Creating a DLL with forwarded functions

[Vortex]

The simplest solution is to call the functions with their original name :

Code Select Expand


.386
.model flat, stdcall
option casemap :none

include             \masm32\include\windows.inc
include             \masm32\include\kernel32.inc
includelib         \masm32\lib\kernel32.lib
includelib         console.lib

.data
library             db 'Console.dll',0
message             db 'Hello from function with ordinal number 3',13,10,0

StdOut              PROTO :DWORD

.code

start:

    invoke  StdOut,ADDR message
    invoke  ExitProcess,0

END start

Examining under Ollydbg :

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PUSH Demo.0040300C
CALL <JMP.&console.#3>
PUSH 0
CALL <JMP.&kernel32.ExitProcess>
INT3
JMP DWORD PTR DS:[<&kernel32.ExitProcess>;  kernel32.ExitProcess
JMP DWORD PTR DS:[<&console.#3>]         ;  console.#3
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[Vortex]

Creating an import library with Polib is easy, rewrite the functions in decorated form :

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LIBRARY console
EXPORTS

"_StrLen@4" @1 NONAME
"_locate@8" @2 NONAME
"_StdOut@4" @3 NONAME
"_ClearScreen@0" @4 NONAME
"_InitLoadTimeDynLink@0" @5

Building the import library :

Code Select Expand

\pellesc\bin\polib /OUT:console.lib /DEF:console.def /MACHINE:IX86

[gwapo]

Hi,

> how to export a nameless function (exported by ordinal) in MASM?

the MS linker understands "NONAME" in the .DEF file:

EXPORTS
MyProc   @1 NONAME

IIRC newer versions of POLINK also accept this.

Thanks, that's good to know that there's easier approach :U

What would be the purpose of killing the name of an exported function?

My main purpose is because I am writting a DLL from MASM for use by high-level languages, C++/C#, but some exported functions requires some kind of initializations, as it may crash the calling program (i.e., priviledge issues) if not properly initialized. Exporting by ordinal seems a good way to "hide" these critical functions, and I am only accessing these functions by means of "wrapper DLLs" which contains the proper initialization routines for my DLLs.

Of course, there are better approach than "hiding" function names.

Cheers,

-chris

[PBrennick]

gwapo,
It makes sense to me now and I am very interested in ordinals for something I might do in my project.

Paul

[MichaelW]

I didn't post this link because I was sure that someone else would.

http://blogs.msdn.com/andypennell/archive/2004/08/11/212982.aspx