fs/verity/hash_algs.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * fs-verity hash algorithms
  *
  * Copyright 2019 Google LLC
  */

 #include "fsverity_private.h"

 #include <crypto/hash.h>

 /* The hash algorithms supported by fs-verity */
 struct fsverity_hash_alg fsverity_hash_algs[] = {
 	[FS_VERITY_HASH_ALG_SHA256] = {
 		.name = "sha256",
 		.digest_size = SHA256_DIGEST_SIZE,
 		.block_size = SHA256_BLOCK_SIZE,
 		.algo_id = HASH_ALGO_SHA256,
 	},
 	[FS_VERITY_HASH_ALG_SHA512] = {
 		.name = "sha512",
 		.digest_size = SHA512_DIGEST_SIZE,
 		.block_size = SHA512_BLOCK_SIZE,
 		.algo_id = HASH_ALGO_SHA512,
 	},
 };

 static DEFINE_MUTEX(fsverity_hash_alg_init_mutex);

 /**
  * fsverity_get_hash_alg() - validate and prepare a hash algorithm
  * @inode: optional inode for logging purposes
  * @num: the hash algorithm number
  *
  * Get the struct fsverity_hash_alg for the given hash algorithm number, and
  * ensure it has a hash transform ready to go.  The hash transforms are
  * allocated on-demand so that we don't waste resources unnecessarily, and
  * because the crypto modules may be initialized later than fs/verity/.
  *
  * Return: pointer to the hash alg on success, else an ERR_PTR()
  */
 const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
 						      unsigned int num)
 {
 	struct fsverity_hash_alg *alg;
 	struct crypto_shash *tfm;
 	int err;

 	if (num >= ARRAY_SIZE(fsverity_hash_algs) ||
 	    !fsverity_hash_algs[num].name) {
 		fsverity_warn(inode, "Unknown hash algorithm number: %u", num);
 		return ERR_PTR(-EINVAL);
 	}
 	alg = &fsverity_hash_algs[num];

 	/* pairs with smp_store_release() below */
 	if (likely(smp_load_acquire(&alg->tfm) != NULL))
 		return alg;

 	mutex_lock(&fsverity_hash_alg_init_mutex);

 	if (alg->tfm != NULL)
 		goto out_unlock;

 	tfm = crypto_alloc_shash(alg->name, 0, 0);
 	if (IS_ERR(tfm)) {
 		if (PTR_ERR(tfm) == -ENOENT) {
 			fsverity_warn(inode,
 				      "Missing crypto API support for hash algorithm \"%s\"",
 				      alg->name);
 			alg = ERR_PTR(-ENOPKG);
 			goto out_unlock;
 		}
 		fsverity_err(inode,
 			     "Error allocating hash algorithm \"%s\": %ld",
 			     alg->name, PTR_ERR(tfm));
 		alg = ERR_CAST(tfm);
 		goto out_unlock;
 	}

 	err = -EINVAL;
 	if (WARN_ON_ONCE(alg->digest_size != crypto_shash_digestsize(tfm)))
 		goto err_free_tfm;
 	if (WARN_ON_ONCE(alg->block_size != crypto_shash_blocksize(tfm)))
 		goto err_free_tfm;

 	pr_info("%s using implementation \"%s\"\n",
 		alg->name, crypto_shash_driver_name(tfm));

 	/* pairs with smp_load_acquire() above */
 	smp_store_release(&alg->tfm, tfm);
 	goto out_unlock;

 err_free_tfm:
 	crypto_free_shash(tfm);
 	alg = ERR_PTR(err);
 out_unlock:
 	mutex_unlock(&fsverity_hash_alg_init_mutex);
 	return alg;
 }

 /**
  * fsverity_prepare_hash_state() - precompute the initial hash state
  * @alg: hash algorithm
  * @salt: a salt which is to be prepended to all data to be hashed
  * @salt_size: salt size in bytes, possibly 0
  *
  * Return: NULL if the salt is empty, otherwise the kmalloc()'ed precomputed
  *	   initial hash state on success or an ERR_PTR() on failure.
  */
 const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
 				      const u8 *salt, size_t salt_size)
 {
 	u8 *hashstate = NULL;
 	SHASH_DESC_ON_STACK(desc, alg->tfm);
 	u8 *padded_salt = NULL;
 	size_t padded_salt_size;
 	int err;

 	desc->tfm = alg->tfm;

 	if (salt_size == 0)
 		return NULL;

 	hashstate = kmalloc(crypto_shash_statesize(alg->tfm), GFP_KERNEL);
 	if (!hashstate)
 		return ERR_PTR(-ENOMEM);

 	/*
 	 * Zero-pad the salt to the next multiple of the input size of the hash
 	 * algorithm's compression function, e.g. 64 bytes for SHA-256 or 128
 	 * bytes for SHA-512.  This ensures that the hash algorithm won't have
 	 * any bytes buffered internally after processing the salt, thus making
 	 * salted hashing just as fast as unsalted hashing.
 	 */
 	padded_salt_size = round_up(salt_size, alg->block_size);
 	padded_salt = kzalloc(padded_salt_size, GFP_KERNEL);
 	if (!padded_salt) {
 		err = -ENOMEM;
 		goto err_free;
 	}
 	memcpy(padded_salt, salt, salt_size);
 	err = crypto_shash_init(desc);
 	if (err)
 		goto err_free;

 	err = crypto_shash_update(desc, padded_salt, padded_salt_size);
 	if (err)
 		goto err_free;

 	err = crypto_shash_export(desc, hashstate);
 	if (err)
 		goto err_free;
 out:
 	kfree(padded_salt);
 	return hashstate;

 err_free:
 	kfree(hashstate);
 	hashstate = ERR_PTR(err);
 	goto out;
 }

 /**
  * fsverity_hash_block() - hash a single data or hash block
  * @params: the Merkle tree's parameters
  * @inode: inode for which the hashing is being done
  * @data: virtual address of a buffer containing the block to hash
  * @out: output digest, size 'params->digest_size' bytes
  *
  * Hash a single data or hash block.  The hash is salted if a salt is specified
  * in the Merkle tree parameters.
  *
  * Return: 0 on success, -errno on failure
  */
 int fsverity_hash_block(const struct merkle_tree_params *params,
 			const struct inode *inode, const void *data, u8 *out)
 {
 	SHASH_DESC_ON_STACK(desc, params->hash_alg->tfm);
 	int err;

 	desc->tfm = params->hash_alg->tfm;

 	if (params->hashstate) {
 		err = crypto_shash_import(desc, params->hashstate);
 		if (err) {
 			fsverity_err(inode,
 				     "Error %d importing hash state", err);
 			return err;
 		}
 		err = crypto_shash_finup(desc, data, params->block_size, out);
 	} else {
 		err = crypto_shash_digest(desc, data, params->block_size, out);
 	}
 	if (err)
 		fsverity_err(inode, "Error %d computing block hash", err);
 	return err;
 }

 /**
  * fsverity_hash_buffer() - hash some data
  * @alg: the hash algorithm to use
  * @data: the data to hash
  * @size: size of data to hash, in bytes
  * @out: output digest, size 'alg->digest_size' bytes
  *
  * Return: 0 on success, -errno on failure
  */
 int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
 			 const void *data, size_t size, u8 *out)
 {
 	return crypto_shash_tfm_digest(alg->tfm, data, size, out);
 }

 void __init fsverity_check_hash_algs(void)
 {
 	size_t i;

 	/*
 	 * Sanity check the hash algorithms (could be a build-time check, but
 	 * they're in an array)
 	 */
 	for (i = 0; i < ARRAY_SIZE(fsverity_hash_algs); i++) {
 		const struct fsverity_hash_alg *alg = &fsverity_hash_algs[i];

 		if (!alg->name)
 			continue;

 		BUG_ON(alg->digest_size > FS_VERITY_MAX_DIGEST_SIZE);

 		/*
 		 * For efficiency, the implementation currently assumes the
 		 * digest and block sizes are powers of 2.  This limitation can
 		 * be lifted if the code is updated to handle other values.
 		 */
 		BUG_ON(!is_power_of_2(alg->digest_size));
 		BUG_ON(!is_power_of_2(alg->block_size));

 		/* Verify that there is a valid mapping to HASH_ALGO_*. */
 		BUG_ON(alg->algo_id == 0);
 		BUG_ON(alg->digest_size != hash_digest_size[alg->algo_id]);
 	}
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* fs-verity hash algorithms
	*
	* Copyright 2019 Google LLC
	*/

	#include "fsverity_private.h"

	#include <crypto/hash.h>

	/* The hash algorithms supported by fs-verity */
	struct fsverity_hash_alg fsverity_hash_algs[] = {
	[FS_VERITY_HASH_ALG_SHA256] = {
	.name = "sha256",
	.digest_size = SHA256_DIGEST_SIZE,
	.block_size = SHA256_BLOCK_SIZE,
	.algo_id = HASH_ALGO_SHA256,
	},
	[FS_VERITY_HASH_ALG_SHA512] = {
	.name = "sha512",
	.digest_size = SHA512_DIGEST_SIZE,
	.block_size = SHA512_BLOCK_SIZE,
	.algo_id = HASH_ALGO_SHA512,
	},
	};

	static DEFINE_MUTEX(fsverity_hash_alg_init_mutex);

	/**
	* fsverity_get_hash_alg() - validate and prepare a hash algorithm
	* @inode: optional inode for logging purposes
	* @num: the hash algorithm number
	*
	* Get the struct fsverity_hash_alg for the given hash algorithm number, and
	* ensure it has a hash transform ready to go. The hash transforms are
	* allocated on-demand so that we don't waste resources unnecessarily, and
	* because the crypto modules may be initialized later than fs/verity/.
	*
	* Return: pointer to the hash alg on success, else an ERR_PTR()
	*/
	const struct fsverity_hash_alg fsverity_get_hash_alg(const struct inode inode,
	unsigned int num)
	{
	struct fsverity_hash_alg *alg;
	struct crypto_shash *tfm;
	int err;

	if (num >= ARRAY_SIZE(fsverity_hash_algs) \|\|
	!fsverity_hash_algs[num].name) {
	fsverity_warn(inode, "Unknown hash algorithm number: %u", num);
	return ERR_PTR(-EINVAL);
	}
	alg = &fsverity_hash_algs[num];

	/* pairs with smp_store_release() below */
	if (likely(smp_load_acquire(&alg->tfm) != NULL))
	return alg;

	mutex_lock(&fsverity_hash_alg_init_mutex);

	if (alg->tfm != NULL)
	goto out_unlock;

	tfm = crypto_alloc_shash(alg->name, 0, 0);
	if (IS_ERR(tfm)) {
	if (PTR_ERR(tfm) == -ENOENT) {
	fsverity_warn(inode,
	"Missing crypto API support for hash algorithm \"%s\"",
	alg->name);
	alg = ERR_PTR(-ENOPKG);
	goto out_unlock;
	}
	fsverity_err(inode,
	"Error allocating hash algorithm \"%s\": %ld",
	alg->name, PTR_ERR(tfm));
	alg = ERR_CAST(tfm);
	goto out_unlock;
	}

	err = -EINVAL;
	if (WARN_ON_ONCE(alg->digest_size != crypto_shash_digestsize(tfm)))
	goto err_free_tfm;
	if (WARN_ON_ONCE(alg->block_size != crypto_shash_blocksize(tfm)))
	goto err_free_tfm;

	pr_info("%s using implementation \"%s\"\n",
	alg->name, crypto_shash_driver_name(tfm));

	/* pairs with smp_load_acquire() above */
	smp_store_release(&alg->tfm, tfm);
	goto out_unlock;

	err_free_tfm:
	crypto_free_shash(tfm);
	alg = ERR_PTR(err);
	out_unlock:
	mutex_unlock(&fsverity_hash_alg_init_mutex);
	return alg;
	}

	/**
	* fsverity_prepare_hash_state() - precompute the initial hash state
	* @alg: hash algorithm
	* @salt: a salt which is to be prepended to all data to be hashed
	* @salt_size: salt size in bytes, possibly 0
	*
	* Return: NULL if the salt is empty, otherwise the kmalloc()'ed precomputed
	* initial hash state on success or an ERR_PTR() on failure.
	*/
	const u8 fsverity_prepare_hash_state(const struct fsverity_hash_alg alg,
	const u8 *salt, size_t salt_size)
	{
	u8 *hashstate = NULL;
	SHASH_DESC_ON_STACK(desc, alg->tfm);
	u8 *padded_salt = NULL;
	size_t padded_salt_size;
	int err;

	desc->tfm = alg->tfm;

	if (salt_size == 0)
	return NULL;

	hashstate = kmalloc(crypto_shash_statesize(alg->tfm), GFP_KERNEL);
	if (!hashstate)
	return ERR_PTR(-ENOMEM);

	/*
	* Zero-pad the salt to the next multiple of the input size of the hash
	* algorithm's compression function, e.g. 64 bytes for SHA-256 or 128
	* bytes for SHA-512. This ensures that the hash algorithm won't have
	* any bytes buffered internally after processing the salt, thus making
	* salted hashing just as fast as unsalted hashing.
	*/
	padded_salt_size = round_up(salt_size, alg->block_size);
	padded_salt = kzalloc(padded_salt_size, GFP_KERNEL);
	if (!padded_salt) {
	err = -ENOMEM;
	goto err_free;
	}
	memcpy(padded_salt, salt, salt_size);
	err = crypto_shash_init(desc);
	if (err)
	goto err_free;

	err = crypto_shash_update(desc, padded_salt, padded_salt_size);
	if (err)
	goto err_free;

	err = crypto_shash_export(desc, hashstate);
	if (err)
	goto err_free;
	out:
	kfree(padded_salt);
	return hashstate;

	err_free:
	kfree(hashstate);
	hashstate = ERR_PTR(err);
	goto out;
	}

	/**
	* fsverity_hash_block() - hash a single data or hash block
	* @params: the Merkle tree's parameters
	* @inode: inode for which the hashing is being done
	* @data: virtual address of a buffer containing the block to hash
	* @out: output digest, size 'params->digest_size' bytes
	*
	* Hash a single data or hash block. The hash is salted if a salt is specified
	* in the Merkle tree parameters.
	*
	* Return: 0 on success, -errno on failure
	*/
	int fsverity_hash_block(const struct merkle_tree_params *params,
	const struct inode inode, const void data, u8 *out)
	{
	SHASH_DESC_ON_STACK(desc, params->hash_alg->tfm);
	int err;

	desc->tfm = params->hash_alg->tfm;

	if (params->hashstate) {
	err = crypto_shash_import(desc, params->hashstate);
	if (err) {
	fsverity_err(inode,
	"Error %d importing hash state", err);
	return err;
	}
	err = crypto_shash_finup(desc, data, params->block_size, out);
	} else {
	err = crypto_shash_digest(desc, data, params->block_size, out);
	}
	if (err)
	fsverity_err(inode, "Error %d computing block hash", err);
	return err;
	}

	/**
	* fsverity_hash_buffer() - hash some data
	* @alg: the hash algorithm to use
	* @data: the data to hash
	* @size: size of data to hash, in bytes
	* @out: output digest, size 'alg->digest_size' bytes
	*
	* Return: 0 on success, -errno on failure
	*/
	int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
	const void data, size_t size, u8 out)
	{
	return crypto_shash_tfm_digest(alg->tfm, data, size, out);
	}

	void __init fsverity_check_hash_algs(void)
	{
	size_t i;

	/*
	* Sanity check the hash algorithms (could be a build-time check, but
	* they're in an array)
	*/
	for (i = 0; i < ARRAY_SIZE(fsverity_hash_algs); i++) {
	const struct fsverity_hash_alg *alg = &fsverity_hash_algs[i];

	if (!alg->name)
	continue;

	BUG_ON(alg->digest_size > FS_VERITY_MAX_DIGEST_SIZE);

	/*
	* For efficiency, the implementation currently assumes the
	* digest and block sizes are powers of 2. This limitation can
	* be lifted if the code is updated to handle other values.
	*/
	BUG_ON(!is_power_of_2(alg->digest_size));
	BUG_ON(!is_power_of_2(alg->block_size));

	/* Verify that there is a valid mapping to HASH_ALGO_. /
	BUG_ON(alg->algo_id == 0);
	BUG_ON(alg->digest_size != hash_digest_size[alg->algo_id]);
	}
	}