cappie/protocol.py

   1 #!/usr/bin/python
   2 ###############################################################################
   3 #                                                                             #
   4 # Cappie                                                                      #
   5 # Copyright (C) 2010 Michael Tremer                                           #
   6 #                                                                             #
   7 # This program is free software: you can redistribute it and/or modify        #
   8 # it under the terms of the GNU General Public License as published by        #
   9 # the Free Software Foundation, either version 3 of the License, or           #
  10 # (at your option) any later version.                                         #
  11 #                                                                             #
  12 # This program is distributed in the hope that it will be useful,             #
  13 # but WITHOUT ANY WARRANTY; without even the implied warranty of              #
  14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               #
  15 # GNU General Public License for more details.                                #
  16 #                                                                             #
  17 # You should have received a copy of the GNU General Public License           #
  18 # along with this program.  If not, see <http://www.gnu.org/licenses/>.       #
  19 #                                                                             #
  20 ###############################################################################
  21
  22 import struct
  23
  24 import database
  25
  26 from constants import *
  27 from errors import *
  28
  29 def val2int(val):
  30         return int("".join(["%02d" % ord(c) for c in val]), 16)
  31
  32 def val2ip4(val):
  33         return ".".join(["%d" % ord(i) for i in val])
  34
  35 def val2mac(val):
  36         return ":".join(["%02x" % ord(i) for i in val])
  37
  38 def decode_packet(data):
  39         try:
  40                 protocol = val2int(struct.unpack("!2s", data[12:14])[0])
  41         except:
  42                 raise DecodeError
  43
  44         try:
  45                 d = protocol2function[protocol](data)
  46         except KeyErrror:
  47                 raise PacketTypeError, "Could not determine type of packet"
  48
  49         return database.Row(d)
  50
  51 def decode_arp_packet(data):
  52         operationmap = {
  53                 1 : OPERATION_REQUEST,
  54                 2 : OPERATION_RESPONSE,
  55         }
  56
  57         #if not len(data) == 42:
  58         #       raise DecodeError, "Data has wrong length: %d" % len(data)
  59
  60         ret = {
  61                 "type" : TYPE_ARP,
  62         }
  63
  64         #"hwtype" : data[:2],
  65         hw_addr_size = val2int(struct.unpack("!1s", data[18:19])[0])
  66         hw_prot_size = val2int(struct.unpack("!1s", data[19:20])[0])
  67         operation = val2int(struct.unpack("!2s", data[20:22])[0])
  68
  69         # TODO Must check hwtype here...
  70
  71         try:
  72                 ret["operation"] = operationmap[operation]
  73         except KeyError:
  74                 raise DecodeError, "Unknown operation type"
  75
  76         address_length = hw_addr_size + hw_prot_size
  77         unpack_str = "!%ss%ss" % (hw_addr_size, hw_prot_size)
  78
  79         ret["source_address"], ret["source_ip_address"] = \
  80                 struct.unpack(unpack_str, data[22:22 + address_length])
  81
  82         ret["destination_address"], ret["destination_ip_address"] = \
  83                 struct.unpack(unpack_str, data[22 + address_length:22 + address_length * 2])
  84
  85         for i in ("source_address", "destination_address"):
  86                 ret[i] = val2mac(ret[i])
  87
  88         for i in ("source_ip_address", "destination_ip_address"):
  89                 ret[i] = val2ip4(ret[i])
  90
  91         return ret
  92
  93 def decode_ndp_packet(data):
  94         raise PacketTypeError
  95
  96 protocol2function = {
  97         ETHERTYPE_ARP : decode_arp_packet,
  98 }