jitterentropy-kcapi.c 6.2 KB

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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. #include <linux/kernel.h>
  40. #include <linux/module.h>
  41. #include <linux/slab.h>
  42. #include <linux/fips.h>
  43. #include <linux/time.h>
  44. #include <crypto/internal/rng.h>
  45. #include "jitterentropy.h"
  46. /***************************************************************************
  47. * Helper function
  48. ***************************************************************************/
  49. void *jent_zalloc(unsigned int len)
  50. {
  51. return kzalloc(len, GFP_KERNEL);
  52. }
  53. void jent_zfree(void *ptr)
  54. {
  55. kfree_sensitive(ptr);
  56. }
  57. int jent_fips_enabled(void)
  58. {
  59. return fips_enabled;
  60. }
  61. void jent_panic(char *s)
  62. {
  63. panic("%s", s);
  64. }
  65. void jent_memcpy(void *dest, const void *src, unsigned int n)
  66. {
  67. memcpy(dest, src, n);
  68. }
  69. /*
  70. * Obtain a high-resolution time stamp value. The time stamp is used to measure
  71. * the execution time of a given code path and its variations. Hence, the time
  72. * stamp must have a sufficiently high resolution.
  73. *
  74. * Note, if the function returns zero because a given architecture does not
  75. * implement a high-resolution time stamp, the RNG code's runtime test
  76. * will detect it and will not produce output.
  77. */
  78. void jent_get_nstime(__u64 *out)
  79. {
  80. __u64 tmp = 0;
  81. tmp = random_get_entropy();
  82. /*
  83. * If random_get_entropy does not return a value, i.e. it is not
  84. * implemented for a given architecture, use a clock source.
  85. * hoping that there are timers we can work with.
  86. */
  87. if (tmp == 0)
  88. tmp = ktime_get_ns();
  89. *out = tmp;
  90. }
  91. /***************************************************************************
  92. * Kernel crypto API interface
  93. ***************************************************************************/
  94. struct jitterentropy {
  95. spinlock_t jent_lock;
  96. struct rand_data *entropy_collector;
  97. unsigned int reset_cnt;
  98. };
  99. static int jent_kcapi_init(struct crypto_tfm *tfm)
  100. {
  101. struct jitterentropy *rng = crypto_tfm_ctx(tfm);
  102. int ret = 0;
  103. rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
  104. if (!rng->entropy_collector)
  105. ret = -ENOMEM;
  106. spin_lock_init(&rng->jent_lock);
  107. return ret;
  108. }
  109. static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
  110. {
  111. struct jitterentropy *rng = crypto_tfm_ctx(tfm);
  112. spin_lock(&rng->jent_lock);
  113. if (rng->entropy_collector)
  114. jent_entropy_collector_free(rng->entropy_collector);
  115. rng->entropy_collector = NULL;
  116. spin_unlock(&rng->jent_lock);
  117. }
  118. static int jent_kcapi_random(struct crypto_rng *tfm,
  119. const u8 *src, unsigned int slen,
  120. u8 *rdata, unsigned int dlen)
  121. {
  122. struct jitterentropy *rng = crypto_rng_ctx(tfm);
  123. int ret = 0;
  124. spin_lock(&rng->jent_lock);
  125. /* Return a permanent error in case we had too many resets in a row. */
  126. if (rng->reset_cnt > (1<<10)) {
  127. ret = -EFAULT;
  128. goto out;
  129. }
  130. ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
  131. /* Reset RNG in case of health failures */
  132. if (ret < -1) {
  133. pr_warn_ratelimited("Reset Jitter RNG due to health test failure: %s failure\n",
  134. (ret == -2) ? "Repetition Count Test" :
  135. "Adaptive Proportion Test");
  136. rng->reset_cnt++;
  137. ret = -EAGAIN;
  138. } else {
  139. rng->reset_cnt = 0;
  140. /* Convert the Jitter RNG error into a usable error code */
  141. if (ret == -1)
  142. ret = -EINVAL;
  143. }
  144. out:
  145. spin_unlock(&rng->jent_lock);
  146. return ret;
  147. }
  148. static int jent_kcapi_reset(struct crypto_rng *tfm,
  149. const u8 *seed, unsigned int slen)
  150. {
  151. return 0;
  152. }
  153. static struct rng_alg jent_alg = {
  154. .generate = jent_kcapi_random,
  155. .seed = jent_kcapi_reset,
  156. .seedsize = 0,
  157. .base = {
  158. .cra_name = "jitterentropy_rng",
  159. .cra_driver_name = "jitterentropy_rng",
  160. .cra_priority = 100,
  161. .cra_ctxsize = sizeof(struct jitterentropy),
  162. .cra_module = THIS_MODULE,
  163. .cra_init = jent_kcapi_init,
  164. .cra_exit = jent_kcapi_cleanup,
  165. }
  166. };
  167. static int __init jent_mod_init(void)
  168. {
  169. int ret = 0;
  170. ret = jent_entropy_init();
  171. if (ret) {
  172. pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
  173. return -EFAULT;
  174. }
  175. return crypto_register_rng(&jent_alg);
  176. }
  177. static void __exit jent_mod_exit(void)
  178. {
  179. crypto_unregister_rng(&jent_alg);
  180. }
  181. module_init(jent_mod_init);
  182. module_exit(jent_mod_exit);
  183. MODULE_LICENSE("Dual BSD/GPL");
  184. MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
  185. MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
  186. MODULE_ALIAS_CRYPTO("jitterentropy_rng");