blob: b86eae9b77dfaeb04dd2d4efefd6ebc01b9e0a93 [file] [log] [blame]
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 *
Linus Torvaldsa2080a62012-07-04 11:16:01 -0400128 * void add_device_randomness(const void *buf, unsigned int size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129 * void add_input_randomness(unsigned int type, unsigned int code,
130 * unsigned int value);
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400131 * void add_interrupt_randomness(int irq, int irq_flags);
Jarod Wilson442a4ff2011-02-21 21:43:10 +1100132 * void add_disk_randomness(struct gendisk *disk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133 *
Linus Torvaldsa2080a62012-07-04 11:16:01 -0400134 * 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 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 * add_input_randomness() uses the input layer interrupt timing, as well as
143 * the event type information from the hardware.
144 *
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400145 * 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.
Jarod Wilson442a4ff2011-02-21 21:43:10 +1100148 *
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.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154 *
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>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700239#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>
Andrea Righi27ac7922008-07-23 21:28:13 -0700251#include <linux/mm.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252#include <linux/spinlock.h>
253#include <linux/percpu.h>
254#include <linux/cryptohash.h>
Neil Horman5b739ef2009-06-18 19:50:21 +0800255#include <linux/fips.h>
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400256#include <linux/ptrace.h>
Theodore Ts'oe6d49472012-07-05 10:21:01 -0400257#include <linux/kmemcheck.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258
Yinghai Lud178a1e2009-01-11 00:35:42 -0800259#ifdef CONFIG_GENERIC_HARDIRQS
260# include <linux/irq.h>
261#endif
262
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263#include <asm/processor.h>
264#include <asm/uaccess.h>
265#include <asm/irq.h>
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400266#include <asm/irq_regs.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267#include <asm/io.h>
268
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400269#define CREATE_TRACE_POINTS
270#include <trace/events/random.h>
271
Linus Torvalds1da177e2005-04-16 15:20:36 -0700272/*
273 * Configuration information
274 */
275#define INPUT_POOL_WORDS 128
276#define OUTPUT_POOL_WORDS 32
277#define SEC_XFER_SIZE 512
Matt Mackalle954bc92010-05-20 19:55:01 +1000278#define EXTRACT_SIZE 10
Linus Torvalds1da177e2005-04-16 15:20:36 -0700279
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400280#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
281
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282/*
283 * The minimum number of bits of entropy before we wake up a read on
284 * /dev/random. Should be enough to do a significant reseed.
285 */
286static int random_read_wakeup_thresh = 64;
287
288/*
289 * If the entropy count falls under this number of bits, then we
290 * should wake up processes which are selecting or polling on write
291 * access to /dev/random.
292 */
293static int random_write_wakeup_thresh = 128;
294
295/*
296 * When the input pool goes over trickle_thresh, start dropping most
297 * samples to avoid wasting CPU time and reduce lock contention.
298 */
299
Christoph Lameter6c036522005-07-07 17:56:59 -0700300static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700301
Matt Mackall90b75ee2008-04-29 01:02:55 -0700302static DEFINE_PER_CPU(int, trickle_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303
304/*
305 * A pool of size .poolwords is stirred with a primitive polynomial
306 * of degree .poolwords over GF(2). The taps for various sizes are
307 * defined below. They are chosen to be evenly spaced (minimum RMS
308 * distance from evenly spaced; the numbers in the comments are a
309 * scaled squared error sum) except for the last tap, which is 1 to
310 * get the twisting happening as fast as possible.
311 */
312static struct poolinfo {
313 int poolwords;
314 int tap1, tap2, tap3, tap4, tap5;
315} poolinfo_table[] = {
316 /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
317 { 128, 103, 76, 51, 25, 1 },
318 /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
319 { 32, 26, 20, 14, 7, 1 },
320#if 0
321 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
322 { 2048, 1638, 1231, 819, 411, 1 },
323
324 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
325 { 1024, 817, 615, 412, 204, 1 },
326
327 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
328 { 1024, 819, 616, 410, 207, 2 },
329
330 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
331 { 512, 411, 308, 208, 104, 1 },
332
333 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
334 { 512, 409, 307, 206, 102, 2 },
335 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
336 { 512, 409, 309, 205, 103, 2 },
337
338 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
339 { 256, 205, 155, 101, 52, 1 },
340
341 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
342 { 128, 103, 78, 51, 27, 2 },
343
344 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
345 { 64, 52, 39, 26, 14, 1 },
346#endif
347};
348
349#define POOLBITS poolwords*32
350#define POOLBYTES poolwords*4
351
352/*
353 * For the purposes of better mixing, we use the CRC-32 polynomial as
354 * well to make a twisted Generalized Feedback Shift Reigster
355 *
356 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
357 * Transactions on Modeling and Computer Simulation 2(3):179-194.
358 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
359 * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
360 *
361 * Thanks to Colin Plumb for suggesting this.
362 *
363 * We have not analyzed the resultant polynomial to prove it primitive;
364 * in fact it almost certainly isn't. Nonetheless, the irreducible factors
365 * of a random large-degree polynomial over GF(2) are more than large enough
366 * that periodicity is not a concern.
367 *
368 * The input hash is much less sensitive than the output hash. All
369 * that we want of it is that it be a good non-cryptographic hash;
370 * i.e. it not produce collisions when fed "random" data of the sort
371 * we expect to see. As long as the pool state differs for different
372 * inputs, we have preserved the input entropy and done a good job.
373 * The fact that an intelligent attacker can construct inputs that
374 * will produce controlled alterations to the pool's state is not
375 * important because we don't consider such inputs to contribute any
376 * randomness. The only property we need with respect to them is that
377 * the attacker can't increase his/her knowledge of the pool's state.
378 * Since all additions are reversible (knowing the final state and the
379 * input, you can reconstruct the initial state), if an attacker has
380 * any uncertainty about the initial state, he/she can only shuffle
381 * that uncertainty about, but never cause any collisions (which would
382 * decrease the uncertainty).
383 *
384 * The chosen system lets the state of the pool be (essentially) the input
385 * modulo the generator polymnomial. Now, for random primitive polynomials,
386 * this is a universal class of hash functions, meaning that the chance
387 * of a collision is limited by the attacker's knowledge of the generator
388 * polynomail, so if it is chosen at random, an attacker can never force
389 * a collision. Here, we use a fixed polynomial, but we *can* assume that
390 * ###--> it is unknown to the processes generating the input entropy. <-###
391 * Because of this important property, this is a good, collision-resistant
392 * hash; hash collisions will occur no more often than chance.
393 */
394
395/*
396 * Static global variables
397 */
398static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
399static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700400static struct fasync_struct *fasync;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401
402#if 0
Rusty Russell90ab5ee2012-01-13 09:32:20 +1030403static bool debug;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404module_param(debug, bool, 0644);
Matt Mackall90b75ee2008-04-29 01:02:55 -0700405#define DEBUG_ENT(fmt, arg...) do { \
406 if (debug) \
407 printk(KERN_DEBUG "random %04d %04d %04d: " \
408 fmt,\
409 input_pool.entropy_count,\
410 blocking_pool.entropy_count,\
411 nonblocking_pool.entropy_count,\
412 ## arg); } while (0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413#else
414#define DEBUG_ENT(fmt, arg...) do {} while (0)
415#endif
416
417/**********************************************************************
418 *
419 * OS independent entropy store. Here are the functions which handle
420 * storing entropy in an entropy pool.
421 *
422 **********************************************************************/
423
424struct entropy_store;
425struct entropy_store {
Matt Mackall43358202008-04-29 01:03:01 -0700426 /* read-only data: */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700427 struct poolinfo *poolinfo;
428 __u32 *pool;
429 const char *name;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700430 struct entropy_store *pull;
Richard Kennedy4015d9a2010-07-31 19:58:00 +0800431 int limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432
433 /* read-write data: */
Matt Mackall43358202008-04-29 01:03:01 -0700434 spinlock_t lock;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435 unsigned add_ptr;
Theodore Ts'o902c0982012-07-04 10:38:30 -0400436 unsigned input_rotate;
Matt Mackallcda796a2009-01-06 14:42:55 -0800437 int entropy_count;
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400438 int entropy_total;
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400439 unsigned int initialized:1;
Matt Mackalle954bc92010-05-20 19:55:01 +1000440 __u8 last_data[EXTRACT_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700441};
442
443static __u32 input_pool_data[INPUT_POOL_WORDS];
444static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
445static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
446
447static struct entropy_store input_pool = {
448 .poolinfo = &poolinfo_table[0],
449 .name = "input",
450 .limit = 1,
Ingo Molnare4d91912006-07-03 00:24:34 -0700451 .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 .pool = input_pool_data
453};
454
455static struct entropy_store blocking_pool = {
456 .poolinfo = &poolinfo_table[1],
457 .name = "blocking",
458 .limit = 1,
459 .pull = &input_pool,
Ingo Molnare4d91912006-07-03 00:24:34 -0700460 .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700461 .pool = blocking_pool_data
462};
463
464static struct entropy_store nonblocking_pool = {
465 .poolinfo = &poolinfo_table[1],
466 .name = "nonblocking",
467 .pull = &input_pool,
Ingo Molnare4d91912006-07-03 00:24:34 -0700468 .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700469 .pool = nonblocking_pool_data
470};
471
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400472static __u32 const twist_table[8] = {
473 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
474 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
475
Linus Torvalds1da177e2005-04-16 15:20:36 -0700476/*
Matt Mackalle68e5b62008-04-29 01:03:05 -0700477 * This function adds bytes into the entropy "pool". It does not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700478 * update the entropy estimate. The caller should call
Matt Mackalladc782d2008-04-29 01:03:07 -0700479 * credit_entropy_bits if this is appropriate.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 *
481 * The pool is stirred with a primitive polynomial of the appropriate
482 * degree, and then twisted. We twist by three bits at a time because
483 * it's cheap to do so and helps slightly in the expected case where
484 * the entropy is concentrated in the low-order bits.
485 */
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400486static void _mix_pool_bytes(struct entropy_store *r, const void *in,
487 int nbytes, __u8 out[64])
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488{
Matt Mackall993ba212008-04-29 01:03:04 -0700489 unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
Matt Mackallfeee7692008-04-29 01:03:02 -0700490 int input_rotate;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700491 int wordmask = r->poolinfo->poolwords - 1;
Matt Mackalle68e5b62008-04-29 01:03:05 -0700492 const char *bytes = in;
Matt Mackall6d38b822008-04-29 01:03:03 -0700493 __u32 w;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700494
Linus Torvalds1da177e2005-04-16 15:20:36 -0700495 tap1 = r->poolinfo->tap1;
496 tap2 = r->poolinfo->tap2;
497 tap3 = r->poolinfo->tap3;
498 tap4 = r->poolinfo->tap4;
499 tap5 = r->poolinfo->tap5;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500
Theodore Ts'o902c0982012-07-04 10:38:30 -0400501 smp_rmb();
502 input_rotate = ACCESS_ONCE(r->input_rotate);
503 i = ACCESS_ONCE(r->add_ptr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504
Matt Mackalle68e5b62008-04-29 01:03:05 -0700505 /* mix one byte at a time to simplify size handling and churn faster */
506 while (nbytes--) {
507 w = rol32(*bytes++, input_rotate & 31);
Matt Mackall993ba212008-04-29 01:03:04 -0700508 i = (i - 1) & wordmask;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509
510 /* XOR in the various taps */
Matt Mackall993ba212008-04-29 01:03:04 -0700511 w ^= r->pool[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512 w ^= r->pool[(i + tap1) & wordmask];
513 w ^= r->pool[(i + tap2) & wordmask];
514 w ^= r->pool[(i + tap3) & wordmask];
515 w ^= r->pool[(i + tap4) & wordmask];
516 w ^= r->pool[(i + tap5) & wordmask];
Matt Mackall993ba212008-04-29 01:03:04 -0700517
518 /* Mix the result back in with a twist */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700519 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
Matt Mackallfeee7692008-04-29 01:03:02 -0700520
521 /*
522 * Normally, we add 7 bits of rotation to the pool.
523 * At the beginning of the pool, add an extra 7 bits
524 * rotation, so that successive passes spread the
525 * input bits across the pool evenly.
526 */
527 input_rotate += i ? 7 : 14;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528 }
529
Theodore Ts'o902c0982012-07-04 10:38:30 -0400530 ACCESS_ONCE(r->input_rotate) = input_rotate;
531 ACCESS_ONCE(r->add_ptr) = i;
532 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533
Matt Mackall993ba212008-04-29 01:03:04 -0700534 if (out)
535 for (j = 0; j < 16; j++)
Matt Mackalle68e5b62008-04-29 01:03:05 -0700536 ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537}
538
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400539static void __mix_pool_bytes(struct entropy_store *r, const void *in,
Theodore Ts'o902c0982012-07-04 10:38:30 -0400540 int nbytes, __u8 out[64])
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541{
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400542 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
543 _mix_pool_bytes(r, in, nbytes, out);
544}
545
546static void mix_pool_bytes(struct entropy_store *r, const void *in,
547 int nbytes, __u8 out[64])
548{
Theodore Ts'o902c0982012-07-04 10:38:30 -0400549 unsigned long flags;
550
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400551 trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
Theodore Ts'o902c0982012-07-04 10:38:30 -0400552 spin_lock_irqsave(&r->lock, flags);
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400553 _mix_pool_bytes(r, in, nbytes, out);
Theodore Ts'o902c0982012-07-04 10:38:30 -0400554 spin_unlock_irqrestore(&r->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555}
556
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400557struct fast_pool {
558 __u32 pool[4];
559 unsigned long last;
560 unsigned short count;
561 unsigned char rotate;
562 unsigned char last_timer_intr;
563};
564
565/*
566 * This is a fast mixing routine used by the interrupt randomness
567 * collector. It's hardcoded for an 128 bit pool and assumes that any
568 * locks that might be needed are taken by the caller.
569 */
570static void fast_mix(struct fast_pool *f, const void *in, int nbytes)
571{
572 const char *bytes = in;
573 __u32 w;
574 unsigned i = f->count;
575 unsigned input_rotate = f->rotate;
576
577 while (nbytes--) {
578 w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
579 f->pool[(i + 1) & 3];
580 f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
581 input_rotate += (i++ & 3) ? 7 : 14;
582 }
583 f->count = i;
584 f->rotate = input_rotate;
585}
586
Linus Torvalds1da177e2005-04-16 15:20:36 -0700587/*
588 * Credit (or debit) the entropy store with n bits of entropy
589 */
Matt Mackalladc782d2008-04-29 01:03:07 -0700590static void credit_entropy_bits(struct entropy_store *r, int nbits)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591{
Theodore Ts'o902c0982012-07-04 10:38:30 -0400592 int entropy_count, orig;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593
Matt Mackalladc782d2008-04-29 01:03:07 -0700594 if (!nbits)
595 return;
596
Matt Mackalladc782d2008-04-29 01:03:07 -0700597 DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
Theodore Ts'o902c0982012-07-04 10:38:30 -0400598retry:
599 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
Andrew Morton8b76f462008-09-02 14:36:14 -0700600 entropy_count += nbits;
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400601
Andrew Morton8b76f462008-09-02 14:36:14 -0700602 if (entropy_count < 0) {
Matt Mackalladc782d2008-04-29 01:03:07 -0700603 DEBUG_ENT("negative entropy/overflow\n");
Andrew Morton8b76f462008-09-02 14:36:14 -0700604 entropy_count = 0;
605 } else if (entropy_count > r->poolinfo->POOLBITS)
606 entropy_count = r->poolinfo->POOLBITS;
Theodore Ts'o902c0982012-07-04 10:38:30 -0400607 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
608 goto retry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400610 if (!r->initialized && nbits > 0) {
611 r->entropy_total += nbits;
612 if (r->entropy_total > 128)
613 r->initialized = 1;
614 }
615
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400616 trace_credit_entropy_bits(r->name, nbits, entropy_count,
617 r->entropy_total, _RET_IP_);
618
Matt Mackall88c730d2008-04-29 01:02:56 -0700619 /* should we wake readers? */
Andrew Morton8b76f462008-09-02 14:36:14 -0700620 if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
Matt Mackall88c730d2008-04-29 01:02:56 -0700621 wake_up_interruptible(&random_read_wait);
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700622 kill_fasync(&fasync, SIGIO, POLL_IN);
623 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700624}
625
626/*********************************************************************
627 *
628 * Entropy input management
629 *
630 *********************************************************************/
631
632/* There is one of these per entropy source */
633struct timer_rand_state {
634 cycles_t last_time;
Matt Mackall90b75ee2008-04-29 01:02:55 -0700635 long last_delta, last_delta2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636 unsigned dont_count_entropy:1;
637};
638
Linus Torvaldsa2080a62012-07-04 11:16:01 -0400639/*
640 * Add device- or boot-specific data to the input and nonblocking
641 * pools to help initialize them to unique values.
642 *
643 * None of this adds any entropy, it is meant to avoid the
644 * problem of the nonblocking pool having similar initial state
645 * across largely identical devices.
646 */
647void add_device_randomness(const void *buf, unsigned int size)
648{
649 unsigned long time = get_cycles() ^ jiffies;
650
651 mix_pool_bytes(&input_pool, buf, size, NULL);
652 mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
653 mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
654 mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
655}
656EXPORT_SYMBOL(add_device_randomness);
657
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700658static struct timer_rand_state input_timer_state;
659
Linus Torvalds1da177e2005-04-16 15:20:36 -0700660/*
661 * This function adds entropy to the entropy "pool" by using timing
662 * delays. It uses the timer_rand_state structure to make an estimate
663 * of how many bits of entropy this call has added to the pool.
664 *
665 * The number "num" is also added to the pool - it should somehow describe
666 * the type of event which just happened. This is currently 0-255 for
667 * keyboard scan codes, and 256 upwards for interrupts.
668 *
669 */
670static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
671{
672 struct {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700673 long jiffies;
Linus Torvaldscf833d02011-12-22 11:36:22 -0800674 unsigned cycles;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700675 unsigned num;
676 } sample;
677 long delta, delta2, delta3;
678
679 preempt_disable();
680 /* if over the trickle threshold, use only 1 in 4096 samples */
681 if (input_pool.entropy_count > trickle_thresh &&
Christoph Lameterb29c6172010-12-06 11:40:06 -0600682 ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683 goto out;
684
685 sample.jiffies = jiffies;
Theodore Ts'oe6d49472012-07-05 10:21:01 -0400686 sample.cycles = get_cycles();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 sample.num = num;
Theodore Ts'o902c0982012-07-04 10:38:30 -0400688 mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700689
690 /*
691 * Calculate number of bits of randomness we probably added.
692 * We take into account the first, second and third-order deltas
693 * in order to make our estimate.
694 */
695
696 if (!state->dont_count_entropy) {
697 delta = sample.jiffies - state->last_time;
698 state->last_time = sample.jiffies;
699
700 delta2 = delta - state->last_delta;
701 state->last_delta = delta;
702
703 delta3 = delta2 - state->last_delta2;
704 state->last_delta2 = delta2;
705
706 if (delta < 0)
707 delta = -delta;
708 if (delta2 < 0)
709 delta2 = -delta2;
710 if (delta3 < 0)
711 delta3 = -delta3;
712 if (delta > delta2)
713 delta = delta2;
714 if (delta > delta3)
715 delta = delta3;
716
717 /*
718 * delta is now minimum absolute delta.
719 * Round down by 1 bit on general principles,
720 * and limit entropy entimate to 12 bits.
721 */
Matt Mackalladc782d2008-04-29 01:03:07 -0700722 credit_entropy_bits(&input_pool,
723 min_t(int, fls(delta>>1), 11));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725out:
726 preempt_enable();
727}
728
Stephen Hemmingerd2515752006-01-11 12:17:38 -0800729void add_input_randomness(unsigned int type, unsigned int code,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700730 unsigned int value)
731{
732 static unsigned char last_value;
733
734 /* ignore autorepeat and the like */
735 if (value == last_value)
736 return;
737
738 DEBUG_ENT("input event\n");
739 last_value = value;
740 add_timer_randomness(&input_timer_state,
741 (type << 4) ^ code ^ (code >> 4) ^ value);
742}
Dmitry Torokhov80fc9f52006-10-11 01:43:58 -0400743EXPORT_SYMBOL_GPL(add_input_randomness);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400745static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
746
747void add_interrupt_randomness(int irq, int irq_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748{
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400749 struct entropy_store *r;
750 struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness);
751 struct pt_regs *regs = get_irq_regs();
752 unsigned long now = jiffies;
753 __u32 input[4], cycles = get_cycles();
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700754
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400755 input[0] = cycles ^ jiffies;
756 input[1] = irq;
757 if (regs) {
758 __u64 ip = instruction_pointer(regs);
759 input[2] = ip;
760 input[3] = ip >> 32;
761 }
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700762
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400763 fast_mix(fast_pool, input, sizeof(input));
764
765 if ((fast_pool->count & 1023) &&
766 !time_after(now, fast_pool->last + HZ))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700767 return;
768
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400769 fast_pool->last = now;
770
771 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
Theodore Ts'o902c0982012-07-04 10:38:30 -0400772 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400773 /*
774 * If we don't have a valid cycle counter, and we see
775 * back-to-back timer interrupts, then skip giving credit for
776 * any entropy.
777 */
778 if (cycles == 0) {
779 if (irq_flags & __IRQF_TIMER) {
780 if (fast_pool->last_timer_intr)
781 return;
782 fast_pool->last_timer_intr = 1;
783 } else
784 fast_pool->last_timer_intr = 0;
785 }
786 credit_entropy_bits(r, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700787}
788
David Howells93614012006-09-30 20:45:40 +0200789#ifdef CONFIG_BLOCK
Linus Torvalds1da177e2005-04-16 15:20:36 -0700790void add_disk_randomness(struct gendisk *disk)
791{
792 if (!disk || !disk->random)
793 return;
794 /* first major is 1, so we get >= 0x200 here */
Tejun Heof331c022008-09-03 09:01:48 +0200795 DEBUG_ENT("disk event %d:%d\n",
796 MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700797
Tejun Heof331c022008-09-03 09:01:48 +0200798 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700799}
David Howells93614012006-09-30 20:45:40 +0200800#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700801
Linus Torvalds1da177e2005-04-16 15:20:36 -0700802/*********************************************************************
803 *
804 * Entropy extraction routines
805 *
806 *********************************************************************/
807
Matt Mackall90b75ee2008-04-29 01:02:55 -0700808static ssize_t extract_entropy(struct entropy_store *r, void *buf,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809 size_t nbytes, int min, int rsvd);
810
811/*
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300812 * This utility inline function is responsible for transferring entropy
Linus Torvalds1da177e2005-04-16 15:20:36 -0700813 * from the primary pool to the secondary extraction pool. We make
814 * sure we pull enough for a 'catastrophic reseed'.
815 */
816static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
817{
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400818 __u32 tmp[OUTPUT_POOL_WORDS];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700819
820 if (r->pull && r->entropy_count < nbytes * 8 &&
821 r->entropy_count < r->poolinfo->POOLBITS) {
Matt Mackall5a021e92007-07-19 11:30:14 -0700822 /* If we're limited, always leave two wakeup worth's BITS */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700823 int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
Matt Mackall5a021e92007-07-19 11:30:14 -0700824 int bytes = nbytes;
825
826 /* pull at least as many as BYTES as wakeup BITS */
827 bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
828 /* but never more than the buffer size */
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400829 bytes = min_t(int, bytes, sizeof(tmp));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830
831 DEBUG_ENT("going to reseed %s with %d bits "
832 "(%d of %d requested)\n",
833 r->name, bytes * 8, nbytes * 8, r->entropy_count);
834
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400835 bytes = extract_entropy(r->pull, tmp, bytes,
Matt Mackall90b75ee2008-04-29 01:02:55 -0700836 random_read_wakeup_thresh / 8, rsvd);
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400837 mix_pool_bytes(r, tmp, bytes, NULL);
Matt Mackalladc782d2008-04-29 01:03:07 -0700838 credit_entropy_bits(r, bytes*8);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700839 }
840}
841
842/*
843 * These functions extracts randomness from the "entropy pool", and
844 * returns it in a buffer.
845 *
846 * The min parameter specifies the minimum amount we can pull before
847 * failing to avoid races that defeat catastrophic reseeding while the
848 * reserved parameter indicates how much entropy we must leave in the
849 * pool after each pull to avoid starving other readers.
850 *
851 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
852 */
853
854static size_t account(struct entropy_store *r, size_t nbytes, int min,
855 int reserved)
856{
857 unsigned long flags;
858
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859 /* Hold lock while accounting */
860 spin_lock_irqsave(&r->lock, flags);
861
Matt Mackallcda796a2009-01-06 14:42:55 -0800862 BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700863 DEBUG_ENT("trying to extract %d bits from %s\n",
864 nbytes * 8, r->name);
865
866 /* Can we pull enough? */
867 if (r->entropy_count / 8 < min + reserved) {
868 nbytes = 0;
869 } else {
870 /* If limited, never pull more than available */
871 if (r->limit && nbytes + reserved >= r->entropy_count / 8)
872 nbytes = r->entropy_count/8 - reserved;
873
Matt Mackall90b75ee2008-04-29 01:02:55 -0700874 if (r->entropy_count / 8 >= nbytes + reserved)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875 r->entropy_count -= nbytes*8;
876 else
877 r->entropy_count = reserved;
878
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700879 if (r->entropy_count < random_write_wakeup_thresh) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700880 wake_up_interruptible(&random_write_wait);
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700881 kill_fasync(&fasync, SIGIO, POLL_OUT);
882 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700883 }
884
885 DEBUG_ENT("debiting %d entropy credits from %s%s\n",
886 nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
887
888 spin_unlock_irqrestore(&r->lock, flags);
889
890 return nbytes;
891}
892
893static void extract_buf(struct entropy_store *r, __u8 *out)
894{
Matt Mackall602b6ae2007-05-29 21:54:27 -0500895 int i;
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400896 union {
897 __u32 w[5];
898 unsigned long l[LONGS(EXTRACT_SIZE)];
899 } hash;
900 __u32 workspace[SHA_WORKSPACE_WORDS];
Matt Mackalle68e5b62008-04-29 01:03:05 -0700901 __u8 extract[64];
Theodore Ts'o902c0982012-07-04 10:38:30 -0400902 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700903
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700904 /* Generate a hash across the pool, 16 words (512 bits) at a time */
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400905 sha_init(hash.w);
Theodore Ts'o902c0982012-07-04 10:38:30 -0400906 spin_lock_irqsave(&r->lock, flags);
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700907 for (i = 0; i < r->poolinfo->poolwords; i += 16)
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400908 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909
910 /*
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700911 * We mix the hash back into the pool to prevent backtracking
912 * attacks (where the attacker knows the state of the pool
913 * plus the current outputs, and attempts to find previous
914 * ouputs), unless the hash function can be inverted. By
915 * mixing at least a SHA1 worth of hash data back, we make
916 * brute-forcing the feedback as hard as brute-forcing the
917 * hash.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700918 */
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400919 __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
Theodore Ts'o902c0982012-07-04 10:38:30 -0400920 spin_unlock_irqrestore(&r->lock, flags);
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700921
922 /*
923 * To avoid duplicates, we atomically extract a portion of the
924 * pool while mixing, and hash one final time.
925 */
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400926 sha_transform(hash.w, extract, workspace);
Matt Mackallffd8d3f2008-04-29 01:02:59 -0700927 memset(extract, 0, sizeof(extract));
928 memset(workspace, 0, sizeof(workspace));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700929
930 /*
Matt Mackall1c0ad3d2008-04-29 01:03:00 -0700931 * In case the hash function has some recognizable output
932 * pattern, we fold it in half. Thus, we always feed back
933 * twice as much data as we output.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700934 */
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400935 hash.w[0] ^= hash.w[3];
936 hash.w[1] ^= hash.w[4];
937 hash.w[2] ^= rol32(hash.w[2], 16);
938
939 /*
940 * If we have a architectural hardware random number
941 * generator, mix that in, too.
942 */
943 for (i = 0; i < LONGS(EXTRACT_SIZE); i++) {
944 unsigned long v;
945 if (!arch_get_random_long(&v))
946 break;
947 hash.l[i] ^= v;
948 }
949
950 memcpy(out, &hash, EXTRACT_SIZE);
951 memset(&hash, 0, sizeof(hash));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700952}
953
Matt Mackall90b75ee2008-04-29 01:02:55 -0700954static ssize_t extract_entropy(struct entropy_store *r, void *buf,
Theodore Ts'o902c0982012-07-04 10:38:30 -0400955 size_t nbytes, int min, int reserved)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700956{
957 ssize_t ret = 0, i;
958 __u8 tmp[EXTRACT_SIZE];
959
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400960 trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700961 xfer_secondary_pool(r, nbytes);
962 nbytes = account(r, nbytes, min, reserved);
963
964 while (nbytes) {
965 extract_buf(r, tmp);
Neil Horman5b739ef2009-06-18 19:50:21 +0800966
Matt Mackalle954bc92010-05-20 19:55:01 +1000967 if (fips_enabled) {
Theodore Ts'o902c0982012-07-04 10:38:30 -0400968 unsigned long flags;
969
Neil Horman5b739ef2009-06-18 19:50:21 +0800970 spin_lock_irqsave(&r->lock, flags);
971 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
972 panic("Hardware RNG duplicated output!\n");
973 memcpy(r->last_data, tmp, EXTRACT_SIZE);
974 spin_unlock_irqrestore(&r->lock, flags);
975 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700976 i = min_t(int, nbytes, EXTRACT_SIZE);
977 memcpy(buf, tmp, i);
978 nbytes -= i;
979 buf += i;
980 ret += i;
981 }
982
983 /* Wipe data just returned from memory */
984 memset(tmp, 0, sizeof(tmp));
985
986 return ret;
987}
988
989static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
990 size_t nbytes)
991{
992 ssize_t ret = 0, i;
993 __u8 tmp[EXTRACT_SIZE];
994
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400995 trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700996 xfer_secondary_pool(r, nbytes);
997 nbytes = account(r, nbytes, 0, 0);
998
999 while (nbytes) {
1000 if (need_resched()) {
1001 if (signal_pending(current)) {
1002 if (ret == 0)
1003 ret = -ERESTARTSYS;
1004 break;
1005 }
1006 schedule();
1007 }
1008
1009 extract_buf(r, tmp);
1010 i = min_t(int, nbytes, EXTRACT_SIZE);
1011 if (copy_to_user(buf, tmp, i)) {
1012 ret = -EFAULT;
1013 break;
1014 }
1015
1016 nbytes -= i;
1017 buf += i;
1018 ret += i;
1019 }
1020
1021 /* Wipe data just returned from memory */
1022 memset(tmp, 0, sizeof(tmp));
1023
1024 return ret;
1025}
1026
1027/*
1028 * This function is the exported kernel interface. It returns some
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001029 * number of good random numbers, suitable for key generation, seeding
1030 * TCP sequence numbers, etc. It does not use the hw random number
1031 * generator, if available; use get_random_bytes_arch() for that.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001032 */
1033void get_random_bytes(void *buf, int nbytes)
1034{
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001035 extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1036}
1037EXPORT_SYMBOL(get_random_bytes);
1038
1039/*
1040 * This function will use the architecture-specific hardware random
1041 * number generator if it is available. The arch-specific hw RNG will
1042 * almost certainly be faster than what we can do in software, but it
1043 * is impossible to verify that it is implemented securely (as
1044 * opposed, to, say, the AES encryption of a sequence number using a
1045 * key known by the NSA). So it's useful if we need the speed, but
1046 * only if we're willing to trust the hardware manufacturer not to
1047 * have put in a back door.
1048 */
1049void get_random_bytes_arch(void *buf, int nbytes)
1050{
H. Peter Anvin63d77172011-07-31 13:54:50 -07001051 char *p = buf;
1052
Theodore Ts'o00ce1db2012-07-04 16:19:30 -04001053 trace_get_random_bytes(nbytes, _RET_IP_);
H. Peter Anvin63d77172011-07-31 13:54:50 -07001054 while (nbytes) {
1055 unsigned long v;
1056 int chunk = min(nbytes, (int)sizeof(unsigned long));
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001057
H. Peter Anvin63d77172011-07-31 13:54:50 -07001058 if (!arch_get_random_long(&v))
1059 break;
1060
Luck, Tonybd29e562011-11-16 10:50:56 -08001061 memcpy(p, &v, chunk);
H. Peter Anvin63d77172011-07-31 13:54:50 -07001062 p += chunk;
1063 nbytes -= chunk;
1064 }
1065
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001066 if (nbytes)
1067 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001068}
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001069EXPORT_SYMBOL(get_random_bytes_arch);
1070
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071
1072/*
1073 * init_std_data - initialize pool with system data
1074 *
1075 * @r: pool to initialize
1076 *
1077 * This function clears the pool's entropy count and mixes some system
1078 * data into the pool to prepare it for use. The pool is not cleared
1079 * as that can only decrease the entropy in the pool.
1080 */
1081static void init_std_data(struct entropy_store *r)
1082{
Theodore Ts'o3e88bdf2011-12-22 16:28:01 -05001083 int i;
Theodore Ts'o902c0982012-07-04 10:38:30 -04001084 ktime_t now = ktime_get_real();
1085 unsigned long rv;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086
Linus Torvalds1da177e2005-04-16 15:20:36 -07001087 r->entropy_count = 0;
Theodore Ts'o775f4b22012-07-02 07:52:16 -04001088 r->entropy_total = 0;
Theodore Ts'o902c0982012-07-04 10:38:30 -04001089 mix_pool_bytes(r, &now, sizeof(now), NULL);
1090 for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) {
1091 if (!arch_get_random_long(&rv))
Theodore Ts'o3e88bdf2011-12-22 16:28:01 -05001092 break;
Theodore Ts'o902c0982012-07-04 10:38:30 -04001093 mix_pool_bytes(r, &rv, sizeof(rv), NULL);
Theodore Ts'o3e88bdf2011-12-22 16:28:01 -05001094 }
Theodore Ts'o902c0982012-07-04 10:38:30 -04001095 mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096}
1097
Tony Luckcbc96b72012-07-23 09:47:57 -07001098/*
1099 * Note that setup_arch() may call add_device_randomness()
1100 * long before we get here. This allows seeding of the pools
1101 * with some platform dependent data very early in the boot
1102 * process. But it limits our options here. We must use
1103 * statically allocated structures that already have all
1104 * initializations complete at compile time. We should also
1105 * take care not to overwrite the precious per platform data
1106 * we were given.
1107 */
Matt Mackall53c3f632008-04-29 01:02:58 -07001108static int rand_initialize(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001109{
1110 init_std_data(&input_pool);
1111 init_std_data(&blocking_pool);
1112 init_std_data(&nonblocking_pool);
1113 return 0;
1114}
1115module_init(rand_initialize);
1116
David Howells93614012006-09-30 20:45:40 +02001117#ifdef CONFIG_BLOCK
Linus Torvalds1da177e2005-04-16 15:20:36 -07001118void rand_initialize_disk(struct gendisk *disk)
1119{
1120 struct timer_rand_state *state;
1121
1122 /*
Eric Dumazetf8595812007-03-28 14:22:33 -07001123 * If kzalloc returns null, we just won't use that entropy
Linus Torvalds1da177e2005-04-16 15:20:36 -07001124 * source.
1125 */
Eric Dumazetf8595812007-03-28 14:22:33 -07001126 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1127 if (state)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001128 disk->random = state;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001129}
David Howells93614012006-09-30 20:45:40 +02001130#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07001131
1132static ssize_t
Matt Mackall90b75ee2008-04-29 01:02:55 -07001133random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001134{
1135 ssize_t n, retval = 0, count = 0;
1136
1137 if (nbytes == 0)
1138 return 0;
1139
1140 while (nbytes > 0) {
1141 n = nbytes;
1142 if (n > SEC_XFER_SIZE)
1143 n = SEC_XFER_SIZE;
1144
1145 DEBUG_ENT("reading %d bits\n", n*8);
1146
1147 n = extract_entropy_user(&blocking_pool, buf, n);
1148
1149 DEBUG_ENT("read got %d bits (%d still needed)\n",
1150 n*8, (nbytes-n)*8);
1151
1152 if (n == 0) {
1153 if (file->f_flags & O_NONBLOCK) {
1154 retval = -EAGAIN;
1155 break;
1156 }
1157
1158 DEBUG_ENT("sleeping?\n");
1159
1160 wait_event_interruptible(random_read_wait,
1161 input_pool.entropy_count >=
1162 random_read_wakeup_thresh);
1163
1164 DEBUG_ENT("awake\n");
1165
1166 if (signal_pending(current)) {
1167 retval = -ERESTARTSYS;
1168 break;
1169 }
1170
1171 continue;
1172 }
1173
1174 if (n < 0) {
1175 retval = n;
1176 break;
1177 }
1178 count += n;
1179 buf += n;
1180 nbytes -= n;
1181 break; /* This break makes the device work */
1182 /* like a named pipe */
1183 }
1184
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185 return (count ? count : retval);
1186}
1187
1188static ssize_t
Matt Mackall90b75ee2008-04-29 01:02:55 -07001189urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001190{
1191 return extract_entropy_user(&nonblocking_pool, buf, nbytes);
1192}
1193
1194static unsigned int
1195random_poll(struct file *file, poll_table * wait)
1196{
1197 unsigned int mask;
1198
1199 poll_wait(file, &random_read_wait, wait);
1200 poll_wait(file, &random_write_wait, wait);
1201 mask = 0;
1202 if (input_pool.entropy_count >= random_read_wakeup_thresh)
1203 mask |= POLLIN | POLLRDNORM;
1204 if (input_pool.entropy_count < random_write_wakeup_thresh)
1205 mask |= POLLOUT | POLLWRNORM;
1206 return mask;
1207}
1208
Matt Mackall7f397dc2007-05-29 21:58:10 -05001209static int
1210write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1211{
1212 size_t bytes;
1213 __u32 buf[16];
1214 const char __user *p = buffer;
1215
1216 while (count > 0) {
1217 bytes = min(count, sizeof(buf));
1218 if (copy_from_user(&buf, p, bytes))
1219 return -EFAULT;
1220
1221 count -= bytes;
1222 p += bytes;
1223
Theodore Ts'o902c0982012-07-04 10:38:30 -04001224 mix_pool_bytes(r, buf, bytes, NULL);
Matt Mackall91f3f1e2008-02-06 01:37:20 -08001225 cond_resched();
Matt Mackall7f397dc2007-05-29 21:58:10 -05001226 }
1227
1228 return 0;
1229}
1230
Matt Mackall90b75ee2008-04-29 01:02:55 -07001231static ssize_t random_write(struct file *file, const char __user *buffer,
1232 size_t count, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233{
Matt Mackall7f397dc2007-05-29 21:58:10 -05001234 size_t ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001235
Matt Mackall7f397dc2007-05-29 21:58:10 -05001236 ret = write_pool(&blocking_pool, buffer, count);
1237 if (ret)
1238 return ret;
1239 ret = write_pool(&nonblocking_pool, buffer, count);
1240 if (ret)
1241 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001242
Matt Mackall7f397dc2007-05-29 21:58:10 -05001243 return (ssize_t)count;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001244}
1245
Matt Mackall43ae4862008-04-29 01:02:58 -07001246static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247{
1248 int size, ent_count;
1249 int __user *p = (int __user *)arg;
1250 int retval;
1251
1252 switch (cmd) {
1253 case RNDGETENTCNT:
Matt Mackall43ae4862008-04-29 01:02:58 -07001254 /* inherently racy, no point locking */
1255 if (put_user(input_pool.entropy_count, p))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001256 return -EFAULT;
1257 return 0;
1258 case RNDADDTOENTCNT:
1259 if (!capable(CAP_SYS_ADMIN))
1260 return -EPERM;
1261 if (get_user(ent_count, p))
1262 return -EFAULT;
Matt Mackalladc782d2008-04-29 01:03:07 -07001263 credit_entropy_bits(&input_pool, ent_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 return 0;
1265 case RNDADDENTROPY:
1266 if (!capable(CAP_SYS_ADMIN))
1267 return -EPERM;
1268 if (get_user(ent_count, p++))
1269 return -EFAULT;
1270 if (ent_count < 0)
1271 return -EINVAL;
1272 if (get_user(size, p++))
1273 return -EFAULT;
Matt Mackall7f397dc2007-05-29 21:58:10 -05001274 retval = write_pool(&input_pool, (const char __user *)p,
1275 size);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276 if (retval < 0)
1277 return retval;
Matt Mackalladc782d2008-04-29 01:03:07 -07001278 credit_entropy_bits(&input_pool, ent_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001279 return 0;
1280 case RNDZAPENTCNT:
1281 case RNDCLEARPOOL:
1282 /* Clear the entropy pool counters. */
1283 if (!capable(CAP_SYS_ADMIN))
1284 return -EPERM;
Matt Mackall53c3f632008-04-29 01:02:58 -07001285 rand_initialize();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286 return 0;
1287 default:
1288 return -EINVAL;
1289 }
1290}
1291
Jeff Dike9a6f70b2008-04-29 01:03:08 -07001292static int random_fasync(int fd, struct file *filp, int on)
1293{
1294 return fasync_helper(fd, filp, on, &fasync);
1295}
1296
Arjan van de Ven2b8693c2007-02-12 00:55:32 -08001297const struct file_operations random_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001298 .read = random_read,
1299 .write = random_write,
1300 .poll = random_poll,
Matt Mackall43ae4862008-04-29 01:02:58 -07001301 .unlocked_ioctl = random_ioctl,
Jeff Dike9a6f70b2008-04-29 01:03:08 -07001302 .fasync = random_fasync,
Arnd Bergmann6038f372010-08-15 18:52:59 +02001303 .llseek = noop_llseek,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001304};
1305
Arjan van de Ven2b8693c2007-02-12 00:55:32 -08001306const struct file_operations urandom_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307 .read = urandom_read,
1308 .write = random_write,
Matt Mackall43ae4862008-04-29 01:02:58 -07001309 .unlocked_ioctl = random_ioctl,
Jeff Dike9a6f70b2008-04-29 01:03:08 -07001310 .fasync = random_fasync,
Arnd Bergmann6038f372010-08-15 18:52:59 +02001311 .llseek = noop_llseek,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001312};
1313
1314/***************************************************************
1315 * Random UUID interface
1316 *
1317 * Used here for a Boot ID, but can be useful for other kernel
1318 * drivers.
1319 ***************************************************************/
1320
1321/*
1322 * Generate random UUID
1323 */
1324void generate_random_uuid(unsigned char uuid_out[16])
1325{
1326 get_random_bytes(uuid_out, 16);
Adam Buchbinderc41b20e2009-12-11 16:35:39 -05001327 /* Set UUID version to 4 --- truly random generation */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001328 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1329 /* Set the UUID variant to DCE */
1330 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1331}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332EXPORT_SYMBOL(generate_random_uuid);
1333
1334/********************************************************************
1335 *
1336 * Sysctl interface
1337 *
1338 ********************************************************************/
1339
1340#ifdef CONFIG_SYSCTL
1341
1342#include <linux/sysctl.h>
1343
1344static int min_read_thresh = 8, min_write_thresh;
1345static int max_read_thresh = INPUT_POOL_WORDS * 32;
1346static int max_write_thresh = INPUT_POOL_WORDS * 32;
1347static char sysctl_bootid[16];
1348
1349/*
1350 * These functions is used to return both the bootid UUID, and random
1351 * UUID. The difference is in whether table->data is NULL; if it is,
1352 * then a new UUID is generated and returned to the user.
1353 *
1354 * If the user accesses this via the proc interface, it will be returned
1355 * as an ASCII string in the standard UUID format. If accesses via the
1356 * sysctl system call, it is returned as 16 bytes of binary data.
1357 */
Alexey Dobriyan8d65af72009-09-23 15:57:19 -07001358static int proc_do_uuid(ctl_table *table, int write,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001359 void __user *buffer, size_t *lenp, loff_t *ppos)
1360{
1361 ctl_table fake_table;
1362 unsigned char buf[64], tmp_uuid[16], *uuid;
1363
1364 uuid = table->data;
1365 if (!uuid) {
1366 uuid = tmp_uuid;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367 generate_random_uuid(uuid);
Mathieu Desnoyers44e43602012-04-12 12:49:12 -07001368 } else {
1369 static DEFINE_SPINLOCK(bootid_spinlock);
1370
1371 spin_lock(&bootid_spinlock);
1372 if (!uuid[8])
1373 generate_random_uuid(uuid);
1374 spin_unlock(&bootid_spinlock);
1375 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001376
Joe Perches35900772009-12-14 18:01:11 -08001377 sprintf(buf, "%pU", uuid);
1378
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379 fake_table.data = buf;
1380 fake_table.maxlen = sizeof(buf);
1381
Alexey Dobriyan8d65af72009-09-23 15:57:19 -07001382 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383}
1384
Linus Torvalds1da177e2005-04-16 15:20:36 -07001385static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
Theodore Ts'o74feec52012-07-06 14:03:18 -04001386extern ctl_table random_table[];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001387ctl_table random_table[] = {
1388 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001389 .procname = "poolsize",
1390 .data = &sysctl_poolsize,
1391 .maxlen = sizeof(int),
1392 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001393 .proc_handler = proc_dointvec,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394 },
1395 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001396 .procname = "entropy_avail",
1397 .maxlen = sizeof(int),
1398 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001399 .proc_handler = proc_dointvec,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001400 .data = &input_pool.entropy_count,
1401 },
1402 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001403 .procname = "read_wakeup_threshold",
1404 .data = &random_read_wakeup_thresh,
1405 .maxlen = sizeof(int),
1406 .mode = 0644,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001407 .proc_handler = proc_dointvec_minmax,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001408 .extra1 = &min_read_thresh,
1409 .extra2 = &max_read_thresh,
1410 },
1411 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001412 .procname = "write_wakeup_threshold",
1413 .data = &random_write_wakeup_thresh,
1414 .maxlen = sizeof(int),
1415 .mode = 0644,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001416 .proc_handler = proc_dointvec_minmax,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001417 .extra1 = &min_write_thresh,
1418 .extra2 = &max_write_thresh,
1419 },
1420 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421 .procname = "boot_id",
1422 .data = &sysctl_bootid,
1423 .maxlen = 16,
1424 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001425 .proc_handler = proc_do_uuid,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001426 },
1427 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001428 .procname = "uuid",
1429 .maxlen = 16,
1430 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001431 .proc_handler = proc_do_uuid,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001432 },
Eric W. Biederman894d2492009-11-05 14:34:02 -08001433 { }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001434};
1435#endif /* CONFIG_SYSCTL */
1436
David S. Miller6e5714e2011-08-03 20:50:44 -07001437static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001438
David S. Miller6e5714e2011-08-03 20:50:44 -07001439static int __init random_int_secret_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001440{
David S. Miller6e5714e2011-08-03 20:50:44 -07001441 get_random_bytes(random_int_secret, sizeof(random_int_secret));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001442 return 0;
1443}
David S. Miller6e5714e2011-08-03 20:50:44 -07001444late_initcall(random_int_secret_init);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001445
1446/*
1447 * Get a random word for internal kernel use only. Similar to urandom but
1448 * with the goal of minimal entropy pool depletion. As a result, the random
1449 * value is not cryptographically secure but for several uses the cost of
1450 * depleting entropy is too high
1451 */
Theodore Ts'o74feec52012-07-06 14:03:18 -04001452static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001453unsigned int get_random_int(void)
1454{
H. Peter Anvin63d77172011-07-31 13:54:50 -07001455 __u32 *hash;
David S. Miller6e5714e2011-08-03 20:50:44 -07001456 unsigned int ret;
Linus Torvalds8a0a9bd2009-05-05 08:17:43 -07001457
H. Peter Anvin63d77172011-07-31 13:54:50 -07001458 if (arch_get_random_int(&ret))
1459 return ret;
1460
1461 hash = get_cpu_var(get_random_int_hash);
Linus Torvalds8a0a9bd2009-05-05 08:17:43 -07001462
Linus Torvalds26a9a412009-05-19 11:25:35 -07001463 hash[0] += current->pid + jiffies + get_cycles();
David S. Miller6e5714e2011-08-03 20:50:44 -07001464 md5_transform(hash, random_int_secret);
1465 ret = hash[0];
Linus Torvalds8a0a9bd2009-05-05 08:17:43 -07001466 put_cpu_var(get_random_int_hash);
1467
1468 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001469}
1470
1471/*
1472 * randomize_range() returns a start address such that
1473 *
1474 * [...... <range> .....]
1475 * start end
1476 *
1477 * a <range> with size "len" starting at the return value is inside in the
1478 * area defined by [start, end], but is otherwise randomized.
1479 */
1480unsigned long
1481randomize_range(unsigned long start, unsigned long end, unsigned long len)
1482{
1483 unsigned long range = end - len - start;
1484
1485 if (end <= start + len)
1486 return 0;
1487 return PAGE_ALIGN(get_random_int() % range + start);
1488}