[POSTMORTEM] Subkey is not authorized by .guix-authorizations

[Andrew Tropin <andrew@trop.in>]

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* Summary
On 2022-08-06 the commit 3946540[fn:1] was pushed and lead to failing
guix pull:

--8<---------------cut here---------------start------------->8---
guix pull: error: commit 39465409f0481f27d252ce25d2b02d3f5cbc6723 not
signed by an authorized key: 2841 9AC6 5038 7440 C7E9 2FFA 2208 D209
58C1 DEB0
--8<---------------cut here---------------end--------------->8---

It was discovered and reported to IRC almost immediately by a few
people.  The commit itself was signed and benign[fn:2], but it was signed with
subkey.  While primary key was added to .guix-authorizations, guix pull
still rejected commit signed with subkey.

From the point commit pushed there is no easy way to recover guix
pull.  nckx contacted savannah admins and a few hours later master
branch was reset to the state before 3946540 was pushed.

* Impact
- guix pull of latest commit from master branch couldn't be done for a
  few hours, the possible problem of such DoS is known[fn:3].

* What could be done better?
- guix pull could be done from local checkout, before pushing.
- First commit by a fresh commiter could be pushed on a weekday, after
  checking if maintainers and admins are present.

* What to do after?
- Accept subkey on guix pull if master key is in .guix-authorizations.
- Add tip to Commit Access section about pull from local checkout.
- Add pre-push hook, which checks authorization on Savannah.

* Footnotes

[fn:1] https://git.savannah.gnu.org/cgit/guix.git/commit/?id=39465409f0481f27d252ce25d2b02d3f5cbc6723

[fn:2] https://lists.gnu.org/archive/html/help-guix/2022-08/msg00073.html

[fn:3] https://lists.gnu.org/archive/html/guix-devel/2021-03/msg00156.html


-- 
Best regards,
Andrew Tropin

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