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
 48struct rand_data;
 49int jent_read_entropy(struct rand_data *ec, unsigned char *data,
 50		      unsigned int len);
 51int jent_entropy_init(void);
 52struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
 53					       unsigned int flags);
 54void 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
 65void *jent_zalloc(unsigned int len)
 66{
 67	return kzalloc(len, GFP_KERNEL);
 68}
 69
 70void jent_zfree(void *ptr)
 71{
 72	kzfree(ptr);
 73}
 74
 75int jent_fips_enabled(void)
 76{
 77	return fips_enabled;
 78}
 79
 80void jent_panic(char *s)
 81{
 82	panic("%s", s);
 83}
 84
 85void jent_memcpy(void *dest, const void *src, unsigned int n)
 86{
 87	memcpy(dest, src, n);
 88}
 89
 90void 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
116struct jitterentropy {
117	spinlock_t jent_lock;
118	struct rand_data *entropy_collector;
119};
120
121static 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
134static 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
145static 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
159static int jent_kcapi_reset(struct crypto_rng *tfm,
160			    const u8 *seed, unsigned int slen)
161{
162	return 0;
163}
164
165static 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
181static 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
193static void __exit jent_mod_exit(void)
194{
195	crypto_unregister_rng(&jent_alg);
196}
197
198module_init(jent_mod_init);
199module_exit(jent_mod_exit);
200
201MODULE_LICENSE("Dual BSD/GPL");
202MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
203MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
204MODULE_ALIAS_CRYPTO("jitterentropy_rng");