使用gopacket更改目标端口

huangapple
go评论135阅读模式
英文:

Changing destination port using gopacket

问题

我目前正在尝试使用nfqueue读取数据包并对其进行修改。不幸的是，我在更改数据包的目标端口方面遇到了一些困难。请参考下面的代码片段。我的想法是将目标端口从8888改写为8000。

我确实看到修改后的数据包从队列中发送出去，但是如果我想通过连接到端口8888来连接到监听在端口8000上的HTTP服务器，连接会超时。我猜测数据包中有一些格式错误。

  1. package main
  3. import (
  4. 	"os"
  5. 	"os/signal"
  6. 	"syscall"
  8. 	"github.com/chifflier/nfqueue-go/nfqueue"
  9. 	"github.com/coreos/go-iptables/iptables"
  11. 	"github.com/google/gopacket"
  12. 	"github.com/google/gopacket/layers"
  13. )
  15. func sendNewPacket(payload *nfqueue.Payload, layers ...gopacket.SerializableLayer) {
  16. 	buffer := gopacket.NewSerializeBuffer()
  17. 	gopacket.SerializeLayers(buffer, gopacket.SerializeOptions{FixLengths: true, ComputeChecksums: true}, layers...)
  18. 	outgoingPacket := buffer.Bytes()
  19. 	payload.SetVerdictModified(nfqueue.NF_ACCEPT, outgoingPacket)
  20. }
  22. func realCallback(payload *nfqueue.Payload) int {
  23. 	packet := gopacket.NewPacket(payload.Data, layers.LayerTypeIPv4, gopacket.Default)
  24. 	ethLayer := packet.Layer(layers.LayerTypeEthernet)
  25. 	eth, _ := ethLayer.(*layers.Ethernet)
  26. 	if ipLayer := packet.Layer(layers.LayerTypeIPv4); ipLayer != nil {
  27. 		ip, _ := ipLayer.(*layers.IPv4)
  28. 		if tcpLayer := packet.Layer(layers.LayerTypeTCP); tcpLayer != nil {
  29. 			tcp, _ := tcpLayer.(*layers.TCP)
  30. 			if tcp.DstPort == 8888 {
  31. 				tcp.DstPort = 8000
  32. 				sendNewPacket(payload, eth, ip, tcp)
  33. 				return 0
  34. 			}
  35. 			if tcp.SrcPort == 8000 {
  36. 				tcp.SrcPort = 8888
  37. 				sendNewPacket(payload, eth, ip, tcp)
  38. 				return 0
  39. 			}
  40. 		}
  41. 	}
  42. 	payload.SetVerdict(nfqueue.NF_ACCEPT)
  43. 	return 0
  44. }
  46. func main() {
  47. 	ipt, err := iptables.New()
  48. 	if err != nil {
  49. 		panic(err)
  50. 	}
  51. 	ipt.Append("filter", "INPUT", "-p", "tcp", "-j", "NFQUEUE", "--queue-num", "0")
  52. 	ipt.Append("filter", "OUTPUT", "-p", "tcp", "-j", "NFQUEUE", "--queue-num", "0")
  53. 	q := new(nfqueue.Queue)
  54. 	q.SetCallback(realCallback)
  56. 	q.Init()
  57. 	defer q.Close()
  59. 	q.Unbind(syscall.AF_INET)
  60. 	q.Bind(syscall.AF_INET)
  61. 	q.CreateQueue(0)
  63. 	c := make(chan os.Signal, 1)
  64. 	signal.Notify(c, os.Interrupt)
  65. 	go func() {
  66. 		for sig := range c {
  67. 			_ = sig
  68. 			q.Close()
  69. 			err = ipt.ClearChain("filter", "INPUT")
  70. 			err = ipt.ClearChain("filter", "OUTPUT")
  71. 			if err != nil {
  72. 				panic(err)
  73. 			}
  74. 			os.Exit(0)
  75. 		}
  76. 	}()
  77. 	q.TryRun()
  78. }
英文:

I'm currently playing around with reading packages from nfqueue and modifying them.Unfortunately, I'm a bit stuck at changing the destination port of a package. See the code snippet below. Idea is to rewrite dest port 8888 to 8000.
I do see the modified package going out from the queue, but if I want to connect to an HTTP server listening on port 8000 by connecting to port 8888, the connection times out. I assume something mal-formed in the package.

  1. package main
  2. import (
  3. "os"
  4. "os/signal"
  5. "syscall"
  6. "github.com/chifflier/nfqueue-go/nfqueue"
  7. "github.com/coreos/go-iptables/iptables"
  8. "github.com/google/gopacket"
  9. "github.com/google/gopacket/layers"
  10. )
  11. func sendNewPacket(payload *nfqueue.Payload, layers ...gopacket.SerializableLayer) {
  12. buffer := gopacket.NewSerializeBuffer()
  13. gopacket.SerializeLayers(buffer, gopacket.SerializeOptions{FixLengths: true, ComputeChecksums: true}, layers...)
  14. outgoingPacket := buffer.Bytes()
  15. payload.SetVerdictModified(nfqueue.NF_ACCEPT, outgoingPacket)
  16. }
  17. func realCallback(payload *nfqueue.Payload) int {
  18. packet := gopacket.NewPacket(payload.Data, layers.LayerTypeIPv4, gopacket.Default)
  19. ethLayer := packet.Layer(layers.LayerTypeEthernet)
  20. eth, _ := ethLayer.(*layers.Ethernet)
  21. if ipLayer := packet.Layer(layers.LayerTypeIPv4); ipLayer != nil {
  22. ip, _ := ipLayer.(*layers.IPv4)
  23. if tcpLayer := packet.Layer(layers.LayerTypeTCP); tcpLayer != nil {
  24. tcp, _ := tcpLayer.(*layers.TCP)
  25. if tcp.DstPort == 8888 {
  26. tcp.DstPort = 8000
  27. sendNewPacket(payload, eth, ip, tcp)
  28. return 0
  29. }
  30. if tcp.SrcPort == 8000 {
  31. tcp.SrcPort = 8888
  32. sendNewPacket(payload, eth, ip, tcp)
  33. return 0
  34. }
  35. }
  36. }
  37. payload.SetVerdict(nfqueue.NF_ACCEPT)
  38. return 0
  39. }
  40. func main() {
  41. ipt, err := iptables.New()
  42. if err != nil {
  43. panic(err)
  44. }
  45. ipt.Append("filter", "INPUT", "-p", "tcp", "-j", "NFQUEUE", "--queue-num", "0")
  46. ipt.Append("filter", "OUTPUT", "-p", "tcp", "-j", "NFQUEUE", "--queue-num", "0")
  47. q := new(nfqueue.Queue)
  48. q.SetCallback(realCallback)
  49. q.Init()
  50. defer q.Close()
  51. q.Unbind(syscall.AF_INET)
  52. q.Bind(syscall.AF_INET)
  53. q.CreateQueue(0)
  54. c := make(chan os.Signal, 1)
  55. signal.Notify(c, os.Interrupt)
  56. go func() {
  57. for sig := range c {
  58. _ = sig
  59. q.Close()
  60. err = ipt.ClearChain("filter", "INPUT")
  61. err = ipt.ClearChain("filter", "OUTPUT")
  62. if err != nil {
  63. panic(err)
  64. }
  65. os.Exit(0)
  66. }
  67. }()
  68. q.TryRun()
  69. }

答案1

得分: 0

如果你对解决方案感兴趣，可以在这里找到代码：https://github.com/kung-foo/freki

英文:

In case you are interested in the solution, code can be found here: https://github.com/kung-foo/freki

huangapple
  • 本文由 发表于 2016年12月16日 19:31:42
  • 转载请务必保留本文链接：https://go.coder-hub.com/41183466.html
  • go
  • gopacket
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