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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
LT
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 *
a2080a67 128 * void add_device_randomness(const void *buf, unsigned int size);
1da177e4
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129 * void add_input_randomness(unsigned int type, unsigned int code,
130 * unsigned int value);
775f4b29 131 * void add_interrupt_randomness(int irq, int irq_flags);
442a4fff 132 * void add_disk_randomness(struct gendisk *disk);
1da177e4 133 *
a2080a67
LT
134 * add_device_randomness() is for adding data to the random pool that
135 * is likely to differ between two devices (or possibly even per boot).
136 * This would be things like MAC addresses or serial numbers, or the
137 * read-out of the RTC. This does *not* add any actual entropy to the
138 * pool, but it initializes the pool to different values for devices
139 * that might otherwise be identical and have very little entropy
140 * available to them (particularly common in the embedded world).
141 *
1da177e4
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142 * add_input_randomness() uses the input layer interrupt timing, as well as
143 * the event type information from the hardware.
144 *
775f4b29
TT
145 * add_interrupt_randomness() uses the interrupt timing as random
146 * inputs to the entropy pool. Using the cycle counters and the irq source
147 * as inputs, it feeds the randomness roughly once a second.
442a4fff
JW
148 *
149 * add_disk_randomness() uses what amounts to the seek time of block
150 * layer request events, on a per-disk_devt basis, as input to the
151 * entropy pool. Note that high-speed solid state drives with very low
152 * seek times do not make for good sources of entropy, as their seek
153 * times are usually fairly consistent.
1da177e4
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154 *
155 * All of these routines try to estimate how many bits of randomness a
156 * particular randomness source. They do this by keeping track of the
157 * first and second order deltas of the event timings.
158 *
159 * Ensuring unpredictability at system startup
160 * ============================================
161 *
162 * When any operating system starts up, it will go through a sequence
163 * of actions that are fairly predictable by an adversary, especially
164 * if the start-up does not involve interaction with a human operator.
165 * This reduces the actual number of bits of unpredictability in the
166 * entropy pool below the value in entropy_count. In order to
167 * counteract this effect, it helps to carry information in the
168 * entropy pool across shut-downs and start-ups. To do this, put the
169 * following lines an appropriate script which is run during the boot
170 * sequence:
171 *
172 * echo "Initializing random number generator..."
173 * random_seed=/var/run/random-seed
174 * # Carry a random seed from start-up to start-up
175 * # Load and then save the whole entropy pool
176 * if [ -f $random_seed ]; then
177 * cat $random_seed >/dev/urandom
178 * else
179 * touch $random_seed
180 * fi
181 * chmod 600 $random_seed
182 * dd if=/dev/urandom of=$random_seed count=1 bs=512
183 *
184 * and the following lines in an appropriate script which is run as
185 * the system is shutdown:
186 *
187 * # Carry a random seed from shut-down to start-up
188 * # Save the whole entropy pool
189 * echo "Saving random seed..."
190 * random_seed=/var/run/random-seed
191 * touch $random_seed
192 * chmod 600 $random_seed
193 * dd if=/dev/urandom of=$random_seed count=1 bs=512
194 *
195 * For example, on most modern systems using the System V init
196 * scripts, such code fragments would be found in
197 * /etc/rc.d/init.d/random. On older Linux systems, the correct script
198 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
199 *
200 * Effectively, these commands cause the contents of the entropy pool
201 * to be saved at shut-down time and reloaded into the entropy pool at
202 * start-up. (The 'dd' in the addition to the bootup script is to
203 * make sure that /etc/random-seed is different for every start-up,
204 * even if the system crashes without executing rc.0.) Even with
205 * complete knowledge of the start-up activities, predicting the state
206 * of the entropy pool requires knowledge of the previous history of
207 * the system.
208 *
209 * Configuring the /dev/random driver under Linux
210 * ==============================================
211 *
212 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
213 * the /dev/mem major number (#1). So if your system does not have
214 * /dev/random and /dev/urandom created already, they can be created
215 * by using the commands:
216 *
217 * mknod /dev/random c 1 8
218 * mknod /dev/urandom c 1 9
219 *
220 * Acknowledgements:
221 * =================
222 *
223 * Ideas for constructing this random number generator were derived
224 * from Pretty Good Privacy's random number generator, and from private
225 * discussions with Phil Karn. Colin Plumb provided a faster random
226 * number generator, which speed up the mixing function of the entropy
227 * pool, taken from PGPfone. Dale Worley has also contributed many
228 * useful ideas and suggestions to improve this driver.
229 *
230 * Any flaws in the design are solely my responsibility, and should
231 * not be attributed to the Phil, Colin, or any of authors of PGP.
232 *
233 * Further background information on this topic may be obtained from
234 * RFC 1750, "Randomness Recommendations for Security", by Donald
235 * Eastlake, Steve Crocker, and Jeff Schiller.
236 */
237
238#include <linux/utsname.h>
1da177e4
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239#include <linux/module.h>
240#include <linux/kernel.h>
241#include <linux/major.h>
242#include <linux/string.h>
243#include <linux/fcntl.h>
244#include <linux/slab.h>
245#include <linux/random.h>
246#include <linux/poll.h>
247#include <linux/init.h>
248#include <linux/fs.h>
249#include <linux/genhd.h>
250#include <linux/interrupt.h>
27ac792c 251#include <linux/mm.h>
1da177e4
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252#include <linux/spinlock.h>
253#include <linux/percpu.h>
254#include <linux/cryptohash.h>
5b739ef8 255#include <linux/fips.h>
775f4b29 256#include <linux/ptrace.h>
e6d4947b 257#include <linux/kmemcheck.h>
1da177e4 258
d178a1eb
YL
259#ifdef CONFIG_GENERIC_HARDIRQS
260# include <linux/irq.h>
261#endif
262
1da177e4
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263#include <asm/processor.h>
264#include <asm/uaccess.h>
265#include <asm/irq.h>
775f4b29 266#include <asm/irq_regs.h>
1da177e4
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267#include <asm/io.h>
268
00ce1db1
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269#define CREATE_TRACE_POINTS
270#include <trace/events/random.h>
271
1da177e4
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272/*
273 * Configuration information
274 */
275#define INPUT_POOL_WORDS 128
276#define OUTPUT_POOL_WORDS 32
277#define SEC_XFER_SIZE 512
e954bc91 278#define EXTRACT_SIZE 10
1da177e4 279
d2e7c96a
PA
280#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
281
1da177e4
LT
282/*
283 * The minimum number of bits of entropy before we wake up a read on
284 * /dev/random. Should be enough to do a significant reseed.
285 */
286static int random_read_wakeup_thresh = 64;
287
288/*
289 * If the entropy count falls under this number of bits, then we
290 * should wake up processes which are selecting or polling on write
291 * access to /dev/random.
292 */
293static int random_write_wakeup_thresh = 128;
294
295/*
296 * When the input pool goes over trickle_thresh, start dropping most
297 * samples to avoid wasting CPU time and reduce lock contention.
298 */
299
6c036527 300static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
1da177e4 301
90b75ee5 302static DEFINE_PER_CPU(int, trickle_count);
1da177e4
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303
304/*
305 * A pool of size .poolwords is stirred with a primitive polynomial
306 * of degree .poolwords over GF(2). The taps for various sizes are
307 * defined below. They are chosen to be evenly spaced (minimum RMS
308 * distance from evenly spaced; the numbers in the comments are a
309 * scaled squared error sum) except for the last tap, which is 1 to
310 * get the twisting happening as fast as possible.
311 */
312static struct poolinfo {
313 int poolwords;
314 int tap1, tap2, tap3, tap4, tap5;
315} poolinfo_table[] = {
316 /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
317 { 128, 103, 76, 51, 25, 1 },
318 /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
319 { 32, 26, 20, 14, 7, 1 },
320#if 0
321 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
322 { 2048, 1638, 1231, 819, 411, 1 },
323
324 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
325 { 1024, 817, 615, 412, 204, 1 },
326
327 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
328 { 1024, 819, 616, 410, 207, 2 },
329
330 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
331 { 512, 411, 308, 208, 104, 1 },
332
333 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
334 { 512, 409, 307, 206, 102, 2 },
335 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
336 { 512, 409, 309, 205, 103, 2 },
337
338 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
339 { 256, 205, 155, 101, 52, 1 },
340
341 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
342 { 128, 103, 78, 51, 27, 2 },
343
344 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
345 { 64, 52, 39, 26, 14, 1 },
346#endif
347};
348
349#define POOLBITS poolwords*32
350#define POOLBYTES poolwords*4
351
352/*
353 * For the purposes of better mixing, we use the CRC-32 polynomial as
354 * well to make a twisted Generalized Feedback Shift Reigster
355 *
356 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
357 * Transactions on Modeling and Computer Simulation 2(3):179-194.
358 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
359 * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
360 *
361 * Thanks to Colin Plumb for suggesting this.
362 *
363 * We have not analyzed the resultant polynomial to prove it primitive;
364 * in fact it almost certainly isn't. Nonetheless, the irreducible factors
365 * of a random large-degree polynomial over GF(2) are more than large enough
366 * that periodicity is not a concern.
367 *
368 * The input hash is much less sensitive than the output hash. All
369 * that we want of it is that it be a good non-cryptographic hash;
370 * i.e. it not produce collisions when fed "random" data of the sort
371 * we expect to see. As long as the pool state differs for different
372 * inputs, we have preserved the input entropy and done a good job.
373 * The fact that an intelligent attacker can construct inputs that
374 * will produce controlled alterations to the pool's state is not
375 * important because we don't consider such inputs to contribute any
376 * randomness. The only property we need with respect to them is that
377 * the attacker can't increase his/her knowledge of the pool's state.
378 * Since all additions are reversible (knowing the final state and the
379 * input, you can reconstruct the initial state), if an attacker has
380 * any uncertainty about the initial state, he/she can only shuffle
381 * that uncertainty about, but never cause any collisions (which would
382 * decrease the uncertainty).
383 *
384 * The chosen system lets the state of the pool be (essentially) the input
385 * modulo the generator polymnomial. Now, for random primitive polynomials,
386 * this is a universal class of hash functions, meaning that the chance
387 * of a collision is limited by the attacker's knowledge of the generator
388 * polynomail, so if it is chosen at random, an attacker can never force
389 * a collision. Here, we use a fixed polynomial, but we *can* assume that
390 * ###--> it is unknown to the processes generating the input entropy. <-###
391 * Because of this important property, this is a good, collision-resistant
392 * hash; hash collisions will occur no more often than chance.
393 */
394
395/*
396 * Static global variables
397 */
398static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
399static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
9a6f70bb 400static struct fasync_struct *fasync;
1da177e4 401
90ab5ee9 402static bool debug;
1da177e4 403module_param(debug, bool, 0644);
90b75ee5
MM
404#define DEBUG_ENT(fmt, arg...) do { \
405 if (debug) \
406 printk(KERN_DEBUG "random %04d %04d %04d: " \
407 fmt,\
408 input_pool.entropy_count,\
409 blocking_pool.entropy_count,\
410 nonblocking_pool.entropy_count,\
411 ## arg); } while (0)
1da177e4
LT
412
413/**********************************************************************
414 *
415 * OS independent entropy store. Here are the functions which handle
416 * storing entropy in an entropy pool.
417 *
418 **********************************************************************/
419
420struct entropy_store;
421struct entropy_store {
43358209 422 /* read-only data: */
1da177e4
LT
423 struct poolinfo *poolinfo;
424 __u32 *pool;
425 const char *name;
1da177e4 426 struct entropy_store *pull;
4015d9a8 427 int limit;
1da177e4
LT
428
429 /* read-write data: */
43358209 430 spinlock_t lock;
1da177e4 431 unsigned add_ptr;
902c098a 432 unsigned input_rotate;
cda796a3 433 int entropy_count;
775f4b29 434 int entropy_total;
775f4b29 435 unsigned int initialized:1;
ec8f02da 436 bool last_data_init;
e954bc91 437 __u8 last_data[EXTRACT_SIZE];
1da177e4
LT
438};
439
440static __u32 input_pool_data[INPUT_POOL_WORDS];
441static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
442static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
443
444static struct entropy_store input_pool = {
445 .poolinfo = &poolinfo_table[0],
446 .name = "input",
447 .limit = 1,
eece09ec 448 .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
1da177e4
LT
449 .pool = input_pool_data
450};
451
452static struct entropy_store blocking_pool = {
453 .poolinfo = &poolinfo_table[1],
454 .name = "blocking",
455 .limit = 1,
456 .pull = &input_pool,
eece09ec 457 .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
1da177e4
LT
458 .pool = blocking_pool_data
459};
460
461static struct entropy_store nonblocking_pool = {
462 .poolinfo = &poolinfo_table[1],
463 .name = "nonblocking",
464 .pull = &input_pool,
eece09ec 465 .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
1da177e4
LT
466 .pool = nonblocking_pool_data
467};
468
775f4b29
TT
469static __u32 const twist_table[8] = {
470 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
471 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
472
1da177e4 473/*
e68e5b66 474 * This function adds bytes into the entropy "pool". It does not
1da177e4 475 * update the entropy estimate. The caller should call
adc782da 476 * credit_entropy_bits if this is appropriate.
1da177e4
LT
477 *
478 * The pool is stirred with a primitive polynomial of the appropriate
479 * degree, and then twisted. We twist by three bits at a time because
480 * it's cheap to do so and helps slightly in the expected case where
481 * the entropy is concentrated in the low-order bits.
482 */
00ce1db1
TT
483static void _mix_pool_bytes(struct entropy_store *r, const void *in,
484 int nbytes, __u8 out[64])
1da177e4 485{
993ba211 486 unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
feee7697 487 int input_rotate;
1da177e4 488 int wordmask = r->poolinfo->poolwords - 1;
e68e5b66 489 const char *bytes = in;
6d38b827 490 __u32 w;
1da177e4 491
1da177e4
LT
492 tap1 = r->poolinfo->tap1;
493 tap2 = r->poolinfo->tap2;
494 tap3 = r->poolinfo->tap3;
495 tap4 = r->poolinfo->tap4;
496 tap5 = r->poolinfo->tap5;
1da177e4 497
902c098a
TT
498 smp_rmb();
499 input_rotate = ACCESS_ONCE(r->input_rotate);
500 i = ACCESS_ONCE(r->add_ptr);
1da177e4 501
e68e5b66
MM
502 /* mix one byte at a time to simplify size handling and churn faster */
503 while (nbytes--) {
504 w = rol32(*bytes++, input_rotate & 31);
993ba211 505 i = (i - 1) & wordmask;
1da177e4
LT
506
507 /* XOR in the various taps */
993ba211 508 w ^= r->pool[i];
1da177e4
LT
509 w ^= r->pool[(i + tap1) & wordmask];
510 w ^= r->pool[(i + tap2) & wordmask];
511 w ^= r->pool[(i + tap3) & wordmask];
512 w ^= r->pool[(i + tap4) & wordmask];
513 w ^= r->pool[(i + tap5) & wordmask];
993ba211
MM
514
515 /* Mix the result back in with a twist */
1da177e4 516 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
feee7697
MM
517
518 /*
519 * Normally, we add 7 bits of rotation to the pool.
520 * At the beginning of the pool, add an extra 7 bits
521 * rotation, so that successive passes spread the
522 * input bits across the pool evenly.
523 */
524 input_rotate += i ? 7 : 14;
1da177e4
LT
525 }
526
902c098a
TT
527 ACCESS_ONCE(r->input_rotate) = input_rotate;
528 ACCESS_ONCE(r->add_ptr) = i;
529 smp_wmb();
1da177e4 530
993ba211
MM
531 if (out)
532 for (j = 0; j < 16; j++)
e68e5b66 533 ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
1da177e4
LT
534}
535
00ce1db1 536static void __mix_pool_bytes(struct entropy_store *r, const void *in,
902c098a 537 int nbytes, __u8 out[64])
00ce1db1
TT
538{
539 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
540 _mix_pool_bytes(r, in, nbytes, out);
541}
542
543static void mix_pool_bytes(struct entropy_store *r, const void *in,
544 int nbytes, __u8 out[64])
1da177e4 545{
902c098a
TT
546 unsigned long flags;
547
00ce1db1 548 trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
902c098a 549 spin_lock_irqsave(&r->lock, flags);
00ce1db1 550 _mix_pool_bytes(r, in, nbytes, out);
902c098a 551 spin_unlock_irqrestore(&r->lock, flags);
1da177e4
LT
552}
553
775f4b29
TT
554struct fast_pool {
555 __u32 pool[4];
556 unsigned long last;
557 unsigned short count;
558 unsigned char rotate;
559 unsigned char last_timer_intr;
560};
561
562/*
563 * This is a fast mixing routine used by the interrupt randomness
564 * collector. It's hardcoded for an 128 bit pool and assumes that any
565 * locks that might be needed are taken by the caller.
566 */
567static void fast_mix(struct fast_pool *f, const void *in, int nbytes)
568{
569 const char *bytes = in;
570 __u32 w;
571 unsigned i = f->count;
572 unsigned input_rotate = f->rotate;
573
574 while (nbytes--) {
575 w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
576 f->pool[(i + 1) & 3];
577 f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
578 input_rotate += (i++ & 3) ? 7 : 14;
579 }
580 f->count = i;
581 f->rotate = input_rotate;
582}
583
1da177e4
LT
584/*
585 * Credit (or debit) the entropy store with n bits of entropy
586 */
adc782da 587static void credit_entropy_bits(struct entropy_store *r, int nbits)
1da177e4 588{
902c098a 589 int entropy_count, orig;
1da177e4 590
adc782da
MM
591 if (!nbits)
592 return;
593
adc782da 594 DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
902c098a
TT
595retry:
596 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
8b76f46a 597 entropy_count += nbits;
00ce1db1 598
8b76f46a 599 if (entropy_count < 0) {
adc782da 600 DEBUG_ENT("negative entropy/overflow\n");
8b76f46a
AM
601 entropy_count = 0;
602 } else if (entropy_count > r->poolinfo->POOLBITS)
603 entropy_count = r->poolinfo->POOLBITS;
902c098a
TT
604 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
605 goto retry;
1da177e4 606
775f4b29
TT
607 if (!r->initialized && nbits > 0) {
608 r->entropy_total += nbits;
609 if (r->entropy_total > 128)
610 r->initialized = 1;
611 }
612
00ce1db1
TT
613 trace_credit_entropy_bits(r->name, nbits, entropy_count,
614 r->entropy_total, _RET_IP_);
615
88c730da 616 /* should we wake readers? */
8b76f46a 617 if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
88c730da 618 wake_up_interruptible(&random_read_wait);
9a6f70bb
JD
619 kill_fasync(&fasync, SIGIO, POLL_IN);
620 }
1da177e4
LT
621}
622
623/*********************************************************************
624 *
625 * Entropy input management
626 *
627 *********************************************************************/
628
629/* There is one of these per entropy source */
630struct timer_rand_state {
631 cycles_t last_time;
90b75ee5 632 long last_delta, last_delta2;
1da177e4
LT
633 unsigned dont_count_entropy:1;
634};
635
a2080a67
LT
636/*
637 * Add device- or boot-specific data to the input and nonblocking
638 * pools to help initialize them to unique values.
639 *
640 * None of this adds any entropy, it is meant to avoid the
641 * problem of the nonblocking pool having similar initial state
642 * across largely identical devices.
643 */
644void add_device_randomness(const void *buf, unsigned int size)
645{
646 unsigned long time = get_cycles() ^ jiffies;
647
648 mix_pool_bytes(&input_pool, buf, size, NULL);
649 mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
650 mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
651 mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
652}
653EXPORT_SYMBOL(add_device_randomness);
654
3060d6fe
YL
655static struct timer_rand_state input_timer_state;
656
1da177e4
LT
657/*
658 * This function adds entropy to the entropy "pool" by using timing
659 * delays. It uses the timer_rand_state structure to make an estimate
660 * of how many bits of entropy this call has added to the pool.
661 *
662 * The number "num" is also added to the pool - it should somehow describe
663 * the type of event which just happened. This is currently 0-255 for
664 * keyboard scan codes, and 256 upwards for interrupts.
665 *
666 */
667static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
668{
669 struct {
1da177e4 670 long jiffies;
cf833d0b 671 unsigned cycles;
1da177e4
LT
672 unsigned num;
673 } sample;
674 long delta, delta2, delta3;
675
676 preempt_disable();
677 /* if over the trickle threshold, use only 1 in 4096 samples */
678 if (input_pool.entropy_count > trickle_thresh &&
b29c617a 679 ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
1da177e4
LT
680 goto out;
681
682 sample.jiffies = jiffies;
e6d4947b 683 sample.cycles = get_cycles();
1da177e4 684 sample.num = num;
902c098a 685 mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
1da177e4
LT
686
687 /*
688 * Calculate number of bits of randomness we probably added.
689 * We take into account the first, second and third-order deltas
690 * in order to make our estimate.
691 */
692
693 if (!state->dont_count_entropy) {
694 delta = sample.jiffies - state->last_time;
695 state->last_time = sample.jiffies;
696
697 delta2 = delta - state->last_delta;
698 state->last_delta = delta;
699
700 delta3 = delta2 - state->last_delta2;
701 state->last_delta2 = delta2;
702
703 if (delta < 0)
704 delta = -delta;
705 if (delta2 < 0)
706 delta2 = -delta2;
707 if (delta3 < 0)
708 delta3 = -delta3;
709 if (delta > delta2)
710 delta = delta2;
711 if (delta > delta3)
712 delta = delta3;
713
714 /*
715 * delta is now minimum absolute delta.
716 * Round down by 1 bit on general principles,
717 * and limit entropy entimate to 12 bits.
718 */
adc782da
MM
719 credit_entropy_bits(&input_pool,
720 min_t(int, fls(delta>>1), 11));
1da177e4 721 }
1da177e4
LT
722out:
723 preempt_enable();
724}
725
d251575a 726void add_input_randomness(unsigned int type, unsigned int code,
1da177e4
LT
727 unsigned int value)
728{
729 static unsigned char last_value;
730
731 /* ignore autorepeat and the like */
732 if (value == last_value)
733 return;
734
735 DEBUG_ENT("input event\n");
736 last_value = value;
737 add_timer_randomness(&input_timer_state,
738 (type << 4) ^ code ^ (code >> 4) ^ value);
739}
80fc9f53 740EXPORT_SYMBOL_GPL(add_input_randomness);
1da177e4 741
775f4b29
TT
742static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
743
744void add_interrupt_randomness(int irq, int irq_flags)
1da177e4 745{
775f4b29
TT
746 struct entropy_store *r;
747 struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness);
748 struct pt_regs *regs = get_irq_regs();
749 unsigned long now = jiffies;
750 __u32 input[4], cycles = get_cycles();
751
752 input[0] = cycles ^ jiffies;
753 input[1] = irq;
754 if (regs) {
755 __u64 ip = instruction_pointer(regs);
756 input[2] = ip;
757 input[3] = ip >> 32;
758 }
3060d6fe 759
775f4b29 760 fast_mix(fast_pool, input, sizeof(input));
3060d6fe 761
775f4b29
TT
762 if ((fast_pool->count & 1023) &&
763 !time_after(now, fast_pool->last + HZ))
1da177e4
LT
764 return;
765
775f4b29
TT
766 fast_pool->last = now;
767
768 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
902c098a 769 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
775f4b29
TT
770 /*
771 * If we don't have a valid cycle counter, and we see
772 * back-to-back timer interrupts, then skip giving credit for
773 * any entropy.
774 */
775 if (cycles == 0) {
776 if (irq_flags & __IRQF_TIMER) {
777 if (fast_pool->last_timer_intr)
778 return;
779 fast_pool->last_timer_intr = 1;
780 } else
781 fast_pool->last_timer_intr = 0;
782 }
783 credit_entropy_bits(r, 1);
1da177e4
LT
784}
785
9361401e 786#ifdef CONFIG_BLOCK
1da177e4
LT
787void add_disk_randomness(struct gendisk *disk)
788{
789 if (!disk || !disk->random)
790 return;
791 /* first major is 1, so we get >= 0x200 here */
f331c029
TH
792 DEBUG_ENT("disk event %d:%d\n",
793 MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
1da177e4 794
f331c029 795 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1da177e4 796}
9361401e 797#endif
1da177e4 798
1da177e4
LT
799/*********************************************************************
800 *
801 * Entropy extraction routines
802 *
803 *********************************************************************/
804
90b75ee5 805static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1da177e4
LT
806 size_t nbytes, int min, int rsvd);
807
808/*
25985edc 809 * This utility inline function is responsible for transferring entropy
1da177e4
LT
810 * from the primary pool to the secondary extraction pool. We make
811 * sure we pull enough for a 'catastrophic reseed'.
812 */
813static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
814{
d2e7c96a 815 __u32 tmp[OUTPUT_POOL_WORDS];
1da177e4
LT
816
817 if (r->pull && r->entropy_count < nbytes * 8 &&
818 r->entropy_count < r->poolinfo->POOLBITS) {
5a021e9f 819 /* If we're limited, always leave two wakeup worth's BITS */
1da177e4 820 int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
5a021e9f
MM
821 int bytes = nbytes;
822
823 /* pull at least as many as BYTES as wakeup BITS */
824 bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
825 /* but never more than the buffer size */
d2e7c96a 826 bytes = min_t(int, bytes, sizeof(tmp));
1da177e4
LT
827
828 DEBUG_ENT("going to reseed %s with %d bits "
8eb2ffbf 829 "(%zu of %d requested)\n",
1da177e4
LT
830 r->name, bytes * 8, nbytes * 8, r->entropy_count);
831
d2e7c96a 832 bytes = extract_entropy(r->pull, tmp, bytes,
90b75ee5 833 random_read_wakeup_thresh / 8, rsvd);
d2e7c96a 834 mix_pool_bytes(r, tmp, bytes, NULL);
adc782da 835 credit_entropy_bits(r, bytes*8);
1da177e4
LT
836 }
837}
838
839/*
840 * These functions extracts randomness from the "entropy pool", and
841 * returns it in a buffer.
842 *
843 * The min parameter specifies the minimum amount we can pull before
844 * failing to avoid races that defeat catastrophic reseeding while the
845 * reserved parameter indicates how much entropy we must leave in the
846 * pool after each pull to avoid starving other readers.
847 *
848 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
849 */
850
851static size_t account(struct entropy_store *r, size_t nbytes, int min,
852 int reserved)
853{
854 unsigned long flags;
b9809552 855 int wakeup_write = 0;
1da177e4 856
1da177e4
LT
857 /* Hold lock while accounting */
858 spin_lock_irqsave(&r->lock, flags);
859
cda796a3 860 BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
8eb2ffbf 861 DEBUG_ENT("trying to extract %zu bits from %s\n",
1da177e4
LT
862 nbytes * 8, r->name);
863
864 /* Can we pull enough? */
865 if (r->entropy_count / 8 < min + reserved) {
866 nbytes = 0;
867 } else {
10b3a32d
JK
868 int entropy_count, orig;
869retry:
870 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
1da177e4 871 /* If limited, never pull more than available */
10b3a32d
JK
872 if (r->limit && nbytes + reserved >= entropy_count / 8)
873 nbytes = entropy_count/8 - reserved;
874
875 if (entropy_count / 8 >= nbytes + reserved) {
876 entropy_count -= nbytes*8;
877 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
878 goto retry;
879 } else {
880 entropy_count = reserved;
881 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
882 goto retry;
883 }
884
885 if (entropy_count < random_write_wakeup_thresh)
b9809552 886 wakeup_write = 1;
1da177e4
LT
887 }
888
8eb2ffbf 889 DEBUG_ENT("debiting %zu entropy credits from %s%s\n",
1da177e4
LT
890 nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
891
892 spin_unlock_irqrestore(&r->lock, flags);
893
b9809552
TT
894 if (wakeup_write) {
895 wake_up_interruptible(&random_write_wait);
896 kill_fasync(&fasync, SIGIO, POLL_OUT);
897 }
898
1da177e4
LT
899 return nbytes;
900}
901
902static void extract_buf(struct entropy_store *r, __u8 *out)
903{
602b6aee 904 int i;
d2e7c96a
PA
905 union {
906 __u32 w[5];
907 unsigned long l[LONGS(EXTRACT_SIZE)];
908 } hash;
909 __u32 workspace[SHA_WORKSPACE_WORDS];
e68e5b66 910 __u8 extract[64];
902c098a 911 unsigned long flags;
1da177e4 912
1c0ad3d4 913 /* Generate a hash across the pool, 16 words (512 bits) at a time */
d2e7c96a 914 sha_init(hash.w);
902c098a 915 spin_lock_irqsave(&r->lock, flags);
1c0ad3d4 916 for (i = 0; i < r->poolinfo->poolwords; i += 16)
d2e7c96a 917 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1c0ad3d4 918
1da177e4 919 /*
1c0ad3d4
MM
920 * We mix the hash back into the pool to prevent backtracking
921 * attacks (where the attacker knows the state of the pool
922 * plus the current outputs, and attempts to find previous
923 * ouputs), unless the hash function can be inverted. By
924 * mixing at least a SHA1 worth of hash data back, we make
925 * brute-forcing the feedback as hard as brute-forcing the
926 * hash.
1da177e4 927 */
d2e7c96a 928 __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
902c098a 929 spin_unlock_irqrestore(&r->lock, flags);
1da177e4
LT
930
931 /*
1c0ad3d4
MM
932 * To avoid duplicates, we atomically extract a portion of the
933 * pool while mixing, and hash one final time.
1da177e4 934 */
d2e7c96a 935 sha_transform(hash.w, extract, workspace);
ffd8d3fa
MM
936 memset(extract, 0, sizeof(extract));
937 memset(workspace, 0, sizeof(workspace));
1da177e4
LT
938
939 /*
1c0ad3d4
MM
940 * In case the hash function has some recognizable output
941 * pattern, we fold it in half. Thus, we always feed back
942 * twice as much data as we output.
1da177e4 943 */
d2e7c96a
PA
944 hash.w[0] ^= hash.w[3];
945 hash.w[1] ^= hash.w[4];
946 hash.w[2] ^= rol32(hash.w[2], 16);
947
948 /*
949 * If we have a architectural hardware random number
950 * generator, mix that in, too.
951 */
952 for (i = 0; i < LONGS(EXTRACT_SIZE); i++) {
953 unsigned long v;
954 if (!arch_get_random_long(&v))
955 break;
956 hash.l[i] ^= v;
957 }
958
959 memcpy(out, &hash, EXTRACT_SIZE);
960 memset(&hash, 0, sizeof(hash));
1da177e4
LT
961}
962
90b75ee5 963static ssize_t extract_entropy(struct entropy_store *r, void *buf,
902c098a 964 size_t nbytes, int min, int reserved)
1da177e4
LT
965{
966 ssize_t ret = 0, i;
967 __u8 tmp[EXTRACT_SIZE];
1e7e2e05 968 unsigned long flags;
1da177e4 969
ec8f02da 970 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1e7e2e05
JW
971 if (fips_enabled) {
972 spin_lock_irqsave(&r->lock, flags);
973 if (!r->last_data_init) {
974 r->last_data_init = true;
975 spin_unlock_irqrestore(&r->lock, flags);
976 trace_extract_entropy(r->name, EXTRACT_SIZE,
977 r->entropy_count, _RET_IP_);
978 xfer_secondary_pool(r, EXTRACT_SIZE);
979 extract_buf(r, tmp);
980 spin_lock_irqsave(&r->lock, flags);
981 memcpy(r->last_data, tmp, EXTRACT_SIZE);
982 }
983 spin_unlock_irqrestore(&r->lock, flags);
984 }
ec8f02da 985
00ce1db1 986 trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
1da177e4
LT
987 xfer_secondary_pool(r, nbytes);
988 nbytes = account(r, nbytes, min, reserved);
989
990 while (nbytes) {
991 extract_buf(r, tmp);
5b739ef8 992
e954bc91 993 if (fips_enabled) {
5b739ef8
NH
994 spin_lock_irqsave(&r->lock, flags);
995 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
996 panic("Hardware RNG duplicated output!\n");
997 memcpy(r->last_data, tmp, EXTRACT_SIZE);
998 spin_unlock_irqrestore(&r->lock, flags);
999 }
1da177e4
LT
1000 i = min_t(int, nbytes, EXTRACT_SIZE);
1001 memcpy(buf, tmp, i);
1002 nbytes -= i;
1003 buf += i;
1004 ret += i;
1005 }
1006
1007 /* Wipe data just returned from memory */
1008 memset(tmp, 0, sizeof(tmp));
1009
1010 return ret;
1011}
1012
1013static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1014 size_t nbytes)
1015{
1016 ssize_t ret = 0, i;
1017 __u8 tmp[EXTRACT_SIZE];
1018
00ce1db1 1019 trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
1da177e4
LT
1020 xfer_secondary_pool(r, nbytes);
1021 nbytes = account(r, nbytes, 0, 0);
1022
1023 while (nbytes) {
1024 if (need_resched()) {
1025 if (signal_pending(current)) {
1026 if (ret == 0)
1027 ret = -ERESTARTSYS;
1028 break;
1029 }
1030 schedule();
1031 }
1032
1033 extract_buf(r, tmp);
1034 i = min_t(int, nbytes, EXTRACT_SIZE);
1035 if (copy_to_user(buf, tmp, i)) {
1036 ret = -EFAULT;
1037 break;
1038 }
1039
1040 nbytes -= i;
1041 buf += i;
1042 ret += i;
1043 }
1044
1045 /* Wipe data just returned from memory */
1046 memset(tmp, 0, sizeof(tmp));
1047
1048 return ret;
1049}
1050
1051/*
1052 * This function is the exported kernel interface. It returns some
c2557a30
TT
1053 * number of good random numbers, suitable for key generation, seeding
1054 * TCP sequence numbers, etc. It does not use the hw random number
1055 * generator, if available; use get_random_bytes_arch() for that.
1da177e4
LT
1056 */
1057void get_random_bytes(void *buf, int nbytes)
c2557a30
TT
1058{
1059 extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1060}
1061EXPORT_SYMBOL(get_random_bytes);
1062
1063/*
1064 * This function will use the architecture-specific hardware random
1065 * number generator if it is available. The arch-specific hw RNG will
1066 * almost certainly be faster than what we can do in software, but it
1067 * is impossible to verify that it is implemented securely (as
1068 * opposed, to, say, the AES encryption of a sequence number using a
1069 * key known by the NSA). So it's useful if we need the speed, but
1070 * only if we're willing to trust the hardware manufacturer not to
1071 * have put in a back door.
1072 */
1073void get_random_bytes_arch(void *buf, int nbytes)
1da177e4 1074{
63d77173
PA
1075 char *p = buf;
1076
00ce1db1 1077 trace_get_random_bytes(nbytes, _RET_IP_);
63d77173
PA
1078 while (nbytes) {
1079 unsigned long v;
1080 int chunk = min(nbytes, (int)sizeof(unsigned long));
c2557a30 1081
63d77173
PA
1082 if (!arch_get_random_long(&v))
1083 break;
1084
bd29e568 1085 memcpy(p, &v, chunk);
63d77173
PA
1086 p += chunk;
1087 nbytes -= chunk;
1088 }
1089
c2557a30
TT
1090 if (nbytes)
1091 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1da177e4 1092}
c2557a30
TT
1093EXPORT_SYMBOL(get_random_bytes_arch);
1094
1da177e4
LT
1095
1096/*
1097 * init_std_data - initialize pool with system data
1098 *
1099 * @r: pool to initialize
1100 *
1101 * This function clears the pool's entropy count and mixes some system
1102 * data into the pool to prepare it for use. The pool is not cleared
1103 * as that can only decrease the entropy in the pool.
1104 */
1105static void init_std_data(struct entropy_store *r)
1106{
3e88bdff 1107 int i;
902c098a
TT
1108 ktime_t now = ktime_get_real();
1109 unsigned long rv;
1da177e4 1110
1da177e4 1111 r->entropy_count = 0;
775f4b29 1112 r->entropy_total = 0;
ec8f02da 1113 r->last_data_init = false;
902c098a
TT
1114 mix_pool_bytes(r, &now, sizeof(now), NULL);
1115 for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) {
1116 if (!arch_get_random_long(&rv))
3e88bdff 1117 break;
902c098a 1118 mix_pool_bytes(r, &rv, sizeof(rv), NULL);
3e88bdff 1119 }
902c098a 1120 mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
1da177e4
LT
1121}
1122
cbc96b75
TL
1123/*
1124 * Note that setup_arch() may call add_device_randomness()
1125 * long before we get here. This allows seeding of the pools
1126 * with some platform dependent data very early in the boot
1127 * process. But it limits our options here. We must use
1128 * statically allocated structures that already have all
1129 * initializations complete at compile time. We should also
1130 * take care not to overwrite the precious per platform data
1131 * we were given.
1132 */
53c3f63e 1133static int rand_initialize(void)
1da177e4
LT
1134{
1135 init_std_data(&input_pool);
1136 init_std_data(&blocking_pool);
1137 init_std_data(&nonblocking_pool);
1138 return 0;
1139}
1140module_init(rand_initialize);
1141
9361401e 1142#ifdef CONFIG_BLOCK
1da177e4
LT
1143void rand_initialize_disk(struct gendisk *disk)
1144{
1145 struct timer_rand_state *state;
1146
1147 /*
f8595815 1148 * If kzalloc returns null, we just won't use that entropy
1da177e4
LT
1149 * source.
1150 */
f8595815
ED
1151 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1152 if (state)
1da177e4 1153 disk->random = state;
1da177e4 1154}
9361401e 1155#endif
1da177e4
LT
1156
1157static ssize_t
90b75ee5 1158random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1da177e4
LT
1159{
1160 ssize_t n, retval = 0, count = 0;
1161
1162 if (nbytes == 0)
1163 return 0;
1164
1165 while (nbytes > 0) {
1166 n = nbytes;
1167 if (n > SEC_XFER_SIZE)
1168 n = SEC_XFER_SIZE;
1169
8eb2ffbf 1170 DEBUG_ENT("reading %zu bits\n", n*8);
1da177e4
LT
1171
1172 n = extract_entropy_user(&blocking_pool, buf, n);
1173
8eb2ffbf
JK
1174 if (n < 0) {
1175 retval = n;
1176 break;
1177 }
1178
1179 DEBUG_ENT("read got %zd bits (%zd still needed)\n",
1da177e4
LT
1180 n*8, (nbytes-n)*8);
1181
1182 if (n == 0) {
1183 if (file->f_flags & O_NONBLOCK) {
1184 retval = -EAGAIN;
1185 break;
1186 }
1187
1188 DEBUG_ENT("sleeping?\n");
1189
1190 wait_event_interruptible(random_read_wait,
1191 input_pool.entropy_count >=
1192 random_read_wakeup_thresh);
1193
1194 DEBUG_ENT("awake\n");
1195
1196 if (signal_pending(current)) {
1197 retval = -ERESTARTSYS;
1198 break;
1199 }
1200
1201 continue;
1202 }
1203
1da177e4
LT
1204 count += n;
1205 buf += n;
1206 nbytes -= n;
1207 break; /* This break makes the device work */
1208 /* like a named pipe */
1209 }
1210
1da177e4
LT
1211 return (count ? count : retval);
1212}
1213
1214static ssize_t
90b75ee5 1215urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1da177e4
LT
1216{
1217 return extract_entropy_user(&nonblocking_pool, buf, nbytes);
1218}
1219
1220static unsigned int
1221random_poll(struct file *file, poll_table * wait)
1222{
1223 unsigned int mask;
1224
1225 poll_wait(file, &random_read_wait, wait);
1226 poll_wait(file, &random_write_wait, wait);
1227 mask = 0;
1228 if (input_pool.entropy_count >= random_read_wakeup_thresh)
1229 mask |= POLLIN | POLLRDNORM;
1230 if (input_pool.entropy_count < random_write_wakeup_thresh)
1231 mask |= POLLOUT | POLLWRNORM;
1232 return mask;
1233}
1234
7f397dcd
MM
1235static int
1236write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1da177e4 1237{
1da177e4
LT
1238 size_t bytes;
1239 __u32 buf[16];
1240 const char __user *p = buffer;
1da177e4 1241
7f397dcd
MM
1242 while (count > 0) {
1243 bytes = min(count, sizeof(buf));
1244 if (copy_from_user(&buf, p, bytes))
1245 return -EFAULT;
1da177e4 1246
7f397dcd 1247 count -= bytes;
1da177e4
LT
1248 p += bytes;
1249
902c098a 1250 mix_pool_bytes(r, buf, bytes, NULL);
91f3f1e3 1251 cond_resched();
1da177e4 1252 }
7f397dcd
MM
1253
1254 return 0;
1255}
1256
90b75ee5
MM
1257static ssize_t random_write(struct file *file, const char __user *buffer,
1258 size_t count, loff_t *ppos)
7f397dcd
MM
1259{
1260 size_t ret;
7f397dcd
MM
1261
1262 ret = write_pool(&blocking_pool, buffer, count);
1263 if (ret)
1264 return ret;
1265 ret = write_pool(&nonblocking_pool, buffer, count);
1266 if (ret)
1267 return ret;
1268
7f397dcd 1269 return (ssize_t)count;
1da177e4
LT
1270}
1271
43ae4860 1272static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1da177e4
LT
1273{
1274 int size, ent_count;
1275 int __user *p = (int __user *)arg;
1276 int retval;
1277
1278 switch (cmd) {
1279 case RNDGETENTCNT:
43ae4860
MM
1280 /* inherently racy, no point locking */
1281 if (put_user(input_pool.entropy_count, p))
1da177e4
LT
1282 return -EFAULT;
1283 return 0;
1284 case RNDADDTOENTCNT:
1285 if (!capable(CAP_SYS_ADMIN))
1286 return -EPERM;
1287 if (get_user(ent_count, p))
1288 return -EFAULT;
adc782da 1289 credit_entropy_bits(&input_pool, ent_count);
1da177e4
LT
1290 return 0;
1291 case RNDADDENTROPY:
1292 if (!capable(CAP_SYS_ADMIN))
1293 return -EPERM;
1294 if (get_user(ent_count, p++))
1295 return -EFAULT;
1296 if (ent_count < 0)
1297 return -EINVAL;
1298 if (get_user(size, p++))
1299 return -EFAULT;
7f397dcd
MM
1300 retval = write_pool(&input_pool, (const char __user *)p,
1301 size);
1da177e4
LT
1302 if (retval < 0)
1303 return retval;
adc782da 1304 credit_entropy_bits(&input_pool, ent_count);
1da177e4
LT
1305 return 0;
1306 case RNDZAPENTCNT:
1307 case RNDCLEARPOOL:
1308 /* Clear the entropy pool counters. */
1309 if (!capable(CAP_SYS_ADMIN))
1310 return -EPERM;
53c3f63e 1311 rand_initialize();
1da177e4
LT
1312 return 0;
1313 default:
1314 return -EINVAL;
1315 }
1316}
1317
9a6f70bb
JD
1318static int random_fasync(int fd, struct file *filp, int on)
1319{
1320 return fasync_helper(fd, filp, on, &fasync);
1321}
1322
2b8693c0 1323const struct file_operations random_fops = {
1da177e4
LT
1324 .read = random_read,
1325 .write = random_write,
1326 .poll = random_poll,
43ae4860 1327 .unlocked_ioctl = random_ioctl,
9a6f70bb 1328 .fasync = random_fasync,
6038f373 1329 .llseek = noop_llseek,
1da177e4
LT
1330};
1331
2b8693c0 1332const struct file_operations urandom_fops = {
1da177e4
LT
1333 .read = urandom_read,
1334 .write = random_write,
43ae4860 1335 .unlocked_ioctl = random_ioctl,
9a6f70bb 1336 .fasync = random_fasync,
6038f373 1337 .llseek = noop_llseek,
1da177e4
LT
1338};
1339
1340/***************************************************************
1341 * Random UUID interface
1342 *
1343 * Used here for a Boot ID, but can be useful for other kernel
1344 * drivers.
1345 ***************************************************************/
1346
1347/*
1348 * Generate random UUID
1349 */
1350void generate_random_uuid(unsigned char uuid_out[16])
1351{
1352 get_random_bytes(uuid_out, 16);
c41b20e7 1353 /* Set UUID version to 4 --- truly random generation */
1da177e4
LT
1354 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1355 /* Set the UUID variant to DCE */
1356 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1357}
1da177e4
LT
1358EXPORT_SYMBOL(generate_random_uuid);
1359
1360/********************************************************************
1361 *
1362 * Sysctl interface
1363 *
1364 ********************************************************************/
1365
1366#ifdef CONFIG_SYSCTL
1367
1368#include <linux/sysctl.h>
1369
1370static int min_read_thresh = 8, min_write_thresh;
1371static int max_read_thresh = INPUT_POOL_WORDS * 32;
1372static int max_write_thresh = INPUT_POOL_WORDS * 32;
1373static char sysctl_bootid[16];
1374
1375/*
1376 * These functions is used to return both the bootid UUID, and random
1377 * UUID. The difference is in whether table->data is NULL; if it is,
1378 * then a new UUID is generated and returned to the user.
1379 *
1380 * If the user accesses this via the proc interface, it will be returned
1381 * as an ASCII string in the standard UUID format. If accesses via the
1382 * sysctl system call, it is returned as 16 bytes of binary data.
1383 */
8d65af78 1384static int proc_do_uuid(ctl_table *table, int write,
1da177e4
LT
1385 void __user *buffer, size_t *lenp, loff_t *ppos)
1386{
1387 ctl_table fake_table;
1388 unsigned char buf[64], tmp_uuid[16], *uuid;
1389
1390 uuid = table->data;
1391 if (!uuid) {
1392 uuid = tmp_uuid;
1da177e4 1393 generate_random_uuid(uuid);
44e4360f
MD
1394 } else {
1395 static DEFINE_SPINLOCK(bootid_spinlock);
1396
1397 spin_lock(&bootid_spinlock);
1398 if (!uuid[8])
1399 generate_random_uuid(uuid);
1400 spin_unlock(&bootid_spinlock);
1401 }
1da177e4 1402
35900771
JP
1403 sprintf(buf, "%pU", uuid);
1404
1da177e4
LT
1405 fake_table.data = buf;
1406 fake_table.maxlen = sizeof(buf);
1407
8d65af78 1408 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1da177e4
LT
1409}
1410
1da177e4 1411static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
74feec5d 1412extern ctl_table random_table[];
1da177e4
LT
1413ctl_table random_table[] = {
1414 {
1da177e4
LT
1415 .procname = "poolsize",
1416 .data = &sysctl_poolsize,
1417 .maxlen = sizeof(int),
1418 .mode = 0444,
6d456111 1419 .proc_handler = proc_dointvec,
1da177e4
LT
1420 },
1421 {
1da177e4
LT
1422 .procname = "entropy_avail",
1423 .maxlen = sizeof(int),
1424 .mode = 0444,
6d456111 1425 .proc_handler = proc_dointvec,
1da177e4
LT
1426 .data = &input_pool.entropy_count,
1427 },
1428 {
1da177e4
LT
1429 .procname = "read_wakeup_threshold",
1430 .data = &random_read_wakeup_thresh,
1431 .maxlen = sizeof(int),
1432 .mode = 0644,
6d456111 1433 .proc_handler = proc_dointvec_minmax,
1da177e4
LT
1434 .extra1 = &min_read_thresh,
1435 .extra2 = &max_read_thresh,
1436 },
1437 {
1da177e4
LT
1438 .procname = "write_wakeup_threshold",
1439 .data = &random_write_wakeup_thresh,
1440 .maxlen = sizeof(int),
1441 .mode = 0644,
6d456111 1442 .proc_handler = proc_dointvec_minmax,
1da177e4
LT
1443 .extra1 = &min_write_thresh,
1444 .extra2 = &max_write_thresh,
1445 },
1446 {
1da177e4
LT
1447 .procname = "boot_id",
1448 .data = &sysctl_bootid,
1449 .maxlen = 16,
1450 .mode = 0444,
6d456111 1451 .proc_handler = proc_do_uuid,
1da177e4
LT
1452 },
1453 {
1da177e4
LT
1454 .procname = "uuid",
1455 .maxlen = 16,
1456 .mode = 0444,
6d456111 1457 .proc_handler = proc_do_uuid,
1da177e4 1458 },
894d2491 1459 { }
1da177e4
LT
1460};
1461#endif /* CONFIG_SYSCTL */
1462
6e5714ea 1463static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1da177e4 1464
6e5714ea 1465static int __init random_int_secret_init(void)
1da177e4 1466{
6e5714ea 1467 get_random_bytes(random_int_secret, sizeof(random_int_secret));
1da177e4
LT
1468 return 0;
1469}
6e5714ea 1470late_initcall(random_int_secret_init);
1da177e4
LT
1471
1472/*
1473 * Get a random word for internal kernel use only. Similar to urandom but
1474 * with the goal of minimal entropy pool depletion. As a result, the random
1475 * value is not cryptographically secure but for several uses the cost of
1476 * depleting entropy is too high
1477 */
74feec5d 1478static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1da177e4
LT
1479unsigned int get_random_int(void)
1480{
63d77173 1481 __u32 *hash;
6e5714ea 1482 unsigned int ret;
8a0a9bd4 1483
63d77173
PA
1484 if (arch_get_random_int(&ret))
1485 return ret;
1486
1487 hash = get_cpu_var(get_random_int_hash);
8a0a9bd4 1488
26a9a418 1489 hash[0] += current->pid + jiffies + get_cycles();
6e5714ea
DM
1490 md5_transform(hash, random_int_secret);
1491 ret = hash[0];
8a0a9bd4
LT
1492 put_cpu_var(get_random_int_hash);
1493
1494 return ret;
1da177e4 1495}
16c7fa05 1496EXPORT_SYMBOL(get_random_int);
1da177e4
LT
1497
1498/*
1499 * randomize_range() returns a start address such that
1500 *
1501 * [...... <range> .....]
1502 * start end
1503 *
1504 * a <range> with size "len" starting at the return value is inside in the
1505 * area defined by [start, end], but is otherwise randomized.
1506 */
1507unsigned long
1508randomize_range(unsigned long start, unsigned long end, unsigned long len)
1509{
1510 unsigned long range = end - len - start;
1511
1512 if (end <= start + len)
1513 return 0;
1514 return PAGE_ALIGN(get_random_int() % range + start);
1515}