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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/cryptohash.h>
331 : : #include <linux/fips.h>
332 : : #include <linux/ptrace.h>
333 : : #include <linux/workqueue.h>
334 : : #include <linux/irq.h>
335 : : #include <linux/ratelimit.h>
336 : : #include <linux/syscalls.h>
337 : : #include <linux/completion.h>
338 : : #include <linux/uuid.h>
339 : : #include <crypto/chacha.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 : 18165 : static void _mix_pool_bytes(struct entropy_store *r, const void *in,
538 : : int nbytes)
539 : : {
540 : 18165 : unsigned long i, tap1, tap2, tap3, tap4, tap5;
541 : 18165 : int input_rotate;
542 : 18165 : int wordmask = r->poolinfo->poolwords - 1;
543 : 18165 : const char *bytes = in;
544 : 18165 : __u32 w;
545 : :
546 : 18165 : tap1 = r->poolinfo->tap1;
547 : 18165 : tap2 = r->poolinfo->tap2;
548 : 18165 : tap3 = r->poolinfo->tap3;
549 : 18165 : tap4 = r->poolinfo->tap4;
550 : 18165 : tap5 = r->poolinfo->tap5;
551 : :
552 : 18165 : input_rotate = r->input_rotate;
553 : 18165 : i = r->add_ptr;
554 : :
555 : : /* mix one byte at a time to simplify size handling and churn faster */
556 [ + + ]: 193527 : while (nbytes--) {
557 [ + + ]: 175362 : w = rol32(*bytes++, input_rotate);
558 : 175362 : i = (i - 1) & wordmask;
559 : :
560 : : /* XOR in the various taps */
561 : 175362 : w ^= r->pool[i];
562 : 175362 : w ^= r->pool[(i + tap1) & wordmask];
563 : 175362 : w ^= r->pool[(i + tap2) & wordmask];
564 : 175362 : w ^= r->pool[(i + tap3) & wordmask];
565 : 175362 : w ^= r->pool[(i + tap4) & wordmask];
566 : 175362 : w ^= r->pool[(i + tap5) & wordmask];
567 : :
568 : : /* Mix the result back in with a twist */
569 : 175362 : 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 [ + + ]: 176731 : input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
578 : : }
579 : :
580 : 18165 : r->input_rotate = input_rotate;
581 : 18165 : r->add_ptr = i;
582 : 18165 : }
583 : :
584 : 132 : static void __mix_pool_bytes(struct entropy_store *r, const void *in,
585 : : int nbytes)
586 : : {
587 : 132 : trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
588 : 132 : _mix_pool_bytes(r, in, nbytes);
589 : 132 : }
590 : :
591 : 3183 : static void mix_pool_bytes(struct entropy_store *r, const void *in,
592 : : int nbytes)
593 : : {
594 : 3183 : unsigned long flags;
595 : :
596 : 3183 : trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
597 : 3183 : spin_lock_irqsave(&r->lock, flags);
598 : 3183 : _mix_pool_bytes(r, in, nbytes);
599 : 3183 : spin_unlock_irqrestore(&r->lock, flags);
600 : 3183 : }
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 : 7752 : static void fast_mix(struct fast_pool *f)
615 : : {
616 : 7752 : __u32 a = f->pool[0], b = f->pool[1];
617 : 7752 : __u32 c = f->pool[2], d = f->pool[3];
618 : :
619 : 7752 : a += b; c += d;
620 : 7752 : b = rol32(b, 6); d = rol32(d, 27);
621 : 7752 : d ^= a; b ^= c;
622 : :
623 : 7752 : a += b; c += d;
624 : 7752 : b = rol32(b, 16); d = rol32(d, 14);
625 : 7752 : d ^= a; b ^= c;
626 : :
627 : 7752 : a += b; c += d;
628 : 7752 : b = rol32(b, 6); d = rol32(d, 27);
629 : 7752 : d ^= a; b ^= c;
630 : :
631 : 7752 : a += b; c += d;
632 : 7752 : b = rol32(b, 16); d = rol32(d, 14);
633 : 7752 : d ^= a; b ^= c;
634 : :
635 : 7752 : f->pool[0] = a; f->pool[1] = b;
636 : 7752 : f->pool[2] = c; f->pool[3] = d;
637 : 7752 : f->count++;
638 : 7752 : }
639 : :
640 : 3 : static void process_random_ready_list(void)
641 : : {
642 : 3 : unsigned long flags;
643 : 3 : struct random_ready_callback *rdy, *tmp;
644 : :
645 : 3 : spin_lock_irqsave(&random_ready_list_lock, flags);
646 [ + + ]: 6 : list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
647 : 3 : struct module *owner = rdy->owner;
648 : :
649 : 3 : list_del_init(&rdy->list);
650 : 3 : rdy->func(rdy);
651 : 3 : module_put(owner);
652 : : }
653 : 3 : spin_unlock_irqrestore(&random_ready_list_lock, flags);
654 : 3 : }
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 : 3093 : static void credit_entropy_bits(struct entropy_store *r, int nbits)
662 : : {
663 : 3093 : int entropy_count, orig, has_initialized = 0;
664 : 3093 : const int pool_size = r->poolinfo->poolfracbits;
665 : 3093 : int nfrac = nbits << ENTROPY_SHIFT;
666 : :
667 [ + + ]: 3093 : if (!nbits)
668 : : return;
669 : :
670 : 451 : retry:
671 [ - + ]: 451 : entropy_count = orig = READ_ONCE(r->entropy_count);
672 [ - + ]: 451 : 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 : 451 : int pnfrac = nfrac;
698 : 451 : const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
699 : : /* The +2 corresponds to the /4 in the denominator */
700 : :
701 : 451 : do {
702 : 451 : unsigned int anfrac = min(pnfrac, pool_size/2);
703 : 451 : unsigned int add =
704 : 451 : ((pool_size - entropy_count)*anfrac*3) >> s;
705 : :
706 : 451 : entropy_count += add;
707 : 451 : pnfrac -= anfrac;
708 [ + - - + ]: 451 : } while (unlikely(entropy_count < pool_size-2 && pnfrac));
709 : : }
710 : :
711 [ - + - + ]: 451 : 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 : 451 : } else if (entropy_count > pool_size)
716 : : entropy_count = pool_size;
717 [ - + ]: 451 : if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
718 : 0 : goto retry;
719 : :
720 : 451 : if (has_initialized) {
721 : : r->initialized = 1;
722 : : kill_fasync(&fasync, SIGIO, POLL_IN);
723 : : }
724 : :
725 : 451 : trace_credit_entropy_bits(r->name, nbits,
726 : 451 : entropy_count >> ENTROPY_SHIFT, _RET_IP_);
727 : :
728 [ + - ]: 451 : if (r == &input_pool) {
729 : 451 : int entropy_bits = entropy_count >> ENTROPY_SHIFT;
730 : :
731 [ + + ]: 451 : if (crng_init < 2) {
732 [ + + ]: 289 : if (entropy_bits < 128)
733 : : return;
734 : 3 : crng_reseed(&primary_crng, r);
735 : 3 : 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 : 6 : static void crng_initialize(struct crng_state *crng)
785 : : {
786 : 6 : int i;
787 : 6 : int arch_init = 1;
788 : 6 : unsigned long rv;
789 : :
790 : 6 : memcpy(&crng->state[0], "expand 32-byte k", 16);
791 [ + + ]: 6 : if (crng == &primary_crng)
792 : 3 : _extract_entropy(&input_pool, &crng->state[4],
793 : : sizeof(__u32) * 12, 0);
794 : : else
795 : 3 : _get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
796 [ + + ]: 78 : for (i = 4; i < 16; i++) {
797 [ + - + - ]: 144 : if (!arch_get_random_seed_long(&rv) &&
798 : 72 : !arch_get_random_long(&rv)) {
799 : 72 : rv = random_get_entropy();
800 : 72 : arch_init = 0;
801 : : }
802 : 72 : crng->state[i] ^= rv;
803 : : }
804 [ - + - - : 6 : if (trust_cpu && arch_init && crng == &primary_crng) {
- - ]
805 : 0 : invalidate_batched_entropy();
806 : 0 : numa_crng_init();
807 : 0 : crng_init = 2;
808 : 0 : pr_notice("crng done (trusting CPU's manufacturer)\n");
809 : : }
810 : 6 : crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
811 : 6 : }
812 : :
813 : : #ifdef CONFIG_NUMA
814 : 3 : static void do_numa_crng_init(struct work_struct *work)
815 : : {
816 : 3 : int i;
817 : 3 : struct crng_state *crng;
818 : 3 : struct crng_state **pool;
819 : :
820 : 3 : pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
821 [ + + ]: 9 : for_each_online_node(i) {
822 : 3 : crng = kmalloc_node(sizeof(struct crng_state),
823 : : GFP_KERNEL | __GFP_NOFAIL, i);
824 : 3 : spin_lock_init(&crng->lock);
825 : 3 : crng_initialize(crng);
826 : 3 : pool[i] = crng;
827 : : }
828 : 3 : mb();
829 [ - + ]: 3 : if (cmpxchg(&crng_node_pool, NULL, pool)) {
830 [ # # ]: 0 : for_each_node(i)
831 : 0 : kfree(pool[i]);
832 : 0 : kfree(pool);
833 : : }
834 : 3 : }
835 : :
836 : : static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init);
837 : :
838 : 3 : static void numa_crng_init(void)
839 : : {
840 : 0 : schedule_work(&numa_crng_init_work);
841 : : }
842 : : #else
843 : : static void numa_crng_init(void) {}
844 : : #endif
845 : :
846 : : /*
847 : : * crng_fast_load() can be called by code in the interrupt service
848 : : * path. So we can't afford to dilly-dally.
849 : : */
850 : 12 : static int crng_fast_load(const char *cp, size_t len)
851 : : {
852 : 12 : unsigned long flags;
853 : 12 : char *p;
854 : :
855 [ - + ]: 24 : if (!spin_trylock_irqsave(&primary_crng.lock, flags))
856 : 0 : return 0;
857 [ - + ]: 12 : if (crng_init != 0) {
858 : 0 : spin_unlock_irqrestore(&primary_crng.lock, flags);
859 : 0 : return 0;
860 : : }
861 : : p = (unsigned char *) &primary_crng.state[4];
862 [ + + + - ]: 204 : while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
863 : 192 : p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp;
864 : 192 : cp++; crng_init_cnt++; len--;
865 : : }
866 : 12 : spin_unlock_irqrestore(&primary_crng.lock, flags);
867 [ + + ]: 12 : if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
868 : 3 : invalidate_batched_entropy();
869 : 3 : crng_init = 1;
870 : 3 : pr_notice("fast init done\n");
871 : : }
872 : : return 1;
873 : : }
874 : :
875 : : /*
876 : : * crng_slow_load() is called by add_device_randomness, which has two
877 : : * attributes. (1) We can't trust the buffer passed to it is
878 : : * guaranteed to be unpredictable (so it might not have any entropy at
879 : : * all), and (2) it doesn't have the performance constraints of
880 : : * crng_fast_load().
881 : : *
882 : : * So we do something more comprehensive which is guaranteed to touch
883 : : * all of the primary_crng's state, and which uses a LFSR with a
884 : : * period of 255 as part of the mixing algorithm. Finally, we do
885 : : * *not* advance crng_init_cnt since buffer we may get may be something
886 : : * like a fixed DMI table (for example), which might very well be
887 : : * unique to the machine, but is otherwise unvarying.
888 : : */
889 : 284 : static int crng_slow_load(const char *cp, size_t len)
890 : : {
891 : 284 : unsigned long flags;
892 : 284 : static unsigned char lfsr = 1;
893 : 284 : unsigned char tmp;
894 : 284 : unsigned i, max = CHACHA_KEY_SIZE;
895 : 284 : const char * src_buf = cp;
896 : 284 : char * dest_buf = (char *) &primary_crng.state[4];
897 : :
898 [ - + ]: 568 : if (!spin_trylock_irqsave(&primary_crng.lock, flags))
899 : 0 : return 0;
900 [ + + ]: 284 : if (crng_init != 0) {
901 : 113 : spin_unlock_irqrestore(&primary_crng.lock, flags);
902 : 113 : return 0;
903 : : }
904 : 171 : if (len > max)
905 : : max = len;
906 : :
907 [ + + ]: 9267 : for (i = 0; i < max ; i++) {
908 : 9096 : tmp = lfsr;
909 : 9096 : lfsr >>= 1;
910 [ + + ]: 9096 : if (tmp & 1)
911 : 4579 : lfsr ^= 0xE1;
912 : 9096 : tmp = dest_buf[i % CHACHA_KEY_SIZE];
913 : 9096 : dest_buf[i % CHACHA_KEY_SIZE] ^= src_buf[i % len] ^ lfsr;
914 : 9096 : lfsr += (tmp << 3) | (tmp >> 5);
915 : : }
916 : 171 : spin_unlock_irqrestore(&primary_crng.lock, flags);
917 : 171 : return 1;
918 : : }
919 : :
920 : 6 : static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
921 : : {
922 : 6 : unsigned long flags;
923 : 6 : int i, num;
924 : 6 : union {
925 : : __u8 block[CHACHA_BLOCK_SIZE];
926 : : __u32 key[8];
927 : : } buf;
928 : :
929 [ + + ]: 6 : if (r) {
930 : 3 : num = extract_entropy(r, &buf, 32, 16, 0);
931 [ - + ]: 3 : if (num == 0)
932 : 0 : return;
933 : : } else {
934 : 3 : _extract_crng(&primary_crng, buf.block);
935 : 3 : _crng_backtrack_protect(&primary_crng, buf.block,
936 : : CHACHA_KEY_SIZE);
937 : : }
938 : 6 : spin_lock_irqsave(&crng->lock, flags);
939 [ + + ]: 60 : for (i = 0; i < 8; i++) {
940 : 48 : unsigned long rv;
941 [ + - + - ]: 96 : if (!arch_get_random_seed_long(&rv) &&
942 : 48 : !arch_get_random_long(&rv))
943 : 48 : rv = random_get_entropy();
944 : 48 : crng->state[i+4] ^= buf.key[i] ^ rv;
945 : : }
946 : 6 : memzero_explicit(&buf, sizeof(buf));
947 : 6 : crng->init_time = jiffies;
948 : 6 : spin_unlock_irqrestore(&crng->lock, flags);
949 [ + + + - ]: 6 : if (crng == &primary_crng && crng_init < 2) {
950 : 3 : invalidate_batched_entropy();
951 : 3 : numa_crng_init();
952 : 3 : crng_init = 2;
953 : 3 : process_random_ready_list();
954 : 3 : wake_up_interruptible(&crng_init_wait);
955 : 3 : kill_fasync(&fasync, SIGIO, POLL_IN);
956 : 3 : pr_notice("crng init done\n");
957 [ - + ]: 3 : if (unseeded_warning.missed) {
958 : 0 : pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n",
959 : : unseeded_warning.missed);
960 : 0 : unseeded_warning.missed = 0;
961 : : }
962 [ + - ]: 3 : if (urandom_warning.missed) {
963 : 3 : pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
964 : : urandom_warning.missed);
965 : 3 : urandom_warning.missed = 0;
966 : : }
967 : : }
968 : : }
969 : :
970 : 16155 : static void _extract_crng(struct crng_state *crng,
971 : : __u8 out[CHACHA_BLOCK_SIZE])
972 : : {
973 : 16155 : unsigned long v, flags;
974 : :
975 [ + + ]: 16155 : if (crng_ready() &&
976 [ + + ]: 15308 : (time_after(crng_global_init_time, crng->init_time) ||
977 [ - + ]: 15305 : time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
978 [ + - ]: 6 : crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
979 : 16155 : spin_lock_irqsave(&crng->lock, flags);
980 [ - + ]: 16155 : if (arch_get_random_long(&v))
981 : 0 : crng->state[14] ^= v;
982 : 16155 : chacha20_block(&crng->state[0], out);
983 [ - + ]: 16155 : if (crng->state[12] == 0)
984 : 0 : crng->state[13]++;
985 : 16155 : spin_unlock_irqrestore(&crng->lock, flags);
986 : 16155 : }
987 : :
988 : 16152 : static void extract_crng(__u8 out[CHACHA_BLOCK_SIZE])
989 : : {
990 : 16152 : struct crng_state *crng = NULL;
991 : :
992 : : #ifdef CONFIG_NUMA
993 [ + + ]: 16152 : if (crng_node_pool)
994 [ - + ]: 15299 : crng = crng_node_pool[numa_node_id()];
995 [ - + ]: 15299 : if (crng == NULL)
996 : : #endif
997 : : crng = &primary_crng;
998 : 16152 : _extract_crng(crng, out);
999 : 16152 : }
1000 : :
1001 : : /*
1002 : : * Use the leftover bytes from the CRNG block output (if there is
1003 : : * enough) to mutate the CRNG key to provide backtracking protection.
1004 : : */
1005 : 9246 : static void _crng_backtrack_protect(struct crng_state *crng,
1006 : : __u8 tmp[CHACHA_BLOCK_SIZE], int used)
1007 : : {
1008 : 9246 : unsigned long flags;
1009 : 9246 : __u32 *s, *d;
1010 : 9246 : int i;
1011 : :
1012 : 9246 : used = round_up(used, sizeof(__u32));
1013 [ + + ]: 9246 : if (used + CHACHA_KEY_SIZE > CHACHA_BLOCK_SIZE) {
1014 : 6 : extract_crng(tmp);
1015 : 6 : used = 0;
1016 : : }
1017 : 9246 : spin_lock_irqsave(&crng->lock, flags);
1018 : 9246 : s = (__u32 *) &tmp[used];
1019 : 9246 : d = &crng->state[4];
1020 [ + + ]: 83214 : for (i=0; i < 8; i++)
1021 : 73968 : *d++ ^= *s++;
1022 : 9246 : spin_unlock_irqrestore(&crng->lock, flags);
1023 : 9246 : }
1024 : :
1025 : 9243 : static void crng_backtrack_protect(__u8 tmp[CHACHA_BLOCK_SIZE], int used)
1026 : : {
1027 : 9243 : struct crng_state *crng = NULL;
1028 : :
1029 : : #ifdef CONFIG_NUMA
1030 [ + + ]: 9243 : if (crng_node_pool)
1031 [ - + ]: 8602 : crng = crng_node_pool[numa_node_id()];
1032 [ - + ]: 8602 : if (crng == NULL)
1033 : : #endif
1034 : : crng = &primary_crng;
1035 : 9243 : _crng_backtrack_protect(crng, tmp, used);
1036 : 9243 : }
1037 : :
1038 : 1541 : static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
1039 : : {
1040 : 1541 : ssize_t ret = 0, i = CHACHA_BLOCK_SIZE;
1041 : 1541 : __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1042 : 1541 : int large_request = (nbytes > 256);
1043 : :
1044 [ + + ]: 3103 : while (nbytes) {
1045 [ + + - + ]: 1586 : if (large_request && need_resched()) {
1046 [ # # ]: 0 : if (signal_pending(current)) {
1047 [ # # ]: 0 : if (ret == 0)
1048 : 0 : ret = -ERESTARTSYS;
1049 : : break;
1050 : : }
1051 : 0 : schedule();
1052 : : }
1053 : :
1054 : 1562 : extract_crng(tmp);
1055 : 1562 : i = min_t(int, nbytes, CHACHA_BLOCK_SIZE);
1056 [ - + + - ]: 3124 : if (copy_to_user(buf, tmp, i)) {
1057 : : ret = -EFAULT;
1058 : : break;
1059 : : }
1060 : :
1061 : 1562 : nbytes -= i;
1062 : 1562 : buf += i;
1063 : 1562 : ret += i;
1064 : : }
1065 : 1541 : crng_backtrack_protect(tmp, i);
1066 : :
1067 : : /* Wipe data just written to memory */
1068 : 1541 : memzero_explicit(tmp, sizeof(tmp));
1069 : :
1070 : 1541 : return ret;
1071 : : }
1072 : :
1073 : :
1074 : : /*********************************************************************
1075 : : *
1076 : : * Entropy input management
1077 : : *
1078 : : *********************************************************************/
1079 : :
1080 : : /* There is one of these per entropy source */
1081 : : struct timer_rand_state {
1082 : : cycles_t last_time;
1083 : : long last_delta, last_delta2;
1084 : : };
1085 : :
1086 : : #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
1087 : :
1088 : : /*
1089 : : * Add device- or boot-specific data to the input pool to help
1090 : : * initialize it.
1091 : : *
1092 : : * None of this adds any entropy; it is meant to avoid the problem of
1093 : : * the entropy pool having similar initial state across largely
1094 : : * identical devices.
1095 : : */
1096 : 7425 : void add_device_randomness(const void *buf, unsigned int size)
1097 : : {
1098 : 7425 : unsigned long time = random_get_entropy() ^ jiffies;
1099 : 7425 : unsigned long flags;
1100 : :
1101 [ + + + - ]: 7425 : if (!crng_ready() && size)
1102 : 284 : crng_slow_load(buf, size);
1103 : :
1104 : 7425 : trace_add_device_randomness(size, _RET_IP_);
1105 : 7425 : spin_lock_irqsave(&input_pool.lock, flags);
1106 : 7425 : _mix_pool_bytes(&input_pool, buf, size);
1107 : 7425 : _mix_pool_bytes(&input_pool, &time, sizeof(time));
1108 : 7425 : spin_unlock_irqrestore(&input_pool.lock, flags);
1109 : 7425 : }
1110 : : EXPORT_SYMBOL(add_device_randomness);
1111 : :
1112 : : static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
1113 : :
1114 : : /*
1115 : : * This function adds entropy to the entropy "pool" by using timing
1116 : : * delays. It uses the timer_rand_state structure to make an estimate
1117 : : * of how many bits of entropy this call has added to the pool.
1118 : : *
1119 : : * The number "num" is also added to the pool - it should somehow describe
1120 : : * the type of event which just happened. This is currently 0-255 for
1121 : : * keyboard scan codes, and 256 upwards for interrupts.
1122 : : *
1123 : : */
1124 : 2982 : static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
1125 : : {
1126 : 2982 : struct entropy_store *r;
1127 : 2982 : struct {
1128 : : long jiffies;
1129 : : unsigned cycles;
1130 : : unsigned num;
1131 : : } sample;
1132 : 2982 : long delta, delta2, delta3;
1133 : :
1134 : 2982 : sample.jiffies = jiffies;
1135 : 2982 : sample.cycles = random_get_entropy();
1136 : 2982 : sample.num = num;
1137 : 2982 : r = &input_pool;
1138 : 2982 : mix_pool_bytes(r, &sample, sizeof(sample));
1139 : :
1140 : : /*
1141 : : * Calculate number of bits of randomness we probably added.
1142 : : * We take into account the first, second and third-order deltas
1143 : : * in order to make our estimate.
1144 : : */
1145 : 2982 : delta = sample.jiffies - state->last_time;
1146 : 2982 : state->last_time = sample.jiffies;
1147 : :
1148 : 2982 : delta2 = delta - state->last_delta;
1149 : 2982 : state->last_delta = delta;
1150 : :
1151 : 2982 : delta3 = delta2 - state->last_delta2;
1152 : 2982 : state->last_delta2 = delta2;
1153 : :
1154 : 2982 : if (delta < 0)
1155 : : delta = -delta;
1156 [ + + ]: 2982 : if (delta2 < 0)
1157 : 1012 : delta2 = -delta2;
1158 [ + + ]: 2982 : if (delta3 < 0)
1159 : 1053 : delta3 = -delta3;
1160 : 2982 : if (delta > delta2)
1161 : : delta = delta2;
1162 : 2982 : if (delta > delta3)
1163 : : delta = delta3;
1164 : :
1165 : : /*
1166 : : * delta is now minimum absolute delta.
1167 : : * Round down by 1 bit on general principles,
1168 : : * and limit entropy estimate to 12 bits.
1169 : : */
1170 : 2982 : credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1171 : 2982 : }
1172 : :
1173 : 3 : void add_input_randomness(unsigned int type, unsigned int code,
1174 : : unsigned int value)
1175 : : {
1176 : 3 : static unsigned char last_value;
1177 : :
1178 : : /* ignore autorepeat and the like */
1179 [ + - ]: 3 : if (value == last_value)
1180 : : return;
1181 : :
1182 : 3 : last_value = value;
1183 : 3 : add_timer_randomness(&input_timer_state,
1184 : 3 : (type << 4) ^ code ^ (code >> 4) ^ value);
1185 : 3 : trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1186 : : }
1187 : : EXPORT_SYMBOL_GPL(add_input_randomness);
1188 : :
1189 : : static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
1190 : :
1191 : : #ifdef ADD_INTERRUPT_BENCH
1192 : : static unsigned long avg_cycles, avg_deviation;
1193 : :
1194 : : #define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
1195 : : #define FIXED_1_2 (1 << (AVG_SHIFT-1))
1196 : :
1197 : : static void add_interrupt_bench(cycles_t start)
1198 : : {
1199 : : long delta = random_get_entropy() - start;
1200 : :
1201 : : /* Use a weighted moving average */
1202 : : delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
1203 : : avg_cycles += delta;
1204 : : /* And average deviation */
1205 : : delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
1206 : : avg_deviation += delta;
1207 : : }
1208 : : #else
1209 : : #define add_interrupt_bench(x)
1210 : : #endif
1211 : :
1212 : 0 : static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
1213 : : {
1214 : 0 : __u32 *ptr = (__u32 *) regs;
1215 : 0 : unsigned int idx;
1216 : :
1217 : 0 : if (regs == NULL)
1218 : : return 0;
1219 [ # # ]: 0 : idx = READ_ONCE(f->reg_idx);
1220 [ # # ]: 0 : if (idx >= sizeof(struct pt_regs) / sizeof(__u32))
1221 : 0 : idx = 0;
1222 : 0 : ptr += idx++;
1223 : 0 : WRITE_ONCE(f->reg_idx, idx);
1224 : 0 : return *ptr;
1225 : : }
1226 : :
1227 : 7752 : void add_interrupt_randomness(int irq, int irq_flags)
1228 : : {
1229 : 7752 : struct entropy_store *r;
1230 : 7752 : struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
1231 : 7752 : struct pt_regs *regs = get_irq_regs();
1232 : 7752 : unsigned long now = jiffies;
1233 : 7752 : cycles_t cycles = random_get_entropy();
1234 : 7752 : __u32 c_high, j_high;
1235 : 7752 : __u64 ip;
1236 : 7752 : unsigned long seed;
1237 : 7752 : int credit = 0;
1238 : :
1239 [ - + ]: 7752 : if (cycles == 0)
1240 [ # # ]: 0 : cycles = get_reg(fast_pool, regs);
1241 : 7752 : c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
1242 : 7752 : j_high = (sizeof(now) > 4) ? now >> 32 : 0;
1243 : 7752 : fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
1244 : 7752 : fast_pool->pool[1] ^= now ^ c_high;
1245 [ + - ]: 7752 : ip = regs ? instruction_pointer(regs) : _RET_IP_;
1246 : 7752 : fast_pool->pool[2] ^= ip;
1247 : 7752 : fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
1248 : : get_reg(fast_pool, regs);
1249 : :
1250 : 7752 : fast_mix(fast_pool);
1251 : 7752 : add_interrupt_bench(cycles);
1252 : :
1253 [ + + ]: 7752 : if (unlikely(crng_init == 0)) {
1254 [ + + + - ]: 780 : if ((fast_pool->count >= 64) &&
1255 : 12 : crng_fast_load((char *) fast_pool->pool,
1256 : : sizeof(fast_pool->pool))) {
1257 : 12 : fast_pool->count = 0;
1258 : 12 : fast_pool->last = now;
1259 : : }
1260 : 7641 : return;
1261 : : }
1262 : :
1263 [ + + ]: 6984 : if ((fast_pool->count < 64) &&
1264 [ + + ]: 6879 : !time_after(now, fast_pool->last + HZ))
1265 : : return;
1266 : :
1267 : 111 : r = &input_pool;
1268 [ + - ]: 111 : if (!spin_trylock(&r->lock))
1269 : : return;
1270 : :
1271 : 111 : fast_pool->last = now;
1272 : 111 : __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
1273 : :
1274 : : /*
1275 : : * If we have architectural seed generator, produce a seed and
1276 : : * add it to the pool. For the sake of paranoia don't let the
1277 : : * architectural seed generator dominate the input from the
1278 : : * interrupt noise.
1279 : : */
1280 [ - + ]: 111 : if (arch_get_random_seed_long(&seed)) {
1281 : 0 : __mix_pool_bytes(r, &seed, sizeof(seed));
1282 : 0 : credit = 1;
1283 : : }
1284 : 111 : spin_unlock(&r->lock);
1285 : :
1286 : 111 : fast_pool->count = 0;
1287 : :
1288 : : /* award one bit for the contents of the fast pool */
1289 : 111 : credit_entropy_bits(r, credit + 1);
1290 : : }
1291 : : EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1292 : :
1293 : : #ifdef CONFIG_BLOCK
1294 : 3219 : void add_disk_randomness(struct gendisk *disk)
1295 : : {
1296 [ + + + - ]: 3219 : if (!disk || !disk->random)
1297 : : return;
1298 : : /* first major is 1, so we get >= 0x200 here */
1299 : 2979 : add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1300 : 2979 : trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1301 : : }
1302 : : EXPORT_SYMBOL_GPL(add_disk_randomness);
1303 : : #endif
1304 : :
1305 : : /*********************************************************************
1306 : : *
1307 : : * Entropy extraction routines
1308 : : *
1309 : : *********************************************************************/
1310 : :
1311 : : /*
1312 : : * This function decides how many bytes to actually take from the
1313 : : * given pool, and also debits the entropy count accordingly.
1314 : : */
1315 : 3 : static size_t account(struct entropy_store *r, size_t nbytes, int min,
1316 : : int reserved)
1317 : : {
1318 : 3 : int entropy_count, orig, have_bytes;
1319 : 3 : size_t ibytes, nfrac;
1320 : :
1321 [ - + ]: 3 : BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1322 : :
1323 : : /* Can we pull enough? */
1324 : 3 : retry:
1325 [ - + ]: 3 : entropy_count = orig = READ_ONCE(r->entropy_count);
1326 : 3 : ibytes = nbytes;
1327 : : /* never pull more than available */
1328 : 3 : have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1329 : :
1330 : 3 : if ((have_bytes -= reserved) < 0)
1331 : : have_bytes = 0;
1332 : 3 : ibytes = min_t(size_t, ibytes, have_bytes);
1333 [ - + ]: 3 : if (ibytes < min)
1334 : 0 : ibytes = 0;
1335 : :
1336 [ - + - + ]: 3 : if (WARN_ON(entropy_count < 0)) {
1337 : 0 : pr_warn("negative entropy count: pool %s count %d\n",
1338 : : r->name, entropy_count);
1339 : 0 : entropy_count = 0;
1340 : : }
1341 : 3 : nfrac = ibytes << (ENTROPY_SHIFT + 3);
1342 [ + - ]: 3 : if ((size_t) entropy_count > nfrac)
1343 : 3 : entropy_count -= nfrac;
1344 : : else
1345 : : entropy_count = 0;
1346 : :
1347 [ - + ]: 3 : if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1348 : 0 : goto retry;
1349 : :
1350 : 3 : trace_debit_entropy(r->name, 8 * ibytes);
1351 [ + - + - ]: 3 : if (ibytes && ENTROPY_BITS(r) < random_write_wakeup_bits) {
1352 : 3 : wake_up_interruptible(&random_write_wait);
1353 : 3 : kill_fasync(&fasync, SIGIO, POLL_OUT);
1354 : : }
1355 : :
1356 : 3 : return ibytes;
1357 : : }
1358 : :
1359 : : /*
1360 : : * This function does the actual extraction for extract_entropy and
1361 : : * extract_entropy_user.
1362 : : *
1363 : : * Note: we assume that .poolwords is a multiple of 16 words.
1364 : : */
1365 : 21 : static void extract_buf(struct entropy_store *r, __u8 *out)
1366 : : {
1367 : 21 : int i;
1368 : 21 : union {
1369 : : __u32 w[5];
1370 : : unsigned long l[LONGS(20)];
1371 : : } hash;
1372 : 21 : __u32 workspace[SHA_WORKSPACE_WORDS];
1373 : 21 : unsigned long flags;
1374 : :
1375 : : /*
1376 : : * If we have an architectural hardware random number
1377 : : * generator, use it for SHA's initial vector
1378 : : */
1379 : 21 : sha_init(hash.w);
1380 [ + - ]: 42 : for (i = 0; i < LONGS(20); i++) {
1381 : 21 : unsigned long v;
1382 [ - + ]: 21 : if (!arch_get_random_long(&v))
1383 : : break;
1384 : 0 : hash.l[i] = v;
1385 : : }
1386 : :
1387 : : /* Generate a hash across the pool, 16 words (512 bits) at a time */
1388 : 21 : spin_lock_irqsave(&r->lock, flags);
1389 [ + + ]: 210 : for (i = 0; i < r->poolinfo->poolwords; i += 16)
1390 : 168 : sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1391 : :
1392 : : /*
1393 : : * We mix the hash back into the pool to prevent backtracking
1394 : : * attacks (where the attacker knows the state of the pool
1395 : : * plus the current outputs, and attempts to find previous
1396 : : * ouputs), unless the hash function can be inverted. By
1397 : : * mixing at least a SHA1 worth of hash data back, we make
1398 : : * brute-forcing the feedback as hard as brute-forcing the
1399 : : * hash.
1400 : : */
1401 : 21 : __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1402 : 21 : spin_unlock_irqrestore(&r->lock, flags);
1403 : :
1404 : 21 : memzero_explicit(workspace, sizeof(workspace));
1405 : :
1406 : : /*
1407 : : * In case the hash function has some recognizable output
1408 : : * pattern, we fold it in half. Thus, we always feed back
1409 : : * twice as much data as we output.
1410 : : */
1411 : 21 : hash.w[0] ^= hash.w[3];
1412 : 21 : hash.w[1] ^= hash.w[4];
1413 : 21 : hash.w[2] ^= rol32(hash.w[2], 16);
1414 : :
1415 : 21 : memcpy(out, &hash, EXTRACT_SIZE);
1416 : 21 : memzero_explicit(&hash, sizeof(hash));
1417 : 21 : }
1418 : :
1419 : 6 : static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
1420 : : size_t nbytes, int fips)
1421 : : {
1422 : 6 : ssize_t ret = 0, i;
1423 : 6 : __u8 tmp[EXTRACT_SIZE];
1424 : 6 : unsigned long flags;
1425 : :
1426 [ + + ]: 27 : while (nbytes) {
1427 : 21 : extract_buf(r, tmp);
1428 : :
1429 [ - + ]: 21 : if (fips) {
1430 : 0 : spin_lock_irqsave(&r->lock, flags);
1431 [ # # ]: 0 : if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1432 : 0 : panic("Hardware RNG duplicated output!\n");
1433 : 0 : memcpy(r->last_data, tmp, EXTRACT_SIZE);
1434 : 0 : spin_unlock_irqrestore(&r->lock, flags);
1435 : : }
1436 : 21 : i = min_t(int, nbytes, EXTRACT_SIZE);
1437 : 21 : memcpy(buf, tmp, i);
1438 : 21 : nbytes -= i;
1439 : 21 : buf += i;
1440 : 21 : ret += i;
1441 : : }
1442 : :
1443 : : /* Wipe data just returned from memory */
1444 : 6 : memzero_explicit(tmp, sizeof(tmp));
1445 : :
1446 : 6 : return ret;
1447 : : }
1448 : :
1449 : : /*
1450 : : * This function extracts randomness from the "entropy pool", and
1451 : : * returns it in a buffer.
1452 : : *
1453 : : * The min parameter specifies the minimum amount we can pull before
1454 : : * failing to avoid races that defeat catastrophic reseeding while the
1455 : : * reserved parameter indicates how much entropy we must leave in the
1456 : : * pool after each pull to avoid starving other readers.
1457 : : */
1458 : 3 : static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1459 : : size_t nbytes, int min, int reserved)
1460 : : {
1461 : 3 : __u8 tmp[EXTRACT_SIZE];
1462 : 3 : unsigned long flags;
1463 : :
1464 : : /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1465 : 3 : if (fips_enabled) {
1466 : : spin_lock_irqsave(&r->lock, flags);
1467 : : if (!r->last_data_init) {
1468 : : r->last_data_init = 1;
1469 : : spin_unlock_irqrestore(&r->lock, flags);
1470 : : trace_extract_entropy(r->name, EXTRACT_SIZE,
1471 : : ENTROPY_BITS(r), _RET_IP_);
1472 : : extract_buf(r, tmp);
1473 : : spin_lock_irqsave(&r->lock, flags);
1474 : : memcpy(r->last_data, tmp, EXTRACT_SIZE);
1475 : : }
1476 : : spin_unlock_irqrestore(&r->lock, flags);
1477 : : }
1478 : :
1479 : 3 : trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1480 : 3 : nbytes = account(r, nbytes, min, reserved);
1481 : :
1482 : 3 : return _extract_entropy(r, buf, nbytes, fips_enabled);
1483 : : }
1484 : :
1485 : : #define warn_unseeded_randomness(previous) \
1486 : : _warn_unseeded_randomness(__func__, (void *) _RET_IP_, (previous))
1487 : :
1488 : 73659 : static void _warn_unseeded_randomness(const char *func_name, void *caller,
1489 : : void **previous)
1490 : : {
1491 : : #ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1492 : : const bool print_once = false;
1493 : : #else
1494 : 73659 : static bool print_once __read_mostly;
1495 : : #endif
1496 : :
1497 [ + + ]: 73659 : if (print_once ||
1498 [ + - + - ]: 3 : crng_ready() ||
1499 [ + - ]: 3 : (previous && (caller == READ_ONCE(*previous))))
1500 : : return;
1501 : 3 : WRITE_ONCE(*previous, caller);
1502 : : #ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1503 : 3 : print_once = true;
1504 : : #endif
1505 [ + - ]: 3 : if (__ratelimit(&unseeded_warning))
1506 : 3 : printk_deferred(KERN_NOTICE "random: %s called from %pS "
1507 : : "with crng_init=%d\n", func_name, caller,
1508 : : crng_init);
1509 : : }
1510 : :
1511 : : /*
1512 : : * This function is the exported kernel interface. It returns some
1513 : : * number of good random numbers, suitable for key generation, seeding
1514 : : * TCP sequence numbers, etc. It does not rely on the hardware random
1515 : : * number generator. For random bytes direct from the hardware RNG
1516 : : * (when available), use get_random_bytes_arch(). In order to ensure
1517 : : * that the randomness provided by this function is okay, the function
1518 : : * wait_for_random_bytes() should be called and return 0 at least once
1519 : : * at any point prior.
1520 : : */
1521 : 7702 : static void _get_random_bytes(void *buf, int nbytes)
1522 : : {
1523 : 7702 : __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1524 : :
1525 : 7702 : trace_get_random_bytes(nbytes, _RET_IP_);
1526 : :
1527 [ - + ]: 7702 : while (nbytes >= CHACHA_BLOCK_SIZE) {
1528 : 0 : extract_crng(buf);
1529 : 0 : buf += CHACHA_BLOCK_SIZE;
1530 : 0 : nbytes -= CHACHA_BLOCK_SIZE;
1531 : : }
1532 : :
1533 [ + - ]: 7702 : if (nbytes > 0) {
1534 : 7702 : extract_crng(tmp);
1535 : 7702 : memcpy(buf, tmp, nbytes);
1536 : 7702 : crng_backtrack_protect(tmp, nbytes);
1537 : : } else
1538 : 0 : crng_backtrack_protect(tmp, CHACHA_BLOCK_SIZE);
1539 : 7702 : memzero_explicit(tmp, sizeof(tmp));
1540 : 7702 : }
1541 : :
1542 : 7699 : void get_random_bytes(void *buf, int nbytes)
1543 : : {
1544 : 7699 : static void *previous;
1545 : :
1546 : 7699 : warn_unseeded_randomness(&previous);
1547 : 7699 : _get_random_bytes(buf, nbytes);
1548 : 7699 : }
1549 : : EXPORT_SYMBOL(get_random_bytes);
1550 : :
1551 : :
1552 : : /*
1553 : : * Each time the timer fires, we expect that we got an unpredictable
1554 : : * jump in the cycle counter. Even if the timer is running on another
1555 : : * CPU, the timer activity will be touching the stack of the CPU that is
1556 : : * generating entropy..
1557 : : *
1558 : : * Note that we don't re-arm the timer in the timer itself - we are
1559 : : * happy to be scheduled away, since that just makes the load more
1560 : : * complex, but we do not want the timer to keep ticking unless the
1561 : : * entropy loop is running.
1562 : : *
1563 : : * So the re-arming always happens in the entropy loop itself.
1564 : : */
1565 : 0 : static void entropy_timer(struct timer_list *t)
1566 : : {
1567 : 0 : credit_entropy_bits(&input_pool, 1);
1568 : 0 : }
1569 : :
1570 : : /*
1571 : : * If we have an actual cycle counter, see if we can
1572 : : * generate enough entropy with timing noise
1573 : : */
1574 : 0 : static void try_to_generate_entropy(void)
1575 : : {
1576 : 0 : struct {
1577 : : unsigned long now;
1578 : : struct timer_list timer;
1579 : : } stack;
1580 : :
1581 : 0 : stack.now = random_get_entropy();
1582 : :
1583 : : /* Slow counter - or none. Don't even bother */
1584 [ # # ]: 0 : if (stack.now == random_get_entropy())
1585 : 0 : return;
1586 : :
1587 : 0 : timer_setup_on_stack(&stack.timer, entropy_timer, 0);
1588 [ # # ]: 0 : while (!crng_ready()) {
1589 [ # # ]: 0 : if (!timer_pending(&stack.timer))
1590 : 0 : mod_timer(&stack.timer, jiffies+1);
1591 : 0 : mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
1592 : 0 : schedule();
1593 : 0 : stack.now = random_get_entropy();
1594 : : }
1595 : :
1596 : 0 : del_timer_sync(&stack.timer);
1597 : 0 : destroy_timer_on_stack(&stack.timer);
1598 : 0 : mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
1599 : : }
1600 : :
1601 : : /*
1602 : : * Wait for the urandom pool to be seeded and thus guaranteed to supply
1603 : : * cryptographically secure random numbers. This applies to: the /dev/urandom
1604 : : * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
1605 : : * family of functions. Using any of these functions without first calling
1606 : : * this function forfeits the guarantee of security.
1607 : : *
1608 : : * Returns: 0 if the urandom pool has been seeded.
1609 : : * -ERESTARTSYS if the function was interrupted by a signal.
1610 : : */
1611 : 0 : int wait_for_random_bytes(void)
1612 : : {
1613 [ # # ]: 0 : if (likely(crng_ready()))
1614 : : return 0;
1615 : :
1616 : 0 : do {
1617 : 0 : int ret;
1618 [ # # # # : 0 : ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
# # # # ]
1619 [ # # ]: 0 : if (ret)
1620 : 0 : return ret > 0 ? 0 : ret;
1621 : :
1622 : 0 : try_to_generate_entropy();
1623 [ # # ]: 0 : } while (!crng_ready());
1624 : :
1625 : : return 0;
1626 : : }
1627 : : EXPORT_SYMBOL(wait_for_random_bytes);
1628 : :
1629 : : /*
1630 : : * Returns whether or not the urandom pool has been seeded and thus guaranteed
1631 : : * to supply cryptographically secure random numbers. This applies to: the
1632 : : * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
1633 : : * ,u64,int,long} family of functions.
1634 : : *
1635 : : * Returns: true if the urandom pool has been seeded.
1636 : : * false if the urandom pool has not been seeded.
1637 : : */
1638 : 0 : bool rng_is_initialized(void)
1639 : : {
1640 : 0 : return crng_ready();
1641 : : }
1642 : : EXPORT_SYMBOL(rng_is_initialized);
1643 : :
1644 : : /*
1645 : : * Add a callback function that will be invoked when the nonblocking
1646 : : * pool is initialised.
1647 : : *
1648 : : * returns: 0 if callback is successfully added
1649 : : * -EALREADY if pool is already initialised (callback not called)
1650 : : * -ENOENT if module for callback is not alive
1651 : : */
1652 : 3 : int add_random_ready_callback(struct random_ready_callback *rdy)
1653 : : {
1654 : 3 : struct module *owner;
1655 : 3 : unsigned long flags;
1656 : 3 : int err = -EALREADY;
1657 : :
1658 [ + - ]: 3 : if (crng_ready())
1659 : : return err;
1660 : :
1661 : 3 : owner = rdy->owner;
1662 [ + - ]: 3 : if (!try_module_get(owner))
1663 : : return -ENOENT;
1664 : :
1665 : 3 : spin_lock_irqsave(&random_ready_list_lock, flags);
1666 [ - + ]: 3 : if (crng_ready())
1667 : 0 : goto out;
1668 : :
1669 : 3 : owner = NULL;
1670 : :
1671 : 3 : list_add(&rdy->list, &random_ready_list);
1672 : 3 : err = 0;
1673 : :
1674 : 3 : out:
1675 : 3 : spin_unlock_irqrestore(&random_ready_list_lock, flags);
1676 : :
1677 : 3 : module_put(owner);
1678 : :
1679 : 3 : return err;
1680 : : }
1681 : : EXPORT_SYMBOL(add_random_ready_callback);
1682 : :
1683 : : /*
1684 : : * Delete a previously registered readiness callback function.
1685 : : */
1686 : 0 : void del_random_ready_callback(struct random_ready_callback *rdy)
1687 : : {
1688 : 0 : unsigned long flags;
1689 : 0 : struct module *owner = NULL;
1690 : :
1691 : 0 : spin_lock_irqsave(&random_ready_list_lock, flags);
1692 [ # # ]: 0 : if (!list_empty(&rdy->list)) {
1693 : 0 : list_del_init(&rdy->list);
1694 : 0 : owner = rdy->owner;
1695 : : }
1696 : 0 : spin_unlock_irqrestore(&random_ready_list_lock, flags);
1697 : :
1698 : 0 : module_put(owner);
1699 : 0 : }
1700 : : EXPORT_SYMBOL(del_random_ready_callback);
1701 : :
1702 : : /*
1703 : : * This function will use the architecture-specific hardware random
1704 : : * number generator if it is available. The arch-specific hw RNG will
1705 : : * almost certainly be faster than what we can do in software, but it
1706 : : * is impossible to verify that it is implemented securely (as
1707 : : * opposed, to, say, the AES encryption of a sequence number using a
1708 : : * key known by the NSA). So it's useful if we need the speed, but
1709 : : * only if we're willing to trust the hardware manufacturer not to
1710 : : * have put in a back door.
1711 : : *
1712 : : * Return number of bytes filled in.
1713 : : */
1714 : 3 : int __must_check get_random_bytes_arch(void *buf, int nbytes)
1715 : : {
1716 : 3 : int left = nbytes;
1717 : 3 : char *p = buf;
1718 : :
1719 : 3 : trace_get_random_bytes_arch(left, _RET_IP_);
1720 [ + - ]: 3 : while (left) {
1721 : 3 : unsigned long v;
1722 : 3 : int chunk = min_t(int, left, sizeof(unsigned long));
1723 : :
1724 [ - + ]: 3 : if (!arch_get_random_long(&v))
1725 : : break;
1726 : :
1727 : 0 : memcpy(p, &v, chunk);
1728 : 0 : p += chunk;
1729 : 0 : left -= chunk;
1730 : : }
1731 : :
1732 : 3 : return nbytes - left;
1733 : : }
1734 : : EXPORT_SYMBOL(get_random_bytes_arch);
1735 : :
1736 : : /*
1737 : : * init_std_data - initialize pool with system data
1738 : : *
1739 : : * @r: pool to initialize
1740 : : *
1741 : : * This function clears the pool's entropy count and mixes some system
1742 : : * data into the pool to prepare it for use. The pool is not cleared
1743 : : * as that can only decrease the entropy in the pool.
1744 : : */
1745 : 3 : static void __init init_std_data(struct entropy_store *r)
1746 : : {
1747 : 3 : int i;
1748 : 3 : ktime_t now = ktime_get_real();
1749 : 3 : unsigned long rv;
1750 : :
1751 : 3 : mix_pool_bytes(r, &now, sizeof(now));
1752 [ + + ]: 195 : for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1753 [ + - + - ]: 384 : if (!arch_get_random_seed_long(&rv) &&
1754 : 192 : !arch_get_random_long(&rv))
1755 : 192 : rv = random_get_entropy();
1756 : 192 : mix_pool_bytes(r, &rv, sizeof(rv));
1757 : : }
1758 : 3 : mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1759 : 3 : }
1760 : :
1761 : : /*
1762 : : * Note that setup_arch() may call add_device_randomness()
1763 : : * long before we get here. This allows seeding of the pools
1764 : : * with some platform dependent data very early in the boot
1765 : : * process. But it limits our options here. We must use
1766 : : * statically allocated structures that already have all
1767 : : * initializations complete at compile time. We should also
1768 : : * take care not to overwrite the precious per platform data
1769 : : * we were given.
1770 : : */
1771 : 3 : int __init rand_initialize(void)
1772 : : {
1773 : 3 : init_std_data(&input_pool);
1774 : 3 : crng_initialize(&primary_crng);
1775 : 3 : crng_global_init_time = jiffies;
1776 [ - + ]: 3 : if (ratelimit_disable) {
1777 : 0 : urandom_warning.interval = 0;
1778 : 0 : unseeded_warning.interval = 0;
1779 : : }
1780 : 3 : return 0;
1781 : : }
1782 : :
1783 : : #ifdef CONFIG_BLOCK
1784 : 45 : void rand_initialize_disk(struct gendisk *disk)
1785 : : {
1786 : 45 : struct timer_rand_state *state;
1787 : :
1788 : : /*
1789 : : * If kzalloc returns null, we just won't use that entropy
1790 : : * source.
1791 : : */
1792 : 45 : state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1793 [ + - ]: 45 : if (state) {
1794 : 45 : state->last_time = INITIAL_JIFFIES;
1795 : 45 : disk->random = state;
1796 : : }
1797 : 45 : }
1798 : : #endif
1799 : :
1800 : : static ssize_t
1801 : : urandom_read_nowarn(struct file *file, char __user *buf, size_t nbytes,
1802 : : loff_t *ppos)
1803 : : {
1804 : : int ret;
1805 : :
1806 : : nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1807 : : ret = extract_crng_user(buf, nbytes);
1808 : : trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
1809 : : return ret;
1810 : : }
1811 : :
1812 : : static ssize_t
1813 : 204 : urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1814 : : {
1815 : 204 : unsigned long flags;
1816 : 204 : static int maxwarn = 10;
1817 : :
1818 [ + + + + ]: 204 : if (!crng_ready() && maxwarn > 0) {
1819 : 30 : maxwarn--;
1820 [ + + ]: 30 : if (__ratelimit(&urandom_warning))
1821 : 9 : pr_notice("%s: uninitialized urandom read (%zd bytes read)\n",
1822 : : current->comm, nbytes);
1823 : 30 : spin_lock_irqsave(&primary_crng.lock, flags);
1824 : 30 : crng_init_cnt = 0;
1825 : 30 : spin_unlock_irqrestore(&primary_crng.lock, flags);
1826 : : }
1827 : :
1828 : 204 : return urandom_read_nowarn(file, buf, nbytes, ppos);
1829 : : }
1830 : :
1831 : : static ssize_t
1832 : 0 : random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1833 : : {
1834 : 0 : int ret;
1835 : :
1836 : 0 : ret = wait_for_random_bytes();
1837 [ # # ]: 0 : if (ret != 0)
1838 : 0 : return ret;
1839 : 0 : return urandom_read_nowarn(file, buf, nbytes, ppos);
1840 : : }
1841 : :
1842 : : static __poll_t
1843 : 0 : random_poll(struct file *file, poll_table * wait)
1844 : : {
1845 : 0 : __poll_t mask;
1846 : :
1847 [ # # ]: 0 : poll_wait(file, &crng_init_wait, wait);
1848 [ # # ]: 0 : poll_wait(file, &random_write_wait, wait);
1849 : 0 : mask = 0;
1850 [ # # ]: 0 : if (crng_ready())
1851 : 0 : mask |= EPOLLIN | EPOLLRDNORM;
1852 [ # # ]: 0 : if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1853 : 0 : mask |= EPOLLOUT | EPOLLWRNORM;
1854 : 0 : return mask;
1855 : : }
1856 : :
1857 : : static int
1858 : 3 : write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1859 : : {
1860 : 3 : size_t bytes;
1861 : 3 : __u32 t, buf[16];
1862 : 3 : const char __user *p = buffer;
1863 : :
1864 [ + + ]: 6 : while (count > 0) {
1865 : 3 : int b, i = 0;
1866 : :
1867 : 3 : bytes = min(count, sizeof(buf));
1868 [ + - ]: 3 : if (copy_from_user(&buf, p, bytes))
1869 : : return -EFAULT;
1870 : :
1871 [ + - ]: 3 : for (b = bytes ; b > 0 ; b -= sizeof(__u32), i++) {
1872 [ - + ]: 3 : if (!arch_get_random_int(&t))
1873 : : break;
1874 : 0 : buf[i] ^= t;
1875 : : }
1876 : :
1877 : 3 : count -= bytes;
1878 : 3 : p += bytes;
1879 : :
1880 : 3 : mix_pool_bytes(r, buf, bytes);
1881 : 3 : cond_resched();
1882 : : }
1883 : :
1884 : : return 0;
1885 : : }
1886 : :
1887 : 3 : static ssize_t random_write(struct file *file, const char __user *buffer,
1888 : : size_t count, loff_t *ppos)
1889 : : {
1890 : 3 : size_t ret;
1891 : :
1892 : 3 : ret = write_pool(&input_pool, buffer, count);
1893 [ - + ]: 3 : if (ret)
1894 : 0 : return ret;
1895 : :
1896 : 3 : return (ssize_t)count;
1897 : : }
1898 : :
1899 : 0 : static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1900 : : {
1901 : 0 : int size, ent_count;
1902 : 0 : int __user *p = (int __user *)arg;
1903 : 0 : int retval;
1904 : :
1905 [ # # # # : 0 : switch (cmd) {
# # ]
1906 : 0 : case RNDGETENTCNT:
1907 : : /* inherently racy, no point locking */
1908 : 0 : ent_count = ENTROPY_BITS(&input_pool);
1909 [ # # ]: 0 : if (put_user(ent_count, p))
1910 : 0 : return -EFAULT;
1911 : : return 0;
1912 : 0 : case RNDADDTOENTCNT:
1913 [ # # ]: 0 : if (!capable(CAP_SYS_ADMIN))
1914 : : return -EPERM;
1915 [ # # ]: 0 : if (get_user(ent_count, p))
1916 : : return -EFAULT;
1917 [ # # ]: 0 : return credit_entropy_bits_safe(&input_pool, ent_count);
1918 : 0 : case RNDADDENTROPY:
1919 [ # # ]: 0 : if (!capable(CAP_SYS_ADMIN))
1920 : : return -EPERM;
1921 [ # # ]: 0 : if (get_user(ent_count, p++))
1922 : : return -EFAULT;
1923 [ # # ]: 0 : if (ent_count < 0)
1924 : : return -EINVAL;
1925 [ # # ]: 0 : if (get_user(size, p++))
1926 : : return -EFAULT;
1927 : 0 : retval = write_pool(&input_pool, (const char __user *)p,
1928 : : size);
1929 [ # # ]: 0 : if (retval < 0)
1930 : 0 : return retval;
1931 : 0 : return credit_entropy_bits_safe(&input_pool, ent_count);
1932 : 0 : case RNDZAPENTCNT:
1933 : : case RNDCLEARPOOL:
1934 : : /*
1935 : : * Clear the entropy pool counters. We no longer clear
1936 : : * the entropy pool, as that's silly.
1937 : : */
1938 [ # # ]: 0 : if (!capable(CAP_SYS_ADMIN))
1939 : : return -EPERM;
1940 : 0 : input_pool.entropy_count = 0;
1941 : 0 : return 0;
1942 : 0 : case RNDRESEEDCRNG:
1943 [ # # ]: 0 : if (!capable(CAP_SYS_ADMIN))
1944 : : return -EPERM;
1945 [ # # ]: 0 : if (crng_init < 2)
1946 : : return -ENODATA;
1947 : 0 : crng_reseed(&primary_crng, NULL);
1948 : 0 : crng_global_init_time = jiffies - 1;
1949 : 0 : return 0;
1950 : : default:
1951 : : return -EINVAL;
1952 : : }
1953 : : }
1954 : :
1955 : 0 : static int random_fasync(int fd, struct file *filp, int on)
1956 : : {
1957 : 0 : return fasync_helper(fd, filp, on, &fasync);
1958 : : }
1959 : :
1960 : : const struct file_operations random_fops = {
1961 : : .read = random_read,
1962 : : .write = random_write,
1963 : : .poll = random_poll,
1964 : : .unlocked_ioctl = random_ioctl,
1965 : : .compat_ioctl = compat_ptr_ioctl,
1966 : : .fasync = random_fasync,
1967 : : .llseek = noop_llseek,
1968 : : };
1969 : :
1970 : : const struct file_operations urandom_fops = {
1971 : : .read = urandom_read,
1972 : : .write = random_write,
1973 : : .unlocked_ioctl = random_ioctl,
1974 : : .compat_ioctl = compat_ptr_ioctl,
1975 : : .fasync = random_fasync,
1976 : : .llseek = noop_llseek,
1977 : : };
1978 : :
1979 : 18556 : SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1980 : : unsigned int, flags)
1981 : : {
1982 : 9278 : int ret;
1983 : :
1984 [ + - ]: 9278 : if (flags & ~(GRND_NONBLOCK|GRND_RANDOM|GRND_INSECURE))
1985 : : return -EINVAL;
1986 : :
1987 : : /*
1988 : : * Requesting insecure and blocking randomness at the same time makes
1989 : : * no sense.
1990 : : */
1991 [ + - ]: 9278 : if ((flags & (GRND_INSECURE|GRND_RANDOM)) == (GRND_INSECURE|GRND_RANDOM))
1992 : : return -EINVAL;
1993 : :
1994 : 9278 : if (count > INT_MAX)
1995 : : count = INT_MAX;
1996 : :
1997 [ + - + + ]: 9278 : if (!(flags & GRND_INSECURE) && !crng_ready()) {
1998 [ - + ]: 7941 : if (flags & GRND_NONBLOCK)
1999 : : return -EAGAIN;
2000 : 0 : ret = wait_for_random_bytes();
2001 [ # # ]: 0 : if (unlikely(ret))
2002 : 0 : return ret;
2003 : : }
2004 : 1337 : return urandom_read_nowarn(NULL, buf, count, NULL);
2005 : : }
2006 : :
2007 : : /********************************************************************
2008 : : *
2009 : : * Sysctl interface
2010 : : *
2011 : : ********************************************************************/
2012 : :
2013 : : #ifdef CONFIG_SYSCTL
2014 : :
2015 : : #include <linux/sysctl.h>
2016 : :
2017 : : static int min_write_thresh;
2018 : : static int max_write_thresh = INPUT_POOL_WORDS * 32;
2019 : : static int random_min_urandom_seed = 60;
2020 : : static char sysctl_bootid[16];
2021 : :
2022 : : /*
2023 : : * This function is used to return both the bootid UUID, and random
2024 : : * UUID. The difference is in whether table->data is NULL; if it is,
2025 : : * then a new UUID is generated and returned to the user.
2026 : : *
2027 : : * If the user accesses this via the proc interface, the UUID will be
2028 : : * returned as an ASCII string in the standard UUID format; if via the
2029 : : * sysctl system call, as 16 bytes of binary data.
2030 : : */
2031 : 36 : static int proc_do_uuid(struct ctl_table *table, int write,
2032 : : void __user *buffer, size_t *lenp, loff_t *ppos)
2033 : : {
2034 : 36 : struct ctl_table fake_table;
2035 : 36 : unsigned char buf[64], tmp_uuid[16], *uuid;
2036 : :
2037 : 36 : uuid = table->data;
2038 [ - + ]: 36 : if (!uuid) {
2039 : 0 : uuid = tmp_uuid;
2040 : 0 : generate_random_uuid(uuid);
2041 : : } else {
2042 : 36 : static DEFINE_SPINLOCK(bootid_spinlock);
2043 : :
2044 : 36 : spin_lock(&bootid_spinlock);
2045 [ + + ]: 36 : if (!uuid[8])
2046 : 3 : generate_random_uuid(uuid);
2047 : 36 : spin_unlock(&bootid_spinlock);
2048 : : }
2049 : :
2050 : 36 : sprintf(buf, "%pU", uuid);
2051 : :
2052 : 36 : fake_table.data = buf;
2053 : 36 : fake_table.maxlen = sizeof(buf);
2054 : :
2055 : 36 : return proc_dostring(&fake_table, write, buffer, lenp, ppos);
2056 : : }
2057 : :
2058 : : /*
2059 : : * Return entropy available scaled to integral bits
2060 : : */
2061 : 0 : static int proc_do_entropy(struct ctl_table *table, int write,
2062 : : void __user *buffer, size_t *lenp, loff_t *ppos)
2063 : : {
2064 : 0 : struct ctl_table fake_table;
2065 : 0 : int entropy_count;
2066 : :
2067 : 0 : entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
2068 : :
2069 : 0 : fake_table.data = &entropy_count;
2070 : 0 : fake_table.maxlen = sizeof(entropy_count);
2071 : :
2072 : 0 : return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
2073 : : }
2074 : :
2075 : : static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
2076 : : extern struct ctl_table random_table[];
2077 : : struct ctl_table random_table[] = {
2078 : : {
2079 : : .procname = "poolsize",
2080 : : .data = &sysctl_poolsize,
2081 : : .maxlen = sizeof(int),
2082 : : .mode = 0444,
2083 : : .proc_handler = proc_dointvec,
2084 : : },
2085 : : {
2086 : : .procname = "entropy_avail",
2087 : : .maxlen = sizeof(int),
2088 : : .mode = 0444,
2089 : : .proc_handler = proc_do_entropy,
2090 : : .data = &input_pool.entropy_count,
2091 : : },
2092 : : {
2093 : : .procname = "write_wakeup_threshold",
2094 : : .data = &random_write_wakeup_bits,
2095 : : .maxlen = sizeof(int),
2096 : : .mode = 0644,
2097 : : .proc_handler = proc_dointvec_minmax,
2098 : : .extra1 = &min_write_thresh,
2099 : : .extra2 = &max_write_thresh,
2100 : : },
2101 : : {
2102 : : .procname = "urandom_min_reseed_secs",
2103 : : .data = &random_min_urandom_seed,
2104 : : .maxlen = sizeof(int),
2105 : : .mode = 0644,
2106 : : .proc_handler = proc_dointvec,
2107 : : },
2108 : : {
2109 : : .procname = "boot_id",
2110 : : .data = &sysctl_bootid,
2111 : : .maxlen = 16,
2112 : : .mode = 0444,
2113 : : .proc_handler = proc_do_uuid,
2114 : : },
2115 : : {
2116 : : .procname = "uuid",
2117 : : .maxlen = 16,
2118 : : .mode = 0444,
2119 : : .proc_handler = proc_do_uuid,
2120 : : },
2121 : : #ifdef ADD_INTERRUPT_BENCH
2122 : : {
2123 : : .procname = "add_interrupt_avg_cycles",
2124 : : .data = &avg_cycles,
2125 : : .maxlen = sizeof(avg_cycles),
2126 : : .mode = 0444,
2127 : : .proc_handler = proc_doulongvec_minmax,
2128 : : },
2129 : : {
2130 : : .procname = "add_interrupt_avg_deviation",
2131 : : .data = &avg_deviation,
2132 : : .maxlen = sizeof(avg_deviation),
2133 : : .mode = 0444,
2134 : : .proc_handler = proc_doulongvec_minmax,
2135 : : },
2136 : : #endif
2137 : : { }
2138 : : };
2139 : : #endif /* CONFIG_SYSCTL */
2140 : :
2141 : : struct batched_entropy {
2142 : : union {
2143 : : u64 entropy_u64[CHACHA_BLOCK_SIZE / sizeof(u64)];
2144 : : u32 entropy_u32[CHACHA_BLOCK_SIZE / sizeof(u32)];
2145 : : };
2146 : : unsigned int position;
2147 : : spinlock_t batch_lock;
2148 : : };
2149 : :
2150 : : /*
2151 : : * Get a random word for internal kernel use only. The quality of the random
2152 : : * number is either as good as RDRAND or as good as /dev/urandom, with the
2153 : : * goal of being quite fast and not depleting entropy. In order to ensure
2154 : : * that the randomness provided by this function is okay, the function
2155 : : * wait_for_random_bytes() should be called and return 0 at least once
2156 : : * at any point prior.
2157 : : */
2158 : : static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = {
2159 : : .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u64.lock),
2160 : : };
2161 : :
2162 : 43988 : u64 get_random_u64(void)
2163 : : {
2164 : 43988 : u64 ret;
2165 : 43988 : unsigned long flags;
2166 : 43988 : struct batched_entropy *batch;
2167 : 43988 : static void *previous;
2168 : :
2169 : : #if BITS_PER_LONG == 64
2170 [ - + ]: 43988 : if (arch_get_random_long((unsigned long *)&ret))
2171 : 0 : return ret;
2172 : : #else
2173 : : if (arch_get_random_long((unsigned long *)&ret) &&
2174 : : arch_get_random_long((unsigned long *)&ret + 1))
2175 : : return ret;
2176 : : #endif
2177 : :
2178 : 43988 : warn_unseeded_randomness(&previous);
2179 : :
2180 : 43988 : batch = raw_cpu_ptr(&batched_entropy_u64);
2181 : 43988 : spin_lock_irqsave(&batch->batch_lock, flags);
2182 [ + + ]: 43988 : if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
2183 : 5502 : extract_crng((u8 *)batch->entropy_u64);
2184 : 5502 : batch->position = 0;
2185 : : }
2186 : 43988 : ret = batch->entropy_u64[batch->position++];
2187 : 43988 : spin_unlock_irqrestore(&batch->batch_lock, flags);
2188 : 43988 : return ret;
2189 : : }
2190 : : EXPORT_SYMBOL(get_random_u64);
2191 : :
2192 : : static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = {
2193 : : .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u32.lock),
2194 : : };
2195 : 21972 : u32 get_random_u32(void)
2196 : : {
2197 : 21972 : u32 ret;
2198 : 21972 : unsigned long flags;
2199 : 21972 : struct batched_entropy *batch;
2200 : 21972 : static void *previous;
2201 : :
2202 [ - + ]: 21972 : if (arch_get_random_int(&ret))
2203 : 0 : return ret;
2204 : :
2205 : 21972 : warn_unseeded_randomness(&previous);
2206 : :
2207 : 21972 : batch = raw_cpu_ptr(&batched_entropy_u32);
2208 : 21972 : spin_lock_irqsave(&batch->batch_lock, flags);
2209 [ + + ]: 21972 : if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
2210 : 1380 : extract_crng((u8 *)batch->entropy_u32);
2211 : 1380 : batch->position = 0;
2212 : : }
2213 : 21972 : ret = batch->entropy_u32[batch->position++];
2214 : 21972 : spin_unlock_irqrestore(&batch->batch_lock, flags);
2215 : 21972 : return ret;
2216 : : }
2217 : : EXPORT_SYMBOL(get_random_u32);
2218 : :
2219 : : /* It's important to invalidate all potential batched entropy that might
2220 : : * be stored before the crng is initialized, which we can do lazily by
2221 : : * simply resetting the counter to zero so that it's re-extracted on the
2222 : : * next usage. */
2223 : 6 : static void invalidate_batched_entropy(void)
2224 : : {
2225 : 6 : int cpu;
2226 : 6 : unsigned long flags;
2227 : :
2228 [ + + ]: 12 : for_each_possible_cpu (cpu) {
2229 : 6 : struct batched_entropy *batched_entropy;
2230 : :
2231 : 6 : batched_entropy = per_cpu_ptr(&batched_entropy_u32, cpu);
2232 : 6 : spin_lock_irqsave(&batched_entropy->batch_lock, flags);
2233 : 6 : batched_entropy->position = 0;
2234 : 6 : spin_unlock(&batched_entropy->batch_lock);
2235 : :
2236 : 6 : batched_entropy = per_cpu_ptr(&batched_entropy_u64, cpu);
2237 : 6 : spin_lock(&batched_entropy->batch_lock);
2238 : 6 : batched_entropy->position = 0;
2239 : 6 : spin_unlock_irqrestore(&batched_entropy->batch_lock, flags);
2240 : : }
2241 : 6 : }
2242 : :
2243 : : /**
2244 : : * randomize_page - Generate a random, page aligned address
2245 : : * @start: The smallest acceptable address the caller will take.
2246 : : * @range: The size of the area, starting at @start, within which the
2247 : : * random address must fall.
2248 : : *
2249 : : * If @start + @range would overflow, @range is capped.
2250 : : *
2251 : : * NOTE: Historical use of randomize_range, which this replaces, presumed that
2252 : : * @start was already page aligned. We now align it regardless.
2253 : : *
2254 : : * Return: A page aligned address within [start, start + range). On error,
2255 : : * @start is returned.
2256 : : */
2257 : : unsigned long
2258 : 7275 : randomize_page(unsigned long start, unsigned long range)
2259 : : {
2260 [ - + ]: 7275 : if (!PAGE_ALIGNED(start)) {
2261 : 0 : range -= PAGE_ALIGN(start) - start;
2262 : 0 : start = PAGE_ALIGN(start);
2263 : : }
2264 : :
2265 [ - + ]: 7275 : if (start > ULONG_MAX - range)
2266 : 0 : range = ULONG_MAX - start;
2267 : :
2268 : 7275 : range >>= PAGE_SHIFT;
2269 : :
2270 [ + - ]: 7275 : if (range == 0)
2271 : : return start;
2272 : :
2273 : 7275 : return start + (get_random_long() % range << PAGE_SHIFT);
2274 : : }
2275 : :
2276 : : /* Interface for in-kernel drivers of true hardware RNGs.
2277 : : * Those devices may produce endless random bits and will be throttled
2278 : : * when our pool is full.
2279 : : */
2280 : 0 : void add_hwgenerator_randomness(const char *buffer, size_t count,
2281 : : size_t entropy)
2282 : : {
2283 : 0 : struct entropy_store *poolp = &input_pool;
2284 : :
2285 [ # # ]: 0 : if (unlikely(crng_init == 0)) {
2286 : 0 : crng_fast_load(buffer, count);
2287 : 0 : return;
2288 : : }
2289 : :
2290 : : /* Suspend writing if we're above the trickle threshold.
2291 : : * We'll be woken up again once below random_write_wakeup_thresh,
2292 : : * or when the calling thread is about to terminate.
2293 : : */
2294 [ # # # # : 0 : wait_event_interruptible(random_write_wait, kthread_should_stop() ||
# # # # #
# ]
2295 : : ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
2296 : 0 : mix_pool_bytes(poolp, buffer, count);
2297 : 0 : credit_entropy_bits(poolp, entropy);
2298 : : }
2299 : : EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
2300 : :
2301 : : /* Handle random seed passed by bootloader.
2302 : : * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise
2303 : : * it would be regarded as device data.
2304 : : * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER.
2305 : : */
2306 : 0 : void add_bootloader_randomness(const void *buf, unsigned int size)
2307 : : {
2308 : 0 : if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
2309 : : add_hwgenerator_randomness(buf, size, size * 8);
2310 : : else
2311 : 0 : add_device_randomness(buf, size);
2312 : 0 : }
2313 : : EXPORT_SYMBOL_GPL(add_bootloader_randomness);
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