### Home Classes Methods

### In Files

- lib/packetfu/packet.rb

### Parent

Object

### Methods

- ::can_parse?
- ::force_binary
- ::inherited
- ::layer
- ::layer_symbol
- ::new
- ::parse
- #==
- #clone
- #dissect
- #dissection_table
- #handle_is_identity
- #hexify
- #inspect
- #inspect_hex
- #inspect_style=
- #kind_of?
- #layer
- #layer_symbol
- #length
- #method_missing
- #orig_kind_of?
- #payload
- #payload=
- #peek
- #peek_format
- #proto
- #protocol
- #read
- #recalc
- #respond_to?
- #size
- #to_f
- #to_pcap
- #to_s
- #to_w
- #write

### Files

- .document
- README.rdoc

### Class/Module Index

Quicksearch

- PacketFu
- PacketFu::ARPHeader
- PacketFu::ARPHeaderMixin
- PacketFu::ARPPacket
- PacketFu::AddrIpv6
- PacketFu::Capture
- PacketFu::Config
- PacketFu::EthHeader
- PacketFu::EthHeaderMixin
- PacketFu::EthMac
- PacketFu::EthNic
- PacketFu::EthOui
- PacketFu::EthPacket
- PacketFu::HSRPHeader
- PacketFu::HSRPHeaderMixin
- PacketFu::HSRPPacket
- PacketFu::ICMPHeader
- PacketFu::ICMPHeaderMixin
- PacketFu::ICMPPacket
- PacketFu::IPHeader
- PacketFu::IPHeaderMixin
- PacketFu::IPPacket
- PacketFu::IPv6Header
- PacketFu::IPv6HeaderMixin
- PacketFu::IPv6Packet
- PacketFu::Inject
- PacketFu::InvalidHeader
- PacketFu::InvalidPacket
- PacketFu::LLDPHeader
- PacketFu::LLDPHeaderMixin
- PacketFu::LLDPPacket
- PacketFu::Octets
- PacketFu::Packet
- PacketFu::PcapFile
- PacketFu::PcapHeader
- PacketFu::PcapPacket
- PacketFu::PcapPackets
- PacketFu::Read
- PacketFu::TCPHeader
- PacketFu::TCPHeaderMixin
- PacketFu::TCPPacket
- PacketFu::TcpEcn
- PacketFu::TcpFlags
- PacketFu::TcpHlen
- PacketFu::TcpOption
- PacketFu::TcpOption::ECHO
- PacketFu::TcpOption::ECHOREPLY
- PacketFu::TcpOption::EOL
- PacketFu::TcpOption::MSS
- PacketFu::TcpOption::NOP
- PacketFu::TcpOption::SACK
- PacketFu::TcpOption::SACKOK
- PacketFu::TcpOption::TS
- PacketFu::TcpOption::WS
- PacketFu::TcpOptions
- PacketFu::TcpReserved
- PacketFu::Timestamp
- PacketFu::UDPHeader
- PacketFu::UDPHeaderMixin
- PacketFu::UDPPacket
- PacketFu::Utils
- PacketFu::Write
- StructFu
- StructFu::Int
- StructFu::Int16
- StructFu::Int16be
- StructFu::Int16le
- StructFu::Int32
- StructFu::Int32be
- StructFu::Int32le
- StructFu::Int8
- StructFu::IntString
- StructFu::String
- Struct

No matching classes.

# PacketFu::Packet

Packet is the parent class of EthPacket, IPPacket, UDPPacket, TCPPacket, and all other packets. It acts as both a singleton class, so things like Packet.parse can happen, and as an abstract class to provide subclasses some structure.

### Attributes

flavor[R]
headers[RW]
iface[RW]
inspect_style[RW]

### Public Class Methods

can_parse?(str) click to toggle source

Packet subclasses must override this, since the Packet superclass can't actually parse anything.

    # File lib/packetfu/packet.rb, line 281
    def self.can_parse?(str)
      false
    end

force_binary(str) click to toggle source

Force strings into binary.

    # File lib/packetfu/packet.rb, line 21
    def self.force_binary(str)
      str.force_encoding Encoding::BINARY if str.respond_to? :force_encoding
    end

inherited(subclass) click to toggle source

Register subclasses in PacketFu.packet_class to do all kinds of neat things that obviates those long if/else trees for parsing. It's pretty sweet.

    # File lib/packetfu/packet.rb, line 16
    def self.inherited(subclass)
      PacketFu.add_packet_class(subclass)
    end

layer() click to toggle source

Defines the layer this packet type lives at, based on the number of headers it requires. Note that this has little to do with the OSI model, since TCP/IP doesn't really have Session and Presentation layers.

Ethernet and the like are layer 1, IP, IPv6, and ARP are layer 2, TCP, UDP, and other transport protocols are layer 3, and application protocols are at layer 4 or higher. InvalidPackets have an arbitrary layer 0 to distinguish them.

Because these don't change much, it's cheaper just to case through them, and only resort to counting headers if we don't have a match -- this makes adding protocols somewhat easier, but of course you can just override this method over there, too. This is merely optimized for the most likely protocols you see on the Internet.

    # File lib/packetfu/packet.rb, line 250
    def self.layer
      case self.name # Lol ran into case's fancy treatment of classes
      when /InvalidPacket$/; 0
      when /EthPacket$/; 1
      when /IPPacket$/, /ARPPacket$/, /LLDPPacket$/, /IPv6Packet$/; 2
      when /TCPPacket$/, /UDPPacket$/, /ICMPPacket$/; 3
      when /HSRPPacket$/; 4
      else; self.new.headers.size
      end
    end

layer_symbol() click to toggle source

    # File lib/packetfu/packet.rb, line 265
    def self.layer_symbol
      case self.layer
      when 0; :invalid
      when 1; :link
      when 2; :internet
      when 3; :transport
      else; :application
      end
    end

new(args={}) click to toggle source

the Packet class should not be instantiated directly, since it's an abstract class that real packet types inherit from. Sadly, this makes the Packet class more difficult to test directly.

    # File lib/packetfu/packet.rb, line 466
    def initialize(args={})
      if self.class.name =~ /(::|^)PacketFu::Packet$/
        raise NoMethodError, "method `new' called for abstract class #{self.class.name}"
      end
      @inspect_style = args[:inspect_style] || PacketFu.inspect_style || :dissect
      if args[:config]
        args[:config].each_pair do |k,v|
          case k
          when :eth_daddr; @eth_header.eth_daddr=v if @eth_header
          when :eth_saddr; @eth_header.eth_saddr=v if @eth_header
          when :ip_saddr; @ip_header.ip_saddr=v          if @ip_header
          when :iface; @iface = v
          end
        end
      end
    end

parse(packet=nil,args={}) click to toggle source

Parse() creates the correct packet type based on the data, and returns the apporpiate Packet subclass object.

There is an assumption here that all incoming packets are either EthPacket or InvalidPacket types. This will be addressed pretty soon.

If application-layer parsing is /not/ desired, that should be indicated explicitly with an argument of :parse_app => false. Otherwise, app-layer parsing will happen.

It is no longer neccisary to manually add packet types here.

    # File lib/packetfu/packet.rb, line 35
    def self.parse(packet=nil,args={})
      parse_app = true if(args[:parse_app].nil? or args[:parse_app])
      force_binary(packet)
      if parse_app
        classes = PacketFu.packet_classes.select {|pclass| pclass.can_parse? packet}
      else
        classes = PacketFu.packet_classes.select {|pclass| pclass.can_parse? packet}.reject {|pclass| pclass.layer_symbol == :application}
      end
      p = classes.sort {|x,y| x.layer <=> y.layer}.last.new
      parsed_packet = p.read(packet,args)
    end

### Public Instance Methods

==(other) click to toggle source

If two packets are represented as the same binary string, and they're both actually PacketFu packets of the same sort, they're equal.

The intuitive result is that a packet of a higher layer (like DNSPacket) can be equal to a packet of a lower level (like UDPPacket) as long as the bytes are equal (this can come up if a transport-layer packet has a hand-crafted payload that is identical to what would have been created by using an application layer packet)

    # File lib/packetfu/packet.rb, line 188
    def ==(other)
      return false unless other.kind_of? self.class
      return false unless other.respond_to? :to_s
      self.to_s == other.to_s
    end

clone() click to toggle source

Packets are bundles of lots of objects, so copying them is a little complicated -- a dup of a packet is actually full of pass-by-reference stuff in the @headers, so if you change one, you're changing all this copies, too.

Normally, this doesn't seem to be a big deal, and it's a pretty decent performance tradeoff. But, if you're going to be creating a template packet to base a bunch of slightly different ones off of (like a fuzzer might), you'll want to use clone()

    # File lib/packetfu/packet.rb, line 176
    def clone
      Packet.parse(self.to_s)
    end

dissect() click to toggle source

Renders the dissection_table suitable for screen printing. Can take one or two arguments. If just the one, only that layer will be displayed take either a range or a number -- if a range, only protos within that range will be rendered. If an integer, only that proto will be rendered.

    # File lib/packetfu/packet.rb, line 359
    def dissect
      dtable = self.dissection_table
      hex_body = nil
      if dtable.last.kind_of?(Array) and dtable.last.first == :body
        body = dtable.pop
        hex_body = hexify(body[1])
      end
      elem_widths = [0,0,0]
      dtable.each do |proto_table|
        proto_table[1].each do |elems|
          elems.each_with_index do |e,i|
            width = e.size
            elem_widths[i] = width if width > elem_widths[i]
          end
        end
      end
      total_width = elem_widths.inject(0) {|sum,x| sum+x}
      table = ""
      dtable.each do |proto|
        table << "--"
        table << proto[0]
        if total_width > proto[0].size
          table << ("-" * (total_width - proto[0].size + 2))
        else
          table << ("-" * (total_width + 2))
        end
        table << "\n"
        proto[1].each do |elems|
          table << "  "
          elems_table = []
          (0..2).each do |i|
            elems_table << ("%-#{elem_widths[i]}s" % elems[i])
          end
          table << elems_table.join("\s")
          table << "\n"
        end
      end
      if hex_body && !hex_body.empty?
        table << "-" * 66
        table << "\n"
        table << "00-01-02-03-04-05-06-07-08-09-0a-0b-0c-0d-0e-0f---0123456789abcdef\n"
        table << "-" * 66
        table << "\n"
        table << hex_body
      end
      table
    end

dissection_table() click to toggle source

    # File lib/packetfu/packet.rb, line 327
    def dissection_table
      table = []
      @headers.each_with_index do |header,table_idx|
        proto = header.class.name.sub(/^.*::/,"")
        table << [proto,[]]
        header.class.members.each do |elem|
          elem_sym = elem.to_sym # to_sym needed for 1.8
          next if elem_sym == :body
          elem_type_value = []
          elem_type_value[0] = elem
          readable_element = "#{elem}_readable"
          if header.respond_to? readable_element
            elem_type_value[1] = header.send(readable_element)
          else
            elem_type_value[1] = header.send(elem)
          end
          elem_type_value[2] = header[elem.to_sym].class.name
          table[table_idx][1] << elem_type_value
        end
      end
      table
      if @headers.last.members.map {|x| x.to_sym }.include? :body
        body_part = [:body, self.payload, @headers.last.body.class.name]
      end
      table << body_part
    end

handle_is_identity(ptype) click to toggle source

    # File lib/packetfu/packet.rb, line 47
    def handle_is_identity(ptype)
      idx = PacketFu.packet_prefixes.index(ptype.to_s.downcase)
      if idx
        self.kind_of? PacketFu.packet_classes[idx]
      else
        raise NoMethodError, "Undefined method `is_#{ptype}?' for #{self.class}."
      end
    end

hexify(str) click to toggle source

Hexify provides a neatly-formatted dump of binary data, familar to hex readers.

    # File lib/packetfu/packet.rb, line 286
    def hexify(str)
      str.force_encoding(Encoding::BINARY) if str.respond_to? :force_encoding
      hexascii_lines = str.to_s.unpack("H*")[0].scan(/.{1,32}/)
      regex = Regexp.new('[\x00-\x1f\x7f-\xff]', nil, 'n')
      chars = str.to_s.gsub(regex,'.')
      chars_lines = chars.scan(/.{1,16}/)
      ret = []
      hexascii_lines.size.times {|i| ret << "%-48s  %s" % [hexascii_lines[i].gsub(/(.{2})/,"\\1 "),chars_lines[i]]}
      ret.join("\n")
    end

inspect() click to toggle source

For packets, inspect is overloaded as inspect_hex(0). Not sure if this is a great idea yet, but it sure makes the irb output more sane.

If you hate this, you can run PacketFu.toggle_inspect to return to the typical (and often unreadable) Object#inspect format.

    # File lib/packetfu/packet.rb, line 428
    def inspect
      case @inspect_style
      when :dissect
        self.dissect
      when :hex
        self.proto.join("|") + "\n" + self.inspect_hex
      else
        super
      end
    end

inspect_hex(arg=0) click to toggle source

If @inspect_style is :default (or :ugly), the inspect output is the usual inspect.

If @inspect_style is :hex (or :pretty), the inspect output is a much more compact hexdump-style, with a shortened set of packet header names at the top.

If @inspect_style is :dissect (or :verbose), the inspect output is the longer, but more readable, dissection of the packet. This is the default.

TODO: Have an option for colors. Everyone loves colorized irb output.

    # File lib/packetfu/packet.rb, line 308
    def inspect_hex(arg=0)
      case arg
      when :layers
        ret = []
        @headers.size.times do |i|
          ret << hexify(@headers[i])
        end
        ret
      when (0..9)
        if @headers[arg]
          hexify(@headers[arg])
        else
          nil
        end
      when :all
        inspect_hex(0)
      end
    end

inspect_style=() click to toggle source

Delegate to PacketFu's inspect_style, since the class variable name is the same. Yay for namespace pollution!

    # File lib/packetfu/packet.rb, line 486
    def inspect_style=()
      PacketFu.inspect_style(arg)
    end

kind_of?(klass) click to toggle source

    # File lib/packetfu/packet.rb, line 409
    def kind_of?(klass)
      return true if orig_kind_of? klass
      packet_types = proto.map {|p| PacketFu.const_get("#{p}Packet")}
      match = false
      packet_types.each do |p|
        if p.ancestors.include? klass
          match =  true
          break
        end
      end
      return match
    end

Also aliased as: orig_kind_of?
layer() click to toggle source

    # File lib/packetfu/packet.rb, line 261
    def layer
      self.class.layer
    end

layer_symbol() click to toggle source

    # File lib/packetfu/packet.rb, line 275
    def layer_symbol
      self.class.layer_symbol
    end

length() click to toggle source
Alias for: size
method_missing(sym, *args, &block) click to toggle source

method_missing() delegates protocol-specific field actions to the apporpraite class variable (which contains the associated packet type) This register-of-protocols style switch will work for the forseeable future (there aren't /that/ many packet types), and it's a handy way to know at a glance what packet types are supported.

    # File lib/packetfu/packet.rb, line 495
    def method_missing(sym, *args, &block)
      case sym.to_s
      when /^is_([a-zA-Z0-9]+)\?/
        ptype = $1
        if PacketFu.packet_prefixes.index(ptype)
          self.send(:handle_is_identity, $1)
        else
          super
        end
      when /^([a-zA-Z0-9]+)_.+/
        ptype = $1
        if PacketFu.packet_prefixes.index(ptype)
          self.instance_variable_get("@#{ptype}_header").send(sym,*args, &block)
        else
          super
        end
      else
        super
      end
    end

orig_kind_of?(klass) click to toggle source
Alias for: kind_of?
payload() click to toggle source

Get the outermost payload (body) of the packet; this is why all packet headers should have a body type.

    # File lib/packetfu/packet.rb, line 68
    def payload
      @headers.last.body
    end

payload=(args) click to toggle source

Set the outermost payload (body) of the packet.

    # File lib/packetfu/packet.rb, line 73
    def payload=(args)
      @headers.last.body=(args)
    end

peek(args={}) click to toggle source

Peek provides summary data on packet contents.

Each packet type should provide a peek_format.

    # File lib/packetfu/packet.rb, line 197
    def peek(args={})
      idx = @headers.reverse.map {|h| h.respond_to? peek_format}.index(true)
      if idx
        @headers.reverse[idx].peek_format
      else
        peek_format
      end
    end

peek_format() click to toggle source

The peek_format is used to display a single line of packet data useful for eyeballing. It should not exceed 80 characters. The Packet superclass defines an example peek_format, but it should hardly ever be triggered, since peek traverses the @header list in reverse to find a suitable format.

### Format

    * A one or two character protocol initial. It should be unique
    * The packet size
    * Useful data in a human-usable form.

Ideally, related peek_formats will all line up with each other when printed to the screen.

### Example

    tcp_packet.peek
    #=> "T  1054 10.10.10.105:55000   ->   192.168.145.105:80 [......] S:adc7155b|I:8dd0"
    tcp_packet.peek.size
    #=> 79

    # File lib/packetfu/packet.rb, line 229
    def peek_format
      peek_data = ["?  "]
      peek_data << "%-5d" % self.to_s.size
      peek_data << "%68s" % self.to_s[0,34].unpack("H*")[0]
      peek_data.join
    end

proto() click to toggle source

Returns an array of protocols contained in this packet. For example:

    t = PacketFu::TCPPacket.new
    => 00 1a c5 00 00 00 00 1a c5 00 00 00 08 00 45 00   ..............E.
    00 28 3c ab 00 00 ff 06 7f 25 00 00 00 00 00 00   .(<......%......
    00 00 93 5e 00 00 ad 4f e4 a4 00 00 00 00 50 00   ...^...O......P.
    40 00 4a 92 00 00                                 @.J...
    t.proto
    => ["Eth", "IP", "TCP"]

    # File lib/packetfu/packet.rb, line 454
    def proto
      type_array = []
      self.headers.each {|header| type_array << header.class.to_s.split('::').last.gsub(/Header$/,'')}
      type_array
    end

Also aliased as: protocol
protocol() click to toggle source
Alias for: proto
read(args={}) click to toggle source

Read() takes (and trusts) the io input and shoves it all into a well-formed Packet. Note that read is a destructive process, so any existing data will be lost.

A note on the :strip => true argument: If :strip is set, defined lengths of data will be believed, and any trailers (such as frame check sequences) will be chopped off. This helps to ensure well-formed packets, at the cost of losing perhaps important FCS data.

If :strip is false, header lengths are /not/ believed, and all data will be piped in. When capturing from the wire, this is usually fine, but recalculating the length before saving or re-transmitting will absolutely change the data payload; FCS data will become part of the TCP data as far as tcp_len is concerned. Some effort has been made to preserve the "real" payload for the purposes of checksums, but currently, it's impossible to seperate new payload data from old trailers, so things like pkt.payload += "some data" will not work correctly.

So, to summarize; if you intend to alter the data, use :strip. If you don't, don't. Also, this is a horrid hack. Stripping is useful (and fun!), but the default behavior really should be to create payloads correctly, and /not/ treat extra FCS data as a payload.

Finally, packet subclasses should take two arguments: the string that is the data to be transmuted into a packet, as well as args. This superclass method is merely concerned with handling args common to many packet formats (namely, fixing packets on the fly)

    # File lib/packetfu/packet.rb, line 158
    def read(args={})
      if args[:fix] || args[:recalc]
        ip_recalc(:ip_sum) if self.is_ip?
        recalc(:tcp) if self.is_tcp?
        recalc(:udp) if self.is_udp?
      end
    end

recalc(arg=:all) click to toggle source

Recalculates all the calcuated fields for all headers in the packet. This is important since read() wipes out all the calculated fields such as length and checksum and what all.

    # File lib/packetfu/packet.rb, line 114
    def recalc(arg=:all)
      case arg
      when :ip
        ip_recalc(:all)
      when :icmp
        icmp_recalc(:all)
      when :udp
        udp_recalc(:all)
      when :tcp
        tcp_recalc(:all)
      when :all
        ip_recalc(:all) if @ip_header
        icmp_recalc(:all) if @icmp_header
        udp_recalc(:all) if @udp_header
        tcp_recalc(:all) if @tcp_header
      else
        raise ArgumentError, "Recalculating `#{arg}' unsupported. Try :all"
      end
      @headers[0]
    end

respond_to?(sym, include_private = false) click to toggle source

    # File lib/packetfu/packet.rb, line 516
    def respond_to?(sym, include_private = false)
      if sym.to_s =~ /^(invalid|eth|arp|ip|icmp|udp|hsrp|tcp|ipv6)_/
        self.instance_variable_get("@#{$1}_header").respond_to? sym
      elsif sym.to_s =~ /^is_([a-zA-Z0-9]+)\?/
        if PacketFu.packet_prefixes.index($1)
          true
        else
          super
        end
      else
        super
      end
    end

size() click to toggle source

Returns the size of the packet (as a binary string)

    # File lib/packetfu/packet.rb, line 440
    def size
      self.to_s.size
    end

Also aliased as: length
to_f(filename=nil,mode='w') click to toggle source

Put the entire packet into a libpcap file. XXX: this is a hack for now just to confirm that packets are getting created correctly. Now with append! XXX: Document this!

    # File lib/packetfu/packet.rb, line 89
    def to_f(filename=nil,mode='w')
      filename ||= 'out.pcap'
      mode = mode.to_s[0,1] + "b"
      raise ArgumentError, "Unknown mode: #{mode.to_s}" unless mode =~ /^[wa]/
      if(mode == 'w' || !(File.exists?(filename)))
        data = [PcapHeader.new, self.to_pcap].map {|x| x.to_s}.join
      else
        data = self.to_pcap
      end
      File.open(filename, mode) {|f| f.write data}
      return [filename, 1, data.size]
    end

to_pcap(args={}) click to toggle source

Converts a packet to libpcap format. Bit of a hack?

    # File lib/packetfu/packet.rb, line 78
    def to_pcap(args={})
      p = PcapPacket.new(:endian => args[:endian],
                        :timestamp => Timestamp.new.to_s,
                        :incl_len => self.to_s.size,
                        :orig_len => self.to_s.size,
                        :data => self)
    end

to_s() click to toggle source

Get the binary string of the entire packet.

    # File lib/packetfu/packet.rb, line 57
    def to_s
      @headers[0].to_s
    end

to_w(iface=nil) click to toggle source

Put the entire packet on the wire by creating a temporary PacketFu::Inject object. TODO: Do something with auto-checksumming?

    # File lib/packetfu/packet.rb, line 104
    def to_w(iface=nil)
      iface = (iface || self.iface || PacketFu::Config.new.config[:iface]).to_s
      inj = PacketFu::Inject.new(:iface => iface)
      inj.array = [@headers[0].to_s]
      inj.inject
    end

write(io) click to toggle source

In the event of no proper decoding, at least send it to the inner-most header.

    # File lib/packetfu/packet.rb, line 62
    def write(io)
      @headers[0].write(io)
    end

[Validate]

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