使用JAXB XMLStreamReader防止XXE攻击

问题描述

我对JAXB并不陌生，在我们的代码审核中，有人建议用JAXB防止XXE攻击.我找到了相关的答案:使用JAXB防止XXE攻击

我现有的代码如下:

if (properties.getProperty(MANIFEST) != null && !properties.getProperty(MANIFEST).isEmpty()) {
                String manifestString =  properties.getProperty(MANIFEST);
                ByteArrayInputStream is = new ByteArrayInputStream(manifestString.getBytes());
                try {
                    this.manifest = (Manifest) getJaxbContext().createUnmarshaller().unmarshal(is);
                }
                catch (JAXBException e) {
                    LOG.warn("There was an error trying to convert xml String to Manifest - {}", e.getMessage(), e);
                }
                
            }

基于答案，而不是使用ByteArrayInputStream，我应该使用具有某些属性false的XMLStreamReader.

在建议的答案中，它表示:

XMLStreamReader xsr = xif.createXMLStreamReader(new StreamSource("src/xxe/input.xml"));

我不知道什么是"src/xxe/input.xml"，它对于我的解决方案来说是必需的.谁能解释一下?

解决方案

另一个问题的答案中的src/xxe/input.xml是该问题正在处理的XML的源位置-即作为URL资源访问的文件名. /p>

在您的情况下，您的XML在String manifestString中提供-因此，需要为您的StreamSource提供此字符串作为其来源，而不是文件位置.

这可以通过StringReader完成:

 import java.io.StringReader

...

StringReader manifestReader = new StringReader(manifestString); 
XMLStreamReader xsr = xif.createXMLStreamReader(new StreamSource(manifestReader));
 

我将代码分成两行以使其更清晰-但您可以根据需要将它们折叠回一行:

 XMLStreamReader xsr = xif.createXMLStreamReader(
        new StreamSource(new StringReader(manifestString)));
 

上面的代码假定您已经创建了上下文和xif输入工厂:

 JAXBContext jc = JAXBContext.newInstance(Manifest.class);
XMLInputFactory xif = XMLInputFactory.newFactory();
xif.setProperty(XMLInputFactory.IS_SUPPORTING_EXTERNAL_ENTITIES, false);
xif.setProperty(XMLInputFactory.SUPPORT_DTD, false);
 

然后，您可以按照通常的方式进行封送:

 Unmarshaller unmarshaller = jc.createUnmarshaller();
Manifest manifest = (Manifest) unmarshaller.unmarshal(xsr);
 

I am very new to JAXB and in our code audit, there was suggestion on preventing XXE attack with JAXB. I found related answer: Prevent XXE Attack with JAXB

My existing code looks like this:

if (properties.getProperty(MANIFEST) != null && !properties.getProperty(MANIFEST).isEmpty()) {
                String manifestString =  properties.getProperty(MANIFEST);
                ByteArrayInputStream is = new ByteArrayInputStream(manifestString.getBytes());
                try {
                    this.manifest = (Manifest) getJaxbContext().createUnmarshaller().unmarshal(is);
                }
                catch (JAXBException e) {
                    LOG.warn("There was an error trying to convert xml String to Manifest - {}", e.getMessage(), e);
                }
                
            }

Based on the answer, instead of using ByteArrayInputStream, I am supposed to use XMLStreamReader with some properties false.

In suggested answer, it says:

XMLStreamReader xsr = xif.createXMLStreamReader(new StreamSource("src/xxe/input.xml"));

I don't understand what 'src/xxe/input.xml' is and what it needs to be for my solution. Can anyone please explain?

解决方案

The src/xxe/input.xml from the answer in the other question is that question's source location for the XML being processed - namely a filename, accessed as a URL resource.

In your case, your XML is provided in String manifestString - therefore your StreamSource needs to be given this string as its source, not a file location.

This can be done using a StringReader:

import java.io.StringReader

...

StringReader manifestReader = new StringReader(manifestString); 
XMLStreamReader xsr = xif.createXMLStreamReader(new StreamSource(manifestReader));

I split the code into 2 lines to make it clearer - but you can collapse them back to one line if you prefer:

XMLStreamReader xsr = xif.createXMLStreamReader(
        new StreamSource(new StringReader(manifestString)));

The above code assumes you have already created your context and the xif input factory:

JAXBContext jc = JAXBContext.newInstance(Manifest.class);
XMLInputFactory xif = XMLInputFactory.newFactory();
xif.setProperty(XMLInputFactory.IS_SUPPORTING_EXTERNAL_ENTITIES, false);
xif.setProperty(XMLInputFactory.SUPPORT_DTD, false);

Then you can unmarshal in the usual way:

Unmarshaller unmarshaller = jc.createUnmarshaller();
Manifest manifest = (Manifest) unmarshaller.unmarshal(xsr);

这篇关于使用JAXB XMLStreamReader防止XXE攻击的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！