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1da177e4 LT |
1 | /* |
2 | * random.c -- A strong random number generator | |
3 | * | |
9e95ce27 | 4 | * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005 |
1da177e4 LT |
5 | * |
6 | * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All | |
7 | * rights reserved. | |
8 | * | |
9 | * Redistribution and use in source and binary forms, with or without | |
10 | * modification, are permitted provided that the following conditions | |
11 | * are met: | |
12 | * 1. Redistributions of source code must retain the above copyright | |
13 | * notice, and the entire permission notice in its entirety, | |
14 | * including the disclaimer of warranties. | |
15 | * 2. Redistributions in binary form must reproduce the above copyright | |
16 | * notice, this list of conditions and the following disclaimer in the | |
17 | * documentation and/or other materials provided with the distribution. | |
18 | * 3. The name of the author may not be used to endorse or promote | |
19 | * products derived from this software without specific prior | |
20 | * written permission. | |
21 | * | |
22 | * ALTERNATIVELY, this product may be distributed under the terms of | |
23 | * the GNU General Public License, in which case the provisions of the GPL are | |
24 | * required INSTEAD OF the above restrictions. (This clause is | |
25 | * necessary due to a potential bad interaction between the GPL and | |
26 | * the restrictions contained in a BSD-style copyright.) | |
27 | * | |
28 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED | |
29 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
30 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF | |
31 | * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE | |
32 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
33 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT | |
34 | * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR | |
35 | * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
36 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
37 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE | |
38 | * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH | |
39 | * DAMAGE. | |
40 | */ | |
41 | ||
42 | /* | |
43 | * (now, with legal B.S. out of the way.....) | |
44 | * | |
45 | * This routine gathers environmental noise from device drivers, etc., | |
46 | * and returns good random numbers, suitable for cryptographic use. | |
47 | * Besides the obvious cryptographic uses, these numbers are also good | |
48 | * for seeding TCP sequence numbers, and other places where it is | |
49 | * desirable to have numbers which are not only random, but hard to | |
50 | * predict by an attacker. | |
51 | * | |
52 | * Theory of operation | |
53 | * =================== | |
54 | * | |
55 | * Computers are very predictable devices. Hence it is extremely hard | |
56 | * to produce truly random numbers on a computer --- as opposed to | |
57 | * pseudo-random numbers, which can easily generated by using a | |
58 | * algorithm. Unfortunately, it is very easy for attackers to guess | |
59 | * the sequence of pseudo-random number generators, and for some | |
60 | * applications this is not acceptable. So instead, we must try to | |
61 | * gather "environmental noise" from the computer's environment, which | |
62 | * must be hard for outside attackers to observe, and use that to | |
63 | * generate random numbers. In a Unix environment, this is best done | |
64 | * from inside the kernel. | |
65 | * | |
66 | * Sources of randomness from the environment include inter-keyboard | |
67 | * timings, inter-interrupt timings from some interrupts, and other | |
68 | * events which are both (a) non-deterministic and (b) hard for an | |
69 | * outside observer to measure. Randomness from these sources are | |
70 | * added to an "entropy pool", which is mixed using a CRC-like function. | |
71 | * This is not cryptographically strong, but it is adequate assuming | |
72 | * the randomness is not chosen maliciously, and it is fast enough that | |
73 | * the overhead of doing it on every interrupt is very reasonable. | |
74 | * As random bytes are mixed into the entropy pool, the routines keep | |
75 | * an *estimate* of how many bits of randomness have been stored into | |
76 | * the random number generator's internal state. | |
77 | * | |
78 | * When random bytes are desired, they are obtained by taking the SHA | |
79 | * hash of the contents of the "entropy pool". The SHA hash avoids | |
80 | * exposing the internal state of the entropy pool. It is believed to | |
81 | * be computationally infeasible to derive any useful information | |
82 | * about the input of SHA from its output. Even if it is possible to | |
83 | * analyze SHA in some clever way, as long as the amount of data | |
84 | * returned from the generator is less than the inherent entropy in | |
85 | * the pool, the output data is totally unpredictable. For this | |
86 | * reason, the routine decreases its internal estimate of how many | |
87 | * bits of "true randomness" are contained in the entropy pool as it | |
88 | * outputs random numbers. | |
89 | * | |
90 | * If this estimate goes to zero, the routine can still generate | |
91 | * random numbers; however, an attacker may (at least in theory) be | |
92 | * able to infer the future output of the generator from prior | |
93 | * outputs. This requires successful cryptanalysis of SHA, which is | |
94 | * not believed to be feasible, but there is a remote possibility. | |
95 | * Nonetheless, these numbers should be useful for the vast majority | |
96 | * of purposes. | |
97 | * | |
98 | * Exported interfaces ---- output | |
99 | * =============================== | |
100 | * | |
101 | * There are three exported interfaces; the first is one designed to | |
102 | * be used from within the kernel: | |
103 | * | |
104 | * void get_random_bytes(void *buf, int nbytes); | |
105 | * | |
106 | * This interface will return the requested number of random bytes, | |
107 | * and place it in the requested buffer. | |
108 | * | |
109 | * The two other interfaces are two character devices /dev/random and | |
110 | * /dev/urandom. /dev/random is suitable for use when very high | |
111 | * quality randomness is desired (for example, for key generation or | |
112 | * one-time pads), as it will only return a maximum of the number of | |
113 | * bits of randomness (as estimated by the random number generator) | |
114 | * contained in the entropy pool. | |
115 | * | |
116 | * The /dev/urandom device does not have this limit, and will return | |
117 | * as many bytes as are requested. As more and more random bytes are | |
118 | * requested without giving time for the entropy pool to recharge, | |
119 | * this will result in random numbers that are merely cryptographically | |
120 | * strong. For many applications, however, this is acceptable. | |
121 | * | |
122 | * Exported interfaces ---- input | |
123 | * ============================== | |
124 | * | |
125 | * The current exported interfaces for gathering environmental noise | |
126 | * from the devices are: | |
127 | * | |
a2080a67 | 128 | * void add_device_randomness(const void *buf, unsigned int size); |
1da177e4 LT |
129 | * void add_input_randomness(unsigned int type, unsigned int code, |
130 | * unsigned int value); | |
775f4b29 | 131 | * void add_interrupt_randomness(int irq, int irq_flags); |
442a4fff | 132 | * void add_disk_randomness(struct gendisk *disk); |
1da177e4 | 133 | * |
a2080a67 LT |
134 | * add_device_randomness() is for adding data to the random pool that |
135 | * is likely to differ between two devices (or possibly even per boot). | |
136 | * This would be things like MAC addresses or serial numbers, or the | |
137 | * read-out of the RTC. This does *not* add any actual entropy to the | |
138 | * pool, but it initializes the pool to different values for devices | |
139 | * that might otherwise be identical and have very little entropy | |
140 | * available to them (particularly common in the embedded world). | |
141 | * | |
1da177e4 LT |
142 | * add_input_randomness() uses the input layer interrupt timing, as well as |
143 | * the event type information from the hardware. | |
144 | * | |
775f4b29 TT |
145 | * add_interrupt_randomness() uses the interrupt timing as random |
146 | * inputs to the entropy pool. Using the cycle counters and the irq source | |
147 | * as inputs, it feeds the randomness roughly once a second. | |
442a4fff JW |
148 | * |
149 | * add_disk_randomness() uses what amounts to the seek time of block | |
150 | * layer request events, on a per-disk_devt basis, as input to the | |
151 | * entropy pool. Note that high-speed solid state drives with very low | |
152 | * seek times do not make for good sources of entropy, as their seek | |
153 | * times are usually fairly consistent. | |
1da177e4 LT |
154 | * |
155 | * All of these routines try to estimate how many bits of randomness a | |
156 | * particular randomness source. They do this by keeping track of the | |
157 | * first and second order deltas of the event timings. | |
158 | * | |
159 | * Ensuring unpredictability at system startup | |
160 | * ============================================ | |
161 | * | |
162 | * When any operating system starts up, it will go through a sequence | |
163 | * of actions that are fairly predictable by an adversary, especially | |
164 | * if the start-up does not involve interaction with a human operator. | |
165 | * This reduces the actual number of bits of unpredictability in the | |
166 | * entropy pool below the value in entropy_count. In order to | |
167 | * counteract this effect, it helps to carry information in the | |
168 | * entropy pool across shut-downs and start-ups. To do this, put the | |
169 | * following lines an appropriate script which is run during the boot | |
170 | * sequence: | |
171 | * | |
172 | * echo "Initializing random number generator..." | |
173 | * random_seed=/var/run/random-seed | |
174 | * # Carry a random seed from start-up to start-up | |
175 | * # Load and then save the whole entropy pool | |
176 | * if [ -f $random_seed ]; then | |
177 | * cat $random_seed >/dev/urandom | |
178 | * else | |
179 | * touch $random_seed | |
180 | * fi | |
181 | * chmod 600 $random_seed | |
182 | * dd if=/dev/urandom of=$random_seed count=1 bs=512 | |
183 | * | |
184 | * and the following lines in an appropriate script which is run as | |
185 | * the system is shutdown: | |
186 | * | |
187 | * # Carry a random seed from shut-down to start-up | |
188 | * # Save the whole entropy pool | |
189 | * echo "Saving random seed..." | |
190 | * random_seed=/var/run/random-seed | |
191 | * touch $random_seed | |
192 | * chmod 600 $random_seed | |
193 | * dd if=/dev/urandom of=$random_seed count=1 bs=512 | |
194 | * | |
195 | * For example, on most modern systems using the System V init | |
196 | * scripts, such code fragments would be found in | |
197 | * /etc/rc.d/init.d/random. On older Linux systems, the correct script | |
198 | * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0. | |
199 | * | |
200 | * Effectively, these commands cause the contents of the entropy pool | |
201 | * to be saved at shut-down time and reloaded into the entropy pool at | |
202 | * start-up. (The 'dd' in the addition to the bootup script is to | |
203 | * make sure that /etc/random-seed is different for every start-up, | |
204 | * even if the system crashes without executing rc.0.) Even with | |
205 | * complete knowledge of the start-up activities, predicting the state | |
206 | * of the entropy pool requires knowledge of the previous history of | |
207 | * the system. | |
208 | * | |
209 | * Configuring the /dev/random driver under Linux | |
210 | * ============================================== | |
211 | * | |
212 | * The /dev/random driver under Linux uses minor numbers 8 and 9 of | |
213 | * the /dev/mem major number (#1). So if your system does not have | |
214 | * /dev/random and /dev/urandom created already, they can be created | |
215 | * by using the commands: | |
216 | * | |
217 | * mknod /dev/random c 1 8 | |
218 | * mknod /dev/urandom c 1 9 | |
219 | * | |
220 | * Acknowledgements: | |
221 | * ================= | |
222 | * | |
223 | * Ideas for constructing this random number generator were derived | |
224 | * from Pretty Good Privacy's random number generator, and from private | |
225 | * discussions with Phil Karn. Colin Plumb provided a faster random | |
226 | * number generator, which speed up the mixing function of the entropy | |
227 | * pool, taken from PGPfone. Dale Worley has also contributed many | |
228 | * useful ideas and suggestions to improve this driver. | |
229 | * | |
230 | * Any flaws in the design are solely my responsibility, and should | |
231 | * not be attributed to the Phil, Colin, or any of authors of PGP. | |
232 | * | |
233 | * Further background information on this topic may be obtained from | |
234 | * RFC 1750, "Randomness Recommendations for Security", by Donald | |
235 | * Eastlake, Steve Crocker, and Jeff Schiller. | |
236 | */ | |
237 | ||
238 | #include <linux/utsname.h> | |
1da177e4 LT |
239 | #include <linux/module.h> |
240 | #include <linux/kernel.h> | |
241 | #include <linux/major.h> | |
242 | #include <linux/string.h> | |
243 | #include <linux/fcntl.h> | |
244 | #include <linux/slab.h> | |
245 | #include <linux/random.h> | |
246 | #include <linux/poll.h> | |
247 | #include <linux/init.h> | |
248 | #include <linux/fs.h> | |
249 | #include <linux/genhd.h> | |
250 | #include <linux/interrupt.h> | |
27ac792c | 251 | #include <linux/mm.h> |
1da177e4 LT |
252 | #include <linux/spinlock.h> |
253 | #include <linux/percpu.h> | |
254 | #include <linux/cryptohash.h> | |
5b739ef8 | 255 | #include <linux/fips.h> |
775f4b29 | 256 | #include <linux/ptrace.h> |
e6d4947b | 257 | #include <linux/kmemcheck.h> |
1da177e4 | 258 | |
d178a1eb YL |
259 | #ifdef CONFIG_GENERIC_HARDIRQS |
260 | # include <linux/irq.h> | |
261 | #endif | |
262 | ||
1da177e4 LT |
263 | #include <asm/processor.h> |
264 | #include <asm/uaccess.h> | |
265 | #include <asm/irq.h> | |
775f4b29 | 266 | #include <asm/irq_regs.h> |
1da177e4 LT |
267 | #include <asm/io.h> |
268 | ||
269 | /* | |
270 | * Configuration information | |
271 | */ | |
272 | #define INPUT_POOL_WORDS 128 | |
273 | #define OUTPUT_POOL_WORDS 32 | |
274 | #define SEC_XFER_SIZE 512 | |
e954bc91 | 275 | #define EXTRACT_SIZE 10 |
1da177e4 LT |
276 | |
277 | /* | |
278 | * The minimum number of bits of entropy before we wake up a read on | |
279 | * /dev/random. Should be enough to do a significant reseed. | |
280 | */ | |
281 | static int random_read_wakeup_thresh = 64; | |
282 | ||
283 | /* | |
284 | * If the entropy count falls under this number of bits, then we | |
285 | * should wake up processes which are selecting or polling on write | |
286 | * access to /dev/random. | |
287 | */ | |
288 | static int random_write_wakeup_thresh = 128; | |
289 | ||
290 | /* | |
291 | * When the input pool goes over trickle_thresh, start dropping most | |
292 | * samples to avoid wasting CPU time and reduce lock contention. | |
293 | */ | |
294 | ||
6c036527 | 295 | static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28; |
1da177e4 | 296 | |
90b75ee5 | 297 | static DEFINE_PER_CPU(int, trickle_count); |
1da177e4 LT |
298 | |
299 | /* | |
300 | * A pool of size .poolwords is stirred with a primitive polynomial | |
301 | * of degree .poolwords over GF(2). The taps for various sizes are | |
302 | * defined below. They are chosen to be evenly spaced (minimum RMS | |
303 | * distance from evenly spaced; the numbers in the comments are a | |
304 | * scaled squared error sum) except for the last tap, which is 1 to | |
305 | * get the twisting happening as fast as possible. | |
306 | */ | |
307 | static struct poolinfo { | |
308 | int poolwords; | |
309 | int tap1, tap2, tap3, tap4, tap5; | |
310 | } poolinfo_table[] = { | |
311 | /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */ | |
312 | { 128, 103, 76, 51, 25, 1 }, | |
313 | /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */ | |
314 | { 32, 26, 20, 14, 7, 1 }, | |
315 | #if 0 | |
316 | /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */ | |
317 | { 2048, 1638, 1231, 819, 411, 1 }, | |
318 | ||
319 | /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */ | |
320 | { 1024, 817, 615, 412, 204, 1 }, | |
321 | ||
322 | /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */ | |
323 | { 1024, 819, 616, 410, 207, 2 }, | |
324 | ||
325 | /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */ | |
326 | { 512, 411, 308, 208, 104, 1 }, | |
327 | ||
328 | /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */ | |
329 | { 512, 409, 307, 206, 102, 2 }, | |
330 | /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */ | |
331 | { 512, 409, 309, 205, 103, 2 }, | |
332 | ||
333 | /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */ | |
334 | { 256, 205, 155, 101, 52, 1 }, | |
335 | ||
336 | /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */ | |
337 | { 128, 103, 78, 51, 27, 2 }, | |
338 | ||
339 | /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */ | |
340 | { 64, 52, 39, 26, 14, 1 }, | |
341 | #endif | |
342 | }; | |
343 | ||
344 | #define POOLBITS poolwords*32 | |
345 | #define POOLBYTES poolwords*4 | |
346 | ||
347 | /* | |
348 | * For the purposes of better mixing, we use the CRC-32 polynomial as | |
349 | * well to make a twisted Generalized Feedback Shift Reigster | |
350 | * | |
351 | * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM | |
352 | * Transactions on Modeling and Computer Simulation 2(3):179-194. | |
353 | * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators | |
354 | * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266) | |
355 | * | |
356 | * Thanks to Colin Plumb for suggesting this. | |
357 | * | |
358 | * We have not analyzed the resultant polynomial to prove it primitive; | |
359 | * in fact it almost certainly isn't. Nonetheless, the irreducible factors | |
360 | * of a random large-degree polynomial over GF(2) are more than large enough | |
361 | * that periodicity is not a concern. | |
362 | * | |
363 | * The input hash is much less sensitive than the output hash. All | |
364 | * that we want of it is that it be a good non-cryptographic hash; | |
365 | * i.e. it not produce collisions when fed "random" data of the sort | |
366 | * we expect to see. As long as the pool state differs for different | |
367 | * inputs, we have preserved the input entropy and done a good job. | |
368 | * The fact that an intelligent attacker can construct inputs that | |
369 | * will produce controlled alterations to the pool's state is not | |
370 | * important because we don't consider such inputs to contribute any | |
371 | * randomness. The only property we need with respect to them is that | |
372 | * the attacker can't increase his/her knowledge of the pool's state. | |
373 | * Since all additions are reversible (knowing the final state and the | |
374 | * input, you can reconstruct the initial state), if an attacker has | |
375 | * any uncertainty about the initial state, he/she can only shuffle | |
376 | * that uncertainty about, but never cause any collisions (which would | |
377 | * decrease the uncertainty). | |
378 | * | |
379 | * The chosen system lets the state of the pool be (essentially) the input | |
380 | * modulo the generator polymnomial. Now, for random primitive polynomials, | |
381 | * this is a universal class of hash functions, meaning that the chance | |
382 | * of a collision is limited by the attacker's knowledge of the generator | |
383 | * polynomail, so if it is chosen at random, an attacker can never force | |
384 | * a collision. Here, we use a fixed polynomial, but we *can* assume that | |
385 | * ###--> it is unknown to the processes generating the input entropy. <-### | |
386 | * Because of this important property, this is a good, collision-resistant | |
387 | * hash; hash collisions will occur no more often than chance. | |
388 | */ | |
389 | ||
390 | /* | |
391 | * Static global variables | |
392 | */ | |
393 | static DECLARE_WAIT_QUEUE_HEAD(random_read_wait); | |
394 | static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); | |
9a6f70bb | 395 | static struct fasync_struct *fasync; |
1da177e4 LT |
396 | |
397 | #if 0 | |
90ab5ee9 | 398 | static bool debug; |
1da177e4 | 399 | module_param(debug, bool, 0644); |
90b75ee5 MM |
400 | #define DEBUG_ENT(fmt, arg...) do { \ |
401 | if (debug) \ | |
402 | printk(KERN_DEBUG "random %04d %04d %04d: " \ | |
403 | fmt,\ | |
404 | input_pool.entropy_count,\ | |
405 | blocking_pool.entropy_count,\ | |
406 | nonblocking_pool.entropy_count,\ | |
407 | ## arg); } while (0) | |
1da177e4 LT |
408 | #else |
409 | #define DEBUG_ENT(fmt, arg...) do {} while (0) | |
410 | #endif | |
411 | ||
412 | /********************************************************************** | |
413 | * | |
414 | * OS independent entropy store. Here are the functions which handle | |
415 | * storing entropy in an entropy pool. | |
416 | * | |
417 | **********************************************************************/ | |
418 | ||
419 | struct entropy_store; | |
420 | struct entropy_store { | |
43358209 | 421 | /* read-only data: */ |
1da177e4 LT |
422 | struct poolinfo *poolinfo; |
423 | __u32 *pool; | |
424 | const char *name; | |
1da177e4 | 425 | struct entropy_store *pull; |
4015d9a8 | 426 | int limit; |
1da177e4 LT |
427 | |
428 | /* read-write data: */ | |
43358209 | 429 | spinlock_t lock; |
1da177e4 | 430 | unsigned add_ptr; |
902c098a | 431 | unsigned input_rotate; |
cda796a3 | 432 | int entropy_count; |
775f4b29 | 433 | int entropy_total; |
775f4b29 | 434 | unsigned int initialized:1; |
e954bc91 | 435 | __u8 last_data[EXTRACT_SIZE]; |
1da177e4 LT |
436 | }; |
437 | ||
438 | static __u32 input_pool_data[INPUT_POOL_WORDS]; | |
439 | static __u32 blocking_pool_data[OUTPUT_POOL_WORDS]; | |
440 | static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS]; | |
441 | ||
442 | static struct entropy_store input_pool = { | |
443 | .poolinfo = &poolinfo_table[0], | |
444 | .name = "input", | |
445 | .limit = 1, | |
e4d91918 | 446 | .lock = __SPIN_LOCK_UNLOCKED(&input_pool.lock), |
1da177e4 LT |
447 | .pool = input_pool_data |
448 | }; | |
449 | ||
450 | static struct entropy_store blocking_pool = { | |
451 | .poolinfo = &poolinfo_table[1], | |
452 | .name = "blocking", | |
453 | .limit = 1, | |
454 | .pull = &input_pool, | |
e4d91918 | 455 | .lock = __SPIN_LOCK_UNLOCKED(&blocking_pool.lock), |
1da177e4 LT |
456 | .pool = blocking_pool_data |
457 | }; | |
458 | ||
459 | static struct entropy_store nonblocking_pool = { | |
460 | .poolinfo = &poolinfo_table[1], | |
461 | .name = "nonblocking", | |
462 | .pull = &input_pool, | |
e4d91918 | 463 | .lock = __SPIN_LOCK_UNLOCKED(&nonblocking_pool.lock), |
1da177e4 LT |
464 | .pool = nonblocking_pool_data |
465 | }; | |
466 | ||
775f4b29 TT |
467 | static __u32 const twist_table[8] = { |
468 | 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158, | |
469 | 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; | |
470 | ||
1da177e4 | 471 | /* |
e68e5b66 | 472 | * This function adds bytes into the entropy "pool". It does not |
1da177e4 | 473 | * update the entropy estimate. The caller should call |
adc782da | 474 | * credit_entropy_bits if this is appropriate. |
1da177e4 LT |
475 | * |
476 | * The pool is stirred with a primitive polynomial of the appropriate | |
477 | * degree, and then twisted. We twist by three bits at a time because | |
478 | * it's cheap to do so and helps slightly in the expected case where | |
479 | * the entropy is concentrated in the low-order bits. | |
480 | */ | |
902c098a TT |
481 | static void __mix_pool_bytes(struct entropy_store *r, const void *in, |
482 | int nbytes, __u8 out[64]) | |
1da177e4 | 483 | { |
993ba211 | 484 | unsigned long i, j, tap1, tap2, tap3, tap4, tap5; |
feee7697 | 485 | int input_rotate; |
1da177e4 | 486 | int wordmask = r->poolinfo->poolwords - 1; |
e68e5b66 | 487 | const char *bytes = in; |
6d38b827 | 488 | __u32 w; |
1da177e4 | 489 | |
1da177e4 LT |
490 | tap1 = r->poolinfo->tap1; |
491 | tap2 = r->poolinfo->tap2; | |
492 | tap3 = r->poolinfo->tap3; | |
493 | tap4 = r->poolinfo->tap4; | |
494 | tap5 = r->poolinfo->tap5; | |
1da177e4 | 495 | |
902c098a TT |
496 | smp_rmb(); |
497 | input_rotate = ACCESS_ONCE(r->input_rotate); | |
498 | i = ACCESS_ONCE(r->add_ptr); | |
1da177e4 | 499 | |
e68e5b66 MM |
500 | /* mix one byte at a time to simplify size handling and churn faster */ |
501 | while (nbytes--) { | |
502 | w = rol32(*bytes++, input_rotate & 31); | |
993ba211 | 503 | i = (i - 1) & wordmask; |
1da177e4 LT |
504 | |
505 | /* XOR in the various taps */ | |
993ba211 | 506 | w ^= r->pool[i]; |
1da177e4 LT |
507 | w ^= r->pool[(i + tap1) & wordmask]; |
508 | w ^= r->pool[(i + tap2) & wordmask]; | |
509 | w ^= r->pool[(i + tap3) & wordmask]; | |
510 | w ^= r->pool[(i + tap4) & wordmask]; | |
511 | w ^= r->pool[(i + tap5) & wordmask]; | |
993ba211 MM |
512 | |
513 | /* Mix the result back in with a twist */ | |
1da177e4 | 514 | r->pool[i] = (w >> 3) ^ twist_table[w & 7]; |
feee7697 MM |
515 | |
516 | /* | |
517 | * Normally, we add 7 bits of rotation to the pool. | |
518 | * At the beginning of the pool, add an extra 7 bits | |
519 | * rotation, so that successive passes spread the | |
520 | * input bits across the pool evenly. | |
521 | */ | |
522 | input_rotate += i ? 7 : 14; | |
1da177e4 LT |
523 | } |
524 | ||
902c098a TT |
525 | ACCESS_ONCE(r->input_rotate) = input_rotate; |
526 | ACCESS_ONCE(r->add_ptr) = i; | |
527 | smp_wmb(); | |
1da177e4 | 528 | |
993ba211 MM |
529 | if (out) |
530 | for (j = 0; j < 16; j++) | |
e68e5b66 | 531 | ((__u32 *)out)[j] = r->pool[(i - j) & wordmask]; |
1da177e4 LT |
532 | } |
533 | ||
902c098a TT |
534 | static void mix_pool_bytes(struct entropy_store *r, const void *in, |
535 | int nbytes, __u8 out[64]) | |
1da177e4 | 536 | { |
902c098a TT |
537 | unsigned long flags; |
538 | ||
539 | spin_lock_irqsave(&r->lock, flags); | |
540 | __mix_pool_bytes(r, in, nbytes, out); | |
541 | spin_unlock_irqrestore(&r->lock, flags); | |
1da177e4 LT |
542 | } |
543 | ||
775f4b29 TT |
544 | struct fast_pool { |
545 | __u32 pool[4]; | |
546 | unsigned long last; | |
547 | unsigned short count; | |
548 | unsigned char rotate; | |
549 | unsigned char last_timer_intr; | |
550 | }; | |
551 | ||
552 | /* | |
553 | * This is a fast mixing routine used by the interrupt randomness | |
554 | * collector. It's hardcoded for an 128 bit pool and assumes that any | |
555 | * locks that might be needed are taken by the caller. | |
556 | */ | |
557 | static void fast_mix(struct fast_pool *f, const void *in, int nbytes) | |
558 | { | |
559 | const char *bytes = in; | |
560 | __u32 w; | |
561 | unsigned i = f->count; | |
562 | unsigned input_rotate = f->rotate; | |
563 | ||
564 | while (nbytes--) { | |
565 | w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^ | |
566 | f->pool[(i + 1) & 3]; | |
567 | f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7]; | |
568 | input_rotate += (i++ & 3) ? 7 : 14; | |
569 | } | |
570 | f->count = i; | |
571 | f->rotate = input_rotate; | |
572 | } | |
573 | ||
1da177e4 LT |
574 | /* |
575 | * Credit (or debit) the entropy store with n bits of entropy | |
576 | */ | |
adc782da | 577 | static void credit_entropy_bits(struct entropy_store *r, int nbits) |
1da177e4 | 578 | { |
902c098a | 579 | int entropy_count, orig; |
1da177e4 | 580 | |
adc782da MM |
581 | if (!nbits) |
582 | return; | |
583 | ||
adc782da | 584 | DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name); |
902c098a TT |
585 | retry: |
586 | entropy_count = orig = ACCESS_ONCE(r->entropy_count); | |
8b76f46a AM |
587 | entropy_count += nbits; |
588 | if (entropy_count < 0) { | |
adc782da | 589 | DEBUG_ENT("negative entropy/overflow\n"); |
8b76f46a AM |
590 | entropy_count = 0; |
591 | } else if (entropy_count > r->poolinfo->POOLBITS) | |
592 | entropy_count = r->poolinfo->POOLBITS; | |
902c098a TT |
593 | if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) |
594 | goto retry; | |
1da177e4 | 595 | |
775f4b29 TT |
596 | if (!r->initialized && nbits > 0) { |
597 | r->entropy_total += nbits; | |
598 | if (r->entropy_total > 128) | |
599 | r->initialized = 1; | |
600 | } | |
601 | ||
88c730da | 602 | /* should we wake readers? */ |
8b76f46a | 603 | if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) { |
88c730da | 604 | wake_up_interruptible(&random_read_wait); |
9a6f70bb JD |
605 | kill_fasync(&fasync, SIGIO, POLL_IN); |
606 | } | |
1da177e4 LT |
607 | } |
608 | ||
609 | /********************************************************************* | |
610 | * | |
611 | * Entropy input management | |
612 | * | |
613 | *********************************************************************/ | |
614 | ||
615 | /* There is one of these per entropy source */ | |
616 | struct timer_rand_state { | |
617 | cycles_t last_time; | |
90b75ee5 | 618 | long last_delta, last_delta2; |
1da177e4 LT |
619 | unsigned dont_count_entropy:1; |
620 | }; | |
621 | ||
d7e51e66 | 622 | #ifndef CONFIG_GENERIC_HARDIRQS |
2f983570 YL |
623 | |
624 | static struct timer_rand_state *irq_timer_state[NR_IRQS]; | |
625 | ||
626 | static struct timer_rand_state *get_timer_rand_state(unsigned int irq) | |
627 | { | |
628 | return irq_timer_state[irq]; | |
629 | } | |
630 | ||
631 | static void set_timer_rand_state(unsigned int irq, | |
632 | struct timer_rand_state *state) | |
633 | { | |
634 | irq_timer_state[irq] = state; | |
635 | } | |
636 | ||
637 | #else | |
638 | ||
639 | static struct timer_rand_state *get_timer_rand_state(unsigned int irq) | |
640 | { | |
641 | struct irq_desc *desc; | |
642 | ||
643 | desc = irq_to_desc(irq); | |
644 | ||
645 | return desc->timer_rand_state; | |
646 | } | |
647 | ||
648 | static void set_timer_rand_state(unsigned int irq, | |
649 | struct timer_rand_state *state) | |
650 | { | |
651 | struct irq_desc *desc; | |
652 | ||
653 | desc = irq_to_desc(irq); | |
654 | ||
655 | desc->timer_rand_state = state; | |
656 | } | |
0b8f1efa | 657 | #endif |
3060d6fe | 658 | |
a2080a67 LT |
659 | /* |
660 | * Add device- or boot-specific data to the input and nonblocking | |
661 | * pools to help initialize them to unique values. | |
662 | * | |
663 | * None of this adds any entropy, it is meant to avoid the | |
664 | * problem of the nonblocking pool having similar initial state | |
665 | * across largely identical devices. | |
666 | */ | |
667 | void add_device_randomness(const void *buf, unsigned int size) | |
668 | { | |
669 | unsigned long time = get_cycles() ^ jiffies; | |
670 | ||
671 | mix_pool_bytes(&input_pool, buf, size, NULL); | |
672 | mix_pool_bytes(&input_pool, &time, sizeof(time), NULL); | |
673 | mix_pool_bytes(&nonblocking_pool, buf, size, NULL); | |
674 | mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL); | |
675 | } | |
676 | EXPORT_SYMBOL(add_device_randomness); | |
677 | ||
3060d6fe YL |
678 | static struct timer_rand_state input_timer_state; |
679 | ||
1da177e4 LT |
680 | /* |
681 | * This function adds entropy to the entropy "pool" by using timing | |
682 | * delays. It uses the timer_rand_state structure to make an estimate | |
683 | * of how many bits of entropy this call has added to the pool. | |
684 | * | |
685 | * The number "num" is also added to the pool - it should somehow describe | |
686 | * the type of event which just happened. This is currently 0-255 for | |
687 | * keyboard scan codes, and 256 upwards for interrupts. | |
688 | * | |
689 | */ | |
690 | static void add_timer_randomness(struct timer_rand_state *state, unsigned num) | |
691 | { | |
692 | struct { | |
1da177e4 | 693 | long jiffies; |
cf833d0b | 694 | unsigned cycles; |
1da177e4 LT |
695 | unsigned num; |
696 | } sample; | |
697 | long delta, delta2, delta3; | |
698 | ||
699 | preempt_disable(); | |
700 | /* if over the trickle threshold, use only 1 in 4096 samples */ | |
701 | if (input_pool.entropy_count > trickle_thresh && | |
b29c617a | 702 | ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff)) |
1da177e4 LT |
703 | goto out; |
704 | ||
705 | sample.jiffies = jiffies; | |
e6d4947b | 706 | sample.cycles = get_cycles(); |
1da177e4 | 707 | sample.num = num; |
902c098a | 708 | mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL); |
1da177e4 LT |
709 | |
710 | /* | |
711 | * Calculate number of bits of randomness we probably added. | |
712 | * We take into account the first, second and third-order deltas | |
713 | * in order to make our estimate. | |
714 | */ | |
715 | ||
716 | if (!state->dont_count_entropy) { | |
717 | delta = sample.jiffies - state->last_time; | |
718 | state->last_time = sample.jiffies; | |
719 | ||
720 | delta2 = delta - state->last_delta; | |
721 | state->last_delta = delta; | |
722 | ||
723 | delta3 = delta2 - state->last_delta2; | |
724 | state->last_delta2 = delta2; | |
725 | ||
726 | if (delta < 0) | |
727 | delta = -delta; | |
728 | if (delta2 < 0) | |
729 | delta2 = -delta2; | |
730 | if (delta3 < 0) | |
731 | delta3 = -delta3; | |
732 | if (delta > delta2) | |
733 | delta = delta2; | |
734 | if (delta > delta3) | |
735 | delta = delta3; | |
736 | ||
737 | /* | |
738 | * delta is now minimum absolute delta. | |
739 | * Round down by 1 bit on general principles, | |
740 | * and limit entropy entimate to 12 bits. | |
741 | */ | |
adc782da MM |
742 | credit_entropy_bits(&input_pool, |
743 | min_t(int, fls(delta>>1), 11)); | |
1da177e4 | 744 | } |
1da177e4 LT |
745 | out: |
746 | preempt_enable(); | |
747 | } | |
748 | ||
d251575a | 749 | void add_input_randomness(unsigned int type, unsigned int code, |
1da177e4 LT |
750 | unsigned int value) |
751 | { | |
752 | static unsigned char last_value; | |
753 | ||
754 | /* ignore autorepeat and the like */ | |
755 | if (value == last_value) | |
756 | return; | |
757 | ||
758 | DEBUG_ENT("input event\n"); | |
759 | last_value = value; | |
760 | add_timer_randomness(&input_timer_state, | |
761 | (type << 4) ^ code ^ (code >> 4) ^ value); | |
762 | } | |
80fc9f53 | 763 | EXPORT_SYMBOL_GPL(add_input_randomness); |
1da177e4 | 764 | |
775f4b29 TT |
765 | static DEFINE_PER_CPU(struct fast_pool, irq_randomness); |
766 | ||
767 | void add_interrupt_randomness(int irq, int irq_flags) | |
1da177e4 | 768 | { |
775f4b29 TT |
769 | struct entropy_store *r; |
770 | struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness); | |
771 | struct pt_regs *regs = get_irq_regs(); | |
772 | unsigned long now = jiffies; | |
773 | __u32 input[4], cycles = get_cycles(); | |
774 | ||
775 | input[0] = cycles ^ jiffies; | |
776 | input[1] = irq; | |
777 | if (regs) { | |
778 | __u64 ip = instruction_pointer(regs); | |
779 | input[2] = ip; | |
780 | input[3] = ip >> 32; | |
781 | } | |
3060d6fe | 782 | |
775f4b29 | 783 | fast_mix(fast_pool, input, sizeof(input)); |
3060d6fe | 784 | |
775f4b29 TT |
785 | if ((fast_pool->count & 1023) && |
786 | !time_after(now, fast_pool->last + HZ)) | |
1da177e4 LT |
787 | return; |
788 | ||
775f4b29 TT |
789 | fast_pool->last = now; |
790 | ||
791 | r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool; | |
902c098a | 792 | __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL); |
775f4b29 TT |
793 | /* |
794 | * If we don't have a valid cycle counter, and we see | |
795 | * back-to-back timer interrupts, then skip giving credit for | |
796 | * any entropy. | |
797 | */ | |
798 | if (cycles == 0) { | |
799 | if (irq_flags & __IRQF_TIMER) { | |
800 | if (fast_pool->last_timer_intr) | |
801 | return; | |
802 | fast_pool->last_timer_intr = 1; | |
803 | } else | |
804 | fast_pool->last_timer_intr = 0; | |
805 | } | |
806 | credit_entropy_bits(r, 1); | |
1da177e4 LT |
807 | } |
808 | ||
9361401e | 809 | #ifdef CONFIG_BLOCK |
1da177e4 LT |
810 | void add_disk_randomness(struct gendisk *disk) |
811 | { | |
812 | if (!disk || !disk->random) | |
813 | return; | |
814 | /* first major is 1, so we get >= 0x200 here */ | |
f331c029 TH |
815 | DEBUG_ENT("disk event %d:%d\n", |
816 | MAJOR(disk_devt(disk)), MINOR(disk_devt(disk))); | |
1da177e4 | 817 | |
f331c029 | 818 | add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); |
1da177e4 | 819 | } |
9361401e | 820 | #endif |
1da177e4 | 821 | |
1da177e4 LT |
822 | /********************************************************************* |
823 | * | |
824 | * Entropy extraction routines | |
825 | * | |
826 | *********************************************************************/ | |
827 | ||
90b75ee5 | 828 | static ssize_t extract_entropy(struct entropy_store *r, void *buf, |
1da177e4 LT |
829 | size_t nbytes, int min, int rsvd); |
830 | ||
831 | /* | |
25985edc | 832 | * This utility inline function is responsible for transferring entropy |
1da177e4 LT |
833 | * from the primary pool to the secondary extraction pool. We make |
834 | * sure we pull enough for a 'catastrophic reseed'. | |
835 | */ | |
836 | static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes) | |
837 | { | |
e6d4947b TT |
838 | union { |
839 | __u32 tmp[OUTPUT_POOL_WORDS]; | |
840 | long hwrand[4]; | |
841 | } u; | |
842 | int i; | |
1da177e4 LT |
843 | |
844 | if (r->pull && r->entropy_count < nbytes * 8 && | |
845 | r->entropy_count < r->poolinfo->POOLBITS) { | |
5a021e9f | 846 | /* If we're limited, always leave two wakeup worth's BITS */ |
1da177e4 | 847 | int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4; |
5a021e9f MM |
848 | int bytes = nbytes; |
849 | ||
850 | /* pull at least as many as BYTES as wakeup BITS */ | |
851 | bytes = max_t(int, bytes, random_read_wakeup_thresh / 8); | |
852 | /* but never more than the buffer size */ | |
e6d4947b | 853 | bytes = min_t(int, bytes, sizeof(u.tmp)); |
1da177e4 LT |
854 | |
855 | DEBUG_ENT("going to reseed %s with %d bits " | |
856 | "(%d of %d requested)\n", | |
857 | r->name, bytes * 8, nbytes * 8, r->entropy_count); | |
858 | ||
e6d4947b | 859 | bytes = extract_entropy(r->pull, u.tmp, bytes, |
90b75ee5 | 860 | random_read_wakeup_thresh / 8, rsvd); |
e6d4947b | 861 | mix_pool_bytes(r, u.tmp, bytes, NULL); |
adc782da | 862 | credit_entropy_bits(r, bytes*8); |
1da177e4 | 863 | } |
e6d4947b TT |
864 | kmemcheck_mark_initialized(&u.hwrand, sizeof(u.hwrand)); |
865 | for (i = 0; i < 4; i++) | |
866 | if (arch_get_random_long(&u.hwrand[i])) | |
867 | break; | |
868 | if (i) | |
869 | mix_pool_bytes(r, &u.hwrand, sizeof(u.hwrand), 0); | |
1da177e4 LT |
870 | } |
871 | ||
872 | /* | |
873 | * These functions extracts randomness from the "entropy pool", and | |
874 | * returns it in a buffer. | |
875 | * | |
876 | * The min parameter specifies the minimum amount we can pull before | |
877 | * failing to avoid races that defeat catastrophic reseeding while the | |
878 | * reserved parameter indicates how much entropy we must leave in the | |
879 | * pool after each pull to avoid starving other readers. | |
880 | * | |
881 | * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words. | |
882 | */ | |
883 | ||
884 | static size_t account(struct entropy_store *r, size_t nbytes, int min, | |
885 | int reserved) | |
886 | { | |
887 | unsigned long flags; | |
888 | ||
1da177e4 LT |
889 | /* Hold lock while accounting */ |
890 | spin_lock_irqsave(&r->lock, flags); | |
891 | ||
cda796a3 | 892 | BUG_ON(r->entropy_count > r->poolinfo->POOLBITS); |
1da177e4 LT |
893 | DEBUG_ENT("trying to extract %d bits from %s\n", |
894 | nbytes * 8, r->name); | |
895 | ||
896 | /* Can we pull enough? */ | |
897 | if (r->entropy_count / 8 < min + reserved) { | |
898 | nbytes = 0; | |
899 | } else { | |
900 | /* If limited, never pull more than available */ | |
901 | if (r->limit && nbytes + reserved >= r->entropy_count / 8) | |
902 | nbytes = r->entropy_count/8 - reserved; | |
903 | ||
90b75ee5 | 904 | if (r->entropy_count / 8 >= nbytes + reserved) |
1da177e4 LT |
905 | r->entropy_count -= nbytes*8; |
906 | else | |
907 | r->entropy_count = reserved; | |
908 | ||
9a6f70bb | 909 | if (r->entropy_count < random_write_wakeup_thresh) { |
1da177e4 | 910 | wake_up_interruptible(&random_write_wait); |
9a6f70bb JD |
911 | kill_fasync(&fasync, SIGIO, POLL_OUT); |
912 | } | |
1da177e4 LT |
913 | } |
914 | ||
915 | DEBUG_ENT("debiting %d entropy credits from %s%s\n", | |
916 | nbytes * 8, r->name, r->limit ? "" : " (unlimited)"); | |
917 | ||
918 | spin_unlock_irqrestore(&r->lock, flags); | |
919 | ||
920 | return nbytes; | |
921 | } | |
922 | ||
923 | static void extract_buf(struct entropy_store *r, __u8 *out) | |
924 | { | |
602b6aee | 925 | int i; |
e68e5b66 MM |
926 | __u32 hash[5], workspace[SHA_WORKSPACE_WORDS]; |
927 | __u8 extract[64]; | |
902c098a | 928 | unsigned long flags; |
1da177e4 | 929 | |
1c0ad3d4 | 930 | /* Generate a hash across the pool, 16 words (512 bits) at a time */ |
ffd8d3fa | 931 | sha_init(hash); |
902c098a | 932 | spin_lock_irqsave(&r->lock, flags); |
1c0ad3d4 MM |
933 | for (i = 0; i < r->poolinfo->poolwords; i += 16) |
934 | sha_transform(hash, (__u8 *)(r->pool + i), workspace); | |
935 | ||
1da177e4 | 936 | /* |
1c0ad3d4 MM |
937 | * We mix the hash back into the pool to prevent backtracking |
938 | * attacks (where the attacker knows the state of the pool | |
939 | * plus the current outputs, and attempts to find previous | |
940 | * ouputs), unless the hash function can be inverted. By | |
941 | * mixing at least a SHA1 worth of hash data back, we make | |
942 | * brute-forcing the feedback as hard as brute-forcing the | |
943 | * hash. | |
1da177e4 | 944 | */ |
902c098a TT |
945 | __mix_pool_bytes(r, hash, sizeof(hash), extract); |
946 | spin_unlock_irqrestore(&r->lock, flags); | |
1da177e4 LT |
947 | |
948 | /* | |
1c0ad3d4 MM |
949 | * To avoid duplicates, we atomically extract a portion of the |
950 | * pool while mixing, and hash one final time. | |
1da177e4 | 951 | */ |
e68e5b66 | 952 | sha_transform(hash, extract, workspace); |
ffd8d3fa MM |
953 | memset(extract, 0, sizeof(extract)); |
954 | memset(workspace, 0, sizeof(workspace)); | |
1da177e4 LT |
955 | |
956 | /* | |
1c0ad3d4 MM |
957 | * In case the hash function has some recognizable output |
958 | * pattern, we fold it in half. Thus, we always feed back | |
959 | * twice as much data as we output. | |
1da177e4 | 960 | */ |
ffd8d3fa MM |
961 | hash[0] ^= hash[3]; |
962 | hash[1] ^= hash[4]; | |
963 | hash[2] ^= rol32(hash[2], 16); | |
964 | memcpy(out, hash, EXTRACT_SIZE); | |
965 | memset(hash, 0, sizeof(hash)); | |
1da177e4 LT |
966 | } |
967 | ||
90b75ee5 | 968 | static ssize_t extract_entropy(struct entropy_store *r, void *buf, |
902c098a | 969 | size_t nbytes, int min, int reserved) |
1da177e4 LT |
970 | { |
971 | ssize_t ret = 0, i; | |
972 | __u8 tmp[EXTRACT_SIZE]; | |
973 | ||
974 | xfer_secondary_pool(r, nbytes); | |
975 | nbytes = account(r, nbytes, min, reserved); | |
976 | ||
977 | while (nbytes) { | |
978 | extract_buf(r, tmp); | |
5b739ef8 | 979 | |
e954bc91 | 980 | if (fips_enabled) { |
902c098a TT |
981 | unsigned long flags; |
982 | ||
5b739ef8 NH |
983 | spin_lock_irqsave(&r->lock, flags); |
984 | if (!memcmp(tmp, r->last_data, EXTRACT_SIZE)) | |
985 | panic("Hardware RNG duplicated output!\n"); | |
986 | memcpy(r->last_data, tmp, EXTRACT_SIZE); | |
987 | spin_unlock_irqrestore(&r->lock, flags); | |
988 | } | |
1da177e4 LT |
989 | i = min_t(int, nbytes, EXTRACT_SIZE); |
990 | memcpy(buf, tmp, i); | |
991 | nbytes -= i; | |
992 | buf += i; | |
993 | ret += i; | |
994 | } | |
995 | ||
996 | /* Wipe data just returned from memory */ | |
997 | memset(tmp, 0, sizeof(tmp)); | |
998 | ||
999 | return ret; | |
1000 | } | |
1001 | ||
1002 | static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, | |
1003 | size_t nbytes) | |
1004 | { | |
1005 | ssize_t ret = 0, i; | |
1006 | __u8 tmp[EXTRACT_SIZE]; | |
1007 | ||
1008 | xfer_secondary_pool(r, nbytes); | |
1009 | nbytes = account(r, nbytes, 0, 0); | |
1010 | ||
1011 | while (nbytes) { | |
1012 | if (need_resched()) { | |
1013 | if (signal_pending(current)) { | |
1014 | if (ret == 0) | |
1015 | ret = -ERESTARTSYS; | |
1016 | break; | |
1017 | } | |
1018 | schedule(); | |
1019 | } | |
1020 | ||
1021 | extract_buf(r, tmp); | |
1022 | i = min_t(int, nbytes, EXTRACT_SIZE); | |
1023 | if (copy_to_user(buf, tmp, i)) { | |
1024 | ret = -EFAULT; | |
1025 | break; | |
1026 | } | |
1027 | ||
1028 | nbytes -= i; | |
1029 | buf += i; | |
1030 | ret += i; | |
1031 | } | |
1032 | ||
1033 | /* Wipe data just returned from memory */ | |
1034 | memset(tmp, 0, sizeof(tmp)); | |
1035 | ||
1036 | return ret; | |
1037 | } | |
1038 | ||
1039 | /* | |
1040 | * This function is the exported kernel interface. It returns some | |
c2557a30 TT |
1041 | * number of good random numbers, suitable for key generation, seeding |
1042 | * TCP sequence numbers, etc. It does not use the hw random number | |
1043 | * generator, if available; use get_random_bytes_arch() for that. | |
1da177e4 LT |
1044 | */ |
1045 | void get_random_bytes(void *buf, int nbytes) | |
c2557a30 TT |
1046 | { |
1047 | extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0); | |
1048 | } | |
1049 | EXPORT_SYMBOL(get_random_bytes); | |
1050 | ||
1051 | /* | |
1052 | * This function will use the architecture-specific hardware random | |
1053 | * number generator if it is available. The arch-specific hw RNG will | |
1054 | * almost certainly be faster than what we can do in software, but it | |
1055 | * is impossible to verify that it is implemented securely (as | |
1056 | * opposed, to, say, the AES encryption of a sequence number using a | |
1057 | * key known by the NSA). So it's useful if we need the speed, but | |
1058 | * only if we're willing to trust the hardware manufacturer not to | |
1059 | * have put in a back door. | |
1060 | */ | |
1061 | void get_random_bytes_arch(void *buf, int nbytes) | |
1da177e4 | 1062 | { |
63d77173 PA |
1063 | char *p = buf; |
1064 | ||
1065 | while (nbytes) { | |
1066 | unsigned long v; | |
1067 | int chunk = min(nbytes, (int)sizeof(unsigned long)); | |
c2557a30 | 1068 | |
63d77173 PA |
1069 | if (!arch_get_random_long(&v)) |
1070 | break; | |
1071 | ||
bd29e568 | 1072 | memcpy(p, &v, chunk); |
63d77173 PA |
1073 | p += chunk; |
1074 | nbytes -= chunk; | |
1075 | } | |
1076 | ||
c2557a30 TT |
1077 | if (nbytes) |
1078 | extract_entropy(&nonblocking_pool, p, nbytes, 0, 0); | |
1da177e4 | 1079 | } |
c2557a30 TT |
1080 | EXPORT_SYMBOL(get_random_bytes_arch); |
1081 | ||
1da177e4 LT |
1082 | |
1083 | /* | |
1084 | * init_std_data - initialize pool with system data | |
1085 | * | |
1086 | * @r: pool to initialize | |
1087 | * | |
1088 | * This function clears the pool's entropy count and mixes some system | |
1089 | * data into the pool to prepare it for use. The pool is not cleared | |
1090 | * as that can only decrease the entropy in the pool. | |
1091 | */ | |
1092 | static void init_std_data(struct entropy_store *r) | |
1093 | { | |
3e88bdff | 1094 | int i; |
902c098a TT |
1095 | ktime_t now = ktime_get_real(); |
1096 | unsigned long rv; | |
1da177e4 | 1097 | |
1da177e4 | 1098 | r->entropy_count = 0; |
775f4b29 | 1099 | r->entropy_total = 0; |
902c098a TT |
1100 | mix_pool_bytes(r, &now, sizeof(now), NULL); |
1101 | for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) { | |
1102 | if (!arch_get_random_long(&rv)) | |
3e88bdff | 1103 | break; |
902c098a | 1104 | mix_pool_bytes(r, &rv, sizeof(rv), NULL); |
3e88bdff | 1105 | } |
902c098a | 1106 | mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL); |
1da177e4 LT |
1107 | } |
1108 | ||
53c3f63e | 1109 | static int rand_initialize(void) |
1da177e4 LT |
1110 | { |
1111 | init_std_data(&input_pool); | |
1112 | init_std_data(&blocking_pool); | |
1113 | init_std_data(&nonblocking_pool); | |
1114 | return 0; | |
1115 | } | |
1116 | module_init(rand_initialize); | |
1117 | ||
1118 | void rand_initialize_irq(int irq) | |
1119 | { | |
1120 | struct timer_rand_state *state; | |
1121 | ||
3060d6fe YL |
1122 | state = get_timer_rand_state(irq); |
1123 | ||
1124 | if (state) | |
1da177e4 LT |
1125 | return; |
1126 | ||
1127 | /* | |
f8595815 | 1128 | * If kzalloc returns null, we just won't use that entropy |
1da177e4 LT |
1129 | * source. |
1130 | */ | |
f8595815 ED |
1131 | state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); |
1132 | if (state) | |
3060d6fe | 1133 | set_timer_rand_state(irq, state); |
1da177e4 LT |
1134 | } |
1135 | ||
9361401e | 1136 | #ifdef CONFIG_BLOCK |
1da177e4 LT |
1137 | void rand_initialize_disk(struct gendisk *disk) |
1138 | { | |
1139 | struct timer_rand_state *state; | |
1140 | ||
1141 | /* | |
f8595815 | 1142 | * If kzalloc returns null, we just won't use that entropy |
1da177e4 LT |
1143 | * source. |
1144 | */ | |
f8595815 ED |
1145 | state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); |
1146 | if (state) | |
1da177e4 | 1147 | disk->random = state; |
1da177e4 | 1148 | } |
9361401e | 1149 | #endif |
1da177e4 LT |
1150 | |
1151 | static ssize_t | |
90b75ee5 | 1152 | random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) |
1da177e4 LT |
1153 | { |
1154 | ssize_t n, retval = 0, count = 0; | |
1155 | ||
1156 | if (nbytes == 0) | |
1157 | return 0; | |
1158 | ||
1159 | while (nbytes > 0) { | |
1160 | n = nbytes; | |
1161 | if (n > SEC_XFER_SIZE) | |
1162 | n = SEC_XFER_SIZE; | |
1163 | ||
1164 | DEBUG_ENT("reading %d bits\n", n*8); | |
1165 | ||
1166 | n = extract_entropy_user(&blocking_pool, buf, n); | |
1167 | ||
1168 | DEBUG_ENT("read got %d bits (%d still needed)\n", | |
1169 | n*8, (nbytes-n)*8); | |
1170 | ||
1171 | if (n == 0) { | |
1172 | if (file->f_flags & O_NONBLOCK) { | |
1173 | retval = -EAGAIN; | |
1174 | break; | |
1175 | } | |
1176 | ||
1177 | DEBUG_ENT("sleeping?\n"); | |
1178 | ||
1179 | wait_event_interruptible(random_read_wait, | |
1180 | input_pool.entropy_count >= | |
1181 | random_read_wakeup_thresh); | |
1182 | ||
1183 | DEBUG_ENT("awake\n"); | |
1184 | ||
1185 | if (signal_pending(current)) { | |
1186 | retval = -ERESTARTSYS; | |
1187 | break; | |
1188 | } | |
1189 | ||
1190 | continue; | |
1191 | } | |
1192 | ||
1193 | if (n < 0) { | |
1194 | retval = n; | |
1195 | break; | |
1196 | } | |
1197 | count += n; | |
1198 | buf += n; | |
1199 | nbytes -= n; | |
1200 | break; /* This break makes the device work */ | |
1201 | /* like a named pipe */ | |
1202 | } | |
1203 | ||
1da177e4 LT |
1204 | return (count ? count : retval); |
1205 | } | |
1206 | ||
1207 | static ssize_t | |
90b75ee5 | 1208 | urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) |
1da177e4 LT |
1209 | { |
1210 | return extract_entropy_user(&nonblocking_pool, buf, nbytes); | |
1211 | } | |
1212 | ||
1213 | static unsigned int | |
1214 | random_poll(struct file *file, poll_table * wait) | |
1215 | { | |
1216 | unsigned int mask; | |
1217 | ||
1218 | poll_wait(file, &random_read_wait, wait); | |
1219 | poll_wait(file, &random_write_wait, wait); | |
1220 | mask = 0; | |
1221 | if (input_pool.entropy_count >= random_read_wakeup_thresh) | |
1222 | mask |= POLLIN | POLLRDNORM; | |
1223 | if (input_pool.entropy_count < random_write_wakeup_thresh) | |
1224 | mask |= POLLOUT | POLLWRNORM; | |
1225 | return mask; | |
1226 | } | |
1227 | ||
7f397dcd MM |
1228 | static int |
1229 | write_pool(struct entropy_store *r, const char __user *buffer, size_t count) | |
1da177e4 | 1230 | { |
1da177e4 LT |
1231 | size_t bytes; |
1232 | __u32 buf[16]; | |
1233 | const char __user *p = buffer; | |
1da177e4 | 1234 | |
7f397dcd MM |
1235 | while (count > 0) { |
1236 | bytes = min(count, sizeof(buf)); | |
1237 | if (copy_from_user(&buf, p, bytes)) | |
1238 | return -EFAULT; | |
1da177e4 | 1239 | |
7f397dcd | 1240 | count -= bytes; |
1da177e4 LT |
1241 | p += bytes; |
1242 | ||
902c098a | 1243 | mix_pool_bytes(r, buf, bytes, NULL); |
91f3f1e3 | 1244 | cond_resched(); |
1da177e4 | 1245 | } |
7f397dcd MM |
1246 | |
1247 | return 0; | |
1248 | } | |
1249 | ||
90b75ee5 MM |
1250 | static ssize_t random_write(struct file *file, const char __user *buffer, |
1251 | size_t count, loff_t *ppos) | |
7f397dcd MM |
1252 | { |
1253 | size_t ret; | |
7f397dcd MM |
1254 | |
1255 | ret = write_pool(&blocking_pool, buffer, count); | |
1256 | if (ret) | |
1257 | return ret; | |
1258 | ret = write_pool(&nonblocking_pool, buffer, count); | |
1259 | if (ret) | |
1260 | return ret; | |
1261 | ||
7f397dcd | 1262 | return (ssize_t)count; |
1da177e4 LT |
1263 | } |
1264 | ||
43ae4860 | 1265 | static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) |
1da177e4 LT |
1266 | { |
1267 | int size, ent_count; | |
1268 | int __user *p = (int __user *)arg; | |
1269 | int retval; | |
1270 | ||
1271 | switch (cmd) { | |
1272 | case RNDGETENTCNT: | |
43ae4860 MM |
1273 | /* inherently racy, no point locking */ |
1274 | if (put_user(input_pool.entropy_count, p)) | |
1da177e4 LT |
1275 | return -EFAULT; |
1276 | return 0; | |
1277 | case RNDADDTOENTCNT: | |
1278 | if (!capable(CAP_SYS_ADMIN)) | |
1279 | return -EPERM; | |
1280 | if (get_user(ent_count, p)) | |
1281 | return -EFAULT; | |
adc782da | 1282 | credit_entropy_bits(&input_pool, ent_count); |
1da177e4 LT |
1283 | return 0; |
1284 | case RNDADDENTROPY: | |
1285 | if (!capable(CAP_SYS_ADMIN)) | |
1286 | return -EPERM; | |
1287 | if (get_user(ent_count, p++)) | |
1288 | return -EFAULT; | |
1289 | if (ent_count < 0) | |
1290 | return -EINVAL; | |
1291 | if (get_user(size, p++)) | |
1292 | return -EFAULT; | |
7f397dcd MM |
1293 | retval = write_pool(&input_pool, (const char __user *)p, |
1294 | size); | |
1da177e4 LT |
1295 | if (retval < 0) |
1296 | return retval; | |
adc782da | 1297 | credit_entropy_bits(&input_pool, ent_count); |
1da177e4 LT |
1298 | return 0; |
1299 | case RNDZAPENTCNT: | |
1300 | case RNDCLEARPOOL: | |
1301 | /* Clear the entropy pool counters. */ | |
1302 | if (!capable(CAP_SYS_ADMIN)) | |
1303 | return -EPERM; | |
53c3f63e | 1304 | rand_initialize(); |
1da177e4 LT |
1305 | return 0; |
1306 | default: | |
1307 | return -EINVAL; | |
1308 | } | |
1309 | } | |
1310 | ||
9a6f70bb JD |
1311 | static int random_fasync(int fd, struct file *filp, int on) |
1312 | { | |
1313 | return fasync_helper(fd, filp, on, &fasync); | |
1314 | } | |
1315 | ||
2b8693c0 | 1316 | const struct file_operations random_fops = { |
1da177e4 LT |
1317 | .read = random_read, |
1318 | .write = random_write, | |
1319 | .poll = random_poll, | |
43ae4860 | 1320 | .unlocked_ioctl = random_ioctl, |
9a6f70bb | 1321 | .fasync = random_fasync, |
6038f373 | 1322 | .llseek = noop_llseek, |
1da177e4 LT |
1323 | }; |
1324 | ||
2b8693c0 | 1325 | const struct file_operations urandom_fops = { |
1da177e4 LT |
1326 | .read = urandom_read, |
1327 | .write = random_write, | |
43ae4860 | 1328 | .unlocked_ioctl = random_ioctl, |
9a6f70bb | 1329 | .fasync = random_fasync, |
6038f373 | 1330 | .llseek = noop_llseek, |
1da177e4 LT |
1331 | }; |
1332 | ||
1333 | /*************************************************************** | |
1334 | * Random UUID interface | |
1335 | * | |
1336 | * Used here for a Boot ID, but can be useful for other kernel | |
1337 | * drivers. | |
1338 | ***************************************************************/ | |
1339 | ||
1340 | /* | |
1341 | * Generate random UUID | |
1342 | */ | |
1343 | void generate_random_uuid(unsigned char uuid_out[16]) | |
1344 | { | |
1345 | get_random_bytes(uuid_out, 16); | |
c41b20e7 | 1346 | /* Set UUID version to 4 --- truly random generation */ |
1da177e4 LT |
1347 | uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40; |
1348 | /* Set the UUID variant to DCE */ | |
1349 | uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80; | |
1350 | } | |
1da177e4 LT |
1351 | EXPORT_SYMBOL(generate_random_uuid); |
1352 | ||
1353 | /******************************************************************** | |
1354 | * | |
1355 | * Sysctl interface | |
1356 | * | |
1357 | ********************************************************************/ | |
1358 | ||
1359 | #ifdef CONFIG_SYSCTL | |
1360 | ||
1361 | #include <linux/sysctl.h> | |
1362 | ||
1363 | static int min_read_thresh = 8, min_write_thresh; | |
1364 | static int max_read_thresh = INPUT_POOL_WORDS * 32; | |
1365 | static int max_write_thresh = INPUT_POOL_WORDS * 32; | |
1366 | static char sysctl_bootid[16]; | |
1367 | ||
1368 | /* | |
1369 | * These functions is used to return both the bootid UUID, and random | |
1370 | * UUID. The difference is in whether table->data is NULL; if it is, | |
1371 | * then a new UUID is generated and returned to the user. | |
1372 | * | |
1373 | * If the user accesses this via the proc interface, it will be returned | |
1374 | * as an ASCII string in the standard UUID format. If accesses via the | |
1375 | * sysctl system call, it is returned as 16 bytes of binary data. | |
1376 | */ | |
8d65af78 | 1377 | static int proc_do_uuid(ctl_table *table, int write, |
1da177e4 LT |
1378 | void __user *buffer, size_t *lenp, loff_t *ppos) |
1379 | { | |
1380 | ctl_table fake_table; | |
1381 | unsigned char buf[64], tmp_uuid[16], *uuid; | |
1382 | ||
1383 | uuid = table->data; | |
1384 | if (!uuid) { | |
1385 | uuid = tmp_uuid; | |
1da177e4 | 1386 | generate_random_uuid(uuid); |
44e4360f MD |
1387 | } else { |
1388 | static DEFINE_SPINLOCK(bootid_spinlock); | |
1389 | ||
1390 | spin_lock(&bootid_spinlock); | |
1391 | if (!uuid[8]) | |
1392 | generate_random_uuid(uuid); | |
1393 | spin_unlock(&bootid_spinlock); | |
1394 | } | |
1da177e4 | 1395 | |
35900771 JP |
1396 | sprintf(buf, "%pU", uuid); |
1397 | ||
1da177e4 LT |
1398 | fake_table.data = buf; |
1399 | fake_table.maxlen = sizeof(buf); | |
1400 | ||
8d65af78 | 1401 | return proc_dostring(&fake_table, write, buffer, lenp, ppos); |
1da177e4 LT |
1402 | } |
1403 | ||
1da177e4 | 1404 | static int sysctl_poolsize = INPUT_POOL_WORDS * 32; |
74feec5d | 1405 | extern ctl_table random_table[]; |
1da177e4 LT |
1406 | ctl_table random_table[] = { |
1407 | { | |
1da177e4 LT |
1408 | .procname = "poolsize", |
1409 | .data = &sysctl_poolsize, | |
1410 | .maxlen = sizeof(int), | |
1411 | .mode = 0444, | |
6d456111 | 1412 | .proc_handler = proc_dointvec, |
1da177e4 LT |
1413 | }, |
1414 | { | |
1da177e4 LT |
1415 | .procname = "entropy_avail", |
1416 | .maxlen = sizeof(int), | |
1417 | .mode = 0444, | |
6d456111 | 1418 | .proc_handler = proc_dointvec, |
1da177e4 LT |
1419 | .data = &input_pool.entropy_count, |
1420 | }, | |
1421 | { | |
1da177e4 LT |
1422 | .procname = "read_wakeup_threshold", |
1423 | .data = &random_read_wakeup_thresh, | |
1424 | .maxlen = sizeof(int), | |
1425 | .mode = 0644, | |
6d456111 | 1426 | .proc_handler = proc_dointvec_minmax, |
1da177e4 LT |
1427 | .extra1 = &min_read_thresh, |
1428 | .extra2 = &max_read_thresh, | |
1429 | }, | |
1430 | { | |
1da177e4 LT |
1431 | .procname = "write_wakeup_threshold", |
1432 | .data = &random_write_wakeup_thresh, | |
1433 | .maxlen = sizeof(int), | |
1434 | .mode = 0644, | |
6d456111 | 1435 | .proc_handler = proc_dointvec_minmax, |
1da177e4 LT |
1436 | .extra1 = &min_write_thresh, |
1437 | .extra2 = &max_write_thresh, | |
1438 | }, | |
1439 | { | |
1da177e4 LT |
1440 | .procname = "boot_id", |
1441 | .data = &sysctl_bootid, | |
1442 | .maxlen = 16, | |
1443 | .mode = 0444, | |
6d456111 | 1444 | .proc_handler = proc_do_uuid, |
1da177e4 LT |
1445 | }, |
1446 | { | |
1da177e4 LT |
1447 | .procname = "uuid", |
1448 | .maxlen = 16, | |
1449 | .mode = 0444, | |
6d456111 | 1450 | .proc_handler = proc_do_uuid, |
1da177e4 | 1451 | }, |
894d2491 | 1452 | { } |
1da177e4 LT |
1453 | }; |
1454 | #endif /* CONFIG_SYSCTL */ | |
1455 | ||
6e5714ea | 1456 | static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned; |
1da177e4 | 1457 | |
6e5714ea | 1458 | static int __init random_int_secret_init(void) |
1da177e4 | 1459 | { |
6e5714ea | 1460 | get_random_bytes(random_int_secret, sizeof(random_int_secret)); |
1da177e4 LT |
1461 | return 0; |
1462 | } | |
6e5714ea | 1463 | late_initcall(random_int_secret_init); |
1da177e4 LT |
1464 | |
1465 | /* | |
1466 | * Get a random word for internal kernel use only. Similar to urandom but | |
1467 | * with the goal of minimal entropy pool depletion. As a result, the random | |
1468 | * value is not cryptographically secure but for several uses the cost of | |
1469 | * depleting entropy is too high | |
1470 | */ | |
74feec5d | 1471 | static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash); |
1da177e4 LT |
1472 | unsigned int get_random_int(void) |
1473 | { | |
63d77173 | 1474 | __u32 *hash; |
6e5714ea | 1475 | unsigned int ret; |
8a0a9bd4 | 1476 | |
63d77173 PA |
1477 | if (arch_get_random_int(&ret)) |
1478 | return ret; | |
1479 | ||
1480 | hash = get_cpu_var(get_random_int_hash); | |
8a0a9bd4 | 1481 | |
26a9a418 | 1482 | hash[0] += current->pid + jiffies + get_cycles(); |
6e5714ea DM |
1483 | md5_transform(hash, random_int_secret); |
1484 | ret = hash[0]; | |
8a0a9bd4 LT |
1485 | put_cpu_var(get_random_int_hash); |
1486 | ||
1487 | return ret; | |
1da177e4 LT |
1488 | } |
1489 | ||
1490 | /* | |
1491 | * randomize_range() returns a start address such that | |
1492 | * | |
1493 | * [...... <range> .....] | |
1494 | * start end | |
1495 | * | |
1496 | * a <range> with size "len" starting at the return value is inside in the | |
1497 | * area defined by [start, end], but is otherwise randomized. | |
1498 | */ | |
1499 | unsigned long | |
1500 | randomize_range(unsigned long start, unsigned long end, unsigned long len) | |
1501 | { | |
1502 | unsigned long range = end - len - start; | |
1503 | ||
1504 | if (end <= start + len) | |
1505 | return 0; | |
1506 | return PAGE_ALIGN(get_random_int() % range + start); | |
1507 | } |