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Date: Mon, 28 Aug 2017 20:18:55 +0800 From: Anand Jain <anand.jain@...cle.com> To: Eric Biggers <ebiggers3@...il.com> Cc: "Theodore Y . Ts'o" <tytso@....edu>, linux-fscrypt@...r.kernel.org, linux-doc@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org, Jaegeuk Kim <jaegeuk@...nel.org>, Richard Weinberger <richard@....at>, Michael Halcrow <mhalcrow@...gle.com>, Eric Biggers <ebiggers@...gle.com> Subject: Re: [PATCH] fscrypt: add a documentation file for filesystem-level encryption 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, 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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