nix-configs/modules/services/oauth2Proxy/integration.nix

{
  lib,
  config,
  ...
}:
let
  inherit (lib)
    mkIf
    mkOption
    mkMerge
    attrNames
    mapAttrsToList
    ;
  inherit (lib.types)
    str
    nullOr
    submodule
    listOf
    attrsOf
    ;
  cfg = config.xyno.services.oauth2Proxy;
  kanidmCfg = config.xyno.services.kanidm;
  oauth2ProxyInternalHostPort = "127.0.0.4:4180";
  oauth2ProxyInternalHostPortMetrics = "127.0.0.4:4181";
in
{
  options.xyno.services.oauth2Proxy = {
    domain = mkOption {
      default = "oauth.xyno.systems";
      type = str;
    };
    hosts = mkOption {
      type = attrsOf (
        submodule (
          { name, ... }:
          {
            options.allowedGroups = mkOption {
              type = nullOr (listOf str);
              default = null;
            };
            options.allowed_email_domains = mkOption {
              type = nullOr (listOf str);
              default = null;
            };
            options.allowed_emails = mkOption {
              type = nullOr (listOf str);
              default = null;
            };
            options.middlewares = mkOption {
              type = listOf str;
              description = "add to your service";
              default = [
                "oauth-errors"
                "oauth-host-${name}"
              ];
            };
          }
        )
      );
      example = {
        "navidrome.xyno.systems" = {
          allowedGroups = [ "navidrome_access@idm.xyno.systems" ];
        };
      };
      default = { };
    };
  };
  config = mkIf (cfg.enable && config.xyno.services.kanidm.enable) {
    services.kanidm.provision = {
      groups = {
        proxy_users.members = [ "application_admins" ];
      };
      systems.oauth2.oauth2_proxy = {
        displayName = "oauth2 proxy";
        originUrl = [
          "https://${cfg.domain}/oauth2/callback"
        ]
        ++ (mapAttrsToList (n: v: "https://${n}/oauth2/callback") cfg.hosts);
        originLanding = "https://${cfg.domain}/oauth2/sign_in";
        preferShortUsername = true;
        claimMaps = {
          "proxy_group" = {
            joinType = "array";
            valuesByGroup = {
              "proxy_users" = [
                "proxy_users"
              ];
            };
          };
        };
        scopeMaps."proxy_users" = [
          "email"
          "openid"
        ];
      };
    };
    xyno.services.kanidm.templates.oauth2_proxy = {
      wantedBy = [
        "oauth2-proxy.service"
      ];
      text = p: ''
        OAUTH2_PROXY_CLIENT_ID=${p.clientId}
        OAUTH2_PROXY_CLIENT_SECRET=${p.basicSecret}
        OAUTH2_PROXY_COOKIE_SECRET=${p.env "COOKIE_SECRET"}
        OAUTH2_PROXY_OIDC_ISSUER_URL=https://${kanidmCfg.domain}/oauth2/openid/${p.clientId}
      '';
      environmentFiles = [ config.sops.templates.oauth2ProxyEnv.path ];
    };
    sops.secrets."oauth2Proxy/cookieSecret" = {
      sopsFile = ../../../instances/${config.networking.hostName}/secrets/kanidm.yaml;
    };
    sops.templates."oauth2ProxyEnv" = {
      restartUnits = [ "generate-kanidm-template-oauth2_proxy.service" ];
      content = ''
        COOKIE_SECRET=${config.sops.placeholder."oauth2Proxy/cookieSecret"}
      '';
    };

    xyno.services.monitoring.exporters.oauth2Proxy = "http://${oauth2ProxyInternalHostPortMetrics}";

    systemd.services.oauth2Proxy.after = [ "traefik.service" ];
    xyno.services.oauth2Proxy = {
      environmentFiles = [ kanidmCfg.templates.oauth2_proxy.path ];
      settings = mkMerge [
        {
          provider = "oidc";
          scope = "openid email";
          oidc_groups_claim = "proxy_group";
          allowed_groups = [ "proxy_users" ];

          http_address = "${oauth2ProxyInternalHostPort}";
          https_address = "";
          whitelist_domains = attrNames cfg.hosts;
          email_domains = "*";
          skip_provider_button = true;
          code_challenge_method = "S256";
          set_xauthrequest = true;
        }
        (mkIf config.xyno.services.monitoring.enable {
          metrics_address = "http://${oauth2ProxyInternalHostPortMetrics}";

        })
      ];
    };

    xyno.services.traefik.simpleProxy = mkMerge (
      [
        {
          oauth = {
            rule = "Host(`${cfg.domain}`) && PathPrefix(`/oauth2`)";
            internal = "http://${oauth2ProxyInternalHostPort}";
            middlewares = [ "auth-headers" ];
            host = cfg.domain;
          };
        }
      ]
      ++ (mapAttrsToList (n: v: {
        "oauth-host-${n}" = {
          rule = "Host(`${n}`) && PathPrefix(`/oauth2`)";
          internal = "http://${oauth2ProxyInternalHostPort}";
          middlewares = [ "auth-headers" ];
          host = n;
        };
      }) cfg.hosts)
    );
    services.traefik.dynamicConfigOptions.http.middlewares = mkMerge (
      (mapAttrsToList (n: v: {
        "oauth-host-${n}" =
          let
            maybeQueryArg =
              name: value:
              if name == "middlewares" || value == null then
                null
              else
                "${name}=${lib.concatStringsSep "," (builtins.map lib.escapeURL value)}";
            allArgs = lib.mapAttrsToList maybeQueryArg v;
            cleanArgs = builtins.filter (x: x != null) allArgs;
            cleanArgsStr = lib.concatStringsSep "&" cleanArgs;
          in
          {
            forwardAuth = {
              address = "https://${cfg.domain}/oauth2/auth?${cleanArgsStr}";
              authResponseHeaders = [
                "X-Auth-Request-User"
                "X-Auth-Request-Groups"
                "X-Auth-Request-Email"
                "X-Auth-Request-Preferred-Username"
              ];
              trustForwardHeader = true;
            };
          };
      }) cfg.hosts)
      ++ [
        {
          auth-headers.headers = {
            frameDeny = true;
            contentTypeNosniff = true;
          };
          oauth-errors.errors = {
            status = [ "401-403" ];
            service = config.xyno.services.traefik.simpleProxy.oauth.serviceName;
            query = "/oauth2/sign_in?rd={url}";
          };
        }
      ]
    );
  };
}