Messages in this thread | | | Date | Wed, 7 Oct 2020 14:00:40 -0700 | From | Eric Biggers <> | Subject | Re: [PATCH 0/3] add support for metadata encryption to F2FS |
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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.
> 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".
- Eric
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