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Re: [Gnu-arch-users] Re: signatures and checking


From: Andrew Suffield
Subject: Re: [Gnu-arch-users] Re: signatures and checking
Date: Tue, 27 Jan 2004 02:19:44 +0000
User-agent: Mutt/1.5.5.1+cvs20040105i

On Mon, Jan 26, 2004 at 05:50:42PM -0800, Tom Lord wrote:
> 
>     > From: Miles Bader <address@hidden>
> 
>     > Surely you can just treat the two cases separately:
> 
>     > Ask gpg (or whatever) to deliver the contents in case (2), by having a
>     > `.arch-params/signing/*.contents' script, and just parse them directly 
> in
>     > case (1) (which is when you _don't_ have the script).
> 
>     > This would do the right thing, be simple to implement, not require any
>     > awk scripts, and not require any new options to gpg....
> 
> 
> Interesting idea but no.
> 
> That would create a partial exploit in which non .check'ing clients
> saw different checksum data from .check'ing clients.
> 
> I don't immediately see any obvious way to turn that partial exploit
> into a complete one --- but it seems needlessly fragile, nevertheless.

Clients that are not checking signatures are only interested in
checksums for integrity checking against random bit errors; they have
no defences at all against hostile attackers. So exploits of this form
are not very interesting - there are much easier ways to exploit these
clients.

On the other hand, clients that are checking signatures *are*
interested in avoiding exploits from hostile attackers. The safest
thing to do there is to let gpg tell us what the signed data is; doing
something more complicated is more likely to introduce new bugs.

Incidentally, you don't need a different script, you can use stdout
from the existing check script.

-- 
  .''`.  ** Debian GNU/Linux ** | Andrew Suffield
 : :' :  http://www.debian.org/ |
 `. `'                          |
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