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572 lines
16 KiB
572 lines
16 KiB
// Copyright 2016 Google, Inc. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the LICENSE file in the root of the source
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// tree.
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package layers
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"fmt"
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"net"
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"github.com/google/gopacket"
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)
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// DHCPOp rerprents a bootp operation
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type DHCPOp byte
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// bootp operations
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const (
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DHCPOpRequest DHCPOp = 1
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DHCPOpReply DHCPOp = 2
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)
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// String returns a string version of a DHCPOp.
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func (o DHCPOp) String() string {
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switch o {
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case DHCPOpRequest:
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return "Request"
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case DHCPOpReply:
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return "Reply"
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default:
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return "Unknown"
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}
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}
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// DHCPMsgType represents a DHCP operation
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type DHCPMsgType byte
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// Constants that represent DHCP operations
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const (
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DHCPMsgTypeUnspecified DHCPMsgType = iota
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DHCPMsgTypeDiscover
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DHCPMsgTypeOffer
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DHCPMsgTypeRequest
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DHCPMsgTypeDecline
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DHCPMsgTypeAck
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DHCPMsgTypeNak
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DHCPMsgTypeRelease
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DHCPMsgTypeInform
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)
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// String returns a string version of a DHCPMsgType.
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func (o DHCPMsgType) String() string {
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switch o {
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case DHCPMsgTypeUnspecified:
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return "Unspecified"
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case DHCPMsgTypeDiscover:
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return "Discover"
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case DHCPMsgTypeOffer:
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return "Offer"
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case DHCPMsgTypeRequest:
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return "Request"
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case DHCPMsgTypeDecline:
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return "Decline"
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case DHCPMsgTypeAck:
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return "Ack"
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case DHCPMsgTypeNak:
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return "Nak"
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case DHCPMsgTypeRelease:
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return "Release"
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case DHCPMsgTypeInform:
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return "Inform"
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default:
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return "Unknown"
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}
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}
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//DHCPMagic is the RFC 2131 "magic cooke" for DHCP.
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var DHCPMagic uint32 = 0x63825363
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// DHCPv4 contains data for a single DHCP packet.
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type DHCPv4 struct {
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BaseLayer
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Operation DHCPOp
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HardwareType LinkType
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HardwareLen uint8
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HardwareOpts uint8
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Xid uint32
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Secs uint16
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Flags uint16
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ClientIP net.IP
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YourClientIP net.IP
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NextServerIP net.IP
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RelayAgentIP net.IP
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ClientHWAddr net.HardwareAddr
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ServerName []byte
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File []byte
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Options DHCPOptions
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}
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// DHCPOptions is used to get nicely printed option lists which would normally
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// be cut off after 5 options.
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type DHCPOptions []DHCPOption
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// String returns a string version of the options list.
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func (o DHCPOptions) String() string {
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buf := &bytes.Buffer{}
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buf.WriteByte('[')
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for i, opt := range o {
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buf.WriteString(opt.String())
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if i+1 != len(o) {
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buf.WriteString(", ")
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}
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}
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buf.WriteByte(']')
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return buf.String()
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}
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// LayerType returns gopacket.LayerTypeDHCPv4
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func (d *DHCPv4) LayerType() gopacket.LayerType { return LayerTypeDHCPv4 }
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// DecodeFromBytes decodes the given bytes into this layer.
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func (d *DHCPv4) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
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d.Operation = DHCPOp(data[0])
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d.HardwareType = LinkType(data[1])
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d.HardwareLen = data[2]
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d.HardwareOpts = data[3]
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d.Xid = binary.BigEndian.Uint32(data[4:8])
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d.Secs = binary.BigEndian.Uint16(data[8:10])
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d.Flags = binary.BigEndian.Uint16(data[10:12])
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d.ClientIP = net.IP(data[12:16])
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d.YourClientIP = net.IP(data[16:20])
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d.NextServerIP = net.IP(data[20:24])
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d.RelayAgentIP = net.IP(data[24:28])
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d.ClientHWAddr = net.HardwareAddr(data[28 : 28+d.HardwareLen])
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d.ServerName = data[44:108]
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d.File = data[108:236]
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if binary.BigEndian.Uint32(data[236:240]) != DHCPMagic {
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return errors.New("Bad DHCP header")
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}
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if len(data) <= 240 {
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// DHCP Packet could have no option (??)
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return nil
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}
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options := data[240:]
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stop := len(options)
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start := 0
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for start < stop {
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o := DHCPOption{}
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if err := o.decode(options[start:]); err != nil {
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return err
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}
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if o.Type == DHCPOptEnd {
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break
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}
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d.Options = append(d.Options, o)
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// Check if the option is a single byte pad
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if o.Type == DHCPOptPad {
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start++
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} else {
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start += int(o.Length) + 2
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}
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}
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return nil
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}
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// Len returns the length of a DHCPv4 packet.
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func (d *DHCPv4) Len() uint16 {
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n := uint16(240)
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for _, o := range d.Options {
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if o.Type == DHCPOptPad {
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n++
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} else {
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n += uint16(o.Length) + 2
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}
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}
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n++ // for opt end
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return n
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}
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// SerializeTo writes the serialized form of this layer into the
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// SerializationBuffer, implementing gopacket.SerializableLayer.
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// See the docs for gopacket.SerializableLayer for more info.
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func (d *DHCPv4) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
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plen := int(d.Len())
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data, err := b.PrependBytes(plen)
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if err != nil {
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return err
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}
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data[0] = byte(d.Operation)
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data[1] = byte(d.HardwareType)
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if opts.FixLengths {
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d.HardwareLen = uint8(len(d.ClientHWAddr))
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}
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data[2] = d.HardwareLen
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data[3] = d.HardwareOpts
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binary.BigEndian.PutUint32(data[4:8], d.Xid)
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binary.BigEndian.PutUint16(data[8:10], d.Secs)
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binary.BigEndian.PutUint16(data[10:12], d.Flags)
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copy(data[12:16], d.ClientIP.To4())
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copy(data[16:20], d.YourClientIP.To4())
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copy(data[20:24], d.NextServerIP.To4())
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copy(data[24:28], d.RelayAgentIP.To4())
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copy(data[28:44], d.ClientHWAddr)
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copy(data[44:108], d.ServerName)
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copy(data[108:236], d.File)
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binary.BigEndian.PutUint32(data[236:240], DHCPMagic)
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if len(d.Options) > 0 {
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offset := 240
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for _, o := range d.Options {
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if err := o.encode(data[offset:]); err != nil {
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return err
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}
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// A pad option is only a single byte
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if o.Type == DHCPOptPad {
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offset++
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} else {
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offset += 2 + len(o.Data)
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}
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}
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optend := NewDHCPOption(DHCPOptEnd, nil)
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if err := optend.encode(data[offset:]); err != nil {
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return err
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}
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}
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return nil
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}
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// CanDecode returns the set of layer types that this DecodingLayer can decode.
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func (d *DHCPv4) CanDecode() gopacket.LayerClass {
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return LayerTypeDHCPv4
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}
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// NextLayerType returns the layer type contained by this DecodingLayer.
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func (d *DHCPv4) NextLayerType() gopacket.LayerType {
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return gopacket.LayerTypePayload
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}
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func decodeDHCPv4(data []byte, p gopacket.PacketBuilder) error {
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dhcp := &DHCPv4{}
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err := dhcp.DecodeFromBytes(data, p)
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if err != nil {
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return err
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}
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p.AddLayer(dhcp)
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return p.NextDecoder(gopacket.LayerTypePayload)
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}
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// DHCPOpt represents a DHCP option or parameter from RFC-2132
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type DHCPOpt byte
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// Constants for the DHCPOpt options.
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const (
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DHCPOptPad DHCPOpt = 0
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DHCPOptSubnetMask DHCPOpt = 1 // 4, net.IP
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DHCPOptTimeOffset DHCPOpt = 2 // 4, int32 (signed seconds from UTC)
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DHCPOptRouter DHCPOpt = 3 // n*4, [n]net.IP
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DHCPOptTimeServer DHCPOpt = 4 // n*4, [n]net.IP
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DHCPOptNameServer DHCPOpt = 5 // n*4, [n]net.IP
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DHCPOptDNS DHCPOpt = 6 // n*4, [n]net.IP
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DHCPOptLogServer DHCPOpt = 7 // n*4, [n]net.IP
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DHCPOptCookieServer DHCPOpt = 8 // n*4, [n]net.IP
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DHCPOptLPRServer DHCPOpt = 9 // n*4, [n]net.IP
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DHCPOptImpressServer DHCPOpt = 10 // n*4, [n]net.IP
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DHCPOptResLocServer DHCPOpt = 11 // n*4, [n]net.IP
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DHCPOptHostname DHCPOpt = 12 // n, string
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DHCPOptBootfileSize DHCPOpt = 13 // 2, uint16
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DHCPOptMeritDumpFile DHCPOpt = 14 // >1, string
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DHCPOptDomainName DHCPOpt = 15 // n, string
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DHCPOptSwapServer DHCPOpt = 16 // n*4, [n]net.IP
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DHCPOptRootPath DHCPOpt = 17 // n, string
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DHCPOptExtensionsPath DHCPOpt = 18 // n, string
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DHCPOptIPForwarding DHCPOpt = 19 // 1, bool
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DHCPOptSourceRouting DHCPOpt = 20 // 1, bool
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DHCPOptPolicyFilter DHCPOpt = 21 // 8*n, [n]{net.IP/net.IP}
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DHCPOptDatagramMTU DHCPOpt = 22 // 2, uint16
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DHCPOptDefaultTTL DHCPOpt = 23 // 1, byte
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DHCPOptPathMTUAgingTimeout DHCPOpt = 24 // 4, uint32
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DHCPOptPathPlateuTableOption DHCPOpt = 25 // 2*n, []uint16
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DHCPOptInterfaceMTU DHCPOpt = 26 // 2, uint16
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DHCPOptAllSubsLocal DHCPOpt = 27 // 1, bool
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DHCPOptBroadcastAddr DHCPOpt = 28 // 4, net.IP
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DHCPOptMaskDiscovery DHCPOpt = 29 // 1, bool
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DHCPOptMaskSupplier DHCPOpt = 30 // 1, bool
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DHCPOptRouterDiscovery DHCPOpt = 31 // 1, bool
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DHCPOptSolicitAddr DHCPOpt = 32 // 4, net.IP
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DHCPOptStaticRoute DHCPOpt = 33 // n*8, [n]{net.IP/net.IP} -- note the 2nd is router not mask
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DHCPOptARPTrailers DHCPOpt = 34 // 1, bool
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DHCPOptARPTimeout DHCPOpt = 35 // 4, uint32
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DHCPOptEthernetEncap DHCPOpt = 36 // 1, bool
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DHCPOptTCPTTL DHCPOpt = 37 // 1, byte
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DHCPOptTCPKeepAliveInt DHCPOpt = 38 // 4, uint32
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DHCPOptTCPKeepAliveGarbage DHCPOpt = 39 // 1, bool
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DHCPOptNISDomain DHCPOpt = 40 // n, string
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DHCPOptNISServers DHCPOpt = 41 // 4*n, [n]net.IP
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DHCPOptNTPServers DHCPOpt = 42 // 4*n, [n]net.IP
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DHCPOptVendorOption DHCPOpt = 43 // n, [n]byte // may be encapsulated.
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DHCPOptNetBIOSTCPNS DHCPOpt = 44 // 4*n, [n]net.IP
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DHCPOptNetBIOSTCPDDS DHCPOpt = 45 // 4*n, [n]net.IP
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DHCPOptNETBIOSTCPNodeType DHCPOpt = 46 // 1, magic byte
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DHCPOptNetBIOSTCPScope DHCPOpt = 47 // n, string
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DHCPOptXFontServer DHCPOpt = 48 // n, string
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DHCPOptXDisplayManager DHCPOpt = 49 // n, string
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DHCPOptRequestIP DHCPOpt = 50 // 4, net.IP
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DHCPOptLeaseTime DHCPOpt = 51 // 4, uint32
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DHCPOptExtOptions DHCPOpt = 52 // 1, 1/2/3
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DHCPOptMessageType DHCPOpt = 53 // 1, 1-7
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DHCPOptServerID DHCPOpt = 54 // 4, net.IP
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DHCPOptParamsRequest DHCPOpt = 55 // n, []byte
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DHCPOptMessage DHCPOpt = 56 // n, 3
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DHCPOptMaxMessageSize DHCPOpt = 57 // 2, uint16
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DHCPOptT1 DHCPOpt = 58 // 4, uint32
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DHCPOptT2 DHCPOpt = 59 // 4, uint32
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DHCPOptClassID DHCPOpt = 60 // n, []byte
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DHCPOptClientID DHCPOpt = 61 // n >= 2, []byte
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DHCPOptDomainSearch DHCPOpt = 119 // n, string
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DHCPOptSIPServers DHCPOpt = 120 // n, url
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DHCPOptClasslessStaticRoute DHCPOpt = 121 //
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DHCPOptEnd DHCPOpt = 255
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)
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// String returns a string version of a DHCPOpt.
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func (o DHCPOpt) String() string {
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switch o {
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case DHCPOptPad:
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return "(padding)"
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case DHCPOptSubnetMask:
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return "SubnetMask"
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case DHCPOptTimeOffset:
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return "TimeOffset"
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case DHCPOptRouter:
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return "Router"
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case DHCPOptTimeServer:
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return "rfc868" // old time server protocol stringified to dissuade confusion w. NTP
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case DHCPOptNameServer:
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return "ien116" // obscure nameserver protocol stringified to dissuade confusion w. DNS
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case DHCPOptDNS:
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return "DNS"
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case DHCPOptLogServer:
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return "mitLCS" // MIT LCS server protocol yada yada w. Syslog
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case DHCPOptCookieServer:
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return "CookieServer"
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case DHCPOptLPRServer:
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return "LPRServer"
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case DHCPOptImpressServer:
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return "ImpressServer"
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case DHCPOptResLocServer:
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return "ResourceLocationServer"
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case DHCPOptHostname:
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return "Hostname"
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case DHCPOptBootfileSize:
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return "BootfileSize"
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case DHCPOptMeritDumpFile:
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return "MeritDumpFile"
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case DHCPOptDomainName:
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return "DomainName"
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case DHCPOptSwapServer:
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return "SwapServer"
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case DHCPOptRootPath:
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return "RootPath"
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case DHCPOptExtensionsPath:
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return "ExtensionsPath"
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case DHCPOptIPForwarding:
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return "IPForwarding"
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case DHCPOptSourceRouting:
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return "SourceRouting"
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case DHCPOptPolicyFilter:
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return "PolicyFilter"
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case DHCPOptDatagramMTU:
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return "DatagramMTU"
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case DHCPOptDefaultTTL:
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return "DefaultTTL"
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case DHCPOptPathMTUAgingTimeout:
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return "PathMTUAgingTimeout"
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case DHCPOptPathPlateuTableOption:
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return "PathPlateuTableOption"
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case DHCPOptInterfaceMTU:
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return "InterfaceMTU"
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case DHCPOptAllSubsLocal:
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return "AllSubsLocal"
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case DHCPOptBroadcastAddr:
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return "BroadcastAddress"
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case DHCPOptMaskDiscovery:
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return "MaskDiscovery"
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case DHCPOptMaskSupplier:
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return "MaskSupplier"
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case DHCPOptRouterDiscovery:
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return "RouterDiscovery"
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case DHCPOptSolicitAddr:
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return "SolicitAddr"
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case DHCPOptStaticRoute:
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return "StaticRoute"
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case DHCPOptARPTrailers:
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return "ARPTrailers"
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case DHCPOptARPTimeout:
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return "ARPTimeout"
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case DHCPOptEthernetEncap:
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return "EthernetEncap"
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case DHCPOptTCPTTL:
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return "TCPTTL"
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case DHCPOptTCPKeepAliveInt:
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return "TCPKeepAliveInt"
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case DHCPOptTCPKeepAliveGarbage:
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return "TCPKeepAliveGarbage"
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case DHCPOptNISDomain:
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return "NISDomain"
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case DHCPOptNISServers:
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return "NISServers"
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case DHCPOptNTPServers:
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return "NTPServers"
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case DHCPOptVendorOption:
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return "VendorOption"
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case DHCPOptNetBIOSTCPNS:
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return "NetBIOSOverTCPNS"
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case DHCPOptNetBIOSTCPDDS:
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return "NetBiosOverTCPDDS"
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case DHCPOptNETBIOSTCPNodeType:
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return "NetBIOSOverTCPNodeType"
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case DHCPOptNetBIOSTCPScope:
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return "NetBIOSOverTCPScope"
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case DHCPOptXFontServer:
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return "XFontServer"
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case DHCPOptXDisplayManager:
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return "XDisplayManager"
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case DHCPOptEnd:
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return "(end)"
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case DHCPOptSIPServers:
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return "SipServers"
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case DHCPOptRequestIP:
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return "RequestIP"
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case DHCPOptLeaseTime:
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return "LeaseTime"
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case DHCPOptExtOptions:
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return "ExtOpts"
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case DHCPOptMessageType:
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return "MessageType"
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case DHCPOptServerID:
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return "ServerID"
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case DHCPOptParamsRequest:
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return "ParamsRequest"
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case DHCPOptMessage:
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return "Message"
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case DHCPOptMaxMessageSize:
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return "MaxDHCPSize"
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case DHCPOptT1:
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return "Timer1"
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case DHCPOptT2:
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return "Timer2"
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case DHCPOptClassID:
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return "ClassID"
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case DHCPOptClientID:
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return "ClientID"
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case DHCPOptDomainSearch:
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return "DomainSearch"
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case DHCPOptClasslessStaticRoute:
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return "ClasslessStaticRoute"
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default:
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return "Unknown"
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}
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}
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// DHCPOption rerpresents a DHCP option.
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type DHCPOption struct {
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Type DHCPOpt
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Length uint8
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Data []byte
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}
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// String returns a string version of a DHCP Option.
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func (o DHCPOption) String() string {
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switch o.Type {
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case DHCPOptHostname, DHCPOptMeritDumpFile, DHCPOptDomainName, DHCPOptRootPath,
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DHCPOptExtensionsPath, DHCPOptNISDomain, DHCPOptNetBIOSTCPScope, DHCPOptXFontServer,
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DHCPOptXDisplayManager, DHCPOptMessage, DHCPOptDomainSearch: // string
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return fmt.Sprintf("Option(%s:%s)", o.Type, string(o.Data))
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case DHCPOptMessageType:
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if len(o.Data) != 1 {
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return fmt.Sprintf("Option(%s:INVALID)", o.Type)
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}
|
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return fmt.Sprintf("Option(%s:%s)", o.Type, DHCPMsgType(o.Data[0]))
|
|
|
|
case DHCPOptSubnetMask, DHCPOptServerID, DHCPOptBroadcastAddr,
|
|
DHCPOptSolicitAddr, DHCPOptRequestIP: // net.IP
|
|
if len(o.Data) < 4 {
|
|
return fmt.Sprintf("Option(%s:INVALID)", o.Type)
|
|
}
|
|
return fmt.Sprintf("Option(%s:%s)", o.Type, net.IP(o.Data))
|
|
|
|
case DHCPOptT1, DHCPOptT2, DHCPOptLeaseTime, DHCPOptPathMTUAgingTimeout,
|
|
DHCPOptARPTimeout, DHCPOptTCPKeepAliveInt: // uint32
|
|
if len(o.Data) != 4 {
|
|
return fmt.Sprintf("Option(%s:INVALID)", o.Type)
|
|
}
|
|
return fmt.Sprintf("Option(%s:%d)", o.Type,
|
|
uint32(o.Data[0])<<24|uint32(o.Data[1])<<16|uint32(o.Data[2])<<8|uint32(o.Data[3]))
|
|
|
|
case DHCPOptParamsRequest:
|
|
buf := &bytes.Buffer{}
|
|
buf.WriteString(fmt.Sprintf("Option(%s:", o.Type))
|
|
for i, v := range o.Data {
|
|
buf.WriteString(DHCPOpt(v).String())
|
|
if i+1 != len(o.Data) {
|
|
buf.WriteByte(',')
|
|
}
|
|
}
|
|
buf.WriteString(")")
|
|
return buf.String()
|
|
|
|
default:
|
|
return fmt.Sprintf("Option(%s:%v)", o.Type, o.Data)
|
|
}
|
|
}
|
|
|
|
// NewDHCPOption constructs a new DHCPOption with a given type and data.
|
|
func NewDHCPOption(t DHCPOpt, data []byte) DHCPOption {
|
|
o := DHCPOption{Type: t}
|
|
if data != nil {
|
|
o.Data = data
|
|
o.Length = uint8(len(data))
|
|
}
|
|
return o
|
|
}
|
|
|
|
func (o *DHCPOption) encode(b []byte) error {
|
|
switch o.Type {
|
|
case DHCPOptPad, DHCPOptEnd:
|
|
b[0] = byte(o.Type)
|
|
default:
|
|
if o.Length > 253 {
|
|
return errors.New("data too long to encode")
|
|
}
|
|
b[0] = byte(o.Type)
|
|
b[1] = o.Length
|
|
copy(b[2:], o.Data)
|
|
}
|
|
return nil
|
|
}
|
|
|
|
func (o *DHCPOption) decode(data []byte) error {
|
|
if len(data) < 1 {
|
|
// Pad/End have a length of 1
|
|
return errors.New("Not enough data to decode")
|
|
}
|
|
o.Type = DHCPOpt(data[0])
|
|
switch o.Type {
|
|
case DHCPOptPad, DHCPOptEnd:
|
|
o.Data = nil
|
|
default:
|
|
if len(data) < 3 {
|
|
return errors.New("Not enough data to decode")
|
|
}
|
|
o.Length = data[1]
|
|
if o.Length > 253 {
|
|
return errors.New("data too long to decode")
|
|
}
|
|
o.Data = data[2 : 2+o.Length]
|
|
}
|
|
return nil
|
|
}
|