Handling HTTP Authentication
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4/8/2010
When handling HTTP authentication, the application can use several functions: InternetErrorDlg, or a function that uses InternetSetOption that sets its own Internet options. InternetErrorDlg checks the headers associated with an HINTERNET handle to find hidden errors, such as status codes from a proxy or server. InternetSetOption can be used to set the user name and password for the proxy and server.
For any customized function that adds its own WWW-Authenticate or Proxy-Authenticate headers, the INTERNET_FLAG_NO_AUTH flag should be set to disable the Windows Internet Services (WinInet) API authentication.
In the example, dwErrorCode is used to store any errors associated with the call to HttpSendRequest. HttpSendRequest completes successfully, even if the proxy or server requires authentication. When the FLAGS_ERROR_UI_FILTER_FOR_ERRORS flag is passed to InternetErrorDlg, the function checks the headers for any hidden errors. These hidden errors would include any requests for authentication. InternetErrorDlg displays the appropriate dialog box to prompt the user for the necessary data. The FLAGS_ERROR_UI_FLAGS_GENERATE_DATA and FLAGS_ERROR_UI_FLAGS_CHANGE_OPTIONS flags should also be passed to InternetErrorDlg, so that the function constructs the appropriate data structure for the error and stores the results of the dialog box in the HINTERNET handle.