[Dovecot] Disk Encryption

[Xin Li]

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On 3/25/13 6:24 AM, Simon Brereton wrote:
> On 25 March 2013 12:30, Robert Schetterer <rs at sys4.de> wrote:
>> Am 25.03.2013 11:03, schrieb Simon Brereton:
>>> Hi
>>> 
>>> As I understand it email headers need to be unencrypted
>>> (otherwise DKIM doesn't work).  From the MUA to either Postfix,
>>> or Dovecot the connection is (or can/should be) secured with
>>> TLS/SSL.
>>> 
>>> What I would like to know is if it is possible to encrypt the 
>>> mailstore?  Postfix is using Dovecot for delivery so it's only
>>> Dovecot that would need to encrypt/decrypt the mailstore.
>>> 
>>> Is this possible?  Is there a terrible reason to do it even if
>>> it is possible?
>>> 
>>> I realise that from MTA to MTA there's no guarantee of
>>> encryption (and in fact it's very unlikely unless keys have
>>> been exchanged), but my primary goal is supplement the physical
>>> security of the mail store of mails we already have or have
>>> sent.
>>> 
>>> Mostly just idle curiosity as to what has been done, or what
>>> could be done.  What is worth doing is a separate thread
>>> entirely.
>>> 
>>> Thanks.
>>> 
>>> Simon
>>> 
>> 
>> my meaning
>> 
>> crypted mailstore makes sense in a mail archive, in germany you
>> have to have a mail archive for some kind of company emails all
>> these solutions have some crypted mailstore , and some more
>> features for data security, but thats a big theme, to big for
>> here
>> 
>> crypt storage isnt "the saveness" per default, someone hacking
>> the system and get root may hack your crypt storage too etc, also
>> to big theme for here
> 
> Robert, indeed, this is sort of my point.  If we encrypt laptop 
> harddrives to prevent unauthorised access, that doesn't prevent
> the possiblity of someone who already has admin access to the
> device from decrypting/viewing/moving files.  What it does do is
> prevent unauthorised access to the data if there is no admin
> access.
> 
> Currently my mail store isn't encrypted and I would like to know if
> it is possible to do that, and if so, maybe get some pointers.

Let's say you operate a mail server which uses a RAID array (or ZFS
pool) as backend storage and one day one disks goes bad and needs to
be replaced.  You don't want information being leak from that bad disk
when returning to vendor for replacement.

There are a lot of solutions to this issue.  One possible way is to
use FreeBSD's full disk encryption, geli(4), to encrypt all hard
drives and have the email server hold the key on its boot partition,
but don't protect it with a password so that the mail server can boot
without any human intervention.

Encrypting individual user's mail store make little sense as one can
still get your decryption key if they got root privilege, usually by
tracing the login process or just replace it with something that can
do the login but also save login credentials.  In short, if root have
been compromised, it's game over already.

Cheers,

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