Setting up GitBash with SSH on Windows

Introduction

Git is a everyday tool for me. I remember reading about Distributed Version Control from Joel Spolsky years ago, when we decided to switch from SVN to GIT.

Although I use it daily, most of the time it is - set and forget, when it comes to SSH keys to repositories. So whenever I get a new laptop or need to re-initialize repo, I have to re-teach myself the steps to get it working. So this is a bit of a guide, to help me navigate and get back on track when im lost next time.

When we first start GitBash we are started in a home directory and it looks something like below.

If we want to clone a git repository we would type something like the below

git clone git@github.com:username/test.git

Create a New SSH Key

When we do this we are faced with Permission denied error. So we need to setup a SSH key locally and on the git server. Substitute with your email address.

ssh-keygen -t ed25519 -C "User.Name@test.com"

If your using a legacy system that doesn’t support ED25519 use below;

ssh-keygen -t rsa -b 4096 -C "User.Name@test.com"

This will create 2 key files locally one publickey with postfix of .pub and one passphrase protected key with no postfix.

Local Setup

Although this key is registered we need to run the ssh-agent and add the key to it.

# start the ssh-agent in the background
$ eval "$(ssh-agent -s)"
> Agent pid 59566

Add your SSH private key to the ssh-agent. If you created the key with a different name, replace the id_rsa with the name of your key.

ssh-add /c/NotBackedUp/id_rsa

Remote Setup

Not it is registered locally, we also need to give the key to the repository. So we sign into github and add the key

Navigate to Settings > SSH and GPG Keys

Click on New SSH Key

and copy and paste the contents of the .pub file extension that was created earlier.

Now we can attempt to clone the directory again.

git clone git@github.com:username/test.git

Yay, it is working. Well, Yes and No, if you close gitbash and reopen it, these setting will all be forgotten so you would need to follow the “local” steps Each time you relaunch gitbash. Not really ideal.

Automate the launching of Agent and Keys

In gitbash if we setup a .ssh directory and a loading script we can have gitbash auto associate the keys and load the agents.

mkdir -p ~/.ssh

We can also create the following files if they don’t exist

touch ~/.ssh/config
touch ~/.bash_profile
touch ~/.bashrc

If you open up ~/.ssh/config you can add the following text

 Host github.com
 Hostname github.com
 IdentityFile ~/.ssh/id_rsa

The Host and HostName may differ if you have different repository URL’s you use at work.

Now we need to make sure the SSH Agent Starts whenever Git Bash is started. So we edit the ~/.bash_profile

test -f ~/.profile &&.~/.profile
test -f ~/.bashrc &&.~/.bashrc

and lastly edit the ~/.bashrc

# Start SSH Agent
#----------------------------

SSH_ENV="$HOME/.ssh/environment"

function run_ssh_env {
    ."${SSH_ENV}"> /dev/null
}

function start_ssh_agent {
    echo "Initializing new SSH agent..."
    ssh-agent | sed 's/^echo/#echo/'> "{SSH_ENV}"
    echo"succeeded"  
    chmod 600 "${SSH_ENV}"  
    
    run_ssh_env;  
    
    ssh-add ~/.ssh/id_rsa;
}

if [ -f"${SSH_ENV}" ];then  
    run_ssh_env;  
    ps -ef | grep ${SSH_AGENT_PID}| grep ssh-agent$ > /dev/null || {      
        start_ssh_agent;  
    }
else  
    start_ssh_agent;
fi

Test to see if it all works, close gitbash and re-open. Navigate to a repository and run;

cd test
git pull test

It will ask you for your passphrase and will authenticate.

Chris Hillman