[1/2] crypto: jitter - replace LFSR with SHA3-256

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 9c86f7045157..113dee4b167b 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1277,6 +1277,7 @@  endif	# if CRYPTO_DRBG_MENU
 config CRYPTO_JITTERENTROPY
 	tristate "CPU Jitter Non-Deterministic RNG (Random Number Generator)"
 	select CRYPTO_RNG
+	select CRYPTO_SHA3
 	help
 	  CPU Jitter RNG (Random Number Generator) from the Jitterentropy library
 
diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c
index b9edfaa51b27..228b10cab55f 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
@@ -91,6 +90,91 @@  void jent_get_nstime(__u64 *out)
 	*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
  ***************************************************************************/
@@ -98,32 +182,78 @@  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;
+
+	/*
+	 * 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;
+
+	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)
@@ -180,15 +310,24 @@  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();
+	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);
+	crypto_free_shash(tfm);
+	shash_desc_zero(desc);
 	if (ret) {
 		/* Handle permanent health test error */
 		if (fips_enabled)
diff --git a/crypto/jitterentropy.c b/crypto/jitterentropy.c
index 22f48bf4c6f5..dc423210c9f9 100644
--- a/crypto/jitterentropy.c
+++ b/crypto/jitterentropy.c
@@ -2,7 +2,7 @@ 
  * 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
  * ======
@@ -47,7 +47,7 @@ 
 
 /*
  * 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__
@@ -57,21 +57,22 @@ 
 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
@@ -302,15 +303,13 @@  static int jent_permanent_health_failure(struct rand_data *ec)
  * 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;
@@ -318,12 +317,7 @@  static __u64 jent_loop_shuffle(struct rand_data *ec,
 	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.
@@ -345,81 +339,32 @@  static __u64 jent_loop_shuffle(struct rand_data *ec,
  *			      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);
 }
 
 /*
@@ -453,7 +398,7 @@  static void jent_memaccess(struct rand_data *ec, __u64 loop_cnt)
 #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;
@@ -521,14 +466,15 @@  static int jent_measure_jitter(struct rand_data *ec)
 	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
  */
@@ -575,7 +521,7 @@  static void jent_gen_entropy(struct rand_data *ec)
  * @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
  */
@@ -605,7 +551,7 @@  int jent_read_entropy(struct rand_data *ec, unsigned char *data,
 			 * 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;
@@ -615,7 +561,8 @@  int jent_read_entropy(struct rand_data *ec, unsigned char *data,
 			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;
@@ -629,7 +576,8 @@  int jent_read_entropy(struct rand_data *ec, unsigned char *data,
  ***************************************************************************/
 
 struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
-					       unsigned int flags)
+					       unsigned int flags,
+					       void *hash_state)
 {
 	struct rand_data *entropy_collector;
 
@@ -656,6 +604,8 @@  struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
 		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);
 
@@ -669,7 +619,7 @@  void jent_entropy_collector_free(struct rand_data *entropy_collector)
 	jent_zfree(entropy_collector);
 }
 
-int jent_entropy_init(void)
+int jent_entropy_init(void *hash_state)
 {
 	int i;
 	__u64 delta_sum = 0;
@@ -682,6 +632,7 @@  int jent_entropy_init(void)
 
 	/* 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
@@ -719,7 +670,7 @@  int jent_entropy_init(void)
 		/* 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 */
diff --git a/crypto/jitterentropy.h b/crypto/jitterentropy.h
index 5cc583f6bc6b..b3890ff26a02 100644
--- a/crypto/jitterentropy.h
+++ b/crypto/jitterentropy.h
@@ -2,14 +2,18 @@ 
 
 extern void *jent_zalloc(unsigned int len);
 extern void jent_zfree(void *ptr);
-extern void jent_memcpy(void *dest, const void *src, unsigned int n);
 extern void jent_get_nstime(__u64 *out);
+extern int jent_hash_time(void *hash_state, __u64 time, u8 *addtl,
+			  unsigned int addtl_len, __u64 hash_loop_cnt,
+			  unsigned int stuck);
+int jent_read_random_block(void *hash_state, char *dst, unsigned int dst_len);
 
 struct rand_data;
-extern int jent_entropy_init(void);
+extern int jent_entropy_init(void *hash_state);
 extern int jent_read_entropy(struct rand_data *ec, unsigned char *data,
 			     unsigned int len);
 
 extern struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
-						      unsigned int flags);
+						      unsigned int flags,
+						      void *hash_state);
 extern void jent_entropy_collector_free(struct rand_data *entropy_collector);