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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 static DEFINE_SPINLOCK(random_ready_list_lock);
413 static LIST_HEAD(random_ready_list);
414 
415 /**********************************************************************
416  *
417  * OS independent entropy store.   Here are the functions which handle
418  * storing entropy in an entropy pool.
419  *
420  **********************************************************************/
421 
422 struct entropy_store;
423 struct entropy_store {
424         /* read-only data: */
425         const struct poolinfo *poolinfo;
426         __u32 *pool;
427         const char *name;
428         struct entropy_store *pull;
429         struct work_struct push_work;
430 
431         /* read-write data: */
432         unsigned long last_pulled;
433         spinlock_t lock;
434         unsigned short add_ptr;
435         unsigned short input_rotate;
436         int entropy_count;
437         int entropy_total;
438         unsigned int initialized:1;
439         unsigned int limit:1;
440         unsigned int last_data_init:1;
441         __u8 last_data[EXTRACT_SIZE];
442 };
443 
444 static void push_to_pool(struct work_struct *work);
445 static __u32 input_pool_data[INPUT_POOL_WORDS];
446 static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
447 static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
448 
449 static struct entropy_store input_pool = {
450         .poolinfo = &poolinfo_table[0],
451         .name = "input",
452         .limit = 1,
453         .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
454         .pool = input_pool_data
455 };
456 
457 static struct entropy_store blocking_pool = {
458         .poolinfo = &poolinfo_table[1],
459         .name = "blocking",
460         .limit = 1,
461         .pull = &input_pool,
462         .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
463         .pool = blocking_pool_data,
464         .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
465                                         push_to_pool),
466 };
467 
468 static struct entropy_store nonblocking_pool = {
469         .poolinfo = &poolinfo_table[1],
470         .name = "nonblocking",
471         .pull = &input_pool,
472         .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
473         .pool = nonblocking_pool_data,
474         .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
475                                         push_to_pool),
476 };
477 
478 static __u32 const twist_table[8] = {
479         0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
480         0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
481 
482 /*
483  * This function adds bytes into the entropy "pool".  It does not
484  * update the entropy estimate.  The caller should call
485  * credit_entropy_bits if this is appropriate.
486  *
487  * The pool is stirred with a primitive polynomial of the appropriate
488  * degree, and then twisted.  We twist by three bits at a time because
489  * it's cheap to do so and helps slightly in the expected case where
490  * the entropy is concentrated in the low-order bits.
491  */
492 static void _mix_pool_bytes(struct entropy_store *r, const void *in,
493                             int nbytes)
494 {
495         unsigned long i, tap1, tap2, tap3, tap4, tap5;
496         int input_rotate;
497         int wordmask = r->poolinfo->poolwords - 1;
498         const char *bytes = in;
499         __u32 w;
500 
501         tap1 = r->poolinfo->tap1;
502         tap2 = r->poolinfo->tap2;
503         tap3 = r->poolinfo->tap3;
504         tap4 = r->poolinfo->tap4;
505         tap5 = r->poolinfo->tap5;
506 
507         input_rotate = r->input_rotate;
508         i = r->add_ptr;
509 
510         /* mix one byte at a time to simplify size handling and churn faster */
511         while (nbytes--) {
512                 w = rol32(*bytes++, input_rotate);
513                 i = (i - 1) & wordmask;
514 
515                 /* XOR in the various taps */
516                 w ^= r->pool[i];
517                 w ^= r->pool[(i + tap1) & wordmask];
518                 w ^= r->pool[(i + tap2) & wordmask];
519                 w ^= r->pool[(i + tap3) & wordmask];
520                 w ^= r->pool[(i + tap4) & wordmask];
521                 w ^= r->pool[(i + tap5) & wordmask];
522 
523                 /* Mix the result back in with a twist */
524                 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
525 
526                 /*
527                  * Normally, we add 7 bits of rotation to the pool.
528                  * At the beginning of the pool, add an extra 7 bits
529                  * rotation, so that successive passes spread the
530                  * input bits across the pool evenly.
531                  */
532                 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
533         }
534 
535         r->input_rotate = input_rotate;
536         r->add_ptr = i;
537 }
538 
539 static void __mix_pool_bytes(struct entropy_store *r, const void *in,
540                              int nbytes)
541 {
542         trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
543         _mix_pool_bytes(r, in, nbytes);
544 }
545 
546 static void mix_pool_bytes(struct entropy_store *r, const void *in,
547                            int nbytes)
548 {
549         unsigned long flags;
550 
551         trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
552         spin_lock_irqsave(&r->lock, flags);
553         _mix_pool_bytes(r, in, nbytes);
554         spin_unlock_irqrestore(&r->lock, flags);
555 }
556 
557 struct fast_pool {
558         __u32           pool[4];
559         unsigned long   last;
560         unsigned short  reg_idx;
561         unsigned char   count;
562 };
563 
564 /*
565  * This is a fast mixing routine used by the interrupt randomness
566  * collector.  It's hardcoded for an 128 bit pool and assumes that any
567  * locks that might be needed are taken by the caller.
568  */
569 static void fast_mix(struct fast_pool *f)
570 {
571         __u32 a = f->pool[0],   b = f->pool[1];
572         __u32 c = f->pool[2],   d = f->pool[3];
573 
574         a += b;                 c += d;
575         b = rol32(b, 6);        d = rol32(d, 27);
576         d ^= a;                 b ^= c;
577 
578         a += b;                 c += d;
579         b = rol32(b, 16);       d = rol32(d, 14);
580         d ^= a;                 b ^= c;
581 
582         a += b;                 c += d;
583         b = rol32(b, 6);        d = rol32(d, 27);
584         d ^= a;                 b ^= c;
585 
586         a += b;                 c += d;
587         b = rol32(b, 16);       d = rol32(d, 14);
588         d ^= a;                 b ^= c;
589 
590         f->pool[0] = a;  f->pool[1] = b;
591         f->pool[2] = c;  f->pool[3] = d;
592         f->count++;
593 }
594 
595 static void process_random_ready_list(void)
596 {
597         unsigned long flags;
598         struct random_ready_callback *rdy, *tmp;
599 
600         spin_lock_irqsave(&random_ready_list_lock, flags);
601         list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
602                 struct module *owner = rdy->owner;
603 
604                 list_del_init(&rdy->list);
605                 rdy->func(rdy);
606                 module_put(owner);
607         }
608         spin_unlock_irqrestore(&random_ready_list_lock, flags);
609 }
610 
611 /*
612  * Credit (or debit) the entropy store with n bits of entropy.
613  * Use credit_entropy_bits_safe() if the value comes from userspace
614  * or otherwise should be checked for extreme values.
615  */
616 static void credit_entropy_bits(struct entropy_store *r, int nbits)
617 {
618         int entropy_count, orig;
619         const int pool_size = r->poolinfo->poolfracbits;
620         int nfrac = nbits << ENTROPY_SHIFT;
621 
622         if (!nbits)
623                 return;
624 
625 retry:
626         entropy_count = orig = ACCESS_ONCE(r->entropy_count);
627         if (nfrac < 0) {
628                 /* Debit */
629                 entropy_count += nfrac;
630         } else {
631                 /*
632                  * Credit: we have to account for the possibility of
633                  * overwriting already present entropy.  Even in the
634                  * ideal case of pure Shannon entropy, new contributions
635                  * approach the full value asymptotically:
636                  *
637                  * entropy <- entropy + (pool_size - entropy) *
638                  *      (1 - exp(-add_entropy/pool_size))
639                  *
640                  * For add_entropy <= pool_size/2 then
641                  * (1 - exp(-add_entropy/pool_size)) >=
642                  *    (add_entropy/pool_size)*0.7869...
643                  * so we can approximate the exponential with
644                  * 3/4*add_entropy/pool_size and still be on the
645                  * safe side by adding at most pool_size/2 at a time.
646                  *
647                  * The use of pool_size-2 in the while statement is to
648                  * prevent rounding artifacts from making the loop
649                  * arbitrarily long; this limits the loop to log2(pool_size)*2
650                  * turns no matter how large nbits is.
651                  */
652                 int pnfrac = nfrac;
653                 const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
654                 /* The +2 corresponds to the /4 in the denominator */
655 
656                 do {
657                         unsigned int anfrac = min(pnfrac, pool_size/2);
658                         unsigned int add =
659                                 ((pool_size - entropy_count)*anfrac*3) >> s;
660 
661                         entropy_count += add;
662                         pnfrac -= anfrac;
663                 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
664         }
665 
666         if (unlikely(entropy_count < 0)) {
667                 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
668                         r->name, entropy_count);
669                 WARN_ON(1);
670                 entropy_count = 0;
671         } else if (entropy_count > pool_size)
672                 entropy_count = pool_size;
673         if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
674                 goto retry;
675 
676         r->entropy_total += nbits;
677         if (!r->initialized && r->entropy_total > 128) {
678                 r->initialized = 1;
679                 r->entropy_total = 0;
680                 if (r == &nonblocking_pool) {
681                         prandom_reseed_late();
682                         process_random_ready_list();
683                         wake_up_all(&urandom_init_wait);
684                         pr_notice("random: %s pool is initialized\n", r->name);
685                 }
686         }
687 
688         trace_credit_entropy_bits(r->name, nbits,
689                                   entropy_count >> ENTROPY_SHIFT,
690                                   r->entropy_total, _RET_IP_);
691 
692         if (r == &input_pool) {
693                 int entropy_bits = entropy_count >> ENTROPY_SHIFT;
694 
695                 /* should we wake readers? */
696                 if (entropy_bits >= random_read_wakeup_bits) {
697                         wake_up_interruptible(&random_read_wait);
698                         kill_fasync(&fasync, SIGIO, POLL_IN);
699                 }
700                 /* If the input pool is getting full, send some
701                  * entropy to the two output pools, flipping back and
702                  * forth between them, until the output pools are 75%
703                  * full.
704                  */
705                 if (entropy_bits > random_write_wakeup_bits &&
706                     r->initialized &&
707                     r->entropy_total >= 2*random_read_wakeup_bits) {
708                         static struct entropy_store *last = &blocking_pool;
709                         struct entropy_store *other = &blocking_pool;
710 
711                         if (last == &blocking_pool)
712                                 other = &nonblocking_pool;
713                         if (other->entropy_count <=
714                             3 * other->poolinfo->poolfracbits / 4)
715                                 last = other;
716                         if (last->entropy_count <=
717                             3 * last->poolinfo->poolfracbits / 4) {
718                                 schedule_work(&last->push_work);
719                                 r->entropy_total = 0;
720                         }
721                 }
722         }
723 }
724 
725 static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
726 {
727         const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
728 
729         /* Cap the value to avoid overflows */
730         nbits = min(nbits,  nbits_max);
731         nbits = max(nbits, -nbits_max);
732 
733         credit_entropy_bits(r, nbits);
734 }
735 
736 /*********************************************************************
737  *
738  * Entropy input management
739  *
740  *********************************************************************/
741 
742 /* There is one of these per entropy source */
743 struct timer_rand_state {
744         cycles_t last_time;
745         long last_delta, last_delta2;
746         unsigned dont_count_entropy:1;
747 };
748 
749 #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
750 
751 /*
752  * Add device- or boot-specific data to the input and nonblocking
753  * pools to help initialize them to unique values.
754  *
755  * None of this adds any entropy, it is meant to avoid the
756  * problem of the nonblocking pool having similar initial state
757  * across largely identical devices.
758  */
759 void add_device_randomness(const void *buf, unsigned int size)
760 {
761         unsigned long time = random_get_entropy() ^ jiffies;
762         unsigned long flags;
763 
764         trace_add_device_randomness(size, _RET_IP_);
765         spin_lock_irqsave(&input_pool.lock, flags);
766         _mix_pool_bytes(&input_pool, buf, size);
767         _mix_pool_bytes(&input_pool, &time, sizeof(time));
768         spin_unlock_irqrestore(&input_pool.lock, flags);
769 
770         spin_lock_irqsave(&nonblocking_pool.lock, flags);
771         _mix_pool_bytes(&nonblocking_pool, buf, size);
772         _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
773         spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
774 }
775 EXPORT_SYMBOL(add_device_randomness);
776 
777 static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
778 
779 /*
780  * This function adds entropy to the entropy "pool" by using timing
781  * delays.  It uses the timer_rand_state structure to make an estimate
782  * of how many bits of entropy this call has added to the pool.
783  *
784  * The number "num" is also added to the pool - it should somehow describe
785  * the type of event which just happened.  This is currently 0-255 for
786  * keyboard scan codes, and 256 upwards for interrupts.
787  *
788  */
789 static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
790 {
791         struct entropy_store    *r;
792         struct {
793                 long jiffies;
794                 unsigned cycles;
795                 unsigned num;
796         } sample;
797         long delta, delta2, delta3;
798 
799         preempt_disable();
800 
801         sample.jiffies = jiffies;
802         sample.cycles = random_get_entropy();
803         sample.num = num;
804         r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
805         mix_pool_bytes(r, &sample, sizeof(sample));
806 
807         /*
808          * Calculate number of bits of randomness we probably added.
809          * We take into account the first, second and third-order deltas
810          * in order to make our estimate.
811          */
812 
813         if (!state->dont_count_entropy) {
814                 delta = sample.jiffies - state->last_time;
815                 state->last_time = sample.jiffies;
816 
817                 delta2 = delta - state->last_delta;
818                 state->last_delta = delta;
819 
820                 delta3 = delta2 - state->last_delta2;
821                 state->last_delta2 = delta2;
822 
823                 if (delta < 0)
824                         delta = -delta;
825                 if (delta2 < 0)
826                         delta2 = -delta2;
827                 if (delta3 < 0)
828                         delta3 = -delta3;
829                 if (delta > delta2)
830                         delta = delta2;
831                 if (delta > delta3)
832                         delta = delta3;
833 
834                 /*
835                  * delta is now minimum absolute delta.
836                  * Round down by 1 bit on general principles,
837                  * and limit entropy entimate to 12 bits.
838                  */
839                 credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
840         }
841         preempt_enable();
842 }
843 
844 void add_input_randomness(unsigned int type, unsigned int code,
845                                  unsigned int value)
846 {
847         static unsigned char last_value;
848 
849         /* ignore autorepeat and the like */
850         if (value == last_value)
851                 return;
852 
853         last_value = value;
854         add_timer_randomness(&input_timer_state,
855                              (type << 4) ^ code ^ (code >> 4) ^ value);
856         trace_add_input_randomness(ENTROPY_BITS(&input_pool));
857 }
858 EXPORT_SYMBOL_GPL(add_input_randomness);
859 
860 static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
861 
862 #ifdef ADD_INTERRUPT_BENCH
863 static unsigned long avg_cycles, avg_deviation;
864 
865 #define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
866 #define FIXED_1_2 (1 << (AVG_SHIFT-1))
867 
868 static void add_interrupt_bench(cycles_t start)
869 {
870         long delta = random_get_entropy() - start;
871 
872         /* Use a weighted moving average */
873         delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
874         avg_cycles += delta;
875         /* And average deviation */
876         delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
877         avg_deviation += delta;
878 }
879 #else
880 #define add_interrupt_bench(x)
881 #endif
882 
883 static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
884 {
885         __u32 *ptr = (__u32 *) regs;
886 
887         if (regs == NULL)
888                 return 0;
889         if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
890                 f->reg_idx = 0;
891         return *(ptr + f->reg_idx++);
892 }
893 
894 void add_interrupt_randomness(int irq, int irq_flags)
895 {
896         struct entropy_store    *r;
897         struct fast_pool        *fast_pool = this_cpu_ptr(&irq_randomness);
898         struct pt_regs          *regs = get_irq_regs();
899         unsigned long           now = jiffies;
900         cycles_t                cycles = random_get_entropy();
901         __u32                   c_high, j_high;
902         __u64                   ip;
903         unsigned long           seed;
904         int                     credit = 0;
905 
906         if (cycles == 0)
907                 cycles = get_reg(fast_pool, regs);
908         c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
909         j_high = (sizeof(now) > 4) ? now >> 32 : 0;
910         fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
911         fast_pool->pool[1] ^= now ^ c_high;
912         ip = regs ? instruction_pointer(regs) : _RET_IP_;
913         fast_pool->pool[2] ^= ip;
914         fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
915                 get_reg(fast_pool, regs);
916 
917         fast_mix(fast_pool);
918         add_interrupt_bench(cycles);
919 
920         if ((fast_pool->count < 64) &&
921             !time_after(now, fast_pool->last + HZ))
922                 return;
923 
924         r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
925         if (!spin_trylock(&r->lock))
926                 return;
927 
928         fast_pool->last = now;
929         __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
930 
931         /*
932          * If we have architectural seed generator, produce a seed and
933          * add it to the pool.  For the sake of paranoia don't let the
934          * architectural seed generator dominate the input from the
935          * interrupt noise.
936          */
937         if (arch_get_random_seed_long(&seed)) {
938                 __mix_pool_bytes(r, &seed, sizeof(seed));
939                 credit = 1;
940         }
941         spin_unlock(&r->lock);
942 
943         fast_pool->count = 0;
944 
945         /* award one bit for the contents of the fast pool */
946         credit_entropy_bits(r, credit + 1);
947 }
948 
949 #ifdef CONFIG_BLOCK
950 void add_disk_randomness(struct gendisk *disk)
951 {
952         if (!disk || !disk->random)
953                 return;
954         /* first major is 1, so we get >= 0x200 here */
955         add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
956         trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
957 }
958 EXPORT_SYMBOL_GPL(add_disk_randomness);
959 #endif
960 
961 /*********************************************************************
962  *
963  * Entropy extraction routines
964  *
965  *********************************************************************/
966 
967 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
968                                size_t nbytes, int min, int rsvd);
969 
970 /*
971  * This utility inline function is responsible for transferring entropy
972  * from the primary pool to the secondary extraction pool. We make
973  * sure we pull enough for a 'catastrophic reseed'.
974  */
975 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
976 static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
977 {
978         if (!r->pull ||
979             r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
980             r->entropy_count > r->poolinfo->poolfracbits)
981                 return;
982 
983         if (r->limit == 0 && random_min_urandom_seed) {
984                 unsigned long now = jiffies;
985 
986                 if (time_before(now,
987                                 r->last_pulled + random_min_urandom_seed * HZ))
988                         return;
989                 r->last_pulled = now;
990         }
991 
992         _xfer_secondary_pool(r, nbytes);
993 }
994 
995 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
996 {
997         __u32   tmp[OUTPUT_POOL_WORDS];
998 
999         /* For /dev/random's pool, always leave two wakeups' worth */
1000         int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
1001         int bytes = nbytes;
1002 
1003         /* pull at least as much as a wakeup */
1004         bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
1005         /* but never more than the buffer size */
1006         bytes = min_t(int, bytes, sizeof(tmp));
1007 
1008         trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
1009                                   ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
1010         bytes = extract_entropy(r->pull, tmp, bytes,
1011                                 random_read_wakeup_bits / 8, rsvd_bytes);
1012         mix_pool_bytes(r, tmp, bytes);
1013         credit_entropy_bits(r, bytes*8);
1014 }
1015 
1016 /*
1017  * Used as a workqueue function so that when the input pool is getting
1018  * full, we can "spill over" some entropy to the output pools.  That
1019  * way the output pools can store some of the excess entropy instead
1020  * of letting it go to waste.
1021  */
1022 static void push_to_pool(struct work_struct *work)
1023 {
1024         struct entropy_store *r = container_of(work, struct entropy_store,
1025                                               push_work);
1026         BUG_ON(!r);
1027         _xfer_secondary_pool(r, random_read_wakeup_bits/8);
1028         trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1029                            r->pull->entropy_count >> ENTROPY_SHIFT);
1030 }
1031 
1032 /*
1033  * This function decides how many bytes to actually take from the
1034  * given pool, and also debits the entropy count accordingly.
1035  */
1036 static size_t account(struct entropy_store *r, size_t nbytes, int min,
1037                       int reserved)
1038 {
1039         int entropy_count, orig;
1040         size_t ibytes, nfrac;
1041 
1042         BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1043 
1044         /* Can we pull enough? */
1045 retry:
1046         entropy_count = orig = ACCESS_ONCE(r->entropy_count);
1047         ibytes = nbytes;
1048         /* If limited, never pull more than available */
1049         if (r->limit) {
1050                 int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1051 
1052                 if ((have_bytes -= reserved) < 0)
1053                         have_bytes = 0;
1054                 ibytes = min_t(size_t, ibytes, have_bytes);
1055         }
1056         if (ibytes < min)
1057                 ibytes = 0;
1058 
1059         if (unlikely(entropy_count < 0)) {
1060                 pr_warn("random: negative entropy count: pool %s count %d\n",
1061                         r->name, entropy_count);
1062                 WARN_ON(1);
1063                 entropy_count = 0;
1064         }
1065         nfrac = ibytes << (ENTROPY_SHIFT + 3);
1066         if ((size_t) entropy_count > nfrac)
1067                 entropy_count -= nfrac;
1068         else
1069                 entropy_count = 0;
1070 
1071         if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1072                 goto retry;
1073 
1074         trace_debit_entropy(r->name, 8 * ibytes);
1075         if (ibytes &&
1076             (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1077                 wake_up_interruptible(&random_write_wait);
1078                 kill_fasync(&fasync, SIGIO, POLL_OUT);
1079         }
1080 
1081         return ibytes;
1082 }
1083 
1084 /*
1085  * This function does the actual extraction for extract_entropy and
1086  * extract_entropy_user.
1087  *
1088  * Note: we assume that .poolwords is a multiple of 16 words.
1089  */
1090 static void extract_buf(struct entropy_store *r, __u8 *out)
1091 {
1092         int i;
1093         union {
1094                 __u32 w[5];
1095                 unsigned long l[LONGS(20)];
1096         } hash;
1097         __u32 workspace[SHA_WORKSPACE_WORDS];
1098         unsigned long flags;
1099 
1100         /*
1101          * If we have an architectural hardware random number
1102          * generator, use it for SHA's initial vector
1103          */
1104         sha_init(hash.w);
1105         for (i = 0; i < LONGS(20); i++) {
1106                 unsigned long v;
1107                 if (!arch_get_random_long(&v))
1108                         break;
1109                 hash.l[i] = v;
1110         }
1111 
1112         /* Generate a hash across the pool, 16 words (512 bits) at a time */
1113         spin_lock_irqsave(&r->lock, flags);
1114         for (i = 0; i < r->poolinfo->poolwords; i += 16)
1115                 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1116 
1117         /*
1118          * We mix the hash back into the pool to prevent backtracking
1119          * attacks (where the attacker knows the state of the pool
1120          * plus the current outputs, and attempts to find previous
1121          * ouputs), unless the hash function can be inverted. By
1122          * mixing at least a SHA1 worth of hash data back, we make
1123          * brute-forcing the feedback as hard as brute-forcing the
1124          * hash.
1125          */
1126         __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1127         spin_unlock_irqrestore(&r->lock, flags);
1128 
1129         memzero_explicit(workspace, sizeof(workspace));
1130 
1131         /*
1132          * In case the hash function has some recognizable output
1133          * pattern, we fold it in half. Thus, we always feed back
1134          * twice as much data as we output.
1135          */
1136         hash.w[0] ^= hash.w[3];
1137         hash.w[1] ^= hash.w[4];
1138         hash.w[2] ^= rol32(hash.w[2], 16);
1139 
1140         memcpy(out, &hash, EXTRACT_SIZE);
1141         memzero_explicit(&hash, sizeof(hash));
1142 }
1143 
1144 /*
1145  * This function extracts randomness from the "entropy pool", and
1146  * returns it in a buffer.
1147  *
1148  * The min parameter specifies the minimum amount we can pull before
1149  * failing to avoid races that defeat catastrophic reseeding while the
1150  * reserved parameter indicates how much entropy we must leave in the
1151  * pool after each pull to avoid starving other readers.
1152  */
1153 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1154                                  size_t nbytes, int min, int reserved)
1155 {
1156         ssize_t ret = 0, i;
1157         __u8 tmp[EXTRACT_SIZE];
1158         unsigned long flags;
1159 
1160         /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1161         if (fips_enabled) {
1162                 spin_lock_irqsave(&r->lock, flags);
1163                 if (!r->last_data_init) {
1164                         r->last_data_init = 1;
1165                         spin_unlock_irqrestore(&r->lock, flags);
1166                         trace_extract_entropy(r->name, EXTRACT_SIZE,
1167                                               ENTROPY_BITS(r), _RET_IP_);
1168                         xfer_secondary_pool(r, EXTRACT_SIZE);
1169                         extract_buf(r, tmp);
1170                         spin_lock_irqsave(&r->lock, flags);
1171                         memcpy(r->last_data, tmp, EXTRACT_SIZE);
1172                 }
1173                 spin_unlock_irqrestore(&r->lock, flags);
1174         }
1175 
1176         trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1177         xfer_secondary_pool(r, nbytes);
1178         nbytes = account(r, nbytes, min, reserved);
1179 
1180         while (nbytes) {
1181                 extract_buf(r, tmp);
1182 
1183                 if (fips_enabled) {
1184                         spin_lock_irqsave(&r->lock, flags);
1185                         if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1186                                 panic("Hardware RNG duplicated output!\n");
1187                         memcpy(r->last_data, tmp, EXTRACT_SIZE);
1188                         spin_unlock_irqrestore(&r->lock, flags);
1189                 }
1190                 i = min_t(int, nbytes, EXTRACT_SIZE);
1191                 memcpy(buf, tmp, i);
1192                 nbytes -= i;
1193                 buf += i;
1194                 ret += i;
1195         }
1196 
1197         /* Wipe data just returned from memory */
1198         memzero_explicit(tmp, sizeof(tmp));
1199 
1200         return ret;
1201 }
1202 
1203 /*
1204  * This function extracts randomness from the "entropy pool", and
1205  * returns it in a userspace buffer.
1206  */
1207 static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1208                                     size_t nbytes)
1209 {
1210         ssize_t ret = 0, i;
1211         __u8 tmp[EXTRACT_SIZE];
1212         int large_request = (nbytes > 256);
1213 
1214         trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1215         xfer_secondary_pool(r, nbytes);
1216         nbytes = account(r, nbytes, 0, 0);
1217 
1218         while (nbytes) {
1219                 if (large_request && need_resched()) {
1220                         if (signal_pending(current)) {
1221                                 if (ret == 0)
1222                                         ret = -ERESTARTSYS;
1223                                 break;
1224                         }
1225                         schedule();
1226                 }
1227 
1228                 extract_buf(r, tmp);
1229                 i = min_t(int, nbytes, EXTRACT_SIZE);
1230                 if (copy_to_user(buf, tmp, i)) {
1231                         ret = -EFAULT;
1232                         break;
1233                 }
1234 
1235                 nbytes -= i;
1236                 buf += i;
1237                 ret += i;
1238         }
1239 
1240         /* Wipe data just returned from memory */
1241         memzero_explicit(tmp, sizeof(tmp));
1242 
1243         return ret;
1244 }
1245 
1246 /*
1247  * This function is the exported kernel interface.  It returns some
1248  * number of good random numbers, suitable for key generation, seeding
1249  * TCP sequence numbers, etc.  It does not rely on the hardware random
1250  * number generator.  For random bytes direct from the hardware RNG
1251  * (when available), use get_random_bytes_arch().
1252  */
1253 void get_random_bytes(void *buf, int nbytes)
1254 {
1255 #if DEBUG_RANDOM_BOOT > 0
1256         if (unlikely(nonblocking_pool.initialized == 0))
1257                 printk(KERN_NOTICE "random: %pF get_random_bytes called "
1258                        "with %d bits of entropy available\n",
1259                        (void *) _RET_IP_,
1260                        nonblocking_pool.entropy_total);
1261 #endif
1262         trace_get_random_bytes(nbytes, _RET_IP_);
1263         extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1264 }
1265 EXPORT_SYMBOL(get_random_bytes);
1266 
1267 /*
1268  * Add a callback function that will be invoked when the nonblocking
1269  * pool is initialised.
1270  *
1271  * returns: 0 if callback is successfully added
1272  *          -EALREADY if pool is already initialised (callback not called)
1273  *          -ENOENT if module for callback is not alive
1274  */
1275 int add_random_ready_callback(struct random_ready_callback *rdy)
1276 {
1277         struct module *owner;
1278         unsigned long flags;
1279         int err = -EALREADY;
1280 
1281         if (likely(nonblocking_pool.initialized))
1282                 return err;
1283 
1284         owner = rdy->owner;
1285         if (!try_module_get(owner))
1286                 return -ENOENT;
1287 
1288         spin_lock_irqsave(&random_ready_list_lock, flags);
1289         if (nonblocking_pool.initialized)
1290                 goto out;
1291 
1292         owner = NULL;
1293 
1294         list_add(&rdy->list, &random_ready_list);
1295         err = 0;
1296 
1297 out:
1298         spin_unlock_irqrestore(&random_ready_list_lock, flags);
1299 
1300         module_put(owner);
1301 
1302         return err;
1303 }
1304 EXPORT_SYMBOL(add_random_ready_callback);
1305 
1306 /*
1307  * Delete a previously registered readiness callback function.
1308  */
1309 void del_random_ready_callback(struct random_ready_callback *rdy)
1310 {
1311         unsigned long flags;
1312         struct module *owner = NULL;
1313 
1314         spin_lock_irqsave(&random_ready_list_lock, flags);
1315         if (!list_empty(&rdy->list)) {
1316                 list_del_init(&rdy->list);
1317                 owner = rdy->owner;
1318         }
1319         spin_unlock_irqrestore(&random_ready_list_lock, flags);
1320 
1321         module_put(owner);
1322 }
1323 EXPORT_SYMBOL(del_random_ready_callback);
1324 
1325 /*
1326  * This function will use the architecture-specific hardware random
1327  * number generator if it is available.  The arch-specific hw RNG will
1328  * almost certainly be faster than what we can do in software, but it
1329  * is impossible to verify that it is implemented securely (as
1330  * opposed, to, say, the AES encryption of a sequence number using a
1331  * key known by the NSA).  So it's useful if we need the speed, but
1332  * only if we're willing to trust the hardware manufacturer not to
1333  * have put in a back door.
1334  */
1335 void get_random_bytes_arch(void *buf, int nbytes)
1336 {
1337         char *p = buf;
1338 
1339         trace_get_random_bytes_arch(nbytes, _RET_IP_);
1340         while (nbytes) {
1341                 unsigned long v;
1342                 int chunk = min(nbytes, (int)sizeof(unsigned long));
1343 
1344                 if (!arch_get_random_long(&v))
1345                         break;
1346                 
1347                 memcpy(p, &v, chunk);
1348                 p += chunk;
1349                 nbytes -= chunk;
1350         }
1351 
1352         if (nbytes)
1353                 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1354 }
1355 EXPORT_SYMBOL(get_random_bytes_arch);
1356 
1357 
1358 /*
1359  * init_std_data - initialize pool with system data
1360  *
1361  * @r: pool to initialize
1362  *
1363  * This function clears the pool's entropy count and mixes some system
1364  * data into the pool to prepare it for use. The pool is not cleared
1365  * as that can only decrease the entropy in the pool.
1366  */
1367 static void init_std_data(struct entropy_store *r)
1368 {
1369         int i;
1370         ktime_t now = ktime_get_real();
1371         unsigned long rv;
1372 
1373         r->last_pulled = jiffies;
1374         mix_pool_bytes(r, &now, sizeof(now));
1375         for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1376                 if (!arch_get_random_seed_long(&rv) &&
1377                     !arch_get_random_long(&rv))
1378                         rv = random_get_entropy();
1379                 mix_pool_bytes(r, &rv, sizeof(rv));
1380         }
1381         mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1382 }
1383 
1384 /*
1385  * Note that setup_arch() may call add_device_randomness()
1386  * long before we get here. This allows seeding of the pools
1387  * with some platform dependent data very early in the boot
1388  * process. But it limits our options here. We must use
1389  * statically allocated structures that already have all
1390  * initializations complete at compile time. We should also
1391  * take care not to overwrite the precious per platform data
1392  * we were given.
1393  */
1394 static int rand_initialize(void)
1395 {
1396         init_std_data(&input_pool);
1397         init_std_data(&blocking_pool);
1398         init_std_data(&nonblocking_pool);
1399         return 0;
1400 }
1401 early_initcall(rand_initialize);
1402 
1403 #ifdef CONFIG_BLOCK
1404 void rand_initialize_disk(struct gendisk *disk)
1405 {
1406         struct timer_rand_state *state;
1407 
1408         /*
1409          * If kzalloc returns null, we just won't use that entropy
1410          * source.
1411          */
1412         state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1413         if (state) {
1414                 state->last_time = INITIAL_JIFFIES;
1415                 disk->random = state;
1416         }
1417 }
1418 #endif
1419 
1420 static ssize_t
1421 _random_read(int nonblock, char __user *buf, size_t nbytes)
1422 {
1423         ssize_t n;
1424 
1425         if (nbytes == 0)
1426                 return 0;
1427 
1428         nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1429         while (1) {
1430                 n = extract_entropy_user(&blocking_pool, buf, nbytes);
1431                 if (n < 0)
1432                         return n;
1433                 trace_random_read(n*8, (nbytes-n)*8,
1434                                   ENTROPY_BITS(&blocking_pool),
1435                                   ENTROPY_BITS(&input_pool));
1436                 if (n > 0)
1437                         return n;
1438 
1439                 /* Pool is (near) empty.  Maybe wait and retry. */
1440                 if (nonblock)
1441                         return -EAGAIN;
1442 
1443                 wait_event_interruptible(random_read_wait,
1444                         ENTROPY_BITS(&input_pool) >=
1445                         random_read_wakeup_bits);
1446                 if (signal_pending(current))
1447                         return -ERESTARTSYS;
1448         }
1449 }
1450 
1451 static ssize_t
1452 random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1453 {
1454         return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1455 }
1456 
1457 static ssize_t
1458 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1459 {
1460         int ret;
1461 
1462         if (unlikely(nonblocking_pool.initialized == 0))
1463                 printk_once(KERN_NOTICE "random: %s urandom read "
1464                             "with %d bits of entropy available\n",
1465                             current->comm, nonblocking_pool.entropy_total);
1466 
1467         nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1468         ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
1469 
1470         trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
1471                            ENTROPY_BITS(&input_pool));
1472         return ret;
1473 }
1474 
1475 static unsigned int
1476 random_poll(struct file *file, poll_table * wait)
1477 {
1478         unsigned int mask;
1479 
1480         poll_wait(file, &random_read_wait, wait);
1481         poll_wait(file, &random_write_wait, wait);
1482         mask = 0;
1483         if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1484                 mask |= POLLIN | POLLRDNORM;
1485         if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1486                 mask |= POLLOUT | POLLWRNORM;
1487         return mask;
1488 }
1489 
1490 static int
1491 write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1492 {
1493         size_t bytes;
1494         __u32 buf[16];
1495         const char __user *p = buffer;
1496 
1497         while (count > 0) {
1498                 bytes = min(count, sizeof(buf));
1499                 if (copy_from_user(&buf, p, bytes))
1500                         return -EFAULT;
1501 
1502                 count -= bytes;
1503                 p += bytes;
1504 
1505                 mix_pool_bytes(r, buf, bytes);
1506                 cond_resched();
1507         }
1508 
1509         return 0;
1510 }
1511 
1512 static ssize_t random_write(struct file *file, const char __user *buffer,
1513                             size_t count, loff_t *ppos)
1514 {
1515         size_t ret;
1516 
1517         ret = write_pool(&blocking_pool, buffer, count);
1518         if (ret)
1519                 return ret;
1520         ret = write_pool(&nonblocking_pool, buffer, count);
1521         if (ret)
1522                 return ret;
1523 
1524         return (ssize_t)count;
1525 }
1526 
1527 static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1528 {
1529         int size, ent_count;
1530         int __user *p = (int __user *)arg;
1531         int retval;
1532 
1533         switch (cmd) {
1534         case RNDGETENTCNT:
1535                 /* inherently racy, no point locking */
1536                 ent_count = ENTROPY_BITS(&input_pool);
1537                 if (put_user(ent_count, p))
1538                         return -EFAULT;
1539                 return 0;
1540         case RNDADDTOENTCNT:
1541                 if (!capable(CAP_SYS_ADMIN))
1542                         return -EPERM;
1543                 if (get_user(ent_count, p))
1544                         return -EFAULT;
1545                 credit_entropy_bits_safe(&input_pool, ent_count);
1546                 return 0;
1547         case RNDADDENTROPY:
1548                 if (!capable(CAP_SYS_ADMIN))
1549                         return -EPERM;
1550                 if (get_user(ent_count, p++))
1551                         return -EFAULT;
1552                 if (ent_count < 0)
1553                         return -EINVAL;
1554                 if (get_user(size, p++))
1555                         return -EFAULT;
1556                 retval = write_pool(&input_pool, (const char __user *)p,
1557                                     size);
1558                 if (retval < 0)
1559                         return retval;
1560                 credit_entropy_bits_safe(&input_pool, ent_count);
1561                 return 0;
1562         case RNDZAPENTCNT:
1563         case RNDCLEARPOOL:
1564                 /*
1565                  * Clear the entropy pool counters. We no longer clear
1566                  * the entropy pool, as that's silly.
1567                  */
1568                 if (!capable(CAP_SYS_ADMIN))
1569                         return -EPERM;
1570                 input_pool.entropy_count = 0;
1571                 nonblocking_pool.entropy_count = 0;
1572                 blocking_pool.entropy_count = 0;
1573                 return 0;
1574         default:
1575                 return -EINVAL;
1576         }
1577 }
1578 
1579 static int random_fasync(int fd, struct file *filp, int on)
1580 {
1581         return fasync_helper(fd, filp, on, &fasync);
1582 }
1583 
1584 const struct file_operations random_fops = {
1585         .read  = random_read,
1586         .write = random_write,
1587         .poll  = random_poll,
1588         .unlocked_ioctl = random_ioctl,
1589         .fasync = random_fasync,
1590         .llseek = noop_llseek,
1591 };
1592 
1593 const struct file_operations urandom_fops = {
1594         .read  = urandom_read,
1595         .write = random_write,
1596         .unlocked_ioctl = random_ioctl,
1597         .fasync = random_fasync,
1598         .llseek = noop_llseek,
1599 };
1600 
1601 SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1602                 unsigned int, flags)
1603 {
1604         if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
1605                 return -EINVAL;
1606 
1607         if (count > INT_MAX)
1608                 count = INT_MAX;
1609 
1610         if (flags & GRND_RANDOM)
1611                 return _random_read(flags & GRND_NONBLOCK, buf, count);
1612 
1613         if (unlikely(nonblocking_pool.initialized == 0)) {
1614                 if (flags & GRND_NONBLOCK)
1615                         return -EAGAIN;
1616                 wait_event_interruptible(urandom_init_wait,
1617                                          nonblocking_pool.initialized);
1618                 if (signal_pending(current))
1619                         return -ERESTARTSYS;
1620         }
1621         return urandom_read(NULL, buf, count, NULL);
1622 }
1623 
1624 /***************************************************************
1625  * Random UUID interface
1626  *
1627  * Used here for a Boot ID, but can be useful for other kernel
1628  * drivers.
1629  ***************************************************************/
1630 
1631 /*
1632  * Generate random UUID
1633  */
1634 void generate_random_uuid(unsigned char uuid_out[16])
1635 {
1636         get_random_bytes(uuid_out, 16);
1637         /* Set UUID version to 4 --- truly random generation */
1638         uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1639         /* Set the UUID variant to DCE */
1640         uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1641 }
1642 EXPORT_SYMBOL(generate_random_uuid);
1643 
1644 /********************************************************************
1645  *
1646  * Sysctl interface
1647  *
1648  ********************************************************************/
1649 
1650 #ifdef CONFIG_SYSCTL
1651 
1652 #include <linux/sysctl.h>
1653 
1654 static int min_read_thresh = 8, min_write_thresh;
1655 static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1656 static int max_write_thresh = INPUT_POOL_WORDS * 32;
1657 static char sysctl_bootid[16];
1658 
1659 /*
1660  * This function is used to return both the bootid UUID, and random
1661  * UUID.  The difference is in whether table->data is NULL; if it is,
1662  * then a new UUID is generated and returned to the user.
1663  *
1664  * If the user accesses this via the proc interface, the UUID will be
1665  * returned as an ASCII string in the standard UUID format; if via the
1666  * sysctl system call, as 16 bytes of binary data.
1667  */
1668 static int proc_do_uuid(struct ctl_table *table, int write,
1669                         void __user *buffer, size_t *lenp, loff_t *ppos)
1670 {
1671         struct ctl_table fake_table;
1672         unsigned char buf[64], tmp_uuid[16], *uuid;
1673 
1674         uuid = table->data;
1675         if (!uuid) {
1676                 uuid = tmp_uuid;
1677                 generate_random_uuid(uuid);
1678         } else {
1679                 static DEFINE_SPINLOCK(bootid_spinlock);
1680 
1681                 spin_lock(&bootid_spinlock);
1682                 if (!uuid[8])
1683                         generate_random_uuid(uuid);
1684                 spin_unlock(&bootid_spinlock);
1685         }
1686 
1687         sprintf(buf, "%pU", uuid);
1688 
1689         fake_table.data = buf;
1690         fake_table.maxlen = sizeof(buf);
1691 
1692         return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1693 }
1694 
1695 /*
1696  * Return entropy available scaled to integral bits
1697  */
1698 static int proc_do_entropy(struct ctl_table *table, int write,
1699                            void __user *buffer, size_t *lenp, loff_t *ppos)
1700 {
1701         struct ctl_table fake_table;
1702         int entropy_count;
1703 
1704         entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1705 
1706         fake_table.data = &entropy_count;
1707         fake_table.maxlen = sizeof(entropy_count);
1708 
1709         return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1710 }
1711 
1712 static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1713 extern struct ctl_table random_table[];
1714 struct ctl_table random_table[] = {
1715         {
1716                 .procname       = "poolsize",
1717                 .data           = &sysctl_poolsize,
1718                 .maxlen         = sizeof(int),
1719                 .mode           = 0444,
1720                 .proc_handler   = proc_dointvec,
1721         },
1722         {
1723                 .procname       = "entropy_avail",
1724                 .maxlen         = sizeof(int),
1725                 .mode           = 0444,
1726                 .proc_handler   = proc_do_entropy,
1727                 .data           = &input_pool.entropy_count,
1728         },
1729         {
1730                 .procname       = "read_wakeup_threshold",
1731                 .data           = &random_read_wakeup_bits,
1732                 .maxlen         = sizeof(int),
1733                 .mode           = 0644,
1734                 .proc_handler   = proc_dointvec_minmax,
1735                 .extra1         = &min_read_thresh,
1736                 .extra2         = &max_read_thresh,
1737         },
1738         {
1739                 .procname       = "write_wakeup_threshold",
1740                 .data           = &random_write_wakeup_bits,
1741                 .maxlen         = sizeof(int),
1742                 .mode           = 0644,
1743                 .proc_handler   = proc_dointvec_minmax,
1744                 .extra1         = &min_write_thresh,
1745                 .extra2         = &max_write_thresh,
1746         },
1747         {
1748                 .procname       = "urandom_min_reseed_secs",
1749                 .data           = &random_min_urandom_seed,
1750                 .maxlen         = sizeof(int),
1751                 .mode           = 0644,
1752                 .proc_handler   = proc_dointvec,
1753         },
1754         {
1755                 .procname       = "boot_id",
1756                 .data           = &sysctl_bootid,
1757                 .maxlen         = 16,
1758                 .mode           = 0444,
1759                 .proc_handler   = proc_do_uuid,
1760         },
1761         {
1762                 .procname       = "uuid",
1763                 .maxlen         = 16,
1764                 .mode           = 0444,
1765                 .proc_handler   = proc_do_uuid,
1766         },
1767 #ifdef ADD_INTERRUPT_BENCH
1768         {
1769                 .procname       = "add_interrupt_avg_cycles",
1770                 .data           = &avg_cycles,
1771                 .maxlen         = sizeof(avg_cycles),
1772                 .mode           = 0444,
1773                 .proc_handler   = proc_doulongvec_minmax,
1774         },
1775         {
1776                 .procname       = "add_interrupt_avg_deviation",
1777                 .data           = &avg_deviation,
1778                 .maxlen         = sizeof(avg_deviation),
1779                 .mode           = 0444,
1780                 .proc_handler   = proc_doulongvec_minmax,
1781         },
1782 #endif
1783         { }
1784 };
1785 #endif  /* CONFIG_SYSCTL */
1786 
1787 static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1788 
1789 int random_int_secret_init(void)
1790 {
1791         get_random_bytes(random_int_secret, sizeof(random_int_secret));
1792         return 0;
1793 }
1794 
1795 /*
1796  * Get a random word for internal kernel use only. Similar to urandom but
1797  * with the goal of minimal entropy pool depletion. As a result, the random
1798  * value is not cryptographically secure but for several uses the cost of
1799  * depleting entropy is too high
1800  */
1801 static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1802 unsigned int get_random_int(void)
1803 {
1804         __u32 *hash;
1805         unsigned int ret;
1806 
1807         if (arch_get_random_int(&ret))
1808                 return ret;
1809 
1810         hash = get_cpu_var(get_random_int_hash);
1811 
1812         hash[0] += current->pid + jiffies + random_get_entropy();
1813         md5_transform(hash, random_int_secret);
1814         ret = hash[0];
1815         put_cpu_var(get_random_int_hash);
1816 
1817         return ret;
1818 }
1819 EXPORT_SYMBOL(get_random_int);
1820 
1821 /*
1822  * Same as get_random_int(), but returns unsigned long.
1823  */
1824 unsigned long get_random_long(void)
1825 {
1826         __u32 *hash;
1827         unsigned long ret;
1828 
1829         if (arch_get_random_long(&ret))
1830                 return ret;
1831 
1832         hash = get_cpu_var(get_random_int_hash);
1833 
1834         hash[0] += current->pid + jiffies + random_get_entropy();
1835         md5_transform(hash, random_int_secret);
1836         ret = *(unsigned long *)hash;
1837         put_cpu_var(get_random_int_hash);
1838 
1839         return ret;
1840 }
1841 EXPORT_SYMBOL(get_random_long);
1842 
1843 /*
1844  * randomize_range() returns a start address such that
1845  *
1846  *    [...... <range> .....]
1847  *  start                  end
1848  *
1849  * a <range> with size "len" starting at the return value is inside in the
1850  * area defined by [start, end], but is otherwise randomized.
1851  */
1852 unsigned long
1853 randomize_range(unsigned long start, unsigned long end, unsigned long len)
1854 {
1855         unsigned long range = end - len - start;
1856 
1857         if (end <= start + len)
1858                 return 0;
1859         return PAGE_ALIGN(get_random_int() % range + start);
1860 }
1861 
1862 /* Interface for in-kernel drivers of true hardware RNGs.
1863  * Those devices may produce endless random bits and will be throttled
1864  * when our pool is full.
1865  */
1866 void add_hwgenerator_randomness(const char *buffer, size_t count,
1867                                 size_t entropy)
1868 {
1869         struct entropy_store *poolp = &input_pool;
1870 
1871         /* Suspend writing if we're above the trickle threshold.
1872          * We'll be woken up again once below random_write_wakeup_thresh,
1873          * or when the calling thread is about to terminate.
1874          */
1875         wait_event_interruptible(random_write_wait, kthread_should_stop() ||
1876                         ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
1877         mix_pool_bytes(poolp, buffer, count);
1878         credit_entropy_bits(poolp, entropy);
1879 }
1880 EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
1881 

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