Re: [PATCH] fscrypt: add a documentation file for filesystem-level encryption

From: Anand Jain <anand.jain@oracle.com>
To: Eric Biggers <ebiggers3@gmail.com>, "Theodore Y . Ts'o" <tytso@mit.edu>
Cc: linux-fscrypt@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	Jaegeuk Kim <jaegeuk@kernel.org>,
	Richard Weinberger <richard@nod.at>,
	Michael Halcrow <mhalcrow@google.com>,
	Eric Biggers <ebiggers@google.com>
Subject: Re: [PATCH] fscrypt: add a documentation file for filesystem-level encryption
Date: Tue, 22 Aug 2017 10:22:13 +0800	[thread overview]
Message-ID: <7a34337d-3214-0a8a-5521-7727364cceb4@oracle.com> (raw)
In-Reply-To: <20170821230821.GB8847@gmail.com>

>>> +fscrypt is not guaranteed to protect confidentiality or authenticity
>>> +if an attacker is able to manipulate the filesystem offline prior to
>>> +an authorized user later accessing the filesystem.
>>
>>   How does fscrypt / Android protect against Evil Maid attack. ?

> _However_, an "Evil Maid" attacker can probably still do other, perhaps much
> more effective attacks --- e.g.
::
>.  Or they could attack the actual
> file contents encryption which is not authenticated.  Or they could mess around
> with filesystem metadata on the userdata partition, which is neither encrypted
> nor authenticated.

   In specific, the scenario I had in mind was the above threat.

> I suppose that dm-integrity could be used to protect against some of those
> attacks, but of course it would not protect against hardware key loggers, etc.

   OK.

   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
-----

Thanks, Anand