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Diffstat (limited to 'crypto/jitterentropy-kcapi.c')
| -rw-r--r-- | crypto/jitterentropy-kcapi.c | 364 |
1 files changed, 364 insertions, 0 deletions
diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c new file mode 100644 index 000000000..7d1463a15 --- /dev/null +++ b/crypto/jitterentropy-kcapi.c @@ -0,0 +1,364 @@ +/* + * Non-physical true random number generator based on timing jitter -- + * Linux Kernel Crypto API specific code + * + * Copyright Stephan Mueller <smueller@chronox.de>, 2015 - 2023 + * + * 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 <crypto/hash.h> +#include <crypto/sha3.h> +#include <linux/fips.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/time.h> +#include <crypto/internal/rng.h> + +#include "jitterentropy.h" + +#define JENT_CONDITIONING_HASH "sha3-256-generic" + +/*************************************************************************** + * Helper function + ***************************************************************************/ + +void *jent_zalloc(unsigned int len) +{ + return kzalloc(len, GFP_KERNEL); +} + +void jent_zfree(void *ptr) +{ + kfree_sensitive(ptr); +} + +/* + * 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; + jent_raw_hires_entropy_store(tmp); +} + +int jent_hash_time(void *hash_state, __u64 time, u8 *addtl, + unsigned int addtl_len, __u64 hash_loop_cnt, + unsigned int stuck) +{ + struct shash_desc *hash_state_desc = (struct shash_desc *)hash_state; + SHASH_DESC_ON_STACK(desc, hash_state_desc->tfm); + u8 intermediary[SHA3_256_DIGEST_SIZE]; + __u64 j = 0; + int ret; + + desc->tfm = hash_state_desc->tfm; + + if (sizeof(intermediary) != crypto_shash_digestsize(desc->tfm)) { + pr_warn_ratelimited("Unexpected digest size\n"); + return -EINVAL; + } + + /* + * This loop fills a buffer which is injected into the entropy pool. + * The main reason for this loop is to execute something over which we + * can perform a timing measurement. The injection of the resulting + * data into the pool is performed to ensure the result is used and + * the compiler cannot optimize the loop away in case the result is not + * used at all. Yet that data is considered "additional information" + * considering the terminology from SP800-90A without any entropy. + * + * Note, it does not matter which or how much data you inject, we are + * interested in one Keccack1600 compression operation performed with + * the crypto_shash_final. + */ + for (j = 0; j < hash_loop_cnt; j++) { + ret = crypto_shash_init(desc) ?: + crypto_shash_update(desc, intermediary, + sizeof(intermediary)) ?: + crypto_shash_finup(desc, addtl, addtl_len, intermediary); + if (ret) + goto err; + } + + /* + * Inject the data from the previous loop into the pool. This data is + * not considered to contain any entropy, but it stirs the pool a bit. + */ + ret = crypto_shash_update(desc, intermediary, sizeof(intermediary)); + if (ret) + goto err; + + /* + * Insert the time stamp into the hash context representing the pool. + * + * If the time stamp is stuck, do not finally insert the value into the + * entropy pool. Although this operation should not do any harm even + * when the time stamp has no entropy, SP800-90B requires that any + * conditioning operation to have an identical amount of input data + * according to section 3.1.5. + */ + if (!stuck) { + ret = crypto_shash_update(hash_state_desc, (u8 *)&time, + sizeof(__u64)); + } + +err: + shash_desc_zero(desc); + memzero_explicit(intermediary, sizeof(intermediary)); + + return ret; +} + +int jent_read_random_block(void *hash_state, char *dst, unsigned int dst_len) +{ + struct shash_desc *hash_state_desc = (struct shash_desc *)hash_state; + u8 jent_block[SHA3_256_DIGEST_SIZE]; + /* Obtain data from entropy pool and re-initialize it */ + int ret = crypto_shash_final(hash_state_desc, jent_block) ?: + crypto_shash_init(hash_state_desc) ?: + crypto_shash_update(hash_state_desc, jent_block, + sizeof(jent_block)); + + if (!ret && dst_len) + memcpy(dst, jent_block, dst_len); + + memzero_explicit(jent_block, sizeof(jent_block)); + return ret; +} + +/*************************************************************************** + * Kernel crypto API interface + ***************************************************************************/ + +struct jitterentropy { + spinlock_t jent_lock; + struct rand_data *entropy_collector; + struct crypto_shash *tfm; + struct shash_desc *sdesc; +}; + +static void jent_kcapi_cleanup(struct crypto_tfm *tfm) +{ + struct jitterentropy *rng = crypto_tfm_ctx(tfm); + + spin_lock(&rng->jent_lock); + + if (rng->sdesc) { + shash_desc_zero(rng->sdesc); + kfree(rng->sdesc); + } + rng->sdesc = NULL; + + if (rng->tfm) + crypto_free_shash(rng->tfm); + rng->tfm = NULL; + + if (rng->entropy_collector) + jent_entropy_collector_free(rng->entropy_collector); + rng->entropy_collector = NULL; + spin_unlock(&rng->jent_lock); +} + +static int jent_kcapi_init(struct crypto_tfm *tfm) +{ + struct jitterentropy *rng = crypto_tfm_ctx(tfm); + struct crypto_shash *hash; + struct shash_desc *sdesc; + int size, ret = 0; + + spin_lock_init(&rng->jent_lock); + + /* + * Use SHA3-256 as conditioner. We allocate only the generic + * implementation as we are not interested in high-performance. The + * execution time of the SHA3 operation is measured and adds to the + * Jitter RNG's unpredictable behavior. If we have a slower hash + * implementation, the execution timing variations are larger. When + * using a fast implementation, we would need to call it more often + * as its variations are lower. + */ + hash = crypto_alloc_shash(JENT_CONDITIONING_HASH, 0, 0); + if (IS_ERR(hash)) { + pr_err("Cannot allocate conditioning digest\n"); + return PTR_ERR(hash); + } + rng->tfm = hash; + + size = sizeof(struct shash_desc) + crypto_shash_descsize(hash); + sdesc = kmalloc(size, GFP_KERNEL); + if (!sdesc) { + ret = -ENOMEM; + goto err; + } + + sdesc->tfm = hash; + crypto_shash_init(sdesc); + rng->sdesc = sdesc; + + rng->entropy_collector = jent_entropy_collector_alloc(1, 0, sdesc); + if (!rng->entropy_collector) { + ret = -ENOMEM; + goto err; + } + + spin_lock_init(&rng->jent_lock); + return 0; + +err: + jent_kcapi_cleanup(tfm); + return ret; +} + +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); + + ret = jent_read_entropy(rng->entropy_collector, rdata, dlen); + + if (ret == -3) { + /* Handle permanent health test error */ + /* + * If the kernel was booted with fips=1, it implies that + * the entire kernel acts as a FIPS 140 module. In this case + * an SP800-90B permanent health test error is treated as + * a FIPS module error. + */ + if (fips_enabled) + panic("Jitter RNG permanent health test failure\n"); + + pr_err("Jitter RNG permanent health test failure\n"); + ret = -EFAULT; + } else if (ret == -2) { + /* Handle intermittent health test error */ + pr_warn_ratelimited("Reset Jitter RNG due to intermittent health test failure\n"); + ret = -EAGAIN; + } else if (ret == -1) { + /* Handle other errors */ + ret = -EINVAL; + } + + 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) +{ + SHASH_DESC_ON_STACK(desc, tfm); + struct crypto_shash *tfm; + int ret = 0; + + jent_testing_init(); + + tfm = crypto_alloc_shash(JENT_CONDITIONING_HASH, 0, 0); + if (IS_ERR(tfm)) { + jent_testing_exit(); + return PTR_ERR(tfm); + } + + desc->tfm = tfm; + crypto_shash_init(desc); + ret = jent_entropy_init(desc); + shash_desc_zero(desc); + crypto_free_shash(tfm); + if (ret) { + /* Handle permanent health test error */ + if (fips_enabled) + panic("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret); + + jent_testing_exit(); + 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) +{ + jent_testing_exit(); + 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"); |