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纯C语言实现HTTPS客户端

C语言实现HTTPS请求,下面是代码

#include <stdio.h>
#include <memory.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>

#include <openssl/crypto.h>
#include <openssl/x509.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>
#include <openssl/err.h>

void main(int argc, char **argv)
{
SSL *ssl = NULL;
SSL_CTX *ctx = NULL;
const SSL_METHOD *client_method;
X509 *server_cert;
int sd,err;
char *str,*hostname,outbuf[4096],inbuf[4096],host_header[512];
struct hostent *host_entry;
struct sockaddr_in server_socket_address;
struct in_addr ip;

/* (1) 初始化openssl库 */
SSL_library_init();
ERR_load_crypto_strings();
SSL_load_error_strings();
OpenSSL_add_all_algorithms();

client_method = SSL上网3_client_method( );
ctx = SSL_CTX_new(client_method);
if (!ctx) {
fprintf (stderr, "SSL_CTX_new failed:\n");
ERR_print_errors_fp (stderr);
return;
}
printf("(1) SSL context initialized\n\n");

/* (2) 把域名转换成ip地址 */
hostname = argv[1];
host_entry = gethostbyname(hostname);
bcopy(host_entry->h_addr, &(ip.s_addr), host_entry->h_length);
printf("(2) '%s' has IP address '%s'\n\n", hostname, inet_ntoa(ip));

/* (3) 用tcp连接到server的443端口 */
sd = socket(AF_INET, SOCK_STREAM, 0);
memset(&server_socket_address, '\0', sizeof(server_socket_address));
server_socket_address.sin_family = AF_INET;
server_socket_address.sin_port = htons(443);
memcpy(&(server_socket_address.sin_addr.s_addr),
host_entry->h_addr, host_entry->h_length);
err = connect(sd, (struct sockaddr*) &server_socket_address,
sizeof(server_socket_address));
if (err < 0) { perror("can't connect to server port"); exit(1); }
printf("(3) TCP connection open to host '%s', port %d\n\n",
hostname, server_socket_address.sin_port);

/* (4) 在tcp连接上进行ssl握手 */
ssl = SSL_new(ctx); /* 创建ssl句柄 ,之后的send,recv都在ssl句柄上进行 */
if (!ssl) {
fprintf (stderr, "SSL_new failed:\n");
ERR_print_errors_fp (stderr);
return;
}

SSL_set_fd(ssl, sd); /* 把ssl句柄绑定到scoket */
err = SSL_connect(ssl); /* 启动ssl握手 */
printf("(4) SSL endpoint created & handshake completed\n\n");

/* (5) 打印出协商的好的加密密文 */
printf("(5) SSL connected with cipher: %s\n\n", SSL_get_cipher(ssl));

/* (6) 打印服务器的证书 */
server_cert = SSL_get_peer_certificate(ssl);
printf("(6) server's certificate was received:\n\n");
str = X509_NAME_oneline(X509_get_subject_name(server_cert), 0, 0);
printf(" subject: %s\n", str);
str = X509_NAME_oneline(X509_get_issuer_name(server_cert), 0, 0);
printf(" issuer: %s\n\n", str);
/* 这里对证书进行验证 */
X509_free(server_cert);

/* (7) 握手完成 --- 开始在ssl上发送http请求 */
sprintf(host_header,"Host: %s:443\r\n",hostname);
strcpy(outbuf,"GET / HTTP/1.1\r\n");
strcat(outbuf,host_header);
strcat(outbuf,"Connection: close\r\n");
strcat(outbuf,"\r\n");
err = SSL_write(ssl, outbuf, strlen(outbuf));
shutdown (sd, 1); /* send EOF to server */
printf("(7) sent HTTP request over encrypted channel:\n\n%s\n",outbuf);


/* (8) 通过ssl句柄读取服务器响应 */
printf ("(8) got back %d bytes of HTTP response:\n");
do{
memset(inbuf, 0, sizeof(inbuf));
err = SSL_read(ssl, inbuf, sizeof(inbuf) - 1);
printf ("%s",inbuf);
inbuf[err] = '\0';
}while(err > 0);
/* (9) 释放连接,句柄 */
SSL_shutdown(ssl);
close(sd);
SSL_free(ssl);
SSL_CTX_free(ctx);
printf("(9) all done, cleaned up and closed connection\n\n");
}

编译运行

如果提示找不到openssl的头文件, 自行搜索openssl库的安装

gcc -o https_client https_client.c -lssl -lcrypto

访问百度

./https_client www.baidu.com

如果域名不能解析, 自己代码中去掉域名解析的部分,自己把地址替换成ip

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