Delphi - Possible to write to resources of an application withing another application?

Question

Just out of curiosity, do you think this is possible: Writing to the resources of a file, stored in the resources of the same file. Let's say we have a builder and a stub. Usually you would use the builder to write settings to the resources of another extracted file named "stub.exe".

Now I want to know, is it possible(in delphi 7) to write the settings to the resources of "stub.exe" when stored in the resources of the builder? Sounds better when I ask it in my head, hope you understand what I mean.

Answer 1

The resources of a file are stored in read only memory. In order to be able to write to them you would need to use VirtualProtect to make the memory writeable. This simple program proves the concept:

{$APPTYPE CONSOLE}

{$R *.res}

uses
  SysUtils, Math, Windows, Classes;

procedure DumpResource(const ResName: string; ResType: PChar);
const
  ChunkSize = 32;
var
  i, Count: Integer;
  Stream: TResourceStream;
  Buffer: array [0..ChunkSize-1] of Byte;
  HexBuffer: array [0..2*ChunkSize-1] of Char;
  Text: string;
begin
  Stream := TResourceStream.Create(HInstance, ResName, ResType);
  try
    while Stream.Position < Stream.Size do
    begin
      Count := Min(ChunkSize, Stream.Size - Stream.Position);
      Stream.ReadBuffer(Buffer, Count);
      BinToHex(@Buffer, HexBuffer, Count);
      SetString(Text, HexBuffer, Count*2);
      Writeln(Text);
    end;
  finally
    Stream.Free;
  end;
end;

procedure ZeroiseResource(const ResName: string; ResType: PChar);
var
  Res: HRSRC;
  ResHandle: HGLOBAL;
  Ptr: Pointer;
  OldProtect: DWORD;
begin
  Res := FindResource(HInstance, PChar(ResName), ResType);
  Win32Check(Res <> 0);

  ResHandle := LoadResource(HInstance, Res);
  Win32Check(ResHandle <> 0);

  Ptr := LockResource(ResHandle);
  Win32Check(Ptr <> nil);

  Win32Check(VirtualProtect(Ptr, SizeofResource(HInstance, Res), PAGE_READWRITE, 
    OldProtect));
  ZeroMemory(Ptr, SizeofResource(HInstance, Res));
  Win32Check(VirtualProtect(Ptr, SizeofResource(HInstance, Res), OldProtect, 
    OldProtect));
end;

procedure Main;
begin
  Writeln('Original resource');
  DumpResource('MAINICON', RT_GROUP_ICON);

  ZeroiseResource('MAINICON', RT_GROUP_ICON);

  Writeln('Modified resource');
  DumpResource('MAINICON', RT_GROUP_ICON);
end;

begin
  try
    Main;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
  Readln;
end.

However, I don't think that I would take this path. I would do the following.

• Allocate memory in your builder process to hold a copy of the executable being built.
• Copy the version of the executable stored in the resource to the memory you just allocated.
• Modify the executable in that memory.
• Write the executable from memory to disk.

Note that I'm assuming in all this that your goal is to make the modifications before you save the executable to disk.