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Linux/crypto/jitterentropy-kcapi.c

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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/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 void jent_get_nstime(__u64 *out)
 91 {
 92         struct timespec ts;
 93         __u64 tmp = 0;
 94 
 95         tmp = random_get_entropy();
 96 
 97         /*
 98          * If random_get_entropy does not return a value (which is possible on,
 99          * for example, MIPS), invoke __getnstimeofday
100          * hoping that there are timers we can work with.
101          */
102         if ((0 == tmp) &&
103            (0 == __getnstimeofday(&ts))) {
104                 tmp = ts.tv_sec;
105                 tmp = tmp << 32;
106                 tmp = tmp | ts.tv_nsec;
107         }
108 
109         *out = tmp;
110 }
111 
112 /***************************************************************************
113  * Kernel crypto API interface
114  ***************************************************************************/
115 
116 struct jitterentropy {
117         spinlock_t jent_lock;
118         struct rand_data *entropy_collector;
119 };
120 
121 static int jent_kcapi_init(struct crypto_tfm *tfm)
122 {
123         struct jitterentropy *rng = crypto_tfm_ctx(tfm);
124         int ret = 0;
125 
126         rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
127         if (!rng->entropy_collector)
128                 ret = -ENOMEM;
129 
130         spin_lock_init(&rng->jent_lock);
131         return ret;
132 }
133 
134 static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
135 {
136         struct jitterentropy *rng = crypto_tfm_ctx(tfm);
137 
138         spin_lock(&rng->jent_lock);
139         if (rng->entropy_collector)
140                 jent_entropy_collector_free(rng->entropy_collector);
141         rng->entropy_collector = NULL;
142         spin_unlock(&rng->jent_lock);
143 }
144 
145 static int jent_kcapi_random(struct crypto_rng *tfm,
146                              const u8 *src, unsigned int slen,
147                              u8 *rdata, unsigned int dlen)
148 {
149         struct jitterentropy *rng = crypto_rng_ctx(tfm);
150         int ret = 0;
151 
152         spin_lock(&rng->jent_lock);
153         ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
154         spin_unlock(&rng->jent_lock);
155 
156         return ret;
157 }
158 
159 static int jent_kcapi_reset(struct crypto_rng *tfm,
160                             const u8 *seed, unsigned int slen)
161 {
162         return 0;
163 }
164 
165 static struct rng_alg jent_alg = {
166         .generate               = jent_kcapi_random,
167         .seed                   = jent_kcapi_reset,
168         .seedsize               = 0,
169         .base                   = {
170                 .cra_name               = "jitterentropy_rng",
171                 .cra_driver_name        = "jitterentropy_rng",
172                 .cra_priority           = 100,
173                 .cra_ctxsize            = sizeof(struct jitterentropy),
174                 .cra_module             = THIS_MODULE,
175                 .cra_init               = jent_kcapi_init,
176                 .cra_exit               = jent_kcapi_cleanup,
177 
178         }
179 };
180 
181 static int __init jent_mod_init(void)
182 {
183         int ret = 0;
184 
185         ret = jent_entropy_init();
186         if (ret) {
187                 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
188                 return -EFAULT;
189         }
190         return crypto_register_rng(&jent_alg);
191 }
192 
193 static void __exit jent_mod_exit(void)
194 {
195         crypto_unregister_rng(&jent_alg);
196 }
197 
198 module_init(jent_mod_init);
199 module_exit(jent_mod_exit);
200 
201 MODULE_LICENSE("Dual BSD/GPL");
202 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
203 MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
204 MODULE_ALIAS_CRYPTO("jitterentropy_rng");
205 

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