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. ----- #define FS_AES_256_GCM_KEY_SIZE 32 -----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, AnandEricWhere 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 -- To unsubscribe from this list: send the line "unsubscribe linux-fscrypt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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