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// Copyright 2016 Google, Inc. All rights reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the LICENSE file in the root of the source
// tree.
package layers
import (
"bytes"
"encoding/binary"
"fmt"
"net"
"github.com/google/gopacket"
)
// DHCPOp rerprents a bootp operation
type DHCPOp byte
// bootp operations
const (
DHCPOpRequest DHCPOp = 1
DHCPOpReply DHCPOp = 2
)
// String returns a string version of a DHCPOp.
func (o DHCPOp) String() string {
switch o {
case DHCPOpRequest:
return "Request"
case DHCPOpReply:
return "Reply"
default:
return "Unknown"
}
}
// DHCPMsgType represents a DHCP operation
type DHCPMsgType byte
// Constants that represent DHCP operations
const (
DHCPMsgTypeUnspecified DHCPMsgType = iota
DHCPMsgTypeDiscover
DHCPMsgTypeOffer
DHCPMsgTypeRequest
DHCPMsgTypeDecline
DHCPMsgTypeAck
DHCPMsgTypeNak
DHCPMsgTypeRelease
DHCPMsgTypeInform
)
// String returns a string version of a DHCPMsgType.
func (o DHCPMsgType) String() string {
switch o {
case DHCPMsgTypeUnspecified:
return "Unspecified"
case DHCPMsgTypeDiscover:
return "Discover"
case DHCPMsgTypeOffer:
return "Offer"
case DHCPMsgTypeRequest:
return "Request"
case DHCPMsgTypeDecline:
return "Decline"
case DHCPMsgTypeAck:
return "Ack"
case DHCPMsgTypeNak:
return "Nak"
case DHCPMsgTypeRelease:
return "Release"
case DHCPMsgTypeInform:
return "Inform"
default:
return "Unknown"
}
}
//DHCPMagic is the RFC 2131 "magic cooke" for DHCP.
var DHCPMagic uint32 = 0x63825363
// DHCPv4 contains data for a single DHCP packet.
type DHCPv4 struct {
BaseLayer
Operation DHCPOp
HardwareType LinkType
HardwareLen uint8
HardwareOpts uint8
Xid uint32
Secs uint16
Flags uint16
ClientIP net.IP
YourClientIP net.IP
NextServerIP net.IP
RelayAgentIP net.IP
ClientHWAddr net.HardwareAddr
ServerName []byte
File []byte
Options DHCPOptions
}
// DHCPOptions is used to get nicely printed option lists which would normally
// be cut off after 5 options.
type DHCPOptions []DHCPOption
// String returns a string version of the options list.
func (o DHCPOptions) String() string {
buf := &bytes.Buffer{}
buf.WriteByte('[')
for i, opt := range o {
buf.WriteString(opt.String())
if i+1 != len(o) {
buf.WriteString(", ")
}
}
buf.WriteByte(']')
return buf.String()
}
// LayerType returns gopacket.LayerTypeDHCPv4
func (d *DHCPv4) LayerType() gopacket.LayerType { return LayerTypeDHCPv4 }
// DecodeFromBytes decodes the given bytes into this layer.
func (d *DHCPv4) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
d.Options = d.Options[:0]
d.Operation = DHCPOp(data[0])
d.HardwareType = LinkType(data[1])
d.HardwareLen = data[2]
d.HardwareOpts = data[3]
d.Xid = binary.BigEndian.Uint32(data[4:8])
d.Secs = binary.BigEndian.Uint16(data[8:10])
d.Flags = binary.BigEndian.Uint16(data[10:12])
d.ClientIP = net.IP(data[12:16])
d.YourClientIP = net.IP(data[16:20])
d.NextServerIP = net.IP(data[20:24])
d.RelayAgentIP = net.IP(data[24:28])
d.ClientHWAddr = net.HardwareAddr(data[28 : 28+d.HardwareLen])
d.ServerName = data[44:108]
d.File = data[108:236]
if binary.BigEndian.Uint32(data[236:240]) != DHCPMagic {
return InvalidMagicCookie
}
if len(data) <= 240 {
// DHCP Packet could have no option (??)
return nil
}
options := data[240:]
stop := len(options)
start := 0
for start < stop {
o := DHCPOption{}
if err := o.decode(options[start:]); err != nil {
return err
}
if o.Type == DHCPOptEnd {
break
}
d.Options = append(d.Options, o)
// Check if the option is a single byte pad
if o.Type == DHCPOptPad {
start++
} else {
start += int(o.Length) + 2
}
}
return nil
}
// Len returns the length of a DHCPv4 packet.
func (d *DHCPv4) Len() uint16 {
n := uint16(240)
for _, o := range d.Options {
if o.Type == DHCPOptPad {
n++
} else {
n += uint16(o.Length) + 2
}
}
n++ // for opt end
return n
}
// SerializeTo writes the serialized form of this layer into the
// SerializationBuffer, implementing gopacket.SerializableLayer.
// See the docs for gopacket.SerializableLayer for more info.
func (d *DHCPv4) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
plen := int(d.Len())
data, err := b.PrependBytes(plen)
if err != nil {
return err
}
data[0] = byte(d.Operation)
data[1] = byte(d.HardwareType)
if opts.FixLengths {
d.HardwareLen = uint8(len(d.ClientHWAddr))
}
data[2] = d.HardwareLen
data[3] = d.HardwareOpts
binary.BigEndian.PutUint32(data[4:8], d.Xid)
binary.BigEndian.PutUint16(data[8:10], d.Secs)
binary.BigEndian.PutUint16(data[10:12], d.Flags)
copy(data[12:16], d.ClientIP.To4())
copy(data[16:20], d.YourClientIP.To4())
copy(data[20:24], d.NextServerIP.To4())
copy(data[24:28], d.RelayAgentIP.To4())
copy(data[28:44], d.ClientHWAddr)
copy(data[44:108], d.ServerName)
copy(data[108:236], d.File)
binary.BigEndian.PutUint32(data[236:240], DHCPMagic)
if len(d.Options) > 0 {
offset := 240
for _, o := range d.Options {
if err := o.encode(data[offset:]); err != nil {
return err
}
// A pad option is only a single byte
if o.Type == DHCPOptPad {
offset++
} else {
offset += 2 + len(o.Data)
}
}
optend := NewDHCPOption(DHCPOptEnd, nil)
if err := optend.encode(data[offset:]); err != nil {
return err
}
}
return nil
}
// CanDecode returns the set of layer types that this DecodingLayer can decode.
func (d *DHCPv4) CanDecode() gopacket.LayerClass {
return LayerTypeDHCPv4
}
// NextLayerType returns the layer type contained by this DecodingLayer.
func (d *DHCPv4) NextLayerType() gopacket.LayerType {
return gopacket.LayerTypePayload
}
func decodeDHCPv4(data []byte, p gopacket.PacketBuilder) error {
dhcp := &DHCPv4{}
err := dhcp.DecodeFromBytes(data, p)
if err != nil {
return err
}
p.AddLayer(dhcp)
return p.NextDecoder(gopacket.LayerTypePayload)
}
// DHCPOpt represents a DHCP option or parameter from RFC-2132
type DHCPOpt byte
// Constants for the DHCPOpt options.
const (
DHCPOptPad DHCPOpt = 0
DHCPOptSubnetMask DHCPOpt = 1 // 4, net.IP
DHCPOptTimeOffset DHCPOpt = 2 // 4, int32 (signed seconds from UTC)
DHCPOptRouter DHCPOpt = 3 // n*4, [n]net.IP
DHCPOptTimeServer DHCPOpt = 4 // n*4, [n]net.IP
DHCPOptNameServer DHCPOpt = 5 // n*4, [n]net.IP
DHCPOptDNS DHCPOpt = 6 // n*4, [n]net.IP
DHCPOptLogServer DHCPOpt = 7 // n*4, [n]net.IP
DHCPOptCookieServer DHCPOpt = 8 // n*4, [n]net.IP
DHCPOptLPRServer DHCPOpt = 9 // n*4, [n]net.IP
DHCPOptImpressServer DHCPOpt = 10 // n*4, [n]net.IP
DHCPOptResLocServer DHCPOpt = 11 // n*4, [n]net.IP
DHCPOptHostname DHCPOpt = 12 // n, string
DHCPOptBootfileSize DHCPOpt = 13 // 2, uint16
DHCPOptMeritDumpFile DHCPOpt = 14 // >1, string
DHCPOptDomainName DHCPOpt = 15 // n, string
DHCPOptSwapServer DHCPOpt = 16 // n*4, [n]net.IP
DHCPOptRootPath DHCPOpt = 17 // n, string
DHCPOptExtensionsPath DHCPOpt = 18 // n, string
DHCPOptIPForwarding DHCPOpt = 19 // 1, bool
DHCPOptSourceRouting DHCPOpt = 20 // 1, bool
DHCPOptPolicyFilter DHCPOpt = 21 // 8*n, [n]{net.IP/net.IP}
DHCPOptDatagramMTU DHCPOpt = 22 // 2, uint16
DHCPOptDefaultTTL DHCPOpt = 23 // 1, byte
DHCPOptPathMTUAgingTimeout DHCPOpt = 24 // 4, uint32
DHCPOptPathPlateuTableOption DHCPOpt = 25 // 2*n, []uint16
DHCPOptInterfaceMTU DHCPOpt = 26 // 2, uint16
DHCPOptAllSubsLocal DHCPOpt = 27 // 1, bool
DHCPOptBroadcastAddr DHCPOpt = 28 // 4, net.IP
DHCPOptMaskDiscovery DHCPOpt = 29 // 1, bool
DHCPOptMaskSupplier DHCPOpt = 30 // 1, bool
DHCPOptRouterDiscovery DHCPOpt = 31 // 1, bool
DHCPOptSolicitAddr DHCPOpt = 32 // 4, net.IP
DHCPOptStaticRoute DHCPOpt = 33 // n*8, [n]{net.IP/net.IP} -- note the 2nd is router not mask
DHCPOptARPTrailers DHCPOpt = 34 // 1, bool
DHCPOptARPTimeout DHCPOpt = 35 // 4, uint32
DHCPOptEthernetEncap DHCPOpt = 36 // 1, bool
DHCPOptTCPTTL DHCPOpt = 37 // 1, byte
DHCPOptTCPKeepAliveInt DHCPOpt = 38 // 4, uint32
DHCPOptTCPKeepAliveGarbage DHCPOpt = 39 // 1, bool
DHCPOptNISDomain DHCPOpt = 40 // n, string
DHCPOptNISServers DHCPOpt = 41 // 4*n, [n]net.IP
DHCPOptNTPServers DHCPOpt = 42 // 4*n, [n]net.IP
DHCPOptVendorOption DHCPOpt = 43 // n, [n]byte // may be encapsulated.
DHCPOptNetBIOSTCPNS DHCPOpt = 44 // 4*n, [n]net.IP
DHCPOptNetBIOSTCPDDS DHCPOpt = 45 // 4*n, [n]net.IP
DHCPOptNETBIOSTCPNodeType DHCPOpt = 46 // 1, magic byte
DHCPOptNetBIOSTCPScope DHCPOpt = 47 // n, string
DHCPOptXFontServer DHCPOpt = 48 // n, string
DHCPOptXDisplayManager DHCPOpt = 49 // n, string
DHCPOptRequestIP DHCPOpt = 50 // 4, net.IP
DHCPOptLeaseTime DHCPOpt = 51 // 4, uint32
DHCPOptExtOptions DHCPOpt = 52 // 1, 1/2/3
DHCPOptMessageType DHCPOpt = 53 // 1, 1-7
DHCPOptServerID DHCPOpt = 54 // 4, net.IP
DHCPOptParamsRequest DHCPOpt = 55 // n, []byte
DHCPOptMessage DHCPOpt = 56 // n, 3
DHCPOptMaxMessageSize DHCPOpt = 57 // 2, uint16
DHCPOptT1 DHCPOpt = 58 // 4, uint32
DHCPOptT2 DHCPOpt = 59 // 4, uint32
DHCPOptClassID DHCPOpt = 60 // n, []byte
DHCPOptClientID DHCPOpt = 61 // n >= 2, []byte
DHCPOptDomainSearch DHCPOpt = 119 // n, string
DHCPOptSIPServers DHCPOpt = 120 // n, url
DHCPOptClasslessStaticRoute DHCPOpt = 121 //
DHCPOptEnd DHCPOpt = 255
)
// String returns a string version of a DHCPOpt.
func (o DHCPOpt) String() string {
switch o {
case DHCPOptPad:
return "(padding)"
case DHCPOptSubnetMask:
return "SubnetMask"
case DHCPOptTimeOffset:
return "TimeOffset"
case DHCPOptRouter:
return "Router"
case DHCPOptTimeServer:
return "rfc868" // old time server protocol stringified to dissuade confusion w. NTP
case DHCPOptNameServer:
return "ien116" // obscure nameserver protocol stringified to dissuade confusion w. DNS
case DHCPOptDNS:
return "DNS"
case DHCPOptLogServer:
return "mitLCS" // MIT LCS server protocol yada yada w. Syslog
case DHCPOptCookieServer:
return "CookieServer"
case DHCPOptLPRServer:
return "LPRServer"
case DHCPOptImpressServer:
return "ImpressServer"
case DHCPOptResLocServer:
return "ResourceLocationServer"
case DHCPOptHostname:
return "Hostname"
case DHCPOptBootfileSize:
return "BootfileSize"
case DHCPOptMeritDumpFile:
return "MeritDumpFile"
case DHCPOptDomainName:
return "DomainName"
case DHCPOptSwapServer:
return "SwapServer"
case DHCPOptRootPath:
return "RootPath"
case DHCPOptExtensionsPath:
return "ExtensionsPath"
case DHCPOptIPForwarding:
return "IPForwarding"
case DHCPOptSourceRouting:
return "SourceRouting"
case DHCPOptPolicyFilter:
return "PolicyFilter"
case DHCPOptDatagramMTU:
return "DatagramMTU"
case DHCPOptDefaultTTL:
return "DefaultTTL"
case DHCPOptPathMTUAgingTimeout:
return "PathMTUAgingTimeout"
case DHCPOptPathPlateuTableOption:
return "PathPlateuTableOption"
case DHCPOptInterfaceMTU:
return "InterfaceMTU"
case DHCPOptAllSubsLocal:
return "AllSubsLocal"
case DHCPOptBroadcastAddr:
return "BroadcastAddress"
case DHCPOptMaskDiscovery:
return "MaskDiscovery"
case DHCPOptMaskSupplier:
return "MaskSupplier"
case DHCPOptRouterDiscovery:
return "RouterDiscovery"
case DHCPOptSolicitAddr:
return "SolicitAddr"
case DHCPOptStaticRoute:
return "StaticRoute"
case DHCPOptARPTrailers:
return "ARPTrailers"
case DHCPOptARPTimeout:
return "ARPTimeout"
case DHCPOptEthernetEncap:
return "EthernetEncap"
case DHCPOptTCPTTL:
return "TCPTTL"
case DHCPOptTCPKeepAliveInt:
return "TCPKeepAliveInt"
case DHCPOptTCPKeepAliveGarbage:
return "TCPKeepAliveGarbage"
case DHCPOptNISDomain:
return "NISDomain"
case DHCPOptNISServers:
return "NISServers"
case DHCPOptNTPServers:
return "NTPServers"
case DHCPOptVendorOption:
return "VendorOption"
case DHCPOptNetBIOSTCPNS:
return "NetBIOSOverTCPNS"
case DHCPOptNetBIOSTCPDDS:
return "NetBiosOverTCPDDS"
case DHCPOptNETBIOSTCPNodeType:
return "NetBIOSOverTCPNodeType"
case DHCPOptNetBIOSTCPScope:
return "NetBIOSOverTCPScope"
case DHCPOptXFontServer:
return "XFontServer"
case DHCPOptXDisplayManager:
return "XDisplayManager"
case DHCPOptEnd:
return "(end)"
case DHCPOptSIPServers:
return "SipServers"
case DHCPOptRequestIP:
return "RequestIP"
case DHCPOptLeaseTime:
return "LeaseTime"
case DHCPOptExtOptions:
return "ExtOpts"
case DHCPOptMessageType:
return "MessageType"
case DHCPOptServerID:
return "ServerID"
case DHCPOptParamsRequest:
return "ParamsRequest"
case DHCPOptMessage:
return "Message"
case DHCPOptMaxMessageSize:
return "MaxDHCPSize"
case DHCPOptT1:
return "Timer1"
case DHCPOptT2:
return "Timer2"
case DHCPOptClassID:
return "ClassID"
case DHCPOptClientID:
return "ClientID"
case DHCPOptDomainSearch:
return "DomainSearch"
case DHCPOptClasslessStaticRoute:
return "ClasslessStaticRoute"
default:
return "Unknown"
}
}
// DHCPOption rerpresents a DHCP option.
type DHCPOption struct {
Type DHCPOpt
Length uint8
Data []byte
}
// String returns a string version of a DHCP Option.
func (o DHCPOption) String() string {
switch o.Type {
case DHCPOptHostname, DHCPOptMeritDumpFile, DHCPOptDomainName, DHCPOptRootPath,
DHCPOptExtensionsPath, DHCPOptNISDomain, DHCPOptNetBIOSTCPScope, DHCPOptXFontServer,
DHCPOptXDisplayManager, DHCPOptMessage, DHCPOptDomainSearch: // string
return fmt.Sprintf("Option(%s:%s)", o.Type, string(o.Data))
case DHCPOptMessageType:
if len(o.Data) != 1 {
return fmt.Sprintf("Option(%s:INVALID)", o.Type)
}
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:
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 DecOptionNotEnoughData
}
o.Type = DHCPOpt(data[0])
switch o.Type {
case DHCPOptPad, DHCPOptEnd:
o.Data = nil
default:
if len(data) < 2 {
return DecOptionNotEnoughData
}
o.Length = data[1]
if int(o.Length) > len(data[2:]) {
return DecOptionMalformed
}
o.Data = data[2 : 2+int(o.Length)]
}
return nil
}
// DHCPv4Error is used for constant errors for DHCPv4. It is needed for test asserts.
type DHCPv4Error string
// DHCPv4Error implements error interface.
func (d DHCPv4Error) Error() string {
return string(d)
}
const (
// DecOptionNotEnoughData is returned when there is not enough data during option's decode process
DecOptionNotEnoughData = DHCPv4Error("Not enough data to decode")
// DecOptionMalformed is returned when the option is malformed
DecOptionMalformed = DHCPv4Error("Option is malformed")
// InvalidMagicCookie is returned when Magic cookie is missing into BOOTP header
InvalidMagicCookie = DHCPv4Error("Bad DHCP header")
)