1 /*
2 * random.c -- A strong random number generator
3 *
4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
5 *
6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
7 * rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, and the entire permission notice in its entirety,
14 * including the disclaimer of warranties.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. The name of the author may not be used to endorse or promote
19 * products derived from this software without specific prior
20 * written permission.
21 *
22 * ALTERNATIVELY, this product may be distributed under the terms of
23 * the GNU General Public License, in which case the provisions of the GPL are
24 * required INSTEAD OF the above restrictions. (This clause is
25 * necessary due to a potential bad interaction between the GPL and
26 * the restrictions contained in a BSD-style copyright.)
27 *
28 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
31 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
32 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
34 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
35 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
36 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
38 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
39 * DAMAGE.
40 */
41
42 /*
43 * (now, with legal B.S. out of the way.....)
44 *
45 * This routine gathers environmental noise from device drivers, etc.,
46 * and returns good random numbers, suitable for cryptographic use.
47 * Besides the obvious cryptographic uses, these numbers are also good
48 * for seeding TCP sequence numbers, and other places where it is
49 * desirable to have numbers which are not only random, but hard to
50 * predict by an attacker.
51 *
52 * Theory of operation
53 * ===================
54 *
55 * Computers are very predictable devices. Hence it is extremely hard
56 * to produce truly random numbers on a computer --- as opposed to
57 * pseudo-random numbers, which can easily generated by using a
58 * algorithm. Unfortunately, it is very easy for attackers to guess
59 * the sequence of pseudo-random number generators, and for some
60 * applications this is not acceptable. So instead, we must try to
61 * gather "environmental noise" from the computer's environment, which
62 * must be hard for outside attackers to observe, and use that to
63 * generate random numbers. In a Unix environment, this is best done
64 * from inside the kernel.
65 *
66 * Sources of randomness from the environment include inter-keyboard
67 * timings, inter-interrupt timings from some interrupts, and other
68 * events which are both (a) non-deterministic and (b) hard for an
69 * outside observer to measure. Randomness from these sources are
70 * added to an "entropy pool", which is mixed using a CRC-like function.
71 * This is not cryptographically strong, but it is adequate assuming
72 * the randomness is not chosen maliciously, and it is fast enough that
73 * the overhead of doing it on every interrupt is very reasonable.
74 * As random bytes are mixed into the entropy pool, the routines keep
75 * an *estimate* of how many bits of randomness have been stored into
76 * the random number generator's internal state.
77 *
78 * When random bytes are desired, they are obtained by taking the SHA
79 * hash of the contents of the "entropy pool". The SHA hash avoids
80 * exposing the internal state of the entropy pool. It is believed to
81 * be computationally infeasible to derive any useful information
82 * about the input of SHA from its output. Even if it is possible to
83 * analyze SHA in some clever way, as long as the amount of data
84 * returned from the generator is less than the inherent entropy in
85 * the pool, the output data is totally unpredictable. For this
86 * reason, the routine decreases its internal estimate of how many
87 * bits of "true randomness" are contained in the entropy pool as it
88 * outputs random numbers.
89 *
90 * If this estimate goes to zero, the routine can still generate
91 * random numbers; however, an attacker may (at least in theory) be
92 * able to infer the future output of the generator from prior
93 * outputs. This requires successful cryptanalysis of SHA, which is
94 * not believed to be feasible, but there is a remote possibility.
95 * Nonetheless, these numbers should be useful for the vast majority
96 * of purposes.
97 *
98 * Exported interfaces ---- output
99 * ===============================
100 *
101 * There are three exported interfaces; the first is one designed to
102 * be used from within the kernel:
103 *
104 * void get_random_bytes(void *buf, int nbytes);
105 *
106 * This interface will return the requested number of random bytes,
107 * and place it in the requested buffer.
108 *
109 * The two other interfaces are two character devices /dev/random and
110 * /dev/urandom. /dev/random is suitable for use when very high
111 * quality randomness is desired (for example, for key generation or
112 * one-time pads), as it will only return a maximum of the number of
113 * bits of randomness (as estimated by the random number generator)
114 * contained in the entropy pool.
115 *
116 * The /dev/urandom device does not have this limit, and will return
117 * as many bytes as are requested. As more and more random bytes are
118 * requested without giving time for the entropy pool to recharge,
119 * this will result in random numbers that are merely cryptographically
120 * strong. For many applications, however, this is acceptable.
121 *
122 * Exported interfaces ---- input
123 * ==============================
124 *
125 * The current exported interfaces for gathering environmental noise
126 * from the devices are:
127 *
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);
133 *
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).
141 *
142 * add_input_randomness() uses the input layer interrupt timing, as well as
143 * the event type information from the hardware.
144 *
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.
148 *
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.
154 *
155 * All of these routines try to estimate how many bits of randomness a
156 * particular randomness source. They do this by keeping track of the
157 * first and second order deltas of the event timings.
158 *
159 * Ensuring unpredictability at system startup
160 * ============================================
161 *
162 * When any operating system starts up, it will go through a sequence
163 * of actions that are fairly predictable by an adversary, especially
164 * if the start-up does not involve interaction with a human operator.
165 * This reduces the actual number of bits of unpredictability in the
166 * entropy pool below the value in entropy_count. In order to
167 * counteract this effect, it helps to carry information in the
168 * entropy pool across shut-downs and start-ups. To do this, put the
169 * following lines an appropriate script which is run during the boot
170 * sequence:
171 *
172 * echo "Initializing random number generator..."
173 * random_seed=/var/run/random-seed
174 * # Carry a random seed from start-up to start-up
175 * # Load and then save the whole entropy pool
176 * if [ -f $random_seed ]; then
177 * cat $random_seed >/dev/urandom
178 * else
179 * touch $random_seed
180 * fi
181 * chmod 600 $random_seed
182 * dd if=/dev/urandom of=$random_seed count=1 bs=512
183 *
184 * and the following lines in an appropriate script which is run as
185 * the system is shutdown:
186 *
187 * # Carry a random seed from shut-down to start-up
188 * # Save the whole entropy pool
189 * echo "Saving random seed..."
190 * random_seed=/var/run/random-seed
191 * touch $random_seed
192 * chmod 600 $random_seed
193 * dd if=/dev/urandom of=$random_seed count=1 bs=512
194 *
195 * For example, on most modern systems using the System V init
196 * scripts, such code fragments would be found in
197 * /etc/rc.d/init.d/random. On older Linux systems, the correct script
198 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
199 *
200 * Effectively, these commands cause the contents of the entropy pool
201 * to be saved at shut-down time and reloaded into the entropy pool at
202 * start-up. (The 'dd' in the addition to the bootup script is to
203 * make sure that /etc/random-seed is different for every start-up,
204 * even if the system crashes without executing rc.0.) Even with
205 * complete knowledge of the start-up activities, predicting the state
206 * of the entropy pool requires knowledge of the previous history of
207 * the system.
208 *
209 * Configuring the /dev/random driver under Linux
210 * ==============================================
211 *
212 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
213 * the /dev/mem major number (#1). So if your system does not have
214 * /dev/random and /dev/urandom created already, they can be created
215 * by using the commands:
216 *
217 * mknod /dev/random c 1 8
218 * mknod /dev/urandom c 1 9
219 *
220 * Acknowledgements:
221 * =================
222 *
223 * Ideas for constructing this random number generator were derived
224 * from Pretty Good Privacy's random number generator, and from private
225 * discussions with Phil Karn. Colin Plumb provided a faster random
226 * number generator, which speed up the mixing function of the entropy
227 * pool, taken from PGPfone. Dale Worley has also contributed many
228 * useful ideas and suggestions to improve this driver.
229 *
230 * Any flaws in the design are solely my responsibility, and should
231 * not be attributed to the Phil, Colin, or any of authors of PGP.
232 *
233 * Further background information on this topic may be obtained from
234 * RFC 1750, "Randomness Recommendations for Security", by Donald
235 * Eastlake, Steve Crocker, and Jeff Schiller.
236 */
237
238 #include <linux/utsname.h>
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
259 #ifdef CONFIG_GENERIC_HARDIRQS
260 # include <linux/irq.h>
261 #endif
262
263 #include <asm/processor.h>
264 #include <asm/uaccess.h>
265 #include <asm/irq.h>
266 #include <asm/irq_regs.h>
267 #include <asm/io.h>
268
269 #define CREATE_TRACE_POINTS
270 #include <trace/events/random.h>
271
272 /*
273 * Configuration information
274 */
275 #define INPUT_POOL_WORDS 128
276 #define OUTPUT_POOL_WORDS 32
277 #define SEC_XFER_SIZE 512
278 #define EXTRACT_SIZE 10
279
280 #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
281
282 /*
283 * The minimum number of bits of entropy before we wake up a read on
284 * /dev/random. Should be enough to do a significant reseed.
285 */
286 static int random_read_wakeup_thresh = 64;
287
288 /*
289 * If the entropy count falls under this number of bits, then we
290 * should wake up processes which are selecting or polling on write
291 * access to /dev/random.
292 */
293 static int random_write_wakeup_thresh = 128;
294
295 /*
296 * When the input pool goes over trickle_thresh, start dropping most
297 * samples to avoid wasting CPU time and reduce lock contention.
298 */
299
300 static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
301
302 static DEFINE_PER_CPU(int, trickle_count);
303
304 /*
305 * A pool of size .poolwords is stirred with a primitive polynomial
306 * of degree .poolwords over GF(2). The taps for various sizes are
307 * defined below. They are chosen to be evenly spaced (minimum RMS
308 * distance from evenly spaced; the numbers in the comments are a
309 * scaled squared error sum) except for the last tap, which is 1 to
310 * get the twisting happening as fast as possible.
311 */
312 static struct poolinfo {
313 int poolwords;
314 int tap1, tap2, tap3, tap4, tap5;
315 } poolinfo_table[] = {
316 /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
317 { 128, 103, 76, 51, 25, 1 },
318 /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
319 { 32, 26, 20, 14, 7, 1 },
320 #if 0
321 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
322 { 2048, 1638, 1231, 819, 411, 1 },
323
324 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
325 { 1024, 817, 615, 412, 204, 1 },
326
327 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
328 { 1024, 819, 616, 410, 207, 2 },
329
330 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
331 { 512, 411, 308, 208, 104, 1 },
332
333 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
334 { 512, 409, 307, 206, 102, 2 },
335 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
336 { 512, 409, 309, 205, 103, 2 },
337
338 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
339 { 256, 205, 155, 101, 52, 1 },
340
341 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
342 { 128, 103, 78, 51, 27, 2 },
343
344 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
345 { 64, 52, 39, 26, 14, 1 },
346 #endif
347 };
348
349 #define POOLBITS poolwords*32
350 #define POOLBYTES poolwords*4
351
352 /*
353 * For the purposes of better mixing, we use the CRC-32 polynomial as
354 * well to make a twisted Generalized Feedback Shift Reigster
355 *
356 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
357 * Transactions on Modeling and Computer Simulation 2(3):179-194.
358 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
359 * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
360 *
361 * Thanks to Colin Plumb for suggesting this.
362 *
363 * We have not analyzed the resultant polynomial to prove it primitive;
364 * in fact it almost certainly isn't. Nonetheless, the irreducible factors
365 * of a random large-degree polynomial over GF(2) are more than large enough
366 * that periodicity is not a concern.
367 *
368 * The input hash is much less sensitive than the output hash. All
369 * that we want of it is that it be a good non-cryptographic hash;
370 * i.e. it not produce collisions when fed "random" data of the sort
371 * we expect to see. As long as the pool state differs for different
372 * inputs, we have preserved the input entropy and done a good job.
373 * The fact that an intelligent attacker can construct inputs that
374 * will produce controlled alterations to the pool's state is not
375 * important because we don't consider such inputs to contribute any
376 * randomness. The only property we need with respect to them is that
377 * the attacker can't increase his/her knowledge of the pool's state.
378 * Since all additions are reversible (knowing the final state and the
379 * input, you can reconstruct the initial state), if an attacker has
380 * any uncertainty about the initial state, he/she can only shuffle
381 * that uncertainty about, but never cause any collisions (which would
382 * decrease the uncertainty).
383 *
384 * The chosen system lets the state of the pool be (essentially) the input
385 * modulo the generator polymnomial. Now, for random primitive polynomials,
386 * this is a universal class of hash functions, meaning that the chance
387 * of a collision is limited by the attacker's knowledge of the generator
388 * polynomail, so if it is chosen at random, an attacker can never force
389 * a collision. Here, we use a fixed polynomial, but we *can* assume that
390 * ###--> it is unknown to the processes generating the input entropy. <-###
391 * Because of this important property, this is a good, collision-resistant
392 * hash; hash collisions will occur no more often than chance.
393 */
394
395 /*
396 * Static global variables
397 */
398 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
399 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
400 static struct fasync_struct *fasync;
401
402 #if 0
403 static bool debug;
404 module_param(debug, bool, 0644);
405 #define DEBUG_ENT(fmt, arg...) do { \
406 if (debug) \
407 printk(KERN_DEBUG "random %04d %04d %04d: " \
408 fmt,\
409 input_pool.entropy_count,\
410 blocking_pool.entropy_count,\
411 nonblocking_pool.entropy_count,\
412 ## arg); } while (0)
413 #else
414 #define DEBUG_ENT(fmt, arg...) do {} while (0)
415 #endif
416
417 /**********************************************************************
418 *
419 * OS independent entropy store. Here are the functions which handle
420 * storing entropy in an entropy pool.
421 *
422 **********************************************************************/
423
424 struct entropy_store;
425 struct entropy_store {
426 /* read-only data: */
427 struct poolinfo *poolinfo;
428 __u32 *pool;
429 const char *name;
430 struct entropy_store *pull;
431 int limit;
432
433 /* read-write data: */
434 spinlock_t lock;
435 unsigned add_ptr;
436 unsigned input_rotate;
437 int entropy_count;
438 int entropy_total;
439 unsigned int initialized:1;
440 __u8 last_data[EXTRACT_SIZE];
441 };
442
443 static __u32 input_pool_data[INPUT_POOL_WORDS];
444 static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
445 static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
446
447 static struct entropy_store input_pool = {
448 .poolinfo = &poolinfo_table[0],
449 .name = "input",
450 .limit = 1,
451 .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock),
452 .pool = input_pool_data
453 };
454
455 static struct entropy_store blocking_pool = {
456 .poolinfo = &poolinfo_table[1],
457 .name = "blocking",
458 .limit = 1,
459 .pull = &input_pool,
460 .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock),
461 .pool = blocking_pool_data
462 };
463
464 static struct entropy_store nonblocking_pool = {
465 .poolinfo = &poolinfo_table[1],
466 .name = "nonblocking",
467 .pull = &input_pool,
468 .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock),
469 .pool = nonblocking_pool_data
470 };
471
472 static __u32 const twist_table[8] = {
473 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
474 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
475
476 /*
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.
480 *
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.
485 */
_mix_pool_bytes(struct entropy_store * r,const void * in,int nbytes,__u8 out[64])486 static void _mix_pool_bytes(struct entropy_store *r, const void *in,
487 int nbytes, __u8 out[64])
488 {
489 unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
490 int input_rotate;
491 int wordmask = r->poolinfo->poolwords - 1;
492 const char *bytes = in;
493 __u32 w;
494
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;
500
501 smp_rmb();
502 input_rotate = ACCESS_ONCE(r->input_rotate);
503 i = ACCESS_ONCE(r->add_ptr);
504
505 /* mix one byte at a time to simplify size handling and churn faster */
506 while (nbytes--) {
507 w = rol32(*bytes++, input_rotate & 31);
508 i = (i - 1) & wordmask;
509
510 /* XOR in the various taps */
511 w ^= r->pool[i];
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];
517
518 /* Mix the result back in with a twist */
519 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
520
521 /*
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.
526 */
527 input_rotate += i ? 7 : 14;
528 }
529
530 ACCESS_ONCE(r->input_rotate) = input_rotate;
531 ACCESS_ONCE(r->add_ptr) = i;
532 smp_wmb();
533
534 if (out)
535 for (j = 0; j < 16; j++)
536 ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
537 }
538
__mix_pool_bytes(struct entropy_store * r,const void * in,int nbytes,__u8 out[64])539 static void __mix_pool_bytes(struct entropy_store *r, const void *in,
540 int nbytes, __u8 out[64])
541 {
542 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
543 _mix_pool_bytes(r, in, nbytes, out);
544 }
545
mix_pool_bytes(struct entropy_store * r,const void * in,int nbytes,__u8 out[64])546 static void mix_pool_bytes(struct entropy_store *r, const void *in,
547 int nbytes, __u8 out[64])
548 {
549 unsigned long flags;
550
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);
555 }
556
557 struct fast_pool {
558 __u32 pool[4];
559 unsigned long last;
560 unsigned short count;
561 unsigned char rotate;
562 unsigned char last_timer_intr;
563 };
564
565 /*
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.
569 */
fast_mix(struct fast_pool * f,const void * in,int nbytes)570 static void fast_mix(struct fast_pool *f, const void *in, int nbytes)
571 {
572 const char *bytes = in;
573 __u32 w;
574 unsigned i = f->count;
575 unsigned input_rotate = f->rotate;
576
577 while (nbytes--) {
578 w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
579 f->pool[(i + 1) & 3];
580 f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
581 input_rotate += (i++ & 3) ? 7 : 14;
582 }
583 f->count = i;
584 f->rotate = input_rotate;
585 }
586
587 /*
588 * Credit (or debit) the entropy store with n bits of entropy
589 */
credit_entropy_bits(struct entropy_store * r,int nbits)590 static void credit_entropy_bits(struct entropy_store *r, int nbits)
591 {
592 int entropy_count, orig;
593
594 if (!nbits)
595 return;
596
597 DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
598 retry:
599 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
600 entropy_count += nbits;
601
602 if (entropy_count < 0) {
603 DEBUG_ENT("negative entropy/overflow\n");
604 entropy_count = 0;
605 } else if (entropy_count > r->poolinfo->POOLBITS)
606 entropy_count = r->poolinfo->POOLBITS;
607 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
608 goto retry;
609
610 if (!r->initialized && nbits > 0) {
611 r->entropy_total += nbits;
612 if (r->entropy_total > 128)
613 r->initialized = 1;
614 }
615
616 trace_credit_entropy_bits(r->name, nbits, entropy_count,
617 r->entropy_total, _RET_IP_);
618
619 /* should we wake readers? */
620 if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
621 wake_up_interruptible(&random_read_wait);
622 kill_fasync(&fasync, SIGIO, POLL_IN);
623 }
624 }
625
626 /*********************************************************************
627 *
628 * Entropy input management
629 *
630 *********************************************************************/
631
632 /* There is one of these per entropy source */
633 struct timer_rand_state {
634 cycles_t last_time;
635 long last_delta, last_delta2;
636 unsigned dont_count_entropy:1;
637 };
638
639 /*
640 * Add device- or boot-specific data to the input and nonblocking
641 * pools to help initialize them to unique values.
642 *
643 * None of this adds any entropy, it is meant to avoid the
644 * problem of the nonblocking pool having similar initial state
645 * across largely identical devices.
646 */
add_device_randomness(const void * buf,unsigned int size)647 void add_device_randomness(const void *buf, unsigned int size)
648 {
649 unsigned long time = get_cycles() ^ jiffies;
650
651 mix_pool_bytes(&input_pool, buf, size, NULL);
652 mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
653 mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
654 mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
655 }
656 EXPORT_SYMBOL(add_device_randomness);
657
658 static struct timer_rand_state input_timer_state;
659
660 /*
661 * This function adds entropy to the entropy "pool" by using timing
662 * delays. It uses the timer_rand_state structure to make an estimate
663 * of how many bits of entropy this call has added to the pool.
664 *
665 * The number "num" is also added to the pool - it should somehow describe
666 * the type of event which just happened. This is currently 0-255 for
667 * keyboard scan codes, and 256 upwards for interrupts.
668 *
669 */
add_timer_randomness(struct timer_rand_state * state,unsigned num)670 static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
671 {
672 struct {
673 long jiffies;
674 unsigned cycles;
675 unsigned num;
676 } sample;
677 long delta, delta2, delta3;
678
679 preempt_disable();
680 /* if over the trickle threshold, use only 1 in 4096 samples */
681 if (input_pool.entropy_count > trickle_thresh &&
682 ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
683 goto out;
684
685 sample.jiffies = jiffies;
686 sample.cycles = get_cycles();
687 sample.num = num;
688 mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
689
690 /*
691 * Calculate number of bits of randomness we probably added.
692 * We take into account the first, second and third-order deltas
693 * in order to make our estimate.
694 */
695
696 if (!state->dont_count_entropy) {
697 delta = sample.jiffies - state->last_time;
698 state->last_time = sample.jiffies;
699
700 delta2 = delta - state->last_delta;
701 state->last_delta = delta;
702
703 delta3 = delta2 - state->last_delta2;
704 state->last_delta2 = delta2;
705
706 if (delta < 0)
707 delta = -delta;
708 if (delta2 < 0)
709 delta2 = -delta2;
710 if (delta3 < 0)
711 delta3 = -delta3;
712 if (delta > delta2)
713 delta = delta2;
714 if (delta > delta3)
715 delta = delta3;
716
717 /*
718 * delta is now minimum absolute delta.
719 * Round down by 1 bit on general principles,
720 * and limit entropy entimate to 12 bits.
721 */
722 credit_entropy_bits(&input_pool,
723 min_t(int, fls(delta>>1), 11));
724 }
725 out:
726 preempt_enable();
727 }
728
add_input_randomness(unsigned int type,unsigned int code,unsigned int value)729 void add_input_randomness(unsigned int type, unsigned int code,
730 unsigned int value)
731 {
732 static unsigned char last_value;
733
734 /* ignore autorepeat and the like */
735 if (value == last_value)
736 return;
737
738 DEBUG_ENT("input event\n");
739 last_value = value;
740 add_timer_randomness(&input_timer_state,
741 (type << 4) ^ code ^ (code >> 4) ^ value);
742 }
743 EXPORT_SYMBOL_GPL(add_input_randomness);
744
745 static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
746
add_interrupt_randomness(int irq,int irq_flags)747 void add_interrupt_randomness(int irq, int irq_flags)
748 {
749 struct entropy_store *r;
750 struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness);
751 struct pt_regs *regs = get_irq_regs();
752 unsigned long now = jiffies;
753 __u32 input[4], cycles = get_cycles();
754
755 input[0] = cycles ^ jiffies;
756 input[1] = irq;
757 if (regs) {
758 __u64 ip = instruction_pointer(regs);
759 input[2] = ip;
760 input[3] = ip >> 32;
761 }
762
763 fast_mix(fast_pool, input, sizeof(input));
764
765 if ((fast_pool->count & 1023) &&
766 !time_after(now, fast_pool->last + HZ))
767 return;
768
769 fast_pool->last = now;
770
771 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
772 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
773 /*
774 * If we don't have a valid cycle counter, and we see
775 * back-to-back timer interrupts, then skip giving credit for
776 * any entropy.
777 */
778 if (cycles == 0) {
779 if (irq_flags & __IRQF_TIMER) {
780 if (fast_pool->last_timer_intr)
781 return;
782 fast_pool->last_timer_intr = 1;
783 } else
784 fast_pool->last_timer_intr = 0;
785 }
786 credit_entropy_bits(r, 1);
787 }
788
789 #ifdef CONFIG_BLOCK
add_disk_randomness(struct gendisk * disk)790 void add_disk_randomness(struct gendisk *disk)
791 {
792 if (!disk || !disk->random)
793 return;
794 /* first major is 1, so we get >= 0x200 here */
795 DEBUG_ENT("disk event %d:%d\n",
796 MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
797
798 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
799 }
800 #endif
801
802 /*********************************************************************
803 *
804 * Entropy extraction routines
805 *
806 *********************************************************************/
807
808 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
809 size_t nbytes, int min, int rsvd);
810
811 /*
812 * This utility inline function is responsible for transferring entropy
813 * from the primary pool to the secondary extraction pool. We make
814 * sure we pull enough for a 'catastrophic reseed'.
815 */
xfer_secondary_pool(struct entropy_store * r,size_t nbytes)816 static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
817 {
818 __u32 tmp[OUTPUT_POOL_WORDS];
819
820 if (r->pull && r->entropy_count < nbytes * 8 &&
821 r->entropy_count < r->poolinfo->POOLBITS) {
822 /* If we're limited, always leave two wakeup worth's BITS */
823 int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
824 int bytes = nbytes;
825
826 /* pull at least as many as BYTES as wakeup BITS */
827 bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
828 /* but never more than the buffer size */
829 bytes = min_t(int, bytes, sizeof(tmp));
830
831 DEBUG_ENT("going to reseed %s with %d bits "
832 "(%d of %d requested)\n",
833 r->name, bytes * 8, nbytes * 8, r->entropy_count);
834
835 bytes = extract_entropy(r->pull, tmp, bytes,
836 random_read_wakeup_thresh / 8, rsvd);
837 mix_pool_bytes(r, tmp, bytes, NULL);
838 credit_entropy_bits(r, bytes*8);
839 }
840 }
841
842 /*
843 * These functions extracts randomness from the "entropy pool", and
844 * returns it in a buffer.
845 *
846 * The min parameter specifies the minimum amount we can pull before
847 * failing to avoid races that defeat catastrophic reseeding while the
848 * reserved parameter indicates how much entropy we must leave in the
849 * pool after each pull to avoid starving other readers.
850 *
851 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
852 */
853
account(struct entropy_store * r,size_t nbytes,int min,int reserved)854 static size_t account(struct entropy_store *r, size_t nbytes, int min,
855 int reserved)
856 {
857 unsigned long flags;
858
859 /* Hold lock while accounting */
860 spin_lock_irqsave(&r->lock, flags);
861
862 BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
863 DEBUG_ENT("trying to extract %d bits from %s\n",
864 nbytes * 8, r->name);
865
866 /* Can we pull enough? */
867 if (r->entropy_count / 8 < min + reserved) {
868 nbytes = 0;
869 } else {
870 int entropy_count, orig;
871 retry:
872 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
873 /* If limited, never pull more than available */
874 if (r->limit && nbytes + reserved >= entropy_count / 8)
875 nbytes = entropy_count/8 - reserved;
876
877 if (entropy_count / 8 >= nbytes + reserved) {
878 entropy_count -= nbytes*8;
879 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
880 goto retry;
881 } else {
882 entropy_count = reserved;
883 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
884 goto retry;
885 }
886
887 if (entropy_count < random_write_wakeup_thresh) {
888 wake_up_interruptible(&random_write_wait);
889 kill_fasync(&fasync, SIGIO, POLL_OUT);
890 }
891 }
892
893 DEBUG_ENT("debiting %d entropy credits from %s%s\n",
894 nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
895
896 spin_unlock_irqrestore(&r->lock, flags);
897
898 return nbytes;
899 }
900
extract_buf(struct entropy_store * r,__u8 * out)901 static void extract_buf(struct entropy_store *r, __u8 *out)
902 {
903 int i;
904 union {
905 __u32 w[5];
906 unsigned long l[LONGS(EXTRACT_SIZE)];
907 } hash;
908 __u32 workspace[SHA_WORKSPACE_WORDS];
909 __u8 extract[64];
910 unsigned long flags;
911
912 /* Generate a hash across the pool, 16 words (512 bits) at a time */
913 sha_init(hash.w);
914 spin_lock_irqsave(&r->lock, flags);
915 for (i = 0; i < r->poolinfo->poolwords; i += 16)
916 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
917
918 /*
919 * We mix the hash back into the pool to prevent backtracking
920 * attacks (where the attacker knows the state of the pool
921 * plus the current outputs, and attempts to find previous
922 * ouputs), unless the hash function can be inverted. By
923 * mixing at least a SHA1 worth of hash data back, we make
924 * brute-forcing the feedback as hard as brute-forcing the
925 * hash.
926 */
927 __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
928 spin_unlock_irqrestore(&r->lock, flags);
929
930 /*
931 * To avoid duplicates, we atomically extract a portion of the
932 * pool while mixing, and hash one final time.
933 */
934 sha_transform(hash.w, extract, workspace);
935 memset(extract, 0, sizeof(extract));
936 memset(workspace, 0, sizeof(workspace));
937
938 /*
939 * In case the hash function has some recognizable output
940 * pattern, we fold it in half. Thus, we always feed back
941 * twice as much data as we output.
942 */
943 hash.w[0] ^= hash.w[3];
944 hash.w[1] ^= hash.w[4];
945 hash.w[2] ^= rol32(hash.w[2], 16);
946
947 /*
948 * If we have a architectural hardware random number
949 * generator, mix that in, too.
950 */
951 for (i = 0; i < LONGS(EXTRACT_SIZE); i++) {
952 unsigned long v;
953 if (!arch_get_random_long(&v))
954 break;
955 hash.l[i] ^= v;
956 }
957
958 memcpy(out, &hash, EXTRACT_SIZE);
959 memset(&hash, 0, sizeof(hash));
960 }
961
extract_entropy(struct entropy_store * r,void * buf,size_t nbytes,int min,int reserved)962 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
963 size_t nbytes, int min, int reserved)
964 {
965 ssize_t ret = 0, i;
966 __u8 tmp[EXTRACT_SIZE];
967
968 trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
969 xfer_secondary_pool(r, nbytes);
970 nbytes = account(r, nbytes, min, reserved);
971
972 while (nbytes) {
973 extract_buf(r, tmp);
974
975 if (fips_enabled) {
976 unsigned long flags;
977
978 spin_lock_irqsave(&r->lock, flags);
979 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
980 panic("Hardware RNG duplicated output!\n");
981 memcpy(r->last_data, tmp, EXTRACT_SIZE);
982 spin_unlock_irqrestore(&r->lock, flags);
983 }
984 i = min_t(int, nbytes, EXTRACT_SIZE);
985 memcpy(buf, tmp, i);
986 nbytes -= i;
987 buf += i;
988 ret += i;
989 }
990
991 /* Wipe data just returned from memory */
992 memset(tmp, 0, sizeof(tmp));
993
994 return ret;
995 }
996
extract_entropy_user(struct entropy_store * r,void __user * buf,size_t nbytes)997 static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
998 size_t nbytes)
999 {
1000 ssize_t ret = 0, i;
1001 __u8 tmp[EXTRACT_SIZE];
1002
1003 trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
1004 xfer_secondary_pool(r, nbytes);
1005 nbytes = account(r, nbytes, 0, 0);
1006
1007 while (nbytes) {
1008 if (need_resched()) {
1009 if (signal_pending(current)) {
1010 if (ret == 0)
1011 ret = -ERESTARTSYS;
1012 break;
1013 }
1014 schedule();
1015 }
1016
1017 extract_buf(r, tmp);
1018 i = min_t(int, nbytes, EXTRACT_SIZE);
1019 if (copy_to_user(buf, tmp, i)) {
1020 ret = -EFAULT;
1021 break;
1022 }
1023
1024 nbytes -= i;
1025 buf += i;
1026 ret += i;
1027 }
1028
1029 /* Wipe data just returned from memory */
1030 memset(tmp, 0, sizeof(tmp));
1031
1032 return ret;
1033 }
1034
1035 /*
1036 * This function is the exported kernel interface. It returns some
1037 * number of good random numbers, suitable for key generation, seeding
1038 * TCP sequence numbers, etc. It does not use the hw random number
1039 * generator, if available; use get_random_bytes_arch() for that.
1040 */
get_random_bytes(void * buf,int nbytes)1041 void get_random_bytes(void *buf, int nbytes)
1042 {
1043 extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1044 }
1045 EXPORT_SYMBOL(get_random_bytes);
1046
1047 /*
1048 * This function will use the architecture-specific hardware random
1049 * number generator if it is available. The arch-specific hw RNG will
1050 * almost certainly be faster than what we can do in software, but it
1051 * is impossible to verify that it is implemented securely (as
1052 * opposed, to, say, the AES encryption of a sequence number using a
1053 * key known by the NSA). So it's useful if we need the speed, but
1054 * only if we're willing to trust the hardware manufacturer not to
1055 * have put in a back door.
1056 */
get_random_bytes_arch(void * buf,int nbytes)1057 void get_random_bytes_arch(void *buf, int nbytes)
1058 {
1059 char *p = buf;
1060
1061 trace_get_random_bytes(nbytes, _RET_IP_);
1062 while (nbytes) {
1063 unsigned long v;
1064 int chunk = min(nbytes, (int)sizeof(unsigned long));
1065
1066 if (!arch_get_random_long(&v))
1067 break;
1068
1069 memcpy(p, &v, chunk);
1070 p += chunk;
1071 nbytes -= chunk;
1072 }
1073
1074 if (nbytes)
1075 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1076 }
1077 EXPORT_SYMBOL(get_random_bytes_arch);
1078
1079
1080 /*
1081 * init_std_data - initialize pool with system data
1082 *
1083 * @r: pool to initialize
1084 *
1085 * This function clears the pool's entropy count and mixes some system
1086 * data into the pool to prepare it for use. The pool is not cleared
1087 * as that can only decrease the entropy in the pool.
1088 */
init_std_data(struct entropy_store * r)1089 static void init_std_data(struct entropy_store *r)
1090 {
1091 int i;
1092 ktime_t now = ktime_get_real();
1093 unsigned long rv;
1094
1095 r->entropy_count = 0;
1096 r->entropy_total = 0;
1097 mix_pool_bytes(r, &now, sizeof(now), NULL);
1098 for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) {
1099 if (!arch_get_random_long(&rv))
1100 break;
1101 mix_pool_bytes(r, &rv, sizeof(rv), NULL);
1102 }
1103 mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
1104 }
1105
1106 /*
1107 * Note that setup_arch() may call add_device_randomness()
1108 * long before we get here. This allows seeding of the pools
1109 * with some platform dependent data very early in the boot
1110 * process. But it limits our options here. We must use
1111 * statically allocated structures that already have all
1112 * initializations complete at compile time. We should also
1113 * take care not to overwrite the precious per platform data
1114 * we were given.
1115 */
rand_initialize(void)1116 static int rand_initialize(void)
1117 {
1118 init_std_data(&input_pool);
1119 init_std_data(&blocking_pool);
1120 init_std_data(&nonblocking_pool);
1121 return 0;
1122 }
1123 module_init(rand_initialize);
1124
1125 #ifdef CONFIG_BLOCK
rand_initialize_disk(struct gendisk * disk)1126 void rand_initialize_disk(struct gendisk *disk)
1127 {
1128 struct timer_rand_state *state;
1129
1130 /*
1131 * If kzalloc returns null, we just won't use that entropy
1132 * source.
1133 */
1134 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1135 if (state)
1136 disk->random = state;
1137 }
1138 #endif
1139
1140 static ssize_t
random_read(struct file * file,char __user * buf,size_t nbytes,loff_t * ppos)1141 random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1142 {
1143 ssize_t n, retval = 0, count = 0;
1144
1145 if (nbytes == 0)
1146 return 0;
1147
1148 while (nbytes > 0) {
1149 n = nbytes;
1150 if (n > SEC_XFER_SIZE)
1151 n = SEC_XFER_SIZE;
1152
1153 DEBUG_ENT("reading %d bits\n", n*8);
1154
1155 n = extract_entropy_user(&blocking_pool, buf, n);
1156
1157 DEBUG_ENT("read got %d bits (%d still needed)\n",
1158 n*8, (nbytes-n)*8);
1159
1160 if (n == 0) {
1161 if (file->f_flags & O_NONBLOCK) {
1162 retval = -EAGAIN;
1163 break;
1164 }
1165
1166 DEBUG_ENT("sleeping?\n");
1167
1168 wait_event_interruptible(random_read_wait,
1169 input_pool.entropy_count >=
1170 random_read_wakeup_thresh);
1171
1172 DEBUG_ENT("awake\n");
1173
1174 if (signal_pending(current)) {
1175 retval = -ERESTARTSYS;
1176 break;
1177 }
1178
1179 continue;
1180 }
1181
1182 if (n < 0) {
1183 retval = n;
1184 break;
1185 }
1186 count += n;
1187 buf += n;
1188 nbytes -= n;
1189 break; /* This break makes the device work */
1190 /* like a named pipe */
1191 }
1192
1193 return (count ? count : retval);
1194 }
1195
1196 static ssize_t
urandom_read(struct file * file,char __user * buf,size_t nbytes,loff_t * ppos)1197 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1198 {
1199 return extract_entropy_user(&nonblocking_pool, buf, nbytes);
1200 }
1201
1202 static unsigned int
random_poll(struct file * file,poll_table * wait)1203 random_poll(struct file *file, poll_table * wait)
1204 {
1205 unsigned int mask;
1206
1207 poll_wait(file, &random_read_wait, wait);
1208 poll_wait(file, &random_write_wait, wait);
1209 mask = 0;
1210 if (input_pool.entropy_count >= random_read_wakeup_thresh)
1211 mask |= POLLIN | POLLRDNORM;
1212 if (input_pool.entropy_count < random_write_wakeup_thresh)
1213 mask |= POLLOUT | POLLWRNORM;
1214 return mask;
1215 }
1216
1217 static int
write_pool(struct entropy_store * r,const char __user * buffer,size_t count)1218 write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1219 {
1220 size_t bytes;
1221 __u32 buf[16];
1222 const char __user *p = buffer;
1223
1224 while (count > 0) {
1225 bytes = min(count, sizeof(buf));
1226 if (copy_from_user(&buf, p, bytes))
1227 return -EFAULT;
1228
1229 count -= bytes;
1230 p += bytes;
1231
1232 mix_pool_bytes(r, buf, bytes, NULL);
1233 cond_resched();
1234 }
1235
1236 return 0;
1237 }
1238
random_write(struct file * file,const char __user * buffer,size_t count,loff_t * ppos)1239 static ssize_t random_write(struct file *file, const char __user *buffer,
1240 size_t count, loff_t *ppos)
1241 {
1242 size_t ret;
1243
1244 ret = write_pool(&blocking_pool, buffer, count);
1245 if (ret)
1246 return ret;
1247 ret = write_pool(&nonblocking_pool, buffer, count);
1248 if (ret)
1249 return ret;
1250
1251 return (ssize_t)count;
1252 }
1253
random_ioctl(struct file * f,unsigned int cmd,unsigned long arg)1254 static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1255 {
1256 int size, ent_count;
1257 int __user *p = (int __user *)arg;
1258 int retval;
1259
1260 switch (cmd) {
1261 case RNDGETENTCNT:
1262 /* inherently racy, no point locking */
1263 if (put_user(input_pool.entropy_count, p))
1264 return -EFAULT;
1265 return 0;
1266 case RNDADDTOENTCNT:
1267 if (!capable(CAP_SYS_ADMIN))
1268 return -EPERM;
1269 if (get_user(ent_count, p))
1270 return -EFAULT;
1271 credit_entropy_bits(&input_pool, ent_count);
1272 return 0;
1273 case RNDADDENTROPY:
1274 if (!capable(CAP_SYS_ADMIN))
1275 return -EPERM;
1276 if (get_user(ent_count, p++))
1277 return -EFAULT;
1278 if (ent_count < 0)
1279 return -EINVAL;
1280 if (get_user(size, p++))
1281 return -EFAULT;
1282 retval = write_pool(&input_pool, (const char __user *)p,
1283 size);
1284 if (retval < 0)
1285 return retval;
1286 credit_entropy_bits(&input_pool, ent_count);
1287 return 0;
1288 case RNDZAPENTCNT:
1289 case RNDCLEARPOOL:
1290 /* Clear the entropy pool counters. */
1291 if (!capable(CAP_SYS_ADMIN))
1292 return -EPERM;
1293 rand_initialize();
1294 return 0;
1295 default:
1296 return -EINVAL;
1297 }
1298 }
1299
random_fasync(int fd,struct file * filp,int on)1300 static int random_fasync(int fd, struct file *filp, int on)
1301 {
1302 return fasync_helper(fd, filp, on, &fasync);
1303 }
1304
1305 const struct file_operations random_fops = {
1306 .read = random_read,
1307 .write = random_write,
1308 .poll = random_poll,
1309 .unlocked_ioctl = random_ioctl,
1310 .fasync = random_fasync,
1311 .llseek = noop_llseek,
1312 };
1313
1314 const struct file_operations urandom_fops = {
1315 .read = urandom_read,
1316 .write = random_write,
1317 .unlocked_ioctl = random_ioctl,
1318 .fasync = random_fasync,
1319 .llseek = noop_llseek,
1320 };
1321
1322 /***************************************************************
1323 * Random UUID interface
1324 *
1325 * Used here for a Boot ID, but can be useful for other kernel
1326 * drivers.
1327 ***************************************************************/
1328
1329 /*
1330 * Generate random UUID
1331 */
generate_random_uuid(unsigned char uuid_out[16])1332 void generate_random_uuid(unsigned char uuid_out[16])
1333 {
1334 get_random_bytes(uuid_out, 16);
1335 /* Set UUID version to 4 --- truly random generation */
1336 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1337 /* Set the UUID variant to DCE */
1338 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1339 }
1340 EXPORT_SYMBOL(generate_random_uuid);
1341
1342 /********************************************************************
1343 *
1344 * Sysctl interface
1345 *
1346 ********************************************************************/
1347
1348 #ifdef CONFIG_SYSCTL
1349
1350 #include <linux/sysctl.h>
1351
1352 static int min_read_thresh = 8, min_write_thresh;
1353 static int max_read_thresh = INPUT_POOL_WORDS * 32;
1354 static int max_write_thresh = INPUT_POOL_WORDS * 32;
1355 static char sysctl_bootid[16];
1356
1357 /*
1358 * These functions is used to return both the bootid UUID, and random
1359 * UUID. The difference is in whether table->data is NULL; if it is,
1360 * then a new UUID is generated and returned to the user.
1361 *
1362 * If the user accesses this via the proc interface, it will be returned
1363 * as an ASCII string in the standard UUID format. If accesses via the
1364 * sysctl system call, it is returned as 16 bytes of binary data.
1365 */
proc_do_uuid(ctl_table * table,int write,void __user * buffer,size_t * lenp,loff_t * ppos)1366 static int proc_do_uuid(ctl_table *table, int write,
1367 void __user *buffer, size_t *lenp, loff_t *ppos)
1368 {
1369 ctl_table fake_table;
1370 unsigned char buf[64], tmp_uuid[16], *uuid;
1371
1372 uuid = table->data;
1373 if (!uuid) {
1374 uuid = tmp_uuid;
1375 generate_random_uuid(uuid);
1376 } else {
1377 static DEFINE_SPINLOCK(bootid_spinlock);
1378
1379 spin_lock(&bootid_spinlock);
1380 if (!uuid[8])
1381 generate_random_uuid(uuid);
1382 spin_unlock(&bootid_spinlock);
1383 }
1384
1385 sprintf(buf, "%pU", uuid);
1386
1387 fake_table.data = buf;
1388 fake_table.maxlen = sizeof(buf);
1389
1390 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1391 }
1392
1393 static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1394 ctl_table random_table[] = {
1395 {
1396 .procname = "poolsize",
1397 .data = &sysctl_poolsize,
1398 .maxlen = sizeof(int),
1399 .mode = 0444,
1400 .proc_handler = proc_dointvec,
1401 },
1402 {
1403 .procname = "entropy_avail",
1404 .maxlen = sizeof(int),
1405 .mode = 0444,
1406 .proc_handler = proc_dointvec,
1407 .data = &input_pool.entropy_count,
1408 },
1409 {
1410 .procname = "read_wakeup_threshold",
1411 .data = &random_read_wakeup_thresh,
1412 .maxlen = sizeof(int),
1413 .mode = 0644,
1414 .proc_handler = proc_dointvec_minmax,
1415 .extra1 = &min_read_thresh,
1416 .extra2 = &max_read_thresh,
1417 },
1418 {
1419 .procname = "write_wakeup_threshold",
1420 .data = &random_write_wakeup_thresh,
1421 .maxlen = sizeof(int),
1422 .mode = 0644,
1423 .proc_handler = proc_dointvec_minmax,
1424 .extra1 = &min_write_thresh,
1425 .extra2 = &max_write_thresh,
1426 },
1427 {
1428 .procname = "boot_id",
1429 .data = &sysctl_bootid,
1430 .maxlen = 16,
1431 .mode = 0444,
1432 .proc_handler = proc_do_uuid,
1433 },
1434 {
1435 .procname = "uuid",
1436 .maxlen = 16,
1437 .mode = 0444,
1438 .proc_handler = proc_do_uuid,
1439 },
1440 { }
1441 };
1442 #endif /* CONFIG_SYSCTL */
1443
1444 static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1445
random_int_secret_init(void)1446 int random_int_secret_init(void)
1447 {
1448 get_random_bytes(random_int_secret, sizeof(random_int_secret));
1449 return 0;
1450 }
1451
1452 /*
1453 * Get a random word for internal kernel use only. Similar to urandom but
1454 * with the goal of minimal entropy pool depletion. As a result, the random
1455 * value is not cryptographically secure but for several uses the cost of
1456 * depleting entropy is too high
1457 */
1458 DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
get_random_int(void)1459 unsigned int get_random_int(void)
1460 {
1461 __u32 *hash;
1462 unsigned int ret;
1463
1464 if (arch_get_random_int(&ret))
1465 return ret;
1466
1467 hash = get_cpu_var(get_random_int_hash);
1468
1469 hash[0] += current->pid + jiffies + get_cycles();
1470 md5_transform(hash, random_int_secret);
1471 ret = hash[0];
1472 put_cpu_var(get_random_int_hash);
1473
1474 return ret;
1475 }
1476
1477 /*
1478 * randomize_range() returns a start address such that
1479 *
1480 * [...... <range> .....]
1481 * start end
1482 *
1483 * a <range> with size "len" starting at the return value is inside in the
1484 * area defined by [start, end], but is otherwise randomized.
1485 */
1486 unsigned long
randomize_range(unsigned long start,unsigned long end,unsigned long len)1487 randomize_range(unsigned long start, unsigned long end, unsigned long len)
1488 {
1489 unsigned long range = end - len - start;
1490
1491 if (end <= start + len)
1492 return 0;
1493 return PAGE_ALIGN(get_random_int() % range + start);
1494 }
1495