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dfc9fa91 SM |
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 | ||
0c3dc787 | 40 | #include <linux/kernel.h> |
dfc9fa91 SM |
41 | #include <linux/module.h> |
42 | #include <linux/slab.h> | |
dfc9fa91 | 43 | #include <linux/time.h> |
dfc9fa91 SM |
44 | #include <crypto/internal/rng.h> |
45 | ||
965d7286 | 46 | #include "jitterentropy.h" |
dfc9fa91 SM |
47 | |
48 | /*************************************************************************** | |
49 | * Helper function | |
50 | ***************************************************************************/ | |
51 | ||
dfc9fa91 SM |
52 | void *jent_zalloc(unsigned int len) |
53 | { | |
54 | return kzalloc(len, GFP_KERNEL); | |
55 | } | |
56 | ||
57 | void jent_zfree(void *ptr) | |
58 | { | |
453431a5 | 59 | kfree_sensitive(ptr); |
dfc9fa91 SM |
60 | } |
61 | ||
dfc9fa91 SM |
62 | void jent_panic(char *s) |
63 | { | |
0c5f0aa5 | 64 | panic("%s", s); |
dfc9fa91 SM |
65 | } |
66 | ||
67 | void jent_memcpy(void *dest, const void *src, unsigned int n) | |
68 | { | |
69 | memcpy(dest, src, n); | |
70 | } | |
71 | ||
b578456c SM |
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 | */ | |
dfc9fa91 SM |
81 | void jent_get_nstime(__u64 *out) |
82 | { | |
dfc9fa91 SM |
83 | __u64 tmp = 0; |
84 | ||
85 | tmp = random_get_entropy(); | |
86 | ||
87 | /* | |
b578456c SM |
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. | |
dfc9fa91 | 90 | * hoping that there are timers we can work with. |
dfc9fa91 | 91 | */ |
b578456c SM |
92 | if (tmp == 0) |
93 | tmp = ktime_get_ns(); | |
dfc9fa91 SM |
94 | |
95 | *out = tmp; | |
96 | } | |
97 | ||
98 | /*************************************************************************** | |
99 | * Kernel crypto API interface | |
100 | ***************************************************************************/ | |
101 | ||
102 | struct jitterentropy { | |
103 | spinlock_t jent_lock; | |
104 | struct rand_data *entropy_collector; | |
764428fe | 105 | unsigned int reset_cnt; |
dfc9fa91 SM |
106 | }; |
107 | ||
108 | static 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 | ||
121 | static 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 | ||
132 | static 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); | |
764428fe SM |
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 | ||
dfc9fa91 | 147 | ret = jent_read_entropy(rng->entropy_collector, rdata, dlen); |
764428fe SM |
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 | ||
166 | out: | |
dfc9fa91 SM |
167 | spin_unlock(&rng->jent_lock); |
168 | ||
169 | return ret; | |
170 | } | |
171 | ||
172 | static int jent_kcapi_reset(struct crypto_rng *tfm, | |
173 | const u8 *seed, unsigned int slen) | |
174 | { | |
175 | return 0; | |
176 | } | |
177 | ||
178 | static 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 | ||
194 | static 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 | ||
206 | static void __exit jent_mod_exit(void) | |
207 | { | |
208 | crypto_unregister_rng(&jent_alg); | |
209 | } | |
210 | ||
9c5b34c2 | 211 | module_init(jent_mod_init); |
dfc9fa91 SM |
212 | module_exit(jent_mod_exit); |
213 | ||
214 | MODULE_LICENSE("Dual BSD/GPL"); | |
215 | MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>"); | |
216 | MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter"); | |
217 | MODULE_ALIAS_CRYPTO("jitterentropy_rng"); |