The newfangled approach is something like HashiCorp's Vault, which is a dream when you're looking at more than half a dozen systems with similar roles. A different approach that I like to use for single or smaller cluster systems is Ansible's Vault and rolling out config files based on templates per environment. All actual config files are gitignored so I don't have do deal with conflicts on the server if I use a git-pull style deployment, and ansible itself can backup/version whenever they change.

Additionally, git does keep that history (as it's supposed to), so if you just delete the key from a private repo as you're trying to make the repo public, it's trivial for someone to walk the commit history looking for historical API keys that might not have been rotated. In order to purge that information from git, you then have to go re-write the commit graph from the point of the key's insertion (with it removed) all the way to the present. It's not impossible to do, it's just a major pain.

I'm aware of the implications concerning the history, but sorry, the machine park is two machines. Setting up vault would just be total overkill. The people that have access to that repo change like once every few years. The repo will never go public. Let's keep the solution at least somewhat tailored to the problem.

Hey, I'm not arguing one way or the other. I like using Ansible for configuration in the way I work. I can trust that I can show my best friend and my worst enemy my project and they won't have the capability of making my life hell. Rock on though. Use the simplest solution for the problem at hand. If you're just managing two boxes though, I'd have a hard time coming up with an argument for adding more complexity to the setup to essentially make it unchanged.

It's all chef-based so we could be using encrypted databags, but as anybody with access to the repo has root on the machines anyways, there's little to gain there as well, especially given the very limited security implications. I'd be more worried that somebody adds his account to the sudoers list that stealing the secret data. But hey, things were that way when I joined and there's better places to spend my time to improve security.

All keys are tracked in git's history, so it's a possible attack vector for hackers. You could use https://github.com/sobolevn/git-secret. But beware, anytime you revoke someone's access, you should regenerate all secrets stored in there. In any case you should always regenerate the keys whenever someone's access is revoked

It's a perfectly defensible decision. The standard cryptographer's reply at this point would be, what is your threat model?

If "A developer could have their GitHub account broken into" or "Someone could break into GitHub deeply enough that they could access private repos" are in your threat model, you shouldn't be using GitHub at all for anything, including code, because it would be straightforward to use that access to subvert your site in other ways. Which is to say, especially for small sites, that's not a useful threat model.

If "You might do a git commit to remove them, then push the repo somewhere" is in your threat model, then the answer is just "Don't do that" (or more precisely, "Make sure everyone on the team understands that can't be done without precautions"). The easiest way to don't-do-that is to have them in a separate git repo from your code. But either way, as projects grow, there's going to be stuff in your git history you don't want to be public (like, oh, git commit -m "Implementing this stupid feature because this customer is stupid") because human error happens sometimes. So if you want to publish a previously-private codebase, the only robust approach is to copy all the files into a new non-git repo and make a new commit.

And the other part of the cryptographer's reply is, where else are you going to store the secrets and what are its security properties?

yes, indeed I am. I'm all in favor of keeping the tools used to a level where the effort makes sense to protect the value of the goods. I totally could lock up my newrelic api key in a bank safe, double encrypted with two persons 4096 bit GPG keys, but that would be a little overkill, wouldn't it? Do you do that? I'd be moderately annoyed if somebody started pushing false metrics to my NR account, but that's about all the damage they could do with the information in that repo. So what level of effort would you propose?

Agreed, we do this as well at some scale. The vast majority of application configuration falls into this category. The advantage of storing them in a git repo (we use a different git repo to the main codebase) is that you can re-use the same access control mechanisms (note that is not the same as giving the same people access to the different repos) and you get strong change history.