nixos/stunnel: add module (#33151)

nixos/modules/module-list.nix

···
   ./services/networking/ssh/lshd.nix
   ./services/networking/ssh/sshd.nix
   ./services/networking/strongswan.nix
+  ./services/networking/stunnel.nix
   ./services/networking/supplicant.nix
   ./services/networking/supybot.nix
   ./services/networking/syncthing.nix

nixos/modules/services/networking/stunnel.nix

···
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.services.stunnel;
+  yesNo = val: if val then "yes" else "no";
+
+  verifyChainPathAssert = n: c: {
+    assertion = c.verifyHostname == null || (c.verifyChain || c.verifyPeer);
+    message =  "stunnel: \"${n}\" client configuration - hostname verification " +
+      "is not possible without either verifyChain or verifyPeer enabled";
+  };
+
+  serverConfig = {
+    options = {
+      accept = mkOption {
+        type = types.int;
+        description = "On which port stunnel should listen for incoming TLS connections.";
+      };
+
+      connect = mkOption {
+        type = types.int;
+        description = "To which port the decrypted connection should be forwarded.";
+      };
+
+      cert = mkOption {
+        type = types.path;
+        description = "File containing both the private and public keys.";
+      };
+    };
+  };
+
+  clientConfig = {
+    options = {
+      accept = mkOption {
+        type = types.string;
+        description = "IP:Port on which connections should be accepted.";
+      };
+
+      connect = mkOption {
+        type = types.string;
+        description = "IP:Port destination to connect to.";
+      };
+
+      verifyChain = mkOption {
+        type = types.bool;
+        default = true;
+        description = "Check if the provided certificate has a valid certificate chain (against CAPath).";
+      };
+
+      verifyPeer = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Check if the provided certificate is contained in CAPath.";
+      };
+
+      CAPath = mkOption {
+        type = types.path;
+        default = "${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt";
+        description = "Path to a file containing certificates to validate against.";
+      };
+
+      verifyHostname = mkOption {
+        type = with types; nullOr string;
+        default = null;
+        description = "If set, stunnel checks if the provided certificate is valid for the given hostname.";
+      };
+    };
+  };
+
+
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    services.stunnel = {
+
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Whether to enable the stunnel TLS tunneling service.";
+      };
+
+      user = mkOption {
+        type = with types; nullOr string;
+        default = "nobody";
+        description = "The user under which stunnel runs.";
+      };
+
+      group = mkOption {
+        type = with types; nullOr string;
+        default = "nogroup";
+        description = "The group under which stunnel runs.";
+      };
+
+      logLevel = mkOption {
+        type = types.enum [ "emerg" "alert" "crit" "err" "warning" "notice" "info" "debug" ];
+        default = "info";
+        description = "Verbosity of stunnel output.";
+      };
+
+      fipsMode = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Enable FIPS 140-2 mode required for compliance.";
+      };
+
+      enableInsecureSSLv3 = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Enable support for the insecure SSLv3 protocol.";
+      };
+
+
+      servers = mkOption {
+        description = "Define the server configuations.";
+        type = with types; attrsOf (submodule serverConfig);
+        example = {
+          fancyWebserver = {
+            enable = true;
+            accept = 443;
+            connect = 8080;
+            cert = "/path/to/pem/file";
+          };
+        };
+        default = { };
+      };
+
+      clients = mkOption {
+        description = "Define the client configurations.";
+        type = with types; attrsOf (submodule clientConfig);
+        example = {
+          foobar = {
+            accept = "0.0.0.0:8080";
+            connect = "nixos.org:443";
+            verifyChain = false;
+          };
+        };
+        default = { };
+      };
+    };
+  };
+
+
+  ###### implementation
+
+  config = mkIf cfg.enable {
+
+    assertions = concatLists [
+      (singleton {
+        assertion = (length (attrValues cfg.servers) != 0) || ((length (attrValues cfg.clients)) != 0);
+        message = "stunnel: At least one server- or client-configuration has to be present.";
+      })
+
+      (mapAttrsToList verifyChainPathAssert cfg.clients)
+    ];
+
+    environment.systemPackages = [ pkgs.stunnel ];
+
+    environment.etc."stunnel.cfg".text = ''
+      ${ if cfg.user != null then "setuid = ${cfg.user}" else "" }
+      ${ if cfg.group != null then "setgid = ${cfg.group}" else "" }
+
+      debug = ${cfg.logLevel}
+
+      ${ optionalString cfg.fipsMode "fips = yes" }
+      ${ optionalString cfg.enableInsecureSSLv3 "options = -NO_SSLv3" }
+
+      ; ----- SERVER CONFIGURATIONS -----
+      ${ lib.concatStringsSep "\n"
+           (lib.mapAttrsToList
+             (n: v: ''
+               [${n}]
+               accept = ${toString v.accept}
+               connect = ${toString v.connect}
+               cert = ${v.cert}
+
+             '')
+           cfg.servers)
+      }
+
+      ; ----- CLIENT CONFIGURATIONS -----
+      ${ lib.concatStringsSep "\n"
+           (lib.mapAttrsToList
+             (n: v: ''
+               [${n}]
+               client = yes
+               accept = ${v.accept}
+               connect = ${v.connect}
+               verifyChain = ${yesNo v.verifyChain}
+               verifyPeer = ${yesNo v.verifyPeer}
+               ${optionalString (v.CAPath != null) "CApath = ${v.CAPath}"}
+               ${optionalString (v.verifyHostname != null) "checkHost = ${v.verifyHostname}"}
+               OCSPaia = yes
+
+             '')
+           cfg.clients)
+      }
+    '';
+
+    systemd.services.stunnel = {
+      description = "stunnel TLS tunneling service";
+      after = [ "network.target" ];
+      wants = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+      restartTriggers = [ config.environment.etc."stunnel.cfg".source ];
+      serviceConfig = {
+        ExecStart = "${pkgs.stunnel}/bin/stunnel ${config.environment.etc."stunnel.cfg".source}";
+        Type = "forking";
+      };
+    };
+
+  };
+
+}