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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 *
a2080a67 128 * void add_device_randomness(const void *buf, unsigned int size);
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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 *
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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 *
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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
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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>
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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
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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>
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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
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279
280/*
281 * The minimum number of bits of entropy before we wake up a read on
282 * /dev/random. Should be enough to do a significant reseed.
283 */
284static int random_read_wakeup_thresh = 64;
285
286/*
287 * If the entropy count falls under this number of bits, then we
288 * should wake up processes which are selecting or polling on write
289 * access to /dev/random.
290 */
291static int random_write_wakeup_thresh = 128;
292
293/*
294 * When the input pool goes over trickle_thresh, start dropping most
295 * samples to avoid wasting CPU time and reduce lock contention.
296 */
297
6c036527 298static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
1da177e4 299
90b75ee5 300static DEFINE_PER_CPU(int, trickle_count);
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301
302/*
303 * A pool of size .poolwords is stirred with a primitive polynomial
304 * of degree .poolwords over GF(2). The taps for various sizes are
305 * defined below. They are chosen to be evenly spaced (minimum RMS
306 * distance from evenly spaced; the numbers in the comments are a
307 * scaled squared error sum) except for the last tap, which is 1 to
308 * get the twisting happening as fast as possible.
309 */
310static struct poolinfo {
311 int poolwords;
312 int tap1, tap2, tap3, tap4, tap5;
313} poolinfo_table[] = {
314 /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
315 { 128, 103, 76, 51, 25, 1 },
316 /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
317 { 32, 26, 20, 14, 7, 1 },
318#if 0
319 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
320 { 2048, 1638, 1231, 819, 411, 1 },
321
322 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
323 { 1024, 817, 615, 412, 204, 1 },
324
325 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
326 { 1024, 819, 616, 410, 207, 2 },
327
328 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
329 { 512, 411, 308, 208, 104, 1 },
330
331 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
332 { 512, 409, 307, 206, 102, 2 },
333 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
334 { 512, 409, 309, 205, 103, 2 },
335
336 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
337 { 256, 205, 155, 101, 52, 1 },
338
339 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
340 { 128, 103, 78, 51, 27, 2 },
341
342 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
343 { 64, 52, 39, 26, 14, 1 },
344#endif
345};
346
347#define POOLBITS poolwords*32
348#define POOLBYTES poolwords*4
349
350/*
351 * For the purposes of better mixing, we use the CRC-32 polynomial as
352 * well to make a twisted Generalized Feedback Shift Reigster
353 *
354 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
355 * Transactions on Modeling and Computer Simulation 2(3):179-194.
356 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
357 * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
358 *
359 * Thanks to Colin Plumb for suggesting this.
360 *
361 * We have not analyzed the resultant polynomial to prove it primitive;
362 * in fact it almost certainly isn't. Nonetheless, the irreducible factors
363 * of a random large-degree polynomial over GF(2) are more than large enough
364 * that periodicity is not a concern.
365 *
366 * The input hash is much less sensitive than the output hash. All
367 * that we want of it is that it be a good non-cryptographic hash;
368 * i.e. it not produce collisions when fed "random" data of the sort
369 * we expect to see. As long as the pool state differs for different
370 * inputs, we have preserved the input entropy and done a good job.
371 * The fact that an intelligent attacker can construct inputs that
372 * will produce controlled alterations to the pool's state is not
373 * important because we don't consider such inputs to contribute any
374 * randomness. The only property we need with respect to them is that
375 * the attacker can't increase his/her knowledge of the pool's state.
376 * Since all additions are reversible (knowing the final state and the
377 * input, you can reconstruct the initial state), if an attacker has
378 * any uncertainty about the initial state, he/she can only shuffle
379 * that uncertainty about, but never cause any collisions (which would
380 * decrease the uncertainty).
381 *
382 * The chosen system lets the state of the pool be (essentially) the input
383 * modulo the generator polymnomial. Now, for random primitive polynomials,
384 * this is a universal class of hash functions, meaning that the chance
385 * of a collision is limited by the attacker's knowledge of the generator
386 * polynomail, so if it is chosen at random, an attacker can never force
387 * a collision. Here, we use a fixed polynomial, but we *can* assume that
388 * ###--> it is unknown to the processes generating the input entropy. <-###
389 * Because of this important property, this is a good, collision-resistant
390 * hash; hash collisions will occur no more often than chance.
391 */
392
393/*
394 * Static global variables
395 */
396static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
397static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
9a6f70bb 398static struct fasync_struct *fasync;
1da177e4
LT
399
400#if 0
90ab5ee9 401static bool debug;
1da177e4 402module_param(debug, bool, 0644);
90b75ee5
MM
403#define DEBUG_ENT(fmt, arg...) do { \
404 if (debug) \
405 printk(KERN_DEBUG "random %04d %04d %04d: " \
406 fmt,\
407 input_pool.entropy_count,\
408 blocking_pool.entropy_count,\
409 nonblocking_pool.entropy_count,\
410 ## arg); } while (0)
1da177e4
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411#else
412#define DEBUG_ENT(fmt, arg...) do {} while (0)
413#endif
414
415/**********************************************************************
416 *
417 * OS independent entropy store. Here are the functions which handle
418 * storing entropy in an entropy pool.
419 *
420 **********************************************************************/
421
422struct entropy_store;
423struct entropy_store {
43358209 424 /* read-only data: */
1da177e4
LT
425 struct poolinfo *poolinfo;
426 __u32 *pool;
427 const char *name;
1da177e4 428 struct entropy_store *pull;
4015d9a8 429 int limit;
1da177e4
LT
430
431 /* read-write data: */
43358209 432 spinlock_t lock;
1da177e4 433 unsigned add_ptr;
902c098a 434 unsigned input_rotate;
cda796a3 435 int entropy_count;
775f4b29 436 int entropy_total;
775f4b29 437 unsigned int initialized:1;
e954bc91 438 __u8 last_data[EXTRACT_SIZE];
1da177e4
LT
439};
440
441static __u32 input_pool_data[INPUT_POOL_WORDS];
442static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
443static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
444
445static struct entropy_store input_pool = {
446 .poolinfo = &poolinfo_table[0],
447 .name = "input",
448 .limit = 1,
e4d91918 449 .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock),
1da177e4
LT
450 .pool = input_pool_data
451};
452
453static struct entropy_store blocking_pool = {
454 .poolinfo = &poolinfo_table[1],
455 .name = "blocking",
456 .limit = 1,
457 .pull = &input_pool,
e4d91918 458 .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock),
1da177e4
LT
459 .pool = blocking_pool_data
460};
461
462static struct entropy_store nonblocking_pool = {
463 .poolinfo = &poolinfo_table[1],
464 .name = "nonblocking",
465 .pull = &input_pool,
e4d91918 466 .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock),
1da177e4
LT
467 .pool = nonblocking_pool_data
468};
469
775f4b29
TT
470static __u32 const twist_table[8] = {
471 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
472 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
473
1da177e4 474/*
e68e5b66 475 * This function adds bytes into the entropy "pool". It does not
1da177e4 476 * update the entropy estimate. The caller should call
adc782da 477 * credit_entropy_bits if this is appropriate.
1da177e4
LT
478 *
479 * The pool is stirred with a primitive polynomial of the appropriate
480 * degree, and then twisted. We twist by three bits at a time because
481 * it's cheap to do so and helps slightly in the expected case where
482 * the entropy is concentrated in the low-order bits.
483 */
00ce1db1
TT
484static void _mix_pool_bytes(struct entropy_store *r, const void *in,
485 int nbytes, __u8 out[64])
1da177e4 486{
993ba211 487 unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
feee7697 488 int input_rotate;
1da177e4 489 int wordmask = r->poolinfo->poolwords - 1;
e68e5b66 490 const char *bytes = in;
6d38b827 491 __u32 w;
1da177e4 492
1da177e4
LT
493 tap1 = r->poolinfo->tap1;
494 tap2 = r->poolinfo->tap2;
495 tap3 = r->poolinfo->tap3;
496 tap4 = r->poolinfo->tap4;
497 tap5 = r->poolinfo->tap5;
1da177e4 498
902c098a
TT
499 smp_rmb();
500 input_rotate = ACCESS_ONCE(r->input_rotate);
501 i = ACCESS_ONCE(r->add_ptr);
1da177e4 502
e68e5b66
MM
503 /* mix one byte at a time to simplify size handling and churn faster */
504 while (nbytes--) {
505 w = rol32(*bytes++, input_rotate & 31);
993ba211 506 i = (i - 1) & wordmask;
1da177e4
LT
507
508 /* XOR in the various taps */
993ba211 509 w ^= r->pool[i];
1da177e4
LT
510 w ^= r->pool[(i + tap1) & wordmask];
511 w ^= r->pool[(i + tap2) & wordmask];
512 w ^= r->pool[(i + tap3) & wordmask];
513 w ^= r->pool[(i + tap4) & wordmask];
514 w ^= r->pool[(i + tap5) & wordmask];
993ba211
MM
515
516 /* Mix the result back in with a twist */
1da177e4 517 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
feee7697
MM
518
519 /*
520 * Normally, we add 7 bits of rotation to the pool.
521 * At the beginning of the pool, add an extra 7 bits
522 * rotation, so that successive passes spread the
523 * input bits across the pool evenly.
524 */
525 input_rotate += i ? 7 : 14;
1da177e4
LT
526 }
527
902c098a
TT
528 ACCESS_ONCE(r->input_rotate) = input_rotate;
529 ACCESS_ONCE(r->add_ptr) = i;
530 smp_wmb();
1da177e4 531
993ba211
MM
532 if (out)
533 for (j = 0; j < 16; j++)
e68e5b66 534 ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
1da177e4
LT
535}
536
00ce1db1 537static void __mix_pool_bytes(struct entropy_store *r, const void *in,
902c098a 538 int nbytes, __u8 out[64])
00ce1db1
TT
539{
540 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
541 _mix_pool_bytes(r, in, nbytes, out);
542}
543
544static void mix_pool_bytes(struct entropy_store *r, const void *in,
545 int nbytes, __u8 out[64])
1da177e4 546{
902c098a
TT
547 unsigned long flags;
548
00ce1db1 549 trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
902c098a 550 spin_lock_irqsave(&r->lock, flags);
00ce1db1 551 _mix_pool_bytes(r, in, nbytes, out);
902c098a 552 spin_unlock_irqrestore(&r->lock, flags);
1da177e4
LT
553}
554
775f4b29
TT
555struct fast_pool {
556 __u32 pool[4];
557 unsigned long last;
558 unsigned short count;
559 unsigned char rotate;
560 unsigned char last_timer_intr;
561};
562
563/*
564 * This is a fast mixing routine used by the interrupt randomness
565 * collector. It's hardcoded for an 128 bit pool and assumes that any
566 * locks that might be needed are taken by the caller.
567 */
568static void fast_mix(struct fast_pool *f, const void *in, int nbytes)
569{
570 const char *bytes = in;
571 __u32 w;
572 unsigned i = f->count;
573 unsigned input_rotate = f->rotate;
574
575 while (nbytes--) {
576 w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
577 f->pool[(i + 1) & 3];
578 f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
579 input_rotate += (i++ & 3) ? 7 : 14;
580 }
581 f->count = i;
582 f->rotate = input_rotate;
583}
584
1da177e4
LT
585/*
586 * Credit (or debit) the entropy store with n bits of entropy
587 */
adc782da 588static void credit_entropy_bits(struct entropy_store *r, int nbits)
1da177e4 589{
902c098a 590 int entropy_count, orig;
1da177e4 591
adc782da
MM
592 if (!nbits)
593 return;
594
adc782da 595 DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
902c098a
TT
596retry:
597 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
8b76f46a 598 entropy_count += nbits;
00ce1db1 599
8b76f46a 600 if (entropy_count < 0) {
adc782da 601 DEBUG_ENT("negative entropy/overflow\n");
8b76f46a
AM
602 entropy_count = 0;
603 } else if (entropy_count > r->poolinfo->POOLBITS)
604 entropy_count = r->poolinfo->POOLBITS;
902c098a
TT
605 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
606 goto retry;
1da177e4 607
775f4b29
TT
608 if (!r->initialized && nbits > 0) {
609 r->entropy_total += nbits;
610 if (r->entropy_total > 128)
611 r->initialized = 1;
612 }
613
00ce1db1
TT
614 trace_credit_entropy_bits(r->name, nbits, entropy_count,
615 r->entropy_total, _RET_IP_);
616
88c730da 617 /* should we wake readers? */
8b76f46a 618 if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
88c730da 619 wake_up_interruptible(&random_read_wait);
9a6f70bb
JD
620 kill_fasync(&fasync, SIGIO, POLL_IN);
621 }
1da177e4
LT
622}
623
624/*********************************************************************
625 *
626 * Entropy input management
627 *
628 *********************************************************************/
629
630/* There is one of these per entropy source */
631struct timer_rand_state {
632 cycles_t last_time;
90b75ee5 633 long last_delta, last_delta2;
1da177e4
LT
634 unsigned dont_count_entropy:1;
635};
636
a2080a67
LT
637/*
638 * Add device- or boot-specific data to the input and nonblocking
639 * pools to help initialize them to unique values.
640 *
641 * None of this adds any entropy, it is meant to avoid the
642 * problem of the nonblocking pool having similar initial state
643 * across largely identical devices.
644 */
645void add_device_randomness(const void *buf, unsigned int size)
646{
647 unsigned long time = get_cycles() ^ jiffies;
648
649 mix_pool_bytes(&input_pool, buf, size, NULL);
650 mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
651 mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
652 mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
653}
654EXPORT_SYMBOL(add_device_randomness);
655
3060d6fe
YL
656static struct timer_rand_state input_timer_state;
657
1da177e4
LT
658/*
659 * This function adds entropy to the entropy "pool" by using timing
660 * delays. It uses the timer_rand_state structure to make an estimate
661 * of how many bits of entropy this call has added to the pool.
662 *
663 * The number "num" is also added to the pool - it should somehow describe
664 * the type of event which just happened. This is currently 0-255 for
665 * keyboard scan codes, and 256 upwards for interrupts.
666 *
667 */
668static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
669{
670 struct {
1da177e4 671 long jiffies;
cf833d0b 672 unsigned cycles;
1da177e4
LT
673 unsigned num;
674 } sample;
675 long delta, delta2, delta3;
676
677 preempt_disable();
678 /* if over the trickle threshold, use only 1 in 4096 samples */
679 if (input_pool.entropy_count > trickle_thresh &&
b29c617a 680 ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
1da177e4
LT
681 goto out;
682
683 sample.jiffies = jiffies;
e6d4947b 684 sample.cycles = get_cycles();
1da177e4 685 sample.num = num;
902c098a 686 mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
1da177e4
LT
687
688 /*
689 * Calculate number of bits of randomness we probably added.
690 * We take into account the first, second and third-order deltas
691 * in order to make our estimate.
692 */
693
694 if (!state->dont_count_entropy) {
695 delta = sample.jiffies - state->last_time;
696 state->last_time = sample.jiffies;
697
698 delta2 = delta - state->last_delta;
699 state->last_delta = delta;
700
701 delta3 = delta2 - state->last_delta2;
702 state->last_delta2 = delta2;
703
704 if (delta < 0)
705 delta = -delta;
706 if (delta2 < 0)
707 delta2 = -delta2;
708 if (delta3 < 0)
709 delta3 = -delta3;
710 if (delta > delta2)
711 delta = delta2;
712 if (delta > delta3)
713 delta = delta3;
714
715 /*
716 * delta is now minimum absolute delta.
717 * Round down by 1 bit on general principles,
718 * and limit entropy entimate to 12 bits.
719 */
adc782da
MM
720 credit_entropy_bits(&input_pool,
721 min_t(int, fls(delta>>1), 11));
1da177e4 722 }
1da177e4
LT
723out:
724 preempt_enable();
725}
726
d251575a 727void add_input_randomness(unsigned int type, unsigned int code,
1da177e4
LT
728 unsigned int value)
729{
730 static unsigned char last_value;
731
732 /* ignore autorepeat and the like */
733 if (value == last_value)
734 return;
735
736 DEBUG_ENT("input event\n");
737 last_value = value;
738 add_timer_randomness(&input_timer_state,
739 (type << 4) ^ code ^ (code >> 4) ^ value);
740}
80fc9f53 741EXPORT_SYMBOL_GPL(add_input_randomness);
1da177e4 742
775f4b29
TT
743static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
744
745void add_interrupt_randomness(int irq, int irq_flags)
1da177e4 746{
775f4b29
TT
747 struct entropy_store *r;
748 struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness);
749 struct pt_regs *regs = get_irq_regs();
750 unsigned long now = jiffies;
751 __u32 input[4], cycles = get_cycles();
752
753 input[0] = cycles ^ jiffies;
754 input[1] = irq;
755 if (regs) {
756 __u64 ip = instruction_pointer(regs);
757 input[2] = ip;
758 input[3] = ip >> 32;
759 }
3060d6fe 760
775f4b29 761 fast_mix(fast_pool, input, sizeof(input));
3060d6fe 762
775f4b29
TT
763 if ((fast_pool->count & 1023) &&
764 !time_after(now, fast_pool->last + HZ))
1da177e4
LT
765 return;
766
775f4b29
TT
767 fast_pool->last = now;
768
769 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
902c098a 770 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
775f4b29
TT
771 /*
772 * If we don't have a valid cycle counter, and we see
773 * back-to-back timer interrupts, then skip giving credit for
774 * any entropy.
775 */
776 if (cycles == 0) {
777 if (irq_flags & __IRQF_TIMER) {
778 if (fast_pool->last_timer_intr)
779 return;
780 fast_pool->last_timer_intr = 1;
781 } else
782 fast_pool->last_timer_intr = 0;
783 }
784 credit_entropy_bits(r, 1);
1da177e4
LT
785}
786
9361401e 787#ifdef CONFIG_BLOCK
1da177e4
LT
788void add_disk_randomness(struct gendisk *disk)
789{
790 if (!disk || !disk->random)
791 return;
792 /* first major is 1, so we get >= 0x200 here */
f331c029
TH
793 DEBUG_ENT("disk event %d:%d\n",
794 MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
1da177e4 795
f331c029 796 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1da177e4 797}
9361401e 798#endif
1da177e4 799
1da177e4
LT
800/*********************************************************************
801 *
802 * Entropy extraction routines
803 *
804 *********************************************************************/
805
90b75ee5 806static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1da177e4
LT
807 size_t nbytes, int min, int rsvd);
808
809/*
25985edc 810 * This utility inline function is responsible for transferring entropy
1da177e4
LT
811 * from the primary pool to the secondary extraction pool. We make
812 * sure we pull enough for a 'catastrophic reseed'.
813 */
814static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
815{
e6d4947b
TT
816 union {
817 __u32 tmp[OUTPUT_POOL_WORDS];
818 long hwrand[4];
819 } u;
820 int i;
1da177e4
LT
821
822 if (r->pull && r->entropy_count < nbytes * 8 &&
823 r->entropy_count < r->poolinfo->POOLBITS) {
5a021e9f 824 /* If we're limited, always leave two wakeup worth's BITS */
1da177e4 825 int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
5a021e9f
MM
826 int bytes = nbytes;
827
828 /* pull at least as many as BYTES as wakeup BITS */
829 bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
830 /* but never more than the buffer size */
e6d4947b 831 bytes = min_t(int, bytes, sizeof(u.tmp));
1da177e4
LT
832
833 DEBUG_ENT("going to reseed %s with %d bits "
834 "(%d of %d requested)\n",
835 r->name, bytes * 8, nbytes * 8, r->entropy_count);
836
e6d4947b 837 bytes = extract_entropy(r->pull, u.tmp, bytes,
90b75ee5 838 random_read_wakeup_thresh / 8, rsvd);
e6d4947b 839 mix_pool_bytes(r, u.tmp, bytes, NULL);
adc782da 840 credit_entropy_bits(r, bytes*8);
1da177e4 841 }
e6d4947b
TT
842 kmemcheck_mark_initialized(&u.hwrand, sizeof(u.hwrand));
843 for (i = 0; i < 4; i++)
844 if (arch_get_random_long(&u.hwrand[i]))
845 break;
846 if (i)
847 mix_pool_bytes(r, &u.hwrand, sizeof(u.hwrand), 0);
1da177e4
LT
848}
849
850/*
851 * These functions extracts randomness from the "entropy pool", and
852 * returns it in a buffer.
853 *
854 * The min parameter specifies the minimum amount we can pull before
855 * failing to avoid races that defeat catastrophic reseeding while the
856 * reserved parameter indicates how much entropy we must leave in the
857 * pool after each pull to avoid starving other readers.
858 *
859 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
860 */
861
862static size_t account(struct entropy_store *r, size_t nbytes, int min,
863 int reserved)
864{
865 unsigned long flags;
866
1da177e4
LT
867 /* Hold lock while accounting */
868 spin_lock_irqsave(&r->lock, flags);
869
cda796a3 870 BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
1da177e4
LT
871 DEBUG_ENT("trying to extract %d bits from %s\n",
872 nbytes * 8, r->name);
873
874 /* Can we pull enough? */
875 if (r->entropy_count / 8 < min + reserved) {
876 nbytes = 0;
877 } else {
878 /* If limited, never pull more than available */
879 if (r->limit && nbytes + reserved >= r->entropy_count / 8)
880 nbytes = r->entropy_count/8 - reserved;
881
90b75ee5 882 if (r->entropy_count / 8 >= nbytes + reserved)
1da177e4
LT
883 r->entropy_count -= nbytes*8;
884 else
885 r->entropy_count = reserved;
886
9a6f70bb 887 if (r->entropy_count < random_write_wakeup_thresh) {
1da177e4 888 wake_up_interruptible(&random_write_wait);
9a6f70bb
JD
889 kill_fasync(&fasync, SIGIO, POLL_OUT);
890 }
1da177e4
LT
891 }
892
893 DEBUG_ENT("debiting %d entropy credits from %s%s\n",
894 nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
895
896 spin_unlock_irqrestore(&r->lock, flags);
897
898 return nbytes;
899}
900
901static void extract_buf(struct entropy_store *r, __u8 *out)
902{
602b6aee 903 int i;
e68e5b66
MM
904 __u32 hash[5], workspace[SHA_WORKSPACE_WORDS];
905 __u8 extract[64];
902c098a 906 unsigned long flags;
1da177e4 907
1c0ad3d4 908 /* Generate a hash across the pool, 16 words (512 bits) at a time */
ffd8d3fa 909 sha_init(hash);
902c098a 910 spin_lock_irqsave(&r->lock, flags);
1c0ad3d4
MM
911 for (i = 0; i < r->poolinfo->poolwords; i += 16)
912 sha_transform(hash, (__u8 *)(r->pool + i), workspace);
913
1da177e4 914 /*
1c0ad3d4
MM
915 * We mix the hash back into the pool to prevent backtracking
916 * attacks (where the attacker knows the state of the pool
917 * plus the current outputs, and attempts to find previous
918 * ouputs), unless the hash function can be inverted. By
919 * mixing at least a SHA1 worth of hash data back, we make
920 * brute-forcing the feedback as hard as brute-forcing the
921 * hash.
1da177e4 922 */
902c098a
TT
923 __mix_pool_bytes(r, hash, sizeof(hash), extract);
924 spin_unlock_irqrestore(&r->lock, flags);
1da177e4
LT
925
926 /*
1c0ad3d4
MM
927 * To avoid duplicates, we atomically extract a portion of the
928 * pool while mixing, and hash one final time.
1da177e4 929 */
e68e5b66 930 sha_transform(hash, extract, workspace);
ffd8d3fa
MM
931 memset(extract, 0, sizeof(extract));
932 memset(workspace, 0, sizeof(workspace));
1da177e4
LT
933
934 /*
1c0ad3d4
MM
935 * In case the hash function has some recognizable output
936 * pattern, we fold it in half. Thus, we always feed back
937 * twice as much data as we output.
1da177e4 938 */
ffd8d3fa
MM
939 hash[0] ^= hash[3];
940 hash[1] ^= hash[4];
941 hash[2] ^= rol32(hash[2], 16);
942 memcpy(out, hash, EXTRACT_SIZE);
943 memset(hash, 0, sizeof(hash));
1da177e4
LT
944}
945
90b75ee5 946static ssize_t extract_entropy(struct entropy_store *r, void *buf,
902c098a 947 size_t nbytes, int min, int reserved)
1da177e4
LT
948{
949 ssize_t ret = 0, i;
950 __u8 tmp[EXTRACT_SIZE];
951
00ce1db1 952 trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
1da177e4
LT
953 xfer_secondary_pool(r, nbytes);
954 nbytes = account(r, nbytes, min, reserved);
955
956 while (nbytes) {
957 extract_buf(r, tmp);
5b739ef8 958
e954bc91 959 if (fips_enabled) {
902c098a
TT
960 unsigned long flags;
961
5b739ef8
NH
962 spin_lock_irqsave(&r->lock, flags);
963 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
964 panic("Hardware RNG duplicated output!\n");
965 memcpy(r->last_data, tmp, EXTRACT_SIZE);
966 spin_unlock_irqrestore(&r->lock, flags);
967 }
1da177e4
LT
968 i = min_t(int, nbytes, EXTRACT_SIZE);
969 memcpy(buf, tmp, i);
970 nbytes -= i;
971 buf += i;
972 ret += i;
973 }
974
975 /* Wipe data just returned from memory */
976 memset(tmp, 0, sizeof(tmp));
977
978 return ret;
979}
980
981static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
982 size_t nbytes)
983{
984 ssize_t ret = 0, i;
985 __u8 tmp[EXTRACT_SIZE];
986
00ce1db1 987 trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
1da177e4
LT
988 xfer_secondary_pool(r, nbytes);
989 nbytes = account(r, nbytes, 0, 0);
990
991 while (nbytes) {
992 if (need_resched()) {
993 if (signal_pending(current)) {
994 if (ret == 0)
995 ret = -ERESTARTSYS;
996 break;
997 }
998 schedule();
999 }
1000
1001 extract_buf(r, tmp);
1002 i = min_t(int, nbytes, EXTRACT_SIZE);
1003 if (copy_to_user(buf, tmp, i)) {
1004 ret = -EFAULT;
1005 break;
1006 }
1007
1008 nbytes -= i;
1009 buf += i;
1010 ret += i;
1011 }
1012
1013 /* Wipe data just returned from memory */
1014 memset(tmp, 0, sizeof(tmp));
1015
1016 return ret;
1017}
1018
1019/*
1020 * This function is the exported kernel interface. It returns some
c2557a30
TT
1021 * number of good random numbers, suitable for key generation, seeding
1022 * TCP sequence numbers, etc. It does not use the hw random number
1023 * generator, if available; use get_random_bytes_arch() for that.
1da177e4
LT
1024 */
1025void get_random_bytes(void *buf, int nbytes)
c2557a30
TT
1026{
1027 extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1028}
1029EXPORT_SYMBOL(get_random_bytes);
1030
1031/*
1032 * This function will use the architecture-specific hardware random
1033 * number generator if it is available. The arch-specific hw RNG will
1034 * almost certainly be faster than what we can do in software, but it
1035 * is impossible to verify that it is implemented securely (as
1036 * opposed, to, say, the AES encryption of a sequence number using a
1037 * key known by the NSA). So it's useful if we need the speed, but
1038 * only if we're willing to trust the hardware manufacturer not to
1039 * have put in a back door.
1040 */
1041void get_random_bytes_arch(void *buf, int nbytes)
1da177e4 1042{
63d77173
PA
1043 char *p = buf;
1044
00ce1db1 1045 trace_get_random_bytes(nbytes, _RET_IP_);
63d77173
PA
1046 while (nbytes) {
1047 unsigned long v;
1048 int chunk = min(nbytes, (int)sizeof(unsigned long));
c2557a30 1049
63d77173
PA
1050 if (!arch_get_random_long(&v))
1051 break;
1052
bd29e568 1053 memcpy(p, &v, chunk);
63d77173
PA
1054 p += chunk;
1055 nbytes -= chunk;
1056 }
1057
c2557a30
TT
1058 if (nbytes)
1059 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1da177e4 1060}
c2557a30
TT
1061EXPORT_SYMBOL(get_random_bytes_arch);
1062
1da177e4
LT
1063
1064/*
1065 * init_std_data - initialize pool with system data
1066 *
1067 * @r: pool to initialize
1068 *
1069 * This function clears the pool's entropy count and mixes some system
1070 * data into the pool to prepare it for use. The pool is not cleared
1071 * as that can only decrease the entropy in the pool.
1072 */
1073static void init_std_data(struct entropy_store *r)
1074{
3e88bdff 1075 int i;
902c098a
TT
1076 ktime_t now = ktime_get_real();
1077 unsigned long rv;
1da177e4 1078
1da177e4 1079 r->entropy_count = 0;
775f4b29 1080 r->entropy_total = 0;
902c098a
TT
1081 mix_pool_bytes(r, &now, sizeof(now), NULL);
1082 for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) {
1083 if (!arch_get_random_long(&rv))
3e88bdff 1084 break;
902c098a 1085 mix_pool_bytes(r, &rv, sizeof(rv), NULL);
3e88bdff 1086 }
902c098a 1087 mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
1da177e4
LT
1088}
1089
cbc96b75
TL
1090/*
1091 * Note that setup_arch() may call add_device_randomness()
1092 * long before we get here. This allows seeding of the pools
1093 * with some platform dependent data very early in the boot
1094 * process. But it limits our options here. We must use
1095 * statically allocated structures that already have all
1096 * initializations complete at compile time. We should also
1097 * take care not to overwrite the precious per platform data
1098 * we were given.
1099 */
53c3f63e 1100static int rand_initialize(void)
1da177e4
LT
1101{
1102 init_std_data(&input_pool);
1103 init_std_data(&blocking_pool);
1104 init_std_data(&nonblocking_pool);
1105 return 0;
1106}
1107module_init(rand_initialize);
1108
9361401e 1109#ifdef CONFIG_BLOCK
1da177e4
LT
1110void rand_initialize_disk(struct gendisk *disk)
1111{
1112 struct timer_rand_state *state;
1113
1114 /*
f8595815 1115 * If kzalloc returns null, we just won't use that entropy
1da177e4
LT
1116 * source.
1117 */
f8595815
ED
1118 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1119 if (state)
1da177e4 1120 disk->random = state;
1da177e4 1121}
9361401e 1122#endif
1da177e4
LT
1123
1124static ssize_t
90b75ee5 1125random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1da177e4
LT
1126{
1127 ssize_t n, retval = 0, count = 0;
1128
1129 if (nbytes == 0)
1130 return 0;
1131
1132 while (nbytes > 0) {
1133 n = nbytes;
1134 if (n > SEC_XFER_SIZE)
1135 n = SEC_XFER_SIZE;
1136
1137 DEBUG_ENT("reading %d bits\n", n*8);
1138
1139 n = extract_entropy_user(&blocking_pool, buf, n);
1140
1141 DEBUG_ENT("read got %d bits (%d still needed)\n",
1142 n*8, (nbytes-n)*8);
1143
1144 if (n == 0) {
1145 if (file->f_flags & O_NONBLOCK) {
1146 retval = -EAGAIN;
1147 break;
1148 }
1149
1150 DEBUG_ENT("sleeping?\n");
1151
1152 wait_event_interruptible(random_read_wait,
1153 input_pool.entropy_count >=
1154 random_read_wakeup_thresh);
1155
1156 DEBUG_ENT("awake\n");
1157
1158 if (signal_pending(current)) {
1159 retval = -ERESTARTSYS;
1160 break;
1161 }
1162
1163 continue;
1164 }
1165
1166 if (n < 0) {
1167 retval = n;
1168 break;
1169 }
1170 count += n;
1171 buf += n;
1172 nbytes -= n;
1173 break; /* This break makes the device work */
1174 /* like a named pipe */
1175 }
1176
1da177e4
LT
1177 return (count ? count : retval);
1178}
1179
1180static ssize_t
90b75ee5 1181urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1da177e4
LT
1182{
1183 return extract_entropy_user(&nonblocking_pool, buf, nbytes);
1184}
1185
1186static unsigned int
1187random_poll(struct file *file, poll_table * wait)
1188{
1189 unsigned int mask;
1190
1191 poll_wait(file, &random_read_wait, wait);
1192 poll_wait(file, &random_write_wait, wait);
1193 mask = 0;
1194 if (input_pool.entropy_count >= random_read_wakeup_thresh)
1195 mask |= POLLIN | POLLRDNORM;
1196 if (input_pool.entropy_count < random_write_wakeup_thresh)
1197 mask |= POLLOUT | POLLWRNORM;
1198 return mask;
1199}
1200
7f397dcd
MM
1201static int
1202write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1da177e4 1203{
1da177e4
LT
1204 size_t bytes;
1205 __u32 buf[16];
1206 const char __user *p = buffer;
1da177e4 1207
7f397dcd
MM
1208 while (count > 0) {
1209 bytes = min(count, sizeof(buf));
1210 if (copy_from_user(&buf, p, bytes))
1211 return -EFAULT;
1da177e4 1212
7f397dcd 1213 count -= bytes;
1da177e4
LT
1214 p += bytes;
1215
902c098a 1216 mix_pool_bytes(r, buf, bytes, NULL);
91f3f1e3 1217 cond_resched();
1da177e4 1218 }
7f397dcd
MM
1219
1220 return 0;
1221}
1222
90b75ee5
MM
1223static ssize_t random_write(struct file *file, const char __user *buffer,
1224 size_t count, loff_t *ppos)
7f397dcd
MM
1225{
1226 size_t ret;
7f397dcd
MM
1227
1228 ret = write_pool(&blocking_pool, buffer, count);
1229 if (ret)
1230 return ret;
1231 ret = write_pool(&nonblocking_pool, buffer, count);
1232 if (ret)
1233 return ret;
1234
7f397dcd 1235 return (ssize_t)count;
1da177e4
LT
1236}
1237
43ae4860 1238static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1da177e4
LT
1239{
1240 int size, ent_count;
1241 int __user *p = (int __user *)arg;
1242 int retval;
1243
1244 switch (cmd) {
1245 case RNDGETENTCNT:
43ae4860
MM
1246 /* inherently racy, no point locking */
1247 if (put_user(input_pool.entropy_count, p))
1da177e4
LT
1248 return -EFAULT;
1249 return 0;
1250 case RNDADDTOENTCNT:
1251 if (!capable(CAP_SYS_ADMIN))
1252 return -EPERM;
1253 if (get_user(ent_count, p))
1254 return -EFAULT;
adc782da 1255 credit_entropy_bits(&input_pool, ent_count);
1da177e4
LT
1256 return 0;
1257 case RNDADDENTROPY:
1258 if (!capable(CAP_SYS_ADMIN))
1259 return -EPERM;
1260 if (get_user(ent_count, p++))
1261 return -EFAULT;
1262 if (ent_count < 0)
1263 return -EINVAL;
1264 if (get_user(size, p++))
1265 return -EFAULT;
7f397dcd
MM
1266 retval = write_pool(&input_pool, (const char __user *)p,
1267 size);
1da177e4
LT
1268 if (retval < 0)
1269 return retval;
adc782da 1270 credit_entropy_bits(&input_pool, ent_count);
1da177e4
LT
1271 return 0;
1272 case RNDZAPENTCNT:
1273 case RNDCLEARPOOL:
1274 /* Clear the entropy pool counters. */
1275 if (!capable(CAP_SYS_ADMIN))
1276 return -EPERM;
53c3f63e 1277 rand_initialize();
1da177e4
LT
1278 return 0;
1279 default:
1280 return -EINVAL;
1281 }
1282}
1283
9a6f70bb
JD
1284static int random_fasync(int fd, struct file *filp, int on)
1285{
1286 return fasync_helper(fd, filp, on, &fasync);
1287}
1288
2b8693c0 1289const struct file_operations random_fops = {
1da177e4
LT
1290 .read = random_read,
1291 .write = random_write,
1292 .poll = random_poll,
43ae4860 1293 .unlocked_ioctl = random_ioctl,
9a6f70bb 1294 .fasync = random_fasync,
6038f373 1295 .llseek = noop_llseek,
1da177e4
LT
1296};
1297
2b8693c0 1298const struct file_operations urandom_fops = {
1da177e4
LT
1299 .read = urandom_read,
1300 .write = random_write,
43ae4860 1301 .unlocked_ioctl = random_ioctl,
9a6f70bb 1302 .fasync = random_fasync,
6038f373 1303 .llseek = noop_llseek,
1da177e4
LT
1304};
1305
1306/***************************************************************
1307 * Random UUID interface
1308 *
1309 * Used here for a Boot ID, but can be useful for other kernel
1310 * drivers.
1311 ***************************************************************/
1312
1313/*
1314 * Generate random UUID
1315 */
1316void generate_random_uuid(unsigned char uuid_out[16])
1317{
1318 get_random_bytes(uuid_out, 16);
c41b20e7 1319 /* Set UUID version to 4 --- truly random generation */
1da177e4
LT
1320 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1321 /* Set the UUID variant to DCE */
1322 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1323}
1da177e4
LT
1324EXPORT_SYMBOL(generate_random_uuid);
1325
1326/********************************************************************
1327 *
1328 * Sysctl interface
1329 *
1330 ********************************************************************/
1331
1332#ifdef CONFIG_SYSCTL
1333
1334#include <linux/sysctl.h>
1335
1336static int min_read_thresh = 8, min_write_thresh;
1337static int max_read_thresh = INPUT_POOL_WORDS * 32;
1338static int max_write_thresh = INPUT_POOL_WORDS * 32;
1339static char sysctl_bootid[16];
1340
1341/*
1342 * These functions is used to return both the bootid UUID, and random
1343 * UUID. The difference is in whether table->data is NULL; if it is,
1344 * then a new UUID is generated and returned to the user.
1345 *
1346 * If the user accesses this via the proc interface, it will be returned
1347 * as an ASCII string in the standard UUID format. If accesses via the
1348 * sysctl system call, it is returned as 16 bytes of binary data.
1349 */
8d65af78 1350static int proc_do_uuid(ctl_table *table, int write,
1da177e4
LT
1351 void __user *buffer, size_t *lenp, loff_t *ppos)
1352{
1353 ctl_table fake_table;
1354 unsigned char buf[64], tmp_uuid[16], *uuid;
1355
1356 uuid = table->data;
1357 if (!uuid) {
1358 uuid = tmp_uuid;
1da177e4 1359 generate_random_uuid(uuid);
44e4360f
MD
1360 } else {
1361 static DEFINE_SPINLOCK(bootid_spinlock);
1362
1363 spin_lock(&bootid_spinlock);
1364 if (!uuid[8])
1365 generate_random_uuid(uuid);
1366 spin_unlock(&bootid_spinlock);
1367 }
1da177e4 1368
35900771
JP
1369 sprintf(buf, "%pU", uuid);
1370
1da177e4
LT
1371 fake_table.data = buf;
1372 fake_table.maxlen = sizeof(buf);
1373
8d65af78 1374 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1da177e4
LT
1375}
1376
1da177e4 1377static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
74feec5d 1378extern ctl_table random_table[];
1da177e4
LT
1379ctl_table random_table[] = {
1380 {
1da177e4
LT
1381 .procname = "poolsize",
1382 .data = &sysctl_poolsize,
1383 .maxlen = sizeof(int),
1384 .mode = 0444,
6d456111 1385 .proc_handler = proc_dointvec,
1da177e4
LT
1386 },
1387 {
1da177e4
LT
1388 .procname = "entropy_avail",
1389 .maxlen = sizeof(int),
1390 .mode = 0444,
6d456111 1391 .proc_handler = proc_dointvec,
1da177e4
LT
1392 .data = &input_pool.entropy_count,
1393 },
1394 {
1da177e4
LT
1395 .procname = "read_wakeup_threshold",
1396 .data = &random_read_wakeup_thresh,
1397 .maxlen = sizeof(int),
1398 .mode = 0644,
6d456111 1399 .proc_handler = proc_dointvec_minmax,
1da177e4
LT
1400 .extra1 = &min_read_thresh,
1401 .extra2 = &max_read_thresh,
1402 },
1403 {
1da177e4
LT
1404 .procname = "write_wakeup_threshold",
1405 .data = &random_write_wakeup_thresh,
1406 .maxlen = sizeof(int),
1407 .mode = 0644,
6d456111 1408 .proc_handler = proc_dointvec_minmax,
1da177e4
LT
1409 .extra1 = &min_write_thresh,
1410 .extra2 = &max_write_thresh,
1411 },
1412 {
1da177e4
LT
1413 .procname = "boot_id",
1414 .data = &sysctl_bootid,
1415 .maxlen = 16,
1416 .mode = 0444,
6d456111 1417 .proc_handler = proc_do_uuid,
1da177e4
LT
1418 },
1419 {
1da177e4
LT
1420 .procname = "uuid",
1421 .maxlen = 16,
1422 .mode = 0444,
6d456111 1423 .proc_handler = proc_do_uuid,
1da177e4 1424 },
894d2491 1425 { }
1da177e4
LT
1426};
1427#endif /* CONFIG_SYSCTL */
1428
6e5714ea 1429static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1da177e4 1430
6e5714ea 1431static int __init random_int_secret_init(void)
1da177e4 1432{
6e5714ea 1433 get_random_bytes(random_int_secret, sizeof(random_int_secret));
1da177e4
LT
1434 return 0;
1435}
6e5714ea 1436late_initcall(random_int_secret_init);
1da177e4
LT
1437
1438/*
1439 * Get a random word for internal kernel use only. Similar to urandom but
1440 * with the goal of minimal entropy pool depletion. As a result, the random
1441 * value is not cryptographically secure but for several uses the cost of
1442 * depleting entropy is too high
1443 */
74feec5d 1444static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1da177e4
LT
1445unsigned int get_random_int(void)
1446{
63d77173 1447 __u32 *hash;
6e5714ea 1448 unsigned int ret;
8a0a9bd4 1449
63d77173
PA
1450 if (arch_get_random_int(&ret))
1451 return ret;
1452
1453 hash = get_cpu_var(get_random_int_hash);
8a0a9bd4 1454
26a9a418 1455 hash[0] += current->pid + jiffies + get_cycles();
6e5714ea
DM
1456 md5_transform(hash, random_int_secret);
1457 ret = hash[0];
8a0a9bd4
LT
1458 put_cpu_var(get_random_int_hash);
1459
1460 return ret;
1da177e4
LT
1461}
1462
1463/*
1464 * randomize_range() returns a start address such that
1465 *
1466 * [...... <range> .....]
1467 * start end
1468 *
1469 * a <range> with size "len" starting at the return value is inside in the
1470 * area defined by [start, end], but is otherwise randomized.
1471 */
1472unsigned long
1473randomize_range(unsigned long start, unsigned long end, unsigned long len)
1474{
1475 unsigned long range = end - len - start;
1476
1477 if (end <= start + len)
1478 return 0;
1479 return PAGE_ALIGN(get_random_int() % range + start);
1480}