[PATCH 0/8] Support for Casefolding and Encryption

Daniel Rosenberg
2019-12-03T05:11:20Z

Ext4 and F2FS currently both support casefolding and encryption, but not at the
same time. These patches aim to rectify that.

Since directory names are stored case preserved, we cannot just take the hash
of the ciphertext. Instead we use the siphash of the casefolded name. With this
we no longer have a direct path from an encrypted name to the hash without the
key. To deal with this, fscrypt now always includes the hash in the name it
presents when the key is not present. There is a pre-existing bug where you can
change parts of the hash and still match the name so long as the disruption to
the hash does not happen to affect lookup on that filesystem. I'm not sure how
to fix that without making ext4 lookups slower in the more common case.

I moved the identical dcache operations for ext4 and f2fs into the VFS, as any
filesystem that uses casefolding will need the same code. This will also allow
further optimizations to that path, although my current changes don't take
advantage of that yet.

For Ext4, this also means that we need to store the hash on disk. We only do so
for encrypted and casefolded directories to avoid on disk format changes.
Previously encryption and casefolding could not live on the same filesystem,
and we're relaxing that requirement. F2fs is a bit more straightforward since
it already stores hashes on disk.

I've updated the related tools with just enough to enable the feature. I still
need to adjust their respective fsck's, although without access to the keys,
they won't be able to verify the hashes of casefolded and encrypted names.

Daniel Rosenberg (8):
fscrypt: Add siphash and hash key for policy v2
fscrypt: Don't allow v1 policies with casefolding
fscrypt: Change format of no-key token
vfs: Fold casefolding into vfs
f2fs: Handle casefolding with Encryption
ext4: Use struct super_blocks' casefold data
ext4: Hande casefolding with encryption
ext4: Optimize match for casefolded encrypted dirs

Documentation/filesystems/ext4/directory.rst | 27 ++
fs/crypto/Kconfig | 1 +
fs/crypto/fname.c | 204 +++++++++---
fs/crypto/fscrypt_private.h | 9 +
fs/crypto/keysetup.c | 29 +-
fs/crypto/policy.c | 26 +-
fs/dcache.c | 35 ++
fs/ext4/dir.c | 72 +----
fs/ext4/ext4.h | 87 +++--
fs/ext4/hash.c | 26 +-
fs/ext4/ialloc.c | 5 +-
fs/ext4/inline.c | 41 +--
fs/ext4/namei.c | 318 ++++++++++++-------
fs/ext4/super.c | 21 +-
fs/f2fs/dir.c | 115 +++----
fs/f2fs/f2fs.h | 14 +-
fs/f2fs/hash.c | 25 +-
fs/f2fs/inline.c | 9 +-
fs/f2fs/super.c | 17 +-
fs/f2fs/sysfs.c | 8 +-
fs/inode.c | 8 +
fs/namei.c | 43 ++-
include/linux/fs.h | 12 +
include/linux/fscrypt.h | 107 +++----
24 files changed, 797 insertions(+), 462 deletions(-)

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2.24.0.393.g34dc348eaf-goog