Re: Building from git

[Wojtek Kosior via "Development of GNU Guix and the GNU System distribution." <guix-devel@gnu.org>]

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Hello Josselin

> wolf <wolf@wolfsden.cz> writes:
> 
> > Hmm, but the recipe for the authenticate rule comes from the (possibly)
> > compromised source, no?  So the attacker can just modify the recipe instead of
> > the command going the authentication.  Am I missing something?  
> 
> You can use a previously trusted guix to do the authentication.  `make
> authenticate` is here for committers to check that their commits are all
> properly signed before pushing (it's used as a pre-push hook).

From my understanding of the documentation, `make authenticate` is not
just for committers but for all people who do a `git pull` in Guix tree
and want to verify that the newly pulled commits do come from the
committers. It it is not the case, then the documentation should
probably be modified to make it clear.

The recipe is not from an untrusted source mecause the Makefile is not
tracked by git. Rather, it gets generated when first building Guix. And
— as the documentation instructs — the initial checkout gets
authenticated with `guix git authenticate` rather than with `make
authenticate` so it can't get compromised that easily.

Had someone managed to serve us a commit that adds another Makefile
with a backdoor, git would report a conflict upon pulling. I believe
this is what the implementors had in mind. Please clarify if this is
wrong.

I do see 1 loophole here, though. One could serve a compromised
makefile under the name "GNUmakefile" and `make authenticate` would
happily choose it over the non-compromised "Makefile". I was planning
to start a new thread about it for some time... but this one seems like
a just as appropriate place to mention the issue.

It shouldn't be hard to fix. It boils down to having ./configure create
a GNUmakefile as well. Perhaps as a symlink to the original Makefile?

Best,
Wojtek

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On Fri, 08 Sep 2023 11:10:37 +0200 Josselin Poiret <dev@jpoiret.xyz> wrote:

> Hi,
> 
> wolf <wolf@wolfsden.cz> writes:
> 
> > Hmm, but the recipe for the authenticate rule comes from the (possibly)
> > compromised source, no?  So the attacker can just modify the recipe instead of
> > the command going the authentication.  Am I missing something?  
> 
> You can use a previously trusted guix to do the authentication.  `make
> authenticate` is here for committers to check that their commits are all
> properly signed before pushing (it's used as a pre-push hook).
> 
> Best,

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