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 static DEFINE_SPINLOCK(random_ready_list_lock
);
413 static LIST_HEAD(random_ready_list
);
415 /**********************************************************************
417 * OS independent entropy store. Here are the functions which handle
418 * storing entropy in an entropy pool.
420 **********************************************************************/
422 struct entropy_store
;
423 struct entropy_store
{
424 /* read-only data: */
425 const struct poolinfo
*poolinfo
;
428 struct entropy_store
*pull
;
429 struct work_struct push_work
;
431 /* read-write data: */
432 unsigned long last_pulled
;
434 unsigned short add_ptr
;
435 unsigned short input_rotate
;
438 unsigned int initialized
:1;
439 unsigned int limit
:1;
440 unsigned int last_data_init
:1;
441 __u8 last_data
[EXTRACT_SIZE
];
444 static void push_to_pool(struct work_struct
*work
);
445 static __u32 input_pool_data
[INPUT_POOL_WORDS
];
446 static __u32 blocking_pool_data
[OUTPUT_POOL_WORDS
];
447 static __u32 nonblocking_pool_data
[OUTPUT_POOL_WORDS
];
449 static struct entropy_store input_pool
= {
450 .poolinfo
= &poolinfo_table
[0],
453 .lock
= __SPIN_LOCK_UNLOCKED(input_pool
.lock
),
454 .pool
= input_pool_data
457 static struct entropy_store blocking_pool
= {
458 .poolinfo
= &poolinfo_table
[1],
462 .lock
= __SPIN_LOCK_UNLOCKED(blocking_pool
.lock
),
463 .pool
= blocking_pool_data
,
464 .push_work
= __WORK_INITIALIZER(blocking_pool
.push_work
,
468 static struct entropy_store nonblocking_pool
= {
469 .poolinfo
= &poolinfo_table
[1],
470 .name
= "nonblocking",
472 .lock
= __SPIN_LOCK_UNLOCKED(nonblocking_pool
.lock
),
473 .pool
= nonblocking_pool_data
,
474 .push_work
= __WORK_INITIALIZER(nonblocking_pool
.push_work
,
478 static __u32
const twist_table
[8] = {
479 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
480 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
483 * This function adds bytes into the entropy "pool". It does not
484 * update the entropy estimate. The caller should call
485 * credit_entropy_bits if this is appropriate.
487 * The pool is stirred with a primitive polynomial of the appropriate
488 * degree, and then twisted. We twist by three bits at a time because
489 * it's cheap to do so and helps slightly in the expected case where
490 * the entropy is concentrated in the low-order bits.
492 static void _mix_pool_bytes(struct entropy_store
*r
, const void *in
,
495 unsigned long i
, tap1
, tap2
, tap3
, tap4
, tap5
;
497 int wordmask
= r
->poolinfo
->poolwords
- 1;
498 const char *bytes
= in
;
501 tap1
= r
->poolinfo
->tap1
;
502 tap2
= r
->poolinfo
->tap2
;
503 tap3
= r
->poolinfo
->tap3
;
504 tap4
= r
->poolinfo
->tap4
;
505 tap5
= r
->poolinfo
->tap5
;
507 input_rotate
= r
->input_rotate
;
510 /* mix one byte at a time to simplify size handling and churn faster */
512 w
= rol32(*bytes
++, input_rotate
);
513 i
= (i
- 1) & wordmask
;
515 /* XOR in the various taps */
517 w
^= r
->pool
[(i
+ tap1
) & wordmask
];
518 w
^= r
->pool
[(i
+ tap2
) & wordmask
];
519 w
^= r
->pool
[(i
+ tap3
) & wordmask
];
520 w
^= r
->pool
[(i
+ tap4
) & wordmask
];
521 w
^= r
->pool
[(i
+ tap5
) & wordmask
];
523 /* Mix the result back in with a twist */
524 r
->pool
[i
] = (w
>> 3) ^ twist_table
[w
& 7];
527 * Normally, we add 7 bits of rotation to the pool.
528 * At the beginning of the pool, add an extra 7 bits
529 * rotation, so that successive passes spread the
530 * input bits across the pool evenly.
532 input_rotate
= (input_rotate
+ (i
? 7 : 14)) & 31;
535 r
->input_rotate
= input_rotate
;
539 static void __mix_pool_bytes(struct entropy_store
*r
, const void *in
,
542 trace_mix_pool_bytes_nolock(r
->name
, nbytes
, _RET_IP_
);
543 _mix_pool_bytes(r
, in
, nbytes
);
546 static void mix_pool_bytes(struct entropy_store
*r
, const void *in
,
551 trace_mix_pool_bytes(r
->name
, nbytes
, _RET_IP_
);
552 spin_lock_irqsave(&r
->lock
, flags
);
553 _mix_pool_bytes(r
, in
, nbytes
);
554 spin_unlock_irqrestore(&r
->lock
, flags
);
560 unsigned short reg_idx
;
565 * This is a fast mixing routine used by the interrupt randomness
566 * collector. It's hardcoded for an 128 bit pool and assumes that any
567 * locks that might be needed are taken by the caller.
569 static void fast_mix(struct fast_pool
*f
)
571 __u32 a
= f
->pool
[0], b
= f
->pool
[1];
572 __u32 c
= f
->pool
[2], d
= f
->pool
[3];
575 b
= rol32(b
, 6); d
= rol32(d
, 27);
579 b
= rol32(b
, 16); d
= rol32(d
, 14);
583 b
= rol32(b
, 6); d
= rol32(d
, 27);
587 b
= rol32(b
, 16); d
= rol32(d
, 14);
590 f
->pool
[0] = a
; f
->pool
[1] = b
;
591 f
->pool
[2] = c
; f
->pool
[3] = d
;
595 static void process_random_ready_list(void)
598 struct random_ready_callback
*rdy
, *tmp
;
600 spin_lock_irqsave(&random_ready_list_lock
, flags
);
601 list_for_each_entry_safe(rdy
, tmp
, &random_ready_list
, list
) {
602 struct module
*owner
= rdy
->owner
;
604 list_del_init(&rdy
->list
);
608 spin_unlock_irqrestore(&random_ready_list_lock
, flags
);
612 * Credit (or debit) the entropy store with n bits of entropy.
613 * Use credit_entropy_bits_safe() if the value comes from userspace
614 * or otherwise should be checked for extreme values.
616 static void credit_entropy_bits(struct entropy_store
*r
, int nbits
)
618 int entropy_count
, orig
;
619 const int pool_size
= r
->poolinfo
->poolfracbits
;
620 int nfrac
= nbits
<< ENTROPY_SHIFT
;
626 entropy_count
= orig
= ACCESS_ONCE(r
->entropy_count
);
629 entropy_count
+= nfrac
;
632 * Credit: we have to account for the possibility of
633 * overwriting already present entropy. Even in the
634 * ideal case of pure Shannon entropy, new contributions
635 * approach the full value asymptotically:
637 * entropy <- entropy + (pool_size - entropy) *
638 * (1 - exp(-add_entropy/pool_size))
640 * For add_entropy <= pool_size/2 then
641 * (1 - exp(-add_entropy/pool_size)) >=
642 * (add_entropy/pool_size)*0.7869...
643 * so we can approximate the exponential with
644 * 3/4*add_entropy/pool_size and still be on the
645 * safe side by adding at most pool_size/2 at a time.
647 * The use of pool_size-2 in the while statement is to
648 * prevent rounding artifacts from making the loop
649 * arbitrarily long; this limits the loop to log2(pool_size)*2
650 * turns no matter how large nbits is.
653 const int s
= r
->poolinfo
->poolbitshift
+ ENTROPY_SHIFT
+ 2;
654 /* The +2 corresponds to the /4 in the denominator */
657 unsigned int anfrac
= min(pnfrac
, pool_size
/2);
659 ((pool_size
- entropy_count
)*anfrac
*3) >> s
;
661 entropy_count
+= add
;
663 } while (unlikely(entropy_count
< pool_size
-2 && pnfrac
));
666 if (unlikely(entropy_count
< 0)) {
667 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
668 r
->name
, entropy_count
);
671 } else if (entropy_count
> pool_size
)
672 entropy_count
= pool_size
;
673 if (cmpxchg(&r
->entropy_count
, orig
, entropy_count
) != orig
)
676 r
->entropy_total
+= nbits
;
677 if (!r
->initialized
&& r
->entropy_total
> 128) {
679 r
->entropy_total
= 0;
680 if (r
== &nonblocking_pool
) {
681 prandom_reseed_late();
682 process_random_ready_list();
683 wake_up_all(&urandom_init_wait
);
684 pr_notice("random: %s pool is initialized\n", r
->name
);
688 trace_credit_entropy_bits(r
->name
, nbits
,
689 entropy_count
>> ENTROPY_SHIFT
,
690 r
->entropy_total
, _RET_IP_
);
692 if (r
== &input_pool
) {
693 int entropy_bits
= entropy_count
>> ENTROPY_SHIFT
;
695 /* should we wake readers? */
696 if (entropy_bits
>= random_read_wakeup_bits
) {
697 wake_up_interruptible(&random_read_wait
);
698 kill_fasync(&fasync
, SIGIO
, POLL_IN
);
700 /* If the input pool is getting full, send some
701 * entropy to the two output pools, flipping back and
702 * forth between them, until the output pools are 75%
705 if (entropy_bits
> random_write_wakeup_bits
&&
707 r
->entropy_total
>= 2*random_read_wakeup_bits
) {
708 static struct entropy_store
*last
= &blocking_pool
;
709 struct entropy_store
*other
= &blocking_pool
;
711 if (last
== &blocking_pool
)
712 other
= &nonblocking_pool
;
713 if (other
->entropy_count
<=
714 3 * other
->poolinfo
->poolfracbits
/ 4)
716 if (last
->entropy_count
<=
717 3 * last
->poolinfo
->poolfracbits
/ 4) {
718 schedule_work(&last
->push_work
);
719 r
->entropy_total
= 0;
725 static int credit_entropy_bits_safe(struct entropy_store
*r
, int nbits
)
727 const int nbits_max
= r
->poolinfo
->poolwords
* 32;
732 /* Cap the value to avoid overflows */
733 nbits
= min(nbits
, nbits_max
);
735 credit_entropy_bits(r
, nbits
);
739 /*********************************************************************
741 * Entropy input management
743 *********************************************************************/
745 /* There is one of these per entropy source */
746 struct timer_rand_state
{
748 long last_delta
, last_delta2
;
749 unsigned dont_count_entropy
:1;
752 #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
755 * Add device- or boot-specific data to the input and nonblocking
756 * pools to help initialize them to unique values.
758 * None of this adds any entropy, it is meant to avoid the
759 * problem of the nonblocking pool having similar initial state
760 * across largely identical devices.
762 void add_device_randomness(const void *buf
, unsigned int size
)
764 unsigned long time
= random_get_entropy() ^ jiffies
;
767 trace_add_device_randomness(size
, _RET_IP_
);
768 spin_lock_irqsave(&input_pool
.lock
, flags
);
769 _mix_pool_bytes(&input_pool
, buf
, size
);
770 _mix_pool_bytes(&input_pool
, &time
, sizeof(time
));
771 spin_unlock_irqrestore(&input_pool
.lock
, flags
);
773 spin_lock_irqsave(&nonblocking_pool
.lock
, flags
);
774 _mix_pool_bytes(&nonblocking_pool
, buf
, size
);
775 _mix_pool_bytes(&nonblocking_pool
, &time
, sizeof(time
));
776 spin_unlock_irqrestore(&nonblocking_pool
.lock
, flags
);
778 EXPORT_SYMBOL(add_device_randomness
);
780 static struct timer_rand_state input_timer_state
= INIT_TIMER_RAND_STATE
;
783 * This function adds entropy to the entropy "pool" by using timing
784 * delays. It uses the timer_rand_state structure to make an estimate
785 * of how many bits of entropy this call has added to the pool.
787 * The number "num" is also added to the pool - it should somehow describe
788 * the type of event which just happened. This is currently 0-255 for
789 * keyboard scan codes, and 256 upwards for interrupts.
792 static void add_timer_randomness(struct timer_rand_state
*state
, unsigned num
)
794 struct entropy_store
*r
;
800 long delta
, delta2
, delta3
;
804 sample
.jiffies
= jiffies
;
805 sample
.cycles
= random_get_entropy();
807 r
= nonblocking_pool
.initialized
? &input_pool
: &nonblocking_pool
;
808 mix_pool_bytes(r
, &sample
, sizeof(sample
));
811 * Calculate number of bits of randomness we probably added.
812 * We take into account the first, second and third-order deltas
813 * in order to make our estimate.
816 if (!state
->dont_count_entropy
) {
817 delta
= sample
.jiffies
- state
->last_time
;
818 state
->last_time
= sample
.jiffies
;
820 delta2
= delta
- state
->last_delta
;
821 state
->last_delta
= delta
;
823 delta3
= delta2
- state
->last_delta2
;
824 state
->last_delta2
= delta2
;
838 * delta is now minimum absolute delta.
839 * Round down by 1 bit on general principles,
840 * and limit entropy entimate to 12 bits.
842 credit_entropy_bits(r
, min_t(int, fls(delta
>>1), 11));
847 void add_input_randomness(unsigned int type
, unsigned int code
,
850 static unsigned char last_value
;
852 /* ignore autorepeat and the like */
853 if (value
== last_value
)
857 add_timer_randomness(&input_timer_state
,
858 (type
<< 4) ^ code
^ (code
>> 4) ^ value
);
859 trace_add_input_randomness(ENTROPY_BITS(&input_pool
));
861 EXPORT_SYMBOL_GPL(add_input_randomness
);
863 static DEFINE_PER_CPU(struct fast_pool
, irq_randomness
);
865 #ifdef ADD_INTERRUPT_BENCH
866 static unsigned long avg_cycles
, avg_deviation
;
868 #define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
869 #define FIXED_1_2 (1 << (AVG_SHIFT-1))
871 static void add_interrupt_bench(cycles_t start
)
873 long delta
= random_get_entropy() - start
;
875 /* Use a weighted moving average */
876 delta
= delta
- ((avg_cycles
+ FIXED_1_2
) >> AVG_SHIFT
);
878 /* And average deviation */
879 delta
= abs(delta
) - ((avg_deviation
+ FIXED_1_2
) >> AVG_SHIFT
);
880 avg_deviation
+= delta
;
883 #define add_interrupt_bench(x)
886 static __u32
get_reg(struct fast_pool
*f
, struct pt_regs
*regs
)
888 __u32
*ptr
= (__u32
*) regs
;
893 idx
= READ_ONCE(f
->reg_idx
);
894 if (idx
>= sizeof(struct pt_regs
) / sizeof(__u32
))
897 WRITE_ONCE(f
->reg_idx
, idx
);
901 void add_interrupt_randomness(int irq
, int irq_flags
)
903 struct entropy_store
*r
;
904 struct fast_pool
*fast_pool
= this_cpu_ptr(&irq_randomness
);
905 struct pt_regs
*regs
= get_irq_regs();
906 unsigned long now
= jiffies
;
907 cycles_t cycles
= random_get_entropy();
908 __u32 c_high
, j_high
;
914 cycles
= get_reg(fast_pool
, regs
);
915 c_high
= (sizeof(cycles
) > 4) ? cycles
>> 32 : 0;
916 j_high
= (sizeof(now
) > 4) ? now
>> 32 : 0;
917 fast_pool
->pool
[0] ^= cycles
^ j_high
^ irq
;
918 fast_pool
->pool
[1] ^= now
^ c_high
;
919 ip
= regs
? instruction_pointer(regs
) : _RET_IP_
;
920 fast_pool
->pool
[2] ^= ip
;
921 fast_pool
->pool
[3] ^= (sizeof(ip
) > 4) ? ip
>> 32 :
922 get_reg(fast_pool
, regs
);
925 add_interrupt_bench(cycles
);
927 if ((fast_pool
->count
< 64) &&
928 !time_after(now
, fast_pool
->last
+ HZ
))
931 r
= nonblocking_pool
.initialized
? &input_pool
: &nonblocking_pool
;
932 if (!spin_trylock(&r
->lock
))
935 fast_pool
->last
= now
;
936 __mix_pool_bytes(r
, &fast_pool
->pool
, sizeof(fast_pool
->pool
));
939 * If we have architectural seed generator, produce a seed and
940 * add it to the pool. For the sake of paranoia don't let the
941 * architectural seed generator dominate the input from the
944 if (arch_get_random_seed_long(&seed
)) {
945 __mix_pool_bytes(r
, &seed
, sizeof(seed
));
948 spin_unlock(&r
->lock
);
950 fast_pool
->count
= 0;
952 /* award one bit for the contents of the fast pool */
953 credit_entropy_bits(r
, credit
+ 1);
955 EXPORT_SYMBOL_GPL(add_interrupt_randomness
);
958 void add_disk_randomness(struct gendisk
*disk
)
960 if (!disk
|| !disk
->random
)
962 /* first major is 1, so we get >= 0x200 here */
963 add_timer_randomness(disk
->random
, 0x100 + disk_devt(disk
));
964 trace_add_disk_randomness(disk_devt(disk
), ENTROPY_BITS(&input_pool
));
966 EXPORT_SYMBOL_GPL(add_disk_randomness
);
969 /*********************************************************************
971 * Entropy extraction routines
973 *********************************************************************/
975 static ssize_t
extract_entropy(struct entropy_store
*r
, void *buf
,
976 size_t nbytes
, int min
, int rsvd
);
979 * This utility inline function is responsible for transferring entropy
980 * from the primary pool to the secondary extraction pool. We make
981 * sure we pull enough for a 'catastrophic reseed'.
983 static void _xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
);
984 static void xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
)
987 r
->entropy_count
>= (nbytes
<< (ENTROPY_SHIFT
+ 3)) ||
988 r
->entropy_count
> r
->poolinfo
->poolfracbits
)
991 if (r
->limit
== 0 && random_min_urandom_seed
) {
992 unsigned long now
= jiffies
;
995 r
->last_pulled
+ random_min_urandom_seed
* HZ
))
997 r
->last_pulled
= now
;
1000 _xfer_secondary_pool(r
, nbytes
);
1003 static void _xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
)
1005 __u32 tmp
[OUTPUT_POOL_WORDS
];
1007 /* For /dev/random's pool, always leave two wakeups' worth */
1008 int rsvd_bytes
= r
->limit
? 0 : random_read_wakeup_bits
/ 4;
1011 /* pull at least as much as a wakeup */
1012 bytes
= max_t(int, bytes
, random_read_wakeup_bits
/ 8);
1013 /* but never more than the buffer size */
1014 bytes
= min_t(int, bytes
, sizeof(tmp
));
1016 trace_xfer_secondary_pool(r
->name
, bytes
* 8, nbytes
* 8,
1017 ENTROPY_BITS(r
), ENTROPY_BITS(r
->pull
));
1018 bytes
= extract_entropy(r
->pull
, tmp
, bytes
,
1019 random_read_wakeup_bits
/ 8, rsvd_bytes
);
1020 mix_pool_bytes(r
, tmp
, bytes
);
1021 credit_entropy_bits(r
, bytes
*8);
1025 * Used as a workqueue function so that when the input pool is getting
1026 * full, we can "spill over" some entropy to the output pools. That
1027 * way the output pools can store some of the excess entropy instead
1028 * of letting it go to waste.
1030 static void push_to_pool(struct work_struct
*work
)
1032 struct entropy_store
*r
= container_of(work
, struct entropy_store
,
1035 _xfer_secondary_pool(r
, random_read_wakeup_bits
/8);
1036 trace_push_to_pool(r
->name
, r
->entropy_count
>> ENTROPY_SHIFT
,
1037 r
->pull
->entropy_count
>> ENTROPY_SHIFT
);
1041 * This function decides how many bytes to actually take from the
1042 * given pool, and also debits the entropy count accordingly.
1044 static size_t account(struct entropy_store
*r
, size_t nbytes
, int min
,
1047 int entropy_count
, orig
;
1048 size_t ibytes
, nfrac
;
1050 BUG_ON(r
->entropy_count
> r
->poolinfo
->poolfracbits
);
1052 /* Can we pull enough? */
1054 entropy_count
= orig
= ACCESS_ONCE(r
->entropy_count
);
1056 /* If limited, never pull more than available */
1058 int have_bytes
= entropy_count
>> (ENTROPY_SHIFT
+ 3);
1060 if ((have_bytes
-= reserved
) < 0)
1062 ibytes
= min_t(size_t, ibytes
, have_bytes
);
1067 if (unlikely(entropy_count
< 0)) {
1068 pr_warn("random: negative entropy count: pool %s count %d\n",
1069 r
->name
, entropy_count
);
1073 nfrac
= ibytes
<< (ENTROPY_SHIFT
+ 3);
1074 if ((size_t) entropy_count
> nfrac
)
1075 entropy_count
-= nfrac
;
1079 if (cmpxchg(&r
->entropy_count
, orig
, entropy_count
) != orig
)
1082 trace_debit_entropy(r
->name
, 8 * ibytes
);
1084 (r
->entropy_count
>> ENTROPY_SHIFT
) < random_write_wakeup_bits
) {
1085 wake_up_interruptible(&random_write_wait
);
1086 kill_fasync(&fasync
, SIGIO
, POLL_OUT
);
1093 * This function does the actual extraction for extract_entropy and
1094 * extract_entropy_user.
1096 * Note: we assume that .poolwords is a multiple of 16 words.
1098 static void extract_buf(struct entropy_store
*r
, __u8
*out
)
1103 unsigned long l
[LONGS(20)];
1105 __u32 workspace
[SHA_WORKSPACE_WORDS
];
1106 unsigned long flags
;
1109 * If we have an architectural hardware random number
1110 * generator, use it for SHA's initial vector
1113 for (i
= 0; i
< LONGS(20); i
++) {
1115 if (!arch_get_random_long(&v
))
1120 /* Generate a hash across the pool, 16 words (512 bits) at a time */
1121 spin_lock_irqsave(&r
->lock
, flags
);
1122 for (i
= 0; i
< r
->poolinfo
->poolwords
; i
+= 16)
1123 sha_transform(hash
.w
, (__u8
*)(r
->pool
+ i
), workspace
);
1126 * We mix the hash back into the pool to prevent backtracking
1127 * attacks (where the attacker knows the state of the pool
1128 * plus the current outputs, and attempts to find previous
1129 * ouputs), unless the hash function can be inverted. By
1130 * mixing at least a SHA1 worth of hash data back, we make
1131 * brute-forcing the feedback as hard as brute-forcing the
1134 __mix_pool_bytes(r
, hash
.w
, sizeof(hash
.w
));
1135 spin_unlock_irqrestore(&r
->lock
, flags
);
1137 memzero_explicit(workspace
, sizeof(workspace
));
1140 * In case the hash function has some recognizable output
1141 * pattern, we fold it in half. Thus, we always feed back
1142 * twice as much data as we output.
1144 hash
.w
[0] ^= hash
.w
[3];
1145 hash
.w
[1] ^= hash
.w
[4];
1146 hash
.w
[2] ^= rol32(hash
.w
[2], 16);
1148 memcpy(out
, &hash
, EXTRACT_SIZE
);
1149 memzero_explicit(&hash
, sizeof(hash
));
1153 * This function extracts randomness from the "entropy pool", and
1154 * returns it in a buffer.
1156 * The min parameter specifies the minimum amount we can pull before
1157 * failing to avoid races that defeat catastrophic reseeding while the
1158 * reserved parameter indicates how much entropy we must leave in the
1159 * pool after each pull to avoid starving other readers.
1161 static ssize_t
extract_entropy(struct entropy_store
*r
, void *buf
,
1162 size_t nbytes
, int min
, int reserved
)
1165 __u8 tmp
[EXTRACT_SIZE
];
1166 unsigned long flags
;
1168 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1170 spin_lock_irqsave(&r
->lock
, flags
);
1171 if (!r
->last_data_init
) {
1172 r
->last_data_init
= 1;
1173 spin_unlock_irqrestore(&r
->lock
, flags
);
1174 trace_extract_entropy(r
->name
, EXTRACT_SIZE
,
1175 ENTROPY_BITS(r
), _RET_IP_
);
1176 xfer_secondary_pool(r
, EXTRACT_SIZE
);
1177 extract_buf(r
, tmp
);
1178 spin_lock_irqsave(&r
->lock
, flags
);
1179 memcpy(r
->last_data
, tmp
, EXTRACT_SIZE
);
1181 spin_unlock_irqrestore(&r
->lock
, flags
);
1184 trace_extract_entropy(r
->name
, nbytes
, ENTROPY_BITS(r
), _RET_IP_
);
1185 xfer_secondary_pool(r
, nbytes
);
1186 nbytes
= account(r
, nbytes
, min
, reserved
);
1189 extract_buf(r
, tmp
);
1192 spin_lock_irqsave(&r
->lock
, flags
);
1193 if (!memcmp(tmp
, r
->last_data
, EXTRACT_SIZE
))
1194 panic("Hardware RNG duplicated output!\n");
1195 memcpy(r
->last_data
, tmp
, EXTRACT_SIZE
);
1196 spin_unlock_irqrestore(&r
->lock
, flags
);
1198 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
1199 memcpy(buf
, tmp
, i
);
1205 /* Wipe data just returned from memory */
1206 memzero_explicit(tmp
, sizeof(tmp
));
1212 * This function extracts randomness from the "entropy pool", and
1213 * returns it in a userspace buffer.
1215 static ssize_t
extract_entropy_user(struct entropy_store
*r
, void __user
*buf
,
1219 __u8 tmp
[EXTRACT_SIZE
];
1220 int large_request
= (nbytes
> 256);
1222 trace_extract_entropy_user(r
->name
, nbytes
, ENTROPY_BITS(r
), _RET_IP_
);
1223 xfer_secondary_pool(r
, nbytes
);
1224 nbytes
= account(r
, nbytes
, 0, 0);
1227 if (large_request
&& need_resched()) {
1228 if (signal_pending(current
)) {
1236 extract_buf(r
, tmp
);
1237 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
1238 if (copy_to_user(buf
, tmp
, i
)) {
1248 /* Wipe data just returned from memory */
1249 memzero_explicit(tmp
, sizeof(tmp
));
1255 * This function is the exported kernel interface. It returns some
1256 * number of good random numbers, suitable for key generation, seeding
1257 * TCP sequence numbers, etc. It does not rely on the hardware random
1258 * number generator. For random bytes direct from the hardware RNG
1259 * (when available), use get_random_bytes_arch().
1261 void get_random_bytes(void *buf
, int nbytes
)
1263 #if DEBUG_RANDOM_BOOT > 0
1264 if (unlikely(nonblocking_pool
.initialized
== 0))
1265 printk(KERN_NOTICE
"random: %pF get_random_bytes called "
1266 "with %d bits of entropy available\n",
1268 nonblocking_pool
.entropy_total
);
1270 trace_get_random_bytes(nbytes
, _RET_IP_
);
1271 extract_entropy(&nonblocking_pool
, buf
, nbytes
, 0, 0);
1273 EXPORT_SYMBOL(get_random_bytes
);
1276 * Add a callback function that will be invoked when the nonblocking
1277 * pool is initialised.
1279 * returns: 0 if callback is successfully added
1280 * -EALREADY if pool is already initialised (callback not called)
1281 * -ENOENT if module for callback is not alive
1283 int add_random_ready_callback(struct random_ready_callback
*rdy
)
1285 struct module
*owner
;
1286 unsigned long flags
;
1287 int err
= -EALREADY
;
1289 if (likely(nonblocking_pool
.initialized
))
1293 if (!try_module_get(owner
))
1296 spin_lock_irqsave(&random_ready_list_lock
, flags
);
1297 if (nonblocking_pool
.initialized
)
1302 list_add(&rdy
->list
, &random_ready_list
);
1306 spin_unlock_irqrestore(&random_ready_list_lock
, flags
);
1312 EXPORT_SYMBOL(add_random_ready_callback
);
1315 * Delete a previously registered readiness callback function.
1317 void del_random_ready_callback(struct random_ready_callback
*rdy
)
1319 unsigned long flags
;
1320 struct module
*owner
= NULL
;
1322 spin_lock_irqsave(&random_ready_list_lock
, flags
);
1323 if (!list_empty(&rdy
->list
)) {
1324 list_del_init(&rdy
->list
);
1327 spin_unlock_irqrestore(&random_ready_list_lock
, flags
);
1331 EXPORT_SYMBOL(del_random_ready_callback
);
1334 * This function will use the architecture-specific hardware random
1335 * number generator if it is available. The arch-specific hw RNG will
1336 * almost certainly be faster than what we can do in software, but it
1337 * is impossible to verify that it is implemented securely (as
1338 * opposed, to, say, the AES encryption of a sequence number using a
1339 * key known by the NSA). So it's useful if we need the speed, but
1340 * only if we're willing to trust the hardware manufacturer not to
1341 * have put in a back door.
1343 void get_random_bytes_arch(void *buf
, int nbytes
)
1347 trace_get_random_bytes_arch(nbytes
, _RET_IP_
);
1350 int chunk
= min(nbytes
, (int)sizeof(unsigned long));
1352 if (!arch_get_random_long(&v
))
1355 memcpy(p
, &v
, chunk
);
1361 extract_entropy(&nonblocking_pool
, p
, nbytes
, 0, 0);
1363 EXPORT_SYMBOL(get_random_bytes_arch
);
1367 * init_std_data - initialize pool with system data
1369 * @r: pool to initialize
1371 * This function clears the pool's entropy count and mixes some system
1372 * data into the pool to prepare it for use. The pool is not cleared
1373 * as that can only decrease the entropy in the pool.
1375 static void init_std_data(struct entropy_store
*r
)
1378 ktime_t now
= ktime_get_real();
1381 r
->last_pulled
= jiffies
;
1382 mix_pool_bytes(r
, &now
, sizeof(now
));
1383 for (i
= r
->poolinfo
->poolbytes
; i
> 0; i
-= sizeof(rv
)) {
1384 if (!arch_get_random_seed_long(&rv
) &&
1385 !arch_get_random_long(&rv
))
1386 rv
= random_get_entropy();
1387 mix_pool_bytes(r
, &rv
, sizeof(rv
));
1389 mix_pool_bytes(r
, utsname(), sizeof(*(utsname())));
1393 * Note that setup_arch() may call add_device_randomness()
1394 * long before we get here. This allows seeding of the pools
1395 * with some platform dependent data very early in the boot
1396 * process. But it limits our options here. We must use
1397 * statically allocated structures that already have all
1398 * initializations complete at compile time. We should also
1399 * take care not to overwrite the precious per platform data
1402 static int rand_initialize(void)
1404 init_std_data(&input_pool
);
1405 init_std_data(&blocking_pool
);
1406 init_std_data(&nonblocking_pool
);
1409 early_initcall(rand_initialize
);
1412 void rand_initialize_disk(struct gendisk
*disk
)
1414 struct timer_rand_state
*state
;
1417 * If kzalloc returns null, we just won't use that entropy
1420 state
= kzalloc(sizeof(struct timer_rand_state
), GFP_KERNEL
);
1422 state
->last_time
= INITIAL_JIFFIES
;
1423 disk
->random
= state
;
1429 _random_read(int nonblock
, char __user
*buf
, size_t nbytes
)
1436 nbytes
= min_t(size_t, nbytes
, SEC_XFER_SIZE
);
1438 n
= extract_entropy_user(&blocking_pool
, buf
, nbytes
);
1441 trace_random_read(n
*8, (nbytes
-n
)*8,
1442 ENTROPY_BITS(&blocking_pool
),
1443 ENTROPY_BITS(&input_pool
));
1447 /* Pool is (near) empty. Maybe wait and retry. */
1451 wait_event_interruptible(random_read_wait
,
1452 ENTROPY_BITS(&input_pool
) >=
1453 random_read_wakeup_bits
);
1454 if (signal_pending(current
))
1455 return -ERESTARTSYS
;
1460 random_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
1462 return _random_read(file
->f_flags
& O_NONBLOCK
, buf
, nbytes
);
1466 urandom_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
1468 static int maxwarn
= 10;
1471 if (unlikely(nonblocking_pool
.initialized
== 0) &&
1474 printk(KERN_NOTICE
"random: %s: uninitialized urandom read "
1475 "(%zd bytes read, %d bits of entropy available)\n",
1476 current
->comm
, nbytes
, nonblocking_pool
.entropy_total
);
1479 nbytes
= min_t(size_t, nbytes
, INT_MAX
>> (ENTROPY_SHIFT
+ 3));
1480 ret
= extract_entropy_user(&nonblocking_pool
, buf
, nbytes
);
1482 trace_urandom_read(8 * nbytes
, ENTROPY_BITS(&nonblocking_pool
),
1483 ENTROPY_BITS(&input_pool
));
1488 random_poll(struct file
*file
, poll_table
* wait
)
1492 poll_wait(file
, &random_read_wait
, wait
);
1493 poll_wait(file
, &random_write_wait
, wait
);
1495 if (ENTROPY_BITS(&input_pool
) >= random_read_wakeup_bits
)
1496 mask
|= POLLIN
| POLLRDNORM
;
1497 if (ENTROPY_BITS(&input_pool
) < random_write_wakeup_bits
)
1498 mask
|= POLLOUT
| POLLWRNORM
;
1503 write_pool(struct entropy_store
*r
, const char __user
*buffer
, size_t count
)
1507 const char __user
*p
= buffer
;
1512 bytes
= min(count
, sizeof(buf
));
1513 if (copy_from_user(&buf
, p
, bytes
))
1516 for (b
= bytes
; b
> 0 ; b
-= sizeof(__u32
), i
++) {
1517 if (!arch_get_random_int(&t
))
1525 mix_pool_bytes(r
, buf
, bytes
);
1532 static ssize_t
random_write(struct file
*file
, const char __user
*buffer
,
1533 size_t count
, loff_t
*ppos
)
1537 ret
= write_pool(&blocking_pool
, buffer
, count
);
1540 ret
= write_pool(&nonblocking_pool
, buffer
, count
);
1544 return (ssize_t
)count
;
1547 static long random_ioctl(struct file
*f
, unsigned int cmd
, unsigned long arg
)
1549 int size
, ent_count
;
1550 int __user
*p
= (int __user
*)arg
;
1555 /* inherently racy, no point locking */
1556 ent_count
= ENTROPY_BITS(&input_pool
);
1557 if (put_user(ent_count
, p
))
1560 case RNDADDTOENTCNT
:
1561 if (!capable(CAP_SYS_ADMIN
))
1563 if (get_user(ent_count
, p
))
1565 return credit_entropy_bits_safe(&input_pool
, ent_count
);
1567 if (!capable(CAP_SYS_ADMIN
))
1569 if (get_user(ent_count
, p
++))
1573 if (get_user(size
, p
++))
1575 retval
= write_pool(&input_pool
, (const char __user
*)p
,
1579 return credit_entropy_bits_safe(&input_pool
, ent_count
);
1583 * Clear the entropy pool counters. We no longer clear
1584 * the entropy pool, as that's silly.
1586 if (!capable(CAP_SYS_ADMIN
))
1588 input_pool
.entropy_count
= 0;
1589 nonblocking_pool
.entropy_count
= 0;
1590 blocking_pool
.entropy_count
= 0;
1597 static int random_fasync(int fd
, struct file
*filp
, int on
)
1599 return fasync_helper(fd
, filp
, on
, &fasync
);
1602 const struct file_operations random_fops
= {
1603 .read
= random_read
,
1604 .write
= random_write
,
1605 .poll
= random_poll
,
1606 .unlocked_ioctl
= random_ioctl
,
1607 .fasync
= random_fasync
,
1608 .llseek
= noop_llseek
,
1611 const struct file_operations urandom_fops
= {
1612 .read
= urandom_read
,
1613 .write
= random_write
,
1614 .unlocked_ioctl
= random_ioctl
,
1615 .fasync
= random_fasync
,
1616 .llseek
= noop_llseek
,
1619 SYSCALL_DEFINE3(getrandom
, char __user
*, buf
, size_t, count
,
1620 unsigned int, flags
)
1622 if (flags
& ~(GRND_NONBLOCK
|GRND_RANDOM
))
1625 if (count
> INT_MAX
)
1628 if (flags
& GRND_RANDOM
)
1629 return _random_read(flags
& GRND_NONBLOCK
, buf
, count
);
1631 if (unlikely(nonblocking_pool
.initialized
== 0)) {
1632 if (flags
& GRND_NONBLOCK
)
1634 wait_event_interruptible(urandom_init_wait
,
1635 nonblocking_pool
.initialized
);
1636 if (signal_pending(current
))
1637 return -ERESTARTSYS
;
1639 return urandom_read(NULL
, buf
, count
, NULL
);
1642 /***************************************************************
1643 * Random UUID interface
1645 * Used here for a Boot ID, but can be useful for other kernel
1647 ***************************************************************/
1650 * Generate random UUID
1652 void generate_random_uuid(unsigned char uuid_out
[16])
1654 get_random_bytes(uuid_out
, 16);
1655 /* Set UUID version to 4 --- truly random generation */
1656 uuid_out
[6] = (uuid_out
[6] & 0x0F) | 0x40;
1657 /* Set the UUID variant to DCE */
1658 uuid_out
[8] = (uuid_out
[8] & 0x3F) | 0x80;
1660 EXPORT_SYMBOL(generate_random_uuid
);
1662 /********************************************************************
1666 ********************************************************************/
1668 #ifdef CONFIG_SYSCTL
1670 #include <linux/sysctl.h>
1672 static int min_read_thresh
= 8, min_write_thresh
;
1673 static int max_read_thresh
= OUTPUT_POOL_WORDS
* 32;
1674 static int max_write_thresh
= INPUT_POOL_WORDS
* 32;
1675 static char sysctl_bootid
[16];
1678 * This function is used to return both the bootid UUID, and random
1679 * UUID. The difference is in whether table->data is NULL; if it is,
1680 * then a new UUID is generated and returned to the user.
1682 * If the user accesses this via the proc interface, the UUID will be
1683 * returned as an ASCII string in the standard UUID format; if via the
1684 * sysctl system call, as 16 bytes of binary data.
1686 static int proc_do_uuid(struct ctl_table
*table
, int write
,
1687 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1689 struct ctl_table fake_table
;
1690 unsigned char buf
[64], tmp_uuid
[16], *uuid
;
1695 generate_random_uuid(uuid
);
1697 static DEFINE_SPINLOCK(bootid_spinlock
);
1699 spin_lock(&bootid_spinlock
);
1701 generate_random_uuid(uuid
);
1702 spin_unlock(&bootid_spinlock
);
1705 sprintf(buf
, "%pU", uuid
);
1707 fake_table
.data
= buf
;
1708 fake_table
.maxlen
= sizeof(buf
);
1710 return proc_dostring(&fake_table
, write
, buffer
, lenp
, ppos
);
1714 * Return entropy available scaled to integral bits
1716 static int proc_do_entropy(struct ctl_table
*table
, int write
,
1717 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1719 struct ctl_table fake_table
;
1722 entropy_count
= *(int *)table
->data
>> ENTROPY_SHIFT
;
1724 fake_table
.data
= &entropy_count
;
1725 fake_table
.maxlen
= sizeof(entropy_count
);
1727 return proc_dointvec(&fake_table
, write
, buffer
, lenp
, ppos
);
1730 static int sysctl_poolsize
= INPUT_POOL_WORDS
* 32;
1731 extern struct ctl_table random_table
[];
1732 struct ctl_table random_table
[] = {
1734 .procname
= "poolsize",
1735 .data
= &sysctl_poolsize
,
1736 .maxlen
= sizeof(int),
1738 .proc_handler
= proc_dointvec
,
1741 .procname
= "entropy_avail",
1742 .maxlen
= sizeof(int),
1744 .proc_handler
= proc_do_entropy
,
1745 .data
= &input_pool
.entropy_count
,
1748 .procname
= "read_wakeup_threshold",
1749 .data
= &random_read_wakeup_bits
,
1750 .maxlen
= sizeof(int),
1752 .proc_handler
= proc_dointvec_minmax
,
1753 .extra1
= &min_read_thresh
,
1754 .extra2
= &max_read_thresh
,
1757 .procname
= "write_wakeup_threshold",
1758 .data
= &random_write_wakeup_bits
,
1759 .maxlen
= sizeof(int),
1761 .proc_handler
= proc_dointvec_minmax
,
1762 .extra1
= &min_write_thresh
,
1763 .extra2
= &max_write_thresh
,
1766 .procname
= "urandom_min_reseed_secs",
1767 .data
= &random_min_urandom_seed
,
1768 .maxlen
= sizeof(int),
1770 .proc_handler
= proc_dointvec
,
1773 .procname
= "boot_id",
1774 .data
= &sysctl_bootid
,
1777 .proc_handler
= proc_do_uuid
,
1783 .proc_handler
= proc_do_uuid
,
1785 #ifdef ADD_INTERRUPT_BENCH
1787 .procname
= "add_interrupt_avg_cycles",
1788 .data
= &avg_cycles
,
1789 .maxlen
= sizeof(avg_cycles
),
1791 .proc_handler
= proc_doulongvec_minmax
,
1794 .procname
= "add_interrupt_avg_deviation",
1795 .data
= &avg_deviation
,
1796 .maxlen
= sizeof(avg_deviation
),
1798 .proc_handler
= proc_doulongvec_minmax
,
1803 #endif /* CONFIG_SYSCTL */
1805 static u32 random_int_secret
[MD5_MESSAGE_BYTES
/ 4] ____cacheline_aligned
;
1807 int random_int_secret_init(void)
1809 get_random_bytes(random_int_secret
, sizeof(random_int_secret
));
1813 static DEFINE_PER_CPU(__u32
[MD5_DIGEST_WORDS
], get_random_int_hash
)
1814 __aligned(sizeof(unsigned long));
1817 * Get a random word for internal kernel use only. Similar to urandom but
1818 * with the goal of minimal entropy pool depletion. As a result, the random
1819 * value is not cryptographically secure but for several uses the cost of
1820 * depleting entropy is too high
1822 unsigned int get_random_int(void)
1827 if (arch_get_random_int(&ret
))
1830 hash
= get_cpu_var(get_random_int_hash
);
1832 hash
[0] += current
->pid
+ jiffies
+ random_get_entropy();
1833 md5_transform(hash
, random_int_secret
);
1835 put_cpu_var(get_random_int_hash
);
1839 EXPORT_SYMBOL(get_random_int
);
1842 * Same as get_random_int(), but returns unsigned long.
1844 unsigned long get_random_long(void)
1849 if (arch_get_random_long(&ret
))
1852 hash
= get_cpu_var(get_random_int_hash
);
1854 hash
[0] += current
->pid
+ jiffies
+ random_get_entropy();
1855 md5_transform(hash
, random_int_secret
);
1856 ret
= *(unsigned long *)hash
;
1857 put_cpu_var(get_random_int_hash
);
1861 EXPORT_SYMBOL(get_random_long
);
1864 * randomize_range() returns a start address such that
1866 * [...... <range> .....]
1869 * a <range> with size "len" starting at the return value is inside in the
1870 * area defined by [start, end], but is otherwise randomized.
1873 randomize_range(unsigned long start
, unsigned long end
, unsigned long len
)
1875 unsigned long range
= end
- len
- start
;
1877 if (end
<= start
+ len
)
1879 return PAGE_ALIGN(get_random_int() % range
+ start
);
1882 /* Interface for in-kernel drivers of true hardware RNGs.
1883 * Those devices may produce endless random bits and will be throttled
1884 * when our pool is full.
1886 void add_hwgenerator_randomness(const char *buffer
, size_t count
,
1889 struct entropy_store
*poolp
= &input_pool
;
1891 if (unlikely(nonblocking_pool
.initialized
== 0))
1892 poolp
= &nonblocking_pool
;
1894 /* Suspend writing if we're above the trickle
1895 * threshold. We'll be woken up again once below
1896 * random_write_wakeup_thresh, or when the calling
1897 * thread is about to terminate.
1899 wait_event_interruptible(random_write_wait
,
1900 kthread_should_stop() ||
1901 ENTROPY_BITS(&input_pool
) <= random_write_wakeup_bits
);
1903 mix_pool_bytes(poolp
, buffer
, count
);
1904 credit_entropy_bits(poolp
, entropy
);
1906 EXPORT_SYMBOL_GPL(add_hwgenerator_randomness
);