*SSLPrivateKeyMethod does not correctly report back signing errors

Motivation:

Due a bug we did not correctly report back signing errors and just silently convert these to a success

Modifications:

- Explict check the result value
- Set resultBytes to null on failure

Result:

Correctly handle signing failures

Author: normanmaurer

openssl-classes/src/main/java/io/netty/internal/tcnative/SSLPrivateKeyMethodTask.java

@@ -16,7 +16,6 @@
 package io.netty.internal.tcnative;
 
 abstract class SSLPrivateKeyMethodTask extends SSLTask implements AsyncTask {
-    private static final byte[] EMPTY = new byte[0];
     private final AsyncSSLPrivateKeyMethod method;
 
     // Will be accessed via JNI.
@@ -45,7 +44,7 @@ public void onSuccess(long ssl, byte[] result) {
             @Override
             public void onError(long ssl, Throwable cause) {
                 // Return 0 as this signals back that the operation failed.
-                resultBytes = EMPTY;
+                resultBytes = null;
                 callback.onResult(ssl, 0);
             }
         });

openssl-dynamic/src/main/c/sslcontext.c

@@ -2381,12 +2381,13 @@ static enum ssl_private_key_result_t tcn_private_key_complete_java(SSL *ssl, uin
         }
 
         // The task is complete, retrieve the return value that should be signaled back.
+        jint returnValue = (*e)->GetIntField(e, state->ssl_task->task, sslTask_returnValue);
         jbyteArray resultBytes = (*e)->GetObjectField(e, state->ssl_task->task, sslPrivateKeyMethodTask_resultBytes);
 
         tcn_ssl_task_free(e, state->ssl_task);
         state->ssl_task = NULL;
 
-        if (resultBytes == NULL) {
+        if (returnValue != 1 || resultBytes == NULL) {
             return ssl_private_key_failure;
         }