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Source at commit 6c17a31f1fc515425221067cb3ece599c09dbc5d created 12 years 8 months ago. By Werner Almesberger, atusb, atben: moved from spi/ to ieee802154/; renamed atusb to spi_atusb | |
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1 | /* |
2 | * PRNG: Pseudo Random Number Generator |
3 | * Based on NIST Recommended PRNG From ANSI X9.31 Appendix A.2.4 using |
4 | * AES 128 cipher |
5 | * |
6 | * (C) Neil Horman <nhorman@tuxdriver.com> |
7 | * |
8 | * This program is free software; you can redistribute it and/or modify it |
9 | * under the terms of the GNU General Public License as published by the |
10 | * Free Software Foundation; either version 2 of the License, or (at your |
11 | * any later version. |
12 | * |
13 | * |
14 | */ |
15 | |
16 | #include <crypto/internal/rng.h> |
17 | #include <linux/err.h> |
18 | #include <linux/init.h> |
19 | #include <linux/module.h> |
20 | #include <linux/moduleparam.h> |
21 | #include <linux/string.h> |
22 | |
23 | #include "internal.h" |
24 | |
25 | #define DEFAULT_PRNG_KEY "0123456789abcdef" |
26 | #define DEFAULT_PRNG_KSZ 16 |
27 | #define DEFAULT_BLK_SZ 16 |
28 | #define DEFAULT_V_SEED "zaybxcwdveuftgsh" |
29 | |
30 | /* |
31 | * Flags for the prng_context flags field |
32 | */ |
33 | |
34 | #define PRNG_FIXED_SIZE 0x1 |
35 | #define PRNG_NEED_RESET 0x2 |
36 | |
37 | /* |
38 | * Note: DT is our counter value |
39 | * I is our intermediate value |
40 | * V is our seed vector |
41 | * See http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf |
42 | * for implementation details |
43 | */ |
44 | |
45 | |
46 | struct prng_context { |
47 | spinlock_t prng_lock; |
48 | unsigned char rand_data[DEFAULT_BLK_SZ]; |
49 | unsigned char last_rand_data[DEFAULT_BLK_SZ]; |
50 | unsigned char DT[DEFAULT_BLK_SZ]; |
51 | unsigned char I[DEFAULT_BLK_SZ]; |
52 | unsigned char V[DEFAULT_BLK_SZ]; |
53 | u32 rand_data_valid; |
54 | struct crypto_cipher *tfm; |
55 | u32 flags; |
56 | }; |
57 | |
58 | static int dbg; |
59 | |
60 | static void hexdump(char *note, unsigned char *buf, unsigned int len) |
61 | { |
62 | if (dbg) { |
63 | printk(KERN_CRIT "%s", note); |
64 | print_hex_dump(KERN_CONT, "", DUMP_PREFIX_OFFSET, |
65 | 16, 1, |
66 | buf, len, false); |
67 | } |
68 | } |
69 | |
70 | #define dbgprint(format, args...) do {\ |
71 | if (dbg)\ |
72 | printk(format, ##args);\ |
73 | } while (0) |
74 | |
75 | static void xor_vectors(unsigned char *in1, unsigned char *in2, |
76 | unsigned char *out, unsigned int size) |
77 | { |
78 | int i; |
79 | |
80 | for (i = 0; i < size; i++) |
81 | out[i] = in1[i] ^ in2[i]; |
82 | |
83 | } |
84 | /* |
85 | * Returns DEFAULT_BLK_SZ bytes of random data per call |
86 | * returns 0 if generation succeded, <0 if something went wrong |
87 | */ |
88 | static int _get_more_prng_bytes(struct prng_context *ctx, int cont_test) |
89 | { |
90 | int i; |
91 | unsigned char tmp[DEFAULT_BLK_SZ]; |
92 | unsigned char *output = NULL; |
93 | |
94 | |
95 | dbgprint(KERN_CRIT "Calling _get_more_prng_bytes for context %p\n", |
96 | ctx); |
97 | |
98 | hexdump("Input DT: ", ctx->DT, DEFAULT_BLK_SZ); |
99 | hexdump("Input I: ", ctx->I, DEFAULT_BLK_SZ); |
100 | hexdump("Input V: ", ctx->V, DEFAULT_BLK_SZ); |
101 | |
102 | /* |
103 | * This algorithm is a 3 stage state machine |
104 | */ |
105 | for (i = 0; i < 3; i++) { |
106 | |
107 | switch (i) { |
108 | case 0: |
109 | /* |
110 | * Start by encrypting the counter value |
111 | * This gives us an intermediate value I |
112 | */ |
113 | memcpy(tmp, ctx->DT, DEFAULT_BLK_SZ); |
114 | output = ctx->I; |
115 | hexdump("tmp stage 0: ", tmp, DEFAULT_BLK_SZ); |
116 | break; |
117 | case 1: |
118 | |
119 | /* |
120 | * Next xor I with our secret vector V |
121 | * encrypt that result to obtain our |
122 | * pseudo random data which we output |
123 | */ |
124 | xor_vectors(ctx->I, ctx->V, tmp, DEFAULT_BLK_SZ); |
125 | hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ); |
126 | output = ctx->rand_data; |
127 | break; |
128 | case 2: |
129 | /* |
130 | * First check that we didn't produce the same |
131 | * random data that we did last time around through this |
132 | */ |
133 | if (!memcmp(ctx->rand_data, ctx->last_rand_data, |
134 | DEFAULT_BLK_SZ)) { |
135 | if (cont_test) { |
136 | panic("cprng %p Failed repetition check!\n", |
137 | ctx); |
138 | } |
139 | |
140 | printk(KERN_ERR |
141 | "ctx %p Failed repetition check!\n", |
142 | ctx); |
143 | |
144 | ctx->flags |= PRNG_NEED_RESET; |
145 | return -EINVAL; |
146 | } |
147 | memcpy(ctx->last_rand_data, ctx->rand_data, |
148 | DEFAULT_BLK_SZ); |
149 | |
150 | /* |
151 | * Lastly xor the random data with I |
152 | * and encrypt that to obtain a new secret vector V |
153 | */ |
154 | xor_vectors(ctx->rand_data, ctx->I, tmp, |
155 | DEFAULT_BLK_SZ); |
156 | output = ctx->V; |
157 | hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ); |
158 | break; |
159 | } |
160 | |
161 | |
162 | /* do the encryption */ |
163 | crypto_cipher_encrypt_one(ctx->tfm, output, tmp); |
164 | |
165 | } |
166 | |
167 | /* |
168 | * Now update our DT value |
169 | */ |
170 | for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) { |
171 | ctx->DT[i] += 1; |
172 | if (ctx->DT[i] != 0) |
173 | break; |
174 | } |
175 | |
176 | dbgprint("Returning new block for context %p\n", ctx); |
177 | ctx->rand_data_valid = 0; |
178 | |
179 | hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ); |
180 | hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ); |
181 | hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ); |
182 | hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ); |
183 | |
184 | return 0; |
185 | } |
186 | |
187 | /* Our exported functions */ |
188 | static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx, |
189 | int do_cont_test) |
190 | { |
191 | unsigned char *ptr = buf; |
192 | unsigned int byte_count = (unsigned int)nbytes; |
193 | int err; |
194 | |
195 | |
196 | spin_lock_bh(&ctx->prng_lock); |
197 | |
198 | err = -EINVAL; |
199 | if (ctx->flags & PRNG_NEED_RESET) |
200 | goto done; |
201 | |
202 | /* |
203 | * If the FIXED_SIZE flag is on, only return whole blocks of |
204 | * pseudo random data |
205 | */ |
206 | err = -EINVAL; |
207 | if (ctx->flags & PRNG_FIXED_SIZE) { |
208 | if (nbytes < DEFAULT_BLK_SZ) |
209 | goto done; |
210 | byte_count = DEFAULT_BLK_SZ; |
211 | } |
212 | |
213 | err = byte_count; |
214 | |
215 | dbgprint(KERN_CRIT "getting %d random bytes for context %p\n", |
216 | byte_count, ctx); |
217 | |
218 | |
219 | remainder: |
220 | if (ctx->rand_data_valid == DEFAULT_BLK_SZ) { |
221 | if (_get_more_prng_bytes(ctx, do_cont_test) < 0) { |
222 | memset(buf, 0, nbytes); |
223 | err = -EINVAL; |
224 | goto done; |
225 | } |
226 | } |
227 | |
228 | /* |
229 | * Copy any data less than an entire block |
230 | */ |
231 | if (byte_count < DEFAULT_BLK_SZ) { |
232 | empty_rbuf: |
233 | for (; ctx->rand_data_valid < DEFAULT_BLK_SZ; |
234 | ctx->rand_data_valid++) { |
235 | *ptr = ctx->rand_data[ctx->rand_data_valid]; |
236 | ptr++; |
237 | byte_count--; |
238 | if (byte_count == 0) |
239 | goto done; |
240 | } |
241 | } |
242 | |
243 | /* |
244 | * Now copy whole blocks |
245 | */ |
246 | for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) { |
247 | if (ctx->rand_data_valid == DEFAULT_BLK_SZ) { |
248 | if (_get_more_prng_bytes(ctx, do_cont_test) < 0) { |
249 | memset(buf, 0, nbytes); |
250 | err = -EINVAL; |
251 | goto done; |
252 | } |
253 | } |
254 | if (ctx->rand_data_valid > 0) |
255 | goto empty_rbuf; |
256 | memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ); |
257 | ctx->rand_data_valid += DEFAULT_BLK_SZ; |
258 | ptr += DEFAULT_BLK_SZ; |
259 | } |
260 | |
261 | /* |
262 | * Now go back and get any remaining partial block |
263 | */ |
264 | if (byte_count) |
265 | goto remainder; |
266 | |
267 | done: |
268 | spin_unlock_bh(&ctx->prng_lock); |
269 | dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n", |
270 | err, ctx); |
271 | return err; |
272 | } |
273 | |
274 | static void free_prng_context(struct prng_context *ctx) |
275 | { |
276 | crypto_free_cipher(ctx->tfm); |
277 | } |
278 | |
279 | static int reset_prng_context(struct prng_context *ctx, |
280 | unsigned char *key, size_t klen, |
281 | unsigned char *V, unsigned char *DT) |
282 | { |
283 | int ret; |
284 | unsigned char *prng_key; |
285 | |
286 | spin_lock_bh(&ctx->prng_lock); |
287 | ctx->flags |= PRNG_NEED_RESET; |
288 | |
289 | prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY; |
290 | |
291 | if (!key) |
292 | klen = DEFAULT_PRNG_KSZ; |
293 | |
294 | if (V) |
295 | memcpy(ctx->V, V, DEFAULT_BLK_SZ); |
296 | else |
297 | memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ); |
298 | |
299 | if (DT) |
300 | memcpy(ctx->DT, DT, DEFAULT_BLK_SZ); |
301 | else |
302 | memset(ctx->DT, 0, DEFAULT_BLK_SZ); |
303 | |
304 | memset(ctx->rand_data, 0, DEFAULT_BLK_SZ); |
305 | memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ); |
306 | |
307 | ctx->rand_data_valid = DEFAULT_BLK_SZ; |
308 | |
309 | ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen); |
310 | if (ret) { |
311 | dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n", |
312 | crypto_cipher_get_flags(ctx->tfm)); |
313 | goto out; |
314 | } |
315 | |
316 | ret = 0; |
317 | ctx->flags &= ~PRNG_NEED_RESET; |
318 | out: |
319 | spin_unlock_bh(&ctx->prng_lock); |
320 | return ret; |
321 | } |
322 | |
323 | static int cprng_init(struct crypto_tfm *tfm) |
324 | { |
325 | struct prng_context *ctx = crypto_tfm_ctx(tfm); |
326 | |
327 | spin_lock_init(&ctx->prng_lock); |
328 | ctx->tfm = crypto_alloc_cipher("aes", 0, 0); |
329 | if (IS_ERR(ctx->tfm)) { |
330 | dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n", |
331 | ctx); |
332 | return PTR_ERR(ctx->tfm); |
333 | } |
334 | |
335 | if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0) |
336 | return -EINVAL; |
337 | |
338 | /* |
339 | * after allocation, we should always force the user to reset |
340 | * so they don't inadvertently use the insecure default values |
341 | * without specifying them intentially |
342 | */ |
343 | ctx->flags |= PRNG_NEED_RESET; |
344 | return 0; |
345 | } |
346 | |
347 | static void cprng_exit(struct crypto_tfm *tfm) |
348 | { |
349 | free_prng_context(crypto_tfm_ctx(tfm)); |
350 | } |
351 | |
352 | static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata, |
353 | unsigned int dlen) |
354 | { |
355 | struct prng_context *prng = crypto_rng_ctx(tfm); |
356 | |
357 | return get_prng_bytes(rdata, dlen, prng, 0); |
358 | } |
359 | |
360 | /* |
361 | * This is the cprng_registered reset method the seed value is |
362 | * interpreted as the tuple { V KEY DT} |
363 | * V and KEY are required during reset, and DT is optional, detected |
364 | * as being present by testing the length of the seed |
365 | */ |
366 | static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen) |
367 | { |
368 | struct prng_context *prng = crypto_rng_ctx(tfm); |
369 | u8 *key = seed + DEFAULT_BLK_SZ; |
370 | u8 *dt = NULL; |
371 | |
372 | if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ) |
373 | return -EINVAL; |
374 | |
375 | if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ)) |
376 | dt = key + DEFAULT_PRNG_KSZ; |
377 | |
378 | reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt); |
379 | |
380 | if (prng->flags & PRNG_NEED_RESET) |
381 | return -EINVAL; |
382 | return 0; |
383 | } |
384 | |
385 | static struct crypto_alg rng_alg = { |
386 | .cra_name = "stdrng", |
387 | .cra_driver_name = "ansi_cprng", |
388 | .cra_priority = 100, |
389 | .cra_flags = CRYPTO_ALG_TYPE_RNG, |
390 | .cra_ctxsize = sizeof(struct prng_context), |
391 | .cra_type = &crypto_rng_type, |
392 | .cra_module = THIS_MODULE, |
393 | .cra_list = LIST_HEAD_INIT(rng_alg.cra_list), |
394 | .cra_init = cprng_init, |
395 | .cra_exit = cprng_exit, |
396 | .cra_u = { |
397 | .rng = { |
398 | .rng_make_random = cprng_get_random, |
399 | .rng_reset = cprng_reset, |
400 | .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ, |
401 | } |
402 | } |
403 | }; |
404 | |
405 | #ifdef CONFIG_CRYPTO_FIPS |
406 | static int fips_cprng_get_random(struct crypto_rng *tfm, u8 *rdata, |
407 | unsigned int dlen) |
408 | { |
409 | struct prng_context *prng = crypto_rng_ctx(tfm); |
410 | |
411 | return get_prng_bytes(rdata, dlen, prng, 1); |
412 | } |
413 | |
414 | static int fips_cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen) |
415 | { |
416 | u8 rdata[DEFAULT_BLK_SZ]; |
417 | int rc; |
418 | |
419 | struct prng_context *prng = crypto_rng_ctx(tfm); |
420 | |
421 | rc = cprng_reset(tfm, seed, slen); |
422 | |
423 | if (!rc) |
424 | goto out; |
425 | |
426 | /* this primes our continuity test */ |
427 | rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0); |
428 | prng->rand_data_valid = DEFAULT_BLK_SZ; |
429 | |
430 | out: |
431 | return rc; |
432 | } |
433 | |
434 | static struct crypto_alg fips_rng_alg = { |
435 | .cra_name = "fips(ansi_cprng)", |
436 | .cra_driver_name = "fips_ansi_cprng", |
437 | .cra_priority = 300, |
438 | .cra_flags = CRYPTO_ALG_TYPE_RNG, |
439 | .cra_ctxsize = sizeof(struct prng_context), |
440 | .cra_type = &crypto_rng_type, |
441 | .cra_module = THIS_MODULE, |
442 | .cra_list = LIST_HEAD_INIT(rng_alg.cra_list), |
443 | .cra_init = cprng_init, |
444 | .cra_exit = cprng_exit, |
445 | .cra_u = { |
446 | .rng = { |
447 | .rng_make_random = fips_cprng_get_random, |
448 | .rng_reset = fips_cprng_reset, |
449 | .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ, |
450 | } |
451 | } |
452 | }; |
453 | #endif |
454 | |
455 | /* Module initalization */ |
456 | static int __init prng_mod_init(void) |
457 | { |
458 | int rc = 0; |
459 | |
460 | rc = crypto_register_alg(&rng_alg); |
461 | #ifdef CONFIG_CRYPTO_FIPS |
462 | if (rc) |
463 | goto out; |
464 | |
465 | rc = crypto_register_alg(&fips_rng_alg); |
466 | |
467 | out: |
468 | #endif |
469 | return rc; |
470 | } |
471 | |
472 | static void __exit prng_mod_fini(void) |
473 | { |
474 | crypto_unregister_alg(&rng_alg); |
475 | #ifdef CONFIG_CRYPTO_FIPS |
476 | crypto_unregister_alg(&fips_rng_alg); |
477 | #endif |
478 | return; |
479 | } |
480 | |
481 | MODULE_LICENSE("GPL"); |
482 | MODULE_DESCRIPTION("Software Pseudo Random Number Generator"); |
483 | MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>"); |
484 | module_param(dbg, int, 0); |
485 | MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)"); |
486 | module_init(prng_mod_init); |
487 | module_exit(prng_mod_fini); |
488 | MODULE_ALIAS("stdrng"); |
489 |
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