Line data Source code
1 : /*
2 : * random.c -- A strong random number generator
3 : *
4 : * Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All
5 : * Rights Reserved.
6 : *
7 : * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
8 : *
9 : * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
10 : * rights reserved.
11 : *
12 : * Redistribution and use in source and binary forms, with or without
13 : * modification, are permitted provided that the following conditions
14 : * are met:
15 : * 1. Redistributions of source code must retain the above copyright
16 : * notice, and the entire permission notice in its entirety,
17 : * including the disclaimer of warranties.
18 : * 2. Redistributions in binary form must reproduce the above copyright
19 : * notice, this list of conditions and the following disclaimer in the
20 : * documentation and/or other materials provided with the distribution.
21 : * 3. The name of the author may not be used to endorse or promote
22 : * products derived from this software without specific prior
23 : * written permission.
24 : *
25 : * ALTERNATIVELY, this product may be distributed under the terms of
26 : * the GNU General Public License, in which case the provisions of the GPL are
27 : * required INSTEAD OF the above restrictions. (This clause is
28 : * necessary due to a potential bad interaction between the GPL and
29 : * the restrictions contained in a BSD-style copyright.)
30 : *
31 : * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
32 : * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
33 : * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
34 : * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
35 : * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
36 : * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
37 : * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
38 : * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
39 : * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40 : * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
41 : * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
42 : * DAMAGE.
43 : */
44 :
45 : /*
46 : * (now, with legal B.S. out of the way.....)
47 : *
48 : * This routine gathers environmental noise from device drivers, etc.,
49 : * and returns good random numbers, suitable for cryptographic use.
50 : * Besides the obvious cryptographic uses, these numbers are also good
51 : * for seeding TCP sequence numbers, and other places where it is
52 : * desirable to have numbers which are not only random, but hard to
53 : * predict by an attacker.
54 : *
55 : * Theory of operation
56 : * ===================
57 : *
58 : * Computers are very predictable devices. Hence it is extremely hard
59 : * to produce truly random numbers on a computer --- as opposed to
60 : * pseudo-random numbers, which can easily generated by using a
61 : * algorithm. Unfortunately, it is very easy for attackers to guess
62 : * the sequence of pseudo-random number generators, and for some
63 : * applications this is not acceptable. So instead, we must try to
64 : * gather "environmental noise" from the computer's environment, which
65 : * must be hard for outside attackers to observe, and use that to
66 : * generate random numbers. In a Unix environment, this is best done
67 : * from inside the kernel.
68 : *
69 : * Sources of randomness from the environment include inter-keyboard
70 : * timings, inter-interrupt timings from some interrupts, and other
71 : * events which are both (a) non-deterministic and (b) hard for an
72 : * outside observer to measure. Randomness from these sources are
73 : * added to an "entropy pool", which is mixed using a CRC-like function.
74 : * This is not cryptographically strong, but it is adequate assuming
75 : * the randomness is not chosen maliciously, and it is fast enough that
76 : * the overhead of doing it on every interrupt is very reasonable.
77 : * As random bytes are mixed into the entropy pool, the routines keep
78 : * an *estimate* of how many bits of randomness have been stored into
79 : * the random number generator's internal state.
80 : *
81 : * When random bytes are desired, they are obtained by taking the SHA
82 : * hash of the contents of the "entropy pool". The SHA hash avoids
83 : * exposing the internal state of the entropy pool. It is believed to
84 : * be computationally infeasible to derive any useful information
85 : * about the input of SHA from its output. Even if it is possible to
86 : * analyze SHA in some clever way, as long as the amount of data
87 : * returned from the generator is less than the inherent entropy in
88 : * the pool, the output data is totally unpredictable. For this
89 : * reason, the routine decreases its internal estimate of how many
90 : * bits of "true randomness" are contained in the entropy pool as it
91 : * outputs random numbers.
92 : *
93 : * If this estimate goes to zero, the routine can still generate
94 : * random numbers; however, an attacker may (at least in theory) be
95 : * able to infer the future output of the generator from prior
96 : * outputs. This requires successful cryptanalysis of SHA, which is
97 : * not believed to be feasible, but there is a remote possibility.
98 : * Nonetheless, these numbers should be useful for the vast majority
99 : * of purposes.
100 : *
101 : * Exported interfaces ---- output
102 : * ===============================
103 : *
104 : * There are four exported interfaces; two for use within the kernel,
105 : * and two or use from userspace.
106 : *
107 : * Exported interfaces ---- userspace output
108 : * -----------------------------------------
109 : *
110 : * The userspace interfaces are two character devices /dev/random and
111 : * /dev/urandom. /dev/random is suitable for use when very high
112 : * quality randomness is desired (for example, for key generation or
113 : * one-time pads), as it will only return a maximum of the number of
114 : * bits of randomness (as estimated by the random number generator)
115 : * contained in the entropy pool.
116 : *
117 : * The /dev/urandom device does not have this limit, and will return
118 : * as many bytes as are requested. As more and more random bytes are
119 : * requested without giving time for the entropy pool to recharge,
120 : * this will result in random numbers that are merely cryptographically
121 : * strong. For many applications, however, this is acceptable.
122 : *
123 : * Exported interfaces ---- kernel output
124 : * --------------------------------------
125 : *
126 : * The primary kernel interface is
127 : *
128 : * void get_random_bytes(void *buf, int nbytes);
129 : *
130 : * This interface will return the requested number of random bytes,
131 : * and place it in the requested buffer. This is equivalent to a
132 : * read from /dev/urandom.
133 : *
134 : * For less critical applications, there are the functions:
135 : *
136 : * u32 get_random_u32()
137 : * u64 get_random_u64()
138 : * unsigned int get_random_int()
139 : * unsigned long get_random_long()
140 : *
141 : * These are produced by a cryptographic RNG seeded from get_random_bytes,
142 : * and so do not deplete the entropy pool as much. These are recommended
143 : * for most in-kernel operations *if the result is going to be stored in
144 : * the kernel*.
145 : *
146 : * Specifically, the get_random_int() family do not attempt to do
147 : * "anti-backtracking". If you capture the state of the kernel (e.g.
148 : * by snapshotting the VM), you can figure out previous get_random_int()
149 : * return values. But if the value is stored in the kernel anyway,
150 : * this is not a problem.
151 : *
152 : * It *is* safe to expose get_random_int() output to attackers (e.g. as
153 : * network cookies); given outputs 1..n, it's not feasible to predict
154 : * outputs 0 or n+1. The only concern is an attacker who breaks into
155 : * the kernel later; the get_random_int() engine is not reseeded as
156 : * often as the get_random_bytes() one.
157 : *
158 : * get_random_bytes() is needed for keys that need to stay secret after
159 : * they are erased from the kernel. For example, any key that will
160 : * be wrapped and stored encrypted. And session encryption keys: we'd
161 : * like to know that after the session is closed and the keys erased,
162 : * the plaintext is unrecoverable to someone who recorded the ciphertext.
163 : *
164 : * But for network ports/cookies, stack canaries, PRNG seeds, address
165 : * space layout randomization, session *authentication* keys, or other
166 : * applications where the sensitive data is stored in the kernel in
167 : * plaintext for as long as it's sensitive, the get_random_int() family
168 : * is just fine.
169 : *
170 : * Consider ASLR. We want to keep the address space secret from an
171 : * outside attacker while the process is running, but once the address
172 : * space is torn down, it's of no use to an attacker any more. And it's
173 : * stored in kernel data structures as long as it's alive, so worrying
174 : * about an attacker's ability to extrapolate it from the get_random_int()
175 : * CRNG is silly.
176 : *
177 : * Even some cryptographic keys are safe to generate with get_random_int().
178 : * In particular, keys for SipHash are generally fine. Here, knowledge
179 : * of the key authorizes you to do something to a kernel object (inject
180 : * packets to a network connection, or flood a hash table), and the
181 : * key is stored with the object being protected. Once it goes away,
182 : * we no longer care if anyone knows the key.
183 : *
184 : * prandom_u32()
185 : * -------------
186 : *
187 : * For even weaker applications, see the pseudorandom generator
188 : * prandom_u32(), prandom_max(), and prandom_bytes(). If the random
189 : * numbers aren't security-critical at all, these are *far* cheaper.
190 : * Useful for self-tests, random error simulation, randomized backoffs,
191 : * and any other application where you trust that nobody is trying to
192 : * maliciously mess with you by guessing the "random" numbers.
193 : *
194 : * Exported interfaces ---- input
195 : * ==============================
196 : *
197 : * The current exported interfaces for gathering environmental noise
198 : * from the devices are:
199 : *
200 : * void add_device_randomness(const void *buf, unsigned int size);
201 : * void add_input_randomness(unsigned int type, unsigned int code,
202 : * unsigned int value);
203 : * void add_interrupt_randomness(int irq, int irq_flags);
204 : * void add_disk_randomness(struct gendisk *disk);
205 : *
206 : * add_device_randomness() is for adding data to the random pool that
207 : * is likely to differ between two devices (or possibly even per boot).
208 : * This would be things like MAC addresses or serial numbers, or the
209 : * read-out of the RTC. This does *not* add any actual entropy to the
210 : * pool, but it initializes the pool to different values for devices
211 : * that might otherwise be identical and have very little entropy
212 : * available to them (particularly common in the embedded world).
213 : *
214 : * add_input_randomness() uses the input layer interrupt timing, as well as
215 : * the event type information from the hardware.
216 : *
217 : * add_interrupt_randomness() uses the interrupt timing as random
218 : * inputs to the entropy pool. Using the cycle counters and the irq source
219 : * as inputs, it feeds the randomness roughly once a second.
220 : *
221 : * add_disk_randomness() uses what amounts to the seek time of block
222 : * layer request events, on a per-disk_devt basis, as input to the
223 : * entropy pool. Note that high-speed solid state drives with very low
224 : * seek times do not make for good sources of entropy, as their seek
225 : * times are usually fairly consistent.
226 : *
227 : * All of these routines try to estimate how many bits of randomness a
228 : * particular randomness source. They do this by keeping track of the
229 : * first and second order deltas of the event timings.
230 : *
231 : * Ensuring unpredictability at system startup
232 : * ============================================
233 : *
234 : * When any operating system starts up, it will go through a sequence
235 : * of actions that are fairly predictable by an adversary, especially
236 : * if the start-up does not involve interaction with a human operator.
237 : * This reduces the actual number of bits of unpredictability in the
238 : * entropy pool below the value in entropy_count. In order to
239 : * counteract this effect, it helps to carry information in the
240 : * entropy pool across shut-downs and start-ups. To do this, put the
241 : * following lines an appropriate script which is run during the boot
242 : * sequence:
243 : *
244 : * echo "Initializing random number generator..."
245 : * random_seed=/var/run/random-seed
246 : * # Carry a random seed from start-up to start-up
247 : * # Load and then save the whole entropy pool
248 : * if [ -f $random_seed ]; then
249 : * cat $random_seed >/dev/urandom
250 : * else
251 : * touch $random_seed
252 : * fi
253 : * chmod 600 $random_seed
254 : * dd if=/dev/urandom of=$random_seed count=1 bs=512
255 : *
256 : * and the following lines in an appropriate script which is run as
257 : * the system is shutdown:
258 : *
259 : * # Carry a random seed from shut-down to start-up
260 : * # Save the whole entropy pool
261 : * echo "Saving random seed..."
262 : * random_seed=/var/run/random-seed
263 : * touch $random_seed
264 : * chmod 600 $random_seed
265 : * dd if=/dev/urandom of=$random_seed count=1 bs=512
266 : *
267 : * For example, on most modern systems using the System V init
268 : * scripts, such code fragments would be found in
269 : * /etc/rc.d/init.d/random. On older Linux systems, the correct script
270 : * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
271 : *
272 : * Effectively, these commands cause the contents of the entropy pool
273 : * to be saved at shut-down time and reloaded into the entropy pool at
274 : * start-up. (The 'dd' in the addition to the bootup script is to
275 : * make sure that /etc/random-seed is different for every start-up,
276 : * even if the system crashes without executing rc.0.) Even with
277 : * complete knowledge of the start-up activities, predicting the state
278 : * of the entropy pool requires knowledge of the previous history of
279 : * the system.
280 : *
281 : * Configuring the /dev/random driver under Linux
282 : * ==============================================
283 : *
284 : * The /dev/random driver under Linux uses minor numbers 8 and 9 of
285 : * the /dev/mem major number (#1). So if your system does not have
286 : * /dev/random and /dev/urandom created already, they can be created
287 : * by using the commands:
288 : *
289 : * mknod /dev/random c 1 8
290 : * mknod /dev/urandom c 1 9
291 : *
292 : * Acknowledgements:
293 : * =================
294 : *
295 : * Ideas for constructing this random number generator were derived
296 : * from Pretty Good Privacy's random number generator, and from private
297 : * discussions with Phil Karn. Colin Plumb provided a faster random
298 : * number generator, which speed up the mixing function of the entropy
299 : * pool, taken from PGPfone. Dale Worley has also contributed many
300 : * useful ideas and suggestions to improve this driver.
301 : *
302 : * Any flaws in the design are solely my responsibility, and should
303 : * not be attributed to the Phil, Colin, or any of authors of PGP.
304 : *
305 : * Further background information on this topic may be obtained from
306 : * RFC 1750, "Randomness Recommendations for Security", by Donald
307 : * Eastlake, Steve Crocker, and Jeff Schiller.
308 : */
309 :
310 : #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
311 :
312 : #include <linux/utsname.h>
313 : #include <linux/module.h>
314 : #include <linux/kernel.h>
315 : #include <linux/major.h>
316 : #include <linux/string.h>
317 : #include <linux/fcntl.h>
318 : #include <linux/slab.h>
319 : #include <linux/random.h>
320 : #include <linux/poll.h>
321 : #include <linux/init.h>
322 : #include <linux/fs.h>
323 : #include <linux/genhd.h>
324 : #include <linux/interrupt.h>
325 : #include <linux/mm.h>
326 : #include <linux/nodemask.h>
327 : #include <linux/spinlock.h>
328 : #include <linux/kthread.h>
329 : #include <linux/percpu.h>
330 : #include <linux/fips.h>
331 : #include <linux/ptrace.h>
332 : #include <linux/workqueue.h>
333 : #include <linux/irq.h>
334 : #include <linux/ratelimit.h>
335 : #include <linux/syscalls.h>
336 : #include <linux/completion.h>
337 : #include <linux/uuid.h>
338 : #include <crypto/chacha.h>
339 : #include <crypto/sha1.h>
340 :
341 : #include <asm/processor.h>
342 : #include <linux/uaccess.h>
343 : #include <asm/irq.h>
344 : #include <asm/irq_regs.h>
345 : #include <asm/io.h>
346 :
347 : #define CREATE_TRACE_POINTS
348 : #include <trace/events/random.h>
349 :
350 : /* #define ADD_INTERRUPT_BENCH */
351 :
352 : /*
353 : * Configuration information
354 : */
355 : #define INPUT_POOL_SHIFT 12
356 : #define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
357 : #define OUTPUT_POOL_SHIFT 10
358 : #define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
359 : #define EXTRACT_SIZE 10
360 :
361 :
362 : #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
363 :
364 : /*
365 : * To allow fractional bits to be tracked, the entropy_count field is
366 : * denominated in units of 1/8th bits.
367 : *
368 : * 2*(ENTROPY_SHIFT + poolbitshift) must <= 31, or the multiply in
369 : * credit_entropy_bits() needs to be 64 bits wide.
370 : */
371 : #define ENTROPY_SHIFT 3
372 : #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
373 :
374 : /*
375 : * If the entropy count falls under this number of bits, then we
376 : * should wake up processes which are selecting or polling on write
377 : * access to /dev/random.
378 : */
379 : static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
380 :
381 : /*
382 : * Originally, we used a primitive polynomial of degree .poolwords
383 : * over GF(2). The taps for various sizes are defined below. They
384 : * were chosen to be evenly spaced except for the last tap, which is 1
385 : * to get the twisting happening as fast as possible.
386 : *
387 : * For the purposes of better mixing, we use the CRC-32 polynomial as
388 : * well to make a (modified) twisted Generalized Feedback Shift
389 : * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
390 : * generators. ACM Transactions on Modeling and Computer Simulation
391 : * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
392 : * GFSR generators II. ACM Transactions on Modeling and Computer
393 : * Simulation 4:254-266)
394 : *
395 : * Thanks to Colin Plumb for suggesting this.
396 : *
397 : * The mixing operation is much less sensitive than the output hash,
398 : * where we use SHA-1. All that we want of mixing operation is that
399 : * it be a good non-cryptographic hash; i.e. it not produce collisions
400 : * when fed "random" data of the sort we expect to see. As long as
401 : * the pool state differs for different inputs, we have preserved the
402 : * input entropy and done a good job. The fact that an intelligent
403 : * attacker can construct inputs that will produce controlled
404 : * alterations to the pool's state is not important because we don't
405 : * consider such inputs to contribute any randomness. The only
406 : * property we need with respect to them is that the attacker can't
407 : * increase his/her knowledge of the pool's state. Since all
408 : * additions are reversible (knowing the final state and the input,
409 : * you can reconstruct the initial state), if an attacker has any
410 : * uncertainty about the initial state, he/she can only shuffle that
411 : * uncertainty about, but never cause any collisions (which would
412 : * decrease the uncertainty).
413 : *
414 : * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
415 : * Videau in their paper, "The Linux Pseudorandom Number Generator
416 : * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
417 : * paper, they point out that we are not using a true Twisted GFSR,
418 : * since Matsumoto & Kurita used a trinomial feedback polynomial (that
419 : * is, with only three taps, instead of the six that we are using).
420 : * As a result, the resulting polynomial is neither primitive nor
421 : * irreducible, and hence does not have a maximal period over
422 : * GF(2**32). They suggest a slight change to the generator
423 : * polynomial which improves the resulting TGFSR polynomial to be
424 : * irreducible, which we have made here.
425 : */
426 : static const struct poolinfo {
427 : int poolbitshift, poolwords, poolbytes, poolfracbits;
428 : #define S(x) ilog2(x)+5, (x), (x)*4, (x) << (ENTROPY_SHIFT+5)
429 : int tap1, tap2, tap3, tap4, tap5;
430 : } poolinfo_table[] = {
431 : /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
432 : /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
433 : { S(128), 104, 76, 51, 25, 1 },
434 : };
435 :
436 : /*
437 : * Static global variables
438 : */
439 : static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
440 : static struct fasync_struct *fasync;
441 :
442 : static DEFINE_SPINLOCK(random_ready_list_lock);
443 : static LIST_HEAD(random_ready_list);
444 :
445 : struct crng_state {
446 : __u32 state[16];
447 : unsigned long init_time;
448 : spinlock_t lock;
449 : };
450 :
451 : static struct crng_state primary_crng = {
452 : .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
453 : };
454 :
455 : /*
456 : * crng_init = 0 --> Uninitialized
457 : * 1 --> Initialized
458 : * 2 --> Initialized from input_pool
459 : *
460 : * crng_init is protected by primary_crng->lock, and only increases
461 : * its value (from 0->1->2).
462 : */
463 : static int crng_init = 0;
464 : #define crng_ready() (likely(crng_init > 1))
465 : static int crng_init_cnt = 0;
466 : static unsigned long crng_global_init_time = 0;
467 : #define CRNG_INIT_CNT_THRESH (2*CHACHA_KEY_SIZE)
468 : static void _extract_crng(struct crng_state *crng, __u8 out[CHACHA_BLOCK_SIZE]);
469 : static void _crng_backtrack_protect(struct crng_state *crng,
470 : __u8 tmp[CHACHA_BLOCK_SIZE], int used);
471 : static void process_random_ready_list(void);
472 : static void _get_random_bytes(void *buf, int nbytes);
473 :
474 : static struct ratelimit_state unseeded_warning =
475 : RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
476 : static struct ratelimit_state urandom_warning =
477 : RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
478 :
479 : static int ratelimit_disable __read_mostly;
480 :
481 : module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
482 : MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
483 :
484 : /**********************************************************************
485 : *
486 : * OS independent entropy store. Here are the functions which handle
487 : * storing entropy in an entropy pool.
488 : *
489 : **********************************************************************/
490 :
491 : struct entropy_store;
492 : struct entropy_store {
493 : /* read-only data: */
494 : const struct poolinfo *poolinfo;
495 : __u32 *pool;
496 : const char *name;
497 :
498 : /* read-write data: */
499 : spinlock_t lock;
500 : unsigned short add_ptr;
501 : unsigned short input_rotate;
502 : int entropy_count;
503 : unsigned int initialized:1;
504 : unsigned int last_data_init:1;
505 : __u8 last_data[EXTRACT_SIZE];
506 : };
507 :
508 : static ssize_t extract_entropy(struct entropy_store *r, void *buf,
509 : size_t nbytes, int min, int rsvd);
510 : static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
511 : size_t nbytes, int fips);
512 :
513 : static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
514 : static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy;
515 :
516 : static struct entropy_store input_pool = {
517 : .poolinfo = &poolinfo_table[0],
518 : .name = "input",
519 : .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
520 : .pool = input_pool_data
521 : };
522 :
523 : static __u32 const twist_table[8] = {
524 : 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
525 : 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
526 :
527 : /*
528 : * This function adds bytes into the entropy "pool". It does not
529 : * update the entropy estimate. The caller should call
530 : * credit_entropy_bits if this is appropriate.
531 : *
532 : * The pool is stirred with a primitive polynomial of the appropriate
533 : * degree, and then twisted. We twist by three bits at a time because
534 : * it's cheap to do so and helps slightly in the expected case where
535 : * the entropy is concentrated in the low-order bits.
536 : */
537 3865 : static void _mix_pool_bytes(struct entropy_store *r, const void *in,
538 : int nbytes)
539 : {
540 3865 : unsigned long i, tap1, tap2, tap3, tap4, tap5;
541 3865 : int input_rotate;
542 3865 : int wordmask = r->poolinfo->poolwords - 1;
543 3865 : const char *bytes = in;
544 3865 : __u32 w;
545 :
546 3865 : tap1 = r->poolinfo->tap1;
547 3865 : tap2 = r->poolinfo->tap2;
548 3865 : tap3 = r->poolinfo->tap3;
549 3865 : tap4 = r->poolinfo->tap4;
550 3865 : tap5 = r->poolinfo->tap5;
551 :
552 3865 : input_rotate = r->input_rotate;
553 3865 : i = r->add_ptr;
554 :
555 : /* mix one byte at a time to simplify size handling and churn faster */
556 36586 : while (nbytes--) {
557 32721 : w = rol32(*bytes++, input_rotate);
558 32721 : i = (i - 1) & wordmask;
559 :
560 : /* XOR in the various taps */
561 32721 : w ^= r->pool[i];
562 32721 : w ^= r->pool[(i + tap1) & wordmask];
563 32721 : w ^= r->pool[(i + tap2) & wordmask];
564 32721 : w ^= r->pool[(i + tap3) & wordmask];
565 32721 : w ^= r->pool[(i + tap4) & wordmask];
566 32721 : w ^= r->pool[(i + tap5) & wordmask];
567 :
568 : /* Mix the result back in with a twist */
569 32721 : r->pool[i] = (w >> 3) ^ twist_table[w & 7];
570 :
571 : /*
572 : * Normally, we add 7 bits of rotation to the pool.
573 : * At the beginning of the pool, add an extra 7 bits
574 : * rotation, so that successive passes spread the
575 : * input bits across the pool evenly.
576 : */
577 32976 : input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
578 : }
579 :
580 3865 : r->input_rotate = input_rotate;
581 3865 : r->add_ptr = i;
582 3865 : }
583 :
584 106 : static void __mix_pool_bytes(struct entropy_store *r, const void *in,
585 : int nbytes)
586 : {
587 106 : trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
588 106 : _mix_pool_bytes(r, in, nbytes);
589 106 : }
590 :
591 75 : static void mix_pool_bytes(struct entropy_store *r, const void *in,
592 : int nbytes)
593 : {
594 75 : unsigned long flags;
595 :
596 75 : trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
597 75 : spin_lock_irqsave(&r->lock, flags);
598 75 : _mix_pool_bytes(r, in, nbytes);
599 75 : spin_unlock_irqrestore(&r->lock, flags);
600 75 : }
601 :
602 : struct fast_pool {
603 : __u32 pool[4];
604 : unsigned long last;
605 : unsigned short reg_idx;
606 : unsigned char count;
607 : };
608 :
609 : /*
610 : * This is a fast mixing routine used by the interrupt randomness
611 : * collector. It's hardcoded for an 128 bit pool and assumes that any
612 : * locks that might be needed are taken by the caller.
613 : */
614 3660 : static void fast_mix(struct fast_pool *f)
615 : {
616 3660 : __u32 a = f->pool[0], b = f->pool[1];
617 3660 : __u32 c = f->pool[2], d = f->pool[3];
618 :
619 3660 : a += b; c += d;
620 3660 : b = rol32(b, 6); d = rol32(d, 27);
621 3660 : d ^= a; b ^= c;
622 :
623 3660 : a += b; c += d;
624 3660 : b = rol32(b, 16); d = rol32(d, 14);
625 3660 : d ^= a; b ^= c;
626 :
627 3660 : a += b; c += d;
628 3660 : b = rol32(b, 6); d = rol32(d, 27);
629 3660 : d ^= a; b ^= c;
630 :
631 3660 : a += b; c += d;
632 3660 : b = rol32(b, 16); d = rol32(d, 14);
633 3660 : d ^= a; b ^= c;
634 :
635 3660 : f->pool[0] = a; f->pool[1] = b;
636 3660 : f->pool[2] = c; f->pool[3] = d;
637 3660 : f->count++;
638 3660 : }
639 :
640 0 : static void process_random_ready_list(void)
641 : {
642 0 : unsigned long flags;
643 0 : struct random_ready_callback *rdy, *tmp;
644 :
645 0 : spin_lock_irqsave(&random_ready_list_lock, flags);
646 0 : list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
647 0 : struct module *owner = rdy->owner;
648 :
649 0 : list_del_init(&rdy->list);
650 0 : rdy->func(rdy);
651 0 : module_put(owner);
652 : }
653 0 : spin_unlock_irqrestore(&random_ready_list_lock, flags);
654 0 : }
655 :
656 : /*
657 : * Credit (or debit) the entropy store with n bits of entropy.
658 : * Use credit_entropy_bits_safe() if the value comes from userspace
659 : * or otherwise should be checked for extreme values.
660 : */
661 101 : static void credit_entropy_bits(struct entropy_store *r, int nbits)
662 : {
663 101 : int entropy_count, orig, has_initialized = 0;
664 101 : const int pool_size = r->poolinfo->poolfracbits;
665 101 : int nfrac = nbits << ENTROPY_SHIFT;
666 :
667 101 : if (!nbits)
668 : return;
669 :
670 101 : retry:
671 101 : entropy_count = orig = READ_ONCE(r->entropy_count);
672 101 : if (nfrac < 0) {
673 : /* Debit */
674 0 : entropy_count += nfrac;
675 : } else {
676 : /*
677 : * Credit: we have to account for the possibility of
678 : * overwriting already present entropy. Even in the
679 : * ideal case of pure Shannon entropy, new contributions
680 : * approach the full value asymptotically:
681 : *
682 : * entropy <- entropy + (pool_size - entropy) *
683 : * (1 - exp(-add_entropy/pool_size))
684 : *
685 : * For add_entropy <= pool_size/2 then
686 : * (1 - exp(-add_entropy/pool_size)) >=
687 : * (add_entropy/pool_size)*0.7869...
688 : * so we can approximate the exponential with
689 : * 3/4*add_entropy/pool_size and still be on the
690 : * safe side by adding at most pool_size/2 at a time.
691 : *
692 : * The use of pool_size-2 in the while statement is to
693 : * prevent rounding artifacts from making the loop
694 : * arbitrarily long; this limits the loop to log2(pool_size)*2
695 : * turns no matter how large nbits is.
696 : */
697 101 : int pnfrac = nfrac;
698 101 : const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
699 : /* The +2 corresponds to the /4 in the denominator */
700 :
701 101 : do {
702 101 : unsigned int anfrac = min(pnfrac, pool_size/2);
703 101 : unsigned int add =
704 101 : ((pool_size - entropy_count)*anfrac*3) >> s;
705 :
706 101 : entropy_count += add;
707 101 : pnfrac -= anfrac;
708 101 : } while (unlikely(entropy_count < pool_size-2 && pnfrac));
709 : }
710 :
711 101 : if (WARN_ON(entropy_count < 0)) {
712 0 : pr_warn("negative entropy/overflow: pool %s count %d\n",
713 : r->name, entropy_count);
714 0 : entropy_count = 0;
715 101 : } else if (entropy_count > pool_size)
716 : entropy_count = pool_size;
717 101 : if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
718 0 : goto retry;
719 :
720 101 : if (has_initialized) {
721 : r->initialized = 1;
722 : kill_fasync(&fasync, SIGIO, POLL_IN);
723 : }
724 :
725 101 : trace_credit_entropy_bits(r->name, nbits,
726 101 : entropy_count >> ENTROPY_SHIFT, _RET_IP_);
727 :
728 101 : if (r == &input_pool) {
729 101 : int entropy_bits = entropy_count >> ENTROPY_SHIFT;
730 :
731 101 : if (crng_init < 2) {
732 0 : if (entropy_bits < 128)
733 : return;
734 0 : crng_reseed(&primary_crng, r);
735 0 : entropy_bits = ENTROPY_BITS(r);
736 : }
737 : }
738 : }
739 :
740 0 : static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
741 : {
742 0 : const int nbits_max = r->poolinfo->poolwords * 32;
743 :
744 0 : if (nbits < 0)
745 : return -EINVAL;
746 :
747 : /* Cap the value to avoid overflows */
748 0 : nbits = min(nbits, nbits_max);
749 :
750 0 : credit_entropy_bits(r, nbits);
751 0 : return 0;
752 : }
753 :
754 : /*********************************************************************
755 : *
756 : * CRNG using CHACHA20
757 : *
758 : *********************************************************************/
759 :
760 : #define CRNG_RESEED_INTERVAL (300*HZ)
761 :
762 : static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
763 :
764 : #ifdef CONFIG_NUMA
765 : /*
766 : * Hack to deal with crazy userspace progams when they are all trying
767 : * to access /dev/urandom in parallel. The programs are almost
768 : * certainly doing something terribly wrong, but we'll work around
769 : * their brain damage.
770 : */
771 : static struct crng_state **crng_node_pool __read_mostly;
772 : #endif
773 :
774 : static void invalidate_batched_entropy(void);
775 : static void numa_crng_init(void);
776 :
777 : static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
778 0 : static int __init parse_trust_cpu(char *arg)
779 : {
780 0 : return kstrtobool(arg, &trust_cpu);
781 : }
782 : early_param("random.trust_cpu", parse_trust_cpu);
783 :
784 1 : static bool crng_init_try_arch(struct crng_state *crng)
785 : {
786 1 : int i;
787 1 : bool arch_init = true;
788 1 : unsigned long rv;
789 :
790 13 : for (i = 4; i < 16; i++) {
791 24 : if (!arch_get_random_seed_long(&rv) &&
792 12 : !arch_get_random_long(&rv)) {
793 0 : rv = random_get_entropy();
794 0 : arch_init = false;
795 : }
796 12 : crng->state[i] ^= rv;
797 : }
798 :
799 1 : return arch_init;
800 : }
801 :
802 1 : static bool __init crng_init_try_arch_early(struct crng_state *crng)
803 : {
804 1 : int i;
805 1 : bool arch_init = true;
806 1 : unsigned long rv;
807 :
808 13 : for (i = 4; i < 16; i++) {
809 24 : if (!arch_get_random_seed_long_early(&rv) &&
810 12 : !arch_get_random_long_early(&rv)) {
811 0 : rv = random_get_entropy();
812 0 : arch_init = false;
813 : }
814 12 : crng->state[i] ^= rv;
815 : }
816 :
817 1 : return arch_init;
818 : }
819 :
820 1 : static void __maybe_unused crng_initialize_secondary(struct crng_state *crng)
821 : {
822 1 : memcpy(&crng->state[0], "expand 32-byte k", 16);
823 1 : _get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
824 1 : crng_init_try_arch(crng);
825 1 : crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
826 1 : }
827 :
828 1 : static void __init crng_initialize_primary(struct crng_state *crng)
829 : {
830 1 : memcpy(&crng->state[0], "expand 32-byte k", 16);
831 1 : _extract_entropy(&input_pool, &crng->state[4], sizeof(__u32) * 12, 0);
832 1 : if (crng_init_try_arch_early(crng) && trust_cpu) {
833 1 : invalidate_batched_entropy();
834 1 : numa_crng_init();
835 1 : crng_init = 2;
836 1 : pr_notice("crng done (trusting CPU's manufacturer)\n");
837 : }
838 1 : crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
839 1 : }
840 :
841 : #ifdef CONFIG_NUMA
842 1 : static void do_numa_crng_init(struct work_struct *work)
843 : {
844 1 : int i;
845 1 : struct crng_state *crng;
846 1 : struct crng_state **pool;
847 :
848 1 : pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
849 2 : for_each_online_node(i) {
850 1 : crng = kmalloc_node(sizeof(struct crng_state),
851 : GFP_KERNEL | __GFP_NOFAIL, i);
852 1 : spin_lock_init(&crng->lock);
853 1 : crng_initialize_secondary(crng);
854 1 : pool[i] = crng;
855 : }
856 1 : mb();
857 1 : if (cmpxchg(&crng_node_pool, NULL, pool)) {
858 0 : for_each_node(i)
859 0 : kfree(pool[i]);
860 0 : kfree(pool);
861 : }
862 1 : }
863 :
864 : static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init);
865 :
866 1 : static void numa_crng_init(void)
867 : {
868 1 : schedule_work(&numa_crng_init_work);
869 : }
870 : #else
871 : static void numa_crng_init(void) {}
872 : #endif
873 :
874 : /*
875 : * crng_fast_load() can be called by code in the interrupt service
876 : * path. So we can't afford to dilly-dally.
877 : */
878 0 : static int crng_fast_load(const char *cp, size_t len)
879 : {
880 0 : unsigned long flags;
881 0 : char *p;
882 :
883 0 : if (!spin_trylock_irqsave(&primary_crng.lock, flags))
884 0 : return 0;
885 0 : if (crng_init != 0) {
886 0 : spin_unlock_irqrestore(&primary_crng.lock, flags);
887 0 : return 0;
888 : }
889 0 : p = (unsigned char *) &primary_crng.state[4];
890 0 : while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
891 0 : p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp;
892 0 : cp++; crng_init_cnt++; len--;
893 : }
894 0 : spin_unlock_irqrestore(&primary_crng.lock, flags);
895 0 : if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
896 0 : invalidate_batched_entropy();
897 0 : crng_init = 1;
898 0 : pr_notice("fast init done\n");
899 : }
900 : return 1;
901 : }
902 :
903 : /*
904 : * crng_slow_load() is called by add_device_randomness, which has two
905 : * attributes. (1) We can't trust the buffer passed to it is
906 : * guaranteed to be unpredictable (so it might not have any entropy at
907 : * all), and (2) it doesn't have the performance constraints of
908 : * crng_fast_load().
909 : *
910 : * So we do something more comprehensive which is guaranteed to touch
911 : * all of the primary_crng's state, and which uses a LFSR with a
912 : * period of 255 as part of the mixing algorithm. Finally, we do
913 : * *not* advance crng_init_cnt since buffer we may get may be something
914 : * like a fixed DMI table (for example), which might very well be
915 : * unique to the machine, but is otherwise unvarying.
916 : */
917 0 : static int crng_slow_load(const char *cp, size_t len)
918 : {
919 0 : unsigned long flags;
920 0 : static unsigned char lfsr = 1;
921 0 : unsigned char tmp;
922 0 : unsigned i, max = CHACHA_KEY_SIZE;
923 0 : const char * src_buf = cp;
924 0 : char * dest_buf = (char *) &primary_crng.state[4];
925 :
926 0 : if (!spin_trylock_irqsave(&primary_crng.lock, flags))
927 0 : return 0;
928 0 : if (crng_init != 0) {
929 0 : spin_unlock_irqrestore(&primary_crng.lock, flags);
930 0 : return 0;
931 : }
932 0 : if (len > max)
933 : max = len;
934 :
935 0 : for (i = 0; i < max ; i++) {
936 0 : tmp = lfsr;
937 0 : lfsr >>= 1;
938 0 : if (tmp & 1)
939 0 : lfsr ^= 0xE1;
940 0 : tmp = dest_buf[i % CHACHA_KEY_SIZE];
941 0 : dest_buf[i % CHACHA_KEY_SIZE] ^= src_buf[i % len] ^ lfsr;
942 0 : lfsr += (tmp << 3) | (tmp >> 5);
943 : }
944 0 : spin_unlock_irqrestore(&primary_crng.lock, flags);
945 0 : return 1;
946 : }
947 :
948 4 : static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
949 : {
950 4 : unsigned long flags;
951 4 : int i, num;
952 4 : union {
953 : __u8 block[CHACHA_BLOCK_SIZE];
954 : __u32 key[8];
955 : } buf;
956 :
957 4 : if (r) {
958 3 : num = extract_entropy(r, &buf, 32, 16, 0);
959 3 : if (num == 0)
960 3 : return;
961 : } else {
962 1 : _extract_crng(&primary_crng, buf.block);
963 1 : _crng_backtrack_protect(&primary_crng, buf.block,
964 : CHACHA_KEY_SIZE);
965 : }
966 1 : spin_lock_irqsave(&crng->lock, flags);
967 10 : for (i = 0; i < 8; i++) {
968 8 : unsigned long rv;
969 16 : if (!arch_get_random_seed_long(&rv) &&
970 8 : !arch_get_random_long(&rv))
971 0 : rv = random_get_entropy();
972 8 : crng->state[i+4] ^= buf.key[i] ^ rv;
973 : }
974 1 : memzero_explicit(&buf, sizeof(buf));
975 1 : crng->init_time = jiffies;
976 1 : spin_unlock_irqrestore(&crng->lock, flags);
977 1 : if (crng == &primary_crng && crng_init < 2) {
978 0 : invalidate_batched_entropy();
979 0 : numa_crng_init();
980 0 : crng_init = 2;
981 0 : process_random_ready_list();
982 0 : wake_up_interruptible(&crng_init_wait);
983 0 : kill_fasync(&fasync, SIGIO, POLL_IN);
984 0 : pr_notice("crng init done\n");
985 0 : if (unseeded_warning.missed) {
986 0 : pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n",
987 : unseeded_warning.missed);
988 0 : unseeded_warning.missed = 0;
989 : }
990 0 : if (urandom_warning.missed) {
991 0 : pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
992 : urandom_warning.missed);
993 0 : urandom_warning.missed = 0;
994 : }
995 : }
996 : }
997 :
998 2849 : static void _extract_crng(struct crng_state *crng,
999 : __u8 out[CHACHA_BLOCK_SIZE])
1000 : {
1001 2849 : unsigned long v, flags;
1002 :
1003 2849 : if (crng_ready() &&
1004 2849 : (time_after(crng_global_init_time, crng->init_time) ||
1005 2845 : time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
1006 5 : crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
1007 2849 : spin_lock_irqsave(&crng->lock, flags);
1008 2849 : if (arch_get_random_long(&v))
1009 2849 : crng->state[14] ^= v;
1010 2849 : chacha20_block(&crng->state[0], out);
1011 2849 : if (crng->state[12] == 0)
1012 0 : crng->state[13]++;
1013 2849 : spin_unlock_irqrestore(&crng->lock, flags);
1014 2849 : }
1015 :
1016 2848 : static void extract_crng(__u8 out[CHACHA_BLOCK_SIZE])
1017 : {
1018 2848 : struct crng_state *crng = NULL;
1019 :
1020 : #ifdef CONFIG_NUMA
1021 2848 : if (crng_node_pool)
1022 2846 : crng = crng_node_pool[numa_node_id()];
1023 2846 : if (crng == NULL)
1024 : #endif
1025 : crng = &primary_crng;
1026 2848 : _extract_crng(crng, out);
1027 2848 : }
1028 :
1029 : /*
1030 : * Use the leftover bytes from the CRNG block output (if there is
1031 : * enough) to mutate the CRNG key to provide backtracking protection.
1032 : */
1033 1576 : static void _crng_backtrack_protect(struct crng_state *crng,
1034 : __u8 tmp[CHACHA_BLOCK_SIZE], int used)
1035 : {
1036 1576 : unsigned long flags;
1037 1576 : __u32 *s, *d;
1038 1576 : int i;
1039 :
1040 1576 : used = round_up(used, sizeof(__u32));
1041 1576 : if (used + CHACHA_KEY_SIZE > CHACHA_BLOCK_SIZE) {
1042 2 : extract_crng(tmp);
1043 2 : used = 0;
1044 : }
1045 1576 : spin_lock_irqsave(&crng->lock, flags);
1046 1576 : s = (__u32 *) &tmp[used];
1047 1576 : d = &crng->state[4];
1048 14184 : for (i=0; i < 8; i++)
1049 12608 : *d++ ^= *s++;
1050 1576 : spin_unlock_irqrestore(&crng->lock, flags);
1051 1576 : }
1052 :
1053 1575 : static void crng_backtrack_protect(__u8 tmp[CHACHA_BLOCK_SIZE], int used)
1054 : {
1055 1575 : struct crng_state *crng = NULL;
1056 :
1057 : #ifdef CONFIG_NUMA
1058 1575 : if (crng_node_pool)
1059 1574 : crng = crng_node_pool[numa_node_id()];
1060 1574 : if (crng == NULL)
1061 : #endif
1062 : crng = &primary_crng;
1063 1575 : _crng_backtrack_protect(crng, tmp, used);
1064 1575 : }
1065 :
1066 20 : static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
1067 : {
1068 20 : ssize_t ret = 0, i = CHACHA_BLOCK_SIZE;
1069 20 : __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1070 20 : int large_request = (nbytes > 256);
1071 :
1072 47 : while (nbytes) {
1073 35 : if (large_request && need_resched()) {
1074 0 : if (signal_pending(current)) {
1075 0 : if (ret == 0)
1076 0 : ret = -ERESTARTSYS;
1077 : break;
1078 : }
1079 0 : schedule();
1080 : }
1081 :
1082 27 : extract_crng(tmp);
1083 27 : i = min_t(int, nbytes, CHACHA_BLOCK_SIZE);
1084 54 : if (copy_to_user(buf, tmp, i)) {
1085 : ret = -EFAULT;
1086 : break;
1087 : }
1088 :
1089 27 : nbytes -= i;
1090 27 : buf += i;
1091 27 : ret += i;
1092 : }
1093 20 : crng_backtrack_protect(tmp, i);
1094 :
1095 : /* Wipe data just written to memory */
1096 20 : memzero_explicit(tmp, sizeof(tmp));
1097 :
1098 20 : return ret;
1099 : }
1100 :
1101 :
1102 : /*********************************************************************
1103 : *
1104 : * Entropy input management
1105 : *
1106 : *********************************************************************/
1107 :
1108 : /* There is one of these per entropy source */
1109 : struct timer_rand_state {
1110 : cycles_t last_time;
1111 : long last_delta, last_delta2;
1112 : };
1113 :
1114 : #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
1115 :
1116 : /*
1117 : * Add device- or boot-specific data to the input pool to help
1118 : * initialize it.
1119 : *
1120 : * None of this adds any entropy; it is meant to avoid the problem of
1121 : * the entropy pool having similar initial state across largely
1122 : * identical devices.
1123 : */
1124 1842 : void add_device_randomness(const void *buf, unsigned int size)
1125 : {
1126 1842 : unsigned long time = random_get_entropy() ^ jiffies;
1127 1842 : unsigned long flags;
1128 :
1129 1842 : if (!crng_ready() && size)
1130 0 : crng_slow_load(buf, size);
1131 :
1132 1842 : trace_add_device_randomness(size, _RET_IP_);
1133 1842 : spin_lock_irqsave(&input_pool.lock, flags);
1134 1842 : _mix_pool_bytes(&input_pool, buf, size);
1135 1842 : _mix_pool_bytes(&input_pool, &time, sizeof(time));
1136 1842 : spin_unlock_irqrestore(&input_pool.lock, flags);
1137 1842 : }
1138 : EXPORT_SYMBOL(add_device_randomness);
1139 :
1140 : static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
1141 :
1142 : /*
1143 : * This function adds entropy to the entropy "pool" by using timing
1144 : * delays. It uses the timer_rand_state structure to make an estimate
1145 : * of how many bits of entropy this call has added to the pool.
1146 : *
1147 : * The number "num" is also added to the pool - it should somehow describe
1148 : * the type of event which just happened. This is currently 0-255 for
1149 : * keyboard scan codes, and 256 upwards for interrupts.
1150 : *
1151 : */
1152 0 : static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
1153 : {
1154 0 : struct entropy_store *r;
1155 0 : struct {
1156 : long jiffies;
1157 : unsigned cycles;
1158 : unsigned num;
1159 : } sample;
1160 0 : long delta, delta2, delta3;
1161 :
1162 0 : sample.jiffies = jiffies;
1163 0 : sample.cycles = random_get_entropy();
1164 0 : sample.num = num;
1165 0 : r = &input_pool;
1166 0 : mix_pool_bytes(r, &sample, sizeof(sample));
1167 :
1168 : /*
1169 : * Calculate number of bits of randomness we probably added.
1170 : * We take into account the first, second and third-order deltas
1171 : * in order to make our estimate.
1172 : */
1173 0 : delta = sample.jiffies - READ_ONCE(state->last_time);
1174 0 : WRITE_ONCE(state->last_time, sample.jiffies);
1175 :
1176 0 : delta2 = delta - READ_ONCE(state->last_delta);
1177 0 : WRITE_ONCE(state->last_delta, delta);
1178 :
1179 0 : delta3 = delta2 - READ_ONCE(state->last_delta2);
1180 0 : WRITE_ONCE(state->last_delta2, delta2);
1181 :
1182 0 : if (delta < 0)
1183 : delta = -delta;
1184 0 : if (delta2 < 0)
1185 0 : delta2 = -delta2;
1186 0 : if (delta3 < 0)
1187 0 : delta3 = -delta3;
1188 0 : if (delta > delta2)
1189 : delta = delta2;
1190 0 : if (delta > delta3)
1191 : delta = delta3;
1192 :
1193 : /*
1194 : * delta is now minimum absolute delta.
1195 : * Round down by 1 bit on general principles,
1196 : * and limit entropy estimate to 12 bits.
1197 : */
1198 0 : credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1199 0 : }
1200 :
1201 0 : void add_input_randomness(unsigned int type, unsigned int code,
1202 : unsigned int value)
1203 : {
1204 0 : static unsigned char last_value;
1205 :
1206 : /* ignore autorepeat and the like */
1207 0 : if (value == last_value)
1208 : return;
1209 :
1210 0 : last_value = value;
1211 0 : add_timer_randomness(&input_timer_state,
1212 0 : (type << 4) ^ code ^ (code >> 4) ^ value);
1213 0 : trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1214 : }
1215 : EXPORT_SYMBOL_GPL(add_input_randomness);
1216 :
1217 : static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
1218 :
1219 : #ifdef ADD_INTERRUPT_BENCH
1220 : static unsigned long avg_cycles, avg_deviation;
1221 :
1222 : #define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
1223 : #define FIXED_1_2 (1 << (AVG_SHIFT-1))
1224 :
1225 : static void add_interrupt_bench(cycles_t start)
1226 : {
1227 : long delta = random_get_entropy() - start;
1228 :
1229 : /* Use a weighted moving average */
1230 : delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
1231 : avg_cycles += delta;
1232 : /* And average deviation */
1233 : delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
1234 : avg_deviation += delta;
1235 : }
1236 : #else
1237 : #define add_interrupt_bench(x)
1238 : #endif
1239 :
1240 0 : static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
1241 : {
1242 0 : __u32 *ptr = (__u32 *) regs;
1243 0 : unsigned int idx;
1244 :
1245 0 : if (regs == NULL)
1246 : return 0;
1247 0 : idx = READ_ONCE(f->reg_idx);
1248 0 : if (idx >= sizeof(struct pt_regs) / sizeof(__u32))
1249 0 : idx = 0;
1250 0 : ptr += idx++;
1251 0 : WRITE_ONCE(f->reg_idx, idx);
1252 0 : return *ptr;
1253 : }
1254 :
1255 3657 : void add_interrupt_randomness(int irq, int irq_flags)
1256 : {
1257 3657 : struct entropy_store *r;
1258 3657 : struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
1259 3657 : struct pt_regs *regs = get_irq_regs();
1260 3657 : unsigned long now = jiffies;
1261 3657 : cycles_t cycles = random_get_entropy();
1262 3657 : __u32 c_high, j_high;
1263 3657 : __u64 ip;
1264 :
1265 3657 : if (cycles == 0)
1266 0 : cycles = get_reg(fast_pool, regs);
1267 3657 : c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
1268 3657 : j_high = (sizeof(now) > 4) ? now >> 32 : 0;
1269 3657 : fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
1270 3657 : fast_pool->pool[1] ^= now ^ c_high;
1271 3657 : ip = regs ? instruction_pointer(regs) : _RET_IP_;
1272 3657 : fast_pool->pool[2] ^= ip;
1273 3657 : fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
1274 : get_reg(fast_pool, regs);
1275 :
1276 3657 : fast_mix(fast_pool);
1277 3657 : add_interrupt_bench(cycles);
1278 :
1279 3657 : if (unlikely(crng_init == 0)) {
1280 0 : if ((fast_pool->count >= 64) &&
1281 0 : crng_fast_load((char *) fast_pool->pool,
1282 : sizeof(fast_pool->pool))) {
1283 0 : fast_pool->count = 0;
1284 0 : fast_pool->last = now;
1285 : }
1286 0 : return;
1287 : }
1288 :
1289 3657 : if ((fast_pool->count < 64) &&
1290 3613 : !time_after(now, fast_pool->last + HZ))
1291 : return;
1292 :
1293 101 : r = &input_pool;
1294 101 : if (!spin_trylock(&r->lock))
1295 : return;
1296 :
1297 101 : fast_pool->last = now;
1298 101 : __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
1299 101 : spin_unlock(&r->lock);
1300 :
1301 101 : fast_pool->count = 0;
1302 :
1303 : /* award one bit for the contents of the fast pool */
1304 101 : credit_entropy_bits(r, 1);
1305 : }
1306 : EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1307 :
1308 : #ifdef CONFIG_BLOCK
1309 0 : void add_disk_randomness(struct gendisk *disk)
1310 : {
1311 0 : if (!disk || !disk->random)
1312 : return;
1313 : /* first major is 1, so we get >= 0x200 here */
1314 0 : add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1315 0 : trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1316 : }
1317 : EXPORT_SYMBOL_GPL(add_disk_randomness);
1318 : #endif
1319 :
1320 : /*********************************************************************
1321 : *
1322 : * Entropy extraction routines
1323 : *
1324 : *********************************************************************/
1325 :
1326 : /*
1327 : * This function decides how many bytes to actually take from the
1328 : * given pool, and also debits the entropy count accordingly.
1329 : */
1330 3 : static size_t account(struct entropy_store *r, size_t nbytes, int min,
1331 : int reserved)
1332 : {
1333 3 : int entropy_count, orig, have_bytes;
1334 3 : size_t ibytes, nfrac;
1335 :
1336 3 : BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1337 :
1338 : /* Can we pull enough? */
1339 3 : retry:
1340 3 : entropy_count = orig = READ_ONCE(r->entropy_count);
1341 3 : ibytes = nbytes;
1342 : /* never pull more than available */
1343 3 : have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1344 :
1345 3 : if ((have_bytes -= reserved) < 0)
1346 : have_bytes = 0;
1347 3 : ibytes = min_t(size_t, ibytes, have_bytes);
1348 3 : if (ibytes < min)
1349 3 : ibytes = 0;
1350 :
1351 3 : if (WARN_ON(entropy_count < 0)) {
1352 0 : pr_warn("negative entropy count: pool %s count %d\n",
1353 : r->name, entropy_count);
1354 0 : entropy_count = 0;
1355 : }
1356 3 : nfrac = ibytes << (ENTROPY_SHIFT + 3);
1357 3 : if ((size_t) entropy_count > nfrac)
1358 0 : entropy_count -= nfrac;
1359 : else
1360 : entropy_count = 0;
1361 :
1362 3 : if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1363 0 : goto retry;
1364 :
1365 3 : trace_debit_entropy(r->name, 8 * ibytes);
1366 3 : if (ibytes && ENTROPY_BITS(r) < random_write_wakeup_bits) {
1367 0 : wake_up_interruptible(&random_write_wait);
1368 0 : kill_fasync(&fasync, SIGIO, POLL_OUT);
1369 : }
1370 :
1371 3 : return ibytes;
1372 : }
1373 :
1374 : /*
1375 : * This function does the actual extraction for extract_entropy and
1376 : * extract_entropy_user.
1377 : *
1378 : * Note: we assume that .poolwords is a multiple of 16 words.
1379 : */
1380 5 : static void extract_buf(struct entropy_store *r, __u8 *out)
1381 : {
1382 5 : int i;
1383 5 : union {
1384 : __u32 w[5];
1385 : unsigned long l[LONGS(20)];
1386 : } hash;
1387 5 : __u32 workspace[SHA1_WORKSPACE_WORDS];
1388 5 : unsigned long flags;
1389 :
1390 : /*
1391 : * If we have an architectural hardware random number
1392 : * generator, use it for SHA's initial vector
1393 : */
1394 5 : sha1_init(hash.w);
1395 25 : for (i = 0; i < LONGS(20); i++) {
1396 15 : unsigned long v;
1397 15 : if (!arch_get_random_long(&v))
1398 : break;
1399 15 : hash.l[i] = v;
1400 : }
1401 :
1402 : /* Generate a hash across the pool, 16 words (512 bits) at a time */
1403 5 : spin_lock_irqsave(&r->lock, flags);
1404 50 : for (i = 0; i < r->poolinfo->poolwords; i += 16)
1405 40 : sha1_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1406 :
1407 : /*
1408 : * We mix the hash back into the pool to prevent backtracking
1409 : * attacks (where the attacker knows the state of the pool
1410 : * plus the current outputs, and attempts to find previous
1411 : * ouputs), unless the hash function can be inverted. By
1412 : * mixing at least a SHA1 worth of hash data back, we make
1413 : * brute-forcing the feedback as hard as brute-forcing the
1414 : * hash.
1415 : */
1416 5 : __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1417 5 : spin_unlock_irqrestore(&r->lock, flags);
1418 :
1419 5 : memzero_explicit(workspace, sizeof(workspace));
1420 :
1421 : /*
1422 : * In case the hash function has some recognizable output
1423 : * pattern, we fold it in half. Thus, we always feed back
1424 : * twice as much data as we output.
1425 : */
1426 5 : hash.w[0] ^= hash.w[3];
1427 5 : hash.w[1] ^= hash.w[4];
1428 5 : hash.w[2] ^= rol32(hash.w[2], 16);
1429 :
1430 5 : memcpy(out, &hash, EXTRACT_SIZE);
1431 5 : memzero_explicit(&hash, sizeof(hash));
1432 5 : }
1433 :
1434 4 : static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
1435 : size_t nbytes, int fips)
1436 : {
1437 4 : ssize_t ret = 0, i;
1438 4 : __u8 tmp[EXTRACT_SIZE];
1439 4 : unsigned long flags;
1440 :
1441 9 : while (nbytes) {
1442 5 : extract_buf(r, tmp);
1443 :
1444 5 : if (fips) {
1445 0 : spin_lock_irqsave(&r->lock, flags);
1446 0 : if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1447 0 : panic("Hardware RNG duplicated output!\n");
1448 0 : memcpy(r->last_data, tmp, EXTRACT_SIZE);
1449 0 : spin_unlock_irqrestore(&r->lock, flags);
1450 : }
1451 5 : i = min_t(int, nbytes, EXTRACT_SIZE);
1452 5 : memcpy(buf, tmp, i);
1453 5 : nbytes -= i;
1454 5 : buf += i;
1455 5 : ret += i;
1456 : }
1457 :
1458 : /* Wipe data just returned from memory */
1459 4 : memzero_explicit(tmp, sizeof(tmp));
1460 :
1461 4 : return ret;
1462 : }
1463 :
1464 : /*
1465 : * This function extracts randomness from the "entropy pool", and
1466 : * returns it in a buffer.
1467 : *
1468 : * The min parameter specifies the minimum amount we can pull before
1469 : * failing to avoid races that defeat catastrophic reseeding while the
1470 : * reserved parameter indicates how much entropy we must leave in the
1471 : * pool after each pull to avoid starving other readers.
1472 : */
1473 3 : static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1474 : size_t nbytes, int min, int reserved)
1475 : {
1476 3 : __u8 tmp[EXTRACT_SIZE];
1477 3 : unsigned long flags;
1478 :
1479 : /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1480 3 : if (fips_enabled) {
1481 : spin_lock_irqsave(&r->lock, flags);
1482 : if (!r->last_data_init) {
1483 : r->last_data_init = 1;
1484 : spin_unlock_irqrestore(&r->lock, flags);
1485 : trace_extract_entropy(r->name, EXTRACT_SIZE,
1486 : ENTROPY_BITS(r), _RET_IP_);
1487 : extract_buf(r, tmp);
1488 : spin_lock_irqsave(&r->lock, flags);
1489 : memcpy(r->last_data, tmp, EXTRACT_SIZE);
1490 : }
1491 : spin_unlock_irqrestore(&r->lock, flags);
1492 : }
1493 :
1494 3 : trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1495 3 : nbytes = account(r, nbytes, min, reserved);
1496 :
1497 3 : return _extract_entropy(r, buf, nbytes, fips_enabled);
1498 : }
1499 :
1500 : #define warn_unseeded_randomness(previous) \
1501 : _warn_unseeded_randomness(__func__, (void *) _RET_IP_, (previous))
1502 :
1503 13986 : static void _warn_unseeded_randomness(const char *func_name, void *caller,
1504 : void **previous)
1505 : {
1506 : #ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1507 : const bool print_once = false;
1508 : #else
1509 13986 : static bool print_once __read_mostly;
1510 : #endif
1511 :
1512 13986 : if (print_once ||
1513 13986 : crng_ready() ||
1514 0 : (previous && (caller == READ_ONCE(*previous))))
1515 : return;
1516 0 : WRITE_ONCE(*previous, caller);
1517 : #ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1518 0 : print_once = true;
1519 : #endif
1520 0 : if (__ratelimit(&unseeded_warning))
1521 0 : printk_deferred(KERN_NOTICE "random: %s called from %pS "
1522 : "with crng_init=%d\n", func_name, caller,
1523 : crng_init);
1524 : }
1525 :
1526 : /*
1527 : * This function is the exported kernel interface. It returns some
1528 : * number of good random numbers, suitable for key generation, seeding
1529 : * TCP sequence numbers, etc. It does not rely on the hardware random
1530 : * number generator. For random bytes direct from the hardware RNG
1531 : * (when available), use get_random_bytes_arch(). In order to ensure
1532 : * that the randomness provided by this function is okay, the function
1533 : * wait_for_random_bytes() should be called and return 0 at least once
1534 : * at any point prior.
1535 : */
1536 1555 : static void _get_random_bytes(void *buf, int nbytes)
1537 : {
1538 1555 : __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1539 :
1540 1555 : trace_get_random_bytes(nbytes, _RET_IP_);
1541 :
1542 1555 : while (nbytes >= CHACHA_BLOCK_SIZE) {
1543 0 : extract_crng(buf);
1544 0 : buf += CHACHA_BLOCK_SIZE;
1545 0 : nbytes -= CHACHA_BLOCK_SIZE;
1546 : }
1547 :
1548 1555 : if (nbytes > 0) {
1549 1555 : extract_crng(tmp);
1550 1555 : memcpy(buf, tmp, nbytes);
1551 1555 : crng_backtrack_protect(tmp, nbytes);
1552 : } else
1553 0 : crng_backtrack_protect(tmp, CHACHA_BLOCK_SIZE);
1554 1555 : memzero_explicit(tmp, sizeof(tmp));
1555 1555 : }
1556 :
1557 1554 : void get_random_bytes(void *buf, int nbytes)
1558 : {
1559 1554 : static void *previous;
1560 :
1561 1554 : warn_unseeded_randomness(&previous);
1562 1554 : _get_random_bytes(buf, nbytes);
1563 1554 : }
1564 : EXPORT_SYMBOL(get_random_bytes);
1565 :
1566 :
1567 : /*
1568 : * Each time the timer fires, we expect that we got an unpredictable
1569 : * jump in the cycle counter. Even if the timer is running on another
1570 : * CPU, the timer activity will be touching the stack of the CPU that is
1571 : * generating entropy..
1572 : *
1573 : * Note that we don't re-arm the timer in the timer itself - we are
1574 : * happy to be scheduled away, since that just makes the load more
1575 : * complex, but we do not want the timer to keep ticking unless the
1576 : * entropy loop is running.
1577 : *
1578 : * So the re-arming always happens in the entropy loop itself.
1579 : */
1580 0 : static void entropy_timer(struct timer_list *t)
1581 : {
1582 0 : credit_entropy_bits(&input_pool, 1);
1583 0 : }
1584 :
1585 : /*
1586 : * If we have an actual cycle counter, see if we can
1587 : * generate enough entropy with timing noise
1588 : */
1589 0 : static void try_to_generate_entropy(void)
1590 : {
1591 0 : struct {
1592 : unsigned long now;
1593 : struct timer_list timer;
1594 : } stack;
1595 :
1596 0 : stack.now = random_get_entropy();
1597 :
1598 : /* Slow counter - or none. Don't even bother */
1599 0 : if (stack.now == random_get_entropy())
1600 0 : return;
1601 :
1602 0 : timer_setup_on_stack(&stack.timer, entropy_timer, 0);
1603 0 : while (!crng_ready()) {
1604 0 : if (!timer_pending(&stack.timer))
1605 0 : mod_timer(&stack.timer, jiffies+1);
1606 0 : mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
1607 0 : schedule();
1608 0 : stack.now = random_get_entropy();
1609 : }
1610 :
1611 0 : del_timer_sync(&stack.timer);
1612 0 : destroy_timer_on_stack(&stack.timer);
1613 0 : mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
1614 : }
1615 :
1616 : /*
1617 : * Wait for the urandom pool to be seeded and thus guaranteed to supply
1618 : * cryptographically secure random numbers. This applies to: the /dev/urandom
1619 : * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
1620 : * family of functions. Using any of these functions without first calling
1621 : * this function forfeits the guarantee of security.
1622 : *
1623 : * Returns: 0 if the urandom pool has been seeded.
1624 : * -ERESTARTSYS if the function was interrupted by a signal.
1625 : */
1626 0 : int wait_for_random_bytes(void)
1627 : {
1628 0 : if (likely(crng_ready()))
1629 : return 0;
1630 :
1631 0 : do {
1632 0 : int ret;
1633 0 : ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
1634 0 : if (ret)
1635 0 : return ret > 0 ? 0 : ret;
1636 :
1637 0 : try_to_generate_entropy();
1638 0 : } while (!crng_ready());
1639 :
1640 : return 0;
1641 : }
1642 : EXPORT_SYMBOL(wait_for_random_bytes);
1643 :
1644 : /*
1645 : * Returns whether or not the urandom pool has been seeded and thus guaranteed
1646 : * to supply cryptographically secure random numbers. This applies to: the
1647 : * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
1648 : * ,u64,int,long} family of functions.
1649 : *
1650 : * Returns: true if the urandom pool has been seeded.
1651 : * false if the urandom pool has not been seeded.
1652 : */
1653 0 : bool rng_is_initialized(void)
1654 : {
1655 0 : return crng_ready();
1656 : }
1657 : EXPORT_SYMBOL(rng_is_initialized);
1658 :
1659 : /*
1660 : * Add a callback function that will be invoked when the nonblocking
1661 : * pool is initialised.
1662 : *
1663 : * returns: 0 if callback is successfully added
1664 : * -EALREADY if pool is already initialised (callback not called)
1665 : * -ENOENT if module for callback is not alive
1666 : */
1667 1 : int add_random_ready_callback(struct random_ready_callback *rdy)
1668 : {
1669 1 : struct module *owner;
1670 1 : unsigned long flags;
1671 1 : int err = -EALREADY;
1672 :
1673 1 : if (crng_ready())
1674 : return err;
1675 :
1676 0 : owner = rdy->owner;
1677 0 : if (!try_module_get(owner))
1678 : return -ENOENT;
1679 :
1680 0 : spin_lock_irqsave(&random_ready_list_lock, flags);
1681 0 : if (crng_ready())
1682 0 : goto out;
1683 :
1684 0 : owner = NULL;
1685 :
1686 0 : list_add(&rdy->list, &random_ready_list);
1687 0 : err = 0;
1688 :
1689 0 : out:
1690 0 : spin_unlock_irqrestore(&random_ready_list_lock, flags);
1691 :
1692 0 : module_put(owner);
1693 :
1694 0 : return err;
1695 : }
1696 : EXPORT_SYMBOL(add_random_ready_callback);
1697 :
1698 : /*
1699 : * Delete a previously registered readiness callback function.
1700 : */
1701 0 : void del_random_ready_callback(struct random_ready_callback *rdy)
1702 : {
1703 0 : unsigned long flags;
1704 0 : struct module *owner = NULL;
1705 :
1706 0 : spin_lock_irqsave(&random_ready_list_lock, flags);
1707 0 : if (!list_empty(&rdy->list)) {
1708 0 : list_del_init(&rdy->list);
1709 0 : owner = rdy->owner;
1710 : }
1711 0 : spin_unlock_irqrestore(&random_ready_list_lock, flags);
1712 :
1713 0 : module_put(owner);
1714 0 : }
1715 : EXPORT_SYMBOL(del_random_ready_callback);
1716 :
1717 : /*
1718 : * This function will use the architecture-specific hardware random
1719 : * number generator if it is available. The arch-specific hw RNG will
1720 : * almost certainly be faster than what we can do in software, but it
1721 : * is impossible to verify that it is implemented securely (as
1722 : * opposed, to, say, the AES encryption of a sequence number using a
1723 : * key known by the NSA). So it's useful if we need the speed, but
1724 : * only if we're willing to trust the hardware manufacturer not to
1725 : * have put in a back door.
1726 : *
1727 : * Return number of bytes filled in.
1728 : */
1729 1 : int __must_check get_random_bytes_arch(void *buf, int nbytes)
1730 : {
1731 1 : int left = nbytes;
1732 1 : char *p = buf;
1733 :
1734 1 : trace_get_random_bytes_arch(left, _RET_IP_);
1735 3 : while (left) {
1736 2 : unsigned long v;
1737 2 : int chunk = min_t(int, left, sizeof(unsigned long));
1738 :
1739 2 : if (!arch_get_random_long(&v))
1740 : break;
1741 :
1742 2 : memcpy(p, &v, chunk);
1743 2 : p += chunk;
1744 2 : left -= chunk;
1745 : }
1746 :
1747 1 : return nbytes - left;
1748 : }
1749 : EXPORT_SYMBOL(get_random_bytes_arch);
1750 :
1751 : /*
1752 : * init_std_data - initialize pool with system data
1753 : *
1754 : * @r: pool to initialize
1755 : *
1756 : * This function clears the pool's entropy count and mixes some system
1757 : * data into the pool to prepare it for use. The pool is not cleared
1758 : * as that can only decrease the entropy in the pool.
1759 : */
1760 1 : static void __init init_std_data(struct entropy_store *r)
1761 : {
1762 1 : int i;
1763 1 : ktime_t now = ktime_get_real();
1764 1 : unsigned long rv;
1765 :
1766 1 : mix_pool_bytes(r, &now, sizeof(now));
1767 65 : for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1768 128 : if (!arch_get_random_seed_long(&rv) &&
1769 64 : !arch_get_random_long(&rv))
1770 0 : rv = random_get_entropy();
1771 64 : mix_pool_bytes(r, &rv, sizeof(rv));
1772 : }
1773 1 : mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1774 1 : }
1775 :
1776 : /*
1777 : * Note that setup_arch() may call add_device_randomness()
1778 : * long before we get here. This allows seeding of the pools
1779 : * with some platform dependent data very early in the boot
1780 : * process. But it limits our options here. We must use
1781 : * statically allocated structures that already have all
1782 : * initializations complete at compile time. We should also
1783 : * take care not to overwrite the precious per platform data
1784 : * we were given.
1785 : */
1786 1 : int __init rand_initialize(void)
1787 : {
1788 1 : init_std_data(&input_pool);
1789 1 : crng_initialize_primary(&primary_crng);
1790 1 : crng_global_init_time = jiffies;
1791 1 : if (ratelimit_disable) {
1792 0 : urandom_warning.interval = 0;
1793 0 : unseeded_warning.interval = 0;
1794 : }
1795 1 : return 0;
1796 : }
1797 :
1798 : #ifdef CONFIG_BLOCK
1799 9 : void rand_initialize_disk(struct gendisk *disk)
1800 : {
1801 9 : struct timer_rand_state *state;
1802 :
1803 : /*
1804 : * If kzalloc returns null, we just won't use that entropy
1805 : * source.
1806 : */
1807 9 : state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1808 9 : if (state) {
1809 9 : state->last_time = INITIAL_JIFFIES;
1810 9 : disk->random = state;
1811 : }
1812 9 : }
1813 : #endif
1814 :
1815 : static ssize_t
1816 20 : urandom_read_nowarn(struct file *file, char __user *buf, size_t nbytes,
1817 : loff_t *ppos)
1818 : {
1819 20 : int ret;
1820 :
1821 20 : nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1822 20 : ret = extract_crng_user(buf, nbytes);
1823 20 : trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
1824 20 : return ret;
1825 : }
1826 :
1827 : static ssize_t
1828 7 : urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1829 : {
1830 7 : unsigned long flags;
1831 7 : static int maxwarn = 10;
1832 :
1833 7 : if (!crng_ready() && maxwarn > 0) {
1834 0 : maxwarn--;
1835 0 : if (__ratelimit(&urandom_warning))
1836 0 : pr_notice("%s: uninitialized urandom read (%zd bytes read)\n",
1837 : current->comm, nbytes);
1838 0 : spin_lock_irqsave(&primary_crng.lock, flags);
1839 0 : crng_init_cnt = 0;
1840 0 : spin_unlock_irqrestore(&primary_crng.lock, flags);
1841 : }
1842 :
1843 7 : return urandom_read_nowarn(file, buf, nbytes, ppos);
1844 : }
1845 :
1846 : static ssize_t
1847 0 : random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1848 : {
1849 0 : int ret;
1850 :
1851 0 : ret = wait_for_random_bytes();
1852 0 : if (ret != 0)
1853 0 : return ret;
1854 0 : return urandom_read_nowarn(file, buf, nbytes, ppos);
1855 : }
1856 :
1857 : static __poll_t
1858 0 : random_poll(struct file *file, poll_table * wait)
1859 : {
1860 0 : __poll_t mask;
1861 :
1862 0 : poll_wait(file, &crng_init_wait, wait);
1863 0 : poll_wait(file, &random_write_wait, wait);
1864 0 : mask = 0;
1865 0 : if (crng_ready())
1866 0 : mask |= EPOLLIN | EPOLLRDNORM;
1867 0 : if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1868 0 : mask |= EPOLLOUT | EPOLLWRNORM;
1869 0 : return mask;
1870 : }
1871 :
1872 : static int
1873 2 : write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1874 : {
1875 2 : size_t bytes;
1876 2 : __u32 t, buf[16];
1877 2 : const char __user *p = buffer;
1878 :
1879 11 : while (count > 0) {
1880 9 : int b, i = 0;
1881 :
1882 9 : bytes = min(count, sizeof(buf));
1883 9 : if (copy_from_user(&buf, p, bytes))
1884 : return -EFAULT;
1885 :
1886 141 : for (b = bytes ; b > 0 ; b -= sizeof(__u32), i++) {
1887 132 : if (!arch_get_random_int(&t))
1888 : break;
1889 132 : buf[i] ^= t;
1890 : }
1891 :
1892 9 : count -= bytes;
1893 9 : p += bytes;
1894 :
1895 9 : mix_pool_bytes(r, buf, bytes);
1896 9 : cond_resched();
1897 : }
1898 :
1899 : return 0;
1900 : }
1901 :
1902 2 : static ssize_t random_write(struct file *file, const char __user *buffer,
1903 : size_t count, loff_t *ppos)
1904 : {
1905 2 : size_t ret;
1906 :
1907 2 : ret = write_pool(&input_pool, buffer, count);
1908 2 : if (ret)
1909 0 : return ret;
1910 :
1911 2 : return (ssize_t)count;
1912 : }
1913 :
1914 0 : static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1915 : {
1916 0 : int size, ent_count;
1917 0 : int __user *p = (int __user *)arg;
1918 0 : int retval;
1919 :
1920 0 : switch (cmd) {
1921 0 : case RNDGETENTCNT:
1922 : /* inherently racy, no point locking */
1923 0 : ent_count = ENTROPY_BITS(&input_pool);
1924 0 : if (put_user(ent_count, p))
1925 0 : return -EFAULT;
1926 : return 0;
1927 0 : case RNDADDTOENTCNT:
1928 0 : if (!capable(CAP_SYS_ADMIN))
1929 : return -EPERM;
1930 0 : if (get_user(ent_count, p))
1931 : return -EFAULT;
1932 0 : return credit_entropy_bits_safe(&input_pool, ent_count);
1933 0 : case RNDADDENTROPY:
1934 0 : if (!capable(CAP_SYS_ADMIN))
1935 : return -EPERM;
1936 0 : if (get_user(ent_count, p++))
1937 : return -EFAULT;
1938 0 : if (ent_count < 0)
1939 : return -EINVAL;
1940 0 : if (get_user(size, p++))
1941 : return -EFAULT;
1942 0 : retval = write_pool(&input_pool, (const char __user *)p,
1943 : size);
1944 0 : if (retval < 0)
1945 0 : return retval;
1946 0 : return credit_entropy_bits_safe(&input_pool, ent_count);
1947 0 : case RNDZAPENTCNT:
1948 : case RNDCLEARPOOL:
1949 : /*
1950 : * Clear the entropy pool counters. We no longer clear
1951 : * the entropy pool, as that's silly.
1952 : */
1953 0 : if (!capable(CAP_SYS_ADMIN))
1954 : return -EPERM;
1955 0 : input_pool.entropy_count = 0;
1956 0 : return 0;
1957 0 : case RNDRESEEDCRNG:
1958 0 : if (!capable(CAP_SYS_ADMIN))
1959 : return -EPERM;
1960 0 : if (crng_init < 2)
1961 : return -ENODATA;
1962 0 : crng_reseed(&primary_crng, &input_pool);
1963 0 : crng_global_init_time = jiffies - 1;
1964 0 : return 0;
1965 : default:
1966 : return -EINVAL;
1967 : }
1968 : }
1969 :
1970 0 : static int random_fasync(int fd, struct file *filp, int on)
1971 : {
1972 0 : return fasync_helper(fd, filp, on, &fasync);
1973 : }
1974 :
1975 : const struct file_operations random_fops = {
1976 : .read = random_read,
1977 : .write = random_write,
1978 : .poll = random_poll,
1979 : .unlocked_ioctl = random_ioctl,
1980 : .compat_ioctl = compat_ptr_ioctl,
1981 : .fasync = random_fasync,
1982 : .llseek = noop_llseek,
1983 : };
1984 :
1985 : const struct file_operations urandom_fops = {
1986 : .read = urandom_read,
1987 : .write = random_write,
1988 : .unlocked_ioctl = random_ioctl,
1989 : .compat_ioctl = compat_ptr_ioctl,
1990 : .fasync = random_fasync,
1991 : .llseek = noop_llseek,
1992 : };
1993 :
1994 26 : SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1995 : unsigned int, flags)
1996 : {
1997 13 : int ret;
1998 :
1999 13 : if (flags & ~(GRND_NONBLOCK|GRND_RANDOM|GRND_INSECURE))
2000 : return -EINVAL;
2001 :
2002 : /*
2003 : * Requesting insecure and blocking randomness at the same time makes
2004 : * no sense.
2005 : */
2006 13 : if ((flags & (GRND_INSECURE|GRND_RANDOM)) == (GRND_INSECURE|GRND_RANDOM))
2007 : return -EINVAL;
2008 :
2009 13 : if (count > INT_MAX)
2010 : count = INT_MAX;
2011 :
2012 13 : if (!(flags & GRND_INSECURE) && !crng_ready()) {
2013 0 : if (flags & GRND_NONBLOCK)
2014 : return -EAGAIN;
2015 0 : ret = wait_for_random_bytes();
2016 0 : if (unlikely(ret))
2017 0 : return ret;
2018 : }
2019 13 : return urandom_read_nowarn(NULL, buf, count, NULL);
2020 : }
2021 :
2022 : /********************************************************************
2023 : *
2024 : * Sysctl interface
2025 : *
2026 : ********************************************************************/
2027 :
2028 : #ifdef CONFIG_SYSCTL
2029 :
2030 : #include <linux/sysctl.h>
2031 :
2032 : static int min_write_thresh;
2033 : static int max_write_thresh = INPUT_POOL_WORDS * 32;
2034 : static int random_min_urandom_seed = 60;
2035 : static char sysctl_bootid[16];
2036 :
2037 : /*
2038 : * This function is used to return both the bootid UUID, and random
2039 : * UUID. The difference is in whether table->data is NULL; if it is,
2040 : * then a new UUID is generated and returned to the user.
2041 : *
2042 : * If the user accesses this via the proc interface, the UUID will be
2043 : * returned as an ASCII string in the standard UUID format; if via the
2044 : * sysctl system call, as 16 bytes of binary data.
2045 : */
2046 16 : static int proc_do_uuid(struct ctl_table *table, int write,
2047 : void *buffer, size_t *lenp, loff_t *ppos)
2048 : {
2049 16 : struct ctl_table fake_table;
2050 16 : unsigned char buf[64], tmp_uuid[16], *uuid;
2051 :
2052 16 : uuid = table->data;
2053 16 : if (!uuid) {
2054 0 : uuid = tmp_uuid;
2055 0 : generate_random_uuid(uuid);
2056 : } else {
2057 16 : static DEFINE_SPINLOCK(bootid_spinlock);
2058 :
2059 16 : spin_lock(&bootid_spinlock);
2060 16 : if (!uuid[8])
2061 1 : generate_random_uuid(uuid);
2062 16 : spin_unlock(&bootid_spinlock);
2063 : }
2064 :
2065 16 : sprintf(buf, "%pU", uuid);
2066 :
2067 16 : fake_table.data = buf;
2068 16 : fake_table.maxlen = sizeof(buf);
2069 :
2070 16 : return proc_dostring(&fake_table, write, buffer, lenp, ppos);
2071 : }
2072 :
2073 : /*
2074 : * Return entropy available scaled to integral bits
2075 : */
2076 0 : static int proc_do_entropy(struct ctl_table *table, int write,
2077 : void *buffer, size_t *lenp, loff_t *ppos)
2078 : {
2079 0 : struct ctl_table fake_table;
2080 0 : int entropy_count;
2081 :
2082 0 : entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
2083 :
2084 0 : fake_table.data = &entropy_count;
2085 0 : fake_table.maxlen = sizeof(entropy_count);
2086 :
2087 0 : return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
2088 : }
2089 :
2090 : static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
2091 : extern struct ctl_table random_table[];
2092 : struct ctl_table random_table[] = {
2093 : {
2094 : .procname = "poolsize",
2095 : .data = &sysctl_poolsize,
2096 : .maxlen = sizeof(int),
2097 : .mode = 0444,
2098 : .proc_handler = proc_dointvec,
2099 : },
2100 : {
2101 : .procname = "entropy_avail",
2102 : .maxlen = sizeof(int),
2103 : .mode = 0444,
2104 : .proc_handler = proc_do_entropy,
2105 : .data = &input_pool.entropy_count,
2106 : },
2107 : {
2108 : .procname = "write_wakeup_threshold",
2109 : .data = &random_write_wakeup_bits,
2110 : .maxlen = sizeof(int),
2111 : .mode = 0644,
2112 : .proc_handler = proc_dointvec_minmax,
2113 : .extra1 = &min_write_thresh,
2114 : .extra2 = &max_write_thresh,
2115 : },
2116 : {
2117 : .procname = "urandom_min_reseed_secs",
2118 : .data = &random_min_urandom_seed,
2119 : .maxlen = sizeof(int),
2120 : .mode = 0644,
2121 : .proc_handler = proc_dointvec,
2122 : },
2123 : {
2124 : .procname = "boot_id",
2125 : .data = &sysctl_bootid,
2126 : .maxlen = 16,
2127 : .mode = 0444,
2128 : .proc_handler = proc_do_uuid,
2129 : },
2130 : {
2131 : .procname = "uuid",
2132 : .maxlen = 16,
2133 : .mode = 0444,
2134 : .proc_handler = proc_do_uuid,
2135 : },
2136 : #ifdef ADD_INTERRUPT_BENCH
2137 : {
2138 : .procname = "add_interrupt_avg_cycles",
2139 : .data = &avg_cycles,
2140 : .maxlen = sizeof(avg_cycles),
2141 : .mode = 0444,
2142 : .proc_handler = proc_doulongvec_minmax,
2143 : },
2144 : {
2145 : .procname = "add_interrupt_avg_deviation",
2146 : .data = &avg_deviation,
2147 : .maxlen = sizeof(avg_deviation),
2148 : .mode = 0444,
2149 : .proc_handler = proc_doulongvec_minmax,
2150 : },
2151 : #endif
2152 : { }
2153 : };
2154 : #endif /* CONFIG_SYSCTL */
2155 :
2156 : struct batched_entropy {
2157 : union {
2158 : u64 entropy_u64[CHACHA_BLOCK_SIZE / sizeof(u64)];
2159 : u32 entropy_u32[CHACHA_BLOCK_SIZE / sizeof(u32)];
2160 : };
2161 : unsigned int position;
2162 : spinlock_t batch_lock;
2163 : };
2164 :
2165 : /*
2166 : * Get a random word for internal kernel use only. The quality of the random
2167 : * number is good as /dev/urandom, but there is no backtrack protection, with
2168 : * the goal of being quite fast and not depleting entropy. In order to ensure
2169 : * that the randomness provided by this function is okay, the function
2170 : * wait_for_random_bytes() should be called and return 0 at least once at any
2171 : * point prior.
2172 : */
2173 : static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = {
2174 : .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u64.lock),
2175 : };
2176 :
2177 7749 : u64 get_random_u64(void)
2178 : {
2179 7749 : u64 ret;
2180 7749 : unsigned long flags;
2181 7749 : struct batched_entropy *batch;
2182 7749 : static void *previous;
2183 :
2184 7749 : warn_unseeded_randomness(&previous);
2185 :
2186 7749 : batch = raw_cpu_ptr(&batched_entropy_u64);
2187 7749 : spin_lock_irqsave(&batch->batch_lock, flags);
2188 7749 : if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
2189 970 : extract_crng((u8 *)batch->entropy_u64);
2190 970 : batch->position = 0;
2191 : }
2192 7749 : ret = batch->entropy_u64[batch->position++];
2193 7749 : spin_unlock_irqrestore(&batch->batch_lock, flags);
2194 7749 : return ret;
2195 : }
2196 : EXPORT_SYMBOL(get_random_u64);
2197 :
2198 : static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = {
2199 : .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u32.lock),
2200 : };
2201 4683 : u32 get_random_u32(void)
2202 : {
2203 4683 : u32 ret;
2204 4683 : unsigned long flags;
2205 4683 : struct batched_entropy *batch;
2206 4683 : static void *previous;
2207 :
2208 4683 : warn_unseeded_randomness(&previous);
2209 :
2210 4683 : batch = raw_cpu_ptr(&batched_entropy_u32);
2211 4683 : spin_lock_irqsave(&batch->batch_lock, flags);
2212 4683 : if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
2213 294 : extract_crng((u8 *)batch->entropy_u32);
2214 294 : batch->position = 0;
2215 : }
2216 4683 : ret = batch->entropy_u32[batch->position++];
2217 4683 : spin_unlock_irqrestore(&batch->batch_lock, flags);
2218 4683 : return ret;
2219 : }
2220 : EXPORT_SYMBOL(get_random_u32);
2221 :
2222 : /* It's important to invalidate all potential batched entropy that might
2223 : * be stored before the crng is initialized, which we can do lazily by
2224 : * simply resetting the counter to zero so that it's re-extracted on the
2225 : * next usage. */
2226 1 : static void invalidate_batched_entropy(void)
2227 : {
2228 1 : int cpu;
2229 1 : unsigned long flags;
2230 :
2231 6 : for_each_possible_cpu (cpu) {
2232 4 : struct batched_entropy *batched_entropy;
2233 :
2234 4 : batched_entropy = per_cpu_ptr(&batched_entropy_u32, cpu);
2235 4 : spin_lock_irqsave(&batched_entropy->batch_lock, flags);
2236 4 : batched_entropy->position = 0;
2237 4 : spin_unlock(&batched_entropy->batch_lock);
2238 :
2239 4 : batched_entropy = per_cpu_ptr(&batched_entropy_u64, cpu);
2240 4 : spin_lock(&batched_entropy->batch_lock);
2241 4 : batched_entropy->position = 0;
2242 9 : spin_unlock_irqrestore(&batched_entropy->batch_lock, flags);
2243 : }
2244 1 : }
2245 :
2246 : /**
2247 : * randomize_page - Generate a random, page aligned address
2248 : * @start: The smallest acceptable address the caller will take.
2249 : * @range: The size of the area, starting at @start, within which the
2250 : * random address must fall.
2251 : *
2252 : * If @start + @range would overflow, @range is capped.
2253 : *
2254 : * NOTE: Historical use of randomize_range, which this replaces, presumed that
2255 : * @start was already page aligned. We now align it regardless.
2256 : *
2257 : * Return: A page aligned address within [start, start + range). On error,
2258 : * @start is returned.
2259 : */
2260 : unsigned long
2261 1547 : randomize_page(unsigned long start, unsigned long range)
2262 : {
2263 1547 : if (!PAGE_ALIGNED(start)) {
2264 0 : range -= PAGE_ALIGN(start) - start;
2265 0 : start = PAGE_ALIGN(start);
2266 : }
2267 :
2268 1547 : if (start > ULONG_MAX - range)
2269 0 : range = ULONG_MAX - start;
2270 :
2271 1547 : range >>= PAGE_SHIFT;
2272 :
2273 1547 : if (range == 0)
2274 : return start;
2275 :
2276 1547 : return start + (get_random_long() % range << PAGE_SHIFT);
2277 : }
2278 :
2279 : /* Interface for in-kernel drivers of true hardware RNGs.
2280 : * Those devices may produce endless random bits and will be throttled
2281 : * when our pool is full.
2282 : */
2283 0 : void add_hwgenerator_randomness(const char *buffer, size_t count,
2284 : size_t entropy)
2285 : {
2286 0 : struct entropy_store *poolp = &input_pool;
2287 :
2288 0 : if (unlikely(crng_init == 0)) {
2289 0 : crng_fast_load(buffer, count);
2290 0 : return;
2291 : }
2292 :
2293 : /* Suspend writing if we're above the trickle threshold.
2294 : * We'll be woken up again once below random_write_wakeup_thresh,
2295 : * or when the calling thread is about to terminate.
2296 : */
2297 0 : wait_event_interruptible(random_write_wait, kthread_should_stop() ||
2298 : ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
2299 0 : mix_pool_bytes(poolp, buffer, count);
2300 0 : credit_entropy_bits(poolp, entropy);
2301 : }
2302 : EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
2303 :
2304 : /* Handle random seed passed by bootloader.
2305 : * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise
2306 : * it would be regarded as device data.
2307 : * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER.
2308 : */
2309 0 : void add_bootloader_randomness(const void *buf, unsigned int size)
2310 : {
2311 0 : if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
2312 : add_hwgenerator_randomness(buf, size, size * 8);
2313 : else
2314 0 : add_device_randomness(buf, size);
2315 0 : }
2316 : EXPORT_SYMBOL_GPL(add_bootloader_randomness);
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