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fsverity: simplify fsverity_get_digest()

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Instead of looking up the algorithm by name in hash_algo_name[] to get
its hash_algo ID, just store the hash_algo ID in the fsverity_hash_alg
struct.  Verify at boot time that every fsverity_hash_alg has a valid
hash_algo ID with matching digest size.

Remove an unnecessary memset() of the whole digest array to 0 before the
digest is copied into it.

Finally, remove the pr_debug statement.  There is already a pr_debug for
the fsverity digest when the file is opened.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Link: https://lore.kernel.org/r/20221129045139.69803-1-ebiggers@kernel.org
This commit is contained in:
Eric Biggers 2022-11-28 20:51:39 -08:00
parent 98dc08bae6
commit a4bbf53d88
3 changed files with 13 additions and 17 deletions
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5
fs/verity/fsverity_private.h
View File

@ -32,6 +32,11 @@ struct fsverity_hash_alg {
unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */
mempool_t req_pool; /* mempool with a preallocated hash request */ mempool_t req_pool; /* mempool with a preallocated hash request */
/*
* The HASH_ALGO_* constant for this algorithm. This is different from
* FS_VERITY_HASH_ALG_*, which uses a different numbering scheme.
*/
enum hash_algo algo_id;
}; };
/* Merkle tree parameters: hash algorithm, initial hash state, and topology */ /* Merkle tree parameters: hash algorithm, initial hash state, and topology */

6
fs/verity/hash_algs.c
View File

@ -16,11 +16,13 @@ struct fsverity_hash_alg fsverity_hash_algs[] = {
.name = "sha256", .name = "sha256",
.digest_size = SHA256_DIGEST_SIZE, .digest_size = SHA256_DIGEST_SIZE,
.block_size = SHA256_BLOCK_SIZE, .block_size = SHA256_BLOCK_SIZE,
.algo_id = HASH_ALGO_SHA256,
}, },
[FS_VERITY_HASH_ALG_SHA512] = { [FS_VERITY_HASH_ALG_SHA512] = {
.name = "sha512", .name = "sha512",
.digest_size = SHA512_DIGEST_SIZE, .digest_size = SHA512_DIGEST_SIZE,
.block_size = SHA512_BLOCK_SIZE, .block_size = SHA512_BLOCK_SIZE,
.algo_id = HASH_ALGO_SHA512,
}, },
}; };
@ -324,5 +326,9 @@ void __init fsverity_check_hash_algs(void)
*/ */
BUG_ON(!is_power_of_2(alg->digest_size)); BUG_ON(!is_power_of_2(alg->digest_size));
BUG_ON(!is_power_of_2(alg->block_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]);
} }
} }

19
fs/verity/measure.c
View File

@ -65,8 +65,7 @@ EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);
* @alg: (out) pointer to the hash algorithm enumeration * @alg: (out) pointer to the hash algorithm enumeration
* *
* Return the file hash algorithm and digest of an fsverity protected file. * Return the file hash algorithm and digest of an fsverity protected file.
* Assumption: before calling fsverity_get_digest(), the file must have been * Assumption: before calling this, the file must have been opened.
* opened.
* *
* Return: 0 on success, -errno on failure * Return: 0 on success, -errno on failure
*/ */
@ -76,27 +75,13 @@ int fsverity_get_digest(struct inode *inode,
{ {
const struct fsverity_info *vi; const struct fsverity_info *vi;
const struct fsverity_hash_alg *hash_alg; const struct fsverity_hash_alg *hash_alg;
int i;
vi = fsverity_get_info(inode); vi = fsverity_get_info(inode);
if (!vi) if (!vi)
return -ENODATA; /* not a verity file */ return -ENODATA; /* not a verity file */
hash_alg = vi->tree_params.hash_alg; hash_alg = vi->tree_params.hash_alg;
memset(digest, 0, FS_VERITY_MAX_DIGEST_SIZE);
/* convert the verity hash algorithm name to a hash_algo_name enum */
i = match_string(hash_algo_name, HASH_ALGO__LAST, hash_alg->name);
if (i < 0)
return -EINVAL;
*alg = i;
if (WARN_ON_ONCE(hash_alg->digest_size != hash_digest_size[*alg]))
return -EINVAL;
memcpy(digest, vi->file_digest, hash_alg->digest_size); memcpy(digest, vi->file_digest, hash_alg->digest_size);
*alg = hash_alg->algo_id;
pr_debug("file digest %s:%*phN\n", hash_algo_name[*alg],
hash_digest_size[*alg], digest);
return 0; return 0;
} }