GPG2, gpg-agent, & preset passphrase on Ubuntu

Purpose

Given an ubuntu linux environment with GPG2 private keys, I want to start a gpg-agent and pre-load the passphrase for one of the keys so that every attempt to sign with that key (by a tool that can use gpg-agent) avoids the passphrase prompt.

User Guide

Build the System

Just run make build.

You must have docker and make installed.

Run the System

Just run make run.

This will start up the Docker image and try to start up a gpg-agent with the passphrase to the key preset. It will also configure git to use that key to sign.

Feel free to follow either of the Approaches below to try to sign something. This repository will be present (via a Docker bind-mount) in your home directory:

~/git-personal/linux-gpg2-agent-preset (master) $ make run
docker run \
		--rm \
		--interactive \
		--tty \
		--volume="/Users/me/git-personal/linux-gpg2-agent-preset":/home/ubuntu/linux-gpg2-agent-preset \
			linux-gpg2-agent-preset
/home/ubuntu/.gnupg/pubring.kbx
-------------------------------
sec   rsa4096/47625A42 2018-08-16 [SC]
uid         [ultimate] Dummy Key (This keypair was generated as part of an example repo; the private key and passphrase are known to the world.) <[email protected]>
ssb   rsa4096/58972FCE 2018-08-16 [E]
...
+ exec bash
ubuntu@3cab7eb59cd2:~$ ls -hal
total 16K
drwxr-xr-x  1 ubuntu root   4.0K Aug 16 02:16 .
drwxr-xr-x  1 root   root   4.0K Aug 16 00:58 ..
-rw-r--r--  1 ubuntu ubuntu   86 Aug 16 02:16 .gitconfig
drwx------  1 ubuntu root   4.0K Aug 16 02:16 .gnupg
drwxr-xr-x 10 ubuntu ubuntu  340 Aug 16 02:07 linux-gpg2-agent-preset

Approaches

Simple

1. Have GPG2 keys
2. Have a ~/.gnupg/gpg-agent.conf
3. Start a gpg-agent as a daemon.
4. Try to encrypt a file with gpg2
   • gpg2 --encrypt --sign --armor -r [email protected] linux-gpg2-agent-preset/README.md

git

1. Have GPG2 keys
2. Have a ~/.gnupg/gpg-agent.conf
3. Start a gpg-agent as a daemon.
4. Configure git to use one of those keys to sign commits
5. Try to commit to this repository cd linux-gpg2-agent-preset hostname >> README.md git add README.md git commit -a -m 'signed commit'

Notes

• GPG keys: docker/files/home/ubuntu/.gnupg
  • UID: 47625A42
  • Passphrase: correct horse battery staple
• gpg2 and gpg-agent versions: docker/installers/apt-get.sh