[GitHub] [flink] rmetzger commented on a change in pull request #14499: [FLINK-15156] Warn user if System.exit() is called in user code

[GitBox <gi...@apache.org>]

rmetzger commented on a change in pull request #14499:
URL: https://github.com/apache/flink/pull/14499#discussion_r551760064



##########
File path: flink-runtime/src/test/java/org/apache/flink/runtime/security/FlinkUserSecurityManagerTest.java
##########
@@ -0,0 +1,187 @@
+/*
+ * 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.flink.runtime.security;
+
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.IllegalConfigurationException;
+import org.apache.flink.configuration.SecurityOptions;
+import org.apache.flink.runtime.UserSystemExitException;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+/**
+ * Tests for {@code FlinkUserSecurityManager}.
+ */
+public class FlinkUserSecurityManagerTest extend TestLogger {

Review comment:
       ```suggestion
   public class FlinkUserSecurityManagerTest extends TestLogger {
   ```

##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/security/FlinkUserSecurityManager.java
##########
@@ -0,0 +1,168 @@
+/*
+ * 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.flink.runtime.security;
+
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.IllegalConfigurationException;
+import org.apache.flink.configuration.SecurityOptions;
+import org.apache.flink.runtime.UserSystemExitException;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.security.Permission;
+
+/**
+ * {@code FlinkUserSecurityManager} to control unexpected user behaviors that potentially impact cluster availability, for
+ * example, it can warn or prevent user code from terminating JVM by System.exit or halt by logging or throwing an exception.
+ * This does not necessarily prevent malicious users who try to tweak security manager on their own, but more for being dependable
+ * against user mistakes by gracefully handling them informing users rather than causing silent unavailability.
+ */
+public class FlinkUserSecurityManager extends SecurityManager {
+
+	/**
+	 * The mode of how to handle user code attempting to exit JVM.
+	 */
+	public enum CheckExitMode {
+		/** No check is enabled, that is allowing exit without any action. */
+		DISABLED,
+		/** Warn by logging but still allowing exit to be performed. */
+		WARN,
+		/** Throw exception when exit is attempted disallowing JVM termination. */
+		THROW,
+	}
+
+	static final Logger LOG = LoggerFactory.getLogger(FlinkUserSecurityManager.class);
+
+	private final SecurityManager originalSecurityManager = System.getSecurityManager();
+	private final ThreadLocal<Boolean> monitorSystemExit = new InheritableThreadLocal<>();
+	private final CheckExitMode checkExitMode;
+
+	public FlinkUserSecurityManager(CheckExitMode checkExitMode) {
+		super();

Review comment:
       ```suggestion
   ```
   According to my IDE, `super()` is not necessary here.

##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/security/FlinkUserSecurityManager.java
##########
@@ -0,0 +1,168 @@
+/*
+ * 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.flink.runtime.security;
+
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.IllegalConfigurationException;
+import org.apache.flink.configuration.SecurityOptions;
+import org.apache.flink.runtime.UserSystemExitException;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.security.Permission;
+
+/**
+ * {@code FlinkUserSecurityManager} to control unexpected user behaviors that potentially impact cluster availability, for
+ * example, it can warn or prevent user code from terminating JVM by System.exit or halt by logging or throwing an exception.
+ * This does not necessarily prevent malicious users who try to tweak security manager on their own, but more for being dependable
+ * against user mistakes by gracefully handling them informing users rather than causing silent unavailability.
+ */
+public class FlinkUserSecurityManager extends SecurityManager {
+
+	/**
+	 * The mode of how to handle user code attempting to exit JVM.
+	 */
+	public enum CheckExitMode {
+		/** No check is enabled, that is allowing exit without any action. */
+		DISABLED,
+		/** Warn by logging but still allowing exit to be performed. */
+		WARN,
+		/** Throw exception when exit is attempted disallowing JVM termination. */
+		THROW,
+	}
+
+	static final Logger LOG = LoggerFactory.getLogger(FlinkUserSecurityManager.class);
+
+	private final SecurityManager originalSecurityManager = System.getSecurityManager();
+	private final ThreadLocal<Boolean> monitorSystemExit = new InheritableThreadLocal<>();
+	private final CheckExitMode checkExitMode;
+
+	public FlinkUserSecurityManager(CheckExitMode checkExitMode) {
+		super();
+		this.checkExitMode = checkExitMode;
+
+		LOG.info("FlinkUserSecurityManager is created with {} system exit check (previous security manager is {})",
+			this.checkExitMode, originalSecurityManager != null ? originalSecurityManager : "not existing");
+	}
+
+	/**
+	 * Instantiate FlinkUserSecurityManager from configuration. Return null if no security manager
+	 * check is needed, so that a caller can skip setting security manager avoiding runtime check cost,
+	 * if there is no security check set up already. Use {@link #setFromConfiguration} helper, which
+	 * handles disabled case.
+	 *
+	 * @param configuration to instantiate the security manager from
+	 *
+	 * @return FlinkUserSecurityManager instantiated based on configuration. Return null if disabled.
+	 */
+	public static FlinkUserSecurityManager fromConfiguration(Configuration configuration) {
+		final String checkExitModeConfig = configuration.getString(SecurityOptions.CHECK_SYSTEM_EXIT);
+		final CheckExitMode checkExitMode;
+
+		try {
+			checkExitMode = CheckExitMode.valueOf(checkExitModeConfig.toUpperCase());
+		} catch (Exception ex) {
+			throw new IllegalConfigurationException(
+				String.format("%s is invalid configuration for %s.", checkExitModeConfig, SecurityOptions.CHECK_SYSTEM_EXIT.key()),
+				ex);
+		}
+
+		// If no check is enabled, return null so that caller can avoid setting security manager not to incur any runtime cost.
+		if (checkExitMode == CheckExitMode.DISABLED) {
+			return null;
+		}
+		// Add more configuration parameters that need user security manager (currently only for system exit).
+		return new FlinkUserSecurityManager(checkExitMode);
+	}
+
+	public static void setFromConfiguration(Configuration configuration) {
+		final FlinkUserSecurityManager flinkUserSecurityManager =
+			FlinkUserSecurityManager.fromConfiguration(configuration);
+		if (flinkUserSecurityManager != null) {
+			System.setSecurityManager(flinkUserSecurityManager);
+		}
+	}
+
+  @Override
+	public void checkPermission(Permission perm) {
+		if (originalSecurityManager != null) {
+			originalSecurityManager.checkPermission(perm);
+		}
+	}
+
+  @Override
+	public void checkPermission(Permission perm, Object context) {
+		if (originalSecurityManager != null) {
+			originalSecurityManager.checkPermission(perm, context);
+		}
+	}
+
+  @Override
+	public void checkExit(int status) {
+		super.checkExit(status);
+		if (!systemExitMonitored()) {
+			return;
+		}
+		switch (checkExitMode) {
+			case DISABLED:
+				break;
+			case WARN:
+				// Add exception trace log to help users to debug where exit came from.
+				LOG.warn("Exiting JVM with status {} is monitored, logging and exiting",
+					status, new UserSystemExitException());
+				break;
+			case THROW:
+				throw new UserSystemExitException();
+			default:
+				// Must not happen if exhaustively handling all modes above. Logging as being already at exit path.
+				LOG.warn("No valid check exit mode configured: {}", checkExitMode);
+		}
+	}
+
+	public SecurityManager getOriginalSecurityManager() {
+		return originalSecurityManager;
+	}
+
+	public void monitorSystemExit() {
+		monitorSystemExit.set(true);
+	}
+
+	public void unmonitorSystemExit() {
+		monitorSystemExit.set(false);
+	}
+
+	public boolean systemExitMonitored() {
+		return Boolean.TRUE.equals(monitorSystemExit.get());
+	}
+
+	public static void monitorSystemExitForCurrentThread() {
+		SecurityManager securityManager = System.getSecurityManager();
+		if (securityManager instanceof  FlinkUserSecurityManager) {

Review comment:
       ```suggestion
   		if (securityManager instanceof  FlinkUserSecurityManager) {
   ```
   ```suggestion
   		if (securityManager instanceof FlinkUserSecurityManager) {
   ```




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