現在來談下驗證碼圖片的獲取方式，帶有驗證碼的地方都會附帶有個刷新按鈕，而刷新按鈕的地方就是獲取驗證碼網址代碼。如果看過前面寫的《模擬網頁行為之工具篇》就會很容易定位到代碼位置。定位到代碼位置后看下圖：

基本可以看到的是獲取驗證碼的網址是：https://ipin.siren24.com/stickyCaptcha。但這還不夠，因為前篇我們還講過關于cookie的概念，需要帶有cookie去刷新驗證碼才是有效的驗證碼，但如何獲取cookie，看下圖：

可見cookie類型是hostonly的，hostonly就是說只能在當前網頁獲取cookie。有了上述抓包分析，那么對驗證碼的流程有了基本的了解。

那么接下來的步驟分為

1.獲取https://ipin.siren24.com/stickyCaptcha的cookie,。

2. 帶cookie刷新驗證碼獲取圖片數據。

獲取hostonly的cookie，c++代碼實現如下：

std::string CWebLoginDlg::GetCookie( std::string url ) {LPSTR lpszData = NULL;DWORD dwSize=0; lpszData= new char[1];memset(lpszData,0, 1);retry: if (!InternetGetCookieA(url.c_str(), "", lpszData, &dwSize)){DWORD er = GetLastError();if (er == ERROR_INSUFFICIENT_BUFFER){delete []lpszData;lpszData = new char[dwSize+1];memset(lpszData,0,dwSize+1);goto retry;}else{ATLTRACE("cookie is null");}}std::string strCookieContent = std::string(lpszData, dwSize);delete [] lpszData;return strCookieContent; }參數即為：https://ipin.siren24.com/stickyCaptcha

若cookie為httponly類型，獲取的方式也不一樣，C++代碼如下：

std::wstring CWebLoginDlg::GetCookieEx( std::wstring url ) {LPWSTR lpszData = NULL;DWORD dwSize=0; lpszData= new wchar_t[1];memset(lpszData,0, sizeof(wchar_t));retry: if (!InternetGetCookieEx(url.c_str(), L"JSESSIONID", lpszData, &dwSize, 0x00002000, NULL)){DWORD er = GetLastError();if (er == ERROR_INSUFFICIENT_BUFFER){delete []lpszData;lpszData = new wchar_t[dwSize+1];memset(lpszData,0,dwSize+1);goto retry;}else{ATLTRACE("cookie is null");}}std::wstring strCookieContent = std::wstring(lpszData, dwSize);delete [] lpszData;return strCookieContent; }

刷新驗證碼圖片數據，我采用的方式是用curl庫，實際上所有網頁走網絡協議方式都可以借助curl來實現，但這里只單純刷驗證碼圖片數據。上面步驟把cookie獲取到后，將其編輯成以下格式，然后將其作為參數cookie，傳入到獲取網頁返回數據函數，c++代碼表示如下：

std::string cookie = GetCookie("https://ipin.siren24.com/stickyCaptcha"); char nline[1024]; sprintf_s(nline, sizeof(nline),"%s; domain=ipin.siren24.com; path=/; hostOnly", cookie.c_str()); m_pCurlClient->GetURLResource("https://ipin.siren24.com/stickyCaptcha", nline, ret);

GetURLResource實現如下：

struct MemoryStruct {char *memory;size_t size; };size_t CurlClient::WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp) {size_t realsize = size * nmemb;if (userp == NULL){return realsize;}struct MemoryStruct *mem = (struct MemoryStruct *)userp;//ATLTRACE("222 chunk addr %x %d %d threaid %d", (DWORD)mem, mem->size, realsize, GetCurrentThreadId());mem->memory = (char*)realloc(mem->memory, mem->size + realsize + 1);if(mem->memory == NULL) {/* out of memory! */ printf("not enough memory (realloc returned NULL)\n");return 0;}memcpy(&(mem->memory[mem->size]), contents, realsize);mem->size += realsize;mem->memory[mem->size] = 0;return realsize; }bool CurlClient::GetURLResource( std::string url, std::string cookie, std::string &rev) {bool ssl = (url.find("https") != std::string::npos);struct MemoryStruct chunk;chunk.memory = (char*)malloc(1); chunk.size = 0; CURL *curl;CURLcode res;curl = curl_easy_init();if (curl){if (!cookie.empty()){char nline[1024];sprintf_s(nline, sizeof(nline),"Set-Cookie: ""%s", cookie.c_str());res = curl_easy_setopt(curl, CURLOPT_COOKIELIST, nline);}curl_easy_setopt(curl, CURLOPT_URL, url.c_str());int agentIndex = m_Multi ? GetCurrentThreadId() % m_UserAgentList.size() : 0;curl_easy_setopt(curl, CURLOPT_USERAGENT, m_UserAgentList[agentIndex].c_str());if (ssl){curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);}curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &CurlClient::WriteMemoryCallback);curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)&chunk);curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1L);curl_easy_setopt(curl, CURLOPT_FORBID_REUSE, 1); //多線程完成任務馬上斷開連接curl_easy_setopt(curl, CURLOPT_TIMEOUT, 30);curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 15);curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);res = curl_easy_perform(curl);if (res != CURLE_OK){char curlerror[1024 * 5] = {0};sprintf_s(curlerror, _countof(curlerror), "返回的信息 %s",curl_easy_strerror(res));m_Error = curlerror;}rev = std::string(chunk.memory, chunk.size);free(chunk.memory);curl_easy_cleanup(curl);}return res == CURLE_OK; }
以上，驗證碼的圖片數據即可獲取。

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