linux-ext4 - Re: [PATCH] fscrypt: add a documentation file for filesystem-level encryption

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Message-ID: <7a34337d-3214-0a8a-5521-7727364cceb4@oracle.com>
Date:   Tue, 22 Aug 2017 10:22:13 +0800
From:   Anand Jain <anand.jain@...cle.com>
To:     Eric Biggers <ebiggers3@...il.com>,
        "Theodore Y . Ts'o" <tytso@....edu>
Cc:     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




>>> +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