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RTMPdump(libRTMP) 源代码分析系列文章:
RTMPDump (libRTMP) 源代码分析2:解析RTMP地址——RTMP_ParseURL()
RTMPdump (libRTMP) 源代码分析3: AMF编码
RTMPdump (libRTMP) 源代码分析4: 连接第一步——握手 (HandShake)
RTMPdump (libRTMP) 源代码分析5: 建立一个流媒体连接 (NetConnection部分)
RTMPdump (libRTMP) 源代码分析6: 建立一个流媒体连接 (NetStream部分 1)
RTMPdump (libRTMP) 源代码分析7: 建立一个流媒体连接 (NetStream部分 2)
RTMPdump (libRTMP) 源代码分析8: 发送消息 (Message)
RTMPdump (libRTMP) 源代码分析9: 接收消息 (Message) (接收视音频数据)
RTMPdump (libRTMP) 源代码分析10: 处理各种消息 (Message)
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函数调用结构图
RTMPDump (libRTMP)的整体的函数调用结构图如下图所示。
详细分析
在这里分析一下RTMPdump(libRTMP)连接到支持RTMP协议的服务器的第一步:握手(Hand Shake)。
RTMP连接的过程曾经分析过:RTMP流媒体播放过程
在这里不再细说,分析一下位于handshake.h文件里面实现握手(HandShake)功能的函数:
注意:handshake.h里面代码量很大,但是很多代码都是为了处理RTMP的加密版协议的,例如rtmps;因此在这里就不做过多分析了,我们只考虑普通的RTMP协议。
static int HandShake(RTMP * r, int FP9HandShake) { int i, offalg = 0; int dhposClient = 0; int digestPosClient = 0; int encrypted = r->Link.protocol & RTMP_FEATURE_ENC; RC4_handle keyIn = 0; RC4_handle keyOut = 0; int32_t *ip; uint32_t uptime; uint8_t clientbuf[RTMP_SIG_SIZE + 4], *clientsig=clientbuf+4; uint8_t serversig[RTMP_SIG_SIZE], client2[RTMP_SIG_SIZE], *reply; uint8_t type; getoff *getdh = NULL, *getdig = NULL; if (encrypted || r->Link.SWFSize) FP9HandShake = TRUE; else //普通的 FP9HandShake = FALSE; r->Link.rc4keyIn = r->Link.rc4keyOut = 0; if (encrypted) { clientsig[-1] = 0x06; /* 0x08 is RTMPE as well */ offalg = 1; } else //0x03代表RTMP协议的版本(客户端要求的) //数组竟然能有“-1”下标 //C0中的字段(1B) clientsig[-1] = 0x03; uptime = htonl(RTMP_GetTime()); //void *memcpy(void *dest, const void *src, int n); //由src指向地址为起始地址的连续n个字节的数据复制到以dest指向地址为起始地址的空间内 //把uptime的前4字节(其实一共就4字节)数据拷贝到clientsig指向的地址中 //C1中的字段(4B) memcpy(clientsig, &uptime, 4); if (FP9HandShake) { /* set version to at least 9.0.115.0 */ if (encrypted) { clientsig[4] = 128; clientsig[6] = 3; } else { clientsig[4] = 10; clientsig[6] = 45; } clientsig[5] = 0; clientsig[7] = 2; RTMP_Log(RTMP_LOGDEBUG, "%s: Client type: %02X", __FUNCTION__, clientsig[-1]); getdig = digoff[offalg]; getdh = dhoff[offalg]; } else { //void *memset(void *s, int ch, size_t n);将s中前n个字节替换为ch并返回s; //将clientsig[4]开始的4个字节替换为0 //这是C1的字段 memset(&clientsig[4], 0, 4); } /* generate random data */ #ifdef _DEBUG //将clientsig+8开始的1528个字节替换为0(这是一种简单的方法) //这是C1中的random字段 memset(clientsig+8, 0, RTMP_SIG_SIZE-8); #else //实际中使用rand()循环生成1528字节的伪随机数 ip = (int32_t *)(clientsig+8); for (i = 2; i < RTMP_SIG_SIZE/4; i++) *ip++ = rand(); #endif /* set handshake digest */ if (FP9HandShake) { if (encrypted) { /* generate Diffie-Hellmann parameters */ r->Link.dh = DHInit(1024); if (!r->Link.dh) { RTMP_Log(RTMP_LOGERROR, "%s: Couldn't initialize Diffie-Hellmann!", __FUNCTION__); return FALSE; } dhposClient = getdh(clientsig, RTMP_SIG_SIZE); RTMP_Log(RTMP_LOGDEBUG, "%s: DH pubkey position: %d", __FUNCTION__, dhposClient); if (!DHGenerateKey((DH *)r->Link.dh)) { RTMP_Log(RTMP_LOGERROR, "%s: Couldn't generate Diffie-Hellmann public key!", __FUNCTION__); return FALSE; } if (!DHGetPublicKey((DH *)r->Link.dh, &clientsig[dhposClient], 128)) { RTMP_Log(RTMP_LOGERROR, "%s: Couldn't write public key!", __FUNCTION__); return FALSE; } } digestPosClient = getdig(clientsig, RTMP_SIG_SIZE); /* reuse this value in verification */ RTMP_Log(RTMP_LOGDEBUG, "%s: Client digest offset: %d", __FUNCTION__, digestPosClient); CalculateDigest(digestPosClient, clientsig, GenuineFPKey, 30, &clientsig[digestPosClient]); RTMP_Log(RTMP_LOGDEBUG, "%s: Initial client digest: ", __FUNCTION__); RTMP_LogHex(RTMP_LOGDEBUG, clientsig + digestPosClient, SHA256_DIGEST_LENGTH); } #ifdef _DEBUG RTMP_Log(RTMP_LOGDEBUG, "Clientsig: "); RTMP_LogHex(RTMP_LOGDEBUG, clientsig, RTMP_SIG_SIZE); #endif //发送数据报C0+C1 //从clientsig-1开始发,长度1536+1,两个包合并 //握手---------------- r->dlg->AppendCInfo("建立连接:第1次连接。发送握手数据C0+C1"); //----------------------------- if (!WriteN(r, (char *)clientsig-1, RTMP_SIG_SIZE + 1)) return FALSE; //读取数据报,长度1,存入type //是服务器的S0,表示服务器使用的RTMP版本 if (ReadN(r, (char *)&type, 1) != 1) /* 0x03 or 0x06 */ return FALSE; //握手---------------- r->dlg->AppendCInfo("建立连接:第1次连接。接收握手数据S0"); //----------------------------- RTMP_Log(RTMP_LOGDEBUG, "%s: Type Answer : %02X", __FUNCTION__, type); //客户端要求的版本和服务器提供的版本不同 if (type != clientsig[-1]) RTMP_Log(RTMP_LOGWARNING, "%s: Type mismatch: client sent %d, server answered %d", __FUNCTION__, clientsig[-1], type); //握手---------------- r->dlg->AppendCInfo("建立连接:第1次连接。成功接收握手数据S0,服务器和客户端版本相同"); //----------------------------- //客户端和服务端随机序列长度是否相同 //握手---------------- r->dlg->AppendCInfo("建立连接:第1次连接。接收握手数据S1"); //----------------------------- if (ReadN(r, (char *)serversig, RTMP_SIG_SIZE) != RTMP_SIG_SIZE) return FALSE; /* decode server response */ //把serversig的前四个字节赋值给uptime memcpy(&uptime, serversig, 4); //大端转小端 uptime = ntohl(uptime); RTMP_Log(RTMP_LOGDEBUG, "%s: Server Uptime : %d", __FUNCTION__, uptime); RTMP_Log(RTMP_LOGDEBUG, "%s: FMS Version : %d.%d.%d.%d", __FUNCTION__, serversig[4], serversig[5], serversig[6], serversig[7]); if (FP9HandShake && type == 3 && !serversig[4]) FP9HandShake = FALSE; #ifdef _DEBUG RTMP_Log(RTMP_LOGDEBUG, "Server signature:"); RTMP_LogHex(RTMP_LOGDEBUG, serversig, RTMP_SIG_SIZE); #endif if (FP9HandShake) { uint8_t digestResp[SHA256_DIGEST_LENGTH]; uint8_t *signatureResp = NULL; /* we have to use this signature now to find the correct algorithms for getting the digest and DH positions */ int digestPosServer = getdig(serversig, RTMP_SIG_SIZE); if (!VerifyDigest(digestPosServer, serversig, GenuineFMSKey, 36)) { RTMP_Log(RTMP_LOGWARNING, "Trying different position for server digest!"); offalg ^= 1; getdig = digoff[offalg]; getdh = dhoff[offalg]; digestPosServer = getdig(serversig, RTMP_SIG_SIZE); if (!VerifyDigest(digestPosServer, serversig, GenuineFMSKey, 36)) { RTMP_Log(RTMP_LOGERROR, "Couldn't verify the server digest"); /* continuing anyway will probably fail */ return FALSE; } } /* generate SWFVerification token (SHA256 HMAC hash of decompressed SWF, key are the last 32 bytes of the server handshake) */ if (r->Link.SWFSize) { const char swfVerify[] = { 0x01, 0x01 }; char *vend = r->Link.SWFVerificationResponse+sizeof(r->Link.SWFVerificationResponse); memcpy(r->Link.SWFVerificationResponse, swfVerify, 2); AMF_EncodeInt32(&r->Link.SWFVerificationResponse[2], vend, r->Link.SWFSize); AMF_EncodeInt32(&r->Link.SWFVerificationResponse[6], vend, r->Link.SWFSize); HMACsha256(r->Link.SWFHash, SHA256_DIGEST_LENGTH, &serversig[RTMP_SIG_SIZE - SHA256_DIGEST_LENGTH], SHA256_DIGEST_LENGTH, (uint8_t *)&r->Link.SWFVerificationResponse[10]); } /* do Diffie-Hellmann Key exchange for encrypted RTMP */ if (encrypted) { /* compute secret key */ uint8_t secretKey[128] = { 0 }; int len, dhposServer; dhposServer = getdh(serversig, RTMP_SIG_SIZE); RTMP_Log(RTMP_LOGDEBUG, "%s: Server DH public key offset: %d", __FUNCTION__, dhposServer); len = DHComputeSharedSecretKey((DH *)r->Link.dh, &serversig[dhposServer], 128, secretKey); if (len < 0) { RTMP_Log(RTMP_LOGDEBUG, "%s: Wrong secret key position!", __FUNCTION__); return FALSE; } RTMP_Log(RTMP_LOGDEBUG, "%s: Secret key: ", __FUNCTION__); RTMP_LogHex(RTMP_LOGDEBUG, secretKey, 128); InitRC4Encryption(secretKey, (uint8_t *) & serversig[dhposServer], (uint8_t *) & clientsig[dhposClient], &keyIn, &keyOut); } reply = client2; #ifdef _DEBUG memset(reply, 0xff, RTMP_SIG_SIZE); #else ip = (int32_t *)reply; for (i = 0; i < RTMP_SIG_SIZE/4; i++) *ip++ = rand(); #endif /* calculate response now */ signatureResp = reply+RTMP_SIG_SIZE-SHA256_DIGEST_LENGTH; HMACsha256(&serversig[digestPosServer], SHA256_DIGEST_LENGTH, GenuineFPKey, sizeof(GenuineFPKey), digestResp); HMACsha256(reply, RTMP_SIG_SIZE - SHA256_DIGEST_LENGTH, digestResp, SHA256_DIGEST_LENGTH, signatureResp); /* some info output */ RTMP_Log(RTMP_LOGDEBUG, "%s: Calculated digest key from secure key and server digest: ", __FUNCTION__); RTMP_LogHex(RTMP_LOGDEBUG, digestResp, SHA256_DIGEST_LENGTH); #ifdef FP10 if (type == 8 ) { uint8_t *dptr = digestResp; uint8_t *sig = signatureResp; /* encrypt signatureResp */ for (i=0; i<SHA256_DIGEST_LENGTH; i+=8) rtmpe8_sig(sig+i, sig+i, dptr[i] % 15); } #if 0 else if (type == 9)) { uint8_t *dptr = digestResp; uint8_t *sig = signatureResp; /* encrypt signatureResp */ for (i=0; i<SHA256_DIGEST_LENGTH; i+=8) rtmpe9_sig(sig+i, sig+i, dptr[i] % 15); } #endif #endif RTMP_Log(RTMP_LOGDEBUG, "%s: Client signature calculated:", __FUNCTION__); RTMP_LogHex(RTMP_LOGDEBUG, signatureResp, SHA256_DIGEST_LENGTH); } else { //直接赋值 reply = serversig; #if 0 uptime = htonl(RTMP_GetTime()); memcpy(reply+4, &uptime, 4); #endif } #ifdef _DEBUG RTMP_Log(RTMP_LOGDEBUG, "%s: Sending handshake response: ", __FUNCTION__); RTMP_LogHex(RTMP_LOGDEBUG, reply, RTMP_SIG_SIZE); #endif //把reply中的1536字节数据发送出去 //对应C2 //握手---------------- r->dlg->AppendCInfo("建立连接:第1次连接。发送握手数据C2"); //----------------------------- if (!WriteN(r, (char *)reply, RTMP_SIG_SIZE)) return FALSE; /* 2nd part of handshake */ //读取1536字节数据到serversig //握手---------------- r->dlg->AppendCInfo("建立连接:第1次连接。读取握手数据S2"); //----------------------------- if (ReadN(r, (char *)serversig, RTMP_SIG_SIZE) != RTMP_SIG_SIZE) return FALSE; #ifdef _DEBUG RTMP_Log(RTMP_LOGDEBUG, "%s: 2nd handshake: ", __FUNCTION__); RTMP_LogHex(RTMP_LOGDEBUG, serversig, RTMP_SIG_SIZE); #endif if (FP9HandShake) { uint8_t signature[SHA256_DIGEST_LENGTH]; uint8_t digest[SHA256_DIGEST_LENGTH]; if (serversig[4] == 0 && serversig[5] == 0 && serversig[6] == 0 && serversig[7] == 0) { RTMP_Log(RTMP_LOGDEBUG, "%s: Wait, did the server just refuse signed authentication?", __FUNCTION__); } RTMP_Log(RTMP_LOGDEBUG, "%s: Server sent signature:", __FUNCTION__); RTMP_LogHex(RTMP_LOGDEBUG, &serversig[RTMP_SIG_SIZE - SHA256_DIGEST_LENGTH], SHA256_DIGEST_LENGTH); /* verify server response */ HMACsha256(&clientsig[digestPosClient], SHA256_DIGEST_LENGTH, GenuineFMSKey, sizeof(GenuineFMSKey), digest); HMACsha256(serversig, RTMP_SIG_SIZE - SHA256_DIGEST_LENGTH, digest, SHA256_DIGEST_LENGTH, signature); /* show some information */ RTMP_Log(RTMP_LOGDEBUG, "%s: Digest key: ", __FUNCTION__); RTMP_LogHex(RTMP_LOGDEBUG, digest, SHA256_DIGEST_LENGTH); #ifdef FP10 if (type == 8 ) { uint8_t *dptr = digest; uint8_t *sig = signature; /* encrypt signature */ for (i=0; i<SHA256_DIGEST_LENGTH; i+=8) rtmpe8_sig(sig+i, sig+i, dptr[i] % 15); } #if 0 else if (type == 9) { uint8_t *dptr = digest; uint8_t *sig = signature; /* encrypt signatureResp */ for (i=0; i<SHA256_DIGEST_LENGTH; i+=8) rtmpe9_sig(sig+i, sig+i, dptr[i] % 15); } #endif #endif RTMP_Log(RTMP_LOGDEBUG, "%s: Signature calculated:", __FUNCTION__); RTMP_LogHex(RTMP_LOGDEBUG, signature, SHA256_DIGEST_LENGTH); if (memcmp (signature, &serversig[RTMP_SIG_SIZE - SHA256_DIGEST_LENGTH], SHA256_DIGEST_LENGTH) != 0) { RTMP_Log(RTMP_LOGWARNING, "%s: Server not genuine Adobe!", __FUNCTION__); return FALSE; } else { RTMP_Log(RTMP_LOGDEBUG, "%s: Genuine Adobe Flash Media Server", __FUNCTION__); } if (encrypted) { char buff[RTMP_SIG_SIZE]; /* set keys for encryption from now on */ r->Link.rc4keyIn = keyIn; r->Link.rc4keyOut = keyOut; /* update the keystreams */ if (r->Link.rc4keyIn) { RC4_encrypt((RC4_KEY *)r->Link.rc4keyIn, RTMP_SIG_SIZE, (uint8_t *) buff); } if (r->Link.rc4keyOut) { RC4_encrypt((RC4_KEY *)r->Link.rc4keyOut, RTMP_SIG_SIZE, (uint8_t *) buff); } } } else { //int memcmp(const void *buf1, const void *buf2, unsigned int count); 当buf1=buf2时,返回值=0 //比较serversig和clientsig是否相等 //握手---------------- r->dlg->AppendCInfo("建立连接:第1次连接。比较握手数据签名"); //----------------------------- if (memcmp(serversig, clientsig, RTMP_SIG_SIZE) != 0) { //握手---------------- r->dlg->AppendCInfo("建立连接:第1次连接。握手数据签名不匹配!"); //----------------------------- RTMP_Log(RTMP_LOGWARNING, "%s: client signature does not match!", __FUNCTION__); } } //握手---------------- r->dlg->AppendCInfo("建立连接:第1次连接。握手成功"); //----------------------------- RTMP_Log(RTMP_LOGDEBUG, "%s: Handshaking finished....", __FUNCTION__); return TRUE; }
rtmpdump源代码(Linux):http://download.csdn.net/detail/leixiaohua1020/6376561
rtmpdump源代码(VC 2005 工程):http://download.csdn.net/detail/leixiaohua1020/6563163