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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> |
6265e169 | 258 | #include <linux/workqueue.h> |
1da177e4 | 259 | |
d178a1eb YL |
260 | #ifdef CONFIG_GENERIC_HARDIRQS |
261 | # include <linux/irq.h> | |
262 | #endif | |
263 | ||
1da177e4 LT |
264 | #include <asm/processor.h> |
265 | #include <asm/uaccess.h> | |
266 | #include <asm/irq.h> | |
775f4b29 | 267 | #include <asm/irq_regs.h> |
1da177e4 LT |
268 | #include <asm/io.h> |
269 | ||
00ce1db1 TT |
270 | #define CREATE_TRACE_POINTS |
271 | #include <trace/events/random.h> | |
272 | ||
1da177e4 LT |
273 | /* |
274 | * Configuration information | |
275 | */ | |
30e37ec5 PA |
276 | #define INPUT_POOL_SHIFT 12 |
277 | #define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5)) | |
278 | #define OUTPUT_POOL_SHIFT 10 | |
279 | #define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5)) | |
280 | #define SEC_XFER_SIZE 512 | |
281 | #define EXTRACT_SIZE 10 | |
1da177e4 | 282 | |
d2e7c96a PA |
283 | #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long)) |
284 | ||
a283b5c4 | 285 | /* |
95b709b6 TT |
286 | * To allow fractional bits to be tracked, the entropy_count field is |
287 | * denominated in units of 1/8th bits. | |
30e37ec5 PA |
288 | * |
289 | * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in | |
290 | * credit_entropy_bits() needs to be 64 bits wide. | |
a283b5c4 PA |
291 | */ |
292 | #define ENTROPY_SHIFT 3 | |
293 | #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT) | |
294 | ||
1da177e4 LT |
295 | /* |
296 | * The minimum number of bits of entropy before we wake up a read on | |
297 | * /dev/random. Should be enough to do a significant reseed. | |
298 | */ | |
299 | static int random_read_wakeup_thresh = 64; | |
300 | ||
301 | /* | |
302 | * If the entropy count falls under this number of bits, then we | |
303 | * should wake up processes which are selecting or polling on write | |
304 | * access to /dev/random. | |
305 | */ | |
6265e169 | 306 | static int random_write_wakeup_thresh = 28 * OUTPUT_POOL_WORDS; |
1da177e4 | 307 | |
f5c2742c TT |
308 | /* |
309 | * The minimum number of seconds between urandom pool resending. We | |
310 | * do this to limit the amount of entropy that can be drained from the | |
311 | * input pool even if there are heavy demands on /dev/urandom. | |
312 | */ | |
313 | static int random_min_urandom_seed = 60; | |
314 | ||
1da177e4 | 315 | /* |
6e9fa2c8 TT |
316 | * Originally, we used a primitive polynomial of degree .poolwords |
317 | * over GF(2). The taps for various sizes are defined below. They | |
318 | * were chosen to be evenly spaced except for the last tap, which is 1 | |
319 | * to get the twisting happening as fast as possible. | |
320 | * | |
321 | * For the purposes of better mixing, we use the CRC-32 polynomial as | |
322 | * well to make a (modified) twisted Generalized Feedback Shift | |
323 | * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR | |
324 | * generators. ACM Transactions on Modeling and Computer Simulation | |
325 | * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted | |
326 | * GFSR generators II. ACM Transactions on Mdeling and Computer | |
327 | * Simulation 4:254-266) | |
328 | * | |
329 | * Thanks to Colin Plumb for suggesting this. | |
330 | * | |
331 | * The mixing operation is much less sensitive than the output hash, | |
332 | * where we use SHA-1. All that we want of mixing operation is that | |
333 | * it be a good non-cryptographic hash; i.e. it not produce collisions | |
334 | * when fed "random" data of the sort we expect to see. As long as | |
335 | * the pool state differs for different inputs, we have preserved the | |
336 | * input entropy and done a good job. The fact that an intelligent | |
337 | * attacker can construct inputs that will produce controlled | |
338 | * alterations to the pool's state is not important because we don't | |
339 | * consider such inputs to contribute any randomness. The only | |
340 | * property we need with respect to them is that the attacker can't | |
341 | * increase his/her knowledge of the pool's state. Since all | |
342 | * additions are reversible (knowing the final state and the input, | |
343 | * you can reconstruct the initial state), if an attacker has any | |
344 | * uncertainty about the initial state, he/she can only shuffle that | |
345 | * uncertainty about, but never cause any collisions (which would | |
346 | * decrease the uncertainty). | |
347 | * | |
348 | * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and | |
349 | * Videau in their paper, "The Linux Pseudorandom Number Generator | |
350 | * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their | |
351 | * paper, they point out that we are not using a true Twisted GFSR, | |
352 | * since Matsumoto & Kurita used a trinomial feedback polynomial (that | |
353 | * is, with only three taps, instead of the six that we are using). | |
354 | * As a result, the resulting polynomial is neither primitive nor | |
355 | * irreducible, and hence does not have a maximal period over | |
356 | * GF(2**32). They suggest a slight change to the generator | |
357 | * polynomial which improves the resulting TGFSR polynomial to be | |
358 | * irreducible, which we have made here. | |
1da177e4 LT |
359 | */ |
360 | static struct poolinfo { | |
a283b5c4 PA |
361 | int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits; |
362 | #define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5) | |
1da177e4 LT |
363 | int tap1, tap2, tap3, tap4, tap5; |
364 | } poolinfo_table[] = { | |
6e9fa2c8 TT |
365 | /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */ |
366 | /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */ | |
367 | { S(128), 104, 76, 51, 25, 1 }, | |
368 | /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */ | |
369 | /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */ | |
370 | { S(32), 26, 19, 14, 7, 1 }, | |
1da177e4 LT |
371 | #if 0 |
372 | /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */ | |
9ed17b70 | 373 | { S(2048), 1638, 1231, 819, 411, 1 }, |
1da177e4 LT |
374 | |
375 | /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */ | |
9ed17b70 | 376 | { S(1024), 817, 615, 412, 204, 1 }, |
1da177e4 LT |
377 | |
378 | /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */ | |
9ed17b70 | 379 | { S(1024), 819, 616, 410, 207, 2 }, |
1da177e4 LT |
380 | |
381 | /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */ | |
9ed17b70 | 382 | { S(512), 411, 308, 208, 104, 1 }, |
1da177e4 LT |
383 | |
384 | /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */ | |
9ed17b70 | 385 | { S(512), 409, 307, 206, 102, 2 }, |
1da177e4 | 386 | /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */ |
9ed17b70 | 387 | { S(512), 409, 309, 205, 103, 2 }, |
1da177e4 LT |
388 | |
389 | /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */ | |
9ed17b70 | 390 | { S(256), 205, 155, 101, 52, 1 }, |
1da177e4 LT |
391 | |
392 | /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */ | |
9ed17b70 | 393 | { S(128), 103, 78, 51, 27, 2 }, |
1da177e4 LT |
394 | |
395 | /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */ | |
9ed17b70 | 396 | { S(64), 52, 39, 26, 14, 1 }, |
1da177e4 LT |
397 | #endif |
398 | }; | |
399 | ||
1da177e4 LT |
400 | /* |
401 | * Static global variables | |
402 | */ | |
403 | static DECLARE_WAIT_QUEUE_HEAD(random_read_wait); | |
404 | static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); | |
9a6f70bb | 405 | static struct fasync_struct *fasync; |
1da177e4 | 406 | |
1da177e4 LT |
407 | /********************************************************************** |
408 | * | |
409 | * OS independent entropy store. Here are the functions which handle | |
410 | * storing entropy in an entropy pool. | |
411 | * | |
412 | **********************************************************************/ | |
413 | ||
414 | struct entropy_store; | |
415 | struct entropy_store { | |
43358209 | 416 | /* read-only data: */ |
30e37ec5 | 417 | const struct poolinfo *poolinfo; |
1da177e4 LT |
418 | __u32 *pool; |
419 | const char *name; | |
1da177e4 | 420 | struct entropy_store *pull; |
6265e169 | 421 | struct work_struct push_work; |
1da177e4 LT |
422 | |
423 | /* read-write data: */ | |
f5c2742c | 424 | unsigned long last_pulled; |
43358209 | 425 | spinlock_t lock; |
c59974ae TT |
426 | unsigned short add_ptr; |
427 | unsigned short input_rotate; | |
cda796a3 | 428 | int entropy_count; |
775f4b29 | 429 | int entropy_total; |
775f4b29 | 430 | unsigned int initialized:1; |
c59974ae TT |
431 | unsigned int limit:1; |
432 | unsigned int last_data_init:1; | |
e954bc91 | 433 | __u8 last_data[EXTRACT_SIZE]; |
1da177e4 LT |
434 | }; |
435 | ||
6265e169 | 436 | static void push_to_pool(struct work_struct *work); |
1da177e4 LT |
437 | static __u32 input_pool_data[INPUT_POOL_WORDS]; |
438 | static __u32 blocking_pool_data[OUTPUT_POOL_WORDS]; | |
439 | static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS]; | |
440 | ||
441 | static struct entropy_store input_pool = { | |
442 | .poolinfo = &poolinfo_table[0], | |
443 | .name = "input", | |
444 | .limit = 1, | |
eece09ec | 445 | .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), |
1da177e4 LT |
446 | .pool = input_pool_data |
447 | }; | |
448 | ||
449 | static struct entropy_store blocking_pool = { | |
450 | .poolinfo = &poolinfo_table[1], | |
451 | .name = "blocking", | |
452 | .limit = 1, | |
453 | .pull = &input_pool, | |
eece09ec | 454 | .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock), |
6265e169 TT |
455 | .pool = blocking_pool_data, |
456 | .push_work = __WORK_INITIALIZER(blocking_pool.push_work, | |
457 | push_to_pool), | |
1da177e4 LT |
458 | }; |
459 | ||
460 | static struct entropy_store nonblocking_pool = { | |
461 | .poolinfo = &poolinfo_table[1], | |
462 | .name = "nonblocking", | |
463 | .pull = &input_pool, | |
eece09ec | 464 | .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock), |
6265e169 TT |
465 | .pool = nonblocking_pool_data, |
466 | .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work, | |
467 | push_to_pool), | |
1da177e4 LT |
468 | }; |
469 | ||
775f4b29 TT |
470 | static __u32 const twist_table[8] = { |
471 | 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158, | |
472 | 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; | |
473 | ||
1da177e4 | 474 | /* |
e68e5b66 | 475 | * This function adds bytes into the entropy "pool". It does not |
1da177e4 | 476 | * update the entropy estimate. The caller should call |
adc782da | 477 | * credit_entropy_bits if this is appropriate. |
1da177e4 LT |
478 | * |
479 | * The pool is stirred with a primitive polynomial of the appropriate | |
480 | * degree, and then twisted. We twist by three bits at a time because | |
481 | * it's cheap to do so and helps slightly in the expected case where | |
482 | * the entropy is concentrated in the low-order bits. | |
483 | */ | |
00ce1db1 TT |
484 | static void _mix_pool_bytes(struct entropy_store *r, const void *in, |
485 | int nbytes, __u8 out[64]) | |
1da177e4 | 486 | { |
993ba211 | 487 | unsigned long i, j, tap1, tap2, tap3, tap4, tap5; |
feee7697 | 488 | int input_rotate; |
1da177e4 | 489 | int wordmask = r->poolinfo->poolwords - 1; |
e68e5b66 | 490 | const char *bytes = in; |
6d38b827 | 491 | __u32 w; |
1da177e4 | 492 | |
1da177e4 LT |
493 | tap1 = r->poolinfo->tap1; |
494 | tap2 = r->poolinfo->tap2; | |
495 | tap3 = r->poolinfo->tap3; | |
496 | tap4 = r->poolinfo->tap4; | |
497 | tap5 = r->poolinfo->tap5; | |
1da177e4 | 498 | |
902c098a TT |
499 | smp_rmb(); |
500 | input_rotate = ACCESS_ONCE(r->input_rotate); | |
501 | i = ACCESS_ONCE(r->add_ptr); | |
1da177e4 | 502 | |
e68e5b66 MM |
503 | /* mix one byte at a time to simplify size handling and churn faster */ |
504 | while (nbytes--) { | |
c59974ae | 505 | w = rol32(*bytes++, input_rotate); |
993ba211 | 506 | i = (i - 1) & wordmask; |
1da177e4 LT |
507 | |
508 | /* XOR in the various taps */ | |
993ba211 | 509 | w ^= r->pool[i]; |
1da177e4 LT |
510 | w ^= r->pool[(i + tap1) & wordmask]; |
511 | w ^= r->pool[(i + tap2) & wordmask]; | |
512 | w ^= r->pool[(i + tap3) & wordmask]; | |
513 | w ^= r->pool[(i + tap4) & wordmask]; | |
514 | w ^= r->pool[(i + tap5) & wordmask]; | |
993ba211 MM |
515 | |
516 | /* Mix the result back in with a twist */ | |
1da177e4 | 517 | r->pool[i] = (w >> 3) ^ twist_table[w & 7]; |
feee7697 MM |
518 | |
519 | /* | |
520 | * Normally, we add 7 bits of rotation to the pool. | |
521 | * At the beginning of the pool, add an extra 7 bits | |
522 | * rotation, so that successive passes spread the | |
523 | * input bits across the pool evenly. | |
524 | */ | |
c59974ae | 525 | input_rotate = (input_rotate + (i ? 7 : 14)) & 31; |
1da177e4 LT |
526 | } |
527 | ||
902c098a TT |
528 | ACCESS_ONCE(r->input_rotate) = input_rotate; |
529 | ACCESS_ONCE(r->add_ptr) = i; | |
530 | smp_wmb(); | |
1da177e4 | 531 | |
993ba211 MM |
532 | if (out) |
533 | for (j = 0; j < 16; j++) | |
e68e5b66 | 534 | ((__u32 *)out)[j] = r->pool[(i - j) & wordmask]; |
1da177e4 LT |
535 | } |
536 | ||
00ce1db1 | 537 | static void __mix_pool_bytes(struct entropy_store *r, const void *in, |
902c098a | 538 | int nbytes, __u8 out[64]) |
00ce1db1 TT |
539 | { |
540 | trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_); | |
541 | _mix_pool_bytes(r, in, nbytes, out); | |
542 | } | |
543 | ||
544 | static void mix_pool_bytes(struct entropy_store *r, const void *in, | |
545 | int nbytes, __u8 out[64]) | |
1da177e4 | 546 | { |
902c098a TT |
547 | unsigned long flags; |
548 | ||
00ce1db1 | 549 | trace_mix_pool_bytes(r->name, nbytes, _RET_IP_); |
902c098a | 550 | spin_lock_irqsave(&r->lock, flags); |
00ce1db1 | 551 | _mix_pool_bytes(r, in, nbytes, out); |
902c098a | 552 | spin_unlock_irqrestore(&r->lock, flags); |
1da177e4 LT |
553 | } |
554 | ||
775f4b29 TT |
555 | struct fast_pool { |
556 | __u32 pool[4]; | |
557 | unsigned long last; | |
558 | unsigned short count; | |
559 | unsigned char rotate; | |
560 | unsigned char last_timer_intr; | |
561 | }; | |
562 | ||
563 | /* | |
564 | * This is a fast mixing routine used by the interrupt randomness | |
565 | * collector. It's hardcoded for an 128 bit pool and assumes that any | |
566 | * locks that might be needed are taken by the caller. | |
567 | */ | |
655b2264 | 568 | static void fast_mix(struct fast_pool *f, __u32 input[4]) |
775f4b29 | 569 | { |
775f4b29 | 570 | __u32 w; |
775f4b29 TT |
571 | unsigned input_rotate = f->rotate; |
572 | ||
655b2264 TT |
573 | w = rol32(input[0], input_rotate) ^ f->pool[0] ^ f->pool[3]; |
574 | f->pool[0] = (w >> 3) ^ twist_table[w & 7]; | |
575 | input_rotate = (input_rotate + 14) & 31; | |
576 | w = rol32(input[1], input_rotate) ^ f->pool[1] ^ f->pool[0]; | |
577 | f->pool[1] = (w >> 3) ^ twist_table[w & 7]; | |
578 | input_rotate = (input_rotate + 7) & 31; | |
579 | w = rol32(input[2], input_rotate) ^ f->pool[2] ^ f->pool[1]; | |
580 | f->pool[2] = (w >> 3) ^ twist_table[w & 7]; | |
581 | input_rotate = (input_rotate + 7) & 31; | |
582 | w = rol32(input[3], input_rotate) ^ f->pool[3] ^ f->pool[2]; | |
583 | f->pool[3] = (w >> 3) ^ twist_table[w & 7]; | |
584 | input_rotate = (input_rotate + 7) & 31; | |
585 | ||
775f4b29 | 586 | f->rotate = input_rotate; |
655b2264 | 587 | f->count++; |
775f4b29 TT |
588 | } |
589 | ||
1da177e4 | 590 | /* |
a283b5c4 PA |
591 | * Credit (or debit) the entropy store with n bits of entropy. |
592 | * Use credit_entropy_bits_safe() if the value comes from userspace | |
593 | * or otherwise should be checked for extreme values. | |
1da177e4 | 594 | */ |
adc782da | 595 | static void credit_entropy_bits(struct entropy_store *r, int nbits) |
1da177e4 | 596 | { |
902c098a | 597 | int entropy_count, orig; |
30e37ec5 PA |
598 | const int pool_size = r->poolinfo->poolfracbits; |
599 | int nfrac = nbits << ENTROPY_SHIFT; | |
1da177e4 | 600 | |
adc782da MM |
601 | if (!nbits) |
602 | return; | |
603 | ||
902c098a TT |
604 | retry: |
605 | entropy_count = orig = ACCESS_ONCE(r->entropy_count); | |
30e37ec5 PA |
606 | if (nfrac < 0) { |
607 | /* Debit */ | |
608 | entropy_count += nfrac; | |
609 | } else { | |
610 | /* | |
611 | * Credit: we have to account for the possibility of | |
612 | * overwriting already present entropy. Even in the | |
613 | * ideal case of pure Shannon entropy, new contributions | |
614 | * approach the full value asymptotically: | |
615 | * | |
616 | * entropy <- entropy + (pool_size - entropy) * | |
617 | * (1 - exp(-add_entropy/pool_size)) | |
618 | * | |
619 | * For add_entropy <= pool_size/2 then | |
620 | * (1 - exp(-add_entropy/pool_size)) >= | |
621 | * (add_entropy/pool_size)*0.7869... | |
622 | * so we can approximate the exponential with | |
623 | * 3/4*add_entropy/pool_size and still be on the | |
624 | * safe side by adding at most pool_size/2 at a time. | |
625 | * | |
626 | * The use of pool_size-2 in the while statement is to | |
627 | * prevent rounding artifacts from making the loop | |
628 | * arbitrarily long; this limits the loop to log2(pool_size)*2 | |
629 | * turns no matter how large nbits is. | |
630 | */ | |
631 | int pnfrac = nfrac; | |
632 | const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2; | |
633 | /* The +2 corresponds to the /4 in the denominator */ | |
634 | ||
635 | do { | |
636 | unsigned int anfrac = min(pnfrac, pool_size/2); | |
637 | unsigned int add = | |
638 | ((pool_size - entropy_count)*anfrac*3) >> s; | |
639 | ||
640 | entropy_count += add; | |
641 | pnfrac -= anfrac; | |
642 | } while (unlikely(entropy_count < pool_size-2 && pnfrac)); | |
643 | } | |
00ce1db1 | 644 | |
8b76f46a | 645 | if (entropy_count < 0) { |
f80bbd8b TT |
646 | pr_warn("random: negative entropy/overflow: pool %s count %d\n", |
647 | r->name, entropy_count); | |
648 | WARN_ON(1); | |
8b76f46a | 649 | entropy_count = 0; |
30e37ec5 PA |
650 | } else if (entropy_count > pool_size) |
651 | entropy_count = pool_size; | |
902c098a TT |
652 | if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) |
653 | goto retry; | |
1da177e4 | 654 | |
6265e169 | 655 | r->entropy_total += nbits; |
775f4b29 | 656 | if (!r->initialized && nbits > 0) { |
6265e169 | 657 | if (r->entropy_total > 128) { |
775f4b29 | 658 | r->initialized = 1; |
6265e169 TT |
659 | r->entropy_total = 0; |
660 | } | |
775f4b29 TT |
661 | } |
662 | ||
a283b5c4 PA |
663 | trace_credit_entropy_bits(r->name, nbits, |
664 | entropy_count >> ENTROPY_SHIFT, | |
00ce1db1 TT |
665 | r->entropy_total, _RET_IP_); |
666 | ||
6265e169 TT |
667 | if (r == &input_pool) { |
668 | int entropy_bytes = entropy_count >> ENTROPY_SHIFT; | |
669 | ||
670 | /* should we wake readers? */ | |
671 | if (entropy_bytes >= random_read_wakeup_thresh) { | |
672 | wake_up_interruptible(&random_read_wait); | |
673 | kill_fasync(&fasync, SIGIO, POLL_IN); | |
674 | } | |
675 | /* If the input pool is getting full, send some | |
676 | * entropy to the two output pools, flipping back and | |
677 | * forth between them, until the output pools are 75% | |
678 | * full. | |
679 | */ | |
680 | if (entropy_bytes > random_write_wakeup_thresh && | |
681 | r->initialized && | |
682 | r->entropy_total >= 2*random_read_wakeup_thresh) { | |
683 | static struct entropy_store *last = &blocking_pool; | |
684 | struct entropy_store *other = &blocking_pool; | |
685 | ||
686 | if (last == &blocking_pool) | |
687 | other = &nonblocking_pool; | |
688 | if (other->entropy_count <= | |
689 | 3 * other->poolinfo->poolfracbits / 4) | |
690 | last = other; | |
691 | if (last->entropy_count <= | |
692 | 3 * last->poolinfo->poolfracbits / 4) { | |
693 | schedule_work(&last->push_work); | |
694 | r->entropy_total = 0; | |
695 | } | |
696 | } | |
9a6f70bb | 697 | } |
1da177e4 LT |
698 | } |
699 | ||
a283b5c4 PA |
700 | static void credit_entropy_bits_safe(struct entropy_store *r, int nbits) |
701 | { | |
702 | const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1)); | |
703 | ||
704 | /* Cap the value to avoid overflows */ | |
705 | nbits = min(nbits, nbits_max); | |
706 | nbits = max(nbits, -nbits_max); | |
707 | ||
708 | credit_entropy_bits(r, nbits); | |
709 | } | |
710 | ||
1da177e4 LT |
711 | /********************************************************************* |
712 | * | |
713 | * Entropy input management | |
714 | * | |
715 | *********************************************************************/ | |
716 | ||
717 | /* There is one of these per entropy source */ | |
718 | struct timer_rand_state { | |
719 | cycles_t last_time; | |
90b75ee5 | 720 | long last_delta, last_delta2; |
1da177e4 LT |
721 | unsigned dont_count_entropy:1; |
722 | }; | |
723 | ||
a2080a67 LT |
724 | /* |
725 | * Add device- or boot-specific data to the input and nonblocking | |
726 | * pools to help initialize them to unique values. | |
727 | * | |
728 | * None of this adds any entropy, it is meant to avoid the | |
729 | * problem of the nonblocking pool having similar initial state | |
730 | * across largely identical devices. | |
731 | */ | |
732 | void add_device_randomness(const void *buf, unsigned int size) | |
733 | { | |
61875f30 | 734 | unsigned long time = random_get_entropy() ^ jiffies; |
3ef4cb2d | 735 | unsigned long flags; |
a2080a67 | 736 | |
5910895f | 737 | trace_add_device_randomness(size, _RET_IP_); |
3ef4cb2d TT |
738 | spin_lock_irqsave(&input_pool.lock, flags); |
739 | _mix_pool_bytes(&input_pool, buf, size, NULL); | |
740 | _mix_pool_bytes(&input_pool, &time, sizeof(time), NULL); | |
741 | spin_unlock_irqrestore(&input_pool.lock, flags); | |
742 | ||
743 | spin_lock_irqsave(&nonblocking_pool.lock, flags); | |
744 | _mix_pool_bytes(&nonblocking_pool, buf, size, NULL); | |
745 | _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL); | |
746 | spin_unlock_irqrestore(&nonblocking_pool.lock, flags); | |
a2080a67 LT |
747 | } |
748 | EXPORT_SYMBOL(add_device_randomness); | |
749 | ||
3060d6fe YL |
750 | static struct timer_rand_state input_timer_state; |
751 | ||
1da177e4 LT |
752 | /* |
753 | * This function adds entropy to the entropy "pool" by using timing | |
754 | * delays. It uses the timer_rand_state structure to make an estimate | |
755 | * of how many bits of entropy this call has added to the pool. | |
756 | * | |
757 | * The number "num" is also added to the pool - it should somehow describe | |
758 | * the type of event which just happened. This is currently 0-255 for | |
759 | * keyboard scan codes, and 256 upwards for interrupts. | |
760 | * | |
761 | */ | |
762 | static void add_timer_randomness(struct timer_rand_state *state, unsigned num) | |
763 | { | |
764 | struct { | |
1da177e4 | 765 | long jiffies; |
cf833d0b | 766 | unsigned cycles; |
1da177e4 LT |
767 | unsigned num; |
768 | } sample; | |
769 | long delta, delta2, delta3; | |
770 | ||
771 | preempt_disable(); | |
1da177e4 LT |
772 | |
773 | sample.jiffies = jiffies; | |
61875f30 | 774 | sample.cycles = random_get_entropy(); |
1da177e4 | 775 | sample.num = num; |
902c098a | 776 | mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL); |
1da177e4 LT |
777 | |
778 | /* | |
779 | * Calculate number of bits of randomness we probably added. | |
780 | * We take into account the first, second and third-order deltas | |
781 | * in order to make our estimate. | |
782 | */ | |
783 | ||
784 | if (!state->dont_count_entropy) { | |
785 | delta = sample.jiffies - state->last_time; | |
786 | state->last_time = sample.jiffies; | |
787 | ||
788 | delta2 = delta - state->last_delta; | |
789 | state->last_delta = delta; | |
790 | ||
791 | delta3 = delta2 - state->last_delta2; | |
792 | state->last_delta2 = delta2; | |
793 | ||
794 | if (delta < 0) | |
795 | delta = -delta; | |
796 | if (delta2 < 0) | |
797 | delta2 = -delta2; | |
798 | if (delta3 < 0) | |
799 | delta3 = -delta3; | |
800 | if (delta > delta2) | |
801 | delta = delta2; | |
802 | if (delta > delta3) | |
803 | delta = delta3; | |
804 | ||
805 | /* | |
806 | * delta is now minimum absolute delta. | |
807 | * Round down by 1 bit on general principles, | |
808 | * and limit entropy entimate to 12 bits. | |
809 | */ | |
adc782da MM |
810 | credit_entropy_bits(&input_pool, |
811 | min_t(int, fls(delta>>1), 11)); | |
1da177e4 | 812 | } |
1da177e4 LT |
813 | preempt_enable(); |
814 | } | |
815 | ||
d251575a | 816 | void add_input_randomness(unsigned int type, unsigned int code, |
1da177e4 LT |
817 | unsigned int value) |
818 | { | |
819 | static unsigned char last_value; | |
820 | ||
821 | /* ignore autorepeat and the like */ | |
822 | if (value == last_value) | |
823 | return; | |
824 | ||
1da177e4 LT |
825 | last_value = value; |
826 | add_timer_randomness(&input_timer_state, | |
827 | (type << 4) ^ code ^ (code >> 4) ^ value); | |
f80bbd8b | 828 | trace_add_input_randomness(ENTROPY_BITS(&input_pool)); |
1da177e4 | 829 | } |
80fc9f53 | 830 | EXPORT_SYMBOL_GPL(add_input_randomness); |
1da177e4 | 831 | |
775f4b29 TT |
832 | static DEFINE_PER_CPU(struct fast_pool, irq_randomness); |
833 | ||
834 | void add_interrupt_randomness(int irq, int irq_flags) | |
1da177e4 | 835 | { |
775f4b29 TT |
836 | struct entropy_store *r; |
837 | struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness); | |
838 | struct pt_regs *regs = get_irq_regs(); | |
839 | unsigned long now = jiffies; | |
655b2264 TT |
840 | cycles_t cycles = random_get_entropy(); |
841 | __u32 input[4], c_high, j_high; | |
842 | __u64 ip; | |
843 | ||
844 | c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0; | |
845 | j_high = (sizeof(now) > 4) ? now >> 32 : 0; | |
846 | input[0] = cycles ^ j_high ^ irq; | |
847 | input[1] = now ^ c_high; | |
848 | ip = regs ? instruction_pointer(regs) : _RET_IP_; | |
849 | input[2] = ip; | |
850 | input[3] = ip >> 32; | |
3060d6fe | 851 | |
655b2264 | 852 | fast_mix(fast_pool, input); |
3060d6fe | 853 | |
655b2264 | 854 | if ((fast_pool->count & 63) && !time_after(now, fast_pool->last + HZ)) |
1da177e4 LT |
855 | return; |
856 | ||
775f4b29 TT |
857 | fast_pool->last = now; |
858 | ||
859 | r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool; | |
902c098a | 860 | __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL); |
775f4b29 TT |
861 | /* |
862 | * If we don't have a valid cycle counter, and we see | |
863 | * back-to-back timer interrupts, then skip giving credit for | |
864 | * any entropy. | |
865 | */ | |
866 | if (cycles == 0) { | |
867 | if (irq_flags & __IRQF_TIMER) { | |
868 | if (fast_pool->last_timer_intr) | |
869 | return; | |
870 | fast_pool->last_timer_intr = 1; | |
871 | } else | |
872 | fast_pool->last_timer_intr = 0; | |
873 | } | |
874 | credit_entropy_bits(r, 1); | |
1da177e4 LT |
875 | } |
876 | ||
9361401e | 877 | #ifdef CONFIG_BLOCK |
1da177e4 LT |
878 | void add_disk_randomness(struct gendisk *disk) |
879 | { | |
880 | if (!disk || !disk->random) | |
881 | return; | |
882 | /* first major is 1, so we get >= 0x200 here */ | |
f331c029 | 883 | add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); |
f80bbd8b | 884 | trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool)); |
1da177e4 | 885 | } |
9361401e | 886 | #endif |
1da177e4 | 887 | |
1da177e4 LT |
888 | /********************************************************************* |
889 | * | |
890 | * Entropy extraction routines | |
891 | * | |
892 | *********************************************************************/ | |
893 | ||
90b75ee5 | 894 | static ssize_t extract_entropy(struct entropy_store *r, void *buf, |
1da177e4 LT |
895 | size_t nbytes, int min, int rsvd); |
896 | ||
897 | /* | |
25985edc | 898 | * This utility inline function is responsible for transferring entropy |
1da177e4 LT |
899 | * from the primary pool to the secondary extraction pool. We make |
900 | * sure we pull enough for a 'catastrophic reseed'. | |
901 | */ | |
6265e169 | 902 | static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes); |
1da177e4 LT |
903 | static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes) |
904 | { | |
f5c2742c TT |
905 | if (r->limit == 0 && random_min_urandom_seed) { |
906 | unsigned long now = jiffies; | |
907 | ||
908 | if (time_before(now, | |
909 | r->last_pulled + random_min_urandom_seed * HZ)) | |
910 | return; | |
911 | r->last_pulled = now; | |
912 | } | |
a283b5c4 PA |
913 | if (r->pull && |
914 | r->entropy_count < (nbytes << (ENTROPY_SHIFT + 3)) && | |
6265e169 TT |
915 | r->entropy_count < r->poolinfo->poolfracbits) |
916 | _xfer_secondary_pool(r, nbytes); | |
917 | } | |
918 | ||
919 | static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes) | |
920 | { | |
921 | __u32 tmp[OUTPUT_POOL_WORDS]; | |
922 | ||
923 | /* For /dev/random's pool, always leave two wakeup worth's BITS */ | |
924 | int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4; | |
925 | int bytes = nbytes; | |
926 | ||
927 | /* pull at least as many as BYTES as wakeup BITS */ | |
928 | bytes = max_t(int, bytes, random_read_wakeup_thresh / 8); | |
929 | /* but never more than the buffer size */ | |
930 | bytes = min_t(int, bytes, sizeof(tmp)); | |
931 | ||
f80bbd8b TT |
932 | trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8, |
933 | ENTROPY_BITS(r), ENTROPY_BITS(r->pull)); | |
6265e169 TT |
934 | bytes = extract_entropy(r->pull, tmp, bytes, |
935 | random_read_wakeup_thresh / 8, rsvd); | |
936 | mix_pool_bytes(r, tmp, bytes, NULL); | |
937 | credit_entropy_bits(r, bytes*8); | |
938 | } | |
939 | ||
940 | /* | |
941 | * Used as a workqueue function so that when the input pool is getting | |
942 | * full, we can "spill over" some entropy to the output pools. That | |
943 | * way the output pools can store some of the excess entropy instead | |
944 | * of letting it go to waste. | |
945 | */ | |
946 | static void push_to_pool(struct work_struct *work) | |
947 | { | |
948 | struct entropy_store *r = container_of(work, struct entropy_store, | |
949 | push_work); | |
950 | BUG_ON(!r); | |
951 | _xfer_secondary_pool(r, random_read_wakeup_thresh/8); | |
952 | trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT, | |
953 | r->pull->entropy_count >> ENTROPY_SHIFT); | |
1da177e4 LT |
954 | } |
955 | ||
956 | /* | |
957 | * These functions extracts randomness from the "entropy pool", and | |
958 | * returns it in a buffer. | |
959 | * | |
960 | * The min parameter specifies the minimum amount we can pull before | |
961 | * failing to avoid races that defeat catastrophic reseeding while the | |
962 | * reserved parameter indicates how much entropy we must leave in the | |
963 | * pool after each pull to avoid starving other readers. | |
964 | * | |
965 | * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words. | |
966 | */ | |
967 | ||
968 | static size_t account(struct entropy_store *r, size_t nbytes, int min, | |
969 | int reserved) | |
970 | { | |
971 | unsigned long flags; | |
b9809552 | 972 | int wakeup_write = 0; |
a283b5c4 PA |
973 | int have_bytes; |
974 | int entropy_count, orig; | |
975 | size_t ibytes; | |
1da177e4 | 976 | |
1da177e4 LT |
977 | /* Hold lock while accounting */ |
978 | spin_lock_irqsave(&r->lock, flags); | |
979 | ||
a283b5c4 | 980 | BUG_ON(r->entropy_count > r->poolinfo->poolfracbits); |
1da177e4 LT |
981 | |
982 | /* Can we pull enough? */ | |
10b3a32d | 983 | retry: |
a283b5c4 PA |
984 | entropy_count = orig = ACCESS_ONCE(r->entropy_count); |
985 | have_bytes = entropy_count >> (ENTROPY_SHIFT + 3); | |
986 | ibytes = nbytes; | |
987 | if (have_bytes < min + reserved) { | |
988 | ibytes = 0; | |
989 | } else { | |
1da177e4 | 990 | /* If limited, never pull more than available */ |
a283b5c4 PA |
991 | if (r->limit && ibytes + reserved >= have_bytes) |
992 | ibytes = have_bytes - reserved; | |
993 | ||
994 | if (have_bytes >= ibytes + reserved) | |
995 | entropy_count -= ibytes << (ENTROPY_SHIFT + 3); | |
996 | else | |
997 | entropy_count = reserved << (ENTROPY_SHIFT + 3); | |
10b3a32d | 998 | |
a283b5c4 PA |
999 | if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) |
1000 | goto retry; | |
1001 | ||
1002 | if ((r->entropy_count >> ENTROPY_SHIFT) | |
1003 | < random_write_wakeup_thresh) | |
b9809552 | 1004 | wakeup_write = 1; |
1da177e4 | 1005 | } |
1da177e4 LT |
1006 | spin_unlock_irqrestore(&r->lock, flags); |
1007 | ||
f80bbd8b | 1008 | trace_debit_entropy(r->name, 8 * ibytes); |
b9809552 TT |
1009 | if (wakeup_write) { |
1010 | wake_up_interruptible(&random_write_wait); | |
1011 | kill_fasync(&fasync, SIGIO, POLL_OUT); | |
1012 | } | |
1013 | ||
a283b5c4 | 1014 | return ibytes; |
1da177e4 LT |
1015 | } |
1016 | ||
1017 | static void extract_buf(struct entropy_store *r, __u8 *out) | |
1018 | { | |
602b6aee | 1019 | int i; |
d2e7c96a PA |
1020 | union { |
1021 | __u32 w[5]; | |
85a1f777 | 1022 | unsigned long l[LONGS(20)]; |
d2e7c96a PA |
1023 | } hash; |
1024 | __u32 workspace[SHA_WORKSPACE_WORDS]; | |
e68e5b66 | 1025 | __u8 extract[64]; |
902c098a | 1026 | unsigned long flags; |
1da177e4 | 1027 | |
1c0ad3d4 | 1028 | /* Generate a hash across the pool, 16 words (512 bits) at a time */ |
d2e7c96a | 1029 | sha_init(hash.w); |
902c098a | 1030 | spin_lock_irqsave(&r->lock, flags); |
1c0ad3d4 | 1031 | for (i = 0; i < r->poolinfo->poolwords; i += 16) |
d2e7c96a | 1032 | sha_transform(hash.w, (__u8 *)(r->pool + i), workspace); |
1c0ad3d4 | 1033 | |
85a1f777 TT |
1034 | /* |
1035 | * If we have a architectural hardware random number | |
1036 | * generator, mix that in, too. | |
1037 | */ | |
1038 | for (i = 0; i < LONGS(20); i++) { | |
1039 | unsigned long v; | |
1040 | if (!arch_get_random_long(&v)) | |
1041 | break; | |
1042 | hash.l[i] ^= v; | |
1043 | } | |
1044 | ||
1da177e4 | 1045 | /* |
1c0ad3d4 MM |
1046 | * We mix the hash back into the pool to prevent backtracking |
1047 | * attacks (where the attacker knows the state of the pool | |
1048 | * plus the current outputs, and attempts to find previous | |
1049 | * ouputs), unless the hash function can be inverted. By | |
1050 | * mixing at least a SHA1 worth of hash data back, we make | |
1051 | * brute-forcing the feedback as hard as brute-forcing the | |
1052 | * hash. | |
1da177e4 | 1053 | */ |
d2e7c96a | 1054 | __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract); |
902c098a | 1055 | spin_unlock_irqrestore(&r->lock, flags); |
1da177e4 LT |
1056 | |
1057 | /* | |
1c0ad3d4 MM |
1058 | * To avoid duplicates, we atomically extract a portion of the |
1059 | * pool while mixing, and hash one final time. | |
1da177e4 | 1060 | */ |
d2e7c96a | 1061 | sha_transform(hash.w, extract, workspace); |
ffd8d3fa MM |
1062 | memset(extract, 0, sizeof(extract)); |
1063 | memset(workspace, 0, sizeof(workspace)); | |
1da177e4 LT |
1064 | |
1065 | /* | |
1c0ad3d4 MM |
1066 | * In case the hash function has some recognizable output |
1067 | * pattern, we fold it in half. Thus, we always feed back | |
1068 | * twice as much data as we output. | |
1da177e4 | 1069 | */ |
d2e7c96a PA |
1070 | hash.w[0] ^= hash.w[3]; |
1071 | hash.w[1] ^= hash.w[4]; | |
1072 | hash.w[2] ^= rol32(hash.w[2], 16); | |
1073 | ||
d2e7c96a PA |
1074 | memcpy(out, &hash, EXTRACT_SIZE); |
1075 | memset(&hash, 0, sizeof(hash)); | |
1da177e4 LT |
1076 | } |
1077 | ||
90b75ee5 | 1078 | static ssize_t extract_entropy(struct entropy_store *r, void *buf, |
902c098a | 1079 | size_t nbytes, int min, int reserved) |
1da177e4 LT |
1080 | { |
1081 | ssize_t ret = 0, i; | |
1082 | __u8 tmp[EXTRACT_SIZE]; | |
1e7e2e05 | 1083 | unsigned long flags; |
1da177e4 | 1084 | |
ec8f02da | 1085 | /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */ |
1e7e2e05 JW |
1086 | if (fips_enabled) { |
1087 | spin_lock_irqsave(&r->lock, flags); | |
1088 | if (!r->last_data_init) { | |
c59974ae | 1089 | r->last_data_init = 1; |
1e7e2e05 JW |
1090 | spin_unlock_irqrestore(&r->lock, flags); |
1091 | trace_extract_entropy(r->name, EXTRACT_SIZE, | |
a283b5c4 | 1092 | ENTROPY_BITS(r), _RET_IP_); |
1e7e2e05 JW |
1093 | xfer_secondary_pool(r, EXTRACT_SIZE); |
1094 | extract_buf(r, tmp); | |
1095 | spin_lock_irqsave(&r->lock, flags); | |
1096 | memcpy(r->last_data, tmp, EXTRACT_SIZE); | |
1097 | } | |
1098 | spin_unlock_irqrestore(&r->lock, flags); | |
1099 | } | |
ec8f02da | 1100 | |
a283b5c4 | 1101 | trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_); |
1da177e4 LT |
1102 | xfer_secondary_pool(r, nbytes); |
1103 | nbytes = account(r, nbytes, min, reserved); | |
1104 | ||
1105 | while (nbytes) { | |
1106 | extract_buf(r, tmp); | |
5b739ef8 | 1107 | |
e954bc91 | 1108 | if (fips_enabled) { |
5b739ef8 NH |
1109 | spin_lock_irqsave(&r->lock, flags); |
1110 | if (!memcmp(tmp, r->last_data, EXTRACT_SIZE)) | |
1111 | panic("Hardware RNG duplicated output!\n"); | |
1112 | memcpy(r->last_data, tmp, EXTRACT_SIZE); | |
1113 | spin_unlock_irqrestore(&r->lock, flags); | |
1114 | } | |
1da177e4 LT |
1115 | i = min_t(int, nbytes, EXTRACT_SIZE); |
1116 | memcpy(buf, tmp, i); | |
1117 | nbytes -= i; | |
1118 | buf += i; | |
1119 | ret += i; | |
1120 | } | |
1121 | ||
1122 | /* Wipe data just returned from memory */ | |
1123 | memset(tmp, 0, sizeof(tmp)); | |
1124 | ||
1125 | return ret; | |
1126 | } | |
1127 | ||
1128 | static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, | |
1129 | size_t nbytes) | |
1130 | { | |
1131 | ssize_t ret = 0, i; | |
1132 | __u8 tmp[EXTRACT_SIZE]; | |
1133 | ||
a283b5c4 | 1134 | trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_); |
1da177e4 LT |
1135 | xfer_secondary_pool(r, nbytes); |
1136 | nbytes = account(r, nbytes, 0, 0); | |
1137 | ||
1138 | while (nbytes) { | |
1139 | if (need_resched()) { | |
1140 | if (signal_pending(current)) { | |
1141 | if (ret == 0) | |
1142 | ret = -ERESTARTSYS; | |
1143 | break; | |
1144 | } | |
1145 | schedule(); | |
1146 | } | |
1147 | ||
1148 | extract_buf(r, tmp); | |
1149 | i = min_t(int, nbytes, EXTRACT_SIZE); | |
1150 | if (copy_to_user(buf, tmp, i)) { | |
1151 | ret = -EFAULT; | |
1152 | break; | |
1153 | } | |
1154 | ||
1155 | nbytes -= i; | |
1156 | buf += i; | |
1157 | ret += i; | |
1158 | } | |
1159 | ||
1160 | /* Wipe data just returned from memory */ | |
1161 | memset(tmp, 0, sizeof(tmp)); | |
1162 | ||
1163 | return ret; | |
1164 | } | |
1165 | ||
1166 | /* | |
1167 | * This function is the exported kernel interface. It returns some | |
c2557a30 TT |
1168 | * number of good random numbers, suitable for key generation, seeding |
1169 | * TCP sequence numbers, etc. It does not use the hw random number | |
1170 | * generator, if available; use get_random_bytes_arch() for that. | |
1da177e4 LT |
1171 | */ |
1172 | void get_random_bytes(void *buf, int nbytes) | |
c2557a30 | 1173 | { |
5910895f | 1174 | trace_get_random_bytes(nbytes, _RET_IP_); |
c2557a30 TT |
1175 | extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0); |
1176 | } | |
1177 | EXPORT_SYMBOL(get_random_bytes); | |
1178 | ||
1179 | /* | |
1180 | * This function will use the architecture-specific hardware random | |
1181 | * number generator if it is available. The arch-specific hw RNG will | |
1182 | * almost certainly be faster than what we can do in software, but it | |
1183 | * is impossible to verify that it is implemented securely (as | |
1184 | * opposed, to, say, the AES encryption of a sequence number using a | |
1185 | * key known by the NSA). So it's useful if we need the speed, but | |
1186 | * only if we're willing to trust the hardware manufacturer not to | |
1187 | * have put in a back door. | |
1188 | */ | |
1189 | void get_random_bytes_arch(void *buf, int nbytes) | |
1da177e4 | 1190 | { |
63d77173 PA |
1191 | char *p = buf; |
1192 | ||
5910895f | 1193 | trace_get_random_bytes_arch(nbytes, _RET_IP_); |
63d77173 PA |
1194 | while (nbytes) { |
1195 | unsigned long v; | |
1196 | int chunk = min(nbytes, (int)sizeof(unsigned long)); | |
c2557a30 | 1197 | |
63d77173 PA |
1198 | if (!arch_get_random_long(&v)) |
1199 | break; | |
1200 | ||
bd29e568 | 1201 | memcpy(p, &v, chunk); |
63d77173 PA |
1202 | p += chunk; |
1203 | nbytes -= chunk; | |
1204 | } | |
1205 | ||
c2557a30 TT |
1206 | if (nbytes) |
1207 | extract_entropy(&nonblocking_pool, p, nbytes, 0, 0); | |
1da177e4 | 1208 | } |
c2557a30 TT |
1209 | EXPORT_SYMBOL(get_random_bytes_arch); |
1210 | ||
1da177e4 LT |
1211 | |
1212 | /* | |
1213 | * init_std_data - initialize pool with system data | |
1214 | * | |
1215 | * @r: pool to initialize | |
1216 | * | |
1217 | * This function clears the pool's entropy count and mixes some system | |
1218 | * data into the pool to prepare it for use. The pool is not cleared | |
1219 | * as that can only decrease the entropy in the pool. | |
1220 | */ | |
1221 | static void init_std_data(struct entropy_store *r) | |
1222 | { | |
3e88bdff | 1223 | int i; |
902c098a TT |
1224 | ktime_t now = ktime_get_real(); |
1225 | unsigned long rv; | |
1da177e4 | 1226 | |
1da177e4 | 1227 | r->entropy_count = 0; |
775f4b29 | 1228 | r->entropy_total = 0; |
c59974ae | 1229 | r->last_data_init = 0; |
f5c2742c | 1230 | r->last_pulled = jiffies; |
902c098a | 1231 | mix_pool_bytes(r, &now, sizeof(now), NULL); |
9ed17b70 | 1232 | for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) { |
902c098a | 1233 | if (!arch_get_random_long(&rv)) |
3e88bdff | 1234 | break; |
902c098a | 1235 | mix_pool_bytes(r, &rv, sizeof(rv), NULL); |
3e88bdff | 1236 | } |
902c098a | 1237 | mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL); |
1da177e4 LT |
1238 | } |
1239 | ||
cbc96b75 TL |
1240 | /* |
1241 | * Note that setup_arch() may call add_device_randomness() | |
1242 | * long before we get here. This allows seeding of the pools | |
1243 | * with some platform dependent data very early in the boot | |
1244 | * process. But it limits our options here. We must use | |
1245 | * statically allocated structures that already have all | |
1246 | * initializations complete at compile time. We should also | |
1247 | * take care not to overwrite the precious per platform data | |
1248 | * we were given. | |
1249 | */ | |
53c3f63e | 1250 | static int rand_initialize(void) |
1da177e4 LT |
1251 | { |
1252 | init_std_data(&input_pool); | |
1253 | init_std_data(&blocking_pool); | |
1254 | init_std_data(&nonblocking_pool); | |
1255 | return 0; | |
1256 | } | |
1257 | module_init(rand_initialize); | |
1258 | ||
9361401e | 1259 | #ifdef CONFIG_BLOCK |
1da177e4 LT |
1260 | void rand_initialize_disk(struct gendisk *disk) |
1261 | { | |
1262 | struct timer_rand_state *state; | |
1263 | ||
1264 | /* | |
f8595815 | 1265 | * If kzalloc returns null, we just won't use that entropy |
1da177e4 LT |
1266 | * source. |
1267 | */ | |
f8595815 ED |
1268 | state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); |
1269 | if (state) | |
1da177e4 | 1270 | disk->random = state; |
1da177e4 | 1271 | } |
9361401e | 1272 | #endif |
1da177e4 LT |
1273 | |
1274 | static ssize_t | |
90b75ee5 | 1275 | random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) |
1da177e4 LT |
1276 | { |
1277 | ssize_t n, retval = 0, count = 0; | |
1278 | ||
1279 | if (nbytes == 0) | |
1280 | return 0; | |
1281 | ||
1282 | while (nbytes > 0) { | |
1283 | n = nbytes; | |
1284 | if (n > SEC_XFER_SIZE) | |
1285 | n = SEC_XFER_SIZE; | |
1286 | ||
1da177e4 LT |
1287 | n = extract_entropy_user(&blocking_pool, buf, n); |
1288 | ||
8eb2ffbf JK |
1289 | if (n < 0) { |
1290 | retval = n; | |
1291 | break; | |
1292 | } | |
1293 | ||
f80bbd8b TT |
1294 | trace_random_read(n*8, (nbytes-n)*8, |
1295 | ENTROPY_BITS(&blocking_pool), | |
1296 | ENTROPY_BITS(&input_pool)); | |
1da177e4 LT |
1297 | |
1298 | if (n == 0) { | |
1299 | if (file->f_flags & O_NONBLOCK) { | |
1300 | retval = -EAGAIN; | |
1301 | break; | |
1302 | } | |
1303 | ||
1da177e4 | 1304 | wait_event_interruptible(random_read_wait, |
a283b5c4 PA |
1305 | ENTROPY_BITS(&input_pool) >= |
1306 | random_read_wakeup_thresh); | |
1da177e4 | 1307 | |
1da177e4 LT |
1308 | if (signal_pending(current)) { |
1309 | retval = -ERESTARTSYS; | |
1310 | break; | |
1311 | } | |
1312 | ||
1313 | continue; | |
1314 | } | |
1315 | ||
1da177e4 LT |
1316 | count += n; |
1317 | buf += n; | |
1318 | nbytes -= n; | |
1319 | break; /* This break makes the device work */ | |
1320 | /* like a named pipe */ | |
1321 | } | |
1322 | ||
1da177e4 LT |
1323 | return (count ? count : retval); |
1324 | } | |
1325 | ||
1326 | static ssize_t | |
90b75ee5 | 1327 | urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) |
1da177e4 | 1328 | { |
f80bbd8b TT |
1329 | int ret = extract_entropy_user(&nonblocking_pool, buf, nbytes); |
1330 | ||
1331 | trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool), | |
1332 | ENTROPY_BITS(&input_pool)); | |
1333 | return ret; | |
1da177e4 LT |
1334 | } |
1335 | ||
1336 | static unsigned int | |
1337 | random_poll(struct file *file, poll_table * wait) | |
1338 | { | |
1339 | unsigned int mask; | |
1340 | ||
1341 | poll_wait(file, &random_read_wait, wait); | |
1342 | poll_wait(file, &random_write_wait, wait); | |
1343 | mask = 0; | |
a283b5c4 | 1344 | if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_thresh) |
1da177e4 | 1345 | mask |= POLLIN | POLLRDNORM; |
a283b5c4 | 1346 | if (ENTROPY_BITS(&input_pool) < random_write_wakeup_thresh) |
1da177e4 LT |
1347 | mask |= POLLOUT | POLLWRNORM; |
1348 | return mask; | |
1349 | } | |
1350 | ||
7f397dcd MM |
1351 | static int |
1352 | write_pool(struct entropy_store *r, const char __user *buffer, size_t count) | |
1da177e4 | 1353 | { |
1da177e4 LT |
1354 | size_t bytes; |
1355 | __u32 buf[16]; | |
1356 | const char __user *p = buffer; | |
1da177e4 | 1357 | |
7f397dcd MM |
1358 | while (count > 0) { |
1359 | bytes = min(count, sizeof(buf)); | |
1360 | if (copy_from_user(&buf, p, bytes)) | |
1361 | return -EFAULT; | |
1da177e4 | 1362 | |
7f397dcd | 1363 | count -= bytes; |
1da177e4 LT |
1364 | p += bytes; |
1365 | ||
902c098a | 1366 | mix_pool_bytes(r, buf, bytes, NULL); |
91f3f1e3 | 1367 | cond_resched(); |
1da177e4 | 1368 | } |
7f397dcd MM |
1369 | |
1370 | return 0; | |
1371 | } | |
1372 | ||
90b75ee5 MM |
1373 | static ssize_t random_write(struct file *file, const char __user *buffer, |
1374 | size_t count, loff_t *ppos) | |
7f397dcd MM |
1375 | { |
1376 | size_t ret; | |
7f397dcd MM |
1377 | |
1378 | ret = write_pool(&blocking_pool, buffer, count); | |
1379 | if (ret) | |
1380 | return ret; | |
1381 | ret = write_pool(&nonblocking_pool, buffer, count); | |
1382 | if (ret) | |
1383 | return ret; | |
1384 | ||
7f397dcd | 1385 | return (ssize_t)count; |
1da177e4 LT |
1386 | } |
1387 | ||
43ae4860 | 1388 | static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) |
1da177e4 LT |
1389 | { |
1390 | int size, ent_count; | |
1391 | int __user *p = (int __user *)arg; | |
1392 | int retval; | |
1393 | ||
1394 | switch (cmd) { | |
1395 | case RNDGETENTCNT: | |
43ae4860 | 1396 | /* inherently racy, no point locking */ |
a283b5c4 PA |
1397 | ent_count = ENTROPY_BITS(&input_pool); |
1398 | if (put_user(ent_count, p)) | |
1da177e4 LT |
1399 | return -EFAULT; |
1400 | return 0; | |
1401 | case RNDADDTOENTCNT: | |
1402 | if (!capable(CAP_SYS_ADMIN)) | |
1403 | return -EPERM; | |
1404 | if (get_user(ent_count, p)) | |
1405 | return -EFAULT; | |
a283b5c4 | 1406 | credit_entropy_bits_safe(&input_pool, ent_count); |
1da177e4 LT |
1407 | return 0; |
1408 | case RNDADDENTROPY: | |
1409 | if (!capable(CAP_SYS_ADMIN)) | |
1410 | return -EPERM; | |
1411 | if (get_user(ent_count, p++)) | |
1412 | return -EFAULT; | |
1413 | if (ent_count < 0) | |
1414 | return -EINVAL; | |
1415 | if (get_user(size, p++)) | |
1416 | return -EFAULT; | |
7f397dcd MM |
1417 | retval = write_pool(&input_pool, (const char __user *)p, |
1418 | size); | |
1da177e4 LT |
1419 | if (retval < 0) |
1420 | return retval; | |
a283b5c4 | 1421 | credit_entropy_bits_safe(&input_pool, ent_count); |
1da177e4 LT |
1422 | return 0; |
1423 | case RNDZAPENTCNT: | |
1424 | case RNDCLEARPOOL: | |
1425 | /* Clear the entropy pool counters. */ | |
1426 | if (!capable(CAP_SYS_ADMIN)) | |
1427 | return -EPERM; | |
53c3f63e | 1428 | rand_initialize(); |
1da177e4 LT |
1429 | return 0; |
1430 | default: | |
1431 | return -EINVAL; | |
1432 | } | |
1433 | } | |
1434 | ||
9a6f70bb JD |
1435 | static int random_fasync(int fd, struct file *filp, int on) |
1436 | { | |
1437 | return fasync_helper(fd, filp, on, &fasync); | |
1438 | } | |
1439 | ||
2b8693c0 | 1440 | const struct file_operations random_fops = { |
1da177e4 LT |
1441 | .read = random_read, |
1442 | .write = random_write, | |
1443 | .poll = random_poll, | |
43ae4860 | 1444 | .unlocked_ioctl = random_ioctl, |
9a6f70bb | 1445 | .fasync = random_fasync, |
6038f373 | 1446 | .llseek = noop_llseek, |
1da177e4 LT |
1447 | }; |
1448 | ||
2b8693c0 | 1449 | const struct file_operations urandom_fops = { |
1da177e4 LT |
1450 | .read = urandom_read, |
1451 | .write = random_write, | |
43ae4860 | 1452 | .unlocked_ioctl = random_ioctl, |
9a6f70bb | 1453 | .fasync = random_fasync, |
6038f373 | 1454 | .llseek = noop_llseek, |
1da177e4 LT |
1455 | }; |
1456 | ||
1457 | /*************************************************************** | |
1458 | * Random UUID interface | |
1459 | * | |
1460 | * Used here for a Boot ID, but can be useful for other kernel | |
1461 | * drivers. | |
1462 | ***************************************************************/ | |
1463 | ||
1464 | /* | |
1465 | * Generate random UUID | |
1466 | */ | |
1467 | void generate_random_uuid(unsigned char uuid_out[16]) | |
1468 | { | |
1469 | get_random_bytes(uuid_out, 16); | |
c41b20e7 | 1470 | /* Set UUID version to 4 --- truly random generation */ |
1da177e4 LT |
1471 | uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40; |
1472 | /* Set the UUID variant to DCE */ | |
1473 | uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80; | |
1474 | } | |
1da177e4 LT |
1475 | EXPORT_SYMBOL(generate_random_uuid); |
1476 | ||
1477 | /******************************************************************** | |
1478 | * | |
1479 | * Sysctl interface | |
1480 | * | |
1481 | ********************************************************************/ | |
1482 | ||
1483 | #ifdef CONFIG_SYSCTL | |
1484 | ||
1485 | #include <linux/sysctl.h> | |
1486 | ||
1487 | static int min_read_thresh = 8, min_write_thresh; | |
1488 | static int max_read_thresh = INPUT_POOL_WORDS * 32; | |
1489 | static int max_write_thresh = INPUT_POOL_WORDS * 32; | |
1490 | static char sysctl_bootid[16]; | |
1491 | ||
1492 | /* | |
1493 | * These functions is used to return both the bootid UUID, and random | |
1494 | * UUID. The difference is in whether table->data is NULL; if it is, | |
1495 | * then a new UUID is generated and returned to the user. | |
1496 | * | |
1497 | * If the user accesses this via the proc interface, it will be returned | |
1498 | * as an ASCII string in the standard UUID format. If accesses via the | |
1499 | * sysctl system call, it is returned as 16 bytes of binary data. | |
1500 | */ | |
a151427e | 1501 | static int proc_do_uuid(struct ctl_table *table, int write, |
1da177e4 LT |
1502 | void __user *buffer, size_t *lenp, loff_t *ppos) |
1503 | { | |
a151427e | 1504 | struct ctl_table fake_table; |
1da177e4 LT |
1505 | unsigned char buf[64], tmp_uuid[16], *uuid; |
1506 | ||
1507 | uuid = table->data; | |
1508 | if (!uuid) { | |
1509 | uuid = tmp_uuid; | |
1da177e4 | 1510 | generate_random_uuid(uuid); |
44e4360f MD |
1511 | } else { |
1512 | static DEFINE_SPINLOCK(bootid_spinlock); | |
1513 | ||
1514 | spin_lock(&bootid_spinlock); | |
1515 | if (!uuid[8]) | |
1516 | generate_random_uuid(uuid); | |
1517 | spin_unlock(&bootid_spinlock); | |
1518 | } | |
1da177e4 | 1519 | |
35900771 JP |
1520 | sprintf(buf, "%pU", uuid); |
1521 | ||
1da177e4 LT |
1522 | fake_table.data = buf; |
1523 | fake_table.maxlen = sizeof(buf); | |
1524 | ||
8d65af78 | 1525 | return proc_dostring(&fake_table, write, buffer, lenp, ppos); |
1da177e4 LT |
1526 | } |
1527 | ||
a283b5c4 PA |
1528 | /* |
1529 | * Return entropy available scaled to integral bits | |
1530 | */ | |
1531 | static int proc_do_entropy(ctl_table *table, int write, | |
1532 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
1533 | { | |
1534 | ctl_table fake_table; | |
1535 | int entropy_count; | |
1536 | ||
1537 | entropy_count = *(int *)table->data >> ENTROPY_SHIFT; | |
1538 | ||
1539 | fake_table.data = &entropy_count; | |
1540 | fake_table.maxlen = sizeof(entropy_count); | |
1541 | ||
1542 | return proc_dointvec(&fake_table, write, buffer, lenp, ppos); | |
1543 | } | |
1544 | ||
1da177e4 | 1545 | static int sysctl_poolsize = INPUT_POOL_WORDS * 32; |
a151427e JP |
1546 | extern struct ctl_table random_table[]; |
1547 | struct ctl_table random_table[] = { | |
1da177e4 | 1548 | { |
1da177e4 LT |
1549 | .procname = "poolsize", |
1550 | .data = &sysctl_poolsize, | |
1551 | .maxlen = sizeof(int), | |
1552 | .mode = 0444, | |
6d456111 | 1553 | .proc_handler = proc_dointvec, |
1da177e4 LT |
1554 | }, |
1555 | { | |
1da177e4 LT |
1556 | .procname = "entropy_avail", |
1557 | .maxlen = sizeof(int), | |
1558 | .mode = 0444, | |
a283b5c4 | 1559 | .proc_handler = proc_do_entropy, |
1da177e4 LT |
1560 | .data = &input_pool.entropy_count, |
1561 | }, | |
1562 | { | |
1da177e4 LT |
1563 | .procname = "read_wakeup_threshold", |
1564 | .data = &random_read_wakeup_thresh, | |
1565 | .maxlen = sizeof(int), | |
1566 | .mode = 0644, | |
6d456111 | 1567 | .proc_handler = proc_dointvec_minmax, |
1da177e4 LT |
1568 | .extra1 = &min_read_thresh, |
1569 | .extra2 = &max_read_thresh, | |
1570 | }, | |
1571 | { | |
1da177e4 LT |
1572 | .procname = "write_wakeup_threshold", |
1573 | .data = &random_write_wakeup_thresh, | |
1574 | .maxlen = sizeof(int), | |
1575 | .mode = 0644, | |
6d456111 | 1576 | .proc_handler = proc_dointvec_minmax, |
1da177e4 LT |
1577 | .extra1 = &min_write_thresh, |
1578 | .extra2 = &max_write_thresh, | |
1579 | }, | |
f5c2742c TT |
1580 | { |
1581 | .procname = "urandom_min_reseed_secs", | |
1582 | .data = &random_min_urandom_seed, | |
1583 | .maxlen = sizeof(int), | |
1584 | .mode = 0644, | |
1585 | .proc_handler = proc_dointvec, | |
1586 | }, | |
1da177e4 | 1587 | { |
1da177e4 LT |
1588 | .procname = "boot_id", |
1589 | .data = &sysctl_bootid, | |
1590 | .maxlen = 16, | |
1591 | .mode = 0444, | |
6d456111 | 1592 | .proc_handler = proc_do_uuid, |
1da177e4 LT |
1593 | }, |
1594 | { | |
1da177e4 LT |
1595 | .procname = "uuid", |
1596 | .maxlen = 16, | |
1597 | .mode = 0444, | |
6d456111 | 1598 | .proc_handler = proc_do_uuid, |
1da177e4 | 1599 | }, |
894d2491 | 1600 | { } |
1da177e4 LT |
1601 | }; |
1602 | #endif /* CONFIG_SYSCTL */ | |
1603 | ||
6e5714ea | 1604 | static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned; |
1da177e4 | 1605 | |
47d06e53 | 1606 | int random_int_secret_init(void) |
1da177e4 | 1607 | { |
6e5714ea | 1608 | get_random_bytes(random_int_secret, sizeof(random_int_secret)); |
1da177e4 LT |
1609 | return 0; |
1610 | } | |
1da177e4 LT |
1611 | |
1612 | /* | |
1613 | * Get a random word for internal kernel use only. Similar to urandom but | |
1614 | * with the goal of minimal entropy pool depletion. As a result, the random | |
1615 | * value is not cryptographically secure but for several uses the cost of | |
1616 | * depleting entropy is too high | |
1617 | */ | |
74feec5d | 1618 | static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash); |
1da177e4 LT |
1619 | unsigned int get_random_int(void) |
1620 | { | |
63d77173 | 1621 | __u32 *hash; |
6e5714ea | 1622 | unsigned int ret; |
8a0a9bd4 | 1623 | |
63d77173 PA |
1624 | if (arch_get_random_int(&ret)) |
1625 | return ret; | |
1626 | ||
1627 | hash = get_cpu_var(get_random_int_hash); | |
8a0a9bd4 | 1628 | |
61875f30 | 1629 | hash[0] += current->pid + jiffies + random_get_entropy(); |
6e5714ea DM |
1630 | md5_transform(hash, random_int_secret); |
1631 | ret = hash[0]; | |
8a0a9bd4 LT |
1632 | put_cpu_var(get_random_int_hash); |
1633 | ||
1634 | return ret; | |
1da177e4 | 1635 | } |
16c7fa05 | 1636 | EXPORT_SYMBOL(get_random_int); |
1da177e4 LT |
1637 | |
1638 | /* | |
1639 | * randomize_range() returns a start address such that | |
1640 | * | |
1641 | * [...... <range> .....] | |
1642 | * start end | |
1643 | * | |
1644 | * a <range> with size "len" starting at the return value is inside in the | |
1645 | * area defined by [start, end], but is otherwise randomized. | |
1646 | */ | |
1647 | unsigned long | |
1648 | randomize_range(unsigned long start, unsigned long end, unsigned long len) | |
1649 | { | |
1650 | unsigned long range = end - len - start; | |
1651 | ||
1652 | if (end <= start + len) | |
1653 | return 0; | |
1654 | return PAGE_ALIGN(get_random_int() % range + start); | |
1655 | } |