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sconf.ClientAuth = tls.RequireAndVerifyClientCert","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"另外，筆者在","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"main.go","attrs":{}}],"attrs":{}},{"type":"text","text":"同目錄下留有測試用的根證書、服務端證書和客戶端證書，爲了保證雙向認證的順利運行請將根證書安裝爲受用戶信任的證書。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面是筆者運行Demo打印的調試信息：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/53/5365946d1ccbdb044546fb3e8074ef50.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"同單向認證一樣，筆者將調試信息轉換爲下述時序圖。 ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/ea/eaa29576d95429f7be4e0d74756acf63.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"雙向認證和單向認證相比，Server發消息給Client時會額外發送一個","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateRequestMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"消息，Client收到此消息後會將證書信息（","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"）和簽名信息（","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"）發送給Server。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"雙向認證中，Client和Server發送消息變多了，但是總的數據收發仍然只有","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"三次","attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"總結","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1、TLS1.3和TLS1.2握手流程是有區別的，這一點需要注意。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2、單向認證和雙向認證中，總的數據收發僅三次，單次發送的數據中包含一個或者多個消息。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"未經過加密，之後發送的消息均做了加密處理。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"4、Client和Server會各自計算兩次密鑰，計算時機分別是讀取到對方的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"HelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"之後。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"注","attrs":{}},{"type":"text","text":"：上述第3點和第4點分析過程詳見後文。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Client發送HelloMsg","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在TLS握手過程中的第一步是Client發送HelloMsg，所以針對TLS握手流程的分析也從這一步開始。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Server對於Client的基本信息瞭解完全依賴於Client主動告知Server，而其中比較關鍵的信息分別是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"客戶端支持的TLS版本","attrs":{}}],"attrs":{}},{"type":"text","text":"、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"客戶端支持的加密套件（cipherSuites）","attrs":{}}],"attrs":{}},{"type":"text","text":"、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"客戶端支持的簽名算法","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"客戶端支持的密鑰交換協議以及其對應的公鑰","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"客戶端支持的TLS版本：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"客戶端支持的TLS版本主要通過tls包中","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"(*Config).supportedVersions","attrs":{}}],"attrs":{}},{"type":"text","text":"方法計算。對TLS1.3來說默認支持的TLS版本如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"var supportedVersions = []uint16{\n\tVersionTLS13,\n\tVersionTLS12,\n\tVersionTLS11,\n\tVersionTLS10,\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在發起請求時如果用戶手動設置了","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"tls.Config","attrs":{}}],"attrs":{}},{"type":"text","text":"中的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"MaxVersion","attrs":{}}],"attrs":{}},{"type":"text","text":"或者","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"MinVersion","attrs":{}}],"attrs":{}},{"type":"text","text":"，則客戶端支持的TLS版本會發生變化。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"例如發起請求時，設置了","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"conf.MaxVersion = tls.VersionTLS12","attrs":{}}],"attrs":{}},{"type":"text","text":"，此時","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"(*Config).supportedVersions","attrs":{}}],"attrs":{}},{"type":"text","text":"返回的版本爲：","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"[]uint16{\n\tVersionTLS12,\n\tVersionTLS11,\n\tVersionTLS10,\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ps: 如果有興趣的小夥伴可以在克隆筆者的demo後手動設置Config.MaxVersion，設置後可以調試TLS1.2的握手流程。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"客戶端支持的加密套件（cipherSuites）：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"說實話，加密套件已經進入筆者的知識盲區了，其作用筆者會在下一小節講明白，故本小節筆者直接貼出計算後的結果。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/eb/eb7d21a5652e847b40bfc868cc0c7d3d.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"圖中籃框部分爲當前Client支持加密套件Id，紅框部分爲計算邏輯。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"客戶端支持的簽名算法：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"客戶端支持的簽名算法，僅在客戶端支持的最大TLS版本大於等於TLS1.2時生效。此時客戶端支持的簽名算法如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"var supportedSignatureAlgorithms = []SignatureScheme{\n\tPSSWithSHA256,\n\tECDSAWithP256AndSHA256,\n\tEd25519,\n\tPSSWithSHA384,\n\tPSSWithSHA512,\n\tPKCS1WithSHA256,\n\tPKCS1WithSHA384,\n\tPKCS1WithSHA512,\n\tECDSAWithP384AndSHA384,\n\tECDSAWithP521AndSHA512,\n\tPKCS1WithSHA1,\n\tECDSAWithSHA1,\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"客戶端支持的密鑰交換協議及其對應的公鑰：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這一塊兒邏輯僅在客戶端支持的最大TLS版本是TLS1.3時生效。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"if hello.supportedVersions[0] == VersionTLS13 {\n\thello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13()...)\n\n\tcurveID := config.curvePreferences()[0]\n\tif _, ok := curveForCurveID(curveID); curveID != X25519 && !ok {\n\t\treturn nil, nil, errors.New(\"tls: CurvePreferences includes unsupported curve\")\n\t}\n\tparams, err = generateECDHEParameters(config.rand(), curveID)\n\tif err != nil {\n\t\treturn nil, nil, err\n\t}\n\thello.keyShares = []keyShare{{group: curveID, data: params.PublicKey()}}\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中，方法","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"config.curvePreferences","attrs":{}}],"attrs":{}},{"type":"text","text":"的邏輯爲：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"var defaultCurvePreferences = []CurveID{X25519, CurveP256, CurveP384, CurveP521}\nfunc (c *Config) curvePreferences() []CurveID {\n\tif c == nil || len(c.CurvePreferences) == 0 {\n\t\treturn defaultCurvePreferences\n\t}\n\treturn c.CurvePreferences\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在本篇中，筆者未手動設置優先可供選擇的曲線，故","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"curveID","attrs":{}}],"attrs":{}},{"type":"text","text":"的值爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"X25519","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"函數的作用是根據曲線Id生成一種橢圓曲線密鑰交換協議的實現。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果客戶端支持的最大TLS版本是TLS1.3時，會爲Client支持的加密套件增加TLS1.3默認的加密套件，同時還會選擇","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Curve25519","attrs":{}},{"type":"text","text":"密鑰交換協議生成","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"keyShare","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節介紹了在TLS1.3中Client需要告知Server客戶端支持的TLS版本號、客戶端支持的加密套件、客戶端支持的簽名算法和客戶端支持的密鑰交換協議。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Server讀HelloMsg&發送消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Server讀到","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"之後會根據客戶端支持的TLS版本和本地支持的TLS版本做對比，得到Client和Server均支持的TLS版本最大值，該值作爲後續繼續通信的標準。本篇中Client和Server都支持TLS1.3，因此Server進入TLS1.3的握手流程。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"處理clientHelloMsg","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Server進入TLS1.3握手流程之後，還需要繼續處理clientHelloMsg，同時構建","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Server支持的TLS版本","attrs":{}},{"type":"text","text":":","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"進入TLS1.3握手流程之前，Server已經計算出兩端均支持的TLS版本，但是Client還無法得知Server支持的TLS版本，因此開始繼續處理clientHelloMsg時，Server將已經計算得到的TLS版本賦值給","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"supportedVersion","attrs":{}}],"attrs":{}},{"type":"text","text":"以告知客戶端。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"// client讀取到serverHelloMsg後，通過讀取此字段計算兩端均支持的TLS版本\nhs.hello.supportedVersion = c.vers","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Server計算兩端均支持的加密套件","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"中含有Client支持的加密套件信息，Server讀取該信息並和本地支持的加密套件做對比計算出兩端均支持的加密套件。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏需要注意的是，如果Server的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"tls.Config.PreferServerCipherSuites","attrs":{}}],"attrs":{}},{"type":"text","text":"爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"true","attrs":{}}],"attrs":{}},{"type":"text","text":"則選擇Server第一個在兩端均支持的加密套件，否則選擇Client第一個在兩端均支持的加密套件。筆者通過Debug得到兩端均支持的加密套件id爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"4865","attrs":{}}],"attrs":{}},{"type":"text","text":"（其常量爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"tls.TLS","attrs":{}},{"type":"text","marks":[{"type":"italic","attrs":{}}],"text":"AES","attrs":{}},{"type":"text","text":"128_GCM_SHA256","attrs":{}}],"attrs":{}},{"type":"text","text":"），詳情見下圖：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/31/31924f987ea466b2cac89138ec90e483.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上圖中的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"mutualCipherSuiteTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"函數會從","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuitesTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"變量中選擇匹配的加密套件。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"var cipherSuitesTLS13 = []*cipherSuiteTLS13{\n\t{TLS_AES_128_GCM_SHA256, 16, aeadAESGCMTLS13, crypto.SHA256},\n\t{TLS_CHACHA20_POLY1305_SHA256, 32, aeadChaCha20Poly1305, crypto.SHA256},\n\t{TLS_AES_256_GCM_SHA384, 32, aeadAESGCMTLS13, crypto.SHA384},\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"結合前面的Debug信息知，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.suite","attrs":{}}],"attrs":{}},{"type":"text","text":"爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuiteTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"結構體的變量且其值爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuitesTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"切片的第一個。","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuiteTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"結構體定義如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"type cipherSuiteTLS13 struct {\n\tid uint16\n\tkeyLen int\n\taead func(key, fixedNonce []byte) aead\n\thash crypto.Hash\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，Server已經計算出雙端均支持的加密套件，Server通過設置","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuite","attrs":{}}],"attrs":{}},{"type":"text","text":"將雙端均支持的加密套件告知Client：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"hs.hello.cipherSuite = hs.suite.id\nhs.transcript = hs.suite.hash.New()","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在後續計算密鑰時需要對Client和Server之間的所有消息計算Hash摘要。根據前面計算出的加密套件知，本篇中計算消息摘要的Hash算法爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"SHA256","attrs":{}}],"attrs":{}},{"type":"text","text":"，此算法的實現賦值給","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.transcript","attrs":{}}],"attrs":{}},{"type":"text","text":"變量，後續計算消息摘要時均通過該變量實現。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Server計算雙端均支持的密鑰交換協議以及對應的公鑰","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg.keyShares","attrs":{}}],"attrs":{}},{"type":"text","text":"變量記錄着Client支持的曲線Id以及對應的公鑰。Server通過對比本地支持的曲線Id計算出雙端均支持的密鑰交換協議。根據前面","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Client發送HelloMsg","attrs":{}},{"type":"text","text":"這一小節的內容以及筆者實際調試的結果，雙端均支持的曲線爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"Curve25519","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Server計算出雙端均支持的曲線後，調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"方法得到對應密鑰交換協議的實現，即Curve25519密鑰交換協議。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"Curve25519","attrs":{}}],"attrs":{}},{"type":"text","text":"是橢圓曲線迪菲-赫爾曼（Elliptic-curve Diffie–Hellman ，縮寫爲ECDH）密鑰交換方案之一，同時也是最快的ECC（Elliptic-curve cryptography）曲線之一。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"ECDH","attrs":{}}],"attrs":{}},{"type":"text","text":"可以爲Client和Server在不安全的通道上爲雙方建立共享密鑰，並且Client和Server需要各自持有一組橢圓曲線公私密鑰對。當Client和Server需要建立共享密鑰時僅需要公佈各自的公鑰，Client和Server通過對方的公鑰以及自己的私鑰即可計算出相等的密鑰。如果公鑰被第三方截獲也無關緊要，因爲第三方沒有私鑰無法計算出共享密鑰除非第三方能夠解決橢圓曲線Diffie–Hellman問題。","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ECDHE","attrs":{}}],"attrs":{}},{"type":"text","text":"爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ECDH","attrs":{}}],"attrs":{}},{"type":"text","text":"的一個變種，其區別僅僅是私鑰和公鑰在每次建立共享密鑰時均需重新生成（以上爲筆者對維基百科中ECDH的理解）。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"對","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ECDHE","attrs":{}}],"attrs":{}},{"type":"text","text":"有了一定的理解後，我們現在看一下","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"函數中的部分源碼：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"func generateECDHEParameters(rand io.Reader, curveID CurveID) (ecdheParameters, error) {\n\tif curveID == X25519 {\n\t\tprivateKey := make([]byte, curve25519.ScalarSize)\n\t\tif _, err := io.ReadFull(rand, privateKey); err != nil {\n\t\t\treturn nil, err\n\t\t}\n\t\tpublicKey, err := curve25519.X25519(privateKey, curve25519.Basepoint)\n\t\tif err != nil {\n\t\t\treturn nil, err\n\t\t}\n\t\treturn &x25519Parameters{privateKey: privateKey, publicKey: publicKey}, nil\n\t}\n // 此處省略代碼\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"每次調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"函數時均會生成一組新的橢圓曲線公私密鑰對。","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg.keyShares","attrs":{}}],"attrs":{}},{"type":"text","text":"變量存有Client的公鑰，因此Server已經可以計算共享密鑰：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"params, err := generateECDHEParameters(c.config.rand(), selectedGroup)\nif err != nil {\n c.sendAlert(alertInternalError)\n return err\n}\nhs.hello.serverShare = keyShare{group: selectedGroup, data: params.PublicKey()}\nhs.sharedKey = params.SharedKey(clientKeyShare.data) // 共享密鑰","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中Server已經計算出共享密鑰，之後可以通過此密鑰派生出其他密鑰爲數據加密。Client因爲無Server的公鑰還無法計算出共享密鑰，所以Server通過設置","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverShare","attrs":{}}],"attrs":{}},{"type":"text","text":"變量告知Client服務端的公鑰。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，Server對Client發來的helloMsg已經處理完畢。筆者在這裏額外提醒一句，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"中仍然有Client和Server生成的隨機數，但是在TLS1.3中這兩個隨機數已經和密鑰交換無關了。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節介紹了Server讀取","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"後會計算雙端支持的TLS版本以及雙端支持的加密套件和密鑰交換協議，同時還介紹了共享密鑰的生成以及ECDH的概念。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"選擇合適的證書以及簽名算法","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在Server選擇和當前Client匹配的證書前其實還有關於預共享密鑰模式的處理，該模式需要實現","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ClientSessionCache","attrs":{}}],"attrs":{}},{"type":"text","text":"接口，鑑於其不影響握手流程的分析，故本篇不討論預共享密鑰模式。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一個Server可能給多個Host提供服務，因此Server可能持有多個證書，那麼選擇一個和當前Client匹配的證書是十分必要的，其實現邏輯參見","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"(*Config).getCertificate","attrs":{}}],"attrs":{}},{"type":"text","text":"方法。本篇中的Demo只有一個證書，故該方法會直接返回此證書。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"證書中是包含公鑰的，不同的公鑰支持的簽名算法是不同的，在本例中Server支持的簽名算法和最終雙端均支持的簽名算法見下面的Debug結果：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/bb/bbd67e99ae3eff7fd050fc3d02e696ec.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上圖中紅框部分爲Server支持的簽名算法，藍框爲選定的雙端均支持的簽名算法。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節主要介紹了Server選擇匹配當前Client的證書和簽名算法。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"計算握手階段的密鑰以及發送Server的參數","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在這個階段Server會將","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"寫入緩衝區，寫完之後再寫入一個","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ChangeCipherSpec","attrs":{}}],"attrs":{}},{"type":"text","text":"（TLS1.3不會處理此消息）消息，需要注意的是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"未進行加密發送。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"計算握手階段的密鑰","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"前面提到過計算密鑰需要計算消息摘要：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"hs.transcript.Write(hs.clientHello.marshal())\nhs.transcript.Write(hs.hello.marshal()) // hs.hello爲serverHelloMsg","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.transcript","attrs":{}}],"attrs":{}},{"type":"text","text":"在前面已經提到過是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"SHA256","attrs":{}}],"attrs":{}},{"type":"text","text":"Hash算法的一種實現。下面我們逐步分析源碼中Server第一次計算密鑰的過程。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先，派生出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"handshakeSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"earlySecret := hs.earlySecret \nif earlySecret == nil {\n earlySecret = hs.suite.extract(nil, nil)\n}\nhs.handshakeSecret = hs.suite.extract(hs.sharedKey, \nhs.suite.deriveSecret(earlySecret, \"derived\", 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extract(newSecret, currentSecret []byte) []byte {\n\tif newSecret == nil {\n\t\tnewSecret = make([]byte, c.hash.Size())\n\t}\n\treturn hkdf.Extract(c.hash.New, newSecret, 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c.hash.Size())\n\tverifyData := hmac.New(c.hash.New, finishedKey)\n\tverifyData.Write(transcript.Sum(nil))\n\treturn verifyData.Sum(nil)\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"HMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"是一種利用密碼學中的散列函數來進行消息認證的一種機制，所能提供的消息認證包括兩方面內容（此內容摘自百度百科）：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"消息完整性認證：能夠證明消息內容在傳送過程沒有被修改。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"信源身份認證：因爲通信雙方共享了認證的密鑰，接收方能夠認證發送該數據的信源與所宣稱的一致，即能夠可靠地確認接收的消息與發送的一致。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"c.expandLabel","attrs":{}}],"attrs":{}},{"type":"text","text":"最種會調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hkdf.Expand","attrs":{}}],"attrs":{}},{"type":"text","text":"派生出新的密鑰。最後用新的密鑰以及消息摘要通過","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"HMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"算法計算出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"verifyData","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"收到","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"一方通過同樣的方式在本地計算出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"verifyData'","attrs":{}}],"attrs":{}},{"type":"text","text":"，如果","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"verifyData'","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"verifyData","attrs":{}}],"attrs":{}},{"type":"text","text":"相等，則證明此消息未被修改且來源可信。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"再次計算密鑰","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本次計算密鑰的過程和前面計算密鑰的流程相似，所以直接上代碼：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"hs.masterSecret = hs.suite.extract(nil,\n\ths.suite.deriveSecret(hs.handshakeSecret, \"derived\", nil))\n\nhs.trafficSecret = hs.suite.deriveSecret(hs.masterSecret,\n\tclientApplicationTrafficLabel, hs.transcript)\nserverSecret := hs.suite.deriveSecret(hs.masterSecret,\n\tserverApplicationTrafficLabel, hs.transcript)\nc.out.setTrafficSecret(hs.suite, serverSecret)","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先，利用前文已經生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"handshakeSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"\t再次派生出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"masterSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"，然後再從","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"masterSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"派生出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"，最後調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"c.out.setTrafficSecret(hs.suite, serverSecret)","attrs":{}}],"attrs":{}},{"type":"text","text":"計算出Server發送數據時的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"AEAD","attrs":{}}],"attrs":{}},{"type":"text","text":"加密算法。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"需要注意的是，此時利用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"AEAD","attrs":{}}],"attrs":{}},{"type":"text","text":"加密算法會用於握手結束後對要發送的業務數據進行加密。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"此階段結束後，Server會調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"c.flush()","attrs":{}}],"attrs":{}},{"type":"text","text":"方法，將前面提到的消息一次性發送給Client。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1、本節介紹了","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"的生成過程，其中","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg.verifyData","attrs":{}}],"attrs":{}},{"type":"text","text":"通過","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"HMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"算法計算得出。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"的作用是確保握手過程中發送的消息未被篡改，且數據來源可信。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3、計算Server發送業務數據時的加密密鑰。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Client讀消息&發送消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Client讀到","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"之後會讀取服務端支持的TLS版本並和本地支持的版本做對比，前文已經提到過服務端支持的TLS版本是TLS1.3，因此Client也進入TLS1.3握手流程。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"讀取serverHelloMsg並計算密鑰","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Client進入TLS1.3握手流程後，有一系列的檢查邏輯，這些邏輯比較長而且筆者也不需要考慮這些異常，因此筆者化繁爲簡，在下面列出關鍵邏輯：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"selectedSuite := mutualCipherSuiteTLS13(hs.hello.cipherSuites,\n\ths.serverHello.cipherSuite) // 結合Server支持的加密套件選擇雙端均支持的加密套件\nhs.suite = selectedSuite\nhs.transcript = hs.suite.hash.New()\nhs.transcript.Write(hs.hello.marshal()) // hs.hello爲clientHelloMsg\nhs.transcript.Write(hs.serverHello.marshal())","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上面這一段代碼邏輯和Server處理加密套件以及通過加密套件構建消息摘要算法的實現邏輯相對應，因此筆者不再過多贅述。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面我們看一下計算握手階段的密鑰以及","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"masterSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"的生成：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"sharedKey := hs.ecdheParams.SharedKey(hs.serverHello.serverShare.data)\nearlySecret := hs.earlySecret\nif !hs.usingPSK {\n earlySecret = hs.suite.extract(nil, nil)\n}\nhandshakeSecret := hs.suite.extract(sharedKey,\n\ths.suite.deriveSecret(earlySecret, \"derived\", nil)) // 通過共享密鑰派生出handshakeSecret\n\nclientSecret := hs.suite.deriveSecret(handshakeSecret,\n\tclientHandshakeTrafficLabel, hs.transcript) // 通過handshakeSecret派生出clientSecret\nc.out.setTrafficSecret(hs.suite, clientSecret)\nserverSecret := hs.suite.deriveSecret(handshakeSecret,\n\tserverHandshakeTrafficLabel, hs.transcript) // 通過handshakeSecret派生出serverSecret\nc.in.setTrafficSecret(hs.suite, serverSecret)\nhs.masterSecret = hs.suite.extract(nil,\n\ths.suite.deriveSecret(handshakeSecret, \"derived\", nil)) // 通過handshakeSecret派生出masterSecret","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏需要提一嘴的是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.ecdheParams","attrs":{}}],"attrs":{}},{"type":"text","text":"，該值爲","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Client發送HelloMsg","attrs":{}},{"type":"text","text":"這一小節調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"函數生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"params","attrs":{}}],"attrs":{}},{"type":"text","text":"。其他邏輯和Server生成握手階段的密鑰保持一致，硬要說不同的話也就只有","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"masterSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"生成的階段不同。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"在客戶端用於對要發送的數據進行加密，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"在客戶端對收到的數據進行解密。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節梳理了客戶端處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"的邏輯和生成握手階段密鑰的邏輯。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"處理Server發送的參數","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在客戶端需要處理的Server參數只有一個","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"encryptedExtensionsMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息。而且處理邏輯也十分簡單：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"msg, err := c.readHandshake()\nencryptedExtensions, ok := msg.(*encryptedExtensionsMsg)\nhs.transcript.Write(encryptedExtensions.marshal())\nc.clientProtocol = encryptedExtensions.alpnProtocol","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果客戶端讀取到","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"encryptedExtensionsMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息，則直接將Server支持的HTTP協議賦值給","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"c.clientProtocol","attrs":{}}],"attrs":{}},{"type":"text","text":"。在之後的HTTP請求中會根據TLS握手狀態以及服務端是否支持","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"h2","attrs":{}}],"attrs":{}},{"type":"text","text":"決定是否將本次請求升級爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"http2","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"驗證證書和簽名","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本小節仍然繼續處理Server發送的消息，主要包含","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateRequestMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"，這三個消息均和證書相關。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先，處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateRequestMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"消息，僅在雙向認證時，服務端才發送此消息。在本階段的處理邏輯也很簡單，讀取該消息並記錄。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"msg, err := c.readHandshake()\ncertReq, ok := msg.(*certificateRequestMsgTLS13)\nif ok {\n hs.transcript.Write(certReq.marshal())\n hs.certReq = certReq\n msg, err = c.readHandshake()\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其次，處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"消息，該消息中主要包含證書信息，Client在獲取到證書信息後要校驗證書是否過期以及是否可信任。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"if err := c.verifyServerCertificate(certMsg.certificate.Certificate); err != nil {\n return err\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"c.verifyServerCertificate","attrs":{}}],"attrs":{}},{"type":"text","text":"的內部邏輯如果各位讀者有興趣可以下載Demo調試一番，筆者在這裏就不對該方法做深入的展開和分析了。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息。前面在處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"時已經驗證了證書可信任或者Client可以忽略不受信任的證書，但是Client仍無法確信提供這個證書的服務器是否持有該證書，而驗證簽名的意義就在於確保該服務確實持有該證書。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在Server發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息時已經使用了證書對應的私鑰對需要簽名的數據進行簽名，客戶端利用證書的公鑰解密該簽名並和本地的待簽名數據做對比以確保服務端確實持有該證書。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"// 根據簽名算法返回對應的算法類型和hash算法\nsigType, sigHash, err := typeAndHashFromSignatureScheme(certVerify.signatureAlgorithm)\nsigned := signedMessage(sigHash, serverSignatureContext, hs.transcript)\nif err := verifyHandshakeSignature(sigType, c.peerCertificates[0].PublicKey,\n\tsigHash, signed, certVerify.signature); err != nil {\n c.sendAlert(alertDecryptError)\n return errors.New(\"tls: invalid signature by the server certificate: \" + err.Error())\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"typeAndHashFromSignatureScheme","attrs":{}}],"attrs":{}},{"type":"text","text":"函數和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"signedMessage","attrs":{}}],"attrs":{}},{"type":"text","text":"函數在前文已經提到過，因此不再做重複敘述。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"verifyHandshakeSignature","attrs":{}}],"attrs":{}},{"type":"text","text":"函數的內部實現涉及到非對稱加密算法的加解密，因筆者的知識有限，確實無法做更進一步的分析，在這裏給各位讀者道個歉～","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：在這一小節簡單介紹了客戶端證書的驗證以及簽名的驗證。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"處理finishedMsg並再次計算密鑰","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"客戶端對證書籤名驗證通過後，接下來還需要驗證消息的完整性。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"finished, ok := msg.(*finishedMsg)\nexpectedMAC := hs.suite.finishedHash(c.in.trafficSecret, hs.transcript)\nif !hmac.Equal(expectedMAC, finished.verifyData) {\n c.sendAlert(alertDecryptError)\n return errors.New(\"tls: invalid server finished hash\")\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"finishedHash","attrs":{}}],"attrs":{}},{"type":"text","text":"方法說明請參考","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"發送finishedMsg並再次計算密鑰","attrs":{}},{"type":"text","text":"這一小節。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"只有當客戶端計算的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"expectedMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg.verifyData","attrs":{}}],"attrs":{}},{"type":"text","text":"一致時纔可繼續後續操作，即客戶端二次計算密鑰。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"hs.trafficSecret = hs.suite.deriveSecret(hs.masterSecret,\n\tclientApplicationTrafficLabel, hs.transcript)\nserverSecret := hs.suite.deriveSecret(hs.masterSecret,\n\tserverApplicationTrafficLabel, hs.transcript)\nc.in.setTrafficSecret(hs.suite, serverSecret)","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"二次計算密鑰時分別派生出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"兩個密鑰。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"需要注意的是，此時利用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"AEAD","attrs":{}}],"attrs":{}},{"type":"text","text":"加密算法會用於握手結束後對收到的業務數據進行解密。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，Server發送給客戶端的消息已經全部處理完畢。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節主要介紹了客戶端通過","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"HMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"算法確保收到的消息未被篡改以及二次計算密鑰。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"Client發送最後的消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"客戶端已經驗證了服務端消息的完整性，但是服務端還未驗證客戶端消息的完整性，因此客戶端還需要發送最後一次數據給服務端。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先判斷是否需要發送證書給Server：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"if hs.certReq == nil {\n return nil\n}\ncertMsg := new(certificateMsgTLS13)\n// 此處省略代碼\ncertVerifyMsg := new(certificateVerifyMsg)\ncertVerifyMsg.hasSignatureAlgorithm = true\n// 此處省略代碼","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"根據","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"驗證證書和簽名","attrs":{}},{"type":"text","text":"這一小節的描述，如果服務端要求客戶端發送證書則","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.certReq","attrs":{}}],"attrs":{}},{"type":"text","text":"不爲nil。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"的主體也是證書，該證書的來源爲客戶端","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"tls.Config","attrs":{}}],"attrs":{}},{"type":"text","text":"配置的證書，在本例中客戶端配置證書邏輯如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"tlsConf.NextProtos = append(tlsConf.NextProtos, \"h2\", \"http/1.1\")\ntlsConf.Certificates = make([]tls.Certificate, 1)\nif len(certFile) > 0 && len(keyFile) > 0 {\n var err error\n tlsConf.Certificates[0], err = tls.LoadX509KeyPair(certFile, keyFile)\n if err != nil {\n return nil, err\n }\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"既然要發送證書給服務端，那麼同服務端邏輯一樣也需要發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"提供消息簽名的信息。客戶端簽名邏輯和服務端簽名邏輯一致，因此筆者不再贅述。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，客戶端需要發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"給服務端：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"finished := &finishedMsg{\n verifyData: hs.suite.finishedHash(c.out.trafficSecret, hs.transcript),\n}\nhs.transcript.Write(finished.marshal())\nc.out.setTrafficSecret(hs.suite, hs.trafficSecret)","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"需要注意的是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"在第二次計算密鑰時就已經被賦值，當","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"發送後，利用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"AEAD","attrs":{}}],"attrs":{}},{"type":"text","text":"加密算法會對客戶端要發送的業務數據進行加密。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，客戶端的握手流程全部完成。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1、如果服務端要求客戶端發送證書，則客戶端會發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2、發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息並設置發送業務數據時的密鑰信息。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Server讀Client最後的消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先，服務端在TLS握手的最後階段，會先判斷是否要求客戶端發送證書，如果要求客戶端發送證書則處理客戶端發送的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息。服務端處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息的邏輯和客戶端處理這兩個消息的邏輯類似。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其次，讀取客戶端發送的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"， 並驗證消息的完整性，驗證邏輯和客戶端驗證","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"邏輯一致。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，設置服務端讀取業務數據時的加密信息：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"c.in.setTrafficSecret(hs.suite, hs.trafficSecret)","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"hs.trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"在服務端第二次計算加密信息時就已經賦值，當讀完客戶端發送的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"之後再執行此步驟是爲了避免無法解密客戶端發送的握手信息。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，服務端的握手流程全部完成。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"握手完成之後","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"完成上述流程後，筆者還想試試看能不能從握手過程獲取的密鑰信息對業務數據進行解密。說幹就幹，下面是筆者在TLS握手完成之後用Client連接發送了一條消息的代碼。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"// main.go 握手完成之後，client發送了一條數據\nclient.Write([]byte(\"點贊關注：新世界雜貨鋪\"))","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面是運行Demo後的輸出截圖：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/88/883a1a9dd9a6cad0ecf7517924963124.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"圖中紅色箭頭部分爲在Internet中真實傳輸的數據，藍色箭頭部分爲其解密結果。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"一點感慨","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"關於TLS握手流程的文章筆者想寫很久了，現在總算得償所願。筆者不敢保證把TLS握手過程的每一個細節都描述清楚，所以如果中間有什麼問題還請各位讀者及時指出，大家相互學習。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"寫到這裏時筆者的內心也略有忐忑，畢竟這中間涉及了很多密碼學相關的知識，而在筆者各種瘋狂查資料期間發現國內具有權威性的文章還是太少。像","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ECDH","attrs":{}}],"attrs":{}},{"type":"text","text":"之類的關鍵詞在百度百科都沒有收錄，果然維基百科纔是爸爸呀。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後一點感概是關於Go中","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"io.Reader ","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"io.Writer","attrs":{}}],"attrs":{}},{"type":"text","text":"這兩個接口的，不得不說這兩個接口的設計真的很簡單但是真的非常通用。筆者的Demo正是基於這兩個接口實現，否則筆者的心願很難完成。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"挖坑","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在上一篇文章中，筆者給了一條彩蛋——“下一期TLS/SSL握手流程敬請期待”。哇，這可真的是自己坑自己了，本篇文章未完成之前，筆者愣是斷更了也沒敢發別的文章。果然自己作的死，哭着也要作完。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有了前車之鑑，筆者決定以後不再放彩蛋，而是挖坑（填坑時間待定😊）：本篇中主要介紹了TLS1.3的握手流程，那麼TLS1.2也快了～","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，衷心希望本文能夠對各位讀者有一定的幫助。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"注","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1. 寫本文時， 筆者所用go版本爲: go1.15.2","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2. 文章中所用完整例子：https://github.com/Isites/go-coder/blob/master/http2/tls/main.go","attrs":{}}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}
碼了2000多行代碼就是爲了講清楚TLS握手流程
{"type":"doc","content":[{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"來自公衆號：新世界雜貨鋪","attrs":{}}]}],"attrs":{}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"前言","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"呼，這篇文章的準備週期可謂是相當的長了！原本是想直接通過源碼進行分析的，但是發現TLS握手流程調試起來非常不方便，筆者怒了，於是實現了一個極簡的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"net.Conn","attrs":{}}],"attrs":{}},{"type":"text","text":"接口以方便調試。碼着碼着，筆者哭了，因爲現在這個調試Demo已經達到2000多行代碼了！","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/be/be39ad48832a087d5fa3438b7403d43f.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"雖然碼了兩千多行代碼，但是目前只能夠解析TLS1.3握手流程中發送的消息，因此本篇主要分析TLS1.3的握手流程。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"特別提醒：有想在本地調試一番的小夥伴請至文末獲取本篇源碼。","attrs":{}}]}],"attrs":{}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"結論先行","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"鑑於本文篇幅較長，筆者決定結論先行，以助各位讀者理解後文詳細的分析內容。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"HTTPS單向認證","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"單向認證客戶端不需要證書，客戶端只要驗證服務端證書合法即可訪問。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面是筆者運行Demo打印的調試信息：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/8c/8cd8c2688e51b3f497477830ca2b88f2.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"根據調試信息知，在TLS1.3單向認證中，總共收發數據","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"三次","attrs":{}},{"type":"text","text":"，Client和Server從這三次數據中分別讀取不同的信息以達到握手的目的。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"注意","attrs":{}},{"type":"text","text":"：TLS1.3不處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ChangeCipherSpec","attrs":{}}],"attrs":{}},{"type":"text","text":"類型的數據，而該數據在TLS1.2中是需要處理的。因本篇主要分析TLS1.3握手流程，故後續不會再提及","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ChangeCipherSpec","attrs":{}}],"attrs":{}},{"type":"text","text":"，同時","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"時序圖中也會忽略此消息","attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"筆者將調試信息轉換爲下述時序圖，以方便各位讀者理解。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/3c/3cfe4fd7fce54a79e2a5e1882b1b995a.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"HTTPS雙向認證","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"雙向認證不僅服務端要有證書，客戶端也需要證書，只有客戶端和服務端證書均合法纔可繼續訪問。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"筆者在這裏特別提醒，開啓雙向認證很簡單，在筆者的Demo中取消下面代碼的註釋即可。","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"// sconf.ClientAuth = tls.RequireAndVerifyClientCert","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"另外，筆者在","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"main.go","attrs":{}}],"attrs":{}},{"type":"text","text":"同目錄下留有測試用的根證書、服務端證書和客戶端證書，爲了保證雙向認證的順利運行請將根證書安裝爲受用戶信任的證書。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面是筆者運行Demo打印的調試信息：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/53/5365946d1ccbdb044546fb3e8074ef50.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"同單向認證一樣，筆者將調試信息轉換爲下述時序圖。 ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/ea/eaa29576d95429f7be4e0d74756acf63.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"雙向認證和單向認證相比，Server發消息給Client時會額外發送一個","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateRequestMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"消息，Client收到此消息後會將證書信息（","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"）和簽名信息（","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"）發送給Server。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"雙向認證中，Client和Server發送消息變多了，但是總的數據收發仍然只有","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"三次","attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"總結","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1、TLS1.3和TLS1.2握手流程是有區別的，這一點需要注意。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2、單向認證和雙向認證中，總的數據收發僅三次，單次發送的數據中包含一個或者多個消息。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"未經過加密，之後發送的消息均做了加密處理。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"4、Client和Server會各自計算兩次密鑰，計算時機分別是讀取到對方的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"HelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"之後。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"注","attrs":{}},{"type":"text","text":"：上述第3點和第4點分析過程詳見後文。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Client發送HelloMsg","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在TLS握手過程中的第一步是Client發送HelloMsg，所以針對TLS握手流程的分析也從這一步開始。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Server對於Client的基本信息瞭解完全依賴於Client主動告知Server，而其中比較關鍵的信息分別是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"客戶端支持的TLS版本","attrs":{}}],"attrs":{}},{"type":"text","text":"、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"客戶端支持的加密套件（cipherSuites）","attrs":{}}],"attrs":{}},{"type":"text","text":"、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"客戶端支持的簽名算法","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"客戶端支持的密鑰交換協議以及其對應的公鑰","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"客戶端支持的TLS版本：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"客戶端支持的TLS版本主要通過tls包中","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"(*Config).supportedVersions","attrs":{}}],"attrs":{}},{"type":"text","text":"方法計算。對TLS1.3來說默認支持的TLS版本如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"var supportedVersions = []uint16{\n\tVersionTLS13,\n\tVersionTLS12,\n\tVersionTLS11,\n\tVersionTLS10,\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在發起請求時如果用戶手動設置了","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"tls.Config","attrs":{}}],"attrs":{}},{"type":"text","text":"中的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"MaxVersion","attrs":{}}],"attrs":{}},{"type":"text","text":"或者","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"MinVersion","attrs":{}}],"attrs":{}},{"type":"text","text":"，則客戶端支持的TLS版本會發生變化。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"例如發起請求時，設置了","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"conf.MaxVersion = tls.VersionTLS12","attrs":{}}],"attrs":{}},{"type":"text","text":"，此時","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"(*Config).supportedVersions","attrs":{}}],"attrs":{}},{"type":"text","text":"返回的版本爲：","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"[]uint16{\n\tVersionTLS12,\n\tVersionTLS11,\n\tVersionTLS10,\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ps: 如果有興趣的小夥伴可以在克隆筆者的demo後手動設置Config.MaxVersion，設置後可以調試TLS1.2的握手流程。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"客戶端支持的加密套件（cipherSuites）：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"說實話，加密套件已經進入筆者的知識盲區了，其作用筆者會在下一小節講明白，故本小節筆者直接貼出計算後的結果。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/eb/eb7d21a5652e847b40bfc868cc0c7d3d.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"圖中籃框部分爲當前Client支持加密套件Id，紅框部分爲計算邏輯。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"客戶端支持的簽名算法：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"客戶端支持的簽名算法，僅在客戶端支持的最大TLS版本大於等於TLS1.2時生效。此時客戶端支持的簽名算法如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"var supportedSignatureAlgorithms = []SignatureScheme{\n\tPSSWithSHA256,\n\tECDSAWithP256AndSHA256,\n\tEd25519,\n\tPSSWithSHA384,\n\tPSSWithSHA512,\n\tPKCS1WithSHA256,\n\tPKCS1WithSHA384,\n\tPKCS1WithSHA512,\n\tECDSAWithP384AndSHA384,\n\tECDSAWithP521AndSHA512,\n\tPKCS1WithSHA1,\n\tECDSAWithSHA1,\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"客戶端支持的密鑰交換協議及其對應的公鑰：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這一塊兒邏輯僅在客戶端支持的最大TLS版本是TLS1.3時生效。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"if hello.supportedVersions[0] == VersionTLS13 {\n\thello.cipherSuites = append(hello.cipherSuites, defaultCipherSuitesTLS13()...)\n\n\tcurveID := config.curvePreferences()[0]\n\tif _, ok := curveForCurveID(curveID); curveID != X25519 && !ok {\n\t\treturn nil, nil, errors.New(\"tls: CurvePreferences includes unsupported curve\")\n\t}\n\tparams, err = generateECDHEParameters(config.rand(), curveID)\n\tif err != nil {\n\t\treturn nil, nil, err\n\t}\n\thello.keyShares = []keyShare{{group: curveID, data: params.PublicKey()}}\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中，方法","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"config.curvePreferences","attrs":{}}],"attrs":{}},{"type":"text","text":"的邏輯爲：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"var defaultCurvePreferences = []CurveID{X25519, CurveP256, CurveP384, CurveP521}\nfunc (c *Config) curvePreferences() []CurveID {\n\tif c == nil || len(c.CurvePreferences) == 0 {\n\t\treturn defaultCurvePreferences\n\t}\n\treturn c.CurvePreferences\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在本篇中，筆者未手動設置優先可供選擇的曲線，故","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"curveID","attrs":{}}],"attrs":{}},{"type":"text","text":"的值爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"X25519","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"函數的作用是根據曲線Id生成一種橢圓曲線密鑰交換協議的實現。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果客戶端支持的最大TLS版本是TLS1.3時，會爲Client支持的加密套件增加TLS1.3默認的加密套件，同時還會選擇","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Curve25519","attrs":{}},{"type":"text","text":"密鑰交換協議生成","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"keyShare","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節介紹了在TLS1.3中Client需要告知Server客戶端支持的TLS版本號、客戶端支持的加密套件、客戶端支持的簽名算法和客戶端支持的密鑰交換協議。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Server讀HelloMsg&發送消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Server讀到","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"之後會根據客戶端支持的TLS版本和本地支持的TLS版本做對比，得到Client和Server均支持的TLS版本最大值，該值作爲後續繼續通信的標準。本篇中Client和Server都支持TLS1.3，因此Server進入TLS1.3的握手流程。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"處理clientHelloMsg","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Server進入TLS1.3握手流程之後，還需要繼續處理clientHelloMsg，同時構建","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Server支持的TLS版本","attrs":{}},{"type":"text","text":":","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"進入TLS1.3握手流程之前，Server已經計算出兩端均支持的TLS版本，但是Client還無法得知Server支持的TLS版本，因此開始繼續處理clientHelloMsg時，Server將已經計算得到的TLS版本賦值給","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"supportedVersion","attrs":{}}],"attrs":{}},{"type":"text","text":"以告知客戶端。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"// client讀取到serverHelloMsg後，通過讀取此字段計算兩端均支持的TLS版本\nhs.hello.supportedVersion = c.vers","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Server計算兩端均支持的加密套件","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"中含有Client支持的加密套件信息，Server讀取該信息並和本地支持的加密套件做對比計算出兩端均支持的加密套件。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏需要注意的是，如果Server的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"tls.Config.PreferServerCipherSuites","attrs":{}}],"attrs":{}},{"type":"text","text":"爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"true","attrs":{}}],"attrs":{}},{"type":"text","text":"則選擇Server第一個在兩端均支持的加密套件，否則選擇Client第一個在兩端均支持的加密套件。筆者通過Debug得到兩端均支持的加密套件id爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"4865","attrs":{}}],"attrs":{}},{"type":"text","text":"（其常量爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"tls.TLS","attrs":{}},{"type":"text","marks":[{"type":"italic","attrs":{}}],"text":"AES","attrs":{}},{"type":"text","text":"128_GCM_SHA256","attrs":{}}],"attrs":{}},{"type":"text","text":"），詳情見下圖：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/31/31924f987ea466b2cac89138ec90e483.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上圖中的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"mutualCipherSuiteTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"函數會從","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuitesTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"變量中選擇匹配的加密套件。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"var cipherSuitesTLS13 = []*cipherSuiteTLS13{\n\t{TLS_AES_128_GCM_SHA256, 16, aeadAESGCMTLS13, crypto.SHA256},\n\t{TLS_CHACHA20_POLY1305_SHA256, 32, aeadChaCha20Poly1305, crypto.SHA256},\n\t{TLS_AES_256_GCM_SHA384, 32, aeadAESGCMTLS13, crypto.SHA384},\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"結合前面的Debug信息知，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.suite","attrs":{}}],"attrs":{}},{"type":"text","text":"爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuiteTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"結構體的變量且其值爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuitesTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"切片的第一個。","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuiteTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"結構體定義如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"type cipherSuiteTLS13 struct {\n\tid uint16\n\tkeyLen int\n\taead func(key, fixedNonce []byte) aead\n\thash crypto.Hash\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，Server已經計算出雙端均支持的加密套件，Server通過設置","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"cipherSuite","attrs":{}}],"attrs":{}},{"type":"text","text":"將雙端均支持的加密套件告知Client：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"hs.hello.cipherSuite = hs.suite.id\nhs.transcript = hs.suite.hash.New()","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在後續計算密鑰時需要對Client和Server之間的所有消息計算Hash摘要。根據前面計算出的加密套件知，本篇中計算消息摘要的Hash算法爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"SHA256","attrs":{}}],"attrs":{}},{"type":"text","text":"，此算法的實現賦值給","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.transcript","attrs":{}}],"attrs":{}},{"type":"text","text":"變量，後續計算消息摘要時均通過該變量實現。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Server計算雙端均支持的密鑰交換協議以及對應的公鑰","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg.keyShares","attrs":{}}],"attrs":{}},{"type":"text","text":"變量記錄着Client支持的曲線Id以及對應的公鑰。Server通過對比本地支持的曲線Id計算出雙端均支持的密鑰交換協議。根據前面","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Client發送HelloMsg","attrs":{}},{"type":"text","text":"這一小節的內容以及筆者實際調試的結果，雙端均支持的曲線爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"Curve25519","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Server計算出雙端均支持的曲線後，調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"方法得到對應密鑰交換協議的實現，即Curve25519密鑰交換協議。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"Curve25519","attrs":{}}],"attrs":{}},{"type":"text","text":"是橢圓曲線迪菲-赫爾曼（Elliptic-curve Diffie–Hellman ，縮寫爲ECDH）密鑰交換方案之一，同時也是最快的ECC（Elliptic-curve cryptography）曲線之一。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"ECDH","attrs":{}}],"attrs":{}},{"type":"text","text":"可以爲Client和Server在不安全的通道上爲雙方建立共享密鑰，並且Client和Server需要各自持有一組橢圓曲線公私密鑰對。當Client和Server需要建立共享密鑰時僅需要公佈各自的公鑰，Client和Server通過對方的公鑰以及自己的私鑰即可計算出相等的密鑰。如果公鑰被第三方截獲也無關緊要，因爲第三方沒有私鑰無法計算出共享密鑰除非第三方能夠解決橢圓曲線Diffie–Hellman問題。","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ECDHE","attrs":{}}],"attrs":{}},{"type":"text","text":"爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ECDH","attrs":{}}],"attrs":{}},{"type":"text","text":"的一個變種，其區別僅僅是私鑰和公鑰在每次建立共享密鑰時均需重新生成（以上爲筆者對維基百科中ECDH的理解）。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"對","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ECDHE","attrs":{}}],"attrs":{}},{"type":"text","text":"有了一定的理解後，我們現在看一下","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"函數中的部分源碼：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"func generateECDHEParameters(rand io.Reader, curveID CurveID) (ecdheParameters, error) {\n\tif curveID == X25519 {\n\t\tprivateKey := make([]byte, curve25519.ScalarSize)\n\t\tif _, err := io.ReadFull(rand, privateKey); err != nil {\n\t\t\treturn nil, err\n\t\t}\n\t\tpublicKey, err := curve25519.X25519(privateKey, curve25519.Basepoint)\n\t\tif err != nil {\n\t\t\treturn nil, err\n\t\t}\n\t\treturn &x25519Parameters{privateKey: privateKey, publicKey: publicKey}, nil\n\t}\n // 此處省略代碼\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"每次調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"函數時均會生成一組新的橢圓曲線公私密鑰對。","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg.keyShares","attrs":{}}],"attrs":{}},{"type":"text","text":"變量存有Client的公鑰，因此Server已經可以計算共享密鑰：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"params, err := generateECDHEParameters(c.config.rand(), selectedGroup)\nif err != nil {\n c.sendAlert(alertInternalError)\n return err\n}\nhs.hello.serverShare = keyShare{group: selectedGroup, data: params.PublicKey()}\nhs.sharedKey = params.SharedKey(clientKeyShare.data) // 共享密鑰","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中Server已經計算出共享密鑰，之後可以通過此密鑰派生出其他密鑰爲數據加密。Client因爲無Server的公鑰還無法計算出共享密鑰，所以Server通過設置","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverShare","attrs":{}}],"attrs":{}},{"type":"text","text":"變量告知Client服務端的公鑰。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，Server對Client發來的helloMsg已經處理完畢。筆者在這裏額外提醒一句，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"中仍然有Client和Server生成的隨機數，但是在TLS1.3中這兩個隨機數已經和密鑰交換無關了。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節介紹了Server讀取","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"後會計算雙端支持的TLS版本以及雙端支持的加密套件和密鑰交換協議，同時還介紹了共享密鑰的生成以及ECDH的概念。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"選擇合適的證書以及簽名算法","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在Server選擇和當前Client匹配的證書前其實還有關於預共享密鑰模式的處理，該模式需要實現","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ClientSessionCache","attrs":{}}],"attrs":{}},{"type":"text","text":"接口，鑑於其不影響握手流程的分析，故本篇不討論預共享密鑰模式。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一個Server可能給多個Host提供服務，因此Server可能持有多個證書，那麼選擇一個和當前Client匹配的證書是十分必要的，其實現邏輯參見","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"(*Config).getCertificate","attrs":{}}],"attrs":{}},{"type":"text","text":"方法。本篇中的Demo只有一個證書，故該方法會直接返回此證書。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"證書中是包含公鑰的，不同的公鑰支持的簽名算法是不同的，在本例中Server支持的簽名算法和最終雙端均支持的簽名算法見下面的Debug結果：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/bb/bbd67e99ae3eff7fd050fc3d02e696ec.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上圖中紅框部分爲Server支持的簽名算法，藍框爲選定的雙端均支持的簽名算法。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節主要介紹了Server選擇匹配當前Client的證書和簽名算法。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"計算握手階段的密鑰以及發送Server的參數","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在這個階段Server會將","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"寫入緩衝區，寫完之後再寫入一個","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ChangeCipherSpec","attrs":{}}],"attrs":{}},{"type":"text","text":"（TLS1.3不會處理此消息）消息，需要注意的是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"未進行加密發送。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"計算握手階段的密鑰","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"前面提到過計算密鑰需要計算消息摘要：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"hs.transcript.Write(hs.clientHello.marshal())\nhs.transcript.Write(hs.hello.marshal()) // hs.hello爲serverHelloMsg","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.transcript","attrs":{}}],"attrs":{}},{"type":"text","text":"在前面已經提到過是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"SHA256","attrs":{}}],"attrs":{}},{"type":"text","text":"Hash算法的一種實現。下面我們逐步分析源碼中Server第一次計算密鑰的過程。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先，派生出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"handshakeSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"earlySecret := hs.earlySecret \nif earlySecret == nil {\n earlySecret = hs.suite.extract(nil, nil)\n}\nhs.handshakeSecret = hs.suite.extract(hs.sharedKey, \nhs.suite.deriveSecret(earlySecret, \"derived\", 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extract(newSecret, currentSecret []byte) []byte {\n\tif newSecret == nil {\n\t\tnewSecret = make([]byte, c.hash.Size())\n\t}\n\treturn hkdf.Extract(c.hash.New, newSecret, 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c.hash.Size())\n\tverifyData := hmac.New(c.hash.New, finishedKey)\n\tverifyData.Write(transcript.Sum(nil))\n\treturn verifyData.Sum(nil)\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"HMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"是一種利用密碼學中的散列函數來進行消息認證的一種機制，所能提供的消息認證包括兩方面內容（此內容摘自百度百科）：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"消息完整性認證：能夠證明消息內容在傳送過程沒有被修改。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"信源身份認證：因爲通信雙方共享了認證的密鑰，接收方能夠認證發送該數據的信源與所宣稱的一致，即能夠可靠地確認接收的消息與發送的一致。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述代碼中，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"c.expandLabel","attrs":{}}],"attrs":{}},{"type":"text","text":"最種會調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hkdf.Expand","attrs":{}}],"attrs":{}},{"type":"text","text":"派生出新的密鑰。最後用新的密鑰以及消息摘要通過","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"HMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"算法計算出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"verifyData","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"收到","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"一方通過同樣的方式在本地計算出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"verifyData'","attrs":{}}],"attrs":{}},{"type":"text","text":"，如果","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"verifyData'","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"verifyData","attrs":{}}],"attrs":{}},{"type":"text","text":"相等，則證明此消息未被修改且來源可信。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"再次計算密鑰","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本次計算密鑰的過程和前面計算密鑰的流程相似，所以直接上代碼：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"hs.masterSecret = hs.suite.extract(nil,\n\ths.suite.deriveSecret(hs.handshakeSecret, \"derived\", nil))\n\nhs.trafficSecret = hs.suite.deriveSecret(hs.masterSecret,\n\tclientApplicationTrafficLabel, hs.transcript)\nserverSecret := hs.suite.deriveSecret(hs.masterSecret,\n\tserverApplicationTrafficLabel, hs.transcript)\nc.out.setTrafficSecret(hs.suite, serverSecret)","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先，利用前文已經生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"handshakeSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"\t再次派生出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"masterSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"，然後再從","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"masterSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"派生出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"，最後調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"c.out.setTrafficSecret(hs.suite, serverSecret)","attrs":{}}],"attrs":{}},{"type":"text","text":"計算出Server發送數據時的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"AEAD","attrs":{}}],"attrs":{}},{"type":"text","text":"加密算法。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"需要注意的是，此時利用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"AEAD","attrs":{}}],"attrs":{}},{"type":"text","text":"加密算法會用於握手結束後對要發送的業務數據進行加密。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"此階段結束後，Server會調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"c.flush()","attrs":{}}],"attrs":{}},{"type":"text","text":"方法，將前面提到的消息一次性發送給Client。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1、本節介紹了","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"的生成過程，其中","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg.verifyData","attrs":{}}],"attrs":{}},{"type":"text","text":"通過","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"HMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"算法計算得出。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"的作用是確保握手過程中發送的消息未被篡改，且數據來源可信。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3、計算Server發送業務數據時的加密密鑰。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Client讀消息&發送消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Client讀到","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"之後會讀取服務端支持的TLS版本並和本地支持的版本做對比，前文已經提到過服務端支持的TLS版本是TLS1.3，因此Client也進入TLS1.3握手流程。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"讀取serverHelloMsg並計算密鑰","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Client進入TLS1.3握手流程後，有一系列的檢查邏輯，這些邏輯比較長而且筆者也不需要考慮這些異常，因此筆者化繁爲簡，在下面列出關鍵邏輯：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"selectedSuite := mutualCipherSuiteTLS13(hs.hello.cipherSuites,\n\ths.serverHello.cipherSuite) // 結合Server支持的加密套件選擇雙端均支持的加密套件\nhs.suite = selectedSuite\nhs.transcript = hs.suite.hash.New()\nhs.transcript.Write(hs.hello.marshal()) // hs.hello爲clientHelloMsg\nhs.transcript.Write(hs.serverHello.marshal())","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上面這一段代碼邏輯和Server處理加密套件以及通過加密套件構建消息摘要算法的實現邏輯相對應，因此筆者不再過多贅述。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面我們看一下計算握手階段的密鑰以及","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"masterSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"的生成：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"sharedKey := hs.ecdheParams.SharedKey(hs.serverHello.serverShare.data)\nearlySecret := hs.earlySecret\nif !hs.usingPSK {\n earlySecret = hs.suite.extract(nil, nil)\n}\nhandshakeSecret := hs.suite.extract(sharedKey,\n\ths.suite.deriveSecret(earlySecret, \"derived\", nil)) // 通過共享密鑰派生出handshakeSecret\n\nclientSecret := hs.suite.deriveSecret(handshakeSecret,\n\tclientHandshakeTrafficLabel, hs.transcript) // 通過handshakeSecret派生出clientSecret\nc.out.setTrafficSecret(hs.suite, clientSecret)\nserverSecret := hs.suite.deriveSecret(handshakeSecret,\n\tserverHandshakeTrafficLabel, hs.transcript) // 通過handshakeSecret派生出serverSecret\nc.in.setTrafficSecret(hs.suite, serverSecret)\nhs.masterSecret = hs.suite.extract(nil,\n\ths.suite.deriveSecret(handshakeSecret, \"derived\", nil)) // 通過handshakeSecret派生出masterSecret","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏需要提一嘴的是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.ecdheParams","attrs":{}}],"attrs":{}},{"type":"text","text":"，該值爲","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Client發送HelloMsg","attrs":{}},{"type":"text","text":"這一小節調用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"generateECDHEParameters","attrs":{}}],"attrs":{}},{"type":"text","text":"函數生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"params","attrs":{}}],"attrs":{}},{"type":"text","text":"。其他邏輯和Server生成握手階段的密鑰保持一致，硬要說不同的話也就只有","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"masterSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"生成的階段不同。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"clientSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"在客戶端用於對要發送的數據進行加密，","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"在客戶端對收到的數據進行解密。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節梳理了客戶端處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverHelloMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"的邏輯和生成握手階段密鑰的邏輯。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"處理Server發送的參數","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在客戶端需要處理的Server參數只有一個","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"encryptedExtensionsMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息。而且處理邏輯也十分簡單：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"msg, err := c.readHandshake()\nencryptedExtensions, ok := msg.(*encryptedExtensionsMsg)\nhs.transcript.Write(encryptedExtensions.marshal())\nc.clientProtocol = encryptedExtensions.alpnProtocol","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果客戶端讀取到","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"encryptedExtensionsMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息，則直接將Server支持的HTTP協議賦值給","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"c.clientProtocol","attrs":{}}],"attrs":{}},{"type":"text","text":"。在之後的HTTP請求中會根據TLS握手狀態以及服務端是否支持","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"h2","attrs":{}}],"attrs":{}},{"type":"text","text":"決定是否將本次請求升級爲","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"http2","attrs":{}}],"attrs":{}},{"type":"text","text":"。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"驗證證書和簽名","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本小節仍然繼續處理Server發送的消息，主要包含","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateRequestMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"、","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"，這三個消息均和證書相關。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先，處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateRequestMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"消息，僅在雙向認證時，服務端才發送此消息。在本階段的處理邏輯也很簡單，讀取該消息並記錄。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"msg, err := c.readHandshake()\ncertReq, ok := msg.(*certificateRequestMsgTLS13)\nif ok {\n hs.transcript.Write(certReq.marshal())\n hs.certReq = certReq\n msg, err = c.readHandshake()\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其次，處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"消息，該消息中主要包含證書信息，Client在獲取到證書信息後要校驗證書是否過期以及是否可信任。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"if err := c.verifyServerCertificate(certMsg.certificate.Certificate); err != nil {\n return err\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"c.verifyServerCertificate","attrs":{}}],"attrs":{}},{"type":"text","text":"的內部邏輯如果各位讀者有興趣可以下載Demo調試一番，筆者在這裏就不對該方法做深入的展開和分析了。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息。前面在處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"時已經驗證了證書可信任或者Client可以忽略不受信任的證書，但是Client仍無法確信提供這個證書的服務器是否持有該證書，而驗證簽名的意義就在於確保該服務確實持有該證書。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在Server發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息時已經使用了證書對應的私鑰對需要簽名的數據進行簽名，客戶端利用證書的公鑰解密該簽名並和本地的待簽名數據做對比以確保服務端確實持有該證書。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"// 根據簽名算法返回對應的算法類型和hash算法\nsigType, sigHash, err := typeAndHashFromSignatureScheme(certVerify.signatureAlgorithm)\nsigned := signedMessage(sigHash, serverSignatureContext, hs.transcript)\nif err := verifyHandshakeSignature(sigType, c.peerCertificates[0].PublicKey,\n\tsigHash, signed, certVerify.signature); err != nil {\n c.sendAlert(alertDecryptError)\n return errors.New(\"tls: invalid signature by the server certificate: \" + err.Error())\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"typeAndHashFromSignatureScheme","attrs":{}}],"attrs":{}},{"type":"text","text":"函數和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"signedMessage","attrs":{}}],"attrs":{}},{"type":"text","text":"函數在前文已經提到過，因此不再做重複敘述。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"verifyHandshakeSignature","attrs":{}}],"attrs":{}},{"type":"text","text":"函數的內部實現涉及到非對稱加密算法的加解密，因筆者的知識有限，確實無法做更進一步的分析，在這裏給各位讀者道個歉～","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：在這一小節簡單介紹了客戶端證書的驗證以及簽名的驗證。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"處理finishedMsg並再次計算密鑰","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"客戶端對證書籤名驗證通過後，接下來還需要驗證消息的完整性。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"finished, ok := msg.(*finishedMsg)\nexpectedMAC := hs.suite.finishedHash(c.in.trafficSecret, hs.transcript)\nif !hmac.Equal(expectedMAC, finished.verifyData) {\n c.sendAlert(alertDecryptError)\n return errors.New(\"tls: invalid server finished hash\")\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"finishedHash","attrs":{}}],"attrs":{}},{"type":"text","text":"方法說明請參考","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"發送finishedMsg並再次計算密鑰","attrs":{}},{"type":"text","text":"這一小節。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"只有當客戶端計算的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"expectedMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg.verifyData","attrs":{}}],"attrs":{}},{"type":"text","text":"一致時纔可繼續後續操作，即客戶端二次計算密鑰。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"hs.trafficSecret = hs.suite.deriveSecret(hs.masterSecret,\n\tclientApplicationTrafficLabel, hs.transcript)\nserverSecret := hs.suite.deriveSecret(hs.masterSecret,\n\tserverApplicationTrafficLabel, hs.transcript)\nc.in.setTrafficSecret(hs.suite, serverSecret)","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"二次計算密鑰時分別派生出","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"兩個密鑰。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"需要注意的是，此時利用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"serverSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"AEAD","attrs":{}}],"attrs":{}},{"type":"text","text":"加密算法會用於握手結束後對收到的業務數據進行解密。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，Server發送給客戶端的消息已經全部處理完畢。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：本節主要介紹了客戶端通過","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"HMAC","attrs":{}}],"attrs":{}},{"type":"text","text":"算法確保收到的消息未被篡改以及二次計算密鑰。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"Client發送最後的消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"客戶端已經驗證了服務端消息的完整性，但是服務端還未驗證客戶端消息的完整性，因此客戶端還需要發送最後一次數據給服務端。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先判斷是否需要發送證書給Server：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"if hs.certReq == nil {\n return nil\n}\ncertMsg := new(certificateMsgTLS13)\n// 此處省略代碼\ncertVerifyMsg := new(certificateVerifyMsg)\ncertVerifyMsg.hasSignatureAlgorithm = true\n// 此處省略代碼","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"根據","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"驗證證書和簽名","attrs":{}},{"type":"text","text":"這一小節的描述，如果服務端要求客戶端發送證書則","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.certReq","attrs":{}}],"attrs":{}},{"type":"text","text":"不爲nil。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"的主體也是證書，該證書的來源爲客戶端","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"tls.Config","attrs":{}}],"attrs":{}},{"type":"text","text":"配置的證書，在本例中客戶端配置證書邏輯如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"tlsConf.NextProtos = append(tlsConf.NextProtos, \"h2\", \"http/1.1\")\ntlsConf.Certificates = make([]tls.Certificate, 1)\nif len(certFile) > 0 && len(keyFile) > 0 {\n var err error\n tlsConf.Certificates[0], err = tls.LoadX509KeyPair(certFile, keyFile)\n if err != nil {\n return nil, err\n }\n}","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"既然要發送證書給服務端，那麼同服務端邏輯一樣也需要發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"提供消息簽名的信息。客戶端簽名邏輯和服務端簽名邏輯一致，因此筆者不再贅述。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，客戶端需要發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"給服務端：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"finished := &finishedMsg{\n verifyData: hs.suite.finishedHash(c.out.trafficSecret, hs.transcript),\n}\nhs.transcript.Write(finished.marshal())\nc.out.setTrafficSecret(hs.suite, hs.trafficSecret)","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"需要注意的是","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"在第二次計算密鑰時就已經被賦值，當","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"發送後，利用","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"hs.trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"生成的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"AEAD","attrs":{}}],"attrs":{}},{"type":"text","text":"加密算法會對客戶端要發送的業務數據進行加密。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，客戶端的握手流程全部完成。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"小結","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1、如果服務端要求客戶端發送證書，則客戶端會發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2、發送","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息並設置發送業務數據時的密鑰信息。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Server讀Client最後的消息","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先，服務端在TLS握手的最後階段，會先判斷是否要求客戶端發送證書，如果要求客戶端發送證書則處理客戶端發送的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息。服務端處理","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateMsgTLS13","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"certificateVerifyMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"消息的邏輯和客戶端處理這兩個消息的邏輯類似。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其次，讀取客戶端發送的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"， 並驗證消息的完整性，驗證邏輯和客戶端驗證","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"邏輯一致。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，設置服務端讀取業務數據時的加密信息：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"c.in.setTrafficSecret(hs.suite, hs.trafficSecret)","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"hs.trafficSecret","attrs":{}}],"attrs":{}},{"type":"text","text":"在服務端第二次計算加密信息時就已經賦值，當讀完客戶端發送的","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"finishedMsg","attrs":{}}],"attrs":{}},{"type":"text","text":"之後再執行此步驟是爲了避免無法解密客戶端發送的握手信息。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"至此，服務端的握手流程全部完成。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"握手完成之後","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"完成上述流程後，筆者還想試試看能不能從握手過程獲取的密鑰信息對業務數據進行解密。說幹就幹，下面是筆者在TLS握手完成之後用Client連接發送了一條消息的代碼。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"go"},"content":[{"type":"text","text":"// main.go 握手完成之後，client發送了一條數據\nclient.Write([]byte(\"點贊關注：新世界雜貨鋪\"))","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面是運行Demo後的輸出截圖：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/88/883a1a9dd9a6cad0ecf7517924963124.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"圖中紅色箭頭部分爲在Internet中真實傳輸的數據，藍色箭頭部分爲其解密結果。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"一點感慨","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"關於TLS握手流程的文章筆者想寫很久了，現在總算得償所願。筆者不敢保證把TLS握手過程的每一個細節都描述清楚，所以如果中間有什麼問題還請各位讀者及時指出，大家相互學習。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"寫到這裏時筆者的內心也略有忐忑，畢竟這中間涉及了很多密碼學相關的知識，而在筆者各種瘋狂查資料期間發現國內具有權威性的文章還是太少。像","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"ECDH","attrs":{}}],"attrs":{}},{"type":"text","text":"之類的關鍵詞在百度百科都沒有收錄，果然維基百科纔是爸爸呀。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後一點感概是關於Go中","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"io.Reader ","attrs":{}}],"attrs":{}},{"type":"text","text":"和","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"io.Writer","attrs":{}}],"attrs":{}},{"type":"text","text":"這兩個接口的，不得不說這兩個接口的設計真的很簡單但是真的非常通用。筆者的Demo正是基於這兩個接口實現，否則筆者的心願很難完成。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"挖坑","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在上一篇文章中，筆者給了一條彩蛋——“下一期TLS/SSL握手流程敬請期待”。哇，這可真的是自己坑自己了，本篇文章未完成之前，筆者愣是斷更了也沒敢發別的文章。果然自己作的死，哭着也要作完。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有了前車之鑑，筆者決定以後不再放彩蛋，而是挖坑（填坑時間待定😊）：本篇中主要介紹了TLS1.3的握手流程，那麼TLS1.2也快了～","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後，衷心希望本文能夠對各位讀者有一定的幫助。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"注","attrs":{}},{"type":"text","text":"：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1. 寫本文時， 筆者所用go版本爲: go1.15.2","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2. 文章中所用完整例子：https://github.com/Isites/go-coder/blob/master/http2/tls/main.go","attrs":{}}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}
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