How to extract port number from shellcode

Question

I saw this shellcode and when they use the connect function they pass the port number 4444:

set_address:
  push byte 0x05         ; retry counter
  push 0x0100007F        ; host 127.0.0.1
  push 0x5C110002        ; family AF_INET and port 4444
  mov esi, esp           ; save pointer to sockaddr struct

Or in other website like that:

0000001A      push dword 0x5c110002   ; [0x5c110002, 0x81caa8c0, 0x1, 0x0] // sin_port and sin_family (4444, 0x0002)

But they push 0x5C110002, how they extract 4444 from 0x5C110002?

Answer 1

The connect syscall takes a sockaddr structure as an argument, which looks something like this:

struct sockaddr_in {
        short   sin_family;
        u_short sin_port;
        struct  in_addr sin_addr;
        char    sin_zero[8];
};

They aren't extracting 4444, it's simply passed on the stack as a two-byte short. You are passing to connect, in little-endian order:

• sin_family: 0x0002 (AF_INET)
• sin_port: 0x5c11 (4444 in hex, little endian)
• sin_addr: 0x0100007F ([127] [0] [0] [1], little endian)

Answer 2

I found here how to convert it with python.

import socket
port = 4444
hex(socket.htons(port))
Result : 0x5c11 

The opposite is like that:

socket.htons(0x5c11)