Add anonymous SASL mechanism

Author: acogoluegnes

src/main/java/com/rabbitmq/stream/sasl/AnonymousSaslMechanism.java

@@ -0,0 +1,33 @@
+// Copyright (c) 2020-2023 Broadcom. All Rights Reserved.
+// The term "Broadcom" refers to Broadcom Inc. and/or its subsidiaries.
+//
+// This software, the RabbitMQ Stream Java client library, is dual-licensed under the
+// Mozilla Public License 2.0 ("MPL"), and the Apache License version 2 ("ASL").
+// For the MPL, please see LICENSE-MPL-RabbitMQ. For the ASL,
+// please see LICENSE-APACHE2.
+//
+// This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND,
+// either express or implied. See the LICENSE file for specific language governing
+// rights and limitations of this software.
+//
+// If you have any questions regarding licensing, please contact us at
+// [email protected].
+package com.rabbitmq.stream.sasl;
+
+import java.nio.charset.StandardCharsets;
+
+/** The <code>ANONYMOUS</code> {@link SaslMechanism}. */
+public final class AnonymousSaslMechanism implements SaslMechanism {
+
+  public static final SaslMechanism INSTANCE = new AnonymousSaslMechanism();
+
+  @Override
+  public String getName() {
+    return "ANONYMOUS";
+  }
+
+  @Override
+  public byte[] handleChallenge(byte[] challenge, CredentialsProvider credentialsProvider) {
+    return "".getBytes(StandardCharsets.UTF_8);
+  }
+}

src/main/java/com/rabbitmq/stream/sasl/DefaultSaslConfiguration.java

@@ -28,13 +28,16 @@ public final class DefaultSaslConfiguration implements SaslConfiguration {
       new DefaultSaslConfiguration(PlainSaslMechanism.INSTANCE.getName());
   public static final SaslConfiguration EXTERNAL =
       new DefaultSaslConfiguration(ExternalSaslMechanism.INSTANCE.getName());
+  public static final SaslConfiguration ANONYMOUS =
+      new DefaultSaslConfiguration(AnonymousSaslMechanism.INSTANCE.getName());
 
   private final Map<String, SaslMechanism> mechanisms =
       Collections.unmodifiableMap(
           new HashMap<String, SaslMechanism>() {
             {
               put(PlainSaslMechanism.INSTANCE.getName(), PlainSaslMechanism.INSTANCE);
               put(ExternalSaslMechanism.INSTANCE.getName(), ExternalSaslMechanism.INSTANCE);
+              put(AnonymousSaslMechanism.INSTANCE.getName(), AnonymousSaslMechanism.INSTANCE);
             }
           });
   private final String mechanism;

src/test/java/com/rabbitmq/stream/impl/AuthenticationTest.java

@@ -147,6 +147,14 @@ void updateSecret() throws Exception {
     }
   }
 
+  @Test
+  @TestUtils.BrokerVersionAtLeast(TestUtils.BrokerVersion.RABBITMQ_4_0_0)
+  void anonymousAuthenticationShouldWork() {
+    try (Client ignored =
+        cf.get(
+            new Client.ClientParameters().saslConfiguration(DefaultSaslConfiguration.ANONYMOUS))) {}
+  }
+
   private static CredentialsProvider credentialsProvider(String username, String password) {
     return new DefaultUsernamePasswordCredentialsProvider(username, password);
   }

src/test/java/com/rabbitmq/stream/impl/TestUtils.java

@@ -1034,7 +1034,8 @@ public enum BrokerVersion {
     RABBITMQ_3_11_9("3.11.9"),
     RABBITMQ_3_11_11("3.11.11"),
     RABBITMQ_3_11_14("3.11.14"),
-    RABBITMQ_3_13_0("3.13.0");
+    RABBITMQ_3_13_0("3.13.0"),
+    RABBITMQ_4_0_0("4.0.0");
 
     final String value;