GPG sign commit does not work for loopback mode

[xudyang1]

Issue

Version 2.47.0 and newer breaks gpg sign commit when using loopback mode. The loopback mode does not work as expected, thus an user can not enter passphrase to sign the commit.

Reproduce

1. download git from scoop or other means

• latest: scoop install git
• or,
• version 2.47.0: scoop install https://raw.githubusercontent.com/ScoopInstaller/Main/788e274292442e9fea6d944ca61a62be0ebacab4/bucket/git.json

2. enable sign commit: git config --global commit.gpgsign true
3. enable lookback pinentry mode:

• ~/.bashrc:

GPG_TTY=$(tty)
export GPG_TTY

• ~/.gnupg/gpg-agent.conf:

# disable pinentry modal popup
allow-loopback-pinentry

• ~/.gnupg/gpg.conf

use-agent

# disable pinentry modal popup
pinentry-mode loopback

4. testing commands:

• mkdir test-gpg; cd test-gpg; git init; echo '123' >> a.txt; git add -A; GIT_TRACE=1 git commit -m "test";
• The loopback mode does not work because tty does not ask for passphrase. With error message:

... 
gpg: cannot open 'no tty': No such file or directory
error: gpg failed to sign the data:
....

More

• version 2.46.2 works fine:
  • download git by scoop install https://raw.githubusercontent.com/ScoopInstaller/Main/6ef718a96949c6d1aece63b6cea83d3aedc7125d/bucket/git.json
  • manifest link https://github.com/ScoopInstaller/Main/commit/6ef718a96949c6d1aece63b6cea83d3aedc7125d

[dscho]

gpg: cannot open 'no tty': No such file or directory

That sounds as if your GPG_TTY=$(tty) sets GPG_TTY to no tty. Try running tty stand-alone, and I am convinced you will have a much, much smaller reproducer.

For what it's worth, I cannot reproduce locally:

$ git version
git version 2.48.1.windows.1

me@work MINGW64 ~
$ tty
/dev/pty0

Therefore, I expect something to be very special about your setup that you haven't revealed yet.

[xudyang1]

• old version:

$ git --version
git version 2.46.2.windows.1
$ tty
/dev/cons0

• new version:

$ git --version
git version 2.48.1.windows.1
$ tty
/dev/cons0

I don't think the issue is $GPG_TTY, as the issue only occurs after version 2.47.0. It's possible that something went wrong in gpg-interface.c from v2.46.2.windows.1 .. v2.47.0.windows.1.

$ git diff v2.46.2.windows.2..v2.47.0.windows.1 gpg-interface.*

[dscho]

I don't think the issue is $GPG_TTY, as the issue only occurs after version 2.47.0. It's possible that something went wrong in gpg-interface.c from v2.46.2.windows.1 .. v2.47.0.windows.1.

You could bisect that, to find out...

[huw0]

I am also experiencing this issue with GPG loopback since upgrading.