CODEWITHSUNDEEP
javadocumentdtd
joe
joe

Reputation: 17478

Make DocumentBuilder.parse ignore DTD references

When I parse my xml file (variable f) in this method, I get an error

C:\Documents and Settings\joe\Desktop\aicpcudev\OnlineModule\map.dtd (The system cannot find the path specified)

I know I do not have the dtd, nor do I need it. How can I parse this File object into a Document object while ignoring DTD reference errors?

private static Document getDoc(File f, String docId) throws Exception{
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    DocumentBuilder db = dbf.newDocumentBuilder();
    Document doc = db.parse(f);


    return doc;
}

Upvotes: 90

Views: 90790

Answers (7)

McCoy
McCoy

Reputation: 820

I'm working with sonarqube, and sonarlint for eclipse showed me Untrusted XML should be parsed without resolving external data (squid:S2755)

I managed to solve it using:

    factory = DocumentBuilderFactory.newInstance();

    factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", 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
    factory.setFeature("http://xml.org/sax/features/external-general-entities", 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
    factory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);

    // Disable external DTDs as well
    factory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);

    // and these as well, per Timothy Morgan's 2014 paper: "XML Schema, DTD, and Entity Attacks"
    factory.setXIncludeAware(false);
    factory.setExpandEntityReferences(false);

Upvotes: 0

Peter J
Peter J

Reputation: 61

I found an issue where the DTD file was in the jar file along with the XML. I solved the issue based on the examples here, as follows: -

DocumentBuilder db = dbf.newDocumentBuilder();
db.setEntityResolver(new EntityResolver() {
    public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
        if (systemId.contains("doc.dtd")) {
             InputStream dtdStream = MyClass.class
                     .getResourceAsStream("/my/package/doc.dtd");
             return new InputSource(dtdStream);
         } else {
             return null;
         }
      }
});

Upvotes: 6

Shoaib Khan
Shoaib Khan

Reputation: 939

Source XML (With DTD)

<!DOCTYPE MYSERVICE SYSTEM "./MYSERVICE.DTD">
<MYACCSERVICE>
   <REQ_PAYLOAD>
      <ACCOUNT>1234567890</ACCOUNT>
      <BRANCH>001</BRANCH>
      <CURRENCY>USD</CURRENCY>
      <TRANS_REFERENCE>201611100000777</TRANS_REFERENCE>
   </REQ_PAYLOAD>
</MYACCSERVICE>

Java DOM implementation for accepting above XML as String and removing DTD declaration 

public Document removeDTDFromXML(String payload) throws Exception {

    System.out.println("### Payload received in XMlDTDRemover: " + payload);

    Document doc = null;
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    try {

        dbf.setValidating(false);
        dbf.setNamespaceAware(true);
        dbf.setFeature("http://xml.org/sax/features/namespaces", false);
        dbf.setFeature("http://xml.org/sax/features/validation", false);
        dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", false);
        dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);

        DocumentBuilder db = dbf.newDocumentBuilder();

        InputSource is = new InputSource();
        is.setCharacterStream(new StringReader(payload));
        doc = db.parse(is); 

    } catch (ParserConfigurationException e) {
        System.out.println("Parse Error: " + e.getMessage());
        return null;
    } catch (SAXException e) {
        System.out.println("SAX Error: " + e.getMessage());
        return null;
    } catch (IOException e) {
        System.out.println("IO Error: " + e.getMessage());
        return null;
    }
    return doc;

}

Destination XML (Without DTD)

<MYACCSERVICE>
   <REQ_PAYLOAD>
      <ACCOUNT>1234567890</ACCOUNT>
      <BRANCH>001</BRANCH>
      <CURRENCY>USD</CURRENCY>
      <TRANS_REFERENCE>201611100000777</TRANS_REFERENCE>
   </REQ_PAYLOAD>
</MYACCSERVICE>

Upvotes: 6

jt.
jt.

Reputation: 7705

Try setting features on the DocumentBuilderFactory: 

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

dbf.setValidating(false);
dbf.setNamespaceAware(true);
dbf.setFeature("http://xml.org/sax/features/namespaces", false);
dbf.setFeature("http://xml.org/sax/features/validation", false);
dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", false);
dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);

DocumentBuilder db = dbf.newDocumentBuilder();
...

Ultimately, I think the options are specific to the parser implementation. Here is some documentation for Xerces2 if that helps.

Upvotes: 149

toolkit
toolkit

Reputation: 50237

A similar approach to the one suggested by @anjanb

    builder.setEntityResolver(new EntityResolver() {
        @Override
        public InputSource resolveEntity(String publicId, String systemId)
                throws SAXException, IOException {
            if (systemId.contains("foo.dtd")) {
                return new InputSource(new StringReader(""));
            } else {
                return null;
            }
        }
    });

I found that simply returning an empty InputSource worked just as well?

Upvotes: 61

anjanb
anjanb

Reputation: 13867

here's another user who got the same issue : http://forums.sun.com/thread.jspa?threadID=284209&forumID=34

user ddssot on that post says

myDocumentBuilder.setEntityResolver(new EntityResolver() {
          public InputSource resolveEntity(java.lang.String publicId, java.lang.String systemId)
                 throws SAXException, java.io.IOException
          {
            if (publicId.equals("--myDTDpublicID--"))
              // this deactivates the open office DTD
              return new InputSource(new ByteArrayInputStream("<?xml version='1.0' encoding='UTF-8'?>".getBytes()));
            else return null;
          }
});

The user further mentions "As you can see, when the parser hits the DTD, the entity resolver is called. I recognize my DTD with its specific ID and return an empty XML doc instead of the real DTD, stopping all validation..."

Hope this helps.

Upvotes: 2

Edward Z. Yang
Edward Z. Yang

Reputation: 26742

I know I do not have the dtd, nor do I need it.

I am suspicious of this statement; does your document contain any entity references? If so, you definitely need the DTD.

Anyway, the usual way of preventing this from happening is using an XML catalog to define a local path for "map.dtd".

Upvotes: 2

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