How to deal with multi-step WWW-Authenticate with the new HttpClient

[Weijun Wang]

Hi, All,

I am trying the new HttpClient to deal with a multi-step Negotiate 
authentication with Windows IIS, and here is my code.

HttpClient hc = HttpClient.newBuilder().build();
var req = HttpRequest.newBuilder().uri(new URI(args[0]));
while (true) {
    var resp = hc.send(req.build(), HttpResponse.BodyHandlers.ofString());
    System.out.println("--------------------");
    System.out.println(resp.statusCode());
    String auth = resp.headers().allValues("WWW-Authenticate")
            .stream()
            .filter(s -> s.startsWith("Negotiate"))
            .findFirst()
            .orElseThrow()
            .substring(9)
            .trim();
    System.out.println("incoming " + auth);
    byte[] in = auth.isEmpty() ? new byte[0] :Base64.getDecoder().decode(auth);
    byte[] out = calculate_token_from_incoming(in);
    if (out == null) break; // if status is still >400. No way to continue
    String sent = Base64.getEncoder().encodeToString(out);
    System.out.println("--------------------");
    System.out.println("outgoing " + sent);
    req.header("Authorization", "Negotiate " + sent);
}

This works when there is only one request and one reply, but fails when there 
is more.

Is this the correct way? Is there some keep-connnection thing I need to care 
about?

Thanks,
Max

p.s. Or maybe there is something wrong with IIS. This is a corner case.