Program 2: Scapy Packet Crafting and Firewall Testing (Source 2)

This program uses a custom Python script with Scapy to craft and send ICMP, TCP, and UDP packets to a target Ubuntu VM configured with the UFW firewall.

Phase            System        Steps and Commands

1. Network Setup  Kali/Ubuntu  Check the IP addresses using the ifconfig command.

2. Configure Firewall  Ubuntu (Target)
   1. Enable UFW: sudo ufw enable.
   2. Add rules: sudo ufw deny 80/tcp (block web traffic) and sudo ufw allow 22/tcp (allow SSH).
   3. Block ICMP echo requests (Pings): sudo iptables -I INPUT 1 -p icmp --icmp-type echo-request -j DROP.

3. Scapy Script  Kali Linux
   Write the packet_lab.py script (provided below).

#!/usr/bin/env python3
from scapy.all import *
import time

# Configuration
TARGET_IP = "192.168.56.103"  # Ubuntu VM
DEST_PORT = 80                # HTTP port
DEST_PORT2 = 22               # SSH port
UDP_PORT = 53                 # DNS port
PACKET_DELAY = 1              # Delay between packets

def banner():
    print("\n========================================")
    print(" SCAPY PACKET-CRAFTING LAB SCRIPT")
    print("========================================\n")

def send_icmp():
    print("[*] Sending ICMP Echo Request...")
    packet = IP(dst=TARGET_IP) / ICMP()
    send(packet, verbose=0)
    print("[+] ICMP packet sent.\n")

def send_tcp_syn(destination_port):
    print(f"[*] Sending TCP SYN to port {destination_port}...")
    packet = IP(dst=TARGET_IP) / TCP(dport=destination_port, flags="S")
    send(packet, verbose=0)
    print("[+] TCP SYN sent.\n")

def send_tcp_null(destination_port):
    print("[*] Sending TCP NULL packet...")
    packet = IP(dst=TARGET_IP) / TCP(dport=destination_port, flags=0)
    send(packet, verbose=0)
    print("[+] NULL packet sent.\n")

def send_tcp_fin(destination_port):
    print("[*] Sending TCP FIN packet...")
    packet = IP(dst=TARGET_IP) / TCP(dport=destination_port, flags="F")
    send(packet, verbose=0)
    print("[+] FIN sent.\n")

def send_udp():
    print(f"[*] Sending UDP to port {UDP_PORT}...")
    packet = IP(dst=TARGET_IP) / UDP(dport=UDP_PORT) / Raw(load="TestUDP")
    send(packet, verbose=0)
    print("[+] UDP sent.\n")

def send_custom_payload():
    print("[*] Sending TCP packet with custom payload...")
    packet = IP(dst=TARGET_IP) / TCP(dport=DEST_PORT, flags="PA") / Raw(load="HelloFromScapy")
    send(packet, verbose=0)
    print("[+] Payload packet sent.\n")

def main():
    banner()
    time.sleep(1)

    # Send packets step by step
    send_icmp()
    time.sleep(PACKET_DELAY)

    send_tcp_syn(DEST_PORT2)
    time.sleep(PACKET_DELAY)

    send_tcp_null(DEST_PORT2)
    time.sleep(PACKET_DELAY)

    send_tcp_fin(DEST_PORT2)
    time.sleep(PACKET_DELAY)

    send_udp()
    time.sleep(PACKET_DELAY)

    send_custom_payload()

    print("\n[+] Experiment Completed.")

if __name__ == "__main__":
    main()


4. Execution & Capture  Kali Linux
   1. Start Wireshark, select the interface (e.g., eth0).
   2. Run the script: sudo python3 packet_lab.py.

5. Observation & Cleanup  Kali/Ubuntu
   1. Check Wireshark output using filters like icmp, 
tcp.flags.syn==1 we will see TCP [SYN] Kali-> Unix(port 80).. then no RST, no Syn/Ack. , or 
tcp.port==22 In wireshark we will see TCP[SYN] kali -> Ubuntu Tcp[Syn, ACk] Ubuntu-> kali
TCP [ACK] Kali-> Ubuntu.
   2. Test connections manually (optional): ping <Ubuntu-ip>, nc –v <Ubuntu-ip> 80, nc –v <Ubuntu-ip> 22, or ssh ubuntu@<ubuntu-ip>.
   3. Remove the iptables rule: sudo iptables –D INPUT -p icmp --icmp-type echo-request -j DROP.

Shortened Scapy Code (packet_lab.py)

#!/usr/bin/env python3
from scapy.all import *

# Configuration Variables
TARGET_IP = "192.168.56.103"  # Target Ubuntu VM IP (UPDATE THIS)
DEST_PORT_BLOCKED = 80       # Denied port (from UFW rule)
DEST_PORT_ALLOWED = 22       # Allowed port (SSH)
UDP_PORT = 53

def main():
    # 1. ICMP Echo Request (should be dropped by iptables rule)
    print("[*] Sending ICMP Echo Request...")
    send(IP(dst=TARGET_IP) / ICMP(), verbose=0)

    # 2. TCP SYN (to allowed port 22 - expected SYN/ACK response)
    print(f"[*] Sending TCP SYN to port {DEST_PORT_ALLOWED}...")
    send(IP(dst=TARGET_IP) / TCP(dport=DEST_PORT_ALLOWED, flags="S"), verbose=0)

    # 3. TCP NULL (to allowed port 22 - expected RST response if no service running, or dropped)
    print(f"[*] Sending TCP NULL packet (No flags)...")
    send(IP(dst=TARGET_IP) / TCP(dport=DEST_PORT_ALLOWED, flags=0), verbose=0)

    # 4. TCP FIN (to allowed port 22 - expected RST response if no service running, or dropped)
    print(f"[*] Sending TCP FIN packet...")
    send(IP(dst=TARGET_IP) / TCP(dport=DEST_PORT_ALLOWED, flags="F"), verbose=0)

    # 5. UDP Packet (to port 53 - may generate ICMP port unreachable if no listener)
    print(f"[*] Sending UDP to port {UDP_PORT}...")
    send(IP(dst=TARGET_IP) / UDP(dport=UDP_PORT) / Raw(load="TestUDP"), verbose=0)

    # 6. TCP Packet with Custom Payload (to blocked port 80 - expected RST or dropped)
    print("[*] Sending TCP packet with custom payload to blocked port...")
    send(IP(dst=TARGET_IP) / TCP(dport=DEST_PORT_BLOCKED, flags="PA") / Raw(load="HelloFromScapy"), verbose=0)

    print("\n[+] Experiment Completed.")

if __name__ == "__main__":
    main()