用libcurl 登录网站

libcurl 可以发送和接收HTTP消息，因此可以发送用户名、密码和验证码来登录网站，网上有不少这方面的内容，但不甚完整，我摸索了两天，将其中要点记录下来。

基本步骤

1. 正常访问登录页面，访问时，设置CURL参数，指定COOKIE文件。
2. 获取验证码的图片。
3. 发送用户名，密码和验证码（附加上第一次访问时指定的COOKIE）。

 /*首次访问页面，指定COOKIE文件，因为我们后面发送登录的账户和密码时，需要这个COOKIE*/
 1 void accessFirstTime(){
     void* curl = curl_easy_init();
     curl_easy_setopt(curl, CURLOPT_URL, POSTURL);
     curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
     curl_easy_setopt(curl, CURLOPT_WRITEDATA, );
     curl_easy_setopt(curl, CURLOPT_VERBOSE,);
     curl_easy_setopt(curl, CURLOPT_COOKIEJAR, "D:/dearTony/t1.cookie");
     curl_easy_setopt(curl,CURLOPT_SSL_VERIFYPEER,false);//设定为不验证证书和HOST
     curl_easy_setopt(curl,CURLOPT_SSL_VERIFYHOST,false);
     CURLcode res = curl_easy_perform(curl);
     curl_easy_cleanup(curl);
     return;
 }

上面代码中，line 3, POSTURL 是需要访问得登录页面地址。 特别要注意的是，line 7, 8, 9 第七行告诉libcurl 将服务器发送过来的COOKIE存在哪个文件， 8,9行告诉服务器不需要SSL验证。

 /*将图片存盘*/
 size_t downImage(void *buffer, size_t size, size_t nmemb, void *userp){
     FILE *fp = fopen("d:/dearTony/validateImg","wb");
     fwrite(buffer,size, nmemb, fp);
     fclose(fp);
     return true;
 }

 /*获取验证码*/
 void getYZM(){
     const char* targetUrl= "https://***.***.com/cgi-bin/img/validateimg"; //图片的URL
     void* curl = curl_easy_init();  

     curl_easy_setopt(curl, CURLOPT_URL, targetUrl);
     curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, downImage);
     curl_easy_setopt(curl, CURLOPT_WRITEDATA, );
     curl_easy_setopt(curl, CURLOPT_VERBOSE,);
     curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "D:/dearTony/t1.cookie");
     curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER,);//设定为不验证证书和HOST
     curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST,);

     CURLcode res = curl_easy_perform(curl);
     curl_easy_cleanup(curl);
     return;
 }

注意line 19,20,21  , 如果不附加COOKIE，  则获取的验证图片内容不对。

最后，发送账户名，密码和验证码。

 #define POSTURL "https://***.***.com/cgi-bin/user/Login"
 #define POSTFIELDS "fundAccount=28000000****&isSaveAccount=1&mac=&normalpassword=&\
 password=23c0d43c50972a7c6b927e61c52f15bd3d71c03e05ae9fce\
 fd8b7ac29d19b293c25d72c651756050c4e843e31de0c05b9bca6e8b547\
 9a90f5f1bb59818e0b983991b4259bbdd35d9ae423ef5602c8956bae122270f68908c229ca63a40114d4586c4bfcb90764&\
 password_Controls=normal&\
 retUrl=&ticket=%&type=Z"

 /*登录，ticket是上一步取得的验证码*/
 bool login(QString& ticket){
     QString postf = QString(POSTFIELDS).arg(ticket);
     std::string tstr = postf.toStdString();
     void* curl = curl_easy_init();
     const char *postArg = tstr.c_str();
     struct curl_slist *chunk = NULL;
     chunk = curl_slist_append(chunk, "Accept: image/gif, image/jpeg, image/pjpeg, application/x-ms-application, application/xaml+xml, application/x-ms-xbap, application/msword, application/vnd.ms-powerpoint, application/vnd.ms-excel, */*");
     chunk = curl_slist_append(chunk, "Accept-Encoding: text/plain");
     chunk = curl_slist_append(chunk, "Accept-Language: zh-Hans-CN, zh-Hans; q=0.8, en-US; q=0.5, en; q=0.3");
     chunk = curl_slist_append(chunk, "Connection: Keep-Alive");
     chunk = curl_slist_append(chunk, "Cache-Control: no-cache");
     chunk = curl_slist_append(chunk, "Host: ***.***.com");
     chunk = curl_slist_append(chunk, "Content-Type: application/x-www-form-urlencoded");
     chunk = curl_slist_append(chunk, "Referer: https://***.***.com/cgi-bin/user/Login");
     chunk = curl_slist_append(chunk, "User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 10.0; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; .NET CLR 2.0.50727; .NET CLR 3.0.30729; .NET CLR 3.5.30729)");

     curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
     curl_easy_setopt(curl, CURLOPT_URL, POSTURL);
     curl_easy_setopt(curl, CURLOPT_POSTFIELDS, postArg);    /*POST的参数，通过F12抓包得到*/
     curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
     curl_easy_setopt(curl, CURLOPT_WRITEDATA, );
     curl_easy_setopt(curl, CURLOPT_POST, );    /*表明是POST方法*/
     curl_easy_setopt(curl, CURLOPT_VERBOSE,);
     curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "D:/dearTony/t1.cookie");  //一定要带上
     curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER,);//设定为不验证证书和HOST
     curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST,);

     int response_code = ;
     CURLcode res = curl_easy_perform(curl);
     curl_easy_cleanup(curl);
     curl_slist_free_all(chunk);
     return true;
 }

line15~24是HTTP头，可以用浏览器的F12功能抓包得到。

总结： 一定要注意COOKIE选择和 SSL 选项。