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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 *
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>
Theodore Ts'o6265e162013-10-03 01:08:15 -0400258#include <linux/workqueue.h>
Martin Schwidefsky0244ad02013-08-30 09:39:53 +0200259#include <linux/irq.h>
Yinghai Lud178a1e2009-01-11 00:35:42 -0800260
Linus Torvalds1da177e2005-04-16 15:20:36 -0700261#include <asm/processor.h>
262#include <asm/uaccess.h>
263#include <asm/irq.h>
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400264#include <asm/irq_regs.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265#include <asm/io.h>
266
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400267#define CREATE_TRACE_POINTS
268#include <trace/events/random.h>
269
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270/*
271 * Configuration information
272 */
H. Peter Anvin30e37ec2013-09-10 23:16:17 -0400273#define INPUT_POOL_SHIFT 12
274#define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
275#define OUTPUT_POOL_SHIFT 10
276#define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
277#define SEC_XFER_SIZE 512
278#define EXTRACT_SIZE 10
Linus Torvalds1da177e2005-04-16 15:20:36 -0700279
Theodore Ts'o392a5462013-11-03 18:24:08 -0500280#define DEBUG_RANDOM_BOOT 0
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281
H. Peter Anvind2e7c962012-07-27 22:26:08 -0400282#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
283
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284/*
Theodore Ts'o95b709b2013-10-02 21:10:35 -0400285 * To allow fractional bits to be tracked, the entropy_count field is
286 * denominated in units of 1/8th bits.
H. Peter Anvin30e37ec2013-09-10 23:16:17 -0400287 *
288 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
289 * credit_entropy_bits() needs to be 64 bits wide.
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400290 */
291#define ENTROPY_SHIFT 3
292#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
293
294/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700295 * The minimum number of bits of entropy before we wake up a read on
296 * /dev/random. Should be enough to do a significant reseed.
297 */
Greg Price2132a962013-12-06 21:28:03 -0500298static int random_read_wakeup_bits = 64;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299
300/*
301 * If the entropy count falls under this number of bits, then we
302 * should wake up processes which are selecting or polling on write
303 * access to /dev/random.
304 */
Greg Price2132a962013-12-06 21:28:03 -0500305static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306
307/*
Greg Pricedfd38752013-11-29 14:58:06 -0500308 * The minimum number of seconds between urandom pool reseeding. We
Theodore Ts'of5c27422013-09-22 15:14:32 -0400309 * do this to limit the amount of entropy that can be drained from the
310 * input pool even if there are heavy demands on /dev/urandom.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311 */
Theodore Ts'of5c27422013-09-22 15:14:32 -0400312static int random_min_urandom_seed = 60;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313
314/*
Theodore Ts'o6e9fa2c2013-09-22 16:04:19 -0400315 * Originally, we used a primitive polynomial of degree .poolwords
316 * over GF(2). The taps for various sizes are defined below. They
317 * were chosen to be evenly spaced except for the last tap, which is 1
318 * to get the twisting happening as fast as possible.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700319 *
Theodore Ts'o6e9fa2c2013-09-22 16:04:19 -0400320 * For the purposes of better mixing, we use the CRC-32 polynomial as
321 * well to make a (modified) twisted Generalized Feedback Shift
322 * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
323 * generators. ACM Transactions on Modeling and Computer Simulation
324 * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
Greg Pricedfd38752013-11-29 14:58:06 -0500325 * GFSR generators II. ACM Transactions on Modeling and Computer
Theodore Ts'o6e9fa2c2013-09-22 16:04:19 -0400326 * Simulation 4:254-266)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700327 *
328 * Thanks to Colin Plumb for suggesting this.
329 *
Theodore Ts'o6e9fa2c2013-09-22 16:04:19 -0400330 * The mixing operation is much less sensitive than the output hash,
331 * where we use SHA-1. All that we want of mixing operation is that
332 * it be a good non-cryptographic hash; i.e. it not produce collisions
333 * when fed "random" data of the sort we expect to see. As long as
334 * the pool state differs for different inputs, we have preserved the
335 * input entropy and done a good job. The fact that an intelligent
336 * attacker can construct inputs that will produce controlled
337 * alterations to the pool's state is not important because we don't
338 * consider such inputs to contribute any randomness. The only
339 * property we need with respect to them is that the attacker can't
340 * increase his/her knowledge of the pool's state. Since all
341 * additions are reversible (knowing the final state and the input,
342 * you can reconstruct the initial state), if an attacker has any
343 * uncertainty about the initial state, he/she can only shuffle that
344 * uncertainty about, but never cause any collisions (which would
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345 * decrease the uncertainty).
346 *
Theodore Ts'o6e9fa2c2013-09-22 16:04:19 -0400347 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
348 * Videau in their paper, "The Linux Pseudorandom Number Generator
349 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
350 * paper, they point out that we are not using a true Twisted GFSR,
351 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
352 * is, with only three taps, instead of the six that we are using).
353 * As a result, the resulting polynomial is neither primitive nor
354 * irreducible, and hence does not have a maximal period over
355 * GF(2**32). They suggest a slight change to the generator
356 * polynomial which improves the resulting TGFSR polynomial to be
357 * irreducible, which we have made here.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359static struct poolinfo {
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400360 int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
361#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362 int tap1, tap2, tap3, tap4, tap5;
363} poolinfo_table[] = {
Theodore Ts'o6e9fa2c2013-09-22 16:04:19 -0400364 /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
365 /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
366 { S(128), 104, 76, 51, 25, 1 },
367 /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
368 /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
369 { S(32), 26, 19, 14, 7, 1 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370#if 0
371 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
H. Peter Anvin9ed17b72013-09-10 23:16:17 -0400372 { S(2048), 1638, 1231, 819, 411, 1 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373
374 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
H. Peter Anvin9ed17b72013-09-10 23:16:17 -0400375 { S(1024), 817, 615, 412, 204, 1 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376
377 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
H. Peter Anvin9ed17b72013-09-10 23:16:17 -0400378 { S(1024), 819, 616, 410, 207, 2 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700379
380 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
H. Peter Anvin9ed17b72013-09-10 23:16:17 -0400381 { S(512), 411, 308, 208, 104, 1 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382
383 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
H. Peter Anvin9ed17b72013-09-10 23:16:17 -0400384 { S(512), 409, 307, 206, 102, 2 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
H. Peter Anvin9ed17b72013-09-10 23:16:17 -0400386 { S(512), 409, 309, 205, 103, 2 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387
388 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
H. Peter Anvin9ed17b72013-09-10 23:16:17 -0400389 { S(256), 205, 155, 101, 52, 1 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390
391 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
H. Peter Anvin9ed17b72013-09-10 23:16:17 -0400392 { S(128), 103, 78, 51, 27, 2 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393
394 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
H. Peter Anvin9ed17b72013-09-10 23:16:17 -0400395 { S(64), 52, 39, 26, 14, 1 },
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396#endif
397};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700398
399/*
400 * Static global variables
401 */
402static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
403static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700404static struct fasync_struct *fasync;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405
Linus Torvalds1da177e2005-04-16 15:20:36 -0700406/**********************************************************************
407 *
408 * OS independent entropy store. Here are the functions which handle
409 * storing entropy in an entropy pool.
410 *
411 **********************************************************************/
412
413struct entropy_store;
414struct entropy_store {
Matt Mackall43358202008-04-29 01:03:01 -0700415 /* read-only data: */
H. Peter Anvin30e37ec2013-09-10 23:16:17 -0400416 const struct poolinfo *poolinfo;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417 __u32 *pool;
418 const char *name;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700419 struct entropy_store *pull;
Theodore Ts'o6265e162013-10-03 01:08:15 -0400420 struct work_struct push_work;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700421
422 /* read-write data: */
Theodore Ts'of5c27422013-09-22 15:14:32 -0400423 unsigned long last_pulled;
Matt Mackall43358202008-04-29 01:03:01 -0700424 spinlock_t lock;
Theodore Ts'oc59974a2013-09-21 19:42:41 -0400425 unsigned short add_ptr;
426 unsigned short input_rotate;
Matt Mackallcda796a2009-01-06 14:42:55 -0800427 int entropy_count;
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400428 int entropy_total;
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400429 unsigned int initialized:1;
Theodore Ts'oc59974a2013-09-21 19:42:41 -0400430 unsigned int limit:1;
431 unsigned int last_data_init:1;
Matt Mackalle954bc92010-05-20 19:55:01 +1000432 __u8 last_data[EXTRACT_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433};
434
Theodore Ts'o6265e162013-10-03 01:08:15 -0400435static void push_to_pool(struct work_struct *work);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700436static __u32 input_pool_data[INPUT_POOL_WORDS];
437static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
438static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
439
440static struct entropy_store input_pool = {
441 .poolinfo = &poolinfo_table[0],
442 .name = "input",
443 .limit = 1,
Thomas Gleixnereece09e2011-07-17 21:25:03 +0200444 .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 .pool = input_pool_data
446};
447
448static struct entropy_store blocking_pool = {
449 .poolinfo = &poolinfo_table[1],
450 .name = "blocking",
451 .limit = 1,
452 .pull = &input_pool,
Thomas Gleixnereece09e2011-07-17 21:25:03 +0200453 .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
Theodore Ts'o6265e162013-10-03 01:08:15 -0400454 .pool = blocking_pool_data,
455 .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
456 push_to_pool),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700457};
458
459static struct entropy_store nonblocking_pool = {
460 .poolinfo = &poolinfo_table[1],
461 .name = "nonblocking",
462 .pull = &input_pool,
Thomas Gleixnereece09e2011-07-17 21:25:03 +0200463 .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
Theodore Ts'o6265e162013-10-03 01:08:15 -0400464 .pool = nonblocking_pool_data,
465 .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
466 push_to_pool),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700467};
468
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400469static __u32 const twist_table[8] = {
470 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
471 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
472
Linus Torvalds1da177e2005-04-16 15:20:36 -0700473/*
Matt Mackalle68e5b62008-04-29 01:03:05 -0700474 * This function adds bytes into the entropy "pool". It does not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 * update the entropy estimate. The caller should call
Matt Mackalladc782d2008-04-29 01:03:07 -0700476 * credit_entropy_bits if this is appropriate.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700477 *
478 * The pool is stirred with a primitive polynomial of the appropriate
479 * degree, and then twisted. We twist by three bits at a time because
480 * it's cheap to do so and helps slightly in the expected case where
481 * the entropy is concentrated in the low-order bits.
482 */
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400483static void _mix_pool_bytes(struct entropy_store *r, const void *in,
484 int nbytes, __u8 out[64])
Linus Torvalds1da177e2005-04-16 15:20:36 -0700485{
Matt Mackall993ba212008-04-29 01:03:04 -0700486 unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
Matt Mackallfeee7692008-04-29 01:03:02 -0700487 int input_rotate;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488 int wordmask = r->poolinfo->poolwords - 1;
Matt Mackalle68e5b62008-04-29 01:03:05 -0700489 const char *bytes = in;
Matt Mackall6d38b822008-04-29 01:03:03 -0700490 __u32 w;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700491
Linus Torvalds1da177e2005-04-16 15:20:36 -0700492 tap1 = r->poolinfo->tap1;
493 tap2 = r->poolinfo->tap2;
494 tap3 = r->poolinfo->tap3;
495 tap4 = r->poolinfo->tap4;
496 tap5 = r->poolinfo->tap5;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497
Theodore Ts'o902c0982012-07-04 10:38:30 -0400498 smp_rmb();
499 input_rotate = ACCESS_ONCE(r->input_rotate);
500 i = ACCESS_ONCE(r->add_ptr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700501
Matt Mackalle68e5b62008-04-29 01:03:05 -0700502 /* mix one byte at a time to simplify size handling and churn faster */
503 while (nbytes--) {
Theodore Ts'oc59974a2013-09-21 19:42:41 -0400504 w = rol32(*bytes++, input_rotate);
Matt Mackall993ba212008-04-29 01:03:04 -0700505 i = (i - 1) & wordmask;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506
507 /* XOR in the various taps */
Matt Mackall993ba212008-04-29 01:03:04 -0700508 w ^= r->pool[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509 w ^= r->pool[(i + tap1) & wordmask];
510 w ^= r->pool[(i + tap2) & wordmask];
511 w ^= r->pool[(i + tap3) & wordmask];
512 w ^= r->pool[(i + tap4) & wordmask];
513 w ^= r->pool[(i + tap5) & wordmask];
Matt Mackall993ba212008-04-29 01:03:04 -0700514
515 /* Mix the result back in with a twist */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
Matt Mackallfeee7692008-04-29 01:03:02 -0700517
518 /*
519 * Normally, we add 7 bits of rotation to the pool.
520 * At the beginning of the pool, add an extra 7 bits
521 * rotation, so that successive passes spread the
522 * input bits across the pool evenly.
523 */
Theodore Ts'oc59974a2013-09-21 19:42:41 -0400524 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 }
526
Theodore Ts'o902c0982012-07-04 10:38:30 -0400527 ACCESS_ONCE(r->input_rotate) = input_rotate;
528 ACCESS_ONCE(r->add_ptr) = i;
529 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530
Matt Mackall993ba212008-04-29 01:03:04 -0700531 if (out)
532 for (j = 0; j < 16; j++)
Matt Mackalle68e5b62008-04-29 01:03:05 -0700533 ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700534}
535
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400536static void __mix_pool_bytes(struct entropy_store *r, const void *in,
Theodore Ts'o902c0982012-07-04 10:38:30 -0400537 int nbytes, __u8 out[64])
Linus Torvalds1da177e2005-04-16 15:20:36 -0700538{
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400539 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
540 _mix_pool_bytes(r, in, nbytes, out);
541}
542
543static void mix_pool_bytes(struct entropy_store *r, const void *in,
544 int nbytes, __u8 out[64])
545{
Theodore Ts'o902c0982012-07-04 10:38:30 -0400546 unsigned long flags;
547
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400548 trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
Theodore Ts'o902c0982012-07-04 10:38:30 -0400549 spin_lock_irqsave(&r->lock, flags);
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400550 _mix_pool_bytes(r, in, nbytes, out);
Theodore Ts'o902c0982012-07-04 10:38:30 -0400551 spin_unlock_irqrestore(&r->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552}
553
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400554struct fast_pool {
555 __u32 pool[4];
556 unsigned long last;
557 unsigned short count;
558 unsigned char rotate;
559 unsigned char last_timer_intr;
560};
561
562/*
563 * This is a fast mixing routine used by the interrupt randomness
564 * collector. It's hardcoded for an 128 bit pool and assumes that any
565 * locks that might be needed are taken by the caller.
566 */
Theodore Ts'o655b2262013-09-22 15:24:02 -0400567static void fast_mix(struct fast_pool *f, __u32 input[4])
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400568{
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400569 __u32 w;
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400570 unsigned input_rotate = f->rotate;
571
Theodore Ts'o655b2262013-09-22 15:24:02 -0400572 w = rol32(input[0], input_rotate) ^ f->pool[0] ^ f->pool[3];
573 f->pool[0] = (w >> 3) ^ twist_table[w & 7];
574 input_rotate = (input_rotate + 14) & 31;
575 w = rol32(input[1], input_rotate) ^ f->pool[1] ^ f->pool[0];
576 f->pool[1] = (w >> 3) ^ twist_table[w & 7];
577 input_rotate = (input_rotate + 7) & 31;
578 w = rol32(input[2], input_rotate) ^ f->pool[2] ^ f->pool[1];
579 f->pool[2] = (w >> 3) ^ twist_table[w & 7];
580 input_rotate = (input_rotate + 7) & 31;
581 w = rol32(input[3], input_rotate) ^ f->pool[3] ^ f->pool[2];
582 f->pool[3] = (w >> 3) ^ twist_table[w & 7];
583 input_rotate = (input_rotate + 7) & 31;
584
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400585 f->rotate = input_rotate;
Theodore Ts'o655b2262013-09-22 15:24:02 -0400586 f->count++;
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400587}
588
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589/*
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400590 * Credit (or debit) the entropy store with n bits of entropy.
591 * Use credit_entropy_bits_safe() if the value comes from userspace
592 * or otherwise should be checked for extreme values.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593 */
Matt Mackalladc782d2008-04-29 01:03:07 -0700594static void credit_entropy_bits(struct entropy_store *r, int nbits)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700595{
Theodore Ts'o902c0982012-07-04 10:38:30 -0400596 int entropy_count, orig;
H. Peter Anvin30e37ec2013-09-10 23:16:17 -0400597 const int pool_size = r->poolinfo->poolfracbits;
598 int nfrac = nbits << ENTROPY_SHIFT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599
Matt Mackalladc782d2008-04-29 01:03:07 -0700600 if (!nbits)
601 return;
602
Theodore Ts'o902c0982012-07-04 10:38:30 -0400603retry:
604 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
H. Peter Anvin30e37ec2013-09-10 23:16:17 -0400605 if (nfrac < 0) {
606 /* Debit */
607 entropy_count += nfrac;
608 } else {
609 /*
610 * Credit: we have to account for the possibility of
611 * overwriting already present entropy. Even in the
612 * ideal case of pure Shannon entropy, new contributions
613 * approach the full value asymptotically:
614 *
615 * entropy <- entropy + (pool_size - entropy) *
616 * (1 - exp(-add_entropy/pool_size))
617 *
618 * For add_entropy <= pool_size/2 then
619 * (1 - exp(-add_entropy/pool_size)) >=
620 * (add_entropy/pool_size)*0.7869...
621 * so we can approximate the exponential with
622 * 3/4*add_entropy/pool_size and still be on the
623 * safe side by adding at most pool_size/2 at a time.
624 *
625 * The use of pool_size-2 in the while statement is to
626 * prevent rounding artifacts from making the loop
627 * arbitrarily long; this limits the loop to log2(pool_size)*2
628 * turns no matter how large nbits is.
629 */
630 int pnfrac = nfrac;
631 const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
632 /* The +2 corresponds to the /4 in the denominator */
633
634 do {
635 unsigned int anfrac = min(pnfrac, pool_size/2);
636 unsigned int add =
637 ((pool_size - entropy_count)*anfrac*3) >> s;
638
639 entropy_count += add;
640 pnfrac -= anfrac;
641 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
642 }
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400643
Andrew Morton8b76f462008-09-02 14:36:14 -0700644 if (entropy_count < 0) {
Theodore Ts'of80bbd82013-10-03 12:02:37 -0400645 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
646 r->name, entropy_count);
647 WARN_ON(1);
Andrew Morton8b76f462008-09-02 14:36:14 -0700648 entropy_count = 0;
H. Peter Anvin30e37ec2013-09-10 23:16:17 -0400649 } else if (entropy_count > pool_size)
650 entropy_count = pool_size;
Theodore Ts'o902c0982012-07-04 10:38:30 -0400651 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
652 goto retry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700653
Theodore Ts'o6265e162013-10-03 01:08:15 -0400654 r->entropy_total += nbits;
Linus Torvalds0891ad82013-11-16 10:19:15 -0800655 if (!r->initialized && r->entropy_total > 128) {
656 r->initialized = 1;
657 r->entropy_total = 0;
658 if (r == &nonblocking_pool) {
659 prandom_reseed_late();
660 pr_notice("random: %s pool is initialized\n", r->name);
Hannes Frederic Sowa4af712e2013-11-11 12:20:34 +0100661 }
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400662 }
663
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400664 trace_credit_entropy_bits(r->name, nbits,
665 entropy_count >> ENTROPY_SHIFT,
Theodore Ts'o00ce1db2012-07-04 16:19:30 -0400666 r->entropy_total, _RET_IP_);
667
Theodore Ts'o6265e162013-10-03 01:08:15 -0400668 if (r == &input_pool) {
Greg Price7d1b08c2013-12-07 09:49:55 -0500669 int entropy_bits = entropy_count >> ENTROPY_SHIFT;
Theodore Ts'o6265e162013-10-03 01:08:15 -0400670
671 /* should we wake readers? */
Greg Price2132a962013-12-06 21:28:03 -0500672 if (entropy_bits >= random_read_wakeup_bits) {
Theodore Ts'o6265e162013-10-03 01:08:15 -0400673 wake_up_interruptible(&random_read_wait);
674 kill_fasync(&fasync, SIGIO, POLL_IN);
675 }
676 /* If the input pool is getting full, send some
677 * entropy to the two output pools, flipping back and
678 * forth between them, until the output pools are 75%
679 * full.
680 */
Greg Price2132a962013-12-06 21:28:03 -0500681 if (entropy_bits > random_write_wakeup_bits &&
Theodore Ts'o6265e162013-10-03 01:08:15 -0400682 r->initialized &&
Greg Price2132a962013-12-06 21:28:03 -0500683 r->entropy_total >= 2*random_read_wakeup_bits) {
Theodore Ts'o6265e162013-10-03 01:08:15 -0400684 static struct entropy_store *last = &blocking_pool;
685 struct entropy_store *other = &blocking_pool;
686
687 if (last == &blocking_pool)
688 other = &nonblocking_pool;
689 if (other->entropy_count <=
690 3 * other->poolinfo->poolfracbits / 4)
691 last = other;
692 if (last->entropy_count <=
693 3 * last->poolinfo->poolfracbits / 4) {
694 schedule_work(&last->push_work);
695 r->entropy_total = 0;
696 }
697 }
Jeff Dike9a6f70b2008-04-29 01:03:08 -0700698 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699}
700
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400701static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
702{
703 const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
704
705 /* Cap the value to avoid overflows */
706 nbits = min(nbits, nbits_max);
707 nbits = max(nbits, -nbits_max);
708
709 credit_entropy_bits(r, nbits);
710}
711
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712/*********************************************************************
713 *
714 * Entropy input management
715 *
716 *********************************************************************/
717
718/* There is one of these per entropy source */
719struct timer_rand_state {
720 cycles_t last_time;
Matt Mackall90b75ee2008-04-29 01:02:55 -0700721 long last_delta, last_delta2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722 unsigned dont_count_entropy:1;
723};
724
Theodore Ts'o644008d2013-11-03 16:40:53 -0500725#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
726
Linus Torvaldsa2080a62012-07-04 11:16:01 -0400727/*
728 * Add device- or boot-specific data to the input and nonblocking
729 * pools to help initialize them to unique values.
730 *
731 * None of this adds any entropy, it is meant to avoid the
732 * problem of the nonblocking pool having similar initial state
733 * across largely identical devices.
734 */
735void add_device_randomness(const void *buf, unsigned int size)
736{
Theodore Ts'o61875f32013-09-21 13:58:22 -0400737 unsigned long time = random_get_entropy() ^ jiffies;
Theodore Ts'o3ef4cb22013-09-12 14:27:22 -0400738 unsigned long flags;
Linus Torvaldsa2080a62012-07-04 11:16:01 -0400739
Theodore Ts'o59108952013-09-12 14:10:25 -0400740 trace_add_device_randomness(size, _RET_IP_);
Theodore Ts'o3ef4cb22013-09-12 14:27:22 -0400741 spin_lock_irqsave(&input_pool.lock, flags);
742 _mix_pool_bytes(&input_pool, buf, size, NULL);
743 _mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
744 spin_unlock_irqrestore(&input_pool.lock, flags);
745
746 spin_lock_irqsave(&nonblocking_pool.lock, flags);
747 _mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
748 _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
749 spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
Linus Torvaldsa2080a62012-07-04 11:16:01 -0400750}
751EXPORT_SYMBOL(add_device_randomness);
752
Theodore Ts'o644008d2013-11-03 16:40:53 -0500753static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700754
Linus Torvalds1da177e2005-04-16 15:20:36 -0700755/*
756 * This function adds entropy to the entropy "pool" by using timing
757 * delays. It uses the timer_rand_state structure to make an estimate
758 * of how many bits of entropy this call has added to the pool.
759 *
760 * The number "num" is also added to the pool - it should somehow describe
761 * the type of event which just happened. This is currently 0-255 for
762 * keyboard scan codes, and 256 upwards for interrupts.
763 *
764 */
765static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
766{
Theodore Ts'o40db23e2013-11-03 00:15:05 -0400767 struct entropy_store *r;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 struct {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700769 long jiffies;
Linus Torvaldscf833d02011-12-22 11:36:22 -0800770 unsigned cycles;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771 unsigned num;
772 } sample;
773 long delta, delta2, delta3;
774
775 preempt_disable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700776
777 sample.jiffies = jiffies;
Theodore Ts'o61875f32013-09-21 13:58:22 -0400778 sample.cycles = random_get_entropy();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700779 sample.num = num;
Theodore Ts'o40db23e2013-11-03 00:15:05 -0400780 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
781 mix_pool_bytes(r, &sample, sizeof(sample), NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700782
783 /*
784 * Calculate number of bits of randomness we probably added.
785 * We take into account the first, second and third-order deltas
786 * in order to make our estimate.
787 */
788
789 if (!state->dont_count_entropy) {
790 delta = sample.jiffies - state->last_time;
791 state->last_time = sample.jiffies;
792
793 delta2 = delta - state->last_delta;
794 state->last_delta = delta;
795
796 delta3 = delta2 - state->last_delta2;
797 state->last_delta2 = delta2;
798
799 if (delta < 0)
800 delta = -delta;
801 if (delta2 < 0)
802 delta2 = -delta2;
803 if (delta3 < 0)
804 delta3 = -delta3;
805 if (delta > delta2)
806 delta = delta2;
807 if (delta > delta3)
808 delta = delta3;
809
810 /*
811 * delta is now minimum absolute delta.
812 * Round down by 1 bit on general principles,
813 * and limit entropy entimate to 12 bits.
814 */
Theodore Ts'o40db23e2013-11-03 00:15:05 -0400815 credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700816 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700817 preempt_enable();
818}
819
Stephen Hemmingerd2515752006-01-11 12:17:38 -0800820void add_input_randomness(unsigned int type, unsigned int code,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821 unsigned int value)
822{
823 static unsigned char last_value;
824
825 /* ignore autorepeat and the like */
826 if (value == last_value)
827 return;
828
Linus Torvalds1da177e2005-04-16 15:20:36 -0700829 last_value = value;
830 add_timer_randomness(&input_timer_state,
831 (type << 4) ^ code ^ (code >> 4) ^ value);
Theodore Ts'of80bbd82013-10-03 12:02:37 -0400832 trace_add_input_randomness(ENTROPY_BITS(&input_pool));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833}
Dmitry Torokhov80fc9f52006-10-11 01:43:58 -0400834EXPORT_SYMBOL_GPL(add_input_randomness);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700835
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400836static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
837
838void add_interrupt_randomness(int irq, int irq_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700839{
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400840 struct entropy_store *r;
841 struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness);
842 struct pt_regs *regs = get_irq_regs();
843 unsigned long now = jiffies;
Theodore Ts'o655b2262013-09-22 15:24:02 -0400844 cycles_t cycles = random_get_entropy();
845 __u32 input[4], c_high, j_high;
846 __u64 ip;
H. Peter Anvin83664a62014-03-17 16:36:28 -0700847 unsigned long seed;
848 int credit;
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700849
Theodore Ts'o655b2262013-09-22 15:24:02 -0400850 c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
851 j_high = (sizeof(now) > 4) ? now >> 32 : 0;
852 input[0] = cycles ^ j_high ^ irq;
853 input[1] = now ^ c_high;
854 ip = regs ? instruction_pointer(regs) : _RET_IP_;
855 input[2] = ip;
856 input[3] = ip >> 32;
Yinghai Lu3060d6f2008-08-19 20:50:08 -0700857
Theodore Ts'o655b2262013-09-22 15:24:02 -0400858 fast_mix(fast_pool, input);
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400859
Theodore Ts'o655b2262013-09-22 15:24:02 -0400860 if ((fast_pool->count & 63) && !time_after(now, fast_pool->last + HZ))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700861 return;
862
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400863 fast_pool->last = now;
864
865 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
Theodore Ts'o902c0982012-07-04 10:38:30 -0400866 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
H. Peter Anvin83664a62014-03-17 16:36:28 -0700867
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400868 /*
869 * If we don't have a valid cycle counter, and we see
870 * back-to-back timer interrupts, then skip giving credit for
H. Peter Anvin83664a62014-03-17 16:36:28 -0700871 * any entropy, otherwise credit 1 bit.
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400872 */
H. Peter Anvin83664a62014-03-17 16:36:28 -0700873 credit = 1;
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400874 if (cycles == 0) {
875 if (irq_flags & __IRQF_TIMER) {
876 if (fast_pool->last_timer_intr)
H. Peter Anvin83664a62014-03-17 16:36:28 -0700877 credit = 0;
Theodore Ts'o775f4b22012-07-02 07:52:16 -0400878 fast_pool->last_timer_intr = 1;
879 } else
880 fast_pool->last_timer_intr = 0;
881 }
H. Peter Anvin83664a62014-03-17 16:36:28 -0700882
883 /*
884 * If we have architectural seed generator, produce a seed and
885 * add it to the pool. For the sake of paranoia count it as
886 * 50% entropic.
887 */
888 if (arch_get_random_seed_long(&seed)) {
889 __mix_pool_bytes(r, &seed, sizeof(seed), NULL);
890 credit += sizeof(seed) * 4;
891 }
892
893 credit_entropy_bits(r, credit);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700894}
895
David Howells93614012006-09-30 20:45:40 +0200896#ifdef CONFIG_BLOCK
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897void add_disk_randomness(struct gendisk *disk)
898{
899 if (!disk || !disk->random)
900 return;
901 /* first major is 1, so we get >= 0x200 here */
Tejun Heof331c022008-09-03 09:01:48 +0200902 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
Theodore Ts'of80bbd82013-10-03 12:02:37 -0400903 trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904}
David Howells93614012006-09-30 20:45:40 +0200905#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906
Linus Torvalds1da177e2005-04-16 15:20:36 -0700907/*********************************************************************
908 *
909 * Entropy extraction routines
910 *
911 *********************************************************************/
912
Matt Mackall90b75ee2008-04-29 01:02:55 -0700913static ssize_t extract_entropy(struct entropy_store *r, void *buf,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700914 size_t nbytes, int min, int rsvd);
915
916/*
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300917 * This utility inline function is responsible for transferring entropy
Linus Torvalds1da177e2005-04-16 15:20:36 -0700918 * from the primary pool to the secondary extraction pool. We make
919 * sure we pull enough for a 'catastrophic reseed'.
920 */
Theodore Ts'o6265e162013-10-03 01:08:15 -0400921static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
923{
Theodore Ts'of5c27422013-09-22 15:14:32 -0400924 if (r->limit == 0 && random_min_urandom_seed) {
925 unsigned long now = jiffies;
926
927 if (time_before(now,
928 r->last_pulled + random_min_urandom_seed * HZ))
929 return;
930 r->last_pulled = now;
931 }
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400932 if (r->pull &&
933 r->entropy_count < (nbytes << (ENTROPY_SHIFT + 3)) &&
Theodore Ts'o6265e162013-10-03 01:08:15 -0400934 r->entropy_count < r->poolinfo->poolfracbits)
935 _xfer_secondary_pool(r, nbytes);
936}
Matt Mackall5a021e92007-07-19 11:30:14 -0700937
Theodore Ts'o6265e162013-10-03 01:08:15 -0400938static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
939{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700940 __u32 tmp[OUTPUT_POOL_WORDS];
941
Greg Price2132a962013-12-06 21:28:03 -0500942 /* For /dev/random's pool, always leave two wakeups' worth */
943 int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
Theodore Ts'o6265e162013-10-03 01:08:15 -0400944 int bytes = nbytes;
Matt Mackall5a021e92007-07-19 11:30:14 -0700945
Greg Price2132a962013-12-06 21:28:03 -0500946 /* pull at least as much as a wakeup */
947 bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
Theodore Ts'o6265e162013-10-03 01:08:15 -0400948 /* but never more than the buffer size */
949 bytes = min_t(int, bytes, sizeof(tmp));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700950
Theodore Ts'of80bbd82013-10-03 12:02:37 -0400951 trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
952 ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
Theodore Ts'o6265e162013-10-03 01:08:15 -0400953 bytes = extract_entropy(r->pull, tmp, bytes,
Greg Price2132a962013-12-06 21:28:03 -0500954 random_read_wakeup_bits / 8, rsvd_bytes);
Theodore Ts'o6265e162013-10-03 01:08:15 -0400955 mix_pool_bytes(r, tmp, bytes, NULL);
956 credit_entropy_bits(r, bytes*8);
957}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700958
Theodore Ts'o6265e162013-10-03 01:08:15 -0400959/*
960 * Used as a workqueue function so that when the input pool is getting
961 * full, we can "spill over" some entropy to the output pools. That
962 * way the output pools can store some of the excess entropy instead
963 * of letting it go to waste.
964 */
965static void push_to_pool(struct work_struct *work)
966{
967 struct entropy_store *r = container_of(work, struct entropy_store,
968 push_work);
969 BUG_ON(!r);
Greg Price2132a962013-12-06 21:28:03 -0500970 _xfer_secondary_pool(r, random_read_wakeup_bits/8);
Theodore Ts'o6265e162013-10-03 01:08:15 -0400971 trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
972 r->pull->entropy_count >> ENTROPY_SHIFT);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700973}
974
975/*
Greg Price19fa5be2013-11-29 15:50:06 -0500976 * This function decides how many bytes to actually take from the
977 * given pool, and also debits the entropy count accordingly.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700978 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700979static size_t account(struct entropy_store *r, size_t nbytes, int min,
980 int reserved)
981{
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400982 int have_bytes;
983 int entropy_count, orig;
984 size_t ibytes;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700985
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400986 BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987
988 /* Can we pull enough? */
Jiri Kosina10b3a322013-05-24 15:55:33 -0700989retry:
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400990 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
991 have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
992 ibytes = nbytes;
Greg Price0fb7a012013-12-05 19:32:19 -0500993 /* If limited, never pull more than available */
994 if (r->limit)
995 ibytes = min_t(size_t, ibytes, have_bytes - reserved);
996 if (ibytes < min)
H. Peter Anvina283b5c2013-09-10 23:16:17 -0400997 ibytes = 0;
Greg Price0fb7a012013-12-05 19:32:19 -0500998 entropy_count = max_t(int, 0,
999 entropy_count - (ibytes << (ENTROPY_SHIFT + 3)));
1000 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1001 goto retry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001002
Theodore Ts'of80bbd82013-10-03 12:02:37 -04001003 trace_debit_entropy(r->name, 8 * ibytes);
Greg Price0fb7a012013-12-05 19:32:19 -05001004 if (ibytes &&
Greg Price2132a962013-12-06 21:28:03 -05001005 (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
Theodore Ts'ob9809552013-03-04 11:59:12 -05001006 wake_up_interruptible(&random_write_wait);
1007 kill_fasync(&fasync, SIGIO, POLL_OUT);
1008 }
1009
H. Peter Anvina283b5c2013-09-10 23:16:17 -04001010 return ibytes;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011}
1012
Greg Price19fa5be2013-11-29 15:50:06 -05001013/*
1014 * This function does the actual extraction for extract_entropy and
1015 * extract_entropy_user.
1016 *
1017 * Note: we assume that .poolwords is a multiple of 16 words.
1018 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001019static void extract_buf(struct entropy_store *r, __u8 *out)
1020{
Matt Mackall602b6ae2007-05-29 21:54:27 -05001021 int i;
H. Peter Anvind2e7c962012-07-27 22:26:08 -04001022 union {
1023 __u32 w[5];
Theodore Ts'o85a1f772013-09-21 18:06:02 -04001024 unsigned long l[LONGS(20)];
H. Peter Anvind2e7c962012-07-27 22:26:08 -04001025 } hash;
1026 __u32 workspace[SHA_WORKSPACE_WORDS];
Matt Mackalle68e5b62008-04-29 01:03:05 -07001027 __u8 extract[64];
Theodore Ts'o902c0982012-07-04 10:38:30 -04001028 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030 /*
Greg Pricedfd38752013-11-29 14:58:06 -05001031 * If we have an architectural hardware random number
Theodore Ts'o46884442013-12-17 21:16:39 -05001032 * generator, use it for SHA's initial vector
Theodore Ts'o85a1f772013-09-21 18:06:02 -04001033 */
Theodore Ts'o46884442013-12-17 21:16:39 -05001034 sha_init(hash.w);
Theodore Ts'o85a1f772013-09-21 18:06:02 -04001035 for (i = 0; i < LONGS(20); i++) {
1036 unsigned long v;
1037 if (!arch_get_random_long(&v))
1038 break;
Theodore Ts'o46884442013-12-17 21:16:39 -05001039 hash.l[i] = v;
Theodore Ts'o85a1f772013-09-21 18:06:02 -04001040 }
1041
Theodore Ts'o46884442013-12-17 21:16:39 -05001042 /* Generate a hash across the pool, 16 words (512 bits) at a time */
1043 spin_lock_irqsave(&r->lock, flags);
1044 for (i = 0; i < r->poolinfo->poolwords; i += 16)
1045 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1046
Theodore Ts'o85a1f772013-09-21 18:06:02 -04001047 /*
Matt Mackall1c0ad3d2008-04-29 01:03:00 -07001048 * We mix the hash back into the pool to prevent backtracking
1049 * attacks (where the attacker knows the state of the pool
1050 * plus the current outputs, and attempts to find previous
1051 * ouputs), unless the hash function can be inverted. By
1052 * mixing at least a SHA1 worth of hash data back, we make
1053 * brute-forcing the feedback as hard as brute-forcing the
1054 * hash.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055 */
H. Peter Anvind2e7c962012-07-27 22:26:08 -04001056 __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
Theodore Ts'o902c0982012-07-04 10:38:30 -04001057 spin_unlock_irqrestore(&r->lock, flags);
Matt Mackall1c0ad3d2008-04-29 01:03:00 -07001058
1059 /*
1060 * To avoid duplicates, we atomically extract a portion of the
1061 * pool while mixing, and hash one final time.
1062 */
H. Peter Anvind2e7c962012-07-27 22:26:08 -04001063 sha_transform(hash.w, extract, workspace);
Matt Mackallffd8d3f2008-04-29 01:02:59 -07001064 memset(extract, 0, sizeof(extract));
1065 memset(workspace, 0, sizeof(workspace));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066
1067 /*
Matt Mackall1c0ad3d2008-04-29 01:03:00 -07001068 * In case the hash function has some recognizable output
1069 * pattern, we fold it in half. Thus, we always feed back
1070 * twice as much data as we output.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071 */
H. Peter Anvind2e7c962012-07-27 22:26:08 -04001072 hash.w[0] ^= hash.w[3];
1073 hash.w[1] ^= hash.w[4];
1074 hash.w[2] ^= rol32(hash.w[2], 16);
1075
H. Peter Anvind2e7c962012-07-27 22:26:08 -04001076 memcpy(out, &hash, EXTRACT_SIZE);
1077 memset(&hash, 0, sizeof(hash));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078}
1079
Greg Price19fa5be2013-11-29 15:50:06 -05001080/*
1081 * This function extracts randomness from the "entropy pool", and
1082 * returns it in a buffer.
1083 *
1084 * The min parameter specifies the minimum amount we can pull before
1085 * failing to avoid races that defeat catastrophic reseeding while the
1086 * reserved parameter indicates how much entropy we must leave in the
1087 * pool after each pull to avoid starving other readers.
1088 */
Matt Mackall90b75ee2008-04-29 01:02:55 -07001089static ssize_t extract_entropy(struct entropy_store *r, void *buf,
Theodore Ts'o902c0982012-07-04 10:38:30 -04001090 size_t nbytes, int min, int reserved)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001091{
1092 ssize_t ret = 0, i;
1093 __u8 tmp[EXTRACT_SIZE];
Jarod Wilson1e7e2e02013-05-24 15:55:31 -07001094 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095
Jarod Wilsonec8f02da2012-11-06 10:42:42 -05001096 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
Jarod Wilson1e7e2e02013-05-24 15:55:31 -07001097 if (fips_enabled) {
1098 spin_lock_irqsave(&r->lock, flags);
1099 if (!r->last_data_init) {
Theodore Ts'oc59974a2013-09-21 19:42:41 -04001100 r->last_data_init = 1;
Jarod Wilson1e7e2e02013-05-24 15:55:31 -07001101 spin_unlock_irqrestore(&r->lock, flags);
1102 trace_extract_entropy(r->name, EXTRACT_SIZE,
H. Peter Anvina283b5c2013-09-10 23:16:17 -04001103 ENTROPY_BITS(r), _RET_IP_);
Jarod Wilson1e7e2e02013-05-24 15:55:31 -07001104 xfer_secondary_pool(r, EXTRACT_SIZE);
1105 extract_buf(r, tmp);
1106 spin_lock_irqsave(&r->lock, flags);
1107 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1108 }
1109 spin_unlock_irqrestore(&r->lock, flags);
1110 }
Jarod Wilsonec8f02da2012-11-06 10:42:42 -05001111
H. Peter Anvina283b5c2013-09-10 23:16:17 -04001112 trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001113 xfer_secondary_pool(r, nbytes);
1114 nbytes = account(r, nbytes, min, reserved);
1115
1116 while (nbytes) {
1117 extract_buf(r, tmp);
Neil Horman5b739ef2009-06-18 19:50:21 +08001118
Matt Mackalle954bc92010-05-20 19:55:01 +10001119 if (fips_enabled) {
Neil Horman5b739ef2009-06-18 19:50:21 +08001120 spin_lock_irqsave(&r->lock, flags);
1121 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1122 panic("Hardware RNG duplicated output!\n");
1123 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1124 spin_unlock_irqrestore(&r->lock, flags);
1125 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126 i = min_t(int, nbytes, EXTRACT_SIZE);
1127 memcpy(buf, tmp, i);
1128 nbytes -= i;
1129 buf += i;
1130 ret += i;
1131 }
1132
1133 /* Wipe data just returned from memory */
1134 memset(tmp, 0, sizeof(tmp));
1135
1136 return ret;
1137}
1138
Greg Price19fa5be2013-11-29 15:50:06 -05001139/*
1140 * This function extracts randomness from the "entropy pool", and
1141 * returns it in a userspace buffer.
1142 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001143static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1144 size_t nbytes)
1145{
1146 ssize_t ret = 0, i;
1147 __u8 tmp[EXTRACT_SIZE];
1148
H. Peter Anvina283b5c2013-09-10 23:16:17 -04001149 trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001150 xfer_secondary_pool(r, nbytes);
1151 nbytes = account(r, nbytes, 0, 0);
1152
1153 while (nbytes) {
1154 if (need_resched()) {
1155 if (signal_pending(current)) {
1156 if (ret == 0)
1157 ret = -ERESTARTSYS;
1158 break;
1159 }
1160 schedule();
1161 }
1162
1163 extract_buf(r, tmp);
1164 i = min_t(int, nbytes, EXTRACT_SIZE);
1165 if (copy_to_user(buf, tmp, i)) {
1166 ret = -EFAULT;
1167 break;
1168 }
1169
1170 nbytes -= i;
1171 buf += i;
1172 ret += i;
1173 }
1174
1175 /* Wipe data just returned from memory */
1176 memset(tmp, 0, sizeof(tmp));
1177
1178 return ret;
1179}
1180
1181/*
1182 * This function is the exported kernel interface. It returns some
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001183 * number of good random numbers, suitable for key generation, seeding
Greg Price18e9cea2013-11-29 14:59:45 -05001184 * TCP sequence numbers, etc. It does not rely on the hardware random
1185 * number generator. For random bytes direct from the hardware RNG
1186 * (when available), use get_random_bytes_arch().
Linus Torvalds1da177e2005-04-16 15:20:36 -07001187 */
1188void get_random_bytes(void *buf, int nbytes)
1189{
Theodore Ts'o392a5462013-11-03 18:24:08 -05001190#if DEBUG_RANDOM_BOOT > 0
1191 if (unlikely(nonblocking_pool.initialized == 0))
1192 printk(KERN_NOTICE "random: %pF get_random_bytes called "
1193 "with %d bits of entropy available\n",
1194 (void *) _RET_IP_,
1195 nonblocking_pool.entropy_total);
1196#endif
Theodore Ts'o59108952013-09-12 14:10:25 -04001197 trace_get_random_bytes(nbytes, _RET_IP_);
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001198 extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1199}
1200EXPORT_SYMBOL(get_random_bytes);
1201
1202/*
1203 * This function will use the architecture-specific hardware random
1204 * number generator if it is available. The arch-specific hw RNG will
1205 * almost certainly be faster than what we can do in software, but it
1206 * is impossible to verify that it is implemented securely (as
1207 * opposed, to, say, the AES encryption of a sequence number using a
1208 * key known by the NSA). So it's useful if we need the speed, but
1209 * only if we're willing to trust the hardware manufacturer not to
1210 * have put in a back door.
1211 */
1212void get_random_bytes_arch(void *buf, int nbytes)
1213{
H. Peter Anvin63d77172011-07-31 13:54:50 -07001214 char *p = buf;
1215
Theodore Ts'o59108952013-09-12 14:10:25 -04001216 trace_get_random_bytes_arch(nbytes, _RET_IP_);
H. Peter Anvin63d77172011-07-31 13:54:50 -07001217 while (nbytes) {
1218 unsigned long v;
1219 int chunk = min(nbytes, (int)sizeof(unsigned long));
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001220
H. Peter Anvin63d77172011-07-31 13:54:50 -07001221 if (!arch_get_random_long(&v))
1222 break;
1223
Luck, Tonybd29e562011-11-16 10:50:56 -08001224 memcpy(p, &v, chunk);
H. Peter Anvin63d77172011-07-31 13:54:50 -07001225 p += chunk;
1226 nbytes -= chunk;
1227 }
1228
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001229 if (nbytes)
1230 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231}
Theodore Ts'oc2557a32012-07-05 10:35:23 -04001232EXPORT_SYMBOL(get_random_bytes_arch);
1233
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234
1235/*
1236 * init_std_data - initialize pool with system data
1237 *
1238 * @r: pool to initialize
1239 *
1240 * This function clears the pool's entropy count and mixes some system
1241 * data into the pool to prepare it for use. The pool is not cleared
1242 * as that can only decrease the entropy in the pool.
1243 */
1244static void init_std_data(struct entropy_store *r)
1245{
Theodore Ts'o3e88bdf2011-12-22 16:28:01 -05001246 int i;
Theodore Ts'o902c0982012-07-04 10:38:30 -04001247 ktime_t now = ktime_get_real();
1248 unsigned long rv;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001249
Theodore Ts'of5c27422013-09-22 15:14:32 -04001250 r->last_pulled = jiffies;
Theodore Ts'o902c0982012-07-04 10:38:30 -04001251 mix_pool_bytes(r, &now, sizeof(now), NULL);
H. Peter Anvin9ed17b72013-09-10 23:16:17 -04001252 for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
H. Peter Anvin83664a62014-03-17 16:36:28 -07001253 if (!arch_get_random_seed_long(&rv) &&
1254 !arch_get_random_long(&rv))
Theodore Ts'oae9ecd92013-11-03 07:56:17 -05001255 rv = random_get_entropy();
Theodore Ts'o902c0982012-07-04 10:38:30 -04001256 mix_pool_bytes(r, &rv, sizeof(rv), NULL);
Theodore Ts'o3e88bdf2011-12-22 16:28:01 -05001257 }
Theodore Ts'o902c0982012-07-04 10:38:30 -04001258 mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259}
1260
Tony Luckcbc96b72012-07-23 09:47:57 -07001261/*
1262 * Note that setup_arch() may call add_device_randomness()
1263 * long before we get here. This allows seeding of the pools
1264 * with some platform dependent data very early in the boot
1265 * process. But it limits our options here. We must use
1266 * statically allocated structures that already have all
1267 * initializations complete at compile time. We should also
1268 * take care not to overwrite the precious per platform data
1269 * we were given.
1270 */
Matt Mackall53c3f632008-04-29 01:02:58 -07001271static int rand_initialize(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001272{
1273 init_std_data(&input_pool);
1274 init_std_data(&blocking_pool);
1275 init_std_data(&nonblocking_pool);
1276 return 0;
1277}
Theodore Ts'oae9ecd92013-11-03 07:56:17 -05001278early_initcall(rand_initialize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001279
David Howells93614012006-09-30 20:45:40 +02001280#ifdef CONFIG_BLOCK
Linus Torvalds1da177e2005-04-16 15:20:36 -07001281void rand_initialize_disk(struct gendisk *disk)
1282{
1283 struct timer_rand_state *state;
1284
1285 /*
Eric Dumazetf8595812007-03-28 14:22:33 -07001286 * If kzalloc returns null, we just won't use that entropy
Linus Torvalds1da177e2005-04-16 15:20:36 -07001287 * source.
1288 */
Eric Dumazetf8595812007-03-28 14:22:33 -07001289 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
Theodore Ts'o644008d2013-11-03 16:40:53 -05001290 if (state) {
1291 state->last_time = INITIAL_JIFFIES;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292 disk->random = state;
Theodore Ts'o644008d2013-11-03 16:40:53 -05001293 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001294}
David Howells93614012006-09-30 20:45:40 +02001295#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07001296
H. Peter Anvin331c6492014-03-17 16:36:29 -07001297/*
1298 * Attempt an emergency refill using arch_get_random_seed_long().
1299 *
1300 * As with add_interrupt_randomness() be paranoid and only
1301 * credit the output as 50% entropic.
1302 */
1303static int arch_random_refill(void)
1304{
1305 const unsigned int nlongs = 64; /* Arbitrary number */
1306 unsigned int n = 0;
1307 unsigned int i;
1308 unsigned long buf[nlongs];
1309
H. Peter Anvin7b878d42014-03-17 16:36:30 -07001310 if (!arch_has_random_seed())
1311 return 0;
1312
H. Peter Anvin331c6492014-03-17 16:36:29 -07001313 for (i = 0; i < nlongs; i++) {
1314 if (arch_get_random_seed_long(&buf[n]))
1315 n++;
1316 }
1317
1318 if (n) {
1319 unsigned int rand_bytes = n * sizeof(unsigned long);
1320
1321 mix_pool_bytes(&input_pool, buf, rand_bytes, NULL);
1322 credit_entropy_bits(&input_pool, rand_bytes*4);
1323 }
1324
1325 return n;
1326}
1327
Linus Torvalds1da177e2005-04-16 15:20:36 -07001328static ssize_t
Matt Mackall90b75ee2008-04-29 01:02:55 -07001329random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330{
Greg Price12ff3a52013-11-29 15:02:33 -05001331 ssize_t n;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332
1333 if (nbytes == 0)
1334 return 0;
1335
Greg Price12ff3a52013-11-29 15:02:33 -05001336 nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1337 while (1) {
1338 n = extract_entropy_user(&blocking_pool, buf, nbytes);
1339 if (n < 0)
1340 return n;
Theodore Ts'of80bbd82013-10-03 12:02:37 -04001341 trace_random_read(n*8, (nbytes-n)*8,
1342 ENTROPY_BITS(&blocking_pool),
1343 ENTROPY_BITS(&input_pool));
Greg Price12ff3a52013-11-29 15:02:33 -05001344 if (n > 0)
1345 return n;
H. Peter Anvin331c6492014-03-17 16:36:29 -07001346
Greg Price12ff3a52013-11-29 15:02:33 -05001347 /* Pool is (near) empty. Maybe wait and retry. */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348
H. Peter Anvin331c6492014-03-17 16:36:29 -07001349 /* First try an emergency refill */
1350 if (arch_random_refill())
1351 continue;
1352
Greg Price12ff3a52013-11-29 15:02:33 -05001353 if (file->f_flags & O_NONBLOCK)
1354 return -EAGAIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001355
Greg Price12ff3a52013-11-29 15:02:33 -05001356 wait_event_interruptible(random_read_wait,
1357 ENTROPY_BITS(&input_pool) >=
Greg Price2132a962013-12-06 21:28:03 -05001358 random_read_wakeup_bits);
Greg Price12ff3a52013-11-29 15:02:33 -05001359 if (signal_pending(current))
1360 return -ERESTARTSYS;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001361 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001362}
1363
1364static ssize_t
Matt Mackall90b75ee2008-04-29 01:02:55 -07001365urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001366{
Theodore Ts'o301f0592013-11-03 06:54:51 -05001367 int ret;
1368
1369 if (unlikely(nonblocking_pool.initialized == 0))
1370 printk_once(KERN_NOTICE "random: %s urandom read "
1371 "with %d bits of entropy available\n",
1372 current->comm, nonblocking_pool.entropy_total);
1373
1374 ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
Theodore Ts'of80bbd82013-10-03 12:02:37 -04001375
1376 trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
1377 ENTROPY_BITS(&input_pool));
1378 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379}
1380
1381static unsigned int
1382random_poll(struct file *file, poll_table * wait)
1383{
1384 unsigned int mask;
1385
1386 poll_wait(file, &random_read_wait, wait);
1387 poll_wait(file, &random_write_wait, wait);
1388 mask = 0;
Greg Price2132a962013-12-06 21:28:03 -05001389 if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001390 mask |= POLLIN | POLLRDNORM;
Greg Price2132a962013-12-06 21:28:03 -05001391 if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001392 mask |= POLLOUT | POLLWRNORM;
1393 return mask;
1394}
1395
Matt Mackall7f397dc2007-05-29 21:58:10 -05001396static int
1397write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1398{
1399 size_t bytes;
1400 __u32 buf[16];
1401 const char __user *p = buffer;
1402
1403 while (count > 0) {
1404 bytes = min(count, sizeof(buf));
1405 if (copy_from_user(&buf, p, bytes))
1406 return -EFAULT;
1407
1408 count -= bytes;
1409 p += bytes;
1410
Theodore Ts'o902c0982012-07-04 10:38:30 -04001411 mix_pool_bytes(r, buf, bytes, NULL);
Matt Mackall91f3f1e2008-02-06 01:37:20 -08001412 cond_resched();
Matt Mackall7f397dc2007-05-29 21:58:10 -05001413 }
1414
1415 return 0;
1416}
1417
Matt Mackall90b75ee2008-04-29 01:02:55 -07001418static ssize_t random_write(struct file *file, const char __user *buffer,
1419 size_t count, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001420{
Matt Mackall7f397dc2007-05-29 21:58:10 -05001421 size_t ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001422
Matt Mackall7f397dc2007-05-29 21:58:10 -05001423 ret = write_pool(&blocking_pool, buffer, count);
1424 if (ret)
1425 return ret;
1426 ret = write_pool(&nonblocking_pool, buffer, count);
1427 if (ret)
1428 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001429
Matt Mackall7f397dc2007-05-29 21:58:10 -05001430 return (ssize_t)count;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001431}
1432
Matt Mackall43ae4862008-04-29 01:02:58 -07001433static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001434{
1435 int size, ent_count;
1436 int __user *p = (int __user *)arg;
1437 int retval;
1438
1439 switch (cmd) {
1440 case RNDGETENTCNT:
Matt Mackall43ae4862008-04-29 01:02:58 -07001441 /* inherently racy, no point locking */
H. Peter Anvina283b5c2013-09-10 23:16:17 -04001442 ent_count = ENTROPY_BITS(&input_pool);
1443 if (put_user(ent_count, p))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001444 return -EFAULT;
1445 return 0;
1446 case RNDADDTOENTCNT:
1447 if (!capable(CAP_SYS_ADMIN))
1448 return -EPERM;
1449 if (get_user(ent_count, p))
1450 return -EFAULT;
H. Peter Anvina283b5c2013-09-10 23:16:17 -04001451 credit_entropy_bits_safe(&input_pool, ent_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001452 return 0;
1453 case RNDADDENTROPY:
1454 if (!capable(CAP_SYS_ADMIN))
1455 return -EPERM;
1456 if (get_user(ent_count, p++))
1457 return -EFAULT;
1458 if (ent_count < 0)
1459 return -EINVAL;
1460 if (get_user(size, p++))
1461 return -EFAULT;
Matt Mackall7f397dc2007-05-29 21:58:10 -05001462 retval = write_pool(&input_pool, (const char __user *)p,
1463 size);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 if (retval < 0)
1465 return retval;
H. Peter Anvina283b5c2013-09-10 23:16:17 -04001466 credit_entropy_bits_safe(&input_pool, ent_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001467 return 0;
1468 case RNDZAPENTCNT:
1469 case RNDCLEARPOOL:
Theodore Ts'oae9ecd92013-11-03 07:56:17 -05001470 /*
1471 * Clear the entropy pool counters. We no longer clear
1472 * the entropy pool, as that's silly.
1473 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001474 if (!capable(CAP_SYS_ADMIN))
1475 return -EPERM;
Theodore Ts'oae9ecd92013-11-03 07:56:17 -05001476 input_pool.entropy_count = 0;
1477 nonblocking_pool.entropy_count = 0;
1478 blocking_pool.entropy_count = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001479 return 0;
1480 default:
1481 return -EINVAL;
1482 }
1483}
1484
Jeff Dike9a6f70b2008-04-29 01:03:08 -07001485static int random_fasync(int fd, struct file *filp, int on)
1486{
1487 return fasync_helper(fd, filp, on, &fasync);
1488}
1489
Arjan van de Ven2b8693c2007-02-12 00:55:32 -08001490const struct file_operations random_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001491 .read = random_read,
1492 .write = random_write,
1493 .poll = random_poll,
Matt Mackall43ae4862008-04-29 01:02:58 -07001494 .unlocked_ioctl = random_ioctl,
Jeff Dike9a6f70b2008-04-29 01:03:08 -07001495 .fasync = random_fasync,
Arnd Bergmann6038f372010-08-15 18:52:59 +02001496 .llseek = noop_llseek,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001497};
1498
Arjan van de Ven2b8693c2007-02-12 00:55:32 -08001499const struct file_operations urandom_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 .read = urandom_read,
1501 .write = random_write,
Matt Mackall43ae4862008-04-29 01:02:58 -07001502 .unlocked_ioctl = random_ioctl,
Jeff Dike9a6f70b2008-04-29 01:03:08 -07001503 .fasync = random_fasync,
Arnd Bergmann6038f372010-08-15 18:52:59 +02001504 .llseek = noop_llseek,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001505};
1506
1507/***************************************************************
1508 * Random UUID interface
1509 *
1510 * Used here for a Boot ID, but can be useful for other kernel
1511 * drivers.
1512 ***************************************************************/
1513
1514/*
1515 * Generate random UUID
1516 */
1517void generate_random_uuid(unsigned char uuid_out[16])
1518{
1519 get_random_bytes(uuid_out, 16);
Adam Buchbinderc41b20e2009-12-11 16:35:39 -05001520 /* Set UUID version to 4 --- truly random generation */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001521 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1522 /* Set the UUID variant to DCE */
1523 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1524}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001525EXPORT_SYMBOL(generate_random_uuid);
1526
1527/********************************************************************
1528 *
1529 * Sysctl interface
1530 *
1531 ********************************************************************/
1532
1533#ifdef CONFIG_SYSCTL
1534
1535#include <linux/sysctl.h>
1536
1537static int min_read_thresh = 8, min_write_thresh;
Greg Price8c2aa332013-12-05 19:19:29 -05001538static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001539static int max_write_thresh = INPUT_POOL_WORDS * 32;
1540static char sysctl_bootid[16];
1541
1542/*
Greg Pricef22052b2013-11-29 14:58:16 -05001543 * This function is used to return both the bootid UUID, and random
Linus Torvalds1da177e2005-04-16 15:20:36 -07001544 * UUID. The difference is in whether table->data is NULL; if it is,
1545 * then a new UUID is generated and returned to the user.
1546 *
Greg Pricef22052b2013-11-29 14:58:16 -05001547 * If the user accesses this via the proc interface, the UUID will be
1548 * returned as an ASCII string in the standard UUID format; if via the
1549 * sysctl system call, as 16 bytes of binary data.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001550 */
Joe Perchesa1514272013-06-13 19:37:35 -07001551static int proc_do_uuid(struct ctl_table *table, int write,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552 void __user *buffer, size_t *lenp, loff_t *ppos)
1553{
Joe Perchesa1514272013-06-13 19:37:35 -07001554 struct ctl_table fake_table;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001555 unsigned char buf[64], tmp_uuid[16], *uuid;
1556
1557 uuid = table->data;
1558 if (!uuid) {
1559 uuid = tmp_uuid;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560 generate_random_uuid(uuid);
Mathieu Desnoyers44e43602012-04-12 12:49:12 -07001561 } else {
1562 static DEFINE_SPINLOCK(bootid_spinlock);
1563
1564 spin_lock(&bootid_spinlock);
1565 if (!uuid[8])
1566 generate_random_uuid(uuid);
1567 spin_unlock(&bootid_spinlock);
1568 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001569
Joe Perches35900772009-12-14 18:01:11 -08001570 sprintf(buf, "%pU", uuid);
1571
Linus Torvalds1da177e2005-04-16 15:20:36 -07001572 fake_table.data = buf;
1573 fake_table.maxlen = sizeof(buf);
1574
Alexey Dobriyan8d65af72009-09-23 15:57:19 -07001575 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576}
1577
H. Peter Anvina283b5c2013-09-10 23:16:17 -04001578/*
1579 * Return entropy available scaled to integral bits
1580 */
1581static int proc_do_entropy(ctl_table *table, int write,
1582 void __user *buffer, size_t *lenp, loff_t *ppos)
1583{
1584 ctl_table fake_table;
1585 int entropy_count;
1586
1587 entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1588
1589 fake_table.data = &entropy_count;
1590 fake_table.maxlen = sizeof(entropy_count);
1591
1592 return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1593}
1594
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
Joe Perchesa1514272013-06-13 19:37:35 -07001596extern struct ctl_table random_table[];
1597struct ctl_table random_table[] = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001598 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001599 .procname = "poolsize",
1600 .data = &sysctl_poolsize,
1601 .maxlen = sizeof(int),
1602 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001603 .proc_handler = proc_dointvec,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001604 },
1605 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001606 .procname = "entropy_avail",
1607 .maxlen = sizeof(int),
1608 .mode = 0444,
H. Peter Anvina283b5c2013-09-10 23:16:17 -04001609 .proc_handler = proc_do_entropy,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001610 .data = &input_pool.entropy_count,
1611 },
1612 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613 .procname = "read_wakeup_threshold",
Greg Price2132a962013-12-06 21:28:03 -05001614 .data = &random_read_wakeup_bits,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001615 .maxlen = sizeof(int),
1616 .mode = 0644,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001617 .proc_handler = proc_dointvec_minmax,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001618 .extra1 = &min_read_thresh,
1619 .extra2 = &max_read_thresh,
1620 },
1621 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622 .procname = "write_wakeup_threshold",
Greg Price2132a962013-12-06 21:28:03 -05001623 .data = &random_write_wakeup_bits,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001624 .maxlen = sizeof(int),
1625 .mode = 0644,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001626 .proc_handler = proc_dointvec_minmax,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001627 .extra1 = &min_write_thresh,
1628 .extra2 = &max_write_thresh,
1629 },
1630 {
Theodore Ts'of5c27422013-09-22 15:14:32 -04001631 .procname = "urandom_min_reseed_secs",
1632 .data = &random_min_urandom_seed,
1633 .maxlen = sizeof(int),
1634 .mode = 0644,
1635 .proc_handler = proc_dointvec,
1636 },
1637 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001638 .procname = "boot_id",
1639 .data = &sysctl_bootid,
1640 .maxlen = 16,
1641 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001642 .proc_handler = proc_do_uuid,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001643 },
1644 {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 .procname = "uuid",
1646 .maxlen = 16,
1647 .mode = 0444,
Eric W. Biederman6d456112009-11-16 03:11:48 -08001648 .proc_handler = proc_do_uuid,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001649 },
Eric W. Biederman894d2492009-11-05 14:34:02 -08001650 { }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001651};
1652#endif /* CONFIG_SYSCTL */
1653
David S. Miller6e5714e2011-08-03 20:50:44 -07001654static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655
Theodore Ts'o47d06e52013-09-10 10:52:35 -04001656int random_int_secret_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001657{
David S. Miller6e5714e2011-08-03 20:50:44 -07001658 get_random_bytes(random_int_secret, sizeof(random_int_secret));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001659 return 0;
1660}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001661
1662/*
1663 * Get a random word for internal kernel use only. Similar to urandom but
1664 * with the goal of minimal entropy pool depletion. As a result, the random
1665 * value is not cryptographically secure but for several uses the cost of
1666 * depleting entropy is too high
1667 */
Theodore Ts'o74feec52012-07-06 14:03:18 -04001668static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669unsigned int get_random_int(void)
1670{
H. Peter Anvin63d77172011-07-31 13:54:50 -07001671 __u32 *hash;
David S. Miller6e5714e2011-08-03 20:50:44 -07001672 unsigned int ret;
Linus Torvalds8a0a9bd2009-05-05 08:17:43 -07001673
H. Peter Anvin63d77172011-07-31 13:54:50 -07001674 if (arch_get_random_int(&ret))
1675 return ret;
1676
1677 hash = get_cpu_var(get_random_int_hash);
Linus Torvalds8a0a9bd2009-05-05 08:17:43 -07001678
Theodore Ts'o61875f32013-09-21 13:58:22 -04001679 hash[0] += current->pid + jiffies + random_get_entropy();
David S. Miller6e5714e2011-08-03 20:50:44 -07001680 md5_transform(hash, random_int_secret);
1681 ret = hash[0];
Linus Torvalds8a0a9bd2009-05-05 08:17:43 -07001682 put_cpu_var(get_random_int_hash);
1683
1684 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001685}
Andy Shevchenko16c7fa02013-04-30 15:27:30 -07001686EXPORT_SYMBOL(get_random_int);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001687
1688/*
1689 * randomize_range() returns a start address such that
1690 *
1691 * [...... <range> .....]
1692 * start end
1693 *
1694 * a <range> with size "len" starting at the return value is inside in the
1695 * area defined by [start, end], but is otherwise randomized.
1696 */
1697unsigned long
1698randomize_range(unsigned long start, unsigned long end, unsigned long len)
1699{
1700 unsigned long range = end - len - start;
1701
1702 if (end <= start + len)
1703 return 0;
1704 return PAGE_ALIGN(get_random_int() % range + start);
1705}