This answer comes late, but we just have hit the problem (I can’t believe it, it seems a very big bug).
All what it said seems true, but it’s not default HostnameVerifier the culprit but the troubleshooter. When HttpsClient do afterConnect first try to establish setHost (only when socket is SSLSocketImpl):
SSLSocketFactory factory = sslSocketFactory;
try {
if (!(serverSocket instanceof SSLSocket)) {
s = (SSLSocket)factory.createSocket(serverSocket,
host, port, true);
} else {
s = (SSLSocket)serverSocket;
if (s instanceof SSLSocketImpl) {
((SSLSocketImpl)s).setHost(host);
}
}
} catch (IOException ex) {
// If we fail to connect through the tunnel, try it
// locally, as a last resort. If this doesn't work,
// throw the original exception.
try {
s = (SSLSocket)factory.createSocket(host, port);
} catch (IOException ignored) {
throw ex;
}
}
If you use a custom SSLSocketFactory without override createSocket() (the method without parameters), the createSocket well parametrized is used and all works as expected (with client sni extension). But when second way it’s used (try to setHost en SSLSocketImpl) the code executed is:
// ONLY used by HttpsClient to setup the URI specified hostname
//
// Please NOTE that this method MUST be called before calling to
// SSLSocket.setSSLParameters(). Otherwise, the {@code host} parameter
// may override SNIHostName in the customized server name indication.
synchronized public void setHost(String host) {
this.host = host;
this.serverNames =
Utilities.addToSNIServerNameList(this.serverNames, this.host);
}
The comments say all. You need to call setSSLParameters before client handshake. If you use default HostnameVerifier, HttpsClient will call setSSLParameters. But there is no setSSLParameters execution in the opposite way. The fix should be very easy for Oracle:
SSLParameters paramaters = s.getSSLParameters();
if (isDefaultHostnameVerifier) {
// If the HNV is the default from HttpsURLConnection, we
// will do the spoof checks in SSLSocket.
paramaters.setEndpointIdentificationAlgorithm("HTTPS");
needToCheckSpoofing = false;
}
s.setSSLParameters(paramaters);
Java 9 is working as expected in SNI. But they (Oracle) seem not to want fix this: