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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * PRNG: Pseudo Random Number Generator
4 * Based on NIST Recommended PRNG From ANSI X9.31 Appendix A.2.4 using
5 * AES 128 cipher
6 *
7 * (C) Neil Horman <nhorman@tuxdriver.com>
8 */
9
10#include <crypto/internal/cipher.h>
11#include <crypto/internal/rng.h>
12#include <linux/err.h>
13#include <linux/init.h>
14#include <linux/module.h>
15#include <linux/moduleparam.h>
16#include <linux/string.h>
17
18#define DEFAULT_PRNG_KEY "0123456789abcdef"
19#define DEFAULT_PRNG_KSZ 16
20#define DEFAULT_BLK_SZ 16
21#define DEFAULT_V_SEED "zaybxcwdveuftgsh"
22
23/*
24 * Flags for the prng_context flags field
25 */
26
27#define PRNG_FIXED_SIZE 0x1
28#define PRNG_NEED_RESET 0x2
29
30/*
31 * Note: DT is our counter value
32 * I is our intermediate value
33 * V is our seed vector
34 * See http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
35 * for implementation details
36 */
37
38
39struct prng_context {
40 spinlock_t prng_lock;
41 unsigned char rand_data[DEFAULT_BLK_SZ];
42 unsigned char last_rand_data[DEFAULT_BLK_SZ];
43 unsigned char DT[DEFAULT_BLK_SZ];
44 unsigned char I[DEFAULT_BLK_SZ];
45 unsigned char V[DEFAULT_BLK_SZ];
46 u32 rand_data_valid;
47 struct crypto_cipher *tfm;
48 u32 flags;
49};
50
51static int dbg;
52
53static void hexdump(char *note, unsigned char *buf, unsigned int len)
54{
55 if (dbg) {
56 printk(KERN_CRIT "%s", note);
57 print_hex_dump(KERN_CONT, "", DUMP_PREFIX_OFFSET,
58 16, 1,
59 buf, len, false);
60 }
61}
62
63#define dbgprint(format, args...) do {\
64if (dbg)\
65 printk(format, ##args);\
66} while (0)
67
68static void xor_vectors(unsigned char *in1, unsigned char *in2,
69 unsigned char *out, unsigned int size)
70{
71 int i;
72
73 for (i = 0; i < size; i++)
74 out[i] = in1[i] ^ in2[i];
75
76}
77/*
78 * Returns DEFAULT_BLK_SZ bytes of random data per call
79 * returns 0 if generation succeeded, <0 if something went wrong
80 */
81static int _get_more_prng_bytes(struct prng_context *ctx, int cont_test)
82{
83 int i;
84 unsigned char tmp[DEFAULT_BLK_SZ];
85 unsigned char *output = NULL;
86
87
88 dbgprint(KERN_CRIT "Calling _get_more_prng_bytes for context %p\n",
89 ctx);
90
91 hexdump("Input DT: ", ctx->DT, DEFAULT_BLK_SZ);
92 hexdump("Input I: ", ctx->I, DEFAULT_BLK_SZ);
93 hexdump("Input V: ", ctx->V, DEFAULT_BLK_SZ);
94
95 /*
96 * This algorithm is a 3 stage state machine
97 */
98 for (i = 0; i < 3; i++) {
99
100 switch (i) {
101 case 0:
102 /*
103 * Start by encrypting the counter value
104 * This gives us an intermediate value I
105 */
106 memcpy(tmp, ctx->DT, DEFAULT_BLK_SZ);
107 output = ctx->I;
108 hexdump("tmp stage 0: ", tmp, DEFAULT_BLK_SZ);
109 break;
110 case 1:
111
112 /*
113 * Next xor I with our secret vector V
114 * encrypt that result to obtain our
115 * pseudo random data which we output
116 */
117 xor_vectors(ctx->I, ctx->V, tmp, DEFAULT_BLK_SZ);
118 hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ);
119 output = ctx->rand_data;
120 break;
121 case 2:
122 /*
123 * First check that we didn't produce the same
124 * random data that we did last time around through this
125 */
126 if (!memcmp(ctx->rand_data, ctx->last_rand_data,
127 DEFAULT_BLK_SZ)) {
128 if (cont_test) {
129 panic("cprng %p Failed repetition check!\n",
130 ctx);
131 }
132
133 printk(KERN_ERR
134 "ctx %p Failed repetition check!\n",
135 ctx);
136
137 ctx->flags |= PRNG_NEED_RESET;
138 return -EINVAL;
139 }
140 memcpy(ctx->last_rand_data, ctx->rand_data,
141 DEFAULT_BLK_SZ);
142
143 /*
144 * Lastly xor the random data with I
145 * and encrypt that to obtain a new secret vector V
146 */
147 xor_vectors(ctx->rand_data, ctx->I, tmp,
148 DEFAULT_BLK_SZ);
149 output = ctx->V;
150 hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ);
151 break;
152 }
153
154
155 /* do the encryption */
156 crypto_cipher_encrypt_one(ctx->tfm, output, tmp);
157
158 }
159
160 /*
161 * Now update our DT value
162 */
163 for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) {
164 ctx->DT[i] += 1;
165 if (ctx->DT[i] != 0)
166 break;
167 }
168
169 dbgprint("Returning new block for context %p\n", ctx);
170 ctx->rand_data_valid = 0;
171
172 hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ);
173 hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ);
174 hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ);
175 hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ);
176
177 return 0;
178}
179
180/* Our exported functions */
181static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx,
182 int do_cont_test)
183{
184 unsigned char *ptr = buf;
185 unsigned int byte_count = (unsigned int)nbytes;
186 int err;
187
188
189 spin_lock_bh(&ctx->prng_lock);
190
191 err = -EINVAL;
192 if (ctx->flags & PRNG_NEED_RESET)
193 goto done;
194
195 /*
196 * If the FIXED_SIZE flag is on, only return whole blocks of
197 * pseudo random data
198 */
199 err = -EINVAL;
200 if (ctx->flags & PRNG_FIXED_SIZE) {
201 if (nbytes < DEFAULT_BLK_SZ)
202 goto done;
203 byte_count = DEFAULT_BLK_SZ;
204 }
205
206 /*
207 * Return 0 in case of success as mandated by the kernel
208 * crypto API interface definition.
209 */
210 err = 0;
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, do_cont_test) < 0) {
219 memset(buf, 0, nbytes);
220 err = -EINVAL;
221 goto done;
222 }
223 }
224
225 /*
226 * Copy any data less than an entire block
227 */
228 if (byte_count < DEFAULT_BLK_SZ) {
229empty_rbuf:
230 while (ctx->rand_data_valid < DEFAULT_BLK_SZ) {
231 *ptr = ctx->rand_data[ctx->rand_data_valid];
232 ptr++;
233 byte_count--;
234 ctx->rand_data_valid++;
235 if (byte_count == 0)
236 goto done;
237 }
238 }
239
240 /*
241 * Now copy whole blocks
242 */
243 for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
244 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
245 if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
246 memset(buf, 0, nbytes);
247 err = -EINVAL;
248 goto done;
249 }
250 }
251 if (ctx->rand_data_valid > 0)
252 goto empty_rbuf;
253 memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
254 ctx->rand_data_valid += DEFAULT_BLK_SZ;
255 ptr += DEFAULT_BLK_SZ;
256 }
257
258 /*
259 * Now go back and get any remaining partial block
260 */
261 if (byte_count)
262 goto remainder;
263
264done:
265 spin_unlock_bh(&ctx->prng_lock);
266 dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",
267 err, ctx);
268 return err;
269}
270
271static void free_prng_context(struct prng_context *ctx)
272{
273 crypto_free_cipher(ctx->tfm);
274}
275
276static int reset_prng_context(struct prng_context *ctx,
277 const unsigned char *key, size_t klen,
278 const unsigned char *V, const unsigned char *DT)
279{
280 int ret;
281 const unsigned char *prng_key;
282
283 spin_lock_bh(&ctx->prng_lock);
284 ctx->flags |= PRNG_NEED_RESET;
285
286 prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY;
287
288 if (!key)
289 klen = DEFAULT_PRNG_KSZ;
290
291 if (V)
292 memcpy(ctx->V, V, DEFAULT_BLK_SZ);
293 else
294 memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ);
295
296 if (DT)
297 memcpy(ctx->DT, DT, DEFAULT_BLK_SZ);
298 else
299 memset(ctx->DT, 0, DEFAULT_BLK_SZ);
300
301 memset(ctx->rand_data, 0, DEFAULT_BLK_SZ);
302 memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ);
303
304 ctx->rand_data_valid = DEFAULT_BLK_SZ;
305
306 ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen);
307 if (ret) {
308 dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
309 crypto_cipher_get_flags(ctx->tfm));
310 goto out;
311 }
312
313 ret = 0;
314 ctx->flags &= ~PRNG_NEED_RESET;
315out:
316 spin_unlock_bh(&ctx->prng_lock);
317 return ret;
318}
319
320static int cprng_init(struct crypto_tfm *tfm)
321{
322 struct prng_context *ctx = crypto_tfm_ctx(tfm);
323
324 spin_lock_init(&ctx->prng_lock);
325 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
326 if (IS_ERR(ctx->tfm)) {
327 dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n",
328 ctx);
329 return PTR_ERR(ctx->tfm);
330 }
331
332 if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0)
333 return -EINVAL;
334
335 /*
336 * after allocation, we should always force the user to reset
337 * so they don't inadvertently use the insecure default values
338 * without specifying them intentially
339 */
340 ctx->flags |= PRNG_NEED_RESET;
341 return 0;
342}
343
344static void cprng_exit(struct crypto_tfm *tfm)
345{
346 free_prng_context(crypto_tfm_ctx(tfm));
347}
348
349static int cprng_get_random(struct crypto_rng *tfm,
350 const u8 *src, unsigned int slen,
351 u8 *rdata, unsigned int dlen)
352{
353 struct prng_context *prng = crypto_rng_ctx(tfm);
354
355 return get_prng_bytes(rdata, dlen, prng, 0);
356}
357
358/*
359 * This is the cprng_registered reset method the seed value is
360 * interpreted as the tuple { V KEY DT}
361 * V and KEY are required during reset, and DT is optional, detected
362 * as being present by testing the length of the seed
363 */
364static int cprng_reset(struct crypto_rng *tfm,
365 const u8 *seed, unsigned int slen)
366{
367 struct prng_context *prng = crypto_rng_ctx(tfm);
368 const u8 *key = seed + DEFAULT_BLK_SZ;
369 const u8 *dt = NULL;
370
371 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
372 return -EINVAL;
373
374 if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ))
375 dt = key + DEFAULT_PRNG_KSZ;
376
377 reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt);
378
379 if (prng->flags & PRNG_NEED_RESET)
380 return -EINVAL;
381 return 0;
382}
383
384#ifdef CONFIG_CRYPTO_FIPS
385static int fips_cprng_get_random(struct crypto_rng *tfm,
386 const u8 *src, unsigned int slen,
387 u8 *rdata, unsigned int dlen)
388{
389 struct prng_context *prng = crypto_rng_ctx(tfm);
390
391 return get_prng_bytes(rdata, dlen, prng, 1);
392}
393
394static int fips_cprng_reset(struct crypto_rng *tfm,
395 const u8 *seed, unsigned int slen)
396{
397 u8 rdata[DEFAULT_BLK_SZ];
398 const u8 *key = seed + DEFAULT_BLK_SZ;
399 int rc;
400
401 struct prng_context *prng = crypto_rng_ctx(tfm);
402
403 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
404 return -EINVAL;
405
406 /* fips strictly requires seed != key */
407 if (!memcmp(seed, key, DEFAULT_PRNG_KSZ))
408 return -EINVAL;
409
410 rc = cprng_reset(tfm, seed, slen);
411
412 if (!rc)
413 goto out;
414
415 /* this primes our continuity test */
416 rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0);
417 prng->rand_data_valid = DEFAULT_BLK_SZ;
418
419out:
420 return rc;
421}
422#endif
423
424static struct rng_alg rng_algs[] = { {
425 .generate = cprng_get_random,
426 .seed = cprng_reset,
427 .seedsize = DEFAULT_PRNG_KSZ + 2 * DEFAULT_BLK_SZ,
428 .base = {
429 .cra_name = "stdrng",
430 .cra_driver_name = "ansi_cprng",
431 .cra_priority = 100,
432 .cra_ctxsize = sizeof(struct prng_context),
433 .cra_module = THIS_MODULE,
434 .cra_init = cprng_init,
435 .cra_exit = cprng_exit,
436 }
437#ifdef CONFIG_CRYPTO_FIPS
438}, {
439 .generate = fips_cprng_get_random,
440 .seed = fips_cprng_reset,
441 .seedsize = DEFAULT_PRNG_KSZ + 2 * DEFAULT_BLK_SZ,
442 .base = {
443 .cra_name = "fips(ansi_cprng)",
444 .cra_driver_name = "fips_ansi_cprng",
445 .cra_priority = 300,
446 .cra_ctxsize = sizeof(struct prng_context),
447 .cra_module = THIS_MODULE,
448 .cra_init = cprng_init,
449 .cra_exit = cprng_exit,
450 }
451#endif
452} };
453
454/* Module initalization */
455static int __init prng_mod_init(void)
456{
457 return crypto_register_rngs(rng_algs, ARRAY_SIZE(rng_algs));
458}
459
460static void __exit prng_mod_fini(void)
461{
462 crypto_unregister_rngs(rng_algs, ARRAY_SIZE(rng_algs));
463}
464
465MODULE_LICENSE("GPL");
466MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
467MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
468module_param(dbg, int, 0);
469MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
470subsys_initcall(prng_mod_init);
471module_exit(prng_mod_fini);
472MODULE_ALIAS_CRYPTO("stdrng");
473MODULE_ALIAS_CRYPTO("ansi_cprng");
474MODULE_IMPORT_NS(CRYPTO_INTERNAL);
1/*
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 succeeded, <0 if something went wrong
87 */
88static int _get_more_prng_bytes(struct prng_context *ctx, int cont_test)
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)) {
135 if (cont_test) {
136 panic("cprng %p Failed repetition check!\n",
137 ctx);
138 }
139
140 printk(KERN_ERR
141 "ctx %p Failed repetition check!\n",
142 ctx);
143
144 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 */
170 for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) {
171 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 int do_cont_test)
190{
191 unsigned char *ptr = buf;
192 unsigned int byte_count = (unsigned int)nbytes;
193 int err;
194
195
196 spin_lock_bh(&ctx->prng_lock);
197
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
213 err = byte_count;
214
215 dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",
216 byte_count, ctx);
217
218
219remainder:
220 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
221 if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
222 memset(buf, 0, nbytes);
223 err = -EINVAL;
224 goto done;
225 }
226 }
227
228 /*
229 * Copy any data less than an entire block
230 */
231 if (byte_count < DEFAULT_BLK_SZ) {
232empty_rbuf:
233 for (; ctx->rand_data_valid < DEFAULT_BLK_SZ;
234 ctx->rand_data_valid++) {
235 *ptr = ctx->rand_data[ctx->rand_data_valid];
236 ptr++;
237 byte_count--;
238 if (byte_count == 0)
239 goto done;
240 }
241 }
242
243 /*
244 * Now copy whole blocks
245 */
246 for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
247 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
248 if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
249 memset(buf, 0, nbytes);
250 err = -EINVAL;
251 goto done;
252 }
253 }
254 if (ctx->rand_data_valid > 0)
255 goto empty_rbuf;
256 memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
257 ctx->rand_data_valid += DEFAULT_BLK_SZ;
258 ptr += DEFAULT_BLK_SZ;
259 }
260
261 /*
262 * Now go back and get any remaining partial block
263 */
264 if (byte_count)
265 goto remainder;
266
267done:
268 spin_unlock_bh(&ctx->prng_lock);
269 dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",
270 err, ctx);
271 return err;
272}
273
274static void free_prng_context(struct prng_context *ctx)
275{
276 crypto_free_cipher(ctx->tfm);
277}
278
279static int reset_prng_context(struct prng_context *ctx,
280 unsigned char *key, size_t klen,
281 unsigned char *V, unsigned char *DT)
282{
283 int ret;
284 unsigned char *prng_key;
285
286 spin_lock_bh(&ctx->prng_lock);
287 ctx->flags |= PRNG_NEED_RESET;
288
289 prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY;
290
291 if (!key)
292 klen = DEFAULT_PRNG_KSZ;
293
294 if (V)
295 memcpy(ctx->V, V, DEFAULT_BLK_SZ);
296 else
297 memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ);
298
299 if (DT)
300 memcpy(ctx->DT, DT, DEFAULT_BLK_SZ);
301 else
302 memset(ctx->DT, 0, DEFAULT_BLK_SZ);
303
304 memset(ctx->rand_data, 0, DEFAULT_BLK_SZ);
305 memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ);
306
307 ctx->rand_data_valid = DEFAULT_BLK_SZ;
308
309 ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen);
310 if (ret) {
311 dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
312 crypto_cipher_get_flags(ctx->tfm));
313 goto out;
314 }
315
316 ret = 0;
317 ctx->flags &= ~PRNG_NEED_RESET;
318out:
319 spin_unlock_bh(&ctx->prng_lock);
320 return ret;
321}
322
323static int cprng_init(struct crypto_tfm *tfm)
324{
325 struct prng_context *ctx = crypto_tfm_ctx(tfm);
326
327 spin_lock_init(&ctx->prng_lock);
328 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
329 if (IS_ERR(ctx->tfm)) {
330 dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n",
331 ctx);
332 return PTR_ERR(ctx->tfm);
333 }
334
335 if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0)
336 return -EINVAL;
337
338 /*
339 * after allocation, we should always force the user to reset
340 * so they don't inadvertently use the insecure default values
341 * without specifying them intentially
342 */
343 ctx->flags |= PRNG_NEED_RESET;
344 return 0;
345}
346
347static void cprng_exit(struct crypto_tfm *tfm)
348{
349 free_prng_context(crypto_tfm_ctx(tfm));
350}
351
352static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata,
353 unsigned int dlen)
354{
355 struct prng_context *prng = crypto_rng_ctx(tfm);
356
357 return get_prng_bytes(rdata, dlen, prng, 0);
358}
359
360/*
361 * This is the cprng_registered reset method the seed value is
362 * interpreted as the tuple { V KEY DT}
363 * V and KEY are required during reset, and DT is optional, detected
364 * as being present by testing the length of the seed
365 */
366static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
367{
368 struct prng_context *prng = crypto_rng_ctx(tfm);
369 u8 *key = seed + DEFAULT_BLK_SZ;
370 u8 *dt = NULL;
371
372 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
373 return -EINVAL;
374
375 if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ))
376 dt = key + DEFAULT_PRNG_KSZ;
377
378 reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt);
379
380 if (prng->flags & PRNG_NEED_RESET)
381 return -EINVAL;
382 return 0;
383}
384
385static struct crypto_alg rng_alg = {
386 .cra_name = "stdrng",
387 .cra_driver_name = "ansi_cprng",
388 .cra_priority = 100,
389 .cra_flags = CRYPTO_ALG_TYPE_RNG,
390 .cra_ctxsize = sizeof(struct prng_context),
391 .cra_type = &crypto_rng_type,
392 .cra_module = THIS_MODULE,
393 .cra_list = LIST_HEAD_INIT(rng_alg.cra_list),
394 .cra_init = cprng_init,
395 .cra_exit = cprng_exit,
396 .cra_u = {
397 .rng = {
398 .rng_make_random = cprng_get_random,
399 .rng_reset = cprng_reset,
400 .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
401 }
402 }
403};
404
405#ifdef CONFIG_CRYPTO_FIPS
406static int fips_cprng_get_random(struct crypto_rng *tfm, u8 *rdata,
407 unsigned int dlen)
408{
409 struct prng_context *prng = crypto_rng_ctx(tfm);
410
411 return get_prng_bytes(rdata, dlen, prng, 1);
412}
413
414static int fips_cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
415{
416 u8 rdata[DEFAULT_BLK_SZ];
417 int rc;
418
419 struct prng_context *prng = crypto_rng_ctx(tfm);
420
421 rc = cprng_reset(tfm, seed, slen);
422
423 if (!rc)
424 goto out;
425
426 /* this primes our continuity test */
427 rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0);
428 prng->rand_data_valid = DEFAULT_BLK_SZ;
429
430out:
431 return rc;
432}
433
434static struct crypto_alg fips_rng_alg = {
435 .cra_name = "fips(ansi_cprng)",
436 .cra_driver_name = "fips_ansi_cprng",
437 .cra_priority = 300,
438 .cra_flags = CRYPTO_ALG_TYPE_RNG,
439 .cra_ctxsize = sizeof(struct prng_context),
440 .cra_type = &crypto_rng_type,
441 .cra_module = THIS_MODULE,
442 .cra_list = LIST_HEAD_INIT(rng_alg.cra_list),
443 .cra_init = cprng_init,
444 .cra_exit = cprng_exit,
445 .cra_u = {
446 .rng = {
447 .rng_make_random = fips_cprng_get_random,
448 .rng_reset = fips_cprng_reset,
449 .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
450 }
451 }
452};
453#endif
454
455/* Module initalization */
456static int __init prng_mod_init(void)
457{
458 int rc = 0;
459
460 rc = crypto_register_alg(&rng_alg);
461#ifdef CONFIG_CRYPTO_FIPS
462 if (rc)
463 goto out;
464
465 rc = crypto_register_alg(&fips_rng_alg);
466
467out:
468#endif
469 return rc;
470}
471
472static void __exit prng_mod_fini(void)
473{
474 crypto_unregister_alg(&rng_alg);
475#ifdef CONFIG_CRYPTO_FIPS
476 crypto_unregister_alg(&fips_rng_alg);
477#endif
478 return;
479}
480
481MODULE_LICENSE("GPL");
482MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
483MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
484module_param(dbg, int, 0);
485MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
486module_init(prng_mod_init);
487module_exit(prng_mod_fini);
488MODULE_ALIAS("stdrng");