WebClient through kerberos secured proxy is not working

Questions

I am trying to access a website using the vert.x WebClient but it seems that the WebClient is not able to make the connection.

Checked the "httpclient" inside org.apache.httpcomponents, and I can go through the proxy without issues, but I am using vert.x so need the WebClient to work.

Looked into the org.apache.httpcomponents code and found this is what its doing:

1. Create a socket connection to the secure proxy.
2. Issue a connect request to the proxy server over the socket.
3. The proxy server challenge the connect request and returns back headers that includes "Negotiate".
4. Generate a kerberos token from the KDC for the proxy server.
5. Send over the socket the connect request again with the header: "Proxy-Authorization: Negotiate "
6. The connection is then successful.
7. The socket is then upgraded to TLS.

WebClient is not able to do that, I tried to do the bits of obtaining the Token and passing it in the "Proxy-Authorization" header in a connect request, but its not working, Still getting "407 Proxy Authentication Required".

Version

Same issue on 4.4.3 and 4.5.3

Context

I encountered an exception which looks suspicious while ...

Do you have a reproducer?

No

Steps to reproduce

Just a simple WebClient.getAbs(...) request where ProxyOptions are specified.