On 08/23/2017 01:36 AM, Eric Biggers wrote:
On Tue, Aug 22, 2017 at 11:35:20PM +0800, Anand Jain wrote:
I think AE is the only good solution for this, File-name encryption at
this stage won't solve any kind of Evil Maid attack, (as it was quoted
somewhere else in ML).
Further, below, is define but not used.
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#define FS_AES_256_GCM_KEY_SIZE 32
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Yes, authenticated encryption with AES-256-GCM was in an older version of the
ext4 encryption design document. But unfortunately it was never really thought
through. The primary problem, even ignoring rollback protection, is that there
is nowhere to store the per-block metadata (GCM authentication tag and IV) *and*
have it updated atomicly with the block contents. Recently, dm-integrity solves
this at the block device layer, but it uses data journaling which is very
inefficient. This maybe could be implemented more efficiently on a COW
filesystem like BTRFS. But even after that, another problem is that
authenticated encryption of file contents only would not stop an attacker from
swapping around blocks, files, directories, or creating links, etc.
Some of the problems to be solved in this area are quite
interesting and challenging and IMO BTRFS fits nicely. Per extent AE
for BTRFS is drafted, it needs scrutiny and constructive feedback.
Thanks, Anand
Eric
Where is the code? Is there a design document, and it is it readable by people
not as familiar with btrfs? Is the API compatible with ext4, f2fs, and ubifs?
Eric
(sorry for the delay in replay due to my vacation).
Eric, No code yet, proposed encryption method is seeking review. Link
sent to you.
Thanks, Anand
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