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sm-discuss - Re: [SM-Discuss] STRONGER POLICY for gpg signatures to replace MD5[*] and ALSO new SOURCE_HASH support

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  • From: "Sergey A. Lipnevich" <sergey AT optimaltec.com>
  • To: sm-discuss AT lists.ibiblio.org
  • Subject: Re: [SM-Discuss] STRONGER POLICY for gpg signatures to replace MD5[*] and ALSO new SOURCE_HASH support
  • Date: Mon, 29 Aug 2005 12:35:23 -0400

Quoting Eric Sandall <eric AT sandall.us>:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Mon, 29 Aug 2005, Sergey A. Lipnevich wrote:
Quoting Seth Alan Woolley <seth AT positivism.org>:

DRAFT, although this is one case where we're actually moving on it
quickly, so it's more of a last call for objections.


So here goes: I object.

1. Hash collision is not a problem when it comes to source tarballs, so please
don't use it as a reason to switch to signatures. We could've as easily hashed
them with CRC32 or with 10K-bit hash. *Either* way provides *no* security.

Care to explain? The nice part about GPG is that we can change
hashsums without changing which tool (GPG) we're using.

The reasoning on why GPG signing must be mandatory is convoluted. I would like
to remove this particular reason from the list, because it's simply wrong. Hash
collision doesn't mean we have to move to GPG signatures. It doesn't consitute a
security hazard or absence of it.

2. There's no way I can sign a bunch of code I didn't read through and
understand. It's an impossible task in a distribution, so it's shorter to say
that I can't sign a bunch of code, period.

You must have forgotten to read the prior conversations. We are /not/
guaranteeing that these files are trojan/virus/malware/whatever-free.
What we are guaranteeing is that the tarball the user downloaded is
the same as the one the guru tested with. Nothing less, nothing more.

So let's use the appropriate means of soing that. Hash is appropriate and
sufficient, GPG signatures are too much.

3. Let's be frank Seth, tarballs that you, or anyone else besides the authors,
signed are as *insecure* as they were before you did that. It didn't format
your hard drive? Good for you. Maybe it's designed to format only *mine*. Or
the drive of the guy who works for CIA ot Chinese government. You don't know
that.

We have that problem now. Your point?

My point is that regardless of the disclaimer, we're accepting responsibility
for what we sign. I don't want this responsibility. Moreover, the disclaimer
doesn't change perception: you signed it, so you know a) it's good, b) what's
inside, c) it's not malicious. But a-c are relative and are very difficult to
ascertain.

4. Combination of #2 and #3 leads me to believe that we do not provide *any*
additional security over unsigned tarballs, so let's focus on *integrity*.
Integrity is *perfectly* verified by the hash. Stronger hash if necessary, but
nevertheless a hash. Non-personified piece of information.
5. What people keep saying on the list amounts to: let's call it blue even
though it's black. Meaning, let's call GPG signature a means to verify
integrity even though it's a means to verify source and integrity. I don't buy
that.

Don't get me wrong, I believe that PGP and GPG are one of the most overlooked
technologies of the present time, in the light of PKI having so many
unresolved
and abandoned issues. So, I support use of GPG signatures, but for the correct
purpose. Verifying integrity of the source tarballs is not a sufficient
purpose.

Sergey.

You seem to have missed the entire conversation. That's exactly what
we've been saying the entire time and we've corrected people who
posted misunderstandings: GPG is being used to verify the tarball is
what the guru used, nothing more, nothing less.

No I didn't. And my answer to this is as I said before: you're trying to
substitute a different meaning for something that already has a meaning. Please
read my original item #4. Using Jeremy's analogy, signing an email doesn't mean
that you always agree with it, in 10 years or otherwise. But, it *does* mean
that whatever is written is coming from *you* and you vouch for it. If you
wrote that you wanted to rob a bank, in ten years you might regret it, but your
malicios intent will be beyong doubt.

Moreover, in Jeremy's analogy with mail package and a neighbor, I think now the
package corresponds to a tarball, and our *spell* corresponds to a wrapping,
backtrace, etc. So, I would agree to sign the *spell* that I altered, but not
the *source* coming from a 3rd party web site.

Sergey.





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