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packet.go
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package ztrace
import (
"bytes"
"crypto/sha1"
"encoding/binary"
"fmt"
"net"
"github.com/sirupsen/logrus"
"golang.org/x/net/ipv4"
)
func GetHash(src net.IP, dst net.IP, srcPort uint16, dstPort uint16, proto uint16) string {
h := sha1.New()
h.Write(src)
h.Write(dst)
p := make([]byte, 2)
binary.BigEndian.PutUint16(p, srcPort)
h.Write(p)
binary.BigEndian.PutUint16(p, dstPort)
h.Write(p)
binary.BigEndian.PutUint16(p, proto)
h.Write(p)
return fmt.Sprintf("%x", h.Sum(nil))
}
type UDPHeader struct {
Src uint16
Dst uint16
Length uint16
Chksum uint16
}
const (
TCP_FIN = 1 << 0
TCP_SYN = 1 << 1
TCP_RST = 1 << 2
TCP_PSH = 1 << 3
TCP_ACK = 1 << 4
TCP_URG = 1 << 5
)
type TCPHeader struct {
Src uint16
Dst uint16
SeqNum uint32
AckNum uint32
DataOffset uint8 // only use high 4 bits
Flags uint8 // only use low 6 bits
Window uint16
Checksum uint16
Urgent uint16
}
//checksum function
func checkSum(buf []byte) uint16 {
sum := uint32(0)
for ; len(buf) >= 2; buf = buf[2:] {
sum += uint32(buf[0])<<8 | uint32(buf[1])
}
if len(buf) > 0 {
sum += uint32(buf[0]) << 8
}
for sum > 0xffff {
sum = (sum >> 16) + (sum & 0xffff)
}
csum := ^uint16(sum)
/*
* From RFC 768:
* If the computed checksum is zero, it is transmitted as all ones (the
* equivalent in one's complement arithmetic). An all zero transmitted
* checksum value means that the transmitter generated no checksum (for
* debugging or for higher level protocols that don't care).
*/
if csum == 0 {
csum = 0xffff
}
return csum
}
func (u *UDPHeader) checksum(ip *ipv4.Header, payload []byte) {
var pseudoHeader []byte
pseudoHeader = append(pseudoHeader, ip.Src.To4()...)
pseudoHeader = append(pseudoHeader, ip.Dst.To4()...)
pseudoHeader = append(pseudoHeader, []byte{
0,
17,
0, byte(u.Length),
}...)
var b bytes.Buffer
binary.Write(&b, binary.BigEndian, pseudoHeader)
binary.Write(&b, binary.BigEndian, u)
binary.Write(&b, binary.BigEndian, &payload)
u.Chksum = checkSum(b.Bytes())
}
func (t *TCPHeader) checksum(ip *ipv4.Header, payload []byte) {
var pseudoHeader []byte
pseudoHeader = append(pseudoHeader, ip.Src.To4()...)
pseudoHeader = append(pseudoHeader, ip.Dst.To4()...)
pseudoHeader = append(pseudoHeader, []byte{
0,
6,
0, byte(len(payload) + 20),
}...)
var b bytes.Buffer
binary.Write(&b, binary.BigEndian, pseudoHeader)
binary.Write(&b, binary.BigEndian, t)
binary.Write(&b, binary.BigEndian, &payload)
t.Checksum = checkSum(b.Bytes())
}
func (t *TraceRoute) BuildIPv4UDPkt(srcPort uint16, dstPort uint16, ttl uint8, id uint16, tos int) (*ipv4.Header, []byte) {
iph := &ipv4.Header{
Version: ipv4.Version,
TOS: tos,
Len: ipv4.HeaderLen,
TotalLen: 60,
ID: int(id),
Flags: 0,
FragOff: 0,
TTL: int(ttl),
Protocol: 17,
Checksum: 0,
Src: t.NetSrcAddr,
Dst: t.NetDstAddr,
}
h, err := iph.Marshal()
if err != nil {
logrus.Error(err)
return nil, nil
}
iph.Checksum = int(checkSum(h))
udp := UDPHeader{
Src: srcPort,
Dst: dstPort,
}
payload := make([]byte, 32)
for i := 0; i < 32; i++ {
payload[i] = uint8(i + 64)
}
udp.Length = uint16(len(payload) + 8)
udp.checksum(iph, payload)
var buf bytes.Buffer
binary.Write(&buf, binary.BigEndian, &udp)
binary.Write(&buf, binary.BigEndian, &payload)
return iph, buf.Bytes()
}
func (t *TraceRoute) BuildIPv4TCPSYN(srcPort uint16, dstPort uint16, ttl uint8, seq uint32, tos int) (*ipv4.Header, []byte) {
iph := &ipv4.Header{
Version: ipv4.Version,
TOS: tos,
Len: ipv4.HeaderLen,
TotalLen: 60,
ID: 0,
Flags: 0,
FragOff: 0,
TTL: int(ttl),
Protocol: 6,
Checksum: 0,
Src: t.NetSrcAddr,
Dst: t.NetDstAddr,
}
h, err := iph.Marshal()
if err != nil {
logrus.Error(err)
return nil, nil
}
iph.Checksum = int(checkSum(h))
tcp := TCPHeader{
Src: srcPort,
Dst: dstPort,
SeqNum: seq,
AckNum: 0,
DataOffset: 160,
Flags: TCP_SYN,
Window: 64240,
Urgent: 0,
}
payload := []byte{0x02, 0x04, 0x05, 0xb4, 0x04, 0x02, 0x08, 0x0a, 0x7f, 0x73, 0xf9, 0x3a, 0x00, 0x00, 0x00, 0x00, 0x01, 0x03, 0x03, 0x07}
tcp.checksum(iph, payload)
var buf bytes.Buffer
binary.Write(&buf, binary.BigEndian, &tcp)
binary.Write(&buf, binary.BigEndian, &payload)
return iph, buf.Bytes()
}
func (t *TraceRoute) BuildIPv4TCPPRST(srcPort uint16, dstPort uint16, ttl uint8, seq uint32, tos int) (*ipv4.Header, []byte) {
iph := &ipv4.Header{
Version: ipv4.Version,
TOS: tos,
Len: ipv4.HeaderLen,
TotalLen: 40,
ID: 0,
Flags: 0,
FragOff: 0,
TTL: int(ttl),
Protocol: 6,
Checksum: 0,
Src: t.NetSrcAddr,
Dst: t.NetDstAddr,
}
h, err := iph.Marshal()
if err != nil {
logrus.Error(err)
return nil, nil
}
iph.Checksum = int(checkSum(h))
tcp := TCPHeader{
Src: srcPort,
Dst: dstPort,
SeqNum: seq,
AckNum: 0,
DataOffset: 80,
Flags: TCP_RST,
Window: 0,
Urgent: 0,
}
tcp.checksum(iph, nil)
var buf bytes.Buffer
binary.Write(&buf, binary.BigEndian, &tcp)
return iph, buf.Bytes()
}
type ICMPHeader struct {
IType uint8
ICode uint8
Checksum uint16
ID uint16
Seq uint16
}
func (t *TraceRoute) BuildIPv4ICMP(ttl uint8, id, seq uint16, tos int) (*ipv4.Header, []byte) {
iph := &ipv4.Header{
Version: ipv4.Version,
TOS: tos,
Len: ipv4.HeaderLen,
TotalLen: 40,
ID: int(id),
Flags: 0,
FragOff: 0,
TTL: int(ttl),
Protocol: 1,
Checksum: 0,
Src: t.NetSrcAddr,
Dst: t.NetDstAddr,
}
h, err := iph.Marshal()
if err != nil {
logrus.Error(err)
return nil, nil
}
iph.Checksum = int(checkSum(h))
icmp := ICMPHeader{
IType: 8,
ICode: 0,
Checksum: 0,
ID: id,
Seq: seq,
}
payload := make([]byte, 32)
for i := 0; i < 32; i++ {
payload[i] = uint8(i + 64)
}
var b bytes.Buffer
binary.Write(&b, binary.BigEndian, icmp)
binary.Write(&b, binary.BigEndian, &payload)
icmp.Checksum = checkSum(b.Bytes())
var buf bytes.Buffer
binary.Write(&buf, binary.BigEndian, &icmp)
binary.Write(&buf, binary.BigEndian, &payload)
return iph, buf.Bytes()
}
func (t *TraceRoute) dnsResolve(hostName string, dst *net.IPAddr) (net.IP, error) {
isIPv6 := false
if t.Af == "ip6"{
isIPv6 = true
}
ipAddr := net.ParseIP(hostName)
if isIPv6 && ipAddr.To16() != nil {
dst.IP = ipAddr
} else if !isIPv6 && ipAddr.To4() != nil {
dst.IP = ipAddr
} else {
ips, err := net.LookupIP(hostName)
if err != nil {
logrus.Error("Could not resolve ", hostName)
return nil, err
}
for _, ip := range ips {
if isIPv6 && ip.To16() != nil {
dst.IP = ip
break
} else if !isIPv6 && ip.To4() != nil {
dst.IP = ip
break
}
}
if dst.IP == nil {
logrus.Error("Could not find a valid record for ", hostName)
return nil, fmt.Errorf("Could not find a valid record for %s\n", hostName)
}
}
return dst.IP, nil
}