golang使用gopacket包进行数据包捕获，注入和分析-工具盒子

使用golang实现网络抓包是非常容易的，可以使用谷歌的包github.com/google/gopacket。由于gopacket构建在libpcap之上，我强烈建议您了解该库的工作原理。您可以在C中学习如何使用libpcap进行更深入的了解。
1.libpcap

gopacket是基于 libpcap（数据包捕获函数库）的，该库提供的C函数接口用于捕捉经过指定网络接口的数据包，该接口应该是被设为混杂模式。著名的软件TCPDUMP就是在Libpcap的基础上开发而成的。Libpcap提供的接口函数实现和封装了与数据包截获有关的过程。Libpcap可以在绝大多数Linux平台上运行。
主要有以下功能：

数据包捕获：捕获流经网卡的原始数据包

自定义数据包发送：构造任何格式的原始数据包

流量采集与统计：采集网络中的流量信息

规则过滤：提供自带规则过滤功能，按需要选择过滤规则

2.先决条件

# Get the gopacket package from GitHub
go get github.com/google/gopacket
# Pcap dev headers might be necessary
sudo apt-get install libpcap-dev

3.获取所有的网络设备信息

package main

import (
"fmt"
"log"


    "github.com/google/gopacket/pcap"




)


func main() {
// Find all devices
devices, err := pcap.FindAllDevs()
if err != nil {
log.Fatal(err)
}


    // Print device information
    fmt.Println("Devices found:")
    for _, d := range devices {
        fmt.Println("\nName: ", d.Name)
        fmt.Println("Description: ", d.Description)
        fmt.Println("Devices addresses: ", d.Addresses)

        for _, address := range d.Addresses {
            fmt.Println("- IP address: ", address.IP)
            fmt.Println("- Subnet mask: ", address.Netmask)
        }
    }



`}`

4.打开设备实时捕捉

package main

import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/pcap"
"log"
"time"
)


var (
device       string = "你的网卡名称，可以通过上面3获取所有设备获取到(Name)"
snapshot_len int32  = 1024
promiscuous  bool   = false
err          error
timeout      time.Duration = 30 \* time.Second
handle       pcap.Handle
)


func main() {
// Open device
handle, err := pcap.OpenLive(device, snapshot_len, promiscuous, timeout)
if err != nil {
log.Fatal(err)
}
defer handle.Close()


    // Use the handle as a packet source to process all packets
    packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
    for packet := range packetSource.Packets() {
        // Process packet here
        fmt.Println(packet)
    }



`}
`

5.抓取结果保存为pcap格式文件

package main

import (
"fmt"
"os"
"time"


    "github.com/google/gopacket"
    "github.com/google/gopacket/layers"
    "github.com/google/gopacket/pcap"
    "github.com/google/gopacket/pcapgo"




)


var (
//deviceName  string = "eth0"
deviceName string = "\\Device\\NPF_{9A3E6D9C-B24F-4CD0-9C4A-E7ACF6F09ABF}"
snapshotLen int32  = 1024
promiscuous bool   = false
err         error
timeout     time.Duration = 1 \* time.Second
handle      pcap.Handle
packetCount int = 0
)


func main() {
// Open output pcap file and write header
f, _ := os.Create("test.pcap")
w := pcapgo.NewWriter(f)
w.WriteFileHeader(uint32(snapshotLen), layers.LinkTypeEthernet)
defer f.Close()


    // Open the device for capturing
    handle, err := pcap.OpenLive(deviceName, snapshotLen, promiscuous, timeout)
    if err != nil {
        fmt.Printf("Error opening device %s: %v", deviceName, err)
        os.Exit(1)
    }
    defer handle.Close()

    // Start processing packets
    packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
    for packet := range packetSource.Packets() {
        // Process packet here
        fmt.Println(packet)
        w.WritePacket(packet.Metadata().CaptureInfo, packet.Data())
        packetCount++

        // Only capture 100 and then stop
        if packetCount &gt; 100 {
            break
        }
    }



`}
`

6.读取pcap格式文件来查看分析网络数据包

package main

import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/pcap"
"log"
)


var (
pcapFile string = "test.pcap"
handle   \*pcap.Handle
err      error
)


func main() {
// Open file instead of device
handle, err = pcap.OpenOffline(pcapFile)
if err != nil {
log.Fatal(err)
}
defer handle.Close()


    // Loop through packets in file
    packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
    for packet := range packetSource.Packets() {
        fmt.Println(packet)
    }



`}
`

7.设置过滤器
只抓取tcp协议80端口的数据
filter没看懂是怎么写的

package main

import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/pcap"
"log"
"time"
)


var (
//device       string = "eth0"
device string = "\\Device\\NPF_{9A3E6D9C-B24F-4CD0-9C4A-E7ACF6F09ABF}"
snapshot_len int32  = 1024
promiscuous  bool   = false
err          error
timeout      time.Duration = 30 \* time.Second
handle       pcap.Handle
)


func main() {
// Open device
handle, err := pcap.OpenLive(device, snapshot_len, promiscuous, timeout)
if err != nil {
log.Fatal(err)
}
defer handle.Close()


    // Set filter
    var filter string = "tcp and port 80"
    err = handle.SetBPFFilter(filter)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println("Only capturing TCP port 80 packets.")

    packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
    for packet := range packetSource.Packets() {
        // Do something with a packet here.
        fmt.Println(packet)
    }



`}
`

8.解码抓取的数据

我们可以使用原始数据包，并且可将其转换为已知格式。它与不同的层兼容，所以我们可以轻松访问以太网，IP和TCP层。layers包是Go库中新增的，在底层pcap库中不可用。这是一个令人难以置信的有用的包，它是gopacket库的一部分。它允许我们容易地识别包是否包含特定类型的层。该代码示例将显示如何使用layers包来查看数据包是以太网，IP和TCP，并轻松访问这些头文件中的元素。
查找有效载荷取决于所涉及的所有层。每个协议是不同的，必须相应地计算。这就是layer包的魅力所在。 gopacket的作者花了时间为诸如以太网，IP，UDP和TCP等众多已知层创建了相应类型。有效载荷是应用层的一部分。

package main

import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
"log"
"strings"
"time"
)


var (
//device      string = "eth0"
device string = "\\Device\\NPF_{9A3E6D9C-B24F-4CD0-9C4A-E7ACF6F09ABF}"
snapshotLen int32  = 1024
promiscuous bool   = false
err         error
timeout     time.Duration = 30 \* time.Second
handle      pcap.Handle
)


func main() {
// Open device
handle, err := pcap.OpenLive(device, snapshotLen, promiscuous, timeout)
if err != nil {
log.Fatal(err)
}
defer handle.Close()


    packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
    for packet := range packetSource.Packets() {
        printPacketInfo(packet)
    }




}


func printPacketInfo(packet gopacket.Packet) {
// Let's see if the packet is an ethernet packet
ethernetLayer := packet.Layer(layers.LayerTypeEthernet)
if ethernetLayer != nil {
fmt.Println("Ethernet layer detected.")
ethernetPacket, _ := ethernetLayer.(\*layers.Ethernet)
fmt.Println("Source MAC: ", ethernetPacket.SrcMAC)
fmt.Println("Destination MAC: ", ethernetPacket.DstMAC)
// Ethernet type is typically IPv4 but could be ARP or other
fmt.Println("Ethernet type: ", ethernetPacket.EthernetType)
fmt.Println()
}


    // Let's see if the packet is IP (even though the ether type told us)
    ipLayer := packet.Layer(layers.LayerTypeIPv4)
    if ipLayer != nil {
        fmt.Println("IPv4 layer detected.")
        ip, _ := ipLayer.(*layers.IPv4)

        // IP layer variables:
        // Version (Either 4 or 6)
        // IHL (IP Header Length in 32-bit words)
        // TOS, Length, Id, Flags, FragOffset, TTL, Protocol (TCP?),
        // Checksum, SrcIP, DstIP
        fmt.Printf("From %s to %s\n", ip.SrcIP, ip.DstIP)
        fmt.Println("Protocol: ", ip.Protocol)
        fmt.Println()
    }

    // Let's see if the packet is TCP
    tcpLayer := packet.Layer(layers.LayerTypeTCP)
    if tcpLayer != nil {
        fmt.Println("TCP layer detected.")
        tcp, _ := tcpLayer.(*layers.TCP)

        // TCP layer variables:
        // SrcPort, DstPort, Seq, Ack, DataOffset, Window, Checksum, Urgent
        // Bool flags: FIN, SYN, RST, PSH, ACK, URG, ECE, CWR, NS
        fmt.Printf("From port %d to %d\n", tcp.SrcPort, tcp.DstPort)
        fmt.Println("Sequence number: ", tcp.Seq)
        fmt.Println()
    }

    // Iterate over all layers, printing out each layer type
    fmt.Println("All packet layers:")
    for _, layer := range packet.Layers() {
        fmt.Println("- ", layer.LayerType())
    }

    // When iterating through packet.Layers() above,
    // if it lists Payload layer then that is the same as
    // this applicationLayer. applicationLayer contains the payload
    applicationLayer := packet.ApplicationLayer()
    if applicationLayer != nil {
        fmt.Println("Application layer/Payload found.")
        fmt.Printf("%s\n", applicationLayer.Payload())

        // Search for a string inside the payload
        if strings.Contains(string(applicationLayer.Payload()), "HTTP") {
            fmt.Println("HTTP found!")
        }
    }

    // Check for errors
    if err := packet.ErrorLayer(); err != nil {
        fmt.Println("Error decoding some part of the packet:", err)
    }



`}
`

8.构造发送数据包

这个例子做了几件事情。首先将显示如何使用网络设备发送原始字节。这样就可以像串行连接一样使用它来发送数据。这对于真正的低层数据传输非常有用，但如果您想与应用程序进行交互，您应该构建可以识别该数据包的其他硬件和软件。接下来，它将显示如何使用以太网，IP和TCP层创建一个数据包。一切都是默认空的。要完成它，我们创建另一个数据包，但实际上填写了以太网层的一些MAC地址，IPv4的一些IP地址和TCP层的端口号。你应该看到如何伪装数据包和仿冒网络设备。TCP层结构体具有可读取和可设置的SYN，FIN，ACK标志。这有助于操纵和模糊TCP三次握手，会话和端口扫描。pcap库提供了一种发送字节的简单方法，但gopacket中的图层可帮助我们为多层创建字节结构。

package main

import (
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
"log"
"net"
"time"
)


var (
//device       string = "eth0"
device string = "\\Device\\NPF_{9A3E6D9C-B24F-4CD0-9C4A-E7ACF6F09ABF}"


    snapshot_len int32 = 1024
    promiscuous  bool  = false
    err          error
    timeout      time.Duration = 30 * time.Second
    handle       pcap.Handle
    buffer       gopacket.SerializeBuffer
    options      gopacket.SerializeOptions




)


func main() {
// Open device
handle, err := pcap.OpenLive(device, snapshot_len, promiscuous, timeout)
if err != nil {
log.Fatal(err)
}
defer handle.Close()


    // Send raw bytes over wire
    rawBytes := []byte{10, 20, 30}
    err = handle.WritePacketData(rawBytes)
    if err != nil {
        log.Fatal(err)
    }

    // Create a properly formed packet, just with
    // empty details. Should fill out MAC addresses,
    // IP addresses, etc.
    buffer = gopacket.NewSerializeBuffer()
    gopacket.SerializeLayers(buffer, options,
        &amp;layers.Ethernet{},
        &amp;layers.IPv4{},
        &amp;layers.TCP{},
        gopacket.Payload(rawBytes),
    )
    outgoingPacket := buffer.Bytes()
    // Send our packet
    err = handle.WritePacketData(outgoingPacket)
    if err != nil {
        log.Fatal(err)
    }

    // This time lets fill out some information
    ipLayer := &amp;layers.IPv4{
        SrcIP: net.IP{127, 0, 0, 1},
        DstIP: net.IP{8, 8, 8, 8},
    }
    ethernetLayer := &amp;layers.Ethernet{
        SrcMAC: net.HardwareAddr{0xFF, 0xAA, 0xFA, 0xAA, 0xFF, 0xAA},
        DstMAC: net.HardwareAddr{0xBD, 0xBD, 0xBD, 0xBD, 0xBD, 0xBD},
    }
    tcpLayer := &amp;layers.TCP{
        SrcPort: layers.TCPPort(4321),
        DstPort: layers.TCPPort(80),
    }
    // And create the packet with the layers
    buffer = gopacket.NewSerializeBuffer()
    gopacket.SerializeLayers(buffer, options,
        ethernetLayer,
        ipLayer,
        tcpLayer,
        gopacket.Payload(rawBytes),
    )
    outgoingPacket = buffer.Bytes()



`}
`

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golang使用gopacket包进行数据包捕获，注入和分析

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