XML external injection resolutions

https://www.owasp.org/index.php/XML_External_Entity_(XXE)_Prevention_Cheat_Sheet
http://www.gonandy.com/2016/12/xxe-injection/

DocumentBuilderFactory

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DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();     String FEATURE = null;       // This is the PRIMARY defense. If DTDs (doctypes) are disallowed, almost all XML entity attacks are prevented       // Xerces 2 only - http://xerces.apache.org/xerces2-j/features.html#disallow-doctype-decl       FEATURE = "http://apache.org/xml/features/disallow-doctype-decl";       dbf.setFeature(FEATURE, true);         // If you can't completely disable DTDs, then at least do the following:       // Xerces 1 - http://xerces.apache.org/xerces-j/features.html#external-general-entities       // Xerces 2 - http://xerces.apache.org/xerces2-j/features.html#external-general-entities       // JDK7+ - http://xml.org/sax/features/external-general-entities           FEATURE = "http://xml.org/sax/features/external-general-entities";       dbf.setFeature(FEATURE, false);         // Xerces 1 - http://xerces.apache.org/xerces-j/features.html#external-parameter-entities       // Xerces 2 - http://xerces.apache.org/xerces2-j/features.html#external-parameter-entities       // JDK7+ - http://xml.org/sax/features/external-parameter-entities           FEATURE = "http://xml.org/sax/features/external-parameter-entities";       dbf.setFeature(FEATURE, false);         // Disable external DTDs as well       FEATURE = "http://apache.org/xml/features/nonvalidating/load-external-dtd";       dbf.setFeature(FEATURE, false);         // and these as well, per Timothy Morgan's 2014 paper: "XML Schema, DTD, and Entity Attacks" (see reference below)       dbf.setXIncludeAware(false);       dbf.setExpandEntityReferences(false);

StAX and XMLInputFactory

StAX parsers such as XMLInputFactory allow various properties and features to be set.

To protect a Java XMLInputFactory from XXE, do this:

• xmlInputFactory.setProperty(XMLInputFactory.SUPPORT_DTD, false); // This disables DTDs entirely for that factory
• xmlInputFactory.setProperty(“javax.xml.stream.isSupportingExternalEntities”, false); // disable external entities

TransformerFactory(JDK7)

To protect a Java TransformerFactory from XXE, do this:

• TransformerFactory tf = TransformerFactory.newInstance();
• tf.setAttribute(XMLConstants.ACCESS_EXTERNAL_DTD, “”);
• tf.setAttribute(XMLConstants.ACCESS_EXTERNAL_STYLESHEET, “”);
• tf.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING,true);

Validator

To protect a Java Validator from XXE, do this:

• SchemaFactory factory = SchemaFactory.newInstance(“http://www.w3.org/2001/XMLSchema“);
• Schema schema = factory.newSchema();
• Validator validator = schema.newValidator();
• validator.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, “”);
• validator.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, “”);

SchemaFactory

To protect a SchemaFactory from XXE, do this:

• SchemaFactory factory = SchemaFactory.newInstance(“http://www.w3.org/2001/XMLSchema“);
• factory.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, “”);
• factory.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, “”);
• Schema schema = factory.newSchema(Source);

SAXTransformerFactory

To protect a Java SAXTransformerFactory from XXE, do this:

• SAXTransformerFactory sf = SAXTransformerFactory.newInstance();
• sf.setAttribute(XMLConstants.ACCESS_EXTERNAL_DTD, “”);
• sf.setAttribute(XMLConstants.ACCESS_EXTERNAL_STYLESHEET, “”);
• sf.newXMLFilter(Source);

XMLReader

To protect a Java XMLReader from XXE, do this:

• XMLReader spf = XMLReaderFactory.createXMLReader();
• spf.setFeature(“http://xml.org/sax/features/external-general-entities”, false);
• spf.setFeature(“http://xml.org/sax/features/external-parameter-entities“, false);
• spf.setFeature(“http://apache.org/xml/features/nonvalidating/load-external-dtd”,false);

Unmarshaller

Since an Unmarshaller parses XML and does not support any flags for disabling XXE, it’s imperative to parse the untrusted XML through a configurable secure parser first, generate a Source object as a result, and pass the source object to the Unmarshaller. For example:

• SAXParserFactory spf = SAXParserFactory.newInstance();
• spf.setFeature(“http://xml.org/sax/features/external-general-entities”, false);
• spf.setFeature(“http://xml.org/sax/features/external-parameter-entities“, false);
• spf.setFeature(“http://apache.org/xml/features/nonvalidating/load-external-dtd“, false);

• Source xmlSource = new SAXSource(spf.newSAXParser().getXMLReader(), new InputSource(new StringReader(xml)));
• JAXBContext jc = JAXBContext.newInstance(Object.class);
• Unmarshaller um = jc.createUnmarshaller();
• um.unmarshal(xmlSource);

XPathExpression

An XPathExpression is similar to an Unmarshaller where it can’t be configured securely by itself, so the untrusted data must be parsed through another securable XML parser first. For example:

• DocumentBuilderFactory df =DocumentBuilderFactory.newInstance();
• df.setAttribute(XMLConstants.ACCESS_EXTERNAL_DTD, “”);
• df.setAttribute(XMLConstants.ACCESS_EXTERNAL_SCHEMA, “”);
• builder = df.newDocumentBuilder();
• xPathExpression.evaluate( builder.parse(new ByteArrayInputStream(xml.getBytes())) );

Reverse DNS lookup and Java

http://archive.oreilly.com/pub/post/reverse_dns_lookup_and_java.html

Check your code dependency vulnerabilities

Here is the CLI tool from OWASP. This basically detect publicly disclosed vulnerabilities with your code dependency libraries.

https://jeremylong.github.io/DependencyCheck/dependency-check-cli/index.html

Best Practice: Don't combine Refactoring commit with the actual fix changes

For a better code reviewability, don't combine refactoring changes and fix changes into a single commit.

If it's a very small refactoring change, it's completely fine, we can combine together. Otherwise, it's going to be difficult for the reviewer to read the code and understand it. The Reviewer has to change the context from refactoring to an actual fix and vice versa, and in the process, we tend to ignore the actual fix code and that leads a problem again!


Let me point to a first resource which I found when googled it about this subject.
http://jakegoulding.com/blog/2012/11/04/refactor-and-make-changes-in-different-commits/

Programmatically executing a command in eclipse

If you know the eclipse command and you want to execute that in the programmatical way, you need to use IHandlerService.

Below is the example to perform toggle full-screen command from eclipse.

IHandlerService handlerService =

 (IHandlerService) PlatformUI.getWorkbench().getService(IHandlerService.class);

if (handlerService == null)

{

                 return null;

}

try

{

   handlerService.executeCommand("org.eclipse.ui.cocoa.fullscreenWindow", null);

}

catch (Exception ex)

{

//log exception

}

OSGI bundle/plugin class loading

Being a programmer, I would ask you to take a look at this class.

Plugin:
org.eclipse.osgi_3.10.2.v20150203-1939.jar

Class:
BundleLoader

Below 2 methods will give lot of understanding:

Class<?> findClass(String name, boolean checkParent) throws ClassNotFoundException {

if (checkParent && parent != null && name.startsWith(JAVA_PACKAGE))

// 1) if startsWith "java." delegate to parent and terminate search

// we want to throw ClassNotFoundExceptions if a java.* class cannot be loaded from the parent.

return parent.loadClass(name);

return findClassInternal(name, checkParent);

}

private Class<?> findClassInternal(String name, boolean checkParent) throws ClassNotFoundException {

if (debug.DEBUG_LOADER)

Debug.println("BundleLoader[" + this + "].findClassInternal(" + name + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$

String pkgName = getPackageName(name);

boolean bootDelegation = false;

// follow the OSGi delegation model

if (checkParent && parent != null && container.isBootDelegationPackage(pkgName))

// 2) if part of the bootdelegation list then delegate to parent and continue of failure

try {

return parent.loadClass(name);

} catch (ClassNotFoundException cnfe) {

// we want to continue

bootDelegation = true;

}

Class<?> result = null;

try {

result = (Class<?>) searchHooks(name, PRE_CLASS);

} catch (ClassNotFoundException e) {

throw e;

} catch (FileNotFoundException e) {

// will not happen

}

if (result != null)

return result;

// 3) search the imported packages

PackageSource source = findImportedSource(pkgName, null);

if (source != null) {

if (debug.DEBUG_LOADER) {

Debug.println("BundleLoader[" + this + "] loading from import package: " + source); //$NON-NLS-1$ //$NON-NLS-2$

}

// 3) found import source terminate search at the source

result = source.loadClass(name);

if (result != null)

return result;

throw new ClassNotFoundException(name + " cannot be found by " + this); //$NON-NLS-1$

}

// 4) search the required bundles

source = findRequiredSource(pkgName, null);

if (source != null) {

if (debug.DEBUG_LOADER) {

Debug.println("BundleLoader[" + this + "] loading from required bundle package: " + source); //$NON-NLS-1$ //$NON-NLS-2$

}

// 4) attempt to load from source but continue on failure

result = source.loadClass(name);

}

// 5) search the local bundle

if (result == null)

result = findLocalClass(name);

if (result != null)

return result;

// 6) attempt to find a dynamic import source; only do this if a required source was not found

if (source == null) {

source = findDynamicSource(pkgName);

if (source != null) {

result = source.loadClass(name);

if (result != null)

return result;

// must throw CNFE if dynamic import source does not have the class

throw new ClassNotFoundException(name + " cannot be found by " + this); //$NON-NLS-1$

}

}

if (result == null)

try {

result = (Class<?>) searchHooks(name, POST_CLASS);

} catch (ClassNotFoundException e) {

throw e;

} catch (FileNotFoundException e) {

// will not happen

}

// do buddy policy loading

if (result == null && policy != null)

result = policy.doBuddyClassLoading(name);

if (result != null)

return result;

// hack to support backwards compatibility for bootdelegation

// or last resort; do class context trick to work around VM bugs

if (parent != null && !bootDelegation && ((checkParent && container.getConfiguration().compatibilityBootDelegation) || isRequestFromVM()))

// we don't need to continue if a CNFE is thrown here.

try {

return parent.loadClass(name);

} catch (ClassNotFoundException e) {

// we want to generate our own exception below

}

throw new ClassNotFoundException(name + " cannot be found by " + this); //$NON-NLS-1$

}

Resources:

http://moi.vonos.net/java/osgi-classloaders/