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
47 struct rand_data;
48 int jent_read_entropy(struct rand_data *ec, unsigned char *data,
49 unsigned int len);
50 int jent_entropy_init(void);
51 struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
52 unsigned int flags);
53 void jent_entropy_collector_free(struct rand_data *entropy_collector);
54
55 /***************************************************************************
56 * Helper function
57 ***************************************************************************/
58
jent_rol64(__u64 word,unsigned int shift)59 __u64 jent_rol64(__u64 word, unsigned int shift)
60 {
61 return rol64(word, shift);
62 }
63
jent_zalloc(unsigned int len)64 void *jent_zalloc(unsigned int len)
65 {
66 return kzalloc(len, GFP_KERNEL);
67 }
68
jent_zfree(void * ptr)69 void jent_zfree(void *ptr)
70 {
71 kzfree(ptr);
72 }
73
jent_fips_enabled(void)74 int jent_fips_enabled(void)
75 {
76 return fips_enabled;
77 }
78
jent_panic(char * s)79 void jent_panic(char *s)
80 {
81 panic("%s", s);
82 }
83
jent_memcpy(void * dest,const void * src,unsigned int n)84 void jent_memcpy(void *dest, const void *src, unsigned int n)
85 {
86 memcpy(dest, src, n);
87 }
88
89 /*
90 * Obtain a high-resolution time stamp value. The time stamp is used to measure
91 * the execution time of a given code path and its variations. Hence, the time
92 * stamp must have a sufficiently high resolution.
93 *
94 * Note, if the function returns zero because a given architecture does not
95 * implement a high-resolution time stamp, the RNG code's runtime test
96 * will detect it and will not produce output.
97 */
jent_get_nstime(__u64 * out)98 void jent_get_nstime(__u64 *out)
99 {
100 __u64 tmp = 0;
101
102 tmp = random_get_entropy();
103
104 /*
105 * If random_get_entropy does not return a value, i.e. it is not
106 * implemented for a given architecture, use a clock source.
107 * hoping that there are timers we can work with.
108 */
109 if (tmp == 0)
110 tmp = ktime_get_ns();
111
112 *out = tmp;
113 }
114
115 /***************************************************************************
116 * Kernel crypto API interface
117 ***************************************************************************/
118
119 struct jitterentropy {
120 spinlock_t jent_lock;
121 struct rand_data *entropy_collector;
122 };
123
jent_kcapi_init(struct crypto_tfm * tfm)124 static int jent_kcapi_init(struct crypto_tfm *tfm)
125 {
126 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
127 int ret = 0;
128
129 rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
130 if (!rng->entropy_collector)
131 ret = -ENOMEM;
132
133 spin_lock_init(&rng->jent_lock);
134 return ret;
135 }
136
jent_kcapi_cleanup(struct crypto_tfm * tfm)137 static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
138 {
139 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
140
141 spin_lock(&rng->jent_lock);
142 if (rng->entropy_collector)
143 jent_entropy_collector_free(rng->entropy_collector);
144 rng->entropy_collector = NULL;
145 spin_unlock(&rng->jent_lock);
146 }
147
jent_kcapi_random(struct crypto_rng * tfm,const u8 * src,unsigned int slen,u8 * rdata,unsigned int dlen)148 static int jent_kcapi_random(struct crypto_rng *tfm,
149 const u8 *src, unsigned int slen,
150 u8 *rdata, unsigned int dlen)
151 {
152 struct jitterentropy *rng = crypto_rng_ctx(tfm);
153 int ret = 0;
154
155 spin_lock(&rng->jent_lock);
156 ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
157 spin_unlock(&rng->jent_lock);
158
159 return ret;
160 }
161
jent_kcapi_reset(struct crypto_rng * tfm,const u8 * seed,unsigned int slen)162 static int jent_kcapi_reset(struct crypto_rng *tfm,
163 const u8 *seed, unsigned int slen)
164 {
165 return 0;
166 }
167
168 static struct rng_alg jent_alg = {
169 .generate = jent_kcapi_random,
170 .seed = jent_kcapi_reset,
171 .seedsize = 0,
172 .base = {
173 .cra_name = "jitterentropy_rng",
174 .cra_driver_name = "jitterentropy_rng",
175 .cra_priority = 100,
176 .cra_ctxsize = sizeof(struct jitterentropy),
177 .cra_module = THIS_MODULE,
178 .cra_init = jent_kcapi_init,
179 .cra_exit = jent_kcapi_cleanup,
180
181 }
182 };
183
jent_mod_init(void)184 static int __init jent_mod_init(void)
185 {
186 int ret = 0;
187
188 ret = jent_entropy_init();
189 if (ret) {
190 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
191 return -EFAULT;
192 }
193 return crypto_register_rng(&jent_alg);
194 }
195
jent_mod_exit(void)196 static void __exit jent_mod_exit(void)
197 {
198 crypto_unregister_rng(&jent_alg);
199 }
200
201 module_init(jent_mod_init);
202 module_exit(jent_mod_exit);
203
204 MODULE_LICENSE("Dual BSD/GPL");
205 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
206 MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
207 MODULE_ALIAS_CRYPTO("jitterentropy_rng");
208