Proxy support does not work properly with CONNECT on https requests

Describe the bug

Using Axios 0.26.1 behind a corporate HTTP tunneling proxy to an HTTPS destination, once the proxy connection is made, a POST method is issued, rather than a CONNECT to establish the TLS tunnel to the destination host where the POST should be sent. Result is Error: socket hang up, as the proxy expects a CONNECT to be issued and drops the connection

Specifically, using wireshark to monitor the activity of the script goes as follow:

TCP SYN < TCP SYN, ACK TCP ACK HTTP POST < TCP FIN, ACK TCP ACK

If you use curl with the same environment, the packets are as follows:

TCP SYN < TCP SYN, ACK TCP ACK HTTP CONNECT < HTTP Connection established TCP ACK TLS Client Hello < TLS Server Hello … encrypted POST and response follows

To Reproduce

export http_proxy="http://user:password@10.123.173.125:80"
export https_proxy="http://user:password@10.123.173.125:80"

http.post('https://api.github.com/user/repos', {});

Expected behavior

When connecting to an HTTPS server through a tunneling HTTP proxy, the CONNECT method should be used to establish the TLS handshake before issuing the POST

Environment

• Axios Version 0.26.1
• Adapter HTTP
• Node.js Version 14.8.0
• OS: Windows 10 (10.0.19042.1526)

[ppati000]

If anyone is interested in trying out HTTPS-over-HTTP support in Axios, feel free to check https://github.com/axios/axios/pull/5037. The implementation has some limitations (no redirects) but maybe it still fits your use cases. Would love to hear back from you!

Edit: Not directly related to this issue, but please note that there is currently (as of 1.1.2) some trouble around a breaking change in the proxy configuration: https://github.com/axios/axios/issues/5079

[Nevon]

Why is the “possible bug” label removed? Clearly the automatic proxy configuration is incorrect. If the protocol is HTTPS and the HTTPS_PROXY environment variable set, the client should use the tunnel protocol by sending a CONNECT request, wait to get a 200 OK back and then send the original request on the same connection.