blob: d80ed4c1e009da061b4d35d2e4bf3187e267b454 [file] [log] [blame]
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
86 * returns 0 if generation succeded, <0 if something went wrong
87 */
88static 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)) {
Neil Hormanc5b1e542009-02-05 16:01:38 +1100135 if (fips_enabled) {
136 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 */
188static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx)
189{
190 unsigned long flags;
191 unsigned char *ptr = buf;
192 unsigned int byte_count = (unsigned int)nbytes;
193 int err;
194
195
196 if (nbytes < 0)
197 return -EINVAL;
198
199 spin_lock_irqsave(&ctx->prng_lock, flags);
200
201 err = -EINVAL;
202 if (ctx->flags & PRNG_NEED_RESET)
203 goto done;
204
205 /*
206 * If the FIXED_SIZE flag is on, only return whole blocks of
207 * pseudo random data
208 */
209 err = -EINVAL;
210 if (ctx->flags & PRNG_FIXED_SIZE) {
211 if (nbytes < DEFAULT_BLK_SZ)
212 goto done;
213 byte_count = DEFAULT_BLK_SZ;
214 }
215
216 err = byte_count;
217
218 dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",
219 byte_count, ctx);
220
221
222remainder:
223 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
224 if (_get_more_prng_bytes(ctx) < 0) {
225 memset(buf, 0, nbytes);
226 err = -EINVAL;
227 goto done;
228 }
229 }
230
231 /*
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800232 * Copy any data less than an entire block
Neil Horman17f0f4a2008-08-14 22:15:52 +1000233 */
234 if (byte_count < DEFAULT_BLK_SZ) {
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800235empty_rbuf:
Neil Horman17f0f4a2008-08-14 22:15:52 +1000236 for (; ctx->rand_data_valid < DEFAULT_BLK_SZ;
237 ctx->rand_data_valid++) {
238 *ptr = ctx->rand_data[ctx->rand_data_valid];
239 ptr++;
240 byte_count--;
241 if (byte_count == 0)
242 goto done;
243 }
244 }
245
246 /*
247 * Now copy whole blocks
248 */
249 for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800250 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
251 if (_get_more_prng_bytes(ctx) < 0) {
252 memset(buf, 0, nbytes);
253 err = -EINVAL;
254 goto done;
255 }
Neil Horman17f0f4a2008-08-14 22:15:52 +1000256 }
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800257 if (ctx->rand_data_valid > 0)
258 goto empty_rbuf;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000259 memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
260 ctx->rand_data_valid += DEFAULT_BLK_SZ;
261 ptr += DEFAULT_BLK_SZ;
262 }
263
264 /*
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800265 * Now go back and get any remaining partial block
Neil Horman17f0f4a2008-08-14 22:15:52 +1000266 */
267 if (byte_count)
268 goto remainder;
269
270done:
271 spin_unlock_irqrestore(&ctx->prng_lock, flags);
272 dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",
273 err, ctx);
274 return err;
275}
276
277static void free_prng_context(struct prng_context *ctx)
278{
279 crypto_free_cipher(ctx->tfm);
280}
281
282static int reset_prng_context(struct prng_context *ctx,
283 unsigned char *key, size_t klen,
284 unsigned char *V, unsigned char *DT)
285{
286 int ret;
287 int rc = -EINVAL;
288 unsigned char *prng_key;
289
290 spin_lock(&ctx->prng_lock);
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
311 if (ctx->tfm)
312 crypto_free_cipher(ctx->tfm);
313
314 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
315 if (IS_ERR(ctx->tfm)) {
316 dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n",
317 ctx);
318 ctx->tfm = NULL;
319 goto out;
320 }
321
322 ctx->rand_data_valid = DEFAULT_BLK_SZ;
323
324 ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen);
325 if (ret) {
326 dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
327 crypto_cipher_get_flags(ctx->tfm));
328 crypto_free_cipher(ctx->tfm);
329 goto out;
330 }
331
332 rc = 0;
333 ctx->flags &= ~PRNG_NEED_RESET;
334out:
335 spin_unlock(&ctx->prng_lock);
336
337 return rc;
338
339}
340
341static int cprng_init(struct crypto_tfm *tfm)
342{
343 struct prng_context *ctx = crypto_tfm_ctx(tfm);
344
345 spin_lock_init(&ctx->prng_lock);
346
Neil Hormand7992f42009-01-28 15:20:51 +1100347 if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0)
348 return -EINVAL;
349
350 /*
351 * after allocation, we should always force the user to reset
352 * so they don't inadvertently use the insecure default values
353 * without specifying them intentially
354 */
355 ctx->flags |= PRNG_NEED_RESET;
356 return 0;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000357}
358
359static void cprng_exit(struct crypto_tfm *tfm)
360{
361 free_prng_context(crypto_tfm_ctx(tfm));
362}
363
364static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata,
365 unsigned int dlen)
366{
367 struct prng_context *prng = crypto_rng_ctx(tfm);
368
369 return get_prng_bytes(rdata, dlen, prng);
370}
371
Neil Horman25665782008-11-05 12:13:14 +0800372/*
373 * This is the cprng_registered reset method the seed value is
374 * interpreted as the tuple { V KEY DT}
375 * V and KEY are required during reset, and DT is optional, detected
376 * as being present by testing the length of the seed
377 */
Neil Horman17f0f4a2008-08-14 22:15:52 +1000378static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
379{
380 struct prng_context *prng = crypto_rng_ctx(tfm);
Neil Horman25665782008-11-05 12:13:14 +0800381 u8 *key = seed + DEFAULT_BLK_SZ;
382 u8 *dt = NULL;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000383
384 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
385 return -EINVAL;
386
Neil Horman25665782008-11-05 12:13:14 +0800387 if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ))
388 dt = key + DEFAULT_PRNG_KSZ;
389
390 reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000391
392 if (prng->flags & PRNG_NEED_RESET)
393 return -EINVAL;
394 return 0;
395}
396
397static struct crypto_alg rng_alg = {
398 .cra_name = "stdrng",
399 .cra_driver_name = "ansi_cprng",
400 .cra_priority = 100,
401 .cra_flags = CRYPTO_ALG_TYPE_RNG,
402 .cra_ctxsize = sizeof(struct prng_context),
403 .cra_type = &crypto_rng_type,
404 .cra_module = THIS_MODULE,
405 .cra_list = LIST_HEAD_INIT(rng_alg.cra_list),
406 .cra_init = cprng_init,
407 .cra_exit = cprng_exit,
408 .cra_u = {
409 .rng = {
410 .rng_make_random = cprng_get_random,
411 .rng_reset = cprng_reset,
Neil Horman25665782008-11-05 12:13:14 +0800412 .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
Neil Horman17f0f4a2008-08-14 22:15:52 +1000413 }
414 }
415};
416
417
418/* Module initalization */
419static int __init prng_mod_init(void)
420{
421 int ret = 0;
422
423 if (fips_enabled)
424 rng_alg.cra_priority += 200;
425
426 ret = crypto_register_alg(&rng_alg);
427
428 if (ret)
429 goto out;
430out:
431 return 0;
432}
433
434static void __exit prng_mod_fini(void)
435{
436 crypto_unregister_alg(&rng_alg);
437 return;
438}
439
440MODULE_LICENSE("GPL");
441MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
442MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
443module_param(dbg, int, 0);
444MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
445module_init(prng_mod_init);
446module_exit(prng_mod_fini);
447MODULE_ALIAS("stdrng");