using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Net.Sockets;
using System.Net;
 
namespace MJsniffer
{
    public enum Protocol
    {
        TCP = 6,
        UDP = 17,
        Unknown = -1
    };
 
    public partial class MJsnifferForm : Form
    {
        private Socket mainSocket; // Socket który przechwytuje wszystkie pakiety
        private byte[] byteData = new byte[4096];
        private bool bContinueCapturing = false; // flaga która sprawdza czy pakiety zostały złapane poprawnie
        private delegate void AddTreeNode(TreeNode node);
 
        public MJsnifferForm()
        {
            InitializeComponent();
        }
 
        private void btnStart_Click(object sender, EventArgs e)
        {
            if (cmbInterfaces.Text == "")
            {
                MessageBox.Show("Select an Interface to capture the packets.", "Sniffer",
                    MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }
 
            try
            {
                if (!bContinueCapturing)
                {
                    btnStart.Text = "&Stop";
                    bContinueCapturing = true;
 
                    mainSocket = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.IP);
                    mainSocket.Bind(new IPEndPoint(IPAddress.Parse(cmbInterfaces.Text), 0));
 
                    mainSocket.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.HeaderIncluded, true);
 
                    byte[] byTrue = new byte[4] { 1, 0, 0, 0 };
                    byte[] byOut = new byte[4] { 1, 0, 0, 0 };
 
                    mainSocket.IOControl(IOControlCode.ReceiveAll, byTrue, byOut);
 
                    mainSocket.BeginReceive(byteData, 0, byteData.Length, SocketFlags.None,
                        new AsyncCallback(OnReceive), null);
                }
                else
                {
                    btnStart.Text = "&Start";
                    bContinueCapturing = false;
                    mainSocket.Close();
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Sniffer", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
 
        private void OnReceive(IAsyncResult ar)
        {
            try
            {
                int nReceived = mainSocket.EndReceive(ar);
                ParseData(byteData, nReceived);
 
                if (bContinueCapturing)
                {
                    byteData = new byte[4096];
                    mainSocket.BeginReceive(byteData, 0, byteData.Length, SocketFlags.None,
                        new AsyncCallback(OnReceive), null);
                }
            }
            catch (ObjectDisposedException) { }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Sniffer", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
 
        private void ParseData(byte[] byteData, int nReceived)
        {
            TreeNode rootNode = new TreeNode();
            IPHeader ipHeader = new IPHeader(byteData, nReceived);
            TreeNode ipNode = MakeIPTreeNode(ipHeader);
            rootNode.Nodes.Add(ipNode);
 
            switch (ipHeader.ProtocolType)
            {
                case Protocol.TCP:
                    TCPHeader tcpHeader = new TCPHeader(ipHeader.Data, ipHeader.MessageLength);
                    TreeNode tcpNode = MakeTCPTreeNode(tcpHeader);
                    rootNode.Nodes.Add(tcpNode);
 
                    if (tcpHeader.DestinationPort == "53" || tcpHeader.SourcePort == "53")
                    {
                        TreeNode dnsNode = MakeDNSTreeNode(tcpHeader.Data, (int)tcpHeader.MessageLength);
                        rootNode.Nodes.Add(dnsNode);
                    }
                    break;
 
                case Protocol.UDP:
                    UDPHeader udpHeader = new UDPHeader(ipHeader.Data, (int)ipHeader.MessageLength);
                    TreeNode udpNode = MakeUDPTreeNode(udpHeader);
                    rootNode.Nodes.Add(udpNode);
 
                    if (udpHeader.DestinationPort == "53" || udpHeader.SourcePort == "53")
                    {
                        TreeNode dnsNode = MakeDNSTreeNode(udpHeader.Data,
                            Convert.ToInt32(udpHeader.Length) - 8);
                        rootNode.Nodes.Add(dnsNode);
                    }
                    break;
 
                case Protocol.Unknown:
                    break;
            }
 
            AddTreeNode addTreeNode = new AddTreeNode(OnAddTreeNode);
            rootNode.Text = ipHeader.SourceAddress.ToString() + " - " + ipHeader.DestinationAddress.ToString();
            treeView.Invoke(addTreeNode, new object[] { rootNode });
        }
 
        private TreeNode MakeIPTreeNode(IPHeader ipHeader)
        {
            TreeNode ipNode = new TreeNode("IP");
            ipNode.Nodes.Add("Ver: " + ipHeader.Version);
            ipNode.Nodes.Add("Header Length: " + ipHeader.HeaderLength);
            ipNode.Nodes.Add("Differentiated Services: " + ipHeader.DifferentiatedServices);
            ipNode.Nodes.Add("Total Length: " + ipHeader.TotalLength);
            ipNode.Nodes.Add("Identification: " + ipHeader.Identification);
            ipNode.Nodes.Add("Flags: " + ipHeader.Flags);
            ipNode.Nodes.Add("Fragmentation Offset: " + ipHeader.FragmentationOffset);
            ipNode.Nodes.Add("Time to live: " + ipHeader.TTL);
 
            string protocolStr = ipHeader.ProtocolType switch
            {
                Protocol.TCP => "TCP",
                Protocol.UDP => "UDP",
                _ => "Unknown"
            };
            ipNode.Nodes.Add("Protocol: " + protocolStr);
 
            ipNode.Nodes.Add("Checksum: " + ipHeader.Checksum);
            ipNode.Nodes.Add("Source: " + ipHeader.SourceAddress.ToString());
            ipNode.Nodes.Add("Destination: " + ipHeader.DestinationAddress.ToString());
 
            return ipNode;
        }
 
        private TreeNode MakeTCPTreeNode(TCPHeader tcpHeader)
        {
            TreeNode tcpNode = new TreeNode("TCP");
            tcpNode.Nodes.Add("Source Port: " + tcpHeader.SourcePort);
            tcpNode.Nodes.Add("Destination Port: " + tcpHeader.DestinationPort);
            tcpNode.Nodes.Add("Sequence Number: " + tcpHeader.SequenceNumber);
 
            if (!string.IsNullOrEmpty(tcpHeader.AcknowledgementNumber))
                tcpNode.Nodes.Add("Acknowledgement Number: " + tcpHeader.AcknowledgementNumber);
 
            tcpNode.Nodes.Add("Header Length: " + tcpHeader.HeaderLength);
            tcpNode.Nodes.Add("Flags: " + tcpHeader.Flags);
            tcpNode.Nodes.Add("Window Size: " + tcpHeader.WindowSize);
            tcpNode.Nodes.Add("Checksum: " + tcpHeader.Checksum);
 
            if (!string.IsNullOrEmpty(tcpHeader.UrgentPointer))
                tcpNode.Nodes.Add("Urgent Pointer: " + tcpHeader.UrgentPointer);
 
            return tcpNode;
        }
 
        private TreeNode MakeUDPTreeNode(UDPHeader udpHeader)
        {
            TreeNode udpNode = new TreeNode("UDP");
            udpNode.Nodes.Add("Source Port: " + udpHeader.SourcePort);
            udpNode.Nodes.Add("Destination Port: " + udpHeader.DestinationPort);
            udpNode.Nodes.Add("Length: " + udpHeader.Length);
            udpNode.Nodes.Add("Checksum: " + udpHeader.Checksum);
            return udpNode;
        }
 
        private TreeNode MakeDNSTreeNode(byte[] byteData, int nLength)
        {
            DNSHeader dnsHeader = new DNSHeader(byteData, nLength);
            TreeNode dnsNode = new TreeNode("DNS");
            dnsNode.Nodes.Add("Identification: " + dnsHeader.Identification);
            dnsNode.Nodes.Add("Flags: " + dnsHeader.Flags);
            dnsNode.Nodes.Add("Questions: " + dnsHeader.TotalQuestions);
            dnsNode.Nodes.Add("Answer RRs: " + dnsHeader.TotalAnswerRRs);
            dnsNode.Nodes.Add("Authority RRs: " + dnsHeader.TotalAuthorityRRs);
            dnsNode.Nodes.Add("Additional RRs: " + dnsHeader.TotalAdditionalRRs);
            return dnsNode;
        }
 
        private void OnAddTreeNode(TreeNode node)
        {
            treeView.Nodes.Add(node);
        }
 
        private void SnifferForm_Load(object sender, EventArgs e)
        {
            string strIP = null;
            IPHostEntry hostEntry = Dns.GetHostEntry(Dns.GetHostName());
 
            if (hostEntry.AddressList.Length > 0)
            {
                foreach (IPAddress ip in hostEntry.AddressList)
                {
                    strIP = ip.ToString();
                    cmbInterfaces.Items.Add(strIP);
                }
            }
        }
 
        private void SnifferForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (bContinueCapturing)
            {
                mainSocket.Close();
            }
        }
 
        private void treeView_AfterSelect(object sender, TreeViewEventArgs e) { }
 
        private void label1_Click(object sender, EventArgs e) { }
    }
}