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Re: [PATCH 0/4] Expose gpgsig in pretty-print




On Wed, 2018-12-19 at 00:59 -0500, John Passaro wrote:
> On Fri, Dec 14, 2018 at 6:10 PM John Passaro wrote:
> > All seems to work fine when I treat %Gs as a detached signature.
> 
> In light of this, my best guess as to why the cleartext PGP message
> didn't verify properly is that the commit data normally doesn't end
> with \n, but as far as I can tell there's no way to express that in
> the cleartext format. I don't see a way around this.

You are most likely right.  I've just skimmed through RFC 4880
and indeed it seems to rely on the newline encoding being quite
normalized in the message.

> However, as long
> as the following works, I think we have proof-of-concept that this
> enhancement allows you to play with signature data however you please
> without leaving it to git under the hood:
> 
> gpg --verify <(git show -s --format=format:%Gs commit) <(git show -s
> --format=format:%Gp commit)

That's a nice trick.  Thanks for the effort you're putting into this!

> 
> On Mon, Dec 17, 2018 at 3:24 PM Jeff King <peff@xxxxxxxx> wrote:
> > 
> > On Fri, Dec 14, 2018 at 11:07:03AM -0500, John Passaro wrote:
> > 
> > > Then I might rename the other new placeholders too:
> > > 
> > > %Gs: signed commit signature (blank when unsigned)
> > > %Gp: signed commit payload (i.e. in practice minus the gpgsig header;
> > > also blank when unsigned as well)
> > 
> > One complication: the pretty-printing code sees the commit data in the
> > i18n.logOutputEncoding charset (utf8 by default). But the signature will
> > be over the raw commit data. That's also utf8 by default, but there may
> > be an encoding header indicating that it's something else. In that case,
> > you couldn't actually verify the signature from the "%Gs%Gp" pair.
> > 
> > I don't think that's insurmountable in the code. You'll have to jump
> > through a few hoops to make sure you have the _original_ payload, but we
> > obviously do have that data. However, it does feel a little weird to
> > include content from a different encoding in the middle of the log
> > output stream which claims to be i18n.logOutputEncoding.
> > 
> 
> Thanks for the feedback! This is an interesting conflict. If the user
> requests %Gp, the payload for the signature, they almost certainly do
> want it in the original encoding; if i18n.logOutputEncoding is
> something incompatible, whether explicitly or by default, that seems
> like an error. Not much we can do to reconcile the two requests
> (commit encoding vs output encoding) so seems reasonable to treat it
> as fatal.
> 
> Updated patch coming as soon as I work out Peff's aforementioned "few
> hoops" to get properly encoded data -- and also how to test success
> and failure!

-- 
Best regards,
Michał Górny

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