tasiaiso.vulpecula.zone/docs/posts/nixos-wifi-agenix.md

---
date: 2024-08-07
unlisted: false
---

# NixOS: Declarative WiFi connections with agenix and NetworkManager

Here I'll show you how to declare WiFi connections for NetworkManager in NixOS, using agenix to store encrypted pre-shared keys.
Thanks to [@TLATER](https://discourse.nixos.org/u/TLATER) for the [answer](https://discourse.nixos.org/t/storing-wifi-passwords-with-agenix-using-networkmanager/50215/2)!

## The agenix part

Here I'll assume you got agenix working. If not, follow [this wiki article](https://nixos.wiki/wiki/Agenix).
  
Create an age-encrypted [environment file](https://www.baeldung.com/linux/environment-variables-file) so that:  
  
```bash
  $ agenix -d crypto/nm-secrets.age
  STARLINK_PSK=MyPSKHere
```

Tell your NixOS config to import it:

```nix
  age.secrets.nm-secrets = {
    file = ../../crypto/nm-secrets.age;
    owner = "root";
    group = "root";
  };
```

## Importing the secrets into NixOS

Now tell NetworkManager to ensure your profile is installed.
To achieve this we'll be using `networking.networkmanager.ensureProfiles.profiles` and `networking.networkmanager.ensureProfiles.environmentFiles`:

```nix
  networking.networkmanager.ensureProfiles = {
    environmentFiles = [
      config.age.secrets.nm-secrets.path
    ];
  
    profiles = {
      Starlink = {
        connection = {
          id = "Starlink";
          type = "wifi";
        };
        ipv4 = {
          method = "auto";
        };
        ipv6 = {
          addr-gen-mode = "stable-privacy";
          method = "auto";
        };
        wifi = {
          mode = "infrastructure";
          ssid = "Starlink";
        };
        wifi-security = {
          key-mgmt = "wpa-psk";
          psk = "$STARLINK_PSK";
        };
      };
    };
  };
```

`networking.networkmanager.ensureProfiles.profiles` first builds a configuration file NetworkManager can understand from the attribute set we pass it, and `networking.networkmanager.ensureProfiles.environmentFiles` tells NixOS to take the configuration and to substitute variable identifiers by their value stored in the `nm-secrets.age` file.

Adjust this configuration as needed using [this documentation](https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/8/html/configuring_and_managing_networking/assembly_networkmanager-connection-profiles-in-keyfile-format_configuring-and-managing-networking).
Rebuild and everything should just work!

## Security considerations

**DISCLAIMER**: I'm pretty sure what I'm saying here is accurate, but I do not have the time nor skills to check this in depth.
Take what I'm saying here with a grain of salt. If I'm wrong, please send me an email containing a minimum of 3 insults.

agenix stores your secrets in an encrypted format in the publicly-available Nix store (`/nix/store/*-nm-secrets.age`) and exposes them in plaintext at `/run/agenix.d/*/nm-secrets` to `root` only.
After decryption, the password is stored in plaintext as part of the connection configuration at `/run/NetworkManager/system-connections/'Starlink'.nmconnection` in a tmpfs only available to `root`.
Additionnally, NetworkManager exposes the PSK to all members of the `networkmanager` group.

To me this looks like a reasonably secure way to store WiFi credentials.