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05.18.2008 at 08:42AM PDT, ID: 23411974
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9.4

hookapi ws2_32.dll, send function increase packet length

Asked by hermematon in Delphi Programming

Tags:

Im made a dll to intercept the "send" calls to the ws2_32.dll and modify the buffer before send the info. I need increase 1 byte the packet length to add a byte to the of the buffer. I use this dll to inject in a game EXE and encrypt/modify the packets for security.

I need that the process will be transparent for the gameexe, so the packets will be send without the gameexe notice the change.

The dll works but the GameEXe make a little weird things.

1) Send the packets more fast (dont wait). I capture the packets and see that when i modify the packet length the info are send to the server atleat the double of fast that when i dont modifu the packet length.

2) The Buffer Stack are affected too. When i capture the packets see that in certain point the "send" function send packets with wrong lenght.

What im donig wrong? There are another way to send modified packets?

Regards.Start Free Trial 
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library Prueba;
 
uses
  Windows,
  Winsock,
  SysUtils,
  madRemote,
  madCodeHook,
  dialogs;
 
{$R *.RES}
 
var
  sendNextHook: function(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall;
  recvNextHook: function(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall;
 
function ConvertDataToAscii(Buffer: pointer; Length: Word): string;
var
  Iterator: integer;
  AsciiBuffer: string;
begin
  AsciiBuffer := '';
  for Iterator := 0 to Length - 1 do
  begin
    if char(pointer(integer(Buffer) + Iterator)^) in [#32..#127] then
      AsciiBuffer := AsciiBuffer + ' ' + char(pointer(integer(Buffer) + Iterator)^) + ' '
    else
      AsciiBuffer := AsciiBuffer + ' . ';
  end;
  Result := AsciiBuffer;
end;
 
function ConvertDataToHex(Buffer: pointer; Length: Word): string;
var
  Iterator: integer;
  HexBuffer: string;
begin
  HexBuffer := '';
  for Iterator := 0 to Length - 1 do
  begin
    HexBuffer := HexBuffer + IntToHex(Ord(char(pointer(integer(Buffer) + Iterator)^)), 2) + ' ';
  end;
  Result := HexBuffer;
end;
 
function EncriptarCadena(Buffer: pointer; Length: Word): String;
var
  Iterator: integer;
  AsciiBuffer: string;
  c, x: Byte;
begin
  for Iterator := 0 to Length - 1 do
  begin
      c:= Integer(pointer(integer(Buffer) + Iterator)^);
      AsciiBuffer := AsciiBuffer + char(c);
  end;
  AsciiBuffer := AsciiBuffer + 'A';
  Result := AsciiBuffer;
end;
 
function DesEncriptarCadena(Buffer: pointer; Length: Word): String;
var
  Iterator: integer;
  AsciiBuffer: string;
  c, x: Byte;
begin
  AsciiBuffer := '';
  for Iterator := 0 to Length - 1 do
  begin
      c:= Integer(pointer(integer(Buffer) + Iterator)^);
      AsciiBuffer := AsciiBuffer + char(c);
  end;
  Result := AsciiBuffer;
end;
 
function recvHookProc(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall;
var
  Cadena: String;
begin
  Result :=  recvNextHook(s, Buf, len, flags);
  Cadena:= DesEncriptarCadena(@Buf, Result);
  CopyMemory(@Buf,pointer(Cadena),Result);
end;
 
function sendHookProc(s: TSocket; var Buf; len, flags: Integer): Integer; stdcall;
var
  X: Integer;
  Cadena: String;
begin
  X:= 1; // 1 Byte to Add
  Cadena:= EncriptarCadena(@Buf, len); // Return @buf more the additional byte to the end of string.
  CopyMemory(@Buf, pointer(cadena), len+X); // Copy the info to Buf
  Result := sendNextHook(s, Buf, len+X, flags) - X; // Call the original function and rest 1 to the result to the function return the original number of bytes
end;
 
procedure Pruebas;
begin
end;
 
exports Pruebas;
 
begin
Randomize;
hookapi('ws2_32.dll','send', @sendHookProc, @sendNextHook);
hookapi('ws2_32.dll','recv', @recvHookProc, @recvNextHook);
end.
 
Keywords: hookapi ws2_32.dll, send functio…
Title
1 Solve my home-baked encryption
2 Constructing and sending a variable len…
3 Intercepting Packets
4 SQL injection protection
5 Packets...
6 Preventing SQL injection
 
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[+][-]05.18.2008 at 10:58AM PDT, ID: 21593437

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[+][-]05.18.2008 at 11:00AM PDT, ID: 21593448

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About this solution

Zone: Delphi Programming
Tags: Delphi 7
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Solution Provided By: ThievingSix
Participating Experts: 1
Solution Grade: B
 
 
 
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