114 lines
4.5 KiB
Plaintext
114 lines
4.5 KiB
Plaintext
== Why is this an issue?
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include::../description.adoc[]
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=== Noncompliant code example
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For https://docs.oracle.com/javase/9/docs/api/javax/xml/parsers/DocumentBuilderFactory.html[DocumentBuilder], https://docs.oracle.com/javase/9/docs/api/javax/xml/parsers/SAXParserFactory.html[SAXParser] and https://docs.oracle.com/javase/9/docs/api/javax/xml/validation/SchemaFactory.html[Schema] JAPX factories:
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[source,java]
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----
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DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
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factory.setValidating(true); // Noncompliant
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factory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", true); // Noncompliant
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SAXParserFactory factory = SAXParserFactory.newInstance();
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factory.setValidating(true); // Noncompliant
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factory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", true); // Noncompliant
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SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
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schemaFactory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", true); // Noncompliant
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----
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For https://dom4j.github.io/[Dom4j] library:
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[source,java]
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----
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SAXReader xmlReader = new SAXReader(); // Noncompliant
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xmlReader.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", true); // Noncompliant
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----
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For http://www.jdom.org/[Jdom2] library:
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[source,java]
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----
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SAXBuilder builder = new SAXBuilder();
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builder.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", true); // Noncompliant
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----
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=== Compliant solution
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For https://docs.oracle.com/javase/9/docs/api/javax/xml/parsers/DocumentBuilderFactory.html[DocumentBuilder], https://docs.oracle.com/javase/9/docs/api/javax/xml/parsers/SAXParserFactory.html[SAXParser] and https://docs.oracle.com/javase/9/docs/api/javax/xml/validation/SchemaFactory.html[Schema] JAPX factories:
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[source,java]
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----
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DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
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factory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
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SAXParserFactory factory = SAXParserFactory.newInstance();
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factory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
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SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
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schemaFactory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
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----
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For https://dom4j.github.io/[Dom4j] library:
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[source,java]
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----
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SAXReader xmlReader = new SAXReader(); // Noncompliant
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xmlReader.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
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----
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For http://www.jdom.org/[Jdom2] library:
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[source,java]
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----
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SAXBuilder builder = new SAXBuilder();
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builder.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
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----
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=== Exceptions
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This rules does not raise an issue when an `EntityResolver` is set.
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[source,java]
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----
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DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
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factory.setValidating(true);
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DocumentBuilder builder = factory.newDocumentBuilder();
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builder.setEntityResolver(new MyEntityResolver());
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SAXBuilder builder = new SAXBuilder();
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builder.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", true);
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builder.setEntityResolver(new EntityResolver());
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----
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== Resources
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* https://docs.oracle.com/en/java/javase/13/security/java-api-xml-processing-jaxp-security-guide.html#GUID-8CD65EF5-D113-4D5C-A564-B875C8625FAC[Oracle Java Documentation] - XML External Entity Injection Attack
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* OWASP - https://owasp.org/www-project-top-ten/2017/A4_2017-XML_External_Entities_(XXE)[Top 10 2017 Category A4 - XML External Entities (XXE)]
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* https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html#java[OWASP XXE Prevention Cheat Sheet]
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* CWE - https://cwe.mitre.org/data/definitions/611[CWE-611 - Information Exposure Through XML External Entity Reference]
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* CWE - https://cwe.mitre.org/data/definitions/827[CWE-827 - Improper Control of Document Type Definition]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Disable loading of external schemas in XML parsing.
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'''
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== Comments And Links
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(visible only on this page)
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=== on 25 Jan 2022, 10:34:00 Quentin Jaquier wrote:
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Quick fixes (for Java): even if it is technically possible to provide a fix that would result in compliant code, it does not sound wise to set properties blindly, as it can have side effects. Fixing the issue requires a careful and good understanding of the overall context of the code.
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endif::env-github,rspecator-view[]
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