On Wed, Oct 07, 2020 at 02:00:40PM -0700, Eric Biggers wrote: > On Mon, Oct 05, 2020 at 07:36:03AM +0000, Satya Tangirala wrote: > > This patch series adds support for metadata encryption to F2FS using > > blk-crypto. > > This patch series needs more explanation about what "metadata encryption" is, > why people will want to use it (as opposed to either not using it, or using > fscrypt + dm-crypt instead), and why this is the best implementation of it. > Sure, I'll add that in the next version > > Patch 2 introduces some functions to fscrypt that help filesystems perform > > metadata encryption. Any filesystem that wants to use metadata encryption > > can call fscrypt_setup_metadata_encryption() with the super_block of the > > filesystem, the encryption algorithm and the descriptor of the encryption > > key. The descriptor is looked up in the logon keyring of the current > > session with "fscrypt:" as the prefix of the descriptor. > > I notice this is missing the step I suggested to include the metadata encryption > key in the HKDF application-specific info string when deriving subkeys from the > fscrypt master keys. > > The same effect could also be achieved by adding an additional level to the key > hierarchy: each HKDF key would be derived from a fscrypt master key and the > metadata encryption key. > > We need one of those, to guarantee that the file contents encryption is at least > as strong as the "metadata encryption". > Yes - I didn't get around to that in the first version, but I'll add that too in the next version. I was going to go with the first approach before I saw your comment - is there one method you'd recommend going with over the other? > - Eric
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