TLS协议

TLS简介

TLS协议基于面向连接的TCP协议，它可被看作由两个主要部分组成：TLS记录协议(TLS Record Protocol)和TLS握手协议(TLS Handshake Protocol)。它可以实现传输应用数据前的通信双方身份的认证，加密套件(对称加密算法，签名算法等)的协商，会话密钥的协商，以及握手完成后的数据加密、压缩传输、以及数据完整性的校验。

TLS握手具体的过程

1.TCP三次握手

TCP的三次握手过程，建立TCP连接。

2.TLS握手过程

(1)TLS的握手是建立在TCP连接之上的。
(2)客户端向服务器发送client hello数据包。
在client hello数据包中说明了客户端使用的协议版本号、随机数、加密套件以及其他的扩展。wireshark抓包结果如下图：

(3)服务器收到client hello后向客户端发送server hello数据包。
在server hello中包含了协议版本号、随机数、服务器选择的加密套件以及其他的扩展。wireshark抓包结果如下图：

(4)服务器向客户端发送证书。wireshark抓包结果如下图：

(5)服务器向客户端发送server key exchange，其中包含了pubkey，wireshark抓包结果如下图：

(6)服务器向客户端发送server hello done，wireshark抓包结果如下图：

(7)客户端向服务器发送client key exchange、change cipher spec，wireshark抓包结果如下图：

(8)服务器向客户端发送new session ticket，wireshark抓包结果如下图：

(9)服务器向客户端发送change cipher spec， wireshark抓包结果如下图:

(10)服务器向客户端发送hello request， wireshark抓包结果如下图:
服务器向客户端发送change cipher spec， wireshark抓包结果如下图:

(11)客户端向服务器发送数据，wireshark抓包结果如下图:

openssl实现TLS

1.证书准备

在tls的通信中可以设置，双方认证和单向认证。如果需要双向的认证，需要有通信双方的证书。通过openssl的提供的应用程序功能可以搭建自己的简单的CA，从而颁发证书。

2.基于openssl的TLS实现

客户端程序

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define MAXBUF 1024

#define CA_FILE "/home/xx/桌面/Untitled Folder/CA/ca.crt"
#define CLIENT_KEY "/home/xx/桌面/Untitled Folder/Client/client.key"
#define CLIENT_CERT "/home/xx/桌面/Untitled Folder/Client/client.crt"


/*打印对方主体和颁发者信息*/
void ShowCerts(SSL * ssl)
{
    X509 *cert;
    char *line;
    cert = SSL_get_peer_certificate(ssl);
    if (cert != NULL) {
        printf("数字证书信息:\n");
        line = X509_NAME_oneline(X509_get_subject_name(cert), 0, 0);
        printf("证书: %s\n", line);
        free(line);
        line = X509_NAME_oneline(X509_get_issuer_name(cert), 0, 0);
        printf("颁发者: %s\n", line);
        free(line);
        X509_free(cert);
    } else {
        printf("无证书信息！\n");
    }
}

int main(int argc, char **argv)
{
    int sockfd, len;
    long int result = LONG_MAX;
    struct sockaddr_in dest;
    char buffer[MAXBUF + 1];
    SSL_CTX *ctx;
    SSL *ssl;
    const SSL_METHOD *method;

    /*初始化工作*/
    SSL_library_init();
    SSL_load_error_strings();
    OpenSSL_add_all_algorithms();  
    method = TLSv1_2_client_method();
    ctx = SSL_CTX_new(method);
    if (!ctx) {
        printf("create ctx is failed.\n");
    }
    /*设置会话的握手方式*/ 
    SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT, 0);

    /*加载CA FILE*/
    if (SSL_CTX_load_verify_locations(ctx, CA_FILE, 0) != 1) {
        SSL_CTX_free(ctx);
        printf("Failed to load CA file %s", CA_FILE);
    }
    if (SSL_CTX_set_default_verify_paths(ctx) != 1) {
        SSL_CTX_free(ctx);
        printf("Call to SSL_CTX_set_default_verify_paths failed");
    }
    /*设置证书链的最大深度*/
    SSL_CTX_set_verify_depth(ctx,1);

    /*加载客户端证书*/
    if (SSL_CTX_use_certificate_file(ctx, CLIENT_CERT, SSL_FILETYPE_PEM) != 1) {
        SSL_CTX_free(ctx);
        printf("Failed to load client certificate from %s", CLIENT_KEY);
    }
    /*加载客户端私钥*/
    if (SSL_CTX_use_PrivateKey_file(ctx, CLIENT_KEY, SSL_FILETYPE_PEM) != 1) {
        SSL_CTX_free(ctx);
        printf("Failed to load client private key from %s", CLIENT_KEY);
    }
    /*验证私钥*/
    if (SSL_CTX_check_private_key(ctx) != 1) {
        SSL_CTX_free(ctx);
        printf("SSL_CTX_check_private_key failed");
    }

    /*处理握手多次*/  
    SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY); 

    /*创建tcp套接字*/
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
        perror("Socket");
        exit(errno);
    }
    bzero(&dest, sizeof(dest));
    dest.sin_family = AF_INET;
    dest.sin_port = htons(atoi(argv[2]));
    if (inet_aton(argv[1], (struct in_addr *) &dest.sin_addr.s_addr) == 0{
        perror(argv[1]);
        exit(errno);
    }

    if (connect(sockfd, (struct sockaddr *) &dest, sizeof(dest)) != 0) {
        perror("Connect ");
        exit(errno);
    }

    /*创建SSL*/
    ssl = SSL_new(ctx);
    if (ssl == NULL) {
        printf("SSL_new error.\n");
    }
    /*将fd添加到ssl层*/
    SSL_set_fd(ssl, sockfd);

    /*TLS握手*/
    if (SSL_connect(ssl) == -1) {
        printf("SSL_connect fail.\n");
        ERR_print_errors_fp(stderr);
    } else {
        printf("Connected with %s encryption\n", SSL_get_cipher(ssl));
        ShowCerts(ssl);
    }
    result=SSL_get_verify_result(ssl);
    if(result != X509_V_OK)
    {
        printf("There are some mistakes in verification:error %ld\n",result);
    }
    else
    {
        printf("Verification success!\n");
    }
    bzero(buffer, MAXBUF + 1);
    len = SSL_read(ssl, buffer, MAXBUF);
    if (len > 0) {
        printf("接收消息成功:'%s'，共%d个字节的数据\n", buffer, len);
    } else {
        printf("消息接收失败！错误代码是%d，错误信息是'%s'\n", errno, strerror(errno));
        goto exit;
    }
    bzero(buffer, MAXBUF + 1);
    strcpy(buffer, "from client->server");

    len = SSL_write(ssl, buffer, strlen(buffer));
    if (len < 0) {
        printf("消息'%s'发送失败！错误代码是%d，错误信息是'%s'\n", buffer, errno, strerror(errno));
    } else {
        printf("消息'%s'发送成功，共发送了%d个字节！\n", buffer, len);
    }

exit
    SSL_shutdown(ssl);
    SSL_free(ssl);
    close(sockfd);
    SSL_CTX_free(ctx);
    return 0;

}

服务器端程序

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define MAXBUF 1024

#define CA_FILE "/home/xx/桌面/Untitled Folder/CA/ca.crt"
#define SERVER_KEY "/home/xx/桌面/Untitled Folder/Server/server.key"
#define SERVER_CERT "/home/xx/桌面/Untitled Folder/Server/server.crt"

void ShowCerts(SSL * ssl)    
{    
    X509 *cert;    
    char *line;
    cert = SSL_get_peer_certificate(ssl);    
    if (cert != NULL) {    
        printf("num cert messsage:\n");    
        line = X509_NAME_oneline(X509_get_subject_name(cert), 0, 0);    
        printf("cert: %s\n", line);    
        free(line);    
        line = X509_NAME_oneline(X509_get_issuer_name(cert), 0, 0);    
        printf("Issuer: %s\n", line);    
        free(line);    
        X509_free(cert);    
    } else   
      printf("no cert message \n");    
} 



int main(int argc, char **argv)
{
    int sockfd, new_fd;
    int reuse = 0;
    long int result = LONG_MAX;
    socklen_t len;
    struct sockaddr_in my_addr, their_addr;
    unsigned int myport, lisnum;
    char buf[MAXBUF + 1];
    SSL_CTX *ctx;
    const SSL_METHOD *method;

    if (argv[1]) {
        myport = atoi(argv[1]);
    } else {
        myport = 7838;
    }

    if (argv[2]) {
        lisnum = atoi(argv[2]);
    } else {
        lisnum = 2;
    }

    SSL_library_init();
    OpenSSL_add_all_algorithms();
    SSL_load_error_strings();

    method = TLSv1_2_server_method();
    ctx = SSL_CTX_new(method);
    if (ctx == NULL) {
        ERR_print_errors_fp(stdout);
        exit(1);
    }

    /*设置认证方式，要求认证客户端，实现双向认证*/
    SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, 0);
    /*加载CA FILE*/
    if (SSL_CTX_load_verify_locations(ctx, CA_FILE, 0) != 1) {
        SSL_CTX_free(ctx);
        printf("Failed to load CA file %s", CA_FILE);
    }
    /*加载服务端证书*/
    if (SSL_CTX_use_certificate_file(ctx, SERVER_CERT, SSL_FILETYPE_PEM) <= 0) {
        ERR_print_errors_fp(stdout);
        exit(1);
    }
    /*加载服务端私钥*/
    if (SSL_CTX_use_PrivateKey_file(ctx, SERVER_KEY, SSL_FILETYPE_PEM) <= 0) {
        printf("use private key fail.\n");
        ERR_print_errors_fp(stdout);
        exit(1);
    }
    /*验证私钥*/
    if (!SSL_CTX_check_private_key(ctx)) {
        ERR_print_errors_fp(stdout);
        exit(1);
    }
    //处理握手多次  
    SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY); 

    if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
        perror("socket");
        exit(1);
    } else {
        printf("socket created\n");
    }

    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse)) < 0){
        printf("setsockopet error\n");
        return -1;
    }

    bzero(&my_addr, sizeof(my_addr));
    my_addr.sin_family = PF_INET;
    my_addr.sin_port = htons(myport);
    my_addr.sin_addr.s_addr = INADDR_ANY;

    if (bind(sockfd, (struct sockaddr *) &my_addr, sizeof(struct sockaddr)) == -1) {
        perror("bind");
        exit(1);
    } 
    printf("Server bind success.\n");

    if (listen(sockfd, lisnum) == -1) {
        perror("listen");
        exit(1);
    } 
    printf("Server begin to listen\n");

    while (1) {
        SSL *ssl;
        len = sizeof(struct sockaddr);

        if ((new_fd = accept(sockfd, (struct sockaddr *) &their_addr, &len)) == -1) {
            perror("accept");
            exit(errno);
        } 

        printf("Server: receive a connection from %s, port %d, socket %d\n", inet_ntoa(their_addr.sin_addr), ntohs(their_addr.sin_port), new_fd);

        ssl = SSL_new(ctx);
        if (ssl == NULL) {
            printf("SSL_new error.\n");
        }

        SSL_set_fd(ssl, new_fd);

        if (SSL_accept(ssl) == -1) {
            perror("accept");
            ERR_print_errors_fp(stderr);  
            close(new_fd);
            break;
        }
        printf("Server with %s encryption\n", SSL_get_cipher(ssl));
        ShowCerts(ssl);
        result=SSL_get_verify_result(ssl);
        if(result != X509_V_OK)
        {
            printf("There are some mistakes in verification:error %ld\n",result);
        }
        else
        {
            printf("Verification success!\n");
        }

        bzero(buf, MAXBUF + 1);
        strcpy(buf, "server->client");
        len = SSL_write(ssl, buf, strlen(buf));
        if (len <= 0) {
            printf("消息'%s'发送失败！错误代码是%d，错误信息是'%s'\n", buf, errno, strerror(errno));
            goto exit;
        } else {
            printf("消息'%s'发送成功，共发送了%d个字节！\n", buf, len);
        }

        bzero(buf, MAXBUF + 1);
        len = SSL_read(ssl, buf, MAXBUF);
        if (len > 0) {
            printf("接收消息成功:'%s'，共%d个字节的数据\n", buf, len);
        } else {
            printf("消息接收失败！错误代码是%d，错误信息是'%s'\n", errno, strerror(errno));
        }
exit:
        SSL_shutdown(ssl);
        SSL_free(ssl);
        close(new_fd);
    }

    close(sockfd);
    SSL_CTX_free(ctx);
    return 0;
}

参考

http://blog.csdn.net/liangyihuai/article/details/53098482