDS];
 978
 979        /* For /dev/random's pool, always leave two wakeups' worth */
 980        int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
 981        int bytes = nbytes;
 982
 983        /* pull at least as much as a wakeup */
 984        bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
 985        /* but never more than the buffer size */
 986        bytes = min_t(int, bytes, sizeof(tmp));
 987
 988        trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
 989                                  ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
 990        bytes = extract_entropy(r->pull, tmp, bytes,
 991                                random_read_wakeup_bits / 8, rsvd_bytes);
 992        mix_pool_bytes(r, tmp, bytes);
 993        credit_entropy_bits(r, bytes*8);
 994}
 995
 996/*
 997 * Used as a workqueue function so that when the input pool is getting
 998 * full, we can "spill over" some entropy to the output pools.  That
 999 * way the output pools can store some of the excess entropy instead
1000 * of letting it go to waste.
1001 */
1002static void push_to_pool(struct work_struct *work)
1003{
1004        struct entropy_store *r = container_of(work, struct entropy_store,
1005                                              push_work);
1006        BUG_ON(!r);
1007        _xfer_secondary_pool(r, random_read_wakeup_bits/8);
1008        trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1009                           r->pull->entropy_count >> ENTROPY_SHIFT);
1010}
1011
1012/*
1013 * This function decides how many bytes to actually take from the
1014 * given pool, and also debits the entropy count accordingly.
1015 */
1016static size_t account(struct entropy_store *r, size_t nbytes, int min,
1017                      int reserved)
1018{
1019        int entropy_count, orig;
1020        size_t ibytes, nfrac;
1021
1022        BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1023
1024        /* Can we pull enough? */
1025retry:
1026        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
1027        ibytes = nbytes;
1028        /* If limited, never pull more than available */
1029        if (r->limit) {
1030                int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1031
1032                if ((have_bytes -= reserved) < 0)
1033                        have_bytes = 0;
1034                ibytes = min_t(size_t, ibytes, have_bytes);
1035        }
1036        if (ibytes < min)
1037                ibytes = 0;
1038
1039        if (unlikely(entropy_count < 0)) {
1040                pr_warn("random: negative entropy count: pool %s count %d\n",
1041                        r->name, entropy_count);
1042                WARN_ON(1);
1043                entropy_count = 0;
1044        }
1045        nfrac = ibytes << (ENTROPY_SHIFT + 3);
1046        if ((size_t) entropy_count > nfrac)
1047                entropy_count -= nfrac;
1048        else
1049                entropy_count = 0;
1050
1051        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1052                goto retry;
1053
1054        trace_debit_entropy(r->name, 8 * ibytes);
1055        if (ibytes &&
1056            (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1057                wake_up_interruptible(&random_write_wait);
1058                kill_fasync(&fasync, SIGIO, POLL_OUT);
1059        }
1060
1061        return ibytes;
1062}
1063
1064/*
1065 * This function does the actual extraction for extract_entropy and
1066 * extract_entropy_user.
1067 *
1068 * Note: we assume that .poolwords is a multiple of 16 words.
1069 */
1070static void extract_buf(struct entropy_store *r, __u8 *out)
1071{
1072        int i;
1073        union {
1074                __u32 w[5];
1075                unsigned long l[LONGS(20)];
1076        } hash;
1077        __u32 workspace[SHA_WORKSPACE_WORDS];
1078        unsigned long flags;
1079
1080        /*
1081         * If we have an architectural hardware random number
1082         * generator, use it for SHA's initial vector
1083         */
1084        sha_init(hash.w);
1085        for (i = 0; i < LONGS(20); i++) {
1086                unsigned long v;
1087                if (!arch_get_random_long(&v))
1088                        break;
1089                hash.l[i] = v;
1090        }
1091
1092        /* Generate a hash across the pool, 16 words (512 bits) at a time */
1093        spin_lock_irqsave(&r->lock, flags);
1094        for (i = 0; i < r->poolinfo->poolwords; i += 16)
1095                sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1096
1097        /*
1098         * We mix the hash back into the pool to prevent backtracking
1099         * attacks (where the attacker knows the state of the pool
1100         * plus the current outputs, and attempts to find previous
1101         * ouputs), unless the hash function can be inverted. By
1102         * mixing at least a SHA1 worth of hash data back, we make
1103         * brute-forcing the feedback as hard as brute-forcing the
1104         * hash.
1105         */
1106        __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1107        spin_unlock_irqrestore(&r->lock, flags);
1108
1109        memzero_explicit(workspace, sizeof(workspace));
1110
1111        /*
1112         * In case the hash function has some recognizable output
1113         * pattern, we fold it in half. Thus, we always feed back
1114         * twice as much data as we output.
1115         */
1116        hash.w[0] ^= hash.w[3];
1117        hash.w[1] ^= hash.w[4];
1118        hash.w[2] ^= rol32(hash.w[2], 16);
1119
1120        memcpy(out, &hash, EXTRACT_SIZE);
1121        memzero_explicit(&hash, sizeof(hash));
1122}
1123
1124/*
1125 * This function extracts randomness from the "entropy pool", and
1126 * returns it in a buffer.
1127 *
1128 * The min parameter specifies the minimum amount we can pull before
1129 * failing to avoid races that defeat catastrophic reseeding while the
1130 * reserved parameter indicates how much entropy we must leave in the
1131 * pool after each pull to avoid starving other readers.
1132 */
1133static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1134                                 size_t nbytes, int min, int reserved)
1135{
1136        ssize_t ret = 0, i;
1137        __u8 tmp[EXTRACT_SIZE];
1138        unsigned long flags;
1139
1140        /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1141        if (fips_enabled) {
1142                spin_lock_irqsave(&r->lock, flags);
1143                if (!r->last_data_init) {
1144                        r->last_data_init = 1;
1145                        spin_unlock_irqrestore(&r->lock, flags);
1146                        trace_extract_entropy(r->name, EXTRACT_SIZE,
1147                                              ENTROPY_BITS(r), _RET_IP_);
1148                        xfer_secondary_pool(r, EXTRACT_SIZE);
1149                        extract_buf(r, tmp);
1150                        spin_lock_irqsave(&r->lock, flags);
1151                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
1152                }
1153                spin_unlock_irqrestore(&r->lock, flags);
1154        }
1155
1156        trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1157        xfer_secondary_pool(r, nbytes);
1158        nbytes = account(r, nbytes, min, reserved);
1159
1160        while (nbytes) {
1161                extract_buf(r, tmp);
1162
1163                if (fips_enabled) {
1164                        spin_lock_irqsave(&r->lock, flags);
1165                        if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1166                                panic("Hardware RNG duplicated output!\n");
1167                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
1168                        spin_unlock_irqrestore(&r->lock, flags);
1169                }
1170                i = min_t(int, nbytes, EXTRACT_SIZE);
1171                memcpy(buf, tmp, i);
1172                nbytes -= i;
1173                buf += i;
1174                ret += i;
1175        }
1176
1177        /* Wipe data just returned from memory */
1178        memzero_explicit(tmp, sizeof(tmp));
1179
1180        return ret;
1181}
1182
1183/*
1184 * This function extracts randomness from the "entropy pool", and
1185 * returns it in a userspace buffer.
1186 */
1187static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1188                                    size_t nbytes)
1189{
1190        ssize_t ret = 0, i;
1191        __u8 tmp[EXTRACT_SIZE];
1192        int large_request = (nbytes > 256);
1193
1194        trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1195        xfer_secondary_pool(r, nbytes);
1196        nbytes = account(r, nbytes, 0, 0);
1197
1198        while (nbytes) {
1199                if (large_request && need_resched()) {
1200                        if (signal_pending(current)) {
1201                                if (ret == 0)
1202                                        ret = -ERESTARTSYS;
1203                                break;
1204                        }
1205                        schedule();
1206                }
1207
1208                extract_buf(r, tmp);
1209                i = min_t(int, nbytes, EXTRACT_SIZE);
1210                if (copy_to_user(buf, tmp, i)) {
1211                        ret = -EFAULT;
1212                        break;
1213                }
1214
1215                nbytes -= i;
1216                buf += i;
1217                ret += i;
1218        }
1219
1220        /* Wipe data just returned from memory */
1221        memzero_explicit(tmp, sizeof(tmp));
1222
1223        return ret;
1224}
1225
1226/*
1227 * This function is the exported kernel interface.  It returns some
1228 * number of good random numbers, suitable for key generation, seeding
1229 * TCP sequence numbers, etc.  It does not rely on the hardware random
1230 * number generator.  For random bytes direct from the hardware RNG
1231 * (when available), use get_random_bytes_arch().
1232 */
1233void get_random_bytes(void *buf, int nbytes)
1234{
1235#if DEBUG_RANDOM_BOOT > 0
1236        if (unlikely(nonblocking_pool.initialized == 0))
1237                printk(KERN_NOTICE "random: %pF get_random_bytes called "
1238                       "with %d bits of entropy available\n",
1239                       (void *) _RET_IP_,
1240                       nonblocking_pool.entropy_total);
1241#endif
1242        trace_get_random_bytes(nbytes, _RET_IP_);
1243        extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1244}
1245EXPORT_SYMBOL(get_random_bytes);
1246
1247/*
1248 * This function will use the architecture-specific hardware random
1249 * number generator if it is available.  The arch-specific hw RNG will
1250 * almost certainly be faster than what we can do in software, but it
1251 * is impossible to verify that it is implemented securely (as
1252 * opposed, to, say, the AES encryption of a sequence number using a
1253 * key known by the NSA).  So it's useful if we need the speed, but
1254 * only if we're willing to trust the hardware manufacturer not to
1255 * have put in a back door.
1256 */
1257void get_random_bytes_arch(void *buf, int nbytes)
1258{
1259        char *p = buf;
1260
1261        trace_get_random_bytes_arch(nbytes, _RET_IP_);
1262        while (nbytes) {
1263                unsigned long v;
1264                int chunk = min(nbytes, (int)sizeof(unsigned long));
1265
1266                if (!arch_get_random_long(&v))
1267                        break;
1268                
1269                memcpy(p, &v, chunk);
1270                p += chunk;
1271                nbytes -= chunk;
1272        }
1273
1274        if (nbytes)
1275                extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1276}
1277EXPORT_SYMBOL(get_random_bytes_arch);
1278
1279
1280/*
1281 * init_std_data - initialize pool with system data
1282 *
1283 * @r: pool to initialize
1284 *
1285 * This function clears the pool's entropy count and mixes some system
1286 * data into the pool to prepare it for use. The pool is not cleared
1287 * as that can only decrease the entropy in the pool.
1288 */
1289static void init_std_data(struct entropy_store *r)
1290{
1291        int i;
1292        ktime_t now = ktime_get_real();
1293        unsigned long rv;
1294
1295        r->last_pulled = jiffies;
1296        mix_pool_bytes(r, &now, sizeof(now));
1297        for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1298                if (!arch_get_random_seed_long(&rv) &&
1299                    !arch_get_random_long(&rv))
1300                        rv = random_get_entropy();
1301                mix_pool_bytes(r, &rv, sizeof(rv));
1302        }
1303        mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1304}
1305
1306/*
1307 * Note that setup_arch() may call add_device_randomness()
1308 * long before we get here. This allows seeding of the pools
1309 * with some platform dependent data very early in the boot
1310 * process. But it limits our options here. We must use
1311 * statically allocated structures that already have all
1312 * initializations complete at compile time. We should also
1313 * take care not to overwrite the precious per platform data
1314 * we were given.
1315 */
1316static int rand_initialize(void)
1317{
1318        init_std_data(&input_pool);
1319        init_std_data(&blocking_pool);
1320        init_std_data(&nonblocking_pool);
1321        return 0;
1322}
1323early_initcall(rand_initialize);
1324
1325#ifdef CONFIG_BLOCK
1326void rand_initialize_disk(struct gendisk *disk)
1327{
1328        struct timer_rand_state *state;
1329
1330        /*
1331         * If kzalloc returns null, we just won't use that entropy
1332         * source.
1333         */
1334        state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1335        if (state) {
1336                state->last_time = INITIAL_JIFFIES;
1337                disk->random = state;
1338        }
1339}
1340#endif
1341
1342static ssize_t
1343_random_read(int nonblock, char __user *buf, size_t nbytes)
1344{
1345        ssize_t n;
1346
1347        if (nbytes == 0)
1348                return 0;
1349
1350        nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1351        while (1) {
1352                n = extract_entropy_user(&blocking_pool, buf, nbytes);
1353                if (n < 0)
1354                        return n;
1355                trace_random_read(n*8, (nbytes-n)*8,
1356                                  ENTROPY_BITS(&blocking_pool),
1357                                  ENTROPY_BITS(&input_pool));
1358                if (n > 0)
1359                        return n;
1360
1361                /* Pool is (near) empty.  Maybe wait and retry. */
1362                if (nonblock)
1363                        return -EAGAIN;
1364
1365                wait_event_interruptible(random_read_wait,
1366                        ENTROPY_BITS(&input_pool) >=
1367                        random_read_wakeup_bits);
1368                if (signal_pending(current))
1369                        return -ERESTARTSYS;
1370        }
1371}
1372
1373static ssize_t
1374random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1375{
1376        return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1377}
1378
1379static ssize_t
1380urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1381{
1382        int ret;
1383
1384        if (unlikely(nonblocking_pool.initialized == 0))
1385                printk_once(KERN_NOTICE "random: %s urandom read "
1386                            "with %d bits of entropy available\n",
1387                            current->comm, nonblocking_pool.entropy_total);
1388
1389        nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1390        ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
1391
1392        trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
1393                           ENTROPY_BITS(&input_pool));
1394        return ret;
1395}
1396
1397static unsigned int
1398random_poll(struct file *file, poll_table * wait)
1399{
1400        unsigned int mask;
1401
1402        poll_wait(file, &random_read_wait, wait);
1403        poll_wait(file, &random_write_wait, wait);
1404        mask = 0;
1405        if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1406                mask |= POLLIN | POLLRDNORM;
1407        if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1408                mask |= POLLOUT | POLLWRNORM;
1409        return mask;
1410}
1411
1412static int
1413write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1414{
1415        size_t bytes;
1416        __u32 buf[16];
1417        const char __user *p = buffer;
1418
1419        while (count > 0) {
1420                bytes = min(count, sizeof(buf));
1421                if (copy_from_user(&buf, p, bytes))
1422                        return -EFAULT;
1423
1424                count -= bytes;
1425                p += bytes;
1426
1427                mix_pool_bytes(r, buf, bytes);
1428                cond_resched();
1429        }
1430
1431        return 0;
1432}
1433
1434static ssize_t random_write(struct file *file, const char __user *buffer,
1435                            size_t count, loff_t *ppos)
1436{
1437        size_t ret;
1438
1439        ret = write_pool(&blocking_pool, buffer, count);
1440        if (ret)
1441                return ret;
1442        ret = write_pool(&nonblocking_pool, buffer, count);
1443        if (ret)
1444                return ret;
1445
1446        return (ssize_t)count;
1447}
1448
1449static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1450{
1451        int size, ent_count;
1452        int __user *p = (int __user *)arg;
1453        int retval;
1454
1455        switch (cmd) {
1456        case RNDGETENTCNT:
1457                /* inherently racy, no point locking */
1458                ent_count = ENTROPY_BITS(&input_pool);
1459                if (put_user(ent_count, p))
1460                        return -EFAULT;
1461                return 0;
1462        case RNDADDTOENTCNT:
1463                if (!capable(CAP_SYS_ADMIN))
1464                        return -EPERM;
1465                if (get_user(ent_count, p))
1466                        return -EFAULT;
1467                credit_entropy_bits_safe(&input_pool, ent_count);
1468                return 0;
1469        case RNDADDENTROPY:
1470                if (!capable(CAP_SYS_ADMIN))
1471                        return -EPERM;
1472                if (get_user(ent_count, p++))
1473                        return -EFAULT;
1474                if (ent_count < 0)
1475                        return -EINVAL;
1476                if (get_user(size, p++))
1477                        return -EFAULT;
1478                retval = write_pool(&input_pool, (const char __user *)p,
1479                                    size);
1480                if (retval < 0)
1481                        return retval;
1482                credit_entropy_bits_safe(&input_pool, ent_count);
1483                return 0;
1484        case RNDZAPENTCNT:
1485        case RNDCLEARPOOL:
1486                /*
1487                 * Clear the entropy pool counters. We no longer clear
1488                 * the entropy pool, as that's silly.
1489                 */
1490                if (!capable(CAP_SYS_ADMIN))
1491                        return -EPERM;
1492                input_pool.entropy_count = 0;
1493                nonblocking_pool.entropy_count = 0;
1494                blocking_pool.entropy_count = 0;
1495                return 0;
1496        default:
1497                return -EINVAL;
1498        }
1499}
1500
1501static int random_fasync(int fd, struct file *filp, int on)
1502{
1503        return fasync_helper(fd, filp, on, &fasync);
1504}
1505
1506const struct file_operations random_fops = {
1507        .read  = random_read,
1508        .write = random_write,
1509        .poll  = random_poll,
1510        .unlocked_ioctl = random_ioctl,
1511        .fasync = random_fasync,
1512        .llseek = noop_llseek,
1513};
1514
1515const struct file_operations urandom_fops = {
1516        .read  = urandom_read,
1517        .write = random_write,
1518        .unlocked_ioctl = random_ioctl,
1519        .fasync = random_fasync,
1520        .llseek = noop_llseek,
1521};
1522
1523SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1524                unsigned int, flags)
1525{
1526        if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
1527                return -EINVAL;
1528
1529        if (count > INT_MAX)
1530                count = INT_MAX;
1531
1532        if (flags & GRND_RANDOM)
1533                return _random_read(flags & GRND_NONBLOCK, buf, count);
1534
1535        if (unlikely(nonblocking_pool.initialized == 0)) {
1536                if (flags & GRND_NONBLOCK)
1537                        return -EAGAIN;
1538                wait_event_interruptible(urandom_init_wait,
1539                                         nonblocking_pool.initialized);
1540                if (signal_pending(current))
1541                        return -ERESTARTSYS;
1542        }
1543        return urandom_read(NULL, buf, count, NULL);
1544}
1545
1546/***************************************************************
1547 * Random UUID interface
1548 *
1549 * Used here for a Boot ID, but can be useful for other kernel
1550 * drivers.
1551 ***************************************************************/
1552
1553/*
1554 * Generate random UUID
1555 */
1556void generate_random_uuid(unsigned char uuid_out[16])
1557{
1558        get_random_bytes(uuid_out, 16);
1559        /* Set UUID version to 4 --- truly random generation */
1560        uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1561        /* Set the UUID variant to DCE */
1562        uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1563}
1564EXPORT_SYMBOL(generate_random_uuid);
1565
1566/********************************************************************
1567 *
1568 * Sysctl interface
1569 *
1570 ********************************************************************/
1571
1572#ifdef CONFIG_SYSCTL
1573
1574#include <linux/sysctl.h>
1575
1576static int min_read_thresh = 8, min_write_thresh;
1577static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1578static int max_write_thresh = INPUT_POOL_WORDS * 32;
1579static char sysctl_bootid[16];
1580
1581/*
1582 * This function is used to return both the bootid UUID, and random
1583 * UUID.  The difference is in whether table->data is NULL; if it is,
1584 * then a new UUID is generated and returned to the user.
1585 *
1586 * If the user accesses this via the proc interface, the UUID will be
1587 * returned as an ASCII string in the standard UUID format; if via the
1588 * sysctl system call, as 16 bytes of binary data.
1589 */
1590static int proc_do_uuid(struct ctl_table *table, int write,
1591                        void __user *buffer, size_t *lenp, loff_t *ppos)
1592{
1593        struct ctl_table fake_table;
1594        unsigned char buf[64], tmp_uuid[16], *uuid;
1595
1596        uuid = table->data;
1597        if (!uuid) {
1598                uuid = tmp_uuid;
1599                generate_random_uuid(uuid);
1600        } else {
1601                static DEFINE_SPINLOCK(bootid_spinlock);
1602
1603                spin_lock(&bootid_spinlock);
1604                if (!uuid[8])
1605                        generate_random_uuid(uuid);
1606                spin_unlock(&bootid_spinlock);
1607        }
1608
1609        sprintf(buf, "%pU", uuid);
1610
1611        fake_table.data = buf;
1612        fake_table.maxlen = sizeof(buf);
1613
1614        return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1615}
1616
1617/*
1618 * Return entropy available scaled to integral bits
1619 */
1620static int proc_do_entropy(struct ctl_table *table, int write,
1621                           void __user *buffer, size_t *lenp, loff_t *ppos)
1622{
1623        struct ctl_table fake_table;
1624        int entropy_count;
1625
1626        entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1627
1628        fake_table.data = &entropy_count;
1629        fake_table.maxlen = sizeof(entropy_count);
1630
1631        return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1632}
1633
1634static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1635extern struct ctl_table random_table[];
1636struct ctl_table random_table[] = {
1637        {
1638                .procname       = "poolsize",
1639                .data           = &sysctl_poolsize,
1640                .maxlen         = sizeof(int),
1641                .mode           = 0444,
1642                .proc_handler   = proc_dointvec,
1643        },
1644        {
1645                .procname       = "entropy_avail",
1646                .maxlen         = sizeof(int),
1647                .mode           = 0444,
1648                .proc_handler   = proc_do_entropy,
1649                .data           = &input_pool.entropy_count,
1650        },
1651        {
1652                .procname       = "read_wakeup_threshold",
1653                .data           = &random_read_wakeup_bits,
1654                .maxlen         = sizeof(int),
1655                .mode           = 0644,
1656                .proc_handler   = proc_dointvec_minmax,
1657                .extra1         = &min_read_thresh,
1658                .extra2         = &max_read_thresh,
1659        },
1660        {
1661                .procname       = "write_wakeup_threshold",
1662                .data           = &random_write_wakeup_bits,
1663                .maxlen         = sizeof(int),
1664                .mode           = 0644,
1665                .proc_handler   = proc_dointvec_minmax,
1666                .extra1         = &min_write_thresh,
1667                .extra2         = &max_write_thresh,
1668        },
1669        {
1670                .procname       = "urandom_min_reseed_secs",
1671                .data           = &random_min_urandom_seed,
1672                .maxlen         = sizeof(int),
1673                .mode           = 0644,
1674                .proc_handler   = proc_dointvec,
1675        },
1676        {
1677                .procname       = "boot_id",
1678                .data           = &sysctl_bootid,
1679                .maxlen         = 16,
1680                .mode           = 0444,
1681                .proc_handler   = proc_do_uuid,
1682        },
1683        {
1684                .procname       = "uuid",
1685                .maxlen         = 16,
1686                .mode           = 0444,
1687                .proc_handler   = proc_do_uuid,
1688        },
1689#ifdef ADD_INTERRUPT_BENCH
1690        {
1691                .procname       = "add_interrupt_avg_cycles",
1692                .data           = &avg_cycles,
1693                .maxlen         = sizeof(avg_cycles),
1694                .mode           = 0444,
1695                .proc_handler   = proc_doulongvec_minmax,
1696        },
1697        {
1698                .procname       = "add_interrupt_avg_deviation",
1699                .data           = &avg_deviation,
1700                .maxlen         = sizeof(avg_deviation),
1701                .mode           = 0444,
1702                .proc_handler   = proc_doulongvec_minmax,
1703        },
1704#endif
1705        { }
1706};
1707#endif  /* CONFIG_SYSCTL */
1708
1709static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1710
1711int random_int_secret_init(void)
1712{
1713        get_random_bytes(random_int_secret, sizeof(random_int_secret));
1714        return 0;
1715}
1716
1717/*
1718 * Get a random word for internal kernel use only. Similar to urandom but
1719 * with the goal of minimal entropy pool depletion. As a result, the random
1720 * value is not cryptographically secure but for several uses the cost of
1721 * depleting entropy is too high
1722 */
1723static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1724unsigned int get_random_int(void)
1725{
1726        __u32 *hash;
1727        unsigned int ret;
1728
1729        if (arch_get_random_int(&ret))
1730                return ret;
1731
1732        hash = get_cpu_var(get_random_int_hash);
1733
1734        hash[0] += current->pid + jiffies + random_get_entropy();
1735        md5_transform(hash, random_int_secret);
1736        ret = hash[0];
1737        put_cpu_var(get_random_int_hash);
1738
1739        return ret;
1740}
1741EXPORT_SYMBOL(get_random_int);
1742
1743/*
1744 * randomize_range() returns a start address such that
1745 *
1746 *    [...... <range> .....]
1747 *  start                  end
1748 *
1749 * a <range> with size "len" starting at the return value is inside in the
1750 * area defined by [start, end], but is otherwise randomized.
1751 */
1752unsigned long
1753randomize_range(unsigned long start, unsigned long end, unsigned long len)
1754{
1755        unsigned long range = end - len - start;
1756
1757        if (end <= start + len)
1758                return 0;
1759        return PAGE_ALIGN(get_random_int() % range + start);
1760}
1761
1762/* Interface for in-kernel drivers of true hardware RNGs.
1763 * Those devices may produce endless random bits and will be throttled
1764 * when our pool is full.
1765 */
1766void add_hwgenerator_randomness(const char *buffer, size_t count,
1767                                size_t entropy)
1768{
1769        struct entropy_store *poolp = &input_pool;
1770
1771        /* Suspend writing if we're above the trickle threshold.
1772         * We'll be woken up again once below random_write_wakeup_thresh,
1773         * or when the calling thread is about to terminate.
1774         */
1775        wait_event_interruptible(random_write_wait, kthread_should_stop() ||
1776                        ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
1777        mix_pool_bytes(poolp, buffer, count);
1778        credit_entropy_bits(poolp, entropy);
1779}
1780EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
1781
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