From a4bbf53d88c728da9ff6c316b1e4ded63a8f3940 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 28 Nov 2022 20:51:39 -0800 Subject: [PATCH] fsverity: simplify fsverity_get_digest() 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 Reviewed-by: Mimi Zohar Link: https://lore.kernel.org/r/20221129045139.69803-1-ebiggers@kernel.org --- fs/verity/fsverity_private.h | 5 +++++ fs/verity/hash_algs.c | 6 ++++++ fs/verity/measure.c | 19 ++----------------- 3 files changed, 13 insertions(+), 17 deletions(-) diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h index dbe1ce5b450a..c7fcb855e068 100644 --- a/fs/verity/fsverity_private.h +++ b/fs/verity/fsverity_private.h @@ -32,6 +32,11 @@ struct fsverity_hash_alg { 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 */ 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 */ diff --git a/fs/verity/hash_algs.c b/fs/verity/hash_algs.c index 71d0fccb6d4c..6f8170cf4ae7 100644 --- a/fs/verity/hash_algs.c +++ b/fs/verity/hash_algs.c @@ -16,11 +16,13 @@ struct fsverity_hash_alg fsverity_hash_algs[] = { .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, }, }; @@ -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->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]); } } diff --git a/fs/verity/measure.c b/fs/verity/measure.c index e99c00350c28..5c79ea1b2468 100644 --- a/fs/verity/measure.c +++ b/fs/verity/measure.c @@ -65,8 +65,7 @@ EXPORT_SYMBOL_GPL(fsverity_ioctl_measure); * @alg: (out) pointer to the hash algorithm enumeration * * Return the file hash algorithm and digest of an fsverity protected file. - * Assumption: before calling fsverity_get_digest(), the file must have been - * opened. + * Assumption: before calling this, the file must have been opened. * * 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_hash_alg *hash_alg; - int i; vi = fsverity_get_info(inode); if (!vi) return -ENODATA; /* not a verity file */ 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); - - pr_debug("file digest %s:%*phN\n", hash_algo_name[*alg], - hash_digest_size[*alg], digest); - + *alg = hash_alg->algo_id; return 0; }