Commit | Line | Data |
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59e0b61c | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
17f0f4a4 NH |
2 | /* |
3 | * PRNG: Pseudo Random Number Generator | |
4 | * Based on NIST Recommended PRNG From ANSI X9.31 Appendix A.2.4 using | |
5 | * AES 128 cipher | |
6 | * | |
7 | * (C) Neil Horman <nhorman@tuxdriver.com> | |
17f0f4a4 NH |
8 | */ |
9 | ||
10 | #include <crypto/internal/rng.h> | |
11 | #include <linux/err.h> | |
12 | #include <linux/init.h> | |
13 | #include <linux/module.h> | |
14 | #include <linux/moduleparam.h> | |
15 | #include <linux/string.h> | |
16 | ||
17f0f4a4 NH |
17 | #define DEFAULT_PRNG_KEY "0123456789abcdef" |
18 | #define DEFAULT_PRNG_KSZ 16 | |
19 | #define DEFAULT_BLK_SZ 16 | |
20 | #define DEFAULT_V_SEED "zaybxcwdveuftgsh" | |
21 | ||
22 | /* | |
23 | * Flags for the prng_context flags field | |
24 | */ | |
25 | ||
26 | #define PRNG_FIXED_SIZE 0x1 | |
27 | #define PRNG_NEED_RESET 0x2 | |
28 | ||
29 | /* | |
30 | * Note: DT is our counter value | |
31 | * I is our intermediate value | |
32 | * V is our seed vector | |
33 | * See http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf | |
34 | * for implementation details | |
35 | */ | |
36 | ||
37 | ||
38 | struct prng_context { | |
39 | spinlock_t prng_lock; | |
40 | unsigned char rand_data[DEFAULT_BLK_SZ]; | |
41 | unsigned char last_rand_data[DEFAULT_BLK_SZ]; | |
42 | unsigned char DT[DEFAULT_BLK_SZ]; | |
43 | unsigned char I[DEFAULT_BLK_SZ]; | |
44 | unsigned char V[DEFAULT_BLK_SZ]; | |
45 | u32 rand_data_valid; | |
46 | struct crypto_cipher *tfm; | |
47 | u32 flags; | |
48 | }; | |
49 | ||
50 | static int dbg; | |
51 | ||
52 | static void hexdump(char *note, unsigned char *buf, unsigned int len) | |
53 | { | |
54 | if (dbg) { | |
55 | printk(KERN_CRIT "%s", note); | |
56 | print_hex_dump(KERN_CONT, "", DUMP_PREFIX_OFFSET, | |
57 | 16, 1, | |
58 | buf, len, false); | |
59 | } | |
60 | } | |
61 | ||
62 | #define dbgprint(format, args...) do {\ | |
63 | if (dbg)\ | |
64 | printk(format, ##args);\ | |
65 | } while (0) | |
66 | ||
67 | static void xor_vectors(unsigned char *in1, unsigned char *in2, | |
68 | unsigned char *out, unsigned int size) | |
69 | { | |
70 | int i; | |
71 | ||
72 | for (i = 0; i < size; i++) | |
73 | out[i] = in1[i] ^ in2[i]; | |
74 | ||
75 | } | |
76 | /* | |
77 | * Returns DEFAULT_BLK_SZ bytes of random data per call | |
25985edc | 78 | * returns 0 if generation succeeded, <0 if something went wrong |
17f0f4a4 | 79 | */ |
667b6294 | 80 | static int _get_more_prng_bytes(struct prng_context *ctx, int cont_test) |
17f0f4a4 NH |
81 | { |
82 | int i; | |
83 | unsigned char tmp[DEFAULT_BLK_SZ]; | |
84 | unsigned char *output = NULL; | |
85 | ||
86 | ||
87 | dbgprint(KERN_CRIT "Calling _get_more_prng_bytes for context %p\n", | |
88 | ctx); | |
89 | ||
90 | hexdump("Input DT: ", ctx->DT, DEFAULT_BLK_SZ); | |
91 | hexdump("Input I: ", ctx->I, DEFAULT_BLK_SZ); | |
92 | hexdump("Input V: ", ctx->V, DEFAULT_BLK_SZ); | |
93 | ||
94 | /* | |
95 | * This algorithm is a 3 stage state machine | |
96 | */ | |
97 | for (i = 0; i < 3; i++) { | |
98 | ||
99 | switch (i) { | |
100 | case 0: | |
101 | /* | |
102 | * Start by encrypting the counter value | |
103 | * This gives us an intermediate value I | |
104 | */ | |
105 | memcpy(tmp, ctx->DT, DEFAULT_BLK_SZ); | |
106 | output = ctx->I; | |
107 | hexdump("tmp stage 0: ", tmp, DEFAULT_BLK_SZ); | |
108 | break; | |
109 | case 1: | |
110 | ||
111 | /* | |
112 | * Next xor I with our secret vector V | |
113 | * encrypt that result to obtain our | |
114 | * pseudo random data which we output | |
115 | */ | |
116 | xor_vectors(ctx->I, ctx->V, tmp, DEFAULT_BLK_SZ); | |
117 | hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ); | |
118 | output = ctx->rand_data; | |
119 | break; | |
120 | case 2: | |
121 | /* | |
122 | * First check that we didn't produce the same | |
123 | * random data that we did last time around through this | |
124 | */ | |
125 | if (!memcmp(ctx->rand_data, ctx->last_rand_data, | |
126 | DEFAULT_BLK_SZ)) { | |
667b6294 | 127 | if (cont_test) { |
c5b1e545 NH |
128 | panic("cprng %p Failed repetition check!\n", |
129 | ctx); | |
130 | } | |
131 | ||
17f0f4a4 NH |
132 | printk(KERN_ERR |
133 | "ctx %p Failed repetition check!\n", | |
134 | ctx); | |
c5b1e545 | 135 | |
17f0f4a4 NH |
136 | ctx->flags |= PRNG_NEED_RESET; |
137 | return -EINVAL; | |
138 | } | |
139 | memcpy(ctx->last_rand_data, ctx->rand_data, | |
140 | DEFAULT_BLK_SZ); | |
141 | ||
142 | /* | |
143 | * Lastly xor the random data with I | |
144 | * and encrypt that to obtain a new secret vector V | |
145 | */ | |
146 | xor_vectors(ctx->rand_data, ctx->I, tmp, | |
147 | DEFAULT_BLK_SZ); | |
148 | output = ctx->V; | |
149 | hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ); | |
150 | break; | |
151 | } | |
152 | ||
153 | ||
154 | /* do the encryption */ | |
155 | crypto_cipher_encrypt_one(ctx->tfm, output, tmp); | |
156 | ||
157 | } | |
158 | ||
159 | /* | |
160 | * Now update our DT value | |
161 | */ | |
09fbf7c0 | 162 | for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) { |
17f0f4a4 NH |
163 | ctx->DT[i] += 1; |
164 | if (ctx->DT[i] != 0) | |
165 | break; | |
166 | } | |
167 | ||
168 | dbgprint("Returning new block for context %p\n", ctx); | |
169 | ctx->rand_data_valid = 0; | |
170 | ||
171 | hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ); | |
172 | hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ); | |
173 | hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ); | |
174 | hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ); | |
175 | ||
176 | return 0; | |
177 | } | |
178 | ||
179 | /* Our exported functions */ | |
667b6294 NH |
180 | static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx, |
181 | int do_cont_test) | |
17f0f4a4 | 182 | { |
17f0f4a4 NH |
183 | unsigned char *ptr = buf; |
184 | unsigned int byte_count = (unsigned int)nbytes; | |
185 | int err; | |
186 | ||
187 | ||
ed940700 | 188 | spin_lock_bh(&ctx->prng_lock); |
17f0f4a4 NH |
189 | |
190 | err = -EINVAL; | |
191 | if (ctx->flags & PRNG_NEED_RESET) | |
192 | goto done; | |
193 | ||
194 | /* | |
195 | * If the FIXED_SIZE flag is on, only return whole blocks of | |
196 | * pseudo random data | |
197 | */ | |
198 | err = -EINVAL; | |
199 | if (ctx->flags & PRNG_FIXED_SIZE) { | |
200 | if (nbytes < DEFAULT_BLK_SZ) | |
201 | goto done; | |
202 | byte_count = DEFAULT_BLK_SZ; | |
203 | } | |
204 | ||
cde001e4 SM |
205 | /* |
206 | * Return 0 in case of success as mandated by the kernel | |
207 | * crypto API interface definition. | |
208 | */ | |
209 | err = 0; | |
17f0f4a4 NH |
210 | |
211 | dbgprint(KERN_CRIT "getting %d random bytes for context %p\n", | |
212 | byte_count, ctx); | |
213 | ||
214 | ||
215 | remainder: | |
216 | if (ctx->rand_data_valid == DEFAULT_BLK_SZ) { | |
667b6294 | 217 | if (_get_more_prng_bytes(ctx, do_cont_test) < 0) { |
17f0f4a4 NH |
218 | memset(buf, 0, nbytes); |
219 | err = -EINVAL; | |
220 | goto done; | |
221 | } | |
222 | } | |
223 | ||
224 | /* | |
aa1a85db | 225 | * Copy any data less than an entire block |
17f0f4a4 NH |
226 | */ |
227 | if (byte_count < DEFAULT_BLK_SZ) { | |
aa1a85db | 228 | empty_rbuf: |
714b33d1 | 229 | while (ctx->rand_data_valid < DEFAULT_BLK_SZ) { |
17f0f4a4 NH |
230 | *ptr = ctx->rand_data[ctx->rand_data_valid]; |
231 | ptr++; | |
232 | byte_count--; | |
714b33d1 | 233 | ctx->rand_data_valid++; |
17f0f4a4 NH |
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) { | |
aa1a85db | 243 | if (ctx->rand_data_valid == DEFAULT_BLK_SZ) { |
667b6294 | 244 | if (_get_more_prng_bytes(ctx, do_cont_test) < 0) { |
aa1a85db JW |
245 | memset(buf, 0, nbytes); |
246 | err = -EINVAL; | |
247 | goto done; | |
248 | } | |
17f0f4a4 | 249 | } |
aa1a85db JW |
250 | if (ctx->rand_data_valid > 0) |
251 | goto empty_rbuf; | |
17f0f4a4 NH |
252 | memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ); |
253 | ctx->rand_data_valid += DEFAULT_BLK_SZ; | |
254 | ptr += DEFAULT_BLK_SZ; | |
255 | } | |
256 | ||
257 | /* | |
aa1a85db | 258 | * Now go back and get any remaining partial block |
17f0f4a4 NH |
259 | */ |
260 | if (byte_count) | |
261 | goto remainder; | |
262 | ||
263 | done: | |
ed940700 | 264 | spin_unlock_bh(&ctx->prng_lock); |
17f0f4a4 NH |
265 | dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n", |
266 | err, ctx); | |
267 | return err; | |
268 | } | |
269 | ||
270 | static void free_prng_context(struct prng_context *ctx) | |
271 | { | |
272 | crypto_free_cipher(ctx->tfm); | |
273 | } | |
274 | ||
275 | static int reset_prng_context(struct prng_context *ctx, | |
e7c2422a HX |
276 | const unsigned char *key, size_t klen, |
277 | const unsigned char *V, const unsigned char *DT) | |
17f0f4a4 NH |
278 | { |
279 | int ret; | |
e7c2422a | 280 | const unsigned char *prng_key; |
17f0f4a4 | 281 | |
ed940700 | 282 | spin_lock_bh(&ctx->prng_lock); |
17f0f4a4 NH |
283 | ctx->flags |= PRNG_NEED_RESET; |
284 | ||
285 | prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY; | |
286 | ||
287 | if (!key) | |
288 | klen = DEFAULT_PRNG_KSZ; | |
289 | ||
290 | if (V) | |
291 | memcpy(ctx->V, V, DEFAULT_BLK_SZ); | |
292 | else | |
293 | memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ); | |
294 | ||
295 | if (DT) | |
296 | memcpy(ctx->DT, DT, DEFAULT_BLK_SZ); | |
297 | else | |
298 | memset(ctx->DT, 0, DEFAULT_BLK_SZ); | |
299 | ||
300 | memset(ctx->rand_data, 0, DEFAULT_BLK_SZ); | |
301 | memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ); | |
302 | ||
17f0f4a4 NH |
303 | ctx->rand_data_valid = DEFAULT_BLK_SZ; |
304 | ||
305 | ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen); | |
306 | if (ret) { | |
307 | dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n", | |
308 | crypto_cipher_get_flags(ctx->tfm)); | |
17f0f4a4 NH |
309 | goto out; |
310 | } | |
311 | ||
fd09d7fa | 312 | ret = 0; |
17f0f4a4 NH |
313 | ctx->flags &= ~PRNG_NEED_RESET; |
314 | out: | |
ed940700 | 315 | spin_unlock_bh(&ctx->prng_lock); |
fd09d7fa | 316 | return ret; |
17f0f4a4 NH |
317 | } |
318 | ||
319 | static int cprng_init(struct crypto_tfm *tfm) | |
320 | { | |
321 | struct prng_context *ctx = crypto_tfm_ctx(tfm); | |
322 | ||
323 | spin_lock_init(&ctx->prng_lock); | |
fd09d7fa SAS |
324 | ctx->tfm = crypto_alloc_cipher("aes", 0, 0); |
325 | if (IS_ERR(ctx->tfm)) { | |
326 | dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n", | |
327 | ctx); | |
328 | return PTR_ERR(ctx->tfm); | |
329 | } | |
17f0f4a4 | 330 | |
d7992f42 NH |
331 | if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0) |
332 | return -EINVAL; | |
333 | ||
334 | /* | |
335 | * after allocation, we should always force the user to reset | |
336 | * so they don't inadvertently use the insecure default values | |
337 | * without specifying them intentially | |
338 | */ | |
339 | ctx->flags |= PRNG_NEED_RESET; | |
340 | return 0; | |
17f0f4a4 NH |
341 | } |
342 | ||
343 | static void cprng_exit(struct crypto_tfm *tfm) | |
344 | { | |
345 | free_prng_context(crypto_tfm_ctx(tfm)); | |
346 | } | |
347 | ||
e7c2422a HX |
348 | static int cprng_get_random(struct crypto_rng *tfm, |
349 | const u8 *src, unsigned int slen, | |
350 | u8 *rdata, unsigned int dlen) | |
17f0f4a4 NH |
351 | { |
352 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
353 | ||
667b6294 NH |
354 | return get_prng_bytes(rdata, dlen, prng, 0); |
355 | } | |
356 | ||
2566578a NH |
357 | /* |
358 | * This is the cprng_registered reset method the seed value is | |
359 | * interpreted as the tuple { V KEY DT} | |
360 | * V and KEY are required during reset, and DT is optional, detected | |
361 | * as being present by testing the length of the seed | |
362 | */ | |
e7c2422a HX |
363 | static int cprng_reset(struct crypto_rng *tfm, |
364 | const u8 *seed, unsigned int slen) | |
17f0f4a4 NH |
365 | { |
366 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
e7c2422a HX |
367 | const u8 *key = seed + DEFAULT_BLK_SZ; |
368 | const u8 *dt = NULL; | |
17f0f4a4 NH |
369 | |
370 | if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ) | |
371 | return -EINVAL; | |
372 | ||
2566578a NH |
373 | if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ)) |
374 | dt = key + DEFAULT_PRNG_KSZ; | |
375 | ||
376 | reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt); | |
17f0f4a4 NH |
377 | |
378 | if (prng->flags & PRNG_NEED_RESET) | |
379 | return -EINVAL; | |
380 | return 0; | |
381 | } | |
382 | ||
667b6294 | 383 | #ifdef CONFIG_CRYPTO_FIPS |
e7c2422a HX |
384 | static int fips_cprng_get_random(struct crypto_rng *tfm, |
385 | const u8 *src, unsigned int slen, | |
386 | u8 *rdata, unsigned int dlen) | |
2f32bfd8 JSR |
387 | { |
388 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
389 | ||
390 | return get_prng_bytes(rdata, dlen, prng, 1); | |
391 | } | |
392 | ||
e7c2422a HX |
393 | static int fips_cprng_reset(struct crypto_rng *tfm, |
394 | const u8 *seed, unsigned int slen) | |
2f32bfd8 JSR |
395 | { |
396 | u8 rdata[DEFAULT_BLK_SZ]; | |
e7c2422a | 397 | const u8 *key = seed + DEFAULT_BLK_SZ; |
2f32bfd8 JSR |
398 | int rc; |
399 | ||
400 | struct prng_context *prng = crypto_rng_ctx(tfm); | |
401 | ||
505172e1 JW |
402 | if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ) |
403 | return -EINVAL; | |
404 | ||
405 | /* fips strictly requires seed != key */ | |
406 | if (!memcmp(seed, key, DEFAULT_PRNG_KSZ)) | |
407 | return -EINVAL; | |
408 | ||
2f32bfd8 JSR |
409 | rc = cprng_reset(tfm, seed, slen); |
410 | ||
411 | if (!rc) | |
412 | goto out; | |
413 | ||
414 | /* this primes our continuity test */ | |
415 | rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0); | |
416 | prng->rand_data_valid = DEFAULT_BLK_SZ; | |
417 | ||
418 | out: | |
419 | return rc; | |
420 | } | |
8fc229a5 | 421 | #endif |
2f32bfd8 | 422 | |
e7c2422a HX |
423 | static struct rng_alg rng_algs[] = { { |
424 | .generate = cprng_get_random, | |
425 | .seed = cprng_reset, | |
426 | .seedsize = DEFAULT_PRNG_KSZ + 2 * DEFAULT_BLK_SZ, | |
427 | .base = { | |
428 | .cra_name = "stdrng", | |
429 | .cra_driver_name = "ansi_cprng", | |
430 | .cra_priority = 100, | |
431 | .cra_ctxsize = sizeof(struct prng_context), | |
432 | .cra_module = THIS_MODULE, | |
433 | .cra_init = cprng_init, | |
434 | .cra_exit = cprng_exit, | |
8fc229a5 JK |
435 | } |
436 | #ifdef CONFIG_CRYPTO_FIPS | |
437 | }, { | |
e7c2422a HX |
438 | .generate = fips_cprng_get_random, |
439 | .seed = fips_cprng_reset, | |
440 | .seedsize = DEFAULT_PRNG_KSZ + 2 * DEFAULT_BLK_SZ, | |
441 | .base = { | |
442 | .cra_name = "fips(ansi_cprng)", | |
443 | .cra_driver_name = "fips_ansi_cprng", | |
444 | .cra_priority = 300, | |
445 | .cra_ctxsize = sizeof(struct prng_context), | |
446 | .cra_module = THIS_MODULE, | |
447 | .cra_init = cprng_init, | |
448 | .cra_exit = cprng_exit, | |
667b6294 | 449 | } |
667b6294 | 450 | #endif |
8fc229a5 | 451 | } }; |
17f0f4a4 NH |
452 | |
453 | /* Module initalization */ | |
454 | static int __init prng_mod_init(void) | |
455 | { | |
e7c2422a | 456 | return crypto_register_rngs(rng_algs, ARRAY_SIZE(rng_algs)); |
17f0f4a4 NH |
457 | } |
458 | ||
459 | static void __exit prng_mod_fini(void) | |
460 | { | |
e7c2422a | 461 | crypto_unregister_rngs(rng_algs, ARRAY_SIZE(rng_algs)); |
17f0f4a4 NH |
462 | } |
463 | ||
464 | MODULE_LICENSE("GPL"); | |
465 | MODULE_DESCRIPTION("Software Pseudo Random Number Generator"); | |
466 | MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>"); | |
467 | module_param(dbg, int, 0); | |
468 | MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)"); | |
c4741b23 | 469 | subsys_initcall(prng_mod_init); |
17f0f4a4 | 470 | module_exit(prng_mod_fini); |
5d26a105 | 471 | MODULE_ALIAS_CRYPTO("stdrng"); |
3e14dcf7 | 472 | MODULE_ALIAS_CRYPTO("ansi_cprng"); |