Simple portable executable encryptor using intel x86 assembly

PE Encryptor

.486
.model    flat, stdcall
option    casemap :none   ; case sensitive

include        base.inc

.code
start:
    invoke    GetModuleHandle, NULL
    mov    hInstance, eax
    invoke    DialogBoxParam, hInstance, 101, 0, ADDR DlgProc, 0
    invoke    ExitProcess, eax
    
SetOK proc hList : DWORD
    LOCAL pText : DWORD
    invoke SendMessage, hList, LB_GETCOUNT, 0, 0
    dec eax
    push eax
    invoke SendMessage, hList, LB_GETTEXTLEN, eax, 0
    invoke VirtualAlloc, NULL, eax, MEM_COMMIT, PAGE_READWRITE
    mov pText, eax
    pop eax
    push eax
    invoke SendMessage, hList, LB_GETTEXT, eax, pText
    invoke lstrcat, pText, lpStr(" [ OK ]")
    pop eax
    invoke SendMessage, hList, LB_DELETESTRING, eax, 0
    invoke SendMessage, hList, LB_ADDSTRING, 0, pText
    Ret
SetOK EndP
    
PEThread proc hWin : DWORD
    LOCAL hFile : DWORD
    LOCAL hList : DWORD
    LOCAL pMemory : DWORD
    LOCAL W: DWORD
    LOCAL dwRawEP : DWORD
    LOCAL dwSize : DWORD
    LOCAL dwRaw : DWORD
    invoke GetDlgItem, hWin, 1005
    mov hList, eax
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Starting encriptor...")
    invoke GetDlgItem, hWin, 1001
    invoke GetDlgItemText, hWin, 1001, addr lpBuff, sizeof lpBuff
    invoke SetOK, hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Creating backup file...")
    invoke lstrlen, addr lpBuff
    invoke RtlMoveMemory, addr szBuff, addr lpBuff, eax
    invoke lstrcat, addr szBuff, lpStr(".bak")
    invoke CopyFile, addr lpBuff, addr szBuff, TRUE
    invoke SetOK, hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Starting encryption process...")
    invoke CreateFile, addr lpBuff, GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ or FILE_SHARE_WRITE, NULL,OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL
    .if    (eax == INVALID_HANDLE_VALUE)
        invoke GetLastError
        invoke wsprintf, addr lpBuff, lpStr("Error on CreateFile, Error Code: %X (%d)"),  eax, eax
        invoke SendMessage, hList, LB_ADDSTRING, 0, addr lpBuff
        ret
    .endif
    mov hFile, eax
    invoke SetOK, hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Creating decryption section...")
    invoke RtlZeroMemory, addr lpBuff, sizeof lpBuff
    invoke lstrlen, addr lpDirectory
    invoke RtlMoveMemory, addr lpBuff, addr lpDirectory, eax
    invoke lstrcat, addr lpBuff, lpStr("\asModule.dll")
    invoke LoadLibrary, addr lpBuff
    invoke GetProcAddress, eax, lpStr("AddPESection")
    push 0E0000020h
    push sizeof dwStub
    push ofStr(".ace")
    push hFile
    call eax
    .if    (eax == -1)
        invoke GetLastError
        invoke wsprintf, addr lpBuff, lpStr("Error on creating the section, Error Code: %X (%d)"),  eax, eax
        invoke SendMessage, hList, LB_ADDSTRING, 0, addr lpBuff
        ret
    .endif
    mov dwRaw, eax
    invoke SetOK, hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Retrieving file informations...")
    invoke SetFilePointer, hFile, 0, 0, FILE_BEGIN
    invoke GetFileSize, hFile, NULL
    mov dwSize, eax
    invoke VirtualAlloc, NULL, eax, MEM_COMMIT, PAGE_READWRITE
    mov pMemory, eax
    invoke ReadFile, hFile, pMemory, dwSize, addr W, NULL
    .if    (eax == 0)
        invoke GetLastError
        invoke wsprintf, addr lpBuff, lpStr("Error on ReadFile, Error Code: %X (%d)"),  eax, eax
        invoke SendMessage, hList, LB_ADDSTRING, 0, addr lpBuff
        ret
    .endif
    mov edi, pMemory
    assume edi : ptr IMAGE_DOS_HEADER
    add edi, [edi].e_lfanew
    mov esi, edi
    assume esi : ptr IMAGE_NT_HEADERS
    add edi, sizeof IMAGE_NT_HEADERS
    assume edi : ptr IMAGE_SECTION_HEADER
    mov ebx, [esi].OptionalHeader.ImageBase
    add ebx, [esi].OptionalHeader.AddressOfEntryPoint
    sub ebx, [esi].OptionalHeader.ImageBase
    add ebx, [edi].PointerToRawData
    sub ebx, [edi].VirtualAddress
    mov dwRawEP, ebx
    or [edi].Characteristics, IMAGE_SCN_MEM_WRITE
    invoke SetOK, hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Encrypting code section...")
    mov ecx, [edi].PointerToRawData
    add ecx, pMemory
    add ecx, [edi].SizeOfRawData
    mov ebx, pMemory
    add ebx, [edi].PointerToRawData
    .while    (ebx <= ecx)
        mov al, byte ptr ds:[ebx]
        .if    (al == 0)
            mov al, 0FFh
        .else
            dec al
        .endif
        mov byte ptr ds:[ebx], al
        inc ebx
    .endw
    invoke SetOK, hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Redirecting EntryPoint")
    xor ebx, ebx
    .while (bx <= [esi].FileHeader.NumberOfSections)
        
        mov eax, pMemory
        assume eax : ptr IMAGE_DOS_HEADER
        add eax, [eax].e_lfanew
        add eax, sizeof IMAGE_NT_HEADERS
        movzx ecx, bx
        imul ecx, sizeof IMAGE_SECTION_HEADER
        add eax, ecx
        push eax
        assume eax : ptr IMAGE_SECTION_HEADER
        invoke lstrcmp, addr [eax].Name1, lpStr(".ace")
        .if    (eax == 0)
            invoke SetOK, hList
    
            invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Writting decryption code...")
            pop eax
            mov [eax].SizeOfRawData, sizeof dwRaw+2
            mov [eax].Misc.VirtualSize, sizeof dwRaw+2
            mov ecx, [esi].OptionalHeader.BaseOfCode
            add ecx, [esi].OptionalHeader.ImageBase
            mov dword ptr ds:[dwStub+4], ecx
            mov ecx, [edi].Misc.VirtualSize
            mov dword ptr ds:[dwStub+9], ecx
            mov ecx, [esi].OptionalHeader.AddressOfEntryPoint
            sub ecx, [eax].VirtualAddress
            sub ecx, sizeof dwStub
            inc ecx
            mov edx, sizeof dwStub
            sub edx, 5    
            mov dword ptr ds:[dwStub+edx], ecx 
            push eax
            mov ebx, [eax].PointerToRawData
            add ebx, pMemory
            invoke RtlMoveMemory, ebx, addr dwStub, sizeof dwStub
            pop eax
            mov ebx, [eax].VirtualAddress
            mov [esi].OptionalHeader.AddressOfEntryPoint, ebx
            mov ebx, eax
            jmp @EndOfLoop
        .endif
        inc bx
    .endw
    @EndOfLoop:
    push ebx
    invoke SetOK, hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Saving file...")
    invoke SetFilePointer, hFile, 0, 0, FILE_BEGIN
    invoke GetFileSize, hFile, 0
    mov ebx, eax
    invoke WriteFile, hFile, pMemory, ebx, addr W, NULL
    .if    (eax == 0)
        invoke GetLastError
        invoke wsprintf, addr lpBuff, lpStr("Error on WriteFile, Error Code: %X (%d)"),  eax, eax
        invoke SendMessage, hList, LB_ADDSTRING, 0, addr lpBuff
        ret
    .endif
    invoke SetOK, hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Compressing code...")
    invoke SetFilePointer, hFile, dwRaw, 0, FILE_BEGIN
    invoke SetFilePointer, hFile, sizeof dwStub+2, 0, FILE_CURRENT
    invoke SetEndOfFile, hFile
    invoke SetOK,hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("Closing handles...")
    invoke VirtualFree, pMemory, dwSize, MEM_RELEASE
    invoke SetOK, hList
    
    invoke SendMessage, hList, LB_ADDSTRING, 0, lpStr("DONE!")
    invoke CloseHandle, hFile
    Ret
PEThread EndP

GetFileName proc hParent:DWORD,lpTitle:DWORD,lpFilter:DWORD
    mov ofn.lStructSize,        sizeof OPENFILENAME
    m2m ofn.hWndOwner,          hParent
    m2m ofn.hInstance,          hInstance
    m2m ofn.lpstrFilter,        lpFilter
    m2m ofn.lpstrFile,          offset lpBuff
    mov ofn.nMaxFile,           sizeof lpBuff
    m2m ofn.lpstrTitle,         lpTitle
    mov ofn.Flags,              OFN_EXPLORER or OFN_FILEMUSTEXIST or OFN_LONGNAMES
    invoke GetOpenFileName,ADDR ofn
    ret
GetFileName endp


DlgProc    proc    hWin    :DWORD,
        uMsg    :DWORD,
        wParam    :DWORD,
        lParam    :DWORD
        LOCAL dwSize : DWORD
        LOCAL hFile : DWORD
        LOCAL pRes : DWORD
        LOCAL W : DWORD
    .if    uMsg == WM_COMMAND
        .if    wParam == IDC_OK
            invoke CreateThread, 0, 0, addr PEThread, hWin, NULL, NULL
        .elseif    wParam == 1016
            invoke GetFileName, hWin, ofStr("Select a Portable Executable (exe)"), offset lpFilter1
            invoke SetDlgItemText, hWin, 1001, addr lpBuff
        .endif
    .elseif    uMsg == WM_CLOSE
        invoke    EndDialog,hWin,0
    .elseif    uMsg == WM_INITDIALOG
        invoke GetDlgItem, hWin, 1006
        invoke SendMessage, eax, BM_SETCHECK, BST_CHECKED, 0
        invoke GetDlgItem, hWin, 1012
        invoke SendMessage, eax, BM_SETCHECK, BST_CHECKED, 0
        invoke GetCurrentDirectory, sizeof lpDirectory, addr lpDirectory
        
        invoke FindResource, hInstance, 10,RT_RCDATA
        mov esi, eax
        invoke SizeofResource, hInstance, eax
        mov dwSize, eax
        invoke LoadResource, hInstance, esi
        push eax
        invoke LockResource, eax
        mov pRes, eax
        invoke lstrlen, addr lpDirectory
        invoke RtlMoveMemory, addr lpBuff, addr lpDirectory, eax
        invoke lstrcat, addr lpBuff, lpStr("\asModule.dll")
        @Create:
        invoke CreateFile, addr lpBuff,GENERIC_READ or GENERIC_WRITE,FILE_SHARE_READ or FILE_SHARE_WRITE, NULL, CREATE_NEW,FILE_ATTRIBUTE_NORMAL, NULL
        .if    eax == INVALID_HANDLE_VALUE
            call GetLastError
            .if    eax == 50h
                invoke DeleteFile, addr lpBuff
                jmp @Create
            .endif
        .endif
        mov hFile, eax
        invoke WriteFile, hFile, pRes, dwSize, addr W, NULL
        pop eax
        invoke FreeResource, eax
        invoke CloseHandle, hFile
    .elseif    uMsg == WM_CTLCOLORLISTBOX    
        invoke SetBkColor, wParam, 0
        invoke SetTextColor, wParam, 0FF00h
        invoke CreateSolidBrush, 0
        ret
    .endif

    xor    eax,eax
    ret
DlgProc    endp

end start