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Neil Horman17f0f4a2008-08-14 22:15:52 +10001/*
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
46struct 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
58static int dbg;
59
60static 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 {\
71if (dbg)\
72 printk(format, ##args);\
73} while (0)
74
75static 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
Lucas De Marchi25985ed2011-03-30 22:57:33 -030086 * returns 0 if generation succeeded, <0 if something went wrong
Neil Horman17f0f4a2008-08-14 22:15:52 +100087 */
Neil Horman667b6292009-10-19 11:57:02 +090088static int _get_more_prng_bytes(struct prng_context *ctx, int cont_test)
Neil Horman17f0f4a2008-08-14 22:15:52 +100089{
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)) {
Neil Horman667b6292009-10-19 11:57:02 +0900135 if (cont_test) {
Neil Hormanc5b1e542009-02-05 16:01:38 +1100136 panic("cprng %p Failed repetition check!\n",
137 ctx);
138 }
139
Neil Horman17f0f4a2008-08-14 22:15:52 +1000140 printk(KERN_ERR
141 "ctx %p Failed repetition check!\n",
142 ctx);
Neil Hormanc5b1e542009-02-05 16:01:38 +1100143
Neil Horman17f0f4a2008-08-14 22:15:52 +1000144 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 */
Jarod Wilson09fbf7c2008-11-24 21:20:13 +0800170 for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) {
Neil Horman17f0f4a2008-08-14 22:15:52 +1000171 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 */
Neil Horman667b6292009-10-19 11:57:02 +0900188static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx,
189 int do_cont_test)
Neil Horman17f0f4a2008-08-14 22:15:52 +1000190{
Neil Horman17f0f4a2008-08-14 22:15:52 +1000191 unsigned char *ptr = buf;
192 unsigned int byte_count = (unsigned int)nbytes;
193 int err;
194
195
Sebastian Andrzej Siewiored940702009-07-03 12:09:41 +0800196 spin_lock_bh(&ctx->prng_lock);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000197
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
Stephan Muellercde001e2015-03-06 08:26:31 +0100213 /*
214 * Return 0 in case of success as mandated by the kernel
215 * crypto API interface definition.
216 */
217 err = 0;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000218
219 dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",
220 byte_count, ctx);
221
222
223remainder:
224 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
Neil Horman667b6292009-10-19 11:57:02 +0900225 if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
Neil Horman17f0f4a2008-08-14 22:15:52 +1000226 memset(buf, 0, nbytes);
227 err = -EINVAL;
228 goto done;
229 }
230 }
231
232 /*
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800233 * Copy any data less than an entire block
Neil Horman17f0f4a2008-08-14 22:15:52 +1000234 */
235 if (byte_count < DEFAULT_BLK_SZ) {
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800236empty_rbuf:
Neil Horman714b33d2013-09-17 08:33:11 -0400237 while (ctx->rand_data_valid < DEFAULT_BLK_SZ) {
Neil Horman17f0f4a2008-08-14 22:15:52 +1000238 *ptr = ctx->rand_data[ctx->rand_data_valid];
239 ptr++;
240 byte_count--;
Neil Horman714b33d2013-09-17 08:33:11 -0400241 ctx->rand_data_valid++;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000242 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) {
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800251 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
Neil Horman667b6292009-10-19 11:57:02 +0900252 if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800253 memset(buf, 0, nbytes);
254 err = -EINVAL;
255 goto done;
256 }
Neil Horman17f0f4a2008-08-14 22:15:52 +1000257 }
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800258 if (ctx->rand_data_valid > 0)
259 goto empty_rbuf;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000260 memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
261 ctx->rand_data_valid += DEFAULT_BLK_SZ;
262 ptr += DEFAULT_BLK_SZ;
263 }
264
265 /*
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800266 * Now go back and get any remaining partial block
Neil Horman17f0f4a2008-08-14 22:15:52 +1000267 */
268 if (byte_count)
269 goto remainder;
270
271done:
Sebastian Andrzej Siewiored940702009-07-03 12:09:41 +0800272 spin_unlock_bh(&ctx->prng_lock);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000273 dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",
274 err, ctx);
275 return err;
276}
277
278static void free_prng_context(struct prng_context *ctx)
279{
280 crypto_free_cipher(ctx->tfm);
281}
282
283static 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;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000288 unsigned char *prng_key;
289
Sebastian Andrzej Siewiored940702009-07-03 12:09:41 +0800290 spin_lock_bh(&ctx->prng_lock);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000291 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
Neil Horman17f0f4a2008-08-14 22:15:52 +1000311 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));
Neil Horman17f0f4a2008-08-14 22:15:52 +1000317 goto out;
318 }
319
Sebastian Andrzej Siewiorfd09d7f2009-07-03 12:10:47 +0800320 ret = 0;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000321 ctx->flags &= ~PRNG_NEED_RESET;
322out:
Sebastian Andrzej Siewiored940702009-07-03 12:09:41 +0800323 spin_unlock_bh(&ctx->prng_lock);
Sebastian Andrzej Siewiorfd09d7f2009-07-03 12:10:47 +0800324 return ret;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000325}
326
327static 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);
Sebastian Andrzej Siewiorfd09d7f2009-07-03 12:10:47 +0800332 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 }
Neil Horman17f0f4a2008-08-14 22:15:52 +1000338
Neil Hormand7992f42009-01-28 15:20:51 +1100339 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;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000349}
350
351static void cprng_exit(struct crypto_tfm *tfm)
352{
353 free_prng_context(crypto_tfm_ctx(tfm));
354}
355
356static 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
Neil Horman667b6292009-10-19 11:57:02 +0900361 return get_prng_bytes(rdata, dlen, prng, 0);
362}
363
Neil Horman25665782008-11-05 12:13:14 +0800364/*
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 */
Neil Horman17f0f4a2008-08-14 22:15:52 +1000370static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
371{
372 struct prng_context *prng = crypto_rng_ctx(tfm);
Neil Horman25665782008-11-05 12:13:14 +0800373 u8 *key = seed + DEFAULT_BLK_SZ;
374 u8 *dt = NULL;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000375
376 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
377 return -EINVAL;
378
Neil Horman25665782008-11-05 12:13:14 +0800379 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);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000383
384 if (prng->flags & PRNG_NEED_RESET)
385 return -EINVAL;
386 return 0;
387}
388
Neil Horman667b6292009-10-19 11:57:02 +0900389#ifdef CONFIG_CRYPTO_FIPS
Jaswinder Singh Rajput2f32bfd2009-11-23 20:25:50 +0800390static 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
398static int fips_cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
399{
400 u8 rdata[DEFAULT_BLK_SZ];
Jarod Wilson505172e2011-11-09 12:04:06 +0800401 u8 *key = seed + DEFAULT_BLK_SZ;
Jaswinder Singh Rajput2f32bfd2009-11-23 20:25:50 +0800402 int rc;
403
404 struct prng_context *prng = crypto_rng_ctx(tfm);
405
Jarod Wilson505172e2011-11-09 12:04:06 +0800406 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
Jaswinder Singh Rajput2f32bfd2009-11-23 20:25:50 +0800413 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
422out:
423 return rc;
424}
Jussi Kivilinna8fc229a2012-07-11 14:20:15 +0300425#endif
Jaswinder Singh Rajput2f32bfd2009-11-23 20:25:50 +0800426
Jussi Kivilinna8fc229a2012-07-11 14:20:15 +0300427static 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}, {
Neil Horman667b6292009-10-19 11:57:02 +0900446 .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,
Neil Horman667b6292009-10-19 11:57:02 +0900453 .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 }
Neil Horman667b6292009-10-19 11:57:02 +0900462#endif
Jussi Kivilinna8fc229a2012-07-11 14:20:15 +0300463} };
Neil Horman17f0f4a2008-08-14 22:15:52 +1000464
465/* Module initalization */
466static int __init prng_mod_init(void)
467{
Jussi Kivilinna8fc229a2012-07-11 14:20:15 +0300468 return crypto_register_algs(rng_algs, ARRAY_SIZE(rng_algs));
Neil Horman17f0f4a2008-08-14 22:15:52 +1000469}
470
471static void __exit prng_mod_fini(void)
472{
Jussi Kivilinna8fc229a2012-07-11 14:20:15 +0300473 crypto_unregister_algs(rng_algs, ARRAY_SIZE(rng_algs));
Neil Horman17f0f4a2008-08-14 22:15:52 +1000474}
475
476MODULE_LICENSE("GPL");
477MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
478MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
479module_param(dbg, int, 0);
480MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
481module_init(prng_mod_init);
482module_exit(prng_mod_fini);
Kees Cook5d26a102014-11-20 17:05:53 -0800483MODULE_ALIAS_CRYPTO("stdrng");
Mathias Krause3e14dcf2015-01-11 18:17:42 +0100484MODULE_ALIAS_CRYPTO("ansi_cprng");