4、应用层https27

**HTTPS应用层**

HTTPS（Hypertext Transfer Protocol Secure）是HTTP协议的安全版本，通过SSL/TLS（Secure Sockets Layer/Transport Layer Security）加密传输数据。HTTPS应用层主要负责处理客户端和服务器之间的通信。

### HTTPS工作原理1. **建立连接**: 客户端向服务器发送一个请求，要求建立一个HTTPS连接。
2. **证书验证**:服务器返回一个证书给客户端，证书中包含了服务器的公钥和身份信息。
3. **密钥交换**: 客户端使用证书中的公钥加密一份随机数，并将其发送回服务器。服务器使用自己的私钥解密该随机数，然后用它来加密数据。
4. **数据传输**: 客户端和服务器之间开始传输加密的数据。

### HTTPS应用层实现####1. SSL/TLS握手协议SSL/TLS握手协议是HTTPS连接建立过程中的一个重要部分。下面是一个简单的示例：

c// Client-side codevoid ssl_handshake() {
 // Step1: Client sends a "Client Hello" message to the server struct client_hello_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t cipher_suite;
 uint8_t random_number[32];
 } client_hello;

 // ...

 // Step2: Server responds with a "Server Hello" message struct server_hello_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t cipher_suite;
 uint8_t random_number[32];
 } server_hello;

 // ...

 // Step3: Client and server exchange certificates struct certificate_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t serial_number;
 uint8_t subject_name[256];
 uint8_t issuer_name[256];
 uint8_t public_key[512];
 } client_cert, server_cert;

 // ...

 // Step4: Client and server perform key exchange struct key_exchange_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t session_id;
 uint8_t random_number[32];
 } client_key_exchange, server_key_exchange;

 // ...
}

// Server-side codevoid ssl_handshake() {
 // ...

 // Step1: Server sends a "Server Hello" message to the client struct server_hello_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t cipher_suite;
 uint8_t random_number[32];
 } server_hello;

 // ...

 // Step2: Client responds with a "Client Key Exchange" message struct client_key_exchange_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t session_id;
 uint8_t random_number[32];
 } client_key_exchange;

 // ...
}

c// Client-side codevoid  {
 // Step1: Client sends an HTTP request to the server struct  {
 uint8_t method;
 uint16_t uri;
 uint16_t version;
 uint8_t headers[256];
 uint8_t body[1024];
 }  />
 // ...

 // Step2: Server responds with an HTTP response struct  {
 uint8_t status_code;
 uint16_t reason_phrase;
 uint16_t version;
 uint8_t headers[256];
 uint8_t body[1024];
 }  />
 // ...
}

// Server-side codevoid  {
 // ...

 // Step1: Server receives an HTTP request from the client struct  {
 uint8_t method;
 uint16_t uri;
 uint16_t version;
 uint8_t headers[256];
 uint8_t body[1024];
 }  />
 // ...

 // Step2: Server generates an HTTP response and sends it back to the client struct  {
 uint8_t status_code;
 uint16_t reason_phrase;
 uint16_t version;
 uint8_t headers[256];
 uint8_t body[1024];
 }  />
 // ...
}

c// Client-side codevoid  {
 // Step1: Client sends a "Client Hello" message to the server struct client_hello_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t cipher_suite;
 uint8_t random_number[32];
 } client_hello;

 // ...

 // Step2: Server responds with a "Server Hello" message struct server_hello_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t cipher_suite;
 uint8_t random_number[32];
 } server_hello;

 // ...

 // Step3: Client and server exchange certificates struct certificate_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t serial_number;
 uint8_t subject_name[256];
 uint8_t issuer_name[256];
 uint8_t public_key[512];
 } client_cert, server_cert;

 // ...

 // Step4: Client and server perform key exchange struct key_exchange_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t session_id;
 uint8_t random_number[32];
 } client_key_exchange, server_key_exchange;

 // ...
}

// Server-side codevoid  {
 // ...

 // Step1: Server sends a "Server Hello" message to the client struct server_hello_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t cipher_suite;
 uint8_t random_number[32];
 } server_hello;

 // ...

 // Step2: Client responds with a "Client Key Exchange" message struct client_key_exchange_msg {
 uint8_t msg_type;
 uint16_t version;
 uint16_t session_id;
 uint8_t random_number[32];
 } client_key_exchange;

 // ...
}