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PacketFu::IPHeader

IPHeader is a complete IP struct, used in IPPacket. Most traffic on most networks today is IP-based.

For more on IP packets, see www.networksorcery.com/enp/protocol/ip.htm

Header Definition

Fixnum (4 bits)  :ip_v,     Default: 4
Fixnum (4 bits)  :ip_hl,    Default: 5
Int8             :ip_tos,   Default: 0           # TODO: Break out the bits
Int16            :ip_len,   Default: calculated 
Int16            :ip_id,    Default: calculated  # IRL, hardly random. 
Int16            :ip_frag,  Default: 0           # TODO: Break out the bits
Int8             :ip_ttl,   Default: 0xff        # Changes per flavor
Int8             :ip_proto, Default: 0x01        # TCP: 0x06, UDP 0x11, ICMP 0x01
Int16            :ip_sum,   Default: calculated 
Octets           :ip_src                       
Octets           :ip_dst                      
String           :body

Note that IPPackets will always be somewhat incorrect upon initalization, and want an IPHeader#recalc() to become correct before a Packet#to_f or Packet#to_w.

Public Class Methods

new(args={}) click to toggle source
# File lib/packetfu/protos/ip/header.rb, line 124
def initialize(args={})
        @random_id = rand(0xffff)
        super(
                (args[:ip_v] || 4),
                (args[:ip_hl] || 5),
                Int8.new(args[:ip_tos]),
                Int16.new(args[:ip_len] || 20),
                Int16.new(args[:ip_id] || ip_calc_id),
                Int16.new(args[:ip_frag]),
                Int8.new(args[:ip_ttl] || 32),
                Int8.new(args[:ip_proto]),
                Int16.new(args[:ip_sum] || ip_calc_sum),
                Octets.new.read(args[:ip_src] || "\x00\x00\x00\x00"),
                Octets.new.read(args[:ip_dst] || "\x00\x00\x00\x00"),
                StructFu::String.new.read(args[:body])
        )
end
octet_array(addr) click to toggle source

Translate various formats of IPv4 Addresses to an array of digits.

# File lib/packetfu/protos/ip/header.rb, line 285
def self.octet_array(addr)
        if addr.class == String
                oa = addr.split('.').collect {|x| x.to_i}
        elsif addr.class == Fixnum
                oa = IPAddr.new(addr, Socket::AF_INET).to_s.split('.')
        elsif addr.class == Bignum
                oa = IPAddr.new(addr, Socket::AF_INET).to_s.split('.')
        elsif addr.class == Array
                oa = addr
        else
                raise ArgumentError, "IP Address should be a dotted quad string, an array of ints, or a bignum"
        end
end

Public Instance Methods

ip_calc_id() click to toggle source

Retrieve the IP ID

# File lib/packetfu/protos/ip/header.rb, line 258
def ip_calc_id
        @random_id
end
ip_calc_len() click to toggle source

Calulcate the true length of the packet.

# File lib/packetfu/protos/ip/header.rb, line 231
def ip_calc_len
        (ip_hl * 4) + body.to_s.length
end
ip_calc_sum() click to toggle source

Calculate the true checksum of the packet. (Yes, this is the long way to do it, but it's e-z-2-read for mathtards like me.)

# File lib/packetfu/protos/ip/header.rb, line 242
def ip_calc_sum
        checksum =  (((self.ip_v  <<  4) + self.ip_hl) << 8) + self.ip_tos
        checksum += self.ip_len
        checksum +=  self.ip_id
        checksum += self.ip_frag
        checksum +=  (self.ip_ttl << 8) + self.ip_proto
        checksum += (self.ip_src >> 16)
        checksum += (self.ip_src & 0xffff)
        checksum += (self.ip_dst >> 16)
        checksum += (self.ip_dst & 0xffff)
        checksum = checksum % 0xffff 
        checksum = 0xffff - checksum
        checksum == 0 ? 0xffff : checksum
end
ip_daddr() click to toggle source

Returns a more readable IP destination address.

# File lib/packetfu/protos/ip/header.rb, line 280
def ip_daddr
        self[:ip_dst].to_x
end
Also aliased as: ip_dst_readable
ip_daddr=(addr) click to toggle source

Sets a more readable IP address.

# File lib/packetfu/protos/ip/header.rb, line 275
def ip_daddr=(addr)
        self[:ip_dst].read_quad(addr)
end
ip_dst() click to toggle source

Getter for the destination IP address.

# File lib/packetfu/protos/ip/header.rb, line 228
def ip_dst; self[:ip_dst].to_i; end
ip_dst=(i) click to toggle source

Setter for the destination IP address.

# File lib/packetfu/protos/ip/header.rb, line 217
def ip_dst=(i)
        case i
        when Numeric
                self[:ip_dst] = Octets.new.read([i].pack("N"))
        when Octets
                self[:ip_dst] = i
        else
                typecast i
        end
end
ip_dst_readable() click to toggle source
Alias for: ip_daddr
ip_frag() click to toggle source

Getter for the fragmentation ID.

# File lib/packetfu/protos/ip/header.rb, line 190
def ip_frag; self[:ip_frag].to_i; end
ip_frag=(i) click to toggle source

Setter for the fragmentation ID.

# File lib/packetfu/protos/ip/header.rb, line 188
def ip_frag=(i); typecast i; end
ip_hl() click to toggle source

Getter for the header length (multiply by 4)

# File lib/packetfu/protos/ip/header.rb, line 174
def ip_hl; self[:ip_hl].to_i; end
ip_hl=(i) click to toggle source

Setter for the header length (divide by 4)

# File lib/packetfu/protos/ip/header.rb, line 172
def ip_hl=(i); self[:ip_hl] = i.to_i; end
ip_hlen() click to toggle source

Return the claimed header length

# File lib/packetfu/protos/ip/header.rb, line 236
def ip_hlen
        (ip_hl * 4)
end
ip_id() click to toggle source

Getter for the identication number.

# File lib/packetfu/protos/ip/header.rb, line 186
def ip_id; self[:ip_id].to_i; end
ip_id=(i) click to toggle source

Setter for the identication number.

# File lib/packetfu/protos/ip/header.rb, line 184
def ip_id=(i); typecast i; end
ip_id_readable() click to toggle source
# File lib/packetfu/protos/ip/header.rb, line 326
def ip_id_readable
        "0x%04x" % ip_id
end
ip_len() click to toggle source

Getter for total length.

# File lib/packetfu/protos/ip/header.rb, line 182
def ip_len; self[:ip_len].to_i; end
ip_len=(i) click to toggle source

Setter for total length.

# File lib/packetfu/protos/ip/header.rb, line 180
def ip_len=(i); typecast i; end
ip_proto() click to toggle source

Getter for the protocol number.

# File lib/packetfu/protos/ip/header.rb, line 198
def ip_proto; self[:ip_proto].to_i; end
ip_proto=(i) click to toggle source

Setter for the protocol number.

# File lib/packetfu/protos/ip/header.rb, line 196
def ip_proto=(i); typecast i; end
ip_recalc(arg=:all) click to toggle source

Recalculate the calculated IP fields. Valid arguments are:

:all 
:ip_len 
:ip_sum 
:ip_id
# File lib/packetfu/protos/ip/header.rb, line 304
def ip_recalc(arg=:all)
        case arg
        when :ip_len
                self.ip_len=ip_calc_len
        when :ip_sum
                self.ip_sum=ip_calc_sum
        when :ip_id
                @random_id = rand(0xffff)
        when :all
                self.ip_id=         ip_calc_id
                self.ip_len=        ip_calc_len
                self.ip_sum=        ip_calc_sum
        else
                raise ArgumentError, "No such field `#{arg}'"
        end
end
ip_saddr() click to toggle source

Returns a more readable IP source address.

# File lib/packetfu/protos/ip/header.rb, line 270
def ip_saddr
        self[:ip_src].to_x
end
Also aliased as: ip_src_readable
ip_saddr=(addr) click to toggle source

Sets a more readable IP address. If you wants to manipulate individual octets, (eg, for host scanning in one network), it would be better use ip_src.o1 through ip_src.o4 instead.

# File lib/packetfu/protos/ip/header.rb, line 265
def ip_saddr=(addr)
        self[:ip_src].read_quad(addr)
end
ip_src() click to toggle source

Getter for the source IP address.

# File lib/packetfu/protos/ip/header.rb, line 215
def ip_src; self[:ip_src].to_i; end
ip_src=(i) click to toggle source

Setter for the source IP address.

# File lib/packetfu/protos/ip/header.rb, line 204
def ip_src=(i)
        case i
        when Numeric
                self[:ip_src] = Octets.new.read([i].pack("N"))
        when Octets
                self[:ip_src] = i
        else
                typecast i
        end
end
ip_src_readable() click to toggle source

Readability aliases

Alias for: ip_saddr
ip_sum() click to toggle source

Getter for the checksum.

# File lib/packetfu/protos/ip/header.rb, line 202
def ip_sum; self[:ip_sum].to_i; end
ip_sum=(i) click to toggle source

Setter for the checksum.

# File lib/packetfu/protos/ip/header.rb, line 200
def ip_sum=(i); typecast i; end
ip_sum_readable() click to toggle source
# File lib/packetfu/protos/ip/header.rb, line 330
def ip_sum_readable
        "0x%04x" % ip_sum
end
ip_tos() click to toggle source

Getter for the differentiated services

# File lib/packetfu/protos/ip/header.rb, line 178
def ip_tos; self[:ip_tos].to_i; end
ip_tos=(i) click to toggle source

Setter for the differentiated services

# File lib/packetfu/protos/ip/header.rb, line 176
def ip_tos=(i); typecast i; end
ip_ttl() click to toggle source

Getter for the time to live.

# File lib/packetfu/protos/ip/header.rb, line 194
def ip_ttl; self[:ip_ttl].to_i; end
ip_ttl=(i) click to toggle source

Setter for the time to live.

# File lib/packetfu/protos/ip/header.rb, line 192
def ip_ttl=(i); typecast i; end
ip_v() click to toggle source

Getter for the version.

# File lib/packetfu/protos/ip/header.rb, line 170
def ip_v; self[:ip_v].to_i; end
ip_v=(i) click to toggle source

Setter for the version.

# File lib/packetfu/protos/ip/header.rb, line 168
def ip_v=(i); self[:ip_v] = i.to_i; end
read(str) click to toggle source

Reads a string to populate the object.

# File lib/packetfu/protos/ip/header.rb, line 149
def read(str)
        force_binary(str)
        return self if str.nil?
        self[:ip_v] = str[0,1].unpack("C").first >> 4
        self[:ip_hl] = str[0,1].unpack("C").first.to_i & 0x0f
        self[:ip_tos].read(str[1,1])
        self[:ip_len].read(str[2,2])
        self[:ip_id].read(str[4,2])
        self[:ip_frag].read(str[6,2])
        self[:ip_ttl].read(str[8,1])
        self[:ip_proto].read(str[9,1])
        self[:ip_sum].read(str[10,2])
        self[:ip_src].read(str[12,4])
        self[:ip_dst].read(str[16,4])
        self[:body].read(str[20,str.size]) if str.size > 20
        self
end
to_s() click to toggle source

Returns the object in string form.

# File lib/packetfu/protos/ip/header.rb, line 143
def to_s
        byte_v_hl = [(self.ip_v << 4) + self.ip_hl].pack("C")
        byte_v_hl + (self.to_a[2,10].map {|x| x.to_s}.join)
end

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