From 947191ac8caba85e25e0e036b0f097fee9e817f3 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Fri, 15 Jan 2021 10:18:18 -0800 Subject: fs-verity: support reading descriptor with ioctl Add support for FS_VERITY_METADATA_TYPE_DESCRIPTOR to FS_IOC_READ_VERITY_METADATA. This allows a userspace server program to retrieve the fs-verity descriptor of a file for serving to a client which implements fs-verity compatible verification. See the patch which introduced FS_IOC_READ_VERITY_METADATA for more details. "fs-verity descriptor" here means only the part that userspace cares about because it is hashed to produce the file digest. It doesn't include the signature which ext4 and f2fs append to the fsverity_descriptor struct when storing it on-disk, since that way of storing the signature is an implementation detail. The next patch adds a separate metadata_type value for retrieving the signature separately. This has been tested using a new xfstest which calls this ioctl via a new subcommand for the 'fsverity' program from fsverity-utils. Link: https://lore.kernel.org/r/20210115181819.34732-6-ebiggers@kernel.org Reviewed-by: Victor Hsieh Reviewed-by: Jaegeuk Kim Reviewed-by: Chao Yu Signed-off-by: Eric Biggers --- Documentation/filesystems/fsverity.rst | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'Documentation/filesystems/fsverity.rst') diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index 50b47a6d9ea1..6dc5772037ef 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -235,6 +235,7 @@ need this ioctl. This ioctl takes in a pointer to the following structure:: #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 + #define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 struct fsverity_read_metadata_arg { __u64 metadata_type; @@ -252,6 +253,9 @@ This ioctl takes in a pointer to the following structure:: the same order that their hashes are themselves hashed. See `Merkle tree`_ for more information. +- ``FS_VERITY_METADATA_TYPE_DESCRIPTOR`` reads the fs-verity + descriptor. See `fs-verity descriptor`_. + The semantics are similar to those of ``pread()``. ``offset`` specifies the offset in bytes into the metadata item to read from, and ``length`` specifies the maximum number of bytes to read from the -- cgit v1.2.3