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1da177e4 LT |
1 | /* |
2 | * random.c -- A strong random number generator | |
3 | * | |
9f9eff85 | 4 | * Copyright (C) 2017-2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. |
b169c13d | 5 | * |
9e95ce27 | 6 | * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005 |
1da177e4 LT |
7 | * |
8 | * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All | |
9 | * rights reserved. | |
10 | * | |
11 | * Redistribution and use in source and binary forms, with or without | |
12 | * modification, are permitted provided that the following conditions | |
13 | * are met: | |
14 | * 1. Redistributions of source code must retain the above copyright | |
15 | * notice, and the entire permission notice in its entirety, | |
16 | * including the disclaimer of warranties. | |
17 | * 2. Redistributions in binary form must reproduce the above copyright | |
18 | * notice, this list of conditions and the following disclaimer in the | |
19 | * documentation and/or other materials provided with the distribution. | |
20 | * 3. The name of the author may not be used to endorse or promote | |
21 | * products derived from this software without specific prior | |
22 | * written permission. | |
23 | * | |
24 | * ALTERNATIVELY, this product may be distributed under the terms of | |
25 | * the GNU General Public License, in which case the provisions of the GPL are | |
26 | * required INSTEAD OF the above restrictions. (This clause is | |
27 | * necessary due to a potential bad interaction between the GPL and | |
28 | * the restrictions contained in a BSD-style copyright.) | |
29 | * | |
30 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED | |
31 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
32 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF | |
33 | * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE | |
34 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
35 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT | |
36 | * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR | |
37 | * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
38 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
39 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE | |
40 | * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH | |
41 | * DAMAGE. | |
42 | */ | |
43 | ||
44 | /* | |
45 | * (now, with legal B.S. out of the way.....) | |
46 | * | |
47 | * This routine gathers environmental noise from device drivers, etc., | |
48 | * and returns good random numbers, suitable for cryptographic use. | |
49 | * Besides the obvious cryptographic uses, these numbers are also good | |
50 | * for seeding TCP sequence numbers, and other places where it is | |
51 | * desirable to have numbers which are not only random, but hard to | |
52 | * predict by an attacker. | |
53 | * | |
54 | * Theory of operation | |
55 | * =================== | |
56 | * | |
57 | * Computers are very predictable devices. Hence it is extremely hard | |
58 | * to produce truly random numbers on a computer --- as opposed to | |
59 | * pseudo-random numbers, which can easily generated by using a | |
60 | * algorithm. Unfortunately, it is very easy for attackers to guess | |
61 | * the sequence of pseudo-random number generators, and for some | |
62 | * applications this is not acceptable. So instead, we must try to | |
63 | * gather "environmental noise" from the computer's environment, which | |
64 | * must be hard for outside attackers to observe, and use that to | |
65 | * generate random numbers. In a Unix environment, this is best done | |
66 | * from inside the kernel. | |
67 | * | |
68 | * Sources of randomness from the environment include inter-keyboard | |
69 | * timings, inter-interrupt timings from some interrupts, and other | |
70 | * events which are both (a) non-deterministic and (b) hard for an | |
71 | * outside observer to measure. Randomness from these sources are | |
72 | * added to an "entropy pool", which is mixed using a CRC-like function. | |
73 | * This is not cryptographically strong, but it is adequate assuming | |
74 | * the randomness is not chosen maliciously, and it is fast enough that | |
75 | * the overhead of doing it on every interrupt is very reasonable. | |
76 | * As random bytes are mixed into the entropy pool, the routines keep | |
77 | * an *estimate* of how many bits of randomness have been stored into | |
78 | * the random number generator's internal state. | |
79 | * | |
9f9eff85 JD |
80 | * When random bytes are desired, they are obtained by taking the BLAKE2s |
81 | * hash of the contents of the "entropy pool". The BLAKE2s hash avoids | |
1da177e4 LT |
82 | * exposing the internal state of the entropy pool. It is believed to |
83 | * be computationally infeasible to derive any useful information | |
9f9eff85 JD |
84 | * about the input of BLAKE2s from its output. Even if it is possible to |
85 | * analyze BLAKE2s in some clever way, as long as the amount of data | |
1da177e4 LT |
86 | * returned from the generator is less than the inherent entropy in |
87 | * the pool, the output data is totally unpredictable. For this | |
88 | * reason, the routine decreases its internal estimate of how many | |
89 | * bits of "true randomness" are contained in the entropy pool as it | |
90 | * outputs random numbers. | |
91 | * | |
92 | * If this estimate goes to zero, the routine can still generate | |
93 | * random numbers; however, an attacker may (at least in theory) be | |
94 | * able to infer the future output of the generator from prior | |
9f9eff85 | 95 | * outputs. This requires successful cryptanalysis of BLAKE2s, which is |
1da177e4 LT |
96 | * not believed to be feasible, but there is a remote possibility. |
97 | * Nonetheless, these numbers should be useful for the vast majority | |
98 | * of purposes. | |
99 | * | |
100 | * Exported interfaces ---- output | |
101 | * =============================== | |
102 | * | |
92e507d2 | 103 | * There are four exported interfaces; two for use within the kernel, |
c0a8a61e | 104 | * and two for use from userspace. |
1da177e4 | 105 | * |
92e507d2 GS |
106 | * Exported interfaces ---- userspace output |
107 | * ----------------------------------------- | |
1da177e4 | 108 | * |
92e507d2 | 109 | * The userspace interfaces are two character devices /dev/random and |
1da177e4 LT |
110 | * /dev/urandom. /dev/random is suitable for use when very high |
111 | * quality randomness is desired (for example, for key generation or | |
112 | * one-time pads), as it will only return a maximum of the number of | |
113 | * bits of randomness (as estimated by the random number generator) | |
114 | * contained in the entropy pool. | |
115 | * | |
116 | * The /dev/urandom device does not have this limit, and will return | |
117 | * as many bytes as are requested. As more and more random bytes are | |
118 | * requested without giving time for the entropy pool to recharge, | |
119 | * this will result in random numbers that are merely cryptographically | |
120 | * strong. For many applications, however, this is acceptable. | |
121 | * | |
92e507d2 GS |
122 | * Exported interfaces ---- kernel output |
123 | * -------------------------------------- | |
124 | * | |
125 | * The primary kernel interface is | |
126 | * | |
248045b8 | 127 | * void get_random_bytes(void *buf, int nbytes); |
92e507d2 GS |
128 | * |
129 | * This interface will return the requested number of random bytes, | |
130 | * and place it in the requested buffer. This is equivalent to a | |
131 | * read from /dev/urandom. | |
132 | * | |
133 | * For less critical applications, there are the functions: | |
134 | * | |
248045b8 JD |
135 | * u32 get_random_u32() |
136 | * u64 get_random_u64() | |
137 | * unsigned int get_random_int() | |
138 | * unsigned long get_random_long() | |
92e507d2 GS |
139 | * |
140 | * These are produced by a cryptographic RNG seeded from get_random_bytes, | |
141 | * and so do not deplete the entropy pool as much. These are recommended | |
142 | * for most in-kernel operations *if the result is going to be stored in | |
143 | * the kernel*. | |
144 | * | |
145 | * Specifically, the get_random_int() family do not attempt to do | |
146 | * "anti-backtracking". If you capture the state of the kernel (e.g. | |
147 | * by snapshotting the VM), you can figure out previous get_random_int() | |
148 | * return values. But if the value is stored in the kernel anyway, | |
149 | * this is not a problem. | |
150 | * | |
151 | * It *is* safe to expose get_random_int() output to attackers (e.g. as | |
152 | * network cookies); given outputs 1..n, it's not feasible to predict | |
153 | * outputs 0 or n+1. The only concern is an attacker who breaks into | |
154 | * the kernel later; the get_random_int() engine is not reseeded as | |
155 | * often as the get_random_bytes() one. | |
156 | * | |
157 | * get_random_bytes() is needed for keys that need to stay secret after | |
158 | * they are erased from the kernel. For example, any key that will | |
159 | * be wrapped and stored encrypted. And session encryption keys: we'd | |
160 | * like to know that after the session is closed and the keys erased, | |
161 | * the plaintext is unrecoverable to someone who recorded the ciphertext. | |
162 | * | |
163 | * But for network ports/cookies, stack canaries, PRNG seeds, address | |
164 | * space layout randomization, session *authentication* keys, or other | |
165 | * applications where the sensitive data is stored in the kernel in | |
166 | * plaintext for as long as it's sensitive, the get_random_int() family | |
167 | * is just fine. | |
168 | * | |
169 | * Consider ASLR. We want to keep the address space secret from an | |
170 | * outside attacker while the process is running, but once the address | |
171 | * space is torn down, it's of no use to an attacker any more. And it's | |
172 | * stored in kernel data structures as long as it's alive, so worrying | |
173 | * about an attacker's ability to extrapolate it from the get_random_int() | |
174 | * CRNG is silly. | |
175 | * | |
176 | * Even some cryptographic keys are safe to generate with get_random_int(). | |
177 | * In particular, keys for SipHash are generally fine. Here, knowledge | |
178 | * of the key authorizes you to do something to a kernel object (inject | |
179 | * packets to a network connection, or flood a hash table), and the | |
180 | * key is stored with the object being protected. Once it goes away, | |
181 | * we no longer care if anyone knows the key. | |
182 | * | |
183 | * prandom_u32() | |
184 | * ------------- | |
185 | * | |
186 | * For even weaker applications, see the pseudorandom generator | |
187 | * prandom_u32(), prandom_max(), and prandom_bytes(). If the random | |
188 | * numbers aren't security-critical at all, these are *far* cheaper. | |
189 | * Useful for self-tests, random error simulation, randomized backoffs, | |
190 | * and any other application where you trust that nobody is trying to | |
191 | * maliciously mess with you by guessing the "random" numbers. | |
192 | * | |
1da177e4 LT |
193 | * Exported interfaces ---- input |
194 | * ============================== | |
195 | * | |
196 | * The current exported interfaces for gathering environmental noise | |
197 | * from the devices are: | |
198 | * | |
a2080a67 | 199 | * void add_device_randomness(const void *buf, unsigned int size); |
248045b8 | 200 | * void add_input_randomness(unsigned int type, unsigned int code, |
1da177e4 | 201 | * unsigned int value); |
703f7066 | 202 | * void add_interrupt_randomness(int irq); |
248045b8 | 203 | * void add_disk_randomness(struct gendisk *disk); |
2b6c6e3d MB |
204 | * void add_hwgenerator_randomness(const char *buffer, size_t count, |
205 | * size_t entropy); | |
206 | * void add_bootloader_randomness(const void *buf, unsigned int size); | |
1da177e4 | 207 | * |
a2080a67 LT |
208 | * add_device_randomness() is for adding data to the random pool that |
209 | * is likely to differ between two devices (or possibly even per boot). | |
210 | * This would be things like MAC addresses or serial numbers, or the | |
211 | * read-out of the RTC. This does *not* add any actual entropy to the | |
212 | * pool, but it initializes the pool to different values for devices | |
213 | * that might otherwise be identical and have very little entropy | |
214 | * available to them (particularly common in the embedded world). | |
215 | * | |
1da177e4 LT |
216 | * add_input_randomness() uses the input layer interrupt timing, as well as |
217 | * the event type information from the hardware. | |
218 | * | |
775f4b29 TT |
219 | * add_interrupt_randomness() uses the interrupt timing as random |
220 | * inputs to the entropy pool. Using the cycle counters and the irq source | |
221 | * as inputs, it feeds the randomness roughly once a second. | |
442a4fff JW |
222 | * |
223 | * add_disk_randomness() uses what amounts to the seek time of block | |
224 | * layer request events, on a per-disk_devt basis, as input to the | |
225 | * entropy pool. Note that high-speed solid state drives with very low | |
226 | * seek times do not make for good sources of entropy, as their seek | |
227 | * times are usually fairly consistent. | |
1da177e4 LT |
228 | * |
229 | * All of these routines try to estimate how many bits of randomness a | |
230 | * particular randomness source. They do this by keeping track of the | |
231 | * first and second order deltas of the event timings. | |
232 | * | |
2b6c6e3d MB |
233 | * add_hwgenerator_randomness() is for true hardware RNGs, and will credit |
234 | * entropy as specified by the caller. If the entropy pool is full it will | |
235 | * block until more entropy is needed. | |
236 | * | |
237 | * add_bootloader_randomness() is the same as add_hwgenerator_randomness() or | |
238 | * add_device_randomness(), depending on whether or not the configuration | |
239 | * option CONFIG_RANDOM_TRUST_BOOTLOADER is set. | |
240 | * | |
1da177e4 LT |
241 | * Ensuring unpredictability at system startup |
242 | * ============================================ | |
243 | * | |
244 | * When any operating system starts up, it will go through a sequence | |
245 | * of actions that are fairly predictable by an adversary, especially | |
246 | * if the start-up does not involve interaction with a human operator. | |
247 | * This reduces the actual number of bits of unpredictability in the | |
248 | * entropy pool below the value in entropy_count. In order to | |
249 | * counteract this effect, it helps to carry information in the | |
250 | * entropy pool across shut-downs and start-ups. To do this, put the | |
251 | * following lines an appropriate script which is run during the boot | |
252 | * sequence: | |
253 | * | |
254 | * echo "Initializing random number generator..." | |
255 | * random_seed=/var/run/random-seed | |
256 | * # Carry a random seed from start-up to start-up | |
257 | * # Load and then save the whole entropy pool | |
258 | * if [ -f $random_seed ]; then | |
259 | * cat $random_seed >/dev/urandom | |
260 | * else | |
261 | * touch $random_seed | |
262 | * fi | |
263 | * chmod 600 $random_seed | |
264 | * dd if=/dev/urandom of=$random_seed count=1 bs=512 | |
265 | * | |
266 | * and the following lines in an appropriate script which is run as | |
267 | * the system is shutdown: | |
268 | * | |
269 | * # Carry a random seed from shut-down to start-up | |
270 | * # Save the whole entropy pool | |
271 | * echo "Saving random seed..." | |
272 | * random_seed=/var/run/random-seed | |
273 | * touch $random_seed | |
274 | * chmod 600 $random_seed | |
275 | * dd if=/dev/urandom of=$random_seed count=1 bs=512 | |
276 | * | |
277 | * For example, on most modern systems using the System V init | |
278 | * scripts, such code fragments would be found in | |
279 | * /etc/rc.d/init.d/random. On older Linux systems, the correct script | |
280 | * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0. | |
281 | * | |
282 | * Effectively, these commands cause the contents of the entropy pool | |
283 | * to be saved at shut-down time and reloaded into the entropy pool at | |
284 | * start-up. (The 'dd' in the addition to the bootup script is to | |
285 | * make sure that /etc/random-seed is different for every start-up, | |
286 | * even if the system crashes without executing rc.0.) Even with | |
287 | * complete knowledge of the start-up activities, predicting the state | |
288 | * of the entropy pool requires knowledge of the previous history of | |
289 | * the system. | |
290 | * | |
291 | * Configuring the /dev/random driver under Linux | |
292 | * ============================================== | |
293 | * | |
294 | * The /dev/random driver under Linux uses minor numbers 8 and 9 of | |
295 | * the /dev/mem major number (#1). So if your system does not have | |
296 | * /dev/random and /dev/urandom created already, they can be created | |
297 | * by using the commands: | |
298 | * | |
248045b8 JD |
299 | * mknod /dev/random c 1 8 |
300 | * mknod /dev/urandom c 1 9 | |
1da177e4 LT |
301 | * |
302 | * Acknowledgements: | |
303 | * ================= | |
304 | * | |
305 | * Ideas for constructing this random number generator were derived | |
306 | * from Pretty Good Privacy's random number generator, and from private | |
307 | * discussions with Phil Karn. Colin Plumb provided a faster random | |
308 | * number generator, which speed up the mixing function of the entropy | |
309 | * pool, taken from PGPfone. Dale Worley has also contributed many | |
310 | * useful ideas and suggestions to improve this driver. | |
311 | * | |
312 | * Any flaws in the design are solely my responsibility, and should | |
313 | * not be attributed to the Phil, Colin, or any of authors of PGP. | |
314 | * | |
315 | * Further background information on this topic may be obtained from | |
316 | * RFC 1750, "Randomness Recommendations for Security", by Donald | |
317 | * Eastlake, Steve Crocker, and Jeff Schiller. | |
318 | */ | |
319 | ||
12cd53af YL |
320 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
321 | ||
1da177e4 | 322 | #include <linux/utsname.h> |
1da177e4 LT |
323 | #include <linux/module.h> |
324 | #include <linux/kernel.h> | |
325 | #include <linux/major.h> | |
326 | #include <linux/string.h> | |
327 | #include <linux/fcntl.h> | |
328 | #include <linux/slab.h> | |
329 | #include <linux/random.h> | |
330 | #include <linux/poll.h> | |
331 | #include <linux/init.h> | |
332 | #include <linux/fs.h> | |
333 | #include <linux/genhd.h> | |
334 | #include <linux/interrupt.h> | |
27ac792c | 335 | #include <linux/mm.h> |
dd0f0cf5 | 336 | #include <linux/nodemask.h> |
1da177e4 | 337 | #include <linux/spinlock.h> |
c84dbf61 | 338 | #include <linux/kthread.h> |
1da177e4 | 339 | #include <linux/percpu.h> |
775f4b29 | 340 | #include <linux/ptrace.h> |
6265e169 | 341 | #include <linux/workqueue.h> |
0244ad00 | 342 | #include <linux/irq.h> |
4e00b339 | 343 | #include <linux/ratelimit.h> |
c6e9d6f3 TT |
344 | #include <linux/syscalls.h> |
345 | #include <linux/completion.h> | |
8da4b8c4 | 346 | #include <linux/uuid.h> |
1ca1b917 | 347 | #include <crypto/chacha.h> |
9f9eff85 | 348 | #include <crypto/blake2s.h> |
d178a1eb | 349 | |
1da177e4 | 350 | #include <asm/processor.h> |
7c0f6ba6 | 351 | #include <linux/uaccess.h> |
1da177e4 | 352 | #include <asm/irq.h> |
775f4b29 | 353 | #include <asm/irq_regs.h> |
1da177e4 LT |
354 | #include <asm/io.h> |
355 | ||
00ce1db1 TT |
356 | #define CREATE_TRACE_POINTS |
357 | #include <trace/events/random.h> | |
358 | ||
43759d4f TT |
359 | /* #define ADD_INTERRUPT_BENCH */ |
360 | ||
1da177e4 LT |
361 | /* |
362 | * If the entropy count falls under this number of bits, then we | |
363 | * should wake up processes which are selecting or polling on write | |
364 | * access to /dev/random. | |
365 | */ | |
0f637027 | 366 | static int random_write_wakeup_bits = 28 * (1 << 5); |
1da177e4 | 367 | |
1da177e4 | 368 | /* |
6e9fa2c8 TT |
369 | * Originally, we used a primitive polynomial of degree .poolwords |
370 | * over GF(2). The taps for various sizes are defined below. They | |
371 | * were chosen to be evenly spaced except for the last tap, which is 1 | |
372 | * to get the twisting happening as fast as possible. | |
373 | * | |
374 | * For the purposes of better mixing, we use the CRC-32 polynomial as | |
375 | * well to make a (modified) twisted Generalized Feedback Shift | |
376 | * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR | |
377 | * generators. ACM Transactions on Modeling and Computer Simulation | |
378 | * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted | |
dfd38750 | 379 | * GFSR generators II. ACM Transactions on Modeling and Computer |
6e9fa2c8 TT |
380 | * Simulation 4:254-266) |
381 | * | |
382 | * Thanks to Colin Plumb for suggesting this. | |
383 | * | |
384 | * The mixing operation is much less sensitive than the output hash, | |
9f9eff85 | 385 | * where we use BLAKE2s. All that we want of mixing operation is that |
6e9fa2c8 TT |
386 | * it be a good non-cryptographic hash; i.e. it not produce collisions |
387 | * when fed "random" data of the sort we expect to see. As long as | |
388 | * the pool state differs for different inputs, we have preserved the | |
389 | * input entropy and done a good job. The fact that an intelligent | |
390 | * attacker can construct inputs that will produce controlled | |
391 | * alterations to the pool's state is not important because we don't | |
392 | * consider such inputs to contribute any randomness. The only | |
393 | * property we need with respect to them is that the attacker can't | |
394 | * increase his/her knowledge of the pool's state. Since all | |
395 | * additions are reversible (knowing the final state and the input, | |
396 | * you can reconstruct the initial state), if an attacker has any | |
397 | * uncertainty about the initial state, he/she can only shuffle that | |
398 | * uncertainty about, but never cause any collisions (which would | |
399 | * decrease the uncertainty). | |
400 | * | |
401 | * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and | |
402 | * Videau in their paper, "The Linux Pseudorandom Number Generator | |
403 | * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their | |
404 | * paper, they point out that we are not using a true Twisted GFSR, | |
405 | * since Matsumoto & Kurita used a trinomial feedback polynomial (that | |
406 | * is, with only three taps, instead of the six that we are using). | |
407 | * As a result, the resulting polynomial is neither primitive nor | |
408 | * irreducible, and hence does not have a maximal period over | |
409 | * GF(2**32). They suggest a slight change to the generator | |
410 | * polynomial which improves the resulting TGFSR polynomial to be | |
411 | * irreducible, which we have made here. | |
1da177e4 | 412 | */ |
91ec0fe1 JD |
413 | enum poolinfo { |
414 | POOL_WORDS = 128, | |
415 | POOL_WORDMASK = POOL_WORDS - 1, | |
416 | POOL_BYTES = POOL_WORDS * sizeof(u32), | |
417 | POOL_BITS = POOL_BYTES * 8, | |
18263c4e JD |
418 | POOL_BITSHIFT = ilog2(POOL_BITS), |
419 | ||
420 | /* To allow fractional bits to be tracked, the entropy_count field is | |
421 | * denominated in units of 1/8th bits. */ | |
422 | POOL_ENTROPY_SHIFT = 3, | |
423 | #define POOL_ENTROPY_BITS() (input_pool.entropy_count >> POOL_ENTROPY_SHIFT) | |
424 | POOL_FRACBITS = POOL_BITS << POOL_ENTROPY_SHIFT, | |
91ec0fe1 | 425 | |
6e9fa2c8 | 426 | /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */ |
91ec0fe1 JD |
427 | POOL_TAP1 = 104, |
428 | POOL_TAP2 = 76, | |
429 | POOL_TAP3 = 51, | |
430 | POOL_TAP4 = 25, | |
5b87adf3 JD |
431 | POOL_TAP5 = 1, |
432 | ||
433 | EXTRACT_SIZE = BLAKE2S_HASH_SIZE / 2 | |
1da177e4 LT |
434 | }; |
435 | ||
1da177e4 LT |
436 | /* |
437 | * Static global variables | |
438 | */ | |
a11e1d43 | 439 | static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); |
9a6f70bb | 440 | static struct fasync_struct *fasync; |
1da177e4 | 441 | |
205a525c HX |
442 | static DEFINE_SPINLOCK(random_ready_list_lock); |
443 | static LIST_HEAD(random_ready_list); | |
444 | ||
e192be9d | 445 | struct crng_state { |
248045b8 JD |
446 | u32 state[16]; |
447 | unsigned long init_time; | |
448 | spinlock_t lock; | |
e192be9d TT |
449 | }; |
450 | ||
764ed189 | 451 | static struct crng_state primary_crng = { |
e192be9d | 452 | .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock), |
96562f28 DB |
453 | .state[0] = CHACHA_CONSTANT_EXPA, |
454 | .state[1] = CHACHA_CONSTANT_ND_3, | |
455 | .state[2] = CHACHA_CONSTANT_2_BY, | |
456 | .state[3] = CHACHA_CONSTANT_TE_K, | |
e192be9d TT |
457 | }; |
458 | ||
459 | /* | |
460 | * crng_init = 0 --> Uninitialized | |
461 | * 1 --> Initialized | |
462 | * 2 --> Initialized from input_pool | |
463 | * | |
464 | * crng_init is protected by primary_crng->lock, and only increases | |
465 | * its value (from 0->1->2). | |
466 | */ | |
467 | static int crng_init = 0; | |
f7e67b8e | 468 | static bool crng_need_final_init = false; |
43838a23 | 469 | #define crng_ready() (likely(crng_init > 1)) |
e192be9d | 470 | static int crng_init_cnt = 0; |
d848e5f8 | 471 | static unsigned long crng_global_init_time = 0; |
248045b8 | 472 | #define CRNG_INIT_CNT_THRESH (2 * CHACHA_KEY_SIZE) |
d38bb085 | 473 | static void _extract_crng(struct crng_state *crng, u8 out[CHACHA_BLOCK_SIZE]); |
c92e040d | 474 | static void _crng_backtrack_protect(struct crng_state *crng, |
d38bb085 | 475 | u8 tmp[CHACHA_BLOCK_SIZE], int used); |
e192be9d | 476 | static void process_random_ready_list(void); |
eecabf56 | 477 | static void _get_random_bytes(void *buf, int nbytes); |
e192be9d | 478 | |
4e00b339 TT |
479 | static struct ratelimit_state unseeded_warning = |
480 | RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3); | |
481 | static struct ratelimit_state urandom_warning = | |
482 | RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3); | |
483 | ||
484 | static int ratelimit_disable __read_mostly; | |
485 | ||
486 | module_param_named(ratelimit_disable, ratelimit_disable, int, 0644); | |
487 | MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression"); | |
488 | ||
1da177e4 LT |
489 | /********************************************************************** |
490 | * | |
491 | * OS independent entropy store. Here are the functions which handle | |
492 | * storing entropy in an entropy pool. | |
493 | * | |
494 | **********************************************************************/ | |
495 | ||
5b87adf3 | 496 | static u32 input_pool_data[POOL_WORDS] __latent_entropy; |
90ed1e67 JD |
497 | |
498 | static struct { | |
43358209 | 499 | spinlock_t lock; |
d38bb085 JD |
500 | u16 add_ptr; |
501 | u16 input_rotate; | |
cda796a3 | 502 | int entropy_count; |
90ed1e67 | 503 | } input_pool = { |
eece09ec | 504 | .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), |
1da177e4 LT |
505 | }; |
506 | ||
90ed1e67 JD |
507 | static ssize_t extract_entropy(void *buf, size_t nbytes, int min); |
508 | static ssize_t _extract_entropy(void *buf, size_t nbytes); | |
509 | ||
510 | static void crng_reseed(struct crng_state *crng, bool use_input_pool); | |
511 | ||
248045b8 | 512 | static const u32 twist_table[8] = { |
775f4b29 TT |
513 | 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158, |
514 | 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; | |
515 | ||
1da177e4 | 516 | /* |
e68e5b66 | 517 | * This function adds bytes into the entropy "pool". It does not |
1da177e4 | 518 | * update the entropy estimate. The caller should call |
adc782da | 519 | * credit_entropy_bits if this is appropriate. |
1da177e4 LT |
520 | * |
521 | * The pool is stirred with a primitive polynomial of the appropriate | |
522 | * degree, and then twisted. We twist by three bits at a time because | |
523 | * it's cheap to do so and helps slightly in the expected case where | |
524 | * the entropy is concentrated in the low-order bits. | |
525 | */ | |
90ed1e67 | 526 | static void _mix_pool_bytes(const void *in, int nbytes) |
1da177e4 | 527 | { |
91ec0fe1 | 528 | unsigned long i; |
feee7697 | 529 | int input_rotate; |
d38bb085 JD |
530 | const u8 *bytes = in; |
531 | u32 w; | |
1da177e4 | 532 | |
90ed1e67 JD |
533 | input_rotate = input_pool.input_rotate; |
534 | i = input_pool.add_ptr; | |
1da177e4 | 535 | |
e68e5b66 MM |
536 | /* mix one byte at a time to simplify size handling and churn faster */ |
537 | while (nbytes--) { | |
c59974ae | 538 | w = rol32(*bytes++, input_rotate); |
91ec0fe1 | 539 | i = (i - 1) & POOL_WORDMASK; |
1da177e4 LT |
540 | |
541 | /* XOR in the various taps */ | |
6c0eace6 JD |
542 | w ^= input_pool_data[i]; |
543 | w ^= input_pool_data[(i + POOL_TAP1) & POOL_WORDMASK]; | |
544 | w ^= input_pool_data[(i + POOL_TAP2) & POOL_WORDMASK]; | |
545 | w ^= input_pool_data[(i + POOL_TAP3) & POOL_WORDMASK]; | |
546 | w ^= input_pool_data[(i + POOL_TAP4) & POOL_WORDMASK]; | |
547 | w ^= input_pool_data[(i + POOL_TAP5) & POOL_WORDMASK]; | |
993ba211 MM |
548 | |
549 | /* Mix the result back in with a twist */ | |
6c0eace6 | 550 | input_pool_data[i] = (w >> 3) ^ twist_table[w & 7]; |
feee7697 MM |
551 | |
552 | /* | |
553 | * Normally, we add 7 bits of rotation to the pool. | |
554 | * At the beginning of the pool, add an extra 7 bits | |
555 | * rotation, so that successive passes spread the | |
556 | * input bits across the pool evenly. | |
557 | */ | |
c59974ae | 558 | input_rotate = (input_rotate + (i ? 7 : 14)) & 31; |
1da177e4 LT |
559 | } |
560 | ||
90ed1e67 JD |
561 | input_pool.input_rotate = input_rotate; |
562 | input_pool.add_ptr = i; | |
1da177e4 LT |
563 | } |
564 | ||
90ed1e67 | 565 | static void __mix_pool_bytes(const void *in, int nbytes) |
00ce1db1 | 566 | { |
90ed1e67 JD |
567 | trace_mix_pool_bytes_nolock(nbytes, _RET_IP_); |
568 | _mix_pool_bytes(in, nbytes); | |
00ce1db1 TT |
569 | } |
570 | ||
90ed1e67 | 571 | static void mix_pool_bytes(const void *in, int nbytes) |
1da177e4 | 572 | { |
902c098a TT |
573 | unsigned long flags; |
574 | ||
90ed1e67 JD |
575 | trace_mix_pool_bytes(nbytes, _RET_IP_); |
576 | spin_lock_irqsave(&input_pool.lock, flags); | |
577 | _mix_pool_bytes(in, nbytes); | |
578 | spin_unlock_irqrestore(&input_pool.lock, flags); | |
1da177e4 LT |
579 | } |
580 | ||
775f4b29 | 581 | struct fast_pool { |
248045b8 JD |
582 | u32 pool[4]; |
583 | unsigned long last; | |
584 | u16 reg_idx; | |
585 | u8 count; | |
775f4b29 TT |
586 | }; |
587 | ||
588 | /* | |
589 | * This is a fast mixing routine used by the interrupt randomness | |
590 | * collector. It's hardcoded for an 128 bit pool and assumes that any | |
591 | * locks that might be needed are taken by the caller. | |
592 | */ | |
43759d4f | 593 | static void fast_mix(struct fast_pool *f) |
775f4b29 | 594 | { |
d38bb085 JD |
595 | u32 a = f->pool[0], b = f->pool[1]; |
596 | u32 c = f->pool[2], d = f->pool[3]; | |
43759d4f TT |
597 | |
598 | a += b; c += d; | |
19acc77a | 599 | b = rol32(b, 6); d = rol32(d, 27); |
43759d4f TT |
600 | d ^= a; b ^= c; |
601 | ||
602 | a += b; c += d; | |
19acc77a | 603 | b = rol32(b, 16); d = rol32(d, 14); |
43759d4f TT |
604 | d ^= a; b ^= c; |
605 | ||
606 | a += b; c += d; | |
19acc77a | 607 | b = rol32(b, 6); d = rol32(d, 27); |
43759d4f TT |
608 | d ^= a; b ^= c; |
609 | ||
610 | a += b; c += d; | |
19acc77a | 611 | b = rol32(b, 16); d = rol32(d, 14); |
43759d4f TT |
612 | d ^= a; b ^= c; |
613 | ||
614 | f->pool[0] = a; f->pool[1] = b; | |
615 | f->pool[2] = c; f->pool[3] = d; | |
655b2264 | 616 | f->count++; |
775f4b29 TT |
617 | } |
618 | ||
205a525c HX |
619 | static void process_random_ready_list(void) |
620 | { | |
621 | unsigned long flags; | |
622 | struct random_ready_callback *rdy, *tmp; | |
623 | ||
624 | spin_lock_irqsave(&random_ready_list_lock, flags); | |
625 | list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) { | |
626 | struct module *owner = rdy->owner; | |
627 | ||
628 | list_del_init(&rdy->list); | |
629 | rdy->func(rdy); | |
630 | module_put(owner); | |
631 | } | |
632 | spin_unlock_irqrestore(&random_ready_list_lock, flags); | |
633 | } | |
634 | ||
1da177e4 | 635 | /* |
a283b5c4 PA |
636 | * Credit (or debit) the entropy store with n bits of entropy. |
637 | * Use credit_entropy_bits_safe() if the value comes from userspace | |
638 | * or otherwise should be checked for extreme values. | |
1da177e4 | 639 | */ |
90ed1e67 | 640 | static void credit_entropy_bits(int nbits) |
1da177e4 | 641 | { |
90ed1e67 | 642 | int entropy_count, entropy_bits, orig; |
b3d51c1f | 643 | int nfrac = nbits << POOL_ENTROPY_SHIFT; |
1da177e4 | 644 | |
18263c4e JD |
645 | /* Ensure that the multiplication can avoid being 64 bits wide. */ |
646 | BUILD_BUG_ON(2 * (POOL_ENTROPY_SHIFT + POOL_BITSHIFT) > 31); | |
647 | ||
adc782da MM |
648 | if (!nbits) |
649 | return; | |
650 | ||
902c098a | 651 | retry: |
90ed1e67 | 652 | entropy_count = orig = READ_ONCE(input_pool.entropy_count); |
30e37ec5 PA |
653 | if (nfrac < 0) { |
654 | /* Debit */ | |
655 | entropy_count += nfrac; | |
656 | } else { | |
657 | /* | |
658 | * Credit: we have to account for the possibility of | |
659 | * overwriting already present entropy. Even in the | |
660 | * ideal case of pure Shannon entropy, new contributions | |
661 | * approach the full value asymptotically: | |
662 | * | |
663 | * entropy <- entropy + (pool_size - entropy) * | |
664 | * (1 - exp(-add_entropy/pool_size)) | |
665 | * | |
666 | * For add_entropy <= pool_size/2 then | |
667 | * (1 - exp(-add_entropy/pool_size)) >= | |
668 | * (add_entropy/pool_size)*0.7869... | |
669 | * so we can approximate the exponential with | |
670 | * 3/4*add_entropy/pool_size and still be on the | |
671 | * safe side by adding at most pool_size/2 at a time. | |
672 | * | |
673 | * The use of pool_size-2 in the while statement is to | |
674 | * prevent rounding artifacts from making the loop | |
675 | * arbitrarily long; this limits the loop to log2(pool_size)*2 | |
676 | * turns no matter how large nbits is. | |
677 | */ | |
678 | int pnfrac = nfrac; | |
b3d51c1f | 679 | const int s = POOL_BITSHIFT + POOL_ENTROPY_SHIFT + 2; |
30e37ec5 PA |
680 | /* The +2 corresponds to the /4 in the denominator */ |
681 | ||
682 | do { | |
18263c4e | 683 | unsigned int anfrac = min(pnfrac, POOL_FRACBITS / 2); |
30e37ec5 | 684 | unsigned int add = |
18263c4e | 685 | ((POOL_FRACBITS - entropy_count) * anfrac * 3) >> s; |
30e37ec5 PA |
686 | |
687 | entropy_count += add; | |
688 | pnfrac -= anfrac; | |
18263c4e | 689 | } while (unlikely(entropy_count < POOL_FRACBITS - 2 && pnfrac)); |
30e37ec5 | 690 | } |
00ce1db1 | 691 | |
870e05b1 | 692 | if (WARN_ON(entropy_count < 0)) { |
90ed1e67 | 693 | pr_warn("negative entropy/overflow: count %d\n", entropy_count); |
8b76f46a | 694 | entropy_count = 0; |
91ec0fe1 JD |
695 | } else if (entropy_count > POOL_FRACBITS) |
696 | entropy_count = POOL_FRACBITS; | |
90ed1e67 | 697 | if (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig) |
902c098a | 698 | goto retry; |
1da177e4 | 699 | |
b3d51c1f | 700 | trace_credit_entropy_bits(nbits, entropy_count >> POOL_ENTROPY_SHIFT, _RET_IP_); |
00ce1db1 | 701 | |
b3d51c1f | 702 | entropy_bits = entropy_count >> POOL_ENTROPY_SHIFT; |
90ed1e67 JD |
703 | if (crng_init < 2 && entropy_bits >= 128) |
704 | crng_reseed(&primary_crng, true); | |
1da177e4 LT |
705 | } |
706 | ||
90ed1e67 | 707 | static int credit_entropy_bits_safe(int nbits) |
a283b5c4 | 708 | { |
86a574de TT |
709 | if (nbits < 0) |
710 | return -EINVAL; | |
711 | ||
a283b5c4 | 712 | /* Cap the value to avoid overflows */ |
248045b8 | 713 | nbits = min(nbits, POOL_BITS); |
a283b5c4 | 714 | |
90ed1e67 | 715 | credit_entropy_bits(nbits); |
86a574de | 716 | return 0; |
a283b5c4 PA |
717 | } |
718 | ||
e192be9d TT |
719 | /********************************************************************* |
720 | * | |
721 | * CRNG using CHACHA20 | |
722 | * | |
723 | *********************************************************************/ | |
724 | ||
248045b8 | 725 | #define CRNG_RESEED_INTERVAL (300 * HZ) |
e192be9d TT |
726 | |
727 | static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); | |
728 | ||
1e7f583a TT |
729 | /* |
730 | * Hack to deal with crazy userspace progams when they are all trying | |
731 | * to access /dev/urandom in parallel. The programs are almost | |
732 | * certainly doing something terribly wrong, but we'll work around | |
733 | * their brain damage. | |
734 | */ | |
735 | static struct crng_state **crng_node_pool __read_mostly; | |
1e7f583a | 736 | |
b169c13d | 737 | static void invalidate_batched_entropy(void); |
fe6f1a6a | 738 | static void numa_crng_init(void); |
b169c13d | 739 | |
9b254366 KC |
740 | static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); |
741 | static int __init parse_trust_cpu(char *arg) | |
742 | { | |
743 | return kstrtobool(arg, &trust_cpu); | |
744 | } | |
745 | early_param("random.trust_cpu", parse_trust_cpu); | |
746 | ||
5cbe0f13 | 747 | static bool crng_init_try_arch(struct crng_state *crng) |
e192be9d | 748 | { |
248045b8 JD |
749 | int i; |
750 | bool arch_init = true; | |
751 | unsigned long rv; | |
e192be9d | 752 | |
e192be9d TT |
753 | for (i = 4; i < 16; i++) { |
754 | if (!arch_get_random_seed_long(&rv) && | |
39a8883a | 755 | !arch_get_random_long(&rv)) { |
e192be9d | 756 | rv = random_get_entropy(); |
5cbe0f13 | 757 | arch_init = false; |
39a8883a | 758 | } |
e192be9d TT |
759 | crng->state[i] ^= rv; |
760 | } | |
5cbe0f13 MR |
761 | |
762 | return arch_init; | |
763 | } | |
764 | ||
ebf76063 | 765 | static bool __init crng_init_try_arch_early(void) |
253d3194 | 766 | { |
248045b8 JD |
767 | int i; |
768 | bool arch_init = true; | |
769 | unsigned long rv; | |
253d3194 MR |
770 | |
771 | for (i = 4; i < 16; i++) { | |
772 | if (!arch_get_random_seed_long_early(&rv) && | |
773 | !arch_get_random_long_early(&rv)) { | |
774 | rv = random_get_entropy(); | |
775 | arch_init = false; | |
776 | } | |
ebf76063 | 777 | primary_crng.state[i] ^= rv; |
253d3194 MR |
778 | } |
779 | ||
780 | return arch_init; | |
781 | } | |
782 | ||
7b873241 | 783 | static void crng_initialize_secondary(struct crng_state *crng) |
5cbe0f13 | 784 | { |
a181e0fd | 785 | chacha_init_consts(crng->state); |
d38bb085 | 786 | _get_random_bytes(&crng->state[4], sizeof(u32) * 12); |
5cbe0f13 MR |
787 | crng_init_try_arch(crng); |
788 | crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1; | |
789 | } | |
790 | ||
ebf76063 | 791 | static void __init crng_initialize_primary(void) |
5cbe0f13 | 792 | { |
ebf76063 DB |
793 | _extract_entropy(&primary_crng.state[4], sizeof(u32) * 12); |
794 | if (crng_init_try_arch_early() && trust_cpu && crng_init < 2) { | |
fe6f1a6a JD |
795 | invalidate_batched_entropy(); |
796 | numa_crng_init(); | |
39a8883a | 797 | crng_init = 2; |
161212c7 | 798 | pr_notice("crng init done (trusting CPU's manufacturer)\n"); |
39a8883a | 799 | } |
ebf76063 | 800 | primary_crng.init_time = jiffies - CRNG_RESEED_INTERVAL - 1; |
e192be9d TT |
801 | } |
802 | ||
f7e67b8e DB |
803 | static void crng_finalize_init(struct crng_state *crng) |
804 | { | |
805 | if (crng != &primary_crng || crng_init >= 2) | |
806 | return; | |
807 | if (!system_wq) { | |
808 | /* We can't call numa_crng_init until we have workqueues, | |
809 | * so mark this for processing later. */ | |
810 | crng_need_final_init = true; | |
811 | return; | |
812 | } | |
813 | ||
814 | invalidate_batched_entropy(); | |
815 | numa_crng_init(); | |
816 | crng_init = 2; | |
817 | process_random_ready_list(); | |
818 | wake_up_interruptible(&crng_init_wait); | |
819 | kill_fasync(&fasync, SIGIO, POLL_IN); | |
820 | pr_notice("crng init done\n"); | |
821 | if (unseeded_warning.missed) { | |
822 | pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n", | |
823 | unseeded_warning.missed); | |
824 | unseeded_warning.missed = 0; | |
825 | } | |
826 | if (urandom_warning.missed) { | |
827 | pr_notice("%d urandom warning(s) missed due to ratelimiting\n", | |
828 | urandom_warning.missed); | |
829 | urandom_warning.missed = 0; | |
830 | } | |
831 | } | |
832 | ||
6c1e851c | 833 | static void do_numa_crng_init(struct work_struct *work) |
8ef35c86 TT |
834 | { |
835 | int i; | |
836 | struct crng_state *crng; | |
837 | struct crng_state **pool; | |
838 | ||
248045b8 | 839 | pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL | __GFP_NOFAIL); |
8ef35c86 TT |
840 | for_each_online_node(i) { |
841 | crng = kmalloc_node(sizeof(struct crng_state), | |
842 | GFP_KERNEL | __GFP_NOFAIL, i); | |
843 | spin_lock_init(&crng->lock); | |
5cbe0f13 | 844 | crng_initialize_secondary(crng); |
8ef35c86 TT |
845 | pool[i] = crng; |
846 | } | |
5d73d1e3 EB |
847 | /* pairs with READ_ONCE() in select_crng() */ |
848 | if (cmpxchg_release(&crng_node_pool, NULL, pool) != NULL) { | |
8ef35c86 TT |
849 | for_each_node(i) |
850 | kfree(pool[i]); | |
851 | kfree(pool); | |
852 | } | |
853 | } | |
6c1e851c TT |
854 | |
855 | static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init); | |
856 | ||
857 | static void numa_crng_init(void) | |
858 | { | |
7b873241 JD |
859 | if (IS_ENABLED(CONFIG_NUMA)) |
860 | schedule_work(&numa_crng_init_work); | |
6c1e851c | 861 | } |
5d73d1e3 EB |
862 | |
863 | static struct crng_state *select_crng(void) | |
864 | { | |
7b873241 JD |
865 | if (IS_ENABLED(CONFIG_NUMA)) { |
866 | struct crng_state **pool; | |
867 | int nid = numa_node_id(); | |
868 | ||
869 | /* pairs with cmpxchg_release() in do_numa_crng_init() */ | |
870 | pool = READ_ONCE(crng_node_pool); | |
871 | if (pool && pool[nid]) | |
872 | return pool[nid]; | |
873 | } | |
5d73d1e3 | 874 | |
5d73d1e3 EB |
875 | return &primary_crng; |
876 | } | |
8ef35c86 | 877 | |
dc12baac TT |
878 | /* |
879 | * crng_fast_load() can be called by code in the interrupt service | |
73c7733f JD |
880 | * path. So we can't afford to dilly-dally. Returns the number of |
881 | * bytes processed from cp. | |
dc12baac | 882 | */ |
d38bb085 | 883 | static size_t crng_fast_load(const u8 *cp, size_t len) |
e192be9d TT |
884 | { |
885 | unsigned long flags; | |
d38bb085 | 886 | u8 *p; |
73c7733f | 887 | size_t ret = 0; |
e192be9d TT |
888 | |
889 | if (!spin_trylock_irqsave(&primary_crng.lock, flags)) | |
890 | return 0; | |
43838a23 | 891 | if (crng_init != 0) { |
e192be9d TT |
892 | spin_unlock_irqrestore(&primary_crng.lock, flags); |
893 | return 0; | |
894 | } | |
248045b8 | 895 | p = (u8 *)&primary_crng.state[4]; |
e192be9d | 896 | while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) { |
1ca1b917 | 897 | p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp; |
73c7733f | 898 | cp++; crng_init_cnt++; len--; ret++; |
e192be9d | 899 | } |
4a072c71 | 900 | spin_unlock_irqrestore(&primary_crng.lock, flags); |
e192be9d | 901 | if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { |
b169c13d | 902 | invalidate_batched_entropy(); |
e192be9d | 903 | crng_init = 1; |
12cd53af | 904 | pr_notice("fast init done\n"); |
e192be9d | 905 | } |
73c7733f | 906 | return ret; |
e192be9d TT |
907 | } |
908 | ||
dc12baac TT |
909 | /* |
910 | * crng_slow_load() is called by add_device_randomness, which has two | |
911 | * attributes. (1) We can't trust the buffer passed to it is | |
912 | * guaranteed to be unpredictable (so it might not have any entropy at | |
913 | * all), and (2) it doesn't have the performance constraints of | |
914 | * crng_fast_load(). | |
915 | * | |
916 | * So we do something more comprehensive which is guaranteed to touch | |
917 | * all of the primary_crng's state, and which uses a LFSR with a | |
918 | * period of 255 as part of the mixing algorithm. Finally, we do | |
919 | * *not* advance crng_init_cnt since buffer we may get may be something | |
920 | * like a fixed DMI table (for example), which might very well be | |
921 | * unique to the machine, but is otherwise unvarying. | |
922 | */ | |
d38bb085 | 923 | static int crng_slow_load(const u8 *cp, size_t len) |
dc12baac | 924 | { |
248045b8 JD |
925 | unsigned long flags; |
926 | static u8 lfsr = 1; | |
927 | u8 tmp; | |
928 | unsigned int i, max = CHACHA_KEY_SIZE; | |
929 | const u8 *src_buf = cp; | |
930 | u8 *dest_buf = (u8 *)&primary_crng.state[4]; | |
dc12baac TT |
931 | |
932 | if (!spin_trylock_irqsave(&primary_crng.lock, flags)) | |
933 | return 0; | |
934 | if (crng_init != 0) { | |
935 | spin_unlock_irqrestore(&primary_crng.lock, flags); | |
936 | return 0; | |
937 | } | |
938 | if (len > max) | |
939 | max = len; | |
940 | ||
248045b8 | 941 | for (i = 0; i < max; i++) { |
dc12baac TT |
942 | tmp = lfsr; |
943 | lfsr >>= 1; | |
944 | if (tmp & 1) | |
945 | lfsr ^= 0xE1; | |
1ca1b917 EB |
946 | tmp = dest_buf[i % CHACHA_KEY_SIZE]; |
947 | dest_buf[i % CHACHA_KEY_SIZE] ^= src_buf[i % len] ^ lfsr; | |
dc12baac TT |
948 | lfsr += (tmp << 3) | (tmp >> 5); |
949 | } | |
950 | spin_unlock_irqrestore(&primary_crng.lock, flags); | |
951 | return 1; | |
952 | } | |
953 | ||
90ed1e67 | 954 | static void crng_reseed(struct crng_state *crng, bool use_input_pool) |
e192be9d | 955 | { |
248045b8 JD |
956 | unsigned long flags; |
957 | int i, num; | |
e192be9d | 958 | union { |
248045b8 JD |
959 | u8 block[CHACHA_BLOCK_SIZE]; |
960 | u32 key[8]; | |
e192be9d TT |
961 | } buf; |
962 | ||
90ed1e67 JD |
963 | if (use_input_pool) { |
964 | num = extract_entropy(&buf, 32, 16); | |
e192be9d TT |
965 | if (num == 0) |
966 | return; | |
c92e040d | 967 | } else { |
1e7f583a | 968 | _extract_crng(&primary_crng, buf.block); |
c92e040d | 969 | _crng_backtrack_protect(&primary_crng, buf.block, |
1ca1b917 | 970 | CHACHA_KEY_SIZE); |
c92e040d | 971 | } |
0bb29a84 | 972 | spin_lock_irqsave(&crng->lock, flags); |
e192be9d | 973 | for (i = 0; i < 8; i++) { |
248045b8 | 974 | unsigned long rv; |
e192be9d TT |
975 | if (!arch_get_random_seed_long(&rv) && |
976 | !arch_get_random_long(&rv)) | |
977 | rv = random_get_entropy(); | |
248045b8 | 978 | crng->state[i + 4] ^= buf.key[i] ^ rv; |
e192be9d TT |
979 | } |
980 | memzero_explicit(&buf, sizeof(buf)); | |
009ba856 | 981 | WRITE_ONCE(crng->init_time, jiffies); |
0bb29a84 | 982 | spin_unlock_irqrestore(&crng->lock, flags); |
f7e67b8e | 983 | crng_finalize_init(crng); |
e192be9d TT |
984 | } |
985 | ||
248045b8 | 986 | static void _extract_crng(struct crng_state *crng, u8 out[CHACHA_BLOCK_SIZE]) |
e192be9d | 987 | { |
2ee25b69 | 988 | unsigned long flags, init_time; |
009ba856 EB |
989 | |
990 | if (crng_ready()) { | |
991 | init_time = READ_ONCE(crng->init_time); | |
992 | if (time_after(READ_ONCE(crng_global_init_time), init_time) || | |
993 | time_after(jiffies, init_time + CRNG_RESEED_INTERVAL)) | |
90ed1e67 | 994 | crng_reseed(crng, crng == &primary_crng); |
009ba856 | 995 | } |
e192be9d | 996 | spin_lock_irqsave(&crng->lock, flags); |
e192be9d TT |
997 | chacha20_block(&crng->state[0], out); |
998 | if (crng->state[12] == 0) | |
999 | crng->state[13]++; | |
1000 | spin_unlock_irqrestore(&crng->lock, flags); | |
1001 | } | |
1002 | ||
d38bb085 | 1003 | static void extract_crng(u8 out[CHACHA_BLOCK_SIZE]) |
1e7f583a | 1004 | { |
5d73d1e3 | 1005 | _extract_crng(select_crng(), out); |
1e7f583a TT |
1006 | } |
1007 | ||
c92e040d TT |
1008 | /* |
1009 | * Use the leftover bytes from the CRNG block output (if there is | |
1010 | * enough) to mutate the CRNG key to provide backtracking protection. | |
1011 | */ | |
1012 | static void _crng_backtrack_protect(struct crng_state *crng, | |
d38bb085 | 1013 | u8 tmp[CHACHA_BLOCK_SIZE], int used) |
c92e040d | 1014 | { |
248045b8 JD |
1015 | unsigned long flags; |
1016 | u32 *s, *d; | |
1017 | int i; | |
c92e040d | 1018 | |
d38bb085 | 1019 | used = round_up(used, sizeof(u32)); |
1ca1b917 | 1020 | if (used + CHACHA_KEY_SIZE > CHACHA_BLOCK_SIZE) { |
c92e040d TT |
1021 | extract_crng(tmp); |
1022 | used = 0; | |
1023 | } | |
1024 | spin_lock_irqsave(&crng->lock, flags); | |
248045b8 | 1025 | s = (u32 *)&tmp[used]; |
c92e040d | 1026 | d = &crng->state[4]; |
248045b8 | 1027 | for (i = 0; i < 8; i++) |
c92e040d TT |
1028 | *d++ ^= *s++; |
1029 | spin_unlock_irqrestore(&crng->lock, flags); | |
1030 | } | |
1031 | ||
d38bb085 | 1032 | static void crng_backtrack_protect(u8 tmp[CHACHA_BLOCK_SIZE], int used) |
c92e040d | 1033 | { |
5d73d1e3 | 1034 | _crng_backtrack_protect(select_crng(), tmp, used); |
c92e040d TT |
1035 | } |
1036 | ||
e192be9d TT |
1037 | static ssize_t extract_crng_user(void __user *buf, size_t nbytes) |
1038 | { | |
1ca1b917 | 1039 | ssize_t ret = 0, i = CHACHA_BLOCK_SIZE; |
d38bb085 | 1040 | u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4); |
e192be9d TT |
1041 | int large_request = (nbytes > 256); |
1042 | ||
1043 | while (nbytes) { | |
1044 | if (large_request && need_resched()) { | |
1045 | if (signal_pending(current)) { | |
1046 | if (ret == 0) | |
1047 | ret = -ERESTARTSYS; | |
1048 | break; | |
1049 | } | |
1050 | schedule(); | |
1051 | } | |
1052 | ||
1053 | extract_crng(tmp); | |
1ca1b917 | 1054 | i = min_t(int, nbytes, CHACHA_BLOCK_SIZE); |
e192be9d TT |
1055 | if (copy_to_user(buf, tmp, i)) { |
1056 | ret = -EFAULT; | |
1057 | break; | |
1058 | } | |
1059 | ||
1060 | nbytes -= i; | |
1061 | buf += i; | |
1062 | ret += i; | |
1063 | } | |
c92e040d | 1064 | crng_backtrack_protect(tmp, i); |
e192be9d TT |
1065 | |
1066 | /* Wipe data just written to memory */ | |
1067 | memzero_explicit(tmp, sizeof(tmp)); | |
1068 | ||
1069 | return ret; | |
1070 | } | |
1071 | ||
1da177e4 LT |
1072 | /********************************************************************* |
1073 | * | |
1074 | * Entropy input management | |
1075 | * | |
1076 | *********************************************************************/ | |
1077 | ||
1078 | /* There is one of these per entropy source */ | |
1079 | struct timer_rand_state { | |
1080 | cycles_t last_time; | |
90b75ee5 | 1081 | long last_delta, last_delta2; |
1da177e4 LT |
1082 | }; |
1083 | ||
644008df TT |
1084 | #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, }; |
1085 | ||
a2080a67 | 1086 | /* |
e192be9d TT |
1087 | * Add device- or boot-specific data to the input pool to help |
1088 | * initialize it. | |
a2080a67 | 1089 | * |
e192be9d TT |
1090 | * None of this adds any entropy; it is meant to avoid the problem of |
1091 | * the entropy pool having similar initial state across largely | |
1092 | * identical devices. | |
a2080a67 LT |
1093 | */ |
1094 | void add_device_randomness(const void *buf, unsigned int size) | |
1095 | { | |
61875f30 | 1096 | unsigned long time = random_get_entropy() ^ jiffies; |
3ef4cb2d | 1097 | unsigned long flags; |
a2080a67 | 1098 | |
dc12baac TT |
1099 | if (!crng_ready() && size) |
1100 | crng_slow_load(buf, size); | |
ee7998c5 | 1101 | |
5910895f | 1102 | trace_add_device_randomness(size, _RET_IP_); |
3ef4cb2d | 1103 | spin_lock_irqsave(&input_pool.lock, flags); |
90ed1e67 JD |
1104 | _mix_pool_bytes(buf, size); |
1105 | _mix_pool_bytes(&time, sizeof(time)); | |
3ef4cb2d | 1106 | spin_unlock_irqrestore(&input_pool.lock, flags); |
a2080a67 LT |
1107 | } |
1108 | EXPORT_SYMBOL(add_device_randomness); | |
1109 | ||
644008df | 1110 | static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE; |
3060d6fe | 1111 | |
1da177e4 LT |
1112 | /* |
1113 | * This function adds entropy to the entropy "pool" by using timing | |
1114 | * delays. It uses the timer_rand_state structure to make an estimate | |
1115 | * of how many bits of entropy this call has added to the pool. | |
1116 | * | |
1117 | * The number "num" is also added to the pool - it should somehow describe | |
1118 | * the type of event which just happened. This is currently 0-255 for | |
1119 | * keyboard scan codes, and 256 upwards for interrupts. | |
1120 | * | |
1121 | */ | |
1122 | static void add_timer_randomness(struct timer_rand_state *state, unsigned num) | |
1123 | { | |
1124 | struct { | |
1da177e4 | 1125 | long jiffies; |
d38bb085 JD |
1126 | unsigned int cycles; |
1127 | unsigned int num; | |
1da177e4 LT |
1128 | } sample; |
1129 | long delta, delta2, delta3; | |
1130 | ||
1da177e4 | 1131 | sample.jiffies = jiffies; |
61875f30 | 1132 | sample.cycles = random_get_entropy(); |
1da177e4 | 1133 | sample.num = num; |
90ed1e67 | 1134 | mix_pool_bytes(&sample, sizeof(sample)); |
1da177e4 LT |
1135 | |
1136 | /* | |
1137 | * Calculate number of bits of randomness we probably added. | |
1138 | * We take into account the first, second and third-order deltas | |
1139 | * in order to make our estimate. | |
1140 | */ | |
e00d996a QC |
1141 | delta = sample.jiffies - READ_ONCE(state->last_time); |
1142 | WRITE_ONCE(state->last_time, sample.jiffies); | |
5e747dd9 | 1143 | |
e00d996a QC |
1144 | delta2 = delta - READ_ONCE(state->last_delta); |
1145 | WRITE_ONCE(state->last_delta, delta); | |
5e747dd9 | 1146 | |
e00d996a QC |
1147 | delta3 = delta2 - READ_ONCE(state->last_delta2); |
1148 | WRITE_ONCE(state->last_delta2, delta2); | |
5e747dd9 RV |
1149 | |
1150 | if (delta < 0) | |
1151 | delta = -delta; | |
1152 | if (delta2 < 0) | |
1153 | delta2 = -delta2; | |
1154 | if (delta3 < 0) | |
1155 | delta3 = -delta3; | |
1156 | if (delta > delta2) | |
1157 | delta = delta2; | |
1158 | if (delta > delta3) | |
1159 | delta = delta3; | |
1da177e4 | 1160 | |
5e747dd9 RV |
1161 | /* |
1162 | * delta is now minimum absolute delta. | |
1163 | * Round down by 1 bit on general principles, | |
727d499a | 1164 | * and limit entropy estimate to 12 bits. |
5e747dd9 | 1165 | */ |
248045b8 | 1166 | credit_entropy_bits(min_t(int, fls(delta >> 1), 11)); |
1da177e4 LT |
1167 | } |
1168 | ||
d251575a | 1169 | void add_input_randomness(unsigned int type, unsigned int code, |
248045b8 | 1170 | unsigned int value) |
1da177e4 LT |
1171 | { |
1172 | static unsigned char last_value; | |
1173 | ||
1174 | /* ignore autorepeat and the like */ | |
1175 | if (value == last_value) | |
1176 | return; | |
1177 | ||
1da177e4 LT |
1178 | last_value = value; |
1179 | add_timer_randomness(&input_timer_state, | |
1180 | (type << 4) ^ code ^ (code >> 4) ^ value); | |
b3d51c1f | 1181 | trace_add_input_randomness(POOL_ENTROPY_BITS()); |
1da177e4 | 1182 | } |
80fc9f53 | 1183 | EXPORT_SYMBOL_GPL(add_input_randomness); |
1da177e4 | 1184 | |
775f4b29 TT |
1185 | static DEFINE_PER_CPU(struct fast_pool, irq_randomness); |
1186 | ||
43759d4f TT |
1187 | #ifdef ADD_INTERRUPT_BENCH |
1188 | static unsigned long avg_cycles, avg_deviation; | |
1189 | ||
248045b8 JD |
1190 | #define AVG_SHIFT 8 /* Exponential average factor k=1/256 */ |
1191 | #define FIXED_1_2 (1 << (AVG_SHIFT - 1)) | |
43759d4f TT |
1192 | |
1193 | static void add_interrupt_bench(cycles_t start) | |
1194 | { | |
248045b8 | 1195 | long delta = random_get_entropy() - start; |
43759d4f | 1196 | |
248045b8 JD |
1197 | /* Use a weighted moving average */ |
1198 | delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT); | |
1199 | avg_cycles += delta; | |
1200 | /* And average deviation */ | |
1201 | delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT); | |
1202 | avg_deviation += delta; | |
43759d4f TT |
1203 | } |
1204 | #else | |
1205 | #define add_interrupt_bench(x) | |
1206 | #endif | |
1207 | ||
d38bb085 | 1208 | static u32 get_reg(struct fast_pool *f, struct pt_regs *regs) |
ee3e00e9 | 1209 | { |
248045b8 | 1210 | u32 *ptr = (u32 *)regs; |
92e75428 | 1211 | unsigned int idx; |
ee3e00e9 TT |
1212 | |
1213 | if (regs == NULL) | |
1214 | return 0; | |
92e75428 | 1215 | idx = READ_ONCE(f->reg_idx); |
d38bb085 | 1216 | if (idx >= sizeof(struct pt_regs) / sizeof(u32)) |
92e75428 TT |
1217 | idx = 0; |
1218 | ptr += idx++; | |
1219 | WRITE_ONCE(f->reg_idx, idx); | |
9dfa7bba | 1220 | return *ptr; |
ee3e00e9 TT |
1221 | } |
1222 | ||
703f7066 | 1223 | void add_interrupt_randomness(int irq) |
1da177e4 | 1224 | { |
248045b8 JD |
1225 | struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness); |
1226 | struct pt_regs *regs = get_irq_regs(); | |
1227 | unsigned long now = jiffies; | |
1228 | cycles_t cycles = random_get_entropy(); | |
1229 | u32 c_high, j_high; | |
1230 | u64 ip; | |
3060d6fe | 1231 | |
ee3e00e9 TT |
1232 | if (cycles == 0) |
1233 | cycles = get_reg(fast_pool, regs); | |
655b2264 TT |
1234 | c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0; |
1235 | j_high = (sizeof(now) > 4) ? now >> 32 : 0; | |
43759d4f TT |
1236 | fast_pool->pool[0] ^= cycles ^ j_high ^ irq; |
1237 | fast_pool->pool[1] ^= now ^ c_high; | |
655b2264 | 1238 | ip = regs ? instruction_pointer(regs) : _RET_IP_; |
43759d4f | 1239 | fast_pool->pool[2] ^= ip; |
248045b8 JD |
1240 | fast_pool->pool[3] ^= |
1241 | (sizeof(ip) > 4) ? ip >> 32 : get_reg(fast_pool, regs); | |
3060d6fe | 1242 | |
43759d4f | 1243 | fast_mix(fast_pool); |
43759d4f | 1244 | add_interrupt_bench(cycles); |
3060d6fe | 1245 | |
43838a23 | 1246 | if (unlikely(crng_init == 0)) { |
e192be9d | 1247 | if ((fast_pool->count >= 64) && |
d38bb085 | 1248 | crng_fast_load((u8 *)fast_pool->pool, sizeof(fast_pool->pool)) > 0) { |
e192be9d TT |
1249 | fast_pool->count = 0; |
1250 | fast_pool->last = now; | |
1251 | } | |
1252 | return; | |
1253 | } | |
1254 | ||
248045b8 | 1255 | if ((fast_pool->count < 64) && !time_after(now, fast_pool->last + HZ)) |
1da177e4 LT |
1256 | return; |
1257 | ||
90ed1e67 | 1258 | if (!spin_trylock(&input_pool.lock)) |
91fcb532 | 1259 | return; |
83664a69 | 1260 | |
91fcb532 | 1261 | fast_pool->last = now; |
90ed1e67 JD |
1262 | __mix_pool_bytes(&fast_pool->pool, sizeof(fast_pool->pool)); |
1263 | spin_unlock(&input_pool.lock); | |
83664a69 | 1264 | |
ee3e00e9 | 1265 | fast_pool->count = 0; |
83664a69 | 1266 | |
ee3e00e9 | 1267 | /* award one bit for the contents of the fast pool */ |
90ed1e67 | 1268 | credit_entropy_bits(1); |
1da177e4 | 1269 | } |
4b44f2d1 | 1270 | EXPORT_SYMBOL_GPL(add_interrupt_randomness); |
1da177e4 | 1271 | |
9361401e | 1272 | #ifdef CONFIG_BLOCK |
1da177e4 LT |
1273 | void add_disk_randomness(struct gendisk *disk) |
1274 | { | |
1275 | if (!disk || !disk->random) | |
1276 | return; | |
1277 | /* first major is 1, so we get >= 0x200 here */ | |
f331c029 | 1278 | add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); |
b3d51c1f | 1279 | trace_add_disk_randomness(disk_devt(disk), POOL_ENTROPY_BITS()); |
1da177e4 | 1280 | } |
bdcfa3e5 | 1281 | EXPORT_SYMBOL_GPL(add_disk_randomness); |
9361401e | 1282 | #endif |
1da177e4 | 1283 | |
1da177e4 LT |
1284 | /********************************************************************* |
1285 | * | |
1286 | * Entropy extraction routines | |
1287 | * | |
1288 | *********************************************************************/ | |
1289 | ||
1da177e4 | 1290 | /* |
19fa5be1 GP |
1291 | * This function decides how many bytes to actually take from the |
1292 | * given pool, and also debits the entropy count accordingly. | |
1da177e4 | 1293 | */ |
90ed1e67 | 1294 | static size_t account(size_t nbytes, int min) |
1da177e4 | 1295 | { |
a254a0e4 | 1296 | int entropy_count, orig; |
79a84687 | 1297 | size_t ibytes, nfrac; |
1da177e4 | 1298 | |
90ed1e67 | 1299 | BUG_ON(input_pool.entropy_count > POOL_FRACBITS); |
1da177e4 LT |
1300 | |
1301 | /* Can we pull enough? */ | |
10b3a32d | 1302 | retry: |
90ed1e67 | 1303 | entropy_count = orig = READ_ONCE(input_pool.entropy_count); |
870e05b1 | 1304 | if (WARN_ON(entropy_count < 0)) { |
90ed1e67 | 1305 | pr_warn("negative entropy count: count %d\n", entropy_count); |
79a84687 HFS |
1306 | entropy_count = 0; |
1307 | } | |
a254a0e4 JD |
1308 | |
1309 | /* never pull more than available */ | |
1310 | ibytes = min_t(size_t, nbytes, entropy_count >> (POOL_ENTROPY_SHIFT + 3)); | |
1311 | if (ibytes < min) | |
1312 | ibytes = 0; | |
b3d51c1f | 1313 | nfrac = ibytes << (POOL_ENTROPY_SHIFT + 3); |
248045b8 | 1314 | if ((size_t)entropy_count > nfrac) |
79a84687 HFS |
1315 | entropy_count -= nfrac; |
1316 | else | |
e33ba5fa | 1317 | entropy_count = 0; |
f9c6d498 | 1318 | |
90ed1e67 | 1319 | if (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig) |
0fb7a01a | 1320 | goto retry; |
1da177e4 | 1321 | |
90ed1e67 | 1322 | trace_debit_entropy(8 * ibytes); |
b3d51c1f | 1323 | if (ibytes && POOL_ENTROPY_BITS() < random_write_wakeup_bits) { |
a11e1d43 | 1324 | wake_up_interruptible(&random_write_wait); |
b9809552 TT |
1325 | kill_fasync(&fasync, SIGIO, POLL_OUT); |
1326 | } | |
1327 | ||
a283b5c4 | 1328 | return ibytes; |
1da177e4 LT |
1329 | } |
1330 | ||
19fa5be1 | 1331 | /* |
118a4417 | 1332 | * This function does the actual extraction for extract_entropy. |
19fa5be1 GP |
1333 | * |
1334 | * Note: we assume that .poolwords is a multiple of 16 words. | |
1335 | */ | |
90ed1e67 | 1336 | static void extract_buf(u8 *out) |
1da177e4 | 1337 | { |
9f9eff85 JD |
1338 | struct blake2s_state state __aligned(__alignof__(unsigned long)); |
1339 | u8 hash[BLAKE2S_HASH_SIZE]; | |
1340 | unsigned long *salt; | |
902c098a | 1341 | unsigned long flags; |
1da177e4 | 1342 | |
9f9eff85 JD |
1343 | blake2s_init(&state, sizeof(hash)); |
1344 | ||
85a1f777 | 1345 | /* |
dfd38750 | 1346 | * If we have an architectural hardware random number |
9f9eff85 | 1347 | * generator, use it for BLAKE2's salt & personal fields. |
85a1f777 | 1348 | */ |
9f9eff85 JD |
1349 | for (salt = (unsigned long *)&state.h[4]; |
1350 | salt < (unsigned long *)&state.h[8]; ++salt) { | |
85a1f777 TT |
1351 | unsigned long v; |
1352 | if (!arch_get_random_long(&v)) | |
1353 | break; | |
9f9eff85 | 1354 | *salt ^= v; |
85a1f777 TT |
1355 | } |
1356 | ||
9f9eff85 | 1357 | /* Generate a hash across the pool */ |
90ed1e67 | 1358 | spin_lock_irqsave(&input_pool.lock, flags); |
6c0eace6 | 1359 | blake2s_update(&state, (const u8 *)input_pool_data, POOL_BYTES); |
9f9eff85 | 1360 | blake2s_final(&state, hash); /* final zeros out state */ |
46884442 | 1361 | |
1da177e4 | 1362 | /* |
1c0ad3d4 MM |
1363 | * We mix the hash back into the pool to prevent backtracking |
1364 | * attacks (where the attacker knows the state of the pool | |
1365 | * plus the current outputs, and attempts to find previous | |
9f9eff85 JD |
1366 | * outputs), unless the hash function can be inverted. By |
1367 | * mixing at least a hash worth of hash data back, we make | |
1c0ad3d4 MM |
1368 | * brute-forcing the feedback as hard as brute-forcing the |
1369 | * hash. | |
1da177e4 | 1370 | */ |
90ed1e67 JD |
1371 | __mix_pool_bytes(hash, sizeof(hash)); |
1372 | spin_unlock_irqrestore(&input_pool.lock, flags); | |
1da177e4 | 1373 | |
9f9eff85 JD |
1374 | /* Note that EXTRACT_SIZE is half of hash size here, because above |
1375 | * we've dumped the full length back into mixer. By reducing the | |
1376 | * amount that we emit, we retain a level of forward secrecy. | |
1da177e4 | 1377 | */ |
9f9eff85 JD |
1378 | memcpy(out, hash, EXTRACT_SIZE); |
1379 | memzero_explicit(hash, sizeof(hash)); | |
1da177e4 LT |
1380 | } |
1381 | ||
90ed1e67 | 1382 | static ssize_t _extract_entropy(void *buf, size_t nbytes) |
e192be9d TT |
1383 | { |
1384 | ssize_t ret = 0, i; | |
d38bb085 | 1385 | u8 tmp[EXTRACT_SIZE]; |
e192be9d TT |
1386 | |
1387 | while (nbytes) { | |
90ed1e67 | 1388 | extract_buf(tmp); |
e192be9d TT |
1389 | i = min_t(int, nbytes, EXTRACT_SIZE); |
1390 | memcpy(buf, tmp, i); | |
1391 | nbytes -= i; | |
1392 | buf += i; | |
1393 | ret += i; | |
1394 | } | |
1395 | ||
1396 | /* Wipe data just returned from memory */ | |
1397 | memzero_explicit(tmp, sizeof(tmp)); | |
1398 | ||
1399 | return ret; | |
1400 | } | |
1401 | ||
19fa5be1 GP |
1402 | /* |
1403 | * This function extracts randomness from the "entropy pool", and | |
1404 | * returns it in a buffer. | |
1405 | * | |
1406 | * The min parameter specifies the minimum amount we can pull before | |
8b2d953b | 1407 | * failing to avoid races that defeat catastrophic reseeding. |
19fa5be1 | 1408 | */ |
90ed1e67 | 1409 | static ssize_t extract_entropy(void *buf, size_t nbytes, int min) |
1da177e4 | 1410 | { |
b3d51c1f | 1411 | trace_extract_entropy(nbytes, POOL_ENTROPY_BITS(), _RET_IP_); |
90ed1e67 JD |
1412 | nbytes = account(nbytes, min); |
1413 | return _extract_entropy(buf, nbytes); | |
1da177e4 LT |
1414 | } |
1415 | ||
eecabf56 | 1416 | #define warn_unseeded_randomness(previous) \ |
248045b8 | 1417 | _warn_unseeded_randomness(__func__, (void *)_RET_IP_, (previous)) |
eecabf56 | 1418 | |
248045b8 | 1419 | static void _warn_unseeded_randomness(const char *func_name, void *caller, void **previous) |
eecabf56 TT |
1420 | { |
1421 | #ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM | |
1422 | const bool print_once = false; | |
1423 | #else | |
1424 | static bool print_once __read_mostly; | |
1425 | #endif | |
1426 | ||
248045b8 | 1427 | if (print_once || crng_ready() || |
eecabf56 TT |
1428 | (previous && (caller == READ_ONCE(*previous)))) |
1429 | return; | |
1430 | WRITE_ONCE(*previous, caller); | |
1431 | #ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM | |
1432 | print_once = true; | |
1433 | #endif | |
4e00b339 | 1434 | if (__ratelimit(&unseeded_warning)) |
248045b8 JD |
1435 | printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", |
1436 | func_name, caller, crng_init); | |
eecabf56 TT |
1437 | } |
1438 | ||
1da177e4 LT |
1439 | /* |
1440 | * This function is the exported kernel interface. It returns some | |
c2557a30 | 1441 | * number of good random numbers, suitable for key generation, seeding |
18e9cea7 GP |
1442 | * TCP sequence numbers, etc. It does not rely on the hardware random |
1443 | * number generator. For random bytes direct from the hardware RNG | |
e297a783 JD |
1444 | * (when available), use get_random_bytes_arch(). In order to ensure |
1445 | * that the randomness provided by this function is okay, the function | |
1446 | * wait_for_random_bytes() should be called and return 0 at least once | |
1447 | * at any point prior. | |
1da177e4 | 1448 | */ |
eecabf56 | 1449 | static void _get_random_bytes(void *buf, int nbytes) |
c2557a30 | 1450 | { |
d38bb085 | 1451 | u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4); |
e192be9d | 1452 | |
5910895f | 1453 | trace_get_random_bytes(nbytes, _RET_IP_); |
e192be9d | 1454 | |
1ca1b917 | 1455 | while (nbytes >= CHACHA_BLOCK_SIZE) { |
e192be9d | 1456 | extract_crng(buf); |
1ca1b917 EB |
1457 | buf += CHACHA_BLOCK_SIZE; |
1458 | nbytes -= CHACHA_BLOCK_SIZE; | |
e192be9d TT |
1459 | } |
1460 | ||
1461 | if (nbytes > 0) { | |
1462 | extract_crng(tmp); | |
1463 | memcpy(buf, tmp, nbytes); | |
c92e040d TT |
1464 | crng_backtrack_protect(tmp, nbytes); |
1465 | } else | |
1ca1b917 | 1466 | crng_backtrack_protect(tmp, CHACHA_BLOCK_SIZE); |
c92e040d | 1467 | memzero_explicit(tmp, sizeof(tmp)); |
c2557a30 | 1468 | } |
eecabf56 TT |
1469 | |
1470 | void get_random_bytes(void *buf, int nbytes) | |
1471 | { | |
1472 | static void *previous; | |
1473 | ||
1474 | warn_unseeded_randomness(&previous); | |
1475 | _get_random_bytes(buf, nbytes); | |
1476 | } | |
c2557a30 TT |
1477 | EXPORT_SYMBOL(get_random_bytes); |
1478 | ||
50ee7529 LT |
1479 | /* |
1480 | * Each time the timer fires, we expect that we got an unpredictable | |
1481 | * jump in the cycle counter. Even if the timer is running on another | |
1482 | * CPU, the timer activity will be touching the stack of the CPU that is | |
1483 | * generating entropy.. | |
1484 | * | |
1485 | * Note that we don't re-arm the timer in the timer itself - we are | |
1486 | * happy to be scheduled away, since that just makes the load more | |
1487 | * complex, but we do not want the timer to keep ticking unless the | |
1488 | * entropy loop is running. | |
1489 | * | |
1490 | * So the re-arming always happens in the entropy loop itself. | |
1491 | */ | |
1492 | static void entropy_timer(struct timer_list *t) | |
1493 | { | |
90ed1e67 | 1494 | credit_entropy_bits(1); |
50ee7529 LT |
1495 | } |
1496 | ||
1497 | /* | |
1498 | * If we have an actual cycle counter, see if we can | |
1499 | * generate enough entropy with timing noise | |
1500 | */ | |
1501 | static void try_to_generate_entropy(void) | |
1502 | { | |
1503 | struct { | |
1504 | unsigned long now; | |
1505 | struct timer_list timer; | |
1506 | } stack; | |
1507 | ||
1508 | stack.now = random_get_entropy(); | |
1509 | ||
1510 | /* Slow counter - or none. Don't even bother */ | |
1511 | if (stack.now == random_get_entropy()) | |
1512 | return; | |
1513 | ||
1514 | timer_setup_on_stack(&stack.timer, entropy_timer, 0); | |
1515 | while (!crng_ready()) { | |
1516 | if (!timer_pending(&stack.timer)) | |
248045b8 | 1517 | mod_timer(&stack.timer, jiffies + 1); |
90ed1e67 | 1518 | mix_pool_bytes(&stack.now, sizeof(stack.now)); |
50ee7529 LT |
1519 | schedule(); |
1520 | stack.now = random_get_entropy(); | |
1521 | } | |
1522 | ||
1523 | del_timer_sync(&stack.timer); | |
1524 | destroy_timer_on_stack(&stack.timer); | |
90ed1e67 | 1525 | mix_pool_bytes(&stack.now, sizeof(stack.now)); |
50ee7529 LT |
1526 | } |
1527 | ||
e297a783 JD |
1528 | /* |
1529 | * Wait for the urandom pool to be seeded and thus guaranteed to supply | |
1530 | * cryptographically secure random numbers. This applies to: the /dev/urandom | |
1531 | * device, the get_random_bytes function, and the get_random_{u32,u64,int,long} | |
1532 | * family of functions. Using any of these functions without first calling | |
1533 | * this function forfeits the guarantee of security. | |
1534 | * | |
1535 | * Returns: 0 if the urandom pool has been seeded. | |
1536 | * -ERESTARTSYS if the function was interrupted by a signal. | |
1537 | */ | |
1538 | int wait_for_random_bytes(void) | |
1539 | { | |
1540 | if (likely(crng_ready())) | |
1541 | return 0; | |
50ee7529 LT |
1542 | |
1543 | do { | |
1544 | int ret; | |
1545 | ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ); | |
1546 | if (ret) | |
1547 | return ret > 0 ? 0 : ret; | |
1548 | ||
1549 | try_to_generate_entropy(); | |
1550 | } while (!crng_ready()); | |
1551 | ||
1552 | return 0; | |
e297a783 JD |
1553 | } |
1554 | EXPORT_SYMBOL(wait_for_random_bytes); | |
1555 | ||
9a47249d JD |
1556 | /* |
1557 | * Returns whether or not the urandom pool has been seeded and thus guaranteed | |
1558 | * to supply cryptographically secure random numbers. This applies to: the | |
1559 | * /dev/urandom device, the get_random_bytes function, and the get_random_{u32, | |
1560 | * ,u64,int,long} family of functions. | |
1561 | * | |
1562 | * Returns: true if the urandom pool has been seeded. | |
1563 | * false if the urandom pool has not been seeded. | |
1564 | */ | |
1565 | bool rng_is_initialized(void) | |
1566 | { | |
1567 | return crng_ready(); | |
1568 | } | |
1569 | EXPORT_SYMBOL(rng_is_initialized); | |
1570 | ||
205a525c HX |
1571 | /* |
1572 | * Add a callback function that will be invoked when the nonblocking | |
1573 | * pool is initialised. | |
1574 | * | |
1575 | * returns: 0 if callback is successfully added | |
1576 | * -EALREADY if pool is already initialised (callback not called) | |
1577 | * -ENOENT if module for callback is not alive | |
1578 | */ | |
1579 | int add_random_ready_callback(struct random_ready_callback *rdy) | |
1580 | { | |
1581 | struct module *owner; | |
1582 | unsigned long flags; | |
1583 | int err = -EALREADY; | |
1584 | ||
e192be9d | 1585 | if (crng_ready()) |
205a525c HX |
1586 | return err; |
1587 | ||
1588 | owner = rdy->owner; | |
1589 | if (!try_module_get(owner)) | |
1590 | return -ENOENT; | |
1591 | ||
1592 | spin_lock_irqsave(&random_ready_list_lock, flags); | |
e192be9d | 1593 | if (crng_ready()) |
205a525c HX |
1594 | goto out; |
1595 | ||
1596 | owner = NULL; | |
1597 | ||
1598 | list_add(&rdy->list, &random_ready_list); | |
1599 | err = 0; | |
1600 | ||
1601 | out: | |
1602 | spin_unlock_irqrestore(&random_ready_list_lock, flags); | |
1603 | ||
1604 | module_put(owner); | |
1605 | ||
1606 | return err; | |
1607 | } | |
1608 | EXPORT_SYMBOL(add_random_ready_callback); | |
1609 | ||
1610 | /* | |
1611 | * Delete a previously registered readiness callback function. | |
1612 | */ | |
1613 | void del_random_ready_callback(struct random_ready_callback *rdy) | |
1614 | { | |
1615 | unsigned long flags; | |
1616 | struct module *owner = NULL; | |
1617 | ||
1618 | spin_lock_irqsave(&random_ready_list_lock, flags); | |
1619 | if (!list_empty(&rdy->list)) { | |
1620 | list_del_init(&rdy->list); | |
1621 | owner = rdy->owner; | |
1622 | } | |
1623 | spin_unlock_irqrestore(&random_ready_list_lock, flags); | |
1624 | ||
1625 | module_put(owner); | |
1626 | } | |
1627 | EXPORT_SYMBOL(del_random_ready_callback); | |
1628 | ||
c2557a30 TT |
1629 | /* |
1630 | * This function will use the architecture-specific hardware random | |
1631 | * number generator if it is available. The arch-specific hw RNG will | |
1632 | * almost certainly be faster than what we can do in software, but it | |
1633 | * is impossible to verify that it is implemented securely (as | |
1634 | * opposed, to, say, the AES encryption of a sequence number using a | |
1635 | * key known by the NSA). So it's useful if we need the speed, but | |
1636 | * only if we're willing to trust the hardware manufacturer not to | |
1637 | * have put in a back door. | |
753d433b TH |
1638 | * |
1639 | * Return number of bytes filled in. | |
c2557a30 | 1640 | */ |
753d433b | 1641 | int __must_check get_random_bytes_arch(void *buf, int nbytes) |
1da177e4 | 1642 | { |
753d433b | 1643 | int left = nbytes; |
d38bb085 | 1644 | u8 *p = buf; |
63d77173 | 1645 | |
753d433b TH |
1646 | trace_get_random_bytes_arch(left, _RET_IP_); |
1647 | while (left) { | |
63d77173 | 1648 | unsigned long v; |
753d433b | 1649 | int chunk = min_t(int, left, sizeof(unsigned long)); |
c2557a30 | 1650 | |
63d77173 PA |
1651 | if (!arch_get_random_long(&v)) |
1652 | break; | |
8ddd6efa | 1653 | |
bd29e568 | 1654 | memcpy(p, &v, chunk); |
63d77173 | 1655 | p += chunk; |
753d433b | 1656 | left -= chunk; |
63d77173 PA |
1657 | } |
1658 | ||
753d433b | 1659 | return nbytes - left; |
1da177e4 | 1660 | } |
c2557a30 TT |
1661 | EXPORT_SYMBOL(get_random_bytes_arch); |
1662 | ||
1da177e4 LT |
1663 | /* |
1664 | * init_std_data - initialize pool with system data | |
1665 | * | |
1da177e4 LT |
1666 | * This function clears the pool's entropy count and mixes some system |
1667 | * data into the pool to prepare it for use. The pool is not cleared | |
1668 | * as that can only decrease the entropy in the pool. | |
1669 | */ | |
90ed1e67 | 1670 | static void __init init_std_data(void) |
1da177e4 | 1671 | { |
3e88bdff | 1672 | int i; |
902c098a TT |
1673 | ktime_t now = ktime_get_real(); |
1674 | unsigned long rv; | |
1da177e4 | 1675 | |
90ed1e67 | 1676 | mix_pool_bytes(&now, sizeof(now)); |
91ec0fe1 | 1677 | for (i = POOL_BYTES; i > 0; i -= sizeof(rv)) { |
83664a69 PA |
1678 | if (!arch_get_random_seed_long(&rv) && |
1679 | !arch_get_random_long(&rv)) | |
ae9ecd92 | 1680 | rv = random_get_entropy(); |
90ed1e67 | 1681 | mix_pool_bytes(&rv, sizeof(rv)); |
3e88bdff | 1682 | } |
90ed1e67 | 1683 | mix_pool_bytes(utsname(), sizeof(*(utsname()))); |
1da177e4 LT |
1684 | } |
1685 | ||
cbc96b75 TL |
1686 | /* |
1687 | * Note that setup_arch() may call add_device_randomness() | |
1688 | * long before we get here. This allows seeding of the pools | |
1689 | * with some platform dependent data very early in the boot | |
1690 | * process. But it limits our options here. We must use | |
1691 | * statically allocated structures that already have all | |
1692 | * initializations complete at compile time. We should also | |
1693 | * take care not to overwrite the precious per platform data | |
1694 | * we were given. | |
1695 | */ | |
d5553523 | 1696 | int __init rand_initialize(void) |
1da177e4 | 1697 | { |
90ed1e67 | 1698 | init_std_data(); |
f7e67b8e DB |
1699 | if (crng_need_final_init) |
1700 | crng_finalize_init(&primary_crng); | |
ebf76063 | 1701 | crng_initialize_primary(); |
d848e5f8 | 1702 | crng_global_init_time = jiffies; |
4e00b339 TT |
1703 | if (ratelimit_disable) { |
1704 | urandom_warning.interval = 0; | |
1705 | unseeded_warning.interval = 0; | |
1706 | } | |
1da177e4 LT |
1707 | return 0; |
1708 | } | |
1da177e4 | 1709 | |
9361401e | 1710 | #ifdef CONFIG_BLOCK |
1da177e4 LT |
1711 | void rand_initialize_disk(struct gendisk *disk) |
1712 | { | |
1713 | struct timer_rand_state *state; | |
1714 | ||
1715 | /* | |
f8595815 | 1716 | * If kzalloc returns null, we just won't use that entropy |
1da177e4 LT |
1717 | * source. |
1718 | */ | |
f8595815 | 1719 | state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); |
644008df TT |
1720 | if (state) { |
1721 | state->last_time = INITIAL_JIFFIES; | |
1da177e4 | 1722 | disk->random = state; |
644008df | 1723 | } |
1da177e4 | 1724 | } |
9361401e | 1725 | #endif |
1da177e4 | 1726 | |
248045b8 JD |
1727 | static ssize_t urandom_read_nowarn(struct file *file, char __user *buf, |
1728 | size_t nbytes, loff_t *ppos) | |
c6f1deb1 AL |
1729 | { |
1730 | int ret; | |
1731 | ||
b3d51c1f | 1732 | nbytes = min_t(size_t, nbytes, INT_MAX >> (POOL_ENTROPY_SHIFT + 3)); |
c6f1deb1 | 1733 | ret = extract_crng_user(buf, nbytes); |
b3d51c1f | 1734 | trace_urandom_read(8 * nbytes, 0, POOL_ENTROPY_BITS()); |
c6f1deb1 AL |
1735 | return ret; |
1736 | } | |
1737 | ||
248045b8 JD |
1738 | static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, |
1739 | loff_t *ppos) | |
1da177e4 | 1740 | { |
9b4d0087 | 1741 | static int maxwarn = 10; |
301f0595 | 1742 | |
e192be9d | 1743 | if (!crng_ready() && maxwarn > 0) { |
9b4d0087 | 1744 | maxwarn--; |
4e00b339 | 1745 | if (__ratelimit(&urandom_warning)) |
12cd53af YL |
1746 | pr_notice("%s: uninitialized urandom read (%zd bytes read)\n", |
1747 | current->comm, nbytes); | |
9b4d0087 | 1748 | } |
c6f1deb1 AL |
1749 | |
1750 | return urandom_read_nowarn(file, buf, nbytes, ppos); | |
1da177e4 LT |
1751 | } |
1752 | ||
248045b8 JD |
1753 | static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, |
1754 | loff_t *ppos) | |
30c08efe AL |
1755 | { |
1756 | int ret; | |
1757 | ||
1758 | ret = wait_for_random_bytes(); | |
1759 | if (ret != 0) | |
1760 | return ret; | |
1761 | return urandom_read_nowarn(file, buf, nbytes, ppos); | |
1762 | } | |
1763 | ||
248045b8 | 1764 | static __poll_t random_poll(struct file *file, poll_table *wait) |
1da177e4 | 1765 | { |
a11e1d43 | 1766 | __poll_t mask; |
1da177e4 | 1767 | |
30c08efe | 1768 | poll_wait(file, &crng_init_wait, wait); |
a11e1d43 LT |
1769 | poll_wait(file, &random_write_wait, wait); |
1770 | mask = 0; | |
30c08efe | 1771 | if (crng_ready()) |
a9a08845 | 1772 | mask |= EPOLLIN | EPOLLRDNORM; |
b3d51c1f | 1773 | if (POOL_ENTROPY_BITS() < random_write_wakeup_bits) |
a9a08845 | 1774 | mask |= EPOLLOUT | EPOLLWRNORM; |
1da177e4 LT |
1775 | return mask; |
1776 | } | |
1777 | ||
248045b8 | 1778 | static int write_pool(const char __user *buffer, size_t count) |
1da177e4 | 1779 | { |
1da177e4 | 1780 | size_t bytes; |
d38bb085 | 1781 | u32 t, buf[16]; |
1da177e4 | 1782 | const char __user *p = buffer; |
1da177e4 | 1783 | |
7f397dcd | 1784 | while (count > 0) { |
81e69df3 TT |
1785 | int b, i = 0; |
1786 | ||
7f397dcd MM |
1787 | bytes = min(count, sizeof(buf)); |
1788 | if (copy_from_user(&buf, p, bytes)) | |
1789 | return -EFAULT; | |
1da177e4 | 1790 | |
d38bb085 | 1791 | for (b = bytes; b > 0; b -= sizeof(u32), i++) { |
81e69df3 TT |
1792 | if (!arch_get_random_int(&t)) |
1793 | break; | |
1794 | buf[i] ^= t; | |
1795 | } | |
1796 | ||
7f397dcd | 1797 | count -= bytes; |
1da177e4 LT |
1798 | p += bytes; |
1799 | ||
90ed1e67 | 1800 | mix_pool_bytes(buf, bytes); |
91f3f1e3 | 1801 | cond_resched(); |
1da177e4 | 1802 | } |
7f397dcd MM |
1803 | |
1804 | return 0; | |
1805 | } | |
1806 | ||
90b75ee5 MM |
1807 | static ssize_t random_write(struct file *file, const char __user *buffer, |
1808 | size_t count, loff_t *ppos) | |
7f397dcd MM |
1809 | { |
1810 | size_t ret; | |
7f397dcd | 1811 | |
90ed1e67 | 1812 | ret = write_pool(buffer, count); |
7f397dcd MM |
1813 | if (ret) |
1814 | return ret; | |
1815 | ||
7f397dcd | 1816 | return (ssize_t)count; |
1da177e4 LT |
1817 | } |
1818 | ||
43ae4860 | 1819 | static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) |
1da177e4 LT |
1820 | { |
1821 | int size, ent_count; | |
1822 | int __user *p = (int __user *)arg; | |
1823 | int retval; | |
1824 | ||
1825 | switch (cmd) { | |
1826 | case RNDGETENTCNT: | |
43ae4860 | 1827 | /* inherently racy, no point locking */ |
b3d51c1f | 1828 | ent_count = POOL_ENTROPY_BITS(); |
a283b5c4 | 1829 | if (put_user(ent_count, p)) |
1da177e4 LT |
1830 | return -EFAULT; |
1831 | return 0; | |
1832 | case RNDADDTOENTCNT: | |
1833 | if (!capable(CAP_SYS_ADMIN)) | |
1834 | return -EPERM; | |
1835 | if (get_user(ent_count, p)) | |
1836 | return -EFAULT; | |
90ed1e67 | 1837 | return credit_entropy_bits_safe(ent_count); |
1da177e4 LT |
1838 | case RNDADDENTROPY: |
1839 | if (!capable(CAP_SYS_ADMIN)) | |
1840 | return -EPERM; | |
1841 | if (get_user(ent_count, p++)) | |
1842 | return -EFAULT; | |
1843 | if (ent_count < 0) | |
1844 | return -EINVAL; | |
1845 | if (get_user(size, p++)) | |
1846 | return -EFAULT; | |
90ed1e67 | 1847 | retval = write_pool((const char __user *)p, size); |
1da177e4 LT |
1848 | if (retval < 0) |
1849 | return retval; | |
90ed1e67 | 1850 | return credit_entropy_bits_safe(ent_count); |
1da177e4 LT |
1851 | case RNDZAPENTCNT: |
1852 | case RNDCLEARPOOL: | |
ae9ecd92 TT |
1853 | /* |
1854 | * Clear the entropy pool counters. We no longer clear | |
1855 | * the entropy pool, as that's silly. | |
1856 | */ | |
1da177e4 LT |
1857 | if (!capable(CAP_SYS_ADMIN)) |
1858 | return -EPERM; | |
042e293e JD |
1859 | if (xchg(&input_pool.entropy_count, 0) && random_write_wakeup_bits) { |
1860 | wake_up_interruptible(&random_write_wait); | |
1861 | kill_fasync(&fasync, SIGIO, POLL_OUT); | |
1862 | } | |
1da177e4 | 1863 | return 0; |
d848e5f8 TT |
1864 | case RNDRESEEDCRNG: |
1865 | if (!capable(CAP_SYS_ADMIN)) | |
1866 | return -EPERM; | |
1867 | if (crng_init < 2) | |
1868 | return -ENODATA; | |
90ed1e67 | 1869 | crng_reseed(&primary_crng, true); |
009ba856 | 1870 | WRITE_ONCE(crng_global_init_time, jiffies - 1); |
d848e5f8 | 1871 | return 0; |
1da177e4 LT |
1872 | default: |
1873 | return -EINVAL; | |
1874 | } | |
1875 | } | |
1876 | ||
9a6f70bb JD |
1877 | static int random_fasync(int fd, struct file *filp, int on) |
1878 | { | |
1879 | return fasync_helper(fd, filp, on, &fasync); | |
1880 | } | |
1881 | ||
2b8693c0 | 1882 | const struct file_operations random_fops = { |
248045b8 | 1883 | .read = random_read, |
1da177e4 | 1884 | .write = random_write, |
248045b8 | 1885 | .poll = random_poll, |
43ae4860 | 1886 | .unlocked_ioctl = random_ioctl, |
507e4e2b | 1887 | .compat_ioctl = compat_ptr_ioctl, |
9a6f70bb | 1888 | .fasync = random_fasync, |
6038f373 | 1889 | .llseek = noop_llseek, |
1da177e4 LT |
1890 | }; |
1891 | ||
2b8693c0 | 1892 | const struct file_operations urandom_fops = { |
248045b8 | 1893 | .read = urandom_read, |
1da177e4 | 1894 | .write = random_write, |
43ae4860 | 1895 | .unlocked_ioctl = random_ioctl, |
4aa37c46 | 1896 | .compat_ioctl = compat_ptr_ioctl, |
9a6f70bb | 1897 | .fasync = random_fasync, |
6038f373 | 1898 | .llseek = noop_llseek, |
1da177e4 LT |
1899 | }; |
1900 | ||
248045b8 JD |
1901 | SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, |
1902 | flags) | |
c6e9d6f3 | 1903 | { |
e297a783 JD |
1904 | int ret; |
1905 | ||
248045b8 | 1906 | if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE)) |
75551dbf AL |
1907 | return -EINVAL; |
1908 | ||
1909 | /* | |
1910 | * Requesting insecure and blocking randomness at the same time makes | |
1911 | * no sense. | |
1912 | */ | |
248045b8 | 1913 | if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM)) |
c6e9d6f3 TT |
1914 | return -EINVAL; |
1915 | ||
1916 | if (count > INT_MAX) | |
1917 | count = INT_MAX; | |
1918 | ||
75551dbf | 1919 | if (!(flags & GRND_INSECURE) && !crng_ready()) { |
c6e9d6f3 TT |
1920 | if (flags & GRND_NONBLOCK) |
1921 | return -EAGAIN; | |
e297a783 JD |
1922 | ret = wait_for_random_bytes(); |
1923 | if (unlikely(ret)) | |
1924 | return ret; | |
c6e9d6f3 | 1925 | } |
c6f1deb1 | 1926 | return urandom_read_nowarn(NULL, buf, count, NULL); |
c6e9d6f3 TT |
1927 | } |
1928 | ||
1da177e4 LT |
1929 | /******************************************************************** |
1930 | * | |
1931 | * Sysctl interface | |
1932 | * | |
1933 | ********************************************************************/ | |
1934 | ||
1935 | #ifdef CONFIG_SYSCTL | |
1936 | ||
1937 | #include <linux/sysctl.h> | |
1938 | ||
c95ea0c6 | 1939 | static int min_write_thresh; |
5b87adf3 | 1940 | static int max_write_thresh = POOL_BITS; |
db61ffe3 | 1941 | static int random_min_urandom_seed = 60; |
1da177e4 LT |
1942 | static char sysctl_bootid[16]; |
1943 | ||
1944 | /* | |
f22052b2 | 1945 | * This function is used to return both the bootid UUID, and random |
1da177e4 LT |
1946 | * UUID. The difference is in whether table->data is NULL; if it is, |
1947 | * then a new UUID is generated and returned to the user. | |
1948 | * | |
f22052b2 GP |
1949 | * If the user accesses this via the proc interface, the UUID will be |
1950 | * returned as an ASCII string in the standard UUID format; if via the | |
1951 | * sysctl system call, as 16 bytes of binary data. | |
1da177e4 | 1952 | */ |
248045b8 JD |
1953 | static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, |
1954 | size_t *lenp, loff_t *ppos) | |
1da177e4 | 1955 | { |
a151427e | 1956 | struct ctl_table fake_table; |
1da177e4 LT |
1957 | unsigned char buf[64], tmp_uuid[16], *uuid; |
1958 | ||
1959 | uuid = table->data; | |
1960 | if (!uuid) { | |
1961 | uuid = tmp_uuid; | |
1da177e4 | 1962 | generate_random_uuid(uuid); |
44e4360f MD |
1963 | } else { |
1964 | static DEFINE_SPINLOCK(bootid_spinlock); | |
1965 | ||
1966 | spin_lock(&bootid_spinlock); | |
1967 | if (!uuid[8]) | |
1968 | generate_random_uuid(uuid); | |
1969 | spin_unlock(&bootid_spinlock); | |
1970 | } | |
1da177e4 | 1971 | |
35900771 JP |
1972 | sprintf(buf, "%pU", uuid); |
1973 | ||
1da177e4 LT |
1974 | fake_table.data = buf; |
1975 | fake_table.maxlen = sizeof(buf); | |
1976 | ||
8d65af78 | 1977 | return proc_dostring(&fake_table, write, buffer, lenp, ppos); |
1da177e4 LT |
1978 | } |
1979 | ||
a283b5c4 PA |
1980 | /* |
1981 | * Return entropy available scaled to integral bits | |
1982 | */ | |
248045b8 JD |
1983 | static int proc_do_entropy(struct ctl_table *table, int write, void *buffer, |
1984 | size_t *lenp, loff_t *ppos) | |
a283b5c4 | 1985 | { |
5eb10d91 | 1986 | struct ctl_table fake_table; |
a283b5c4 PA |
1987 | int entropy_count; |
1988 | ||
b3d51c1f | 1989 | entropy_count = *(int *)table->data >> POOL_ENTROPY_SHIFT; |
a283b5c4 PA |
1990 | |
1991 | fake_table.data = &entropy_count; | |
1992 | fake_table.maxlen = sizeof(entropy_count); | |
1993 | ||
1994 | return proc_dointvec(&fake_table, write, buffer, lenp, ppos); | |
1995 | } | |
1996 | ||
5b87adf3 | 1997 | static int sysctl_poolsize = POOL_BITS; |
5475e8f0 | 1998 | static struct ctl_table random_table[] = { |
1da177e4 | 1999 | { |
1da177e4 LT |
2000 | .procname = "poolsize", |
2001 | .data = &sysctl_poolsize, | |
2002 | .maxlen = sizeof(int), | |
2003 | .mode = 0444, | |
6d456111 | 2004 | .proc_handler = proc_dointvec, |
1da177e4 LT |
2005 | }, |
2006 | { | |
1da177e4 LT |
2007 | .procname = "entropy_avail", |
2008 | .maxlen = sizeof(int), | |
2009 | .mode = 0444, | |
a283b5c4 | 2010 | .proc_handler = proc_do_entropy, |
1da177e4 LT |
2011 | .data = &input_pool.entropy_count, |
2012 | }, | |
1da177e4 | 2013 | { |
1da177e4 | 2014 | .procname = "write_wakeup_threshold", |
2132a96f | 2015 | .data = &random_write_wakeup_bits, |
1da177e4 LT |
2016 | .maxlen = sizeof(int), |
2017 | .mode = 0644, | |
6d456111 | 2018 | .proc_handler = proc_dointvec_minmax, |
1da177e4 LT |
2019 | .extra1 = &min_write_thresh, |
2020 | .extra2 = &max_write_thresh, | |
2021 | }, | |
f5c2742c TT |
2022 | { |
2023 | .procname = "urandom_min_reseed_secs", | |
2024 | .data = &random_min_urandom_seed, | |
2025 | .maxlen = sizeof(int), | |
2026 | .mode = 0644, | |
2027 | .proc_handler = proc_dointvec, | |
2028 | }, | |
1da177e4 | 2029 | { |
1da177e4 LT |
2030 | .procname = "boot_id", |
2031 | .data = &sysctl_bootid, | |
2032 | .maxlen = 16, | |
2033 | .mode = 0444, | |
6d456111 | 2034 | .proc_handler = proc_do_uuid, |
1da177e4 LT |
2035 | }, |
2036 | { | |
1da177e4 LT |
2037 | .procname = "uuid", |
2038 | .maxlen = 16, | |
2039 | .mode = 0444, | |
6d456111 | 2040 | .proc_handler = proc_do_uuid, |
1da177e4 | 2041 | }, |
43759d4f TT |
2042 | #ifdef ADD_INTERRUPT_BENCH |
2043 | { | |
2044 | .procname = "add_interrupt_avg_cycles", | |
2045 | .data = &avg_cycles, | |
2046 | .maxlen = sizeof(avg_cycles), | |
2047 | .mode = 0444, | |
2048 | .proc_handler = proc_doulongvec_minmax, | |
2049 | }, | |
2050 | { | |
2051 | .procname = "add_interrupt_avg_deviation", | |
2052 | .data = &avg_deviation, | |
2053 | .maxlen = sizeof(avg_deviation), | |
2054 | .mode = 0444, | |
2055 | .proc_handler = proc_doulongvec_minmax, | |
2056 | }, | |
2057 | #endif | |
894d2491 | 2058 | { } |
1da177e4 | 2059 | }; |
5475e8f0 XN |
2060 | |
2061 | /* | |
2062 | * rand_initialize() is called before sysctl_init(), | |
2063 | * so we cannot call register_sysctl_init() in rand_initialize() | |
2064 | */ | |
2065 | static int __init random_sysctls_init(void) | |
2066 | { | |
2067 | register_sysctl_init("kernel/random", random_table); | |
2068 | return 0; | |
2069 | } | |
2070 | device_initcall(random_sysctls_init); | |
248045b8 | 2071 | #endif /* CONFIG_SYSCTL */ |
1da177e4 | 2072 | |
f5b98461 JD |
2073 | struct batched_entropy { |
2074 | union { | |
1ca1b917 EB |
2075 | u64 entropy_u64[CHACHA_BLOCK_SIZE / sizeof(u64)]; |
2076 | u32 entropy_u32[CHACHA_BLOCK_SIZE / sizeof(u32)]; | |
f5b98461 JD |
2077 | }; |
2078 | unsigned int position; | |
b7d5dc21 | 2079 | spinlock_t batch_lock; |
f5b98461 | 2080 | }; |
b1132dea | 2081 | |
1da177e4 | 2082 | /* |
f5b98461 | 2083 | * Get a random word for internal kernel use only. The quality of the random |
69efea71 JD |
2084 | * number is good as /dev/urandom, but there is no backtrack protection, with |
2085 | * the goal of being quite fast and not depleting entropy. In order to ensure | |
e297a783 | 2086 | * that the randomness provided by this function is okay, the function |
69efea71 JD |
2087 | * wait_for_random_bytes() should be called and return 0 at least once at any |
2088 | * point prior. | |
1da177e4 | 2089 | */ |
b7d5dc21 | 2090 | static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = { |
248045b8 | 2091 | .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u64.lock), |
b7d5dc21 SAS |
2092 | }; |
2093 | ||
c440408c | 2094 | u64 get_random_u64(void) |
1da177e4 | 2095 | { |
c440408c | 2096 | u64 ret; |
b7d5dc21 | 2097 | unsigned long flags; |
f5b98461 | 2098 | struct batched_entropy *batch; |
eecabf56 | 2099 | static void *previous; |
8a0a9bd4 | 2100 | |
eecabf56 | 2101 | warn_unseeded_randomness(&previous); |
d06bfd19 | 2102 | |
b7d5dc21 SAS |
2103 | batch = raw_cpu_ptr(&batched_entropy_u64); |
2104 | spin_lock_irqsave(&batch->batch_lock, flags); | |
c440408c | 2105 | if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) { |
a5e9f557 | 2106 | extract_crng((u8 *)batch->entropy_u64); |
f5b98461 JD |
2107 | batch->position = 0; |
2108 | } | |
c440408c | 2109 | ret = batch->entropy_u64[batch->position++]; |
b7d5dc21 | 2110 | spin_unlock_irqrestore(&batch->batch_lock, flags); |
8a0a9bd4 | 2111 | return ret; |
1da177e4 | 2112 | } |
c440408c | 2113 | EXPORT_SYMBOL(get_random_u64); |
1da177e4 | 2114 | |
b7d5dc21 | 2115 | static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = { |
248045b8 | 2116 | .batch_lock = __SPIN_LOCK_UNLOCKED(batched_entropy_u32.lock), |
b7d5dc21 | 2117 | }; |
c440408c | 2118 | u32 get_random_u32(void) |
f5b98461 | 2119 | { |
c440408c | 2120 | u32 ret; |
b7d5dc21 | 2121 | unsigned long flags; |
f5b98461 | 2122 | struct batched_entropy *batch; |
eecabf56 | 2123 | static void *previous; |
ec9ee4ac | 2124 | |
eecabf56 | 2125 | warn_unseeded_randomness(&previous); |
d06bfd19 | 2126 | |
b7d5dc21 SAS |
2127 | batch = raw_cpu_ptr(&batched_entropy_u32); |
2128 | spin_lock_irqsave(&batch->batch_lock, flags); | |
c440408c | 2129 | if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) { |
a5e9f557 | 2130 | extract_crng((u8 *)batch->entropy_u32); |
f5b98461 JD |
2131 | batch->position = 0; |
2132 | } | |
c440408c | 2133 | ret = batch->entropy_u32[batch->position++]; |
b7d5dc21 | 2134 | spin_unlock_irqrestore(&batch->batch_lock, flags); |
ec9ee4ac DC |
2135 | return ret; |
2136 | } | |
c440408c | 2137 | EXPORT_SYMBOL(get_random_u32); |
ec9ee4ac | 2138 | |
b169c13d JD |
2139 | /* It's important to invalidate all potential batched entropy that might |
2140 | * be stored before the crng is initialized, which we can do lazily by | |
2141 | * simply resetting the counter to zero so that it's re-extracted on the | |
2142 | * next usage. */ | |
2143 | static void invalidate_batched_entropy(void) | |
2144 | { | |
2145 | int cpu; | |
2146 | unsigned long flags; | |
2147 | ||
248045b8 | 2148 | for_each_possible_cpu(cpu) { |
b7d5dc21 SAS |
2149 | struct batched_entropy *batched_entropy; |
2150 | ||
2151 | batched_entropy = per_cpu_ptr(&batched_entropy_u32, cpu); | |
2152 | spin_lock_irqsave(&batched_entropy->batch_lock, flags); | |
2153 | batched_entropy->position = 0; | |
2154 | spin_unlock(&batched_entropy->batch_lock); | |
2155 | ||
2156 | batched_entropy = per_cpu_ptr(&batched_entropy_u64, cpu); | |
2157 | spin_lock(&batched_entropy->batch_lock); | |
2158 | batched_entropy->position = 0; | |
2159 | spin_unlock_irqrestore(&batched_entropy->batch_lock, flags); | |
b169c13d | 2160 | } |
b169c13d JD |
2161 | } |
2162 | ||
99fdafde JC |
2163 | /** |
2164 | * randomize_page - Generate a random, page aligned address | |
2165 | * @start: The smallest acceptable address the caller will take. | |
2166 | * @range: The size of the area, starting at @start, within which the | |
2167 | * random address must fall. | |
2168 | * | |
2169 | * If @start + @range would overflow, @range is capped. | |
2170 | * | |
2171 | * NOTE: Historical use of randomize_range, which this replaces, presumed that | |
2172 | * @start was already page aligned. We now align it regardless. | |
2173 | * | |
2174 | * Return: A page aligned address within [start, start + range). On error, | |
2175 | * @start is returned. | |
2176 | */ | |
248045b8 | 2177 | unsigned long randomize_page(unsigned long start, unsigned long range) |
99fdafde JC |
2178 | { |
2179 | if (!PAGE_ALIGNED(start)) { | |
2180 | range -= PAGE_ALIGN(start) - start; | |
2181 | start = PAGE_ALIGN(start); | |
2182 | } | |
2183 | ||
2184 | if (start > ULONG_MAX - range) | |
2185 | range = ULONG_MAX - start; | |
2186 | ||
2187 | range >>= PAGE_SHIFT; | |
2188 | ||
2189 | if (range == 0) | |
2190 | return start; | |
2191 | ||
2192 | return start + (get_random_long() % range << PAGE_SHIFT); | |
2193 | } | |
2194 | ||
c84dbf61 TD |
2195 | /* Interface for in-kernel drivers of true hardware RNGs. |
2196 | * Those devices may produce endless random bits and will be throttled | |
2197 | * when our pool is full. | |
2198 | */ | |
2199 | void add_hwgenerator_randomness(const char *buffer, size_t count, | |
2200 | size_t entropy) | |
2201 | { | |
43838a23 | 2202 | if (unlikely(crng_init == 0)) { |
73c7733f | 2203 | size_t ret = crng_fast_load(buffer, count); |
90ed1e67 | 2204 | mix_pool_bytes(buffer, ret); |
73c7733f JD |
2205 | count -= ret; |
2206 | buffer += ret; | |
2207 | if (!count || crng_init == 0) | |
2208 | return; | |
3371f3da | 2209 | } |
e192be9d | 2210 | |
c321e907 | 2211 | /* Throttle writing if we're above the trickle threshold. |
e192be9d | 2212 | * We'll be woken up again once below random_write_wakeup_thresh, |
c321e907 DB |
2213 | * when the calling thread is about to terminate, or once |
2214 | * CRNG_RESEED_INTERVAL has lapsed. | |
e192be9d | 2215 | */ |
c321e907 | 2216 | wait_event_interruptible_timeout(random_write_wait, |
f7e67b8e | 2217 | !system_wq || kthread_should_stop() || |
c321e907 DB |
2218 | POOL_ENTROPY_BITS() <= random_write_wakeup_bits, |
2219 | CRNG_RESEED_INTERVAL); | |
90ed1e67 JD |
2220 | mix_pool_bytes(buffer, count); |
2221 | credit_entropy_bits(entropy); | |
c84dbf61 TD |
2222 | } |
2223 | EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); | |
428826f5 HYW |
2224 | |
2225 | /* Handle random seed passed by bootloader. | |
2226 | * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise | |
2227 | * it would be regarded as device data. | |
2228 | * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER. | |
2229 | */ | |
2230 | void add_bootloader_randomness(const void *buf, unsigned int size) | |
2231 | { | |
2232 | if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER)) | |
2233 | add_hwgenerator_randomness(buf, size, size * 8); | |
2234 | else | |
2235 | add_device_randomness(buf, size); | |
2236 | } | |
3fd57e7a | 2237 | EXPORT_SYMBOL_GPL(add_bootloader_randomness); |