ppkarwasz commented on code in PR #44: URL: https://github.com/apache/commons-xml/pull/44#discussion_r3856287724
########## src/main/java/org/apache/commons/xml/HardeningXPath.java: ########## @@ -0,0 +1,141 @@ +/* + * 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 + * + * https://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.commons.xml; + +import java.io.IOException; + +import javax.xml.namespace.NamespaceContext; +import javax.xml.namespace.QName; +import javax.xml.parsers.DocumentBuilderFactory; +import javax.xml.parsers.ParserConfigurationException; +import javax.xml.xpath.XPath; +import javax.xml.xpath.XPathExpression; +import javax.xml.xpath.XPathExpressionException; +import javax.xml.xpath.XPathFunctionResolver; +import javax.xml.xpath.XPathVariableResolver; + +import org.w3c.dom.Document; +import org.xml.sax.InputSource; +import org.xml.sax.SAXException; + +/** + * {@link XPath} wrapper that performs the document build behind every {@link InputSource}-taking {@code evaluate} call with a hardened, namespace-aware + * {@link javax.xml.parsers.DocumentBuilder} and evaluates the delegate against the parsed {@link Document}, so the engine's own parser never runs. + * + * <p>The JAXP contract for {@link XPath#evaluate(String, InputSource, QName)} is "build a document from the source, then evaluate against it", and both the + * stock JDK and Apache Xalan provision an internal parser for that build which {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} on the + * {@link javax.xml.xpath.XPathFactory} does not reach. Parsing here puts the build on the library's resolver floor: an external reference inside the document + * resolves to empty content, so it is neither fetched nor leaked, and the evaluation proceeds on whatever the parse produced. {@link #compile(String)} wraps + * the compiled expression in a {@link HardeningXPathExpression} on the same terms.</p> + * + * <p>The {@code evaluateExpression} default methods added to the interface by Java 9 route through the {@code evaluate} overloads overridden here, so they + * carry the same rewrite on newer runtimes even though this class targets Java 8.</p> + */ +final class HardeningXPath implements XPath { + + /** + * Parses the source through a hardened, namespace-aware {@link javax.xml.parsers.DocumentBuilder}, mirroring the namespace awareness of the parser the + * engine would have provisioned. + * + * @param source The document to evaluate against. + * @return The parsed document. + * @throws NullPointerException if {@code source} is {@code null}, per the {@link XPath} contract. + * @throws XPathExpressionException if the source cannot be parsed. + */ + static Document parse(final InputSource source) throws XPathExpressionException { + if (source == null) { + throw new NullPointerException("source cannot be null"); + } + try { + final DocumentBuilderFactory factory = DocumentBuilderHardener.harden(DocumentBuilderFactory.newInstance()); + factory.setNamespaceAware(true); + return factory.newDocumentBuilder().parse(source); + } catch (final ParserConfigurationException | SAXException | IOException e) { + throw new XPathExpressionException(e); + } + } + + private final XPath delegate; + + HardeningXPath(final XPath delegate) { + this.delegate = delegate; Review Comment: I applied the suggested `Objects.requireNonNull` in https://github.com/apache/commons-xml/pull/44/commits/6315ef84d6731d2fc57e2cc6355e354a0db85738, but maybe we should use nullability annotations or comments instead, so we don't introduce a (cheap) runtime check even if no caller ever passes `null`> ########## src/main/java/org/apache/commons/xml/HardeningXPathFactory.java: ########## @@ -0,0 +1,73 @@ +/* + * 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 + * + * https://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.commons.xml; + +import javax.xml.xpath.XPath; +import javax.xml.xpath.XPathFactory; +import javax.xml.xpath.XPathFactoryConfigurationException; +import javax.xml.xpath.XPathFunctionResolver; +import javax.xml.xpath.XPathVariableResolver; + +/** + * {@link XPathFactory} wrapper that returns a {@link HardeningXPath} from {@link #newXPath()}. + * + * <p>Required because {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} on the factory governs only the XPath engine: the stock JDK and Apache Xalan + * implement the {@link org.xml.sax.InputSource}-taking {@code evaluate} entry points by provisioning an internal document parser the feature does not reach. + * The wrapper performs that document build itself through a hardened parser instead; see {@link HardeningXPath}.</p> + */ +final class HardeningXPathFactory extends XPathFactory { + + private final XPathFactory delegate; + + HardeningXPathFactory(final XPathFactory delegate) { + this.delegate = delegate; Review Comment: Fixed in https://github.com/apache/commons-xml/pull/44/commits/6315ef84d6731d2fc57e2cc6355e354a0db85738 -- This is an automated message from the Apache Git Service. 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