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bb5530e4 | 1 | /* |
dfc9fa91 SM |
2 | * Non-physical true random number generator based on timing jitter -- |
3 | * Jitter RNG standalone code. | |
bb5530e4 | 4 | * |
bb897c55 | 5 | * Copyright Stephan Mueller <smueller@chronox.de>, 2015 - 2023 |
bb5530e4 SM |
6 | * |
7 | * Design | |
8 | * ====== | |
9 | * | |
9332a9e7 | 10 | * See https://www.chronox.de/jent.html |
bb5530e4 SM |
11 | * |
12 | * License | |
13 | * ======= | |
14 | * | |
15 | * Redistribution and use in source and binary forms, with or without | |
16 | * modification, are permitted provided that the following conditions | |
17 | * are met: | |
18 | * 1. Redistributions of source code must retain the above copyright | |
19 | * notice, and the entire permission notice in its entirety, | |
20 | * including the disclaimer of warranties. | |
21 | * 2. Redistributions in binary form must reproduce the above copyright | |
22 | * notice, this list of conditions and the following disclaimer in the | |
23 | * documentation and/or other materials provided with the distribution. | |
24 | * 3. The name of the author may not be used to endorse or promote | |
25 | * products derived from this software without specific prior | |
26 | * written permission. | |
27 | * | |
28 | * ALTERNATIVELY, this product may be distributed under the terms of | |
29 | * the GNU General Public License, in which case the provisions of the GPL2 are | |
30 | * required INSTEAD OF the above restrictions. (This clause is | |
31 | * necessary due to a potential bad interaction between the GPL and | |
32 | * the restrictions contained in a BSD-style copyright.) | |
33 | * | |
34 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED | |
35 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
36 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF | |
37 | * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE | |
38 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
39 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT | |
40 | * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR | |
41 | * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
42 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
43 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE | |
44 | * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH | |
45 | * DAMAGE. | |
46 | */ | |
47 | ||
48 | /* | |
49 | * This Jitterentropy RNG is based on the jitterentropy library | |
bb897c55 | 50 | * version 3.4.0 provided at https://www.chronox.de/jent.html |
bb5530e4 SM |
51 | */ |
52 | ||
dfc9fa91 SM |
53 | #ifdef __OPTIMIZE__ |
54 | #error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy.c." | |
55 | #endif | |
56 | ||
57 | typedef unsigned long long __u64; | |
58 | typedef long long __s64; | |
59 | typedef unsigned int __u32; | |
bb897c55 | 60 | typedef unsigned char u8; |
dfc9fa91 | 61 | #define NULL ((void *) 0) |
bb5530e4 | 62 | |
bb5530e4 SM |
63 | /* The entropy pool */ |
64 | struct rand_data { | |
bb897c55 SM |
65 | /* SHA3-256 is used as conditioner */ |
66 | #define DATA_SIZE_BITS 256 | |
bb5530e4 SM |
67 | /* all data values that are vital to maintain the security |
68 | * of the RNG are marked as SENSITIVE. A user must not | |
69 | * access that information while the RNG executes its loops to | |
70 | * calculate the next random value. */ | |
bb897c55 SM |
71 | void *hash_state; /* SENSITIVE hash state entropy pool */ |
72 | __u64 prev_time; /* SENSITIVE Previous time stamp */ | |
73 | __u64 last_delta; /* SENSITIVE stuck test */ | |
74 | __s64 last_delta2; /* SENSITIVE stuck test */ | |
75 | unsigned int osr; /* Oversample rate */ | |
bb5530e4 SM |
76 | #define JENT_MEMORY_BLOCKS 64 |
77 | #define JENT_MEMORY_BLOCKSIZE 32 | |
78 | #define JENT_MEMORY_ACCESSLOOPS 128 | |
79 | #define JENT_MEMORY_SIZE (JENT_MEMORY_BLOCKS*JENT_MEMORY_BLOCKSIZE) | |
80 | unsigned char *mem; /* Memory access location with size of | |
81 | * memblocks * memblocksize */ | |
82 | unsigned int memlocation; /* Pointer to byte in *mem */ | |
83 | unsigned int memblocks; /* Number of memory blocks in *mem */ | |
84 | unsigned int memblocksize; /* Size of one memory block in bytes */ | |
85 | unsigned int memaccessloops; /* Number of memory accesses per random | |
86 | * bit generation */ | |
764428fe SM |
87 | |
88 | /* Repetition Count Test */ | |
3fde2fe9 | 89 | unsigned int rct_count; /* Number of stuck values */ |
764428fe | 90 | |
3fde2fe9 | 91 | /* Intermittent health test failure threshold of 2^-30 */ |
91cb1e14 JV |
92 | /* From an SP800-90B perspective, this RCT cutoff value is equal to 31. */ |
93 | /* However, our RCT implementation starts at 1, so we subtract 1 here. */ | |
94 | #define JENT_RCT_CUTOFF (31 - 1) /* Taken from SP800-90B sec 4.4.1 */ | |
95 | #define JENT_APT_CUTOFF 325 /* Taken from SP800-90B sec 4.4.2 */ | |
3fde2fe9 | 96 | /* Permanent health test failure threshold of 2^-60 */ |
91cb1e14 JV |
97 | /* From an SP800-90B perspective, this RCT cutoff value is equal to 61. */ |
98 | /* However, our RCT implementation starts at 1, so we subtract 1 here. */ | |
99 | #define JENT_RCT_CUTOFF_PERMANENT (61 - 1) | |
3fde2fe9 | 100 | #define JENT_APT_CUTOFF_PERMANENT 355 |
764428fe SM |
101 | #define JENT_APT_WINDOW_SIZE 512 /* Data window size */ |
102 | /* LSB of time stamp to process */ | |
103 | #define JENT_APT_LSB 16 | |
104 | #define JENT_APT_WORD_MASK (JENT_APT_LSB - 1) | |
105 | unsigned int apt_observations; /* Number of collected observations */ | |
106 | unsigned int apt_count; /* APT counter */ | |
107 | unsigned int apt_base; /* APT base reference */ | |
108 | unsigned int apt_base_set:1; /* APT base reference set? */ | |
bb5530e4 SM |
109 | }; |
110 | ||
111 | /* Flags that can be used to initialize the RNG */ | |
bb5530e4 SM |
112 | #define JENT_DISABLE_MEMORY_ACCESS (1<<2) /* Disable memory access for more |
113 | * entropy, saves MEMORY_SIZE RAM for | |
114 | * entropy collector */ | |
115 | ||
bb5530e4 SM |
116 | /* -- error codes for init function -- */ |
117 | #define JENT_ENOTIME 1 /* Timer service not available */ | |
118 | #define JENT_ECOARSETIME 2 /* Timer too coarse for RNG */ | |
119 | #define JENT_ENOMONOTONIC 3 /* Timer is not monotonic increasing */ | |
bb5530e4 SM |
120 | #define JENT_EVARVAR 5 /* Timer does not produce variations of |
121 | * variations (2nd derivation of time is | |
122 | * zero). */ | |
d9d67c87 | 123 | #define JENT_ESTUCK 8 /* Too many stuck results during init. */ |
764428fe | 124 | #define JENT_EHEALTH 9 /* Health test failed during initialization */ |
764428fe | 125 | |
908dffaf SM |
126 | /* |
127 | * The output n bits can receive more than n bits of min entropy, of course, | |
128 | * but the fixed output of the conditioning function can only asymptotically | |
129 | * approach the output size bits of min entropy, not attain that bound. Random | |
130 | * maps will tend to have output collisions, which reduces the creditable | |
131 | * output entropy (that is what SP 800-90B Section 3.1.5.1.2 attempts to bound). | |
132 | * | |
133 | * The value "64" is justified in Appendix A.4 of the current 90C draft, | |
134 | * and aligns with NIST's in "epsilon" definition in this document, which is | |
135 | * that a string can be considered "full entropy" if you can bound the min | |
136 | * entropy in each bit of output to at least 1-epsilon, where epsilon is | |
137 | * required to be <= 2^(-32). | |
138 | */ | |
139 | #define JENT_ENTROPY_SAFETY_FACTOR 64 | |
140 | ||
141 | #include <linux/fips.h> | |
764428fe | 142 | #include "jitterentropy.h" |
bb5530e4 SM |
143 | |
144 | /*************************************************************************** | |
764428fe SM |
145 | * Adaptive Proportion Test |
146 | * | |
147 | * This test complies with SP800-90B section 4.4.2. | |
bb5530e4 SM |
148 | ***************************************************************************/ |
149 | ||
04cb788e | 150 | /* |
764428fe SM |
151 | * Reset the APT counter |
152 | * | |
153 | * @ec [in] Reference to entropy collector | |
154 | */ | |
155 | static void jent_apt_reset(struct rand_data *ec, unsigned int delta_masked) | |
156 | { | |
157 | /* Reset APT counter */ | |
158 | ec->apt_count = 0; | |
159 | ec->apt_base = delta_masked; | |
160 | ec->apt_observations = 0; | |
161 | } | |
162 | ||
04cb788e | 163 | /* |
764428fe SM |
164 | * Insert a new entropy event into APT |
165 | * | |
166 | * @ec [in] Reference to entropy collector | |
167 | * @delta_masked [in] Masked time delta to process | |
168 | */ | |
169 | static void jent_apt_insert(struct rand_data *ec, unsigned int delta_masked) | |
170 | { | |
171 | /* Initialize the base reference */ | |
172 | if (!ec->apt_base_set) { | |
173 | ec->apt_base = delta_masked; | |
174 | ec->apt_base_set = 1; | |
175 | return; | |
176 | } | |
177 | ||
3fde2fe9 | 178 | if (delta_masked == ec->apt_base) |
764428fe SM |
179 | ec->apt_count++; |
180 | ||
764428fe SM |
181 | ec->apt_observations++; |
182 | ||
183 | if (ec->apt_observations >= JENT_APT_WINDOW_SIZE) | |
184 | jent_apt_reset(ec, delta_masked); | |
185 | } | |
186 | ||
3fde2fe9 SM |
187 | /* APT health test failure detection */ |
188 | static int jent_apt_permanent_failure(struct rand_data *ec) | |
189 | { | |
190 | return (ec->apt_count >= JENT_APT_CUTOFF_PERMANENT) ? 1 : 0; | |
191 | } | |
192 | ||
193 | static int jent_apt_failure(struct rand_data *ec) | |
194 | { | |
195 | return (ec->apt_count >= JENT_APT_CUTOFF) ? 1 : 0; | |
196 | } | |
197 | ||
764428fe SM |
198 | /*************************************************************************** |
199 | * Stuck Test and its use as Repetition Count Test | |
200 | * | |
201 | * The Jitter RNG uses an enhanced version of the Repetition Count Test | |
202 | * (RCT) specified in SP800-90B section 4.4.1. Instead of counting identical | |
203 | * back-to-back values, the input to the RCT is the counting of the stuck | |
204 | * values during the generation of one Jitter RNG output block. | |
205 | * | |
206 | * The RCT is applied with an alpha of 2^{-30} compliant to FIPS 140-2 IG 9.8. | |
207 | * | |
208 | * During the counting operation, the Jitter RNG always calculates the RCT | |
209 | * cut-off value of C. If that value exceeds the allowed cut-off value, | |
210 | * the Jitter RNG output block will be calculated completely but discarded at | |
211 | * the end. The caller of the Jitter RNG is informed with an error code. | |
212 | ***************************************************************************/ | |
213 | ||
04cb788e | 214 | /* |
764428fe SM |
215 | * Repetition Count Test as defined in SP800-90B section 4.4.1 |
216 | * | |
217 | * @ec [in] Reference to entropy collector | |
218 | * @stuck [in] Indicator whether the value is stuck | |
219 | */ | |
220 | static void jent_rct_insert(struct rand_data *ec, int stuck) | |
221 | { | |
764428fe SM |
222 | if (stuck) { |
223 | ec->rct_count++; | |
764428fe | 224 | } else { |
3fde2fe9 | 225 | /* Reset RCT */ |
764428fe SM |
226 | ec->rct_count = 0; |
227 | } | |
228 | } | |
229 | ||
764428fe SM |
230 | static inline __u64 jent_delta(__u64 prev, __u64 next) |
231 | { | |
232 | #define JENT_UINT64_MAX (__u64)(~((__u64) 0)) | |
233 | return (prev < next) ? (next - prev) : | |
234 | (JENT_UINT64_MAX - prev + 1 + next); | |
235 | } | |
236 | ||
04cb788e | 237 | /* |
764428fe SM |
238 | * Stuck test by checking the: |
239 | * 1st derivative of the jitter measurement (time delta) | |
240 | * 2nd derivative of the jitter measurement (delta of time deltas) | |
241 | * 3rd derivative of the jitter measurement (delta of delta of time deltas) | |
242 | * | |
243 | * All values must always be non-zero. | |
244 | * | |
245 | * @ec [in] Reference to entropy collector | |
246 | * @current_delta [in] Jitter time delta | |
247 | * | |
248 | * @return | |
249 | * 0 jitter measurement not stuck (good bit) | |
250 | * 1 jitter measurement stuck (reject bit) | |
251 | */ | |
252 | static int jent_stuck(struct rand_data *ec, __u64 current_delta) | |
253 | { | |
254 | __u64 delta2 = jent_delta(ec->last_delta, current_delta); | |
255 | __u64 delta3 = jent_delta(ec->last_delta2, delta2); | |
764428fe SM |
256 | |
257 | ec->last_delta = current_delta; | |
258 | ec->last_delta2 = delta2; | |
259 | ||
260 | /* | |
261 | * Insert the result of the comparison of two back-to-back time | |
262 | * deltas. | |
263 | */ | |
552d03a2 | 264 | jent_apt_insert(ec, current_delta); |
764428fe SM |
265 | |
266 | if (!current_delta || !delta2 || !delta3) { | |
267 | /* RCT with a stuck bit */ | |
268 | jent_rct_insert(ec, 1); | |
269 | return 1; | |
270 | } | |
271 | ||
272 | /* RCT with a non-stuck bit */ | |
273 | jent_rct_insert(ec, 0); | |
274 | ||
275 | return 0; | |
276 | } | |
277 | ||
3fde2fe9 SM |
278 | /* RCT health test failure detection */ |
279 | static int jent_rct_permanent_failure(struct rand_data *ec) | |
280 | { | |
281 | return (ec->rct_count >= JENT_RCT_CUTOFF_PERMANENT) ? 1 : 0; | |
282 | } | |
283 | ||
284 | static int jent_rct_failure(struct rand_data *ec) | |
285 | { | |
286 | return (ec->rct_count >= JENT_RCT_CUTOFF) ? 1 : 0; | |
287 | } | |
288 | ||
289 | /* Report of health test failures */ | |
764428fe SM |
290 | static int jent_health_failure(struct rand_data *ec) |
291 | { | |
3fde2fe9 SM |
292 | return jent_rct_failure(ec) | jent_apt_failure(ec); |
293 | } | |
294 | ||
295 | static int jent_permanent_health_failure(struct rand_data *ec) | |
296 | { | |
297 | return jent_rct_permanent_failure(ec) | jent_apt_permanent_failure(ec); | |
764428fe SM |
298 | } |
299 | ||
300 | /*************************************************************************** | |
301 | * Noise sources | |
302 | ***************************************************************************/ | |
bb5530e4 | 303 | |
04cb788e | 304 | /* |
bb5530e4 SM |
305 | * Update of the loop count used for the next round of |
306 | * an entropy collection. | |
307 | * | |
308 | * Input: | |
bb5530e4 SM |
309 | * @bits is the number of low bits of the timer to consider |
310 | * @min is the number of bits we shift the timer value to the right at | |
311 | * the end to make sure we have a guaranteed minimum value | |
312 | * | |
313 | * @return Newly calculated loop counter | |
314 | */ | |
bb897c55 | 315 | static __u64 jent_loop_shuffle(unsigned int bits, unsigned int min) |
bb5530e4 SM |
316 | { |
317 | __u64 time = 0; | |
318 | __u64 shuffle = 0; | |
319 | unsigned int i = 0; | |
320 | unsigned int mask = (1<<bits) - 1; | |
321 | ||
322 | jent_get_nstime(&time); | |
bb897c55 | 323 | |
bb5530e4 | 324 | /* |
d9d67c87 SM |
325 | * We fold the time value as much as possible to ensure that as many |
326 | * bits of the time stamp are included as possible. | |
bb5530e4 | 327 | */ |
d9d67c87 | 328 | for (i = 0; ((DATA_SIZE_BITS + bits - 1) / bits) > i; i++) { |
bb5530e4 SM |
329 | shuffle ^= time & mask; |
330 | time = time >> bits; | |
331 | } | |
332 | ||
333 | /* | |
334 | * We add a lower boundary value to ensure we have a minimum | |
335 | * RNG loop count. | |
336 | */ | |
337 | return (shuffle + (1<<min)); | |
338 | } | |
339 | ||
04cb788e | 340 | /* |
bb5530e4 SM |
341 | * CPU Jitter noise source -- this is the noise source based on the CPU |
342 | * execution time jitter | |
343 | * | |
d9d67c87 | 344 | * This function injects the individual bits of the time value into the |
bb897c55 | 345 | * entropy pool using a hash. |
bb5530e4 | 346 | * |
bb897c55 SM |
347 | * ec [in] entropy collector |
348 | * time [in] time stamp to be injected | |
349 | * stuck [in] Is the time stamp identified as stuck? | |
bb5530e4 SM |
350 | * |
351 | * Output: | |
bb897c55 | 352 | * updated hash context in the entropy collector or error code |
bb5530e4 | 353 | */ |
bb897c55 | 354 | static int jent_condition_data(struct rand_data *ec, __u64 time, int stuck) |
bb5530e4 | 355 | { |
bb897c55 SM |
356 | #define SHA3_HASH_LOOP (1<<3) |
357 | struct { | |
358 | int rct_count; | |
359 | unsigned int apt_observations; | |
360 | unsigned int apt_count; | |
361 | unsigned int apt_base; | |
362 | } addtl = { | |
363 | ec->rct_count, | |
364 | ec->apt_observations, | |
365 | ec->apt_count, | |
366 | ec->apt_base | |
367 | }; | |
368 | ||
369 | return jent_hash_time(ec->hash_state, time, (u8 *)&addtl, sizeof(addtl), | |
370 | SHA3_HASH_LOOP, stuck); | |
bb5530e4 SM |
371 | } |
372 | ||
04cb788e | 373 | /* |
bb5530e4 SM |
374 | * Memory Access noise source -- this is a noise source based on variations in |
375 | * memory access times | |
376 | * | |
377 | * This function performs memory accesses which will add to the timing | |
378 | * variations due to an unknown amount of CPU wait states that need to be | |
379 | * added when accessing memory. The memory size should be larger than the L1 | |
380 | * caches as outlined in the documentation and the associated testing. | |
381 | * | |
382 | * The L1 cache has a very high bandwidth, albeit its access rate is usually | |
383 | * slower than accessing CPU registers. Therefore, L1 accesses only add minimal | |
384 | * variations as the CPU has hardly to wait. Starting with L2, significant | |
385 | * variations are added because L2 typically does not belong to the CPU any more | |
386 | * and therefore a wider range of CPU wait states is necessary for accesses. | |
387 | * L3 and real memory accesses have even a wider range of wait states. However, | |
388 | * to reliably access either L3 or memory, the ec->mem memory must be quite | |
389 | * large which is usually not desirable. | |
390 | * | |
764428fe SM |
391 | * @ec [in] Reference to the entropy collector with the memory access data -- if |
392 | * the reference to the memory block to be accessed is NULL, this noise | |
393 | * source is disabled | |
394 | * @loop_cnt [in] if a value not equal to 0 is set, use the given value | |
395 | * number of loops to perform the LFSR | |
bb5530e4 | 396 | */ |
764428fe | 397 | static void jent_memaccess(struct rand_data *ec, __u64 loop_cnt) |
bb5530e4 | 398 | { |
bb5530e4 SM |
399 | unsigned int wrap = 0; |
400 | __u64 i = 0; | |
401 | #define MAX_ACC_LOOP_BIT 7 | |
402 | #define MIN_ACC_LOOP_BIT 0 | |
403 | __u64 acc_loop_cnt = | |
bb897c55 | 404 | jent_loop_shuffle(MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT); |
bb5530e4 SM |
405 | |
406 | if (NULL == ec || NULL == ec->mem) | |
764428fe | 407 | return; |
bb5530e4 SM |
408 | wrap = ec->memblocksize * ec->memblocks; |
409 | ||
410 | /* | |
411 | * testing purposes -- allow test app to set the counter, not | |
412 | * needed during runtime | |
413 | */ | |
414 | if (loop_cnt) | |
415 | acc_loop_cnt = loop_cnt; | |
416 | ||
417 | for (i = 0; i < (ec->memaccessloops + acc_loop_cnt); i++) { | |
d9d67c87 | 418 | unsigned char *tmpval = ec->mem + ec->memlocation; |
bb5530e4 SM |
419 | /* |
420 | * memory access: just add 1 to one byte, | |
421 | * wrap at 255 -- memory access implies read | |
422 | * from and write to memory location | |
423 | */ | |
424 | *tmpval = (*tmpval + 1) & 0xff; | |
425 | /* | |
426 | * Addition of memblocksize - 1 to pointer | |
427 | * with wrap around logic to ensure that every | |
428 | * memory location is hit evenly | |
429 | */ | |
430 | ec->memlocation = ec->memlocation + ec->memblocksize - 1; | |
431 | ec->memlocation = ec->memlocation % wrap; | |
432 | } | |
bb5530e4 SM |
433 | } |
434 | ||
435 | /*************************************************************************** | |
436 | * Start of entropy processing logic | |
437 | ***************************************************************************/ | |
04cb788e | 438 | /* |
bb5530e4 | 439 | * This is the heart of the entropy generation: calculate time deltas and |
d9d67c87 SM |
440 | * use the CPU jitter in the time deltas. The jitter is injected into the |
441 | * entropy pool. | |
bb5530e4 SM |
442 | * |
443 | * WARNING: ensure that ->prev_time is primed before using the output | |
444 | * of this function! This can be done by calling this function | |
445 | * and not using its result. | |
446 | * | |
764428fe | 447 | * @ec [in] Reference to entropy collector |
bb5530e4 | 448 | * |
d9d67c87 | 449 | * @return result of stuck test |
bb5530e4 | 450 | */ |
d9d67c87 | 451 | static int jent_measure_jitter(struct rand_data *ec) |
bb5530e4 SM |
452 | { |
453 | __u64 time = 0; | |
bb5530e4 | 454 | __u64 current_delta = 0; |
764428fe | 455 | int stuck; |
bb5530e4 SM |
456 | |
457 | /* Invoke one noise source before time measurement to add variations */ | |
458 | jent_memaccess(ec, 0); | |
459 | ||
460 | /* | |
461 | * Get time stamp and calculate time delta to previous | |
462 | * invocation to measure the timing variations | |
463 | */ | |
464 | jent_get_nstime(&time); | |
764428fe | 465 | current_delta = jent_delta(ec->prev_time, time); |
bb5530e4 SM |
466 | ec->prev_time = time; |
467 | ||
764428fe SM |
468 | /* Check whether we have a stuck measurement. */ |
469 | stuck = jent_stuck(ec, current_delta); | |
470 | ||
d9d67c87 | 471 | /* Now call the next noise sources which also injects the data */ |
bb897c55 SM |
472 | if (jent_condition_data(ec, current_delta, stuck)) |
473 | stuck = 1; | |
bb5530e4 | 474 | |
764428fe | 475 | return stuck; |
bb5530e4 SM |
476 | } |
477 | ||
04cb788e | 478 | /* |
bb5530e4 | 479 | * Generator of one 64 bit random number |
bb897c55 | 480 | * Function fills rand_data->hash_state |
bb5530e4 | 481 | * |
764428fe | 482 | * @ec [in] Reference to entropy collector |
bb5530e4 SM |
483 | */ |
484 | static void jent_gen_entropy(struct rand_data *ec) | |
485 | { | |
908dffaf SM |
486 | unsigned int k = 0, safety_factor = 0; |
487 | ||
488 | if (fips_enabled) | |
489 | safety_factor = JENT_ENTROPY_SAFETY_FACTOR; | |
bb5530e4 SM |
490 | |
491 | /* priming of the ->prev_time value */ | |
492 | jent_measure_jitter(ec); | |
493 | ||
710ce4b8 | 494 | while (!jent_health_failure(ec)) { |
d9d67c87 SM |
495 | /* If a stuck measurement is received, repeat measurement */ |
496 | if (jent_measure_jitter(ec)) | |
bb5530e4 | 497 | continue; |
bb5530e4 SM |
498 | |
499 | /* | |
500 | * We multiply the loop value with ->osr to obtain the | |
501 | * oversampling rate requested by the caller | |
502 | */ | |
908dffaf | 503 | if (++k >= ((DATA_SIZE_BITS + safety_factor) * ec->osr)) |
bb5530e4 SM |
504 | break; |
505 | } | |
bb5530e4 SM |
506 | } |
507 | ||
04cb788e | 508 | /* |
bb5530e4 SM |
509 | * Entry function: Obtain entropy for the caller. |
510 | * | |
511 | * This function invokes the entropy gathering logic as often to generate | |
512 | * as many bytes as requested by the caller. The entropy gathering logic | |
513 | * creates 64 bit per invocation. | |
514 | * | |
515 | * This function truncates the last 64 bit entropy value output to the exact | |
516 | * size specified by the caller. | |
517 | * | |
764428fe SM |
518 | * @ec [in] Reference to entropy collector |
519 | * @data [in] pointer to buffer for storing random data -- buffer must already | |
520 | * exist | |
521 | * @len [in] size of the buffer, specifying also the requested number of random | |
522 | * in bytes | |
bb5530e4 SM |
523 | * |
524 | * @return 0 when request is fulfilled or an error | |
525 | * | |
526 | * The following error codes can occur: | |
bb897c55 | 527 | * -1 entropy_collector is NULL or the generation failed |
3fde2fe9 SM |
528 | * -2 Intermittent health failure |
529 | * -3 Permanent health failure | |
bb5530e4 | 530 | */ |
dfc9fa91 SM |
531 | int jent_read_entropy(struct rand_data *ec, unsigned char *data, |
532 | unsigned int len) | |
bb5530e4 | 533 | { |
dfc9fa91 | 534 | unsigned char *p = data; |
bb5530e4 SM |
535 | |
536 | if (!ec) | |
dfc9fa91 | 537 | return -1; |
bb5530e4 | 538 | |
36c25011 | 539 | while (len > 0) { |
dfc9fa91 | 540 | unsigned int tocopy; |
bb5530e4 SM |
541 | |
542 | jent_gen_entropy(ec); | |
764428fe | 543 | |
3fde2fe9 | 544 | if (jent_permanent_health_failure(ec)) { |
764428fe | 545 | /* |
3fde2fe9 SM |
546 | * At this point, the Jitter RNG instance is considered |
547 | * as a failed instance. There is no rerun of the | |
548 | * startup test any more, because the caller | |
549 | * is assumed to not further use this instance. | |
764428fe | 550 | */ |
3fde2fe9 SM |
551 | return -3; |
552 | } else if (jent_health_failure(ec)) { | |
764428fe | 553 | /* |
3fde2fe9 SM |
554 | * Perform startup health tests and return permanent |
555 | * error if it fails. | |
764428fe | 556 | */ |
bb897c55 | 557 | if (jent_entropy_init(ec->hash_state)) |
3fde2fe9 SM |
558 | return -3; |
559 | ||
560 | return -2; | |
764428fe SM |
561 | } |
562 | ||
bb5530e4 SM |
563 | if ((DATA_SIZE_BITS / 8) < len) |
564 | tocopy = (DATA_SIZE_BITS / 8); | |
565 | else | |
566 | tocopy = len; | |
bb897c55 SM |
567 | if (jent_read_random_block(ec->hash_state, p, tocopy)) |
568 | return -1; | |
bb5530e4 SM |
569 | |
570 | len -= tocopy; | |
571 | p += tocopy; | |
572 | } | |
573 | ||
574 | return 0; | |
575 | } | |
576 | ||
577 | /*************************************************************************** | |
578 | * Initialization logic | |
579 | ***************************************************************************/ | |
580 | ||
dfc9fa91 | 581 | struct rand_data *jent_entropy_collector_alloc(unsigned int osr, |
bb897c55 SM |
582 | unsigned int flags, |
583 | void *hash_state) | |
bb5530e4 SM |
584 | { |
585 | struct rand_data *entropy_collector; | |
586 | ||
dfc9fa91 | 587 | entropy_collector = jent_zalloc(sizeof(struct rand_data)); |
bb5530e4 SM |
588 | if (!entropy_collector) |
589 | return NULL; | |
590 | ||
591 | if (!(flags & JENT_DISABLE_MEMORY_ACCESS)) { | |
592 | /* Allocate memory for adding variations based on memory | |
593 | * access | |
594 | */ | |
dfc9fa91 | 595 | entropy_collector->mem = jent_zalloc(JENT_MEMORY_SIZE); |
bb5530e4 | 596 | if (!entropy_collector->mem) { |
dfc9fa91 | 597 | jent_zfree(entropy_collector); |
bb5530e4 SM |
598 | return NULL; |
599 | } | |
600 | entropy_collector->memblocksize = JENT_MEMORY_BLOCKSIZE; | |
601 | entropy_collector->memblocks = JENT_MEMORY_BLOCKS; | |
602 | entropy_collector->memaccessloops = JENT_MEMORY_ACCESSLOOPS; | |
603 | } | |
604 | ||
605 | /* verify and set the oversampling rate */ | |
36c25011 | 606 | if (osr == 0) |
bb5530e4 SM |
607 | osr = 1; /* minimum sampling rate is 1 */ |
608 | entropy_collector->osr = osr; | |
609 | ||
bb897c55 SM |
610 | entropy_collector->hash_state = hash_state; |
611 | ||
bb5530e4 SM |
612 | /* fill the data pad with non-zero values */ |
613 | jent_gen_entropy(entropy_collector); | |
614 | ||
615 | return entropy_collector; | |
616 | } | |
617 | ||
dfc9fa91 | 618 | void jent_entropy_collector_free(struct rand_data *entropy_collector) |
bb5530e4 | 619 | { |
cea0a3c3 | 620 | jent_zfree(entropy_collector->mem); |
bb5530e4 | 621 | entropy_collector->mem = NULL; |
cea0a3c3 | 622 | jent_zfree(entropy_collector); |
bb5530e4 SM |
623 | } |
624 | ||
bb897c55 | 625 | int jent_entropy_init(void *hash_state) |
bb5530e4 SM |
626 | { |
627 | int i; | |
628 | __u64 delta_sum = 0; | |
629 | __u64 old_delta = 0; | |
764428fe | 630 | unsigned int nonstuck = 0; |
bb5530e4 | 631 | int time_backwards = 0; |
bb5530e4 | 632 | int count_mod = 0; |
d9d67c87 SM |
633 | int count_stuck = 0; |
634 | struct rand_data ec = { 0 }; | |
bb5530e4 | 635 | |
764428fe SM |
636 | /* Required for RCT */ |
637 | ec.osr = 1; | |
bb897c55 | 638 | ec.hash_state = hash_state; |
764428fe | 639 | |
bb5530e4 SM |
640 | /* We could perform statistical tests here, but the problem is |
641 | * that we only have a few loop counts to do testing. These | |
642 | * loop counts may show some slight skew and we produce | |
643 | * false positives. | |
644 | * | |
645 | * Moreover, only old systems show potentially problematic | |
646 | * jitter entropy that could potentially be caught here. But | |
647 | * the RNG is intended for hardware that is available or widely | |
648 | * used, but not old systems that are long out of favor. Thus, | |
649 | * no statistical tests. | |
650 | */ | |
651 | ||
652 | /* | |
653 | * We could add a check for system capabilities such as clock_getres or | |
654 | * check for CONFIG_X86_TSC, but it does not make much sense as the | |
655 | * following sanity checks verify that we have a high-resolution | |
656 | * timer. | |
657 | */ | |
658 | /* | |
659 | * TESTLOOPCOUNT needs some loops to identify edge systems. 100 is | |
660 | * definitely too little. | |
764428fe SM |
661 | * |
662 | * SP800-90B requires at least 1024 initial test cycles. | |
bb5530e4 | 663 | */ |
764428fe | 664 | #define TESTLOOPCOUNT 1024 |
bb5530e4 SM |
665 | #define CLEARCACHE 100 |
666 | for (i = 0; (TESTLOOPCOUNT + CLEARCACHE) > i; i++) { | |
667 | __u64 time = 0; | |
668 | __u64 time2 = 0; | |
bb5530e4 SM |
669 | __u64 delta = 0; |
670 | unsigned int lowdelta = 0; | |
d9d67c87 | 671 | int stuck; |
bb5530e4 | 672 | |
d9d67c87 | 673 | /* Invoke core entropy collection logic */ |
bb5530e4 | 674 | jent_get_nstime(&time); |
d9d67c87 | 675 | ec.prev_time = time; |
bb897c55 | 676 | jent_condition_data(&ec, time, 0); |
bb5530e4 SM |
677 | jent_get_nstime(&time2); |
678 | ||
679 | /* test whether timer works */ | |
680 | if (!time || !time2) | |
681 | return JENT_ENOTIME; | |
764428fe | 682 | delta = jent_delta(time, time2); |
bb5530e4 SM |
683 | /* |
684 | * test whether timer is fine grained enough to provide | |
685 | * delta even when called shortly after each other -- this | |
686 | * implies that we also have a high resolution timer | |
687 | */ | |
688 | if (!delta) | |
689 | return JENT_ECOARSETIME; | |
690 | ||
d9d67c87 SM |
691 | stuck = jent_stuck(&ec, delta); |
692 | ||
bb5530e4 SM |
693 | /* |
694 | * up to here we did not modify any variable that will be | |
695 | * evaluated later, but we already performed some work. Thus we | |
696 | * already have had an impact on the caches, branch prediction, | |
697 | * etc. with the goal to clear it to get the worst case | |
698 | * measurements. | |
699 | */ | |
36c25011 | 700 | if (i < CLEARCACHE) |
bb5530e4 SM |
701 | continue; |
702 | ||
d9d67c87 SM |
703 | if (stuck) |
704 | count_stuck++; | |
764428fe SM |
705 | else { |
706 | nonstuck++; | |
707 | ||
708 | /* | |
709 | * Ensure that the APT succeeded. | |
710 | * | |
711 | * With the check below that count_stuck must be less | |
712 | * than 10% of the overall generated raw entropy values | |
713 | * it is guaranteed that the APT is invoked at | |
714 | * floor((TESTLOOPCOUNT * 0.9) / 64) == 14 times. | |
715 | */ | |
716 | if ((nonstuck % JENT_APT_WINDOW_SIZE) == 0) { | |
717 | jent_apt_reset(&ec, | |
718 | delta & JENT_APT_WORD_MASK); | |
764428fe SM |
719 | } |
720 | } | |
721 | ||
d2365976 SM |
722 | /* Validate health test result */ |
723 | if (jent_health_failure(&ec)) | |
724 | return JENT_EHEALTH; | |
d9d67c87 | 725 | |
bb5530e4 SM |
726 | /* test whether we have an increasing timer */ |
727 | if (!(time2 > time)) | |
728 | time_backwards++; | |
729 | ||
d9d67c87 | 730 | /* use 32 bit value to ensure compilation on 32 bit arches */ |
bb5530e4 SM |
731 | lowdelta = time2 - time; |
732 | if (!(lowdelta % 100)) | |
733 | count_mod++; | |
734 | ||
735 | /* | |
736 | * ensure that we have a varying delta timer which is necessary | |
737 | * for the calculation of entropy -- perform this check | |
738 | * only after the first loop is executed as we need to prime | |
739 | * the old_data value | |
740 | */ | |
d9d67c87 SM |
741 | if (delta > old_delta) |
742 | delta_sum += (delta - old_delta); | |
743 | else | |
744 | delta_sum += (old_delta - delta); | |
bb5530e4 SM |
745 | old_delta = delta; |
746 | } | |
747 | ||
748 | /* | |
749 | * we allow up to three times the time running backwards. | |
750 | * CLOCK_REALTIME is affected by adjtime and NTP operations. Thus, | |
751 | * if such an operation just happens to interfere with our test, it | |
752 | * should not fail. The value of 3 should cover the NTP case being | |
753 | * performed during our test run. | |
754 | */ | |
36c25011 | 755 | if (time_backwards > 3) |
bb5530e4 | 756 | return JENT_ENOMONOTONIC; |
bb5530e4 SM |
757 | |
758 | /* | |
759 | * Variations of deltas of time must on average be larger | |
760 | * than 1 to ensure the entropy estimation | |
761 | * implied with 1 is preserved | |
762 | */ | |
d9d67c87 SM |
763 | if ((delta_sum) <= 1) |
764 | return JENT_EVARVAR; | |
bb5530e4 SM |
765 | |
766 | /* | |
767 | * Ensure that we have variations in the time stamp below 10 for at | |
d9d67c87 SM |
768 | * least 10% of all checks -- on some platforms, the counter increments |
769 | * in multiples of 100, but not always | |
bb5530e4 SM |
770 | */ |
771 | if ((TESTLOOPCOUNT/10 * 9) < count_mod) | |
772 | return JENT_ECOARSETIME; | |
773 | ||
d9d67c87 SM |
774 | /* |
775 | * If we have more than 90% stuck results, then this Jitter RNG is | |
776 | * likely to not work well. | |
777 | */ | |
778 | if ((TESTLOOPCOUNT/10 * 9) < count_stuck) | |
779 | return JENT_ESTUCK; | |
780 | ||
bb5530e4 SM |
781 | return 0; |
782 | } |