/md5server/md5server/Program.cs

// Licensed under Stallman's beard



using System;

using System.Net;

using System.Net.Sockets;

using System.Text;

using System.Security.Cryptography;

using System.Text.RegularExpressions;

using System.IO;



namespace server

{

    class MainClass

    {

        static bool isMD5(string s)

        {

            if (!String.IsNullOrEmpty(s))

            {

                if (Regex.IsMatch(s, @"[a-fA-F0-9]{32}"))

                    return true;

            }

            return false;

        }

		

		static bool logSanity(string logFile){

			StreamReader SR = new StreamReader(logFile);

			StringBuilder stringBuffer = new StringBuilder("");

			string logRegex = @"^[\d/: ]+[AP]M.*Hash: [a-fA-F0-9]{32}.*Last Cracked: \d+$";

			// only needs to check the latest log; that is, the first 3 lines

			for (int i = 0; i < 3; i++){

				stringBuffer.Append(SR.ReadLine());

			}

			Match match = Regex.Match(stringBuffer.ToString(),logRegex,RegexOptions.Singleline);

			if (match.Success){

				return true;

			}

			return false;

		}

		

		static void writeLog(string logFile, string hash, int last){

			if (!File.Exists(logFile)){

				File.Create(logFile);

			}

			StreamReader SR = new StreamReader(logFile);

			StringBuilder textBuffer = new StringBuilder("");

			textBuffer.AppendLine(DateTime.Now.ToString());

			textBuffer.AppendLine("Hash: " + hash);

			textBuffer.AppendLine("Last Cracked: " + last.ToString());

			for (int i = 0; i < 20; i++)

				textBuffer.Append('-');

			textBuffer.AppendLine();

			textBuffer.Append(SR.ReadToEnd());

			SR.Close();

			StreamWriter SW = new StreamWriter(logFile);

			SW.Write(textBuffer.ToString());

			SW.Close();

		}

		

        static void Main(string[] args)

        {

            // TODO: debug that weird 'client started before server' thing (maybe on client)

            // TODO: find minimum byte size



            int start = 0;

            int listeningPort = 8008;

            int remotePort = 8009;

            string returnData = "";

            string plaintext = "";

            string hash = null;

            string logFile = @"./md5log.txt";

            if (File.Exists(logFile))

            {

				if (logSanity(logFile)){

                	StreamReader SR = File.OpenText(logFile);

					SR.ReadLine();

               		string tempmd5 =  SR.ReadLine().Split()[1];

                	if (isMD5(tempmd5))

               		 {

                    	hash = tempmd5;

                   	 	Int32.TryParse(SR.ReadLine().Split()[2], out start);

                	}

                	SR.Close();

				} else {

					Console.WriteLine("Corrupt log file. Proceeding without.");

				}

				

            } else {

				Console.WriteLine("No log found. Proceeding without");

			}



            // check that hash contains a valid MD5 sum

            setHash(ref hash);

            if (hash == null)

            {

                if (args.Length > 0 && isMD5(args[0]))

                    hash = args[0];

                else

                {

                    while (!isMD5(hash))

                    {

                        Console.WriteLine("MD5 hash not present or not valid. Please enter MD5 hash");

                        hash = Console.ReadLine();

                    }

                }

				File.Create(logFile);

				start = 0;

            }

			

			if(!File.Exists(logFile)){

				writeLog(logFile,hash,start);

			}

				

			

            bool complete = false;



            UdpClient udpClient = new UdpClient(listeningPort);

            Byte[] recieveBytes = new Byte[1024]; // buffer to read the data into 1 kilobyte at a time

            //the IP Address.any allows any valid matching address for this machine to be used

            //i.e. loopback, broadcast, IPv4, IPv6

            IPEndPoint remoteIPEndPoint = new IPEndPoint(IPAddress.Any, listeningPort);  //open port 8008 on this machine

            Console.WriteLine("Server is Started");



            //recieve the data from the UDP packet

            //loop until q is sent

            while (true)

            {

                recieveBytes = udpClient.Receive(ref remoteIPEndPoint);

                returnData = Encoding.ASCII.GetString(recieveBytes);

                returnData.TrimEnd();

                if (!complete && returnData.Length > 2)

                { // a bit shitty, checks the packet has something

                    if (returnData.Substring(0, 3) == "NEW")

                    {

                        sendBlock(start, remoteIPEndPoint.Address, remotePort,hash);

						writeLog(logFile,hash,start);

                        start += Int32.Parse(returnData.Substring(3));

                    }

                    if (returnData.Substring(0, 3) == "FIN")

                    {

                        plaintext = returnData.Substring(3);

                        complete = true;

                        Console.WriteLine(plaintext);

                    }

                }

                else

                {

                    sendFin(remoteIPEndPoint.Address, remotePort);

                }



            }

        }

        static void setHash(ref string hash)

        {

            if (!String.IsNullOrEmpty(hash))

            {

                Console.WriteLine("Found hash {0} in file, use this? [Y/n]", hash);

                string response = Console.ReadLine();

                while (true)

                {

                    switch (response)

                    {

                        case "y":

                            return;

                        case "":

                            return;

                        case "n":

                            hash = null;

                            return;

                        default:

                            Console.WriteLine("Please enter y or n");

                            response = Console.ReadLine();

                            break;

                    }

                }

            }

        }



        static void sendBlock(int start, IPAddress dest, int port, string hash)

        {

            UdpClient client = new UdpClient();

            Byte[] sendBytes = new Byte[1024];

            try

            {

                client.Connect(dest, port);

                sendBytes = Encoding.ASCII.GetBytes("NEW" + hash + start);

                client.Send(sendBytes, sendBytes.GetLength(0));

                Console.WriteLine("Sent block {0} to {1}", start, dest.ToString());

            }

            catch (Exception e)

            {

                Console.WriteLine("Error with the Server Name: {0}", e.ToString());

            }

        }

        static void sendFin(IPAddress dest, int port)

        {

            UdpClient client = new UdpClient();

            Byte[] sendBytes = new Byte[1024];

            try

            {

                client.Connect(dest, port);

                sendBytes = Encoding.ASCII.GetBytes("FIN");

                client.Send(sendBytes, sendBytes.GetLength(0));

                Console.WriteLine("Sent FIN to {0}", dest.ToString());

            }

            catch (Exception e)

            {

                Console.WriteLine("Error with the Server Name: {0}", e.ToString());

            }

        }

    }

}