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 LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
286 * To allow fractional bits to be tracked, the entropy_count field is
287 * denominated in units of 1/8th bits.
289 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
290 * credit_entropy_bits() needs to be 64 bits wide.
292 #define ENTROPY_SHIFT 3
293 #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
296 * The minimum number of bits of entropy before we wake up a read on
297 * /dev/random. Should be enough to do a significant reseed.
299 static int random_read_wakeup_thresh
= 64;
302 * If the entropy count falls under this number of bits, then we
303 * should wake up processes which are selecting or polling on write
304 * access to /dev/random.
306 static int random_write_wakeup_thresh
= 28 * OUTPUT_POOL_WORDS
;
309 * The minimum number of seconds between urandom pool resending. We
310 * do this to limit the amount of entropy that can be drained from the
311 * input pool even if there are heavy demands on /dev/urandom.
313 static int random_min_urandom_seed
= 60;
316 * Originally, we used a primitive polynomial of degree .poolwords
317 * over GF(2). The taps for various sizes are defined below. They
318 * were chosen to be evenly spaced except for the last tap, which is 1
319 * to get the twisting happening as fast as possible.
321 * For the purposes of better mixing, we use the CRC-32 polynomial as
322 * well to make a (modified) twisted Generalized Feedback Shift
323 * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
324 * generators. ACM Transactions on Modeling and Computer Simulation
325 * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
326 * GFSR generators II. ACM Transactions on Mdeling and Computer
327 * Simulation 4:254-266)
329 * Thanks to Colin Plumb for suggesting this.
331 * The mixing operation is much less sensitive than the output hash,
332 * where we use SHA-1. All that we want of mixing operation is that
333 * it be a good non-cryptographic hash; i.e. it not produce collisions
334 * when fed "random" data of the sort we expect to see. As long as
335 * the pool state differs for different inputs, we have preserved the
336 * input entropy and done a good job. The fact that an intelligent
337 * attacker can construct inputs that will produce controlled
338 * alterations to the pool's state is not important because we don't
339 * consider such inputs to contribute any randomness. The only
340 * property we need with respect to them is that the attacker can't
341 * increase his/her knowledge of the pool's state. Since all
342 * additions are reversible (knowing the final state and the input,
343 * you can reconstruct the initial state), if an attacker has any
344 * uncertainty about the initial state, he/she can only shuffle that
345 * uncertainty about, but never cause any collisions (which would
346 * decrease the uncertainty).
348 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
349 * Videau in their paper, "The Linux Pseudorandom Number Generator
350 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
351 * paper, they point out that we are not using a true Twisted GFSR,
352 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
353 * is, with only three taps, instead of the six that we are using).
354 * As a result, the resulting polynomial is neither primitive nor
355 * irreducible, and hence does not have a maximal period over
356 * GF(2**32). They suggest a slight change to the generator
357 * polynomial which improves the resulting TGFSR polynomial to be
358 * irreducible, which we have made here.
360 static struct poolinfo
{
361 int poolbitshift
, poolwords
, poolbytes
, poolbits
, poolfracbits
;
362 #define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
363 int tap1
, tap2
, tap3
, tap4
, tap5
;
364 } poolinfo_table
[] = {
365 /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
366 /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
367 { S(128), 104, 76, 51, 25, 1 },
368 /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
369 /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
370 { S(32), 26, 19, 14, 7, 1 },
372 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
373 { S(2048), 1638, 1231, 819, 411, 1 },
375 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
376 { S(1024), 817, 615, 412, 204, 1 },
378 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
379 { S(1024), 819, 616, 410, 207, 2 },
381 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
382 { S(512), 411, 308, 208, 104, 1 },
384 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
385 { S(512), 409, 307, 206, 102, 2 },
386 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
387 { S(512), 409, 309, 205, 103, 2 },
389 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
390 { S(256), 205, 155, 101, 52, 1 },
392 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
393 { S(128), 103, 78, 51, 27, 2 },
395 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
396 { S(64), 52, 39, 26, 14, 1 },
401 * Static global variables
403 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait
);
404 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait
);
405 static struct fasync_struct
*fasync
;
407 /**********************************************************************
409 * OS independent entropy store. Here are the functions which handle
410 * storing entropy in an entropy pool.
412 **********************************************************************/
414 struct entropy_store
;
415 struct entropy_store
{
416 /* read-only data: */
417 const struct poolinfo
*poolinfo
;
420 struct entropy_store
*pull
;
421 struct work_struct push_work
;
423 /* read-write data: */
424 unsigned long last_pulled
;
426 unsigned short add_ptr
;
427 unsigned short input_rotate
;
430 unsigned int initialized
:1;
431 unsigned int limit
:1;
432 unsigned int last_data_init
:1;
433 __u8 last_data
[EXTRACT_SIZE
];
436 static void push_to_pool(struct work_struct
*work
);
437 static __u32 input_pool_data
[INPUT_POOL_WORDS
];
438 static __u32 blocking_pool_data
[OUTPUT_POOL_WORDS
];
439 static __u32 nonblocking_pool_data
[OUTPUT_POOL_WORDS
];
441 static struct entropy_store input_pool
= {
442 .poolinfo
= &poolinfo_table
[0],
445 .lock
= __SPIN_LOCK_UNLOCKED(input_pool
.lock
),
446 .pool
= input_pool_data
449 static struct entropy_store blocking_pool
= {
450 .poolinfo
= &poolinfo_table
[1],
454 .lock
= __SPIN_LOCK_UNLOCKED(blocking_pool
.lock
),
455 .pool
= blocking_pool_data
,
456 .push_work
= __WORK_INITIALIZER(blocking_pool
.push_work
,
460 static struct entropy_store nonblocking_pool
= {
461 .poolinfo
= &poolinfo_table
[1],
462 .name
= "nonblocking",
464 .lock
= __SPIN_LOCK_UNLOCKED(nonblocking_pool
.lock
),
465 .pool
= nonblocking_pool_data
,
466 .push_work
= __WORK_INITIALIZER(nonblocking_pool
.push_work
,
470 static __u32
const twist_table
[8] = {
471 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
472 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
475 * This function adds bytes into the entropy "pool". It does not
476 * update the entropy estimate. The caller should call
477 * credit_entropy_bits if this is appropriate.
479 * The pool is stirred with a primitive polynomial of the appropriate
480 * degree, and then twisted. We twist by three bits at a time because
481 * it's cheap to do so and helps slightly in the expected case where
482 * the entropy is concentrated in the low-order bits.
484 static void _mix_pool_bytes(struct entropy_store
*r
, const void *in
,
485 int nbytes
, __u8 out
[64])
487 unsigned long i
, j
, tap1
, tap2
, tap3
, tap4
, tap5
;
489 int wordmask
= r
->poolinfo
->poolwords
- 1;
490 const char *bytes
= in
;
493 tap1
= r
->poolinfo
->tap1
;
494 tap2
= r
->poolinfo
->tap2
;
495 tap3
= r
->poolinfo
->tap3
;
496 tap4
= r
->poolinfo
->tap4
;
497 tap5
= r
->poolinfo
->tap5
;
500 input_rotate
= ACCESS_ONCE(r
->input_rotate
);
501 i
= ACCESS_ONCE(r
->add_ptr
);
503 /* mix one byte at a time to simplify size handling and churn faster */
505 w
= rol32(*bytes
++, input_rotate
);
506 i
= (i
- 1) & wordmask
;
508 /* XOR in the various taps */
510 w
^= r
->pool
[(i
+ tap1
) & wordmask
];
511 w
^= r
->pool
[(i
+ tap2
) & wordmask
];
512 w
^= r
->pool
[(i
+ tap3
) & wordmask
];
513 w
^= r
->pool
[(i
+ tap4
) & wordmask
];
514 w
^= r
->pool
[(i
+ tap5
) & wordmask
];
516 /* Mix the result back in with a twist */
517 r
->pool
[i
] = (w
>> 3) ^ twist_table
[w
& 7];
520 * Normally, we add 7 bits of rotation to the pool.
521 * At the beginning of the pool, add an extra 7 bits
522 * rotation, so that successive passes spread the
523 * input bits across the pool evenly.
525 input_rotate
= (input_rotate
+ (i
? 7 : 14)) & 31;
528 ACCESS_ONCE(r
->input_rotate
) = input_rotate
;
529 ACCESS_ONCE(r
->add_ptr
) = i
;
533 for (j
= 0; j
< 16; j
++)
534 ((__u32
*)out
)[j
] = r
->pool
[(i
- j
) & wordmask
];
537 static void __mix_pool_bytes(struct entropy_store
*r
, const void *in
,
538 int nbytes
, __u8 out
[64])
540 trace_mix_pool_bytes_nolock(r
->name
, nbytes
, _RET_IP_
);
541 _mix_pool_bytes(r
, in
, nbytes
, out
);
544 static void mix_pool_bytes(struct entropy_store
*r
, const void *in
,
545 int nbytes
, __u8 out
[64])
549 trace_mix_pool_bytes(r
->name
, nbytes
, _RET_IP_
);
550 spin_lock_irqsave(&r
->lock
, flags
);
551 _mix_pool_bytes(r
, in
, nbytes
, out
);
552 spin_unlock_irqrestore(&r
->lock
, flags
);
558 unsigned short count
;
559 unsigned char rotate
;
560 unsigned char last_timer_intr
;
564 * This is a fast mixing routine used by the interrupt randomness
565 * collector. It's hardcoded for an 128 bit pool and assumes that any
566 * locks that might be needed are taken by the caller.
568 static void fast_mix(struct fast_pool
*f
, __u32 input
[4])
571 unsigned input_rotate
= f
->rotate
;
573 w
= rol32(input
[0], input_rotate
) ^ f
->pool
[0] ^ f
->pool
[3];
574 f
->pool
[0] = (w
>> 3) ^ twist_table
[w
& 7];
575 input_rotate
= (input_rotate
+ 14) & 31;
576 w
= rol32(input
[1], input_rotate
) ^ f
->pool
[1] ^ f
->pool
[0];
577 f
->pool
[1] = (w
>> 3) ^ twist_table
[w
& 7];
578 input_rotate
= (input_rotate
+ 7) & 31;
579 w
= rol32(input
[2], input_rotate
) ^ f
->pool
[2] ^ f
->pool
[1];
580 f
->pool
[2] = (w
>> 3) ^ twist_table
[w
& 7];
581 input_rotate
= (input_rotate
+ 7) & 31;
582 w
= rol32(input
[3], input_rotate
) ^ f
->pool
[3] ^ f
->pool
[2];
583 f
->pool
[3] = (w
>> 3) ^ twist_table
[w
& 7];
584 input_rotate
= (input_rotate
+ 7) & 31;
586 f
->rotate
= input_rotate
;
591 * Credit (or debit) the entropy store with n bits of entropy.
592 * Use credit_entropy_bits_safe() if the value comes from userspace
593 * or otherwise should be checked for extreme values.
595 static void credit_entropy_bits(struct entropy_store
*r
, int nbits
)
597 int entropy_count
, orig
;
598 const int pool_size
= r
->poolinfo
->poolfracbits
;
599 int nfrac
= nbits
<< ENTROPY_SHIFT
;
605 entropy_count
= orig
= ACCESS_ONCE(r
->entropy_count
);
608 entropy_count
+= nfrac
;
611 * Credit: we have to account for the possibility of
612 * overwriting already present entropy. Even in the
613 * ideal case of pure Shannon entropy, new contributions
614 * approach the full value asymptotically:
616 * entropy <- entropy + (pool_size - entropy) *
617 * (1 - exp(-add_entropy/pool_size))
619 * For add_entropy <= pool_size/2 then
620 * (1 - exp(-add_entropy/pool_size)) >=
621 * (add_entropy/pool_size)*0.7869...
622 * so we can approximate the exponential with
623 * 3/4*add_entropy/pool_size and still be on the
624 * safe side by adding at most pool_size/2 at a time.
626 * The use of pool_size-2 in the while statement is to
627 * prevent rounding artifacts from making the loop
628 * arbitrarily long; this limits the loop to log2(pool_size)*2
629 * turns no matter how large nbits is.
632 const int s
= r
->poolinfo
->poolbitshift
+ ENTROPY_SHIFT
+ 2;
633 /* The +2 corresponds to the /4 in the denominator */
636 unsigned int anfrac
= min(pnfrac
, pool_size
/2);
638 ((pool_size
- entropy_count
)*anfrac
*3) >> s
;
640 entropy_count
+= add
;
642 } while (unlikely(entropy_count
< pool_size
-2 && pnfrac
));
645 if (entropy_count
< 0) {
646 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
647 r
->name
, entropy_count
);
650 } else if (entropy_count
> pool_size
)
651 entropy_count
= pool_size
;
652 if (cmpxchg(&r
->entropy_count
, orig
, entropy_count
) != orig
)
655 r
->entropy_total
+= nbits
;
656 if (!r
->initialized
&& nbits
> 0) {
657 if (r
->entropy_total
> 128) {
658 if (r
== &nonblocking_pool
)
659 pr_notice("random: %s pool is initialized\n",
662 r
->entropy_total
= 0;
666 trace_credit_entropy_bits(r
->name
, nbits
,
667 entropy_count
>> ENTROPY_SHIFT
,
668 r
->entropy_total
, _RET_IP_
);
670 if (r
== &input_pool
) {
671 int entropy_bytes
= entropy_count
>> ENTROPY_SHIFT
;
673 /* should we wake readers? */
674 if (entropy_bytes
>= random_read_wakeup_thresh
) {
675 wake_up_interruptible(&random_read_wait
);
676 kill_fasync(&fasync
, SIGIO
, POLL_IN
);
678 /* If the input pool is getting full, send some
679 * entropy to the two output pools, flipping back and
680 * forth between them, until the output pools are 75%
683 if (entropy_bytes
> random_write_wakeup_thresh
&&
685 r
->entropy_total
>= 2*random_read_wakeup_thresh
) {
686 static struct entropy_store
*last
= &blocking_pool
;
687 struct entropy_store
*other
= &blocking_pool
;
689 if (last
== &blocking_pool
)
690 other
= &nonblocking_pool
;
691 if (other
->entropy_count
<=
692 3 * other
->poolinfo
->poolfracbits
/ 4)
694 if (last
->entropy_count
<=
695 3 * last
->poolinfo
->poolfracbits
/ 4) {
696 schedule_work(&last
->push_work
);
697 r
->entropy_total
= 0;
703 static void credit_entropy_bits_safe(struct entropy_store
*r
, int nbits
)
705 const int nbits_max
= (int)(~0U >> (ENTROPY_SHIFT
+ 1));
707 /* Cap the value to avoid overflows */
708 nbits
= min(nbits
, nbits_max
);
709 nbits
= max(nbits
, -nbits_max
);
711 credit_entropy_bits(r
, nbits
);
714 /*********************************************************************
716 * Entropy input management
718 *********************************************************************/
720 /* There is one of these per entropy source */
721 struct timer_rand_state
{
723 long last_delta
, last_delta2
;
724 unsigned dont_count_entropy
:1;
728 * Add device- or boot-specific data to the input and nonblocking
729 * pools to help initialize them to unique values.
731 * None of this adds any entropy, it is meant to avoid the
732 * problem of the nonblocking pool having similar initial state
733 * across largely identical devices.
735 void add_device_randomness(const void *buf
, unsigned int size
)
737 unsigned long time
= random_get_entropy() ^ jiffies
;
740 trace_add_device_randomness(size
, _RET_IP_
);
741 spin_lock_irqsave(&input_pool
.lock
, flags
);
742 _mix_pool_bytes(&input_pool
, buf
, size
, NULL
);
743 _mix_pool_bytes(&input_pool
, &time
, sizeof(time
), NULL
);
744 spin_unlock_irqrestore(&input_pool
.lock
, flags
);
746 spin_lock_irqsave(&nonblocking_pool
.lock
, flags
);
747 _mix_pool_bytes(&nonblocking_pool
, buf
, size
, NULL
);
748 _mix_pool_bytes(&nonblocking_pool
, &time
, sizeof(time
), NULL
);
749 spin_unlock_irqrestore(&nonblocking_pool
.lock
, flags
);
751 EXPORT_SYMBOL(add_device_randomness
);
753 static struct timer_rand_state input_timer_state
;
756 * This function adds entropy to the entropy "pool" by using timing
757 * delays. It uses the timer_rand_state structure to make an estimate
758 * of how many bits of entropy this call has added to the pool.
760 * The number "num" is also added to the pool - it should somehow describe
761 * the type of event which just happened. This is currently 0-255 for
762 * keyboard scan codes, and 256 upwards for interrupts.
765 static void add_timer_randomness(struct timer_rand_state
*state
, unsigned num
)
767 struct entropy_store
*r
;
773 long delta
, delta2
, delta3
;
777 sample
.jiffies
= jiffies
;
778 sample
.cycles
= random_get_entropy();
780 r
= nonblocking_pool
.initialized
? &input_pool
: &nonblocking_pool
;
781 mix_pool_bytes(r
, &sample
, sizeof(sample
), NULL
);
784 * Calculate number of bits of randomness we probably added.
785 * We take into account the first, second and third-order deltas
786 * in order to make our estimate.
789 if (!state
->dont_count_entropy
) {
790 delta
= sample
.jiffies
- state
->last_time
;
791 state
->last_time
= sample
.jiffies
;
793 delta2
= delta
- state
->last_delta
;
794 state
->last_delta
= delta
;
796 delta3
= delta2
- state
->last_delta2
;
797 state
->last_delta2
= delta2
;
811 * delta is now minimum absolute delta.
812 * Round down by 1 bit on general principles,
813 * and limit entropy entimate to 12 bits.
815 credit_entropy_bits(r
, min_t(int, fls(delta
>>1), 11));
820 void add_input_randomness(unsigned int type
, unsigned int code
,
823 static unsigned char last_value
;
825 /* ignore autorepeat and the like */
826 if (value
== last_value
)
830 add_timer_randomness(&input_timer_state
,
831 (type
<< 4) ^ code
^ (code
>> 4) ^ value
);
832 trace_add_input_randomness(ENTROPY_BITS(&input_pool
));
834 EXPORT_SYMBOL_GPL(add_input_randomness
);
836 static DEFINE_PER_CPU(struct fast_pool
, irq_randomness
);
838 void add_interrupt_randomness(int irq
, int irq_flags
)
840 struct entropy_store
*r
;
841 struct fast_pool
*fast_pool
= &__get_cpu_var(irq_randomness
);
842 struct pt_regs
*regs
= get_irq_regs();
843 unsigned long now
= jiffies
;
844 cycles_t cycles
= random_get_entropy();
845 __u32 input
[4], c_high
, j_high
;
848 c_high
= (sizeof(cycles
) > 4) ? cycles
>> 32 : 0;
849 j_high
= (sizeof(now
) > 4) ? now
>> 32 : 0;
850 input
[0] = cycles
^ j_high
^ irq
;
851 input
[1] = now
^ c_high
;
852 ip
= regs
? instruction_pointer(regs
) : _RET_IP_
;
856 fast_mix(fast_pool
, input
);
858 if ((fast_pool
->count
& 63) && !time_after(now
, fast_pool
->last
+ HZ
))
861 fast_pool
->last
= now
;
863 r
= nonblocking_pool
.initialized
? &input_pool
: &nonblocking_pool
;
864 __mix_pool_bytes(r
, &fast_pool
->pool
, sizeof(fast_pool
->pool
), NULL
);
866 * If we don't have a valid cycle counter, and we see
867 * back-to-back timer interrupts, then skip giving credit for
871 if (irq_flags
& __IRQF_TIMER
) {
872 if (fast_pool
->last_timer_intr
)
874 fast_pool
->last_timer_intr
= 1;
876 fast_pool
->last_timer_intr
= 0;
878 credit_entropy_bits(r
, 1);
882 void add_disk_randomness(struct gendisk
*disk
)
884 if (!disk
|| !disk
->random
)
886 /* first major is 1, so we get >= 0x200 here */
887 add_timer_randomness(disk
->random
, 0x100 + disk_devt(disk
));
888 trace_add_disk_randomness(disk_devt(disk
), ENTROPY_BITS(&input_pool
));
892 /*********************************************************************
894 * Entropy extraction routines
896 *********************************************************************/
898 static ssize_t
extract_entropy(struct entropy_store
*r
, void *buf
,
899 size_t nbytes
, int min
, int rsvd
);
902 * This utility inline function is responsible for transferring entropy
903 * from the primary pool to the secondary extraction pool. We make
904 * sure we pull enough for a 'catastrophic reseed'.
906 static void _xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
);
907 static void xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
)
909 if (r
->limit
== 0 && random_min_urandom_seed
) {
910 unsigned long now
= jiffies
;
913 r
->last_pulled
+ random_min_urandom_seed
* HZ
))
915 r
->last_pulled
= now
;
918 r
->entropy_count
< (nbytes
<< (ENTROPY_SHIFT
+ 3)) &&
919 r
->entropy_count
< r
->poolinfo
->poolfracbits
)
920 _xfer_secondary_pool(r
, nbytes
);
923 static void _xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
)
925 __u32 tmp
[OUTPUT_POOL_WORDS
];
927 /* For /dev/random's pool, always leave two wakeup worth's BITS */
928 int rsvd
= r
->limit
? 0 : random_read_wakeup_thresh
/4;
931 /* pull at least as many as BYTES as wakeup BITS */
932 bytes
= max_t(int, bytes
, random_read_wakeup_thresh
/ 8);
933 /* but never more than the buffer size */
934 bytes
= min_t(int, bytes
, sizeof(tmp
));
936 trace_xfer_secondary_pool(r
->name
, bytes
* 8, nbytes
* 8,
937 ENTROPY_BITS(r
), ENTROPY_BITS(r
->pull
));
938 bytes
= extract_entropy(r
->pull
, tmp
, bytes
,
939 random_read_wakeup_thresh
/ 8, rsvd
);
940 mix_pool_bytes(r
, tmp
, bytes
, NULL
);
941 credit_entropy_bits(r
, bytes
*8);
945 * Used as a workqueue function so that when the input pool is getting
946 * full, we can "spill over" some entropy to the output pools. That
947 * way the output pools can store some of the excess entropy instead
948 * of letting it go to waste.
950 static void push_to_pool(struct work_struct
*work
)
952 struct entropy_store
*r
= container_of(work
, struct entropy_store
,
955 _xfer_secondary_pool(r
, random_read_wakeup_thresh
/8);
956 trace_push_to_pool(r
->name
, r
->entropy_count
>> ENTROPY_SHIFT
,
957 r
->pull
->entropy_count
>> ENTROPY_SHIFT
);
961 * These functions extracts randomness from the "entropy pool", and
962 * returns it in a buffer.
964 * The min parameter specifies the minimum amount we can pull before
965 * failing to avoid races that defeat catastrophic reseeding while the
966 * reserved parameter indicates how much entropy we must leave in the
967 * pool after each pull to avoid starving other readers.
969 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
972 static size_t account(struct entropy_store
*r
, size_t nbytes
, int min
,
976 int wakeup_write
= 0;
978 int entropy_count
, orig
;
981 /* Hold lock while accounting */
982 spin_lock_irqsave(&r
->lock
, flags
);
984 BUG_ON(r
->entropy_count
> r
->poolinfo
->poolfracbits
);
986 /* Can we pull enough? */
988 entropy_count
= orig
= ACCESS_ONCE(r
->entropy_count
);
989 have_bytes
= entropy_count
>> (ENTROPY_SHIFT
+ 3);
991 if (have_bytes
< min
+ reserved
) {
994 /* If limited, never pull more than available */
995 if (r
->limit
&& ibytes
+ reserved
>= have_bytes
)
996 ibytes
= have_bytes
- reserved
;
998 if (have_bytes
>= ibytes
+ reserved
)
999 entropy_count
-= ibytes
<< (ENTROPY_SHIFT
+ 3);
1001 entropy_count
= reserved
<< (ENTROPY_SHIFT
+ 3);
1003 if (cmpxchg(&r
->entropy_count
, orig
, entropy_count
) != orig
)
1006 if ((r
->entropy_count
>> ENTROPY_SHIFT
)
1007 < random_write_wakeup_thresh
)
1010 spin_unlock_irqrestore(&r
->lock
, flags
);
1012 trace_debit_entropy(r
->name
, 8 * ibytes
);
1014 wake_up_interruptible(&random_write_wait
);
1015 kill_fasync(&fasync
, SIGIO
, POLL_OUT
);
1021 static void extract_buf(struct entropy_store
*r
, __u8
*out
)
1026 unsigned long l
[LONGS(20)];
1028 __u32 workspace
[SHA_WORKSPACE_WORDS
];
1030 unsigned long flags
;
1032 /* Generate a hash across the pool, 16 words (512 bits) at a time */
1034 spin_lock_irqsave(&r
->lock
, flags
);
1035 for (i
= 0; i
< r
->poolinfo
->poolwords
; i
+= 16)
1036 sha_transform(hash
.w
, (__u8
*)(r
->pool
+ i
), workspace
);
1039 * If we have a architectural hardware random number
1040 * generator, mix that in, too.
1042 for (i
= 0; i
< LONGS(20); i
++) {
1044 if (!arch_get_random_long(&v
))
1050 * We mix the hash back into the pool to prevent backtracking
1051 * attacks (where the attacker knows the state of the pool
1052 * plus the current outputs, and attempts to find previous
1053 * ouputs), unless the hash function can be inverted. By
1054 * mixing at least a SHA1 worth of hash data back, we make
1055 * brute-forcing the feedback as hard as brute-forcing the
1058 __mix_pool_bytes(r
, hash
.w
, sizeof(hash
.w
), extract
);
1059 spin_unlock_irqrestore(&r
->lock
, flags
);
1062 * To avoid duplicates, we atomically extract a portion of the
1063 * pool while mixing, and hash one final time.
1065 sha_transform(hash
.w
, extract
, workspace
);
1066 memset(extract
, 0, sizeof(extract
));
1067 memset(workspace
, 0, sizeof(workspace
));
1070 * In case the hash function has some recognizable output
1071 * pattern, we fold it in half. Thus, we always feed back
1072 * twice as much data as we output.
1074 hash
.w
[0] ^= hash
.w
[3];
1075 hash
.w
[1] ^= hash
.w
[4];
1076 hash
.w
[2] ^= rol32(hash
.w
[2], 16);
1078 memcpy(out
, &hash
, EXTRACT_SIZE
);
1079 memset(&hash
, 0, sizeof(hash
));
1082 static ssize_t
extract_entropy(struct entropy_store
*r
, void *buf
,
1083 size_t nbytes
, int min
, int reserved
)
1086 __u8 tmp
[EXTRACT_SIZE
];
1087 unsigned long flags
;
1089 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1091 spin_lock_irqsave(&r
->lock
, flags
);
1092 if (!r
->last_data_init
) {
1093 r
->last_data_init
= 1;
1094 spin_unlock_irqrestore(&r
->lock
, flags
);
1095 trace_extract_entropy(r
->name
, EXTRACT_SIZE
,
1096 ENTROPY_BITS(r
), _RET_IP_
);
1097 xfer_secondary_pool(r
, EXTRACT_SIZE
);
1098 extract_buf(r
, tmp
);
1099 spin_lock_irqsave(&r
->lock
, flags
);
1100 memcpy(r
->last_data
, tmp
, EXTRACT_SIZE
);
1102 spin_unlock_irqrestore(&r
->lock
, flags
);
1105 trace_extract_entropy(r
->name
, nbytes
, ENTROPY_BITS(r
), _RET_IP_
);
1106 xfer_secondary_pool(r
, nbytes
);
1107 nbytes
= account(r
, nbytes
, min
, reserved
);
1110 extract_buf(r
, tmp
);
1113 spin_lock_irqsave(&r
->lock
, flags
);
1114 if (!memcmp(tmp
, r
->last_data
, EXTRACT_SIZE
))
1115 panic("Hardware RNG duplicated output!\n");
1116 memcpy(r
->last_data
, tmp
, EXTRACT_SIZE
);
1117 spin_unlock_irqrestore(&r
->lock
, flags
);
1119 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
1120 memcpy(buf
, tmp
, i
);
1126 /* Wipe data just returned from memory */
1127 memset(tmp
, 0, sizeof(tmp
));
1132 static ssize_t
extract_entropy_user(struct entropy_store
*r
, void __user
*buf
,
1136 __u8 tmp
[EXTRACT_SIZE
];
1138 trace_extract_entropy_user(r
->name
, nbytes
, ENTROPY_BITS(r
), _RET_IP_
);
1139 xfer_secondary_pool(r
, nbytes
);
1140 nbytes
= account(r
, nbytes
, 0, 0);
1143 if (need_resched()) {
1144 if (signal_pending(current
)) {
1152 extract_buf(r
, tmp
);
1153 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
1154 if (copy_to_user(buf
, tmp
, i
)) {
1164 /* Wipe data just returned from memory */
1165 memset(tmp
, 0, sizeof(tmp
));
1171 * This function is the exported kernel interface. It returns some
1172 * number of good random numbers, suitable for key generation, seeding
1173 * TCP sequence numbers, etc. It does not use the hw random number
1174 * generator, if available; use get_random_bytes_arch() for that.
1176 void get_random_bytes(void *buf
, int nbytes
)
1178 trace_get_random_bytes(nbytes
, _RET_IP_
);
1179 extract_entropy(&nonblocking_pool
, buf
, nbytes
, 0, 0);
1181 EXPORT_SYMBOL(get_random_bytes
);
1184 * This function will use the architecture-specific hardware random
1185 * number generator if it is available. The arch-specific hw RNG will
1186 * almost certainly be faster than what we can do in software, but it
1187 * is impossible to verify that it is implemented securely (as
1188 * opposed, to, say, the AES encryption of a sequence number using a
1189 * key known by the NSA). So it's useful if we need the speed, but
1190 * only if we're willing to trust the hardware manufacturer not to
1191 * have put in a back door.
1193 void get_random_bytes_arch(void *buf
, int nbytes
)
1197 trace_get_random_bytes_arch(nbytes
, _RET_IP_
);
1200 int chunk
= min(nbytes
, (int)sizeof(unsigned long));
1202 if (!arch_get_random_long(&v
))
1205 memcpy(p
, &v
, chunk
);
1211 extract_entropy(&nonblocking_pool
, p
, nbytes
, 0, 0);
1213 EXPORT_SYMBOL(get_random_bytes_arch
);
1217 * init_std_data - initialize pool with system data
1219 * @r: pool to initialize
1221 * This function clears the pool's entropy count and mixes some system
1222 * data into the pool to prepare it for use. The pool is not cleared
1223 * as that can only decrease the entropy in the pool.
1225 static void init_std_data(struct entropy_store
*r
)
1228 ktime_t now
= ktime_get_real();
1231 r
->last_pulled
= jiffies
;
1232 mix_pool_bytes(r
, &now
, sizeof(now
), NULL
);
1233 for (i
= r
->poolinfo
->poolbytes
; i
> 0; i
-= sizeof(rv
)) {
1234 if (!arch_get_random_long(&rv
))
1235 rv
= random_get_entropy();
1236 mix_pool_bytes(r
, &rv
, sizeof(rv
), NULL
);
1238 mix_pool_bytes(r
, utsname(), sizeof(*(utsname())), NULL
);
1242 * Note that setup_arch() may call add_device_randomness()
1243 * long before we get here. This allows seeding of the pools
1244 * with some platform dependent data very early in the boot
1245 * process. But it limits our options here. We must use
1246 * statically allocated structures that already have all
1247 * initializations complete at compile time. We should also
1248 * take care not to overwrite the precious per platform data
1251 static int rand_initialize(void)
1253 init_std_data(&input_pool
);
1254 init_std_data(&blocking_pool
);
1255 init_std_data(&nonblocking_pool
);
1258 early_initcall(rand_initialize
);
1261 void rand_initialize_disk(struct gendisk
*disk
)
1263 struct timer_rand_state
*state
;
1266 * If kzalloc returns null, we just won't use that entropy
1269 state
= kzalloc(sizeof(struct timer_rand_state
), GFP_KERNEL
);
1271 disk
->random
= state
;
1276 random_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
1278 ssize_t n
, retval
= 0, count
= 0;
1283 while (nbytes
> 0) {
1285 if (n
> SEC_XFER_SIZE
)
1288 n
= extract_entropy_user(&blocking_pool
, buf
, n
);
1295 trace_random_read(n
*8, (nbytes
-n
)*8,
1296 ENTROPY_BITS(&blocking_pool
),
1297 ENTROPY_BITS(&input_pool
));
1300 if (file
->f_flags
& O_NONBLOCK
) {
1305 wait_event_interruptible(random_read_wait
,
1306 ENTROPY_BITS(&input_pool
) >=
1307 random_read_wakeup_thresh
);
1309 if (signal_pending(current
)) {
1310 retval
= -ERESTARTSYS
;
1320 break; /* This break makes the device work */
1321 /* like a named pipe */
1324 return (count
? count
: retval
);
1328 urandom_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
1332 if (unlikely(nonblocking_pool
.initialized
== 0))
1333 printk_once(KERN_NOTICE
"random: %s urandom read "
1334 "with %d bits of entropy available\n",
1335 current
->comm
, nonblocking_pool
.entropy_total
);
1337 ret
= extract_entropy_user(&nonblocking_pool
, buf
, nbytes
);
1339 trace_urandom_read(8 * nbytes
, ENTROPY_BITS(&nonblocking_pool
),
1340 ENTROPY_BITS(&input_pool
));
1345 random_poll(struct file
*file
, poll_table
* wait
)
1349 poll_wait(file
, &random_read_wait
, wait
);
1350 poll_wait(file
, &random_write_wait
, wait
);
1352 if (ENTROPY_BITS(&input_pool
) >= random_read_wakeup_thresh
)
1353 mask
|= POLLIN
| POLLRDNORM
;
1354 if (ENTROPY_BITS(&input_pool
) < random_write_wakeup_thresh
)
1355 mask
|= POLLOUT
| POLLWRNORM
;
1360 write_pool(struct entropy_store
*r
, const char __user
*buffer
, size_t count
)
1364 const char __user
*p
= buffer
;
1367 bytes
= min(count
, sizeof(buf
));
1368 if (copy_from_user(&buf
, p
, bytes
))
1374 mix_pool_bytes(r
, buf
, bytes
, NULL
);
1381 static ssize_t
random_write(struct file
*file
, const char __user
*buffer
,
1382 size_t count
, loff_t
*ppos
)
1386 ret
= write_pool(&blocking_pool
, buffer
, count
);
1389 ret
= write_pool(&nonblocking_pool
, buffer
, count
);
1393 return (ssize_t
)count
;
1396 static long random_ioctl(struct file
*f
, unsigned int cmd
, unsigned long arg
)
1398 int size
, ent_count
;
1399 int __user
*p
= (int __user
*)arg
;
1404 /* inherently racy, no point locking */
1405 ent_count
= ENTROPY_BITS(&input_pool
);
1406 if (put_user(ent_count
, p
))
1409 case RNDADDTOENTCNT
:
1410 if (!capable(CAP_SYS_ADMIN
))
1412 if (get_user(ent_count
, p
))
1414 credit_entropy_bits_safe(&input_pool
, ent_count
);
1417 if (!capable(CAP_SYS_ADMIN
))
1419 if (get_user(ent_count
, p
++))
1423 if (get_user(size
, p
++))
1425 retval
= write_pool(&input_pool
, (const char __user
*)p
,
1429 credit_entropy_bits_safe(&input_pool
, ent_count
);
1434 * Clear the entropy pool counters. We no longer clear
1435 * the entropy pool, as that's silly.
1437 if (!capable(CAP_SYS_ADMIN
))
1439 input_pool
.entropy_count
= 0;
1440 nonblocking_pool
.entropy_count
= 0;
1441 blocking_pool
.entropy_count
= 0;
1448 static int random_fasync(int fd
, struct file
*filp
, int on
)
1450 return fasync_helper(fd
, filp
, on
, &fasync
);
1453 const struct file_operations random_fops
= {
1454 .read
= random_read
,
1455 .write
= random_write
,
1456 .poll
= random_poll
,
1457 .unlocked_ioctl
= random_ioctl
,
1458 .fasync
= random_fasync
,
1459 .llseek
= noop_llseek
,
1462 const struct file_operations urandom_fops
= {
1463 .read
= urandom_read
,
1464 .write
= random_write
,
1465 .unlocked_ioctl
= random_ioctl
,
1466 .fasync
= random_fasync
,
1467 .llseek
= noop_llseek
,
1470 /***************************************************************
1471 * Random UUID interface
1473 * Used here for a Boot ID, but can be useful for other kernel
1475 ***************************************************************/
1478 * Generate random UUID
1480 void generate_random_uuid(unsigned char uuid_out
[16])
1482 get_random_bytes(uuid_out
, 16);
1483 /* Set UUID version to 4 --- truly random generation */
1484 uuid_out
[6] = (uuid_out
[6] & 0x0F) | 0x40;
1485 /* Set the UUID variant to DCE */
1486 uuid_out
[8] = (uuid_out
[8] & 0x3F) | 0x80;
1488 EXPORT_SYMBOL(generate_random_uuid
);
1490 /********************************************************************
1494 ********************************************************************/
1496 #ifdef CONFIG_SYSCTL
1498 #include <linux/sysctl.h>
1500 static int min_read_thresh
= 8, min_write_thresh
;
1501 static int max_read_thresh
= INPUT_POOL_WORDS
* 32;
1502 static int max_write_thresh
= INPUT_POOL_WORDS
* 32;
1503 static char sysctl_bootid
[16];
1506 * These functions is used to return both the bootid UUID, and random
1507 * UUID. The difference is in whether table->data is NULL; if it is,
1508 * then a new UUID is generated and returned to the user.
1510 * If the user accesses this via the proc interface, it will be returned
1511 * as an ASCII string in the standard UUID format. If accesses via the
1512 * sysctl system call, it is returned as 16 bytes of binary data.
1514 static int proc_do_uuid(struct ctl_table
*table
, int write
,
1515 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1517 struct ctl_table fake_table
;
1518 unsigned char buf
[64], tmp_uuid
[16], *uuid
;
1523 generate_random_uuid(uuid
);
1525 static DEFINE_SPINLOCK(bootid_spinlock
);
1527 spin_lock(&bootid_spinlock
);
1529 generate_random_uuid(uuid
);
1530 spin_unlock(&bootid_spinlock
);
1533 sprintf(buf
, "%pU", uuid
);
1535 fake_table
.data
= buf
;
1536 fake_table
.maxlen
= sizeof(buf
);
1538 return proc_dostring(&fake_table
, write
, buffer
, lenp
, ppos
);
1542 * Return entropy available scaled to integral bits
1544 static int proc_do_entropy(ctl_table
*table
, int write
,
1545 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1547 ctl_table fake_table
;
1550 entropy_count
= *(int *)table
->data
>> ENTROPY_SHIFT
;
1552 fake_table
.data
= &entropy_count
;
1553 fake_table
.maxlen
= sizeof(entropy_count
);
1555 return proc_dointvec(&fake_table
, write
, buffer
, lenp
, ppos
);
1558 static int sysctl_poolsize
= INPUT_POOL_WORDS
* 32;
1559 extern struct ctl_table random_table
[];
1560 struct ctl_table random_table
[] = {
1562 .procname
= "poolsize",
1563 .data
= &sysctl_poolsize
,
1564 .maxlen
= sizeof(int),
1566 .proc_handler
= proc_dointvec
,
1569 .procname
= "entropy_avail",
1570 .maxlen
= sizeof(int),
1572 .proc_handler
= proc_do_entropy
,
1573 .data
= &input_pool
.entropy_count
,
1576 .procname
= "read_wakeup_threshold",
1577 .data
= &random_read_wakeup_thresh
,
1578 .maxlen
= sizeof(int),
1580 .proc_handler
= proc_dointvec_minmax
,
1581 .extra1
= &min_read_thresh
,
1582 .extra2
= &max_read_thresh
,
1585 .procname
= "write_wakeup_threshold",
1586 .data
= &random_write_wakeup_thresh
,
1587 .maxlen
= sizeof(int),
1589 .proc_handler
= proc_dointvec_minmax
,
1590 .extra1
= &min_write_thresh
,
1591 .extra2
= &max_write_thresh
,
1594 .procname
= "urandom_min_reseed_secs",
1595 .data
= &random_min_urandom_seed
,
1596 .maxlen
= sizeof(int),
1598 .proc_handler
= proc_dointvec
,
1601 .procname
= "boot_id",
1602 .data
= &sysctl_bootid
,
1605 .proc_handler
= proc_do_uuid
,
1611 .proc_handler
= proc_do_uuid
,
1615 #endif /* CONFIG_SYSCTL */
1617 static u32 random_int_secret
[MD5_MESSAGE_BYTES
/ 4] ____cacheline_aligned
;
1619 int random_int_secret_init(void)
1621 get_random_bytes(random_int_secret
, sizeof(random_int_secret
));
1626 * Get a random word for internal kernel use only. Similar to urandom but
1627 * with the goal of minimal entropy pool depletion. As a result, the random
1628 * value is not cryptographically secure but for several uses the cost of
1629 * depleting entropy is too high
1631 static DEFINE_PER_CPU(__u32
[MD5_DIGEST_WORDS
], get_random_int_hash
);
1632 unsigned int get_random_int(void)
1637 if (arch_get_random_int(&ret
))
1640 hash
= get_cpu_var(get_random_int_hash
);
1642 hash
[0] += current
->pid
+ jiffies
+ random_get_entropy();
1643 md5_transform(hash
, random_int_secret
);
1645 put_cpu_var(get_random_int_hash
);
1649 EXPORT_SYMBOL(get_random_int
);
1652 * randomize_range() returns a start address such that
1654 * [...... <range> .....]
1657 * a <range> with size "len" starting at the return value is inside in the
1658 * area defined by [start, end], but is otherwise randomized.
1661 randomize_range(unsigned long start
, unsigned long end
, unsigned long len
)
1663 unsigned long range
= end
- len
- start
;
1665 if (end
<= start
+ len
)
1667 return PAGE_ALIGN(get_random_int() % range
+ start
);