2024 Cyber Apocalypse: Stop Drop and Roll

Challenge Information

Attribute	Details
Event	2024 Cyber Apocalypse
Category	Miscellaneous
Challenge	Stop Drop and Roll
Difficulty	Very Easy

Stop Drop and Roll is a miscellaneous coding challenge where participants must script responses to a text-based game. The server presents scenarios (GORGE, PHREAK, or FIRE) and expects corresponding actions (STOP, DROP, or ROLL). The challenge tests basic socket programming and string manipulation skills.

Analysis

The challenge runs a simple remote game server that:

Presents game scenarios in a sequence
Expects players to respond with the correct action mapping:
- GORGE → STOP
- PHREAK → DROP
- FIRE → ROLL
Can present multiple scenarios at once (e.g., “GORGE, FIRE, PHREAK” → “STOP-ROLL-DROP”)
Terminates after all scenarios are completed, returning the flag

The vulnerability (if any) is the necessity to script automation to handle the repetitive scenarios quickly.

Solution

Step 1: Connect to the Server

The server is accessed via socket connection to the provided IP and port:

IP: 94.237.56.248
Port: 58685

Step 2: Send Initial Confirmation

Upon connection, the server presents rules and asks if you’re ready. Respond with ‘y’:

p.sendlineafter(b'(y/n) ', b'y')

Step 3: Parse and Respond to Scenarios

For each prompt, extract the scenario, map each component, and send back the action:

def send_response(sock, scenario, log_file):
    """Send the appropriate response to the server based on the scenario."""
    action_map = {'GORGE': 'STOP', 'PHREAK': 'DROP', 'FIRE': 'ROLL'}
    actions = [action_map[part.strip()] for part in scenario.split(',')]
    response = '-'.join(actions) + '\n'
    sock.sendall(response.encode())
    log_file.write("Sent: " + response)

Step 4: Loop Until Flag

Continue reading prompts and sending responses until the server returns data that doesn’t contain game scenarios. This will be the flag:

while True:
    prompt = recvuntil(sock, b'What do you do?')

    if "What do you do?" not in prompt:
        continue

    scenario_lines = prompt.strip().split('\n')
    scenario = scenario_lines[-1] if scenario_lines[-1] != "What do you do?" else scenario_lines[-2]

    send_response(sock, scenario, log_file)

Complete Solver Script

import socket

def recvuntil(sock, delim=b'\n'):
    data = b''
    try:
        while not data.endswith(delim):
            fragment = sock.recv(1)
            if not fragment:
                break
            data += fragment
    except socket.timeout:
        print("Timeout reached without finding delimiter.")
    return data.decode()

def send_response(sock, scenario, log_file):
    action_map = {'GORGE': 'STOP', 'PHREAK': 'DROP', 'FIRE': 'ROLL'}
    actions = [action_map[part.strip()] for part in scenario.split(',')]
    response = '-'.join(actions) + '\n'
    sock.sendall(response.encode())
    log_file.write("Sent: " + response)

def main(ip, port):
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock, open("game_log.txt", "w") as log_file:
        sock.connect((ip, port))
        sock.settimeout(2)

        intro = recvuntil(sock, b'Are you ready? (y/n)')
        print(intro)
        log_file.write(intro + '\n')
        sock.sendall(b'y\n')

        index = 0
        while True:
            index += 1
            print(f"\nScenario {index}:")
            try:
                prompt = recvuntil(sock, b'What do you do?')
                print(prompt)
                log_file.write("Received: " + prompt + '\n')

                if "What do you do?" not in prompt:
                    continue

                scenario_lines = prompt.strip().split('\n')
                scenario = scenario_lines[-1] if scenario_lines[-1] != "What do you do?" else scenario_lines[-2]

                send_response(sock, scenario, log_file)

            except socket.timeout:
                print("No more data from the server.")
                log_file.write("No more data from the server.\n")
                break

if __name__ == "__main__":
    IP = "94.237.56.248"
    PORT = 58685
    main(IP, PORT)

Key Takeaways

Socket programming fundamentals for remote server communication
String manipulation and parsing of game scenarios
Understanding protocol-based challenges where responses must follow specific rules
Logging output for debugging complex interactions
Timeout handling when dealing with network sockets

Flag: HTB{1_wiLl_sT0p_dR0p_4nD_r0Ll_mY_w4Y_oUt!}