I don't recall if anyone has mentioned http://pgp.cs.uu.nl/ yet. Tragically not available over https, but nowadays that isn't as much of an assurance as once thought, depending on your threat model of course. :)

More below ...

On 09/18/2013 02:37 PM, Philip Jägenstedt wrote:
On Wed, Sep 18, 2013 at 10:23 PM, Peter Lebbing <[email protected]> wrote:
On 18/09/13 22:14, � wrote:
If I assume that the Wayback Machine isn't part of a conspiracy against me

I don't see how this is different than not verifying at all and "assuming
gnupg.org isn't part of a conspiracy against me".

It's one more server which would have to be under the attacker's
control, in addition to gnupg.org, Google cache, mailing list mirrors
and whatever else one might find.

You can spend an enormous amount of time going further and further down the rabbit hole if you choose to. :) At the end of the day the question becomes, "How much extra benefit does this extra work provide me, vs. the cost of any potential attack that not doing the work might permit?"

If you're running a GnuPG binary on a Windows system, then spending more than 2 minutes is probably 1:30 too long. As has been mentioned here before, unless you are qualified to audit all of the existing build tool chain binaries and related libs on your Unix-like OS even building the GnuPG package yourself after thoroughly verifying the signature/key for the source tarball is putting a whole lot of faith in the system. Admittedly in the case of something like a mainstream Linux or BSD system your trust is probably better placed by an order of magnitude, but it's still a lot of trust.

What is your threat model?

When checking the GnuPG dist sig key, the risk is some third party
modifying the source, i.e. that the code I'm getting is not from the
same origin as all the gpg binaries everyone else is using and
trusting with their secrets.

Sorry, all you've done there is restate the problem. What bad things are you concerned will happen to you if you use this non-standard source? You may think that's a totally obvious question, but it's not. And see above for why it's probably the wrong question anyway.

Alternatively, if you use a Linux distro: simply install it with the package
manager. You already implicitly trust that anyway. If somebody got inside the
package manager, they don't need to bother to attack GnuPG specifically.

I suppose technically you're also trusting the maintainer for the package. No
worse than trusting any other maintainer, I think. They all have access to the
binaries you run.

I wanted to try 2.1.0beta3 which isn't in Debian testing, but using
the package manager (which I trust) as yet another cross-check sounds
reasonable, if some package happened to include the dist sig key, but
I haven't found it.

When I was a FreeBSD developer I tried to get the PTB interested in adding standard (albeit opt-in) support for PGP signatures in our ports/packages system. For the source side (ports) I wanted to include the PGP signatures from the distributor of the tarball. On the pre-compiled packages side I wanted our package creation system to create a signature for the package. I even included a POC for the former in the ports I maintained. While the security conscious users liked it, the general consensus was that the SHA-256 checksums we were already using to verify the authenticity of the source tarballs was enough.

My counter-argument was that this is insufficient, since it relies on the (volunteer) maintainer of the port to provide thorough review of new source packages, which is something we had consistency problems with even amongst those with the best of intentions. The Linux package systems I'm familiar with (and admittedly that's not many) seem to share the same "reliability" (pardon the pun) issue. If the maintainer is the one who wants to pwn me, that would theoretically be possible, at least for a time.

FWIW,

Doug



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