Yubikey in WSL2 Ubuntu.md

WSL does now have native support for USB devices, which means it can't detect the Yubikey plugged into your computer. It seems like USB support will come soon, but for now we need to use a workaround.

The workaround consists in exposing a GPG socket from Windows to your WSL Linux instance. That way, your WSL's gpg command will connect to your Windows's gpg software and will be able to detect your USB Yubikey.

1. Install GnuPG on Windows

2. Install Putty on Windows

3. Run the following 2 commands in Powershell to create your GPG conf file:

   # In Poweshell
   mkdir $env:APPDATA/gnupg
   Add-Content -Path $env:APPDATA/gnupg/gpg-agent.conf -Value "enable-putty-support`r`nenable-ssh-support"
   
   mkdir $env:LOCALAPPDATA/gnupg
   Add-Content -Path $env:LOCALAPPDATA/gnupg/gpg-agent.conf -Value "enable-putty-support`r`nenable-ssh-support"

4. If you connect your Yubikey now, you should be able to see it from Windows if you run the following command from Powershell:

   # In Poweshell
   gpg --card-status

   You should also see the Yubikey inside the "Smartcards" tab of the Kleopatra app that was installed together with GnuPG.

5. Now that GPG can see your Yubikey on Windows, it's time to expose it to your WSL Linux. First, install socat in your WSL Linux:

   # In WSL
   sudo apt install socat

6. Now let's install wsl-ssh-pageant using the instructions from their README:

   # In WSL
   windows_destination="/mnt/c/Users/Public/Downloads/wsl2-ssh-pageant.exe"
   linux_destination="$HOME/.ssh/wsl2-ssh-pageant.exe"
   wget -O "$windows_destination" "https://github.com/BlackReloaded/wsl2-ssh-pageant/releases/latest/download/wsl2-ssh-pageant.exe"
   # Set the executable bit.
   chmod +x "$windows_destination"
   # Symlink to linux for ease of use later
   ln -s $windows_destination $linux_destination

7. Finally, add the following config to your .bashrc file. You can open it in vscode from WSL with code ~/.bashrc. IMPORTANT: Replace YOUR-WINDOWS-USERNAME-HERE with your Windows username folder.

   # WSL2-SSH-PAGEANT config
   # https://github.com/BlackReloaded/wsl2-ssh-pageant
   # https://github.com/BlackReloaded/wsl2-ssh-pageant/issues/37
   export SSH_AUTH_SOCK="$HOME/.ssh/agent.sock"
   if ! ss -a | grep -q "$SSH_AUTH_SOCK"; then
      rm -f "$SSH_AUTH_SOCK"
      wsl2_ssh_pageant_bin="$HOME/.ssh/wsl2-ssh-pageant.exe"
      if test -x "$wsl2_ssh_pageant_bin"; then
         (setsid nohup socat UNIX-LISTEN:"$SSH_AUTH_SOCK,fork" EXEC:"$wsl2_ssh_pageant_bin" >/dev/null 2>&1 &)
      else
         echo >&2 "WARNING: $wsl2_ssh_pageant_bin is not executable."
      fi
      unset wsl2_ssh_pageant_bin
   fi
   
   export GPG_AGENT_SOCK="$HOME/.gnupg/S.gpg-agent"
   if ! ss -a | grep -q "$GPG_AGENT_SOCK"; then
      rm -rf "$GPG_AGENT_SOCK"
      wsl2_ssh_pageant_bin="$HOME/.ssh/wsl2-ssh-pageant.exe"
      if test -x "$wsl2_ssh_pageant_bin"; then
         (setsid nohup socat UNIX-LISTEN:"$GPG_AGENT_SOCK,fork" EXEC:"$wsl2_ssh_pageant_bin -gpgConfigBasepath 'C:/Users/YOUR-WINDOWS-USERNAME-HERE/AppData/Local/gnupg' -gpg S.gpg-agent" >/dev/null 2>&1 &)
      else
         echo >&2 "WARNING: $wsl2_ssh_pageant_bin is not executable."
      fi
      unset wsl2_ssh_pageant_bin
   fi

8. Now restart your PC just be sure (or just restart WSL with wsl --shutdown from Powershell)

9. On your WSL Linux, you should now be able to see the Yubikey from GPG:

   # On WSL
   gpg --card-status