Allow use of CONNECT tunneling for unencrypted requests

[NicolasDorier]

I need to create a secure tunnel with HTTP uri, but the HttpConnection only create a tunnel if this the destination is secure, or websocket IsNonSecureWebSocketScheme.

The reason I need it, is that I want to use a Socksv5 HTTP proxy (HTTPTunnelPort on Tor) to access onion website through the HttpClient. Onion website starts by http, but are indeed secure and the HTTP Proxy of Tor only support tunneling.

Our current workaround hack is to code our own HTTP Socks proxy implementation in C#, which does not handle lot's of edge cases in HTTP.

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[scalablecory]

HttpClient will proxy non-secure requests, but only via an HTTP proxy, not a SOCKS proxy. If you're using a HTTP proxy and it's not working for you, can you please supply some code so we can see your usage?

Beyond HTTP proxies, we have an outstanding issue for SOCKS proxy support in #17740, and for HTTPS proxy support in #31113.

Additionally, we'll have a lot more flexibility around this (so you can easily plug in whatever transport you'd like) with #1793.

[NicolasDorier]

@scalablecory HttpClient is proxying HTTP request, the only problem is that it is not creating tunnel for it.

If you proxy to HTTPS or web socket, the first message to the proxy is CONNECT.
If you proxy HTTP, it is GET/POST. TOR HTTP proxy does not support anything else than CONNECT.

I am happy to see direct SOCKS support being worked on though.

[NicolasDorier]

I am excited about the work at #1793 . I hope the flexibility provided will be enough for my use case.

[scalablecory]

Gotcha.

Typically the form "GET http://foo.com" is used for unencrypted requests (this allows for more efficient connection pooling) and "CONNECT foo.com" is used for encrypted requests.

The ask, then, would be to make this selectable. #1793 would allow a CONNECT tunnel to be used, though we might want to add an option to SocketsHttpHandler directly -- will leave this issue open to see if there's more interest.

[NicolasDorier]

Awesome, I am looking forward! Will keep using my home grown proxy for now.