rules:
  - id: documentbuilderfactory-xxe
    languages:
      - clojure
    severity: ERROR
    metadata:
      cwe:
      - 'CWE-611: Improper Restriction of XML External Entity Reference'
      owasp:
      - A04:2017 - XML External Entities (XXE)
      - A05:2021 - Security Misconfiguration
      asvs:
        section: V5 Validation, Sanitization and Encoding
        control_id: 5.5.2 Insecue XML Deserialization
        control_url: https://github.com/OWASP/ASVS/blob/master/4.0/en/0x13-V5-Validation-Sanitization-Encoding.md#v55-deserialization-prevention
        version: '4'
      references:
      - https://semgrep.dev/blog/2022/xml-security-in-java
      - https://semgrep.dev/docs/cheat-sheets/java-xxe/
      - https://xerces.apache.org/xerces2-j/features.html
      source-rule-url: https://github.com/clj-holmes/clj-holmes-rules/blob/main/security/xxe-clojure-xml/xxe-clojure-xml.yml
      category: security
      technology:
      - clojure
      - xml
      cwe2022-top25: true
      cwe2021-top25: true
      subcategory:
      - vuln
      likelihood: LOW
      impact: HIGH
      confidence: HIGH
    message: >-
      DOCTYPE declarations are enabled for javax.xml.parsers.SAXParserFactory.
      Without prohibiting external entity declarations, this is vulnerable to XML external entity attacks.
      Disable this by setting the feature "http://apache.org/xml/features/disallow-doctype-decl" to true.
      Alternatively, allow DOCTYPE declarations and only prohibit external entities declarations.
      This can be done by setting the features "http://xml.org/sax/features/external-general-entities" and
      "http://xml.org/sax/features/external-parameter-entities" to false.
    patterns:
      - pattern-inside: |
          (ns ... (:require [clojure.xml :as ...]))
          ...
      - pattern-either:
          - pattern-inside: |
              (def ... ... ( ... ))
          - pattern-inside: |
              (defn ... ... ( ... ))
      - pattern-either:
        - pattern: (clojure.xml/parse $INPUT)
        - patterns:
          - pattern-inside: |
              (doto (javax.xml.parsers.SAXParserFactory/newInstance) ...)
          - pattern: (.setFeature "http://apache.org/xml/features/disallow-doctype-decl" false)
          - pattern-not-inside: |
              (doto (javax.xml.parsers.SAXParserFactory/newInstance)
                ...
                (.setFeature "http://xml.org/sax/features/external-general-entities" false)
                ...
                (.setFeature "http://xml.org/sax/features/external-parameter-entities" false)
                ...)
          - pattern-not-inside: |
              (doto (javax.xml.parsers.SAXParserFactory/newInstance)
                ...
                (.setFeature "http://xml.org/sax/features/external-parameter-entities" false)
                ...
                (.setFeature "http://xml.org/sax/features/external-general-entities" false)
                ...)