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TLS 握手过程

TLS 握手的详细过程可参考下图：

TLS 握手过程

从 wireshark 抓包，也可以看到握手的详细流程，建议抓包加强理解，以下是抓包 https://q.shanyue.tech 时的握手流程

通过 curl -vvv --head 来查看握手信息:

$ curl -vvv --head  https://q.shanyue.tech
*   Trying 111.6.180.235...
* TCP_NODELAY set
* Connected to q.shanyue.tech (111.6.180.235) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
*   CAfile: /etc/ssl/cert.pem
  CApath: none
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES128-GCM-SHA256
* ALPN, server accepted to use h2
* Server certificate:
*  subject: CN=q.shanyue.tech
*  start date: Dec  2 00:00:00 2019 GMT
*  expire date: Dec  1 12:00:00 2020 GMT
*  subjectAltName: host "q.shanyue.tech" matched cert's "q.shanyue.tech"
*  issuer: C=US; O=DigiCert Inc; OU=www.digicert.com; CN=Encryption Everywhere DV TLS CA - G1
*  SSL certificate verify ok.
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Using Stream ID: 1 (easy handle 0x7f95ba80dc00)

握手过程​

在 TLS 1.2 中，握手协议过程需要耗费两个 RTT，过程如下

  • [OUT] Client Hello，客户端选出自身支持的 TLS 版本号、cipher suites、一个随机数、SessionId 传送给服务器端 (有可能可服用 Session)
  • [IN] Server Hello，服务器端选出双方都支持的 TLS 版本，cipher suite 、一个随机数、SeesionId 给客户端
  • [IN] Certificate，服务器端给客户端发送证书，用以身份验证及提供公钥
  • [IN] Server Key Exchange，服务器端给客户端发送秘钥交换算法的一些参数
  • [IN] Server Finished
  • [OUT] Client Key Exchange，客户端给服务器端发送秘钥交换算法的一些参数，计算出预备主密钥 (pre master key)，作为随机数传递给服务器端 (这个随机数是安全的)。双方根据三个随机数生成对称加密中的秘钥
  • [OUT] Change Cipher Spec，告知对方以后的消息将要使用 TLS 记录层协议进行加密
  • [OUT] Finished，发送第一条加密的消息并完整性验证
  • [IN] Change Cipher Spec，告知以后的消息将要使用 TLS 记录层协议进行加密
  • [IN] Finished，发送第一条加密的消息并完整性验证

参考​