1
2
3
4
5
6
7
8
9
10
11
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
32
33
34#define PRNG_FIXED_SIZE 0x1
35#define PRNG_NEED_RESET 0x2
36
37
38
39
40
41
42
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
86
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
104
105 for (i = 0; i < 3; i++) {
106
107 switch (i) {
108 case 0:
109
110
111
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
121
122
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
131
132
133 if (!memcmp(ctx->rand_data, ctx->last_rand_data,
134 DEFAULT_BLK_SZ)) {
135 printk(KERN_ERR
136 "ctx %p Failed repetition check!\n",
137 ctx);
138 ctx->flags |= PRNG_NEED_RESET;
139 return -EINVAL;
140 }
141 memcpy(ctx->last_rand_data, ctx->rand_data,
142 DEFAULT_BLK_SZ);
143
144
145
146
147
148 xor_vectors(ctx->rand_data, ctx->I, tmp,
149 DEFAULT_BLK_SZ);
150 output = ctx->V;
151 hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ);
152 break;
153 }
154
155
156
157 crypto_cipher_encrypt_one(ctx->tfm, output, tmp);
158
159 }
160
161
162
163
164 for (i = 0; i < DEFAULT_BLK_SZ; i++) {
165 ctx->DT[i] += 1;
166 if (ctx->DT[i] != 0)
167 break;
168 }
169
170 dbgprint("Returning new block for context %p\n", ctx);
171 ctx->rand_data_valid = 0;
172
173 hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ);
174 hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ);
175 hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ);
176 hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ);
177
178 return 0;
179}
180
181
182static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx)
183{
184 unsigned long flags;
185 unsigned char *ptr = buf;
186 unsigned int byte_count = (unsigned int)nbytes;
187 int err;
188
189
190 if (nbytes < 0)
191 return -EINVAL;
192
193 spin_lock_irqsave(&ctx->prng_lock, flags);
194
195 err = -EINVAL;
196 if (ctx->flags & PRNG_NEED_RESET)
197 goto done;
198
199
200
201
202
203 err = -EINVAL;
204 if (ctx->flags & PRNG_FIXED_SIZE) {
205 if (nbytes < DEFAULT_BLK_SZ)
206 goto done;
207 byte_count = DEFAULT_BLK_SZ;
208 }
209
210 err = byte_count;
211
212 dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",
213 byte_count, ctx);
214
215
216remainder:
217 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
218 if (_get_more_prng_bytes(ctx) < 0) {
219 memset(buf, 0, nbytes);
220 err = -EINVAL;
221 goto done;
222 }
223 }
224
225
226
227
228 if (byte_count < DEFAULT_BLK_SZ) {
229 for (; ctx->rand_data_valid < DEFAULT_BLK_SZ;
230 ctx->rand_data_valid++) {
231 *ptr = ctx->rand_data[ctx->rand_data_valid];
232 ptr++;
233 byte_count--;
234 if (byte_count == 0)
235 goto done;
236 }
237 }
238
239
240
241
242 for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
243 if (_get_more_prng_bytes(ctx) < 0) {
244 memset(buf, 0, nbytes);
245 err = -EINVAL;
246 goto done;
247 }
248 memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
249 ctx->rand_data_valid += DEFAULT_BLK_SZ;
250 ptr += DEFAULT_BLK_SZ;
251 }
252
253
254
255
256 if (byte_count)
257 goto remainder;
258
259done:
260 spin_unlock_irqrestore(&ctx->prng_lock, flags);
261 dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",
262 err, ctx);
263 return err;
264}
265
266static void free_prng_context(struct prng_context *ctx)
267{
268 crypto_free_cipher(ctx->tfm);
269}
270
271static int reset_prng_context(struct prng_context *ctx,
272 unsigned char *key, size_t klen,
273 unsigned char *V, unsigned char *DT)
274{
275 int ret;
276 int rc = -EINVAL;
277 unsigned char *prng_key;
278
279 spin_lock(&ctx->prng_lock);
280 ctx->flags |= PRNG_NEED_RESET;
281
282 prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY;
283
284 if (!key)
285 klen = DEFAULT_PRNG_KSZ;
286
287 if (V)
288 memcpy(ctx->V, V, DEFAULT_BLK_SZ);
289 else
290 memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ);
291
292 if (DT)
293 memcpy(ctx->DT, DT, DEFAULT_BLK_SZ);
294 else
295 memset(ctx->DT, 0, DEFAULT_BLK_SZ);
296
297 memset(ctx->rand_data, 0, DEFAULT_BLK_SZ);
298 memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ);
299
300 if (ctx->tfm)
301 crypto_free_cipher(ctx->tfm);
302
303 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
304 if (IS_ERR(ctx->tfm)) {
305 dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n",
306 ctx);
307 ctx->tfm = NULL;
308 goto out;
309 }
310
311 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));
317 crypto_free_cipher(ctx->tfm);
318 goto out;
319 }
320
321 rc = 0;
322 ctx->flags &= ~PRNG_NEED_RESET;
323out:
324 spin_unlock(&ctx->prng_lock);
325
326 return rc;
327
328}
329
330static int cprng_init(struct crypto_tfm *tfm)
331{
332 struct prng_context *ctx = crypto_tfm_ctx(tfm);
333
334 spin_lock_init(&ctx->prng_lock);
335
336 return reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL);
337}
338
339static void cprng_exit(struct crypto_tfm *tfm)
340{
341 free_prng_context(crypto_tfm_ctx(tfm));
342}
343
344static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata,
345 unsigned int dlen)
346{
347 struct prng_context *prng = crypto_rng_ctx(tfm);
348
349 return get_prng_bytes(rdata, dlen, prng);
350}
351
352static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
353{
354 struct prng_context *prng = crypto_rng_ctx(tfm);
355 u8 *key = seed + DEFAULT_PRNG_KSZ;
356
357 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
358 return -EINVAL;
359
360 reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, NULL);
361
362 if (prng->flags & PRNG_NEED_RESET)
363 return -EINVAL;
364 return 0;
365}
366
367static struct crypto_alg rng_alg = {
368 .cra_name = "stdrng",
369 .cra_driver_name = "ansi_cprng",
370 .cra_priority = 100,
371 .cra_flags = CRYPTO_ALG_TYPE_RNG,
372 .cra_ctxsize = sizeof(struct prng_context),
373 .cra_type = &crypto_rng_type,
374 .cra_module = THIS_MODULE,
375 .cra_list = LIST_HEAD_INIT(rng_alg.cra_list),
376 .cra_init = cprng_init,
377 .cra_exit = cprng_exit,
378 .cra_u = {
379 .rng = {
380 .rng_make_random = cprng_get_random,
381 .rng_reset = cprng_reset,
382 .seedsize = DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ,
383 }
384 }
385};
386
387
388
389static int __init prng_mod_init(void)
390{
391 int ret = 0;
392
393 if (fips_enabled)
394 rng_alg.cra_priority += 200;
395
396 ret = crypto_register_alg(&rng_alg);
397
398 if (ret)
399 goto out;
400out:
401 return 0;
402}
403
404static void __exit prng_mod_fini(void)
405{
406 crypto_unregister_alg(&rng_alg);
407 return;
408}
409
410MODULE_LICENSE("GPL");
411MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
412MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
413module_param(dbg, int, 0);
414MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
415module_init(prng_mod_init);
416module_exit(prng_mod_fini);
417MODULE_ALIAS("stdrng");
418
