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