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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> |
cc89abca | 258 | #include <linux/uuid.h> |
1da177e4 | 259 | |
d178a1eb YL |
260 | #ifdef CONFIG_GENERIC_HARDIRQS |
261 | # include <linux/irq.h> | |
262 | #endif | |
263 | ||
54439ba6 TT |
264 | #include <linux/syscalls.h> |
265 | #include <linux/completion.h> | |
266 | ||
1da177e4 LT |
267 | #include <asm/processor.h> |
268 | #include <asm/uaccess.h> | |
269 | #include <asm/irq.h> | |
775f4b29 | 270 | #include <asm/irq_regs.h> |
1da177e4 LT |
271 | #include <asm/io.h> |
272 | ||
00ce1db1 TT |
273 | #define CREATE_TRACE_POINTS |
274 | #include <trace/events/random.h> | |
275 | ||
1da177e4 LT |
276 | /* |
277 | * Configuration information | |
278 | */ | |
279 | #define INPUT_POOL_WORDS 128 | |
280 | #define OUTPUT_POOL_WORDS 32 | |
281 | #define SEC_XFER_SIZE 512 | |
e954bc91 | 282 | #define EXTRACT_SIZE 10 |
1da177e4 | 283 | |
d2e7c96a PA |
284 | #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long)) |
285 | ||
1da177e4 LT |
286 | /* |
287 | * The minimum number of bits of entropy before we wake up a read on | |
288 | * /dev/random. Should be enough to do a significant reseed. | |
289 | */ | |
3c2a0909 S |
290 | #ifdef CONFIG_CRYPTO_FIPS |
291 | static int random_read_wakeup_thresh = 256; | |
292 | #else | |
1da177e4 | 293 | static int random_read_wakeup_thresh = 64; |
3c2a0909 | 294 | #endif |
1da177e4 LT |
295 | /* |
296 | * If the entropy count falls under this number of bits, then we | |
297 | * should wake up processes which are selecting or polling on write | |
298 | * access to /dev/random. | |
299 | */ | |
3c2a0909 S |
300 | #ifdef CONFIG_CRYPTO_FIPS |
301 | static int random_write_wakeup_thresh = 320; | |
302 | #else | |
1da177e4 | 303 | static int random_write_wakeup_thresh = 128; |
3c2a0909 | 304 | #endif |
1da177e4 LT |
305 | |
306 | /* | |
307 | * When the input pool goes over trickle_thresh, start dropping most | |
308 | * samples to avoid wasting CPU time and reduce lock contention. | |
309 | */ | |
310 | ||
6c036527 | 311 | static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28; |
1da177e4 | 312 | |
90b75ee5 | 313 | static DEFINE_PER_CPU(int, trickle_count); |
1da177e4 LT |
314 | |
315 | /* | |
316 | * A pool of size .poolwords is stirred with a primitive polynomial | |
317 | * of degree .poolwords over GF(2). The taps for various sizes are | |
318 | * defined below. They are chosen to be evenly spaced (minimum RMS | |
319 | * distance from evenly spaced; the numbers in the comments are a | |
320 | * scaled squared error sum) except for the last tap, which is 1 to | |
321 | * get the twisting happening as fast as possible. | |
322 | */ | |
323 | static struct poolinfo { | |
324 | int poolwords; | |
325 | int tap1, tap2, tap3, tap4, tap5; | |
326 | } poolinfo_table[] = { | |
327 | /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */ | |
328 | { 128, 103, 76, 51, 25, 1 }, | |
329 | /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */ | |
330 | { 32, 26, 20, 14, 7, 1 }, | |
331 | #if 0 | |
332 | /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */ | |
333 | { 2048, 1638, 1231, 819, 411, 1 }, | |
334 | ||
335 | /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */ | |
336 | { 1024, 817, 615, 412, 204, 1 }, | |
337 | ||
338 | /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */ | |
339 | { 1024, 819, 616, 410, 207, 2 }, | |
340 | ||
341 | /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */ | |
342 | { 512, 411, 308, 208, 104, 1 }, | |
343 | ||
344 | /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */ | |
345 | { 512, 409, 307, 206, 102, 2 }, | |
346 | /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */ | |
347 | { 512, 409, 309, 205, 103, 2 }, | |
348 | ||
349 | /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */ | |
350 | { 256, 205, 155, 101, 52, 1 }, | |
351 | ||
352 | /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */ | |
353 | { 128, 103, 78, 51, 27, 2 }, | |
354 | ||
355 | /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */ | |
356 | { 64, 52, 39, 26, 14, 1 }, | |
357 | #endif | |
358 | }; | |
359 | ||
360 | #define POOLBITS poolwords*32 | |
361 | #define POOLBYTES poolwords*4 | |
362 | ||
363 | /* | |
364 | * For the purposes of better mixing, we use the CRC-32 polynomial as | |
365 | * well to make a twisted Generalized Feedback Shift Reigster | |
366 | * | |
367 | * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM | |
368 | * Transactions on Modeling and Computer Simulation 2(3):179-194. | |
369 | * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators | |
370 | * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266) | |
371 | * | |
372 | * Thanks to Colin Plumb for suggesting this. | |
373 | * | |
374 | * We have not analyzed the resultant polynomial to prove it primitive; | |
375 | * in fact it almost certainly isn't. Nonetheless, the irreducible factors | |
376 | * of a random large-degree polynomial over GF(2) are more than large enough | |
377 | * that periodicity is not a concern. | |
378 | * | |
379 | * The input hash is much less sensitive than the output hash. All | |
380 | * that we want of it is that it be a good non-cryptographic hash; | |
381 | * i.e. it not produce collisions when fed "random" data of the sort | |
382 | * we expect to see. As long as the pool state differs for different | |
383 | * inputs, we have preserved the input entropy and done a good job. | |
384 | * The fact that an intelligent attacker can construct inputs that | |
385 | * will produce controlled alterations to the pool's state is not | |
386 | * important because we don't consider such inputs to contribute any | |
387 | * randomness. The only property we need with respect to them is that | |
388 | * the attacker can't increase his/her knowledge of the pool's state. | |
389 | * Since all additions are reversible (knowing the final state and the | |
390 | * input, you can reconstruct the initial state), if an attacker has | |
391 | * any uncertainty about the initial state, he/she can only shuffle | |
392 | * that uncertainty about, but never cause any collisions (which would | |
393 | * decrease the uncertainty). | |
394 | * | |
395 | * The chosen system lets the state of the pool be (essentially) the input | |
396 | * modulo the generator polymnomial. Now, for random primitive polynomials, | |
397 | * this is a universal class of hash functions, meaning that the chance | |
398 | * of a collision is limited by the attacker's knowledge of the generator | |
399 | * polynomail, so if it is chosen at random, an attacker can never force | |
400 | * a collision. Here, we use a fixed polynomial, but we *can* assume that | |
401 | * ###--> it is unknown to the processes generating the input entropy. <-### | |
402 | * Because of this important property, this is a good, collision-resistant | |
403 | * hash; hash collisions will occur no more often than chance. | |
404 | */ | |
405 | ||
406 | /* | |
407 | * Static global variables | |
408 | */ | |
409 | static DECLARE_WAIT_QUEUE_HEAD(random_read_wait); | |
410 | static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); | |
54439ba6 | 411 | static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait); |
9a6f70bb | 412 | static struct fasync_struct *fasync; |
1da177e4 | 413 | |
90ab5ee9 | 414 | static bool debug; |
1da177e4 | 415 | module_param(debug, bool, 0644); |
90b75ee5 MM |
416 | #define DEBUG_ENT(fmt, arg...) do { \ |
417 | if (debug) \ | |
418 | printk(KERN_DEBUG "random %04d %04d %04d: " \ | |
419 | fmt,\ | |
420 | input_pool.entropy_count,\ | |
421 | blocking_pool.entropy_count,\ | |
422 | nonblocking_pool.entropy_count,\ | |
423 | ## arg); } while (0) | |
1da177e4 LT |
424 | |
425 | /********************************************************************** | |
426 | * | |
427 | * OS independent entropy store. Here are the functions which handle | |
428 | * storing entropy in an entropy pool. | |
429 | * | |
430 | **********************************************************************/ | |
431 | ||
432 | struct entropy_store; | |
433 | struct entropy_store { | |
43358209 | 434 | /* read-only data: */ |
1da177e4 LT |
435 | struct poolinfo *poolinfo; |
436 | __u32 *pool; | |
437 | const char *name; | |
1da177e4 | 438 | struct entropy_store *pull; |
4015d9a8 | 439 | int limit; |
1da177e4 LT |
440 | |
441 | /* read-write data: */ | |
43358209 | 442 | spinlock_t lock; |
1da177e4 | 443 | unsigned add_ptr; |
902c098a | 444 | unsigned input_rotate; |
cda796a3 | 445 | int entropy_count; |
775f4b29 | 446 | int entropy_total; |
775f4b29 | 447 | unsigned int initialized:1; |
ec8f02da | 448 | bool last_data_init; |
e954bc91 | 449 | __u8 last_data[EXTRACT_SIZE]; |
1da177e4 LT |
450 | }; |
451 | ||
452 | static __u32 input_pool_data[INPUT_POOL_WORDS]; | |
453 | static __u32 blocking_pool_data[OUTPUT_POOL_WORDS]; | |
454 | static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS]; | |
455 | ||
456 | static struct entropy_store input_pool = { | |
457 | .poolinfo = &poolinfo_table[0], | |
458 | .name = "input", | |
459 | .limit = 1, | |
eece09ec | 460 | .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), |
1da177e4 LT |
461 | .pool = input_pool_data |
462 | }; | |
463 | ||
464 | static struct entropy_store blocking_pool = { | |
465 | .poolinfo = &poolinfo_table[1], | |
466 | .name = "blocking", | |
467 | .limit = 1, | |
468 | .pull = &input_pool, | |
eece09ec | 469 | .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock), |
1da177e4 LT |
470 | .pool = blocking_pool_data |
471 | }; | |
472 | ||
473 | static struct entropy_store nonblocking_pool = { | |
474 | .poolinfo = &poolinfo_table[1], | |
475 | .name = "nonblocking", | |
476 | .pull = &input_pool, | |
eece09ec | 477 | .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock), |
1da177e4 LT |
478 | .pool = nonblocking_pool_data |
479 | }; | |
480 | ||
775f4b29 TT |
481 | static __u32 const twist_table[8] = { |
482 | 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158, | |
483 | 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; | |
484 | ||
1da177e4 | 485 | /* |
e68e5b66 | 486 | * This function adds bytes into the entropy "pool". It does not |
1da177e4 | 487 | * update the entropy estimate. The caller should call |
adc782da | 488 | * credit_entropy_bits if this is appropriate. |
1da177e4 LT |
489 | * |
490 | * The pool is stirred with a primitive polynomial of the appropriate | |
491 | * degree, and then twisted. We twist by three bits at a time because | |
492 | * it's cheap to do so and helps slightly in the expected case where | |
493 | * the entropy is concentrated in the low-order bits. | |
494 | */ | |
00ce1db1 TT |
495 | static void _mix_pool_bytes(struct entropy_store *r, const void *in, |
496 | int nbytes, __u8 out[64]) | |
1da177e4 | 497 | { |
993ba211 | 498 | unsigned long i, j, tap1, tap2, tap3, tap4, tap5; |
feee7697 | 499 | int input_rotate; |
1da177e4 | 500 | int wordmask = r->poolinfo->poolwords - 1; |
e68e5b66 | 501 | const char *bytes = in; |
6d38b827 | 502 | __u32 w; |
1da177e4 | 503 | |
1da177e4 LT |
504 | tap1 = r->poolinfo->tap1; |
505 | tap2 = r->poolinfo->tap2; | |
506 | tap3 = r->poolinfo->tap3; | |
507 | tap4 = r->poolinfo->tap4; | |
508 | tap5 = r->poolinfo->tap5; | |
1da177e4 | 509 | |
902c098a TT |
510 | smp_rmb(); |
511 | input_rotate = ACCESS_ONCE(r->input_rotate); | |
512 | i = ACCESS_ONCE(r->add_ptr); | |
1da177e4 | 513 | |
e68e5b66 MM |
514 | /* mix one byte at a time to simplify size handling and churn faster */ |
515 | while (nbytes--) { | |
516 | w = rol32(*bytes++, input_rotate & 31); | |
993ba211 | 517 | i = (i - 1) & wordmask; |
1da177e4 LT |
518 | |
519 | /* XOR in the various taps */ | |
993ba211 | 520 | w ^= r->pool[i]; |
1da177e4 LT |
521 | w ^= r->pool[(i + tap1) & wordmask]; |
522 | w ^= r->pool[(i + tap2) & wordmask]; | |
523 | w ^= r->pool[(i + tap3) & wordmask]; | |
524 | w ^= r->pool[(i + tap4) & wordmask]; | |
525 | w ^= r->pool[(i + tap5) & wordmask]; | |
993ba211 MM |
526 | |
527 | /* Mix the result back in with a twist */ | |
1da177e4 | 528 | r->pool[i] = (w >> 3) ^ twist_table[w & 7]; |
feee7697 MM |
529 | |
530 | /* | |
531 | * Normally, we add 7 bits of rotation to the pool. | |
532 | * At the beginning of the pool, add an extra 7 bits | |
533 | * rotation, so that successive passes spread the | |
534 | * input bits across the pool evenly. | |
535 | */ | |
536 | input_rotate += i ? 7 : 14; | |
1da177e4 LT |
537 | } |
538 | ||
902c098a TT |
539 | ACCESS_ONCE(r->input_rotate) = input_rotate; |
540 | ACCESS_ONCE(r->add_ptr) = i; | |
541 | smp_wmb(); | |
1da177e4 | 542 | |
993ba211 MM |
543 | if (out) |
544 | for (j = 0; j < 16; j++) | |
e68e5b66 | 545 | ((__u32 *)out)[j] = r->pool[(i - j) & wordmask]; |
1da177e4 LT |
546 | } |
547 | ||
00ce1db1 | 548 | static void __mix_pool_bytes(struct entropy_store *r, const void *in, |
902c098a | 549 | int nbytes, __u8 out[64]) |
00ce1db1 TT |
550 | { |
551 | trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_); | |
552 | _mix_pool_bytes(r, in, nbytes, out); | |
553 | } | |
554 | ||
555 | static void mix_pool_bytes(struct entropy_store *r, const void *in, | |
556 | int nbytes, __u8 out[64]) | |
1da177e4 | 557 | { |
902c098a TT |
558 | unsigned long flags; |
559 | ||
00ce1db1 | 560 | trace_mix_pool_bytes(r->name, nbytes, _RET_IP_); |
902c098a | 561 | spin_lock_irqsave(&r->lock, flags); |
00ce1db1 | 562 | _mix_pool_bytes(r, in, nbytes, out); |
902c098a | 563 | spin_unlock_irqrestore(&r->lock, flags); |
1da177e4 LT |
564 | } |
565 | ||
775f4b29 TT |
566 | struct fast_pool { |
567 | __u32 pool[4]; | |
568 | unsigned long last; | |
569 | unsigned short count; | |
570 | unsigned char rotate; | |
571 | unsigned char last_timer_intr; | |
572 | }; | |
573 | ||
574 | /* | |
575 | * This is a fast mixing routine used by the interrupt randomness | |
576 | * collector. It's hardcoded for an 128 bit pool and assumes that any | |
577 | * locks that might be needed are taken by the caller. | |
578 | */ | |
579 | static void fast_mix(struct fast_pool *f, const void *in, int nbytes) | |
580 | { | |
581 | const char *bytes = in; | |
582 | __u32 w; | |
583 | unsigned i = f->count; | |
584 | unsigned input_rotate = f->rotate; | |
585 | ||
586 | while (nbytes--) { | |
587 | w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^ | |
588 | f->pool[(i + 1) & 3]; | |
589 | f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7]; | |
590 | input_rotate += (i++ & 3) ? 7 : 14; | |
591 | } | |
592 | f->count = i; | |
593 | f->rotate = input_rotate; | |
594 | } | |
595 | ||
1da177e4 LT |
596 | /* |
597 | * Credit (or debit) the entropy store with n bits of entropy | |
598 | */ | |
adc782da | 599 | static void credit_entropy_bits(struct entropy_store *r, int nbits) |
1da177e4 | 600 | { |
902c098a | 601 | int entropy_count, orig; |
1da177e4 | 602 | |
adc782da MM |
603 | if (!nbits) |
604 | return; | |
605 | ||
adc782da | 606 | DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name); |
902c098a TT |
607 | retry: |
608 | entropy_count = orig = ACCESS_ONCE(r->entropy_count); | |
8b76f46a | 609 | entropy_count += nbits; |
00ce1db1 | 610 | |
8b76f46a | 611 | if (entropy_count < 0) { |
adc782da | 612 | DEBUG_ENT("negative entropy/overflow\n"); |
8b76f46a AM |
613 | entropy_count = 0; |
614 | } else if (entropy_count > r->poolinfo->POOLBITS) | |
615 | entropy_count = r->poolinfo->POOLBITS; | |
902c098a TT |
616 | if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) |
617 | goto retry; | |
1da177e4 | 618 | |
54439ba6 TT |
619 | r->entropy_total += nbits; |
620 | if (!r->initialized && r->entropy_total > 128) { | |
621 | r->initialized = 1; | |
622 | r->entropy_total = 0; | |
623 | if (r == &nonblocking_pool) { | |
624 | prandom_reseed_late(); | |
3fe7fd34 | 625 | wake_up_all(&urandom_init_wait); |
54439ba6 | 626 | pr_notice("random: %s pool is initialized\n", r->name); |
cb7af6c5 | 627 | } |
775f4b29 TT |
628 | } |
629 | ||
00ce1db1 TT |
630 | trace_credit_entropy_bits(r->name, nbits, entropy_count, |
631 | r->entropy_total, _RET_IP_); | |
632 | ||
88c730da | 633 | /* should we wake readers? */ |
8b76f46a | 634 | if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) { |
88c730da | 635 | wake_up_interruptible(&random_read_wait); |
9a6f70bb JD |
636 | kill_fasync(&fasync, SIGIO, POLL_IN); |
637 | } | |
1da177e4 LT |
638 | } |
639 | ||
640 | /********************************************************************* | |
641 | * | |
642 | * Entropy input management | |
643 | * | |
644 | *********************************************************************/ | |
645 | ||
646 | /* There is one of these per entropy source */ | |
647 | struct timer_rand_state { | |
648 | cycles_t last_time; | |
90b75ee5 | 649 | long last_delta, last_delta2; |
1da177e4 LT |
650 | unsigned dont_count_entropy:1; |
651 | }; | |
652 | ||
a2080a67 LT |
653 | /* |
654 | * Add device- or boot-specific data to the input and nonblocking | |
655 | * pools to help initialize them to unique values. | |
656 | * | |
657 | * None of this adds any entropy, it is meant to avoid the | |
658 | * problem of the nonblocking pool having similar initial state | |
659 | * across largely identical devices. | |
660 | */ | |
661 | void add_device_randomness(const void *buf, unsigned int size) | |
662 | { | |
663 | unsigned long time = get_cycles() ^ jiffies; | |
664 | ||
665 | mix_pool_bytes(&input_pool, buf, size, NULL); | |
666 | mix_pool_bytes(&input_pool, &time, sizeof(time), NULL); | |
667 | mix_pool_bytes(&nonblocking_pool, buf, size, NULL); | |
668 | mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL); | |
669 | } | |
670 | EXPORT_SYMBOL(add_device_randomness); | |
671 | ||
3060d6fe YL |
672 | static struct timer_rand_state input_timer_state; |
673 | ||
1da177e4 LT |
674 | /* |
675 | * This function adds entropy to the entropy "pool" by using timing | |
676 | * delays. It uses the timer_rand_state structure to make an estimate | |
677 | * of how many bits of entropy this call has added to the pool. | |
678 | * | |
679 | * The number "num" is also added to the pool - it should somehow describe | |
680 | * the type of event which just happened. This is currently 0-255 for | |
681 | * keyboard scan codes, and 256 upwards for interrupts. | |
682 | * | |
683 | */ | |
684 | static void add_timer_randomness(struct timer_rand_state *state, unsigned num) | |
685 | { | |
686 | struct { | |
1da177e4 | 687 | long jiffies; |
cf833d0b | 688 | unsigned cycles; |
1da177e4 LT |
689 | unsigned num; |
690 | } sample; | |
691 | long delta, delta2, delta3; | |
692 | ||
693 | preempt_disable(); | |
694 | /* if over the trickle threshold, use only 1 in 4096 samples */ | |
695 | if (input_pool.entropy_count > trickle_thresh && | |
b29c617a | 696 | ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff)) |
1da177e4 LT |
697 | goto out; |
698 | ||
699 | sample.jiffies = jiffies; | |
e6d4947b | 700 | sample.cycles = get_cycles(); |
1da177e4 | 701 | sample.num = num; |
902c098a | 702 | mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL); |
1da177e4 LT |
703 | |
704 | /* | |
705 | * Calculate number of bits of randomness we probably added. | |
706 | * We take into account the first, second and third-order deltas | |
707 | * in order to make our estimate. | |
708 | */ | |
709 | ||
710 | if (!state->dont_count_entropy) { | |
711 | delta = sample.jiffies - state->last_time; | |
712 | state->last_time = sample.jiffies; | |
713 | ||
714 | delta2 = delta - state->last_delta; | |
715 | state->last_delta = delta; | |
716 | ||
717 | delta3 = delta2 - state->last_delta2; | |
718 | state->last_delta2 = delta2; | |
719 | ||
720 | if (delta < 0) | |
721 | delta = -delta; | |
722 | if (delta2 < 0) | |
723 | delta2 = -delta2; | |
724 | if (delta3 < 0) | |
725 | delta3 = -delta3; | |
726 | if (delta > delta2) | |
727 | delta = delta2; | |
728 | if (delta > delta3) | |
729 | delta = delta3; | |
730 | ||
731 | /* | |
732 | * delta is now minimum absolute delta. | |
733 | * Round down by 1 bit on general principles, | |
734 | * and limit entropy entimate to 12 bits. | |
735 | */ | |
adc782da MM |
736 | credit_entropy_bits(&input_pool, |
737 | min_t(int, fls(delta>>1), 11)); | |
1da177e4 | 738 | } |
1da177e4 LT |
739 | out: |
740 | preempt_enable(); | |
741 | } | |
742 | ||
d251575a | 743 | void add_input_randomness(unsigned int type, unsigned int code, |
1da177e4 LT |
744 | unsigned int value) |
745 | { | |
746 | static unsigned char last_value; | |
747 | ||
748 | /* ignore autorepeat and the like */ | |
749 | if (value == last_value) | |
750 | return; | |
751 | ||
752 | DEBUG_ENT("input event\n"); | |
753 | last_value = value; | |
754 | add_timer_randomness(&input_timer_state, | |
755 | (type << 4) ^ code ^ (code >> 4) ^ value); | |
756 | } | |
80fc9f53 | 757 | EXPORT_SYMBOL_GPL(add_input_randomness); |
1da177e4 | 758 | |
775f4b29 TT |
759 | static DEFINE_PER_CPU(struct fast_pool, irq_randomness); |
760 | ||
761 | void add_interrupt_randomness(int irq, int irq_flags) | |
1da177e4 | 762 | { |
775f4b29 TT |
763 | struct entropy_store *r; |
764 | struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness); | |
765 | struct pt_regs *regs = get_irq_regs(); | |
766 | unsigned long now = jiffies; | |
767 | __u32 input[4], cycles = get_cycles(); | |
768 | ||
769 | input[0] = cycles ^ jiffies; | |
770 | input[1] = irq; | |
771 | if (regs) { | |
772 | __u64 ip = instruction_pointer(regs); | |
773 | input[2] = ip; | |
774 | input[3] = ip >> 32; | |
775 | } | |
3060d6fe | 776 | |
775f4b29 | 777 | fast_mix(fast_pool, input, sizeof(input)); |
3060d6fe | 778 | |
775f4b29 TT |
779 | if ((fast_pool->count & 1023) && |
780 | !time_after(now, fast_pool->last + HZ)) | |
1da177e4 LT |
781 | return; |
782 | ||
775f4b29 TT |
783 | fast_pool->last = now; |
784 | ||
785 | r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool; | |
902c098a | 786 | __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL); |
775f4b29 TT |
787 | /* |
788 | * If we don't have a valid cycle counter, and we see | |
789 | * back-to-back timer interrupts, then skip giving credit for | |
790 | * any entropy. | |
791 | */ | |
792 | if (cycles == 0) { | |
793 | if (irq_flags & __IRQF_TIMER) { | |
794 | if (fast_pool->last_timer_intr) | |
795 | return; | |
796 | fast_pool->last_timer_intr = 1; | |
797 | } else | |
798 | fast_pool->last_timer_intr = 0; | |
799 | } | |
800 | credit_entropy_bits(r, 1); | |
1da177e4 LT |
801 | } |
802 | ||
9361401e | 803 | #ifdef CONFIG_BLOCK |
1da177e4 LT |
804 | void add_disk_randomness(struct gendisk *disk) |
805 | { | |
806 | if (!disk || !disk->random) | |
807 | return; | |
808 | /* first major is 1, so we get >= 0x200 here */ | |
f331c029 TH |
809 | DEBUG_ENT("disk event %d:%d\n", |
810 | MAJOR(disk_devt(disk)), MINOR(disk_devt(disk))); | |
1da177e4 | 811 | |
f331c029 | 812 | add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); |
1da177e4 | 813 | } |
9361401e | 814 | #endif |
1da177e4 | 815 | |
1da177e4 LT |
816 | /********************************************************************* |
817 | * | |
818 | * Entropy extraction routines | |
819 | * | |
820 | *********************************************************************/ | |
821 | ||
90b75ee5 | 822 | static ssize_t extract_entropy(struct entropy_store *r, void *buf, |
1da177e4 LT |
823 | size_t nbytes, int min, int rsvd); |
824 | ||
825 | /* | |
25985edc | 826 | * This utility inline function is responsible for transferring entropy |
1da177e4 LT |
827 | * from the primary pool to the secondary extraction pool. We make |
828 | * sure we pull enough for a 'catastrophic reseed'. | |
829 | */ | |
830 | static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes) | |
831 | { | |
d2e7c96a | 832 | __u32 tmp[OUTPUT_POOL_WORDS]; |
1da177e4 LT |
833 | |
834 | if (r->pull && r->entropy_count < nbytes * 8 && | |
835 | r->entropy_count < r->poolinfo->POOLBITS) { | |
5a021e9f | 836 | /* If we're limited, always leave two wakeup worth's BITS */ |
1da177e4 | 837 | int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4; |
5a021e9f MM |
838 | int bytes = nbytes; |
839 | ||
840 | /* pull at least as many as BYTES as wakeup BITS */ | |
841 | bytes = max_t(int, bytes, random_read_wakeup_thresh / 8); | |
842 | /* but never more than the buffer size */ | |
d2e7c96a | 843 | bytes = min_t(int, bytes, sizeof(tmp)); |
1da177e4 LT |
844 | |
845 | DEBUG_ENT("going to reseed %s with %d bits " | |
8eb2ffbf | 846 | "(%zu of %d requested)\n", |
1da177e4 LT |
847 | r->name, bytes * 8, nbytes * 8, r->entropy_count); |
848 | ||
d2e7c96a | 849 | bytes = extract_entropy(r->pull, tmp, bytes, |
90b75ee5 | 850 | random_read_wakeup_thresh / 8, rsvd); |
d2e7c96a | 851 | mix_pool_bytes(r, tmp, bytes, NULL); |
adc782da | 852 | credit_entropy_bits(r, bytes*8); |
1da177e4 LT |
853 | } |
854 | } | |
855 | ||
856 | /* | |
857 | * These functions extracts randomness from the "entropy pool", and | |
858 | * returns it in a buffer. | |
859 | * | |
860 | * The min parameter specifies the minimum amount we can pull before | |
861 | * failing to avoid races that defeat catastrophic reseeding while the | |
862 | * reserved parameter indicates how much entropy we must leave in the | |
863 | * pool after each pull to avoid starving other readers. | |
864 | * | |
865 | * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words. | |
866 | */ | |
867 | ||
868 | static size_t account(struct entropy_store *r, size_t nbytes, int min, | |
869 | int reserved) | |
870 | { | |
871 | unsigned long flags; | |
b9809552 | 872 | int wakeup_write = 0; |
1da177e4 | 873 | |
1da177e4 LT |
874 | /* Hold lock while accounting */ |
875 | spin_lock_irqsave(&r->lock, flags); | |
876 | ||
cda796a3 | 877 | BUG_ON(r->entropy_count > r->poolinfo->POOLBITS); |
8eb2ffbf | 878 | DEBUG_ENT("trying to extract %zu bits from %s\n", |
1da177e4 LT |
879 | nbytes * 8, r->name); |
880 | ||
881 | /* Can we pull enough? */ | |
882 | if (r->entropy_count / 8 < min + reserved) { | |
883 | nbytes = 0; | |
884 | } else { | |
10b3a32d JK |
885 | int entropy_count, orig; |
886 | retry: | |
887 | entropy_count = orig = ACCESS_ONCE(r->entropy_count); | |
1da177e4 | 888 | /* If limited, never pull more than available */ |
10b3a32d JK |
889 | if (r->limit && nbytes + reserved >= entropy_count / 8) |
890 | nbytes = entropy_count/8 - reserved; | |
891 | ||
892 | if (entropy_count / 8 >= nbytes + reserved) { | |
893 | entropy_count -= nbytes*8; | |
894 | if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) | |
895 | goto retry; | |
896 | } else { | |
897 | entropy_count = reserved; | |
898 | if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) | |
899 | goto retry; | |
900 | } | |
901 | ||
902 | if (entropy_count < random_write_wakeup_thresh) | |
b9809552 | 903 | wakeup_write = 1; |
1da177e4 LT |
904 | } |
905 | ||
8eb2ffbf | 906 | DEBUG_ENT("debiting %zu entropy credits from %s%s\n", |
1da177e4 LT |
907 | nbytes * 8, r->name, r->limit ? "" : " (unlimited)"); |
908 | ||
909 | spin_unlock_irqrestore(&r->lock, flags); | |
910 | ||
b9809552 TT |
911 | if (wakeup_write) { |
912 | wake_up_interruptible(&random_write_wait); | |
913 | kill_fasync(&fasync, SIGIO, POLL_OUT); | |
914 | } | |
915 | ||
1da177e4 LT |
916 | return nbytes; |
917 | } | |
918 | ||
919 | static void extract_buf(struct entropy_store *r, __u8 *out) | |
920 | { | |
602b6aee | 921 | int i; |
d2e7c96a PA |
922 | union { |
923 | __u32 w[5]; | |
924 | unsigned long l[LONGS(EXTRACT_SIZE)]; | |
925 | } hash; | |
926 | __u32 workspace[SHA_WORKSPACE_WORDS]; | |
e68e5b66 | 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 */ |
d2e7c96a | 931 | sha_init(hash.w); |
902c098a | 932 | spin_lock_irqsave(&r->lock, flags); |
1c0ad3d4 | 933 | for (i = 0; i < r->poolinfo->poolwords; i += 16) |
d2e7c96a | 934 | sha_transform(hash.w, (__u8 *)(r->pool + i), workspace); |
1c0ad3d4 | 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 | */ |
d2e7c96a | 945 | __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract); |
902c098a | 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 | */ |
d2e7c96a | 952 | sha_transform(hash.w, extract, workspace); |
25e1465a DB |
953 | memzero_explicit(extract, sizeof(extract)); |
954 | memzero_explicit(workspace, 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 | */ |
d2e7c96a PA |
961 | hash.w[0] ^= hash.w[3]; |
962 | hash.w[1] ^= hash.w[4]; | |
963 | hash.w[2] ^= rol32(hash.w[2], 16); | |
964 | ||
965 | /* | |
966 | * If we have a architectural hardware random number | |
967 | * generator, mix that in, too. | |
968 | */ | |
969 | for (i = 0; i < LONGS(EXTRACT_SIZE); i++) { | |
970 | unsigned long v; | |
971 | if (!arch_get_random_long(&v)) | |
972 | break; | |
973 | hash.l[i] ^= v; | |
974 | } | |
975 | ||
976 | memcpy(out, &hash, EXTRACT_SIZE); | |
25e1465a | 977 | memzero_explicit(&hash, sizeof(hash)); |
1da177e4 LT |
978 | } |
979 | ||
90b75ee5 | 980 | static ssize_t extract_entropy(struct entropy_store *r, void *buf, |
902c098a | 981 | size_t nbytes, int min, int reserved) |
1da177e4 LT |
982 | { |
983 | ssize_t ret = 0, i; | |
984 | __u8 tmp[EXTRACT_SIZE]; | |
1e7e2e05 | 985 | unsigned long flags; |
1da177e4 | 986 | |
ec8f02da | 987 | /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */ |
1e7e2e05 JW |
988 | if (fips_enabled) { |
989 | spin_lock_irqsave(&r->lock, flags); | |
990 | if (!r->last_data_init) { | |
991 | r->last_data_init = true; | |
992 | spin_unlock_irqrestore(&r->lock, flags); | |
993 | trace_extract_entropy(r->name, EXTRACT_SIZE, | |
994 | r->entropy_count, _RET_IP_); | |
995 | xfer_secondary_pool(r, EXTRACT_SIZE); | |
996 | extract_buf(r, tmp); | |
997 | spin_lock_irqsave(&r->lock, flags); | |
998 | memcpy(r->last_data, tmp, EXTRACT_SIZE); | |
999 | } | |
1000 | spin_unlock_irqrestore(&r->lock, flags); | |
1001 | } | |
ec8f02da | 1002 | |
00ce1db1 | 1003 | trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_); |
1da177e4 LT |
1004 | xfer_secondary_pool(r, nbytes); |
1005 | nbytes = account(r, nbytes, min, reserved); | |
1006 | ||
1007 | while (nbytes) { | |
1008 | extract_buf(r, tmp); | |
5b739ef8 | 1009 | |
e954bc91 | 1010 | if (fips_enabled) { |
5b739ef8 NH |
1011 | spin_lock_irqsave(&r->lock, flags); |
1012 | if (!memcmp(tmp, r->last_data, EXTRACT_SIZE)) | |
1013 | panic("Hardware RNG duplicated output!\n"); | |
1014 | memcpy(r->last_data, tmp, EXTRACT_SIZE); | |
1015 | spin_unlock_irqrestore(&r->lock, flags); | |
1016 | } | |
1da177e4 LT |
1017 | i = min_t(int, nbytes, EXTRACT_SIZE); |
1018 | memcpy(buf, tmp, i); | |
1019 | nbytes -= i; | |
1020 | buf += i; | |
1021 | ret += i; | |
1022 | } | |
1023 | ||
1024 | /* Wipe data just returned from memory */ | |
25e1465a | 1025 | memzero_explicit(tmp, sizeof(tmp)); |
1da177e4 LT |
1026 | |
1027 | return ret; | |
1028 | } | |
1029 | ||
1030 | static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, | |
1031 | size_t nbytes) | |
1032 | { | |
1033 | ssize_t ret = 0, i; | |
1034 | __u8 tmp[EXTRACT_SIZE]; | |
54439ba6 | 1035 | int large_request = (nbytes > 256); |
1da177e4 | 1036 | |
00ce1db1 | 1037 | trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_); |
1da177e4 LT |
1038 | xfer_secondary_pool(r, nbytes); |
1039 | nbytes = account(r, nbytes, 0, 0); | |
1040 | ||
1041 | while (nbytes) { | |
54439ba6 | 1042 | if (large_request && need_resched()) { |
1da177e4 LT |
1043 | if (signal_pending(current)) { |
1044 | if (ret == 0) | |
1045 | ret = -ERESTARTSYS; | |
1046 | break; | |
1047 | } | |
1048 | schedule(); | |
1049 | } | |
1050 | ||
1051 | extract_buf(r, tmp); | |
1052 | i = min_t(int, nbytes, EXTRACT_SIZE); | |
1053 | if (copy_to_user(buf, tmp, i)) { | |
1054 | ret = -EFAULT; | |
1055 | break; | |
1056 | } | |
1057 | ||
1058 | nbytes -= i; | |
1059 | buf += i; | |
1060 | ret += i; | |
1061 | } | |
1062 | ||
1063 | /* Wipe data just returned from memory */ | |
25e1465a | 1064 | memzero_explicit(tmp, sizeof(tmp)); |
1da177e4 LT |
1065 | |
1066 | return ret; | |
1067 | } | |
1068 | ||
1069 | /* | |
1070 | * This function is the exported kernel interface. It returns some | |
c2557a30 TT |
1071 | * number of good random numbers, suitable for key generation, seeding |
1072 | * TCP sequence numbers, etc. It does not use the hw random number | |
1073 | * generator, if available; use get_random_bytes_arch() for that. | |
1da177e4 LT |
1074 | */ |
1075 | void get_random_bytes(void *buf, int nbytes) | |
c2557a30 TT |
1076 | { |
1077 | extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0); | |
1078 | } | |
1079 | EXPORT_SYMBOL(get_random_bytes); | |
1080 | ||
1081 | /* | |
1082 | * This function will use the architecture-specific hardware random | |
1083 | * number generator if it is available. The arch-specific hw RNG will | |
1084 | * almost certainly be faster than what we can do in software, but it | |
1085 | * is impossible to verify that it is implemented securely (as | |
1086 | * opposed, to, say, the AES encryption of a sequence number using a | |
1087 | * key known by the NSA). So it's useful if we need the speed, but | |
1088 | * only if we're willing to trust the hardware manufacturer not to | |
1089 | * have put in a back door. | |
1090 | */ | |
1091 | void get_random_bytes_arch(void *buf, int nbytes) | |
1da177e4 | 1092 | { |
63d77173 PA |
1093 | char *p = buf; |
1094 | ||
00ce1db1 | 1095 | trace_get_random_bytes(nbytes, _RET_IP_); |
63d77173 PA |
1096 | while (nbytes) { |
1097 | unsigned long v; | |
1098 | int chunk = min(nbytes, (int)sizeof(unsigned long)); | |
c2557a30 | 1099 | |
63d77173 PA |
1100 | if (!arch_get_random_long(&v)) |
1101 | break; | |
1102 | ||
bd29e568 | 1103 | memcpy(p, &v, chunk); |
63d77173 PA |
1104 | p += chunk; |
1105 | nbytes -= chunk; | |
1106 | } | |
1107 | ||
c2557a30 TT |
1108 | if (nbytes) |
1109 | extract_entropy(&nonblocking_pool, p, nbytes, 0, 0); | |
1da177e4 | 1110 | } |
c2557a30 TT |
1111 | EXPORT_SYMBOL(get_random_bytes_arch); |
1112 | ||
1da177e4 LT |
1113 | |
1114 | /* | |
1115 | * init_std_data - initialize pool with system data | |
1116 | * | |
1117 | * @r: pool to initialize | |
1118 | * | |
1119 | * This function clears the pool's entropy count and mixes some system | |
1120 | * data into the pool to prepare it for use. The pool is not cleared | |
1121 | * as that can only decrease the entropy in the pool. | |
1122 | */ | |
1123 | static void init_std_data(struct entropy_store *r) | |
1124 | { | |
3e88bdff | 1125 | int i; |
902c098a TT |
1126 | ktime_t now = ktime_get_real(); |
1127 | unsigned long rv; | |
1da177e4 | 1128 | |
1da177e4 | 1129 | r->entropy_count = 0; |
775f4b29 | 1130 | r->entropy_total = 0; |
ec8f02da | 1131 | r->last_data_init = false; |
902c098a TT |
1132 | mix_pool_bytes(r, &now, sizeof(now), NULL); |
1133 | for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) { | |
1134 | if (!arch_get_random_long(&rv)) | |
3e88bdff | 1135 | break; |
902c098a | 1136 | mix_pool_bytes(r, &rv, sizeof(rv), NULL); |
3e88bdff | 1137 | } |
902c098a | 1138 | mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL); |
1da177e4 LT |
1139 | } |
1140 | ||
cbc96b75 TL |
1141 | /* |
1142 | * Note that setup_arch() may call add_device_randomness() | |
1143 | * long before we get here. This allows seeding of the pools | |
1144 | * with some platform dependent data very early in the boot | |
1145 | * process. But it limits our options here. We must use | |
1146 | * statically allocated structures that already have all | |
1147 | * initializations complete at compile time. We should also | |
1148 | * take care not to overwrite the precious per platform data | |
1149 | * we were given. | |
1150 | */ | |
53c3f63e | 1151 | static int rand_initialize(void) |
1da177e4 LT |
1152 | { |
1153 | init_std_data(&input_pool); | |
1154 | init_std_data(&blocking_pool); | |
1155 | init_std_data(&nonblocking_pool); | |
1156 | return 0; | |
1157 | } | |
1158 | module_init(rand_initialize); | |
1159 | ||
9361401e | 1160 | #ifdef CONFIG_BLOCK |
1da177e4 LT |
1161 | void rand_initialize_disk(struct gendisk *disk) |
1162 | { | |
1163 | struct timer_rand_state *state; | |
1164 | ||
1165 | /* | |
f8595815 | 1166 | * If kzalloc returns null, we just won't use that entropy |
1da177e4 LT |
1167 | * source. |
1168 | */ | |
f8595815 ED |
1169 | state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); |
1170 | if (state) | |
1da177e4 | 1171 | disk->random = state; |
1da177e4 | 1172 | } |
9361401e | 1173 | #endif |
1da177e4 LT |
1174 | |
1175 | static ssize_t | |
54439ba6 | 1176 | _random_read(int nonblock, char __user *buf, size_t nbytes) |
1da177e4 LT |
1177 | { |
1178 | ssize_t n, retval = 0, count = 0; | |
1179 | ||
1180 | if (nbytes == 0) | |
1181 | return 0; | |
1182 | ||
1183 | while (nbytes > 0) { | |
1184 | n = nbytes; | |
1185 | if (n > SEC_XFER_SIZE) | |
1186 | n = SEC_XFER_SIZE; | |
1187 | ||
8eb2ffbf | 1188 | DEBUG_ENT("reading %zu bits\n", n*8); |
1da177e4 LT |
1189 | |
1190 | n = extract_entropy_user(&blocking_pool, buf, n); | |
1191 | ||
8eb2ffbf JK |
1192 | if (n < 0) { |
1193 | retval = n; | |
1194 | break; | |
1195 | } | |
1196 | ||
1197 | DEBUG_ENT("read got %zd bits (%zd still needed)\n", | |
1da177e4 LT |
1198 | n*8, (nbytes-n)*8); |
1199 | ||
1200 | if (n == 0) { | |
54439ba6 | 1201 | if (nonblock) { |
1da177e4 LT |
1202 | retval = -EAGAIN; |
1203 | break; | |
1204 | } | |
1205 | ||
1206 | DEBUG_ENT("sleeping?\n"); | |
1207 | ||
1208 | wait_event_interruptible(random_read_wait, | |
1209 | input_pool.entropy_count >= | |
1210 | random_read_wakeup_thresh); | |
1211 | ||
1212 | DEBUG_ENT("awake\n"); | |
1213 | ||
1214 | if (signal_pending(current)) { | |
1215 | retval = -ERESTARTSYS; | |
1216 | break; | |
1217 | } | |
1218 | ||
1219 | continue; | |
1220 | } | |
1221 | ||
1da177e4 LT |
1222 | count += n; |
1223 | buf += n; | |
1224 | nbytes -= n; | |
1225 | break; /* This break makes the device work */ | |
1226 | /* like a named pipe */ | |
1227 | } | |
1228 | ||
1da177e4 LT |
1229 | return (count ? count : retval); |
1230 | } | |
1231 | ||
54439ba6 TT |
1232 | static ssize_t |
1233 | random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) | |
1234 | { | |
1235 | return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes); | |
1236 | } | |
1237 | ||
1da177e4 | 1238 | static ssize_t |
90b75ee5 | 1239 | urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) |
1da177e4 LT |
1240 | { |
1241 | return extract_entropy_user(&nonblocking_pool, buf, nbytes); | |
1242 | } | |
1243 | ||
1244 | static unsigned int | |
1245 | random_poll(struct file *file, poll_table * wait) | |
1246 | { | |
1247 | unsigned int mask; | |
1248 | ||
1249 | poll_wait(file, &random_read_wait, wait); | |
1250 | poll_wait(file, &random_write_wait, wait); | |
1251 | mask = 0; | |
1252 | if (input_pool.entropy_count >= random_read_wakeup_thresh) | |
1253 | mask |= POLLIN | POLLRDNORM; | |
1254 | if (input_pool.entropy_count < random_write_wakeup_thresh) | |
1255 | mask |= POLLOUT | POLLWRNORM; | |
1256 | return mask; | |
1257 | } | |
1258 | ||
7f397dcd MM |
1259 | static int |
1260 | write_pool(struct entropy_store *r, const char __user *buffer, size_t count) | |
1da177e4 | 1261 | { |
1da177e4 LT |
1262 | size_t bytes; |
1263 | __u32 buf[16]; | |
1264 | const char __user *p = buffer; | |
1da177e4 | 1265 | |
7f397dcd MM |
1266 | while (count > 0) { |
1267 | bytes = min(count, sizeof(buf)); | |
1268 | if (copy_from_user(&buf, p, bytes)) | |
1269 | return -EFAULT; | |
1da177e4 | 1270 | |
7f397dcd | 1271 | count -= bytes; |
1da177e4 LT |
1272 | p += bytes; |
1273 | ||
902c098a | 1274 | mix_pool_bytes(r, buf, bytes, NULL); |
91f3f1e3 | 1275 | cond_resched(); |
1da177e4 | 1276 | } |
7f397dcd MM |
1277 | |
1278 | return 0; | |
1279 | } | |
1280 | ||
90b75ee5 MM |
1281 | static ssize_t random_write(struct file *file, const char __user *buffer, |
1282 | size_t count, loff_t *ppos) | |
7f397dcd MM |
1283 | { |
1284 | size_t ret; | |
7f397dcd MM |
1285 | |
1286 | ret = write_pool(&blocking_pool, buffer, count); | |
1287 | if (ret) | |
1288 | return ret; | |
1289 | ret = write_pool(&nonblocking_pool, buffer, count); | |
1290 | if (ret) | |
1291 | return ret; | |
1292 | ||
7f397dcd | 1293 | return (ssize_t)count; |
1da177e4 LT |
1294 | } |
1295 | ||
43ae4860 | 1296 | static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) |
1da177e4 LT |
1297 | { |
1298 | int size, ent_count; | |
1299 | int __user *p = (int __user *)arg; | |
1300 | int retval; | |
1301 | ||
1302 | switch (cmd) { | |
1303 | case RNDGETENTCNT: | |
43ae4860 MM |
1304 | /* inherently racy, no point locking */ |
1305 | if (put_user(input_pool.entropy_count, p)) | |
1da177e4 LT |
1306 | return -EFAULT; |
1307 | return 0; | |
1308 | case RNDADDTOENTCNT: | |
1309 | if (!capable(CAP_SYS_ADMIN)) | |
1310 | return -EPERM; | |
1311 | if (get_user(ent_count, p)) | |
1312 | return -EFAULT; | |
adc782da | 1313 | credit_entropy_bits(&input_pool, ent_count); |
1da177e4 LT |
1314 | return 0; |
1315 | case RNDADDENTROPY: | |
1316 | if (!capable(CAP_SYS_ADMIN)) | |
1317 | return -EPERM; | |
1318 | if (get_user(ent_count, p++)) | |
1319 | return -EFAULT; | |
1320 | if (ent_count < 0) | |
1321 | return -EINVAL; | |
1322 | if (get_user(size, p++)) | |
1323 | return -EFAULT; | |
7f397dcd MM |
1324 | retval = write_pool(&input_pool, (const char __user *)p, |
1325 | size); | |
1da177e4 LT |
1326 | if (retval < 0) |
1327 | return retval; | |
adc782da | 1328 | credit_entropy_bits(&input_pool, ent_count); |
1da177e4 LT |
1329 | return 0; |
1330 | case RNDZAPENTCNT: | |
1331 | case RNDCLEARPOOL: | |
1332 | /* Clear the entropy pool counters. */ | |
1333 | if (!capable(CAP_SYS_ADMIN)) | |
1334 | return -EPERM; | |
53c3f63e | 1335 | rand_initialize(); |
1da177e4 LT |
1336 | return 0; |
1337 | default: | |
1338 | return -EINVAL; | |
1339 | } | |
1340 | } | |
1341 | ||
9a6f70bb JD |
1342 | static int random_fasync(int fd, struct file *filp, int on) |
1343 | { | |
1344 | return fasync_helper(fd, filp, on, &fasync); | |
1345 | } | |
1346 | ||
2b8693c0 | 1347 | const struct file_operations random_fops = { |
1da177e4 LT |
1348 | .read = random_read, |
1349 | .write = random_write, | |
1350 | .poll = random_poll, | |
43ae4860 | 1351 | .unlocked_ioctl = random_ioctl, |
9a6f70bb | 1352 | .fasync = random_fasync, |
6038f373 | 1353 | .llseek = noop_llseek, |
1da177e4 LT |
1354 | }; |
1355 | ||
2b8693c0 | 1356 | const struct file_operations urandom_fops = { |
1da177e4 LT |
1357 | .read = urandom_read, |
1358 | .write = random_write, | |
43ae4860 | 1359 | .unlocked_ioctl = random_ioctl, |
9a6f70bb | 1360 | .fasync = random_fasync, |
6038f373 | 1361 | .llseek = noop_llseek, |
1da177e4 LT |
1362 | }; |
1363 | ||
54439ba6 TT |
1364 | SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, |
1365 | unsigned int, flags) | |
1366 | { | |
1367 | if (flags & ~(GRND_NONBLOCK|GRND_RANDOM)) | |
1368 | return -EINVAL; | |
1369 | if (count > INT_MAX) | |
1370 | count = INT_MAX; | |
1371 | if (flags & GRND_RANDOM) | |
1372 | return _random_read(flags & GRND_NONBLOCK, buf, count); | |
1373 | if (unlikely(nonblocking_pool.initialized == 0)) { | |
1374 | if (flags & GRND_NONBLOCK) | |
1375 | return -EAGAIN; | |
1376 | wait_event_interruptible(urandom_init_wait, | |
1377 | nonblocking_pool.initialized); | |
1378 | if (signal_pending(current)) | |
1379 | return -ERESTARTSYS; | |
1380 | } | |
1381 | return urandom_read(NULL, buf, count, NULL); | |
1382 | } | |
1383 | ||
1da177e4 LT |
1384 | /******************************************************************** |
1385 | * | |
1386 | * Sysctl interface | |
1387 | * | |
1388 | ********************************************************************/ | |
1389 | ||
1390 | #ifdef CONFIG_SYSCTL | |
1391 | ||
1392 | #include <linux/sysctl.h> | |
1393 | ||
1394 | static int min_read_thresh = 8, min_write_thresh; | |
1395 | static int max_read_thresh = INPUT_POOL_WORDS * 32; | |
1396 | static int max_write_thresh = INPUT_POOL_WORDS * 32; | |
1397 | static char sysctl_bootid[16]; | |
1398 | ||
1399 | /* | |
1400 | * These functions is used to return both the bootid UUID, and random | |
1401 | * UUID. The difference is in whether table->data is NULL; if it is, | |
1402 | * then a new UUID is generated and returned to the user. | |
1403 | * | |
1404 | * If the user accesses this via the proc interface, it will be returned | |
1405 | * as an ASCII string in the standard UUID format. If accesses via the | |
1406 | * sysctl system call, it is returned as 16 bytes of binary data. | |
1407 | */ | |
8d65af78 | 1408 | static int proc_do_uuid(ctl_table *table, int write, |
1da177e4 LT |
1409 | void __user *buffer, size_t *lenp, loff_t *ppos) |
1410 | { | |
1411 | ctl_table fake_table; | |
1412 | unsigned char buf[64], tmp_uuid[16], *uuid; | |
1413 | ||
1414 | uuid = table->data; | |
1415 | if (!uuid) { | |
1416 | uuid = tmp_uuid; | |
1da177e4 | 1417 | generate_random_uuid(uuid); |
44e4360f MD |
1418 | } else { |
1419 | static DEFINE_SPINLOCK(bootid_spinlock); | |
1420 | ||
1421 | spin_lock(&bootid_spinlock); | |
1422 | if (!uuid[8]) | |
1423 | generate_random_uuid(uuid); | |
1424 | spin_unlock(&bootid_spinlock); | |
1425 | } | |
1da177e4 | 1426 | |
35900771 JP |
1427 | sprintf(buf, "%pU", uuid); |
1428 | ||
1da177e4 LT |
1429 | fake_table.data = buf; |
1430 | fake_table.maxlen = sizeof(buf); | |
1431 | ||
8d65af78 | 1432 | return proc_dostring(&fake_table, write, buffer, lenp, ppos); |
1da177e4 LT |
1433 | } |
1434 | ||
1da177e4 | 1435 | static int sysctl_poolsize = INPUT_POOL_WORDS * 32; |
74feec5d | 1436 | extern ctl_table random_table[]; |
1da177e4 LT |
1437 | ctl_table random_table[] = { |
1438 | { | |
1da177e4 LT |
1439 | .procname = "poolsize", |
1440 | .data = &sysctl_poolsize, | |
1441 | .maxlen = sizeof(int), | |
1442 | .mode = 0444, | |
6d456111 | 1443 | .proc_handler = proc_dointvec, |
1da177e4 LT |
1444 | }, |
1445 | { | |
1da177e4 LT |
1446 | .procname = "entropy_avail", |
1447 | .maxlen = sizeof(int), | |
1448 | .mode = 0444, | |
6d456111 | 1449 | .proc_handler = proc_dointvec, |
1da177e4 LT |
1450 | .data = &input_pool.entropy_count, |
1451 | }, | |
1452 | { | |
1da177e4 LT |
1453 | .procname = "read_wakeup_threshold", |
1454 | .data = &random_read_wakeup_thresh, | |
1455 | .maxlen = sizeof(int), | |
1456 | .mode = 0644, | |
6d456111 | 1457 | .proc_handler = proc_dointvec_minmax, |
1da177e4 LT |
1458 | .extra1 = &min_read_thresh, |
1459 | .extra2 = &max_read_thresh, | |
1460 | }, | |
1461 | { | |
1da177e4 LT |
1462 | .procname = "write_wakeup_threshold", |
1463 | .data = &random_write_wakeup_thresh, | |
1464 | .maxlen = sizeof(int), | |
1465 | .mode = 0644, | |
6d456111 | 1466 | .proc_handler = proc_dointvec_minmax, |
1da177e4 LT |
1467 | .extra1 = &min_write_thresh, |
1468 | .extra2 = &max_write_thresh, | |
1469 | }, | |
1470 | { | |
1da177e4 LT |
1471 | .procname = "boot_id", |
1472 | .data = &sysctl_bootid, | |
1473 | .maxlen = 16, | |
1474 | .mode = 0444, | |
6d456111 | 1475 | .proc_handler = proc_do_uuid, |
1da177e4 LT |
1476 | }, |
1477 | { | |
1da177e4 LT |
1478 | .procname = "uuid", |
1479 | .maxlen = 16, | |
1480 | .mode = 0444, | |
6d456111 | 1481 | .proc_handler = proc_do_uuid, |
1da177e4 | 1482 | }, |
894d2491 | 1483 | { } |
1da177e4 LT |
1484 | }; |
1485 | #endif /* CONFIG_SYSCTL */ | |
1486 | ||
6e5714ea | 1487 | static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned; |
1da177e4 | 1488 | |
b7a52f51 | 1489 | int random_int_secret_init(void) |
1da177e4 | 1490 | { |
6e5714ea | 1491 | get_random_bytes(random_int_secret, sizeof(random_int_secret)); |
1da177e4 LT |
1492 | return 0; |
1493 | } | |
1da177e4 LT |
1494 | |
1495 | /* | |
1496 | * Get a random word for internal kernel use only. Similar to urandom but | |
1497 | * with the goal of minimal entropy pool depletion. As a result, the random | |
1498 | * value is not cryptographically secure but for several uses the cost of | |
1499 | * depleting entropy is too high | |
1500 | */ | |
74feec5d | 1501 | static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash); |
1da177e4 LT |
1502 | unsigned int get_random_int(void) |
1503 | { | |
63d77173 | 1504 | __u32 *hash; |
6e5714ea | 1505 | unsigned int ret; |
8a0a9bd4 | 1506 | |
63d77173 PA |
1507 | if (arch_get_random_int(&ret)) |
1508 | return ret; | |
1509 | ||
1510 | hash = get_cpu_var(get_random_int_hash); | |
8a0a9bd4 | 1511 | |
26a9a418 | 1512 | hash[0] += current->pid + jiffies + get_cycles(); |
6e5714ea DM |
1513 | md5_transform(hash, random_int_secret); |
1514 | ret = hash[0]; | |
8a0a9bd4 LT |
1515 | put_cpu_var(get_random_int_hash); |
1516 | ||
1517 | return ret; | |
1da177e4 | 1518 | } |
16c7fa05 | 1519 | EXPORT_SYMBOL(get_random_int); |
1da177e4 | 1520 | |
3c2a0909 S |
1521 | /* |
1522 | * Same as get_random_int(), but returns unsigned long. | |
1523 | */ | |
1524 | unsigned long get_random_long(void) | |
1525 | { | |
1526 | __u32 *hash; | |
1527 | unsigned long ret; | |
1528 | ||
1529 | if (arch_get_random_long(&ret)) | |
1530 | return ret; | |
1531 | ||
1532 | hash = get_cpu_var(get_random_int_hash); | |
1533 | ||
1534 | hash[0] += current->pid + jiffies + get_cycles(); | |
1535 | md5_transform(hash, random_int_secret); | |
1536 | ret = *(unsigned long *)hash; | |
1537 | put_cpu_var(get_random_int_hash); | |
1538 | ||
1539 | return ret; | |
1540 | } | |
1541 | EXPORT_SYMBOL(get_random_long); | |
1542 | ||
1da177e4 LT |
1543 | /* |
1544 | * randomize_range() returns a start address such that | |
1545 | * | |
1546 | * [...... <range> .....] | |
1547 | * start end | |
1548 | * | |
1549 | * a <range> with size "len" starting at the return value is inside in the | |
1550 | * area defined by [start, end], but is otherwise randomized. | |
1551 | */ | |
1552 | unsigned long | |
1553 | randomize_range(unsigned long start, unsigned long end, unsigned long len) | |
1554 | { | |
1555 | unsigned long range = end - len - start; | |
1556 | ||
1557 | if (end <= start + len) | |
1558 | return 0; | |
1559 | return PAGE_ALIGN(get_random_int() % range + start); | |
1560 | } |