[OLINGO-1410] Better XMLMetadata parsing

* [OLINGO-1410] Better XMLMetadata parsing
* Minor change in DEFAULT_ALLOWED_CLASSES handling
* Applied code-formatter

ext/client-proxy/src/main/java/org/apache/olingo/ext/proxy/AbstractService.java

@@ -19,21 +19,27 @@
 package org.apache.olingo.ext.proxy;
 
 import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
 import java.io.ObjectInputStream;
 import java.lang.reflect.Proxy;
+import java.util.Collections;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.zip.GZIPInputStream;
 
 import org.apache.commons.codec.binary.Base64;
 import org.apache.commons.io.IOUtils;
+import org.apache.commons.io.serialization.ValidatingObjectInputStream;
 import org.apache.olingo.client.api.EdmEnabledODataClient;
 import org.apache.olingo.client.api.edm.xml.XMLMetadata;
 import org.apache.olingo.client.core.ODataClientFactory;
 import org.apache.olingo.client.core.edm.ClientCsdlEdmProvider;
-import org.apache.olingo.commons.api.ex.ODataRuntimeException;
 import org.apache.olingo.commons.api.edm.Edm;
 import org.apache.olingo.commons.api.edm.constants.ODataServiceVersion;
+import org.apache.olingo.commons.api.ex.ODataRuntimeException;
 import org.apache.olingo.commons.api.format.ContentType;
 import org.apache.olingo.commons.core.edm.EdmProviderImpl;
 import org.apache.olingo.ext.proxy.api.AbstractTerm;
@@ -52,6 +58,14 @@ import org.slf4j.LoggerFactory;
  */
 public abstract class AbstractService<C extends EdmEnabledODataClient> {
 
+  /**
+   * A set of classes which are allowed to be deserialized by default.
+   */
+  private static final Set<String> DEFAULT_ALLOWED_CLASSES;
+  static {
+    DEFAULT_ALLOWED_CLASSES = Collections.singleton("org.apache.olingo.*");
+  }
+
   protected static final Logger LOG = LoggerFactory.getLogger(AbstractService.class);
 
   private final Map<Class<?>, Object> ENTITY_CONTAINERS = new ConcurrentHashMap<Class<?>, Object>();
@@ -75,7 +89,7 @@ public abstract class AbstractService<C extends EdmEnabledODataClient> {
       // use commons codec's Base64 in this fashion to stay compatible with Android
       bais = new ByteArrayInputStream(new Base64().decode(compressedMetadata.getBytes("UTF-8")));
       gzis = new GZIPInputStream(bais);
-      ois = new ObjectInputStream(gzis);
+      ois = createObjectInputStream(gzis);
       metadata = (XMLMetadata) ois.readObject();
     } catch (Exception e) {
       LOG.error("While deserializing compressed metadata", e);
@@ -88,7 +102,7 @@ public abstract class AbstractService<C extends EdmEnabledODataClient> {
     if (metadata != null) {
       ClientCsdlEdmProvider provider = new ClientCsdlEdmProvider(metadata.getSchemaByNsOrAlias());
       edm = new EdmProviderImpl(provider);
-    }else{
+    } else {
       edm = null;
     }
     if (version.compareTo(ODataServiceVersion.V40) < 0) {
@@ -151,4 +165,36 @@ public abstract class AbstractService<C extends EdmEnabledODataClient> {
     }
     return reference.cast(ENTITY_CONTAINERS.get(reference));
   }
+
+  /**
+   * Returns a set of classes which are allowed for deserialization.<br/>
+   * By default, only classes from the "org.apache.olingo" package are allowed.
+   * Subclasses should override this method if they expect other classes to be deserialized.
+   *
+   * @return A set of classes which are allowed for deserialization.
+   */
+  protected Set<String> getAllowedClasses() {
+    return Collections.emptySet();
+  }
+
+  /**
+   * Wraps a specified {@link InputStream} into a {@link ValidatingObjectInputStream}
+   * which allowed only a limited set of classes for deserialization.
+   * The method calls {@link #getAllowedClasses()} to get a set of classes
+   * which allowed for deserialization.
+   *
+   * @param is The input stream to be wrapped.
+   * @return An instance of {@link ValidatingObjectInputStream}.
+   * @throws IOException If something went wrong.
+   */
+  private ObjectInputStream createObjectInputStream(InputStream is) throws IOException {
+    ValidatingObjectInputStream vois = new ValidatingObjectInputStream(is);
+    Set<String> allowedClasses = new HashSet<>();
+    allowedClasses.addAll(DEFAULT_ALLOWED_CLASSES);
+    allowedClasses.addAll(getAllowedClasses());
+    for (String clazz : allowedClasses) {
+      vois.accept(clazz);
+    }
+    return vois;
+  }
 }

fit/src/test/java/org/apache/olingo/fit/proxy/MetadataDeserializationTest.java

@@ -0,0 +1,164 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.olingo.fit.proxy;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.ObjectOutputStream;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.zip.GZIPOutputStream;
+
+import org.apache.commons.codec.binary.Base64;
+import org.apache.olingo.commons.api.edm.constants.ODataServiceVersion;
+import org.apache.olingo.ext.proxy.AbstractService;
+import org.apache.olingo.ext.proxy.api.AbstractTerm;
+import org.custom.CustomXMLMetadata;
+import org.junit.Test;
+
+public class MetadataDeserializationTest {
+
+  @Test
+  public void testDeserializationWithNotAllowedCustomClass() throws IOException {
+    CustomXMLMetadata metadata = new CustomXMLMetadata();
+    assertTrue(CustomXMLMetadata.detectedMethodCalls());
+    CustomXMLMetadata.forgetMethodCalls();
+
+    ByteArrayOutputStream baos = new ByteArrayOutputStream();
+    GZIPOutputStream gos = new GZIPOutputStream(baos);
+    ObjectOutputStream oos = new ObjectOutputStream(gos);
+
+    oos.writeObject(metadata);
+    oos.flush();
+    gos.finish();
+    gos.flush();
+
+    String compressedCustomMetadata = new Base64().encodeToString(baos.toByteArray());
+
+    assertFalse(CustomXMLMetadata.detectedMethodCalls());
+    try {
+      new ServiceImpl(compressedCustomMetadata, "etag", ODataServiceVersion.V40, null, false);
+    } catch (Exception e) {
+      // okay
+    }
+
+    assertFalse(CustomXMLMetadata.detectedMethodCalls());
+  }
+
+  @Test
+  public void testDeserializationWithAllowedCustomClass() throws IOException {
+    CustomXMLMetadata metadata = new CustomXMLMetadata();
+    assertTrue(CustomXMLMetadata.detectedMethodCalls());
+    CustomXMLMetadata.forgetMethodCalls();
+
+    ByteArrayOutputStream baos = new ByteArrayOutputStream();
+    GZIPOutputStream gos = new GZIPOutputStream(baos);
+    ObjectOutputStream oos = new ObjectOutputStream(gos);
+
+    oos.writeObject(metadata);
+    oos.flush();
+    gos.finish();
+    gos.flush();
+
+    String compressedCustomMetadata = new Base64().encodeToString(baos.toByteArray());
+
+    assertFalse(CustomXMLMetadata.detectedMethodCalls());
+    try {
+      new CustomService(compressedCustomMetadata, "etag", ODataServiceVersion.V40, null, false);
+    } catch (Exception e) {
+      // okay
+    }
+
+    assertTrue(CustomXMLMetadata.detectedMethodCalls());
+  }
+
+  private static class ServiceImpl extends AbstractService {
+
+    ServiceImpl(String compressedMetadata, String metadataETag,
+        ODataServiceVersion version, String serviceRoot, boolean transactional) {
+      super(compressedMetadata, metadataETag, version, serviceRoot, transactional);
+    }
+
+    @Override
+    public Class<?> getEntityTypeClass(String name) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Class<?> getComplexTypeClass(String name) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Class<?> getEnumTypeClass(String name) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Class<? extends AbstractTerm> getTermClass(String name) {
+      throw new UnsupportedOperationException();
+    }
+  }
+
+  /*
+   * A service which allows custom XML metadata.
+   */
+  public static class CustomService extends AbstractService {
+
+    CustomService(String compressedMetadata, String metadataETag,
+        ODataServiceVersion version, String serviceRoot, boolean transactional) {
+      super(compressedMetadata, metadataETag, version, serviceRoot, transactional);
+    }
+
+    @Override
+    public Class<?> getEntityTypeClass(String name) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Class<?> getComplexTypeClass(String name) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Class<?> getEnumTypeClass(String name) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Class<? extends AbstractTerm> getTermClass(String name) {
+      throw new UnsupportedOperationException();
+    }
+
+    /*
+     * Allows CustomXMLMetadata.
+     */
+    @Override
+    protected Set<String> getAllowedClasses() {
+      Set<String> classes = new HashSet<>();
+      classes.add(CustomXMLMetadata.class.getCanonicalName());
+      return Collections.unmodifiableSet(classes);
+    }
+  }
+
+}

fit/src/test/java/org/custom/CustomXMLMetadata.java

@@ -0,0 +1,95 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.custom;
+
+import java.io.Serializable;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.olingo.client.api.edm.xml.Reference;
+import org.apache.olingo.client.api.edm.xml.XMLMetadata;
+import org.apache.olingo.commons.api.edm.provider.CsdlSchema;
+
+public class CustomXMLMetadata implements XMLMetadata, Serializable {
+
+  /*
+   * This flag shows if a method of the class was called.
+   */
+  private static boolean methodsCalled = false;
+
+  /*
+   * Clear the methodsCalled flag.
+   */
+  public static void forgetMethodCalls() {
+    methodsCalled = false;
+  }
+
+  /*
+   * Returns true if any method of this class was called.
+   */
+  public static boolean detectedMethodCalls() {
+    return methodsCalled;
+  }
+
+  public CustomXMLMetadata() {
+    methodsCalled = true;
+  }
+
+  @Override
+  public CsdlSchema getSchema(int index) {
+    methodsCalled = true;
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public CsdlSchema getSchema(String key) {
+    methodsCalled = true;
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public List<CsdlSchema> getSchemas() {
+    methodsCalled = true;
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public Map<String, CsdlSchema> getSchemaByNsOrAlias() {
+    methodsCalled = true;
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public List<Reference> getReferences() {
+    methodsCalled = true;
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public List<List<String>> getSchemaNamespaces() {
+    methodsCalled = true;
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public String getEdmVersion() {
+    methodsCalled = true;
+    throw new UnsupportedOperationException();
+  }
+}