blob: c4938497eedbe77ed6e0b70853187d895ee0cb56
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 | |
48 | struct rand_data; |
49 | int jent_read_entropy(struct rand_data *ec, unsigned char *data, |
50 | unsigned int len); |
51 | int jent_entropy_init(void); |
52 | struct rand_data *jent_entropy_collector_alloc(unsigned int osr, |
53 | unsigned int flags); |
54 | void 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 | |
65 | void *jent_zalloc(unsigned int len) |
66 | { |
67 | return kzalloc(len, GFP_KERNEL); |
68 | } |
69 | |
70 | void jent_zfree(void *ptr) |
71 | { |
72 | kzfree(ptr); |
73 | } |
74 | |
75 | int jent_fips_enabled(void) |
76 | { |
77 | return fips_enabled; |
78 | } |
79 | |
80 | void jent_panic(char *s) |
81 | { |
82 | panic("%s", s); |
83 | } |
84 | |
85 | void jent_memcpy(void *dest, const void *src, unsigned int n) |
86 | { |
87 | memcpy(dest, src, n); |
88 | } |
89 | |
90 | /* |
91 | * Obtain a high-resolution time stamp value. The time stamp is used to measure |
92 | * the execution time of a given code path and its variations. Hence, the time |
93 | * stamp must have a sufficiently high resolution. |
94 | * |
95 | * Note, if the function returns zero because a given architecture does not |
96 | * implement a high-resolution time stamp, the RNG code's runtime test |
97 | * will detect it and will not produce output. |
98 | */ |
99 | void jent_get_nstime(__u64 *out) |
100 | { |
101 | __u64 tmp = 0; |
102 | |
103 | tmp = random_get_entropy(); |
104 | |
105 | /* |
106 | * If random_get_entropy does not return a value, i.e. it is not |
107 | * implemented for a given architecture, use a clock source. |
108 | * hoping that there are timers we can work with. |
109 | */ |
110 | if (tmp == 0) |
111 | tmp = ktime_get_ns(); |
112 | |
113 | *out = tmp; |
114 | } |
115 | |
116 | /*************************************************************************** |
117 | * Kernel crypto API interface |
118 | ***************************************************************************/ |
119 | |
120 | struct jitterentropy { |
121 | spinlock_t jent_lock; |
122 | struct rand_data *entropy_collector; |
123 | }; |
124 | |
125 | static int jent_kcapi_init(struct crypto_tfm *tfm) |
126 | { |
127 | struct jitterentropy *rng = crypto_tfm_ctx(tfm); |
128 | int ret = 0; |
129 | |
130 | rng->entropy_collector = jent_entropy_collector_alloc(1, 0); |
131 | if (!rng->entropy_collector) |
132 | ret = -ENOMEM; |
133 | |
134 | spin_lock_init(&rng->jent_lock); |
135 | return ret; |
136 | } |
137 | |
138 | static void jent_kcapi_cleanup(struct crypto_tfm *tfm) |
139 | { |
140 | struct jitterentropy *rng = crypto_tfm_ctx(tfm); |
141 | |
142 | spin_lock(&rng->jent_lock); |
143 | if (rng->entropy_collector) |
144 | jent_entropy_collector_free(rng->entropy_collector); |
145 | rng->entropy_collector = NULL; |
146 | spin_unlock(&rng->jent_lock); |
147 | } |
148 | |
149 | static int jent_kcapi_random(struct crypto_rng *tfm, |
150 | const u8 *src, unsigned int slen, |
151 | u8 *rdata, unsigned int dlen) |
152 | { |
153 | struct jitterentropy *rng = crypto_rng_ctx(tfm); |
154 | int ret = 0; |
155 | |
156 | spin_lock(&rng->jent_lock); |
157 | ret = jent_read_entropy(rng->entropy_collector, rdata, dlen); |
158 | spin_unlock(&rng->jent_lock); |
159 | |
160 | return ret; |
161 | } |
162 | |
163 | static int jent_kcapi_reset(struct crypto_rng *tfm, |
164 | const u8 *seed, unsigned int slen) |
165 | { |
166 | return 0; |
167 | } |
168 | |
169 | static struct rng_alg jent_alg = { |
170 | .generate = jent_kcapi_random, |
171 | .seed = jent_kcapi_reset, |
172 | .seedsize = 0, |
173 | .base = { |
174 | .cra_name = "jitterentropy_rng", |
175 | .cra_driver_name = "jitterentropy_rng", |
176 | .cra_priority = 100, |
177 | .cra_ctxsize = sizeof(struct jitterentropy), |
178 | .cra_module = THIS_MODULE, |
179 | .cra_init = jent_kcapi_init, |
180 | .cra_exit = jent_kcapi_cleanup, |
181 | |
182 | } |
183 | }; |
184 | |
185 | static int __init jent_mod_init(void) |
186 | { |
187 | int ret = 0; |
188 | |
189 | ret = jent_entropy_init(); |
190 | if (ret) { |
191 | pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret); |
192 | return -EFAULT; |
193 | } |
194 | return crypto_register_rng(&jent_alg); |
195 | } |
196 | |
197 | static void __exit jent_mod_exit(void) |
198 | { |
199 | crypto_unregister_rng(&jent_alg); |
200 | } |
201 | |
202 | module_init(jent_mod_init); |
203 | module_exit(jent_mod_exit); |
204 | |
205 | MODULE_LICENSE("Dual BSD/GPL"); |
206 | MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>"); |
207 | MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter"); |
208 | MODULE_ALIAS_CRYPTO("jitterentropy_rng"); |
209 |