Public SourceMage Discussion List

[Seth Alan Woolley <seth AT positivism.org>]

On Wed, Aug 10, 2005 at 10:37:14PM -0700, Eric Sandall wrote:
> On Thu, 11 Aug 2005, Jeremy Blosser (emrys) wrote:
> > [0] https://lists.ibiblio.org/sympa/arc/sm-discuss/2005-April/010332.html 
> > --
> > Seth does note in here that "SOURCE_GPG will be preferred" over
> > SOURCE_HASH, but doesn't say why; I'd assume he means it's preferred
> > because it provides better verification when appropriate key/source
> > verification has been done to back it up.
> 
> IIRC GPG's hash algorithm is better than md5sum, sha1, etc. and can
> easily be 'modified' if a hole/issue is found.

Just want to emphasize, we do not use PGP's hash algorithms directly -- 
it's one component of how PGP is used, however, most of the time sha1 is 
used, which is a bit stronger than md5 at this point.

Secondly, I preferred SOURCE_GPG over SOURCE_HASH to the extent that if 
both methods are available to the spell writer, that they should select 
SOURCE_GPG as the method because it completes the integrity chain back 
to the original author (which can go further, but our responsibility is 
to get it at least back to the original author).  Once the key is added, 
each update carries with it further guarantees of trust -- a MIM 
security attack on older, more used keypair chains is more and more 
difficult even without initial verification.  With HASHes we tend to not 
get it from a source which has an increasing level of security -- each 
new hash is received under similar MIM vulnerable circumstances.

If the hash were gpg signed, though, this concern wouldn't be there, 
however, GPG is still more preferred than the HASH in a non-security 
sense since spell updates require even less effort on each subsequent 
update.

And moreover, the ability to rely on gnupg to update hashes used in PGP 
helps future proof the API.

Since we publish the keys we use to verify the sources the paranoid even 
have the ability to self-check our verification, which makes us a very 
unlikely target for somebody trying to use us as a vector for attack.  
They'd be exposed pretty darn quick unless they could attack both us 
(and every other gpg publishing distro) and the download site at the 
same time.  This element of peer review gives us extra protection.  

Incorrect hashes though tend to be "oh that's a mistake" or "oh we 
updated that tarball".  When this happens in a PGP system, you've got a 
more serious problem than a mistake most of the time.

So having said that, yes, we should be diligent to check our public keys 
just because of the nature of not wanting to have to do a brown-bag 
update of a vendor pgp key, but it is designed to have some amount of 
self-protection built into it.  I'm aware of no other distro with an 
implementation this well-designed (ok, well, I lead design of it, so I'm 
biased ;)).

One possible way to make it easy for gurus is to not have gurus do the 
checking.  They can do very basic checks enough to satisfy themselves 
and commit to devel grimoire with a WIP, at which point it should never 
hit test until a separate key review committee can approve it.  This 
could be composed of trusted members of the community that don't need to 
be coders themselves.  Maybe they have extensive PGP experience and can 
follow the steps necessary to verify a public key, including phone 
calls, email lists, person-to-person contact, following a standard 
agreed upon and interpreted by members of the specific committee.

This puts the pressure off of coders who might not have the time to 
worry about such measures, and yes, they should update our wiki with all 
the methods used to validate each key.

-- 
Seth Alan Woolley [seth at positivism.org], SPAM/UCE is unauthorized
Quality Assurance Team Leader & Security Team: Source Mage GNU/linux
Linux so advanced, it may as well be magic http://www.sourcemage.org
Secretary Pacific Green Party of Oregon http://www.pacificgreens.org
Key id FDCEE733 = 5302 B414 64C4 6112 3454  E082 99F0 69DC FDCE E733

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