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/chacha.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*CHACHA_KEY_SIZE)
435static void _extract_crng(struct crng_state *crng, __u8 out[CHACHA_BLOCK_SIZE]);
436static void _crng_backtrack_protect(struct crng_state *crng,
437 __u8 tmp[CHACHA_BLOCK_SIZE], int used);
438static void process_random_ready_list(void);
439static void _get_random_bytes(void *buf, int nbytes);
440
441static struct ratelimit_state unseeded_warning =
442 RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
443static struct ratelimit_state urandom_warning =
444 RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
445
446static int ratelimit_disable __read_mostly;
447
448module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
449MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
450
451/**********************************************************************
452 *
453 * OS independent entropy store. Here are the functions which handle
454 * storing entropy in an entropy pool.
455 *
456 **********************************************************************/
457
458struct entropy_store;
459struct entropy_store {
460 /* read-only data: */
461 const struct poolinfo *poolinfo;
462 __u32 *pool;
463 const char *name;
464 struct entropy_store *pull;
465 struct work_struct push_work;
466
467 /* read-write data: */
468 unsigned long last_pulled;
469 spinlock_t lock;
470 unsigned short add_ptr;
471 unsigned short input_rotate;
472 int entropy_count;
473 int entropy_total;
474 unsigned int initialized:1;
475 unsigned int last_data_init:1;
476 __u8 last_data[EXTRACT_SIZE];
477};
478
479static ssize_t extract_entropy(struct entropy_store *r, void *buf,
480 size_t nbytes, int min, int rsvd);
481static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
482 size_t nbytes, int fips);
483
484static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
485static void push_to_pool(struct work_struct *work);
486static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy;
487static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy;
488
489static struct entropy_store input_pool = {
490 .poolinfo = &poolinfo_table[0],
491 .name = "input",
492 .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
493 .pool = input_pool_data
494};
495
496static struct entropy_store blocking_pool = {
497 .poolinfo = &poolinfo_table[1],
498 .name = "blocking",
499 .pull = &input_pool,
500 .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
501 .pool = blocking_pool_data,
502 .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
503 push_to_pool),
504};
505
506static __u32 const twist_table[8] = {
507 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
508 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
509
510/*
511 * This function adds bytes into the entropy "pool". It does not
512 * update the entropy estimate. The caller should call
513 * credit_entropy_bits if this is appropriate.
514 *
515 * The pool is stirred with a primitive polynomial of the appropriate
516 * degree, and then twisted. We twist by three bits at a time because
517 * it's cheap to do so and helps slightly in the expected case where
518 * the entropy is concentrated in the low-order bits.
519 */
520static void _mix_pool_bytes(struct entropy_store *r, const void *in,
521 int nbytes)
522{
523 unsigned long i, tap1, tap2, tap3, tap4, tap5;
524 int input_rotate;
525 int wordmask = r->poolinfo->poolwords - 1;
526 const char *bytes = in;
527 __u32 w;
528
529 tap1 = r->poolinfo->tap1;
530 tap2 = r->poolinfo->tap2;
531 tap3 = r->poolinfo->tap3;
532 tap4 = r->poolinfo->tap4;
533 tap5 = r->poolinfo->tap5;
534
535 input_rotate = r->input_rotate;
536 i = r->add_ptr;
537
538 /* mix one byte at a time to simplify size handling and churn faster */
539 while (nbytes--) {
540 w = rol32(*bytes++, input_rotate);
541 i = (i - 1) & wordmask;
542
543 /* XOR in the various taps */
544 w ^= r->pool[i];
545 w ^= r->pool[(i + tap1) & wordmask];
546 w ^= r->pool[(i + tap2) & wordmask];
547 w ^= r->pool[(i + tap3) & wordmask];
548 w ^= r->pool[(i + tap4) & wordmask];
549 w ^= r->pool[(i + tap5) & wordmask];
550
551 /* Mix the result back in with a twist */
552 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
553
554 /*
555 * Normally, we add 7 bits of rotation to the pool.
556 * At the beginning of the pool, add an extra 7 bits
557 * rotation, so that successive passes spread the
558 * input bits across the pool evenly.
559 */
560 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
561 }
562
563 r->input_rotate = input_rotate;
564 r->add_ptr = i;
565}
566
567static void __mix_pool_bytes(struct entropy_store *r, const void *in,
568 int nbytes)
569{
570 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
571 _mix_pool_bytes(r, in, nbytes);
572}
573
574static void mix_pool_bytes(struct entropy_store *r, const void *in,
575 int nbytes)
576{
577 unsigned long flags;
578
579 trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
580 spin_lock_irqsave(&r->lock, flags);
581 _mix_pool_bytes(r, in, nbytes);
582 spin_unlock_irqrestore(&r->lock, flags);
583}
584
585struct fast_pool {
586 __u32 pool[4];
587 unsigned long last;
588 unsigned short reg_idx;
589 unsigned char count;
590};
591
592/*
593 * This is a fast mixing routine used by the interrupt randomness
594 * collector. It's hardcoded for an 128 bit pool and assumes that any
595 * locks that might be needed are taken by the caller.
596 */
597static void fast_mix(struct fast_pool *f)
598{
599 __u32 a = f->pool[0], b = f->pool[1];
600 __u32 c = f->pool[2], d = f->pool[3];
601
602 a += b; c += d;
603 b = rol32(b, 6); d = rol32(d, 27);
604 d ^= a; b ^= c;
605
606 a += b; c += d;
607 b = rol32(b, 16); d = rol32(d, 14);
608 d ^= a; b ^= c;
609
610 a += b; c += d;
611 b = rol32(b, 6); d = rol32(d, 27);
612 d ^= a; b ^= c;
613
614 a += b; c += d;
615 b = rol32(b, 16); d = rol32(d, 14);
616 d ^= a; b ^= c;
617
618 f->pool[0] = a; f->pool[1] = b;
619 f->pool[2] = c; f->pool[3] = d;
620 f->count++;
621}
622
623static void process_random_ready_list(void)
624{
625 unsigned long flags;
626 struct random_ready_callback *rdy, *tmp;
627
628 spin_lock_irqsave(&random_ready_list_lock, flags);
629 list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
630 struct module *owner = rdy->owner;
631
632 list_del_init(&rdy->list);
633 rdy->func(rdy);
634 module_put(owner);
635 }
636 spin_unlock_irqrestore(&random_ready_list_lock, flags);
637}
638
639/*
640 * Credit (or debit) the entropy store with n bits of entropy.
641 * Use credit_entropy_bits_safe() if the value comes from userspace
642 * or otherwise should be checked for extreme values.
643 */
644static void credit_entropy_bits(struct entropy_store *r, int nbits)
645{
646 int entropy_count, orig;
647 const int pool_size = r->poolinfo->poolfracbits;
648 int nfrac = nbits << ENTROPY_SHIFT;
649
650 if (!nbits)
651 return;
652
653retry:
654 entropy_count = orig = READ_ONCE(r->entropy_count);
655 if (nfrac < 0) {
656 /* Debit */
657 entropy_count += nfrac;
658 } else {
659 /*
660 * Credit: we have to account for the possibility of
661 * overwriting already present entropy. Even in the
662 * ideal case of pure Shannon entropy, new contributions
663 * approach the full value asymptotically:
664 *
665 * entropy <- entropy + (pool_size - entropy) *
666 * (1 - exp(-add_entropy/pool_size))
667 *
668 * For add_entropy <= pool_size/2 then
669 * (1 - exp(-add_entropy/pool_size)) >=
670 * (add_entropy/pool_size)*0.7869...
671 * so we can approximate the exponential with
672 * 3/4*add_entropy/pool_size and still be on the
673 * safe side by adding at most pool_size/2 at a time.
674 *
675 * The use of pool_size-2 in the while statement is to
676 * prevent rounding artifacts from making the loop
677 * arbitrarily long; this limits the loop to log2(pool_size)*2
678 * turns no matter how large nbits is.
679 */
680 int pnfrac = nfrac;
681 const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
682 /* The +2 corresponds to the /4 in the denominator */
683
684 do {
685 unsigned int anfrac = min(pnfrac, pool_size/2);
686 unsigned int add =
687 ((pool_size - entropy_count)*anfrac*3) >> s;
688
689 entropy_count += add;
690 pnfrac -= anfrac;
691 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
692 }
693
694 if (unlikely(entropy_count < 0)) {
695 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
696 r->name, entropy_count);
697 WARN_ON(1);
698 entropy_count = 0;
699 } else if (entropy_count > pool_size)
700 entropy_count = pool_size;
701 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
702 goto retry;
703
704 r->entropy_total += nbits;
705 if (!r->initialized && r->entropy_total > 128) {
706 r->initialized = 1;
707 r->entropy_total = 0;
708 }
709
710 trace_credit_entropy_bits(r->name, nbits,
711 entropy_count >> ENTROPY_SHIFT,
712 r->entropy_total, _RET_IP_);
713
714 if (r == &input_pool) {
715 int entropy_bits = entropy_count >> ENTROPY_SHIFT;
716
717 if (crng_init < 2 && entropy_bits >= 128) {
718 crng_reseed(&primary_crng, r);
719 entropy_bits = r->entropy_count >> ENTROPY_SHIFT;
720 }
721
722 /* should we wake readers? */
723 if (entropy_bits >= random_read_wakeup_bits &&
724 wq_has_sleeper(&random_read_wait)) {
725 wake_up_interruptible(&random_read_wait);
726 kill_fasync(&fasync, SIGIO, POLL_IN);
727 }
728 /* If the input pool is getting full, send some
729 * entropy to the blocking pool until it is 75% full.
730 */
731 if (entropy_bits > random_write_wakeup_bits &&
732 r->initialized &&
733 r->entropy_total >= 2*random_read_wakeup_bits) {
734 struct entropy_store *other = &blocking_pool;
735
736 if (other->entropy_count <=
737 3 * other->poolinfo->poolfracbits / 4) {
738 schedule_work(&other->push_work);
739 r->entropy_total = 0;
740 }
741 }
742 }
743}
744
745static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
746{
747 const int nbits_max = r->poolinfo->poolwords * 32;
748
749 if (nbits < 0)
750 return -EINVAL;
751
752 /* Cap the value to avoid overflows */
753 nbits = min(nbits, nbits_max);
754
755 credit_entropy_bits(r, nbits);
756 return 0;
757}
758
759/*********************************************************************
760 *
761 * CRNG using CHACHA20
762 *
763 *********************************************************************/
764
765#define CRNG_RESEED_INTERVAL (300*HZ)
766
767static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
768
769#ifdef CONFIG_NUMA
770/*
771 * Hack to deal with crazy userspace progams when they are all trying
772 * to access /dev/urandom in parallel. The programs are almost
773 * certainly doing something terribly wrong, but we'll work around
774 * their brain damage.
775 */
776static struct crng_state **crng_node_pool __read_mostly;
777#endif
778
779static void invalidate_batched_entropy(void);
780
781static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
782static int __init parse_trust_cpu(char *arg)
783{
784 return kstrtobool(arg, &trust_cpu);
785}
786early_param("random.trust_cpu", parse_trust_cpu);
787
788static void crng_initialize(struct crng_state *crng)
789{
790 int i;
791 int arch_init = 1;
792 unsigned long rv;
793
794 memcpy(&crng->state[0], "expand 32-byte k", 16);
795 if (crng == &primary_crng)
796 _extract_entropy(&input_pool, &crng->state[4],
797 sizeof(__u32) * 12, 0);
798 else
799 _get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
800 for (i = 4; i < 16; i++) {
801 if (!arch_get_random_seed_long(&rv) &&
802 !arch_get_random_long(&rv)) {
803 rv = random_get_entropy();
804 arch_init = 0;
805 }
806 crng->state[i] ^= rv;
807 }
808 if (trust_cpu && arch_init) {
809 crng_init = 2;
810 pr_notice("random: crng done (trusting CPU's manufacturer)\n");
811 }
812 crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
813}
814
815#ifdef CONFIG_NUMA
816static void do_numa_crng_init(struct work_struct *work)
817{
818 int i;
819 struct crng_state *crng;
820 struct crng_state **pool;
821
822 pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
823 for_each_online_node(i) {
824 crng = kmalloc_node(sizeof(struct crng_state),
825 GFP_KERNEL | __GFP_NOFAIL, i);
826 spin_lock_init(&crng->lock);
827 crng_initialize(crng);
828 pool[i] = crng;
829 }
830 mb();
831 if (cmpxchg(&crng_node_pool, NULL, pool)) {
832 for_each_node(i)
833 kfree(pool[i]);
834 kfree(pool);
835 }
836}
837
838static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init);
839
840static void numa_crng_init(void)
841{
842 schedule_work(&numa_crng_init_work);
843}
844#else
845static void numa_crng_init(void) {}
846#endif
847
848/*
849 * crng_fast_load() can be called by code in the interrupt service
850 * path. So we can't afford to dilly-dally.
851 */
852static int crng_fast_load(const char *cp, size_t len)
853{
854 unsigned long flags;
855 char *p;
856
857 if (!spin_trylock_irqsave(&primary_crng.lock, flags))
858 return 0;
859 if (crng_init != 0) {
860 spin_unlock_irqrestore(&primary_crng.lock, flags);
861 return 0;
862 }
863 p = (unsigned char *) &primary_crng.state[4];
864 while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
865 p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp;
866 cp++; crng_init_cnt++; len--;
867 }
868 spin_unlock_irqrestore(&primary_crng.lock, flags);
869 if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
870 invalidate_batched_entropy();
871 crng_init = 1;
872 wake_up_interruptible(&crng_init_wait);
873 pr_notice("random: fast init done\n");
874 }
875 return 1;
876}
877
878/*
879 * crng_slow_load() is called by add_device_randomness, which has two
880 * attributes. (1) We can't trust the buffer passed to it is
881 * guaranteed to be unpredictable (so it might not have any entropy at
882 * all), and (2) it doesn't have the performance constraints of
883 * crng_fast_load().
884 *
885 * So we do something more comprehensive which is guaranteed to touch
886 * all of the primary_crng's state, and which uses a LFSR with a
887 * period of 255 as part of the mixing algorithm. Finally, we do
888 * *not* advance crng_init_cnt since buffer we may get may be something
889 * like a fixed DMI table (for example), which might very well be
890 * unique to the machine, but is otherwise unvarying.
891 */
892static int crng_slow_load(const char *cp, size_t len)
893{
894 unsigned long flags;
895 static unsigned char lfsr = 1;
896 unsigned char tmp;
897 unsigned i, max = CHACHA_KEY_SIZE;
898 const char * src_buf = cp;
899 char * dest_buf = (char *) &primary_crng.state[4];
900
901 if (!spin_trylock_irqsave(&primary_crng.lock, flags))
902 return 0;
903 if (crng_init != 0) {
904 spin_unlock_irqrestore(&primary_crng.lock, flags);
905 return 0;
906 }
907 if (len > max)
908 max = len;
909
910 for (i = 0; i < max ; i++) {
911 tmp = lfsr;
912 lfsr >>= 1;
913 if (tmp & 1)
914 lfsr ^= 0xE1;
915 tmp = dest_buf[i % CHACHA_KEY_SIZE];
916 dest_buf[i % CHACHA_KEY_SIZE] ^= src_buf[i % len] ^ lfsr;
917 lfsr += (tmp << 3) | (tmp >> 5);
918 }
919 spin_unlock_irqrestore(&primary_crng.lock, flags);
920 return 1;
921}
922
923static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
924{
925 unsigned long flags;
926 int i, num;
927 union {
928 __u8 block[CHACHA_BLOCK_SIZE];
929 __u32 key[8];
930 } buf;
931
932 if (r) {
933 num = extract_entropy(r, &buf, 32, 16, 0);
934 if (num == 0)
935 return;
936 } else {
937 _extract_crng(&primary_crng, buf.block);
938 _crng_backtrack_protect(&primary_crng, buf.block,
939 CHACHA_KEY_SIZE);
940 }
941 spin_lock_irqsave(&crng->lock, flags);
942 for (i = 0; i < 8; i++) {
943 unsigned long rv;
944 if (!arch_get_random_seed_long(&rv) &&
945 !arch_get_random_long(&rv))
946 rv = random_get_entropy();
947 crng->state[i+4] ^= buf.key[i] ^ rv;
948 }
949 memzero_explicit(&buf, sizeof(buf));
950 crng->init_time = jiffies;
951 spin_unlock_irqrestore(&crng->lock, flags);
952 if (crng == &primary_crng && crng_init < 2) {
953 invalidate_batched_entropy();
954 numa_crng_init();
955 crng_init = 2;
956 process_random_ready_list();
957 wake_up_interruptible(&crng_init_wait);
958 pr_notice("random: crng init done\n");
959 if (unseeded_warning.missed) {
960 pr_notice("random: %d get_random_xx warning(s) missed "
961 "due to ratelimiting\n",
962 unseeded_warning.missed);
963 unseeded_warning.missed = 0;
964 }
965 if (urandom_warning.missed) {
966 pr_notice("random: %d urandom warning(s) missed "
967 "due to ratelimiting\n",
968 urandom_warning.missed);
969 urandom_warning.missed = 0;
970 }
971 }
972}
973
974static void _extract_crng(struct crng_state *crng,
975 __u8 out[CHACHA_BLOCK_SIZE])
976{
977 unsigned long v, flags;
978
979 if (crng_ready() &&
980 (time_after(crng_global_init_time, crng->init_time) ||
981 time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
982 crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
983 spin_lock_irqsave(&crng->lock, flags);
984 if (arch_get_random_long(&v))
985 crng->state[14] ^= v;
986 chacha20_block(&crng->state[0], out);
987 if (crng->state[12] == 0)
988 crng->state[13]++;
989 spin_unlock_irqrestore(&crng->lock, flags);
990}
991
992static void extract_crng(__u8 out[CHACHA_BLOCK_SIZE])
993{
994 struct crng_state *crng = NULL;
995
996#ifdef CONFIG_NUMA
997 if (crng_node_pool)
998 crng = crng_node_pool[numa_node_id()];
999 if (crng == NULL)
1000#endif
1001 crng = &primary_crng;
1002 _extract_crng(crng, out);
1003}
1004
1005/*
1006 * Use the leftover bytes from the CRNG block output (if there is
1007 * enough) to mutate the CRNG key to provide backtracking protection.
1008 */
1009static void _crng_backtrack_protect(struct crng_state *crng,
1010 __u8 tmp[CHACHA_BLOCK_SIZE], int used)
1011{
1012 unsigned long flags;
1013 __u32 *s, *d;
1014 int i;
1015
1016 used = round_up(used, sizeof(__u32));
1017 if (used + CHACHA_KEY_SIZE > CHACHA_BLOCK_SIZE) {
1018 extract_crng(tmp);
1019 used = 0;
1020 }
1021 spin_lock_irqsave(&crng->lock, flags);
1022 s = (__u32 *) &tmp[used];
1023 d = &crng->state[4];
1024 for (i=0; i < 8; i++)
1025 *d++ ^= *s++;
1026 spin_unlock_irqrestore(&crng->lock, flags);
1027}
1028
1029static void crng_backtrack_protect(__u8 tmp[CHACHA_BLOCK_SIZE], int used)
1030{
1031 struct crng_state *crng = NULL;
1032
1033#ifdef CONFIG_NUMA
1034 if (crng_node_pool)
1035 crng = crng_node_pool[numa_node_id()];
1036 if (crng == NULL)
1037#endif
1038 crng = &primary_crng;
1039 _crng_backtrack_protect(crng, tmp, used);
1040}
1041
1042static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
1043{
1044 ssize_t ret = 0, i = CHACHA_BLOCK_SIZE;
1045 __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1046 int large_request = (nbytes > 256);
1047
1048 while (nbytes) {
1049 if (large_request && need_resched()) {
1050 if (signal_pending(current)) {
1051 if (ret == 0)
1052 ret = -ERESTARTSYS;
1053 break;
1054 }
1055 schedule();
1056 }
1057
1058 extract_crng(tmp);
1059 i = min_t(int, nbytes, CHACHA_BLOCK_SIZE);
1060 if (copy_to_user(buf, tmp, i)) {
1061 ret = -EFAULT;
1062 break;
1063 }
1064
1065 nbytes -= i;
1066 buf += i;
1067 ret += i;
1068 }
1069 crng_backtrack_protect(tmp, i);
1070
1071 /* Wipe data just written to memory */
1072 memzero_explicit(tmp, sizeof(tmp));
1073
1074 return ret;
1075}
1076
1077
1078/*********************************************************************
1079 *
1080 * Entropy input management
1081 *
1082 *********************************************************************/
1083
1084/* There is one of these per entropy source */
1085struct timer_rand_state {
1086 cycles_t last_time;
1087 long last_delta, last_delta2;
1088};
1089
1090#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
1091
1092/*
1093 * Add device- or boot-specific data to the input pool to help
1094 * initialize it.
1095 *
1096 * None of this adds any entropy; it is meant to avoid the problem of
1097 * the entropy pool having similar initial state across largely
1098 * identical devices.
1099 */
1100void add_device_randomness(const void *buf, unsigned int size)
1101{
1102 unsigned long time = random_get_entropy() ^ jiffies;
1103 unsigned long flags;
1104
1105 if (!crng_ready() && size)
1106 crng_slow_load(buf, size);
1107
1108 trace_add_device_randomness(size, _RET_IP_);
1109 spin_lock_irqsave(&input_pool.lock, flags);
1110 _mix_pool_bytes(&input_pool, buf, size);
1111 _mix_pool_bytes(&input_pool, &time, sizeof(time));
1112 spin_unlock_irqrestore(&input_pool.lock, flags);
1113}
1114EXPORT_SYMBOL(add_device_randomness);
1115
1116static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
1117
1118/*
1119 * This function adds entropy to the entropy "pool" by using timing
1120 * delays. It uses the timer_rand_state structure to make an estimate
1121 * of how many bits of entropy this call has added to the pool.
1122 *
1123 * The number "num" is also added to the pool - it should somehow describe
1124 * the type of event which just happened. This is currently 0-255 for
1125 * keyboard scan codes, and 256 upwards for interrupts.
1126 *
1127 */
1128static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
1129{
1130 struct entropy_store *r;
1131 struct {
1132 long jiffies;
1133 unsigned cycles;
1134 unsigned num;
1135 } sample;
1136 long delta, delta2, delta3;
1137
1138 sample.jiffies = jiffies;
1139 sample.cycles = random_get_entropy();
1140 sample.num = num;
1141 r = &input_pool;
1142 mix_pool_bytes(r, &sample, sizeof(sample));
1143
1144 /*
1145 * Calculate number of bits of randomness we probably added.
1146 * We take into account the first, second and third-order deltas
1147 * in order to make our estimate.
1148 */
1149 delta = sample.jiffies - state->last_time;
1150 state->last_time = sample.jiffies;
1151
1152 delta2 = delta - state->last_delta;
1153 state->last_delta = delta;
1154
1155 delta3 = delta2 - state->last_delta2;
1156 state->last_delta2 = delta2;
1157
1158 if (delta < 0)
1159 delta = -delta;
1160 if (delta2 < 0)
1161 delta2 = -delta2;
1162 if (delta3 < 0)
1163 delta3 = -delta3;
1164 if (delta > delta2)
1165 delta = delta2;
1166 if (delta > delta3)
1167 delta = delta3;
1168
1169 /*
1170 * delta is now minimum absolute delta.
1171 * Round down by 1 bit on general principles,
1172 * and limit entropy entimate to 12 bits.
1173 */
1174 credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1175}
1176
1177void add_input_randomness(unsigned int type, unsigned int code,
1178 unsigned int value)
1179{
1180 static unsigned char last_value;
1181
1182 /* ignore autorepeat and the like */
1183 if (value == last_value)
1184 return;
1185
1186 last_value = value;
1187 add_timer_randomness(&input_timer_state,
1188 (type << 4) ^ code ^ (code >> 4) ^ value);
1189 trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1190}
1191EXPORT_SYMBOL_GPL(add_input_randomness);
1192
1193static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
1194
1195#ifdef ADD_INTERRUPT_BENCH
1196static unsigned long avg_cycles, avg_deviation;
1197
1198#define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
1199#define FIXED_1_2 (1 << (AVG_SHIFT-1))
1200
1201static void add_interrupt_bench(cycles_t start)
1202{
1203 long delta = random_get_entropy() - start;
1204
1205 /* Use a weighted moving average */
1206 delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
1207 avg_cycles += delta;
1208 /* And average deviation */
1209 delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
1210 avg_deviation += delta;
1211}
1212#else
1213#define add_interrupt_bench(x)
1214#endif
1215
1216static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
1217{
1218 __u32 *ptr = (__u32 *) regs;
1219 unsigned int idx;
1220
1221 if (regs == NULL)
1222 return 0;
1223 idx = READ_ONCE(f->reg_idx);
1224 if (idx >= sizeof(struct pt_regs) / sizeof(__u32))
1225 idx = 0;
1226 ptr += idx++;
1227 WRITE_ONCE(f->reg_idx, idx);
1228 return *ptr;
1229}
1230
1231void add_interrupt_randomness(int irq, int irq_flags)
1232{
1233 struct entropy_store *r;
1234 struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
1235 struct pt_regs *regs = get_irq_regs();
1236 unsigned long now = jiffies;
1237 cycles_t cycles = random_get_entropy();
1238 __u32 c_high, j_high;
1239 __u64 ip;
1240 unsigned long seed;
1241 int credit = 0;
1242
1243 if (cycles == 0)
1244 cycles = get_reg(fast_pool, regs);
1245 c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
1246 j_high = (sizeof(now) > 4) ? now >> 32 : 0;
1247 fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
1248 fast_pool->pool[1] ^= now ^ c_high;
1249 ip = regs ? instruction_pointer(regs) : _RET_IP_;
1250 fast_pool->pool[2] ^= ip;
1251 fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
1252 get_reg(fast_pool, regs);
1253
1254 fast_mix(fast_pool);
1255 add_interrupt_bench(cycles);
1256
1257 if (unlikely(crng_init == 0)) {
1258 if ((fast_pool->count >= 64) &&
1259 crng_fast_load((char *) fast_pool->pool,
1260 sizeof(fast_pool->pool))) {
1261 fast_pool->count = 0;
1262 fast_pool->last = now;
1263 }
1264 return;
1265 }
1266
1267 if ((fast_pool->count < 64) &&
1268 !time_after(now, fast_pool->last + HZ))
1269 return;
1270
1271 r = &input_pool;
1272 if (!spin_trylock(&r->lock))
1273 return;
1274
1275 fast_pool->last = now;
1276 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
1277
1278 /*
1279 * If we have architectural seed generator, produce a seed and
1280 * add it to the pool. For the sake of paranoia don't let the
1281 * architectural seed generator dominate the input from the
1282 * interrupt noise.
1283 */
1284 if (arch_get_random_seed_long(&seed)) {
1285 __mix_pool_bytes(r, &seed, sizeof(seed));
1286 credit = 1;
1287 }
1288 spin_unlock(&r->lock);
1289
1290 fast_pool->count = 0;
1291
1292 /* award one bit for the contents of the fast pool */
1293 credit_entropy_bits(r, credit + 1);
1294}
1295EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1296
1297#ifdef CONFIG_BLOCK
1298void add_disk_randomness(struct gendisk *disk)
1299{
1300 if (!disk || !disk->random)
1301 return;
1302 /* first major is 1, so we get >= 0x200 here */
1303 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1304 trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1305}
1306EXPORT_SYMBOL_GPL(add_disk_randomness);
1307#endif
1308
1309/*********************************************************************
1310 *
1311 * Entropy extraction routines
1312 *
1313 *********************************************************************/
1314
1315/*
1316 * This utility inline function is responsible for transferring entropy
1317 * from the primary pool to the secondary extraction pool. We make
1318 * sure we pull enough for a 'catastrophic reseed'.
1319 */
1320static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
1321static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1322{
1323 if (!r->pull ||
1324 r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
1325 r->entropy_count > r->poolinfo->poolfracbits)
1326 return;
1327
1328 _xfer_secondary_pool(r, nbytes);
1329}
1330
1331static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1332{
1333 __u32 tmp[OUTPUT_POOL_WORDS];
1334
1335 int bytes = nbytes;
1336
1337 /* pull at least as much as a wakeup */
1338 bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
1339 /* but never more than the buffer size */
1340 bytes = min_t(int, bytes, sizeof(tmp));
1341
1342 trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
1343 ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
1344 bytes = extract_entropy(r->pull, tmp, bytes,
1345 random_read_wakeup_bits / 8, 0);
1346 mix_pool_bytes(r, tmp, bytes);
1347 credit_entropy_bits(r, bytes*8);
1348}
1349
1350/*
1351 * Used as a workqueue function so that when the input pool is getting
1352 * full, we can "spill over" some entropy to the output pools. That
1353 * way the output pools can store some of the excess entropy instead
1354 * of letting it go to waste.
1355 */
1356static void push_to_pool(struct work_struct *work)
1357{
1358 struct entropy_store *r = container_of(work, struct entropy_store,
1359 push_work);
1360 BUG_ON(!r);
1361 _xfer_secondary_pool(r, random_read_wakeup_bits/8);
1362 trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1363 r->pull->entropy_count >> ENTROPY_SHIFT);
1364}
1365
1366/*
1367 * This function decides how many bytes to actually take from the
1368 * given pool, and also debits the entropy count accordingly.
1369 */
1370static size_t account(struct entropy_store *r, size_t nbytes, int min,
1371 int reserved)
1372{
1373 int entropy_count, orig, have_bytes;
1374 size_t ibytes, nfrac;
1375
1376 BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1377
1378 /* Can we pull enough? */
1379retry:
1380 entropy_count = orig = READ_ONCE(r->entropy_count);
1381 ibytes = nbytes;
1382 /* never pull more than available */
1383 have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1384
1385 if ((have_bytes -= reserved) < 0)
1386 have_bytes = 0;
1387 ibytes = min_t(size_t, ibytes, have_bytes);
1388 if (ibytes < min)
1389 ibytes = 0;
1390
1391 if (unlikely(entropy_count < 0)) {
1392 pr_warn("random: negative entropy count: pool %s count %d\n",
1393 r->name, entropy_count);
1394 WARN_ON(1);
1395 entropy_count = 0;
1396 }
1397 nfrac = ibytes << (ENTROPY_SHIFT + 3);
1398 if ((size_t) entropy_count > nfrac)
1399 entropy_count -= nfrac;
1400 else
1401 entropy_count = 0;
1402
1403 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1404 goto retry;
1405
1406 trace_debit_entropy(r->name, 8 * ibytes);
1407 if (ibytes &&
1408 (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1409 wake_up_interruptible(&random_write_wait);
1410 kill_fasync(&fasync, SIGIO, POLL_OUT);
1411 }
1412
1413 return ibytes;
1414}
1415
1416/*
1417 * This function does the actual extraction for extract_entropy and
1418 * extract_entropy_user.
1419 *
1420 * Note: we assume that .poolwords is a multiple of 16 words.
1421 */
1422static void extract_buf(struct entropy_store *r, __u8 *out)
1423{
1424 int i;
1425 union {
1426 __u32 w[5];
1427 unsigned long l[LONGS(20)];
1428 } hash;
1429 __u32 workspace[SHA_WORKSPACE_WORDS];
1430 unsigned long flags;
1431
1432 /*
1433 * If we have an architectural hardware random number
1434 * generator, use it for SHA's initial vector
1435 */
1436 sha_init(hash.w);
1437 for (i = 0; i < LONGS(20); i++) {
1438 unsigned long v;
1439 if (!arch_get_random_long(&v))
1440 break;
1441 hash.l[i] = v;
1442 }
1443
1444 /* Generate a hash across the pool, 16 words (512 bits) at a time */
1445 spin_lock_irqsave(&r->lock, flags);
1446 for (i = 0; i < r->poolinfo->poolwords; i += 16)
1447 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1448
1449 /*
1450 * We mix the hash back into the pool to prevent backtracking
1451 * attacks (where the attacker knows the state of the pool
1452 * plus the current outputs, and attempts to find previous
1453 * ouputs), unless the hash function can be inverted. By
1454 * mixing at least a SHA1 worth of hash data back, we make
1455 * brute-forcing the feedback as hard as brute-forcing the
1456 * hash.
1457 */
1458 __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1459 spin_unlock_irqrestore(&r->lock, flags);
1460
1461 memzero_explicit(workspace, sizeof(workspace));
1462
1463 /*
1464 * In case the hash function has some recognizable output
1465 * pattern, we fold it in half. Thus, we always feed back
1466 * twice as much data as we output.
1467 */
1468 hash.w[0] ^= hash.w[3];
1469 hash.w[1] ^= hash.w[4];
1470 hash.w[2] ^= rol32(hash.w[2], 16);
1471
1472 memcpy(out, &hash, EXTRACT_SIZE);
1473 memzero_explicit(&hash, sizeof(hash));
1474}
1475
1476static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
1477 size_t nbytes, int fips)
1478{
1479 ssize_t ret = 0, i;
1480 __u8 tmp[EXTRACT_SIZE];
1481 unsigned long flags;
1482
1483 while (nbytes) {
1484 extract_buf(r, tmp);
1485
1486 if (fips) {
1487 spin_lock_irqsave(&r->lock, flags);
1488 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1489 panic("Hardware RNG duplicated output!\n");
1490 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1491 spin_unlock_irqrestore(&r->lock, flags);
1492 }
1493 i = min_t(int, nbytes, EXTRACT_SIZE);
1494 memcpy(buf, tmp, i);
1495 nbytes -= i;
1496 buf += i;
1497 ret += i;
1498 }
1499
1500 /* Wipe data just returned from memory */
1501 memzero_explicit(tmp, sizeof(tmp));
1502
1503 return ret;
1504}
1505
1506/*
1507 * This function extracts randomness from the "entropy pool", and
1508 * returns it in a buffer.
1509 *
1510 * The min parameter specifies the minimum amount we can pull before
1511 * failing to avoid races that defeat catastrophic reseeding while the
1512 * reserved parameter indicates how much entropy we must leave in the
1513 * pool after each pull to avoid starving other readers.
1514 */
1515static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1516 size_t nbytes, int min, int reserved)
1517{
1518 __u8 tmp[EXTRACT_SIZE];
1519 unsigned long flags;
1520
1521 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1522 if (fips_enabled) {
1523 spin_lock_irqsave(&r->lock, flags);
1524 if (!r->last_data_init) {
1525 r->last_data_init = 1;
1526 spin_unlock_irqrestore(&r->lock, flags);
1527 trace_extract_entropy(r->name, EXTRACT_SIZE,
1528 ENTROPY_BITS(r), _RET_IP_);
1529 xfer_secondary_pool(r, EXTRACT_SIZE);
1530 extract_buf(r, tmp);
1531 spin_lock_irqsave(&r->lock, flags);
1532 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1533 }
1534 spin_unlock_irqrestore(&r->lock, flags);
1535 }
1536
1537 trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1538 xfer_secondary_pool(r, nbytes);
1539 nbytes = account(r, nbytes, min, reserved);
1540
1541 return _extract_entropy(r, buf, nbytes, fips_enabled);
1542}
1543
1544/*
1545 * This function extracts randomness from the "entropy pool", and
1546 * returns it in a userspace buffer.
1547 */
1548static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1549 size_t nbytes)
1550{
1551 ssize_t ret = 0, i;
1552 __u8 tmp[EXTRACT_SIZE];
1553 int large_request = (nbytes > 256);
1554
1555 trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1556 xfer_secondary_pool(r, nbytes);
1557 nbytes = account(r, nbytes, 0, 0);
1558
1559 while (nbytes) {
1560 if (large_request && need_resched()) {
1561 if (signal_pending(current)) {
1562 if (ret == 0)
1563 ret = -ERESTARTSYS;
1564 break;
1565 }
1566 schedule();
1567 }
1568
1569 extract_buf(r, tmp);
1570 i = min_t(int, nbytes, EXTRACT_SIZE);
1571 if (copy_to_user(buf, tmp, i)) {
1572 ret = -EFAULT;
1573 break;
1574 }
1575
1576 nbytes -= i;
1577 buf += i;
1578 ret += i;
1579 }
1580
1581 /* Wipe data just returned from memory */
1582 memzero_explicit(tmp, sizeof(tmp));
1583
1584 return ret;
1585}
1586
1587#define warn_unseeded_randomness(previous) \
1588 _warn_unseeded_randomness(__func__, (void *) _RET_IP_, (previous))
1589
1590static void _warn_unseeded_randomness(const char *func_name, void *caller,
1591 void **previous)
1592{
1593#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1594 const bool print_once = false;
1595#else
1596 static bool print_once __read_mostly;
1597#endif
1598
1599 if (print_once ||
1600 crng_ready() ||
1601 (previous && (caller == READ_ONCE(*previous))))
1602 return;
1603 WRITE_ONCE(*previous, caller);
1604#ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1605 print_once = true;
1606#endif
1607 if (__ratelimit(&unseeded_warning))
1608 pr_notice("random: %s called from %pS with crng_init=%d\n",
1609 func_name, caller, crng_init);
1610}
1611
1612/*
1613 * This function is the exported kernel interface. It returns some
1614 * number of good random numbers, suitable for key generation, seeding
1615 * TCP sequence numbers, etc. It does not rely on the hardware random
1616 * number generator. For random bytes direct from the hardware RNG
1617 * (when available), use get_random_bytes_arch(). In order to ensure
1618 * that the randomness provided by this function is okay, the function
1619 * wait_for_random_bytes() should be called and return 0 at least once
1620 * at any point prior.
1621 */
1622static void _get_random_bytes(void *buf, int nbytes)
1623{
1624 __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1625
1626 trace_get_random_bytes(nbytes, _RET_IP_);
1627
1628 while (nbytes >= CHACHA_BLOCK_SIZE) {
1629 extract_crng(buf);
1630 buf += CHACHA_BLOCK_SIZE;
1631 nbytes -= CHACHA_BLOCK_SIZE;
1632 }
1633
1634 if (nbytes > 0) {
1635 extract_crng(tmp);
1636 memcpy(buf, tmp, nbytes);
1637 crng_backtrack_protect(tmp, nbytes);
1638 } else
1639 crng_backtrack_protect(tmp, CHACHA_BLOCK_SIZE);
1640 memzero_explicit(tmp, sizeof(tmp));
1641}
1642
1643void get_random_bytes(void *buf, int nbytes)
1644{
1645 static void *previous;
1646
1647 warn_unseeded_randomness(&previous);
1648 _get_random_bytes(buf, nbytes);
1649}
1650EXPORT_SYMBOL(get_random_bytes);
1651
1652/*
1653 * Wait for the urandom pool to be seeded and thus guaranteed to supply
1654 * cryptographically secure random numbers. This applies to: the /dev/urandom
1655 * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
1656 * family of functions. Using any of these functions without first calling
1657 * this function forfeits the guarantee of security.
1658 *
1659 * Returns: 0 if the urandom pool has been seeded.
1660 * -ERESTARTSYS if the function was interrupted by a signal.
1661 */
1662int wait_for_random_bytes(void)
1663{
1664 if (likely(crng_ready()))
1665 return 0;
1666 return wait_event_interruptible(crng_init_wait, crng_ready());
1667}
1668EXPORT_SYMBOL(wait_for_random_bytes);
1669
1670/*
1671 * Returns whether or not the urandom pool has been seeded and thus guaranteed
1672 * to supply cryptographically secure random numbers. This applies to: the
1673 * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
1674 * ,u64,int,long} family of functions.
1675 *
1676 * Returns: true if the urandom pool has been seeded.
1677 * false if the urandom pool has not been seeded.
1678 */
1679bool rng_is_initialized(void)
1680{
1681 return crng_ready();
1682}
1683EXPORT_SYMBOL(rng_is_initialized);
1684
1685/*
1686 * Add a callback function that will be invoked when the nonblocking
1687 * pool is initialised.
1688 *
1689 * returns: 0 if callback is successfully added
1690 * -EALREADY if pool is already initialised (callback not called)
1691 * -ENOENT if module for callback is not alive
1692 */
1693int add_random_ready_callback(struct random_ready_callback *rdy)
1694{
1695 struct module *owner;
1696 unsigned long flags;
1697 int err = -EALREADY;
1698
1699 if (crng_ready())
1700 return err;
1701
1702 owner = rdy->owner;
1703 if (!try_module_get(owner))
1704 return -ENOENT;
1705
1706 spin_lock_irqsave(&random_ready_list_lock, flags);
1707 if (crng_ready())
1708 goto out;
1709
1710 owner = NULL;
1711
1712 list_add(&rdy->list, &random_ready_list);
1713 err = 0;
1714
1715out:
1716 spin_unlock_irqrestore(&random_ready_list_lock, flags);
1717
1718 module_put(owner);
1719
1720 return err;
1721}
1722EXPORT_SYMBOL(add_random_ready_callback);
1723
1724/*
1725 * Delete a previously registered readiness callback function.
1726 */
1727void del_random_ready_callback(struct random_ready_callback *rdy)
1728{
1729 unsigned long flags;
1730 struct module *owner = NULL;
1731
1732 spin_lock_irqsave(&random_ready_list_lock, flags);
1733 if (!list_empty(&rdy->list)) {
1734 list_del_init(&rdy->list);
1735 owner = rdy->owner;
1736 }
1737 spin_unlock_irqrestore(&random_ready_list_lock, flags);
1738
1739 module_put(owner);
1740}
1741EXPORT_SYMBOL(del_random_ready_callback);
1742
1743/*
1744 * This function will use the architecture-specific hardware random
1745 * number generator if it is available. The arch-specific hw RNG will
1746 * almost certainly be faster than what we can do in software, but it
1747 * is impossible to verify that it is implemented securely (as
1748 * opposed, to, say, the AES encryption of a sequence number using a
1749 * key known by the NSA). So it's useful if we need the speed, but
1750 * only if we're willing to trust the hardware manufacturer not to
1751 * have put in a back door.
1752 *
1753 * Return number of bytes filled in.
1754 */
1755int __must_check get_random_bytes_arch(void *buf, int nbytes)
1756{
1757 int left = nbytes;
1758 char *p = buf;
1759
1760 trace_get_random_bytes_arch(left, _RET_IP_);
1761 while (left) {
1762 unsigned long v;
1763 int chunk = min_t(int, left, sizeof(unsigned long));
1764
1765 if (!arch_get_random_long(&v))
1766 break;
1767
1768 memcpy(p, &v, chunk);
1769 p += chunk;
1770 left -= chunk;
1771 }
1772
1773 return nbytes - left;
1774}
1775EXPORT_SYMBOL(get_random_bytes_arch);
1776
1777/*
1778 * init_std_data - initialize pool with system data
1779 *
1780 * @r: pool to initialize
1781 *
1782 * This function clears the pool's entropy count and mixes some system
1783 * data into the pool to prepare it for use. The pool is not cleared
1784 * as that can only decrease the entropy in the pool.
1785 */
1786static void init_std_data(struct entropy_store *r)
1787{
1788 int i;
1789 ktime_t now = ktime_get_real();
1790 unsigned long rv;
1791
1792 r->last_pulled = jiffies;
1793 mix_pool_bytes(r, &now, sizeof(now));
1794 for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1795 if (!arch_get_random_seed_long(&rv) &&
1796 !arch_get_random_long(&rv))
1797 rv = random_get_entropy();
1798 mix_pool_bytes(r, &rv, sizeof(rv));
1799 }
1800 mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1801}
1802
1803/*
1804 * Note that setup_arch() may call add_device_randomness()
1805 * long before we get here. This allows seeding of the pools
1806 * with some platform dependent data very early in the boot
1807 * process. But it limits our options here. We must use
1808 * statically allocated structures that already have all
1809 * initializations complete at compile time. We should also
1810 * take care not to overwrite the precious per platform data
1811 * we were given.
1812 */
1813static int rand_initialize(void)
1814{
1815 init_std_data(&input_pool);
1816 init_std_data(&blocking_pool);
1817 crng_initialize(&primary_crng);
1818 crng_global_init_time = jiffies;
1819 if (ratelimit_disable) {
1820 urandom_warning.interval = 0;
1821 unseeded_warning.interval = 0;
1822 }
1823 return 0;
1824}
1825early_initcall(rand_initialize);
1826
1827#ifdef CONFIG_BLOCK
1828void rand_initialize_disk(struct gendisk *disk)
1829{
1830 struct timer_rand_state *state;
1831
1832 /*
1833 * If kzalloc returns null, we just won't use that entropy
1834 * source.
1835 */
1836 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1837 if (state) {
1838 state->last_time = INITIAL_JIFFIES;
1839 disk->random = state;
1840 }
1841}
1842#endif
1843
1844static ssize_t
1845_random_read(int nonblock, char __user *buf, size_t nbytes)
1846{
1847 ssize_t n;
1848
1849 if (nbytes == 0)
1850 return 0;
1851
1852 nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1853 while (1) {
1854 n = extract_entropy_user(&blocking_pool, buf, nbytes);
1855 if (n < 0)
1856 return n;
1857 trace_random_read(n*8, (nbytes-n)*8,
1858 ENTROPY_BITS(&blocking_pool),
1859 ENTROPY_BITS(&input_pool));
1860 if (n > 0)
1861 return n;
1862
1863 /* Pool is (near) empty. Maybe wait and retry. */
1864 if (nonblock)
1865 return -EAGAIN;
1866
1867 wait_event_interruptible(random_read_wait,
1868 ENTROPY_BITS(&input_pool) >=
1869 random_read_wakeup_bits);
1870 if (signal_pending(current))
1871 return -ERESTARTSYS;
1872 }
1873}
1874
1875static ssize_t
1876random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1877{
1878 return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1879}
1880
1881static ssize_t
1882urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1883{
1884 unsigned long flags;
1885 static int maxwarn = 10;
1886 int ret;
1887
1888 if (!crng_ready() && maxwarn > 0) {
1889 maxwarn--;
1890 if (__ratelimit(&urandom_warning))
1891 printk(KERN_NOTICE "random: %s: uninitialized "
1892 "urandom read (%zd bytes read)\n",
1893 current->comm, nbytes);
1894 spin_lock_irqsave(&primary_crng.lock, flags);
1895 crng_init_cnt = 0;
1896 spin_unlock_irqrestore(&primary_crng.lock, flags);
1897 }
1898 nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1899 ret = extract_crng_user(buf, nbytes);
1900 trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
1901 return ret;
1902}
1903
1904static __poll_t
1905random_poll(struct file *file, poll_table * wait)
1906{
1907 __poll_t mask;
1908
1909 poll_wait(file, &random_read_wait, wait);
1910 poll_wait(file, &random_write_wait, wait);
1911 mask = 0;
1912 if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1913 mask |= EPOLLIN | EPOLLRDNORM;
1914 if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1915 mask |= EPOLLOUT | EPOLLWRNORM;
1916 return mask;
1917}
1918
1919static int
1920write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1921{
1922 size_t bytes;
1923 __u32 t, buf[16];
1924 const char __user *p = buffer;
1925
1926 while (count > 0) {
1927 int b, i = 0;
1928
1929 bytes = min(count, sizeof(buf));
1930 if (copy_from_user(&buf, p, bytes))
1931 return -EFAULT;
1932
1933 for (b = bytes ; b > 0 ; b -= sizeof(__u32), i++) {
1934 if (!arch_get_random_int(&t))
1935 break;
1936 buf[i] ^= t;
1937 }
1938
1939 count -= bytes;
1940 p += bytes;
1941
1942 mix_pool_bytes(r, buf, bytes);
1943 cond_resched();
1944 }
1945
1946 return 0;
1947}
1948
1949static ssize_t random_write(struct file *file, const char __user *buffer,
1950 size_t count, loff_t *ppos)
1951{
1952 size_t ret;
1953
1954 ret = write_pool(&input_pool, buffer, count);
1955 if (ret)
1956 return ret;
1957
1958 return (ssize_t)count;
1959}
1960
1961static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1962{
1963 int size, ent_count;
1964 int __user *p = (int __user *)arg;
1965 int retval;
1966
1967 switch (cmd) {
1968 case RNDGETENTCNT:
1969 /* inherently racy, no point locking */
1970 ent_count = ENTROPY_BITS(&input_pool);
1971 if (put_user(ent_count, p))
1972 return -EFAULT;
1973 return 0;
1974 case RNDADDTOENTCNT:
1975 if (!capable(CAP_SYS_ADMIN))
1976 return -EPERM;
1977 if (get_user(ent_count, p))
1978 return -EFAULT;
1979 return credit_entropy_bits_safe(&input_pool, ent_count);
1980 case RNDADDENTROPY:
1981 if (!capable(CAP_SYS_ADMIN))
1982 return -EPERM;
1983 if (get_user(ent_count, p++))
1984 return -EFAULT;
1985 if (ent_count < 0)
1986 return -EINVAL;
1987 if (get_user(size, p++))
1988 return -EFAULT;
1989 retval = write_pool(&input_pool, (const char __user *)p,
1990 size);
1991 if (retval < 0)
1992 return retval;
1993 return credit_entropy_bits_safe(&input_pool, ent_count);
1994 case RNDZAPENTCNT:
1995 case RNDCLEARPOOL:
1996 /*
1997 * Clear the entropy pool counters. We no longer clear
1998 * the entropy pool, as that's silly.
1999 */
2000 if (!capable(CAP_SYS_ADMIN))
2001 return -EPERM;
2002 input_pool.entropy_count = 0;
2003 blocking_pool.entropy_count = 0;
2004 return 0;
2005 case RNDRESEEDCRNG:
2006 if (!capable(CAP_SYS_ADMIN))
2007 return -EPERM;
2008 if (crng_init < 2)
2009 return -ENODATA;
2010 crng_reseed(&primary_crng, NULL);
2011 crng_global_init_time = jiffies - 1;
2012 return 0;
2013 default:
2014 return -EINVAL;
2015 }
2016}
2017
2018static int random_fasync(int fd, struct file *filp, int on)
2019{
2020 return fasync_helper(fd, filp, on, &fasync);
2021}
2022
2023const struct file_operations random_fops = {
2024 .read = random_read,
2025 .write = random_write,
2026 .poll = random_poll,
2027 .unlocked_ioctl = random_ioctl,
2028 .fasync = random_fasync,
2029 .llseek = noop_llseek,
2030};
2031
2032const struct file_operations urandom_fops = {
2033 .read = urandom_read,
2034 .write = random_write,
2035 .unlocked_ioctl = random_ioctl,
2036 .fasync = random_fasync,
2037 .llseek = noop_llseek,
2038};
2039
2040SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
2041 unsigned int, flags)
2042{
2043 int ret;
2044
2045 if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
2046 return -EINVAL;
2047
2048 if (count > INT_MAX)
2049 count = INT_MAX;
2050
2051 if (flags & GRND_RANDOM)
2052 return _random_read(flags & GRND_NONBLOCK, buf, count);
2053
2054 if (!crng_ready()) {
2055 if (flags & GRND_NONBLOCK)
2056 return -EAGAIN;
2057 ret = wait_for_random_bytes();
2058 if (unlikely(ret))
2059 return ret;
2060 }
2061 return urandom_read(NULL, buf, count, NULL);
2062}
2063
2064/********************************************************************
2065 *
2066 * Sysctl interface
2067 *
2068 ********************************************************************/
2069
2070#ifdef CONFIG_SYSCTL
2071
2072#include <linux/sysctl.h>
2073
2074static int min_read_thresh = 8, min_write_thresh;
2075static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
2076static int max_write_thresh = INPUT_POOL_WORDS * 32;
2077static int random_min_urandom_seed = 60;
2078static char sysctl_bootid[16];
2079
2080/*
2081 * This function is used to return both the bootid UUID, and random
2082 * UUID. The difference is in whether table->data is NULL; if it is,
2083 * then a new UUID is generated and returned to the user.
2084 *
2085 * If the user accesses this via the proc interface, the UUID will be
2086 * returned as an ASCII string in the standard UUID format; if via the
2087 * sysctl system call, as 16 bytes of binary data.
2088 */
2089static int proc_do_uuid(struct ctl_table *table, int write,
2090 void __user *buffer, size_t *lenp, loff_t *ppos)
2091{
2092 struct ctl_table fake_table;
2093 unsigned char buf[64], tmp_uuid[16], *uuid;
2094
2095 uuid = table->data;
2096 if (!uuid) {
2097 uuid = tmp_uuid;
2098 generate_random_uuid(uuid);
2099 } else {
2100 static DEFINE_SPINLOCK(bootid_spinlock);
2101
2102 spin_lock(&bootid_spinlock);
2103 if (!uuid[8])
2104 generate_random_uuid(uuid);
2105 spin_unlock(&bootid_spinlock);
2106 }
2107
2108 sprintf(buf, "%pU", uuid);
2109
2110 fake_table.data = buf;
2111 fake_table.maxlen = sizeof(buf);
2112
2113 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
2114}
2115
2116/*
2117 * Return entropy available scaled to integral bits
2118 */
2119static int proc_do_entropy(struct ctl_table *table, int write,
2120 void __user *buffer, size_t *lenp, loff_t *ppos)
2121{
2122 struct ctl_table fake_table;
2123 int entropy_count;
2124
2125 entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
2126
2127 fake_table.data = &entropy_count;
2128 fake_table.maxlen = sizeof(entropy_count);
2129
2130 return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
2131}
2132
2133static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
2134extern struct ctl_table random_table[];
2135struct ctl_table random_table[] = {
2136 {
2137 .procname = "poolsize",
2138 .data = &sysctl_poolsize,
2139 .maxlen = sizeof(int),
2140 .mode = 0444,
2141 .proc_handler = proc_dointvec,
2142 },
2143 {
2144 .procname = "entropy_avail",
2145 .maxlen = sizeof(int),
2146 .mode = 0444,
2147 .proc_handler = proc_do_entropy,
2148 .data = &input_pool.entropy_count,
2149 },
2150 {
2151 .procname = "read_wakeup_threshold",
2152 .data = &random_read_wakeup_bits,
2153 .maxlen = sizeof(int),
2154 .mode = 0644,
2155 .proc_handler = proc_dointvec_minmax,
2156 .extra1 = &min_read_thresh,
2157 .extra2 = &max_read_thresh,
2158 },
2159 {
2160 .procname = "write_wakeup_threshold",
2161 .data = &random_write_wakeup_bits,
2162 .maxlen = sizeof(int),
2163 .mode = 0644,
2164 .proc_handler = proc_dointvec_minmax,
2165 .extra1 = &min_write_thresh,
2166 .extra2 = &max_write_thresh,
2167 },
2168 {
2169 .procname = "urandom_min_reseed_secs",
2170 .data = &random_min_urandom_seed,
2171 .maxlen = sizeof(int),
2172 .mode = 0644,
2173 .proc_handler = proc_dointvec,
2174 },
2175 {
2176 .procname = "boot_id",
2177 .data = &sysctl_bootid,
2178 .maxlen = 16,
2179 .mode = 0444,
2180 .proc_handler = proc_do_uuid,
2181 },
2182 {
2183 .procname = "uuid",
2184 .maxlen = 16,
2185 .mode = 0444,
2186 .proc_handler = proc_do_uuid,
2187 },
2188#ifdef ADD_INTERRUPT_BENCH
2189 {
2190 .procname = "add_interrupt_avg_cycles",
2191 .data = &avg_cycles,
2192 .maxlen = sizeof(avg_cycles),
2193 .mode = 0444,
2194 .proc_handler = proc_doulongvec_minmax,
2195 },
2196 {
2197 .procname = "add_interrupt_avg_deviation",
2198 .data = &avg_deviation,
2199 .maxlen = sizeof(avg_deviation),
2200 .mode = 0444,
2201 .proc_handler = proc_doulongvec_minmax,
2202 },
2203#endif
2204 { }
2205};
2206#endif /* CONFIG_SYSCTL */
2207
2208struct batched_entropy {
2209 union {
2210 u64 entropy_u64[CHACHA_BLOCK_SIZE / sizeof(u64)];
2211 u32 entropy_u32[CHACHA_BLOCK_SIZE / sizeof(u32)];
2212 };
2213 unsigned int position;
2214};
2215static rwlock_t batched_entropy_reset_lock = __RW_LOCK_UNLOCKED(batched_entropy_reset_lock);
2216
2217/*
2218 * Get a random word for internal kernel use only. The quality of the random
2219 * number is either as good as RDRAND or as good as /dev/urandom, with the
2220 * goal of being quite fast and not depleting entropy. In order to ensure
2221 * that the randomness provided by this function is okay, the function
2222 * wait_for_random_bytes() should be called and return 0 at least once
2223 * at any point prior.
2224 */
2225static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64);
2226u64 get_random_u64(void)
2227{
2228 u64 ret;
2229 bool use_lock;
2230 unsigned long flags = 0;
2231 struct batched_entropy *batch;
2232 static void *previous;
2233
2234#if BITS_PER_LONG == 64
2235 if (arch_get_random_long((unsigned long *)&ret))
2236 return ret;
2237#else
2238 if (arch_get_random_long((unsigned long *)&ret) &&
2239 arch_get_random_long((unsigned long *)&ret + 1))
2240 return ret;
2241#endif
2242
2243 warn_unseeded_randomness(&previous);
2244
2245 use_lock = READ_ONCE(crng_init) < 2;
2246 batch = &get_cpu_var(batched_entropy_u64);
2247 if (use_lock)
2248 read_lock_irqsave(&batched_entropy_reset_lock, flags);
2249 if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
2250 extract_crng((u8 *)batch->entropy_u64);
2251 batch->position = 0;
2252 }
2253 ret = batch->entropy_u64[batch->position++];
2254 if (use_lock)
2255 read_unlock_irqrestore(&batched_entropy_reset_lock, flags);
2256 put_cpu_var(batched_entropy_u64);
2257 return ret;
2258}
2259EXPORT_SYMBOL(get_random_u64);
2260
2261static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32);
2262u32 get_random_u32(void)
2263{
2264 u32 ret;
2265 bool use_lock;
2266 unsigned long flags = 0;
2267 struct batched_entropy *batch;
2268 static void *previous;
2269
2270 if (arch_get_random_int(&ret))
2271 return ret;
2272
2273 warn_unseeded_randomness(&previous);
2274
2275 use_lock = READ_ONCE(crng_init) < 2;
2276 batch = &get_cpu_var(batched_entropy_u32);
2277 if (use_lock)
2278 read_lock_irqsave(&batched_entropy_reset_lock, flags);
2279 if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
2280 extract_crng((u8 *)batch->entropy_u32);
2281 batch->position = 0;
2282 }
2283 ret = batch->entropy_u32[batch->position++];
2284 if (use_lock)
2285 read_unlock_irqrestore(&batched_entropy_reset_lock, flags);
2286 put_cpu_var(batched_entropy_u32);
2287 return ret;
2288}
2289EXPORT_SYMBOL(get_random_u32);
2290
2291/* It's important to invalidate all potential batched entropy that might
2292 * be stored before the crng is initialized, which we can do lazily by
2293 * simply resetting the counter to zero so that it's re-extracted on the
2294 * next usage. */
2295static void invalidate_batched_entropy(void)
2296{
2297 int cpu;
2298 unsigned long flags;
2299
2300 write_lock_irqsave(&batched_entropy_reset_lock, flags);
2301 for_each_possible_cpu (cpu) {
2302 per_cpu_ptr(&batched_entropy_u32, cpu)->position = 0;
2303 per_cpu_ptr(&batched_entropy_u64, cpu)->position = 0;
2304 }
2305 write_unlock_irqrestore(&batched_entropy_reset_lock, flags);
2306}
2307
2308/**
2309 * randomize_page - Generate a random, page aligned address
2310 * @start: The smallest acceptable address the caller will take.
2311 * @range: The size of the area, starting at @start, within which the
2312 * random address must fall.
2313 *
2314 * If @start + @range would overflow, @range is capped.
2315 *
2316 * NOTE: Historical use of randomize_range, which this replaces, presumed that
2317 * @start was already page aligned. We now align it regardless.
2318 *
2319 * Return: A page aligned address within [start, start + range). On error,
2320 * @start is returned.
2321 */
2322unsigned long
2323randomize_page(unsigned long start, unsigned long range)
2324{
2325 if (!PAGE_ALIGNED(start)) {
2326 range -= PAGE_ALIGN(start) - start;
2327 start = PAGE_ALIGN(start);
2328 }
2329
2330 if (start > ULONG_MAX - range)
2331 range = ULONG_MAX - start;
2332
2333 range >>= PAGE_SHIFT;
2334
2335 if (range == 0)
2336 return start;
2337
2338 return start + (get_random_long() % range << PAGE_SHIFT);
2339}
2340
2341/* Interface for in-kernel drivers of true hardware RNGs.
2342 * Those devices may produce endless random bits and will be throttled
2343 * when our pool is full.
2344 */
2345void add_hwgenerator_randomness(const char *buffer, size_t count,
2346 size_t entropy)
2347{
2348 struct entropy_store *poolp = &input_pool;
2349
2350 if (unlikely(crng_init == 0)) {
2351 crng_fast_load(buffer, count);
2352 return;
2353 }
2354
2355 /* Suspend writing if we're above the trickle threshold.
2356 * We'll be woken up again once below random_write_wakeup_thresh,
2357 * or when the calling thread is about to terminate.
2358 */
2359 wait_event_interruptible(random_write_wait, kthread_should_stop() ||
2360 ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
2361 mix_pool_bytes(poolp, buffer, count);
2362 credit_entropy_bits(poolp, entropy);
2363}
2364EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
2365