From c93d8f88580921c84d2213161ef3c22560511b84 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 22 Jul 2019 09:26:24 -0700 Subject: ext4: add basic fs-verity support Add most of fs-verity support to ext4. fs-verity is a filesystem feature that enables transparent integrity protection and authentication of read-only files. It uses a dm-verity like mechanism at the file level: a Merkle tree is used to verify any block in the file in log(filesize) time. It is implemented mainly by helper functions in fs/verity/. See Documentation/filesystems/fsverity.rst for the full documentation. This commit adds all of ext4 fs-verity support except for the actual data verification, including: - Adding a filesystem feature flag and an inode flag for fs-verity. - Implementing the fsverity_operations to support enabling verity on an inode and reading/writing the verity metadata. - Updating ->write_begin(), ->write_end(), and ->writepages() to support writing verity metadata pages. - Calling the fs-verity hooks for ->open(), ->setattr(), and ->ioctl(). ext4 stores the verity metadata (Merkle tree and fsverity_descriptor) past the end of the file, starting at the first 64K boundary beyond i_size. This approach works because (a) verity files are readonly, and (b) pages fully beyond i_size aren't visible to userspace but can be read/written internally by ext4 with only some relatively small changes to ext4. This approach avoids having to depend on the EA_INODE feature and on rearchitecturing ext4's xattr support to support paging multi-gigabyte xattrs into memory, and to support encrypting xattrs. Note that the verity metadata *must* be encrypted when the file is, since it contains hashes of the plaintext data. This patch incorporates work by Theodore Ts'o and Chandan Rajendra. Reviewed-by: Theodore Ts'o Signed-off-by: Eric Biggers --- fs/ext4/ioctl.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'fs/ext4/ioctl.c') diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index 442f7ef873fc..ce811df71690 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -1171,6 +1171,17 @@ out: } case EXT4_IOC_SHUTDOWN: return ext4_shutdown(sb, arg); + + case FS_IOC_ENABLE_VERITY: + if (!ext4_has_feature_verity(sb)) + return -EOPNOTSUPP; + return fsverity_ioctl_enable(filp, (const void __user *)arg); + + case FS_IOC_MEASURE_VERITY: + if (!ext4_has_feature_verity(sb)) + return -EOPNOTSUPP; + return fsverity_ioctl_measure(filp, (void __user *)arg); + default: return -ENOTTY; } @@ -1233,6 +1244,8 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case EXT4_IOC_GET_ENCRYPTION_POLICY: case EXT4_IOC_SHUTDOWN: case FS_IOC_GETFSMAP: + case FS_IOC_ENABLE_VERITY: + case FS_IOC_MEASURE_VERITY: break; default: return -ENOIOCTLCMD; -- cgit v1.2.3