add support for MD5 authentication in HSRP dissector

--HG--
branch : HSRP-fixes

scapy/layers/hsrp.py

@@ -3,6 +3,31 @@
 ## Copyright (C) Philippe Biondi <phil@secdev.org>
 ## This program is published under a GPLv2 license
 
+#############################################################################
+##                                                                         ##
+## hsrp.py --- HSRP  protocol support for Scapy                            ##
+##                                                                         ##
+## Copyright (C) 2010  Mathieu RENARD mathieu.renard(at)gmail.com          ##
+##                                                                         ##
+## This program is free software; you can redistribute it and/or modify it ##
+## under the terms of the GNU General Public License version 2 as          ##
+## published by the Free Software Foundation; version 2.                   ##
+##                                                                         ##
+## 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.                                ##
+##                                                                         ##
+#############################################################################
+## HSRP Version 1
+##  Ref. RFC 2281
+## HSRP Version 2
+##  Ref. http://www.smartnetworks.jp/2006/02/hsrp_8_hsrp_version_2.html
+##
+## $Log: hsrp.py,v $
+## Revision 0.2  2011/05/01 15:23:34  mrenard
+##   Cleanup code
+
 """
 HSRP (Hot Standby Router Protocol): proprietary redundancy protocol for Cisco routers.
 """
@@ -11,22 +36,44 @@ from scapy.fields import *
 from scapy.packet import *
 from scapy.layers.inet import UDP
 
+
 class HSRP(Packet):
     name = "HSRP"
     fields_desc = [
         ByteField("version", 0),
-        ByteEnumField("opcode", 0, { 0:"Hello", 1:"Coup", 2:"Resign", 3:"Advertise"}),
-        ByteEnumField("state", 16, { 0:"Initial", 1:"Learn", 2:"Listen", 4:"Speak", 8:"Standby", 16:"Active"}),
+        ByteEnumField("opcode", 0, {0: "Hello", 1: "Coup", 2: "Resign", 3: "Advertise"}),
+        ByteEnumField("state", 16, {0: "Initial", 1: "Learn", 2: "Listen", 4: "Speak", 8: "Standby", 16: "Active"}),
         ByteField("hellotime", 3),
         ByteField("holdtime", 10),
         ByteField("priority", 120),
         ByteField("group", 1),
         ByteField("reserved", 0),
-        StrFixedLenField("auth","cisco",8),
-        IPField("virtualIP","192.168.1.1") ]
-        
+        StrFixedLenField("auth", "cisco" + "\00" * 3, 8),
+        IPField("virtualIP", "192.168.1.1")]
+
+    def guess_payload_class(self, payload):
+        if self.underlayer.len > 28:
+            return HSRPmd5
+        else:
+            return Packet.guess_payload_class(self, payload)
+
+
+class HSRPmd5(Packet):
+    name = "HSRP MD5 Authentication"
+    fields_desc = [
+        ByteEnumField("type", 4, {4: "MD5 authentication"}),
+        ByteField("len", None),
+        ByteEnumField("algo", 0, {1: "MD5"}),
+        ByteField("padding", 0x00),
+        XShortField("flags", 0x00),
+        IPField("sourceip", None),
+        XIntField("keyid", 0x00),
+        StrFixedLenField("authdigest", "\00" * 16, 16)]
 
+    def post_build(self, p, pay):
+        if self.len is None and pay:
+            l = len(pay)
+            p = p[:1] + hex(l)[30:] + p[30:]
+        return p
 
-        
-        
-bind_layers( UDP,           HSRP,          dport=1985, sport=1985)
+bind_layers(UDP, HSRP, dport=1985, sport=1985)