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Commit | Line | Data |
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17f0f4a4 NH |
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 | |
25985edc | 86 | * returns 0 if generation succeeded, <0 if something went wrong |
17f0f4a4 | 87 | */ |
667b6294 | 88 | static int _get_more_prng_bytes(struct prng_context *ctx, int cont_test) |
17f0f4a4 NH |
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)) { | |
667b6294 | 135 | if (cont_test) { |
c5b1e545 NH |
136 | panic("cprng %p Failed repetition check!\n", |
137 | ctx); | |
138 | } | |
139 | ||
17f0f4a4 NH |
140 | printk(KERN_ERR |
141 | "ctx %p Failed repetition check!\n", | |
142 | ctx); | |
c5b1e545 | 143 | |
17f0f4a4 NH |
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 | */ | |
09fbf7c0 | 170 | for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) { |
17f0f4a4 NH |
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 */ | |
667b6294 NH |
188 | static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx, |
189 | int do_cont_test) | |
17f0f4a4 | 190 | { |
17f0f4a4 NH |
191 | unsigned char *ptr = buf; |
192 | unsigned int byte_count = (unsigned int)nbytes; | |
193 | int err; | |
194 | ||
195 | ||
ed940700 | 196 | spin_lock_bh(&ctx->prng_lock); |
17f0f4a4 NH |
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 | ||
cde001e4 SM |
213 | /* |
214 | * Return 0 in case of success as mandated by the kernel | |
215 | * crypto API interface definition. | |
216 | */ | |
217 | err = 0; | |
17f0f4a4 NH |
218 | |
219 | dbgprint(KERN_CRIT "getting %d random bytes for context %p\n", | |
220 | byte_count, ctx); | |
221 | ||
222 | ||
223 | remainder: | |
224 | if (ctx->rand_data_valid == DEFAULT_BLK_SZ) { | |
667b6294 | 225 | if (_get_more_prng_bytes(ctx, do_cont_test) < 0) { |
17f0f4a4 NH |
226 | memset(buf, 0, nbytes); |
227 | err = -EINVAL; | |
228 | goto done; | |
229 | } | |
230 | } | |
231 | ||
232 | /* | |
aa1a85db | 233 | * Copy any data less than an entire block |
17f0f4a4 NH |
234 | */ |
235 | if (byte_count < DEFAULT_BLK_SZ) { | |
aa1a85db | 236 | empty_rbuf: |
714b33d1 | 237 | while (ctx->rand_data_valid < DEFAULT_BLK_SZ) { |
17f0f4a4 NH |
238 | *ptr = ctx->rand_data[ctx->rand_data_valid]; |
239 | ptr++; | |
240 | byte_count--; | |
714b33d1 | 241 | ctx->rand_data_valid++; |
17f0f4a4 NH |
242 | if (byte_count == 0) |
243 | goto done; | |
244 | } | |
245 | } | |
246 | ||
247 | /* | |
248 | * Now copy whole blocks | |
249 | */ | |
250 | for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) { | |
aa1a85db | 251 | if (ctx->rand_data_valid == DEFAULT_BLK_SZ) { |
667b6294 | 252 | if (_get_more_prng_bytes(ctx, do_cont_test) < 0) { |
aa1a85db JW |
253 | memset(buf, 0, nbytes); |
254 | err = -EINVAL; | |
255 | goto done; | |
256 | } | |
17f0f4a4 | 257 | } |
aa1a85db JW |
258 | if (ctx->rand_data_valid > 0) |
259 | goto empty_rbuf; | |
17f0f4a4 NH |
260 | memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ); |
261 | ctx->rand_data_valid += DEFAULT_BLK_SZ; | |
262 | ptr += DEFAULT_BLK_SZ; | |
263 | } | |
264 | ||
265 | /* | |
aa1a85db | 266 | * Now go back and get any remaining partial block |
17f0f4a4 NH |
267 | */ |
268 | if (byte_count) | |
269 | goto remainder; | |
270 | ||
271 | done: | |
ed940700 | 272 | spin_unlock_bh(&ctx->prng_lock); |
17f0f4a4 NH |
273 | dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n", |
274 | err, ctx); | |
275 | return err; | |
276 | } | |
277 | ||
278 | static void free_prng_context(struct prng_context *ctx) | |
279 | { | |
280 | crypto_free_cipher(ctx->tfm); | |
281 | } | |
282 | ||
283 | static int reset_prng_context(struct prng_context *ctx, | |
284 | unsigned char *key, size_t klen, | |
285 | unsigned char *V, unsigned char *DT) | |
286 | { | |
287 | int ret; | |
17f0f4a4 NH |
288 | unsigned char *prng_key; |
289 | ||
ed940700 | 290 | spin_lock_bh(&ctx->prng_lock); |
17f0f4a4 NH |
291 | ctx->flags |= PRNG_NEED_RESET; |
292 | ||
293 | prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY; | |
294 | ||
295 | if (!key) | |
296 | klen = DEFAULT_PRNG_KSZ; | |
297 | ||
298 | if (V) | |
299 | memcpy(ctx->V, V, DEFAULT_BLK_SZ); | |
300 | else | |
301 | memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ); | |
302 | ||
303 | if (DT) | |
304 | memcpy(ctx->DT, DT, DEFAULT_BLK_SZ); | |
305 | else | |
306 | memset(ctx->DT, 0, DEFAULT_BLK_SZ); | |
307 | ||
308 | memset(ctx->rand_data, 0, DEFAULT_BLK_SZ); | |
309 | memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ); | |
310 | ||
17f0f4a4 NH |
311 | ctx->rand_data_valid = DEFAULT_BLK_SZ; |
312 | ||
313 | ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen); | |
314 | if (ret) { | |
315 | dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n", | |
316 | crypto_cipher_get_flags(ctx->tfm)); | |
17f0f4a4 NH |
317 | goto out; |
318 | } | |
319 | ||
fd09d7fa | 320 | ret = 0; |
17f0f4a4 NH |
321 | ctx->flags &= ~PRNG_NEED_RESET; |
322 | out: | |
ed940700 | 323 | spin_unlock_bh(&ctx->prng_lock); |
fd09d7fa | 324 | return ret; |
17f0f4a4 NH |
325 | } |
326 | ||
327 | static int cprng_init(struct crypto_tfm *tfm) | |
328 | { | |
329 | struct prng_context *ctx = crypto_tfm_ctx(tfm); | |
330 | ||
331 | spin_lock_init(&ctx->prng_lock); | |
fd09d7fa SAS |
332 | ctx->tfm = crypto_alloc_cipher("aes", 0, 0); |
333 | if (IS_ERR(ctx->tfm)) { | |
334 | dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n", | |
335 | ctx); | |
336 | return PTR_ERR(ctx->tfm); | |
337 | } | |
17f0f4a4 | 338 | |
d7992f42 NH |
339 | if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0) |
340 | return -EINVAL; | |
341 | ||
342 | /* | |
343 | * after allocation, we should always force the user to reset | |
344 | * so they don't inadvertently use the insecure default values | |
345 | * without specifying them intentially | |
346 | */ | |
347 | ctx->flags |= PRNG_NEED_RESET; | |
348 | return 0; | |
17f0f4a4 NH |
349 | } |
350 | ||
351 | static void cprng_exit(struct crypto_tfm *tfm) | |
352 | { | |
353 | free_prng_context(crypto_tfm_ctx(tfm)); | |
354 | } | |
355 | ||
356 | static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata, | |
357 | unsigned int dlen) | |
358 | { | |
359 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
360 | ||
667b6294 NH |
361 | return get_prng_bytes(rdata, dlen, prng, 0); |
362 | } | |
363 | ||
2566578a NH |
364 | /* |
365 | * This is the cprng_registered reset method the seed value is | |
366 | * interpreted as the tuple { V KEY DT} | |
367 | * V and KEY are required during reset, and DT is optional, detected | |
368 | * as being present by testing the length of the seed | |
369 | */ | |
17f0f4a4 NH |
370 | static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen) |
371 | { | |
372 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
2566578a NH |
373 | u8 *key = seed + DEFAULT_BLK_SZ; |
374 | u8 *dt = NULL; | |
17f0f4a4 NH |
375 | |
376 | if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ) | |
377 | return -EINVAL; | |
378 | ||
2566578a NH |
379 | if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ)) |
380 | dt = key + DEFAULT_PRNG_KSZ; | |
381 | ||
382 | reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt); | |
17f0f4a4 NH |
383 | |
384 | if (prng->flags & PRNG_NEED_RESET) | |
385 | return -EINVAL; | |
386 | return 0; | |
387 | } | |
388 | ||
667b6294 | 389 | #ifdef CONFIG_CRYPTO_FIPS |
2f32bfd8 JSR |
390 | static int fips_cprng_get_random(struct crypto_rng *tfm, u8 *rdata, |
391 | unsigned int dlen) | |
392 | { | |
393 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
394 | ||
395 | return get_prng_bytes(rdata, dlen, prng, 1); | |
396 | } | |
397 | ||
398 | static int fips_cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen) | |
399 | { | |
400 | u8 rdata[DEFAULT_BLK_SZ]; | |
505172e1 | 401 | u8 *key = seed + DEFAULT_BLK_SZ; |
2f32bfd8 JSR |
402 | int rc; |
403 | ||
404 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
405 | ||
505172e1 JW |
406 | if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ) |
407 | return -EINVAL; | |
408 | ||
409 | /* fips strictly requires seed != key */ | |
410 | if (!memcmp(seed, key, DEFAULT_PRNG_KSZ)) | |
411 | return -EINVAL; | |
412 | ||
2f32bfd8 JSR |
413 | rc = cprng_reset(tfm, seed, slen); |
414 | ||
415 | if (!rc) | |
416 | goto out; | |
417 | ||
418 | /* this primes our continuity test */ | |
419 | rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0); | |
420 | prng->rand_data_valid = DEFAULT_BLK_SZ; | |
421 | ||
422 | out: | |
423 | return rc; | |
424 | } | |
8fc229a5 | 425 | #endif |
2f32bfd8 | 426 | |
8fc229a5 JK |
427 | static struct crypto_alg rng_algs[] = { { |
428 | .cra_name = "stdrng", | |
429 | .cra_driver_name = "ansi_cprng", | |
430 | .cra_priority = 100, | |
431 | .cra_flags = CRYPTO_ALG_TYPE_RNG, | |
432 | .cra_ctxsize = sizeof(struct prng_context), | |
433 | .cra_type = &crypto_rng_type, | |
434 | .cra_module = THIS_MODULE, | |
435 | .cra_init = cprng_init, | |
436 | .cra_exit = cprng_exit, | |
437 | .cra_u = { | |
438 | .rng = { | |
439 | .rng_make_random = cprng_get_random, | |
440 | .rng_reset = cprng_reset, | |
441 | .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ, | |
442 | } | |
443 | } | |
444 | #ifdef CONFIG_CRYPTO_FIPS | |
445 | }, { | |
667b6294 NH |
446 | .cra_name = "fips(ansi_cprng)", |
447 | .cra_driver_name = "fips_ansi_cprng", | |
448 | .cra_priority = 300, | |
449 | .cra_flags = CRYPTO_ALG_TYPE_RNG, | |
450 | .cra_ctxsize = sizeof(struct prng_context), | |
451 | .cra_type = &crypto_rng_type, | |
452 | .cra_module = THIS_MODULE, | |
667b6294 NH |
453 | .cra_init = cprng_init, |
454 | .cra_exit = cprng_exit, | |
455 | .cra_u = { | |
456 | .rng = { | |
457 | .rng_make_random = fips_cprng_get_random, | |
458 | .rng_reset = fips_cprng_reset, | |
459 | .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ, | |
460 | } | |
461 | } | |
667b6294 | 462 | #endif |
8fc229a5 | 463 | } }; |
17f0f4a4 NH |
464 | |
465 | /* Module initalization */ | |
466 | static int __init prng_mod_init(void) | |
467 | { | |
8fc229a5 | 468 | return crypto_register_algs(rng_algs, ARRAY_SIZE(rng_algs)); |
17f0f4a4 NH |
469 | } |
470 | ||
471 | static void __exit prng_mod_fini(void) | |
472 | { | |
8fc229a5 | 473 | crypto_unregister_algs(rng_algs, ARRAY_SIZE(rng_algs)); |
17f0f4a4 NH |
474 | } |
475 | ||
476 | MODULE_LICENSE("GPL"); | |
477 | MODULE_DESCRIPTION("Software Pseudo Random Number Generator"); | |
478 | MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>"); | |
479 | module_param(dbg, int, 0); | |
480 | MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)"); | |
481 | module_init(prng_mod_init); | |
482 | module_exit(prng_mod_fini); | |
5d26a105 | 483 | MODULE_ALIAS_CRYPTO("stdrng"); |
3e14dcf7 | 484 | MODULE_ALIAS_CRYPTO("ansi_cprng"); |