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Re: Ideas how to update archive keys



also sprach Goswin von Brederlow <brederlo@informatik.uni-tuebingen.de> [2005.02.20.1229 +0100]:
> The easiest way to handle the archive key would be to include it
> inside the deb. The drawback of this method is that apt must be
> updated whenever the key is changed for any reason. Since the key
> is used to authenticate updates this would require apt to be
> updated before the archive key is chnaged (which is obviously
> a problem).

I would think it's a bad idea to use the same distribution medium
for key and protected content. Then again, I cannot think of a way
how this could be exploited, given that we manage to get a valid key
to the user somehow else first. Or else we cannot establish a trust
cycle.

> One way around the problem is to allow for an alternate means to
> verify a package: signed debs. My first idea would be to allow apt-get
> to install deb packages from an untrusted source (key expired) if the
> deb in itself can be trusted. The apt deb and depends of it would have
> to be signed by at least one key that is still valid (e.g. a still
> valid DDs key from the stable keyring). That would provide the means
> to savely update at least apt which would update the archive key and
> consequently restore the trust system.

Fundamentally, package signatures are the way to go (I am thinking
dpkg-sig here). They would make the rather complicated archive
signatures be unnecessary and protect DEBs, not an abstract package
in an archive.

However, infrastructure support for dpkg-sig is not there yet.
Worse, it looks like we might need a new revision of the DEB format
to really make use of it.

For APT 0.6, I think we therefore must concentrate on archive
signatures, and we'll look into package signatures later.

> Well, those are my ideas. Show me the flaws.

None really, except we should also work on a policy for the archive
keys. E.g. require a new key to be available on 1 Dec and expire on
31 Jan, 14 months later. Keys then overlap for two months, and the
dak scripts start using the new key on 1 Jan. The new key should be
signed by the old key, and the old key must be revoked on 31 Jan.

Also, I would love to see the keys to be available on www.debian.org
over HTTPS, ideally with a certificate issued by the SPI CA.
I realise this is only a marginal technological security benefit; it
surely has a psychological benefit to executives though.

-- 
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 .''`.     martin f. krafft <madduck@debian.org>
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