我正在开发一个
Android应用程序
android:minSdkVersion="14"
在这个需要解析xml的应用程序中.因为我正在使用像这样的DOM解析器
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = null;
Document doc = null;
try {
dBuilder = dbFactory.newDocumentBuilder();
} catch (ParserConfigurationException e) {
e.printStackTrace();
}
但是当检查代码的安全性时,我遇到了两个安全问题
dBuilder = dbFactory.newDocumentBuilder();,它们是
1.XML Entity Expansion Injection (XML Bomb)
2.XML External Entity Injection (XXE attack)
经过一番研究,我加入了这条线
dbFactory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING,true);
但是现在我执行此行时会遇到异常
javax.xml.parsers.ParserConfigurationException: http://javax.xml.XMLConstants/feature/secure-processing
有谁能够帮我？
解决方法
您是否尝试过
OWASP page的以下代码段？
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException; // catching unsupported features
...
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
// This is the PRIMARY defense. If DTDs (doctypes) are disallowed,almost all XML entity attacks are prevented
// Xerces 2 only - http://xerces.apache.org/xerces2-j/features.html#disallow-doctype-decl
String FEATURE = "http://apache.org/xml/features/disallow-doctype-decl";
dbf.setFeature(FEATURE,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
FEATURE = "http://xml.org/sax/features/external-general-entities";
dbf.setFeature(FEATURE,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
FEATURE = "http://xml.org/sax/features/external-parameter-entities";
dbf.setFeature(FEATURE,false);
// and these as well,per Timothy Morgan's 2014 paper: "XML Schema,DTD,and Entity Attacks" (see reference below)
dbf.setXIncludeAware(false);
dbf.setExpandEntityReferences(false);
// And,per Timothy Morgan: "If for some reason support for inline DOCTYPEs are a requirement,then
// ensure the entity settings are disabled (as shown above) and beware that SSRF attacks
// (http://cwe.mitre.org/data/definitions/918.html) and denial
// of service attacks (such as billion laughs or decompression bombs via "jar:") are a risk."
// remaining parser logic
...
catch (ParserConfigurationException e) {
// This should catch a Failed setFeature feature
logger.info("ParserConfigurationException was thrown. The feature '" +
FEATURE +
"' is probably not supported by your XML processor.");
...
}
catch (SAXException e) {
// On Apache,this should be thrown when disallowing DOCTYPE
logger.warning("A DOCTYPE was passed into the XML document");
...
}
catch (IOException e) {
// XXE that points to a file that doesn't exist
logger.error("IOException occurred,XXE may still possible: " + e.getMessage());
...
}
