Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/drivers/char/random.c
Parent Directory | Revision Log
Revision 630 -
(show annotations)
(download)
Wed Mar 4 11:03:09 2009 UTC (15 years, 3 months ago) by niro
File MIME type: text/plain
File size: 48536 byte(s)
Wed Mar 4 11:03:09 2009 UTC (15 years, 3 months ago) by niro
File MIME type: text/plain
File size: 48536 byte(s)
Tag kernel26-2.6.12-alx-r9
1 | /* |
2 | * random.c -- A strong random number generator |
3 | * |
4 | * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005 |
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 | |
274 | static int trickle_thresh = INPUT_POOL_WORDS * 28; |
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 | |
1557 | |
1558 | |
1559 | /* Generate secure starting point for ephemeral TCP port search */ |
1560 | u32 secure_tcp_port_ephemeral(__u32 saddr, __u32 daddr, __u16 dport) |
1561 | { |
1562 | struct keydata *keyptr = get_keyptr(); |
1563 | u32 hash[4]; |
1564 | |
1565 | /* |
1566 | * Pick a unique starting offset for each ephemeral port search |
1567 | * (saddr, daddr, dport) and 48bits of random data. |
1568 | */ |
1569 | hash[0] = saddr; |
1570 | hash[1] = daddr; |
1571 | hash[2] = dport ^ keyptr->secret[10]; |
1572 | hash[3] = keyptr->secret[11]; |
1573 | |
1574 | return half_md4_transform(hash, keyptr->secret); |
1575 | } |
1576 | |
1577 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) |
1578 | u32 secure_tcpv6_port_ephemeral(const __u32 *saddr, const __u32 *daddr, __u16 dport) |
1579 | { |
1580 | struct keydata *keyptr = get_keyptr(); |
1581 | u32 hash[12]; |
1582 | |
1583 | memcpy(hash, saddr, 16); |
1584 | hash[4] = dport; |
1585 | memcpy(&hash[5],keyptr->secret,sizeof(__u32) * 7); |
1586 | |
1587 | return twothirdsMD4Transform(daddr, hash); |
1588 | } |
1589 | EXPORT_SYMBOL(secure_tcpv6_port_ephemeral); |
1590 | #endif |
1591 | |
1592 | #endif /* CONFIG_INET */ |
1593 | |
1594 | |
1595 | /* |
1596 | * Get a random word for internal kernel use only. Similar to urandom but |
1597 | * with the goal of minimal entropy pool depletion. As a result, the random |
1598 | * value is not cryptographically secure but for several uses the cost of |
1599 | * depleting entropy is too high |
1600 | */ |
1601 | unsigned int get_random_int(void) |
1602 | { |
1603 | /* |
1604 | * Use IP's RNG. It suits our purpose perfectly: it re-keys itself |
1605 | * every second, from the entropy pool (and thus creates a limited |
1606 | * drain on it), and uses halfMD4Transform within the second. We |
1607 | * also mix it with jiffies and the PID: |
1608 | */ |
1609 | return secure_ip_id(current->pid + jiffies); |
1610 | } |
1611 | |
1612 | /* |
1613 | * randomize_range() returns a start address such that |
1614 | * |
1615 | * [...... <range> .....] |
1616 | * start end |
1617 | * |
1618 | * a <range> with size "len" starting at the return value is inside in the |
1619 | * area defined by [start, end], but is otherwise randomized. |
1620 | */ |
1621 | unsigned long |
1622 | randomize_range(unsigned long start, unsigned long end, unsigned long len) |
1623 | { |
1624 | unsigned long range = end - len - start; |
1625 | |
1626 | if (end <= start + len) |
1627 | return 0; |
1628 | return PAGE_ALIGN(get_random_int() % range + start); |
1629 | } |