Re: [PATCH 0/1] Limit search for primary key fingerprint

Hi,

Hans Jerry Illikainen wrote:

As part of implementing signature verification for git clone, I decided
to refactor/unify the code for commit and merge verification to make it
reusable during clones.

Thanks for writing this.

Most of the text in this cover letter would be useful to have in the
commit message.  From the commit message alone, I could see that you
were fixing a bug, but I could not see the motivation or workflow it
is part of.  If I were to later discover an issue triggered by this
commit, I wouldn't have enough information to weigh tradeoffs about
the right way to address such an issue.

Thanks and hope that helps,
Jonathan

This lead me to discover that git requires merge signatures to be
trusted (as opposed to TRUST_UNKNOWN or TRUST_NEVER).  This is unlike
the behavior of verify-tag and verify-commit.

So, I figured that I'd make the minimum trust level configurable to make
the behavior of merge/commit/tag consistent.  And while doing so, I
noticed that parse_gpg_output() in gpg-interface.c assumes that the
VALIDSIG status line has a field with a fingerprint for the primary key;
but that is only the case for OpenPGP signatures [1].

The consequence of that assumption is that the subsequent status line is
interpreted as the primary fingerprint for X509 signatures.  I'm not
sure if the order is hardcoded in GnuPG, but in my testing the TRUST_
status line always came after VALIDSIG -- and that breaks the config
option to set a minimum trust level (not part of this patch):

,----
| $ git log -n1 --format="primary key: %GP" signed-x509
| gpgsm: Signature made 2019-11-16 14:13:09 using certificate ID 0xFA23FD65
| gpgsm: Good signature from "/CN=C O Mitter/O=Example/SN=C O/GN=Mitter"
| gpgsm:                 aka "committer@example.com"
| primary key: TRUST_FULLY 0 shell
`----

[1]: https://git.gnupg.org/cgi-bin/gitweb.cgi?p=gnupg.git;a=blob;f=doc/DETAILS