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1da177e4
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1/*
2 * random.c -- A strong random number generator
3 *
9e95ce27 4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
1da177e4
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5 *
6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
7 * rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, and the entire permission notice in its entirety,
14 * including the disclaimer of warranties.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. The name of the author may not be used to endorse or promote
19 * products derived from this software without specific prior
20 * written permission.
21 *
22 * ALTERNATIVELY, this product may be distributed under the terms of
23 * the GNU General Public License, in which case the provisions of the GPL are
24 * required INSTEAD OF the above restrictions. (This clause is
25 * necessary due to a potential bad interaction between the GPL and
26 * the restrictions contained in a BSD-style copyright.)
27 *
28 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
31 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
32 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
34 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
35 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
36 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
38 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
39 * DAMAGE.
40 */
41
42/*
43 * (now, with legal B.S. out of the way.....)
44 *
45 * This routine gathers environmental noise from device drivers, etc.,
46 * and returns good random numbers, suitable for cryptographic use.
47 * Besides the obvious cryptographic uses, these numbers are also good
48 * for seeding TCP sequence numbers, and other places where it is
49 * desirable to have numbers which are not only random, but hard to
50 * predict by an attacker.
51 *
52 * Theory of operation
53 * ===================
54 *
55 * Computers are very predictable devices. Hence it is extremely hard
56 * to produce truly random numbers on a computer --- as opposed to
57 * pseudo-random numbers, which can easily generated by using a
58 * algorithm. Unfortunately, it is very easy for attackers to guess
59 * the sequence of pseudo-random number generators, and for some
60 * applications this is not acceptable. So instead, we must try to
61 * gather "environmental noise" from the computer's environment, which
62 * must be hard for outside attackers to observe, and use that to
63 * generate random numbers. In a Unix environment, this is best done
64 * from inside the kernel.
65 *
66 * Sources of randomness from the environment include inter-keyboard
67 * timings, inter-interrupt timings from some interrupts, and other
68 * events which are both (a) non-deterministic and (b) hard for an
69 * outside observer to measure. Randomness from these sources are
70 * added to an "entropy pool", which is mixed using a CRC-like function.
71 * This is not cryptographically strong, but it is adequate assuming
72 * the randomness is not chosen maliciously, and it is fast enough that
73 * the overhead of doing it on every interrupt is very reasonable.
74 * As random bytes are mixed into the entropy pool, the routines keep
75 * an *estimate* of how many bits of randomness have been stored into
76 * the random number generator's internal state.
77 *
78 * When random bytes are desired, they are obtained by taking the SHA
79 * hash of the contents of the "entropy pool". The SHA hash avoids
80 * exposing the internal state of the entropy pool. It is believed to
81 * be computationally infeasible to derive any useful information
82 * about the input of SHA from its output. Even if it is possible to
83 * analyze SHA in some clever way, as long as the amount of data
84 * returned from the generator is less than the inherent entropy in
85 * the pool, the output data is totally unpredictable. For this
86 * reason, the routine decreases its internal estimate of how many
87 * bits of "true randomness" are contained in the entropy pool as it
88 * outputs random numbers.
89 *
90 * If this estimate goes to zero, the routine can still generate
91 * random numbers; however, an attacker may (at least in theory) be
92 * able to infer the future output of the generator from prior
93 * outputs. This requires successful cryptanalysis of SHA, which is
94 * not believed to be feasible, but there is a remote possibility.
95 * Nonetheless, these numbers should be useful for the vast majority
96 * of purposes.
97 *
98 * Exported interfaces ---- output
99 * ===============================
100 *
101 * There are three exported interfaces; the first is one designed to
102 * be used from within the kernel:
103 *
104 * void get_random_bytes(void *buf, int nbytes);
105 *
106 * This interface will return the requested number of random bytes,
107 * and place it in the requested buffer.
108 *
109 * The two other interfaces are two character devices /dev/random and
110 * /dev/urandom. /dev/random is suitable for use when very high
111 * quality randomness is desired (for example, for key generation or
112 * one-time pads), as it will only return a maximum of the number of
113 * bits of randomness (as estimated by the random number generator)
114 * contained in the entropy pool.
115 *
116 * The /dev/urandom device does not have this limit, and will return
117 * as many bytes as are requested. As more and more random bytes are
118 * requested without giving time for the entropy pool to recharge,
119 * this will result in random numbers that are merely cryptographically
120 * strong. For many applications, however, this is acceptable.
121 *
122 * Exported interfaces ---- input
123 * ==============================
124 *
125 * The current exported interfaces for gathering environmental noise
126 * from the devices are:
127 *
128 * void add_input_randomness(unsigned int type, unsigned int code,
129 * unsigned int value);
130 * void add_interrupt_randomness(int irq);
442a4fff 131 * void add_disk_randomness(struct gendisk *disk);
1da177e4
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132 *
133 * add_input_randomness() uses the input layer interrupt timing, as well as
134 * the event type information from the hardware.
135 *
136 * add_interrupt_randomness() uses the inter-interrupt timing as random
137 * inputs to the entropy pool. Note that not all interrupts are good
138 * sources of randomness! For example, the timer interrupts is not a
139 * good choice, because the periodicity of the interrupts is too
442a4fff
JW
140 * regular, and hence predictable to an attacker. Network Interface
141 * Controller interrupts are a better measure, since the timing of the
142 * NIC interrupts are more unpredictable.
143 *
144 * add_disk_randomness() uses what amounts to the seek time of block
145 * layer request events, on a per-disk_devt basis, as input to the
146 * entropy pool. Note that high-speed solid state drives with very low
147 * seek times do not make for good sources of entropy, as their seek
148 * times are usually fairly consistent.
1da177e4
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149 *
150 * All of these routines try to estimate how many bits of randomness a
151 * particular randomness source. They do this by keeping track of the
152 * first and second order deltas of the event timings.
153 *
154 * Ensuring unpredictability at system startup
155 * ============================================
156 *
157 * When any operating system starts up, it will go through a sequence
158 * of actions that are fairly predictable by an adversary, especially
159 * if the start-up does not involve interaction with a human operator.
160 * This reduces the actual number of bits of unpredictability in the
161 * entropy pool below the value in entropy_count. In order to
162 * counteract this effect, it helps to carry information in the
163 * entropy pool across shut-downs and start-ups. To do this, put the
164 * following lines an appropriate script which is run during the boot
165 * sequence:
166 *
167 * echo "Initializing random number generator..."
168 * random_seed=/var/run/random-seed
169 * # Carry a random seed from start-up to start-up
170 * # Load and then save the whole entropy pool
171 * if [ -f $random_seed ]; then
172 * cat $random_seed >/dev/urandom
173 * else
174 * touch $random_seed
175 * fi
176 * chmod 600 $random_seed
177 * dd if=/dev/urandom of=$random_seed count=1 bs=512
178 *
179 * and the following lines in an appropriate script which is run as
180 * the system is shutdown:
181 *
182 * # Carry a random seed from shut-down to start-up
183 * # Save the whole entropy pool
184 * echo "Saving random seed..."
185 * random_seed=/var/run/random-seed
186 * touch $random_seed
187 * chmod 600 $random_seed
188 * dd if=/dev/urandom of=$random_seed count=1 bs=512
189 *
190 * For example, on most modern systems using the System V init
191 * scripts, such code fragments would be found in
192 * /etc/rc.d/init.d/random. On older Linux systems, the correct script
193 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
194 *
195 * Effectively, these commands cause the contents of the entropy pool
196 * to be saved at shut-down time and reloaded into the entropy pool at
197 * start-up. (The 'dd' in the addition to the bootup script is to
198 * make sure that /etc/random-seed is different for every start-up,
199 * even if the system crashes without executing rc.0.) Even with
200 * complete knowledge of the start-up activities, predicting the state
201 * of the entropy pool requires knowledge of the previous history of
202 * the system.
203 *
204 * Configuring the /dev/random driver under Linux
205 * ==============================================
206 *
207 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
208 * the /dev/mem major number (#1). So if your system does not have
209 * /dev/random and /dev/urandom created already, they can be created
210 * by using the commands:
211 *
212 * mknod /dev/random c 1 8
213 * mknod /dev/urandom c 1 9
214 *
215 * Acknowledgements:
216 * =================
217 *
218 * Ideas for constructing this random number generator were derived
219 * from Pretty Good Privacy's random number generator, and from private
220 * discussions with Phil Karn. Colin Plumb provided a faster random
221 * number generator, which speed up the mixing function of the entropy
222 * pool, taken from PGPfone. Dale Worley has also contributed many
223 * useful ideas and suggestions to improve this driver.
224 *
225 * Any flaws in the design are solely my responsibility, and should
226 * not be attributed to the Phil, Colin, or any of authors of PGP.
227 *
228 * Further background information on this topic may be obtained from
229 * RFC 1750, "Randomness Recommendations for Security", by Donald
230 * Eastlake, Steve Crocker, and Jeff Schiller.
231 */
232
233#include <linux/utsname.h>
1da177e4
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234#include <linux/module.h>
235#include <linux/kernel.h>
236#include <linux/major.h>
237#include <linux/string.h>
238#include <linux/fcntl.h>
239#include <linux/slab.h>
240#include <linux/random.h>
241#include <linux/poll.h>
242#include <linux/init.h>
243#include <linux/fs.h>
244#include <linux/genhd.h>
245#include <linux/interrupt.h>
27ac792c 246#include <linux/mm.h>
1da177e4
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247#include <linux/spinlock.h>
248#include <linux/percpu.h>
249#include <linux/cryptohash.h>
5b739ef8 250#include <linux/fips.h>
1da177e4 251
d178a1eb
YL
252#ifdef CONFIG_GENERIC_HARDIRQS
253# include <linux/irq.h>
254#endif
255
1da177e4
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256#include <asm/processor.h>
257#include <asm/uaccess.h>
258#include <asm/irq.h>
259#include <asm/io.h>
260
261/*
262 * Configuration information
263 */
264#define INPUT_POOL_WORDS 128
265#define OUTPUT_POOL_WORDS 32
266#define SEC_XFER_SIZE 512
e954bc91 267#define EXTRACT_SIZE 10
1da177e4
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268
269/*
270 * The minimum number of bits of entropy before we wake up a read on
271 * /dev/random. Should be enough to do a significant reseed.
272 */
273static int random_read_wakeup_thresh = 64;
274
275/*
276 * If the entropy count falls under this number of bits, then we
277 * should wake up processes which are selecting or polling on write
278 * access to /dev/random.
279 */
280static int random_write_wakeup_thresh = 128;
281
282/*
283 * When the input pool goes over trickle_thresh, start dropping most
284 * samples to avoid wasting CPU time and reduce lock contention.
285 */
286
6c036527 287static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
1da177e4 288
90b75ee5 289static DEFINE_PER_CPU(int, trickle_count);
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290
291/*
292 * A pool of size .poolwords is stirred with a primitive polynomial
293 * of degree .poolwords over GF(2). The taps for various sizes are
294 * defined below. They are chosen to be evenly spaced (minimum RMS
295 * distance from evenly spaced; the numbers in the comments are a
296 * scaled squared error sum) except for the last tap, which is 1 to
297 * get the twisting happening as fast as possible.
298 */
299static struct poolinfo {
300 int poolwords;
301 int tap1, tap2, tap3, tap4, tap5;
302} poolinfo_table[] = {
303 /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
304 { 128, 103, 76, 51, 25, 1 },
305 /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
306 { 32, 26, 20, 14, 7, 1 },
307#if 0
308 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
309 { 2048, 1638, 1231, 819, 411, 1 },
310
311 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
312 { 1024, 817, 615, 412, 204, 1 },
313
314 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
315 { 1024, 819, 616, 410, 207, 2 },
316
317 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
318 { 512, 411, 308, 208, 104, 1 },
319
320 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
321 { 512, 409, 307, 206, 102, 2 },
322 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
323 { 512, 409, 309, 205, 103, 2 },
324
325 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
326 { 256, 205, 155, 101, 52, 1 },
327
328 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
329 { 128, 103, 78, 51, 27, 2 },
330
331 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
332 { 64, 52, 39, 26, 14, 1 },
333#endif
334};
335
336#define POOLBITS poolwords*32
337#define POOLBYTES poolwords*4
338
339/*
340 * For the purposes of better mixing, we use the CRC-32 polynomial as
341 * well to make a twisted Generalized Feedback Shift Reigster
342 *
343 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
344 * Transactions on Modeling and Computer Simulation 2(3):179-194.
345 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
346 * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
347 *
348 * Thanks to Colin Plumb for suggesting this.
349 *
350 * We have not analyzed the resultant polynomial to prove it primitive;
351 * in fact it almost certainly isn't. Nonetheless, the irreducible factors
352 * of a random large-degree polynomial over GF(2) are more than large enough
353 * that periodicity is not a concern.
354 *
355 * The input hash is much less sensitive than the output hash. All
356 * that we want of it is that it be a good non-cryptographic hash;
357 * i.e. it not produce collisions when fed "random" data of the sort
358 * we expect to see. As long as the pool state differs for different
359 * inputs, we have preserved the input entropy and done a good job.
360 * The fact that an intelligent attacker can construct inputs that
361 * will produce controlled alterations to the pool's state is not
362 * important because we don't consider such inputs to contribute any
363 * randomness. The only property we need with respect to them is that
364 * the attacker can't increase his/her knowledge of the pool's state.
365 * Since all additions are reversible (knowing the final state and the
366 * input, you can reconstruct the initial state), if an attacker has
367 * any uncertainty about the initial state, he/she can only shuffle
368 * that uncertainty about, but never cause any collisions (which would
369 * decrease the uncertainty).
370 *
371 * The chosen system lets the state of the pool be (essentially) the input
372 * modulo the generator polymnomial. Now, for random primitive polynomials,
373 * this is a universal class of hash functions, meaning that the chance
374 * of a collision is limited by the attacker's knowledge of the generator
375 * polynomail, so if it is chosen at random, an attacker can never force
376 * a collision. Here, we use a fixed polynomial, but we *can* assume that
377 * ###--> it is unknown to the processes generating the input entropy. <-###
378 * Because of this important property, this is a good, collision-resistant
379 * hash; hash collisions will occur no more often than chance.
380 */
381
382/*
383 * Static global variables
384 */
385static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
386static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
9a6f70bb 387static struct fasync_struct *fasync;
1da177e4
LT
388
389#if 0
90ab5ee9 390static bool debug;
1da177e4 391module_param(debug, bool, 0644);
90b75ee5
MM
392#define DEBUG_ENT(fmt, arg...) do { \
393 if (debug) \
394 printk(KERN_DEBUG "random %04d %04d %04d: " \
395 fmt,\
396 input_pool.entropy_count,\
397 blocking_pool.entropy_count,\
398 nonblocking_pool.entropy_count,\
399 ## arg); } while (0)
1da177e4
LT
400#else
401#define DEBUG_ENT(fmt, arg...) do {} while (0)
402#endif
403
404/**********************************************************************
405 *
406 * OS independent entropy store. Here are the functions which handle
407 * storing entropy in an entropy pool.
408 *
409 **********************************************************************/
410
411struct entropy_store;
412struct entropy_store {
43358209 413 /* read-only data: */
1da177e4
LT
414 struct poolinfo *poolinfo;
415 __u32 *pool;
416 const char *name;
1da177e4 417 struct entropy_store *pull;
4015d9a8 418 int limit;
1da177e4
LT
419
420 /* read-write data: */
43358209 421 spinlock_t lock;
1da177e4 422 unsigned add_ptr;
cda796a3 423 int entropy_count;
1da177e4 424 int input_rotate;
e954bc91 425 __u8 last_data[EXTRACT_SIZE];
1da177e4
LT
426};
427
428static __u32 input_pool_data[INPUT_POOL_WORDS];
429static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
430static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
431
432static struct entropy_store input_pool = {
433 .poolinfo = &poolinfo_table[0],
434 .name = "input",
435 .limit = 1,
e4d91918 436 .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock),
1da177e4
LT
437 .pool = input_pool_data
438};
439
440static struct entropy_store blocking_pool = {
441 .poolinfo = &poolinfo_table[1],
442 .name = "blocking",
443 .limit = 1,
444 .pull = &input_pool,
e4d91918 445 .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock),
1da177e4
LT
446 .pool = blocking_pool_data
447};
448
449static struct entropy_store nonblocking_pool = {
450 .poolinfo = &poolinfo_table[1],
451 .name = "nonblocking",
452 .pull = &input_pool,
e4d91918 453 .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock),
1da177e4
LT
454 .pool = nonblocking_pool_data
455};
456
457/*
e68e5b66 458 * This function adds bytes into the entropy "pool". It does not
1da177e4 459 * update the entropy estimate. The caller should call
adc782da 460 * credit_entropy_bits if this is appropriate.
1da177e4
LT
461 *
462 * The pool is stirred with a primitive polynomial of the appropriate
463 * degree, and then twisted. We twist by three bits at a time because
464 * it's cheap to do so and helps slightly in the expected case where
465 * the entropy is concentrated in the low-order bits.
466 */
e68e5b66
MM
467static void mix_pool_bytes_extract(struct entropy_store *r, const void *in,
468 int nbytes, __u8 out[64])
1da177e4
LT
469{
470 static __u32 const twist_table[8] = {
471 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
472 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
993ba211 473 unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
feee7697 474 int input_rotate;
1da177e4 475 int wordmask = r->poolinfo->poolwords - 1;
e68e5b66 476 const char *bytes = in;
6d38b827 477 __u32 w;
1da177e4
LT
478 unsigned long flags;
479
480 /* Taps are constant, so we can load them without holding r->lock. */
481 tap1 = r->poolinfo->tap1;
482 tap2 = r->poolinfo->tap2;
483 tap3 = r->poolinfo->tap3;
484 tap4 = r->poolinfo->tap4;
485 tap5 = r->poolinfo->tap5;
1da177e4
LT
486
487 spin_lock_irqsave(&r->lock, flags);
1da177e4 488 input_rotate = r->input_rotate;
993ba211 489 i = r->add_ptr;
1da177e4 490
e68e5b66
MM
491 /* mix one byte at a time to simplify size handling and churn faster */
492 while (nbytes--) {
493 w = rol32(*bytes++, input_rotate & 31);
993ba211 494 i = (i - 1) & wordmask;
1da177e4
LT
495
496 /* XOR in the various taps */
993ba211 497 w ^= r->pool[i];
1da177e4
LT
498 w ^= r->pool[(i + tap1) & wordmask];
499 w ^= r->pool[(i + tap2) & wordmask];
500 w ^= r->pool[(i + tap3) & wordmask];
501 w ^= r->pool[(i + tap4) & wordmask];
502 w ^= r->pool[(i + tap5) & wordmask];
993ba211
MM
503
504 /* Mix the result back in with a twist */
1da177e4 505 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
feee7697
MM
506
507 /*
508 * Normally, we add 7 bits of rotation to the pool.
509 * At the beginning of the pool, add an extra 7 bits
510 * rotation, so that successive passes spread the
511 * input bits across the pool evenly.
512 */
513 input_rotate += i ? 7 : 14;
1da177e4
LT
514 }
515
516 r->input_rotate = input_rotate;
993ba211 517 r->add_ptr = i;
1da177e4 518
993ba211
MM
519 if (out)
520 for (j = 0; j < 16; j++)
e68e5b66 521 ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
1da177e4
LT
522
523 spin_unlock_irqrestore(&r->lock, flags);
524}
525
e68e5b66 526static void mix_pool_bytes(struct entropy_store *r, const void *in, int bytes)
1da177e4 527{
e68e5b66 528 mix_pool_bytes_extract(r, in, bytes, NULL);
1da177e4
LT
529}
530
531/*
532 * Credit (or debit) the entropy store with n bits of entropy
533 */
adc782da 534static void credit_entropy_bits(struct entropy_store *r, int nbits)
1da177e4
LT
535{
536 unsigned long flags;
8b76f46a 537 int entropy_count;
1da177e4 538
adc782da
MM
539 if (!nbits)
540 return;
541
1da177e4
LT
542 spin_lock_irqsave(&r->lock, flags);
543
adc782da 544 DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
8b76f46a
AM
545 entropy_count = r->entropy_count;
546 entropy_count += nbits;
547 if (entropy_count < 0) {
adc782da 548 DEBUG_ENT("negative entropy/overflow\n");
8b76f46a
AM
549 entropy_count = 0;
550 } else if (entropy_count > r->poolinfo->POOLBITS)
551 entropy_count = r->poolinfo->POOLBITS;
552 r->entropy_count = entropy_count;
1da177e4 553
88c730da 554 /* should we wake readers? */
8b76f46a 555 if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
88c730da 556 wake_up_interruptible(&random_read_wait);
9a6f70bb
JD
557 kill_fasync(&fasync, SIGIO, POLL_IN);
558 }
1da177e4
LT
559 spin_unlock_irqrestore(&r->lock, flags);
560}
561
562/*********************************************************************
563 *
564 * Entropy input management
565 *
566 *********************************************************************/
567
568/* There is one of these per entropy source */
569struct timer_rand_state {
570 cycles_t last_time;
90b75ee5 571 long last_delta, last_delta2;
1da177e4
LT
572 unsigned dont_count_entropy:1;
573};
574
d7e51e66 575#ifndef CONFIG_GENERIC_HARDIRQS
2f983570
YL
576
577static struct timer_rand_state *irq_timer_state[NR_IRQS];
578
579static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
580{
581 return irq_timer_state[irq];
582}
583
584static void set_timer_rand_state(unsigned int irq,
585 struct timer_rand_state *state)
586{
587 irq_timer_state[irq] = state;
588}
589
590#else
591
592static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
593{
594 struct irq_desc *desc;
595
596 desc = irq_to_desc(irq);
597
598 return desc->timer_rand_state;
599}
600
601static void set_timer_rand_state(unsigned int irq,
602 struct timer_rand_state *state)
603{
604 struct irq_desc *desc;
605
606 desc = irq_to_desc(irq);
607
608 desc->timer_rand_state = state;
609}
0b8f1efa 610#endif
3060d6fe 611
3060d6fe
YL
612static struct timer_rand_state input_timer_state;
613
1da177e4
LT
614/*
615 * This function adds entropy to the entropy "pool" by using timing
616 * delays. It uses the timer_rand_state structure to make an estimate
617 * of how many bits of entropy this call has added to the pool.
618 *
619 * The number "num" is also added to the pool - it should somehow describe
620 * the type of event which just happened. This is currently 0-255 for
621 * keyboard scan codes, and 256 upwards for interrupts.
622 *
623 */
624static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
625{
626 struct {
1da177e4 627 long jiffies;
cf833d0b 628 unsigned cycles;
1da177e4
LT
629 unsigned num;
630 } sample;
631 long delta, delta2, delta3;
632
633 preempt_disable();
634 /* if over the trickle threshold, use only 1 in 4096 samples */
635 if (input_pool.entropy_count > trickle_thresh &&
b29c617a 636 ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
1da177e4
LT
637 goto out;
638
639 sample.jiffies = jiffies;
cf833d0b
LT
640
641 /* Use arch random value, fall back to cycles */
642 if (!arch_get_random_int(&sample.cycles))
643 sample.cycles = get_cycles();
644
1da177e4 645 sample.num = num;
e68e5b66 646 mix_pool_bytes(&input_pool, &sample, sizeof(sample));
1da177e4
LT
647
648 /*
649 * Calculate number of bits of randomness we probably added.
650 * We take into account the first, second and third-order deltas
651 * in order to make our estimate.
652 */
653
654 if (!state->dont_count_entropy) {
655 delta = sample.jiffies - state->last_time;
656 state->last_time = sample.jiffies;
657
658 delta2 = delta - state->last_delta;
659 state->last_delta = delta;
660
661 delta3 = delta2 - state->last_delta2;
662 state->last_delta2 = delta2;
663
664 if (delta < 0)
665 delta = -delta;
666 if (delta2 < 0)
667 delta2 = -delta2;
668 if (delta3 < 0)
669 delta3 = -delta3;
670 if (delta > delta2)
671 delta = delta2;
672 if (delta > delta3)
673 delta = delta3;
674
675 /*
676 * delta is now minimum absolute delta.
677 * Round down by 1 bit on general principles,
678 * and limit entropy entimate to 12 bits.
679 */
adc782da
MM
680 credit_entropy_bits(&input_pool,
681 min_t(int, fls(delta>>1), 11));
1da177e4 682 }
1da177e4
LT
683out:
684 preempt_enable();
685}
686
d251575a 687void add_input_randomness(unsigned int type, unsigned int code,
1da177e4
LT
688 unsigned int value)
689{
690 static unsigned char last_value;
691
692 /* ignore autorepeat and the like */
693 if (value == last_value)
694 return;
695
696 DEBUG_ENT("input event\n");
697 last_value = value;
698 add_timer_randomness(&input_timer_state,
699 (type << 4) ^ code ^ (code >> 4) ^ value);
700}
80fc9f53 701EXPORT_SYMBOL_GPL(add_input_randomness);
1da177e4
LT
702
703void add_interrupt_randomness(int irq)
704{
3060d6fe
YL
705 struct timer_rand_state *state;
706
707 state = get_timer_rand_state(irq);
708
709 if (state == NULL)
1da177e4
LT
710 return;
711
712 DEBUG_ENT("irq event %d\n", irq);
3060d6fe 713 add_timer_randomness(state, 0x100 + irq);
1da177e4
LT
714}
715
9361401e 716#ifdef CONFIG_BLOCK
1da177e4
LT
717void add_disk_randomness(struct gendisk *disk)
718{
719 if (!disk || !disk->random)
720 return;
721 /* first major is 1, so we get >= 0x200 here */
f331c029
TH
722 DEBUG_ENT("disk event %d:%d\n",
723 MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
1da177e4 724
f331c029 725 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1da177e4 726}
9361401e 727#endif
1da177e4 728
1da177e4
LT
729/*********************************************************************
730 *
731 * Entropy extraction routines
732 *
733 *********************************************************************/
734
90b75ee5 735static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1da177e4
LT
736 size_t nbytes, int min, int rsvd);
737
738/*
25985edc 739 * This utility inline function is responsible for transferring entropy
1da177e4
LT
740 * from the primary pool to the secondary extraction pool. We make
741 * sure we pull enough for a 'catastrophic reseed'.
742 */
743static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
744{
745 __u32 tmp[OUTPUT_POOL_WORDS];
746
747 if (r->pull && r->entropy_count < nbytes * 8 &&
748 r->entropy_count < r->poolinfo->POOLBITS) {
5a021e9f 749 /* If we're limited, always leave two wakeup worth's BITS */
1da177e4 750 int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
5a021e9f
MM
751 int bytes = nbytes;
752
753 /* pull at least as many as BYTES as wakeup BITS */
754 bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
755 /* but never more than the buffer size */
756 bytes = min_t(int, bytes, sizeof(tmp));
1da177e4
LT
757
758 DEBUG_ENT("going to reseed %s with %d bits "
759 "(%d of %d requested)\n",
760 r->name, bytes * 8, nbytes * 8, r->entropy_count);
761
90b75ee5
MM
762 bytes = extract_entropy(r->pull, tmp, bytes,
763 random_read_wakeup_thresh / 8, rsvd);
e68e5b66 764 mix_pool_bytes(r, tmp, bytes);
adc782da 765 credit_entropy_bits(r, bytes*8);
1da177e4
LT
766 }
767}
768
769/*
770 * These functions extracts randomness from the "entropy pool", and
771 * returns it in a buffer.
772 *
773 * The min parameter specifies the minimum amount we can pull before
774 * failing to avoid races that defeat catastrophic reseeding while the
775 * reserved parameter indicates how much entropy we must leave in the
776 * pool after each pull to avoid starving other readers.
777 *
778 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
779 */
780
781static size_t account(struct entropy_store *r, size_t nbytes, int min,
782 int reserved)
783{
784 unsigned long flags;
785
1da177e4
LT
786 /* Hold lock while accounting */
787 spin_lock_irqsave(&r->lock, flags);
788
cda796a3 789 BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
1da177e4
LT
790 DEBUG_ENT("trying to extract %d bits from %s\n",
791 nbytes * 8, r->name);
792
793 /* Can we pull enough? */
794 if (r->entropy_count / 8 < min + reserved) {
795 nbytes = 0;
796 } else {
797 /* If limited, never pull more than available */
798 if (r->limit && nbytes + reserved >= r->entropy_count / 8)
799 nbytes = r->entropy_count/8 - reserved;
800
90b75ee5 801 if (r->entropy_count / 8 >= nbytes + reserved)
1da177e4
LT
802 r->entropy_count -= nbytes*8;
803 else
804 r->entropy_count = reserved;
805
9a6f70bb 806 if (r->entropy_count < random_write_wakeup_thresh) {
1da177e4 807 wake_up_interruptible(&random_write_wait);
9a6f70bb
JD
808 kill_fasync(&fasync, SIGIO, POLL_OUT);
809 }
1da177e4
LT
810 }
811
812 DEBUG_ENT("debiting %d entropy credits from %s%s\n",
813 nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
814
815 spin_unlock_irqrestore(&r->lock, flags);
816
817 return nbytes;
818}
819
820static void extract_buf(struct entropy_store *r, __u8 *out)
821{
602b6aee 822 int i;
e68e5b66
MM
823 __u32 hash[5], workspace[SHA_WORKSPACE_WORDS];
824 __u8 extract[64];
1da177e4 825
1c0ad3d4 826 /* Generate a hash across the pool, 16 words (512 bits) at a time */
ffd8d3fa 827 sha_init(hash);
1c0ad3d4
MM
828 for (i = 0; i < r->poolinfo->poolwords; i += 16)
829 sha_transform(hash, (__u8 *)(r->pool + i), workspace);
830
1da177e4 831 /*
1c0ad3d4
MM
832 * We mix the hash back into the pool to prevent backtracking
833 * attacks (where the attacker knows the state of the pool
834 * plus the current outputs, and attempts to find previous
835 * ouputs), unless the hash function can be inverted. By
836 * mixing at least a SHA1 worth of hash data back, we make
837 * brute-forcing the feedback as hard as brute-forcing the
838 * hash.
1da177e4 839 */
e68e5b66 840 mix_pool_bytes_extract(r, hash, sizeof(hash), extract);
1da177e4
LT
841
842 /*
1c0ad3d4
MM
843 * To avoid duplicates, we atomically extract a portion of the
844 * pool while mixing, and hash one final time.
1da177e4 845 */
e68e5b66 846 sha_transform(hash, extract, workspace);
ffd8d3fa
MM
847 memset(extract, 0, sizeof(extract));
848 memset(workspace, 0, sizeof(workspace));
1da177e4
LT
849
850 /*
1c0ad3d4
MM
851 * In case the hash function has some recognizable output
852 * pattern, we fold it in half. Thus, we always feed back
853 * twice as much data as we output.
1da177e4 854 */
ffd8d3fa
MM
855 hash[0] ^= hash[3];
856 hash[1] ^= hash[4];
857 hash[2] ^= rol32(hash[2], 16);
858 memcpy(out, hash, EXTRACT_SIZE);
859 memset(hash, 0, sizeof(hash));
1da177e4
LT
860}
861
90b75ee5 862static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1da177e4
LT
863 size_t nbytes, int min, int reserved)
864{
865 ssize_t ret = 0, i;
866 __u8 tmp[EXTRACT_SIZE];
5b739ef8 867 unsigned long flags;
1da177e4
LT
868
869 xfer_secondary_pool(r, nbytes);
870 nbytes = account(r, nbytes, min, reserved);
871
872 while (nbytes) {
873 extract_buf(r, tmp);
5b739ef8 874
e954bc91 875 if (fips_enabled) {
5b739ef8
NH
876 spin_lock_irqsave(&r->lock, flags);
877 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
878 panic("Hardware RNG duplicated output!\n");
879 memcpy(r->last_data, tmp, EXTRACT_SIZE);
880 spin_unlock_irqrestore(&r->lock, flags);
881 }
1da177e4
LT
882 i = min_t(int, nbytes, EXTRACT_SIZE);
883 memcpy(buf, tmp, i);
884 nbytes -= i;
885 buf += i;
886 ret += i;
887 }
888
889 /* Wipe data just returned from memory */
890 memset(tmp, 0, sizeof(tmp));
891
892 return ret;
893}
894
895static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
896 size_t nbytes)
897{
898 ssize_t ret = 0, i;
899 __u8 tmp[EXTRACT_SIZE];
900
901 xfer_secondary_pool(r, nbytes);
902 nbytes = account(r, nbytes, 0, 0);
903
904 while (nbytes) {
905 if (need_resched()) {
906 if (signal_pending(current)) {
907 if (ret == 0)
908 ret = -ERESTARTSYS;
909 break;
910 }
911 schedule();
912 }
913
914 extract_buf(r, tmp);
915 i = min_t(int, nbytes, EXTRACT_SIZE);
916 if (copy_to_user(buf, tmp, i)) {
917 ret = -EFAULT;
918 break;
919 }
920
921 nbytes -= i;
922 buf += i;
923 ret += i;
924 }
925
926 /* Wipe data just returned from memory */
927 memset(tmp, 0, sizeof(tmp));
928
929 return ret;
930}
931
932/*
933 * This function is the exported kernel interface. It returns some
934 * number of good random numbers, suitable for seeding TCP sequence
935 * numbers, etc.
936 */
937void get_random_bytes(void *buf, int nbytes)
938{
63d77173
PA
939 char *p = buf;
940
941 while (nbytes) {
942 unsigned long v;
943 int chunk = min(nbytes, (int)sizeof(unsigned long));
944
945 if (!arch_get_random_long(&v))
946 break;
947
bd29e568 948 memcpy(p, &v, chunk);
63d77173
PA
949 p += chunk;
950 nbytes -= chunk;
951 }
952
953 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1da177e4 954}
1da177e4
LT
955EXPORT_SYMBOL(get_random_bytes);
956
957/*
958 * init_std_data - initialize pool with system data
959 *
960 * @r: pool to initialize
961 *
962 * This function clears the pool's entropy count and mixes some system
963 * data into the pool to prepare it for use. The pool is not cleared
964 * as that can only decrease the entropy in the pool.
965 */
966static void init_std_data(struct entropy_store *r)
967{
3e88bdff 968 int i;
f8595815 969 ktime_t now;
1da177e4
LT
970 unsigned long flags;
971
972 spin_lock_irqsave(&r->lock, flags);
973 r->entropy_count = 0;
974 spin_unlock_irqrestore(&r->lock, flags);
975
f8595815 976 now = ktime_get_real();
e68e5b66 977 mix_pool_bytes(r, &now, sizeof(now));
2dac8e54 978 for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof flags) {
3e88bdff
TT
979 if (!arch_get_random_long(&flags))
980 break;
981 mix_pool_bytes(r, &flags, sizeof(flags));
982 }
e68e5b66 983 mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1da177e4
LT
984}
985
53c3f63e 986static int rand_initialize(void)
1da177e4
LT
987{
988 init_std_data(&input_pool);
989 init_std_data(&blocking_pool);
990 init_std_data(&nonblocking_pool);
991 return 0;
992}
993module_init(rand_initialize);
994
995void rand_initialize_irq(int irq)
996{
997 struct timer_rand_state *state;
998
3060d6fe
YL
999 state = get_timer_rand_state(irq);
1000
1001 if (state)
1da177e4
LT
1002 return;
1003
1004 /*
f8595815 1005 * If kzalloc returns null, we just won't use that entropy
1da177e4
LT
1006 * source.
1007 */
f8595815
ED
1008 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1009 if (state)
3060d6fe 1010 set_timer_rand_state(irq, state);
1da177e4
LT
1011}
1012
9361401e 1013#ifdef CONFIG_BLOCK
1da177e4
LT
1014void rand_initialize_disk(struct gendisk *disk)
1015{
1016 struct timer_rand_state *state;
1017
1018 /*
f8595815 1019 * If kzalloc returns null, we just won't use that entropy
1da177e4
LT
1020 * source.
1021 */
f8595815
ED
1022 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1023 if (state)
1da177e4 1024 disk->random = state;
1da177e4 1025}
9361401e 1026#endif
1da177e4
LT
1027
1028static ssize_t
90b75ee5 1029random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1da177e4
LT
1030{
1031 ssize_t n, retval = 0, count = 0;
1032
1033 if (nbytes == 0)
1034 return 0;
1035
1036 while (nbytes > 0) {
1037 n = nbytes;
1038 if (n > SEC_XFER_SIZE)
1039 n = SEC_XFER_SIZE;
1040
1041 DEBUG_ENT("reading %d bits\n", n*8);
1042
1043 n = extract_entropy_user(&blocking_pool, buf, n);
1044
1045 DEBUG_ENT("read got %d bits (%d still needed)\n",
1046 n*8, (nbytes-n)*8);
1047
1048 if (n == 0) {
1049 if (file->f_flags & O_NONBLOCK) {
1050 retval = -EAGAIN;
1051 break;
1052 }
1053
1054 DEBUG_ENT("sleeping?\n");
1055
1056 wait_event_interruptible(random_read_wait,
1057 input_pool.entropy_count >=
1058 random_read_wakeup_thresh);
1059
1060 DEBUG_ENT("awake\n");
1061
1062 if (signal_pending(current)) {
1063 retval = -ERESTARTSYS;
1064 break;
1065 }
1066
1067 continue;
1068 }
1069
1070 if (n < 0) {
1071 retval = n;
1072 break;
1073 }
1074 count += n;
1075 buf += n;
1076 nbytes -= n;
1077 break; /* This break makes the device work */
1078 /* like a named pipe */
1079 }
1080
1da177e4
LT
1081 return (count ? count : retval);
1082}
1083
1084static ssize_t
90b75ee5 1085urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1da177e4
LT
1086{
1087 return extract_entropy_user(&nonblocking_pool, buf, nbytes);
1088}
1089
1090static unsigned int
1091random_poll(struct file *file, poll_table * wait)
1092{
1093 unsigned int mask;
1094
1095 poll_wait(file, &random_read_wait, wait);
1096 poll_wait(file, &random_write_wait, wait);
1097 mask = 0;
1098 if (input_pool.entropy_count >= random_read_wakeup_thresh)
1099 mask |= POLLIN | POLLRDNORM;
1100 if (input_pool.entropy_count < random_write_wakeup_thresh)
1101 mask |= POLLOUT | POLLWRNORM;
1102 return mask;
1103}
1104
7f397dcd
MM
1105static int
1106write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1da177e4 1107{
1da177e4
LT
1108 size_t bytes;
1109 __u32 buf[16];
1110 const char __user *p = buffer;
1da177e4 1111
7f397dcd
MM
1112 while (count > 0) {
1113 bytes = min(count, sizeof(buf));
1114 if (copy_from_user(&buf, p, bytes))
1115 return -EFAULT;
1da177e4 1116
7f397dcd 1117 count -= bytes;
1da177e4
LT
1118 p += bytes;
1119
e68e5b66 1120 mix_pool_bytes(r, buf, bytes);
91f3f1e3 1121 cond_resched();
1da177e4 1122 }
7f397dcd
MM
1123
1124 return 0;
1125}
1126
90b75ee5
MM
1127static ssize_t random_write(struct file *file, const char __user *buffer,
1128 size_t count, loff_t *ppos)
7f397dcd
MM
1129{
1130 size_t ret;
7f397dcd
MM
1131
1132 ret = write_pool(&blocking_pool, buffer, count);
1133 if (ret)
1134 return ret;
1135 ret = write_pool(&nonblocking_pool, buffer, count);
1136 if (ret)
1137 return ret;
1138
7f397dcd 1139 return (ssize_t)count;
1da177e4
LT
1140}
1141
43ae4860 1142static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1da177e4
LT
1143{
1144 int size, ent_count;
1145 int __user *p = (int __user *)arg;
1146 int retval;
1147
1148 switch (cmd) {
1149 case RNDGETENTCNT:
43ae4860
MM
1150 /* inherently racy, no point locking */
1151 if (put_user(input_pool.entropy_count, p))
1da177e4
LT
1152 return -EFAULT;
1153 return 0;
1154 case RNDADDTOENTCNT:
1155 if (!capable(CAP_SYS_ADMIN))
1156 return -EPERM;
1157 if (get_user(ent_count, p))
1158 return -EFAULT;
adc782da 1159 credit_entropy_bits(&input_pool, ent_count);
1da177e4
LT
1160 return 0;
1161 case RNDADDENTROPY:
1162 if (!capable(CAP_SYS_ADMIN))
1163 return -EPERM;
1164 if (get_user(ent_count, p++))
1165 return -EFAULT;
1166 if (ent_count < 0)
1167 return -EINVAL;
1168 if (get_user(size, p++))
1169 return -EFAULT;
7f397dcd
MM
1170 retval = write_pool(&input_pool, (const char __user *)p,
1171 size);
1da177e4
LT
1172 if (retval < 0)
1173 return retval;
adc782da 1174 credit_entropy_bits(&input_pool, ent_count);
1da177e4
LT
1175 return 0;
1176 case RNDZAPENTCNT:
1177 case RNDCLEARPOOL:
1178 /* Clear the entropy pool counters. */
1179 if (!capable(CAP_SYS_ADMIN))
1180 return -EPERM;
53c3f63e 1181 rand_initialize();
1da177e4
LT
1182 return 0;
1183 default:
1184 return -EINVAL;
1185 }
1186}
1187
9a6f70bb
JD
1188static int random_fasync(int fd, struct file *filp, int on)
1189{
1190 return fasync_helper(fd, filp, on, &fasync);
1191}
1192
2b8693c0 1193const struct file_operations random_fops = {
1da177e4
LT
1194 .read = random_read,
1195 .write = random_write,
1196 .poll = random_poll,
43ae4860 1197 .unlocked_ioctl = random_ioctl,
9a6f70bb 1198 .fasync = random_fasync,
6038f373 1199 .llseek = noop_llseek,
1da177e4
LT
1200};
1201
2b8693c0 1202const struct file_operations urandom_fops = {
1da177e4
LT
1203 .read = urandom_read,
1204 .write = random_write,
43ae4860 1205 .unlocked_ioctl = random_ioctl,
9a6f70bb 1206 .fasync = random_fasync,
6038f373 1207 .llseek = noop_llseek,
1da177e4
LT
1208};
1209
1210/***************************************************************
1211 * Random UUID interface
1212 *
1213 * Used here for a Boot ID, but can be useful for other kernel
1214 * drivers.
1215 ***************************************************************/
1216
1217/*
1218 * Generate random UUID
1219 */
1220void generate_random_uuid(unsigned char uuid_out[16])
1221{
1222 get_random_bytes(uuid_out, 16);
c41b20e7 1223 /* Set UUID version to 4 --- truly random generation */
1da177e4
LT
1224 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1225 /* Set the UUID variant to DCE */
1226 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1227}
1da177e4
LT
1228EXPORT_SYMBOL(generate_random_uuid);
1229
1230/********************************************************************
1231 *
1232 * Sysctl interface
1233 *
1234 ********************************************************************/
1235
1236#ifdef CONFIG_SYSCTL
1237
1238#include <linux/sysctl.h>
1239
1240static int min_read_thresh = 8, min_write_thresh;
1241static int max_read_thresh = INPUT_POOL_WORDS * 32;
1242static int max_write_thresh = INPUT_POOL_WORDS * 32;
1243static char sysctl_bootid[16];
1244
1245/*
1246 * These functions is used to return both the bootid UUID, and random
1247 * UUID. The difference is in whether table->data is NULL; if it is,
1248 * then a new UUID is generated and returned to the user.
1249 *
1250 * If the user accesses this via the proc interface, it will be returned
1251 * as an ASCII string in the standard UUID format. If accesses via the
1252 * sysctl system call, it is returned as 16 bytes of binary data.
1253 */
8d65af78 1254static int proc_do_uuid(ctl_table *table, int write,
1da177e4
LT
1255 void __user *buffer, size_t *lenp, loff_t *ppos)
1256{
1257 ctl_table fake_table;
1258 unsigned char buf[64], tmp_uuid[16], *uuid;
1259
1260 uuid = table->data;
1261 if (!uuid) {
1262 uuid = tmp_uuid;
1da177e4 1263 generate_random_uuid(uuid);
44e4360f
MD
1264 } else {
1265 static DEFINE_SPINLOCK(bootid_spinlock);
1266
1267 spin_lock(&bootid_spinlock);
1268 if (!uuid[8])
1269 generate_random_uuid(uuid);
1270 spin_unlock(&bootid_spinlock);
1271 }
1da177e4 1272
35900771
JP
1273 sprintf(buf, "%pU", uuid);
1274
1da177e4
LT
1275 fake_table.data = buf;
1276 fake_table.maxlen = sizeof(buf);
1277
8d65af78 1278 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1da177e4
LT
1279}
1280
1da177e4 1281static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
74feec5d 1282extern ctl_table random_table[];
1da177e4
LT
1283ctl_table random_table[] = {
1284 {
1da177e4
LT
1285 .procname = "poolsize",
1286 .data = &sysctl_poolsize,
1287 .maxlen = sizeof(int),
1288 .mode = 0444,
6d456111 1289 .proc_handler = proc_dointvec,
1da177e4
LT
1290 },
1291 {
1da177e4
LT
1292 .procname = "entropy_avail",
1293 .maxlen = sizeof(int),
1294 .mode = 0444,
6d456111 1295 .proc_handler = proc_dointvec,
1da177e4
LT
1296 .data = &input_pool.entropy_count,
1297 },
1298 {
1da177e4
LT
1299 .procname = "read_wakeup_threshold",
1300 .data = &random_read_wakeup_thresh,
1301 .maxlen = sizeof(int),
1302 .mode = 0644,
6d456111 1303 .proc_handler = proc_dointvec_minmax,
1da177e4
LT
1304 .extra1 = &min_read_thresh,
1305 .extra2 = &max_read_thresh,
1306 },
1307 {
1da177e4
LT
1308 .procname = "write_wakeup_threshold",
1309 .data = &random_write_wakeup_thresh,
1310 .maxlen = sizeof(int),
1311 .mode = 0644,
6d456111 1312 .proc_handler = proc_dointvec_minmax,
1da177e4
LT
1313 .extra1 = &min_write_thresh,
1314 .extra2 = &max_write_thresh,
1315 },
1316 {
1da177e4
LT
1317 .procname = "boot_id",
1318 .data = &sysctl_bootid,
1319 .maxlen = 16,
1320 .mode = 0444,
6d456111 1321 .proc_handler = proc_do_uuid,
1da177e4
LT
1322 },
1323 {
1da177e4
LT
1324 .procname = "uuid",
1325 .maxlen = 16,
1326 .mode = 0444,
6d456111 1327 .proc_handler = proc_do_uuid,
1da177e4 1328 },
894d2491 1329 { }
1da177e4
LT
1330};
1331#endif /* CONFIG_SYSCTL */
1332
6e5714ea 1333static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1da177e4 1334
6e5714ea 1335static int __init random_int_secret_init(void)
1da177e4 1336{
6e5714ea 1337 get_random_bytes(random_int_secret, sizeof(random_int_secret));
1da177e4
LT
1338 return 0;
1339}
6e5714ea 1340late_initcall(random_int_secret_init);
1da177e4
LT
1341
1342/*
1343 * Get a random word for internal kernel use only. Similar to urandom but
1344 * with the goal of minimal entropy pool depletion. As a result, the random
1345 * value is not cryptographically secure but for several uses the cost of
1346 * depleting entropy is too high
1347 */
74feec5d 1348static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1da177e4
LT
1349unsigned int get_random_int(void)
1350{
63d77173 1351 __u32 *hash;
6e5714ea 1352 unsigned int ret;
8a0a9bd4 1353
63d77173
PA
1354 if (arch_get_random_int(&ret))
1355 return ret;
1356
1357 hash = get_cpu_var(get_random_int_hash);
8a0a9bd4 1358
26a9a418 1359 hash[0] += current->pid + jiffies + get_cycles();
6e5714ea
DM
1360 md5_transform(hash, random_int_secret);
1361 ret = hash[0];
8a0a9bd4
LT
1362 put_cpu_var(get_random_int_hash);
1363
1364 return ret;
1da177e4
LT
1365}
1366
1367/*
1368 * randomize_range() returns a start address such that
1369 *
1370 * [...... <range> .....]
1371 * start end
1372 *
1373 * a <range> with size "len" starting at the return value is inside in the
1374 * area defined by [start, end], but is otherwise randomized.
1375 */
1376unsigned long
1377randomize_range(unsigned long start, unsigned long end, unsigned long len)
1378{
1379 unsigned long range = end - len - start;
1380
1381 if (end <= start + len)
1382 return 0;
1383 return PAGE_ALIGN(get_random_int() % range + start);
1384}