A DESCRIPTION OF THE PROBLEM :
I am trying to connect to a web server that uses https through a proxy which requires authentication, but it doesn't work.

The HttpsURLConnection class is sending the first request to open the tunnel without the Proxy-Authorization header even if forced.

In this case the server will return "407 Proxy Authentication Required".

I think that this behavior is caused by the method sun.net.www.protocol.http.HttpURLConnection.sendCONNECTRequest()
It creates a new connect request without adding the Proxy-Authorization header.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
public class TestProxy {

  @Test
  public void testOne() throws IOException {

    final String PROXY_USERNAME = "username";
    final String PROXY_PASSWORD = "password";
    final String PROXY_HOSTNAME = "proxyhostname";
    final int PROXY_PORT = 8080;

    Authenticator.setDefault(
        new Authenticator() {
          @Override
          public PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication(PROXY_USERNAME, PROXY_PASSWORD.toCharArray());
          }
        });

    Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(PROXY_HOSTNAME, PROXY_PORT));

    URL url = new URL("https://www.google.com");

    HttpsURLConnection connection = (HttpsURLConnection) url.openConnection(proxy);

    assertNotEquals(407, connection.getResponseCode());

  }

  @Test
  public void testTwo() throws IOException {

    final String PROXY_USERNAME = "username";
    final String PROXY_PASSWORD = "password";
    final String PROXY_HOSTNAME = "proxyhostname";
    final int PROXY_PORT = 8080;

    Authenticator.setDefault(
        new Authenticator() {
          @Override
          public PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication(PROXY_USERNAME, PROXY_PASSWORD.toCharArray());
          }
        });

    Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(PROXY_HOSTNAME, PROXY_PORT));

    URL url = new URL("https://www.google.com");

    HttpsURLConnection connection = (HttpsURLConnection) url.openConnection(proxy);

    String userCredentials = PROXY_USERNAME + ":" + PROXY_PASSWORD;
    String basicAuth = "Basic " + new String(Base64.getEncoder().encode(userCredentials.getBytes()));
    connection.setRequestProperty("Proxy-Authorization", basicAuth);

    assertNotEquals(407, connection.getResponseCode());

  }

}

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
200 OK
ACTUAL -
407 Proxy Authentication Required

---------- BEGIN SOURCE ----------
I think that this behavior is caused by the method sun.net.www.protocol.http.HttpURLConnection.sendCONNECTRequest()
It creates a new « connect request » without adding the « Proxy-Authorization » header.

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
The workaround is to connect to a http address at first so the proxy server will register the user agent and authorize connecting without adding Proxy-Authorization header

FREQUENCY : always