[PHP知识库]CTFshow php特性 web115

源码

<?php

/*
# -*- coding: utf-8 -*-
# @Author: Firebasky
# @Date:   2020-09-16 11:25:09
# @Last Modified by:   h1xa
# @Last Modified time: 2020-10-01 15:08:19

*/

include('flag.php');
highlight_file(__FILE__);
error_reporting(0);
function filter($num){
    $num=str_replace("0x","1",$num);
    $num=str_replace("0","1",$num);
    $num=str_replace(".","1",$num);
    $num=str_replace("e","1",$num);
    $num=str_replace("+","1",$num);
    return $num;
}
$num=$_GET['num'];
if(is_numeric($num) and $num!=='36' and trim($num)!=='36' and filter($num)=='36'){
    if($num=='36'){
        echo $flag;
    }else{
        echo "hacker!!";
    }
}else{
    echo "hacker!!!";
} hacker!!!

思路

慢慢一层一层在本地尝试

测试
php <?php //来自羽师傅 for (i=0; i <128 ; $i++) { x=chr(i).'1'; if(is_numeric($x)==true){ echo urlencode(chr($i))."\n"; } } // %09 %0A %0B %0C %0D + %2B - . 0 1 2 3 4 5 6 7 8 9

trim不过滤 %0c

题解

?num=%0c36

总结

水题