Sending Raw IP Packets

Problem/Question/Abstract:

How can I send raw IP Packets?

Answer:

This example just showes how to send an UDP packet with customized (spoofed) source ip+port.

Using raw sockets you can SEND raw packets over the internet containing whatever you like.

Keep in mind:

This only works under Window 2000.

You can SEND raw packets. You can NOT RECEIVE raw packets.

You must be Administrator to run this.

This unit requires a form containing a button and a memo.


Usage:

Before you run your program, you must change the SrcIP+SrcPort+ DestIP+DestPort to suitable values!

If you don't understand what this source does: Don't use it.

unit main;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, OleCtrls, Registry;

const
  SrcIP = '123.123.123.1';
  SrcPort = 1234;
  DestIP = '123.123.123.2';
  DestPort = 4321;

  Max_Message = 4068;
  Max_Packet = 4096;

type

  TPacketBuffer = array[0..Max_Packet - 1] of byte;

  TForm1 = class(TForm)
    Button1: TButton;
    Memo1: TMemo;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    procedure SendIt;
  end;

  // IP Header
type
  T_IP_Header = record
    ip_verlen: Byte;
    ip_tos: Byte;
    ip_totallength: Word;
    ip_id: Word;
    ip_offset: Word;
    ip_ttl: Byte;
    ip_protocol: Byte;
    ip_checksum: Word;
    ip_srcaddr: LongWord;
    ip_destaddr: LongWord;
  end;

  // UDP Header
type
  T_UDP_Header = record
    src_portno: Word;
    dst_portno: Word;
    udp_length: Word;
    udp_checksum: Word;
  end;

  // Some Winsock 2 type declarations
  u_char = Char;
  u_short = Word;
  u_int = Integer;
  u_long = Longint;

  SunB = packed record
    s_b1, s_b2, s_b3, s_b4: u_char;
  end;
  SunW = packed record
    s_w1, s_w2: u_short;
  end;
  in_addr = record
    case integer of
      0: (S_un_b: SunB);
      1: (S_un_w: SunW);
      2: (S_addr: u_long);
  end;
  TInAddr = in_addr;
  Sockaddr_in = record
    case Integer of
      0: (sin_family: u_short;
        sin_port: u_short;
        sin_addr: TInAddr;
        sin_zero: array[0..7] of Char);
      1: (sa_family: u_short;
        sa_data: array[0..13] of Char)
  end;
  TSockAddr = Sockaddr_in;
  TSocket = u_int;

const
  WSADESCRIPTION_LEN = 256;
  WSASYS_STATUS_LEN = 128;

type
  PWSAData = ^TWSAData;
  WSAData = record // !!! also WSDATA
    wVersion: Word;
    wHighVersion: Word;
    szDescription: array[0..WSADESCRIPTION_LEN] of Char;
    szSystemStatus: array[0..WSASYS_STATUS_LEN] of Char;
    iMaxSockets: Word;
    iMaxUdpDg: Word;
    lpVendorInfo: PChar;
  end;
  TWSAData = WSAData;

  // Define some winsock 2 functions
function closesocket(s: TSocket): Integer; stdcall;
function socket(af, Struct, protocol: Integer): TSocket; stdcall;
function sendto(s: TSocket; var Buf; len, flags: Integer; var addrto: TSockAddr;
  tolen: Integer): Integer; stdcall; {}
function setsockopt(s: TSocket; level, optname: Integer; optval: PChar;
  optlen: Integer): Integer; stdcall;
function inet_addr(cp: PChar): u_long; stdcall; {PInAddr;} { TInAddr }
function htons(hostshort: u_short): u_short; stdcall;
function WSAGetLastError: Integer; stdcall;
function WSAStartup(wVersionRequired: word; var WSData: TWSAData): Integer; stdcall;
function WSACleanup: Integer; stdcall;

const
  AF_INET = 2; // internetwork: UDP, TCP, etc.

  IP_HDRINCL = 2; // IP Header Include

  SOCK_RAW = 3; // raw-protocol interface

  IPPROTO_IP = 0; // dummy for IP
  IPPROTO_TCP = 6; // tcp
  IPPROTO_UDP = 17; // user datagram protocol
  IPPROTO_RAW = 255; // raw IP packet

  INVALID_SOCKET = TSocket(not (0));
  SOCKET_ERROR = -1;

var
  Form1: TForm1;

implementation

// Import Winsock 2 functions
const
  WinSocket = 'WS2_32.DLL';

function closesocket; external winsocket name 'closesocket';
function socket; external winsocket name 'socket';
function sendto; external winsocket name 'sendto';
function setsockopt; external winsocket name 'setsockopt';
function inet_addr; external winsocket name 'inet_addr';
function htons; external winsocket name 'htons';
function WSAGetLastError; external winsocket name 'WSAGetLastError';
function WSAStartup; external winsocket name 'WSAStartup';
function WSACleanup; external winsocket name 'WSACleanup';

{$R *.DFM}

//
// Function: checksum
//
// Description:
//    This function calculates the 16-bit one's complement sum
//    for the supplied buffer
//

function CheckSum(var Buffer; Size: integer): Word;
type
  TWordArray = array[0..1] of Word;
var
  ChkSum: LongWord;
  i: Integer;
begin
  ChkSum := 0;
  i := 0;
  while Size > 1 do
  begin
    ChkSum := ChkSum + TWordArray(Buffer)[i];
    inc(i);
    Size := Size - SizeOf(Word);
  end;

  if Size = 1 then
    ChkSum := ChkSum + Byte(TWordArray(Buffer)[i]);

  ChkSum := (ChkSum shr 16) + (ChkSum and $FFFF);
  ChkSum := ChkSum + (Chksum shr 16);

  Result := Word(ChkSum);
end;

procedure BuildHeaders(
  FromIP: string;
  iFromPort: Word;
  ToIP: string;
  iToPort: Word;
  StrMessage: string;
  var Buf: TPacketBuffer;
  var remote: TSockAddr;
  var iTotalSize: Word
  );
var
  dwFromIP: LongWord;
  dwToIP: LongWord;

  iIPVersion: Word;
  iIPSize: Word;
  ipHdr: T_IP_Header;
  udpHdr: T_UDP_Header;

  iUdpSize: Word;
  iUdpChecksumSize: Word;
  cksum: Word;

  Ptr: ^Byte;

  procedure IncPtr(Value: Integer);
  begin
    ptr := pointer(integer(ptr) + Value);
  end;

begin
  // Convert ip address'ss

  dwFromIP := inet_Addr(PChar(FromIP));
  dwToIP := inet_Addr(PChar(ToIP));

  // Initalize the IP header
  //
  iTotalSize := sizeof(ipHdr) + sizeof(udpHdr) + length(strMessage);

  iIPVersion := 4;
  iIPSize := sizeof(ipHdr) div sizeof(LongWord);
  //
  // IP version goes in the high order 4 bits of ip_verlen. The
  // IP header length (in 32-bit words) goes in the lower 4 bits.
  //
  ipHdr.ip_verlen := (iIPVersion shl 4) or iIPSize;
  ipHdr.ip_tos := 0; // IP type of service
  ipHdr.ip_totallength := htons(iTotalSize); // Total packet len
  ipHdr.ip_id := 0; // Unique identifier: set to 0
  ipHdr.ip_offset := 0; // Fragment offset field
  ipHdr.ip_ttl := 128; // Time to live
  ipHdr.ip_protocol := $11; // Protocol(UDP)
  ipHdr.ip_checksum := 0; // IP checksum
  ipHdr.ip_srcaddr := dwFromIP; // Source address
  ipHdr.ip_destaddr := dwToIP; // Destination address
  //
  // Initalize the UDP header
  //
  iUdpSize := sizeof(udpHdr) + length(strMessage);

  udpHdr.src_portno := htons(iFromPort);
  udpHdr.dst_portno := htons(iToPort);
  udpHdr.udp_length := htons(iUdpSize);
  udpHdr.udp_checksum := 0;
  //
  // Build the UDP pseudo-header for calculating the UDP checksum.
  // The pseudo-header consists of the 32-bit source IP address,
  // the 32-bit destination IP address, a zero byte, the 8-bit
  // IP protocol field, the 16-bit UDP length, and the UDP
  // header itself along with its data (padded with a 0 if
  // the data is odd length).
  //
  iUdpChecksumSize := 0;

  ptr := @buf[0];
  FillChar(Buf, SizeOf(Buf), 0);

  Move(ipHdr.ip_srcaddr, ptr^, SizeOf(ipHdr.ip_srcaddr));
  IncPtr(SizeOf(ipHdr.ip_srcaddr));

  iUdpChecksumSize := iUdpChecksumSize + sizeof(ipHdr.ip_srcaddr);

  Move(ipHdr.ip_destaddr, ptr^, SizeOf(ipHdr.ip_destaddr));
  IncPtr(SizeOf(ipHdr.ip_destaddr));

  iUdpChecksumSize := iUdpChecksumSize + sizeof(ipHdr.ip_destaddr);

  IncPtr(1);

  Inc(iUdpChecksumSize);

  Move(ipHdr.ip_protocol, ptr^, sizeof(ipHdr.ip_protocol));
  IncPtr(sizeof(ipHdr.ip_protocol));
  iUdpChecksumSize := iUdpChecksumSize + sizeof(ipHdr.ip_protocol);

  Move(udpHdr.udp_length, ptr^, sizeof(udpHdr.udp_length));
  IncPtr(sizeof(udpHdr.udp_length));
  iUdpChecksumSize := iUdpChecksumSize + sizeof(udpHdr.udp_length);

  move(udpHdr, ptr^, sizeof(udpHdr));
  IncPtr(sizeof(udpHdr));
  iUdpChecksumSize := iUdpCheckSumSize + sizeof(udpHdr);

  Move(StrMessage[1], ptr^, Length(strMessage));
  IncPtr(Length(StrMessage));

  iUdpChecksumSize := iUdpChecksumSize + length(strMessage);

  cksum := checksum(buf, iUdpChecksumSize);
  udpHdr.udp_checksum := cksum;

  //
  // Now assemble the IP and UDP headers along with the data
  //  so we can send it
  //
  FillChar(Buf, SizeOf(Buf), 0);
  Ptr := @Buf[0];

  Move(ipHdr, ptr^, SizeOf(ipHdr));
  IncPtr(SizeOf(ipHdr));
  Move(udpHdr, ptr^, SizeOf(udpHdr));
  IncPtr(SizeOf(udpHdr));
  Move(StrMessage[1], ptr^, length(StrMessage));

  // Apparently, this SOCKADDR_IN structure makes no difference.
  // Whatever we put as the destination IP addr in the IP header
  // is what goes. Specifying a different destination in remote
  // will be ignored.
  //
  remote.sin_family := AF_INET;
  remote.sin_port := htons(iToPort);
  remote.sin_addr.s_addr := dwToIP;
end;

procedure TForm1.SendIt;
var
  sh: TSocket;
  bOpt: Integer;
  ret: Integer;
  Buf: TPacketBuffer;
  Remote: TSockAddr;
  Local: TSockAddr;
  iTotalSize: Word;
  wsdata: TWSAdata;

begin
  // Startup Winsock 2
  ret := WSAStartup($0002, wsdata);
  if ret <> 0 then
  begin
    memo1.lines.add('WSA Startup failed.');
    exit;
  end;
  with memo1.lines do
  begin
    add('WSA Startup:');
    add('Desc.:  ' + wsData.szDescription);
    add('Status: ' + wsData.szSystemStatus);
  end;

  try
    // Create socket
    sh := Socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
    if (sh = INVALID_SOCKET) then
    begin
      memo1.lines.add('Socket() failed: ' + IntToStr(WSAGetLastError));
      exit;
    end;
    Memo1.lines.add('Socket Handle = ' + IntToStr(sh));

    // Option: Header Include
    bOpt := 1;
    ret := SetSockOpt(sh, IPPROTO_IP, IP_HDRINCL, @bOpt, SizeOf(bOpt));
    if ret = SOCKET_ERROR then
    begin
      Memo1.lines.add('setsockopt(IP_HDRINCL) failed: ' + IntToStr(WSAGetLastError));
      exit;
    end;

    // Build the packet
    BuildHeaders(SrcIP, SrcPort,
      DestIP, DestPort,
      'THIS IS A TEST PACKET',
      Buf, Remote, iTotalSize);

    // Send the packet
    ret := SendTo(sh, buf, iTotalSize, 0, Remote, SizeOf(Remote));
    if ret = SOCKET_ERROR then
      Memo1.Lines.Add('sendto() failed: ' + IntToStr(WSAGetLastError))
    else
      Memo1.Lines.Add('send ' + IntToStr(ret) + ' bytes.');

    // Close socket
    CloseSocket(sh);
  finally
    // Close Winsock 2
    WSACleanup;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  SendIt;
end;

end.