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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/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 
 59 __u64 jent_rol64(__u64 word, unsigned int shift)
 60 {
 61         return rol64(word, shift);
 62 }
 63 
 64 void *jent_zalloc(unsigned int len)
 65 {
 66         return kzalloc(len, GFP_KERNEL);
 67 }
 68 
 69 void jent_zfree(void *ptr)
 70 {
 71         kzfree(ptr);
 72 }
 73 
 74 int jent_fips_enabled(void)
 75 {
 76         return fips_enabled;
 77 }
 78 
 79 void jent_panic(char *s)
 80 {
 81         panic("%s", s);
 82 }
 83 
 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  */
 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 
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 
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 
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 
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 
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 
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 

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