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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * random.c -- A strong random number generator
3 *
Matt Mackall9e95ce22005-04-16 15:25:56 -07004 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
Linus Torvalds1da177e2005-04-16 15:20:36 -07005 *
6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
7 * rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, and the entire permission notice in its entirety,
14 * including the disclaimer of warranties.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. The name of the author may not be used to endorse or promote
19 * products derived from this software without specific prior
20 * written permission.
21 *
22 * ALTERNATIVELY, this product may be distributed under the terms of
23 * the GNU General Public License, in which case the provisions of the GPL are
24 * required INSTEAD OF the above restrictions. (This clause is
25 * necessary due to a potential bad interaction between the GPL and
26 * the restrictions contained in a BSD-style copyright.)
27 *
28 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
31 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
32 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
34 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
35 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
36 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
38 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
39 * DAMAGE.
40 */
41
42/*
43 * (now, with legal B.S. out of the way.....)
44 *
45 * This routine gathers environmental noise from device drivers, etc.,
46 * and returns good random numbers, suitable for cryptographic use.
47 * Besides the obvious cryptographic uses, these numbers are also good
48 * for seeding TCP sequence numbers, and other places where it is
49 * desirable to have numbers which are not only random, but hard to
50 * predict by an attacker.
51 *
52 * Theory of operation
53 * ===================
54 *
55 * Computers are very predictable devices. Hence it is extremely hard
56 * to produce truly random numbers on a computer --- as opposed to
57 * pseudo-random numbers, which can easily generated by using a
58 * algorithm. Unfortunately, it is very easy for attackers to guess
59 * the sequence of pseudo-random number generators, and for some
60 * applications this is not acceptable. So instead, we must try to
61 * gather "environmental noise" from the computer's environment, which
62 * must be hard for outside attackers to observe, and use that to
63 * generate random numbers. In a Unix environment, this is best done
64 * from inside the kernel.
65 *
66 * Sources of randomness from the environment include inter-keyboard
67 * timings, inter-interrupt timings from some interrupts, and other
68 * events which are both (a) non-deterministic and (b) hard for an
69 * outside observer to measure. Randomness from these sources are
70 * added to an "entropy pool", which is mixed using a CRC-like function.
71 * This is not cryptographically strong, but it is adequate assuming
72 * the randomness is not chosen maliciously, and it is fast enough that
73 * the overhead of doing it on every interrupt is very reasonable.
74 * As random bytes are mixed into the entropy pool, the routines keep
75 * an *estimate* of how many bits of randomness have been stored into
76 * the random number generator's internal state.
77 *
78 * When random bytes are desired, they are obtained by taking the SHA
79 * hash of the contents of the "entropy pool". The SHA hash avoids
80 * exposing the internal state of the entropy pool. It is believed to
81 * be computationally infeasible to derive any useful information
82 * about the input of SHA from its output. Even if it is possible to
83 * analyze SHA in some clever way, as long as the amount of data
84 * returned from the generator is less than the inherent entropy in
85 * the pool, the output data is totally unpredictable. For this
86 * reason, the routine decreases its internal estimate of how many
87 * bits of "true randomness" are contained in the entropy pool as it
88 * outputs random numbers.
89 *
90 * If this estimate goes to zero, the routine can still generate
91 * random numbers; however, an attacker may (at least in theory) be
92 * able to infer the future output of the generator from prior
93 * outputs. This requires successful cryptanalysis of SHA, which is
94 * not believed to be feasible, but there is a remote possibility.
95 * Nonetheless, these numbers should be useful for the vast majority
96 * of purposes.
97 *
98 * Exported interfaces ---- output
99 * ===============================
100 *
101 * There are three exported interfaces; the first is one designed to
102 * be used from within the kernel:
103 *
104 * void get_random_bytes(void *buf, int nbytes);
105 *
106 * This interface will return the requested number of random bytes,
107 * and place it in the requested buffer.
108 *
109 * The two other interfaces are two character devices /dev/random and
110 * /dev/urandom. /dev/random is suitable for use when very high
111 * quality randomness is desired (for example, for key generation or
112 * one-time pads), as it will only return a maximum of the number of
113 * bits of randomness (as estimated by the random number generator)
114 * contained in the entropy pool.
115 *
116 * The /dev/urandom device does not have this limit, and will return
117 * as many bytes as are requested. As more and more random bytes are
118 * requested without giving time for the entropy pool to recharge,
119 * this will result in random numbers that are merely cryptographically
120 * strong. For many applications, however, this is acceptable.
121 *
122 * Exported interfaces ---- input
123 * ==============================
124 *
125 * The current exported interfaces for gathering environmental noise
126 * from the devices are:
127 *
128 * void add_input_randomness(unsigned int type, unsigned int code,
129 * unsigned int value);
130 * void add_interrupt_randomness(int irq);
Jarod Wilson442a4ff2011-02-21 21:43:10 +1100131 * void add_disk_randomness(struct gendisk *disk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132 *
133 * add_input_randomness() uses the input layer interrupt timing, as well as
134 * the event type information from the hardware.
135 *
136 * add_interrupt_randomness() uses the inter-interrupt timing as random
137 * inputs to the entropy pool. Note that not all interrupts are good
138 * sources of randomness! For example, the timer interrupts is not a
139 * good choice, because the periodicity of the interrupts is too
Jarod Wilson442a4ff2011-02-21 21:43:10 +1100140 * regular, and hence predictable to an attacker. Network Interface
141 * Controller interrupts are a better measure, since the timing of the
142 * NIC interrupts are more unpredictable.
143 *
144 * add_disk_randomness() uses what amounts to the seek time of block
145 * layer request events, on a per-disk_devt basis, as input to the
146 * entropy pool. Note that high-speed solid state drives with very low
147 * seek times do not make for good sources of entropy, as their seek
148 * times are usually fairly consistent.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 *
150 * All of these routines try to estimate how many bits of randomness a
151 * particular randomness source. They do this by keeping track of the
152 * first and second order deltas of the event timings.
153 *
154 * Ensuring unpredictability at system startup
155 * ============================================
156 *
157 * When any operating system starts up, it will go through a sequence
158 * of actions that are fairly predictable by an adversary, especially
159 * if the start-up does not involve interaction with a human operator.
160 * This reduces the actual number of bits of unpredictability in the
161 * entropy pool below the value in entropy_count. In order to
162 * counteract this effect, it helps to carry information in the
163 * entropy pool across shut-downs and start-ups. To do this, put the
164 * following lines an appropriate script which is run during the boot
165 * sequence:
166 *
167 * echo "Initializing random number generator..."
168 * random_seed=/var/run/random-seed
169 * # Carry a random seed from start-up to start-up
170 * # Load and then save the whole entropy pool
171 * if [ -f $random_seed ]; then
172 * cat $random_seed >/dev/urandom
173 * else
174 * touch $random_seed
175 * fi
176 * chmod 600 $random_seed
177 * dd if=/dev/urandom of=$random_seed count=1 bs=512
178 *
179 * and the following lines in an appropriate script which is run as
180 * the system is shutdown:
181 *
182 * # Carry a random seed from shut-down to start-up
183 * # Save the whole entropy pool
184 * echo "Saving random seed..."
185 * random_seed=/var/run/random-seed
186 * touch $random_seed
187 * chmod 600 $random_seed
188 * dd if=/dev/urandom of=$random_seed count=1 bs=512
189 *
190 * For example, on most modern systems using the System V init
191 * scripts, such code fragments would be found in
192 * /etc/rc.d/init.d/random. On older Linux systems, the correct script
193 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
194 *
195 * Effectively, these commands cause the contents of the entropy pool
196 * to be saved at shut-down time and reloaded into the entropy pool at
197 * start-up. (The 'dd' in the addition to the bootup script is to
198 * make sure that /etc/random-seed is different for every start-up,
199 * even if the system crashes without executing rc.0.) Even with
200 * complete knowledge of the start-up activities, predicting the state
201 * of the entropy pool requires knowledge of the previous history of
202 * the system.
203 *
204 * Configuring the /dev/random driver under Linux
205 * ==============================================
206 *
207 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
208 * the /dev/mem major number (#1). So if your system does not have
209 * /dev/random and /dev/urandom created already, they can be created
210 * by using the commands:
211 *
212 * mknod /dev/random c 1 8
213 * mknod /dev/urandom c 1 9
214 *
215 * Acknowledgements:
216 * =================
217 *
218 * Ideas for constructing this random number generator were derived
219 * from Pretty Good Privacy's random number generator, and from private
220 * discussions with Phil Karn. Colin Plumb provided a faster random
221 * number generator, which speed up the mixing function of the entropy
222 * pool, taken from PGPfone. Dale Worley has also contributed many
223 * useful ideas and suggestions to improve this driver.
224 *
225 * Any flaws in the design are solely my responsibility, and should
226 * not be attributed to the Phil, Colin, or any of authors of PGP.
227 *
228 * Further background information on this topic may be obtained from
229 * RFC 1750, "Randomness Recommendations for Security", by Donald
230 * Eastlake, Steve Crocker, and Jeff Schiller.
231 */
232
233#include <linux/utsname.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700234#include <linux/module.h>
235#include <linux/kernel.h>
236#include <linux/major.h>
237#include <linux/string.h>
238#include <linux/fcntl.h>
239#include <linux/slab.h>
240#include <linux/random.h>
241#include <linux/poll.h>
242#include <linux/init.h>
243#include <linux/fs.h>
244#include <linux/genhd.h>
245#include <linux/interrupt.h>
Andrea Righi27ac7922008-07-23 21:28:13 -0700246#include <linux/mm.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247#include <linux/spinlock.h>
248#include <linux/percpu.h>
249#include <linux/cryptohash.h>
Neil Horman5b739ef2009-06-18 19:50:21 +0800250#include <linux/fips.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251
Yinghai Lud178a1e2009-01-11 00:35:42 -0800252#ifdef CONFIG_GENERIC_HARDIRQS
253# include <linux/irq.h>
254#endif
255
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256#include <asm/processor.h>
257#include <asm/uaccess.h>
258#include <asm/irq.h>
259#include <asm/io.h>
260
261/*
262 * Configuration information
263 */
264#define INPUT_POOL_WORDS 128
265#define OUTPUT_POOL_WORDS 32
266#define SEC_XFER_SIZE 512
Matt Mackalle954bc92010-05-20 19:55:01 +1000267#define EXTRACT_SIZE 10
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268
269/*
270 * The minimum number of bits of entropy before we wake up a read on
271 * /dev/random. Should be enough to do a significant reseed.
272 */
273static int random_read_wakeup_thresh = 64;
274
275/*
276 * If the entropy count falls under this number of bits, then we
277 * should wake up processes which are selecting or polling on write
278 * access to /dev/random.
279 */
280static int random_write_wakeup_thresh = 128;
281
282/*
283 * When the input pool goes over trickle_thresh, start dropping most
284 * samples to avoid wasting CPU time and reduce lock contention.
285 */
286
Christoph Lameter6c036522005-07-07 17:56:59 -0700287static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700288
Matt Mackall90b75ee2008-04-29 01:02:55 -0700289static DEFINE_PER_CPU(int, trickle_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290
291/*
292 * A pool of size .poolwords is stirred with a primitive polynomial
293 * of degree .poolwords over GF(2). The taps for various sizes are
294 * defined below. They are chosen to be evenly spaced (minimum RMS
295 * distance from evenly spaced; the numbers in the comments are a
296 * scaled squared error sum) except for the last tap, which is 1 to
297 * get the twisting happening as fast as possible.
298 */
299static struct poolinfo {
300 int poolwords;
301 int tap1, tap2, tap3, tap4, tap5;
302} poolinfo_table[] = {
303 /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
304 { 128, 103, 76, 51, 25, 1 },
305 /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
306 { 32, 26, 20, 14, 7, 1 },
307#if 0
308 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
309 { 2048, 1638, 1231, 819, 411, 1 },
310
311 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
312 { 1024, 817, 615, 412, 204, 1 },
313
314 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
315 { 1024, 819, 616, 410, 207, 2 },
316
317 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
318 { 512, 411, 308, 208, 104, 1 },
319
320 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
321 { 512, 409, 307, 206, 102, 2 },
322 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
323 { 512, 409, 309, 205, 103, 2 },
324
325 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
326 { 256, 205, 155, 101, 52, 1 },
327
328 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
329 { 128, 103, 78, 51, 27, 2 },
330
331 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
332 { 64, 52, 39, 26, 14, 1 },
333#endif
334};
335
336#define POOLBITS poolwords*32
337#define POOLBYTES poolwords*4
338
339/*
340 * For the purposes of better mixing, we use the CRC-32 polynomial as
341 * well to make a twisted Generalized Feedback Shift Reigster
342 *
343 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
344 * Transactions on Modeling and Computer Simulation 2(3):179-194.
345 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
346 * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
347 *
348 * Thanks to Colin Plumb for suggesting this.
349 *
350 * We have not analyzed the resultant polynomial to prove it primitive;
351 * in fact it almost certainly isn't. Nonetheless, the irreducible factors
352 * of a random large-degree polynomial over GF(2) are more than large enough
353 * that periodicity is not a concern.
354 *
355 * The input hash is much less sensitive than the output hash. All
356 * that we want of it is that it be a good non-cryptographic hash;
357 * i.e. it not produce collisions when fed "random" data of the sort
358 * we expect to see. As long as the pool state differs for different
359 * inputs, we have preserved the input entropy and done a good job.
360 * The fact that an intelligent attacker can construct inputs that
361 * will produce controlled alterations to the pool's state is not
362 * important because we don't consider such inputs to contribute any
363 * randomness. The only property we need with respect to them is that
364 * the attacker can't increase his/her knowledge of the pool's state.
365 * Since all additions are reversible (knowing the final state and the
366 * input, you can reconstruct the initial state), if an attacker has
367 * any uncertainty about the initial state, he/she can only shuffle
368 * that uncertainty about, but never cause any collisions (which would
369 * decrease the uncertainty).
370 *
371 * The chosen system lets the state of the pool be (essentially) the input
372 * modulo the generator polymnomial. Now, for random primitive polynomials,
373 * this is a universal class of hash functions, meaning that the chance
374 * of a collision is limited by the attacker's knowledge of the generator
375 * polynomail, so if it is chosen at random, an attacker can never force
376 * a collision. Here, we use a fixed polynomial, but we *can* assume that
377 * ###--> it is unknown to the processes generating the input entropy. <-###
378 * Because of this important property, this is a good, collision-resistant
379 * hash; hash collisions will occur no more often than chance.
380 */
381
382/*
383 * Static global variables
384 */
385static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
386static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700387static struct fasync_struct *fasync;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700388
389#if 0
Matt Mackall90b75ee2008-04-29 01:02:55 -0700390static int debug;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391module_param(debug, bool, 0644);
Matt Mackall90b75ee2008-04-29 01:02:55 -0700392#define DEBUG_ENT(fmt, arg...) do { \
393 if (debug) \
394 printk(KERN_DEBUG "random %04d %04d %04d: " \
395 fmt,\
396 input_pool.entropy_count,\
397 blocking_pool.entropy_count,\
398 nonblocking_pool.entropy_count,\
399 ## arg); } while (0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700400#else
401#define DEBUG_ENT(fmt, arg...) do {} while (0)
402#endif
403
404/**********************************************************************
405 *
406 * OS independent entropy store. Here are the functions which handle
407 * storing entropy in an entropy pool.
408 *
409 **********************************************************************/
410
411struct entropy_store;
412struct entropy_store {
Matt Mackall43358202008-04-29 01:03:01 -0700413 /* read-only data: */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700414 struct poolinfo *poolinfo;
415 __u32 *pool;
416 const char *name;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417 struct entropy_store *pull;
Richard Kennedy4015d9a2010-07-31 19:58:00 +0800418 int limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700419
420 /* read-write data: */
Matt Mackall43358202008-04-29 01:03:01 -0700421 spinlock_t lock;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 unsigned add_ptr;
Matt Mackallcda796a2009-01-06 14:42:55 -0800423 int entropy_count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700424 int input_rotate;
Matt Mackalle954bc92010-05-20 19:55:01 +1000425 __u8 last_data[EXTRACT_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426};
427
428static __u32 input_pool_data[INPUT_POOL_WORDS];
429static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
430static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
431
432static struct entropy_store input_pool = {
433 .poolinfo = &poolinfo_table[0],
434 .name = "input",
435 .limit = 1,
Ingo Molnare4d91912006-07-03 00:24:34 -0700436 .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700437 .pool = input_pool_data
438};
439
440static struct entropy_store blocking_pool = {
441 .poolinfo = &poolinfo_table[1],
442 .name = "blocking",
443 .limit = 1,
444 .pull = &input_pool,
Ingo Molnare4d91912006-07-03 00:24:34 -0700445 .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700446 .pool = blocking_pool_data
447};
448
449static struct entropy_store nonblocking_pool = {
450 .poolinfo = &poolinfo_table[1],
451 .name = "nonblocking",
452 .pull = &input_pool,
Ingo Molnare4d91912006-07-03 00:24:34 -0700453 .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454 .pool = nonblocking_pool_data
455};
456
457/*
Matt Mackalle68e5b62008-04-29 01:03:05 -0700458 * This function adds bytes into the entropy "pool". It does not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700459 * update the entropy estimate. The caller should call
Matt Mackalladc782d2008-04-29 01:03:07 -0700460 * credit_entropy_bits if this is appropriate.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700461 *
462 * The pool is stirred with a primitive polynomial of the appropriate
463 * degree, and then twisted. We twist by three bits at a time because
464 * it's cheap to do so and helps slightly in the expected case where
465 * the entropy is concentrated in the low-order bits.
466 */
Matt Mackalle68e5b62008-04-29 01:03:05 -0700467static void mix_pool_bytes_extract(struct entropy_store *r, const void *in,
468 int nbytes, __u8 out[64])
Linus Torvalds1da177e2005-04-16 15:20:36 -0700469{
470 static __u32 const twist_table[8] = {
471 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
472 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
Matt Mackall993ba212008-04-29 01:03:04 -0700473 unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
Matt Mackallfeee7692008-04-29 01:03:02 -0700474 int input_rotate;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 int wordmask = r->poolinfo->poolwords - 1;
Matt Mackalle68e5b62008-04-29 01:03:05 -0700476 const char *bytes = in;
Matt Mackall6d38b822008-04-29 01:03:03 -0700477 __u32 w;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700478 unsigned long flags;
479
480 /* Taps are constant, so we can load them without holding r->lock. */
481 tap1 = r->poolinfo->tap1;
482 tap2 = r->poolinfo->tap2;
483 tap3 = r->poolinfo->tap3;
484 tap4 = r->poolinfo->tap4;
485 tap5 = r->poolinfo->tap5;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700486
487 spin_lock_irqsave(&r->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488 input_rotate = r->input_rotate;
Matt Mackall993ba212008-04-29 01:03:04 -0700489 i = r->add_ptr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490
Matt Mackalle68e5b62008-04-29 01:03:05 -0700491 /* mix one byte at a time to simplify size handling and churn faster */
492 while (nbytes--) {
493 w = rol32(*bytes++, input_rotate & 31);
Matt Mackall993ba212008-04-29 01:03:04 -0700494 i = (i - 1) & wordmask;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700495
496 /* XOR in the various taps */
Matt Mackall993ba212008-04-29 01:03:04 -0700497 w ^= r->pool[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498 w ^= r->pool[(i + tap1) & wordmask];
499 w ^= r->pool[(i + tap2) & wordmask];
500 w ^= r->pool[(i + tap3) & wordmask];
501 w ^= r->pool[(i + tap4) & wordmask];
502 w ^= r->pool[(i + tap5) & wordmask];
Matt Mackall993ba212008-04-29 01:03:04 -0700503
504 /* Mix the result back in with a twist */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700505 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
Matt Mackallfeee7692008-04-29 01:03:02 -0700506
507 /*
508 * Normally, we add 7 bits of rotation to the pool.
509 * At the beginning of the pool, add an extra 7 bits
510 * rotation, so that successive passes spread the
511 * input bits across the pool evenly.
512 */
513 input_rotate += i ? 7 : 14;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700514 }
515
516 r->input_rotate = input_rotate;
Matt Mackall993ba212008-04-29 01:03:04 -0700517 r->add_ptr = i;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518
Matt Mackall993ba212008-04-29 01:03:04 -0700519 if (out)
520 for (j = 0; j < 16; j++)
Matt Mackalle68e5b62008-04-29 01:03:05 -0700521 ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522
523 spin_unlock_irqrestore(&r->lock, flags);
524}
525
Matt Mackalle68e5b62008-04-29 01:03:05 -0700526static void mix_pool_bytes(struct entropy_store *r, const void *in, int bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700527{
Matt Mackalle68e5b62008-04-29 01:03:05 -0700528 mix_pool_bytes_extract(r, in, bytes, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700529}
530
531/*
532 * Credit (or debit) the entropy store with n bits of entropy
533 */
Matt Mackalladc782d2008-04-29 01:03:07 -0700534static void credit_entropy_bits(struct entropy_store *r, int nbits)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700535{
536 unsigned long flags;
Andrew Morton8b76f462008-09-02 14:36:14 -0700537 int entropy_count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700538
Matt Mackalladc782d2008-04-29 01:03:07 -0700539 if (!nbits)
540 return;
541
Linus Torvalds1da177e2005-04-16 15:20:36 -0700542 spin_lock_irqsave(&r->lock, flags);
543
Matt Mackalladc782d2008-04-29 01:03:07 -0700544 DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
Andrew Morton8b76f462008-09-02 14:36:14 -0700545 entropy_count = r->entropy_count;
546 entropy_count += nbits;
547 if (entropy_count < 0) {
Matt Mackalladc782d2008-04-29 01:03:07 -0700548 DEBUG_ENT("negative entropy/overflow\n");
Andrew Morton8b76f462008-09-02 14:36:14 -0700549 entropy_count = 0;
550 } else if (entropy_count > r->poolinfo->POOLBITS)
551 entropy_count = r->poolinfo->POOLBITS;
552 r->entropy_count = entropy_count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553
Matt Mackall88c730d2008-04-29 01:02:56 -0700554 /* should we wake readers? */
Andrew Morton8b76f462008-09-02 14:36:14 -0700555 if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
Matt Mackall88c730d2008-04-29 01:02:56 -0700556 wake_up_interruptible(&random_read_wait);
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700557 kill_fasync(&fasync, SIGIO, POLL_IN);
558 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700559 spin_unlock_irqrestore(&r->lock, flags);
560}
561
562/*********************************************************************
563 *
564 * Entropy input management
565 *
566 *********************************************************************/
567
568/* There is one of these per entropy source */
569struct timer_rand_state {
570 cycles_t last_time;
Matt Mackall90b75ee2008-04-29 01:02:55 -0700571 long last_delta, last_delta2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700572 unsigned dont_count_entropy:1;
573};
574
Yinghai Lud7e51e62009-01-07 15:03:13 -0800575#ifndef CONFIG_GENERIC_HARDIRQS
Yinghai Lu2f983572009-01-03 00:06:34 -0800576
577static struct timer_rand_state *irq_timer_state[NR_IRQS];
578
579static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
580{
581 return irq_timer_state[irq];
582}
583
584static void set_timer_rand_state(unsigned int irq,
585 struct timer_rand_state *state)
586{
587 irq_timer_state[irq] = state;
588}
589
590#else
591
592static struct timer_rand_state *get_timer_rand_state(unsigned int irq)
593{
594 struct irq_desc *desc;
595
596 desc = irq_to_desc(irq);
597
598 return desc->timer_rand_state;
599}
600
601static void set_timer_rand_state(unsigned int irq,
602 struct timer_rand_state *state)
603{
604 struct irq_desc *desc;
605
606 desc = irq_to_desc(irq);
607
608 desc->timer_rand_state = state;
609}
Yinghai Lu0b8f1ef2008-12-05 18:58:31 -0800610#endif
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700611
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700612static struct timer_rand_state input_timer_state;
613
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614/*
615 * This function adds entropy to the entropy "pool" by using timing
616 * delays. It uses the timer_rand_state structure to make an estimate
617 * of how many bits of entropy this call has added to the pool.
618 *
619 * The number "num" is also added to the pool - it should somehow describe
620 * the type of event which just happened. This is currently 0-255 for
621 * keyboard scan codes, and 256 upwards for interrupts.
622 *
623 */
624static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
625{
626 struct {
627 cycles_t cycles;
628 long jiffies;
629 unsigned num;
630 } sample;
631 long delta, delta2, delta3;
632
633 preempt_disable();
634 /* if over the trickle threshold, use only 1 in 4096 samples */
635 if (input_pool.entropy_count > trickle_thresh &&
Christoph Lameterb29c6172010-12-06 11:40:06 -0600636 ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700637 goto out;
638
639 sample.jiffies = jiffies;
640 sample.cycles = get_cycles();
641 sample.num = num;
Matt Mackalle68e5b62008-04-29 01:03:05 -0700642 mix_pool_bytes(&input_pool, &sample, sizeof(sample));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700643
644 /*
645 * Calculate number of bits of randomness we probably added.
646 * We take into account the first, second and third-order deltas
647 * in order to make our estimate.
648 */
649
650 if (!state->dont_count_entropy) {
651 delta = sample.jiffies - state->last_time;
652 state->last_time = sample.jiffies;
653
654 delta2 = delta - state->last_delta;
655 state->last_delta = delta;
656
657 delta3 = delta2 - state->last_delta2;
658 state->last_delta2 = delta2;
659
660 if (delta < 0)
661 delta = -delta;
662 if (delta2 < 0)
663 delta2 = -delta2;
664 if (delta3 < 0)
665 delta3 = -delta3;
666 if (delta > delta2)
667 delta = delta2;
668 if (delta > delta3)
669 delta = delta3;
670
671 /*
672 * delta is now minimum absolute delta.
673 * Round down by 1 bit on general principles,
674 * and limit entropy entimate to 12 bits.
675 */
Matt Mackalladc782d2008-04-29 01:03:07 -0700676 credit_entropy_bits(&input_pool,
677 min_t(int, fls(delta>>1), 11));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700679out:
680 preempt_enable();
681}
682
Stephen Hemmingerd2515752006-01-11 12:17:38 -0800683void add_input_randomness(unsigned int type, unsigned int code,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700684 unsigned int value)
685{
686 static unsigned char last_value;
687
688 /* ignore autorepeat and the like */
689 if (value == last_value)
690 return;
691
692 DEBUG_ENT("input event\n");
693 last_value = value;
694 add_timer_randomness(&input_timer_state,
695 (type << 4) ^ code ^ (code >> 4) ^ value);
696}
Dmitry Torokhov80fc9f52006-10-11 01:43:58 -0400697EXPORT_SYMBOL_GPL(add_input_randomness);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698
699void add_interrupt_randomness(int irq)
700{
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700701 struct timer_rand_state *state;
702
703 state = get_timer_rand_state(irq);
704
705 if (state == NULL)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700706 return;
707
708 DEBUG_ENT("irq event %d\n", irq);
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700709 add_timer_randomness(state, 0x100 + irq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700710}
711
David Howells93614012006-09-30 20:45:40 +0200712#ifdef CONFIG_BLOCK
Linus Torvalds1da177e2005-04-16 15:20:36 -0700713void add_disk_randomness(struct gendisk *disk)
714{
715 if (!disk || !disk->random)
716 return;
717 /* first major is 1, so we get >= 0x200 here */
Tejun Heof331c022008-09-03 09:01:48 +0200718 DEBUG_ENT("disk event %d:%d\n",
719 MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720
Tejun Heof331c022008-09-03 09:01:48 +0200721 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722}
David Howells93614012006-09-30 20:45:40 +0200723#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725/*********************************************************************
726 *
727 * Entropy extraction routines
728 *
729 *********************************************************************/
730
Matt Mackall90b75ee2008-04-29 01:02:55 -0700731static ssize_t extract_entropy(struct entropy_store *r, void *buf,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700732 size_t nbytes, int min, int rsvd);
733
734/*
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300735 * This utility inline function is responsible for transferring entropy
Linus Torvalds1da177e2005-04-16 15:20:36 -0700736 * from the primary pool to the secondary extraction pool. We make
737 * sure we pull enough for a 'catastrophic reseed'.
738 */
739static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
740{
741 __u32 tmp[OUTPUT_POOL_WORDS];
742
743 if (r->pull && r->entropy_count < nbytes * 8 &&
744 r->entropy_count < r->poolinfo->POOLBITS) {
Matt Mackall5a021e92007-07-19 11:30:14 -0700745 /* If we're limited, always leave two wakeup worth's BITS */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700746 int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
Matt Mackall5a021e92007-07-19 11:30:14 -0700747 int bytes = nbytes;
748
749 /* pull at least as many as BYTES as wakeup BITS */
750 bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
751 /* but never more than the buffer size */
752 bytes = min_t(int, bytes, sizeof(tmp));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700753
754 DEBUG_ENT("going to reseed %s with %d bits "
755 "(%d of %d requested)\n",
756 r->name, bytes * 8, nbytes * 8, r->entropy_count);
757
Matt Mackall90b75ee2008-04-29 01:02:55 -0700758 bytes = extract_entropy(r->pull, tmp, bytes,
759 random_read_wakeup_thresh / 8, rsvd);
Matt Mackalle68e5b62008-04-29 01:03:05 -0700760 mix_pool_bytes(r, tmp, bytes);
Matt Mackalladc782d2008-04-29 01:03:07 -0700761 credit_entropy_bits(r, bytes*8);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700762 }
763}
764
765/*
766 * These functions extracts randomness from the "entropy pool", and
767 * returns it in a buffer.
768 *
769 * The min parameter specifies the minimum amount we can pull before
770 * failing to avoid races that defeat catastrophic reseeding while the
771 * reserved parameter indicates how much entropy we must leave in the
772 * pool after each pull to avoid starving other readers.
773 *
774 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
775 */
776
777static size_t account(struct entropy_store *r, size_t nbytes, int min,
778 int reserved)
779{
780 unsigned long flags;
781
Linus Torvalds1da177e2005-04-16 15:20:36 -0700782 /* Hold lock while accounting */
783 spin_lock_irqsave(&r->lock, flags);
784
Matt Mackallcda796a2009-01-06 14:42:55 -0800785 BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700786 DEBUG_ENT("trying to extract %d bits from %s\n",
787 nbytes * 8, r->name);
788
789 /* Can we pull enough? */
790 if (r->entropy_count / 8 < min + reserved) {
791 nbytes = 0;
792 } else {
793 /* If limited, never pull more than available */
794 if (r->limit && nbytes + reserved >= r->entropy_count / 8)
795 nbytes = r->entropy_count/8 - reserved;
796
Matt Mackall90b75ee2008-04-29 01:02:55 -0700797 if (r->entropy_count / 8 >= nbytes + reserved)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700798 r->entropy_count -= nbytes*8;
799 else
800 r->entropy_count = reserved;
801
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700802 if (r->entropy_count < random_write_wakeup_thresh) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700803 wake_up_interruptible(&random_write_wait);
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700804 kill_fasync(&fasync, SIGIO, POLL_OUT);
805 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806 }
807
808 DEBUG_ENT("debiting %d entropy credits from %s%s\n",
809 nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
810
811 spin_unlock_irqrestore(&r->lock, flags);
812
813 return nbytes;
814}
815
816static void extract_buf(struct entropy_store *r, __u8 *out)
817{
Matt Mackall602b6ae2007-05-29 21:54:27 -0500818 int i;
Matt Mackalle68e5b62008-04-29 01:03:05 -0700819 __u32 hash[5], workspace[SHA_WORKSPACE_WORDS];
820 __u8 extract[64];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700822 /* Generate a hash across the pool, 16 words (512 bits) at a time */
Matt Mackallffd8d3f2008-04-29 01:02:59 -0700823 sha_init(hash);
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700824 for (i = 0; i < r->poolinfo->poolwords; i += 16)
Matt Mackallffd8d3f2008-04-29 01:02:59 -0700825 sha_transform(hash, (__u8 *)(r->pool + i), workspace);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700826
827 /*
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700828 * We mix the hash back into the pool to prevent backtracking
829 * attacks (where the attacker knows the state of the pool
830 * plus the current outputs, and attempts to find previous
831 * ouputs), unless the hash function can be inverted. By
832 * mixing at least a SHA1 worth of hash data back, we make
833 * brute-forcing the feedback as hard as brute-forcing the
834 * hash.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700835 */
Matt Mackalle68e5b62008-04-29 01:03:05 -0700836 mix_pool_bytes_extract(r, hash, sizeof(hash), extract);
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700837
838 /*
839 * To avoid duplicates, we atomically extract a portion of the
840 * pool while mixing, and hash one final time.
841 */
Matt Mackalle68e5b62008-04-29 01:03:05 -0700842 sha_transform(hash, extract, workspace);
Matt Mackallffd8d3f2008-04-29 01:02:59 -0700843 memset(extract, 0, sizeof(extract));
844 memset(workspace, 0, sizeof(workspace));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700845
846 /*
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700847 * In case the hash function has some recognizable output
848 * pattern, we fold it in half. Thus, we always feed back
849 * twice as much data as we output.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700850 */
Matt Mackallffd8d3f2008-04-29 01:02:59 -0700851 hash[0] ^= hash[3];
852 hash[1] ^= hash[4];
853 hash[2] ^= rol32(hash[2], 16);
854 memcpy(out, hash, EXTRACT_SIZE);
855 memset(hash, 0, sizeof(hash));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700856}
857
Matt Mackall90b75ee2008-04-29 01:02:55 -0700858static ssize_t extract_entropy(struct entropy_store *r, void *buf,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859 size_t nbytes, int min, int reserved)
860{
861 ssize_t ret = 0, i;
862 __u8 tmp[EXTRACT_SIZE];
Neil Horman5b739ef2009-06-18 19:50:21 +0800863 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864
865 xfer_secondary_pool(r, nbytes);
866 nbytes = account(r, nbytes, min, reserved);
867
868 while (nbytes) {
869 extract_buf(r, tmp);
Neil Horman5b739ef2009-06-18 19:50:21 +0800870
Matt Mackalle954bc92010-05-20 19:55:01 +1000871 if (fips_enabled) {
Neil Horman5b739ef2009-06-18 19:50:21 +0800872 spin_lock_irqsave(&r->lock, flags);
873 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
874 panic("Hardware RNG duplicated output!\n");
875 memcpy(r->last_data, tmp, EXTRACT_SIZE);
876 spin_unlock_irqrestore(&r->lock, flags);
877 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700878 i = min_t(int, nbytes, EXTRACT_SIZE);
879 memcpy(buf, tmp, i);
880 nbytes -= i;
881 buf += i;
882 ret += i;
883 }
884
885 /* Wipe data just returned from memory */
886 memset(tmp, 0, sizeof(tmp));
887
888 return ret;
889}
890
891static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
892 size_t nbytes)
893{
894 ssize_t ret = 0, i;
895 __u8 tmp[EXTRACT_SIZE];
896
897 xfer_secondary_pool(r, nbytes);
898 nbytes = account(r, nbytes, 0, 0);
899
900 while (nbytes) {
901 if (need_resched()) {
902 if (signal_pending(current)) {
903 if (ret == 0)
904 ret = -ERESTARTSYS;
905 break;
906 }
907 schedule();
908 }
909
910 extract_buf(r, tmp);
911 i = min_t(int, nbytes, EXTRACT_SIZE);
912 if (copy_to_user(buf, tmp, i)) {
913 ret = -EFAULT;
914 break;
915 }
916
917 nbytes -= i;
918 buf += i;
919 ret += i;
920 }
921
922 /* Wipe data just returned from memory */
923 memset(tmp, 0, sizeof(tmp));
924
925 return ret;
926}
927
928/*
929 * This function is the exported kernel interface. It returns some
930 * number of good random numbers, suitable for seeding TCP sequence
931 * numbers, etc.
932 */
933void get_random_bytes(void *buf, int nbytes)
934{
H. Peter Anvin63d77172011-07-31 13:54:50 -0700935 char *p = buf;
936
937 while (nbytes) {
938 unsigned long v;
939 int chunk = min(nbytes, (int)sizeof(unsigned long));
940
941 if (!arch_get_random_long(&v))
942 break;
943
Luck, Tonybd29e562011-11-16 10:50:56 -0800944 memcpy(p, &v, chunk);
H. Peter Anvin63d77172011-07-31 13:54:50 -0700945 p += chunk;
946 nbytes -= chunk;
947 }
948
949 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700950}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700951EXPORT_SYMBOL(get_random_bytes);
952
953/*
954 * init_std_data - initialize pool with system data
955 *
956 * @r: pool to initialize
957 *
958 * This function clears the pool's entropy count and mixes some system
959 * data into the pool to prepare it for use. The pool is not cleared
960 * as that can only decrease the entropy in the pool.
961 */
962static void init_std_data(struct entropy_store *r)
963{
Eric Dumazetf8595812007-03-28 14:22:33 -0700964 ktime_t now;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700965 unsigned long flags;
966
967 spin_lock_irqsave(&r->lock, flags);
968 r->entropy_count = 0;
969 spin_unlock_irqrestore(&r->lock, flags);
970
Eric Dumazetf8595812007-03-28 14:22:33 -0700971 now = ktime_get_real();
Matt Mackalle68e5b62008-04-29 01:03:05 -0700972 mix_pool_bytes(r, &now, sizeof(now));
973 mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974}
975
Matt Mackall53c3f632008-04-29 01:02:58 -0700976static int rand_initialize(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977{
978 init_std_data(&input_pool);
979 init_std_data(&blocking_pool);
980 init_std_data(&nonblocking_pool);
981 return 0;
982}
983module_init(rand_initialize);
984
985void rand_initialize_irq(int irq)
986{
987 struct timer_rand_state *state;
988
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700989 state = get_timer_rand_state(irq);
990
991 if (state)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700992 return;
993
994 /*
Eric Dumazetf8595812007-03-28 14:22:33 -0700995 * If kzalloc returns null, we just won't use that entropy
Linus Torvalds1da177e2005-04-16 15:20:36 -0700996 * source.
997 */
Eric Dumazetf8595812007-03-28 14:22:33 -0700998 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
999 if (state)
Yinghai Lu3060d6f2008-08-19 20:50:08 -07001000 set_timer_rand_state(irq, state);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001001}
1002
David Howells93614012006-09-30 20:45:40 +02001003#ifdef CONFIG_BLOCK
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004void rand_initialize_disk(struct gendisk *disk)
1005{
1006 struct timer_rand_state *state;
1007
1008 /*
Eric Dumazetf8595812007-03-28 14:22:33 -07001009 * If kzalloc returns null, we just won't use that entropy
Linus Torvalds1da177e2005-04-16 15:20:36 -07001010 * source.
1011 */
Eric Dumazetf8595812007-03-28 14:22:33 -07001012 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1013 if (state)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014 disk->random = state;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001015}
David Howells93614012006-09-30 20:45:40 +02001016#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017
1018static ssize_t
Matt Mackall90b75ee2008-04-29 01:02:55 -07001019random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020{
1021 ssize_t n, retval = 0, count = 0;
1022
1023 if (nbytes == 0)
1024 return 0;
1025
1026 while (nbytes > 0) {
1027 n = nbytes;
1028 if (n > SEC_XFER_SIZE)
1029 n = SEC_XFER_SIZE;
1030
1031 DEBUG_ENT("reading %d bits\n", n*8);
1032
1033 n = extract_entropy_user(&blocking_pool, buf, n);
1034
1035 DEBUG_ENT("read got %d bits (%d still needed)\n",
1036 n*8, (nbytes-n)*8);
1037
1038 if (n == 0) {
1039 if (file->f_flags & O_NONBLOCK) {
1040 retval = -EAGAIN;
1041 break;
1042 }
1043
1044 DEBUG_ENT("sleeping?\n");
1045
1046 wait_event_interruptible(random_read_wait,
1047 input_pool.entropy_count >=
1048 random_read_wakeup_thresh);
1049
1050 DEBUG_ENT("awake\n");
1051
1052 if (signal_pending(current)) {
1053 retval = -ERESTARTSYS;
1054 break;
1055 }
1056
1057 continue;
1058 }
1059
1060 if (n < 0) {
1061 retval = n;
1062 break;
1063 }
1064 count += n;
1065 buf += n;
1066 nbytes -= n;
1067 break; /* This break makes the device work */
1068 /* like a named pipe */
1069 }
1070
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071 return (count ? count : retval);
1072}
1073
1074static ssize_t
Matt Mackall90b75ee2008-04-29 01:02:55 -07001075urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001076{
1077 return extract_entropy_user(&nonblocking_pool, buf, nbytes);
1078}
1079
1080static unsigned int
1081random_poll(struct file *file, poll_table * wait)
1082{
1083 unsigned int mask;
1084
1085 poll_wait(file, &random_read_wait, wait);
1086 poll_wait(file, &random_write_wait, wait);
1087 mask = 0;
1088 if (input_pool.entropy_count >= random_read_wakeup_thresh)
1089 mask |= POLLIN | POLLRDNORM;
1090 if (input_pool.entropy_count < random_write_wakeup_thresh)
1091 mask |= POLLOUT | POLLWRNORM;
1092 return mask;
1093}
1094
Matt Mackall7f397dc2007-05-29 21:58:10 -05001095static int
1096write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1097{
1098 size_t bytes;
1099 __u32 buf[16];
1100 const char __user *p = buffer;
1101
1102 while (count > 0) {
1103 bytes = min(count, sizeof(buf));
1104 if (copy_from_user(&buf, p, bytes))
1105 return -EFAULT;
1106
1107 count -= bytes;
1108 p += bytes;
1109
Matt Mackalle68e5b62008-04-29 01:03:05 -07001110 mix_pool_bytes(r, buf, bytes);
Matt Mackall91f3f1e2008-02-06 01:37:20 -08001111 cond_resched();
Matt Mackall7f397dc2007-05-29 21:58:10 -05001112 }
1113
1114 return 0;
1115}
1116
Matt Mackall90b75ee2008-04-29 01:02:55 -07001117static ssize_t random_write(struct file *file, const char __user *buffer,
1118 size_t count, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119{
Matt Mackall7f397dc2007-05-29 21:58:10 -05001120 size_t ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121
Matt Mackall7f397dc2007-05-29 21:58:10 -05001122 ret = write_pool(&blocking_pool, buffer, count);
1123 if (ret)
1124 return ret;
1125 ret = write_pool(&nonblocking_pool, buffer, count);
1126 if (ret)
1127 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001128
Matt Mackall7f397dc2007-05-29 21:58:10 -05001129 return (ssize_t)count;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130}
1131
Matt Mackall43ae4862008-04-29 01:02:58 -07001132static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001133{
1134 int size, ent_count;
1135 int __user *p = (int __user *)arg;
1136 int retval;
1137
1138 switch (cmd) {
1139 case RNDGETENTCNT:
Matt Mackall43ae4862008-04-29 01:02:58 -07001140 /* inherently racy, no point locking */
1141 if (put_user(input_pool.entropy_count, p))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001142 return -EFAULT;
1143 return 0;
1144 case RNDADDTOENTCNT:
1145 if (!capable(CAP_SYS_ADMIN))
1146 return -EPERM;
1147 if (get_user(ent_count, p))
1148 return -EFAULT;
Matt Mackalladc782d2008-04-29 01:03:07 -07001149 credit_entropy_bits(&input_pool, ent_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001150 return 0;
1151 case RNDADDENTROPY:
1152 if (!capable(CAP_SYS_ADMIN))
1153 return -EPERM;
1154 if (get_user(ent_count, p++))
1155 return -EFAULT;
1156 if (ent_count < 0)
1157 return -EINVAL;
1158 if (get_user(size, p++))
1159 return -EFAULT;
Matt Mackall7f397dc2007-05-29 21:58:10 -05001160 retval = write_pool(&input_pool, (const char __user *)p,
1161 size);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001162 if (retval < 0)
1163 return retval;
Matt Mackalladc782d2008-04-29 01:03:07 -07001164 credit_entropy_bits(&input_pool, ent_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165 return 0;
1166 case RNDZAPENTCNT:
1167 case RNDCLEARPOOL:
1168 /* Clear the entropy pool counters. */
1169 if (!capable(CAP_SYS_ADMIN))
1170 return -EPERM;
Matt Mackall53c3f632008-04-29 01:02:58 -07001171 rand_initialize();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001172 return 0;
1173 default:
1174 return -EINVAL;
1175 }
1176}
1177
Jeff Dike9a6f70b2008-04-29 01:03:08 -07001178static int random_fasync(int fd, struct file *filp, int on)
1179{
1180 return fasync_helper(fd, filp, on, &fasync);
1181}
1182
Arjan van de Ven2b8693c2007-02-12 00:55:32 -08001183const struct file_operations random_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001184 .read = random_read,
1185 .write = random_write,
1186 .poll = random_poll,
Matt Mackall43ae4862008-04-29 01:02:58 -07001187 .unlocked_ioctl = random_ioctl,
Jeff Dike9a6f70b2008-04-29 01:03:08 -07001188 .fasync = random_fasync,
Arnd Bergmann6038f372010-08-15 18:52:59 +02001189 .llseek = noop_llseek,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001190};
1191
Arjan van de Ven2b8693c2007-02-12 00:55:32 -08001192const struct file_operations urandom_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001193 .read = urandom_read,
1194 .write = random_write,
Matt Mackall43ae4862008-04-29 01:02:58 -07001195 .unlocked_ioctl = random_ioctl,
Jeff Dike9a6f70b2008-04-29 01:03:08 -07001196 .fasync = random_fasync,
Arnd Bergmann6038f372010-08-15 18:52:59 +02001197 .llseek = noop_llseek,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001198};
1199
1200/***************************************************************
1201 * Random UUID interface
1202 *
1203 * Used here for a Boot ID, but can be useful for other kernel
1204 * drivers.
1205 ***************************************************************/
1206
1207/*
1208 * Generate random UUID
1209 */
1210void generate_random_uuid(unsigned char uuid_out[16])
1211{
1212 get_random_bytes(uuid_out, 16);
Adam Buchbinderc41b20e2009-12-11 16:35:39 -05001213 /* Set UUID version to 4 --- truly random generation */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001214 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1215 /* Set the UUID variant to DCE */
1216 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1217}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001218EXPORT_SYMBOL(generate_random_uuid);
1219
1220/********************************************************************
1221 *
1222 * Sysctl interface
1223 *
1224 ********************************************************************/
1225
1226#ifdef CONFIG_SYSCTL
1227
1228#include <linux/sysctl.h>
1229
1230static int min_read_thresh = 8, min_write_thresh;
1231static int max_read_thresh = INPUT_POOL_WORDS * 32;
1232static int max_write_thresh = INPUT_POOL_WORDS * 32;
1233static char sysctl_bootid[16];
1234
1235/*
1236 * These functions is used to return both the bootid UUID, and random
1237 * UUID. The difference is in whether table->data is NULL; if it is,
1238 * then a new UUID is generated and returned to the user.
1239 *
1240 * If the user accesses this via the proc interface, it will be returned
1241 * as an ASCII string in the standard UUID format. If accesses via the
1242 * sysctl system call, it is returned as 16 bytes of binary data.
1243 */
Alexey Dobriyan8d65af72009-09-23 15:57:19 -07001244static int proc_do_uuid(ctl_table *table, int write,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001245 void __user *buffer, size_t *lenp, loff_t *ppos)
1246{
1247 ctl_table fake_table;
1248 unsigned char buf[64], tmp_uuid[16], *uuid;
1249
1250 uuid = table->data;
1251 if (!uuid) {
1252 uuid = tmp_uuid;
1253 uuid[8] = 0;
1254 }
1255 if (uuid[8] == 0)
1256 generate_random_uuid(uuid);
1257
Joe Perches35900772009-12-14 18:01:11 -08001258 sprintf(buf, "%pU", uuid);
1259
Linus Torvalds1da177e2005-04-16 15:20:36 -07001260 fake_table.data = buf;
1261 fake_table.maxlen = sizeof(buf);
1262
Alexey Dobriyan8d65af72009-09-23 15:57:19 -07001263 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264}
1265
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1267ctl_table random_table[] = {
1268 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001269 .procname = "poolsize",
1270 .data = &sysctl_poolsize,
1271 .maxlen = sizeof(int),
1272 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001273 .proc_handler = proc_dointvec,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001274 },
1275 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276 .procname = "entropy_avail",
1277 .maxlen = sizeof(int),
1278 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001279 .proc_handler = proc_dointvec,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001280 .data = &input_pool.entropy_count,
1281 },
1282 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001283 .procname = "read_wakeup_threshold",
1284 .data = &random_read_wakeup_thresh,
1285 .maxlen = sizeof(int),
1286 .mode = 0644,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001287 .proc_handler = proc_dointvec_minmax,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001288 .extra1 = &min_read_thresh,
1289 .extra2 = &max_read_thresh,
1290 },
1291 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292 .procname = "write_wakeup_threshold",
1293 .data = &random_write_wakeup_thresh,
1294 .maxlen = sizeof(int),
1295 .mode = 0644,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001296 .proc_handler = proc_dointvec_minmax,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001297 .extra1 = &min_write_thresh,
1298 .extra2 = &max_write_thresh,
1299 },
1300 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001301 .procname = "boot_id",
1302 .data = &sysctl_bootid,
1303 .maxlen = 16,
1304 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001305 .proc_handler = proc_do_uuid,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001306 },
1307 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001308 .procname = "uuid",
1309 .maxlen = 16,
1310 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001311 .proc_handler = proc_do_uuid,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001312 },
Eric W. Biederman894d2492009-11-05 14:34:02 -08001313 { }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001314};
1315#endif /* CONFIG_SYSCTL */
1316
David S. Miller6e5714e2011-08-03 20:50:44 -07001317static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001318
David S. Miller6e5714e2011-08-03 20:50:44 -07001319static int __init random_int_secret_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001320{
David S. Miller6e5714e2011-08-03 20:50:44 -07001321 get_random_bytes(random_int_secret, sizeof(random_int_secret));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001322 return 0;
1323}
David S. Miller6e5714e2011-08-03 20:50:44 -07001324late_initcall(random_int_secret_init);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001325
1326/*
1327 * Get a random word for internal kernel use only. Similar to urandom but
1328 * with the goal of minimal entropy pool depletion. As a result, the random
1329 * value is not cryptographically secure but for several uses the cost of
1330 * depleting entropy is too high
1331 */
David S. Miller6e5714e2011-08-03 20:50:44 -07001332DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333unsigned int get_random_int(void)
1334{
H. Peter Anvin63d77172011-07-31 13:54:50 -07001335 __u32 *hash;
David S. Miller6e5714e2011-08-03 20:50:44 -07001336 unsigned int ret;
Linus Torvalds8a0a9bd2009-05-05 08:17:43 -07001337
H. Peter Anvin63d77172011-07-31 13:54:50 -07001338 if (arch_get_random_int(&ret))
1339 return ret;
1340
1341 hash = get_cpu_var(get_random_int_hash);
Linus Torvalds8a0a9bd2009-05-05 08:17:43 -07001342
Linus Torvalds26a9a412009-05-19 11:25:35 -07001343 hash[0] += current->pid + jiffies + get_cycles();
David S. Miller6e5714e2011-08-03 20:50:44 -07001344 md5_transform(hash, random_int_secret);
1345 ret = hash[0];
Linus Torvalds8a0a9bd2009-05-05 08:17:43 -07001346 put_cpu_var(get_random_int_hash);
1347
1348 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349}
1350
1351/*
1352 * randomize_range() returns a start address such that
1353 *
1354 * [...... <range> .....]
1355 * start end
1356 *
1357 * a <range> with size "len" starting at the return value is inside in the
1358 * area defined by [start, end], but is otherwise randomized.
1359 */
1360unsigned long
1361randomize_range(unsigned long start, unsigned long end, unsigned long len)
1362{
1363 unsigned long range = end - len - start;
1364
1365 if (end <= start + len)
1366 return 0;
1367 return PAGE_ALIGN(get_random_int() % range + start);
1368}