This repository was archived by the owner on Feb 9, 2023. It is now read-only.
forked from torvalds/linux
-
Notifications
You must be signed in to change notification settings - Fork 25
Expand file tree
/
Copy pathrandom.c
More file actions
2231 lines (1963 loc) · 63.8 KB
/
random.c
File metadata and controls
2231 lines (1963 loc) · 63.8 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/*
* random.c -- A strong random number generator
*
* Copyright (C) 2017 Jason A. Donenfeld <[email protected]>. All
* Rights Reserved.
*
* Copyright Matt Mackall <[email protected]>, 2003, 2004, 2005
*
* Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
* rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, and the entire permission notice in its entirety,
* including the disclaimer of warranties.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* ALTERNATIVELY, this product may be distributed under the terms of
* the GNU General Public License, in which case the provisions of the GPL are
* required INSTEAD OF the above restrictions. (This clause is
* necessary due to a potential bad interaction between the GPL and
* the restrictions contained in a BSD-style copyright.)
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
* WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
* USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*/
/*
* (now, with legal B.S. out of the way.....)
*
* This routine gathers environmental noise from device drivers, etc.,
* and returns good random numbers, suitable for cryptographic use.
* Besides the obvious cryptographic uses, these numbers are also good
* for seeding TCP sequence numbers, and other places where it is
* desirable to have numbers which are not only random, but hard to
* predict by an attacker.
*
* Theory of operation
* ===================
*
* Computers are very predictable devices. Hence it is extremely hard
* to produce truly random numbers on a computer --- as opposed to
* pseudo-random numbers, which can easily generated by using a
* algorithm. Unfortunately, it is very easy for attackers to guess
* the sequence of pseudo-random number generators, and for some
* applications this is not acceptable. So instead, we must try to
* gather "environmental noise" from the computer's environment, which
* must be hard for outside attackers to observe, and use that to
* generate random numbers. In a Unix environment, this is best done
* from inside the kernel.
*
* Sources of randomness from the environment include inter-keyboard
* timings, inter-interrupt timings from some interrupts, and other
* events which are both (a) non-deterministic and (b) hard for an
* outside observer to measure. Randomness from these sources are
* added to an "entropy pool", which is mixed using a CRC-like function.
* This is not cryptographically strong, but it is adequate assuming
* the randomness is not chosen maliciously, and it is fast enough that
* the overhead of doing it on every interrupt is very reasonable.
* As random bytes are mixed into the entropy pool, the routines keep
* an *estimate* of how many bits of randomness have been stored into
* the random number generator's internal state.
*
* When random bytes are desired, they are obtained by taking the SHA
* hash of the contents of the "entropy pool". The SHA hash avoids
* exposing the internal state of the entropy pool. It is believed to
* be computationally infeasible to derive any useful information
* about the input of SHA from its output. Even if it is possible to
* analyze SHA in some clever way, as long as the amount of data
* returned from the generator is less than the inherent entropy in
* the pool, the output data is totally unpredictable. For this
* reason, the routine decreases its internal estimate of how many
* bits of "true randomness" are contained in the entropy pool as it
* outputs random numbers.
*
* If this estimate goes to zero, the routine can still generate
* random numbers; however, an attacker may (at least in theory) be
* able to infer the future output of the generator from prior
* outputs. This requires successful cryptanalysis of SHA, which is
* not believed to be feasible, but there is a remote possibility.
* Nonetheless, these numbers should be useful for the vast majority
* of purposes.
*
* Exported interfaces ---- output
* ===============================
*
* There are three exported interfaces; the first is one designed to
* be used from within the kernel:
*
* void get_random_bytes(void *buf, int nbytes);
*
* This interface will return the requested number of random bytes,
* and place it in the requested buffer.
*
* The two other interfaces are two character devices /dev/random and
* /dev/urandom. /dev/random is suitable for use when very high
* quality randomness is desired (for example, for key generation or
* one-time pads), as it will only return a maximum of the number of
* bits of randomness (as estimated by the random number generator)
* contained in the entropy pool.
*
* The /dev/urandom device does not have this limit, and will return
* as many bytes as are requested. As more and more random bytes are
* requested without giving time for the entropy pool to recharge,
* this will result in random numbers that are merely cryptographically
* strong. For many applications, however, this is acceptable.
*
* Exported interfaces ---- input
* ==============================
*
* The current exported interfaces for gathering environmental noise
* from the devices are:
*
* void add_device_randomness(const void *buf, unsigned int size);
* void add_input_randomness(unsigned int type, unsigned int code,
* unsigned int value);
* void add_interrupt_randomness(int irq, int irq_flags);
* void add_disk_randomness(struct gendisk *disk);
*
* add_device_randomness() is for adding data to the random pool that
* is likely to differ between two devices (or possibly even per boot).
* This would be things like MAC addresses or serial numbers, or the
* read-out of the RTC. This does *not* add any actual entropy to the
* pool, but it initializes the pool to different values for devices
* that might otherwise be identical and have very little entropy
* available to them (particularly common in the embedded world).
*
* add_input_randomness() uses the input layer interrupt timing, as well as
* the event type information from the hardware.
*
* add_interrupt_randomness() uses the interrupt timing as random
* inputs to the entropy pool. Using the cycle counters and the irq source
* as inputs, it feeds the randomness roughly once a second.
*
* add_disk_randomness() uses what amounts to the seek time of block
* layer request events, on a per-disk_devt basis, as input to the
* entropy pool. Note that high-speed solid state drives with very low
* seek times do not make for good sources of entropy, as their seek
* times are usually fairly consistent.
*
* All of these routines try to estimate how many bits of randomness a
* particular randomness source. They do this by keeping track of the
* first and second order deltas of the event timings.
*
* Ensuring unpredictability at system startup
* ============================================
*
* When any operating system starts up, it will go through a sequence
* of actions that are fairly predictable by an adversary, especially
* if the start-up does not involve interaction with a human operator.
* This reduces the actual number of bits of unpredictability in the
* entropy pool below the value in entropy_count. In order to
* counteract this effect, it helps to carry information in the
* entropy pool across shut-downs and start-ups. To do this, put the
* following lines an appropriate script which is run during the boot
* sequence:
*
* echo "Initializing random number generator..."
* random_seed=/var/run/random-seed
* # Carry a random seed from start-up to start-up
* # Load and then save the whole entropy pool
* if [ -f $random_seed ]; then
* cat $random_seed >/dev/urandom
* else
* touch $random_seed
* fi
* chmod 600 $random_seed
* dd if=/dev/urandom of=$random_seed count=1 bs=512
*
* and the following lines in an appropriate script which is run as
* the system is shutdown:
*
* # Carry a random seed from shut-down to start-up
* # Save the whole entropy pool
* echo "Saving random seed..."
* random_seed=/var/run/random-seed
* touch $random_seed
* chmod 600 $random_seed
* dd if=/dev/urandom of=$random_seed count=1 bs=512
*
* For example, on most modern systems using the System V init
* scripts, such code fragments would be found in
* /etc/rc.d/init.d/random. On older Linux systems, the correct script
* location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
*
* Effectively, these commands cause the contents of the entropy pool
* to be saved at shut-down time and reloaded into the entropy pool at
* start-up. (The 'dd' in the addition to the bootup script is to
* make sure that /etc/random-seed is different for every start-up,
* even if the system crashes without executing rc.0.) Even with
* complete knowledge of the start-up activities, predicting the state
* of the entropy pool requires knowledge of the previous history of
* the system.
*
* Configuring the /dev/random driver under Linux
* ==============================================
*
* The /dev/random driver under Linux uses minor numbers 8 and 9 of
* the /dev/mem major number (#1). So if your system does not have
* /dev/random and /dev/urandom created already, they can be created
* by using the commands:
*
* mknod /dev/random c 1 8
* mknod /dev/urandom c 1 9
*
* Acknowledgements:
* =================
*
* Ideas for constructing this random number generator were derived
* from Pretty Good Privacy's random number generator, and from private
* discussions with Phil Karn. Colin Plumb provided a faster random
* number generator, which speed up the mixing function of the entropy
* pool, taken from PGPfone. Dale Worley has also contributed many
* useful ideas and suggestions to improve this driver.
*
* Any flaws in the design are solely my responsibility, and should
* not be attributed to the Phil, Colin, or any of authors of PGP.
*
* Further background information on this topic may be obtained from
* RFC 1750, "Randomness Recommendations for Security", by Donald
* Eastlake, Steve Crocker, and Jeff Schiller.
*/
#include <linux/utsname.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/string.h>
#include <linux/fcntl.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/genhd.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/nodemask.h>
#include <linux/spinlock.h>
#include <linux/kthread.h>
#include <linux/percpu.h>
#include <linux/cryptohash.h>
#include <linux/fips.h>
#include <linux/ptrace.h>
#include <linux/workqueue.h>
#include <linux/irq.h>
#include <linux/syscalls.h>
#include <linux/completion.h>
#include <linux/uuid.h>
#include <crypto/chacha20.h>
#include <asm/processor.h>
#include <linux/uaccess.h>
#include <asm/irq.h>
#include <asm/irq_regs.h>
#include <asm/io.h>
#define CREATE_TRACE_POINTS
#include <trace/events/random.h>
/* #define ADD_INTERRUPT_BENCH */
/*
* Configuration information
*/
#define INPUT_POOL_SHIFT 12
#define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
#define OUTPUT_POOL_SHIFT 10
#define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
#define SEC_XFER_SIZE 512
#define EXTRACT_SIZE 10
#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
/*
* To allow fractional bits to be tracked, the entropy_count field is
* denominated in units of 1/8th bits.
*
* 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
* credit_entropy_bits() needs to be 64 bits wide.
*/
#define ENTROPY_SHIFT 3
#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
/*
* The minimum number of bits of entropy before we wake up a read on
* /dev/random. Should be enough to do a significant reseed.
*/
static int random_read_wakeup_bits = 64;
/*
* If the entropy count falls under this number of bits, then we
* should wake up processes which are selecting or polling on write
* access to /dev/random.
*/
static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
/*
* Originally, we used a primitive polynomial of degree .poolwords
* over GF(2). The taps for various sizes are defined below. They
* were chosen to be evenly spaced except for the last tap, which is 1
* to get the twisting happening as fast as possible.
*
* For the purposes of better mixing, we use the CRC-32 polynomial as
* well to make a (modified) twisted Generalized Feedback Shift
* Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
* generators. ACM Transactions on Modeling and Computer Simulation
* 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
* GFSR generators II. ACM Transactions on Modeling and Computer
* Simulation 4:254-266)
*
* Thanks to Colin Plumb for suggesting this.
*
* The mixing operation is much less sensitive than the output hash,
* where we use SHA-1. All that we want of mixing operation is that
* it be a good non-cryptographic hash; i.e. it not produce collisions
* when fed "random" data of the sort we expect to see. As long as
* the pool state differs for different inputs, we have preserved the
* input entropy and done a good job. The fact that an intelligent
* attacker can construct inputs that will produce controlled
* alterations to the pool's state is not important because we don't
* consider such inputs to contribute any randomness. The only
* property we need with respect to them is that the attacker can't
* increase his/her knowledge of the pool's state. Since all
* additions are reversible (knowing the final state and the input,
* you can reconstruct the initial state), if an attacker has any
* uncertainty about the initial state, he/she can only shuffle that
* uncertainty about, but never cause any collisions (which would
* decrease the uncertainty).
*
* Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
* Videau in their paper, "The Linux Pseudorandom Number Generator
* Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
* paper, they point out that we are not using a true Twisted GFSR,
* since Matsumoto & Kurita used a trinomial feedback polynomial (that
* is, with only three taps, instead of the six that we are using).
* As a result, the resulting polynomial is neither primitive nor
* irreducible, and hence does not have a maximal period over
* GF(2**32). They suggest a slight change to the generator
* polynomial which improves the resulting TGFSR polynomial to be
* irreducible, which we have made here.
*/
static struct poolinfo {
int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
int tap1, tap2, tap3, tap4, tap5;
} poolinfo_table[] = {
/* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
/* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
{ S(128), 104, 76, 51, 25, 1 },
/* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
/* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
{ S(32), 26, 19, 14, 7, 1 },
#if 0
/* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
{ S(2048), 1638, 1231, 819, 411, 1 },
/* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
{ S(1024), 817, 615, 412, 204, 1 },
/* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
{ S(1024), 819, 616, 410, 207, 2 },
/* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
{ S(512), 411, 308, 208, 104, 1 },
/* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
{ S(512), 409, 307, 206, 102, 2 },
/* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
{ S(512), 409, 309, 205, 103, 2 },
/* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
{ S(256), 205, 155, 101, 52, 1 },
/* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
{ S(128), 103, 78, 51, 27, 2 },
/* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
{ S(64), 52, 39, 26, 14, 1 },
#endif
};
/*
* Static global variables
*/
static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
static struct fasync_struct *fasync;
static DEFINE_SPINLOCK(random_ready_list_lock);
static LIST_HEAD(random_ready_list);
struct crng_state {
__u32 state[16];
unsigned long init_time;
spinlock_t lock;
};
struct crng_state primary_crng = {
.lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
};
/*
* crng_init = 0 --> Uninitialized
* 1 --> Initialized
* 2 --> Initialized from input_pool
*
* crng_init is protected by primary_crng->lock, and only increases
* its value (from 0->1->2).
*/
static int crng_init = 0;
#define crng_ready() (likely(crng_init > 0))
static int crng_init_cnt = 0;
#define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
static void _extract_crng(struct crng_state *crng,
__u32 out[CHACHA20_BLOCK_WORDS]);
static void _crng_backtrack_protect(struct crng_state *crng,
__u32 tmp[CHACHA20_BLOCK_WORDS], int used);
static void process_random_ready_list(void);
static void _get_random_bytes(void *buf, int nbytes);
/**********************************************************************
*
* OS independent entropy store. Here are the functions which handle
* storing entropy in an entropy pool.
*
**********************************************************************/
struct entropy_store;
struct entropy_store {
/* read-only data: */
const struct poolinfo *poolinfo;
__u32 *pool;
const char *name;
struct entropy_store *pull;
struct work_struct push_work;
/* read-write data: */
unsigned long last_pulled;
spinlock_t lock;
unsigned short add_ptr;
unsigned short input_rotate;
int entropy_count;
int entropy_total;
unsigned int initialized:1;
unsigned int last_data_init:1;
__u8 last_data[EXTRACT_SIZE];
};
static ssize_t extract_entropy(struct entropy_store *r, void *buf,
size_t nbytes, int min, int rsvd);
static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
size_t nbytes, int fips);
static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
static void push_to_pool(struct work_struct *work);
static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy;
static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy;
static struct entropy_store input_pool = {
.poolinfo = &poolinfo_table[0],
.name = "input",
.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
.pool = input_pool_data
};
static struct entropy_store blocking_pool = {
.poolinfo = &poolinfo_table[1],
.name = "blocking",
.pull = &input_pool,
.lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
.pool = blocking_pool_data,
.push_work = __WORK_INITIALIZER(blocking_pool.push_work,
push_to_pool),
};
static __u32 const twist_table[8] = {
0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
/*
* This function adds bytes into the entropy "pool". It does not
* update the entropy estimate. The caller should call
* credit_entropy_bits if this is appropriate.
*
* The pool is stirred with a primitive polynomial of the appropriate
* degree, and then twisted. We twist by three bits at a time because
* it's cheap to do so and helps slightly in the expected case where
* the entropy is concentrated in the low-order bits.
*/
static void _mix_pool_bytes(struct entropy_store *r, const void *in,
int nbytes)
{
unsigned long i, tap1, tap2, tap3, tap4, tap5;
int input_rotate;
int wordmask = r->poolinfo->poolwords - 1;
const char *bytes = in;
__u32 w;
tap1 = r->poolinfo->tap1;
tap2 = r->poolinfo->tap2;
tap3 = r->poolinfo->tap3;
tap4 = r->poolinfo->tap4;
tap5 = r->poolinfo->tap5;
input_rotate = r->input_rotate;
i = r->add_ptr;
/* mix one byte at a time to simplify size handling and churn faster */
while (nbytes--) {
w = rol32(*bytes++, input_rotate);
i = (i - 1) & wordmask;
/* XOR in the various taps */
w ^= r->pool[i];
w ^= r->pool[(i + tap1) & wordmask];
w ^= r->pool[(i + tap2) & wordmask];
w ^= r->pool[(i + tap3) & wordmask];
w ^= r->pool[(i + tap4) & wordmask];
w ^= r->pool[(i + tap5) & wordmask];
/* Mix the result back in with a twist */
r->pool[i] = (w >> 3) ^ twist_table[w & 7];
/*
* Normally, we add 7 bits of rotation to the pool.
* At the beginning of the pool, add an extra 7 bits
* rotation, so that successive passes spread the
* input bits across the pool evenly.
*/
input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
}
r->input_rotate = input_rotate;
r->add_ptr = i;
}
static void __mix_pool_bytes(struct entropy_store *r, const void *in,
int nbytes)
{
trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
_mix_pool_bytes(r, in, nbytes);
}
static void mix_pool_bytes(struct entropy_store *r, const void *in,
int nbytes)
{
unsigned long flags;
trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
spin_lock_irqsave(&r->lock, flags);
_mix_pool_bytes(r, in, nbytes);
spin_unlock_irqrestore(&r->lock, flags);
}
struct fast_pool {
__u32 pool[4];
unsigned long last;
unsigned short reg_idx;
unsigned char count;
};
/*
* This is a fast mixing routine used by the interrupt randomness
* collector. It's hardcoded for an 128 bit pool and assumes that any
* locks that might be needed are taken by the caller.
*/
static void fast_mix(struct fast_pool *f)
{
__u32 a = f->pool[0], b = f->pool[1];
__u32 c = f->pool[2], d = f->pool[3];
a += b; c += d;
b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
a += b; c += d;
b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
a += b; c += d;
b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
a += b; c += d;
b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
f->pool[0] = a; f->pool[1] = b;
f->pool[2] = c; f->pool[3] = d;
f->count++;
}
static void process_random_ready_list(void)
{
unsigned long flags;
struct random_ready_callback *rdy, *tmp;
spin_lock_irqsave(&random_ready_list_lock, flags);
list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
struct module *owner = rdy->owner;
list_del_init(&rdy->list);
rdy->func(rdy);
module_put(owner);
}
spin_unlock_irqrestore(&random_ready_list_lock, flags);
}
/*
* Credit (or debit) the entropy store with n bits of entropy.
* Use credit_entropy_bits_safe() if the value comes from userspace
* or otherwise should be checked for extreme values.
*/
static void credit_entropy_bits(struct entropy_store *r, int nbits)
{
int entropy_count, orig;
const int pool_size = r->poolinfo->poolfracbits;
int nfrac = nbits << ENTROPY_SHIFT;
if (!nbits)
return;
retry:
entropy_count = orig = READ_ONCE(r->entropy_count);
if (nfrac < 0) {
/* Debit */
entropy_count += nfrac;
} else {
/*
* Credit: we have to account for the possibility of
* overwriting already present entropy. Even in the
* ideal case of pure Shannon entropy, new contributions
* approach the full value asymptotically:
*
* entropy <- entropy + (pool_size - entropy) *
* (1 - exp(-add_entropy/pool_size))
*
* For add_entropy <= pool_size/2 then
* (1 - exp(-add_entropy/pool_size)) >=
* (add_entropy/pool_size)*0.7869...
* so we can approximate the exponential with
* 3/4*add_entropy/pool_size and still be on the
* safe side by adding at most pool_size/2 at a time.
*
* The use of pool_size-2 in the while statement is to
* prevent rounding artifacts from making the loop
* arbitrarily long; this limits the loop to log2(pool_size)*2
* turns no matter how large nbits is.
*/
int pnfrac = nfrac;
const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
/* The +2 corresponds to the /4 in the denominator */
do {
unsigned int anfrac = min(pnfrac, pool_size/2);
unsigned int add =
((pool_size - entropy_count)*anfrac*3) >> s;
entropy_count += add;
pnfrac -= anfrac;
} while (unlikely(entropy_count < pool_size-2 && pnfrac));
}
if (unlikely(entropy_count < 0)) {
pr_warn("random: negative entropy/overflow: pool %s count %d\n",
r->name, entropy_count);
WARN_ON(1);
entropy_count = 0;
} else if (entropy_count > pool_size)
entropy_count = pool_size;
if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
goto retry;
r->entropy_total += nbits;
if (!r->initialized && r->entropy_total > 128) {
r->initialized = 1;
r->entropy_total = 0;
}
trace_credit_entropy_bits(r->name, nbits,
entropy_count >> ENTROPY_SHIFT,
r->entropy_total, _RET_IP_);
if (r == &input_pool) {
int entropy_bits = entropy_count >> ENTROPY_SHIFT;
if (crng_init < 2 && entropy_bits >= 128) {
crng_reseed(&primary_crng, r);
entropy_bits = r->entropy_count >> ENTROPY_SHIFT;
}
/* should we wake readers? */
if (entropy_bits >= random_read_wakeup_bits) {
wake_up_interruptible(&random_read_wait);
kill_fasync(&fasync, SIGIO, POLL_IN);
}
/* If the input pool is getting full, send some
* entropy to the blocking pool until it is 75% full.
*/
if (entropy_bits > random_write_wakeup_bits &&
r->initialized &&
r->entropy_total >= 2*random_read_wakeup_bits) {
struct entropy_store *other = &blocking_pool;
if (other->entropy_count <=
3 * other->poolinfo->poolfracbits / 4) {
schedule_work(&other->push_work);
r->entropy_total = 0;
}
}
}
}
static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
{
const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
if (nbits < 0)
return -EINVAL;
/* Cap the value to avoid overflows */
nbits = min(nbits, nbits_max);
credit_entropy_bits(r, nbits);
return 0;
}
/*********************************************************************
*
* CRNG using CHACHA20
*
*********************************************************************/
#define CRNG_RESEED_INTERVAL (300*HZ)
static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
#ifdef CONFIG_NUMA
/*
* Hack to deal with crazy userspace progams when they are all trying
* to access /dev/urandom in parallel. The programs are almost
* certainly doing something terribly wrong, but we'll work around
* their brain damage.
*/
static struct crng_state **crng_node_pool __read_mostly;
#endif
static void invalidate_batched_entropy(void);
static void crng_initialize(struct crng_state *crng)
{
int i;
unsigned long rv;
memcpy(&crng->state[0], "expand 32-byte k", 16);
if (crng == &primary_crng)
_extract_entropy(&input_pool, &crng->state[4],
sizeof(__u32) * 12, 0);
else
_get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
for (i = 4; i < 16; i++) {
if (!arch_get_random_seed_long(&rv) &&
!arch_get_random_long(&rv))
rv = random_get_entropy();
crng->state[i] ^= rv;
}
crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
}
static int crng_fast_load(const char *cp, size_t len)
{
unsigned long flags;
char *p;
if (!spin_trylock_irqsave(&primary_crng.lock, flags))
return 0;
if (crng_ready()) {
spin_unlock_irqrestore(&primary_crng.lock, flags);
return 0;
}
p = (unsigned char *) &primary_crng.state[4];
while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
p[crng_init_cnt % CHACHA20_KEY_SIZE] ^= *cp;
cp++; crng_init_cnt++; len--;
}
spin_unlock_irqrestore(&primary_crng.lock, flags);
if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
invalidate_batched_entropy();
crng_init = 1;
wake_up_interruptible(&crng_init_wait);
pr_notice("random: fast init done\n");
}
return 1;
}
static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
{
unsigned long flags;
int i, num;
union {
__u32 block[CHACHA20_BLOCK_WORDS];
__u32 key[8];
} buf;
if (r) {
num = extract_entropy(r, &buf, 32, 16, 0);
if (num == 0)
return;
} else {
_extract_crng(&primary_crng, buf.block);
_crng_backtrack_protect(&primary_crng, buf.block,
CHACHA20_KEY_SIZE);
}
spin_lock_irqsave(&primary_crng.lock, flags);
for (i = 0; i < 8; i++) {
unsigned long rv;
if (!arch_get_random_seed_long(&rv) &&
!arch_get_random_long(&rv))
rv = random_get_entropy();
crng->state[i+4] ^= buf.key[i] ^ rv;
}
memzero_explicit(&buf, sizeof(buf));
crng->init_time = jiffies;
spin_unlock_irqrestore(&primary_crng.lock, flags);
if (crng == &primary_crng && crng_init < 2) {
invalidate_batched_entropy();
crng_init = 2;
process_random_ready_list();
wake_up_interruptible(&crng_init_wait);
pr_notice("random: crng init done\n");
}
}
static void _extract_crng(struct crng_state *crng,
__u32 out[CHACHA20_BLOCK_WORDS])
{
unsigned long v, flags;
if (crng_init > 1 &&
time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL))
crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
spin_lock_irqsave(&crng->lock, flags);
if (arch_get_random_long(&v))
crng->state[14] ^= v;
chacha20_block(&crng->state[0], out);
if (crng->state[12] == 0)
crng->state[13]++;
spin_unlock_irqrestore(&crng->lock, flags);
}
static void extract_crng(__u32 out[CHACHA20_BLOCK_WORDS])
{
struct crng_state *crng = NULL;
#ifdef CONFIG_NUMA
if (crng_node_pool)
crng = crng_node_pool[numa_node_id()];
if (crng == NULL)
#endif
crng = &primary_crng;
_extract_crng(crng, out);
}
/*
* Use the leftover bytes from the CRNG block output (if there is
* enough) to mutate the CRNG key to provide backtracking protection.
*/
static void _crng_backtrack_protect(struct crng_state *crng,
__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
{
unsigned long flags;
__u32 *s, *d;
int i;
used = round_up(used, sizeof(__u32));
if (used + CHACHA20_KEY_SIZE > CHACHA20_BLOCK_SIZE) {
extract_crng(tmp);
used = 0;
}
spin_lock_irqsave(&crng->lock, flags);
s = &tmp[used / sizeof(__u32)];
d = &crng->state[4];
for (i=0; i < 8; i++)
*d++ ^= *s++;
spin_unlock_irqrestore(&crng->lock, flags);
}
static void crng_backtrack_protect(__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
{
struct crng_state *crng = NULL;
#ifdef CONFIG_NUMA
if (crng_node_pool)
crng = crng_node_pool[numa_node_id()];
if (crng == NULL)
#endif
crng = &primary_crng;
_crng_backtrack_protect(crng, tmp, used);
}
static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
{
ssize_t ret = 0, i = CHACHA20_BLOCK_SIZE;
__u32 tmp[CHACHA20_BLOCK_WORDS];
int large_request = (nbytes > 256);
while (nbytes) {
if (large_request && need_resched()) {
if (signal_pending(current)) {
if (ret == 0)
ret = -ERESTARTSYS;
break;
}
schedule();
}
extract_crng(tmp);
i = min_t(int, nbytes, CHACHA20_BLOCK_SIZE);
if (copy_to_user(buf, tmp, i)) {
ret = -EFAULT;
break;
}
nbytes -= i;
buf += i;
ret += i;
}
crng_backtrack_protect(tmp, i);
/* Wipe data just written to memory */
memzero_explicit(tmp, sizeof(tmp));
return ret;
}
/*********************************************************************
*
* Entropy input management
*
*********************************************************************/
/* There is one of these per entropy source */
struct timer_rand_state {
cycles_t last_time;
long last_delta, last_delta2;
unsigned dont_count_entropy:1;
};
#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
/*
* Add device- or boot-specific data to the input pool to help
* initialize it.
*
* None of this adds any entropy; it is meant to avoid the problem of
* the entropy pool having similar initial state across largely
* identical devices.
*/
void add_device_randomness(const void *buf, unsigned int size)
{
unsigned long time = random_get_entropy() ^ jiffies;
unsigned long flags;
if (!crng_ready()) {
crng_fast_load(buf, size);
return;
}
trace_add_device_randomness(size, _RET_IP_);
spin_lock_irqsave(&input_pool.lock, flags);
_mix_pool_bytes(&input_pool, buf, size);
_mix_pool_bytes(&input_pool, &time, sizeof(time));
spin_unlock_irqrestore(&input_pool.lock, flags);
}
EXPORT_SYMBOL(add_device_randomness);
static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
/*
* This function adds entropy to the entropy "pool" by using timing