#! /usr/bin/env python
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# This file is part of Scapy
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# Scapy is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 2 of the License, or
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# any later version.
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#
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# Scapy is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with Scapy. If not, see <http://www.gnu.org/licenses/>.
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# scapy.contrib.description = IGMP/IGMPv2
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# scapy.contrib.status = loads
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from __future__ import print_function
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from scapy.packet import *
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from scapy.fields import *
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from scapy.layers.inet import *
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from scapy.layers.l2 import DestMACField, getmacbyip
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from scapy.error import warning
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from scapy.compat import chb, orb
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def isValidMCAddr(ip):
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"""convert dotted quad string to long and check the first octet"""
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FirstOct=atol(ip)>>24 & 0xFF
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return (FirstOct >= 224) and (FirstOct <= 239)
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class IGMP(Packet):
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"""IGMP Message Class for v1 and v2.
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This class is derived from class Packet. You need call "igmpize()"
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so the packet is transformed according the RFC when sent.
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a=Ether(src="00:01:02:03:04:05")
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b=IP(src="1.2.3.4")
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c=IGMP(type=0x12, gaddr="224.2.3.4")
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x = a/b/c
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x[IGMP].igmpize()
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sendp(a/b/c, iface="en0")
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Parameters:
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type IGMP type field, 0x11, 0x12, 0x16 or 0x17
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mrcode Maximum Response time (zero for v1)
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gaddr Multicast Group Address 224.x.x.x/4
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See RFC2236, Section 2. Introduction for definitions of proper
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IGMPv2 message format http://www.faqs.org/rfcs/rfc2236.html
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"""
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name = "IGMP"
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igmptypes = { 0x11 : "Group Membership Query",
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0x12 : "Version 1 - Membership Report",
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0x16 : "Version 2 - Membership Report",
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0x17 : "Leave Group"}
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fields_desc = [ ByteEnumField("type", 0x11, igmptypes),
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ByteField("mrcode", 20),
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XShortField("chksum", None),
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IPField("gaddr", "0.0.0.0")]
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def post_build(self, p, pay):
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"""Called implicitly before a packet is sent to compute and place IGMP checksum.
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Parameters:
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self The instantiation of an IGMP class
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p The IGMP message in hex in network byte order
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pay Additional payload for the IGMP message
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"""
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p += pay
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if self.chksum is None:
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ck = checksum(p)
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p = p[:2]+chb(ck>>8)+chb(ck&0xff)+p[4:]
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return p
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@classmethod
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def dispatch_hook(cls, _pkt=None, *args, **kargs):
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if _pkt and len(_pkt) >= 4:
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from scapy.contrib.igmpv3 import IGMPv3
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if orb(_pkt[0]) in [0x22, 0x30, 0x31, 0x32]:
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return IGMPv3
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if orb(_pkt[0]) == 0x11 and len(_pkt) >= 12:
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return IGMPv3
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return IGMP
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def igmpize(self):
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"""Called to explicitly fixup the packet according to the IGMP RFC
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The rules are:
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General:
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1. the Max Response time is meaningful only in Membership Queries and should be zero
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IP:
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1. Send General Group Query to 224.0.0.1 (all systems)
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2. Send Leave Group to 224.0.0.2 (all routers)
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3a.Otherwise send the packet to the group address
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3b.Send reports/joins to the group address
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4. ttl = 1 (RFC 2236, section 2)
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5. send the packet with the router alert IP option (RFC 2236, section 2)
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Ether:
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1. Recalculate destination
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Returns:
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True The tuple ether/ip/self passed all check and represents
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a proper IGMP packet.
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False One of more validation checks failed and no fields
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were adjusted.
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The function will examine the IGMP message to assure proper format.
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Corrections will be attempted if possible. The IP header is then properly
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adjusted to ensure correct formatting and assignment. The Ethernet header
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is then adjusted to the proper IGMP packet format.
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"""
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gaddr = self.gaddr if hasattr(self, "gaddr") and self.gaddr else "0.0.0.0"
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underlayer = self.underlayer
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if not self.type in [0x11, 0x30]: # General Rule 1
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self.mrcode = 0
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if isinstance(underlayer, IP):
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if (self.type == 0x11):
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if (gaddr == "0.0.0.0"):
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underlayer.dst = "224.0.0.1" # IP rule 1
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elif isValidMCAddr(gaddr):
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underlayer.dst = gaddr # IP rule 3a
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else:
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warning("Invalid IGMP Group Address detected !")
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return False
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elif ((self.type == 0x17) and isValidMCAddr(gaddr)):
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underlayer.dst = "224.0.0.2" # IP rule 2
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elif ((self.type == 0x12) or (self.type == 0x16)) and (isValidMCAddr(gaddr)):
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underlayer.dst = gaddr # IP rule 3b
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else:
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warning("Invalid IGMP Type detected !")
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return False
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if not any(isinstance(x, IPOption_Router_Alert) for x in underlayer.options):
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underlayer.options.append(IPOption_Router_Alert())
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_root = self.firstlayer()
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if _root.haslayer(Ether):
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# Force recalculate Ether dst
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_root[Ether].dst = getmacbyip(underlayer.dst) # Ether rule 1
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from scapy.contrib.igmpv3 import IGMPv3
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if isinstance(self, IGMPv3):
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self.encode_maxrespcode()
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return True
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def mysummary(self):
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"""Display a summary of the IGMP object."""
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if isinstance(self.underlayer, IP):
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return self.underlayer.sprintf("IGMP: %IP.src% > %IP.dst% %IGMP.type% %IGMP.gaddr%")
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else:
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return self.sprintf("IGMP %IGMP.type% %IGMP.gaddr%")
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bind_layers( IP, IGMP, frag=0,
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proto=2,
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ttl=1)
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