Useful to use SSH securely using a smart card / hardware token / yubikey / etc.
Of course, you need to have GPG installed on your system, and possibly some drivers and applications to support your smart card / hardware token if used.
This guide assumes you already have set up GPG and your keys (and possibly hardware token) and now you just want to know how to SSH!
Enabling SSH in the GPG agent
On Mac, nothing further needs to be done. On Windows you have to add
%appdata%\gnupg\gpg-agent.conf and on Linux
~/.gnupg/gpg-agent.conf create these files if they don’t already exist, but make sure the folder has already been there or you’re at the wrong place.
echo 'enable-ssh-support' >> ~/.gnupg/gpg-agent.conf
Using the GPG agent
And make sure you are using the GPG agent by adding this to your “
.profile” or shell’s
rc file (and then restart the terminal session):
Linux (Debian and Ubuntu)
Add the following to your ~/.bashrc
export GPG_TTY="$(tty)" export SSH_AUTH_SOCK="/run/user/$UID/gnupg/S.gpg-agent.ssh" gpg-connect-agent updatestartuptty /bye > /dev/null
Mac (and some Linux distros)
Add the following to your ~/.profile or ~/.bashrc (“macOS Big Sur” users should put this into ~/.zprofile)
export GPG_TTY="$(tty)" export SSH_AUTH_SOCK=$(gpgconf --list-dirs agent-ssh-socket) gpgconf --launch gpg-agent
Windows has no such thing as a shell rc, but instead, you’ll have to manually run commands in the CMD (or create a batch file and add it to autostart) with the following contents:
gpg-connect-agent.exe killagent /bye gpg-connect-agent.exe /bye
Exporting your public key and adding it to the server
gpg --export-ssh-key MY_KEY_ID and copy the output to your remote server’s
Connecting to the SSH server
Now, if you did all the above, simply restart your terminal session and try to SSH to your server as usual. You might now be asked to enter your GPG key passphrase, or the pin of your smart card.
On Windows, you’ll be using PuTTY instead.
I hope this helped.
If I forgot something or you’re running into issues, just leave a comment.
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