summaryrefslogtreecommitdiffstats
path: root/crypto/ansi_cprng.c
blob: 45bd2182cb3660b02a1ecda77d42d42288bb78f9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
/*
 * PRNG: Pseudo Random Number Generator
 *       Based on NIST Recommended PRNG From ANSI X9.31 Appendix A.2.4 using
 *       AES 128 cipher
 *
 *  (C) Neil Horman <nhorman@tuxdriver.com>
 *
 *  This program is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License as published by the
 *  Free Software Foundation; either version 2 of the License, or (at your
 *  any later version.
 *
 *
 */

#include <crypto/internal/rng.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/string.h>

#include "internal.h"

#define DEFAULT_PRNG_KEY "0123456789abcdef"
#define DEFAULT_PRNG_KSZ 16
#define DEFAULT_BLK_SZ 16
#define DEFAULT_V_SEED "zaybxcwdveuftgsh"

/*
 * Flags for the prng_context flags field
 */

#define PRNG_FIXED_SIZE 0x1
#define PRNG_NEED_RESET 0x2

/*
 * Note: DT is our counter value
 *	 I is our intermediate value
 *	 V is our seed vector
 * See http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
 * for implementation details
 */


struct prng_context {
	spinlock_t prng_lock;
	unsigned char rand_data[DEFAULT_BLK_SZ];
	unsigned char last_rand_data[DEFAULT_BLK_SZ];
	unsigned char DT[DEFAULT_BLK_SZ];
	unsigned char I[DEFAULT_BLK_SZ];
	unsigned char V[DEFAULT_BLK_SZ];
	u32 rand_data_valid;
	struct crypto_cipher *tfm;
	u32 flags;
};

static int dbg;

static void hexdump(char *note, unsigned char *buf, unsigned int len)
{
	if (dbg) {
		printk(KERN_CRIT "%s", note);
		print_hex_dump(KERN_CONT, "", DUMP_PREFIX_OFFSET,
				16, 1,
				buf, len, false);
	}
}

#define dbgprint(format, args...) do {\
if (dbg)\
	printk(format, ##args);\
} while (0)

static void xor_vectors(unsigned char *in1, unsigned char *in2,
			unsigned char *out, unsigned int size)
{
	int i;

	for (i = 0; i < size; i++)
		out[i] = in1[i] ^ in2[i];

}
/*
 * Returns DEFAULT_BLK_SZ bytes of random data per call
 * returns 0 if generation succeded, <0 if something went wrong
 */
static int _get_more_prng_bytes(struct prng_context *ctx, int cont_test)
{
	int i;
	unsigned char tmp[DEFAULT_BLK_SZ];
	unsigned char *output = NULL;


	dbgprint(KERN_CRIT "Calling _get_more_prng_bytes for context %p\n",
		ctx);

	hexdump("Input DT: ", ctx->DT, DEFAULT_BLK_SZ);
	hexdump("Input I: ", ctx->I, DEFAULT_BLK_SZ);
	hexdump("Input V: ", ctx->V, DEFAULT_BLK_SZ);

	/*
	 * This algorithm is a 3 stage state machine
	 */
	for (i = 0; i < 3; i++) {

		switch (i) {
		case 0:
			/*
			 * Start by encrypting the counter value
			 * This gives us an intermediate value I
			 */
			memcpy(tmp, ctx->DT, DEFAULT_BLK_SZ);
			output = ctx->I;
			hexdump("tmp stage 0: ", tmp, DEFAULT_BLK_SZ);
			break;
		case 1:

			/*
			 * Next xor I with our secret vector V
			 * encrypt that result to obtain our
			 * pseudo random data which we output
			 */
			xor_vectors(ctx->I, ctx->V, tmp, DEFAULT_BLK_SZ);
			hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ);
			output = ctx->rand_data;
			break;
		case 2:
			/*
			 * First check that we didn't produce the same
			 * random data that we did last time around through this
			 */
			if (!memcmp(ctx->rand_data, ctx->last_rand_data,
					DEFAULT_BLK_SZ)) {
				if (cont_test) {
					panic("cprng %p Failed repetition check!\n",
						ctx);
				}

				printk(KERN_ERR
					"ctx %p Failed repetition check!\n",
					ctx);

				ctx->flags |= PRNG_NEED_RESET;
				return -EINVAL;
			}
			memcpy(ctx->last_rand_data, ctx->rand_data,
				DEFAULT_BLK_SZ);

			/*
			 * Lastly xor the random data with I
			 * and encrypt that to obtain a new secret vector V
			 */
			xor_vectors(ctx->rand_data, ctx->I, tmp,
				DEFAULT_BLK_SZ);
			output = ctx->V;
			hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ);
			break;
		}


		/* do the encryption */
		crypto_cipher_encrypt_one(ctx->tfm, output, tmp);

	}

	/*
	 * Now update our DT value
	 */
	for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) {
		ctx->DT[i] += 1;
		if (ctx->DT[i] != 0)
			break;
	}

	dbgprint("Returning new block for context %p\n", ctx);
	ctx->rand_data_valid = 0;

	hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ);
	hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ);
	hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ);
	hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ);

	return 0;
}

/* Our exported functions */
static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx,
				int do_cont_test)
{
	unsigned char *ptr = buf;
	unsigned int byte_count = (unsigned int)nbytes;
	int err;


	spin_lock_bh(&ctx->prng_lock);

	err = -EINVAL;
	if (ctx->flags & PRNG_NEED_RESET)
		goto done;

	/*
	 * If the FIXED_SIZE flag is on, only return whole blocks of
	 * pseudo random data
	 */
	err = -EINVAL;
	if (ctx->flags & PRNG_FIXED_SIZE) {
		if (nbytes < DEFAULT_BLK_SZ)
			goto done;
		byte_count = DEFAULT_BLK_SZ;
	}

	err = byte_count;

	dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",
		byte_count, ctx);


remainder:
	if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
		if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
			memset(buf, 0, nbytes);
			err = -EINVAL;
			goto done;
		}
	}

	/*
	 * Copy any data less than an entire block
	 */
	if (byte_count < DEFAULT_BLK_SZ) {
empty_rbuf:
		for (; ctx->rand_data_valid < DEFAULT_BLK_SZ;
			ctx->rand_data_valid++) {
			*ptr = ctx->rand_data[ctx->rand_data_valid];
			ptr++;
			byte_count--;
			if (byte_count == 0)
				goto done;
		}
	}

	/*
	 * Now copy whole blocks
	 */
	for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
		if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
			if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
				memset(buf, 0, nbytes);
				err = -EINVAL;
				goto done;
			}
		}
		if (ctx->rand_data_valid > 0)
			goto empty_rbuf;
		memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
		ctx->rand_data_valid += DEFAULT_BLK_SZ;
		ptr += DEFAULT_BLK_SZ;
	}

	/*
	 * Now go back and get any remaining partial block
	 */
	if (byte_count)
		goto remainder;

done:
	spin_unlock_bh(&ctx->prng_lock);
	dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",
		err, ctx);
	return err;
}

static void free_prng_context(struct prng_context *ctx)
{
	crypto_free_cipher(ctx->tfm);
}

static int reset_prng_context(struct prng_context *ctx,
			      unsigned char *key, size_t klen,
			      unsigned char *V, unsigned char *DT)
{
	int ret;
	unsigned char *prng_key;

	spin_lock_bh(&ctx->prng_lock);
	ctx->flags |= PRNG_NEED_RESET;

	prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY;

	if (!key)
		klen = DEFAULT_PRNG_KSZ;

	if (V)
		memcpy(ctx->V, V, DEFAULT_BLK_SZ);
	else
		memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ);

	if (DT)
		memcpy(ctx->DT, DT, DEFAULT_BLK_SZ);
	else
		memset(ctx->DT, 0, DEFAULT_BLK_SZ);

	memset(ctx->rand_data, 0, DEFAULT_BLK_SZ);
	memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ);

	ctx->rand_data_valid = DEFAULT_BLK_SZ;

	ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen);
	if (ret) {
		dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
			crypto_cipher_get_flags(ctx->tfm));
		goto out;
	}

	ret = 0;
	ctx->flags &= ~PRNG_NEED_RESET;
out:
	spin_unlock_bh(&ctx->prng_lock);
	return ret;
}

static int cprng_init(struct crypto_tfm *tfm)
{
	struct prng_context *ctx = crypto_tfm_ctx(tfm);

	spin_lock_init(&ctx->prng_lock);
	ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
	if (IS_ERR(ctx->tfm)) {
		dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n",
				ctx);
		return PTR_ERR(ctx->tfm);
	}

	if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0)
		return -EINVAL;

	/*
	 * after allocation, we should always force the user to reset
	 * so they don't inadvertently use the insecure default values
	 * without specifying them intentially
	 */
	ctx->flags |= PRNG_NEED_RESET;
	return 0;
}

static void cprng_exit(struct crypto_tfm *tfm)
{
	free_prng_context(crypto_tfm_ctx(tfm));
}

static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata,
			    unsigned int dlen)
{
	struct prng_context *prng = crypto_rng_ctx(tfm);

	return get_prng_bytes(rdata, dlen, prng, 0);
}

static int fips_cprng_get_random(struct crypto_rng *tfm, u8 *rdata,
			    unsigned int dlen)
{
	struct prng_context *prng = crypto_rng_ctx(tfm);

	return get_prng_bytes(rdata, dlen, prng, 1);
}

/*
 *  This is the cprng_registered reset method the seed value is
 *  interpreted as the tuple { V KEY DT}
 *  V and KEY are required during reset, and DT is optional, detected
 *  as being present by testing the length of the seed
 */
static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
{
	struct prng_context *prng = crypto_rng_ctx(tfm);
	u8 *key = seed + DEFAULT_BLK_SZ;
	u8 *dt = NULL;

	if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
		return -EINVAL;

	if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ))
		dt = key + DEFAULT_PRNG_KSZ;

	reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt);

	if (prng->flags & PRNG_NEED_RESET)
		return -EINVAL;
	return 0;
}

static int fips_cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
{
	u8 rdata[DEFAULT_BLK_SZ];
	int rc;

	struct prng_context *prng = crypto_rng_ctx(tfm);

	rc = cprng_reset(tfm, seed, slen);

	if (!rc)
		goto out;

	/* this primes our continuity test */
	rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0);
	prng->rand_data_valid = DEFAULT_BLK_SZ;

out:
	return rc;
}

static struct crypto_alg rng_alg = {
	.cra_name		= "stdrng",
	.cra_driver_name	= "ansi_cprng",
	.cra_priority		= 100,
	.cra_flags		= CRYPTO_ALG_TYPE_RNG,
	.cra_ctxsize		= sizeof(struct prng_context),
	.cra_type		= &crypto_rng_type,
	.cra_module		= THIS_MODULE,
	.cra_list		= LIST_HEAD_INIT(rng_alg.cra_list),
	.cra_init		= cprng_init,
	.cra_exit		= cprng_exit,
	.cra_u			= {
		.rng = {
			.rng_make_random	= cprng_get_random,
			.rng_reset		= cprng_reset,
			.seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
		}
	}
};

#ifdef CONFIG_CRYPTO_FIPS
static struct crypto_alg fips_rng_alg = {
	.cra_name		= "fips(ansi_cprng)",
	.cra_driver_name	= "fips_ansi_cprng",
	.cra_priority		= 300,
	.cra_flags		= CRYPTO_ALG_TYPE_RNG,
	.cra_ctxsize		= sizeof(struct prng_context),
	.cra_type		= &crypto_rng_type,
	.cra_module		= THIS_MODULE,
	.cra_list		= LIST_HEAD_INIT(rng_alg.cra_list),
	.cra_init		= cprng_init,
	.cra_exit		= cprng_exit,
	.cra_u			= {
		.rng = {
			.rng_make_random	= fips_cprng_get_random,
			.rng_reset		= fips_cprng_reset,
			.seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
		}
	}
};
#endif

/* Module initalization */
static int __init prng_mod_init(void)
{
	int rc = 0;

	rc = crypto_register_alg(&rng_alg);
#ifdef CONFIG_CRYPTO_FIPS
	if (rc)
		goto out;

	rc = crypto_register_alg(&fips_rng_alg);

out:
#endif
	return rc;
}

static void __exit prng_mod_fini(void)
{
	crypto_unregister_alg(&rng_alg);
#ifdef CONFIG_CRYPTO_FIPS
	crypto_unregister_alg(&fips_rng_alg);
#endif
	return;
}

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
module_param(dbg, int, 0);
MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
module_init(prng_mod_init);
module_exit(prng_mod_fini);
MODULE_ALIAS("stdrng");
OpenPOWER on IntegriCloud