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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
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{
Neil Horman17f0f4a2008-08-14 22:15:52 +1000190 unsigned char *ptr = buf;
191 unsigned int byte_count = (unsigned int)nbytes;
192 int err;
193
194
195 if (nbytes < 0)
196 return -EINVAL;
197
Sebastian Andrzej Siewiored940702009-07-03 12:09:41 +0800198 spin_lock_bh(&ctx->prng_lock);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000199
200 err = -EINVAL;
201 if (ctx->flags & PRNG_NEED_RESET)
202 goto done;
203
204 /*
205 * If the FIXED_SIZE flag is on, only return whole blocks of
206 * pseudo random data
207 */
208 err = -EINVAL;
209 if (ctx->flags & PRNG_FIXED_SIZE) {
210 if (nbytes < DEFAULT_BLK_SZ)
211 goto done;
212 byte_count = DEFAULT_BLK_SZ;
213 }
214
215 err = byte_count;
216
217 dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",
218 byte_count, ctx);
219
220
221remainder:
222 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
223 if (_get_more_prng_bytes(ctx) < 0) {
224 memset(buf, 0, nbytes);
225 err = -EINVAL;
226 goto done;
227 }
228 }
229
230 /*
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800231 * Copy any data less than an entire block
Neil Horman17f0f4a2008-08-14 22:15:52 +1000232 */
233 if (byte_count < DEFAULT_BLK_SZ) {
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800234empty_rbuf:
Neil Horman17f0f4a2008-08-14 22:15:52 +1000235 for (; ctx->rand_data_valid < DEFAULT_BLK_SZ;
236 ctx->rand_data_valid++) {
237 *ptr = ctx->rand_data[ctx->rand_data_valid];
238 ptr++;
239 byte_count--;
240 if (byte_count == 0)
241 goto done;
242 }
243 }
244
245 /*
246 * Now copy whole blocks
247 */
248 for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800249 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
250 if (_get_more_prng_bytes(ctx) < 0) {
251 memset(buf, 0, nbytes);
252 err = -EINVAL;
253 goto done;
254 }
Neil Horman17f0f4a2008-08-14 22:15:52 +1000255 }
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800256 if (ctx->rand_data_valid > 0)
257 goto empty_rbuf;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000258 memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
259 ctx->rand_data_valid += DEFAULT_BLK_SZ;
260 ptr += DEFAULT_BLK_SZ;
261 }
262
263 /*
Jarod Wilsonaa1a85d2008-11-13 22:03:20 +0800264 * Now go back and get any remaining partial block
Neil Horman17f0f4a2008-08-14 22:15:52 +1000265 */
266 if (byte_count)
267 goto remainder;
268
269done:
Sebastian Andrzej Siewiored940702009-07-03 12:09:41 +0800270 spin_unlock_bh(&ctx->prng_lock);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000271 dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",
272 err, ctx);
273 return err;
274}
275
276static void free_prng_context(struct prng_context *ctx)
277{
278 crypto_free_cipher(ctx->tfm);
279}
280
281static int reset_prng_context(struct prng_context *ctx,
282 unsigned char *key, size_t klen,
283 unsigned char *V, unsigned char *DT)
284{
285 int ret;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000286 unsigned char *prng_key;
287
Sebastian Andrzej Siewiored940702009-07-03 12:09:41 +0800288 spin_lock_bh(&ctx->prng_lock);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000289 ctx->flags |= PRNG_NEED_RESET;
290
291 prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY;
292
293 if (!key)
294 klen = DEFAULT_PRNG_KSZ;
295
296 if (V)
297 memcpy(ctx->V, V, DEFAULT_BLK_SZ);
298 else
299 memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ);
300
301 if (DT)
302 memcpy(ctx->DT, DT, DEFAULT_BLK_SZ);
303 else
304 memset(ctx->DT, 0, DEFAULT_BLK_SZ);
305
306 memset(ctx->rand_data, 0, DEFAULT_BLK_SZ);
307 memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ);
308
Neil Horman17f0f4a2008-08-14 22:15:52 +1000309 ctx->rand_data_valid = DEFAULT_BLK_SZ;
310
311 ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen);
312 if (ret) {
313 dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
314 crypto_cipher_get_flags(ctx->tfm));
Neil Horman17f0f4a2008-08-14 22:15:52 +1000315 goto out;
316 }
317
Sebastian Andrzej Siewiorfd09d7f2009-07-03 12:10:47 +0800318 ret = 0;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000319 ctx->flags &= ~PRNG_NEED_RESET;
320out:
Sebastian Andrzej Siewiored940702009-07-03 12:09:41 +0800321 spin_unlock_bh(&ctx->prng_lock);
Sebastian Andrzej Siewiorfd09d7f2009-07-03 12:10:47 +0800322 return ret;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000323}
324
325static int cprng_init(struct crypto_tfm *tfm)
326{
327 struct prng_context *ctx = crypto_tfm_ctx(tfm);
328
329 spin_lock_init(&ctx->prng_lock);
Sebastian Andrzej Siewiorfd09d7f2009-07-03 12:10:47 +0800330 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
331 if (IS_ERR(ctx->tfm)) {
332 dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n",
333 ctx);
334 return PTR_ERR(ctx->tfm);
335 }
Neil Horman17f0f4a2008-08-14 22:15:52 +1000336
Neil Hormand7992f42009-01-28 15:20:51 +1100337 if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0)
338 return -EINVAL;
339
340 /*
341 * after allocation, we should always force the user to reset
342 * so they don't inadvertently use the insecure default values
343 * without specifying them intentially
344 */
345 ctx->flags |= PRNG_NEED_RESET;
346 return 0;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000347}
348
349static void cprng_exit(struct crypto_tfm *tfm)
350{
351 free_prng_context(crypto_tfm_ctx(tfm));
352}
353
354static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata,
355 unsigned int dlen)
356{
357 struct prng_context *prng = crypto_rng_ctx(tfm);
358
359 return get_prng_bytes(rdata, dlen, prng);
360}
361
Neil Horman25665782008-11-05 12:13:14 +0800362/*
363 * This is the cprng_registered reset method the seed value is
364 * interpreted as the tuple { V KEY DT}
365 * V and KEY are required during reset, and DT is optional, detected
366 * as being present by testing the length of the seed
367 */
Neil Horman17f0f4a2008-08-14 22:15:52 +1000368static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
369{
370 struct prng_context *prng = crypto_rng_ctx(tfm);
Neil Horman25665782008-11-05 12:13:14 +0800371 u8 *key = seed + DEFAULT_BLK_SZ;
372 u8 *dt = NULL;
Neil Horman17f0f4a2008-08-14 22:15:52 +1000373
374 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
375 return -EINVAL;
376
Neil Horman25665782008-11-05 12:13:14 +0800377 if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ))
378 dt = key + DEFAULT_PRNG_KSZ;
379
380 reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000381
382 if (prng->flags & PRNG_NEED_RESET)
383 return -EINVAL;
384 return 0;
385}
386
387static struct crypto_alg rng_alg = {
388 .cra_name = "stdrng",
389 .cra_driver_name = "ansi_cprng",
390 .cra_priority = 100,
391 .cra_flags = CRYPTO_ALG_TYPE_RNG,
392 .cra_ctxsize = sizeof(struct prng_context),
393 .cra_type = &crypto_rng_type,
394 .cra_module = THIS_MODULE,
395 .cra_list = LIST_HEAD_INIT(rng_alg.cra_list),
396 .cra_init = cprng_init,
397 .cra_exit = cprng_exit,
398 .cra_u = {
399 .rng = {
400 .rng_make_random = cprng_get_random,
401 .rng_reset = cprng_reset,
Neil Horman25665782008-11-05 12:13:14 +0800402 .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
Neil Horman17f0f4a2008-08-14 22:15:52 +1000403 }
404 }
405};
406
407
408/* Module initalization */
409static int __init prng_mod_init(void)
410{
Neil Horman17f0f4a2008-08-14 22:15:52 +1000411 if (fips_enabled)
412 rng_alg.cra_priority += 200;
413
Steffen Klasserta367b172009-08-29 17:36:25 +1000414 return crypto_register_alg(&rng_alg);
Neil Horman17f0f4a2008-08-14 22:15:52 +1000415}
416
417static void __exit prng_mod_fini(void)
418{
419 crypto_unregister_alg(&rng_alg);
420 return;
421}
422
423MODULE_LICENSE("GPL");
424MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
425MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
426module_param(dbg, int, 0);
427MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
428module_init(prng_mod_init);
429module_exit(prng_mod_fini);
430MODULE_ALIAS("stdrng");