Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 251 insertions, 0 deletions

diff --git a/fs/verity/hash_algs.c b/fs/verity/hash_algs.c
new file mode 100644
index 0000000000..6b08b1d9a7
--- /dev/null
+++ b/fs/verity/hash_algs.c
@@ -0,0 +1,251 @@
+// 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;
+
+		/*
+		 * 0 must never be allocated as an FS_VERITY_HASH_ALG_* value,
+		 * as it is reserved for users that use 0 to mean unspecified or
+		 * a default value.  fs/verity/ itself doesn't care and doesn't
+		 * have a default algorithm, but some users make use of this.
+		 */
+		BUG_ON(i == 0);
+
+		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]);
+	}
+}