nixos-vps/modules/adguard.nix

# AdGuard Home Module
# Provides: Private DNS-over-HTTPS with ClientID-based access control
#
# Usage:
#   myModules.adguard = {
#     enable = true;
#     domain = "dns.example.com";
#     clients = [
#       { name = "phone"; idSecret = "adguard_client_phone"; }
#     ];
#   };

{
  config,
  lib,
  pkgs,
  ...
}:

let
  cfg = config.myModules.adguard;
in
{
  options.myModules.adguard = {
    enable = lib.mkEnableOption "AdGuard Home DNS server";

    domain = lib.mkOption {
      type = lib.types.str;
      example = "dns.example.com";
      description = "Public domain name for DoH endpoint";
    };

    port = lib.mkOption {
      type = lib.types.port;
      default = 3000;
      description = "Internal port for AdGuard HTTP/DoH listener";
    };

    upstreamDoh = lib.mkOption {
      type = lib.types.str;
      default = "https://dns.mullvad.net/dns-query";
      description = "Upstream DoH server URL";
    };

    bootstrapDns = lib.mkOption {
      type = lib.types.listOf (lib.types.str);
      default = [ "194.242.2.2" "2a07:e340::2" ];
      description = "Bootstrap DNS servers for resolving DoH upstream";
    };

    clients = lib.mkOption {
      type = lib.types.listOf (lib.types.submodule {
        options = {
          name = lib.mkOption {
            type = lib.types.str;
            description = "Friendly name for client device";
          };
          idSecret = lib.mkOption {
            type = lib.types.str;
            description = "SOPS secret name containing the ClientID";
          };
        };
      });
      default = [ ];
      description = "List of clients with their ClientID secrets";
    };
  };

  config = lib.mkIf cfg.enable {
    # Ensure Podman is enabled
    myModules.podman.enable = true;

    # AdGuard Home Container
    virtualisation.oci-containers.containers."adguard" = {
      image = "docker.io/adguard/adguardhome:latest";
      ports = [ "127.0.0.1:${toString cfg.port}:3000/tcp" ];
      extraOptions = [
        "--cap-drop=ALL"
        "--read-only"
        "--tmpfs=/tmp"
      ];
      volumes = [
        "${config.sops.templates."adguardhome.yaml".path}:/opt/adguardhome/conf/AdGuardHome.yaml:ro"
        "adguard-data:/opt/adguardhome/work"
      ];
    };

    # SOPS template for AdGuard configuration
    sops.templates."adguardhome.yaml" = {
      content = ''
        http:
          address: 0.0.0.0:3000

        dns:
          upstream_dns:
            - ${cfg.upstreamDoh}
          bootstrap_dns:
            ${lib.concatStringsSep "\n            " (map (d: "- ${d}") cfg.bootstrapDns)}
          querylog_enabled: true
          querylog_file_enabled: true
          statistics_enabled: true

        clients:
          persistent:
            ${lib.concatStringsSep "\n            " (
              map (client: ''
                - name: ${client.name}
                  ids:
                    - ${config.sops.placeholder.${client.idSecret}}
              '') cfg.clients
            )}

        filtering:
          protection_enabled: true
          filtering_enabled: true

        safebrowsing:
          enabled: false

        parental:
          enabled: false

        safesearch:
          enabled: false

        log:
          file: ""
          max_backups: 0
          max_size: 100
          compress: false
          local_time: false
          verbose: false
      '';
    };

    # Auto-declare SOPS secrets for each client
    sops.secrets = lib.mkMerge (
      map (client: {
        ${client.idSecret} = { };
      }) cfg.clients
    );

    # Nginx configuration for DoH endpoint
    services.nginx.virtualHosts."${cfg.domain}" = {
      enableACME = true;
      forceSSL = true;

      # Regex location to match /dns-query and /dns-query/{clientId}
      locations."~ ^/dns-query" = {
        proxyPass = "http://127.0.0.1:${toString cfg.port}";
        extraConfig = ''
          proxy_http_version 1.1;
          proxy_set_header Host $host;
          proxy_set_header X-Real-IP $remote_addr;
          proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
          proxy_set_header X-Forwarded-Proto $scheme;

          # DoH uses POST with application/dns-message
          proxy_pass_request_body on;
          proxy_set_header Content-Type "application/dns-message";

          # Buffer settings for DNS queries
          proxy_buffers 8 16k;
          proxy_buffer_size 32k;
        '';
      };

      # Block all other paths including admin UI
      locations."/" = {
        return = "404";
      };
    };

    # Ensure nginx user can access ACME certs
    users.users.nginx.extraGroups = [ "acme" ];
  };
}