1 files changed, 170 insertions, 20 deletions

diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c
index b9edfaa51b27..7d1463a1562a 100644
--- a/crypto/jitterentropy-kcapi.c
+++ b/crypto/jitterentropy-kcapi.c
@@ -2,7 +2,7 @@
  * 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
@@ -37,6 +37,8 @@
  * DAMAGE.
  */
 
+#include <crypto/hash.h>
+#include <crypto/sha3.h>
 #include <linux/fips.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -46,6 +48,8 @@
 
 #include "jitterentropy.h"
 
+#define JENT_CONDITIONING_HASH	"sha3-256-generic"
+
 /***************************************************************************
  * Helper function
  ***************************************************************************/
@@ -60,11 +64,6 @@ void jent_zfree(void *ptr)
 	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
@@ -89,6 +88,92 @@ void jent_get_nstime(__u64 *out)
 		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;
 }
 
 /***************************************************************************
@@ -98,32 +183,82 @@ void jent_get_nstime(__u64 *out)
 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)
@@ -180,20 +315,34 @@ static struct rng_alg jent_alg = {
 		.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();
+	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;
 	}
@@ -202,6 +351,7 @@ static int __init jent_mod_init(void)
 
 static void __exit jent_mod_exit(void)
 {
+	jent_testing_exit();
 	crypto_unregister_rng(&jent_alg);
 }