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Ts'o" , Jaegeuk Kim , Eric Biggers , Chris Mason , Josef Bacik , David Sterba , linux-fscrypt@vger.kernel.org, linux-btrfs@vger.kernel.org, kernel-team@meta.com Cc: Sweet Tea Dorminy Subject: [PATCH v3 00/22] btrfs: add fscrypt integration Date: Thu, 20 Oct 2022 12:58:19 -0400 Message-Id: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org This is a changeset adding encryption to btrfs. Last October, Omar Sandoval sent out a design document for having fscrypt integration with btrfs [1]. In summary, it proposes btrfs storing its own encryption IVs on a per-file-extent basis. fscrypt usually encrypts files using an IV derived from per-inode information; this would prevent snapshotting or reflinking or data relocation for btrfs. We have refined this into a fscrypt extent context object, opaque to the filesystem, which fscrypt uses to generate an IV associated with each block in an extent. Thus, all the inodes sharing a particular key and file extent may decrypt the extent. This series implements this integration for the simple case, non-compressed data extents, and for verity items. Followup changes will allow encryption of compressed extents, inline extents, and will add tests around subvolume encryption. This series should provide encryption for the simplest cases, but this series should not be used in production, as there are likely bugs. This set hopefully reflects all of the feedback given on v2, with two exceptions: per-extent keys, and fewer fscrypt extent context members of btrfs structures. On v2, Eric Biggers suggested in passing we reconsider having per-extent keys, instead of continuing to rely on per-inode keys. Previously, we'd considered this too memory expensive, as our reference system averaged 4 extents per inode. But if we gave each extent its own key structure, non-dir inodes would no longer need its own keys, making up for the increased memory; and we can free and recreate keys as needed to fit within a smaller memory space, it just results in more churn. Additionally, there's a certain elegance potentially resulting: we could take any number of levels of snapshot, giving each snapshot a new key, and the last snapshot could be readable if you loaded all of the N keys; this is more elegant than just supporting mixed single-key and unencrypted extents. However, after giving this a lengthy try, I found the result too ugly. There seemed just too many ifs in the fscrypt hooks necessary to refer to the parent dir in many places if extent-based, and it seemed too expensive and redundant to just have full fscrypt contexts for both all inodes and all extents. So this version still has only a fscrypt_iv in each fscrypt_extent_context. I would love suggestions on how to elegantly implement per-extent keys; the elegance of their theory is delightful. Secondly, on v2 David Sterba disliked the abundant new fscrypt_context members of multiple structures and hoped they could be smaller or less frequent, and perhaps compiled out if CONFIG_FS_ENCRYPTION is disabled. I didn't split the extent contexts out into separately allocated and freed structures, and I preserved a 1-byte member even when encryption is disabled in order to not ifdef every check for encryption. However, if this turns out too inelegant, I'm happy to amend things further, or separate the objects from extent maps altogether. My impression is that most fscrypt functions have a no-encryption version which returns an error, so their calls don't need to be gated on encryption. I apologize if I missed any past feedback. [1] https://lore.kernel.org/linux-btrfs/YXGyq+buM79A1S0L@relinquished.localdomain/ Changelog: v3: - fscrypt: changed to generate extent contexts the same way as IVs are generated for inode-based encryption, allowing use of any existing policy and making the difference in encryption more minimal. - Changed to use qstr's, then fscrypt_strs, then fscrypt_names only where absolutely necessary, rather than fscrypt_names everywhere. - Reordered changes to put partially-encrypted directories, and no-key name handling, in their own sections at the end of the patchset. - Expanded on descriptions of how no-key name handling works. - Added encryption of verity items (but see notes in change about outstanding questions there) - Stylistic fixes - Renamed flags from FSCRYPT to ENCRYPT in multiple instances. - Made the incompat encrypt superblock flag be set the first time a directory is set to be encrypted, so there isn't a need for a mkfs option. - Hopefully addressed all other minor feedback points. v2: - Amended the fscrypt side to generically add extent contexts, hopefully as per Eric Biggers' past comments. IVs are now entirely abstracted within an extent context, and there is no longer a new encryption policy, as DIRECT_KEY sufficiently encapsulates the needs of extent-based encryption. Documented its usage in btrfs briefly in the documentation. - Adjusted the btrfs side to deal in opaque extent contexts. Improved optimization to skip storing inode contexts if they are the same as the inode's root item's inode context. - Combined 'add fscrypt operation table to superblock' into 'start using fscrypt hooks'. - https://lore.kernel.org/linux-btrfs/cover.1662420176.git.sweettea-kernel@dorminy.me - progs: https://lore.kernel.org/linux-btrfs/cover.1662417859.git.sweettea-kernel@dorminy.me - tests: https://lore.kernel.org/linux-btrfs/cover.1662417905.git.sweettea-kernel@dorminy.me v1: - Recombined the fscrypt changes back into this patchset. - Fixed several races and incorrectly ordered operations. - Improved IV retrieval to correctly distinguish between filename/symlink encryption and encryption of block 0 of a file. - https://lore.kernel.org/linux-btrfs/cover.1660744500.git.sweettea-kernel@dorminy.me - progs: https://lore.kernel.org/linux-btrfs/cover.1660729916.git.sweettea-kernel@dorminy.me - tests: https://lore.kernel.org/linux-btrfs/cover.1660729861.git.sweettea-kernel@dorminy.me RFC v2: - Fixed all warnings and known incorrectnesses. - Split fscrypt changes into their own patchset: https://lore.kernel.org/linux-fscrypt/cover.1658623235.git.sweettea-kernel@dorminy.me - Combined and reordered changes so that enabling fscrypt is the last change. - Removed unnecessary factoring. - Split a cleanup change off. - https://lore.kernel.org/linux-btrfs/cover.1658623319.git.sweettea-kernel@dorminy.me RFC v1: - https://lore.kernel.org/linux-btrfs/cover.1657707686.git.sweettea-kernel@dorminy.me Omar Sandoval (12): fscrypt: expose fscrypt_nokey_name fscrypt: add fscrypt_have_same_policy() to check inode compatibility btrfs: store directory encryption state btrfs: disable various operations on encrypted inodes btrfs: start using fscrypt hooks btrfs: add fscrypt_context items btrfs: translate btrfs encryption flags and encrypted inode flag btrfs: encrypt normal file extent data if appropriate btrfs: Add new FEATURE_INCOMPAT_ENCRYPT feature flag. btrfs: implement fscrypt ioctls btrfs: permit searching for nokey names for removal fscrypt: add flag allowing partially-encrypted directories Sweet Tea Dorminy (10): fscrypt: allow fscrypt_generate_iv() to distinguish filenames fscrypt: add extent-based encryption fscrypt: document btrfs' fscrypt quirks. btrfs: use struct qstr instead of name and namelen btrfs: setup qstrings from dentrys using fscrypt helper btrfs: use struct fscrypt_str instead of struct qstr btrfs: store a fscrypt extent context per normal file extent btrfs: use correct name hash for nokey names btrfs: adapt lookup for partially encrypted directories btrfs: encrypt verity items Documentation/filesystems/fscrypt.rst | 62 ++- fs/btrfs/Makefile | 1 + fs/btrfs/btrfs_inode.h | 3 + fs/btrfs/ctree.h | 96 ++++- fs/btrfs/delayed-inode.c | 36 +- fs/btrfs/delayed-inode.h | 6 +- fs/btrfs/dir-item.c | 193 +++++++-- fs/btrfs/extent_io.c | 94 ++++- fs/btrfs/extent_io.h | 3 + fs/btrfs/extent_map.c | 7 + fs/btrfs/extent_map.h | 4 + fs/btrfs/file-item.c | 25 +- fs/btrfs/file.c | 11 +- fs/btrfs/fscrypt.c | 273 +++++++++++++ fs/btrfs/fscrypt.h | 63 +++ fs/btrfs/inode-item.c | 73 ++-- fs/btrfs/inode-item.h | 20 +- fs/btrfs/inode.c | 559 +++++++++++++++++++------- fs/btrfs/ioctl.c | 55 ++- fs/btrfs/ordered-data.c | 11 +- fs/btrfs/ordered-data.h | 4 +- fs/btrfs/print-tree.c | 4 +- fs/btrfs/reflink.c | 8 + fs/btrfs/root-tree.c | 21 +- fs/btrfs/send.c | 13 +- fs/btrfs/super.c | 10 +- fs/btrfs/transaction.c | 40 +- fs/btrfs/tree-checker.c | 51 ++- fs/btrfs/tree-log.c | 304 +++++++------- fs/btrfs/tree-log.h | 4 +- fs/btrfs/verity.c | 112 +++++- fs/crypto/crypto.c | 29 +- fs/crypto/fname.c | 60 +-- fs/crypto/fscrypt_private.h | 25 +- fs/crypto/inline_crypt.c | 28 +- fs/crypto/policy.c | 105 +++++ include/linux/fscrypt.h | 93 +++++ include/uapi/linux/btrfs.h | 1 + include/uapi/linux/btrfs_tree.h | 28 ++ 39 files changed, 1978 insertions(+), 557 deletions(-) create mode 100644 fs/btrfs/fscrypt.c create mode 100644 fs/btrfs/fscrypt.h -- 2.35.1