A simple web client implemented by WinHTTP service APIs

winHttpClient.cpp

#include <windows.h>
#include <winhttp.h>

#include <array>
#include <iostream>
#include <string>

#pragma comment(lib, "Winhttp.lib")

using namespace std;

/*
 * ref. https://stackoverflow.com/questions/2616011/easy-way-to-parse-a-url-in-c-cross-platform
 */
struct Uri {
	wstring QueryString, Path, Protocol, Host, PortStr;
	unsigned short PortBin;

	static Uri Parse(const wstring &uri) {
		Uri result;
		typedef wstring::const_iterator iterator_t;

		if (uri.length() == 0) return result;

		// get query start
		iterator_t queryStart = find(uri.begin(), uri.end(), L'?');

		// protocol
		iterator_t protocolStart = uri.begin();
		iterator_t protocolEnd = find(protocolStart, uri.end(), L':');	// "://"

		if (protocolEnd != uri.end()) {
			wstring prot = &*(protocolEnd);
			if ((prot.length() > 3) && (prot.substr(0, 3) == L"://")) {
				result.Protocol = wstring(protocolStart, protocolEnd);
				protocolEnd += 3;			// "://""
			} else
				protocolEnd = uri.begin();	// no protocol
		} else
			protocolEnd = uri.begin();		// no protocol

		// host
		iterator_t hostStart = protocolEnd;
		iterator_t pathStart = find(hostStart, uri.end(), L'/');	// get pathStart

		iterator_t hostEnd = find(protocolEnd, (pathStart != uri.end()) ?
								pathStart : queryStart, L':');		// check for port
		result.Host = wstring(hostStart, hostEnd);

		// port
		if ((hostEnd != uri.end()) && ((&*(hostEnd))[0] == L':')) {
			hostEnd++;
			iterator_t portEnd = (pathStart != uri.end()) ? pathStart : queryStart;
			result.PortStr = wstring(hostEnd, portEnd);
			result.PortBin = stoi(result.PortStr.c_str());
		} else {
			for (const auto& [proto, port] : proto_port)
				if (wcsnicmp(result.Protocol.c_str(), proto.c_str(), proto.length()) == 0) {
					result.PortBin = port;
					break;
				}
		}

		// path
		if (pathStart != uri.end())
			result.Path = wstring(pathStart, queryStart);

		// query
		if (queryStart != uri.end())
			result.QueryString = wstring(queryStart, uri.end());

		return result;
	} // Parse

private:
	static inline array<pair<wstring, int>, 2> proto_port = {
												make_pair<>(wstring(L"https"), 443),
												make_pair<>(wstring(L"http"),   80)
												};
}; // uri

static size_t _iconv(const string& from, wstring &to) {
	const char *str = from.c_str();
	size_t retSize = 0, len = from.length();
	wchar_t *wstr = new wchar_t[len + 1];
	if (!wstr) return 0;
	SecureZeroMemory(wstr, sizeof(wchar_t) * (len + 1));

	errno_t err = mbstowcs_s(&retSize, wstr, len + 1, str, len);
	if (0 == err) to.assign(wstr);
	delete [] wstr;

	return 0 == err ? retSize : 0;
}

static void _usage(const char* app) {
	cout << "Usage : " << app << " <URL> [--no-cert-check]" << endl;
}

int SimpleHttpsClient (
	const wstring& Host,
	const unsigned short& Port,
	const wstring& Uri,
	bool useHttps = false,
	bool ignoreSslCert = false
)
{
	HINTERNET hSession = 0;
	HINTERNET hConnect = 0;
	HINTERNET hRequest = 0;

	hSession = WinHttpOpen(
				L"Simple WinHttp Client/1.0", WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
				WINHTTP_NO_PROXY_NAME, WINHTTP_NO_PROXY_BYPASS, 0);
	if (!hSession) {
		cerr << "WinHttpOpen() error (" << GetLastError() << ")\n";
		goto error;
	}

	hConnect = WinHttpConnect(hSession, Host.c_str(), Port, 0);
	if (!hConnect) {
		cerr << "WinHttpConnect() error (" << GetLastError() << ")\n";
		goto error;
	}

	hRequest = WinHttpOpenRequest(
				hConnect, L"GET", Uri.c_str(), NULL, WINHTTP_NO_REFERER,
				WINHTTP_DEFAULT_ACCEPT_TYPES, useHttps ? WINHTTP_FLAG_SECURE : 0);
	if (!hRequest) {
		cerr << "WinHttpOpenRequest() error (" << GetLastError() << ")\n";
		goto error;
	}

	bool retry;
	do {
		retry = false;
		DWORD result = NO_ERROR;

		if (WinHttpSendRequest(
				hRequest, WINHTTP_NO_ADDITIONAL_HEADERS, 0,
				WINHTTP_NO_REQUEST_DATA, 0, 0, 0) == FALSE
			)
		{
			result = GetLastError();
			// try again if Certificate is invaid yet client allows it
			if (result == ERROR_WINHTTP_SECURE_FAILURE && ignoreSslCert) {
				DWORD dwFlags = SECURITY_FLAG_IGNORE_UNKNOWN_CA |
								SECURITY_FLAG_IGNORE_CERT_WRONG_USAGE |
								SECURITY_FLAG_IGNORE_CERT_CN_INVALID |
								SECURITY_FLAG_IGNORE_CERT_DATE_INVALID;
				if (WinHttpSetOption(hRequest, WINHTTP_OPTION_SECURITY_FLAGS, &dwFlags, sizeof(dwFlags)))
					retry = true;
			} else if (result == ERROR_WINHTTP_RESEND_REQUEST) {
				/*
				 * Some authentication schemes require multiple transactions WinHttpSendRequest could return the
				 * error, ERROR_WINHTTP_RESEND_REQUEST. When this error is encountered, the application should
				 * continue to resend the request until a response is received that does not contain a 401 or 407
				 * status code. A 200 status code indicates that the resource is available and the request is
				 * successful.
				 *
				 * ref. http://msdn.microsoft.com/en-us/library/windows/desktop/aa383144%28v=vs.85%29.aspx
				 */
				retry = true;
			}
		}
	} while (retry);

	if (!WinHttpReceiveResponse(hRequest, NULL)) {
		cerr << "WinHttpReceiveResponse() error (" << GetLastError() << ")\n";
		goto error;
	}

	DWORD dwAvailable = 0, dwReceived = 0, dwTotal = 0;
	/*
	 * ... you could instead start with an appropriately-sized buffer (perhaps 1 megabyte), and resize that
	 * if necessary. In practice, WinHttpQueryDataAvailable returns no more than 8 kilobytes.
	 *
	 * ref. https://learn.microsoft.com/en-us/windows/win32/api/winhttp/nf-winhttp-winhttpquerydataavailable
	 */
	array<char, 8 * 1024> buffer;
	char *pBuffer = &buffer[0];
	while (WinHttpQueryDataAvailable(hRequest, &dwAvailable) && dwAvailable) {
		WinHttpReadData(hRequest, pBuffer, dwAvailable, &dwReceived);
		cout << pBuffer;

		dwTotal += dwReceived;
		dwReceived = 0;
		buffer.fill(0);
	}

	cout << "\nReceived " << dwTotal << " bytes data.\n";

error:
	if (hRequest) WinHttpCloseHandle(hRequest);
	if (hConnect) WinHttpCloseHandle(hConnect);
	if (hSession) WinHttpCloseHandle(hSession);

	return 0;
}

int main(int argc, char *argv[])
{
	wstring request;
	bool useHttps = false, ignoreCert = false;

	if (argc < 2) {
		_usage(argv[0]);
		return 0;
	}

	_iconv(argv[1], request);
	Uri query = Uri::Parse(request);

	if (0 == wcsnicmp(query.Protocol.c_str(), L"https", 5))
		useHttps = true;

	if (argc >= 3) {
		if (0 == strnicmp(argv[2], "--no-cert-check", 16)) {
			ignoreCert = true;
		} else {
			cout << "Unknown parameter " << argv[2] << endl;
			_usage(argv[0]);
			return 0;
		}
	}

#ifdef _DEBUG
	wcout << (useHttps ? L"https://" : L"http://") << query.Host << L":" << query.PortBin
			<< query.Path << L" " << (ignoreCert ? L"(no-cert-check)" : L"(cert-check)") << endl;
#endif

	return SimpleHttpsClient(query.Host, query.PortBin, query.Path, useHttps, ignoreCert);
}

// cl /EHsc /Ox /std:c++17 winHttpsClient.cpp