How can I add an extra http header using IHTTPNegotiate?

Question

How can I add an extra header to the request using IHTTPNegotiate? I added the interface but functions BeginningTransaction & OnResponse never get called.

TNameSpaceHandler = class(TComObject, IInternetProtocol, IHttpNegotiate)  
...
    function BeginningTransaction(szURL, szHeaders: LPCWSTR; dwReserved: DWORD;
        out szAdditionalHeaders: LPWSTR): HResult; stdcall;
    function OnResponse(dwResponseCode: DWORD; szResponseHeaders, szRequestHeaders: LPCWSTR;
        out szAdditionalRequestHeaders: LPWSTR): HResult; stdcall;
...
end;

Can you show more code? If you're implementing a [pass-through pluggable protocol handler](http://stackoverflow.com/a/3711662/1768303) for your URL namespace, there should be a separate object implementing `IInternetProtocolSink` to be passed to the up-stream protocol handler. That's the object that should also be implementing `IServiceProvider` and `IHttpNegotiate`. — noseratio, Oct 13 '13 at 02:21

Stijn Sanders · Accepted Answer · 2013-10-11T18:32:14.923

2

I'm silently assuming you're intercepting traffic by both implementing IInternetProcol and the IInternetProtocolSink and IInternetBindInfo interfaces, and call the original IInternetProtocol to have the work done. In that case it's important to know the direction of who calls who.

If the original handler want the additional headers, it will first cast your IInternetProtocolSink into a IServiceProvider interface (with QueryInterface), and call QueryService for an IHttpNegotiate instance. By convenience you can add the current object instance and also implement IHttpNegotiate on the same object, but this is not required.

When the BeginTransaction method of your IHttpNegotiate gets called, get a IHttpNegotiate instance on the ProtSink of the Start call, call BeginTransaction and add your header(s) before passing them to the caller.

edited Oct 11 '13 at 18:32

answered Oct 09 '13 at 17:54

Stijn Sanders

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I don't think this will add a header to the request. – Oct 09 '13 at 17:56
This will only get request headers. But it will not add an additional header. – Oct 11 '13 at 15:43
Read the last paragraph again. Closely. – Stijn Sanders Oct 11 '13 at 17:50
I have tried what you said but it will not work. It needs an actual code example. By the way have you tested this before? Could you add extra headers? – Oct 11 '13 at 17:53
Just to be sure I understand: do you want an extra header to arrive into the browser, or do you want an extra header on the outgoing request to the webserver? – Stijn Sanders Oct 11 '13 at 18:11
Yes an extra header before it sends a HTTP request to the Webserver. Which is what `IHttpNegotiate::BeginningTransaction` does. – Oct 11 '13 at 18:14
how would I send an extra header to the browser – GreatAndPowerfulOz Feb 27 '20 at 17:35

How can I add an extra http header using IHTTPNegotiate?

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