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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 | |
86 | * returns 0 if generation succeded, <0 if something went wrong | |
87 | */ | |
88 | static int _get_more_prng_bytes(struct prng_context *ctx) | |
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 | printk(KERN_ERR | |
136 | "ctx %p Failed repetition check!\n", | |
137 | ctx); | |
138 | ctx->flags |= PRNG_NEED_RESET; | |
139 | return -EINVAL; | |
140 | } | |
141 | memcpy(ctx->last_rand_data, ctx->rand_data, | |
142 | DEFAULT_BLK_SZ); | |
143 | ||
144 | /* | |
145 | * Lastly xor the random data with I | |
146 | * and encrypt that to obtain a new secret vector V | |
147 | */ | |
148 | xor_vectors(ctx->rand_data, ctx->I, tmp, | |
149 | DEFAULT_BLK_SZ); | |
150 | output = ctx->V; | |
151 | hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ); | |
152 | break; | |
153 | } | |
154 | ||
155 | ||
156 | /* do the encryption */ | |
157 | crypto_cipher_encrypt_one(ctx->tfm, output, tmp); | |
158 | ||
159 | } | |
160 | ||
161 | /* | |
162 | * Now update our DT value | |
163 | */ | |
164 | for (i = 0; i < DEFAULT_BLK_SZ; i++) { | |
165 | ctx->DT[i] += 1; | |
166 | if (ctx->DT[i] != 0) | |
167 | break; | |
168 | } | |
169 | ||
170 | dbgprint("Returning new block for context %p\n", ctx); | |
171 | ctx->rand_data_valid = 0; | |
172 | ||
173 | hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ); | |
174 | hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ); | |
175 | hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ); | |
176 | hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ); | |
177 | ||
178 | return 0; | |
179 | } | |
180 | ||
181 | /* Our exported functions */ | |
182 | static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx) | |
183 | { | |
184 | unsigned long flags; | |
185 | unsigned char *ptr = buf; | |
186 | unsigned int byte_count = (unsigned int)nbytes; | |
187 | int err; | |
188 | ||
189 | ||
190 | if (nbytes < 0) | |
191 | return -EINVAL; | |
192 | ||
193 | spin_lock_irqsave(&ctx->prng_lock, flags); | |
194 | ||
195 | err = -EINVAL; | |
196 | if (ctx->flags & PRNG_NEED_RESET) | |
197 | goto done; | |
198 | ||
199 | /* | |
200 | * If the FIXED_SIZE flag is on, only return whole blocks of | |
201 | * pseudo random data | |
202 | */ | |
203 | err = -EINVAL; | |
204 | if (ctx->flags & PRNG_FIXED_SIZE) { | |
205 | if (nbytes < DEFAULT_BLK_SZ) | |
206 | goto done; | |
207 | byte_count = DEFAULT_BLK_SZ; | |
208 | } | |
209 | ||
210 | err = byte_count; | |
211 | ||
212 | dbgprint(KERN_CRIT "getting %d random bytes for context %p\n", | |
213 | byte_count, ctx); | |
214 | ||
215 | ||
216 | remainder: | |
217 | if (ctx->rand_data_valid == DEFAULT_BLK_SZ) { | |
218 | if (_get_more_prng_bytes(ctx) < 0) { | |
219 | memset(buf, 0, nbytes); | |
220 | err = -EINVAL; | |
221 | goto done; | |
222 | } | |
223 | } | |
224 | ||
225 | /* | |
226 | * Copy up to the next whole block size | |
227 | */ | |
228 | if (byte_count < DEFAULT_BLK_SZ) { | |
229 | for (; ctx->rand_data_valid < DEFAULT_BLK_SZ; | |
230 | ctx->rand_data_valid++) { | |
231 | *ptr = ctx->rand_data[ctx->rand_data_valid]; | |
232 | ptr++; | |
233 | byte_count--; | |
234 | if (byte_count == 0) | |
235 | goto done; | |
236 | } | |
237 | } | |
238 | ||
239 | /* | |
240 | * Now copy whole blocks | |
241 | */ | |
242 | for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) { | |
243 | if (_get_more_prng_bytes(ctx) < 0) { | |
244 | memset(buf, 0, nbytes); | |
245 | err = -EINVAL; | |
246 | goto done; | |
247 | } | |
248 | memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ); | |
249 | ctx->rand_data_valid += DEFAULT_BLK_SZ; | |
250 | ptr += DEFAULT_BLK_SZ; | |
251 | } | |
252 | ||
253 | /* | |
254 | * Now copy any extra partial data | |
255 | */ | |
256 | if (byte_count) | |
257 | goto remainder; | |
258 | ||
259 | done: | |
260 | spin_unlock_irqrestore(&ctx->prng_lock, flags); | |
261 | dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n", | |
262 | err, ctx); | |
263 | return err; | |
264 | } | |
265 | ||
266 | static void free_prng_context(struct prng_context *ctx) | |
267 | { | |
268 | crypto_free_cipher(ctx->tfm); | |
269 | } | |
270 | ||
271 | static int reset_prng_context(struct prng_context *ctx, | |
272 | unsigned char *key, size_t klen, | |
273 | unsigned char *V, unsigned char *DT) | |
274 | { | |
275 | int ret; | |
276 | int rc = -EINVAL; | |
277 | unsigned char *prng_key; | |
278 | ||
279 | spin_lock(&ctx->prng_lock); | |
280 | ctx->flags |= PRNG_NEED_RESET; | |
281 | ||
282 | prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY; | |
283 | ||
284 | if (!key) | |
285 | klen = DEFAULT_PRNG_KSZ; | |
286 | ||
287 | if (V) | |
288 | memcpy(ctx->V, V, DEFAULT_BLK_SZ); | |
289 | else | |
290 | memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ); | |
291 | ||
292 | if (DT) | |
293 | memcpy(ctx->DT, DT, DEFAULT_BLK_SZ); | |
294 | else | |
295 | memset(ctx->DT, 0, DEFAULT_BLK_SZ); | |
296 | ||
297 | memset(ctx->rand_data, 0, DEFAULT_BLK_SZ); | |
298 | memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ); | |
299 | ||
300 | if (ctx->tfm) | |
301 | crypto_free_cipher(ctx->tfm); | |
302 | ||
303 | ctx->tfm = crypto_alloc_cipher("aes", 0, 0); | |
304 | if (IS_ERR(ctx->tfm)) { | |
305 | dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n", | |
306 | ctx); | |
307 | ctx->tfm = NULL; | |
308 | goto out; | |
309 | } | |
310 | ||
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)); | |
317 | crypto_free_cipher(ctx->tfm); | |
318 | goto out; | |
319 | } | |
320 | ||
321 | rc = 0; | |
322 | ctx->flags &= ~PRNG_NEED_RESET; | |
323 | out: | |
324 | spin_unlock(&ctx->prng_lock); | |
325 | ||
326 | return rc; | |
327 | ||
328 | } | |
329 | ||
330 | static int cprng_init(struct crypto_tfm *tfm) | |
331 | { | |
332 | struct prng_context *ctx = crypto_tfm_ctx(tfm); | |
333 | ||
334 | spin_lock_init(&ctx->prng_lock); | |
335 | ||
336 | return reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL); | |
337 | } | |
338 | ||
339 | static void cprng_exit(struct crypto_tfm *tfm) | |
340 | { | |
341 | free_prng_context(crypto_tfm_ctx(tfm)); | |
342 | } | |
343 | ||
344 | static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata, | |
345 | unsigned int dlen) | |
346 | { | |
347 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
348 | ||
349 | return get_prng_bytes(rdata, dlen, prng); | |
350 | } | |
351 | ||
352 | static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen) | |
353 | { | |
354 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
355 | u8 *key = seed + DEFAULT_PRNG_KSZ; | |
356 | ||
357 | if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ) | |
358 | return -EINVAL; | |
359 | ||
360 | reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, NULL); | |
361 | ||
362 | if (prng->flags & PRNG_NEED_RESET) | |
363 | return -EINVAL; | |
364 | return 0; | |
365 | } | |
366 | ||
367 | static struct crypto_alg rng_alg = { | |
368 | .cra_name = "stdrng", | |
369 | .cra_driver_name = "ansi_cprng", | |
370 | .cra_priority = 100, | |
371 | .cra_flags = CRYPTO_ALG_TYPE_RNG, | |
372 | .cra_ctxsize = sizeof(struct prng_context), | |
373 | .cra_type = &crypto_rng_type, | |
374 | .cra_module = THIS_MODULE, | |
375 | .cra_list = LIST_HEAD_INIT(rng_alg.cra_list), | |
376 | .cra_init = cprng_init, | |
377 | .cra_exit = cprng_exit, | |
378 | .cra_u = { | |
379 | .rng = { | |
380 | .rng_make_random = cprng_get_random, | |
381 | .rng_reset = cprng_reset, | |
382 | .seedsize = DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ, | |
383 | } | |
384 | } | |
385 | }; | |
386 | ||
387 | ||
388 | /* Module initalization */ | |
389 | static int __init prng_mod_init(void) | |
390 | { | |
391 | int ret = 0; | |
392 | ||
393 | if (fips_enabled) | |
394 | rng_alg.cra_priority += 200; | |
395 | ||
396 | ret = crypto_register_alg(&rng_alg); | |
397 | ||
398 | if (ret) | |
399 | goto out; | |
400 | out: | |
401 | return 0; | |
402 | } | |
403 | ||
404 | static void __exit prng_mod_fini(void) | |
405 | { | |
406 | crypto_unregister_alg(&rng_alg); | |
407 | return; | |
408 | } | |
409 | ||
410 | MODULE_LICENSE("GPL"); | |
411 | MODULE_DESCRIPTION("Software Pseudo Random Number Generator"); | |
412 | MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>"); | |
413 | module_param(dbg, int, 0); | |
414 | MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)"); | |
415 | module_init(prng_mod_init); | |
416 | module_exit(prng_mod_fini); | |
417 | MODULE_ALIAS("stdrng"); |