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1da177e4 LT |
1 | /* |
2 | * random.c -- A strong random number generator | |
3 | * | |
9e95ce27 | 4 | * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005 |
1da177e4 LT |
5 | * |
6 | * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All | |
7 | * rights reserved. | |
8 | * | |
9 | * Redistribution and use in source and binary forms, with or without | |
10 | * modification, are permitted provided that the following conditions | |
11 | * are met: | |
12 | * 1. Redistributions of source code must retain the above copyright | |
13 | * notice, and the entire permission notice in its entirety, | |
14 | * including the disclaimer of warranties. | |
15 | * 2. Redistributions in binary form must reproduce the above copyright | |
16 | * notice, this list of conditions and the following disclaimer in the | |
17 | * documentation and/or other materials provided with the distribution. | |
18 | * 3. The name of the author may not be used to endorse or promote | |
19 | * products derived from this software without specific prior | |
20 | * written permission. | |
21 | * | |
22 | * ALTERNATIVELY, this product may be distributed under the terms of | |
23 | * the GNU General Public License, in which case the provisions of the GPL are | |
24 | * required INSTEAD OF the above restrictions. (This clause is | |
25 | * necessary due to a potential bad interaction between the GPL and | |
26 | * the restrictions contained in a BSD-style copyright.) | |
27 | * | |
28 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED | |
29 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
30 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF | |
31 | * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE | |
32 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
33 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT | |
34 | * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR | |
35 | * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
36 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
37 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE | |
38 | * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH | |
39 | * DAMAGE. | |
40 | */ | |
41 | ||
42 | /* | |
43 | * (now, with legal B.S. out of the way.....) | |
44 | * | |
45 | * This routine gathers environmental noise from device drivers, etc., | |
46 | * and returns good random numbers, suitable for cryptographic use. | |
47 | * Besides the obvious cryptographic uses, these numbers are also good | |
48 | * for seeding TCP sequence numbers, and other places where it is | |
49 | * desirable to have numbers which are not only random, but hard to | |
50 | * predict by an attacker. | |
51 | * | |
52 | * Theory of operation | |
53 | * =================== | |
54 | * | |
55 | * Computers are very predictable devices. Hence it is extremely hard | |
56 | * to produce truly random numbers on a computer --- as opposed to | |
57 | * pseudo-random numbers, which can easily generated by using a | |
58 | * algorithm. Unfortunately, it is very easy for attackers to guess | |
59 | * the sequence of pseudo-random number generators, and for some | |
60 | * applications this is not acceptable. So instead, we must try to | |
61 | * gather "environmental noise" from the computer's environment, which | |
62 | * must be hard for outside attackers to observe, and use that to | |
63 | * generate random numbers. In a Unix environment, this is best done | |
64 | * from inside the kernel. | |
65 | * | |
66 | * Sources of randomness from the environment include inter-keyboard | |
67 | * timings, inter-interrupt timings from some interrupts, and other | |
68 | * events which are both (a) non-deterministic and (b) hard for an | |
69 | * outside observer to measure. Randomness from these sources are | |
70 | * added to an "entropy pool", which is mixed using a CRC-like function. | |
71 | * This is not cryptographically strong, but it is adequate assuming | |
72 | * the randomness is not chosen maliciously, and it is fast enough that | |
73 | * the overhead of doing it on every interrupt is very reasonable. | |
74 | * As random bytes are mixed into the entropy pool, the routines keep | |
75 | * an *estimate* of how many bits of randomness have been stored into | |
76 | * the random number generator's internal state. | |
77 | * | |
78 | * When random bytes are desired, they are obtained by taking the SHA | |
79 | * hash of the contents of the "entropy pool". The SHA hash avoids | |
80 | * exposing the internal state of the entropy pool. It is believed to | |
81 | * be computationally infeasible to derive any useful information | |
82 | * about the input of SHA from its output. Even if it is possible to | |
83 | * analyze SHA in some clever way, as long as the amount of data | |
84 | * returned from the generator is less than the inherent entropy in | |
85 | * the pool, the output data is totally unpredictable. For this | |
86 | * reason, the routine decreases its internal estimate of how many | |
87 | * bits of "true randomness" are contained in the entropy pool as it | |
88 | * outputs random numbers. | |
89 | * | |
90 | * If this estimate goes to zero, the routine can still generate | |
91 | * random numbers; however, an attacker may (at least in theory) be | |
92 | * able to infer the future output of the generator from prior | |
93 | * outputs. This requires successful cryptanalysis of SHA, which is | |
94 | * not believed to be feasible, but there is a remote possibility. | |
95 | * Nonetheless, these numbers should be useful for the vast majority | |
96 | * of purposes. | |
97 | * | |
98 | * Exported interfaces ---- output | |
99 | * =============================== | |
100 | * | |
101 | * There are three exported interfaces; the first is one designed to | |
102 | * be used from within the kernel: | |
103 | * | |
104 | * void get_random_bytes(void *buf, int nbytes); | |
105 | * | |
106 | * This interface will return the requested number of random bytes, | |
107 | * and place it in the requested buffer. | |
108 | * | |
109 | * The two other interfaces are two character devices /dev/random and | |
110 | * /dev/urandom. /dev/random is suitable for use when very high | |
111 | * quality randomness is desired (for example, for key generation or | |
112 | * one-time pads), as it will only return a maximum of the number of | |
113 | * bits of randomness (as estimated by the random number generator) | |
114 | * contained in the entropy pool. | |
115 | * | |
116 | * The /dev/urandom device does not have this limit, and will return | |
117 | * as many bytes as are requested. As more and more random bytes are | |
118 | * requested without giving time for the entropy pool to recharge, | |
119 | * this will result in random numbers that are merely cryptographically | |
120 | * strong. For many applications, however, this is acceptable. | |
121 | * | |
122 | * Exported interfaces ---- input | |
123 | * ============================== | |
124 | * | |
125 | * The current exported interfaces for gathering environmental noise | |
126 | * from the devices are: | |
127 | * | |
128 | * void add_input_randomness(unsigned int type, unsigned int code, | |
129 | * unsigned int value); | |
130 | * void add_interrupt_randomness(int irq); | |
131 | * | |
132 | * add_input_randomness() uses the input layer interrupt timing, as well as | |
133 | * the event type information from the hardware. | |
134 | * | |
135 | * add_interrupt_randomness() uses the inter-interrupt timing as random | |
136 | * inputs to the entropy pool. Note that not all interrupts are good | |
137 | * sources of randomness! For example, the timer interrupts is not a | |
138 | * good choice, because the periodicity of the interrupts is too | |
139 | * regular, and hence predictable to an attacker. Disk interrupts are | |
140 | * a better measure, since the timing of the disk interrupts are more | |
141 | * unpredictable. | |
142 | * | |
143 | * All of these routines try to estimate how many bits of randomness a | |
144 | * particular randomness source. They do this by keeping track of the | |
145 | * first and second order deltas of the event timings. | |
146 | * | |
147 | * Ensuring unpredictability at system startup | |
148 | * ============================================ | |
149 | * | |
150 | * When any operating system starts up, it will go through a sequence | |
151 | * of actions that are fairly predictable by an adversary, especially | |
152 | * if the start-up does not involve interaction with a human operator. | |
153 | * This reduces the actual number of bits of unpredictability in the | |
154 | * entropy pool below the value in entropy_count. In order to | |
155 | * counteract this effect, it helps to carry information in the | |
156 | * entropy pool across shut-downs and start-ups. To do this, put the | |
157 | * following lines an appropriate script which is run during the boot | |
158 | * sequence: | |
159 | * | |
160 | * echo "Initializing random number generator..." | |
161 | * random_seed=/var/run/random-seed | |
162 | * # Carry a random seed from start-up to start-up | |
163 | * # Load and then save the whole entropy pool | |
164 | * if [ -f $random_seed ]; then | |
165 | * cat $random_seed >/dev/urandom | |
166 | * else | |
167 | * touch $random_seed | |
168 | * fi | |
169 | * chmod 600 $random_seed | |
170 | * dd if=/dev/urandom of=$random_seed count=1 bs=512 | |
171 | * | |
172 | * and the following lines in an appropriate script which is run as | |
173 | * the system is shutdown: | |
174 | * | |
175 | * # Carry a random seed from shut-down to start-up | |
176 | * # Save the whole entropy pool | |
177 | * echo "Saving random seed..." | |
178 | * random_seed=/var/run/random-seed | |
179 | * touch $random_seed | |
180 | * chmod 600 $random_seed | |
181 | * dd if=/dev/urandom of=$random_seed count=1 bs=512 | |
182 | * | |
183 | * For example, on most modern systems using the System V init | |
184 | * scripts, such code fragments would be found in | |
185 | * /etc/rc.d/init.d/random. On older Linux systems, the correct script | |
186 | * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0. | |
187 | * | |
188 | * Effectively, these commands cause the contents of the entropy pool | |
189 | * to be saved at shut-down time and reloaded into the entropy pool at | |
190 | * start-up. (The 'dd' in the addition to the bootup script is to | |
191 | * make sure that /etc/random-seed is different for every start-up, | |
192 | * even if the system crashes without executing rc.0.) Even with | |
193 | * complete knowledge of the start-up activities, predicting the state | |
194 | * of the entropy pool requires knowledge of the previous history of | |
195 | * the system. | |
196 | * | |
197 | * Configuring the /dev/random driver under Linux | |
198 | * ============================================== | |
199 | * | |
200 | * The /dev/random driver under Linux uses minor numbers 8 and 9 of | |
201 | * the /dev/mem major number (#1). So if your system does not have | |
202 | * /dev/random and /dev/urandom created already, they can be created | |
203 | * by using the commands: | |
204 | * | |
205 | * mknod /dev/random c 1 8 | |
206 | * mknod /dev/urandom c 1 9 | |
207 | * | |
208 | * Acknowledgements: | |
209 | * ================= | |
210 | * | |
211 | * Ideas for constructing this random number generator were derived | |
212 | * from Pretty Good Privacy's random number generator, and from private | |
213 | * discussions with Phil Karn. Colin Plumb provided a faster random | |
214 | * number generator, which speed up the mixing function of the entropy | |
215 | * pool, taken from PGPfone. Dale Worley has also contributed many | |
216 | * useful ideas and suggestions to improve this driver. | |
217 | * | |
218 | * Any flaws in the design are solely my responsibility, and should | |
219 | * not be attributed to the Phil, Colin, or any of authors of PGP. | |
220 | * | |
221 | * Further background information on this topic may be obtained from | |
222 | * RFC 1750, "Randomness Recommendations for Security", by Donald | |
223 | * Eastlake, Steve Crocker, and Jeff Schiller. | |
224 | */ | |
225 | ||
226 | #include <linux/utsname.h> | |
227 | #include <linux/config.h> | |
228 | #include <linux/module.h> | |
229 | #include <linux/kernel.h> | |
230 | #include <linux/major.h> | |
231 | #include <linux/string.h> | |
232 | #include <linux/fcntl.h> | |
233 | #include <linux/slab.h> | |
234 | #include <linux/random.h> | |
235 | #include <linux/poll.h> | |
236 | #include <linux/init.h> | |
237 | #include <linux/fs.h> | |
238 | #include <linux/genhd.h> | |
239 | #include <linux/interrupt.h> | |
240 | #include <linux/spinlock.h> | |
241 | #include <linux/percpu.h> | |
242 | #include <linux/cryptohash.h> | |
243 | ||
244 | #include <asm/processor.h> | |
245 | #include <asm/uaccess.h> | |
246 | #include <asm/irq.h> | |
247 | #include <asm/io.h> | |
248 | ||
249 | /* | |
250 | * Configuration information | |
251 | */ | |
252 | #define INPUT_POOL_WORDS 128 | |
253 | #define OUTPUT_POOL_WORDS 32 | |
254 | #define SEC_XFER_SIZE 512 | |
255 | ||
256 | /* | |
257 | * The minimum number of bits of entropy before we wake up a read on | |
258 | * /dev/random. Should be enough to do a significant reseed. | |
259 | */ | |
260 | static int random_read_wakeup_thresh = 64; | |
261 | ||
262 | /* | |
263 | * If the entropy count falls under this number of bits, then we | |
264 | * should wake up processes which are selecting or polling on write | |
265 | * access to /dev/random. | |
266 | */ | |
267 | static int random_write_wakeup_thresh = 128; | |
268 | ||
269 | /* | |
270 | * When the input pool goes over trickle_thresh, start dropping most | |
271 | * samples to avoid wasting CPU time and reduce lock contention. | |
272 | */ | |
273 | ||
6c036527 | 274 | static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28; |
1da177e4 LT |
275 | |
276 | static DEFINE_PER_CPU(int, trickle_count) = 0; | |
277 | ||
278 | /* | |
279 | * A pool of size .poolwords is stirred with a primitive polynomial | |
280 | * of degree .poolwords over GF(2). The taps for various sizes are | |
281 | * defined below. They are chosen to be evenly spaced (minimum RMS | |
282 | * distance from evenly spaced; the numbers in the comments are a | |
283 | * scaled squared error sum) except for the last tap, which is 1 to | |
284 | * get the twisting happening as fast as possible. | |
285 | */ | |
286 | static struct poolinfo { | |
287 | int poolwords; | |
288 | int tap1, tap2, tap3, tap4, tap5; | |
289 | } poolinfo_table[] = { | |
290 | /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */ | |
291 | { 128, 103, 76, 51, 25, 1 }, | |
292 | /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */ | |
293 | { 32, 26, 20, 14, 7, 1 }, | |
294 | #if 0 | |
295 | /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */ | |
296 | { 2048, 1638, 1231, 819, 411, 1 }, | |
297 | ||
298 | /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */ | |
299 | { 1024, 817, 615, 412, 204, 1 }, | |
300 | ||
301 | /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */ | |
302 | { 1024, 819, 616, 410, 207, 2 }, | |
303 | ||
304 | /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */ | |
305 | { 512, 411, 308, 208, 104, 1 }, | |
306 | ||
307 | /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */ | |
308 | { 512, 409, 307, 206, 102, 2 }, | |
309 | /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */ | |
310 | { 512, 409, 309, 205, 103, 2 }, | |
311 | ||
312 | /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */ | |
313 | { 256, 205, 155, 101, 52, 1 }, | |
314 | ||
315 | /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */ | |
316 | { 128, 103, 78, 51, 27, 2 }, | |
317 | ||
318 | /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */ | |
319 | { 64, 52, 39, 26, 14, 1 }, | |
320 | #endif | |
321 | }; | |
322 | ||
323 | #define POOLBITS poolwords*32 | |
324 | #define POOLBYTES poolwords*4 | |
325 | ||
326 | /* | |
327 | * For the purposes of better mixing, we use the CRC-32 polynomial as | |
328 | * well to make a twisted Generalized Feedback Shift Reigster | |
329 | * | |
330 | * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM | |
331 | * Transactions on Modeling and Computer Simulation 2(3):179-194. | |
332 | * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators | |
333 | * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266) | |
334 | * | |
335 | * Thanks to Colin Plumb for suggesting this. | |
336 | * | |
337 | * We have not analyzed the resultant polynomial to prove it primitive; | |
338 | * in fact it almost certainly isn't. Nonetheless, the irreducible factors | |
339 | * of a random large-degree polynomial over GF(2) are more than large enough | |
340 | * that periodicity is not a concern. | |
341 | * | |
342 | * The input hash is much less sensitive than the output hash. All | |
343 | * that we want of it is that it be a good non-cryptographic hash; | |
344 | * i.e. it not produce collisions when fed "random" data of the sort | |
345 | * we expect to see. As long as the pool state differs for different | |
346 | * inputs, we have preserved the input entropy and done a good job. | |
347 | * The fact that an intelligent attacker can construct inputs that | |
348 | * will produce controlled alterations to the pool's state is not | |
349 | * important because we don't consider such inputs to contribute any | |
350 | * randomness. The only property we need with respect to them is that | |
351 | * the attacker can't increase his/her knowledge of the pool's state. | |
352 | * Since all additions are reversible (knowing the final state and the | |
353 | * input, you can reconstruct the initial state), if an attacker has | |
354 | * any uncertainty about the initial state, he/she can only shuffle | |
355 | * that uncertainty about, but never cause any collisions (which would | |
356 | * decrease the uncertainty). | |
357 | * | |
358 | * The chosen system lets the state of the pool be (essentially) the input | |
359 | * modulo the generator polymnomial. Now, for random primitive polynomials, | |
360 | * this is a universal class of hash functions, meaning that the chance | |
361 | * of a collision is limited by the attacker's knowledge of the generator | |
362 | * polynomail, so if it is chosen at random, an attacker can never force | |
363 | * a collision. Here, we use a fixed polynomial, but we *can* assume that | |
364 | * ###--> it is unknown to the processes generating the input entropy. <-### | |
365 | * Because of this important property, this is a good, collision-resistant | |
366 | * hash; hash collisions will occur no more often than chance. | |
367 | */ | |
368 | ||
369 | /* | |
370 | * Static global variables | |
371 | */ | |
372 | static DECLARE_WAIT_QUEUE_HEAD(random_read_wait); | |
373 | static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); | |
374 | ||
375 | #if 0 | |
376 | static int debug = 0; | |
377 | module_param(debug, bool, 0644); | |
378 | #define DEBUG_ENT(fmt, arg...) do { if (debug) \ | |
379 | printk(KERN_DEBUG "random %04d %04d %04d: " \ | |
380 | fmt,\ | |
381 | input_pool.entropy_count,\ | |
382 | blocking_pool.entropy_count,\ | |
383 | nonblocking_pool.entropy_count,\ | |
384 | ## arg); } while (0) | |
385 | #else | |
386 | #define DEBUG_ENT(fmt, arg...) do {} while (0) | |
387 | #endif | |
388 | ||
389 | /********************************************************************** | |
390 | * | |
391 | * OS independent entropy store. Here are the functions which handle | |
392 | * storing entropy in an entropy pool. | |
393 | * | |
394 | **********************************************************************/ | |
395 | ||
396 | struct entropy_store; | |
397 | struct entropy_store { | |
398 | /* mostly-read data: */ | |
399 | struct poolinfo *poolinfo; | |
400 | __u32 *pool; | |
401 | const char *name; | |
402 | int limit; | |
403 | struct entropy_store *pull; | |
404 | ||
405 | /* read-write data: */ | |
406 | spinlock_t lock ____cacheline_aligned_in_smp; | |
407 | unsigned add_ptr; | |
408 | int entropy_count; | |
409 | int input_rotate; | |
410 | }; | |
411 | ||
412 | static __u32 input_pool_data[INPUT_POOL_WORDS]; | |
413 | static __u32 blocking_pool_data[OUTPUT_POOL_WORDS]; | |
414 | static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS]; | |
415 | ||
416 | static struct entropy_store input_pool = { | |
417 | .poolinfo = &poolinfo_table[0], | |
418 | .name = "input", | |
419 | .limit = 1, | |
420 | .lock = SPIN_LOCK_UNLOCKED, | |
421 | .pool = input_pool_data | |
422 | }; | |
423 | ||
424 | static struct entropy_store blocking_pool = { | |
425 | .poolinfo = &poolinfo_table[1], | |
426 | .name = "blocking", | |
427 | .limit = 1, | |
428 | .pull = &input_pool, | |
429 | .lock = SPIN_LOCK_UNLOCKED, | |
430 | .pool = blocking_pool_data | |
431 | }; | |
432 | ||
433 | static struct entropy_store nonblocking_pool = { | |
434 | .poolinfo = &poolinfo_table[1], | |
435 | .name = "nonblocking", | |
436 | .pull = &input_pool, | |
437 | .lock = SPIN_LOCK_UNLOCKED, | |
438 | .pool = nonblocking_pool_data | |
439 | }; | |
440 | ||
441 | /* | |
442 | * This function adds a byte into the entropy "pool". It does not | |
443 | * update the entropy estimate. The caller should call | |
444 | * credit_entropy_store if this is appropriate. | |
445 | * | |
446 | * The pool is stirred with a primitive polynomial of the appropriate | |
447 | * degree, and then twisted. We twist by three bits at a time because | |
448 | * it's cheap to do so and helps slightly in the expected case where | |
449 | * the entropy is concentrated in the low-order bits. | |
450 | */ | |
451 | static void __add_entropy_words(struct entropy_store *r, const __u32 *in, | |
452 | int nwords, __u32 out[16]) | |
453 | { | |
454 | static __u32 const twist_table[8] = { | |
455 | 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158, | |
456 | 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; | |
457 | unsigned long i, add_ptr, tap1, tap2, tap3, tap4, tap5; | |
458 | int new_rotate, input_rotate; | |
459 | int wordmask = r->poolinfo->poolwords - 1; | |
460 | __u32 w, next_w; | |
461 | unsigned long flags; | |
462 | ||
463 | /* Taps are constant, so we can load them without holding r->lock. */ | |
464 | tap1 = r->poolinfo->tap1; | |
465 | tap2 = r->poolinfo->tap2; | |
466 | tap3 = r->poolinfo->tap3; | |
467 | tap4 = r->poolinfo->tap4; | |
468 | tap5 = r->poolinfo->tap5; | |
469 | next_w = *in++; | |
470 | ||
471 | spin_lock_irqsave(&r->lock, flags); | |
472 | prefetch_range(r->pool, wordmask); | |
473 | input_rotate = r->input_rotate; | |
474 | add_ptr = r->add_ptr; | |
475 | ||
476 | while (nwords--) { | |
477 | w = rol32(next_w, input_rotate); | |
478 | if (nwords > 0) | |
479 | next_w = *in++; | |
480 | i = add_ptr = (add_ptr - 1) & wordmask; | |
481 | /* | |
482 | * Normally, we add 7 bits of rotation to the pool. | |
483 | * At the beginning of the pool, add an extra 7 bits | |
484 | * rotation, so that successive passes spread the | |
485 | * input bits across the pool evenly. | |
486 | */ | |
487 | new_rotate = input_rotate + 14; | |
488 | if (i) | |
489 | new_rotate = input_rotate + 7; | |
490 | input_rotate = new_rotate & 31; | |
491 | ||
492 | /* XOR in the various taps */ | |
493 | w ^= r->pool[(i + tap1) & wordmask]; | |
494 | w ^= r->pool[(i + tap2) & wordmask]; | |
495 | w ^= r->pool[(i + tap3) & wordmask]; | |
496 | w ^= r->pool[(i + tap4) & wordmask]; | |
497 | w ^= r->pool[(i + tap5) & wordmask]; | |
498 | w ^= r->pool[i]; | |
499 | r->pool[i] = (w >> 3) ^ twist_table[w & 7]; | |
500 | } | |
501 | ||
502 | r->input_rotate = input_rotate; | |
503 | r->add_ptr = add_ptr; | |
504 | ||
505 | if (out) { | |
506 | for (i = 0; i < 16; i++) { | |
507 | out[i] = r->pool[add_ptr]; | |
508 | add_ptr = (add_ptr - 1) & wordmask; | |
509 | } | |
510 | } | |
511 | ||
512 | spin_unlock_irqrestore(&r->lock, flags); | |
513 | } | |
514 | ||
515 | static inline void add_entropy_words(struct entropy_store *r, const __u32 *in, | |
516 | int nwords) | |
517 | { | |
518 | __add_entropy_words(r, in, nwords, NULL); | |
519 | } | |
520 | ||
521 | /* | |
522 | * Credit (or debit) the entropy store with n bits of entropy | |
523 | */ | |
524 | static void credit_entropy_store(struct entropy_store *r, int nbits) | |
525 | { | |
526 | unsigned long flags; | |
527 | ||
528 | spin_lock_irqsave(&r->lock, flags); | |
529 | ||
530 | if (r->entropy_count + nbits < 0) { | |
531 | DEBUG_ENT("negative entropy/overflow (%d+%d)\n", | |
532 | r->entropy_count, nbits); | |
533 | r->entropy_count = 0; | |
534 | } else if (r->entropy_count + nbits > r->poolinfo->POOLBITS) { | |
535 | r->entropy_count = r->poolinfo->POOLBITS; | |
536 | } else { | |
537 | r->entropy_count += nbits; | |
538 | if (nbits) | |
539 | DEBUG_ENT("added %d entropy credits to %s\n", | |
540 | nbits, r->name); | |
541 | } | |
542 | ||
543 | spin_unlock_irqrestore(&r->lock, flags); | |
544 | } | |
545 | ||
546 | /********************************************************************* | |
547 | * | |
548 | * Entropy input management | |
549 | * | |
550 | *********************************************************************/ | |
551 | ||
552 | /* There is one of these per entropy source */ | |
553 | struct timer_rand_state { | |
554 | cycles_t last_time; | |
555 | long last_delta,last_delta2; | |
556 | unsigned dont_count_entropy:1; | |
557 | }; | |
558 | ||
559 | static struct timer_rand_state input_timer_state; | |
560 | static struct timer_rand_state *irq_timer_state[NR_IRQS]; | |
561 | ||
562 | /* | |
563 | * This function adds entropy to the entropy "pool" by using timing | |
564 | * delays. It uses the timer_rand_state structure to make an estimate | |
565 | * of how many bits of entropy this call has added to the pool. | |
566 | * | |
567 | * The number "num" is also added to the pool - it should somehow describe | |
568 | * the type of event which just happened. This is currently 0-255 for | |
569 | * keyboard scan codes, and 256 upwards for interrupts. | |
570 | * | |
571 | */ | |
572 | static void add_timer_randomness(struct timer_rand_state *state, unsigned num) | |
573 | { | |
574 | struct { | |
575 | cycles_t cycles; | |
576 | long jiffies; | |
577 | unsigned num; | |
578 | } sample; | |
579 | long delta, delta2, delta3; | |
580 | ||
581 | preempt_disable(); | |
582 | /* if over the trickle threshold, use only 1 in 4096 samples */ | |
583 | if (input_pool.entropy_count > trickle_thresh && | |
584 | (__get_cpu_var(trickle_count)++ & 0xfff)) | |
585 | goto out; | |
586 | ||
587 | sample.jiffies = jiffies; | |
588 | sample.cycles = get_cycles(); | |
589 | sample.num = num; | |
590 | add_entropy_words(&input_pool, (u32 *)&sample, sizeof(sample)/4); | |
591 | ||
592 | /* | |
593 | * Calculate number of bits of randomness we probably added. | |
594 | * We take into account the first, second and third-order deltas | |
595 | * in order to make our estimate. | |
596 | */ | |
597 | ||
598 | if (!state->dont_count_entropy) { | |
599 | delta = sample.jiffies - state->last_time; | |
600 | state->last_time = sample.jiffies; | |
601 | ||
602 | delta2 = delta - state->last_delta; | |
603 | state->last_delta = delta; | |
604 | ||
605 | delta3 = delta2 - state->last_delta2; | |
606 | state->last_delta2 = delta2; | |
607 | ||
608 | if (delta < 0) | |
609 | delta = -delta; | |
610 | if (delta2 < 0) | |
611 | delta2 = -delta2; | |
612 | if (delta3 < 0) | |
613 | delta3 = -delta3; | |
614 | if (delta > delta2) | |
615 | delta = delta2; | |
616 | if (delta > delta3) | |
617 | delta = delta3; | |
618 | ||
619 | /* | |
620 | * delta is now minimum absolute delta. | |
621 | * Round down by 1 bit on general principles, | |
622 | * and limit entropy entimate to 12 bits. | |
623 | */ | |
624 | credit_entropy_store(&input_pool, | |
625 | min_t(int, fls(delta>>1), 11)); | |
626 | } | |
627 | ||
628 | if(input_pool.entropy_count >= random_read_wakeup_thresh) | |
629 | wake_up_interruptible(&random_read_wait); | |
630 | ||
631 | out: | |
632 | preempt_enable(); | |
633 | } | |
634 | ||
635 | extern void add_input_randomness(unsigned int type, unsigned int code, | |
636 | unsigned int value) | |
637 | { | |
638 | static unsigned char last_value; | |
639 | ||
640 | /* ignore autorepeat and the like */ | |
641 | if (value == last_value) | |
642 | return; | |
643 | ||
644 | DEBUG_ENT("input event\n"); | |
645 | last_value = value; | |
646 | add_timer_randomness(&input_timer_state, | |
647 | (type << 4) ^ code ^ (code >> 4) ^ value); | |
648 | } | |
649 | ||
650 | void add_interrupt_randomness(int irq) | |
651 | { | |
652 | if (irq >= NR_IRQS || irq_timer_state[irq] == 0) | |
653 | return; | |
654 | ||
655 | DEBUG_ENT("irq event %d\n", irq); | |
656 | add_timer_randomness(irq_timer_state[irq], 0x100 + irq); | |
657 | } | |
658 | ||
659 | void add_disk_randomness(struct gendisk *disk) | |
660 | { | |
661 | if (!disk || !disk->random) | |
662 | return; | |
663 | /* first major is 1, so we get >= 0x200 here */ | |
664 | DEBUG_ENT("disk event %d:%d\n", disk->major, disk->first_minor); | |
665 | ||
666 | add_timer_randomness(disk->random, | |
667 | 0x100 + MKDEV(disk->major, disk->first_minor)); | |
668 | } | |
669 | ||
670 | EXPORT_SYMBOL(add_disk_randomness); | |
671 | ||
672 | #define EXTRACT_SIZE 10 | |
673 | ||
674 | /********************************************************************* | |
675 | * | |
676 | * Entropy extraction routines | |
677 | * | |
678 | *********************************************************************/ | |
679 | ||
680 | static ssize_t extract_entropy(struct entropy_store *r, void * buf, | |
681 | size_t nbytes, int min, int rsvd); | |
682 | ||
683 | /* | |
684 | * This utility inline function is responsible for transfering entropy | |
685 | * from the primary pool to the secondary extraction pool. We make | |
686 | * sure we pull enough for a 'catastrophic reseed'. | |
687 | */ | |
688 | static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes) | |
689 | { | |
690 | __u32 tmp[OUTPUT_POOL_WORDS]; | |
691 | ||
692 | if (r->pull && r->entropy_count < nbytes * 8 && | |
693 | r->entropy_count < r->poolinfo->POOLBITS) { | |
694 | int bytes = max_t(int, random_read_wakeup_thresh / 8, | |
695 | min_t(int, nbytes, sizeof(tmp))); | |
696 | int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4; | |
697 | ||
698 | DEBUG_ENT("going to reseed %s with %d bits " | |
699 | "(%d of %d requested)\n", | |
700 | r->name, bytes * 8, nbytes * 8, r->entropy_count); | |
701 | ||
702 | bytes=extract_entropy(r->pull, tmp, bytes, | |
703 | random_read_wakeup_thresh / 8, rsvd); | |
704 | add_entropy_words(r, tmp, (bytes + 3) / 4); | |
705 | credit_entropy_store(r, bytes*8); | |
706 | } | |
707 | } | |
708 | ||
709 | /* | |
710 | * These functions extracts randomness from the "entropy pool", and | |
711 | * returns it in a buffer. | |
712 | * | |
713 | * The min parameter specifies the minimum amount we can pull before | |
714 | * failing to avoid races that defeat catastrophic reseeding while the | |
715 | * reserved parameter indicates how much entropy we must leave in the | |
716 | * pool after each pull to avoid starving other readers. | |
717 | * | |
718 | * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words. | |
719 | */ | |
720 | ||
721 | static size_t account(struct entropy_store *r, size_t nbytes, int min, | |
722 | int reserved) | |
723 | { | |
724 | unsigned long flags; | |
725 | ||
726 | BUG_ON(r->entropy_count > r->poolinfo->POOLBITS); | |
727 | ||
728 | /* Hold lock while accounting */ | |
729 | spin_lock_irqsave(&r->lock, flags); | |
730 | ||
731 | DEBUG_ENT("trying to extract %d bits from %s\n", | |
732 | nbytes * 8, r->name); | |
733 | ||
734 | /* Can we pull enough? */ | |
735 | if (r->entropy_count / 8 < min + reserved) { | |
736 | nbytes = 0; | |
737 | } else { | |
738 | /* If limited, never pull more than available */ | |
739 | if (r->limit && nbytes + reserved >= r->entropy_count / 8) | |
740 | nbytes = r->entropy_count/8 - reserved; | |
741 | ||
742 | if(r->entropy_count / 8 >= nbytes + reserved) | |
743 | r->entropy_count -= nbytes*8; | |
744 | else | |
745 | r->entropy_count = reserved; | |
746 | ||
747 | if (r->entropy_count < random_write_wakeup_thresh) | |
748 | wake_up_interruptible(&random_write_wait); | |
749 | } | |
750 | ||
751 | DEBUG_ENT("debiting %d entropy credits from %s%s\n", | |
752 | nbytes * 8, r->name, r->limit ? "" : " (unlimited)"); | |
753 | ||
754 | spin_unlock_irqrestore(&r->lock, flags); | |
755 | ||
756 | return nbytes; | |
757 | } | |
758 | ||
759 | static void extract_buf(struct entropy_store *r, __u8 *out) | |
760 | { | |
761 | int i, x; | |
762 | __u32 data[16], buf[5 + SHA_WORKSPACE_WORDS]; | |
763 | ||
764 | sha_init(buf); | |
765 | /* | |
766 | * As we hash the pool, we mix intermediate values of | |
767 | * the hash back into the pool. This eliminates | |
768 | * backtracking attacks (where the attacker knows | |
769 | * the state of the pool plus the current outputs, and | |
770 | * attempts to find previous ouputs), unless the hash | |
771 | * function can be inverted. | |
772 | */ | |
773 | for (i = 0, x = 0; i < r->poolinfo->poolwords; i += 16, x+=2) { | |
774 | sha_transform(buf, (__u8 *)r->pool+i, buf + 5); | |
775 | add_entropy_words(r, &buf[x % 5], 1); | |
776 | } | |
777 | ||
778 | /* | |
779 | * To avoid duplicates, we atomically extract a | |
780 | * portion of the pool while mixing, and hash one | |
781 | * final time. | |
782 | */ | |
783 | __add_entropy_words(r, &buf[x % 5], 1, data); | |
784 | sha_transform(buf, (__u8 *)data, buf + 5); | |
785 | ||
786 | /* | |
787 | * In case the hash function has some recognizable | |
788 | * output pattern, we fold it in half. | |
789 | */ | |
790 | ||
791 | buf[0] ^= buf[3]; | |
792 | buf[1] ^= buf[4]; | |
793 | buf[0] ^= rol32(buf[3], 16); | |
794 | memcpy(out, buf, EXTRACT_SIZE); | |
795 | memset(buf, 0, sizeof(buf)); | |
796 | } | |
797 | ||
798 | static ssize_t extract_entropy(struct entropy_store *r, void * buf, | |
799 | size_t nbytes, int min, int reserved) | |
800 | { | |
801 | ssize_t ret = 0, i; | |
802 | __u8 tmp[EXTRACT_SIZE]; | |
803 | ||
804 | xfer_secondary_pool(r, nbytes); | |
805 | nbytes = account(r, nbytes, min, reserved); | |
806 | ||
807 | while (nbytes) { | |
808 | extract_buf(r, tmp); | |
809 | i = min_t(int, nbytes, EXTRACT_SIZE); | |
810 | memcpy(buf, tmp, i); | |
811 | nbytes -= i; | |
812 | buf += i; | |
813 | ret += i; | |
814 | } | |
815 | ||
816 | /* Wipe data just returned from memory */ | |
817 | memset(tmp, 0, sizeof(tmp)); | |
818 | ||
819 | return ret; | |
820 | } | |
821 | ||
822 | static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, | |
823 | size_t nbytes) | |
824 | { | |
825 | ssize_t ret = 0, i; | |
826 | __u8 tmp[EXTRACT_SIZE]; | |
827 | ||
828 | xfer_secondary_pool(r, nbytes); | |
829 | nbytes = account(r, nbytes, 0, 0); | |
830 | ||
831 | while (nbytes) { | |
832 | if (need_resched()) { | |
833 | if (signal_pending(current)) { | |
834 | if (ret == 0) | |
835 | ret = -ERESTARTSYS; | |
836 | break; | |
837 | } | |
838 | schedule(); | |
839 | } | |
840 | ||
841 | extract_buf(r, tmp); | |
842 | i = min_t(int, nbytes, EXTRACT_SIZE); | |
843 | if (copy_to_user(buf, tmp, i)) { | |
844 | ret = -EFAULT; | |
845 | break; | |
846 | } | |
847 | ||
848 | nbytes -= i; | |
849 | buf += i; | |
850 | ret += i; | |
851 | } | |
852 | ||
853 | /* Wipe data just returned from memory */ | |
854 | memset(tmp, 0, sizeof(tmp)); | |
855 | ||
856 | return ret; | |
857 | } | |
858 | ||
859 | /* | |
860 | * This function is the exported kernel interface. It returns some | |
861 | * number of good random numbers, suitable for seeding TCP sequence | |
862 | * numbers, etc. | |
863 | */ | |
864 | void get_random_bytes(void *buf, int nbytes) | |
865 | { | |
866 | extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0); | |
867 | } | |
868 | ||
869 | EXPORT_SYMBOL(get_random_bytes); | |
870 | ||
871 | /* | |
872 | * init_std_data - initialize pool with system data | |
873 | * | |
874 | * @r: pool to initialize | |
875 | * | |
876 | * This function clears the pool's entropy count and mixes some system | |
877 | * data into the pool to prepare it for use. The pool is not cleared | |
878 | * as that can only decrease the entropy in the pool. | |
879 | */ | |
880 | static void init_std_data(struct entropy_store *r) | |
881 | { | |
882 | struct timeval tv; | |
883 | unsigned long flags; | |
884 | ||
885 | spin_lock_irqsave(&r->lock, flags); | |
886 | r->entropy_count = 0; | |
887 | spin_unlock_irqrestore(&r->lock, flags); | |
888 | ||
889 | do_gettimeofday(&tv); | |
890 | add_entropy_words(r, (__u32 *)&tv, sizeof(tv)/4); | |
891 | add_entropy_words(r, (__u32 *)&system_utsname, | |
892 | sizeof(system_utsname)/4); | |
893 | } | |
894 | ||
895 | static int __init rand_initialize(void) | |
896 | { | |
897 | init_std_data(&input_pool); | |
898 | init_std_data(&blocking_pool); | |
899 | init_std_data(&nonblocking_pool); | |
900 | return 0; | |
901 | } | |
902 | module_init(rand_initialize); | |
903 | ||
904 | void rand_initialize_irq(int irq) | |
905 | { | |
906 | struct timer_rand_state *state; | |
907 | ||
908 | if (irq >= NR_IRQS || irq_timer_state[irq]) | |
909 | return; | |
910 | ||
911 | /* | |
912 | * If kmalloc returns null, we just won't use that entropy | |
913 | * source. | |
914 | */ | |
915 | state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL); | |
916 | if (state) { | |
917 | memset(state, 0, sizeof(struct timer_rand_state)); | |
918 | irq_timer_state[irq] = state; | |
919 | } | |
920 | } | |
921 | ||
922 | void rand_initialize_disk(struct gendisk *disk) | |
923 | { | |
924 | struct timer_rand_state *state; | |
925 | ||
926 | /* | |
927 | * If kmalloc returns null, we just won't use that entropy | |
928 | * source. | |
929 | */ | |
930 | state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL); | |
931 | if (state) { | |
932 | memset(state, 0, sizeof(struct timer_rand_state)); | |
933 | disk->random = state; | |
934 | } | |
935 | } | |
936 | ||
937 | static ssize_t | |
938 | random_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos) | |
939 | { | |
940 | ssize_t n, retval = 0, count = 0; | |
941 | ||
942 | if (nbytes == 0) | |
943 | return 0; | |
944 | ||
945 | while (nbytes > 0) { | |
946 | n = nbytes; | |
947 | if (n > SEC_XFER_SIZE) | |
948 | n = SEC_XFER_SIZE; | |
949 | ||
950 | DEBUG_ENT("reading %d bits\n", n*8); | |
951 | ||
952 | n = extract_entropy_user(&blocking_pool, buf, n); | |
953 | ||
954 | DEBUG_ENT("read got %d bits (%d still needed)\n", | |
955 | n*8, (nbytes-n)*8); | |
956 | ||
957 | if (n == 0) { | |
958 | if (file->f_flags & O_NONBLOCK) { | |
959 | retval = -EAGAIN; | |
960 | break; | |
961 | } | |
962 | ||
963 | DEBUG_ENT("sleeping?\n"); | |
964 | ||
965 | wait_event_interruptible(random_read_wait, | |
966 | input_pool.entropy_count >= | |
967 | random_read_wakeup_thresh); | |
968 | ||
969 | DEBUG_ENT("awake\n"); | |
970 | ||
971 | if (signal_pending(current)) { | |
972 | retval = -ERESTARTSYS; | |
973 | break; | |
974 | } | |
975 | ||
976 | continue; | |
977 | } | |
978 | ||
979 | if (n < 0) { | |
980 | retval = n; | |
981 | break; | |
982 | } | |
983 | count += n; | |
984 | buf += n; | |
985 | nbytes -= n; | |
986 | break; /* This break makes the device work */ | |
987 | /* like a named pipe */ | |
988 | } | |
989 | ||
990 | /* | |
991 | * If we gave the user some bytes, update the access time. | |
992 | */ | |
993 | if (count) | |
994 | file_accessed(file); | |
995 | ||
996 | return (count ? count : retval); | |
997 | } | |
998 | ||
999 | static ssize_t | |
1000 | urandom_read(struct file * file, char __user * buf, | |
1001 | size_t nbytes, loff_t *ppos) | |
1002 | { | |
1003 | return extract_entropy_user(&nonblocking_pool, buf, nbytes); | |
1004 | } | |
1005 | ||
1006 | static unsigned int | |
1007 | random_poll(struct file *file, poll_table * wait) | |
1008 | { | |
1009 | unsigned int mask; | |
1010 | ||
1011 | poll_wait(file, &random_read_wait, wait); | |
1012 | poll_wait(file, &random_write_wait, wait); | |
1013 | mask = 0; | |
1014 | if (input_pool.entropy_count >= random_read_wakeup_thresh) | |
1015 | mask |= POLLIN | POLLRDNORM; | |
1016 | if (input_pool.entropy_count < random_write_wakeup_thresh) | |
1017 | mask |= POLLOUT | POLLWRNORM; | |
1018 | return mask; | |
1019 | } | |
1020 | ||
1021 | static ssize_t | |
1022 | random_write(struct file * file, const char __user * buffer, | |
1023 | size_t count, loff_t *ppos) | |
1024 | { | |
1025 | int ret = 0; | |
1026 | size_t bytes; | |
1027 | __u32 buf[16]; | |
1028 | const char __user *p = buffer; | |
1029 | size_t c = count; | |
1030 | ||
1031 | while (c > 0) { | |
1032 | bytes = min(c, sizeof(buf)); | |
1033 | ||
1034 | bytes -= copy_from_user(&buf, p, bytes); | |
1035 | if (!bytes) { | |
1036 | ret = -EFAULT; | |
1037 | break; | |
1038 | } | |
1039 | c -= bytes; | |
1040 | p += bytes; | |
1041 | ||
1042 | add_entropy_words(&input_pool, buf, (bytes + 3) / 4); | |
1043 | } | |
1044 | if (p == buffer) { | |
1045 | return (ssize_t)ret; | |
1046 | } else { | |
1047 | struct inode *inode = file->f_dentry->d_inode; | |
1048 | inode->i_mtime = current_fs_time(inode->i_sb); | |
1049 | mark_inode_dirty(inode); | |
1050 | return (ssize_t)(p - buffer); | |
1051 | } | |
1052 | } | |
1053 | ||
1054 | static int | |
1055 | random_ioctl(struct inode * inode, struct file * file, | |
1056 | unsigned int cmd, unsigned long arg) | |
1057 | { | |
1058 | int size, ent_count; | |
1059 | int __user *p = (int __user *)arg; | |
1060 | int retval; | |
1061 | ||
1062 | switch (cmd) { | |
1063 | case RNDGETENTCNT: | |
1064 | ent_count = input_pool.entropy_count; | |
1065 | if (put_user(ent_count, p)) | |
1066 | return -EFAULT; | |
1067 | return 0; | |
1068 | case RNDADDTOENTCNT: | |
1069 | if (!capable(CAP_SYS_ADMIN)) | |
1070 | return -EPERM; | |
1071 | if (get_user(ent_count, p)) | |
1072 | return -EFAULT; | |
1073 | credit_entropy_store(&input_pool, ent_count); | |
1074 | /* | |
1075 | * Wake up waiting processes if we have enough | |
1076 | * entropy. | |
1077 | */ | |
1078 | if (input_pool.entropy_count >= random_read_wakeup_thresh) | |
1079 | wake_up_interruptible(&random_read_wait); | |
1080 | return 0; | |
1081 | case RNDADDENTROPY: | |
1082 | if (!capable(CAP_SYS_ADMIN)) | |
1083 | return -EPERM; | |
1084 | if (get_user(ent_count, p++)) | |
1085 | return -EFAULT; | |
1086 | if (ent_count < 0) | |
1087 | return -EINVAL; | |
1088 | if (get_user(size, p++)) | |
1089 | return -EFAULT; | |
1090 | retval = random_write(file, (const char __user *) p, | |
1091 | size, &file->f_pos); | |
1092 | if (retval < 0) | |
1093 | return retval; | |
1094 | credit_entropy_store(&input_pool, ent_count); | |
1095 | /* | |
1096 | * Wake up waiting processes if we have enough | |
1097 | * entropy. | |
1098 | */ | |
1099 | if (input_pool.entropy_count >= random_read_wakeup_thresh) | |
1100 | wake_up_interruptible(&random_read_wait); | |
1101 | return 0; | |
1102 | case RNDZAPENTCNT: | |
1103 | case RNDCLEARPOOL: | |
1104 | /* Clear the entropy pool counters. */ | |
1105 | if (!capable(CAP_SYS_ADMIN)) | |
1106 | return -EPERM; | |
1107 | init_std_data(&input_pool); | |
1108 | init_std_data(&blocking_pool); | |
1109 | init_std_data(&nonblocking_pool); | |
1110 | return 0; | |
1111 | default: | |
1112 | return -EINVAL; | |
1113 | } | |
1114 | } | |
1115 | ||
1116 | struct file_operations random_fops = { | |
1117 | .read = random_read, | |
1118 | .write = random_write, | |
1119 | .poll = random_poll, | |
1120 | .ioctl = random_ioctl, | |
1121 | }; | |
1122 | ||
1123 | struct file_operations urandom_fops = { | |
1124 | .read = urandom_read, | |
1125 | .write = random_write, | |
1126 | .ioctl = random_ioctl, | |
1127 | }; | |
1128 | ||
1129 | /*************************************************************** | |
1130 | * Random UUID interface | |
1131 | * | |
1132 | * Used here for a Boot ID, but can be useful for other kernel | |
1133 | * drivers. | |
1134 | ***************************************************************/ | |
1135 | ||
1136 | /* | |
1137 | * Generate random UUID | |
1138 | */ | |
1139 | void generate_random_uuid(unsigned char uuid_out[16]) | |
1140 | { | |
1141 | get_random_bytes(uuid_out, 16); | |
1142 | /* Set UUID version to 4 --- truely random generation */ | |
1143 | uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40; | |
1144 | /* Set the UUID variant to DCE */ | |
1145 | uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80; | |
1146 | } | |
1147 | ||
1148 | EXPORT_SYMBOL(generate_random_uuid); | |
1149 | ||
1150 | /******************************************************************** | |
1151 | * | |
1152 | * Sysctl interface | |
1153 | * | |
1154 | ********************************************************************/ | |
1155 | ||
1156 | #ifdef CONFIG_SYSCTL | |
1157 | ||
1158 | #include <linux/sysctl.h> | |
1159 | ||
1160 | static int min_read_thresh = 8, min_write_thresh; | |
1161 | static int max_read_thresh = INPUT_POOL_WORDS * 32; | |
1162 | static int max_write_thresh = INPUT_POOL_WORDS * 32; | |
1163 | static char sysctl_bootid[16]; | |
1164 | ||
1165 | /* | |
1166 | * These functions is used to return both the bootid UUID, and random | |
1167 | * UUID. The difference is in whether table->data is NULL; if it is, | |
1168 | * then a new UUID is generated and returned to the user. | |
1169 | * | |
1170 | * If the user accesses this via the proc interface, it will be returned | |
1171 | * as an ASCII string in the standard UUID format. If accesses via the | |
1172 | * sysctl system call, it is returned as 16 bytes of binary data. | |
1173 | */ | |
1174 | static int proc_do_uuid(ctl_table *table, int write, struct file *filp, | |
1175 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
1176 | { | |
1177 | ctl_table fake_table; | |
1178 | unsigned char buf[64], tmp_uuid[16], *uuid; | |
1179 | ||
1180 | uuid = table->data; | |
1181 | if (!uuid) { | |
1182 | uuid = tmp_uuid; | |
1183 | uuid[8] = 0; | |
1184 | } | |
1185 | if (uuid[8] == 0) | |
1186 | generate_random_uuid(uuid); | |
1187 | ||
1188 | sprintf(buf, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-" | |
1189 | "%02x%02x%02x%02x%02x%02x", | |
1190 | uuid[0], uuid[1], uuid[2], uuid[3], | |
1191 | uuid[4], uuid[5], uuid[6], uuid[7], | |
1192 | uuid[8], uuid[9], uuid[10], uuid[11], | |
1193 | uuid[12], uuid[13], uuid[14], uuid[15]); | |
1194 | fake_table.data = buf; | |
1195 | fake_table.maxlen = sizeof(buf); | |
1196 | ||
1197 | return proc_dostring(&fake_table, write, filp, buffer, lenp, ppos); | |
1198 | } | |
1199 | ||
1200 | static int uuid_strategy(ctl_table *table, int __user *name, int nlen, | |
1201 | void __user *oldval, size_t __user *oldlenp, | |
1202 | void __user *newval, size_t newlen, void **context) | |
1203 | { | |
1204 | unsigned char tmp_uuid[16], *uuid; | |
1205 | unsigned int len; | |
1206 | ||
1207 | if (!oldval || !oldlenp) | |
1208 | return 1; | |
1209 | ||
1210 | uuid = table->data; | |
1211 | if (!uuid) { | |
1212 | uuid = tmp_uuid; | |
1213 | uuid[8] = 0; | |
1214 | } | |
1215 | if (uuid[8] == 0) | |
1216 | generate_random_uuid(uuid); | |
1217 | ||
1218 | if (get_user(len, oldlenp)) | |
1219 | return -EFAULT; | |
1220 | if (len) { | |
1221 | if (len > 16) | |
1222 | len = 16; | |
1223 | if (copy_to_user(oldval, uuid, len) || | |
1224 | put_user(len, oldlenp)) | |
1225 | return -EFAULT; | |
1226 | } | |
1227 | return 1; | |
1228 | } | |
1229 | ||
1230 | static int sysctl_poolsize = INPUT_POOL_WORDS * 32; | |
1231 | ctl_table random_table[] = { | |
1232 | { | |
1233 | .ctl_name = RANDOM_POOLSIZE, | |
1234 | .procname = "poolsize", | |
1235 | .data = &sysctl_poolsize, | |
1236 | .maxlen = sizeof(int), | |
1237 | .mode = 0444, | |
1238 | .proc_handler = &proc_dointvec, | |
1239 | }, | |
1240 | { | |
1241 | .ctl_name = RANDOM_ENTROPY_COUNT, | |
1242 | .procname = "entropy_avail", | |
1243 | .maxlen = sizeof(int), | |
1244 | .mode = 0444, | |
1245 | .proc_handler = &proc_dointvec, | |
1246 | .data = &input_pool.entropy_count, | |
1247 | }, | |
1248 | { | |
1249 | .ctl_name = RANDOM_READ_THRESH, | |
1250 | .procname = "read_wakeup_threshold", | |
1251 | .data = &random_read_wakeup_thresh, | |
1252 | .maxlen = sizeof(int), | |
1253 | .mode = 0644, | |
1254 | .proc_handler = &proc_dointvec_minmax, | |
1255 | .strategy = &sysctl_intvec, | |
1256 | .extra1 = &min_read_thresh, | |
1257 | .extra2 = &max_read_thresh, | |
1258 | }, | |
1259 | { | |
1260 | .ctl_name = RANDOM_WRITE_THRESH, | |
1261 | .procname = "write_wakeup_threshold", | |
1262 | .data = &random_write_wakeup_thresh, | |
1263 | .maxlen = sizeof(int), | |
1264 | .mode = 0644, | |
1265 | .proc_handler = &proc_dointvec_minmax, | |
1266 | .strategy = &sysctl_intvec, | |
1267 | .extra1 = &min_write_thresh, | |
1268 | .extra2 = &max_write_thresh, | |
1269 | }, | |
1270 | { | |
1271 | .ctl_name = RANDOM_BOOT_ID, | |
1272 | .procname = "boot_id", | |
1273 | .data = &sysctl_bootid, | |
1274 | .maxlen = 16, | |
1275 | .mode = 0444, | |
1276 | .proc_handler = &proc_do_uuid, | |
1277 | .strategy = &uuid_strategy, | |
1278 | }, | |
1279 | { | |
1280 | .ctl_name = RANDOM_UUID, | |
1281 | .procname = "uuid", | |
1282 | .maxlen = 16, | |
1283 | .mode = 0444, | |
1284 | .proc_handler = &proc_do_uuid, | |
1285 | .strategy = &uuid_strategy, | |
1286 | }, | |
1287 | { .ctl_name = 0 } | |
1288 | }; | |
1289 | #endif /* CONFIG_SYSCTL */ | |
1290 | ||
1291 | /******************************************************************** | |
1292 | * | |
1293 | * Random funtions for networking | |
1294 | * | |
1295 | ********************************************************************/ | |
1296 | ||
1297 | /* | |
1298 | * TCP initial sequence number picking. This uses the random number | |
1299 | * generator to pick an initial secret value. This value is hashed | |
1300 | * along with the TCP endpoint information to provide a unique | |
1301 | * starting point for each pair of TCP endpoints. This defeats | |
1302 | * attacks which rely on guessing the initial TCP sequence number. | |
1303 | * This algorithm was suggested by Steve Bellovin. | |
1304 | * | |
1305 | * Using a very strong hash was taking an appreciable amount of the total | |
1306 | * TCP connection establishment time, so this is a weaker hash, | |
1307 | * compensated for by changing the secret periodically. | |
1308 | */ | |
1309 | ||
1310 | /* F, G and H are basic MD4 functions: selection, majority, parity */ | |
1311 | #define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z)))) | |
1312 | #define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z))) | |
1313 | #define H(x, y, z) ((x) ^ (y) ^ (z)) | |
1314 | ||
1315 | /* | |
1316 | * The generic round function. The application is so specific that | |
1317 | * we don't bother protecting all the arguments with parens, as is generally | |
1318 | * good macro practice, in favor of extra legibility. | |
1319 | * Rotation is separate from addition to prevent recomputation | |
1320 | */ | |
1321 | #define ROUND(f, a, b, c, d, x, s) \ | |
1322 | (a += f(b, c, d) + x, a = (a << s) | (a >> (32 - s))) | |
1323 | #define K1 0 | |
1324 | #define K2 013240474631UL | |
1325 | #define K3 015666365641UL | |
1326 | ||
1327 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) | |
1328 | ||
1329 | static __u32 twothirdsMD4Transform (__u32 const buf[4], __u32 const in[12]) | |
1330 | { | |
1331 | __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3]; | |
1332 | ||
1333 | /* Round 1 */ | |
1334 | ROUND(F, a, b, c, d, in[ 0] + K1, 3); | |
1335 | ROUND(F, d, a, b, c, in[ 1] + K1, 7); | |
1336 | ROUND(F, c, d, a, b, in[ 2] + K1, 11); | |
1337 | ROUND(F, b, c, d, a, in[ 3] + K1, 19); | |
1338 | ROUND(F, a, b, c, d, in[ 4] + K1, 3); | |
1339 | ROUND(F, d, a, b, c, in[ 5] + K1, 7); | |
1340 | ROUND(F, c, d, a, b, in[ 6] + K1, 11); | |
1341 | ROUND(F, b, c, d, a, in[ 7] + K1, 19); | |
1342 | ROUND(F, a, b, c, d, in[ 8] + K1, 3); | |
1343 | ROUND(F, d, a, b, c, in[ 9] + K1, 7); | |
1344 | ROUND(F, c, d, a, b, in[10] + K1, 11); | |
1345 | ROUND(F, b, c, d, a, in[11] + K1, 19); | |
1346 | ||
1347 | /* Round 2 */ | |
1348 | ROUND(G, a, b, c, d, in[ 1] + K2, 3); | |
1349 | ROUND(G, d, a, b, c, in[ 3] + K2, 5); | |
1350 | ROUND(G, c, d, a, b, in[ 5] + K2, 9); | |
1351 | ROUND(G, b, c, d, a, in[ 7] + K2, 13); | |
1352 | ROUND(G, a, b, c, d, in[ 9] + K2, 3); | |
1353 | ROUND(G, d, a, b, c, in[11] + K2, 5); | |
1354 | ROUND(G, c, d, a, b, in[ 0] + K2, 9); | |
1355 | ROUND(G, b, c, d, a, in[ 2] + K2, 13); | |
1356 | ROUND(G, a, b, c, d, in[ 4] + K2, 3); | |
1357 | ROUND(G, d, a, b, c, in[ 6] + K2, 5); | |
1358 | ROUND(G, c, d, a, b, in[ 8] + K2, 9); | |
1359 | ROUND(G, b, c, d, a, in[10] + K2, 13); | |
1360 | ||
1361 | /* Round 3 */ | |
1362 | ROUND(H, a, b, c, d, in[ 3] + K3, 3); | |
1363 | ROUND(H, d, a, b, c, in[ 7] + K3, 9); | |
1364 | ROUND(H, c, d, a, b, in[11] + K3, 11); | |
1365 | ROUND(H, b, c, d, a, in[ 2] + K3, 15); | |
1366 | ROUND(H, a, b, c, d, in[ 6] + K3, 3); | |
1367 | ROUND(H, d, a, b, c, in[10] + K3, 9); | |
1368 | ROUND(H, c, d, a, b, in[ 1] + K3, 11); | |
1369 | ROUND(H, b, c, d, a, in[ 5] + K3, 15); | |
1370 | ROUND(H, a, b, c, d, in[ 9] + K3, 3); | |
1371 | ROUND(H, d, a, b, c, in[ 0] + K3, 9); | |
1372 | ROUND(H, c, d, a, b, in[ 4] + K3, 11); | |
1373 | ROUND(H, b, c, d, a, in[ 8] + K3, 15); | |
1374 | ||
1375 | return buf[1] + b; /* "most hashed" word */ | |
1376 | /* Alternative: return sum of all words? */ | |
1377 | } | |
1378 | #endif | |
1379 | ||
1380 | #undef ROUND | |
1381 | #undef F | |
1382 | #undef G | |
1383 | #undef H | |
1384 | #undef K1 | |
1385 | #undef K2 | |
1386 | #undef K3 | |
1387 | ||
1388 | /* This should not be decreased so low that ISNs wrap too fast. */ | |
1389 | #define REKEY_INTERVAL (300 * HZ) | |
1390 | /* | |
1391 | * Bit layout of the tcp sequence numbers (before adding current time): | |
1392 | * bit 24-31: increased after every key exchange | |
1393 | * bit 0-23: hash(source,dest) | |
1394 | * | |
1395 | * The implementation is similar to the algorithm described | |
1396 | * in the Appendix of RFC 1185, except that | |
1397 | * - it uses a 1 MHz clock instead of a 250 kHz clock | |
1398 | * - it performs a rekey every 5 minutes, which is equivalent | |
1399 | * to a (source,dest) tulple dependent forward jump of the | |
1400 | * clock by 0..2^(HASH_BITS+1) | |
1401 | * | |
1402 | * Thus the average ISN wraparound time is 68 minutes instead of | |
1403 | * 4.55 hours. | |
1404 | * | |
1405 | * SMP cleanup and lock avoidance with poor man's RCU. | |
1406 | * Manfred Spraul <manfred@colorfullife.com> | |
1407 | * | |
1408 | */ | |
1409 | #define COUNT_BITS 8 | |
1410 | #define COUNT_MASK ((1 << COUNT_BITS) - 1) | |
1411 | #define HASH_BITS 24 | |
1412 | #define HASH_MASK ((1 << HASH_BITS) - 1) | |
1413 | ||
1414 | static struct keydata { | |
1415 | __u32 count; /* already shifted to the final position */ | |
1416 | __u32 secret[12]; | |
1417 | } ____cacheline_aligned ip_keydata[2]; | |
1418 | ||
1419 | static unsigned int ip_cnt; | |
1420 | ||
1421 | static void rekey_seq_generator(void *private_); | |
1422 | ||
1423 | static DECLARE_WORK(rekey_work, rekey_seq_generator, NULL); | |
1424 | ||
1425 | /* | |
1426 | * Lock avoidance: | |
1427 | * The ISN generation runs lockless - it's just a hash over random data. | |
1428 | * State changes happen every 5 minutes when the random key is replaced. | |
1429 | * Synchronization is performed by having two copies of the hash function | |
1430 | * state and rekey_seq_generator always updates the inactive copy. | |
1431 | * The copy is then activated by updating ip_cnt. | |
1432 | * The implementation breaks down if someone blocks the thread | |
1433 | * that processes SYN requests for more than 5 minutes. Should never | |
1434 | * happen, and even if that happens only a not perfectly compliant | |
1435 | * ISN is generated, nothing fatal. | |
1436 | */ | |
1437 | static void rekey_seq_generator(void *private_) | |
1438 | { | |
1439 | struct keydata *keyptr = &ip_keydata[1 ^ (ip_cnt & 1)]; | |
1440 | ||
1441 | get_random_bytes(keyptr->secret, sizeof(keyptr->secret)); | |
1442 | keyptr->count = (ip_cnt & COUNT_MASK) << HASH_BITS; | |
1443 | smp_wmb(); | |
1444 | ip_cnt++; | |
1445 | schedule_delayed_work(&rekey_work, REKEY_INTERVAL); | |
1446 | } | |
1447 | ||
1448 | static inline struct keydata *get_keyptr(void) | |
1449 | { | |
1450 | struct keydata *keyptr = &ip_keydata[ip_cnt & 1]; | |
1451 | ||
1452 | smp_rmb(); | |
1453 | ||
1454 | return keyptr; | |
1455 | } | |
1456 | ||
1457 | static __init int seqgen_init(void) | |
1458 | { | |
1459 | rekey_seq_generator(NULL); | |
1460 | return 0; | |
1461 | } | |
1462 | late_initcall(seqgen_init); | |
1463 | ||
1464 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) | |
1465 | __u32 secure_tcpv6_sequence_number(__u32 *saddr, __u32 *daddr, | |
1466 | __u16 sport, __u16 dport) | |
1467 | { | |
1468 | struct timeval tv; | |
1469 | __u32 seq; | |
1470 | __u32 hash[12]; | |
1471 | struct keydata *keyptr = get_keyptr(); | |
1472 | ||
1473 | /* The procedure is the same as for IPv4, but addresses are longer. | |
1474 | * Thus we must use twothirdsMD4Transform. | |
1475 | */ | |
1476 | ||
1477 | memcpy(hash, saddr, 16); | |
1478 | hash[4]=(sport << 16) + dport; | |
1479 | memcpy(&hash[5],keyptr->secret,sizeof(__u32) * 7); | |
1480 | ||
1481 | seq = twothirdsMD4Transform(daddr, hash) & HASH_MASK; | |
1482 | seq += keyptr->count; | |
1483 | ||
1484 | do_gettimeofday(&tv); | |
1485 | seq += tv.tv_usec + tv.tv_sec * 1000000; | |
1486 | ||
1487 | return seq; | |
1488 | } | |
1489 | EXPORT_SYMBOL(secure_tcpv6_sequence_number); | |
1490 | #endif | |
1491 | ||
1492 | /* The code below is shamelessly stolen from secure_tcp_sequence_number(). | |
1493 | * All blames to Andrey V. Savochkin <saw@msu.ru>. | |
1494 | */ | |
1495 | __u32 secure_ip_id(__u32 daddr) | |
1496 | { | |
1497 | struct keydata *keyptr; | |
1498 | __u32 hash[4]; | |
1499 | ||
1500 | keyptr = get_keyptr(); | |
1501 | ||
1502 | /* | |
1503 | * Pick a unique starting offset for each IP destination. | |
1504 | * The dest ip address is placed in the starting vector, | |
1505 | * which is then hashed with random data. | |
1506 | */ | |
1507 | hash[0] = daddr; | |
1508 | hash[1] = keyptr->secret[9]; | |
1509 | hash[2] = keyptr->secret[10]; | |
1510 | hash[3] = keyptr->secret[11]; | |
1511 | ||
1512 | return half_md4_transform(hash, keyptr->secret); | |
1513 | } | |
1514 | ||
1515 | #ifdef CONFIG_INET | |
1516 | ||
1517 | __u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr, | |
1518 | __u16 sport, __u16 dport) | |
1519 | { | |
1520 | struct timeval tv; | |
1521 | __u32 seq; | |
1522 | __u32 hash[4]; | |
1523 | struct keydata *keyptr = get_keyptr(); | |
1524 | ||
1525 | /* | |
1526 | * Pick a unique starting offset for each TCP connection endpoints | |
1527 | * (saddr, daddr, sport, dport). | |
1528 | * Note that the words are placed into the starting vector, which is | |
1529 | * then mixed with a partial MD4 over random data. | |
1530 | */ | |
1531 | hash[0]=saddr; | |
1532 | hash[1]=daddr; | |
1533 | hash[2]=(sport << 16) + dport; | |
1534 | hash[3]=keyptr->secret[11]; | |
1535 | ||
1536 | seq = half_md4_transform(hash, keyptr->secret) & HASH_MASK; | |
1537 | seq += keyptr->count; | |
1538 | /* | |
1539 | * As close as possible to RFC 793, which | |
1540 | * suggests using a 250 kHz clock. | |
1541 | * Further reading shows this assumes 2 Mb/s networks. | |
1542 | * For 10 Mb/s Ethernet, a 1 MHz clock is appropriate. | |
1543 | * That's funny, Linux has one built in! Use it! | |
1544 | * (Networks are faster now - should this be increased?) | |
1545 | */ | |
1546 | do_gettimeofday(&tv); | |
1547 | seq += tv.tv_usec + tv.tv_sec * 1000000; | |
1548 | #if 0 | |
1549 | printk("init_seq(%lx, %lx, %d, %d) = %d\n", | |
1550 | saddr, daddr, sport, dport, seq); | |
1551 | #endif | |
1552 | return seq; | |
1553 | } | |
1554 | ||
1555 | EXPORT_SYMBOL(secure_tcp_sequence_number); | |
1556 | ||
a7f5e7f1 ACM |
1557 | /* Generate secure starting point for ephemeral IPV4 transport port search */ |
1558 | u32 secure_ipv4_port_ephemeral(__u32 saddr, __u32 daddr, __u16 dport) | |
1da177e4 LT |
1559 | { |
1560 | struct keydata *keyptr = get_keyptr(); | |
1561 | u32 hash[4]; | |
1562 | ||
1563 | /* | |
1564 | * Pick a unique starting offset for each ephemeral port search | |
1565 | * (saddr, daddr, dport) and 48bits of random data. | |
1566 | */ | |
1567 | hash[0] = saddr; | |
1568 | hash[1] = daddr; | |
1569 | hash[2] = dport ^ keyptr->secret[10]; | |
1570 | hash[3] = keyptr->secret[11]; | |
1571 | ||
1572 | return half_md4_transform(hash, keyptr->secret); | |
1573 | } | |
1574 | ||
1575 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) | |
d8313f5c | 1576 | u32 secure_ipv6_port_ephemeral(const __u32 *saddr, const __u32 *daddr, __u16 dport) |
1da177e4 LT |
1577 | { |
1578 | struct keydata *keyptr = get_keyptr(); | |
1579 | u32 hash[12]; | |
1580 | ||
1581 | memcpy(hash, saddr, 16); | |
1582 | hash[4] = dport; | |
1583 | memcpy(&hash[5],keyptr->secret,sizeof(__u32) * 7); | |
1584 | ||
1585 | return twothirdsMD4Transform(daddr, hash); | |
1586 | } | |
d8313f5c | 1587 | EXPORT_SYMBOL(secure_ipv6_port_ephemeral); |
1da177e4 LT |
1588 | #endif |
1589 | ||
c4365c92 ACM |
1590 | #if defined(CONFIG_IP_DCCP) || defined(CONFIG_IP_DCCP_MODULE) |
1591 | /* Similar to secure_tcp_sequence_number but generate a 48 bit value | |
1592 | * bit's 32-47 increase every key exchange | |
1593 | * 0-31 hash(source, dest) | |
1594 | */ | |
1595 | u64 secure_dccp_sequence_number(__u32 saddr, __u32 daddr, | |
1596 | __u16 sport, __u16 dport) | |
1597 | { | |
1598 | struct timeval tv; | |
1599 | u64 seq; | |
1600 | __u32 hash[4]; | |
1601 | struct keydata *keyptr = get_keyptr(); | |
1602 | ||
1603 | hash[0] = saddr; | |
1604 | hash[1] = daddr; | |
1605 | hash[2] = (sport << 16) + dport; | |
1606 | hash[3] = keyptr->secret[11]; | |
1607 | ||
1608 | seq = half_md4_transform(hash, keyptr->secret); | |
1609 | seq |= ((u64)keyptr->count) << (32 - HASH_BITS); | |
1610 | ||
1611 | do_gettimeofday(&tv); | |
1612 | seq += tv.tv_usec + tv.tv_sec * 1000000; | |
1613 | seq &= (1ull << 48) - 1; | |
1614 | #if 0 | |
1615 | printk("dccp init_seq(%lx, %lx, %d, %d) = %d\n", | |
1616 | saddr, daddr, sport, dport, seq); | |
1617 | #endif | |
1618 | return seq; | |
1619 | } | |
1620 | ||
1621 | EXPORT_SYMBOL(secure_dccp_sequence_number); | |
1622 | #endif | |
1623 | ||
1da177e4 LT |
1624 | #endif /* CONFIG_INET */ |
1625 | ||
1626 | ||
1627 | /* | |
1628 | * Get a random word for internal kernel use only. Similar to urandom but | |
1629 | * with the goal of minimal entropy pool depletion. As a result, the random | |
1630 | * value is not cryptographically secure but for several uses the cost of | |
1631 | * depleting entropy is too high | |
1632 | */ | |
1633 | unsigned int get_random_int(void) | |
1634 | { | |
1635 | /* | |
1636 | * Use IP's RNG. It suits our purpose perfectly: it re-keys itself | |
1637 | * every second, from the entropy pool (and thus creates a limited | |
1638 | * drain on it), and uses halfMD4Transform within the second. We | |
1639 | * also mix it with jiffies and the PID: | |
1640 | */ | |
1641 | return secure_ip_id(current->pid + jiffies); | |
1642 | } | |
1643 | ||
1644 | /* | |
1645 | * randomize_range() returns a start address such that | |
1646 | * | |
1647 | * [...... <range> .....] | |
1648 | * start end | |
1649 | * | |
1650 | * a <range> with size "len" starting at the return value is inside in the | |
1651 | * area defined by [start, end], but is otherwise randomized. | |
1652 | */ | |
1653 | unsigned long | |
1654 | randomize_range(unsigned long start, unsigned long end, unsigned long len) | |
1655 | { | |
1656 | unsigned long range = end - len - start; | |
1657 | ||
1658 | if (end <= start + len) | |
1659 | return 0; | |
1660 | return PAGE_ALIGN(get_random_int() % range + start); | |
1661 | } |