Hooking InternetOpenUrl

Question

I am writing an application that should hook InternetOpenUrl and InternetReadFile in another process.

In the hooked version of InternetOpenUrl, it will check whether lpszUrl passed to it matches a regular expression. If matches, record the handle returned by the actual InternetOpenUrl.

Then in the hooked version of InternetReadFile, it will read from a file instead of calling the actual InternetReadFile if the hFile argument equals to the recorded handle .

I found out that Windows will try to connect to the server provided immediately when calling InternetOpenUrl and the function will return NULL if failed to establish the connection.

But I want this mechanism to work even without Internet connection, so it seems that I can't get a handle by calling the actual InternetOpenUrl in my hooked one when the regular expression matches.

So how can I get it to work?

UPDATE:

Now I call InternetOpen to get a dummy handle. It seems that handles returned by InternetOpen and InternetOpenUrl won't equal.

But I'm not sure whether it is guaranteed, looking for better choices.

Answer 1

So you are attempting to redirect a URL query to a file... You could always host the file, then you will be guaranteed a valid handle in either scenario. However, assuming a local file, I think if you specify the "file://" protocol in the URL it may work in the way you desire.