linux-kernel - Re: email as a bona fide git transport

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Message-ID: <20191018155047.id6r57komlejatvh@LykOS.localdomain>
Date:   Fri, 18 Oct 2019 11:50:48 -0400
From:   Santiago Torres Arias <santiago@....edu>
To:     Nicolas Belouin <nicolas.belouin@...di.net>
Cc:     Willy Tarreau <w@....eu>, Greg KH <greg@...ah.com>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        workflows@...r.kernel.org, Git Mailing List <git@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, Eric Wong <e@...24.org>
Subject: Re: email as a bona fide git transport


On Fri, Oct 18, 2019 at 08:34:17AM +0200, Nicolas Belouin wrote:
> On 10/18/19 4:52 AM, Willy Tarreau wrote:
> > On Thu, Oct 17, 2019 at 09:54:47PM -0400, Konstantin Ryabitsev wrote:
> >> On Thu, Oct 17, 2019 at 06:30:29PM -0700, Greg KH wrote:
> >>>> It could only possibly work if nobody ever adds their own
> >>>> "Signed-Off-By" or
> >>>> any other bylines. I expect this is a deal-breaker for most maintainers.
> >>> Yeah it is :(
> >>>
> >>> But, if we could just have the signature on the code change, not the
> >>> changelog text, that would help with that issue.
> >> We totally should, and I even mused on how we would do that here:
> >> https://urldefense.proofpoint.com/v2/url?u=https-3A__public-2Dinbox.org_git_20190910121324.GA6867-40pure.paranoia.local_&d=DwICaQ&c=slrrB7dE8n7gBJbeO0g-IQ&r=yZMPY-APGKyVIX7HgQFZJA&m=-7NJMybpa_bV7Y1FxWmqo1cUHOsDXAsRR1vvpQmYhyI&s=iFHNwBfYAPr---qMdv0mvKQAxqjXxvf1mAiAYZG6DIE&e= 
> >>
> >> However, since git's PGP signatures are made for the content in the actual
> >> commit record (tree hash, parent, author, commit message, etc), the only way
> >> we could preserve them between the email and the git tree is if we never
> >> modify any of that data. The SOB and other trailers would have to only be
> >> applied to the merge commit, or migrate into commit notes.
> > There's also the possibility to handle this a bit like we do when adding
> > comments before the SOB: a PGP signature would apply to the text *before*
> > it only. We could then have long chains of SOB, PGP, SOB, PGP etc.
> >
> > Willy
> 
> I don't think it can work that easily as the signed content is not just
> the message.
> It would need git to support nesting signatures and to allow amending a
> commit without
> touching the signature and to allow adding one to cover the new content
> and to have a
> way to verify every step.
> Moreover you won't be able to reparent the commit as a maintainer (wich
> I think is
> also a deal-breaker)

For reference, we did something similar here[1]. I'll acknowledge it's
somewhat of a niche use, and there's a danger with multiple signature
types that could mean many different things...

I do wonder if an over-lying tool could probably provide with more
granular verification over mutiple gpg payloads inside of a commit...

Cheers!
-Santiago.

[1] https://dl.acm.org/citation.cfm?id=3196523

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