garydgregory commented on code in PR #44: URL: https://github.com/apache/commons-xml/pull/44#discussion_r3852955416
########## 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; + } + + @Override + public String evaluate(final String expression, final InputSource source) throws XPathExpressionException { + return delegate.evaluate(expression, parse(source)); + } + + @Override + public Object evaluate(final String expression, final InputSource source, final QName returnType) throws XPathExpressionException { + return delegate.evaluate(expression, parse(source), returnType); + } + + @Override + public XPathExpression compile(final String expression) throws XPathExpressionException { + final XPathExpression compiled = delegate.compile(expression); + return compiled == null ? null : new HardeningXPathExpression(compiled); + } + + // <editor-fold defaultstate="collapsed" desc="Trivial delegation"> + @Override + public String evaluate(final String expression, final Object item) throws XPathExpressionException { + return delegate.evaluate(expression, item); + } + + @Override + public Object evaluate(final String expression, final Object item, final QName returnType) throws XPathExpressionException { + return delegate.evaluate(expression, item, returnType); + } + + @Override + public NamespaceContext getNamespaceContext() { + return delegate.getNamespaceContext(); + } + + @Override + public XPathFunctionResolver getXPathFunctionResolver() { + return delegate.getXPathFunctionResolver(); + } + + @Override + public XPathVariableResolver getXPathVariableResolver() { + return delegate.getXPathVariableResolver(); + } + + @Override + public void reset() { + delegate.reset(); + } + + @Override + public void setNamespaceContext(final NamespaceContext nsContext) { + delegate.setNamespaceContext(nsContext); + } + + @Override + public void setXPathFunctionResolver(final XPathFunctionResolver resolver) { + delegate.setXPathFunctionResolver(resolver); + } + + @Override + public void setXPathVariableResolver(final XPathVariableResolver resolver) { + delegate.setXPathVariableResolver(resolver); + } + // </editor-fold> Review Comment: Remove this comment noise please. ########## 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; + } + + @Override + public String evaluate(final String expression, final InputSource source) throws XPathExpressionException { + return delegate.evaluate(expression, parse(source)); + } + + @Override + public Object evaluate(final String expression, final InputSource source, final QName returnType) throws XPathExpressionException { + return delegate.evaluate(expression, parse(source), returnType); + } + + @Override + public XPathExpression compile(final String expression) throws XPathExpressionException { + final XPathExpression compiled = delegate.compile(expression); + return compiled == null ? null : new HardeningXPathExpression(compiled); + } + + // <editor-fold defaultstate="collapsed" desc="Trivial delegation"> Review Comment: Remove this comment noise please. ########## src/test/java/org/apache/commons/xml/ShadingFootprintTest.java: ########## @@ -69,23 +70,25 @@ class ShadingFootprintTest { private static final Set<String> STAX_HARDENER = set("StaxHardener", "HardeningXMLInputFactory", "FallbackIgnoreXMLResolver", HARDENING_EXCEPTION); /** - * TrAX, XPath and schema re-harden their sub-parsers through {@link SAXParserHardener#harden(Source)}, so each builds on the full SAX closure below. + * TrAX, XPath and schema re-harden their sub-parsers through {@link SAXParserHardener#hardenSource(Source)}, so each builds on the full SAX closure below; XPath + * additionally parses InputSource-taking evaluate calls through the DOM hardener, so its closure carries that set too. */ private static final Set<String> TRANSFORMER_HARDENER = saxParsersHardenerPlus("TransformerHardener", "HardeningTransformerFactory", "HardeningTransformer", "HardeningTransformerHandler", "HardeningTemplates", "HardeningTemplatesHandler", "HardeningXMLFilter", "FallbackIgnoreURIResolver", "SaxonProvider", "SaxonProvider$1", "SaxonProvider$HardenedConfiguration" , "SaxonProvider$SaxonProviderConfigurer"); - private static final Set<String> XPATH_HARDENER = saxParsersHardenerPlus("XPathHardener", "FallbackIgnoreURIResolver", "SaxonProvider", "SaxonProvider$1", - "SaxonProvider$HardenedConfiguration", "SaxonProvider$SaxonProviderConfigurer"); + private static final Set<String> XPATH_HARDENER = saxParsersHardenerPlus("XPathHardener", "FallbackIgnoreURIResolver", "SaxonProvider", + "SaxonProvider$1", "SaxonProvider$HardenedConfiguration", "SaxonProvider$SaxonProviderConfigurer", "HardeningXPathFactory", "HardeningXPath", + "HardeningXPathExpression", "DocumentBuilderHardener", "HardeningDocumentBuilder", "HardeningDocumentBuilderFactory"); private static final Set<String> SCHEMA_HARDENER = saxParsersHardenerPlus("SchemaHardener", "HardeningSchemaFactory", "HardeningValidator", "HardeningValidatorHandler", "HardeningSchema", "FallbackIgnoreLSResourceResolver"); /** * Only the public {@link XmlFactories} entry, which news up every hardener, still pulls the whole library; this is its class count. Review Comment: What does "news up" means? Use plain English IMO. ########## src/test/java/org/apache/commons/xml/XPathInputSourceTest.java: ########## @@ -0,0 +1,88 @@ +/* + * 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 static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import javax.xml.xpath.XPathExpressionException; +import javax.xml.xpath.XPathFactory; + +import org.junit.jupiter.api.Tag; +import org.junit.jupiter.api.Test; + +/** + * Checks that the document parse behind {@code XPath.evaluate(String, InputSource)} (and its compiled {@code XPathExpression} counterpart) cannot pull in an + * external general entity. + * + * <p>The stock JDK and Apache Xalan implement the {@link org.xml.sax.InputSource}-taking {@code evaluate} entry points by provisioning an internal document + * parser that {@code FEATURE_SECURE_PROCESSING} on the {@link XPathFactory} does not reach. The {@link HardeningXPathFactory} wrapper parses the input + * through a hardened {@code DocumentBuilder} instead, so the external reference resolves to empty on the floor (or the parse is rejected outright), while the + * evaluation itself still works. Tagged {@code xpath}, so it runs under test-stockjdk, test-xalan and test-xalan-xerces; the Saxon engine takes the separate + * {@code SaxonProvider} path covered by {@code SaxonXPathExternalCallsTest}.</p> + */ +@Tag("xpath") +class XPathInputSourceTest { + + private static final String EXPRESSION = "string(/root/child)"; + + /** {@link AttackTestSupport#xmlBody} content whose single entity reference resolves to {@link AttackTestSupport#LEAKED_MARKER} if the DTD is fetched. */ + private static String entityPayload() { + return "<?xml version=\"1.0\"?>\n" + + "<!DOCTYPE root [\n <!ENTITY xxe SYSTEM \"" + AttackTestSupport.resourceUrl("referenced.txt") + "\">\n]>\n" + + AttackTestSupport.xmlBody("&xxe;"); + } + + @Test + void hardenedXPathEvaluateDoesNotLeak() throws Exception { + final String result; + try { + result = XmlFactories.newXPathFactory().newXPath().evaluate(EXPRESSION, AttackTestSupport.inputSource(entityPayload())); + } catch (final XPathExpressionException blocked) { + return; // Acceptable: the parse rejected the reference rather than resolving it to empty. Review Comment: Same comment as in PR #42 Add a better comment or use `assertThrows()` ########## 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; + } + + @Override + public XPath newXPath() { + final XPath xpath = delegate.newXPath(); + return xpath == null ? null : new HardeningXPath(xpath); + } + + // <editor-fold defaultstate="collapsed" desc="Trivial delegation"> + @Override + public boolean getFeature(final String name) throws XPathFactoryConfigurationException { + return delegate.getFeature(name); + } + + @Override + public boolean isObjectModelSupported(final String objectModel) { + return delegate.isObjectModelSupported(objectModel); + } + + @Override + public void setFeature(final String name, final boolean value) throws XPathFactoryConfigurationException { + delegate.setFeature(name, value); + } + + @Override + public void setXPathFunctionResolver(final XPathFunctionResolver resolver) { + delegate.setXPathFunctionResolver(resolver); + } + + @Override + public void setXPathVariableResolver(final XPathVariableResolver resolver) { + delegate.setXPathVariableResolver(resolver); + } + // </editor-fold> Review Comment: Remove this // comment. ########## 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: Add Objects.requireNonNull(). ########## src/main/java/org/apache/commons/xml/HardeningXPathExpression.java: ########## @@ -0,0 +1,62 @@ +/* + * 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.namespace.QName; +import javax.xml.xpath.XPathExpression; +import javax.xml.xpath.XPathExpressionException; + +import org.xml.sax.InputSource; + +/** + * {@link XPathExpression} wrapper that applies the same {@link InputSource} rewrite as {@link HardeningXPath} to the compiled evaluation entry points. + * + * <p>{@link HardeningXPath#compile(String)} returns one of these, so {@link #evaluate(InputSource)} and {@link #evaluate(InputSource, QName)} build the + * document through a hardened, namespace-aware parser instead of the engine's own; the {@code evaluateExpression} default methods added by Java 9 route + * through these overloads as well.</p> + */ +final class HardeningXPathExpression implements XPathExpression { + + private final XPathExpression delegate; + + HardeningXPathExpression(final XPathExpression delegate) { + this.delegate = delegate; + } + + @Override + public String evaluate(final InputSource source) throws XPathExpressionException { + return delegate.evaluate(HardeningXPath.parse(source)); + } + + @Override + public Object evaluate(final InputSource source, final QName returnType) throws XPathExpressionException { + return delegate.evaluate(HardeningXPath.parse(source), returnType); + } + + // <editor-fold defaultstate="collapsed" desc="Trivial delegation"> + @Override + public String evaluate(final Object item) throws XPathExpressionException { + return delegate.evaluate(item); + } + + @Override + public Object evaluate(final Object item, final QName returnType) throws XPathExpressionException { + return delegate.evaluate(item, returnType); + } + // </editor-fold> Review Comment: Remove this junk // comment. ########## src/test/java/org/apache/commons/xml/ShadingFootprintTest.java: ########## @@ -69,23 +70,25 @@ class ShadingFootprintTest { private static final Set<String> STAX_HARDENER = set("StaxHardener", "HardeningXMLInputFactory", "FallbackIgnoreXMLResolver", HARDENING_EXCEPTION); /** - * TrAX, XPath and schema re-harden their sub-parsers through {@link SAXParserHardener#harden(Source)}, so each builds on the full SAX closure below. + * TrAX, XPath and schema re-harden their sub-parsers through {@link SAXParserHardener#hardenSource(Source)}, so each builds on the full SAX closure below; XPath + * additionally parses InputSource-taking evaluate calls through the DOM hardener, so its closure carries that set too. */ private static final Set<String> TRANSFORMER_HARDENER = saxParsersHardenerPlus("TransformerHardener", "HardeningTransformerFactory", "HardeningTransformer", "HardeningTransformerHandler", "HardeningTemplates", "HardeningTemplatesHandler", "HardeningXMLFilter", "FallbackIgnoreURIResolver", "SaxonProvider", "SaxonProvider$1", "SaxonProvider$HardenedConfiguration" , "SaxonProvider$SaxonProviderConfigurer"); - private static final Set<String> XPATH_HARDENER = saxParsersHardenerPlus("XPathHardener", "FallbackIgnoreURIResolver", "SaxonProvider", "SaxonProvider$1", - "SaxonProvider$HardenedConfiguration", "SaxonProvider$SaxonProviderConfigurer"); + private static final Set<String> XPATH_HARDENER = saxParsersHardenerPlus("XPathHardener", "FallbackIgnoreURIResolver", "SaxonProvider", + "SaxonProvider$1", "SaxonProvider$HardenedConfiguration", "SaxonProvider$SaxonProviderConfigurer", "HardeningXPathFactory", "HardeningXPath", + "HardeningXPathExpression", "DocumentBuilderHardener", "HardeningDocumentBuilder", "HardeningDocumentBuilderFactory"); private static final Set<String> SCHEMA_HARDENER = saxParsersHardenerPlus("SchemaHardener", "HardeningSchemaFactory", "HardeningValidator", "HardeningValidatorHandler", "HardeningSchema", "FallbackIgnoreLSResourceResolver"); /** * Only the public {@link XmlFactories} entry, which news up every hardener, still pulls the whole library; this is its class count. */ - private static final int WHOLE_LIBRARY_SIZE = 32; + private static final int WHOLE_LIBRARY_SIZE = 35; Review Comment: The Javadoc says "class count" but the name uses the ambiguous "SIZE", use "CLASS_COUNT" to remove the confusion. ########## 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: Make invariant obvious: ``` this.delegate = Objects.requireNonNull(delegate, "delegate"); ``` ########## src/test/java/org/apache/commons/xml/XPathInputSourceTest.java: ########## @@ -0,0 +1,88 @@ +/* + * 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 static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import javax.xml.xpath.XPathExpressionException; +import javax.xml.xpath.XPathFactory; + +import org.junit.jupiter.api.Tag; +import org.junit.jupiter.api.Test; + +/** + * Checks that the document parse behind {@code XPath.evaluate(String, InputSource)} (and its compiled {@code XPathExpression} counterpart) cannot pull in an + * external general entity. + * + * <p>The stock JDK and Apache Xalan implement the {@link org.xml.sax.InputSource}-taking {@code evaluate} entry points by provisioning an internal document + * parser that {@code FEATURE_SECURE_PROCESSING} on the {@link XPathFactory} does not reach. The {@link HardeningXPathFactory} wrapper parses the input + * through a hardened {@code DocumentBuilder} instead, so the external reference resolves to empty on the floor (or the parse is rejected outright), while the + * evaluation itself still works. Tagged {@code xpath}, so it runs under test-stockjdk, test-xalan and test-xalan-xerces; the Saxon engine takes the separate + * {@code SaxonProvider} path covered by {@code SaxonXPathExternalCallsTest}.</p> + */ +@Tag("xpath") +class XPathInputSourceTest { + + private static final String EXPRESSION = "string(/root/child)"; + + /** {@link AttackTestSupport#xmlBody} content whose single entity reference resolves to {@link AttackTestSupport#LEAKED_MARKER} if the DTD is fetched. */ + private static String entityPayload() { + return "<?xml version=\"1.0\"?>\n" + + "<!DOCTYPE root [\n <!ENTITY xxe SYSTEM \"" + AttackTestSupport.resourceUrl("referenced.txt") + "\">\n]>\n" + + AttackTestSupport.xmlBody("&xxe;"); + } + + @Test + void hardenedXPathEvaluateDoesNotLeak() throws Exception { + final String result; + try { + result = XmlFactories.newXPathFactory().newXPath().evaluate(EXPRESSION, AttackTestSupport.inputSource(entityPayload())); + } catch (final XPathExpressionException blocked) { + return; // Acceptable: the parse rejected the reference rather than resolving it to empty. + } + assertFalse(result.contains(AttackTestSupport.LEAKED_MARKER), "external entity leaked into the XPath result: " + result); + } + + @Test + void hardenedXPathExpressionEvaluateDoesNotLeak() throws Exception { + final String result; + try { + result = XmlFactories.newXPathFactory().newXPath().compile(EXPRESSION).evaluate(AttackTestSupport.inputSource(entityPayload())); + } catch (final XPathExpressionException blocked) { Review Comment: Same comment as in PR #42 Add a better comment or use `assertThrows()` -- This is an automated message from the Apache Git Service. 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