Flag is: Md5LenghtExtAttackNowYouSee<!--<?php
header("Content-type:text/html;charset=utf-8");
include "_flag.php";
include "salt.php";


$mysalt=SALT;

if(isset($_GET['filepath'])&&!empty($_GET['filepath']) &&isset($_GET['sign']) &&!empty($_GET['sign'])){
	myreadfile($_GET['filepath'],$mysalt,$_GET['sign']);
	
}
else{
	//降低一点复杂度
	var_dump(strlen($mysalt));
	testsign("/etc/hosts",$mysalt);
}


function myhash($message,$mysalt){
		return md5($mysalt.$message);
}
function checksign($message,$mysalt,$sign){
    if($sign==myhash($message,$mysalt)){
    	return True;
    }else{
    	return False;
    }
}
function myreadfile($filepath,$mysalt,$sign){
	$res=checksign($filepath,$mysalt,$sign);
    if($res){
    	echo getfile($filepath);
    }
    else{
    	echo 'sign error!';
    }
}
function testsign($filepath,$mysalt){
	echo myhash($filepath,$mysalt);
}


echo "<!--".file_get_contents(__FILE__);