Custom EXE Template Metasploit 64-bit ASM PE Syntax

Custom EXE Template Metasploit 64-bit ASM PE Syntax

I asked this previously then deleted since I think I asked the question without gearing it towards msfvenom and custom EXE templates.

There is a 64-bit Windows PE written in assembly that ships with Metasploit that I am trying to compile to an EXE and use as a custom template for msfvenom. How do I compile/link/include windows DLL in Kali? I have Mingw installed.

I have tried this:

nasm -fwin64 -o 64exetemplate.o 64exetemplate.nasm

Then tried to link with Mingw like :

86_64-w64-mingw32-ld -o 64exetemplate.exe 64exetemplate.o

How do I get the asm to compile/link? I think there is a path to kernel32.dll missing and I am not sure of the syntax.

Both give errors. From the previous question, I understand I need to tell Mingw/gcc where the windows DLL or kernel32.dll are?

root@box:/ nasm -f win64 64exetemplate.asm -o tiny.o
64exetemplate.asm:7: error: parser: instruction expected
64exetemplate.asm:8: error: symbol `extrn' redefined
64exetemplate.asm:8: error: parser: instruction expected
64exetemplate.asm:12: error: parser: instruction expected
64exetemplate.asm:26: error: symbol `main' redefined
64exetemplate.asm:26: error: parser: instruction expected
64exetemplate.asm:28: error: parser: instruction expected
64exetemplate.asm:29: error: parser: instruction expected
64exetemplate.asm:30: error: comma expected after operand 1
64exetemplate.asm:31: error: symbol `payload' redefined
64exetemplate.asm:31: error: parser: instruction expected



root@box:/ x86_64-w64-mingw32-ld -o 64exetemplate.exe 64exetemplate.o 
64exetemplate.o:(.text+0x1d): undefined reference to `VirtualAlloc'
64exetemplate.o:(.text+0x3d): undefined reference to `ExitProcess'

Original assembly file that was used to create the 64-bit Windows portable execution.

; Author: Stephen Fewer (stephen_fewer[at]harmonysecurity[dot]com)
; Architecture: x64
;
; Assemble and link with the following command:
; "C:\Program Files\Microsoft Visual Studio 9.0\VC\bin\x86_amd64\ml64" template_x64_windows.asm /link /su$

extrn ExitProcess : proc
extrn VirtualAlloc : proc

.code

        main proc
                sub rsp, 40        ;
                mov r9, 40h        ;
                mov r8, 3000h      ;
                mov rdx, 4096      ;
                xor rcx, rcx       ;
                call VirtualAlloc  ; lpPayload = VirtualAlloc( NULL, 4096, MEM_COMMIT | MEM_RESERVE, PAGE$
                mov rcx, 4096      ;
                mov rsi, payload   ;
                mov rdi, rax       ;
                rep movsb          ; memcpy( lpPayload, payload, 4096 );
                call rax           ; lpPayload();
 xor rcx, rcx       ;
                call ExitProcess   ; ExitProcess( 0 );
        main endp

        payload proc
                A byte 'PAYLOAD:'
                B db 4096-8 dup ( 0 )
        payload endp
end

Again, I know that I asked this before (now deleted) but this is a great question for people wanting to edit the PE ASM to create custom EXE templates with msfvenom. I hope I framed this question better.