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1/*
2 * random.c -- A strong random number generator
3 *
4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
5 *
6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
7 * rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, and the entire permission notice in its entirety,
14 * including the disclaimer of warranties.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. The name of the author may not be used to endorse or promote
19 * products derived from this software without specific prior
20 * written permission.
21 *
22 * ALTERNATIVELY, this product may be distributed under the terms of
23 * the GNU General Public License, in which case the provisions of the GPL are
24 * required INSTEAD OF the above restrictions. (This clause is
25 * necessary due to a potential bad interaction between the GPL and
26 * the restrictions contained in a BSD-style copyright.)
27 *
28 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
31 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
32 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
34 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
35 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
36 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
38 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
39 * DAMAGE.
40 */
41
42/*
43 * (now, with legal B.S. out of the way.....)
44 *
45 * This routine gathers environmental noise from device drivers, etc.,
46 * and returns good random numbers, suitable for cryptographic use.
47 * Besides the obvious cryptographic uses, these numbers are also good
48 * for seeding TCP sequence numbers, and other places where it is
49 * desirable to have numbers which are not only random, but hard to
50 * predict by an attacker.
51 *
52 * Theory of operation
53 * ===================
54 *
55 * Computers are very predictable devices. Hence it is extremely hard
56 * to produce truly random numbers on a computer --- as opposed to
57 * pseudo-random numbers, which can easily generated by using a
58 * algorithm. Unfortunately, it is very easy for attackers to guess
59 * the sequence of pseudo-random number generators, and for some
60 * applications this is not acceptable. So instead, we must try to
61 * gather "environmental noise" from the computer's environment, which
62 * must be hard for outside attackers to observe, and use that to
63 * generate random numbers. In a Unix environment, this is best done
64 * from inside the kernel.
65 *
66 * Sources of randomness from the environment include inter-keyboard
67 * timings, inter-interrupt timings from some interrupts, and other
68 * events which are both (a) non-deterministic and (b) hard for an
69 * outside observer to measure. Randomness from these sources are
70 * added to an "entropy pool", which is mixed using a CRC-like function.
71 * This is not cryptographically strong, but it is adequate assuming
72 * the randomness is not chosen maliciously, and it is fast enough that
73 * the overhead of doing it on every interrupt is very reasonable.
74 * As random bytes are mixed into the entropy pool, the routines keep
75 * an *estimate* of how many bits of randomness have been stored into
76 * the random number generator's internal state.
77 *
78 * When random bytes are desired, they are obtained by taking the SHA
79 * hash of the contents of the "entropy pool". The SHA hash avoids
80 * exposing the internal state of the entropy pool. It is believed to
81 * be computationally infeasible to derive any useful information
82 * about the input of SHA from its output. Even if it is possible to
83 * analyze SHA in some clever way, as long as the amount of data
84 * returned from the generator is less than the inherent entropy in
85 * the pool, the output data is totally unpredictable. For this
86 * reason, the routine decreases its internal estimate of how many
87 * bits of "true randomness" are contained in the entropy pool as it
88 * outputs random numbers.
89 *
90 * If this estimate goes to zero, the routine can still generate
91 * random numbers; however, an attacker may (at least in theory) be
92 * able to infer the future output of the generator from prior
93 * outputs. This requires successful cryptanalysis of SHA, which is
94 * not believed to be feasible, but there is a remote possibility.
95 * Nonetheless, these numbers should be useful for the vast majority
96 * of purposes.
97 *
98 * Exported interfaces ---- output
99 * ===============================
100 *
101 * There are three exported interfaces; the first is one designed to
102 * be used from within the kernel:
103 *
104 * void get_random_bytes(void *buf, int nbytes);
105 *
106 * This interface will return the requested number of random bytes,
107 * and place it in the requested buffer.
108 *
109 * The two other interfaces are two character devices /dev/random and
110 * /dev/urandom. /dev/random is suitable for use when very high
111 * quality randomness is desired (for example, for key generation or
112 * one-time pads), as it will only return a maximum of the number of
113 * bits of randomness (as estimated by the random number generator)
114 * contained in the entropy pool.
115 *
116 * The /dev/urandom device does not have this limit, and will return
117 * as many bytes as are requested. As more and more random bytes are
118 * requested without giving time for the entropy pool to recharge,
119 * this will result in random numbers that are merely cryptographically
120 * strong. For many applications, however, this is acceptable.
121 *
122 * Exported interfaces ---- input
123 * ==============================
124 *
125 * The current exported interfaces for gathering environmental noise
126 * from the devices are:
127 *
128 * void add_input_randomness(unsigned int type, unsigned int code,
129 * unsigned int value);
130 * void add_interrupt_randomness(int irq);
131 * void add_disk_randomness(struct gendisk *disk);
132 *
133 * add_input_randomness() uses the input layer interrupt timing, as well as
134 * the event type information from the hardware.
135 *
136 * add_interrupt_randomness() uses the inter-interrupt timing as random
137 * inputs to the entropy pool. Note that not all interrupts are good
138 * sources of randomness! For example, the timer interrupts is not a
139 * good choice, because the periodicity of the interrupts is too
140 * regular, and hence predictable to an attacker. Network Interface
141 * Controller interrupts are a better measure, since the timing of the
142 * NIC interrupts are more unpredictable.
143 *
144 * add_disk_randomness() uses what amounts to the seek time of block
145 * layer request events, on a per-disk_devt basis, as input to the
146 * entropy pool. Note that high-speed solid state drives with very low
147 * seek times do not make for good sources of entropy, as their seek
148 * times are usually fairly consistent.
149 *
150 * All of these routines try to estimate how many bits of randomness a
151 * particular randomness source. They do this by keeping track of the
152 * first and second order deltas of the event timings.
153 *
154 * Ensuring unpredictability at system startup
155 * ============================================
156 *
157 * When any operating system starts up, it will go through a sequence
158 * of actions that are fairly predictable by an adversary, especially
159 * if the start-up does not involve interaction with a human operator.
160 * This reduces the actual number of bits of unpredictability in the
161 * entropy pool below the value in entropy_count. In order to
162 * counteract this effect, it helps to carry information in the
163 * entropy pool across shut-downs and start-ups. To do this, put the
164 * following lines an appropriate script which is run during the boot
165 * sequence:
166 *
167 * echo "Initializing random number generator..."
168 * random_seed=/var/run/random-seed
169 * # Carry a random seed from start-up to start-up
170 * # Load and then save the whole entropy pool
171 * if [ -f $random_seed ]; then
172 * cat $random_seed >/dev/urandom
173 * else
174 * touch $random_seed
175 * fi
176 * chmod 600 $random_seed
177 * dd if=/dev/urandom of=$random_seed count=1 bs=512
178 *
179 * and the following lines in an appropriate script which is run as
180 * the system is shutdown:
181 *
182 * # Carry a random seed from shut-down to start-up
183 * # Save the whole entropy pool
184 * echo "Saving random seed..."
185 * random_seed=/var/run/random-seed
186 * touch $random_seed
187 * chmod 600 $random_seed
188 * dd if=/dev/urandom of=$random_seed count=1 bs=512
189 *
190 * For example, on most modern systems using the System V init
191 * scripts, such code fragments would be found in
192 * /etc/rc.d/init.d/random. On older Linux systems, the correct script
193 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
194 *
195 * Effectively, these commands cause the contents of the entropy pool
196 * to be saved at shut-down time and reloaded into the entropy pool at
197 * start-up. (The 'dd' in the addition to the bootup script is to
198 * make sure that /etc/random-seed is different for every start-up,
199 * even if the system crashes without executing rc.0.) Even with
200 * complete knowledge of the start-up activities, predicting the state
201 * of the entropy pool requires knowledge of the previous history of
202 * the system.
203 *
204 * Configuring the /dev/random driver under Linux
205 * ==============================================
206 *
207 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
208 * the /dev/mem major number (#1). So if your system does not have
209 * /dev/random and /dev/urandom created already, they can be created
210 * by using the commands:
211 *
212 * mknod /dev/random c 1 8
213 * mknod /dev/urandom c 1 9
214 *
215 * Acknowledgements:
216 * =================
217 *
218 * Ideas for constructing this random number generator were derived
219 * from Pretty Good Privacy's random number generator, and from private
220 * discussions with Phil Karn. Colin Plumb provided a faster random
221 * number generator, which speed up the mixing function of the entropy
222 * pool, taken from PGPfone. Dale Worley has also contributed many
223 * useful ideas and suggestions to improve this driver.
224 *
225 * Any flaws in the design are solely my responsibility, and should
226 * not be attributed to the Phil, Colin, or any of authors of PGP.
227 *
228 * Further background information on this topic may be obtained from
229 * RFC 1750, "Randomness Recommendations for Security", by Donald
230 * Eastlake, Steve Crocker, and Jeff Schiller.
231 */
232
233#include <linux/utsname.h>
234#include <linux/module.h>
235#include <linux/kernel.h>
236#include <linux/major.h>
237#include <linux/string.h>
238#include <linux/fcntl.h>
239#include <linux/slab.h>
240#include <linux/random.h>
241#include <linux/poll.h>
242#include <linux/init.h>
243#include <linux/fs.h>
244#include <linux/genhd.h>
245#include <linux/interrupt.h>
246#include <linux/mm.h>
247#include <linux/spinlock.h>
248#include <linux/percpu.h>
249#include <linux/cryptohash.h>
250#include <linux/fips.h>
251
252#ifdef CONFIG_GENERIC_HARDIRQS
253# include <linux/irq.h>
254#endif
255
256#include <asm/processor.h>
257#include <asm/uaccess.h>
258#include <asm/irq.h>
259#include <asm/io.h>
260
261/*
262 * Configuration information
263 */
264#define INPUT_POOL_WORDS 128
265#define OUTPUT_POOL_WORDS 32
266#define SEC_XFER_SIZE 512
267#define EXTRACT_SIZE 10
268
269/*
270 * The minimum number of bits of entropy before we wake up a read on
271 * /dev/random. Should be enough to do a significant reseed.
272 */
273static int random_read_wakeup_thresh = 64;
274
275/*
276 * If the entropy count falls under this number of bits, then we
277 * should wake up processes which are selecting or polling on write
278 * access to /dev/random.
279 */
280static int random_write_wakeup_thresh = 128;
281
282/*
283 * When the input pool goes over trickle_thresh, start dropping most
284 * samples to avoid wasting CPU time and reduce lock contention.
285 */
286
287static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
288
289static DEFINE_PER_CPU(int, trickle_count);
290
291/*
292 * A pool of size .poolwords is stirred with a primitive polynomial
293 * of degree .poolwords over GF(2). The taps for various sizes are
294 * defined below. They are chosen to be evenly spaced (minimum RMS
295 * distance from evenly spaced; the numbers in the comments are a
296 * scaled squared error sum) except for the last tap, which is 1 to
297 * get the twisting happening as fast as possible.
298 */
299static struct poolinfo {
300 int poolwords;
301 int tap1, tap2, tap3, tap4, tap5;
302} poolinfo_table[] = {
303 /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
304 { 128, 103, 76, 51, 25, 1 },
305 /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
306 { 32, 26, 20, 14, 7, 1 },
307#if 0
308 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
309 { 2048, 1638, 1231, 819, 411, 1 },
310
311 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
312 { 1024, 817, 615, 412, 204, 1 },
313
314 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
315 { 1024, 819, 616, 410, 207, 2 },
316
317 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
318 { 512, 411, 308, 208, 104, 1 },
319
320 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
321 { 512, 409, 307, 206, 102, 2 },
322 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
323 { 512, 409, 309, 205, 103, 2 },
324
325 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
326 { 256, 205, 155, 101, 52, 1 },
327
328 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
329 { 128, 103, 78, 51, 27, 2 },
330
331 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
332 { 64, 52, 39, 26, 14, 1 },
333#endif
334};
335
336#define POOLBITS poolwords*32
337#define POOLBYTES poolwords*4
338
339/*
340 * For the purposes of better mixing, we use the CRC-32 polynomial as
341 * well to make a twisted Generalized Feedback Shift Reigster
342 *
343 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
344 * Transactions on Modeling and Computer Simulation 2(3):179-194.
345 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
346 * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
347 *
348 * Thanks to Colin Plumb for suggesting this.
349 *
350 * We have not analyzed the resultant polynomial to prove it primitive;
351 * in fact it almost certainly isn't. Nonetheless, the irreducible factors
352 * of a random large-degree polynomial over GF(2) are more than large enough
353 * that periodicity is not a concern.
354 *
355 * The input hash is much less sensitive than the output hash. All
356 * that we want of it is that it be a good non-cryptographic hash;
357 * i.e. it not produce collisions when fed "random" data of the sort
358 * we expect to see. As long as the pool state differs for different
359 * inputs, we have preserved the input entropy and done a good job.
360 * The fact that an intelligent attacker can construct inputs that
361 * will produce controlled alterations to the pool's state is not
362 * important because we don't consider such inputs to contribute any
363 * randomness. The only property we need with respect to them is that
364 * the attacker can't increase his/her knowledge of the pool's state.
365 * Since all additions are reversible (knowing the final state and the
366 * input, you can reconstruct the initial state), if an attacker has
367 * any uncertainty about the initial state, he/she can only shuffle
368 * that uncertainty about, but never cause any collisions (which would
369 * decrease the uncertainty).
370 *
371 * The chosen system lets the state of the pool be (essentially) the input
372 * modulo the generator polymnomial. Now, for random primitive polynomials,
373 * this is a universal class of hash functions, meaning that the chance
374 * of a collision is limited by the attacker's knowledge of the generator
375 * polynomail, so if it is chosen at random, an attacker can never force
376 * a collision. Here, we use a fixed polynomial, but we *can* assume that
377 * ###--> it is unknown to the processes generating the input entropy. <-###
378 * Because of this important property, this is a good, collision-resistant
379 * hash; hash collisions will occur no more often than chance.
380 */
381
382/*
383 * Static global variables
384 */
385static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
386static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
387static struct fasync_struct *fasync;
388
389#if 0
390static int debug;
391module_param(debug, bool, 0644);
392#define DEBUG_ENT(fmt, arg...) do { \
393 if (debug) \
394 printk(KERN_DEBUG "random %04d %04d %04d: " \
395 fmt,\
396 input_pool.entropy_count,\
397 blocking_pool.entropy_count,\
398 nonblocking_pool.entropy_count,\
399 ## arg); } while (0)
400#else
401#define DEBUG_ENT(fmt, arg...) do {} while (0)
402#endif
403
404/**********************************************************************
405 *
406 * OS independent entropy store. Here are the functions which handle
407 * storing entropy in an entropy pool.
408 *
409 **********************************************************************/
410
411struct entropy_store;
412struct entropy_store {
413 /* read-only data: */
414 struct poolinfo *poolinfo;
415 __u32 *pool;
416 const char *name;
417 struct entropy_store *pull;
418 int limit;
419
420 /* read-write data: */
421 spinlock_t lock;
422 unsigned add_ptr;
423 int entropy_count;
424 int input_rotate;
425 __u8 last_data[EXTRACT_SIZE];
426};
427
428static __u32 input_pool_data[INPUT_POOL_WORDS];
429static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
430static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
431
432static struct entropy_store input_pool = {
433 .poolinfo = &poolinfo_table[0],
434 .name = "input",
435 .limit = 1,
436 .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock),
437 .pool = input_pool_data
438};
439
440static struct entropy_store blocking_pool = {
441 .poolinfo = &poolinfo_table[1],
442 .name = "blocking",
443 .limit = 1,
444 .pull = &input_pool,
445 .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock),
446 .pool = blocking_pool_data
447};
448
449static struct entropy_store nonblocking_pool = {
450 .poolinfo = &poolinfo_table[1],
451 .name = "nonblocking",
452 .pull = &input_pool,
453 .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock),
454 .pool = nonblocking_pool_data
455};
456
457/*
458 * This function adds bytes into the entropy "pool". It does not
459 * update the entropy estimate. The caller should call
460 * credit_entropy_bits if this is appropriate.
461 *
462 * The pool is stirred with a primitive polynomial of the appropriate
463 * degree, and then twisted. We twist by three bits at a time because
464 * it's cheap to do so and helps slightly in the expected case where
465 * the entropy is concentrated in the low-order bits.
466 */
467static void mix_pool_bytes_extract(struct entropy_store *r, const void *in,
468 int nbytes, __u8 out[64])
469{
470 static __u32 const twist_table[8] = {
471 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
472 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
473 unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
474 int input_rotate;
475 int wordmask = r->poolinfo->poolwords - 1;
476 const char *bytes = in;
477 __u32 w;
478 unsigned long flags;
479
480 /* Taps are constant, so we can load them without holding r->lock. */
481 tap1 = r->poolinfo->tap1;
482 tap2 = r->poolinfo->tap2;
483 tap3 = r->poolinfo->tap3;
484 tap4 = r->poolinfo->tap4;
485 tap5 = r->poolinfo->tap5;
486
487 spin_lock_irqsave(&r->lock, flags);
488 input_rotate = r->input_rotate;
489 i = r->add_ptr;
490
491 /* mix one byte at a time to simplify size handling and churn faster */
492 while (nbytes--) {
493 w = rol32(*bytes++, input_rotate & 31);
494 i = (i - 1) & wordmask;
495
496 /* XOR in the various taps */
497 w ^= r->pool[i];
498 w ^= r->pool[(i + tap1) & wordmask];
499 w ^= r->pool[(i + tap2) & wordmask];
500 w ^= r->pool[(i + tap3) & wordmask];
501 w ^= r->pool[(i + tap4) & wordmask];
502 w ^= r->pool[(i + tap5) & wordmask];
503
504 /* Mix the result back in with a twist */
505 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
506
507 /*
508 * Normally, we add 7 bits of rotation to the pool.
509 * At the beginning of the pool, add an extra 7 bits
510 * rotation, so that successive passes spread the
511 * input bits across the pool evenly.
512 */
513 input_rotate += i ? 7 : 14;
514 }
515
516 r->input_rotate = input_rotate;
517 r->add_ptr = i;
518
519 if (out)
520 for (j = 0; j < 16; j++)
521 ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
522
523 spin_unlock_irqrestore(&r->lock, flags);
524}
525
526static void mix_pool_bytes(struct entropy_store *r, const void *in, int bytes)
527{
528 mix_pool_bytes_extract(r, in, bytes, NULL);
529}
530
531/*
532 * Credit (or debit) the entropy store with n bits of entropy
533 */
534static void credit_entropy_bits(struct entropy_store *r, int nbits)
535{
536 unsigned long flags;
537 int entropy_count;
538
539 if (!nbits)
540 return;
541
542 spin_lock_irqsave(&r->lock, flags);
543
544 DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
545 entropy_count = r->entropy_count;
546 entropy_count += nbits;
547 if (entropy_count < 0) {
548 DEBUG_ENT("negative entropy/overflow\n");
549 entropy_count = 0;
550 } else if (entropy_count > r->poolinfo->POOLBITS)
551 entropy_count = r->poolinfo->POOLBITS;
552 r->entropy_count = entropy_count;
553
554 /* should we wake readers? */
555 if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
556 wake_up_interruptible(&random_read_wait);
557 kill_fasync(&fasync, SIGIO, POLL_IN);
558 }
559 spin_unlock_irqrestore(&r->lock, flags);
560}
561
562/*********************************************************************
563 *
564 * Entropy input management
565 *
566 *********************************************************************/
567
568/* There is one of these per entropy source */
569struct timer_rand_state {
570 cycles_t last_time;
571 long last_delta, last_delta2;
572 unsigned dont_count_entropy:1;
573};
574
575#ifndef CONFIG_GENERIC_HARDIRQS
576
577static struct timer_rand_state *irq_timer_state[NR_IRQS];
578
579static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
580{
581 return irq_timer_state[irq];
582}
583
584static void set_timer_rand_state(unsigned int irq,
585 struct timer_rand_state *state)
586{
587 irq_timer_state[irq] = state;
588}
589
590#else
591
592static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
593{
594 struct irq_desc *desc;
595
596 desc = irq_to_desc(irq);
597
598 return desc->timer_rand_state;
599}
600
601static void set_timer_rand_state(unsigned int irq,
602 struct timer_rand_state *state)
603{
604 struct irq_desc *desc;
605
606 desc = irq_to_desc(irq);
607
608 desc->timer_rand_state = state;
609}
610#endif
611
612static struct timer_rand_state input_timer_state;
613
614/*
615 * This function adds entropy to the entropy "pool" by using timing
616 * delays. It uses the timer_rand_state structure to make an estimate
617 * of how many bits of entropy this call has added to the pool.
618 *
619 * The number "num" is also added to the pool - it should somehow describe
620 * the type of event which just happened. This is currently 0-255 for
621 * keyboard scan codes, and 256 upwards for interrupts.
622 *
623 */
624static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
625{
626 struct {
627 cycles_t cycles;
628 long jiffies;
629 unsigned num;
630 } sample;
631 long delta, delta2, delta3;
632
633 preempt_disable();
634 /* if over the trickle threshold, use only 1 in 4096 samples */
635 if (input_pool.entropy_count > trickle_thresh &&
636 ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
637 goto out;
638
639 sample.jiffies = jiffies;
640 sample.cycles = get_cycles();
641 sample.num = num;
642 mix_pool_bytes(&input_pool, &sample, sizeof(sample));
643
644 /*
645 * Calculate number of bits of randomness we probably added.
646 * We take into account the first, second and third-order deltas
647 * in order to make our estimate.
648 */
649
650 if (!state->dont_count_entropy) {
651 delta = sample.jiffies - state->last_time;
652 state->last_time = sample.jiffies;
653
654 delta2 = delta - state->last_delta;
655 state->last_delta = delta;
656
657 delta3 = delta2 - state->last_delta2;
658 state->last_delta2 = delta2;
659
660 if (delta < 0)
661 delta = -delta;
662 if (delta2 < 0)
663 delta2 = -delta2;
664 if (delta3 < 0)
665 delta3 = -delta3;
666 if (delta > delta2)
667 delta = delta2;
668 if (delta > delta3)
669 delta = delta3;
670
671 /*
672 * delta is now minimum absolute delta.
673 * Round down by 1 bit on general principles,
674 * and limit entropy entimate to 12 bits.
675 */
676 credit_entropy_bits(&input_pool,
677 min_t(int, fls(delta>>1), 11));
678 }
679out:
680 preempt_enable();
681}
682
683void add_input_randomness(unsigned int type, unsigned int code,
684 unsigned int value)
685{
686 static unsigned char last_value;
687
688 /* ignore autorepeat and the like */
689 if (value == last_value)
690 return;
691
692 DEBUG_ENT("input event\n");
693 last_value = value;
694 add_timer_randomness(&input_timer_state,
695 (type << 4) ^ code ^ (code >> 4) ^ value);
696}
697EXPORT_SYMBOL_GPL(add_input_randomness);
698
699void add_interrupt_randomness(int irq)
700{
701 struct timer_rand_state *state;
702
703 state = get_timer_rand_state(irq);
704
705 if (state == NULL)
706 return;
707
708 DEBUG_ENT("irq event %d\n", irq);
709 add_timer_randomness(state, 0x100 + irq);
710}
711
712#ifdef CONFIG_BLOCK
713void add_disk_randomness(struct gendisk *disk)
714{
715 if (!disk || !disk->random)
716 return;
717 /* first major is 1, so we get >= 0x200 here */
718 DEBUG_ENT("disk event %d:%d\n",
719 MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
720
721 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
722}
723#endif
724
725/*********************************************************************
726 *
727 * Entropy extraction routines
728 *
729 *********************************************************************/
730
731static ssize_t extract_entropy(struct entropy_store *r, void *buf,
732 size_t nbytes, int min, int rsvd);
733
734/*
735 * This utility inline function is responsible for transferring entropy
736 * from the primary pool to the secondary extraction pool. We make
737 * sure we pull enough for a 'catastrophic reseed'.
738 */
739static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
740{
741 __u32 tmp[OUTPUT_POOL_WORDS];
742
743 if (r->pull && r->entropy_count < nbytes * 8 &&
744 r->entropy_count < r->poolinfo->POOLBITS) {
745 /* If we're limited, always leave two wakeup worth's BITS */
746 int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
747 int bytes = nbytes;
748
749 /* pull at least as many as BYTES as wakeup BITS */
750 bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
751 /* but never more than the buffer size */
752 bytes = min_t(int, bytes, sizeof(tmp));
753
754 DEBUG_ENT("going to reseed %s with %d bits "
755 "(%d of %d requested)\n",
756 r->name, bytes * 8, nbytes * 8, r->entropy_count);
757
758 bytes = extract_entropy(r->pull, tmp, bytes,
759 random_read_wakeup_thresh / 8, rsvd);
760 mix_pool_bytes(r, tmp, bytes);
761 credit_entropy_bits(r, bytes*8);
762 }
763}
764
765/*
766 * These functions extracts randomness from the "entropy pool", and
767 * returns it in a buffer.
768 *
769 * The min parameter specifies the minimum amount we can pull before
770 * failing to avoid races that defeat catastrophic reseeding while the
771 * reserved parameter indicates how much entropy we must leave in the
772 * pool after each pull to avoid starving other readers.
773 *
774 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
775 */
776
777static size_t account(struct entropy_store *r, size_t nbytes, int min,
778 int reserved)
779{
780 unsigned long flags;
781
782 /* Hold lock while accounting */
783 spin_lock_irqsave(&r->lock, flags);
784
785 BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
786 DEBUG_ENT("trying to extract %d bits from %s\n",
787 nbytes * 8, r->name);
788
789 /* Can we pull enough? */
790 if (r->entropy_count / 8 < min + reserved) {
791 nbytes = 0;
792 } else {
793 /* If limited, never pull more than available */
794 if (r->limit && nbytes + reserved >= r->entropy_count / 8)
795 nbytes = r->entropy_count/8 - reserved;
796
797 if (r->entropy_count / 8 >= nbytes + reserved)
798 r->entropy_count -= nbytes*8;
799 else
800 r->entropy_count = reserved;
801
802 if (r->entropy_count < random_write_wakeup_thresh) {
803 wake_up_interruptible(&random_write_wait);
804 kill_fasync(&fasync, SIGIO, POLL_OUT);
805 }
806 }
807
808 DEBUG_ENT("debiting %d entropy credits from %s%s\n",
809 nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
810
811 spin_unlock_irqrestore(&r->lock, flags);
812
813 return nbytes;
814}
815
816static void extract_buf(struct entropy_store *r, __u8 *out)
817{
818 int i;
819 __u32 hash[5], workspace[SHA_WORKSPACE_WORDS];
820 __u8 extract[64];
821
822 /* Generate a hash across the pool, 16 words (512 bits) at a time */
823 sha_init(hash);
824 for (i = 0; i < r->poolinfo->poolwords; i += 16)
825 sha_transform(hash, (__u8 *)(r->pool + i), workspace);
826
827 /*
828 * We mix the hash back into the pool to prevent backtracking
829 * attacks (where the attacker knows the state of the pool
830 * plus the current outputs, and attempts to find previous
831 * ouputs), unless the hash function can be inverted. By
832 * mixing at least a SHA1 worth of hash data back, we make
833 * brute-forcing the feedback as hard as brute-forcing the
834 * hash.
835 */
836 mix_pool_bytes_extract(r, hash, sizeof(hash), extract);
837
838 /*
839 * To avoid duplicates, we atomically extract a portion of the
840 * pool while mixing, and hash one final time.
841 */
842 sha_transform(hash, extract, workspace);
843 memset(extract, 0, sizeof(extract));
844 memset(workspace, 0, sizeof(workspace));
845
846 /*
847 * In case the hash function has some recognizable output
848 * pattern, we fold it in half. Thus, we always feed back
849 * twice as much data as we output.
850 */
851 hash[0] ^= hash[3];
852 hash[1] ^= hash[4];
853 hash[2] ^= rol32(hash[2], 16);
854 memcpy(out, hash, EXTRACT_SIZE);
855 memset(hash, 0, sizeof(hash));
856}
857
858static ssize_t extract_entropy(struct entropy_store *r, void *buf,
859 size_t nbytes, int min, int reserved)
860{
861 ssize_t ret = 0, i;
862 __u8 tmp[EXTRACT_SIZE];
863 unsigned long flags;
864
865 xfer_secondary_pool(r, nbytes);
866 nbytes = account(r, nbytes, min, reserved);
867
868 while (nbytes) {
869 extract_buf(r, tmp);
870
871 if (fips_enabled) {
872 spin_lock_irqsave(&r->lock, flags);
873 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
874 panic("Hardware RNG duplicated output!\n");
875 memcpy(r->last_data, tmp, EXTRACT_SIZE);
876 spin_unlock_irqrestore(&r->lock, flags);
877 }
878 i = min_t(int, nbytes, EXTRACT_SIZE);
879 memcpy(buf, tmp, i);
880 nbytes -= i;
881 buf += i;
882 ret += i;
883 }
884
885 /* Wipe data just returned from memory */
886 memset(tmp, 0, sizeof(tmp));
887
888 return ret;
889}
890
891static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
892 size_t nbytes)
893{
894 ssize_t ret = 0, i;
895 __u8 tmp[EXTRACT_SIZE];
896
897 xfer_secondary_pool(r, nbytes);
898 nbytes = account(r, nbytes, 0, 0);
899
900 while (nbytes) {
901 if (need_resched()) {
902 if (signal_pending(current)) {
903 if (ret == 0)
904 ret = -ERESTARTSYS;
905 break;
906 }
907 schedule();
908 }
909
910 extract_buf(r, tmp);
911 i = min_t(int, nbytes, EXTRACT_SIZE);
912 if (copy_to_user(buf, tmp, i)) {
913 ret = -EFAULT;
914 break;
915 }
916
917 nbytes -= i;
918 buf += i;
919 ret += i;
920 }
921
922 /* Wipe data just returned from memory */
923 memset(tmp, 0, sizeof(tmp));
924
925 return ret;
926}
927
928/*
929 * This function is the exported kernel interface. It returns some
930 * number of good random numbers, suitable for seeding TCP sequence
931 * numbers, etc.
932 */
933void get_random_bytes(void *buf, int nbytes)
934{
935 extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
936}
937EXPORT_SYMBOL(get_random_bytes);
938
939/*
940 * init_std_data - initialize pool with system data
941 *
942 * @r: pool to initialize
943 *
944 * This function clears the pool's entropy count and mixes some system
945 * data into the pool to prepare it for use. The pool is not cleared
946 * as that can only decrease the entropy in the pool.
947 */
948static void init_std_data(struct entropy_store *r)
949{
950 ktime_t now;
951 unsigned long flags;
952
953 spin_lock_irqsave(&r->lock, flags);
954 r->entropy_count = 0;
955 spin_unlock_irqrestore(&r->lock, flags);
956
957 now = ktime_get_real();
958 mix_pool_bytes(r, &now, sizeof(now));
959 mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
960}
961
962static int rand_initialize(void)
963{
964 init_std_data(&input_pool);
965 init_std_data(&blocking_pool);
966 init_std_data(&nonblocking_pool);
967 return 0;
968}
969module_init(rand_initialize);
970
971void rand_initialize_irq(int irq)
972{
973 struct timer_rand_state *state;
974
975 state = get_timer_rand_state(irq);
976
977 if (state)
978 return;
979
980 /*
981 * If kzalloc returns null, we just won't use that entropy
982 * source.
983 */
984 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
985 if (state)
986 set_timer_rand_state(irq, state);
987}
988
989#ifdef CONFIG_BLOCK
990void rand_initialize_disk(struct gendisk *disk)
991{
992 struct timer_rand_state *state;
993
994 /*
995 * If kzalloc returns null, we just won't use that entropy
996 * source.
997 */
998 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
999 if (state)
1000 disk->random = state;
1001}
1002#endif
1003
1004static ssize_t
1005random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1006{
1007 ssize_t n, retval = 0, count = 0;
1008
1009 if (nbytes == 0)
1010 return 0;
1011
1012 while (nbytes > 0) {
1013 n = nbytes;
1014 if (n > SEC_XFER_SIZE)
1015 n = SEC_XFER_SIZE;
1016
1017 DEBUG_ENT("reading %d bits\n", n*8);
1018
1019 n = extract_entropy_user(&blocking_pool, buf, n);
1020
1021 DEBUG_ENT("read got %d bits (%d still needed)\n",
1022 n*8, (nbytes-n)*8);
1023
1024 if (n == 0) {
1025 if (file->f_flags & O_NONBLOCK) {
1026 retval = -EAGAIN;
1027 break;
1028 }
1029
1030 DEBUG_ENT("sleeping?\n");
1031
1032 wait_event_interruptible(random_read_wait,
1033 input_pool.entropy_count >=
1034 random_read_wakeup_thresh);
1035
1036 DEBUG_ENT("awake\n");
1037
1038 if (signal_pending(current)) {
1039 retval = -ERESTARTSYS;
1040 break;
1041 }
1042
1043 continue;
1044 }
1045
1046 if (n < 0) {
1047 retval = n;
1048 break;
1049 }
1050 count += n;
1051 buf += n;
1052 nbytes -= n;
1053 break; /* This break makes the device work */
1054 /* like a named pipe */
1055 }
1056
1057 return (count ? count : retval);
1058}
1059
1060static ssize_t
1061urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1062{
1063 return extract_entropy_user(&nonblocking_pool, buf, nbytes);
1064}
1065
1066static unsigned int
1067random_poll(struct file *file, poll_table * wait)
1068{
1069 unsigned int mask;
1070
1071 poll_wait(file, &random_read_wait, wait);
1072 poll_wait(file, &random_write_wait, wait);
1073 mask = 0;
1074 if (input_pool.entropy_count >= random_read_wakeup_thresh)
1075 mask |= POLLIN | POLLRDNORM;
1076 if (input_pool.entropy_count < random_write_wakeup_thresh)
1077 mask |= POLLOUT | POLLWRNORM;
1078 return mask;
1079}
1080
1081static int
1082write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1083{
1084 size_t bytes;
1085 __u32 buf[16];
1086 const char __user *p = buffer;
1087
1088 while (count > 0) {
1089 bytes = min(count, sizeof(buf));
1090 if (copy_from_user(&buf, p, bytes))
1091 return -EFAULT;
1092
1093 count -= bytes;
1094 p += bytes;
1095
1096 mix_pool_bytes(r, buf, bytes);
1097 cond_resched();
1098 }
1099
1100 return 0;
1101}
1102
1103static ssize_t random_write(struct file *file, const char __user *buffer,
1104 size_t count, loff_t *ppos)
1105{
1106 size_t ret;
1107
1108 ret = write_pool(&blocking_pool, buffer, count);
1109 if (ret)
1110 return ret;
1111 ret = write_pool(&nonblocking_pool, buffer, count);
1112 if (ret)
1113 return ret;
1114
1115 return (ssize_t)count;
1116}
1117
1118static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1119{
1120 int size, ent_count;
1121 int __user *p = (int __user *)arg;
1122 int retval;
1123
1124 switch (cmd) {
1125 case RNDGETENTCNT:
1126 /* inherently racy, no point locking */
1127 if (put_user(input_pool.entropy_count, p))
1128 return -EFAULT;
1129 return 0;
1130 case RNDADDTOENTCNT:
1131 if (!capable(CAP_SYS_ADMIN))
1132 return -EPERM;
1133 if (get_user(ent_count, p))
1134 return -EFAULT;
1135 credit_entropy_bits(&input_pool, ent_count);
1136 return 0;
1137 case RNDADDENTROPY:
1138 if (!capable(CAP_SYS_ADMIN))
1139 return -EPERM;
1140 if (get_user(ent_count, p++))
1141 return -EFAULT;
1142 if (ent_count < 0)
1143 return -EINVAL;
1144 if (get_user(size, p++))
1145 return -EFAULT;
1146 retval = write_pool(&input_pool, (const char __user *)p,
1147 size);
1148 if (retval < 0)
1149 return retval;
1150 credit_entropy_bits(&input_pool, ent_count);
1151 return 0;
1152 case RNDZAPENTCNT:
1153 case RNDCLEARPOOL:
1154 /* Clear the entropy pool counters. */
1155 if (!capable(CAP_SYS_ADMIN))
1156 return -EPERM;
1157 rand_initialize();
1158 return 0;
1159 default:
1160 return -EINVAL;
1161 }
1162}
1163
1164static int random_fasync(int fd, struct file *filp, int on)
1165{
1166 return fasync_helper(fd, filp, on, &fasync);
1167}
1168
1169const struct file_operations random_fops = {
1170 .read = random_read,
1171 .write = random_write,
1172 .poll = random_poll,
1173 .unlocked_ioctl = random_ioctl,
1174 .fasync = random_fasync,
1175 .llseek = noop_llseek,
1176};
1177
1178const struct file_operations urandom_fops = {
1179 .read = urandom_read,
1180 .write = random_write,
1181 .unlocked_ioctl = random_ioctl,
1182 .fasync = random_fasync,
1183 .llseek = noop_llseek,
1184};
1185
1186/***************************************************************
1187 * Random UUID interface
1188 *
1189 * Used here for a Boot ID, but can be useful for other kernel
1190 * drivers.
1191 ***************************************************************/
1192
1193/*
1194 * Generate random UUID
1195 */
1196void generate_random_uuid(unsigned char uuid_out[16])
1197{
1198 get_random_bytes(uuid_out, 16);
1199 /* Set UUID version to 4 --- truly random generation */
1200 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1201 /* Set the UUID variant to DCE */
1202 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1203}
1204EXPORT_SYMBOL(generate_random_uuid);
1205
1206/********************************************************************
1207 *
1208 * Sysctl interface
1209 *
1210 ********************************************************************/
1211
1212#ifdef CONFIG_SYSCTL
1213
1214#include <linux/sysctl.h>
1215
1216static int min_read_thresh = 8, min_write_thresh;
1217static int max_read_thresh = INPUT_POOL_WORDS * 32;
1218static int max_write_thresh = INPUT_POOL_WORDS * 32;
1219static char sysctl_bootid[16];
1220
1221/*
1222 * These functions is used to return both the bootid UUID, and random
1223 * UUID. The difference is in whether table->data is NULL; if it is,
1224 * then a new UUID is generated and returned to the user.
1225 *
1226 * If the user accesses this via the proc interface, it will be returned
1227 * as an ASCII string in the standard UUID format. If accesses via the
1228 * sysctl system call, it is returned as 16 bytes of binary data.
1229 */
1230static int proc_do_uuid(ctl_table *table, int write,
1231 void __user *buffer, size_t *lenp, loff_t *ppos)
1232{
1233 ctl_table fake_table;
1234 unsigned char buf[64], tmp_uuid[16], *uuid;
1235
1236 uuid = table->data;
1237 if (!uuid) {
1238 uuid = tmp_uuid;
1239 uuid[8] = 0;
1240 }
1241 if (uuid[8] == 0)
1242 generate_random_uuid(uuid);
1243
1244 sprintf(buf, "%pU", uuid);
1245
1246 fake_table.data = buf;
1247 fake_table.maxlen = sizeof(buf);
1248
1249 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1250}
1251
1252static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1253ctl_table random_table[] = {
1254 {
1255 .procname = "poolsize",
1256 .data = &sysctl_poolsize,
1257 .maxlen = sizeof(int),
1258 .mode = 0444,
1259 .proc_handler = proc_dointvec,
1260 },
1261 {
1262 .procname = "entropy_avail",
1263 .maxlen = sizeof(int),
1264 .mode = 0444,
1265 .proc_handler = proc_dointvec,
1266 .data = &input_pool.entropy_count,
1267 },
1268 {
1269 .procname = "read_wakeup_threshold",
1270 .data = &random_read_wakeup_thresh,
1271 .maxlen = sizeof(int),
1272 .mode = 0644,
1273 .proc_handler = proc_dointvec_minmax,
1274 .extra1 = &min_read_thresh,
1275 .extra2 = &max_read_thresh,
1276 },
1277 {
1278 .procname = "write_wakeup_threshold",
1279 .data = &random_write_wakeup_thresh,
1280 .maxlen = sizeof(int),
1281 .mode = 0644,
1282 .proc_handler = proc_dointvec_minmax,
1283 .extra1 = &min_write_thresh,
1284 .extra2 = &max_write_thresh,
1285 },
1286 {
1287 .procname = "boot_id",
1288 .data = &sysctl_bootid,
1289 .maxlen = 16,
1290 .mode = 0444,
1291 .proc_handler = proc_do_uuid,
1292 },
1293 {
1294 .procname = "uuid",
1295 .maxlen = 16,
1296 .mode = 0444,
1297 .proc_handler = proc_do_uuid,
1298 },
1299 { }
1300};
1301#endif /* CONFIG_SYSCTL */
1302
1303static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1304
1305static int __init random_int_secret_init(void)
1306{
1307 get_random_bytes(random_int_secret, sizeof(random_int_secret));
1308 return 0;
1309}
1310late_initcall(random_int_secret_init);
1311
1312/*
1313 * Get a random word for internal kernel use only. Similar to urandom but
1314 * with the goal of minimal entropy pool depletion. As a result, the random
1315 * value is not cryptographically secure but for several uses the cost of
1316 * depleting entropy is too high
1317 */
1318DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1319unsigned int get_random_int(void)
1320{
1321 __u32 *hash = get_cpu_var(get_random_int_hash);
1322 unsigned int ret;
1323
1324 hash[0] += current->pid + jiffies + get_cycles();
1325 md5_transform(hash, random_int_secret);
1326 ret = hash[0];
1327 put_cpu_var(get_random_int_hash);
1328
1329 return ret;
1330}
1331
1332/*
1333 * randomize_range() returns a start address such that
1334 *
1335 * [...... <range> .....]
1336 * start end
1337 *
1338 * a <range> with size "len" starting at the return value is inside in the
1339 * area defined by [start, end], but is otherwise randomized.
1340 */
1341unsigned long
1342randomize_range(unsigned long start, unsigned long end, unsigned long len)
1343{
1344 unsigned long range = end - len - start;
1345
1346 if (end <= start + len)
1347 return 0;
1348 return PAGE_ALIGN(get_random_int() % range + start);
1349}
1/*
2 * random.c -- A strong random number generator
3 *
4 * Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All
5 * Rights Reserved.
6 *
7 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
8 *
9 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
10 * rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, and the entire permission notice in its entirety,
17 * including the disclaimer of warranties.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. The name of the author may not be used to endorse or promote
22 * products derived from this software without specific prior
23 * written permission.
24 *
25 * ALTERNATIVELY, this product may be distributed under the terms of
26 * the GNU General Public License, in which case the provisions of the GPL are
27 * required INSTEAD OF the above restrictions. (This clause is
28 * necessary due to a potential bad interaction between the GPL and
29 * the restrictions contained in a BSD-style copyright.)
30 *
31 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
32 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
33 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
34 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
35 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
36 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
37 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
38 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
39 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
41 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
42 * DAMAGE.
43 */
44
45/*
46 * (now, with legal B.S. out of the way.....)
47 *
48 * This routine gathers environmental noise from device drivers, etc.,
49 * and returns good random numbers, suitable for cryptographic use.
50 * Besides the obvious cryptographic uses, these numbers are also good
51 * for seeding TCP sequence numbers, and other places where it is
52 * desirable to have numbers which are not only random, but hard to
53 * predict by an attacker.
54 *
55 * Theory of operation
56 * ===================
57 *
58 * Computers are very predictable devices. Hence it is extremely hard
59 * to produce truly random numbers on a computer --- as opposed to
60 * pseudo-random numbers, which can easily generated by using a
61 * algorithm. Unfortunately, it is very easy for attackers to guess
62 * the sequence of pseudo-random number generators, and for some
63 * applications this is not acceptable. So instead, we must try to
64 * gather "environmental noise" from the computer's environment, which
65 * must be hard for outside attackers to observe, and use that to
66 * generate random numbers. In a Unix environment, this is best done
67 * from inside the kernel.
68 *
69 * Sources of randomness from the environment include inter-keyboard
70 * timings, inter-interrupt timings from some interrupts, and other
71 * events which are both (a) non-deterministic and (b) hard for an
72 * outside observer to measure. Randomness from these sources are
73 * added to an "entropy pool", which is mixed using a CRC-like function.
74 * This is not cryptographically strong, but it is adequate assuming
75 * the randomness is not chosen maliciously, and it is fast enough that
76 * the overhead of doing it on every interrupt is very reasonable.
77 * As random bytes are mixed into the entropy pool, the routines keep
78 * an *estimate* of how many bits of randomness have been stored into
79 * the random number generator's internal state.
80 *
81 * When random bytes are desired, they are obtained by taking the SHA
82 * hash of the contents of the "entropy pool". The SHA hash avoids
83 * exposing the internal state of the entropy pool. It is believed to
84 * be computationally infeasible to derive any useful information
85 * about the input of SHA from its output. Even if it is possible to
86 * analyze SHA in some clever way, as long as the amount of data
87 * returned from the generator is less than the inherent entropy in
88 * the pool, the output data is totally unpredictable. For this
89 * reason, the routine decreases its internal estimate of how many
90 * bits of "true randomness" are contained in the entropy pool as it
91 * outputs random numbers.
92 *
93 * If this estimate goes to zero, the routine can still generate
94 * random numbers; however, an attacker may (at least in theory) be
95 * able to infer the future output of the generator from prior
96 * outputs. This requires successful cryptanalysis of SHA, which is
97 * not believed to be feasible, but there is a remote possibility.
98 * Nonetheless, these numbers should be useful for the vast majority
99 * of purposes.
100 *
101 * Exported interfaces ---- output
102 * ===============================
103 *
104 * There are three exported interfaces; the first is one designed to
105 * be used from within the kernel:
106 *
107 * void get_random_bytes(void *buf, int nbytes);
108 *
109 * This interface will return the requested number of random bytes,
110 * and place it in the requested buffer.
111 *
112 * The two other interfaces are two character devices /dev/random and
113 * /dev/urandom. /dev/random is suitable for use when very high
114 * quality randomness is desired (for example, for key generation or
115 * one-time pads), as it will only return a maximum of the number of
116 * bits of randomness (as estimated by the random number generator)
117 * contained in the entropy pool.
118 *
119 * The /dev/urandom device does not have this limit, and will return
120 * as many bytes as are requested. As more and more random bytes are
121 * requested without giving time for the entropy pool to recharge,
122 * this will result in random numbers that are merely cryptographically
123 * strong. For many applications, however, this is acceptable.
124 *
125 * Exported interfaces ---- input
126 * ==============================
127 *
128 * The current exported interfaces for gathering environmental noise
129 * from the devices are:
130 *
131 * void add_device_randomness(const void *buf, unsigned int size);
132 * void add_input_randomness(unsigned int type, unsigned int code,
133 * unsigned int value);
134 * void add_interrupt_randomness(int irq, int irq_flags);
135 * void add_disk_randomness(struct gendisk *disk);
136 *
137 * add_device_randomness() is for adding data to the random pool that
138 * is likely to differ between two devices (or possibly even per boot).
139 * This would be things like MAC addresses or serial numbers, or the
140 * read-out of the RTC. This does *not* add any actual entropy to the
141 * pool, but it initializes the pool to different values for devices
142 * that might otherwise be identical and have very little entropy
143 * available to them (particularly common in the embedded world).
144 *
145 * add_input_randomness() uses the input layer interrupt timing, as well as
146 * the event type information from the hardware.
147 *
148 * add_interrupt_randomness() uses the interrupt timing as random
149 * inputs to the entropy pool. Using the cycle counters and the irq source
150 * as inputs, it feeds the randomness roughly once a second.
151 *
152 * add_disk_randomness() uses what amounts to the seek time of block
153 * layer request events, on a per-disk_devt basis, as input to the
154 * entropy pool. Note that high-speed solid state drives with very low
155 * seek times do not make for good sources of entropy, as their seek
156 * times are usually fairly consistent.
157 *
158 * All of these routines try to estimate how many bits of randomness a
159 * particular randomness source. They do this by keeping track of the
160 * first and second order deltas of the event timings.
161 *
162 * Ensuring unpredictability at system startup
163 * ============================================
164 *
165 * When any operating system starts up, it will go through a sequence
166 * of actions that are fairly predictable by an adversary, especially
167 * if the start-up does not involve interaction with a human operator.
168 * This reduces the actual number of bits of unpredictability in the
169 * entropy pool below the value in entropy_count. In order to
170 * counteract this effect, it helps to carry information in the
171 * entropy pool across shut-downs and start-ups. To do this, put the
172 * following lines an appropriate script which is run during the boot
173 * sequence:
174 *
175 * echo "Initializing random number generator..."
176 * random_seed=/var/run/random-seed
177 * # Carry a random seed from start-up to start-up
178 * # Load and then save the whole entropy pool
179 * if [ -f $random_seed ]; then
180 * cat $random_seed >/dev/urandom
181 * else
182 * touch $random_seed
183 * fi
184 * chmod 600 $random_seed
185 * dd if=/dev/urandom of=$random_seed count=1 bs=512
186 *
187 * and the following lines in an appropriate script which is run as
188 * the system is shutdown:
189 *
190 * # Carry a random seed from shut-down to start-up
191 * # Save the whole entropy pool
192 * echo "Saving random seed..."
193 * random_seed=/var/run/random-seed
194 * touch $random_seed
195 * chmod 600 $random_seed
196 * dd if=/dev/urandom of=$random_seed count=1 bs=512
197 *
198 * For example, on most modern systems using the System V init
199 * scripts, such code fragments would be found in
200 * /etc/rc.d/init.d/random. On older Linux systems, the correct script
201 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
202 *
203 * Effectively, these commands cause the contents of the entropy pool
204 * to be saved at shut-down time and reloaded into the entropy pool at
205 * start-up. (The 'dd' in the addition to the bootup script is to
206 * make sure that /etc/random-seed is different for every start-up,
207 * even if the system crashes without executing rc.0.) Even with
208 * complete knowledge of the start-up activities, predicting the state
209 * of the entropy pool requires knowledge of the previous history of
210 * the system.
211 *
212 * Configuring the /dev/random driver under Linux
213 * ==============================================
214 *
215 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
216 * the /dev/mem major number (#1). So if your system does not have
217 * /dev/random and /dev/urandom created already, they can be created
218 * by using the commands:
219 *
220 * mknod /dev/random c 1 8
221 * mknod /dev/urandom c 1 9
222 *
223 * Acknowledgements:
224 * =================
225 *
226 * Ideas for constructing this random number generator were derived
227 * from Pretty Good Privacy's random number generator, and from private
228 * discussions with Phil Karn. Colin Plumb provided a faster random
229 * number generator, which speed up the mixing function of the entropy
230 * pool, taken from PGPfone. Dale Worley has also contributed many
231 * useful ideas and suggestions to improve this driver.
232 *
233 * Any flaws in the design are solely my responsibility, and should
234 * not be attributed to the Phil, Colin, or any of authors of PGP.
235 *
236 * Further background information on this topic may be obtained from
237 * RFC 1750, "Randomness Recommendations for Security", by Donald
238 * Eastlake, Steve Crocker, and Jeff Schiller.
239 */
240
241#include <linux/utsname.h>
242#include <linux/module.h>
243#include <linux/kernel.h>
244#include <linux/major.h>
245#include <linux/string.h>
246#include <linux/fcntl.h>
247#include <linux/slab.h>
248#include <linux/random.h>
249#include <linux/poll.h>
250#include <linux/init.h>
251#include <linux/fs.h>
252#include <linux/genhd.h>
253#include <linux/interrupt.h>
254#include <linux/mm.h>
255#include <linux/nodemask.h>
256#include <linux/spinlock.h>
257#include <linux/kthread.h>
258#include <linux/percpu.h>
259#include <linux/cryptohash.h>
260#include <linux/fips.h>
261#include <linux/ptrace.h>
262#include <linux/workqueue.h>
263#include <linux/irq.h>
264#include <linux/ratelimit.h>
265#include <linux/syscalls.h>
266#include <linux/completion.h>
267#include <linux/uuid.h>
268#include <crypto/chacha20.h>
269
270#include <asm/processor.h>
271#include <linux/uaccess.h>
272#include <asm/irq.h>
273#include <asm/irq_regs.h>
274#include <asm/io.h>
275
276#define CREATE_TRACE_POINTS
277#include <trace/events/random.h>
278
279/* #define ADD_INTERRUPT_BENCH */
280
281/*
282 * Configuration information
283 */
284#define INPUT_POOL_SHIFT 12
285#define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
286#define OUTPUT_POOL_SHIFT 10
287#define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
288#define SEC_XFER_SIZE 512
289#define EXTRACT_SIZE 10
290
291
292#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
293
294/*
295 * To allow fractional bits to be tracked, the entropy_count field is
296 * denominated in units of 1/8th bits.
297 *
298 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
299 * credit_entropy_bits() needs to be 64 bits wide.
300 */
301#define ENTROPY_SHIFT 3
302#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
303
304/*
305 * The minimum number of bits of entropy before we wake up a read on
306 * /dev/random. Should be enough to do a significant reseed.
307 */
308static int random_read_wakeup_bits = 64;
309
310/*
311 * If the entropy count falls under this number of bits, then we
312 * should wake up processes which are selecting or polling on write
313 * access to /dev/random.
314 */
315static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
316
317/*
318 * Originally, we used a primitive polynomial of degree .poolwords
319 * over GF(2). The taps for various sizes are defined below. They
320 * were chosen to be evenly spaced except for the last tap, which is 1
321 * to get the twisting happening as fast as possible.
322 *
323 * For the purposes of better mixing, we use the CRC-32 polynomial as
324 * well to make a (modified) twisted Generalized Feedback Shift
325 * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
326 * generators. ACM Transactions on Modeling and Computer Simulation
327 * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
328 * GFSR generators II. ACM Transactions on Modeling and Computer
329 * Simulation 4:254-266)
330 *
331 * Thanks to Colin Plumb for suggesting this.
332 *
333 * The mixing operation is much less sensitive than the output hash,
334 * where we use SHA-1. All that we want of mixing operation is that
335 * it be a good non-cryptographic hash; i.e. it not produce collisions
336 * when fed "random" data of the sort we expect to see. As long as
337 * the pool state differs for different inputs, we have preserved the
338 * input entropy and done a good job. The fact that an intelligent
339 * attacker can construct inputs that will produce controlled
340 * alterations to the pool's state is not important because we don't
341 * consider such inputs to contribute any randomness. The only
342 * property we need with respect to them is that the attacker can't
343 * increase his/her knowledge of the pool's state. Since all
344 * additions are reversible (knowing the final state and the input,
345 * you can reconstruct the initial state), if an attacker has any
346 * uncertainty about the initial state, he/she can only shuffle that
347 * uncertainty about, but never cause any collisions (which would
348 * decrease the uncertainty).
349 *
350 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
351 * Videau in their paper, "The Linux Pseudorandom Number Generator
352 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
353 * paper, they point out that we are not using a true Twisted GFSR,
354 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
355 * is, with only three taps, instead of the six that we are using).
356 * As a result, the resulting polynomial is neither primitive nor
357 * irreducible, and hence does not have a maximal period over
358 * GF(2**32). They suggest a slight change to the generator
359 * polynomial which improves the resulting TGFSR polynomial to be
360 * irreducible, which we have made here.
361 */
362static struct poolinfo {
363 int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
364#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
365 int tap1, tap2, tap3, tap4, tap5;
366} poolinfo_table[] = {
367 /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
368 /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
369 { S(128), 104, 76, 51, 25, 1 },
370 /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
371 /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
372 { S(32), 26, 19, 14, 7, 1 },
373#if 0
374 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
375 { S(2048), 1638, 1231, 819, 411, 1 },
376
377 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
378 { S(1024), 817, 615, 412, 204, 1 },
379
380 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
381 { S(1024), 819, 616, 410, 207, 2 },
382
383 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
384 { S(512), 411, 308, 208, 104, 1 },
385
386 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
387 { S(512), 409, 307, 206, 102, 2 },
388 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
389 { S(512), 409, 309, 205, 103, 2 },
390
391 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
392 { S(256), 205, 155, 101, 52, 1 },
393
394 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
395 { S(128), 103, 78, 51, 27, 2 },
396
397 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
398 { S(64), 52, 39, 26, 14, 1 },
399#endif
400};
401
402/*
403 * Static global variables
404 */
405static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
406static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
407static struct fasync_struct *fasync;
408
409static DEFINE_SPINLOCK(random_ready_list_lock);
410static LIST_HEAD(random_ready_list);
411
412struct crng_state {
413 __u32 state[16];
414 unsigned long init_time;
415 spinlock_t lock;
416};
417
418struct crng_state primary_crng = {
419 .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
420};
421
422/*
423 * crng_init = 0 --> Uninitialized
424 * 1 --> Initialized
425 * 2 --> Initialized from input_pool
426 *
427 * crng_init is protected by primary_crng->lock, and only increases
428 * its value (from 0->1->2).
429 */
430static int crng_init = 0;
431#define crng_ready() (likely(crng_init > 1))
432static int crng_init_cnt = 0;
433static unsigned long crng_global_init_time = 0;
434#define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
435static void _extract_crng(struct crng_state *crng,
436 __u32 out[CHACHA20_BLOCK_WORDS]);
437static void _crng_backtrack_protect(struct crng_state *crng,
438 __u32 tmp[CHACHA20_BLOCK_WORDS], int used);
439static void process_random_ready_list(void);
440static void _get_random_bytes(void *buf, int nbytes);
441
442static struct ratelimit_state unseeded_warning =
443 RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
444static struct ratelimit_state urandom_warning =
445 RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
446
447static int ratelimit_disable __read_mostly;
448
449module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
450MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
451
452/**********************************************************************
453 *
454 * OS independent entropy store. Here are the functions which handle
455 * storing entropy in an entropy pool.
456 *
457 **********************************************************************/
458
459struct entropy_store;
460struct entropy_store {
461 /* read-only data: */
462 const struct poolinfo *poolinfo;
463 __u32 *pool;
464 const char *name;
465 struct entropy_store *pull;
466 struct work_struct push_work;
467
468 /* read-write data: */
469 unsigned long last_pulled;
470 spinlock_t lock;
471 unsigned short add_ptr;
472 unsigned short input_rotate;
473 int entropy_count;
474 int entropy_total;
475 unsigned int initialized:1;
476 unsigned int last_data_init:1;
477 __u8 last_data[EXTRACT_SIZE];
478};
479
480static ssize_t extract_entropy(struct entropy_store *r, void *buf,
481 size_t nbytes, int min, int rsvd);
482static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
483 size_t nbytes, int fips);
484
485static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
486static void push_to_pool(struct work_struct *work);
487static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy;
488static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy;
489
490static struct entropy_store input_pool = {
491 .poolinfo = &poolinfo_table[0],
492 .name = "input",
493 .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
494 .pool = input_pool_data
495};
496
497static struct entropy_store blocking_pool = {
498 .poolinfo = &poolinfo_table[1],
499 .name = "blocking",
500 .pull = &input_pool,
501 .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
502 .pool = blocking_pool_data,
503 .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
504 push_to_pool),
505};
506
507static __u32 const twist_table[8] = {
508 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
509 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
510
511/*
512 * This function adds bytes into the entropy "pool". It does not
513 * update the entropy estimate. The caller should call
514 * credit_entropy_bits if this is appropriate.
515 *
516 * The pool is stirred with a primitive polynomial of the appropriate
517 * degree, and then twisted. We twist by three bits at a time because
518 * it's cheap to do so and helps slightly in the expected case where
519 * the entropy is concentrated in the low-order bits.
520 */
521static void _mix_pool_bytes(struct entropy_store *r, const void *in,
522 int nbytes)
523{
524 unsigned long i, tap1, tap2, tap3, tap4, tap5;
525 int input_rotate;
526 int wordmask = r->poolinfo->poolwords - 1;
527 const char *bytes = in;
528 __u32 w;
529
530 tap1 = r->poolinfo->tap1;
531 tap2 = r->poolinfo->tap2;
532 tap3 = r->poolinfo->tap3;
533 tap4 = r->poolinfo->tap4;
534 tap5 = r->poolinfo->tap5;
535
536 input_rotate = r->input_rotate;
537 i = r->add_ptr;
538
539 /* mix one byte at a time to simplify size handling and churn faster */
540 while (nbytes--) {
541 w = rol32(*bytes++, input_rotate);
542 i = (i - 1) & wordmask;
543
544 /* XOR in the various taps */
545 w ^= r->pool[i];
546 w ^= r->pool[(i + tap1) & wordmask];
547 w ^= r->pool[(i + tap2) & wordmask];
548 w ^= r->pool[(i + tap3) & wordmask];
549 w ^= r->pool[(i + tap4) & wordmask];
550 w ^= r->pool[(i + tap5) & wordmask];
551
552 /* Mix the result back in with a twist */
553 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
554
555 /*
556 * Normally, we add 7 bits of rotation to the pool.
557 * At the beginning of the pool, add an extra 7 bits
558 * rotation, so that successive passes spread the
559 * input bits across the pool evenly.
560 */
561 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
562 }
563
564 r->input_rotate = input_rotate;
565 r->add_ptr = i;
566}
567
568static void __mix_pool_bytes(struct entropy_store *r, const void *in,
569 int nbytes)
570{
571 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
572 _mix_pool_bytes(r, in, nbytes);
573}
574
575static void mix_pool_bytes(struct entropy_store *r, const void *in,
576 int nbytes)
577{
578 unsigned long flags;
579
580 trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
581 spin_lock_irqsave(&r->lock, flags);
582 _mix_pool_bytes(r, in, nbytes);
583 spin_unlock_irqrestore(&r->lock, flags);
584}
585
586struct fast_pool {
587 __u32 pool[4];
588 unsigned long last;
589 unsigned short reg_idx;
590 unsigned char count;
591};
592
593/*
594 * This is a fast mixing routine used by the interrupt randomness
595 * collector. It's hardcoded for an 128 bit pool and assumes that any
596 * locks that might be needed are taken by the caller.
597 */
598static void fast_mix(struct fast_pool *f)
599{
600 __u32 a = f->pool[0], b = f->pool[1];
601 __u32 c = f->pool[2], d = f->pool[3];
602
603 a += b; c += d;
604 b = rol32(b, 6); d = rol32(d, 27);
605 d ^= a; b ^= c;
606
607 a += b; c += d;
608 b = rol32(b, 16); d = rol32(d, 14);
609 d ^= a; b ^= c;
610
611 a += b; c += d;
612 b = rol32(b, 6); d = rol32(d, 27);
613 d ^= a; b ^= c;
614
615 a += b; c += d;
616 b = rol32(b, 16); d = rol32(d, 14);
617 d ^= a; b ^= c;
618
619 f->pool[0] = a; f->pool[1] = b;
620 f->pool[2] = c; f->pool[3] = d;
621 f->count++;
622}
623
624static void process_random_ready_list(void)
625{
626 unsigned long flags;
627 struct random_ready_callback *rdy, *tmp;
628
629 spin_lock_irqsave(&random_ready_list_lock, flags);
630 list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
631 struct module *owner = rdy->owner;
632
633 list_del_init(&rdy->list);
634 rdy->func(rdy);
635 module_put(owner);
636 }
637 spin_unlock_irqrestore(&random_ready_list_lock, flags);
638}
639
640/*
641 * Credit (or debit) the entropy store with n bits of entropy.
642 * Use credit_entropy_bits_safe() if the value comes from userspace
643 * or otherwise should be checked for extreme values.
644 */
645static void credit_entropy_bits(struct entropy_store *r, int nbits)
646{
647 int entropy_count, orig;
648 const int pool_size = r->poolinfo->poolfracbits;
649 int nfrac = nbits << ENTROPY_SHIFT;
650
651 if (!nbits)
652 return;
653
654retry:
655 entropy_count = orig = READ_ONCE(r->entropy_count);
656 if (nfrac < 0) {
657 /* Debit */
658 entropy_count += nfrac;
659 } else {
660 /*
661 * Credit: we have to account for the possibility of
662 * overwriting already present entropy. Even in the
663 * ideal case of pure Shannon entropy, new contributions
664 * approach the full value asymptotically:
665 *
666 * entropy <- entropy + (pool_size - entropy) *
667 * (1 - exp(-add_entropy/pool_size))
668 *
669 * For add_entropy <= pool_size/2 then
670 * (1 - exp(-add_entropy/pool_size)) >=
671 * (add_entropy/pool_size)*0.7869...
672 * so we can approximate the exponential with
673 * 3/4*add_entropy/pool_size and still be on the
674 * safe side by adding at most pool_size/2 at a time.
675 *
676 * The use of pool_size-2 in the while statement is to
677 * prevent rounding artifacts from making the loop
678 * arbitrarily long; this limits the loop to log2(pool_size)*2
679 * turns no matter how large nbits is.
680 */
681 int pnfrac = nfrac;
682 const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
683 /* The +2 corresponds to the /4 in the denominator */
684
685 do {
686 unsigned int anfrac = min(pnfrac, pool_size/2);
687 unsigned int add =
688 ((pool_size - entropy_count)*anfrac*3) >> s;
689
690 entropy_count += add;
691 pnfrac -= anfrac;
692 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
693 }
694
695 if (unlikely(entropy_count < 0)) {
696 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
697 r->name, entropy_count);
698 WARN_ON(1);
699 entropy_count = 0;
700 } else if (entropy_count > pool_size)
701 entropy_count = pool_size;
702 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
703 goto retry;
704
705 r->entropy_total += nbits;
706 if (!r->initialized && r->entropy_total > 128) {
707 r->initialized = 1;
708 r->entropy_total = 0;
709 }
710
711 trace_credit_entropy_bits(r->name, nbits,
712 entropy_count >> ENTROPY_SHIFT,
713 r->entropy_total, _RET_IP_);
714
715 if (r == &input_pool) {
716 int entropy_bits = entropy_count >> ENTROPY_SHIFT;
717
718 if (crng_init < 2 && entropy_bits >= 128) {
719 crng_reseed(&primary_crng, r);
720 entropy_bits = r->entropy_count >> ENTROPY_SHIFT;
721 }
722
723 /* should we wake readers? */
724 if (entropy_bits >= random_read_wakeup_bits &&
725 wq_has_sleeper(&random_read_wait)) {
726 wake_up_interruptible(&random_read_wait);
727 kill_fasync(&fasync, SIGIO, POLL_IN);
728 }
729 /* If the input pool is getting full, send some
730 * entropy to the blocking pool until it is 75% full.
731 */
732 if (entropy_bits > random_write_wakeup_bits &&
733 r->initialized &&
734 r->entropy_total >= 2*random_read_wakeup_bits) {
735 struct entropy_store *other = &blocking_pool;
736
737 if (other->entropy_count <=
738 3 * other->poolinfo->poolfracbits / 4) {
739 schedule_work(&other->push_work);
740 r->entropy_total = 0;
741 }
742 }
743 }
744}
745
746static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
747{
748 const int nbits_max = r->poolinfo->poolwords * 32;
749
750 if (nbits < 0)
751 return -EINVAL;
752
753 /* Cap the value to avoid overflows */
754 nbits = min(nbits, nbits_max);
755
756 credit_entropy_bits(r, nbits);
757 return 0;
758}
759
760/*********************************************************************
761 *
762 * CRNG using CHACHA20
763 *
764 *********************************************************************/
765
766#define CRNG_RESEED_INTERVAL (300*HZ)
767
768static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
769
770#ifdef CONFIG_NUMA
771/*
772 * Hack to deal with crazy userspace progams when they are all trying
773 * to access /dev/urandom in parallel. The programs are almost
774 * certainly doing something terribly wrong, but we'll work around
775 * their brain damage.
776 */
777static struct crng_state **crng_node_pool __read_mostly;
778#endif
779
780static void invalidate_batched_entropy(void);
781
782static void crng_initialize(struct crng_state *crng)
783{
784 int i;
785 unsigned long rv;
786
787 memcpy(&crng->state[0], "expand 32-byte k", 16);
788 if (crng == &primary_crng)
789 _extract_entropy(&input_pool, &crng->state[4],
790 sizeof(__u32) * 12, 0);
791 else
792 _get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
793 for (i = 4; i < 16; i++) {
794 if (!arch_get_random_seed_long(&rv) &&
795 !arch_get_random_long(&rv))
796 rv = random_get_entropy();
797 crng->state[i] ^= rv;
798 }
799 crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
800}
801
802#ifdef CONFIG_NUMA
803static void do_numa_crng_init(struct work_struct *work)
804{
805 int i;
806 struct crng_state *crng;
807 struct crng_state **pool;
808
809 pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
810 for_each_online_node(i) {
811 crng = kmalloc_node(sizeof(struct crng_state),
812 GFP_KERNEL | __GFP_NOFAIL, i);
813 spin_lock_init(&crng->lock);
814 crng_initialize(crng);
815 pool[i] = crng;
816 }
817 mb();
818 if (cmpxchg(&crng_node_pool, NULL, pool)) {
819 for_each_node(i)
820 kfree(pool[i]);
821 kfree(pool);
822 }
823}
824
825static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init);
826
827static void numa_crng_init(void)
828{
829 schedule_work(&numa_crng_init_work);
830}
831#else
832static void numa_crng_init(void) {}
833#endif
834
835/*
836 * crng_fast_load() can be called by code in the interrupt service
837 * path. So we can't afford to dilly-dally.
838 */
839static int crng_fast_load(const char *cp, size_t len)
840{
841 unsigned long flags;
842 char *p;
843
844 if (!spin_trylock_irqsave(&primary_crng.lock, flags))
845 return 0;
846 if (crng_init != 0) {
847 spin_unlock_irqrestore(&primary_crng.lock, flags);
848 return 0;
849 }
850 p = (unsigned char *) &primary_crng.state[4];
851 while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
852 p[crng_init_cnt % CHACHA20_KEY_SIZE] ^= *cp;
853 cp++; crng_init_cnt++; len--;
854 }
855 spin_unlock_irqrestore(&primary_crng.lock, flags);
856 if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
857 invalidate_batched_entropy();
858 crng_init = 1;
859 wake_up_interruptible(&crng_init_wait);
860 pr_notice("random: fast init done\n");
861 }
862 return 1;
863}
864
865/*
866 * crng_slow_load() is called by add_device_randomness, which has two
867 * attributes. (1) We can't trust the buffer passed to it is
868 * guaranteed to be unpredictable (so it might not have any entropy at
869 * all), and (2) it doesn't have the performance constraints of
870 * crng_fast_load().
871 *
872 * So we do something more comprehensive which is guaranteed to touch
873 * all of the primary_crng's state, and which uses a LFSR with a
874 * period of 255 as part of the mixing algorithm. Finally, we do
875 * *not* advance crng_init_cnt since buffer we may get may be something
876 * like a fixed DMI table (for example), which might very well be
877 * unique to the machine, but is otherwise unvarying.
878 */
879static int crng_slow_load(const char *cp, size_t len)
880{
881 unsigned long flags;
882 static unsigned char lfsr = 1;
883 unsigned char tmp;
884 unsigned i, max = CHACHA20_KEY_SIZE;
885 const char * src_buf = cp;
886 char * dest_buf = (char *) &primary_crng.state[4];
887
888 if (!spin_trylock_irqsave(&primary_crng.lock, flags))
889 return 0;
890 if (crng_init != 0) {
891 spin_unlock_irqrestore(&primary_crng.lock, flags);
892 return 0;
893 }
894 if (len > max)
895 max = len;
896
897 for (i = 0; i < max ; i++) {
898 tmp = lfsr;
899 lfsr >>= 1;
900 if (tmp & 1)
901 lfsr ^= 0xE1;
902 tmp = dest_buf[i % CHACHA20_KEY_SIZE];
903 dest_buf[i % CHACHA20_KEY_SIZE] ^= src_buf[i % len] ^ lfsr;
904 lfsr += (tmp << 3) | (tmp >> 5);
905 }
906 spin_unlock_irqrestore(&primary_crng.lock, flags);
907 return 1;
908}
909
910static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
911{
912 unsigned long flags;
913 int i, num;
914 union {
915 __u32 block[CHACHA20_BLOCK_WORDS];
916 __u32 key[8];
917 } buf;
918
919 if (r) {
920 num = extract_entropy(r, &buf, 32, 16, 0);
921 if (num == 0)
922 return;
923 } else {
924 _extract_crng(&primary_crng, buf.block);
925 _crng_backtrack_protect(&primary_crng, buf.block,
926 CHACHA20_KEY_SIZE);
927 }
928 spin_lock_irqsave(&crng->lock, flags);
929 for (i = 0; i < 8; i++) {
930 unsigned long rv;
931 if (!arch_get_random_seed_long(&rv) &&
932 !arch_get_random_long(&rv))
933 rv = random_get_entropy();
934 crng->state[i+4] ^= buf.key[i] ^ rv;
935 }
936 memzero_explicit(&buf, sizeof(buf));
937 crng->init_time = jiffies;
938 spin_unlock_irqrestore(&crng->lock, flags);
939 if (crng == &primary_crng && crng_init < 2) {
940 invalidate_batched_entropy();
941 numa_crng_init();
942 crng_init = 2;
943 process_random_ready_list();
944 wake_up_interruptible(&crng_init_wait);
945 pr_notice("random: crng init done\n");
946 if (unseeded_warning.missed) {
947 pr_notice("random: %d get_random_xx warning(s) missed "
948 "due to ratelimiting\n",
949 unseeded_warning.missed);
950 unseeded_warning.missed = 0;
951 }
952 if (urandom_warning.missed) {
953 pr_notice("random: %d urandom warning(s) missed "
954 "due to ratelimiting\n",
955 urandom_warning.missed);
956 urandom_warning.missed = 0;
957 }
958 }
959}
960
961static void _extract_crng(struct crng_state *crng,
962 __u32 out[CHACHA20_BLOCK_WORDS])
963{
964 unsigned long v, flags;
965
966 if (crng_ready() &&
967 (time_after(crng_global_init_time, crng->init_time) ||
968 time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
969 crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
970 spin_lock_irqsave(&crng->lock, flags);
971 if (arch_get_random_long(&v))
972 crng->state[14] ^= v;
973 chacha20_block(&crng->state[0], out);
974 if (crng->state[12] == 0)
975 crng->state[13]++;
976 spin_unlock_irqrestore(&crng->lock, flags);
977}
978
979static void extract_crng(__u32 out[CHACHA20_BLOCK_WORDS])
980{
981 struct crng_state *crng = NULL;
982
983#ifdef CONFIG_NUMA
984 if (crng_node_pool)
985 crng = crng_node_pool[numa_node_id()];
986 if (crng == NULL)
987#endif
988 crng = &primary_crng;
989 _extract_crng(crng, out);
990}
991
992/*
993 * Use the leftover bytes from the CRNG block output (if there is
994 * enough) to mutate the CRNG key to provide backtracking protection.
995 */
996static void _crng_backtrack_protect(struct crng_state *crng,
997 __u32 tmp[CHACHA20_BLOCK_WORDS], int used)
998{
999 unsigned long flags;
1000 __u32 *s, *d;
1001 int i;
1002
1003 used = round_up(used, sizeof(__u32));
1004 if (used + CHACHA20_KEY_SIZE > CHACHA20_BLOCK_SIZE) {
1005 extract_crng(tmp);
1006 used = 0;
1007 }
1008 spin_lock_irqsave(&crng->lock, flags);
1009 s = &tmp[used / sizeof(__u32)];
1010 d = &crng->state[4];
1011 for (i=0; i < 8; i++)
1012 *d++ ^= *s++;
1013 spin_unlock_irqrestore(&crng->lock, flags);
1014}
1015
1016static void crng_backtrack_protect(__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
1017{
1018 struct crng_state *crng = NULL;
1019
1020#ifdef CONFIG_NUMA
1021 if (crng_node_pool)
1022 crng = crng_node_pool[numa_node_id()];
1023 if (crng == NULL)
1024#endif
1025 crng = &primary_crng;
1026 _crng_backtrack_protect(crng, tmp, used);
1027}
1028
1029static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
1030{
1031 ssize_t ret = 0, i = CHACHA20_BLOCK_SIZE;
1032 __u32 tmp[CHACHA20_BLOCK_WORDS];
1033 int large_request = (nbytes > 256);
1034
1035 while (nbytes) {
1036 if (large_request && need_resched()) {
1037 if (signal_pending(current)) {
1038 if (ret == 0)
1039 ret = -ERESTARTSYS;
1040 break;
1041 }
1042 schedule();
1043 }
1044
1045 extract_crng(tmp);
1046 i = min_t(int, nbytes, CHACHA20_BLOCK_SIZE);
1047 if (copy_to_user(buf, tmp, i)) {
1048 ret = -EFAULT;
1049 break;
1050 }
1051
1052 nbytes -= i;
1053 buf += i;
1054 ret += i;
1055 }
1056 crng_backtrack_protect(tmp, i);
1057
1058 /* Wipe data just written to memory */
1059 memzero_explicit(tmp, sizeof(tmp));
1060
1061 return ret;
1062}
1063
1064
1065/*********************************************************************
1066 *
1067 * Entropy input management
1068 *
1069 *********************************************************************/
1070
1071/* There is one of these per entropy source */
1072struct timer_rand_state {
1073 cycles_t last_time;
1074 long last_delta, last_delta2;
1075};
1076
1077#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
1078
1079/*
1080 * Add device- or boot-specific data to the input pool to help
1081 * initialize it.
1082 *
1083 * None of this adds any entropy; it is meant to avoid the problem of
1084 * the entropy pool having similar initial state across largely
1085 * identical devices.
1086 */
1087void add_device_randomness(const void *buf, unsigned int size)
1088{
1089 unsigned long time = random_get_entropy() ^ jiffies;
1090 unsigned long flags;
1091
1092 if (!crng_ready() && size)
1093 crng_slow_load(buf, size);
1094
1095 trace_add_device_randomness(size, _RET_IP_);
1096 spin_lock_irqsave(&input_pool.lock, flags);
1097 _mix_pool_bytes(&input_pool, buf, size);
1098 _mix_pool_bytes(&input_pool, &time, sizeof(time));
1099 spin_unlock_irqrestore(&input_pool.lock, flags);
1100}
1101EXPORT_SYMBOL(add_device_randomness);
1102
1103static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
1104
1105/*
1106 * This function adds entropy to the entropy "pool" by using timing
1107 * delays. It uses the timer_rand_state structure to make an estimate
1108 * of how many bits of entropy this call has added to the pool.
1109 *
1110 * The number "num" is also added to the pool - it should somehow describe
1111 * the type of event which just happened. This is currently 0-255 for
1112 * keyboard scan codes, and 256 upwards for interrupts.
1113 *
1114 */
1115static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
1116{
1117 struct entropy_store *r;
1118 struct {
1119 long jiffies;
1120 unsigned cycles;
1121 unsigned num;
1122 } sample;
1123 long delta, delta2, delta3;
1124
1125 preempt_disable();
1126
1127 sample.jiffies = jiffies;
1128 sample.cycles = random_get_entropy();
1129 sample.num = num;
1130 r = &input_pool;
1131 mix_pool_bytes(r, &sample, sizeof(sample));
1132
1133 /*
1134 * Calculate number of bits of randomness we probably added.
1135 * We take into account the first, second and third-order deltas
1136 * in order to make our estimate.
1137 */
1138 delta = sample.jiffies - state->last_time;
1139 state->last_time = sample.jiffies;
1140
1141 delta2 = delta - state->last_delta;
1142 state->last_delta = delta;
1143
1144 delta3 = delta2 - state->last_delta2;
1145 state->last_delta2 = delta2;
1146
1147 if (delta < 0)
1148 delta = -delta;
1149 if (delta2 < 0)
1150 delta2 = -delta2;
1151 if (delta3 < 0)
1152 delta3 = -delta3;
1153 if (delta > delta2)
1154 delta = delta2;
1155 if (delta > delta3)
1156 delta = delta3;
1157
1158 /*
1159 * delta is now minimum absolute delta.
1160 * Round down by 1 bit on general principles,
1161 * and limit entropy entimate to 12 bits.
1162 */
1163 credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1164
1165 preempt_enable();
1166}
1167
1168void add_input_randomness(unsigned int type, unsigned int code,
1169 unsigned int value)
1170{
1171 static unsigned char last_value;
1172
1173 /* ignore autorepeat and the like */
1174 if (value == last_value)
1175 return;
1176
1177 last_value = value;
1178 add_timer_randomness(&input_timer_state,
1179 (type << 4) ^ code ^ (code >> 4) ^ value);
1180 trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1181}
1182EXPORT_SYMBOL_GPL(add_input_randomness);
1183
1184static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
1185
1186#ifdef ADD_INTERRUPT_BENCH
1187static unsigned long avg_cycles, avg_deviation;
1188
1189#define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
1190#define FIXED_1_2 (1 << (AVG_SHIFT-1))
1191
1192static void add_interrupt_bench(cycles_t start)
1193{
1194 long delta = random_get_entropy() - start;
1195
1196 /* Use a weighted moving average */
1197 delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
1198 avg_cycles += delta;
1199 /* And average deviation */
1200 delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
1201 avg_deviation += delta;
1202}
1203#else
1204#define add_interrupt_bench(x)
1205#endif
1206
1207static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
1208{
1209 __u32 *ptr = (__u32 *) regs;
1210 unsigned int idx;
1211
1212 if (regs == NULL)
1213 return 0;
1214 idx = READ_ONCE(f->reg_idx);
1215 if (idx >= sizeof(struct pt_regs) / sizeof(__u32))
1216 idx = 0;
1217 ptr += idx++;
1218 WRITE_ONCE(f->reg_idx, idx);
1219 return *ptr;
1220}
1221
1222void add_interrupt_randomness(int irq, int irq_flags)
1223{
1224 struct entropy_store *r;
1225 struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
1226 struct pt_regs *regs = get_irq_regs();
1227 unsigned long now = jiffies;
1228 cycles_t cycles = random_get_entropy();
1229 __u32 c_high, j_high;
1230 __u64 ip;
1231 unsigned long seed;
1232 int credit = 0;
1233
1234 if (cycles == 0)
1235 cycles = get_reg(fast_pool, regs);
1236 c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
1237 j_high = (sizeof(now) > 4) ? now >> 32 : 0;
1238 fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
1239 fast_pool->pool[1] ^= now ^ c_high;
1240 ip = regs ? instruction_pointer(regs) : _RET_IP_;
1241 fast_pool->pool[2] ^= ip;
1242 fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
1243 get_reg(fast_pool, regs);
1244
1245 fast_mix(fast_pool);
1246 add_interrupt_bench(cycles);
1247
1248 if (unlikely(crng_init == 0)) {
1249 if ((fast_pool->count >= 64) &&
1250 crng_fast_load((char *) fast_pool->pool,
1251 sizeof(fast_pool->pool))) {
1252 fast_pool->count = 0;
1253 fast_pool->last = now;
1254 }
1255 return;
1256 }
1257
1258 if ((fast_pool->count < 64) &&
1259 !time_after(now, fast_pool->last + HZ))
1260 return;
1261
1262 r = &input_pool;
1263 if (!spin_trylock(&r->lock))
1264 return;
1265
1266 fast_pool->last = now;
1267 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
1268
1269 /*
1270 * If we have architectural seed generator, produce a seed and
1271 * add it to the pool. For the sake of paranoia don't let the
1272 * architectural seed generator dominate the input from the
1273 * interrupt noise.
1274 */
1275 if (arch_get_random_seed_long(&seed)) {
1276 __mix_pool_bytes(r, &seed, sizeof(seed));
1277 credit = 1;
1278 }
1279 spin_unlock(&r->lock);
1280
1281 fast_pool->count = 0;
1282
1283 /* award one bit for the contents of the fast pool */
1284 credit_entropy_bits(r, credit + 1);
1285}
1286EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1287
1288#ifdef CONFIG_BLOCK
1289void add_disk_randomness(struct gendisk *disk)
1290{
1291 if (!disk || !disk->random)
1292 return;
1293 /* first major is 1, so we get >= 0x200 here */
1294 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1295 trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1296}
1297EXPORT_SYMBOL_GPL(add_disk_randomness);
1298#endif
1299
1300/*********************************************************************
1301 *
1302 * Entropy extraction routines
1303 *
1304 *********************************************************************/
1305
1306/*
1307 * This utility inline function is responsible for transferring entropy
1308 * from the primary pool to the secondary extraction pool. We make
1309 * sure we pull enough for a 'catastrophic reseed'.
1310 */
1311static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
1312static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1313{
1314 if (!r->pull ||
1315 r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
1316 r->entropy_count > r->poolinfo->poolfracbits)
1317 return;
1318
1319 _xfer_secondary_pool(r, nbytes);
1320}
1321
1322static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1323{
1324 __u32 tmp[OUTPUT_POOL_WORDS];
1325
1326 int bytes = nbytes;
1327
1328 /* pull at least as much as a wakeup */
1329 bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
1330 /* but never more than the buffer size */
1331 bytes = min_t(int, bytes, sizeof(tmp));
1332
1333 trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
1334 ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
1335 bytes = extract_entropy(r->pull, tmp, bytes,
1336 random_read_wakeup_bits / 8, 0);
1337 mix_pool_bytes(r, tmp, bytes);
1338 credit_entropy_bits(r, bytes*8);
1339}
1340
1341/*
1342 * Used as a workqueue function so that when the input pool is getting
1343 * full, we can "spill over" some entropy to the output pools. That
1344 * way the output pools can store some of the excess entropy instead
1345 * of letting it go to waste.
1346 */
1347static void push_to_pool(struct work_struct *work)
1348{
1349 struct entropy_store *r = container_of(work, struct entropy_store,
1350 push_work);
1351 BUG_ON(!r);
1352 _xfer_secondary_pool(r, random_read_wakeup_bits/8);
1353 trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1354 r->pull->entropy_count >> ENTROPY_SHIFT);
1355}
1356
1357/*
1358 * This function decides how many bytes to actually take from the
1359 * given pool, and also debits the entropy count accordingly.
1360 */
1361static size_t account(struct entropy_store *r, size_t nbytes, int min,
1362 int reserved)
1363{
1364 int entropy_count, orig, have_bytes;
1365 size_t ibytes, nfrac;
1366
1367 BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1368
1369 /* Can we pull enough? */
1370retry:
1371 entropy_count = orig = READ_ONCE(r->entropy_count);
1372 ibytes = nbytes;
1373 /* never pull more than available */
1374 have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1375
1376 if ((have_bytes -= reserved) < 0)
1377 have_bytes = 0;
1378 ibytes = min_t(size_t, ibytes, have_bytes);
1379 if (ibytes < min)
1380 ibytes = 0;
1381
1382 if (unlikely(entropy_count < 0)) {
1383 pr_warn("random: negative entropy count: pool %s count %d\n",
1384 r->name, entropy_count);
1385 WARN_ON(1);
1386 entropy_count = 0;
1387 }
1388 nfrac = ibytes << (ENTROPY_SHIFT + 3);
1389 if ((size_t) entropy_count > nfrac)
1390 entropy_count -= nfrac;
1391 else
1392 entropy_count = 0;
1393
1394 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1395 goto retry;
1396
1397 trace_debit_entropy(r->name, 8 * ibytes);
1398 if (ibytes &&
1399 (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1400 wake_up_interruptible(&random_write_wait);
1401 kill_fasync(&fasync, SIGIO, POLL_OUT);
1402 }
1403
1404 return ibytes;
1405}
1406
1407/*
1408 * This function does the actual extraction for extract_entropy and
1409 * extract_entropy_user.
1410 *
1411 * Note: we assume that .poolwords is a multiple of 16 words.
1412 */
1413static void extract_buf(struct entropy_store *r, __u8 *out)
1414{
1415 int i;
1416 union {
1417 __u32 w[5];
1418 unsigned long l[LONGS(20)];
1419 } hash;
1420 __u32 workspace[SHA_WORKSPACE_WORDS];
1421 unsigned long flags;
1422
1423 /*
1424 * If we have an architectural hardware random number
1425 * generator, use it for SHA's initial vector
1426 */
1427 sha_init(hash.w);
1428 for (i = 0; i < LONGS(20); i++) {
1429 unsigned long v;
1430 if (!arch_get_random_long(&v))
1431 break;
1432 hash.l[i] = v;
1433 }
1434
1435 /* Generate a hash across the pool, 16 words (512 bits) at a time */
1436 spin_lock_irqsave(&r->lock, flags);
1437 for (i = 0; i < r->poolinfo->poolwords; i += 16)
1438 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1439
1440 /*
1441 * We mix the hash back into the pool to prevent backtracking
1442 * attacks (where the attacker knows the state of the pool
1443 * plus the current outputs, and attempts to find previous
1444 * ouputs), unless the hash function can be inverted. By
1445 * mixing at least a SHA1 worth of hash data back, we make
1446 * brute-forcing the feedback as hard as brute-forcing the
1447 * hash.
1448 */
1449 __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1450 spin_unlock_irqrestore(&r->lock, flags);
1451
1452 memzero_explicit(workspace, sizeof(workspace));
1453
1454 /*
1455 * In case the hash function has some recognizable output
1456 * pattern, we fold it in half. Thus, we always feed back
1457 * twice as much data as we output.
1458 */
1459 hash.w[0] ^= hash.w[3];
1460 hash.w[1] ^= hash.w[4];
1461 hash.w[2] ^= rol32(hash.w[2], 16);
1462
1463 memcpy(out, &hash, EXTRACT_SIZE);
1464 memzero_explicit(&hash, sizeof(hash));
1465}
1466
1467static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
1468 size_t nbytes, int fips)
1469{
1470 ssize_t ret = 0, i;
1471 __u8 tmp[EXTRACT_SIZE];
1472 unsigned long flags;
1473
1474 while (nbytes) {
1475 extract_buf(r, tmp);
1476
1477 if (fips) {
1478 spin_lock_irqsave(&r->lock, flags);
1479 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1480 panic("Hardware RNG duplicated output!\n");
1481 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1482 spin_unlock_irqrestore(&r->lock, flags);
1483 }
1484 i = min_t(int, nbytes, EXTRACT_SIZE);
1485 memcpy(buf, tmp, i);
1486 nbytes -= i;
1487 buf += i;
1488 ret += i;
1489 }
1490
1491 /* Wipe data just returned from memory */
1492 memzero_explicit(tmp, sizeof(tmp));
1493
1494 return ret;
1495}
1496
1497/*
1498 * This function extracts randomness from the "entropy pool", and
1499 * returns it in a buffer.
1500 *
1501 * The min parameter specifies the minimum amount we can pull before
1502 * failing to avoid races that defeat catastrophic reseeding while the
1503 * reserved parameter indicates how much entropy we must leave in the
1504 * pool after each pull to avoid starving other readers.
1505 */
1506static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1507 size_t nbytes, int min, int reserved)
1508{
1509 __u8 tmp[EXTRACT_SIZE];
1510 unsigned long flags;
1511
1512 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1513 if (fips_enabled) {
1514 spin_lock_irqsave(&r->lock, flags);
1515 if (!r->last_data_init) {
1516 r->last_data_init = 1;
1517 spin_unlock_irqrestore(&r->lock, flags);
1518 trace_extract_entropy(r->name, EXTRACT_SIZE,
1519 ENTROPY_BITS(r), _RET_IP_);
1520 xfer_secondary_pool(r, EXTRACT_SIZE);
1521 extract_buf(r, tmp);
1522 spin_lock_irqsave(&r->lock, flags);
1523 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1524 }
1525 spin_unlock_irqrestore(&r->lock, flags);
1526 }
1527
1528 trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1529 xfer_secondary_pool(r, nbytes);
1530 nbytes = account(r, nbytes, min, reserved);
1531
1532 return _extract_entropy(r, buf, nbytes, fips_enabled);
1533}
1534
1535/*
1536 * This function extracts randomness from the "entropy pool", and
1537 * returns it in a userspace buffer.
1538 */
1539static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1540 size_t nbytes)
1541{
1542 ssize_t ret = 0, i;
1543 __u8 tmp[EXTRACT_SIZE];
1544 int large_request = (nbytes > 256);
1545
1546 trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1547 xfer_secondary_pool(r, nbytes);
1548 nbytes = account(r, nbytes, 0, 0);
1549
1550 while (nbytes) {
1551 if (large_request && need_resched()) {
1552 if (signal_pending(current)) {
1553 if (ret == 0)
1554 ret = -ERESTARTSYS;
1555 break;
1556 }
1557 schedule();
1558 }
1559
1560 extract_buf(r, tmp);
1561 i = min_t(int, nbytes, EXTRACT_SIZE);
1562 if (copy_to_user(buf, tmp, i)) {
1563 ret = -EFAULT;
1564 break;
1565 }
1566
1567 nbytes -= i;
1568 buf += i;
1569 ret += i;
1570 }
1571
1572 /* Wipe data just returned from memory */
1573 memzero_explicit(tmp, sizeof(tmp));
1574
1575 return ret;
1576}
1577
1578#define warn_unseeded_randomness(previous) \
1579 _warn_unseeded_randomness(__func__, (void *) _RET_IP_, (previous))
1580
1581static void _warn_unseeded_randomness(const char *func_name, void *caller,
1582 void **previous)
1583{
1584#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1585 const bool print_once = false;
1586#else
1587 static bool print_once __read_mostly;
1588#endif
1589
1590 if (print_once ||
1591 crng_ready() ||
1592 (previous && (caller == READ_ONCE(*previous))))
1593 return;
1594 WRITE_ONCE(*previous, caller);
1595#ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1596 print_once = true;
1597#endif
1598 if (__ratelimit(&unseeded_warning))
1599 pr_notice("random: %s called from %pS with crng_init=%d\n",
1600 func_name, caller, crng_init);
1601}
1602
1603/*
1604 * This function is the exported kernel interface. It returns some
1605 * number of good random numbers, suitable for key generation, seeding
1606 * TCP sequence numbers, etc. It does not rely on the hardware random
1607 * number generator. For random bytes direct from the hardware RNG
1608 * (when available), use get_random_bytes_arch(). In order to ensure
1609 * that the randomness provided by this function is okay, the function
1610 * wait_for_random_bytes() should be called and return 0 at least once
1611 * at any point prior.
1612 */
1613static void _get_random_bytes(void *buf, int nbytes)
1614{
1615 __u32 tmp[CHACHA20_BLOCK_WORDS];
1616
1617 trace_get_random_bytes(nbytes, _RET_IP_);
1618
1619 while (nbytes >= CHACHA20_BLOCK_SIZE) {
1620 extract_crng(buf);
1621 buf += CHACHA20_BLOCK_SIZE;
1622 nbytes -= CHACHA20_BLOCK_SIZE;
1623 }
1624
1625 if (nbytes > 0) {
1626 extract_crng(tmp);
1627 memcpy(buf, tmp, nbytes);
1628 crng_backtrack_protect(tmp, nbytes);
1629 } else
1630 crng_backtrack_protect(tmp, CHACHA20_BLOCK_SIZE);
1631 memzero_explicit(tmp, sizeof(tmp));
1632}
1633
1634void get_random_bytes(void *buf, int nbytes)
1635{
1636 static void *previous;
1637
1638 warn_unseeded_randomness(&previous);
1639 _get_random_bytes(buf, nbytes);
1640}
1641EXPORT_SYMBOL(get_random_bytes);
1642
1643/*
1644 * Wait for the urandom pool to be seeded and thus guaranteed to supply
1645 * cryptographically secure random numbers. This applies to: the /dev/urandom
1646 * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
1647 * family of functions. Using any of these functions without first calling
1648 * this function forfeits the guarantee of security.
1649 *
1650 * Returns: 0 if the urandom pool has been seeded.
1651 * -ERESTARTSYS if the function was interrupted by a signal.
1652 */
1653int wait_for_random_bytes(void)
1654{
1655 if (likely(crng_ready()))
1656 return 0;
1657 return wait_event_interruptible(crng_init_wait, crng_ready());
1658}
1659EXPORT_SYMBOL(wait_for_random_bytes);
1660
1661/*
1662 * Add a callback function that will be invoked when the nonblocking
1663 * pool is initialised.
1664 *
1665 * returns: 0 if callback is successfully added
1666 * -EALREADY if pool is already initialised (callback not called)
1667 * -ENOENT if module for callback is not alive
1668 */
1669int add_random_ready_callback(struct random_ready_callback *rdy)
1670{
1671 struct module *owner;
1672 unsigned long flags;
1673 int err = -EALREADY;
1674
1675 if (crng_ready())
1676 return err;
1677
1678 owner = rdy->owner;
1679 if (!try_module_get(owner))
1680 return -ENOENT;
1681
1682 spin_lock_irqsave(&random_ready_list_lock, flags);
1683 if (crng_ready())
1684 goto out;
1685
1686 owner = NULL;
1687
1688 list_add(&rdy->list, &random_ready_list);
1689 err = 0;
1690
1691out:
1692 spin_unlock_irqrestore(&random_ready_list_lock, flags);
1693
1694 module_put(owner);
1695
1696 return err;
1697}
1698EXPORT_SYMBOL(add_random_ready_callback);
1699
1700/*
1701 * Delete a previously registered readiness callback function.
1702 */
1703void del_random_ready_callback(struct random_ready_callback *rdy)
1704{
1705 unsigned long flags;
1706 struct module *owner = NULL;
1707
1708 spin_lock_irqsave(&random_ready_list_lock, flags);
1709 if (!list_empty(&rdy->list)) {
1710 list_del_init(&rdy->list);
1711 owner = rdy->owner;
1712 }
1713 spin_unlock_irqrestore(&random_ready_list_lock, flags);
1714
1715 module_put(owner);
1716}
1717EXPORT_SYMBOL(del_random_ready_callback);
1718
1719/*
1720 * This function will use the architecture-specific hardware random
1721 * number generator if it is available. The arch-specific hw RNG will
1722 * almost certainly be faster than what we can do in software, but it
1723 * is impossible to verify that it is implemented securely (as
1724 * opposed, to, say, the AES encryption of a sequence number using a
1725 * key known by the NSA). So it's useful if we need the speed, but
1726 * only if we're willing to trust the hardware manufacturer not to
1727 * have put in a back door.
1728 */
1729void get_random_bytes_arch(void *buf, int nbytes)
1730{
1731 char *p = buf;
1732
1733 trace_get_random_bytes_arch(nbytes, _RET_IP_);
1734 while (nbytes) {
1735 unsigned long v;
1736 int chunk = min(nbytes, (int)sizeof(unsigned long));
1737
1738 if (!arch_get_random_long(&v))
1739 break;
1740
1741 memcpy(p, &v, chunk);
1742 p += chunk;
1743 nbytes -= chunk;
1744 }
1745
1746 if (nbytes)
1747 get_random_bytes(p, nbytes);
1748}
1749EXPORT_SYMBOL(get_random_bytes_arch);
1750
1751
1752/*
1753 * init_std_data - initialize pool with system data
1754 *
1755 * @r: pool to initialize
1756 *
1757 * This function clears the pool's entropy count and mixes some system
1758 * data into the pool to prepare it for use. The pool is not cleared
1759 * as that can only decrease the entropy in the pool.
1760 */
1761static void init_std_data(struct entropy_store *r)
1762{
1763 int i;
1764 ktime_t now = ktime_get_real();
1765 unsigned long rv;
1766
1767 r->last_pulled = jiffies;
1768 mix_pool_bytes(r, &now, sizeof(now));
1769 for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1770 if (!arch_get_random_seed_long(&rv) &&
1771 !arch_get_random_long(&rv))
1772 rv = random_get_entropy();
1773 mix_pool_bytes(r, &rv, sizeof(rv));
1774 }
1775 mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1776}
1777
1778/*
1779 * Note that setup_arch() may call add_device_randomness()
1780 * long before we get here. This allows seeding of the pools
1781 * with some platform dependent data very early in the boot
1782 * process. But it limits our options here. We must use
1783 * statically allocated structures that already have all
1784 * initializations complete at compile time. We should also
1785 * take care not to overwrite the precious per platform data
1786 * we were given.
1787 */
1788static int rand_initialize(void)
1789{
1790 init_std_data(&input_pool);
1791 init_std_data(&blocking_pool);
1792 crng_initialize(&primary_crng);
1793 crng_global_init_time = jiffies;
1794 if (ratelimit_disable) {
1795 urandom_warning.interval = 0;
1796 unseeded_warning.interval = 0;
1797 }
1798 return 0;
1799}
1800early_initcall(rand_initialize);
1801
1802#ifdef CONFIG_BLOCK
1803void rand_initialize_disk(struct gendisk *disk)
1804{
1805 struct timer_rand_state *state;
1806
1807 /*
1808 * If kzalloc returns null, we just won't use that entropy
1809 * source.
1810 */
1811 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1812 if (state) {
1813 state->last_time = INITIAL_JIFFIES;
1814 disk->random = state;
1815 }
1816}
1817#endif
1818
1819static ssize_t
1820_random_read(int nonblock, char __user *buf, size_t nbytes)
1821{
1822 ssize_t n;
1823
1824 if (nbytes == 0)
1825 return 0;
1826
1827 nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1828 while (1) {
1829 n = extract_entropy_user(&blocking_pool, buf, nbytes);
1830 if (n < 0)
1831 return n;
1832 trace_random_read(n*8, (nbytes-n)*8,
1833 ENTROPY_BITS(&blocking_pool),
1834 ENTROPY_BITS(&input_pool));
1835 if (n > 0)
1836 return n;
1837
1838 /* Pool is (near) empty. Maybe wait and retry. */
1839 if (nonblock)
1840 return -EAGAIN;
1841
1842 wait_event_interruptible(random_read_wait,
1843 ENTROPY_BITS(&input_pool) >=
1844 random_read_wakeup_bits);
1845 if (signal_pending(current))
1846 return -ERESTARTSYS;
1847 }
1848}
1849
1850static ssize_t
1851random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1852{
1853 return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1854}
1855
1856static ssize_t
1857urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1858{
1859 unsigned long flags;
1860 static int maxwarn = 10;
1861 int ret;
1862
1863 if (!crng_ready() && maxwarn > 0) {
1864 maxwarn--;
1865 if (__ratelimit(&urandom_warning))
1866 printk(KERN_NOTICE "random: %s: uninitialized "
1867 "urandom read (%zd bytes read)\n",
1868 current->comm, nbytes);
1869 spin_lock_irqsave(&primary_crng.lock, flags);
1870 crng_init_cnt = 0;
1871 spin_unlock_irqrestore(&primary_crng.lock, flags);
1872 }
1873 nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1874 ret = extract_crng_user(buf, nbytes);
1875 trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
1876 return ret;
1877}
1878
1879static __poll_t
1880random_poll(struct file *file, poll_table * wait)
1881{
1882 __poll_t mask;
1883
1884 poll_wait(file, &random_read_wait, wait);
1885 poll_wait(file, &random_write_wait, wait);
1886 mask = 0;
1887 if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1888 mask |= EPOLLIN | EPOLLRDNORM;
1889 if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1890 mask |= EPOLLOUT | EPOLLWRNORM;
1891 return mask;
1892}
1893
1894static int
1895write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1896{
1897 size_t bytes;
1898 __u32 buf[16];
1899 const char __user *p = buffer;
1900
1901 while (count > 0) {
1902 bytes = min(count, sizeof(buf));
1903 if (copy_from_user(&buf, p, bytes))
1904 return -EFAULT;
1905
1906 count -= bytes;
1907 p += bytes;
1908
1909 mix_pool_bytes(r, buf, bytes);
1910 cond_resched();
1911 }
1912
1913 return 0;
1914}
1915
1916static ssize_t random_write(struct file *file, const char __user *buffer,
1917 size_t count, loff_t *ppos)
1918{
1919 size_t ret;
1920
1921 ret = write_pool(&input_pool, buffer, count);
1922 if (ret)
1923 return ret;
1924
1925 return (ssize_t)count;
1926}
1927
1928static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1929{
1930 int size, ent_count;
1931 int __user *p = (int __user *)arg;
1932 int retval;
1933
1934 switch (cmd) {
1935 case RNDGETENTCNT:
1936 /* inherently racy, no point locking */
1937 ent_count = ENTROPY_BITS(&input_pool);
1938 if (put_user(ent_count, p))
1939 return -EFAULT;
1940 return 0;
1941 case RNDADDTOENTCNT:
1942 if (!capable(CAP_SYS_ADMIN))
1943 return -EPERM;
1944 if (get_user(ent_count, p))
1945 return -EFAULT;
1946 return credit_entropy_bits_safe(&input_pool, ent_count);
1947 case RNDADDENTROPY:
1948 if (!capable(CAP_SYS_ADMIN))
1949 return -EPERM;
1950 if (get_user(ent_count, p++))
1951 return -EFAULT;
1952 if (ent_count < 0)
1953 return -EINVAL;
1954 if (get_user(size, p++))
1955 return -EFAULT;
1956 retval = write_pool(&input_pool, (const char __user *)p,
1957 size);
1958 if (retval < 0)
1959 return retval;
1960 return credit_entropy_bits_safe(&input_pool, ent_count);
1961 case RNDZAPENTCNT:
1962 case RNDCLEARPOOL:
1963 /*
1964 * Clear the entropy pool counters. We no longer clear
1965 * the entropy pool, as that's silly.
1966 */
1967 if (!capable(CAP_SYS_ADMIN))
1968 return -EPERM;
1969 input_pool.entropy_count = 0;
1970 blocking_pool.entropy_count = 0;
1971 return 0;
1972 case RNDRESEEDCRNG:
1973 if (!capable(CAP_SYS_ADMIN))
1974 return -EPERM;
1975 if (crng_init < 2)
1976 return -ENODATA;
1977 crng_reseed(&primary_crng, NULL);
1978 crng_global_init_time = jiffies - 1;
1979 return 0;
1980 default:
1981 return -EINVAL;
1982 }
1983}
1984
1985static int random_fasync(int fd, struct file *filp, int on)
1986{
1987 return fasync_helper(fd, filp, on, &fasync);
1988}
1989
1990const struct file_operations random_fops = {
1991 .read = random_read,
1992 .write = random_write,
1993 .poll = random_poll,
1994 .unlocked_ioctl = random_ioctl,
1995 .fasync = random_fasync,
1996 .llseek = noop_llseek,
1997};
1998
1999const struct file_operations urandom_fops = {
2000 .read = urandom_read,
2001 .write = random_write,
2002 .unlocked_ioctl = random_ioctl,
2003 .fasync = random_fasync,
2004 .llseek = noop_llseek,
2005};
2006
2007SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
2008 unsigned int, flags)
2009{
2010 int ret;
2011
2012 if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
2013 return -EINVAL;
2014
2015 if (count > INT_MAX)
2016 count = INT_MAX;
2017
2018 if (flags & GRND_RANDOM)
2019 return _random_read(flags & GRND_NONBLOCK, buf, count);
2020
2021 if (!crng_ready()) {
2022 if (flags & GRND_NONBLOCK)
2023 return -EAGAIN;
2024 ret = wait_for_random_bytes();
2025 if (unlikely(ret))
2026 return ret;
2027 }
2028 return urandom_read(NULL, buf, count, NULL);
2029}
2030
2031/********************************************************************
2032 *
2033 * Sysctl interface
2034 *
2035 ********************************************************************/
2036
2037#ifdef CONFIG_SYSCTL
2038
2039#include <linux/sysctl.h>
2040
2041static int min_read_thresh = 8, min_write_thresh;
2042static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
2043static int max_write_thresh = INPUT_POOL_WORDS * 32;
2044static int random_min_urandom_seed = 60;
2045static char sysctl_bootid[16];
2046
2047/*
2048 * This function is used to return both the bootid UUID, and random
2049 * UUID. The difference is in whether table->data is NULL; if it is,
2050 * then a new UUID is generated and returned to the user.
2051 *
2052 * If the user accesses this via the proc interface, the UUID will be
2053 * returned as an ASCII string in the standard UUID format; if via the
2054 * sysctl system call, as 16 bytes of binary data.
2055 */
2056static int proc_do_uuid(struct ctl_table *table, int write,
2057 void __user *buffer, size_t *lenp, loff_t *ppos)
2058{
2059 struct ctl_table fake_table;
2060 unsigned char buf[64], tmp_uuid[16], *uuid;
2061
2062 uuid = table->data;
2063 if (!uuid) {
2064 uuid = tmp_uuid;
2065 generate_random_uuid(uuid);
2066 } else {
2067 static DEFINE_SPINLOCK(bootid_spinlock);
2068
2069 spin_lock(&bootid_spinlock);
2070 if (!uuid[8])
2071 generate_random_uuid(uuid);
2072 spin_unlock(&bootid_spinlock);
2073 }
2074
2075 sprintf(buf, "%pU", uuid);
2076
2077 fake_table.data = buf;
2078 fake_table.maxlen = sizeof(buf);
2079
2080 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
2081}
2082
2083/*
2084 * Return entropy available scaled to integral bits
2085 */
2086static int proc_do_entropy(struct ctl_table *table, int write,
2087 void __user *buffer, size_t *lenp, loff_t *ppos)
2088{
2089 struct ctl_table fake_table;
2090 int entropy_count;
2091
2092 entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
2093
2094 fake_table.data = &entropy_count;
2095 fake_table.maxlen = sizeof(entropy_count);
2096
2097 return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
2098}
2099
2100static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
2101extern struct ctl_table random_table[];
2102struct ctl_table random_table[] = {
2103 {
2104 .procname = "poolsize",
2105 .data = &sysctl_poolsize,
2106 .maxlen = sizeof(int),
2107 .mode = 0444,
2108 .proc_handler = proc_dointvec,
2109 },
2110 {
2111 .procname = "entropy_avail",
2112 .maxlen = sizeof(int),
2113 .mode = 0444,
2114 .proc_handler = proc_do_entropy,
2115 .data = &input_pool.entropy_count,
2116 },
2117 {
2118 .procname = "read_wakeup_threshold",
2119 .data = &random_read_wakeup_bits,
2120 .maxlen = sizeof(int),
2121 .mode = 0644,
2122 .proc_handler = proc_dointvec_minmax,
2123 .extra1 = &min_read_thresh,
2124 .extra2 = &max_read_thresh,
2125 },
2126 {
2127 .procname = "write_wakeup_threshold",
2128 .data = &random_write_wakeup_bits,
2129 .maxlen = sizeof(int),
2130 .mode = 0644,
2131 .proc_handler = proc_dointvec_minmax,
2132 .extra1 = &min_write_thresh,
2133 .extra2 = &max_write_thresh,
2134 },
2135 {
2136 .procname = "urandom_min_reseed_secs",
2137 .data = &random_min_urandom_seed,
2138 .maxlen = sizeof(int),
2139 .mode = 0644,
2140 .proc_handler = proc_dointvec,
2141 },
2142 {
2143 .procname = "boot_id",
2144 .data = &sysctl_bootid,
2145 .maxlen = 16,
2146 .mode = 0444,
2147 .proc_handler = proc_do_uuid,
2148 },
2149 {
2150 .procname = "uuid",
2151 .maxlen = 16,
2152 .mode = 0444,
2153 .proc_handler = proc_do_uuid,
2154 },
2155#ifdef ADD_INTERRUPT_BENCH
2156 {
2157 .procname = "add_interrupt_avg_cycles",
2158 .data = &avg_cycles,
2159 .maxlen = sizeof(avg_cycles),
2160 .mode = 0444,
2161 .proc_handler = proc_doulongvec_minmax,
2162 },
2163 {
2164 .procname = "add_interrupt_avg_deviation",
2165 .data = &avg_deviation,
2166 .maxlen = sizeof(avg_deviation),
2167 .mode = 0444,
2168 .proc_handler = proc_doulongvec_minmax,
2169 },
2170#endif
2171 { }
2172};
2173#endif /* CONFIG_SYSCTL */
2174
2175struct batched_entropy {
2176 union {
2177 u64 entropy_u64[CHACHA20_BLOCK_SIZE / sizeof(u64)];
2178 u32 entropy_u32[CHACHA20_BLOCK_SIZE / sizeof(u32)];
2179 };
2180 unsigned int position;
2181};
2182static rwlock_t batched_entropy_reset_lock = __RW_LOCK_UNLOCKED(batched_entropy_reset_lock);
2183
2184/*
2185 * Get a random word for internal kernel use only. The quality of the random
2186 * number is either as good as RDRAND or as good as /dev/urandom, with the
2187 * goal of being quite fast and not depleting entropy. In order to ensure
2188 * that the randomness provided by this function is okay, the function
2189 * wait_for_random_bytes() should be called and return 0 at least once
2190 * at any point prior.
2191 */
2192static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64);
2193u64 get_random_u64(void)
2194{
2195 u64 ret;
2196 bool use_lock;
2197 unsigned long flags = 0;
2198 struct batched_entropy *batch;
2199 static void *previous;
2200
2201#if BITS_PER_LONG == 64
2202 if (arch_get_random_long((unsigned long *)&ret))
2203 return ret;
2204#else
2205 if (arch_get_random_long((unsigned long *)&ret) &&
2206 arch_get_random_long((unsigned long *)&ret + 1))
2207 return ret;
2208#endif
2209
2210 warn_unseeded_randomness(&previous);
2211
2212 use_lock = READ_ONCE(crng_init) < 2;
2213 batch = &get_cpu_var(batched_entropy_u64);
2214 if (use_lock)
2215 read_lock_irqsave(&batched_entropy_reset_lock, flags);
2216 if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
2217 extract_crng((__u32 *)batch->entropy_u64);
2218 batch->position = 0;
2219 }
2220 ret = batch->entropy_u64[batch->position++];
2221 if (use_lock)
2222 read_unlock_irqrestore(&batched_entropy_reset_lock, flags);
2223 put_cpu_var(batched_entropy_u64);
2224 return ret;
2225}
2226EXPORT_SYMBOL(get_random_u64);
2227
2228static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32);
2229u32 get_random_u32(void)
2230{
2231 u32 ret;
2232 bool use_lock;
2233 unsigned long flags = 0;
2234 struct batched_entropy *batch;
2235 static void *previous;
2236
2237 if (arch_get_random_int(&ret))
2238 return ret;
2239
2240 warn_unseeded_randomness(&previous);
2241
2242 use_lock = READ_ONCE(crng_init) < 2;
2243 batch = &get_cpu_var(batched_entropy_u32);
2244 if (use_lock)
2245 read_lock_irqsave(&batched_entropy_reset_lock, flags);
2246 if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
2247 extract_crng(batch->entropy_u32);
2248 batch->position = 0;
2249 }
2250 ret = batch->entropy_u32[batch->position++];
2251 if (use_lock)
2252 read_unlock_irqrestore(&batched_entropy_reset_lock, flags);
2253 put_cpu_var(batched_entropy_u32);
2254 return ret;
2255}
2256EXPORT_SYMBOL(get_random_u32);
2257
2258/* It's important to invalidate all potential batched entropy that might
2259 * be stored before the crng is initialized, which we can do lazily by
2260 * simply resetting the counter to zero so that it's re-extracted on the
2261 * next usage. */
2262static void invalidate_batched_entropy(void)
2263{
2264 int cpu;
2265 unsigned long flags;
2266
2267 write_lock_irqsave(&batched_entropy_reset_lock, flags);
2268 for_each_possible_cpu (cpu) {
2269 per_cpu_ptr(&batched_entropy_u32, cpu)->position = 0;
2270 per_cpu_ptr(&batched_entropy_u64, cpu)->position = 0;
2271 }
2272 write_unlock_irqrestore(&batched_entropy_reset_lock, flags);
2273}
2274
2275/**
2276 * randomize_page - Generate a random, page aligned address
2277 * @start: The smallest acceptable address the caller will take.
2278 * @range: The size of the area, starting at @start, within which the
2279 * random address must fall.
2280 *
2281 * If @start + @range would overflow, @range is capped.
2282 *
2283 * NOTE: Historical use of randomize_range, which this replaces, presumed that
2284 * @start was already page aligned. We now align it regardless.
2285 *
2286 * Return: A page aligned address within [start, start + range). On error,
2287 * @start is returned.
2288 */
2289unsigned long
2290randomize_page(unsigned long start, unsigned long range)
2291{
2292 if (!PAGE_ALIGNED(start)) {
2293 range -= PAGE_ALIGN(start) - start;
2294 start = PAGE_ALIGN(start);
2295 }
2296
2297 if (start > ULONG_MAX - range)
2298 range = ULONG_MAX - start;
2299
2300 range >>= PAGE_SHIFT;
2301
2302 if (range == 0)
2303 return start;
2304
2305 return start + (get_random_long() % range << PAGE_SHIFT);
2306}
2307
2308/* Interface for in-kernel drivers of true hardware RNGs.
2309 * Those devices may produce endless random bits and will be throttled
2310 * when our pool is full.
2311 */
2312void add_hwgenerator_randomness(const char *buffer, size_t count,
2313 size_t entropy)
2314{
2315 struct entropy_store *poolp = &input_pool;
2316
2317 if (unlikely(crng_init == 0)) {
2318 crng_fast_load(buffer, count);
2319 return;
2320 }
2321
2322 /* Suspend writing if we're above the trickle threshold.
2323 * We'll be woken up again once below random_write_wakeup_thresh,
2324 * or when the calling thread is about to terminate.
2325 */
2326 wait_event_interruptible(random_write_wait, kthread_should_stop() ||
2327 ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
2328 mix_pool_bytes(poolp, buffer, count);
2329 credit_entropy_bits(poolp, entropy);
2330}
2331EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);