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/fips.h>
41 #include <linux/kernel.h>
42 #include <linux/module.h>
43 #include <linux/slab.h>
44 #include <linux/time.h>
45 #include <crypto/internal/rng.h>
46
47 #include "jitterentropy.h"
48
49 /***************************************************************************
50 * Helper function
51 ***************************************************************************/
52
jent_zalloc(unsigned int len)53 void *jent_zalloc(unsigned int len)
54 {
55 return kzalloc(len, GFP_KERNEL);
56 }
57
jent_zfree(void * ptr)58 void jent_zfree(void *ptr)
59 {
60 kfree_sensitive(ptr);
61 }
62
jent_memcpy(void * dest,const void * src,unsigned int n)63 void jent_memcpy(void *dest, const void *src, unsigned int n)
64 {
65 memcpy(dest, src, n);
66 }
67
68 /*
69 * Obtain a high-resolution time stamp value. The time stamp is used to measure
70 * the execution time of a given code path and its variations. Hence, the time
71 * stamp must have a sufficiently high resolution.
72 *
73 * Note, if the function returns zero because a given architecture does not
74 * implement a high-resolution time stamp, the RNG code's runtime test
75 * will detect it and will not produce output.
76 */
jent_get_nstime(__u64 * out)77 void jent_get_nstime(__u64 *out)
78 {
79 __u64 tmp = 0;
80
81 tmp = random_get_entropy();
82
83 /*
84 * If random_get_entropy does not return a value, i.e. it is not
85 * implemented for a given architecture, use a clock source.
86 * hoping that there are timers we can work with.
87 */
88 if (tmp == 0)
89 tmp = ktime_get_ns();
90
91 *out = tmp;
92 }
93
94 /***************************************************************************
95 * Kernel crypto API interface
96 ***************************************************************************/
97
98 struct jitterentropy {
99 spinlock_t jent_lock;
100 struct rand_data *entropy_collector;
101 };
102
jent_kcapi_init(struct crypto_tfm * tfm)103 static int jent_kcapi_init(struct crypto_tfm *tfm)
104 {
105 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
106 int ret = 0;
107
108 rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
109 if (!rng->entropy_collector)
110 ret = -ENOMEM;
111
112 spin_lock_init(&rng->jent_lock);
113 return ret;
114 }
115
jent_kcapi_cleanup(struct crypto_tfm * tfm)116 static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
117 {
118 struct jitterentropy *rng = crypto_tfm_ctx(tfm);
119
120 spin_lock(&rng->jent_lock);
121 if (rng->entropy_collector)
122 jent_entropy_collector_free(rng->entropy_collector);
123 rng->entropy_collector = NULL;
124 spin_unlock(&rng->jent_lock);
125 }
126
jent_kcapi_random(struct crypto_rng * tfm,const u8 * src,unsigned int slen,u8 * rdata,unsigned int dlen)127 static int jent_kcapi_random(struct crypto_rng *tfm,
128 const u8 *src, unsigned int slen,
129 u8 *rdata, unsigned int dlen)
130 {
131 struct jitterentropy *rng = crypto_rng_ctx(tfm);
132 int ret = 0;
133
134 spin_lock(&rng->jent_lock);
135
136 ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
137
138 if (ret == -3) {
139 /* Handle permanent health test error */
140 /*
141 * If the kernel was booted with fips=1, it implies that
142 * the entire kernel acts as a FIPS 140 module. In this case
143 * an SP800-90B permanent health test error is treated as
144 * a FIPS module error.
145 */
146 if (fips_enabled)
147 panic("Jitter RNG permanent health test failure\n");
148
149 pr_err("Jitter RNG permanent health test failure\n");
150 ret = -EFAULT;
151 } else if (ret == -2) {
152 /* Handle intermittent health test error */
153 pr_warn_ratelimited("Reset Jitter RNG due to intermittent health test failure\n");
154 ret = -EAGAIN;
155 } else if (ret == -1) {
156 /* Handle other errors */
157 ret = -EINVAL;
158 }
159
160 spin_unlock(&rng->jent_lock);
161
162 return ret;
163 }
164
jent_kcapi_reset(struct crypto_rng * tfm,const u8 * seed,unsigned int slen)165 static int jent_kcapi_reset(struct crypto_rng *tfm,
166 const u8 *seed, unsigned int slen)
167 {
168 return 0;
169 }
170
171 static struct rng_alg jent_alg = {
172 .generate = jent_kcapi_random,
173 .seed = jent_kcapi_reset,
174 .seedsize = 0,
175 .base = {
176 .cra_name = "jitterentropy_rng",
177 .cra_driver_name = "jitterentropy_rng",
178 .cra_priority = 100,
179 .cra_ctxsize = sizeof(struct jitterentropy),
180 .cra_module = THIS_MODULE,
181 .cra_init = jent_kcapi_init,
182 .cra_exit = jent_kcapi_cleanup,
183
184 }
185 };
186
jent_mod_init(void)187 static int __init jent_mod_init(void)
188 {
189 int ret = 0;
190
191 ret = jent_entropy_init();
192 if (ret) {
193 /* Handle permanent health test error */
194 if (fips_enabled)
195 panic("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
196
197 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
198 return -EFAULT;
199 }
200 return crypto_register_rng(&jent_alg);
201 }
202
jent_mod_exit(void)203 static void __exit jent_mod_exit(void)
204 {
205 crypto_unregister_rng(&jent_alg);
206 }
207
208 module_init(jent_mod_init);
209 module_exit(jent_mod_exit);
210
211 MODULE_LICENSE("Dual BSD/GPL");
212 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
213 MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
214 MODULE_ALIAS_CRYPTO("jitterentropy_rng");
215