nixos/taskserver: Add trust option to config file

The server starts up without that option anyway, but it complains about
its value not being set. As we probably want to have access to that
configuration value anyway, let's expose this via the NixOS module as
well.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

nixos/modules/services/misc/taskserver.nix

@@ -47,6 +47,7 @@ let
     ${mkConfLine "server.crl" cfg.server.crl}
 
     # certificates
+    ${mkConfLine "trust" cfg.server.trust}
     ${if needToCreateCA then ''
       ca.cert = ${cfg.dataDir}/keys/ca.cert
       server.cert = ${cfg.dataDir}/keys/server.cert
@@ -233,6 +234,19 @@ in {
             a configuration file reload before the next request is handled.
           '';
         };
+
+        trust = mkOption {
+          type = types.enum [ "allow all" "strict" ];
+          default = "strict";
+          description = ''
+            Determines how client certificates are validated.
+
+            The value <literal>allow all</literal> performs no client
+            certificate validation. This is not recommended. The value
+            <literal>strict</literal> causes the client certificate to be
+            validated against a CA.
+          '';
+        };
       };
     };
   };