use our SimpleKey impl so that there's less[] copy

... also allows for an empty key to work like MRI
(fixes jruby/jruby#2854)

Author: kares

src/main/java/org/jruby/ext/openssl/HMAC.java

@@ -87,7 +87,7 @@ public static IRubyObject digest(IRubyObject self, IRubyObject digest, IRubyObje
         final ByteList bytes = data.asString().getByteList();
         try {
             Mac mac = getMacInstance(algName);
-            mac.init( new SecretKeySpec(keyBytes, mac.getAlgorithm()) );
+            mac.init( new SimpleSecretKey(mac.getAlgorithm(), keyBytes) );
             mac.update(bytes.getUnsafeBytes(), bytes.getBegin(), bytes.getRealSize());
             return runtime.newString( new ByteList(mac.doFinal(), false) );
         }
@@ -108,7 +108,7 @@ public static IRubyObject hexdigest(IRubyObject self, IRubyObject digest, IRubyO
         final ByteList bytes = data.asString().getByteList();
         try {
             final Mac mac = getMacInstance(algName);
-            mac.init( new SecretKeySpec(keyBytes, mac.getAlgorithm()) );
+            mac.init( new SimpleSecretKey(mac.getAlgorithm(), keyBytes) );
             mac.update(bytes.getUnsafeBytes(), bytes.getBegin(), bytes.getRealSize());
             return runtime.newString( toHEX( mac.doFinal() ) );
         }
@@ -135,7 +135,7 @@ public IRubyObject initialize(IRubyObject key, IRubyObject digest) {
         try {
             this.mac = getMacInstance(algName);
             this.key = key.asString().getBytes();
-            mac.init( new SecretKeySpec(this.key, mac.getAlgorithm()) );
+            mac.init( SimpleSecretKey.copy(mac.getAlgorithm(), this.key) );
         }
         catch (NoSuchAlgorithmException e) {
             throw getRuntime().newNotImplementedError("Unsupported MAC algorithm (HMAC[-]" + algName + ")");
@@ -159,7 +159,7 @@ public IRubyObject initialize_copy(final IRubyObject obj) {
         try {
             this.mac = SecurityHelper.getMac(algName);
             this.key = that.key;
-            mac.init( new SecretKeySpec(key, algName) );
+            mac.init( SimpleSecretKey.copy(algName, key) );
         }
         catch (NoSuchAlgorithmException e) {
             throw getRuntime().newNotImplementedError("Unsupported MAC algorithm (" + algName + ")");

src/test/ruby/test_hmac.rb

@@ -35,4 +35,10 @@ def test_correct_digest
     @h2.update("\xFF") # invalid utf-8 char
     assert_equal('0770623462e782b51bb0689a8ba4f3f1', @h2.hexdigest) # calcualted on MRI
   end
+
+  def test_hexdigest_with_empty_key
+    result = OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('md5'), "", "foo")
+    assert_equal "4acb10ca3965a14a080297db0921950c", result
+  end
+
 end