Making Putty, Windows 10 SSH & WSL work together

Since PuTTY has been the defacto SSH client on Windows since Windows XP, I tend to use PAGEANT.EXE to manage my SSH keys. Now that PUTTYGEN.EXE supports more robust ed25519 keys, I can get good security for my SSH keys and integration with apps such as Git and Emacs.

The only annoyance has been the Windows 10 ssh.exe and WSL1. Typically to get SSH keys working in these environments, you needed to setup keys again with ssh-agent or worse set it up twice - once for ssh.exe and again for WSL1.

Enter wsl-ssh-pageant. This tool allows me to load my keys in PAGEANT.EXE only and then have them be automagically visible in ssh.exe and WSL1. Here’s how to get it working:

• Download the binary from the releases page. Unzip and add it to a folder in your %PATH% somewhere.

• Create an Windows Environment variable SSH_AUTH_SOCK and set the value as \\.\pipe\ssh-pageant

• Create a folder .wsl-ssh-pageant in your %USERPROFILE% directory

• Add the following line to your .bashrc in your %USERPROFILE directory as well as your $HOME folder in WSL1:

  export SSH_AUTH_SOCK=/mnt/c/Users/USERNAME/.wsl-ssh-pageant/ssh-agent.sock

• Add the following line to a batch file and include the batch file in your startup folder

  start wsl-ssh-pageant-amd64-gui.exe --force --systray --winssh ssh-pageant --wsl C:\Users\USERNAME\.wsl-ssh-pageant\ssh-agent.sock

Now launch ssh.exe or bash.exe and type ssh-add -l. Rejoice!

One gotcha that had me stuck for a while though - in your SSH config file, make sure to comment out any IdentitiesOnly yes directives. This can potentially be a problem if you have a lot of SSH keys in PAGEANT.EXE¹ but YMMV.

At the moment, wsl-ssh-pageant does not support WSL2 directly although there is an open issue in the GitHub repo about this.