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From: Christian Baer <christian.baer@informatik.uni-dortmund.de>
Date: Wed, 8 Feb 2006 22:51:09 +0100 (CET)
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Subject: Re: -p with GELI
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On Wed, 8 Feb 2006 21:18:53 +0100 Pawel Jakub Dawidek wrote:

> The '-p' option is gbde(8) is actually only for debug purposes, as other
> users can see it in ps(1) output (if not configured otherwise) and the
> passphrase will be logged via audit mechanism which is currenty merged
> to the tree.

Oops! Doesn't sound to productive if security is an issue. :-)

> What you want to use is '-k' option.
> If you really know what you're doing you can do something like this:

Hmm, I thought the keyfile and the passphrase were treated differently.
Does that mean they are exchangeable, i.e. if I init the provider with a
passphrase I can attach it with a keyfile of the same content as the
passphrase?

> I suggest not to use the same passphrase for all providers.
> You can always do something like:
>
> pass_da0=3D`echo "0${passphrase}0" | sha256`
> pass_da1=3D`echo "1${passphrase}1" | sha256`
> pass_da2=3D`echo "2${passphrase}2" | sha256`

For that to be of any real good[1], the script would have to be on an
encrypted provider - preferably with a *completely* different passphrase
(and as a result a completely different key) itself. But if the attacker
can analyse this script, then a brute forcing the ${passphrase} will grant
access to all providers.

Or am I missing the point here completely?

Regards
Chris

[1] I assume you are trying to prevent that if a brute force attack at
the passphrase works for ad0, the attacker will have the passphrase for
the other providers too.