hakril-PythonForWindows/doc/GetProcAddress_64b.asm

.CODE

start:

MY_FUNC PROC
        call func
        ret
func:
        push rax ;Padding for calling alligned on 16 bytes + ret value
        push rax
        push rbx
        push rcx
        push rdx
        push rsi
        push rdi
        push r8
        push r9
        push r10
        push r11
        push r12
        push r13
        ;TODO save the QUEEN (and the registers !)
        mov rax, 5050505050505050h ; libname
        mov r11, rax 
        mov rax,  5151515151515151h ; function name
        mov r12, rax
        ;String pushed !
        mov rax, GS:[60h] ; PEB
        mov rax, [rax + 6 * 4] ; RAX = ldr (+ 6 for 64 cause of 2 ptr)
        mov rax, [rax + 8 * 4] ; RAX on the first elt of the list (first module)
        mov rdx, rax
a_dest:
        mov rax, rdx
        mov rbx, [rax + 4 * 8] ;RBX : first base ! (base of current module)
        and rbx, rbx ;If no more Module : not fail = fail
        jz a_fail
        mov rcx, [rax + 10 * 8] ;RCX = NAME (UNICODE_STRING.Buffer)

        mov rdi, rcx
        call strlen
        mov rdi, rcx ; set RDI to good value
        mov rcx, rax 
        mov rsi, r11
        repe cmpsw ;cmp with current dll name (unicode)
        test rcx, rcx
        jz dll_found
        mov rdx, [rdx]
        jmp a_dest
a_fail:
        push 42424242h
        ret
dll_found: ;Cool ! : here rbx = base
        mov eax, [rbx + 15 * 4] ;rax = PEBASE RVA
        add rax, rbx ;RAX = PEBASE
        add rax, 24 ;OPTIONAL HEADER
        mov ecx, [rax + 112] ;rcx = RVA export dir
        add rcx, rbx ;rcx = export_dir
        mov rax, rcx ;RAX = export_dir
        push rax ;Save it for after function search
        ; EBX = BASE | EAX = EXPORT DIR
        mov ecx, [rax  + 6 * 4] 
        mov r13, rcx ;r13 = NB names
        mov edx, [rax + 8 * 4] ; EDX = names array RVA
        add rdx, rbx
        xor rcx, rcx
        
 search_loop:
        mov esi, [rdx + rcx * 4] ;Get function name RVA
        add rsi, rbx ;Get name addr
        push rcx ;Save current index (could use x64 register)
        mov rdi, r11
        mov rcx, 17 ;We know we want NtCreateThreadEx
        repe cmpsb ;cmp with current export
        mov eax, ecx
        pop rcx ;Restore current function index
        inc rcx
        test eax, eax
        jnz search_loop ;If not found not handled : WTF GetProcAddress not in Kernel32...
        ; Func found !
        dec rcx
        ; rcx is offset of the name, need to find the offset of the function
        pop rax ;Restore export_dir addr
        mov edx, [rax + 9 * 4] ;EDX = AddressOfNameOrdinals RVX
        add rdx, rbx ;AddressOfNameOrdinals + base
        mov cx, [rdx + rcx * 2] ; ecx = Ieme ordinal (short array)
        and rcx, 0ffffh
        mov edx, [rax + 7 * 4] ; AddressOfFunctions RVA
        add rdx, rbx ; AddressOfFunctions + base
        mov edx, [rdx + rcx * 4] ;functions[ecx] -> functions[ordinals[i]]
        add rdx, rbx 
        mov r13, rdx ; r13 : REAL FUNC ADD
               
        ; room for the thread handle
        push 0
        mov rcx, rsp ; arg1
        mov rdx, 1fffffh ; arg2
        mov r8,  0h ; arg3
        mov r9, 4040404040404040h ; arg4 (handle)
        
        mov rax, 0h
        push rax ; arg11
        push rax ; arg10
        push rax ; arg9
        push rax ; arg8
        push rax ; arg7
        mov rax, 4242424242424242h 
        push rax ; arg6 (param)
        mov rax, 4141414141414141h
        push rax ; arg5 (addr)
        
        ; reserve space for register (calling convention)
        push r9
        push r8
        push rdx
        push rcx
        call r13
        ; Write return value in first stack value pushed
        mov [rsp + 29 * 8], rax
        ; TODO CLEAN stack :D
        add rsp, 8 * 8
        add rsp, 32 + 8
        add rsp, 32
        pop r13
        pop r12
        pop r11
        pop r10
        pop r9
        pop r8
        pop rdi
        pop rsi
        pop rdx
        pop rcx
        pop rbx
        pop rax
        pop rax ; Return value
        ret  
strlen:; arg in RDI
    push rcx
    xor rax, rax
    xor rcx, rcx
    dec rcx
    repne scasw
    not rcx
    dec rcx
    mov rax, rcx
    pop rcx
    ret
MY_FUNC ENDP
END