* Non-physical true random number generator based on timing jitter --
* Linux Kernel Crypto API specific code
*
- * Copyright Stephan Mueller <smueller@chronox.de>, 2015
+ * 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
* DAMAGE.
*/
+#include <crypto/hash.h>
+#include <crypto/sha3.h>
#include <linux/fips.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include "jitterentropy.h"
+#define JENT_CONDITIONING_HASH "sha3-256-generic"
+
/***************************************************************************
* Helper function
***************************************************************************/
kfree_sensitive(ptr);
}
-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
*out = 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 int jent_kcapi_init(struct crypto_tfm *tfm)
+static void jent_kcapi_cleanup(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(&rng->jent_lock);
- spin_lock_init(&rng->jent_lock);
- return ret;
-}
+ if (rng->sdesc) {
+ shash_desc_zero(rng->sdesc);
+ kfree(rng->sdesc);
+ }
+ rng->sdesc = NULL;
-static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
-{
- struct jitterentropy *rng = crypto_tfm_ctx(tfm);
+ if (rng->tfm)
+ crypto_free_shash(rng->tfm);
+ rng->tfm = NULL;
- 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_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)
.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;
- ret = jent_entropy_init();
+ tfm = crypto_alloc_shash(JENT_CONDITIONING_HASH, 0, 0);
+ if (IS_ERR(tfm))
+ 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)
* Non-physical true random number generator based on timing jitter --
* Jitter RNG standalone code.
*
- * Copyright Stephan Mueller <smueller@chronox.de>, 2015 - 2020
+ * Copyright Stephan Mueller <smueller@chronox.de>, 2015 - 2023
*
* Design
* ======
/*
* This Jitterentropy RNG is based on the jitterentropy library
- * version 2.2.0 provided at https://www.chronox.de/jent.html
+ * version 3.4.0 provided at https://www.chronox.de/jent.html
*/
#ifdef __OPTIMIZE__
typedef unsigned long long __u64;
typedef long long __s64;
typedef unsigned int __u32;
+typedef unsigned char u8;
#define NULL ((void *) 0)
/* The entropy pool */
struct rand_data {
+ /* SHA3-256 is used as conditioner */
+#define DATA_SIZE_BITS 256
/* all data values that are vital to maintain the security
* of the RNG are marked as SENSITIVE. A user must not
* access that information while the RNG executes its loops to
* calculate the next random value. */
- __u64 data; /* SENSITIVE Actual random number */
- __u64 old_data; /* SENSITIVE Previous random number */
- __u64 prev_time; /* SENSITIVE Previous time stamp */
-#define DATA_SIZE_BITS ((sizeof(__u64)) * 8)
- __u64 last_delta; /* SENSITIVE stuck test */
- __s64 last_delta2; /* SENSITIVE stuck test */
- unsigned int osr; /* Oversample rate */
+ void *hash_state; /* SENSITIVE hash state entropy pool */
+ __u64 prev_time; /* SENSITIVE Previous time stamp */
+ __u64 last_delta; /* SENSITIVE stuck test */
+ __s64 last_delta2; /* SENSITIVE stuck test */
+ unsigned int osr; /* Oversample rate */
#define JENT_MEMORY_BLOCKS 64
#define JENT_MEMORY_BLOCKSIZE 32
#define JENT_MEMORY_ACCESSLOOPS 128
* an entropy collection.
*
* Input:
- * @ec entropy collector struct -- may be NULL
* @bits is the number of low bits of the timer to consider
* @min is the number of bits we shift the timer value to the right at
* the end to make sure we have a guaranteed minimum value
*
* @return Newly calculated loop counter
*/
-static __u64 jent_loop_shuffle(struct rand_data *ec,
- unsigned int bits, unsigned int min)
+static __u64 jent_loop_shuffle(unsigned int bits, unsigned int min)
{
__u64 time = 0;
__u64 shuffle = 0;
unsigned int mask = (1<<bits) - 1;
jent_get_nstime(&time);
- /*
- * Mix the current state of the random number into the shuffle
- * calculation to balance that shuffle a bit more.
- */
- if (ec)
- time ^= ec->data;
+
/*
* We fold the time value as much as possible to ensure that as many
* bits of the time stamp are included as possible.
* execution time jitter
*
* This function injects the individual bits of the time value into the
- * entropy pool using an LFSR.
+ * entropy pool using a hash.
*
- * The code is deliberately inefficient with respect to the bit shifting
- * and shall stay that way. This function is the root cause why the code
- * shall be compiled without optimization. This function not only acts as
- * folding operation, but this function's execution is used to measure
- * the CPU execution time jitter. Any change to the loop in this function
- * implies that careful retesting must be done.
- *
- * @ec [in] entropy collector struct
- * @time [in] time stamp to be injected
- * @loop_cnt [in] if a value not equal to 0 is set, use the given value as
- * number of loops to perform the folding
- * @stuck [in] Is the time stamp identified as stuck?
+ * ec [in] entropy collector
+ * time [in] time stamp to be injected
+ * stuck [in] Is the time stamp identified as stuck?
*
* Output:
- * updated ec->data
- *
- * @return Number of loops the folding operation is performed
+ * updated hash context in the entropy collector or error code
*/
-static void jent_lfsr_time(struct rand_data *ec, __u64 time, __u64 loop_cnt,
- int stuck)
+static int jent_condition_data(struct rand_data *ec, __u64 time, int stuck)
{
- unsigned int i;
- __u64 j = 0;
- __u64 new = 0;
-#define MAX_FOLD_LOOP_BIT 4
-#define MIN_FOLD_LOOP_BIT 0
- __u64 fold_loop_cnt =
- jent_loop_shuffle(ec, MAX_FOLD_LOOP_BIT, MIN_FOLD_LOOP_BIT);
-
- /*
- * testing purposes -- allow test app to set the counter, not
- * needed during runtime
- */
- if (loop_cnt)
- fold_loop_cnt = loop_cnt;
- for (j = 0; j < fold_loop_cnt; j++) {
- new = ec->data;
- for (i = 1; (DATA_SIZE_BITS) >= i; i++) {
- __u64 tmp = time << (DATA_SIZE_BITS - i);
-
- tmp = tmp >> (DATA_SIZE_BITS - 1);
-
- /*
- * Fibonacci LSFR with polynomial of
- * x^64 + x^61 + x^56 + x^31 + x^28 + x^23 + 1 which is
- * primitive according to
- * http://poincare.matf.bg.ac.rs/~ezivkovm/publications/primpol1.pdf
- * (the shift values are the polynomial values minus one
- * due to counting bits from 0 to 63). As the current
- * position is always the LSB, the polynomial only needs
- * to shift data in from the left without wrap.
- */
- tmp ^= ((new >> 63) & 1);
- tmp ^= ((new >> 60) & 1);
- tmp ^= ((new >> 55) & 1);
- tmp ^= ((new >> 30) & 1);
- tmp ^= ((new >> 27) & 1);
- tmp ^= ((new >> 22) & 1);
- new <<= 1;
- new ^= tmp;
- }
- }
-
- /*
- * 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 (SP800-90B considers the LFSR to be a
- * conditioning operation) to have an identical amount of input
- * data according to section 3.1.5.
- */
- if (!stuck)
- ec->data = new;
+#define SHA3_HASH_LOOP (1<<3)
+ struct {
+ int rct_count;
+ unsigned int apt_observations;
+ unsigned int apt_count;
+ unsigned int apt_base;
+ } addtl = {
+ ec->rct_count,
+ ec->apt_observations,
+ ec->apt_count,
+ ec->apt_base
+ };
+
+ return jent_hash_time(ec->hash_state, time, (u8 *)&addtl, sizeof(addtl),
+ SHA3_HASH_LOOP, stuck);
}
/*
#define MAX_ACC_LOOP_BIT 7
#define MIN_ACC_LOOP_BIT 0
__u64 acc_loop_cnt =
- jent_loop_shuffle(ec, MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT);
+ jent_loop_shuffle(MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT);
if (NULL == ec || NULL == ec->mem)
return;
stuck = jent_stuck(ec, current_delta);
/* Now call the next noise sources which also injects the data */
- jent_lfsr_time(ec, current_delta, 0, stuck);
+ if (jent_condition_data(ec, current_delta, stuck))
+ stuck = 1;
return stuck;
}
/*
* Generator of one 64 bit random number
- * Function fills rand_data->data
+ * Function fills rand_data->hash_state
*
* @ec [in] Reference to entropy collector
*/
* @return 0 when request is fulfilled or an error
*
* The following error codes can occur:
- * -1 entropy_collector is NULL
+ * -1 entropy_collector is NULL or the generation failed
* -2 Intermittent health failure
* -3 Permanent health failure
*/
* Perform startup health tests and return permanent
* error if it fails.
*/
- if (jent_entropy_init())
+ if (jent_entropy_init(ec->hash_state))
return -3;
return -2;
tocopy = (DATA_SIZE_BITS / 8);
else
tocopy = len;
- jent_memcpy(p, &ec->data, tocopy);
+ if (jent_read_random_block(ec->hash_state, p, tocopy))
+ return -1;
len -= tocopy;
p += tocopy;
***************************************************************************/
struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
- unsigned int flags)
+ unsigned int flags,
+ void *hash_state)
{
struct rand_data *entropy_collector;
osr = 1; /* minimum sampling rate is 1 */
entropy_collector->osr = osr;
+ entropy_collector->hash_state = hash_state;
+
/* fill the data pad with non-zero values */
jent_gen_entropy(entropy_collector);
jent_zfree(entropy_collector);
}
-int jent_entropy_init(void)
+int jent_entropy_init(void *hash_state)
{
int i;
__u64 delta_sum = 0;
/* Required for RCT */
ec.osr = 1;
+ ec.hash_state = hash_state;
/* We could perform statistical tests here, but the problem is
* that we only have a few loop counts to do testing. These
/* Invoke core entropy collection logic */
jent_get_nstime(&time);
ec.prev_time = time;
- jent_lfsr_time(&ec, time, 0, 0);
+ jent_condition_data(&ec, time, 0);
jent_get_nstime(&time2);
/* test whether timer works */
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