shellinabox service: intial implementation

nixos/modules/module-list.nix

@@ -383,6 +383,7 @@
   ./services/web-servers/lighttpd/gitweb.nix
   ./services/web-servers/nginx/default.nix
   ./services/web-servers/phpfpm.nix
+  ./services/web-servers/shellinabox.nix
   ./services/web-servers/tomcat.nix
   ./services/web-servers/uwsgi.nix
   ./services/web-servers/varnish/default.nix

nixos/modules/services/web-servers/shellinabox.nix

@@ -0,0 +1,122 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.services.shellinabox;
+
+  # If a certificate file is specified, shellinaboxd requires
+  # a file descriptor to retrieve it
+  fd = "3";
+  createFd = optionalString (cfg.certFile != null) "${fd}<${cfg.certFile}";
+
+  # Command line arguments for the shellinabox daemon
+  args = [ "--background" ]
+   ++ optional (! cfg.enableSSL) "--disable-ssl"
+   ++ optional (cfg.certFile != null) "--cert-fd=${fd}"
+   ++ optional (cfg.certDirectory != null) "--cert=${cfg.certDirectory}"
+   ++ cfg.extraOptions;
+
+  # Command to start shellinaboxd
+  cmd = "${pkgs.shellinabox}/bin/shellinaboxd ${concatStringsSep " " args}";
+
+  # Command to start shellinaboxd if certFile is specified
+  wrappedCmd = "${pkgs.bash}/bin/bash -c 'exec ${createFd} && ${cmd}'";
+
+in
+
+{
+
+  ###### interface
+
+  options = {
+    services.shellinabox = {
+      enable = mkEnableOption "shellinabox daemon";
+
+      user = mkOption {
+        type = types.str;
+        default = "root";
+        description = ''
+          User to run shellinaboxd as. If started as root, the server drops
+          privileges by changing to nobody, unless overridden by the
+          <literal>--user</literal> option.
+        '';
+      };
+
+      enableSSL = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether or not to enable SSL (https) support.
+        '';
+      };
+        
+      certDirectory = mkOption {
+        type = types.nullOr types.path;
+        default = null;
+        example = "/var/certs";
+        description = ''
+          The daemon will look in this directory far any certificates.
+          If the browser negotiated a Server Name Identification the daemon
+          will look for a matching certificate-SERVERNAME.pem file. If no SNI
+          handshake takes place, it will fall back on using the certificate in the
+          certificate.pem file.
+
+          If no suitable certificate is installed, shellinaboxd will attempt to
+          create a new self-signed certificate. This will only succeed if, after
+          dropping privileges, shellinaboxd has write permissions for this
+          directory.
+        '';
+      };
+
+      certFile = mkOption {
+        type = types.nullOr types.path;
+        default = null;
+        example = "/var/certificate.pem";
+        description = "Path to server SSL certificate.";
+      };
+
+      extraOptions = mkOption {
+        type = types.listOf types.str;
+        default = [ ];
+        example = [ "--port=443" "--service /:LOGIN" ];
+        description = ''
+          A list of strings to be appended to the command line arguments
+          for shellinaboxd. Please see the manual page
+          <link xlink:href="https://code.google.com/p/shellinabox/wiki/shellinaboxd_man"/>
+          for a full list of available arguments.
+        '';
+      };
+
+    };
+  };
+
+  ###### implementation
+
+  config = mkIf cfg.enable {
+
+    assertions =
+      [ { assertion = cfg.enableSSL == true
+            -> cfg.certDirectory != null || cfg.certFile != null;
+          message = "SSL is enabled for shellinabox, but no certDirectory or certFile has been specefied."; }
+        { assertion = ! (cfg.certDirectory != null && cfg.certFile != null);
+          message = "Cannot set both certDirectory and certFile for shellinabox."; }
+      ];
+
+    systemd.services.shellinaboxd = {
+      description = "Shellinabox Web Server Daemon";
+
+      wantedBy = [ "multi-user.target" ];
+      requires = [ "sshd.service" ];
+      after = [ "sshd.service" ];
+
+      serviceConfig = {
+        Type = "forking";
+        User = "${cfg.user}";
+        ExecStart = "${if cfg.certFile == null then "${cmd}" else "${wrappedCmd}"}";
+        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
+      };
+    };
+  };
+}