JdkSslContext supported cipher suites incorrect

Motivation:
JdkSslContext builds the list of supported cipher suites, but assumes that ciphers prefixed with SSL_ and TLS_ will be interchangeable. However this is not the case and only applies to a small subset of ciphers. This results in the JdkSslContext attempting to use unsupported ciphers.

Modifications:
- When building the list of ciphers in JdkSslContext we should first check if the engine supports the TLS_ prefix cipher.

Result:
Fixes https://github.com/netty/netty/issues/7673

handler/src/main/java/io/netty/handler/ssl/JdkSslContext.java

@@ -105,7 +105,13 @@ public class JdkSslContext extends SslContext {
             //[3] https://www.ibm.com/developerworks/community/forums/html/topic?id=9b5a56a9-fa46-4031-b33b-df91e28d77c2
             //[4] https://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=71770
             if (supportedCipher.startsWith("SSL_")) {
-                SUPPORTED_CIPHERS.add("TLS_" + supportedCipher.substring("SSL_".length()));
+                final String tlsPrefixedCipherName = "TLS_" + supportedCipher.substring("SSL_".length());
+                try {
+                    engine.setEnabledCipherSuites(new String[]{tlsPrefixedCipherName});
+                    SUPPORTED_CIPHERS.add(tlsPrefixedCipherName);
+                } catch (IllegalArgumentException ignored) {
+                    // The cipher is not supported ... move on to the next cipher.
+                }
             }
         }
         List<String> ciphers = new ArrayList<String>();

handler/src/test/java/io/netty/handler/ssl/SslContextTest.java

@@ -18,12 +18,20 @@ package io.netty.handler.ssl;
 import org.junit.Assert;
 import org.junit.Test;
 
-import javax.net.ssl.SSLException;
 import java.io.File;
 import java.io.IOException;
+import java.security.KeyManagementException;
+import java.security.NoSuchAlgorithmException;
 import java.security.PrivateKey;
 import java.security.spec.InvalidKeySpecException;
 
+import javax.net.ssl.SSLContext;
+import javax.net.ssl.SSLEngine;
+import javax.net.ssl.SSLException;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assume.assumeNotNull;
+
 public abstract class SslContextTest {
 
     @Test(expected = IOException.class)
@@ -85,5 +93,26 @@ public abstract class SslContextTest {
         newServerContext(crtFile, keyFile, "");
     }
 
+    @Test
+    public void testSupportedCiphers() throws KeyManagementException, NoSuchAlgorithmException, SSLException {
+        SSLContext jdkSslContext = SSLContext.getInstance("TLS");
+        jdkSslContext.init(null, null, null);
+        SSLEngine sslEngine = jdkSslContext.createSSLEngine();
+
+        String unsupportedCipher = "TLS_DH_anon_WITH_DES_CBC_SHA";
+        IllegalArgumentException exception = null;
+        try {
+            sslEngine.setEnabledCipherSuites(new String[] {unsupportedCipher});
+        } catch (IllegalArgumentException e) {
+            exception = e;
+        }
+        assumeNotNull(exception);
+        File keyFile = new File(getClass().getResource("test_unencrypted.pem").getFile());
+        File crtFile = new File(getClass().getResource("test.crt").getFile());
+
+        SslContext sslContext = newServerContext(crtFile, keyFile, null);
+        assertFalse(sslContext.cipherSuites().contains(unsupportedCipher));
+    }
+
     protected abstract SslContext newServerContext(File crtFile, File keyFile, String pass) throws SSLException;
 }