Windows, Git, and SSH Keys

Git has the ability to use SSH keys in order to authenticate communications with a remote server. This is a magical thing! Depending on how you set it up, you may never have to enter your password again.

You may find differing opinions, of course. My suggestion is to store password-less keys securely on your development system. This may seem like a bad idea, but it’s a pretty common thing to do to make your life easier.

If your laptop/desktop ever gets stolen, it’s pretty easy to revoke it’s key.

Generating Keys

I do 99% of my development on my Windows computer. Windows doesn’t have any built-in SSH functionality (we’re not talking about WSL right now). That means that you will wind up installing PuTTY. It’s ok… everybody’s doing it!

I like to store my SSH keys in my profile directory. This will make your life a lot easier. The keys will also be slightly protected with your Windows login information. %USERPROFILE% is also the default place were utilities will look for your SSH config file.

In a command Window, type: mkdir %USERPROFILE%\.ssh

Generate your first key:

1. Open up PuTTYGen (might be in your Start menu if you installed it like that)
2. The default settings of 2048 RSA should be ok
3. Press the Generate button
4. Move your mouse over the window to generate some randomness
5. Export these things to your %USERPROFILE%\.ssh folder (you can ignore the without a passphrase warnings):
   • Press Save private key: This will save a file with a .ppk extension. This is your private key; keep it safe! This should stay on your dev machine.
     For this example, name this devmachine.ppk
   • From the menu, select Conversions -> Export OpenSSH Key: This is your private key exported into something that git will use.
     For this example, name this devmachine-openssh-private.txt
   • Keep the Window open… the Public key for pasting is important for a later step.

Here’s a screenshot of my screen after I generated the key:

%USERPROFILE%.ssh\config

The SSH utilities that don’t use the .ppk directly will want to use the devmachine-openssh-private.txt file that you exported above. The easiest way to do this is to create a config file that tells the utilities which keys to use for which hosts.

Run the following command from the command line (careful here, don’t delete the file if it’s already there!):

type NUL >> %USERPROFILE%\.ssh\config

This will create an emtpy file. Now open that file up in your favorite text editor. Here’s a sample configuration for github.com:

Host github.com
    StrictHostKeyChecking no
    IdentityFile C:\Users\myusername\.ssh\devmachine-openssh-private.txt

All utilities that support this kind of thing, such as git, will automatically use this configuration to log in to the remote system (github.com, in this case).

NOTE: This format of .ssh/config is the same for both Windows and Linux.

GitHub

We’re using GitHub in this example, but this holds true for any other remote host that supports SSH keys (even Linux systems).

1. Go into your Settings, and select SSH and GPG keys
2. Press the New SSH key button
3. Give it an appropriate Title
4. Remember the PuTTYGen window you kept open? Copy the text in the Public key for pasting… section (right click, select Select all, then right click and select Copy)
5. Paste that text into the GitHub page were it says Key.
   NOTE: The thing you copy/paste should start with ssh-rsa and probably end with == rsa-key-20171107 (the numbers would change)
6. Press the *Add SSH key button at the bottom of the form.

That’s it! Now you can use git clone to clone your repo using the Clone with SSH option. That will also give you the ability to use git pull and git push without entering in your password.

Bonus: Linux Server

Have a Linux server already using SSH? Great news, you can follow the same basic steps to allow password-less connections!

GitHub gave us a nice web interface to add the keys. No such luck in Linux (depending on what you think of GUIs). Still, its a relatively simple process.

NOTE: These directions really depend on how sshd is configured; the directions below are most common.

1. mkdir -p ~/.ssh
2. vim ~/.ssh/authorized_keys (or use a command-line editor your familiar with)
3. Add in the same text you pasted into GitHub (ssh-rsa.....== rsa...)
4. Save the file
5. IMPORTANT: Change the permissions: chmod -R 600 ~/.ssh (things may not work without this)

Back on your Windows machine, make another entry in %USERPROFILE%\.ssh\config that points to your Linux server.