DHCP traffic analyser

[JRSmile 17]

Hi there,

a long long time ago... i found the time and need to add again something to the examples forum.

I'm currently trying to get better in packet analysing and wrote a proove of concept dhcp protocol analyser.

its no where near a completed state but just to give you a hint what can be done with winpcap.udf and fighting against bits/bytes and horrorbly written RFCs (http://www.networksorcery.com/enp/rfc/rfc1533.txt , http://www.networksorcery.com/enp/protocol/bootp/options.htm).

YOU WILL NEED THE WinPCap - Packet.dll UDF from here: ()

expandcollapse popup

#region ;**** Directives created by AutoIt3Wrapper_GUI ****
#AutoIt3Wrapper_Change2CUI=y
#endregion ;**** Directives created by AutoIt3Wrapper_GUI ****
#include <array.au3>
#include <date.au3>
#include "Winpcap.au3"
$winpcap = _PcapSetup()
If ($winpcap = -1) Then
MsgBox(16, "Pcap error !", "WinPcap not found !")
Exit
EndIf
$pcap_devices = _PcapGetDeviceList()
If ($pcap_devices = -1) Then
MsgBox(16, "Pcap error !", _PcapGetLastError())
Exit
EndIf
For $i = 0 To UBound($pcap_devices) - 1
;~  ConsoleWrite($pcap_devices[$i][0] & " ==> " & $pcap_devices[$i][1] & @CRLF)
Next
$dev_ID = $pcap_devices[0][0]

$i = 0
$pcap = 0
$packet = 0
$pcapfile = 0
$prom = 1
$filter = "port 67" ; DHCP
$pcap = _PcapStartCapture($dev_ID, $filter, $prom)
If ($pcap = -1) Then
MsgBox(16, "Pcap error !", _PcapGetLastError())
Exit
EndIf
$linktype = _PcapGetLinkType($pcap)
If ($linktype[1] <> "EN10MB") Then
MsgBox(16, "Pcap error !", "This example only works for Ethernet captures")
Exit
EndIf
;~ AdlibRegister("stats", 1000 * 60)
While True
If IsPtr($pcap) Then ; If $pcap is a Ptr, then the capture is running
  $time0 = TimerInit()
  While (TimerDiff($time0) < 500) ; Retrieve packets from queue for maximum 500ms before returning to main loop, not to "hang" the window for user
   $packet = _PcapGetPacket($pcap)
   If IsInt($packet) Then ExitLoop
   $udpdata = _UDP_Parser($packet[3])
   $dhcpdata = _DHCP_Parser($udpdata)
  WEnd
EndIf
Sleep(1)
WEnd
_PcapFree()
Exit
Func Stats()
$s = _PcapGetStats($pcap)
Local $stats_txt = ""
For $a = 1 To UBound($s, 1) - 1
  $stats_txt &= $s[$a][1] & ":" & $s[$a][0] & @CRLF
Next
ConsoleWrite($stats_txt)
EndFunc   ;==>Stats
Func _UDP_Parser($data)
If BinaryMid($data, 13, 2) <> "0x0800" Then Return ; Ethertype
If BinaryMid($data, 24, 1) <> "0x11" Then Return ; UDP
Local $srcip = Number(BinaryMid($data, 27, 1)) & "." & Number(BinaryMid($data, 28, 1)) & "." & Number(BinaryMid($data, 29, 1)) & "." & Number(BinaryMid($data, 30, 1))
Local $dstip = Number(BinaryMid($data, 31, 1)) & "." & Number(BinaryMid($data, 32, 1)) & "." & Number(BinaryMid($data, 33, 1)) & "." & Number(BinaryMid($data, 34, 1))
Local $srcport = Number(BinaryMid($data, 35, 1)) * 256 + Number(BinaryMid($data, 36, 1))
Local $dstport = Number(BinaryMid($data, 37, 1)) * 256 + Number(BinaryMid($data, 38, 1))
Local $udplength = Number(BinaryMid($data, 39, 1)) * 256 + Number(BinaryMid($data, 40, 1))
Local $udpchecksum = Number(BinaryMid($data, 41, 1)) * 256 + Number(BinaryMid($data, 42, 1))
ConsoleWrite($srcip & ":" & $srcport & " ==> " & $dstip & ":" & $dstport & " Length: " & $udplength & @CRLF)
Local $udpdata = BinaryMid($data, 43, $udplength)
ConsoleWrite($udpdata & @CRLF)
Return $udpdata
EndFunc   ;==>_UDP_Parser
Func _DHCP_Parser($udpdata)
$op = Number(BinaryMid($udpdata, 1, 1))
Switch $op
  Case 1
   ConsoleWrite("Boot Request ")
  Case 2
   ConsoleWrite("Boot Reply ")
EndSwitch
$htype = Number(BinaryMid($udpdata, 2, 1))
Switch $htype
  Case 1
   ConsoleWrite("via Ethernet ")
  Case 6
   ConsoleWrite("via IEEE 802 ")
  Case 7
   ConsoleWrite("via ARCNET ")
EndSwitch
$hlen = Number(BinaryMid($udpdata, 3, 1))
Switch $hlen
  Case 6
   ConsoleWrite("and a Hardware address Length of a MAC address ")
  Case 2
   ConsoleWrite("and an Unknown Hardware address Length ")
EndSwitch
$hops = Number(BinaryMid($udpdata, 4, 1))
Switch $hops
  Case 0
   ConsoleWrite("send directly ")
  Case Else
   ConsoleWrite("relayed over " & $hops & " DHCP-Relay-Agents ")
EndSwitch
$xid = BinaryMid($udpdata, 5, 4)
ConsoleWrite("and a transaction ID of " & $xid & " ")
$secs = Number(BinaryMid($udpdata, 9, 1)) * 256 + Number(BinaryMid($udpdata, 10, 1))
ConsoleWrite("waiting since " & $secs & " seconds ")
$flags = Number(BinaryMid($udpdata, 11, 1)) ; easy implemetation
Switch $flags
  Case 0
   ConsoleWrite("with an old IP ")
  Case 1
   ConsoleWrite("without an old IP ")
EndSwitch
$ciaddr = Number(BinaryMid($udpdata, 13, 1)) & "." & Number(BinaryMid($udpdata, 14, 1)) & "." & Number(BinaryMid($udpdata, 15, 1)) & "." & Number(BinaryMid($udpdata, 16, 1))
$yiaddr = Number(BinaryMid($udpdata, 17, 1)) & "." & Number(BinaryMid($udpdata, 18, 1)) & "." & Number(BinaryMid($udpdata, 19, 1)) & "." & Number(BinaryMid($udpdata, 20, 1))
$siaddr = Number(BinaryMid($udpdata, 21, 1)) & "." & Number(BinaryMid($udpdata, 22, 1)) & "." & Number(BinaryMid($udpdata, 23, 1)) & "." & Number(BinaryMid($udpdata, 24, 1))
$giaddr = Number(BinaryMid($udpdata, 25, 1)) & "." & Number(BinaryMid($udpdata, 26, 1)) & "." & Number(BinaryMid($udpdata, 27, 1)) & "." & Number(BinaryMid($udpdata, 28, 1))
ConsoleWrite("ClientIP: " & $ciaddr & " Your IP: " & $yiaddr & " Server IP: " & $siaddr & " Relay-Agent-IP-Adress " & $giaddr & " ")
$chaddr = BinaryMid($udpdata, 29, 16)
$chaddr_mac = StringTrimLeft(BinaryMid($udpdata, 29, 6), 2)
$chaddr_pad = StringTrimLeft(BinaryMid($udpdata, 35, 10), 2)
ConsoleWrite("and a client identifier of " & $chaddr & " which results in a client MAC-Address of " & $chaddr_mac & " and padding, ")
$sname = StringReplace(BinaryToString(BinaryMid($udpdata, 45, 64)), Chr(0), "")
Switch $sname
  Case ""
   ConsoleWrite("requesting no special server ")
  Case Else
   ConsoleWrite("requesting Server-Name " & $sname & " ")
EndSwitch
$file = StringReplace(BinaryToString(BinaryMid($udpdata, 109, 128)), Chr(0), "")
Switch $file
  Case ""
   ConsoleWrite("with no boot-file specified ")
  Case Else
   ConsoleWrite("getting following Bootfile '" & $file & "' ")
EndSwitch
$options = StringReplace(BinaryToString(BinaryMid($udpdata, 237)), Chr(0), "")
ConsoleWrite("and the following options: " & $options)
ConsoleWrite(@CRLF)
If BitAND(BinaryMid($udpdata, 237, 4), 0x63825363) Then ; is a DHCP Package
  ConsoleWrite("DHCP options:" & @CRLF)
  _DHCP_Options_Parser(BinaryMid($udpdata, 241))
EndIf
EndFunc   ;==>_DHCP_Parser
Func _DHCP_Options_Parser($options)
$i = 1
Do
  $options_type = Number(BinaryMid($options, $i, 1))
  $length = Number(BinaryMid($options, $i + 1, 1))
  If $options_type = 0 Or $options_type = 255 Then $length = 1
  ConsoleWrite("Count: " & $i & " Option Type: " & $options_type & " Packet Length: " & $length & @CRLF)
  Switch $options_type
   Case 0 ; padding
   Case 1 ; Subnetmask
    $subnetmask = Number(BinaryMid($options, $i + 2, 1)) & "." & Number(BinaryMid($options, $i + 3, 1)) & "." & Number(BinaryMid($options, $i + 4, 1)) & "." & Number(BinaryMid($options, $i + 5, 1))
    ConsoleWrite("Subnetmask: " & $subnetmask & @CRLF)
   Case 2 ; time offset
    $time_offset = Number(BinaryMid($options, $i + 2, 4))
    ConsoleWrite("Time Offset: " & $time_offset & @CRLF)
   Case 3 ; Router Option             ; not working properly
   Case 6 ; DNS-Servers
    $dns_servers_count = $length/4
    for $j = 0 to $dns_servers_count-1
     $dns_servers = Number(BinaryMid($options, $i + 2 + ($j*4), 1)) & "." & Number(BinaryMid($options, $i + 3+ ($j*4), 1)) & "." & Number(BinaryMid($options, $i + 4+ ($j*4), 1)) & "." & Number(BinaryMid($options, $i + 5+ ($j*4), 1))
     ConsoleWrite("dns server: " & $dns_servers & @CRLF)
    Next
   Case 12; Client Hostname
    $Host_Name = StringReplace(BinaryToString(BinaryMid($options, $i + 2, $length)), Chr(0), "")
    ConsoleWrite("Host Name: " & $Host_Name & @CRLF)
   Case 43 ; Vendor-specific information
    $vendor_specific_info = StringReplace(BinaryToString(BinaryMid($options, $i + 2, $length)), Chr(0), "")
    ConsoleWrite("Vendor-specific information: " & $vendor_specific_info & @CRLF)
   Case 51 ; Address lease time           ; not working properly
    $lease_time = Number(BinaryMid($options, $i + 2, 4))
    $sNewDate = _DateAdd('s', $lease_time, _NowCalcDate())
    ConsoleWrite("Lease Time: " & $sNewDate & @CRLF)
   Case 53 ; DHCP Message type
    Switch Number(BinaryMid($options, $i + 2, 1))
     Case 1
      ConsoleWrite("DHCPDISCOVER" & @CRLF)
     Case 2
      ConsoleWrite("DHCPOFFER" & @CRLF)
     Case 3
      ConsoleWrite("DHCPREQUEST" & @CRLF)
     Case 4
      ConsoleWrite("DHCPDECLINE" & @CRLF)
     Case 5
      ConsoleWrite("DHCPACK" & @CRLF)
     Case 6
      ConsoleWrite("DHCPNAK" & @CRLF)
     Case 7
      ConsoleWrite("DHCPRELEASE" & @CRLF)
     Case 8
      ConsoleWrite("DHCPINFORM" & @CRLF)
     Case Else; Armageddon!!!
    EndSwitch
   Case 54 ; Server Identifier
    $server_identifier = Number(BinaryMid($options, $i + 2, 1)) & "." & Number(BinaryMid($options, $i + 3, 1)) & "." & Number(BinaryMid($options, $i + 4, 1)) & "." & Number(BinaryMid($options, $i + 5, 1))
    ConsoleWrite("Server Identifier: " & $server_identifier & @CRLF)
   Case 55 ; Parameter Request List
    $parameter_request_list = BinaryMid($options, $i + 2, $length)
    ConsoleWrite("Parameter Request List: " & $parameter_request_list & @CRLF)
   Case 60 ; Class-Identifier
    $class_identifier = StringReplace(BinaryToString(BinaryMid($options, $i + 2, $length)), Chr(0), "")
    ConsoleWrite("Class-Identifier: " & $class_identifier & @CRLF)
   Case 61 ; Identifier
    $identifier = BinaryMid($options, $i + 2, $length)
    ConsoleWrite("Identifier: " & $identifier & @CRLF)
   Case 81 ; FQDN
    $FQDN = StringReplace(BinaryToString(BinaryMid($options, $i + 2, $length)), Chr(0), "")
    ConsoleWrite("FQDN: " & $FQDN & @CRLF)
   Case 255 ; end
    $i = BinaryLen($options)
   Case Else; Armageddon!!!
  EndSwitch
  $i += (2 + $length)
Until $i >= BinaryLen($options) ; unclean but prevents the loop from continuing infinite if a counting error occures.
Return False ; until everything is in a 2d array.....
EndFunc   ;==>_DHCP_Options_Parser

traffic.au3

Edited November 9, 2011 by JRSmile

[lgvlgv 3]

This is great, thx very mutch