Restrict LDAP access via JNDI

log4j-core/pom.xml

@@ -349,6 +349,11 @@
       <artifactId>awaitility</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.zapodot</groupId>
+      <artifactId>embedded-ldap-junit</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
   <build>
     <plugins>

log4j-core/src/main/java/org/apache/logging/log4j/core/appender/mom/JmsAppender.java

@@ -88,6 +88,15 @@ public static class Builder<B extends Builder<B>> extends AbstractAppender.Build
         @PluginBuilderAttribute
         private boolean immediateFail;
 
+        @PluginBuilderAttribute
+        private String allowedLdapClasses;
+
+        @PluginBuilderAttribute
+        private String allowedLdapHosts;
+
+        @PluginBuilderAttribute
+        private String allowedJndiProtocols;
+
         // Programmatic access only for now.
         private JmsManager jmsManager;
 
@@ -100,8 +109,21 @@ public JmsAppender build() {
             JmsManager actualJmsManager = jmsManager;
             JmsManagerConfiguration configuration = null;
             if (actualJmsManager == null) {
+                Properties additionalProperties = null;
+                if (allowedLdapClasses != null || allowedLdapHosts != null) {
+                    additionalProperties = new Properties();
+                    if (allowedLdapHosts != null) {
+                        additionalProperties.put(JndiManager.ALLOWED_HOSTS, allowedLdapHosts);
+                    }
+                    if (allowedLdapClasses != null) {
+                        additionalProperties.put(JndiManager.ALLOWED_CLASSES, allowedLdapClasses);
+                    }
+                    if (allowedJndiProtocols != null) {
+                        additionalProperties.put(JndiManager.ALLOWED_PROTOCOLS, allowedJndiProtocols);
+                    }
+                }
                 final Properties jndiProperties = JndiManager.createProperties(factoryName, providerUrl, urlPkgPrefixes,
-                        securityPrincipalName, securityCredentials, null);
+                        securityPrincipalName, securityCredentials, additionalProperties);
                 configuration = new JmsManagerConfiguration(jndiProperties, factoryBindingName, destinationBindingName,
                         userName, password, false, reconnectIntervalMillis);
                 actualJmsManager = AbstractManager.getManager(getName(), JmsManager.FACTORY, configuration);
@@ -202,6 +224,21 @@ public Builder setUserName(final String userName) {
             return this;
         }
 
+        public Builder setAllowedLdapClasses(final String allowedLdapClasses) {
+            this.allowedLdapClasses = allowedLdapClasses;
+            return this;
+        }
+
+        public Builder setAllowedLdapHosts(final String allowedLdapHosts) {
+            this.allowedLdapHosts = allowedLdapHosts;
+            return this;
+        }
+
+        public Builder setAllowedJndiProtocols(final String allowedJndiProtocols) {
+            this.allowedJndiProtocols = allowedJndiProtocols;
+            return this;
+        }
+
         /**
          * Does not include the password.
          */
@@ -212,7 +249,8 @@ public String toString() {
                     + ", securityCredentials=" + securityCredentials + ", factoryBindingName=" + factoryBindingName
                     + ", destinationBindingName=" + destinationBindingName + ", username=" + userName + ", layout="
                     + getLayout() + ", filter=" + getFilter() + ", ignoreExceptions=" + isIgnoreExceptions()
-                    + ", jmsManager=" + jmsManager + "]";
+                    + ", jmsManager=" + jmsManager + ", allowedLdapClasses=" + allowedLdapClasses
+                    + ", allowedLdapHosts=" + allowedLdapHosts + ", allowedJndiProtocols=" + allowedJndiProtocols + "]";
         }
 
     }

log4j-core/src/main/java/org/apache/logging/log4j/core/net/JndiManager.java

@@ -17,31 +17,69 @@
 
 package org.apache.logging.log4j.core.net;
 
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
 import java.util.Properties;
 import java.util.concurrent.TimeUnit;
 
 import javax.naming.Context;
-import javax.naming.InitialContext;
+import javax.naming.NamingEnumeration;
 import javax.naming.NamingException;
+import javax.naming.directory.Attribute;
+import javax.naming.directory.Attributes;
+import javax.naming.directory.DirContext;
+import javax.naming.directory.InitialDirContext;
 
 import org.apache.logging.log4j.core.appender.AbstractManager;
 import org.apache.logging.log4j.core.appender.ManagerFactory;
 import org.apache.logging.log4j.core.util.JndiCloser;
+import org.apache.logging.log4j.core.util.NetUtils;
+import org.apache.logging.log4j.util.PropertiesUtil;
 
 /**
- * Manages a JNDI {@link javax.naming.Context}.
+ * Manages a JNDI {@link javax.naming.directory.DirContext}.
  *
  * @since 2.1
  */
 public class JndiManager extends AbstractManager {
 
+    public static final String ALLOWED_HOSTS = "allowedLdapHosts";
+    public static final String ALLOWED_CLASSES = "allowedLdapClasses";
+    public static final String ALLOWED_PROTOCOLS = "allowedJndiProtocols";
+
     private static final JndiManagerFactory FACTORY = new JndiManagerFactory();
+    private static final String PREFIX = "log4j2.";
+    private static final String LDAP = "ldap";
+    private static final String LDAPS = "ldaps";
+    private static final String JAVA = "java";
+    private static final List<String> permanentAllowedHosts = NetUtils.getLocalIps();
+    private static final List<String> permanentAllowedClasses = Arrays.asList(Boolean.class.getName(),
+            Byte.class.getName(), Character.class.getName(), Double.class.getName(), Float.class.getName(),
+            Integer.class.getName(), Long.class.getName(), Short.class.getName(), String.class.getName());
+    private static final List<String> permanentAllowedProtocols = Arrays.asList(JAVA, LDAP, LDAPS);
+    private static final String SERIALIZED_DATA = "javaSerializedData";
+    private static final String CLASS_NAME = "javaClassName";
+    private static final String REFERENCE_ADDRESS = "javaReferenceAddress";
+    private static final String OBJECT_FACTORY = "javaFactory";
+    private final List<String> allowedHosts;
+    private final List<String> allowedClasses;
+    private final List<String> allowedProtocols;
 
-    private final Context context;
+    private final DirContext context;
 
-    private JndiManager(final String name, final Context context) {
+    private JndiManager(final String name, final DirContext context, final List<String> allowedHosts,
+            final List<String> allowedClasses, final List<String> allowedProtocols) {
         super(null, name);
         this.context = context;
+        this.allowedHosts = allowedHosts;
+        this.allowedClasses = allowedClasses;
+        this.allowedProtocols = allowedProtocols;
     }
 
     /**
@@ -168,21 +206,89 @@ protected boolean releaseSub(final long timeout, final TimeUnit timeUnit) {
      * @throws  NamingException if a naming exception is encountered
      */
     @SuppressWarnings("unchecked")
-    public <T> T lookup(final String name) throws NamingException {
+    public synchronized <T> T lookup(final String name) throws NamingException {
+        try {
+            URI uri = new URI(name);
+            if (!allowedProtocols.contains(uri.getScheme().toLowerCase(Locale.ROOT))) {
+                LOGGER.warn("Log4j JNDI does not allow protocol {}", uri.getScheme());
+                return null;
+            }
+            if (LDAP.equalsIgnoreCase(uri.getScheme()) || LDAPS.equalsIgnoreCase(uri.getScheme())) {
+                if (!allowedHosts.contains(uri.getHost())) {
+                    LOGGER.warn("Attempt to access ldap server not in allowed list");
+                    return null;
+                }
+                Attributes attributes = this.context.getAttributes(name);
+                if (attributes != null) {
+                    // In testing the "key" for attributes seems to be lowercase while the attribute id is
+                    // camelcase, but that may just be true for the test LDAP used here. This copies the Attributes
+                    // to a Map ignoring the "key" and using the Attribute's id as the key in the Map so it matches
+                    // the Java schema.
+                    Map<String, Attribute> attributeMap = new HashMap<>();
+                    NamingEnumeration<? extends Attribute> enumeration = attributes.getAll();
+                    while (enumeration.hasMore()) {
+                        Attribute attribute = enumeration.next();
+                        attributeMap.put(attribute.getID(), attribute);
+                    }
+                    Attribute classNameAttr = attributeMap.get(CLASS_NAME);
+                    if (attributeMap.get(SERIALIZED_DATA) != null) {
+                        if (classNameAttr != null) {
+                            String className = classNameAttr.get().toString();
+                            if (!allowedClasses.contains(className)) {
+                                LOGGER.warn("Deserialization of {} is not allowed", className);
+                                return null;
+                            }
+                        } else {
+                            LOGGER.warn("No class name provided for {}", name);
+                            return null;
+                        }
+                    } else if (attributeMap.get(REFERENCE_ADDRESS) != null
+                            || attributeMap.get(OBJECT_FACTORY) != null) {
+                        LOGGER.warn("Referenceable class is not allowed for {}", name);
+                        return null;
+                    }
+                }
+            }
+        } catch (URISyntaxException ex) {
+            // This is OK.
+        }
         return (T) this.context.lookup(name);
     }
 
     private static class JndiManagerFactory implements ManagerFactory<JndiManager, Properties> {
 
         @Override
         public JndiManager createManager(final String name, final Properties data) {
+            String hosts = data != null ? data.getProperty(ALLOWED_HOSTS) : null;
+            String classes = data != null ? data.getProperty(ALLOWED_CLASSES) : null;
+            String protocols = data != null ? data.getProperty(ALLOWED_PROTOCOLS) : null;
+            List<String> allowedHosts = new ArrayList<>();
+            List<String> allowedClasses = new ArrayList<>();
+            List<String> allowedProtocols = new ArrayList<>();
+            addAll(hosts, allowedHosts, permanentAllowedHosts, ALLOWED_HOSTS, data);
+            addAll(classes, allowedClasses, permanentAllowedClasses, ALLOWED_CLASSES, data);
+            addAll(protocols, allowedProtocols, permanentAllowedProtocols, ALLOWED_PROTOCOLS, data);
             try {
-                return new JndiManager(name, new InitialContext(data));
+                return new JndiManager(name, new InitialDirContext(data), allowedHosts, allowedClasses,
+                        allowedProtocols);
             } catch (final NamingException e) {
                 LOGGER.error("Error creating JNDI InitialContext.", e);
                 return null;
             }
         }
+
+        private void addAll(String toSplit, List<String> list, List<String> permanentList, String propertyName,
+                Properties data) {
+            if (toSplit != null) {
+                list.addAll(Arrays.asList(toSplit.split("\\s*,\\s*")));
+                data.remove(propertyName);
+            }
+            toSplit = PropertiesUtil.getProperties().getStringProperty(PREFIX + propertyName);
+            if (toSplit != null) {
+                list.addAll(Arrays.asList(toSplit.split("\\s*,\\s*")));
+            }
+            list.addAll(permanentList);
+        }
     }
 
     @Override

log4j-core/src/main/java/org/apache/logging/log4j/core/util/NetUtils.java

@@ -17,6 +17,8 @@
 package org.apache.logging.log4j.core.util;
 
 import java.io.File;
+import java.net.Inet4Address;
+import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.net.MalformedURLException;
 import java.net.NetworkInterface;
@@ -25,11 +27,14 @@
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.net.UnknownHostException;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Enumeration;
+import java.util.List;
 
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.status.StatusLogger;
+import org.apache.logging.log4j.util.Strings;
 
 /**
  * Networking-related convenience methods.
@@ -79,6 +84,45 @@ public static String getLocalHostname() {
         }
     }
 
+    public static List<String> getLocalIps() {
+        List<String> localIps = new ArrayList<>();
+        localIps.add("localhost");
+        localIps.add("127.0.0.1");
+        try {
+            final InetAddress addr = Inet4Address.getLocalHost();
+            setHostName(addr, localIps);
+        } catch (final UnknownHostException ex) {
+            // Ignore this.
+        }
+        try {
+            final Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
+            if (interfaces != null) {
+                while (interfaces.hasMoreElements()) {
+                    final NetworkInterface nic = interfaces.nextElement();
+                    final Enumeration<InetAddress> addresses = nic.getInetAddresses();
+                    while (addresses.hasMoreElements()) {
+                        final InetAddress address = addresses.nextElement();
+                        setHostName(address, localIps);
+                    }
+                }
+            }
+        } catch (final SocketException se) {
+            // ignore.
+        }
+        return localIps;
+    }
+
+    private static void setHostName(InetAddress address, List<String> localIps) {
+        String[] parts = address.toString().split("\\s*/\\s*");
+        if (parts.length > 0) {
+            for (String part : parts) {
+                if (Strings.isNotBlank(part) && !localIps.contains(part)) {
+                    localIps.add(part);
+                }
+            }
+        }
+    }
+
     /**
      *  Returns the local network interface's MAC address if possible. The local network interface is defined here as
      *  the {@link java.net.NetworkInterface} that is both up and not a loopback interface.

log4j-core/src/test/java/org/apache/logging/log4j/core/lookup/JndiExploit.java

@@ -0,0 +1,36 @@
+/*
+ * 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.logging.log4j.core.lookup;
+
+import javax.naming.Context;
+import javax.naming.Name;
+import javax.naming.spi.ObjectFactory;
+import java.util.Hashtable;
+
+import static org.junit.jupiter.api.Assertions.fail;
+
+/**
+ * Test LDAP object
+ */
+public class JndiExploit implements ObjectFactory {
+    @Override
+    public Object getObjectInstance(Object obj, Name name, Context nameCtx, Hashtable<?, ?> environment)
+            throws Exception {
+        fail("getObjectInstance must not be allowed");
+        return null;
+    }
+}