Source Code for Module Peach.Fixups.checksums

  1   
  2  ''' 
  3  A few standard fixups. 
  4  ''' 
  5   
  6  # 
  7  # Copyright (c) 2008 Michael Eddington 
  8  # 
  9  # Permission is hereby granted, free of charge, to any person obtaining a copy  
 10  # of this software and associated documentation files (the "Software"), to deal 
 11  # in the Software without restriction, including without limitation the rights  
 12  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell  
 13  # copies of the Software, and to permit persons to whom the Software is  
 14  # furnished to do so, subject to the following conditions: 
 15  # 
 16  # The above copyright notice and this permission notice shall be included in     
 17  # all copies or substantial portions of the Software. 
 18  # 
 19  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR  
 20  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  
 21  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE  
 22  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER  
 23  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
 24  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
 25  # SOFTWARE. 
 26  # 
 27   
 28  # Authors: 
 29  #   Michael Eddington (mike@phed.org) 
 30   
 31  # $Id$ 
 32   
 33  import zlib, struct, binascii, array 
 34  from Peach.fixup import Fixup 
 35  from Peach.Engine.common import * 
 36   
 37 -class ExpressionFixup(Fixup): 
 38          ''' 
 39          Sometimes you need to perform some math as the fixup.  This 
 40          relation will take a ref, then an expression (python). 
 41          ''' 
 42           
 43 -        def __init__(self, ref, expression): 
 44                  Fixup.__init__(self) 
 45                  self.ref = ref 
 46                  self.expression = expression 
 47           
 48 -        def fixup(self): 
 49                  ref = self._findDataElementByName(self.ref) 
 50                  stuff = ref.getValue() 
 51                  if stuff == None: 
 52                          raise Exception("Error: ExpressionFixup was unable to locate [%s]" % self.ref) 
 53                   
 54                  return evalEvent(self.expression, { "self" : self, "ref" : ref, "data" : stuff  }) 
 55           
 56   
 57 -class Crc32Fixup(Fixup): 
 58          ''' 
 59          Standard CRC32 as defined by ISO 3309.  Used by PNG, zip, etc. 
 60          ''' 
 61           
 62 -        def __init__(self, ref): 
 63                  Fixup.__init__(self) 
 64                  self.ref = ref 
 65           
 66 -        def fixup(self): 
 67                  stuff = self._findDataElementByName(self.ref).getValue() 
 68                  if stuff == None: 
 69                          raise Exception("Error: Crc32Fixup was unable to locate [%s]" % self.ref) 
 70                   
 71                  return zlib.crc32(stuff) 
 72   
 73   
 74 -class Crc32DualFixup(Fixup): 
 75          ''' 
 76          Standard CRC32 as defined by ISO 3309.  Used by PNG, zip, etc. 
 77          ''' 
 78           
 79 -        def __init__(self, ref1, ref2): 
 80                  Fixup.__init__(self) 
 81                  self.ref1 = ref1 
 82                  self.ref2 = ref2 
 83           
 84 -        def fixup(self): 
 85                  stuff1 = self._findDataElementByName(self.ref1).getValue() 
 86                  stuff2 = self._findDataElementByName(self.ref2).getValue() 
 87                  if stuff1 == None or stuff2 == None: 
 88                          raise Exception("Error: Crc32DualFixup was unable to locate [%s] or [%s]" % (self.ref1, self.ref2)) 
 89                   
 90                  crc1 = zlib.crc32(stuff1) 
 91                  return zlib.crc32(stuff2, crc1) 
 92   
 93   
 94 -class EthernetChecksumFixup(Fixup): 
 95          ''' 
 96          Ethernet Chucksum Fixup. 
 97          ''' 
 98           
 99 -        def __init__(self, ref): 
100                  Fixup.__init__(self) 
101                  self.ref = ref 
102           
103 -        def _checksum(self, checksum_packet): 
104                  """Calculate checksum""" 
105                  ethernetKey = 0x04C11DB7 
106                  return binascii.crc32(checksum_packet, ethernetKey) 
107           
108 -        def fixup(self): 
109                  stuff = self._findDataElementByName(self.ref).getValue() 
110                  if stuff == None: 
111                          raise Exception("Error: EthernetChecksumFixup was unable to locate [%s]" % self.ref) 
112                   
113                  return self._checksum(stuff) 
114   
115   
116 -class IcmpChecksumFixup(Fixup): 
117          ''' 
118          Ethernet Chucksum Fixup. 
119          ''' 
120           
121 -        def __init__(self, ref): 
122                  Fixup.__init__(self) 
123                  self.ref = ref 
124           
125 -        def _checksum(self, checksum_packet): 
126                  """Calculate checksum""" 
127                  # add byte if not dividable by 2 
128                  if len(checksum_packet) & 1:               
129                          checksum_packet = checksum_packet + '\0' 
130                  # split into 16-bit word and insert into a binary array 
131                  words = array.array('h', checksum_packet)  
132                  sum = 0 
133                   
134                  # perform ones complement arithmetic on 16-bit words 
135                  for word in words: 
136                          sum += (word & 0xffff)  
137                   
138                  hi = sum >> 16  
139                  lo = sum & 0xffff  
140                  sum = hi + lo 
141                  sum = sum + (sum >> 16) 
142                   
143                  return (~sum) & 0xffff # return ones complement 
144           
145 -        def fixup(self): 
146                  stuff = self._findDataElementByName(self.ref).getValue() 
147                  if stuff == None: 
148                          raise Exception("Error: IcmpChecksumFixup was unable to locate [%s]" % self.ref) 
149                   
150                  return self._checksum(stuff) 
151   
152  # end 
153