homeage - runtime decrypted age secrets for nix home manager

homeage is a module for home-manager that enables runtime decryption of declarative age files.

Features

• File agnostic declarative secrets that can be used inside your home-manager flakes
• Each secret gets decrypted with its own systemd service integrating seamlessly with home-manager reload and update
• Just normal age encryption, use ssh or age keys
• Add symbolic links to decrypted files
• Extremely little bash script so inspect the source yourself!

Management Scheme

Pre-Build: Files are encrypted by external age key in repository (unencrypted with associated public key on roadmap)

Post-Build: Files are encrypted by external age key while in nix store

Runtime: Files are stored unencrypted in /run/user/$UID/secrets and can be symlinked to other locations

Notes (in progress fixes):

1. All home.file.<name>.symlinks are not cleaned up on new home-manager generation. Therefore a symlink that points to a decrypted yaml file named hello in one generation, instead of being deleted will point to a png file named hello in the next.

2. The /run secrets folder is not cleaned on home-manager activation. Therefore old secrets will exist decrypted until reboot.

3. Use the cpOnService at your own risk, as cleanup is not implemented the decrypted file will exist until manually deleted

Roadmap

• Implement cleanup
• Support passphrases
• Support unencrypted with public key files
• Add activation checks
• Add tests

Getting started

Nix Flakes

While the following below is immense, its mostly just home manager flake boilerplate. All you need to do is import homeage.homeManagerModules.homeage into the configuration and set a valid homeage.identityPaths and your all set.

{
  inputs = {
    nixpkgs.url = "nixpkgs/nixos-unstable";
    home-manager = {
      url = "github:nix-community/home-manager";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    homeage = {
      url = "github:jordanisaacs/homeage";
      # Optional
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { nixpkgs, homeage, ... }@inputs:
    let
      pkgs = import nixpkgs {
        inherit system;
      };
      
      system = "x86-64_linux";
      username = "jd";
      stateVersion = "21.05";
    in {
      homeManagerConfigurations = {
        jd = home-manager.lib.homeManagerConfiguration {
          inherit system stateVersion username pkgs;
          home.homeDirectory = "/home/${username}";

          configuration = {
            home.stateVersion = stateVersion;
            home.username = username;
            home.homeDirectory = "/home/${username}";

            # CHECK HERE for homeage configuration
            homeage.identityPaths = [ "~/.ssh/id_ed25519" ];
            homeage.file."pijulsecretkey" = {
              source = ./secretkey.json.age;
              path = "pijul/secretkey.json";
              symlinks = [ "${config.xdg.configHome}/pijul/secretkey.json" ];
            };

            imports = [ homeage.homeManagerModules.homeage ];
          };
        };
      };
    };
}

Options

Check out all the options

How it works

On home manager build, the age-encrypted files are built into the nix store and symlinked to the provided homeage.folder path. This is achieved through the home-manager home.file option. Notice that all secret files are encrypted while in the nix store. After the symlinks are finished by home-manager, the systemd units are run. Each secret has its own oneshot service that runs a decryption script. This works seamlessly with home-managers updating/reloading of systemd units. The script decrypts the secrets to /run/user/$UID/secrets/ using the identities provided by homeage.identityPaths. It then acts on the decrypted file (changing ownership, linking, etc.). When rebooting, the decrypted files are lost as they are in the /run folder. Therefore, the systemd unit is wanted by default.target so it will run on startup.

Acknowledgments

The inspiration for this came from RaitoBezarius' pull request to agenix. I have been trying to figure out how to do secrets with home manager for a while and that PR laid out the foundational ideas for how to do it!