Adding SSH To GitHub

Between the Thanksgiving holiday and some shifting priorities when I got back to work, I hadn’t made any new commits to my GitHub account for about 10 days. This meant that I didn’t have any new posts to my recently-launched GitCommit site that makes a bit of a microblog from my commit messages. To be honest, putting it together was really an excuse to have something up at the domain I bought, but I really like the way it turned out. After making a fresh commit yesterday, though, I received an email from GitHub telling me:

You recently used a password to access the repository at {repo-name} with git using git/2.25.1.

Basic authentication using a password to Git is deprecated and will soon no longer work.

It also included a link to their authentication requirements documentation. On the whole it made sense to me; I typically would just have git remember my credentials so that I never had to enter them. In the new setup, I would have to enter them, though I could configure how long they would remain cached. On the surface, this didn't bother me, and I went about my day making several additional commits beyond the first. Later on, though, I realized that my new commits weren't appearing on the GitCommit site. The site is hosted by Netlify, and it works by polling my GitHub account via a cron job every 4 hours (I'm hoping to eventually update it to use webhooks to have commit information pushed to it, but I haven't had an opportunity yet.) When a new commit happens, my code pulls the repository, the commit message, and the timestamp. It then updates the HTML and automatically makes an additional commit on its own repository (yes, I included code to avoid an endless repost loop.) Netlify has been configured to look at only the html directory in the repository, dynamically updating whenever a new change is commited to that directory, much like how GitHub Pages or any other CI web hosting works.

Since my new commits weren’t showing up, I first checked the GitHub repo for GitCommit. No new HTML changes had been commited to it. Next, I went to the VPS which executes the cron job. For my own sanity, I long ago learned that I should implement some type of logging for any code that I plan to run automatically so that I can easily troubleshoot it during this exact situation. Checking the log file, I saw that my code did successfully find the new commits and update the appropriate HTML file. It was able to make the expected commit, and running git status even confirmed that my local repository was ahead of the remote by 2 commits. However, running the following didn't work to push my changes up to GitHub so that Netlify could see them:

git push origin main

Suddenly it clicked, and I realized that the change from earlier in the day was the culprit; my code could no longer git push because that was now prompting for a password that would never be typed given that the code was executed by cron. To confirm, I manually executed the script from my SSH session and saw the password prompt appear. Ick.

Fortunately, I realized that I wouldn’t need a password if I was syncing my repository via SSH rather than HTTPS. SSH would allow me to use certificates instead. First, I had to generate a new public-private key pair with:

ssh-keygen -t ed25519 -C "email@email.com"

Yeah, I’m not telling you my email address. I’ll give you a hint; it’s something@unusually.pink. Good luck. The above command asked for a couple of things such as the location where I wanted to store the keys and if I wanted to add a password for accessing them. I just took the defaults. Next up, I had to start a background SSH agent and tell it to use the private key I had just generated:

eval "$(ssh-agent -s)" ssh-add ~/.ssh/id_ed25519

With everything set on the client side, I now had to tell GitHub to use my public key for any SSH interactions. They have very solid documentation available with the exact steps. Just be sure you actually copy the content of the public key into GitHub rather than the private key. GitHub won’t accept the private key because the formatting is wrong, but the very fact that I pasted it there made me paranoid enough to regenerate the pair and do it again.

To test things out, I tried to clone one of my private repositories via the SSH link, which you can select from the tabs when trying to clone anything from GitHub.

That worked successfully and verified that my keys were properly identifying me. The last step was to update the local repository for GitCommit to use a new URL for the remote repository. Regardless of whether I’m using HTTPS or SSH, I still run git push origin main in order to sync it to the remote; the configuration of the local repository is what specifies which URL is used. In order to flip mine from HTTPS to SSH, I simply ran the following from my local directory for GitCommit:

git remote set-url origin git@github.com:{repo-name}

After this, I re-ran my script and git push was able to successfully push my code to the remote without any interaction. After working through many commits today, I verified that my website was updated as expected.

As a bonus note, astute readers may recall the issues I had following the published steps to sync the Dracula theme for git. This was the exact same scenario where the instructions assumed that SSH was in use rather than HTTPS.

Originally published at https://looped.network on December 23, 2020.