Messages in this thread | | | Date | Mon, 28 Mar 2022 11:45:24 +0800 | Subject | Re: [PATCH v7 1/5] fs-verity: define a function to return the integrity protected file digest | From | "Guozihua (Scott)" <> |
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On 2022/3/26 6:38, Mimi Zohar wrote: > Define a function named fsverity_get_digest() to return the verity file > digest and the associated hash algorithm (enum hash_algo). > > This assumes that before calling fsverity_get_digest() the file must have > been opened, which is even true for the IMA measure/appraise on file > open policy rule use case (func=FILE_CHECK). do_open() calls vfs_open() > immediately prior to ima_file_check(). > > Acked-by: Eric Biggers <ebiggers@google.com> > Signed-off-by: Mimi Zohar <zohar@linux.ibm.com> > --- > fs/verity/Kconfig | 1 + > fs/verity/fsverity_private.h | 7 ------ > fs/verity/measure.c | 43 ++++++++++++++++++++++++++++++++++++ > include/linux/fsverity.h | 18 +++++++++++++++ > 4 files changed, 62 insertions(+), 7 deletions(-) > > diff --git a/fs/verity/Kconfig b/fs/verity/Kconfig > index 24d1b54de807..54598cd80145 100644 > --- a/fs/verity/Kconfig > +++ b/fs/verity/Kconfig > @@ -3,6 +3,7 @@ > config FS_VERITY > bool "FS Verity (read-only file-based authenticity protection)" > select CRYPTO > + select CRYPTO_HASH_INFO > # SHA-256 is implied as it's intended to be the default hash algorithm. > # To avoid bloat, other wanted algorithms must be selected explicitly. > # Note that CRYPTO_SHA256 denotes the generic C implementation, but > diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h > index a7920434bae5..c6fb62e0ef1a 100644 > --- a/fs/verity/fsverity_private.h > +++ b/fs/verity/fsverity_private.h > @@ -14,7 +14,6 @@ > > #define pr_fmt(fmt) "fs-verity: " fmt > > -#include <crypto/sha2.h> > #include <linux/fsverity.h> > #include <linux/mempool.h> > > @@ -26,12 +25,6 @@ struct ahash_request; > */ > #define FS_VERITY_MAX_LEVELS 8 > > -/* > - * Largest digest size among all hash algorithms supported by fs-verity. > - * Currently assumed to be <= size of fsverity_descriptor::root_hash. > - */ > -#define FS_VERITY_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE > - > /* A hash algorithm supported by fs-verity */ > struct fsverity_hash_alg { > struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ > diff --git a/fs/verity/measure.c b/fs/verity/measure.c > index f0d7b30c62db..e99c00350c28 100644 > --- a/fs/verity/measure.c > +++ b/fs/verity/measure.c > @@ -57,3 +57,46 @@ int fsverity_ioctl_measure(struct file *filp, void __user *_uarg) > return 0; > } > EXPORT_SYMBOL_GPL(fsverity_ioctl_measure); > + > +/** > + * fsverity_get_digest() - get a verity file's digest > + * @inode: inode to get digest of > + * @digest: (out) pointer to the digest > + * @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. > + * > + * Return: 0 on success, -errno on failure > + */ > +int fsverity_get_digest(struct inode *inode, > + u8 digest[FS_VERITY_MAX_DIGEST_SIZE], > + enum hash_algo *alg) > +{ > + 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);
Hi Mimi,
I would suggest moving this memset downward right before the memcpy.
> + > + /* 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); > + > + return 0; > +} -- Best GUO Zihua
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