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Linux/drivers/char/random.c

  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  */
303 static 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  */
310 static 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  */
317 static 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  */
364 static 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  */
407 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
408 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
409 static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
410 static 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 
419 struct entropy_store;
420 struct 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 
441 static void push_to_pool(struct work_struct *work);
442 static __u32 input_pool_data[INPUT_POOL_WORDS];
443 static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
444 static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
445 
446 static 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 
454 static 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 
465 static 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 
475 static __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  */
489 static 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 
536 static 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 
543 static 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 
554 struct 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  */
566 static 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(a, 6);        d = rol32(c, 27);
573         d ^= a;                 b ^= c;
574 
575         a += b;                 c += d;
576         b = rol32(a, 16);       d = rol32(c, 14);
577         d ^= a;                 b ^= c;
578 
579         a += b;                 c += d;
580         b = rol32(a, 6);        d = rol32(c, 27);
581         d ^= a;                 b ^= c;
582 
583         a += b;                 c += d;
584         b = rol32(a, 16);       d = rol32(c, 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  */
597 static 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 
606 retry:
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 
705 static 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 */
723 struct 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  */
739 void 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 }
755 EXPORT_SYMBOL(add_device_randomness);
756 
757 static 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  */
769 static 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 
824 void 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 }
838 EXPORT_SYMBOL_GPL(add_input_randomness);
839 
840 static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
841 
842 #ifdef ADD_INTERRUPT_BENCH
843 static 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 
848 static 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 
863 static __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 
874 void add_interrupt_randomness(int irq, int irq_flags)
875 {
876         struct entropy_store    *r;
877         struct fast_pool        *fast_pool = &__get_cpu_var(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
930 void 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 }
938 EXPORT_SYMBOL_GPL(add_disk_randomness);
939 #endif
940 
941 /*********************************************************************
942  *
943  * Entropy extraction routines
944  *
945  *********************************************************************/
946 
947 static 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  */
955 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
956 static 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 
975 static 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  */
1002 static 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  */
1016 static 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? */
1025 retry:
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  */
1070 static 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         memset(workspace, 0, 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         memset(&hash, 0, 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  */
1133 static 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         memset(tmp, 0, 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  */
1187 static 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         memset(tmp, 0, 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  */
1233 void 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 }
1245 EXPORT_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  */
1257 void 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 }
1277 EXPORT_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  */
1289 static 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  */
1316 static 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 }
1323 early_initcall(rand_initialize);
1324 
1325 #ifdef CONFIG_BLOCK
1326 void 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 
1342 static 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 
1373 static ssize_t
1374 random_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 
1379 static ssize_t
1380 urandom_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 
1397 static unsigned int
1398 random_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 
1412 static int
1413 write_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 
1434 static 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 
1449 static 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 
1501 static int random_fasync(int fd, struct file *filp, int on)
1502 {
1503         return fasync_helper(fd, filp, on, &fasync);
1504 }
1505 
1506 const 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 
1515 const struct file_operations urandom_fops = {
1516         .read  = urandom_read,
1517         .write = random_write,
1518         .unlocked_ioctl = random_ioctl,
1519         .fasync = random_fasync,
1520         .llseek = noop_llseek,
1521 };
1522 
1523 SYSCALL_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  */
1556 void 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 }
1564 EXPORT_SYMBOL(generate_random_uuid);
1565 
1566 /********************************************************************
1567  *
1568  * Sysctl interface
1569  *
1570  ********************************************************************/
1571 
1572 #ifdef CONFIG_SYSCTL
1573 
1574 #include <linux/sysctl.h>
1575 
1576 static int min_read_thresh = 8, min_write_thresh;
1577 static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1578 static int max_write_thresh = INPUT_POOL_WORDS * 32;
1579 static 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  */
1590 static 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  */
1620 static 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 
1634 static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1635 extern struct ctl_table random_table[];
1636 struct 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 
1709 static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1710 
1711 int 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  */
1723 static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1724 unsigned 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 }
1741 EXPORT_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  */
1752 unsigned long
1753 randomize_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  */
1766 void 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 }
1780 EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
1781 

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