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1 | /* |
2 | * Non-physical true random number generator based on timing jitter. | |
3 | * | |
4 | * Copyright Stephan Mueller <smueller@chronox.de>, 2014 | |
5 | * | |
6 | * Design | |
7 | * ====== | |
8 | * | |
9 | * See http://www.chronox.de/jent.html | |
10 | * | |
11 | * License | |
12 | * ======= | |
13 | * | |
14 | * Redistribution and use in source and binary forms, with or without | |
15 | * modification, are permitted provided that the following conditions | |
16 | * are met: | |
17 | * 1. Redistributions of source code must retain the above copyright | |
18 | * notice, and the entire permission notice in its entirety, | |
19 | * including the disclaimer of warranties. | |
20 | * 2. Redistributions in binary form must reproduce the above copyright | |
21 | * notice, this list of conditions and the following disclaimer in the | |
22 | * documentation and/or other materials provided with the distribution. | |
23 | * 3. The name of the author may not be used to endorse or promote | |
24 | * products derived from this software without specific prior | |
25 | * written permission. | |
26 | * | |
27 | * ALTERNATIVELY, this product may be distributed under the terms of | |
28 | * the GNU General Public License, in which case the provisions of the GPL2 are | |
29 | * required INSTEAD OF the above restrictions. (This clause is | |
30 | * necessary due to a potential bad interaction between the GPL and | |
31 | * the restrictions contained in a BSD-style copyright.) | |
32 | * | |
33 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED | |
34 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
35 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF | |
36 | * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE | |
37 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
38 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT | |
39 | * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR | |
40 | * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
41 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
42 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE | |
43 | * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH | |
44 | * DAMAGE. | |
45 | */ | |
46 | ||
47 | /* | |
48 | * This Jitterentropy RNG is based on the jitterentropy library | |
49 | * version 1.1.0 provided at http://www.chronox.de/jent.html | |
50 | */ | |
51 | ||
52 | #include <linux/module.h> | |
53 | #include <linux/slab.h> | |
54 | #include <linux/module.h> | |
55 | #include <linux/fips.h> | |
56 | #include <linux/time.h> | |
57 | #include <linux/crypto.h> | |
58 | #include <crypto/internal/rng.h> | |
59 | ||
60 | #ifdef __OPTIMIZE__ | |
61 | #error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy.c." | |
62 | #endif | |
63 | ||
64 | /* The entropy pool */ | |
65 | struct rand_data { | |
66 | /* all data values that are vital to maintain the security | |
67 | * of the RNG are marked as SENSITIVE. A user must not | |
68 | * access that information while the RNG executes its loops to | |
69 | * calculate the next random value. */ | |
70 | __u64 data; /* SENSITIVE Actual random number */ | |
71 | __u64 old_data; /* SENSITIVE Previous random number */ | |
72 | __u64 prev_time; /* SENSITIVE Previous time stamp */ | |
73 | #define DATA_SIZE_BITS ((sizeof(__u64)) * 8) | |
74 | __u64 last_delta; /* SENSITIVE stuck test */ | |
75 | __s64 last_delta2; /* SENSITIVE stuck test */ | |
76 | unsigned int stuck:1; /* Time measurement stuck */ | |
77 | unsigned int osr; /* Oversample rate */ | |
78 | unsigned int stir:1; /* Post-processing stirring */ | |
79 | unsigned int disable_unbias:1; /* Deactivate Von-Neuman unbias */ | |
80 | #define JENT_MEMORY_BLOCKS 64 | |
81 | #define JENT_MEMORY_BLOCKSIZE 32 | |
82 | #define JENT_MEMORY_ACCESSLOOPS 128 | |
83 | #define JENT_MEMORY_SIZE (JENT_MEMORY_BLOCKS*JENT_MEMORY_BLOCKSIZE) | |
84 | unsigned char *mem; /* Memory access location with size of | |
85 | * memblocks * memblocksize */ | |
86 | unsigned int memlocation; /* Pointer to byte in *mem */ | |
87 | unsigned int memblocks; /* Number of memory blocks in *mem */ | |
88 | unsigned int memblocksize; /* Size of one memory block in bytes */ | |
89 | unsigned int memaccessloops; /* Number of memory accesses per random | |
90 | * bit generation */ | |
91 | }; | |
92 | ||
93 | /* Flags that can be used to initialize the RNG */ | |
94 | #define JENT_DISABLE_STIR (1<<0) /* Disable stirring the entropy pool */ | |
95 | #define JENT_DISABLE_UNBIAS (1<<1) /* Disable the Von-Neuman Unbiaser */ | |
96 | #define JENT_DISABLE_MEMORY_ACCESS (1<<2) /* Disable memory access for more | |
97 | * entropy, saves MEMORY_SIZE RAM for | |
98 | * entropy collector */ | |
99 | ||
100 | #define DRIVER_NAME "jitterentropy" | |
101 | ||
102 | /* -- error codes for init function -- */ | |
103 | #define JENT_ENOTIME 1 /* Timer service not available */ | |
104 | #define JENT_ECOARSETIME 2 /* Timer too coarse for RNG */ | |
105 | #define JENT_ENOMONOTONIC 3 /* Timer is not monotonic increasing */ | |
106 | #define JENT_EMINVARIATION 4 /* Timer variations too small for RNG */ | |
107 | #define JENT_EVARVAR 5 /* Timer does not produce variations of | |
108 | * variations (2nd derivation of time is | |
109 | * zero). */ | |
110 | #define JENT_EMINVARVAR 6 /* Timer variations of variations is tooi | |
111 | * small. */ | |
112 | ||
113 | /*************************************************************************** | |
114 | * Helper functions | |
115 | ***************************************************************************/ | |
116 | ||
117 | static inline void jent_get_nstime(__u64 *out) | |
118 | { | |
119 | struct timespec ts; | |
120 | __u64 tmp = 0; | |
121 | ||
122 | tmp = random_get_entropy(); | |
123 | ||
124 | /* | |
125 | * If random_get_entropy does not return a value (which is possible on, | |
126 | * for example, MIPS), invoke __getnstimeofday | |
127 | * hoping that there are timers we can work with. | |
128 | * | |
129 | * The list of available timers can be obtained from | |
130 | * /sys/devices/system/clocksource/clocksource0/available_clocksource | |
131 | * and are registered with clocksource_register() | |
132 | */ | |
133 | if ((0 == tmp) && | |
134 | #ifndef MODULE | |
135 | (0 == timekeeping_valid_for_hres()) && | |
136 | #endif | |
137 | (0 == __getnstimeofday(&ts))) { | |
138 | tmp = ts.tv_sec; | |
139 | tmp = tmp << 32; | |
140 | tmp = tmp | ts.tv_nsec; | |
141 | } | |
142 | ||
143 | *out = tmp; | |
144 | } | |
145 | ||
146 | ||
147 | /** | |
148 | * Update of the loop count used for the next round of | |
149 | * an entropy collection. | |
150 | * | |
151 | * Input: | |
152 | * @ec entropy collector struct -- may be NULL | |
153 | * @bits is the number of low bits of the timer to consider | |
154 | * @min is the number of bits we shift the timer value to the right at | |
155 | * the end to make sure we have a guaranteed minimum value | |
156 | * | |
157 | * @return Newly calculated loop counter | |
158 | */ | |
159 | static __u64 jent_loop_shuffle(struct rand_data *ec, | |
160 | unsigned int bits, unsigned int min) | |
161 | { | |
162 | __u64 time = 0; | |
163 | __u64 shuffle = 0; | |
164 | unsigned int i = 0; | |
165 | unsigned int mask = (1<<bits) - 1; | |
166 | ||
167 | jent_get_nstime(&time); | |
168 | /* | |
169 | * mix the current state of the random number into the shuffle | |
170 | * calculation to balance that shuffle a bit more | |
171 | */ | |
172 | if (ec) | |
173 | time ^= ec->data; | |
174 | /* | |
175 | * we fold the time value as much as possible to ensure that as many | |
176 | * bits of the time stamp are included as possible | |
177 | */ | |
178 | for (i = 0; (DATA_SIZE_BITS / bits) > i; i++) { | |
179 | shuffle ^= time & mask; | |
180 | time = time >> bits; | |
181 | } | |
182 | ||
183 | /* | |
184 | * We add a lower boundary value to ensure we have a minimum | |
185 | * RNG loop count. | |
186 | */ | |
187 | return (shuffle + (1<<min)); | |
188 | } | |
189 | ||
190 | /*************************************************************************** | |
191 | * Noise sources | |
192 | ***************************************************************************/ | |
193 | ||
194 | /** | |
195 | * CPU Jitter noise source -- this is the noise source based on the CPU | |
196 | * execution time jitter | |
197 | * | |
198 | * This function folds the time into one bit units by iterating | |
199 | * through the DATA_SIZE_BITS bit time value as follows: assume our time value | |
200 | * is 0xabcd | |
201 | * 1st loop, 1st shift generates 0xd000 | |
202 | * 1st loop, 2nd shift generates 0x000d | |
203 | * 2nd loop, 1st shift generates 0xcd00 | |
204 | * 2nd loop, 2nd shift generates 0x000c | |
205 | * 3rd loop, 1st shift generates 0xbcd0 | |
206 | * 3rd loop, 2nd shift generates 0x000b | |
207 | * 4th loop, 1st shift generates 0xabcd | |
208 | * 4th loop, 2nd shift generates 0x000a | |
209 | * Now, the values at the end of the 2nd shifts are XORed together. | |
210 | * | |
211 | * The code is deliberately inefficient and shall stay that way. This function | |
212 | * is the root cause why the code shall be compiled without optimization. This | |
213 | * function not only acts as folding operation, but this function's execution | |
214 | * is used to measure the CPU execution time jitter. Any change to the loop in | |
215 | * this function implies that careful retesting must be done. | |
216 | * | |
217 | * Input: | |
218 | * @ec entropy collector struct -- may be NULL | |
219 | * @time time stamp to be folded | |
220 | * @loop_cnt if a value not equal to 0 is set, use the given value as number of | |
221 | * loops to perform the folding | |
222 | * | |
223 | * Output: | |
224 | * @folded result of folding operation | |
225 | * | |
226 | * @return Number of loops the folding operation is performed | |
227 | */ | |
228 | static __u64 jent_fold_time(struct rand_data *ec, __u64 time, | |
229 | __u64 *folded, __u64 loop_cnt) | |
230 | { | |
231 | unsigned int i; | |
232 | __u64 j = 0; | |
233 | __u64 new = 0; | |
234 | #define MAX_FOLD_LOOP_BIT 4 | |
235 | #define MIN_FOLD_LOOP_BIT 0 | |
236 | __u64 fold_loop_cnt = | |
237 | jent_loop_shuffle(ec, MAX_FOLD_LOOP_BIT, MIN_FOLD_LOOP_BIT); | |
238 | ||
239 | /* | |
240 | * testing purposes -- allow test app to set the counter, not | |
241 | * needed during runtime | |
242 | */ | |
243 | if (loop_cnt) | |
244 | fold_loop_cnt = loop_cnt; | |
245 | for (j = 0; j < fold_loop_cnt; j++) { | |
246 | new = 0; | |
247 | for (i = 1; (DATA_SIZE_BITS) >= i; i++) { | |
248 | __u64 tmp = time << (DATA_SIZE_BITS - i); | |
249 | ||
250 | tmp = tmp >> (DATA_SIZE_BITS - 1); | |
251 | new ^= tmp; | |
252 | } | |
253 | } | |
254 | *folded = new; | |
255 | return fold_loop_cnt; | |
256 | } | |
257 | ||
258 | /** | |
259 | * Memory Access noise source -- this is a noise source based on variations in | |
260 | * memory access times | |
261 | * | |
262 | * This function performs memory accesses which will add to the timing | |
263 | * variations due to an unknown amount of CPU wait states that need to be | |
264 | * added when accessing memory. The memory size should be larger than the L1 | |
265 | * caches as outlined in the documentation and the associated testing. | |
266 | * | |
267 | * The L1 cache has a very high bandwidth, albeit its access rate is usually | |
268 | * slower than accessing CPU registers. Therefore, L1 accesses only add minimal | |
269 | * variations as the CPU has hardly to wait. Starting with L2, significant | |
270 | * variations are added because L2 typically does not belong to the CPU any more | |
271 | * and therefore a wider range of CPU wait states is necessary for accesses. | |
272 | * L3 and real memory accesses have even a wider range of wait states. However, | |
273 | * to reliably access either L3 or memory, the ec->mem memory must be quite | |
274 | * large which is usually not desirable. | |
275 | * | |
276 | * Input: | |
277 | * @ec Reference to the entropy collector with the memory access data -- if | |
278 | * the reference to the memory block to be accessed is NULL, this noise | |
279 | * source is disabled | |
280 | * @loop_cnt if a value not equal to 0 is set, use the given value as number of | |
281 | * loops to perform the folding | |
282 | * | |
283 | * @return Number of memory access operations | |
284 | */ | |
285 | static unsigned int jent_memaccess(struct rand_data *ec, __u64 loop_cnt) | |
286 | { | |
287 | unsigned char *tmpval = NULL; | |
288 | unsigned int wrap = 0; | |
289 | __u64 i = 0; | |
290 | #define MAX_ACC_LOOP_BIT 7 | |
291 | #define MIN_ACC_LOOP_BIT 0 | |
292 | __u64 acc_loop_cnt = | |
293 | jent_loop_shuffle(ec, MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT); | |
294 | ||
295 | if (NULL == ec || NULL == ec->mem) | |
296 | return 0; | |
297 | wrap = ec->memblocksize * ec->memblocks; | |
298 | ||
299 | /* | |
300 | * testing purposes -- allow test app to set the counter, not | |
301 | * needed during runtime | |
302 | */ | |
303 | if (loop_cnt) | |
304 | acc_loop_cnt = loop_cnt; | |
305 | ||
306 | for (i = 0; i < (ec->memaccessloops + acc_loop_cnt); i++) { | |
307 | tmpval = ec->mem + ec->memlocation; | |
308 | /* | |
309 | * memory access: just add 1 to one byte, | |
310 | * wrap at 255 -- memory access implies read | |
311 | * from and write to memory location | |
312 | */ | |
313 | *tmpval = (*tmpval + 1) & 0xff; | |
314 | /* | |
315 | * Addition of memblocksize - 1 to pointer | |
316 | * with wrap around logic to ensure that every | |
317 | * memory location is hit evenly | |
318 | */ | |
319 | ec->memlocation = ec->memlocation + ec->memblocksize - 1; | |
320 | ec->memlocation = ec->memlocation % wrap; | |
321 | } | |
322 | return i; | |
323 | } | |
324 | ||
325 | /*************************************************************************** | |
326 | * Start of entropy processing logic | |
327 | ***************************************************************************/ | |
328 | ||
329 | /** | |
330 | * Stuck test by checking the: | |
331 | * 1st derivation of the jitter measurement (time delta) | |
332 | * 2nd derivation of the jitter measurement (delta of time deltas) | |
333 | * 3rd derivation of the jitter measurement (delta of delta of time deltas) | |
334 | * | |
335 | * All values must always be non-zero. | |
336 | * | |
337 | * Input: | |
338 | * @ec Reference to entropy collector | |
339 | * @current_delta Jitter time delta | |
340 | * | |
341 | * @return | |
342 | * 0 jitter measurement not stuck (good bit) | |
343 | * 1 jitter measurement stuck (reject bit) | |
344 | */ | |
345 | static void jent_stuck(struct rand_data *ec, __u64 current_delta) | |
346 | { | |
347 | __s64 delta2 = ec->last_delta - current_delta; | |
348 | __s64 delta3 = delta2 - ec->last_delta2; | |
349 | ||
350 | ec->last_delta = current_delta; | |
351 | ec->last_delta2 = delta2; | |
352 | ||
353 | if (!current_delta || !delta2 || !delta3) | |
354 | ec->stuck = 1; | |
355 | } | |
356 | ||
357 | /** | |
358 | * This is the heart of the entropy generation: calculate time deltas and | |
359 | * use the CPU jitter in the time deltas. The jitter is folded into one | |
360 | * bit. You can call this function the "random bit generator" as it | |
361 | * produces one random bit per invocation. | |
362 | * | |
363 | * WARNING: ensure that ->prev_time is primed before using the output | |
364 | * of this function! This can be done by calling this function | |
365 | * and not using its result. | |
366 | * | |
367 | * Input: | |
368 | * @entropy_collector Reference to entropy collector | |
369 | * | |
370 | * @return One random bit | |
371 | */ | |
372 | static __u64 jent_measure_jitter(struct rand_data *ec) | |
373 | { | |
374 | __u64 time = 0; | |
375 | __u64 data = 0; | |
376 | __u64 current_delta = 0; | |
377 | ||
378 | /* Invoke one noise source before time measurement to add variations */ | |
379 | jent_memaccess(ec, 0); | |
380 | ||
381 | /* | |
382 | * Get time stamp and calculate time delta to previous | |
383 | * invocation to measure the timing variations | |
384 | */ | |
385 | jent_get_nstime(&time); | |
386 | current_delta = time - ec->prev_time; | |
387 | ec->prev_time = time; | |
388 | ||
389 | /* Now call the next noise sources which also folds the data */ | |
390 | jent_fold_time(ec, current_delta, &data, 0); | |
391 | ||
392 | /* | |
393 | * Check whether we have a stuck measurement. The enforcement | |
394 | * is performed after the stuck value has been mixed into the | |
395 | * entropy pool. | |
396 | */ | |
397 | jent_stuck(ec, current_delta); | |
398 | ||
399 | return data; | |
400 | } | |
401 | ||
402 | /** | |
403 | * Von Neuman unbias as explained in RFC 4086 section 4.2. As shown in the | |
404 | * documentation of that RNG, the bits from jent_measure_jitter are considered | |
405 | * independent which implies that the Von Neuman unbias operation is applicable. | |
406 | * A proof of the Von-Neumann unbias operation to remove skews is given in the | |
407 | * document "A proposal for: Functionality classes for random number | |
408 | * generators", version 2.0 by Werner Schindler, section 5.4.1. | |
409 | * | |
410 | * Input: | |
411 | * @entropy_collector Reference to entropy collector | |
412 | * | |
413 | * @return One random bit | |
414 | */ | |
415 | static __u64 jent_unbiased_bit(struct rand_data *entropy_collector) | |
416 | { | |
417 | do { | |
418 | __u64 a = jent_measure_jitter(entropy_collector); | |
419 | __u64 b = jent_measure_jitter(entropy_collector); | |
420 | ||
421 | if (a == b) | |
422 | continue; | |
423 | if (1 == a) | |
424 | return 1; | |
425 | else | |
426 | return 0; | |
427 | } while (1); | |
428 | } | |
429 | ||
430 | /** | |
431 | * Shuffle the pool a bit by mixing some value with a bijective function (XOR) | |
432 | * into the pool. | |
433 | * | |
434 | * The function generates a mixer value that depends on the bits set and the | |
435 | * location of the set bits in the random number generated by the entropy | |
436 | * source. Therefore, based on the generated random number, this mixer value | |
437 | * can have 2**64 different values. That mixer value is initialized with the | |
438 | * first two SHA-1 constants. After obtaining the mixer value, it is XORed into | |
439 | * the random number. | |
440 | * | |
441 | * The mixer value is not assumed to contain any entropy. But due to the XOR | |
442 | * operation, it can also not destroy any entropy present in the entropy pool. | |
443 | * | |
444 | * Input: | |
445 | * @entropy_collector Reference to entropy collector | |
446 | */ | |
447 | static void jent_stir_pool(struct rand_data *entropy_collector) | |
448 | { | |
449 | /* | |
450 | * to shut up GCC on 32 bit, we have to initialize the 64 variable | |
451 | * with two 32 bit variables | |
452 | */ | |
453 | union c { | |
454 | __u64 u64; | |
455 | __u32 u32[2]; | |
456 | }; | |
457 | /* | |
458 | * This constant is derived from the first two 32 bit initialization | |
459 | * vectors of SHA-1 as defined in FIPS 180-4 section 5.3.1 | |
460 | */ | |
461 | union c constant; | |
462 | /* | |
463 | * The start value of the mixer variable is derived from the third | |
464 | * and fourth 32 bit initialization vector of SHA-1 as defined in | |
465 | * FIPS 180-4 section 5.3.1 | |
466 | */ | |
467 | union c mixer; | |
468 | unsigned int i = 0; | |
469 | ||
470 | /* | |
471 | * Store the SHA-1 constants in reverse order to make up the 64 bit | |
472 | * value -- this applies to a little endian system, on a big endian | |
473 | * system, it reverses as expected. But this really does not matter | |
474 | * as we do not rely on the specific numbers. We just pick the SHA-1 | |
475 | * constants as they have a good mix of bit set and unset. | |
476 | */ | |
477 | constant.u32[1] = 0x67452301; | |
478 | constant.u32[0] = 0xefcdab89; | |
479 | mixer.u32[1] = 0x98badcfe; | |
480 | mixer.u32[0] = 0x10325476; | |
481 | ||
482 | for (i = 0; i < DATA_SIZE_BITS; i++) { | |
483 | /* | |
484 | * get the i-th bit of the input random number and only XOR | |
485 | * the constant into the mixer value when that bit is set | |
486 | */ | |
487 | if ((entropy_collector->data >> i) & 1) | |
488 | mixer.u64 ^= constant.u64; | |
489 | mixer.u64 = rol64(mixer.u64, 1); | |
490 | } | |
491 | entropy_collector->data ^= mixer.u64; | |
492 | } | |
493 | ||
494 | /** | |
495 | * Generator of one 64 bit random number | |
496 | * Function fills rand_data->data | |
497 | * | |
498 | * Input: | |
499 | * @ec Reference to entropy collector | |
500 | */ | |
501 | static void jent_gen_entropy(struct rand_data *ec) | |
502 | { | |
503 | unsigned int k = 0; | |
504 | ||
505 | /* priming of the ->prev_time value */ | |
506 | jent_measure_jitter(ec); | |
507 | ||
508 | while (1) { | |
509 | __u64 data = 0; | |
510 | ||
511 | if (ec->disable_unbias == 1) | |
512 | data = jent_measure_jitter(ec); | |
513 | else | |
514 | data = jent_unbiased_bit(ec); | |
515 | ||
516 | /* enforcement of the jent_stuck test */ | |
517 | if (ec->stuck) { | |
518 | /* | |
519 | * We only mix in the bit considered not appropriate | |
520 | * without the LSFR. The reason is that if we apply | |
521 | * the LSFR and we do not rotate, the 2nd bit with LSFR | |
522 | * will cancel out the first LSFR application on the | |
523 | * bad bit. | |
524 | * | |
525 | * And we do not rotate as we apply the next bit to the | |
526 | * current bit location again. | |
527 | */ | |
528 | ec->data ^= data; | |
529 | ec->stuck = 0; | |
530 | continue; | |
531 | } | |
532 | ||
533 | /* | |
534 | * Fibonacci LSFR with polynom of | |
535 | * x^64 + x^61 + x^56 + x^31 + x^28 + x^23 + 1 which is | |
536 | * primitive according to | |
537 | * http://poincare.matf.bg.ac.rs/~ezivkovm/publications/primpol1.pdf | |
538 | * (the shift values are the polynom values minus one | |
539 | * due to counting bits from 0 to 63). As the current | |
540 | * position is always the LSB, the polynom only needs | |
541 | * to shift data in from the left without wrap. | |
542 | */ | |
543 | ec->data ^= data; | |
544 | ec->data ^= ((ec->data >> 63) & 1); | |
545 | ec->data ^= ((ec->data >> 60) & 1); | |
546 | ec->data ^= ((ec->data >> 55) & 1); | |
547 | ec->data ^= ((ec->data >> 30) & 1); | |
548 | ec->data ^= ((ec->data >> 27) & 1); | |
549 | ec->data ^= ((ec->data >> 22) & 1); | |
550 | ec->data = rol64(ec->data, 1); | |
551 | ||
552 | /* | |
553 | * We multiply the loop value with ->osr to obtain the | |
554 | * oversampling rate requested by the caller | |
555 | */ | |
556 | if (++k >= (DATA_SIZE_BITS * ec->osr)) | |
557 | break; | |
558 | } | |
559 | if (ec->stir) | |
560 | jent_stir_pool(ec); | |
561 | } | |
562 | ||
563 | /** | |
564 | * The continuous test required by FIPS 140-2 -- the function automatically | |
565 | * primes the test if needed. | |
566 | * | |
567 | * Return: | |
568 | * 0 if FIPS test passed | |
569 | * < 0 if FIPS test failed | |
570 | */ | |
571 | static void jent_fips_test(struct rand_data *ec) | |
572 | { | |
573 | if (!fips_enabled) | |
574 | return; | |
575 | ||
576 | /* prime the FIPS test */ | |
577 | if (!ec->old_data) { | |
578 | ec->old_data = ec->data; | |
579 | jent_gen_entropy(ec); | |
580 | } | |
581 | ||
582 | if (ec->data == ec->old_data) | |
583 | panic(DRIVER_NAME ": Duplicate output detected\n"); | |
584 | ||
585 | ec->old_data = ec->data; | |
586 | } | |
587 | ||
588 | ||
589 | /** | |
590 | * Entry function: Obtain entropy for the caller. | |
591 | * | |
592 | * This function invokes the entropy gathering logic as often to generate | |
593 | * as many bytes as requested by the caller. The entropy gathering logic | |
594 | * creates 64 bit per invocation. | |
595 | * | |
596 | * This function truncates the last 64 bit entropy value output to the exact | |
597 | * size specified by the caller. | |
598 | * | |
599 | * Input: | |
600 | * @ec Reference to entropy collector | |
601 | * @data pointer to buffer for storing random data -- buffer must already | |
602 | * exist | |
603 | * @len size of the buffer, specifying also the requested number of random | |
604 | * in bytes | |
605 | * | |
606 | * @return 0 when request is fulfilled or an error | |
607 | * | |
608 | * The following error codes can occur: | |
609 | * -1 entropy_collector is NULL | |
610 | */ | |
611 | static ssize_t jent_read_entropy(struct rand_data *ec, u8 *data, size_t len) | |
612 | { | |
613 | u8 *p = data; | |
614 | ||
615 | if (!ec) | |
616 | return -EINVAL; | |
617 | ||
618 | while (0 < len) { | |
619 | size_t tocopy; | |
620 | ||
621 | jent_gen_entropy(ec); | |
622 | jent_fips_test(ec); | |
623 | if ((DATA_SIZE_BITS / 8) < len) | |
624 | tocopy = (DATA_SIZE_BITS / 8); | |
625 | else | |
626 | tocopy = len; | |
627 | memcpy(p, &ec->data, tocopy); | |
628 | ||
629 | len -= tocopy; | |
630 | p += tocopy; | |
631 | } | |
632 | ||
633 | return 0; | |
634 | } | |
635 | ||
636 | /*************************************************************************** | |
637 | * Initialization logic | |
638 | ***************************************************************************/ | |
639 | ||
640 | static struct rand_data *jent_entropy_collector_alloc(unsigned int osr, | |
641 | unsigned int flags) | |
642 | { | |
643 | struct rand_data *entropy_collector; | |
644 | ||
645 | entropy_collector = kzalloc(sizeof(struct rand_data), GFP_KERNEL); | |
646 | if (!entropy_collector) | |
647 | return NULL; | |
648 | ||
649 | if (!(flags & JENT_DISABLE_MEMORY_ACCESS)) { | |
650 | /* Allocate memory for adding variations based on memory | |
651 | * access | |
652 | */ | |
653 | entropy_collector->mem = kzalloc(JENT_MEMORY_SIZE, GFP_KERNEL); | |
654 | if (!entropy_collector->mem) { | |
655 | kfree(entropy_collector); | |
656 | return NULL; | |
657 | } | |
658 | entropy_collector->memblocksize = JENT_MEMORY_BLOCKSIZE; | |
659 | entropy_collector->memblocks = JENT_MEMORY_BLOCKS; | |
660 | entropy_collector->memaccessloops = JENT_MEMORY_ACCESSLOOPS; | |
661 | } | |
662 | ||
663 | /* verify and set the oversampling rate */ | |
664 | if (0 == osr) | |
665 | osr = 1; /* minimum sampling rate is 1 */ | |
666 | entropy_collector->osr = osr; | |
667 | ||
668 | entropy_collector->stir = 1; | |
669 | if (flags & JENT_DISABLE_STIR) | |
670 | entropy_collector->stir = 0; | |
671 | if (flags & JENT_DISABLE_UNBIAS) | |
672 | entropy_collector->disable_unbias = 1; | |
673 | ||
674 | /* fill the data pad with non-zero values */ | |
675 | jent_gen_entropy(entropy_collector); | |
676 | ||
677 | return entropy_collector; | |
678 | } | |
679 | ||
680 | static void jent_entropy_collector_free(struct rand_data *entropy_collector) | |
681 | { | |
682 | if (entropy_collector->mem) | |
683 | kzfree(entropy_collector->mem); | |
684 | entropy_collector->mem = NULL; | |
685 | if (entropy_collector) | |
686 | kzfree(entropy_collector); | |
687 | entropy_collector = NULL; | |
688 | } | |
689 | ||
690 | static int jent_entropy_init(void) | |
691 | { | |
692 | int i; | |
693 | __u64 delta_sum = 0; | |
694 | __u64 old_delta = 0; | |
695 | int time_backwards = 0; | |
696 | int count_var = 0; | |
697 | int count_mod = 0; | |
698 | ||
699 | /* We could perform statistical tests here, but the problem is | |
700 | * that we only have a few loop counts to do testing. These | |
701 | * loop counts may show some slight skew and we produce | |
702 | * false positives. | |
703 | * | |
704 | * Moreover, only old systems show potentially problematic | |
705 | * jitter entropy that could potentially be caught here. But | |
706 | * the RNG is intended for hardware that is available or widely | |
707 | * used, but not old systems that are long out of favor. Thus, | |
708 | * no statistical tests. | |
709 | */ | |
710 | ||
711 | /* | |
712 | * We could add a check for system capabilities such as clock_getres or | |
713 | * check for CONFIG_X86_TSC, but it does not make much sense as the | |
714 | * following sanity checks verify that we have a high-resolution | |
715 | * timer. | |
716 | */ | |
717 | /* | |
718 | * TESTLOOPCOUNT needs some loops to identify edge systems. 100 is | |
719 | * definitely too little. | |
720 | */ | |
721 | #define TESTLOOPCOUNT 300 | |
722 | #define CLEARCACHE 100 | |
723 | for (i = 0; (TESTLOOPCOUNT + CLEARCACHE) > i; i++) { | |
724 | __u64 time = 0; | |
725 | __u64 time2 = 0; | |
726 | __u64 folded = 0; | |
727 | __u64 delta = 0; | |
728 | unsigned int lowdelta = 0; | |
729 | ||
730 | jent_get_nstime(&time); | |
731 | jent_fold_time(NULL, time, &folded, 1<<MIN_FOLD_LOOP_BIT); | |
732 | jent_get_nstime(&time2); | |
733 | ||
734 | /* test whether timer works */ | |
735 | if (!time || !time2) | |
736 | return JENT_ENOTIME; | |
737 | delta = time2 - time; | |
738 | /* | |
739 | * test whether timer is fine grained enough to provide | |
740 | * delta even when called shortly after each other -- this | |
741 | * implies that we also have a high resolution timer | |
742 | */ | |
743 | if (!delta) | |
744 | return JENT_ECOARSETIME; | |
745 | ||
746 | /* | |
747 | * up to here we did not modify any variable that will be | |
748 | * evaluated later, but we already performed some work. Thus we | |
749 | * already have had an impact on the caches, branch prediction, | |
750 | * etc. with the goal to clear it to get the worst case | |
751 | * measurements. | |
752 | */ | |
753 | if (CLEARCACHE > i) | |
754 | continue; | |
755 | ||
756 | /* test whether we have an increasing timer */ | |
757 | if (!(time2 > time)) | |
758 | time_backwards++; | |
759 | ||
760 | /* | |
761 | * Avoid modulo of 64 bit integer to allow code to compile | |
762 | * on 32 bit architectures. | |
763 | */ | |
764 | lowdelta = time2 - time; | |
765 | if (!(lowdelta % 100)) | |
766 | count_mod++; | |
767 | ||
768 | /* | |
769 | * ensure that we have a varying delta timer which is necessary | |
770 | * for the calculation of entropy -- perform this check | |
771 | * only after the first loop is executed as we need to prime | |
772 | * the old_data value | |
773 | */ | |
774 | if (i) { | |
775 | if (delta != old_delta) | |
776 | count_var++; | |
777 | if (delta > old_delta) | |
778 | delta_sum += (delta - old_delta); | |
779 | else | |
780 | delta_sum += (old_delta - delta); | |
781 | } | |
782 | old_delta = delta; | |
783 | } | |
784 | ||
785 | /* | |
786 | * we allow up to three times the time running backwards. | |
787 | * CLOCK_REALTIME is affected by adjtime and NTP operations. Thus, | |
788 | * if such an operation just happens to interfere with our test, it | |
789 | * should not fail. The value of 3 should cover the NTP case being | |
790 | * performed during our test run. | |
791 | */ | |
792 | if (3 < time_backwards) | |
793 | return JENT_ENOMONOTONIC; | |
794 | /* Error if the time variances are always identical */ | |
795 | if (!delta_sum) | |
796 | return JENT_EVARVAR; | |
797 | ||
798 | /* | |
799 | * Variations of deltas of time must on average be larger | |
800 | * than 1 to ensure the entropy estimation | |
801 | * implied with 1 is preserved | |
802 | */ | |
803 | if (delta_sum <= 1) | |
804 | return JENT_EMINVARVAR; | |
805 | ||
806 | /* | |
807 | * Ensure that we have variations in the time stamp below 10 for at | |
808 | * least 10% of all checks -- on some platforms, the counter | |
809 | * increments in multiples of 100, but not always | |
810 | */ | |
811 | if ((TESTLOOPCOUNT/10 * 9) < count_mod) | |
812 | return JENT_ECOARSETIME; | |
813 | ||
814 | return 0; | |
815 | } | |
816 | ||
817 | /*************************************************************************** | |
818 | * Kernel crypto API interface | |
819 | ***************************************************************************/ | |
820 | ||
821 | struct jitterentropy { | |
822 | spinlock_t jent_lock; | |
823 | struct rand_data *entropy_collector; | |
824 | }; | |
825 | ||
826 | static int jent_kcapi_init(struct crypto_tfm *tfm) | |
827 | { | |
828 | struct jitterentropy *rng = crypto_tfm_ctx(tfm); | |
829 | int ret = 0; | |
830 | ||
831 | rng->entropy_collector = jent_entropy_collector_alloc(1, 0); | |
832 | if (!rng->entropy_collector) | |
833 | ret = -ENOMEM; | |
834 | ||
835 | spin_lock_init(&rng->jent_lock); | |
836 | return ret; | |
837 | } | |
838 | ||
839 | static void jent_kcapi_cleanup(struct crypto_tfm *tfm) | |
840 | { | |
841 | struct jitterentropy *rng = crypto_tfm_ctx(tfm); | |
842 | ||
843 | spin_lock(&rng->jent_lock); | |
844 | if (rng->entropy_collector) | |
845 | jent_entropy_collector_free(rng->entropy_collector); | |
846 | rng->entropy_collector = NULL; | |
847 | spin_unlock(&rng->jent_lock); | |
848 | } | |
849 | ||
850 | static int jent_kcapi_random(struct crypto_rng *tfm, | |
851 | const u8 *src, unsigned int slen, | |
852 | u8 *rdata, unsigned int dlen) | |
853 | { | |
854 | struct jitterentropy *rng = crypto_rng_ctx(tfm); | |
855 | int ret = 0; | |
856 | ||
857 | spin_lock(&rng->jent_lock); | |
858 | ret = jent_read_entropy(rng->entropy_collector, rdata, dlen); | |
859 | spin_unlock(&rng->jent_lock); | |
860 | ||
861 | return ret; | |
862 | } | |
863 | ||
864 | static int jent_kcapi_reset(struct crypto_rng *tfm, | |
865 | const u8 *seed, unsigned int slen) | |
866 | { | |
867 | return 0; | |
868 | } | |
869 | ||
870 | static struct rng_alg jent_alg = { | |
871 | .generate = jent_kcapi_random, | |
872 | .seed = jent_kcapi_reset, | |
873 | .seedsize = 0, | |
874 | .base = { | |
875 | .cra_name = "jitterentropy_rng", | |
876 | .cra_driver_name = "jitterentropy_rng", | |
877 | .cra_priority = 100, | |
878 | .cra_ctxsize = sizeof(struct jitterentropy), | |
879 | .cra_module = THIS_MODULE, | |
880 | .cra_init = jent_kcapi_init, | |
881 | .cra_exit = jent_kcapi_cleanup, | |
882 | ||
883 | } | |
884 | }; | |
885 | ||
886 | static int __init jent_mod_init(void) | |
887 | { | |
888 | int ret = 0; | |
889 | ||
890 | ret = jent_entropy_init(); | |
891 | if (ret) { | |
892 | pr_info(DRIVER_NAME ": Initialization failed with host not compliant with requirements: %d\n", ret); | |
893 | return -EFAULT; | |
894 | } | |
895 | return crypto_register_rng(&jent_alg); | |
896 | } | |
897 | ||
898 | static void __exit jent_mod_exit(void) | |
899 | { | |
900 | crypto_unregister_rng(&jent_alg); | |
901 | } | |
902 | ||
903 | module_init(jent_mod_init); | |
904 | module_exit(jent_mod_exit); | |
905 | ||
906 | MODULE_LICENSE("Dual BSD/GPL"); | |
907 | MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>"); | |
908 | MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter"); | |
909 | MODULE_ALIAS_CRYPTO("jitterentropy_rng"); |