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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/rng.h>
11#include <linux/err.h>
12#include <linux/init.h>
13#include <linux/module.h>
14#include <linux/moduleparam.h>
15#include <linux/string.h>
16
17#define DEFAULT_PRNG_KEY "0123456789abcdef"
18#define DEFAULT_PRNG_KSZ 16
19#define DEFAULT_BLK_SZ 16
20#define DEFAULT_V_SEED "zaybxcwdveuftgsh"
21
22/*
23 * Flags for the prng_context flags field
24 */
25
26#define PRNG_FIXED_SIZE 0x1
27#define PRNG_NEED_RESET 0x2
28
29/*
30 * Note: DT is our counter value
31 * I is our intermediate value
32 * V is our seed vector
33 * See http://csrc.nist.gov/groups/STM/cavp/documents/rng/931rngext.pdf
34 * for implementation details
35 */
36
37
38struct prng_context {
39 spinlock_t prng_lock;
40 unsigned char rand_data[DEFAULT_BLK_SZ];
41 unsigned char last_rand_data[DEFAULT_BLK_SZ];
42 unsigned char DT[DEFAULT_BLK_SZ];
43 unsigned char I[DEFAULT_BLK_SZ];
44 unsigned char V[DEFAULT_BLK_SZ];
45 u32 rand_data_valid;
46 struct crypto_cipher *tfm;
47 u32 flags;
48};
49
50static int dbg;
51
52static void hexdump(char *note, unsigned char *buf, unsigned int len)
53{
54 if (dbg) {
55 printk(KERN_CRIT "%s", note);
56 print_hex_dump(KERN_CONT, "", DUMP_PREFIX_OFFSET,
57 16, 1,
58 buf, len, false);
59 }
60}
61
62#define dbgprint(format, args...) do {\
63if (dbg)\
64 printk(format, ##args);\
65} while (0)
66
67static void xor_vectors(unsigned char *in1, unsigned char *in2,
68 unsigned char *out, unsigned int size)
69{
70 int i;
71
72 for (i = 0; i < size; i++)
73 out[i] = in1[i] ^ in2[i];
74
75}
76/*
77 * Returns DEFAULT_BLK_SZ bytes of random data per call
78 * returns 0 if generation succeeded, <0 if something went wrong
79 */
80static int _get_more_prng_bytes(struct prng_context *ctx, int cont_test)
81{
82 int i;
83 unsigned char tmp[DEFAULT_BLK_SZ];
84 unsigned char *output = NULL;
85
86
87 dbgprint(KERN_CRIT "Calling _get_more_prng_bytes for context %p\n",
88 ctx);
89
90 hexdump("Input DT: ", ctx->DT, DEFAULT_BLK_SZ);
91 hexdump("Input I: ", ctx->I, DEFAULT_BLK_SZ);
92 hexdump("Input V: ", ctx->V, DEFAULT_BLK_SZ);
93
94 /*
95 * This algorithm is a 3 stage state machine
96 */
97 for (i = 0; i < 3; i++) {
98
99 switch (i) {
100 case 0:
101 /*
102 * Start by encrypting the counter value
103 * This gives us an intermediate value I
104 */
105 memcpy(tmp, ctx->DT, DEFAULT_BLK_SZ);
106 output = ctx->I;
107 hexdump("tmp stage 0: ", tmp, DEFAULT_BLK_SZ);
108 break;
109 case 1:
110
111 /*
112 * Next xor I with our secret vector V
113 * encrypt that result to obtain our
114 * pseudo random data which we output
115 */
116 xor_vectors(ctx->I, ctx->V, tmp, DEFAULT_BLK_SZ);
117 hexdump("tmp stage 1: ", tmp, DEFAULT_BLK_SZ);
118 output = ctx->rand_data;
119 break;
120 case 2:
121 /*
122 * First check that we didn't produce the same
123 * random data that we did last time around through this
124 */
125 if (!memcmp(ctx->rand_data, ctx->last_rand_data,
126 DEFAULT_BLK_SZ)) {
127 if (cont_test) {
128 panic("cprng %p Failed repetition check!\n",
129 ctx);
130 }
131
132 printk(KERN_ERR
133 "ctx %p Failed repetition check!\n",
134 ctx);
135
136 ctx->flags |= PRNG_NEED_RESET;
137 return -EINVAL;
138 }
139 memcpy(ctx->last_rand_data, ctx->rand_data,
140 DEFAULT_BLK_SZ);
141
142 /*
143 * Lastly xor the random data with I
144 * and encrypt that to obtain a new secret vector V
145 */
146 xor_vectors(ctx->rand_data, ctx->I, tmp,
147 DEFAULT_BLK_SZ);
148 output = ctx->V;
149 hexdump("tmp stage 2: ", tmp, DEFAULT_BLK_SZ);
150 break;
151 }
152
153
154 /* do the encryption */
155 crypto_cipher_encrypt_one(ctx->tfm, output, tmp);
156
157 }
158
159 /*
160 * Now update our DT value
161 */
162 for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) {
163 ctx->DT[i] += 1;
164 if (ctx->DT[i] != 0)
165 break;
166 }
167
168 dbgprint("Returning new block for context %p\n", ctx);
169 ctx->rand_data_valid = 0;
170
171 hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ);
172 hexdump("Output I: ", ctx->I, DEFAULT_BLK_SZ);
173 hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ);
174 hexdump("New Random Data: ", ctx->rand_data, DEFAULT_BLK_SZ);
175
176 return 0;
177}
178
179/* Our exported functions */
180static int get_prng_bytes(char *buf, size_t nbytes, struct prng_context *ctx,
181 int do_cont_test)
182{
183 unsigned char *ptr = buf;
184 unsigned int byte_count = (unsigned int)nbytes;
185 int err;
186
187
188 spin_lock_bh(&ctx->prng_lock);
189
190 err = -EINVAL;
191 if (ctx->flags & PRNG_NEED_RESET)
192 goto done;
193
194 /*
195 * If the FIXED_SIZE flag is on, only return whole blocks of
196 * pseudo random data
197 */
198 err = -EINVAL;
199 if (ctx->flags & PRNG_FIXED_SIZE) {
200 if (nbytes < DEFAULT_BLK_SZ)
201 goto done;
202 byte_count = DEFAULT_BLK_SZ;
203 }
204
205 /*
206 * Return 0 in case of success as mandated by the kernel
207 * crypto API interface definition.
208 */
209 err = 0;
210
211 dbgprint(KERN_CRIT "getting %d random bytes for context %p\n",
212 byte_count, ctx);
213
214
215remainder:
216 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
217 if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
218 memset(buf, 0, nbytes);
219 err = -EINVAL;
220 goto done;
221 }
222 }
223
224 /*
225 * Copy any data less than an entire block
226 */
227 if (byte_count < DEFAULT_BLK_SZ) {
228empty_rbuf:
229 while (ctx->rand_data_valid < DEFAULT_BLK_SZ) {
230 *ptr = ctx->rand_data[ctx->rand_data_valid];
231 ptr++;
232 byte_count--;
233 ctx->rand_data_valid++;
234 if (byte_count == 0)
235 goto done;
236 }
237 }
238
239 /*
240 * Now copy whole blocks
241 */
242 for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
243 if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
244 if (_get_more_prng_bytes(ctx, do_cont_test) < 0) {
245 memset(buf, 0, nbytes);
246 err = -EINVAL;
247 goto done;
248 }
249 }
250 if (ctx->rand_data_valid > 0)
251 goto empty_rbuf;
252 memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
253 ctx->rand_data_valid += DEFAULT_BLK_SZ;
254 ptr += DEFAULT_BLK_SZ;
255 }
256
257 /*
258 * Now go back and get any remaining partial block
259 */
260 if (byte_count)
261 goto remainder;
262
263done:
264 spin_unlock_bh(&ctx->prng_lock);
265 dbgprint(KERN_CRIT "returning %d from get_prng_bytes in context %p\n",
266 err, ctx);
267 return err;
268}
269
270static void free_prng_context(struct prng_context *ctx)
271{
272 crypto_free_cipher(ctx->tfm);
273}
274
275static int reset_prng_context(struct prng_context *ctx,
276 const unsigned char *key, size_t klen,
277 const unsigned char *V, const unsigned char *DT)
278{
279 int ret;
280 const unsigned char *prng_key;
281
282 spin_lock_bh(&ctx->prng_lock);
283 ctx->flags |= PRNG_NEED_RESET;
284
285 prng_key = (key != NULL) ? key : (unsigned char *)DEFAULT_PRNG_KEY;
286
287 if (!key)
288 klen = DEFAULT_PRNG_KSZ;
289
290 if (V)
291 memcpy(ctx->V, V, DEFAULT_BLK_SZ);
292 else
293 memcpy(ctx->V, DEFAULT_V_SEED, DEFAULT_BLK_SZ);
294
295 if (DT)
296 memcpy(ctx->DT, DT, DEFAULT_BLK_SZ);
297 else
298 memset(ctx->DT, 0, DEFAULT_BLK_SZ);
299
300 memset(ctx->rand_data, 0, DEFAULT_BLK_SZ);
301 memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ);
302
303 ctx->rand_data_valid = DEFAULT_BLK_SZ;
304
305 ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen);
306 if (ret) {
307 dbgprint(KERN_CRIT "PRNG: setkey() failed flags=%x\n",
308 crypto_cipher_get_flags(ctx->tfm));
309 goto out;
310 }
311
312 ret = 0;
313 ctx->flags &= ~PRNG_NEED_RESET;
314out:
315 spin_unlock_bh(&ctx->prng_lock);
316 return ret;
317}
318
319static int cprng_init(struct crypto_tfm *tfm)
320{
321 struct prng_context *ctx = crypto_tfm_ctx(tfm);
322
323 spin_lock_init(&ctx->prng_lock);
324 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
325 if (IS_ERR(ctx->tfm)) {
326 dbgprint(KERN_CRIT "Failed to alloc tfm for context %p\n",
327 ctx);
328 return PTR_ERR(ctx->tfm);
329 }
330
331 if (reset_prng_context(ctx, NULL, DEFAULT_PRNG_KSZ, NULL, NULL) < 0)
332 return -EINVAL;
333
334 /*
335 * after allocation, we should always force the user to reset
336 * so they don't inadvertently use the insecure default values
337 * without specifying them intentially
338 */
339 ctx->flags |= PRNG_NEED_RESET;
340 return 0;
341}
342
343static void cprng_exit(struct crypto_tfm *tfm)
344{
345 free_prng_context(crypto_tfm_ctx(tfm));
346}
347
348static int cprng_get_random(struct crypto_rng *tfm,
349 const u8 *src, unsigned int slen,
350 u8 *rdata, unsigned int dlen)
351{
352 struct prng_context *prng = crypto_rng_ctx(tfm);
353
354 return get_prng_bytes(rdata, dlen, prng, 0);
355}
356
357/*
358 * This is the cprng_registered reset method the seed value is
359 * interpreted as the tuple { V KEY DT}
360 * V and KEY are required during reset, and DT is optional, detected
361 * as being present by testing the length of the seed
362 */
363static int cprng_reset(struct crypto_rng *tfm,
364 const u8 *seed, unsigned int slen)
365{
366 struct prng_context *prng = crypto_rng_ctx(tfm);
367 const u8 *key = seed + DEFAULT_BLK_SZ;
368 const u8 *dt = NULL;
369
370 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
371 return -EINVAL;
372
373 if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ))
374 dt = key + DEFAULT_PRNG_KSZ;
375
376 reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt);
377
378 if (prng->flags & PRNG_NEED_RESET)
379 return -EINVAL;
380 return 0;
381}
382
383#ifdef CONFIG_CRYPTO_FIPS
384static int fips_cprng_get_random(struct crypto_rng *tfm,
385 const u8 *src, unsigned int slen,
386 u8 *rdata, unsigned int dlen)
387{
388 struct prng_context *prng = crypto_rng_ctx(tfm);
389
390 return get_prng_bytes(rdata, dlen, prng, 1);
391}
392
393static int fips_cprng_reset(struct crypto_rng *tfm,
394 const u8 *seed, unsigned int slen)
395{
396 u8 rdata[DEFAULT_BLK_SZ];
397 const u8 *key = seed + DEFAULT_BLK_SZ;
398 int rc;
399
400 struct prng_context *prng = crypto_rng_ctx(tfm);
401
402 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
403 return -EINVAL;
404
405 /* fips strictly requires seed != key */
406 if (!memcmp(seed, key, DEFAULT_PRNG_KSZ))
407 return -EINVAL;
408
409 rc = cprng_reset(tfm, seed, slen);
410
411 if (!rc)
412 goto out;
413
414 /* this primes our continuity test */
415 rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0);
416 prng->rand_data_valid = DEFAULT_BLK_SZ;
417
418out:
419 return rc;
420}
421#endif
422
423static struct rng_alg rng_algs[] = { {
424 .generate = cprng_get_random,
425 .seed = cprng_reset,
426 .seedsize = DEFAULT_PRNG_KSZ + 2 * DEFAULT_BLK_SZ,
427 .base = {
428 .cra_name = "stdrng",
429 .cra_driver_name = "ansi_cprng",
430 .cra_priority = 100,
431 .cra_ctxsize = sizeof(struct prng_context),
432 .cra_module = THIS_MODULE,
433 .cra_init = cprng_init,
434 .cra_exit = cprng_exit,
435 }
436#ifdef CONFIG_CRYPTO_FIPS
437}, {
438 .generate = fips_cprng_get_random,
439 .seed = fips_cprng_reset,
440 .seedsize = DEFAULT_PRNG_KSZ + 2 * DEFAULT_BLK_SZ,
441 .base = {
442 .cra_name = "fips(ansi_cprng)",
443 .cra_driver_name = "fips_ansi_cprng",
444 .cra_priority = 300,
445 .cra_ctxsize = sizeof(struct prng_context),
446 .cra_module = THIS_MODULE,
447 .cra_init = cprng_init,
448 .cra_exit = cprng_exit,
449 }
450#endif
451} };
452
453/* Module initalization */
454static int __init prng_mod_init(void)
455{
456 return crypto_register_rngs(rng_algs, ARRAY_SIZE(rng_algs));
457}
458
459static void __exit prng_mod_fini(void)
460{
461 crypto_unregister_rngs(rng_algs, ARRAY_SIZE(rng_algs));
462}
463
464MODULE_LICENSE("GPL");
465MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
466MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
467module_param(dbg, int, 0);
468MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
469subsys_initcall(prng_mod_init);
470module_exit(prng_mod_fini);
471MODULE_ALIAS_CRYPTO("stdrng");
472MODULE_ALIAS_CRYPTO("ansi_cprng");
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 u8 *key = seed + DEFAULT_BLK_SZ;
418 int rc;
419
420 struct prng_context *prng = crypto_rng_ctx(tfm);
421
422 if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
423 return -EINVAL;
424
425 /* fips strictly requires seed != key */
426 if (!memcmp(seed, key, DEFAULT_PRNG_KSZ))
427 return -EINVAL;
428
429 rc = cprng_reset(tfm, seed, slen);
430
431 if (!rc)
432 goto out;
433
434 /* this primes our continuity test */
435 rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0);
436 prng->rand_data_valid = DEFAULT_BLK_SZ;
437
438out:
439 return rc;
440}
441
442static struct crypto_alg fips_rng_alg = {
443 .cra_name = "fips(ansi_cprng)",
444 .cra_driver_name = "fips_ansi_cprng",
445 .cra_priority = 300,
446 .cra_flags = CRYPTO_ALG_TYPE_RNG,
447 .cra_ctxsize = sizeof(struct prng_context),
448 .cra_type = &crypto_rng_type,
449 .cra_module = THIS_MODULE,
450 .cra_list = LIST_HEAD_INIT(rng_alg.cra_list),
451 .cra_init = cprng_init,
452 .cra_exit = cprng_exit,
453 .cra_u = {
454 .rng = {
455 .rng_make_random = fips_cprng_get_random,
456 .rng_reset = fips_cprng_reset,
457 .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
458 }
459 }
460};
461#endif
462
463/* Module initalization */
464static int __init prng_mod_init(void)
465{
466 int rc = 0;
467
468 rc = crypto_register_alg(&rng_alg);
469#ifdef CONFIG_CRYPTO_FIPS
470 if (rc)
471 goto out;
472
473 rc = crypto_register_alg(&fips_rng_alg);
474
475out:
476#endif
477 return rc;
478}
479
480static void __exit prng_mod_fini(void)
481{
482 crypto_unregister_alg(&rng_alg);
483#ifdef CONFIG_CRYPTO_FIPS
484 crypto_unregister_alg(&fips_rng_alg);
485#endif
486 return;
487}
488
489MODULE_LICENSE("GPL");
490MODULE_DESCRIPTION("Software Pseudo Random Number Generator");
491MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
492module_param(dbg, int, 0);
493MODULE_PARM_DESC(dbg, "Boolean to enable debugging (0/1 == off/on)");
494module_init(prng_mod_init);
495module_exit(prng_mod_fini);
496MODULE_ALIAS("stdrng");