pinentry does not work for both desktop login and SSH login

[Jeffrey Walton]

I'm working on a Ubuntu 18.04.3 LTS x86_64 machine (fully patched). The machine has a GNOME3 desktop. Sometimes I sit at the workstation, and other times I SSH into the workstation.

When sitting at the workstation Git commit signing works. I use 'git commit -S ... -m ...', and things work as expected. I get a UI prompt for my GnuPG password and the work flows as usual.

When I work remotely on the same workstation over SSH I have to forgo commit signing because:

   $ git commit -S log.h -m "Remove unneeded header"
   error: gpg failed to sign the data
   fatal: failed to write commit object

I'm using a "standard" configuration for SSH, Git and GnuPG. I am not aware of any special configurations for this setup. However, the repo is located on my local LAN (and not GitHub, GitLab, etc):

   $ cat .git/config
   [core]
       repositoryformatversion = 0
       filemode = true
       bare = false
       logallrefupdates = true
    [remote "origin"]
       url = ssh://git@callmaster:/var/callboot-src
       fetch = +refs/heads/*:refs/remotes/origin/*
   [branch "master"]
       remote = origin
       merge = refs/heads/master

There is no specialized GnuPG conf file in $HOME/.gnupg:

   $ ls -A ~/.gnupg/
   3F537D88ADBC1677-private-key.asc pubring.kbx
   private-keys-v1.d trustdb.gpg

Here is pinentry on the machine:

   $ ls -Al /usr/bin/pinentry-*
   -rwxr-xr-x 1 root root 63992 Feb 5 2018 /usr/bin/pinentry-curses
   -rwxr-xr-x 1 root root 72184 Feb 5 2018 /usr/bin/pinentry-gnome3
   lrwxrwxrwx 1 root root 30 Sep 2 19:14 /usr/bin/pinentry-x11 -> /etc/alternatives/pinentry-x11

And then:

   $ ls -Al /etc/alternatives/pinentry-*
   lrwxrwxrwx 1 root root 24 Sep 2 19:14 /etc/alternatives/pinentry-x11 -> /usr/bin/pinentry-gnome3
   lrwxrwxrwx 1 root root 40 Sep 2 19:14 /etc/alternatives/pinentry-x11.1.gz -> /usr/share/man/man1/pinentry-gnome3.1.gz

My .bashrc includes:

   export GPG_TTY=$(tty)

Search is finding a lot about Git signing failures, but not results for this particular situation. I have to turn the problem over to the maintainers since I can't figure it out.

What users like me expect is, things just work regardless of how we are logged in.