Add Google RE2/J linear time regular expression as alternative to Java regex

Author: vivek807

docs/ingestion/data-formats.md

@@ -73,6 +73,74 @@ Besides text formats, Druid also supports binary formats such as [Orc](#orc) and
 Druid supports custom text data formats and can use the Regex input format to parse them. However, be aware doing this to
 parse data is less efficient than writing a native Java `InputFormat` extension, or using an external stream processor. We welcome contributions of new input formats.
 
+## Regex engine configuration
+
+The `regex` input format supports configurable regex engines using the runtime property:
+
+```properties
+druid.regex.engine=JAVA
+```
+
+Supported values:
+
+| Value    | Description                                                              |
+|----------|--------------------------------------------------------------------------|
+| `JAVA`   | Uses Java's built-in `java.util.regex.Pattern` engine.                   |
+| `RE2J`   | Uses `Google's RE2/J` regex engine with linear-time matching guarantees. |
+
+Default value:
+
+```properties
+druid.regex.engine=JAVA
+```
+
+### RE2/J engine
+
+Setting:
+
+```properties
+druid.regex.engine=RE2J
+```
+
+enables the RE2/J regex engine for ingestion task `regex` input formats.
+
+RE2/J helps protect against catastrophic backtracking and Regular Expression Denial of Service (ReDoS) attacks by guaranteeing linear-time regex evaluation.
+
+### Compatibility differences
+
+RE2/J does not support all Java regex features.
+
+Unsupported or partially supported features include:
+- backreferences
+- lookbehind assertions
+- some advanced backtracking behavior
+
+Patterns using unsupported constructs will fail during regex compilation.
+
+### Example of catastrophic backtracking
+
+The following Java regex may cause catastrophic backtracking:
+
+```regex
+^(.*a){20}$
+```
+
+against input such as:
+
+```text
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaX
+```
+
+Using `RE2J` avoids this issue.
+
+### Performance considerations
+
+- `JAVA` may support more advanced regex syntax and behavior.
+- `RE2J` provides safer and more predictable runtime characteristics.
+- For trusted internal ingestion specs, `JAVA` may be preferred for compatibility.
+- For externally supplied regex patterns, `RE2J` is recommended.
+
+
 ## Input format
 
 You can use the `inputFormat` field to specify the data format for your input data.
@@ -897,7 +965,8 @@ This query returns:
 |---------------------|-----------------|
 | `1680795276351`     | `partition-1`   |
 
-## FlattenSpec
+## Flat
+tenSpec
 
 You can use the `flattenSpec` object to flatten nested data, as an alternative to the Druid [nested columns](../querying/nested-columns.md) feature, and for nested input formats unsupported by the feature. It is an object within the `inputFormat` object.
 

extensions-core/druid-kerberos/pom.xml

@@ -248,6 +248,10 @@
           <groupId>org.eclipse.jetty</groupId>
           <artifactId>jetty-servlet</artifactId>
         </exclusion>
+        <exclusion>
+          <groupId>com.google.re2j</groupId>
+          <artifactId>re2j</artifactId>
+        </exclusion>
       </exclusions>
     </dependency>
     <dependency>

licenses.yaml

@@ -5239,7 +5239,7 @@ name: RE2/J
 license_category: binary
 module: java-core
 license_name: The Go license
-version: 1.1
+version: 1.7
 license_file_path: licenses/bin/re2j.GO
 libraries:
   - com.google.re2j: re2j

processing/pom.xml

@@ -292,6 +292,11 @@
       <groupId>io.timeandspace</groupId>
       <artifactId>cron-scheduler</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.google.re2j</groupId>
+      <artifactId>re2j</artifactId>
+      <version>1.7</version>
+    </dependency>
 
     <!-- com.lmax.disruptor is optional in log4j-core, so we explicitly include it here -->
     <dependency>

processing/src/main/java/org/apache/druid/data/input/impl/RegexInputFormat.java

@@ -19,6 +19,7 @@
 
 package org.apache.druid.data.input.impl;
 
+import com.fasterxml.jackson.annotation.JacksonInject;
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonInclude;
@@ -29,12 +30,14 @@
 import org.apache.druid.data.input.InputEntityReader;
 import org.apache.druid.data.input.InputFormat;
 import org.apache.druid.data.input.InputRowSchema;
+import org.apache.druid.regex.RegexConfig;
+import org.apache.druid.regex.RegexPattern;
+import org.apache.druid.regex.RegexPatternFactory;
 import org.apache.druid.utils.CompressionUtils;
 
 import javax.annotation.Nullable;
 import java.io.File;
 import java.util.List;
-import java.util.regex.Pattern;
 
 public class RegexInputFormat implements InputFormat
 {
@@ -44,10 +47,11 @@ public class RegexInputFormat implements InputFormat
   private final String listDelimiter;
   private final List<String> columns;
   @JsonIgnore
-  private final Supplier<Pattern> compiledPatternSupplier;
+  private final Supplier<RegexPattern> compiledPatternSupplier;
 
   @JsonCreator
   public RegexInputFormat(
+      @JacksonInject RegexConfig regexConfig,
       @JsonProperty("pattern") String pattern,
       @JsonProperty("listDelimiter") @Nullable String listDelimiter,
       @JsonProperty("columns") @Nullable List<String> columns
@@ -56,7 +60,7 @@ public RegexInputFormat(
     this.pattern = pattern;
     this.listDelimiter = listDelimiter;
     this.columns = columns;
-    this.compiledPatternSupplier = Suppliers.memoize(() -> Pattern.compile(pattern));
+    this.compiledPatternSupplier = Suppliers.memoize(() -> RegexPatternFactory.compile(regexConfig.getEngine(), pattern));
   }
 
   @JsonProperty

processing/src/main/java/org/apache/druid/data/input/impl/RegexReader.java

@@ -30,19 +30,19 @@
 import org.apache.druid.java.util.common.parsers.ParseException;
 import org.apache.druid.java.util.common.parsers.ParserUtils;
 import org.apache.druid.java.util.common.parsers.Parsers;
+import org.apache.druid.regex.RegexMatcher;
+import org.apache.druid.regex.RegexPattern;
 
 import javax.annotation.Nullable;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
 public class RegexReader extends TextReader.Strings
 {
   private final String pattern;
-  private final Pattern compiledPattern;
+  private final RegexPattern compiledPattern;
   private final Function<String, Object> transformationFunction;
 
   private List<String> columns;
@@ -51,7 +51,7 @@ public class RegexReader extends TextReader.Strings
       InputRowSchema inputRowSchema,
       InputEntity source,
       String pattern,
-      Pattern compiledPattern,
+      RegexPattern compiledPattern,
       @Nullable String listDelimiter,
       @Nullable List<String> columns
   )
@@ -83,7 +83,7 @@ protected List<Map<String, Object>> toMap(String intermediateRow)
   private Map<String, Object> parseLine(String line)
   {
     try {
-      final Matcher matcher = compiledPattern.matcher(line);
+      final RegexMatcher matcher = compiledPattern.matcher(line);
 
       if (!matcher.matches()) {
         throw new ParseException(line, "Incorrect Regex: %s . No match found.", pattern);

processing/src/main/java/org/apache/druid/guice/RegexEngineModule.java

@@ -0,0 +1,35 @@
+/*
+ * 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.druid.guice;
+
+import com.google.inject.Binder;
+import com.google.inject.Module;
+import org.apache.druid.regex.RegexConfig;
+
+/**
+ */
+public class RegexEngineModule implements Module
+{
+  @Override
+  public void configure(Binder binder)
+  {
+    JsonConfigProvider.bind(binder, "druid.regex", RegexConfig.class);
+  }
+}

processing/src/main/java/org/apache/druid/guice/StartupInjectorBuilder.java

@@ -65,6 +65,7 @@ public StartupInjectorBuilder()
         new JacksonModule(),
         new ConfigModule(),
         new ExpressionProcessingModule(),
+        new RegexEngineModule(),
         binder -> binder.bind(DruidSecondaryModule.class),
         binder -> binder.bind(PropertiesValidator.class) // this gets properties injected, later call to validate checks
     );

processing/src/main/java/org/apache/druid/regex/JavaRegexMatcher.java

@@ -0,0 +1,56 @@
+/*
+ * 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.druid.regex;
+
+import java.util.regex.Matcher;
+
+public class JavaRegexMatcher implements RegexMatcher
+{
+  private final Matcher matcher;
+
+  public JavaRegexMatcher(Matcher matcher)
+  {
+    this.matcher = matcher;
+  }
+
+  @Override
+  public boolean matches()
+  {
+    return matcher.matches();
+  }
+
+  @Override
+  public boolean find()
+  {
+    return matcher.find();
+  }
+
+  @Override
+  public String group(int group)
+  {
+    return matcher.group(group);
+  }
+
+  @Override
+  public int groupCount()
+  {
+    return matcher.groupCount();
+  }
+}

processing/src/main/java/org/apache/druid/regex/JavaRegexPattern.java

@@ -0,0 +1,38 @@
+/*
+ * 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.druid.regex;
+
+import java.util.regex.Pattern;
+
+public class JavaRegexPattern implements RegexPattern
+{
+  private final Pattern pattern;
+
+  public JavaRegexPattern(String regex)
+  {
+    this.pattern = Pattern.compile(regex);
+  }
+
+  @Override
+  public RegexMatcher matcher(String input)
+  {
+    return new JavaRegexMatcher(pattern.matcher(input));
+  }
+}