2 * random.c -- A strong random number generator
4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
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
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.)
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
43 * (now, with legal B.S. out of the way.....)
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.
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.
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.
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.
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
98 * Exported interfaces ---- output
99 * ===============================
101 * There are three exported interfaces; the first is one designed to
102 * be used from within the kernel:
104 * void get_random_bytes(void *buf, int nbytes);
106 * This interface will return the requested number of random bytes,
107 * and place it in the requested buffer.
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.
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.
122 * Exported interfaces ---- input
123 * ==============================
125 * The current exported interfaces for gathering environmental noise
126 * from the devices are:
128 * void add_device_randomness(const void *buf, unsigned int size);
129 * void add_input_randomness(unsigned int type, unsigned int code,
130 * unsigned int value);
131 * void add_interrupt_randomness(int irq, int irq_flags);
132 * void add_disk_randomness(struct gendisk *disk);
134 * add_device_randomness() is for adding data to the random pool that
135 * is likely to differ between two devices (or possibly even per boot).
136 * This would be things like MAC addresses or serial numbers, or the
137 * read-out of the RTC. This does *not* add any actual entropy to the
138 * pool, but it initializes the pool to different values for devices
139 * that might otherwise be identical and have very little entropy
140 * available to them (particularly common in the embedded world).
142 * add_input_randomness() uses the input layer interrupt timing, as well as
143 * the event type information from the hardware.
145 * add_interrupt_randomness() uses the interrupt timing as random
146 * inputs to the entropy pool. Using the cycle counters and the irq source
147 * as inputs, it feeds the randomness roughly once a second.
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.
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.
159 * Ensuring unpredictability at system startup
160 * ============================================
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
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
181 * chmod 600 $random_seed
182 * dd if=/dev/urandom of=$random_seed count=1 bs=512
184 * and the following lines in an appropriate script which is run as
185 * the system is shutdown:
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
192 * chmod 600 $random_seed
193 * dd if=/dev/urandom of=$random_seed count=1 bs=512
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.
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
209 * Configuring the /dev/random driver under Linux
210 * ==============================================
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:
217 * mknod /dev/random c 1 8
218 * mknod /dev/urandom c 1 9
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.
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.
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.
238 #include <linux/utsname.h>
239 #include <linux/module.h>
240 #include <linux/kernel.h>
241 #include <linux/major.h>
242 #include <linux/string.h>
243 #include <linux/fcntl.h>
244 #include <linux/slab.h>
245 #include <linux/random.h>
246 #include <linux/poll.h>
247 #include <linux/init.h>
248 #include <linux/fs.h>
249 #include <linux/genhd.h>
250 #include <linux/interrupt.h>
251 #include <linux/mm.h>
252 #include <linux/spinlock.h>
253 #include <linux/kthread.h>
254 #include <linux/percpu.h>
255 #include <linux/cryptohash.h>
256 #include <linux/fips.h>
257 #include <linux/ptrace.h>
258 #include <linux/kmemcheck.h>
259 #include <linux/workqueue.h>
260 #include <linux/irq.h>
261 #include <linux/syscalls.h>
262 #include <linux/completion.h>
264 #include <asm/processor.h>
265 #include <asm/uaccess.h>
267 #include <asm/irq_regs.h>
270 #define CREATE_TRACE_POINTS
271 #include <trace/events/random.h>
273 /* #define ADD_INTERRUPT_BENCH */
276 * Configuration information
278 #define INPUT_POOL_SHIFT 12
279 #define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
280 #define OUTPUT_POOL_SHIFT 10
281 #define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
282 #define SEC_XFER_SIZE 512
283 #define EXTRACT_SIZE 10
285 #define DEBUG_RANDOM_BOOT 0
287 #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
290 * To allow fractional bits to be tracked, the entropy_count field is
291 * denominated in units of 1/8th bits.
293 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
294 * credit_entropy_bits() needs to be 64 bits wide.
296 #define ENTROPY_SHIFT 3
297 #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
300 * The minimum number of bits of entropy before we wake up a read on
301 * /dev/random. Should be enough to do a significant reseed.
303 static int random_read_wakeup_bits = 64;
306 * If the entropy count falls under this number of bits, then we
307 * should wake up processes which are selecting or polling on write
308 * access to /dev/random.
310 static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
313 * The minimum number of seconds between urandom pool reseeding. We
314 * do this to limit the amount of entropy that can be drained from the
315 * input pool even if there are heavy demands on /dev/urandom.
317 static int random_min_urandom_seed = 60;
320 * Originally, we used a primitive polynomial of degree .poolwords
321 * over GF(2). The taps for various sizes are defined below. They
322 * were chosen to be evenly spaced except for the last tap, which is 1
323 * to get the twisting happening as fast as possible.
325 * For the purposes of better mixing, we use the CRC-32 polynomial as
326 * well to make a (modified) twisted Generalized Feedback Shift
327 * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
328 * generators. ACM Transactions on Modeling and Computer Simulation
329 * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
330 * GFSR generators II. ACM Transactions on Modeling and Computer
331 * Simulation 4:254-266)
333 * Thanks to Colin Plumb for suggesting this.
335 * The mixing operation is much less sensitive than the output hash,
336 * where we use SHA-1. All that we want of mixing operation is that
337 * it be a good non-cryptographic hash; i.e. it not produce collisions
338 * when fed "random" data of the sort we expect to see. As long as
339 * the pool state differs for different inputs, we have preserved the
340 * input entropy and done a good job. The fact that an intelligent
341 * attacker can construct inputs that will produce controlled
342 * alterations to the pool's state is not important because we don't
343 * consider such inputs to contribute any randomness. The only
344 * property we need with respect to them is that the attacker can't
345 * increase his/her knowledge of the pool's state. Since all
346 * additions are reversible (knowing the final state and the input,
347 * you can reconstruct the initial state), if an attacker has any
348 * uncertainty about the initial state, he/she can only shuffle that
349 * uncertainty about, but never cause any collisions (which would
350 * decrease the uncertainty).
352 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
353 * Videau in their paper, "The Linux Pseudorandom Number Generator
354 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
355 * paper, they point out that we are not using a true Twisted GFSR,
356 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
357 * is, with only three taps, instead of the six that we are using).
358 * As a result, the resulting polynomial is neither primitive nor
359 * irreducible, and hence does not have a maximal period over
360 * GF(2**32). They suggest a slight change to the generator
361 * polynomial which improves the resulting TGFSR polynomial to be
362 * irreducible, which we have made here.
364 static struct poolinfo {
365 int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
366 #define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
367 int tap1, tap2, tap3, tap4, tap5;
368 } poolinfo_table[] = {
369 /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
370 /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
371 { S(128), 104, 76, 51, 25, 1 },
372 /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
373 /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
374 { S(32), 26, 19, 14, 7, 1 },
376 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
377 { S(2048), 1638, 1231, 819, 411, 1 },
379 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
380 { S(1024), 817, 615, 412, 204, 1 },
382 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
383 { S(1024), 819, 616, 410, 207, 2 },
385 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
386 { S(512), 411, 308, 208, 104, 1 },
388 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
389 { S(512), 409, 307, 206, 102, 2 },
390 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
391 { S(512), 409, 309, 205, 103, 2 },
393 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
394 { S(256), 205, 155, 101, 52, 1 },
396 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
397 { S(128), 103, 78, 51, 27, 2 },
399 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
400 { S(64), 52, 39, 26, 14, 1 },
405 * Static global variables
407 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
408 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
409 static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
410 static struct fasync_struct *fasync;
412 /**********************************************************************
414 * OS independent entropy store. Here are the functions which handle
415 * storing entropy in an entropy pool.
417 **********************************************************************/
419 struct entropy_store;
420 struct entropy_store {
421 /* read-only data: */
422 const struct poolinfo *poolinfo;
425 struct entropy_store *pull;
426 struct work_struct push_work;
428 /* read-write data: */
429 unsigned long last_pulled;
431 unsigned short add_ptr;
432 unsigned short input_rotate;
435 unsigned int initialized:1;
436 unsigned int limit:1;
437 unsigned int last_data_init:1;
438 __u8 last_data[EXTRACT_SIZE];
441 static void push_to_pool(struct work_struct *work);
442 static __u32 input_pool_data[INPUT_POOL_WORDS];
443 static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
444 static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
446 static struct entropy_store input_pool = {
447 .poolinfo = &poolinfo_table[0],
450 .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
451 .pool = input_pool_data
454 static struct entropy_store blocking_pool = {
455 .poolinfo = &poolinfo_table[1],
459 .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
460 .pool = blocking_pool_data,
461 .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
465 static struct entropy_store nonblocking_pool = {
466 .poolinfo = &poolinfo_table[1],
467 .name = "nonblocking",
469 .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
470 .pool = nonblocking_pool_data,
471 .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
475 static __u32 const twist_table[8] = {
476 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
477 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
480 * This function adds bytes into the entropy "pool". It does not
481 * update the entropy estimate. The caller should call
482 * credit_entropy_bits if this is appropriate.
484 * The pool is stirred with a primitive polynomial of the appropriate
485 * degree, and then twisted. We twist by three bits at a time because
486 * it's cheap to do so and helps slightly in the expected case where
487 * the entropy is concentrated in the low-order bits.
489 static void _mix_pool_bytes(struct entropy_store *r, const void *in,
492 unsigned long i, tap1, tap2, tap3, tap4, tap5;
494 int wordmask = r->poolinfo->poolwords - 1;
495 const char *bytes = in;
498 tap1 = r->poolinfo->tap1;
499 tap2 = r->poolinfo->tap2;
500 tap3 = r->poolinfo->tap3;
501 tap4 = r->poolinfo->tap4;
502 tap5 = r->poolinfo->tap5;
504 input_rotate = r->input_rotate;
507 /* mix one byte at a time to simplify size handling and churn faster */
509 w = rol32(*bytes++, input_rotate);
510 i = (i - 1) & wordmask;
512 /* XOR in the various taps */
514 w ^= r->pool[(i + tap1) & wordmask];
515 w ^= r->pool[(i + tap2) & wordmask];
516 w ^= r->pool[(i + tap3) & wordmask];
517 w ^= r->pool[(i + tap4) & wordmask];
518 w ^= r->pool[(i + tap5) & wordmask];
520 /* Mix the result back in with a twist */
521 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
524 * Normally, we add 7 bits of rotation to the pool.
525 * At the beginning of the pool, add an extra 7 bits
526 * rotation, so that successive passes spread the
527 * input bits across the pool evenly.
529 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
532 r->input_rotate = input_rotate;
536 static void __mix_pool_bytes(struct entropy_store *r, const void *in,
539 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
540 _mix_pool_bytes(r, in, nbytes);
543 static void mix_pool_bytes(struct entropy_store *r, const void *in,
548 trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
549 spin_lock_irqsave(&r->lock, flags);
550 _mix_pool_bytes(r, in, nbytes);
551 spin_unlock_irqrestore(&r->lock, flags);
557 unsigned short reg_idx;
562 * This is a fast mixing routine used by the interrupt randomness
563 * collector. It's hardcoded for an 128 bit pool and assumes that any
564 * locks that might be needed are taken by the caller.
566 static void fast_mix(struct fast_pool *f)
568 __u32 a = f->pool[0], b = f->pool[1];
569 __u32 c = f->pool[2], d = f->pool[3];
572 b = rol32(b, 6); d = rol32(d, 27);
576 b = rol32(b, 16); d = rol32(d, 14);
580 b = rol32(b, 6); d = rol32(d, 27);
584 b = rol32(b, 16); d = rol32(d, 14);
587 f->pool[0] = a; f->pool[1] = b;
588 f->pool[2] = c; f->pool[3] = d;
593 * Credit (or debit) the entropy store with n bits of entropy.
594 * Use credit_entropy_bits_safe() if the value comes from userspace
595 * or otherwise should be checked for extreme values.
597 static void credit_entropy_bits(struct entropy_store *r, int nbits)
599 int entropy_count, orig;
600 const int pool_size = r->poolinfo->poolfracbits;
601 int nfrac = nbits << ENTROPY_SHIFT;
607 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
610 entropy_count += nfrac;
613 * Credit: we have to account for the possibility of
614 * overwriting already present entropy. Even in the
615 * ideal case of pure Shannon entropy, new contributions
616 * approach the full value asymptotically:
618 * entropy <- entropy + (pool_size - entropy) *
619 * (1 - exp(-add_entropy/pool_size))
621 * For add_entropy <= pool_size/2 then
622 * (1 - exp(-add_entropy/pool_size)) >=
623 * (add_entropy/pool_size)*0.7869...
624 * so we can approximate the exponential with
625 * 3/4*add_entropy/pool_size and still be on the
626 * safe side by adding at most pool_size/2 at a time.
628 * The use of pool_size-2 in the while statement is to
629 * prevent rounding artifacts from making the loop
630 * arbitrarily long; this limits the loop to log2(pool_size)*2
631 * turns no matter how large nbits is.
634 const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
635 /* The +2 corresponds to the /4 in the denominator */
638 unsigned int anfrac = min(pnfrac, pool_size/2);
640 ((pool_size - entropy_count)*anfrac*3) >> s;
642 entropy_count += add;
644 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
647 if (unlikely(entropy_count < 0)) {
648 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
649 r->name, entropy_count);
652 } else if (entropy_count > pool_size)
653 entropy_count = pool_size;
654 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
657 r->entropy_total += nbits;
658 if (!r->initialized && r->entropy_total > 128) {
660 r->entropy_total = 0;
661 if (r == &nonblocking_pool) {
662 prandom_reseed_late();
663 wake_up_all(&urandom_init_wait);
664 pr_notice("random: %s pool is initialized\n", r->name);
668 trace_credit_entropy_bits(r->name, nbits,
669 entropy_count >> ENTROPY_SHIFT,
670 r->entropy_total, _RET_IP_);
672 if (r == &input_pool) {
673 int entropy_bits = entropy_count >> ENTROPY_SHIFT;
675 /* should we wake readers? */
676 if (entropy_bits >= random_read_wakeup_bits) {
677 wake_up_interruptible(&random_read_wait);
678 kill_fasync(&fasync, SIGIO, POLL_IN);
680 /* If the input pool is getting full, send some
681 * entropy to the two output pools, flipping back and
682 * forth between them, until the output pools are 75%
685 if (entropy_bits > random_write_wakeup_bits &&
687 r->entropy_total >= 2*random_read_wakeup_bits) {
688 static struct entropy_store *last = &blocking_pool;
689 struct entropy_store *other = &blocking_pool;
691 if (last == &blocking_pool)
692 other = &nonblocking_pool;
693 if (other->entropy_count <=
694 3 * other->poolinfo->poolfracbits / 4)
696 if (last->entropy_count <=
697 3 * last->poolinfo->poolfracbits / 4) {
698 schedule_work(&last->push_work);
699 r->entropy_total = 0;
705 static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
707 const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
709 /* Cap the value to avoid overflows */
710 nbits = min(nbits, nbits_max);
711 nbits = max(nbits, -nbits_max);
713 credit_entropy_bits(r, nbits);
716 /*********************************************************************
718 * Entropy input management
720 *********************************************************************/
722 /* There is one of these per entropy source */
723 struct timer_rand_state {
725 long last_delta, last_delta2;
726 unsigned dont_count_entropy:1;
729 #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
732 * Add device- or boot-specific data to the input and nonblocking
733 * pools to help initialize them to unique values.
735 * None of this adds any entropy, it is meant to avoid the
736 * problem of the nonblocking pool having similar initial state
737 * across largely identical devices.
739 void add_device_randomness(const void *buf, unsigned int size)
741 unsigned long time = random_get_entropy() ^ jiffies;
744 trace_add_device_randomness(size, _RET_IP_);
745 spin_lock_irqsave(&input_pool.lock, flags);
746 _mix_pool_bytes(&input_pool, buf, size);
747 _mix_pool_bytes(&input_pool, &time, sizeof(time));
748 spin_unlock_irqrestore(&input_pool.lock, flags);
750 spin_lock_irqsave(&nonblocking_pool.lock, flags);
751 _mix_pool_bytes(&nonblocking_pool, buf, size);
752 _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
753 spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
755 EXPORT_SYMBOL(add_device_randomness);
757 static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
760 * This function adds entropy to the entropy "pool" by using timing
761 * delays. It uses the timer_rand_state structure to make an estimate
762 * of how many bits of entropy this call has added to the pool.
764 * The number "num" is also added to the pool - it should somehow describe
765 * the type of event which just happened. This is currently 0-255 for
766 * keyboard scan codes, and 256 upwards for interrupts.
769 static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
771 struct entropy_store *r;
777 long delta, delta2, delta3;
781 sample.jiffies = jiffies;
782 sample.cycles = random_get_entropy();
784 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
785 mix_pool_bytes(r, &sample, sizeof(sample));
788 * Calculate number of bits of randomness we probably added.
789 * We take into account the first, second and third-order deltas
790 * in order to make our estimate.
793 if (!state->dont_count_entropy) {
794 delta = sample.jiffies - state->last_time;
795 state->last_time = sample.jiffies;
797 delta2 = delta - state->last_delta;
798 state->last_delta = delta;
800 delta3 = delta2 - state->last_delta2;
801 state->last_delta2 = delta2;
815 * delta is now minimum absolute delta.
816 * Round down by 1 bit on general principles,
817 * and limit entropy entimate to 12 bits.
819 credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
824 void add_input_randomness(unsigned int type, unsigned int code,
827 static unsigned char last_value;
829 /* ignore autorepeat and the like */
830 if (value == last_value)
834 add_timer_randomness(&input_timer_state,
835 (type << 4) ^ code ^ (code >> 4) ^ value);
836 trace_add_input_randomness(ENTROPY_BITS(&input_pool));
838 EXPORT_SYMBOL_GPL(add_input_randomness);
840 static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
842 #ifdef ADD_INTERRUPT_BENCH
843 static unsigned long avg_cycles, avg_deviation;
845 #define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
846 #define FIXED_1_2 (1 << (AVG_SHIFT-1))
848 static void add_interrupt_bench(cycles_t start)
850 long delta = random_get_entropy() - start;
852 /* Use a weighted moving average */
853 delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
855 /* And average deviation */
856 delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
857 avg_deviation += delta;
860 #define add_interrupt_bench(x)
863 static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
865 __u32 *ptr = (__u32 *) regs;
869 if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
871 return *(ptr + f->reg_idx++);
874 void add_interrupt_randomness(int irq, int irq_flags)
876 struct entropy_store *r;
877 struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
878 struct pt_regs *regs = get_irq_regs();
879 unsigned long now = jiffies;
880 cycles_t cycles = random_get_entropy();
881 __u32 c_high, j_high;
887 cycles = get_reg(fast_pool, regs);
888 c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
889 j_high = (sizeof(now) > 4) ? now >> 32 : 0;
890 fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
891 fast_pool->pool[1] ^= now ^ c_high;
892 ip = regs ? instruction_pointer(regs) : _RET_IP_;
893 fast_pool->pool[2] ^= ip;
894 fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
895 get_reg(fast_pool, regs);
898 add_interrupt_bench(cycles);
900 if ((fast_pool->count < 64) &&
901 !time_after(now, fast_pool->last + HZ))
904 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
905 if (!spin_trylock(&r->lock))
908 fast_pool->last = now;
909 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
912 * If we have architectural seed generator, produce a seed and
913 * add it to the pool. For the sake of paranoia don't let the
914 * architectural seed generator dominate the input from the
917 if (arch_get_random_seed_long(&seed)) {
918 __mix_pool_bytes(r, &seed, sizeof(seed));
921 spin_unlock(&r->lock);
923 fast_pool->count = 0;
925 /* award one bit for the contents of the fast pool */
926 credit_entropy_bits(r, credit + 1);
930 void add_disk_randomness(struct gendisk *disk)
932 if (!disk || !disk->random)
934 /* first major is 1, so we get >= 0x200 here */
935 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
936 trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
938 EXPORT_SYMBOL_GPL(add_disk_randomness);
941 /*********************************************************************
943 * Entropy extraction routines
945 *********************************************************************/
947 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
948 size_t nbytes, int min, int rsvd);
951 * This utility inline function is responsible for transferring entropy
952 * from the primary pool to the secondary extraction pool. We make
953 * sure we pull enough for a 'catastrophic reseed'.
955 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
956 static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
959 r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
960 r->entropy_count > r->poolinfo->poolfracbits)
963 if (r->limit == 0 && random_min_urandom_seed) {
964 unsigned long now = jiffies;
967 r->last_pulled + random_min_urandom_seed * HZ))
969 r->last_pulled = now;
972 _xfer_secondary_pool(r, nbytes);
975 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
977 __u32 tmp[OUTPUT_POOL_WORDS];
979 /* For /dev/random's pool, always leave two wakeups' worth */
980 int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
983 /* pull at least as much as a wakeup */
984 bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
985 /* but never more than the buffer size */
986 bytes = min_t(int, bytes, sizeof(tmp));
988 trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
989 ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
990 bytes = extract_entropy(r->pull, tmp, bytes,
991 random_read_wakeup_bits / 8, rsvd_bytes);
992 mix_pool_bytes(r, tmp, bytes);
993 credit_entropy_bits(r, bytes*8);
997 * Used as a workqueue function so that when the input pool is getting
998 * full, we can "spill over" some entropy to the output pools. That
999 * way the output pools can store some of the excess entropy instead
1000 * of letting it go to waste.
1002 static void push_to_pool(struct work_struct *work)
1004 struct entropy_store *r = container_of(work, struct entropy_store,
1007 _xfer_secondary_pool(r, random_read_wakeup_bits/8);
1008 trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1009 r->pull->entropy_count >> ENTROPY_SHIFT);
1013 * This function decides how many bytes to actually take from the
1014 * given pool, and also debits the entropy count accordingly.
1016 static size_t account(struct entropy_store *r, size_t nbytes, int min,
1019 int entropy_count, orig;
1020 size_t ibytes, nfrac;
1022 BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1024 /* Can we pull enough? */
1026 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
1028 /* If limited, never pull more than available */
1030 int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1032 if ((have_bytes -= reserved) < 0)
1034 ibytes = min_t(size_t, ibytes, have_bytes);
1039 if (unlikely(entropy_count < 0)) {
1040 pr_warn("random: negative entropy count: pool %s count %d\n",
1041 r->name, entropy_count);
1045 nfrac = ibytes << (ENTROPY_SHIFT + 3);
1046 if ((size_t) entropy_count > nfrac)
1047 entropy_count -= nfrac;
1051 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1054 trace_debit_entropy(r->name, 8 * ibytes);
1056 (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1057 wake_up_interruptible(&random_write_wait);
1058 kill_fasync(&fasync, SIGIO, POLL_OUT);
1065 * This function does the actual extraction for extract_entropy and
1066 * extract_entropy_user.
1068 * Note: we assume that .poolwords is a multiple of 16 words.
1070 static void extract_buf(struct entropy_store *r, __u8 *out)
1075 unsigned long l[LONGS(20)];
1077 __u32 workspace[SHA_WORKSPACE_WORDS];
1078 unsigned long flags;
1081 * If we have an architectural hardware random number
1082 * generator, use it for SHA's initial vector
1085 for (i = 0; i < LONGS(20); i++) {
1087 if (!arch_get_random_long(&v))
1092 /* Generate a hash across the pool, 16 words (512 bits) at a time */
1093 spin_lock_irqsave(&r->lock, flags);
1094 for (i = 0; i < r->poolinfo->poolwords; i += 16)
1095 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1098 * We mix the hash back into the pool to prevent backtracking
1099 * attacks (where the attacker knows the state of the pool
1100 * plus the current outputs, and attempts to find previous
1101 * ouputs), unless the hash function can be inverted. By
1102 * mixing at least a SHA1 worth of hash data back, we make
1103 * brute-forcing the feedback as hard as brute-forcing the
1106 __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1107 spin_unlock_irqrestore(&r->lock, flags);
1109 memzero_explicit(workspace, sizeof(workspace));
1112 * In case the hash function has some recognizable output
1113 * pattern, we fold it in half. Thus, we always feed back
1114 * twice as much data as we output.
1116 hash.w[0] ^= hash.w[3];
1117 hash.w[1] ^= hash.w[4];
1118 hash.w[2] ^= rol32(hash.w[2], 16);
1120 memcpy(out, &hash, EXTRACT_SIZE);
1121 memzero_explicit(&hash, sizeof(hash));
1125 * This function extracts randomness from the "entropy pool", and
1126 * returns it in a buffer.
1128 * The min parameter specifies the minimum amount we can pull before
1129 * failing to avoid races that defeat catastrophic reseeding while the
1130 * reserved parameter indicates how much entropy we must leave in the
1131 * pool after each pull to avoid starving other readers.
1133 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1134 size_t nbytes, int min, int reserved)
1137 __u8 tmp[EXTRACT_SIZE];
1138 unsigned long flags;
1140 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1142 spin_lock_irqsave(&r->lock, flags);
1143 if (!r->last_data_init) {
1144 r->last_data_init = 1;
1145 spin_unlock_irqrestore(&r->lock, flags);
1146 trace_extract_entropy(r->name, EXTRACT_SIZE,
1147 ENTROPY_BITS(r), _RET_IP_);
1148 xfer_secondary_pool(r, EXTRACT_SIZE);
1149 extract_buf(r, tmp);
1150 spin_lock_irqsave(&r->lock, flags);
1151 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1153 spin_unlock_irqrestore(&r->lock, flags);
1156 trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1157 xfer_secondary_pool(r, nbytes);
1158 nbytes = account(r, nbytes, min, reserved);
1161 extract_buf(r, tmp);
1164 spin_lock_irqsave(&r->lock, flags);
1165 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1166 panic("Hardware RNG duplicated output!\n");
1167 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1168 spin_unlock_irqrestore(&r->lock, flags);
1170 i = min_t(int, nbytes, EXTRACT_SIZE);
1171 memcpy(buf, tmp, i);
1177 /* Wipe data just returned from memory */
1178 memzero_explicit(tmp, sizeof(tmp));
1184 * This function extracts randomness from the "entropy pool", and
1185 * returns it in a userspace buffer.
1187 static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1191 __u8 tmp[EXTRACT_SIZE];
1192 int large_request = (nbytes > 256);
1194 trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1195 xfer_secondary_pool(r, nbytes);
1196 nbytes = account(r, nbytes, 0, 0);
1199 if (large_request && need_resched()) {
1200 if (signal_pending(current)) {
1208 extract_buf(r, tmp);
1209 i = min_t(int, nbytes, EXTRACT_SIZE);
1210 if (copy_to_user(buf, tmp, i)) {
1220 /* Wipe data just returned from memory */
1221 memzero_explicit(tmp, sizeof(tmp));
1227 * This function is the exported kernel interface. It returns some
1228 * number of good random numbers, suitable for key generation, seeding
1229 * TCP sequence numbers, etc. It does not rely on the hardware random
1230 * number generator. For random bytes direct from the hardware RNG
1231 * (when available), use get_random_bytes_arch().
1233 void get_random_bytes(void *buf, int nbytes)
1235 #if DEBUG_RANDOM_BOOT > 0
1236 if (unlikely(nonblocking_pool.initialized == 0))
1237 printk(KERN_NOTICE "random: %pF get_random_bytes called "
1238 "with %d bits of entropy available\n",
1240 nonblocking_pool.entropy_total);
1242 trace_get_random_bytes(nbytes, _RET_IP_);
1243 extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1245 EXPORT_SYMBOL(get_random_bytes);
1248 * Equivalent function to get_random_bytes with the difference that this
1249 * function blocks the request until the nonblocking_pool is initialized.
1251 void get_blocking_random_bytes(void *buf, int nbytes)
1253 if (unlikely(nonblocking_pool.initialized == 0))
1254 wait_event(urandom_init_wait, nonblocking_pool.initialized);
1255 extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1257 EXPORT_SYMBOL(get_blocking_random_bytes);
1260 * This function will use the architecture-specific hardware random
1261 * number generator if it is available. The arch-specific hw RNG will
1262 * almost certainly be faster than what we can do in software, but it
1263 * is impossible to verify that it is implemented securely (as
1264 * opposed, to, say, the AES encryption of a sequence number using a
1265 * key known by the NSA). So it's useful if we need the speed, but
1266 * only if we're willing to trust the hardware manufacturer not to
1267 * have put in a back door.
1269 void get_random_bytes_arch(void *buf, int nbytes)
1273 trace_get_random_bytes_arch(nbytes, _RET_IP_);
1276 int chunk = min(nbytes, (int)sizeof(unsigned long));
1278 if (!arch_get_random_long(&v))
1281 memcpy(p, &v, chunk);
1287 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1289 EXPORT_SYMBOL(get_random_bytes_arch);
1293 * init_std_data - initialize pool with system data
1295 * @r: pool to initialize
1297 * This function clears the pool's entropy count and mixes some system
1298 * data into the pool to prepare it for use. The pool is not cleared
1299 * as that can only decrease the entropy in the pool.
1301 static void init_std_data(struct entropy_store *r)
1304 ktime_t now = ktime_get_real();
1307 r->last_pulled = jiffies;
1308 mix_pool_bytes(r, &now, sizeof(now));
1309 for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1310 if (!arch_get_random_seed_long(&rv) &&
1311 !arch_get_random_long(&rv))
1312 rv = random_get_entropy();
1313 mix_pool_bytes(r, &rv, sizeof(rv));
1315 mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1319 * Note that setup_arch() may call add_device_randomness()
1320 * long before we get here. This allows seeding of the pools
1321 * with some platform dependent data very early in the boot
1322 * process. But it limits our options here. We must use
1323 * statically allocated structures that already have all
1324 * initializations complete at compile time. We should also
1325 * take care not to overwrite the precious per platform data
1328 static int rand_initialize(void)
1330 init_std_data(&input_pool);
1331 init_std_data(&blocking_pool);
1332 init_std_data(&nonblocking_pool);
1335 early_initcall(rand_initialize);
1338 void rand_initialize_disk(struct gendisk *disk)
1340 struct timer_rand_state *state;
1343 * If kzalloc returns null, we just won't use that entropy
1346 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1348 state->last_time = INITIAL_JIFFIES;
1349 disk->random = state;
1355 _random_read(int nonblock, char __user *buf, size_t nbytes)
1362 nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1364 n = extract_entropy_user(&blocking_pool, buf, nbytes);
1367 trace_random_read(n*8, (nbytes-n)*8,
1368 ENTROPY_BITS(&blocking_pool),
1369 ENTROPY_BITS(&input_pool));
1373 /* Pool is (near) empty. Maybe wait and retry. */
1377 wait_event_interruptible(random_read_wait,
1378 ENTROPY_BITS(&input_pool) >=
1379 random_read_wakeup_bits);
1380 if (signal_pending(current))
1381 return -ERESTARTSYS;
1386 random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1388 return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1392 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1396 if (unlikely(nonblocking_pool.initialized == 0))
1397 printk_once(KERN_NOTICE "random: %s urandom read "
1398 "with %d bits of entropy available\n",
1399 current->comm, nonblocking_pool.entropy_total);
1401 nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1402 ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
1404 trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
1405 ENTROPY_BITS(&input_pool));
1410 random_poll(struct file *file, poll_table * wait)
1414 poll_wait(file, &random_read_wait, wait);
1415 poll_wait(file, &random_write_wait, wait);
1417 if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1418 mask |= POLLIN | POLLRDNORM;
1419 if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1420 mask |= POLLOUT | POLLWRNORM;
1425 write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1429 const char __user *p = buffer;
1432 bytes = min(count, sizeof(buf));
1433 if (copy_from_user(&buf, p, bytes))
1439 mix_pool_bytes(r, buf, bytes);
1446 static ssize_t random_write(struct file *file, const char __user *buffer,
1447 size_t count, loff_t *ppos)
1451 ret = write_pool(&blocking_pool, buffer, count);
1454 ret = write_pool(&nonblocking_pool, buffer, count);
1458 return (ssize_t)count;
1461 static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1463 int size, ent_count;
1464 int __user *p = (int __user *)arg;
1469 /* inherently racy, no point locking */
1470 ent_count = ENTROPY_BITS(&input_pool);
1471 if (put_user(ent_count, p))
1474 case RNDADDTOENTCNT:
1475 if (!capable(CAP_SYS_ADMIN))
1477 if (get_user(ent_count, p))
1479 credit_entropy_bits_safe(&input_pool, ent_count);
1482 if (!capable(CAP_SYS_ADMIN))
1484 if (get_user(ent_count, p++))
1488 if (get_user(size, p++))
1490 retval = write_pool(&input_pool, (const char __user *)p,
1494 credit_entropy_bits_safe(&input_pool, ent_count);
1499 * Clear the entropy pool counters. We no longer clear
1500 * the entropy pool, as that's silly.
1502 if (!capable(CAP_SYS_ADMIN))
1504 input_pool.entropy_count = 0;
1505 nonblocking_pool.entropy_count = 0;
1506 blocking_pool.entropy_count = 0;
1513 static int random_fasync(int fd, struct file *filp, int on)
1515 return fasync_helper(fd, filp, on, &fasync);
1518 const struct file_operations random_fops = {
1519 .read = random_read,
1520 .write = random_write,
1521 .poll = random_poll,
1522 .unlocked_ioctl = random_ioctl,
1523 .fasync = random_fasync,
1524 .llseek = noop_llseek,
1527 const struct file_operations urandom_fops = {
1528 .read = urandom_read,
1529 .write = random_write,
1530 .unlocked_ioctl = random_ioctl,
1531 .fasync = random_fasync,
1532 .llseek = noop_llseek,
1535 SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1536 unsigned int, flags)
1538 if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
1541 if (count > INT_MAX)
1544 if (flags & GRND_RANDOM)
1545 return _random_read(flags & GRND_NONBLOCK, buf, count);
1547 if (unlikely(nonblocking_pool.initialized == 0)) {
1548 if (flags & GRND_NONBLOCK)
1550 wait_event_interruptible(urandom_init_wait,
1551 nonblocking_pool.initialized);
1552 if (signal_pending(current))
1553 return -ERESTARTSYS;
1555 return urandom_read(NULL, buf, count, NULL);
1558 /***************************************************************
1559 * Random UUID interface
1561 * Used here for a Boot ID, but can be useful for other kernel
1563 ***************************************************************/
1566 * Generate random UUID
1568 void generate_random_uuid(unsigned char uuid_out[16])
1570 get_random_bytes(uuid_out, 16);
1571 /* Set UUID version to 4 --- truly random generation */
1572 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1573 /* Set the UUID variant to DCE */
1574 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1576 EXPORT_SYMBOL(generate_random_uuid);
1578 /********************************************************************
1582 ********************************************************************/
1584 #ifdef CONFIG_SYSCTL
1586 #include <linux/sysctl.h>
1588 static int min_read_thresh = 8, min_write_thresh;
1589 static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1590 static int max_write_thresh = INPUT_POOL_WORDS * 32;
1591 static char sysctl_bootid[16];
1594 * This function is used to return both the bootid UUID, and random
1595 * UUID. The difference is in whether table->data is NULL; if it is,
1596 * then a new UUID is generated and returned to the user.
1598 * If the user accesses this via the proc interface, the UUID will be
1599 * returned as an ASCII string in the standard UUID format; if via the
1600 * sysctl system call, as 16 bytes of binary data.
1602 static int proc_do_uuid(struct ctl_table *table, int write,
1603 void __user *buffer, size_t *lenp, loff_t *ppos)
1605 struct ctl_table fake_table;
1606 unsigned char buf[64], tmp_uuid[16], *uuid;
1611 generate_random_uuid(uuid);
1613 static DEFINE_SPINLOCK(bootid_spinlock);
1615 spin_lock(&bootid_spinlock);
1617 generate_random_uuid(uuid);
1618 spin_unlock(&bootid_spinlock);
1621 sprintf(buf, "%pU", uuid);
1623 fake_table.data = buf;
1624 fake_table.maxlen = sizeof(buf);
1626 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1630 * Return entropy available scaled to integral bits
1632 static int proc_do_entropy(struct ctl_table *table, int write,
1633 void __user *buffer, size_t *lenp, loff_t *ppos)
1635 struct ctl_table fake_table;
1638 entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1640 fake_table.data = &entropy_count;
1641 fake_table.maxlen = sizeof(entropy_count);
1643 return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1646 static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1647 extern struct ctl_table random_table[];
1648 struct ctl_table random_table[] = {
1650 .procname = "poolsize",
1651 .data = &sysctl_poolsize,
1652 .maxlen = sizeof(int),
1654 .proc_handler = proc_dointvec,
1657 .procname = "entropy_avail",
1658 .maxlen = sizeof(int),
1660 .proc_handler = proc_do_entropy,
1661 .data = &input_pool.entropy_count,
1664 .procname = "read_wakeup_threshold",
1665 .data = &random_read_wakeup_bits,
1666 .maxlen = sizeof(int),
1668 .proc_handler = proc_dointvec_minmax,
1669 .extra1 = &min_read_thresh,
1670 .extra2 = &max_read_thresh,
1673 .procname = "write_wakeup_threshold",
1674 .data = &random_write_wakeup_bits,
1675 .maxlen = sizeof(int),
1677 .proc_handler = proc_dointvec_minmax,
1678 .extra1 = &min_write_thresh,
1679 .extra2 = &max_write_thresh,
1682 .procname = "urandom_min_reseed_secs",
1683 .data = &random_min_urandom_seed,
1684 .maxlen = sizeof(int),
1686 .proc_handler = proc_dointvec,
1689 .procname = "boot_id",
1690 .data = &sysctl_bootid,
1693 .proc_handler = proc_do_uuid,
1699 .proc_handler = proc_do_uuid,
1701 #ifdef ADD_INTERRUPT_BENCH
1703 .procname = "add_interrupt_avg_cycles",
1704 .data = &avg_cycles,
1705 .maxlen = sizeof(avg_cycles),
1707 .proc_handler = proc_doulongvec_minmax,
1710 .procname = "add_interrupt_avg_deviation",
1711 .data = &avg_deviation,
1712 .maxlen = sizeof(avg_deviation),
1714 .proc_handler = proc_doulongvec_minmax,
1719 #endif /* CONFIG_SYSCTL */
1721 static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1723 int random_int_secret_init(void)
1725 get_random_bytes(random_int_secret, sizeof(random_int_secret));
1730 * Get a random word for internal kernel use only. Similar to urandom but
1731 * with the goal of minimal entropy pool depletion. As a result, the random
1732 * value is not cryptographically secure but for several uses the cost of
1733 * depleting entropy is too high
1735 static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1736 unsigned int get_random_int(void)
1741 if (arch_get_random_int(&ret))
1744 hash = get_cpu_var(get_random_int_hash);
1746 hash[0] += current->pid + jiffies + random_get_entropy();
1747 md5_transform(hash, random_int_secret);
1749 put_cpu_var(get_random_int_hash);
1753 EXPORT_SYMBOL(get_random_int);
1756 * randomize_range() returns a start address such that
1758 * [...... <range> .....]
1761 * a <range> with size "len" starting at the return value is inside in the
1762 * area defined by [start, end], but is otherwise randomized.
1765 randomize_range(unsigned long start, unsigned long end, unsigned long len)
1767 unsigned long range = end - len - start;
1769 if (end <= start + len)
1771 return PAGE_ALIGN(get_random_int() % range + start);
1774 /* Interface for in-kernel drivers of true hardware RNGs.
1775 * Those devices may produce endless random bits and will be throttled
1776 * when our pool is full.
1778 void add_hwgenerator_randomness(const char *buffer, size_t count,
1781 struct entropy_store *poolp = &input_pool;
1783 /* Suspend writing if we're above the trickle threshold.
1784 * We'll be woken up again once below random_write_wakeup_thresh,
1785 * or when the calling thread is about to terminate.
1787 wait_event_interruptible(random_write_wait, kthread_should_stop() ||
1788 ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
1789 mix_pool_bytes(poolp, buffer, count);
1790 credit_entropy_bits(poolp, entropy);
1792 EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);