8319817: Charset constructor should make defensive copy of aliases

Reviewed-by: rriggs, alanb, bpb, iris, jpai

src/java.base/share/classes/java/nio/charset/Charset.java

@@ -42,7 +42,6 @@ import java.util.Iterator;
 import java.util.Locale;
 import java.util.Map;
 import java.util.NoSuchElementException;
-import java.util.Objects;
 import java.util.ServiceConfigurationError;
 import java.util.ServiceLoader;
 import java.util.Set;
@@ -706,7 +705,12 @@ public abstract class Charset
      *         If the canonical name or any of the aliases are illegal
      */
     protected Charset(String canonicalName, String[] aliases) {
-        String[] as = Objects.requireNonNullElse(aliases, zeroAliases);
+        String[] as =
+            aliases == null ?
+                zeroAliases :
+                VM.isSystemDomainLoader(getClass().getClassLoader()) ?
+                    aliases :
+                    Arrays.copyOf(aliases, aliases.length);
 
         // Skip checks for the standard, built-in Charsets we always load
         // during initialization.

test/jdk/java/nio/charset/Charset/AliasesCopy.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @bug 8319817
+ * @summary Check that aliases cannot be mutated
+ * @run junit AliasesCopy
+ */
+
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CharsetEncoder;
+import java.util.Set;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertIterableEquals;
+
+public class AliasesCopy {
+    private static final Set<String> ALIASES_SET = Set.of("foo-alias");
+    private static final String[] ALIASES_ARRAY = ALIASES_SET.toArray(String[]::new);
+
+    @Test
+    public void aliasesCopy() {
+        final FooCharset cs = new FooCharset(ALIASES_ARRAY);
+        ALIASES_ARRAY[0] = "bar-alias";
+        assertIterableEquals(ALIASES_SET, cs.aliases());
+    }
+
+    private static final class FooCharset extends Charset {
+        private FooCharset(String[] aliases) {
+            super("foo", aliases);
+        }
+
+        @Override
+        public CharsetEncoder newEncoder() {
+            throw new RuntimeException("not implemented");
+        }
+
+        @Override
+        public CharsetDecoder newDecoder() {
+            throw new RuntimeException("not implemented");
+        }
+
+        @Override
+        public boolean contains(Charset cs) {
+            throw new RuntimeException("not implemented");
+        }
+    }
+}