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When we allow indexed directories to use both encryption and casefolding, for the dirhash we can't just hash the ciphertext filenames that are stored on-disk (as is done currently) because the dirhash must be case insensitive, but the stored names are case-preserving. Nor can we hash the plaintext names with an unkeyed hash (or a hash keyed with a value stored on-disk like ext4's s_hash_seed), since that would leak information about the names that encryption is meant to protect. Instead, if we can accept a dirhash that's only computable when the fscrypt key is available, we can hash the plaintext names with a keyed hash using a secret key derived from the directory's fscrypt master key. We'll use SipHash-2-4 for this purpose. Prepare for this by deriving a SipHash key for each casefolded encrypted directory. Make sure to handle deriving the key not only when setting up the directory's fscrypt_info, but also in the case where the casefold flag is enabled after the fscrypt_info was already set up. (We could just always derive the key regardless of casefolding, but that would introduce unnecessary overhead for people not using casefolding.) Signed-off-by: Daniel Rosenberg <drosen@google.com> [EB: improved commit message, updated fscrypt.rst, squashed with change that avoids unnecessarily deriving the key, and many other cleanups] Link: https://lore.kernel.org/r/20200120223201.241390-3-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com> |
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| .. | ||
| caching | ||
| cifs | ||
| configfs | ||
| ext4 | ||
| nfs | ||
| 9p.txt | ||
| adfs.txt | ||
| affs.txt | ||
| afs.txt | ||
| api-summary.rst | ||
| autofs-mount-control.txt | ||
| autofs.rst | ||
| automount-support.txt | ||
| befs.txt | ||
| bfs.txt | ||
| btrfs.txt | ||
| ceph.txt | ||
| coda.txt | ||
| cramfs.txt | ||
| dax.txt | ||
| debugfs.txt | ||
| devpts.txt | ||
| directory-locking.rst | ||
| dlmfs.txt | ||
| dnotify.txt | ||
| ecryptfs.txt | ||
| efivarfs.txt | ||
| erofs.txt | ||
| ext2.txt | ||
| ext3.txt | ||
| f2fs.txt | ||
| fiemap.txt | ||
| files.txt | ||
| fscrypt.rst | ||
| fsverity.rst | ||
| fuse-io.txt | ||
| fuse.txt | ||
| gfs2-glocks.txt | ||
| gfs2-uevents.txt | ||
| gfs2.txt | ||
| hfs.txt | ||
| hfsplus.txt | ||
| hpfs.txt | ||
| index.rst | ||
| inotify.txt | ||
| isofs.txt | ||
| journalling.rst | ||
| locking.rst | ||
| locks.txt | ||
| mandatory-locking.txt | ||
| mount_api.txt | ||
| nilfs2.txt | ||
| ntfs.txt | ||
| ocfs2-online-filecheck.txt | ||
| ocfs2.txt | ||
| omfs.txt | ||
| orangefs.txt | ||
| overlayfs.rst | ||
| path-lookup.rst | ||
| path-lookup.txt | ||
| porting.rst | ||
| proc.txt | ||
| qnx6.txt | ||
| quota.txt | ||
| ramfs-rootfs-initramfs.txt | ||
| relay.txt | ||
| romfs.txt | ||
| seq_file.txt | ||
| sharedsubtree.txt | ||
| splice.rst | ||
| spufs.txt | ||
| squashfs.txt | ||
| sysfs-pci.txt | ||
| sysfs-tagging.txt | ||
| sysfs.txt | ||
| sysv-fs.txt | ||
| tmpfs.txt | ||
| ubifs-authentication.rst | ||
| ubifs.txt | ||
| udf.txt | ||
| vfat.txt | ||
| vfs.rst | ||
| virtiofs.rst | ||
| xfs-delayed-logging-design.txt | ||
| xfs-self-describing-metadata.txt | ||