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listener.py
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listener.py
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from socket import *
import struct
import base64
import select
# see https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol
# section DHCP options
def inet_ntoaX(data):
return ['.'.join(map(str, data[i:i + 4])) for i in range(0, len(data), 4)]
def inet_atonX(ips):
return b''.join(map(inet_aton, ips))
dhcp_message_types = {
1: 'DHCPDISCOVER',
2: 'DHCPOFFER',
3: 'DHCPREQUEST',
4: 'DHCPDECLINE',
5: 'DHCPACK',
6: 'DHCPNAK',
7: 'DHCPRELEASE',
8: 'DHCPINFORM',
}
reversed_dhcp_message_types = dict()
for i, v in dhcp_message_types.items():
reversed_dhcp_message_types[v] = i
shortunpack = lambda data: (data[0] << 8) + data[1]
shortpack = lambda i: bytes([i >> 8, i & 255])
def macunpack(data):
s = base64.b16encode(data)
return ':'.join([s[i:i + 2].decode('ascii') for i in range(0, 12, 2)])
def macpack(mac):
return base64.b16decode(mac.replace(':', '').replace('-', '').encode('ascii'))
def unpackbool(data):
return data[0]
def packbool(bool):
return bytes([bool])
options = [
# RFC1497 vendor extensions
('pad', None, None),
('subnet_mask', inet_ntoa, inet_aton),
('time_offset', None, None),
('router', inet_ntoaX, inet_atonX),
('time_server', inet_ntoaX, inet_atonX),
('name_server', inet_ntoaX, inet_atonX),
('domain_name_server', inet_ntoaX, inet_atonX),
('log_server', inet_ntoaX, inet_atonX),
('cookie_server', inet_ntoaX, inet_atonX),
('lpr_server', inet_ntoaX, inet_atonX),
('impress_server', inet_ntoaX, inet_atonX),
('resource_location_server', inet_ntoaX, inet_atonX),
('host_name', lambda d: d.decode('ASCII'), lambda d: d.encode('ASCII')),
('boot_file_size', None, None),
('merit_dump_file', None, None),
('domain_name', None, None),
('swap_server', inet_ntoa, inet_aton),
('root_path', None, None),
('extensions_path', None, None),
# IP Layer Parameters per Host
('ip_forwarding_enabled', unpackbool, packbool),
('non_local_source_routing_enabled', unpackbool, packbool),
('policy_filer', None, None),
('maximum_datagram_reassembly_size', shortunpack, shortpack),
('default_ip_time_to_live', lambda data: data[0], lambda i: bytes([i])),
('path_mtu_aging_timeout', None, None),
('path_mtu_plateau_table', None, None),
# IP Layer Parameters per Interface
('interface_mtu', None, None),
('all_subnets_are_local', unpackbool, packbool),
('broadcast_address', inet_ntoa, inet_aton),
('perform_mask_discovery', unpackbool, packbool),
('mask_supplier', None, None),
('perform_router_discovery', None, None),
('router_solicitation_address', inet_ntoa, inet_aton),
('static_route', None, None),
# Link Layer Parameters per Interface
('trailer_encapsulation_option', None, None),
('arp_cache_timeout', None, None),
('ethernet_encapsulation', None, None),
# TCP Parameters
('tcp_default_ttl', None, None),
('tcp_keep_alive_interval', None, None),
('tcp_keep_alive_garbage', None, None),
# Application and Service Parameters Part 1
('network_information_service_domain', None, None),
('network_informtaion_servers', inet_ntoaX, inet_atonX),
('network_time_protocol_servers', inet_ntoaX, inet_atonX),
('vendor_specific_information', None, None),
('netbios_over_tcp_ip_name_server', inet_ntoaX, inet_atonX),
('netbios_over_tcp_ip_datagram_distribution_server', inet_ntoaX, inet_atonX),
('netbios_over_tcp_ip_node_type', None, None),
('netbios_over_tcp_ip_scope', None, None),
('x_window_system_font_server', inet_ntoaX, inet_atonX),
('x_window_system_display_manager', inet_ntoaX, inet_atonX),
# DHCP Extensions
('requested_ip_address', inet_ntoa, inet_aton),
('ip_address_lease_time', lambda d: struct.unpack('>I', d)[0], lambda i: struct.pack('>I', i)),
('option_overload', None, None),
('dhcp_message_type', lambda data: dhcp_message_types.get(data[0], data[0]),
(lambda name: bytes([reversed_dhcp_message_types.get(name, name)]))),
('server_identifier', inet_ntoa, inet_aton),
('parameter_request_list', list, bytes),
('message', None, None),
('maximum_dhcp_message_size', shortunpack, shortpack),
('renewal_time_value', None, None),
('rebinding_time_value', None, None),
('vendor_class_identifier', None, None),
('client_identifier', macunpack, macpack),
('tftp_server_name', None, None),
('boot_file_name', None, None),
# Application and Service Parameters Part 2
('network_information_service_domain', None, None),
('network_information_servers', inet_ntoaX, inet_atonX),
('', None, None),
('', None, None),
('mobile_ip_home_agent', inet_ntoaX, inet_atonX),
('smtp_server', inet_ntoaX, inet_atonX),
('pop_servers', inet_ntoaX, inet_atonX),
('nntp_server', inet_ntoaX, inet_atonX),
('default_www_server', inet_ntoaX, inet_atonX),
('default_finger_server', inet_ntoaX, inet_atonX),
('default_irc_server', inet_ntoaX, inet_atonX),
('streettalk_server', inet_ntoaX, inet_atonX),
('stda_server', inet_ntoaX, inet_atonX),
]
assert options[18][0] == 'extensions_path', options[18][0]
assert options[25][0] == 'path_mtu_plateau_table', options[25][0]
assert options[33][0] == 'static_route', options[33][0]
assert options[50][0] == 'requested_ip_address', options[50][0]
assert options[64][0] == 'network_information_service_domain', options[64][0]
assert options[76][0] == 'stda_server', options[76][0]
class ReadBootProtocolPacket(object):
for i, o in enumerate(options):
locals()[o[0]] = None
locals()['option_{0}'.format(i)] = None
del i, o
def __init__(self, data, address=('0.0.0.0', 0)):
self.dhcp_message_type = None
self.data = data
self.address = address
self.host = address[0]
self.port = address[1]
# wireshark = wikipedia = data[...]
self.message_type = self.OP = data[0]
self.hardware_type = self.HTYPE = data[1]
self.hardware_address_length = self.HLEN = data[2]
self.hops = self.HOPS = data[3]
self.XID = self.transaction_id = struct.unpack('>I', data[4:8])[0]
self.seconds_elapsed = self.SECS = shortunpack(data[8:10])
self.bootp_flags = self.FLAGS = shortunpack(data[8:10])
self.client_ip_address = self.CIADDR = inet_ntoa(data[12:16])
self.your_ip_address = self.YIADDR = inet_ntoa(data[16:20])
self.next_server_ip_address = self.SIADDR = inet_ntoa(data[20:24])
self.relay_agent_ip_address = self.GIADDR = inet_ntoa(data[24:28])
self.client_mac_address = self.CHADDR = macunpack(data[28: 28 + self.hardware_address_length])
index = 236
self.magic_cookie = self.magic_cookie = inet_ntoa(data[index:index + 4]);
index += 4
self.options = dict()
self.named_options = dict()
while index < len(data):
option = data[index];
index += 1
if option == 0:
# padding
# Can be used to pad other options so that they are aligned to the word boundary; is not followed by length byte
continue
if option == 255:
# end
break
option_length = data[index];
index += 1
option_data = data[index: index + option_length];
index += option_length
self.options[option] = option_data
if option < len(options):
option_name, function, _ = options[option]
if function:
option_data = function(option_data)
if option_name:
setattr(self, option_name, option_data)
self.named_options[option_name] = option_data
setattr(self, 'option_{}'.format(option), option_data)
def __getitem__(self, key):
print(key, dir(self))
return getattr(self, key, None)
def __contains__(self, key):
return key in self.__dict__
@property
def formatted_named_options(self):
return "\n".join(
"{}:\t{}".format(name.replace('_', ' '), value) for name, value in sorted(self.named_options.items()))
def __str__(self):
return """Message Type: {self.message_type}
client MAC address: {self.client_mac_address}
client IP address: {self.client_ip_address}
your IP address: {self.your_ip_address}
next server IP address: {self.next_server_ip_address}
{self.formatted_named_options}
""".format(self=self)
def __gt__(self, other):
return id(self) < id(other)
data = base64.b16decode(
b'02010600f7b41ad100000000c0a800640000000000000000000000007c7a914bca6c00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000638253633501053604c0a800010104ffffff000304c0a800010604c0a80001ff00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'.upper())
assert data[0] == 2
p = ReadBootProtocolPacket(data)
assert p.message_type == 2
assert p.hardware_type == 1
assert p.hardware_address_length == 6
assert p.hops == 0
assert p.transaction_id == 4155775697
assert p.seconds_elapsed == 0
assert p.bootp_flags == 0
assert p.client_ip_address == '192.168.0.100'
assert p.your_ip_address == '0.0.0.0'
assert p.next_server_ip_address == '0.0.0.0'
assert p.relay_agent_ip_address == '0.0.0.0'
assert p.client_mac_address.lower() == '7c:7a:91:4b:ca:6c'
assert p.magic_cookie == '99.130.83.99'
assert p.dhcp_message_type == 'DHCPACK'
assert p.options[53] == b'\x05'
assert p.server_identifier == '192.168.0.1'
assert p.subnet_mask == '255.255.255.0'
assert p.router == ['192.168.0.1']
assert p.domain_name_server == ['192.168.0.1']
str(p)
if __name__ == '__main__':
s1 = socket(type=SOCK_DGRAM)
s1.setsockopt(SOL_IP, SO_REUSEADDR, 1)
s1.bind(('', 67))
# s2 = socket(type = SOCK_DGRAM)
# s2.setsockopt(SOL_IP, SO_REUSEADDR, 1)
# s2.bind(('', 68))
while 1:
reads = select.select([s1], [], [], 1)[0]
for s in reads:
packet = ReadBootProtocolPacket(*s.recvfrom(4096))
print(packet)