+fun intFromString s =
+ if CharVector.all Char.isDigit s andalso size s > 0 then
+ Int.fromString s
+ else
+ NONE
+
+fun validPort port =
+ case intFromString port of
+ NONE => false
+ | SOME n => n > 0
+
+fun validPortPiece pp =
+ case String.fields (fn ch => ch = #":") pp of
+ [port] => validPort port
+ | [port1, port2] => validPort port1 andalso validPort port2
+
+fun validPorts ports =
+ List.all validPortPiece (String.fields (fn ch => ch = #",") ports)
+
+fun validIp s =
+ case map intFromString (String.fields (fn ch => ch = #".") s) of
+ [SOME n1, SOME n2, SOME n3, SOME n4] =>
+ n1 >= 0 andalso n1 < 256 andalso n2 >= 0 andalso n2 < 256 andalso n3 >= 0 andalso n3 < 256 andalso n4 >= 0 andalso n4 < 256
+ | _ => false
+
+fun isIdent ch = Char.isLower ch orelse Char.isDigit ch
+
+fun validHost s =
+ size s > 0 andalso size s < 20
+ andalso CharVector.all (fn ch => isIdent ch orelse ch = #"-") s
+
+fun validDomain s =
+ size s > 0 andalso size s < 100
+ andalso List.all validHost (String.fields (fn ch => ch = #".") s)
+
+val validHosts = List.all (fn x => validIp x orelse validDomain x)
+
+fun validRule rule =
+ case String.tokens Char.isSpace rule of
+ "Client" :: ports :: hosts => validPorts ports andalso validHosts hosts
+ | "Server" :: ports :: hosts => validPorts ports andalso validHosts hosts
+ | ["LocalServer", ports] => validPorts ports
+ | ["ProxiedServer", ports] => validPorts ports
+ | _ => false
+