#!/usr/bin/env python # # Copyright(C) 2010 Simon Howard # # This program is free software; you can redistribute it and/or # modify it under the terms of the GNU General Public License # as published by the Free Software Foundation; either version 2 # of the License, or (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA # 02111-1307, USA. # # # Chocolate Doom master server. # import socket import struct import simplejson from select import select from time import time, strftime from master_config import * import secure_demo # Maximum length of a query response. MAX_RESPONSE_LEN = 1400 # Normal packet types. NET_PACKET_TYPE_QUERY = 13 NET_PACKET_TYPE_QUERY_RESPONSE = 14 # Packet types, matches the constants in net_defs.h. NET_MASTER_PACKET_TYPE_ADD = 0 NET_MASTER_PACKET_TYPE_ADD_RESPONSE = 1 NET_MASTER_PACKET_TYPE_QUERY = 2 NET_MASTER_PACKET_TYPE_QUERY_RESPONSE = 3 NET_MASTER_PACKET_TYPE_GET_METADATA = 4 NET_MASTER_PACKET_TYPE_GET_METADATA_RESPONSE = 5 NET_MASTER_PACKET_TYPE_SIGN_START = 6 NET_MASTER_PACKET_TYPE_SIGN_START_RESPONSE = 7 NET_MASTER_PACKET_TYPE_SIGN_END = 8 NET_MASTER_PACKET_TYPE_SIGN_END_RESPONSE = 9 def bind_socket_to(sock, config): """ Bind the specified socket to the address/port configuration from the configuration file. """ if config is not None: if config[0] is not None: address = socket.gethostbyname(config[0]) else: address = socket.inet_ntoa(struct.pack(">l", socket.INADDR_ANY)) sock.bind((address, config[1])) # Address and port to listen on. def read_string(packet): """ Given binary packet data, read a NUL-terminated string, returning the remainder of the packet data and the decoded string. """ terminator = struct.pack("b", 0) if terminator not in packet: raise Exception("String terminator not found") strlen = packet.index(terminator) result, = struct.unpack("%ss" % strlen, packet[0:strlen]) return packet[strlen + 1:], result class Server: """ A server that has registered itself. """ def __init__(self, addr): self.addr = addr self.add_time = time() self.verified = False self.metadata = {} self.refresh() def refresh(self): self.refresh_time = time() def age(self): return time() - self.add_time def set_metadata(self, metadata): self.metadata_time = time() self.metadata = metadata def metadata_age(self): return time() - self.metadata_time def timed_out(self): return time() - self.refresh_time > SERVER_TIMEOUT def __str__(self): return "%s:%i" % self.addr class MasterServer: def open_log_file(self): self.log_file = open(LOG_FILE, "a") def log_output(self, addr, s): timestamp = strftime("%b %d %H:%M:%S") if addr is not None: addr_str = "%s:%i" % addr else: addr_str = "-" self.log_file.write("%s %s %s\n" % (timestamp, addr_str, s)) self.log_file.flush() def __init__(self, server_address, query_address): """ Initialise a new master server. """ self.servers = {} self.open_log_file() self.sock = self.open_socket(server_address) self.query_sock = self.open_socket(query_address) if secure_demo.available and SIGNING_KEY: self.signer = secure_demo.SecureSigner(SIGNING_KEY) else: self.signer = None def send_query(self, server): """ Send a query to the specified server. """ packet = struct.pack(">h", NET_PACKET_TYPE_QUERY) self.query_sock.sendto(packet, server.addr) def parse_query_data(self, data): """ Read the data from a query response. """ data, version = read_string(data) server_state, num_players, max_players, mode, mission \ = struct.unpack("bbbbb", data[0:5]) data, server_name = read_string(data[5:]) # Not all of this is of interest to us. Some of it will # be out of date fairly quickly because the master doesn't # query the servers very often. return { "version": version, "max_players": max_players, "name": server_name } def process_query_response(self, data, addr): """ Parse a packet received (presumably) in response to a query that we sent to a server. """ # Unknown? if addr not in self.servers: return server = self.servers[addr] # Check packet type packet_type, = struct.unpack(">h", data[0:2]) if packet_type != NET_PACKET_TYPE_QUERY_RESPONSE: return # Read metadata from query and store it for future use. metadata = self.parse_query_data(data[2:]) metadata["address"], metadata["port"] = addr server.set_metadata(metadata) # Server responded to our query, so it is verified. # We can send a positive response to its add request. if not server.verified: self.log_output(server.addr, "Server responded to query, added") server.verified = True self.send_add_response(server, 1) def send_message(self, addr, message_type, payload): """ Send a message of the specified type to the specified remote address. """ header = struct.pack(">h", message_type) packet = header + payload self.sock.sendto(packet, addr) def strings_to_packets(self, strings): """ Convert a list of strings into a list of payload strings for responding to queries. """ packets = [struct.pack("")] for string in strings: # Encode string along with terminating NUL. encoded_str = struct.pack("%is" % (len(string) + 1), string) # Start a new packet? if len(packets[-1]) + len(encoded_str) > MAX_RESPONSE_LEN: packets.append(struct.pack("")) packets[-1] += encoded_str return packets def send_add_response(self, server, success): """ Send a response to a server's add request. """ self.send_message(server.addr, NET_MASTER_PACKET_TYPE_ADD_RESPONSE, struct.pack(">h", success)) def process_add_to_master(self, addr): """ Process an "add to master" request received from a server. """ if addr in self.servers: self.log_output(addr, "Refresh server") server = self.servers[addr] server.refresh() else: server = Server(addr) self.servers[addr] = server # If the metadata for this server is old, un-verify it # to force a query to refresh it. if server.verified and server.metadata_age() > METADATA_REFRESH_TIME: self.log_output(addr, "Metadata is old, forcing query") server.verified = False # If the server has already been verified, we can send a # reply immediately. Otherwise, query the server via a # different socket first to verify it. # Why is this needed? The server might be behind a NAT # gateway. In this case, the master might be able to # communicate with it, but other machines might not. if server.verified: self.send_add_response(server, 1) else: self.log_output(addr, "Add request, sending query to confirm") self.send_query(server) def process_query(self, addr): """ Process a query message received from a client. """ self.log_output(addr, "Query") # Generate a list of strings representing servers. Only include # verified servers. verified_servers = filter(lambda s: s.verified, self.servers.values()) strings = [ str(server) for server in verified_servers] # Send response packets. for packet in self.strings_to_packets(strings): self.send_message(addr, NET_MASTER_PACKET_TYPE_QUERY_RESPONSE, packet) def process_metadata_request(self, addr): """ Process a metadata request from a client. """ self.log_output(addr, "Metadata request") def metadata_string(server): metadata = server.metadata.copy() metadata["age"] = server.age() return simplejson.dumps(metadata) # Generate a list of strings containing JSON-encoded metadata # about servers. Only include verified servers. verified_servers = filter(lambda s: s.verified, self.servers.values()) strings = [ metadata_string(server) for server in verified_servers] # Send response packets. for packet in self.strings_to_packets(strings): self.send_message(addr, NET_MASTER_PACKET_TYPE_GET_METADATA_RESPONSE, packet) def sign_start_message(self, addr): """ Generate a signed start message and return to the client. """ self.log_output(addr, "Start demo") if self.signer is None: return # Generate start message and send it back. # The nonce also gets sent in a separate field, so the client # doesn't have to parse the signature to get it out. nonce, signature = self.signer.sign_start_message() packet = nonce + signature self.send_message(addr, NET_MASTER_PACKET_TYPE_SIGN_START_RESPONSE, packet) def sign_end_message(self, data, addr): """ Generate a signed end message and return to the client. """ self.log_output(addr, "End demo") if self.signer is None: return # Parse the data. The first part is a 160-bit SHA1 hash, and the # rest of the data is the start message. demo_hash = data[0:20] start_message = data[20:] # Parse the start message and verify the signature, then use it # to generate an end message along with the hash of the demo. signature = self.signer.sign_end_message(start_message, demo_hash) if signature is None: self.log_output(addr, "Failed to verify start message!") else: self.send_message(addr, NET_MASTER_PACKET_TYPE_SIGN_END_RESPONSE, signature) def process_packet(self, data, addr): """ Process a packet received from a server. """ packet_type, = struct.unpack(">h", data[0:2]) if packet_type == NET_MASTER_PACKET_TYPE_ADD: self.process_add_to_master(addr) elif packet_type == NET_MASTER_PACKET_TYPE_QUERY: self.process_query(addr) elif packet_type == NET_MASTER_PACKET_TYPE_GET_METADATA: self.process_metadata_request(addr) elif packet_type == NET_MASTER_PACKET_TYPE_SIGN_START: self.sign_start_message(addr) elif packet_type == NET_MASTER_PACKET_TYPE_SIGN_END: self.sign_end_message(data[2:], addr) def rx_packet(self): """ Invoked when a packet is received. """ data, addr = self.sock.recvfrom(1024) try: self.process_packet(data, addr) except Exception, e: print e def rx_packet_query_sock(self): """ Invoked when a packet is received on the query socket. """ data, addr = self.query_sock.recvfrom(1024) try: self.process_query_response(data, addr) except Exception, e: print e def age_servers(self): """ Check server timestamps and flush out stale servers. """ for server in self.servers.values(): if server.timed_out(): self.log_output(server.addr, "Timed out: no heartbeat in %i secs" % (time() - server.refresh_time)) del self.servers[server.addr] # Expect a response to queries quickly, otherwise add # requests are rejected. elif not server.verified and time() - server.refresh_time > 5: self.log_output(server.addr, "No response to query, add rejected") self.send_add_response(server, 0) del self.servers[server.addr] def open_socket(self, address): """ Open a server socket and bind to the specified address. """ sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) bind_socket_to(sock, address) return sock def run(self): """ Run the server main loop, listening for packets. """ self.log_output(None, "Server started.") while True: r, w, x = select([self.sock, self.query_sock], [], [], 5) self.age_servers() if self.sock in r: self.rx_packet() if self.query_sock in r: self.rx_packet_query_sock() if __name__ == "__main__": server = MasterServer(SERVER_ADDRESS, QUERY_ADDRESS) server.run()