Packetbeat协议扩展开发教程(3)
前面介绍了Packetbeat的项目结构,今天终于要开始写代码了,想想还是有点小激动呢。(你快点吧,拖半天了)
网络传输两大协议TCP和UDP,我们的所有协议都不离这两种,HTTP、MySQL走的是TCP传输协议,DNS走的是UDP协议,在Packetbeat里面,实现一个自己的协议非常简单,继承并实现这两者对应的接口就行了,我们看一下长什么样:
打开一个现有的UDP和HTTP协议接口定义:
/~/Go/src/github.com/elastic/beats/packetbeat/protos/protos.go
- // Functions to be exported by a protocol plugin
- type ProtocolPlugin interface {
- // Called to initialize the Plugin
- Init(test_mode bool, results publisher.Client) error
- // Called to return the configured ports
- GetPorts() []int
- }
- type TcpProtocolPlugin interface {
- ProtocolPlugin
- // Called when TCP payload data is available for parsing.
- Parse(pkt *Packet, tcptuple *common.TcpTuple,
- dir uint8, private ProtocolData) ProtocolData
- // Called when the FIN flag is seen in the TCP stream.
- ReceivedFin(tcptuple *common.TcpTuple, dir uint8,
- private ProtocolData) ProtocolData
- // Called when a packets are missing from the tcp
- // stream.
- GapInStream(tcptuple *common.TcpTuple, dir uint8, nbytes int,
- private ProtocolData) (priv ProtocolData, drop bool)
- // ConnectionTimeout returns the per stream connection timeout.
- // Return <=0 to set default tcp module transaction timeout.
- ConnectionTimeout() time.Duration
- }
- type UdpProtocolPlugin interface {
- ProtocolPlugin
- // ParseUdp is invoked when UDP payload data is available for parsing.
- ParseUdp(pkt *Packet)
- }
TcpProtocolPlugin:TCP协议插件的接口定义,依次是:Parse() 解析Packet,ReceivedFin()处理TCP断开连接,GapInStream()处理空包丢包,ConnectionTimeout()超时时间;
UdpProtocolPlugin: UDP协议的接口定义,UDP协议是不需要握手和保障数据可靠性的,扔出去就结束,速度快,不保证数据可靠送达,所以只有ParseUdp一个方法需要实现,比较简单;
ProtocolPlugin:TCP和UDP都需要实现ProtocolPlugin的基础接口,其实就定义了获取端口和初始化接口。
请问:Packetbeat怎么工作的?
回答:每一个协议都有一个固定的端口用于通信,你要做的事情就是定义协议端口,然后按协议是TCP还是UDP来实现对应的接口,Packetbeat将会截获指定端口的数据包(Packet),然后如果交给你定义的方法来进行解析,TCP是Parse,UDP是ParseUdp,都在上面的接口定义好的,然后将解析出来的结构化数据封装成Json,然后扔给Elasticsearch,后续的就的如何对这些数据做一些有趣的分析和应用了。
貌似很简单嘛!
进入每个端口的数据包,我们假设是一个自来水管,拧开80端口,哗啦啦出来的全是HTTP请求的数据包,Packetbeat里面Http协议监听的是80端口啊,所有这些包统统都交给Packetbeat里面的Http协议模块来进行解析,Http协议会一个个的检查这些数据包,也就是每个数据包都会调用一次Parse接口,到这里提到了传过来一个Packet,我们看看它的数据结构长什么样?
- type Packet struct {
- Ts time.Time
- Tuple common.IpPortTuple
- Payload []byte
- }
Packet结构简单,
Ts是收到数据包的时间戳;
Tuple是一个来源IP+来源端口和目的IP+目的端口的元组;
Payload就是这个包里面的传输的有用的数据,应用层的字节数据,不包括IP和TCP/UDP头信息,是不是处理起来简单许多。
首选我们确定SMTP协议的配置,每个协议在packetbeat.yml的protocol下面都应该有一个配置节点,如下:
- protocols:
- smtp:
- # Configure the ports where to listen for Smtp traffic. You can disable
- # the Smtp protocol by commenting out the list of ports.
- ports: [25]
还需要在对应的config类文件:packetbeat/config/config.go,增加SMTP的结构体,目前只支持一个端口参数,继承基类ProtocolCommon就行,如下:
- git diff config/config.go
- @@ -42,6 +42,7 @@ type Protocols struct {
- Pgsql Pgsql
- Redis Redis
- Thrift Thrift
- + Smtp Smtp
- }
- type Dns struct {
- @@ -118,5 +119,9 @@ type Redis struct {
- Send_response *bool
- }
- +type Smtp struct {
- + ProtocolCommon `yaml:",inline"`
- +}
- +
- // Config Singleton
- var ConfigSingleton Config
在protos文件夹下面,新增smtp目录,并新增空白文件smtp.go,路径:packetbeat/protos/smtp/smtp.go,这里就是解析SMTP协议的地方,也是我们扩展协议的主要的工作。
- ...TODO...
修改protos/protos.go,增加SMTP协议枚举,这里记得保证顺序一致,并且protocol名称必须和配置的节点名称一致,如这里都是smtp。
- git diff protos/protos.go
- @@ -103,6 +103,7 @@ const (
- MongodbProtocol
- DnsProtocol
- MemcacheProtocol
- + SmtpProtocol
- )
- // Protocol names
- @@ -116,6 +117,7 @@ var ProtocolNames = []string{
- "mongodb",
- "dns",
- "memcache",
- + "smtp",
- }
继续修改packetbeat.go主文件,允许SMTP协议并加载。
- git diff packetbeat.go
- @@ -27,6 +27,7 @@ import (
- "github.com/elastic/packetbeat/protos/tcp"
- "github.com/elastic/packetbeat/protos/thrift"
- "github.com/elastic/packetbeat/protos/udp"
- + "github.com/elastic/packetbeat/protos/smtp"
- "github.com/elastic/packetbeat/sniffer"
- )
- @@ -43,6 +44,7 @@ var EnabledProtocolPlugins map[protos.Protocol]protos.ProtocolPlugin = map[proto
- protos.ThriftProtocol: new(thrift.Thrift),
- protos.MongodbProtocol: new(mongodb.Mongodb),
- protos.DnsProtocol: new(dns.Dns),
- + protos.SmtpProtocol: new(smtp.Smtp),
- }
做完上面一系列修改之后,一个空白的SMTP协议的插件的架子就搭好了,并且插件也注册到了Packetbeat里面了,接下来我们再把packetbeat/protos/smtp/smtp.go按照TCPplugin接口的要求实现一下。
说实话TCP处理起来很难,开始之前,我们先明确几个概念,TCP协议是有状态的,并且是流式的,我们关注的是七层应用层的消息,如HTTP里面的一个HTTP请求和返回,但是TCP底层都是一系列数据包,并且不同的请求的数据包是混杂在一起的,也就是说一个数据包里面可能只是一个HTTP请求的一部分也可能包含多条HTTP请求的一部分,所以Parse()里面需要处理跨数据包的状态信息,我们要把这些数据包和具体的七层的应用层的消息关联起来。
现在我们仔细看看Parse()接口的各个参数定义是做什么用的
- Parse(pkt *Packet, tcptuple *common.TcpTuple,
- dir uint8, private ProtocolData) ProtocolData
pkt不用说了,是送进来的数据包,前面已经介绍了其数据结构,tcptuple是该数据包所属的TCP数据流所在的唯一标示(一个未关闭的TCP数据量包含若干数据包,直到TCP链接关闭),使用tcptuple.Hashable()获取唯一值;dir参数标示数据包在TCP数据流中的流向,和第一个TCP数据包方向一致是TcpDirectionOriginal,否则是TcpDirectionReverse;private参数可用来在TCP流中存储状态信息,可在运行时转换成具体的强类型,任意修改和传递给下一个Parse方法,简单来说就是进行中间数据的共享。
下面看段MySQL模块里面的例子
- priv := mysqlPrivateData{}
- if private != nil {
- var ok bool
- priv, ok = private.(mysqlPrivateData)
- if !ok {
- priv = mysqlPrivateData{}
- }
- }
- [ ... ]
- return priv
上面的代码就是将private强制转换成mysqlPrivateData结构,然后再使用。我们再继续看后续怎么处理这些包的一个逻辑例子
- ok, complete := mysqlMessageParser(priv.Data[dir])
- if !ok {
- // drop this tcp stream. Will retry parsing with the next
- // segment in it
- priv.Data[dir] = nil
- logp.Debug("mysql", "Ignore MySQL message. Drop tcp stream.")
- return priv
- }
- if complete {
- mysql.messageComplete(tcptuple, dir, stream)
- } else {
- // wait for more data
- break
- }
mysqlMessageParser是一个解析mysql消息的方法,细节我们忽略,我们只需要关心它的返回,ok标示成功或者失败,true则继续处理,false表示数据包不能用,那就直接忽略;第二个参数complete表示判断这一个MySQL消息是否已经完整了,如果完整了,我们就可以扔出去了,否则继续等待剩下的消息内容。
好的,我们看看SMTP协议怎么折腾吧,先看看一个邮件交互的流程图,来自 RFC5321 (https://tools.ietf.org/html/rfc5321):
由上图可见,发送端和邮件服务器通过一系列命令来执行邮件的发送,下面看看一个具体的命令操作流程(来源: https://zh.wikipedia.org/wiki/简单邮件传输协议 )
- S: 220 www.example.com ESMTP Postfix
- C: HELO mydomain.com
- S: 250 Hello mydomain.com
- C: MAIL FROM:
- S: 250 Ok
- C: RCPT TO:
- S: 250 Ok
- C: DATA
- S: 354 End data with
- C: Subject: test message
- C: From:""< sender@mydomain.com>
- C: To:""< friend@example.com>
- C:
- C: Hello,
- C: This is a test.
- C: Goodbye.
- C: .
- S: 250 Ok: queued as 12345
- C: quit
- S: 221 Bye
上面的过程可以看到就几个命令就能将邮件发送出去,但是其实SMTP协议比较复杂,还包括身份认证、附件、多媒体编码等等,我们今天精简一下,我们目前只关心谁给谁发了邮件,发送内容先不管,这样相比完整的SMTP协议( RFC5321 ),我们只需要关注以下几个命令:
MAIL:开始一份邮件 mail from: xxx@xx.com
RCPT: 标识单个的邮件接收人;常在mail命令后面 可有多个rcpt to: xx@xx.com
QUIT:结束SMTP会话,不一定发送了邮件,注意
RESET:重置会话,当前传输被取消
最终希望通过Packetbeat将这些数据解析并处理成我们想要的如下JSON数据,即大功告成:
- {
- "timestamp":"2016-1-15 12:00:00",
- "from":"medcl@example.co",
- "to":["lcdem@example.co"]
- }
我们还需要一个测试数据,这里有一个下载各种协议测试数据包的地方,由wireshark站点提供: https://wiki.wireshark.org/SampleCaptures/
Ctrl+F找到SMTP的 下载地址(https://wiki.wireshark.org/SampleCaptures?action=AttachFile&do=get&target=smtp.pcap)
用wireshark打开我们刚刚下载的smtp.pcap文件,然后再输入过滤条件:tcp.port == 25,只看25端口的数据,如下图:
上图可以看到25端口的跑的数据有很多,不过我们只关心我们需要的那几个命令就好了。
打开/~/go/src/github.com/elastic/beats/packetbeat/protos/smtp/smtp.go定义smtpPrivateData,里面的Data是一个数组,分别是TCP两个方向的数据,SmtpMessage是解析出来的邮件信息
- type smtpPrivateData struct{
- Data [2]*SmtpStream
- }
- type SmtpStream struct {
- tcptuple *common.TcpTuple
- data []byte
- parseOffset int
- isClient bool
- message *SmtpMessage
- }
- type SmtpMessage struct {
- Ts time.Time
- From string
- To []string
- }
然后参照MySQL协议,定义相应的方法,最终如下:
- package smtp
- import (
- "github.com/elastic/beats/libbeat/common"
- "github.com/elastic/beats/libbeat/logp"
- "github.com/elastic/beats/libbeat/publisher"
- "github.com/elastic/beats/packetbeat/config"
- "github.com/elastic/beats/packetbeat/protos"
- "github.com/elastic/beats/packetbeat/protos/tcp"
- "bytes"
- "time"
- "strings"
- )
- type smtpPrivateData struct{
- Data [2]*SmtpStream
- }
- type SmtpStream struct {
- tcptuple *common.TcpTuple
- data []byte
- parseOffset int
- isClient bool
- message *SmtpMessage
- }
- type SmtpMessage struct {
- start int
- end int
- Ts time.Time
- From string
- To []string
- IgnoreMessage bool
- }
- type Smtp struct {
- SendRequest bool
- SendResponse bool
- transactionTimeout time.Duration
- Ports []int
- results publisher.Client
- }
- func (smtp *Smtp) initDefaults() {
- smtp.SendRequest = false
- smtp.SendResponse = false
- smtp.transactionTimeout = protos.DefaultTransactionExpiration
- }
- func (smtp *Smtp) setFromConfig(config config.Smtp) error {
- smtp.Ports = config.Ports
- if config.SendRequest != nil {
- smtp.SendRequest = *config.SendRequest
- }
- if config.SendResponse != nil {
- smtp.SendResponse = *config.SendResponse
- }
- if config.TransactionTimeout != nil && *config.TransactionTimeout > 0 {
- smtp.transactionTimeout = time.Duration(*config.TransactionTimeout) * time.Second
- }
- return nil
- }
- func (smtp *Smtp) GetPorts() []int {
- return smtp.Ports
- }
- func (smtp *Smtp) Init(test_mode bool, results publisher.Client) error {
- smtp.initDefaults()
- if !test_mode {
- err := smtp.setFromConfig(config.ConfigSingleton.Protocols.Smtp)
- if err != nil {
- return err
- }
- }
- smtp.results = results
- return nil
- }
- func readLine(data []byte, offset int) (bool, string, int) {
- q := bytes.Index(data[offset:], []byte("\r\n"))
- if q == -1 {
- return false, "", 0
- }
- return true, string(data[offset : offset+q]), offset + q + 2
- }
- func (smtp *Smtp) Parse(pkt *protos.Packet, tcptuple *common.TcpTuple, dir uint8, private protos.ProtocolData, ) protos.ProtocolData {
- defer logp.Recover("ParseSmtp exception")
- priv := smtpPrivateData{}
- if private != nil {
- var ok bool
- priv, ok = private.(smtpPrivateData)
- if !ok {
- priv = smtpPrivateData{}
- }
- }
- if priv.Data[dir] == nil {
- priv.Data[dir] = &SmtpStream{
- tcptuple: tcptuple,
- data: pkt.Payload,
- message: &SmtpMessage{Ts: pkt.Ts},
- }
- } else {
- // concatenate bytes
- priv.Data[dir].data = append(priv.Data[dir].data, pkt.Payload...)
- if len(priv.Data[dir].data) > tcp.TCP_MAX_DATA_IN_STREAM {
- logp.Debug("smtp", "Stream data too large, dropping TCP stream")
- priv.Data[dir] = nil
- return priv
- }
- }
- stream := priv.Data[dir]
- for len(stream.data) > 0 {
- if stream.message == nil {
- stream.message = &SmtpMessage{Ts: pkt.Ts}
- }
- ok, complete := stmpMessageParser(priv.Data[dir])
- if !ok {
- // drop this tcp stream. Will retry parsing with the next
- // segment in it
- priv.Data[dir] = nil
- logp.Debug("smtp", "Ignore SMTP message. Drop tcp stream. Try parsing with the next segment")
- return priv
- }
- if complete {
- smtp.messageComplete(tcptuple, dir, stream)
- } else {
- logp.Debug("smtp","still wait message...")
- // wait for more data
- break
- }
- }
- return priv
- }
- func (smtp *Smtp) ConnectionTimeout() time.Duration {
- return smtp.transactionTimeout
- }
- func stmpMessageParser(s *SmtpStream) (bool, bool) {
- var value string=""
- for s.parseOffset < len(s.data) {
- logp.Info("smtp", "Parse message: %s", string(s.data[s.parseOffset]))
- if strings.HasPrefix(string(s.data[s.parseOffset]),"MAIL" ) {
- logp.Debug("smtp", "Hit MAIL command: %s", string(s.data[s.parseOffset]))
- found, line, off := readLine(s.data, s.parseOffset)
- if !found {
- return true, false
- }
- value = line[1:]
- logp.Debug("smtp", "value %s", value)
- s.parseOffset = off
- } else {
- logp.Debug("smtp", "Unexpected message starting with %s", s.data[s.parseOffset:])
- return false, false
- }
- }
- return true, false
- }
- func handleSmtp(stmp *Smtp, m *SmtpMessage, tcptuple *common.TcpTuple,
- dir uint8, raw_msg []byte) {
- logp.Info("smtp","handle smtp message...")
- //TODO
- }
- // Called when the parser has identified a full message.
- func (smtp *Smtp) messageComplete(tcptuple *common.TcpTuple, dir uint8, stream *SmtpStream) {
- logp.Info("smtp","message completed...")
- // all ok, ship it
- msg := stream.data[stream.message.start:stream.message.end]
- if !stream.message.IgnoreMessage {
- handleSmtp(smtp, stream.message, tcptuple, dir, msg)
- }
- // and reset message
- stream.PrepareForNewMessage()
- }
- func (stream *SmtpStream) PrepareForNewMessage() {
- logp.Info("smtp","prepare for new message...")
- stream.data = stream.data[stream.parseOffset:]
- stream.parseOffset = 0
- stream.isClient = false
- stream.message = nil
- }
- func (smtp *Smtp) GapInStream(tcptuple *common.TcpTuple, dir uint8,
- nbytes int, private protos.ProtocolData) (priv protos.ProtocolData, drop bool) {
- defer logp.Recover("GapInStream(smtp) exception")
- if private == nil {
- return private, false
- }
- return private, true
- }
- func (smtp *Smtp) ReceivedFin(tcptuple *common.TcpTuple, dir uint8,
- private protos.ProtocolData) protos.ProtocolData {
- logp.Info("smtp","stream closed...")
- // TODO: check if we have data pending and either drop it to free
- // memory or send it up the stack.
- return private
- }
现在切换到命令行,编译一下
- cd ~/go/src/github.com/elastic/beats/packetbeat
- make
编译成功,一个滚烫的packetbeat可执行文件就躺在当前目录下了,运行一下先,参数-I 指定pcap文件(还记得前面下载的那个测试文件吧)
- ./packetbeat -d "smtp" -c etc/packetbeat.yml -I ~/Downloads/smtp.pcap -e -N
运行查看控制台输出结果:
- ➜ packetbeat git:(smtpbeat) ✗ ./packetbeat -d "smtp" -c etc/packetbeat.yml -I ~/Downloads/smtp.pcap -e -N
- 2016/01/15 10:12:19.058535 publish.go:191: INFO Dry run mode. All output types except the file based one are disabled.
- 2016/01/15 10:12:19.058570 geolite.go:24: INFO GeoIP disabled: No paths were set under output.geoip.paths
- 2016/01/15 10:12:19.058592 publish.go:262: INFO Publisher name: medcls-MacBook.local
- 2016/01/15 10:12:19.058724 beat.go:145: INFO Init Beat: packetbeat; Version: 1.0.0
- 2016/01/15 10:12:19.059758 beat.go:171: INFO packetbeat sucessfully setup. Start running.
- 2016/01/15 10:12:20.155335 smtp.go:163: DBG Parse message: 2
- 2016/01/15 10:12:20.155416 smtp.go:180: DBG Unexpected message starting with 250-xc90.websitewelcome.com Hello GP [122.162.143.157]
- 250-SIZE 52428800
- 250-PIPELINING
- 250-AUTH PLAIN LOGIN
- 250-STARTTLS
- 250 HELP
- 2016/01/15 10:12:22.310974 smtp.go:163: DBG Parse message: F
- 2016/01/15 10:12:22.311025 smtp.go:180: DBG Unexpected message starting with From: "Gurpartap Singh"
- To:
- Subject: SMTP
- Date: Mon, 5 Oct 2009 11:36:07 +0530
- Message-ID: <000301ca4581$ef9e57f0$cedb07d0$@in>
- MIME-Version: 1.0
- ...
成功了,邮件内容都在控制台输出了,但这还不是我们要的最终结果,我需要里面的关键信息,我们继续修改smtp.go这个文件。