//source from https://pay.weixin.qq.com/wiki/doc/api/micropay.php?chapter=23_5
XXE漏洞需要您在回调处理代码里面解析XML之前，加入禁用实体解析的代码，不同语言设置的内容不同，下面提供了几种主流开发语言的设置指引(您可以根据关键字找到xml解析组件采取对应方法升级)：
【PHP】 解析XML代码前加入：
//下一行为关键代码
libxml_disable_entity_loader(true);
$xml = simplexml_load_string($xmlContent);
......【JAVA】
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException; // catching unsupported features
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
String FEATURE = null;
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
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
// JDK7+ - http://xml.org/sax/features/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
// JDK7+ - http://xml.org/sax/features/external-parameter-entities
FEATURE = "http://xml.org/sax/features/external-parameter-entities";
dbf.setFeature(FEATURE, false);
// Disable external DTDs as well
FEATURE = "http://apache.org/xml/features/nonvalidating/load-external-dtd";
dbf.setFeature(FEATURE, false);
// and these as well, per Timothy Morgan's 2014 paper: "XML Schema, DTD, and Entity Attacks"
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());
}
DocumentBuilder safebuilder = dbf.newDocumentBuilder();【.Net】
XmlDocument doc= new XmlDocument();
//下一行为关键代码
doc.XmlResolver = null;
......【ASP】
Set xmldom = Server.CreateObject("MSXML2.DOMDocument")
'下一行为关键代码
xmldom.resolveExternals = false
......【Python】
from lxml import etree
xmlData = etree.parse(xmlSource,etree.XMLParser(resolve_entities=False))
......【c/c++(常用库为libxml2 libxerces-c)】 【libxml2】:
确保关闭配置选项：XML_PARSE_NOENT 和 XML_PARSE_DTDLOAD
2.9版本以上已修复XXE
【Coldfusion/lucee和node.js】 请更新到库的最新版本
【libxerces-c】： 如果用的是XercesDOMParser:
XercesDOMParser *parser = new XercesDOMParser;
parser->setCreateEntityReferenceNodes(false);
如果是用SAXParser:
SAXParser* parser = new SAXParser;
parser->setDisableDefaultEntityResolution(true);
如果是用SAX2XMLReader:
SAX2XMLReader* reader = XMLReaderFactory::createXMLReader();
parser->setFeature(XMLUni::fgXercesDisableDefaultEntityResolution, true);