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1/*
2 * Non-physical true random number generator based on timing jitter --
3 * Linux Kernel Crypto API specific code
4 *
5 * Copyright Stephan Mueller <smueller@chronox.de>, 2015
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, and the entire permission notice in its entirety,
12 * including the disclaimer of warranties.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. The name of the author may not be used to endorse or promote
17 * products derived from this software without specific prior
18 * written permission.
19 *
20 * ALTERNATIVELY, this product may be distributed under the terms of
21 * the GNU General Public License, in which case the provisions of the GPL2 are
22 * required INSTEAD OF the above restrictions. (This clause is
23 * necessary due to a potential bad interaction between the GPL and
24 * the restrictions contained in a BSD-style copyright.)
25 *
26 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
27 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
29 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
30 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
32 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
33 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
36 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
37 * DAMAGE.
38 */
39
40#include <linux/module.h>
41#include <linux/slab.h>
42#include <linux/module.h>
43#include <linux/fips.h>
44#include <linux/time.h>
45#include <linux/crypto.h>
46#include <crypto/internal/rng.h>
47
48struct rand_data;
49int jent_read_entropy(struct rand_data *ec, unsigned char *data,
50 unsigned int len);
51int jent_entropy_init(void);
52struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
53 unsigned int flags);
54void jent_entropy_collector_free(struct rand_data *entropy_collector);
55
56/***************************************************************************
57 * Helper function
58 ***************************************************************************/
59
60__u64 jent_rol64(__u64 word, unsigned int shift)
61{
62 return rol64(word, shift);
63}
64
65void *jent_zalloc(unsigned int len)
66{
67 return kzalloc(len, GFP_KERNEL);
68}
69
70void jent_zfree(void *ptr)
71{
72 kzfree(ptr);
73}
74
75int jent_fips_enabled(void)
76{
77 return fips_enabled;
78}
79
80void jent_panic(char *s)
81{
82 panic("%s", s);
83}
84
85void jent_memcpy(void *dest, const void *src, unsigned int n)
86{
87 memcpy(dest, src, n);
88}
89
90void jent_get_nstime(__u64 *out)
91{
92 struct timespec ts;
93 __u64 tmp = 0;
94
95 tmp = random_get_entropy();
96
97 /*
98 * If random_get_entropy does not return a value (which is possible on,
99 * for example, MIPS), invoke __getnstimeofday
100 * hoping that there are timers we can work with.
101 */
102 if ((0 == tmp) &&
103 (0 == __getnstimeofday(&ts))) {
104 tmp = ts.tv_sec;
105 tmp = tmp << 32;
106 tmp = tmp | ts.tv_nsec;
107 }
108
109 *out = tmp;
110}
111
112/***************************************************************************
113 * Kernel crypto API interface
114 ***************************************************************************/
115
116struct jitterentropy {
117 spinlock_t jent_lock;
118 struct rand_data *entropy_collector;
119};
120
121static int jent_kcapi_init(struct crypto_tfm *tfm)
122{
123 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
124 int ret = 0;
125
126 rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
127 if (!rng->entropy_collector)
128 ret = -ENOMEM;
129
130 spin_lock_init(&rng->jent_lock);
131 return ret;
132}
133
134static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
135{
136 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
137
138 spin_lock(&rng->jent_lock);
139 if (rng->entropy_collector)
140 jent_entropy_collector_free(rng->entropy_collector);
141 rng->entropy_collector = NULL;
142 spin_unlock(&rng->jent_lock);
143}
144
145static int jent_kcapi_random(struct crypto_rng *tfm,
146 const u8 *src, unsigned int slen,
147 u8 *rdata, unsigned int dlen)
148{
149 struct jitterentropy *rng = crypto_rng_ctx(tfm);
150 int ret = 0;
151
152 spin_lock(&rng->jent_lock);
153 ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
154 spin_unlock(&rng->jent_lock);
155
156 return ret;
157}
158
159static int jent_kcapi_reset(struct crypto_rng *tfm,
160 const u8 *seed, unsigned int slen)
161{
162 return 0;
163}
164
165static struct rng_alg jent_alg = {
166 .generate = jent_kcapi_random,
167 .seed = jent_kcapi_reset,
168 .seedsize = 0,
169 .base = {
170 .cra_name = "jitterentropy_rng",
171 .cra_driver_name = "jitterentropy_rng",
172 .cra_priority = 100,
173 .cra_ctxsize = sizeof(struct jitterentropy),
174 .cra_module = THIS_MODULE,
175 .cra_init = jent_kcapi_init,
176 .cra_exit = jent_kcapi_cleanup,
177
178 }
179};
180
181static int __init jent_mod_init(void)
182{
183 int ret = 0;
184
185 ret = jent_entropy_init();
186 if (ret) {
187 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
188 return -EFAULT;
189 }
190 return crypto_register_rng(&jent_alg);
191}
192
193static void __exit jent_mod_exit(void)
194{
195 crypto_unregister_rng(&jent_alg);
196}
197
198module_init(jent_mod_init);
199module_exit(jent_mod_exit);
200
201MODULE_LICENSE("Dual BSD/GPL");
202MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
203MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
204MODULE_ALIAS_CRYPTO("jitterentropy_rng");
1/*
2 * Non-physical true random number generator based on timing jitter --
3 * Linux Kernel Crypto API specific code
4 *
5 * Copyright Stephan Mueller <smueller@chronox.de>, 2015 - 2023
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, and the entire permission notice in its entirety,
12 * including the disclaimer of warranties.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. The name of the author may not be used to endorse or promote
17 * products derived from this software without specific prior
18 * written permission.
19 *
20 * ALTERNATIVELY, this product may be distributed under the terms of
21 * the GNU General Public License, in which case the provisions of the GPL2 are
22 * required INSTEAD OF the above restrictions. (This clause is
23 * necessary due to a potential bad interaction between the GPL and
24 * the restrictions contained in a BSD-style copyright.)
25 *
26 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
27 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
29 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
30 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
32 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
33 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
36 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
37 * DAMAGE.
38 */
39
40#include <crypto/hash.h>
41#include <crypto/sha3.h>
42#include <linux/fips.h>
43#include <linux/kernel.h>
44#include <linux/module.h>
45#include <linux/slab.h>
46#include <linux/time.h>
47#include <crypto/internal/rng.h>
48
49#include "jitterentropy.h"
50
51#define JENT_CONDITIONING_HASH "sha3-256-generic"
52
53/***************************************************************************
54 * Helper function
55 ***************************************************************************/
56
57void *jent_kvzalloc(unsigned int len)
58{
59 return kvzalloc(len, GFP_KERNEL);
60}
61
62void jent_kvzfree(void *ptr, unsigned int len)
63{
64 memzero_explicit(ptr, len);
65 kvfree(ptr);
66}
67
68void *jent_zalloc(unsigned int len)
69{
70 return kzalloc(len, GFP_KERNEL);
71}
72
73void jent_zfree(void *ptr)
74{
75 kfree_sensitive(ptr);
76}
77
78/*
79 * Obtain a high-resolution time stamp value. The time stamp is used to measure
80 * the execution time of a given code path and its variations. Hence, the time
81 * stamp must have a sufficiently high resolution.
82 *
83 * Note, if the function returns zero because a given architecture does not
84 * implement a high-resolution time stamp, the RNG code's runtime test
85 * will detect it and will not produce output.
86 */
87void jent_get_nstime(__u64 *out)
88{
89 __u64 tmp = 0;
90
91 tmp = random_get_entropy();
92
93 /*
94 * If random_get_entropy does not return a value, i.e. it is not
95 * implemented for a given architecture, use a clock source.
96 * hoping that there are timers we can work with.
97 */
98 if (tmp == 0)
99 tmp = ktime_get_ns();
100
101 *out = tmp;
102 jent_raw_hires_entropy_store(tmp);
103}
104
105int jent_hash_time(void *hash_state, __u64 time, u8 *addtl,
106 unsigned int addtl_len, __u64 hash_loop_cnt,
107 unsigned int stuck)
108{
109 struct shash_desc *hash_state_desc = (struct shash_desc *)hash_state;
110 SHASH_DESC_ON_STACK(desc, hash_state_desc->tfm);
111 u8 intermediary[SHA3_256_DIGEST_SIZE];
112 __u64 j = 0;
113 int ret;
114
115 desc->tfm = hash_state_desc->tfm;
116
117 if (sizeof(intermediary) != crypto_shash_digestsize(desc->tfm)) {
118 pr_warn_ratelimited("Unexpected digest size\n");
119 return -EINVAL;
120 }
121
122 /*
123 * This loop fills a buffer which is injected into the entropy pool.
124 * The main reason for this loop is to execute something over which we
125 * can perform a timing measurement. The injection of the resulting
126 * data into the pool is performed to ensure the result is used and
127 * the compiler cannot optimize the loop away in case the result is not
128 * used at all. Yet that data is considered "additional information"
129 * considering the terminology from SP800-90A without any entropy.
130 *
131 * Note, it does not matter which or how much data you inject, we are
132 * interested in one Keccack1600 compression operation performed with
133 * the crypto_shash_final.
134 */
135 for (j = 0; j < hash_loop_cnt; j++) {
136 ret = crypto_shash_init(desc) ?:
137 crypto_shash_update(desc, intermediary,
138 sizeof(intermediary)) ?:
139 crypto_shash_finup(desc, addtl, addtl_len, intermediary);
140 if (ret)
141 goto err;
142 }
143
144 /*
145 * Inject the data from the previous loop into the pool. This data is
146 * not considered to contain any entropy, but it stirs the pool a bit.
147 */
148 ret = crypto_shash_update(desc, intermediary, sizeof(intermediary));
149 if (ret)
150 goto err;
151
152 /*
153 * Insert the time stamp into the hash context representing the pool.
154 *
155 * If the time stamp is stuck, do not finally insert the value into the
156 * entropy pool. Although this operation should not do any harm even
157 * when the time stamp has no entropy, SP800-90B requires that any
158 * conditioning operation to have an identical amount of input data
159 * according to section 3.1.5.
160 */
161 if (!stuck) {
162 ret = crypto_shash_update(hash_state_desc, (u8 *)&time,
163 sizeof(__u64));
164 }
165
166err:
167 shash_desc_zero(desc);
168 memzero_explicit(intermediary, sizeof(intermediary));
169
170 return ret;
171}
172
173int jent_read_random_block(void *hash_state, char *dst, unsigned int dst_len)
174{
175 struct shash_desc *hash_state_desc = (struct shash_desc *)hash_state;
176 u8 jent_block[SHA3_256_DIGEST_SIZE];
177 /* Obtain data from entropy pool and re-initialize it */
178 int ret = crypto_shash_final(hash_state_desc, jent_block) ?:
179 crypto_shash_init(hash_state_desc) ?:
180 crypto_shash_update(hash_state_desc, jent_block,
181 sizeof(jent_block));
182
183 if (!ret && dst_len)
184 memcpy(dst, jent_block, dst_len);
185
186 memzero_explicit(jent_block, sizeof(jent_block));
187 return ret;
188}
189
190/***************************************************************************
191 * Kernel crypto API interface
192 ***************************************************************************/
193
194struct jitterentropy {
195 spinlock_t jent_lock;
196 struct rand_data *entropy_collector;
197 struct crypto_shash *tfm;
198 struct shash_desc *sdesc;
199};
200
201static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
202{
203 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
204
205 spin_lock(&rng->jent_lock);
206
207 if (rng->sdesc) {
208 shash_desc_zero(rng->sdesc);
209 kfree(rng->sdesc);
210 }
211 rng->sdesc = NULL;
212
213 if (rng->tfm)
214 crypto_free_shash(rng->tfm);
215 rng->tfm = NULL;
216
217 if (rng->entropy_collector)
218 jent_entropy_collector_free(rng->entropy_collector);
219 rng->entropy_collector = NULL;
220 spin_unlock(&rng->jent_lock);
221}
222
223static int jent_kcapi_init(struct crypto_tfm *tfm)
224{
225 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
226 struct crypto_shash *hash;
227 struct shash_desc *sdesc;
228 int size, ret = 0;
229
230 spin_lock_init(&rng->jent_lock);
231
232 /*
233 * Use SHA3-256 as conditioner. We allocate only the generic
234 * implementation as we are not interested in high-performance. The
235 * execution time of the SHA3 operation is measured and adds to the
236 * Jitter RNG's unpredictable behavior. If we have a slower hash
237 * implementation, the execution timing variations are larger. When
238 * using a fast implementation, we would need to call it more often
239 * as its variations are lower.
240 */
241 hash = crypto_alloc_shash(JENT_CONDITIONING_HASH, 0, 0);
242 if (IS_ERR(hash)) {
243 pr_err("Cannot allocate conditioning digest\n");
244 return PTR_ERR(hash);
245 }
246 rng->tfm = hash;
247
248 size = sizeof(struct shash_desc) + crypto_shash_descsize(hash);
249 sdesc = kmalloc(size, GFP_KERNEL);
250 if (!sdesc) {
251 ret = -ENOMEM;
252 goto err;
253 }
254
255 sdesc->tfm = hash;
256 crypto_shash_init(sdesc);
257 rng->sdesc = sdesc;
258
259 rng->entropy_collector =
260 jent_entropy_collector_alloc(CONFIG_CRYPTO_JITTERENTROPY_OSR, 0,
261 sdesc);
262 if (!rng->entropy_collector) {
263 ret = -ENOMEM;
264 goto err;
265 }
266
267 spin_lock_init(&rng->jent_lock);
268 return 0;
269
270err:
271 jent_kcapi_cleanup(tfm);
272 return ret;
273}
274
275static int jent_kcapi_random(struct crypto_rng *tfm,
276 const u8 *src, unsigned int slen,
277 u8 *rdata, unsigned int dlen)
278{
279 struct jitterentropy *rng = crypto_rng_ctx(tfm);
280 int ret = 0;
281
282 spin_lock(&rng->jent_lock);
283
284 ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
285
286 if (ret == -3) {
287 /* Handle permanent health test error */
288 /*
289 * If the kernel was booted with fips=1, it implies that
290 * the entire kernel acts as a FIPS 140 module. In this case
291 * an SP800-90B permanent health test error is treated as
292 * a FIPS module error.
293 */
294 if (fips_enabled)
295 panic("Jitter RNG permanent health test failure\n");
296
297 pr_err("Jitter RNG permanent health test failure\n");
298 ret = -EFAULT;
299 } else if (ret == -2) {
300 /* Handle intermittent health test error */
301 pr_warn_ratelimited("Reset Jitter RNG due to intermittent health test failure\n");
302 ret = -EAGAIN;
303 } else if (ret == -1) {
304 /* Handle other errors */
305 ret = -EINVAL;
306 }
307
308 spin_unlock(&rng->jent_lock);
309
310 return ret;
311}
312
313static int jent_kcapi_reset(struct crypto_rng *tfm,
314 const u8 *seed, unsigned int slen)
315{
316 return 0;
317}
318
319static struct rng_alg jent_alg = {
320 .generate = jent_kcapi_random,
321 .seed = jent_kcapi_reset,
322 .seedsize = 0,
323 .base = {
324 .cra_name = "jitterentropy_rng",
325 .cra_driver_name = "jitterentropy_rng",
326 .cra_priority = 100,
327 .cra_ctxsize = sizeof(struct jitterentropy),
328 .cra_module = THIS_MODULE,
329 .cra_init = jent_kcapi_init,
330 .cra_exit = jent_kcapi_cleanup,
331 }
332};
333
334static int __init jent_mod_init(void)
335{
336 SHASH_DESC_ON_STACK(desc, tfm);
337 struct crypto_shash *tfm;
338 int ret = 0;
339
340 jent_testing_init();
341
342 tfm = crypto_alloc_shash(JENT_CONDITIONING_HASH, 0, 0);
343 if (IS_ERR(tfm)) {
344 jent_testing_exit();
345 return PTR_ERR(tfm);
346 }
347
348 desc->tfm = tfm;
349 crypto_shash_init(desc);
350 ret = jent_entropy_init(CONFIG_CRYPTO_JITTERENTROPY_OSR, 0, desc, NULL);
351 shash_desc_zero(desc);
352 crypto_free_shash(tfm);
353 if (ret) {
354 /* Handle permanent health test error */
355 if (fips_enabled)
356 panic("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
357
358 jent_testing_exit();
359 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
360 return -EFAULT;
361 }
362 return crypto_register_rng(&jent_alg);
363}
364
365static void __exit jent_mod_exit(void)
366{
367 jent_testing_exit();
368 crypto_unregister_rng(&jent_alg);
369}
370
371module_init(jent_mod_init);
372module_exit(jent_mod_exit);
373
374MODULE_LICENSE("Dual BSD/GPL");
375MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
376MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
377MODULE_ALIAS_CRYPTO("jitterentropy_rng");