/* * Non-physical true random number generator based on timing jitter -- * Linux Kernel Crypto API specific code * * Copyright Stephan Mueller <smueller@chronox.de>, 2015 * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, and the entire permission notice in its entirety, * including the disclaimer of warranties. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote * products derived from this software without specific prior * written permission. * * ALTERNATIVELY, this product may be distributed under the terms of * the GNU General Public License, in which case the provisions of the GPL2 are * required INSTEAD OF the above restrictions. (This clause is * necessary due to a potential bad interaction between the GPL and * the restrictions contained in a BSD-style copyright.) * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH * DAMAGE. */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/slab.h> #include <linux/fips.h> #include <linux/time.h> #include <crypto/internal/rng.h> #include "jitterentropy.h" /*************************************************************************** * Helper function ***************************************************************************/ void *jent_zalloc(unsigned int len) { return kzalloc(len, GFP_KERNEL); } void jent_zfree(void *ptr) { kfree_sensitive(ptr); } int jent_fips_enabled(void) { return fips_enabled; } void jent_panic(char *s) { panic("%s", s); } void jent_memcpy(void *dest, const void *src, unsigned int n) { memcpy(dest, src, n); } /* * Obtain a high-resolution time stamp value. The time stamp is used to measure * the execution time of a given code path and its variations. Hence, the time * stamp must have a sufficiently high resolution. * * Note, if the function returns zero because a given architecture does not * implement a high-resolution time stamp, the RNG code's runtime test * will detect it and will not produce output. */ void jent_get_nstime(__u64 *out) { __u64 tmp = 0; tmp = random_get_entropy(); /* * If random_get_entropy does not return a value, i.e. it is not * implemented for a given architecture, use a clock source. * hoping that there are timers we can work with. */ if (tmp == 0) tmp = ktime_get_ns(); *out = tmp; } /*************************************************************************** * Kernel crypto API interface ***************************************************************************/ struct jitterentropy { spinlock_t jent_lock; struct rand_data *entropy_collector; unsigned int reset_cnt; }; static int jent_kcapi_init(struct crypto_tfm *tfm) { struct jitterentropy *rng = crypto_tfm_ctx(tfm); int ret = 0; rng->entropy_collector = jent_entropy_collector_alloc(1, 0); if (!rng->entropy_collector) ret = -ENOMEM; spin_lock_init(&rng->jent_lock); return ret; } static void jent_kcapi_cleanup(struct crypto_tfm *tfm) { struct jitterentropy *rng = crypto_tfm_ctx(tfm); spin_lock(&rng->jent_lock); if (rng->entropy_collector) jent_entropy_collector_free(rng->entropy_collector); rng->entropy_collector = NULL; spin_unlock(&rng->jent_lock); } static int jent_kcapi_random(struct crypto_rng *tfm, const u8 *src, unsigned int slen, u8 *rdata, unsigned int dlen) { struct jitterentropy *rng = crypto_rng_ctx(tfm); int ret = 0; spin_lock(&rng->jent_lock); /* Return a permanent error in case we had too many resets in a row. */ if (rng->reset_cnt > (1<<10)) { ret = -EFAULT; goto out; } ret = jent_read_entropy(rng->entropy_collector, rdata, dlen); /* Reset RNG in case of health failures */ if (ret < -1) { pr_warn_ratelimited("Reset Jitter RNG due to health test failure: %s failure\n", (ret == -2) ? "Repetition Count Test" : "Adaptive Proportion Test"); rng->reset_cnt++; ret = -EAGAIN; } else { rng->reset_cnt = 0; /* Convert the Jitter RNG error into a usable error code */ if (ret == -1) ret = -EINVAL; } out: spin_unlock(&rng->jent_lock); return ret; } static int jent_kcapi_reset(struct crypto_rng *tfm, const u8 *seed, unsigned int slen) { return 0; } static struct rng_alg jent_alg = { .generate = jent_kcapi_random, .seed = jent_kcapi_reset, .seedsize = 0, .base = { .cra_name = "jitterentropy_rng", .cra_driver_name = "jitterentropy_rng", .cra_priority = 100, .cra_ctxsize = sizeof(struct jitterentropy), .cra_module = THIS_MODULE, .cra_init = jent_kcapi_init, .cra_exit = jent_kcapi_cleanup, } }; static int __init jent_mod_init(void) { int ret = 0; ret = jent_entropy_init(); if (ret) { pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret); return -EFAULT; } return crypto_register_rng(&jent_alg); } static void __exit jent_mod_exit(void) { crypto_unregister_rng(&jent_alg); } module_init(jent_mod_init); module_exit(jent_mod_exit); MODULE_LICENSE("Dual BSD/GPL"); MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>"); MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter"); MODULE_ALIAS_CRYPTO("jitterentropy_rng");