This is a followup to JDK-8193683.

There is a bug currently in the way ServerHandshakers creates HandshakeHashes. If we do the following valid API pattern:

    SSLServerSocket sslServerSocket =
        (SSLServerSocket) sslssf.createServerSocket(serverPort);
    SSLSocket sslSocket = (SSLSocket) sslServerSocket.accept();

    // This is *AFTER* a SSLSocketImpl was created!!!
    sslSocket.setNeedClientAuth(true);

    InputStream sslIS = sslSocket.getInputStream();
    sslIS.read();

The SSLSocketImpl is initialized with no clientauth required, which creates a ServerHandshaker with no auth, which creates a HandshakeHash(false), which only creates 3 clones. Now return to the app's setNeedClientAuth call, which updates the ServerHandshaker to require the client auth, but it doesn't update HandshakeHash to now require 4 digests.

Actually, this bug could be updated to better calculate the exact number of HandshakeHash clones that are needed.

 102 /**
 103 * Create a new HandshakeHash.
 104 * The number of necessary digest clones is calculated in Handshaker
 105 */
 106 HandshakeHash(int numDigests) {
 107 clonesNeeded = numDigests;
 108 }

 228 try {
 229 finMD = CloneableDigest.getDigest(normalizeAlgName(s), 4);
 230 } catch (NoSuchAlgorithmException e) {
 231 throw new Error(e);
 232 }

and in Handshaker.java

 555 // We accumulate digests of the handshake messages so that
 556 // we can read/write CertificateVerify and Finished messages,
 557 // getting assurance against some particular active attacks.
 558 int numDigests = 2;
 559 if (needCertVerify) {
 560 numDigests++;
 561 }
 562 if (useExtendedMasterSecret) {
 563 numDigests++;
 564 }
 565 handshakeHash = new HandshakeHash(numDigests);

Note that this code also needs a way to update the HandshakeHash if clientAuth is turned on after the Handshaker has been created.