6.4 KiB
agenix - age-encrypted secrets for NixOS
agenix
is a commandline tool for managing secrets encrypted with your existing SSH keys. This project also includes the NixOS module age
for adding encrypted secrets into the Nix store and decrypting them.
Problem and solution
All files in the Nix store are readable by any system user, so it is not a suitable place for including cleartext secrets. Many existing tools (like NixOps deployment.keys) deploy secrets separately from nixos-rebuild
, making deployment, caching, and auditing more difficult. Out-of-band secret management is also less reproducible.
agenix
solves these issues by using your pre-existing SSH key infrastructure and age
to encrypt secrets into the Nix store. Secrets are decrypted using an SSH host private key during NixOS system activation.
Features
- Secrets are encrypted with SSH keys
- system public keys via
ssh-keyscan
- can use public keys available on GitHub for users (for example, https://github.com/ryantm.keys)
- system public keys via
- No GPG
- Very little code, so it should be easy for you to audit
- Encrypted secrets are stored in the Nix store, so a separate distribution mechanism is not necessary
Notices
- Password-protected ssh keys: since the underlying tool age/rage do not support ssh-agent, password-protected ssh keys do not work well. For example, if you need to rekey 20 secrets you will have to enter your password 20 times.
- If you want to manage user's hashed passwords, you must use a version of NixOS with commit e6b8587, so the root-owned secrets can be decrypted before the user activation script runs. Currently available on up to date
20.09
andunstable
.
Installation
Choose one of the following methods:
niv (Current recommendation)
First add it to niv:
$ niv add ryantm/agenix
Module
Then add the following to your configuration.nix in the imports
list:
{
imports = [ "${(import ./nix/sources.nix).agenix}/modules/age" ];
}
nix-channel
As root run:
$ nix-channel --add https://github.com/ryantm/agenix/archive/master.tar.gz agenix
$ nix-channel --update
Than add the following to your configuration.nix in the imports
list:
{
imports = [ <agenix/modules/age> ];
}
fetchTarball
Add the following to your configuration.nix:
{
imports = [ "${builtins.fetchTarball "https://github.com/ryantm/agenix/archive/master.tar.gz"}/modules/age" ];
}
or with pinning:
{
imports = let
# replace this with an actual commit id or tag
commit = "298b235f664f925b433614dc33380f0662adfc3f";
in [
"${builtins.fetchTarball {
url = "https://github.com/ryantm/agenix/archive/${commit}.tar.gz";
# replace this with an actual hash
sha256 = "0000000000000000000000000000000000000000000000000000";
}}/modules/age"
];
}
Flakes
Module
{
inputs.agenix.url = "github:ryantm/agenix";
# optional, not necessary for the module
#inputs.agenix.inputs.nixpkgs.follows = "nixpkgs";
outputs = { self, nixpkgs, agenix }: {
# change `yourhostname` to your actual hostname
nixosConfigurations.yourhostname = nixpkgs.lib.nixosSystem {
# change to your system:
system = "x86_64-linux";
modules = [
./configuration.nix
agenix.nixosModules.age
];
};
};
}
CLI
You don't need to install it,
nix run github:ryantm/agenix -- --help
but, if you want to (change the system based on your system):
{
environment.systemPackages = [ agenix.defaultPackage.x86_64-linux ];
}
Tutorial
-
Make a directory to store secrets and
secrets.nix
file for listing secrets and their public keys:$ mkdir secrets $ cd secrets $ touch secrets.nix
-
Add public keys to
secrets.nix
file (hint: usessh-keyscan
or GitHub (for example, https://github.com/ryantm.keys)):let user1 = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIL0idNvgGiucWgup/mP78zyC23uFjYq0evcWdjGQUaBH"; user2 = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILI6jSq53F/3hEmSs+oq9L4TwOo1PrDMAgcA1uo1CCV/"; users = [ user1 user2 ]; system1 = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPJDyIr/FSz1cJdcoW69R+NrWzwGK/+3gJpqD1t8L2zE"; system2 = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIKzxQgondgEYcLpcPdJLrTdNgZ2gznOHCAxMdaceTUT1"; systems = [ system1 system2 ]; in { "secret1.age".publicKeys = [ user1 system1 ]; "secret2.age".publicKeys = users ++ systems; }
-
Edit secret files (these instructions assume your SSH private key is in ~/.ssh/):
$ agenix -e secret1.age
-
Add secret to a NixOS module config:
age.secrets.secret1.file = ../secrets/secret1.age;
-
NixOS rebuild or use your deployment tool like usual.
The secret will be decrypted to the value of
age.secrets.secret1.path
(/run/secrets/secret1
by default). For per-secret options controlling ownership etc, see modules/age.nix.
Rekeying
If you change the public keys in secrets.nix
, you should rekey your
secrets:
$ agenix --rekey
To rekey a secret, you have to be able to decrypt it. Because of
randomness in age
's encryption algorithms, the files always change
when rekeyed, even if the identities do not. (This eventually could be
improved upon by reading the identities from the age file.)
Threat model/Warnings
This project has not be audited by a security professional.
People unfamiliar with age
might be surprised that secrets are not
authenticated. This means that every attacker that has write access to
the secret files can modify secrets because public keys are exposed.
This seems like not a problem on the first glance because changing the
configuration itself could expose secrets easily. However, reviewing
configuration changes is easier than reviewing random secrets (for
example, 4096-bit rsa keys). This would be solved by having a message
authentication code (MAC) like other implementations like GPG or
sops have, however this was left
out for simplicity in age
.
Acknowledgements
This project is based off of sops-nix created Mic92. Thank you to Mic92 for inspiration and advice.