freeswitch注册过程分析

操作系统：debian8.5_x64
freeswitch 版本： 1.6.8

本文仅描述sip注册的简单场景，即话机直接向处于同一个局域网的fs进行注册。

SIP协议的消息结构

消息框架

SIP协议是基于文本的协议，SIP协议的消息都遵从一个统一的消息结构：起始行（Start-Line）、一个或多个头域（Message-Header）、表明域结束的空行（CRLF），以及可选的消息体（Message-Body）

Start-Line

* Message-Header

CRLF

[Message-Body]

消息头结构

SIP协议定义了大量的消息头域，但在一个基本SIP请求中至少应该包含以下几个消息体头域：

From ：请求发起端地址
To : 请求目的端地址
Call-ID ：呼叫标识
Contract ：联系人信息
CSeq ：消息序号
Max-Forward ：TTL，防止死循环
Via ：消息转发记录
Content-Length : 消息体长度

消息体结构

SIP协议并没有规定消息体的结构，对消息体的应用完全取决于应用自身。

sip协议REGISTER请求格式

  REGISTER sip:{remote_ip} SIP/2.0

  Via: {viaInfo}

  Max-Forwards:

  From: {uacInfo}

  To: {uasInfo}

  Call-ID: {call_id}

  User-Agent: {uaInfo}

  CSeq: {csnum}

  Contact: {contractInfo}

  Expires: {expireSeconds}

  Authorization: {authInfo}

  Content-Length: {msgBodyLength}

第1行的REGISTER表示这是一条注册消息
第2行的via表示sip消息的路由
第3行指出消息最多可以转发多少次，防止死循环
第4行至第9行参考前面的消息头结构
第10行说明本次注册的有效期，单位为秒
第11行是sip认证信息，发送第一次sip register 请求时没有该字段
第12行sip消息体的长度，一般为0

注册流程

终端向服务器发送REGISTER请求

sip消息示例：

REGISTER sip:192.168.168.85 SIP/2.0

Via: SIP/2.0/UDP 192.168.168.168:;branch=z9hG4bK-d87543-1a71103b47634958---d87543-;rport

Max-Forwards:

Contact: <sip:@192.168.168.168:;rinstance=196b0ce810f2e6f5>

To: ""<sip:@192.168.168.85>

From: ""<sip:@192.168.168.85>;tag=2d1fbf20

Call-ID: ZTRiYTBhZmVlYTM1ZDkxOWQ3OWNkNjkwMmYxMWI5Yjk.

CSeq:  REGISTER

Expires:

Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE, SUBSCRIBE, INFO

User-Agent: eyeBeam release 1010f stamp

Content-Length:

服务器回复401，并给出WWW-Authenticate信息

sofia协议栈：

    tport :

        tport_recv_event

            => tport_deliver

    nta :

        agent_recv_request

            => agent_aliases

    nua :

        nua_stack_process_request      

sofia 应用层：

    sofia_reg_handle_sip_i_register

        => sofia_reg_handle_register_token

            => sofia_reg_auth_challenge (回复401)

sip消息示例：

SIP/2.0  Unauthorized

Via: SIP/2.0/UDP 192.168.168.168:;branch=z9hG4bK-d87543-1a71103b47634958---d87543-;rport=

From: "" <sip:@192.168.168.85>;tag=2d1fbf20

To: "" <sip:@192.168.168.85>;tag=m6ecFK1Fy3F0a

Call-ID: ZTRiYTBhZmVlYTM1ZDkxOWQ3OWNkNjkwMmYxMWI5Yjk.

CSeq:  REGISTER

User-Agent: FreeSWITCH-mod_sofia/1.6.+git~20160505T153832Z~99de0ad502~64bit

Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE

Supported: timer, path, replaces

WWW-Authenticate: Digest realm="192.168.168.85", nonce="d54e4bb9-fc22-4e08-8b69-442e1b8774eb", algorithm=MD5, qop="auth"

Content-Length:

终端再次向服务器发送REGISTER请求，并携带认证信息

REGISTER sip:192.168.168.85 SIP/2.0

Via: SIP/2.0/UDP 192.168.168.168:;branch=z9hG4bK-d87543-6371fe0e115be271---d87543-;rport

Max-Forwards:

Contact: <sip:@192.168.168.168:;rinstance=196b0ce810f2e6f5>

To: ""<sip:@192.168.168.85>

From: ""<sip:@192.168.168.85>;tag=2d1fbf20

Call-ID: ZTRiYTBhZmVlYTM1ZDkxOWQ3OWNkNjkwMmYxMWI5Yjk.

CSeq:  REGISTER

Expires:

Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE, SUBSCRIBE, INFO

User-Agent: eyeBeam release 1010f stamp

Authorization: Digest username="",realm="192.168.168.85",nonce="d54e4bb9-fc22-4e08-8b69-442e1b8774eb",uri="sip:192.168.168.85",response="c46ae8e7eaa2ee63a1d61bf575d8c395",cnonce="71c1997e810fc38b53b97fbb33dc8b1e",nc=,qop=auth,algorithm=MD5

Content-Length:

服务器认证后回复200

fs处理过程描述

sofia协议栈：

tport :

    tport_recv_event

        => tport_deliver

nta :

    agent_recv_request

        => agent_aliases

nua :

    nua_stack_process_request

sofia应用层：

sofia_reg_handle_sip_i_register

    => sofia_reg_handle_register_token

        => sofia_reg_parse_auth (执行认证操作) for_the_sake_of_interop标签附近

认证成功后发送200 OK给客户端。

认证算法描述

具体的认证过程可以参考sofia_reg_parse_auth函数，这里描述下sip注册的认证算法。
sip注册认证使用的是www-authenticate认证算法，具体可参考RFC2617文档。下面进行简单的描述

对用户名、认证域(realm)以及密码的合并值计算 MD5 哈希值，结果称为 HA1。
对HTTP方法以及URI的摘要的合并值计算 MD5 哈希值，例如，"REGISTER" 和 "sip:192.168.1.80"，结果称为 HA2。
对 HA1、服务器密码随机数(nonce)、请求计数(nc)、客户端密码随机数(cnonce)、保护质量(qop)以及 HA2 的合并值计算 MD5 哈希值。结果即为客户端提供的 response 值。 response 值由三步计算而成。当多个数值合并的时候，使用冒号作为分割符。

计算HA1

HA1 = MD5(A1) = MD5(username:realm:password)

计算HA2

如果qop值为"auth"或未指定，那么HA2为

    HA2 = MD5(A2) = MD5(method:digestURI)

如果qop值为"auth-init"，那么HA2为

    HA2 = MD5(A2) = MD5(method:digestURI:MD5(entityBody))

计算response

如果qop值为"auth"或"auth-init"，那么response为

    response = MD5(HA1:nonce:nonceCount:clientNonce:qop:HA2)

如果qop未知道，那么response为

    response = MD5(HA1:nonce:HA2)

sip注册涉及数据库

sip_authentication
sip_registrations

注册过程模拟

python模拟注册过程

#! /usr/bin/env python

#-*- coding:utf-8 -*-

# sip reg test

# E-Mail : Mike_Zhang@live.com

import sys,socket,time,traceback

import uuid

import hashlib

svrIp,svrPort = "192.168.168.85",5060

transportType = "udp"

localIp,localPort = "192.168.168.168",17061

uid,passwd = "",""

g_branch,g_callId = uuid.uuid1(),uuid.uuid1()

def getRegHeader(seqNum):

    retStr = "REGISTER sip:{remote_ip} SIP/2.0\r\n"

    retStr += "Via: SIP/2.0/{transport} {local_ip}:{local_port};branch={branch}\r\n"

    retStr += "Max-Forwards: 70\r\n"

    retStr += "From: {uid} <sip:{uid}@{remote_ip}:{remote_port}>;tag={call_number}\r\n"

    retStr += "To: {uid} <sip:{uid}@{remote_ip}:{remote_port}>\r\n"

    retStr += "Call-ID: {call_id}\r\n"

    retStr += "User-Agent: fs testing\r\n"

    retStr += "CSeq: %d REGISTER\r\n"%seqNum

    retStr += "Contact: sip:{uid}@{local_ip}:{local_port}\r\n"

    retStr += "Expires: 3600\r\n"

    return retStr

def formatRegHeader(patternStr):

    retstr = patternStr.format(

        remote_ip=svrIp,

        transport=transportType,

        local_ip=localIp,

        local_port=localPort,

        branch=g_branch,

        uid=uid,

        remote_port=svrPort,

        call_number=uid,

        call_id=g_callId)

    return retstr

class SipRegObj(object):

    def __init__(self,uid,passwd,

        realm="",nonce="",algorithm="MD5",qop="auth"):

        self.uid = uid # "1000"

        self.password = passwd # "1234"

        self.realm = realm

        self.nonce = nonce

        self.algorithm = algorithm

        self.qop = qop

        self.uri = ""

        self.method = "REGISTER"

        self.cnonce = ""

        self.nc = ""

        self.svrIp = svrIp

        #self.transportType = "udp"

    def getReponse(self):

        md5 = hashlib.md5

        ha1 = md5("%s:%s:%s"%(self.uid,self.realm,self.password)).hexdigest()

        ha2 = md5("%s:%s"%(self.method,self.uri)).hexdigest()

        reponse = md5("%s:%s:%s:%s:%s:%s"%(ha1,self.nonce,self.nc,self.cnonce,self.qop,ha2)).hexdigest()

        return reponse

    def getAuthStr(self):

        self.uri,self.cnonce = ("sip:%s"%self.svrIp),uuid.uuid1()

        retStr = ""

        response = self.getReponse()

        retStr += 'Authorization: Digest username="%s",realm="%s",nonce="%s",uri="%s",response="%s",cnonce="%s",nc=%s,qop=%s,algorithm=%s\r\n'%(

            self.uid,self.realm,self.nonce,self.uri,response,self.cnonce,self.nc,self.qop,self.algorithm)

        retStr += 'Content-Length: 0\r\n'

        return retStr

    def genChallengeMsg(self):

        # gen sip reg challenge message

        str1=getRegHeader(1) + "Content-Length: 0\r\n"

        return formatRegHeader(str1)        

    def genAuthMsg(self,retstr1):

        # parse data

        data1 = retstr1.split("\r\n")[-4].split(": Digest")[1]

        data1 = str(data1).replace('MD5','"MD5"')

        tmpList = data1.split(",")

        for item in tmpList :

            #print item

            arrtmp = item.split("=")

            setattr(self,arrtmp[0].strip(),arrtmp[1].strip('"'))

        # gen sip reg message with auth

        str2=getRegHeader(2)

        str2 = formatRegHeader(str2)

        str2 += self.getAuthStr()

        return str2

if __name__ == "__main__":

    treg = SipRegObj(uid,passwd)

    client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    client.bind((localIp,localPort))

    dstHost = (svrIp,svrPort)

    client.sendto(treg.genChallengeMsg(),dstHost)

    print time.time(),' : send success'

    # get response (401 msg)

    retstr1 = client.recv(1024)

    print retstr1

    client.sendto(treg.genAuthMsg(retstr1),dstHost)

    print time.time(),' : send success'

    retstr2 = client.recv(1024)

    print "return str : \r\n",retstr2

    time.sleep(30)

本文github地址：

https://github.com/mike-zhang/mikeBlogEssays/blob/master/2016/20160912_freeswitch注册过程分析.md

欢迎补充