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/percpu.h>
254 #include <linux/cryptohash.h>
255 #include <linux/fips.h>
256 #include <linux/ptrace.h>
257 #include <linux/kmemcheck.h>
258 #include <linux/workqueue.h>
260 #ifdef CONFIG_GENERIC_HARDIRQS
261 # include <linux/irq.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>
274 * Configuration information
276 #define INPUT_POOL_SHIFT 12
277 #define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
278 #define OUTPUT_POOL_SHIFT 10
279 #define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
280 #define SEC_XFER_SIZE 512
281 #define EXTRACT_SIZE 10
283 #define DEBUG_RANDOM_BOOT 0
285 #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
288 * To allow fractional bits to be tracked, the entropy_count field is
289 * denominated in units of 1/8th bits.
291 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
292 * credit_entropy_bits() needs to be 64 bits wide.
294 #define ENTROPY_SHIFT 3
295 #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
298 * The minimum number of bits of entropy before we wake up a read on
299 * /dev/random. Should be enough to do a significant reseed.
301 static int random_read_wakeup_thresh
= 64;
304 * If the entropy count falls under this number of bits, then we
305 * should wake up processes which are selecting or polling on write
306 * access to /dev/random.
308 static int random_write_wakeup_thresh
= 28 * OUTPUT_POOL_WORDS
;
311 * The minimum number of seconds between urandom pool resending. We
312 * do this to limit the amount of entropy that can be drained from the
313 * input pool even if there are heavy demands on /dev/urandom.
315 static int random_min_urandom_seed
= 60;
318 * Originally, we used a primitive polynomial of degree .poolwords
319 * over GF(2). The taps for various sizes are defined below. They
320 * were chosen to be evenly spaced except for the last tap, which is 1
321 * to get the twisting happening as fast as possible.
323 * For the purposes of better mixing, we use the CRC-32 polynomial as
324 * well to make a (modified) twisted Generalized Feedback Shift
325 * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
326 * generators. ACM Transactions on Modeling and Computer Simulation
327 * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
328 * GFSR generators II. ACM Transactions on Mdeling and Computer
329 * Simulation 4:254-266)
331 * Thanks to Colin Plumb for suggesting this.
333 * The mixing operation is much less sensitive than the output hash,
334 * where we use SHA-1. All that we want of mixing operation is that
335 * it be a good non-cryptographic hash; i.e. it not produce collisions
336 * when fed "random" data of the sort we expect to see. As long as
337 * the pool state differs for different inputs, we have preserved the
338 * input entropy and done a good job. The fact that an intelligent
339 * attacker can construct inputs that will produce controlled
340 * alterations to the pool's state is not important because we don't
341 * consider such inputs to contribute any randomness. The only
342 * property we need with respect to them is that the attacker can't
343 * increase his/her knowledge of the pool's state. Since all
344 * additions are reversible (knowing the final state and the input,
345 * you can reconstruct the initial state), if an attacker has any
346 * uncertainty about the initial state, he/she can only shuffle that
347 * uncertainty about, but never cause any collisions (which would
348 * decrease the uncertainty).
350 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
351 * Videau in their paper, "The Linux Pseudorandom Number Generator
352 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
353 * paper, they point out that we are not using a true Twisted GFSR,
354 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
355 * is, with only three taps, instead of the six that we are using).
356 * As a result, the resulting polynomial is neither primitive nor
357 * irreducible, and hence does not have a maximal period over
358 * GF(2**32). They suggest a slight change to the generator
359 * polynomial which improves the resulting TGFSR polynomial to be
360 * irreducible, which we have made here.
362 static struct poolinfo
{
363 int poolbitshift
, poolwords
, poolbytes
, poolbits
, poolfracbits
;
364 #define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
365 int tap1
, tap2
, tap3
, tap4
, tap5
;
366 } poolinfo_table
[] = {
367 /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
368 /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
369 { S(128), 104, 76, 51, 25, 1 },
370 /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
371 /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
372 { S(32), 26, 19, 14, 7, 1 },
374 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
375 { S(2048), 1638, 1231, 819, 411, 1 },
377 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
378 { S(1024), 817, 615, 412, 204, 1 },
380 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
381 { S(1024), 819, 616, 410, 207, 2 },
383 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
384 { S(512), 411, 308, 208, 104, 1 },
386 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
387 { S(512), 409, 307, 206, 102, 2 },
388 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
389 { S(512), 409, 309, 205, 103, 2 },
391 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
392 { S(256), 205, 155, 101, 52, 1 },
394 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
395 { S(128), 103, 78, 51, 27, 2 },
397 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
398 { S(64), 52, 39, 26, 14, 1 },
403 * Static global variables
405 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait
);
406 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait
);
407 static struct fasync_struct
*fasync
;
409 /**********************************************************************
411 * OS independent entropy store. Here are the functions which handle
412 * storing entropy in an entropy pool.
414 **********************************************************************/
416 struct entropy_store
;
417 struct entropy_store
{
418 /* read-only data: */
419 const struct poolinfo
*poolinfo
;
422 struct entropy_store
*pull
;
423 struct work_struct push_work
;
425 /* read-write data: */
426 unsigned long last_pulled
;
428 unsigned short add_ptr
;
429 unsigned short input_rotate
;
432 unsigned int initialized
:1;
433 unsigned int limit
:1;
434 unsigned int last_data_init
:1;
435 __u8 last_data
[EXTRACT_SIZE
];
438 static void push_to_pool(struct work_struct
*work
);
439 static __u32 input_pool_data
[INPUT_POOL_WORDS
];
440 static __u32 blocking_pool_data
[OUTPUT_POOL_WORDS
];
441 static __u32 nonblocking_pool_data
[OUTPUT_POOL_WORDS
];
443 static struct entropy_store input_pool
= {
444 .poolinfo
= &poolinfo_table
[0],
447 .lock
= __SPIN_LOCK_UNLOCKED(input_pool
.lock
),
448 .pool
= input_pool_data
451 static struct entropy_store blocking_pool
= {
452 .poolinfo
= &poolinfo_table
[1],
456 .lock
= __SPIN_LOCK_UNLOCKED(blocking_pool
.lock
),
457 .pool
= blocking_pool_data
,
458 .push_work
= __WORK_INITIALIZER(blocking_pool
.push_work
,
462 static struct entropy_store nonblocking_pool
= {
463 .poolinfo
= &poolinfo_table
[1],
464 .name
= "nonblocking",
466 .lock
= __SPIN_LOCK_UNLOCKED(nonblocking_pool
.lock
),
467 .pool
= nonblocking_pool_data
,
468 .push_work
= __WORK_INITIALIZER(nonblocking_pool
.push_work
,
472 static __u32
const twist_table
[8] = {
473 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
474 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
477 * This function adds bytes into the entropy "pool". It does not
478 * update the entropy estimate. The caller should call
479 * credit_entropy_bits if this is appropriate.
481 * The pool is stirred with a primitive polynomial of the appropriate
482 * degree, and then twisted. We twist by three bits at a time because
483 * it's cheap to do so and helps slightly in the expected case where
484 * the entropy is concentrated in the low-order bits.
486 static void _mix_pool_bytes(struct entropy_store
*r
, const void *in
,
487 int nbytes
, __u8 out
[64])
489 unsigned long i
, j
, tap1
, tap2
, tap3
, tap4
, tap5
;
491 int wordmask
= r
->poolinfo
->poolwords
- 1;
492 const char *bytes
= in
;
495 tap1
= r
->poolinfo
->tap1
;
496 tap2
= r
->poolinfo
->tap2
;
497 tap3
= r
->poolinfo
->tap3
;
498 tap4
= r
->poolinfo
->tap4
;
499 tap5
= r
->poolinfo
->tap5
;
502 input_rotate
= ACCESS_ONCE(r
->input_rotate
);
503 i
= ACCESS_ONCE(r
->add_ptr
);
505 /* mix one byte at a time to simplify size handling and churn faster */
507 w
= rol32(*bytes
++, input_rotate
);
508 i
= (i
- 1) & wordmask
;
510 /* XOR in the various taps */
512 w
^= r
->pool
[(i
+ tap1
) & wordmask
];
513 w
^= r
->pool
[(i
+ tap2
) & wordmask
];
514 w
^= r
->pool
[(i
+ tap3
) & wordmask
];
515 w
^= r
->pool
[(i
+ tap4
) & wordmask
];
516 w
^= r
->pool
[(i
+ tap5
) & wordmask
];
518 /* Mix the result back in with a twist */
519 r
->pool
[i
] = (w
>> 3) ^ twist_table
[w
& 7];
522 * Normally, we add 7 bits of rotation to the pool.
523 * At the beginning of the pool, add an extra 7 bits
524 * rotation, so that successive passes spread the
525 * input bits across the pool evenly.
527 input_rotate
= (input_rotate
+ (i
? 7 : 14)) & 31;
530 ACCESS_ONCE(r
->input_rotate
) = input_rotate
;
531 ACCESS_ONCE(r
->add_ptr
) = i
;
535 for (j
= 0; j
< 16; j
++)
536 ((__u32
*)out
)[j
] = r
->pool
[(i
- j
) & wordmask
];
539 static void __mix_pool_bytes(struct entropy_store
*r
, const void *in
,
540 int nbytes
, __u8 out
[64])
542 trace_mix_pool_bytes_nolock(r
->name
, nbytes
, _RET_IP_
);
543 _mix_pool_bytes(r
, in
, nbytes
, out
);
546 static void mix_pool_bytes(struct entropy_store
*r
, const void *in
,
547 int nbytes
, __u8 out
[64])
551 trace_mix_pool_bytes(r
->name
, nbytes
, _RET_IP_
);
552 spin_lock_irqsave(&r
->lock
, flags
);
553 _mix_pool_bytes(r
, in
, nbytes
, out
);
554 spin_unlock_irqrestore(&r
->lock
, flags
);
560 unsigned short count
;
561 unsigned char rotate
;
562 unsigned char last_timer_intr
;
566 * This is a fast mixing routine used by the interrupt randomness
567 * collector. It's hardcoded for an 128 bit pool and assumes that any
568 * locks that might be needed are taken by the caller.
570 static void fast_mix(struct fast_pool
*f
, __u32 input
[4])
573 unsigned input_rotate
= f
->rotate
;
575 w
= rol32(input
[0], input_rotate
) ^ f
->pool
[0] ^ f
->pool
[3];
576 f
->pool
[0] = (w
>> 3) ^ twist_table
[w
& 7];
577 input_rotate
= (input_rotate
+ 14) & 31;
578 w
= rol32(input
[1], input_rotate
) ^ f
->pool
[1] ^ f
->pool
[0];
579 f
->pool
[1] = (w
>> 3) ^ twist_table
[w
& 7];
580 input_rotate
= (input_rotate
+ 7) & 31;
581 w
= rol32(input
[2], input_rotate
) ^ f
->pool
[2] ^ f
->pool
[1];
582 f
->pool
[2] = (w
>> 3) ^ twist_table
[w
& 7];
583 input_rotate
= (input_rotate
+ 7) & 31;
584 w
= rol32(input
[3], input_rotate
) ^ f
->pool
[3] ^ f
->pool
[2];
585 f
->pool
[3] = (w
>> 3) ^ twist_table
[w
& 7];
586 input_rotate
= (input_rotate
+ 7) & 31;
588 f
->rotate
= input_rotate
;
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 (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
&& nbits
> 0) {
659 if (r
->entropy_total
> 128) {
660 if (r
== &nonblocking_pool
)
661 pr_notice("random: %s pool is initialized\n",
664 r
->entropy_total
= 0;
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_bytes
= entropy_count
>> ENTROPY_SHIFT
;
675 /* should we wake readers? */
676 if (entropy_bytes
>= random_read_wakeup_thresh
) {
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_bytes
> random_write_wakeup_thresh
&&
687 r
->entropy_total
>= 2*random_read_wakeup_thresh
) {
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
, NULL
);
747 _mix_pool_bytes(&input_pool
, &time
, sizeof(time
), NULL
);
748 spin_unlock_irqrestore(&input_pool
.lock
, flags
);
750 spin_lock_irqsave(&nonblocking_pool
.lock
, flags
);
751 _mix_pool_bytes(&nonblocking_pool
, buf
, size
, NULL
);
752 _mix_pool_bytes(&nonblocking_pool
, &time
, sizeof(time
), NULL
);
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
), NULL
);
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 void add_interrupt_randomness(int irq
, int irq_flags
)
844 struct entropy_store
*r
;
845 struct fast_pool
*fast_pool
= &__get_cpu_var(irq_randomness
);
846 struct pt_regs
*regs
= get_irq_regs();
847 unsigned long now
= jiffies
;
848 cycles_t cycles
= random_get_entropy();
849 __u32 input
[4], c_high
, j_high
;
852 c_high
= (sizeof(cycles
) > 4) ? cycles
>> 32 : 0;
853 j_high
= (sizeof(now
) > 4) ? now
>> 32 : 0;
854 input
[0] = cycles
^ j_high
^ irq
;
855 input
[1] = now
^ c_high
;
856 ip
= regs
? instruction_pointer(regs
) : _RET_IP_
;
860 fast_mix(fast_pool
, input
);
862 if ((fast_pool
->count
& 63) && !time_after(now
, fast_pool
->last
+ HZ
))
865 fast_pool
->last
= now
;
867 r
= nonblocking_pool
.initialized
? &input_pool
: &nonblocking_pool
;
868 __mix_pool_bytes(r
, &fast_pool
->pool
, sizeof(fast_pool
->pool
), NULL
);
870 * If we don't have a valid cycle counter, and we see
871 * back-to-back timer interrupts, then skip giving credit for
875 if (irq_flags
& __IRQF_TIMER
) {
876 if (fast_pool
->last_timer_intr
)
878 fast_pool
->last_timer_intr
= 1;
880 fast_pool
->last_timer_intr
= 0;
882 credit_entropy_bits(r
, 1);
886 void add_disk_randomness(struct gendisk
*disk
)
888 if (!disk
|| !disk
->random
)
890 /* first major is 1, so we get >= 0x200 here */
891 add_timer_randomness(disk
->random
, 0x100 + disk_devt(disk
));
892 trace_add_disk_randomness(disk_devt(disk
), ENTROPY_BITS(&input_pool
));
896 /*********************************************************************
898 * Entropy extraction routines
900 *********************************************************************/
902 static ssize_t
extract_entropy(struct entropy_store
*r
, void *buf
,
903 size_t nbytes
, int min
, int rsvd
);
906 * This utility inline function is responsible for transferring entropy
907 * from the primary pool to the secondary extraction pool. We make
908 * sure we pull enough for a 'catastrophic reseed'.
910 static void _xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
);
911 static void xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
)
913 if (r
->limit
== 0 && random_min_urandom_seed
) {
914 unsigned long now
= jiffies
;
917 r
->last_pulled
+ random_min_urandom_seed
* HZ
))
919 r
->last_pulled
= now
;
922 r
->entropy_count
< (nbytes
<< (ENTROPY_SHIFT
+ 3)) &&
923 r
->entropy_count
< r
->poolinfo
->poolfracbits
)
924 _xfer_secondary_pool(r
, nbytes
);
927 static void _xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
)
929 __u32 tmp
[OUTPUT_POOL_WORDS
];
931 /* For /dev/random's pool, always leave two wakeup worth's BITS */
932 int rsvd
= r
->limit
? 0 : random_read_wakeup_thresh
/4;
935 /* pull at least as many as BYTES as wakeup BITS */
936 bytes
= max_t(int, bytes
, random_read_wakeup_thresh
/ 8);
937 /* but never more than the buffer size */
938 bytes
= min_t(int, bytes
, sizeof(tmp
));
940 trace_xfer_secondary_pool(r
->name
, bytes
* 8, nbytes
* 8,
941 ENTROPY_BITS(r
), ENTROPY_BITS(r
->pull
));
942 bytes
= extract_entropy(r
->pull
, tmp
, bytes
,
943 random_read_wakeup_thresh
/ 8, rsvd
);
944 mix_pool_bytes(r
, tmp
, bytes
, NULL
);
945 credit_entropy_bits(r
, bytes
*8);
949 * Used as a workqueue function so that when the input pool is getting
950 * full, we can "spill over" some entropy to the output pools. That
951 * way the output pools can store some of the excess entropy instead
952 * of letting it go to waste.
954 static void push_to_pool(struct work_struct
*work
)
956 struct entropy_store
*r
= container_of(work
, struct entropy_store
,
959 _xfer_secondary_pool(r
, random_read_wakeup_thresh
/8);
960 trace_push_to_pool(r
->name
, r
->entropy_count
>> ENTROPY_SHIFT
,
961 r
->pull
->entropy_count
>> ENTROPY_SHIFT
);
965 * These functions extracts randomness from the "entropy pool", and
966 * returns it in a buffer.
968 * The min parameter specifies the minimum amount we can pull before
969 * failing to avoid races that defeat catastrophic reseeding while the
970 * reserved parameter indicates how much entropy we must leave in the
971 * pool after each pull to avoid starving other readers.
973 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
976 static size_t account(struct entropy_store
*r
, size_t nbytes
, int min
,
980 int wakeup_write
= 0;
982 int entropy_count
, orig
;
985 /* Hold lock while accounting */
986 spin_lock_irqsave(&r
->lock
, flags
);
988 BUG_ON(r
->entropy_count
> r
->poolinfo
->poolfracbits
);
990 /* Can we pull enough? */
992 entropy_count
= orig
= ACCESS_ONCE(r
->entropy_count
);
993 have_bytes
= entropy_count
>> (ENTROPY_SHIFT
+ 3);
995 if (have_bytes
< min
+ reserved
) {
998 /* If limited, never pull more than available */
999 if (r
->limit
&& ibytes
+ reserved
>= have_bytes
)
1000 ibytes
= have_bytes
- reserved
;
1002 if (have_bytes
>= ibytes
+ reserved
)
1003 entropy_count
-= ibytes
<< (ENTROPY_SHIFT
+ 3);
1005 entropy_count
= reserved
<< (ENTROPY_SHIFT
+ 3);
1007 if (cmpxchg(&r
->entropy_count
, orig
, entropy_count
) != orig
)
1010 if ((r
->entropy_count
>> ENTROPY_SHIFT
)
1011 < random_write_wakeup_thresh
)
1014 spin_unlock_irqrestore(&r
->lock
, flags
);
1016 trace_debit_entropy(r
->name
, 8 * ibytes
);
1018 wake_up_interruptible(&random_write_wait
);
1019 kill_fasync(&fasync
, SIGIO
, POLL_OUT
);
1025 static void extract_buf(struct entropy_store
*r
, __u8
*out
)
1030 unsigned long l
[LONGS(20)];
1032 __u32 workspace
[SHA_WORKSPACE_WORDS
];
1034 unsigned long flags
;
1036 /* Generate a hash across the pool, 16 words (512 bits) at a time */
1038 spin_lock_irqsave(&r
->lock
, flags
);
1039 for (i
= 0; i
< r
->poolinfo
->poolwords
; i
+= 16)
1040 sha_transform(hash
.w
, (__u8
*)(r
->pool
+ i
), workspace
);
1043 * If we have a architectural hardware random number
1044 * generator, mix that in, too.
1046 for (i
= 0; i
< LONGS(20); i
++) {
1048 if (!arch_get_random_long(&v
))
1054 * We mix the hash back into the pool to prevent backtracking
1055 * attacks (where the attacker knows the state of the pool
1056 * plus the current outputs, and attempts to find previous
1057 * ouputs), unless the hash function can be inverted. By
1058 * mixing at least a SHA1 worth of hash data back, we make
1059 * brute-forcing the feedback as hard as brute-forcing the
1062 __mix_pool_bytes(r
, hash
.w
, sizeof(hash
.w
), extract
);
1063 spin_unlock_irqrestore(&r
->lock
, flags
);
1066 * To avoid duplicates, we atomically extract a portion of the
1067 * pool while mixing, and hash one final time.
1069 sha_transform(hash
.w
, extract
, workspace
);
1070 memset(extract
, 0, sizeof(extract
));
1071 memset(workspace
, 0, sizeof(workspace
));
1074 * In case the hash function has some recognizable output
1075 * pattern, we fold it in half. Thus, we always feed back
1076 * twice as much data as we output.
1078 hash
.w
[0] ^= hash
.w
[3];
1079 hash
.w
[1] ^= hash
.w
[4];
1080 hash
.w
[2] ^= rol32(hash
.w
[2], 16);
1082 memcpy(out
, &hash
, EXTRACT_SIZE
);
1083 memset(&hash
, 0, sizeof(hash
));
1086 static ssize_t
extract_entropy(struct entropy_store
*r
, void *buf
,
1087 size_t nbytes
, int min
, int reserved
)
1090 __u8 tmp
[EXTRACT_SIZE
];
1091 unsigned long flags
;
1093 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1095 spin_lock_irqsave(&r
->lock
, flags
);
1096 if (!r
->last_data_init
) {
1097 r
->last_data_init
= 1;
1098 spin_unlock_irqrestore(&r
->lock
, flags
);
1099 trace_extract_entropy(r
->name
, EXTRACT_SIZE
,
1100 ENTROPY_BITS(r
), _RET_IP_
);
1101 xfer_secondary_pool(r
, EXTRACT_SIZE
);
1102 extract_buf(r
, tmp
);
1103 spin_lock_irqsave(&r
->lock
, flags
);
1104 memcpy(r
->last_data
, tmp
, EXTRACT_SIZE
);
1106 spin_unlock_irqrestore(&r
->lock
, flags
);
1109 trace_extract_entropy(r
->name
, nbytes
, ENTROPY_BITS(r
), _RET_IP_
);
1110 xfer_secondary_pool(r
, nbytes
);
1111 nbytes
= account(r
, nbytes
, min
, reserved
);
1114 extract_buf(r
, tmp
);
1117 spin_lock_irqsave(&r
->lock
, flags
);
1118 if (!memcmp(tmp
, r
->last_data
, EXTRACT_SIZE
))
1119 panic("Hardware RNG duplicated output!\n");
1120 memcpy(r
->last_data
, tmp
, EXTRACT_SIZE
);
1121 spin_unlock_irqrestore(&r
->lock
, flags
);
1123 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
1124 memcpy(buf
, tmp
, i
);
1130 /* Wipe data just returned from memory */
1131 memset(tmp
, 0, sizeof(tmp
));
1136 static ssize_t
extract_entropy_user(struct entropy_store
*r
, void __user
*buf
,
1140 __u8 tmp
[EXTRACT_SIZE
];
1142 trace_extract_entropy_user(r
->name
, nbytes
, ENTROPY_BITS(r
), _RET_IP_
);
1143 xfer_secondary_pool(r
, nbytes
);
1144 nbytes
= account(r
, nbytes
, 0, 0);
1147 if (need_resched()) {
1148 if (signal_pending(current
)) {
1156 extract_buf(r
, tmp
);
1157 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
1158 if (copy_to_user(buf
, tmp
, i
)) {
1168 /* Wipe data just returned from memory */
1169 memset(tmp
, 0, sizeof(tmp
));
1175 * This function is the exported kernel interface. It returns some
1176 * number of good random numbers, suitable for key generation, seeding
1177 * TCP sequence numbers, etc. It does not use the hw random number
1178 * generator, if available; use get_random_bytes_arch() for that.
1180 void get_random_bytes(void *buf
, int nbytes
)
1182 #if DEBUG_RANDOM_BOOT > 0
1183 if (unlikely(nonblocking_pool
.initialized
== 0))
1184 printk(KERN_NOTICE
"random: %pF get_random_bytes called "
1185 "with %d bits of entropy available\n",
1187 nonblocking_pool
.entropy_total
);
1189 trace_get_random_bytes(nbytes
, _RET_IP_
);
1190 extract_entropy(&nonblocking_pool
, buf
, nbytes
, 0, 0);
1192 EXPORT_SYMBOL(get_random_bytes
);
1195 * This function will use the architecture-specific hardware random
1196 * number generator if it is available. The arch-specific hw RNG will
1197 * almost certainly be faster than what we can do in software, but it
1198 * is impossible to verify that it is implemented securely (as
1199 * opposed, to, say, the AES encryption of a sequence number using a
1200 * key known by the NSA). So it's useful if we need the speed, but
1201 * only if we're willing to trust the hardware manufacturer not to
1202 * have put in a back door.
1204 void get_random_bytes_arch(void *buf
, int nbytes
)
1208 trace_get_random_bytes_arch(nbytes
, _RET_IP_
);
1211 int chunk
= min(nbytes
, (int)sizeof(unsigned long));
1213 if (!arch_get_random_long(&v
))
1216 memcpy(p
, &v
, chunk
);
1222 extract_entropy(&nonblocking_pool
, p
, nbytes
, 0, 0);
1224 EXPORT_SYMBOL(get_random_bytes_arch
);
1228 * init_std_data - initialize pool with system data
1230 * @r: pool to initialize
1232 * This function clears the pool's entropy count and mixes some system
1233 * data into the pool to prepare it for use. The pool is not cleared
1234 * as that can only decrease the entropy in the pool.
1236 static void init_std_data(struct entropy_store
*r
)
1239 ktime_t now
= ktime_get_real();
1242 r
->last_pulled
= jiffies
;
1243 mix_pool_bytes(r
, &now
, sizeof(now
), NULL
);
1244 for (i
= r
->poolinfo
->poolbytes
; i
> 0; i
-= sizeof(rv
)) {
1245 if (!arch_get_random_long(&rv
))
1246 rv
= random_get_entropy();
1247 mix_pool_bytes(r
, &rv
, sizeof(rv
), NULL
);
1249 mix_pool_bytes(r
, utsname(), sizeof(*(utsname())), NULL
);
1253 * Note that setup_arch() may call add_device_randomness()
1254 * long before we get here. This allows seeding of the pools
1255 * with some platform dependent data very early in the boot
1256 * process. But it limits our options here. We must use
1257 * statically allocated structures that already have all
1258 * initializations complete at compile time. We should also
1259 * take care not to overwrite the precious per platform data
1262 static int rand_initialize(void)
1264 init_std_data(&input_pool
);
1265 init_std_data(&blocking_pool
);
1266 init_std_data(&nonblocking_pool
);
1269 early_initcall(rand_initialize
);
1272 void rand_initialize_disk(struct gendisk
*disk
)
1274 struct timer_rand_state
*state
;
1277 * If kzalloc returns null, we just won't use that entropy
1280 state
= kzalloc(sizeof(struct timer_rand_state
), GFP_KERNEL
);
1282 state
->last_time
= INITIAL_JIFFIES
;
1283 disk
->random
= state
;
1289 random_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
1291 ssize_t n
, retval
= 0, count
= 0;
1296 while (nbytes
> 0) {
1298 if (n
> SEC_XFER_SIZE
)
1301 n
= extract_entropy_user(&blocking_pool
, buf
, n
);
1308 trace_random_read(n
*8, (nbytes
-n
)*8,
1309 ENTROPY_BITS(&blocking_pool
),
1310 ENTROPY_BITS(&input_pool
));
1313 if (file
->f_flags
& O_NONBLOCK
) {
1318 wait_event_interruptible(random_read_wait
,
1319 ENTROPY_BITS(&input_pool
) >=
1320 random_read_wakeup_thresh
);
1322 if (signal_pending(current
)) {
1323 retval
= -ERESTARTSYS
;
1333 break; /* This break makes the device work */
1334 /* like a named pipe */
1337 return (count
? count
: retval
);
1341 urandom_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
1345 if (unlikely(nonblocking_pool
.initialized
== 0))
1346 printk_once(KERN_NOTICE
"random: %s urandom read "
1347 "with %d bits of entropy available\n",
1348 current
->comm
, nonblocking_pool
.entropy_total
);
1350 ret
= extract_entropy_user(&nonblocking_pool
, buf
, nbytes
);
1352 trace_urandom_read(8 * nbytes
, ENTROPY_BITS(&nonblocking_pool
),
1353 ENTROPY_BITS(&input_pool
));
1358 random_poll(struct file
*file
, poll_table
* wait
)
1362 poll_wait(file
, &random_read_wait
, wait
);
1363 poll_wait(file
, &random_write_wait
, wait
);
1365 if (ENTROPY_BITS(&input_pool
) >= random_read_wakeup_thresh
)
1366 mask
|= POLLIN
| POLLRDNORM
;
1367 if (ENTROPY_BITS(&input_pool
) < random_write_wakeup_thresh
)
1368 mask
|= POLLOUT
| POLLWRNORM
;
1373 write_pool(struct entropy_store
*r
, const char __user
*buffer
, size_t count
)
1377 const char __user
*p
= buffer
;
1380 bytes
= min(count
, sizeof(buf
));
1381 if (copy_from_user(&buf
, p
, bytes
))
1387 mix_pool_bytes(r
, buf
, bytes
, NULL
);
1394 static ssize_t
random_write(struct file
*file
, const char __user
*buffer
,
1395 size_t count
, loff_t
*ppos
)
1399 ret
= write_pool(&blocking_pool
, buffer
, count
);
1402 ret
= write_pool(&nonblocking_pool
, buffer
, count
);
1406 return (ssize_t
)count
;
1409 static long random_ioctl(struct file
*f
, unsigned int cmd
, unsigned long arg
)
1411 int size
, ent_count
;
1412 int __user
*p
= (int __user
*)arg
;
1417 /* inherently racy, no point locking */
1418 ent_count
= ENTROPY_BITS(&input_pool
);
1419 if (put_user(ent_count
, p
))
1422 case RNDADDTOENTCNT
:
1423 if (!capable(CAP_SYS_ADMIN
))
1425 if (get_user(ent_count
, p
))
1427 credit_entropy_bits_safe(&input_pool
, ent_count
);
1430 if (!capable(CAP_SYS_ADMIN
))
1432 if (get_user(ent_count
, p
++))
1436 if (get_user(size
, p
++))
1438 retval
= write_pool(&input_pool
, (const char __user
*)p
,
1442 credit_entropy_bits_safe(&input_pool
, ent_count
);
1447 * Clear the entropy pool counters. We no longer clear
1448 * the entropy pool, as that's silly.
1450 if (!capable(CAP_SYS_ADMIN
))
1452 input_pool
.entropy_count
= 0;
1453 nonblocking_pool
.entropy_count
= 0;
1454 blocking_pool
.entropy_count
= 0;
1461 static int random_fasync(int fd
, struct file
*filp
, int on
)
1463 return fasync_helper(fd
, filp
, on
, &fasync
);
1466 const struct file_operations random_fops
= {
1467 .read
= random_read
,
1468 .write
= random_write
,
1469 .poll
= random_poll
,
1470 .unlocked_ioctl
= random_ioctl
,
1471 .fasync
= random_fasync
,
1472 .llseek
= noop_llseek
,
1475 const struct file_operations urandom_fops
= {
1476 .read
= urandom_read
,
1477 .write
= random_write
,
1478 .unlocked_ioctl
= random_ioctl
,
1479 .fasync
= random_fasync
,
1480 .llseek
= noop_llseek
,
1483 /***************************************************************
1484 * Random UUID interface
1486 * Used here for a Boot ID, but can be useful for other kernel
1488 ***************************************************************/
1491 * Generate random UUID
1493 void generate_random_uuid(unsigned char uuid_out
[16])
1495 get_random_bytes(uuid_out
, 16);
1496 /* Set UUID version to 4 --- truly random generation */
1497 uuid_out
[6] = (uuid_out
[6] & 0x0F) | 0x40;
1498 /* Set the UUID variant to DCE */
1499 uuid_out
[8] = (uuid_out
[8] & 0x3F) | 0x80;
1501 EXPORT_SYMBOL(generate_random_uuid
);
1503 /********************************************************************
1507 ********************************************************************/
1509 #ifdef CONFIG_SYSCTL
1511 #include <linux/sysctl.h>
1513 static int min_read_thresh
= 8, min_write_thresh
;
1514 static int max_read_thresh
= INPUT_POOL_WORDS
* 32;
1515 static int max_write_thresh
= INPUT_POOL_WORDS
* 32;
1516 static char sysctl_bootid
[16];
1519 * These functions is used to return both the bootid UUID, and random
1520 * UUID. The difference is in whether table->data is NULL; if it is,
1521 * then a new UUID is generated and returned to the user.
1523 * If the user accesses this via the proc interface, it will be returned
1524 * as an ASCII string in the standard UUID format. If accesses via the
1525 * sysctl system call, it is returned as 16 bytes of binary data.
1527 static int proc_do_uuid(struct ctl_table
*table
, int write
,
1528 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1530 struct ctl_table fake_table
;
1531 unsigned char buf
[64], tmp_uuid
[16], *uuid
;
1536 generate_random_uuid(uuid
);
1538 static DEFINE_SPINLOCK(bootid_spinlock
);
1540 spin_lock(&bootid_spinlock
);
1542 generate_random_uuid(uuid
);
1543 spin_unlock(&bootid_spinlock
);
1546 sprintf(buf
, "%pU", uuid
);
1548 fake_table
.data
= buf
;
1549 fake_table
.maxlen
= sizeof(buf
);
1551 return proc_dostring(&fake_table
, write
, buffer
, lenp
, ppos
);
1555 * Return entropy available scaled to integral bits
1557 static int proc_do_entropy(ctl_table
*table
, int write
,
1558 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1560 ctl_table fake_table
;
1563 entropy_count
= *(int *)table
->data
>> ENTROPY_SHIFT
;
1565 fake_table
.data
= &entropy_count
;
1566 fake_table
.maxlen
= sizeof(entropy_count
);
1568 return proc_dointvec(&fake_table
, write
, buffer
, lenp
, ppos
);
1571 static int sysctl_poolsize
= INPUT_POOL_WORDS
* 32;
1572 extern struct ctl_table random_table
[];
1573 struct ctl_table random_table
[] = {
1575 .procname
= "poolsize",
1576 .data
= &sysctl_poolsize
,
1577 .maxlen
= sizeof(int),
1579 .proc_handler
= proc_dointvec
,
1582 .procname
= "entropy_avail",
1583 .maxlen
= sizeof(int),
1585 .proc_handler
= proc_do_entropy
,
1586 .data
= &input_pool
.entropy_count
,
1589 .procname
= "read_wakeup_threshold",
1590 .data
= &random_read_wakeup_thresh
,
1591 .maxlen
= sizeof(int),
1593 .proc_handler
= proc_dointvec_minmax
,
1594 .extra1
= &min_read_thresh
,
1595 .extra2
= &max_read_thresh
,
1598 .procname
= "write_wakeup_threshold",
1599 .data
= &random_write_wakeup_thresh
,
1600 .maxlen
= sizeof(int),
1602 .proc_handler
= proc_dointvec_minmax
,
1603 .extra1
= &min_write_thresh
,
1604 .extra2
= &max_write_thresh
,
1607 .procname
= "urandom_min_reseed_secs",
1608 .data
= &random_min_urandom_seed
,
1609 .maxlen
= sizeof(int),
1611 .proc_handler
= proc_dointvec
,
1614 .procname
= "boot_id",
1615 .data
= &sysctl_bootid
,
1618 .proc_handler
= proc_do_uuid
,
1624 .proc_handler
= proc_do_uuid
,
1628 #endif /* CONFIG_SYSCTL */
1630 static u32 random_int_secret
[MD5_MESSAGE_BYTES
/ 4] ____cacheline_aligned
;
1632 int random_int_secret_init(void)
1634 get_random_bytes(random_int_secret
, sizeof(random_int_secret
));
1639 * Get a random word for internal kernel use only. Similar to urandom but
1640 * with the goal of minimal entropy pool depletion. As a result, the random
1641 * value is not cryptographically secure but for several uses the cost of
1642 * depleting entropy is too high
1644 static DEFINE_PER_CPU(__u32
[MD5_DIGEST_WORDS
], get_random_int_hash
);
1645 unsigned int get_random_int(void)
1650 if (arch_get_random_int(&ret
))
1653 hash
= get_cpu_var(get_random_int_hash
);
1655 hash
[0] += current
->pid
+ jiffies
+ random_get_entropy();
1656 md5_transform(hash
, random_int_secret
);
1658 put_cpu_var(get_random_int_hash
);
1662 EXPORT_SYMBOL(get_random_int
);
1665 * randomize_range() returns a start address such that
1667 * [...... <range> .....]
1670 * a <range> with size "len" starting at the return value is inside in the
1671 * area defined by [start, end], but is otherwise randomized.
1674 randomize_range(unsigned long start
, unsigned long end
, unsigned long len
)
1676 unsigned long range
= end
- len
- start
;
1678 if (end
<= start
+ len
)
1680 return PAGE_ALIGN(get_random_int() % range
+ start
);