On Sat, Dec 08, 2018 at 12:37:20PM +0530, Chandan Rajendra wrote: > On Wednesday, December 5, 2018 5:13:21 AM IST Eric Biggers wrote: > > Hi Chandan, > > > > On Tue, Dec 04, 2018 at 03:26:46PM +0530, Chandan Rajendra wrote: > > > In order to have a common code base for fscrypt "post read" processing > > > for all filesystems which support encryption, this commit removes > > > filesystem specific build config option (e.g. CONFIG_EXT4_FS_ENCRYPTION) > > > and replaces it with a build option (i.e. CONFIG_FS_ENCRYPTION) whose > > > value affects all the filesystems making use of fscrypt. > > > > > > Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx> > > [...] > > > -config F2FS_FS_ENCRYPTION > > > - bool "F2FS Encryption" > > > - depends on F2FS_FS > > > - depends on F2FS_FS_XATTR > > > - select FS_ENCRYPTION > > > - help > > > - Enable encryption of f2fs files and directories. This > > > - feature is similar to ecryptfs, but it is more memory > > > - efficient since it avoids caching the encrypted and > > > - decrypted pages in the page cache. > > > - > > [...] > > > -config UBIFS_FS_ENCRYPTION > > > - bool "UBIFS Encryption" > > > - depends on UBIFS_FS && UBIFS_FS_XATTR && BLOCK > > > - select FS_ENCRYPTION > > > - default n > > > - help > > > - Enable encryption of UBIFS files and directories. This > > > - feature is similar to ecryptfs, but it is more memory > > > - efficient since it avoids caching the encrypted and > > > - decrypted pages in the page cache. > > > > Will it cause problems that now f2fs encryption can be "enabled" without > > F2FS_FS_XATTR, and ubifs encryption without UBIFS_FS_XATTR && BLOCK? > > > > Otherwise I think this patch looks fine. I'm a bit concerned about the bloat > > from making FS_ENCRYPTION non-modular, but given that it will make sharing I/O > > code much easier, it's probably worthwhile. > > > > It would help to strip down the dependencies of FS_ENCRYPTION to just the stuff > > needed for just AES-256-XTS and AES-256-CTS. I already sent out a patch a > > couple months ago (https://patchwork.kernel.org/patch/10589319/) to remove > > CONFIG_CTR which isn't used at all; I'll remind Ted to apply that. But we could > > also drop CONFIG_SHA256, which is only needed for AES-128-CBC contents > > encryption. If we do that, it should be a separate patch, though. > > Hi Eric, > > fscrypt_valid_enc_modes() allows FS_ENCRYPTION_MODE_AES_128_CBC to be used for > encryption of file's contents. This is consistent with what you had mentioned > above. > > static inline bool fscrypt_valid_enc_modes(u32 contents_mode, > u32 filenames_mode) > { > if (contents_mode == FS_ENCRYPTION_MODE_AES_128_CBC && > filenames_mode == FS_ENCRYPTION_MODE_AES_128_CTS) > return true; > > if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS && > filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS) > return true; > > return false; > } > > Hence FS_ENCRYPTION does need to have AES-128-CBC and by extension SHA256 code > compiled in right? > No those algorithms don't have to be compiled in if userspace doesn't use the (FS_ENCRYPTION_MODE_AES_128_CBC, FS_ENCRYPTION_MODE_AES_128_CTS) pair, because the algorithms are allocated dynamically on-demand through the crypto API. - Eric
