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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/kernel.h>
41#include <linux/module.h>
42#include <linux/slab.h>
43#include <linux/time.h>
44#include <crypto/internal/rng.h>
45
46#include "jitterentropy.h"
47
48/***************************************************************************
49 * Helper function
50 ***************************************************************************/
51
52void *jent_zalloc(unsigned int len)
53{
54 return kzalloc(len, GFP_KERNEL);
55}
56
57void jent_zfree(void *ptr)
58{
59 kfree_sensitive(ptr);
60}
61
62void jent_panic(char *s)
63{
64 panic("%s", s);
65}
66
67void jent_memcpy(void *dest, const void *src, unsigned int n)
68{
69 memcpy(dest, src, n);
70}
71
72/*
73 * Obtain a high-resolution time stamp value. The time stamp is used to measure
74 * the execution time of a given code path and its variations. Hence, the time
75 * stamp must have a sufficiently high resolution.
76 *
77 * Note, if the function returns zero because a given architecture does not
78 * implement a high-resolution time stamp, the RNG code's runtime test
79 * will detect it and will not produce output.
80 */
81void jent_get_nstime(__u64 *out)
82{
83 __u64 tmp = 0;
84
85 tmp = random_get_entropy();
86
87 /*
88 * If random_get_entropy does not return a value, i.e. it is not
89 * implemented for a given architecture, use a clock source.
90 * hoping that there are timers we can work with.
91 */
92 if (tmp == 0)
93 tmp = ktime_get_ns();
94
95 *out = tmp;
96}
97
98/***************************************************************************
99 * Kernel crypto API interface
100 ***************************************************************************/
101
102struct jitterentropy {
103 spinlock_t jent_lock;
104 struct rand_data *entropy_collector;
105 unsigned int reset_cnt;
106};
107
108static int jent_kcapi_init(struct crypto_tfm *tfm)
109{
110 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
111 int ret = 0;
112
113 rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
114 if (!rng->entropy_collector)
115 ret = -ENOMEM;
116
117 spin_lock_init(&rng->jent_lock);
118 return ret;
119}
120
121static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
122{
123 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
124
125 spin_lock(&rng->jent_lock);
126 if (rng->entropy_collector)
127 jent_entropy_collector_free(rng->entropy_collector);
128 rng->entropy_collector = NULL;
129 spin_unlock(&rng->jent_lock);
130}
131
132static int jent_kcapi_random(struct crypto_rng *tfm,
133 const u8 *src, unsigned int slen,
134 u8 *rdata, unsigned int dlen)
135{
136 struct jitterentropy *rng = crypto_rng_ctx(tfm);
137 int ret = 0;
138
139 spin_lock(&rng->jent_lock);
140
141 /* Return a permanent error in case we had too many resets in a row. */
142 if (rng->reset_cnt > (1<<10)) {
143 ret = -EFAULT;
144 goto out;
145 }
146
147 ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
148
149 /* Reset RNG in case of health failures */
150 if (ret < -1) {
151 pr_warn_ratelimited("Reset Jitter RNG due to health test failure: %s failure\n",
152 (ret == -2) ? "Repetition Count Test" :
153 "Adaptive Proportion Test");
154
155 rng->reset_cnt++;
156
157 ret = -EAGAIN;
158 } else {
159 rng->reset_cnt = 0;
160
161 /* Convert the Jitter RNG error into a usable error code */
162 if (ret == -1)
163 ret = -EINVAL;
164 }
165
166out:
167 spin_unlock(&rng->jent_lock);
168
169 return ret;
170}
171
172static int jent_kcapi_reset(struct crypto_rng *tfm,
173 const u8 *seed, unsigned int slen)
174{
175 return 0;
176}
177
178static struct rng_alg jent_alg = {
179 .generate = jent_kcapi_random,
180 .seed = jent_kcapi_reset,
181 .seedsize = 0,
182 .base = {
183 .cra_name = "jitterentropy_rng",
184 .cra_driver_name = "jitterentropy_rng",
185 .cra_priority = 100,
186 .cra_ctxsize = sizeof(struct jitterentropy),
187 .cra_module = THIS_MODULE,
188 .cra_init = jent_kcapi_init,
189 .cra_exit = jent_kcapi_cleanup,
190
191 }
192};
193
194static int __init jent_mod_init(void)
195{
196 int ret = 0;
197
198 ret = jent_entropy_init();
199 if (ret) {
200 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
201 return -EFAULT;
202 }
203 return crypto_register_rng(&jent_alg);
204}
205
206static void __exit jent_mod_exit(void)
207{
208 crypto_unregister_rng(&jent_alg);
209}
210
211module_init(jent_mod_init);
212module_exit(jent_mod_exit);
213
214MODULE_LICENSE("Dual BSD/GPL");
215MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
216MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
217MODULE_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
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/fips.h>
43#include <linux/time.h>
44#include <linux/crypto.h>
45#include <crypto/internal/rng.h>
46
47struct rand_data;
48int jent_read_entropy(struct rand_data *ec, unsigned char *data,
49 unsigned int len);
50int jent_entropy_init(void);
51struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
52 unsigned int flags);
53void jent_entropy_collector_free(struct rand_data *entropy_collector);
54
55/***************************************************************************
56 * Helper function
57 ***************************************************************************/
58
59void *jent_zalloc(unsigned int len)
60{
61 return kzalloc(len, GFP_KERNEL);
62}
63
64void jent_zfree(void *ptr)
65{
66 kzfree(ptr);
67}
68
69int jent_fips_enabled(void)
70{
71 return fips_enabled;
72}
73
74void jent_panic(char *s)
75{
76 panic("%s", s);
77}
78
79void jent_memcpy(void *dest, const void *src, unsigned int n)
80{
81 memcpy(dest, src, n);
82}
83
84/*
85 * Obtain a high-resolution time stamp value. The time stamp is used to measure
86 * the execution time of a given code path and its variations. Hence, the time
87 * stamp must have a sufficiently high resolution.
88 *
89 * Note, if the function returns zero because a given architecture does not
90 * implement a high-resolution time stamp, the RNG code's runtime test
91 * will detect it and will not produce output.
92 */
93void jent_get_nstime(__u64 *out)
94{
95 __u64 tmp = 0;
96
97 tmp = random_get_entropy();
98
99 /*
100 * If random_get_entropy does not return a value, i.e. it is not
101 * implemented for a given architecture, use a clock source.
102 * hoping that there are timers we can work with.
103 */
104 if (tmp == 0)
105 tmp = ktime_get_ns();
106
107 *out = tmp;
108}
109
110/***************************************************************************
111 * Kernel crypto API interface
112 ***************************************************************************/
113
114struct jitterentropy {
115 spinlock_t jent_lock;
116 struct rand_data *entropy_collector;
117};
118
119static int jent_kcapi_init(struct crypto_tfm *tfm)
120{
121 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
122 int ret = 0;
123
124 rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
125 if (!rng->entropy_collector)
126 ret = -ENOMEM;
127
128 spin_lock_init(&rng->jent_lock);
129 return ret;
130}
131
132static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
133{
134 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
135
136 spin_lock(&rng->jent_lock);
137 if (rng->entropy_collector)
138 jent_entropy_collector_free(rng->entropy_collector);
139 rng->entropy_collector = NULL;
140 spin_unlock(&rng->jent_lock);
141}
142
143static int jent_kcapi_random(struct crypto_rng *tfm,
144 const u8 *src, unsigned int slen,
145 u8 *rdata, unsigned int dlen)
146{
147 struct jitterentropy *rng = crypto_rng_ctx(tfm);
148 int ret = 0;
149
150 spin_lock(&rng->jent_lock);
151 ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
152 spin_unlock(&rng->jent_lock);
153
154 return ret;
155}
156
157static int jent_kcapi_reset(struct crypto_rng *tfm,
158 const u8 *seed, unsigned int slen)
159{
160 return 0;
161}
162
163static struct rng_alg jent_alg = {
164 .generate = jent_kcapi_random,
165 .seed = jent_kcapi_reset,
166 .seedsize = 0,
167 .base = {
168 .cra_name = "jitterentropy_rng",
169 .cra_driver_name = "jitterentropy_rng",
170 .cra_priority = 100,
171 .cra_ctxsize = sizeof(struct jitterentropy),
172 .cra_module = THIS_MODULE,
173 .cra_init = jent_kcapi_init,
174 .cra_exit = jent_kcapi_cleanup,
175
176 }
177};
178
179static int __init jent_mod_init(void)
180{
181 int ret = 0;
182
183 ret = jent_entropy_init();
184 if (ret) {
185 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
186 return -EFAULT;
187 }
188 return crypto_register_rng(&jent_alg);
189}
190
191static void __exit jent_mod_exit(void)
192{
193 crypto_unregister_rng(&jent_alg);
194}
195
196module_init(jent_mod_init);
197module_exit(jent_mod_exit);
198
199MODULE_LICENSE("Dual BSD/GPL");
200MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
201MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
202MODULE_ALIAS_CRYPTO("jitterentropy_rng");