When I do some calls to SOAP services to SharePoint 2010 site (e.g. CopyIntoItemsLocal from Copy.asmx or CheckInFile from Lists.asmx) I get HTTP 403 Forbidden.

I suspect this is somehow requires specific authentication (like Digest in SharePoint 2013) in addition to standard HTTP credentials passing in response to HTTP 401.

Does anyone know how to handle it with pure HTTP calls?
I use WinInet in native C++ application - so no any specific JavaScript libs available