From c57925d35aed6f89727e938069914b767b9af92d Mon Sep 17 00:00:00 2001 From: Pacman99 Date: Thu, 13 May 2021 10:35:41 -0700 Subject: [PATCH] document agenix integration Co-authored-by: David Arnold --- doc/secrets.md | 110 +++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 101 insertions(+), 9 deletions(-) diff --git a/doc/secrets.md b/doc/secrets.md index de77c5b8..6afe2f6a 100644 --- a/doc/secrets.md +++ b/doc/secrets.md @@ -1,18 +1,110 @@ # Secrets -Secrets are managed using [git-crypt][git-crypt] so you can keep your flake in -a public repository like GitHub without exposing your password or other -sensitive data. +Secrets are managed using [git-crypt][git-crypt] and [agenix][agenix] +so you can keep your flake in a public repository like GitHub without +exposing your password or other sensitive data. By default, everything in the secrets folder is automatically encrypted. Just be sure to run `git-crypt init` before putting anything in here. +## Agenix +Currently, there is [no mechanism][secrets-issue] in nix itself to deploy secrets +within the nix store because it is world-readable. + +Most NixOS modules have the ability to set options to files in the system, outside +the nix store, that contain sensitive information. You can use [agenix][agenix] +to easily setup those secret files declaratively. + +[agenix][agenix] encrypts secrets and stores them as .age files in your repository. +Age files are encrypted with multiple ssh public keys, so any host or user with a +matching ssh private key can read the data. The [age module][age module] will add those +encrypted files to the nix store and decrypt them on activation to `/run/secrets`. + +### Setup +All hosts must have openssh enabled, this is done by default in the core profile. + +You need to populate your `secrets/secrets.nix` with the proper ssh public keys. +Be extra careful to make sure you only add public keys, you should never share a +private key!! + +secrets/secrets.nix: +```nix +let + system = ""; + user = ""; + allKeys = [ system user ]; +in +``` + +On most systems, you can get your systems ssh public key from `/etc/ssh/ssh_host_ed25519_key.pub`. If +this file doesn't exist you likely need to enable openssh and rebuild your system. + +Your users ssh public key is probably stored in `~/.ssh/id_ed25519.pub` or +`~/.ssh/id_rsa.pub`. If you haven't generated a ssh key yet, be sure do so: +```sh +ssh-keygen -t ed25519 +``` + > ##### _Note:_ -> Currently, there is [no mechanism][secrets-issue] in nix to deploy secrets -> within the nix/store so, if they end up in the nix/store after deployment, they -> will be world readable on that machine. -> -> The author of devos intends to implement a workaround for this situation in -> the near future, but for the time being, simple be aware of this. +> The underlying tool used by agenix, rage, doesn't work well with password protected +> ssh keys. So if you have lots of secrets you might have to type in your password many +> times. + + +### Secrets +You will need the `agenix` command to create secrets. DevOS conveniently provides that +in the devShell, so just run `nix develop` whenever you want to edit secrets. Make sure +to always run `agenix` while in the `secrets/` folder, so it can pick up your `secrets.nix`. + +To create secrets, simply add lines to your `secrets/secrets.nix`: +``` +let + ... + allKeys = [ system user ]; +in +{ + "secret.age".publicKeys = allKeys; +} +``` +That would tell agenix to create a `secret.age` file that is encrypted with the `system` +and `user` ssh public key. + +Then go into the `secrets` folder and run: +```sh +agenix -e secret.age +``` +This will create the `secret.age`, if it doesn't already exist, and allow you to edit it. + +If you ever change the `publicKeys` entry of any secret make sure to rekey the secrets: +```sh +agenix --rekey +``` + +### Usage +Once you have your secret file encrypted and ready to use, you can utilize the [age module][age module] +to ensure that your secrets end up in `/run/secrets`. + +In any profile that uses a NixOS module that requires a secret you can enable a particular secret like so: + +```nix +{ self, ... }: +{ + age.secrets.mysecret.file = "${self}/secrets/mysecret.age"; +} +``` + + +Then you can just pass the path `/run/secrets/mysecret` to the module. + +You can make use of the many options provided by the age module to customize where and how +secrets get decrypted. You can learn about them by looking at the +[age module][age module]. + + +> ##### _Note:_ +> You can take a look at the [agenix repository][agenix] for more information +> about the tool. [git-crypt]: https://github.com/AGWA/git-crypt +[agenix]: https://github.com/ryantm/agenix +[age module]: https://github.com/ryantm/agenix/blob/master/modules/age.nix [secrets-issue]: https://github.com/NixOS/nix/issues/8