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SpyBug

Overview

Background

As Pandora made her way through the ancient tombs, she received a message from her contact in the Intergalactic Ministry of Spies. They had intercepted a communication from a rival treasure hunter who was working for the alien species. The message contained information about a digital portal that leads to a software used for intercepting audio from the Ministry's communication channels. Can you hack into the portal and take down the aliens counter-spying operation?

Enumeration

Home page:

In here, we see there's a login page.

In this challenge, we can download a file:

┌[siunam♥earth]-(~/ctf/Cyber-Apocalypse-2023/Web/SpyBug)-[2023.03.21|14:00:33(HKT)]
└> file web_spybug.zip 
web_spybug.zip: Zip archive data, at least v1.0 to extract, compression method=store
┌[siunam♥earth]-(~/ctf/Cyber-Apocalypse-2023/Web/SpyBug)-[2023.03.21|14:00:34(HKT)]
└> unzip web_spybug.zip    
Archive:  web_spybug.zip
   creating: web_spybug/
  inflating: web_spybug/Dockerfile   
  inflating: web_spybug/build-docker.sh  
   creating: web_spybug/challenge/
   creating: web_spybug/challenge/control-panel/
  inflating: web_spybug/challenge/control-panel/example.env  
   creating: web_spybug/challenge/control-panel/middleware/
  inflating: web_spybug/challenge/control-panel/middleware/authagent.js  
  inflating: web_spybug/challenge/control-panel/middleware/authuser.js  
  inflating: web_spybug/challenge/control-panel/index.js  
   creating: web_spybug/challenge/control-panel/utils/
  inflating: web_spybug/challenge/control-panel/utils/database.js  
  inflating: web_spybug/challenge/control-panel/utils/adminbot.js  
   creating: web_spybug/challenge/control-panel/models/
  inflating: web_spybug/challenge/control-panel/models/user.js  
  inflating: web_spybug/challenge/control-panel/models/recordings.js  
  inflating: web_spybug/challenge/control-panel/models/index.js  
  inflating: web_spybug/challenge/control-panel/models/agent.js  
  inflating: web_spybug/challenge/control-panel/package-lock.json  
  inflating: web_spybug/challenge/control-panel/package.json  
   creating: web_spybug/challenge/control-panel/static/
   creating: web_spybug/challenge/control-panel/static/css/
  inflating: web_spybug/challenge/control-panel/static/css/bootstrap.min.css  
  inflating: web_spybug/challenge/control-panel/static/css/custom.css  
  inflating: web_spybug/challenge/control-panel/static/css/bootstrap.min.css.map  
  inflating: web_spybug/challenge/control-panel/static/css/line-awesome.min.css  
   creating: web_spybug/challenge/control-panel/static/js/
  inflating: web_spybug/challenge/control-panel/static/js/bootstrap.min.js  
   creating: web_spybug/challenge/control-panel/static/img/
 extracting: web_spybug/challenge/control-panel/static/img/icon.png  
   creating: web_spybug/challenge/control-panel/static/fonts/
  inflating: web_spybug/challenge/control-panel/static/fonts/la-regular-400.woff  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.ttf  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.eot  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-regular-400.svg  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.woff2  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.woff  
  inflating: web_spybug/challenge/control-panel/static/fonts/Orbitron-Regular.ttf  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.eot  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.ttf  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.woff  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.svg  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.woff2  
  inflating: web_spybug/challenge/control-panel/static/fonts/OFL.txt  
 extracting: web_spybug/challenge/control-panel/static/fonts/la-regular-400.woff2  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-regular-400.eot  
  inflating: web_spybug/challenge/control-panel/static/fonts/Orbitron-VariableFont_wght.ttf  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.svg  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-regular-400.ttf  
   creating: web_spybug/challenge/control-panel/views/
  inflating: web_spybug/challenge/control-panel/views/login.pug  
  inflating: web_spybug/challenge/control-panel/views/head.pug  
  inflating: web_spybug/challenge/control-panel/views/panel.pug  
   creating: web_spybug/challenge/control-panel/routes/
  inflating: web_spybug/challenge/control-panel/routes/generic.js  
  inflating: web_spybug/challenge/control-panel/routes/agents.js  
  inflating: web_spybug/challenge/control-panel/routes/panel.js  
   creating: web_spybug/challenge/agent/
  inflating: web_spybug/challenge/agent/spybug-agent.go  
  inflating: web_spybug/challenge/agent/go.mod  
  inflating: web_spybug/challenge/agent/go.sum  
  inflating: web_spybug/challenge/agent/rec.wav  
  inflating: web_spybug/challenge/.prettierignore  
  inflating: web_spybug/challenge/.gitignore  
   creating: web_spybug/conf/
  inflating: web_spybug/conf/supervisord.conf

Enumeration

Home page:

In here, we see there's a login page.

In this challenge, we can download a file:

┌[siunam♥earth]-(~/ctf/Cyber-Apocalypse-2023/Web/SpyBug)-[2023.03.19|22:25:44(HKT)]
└> file web_spybug.zip              
web_spybug.zip: Zip archive data, at least v1.0 to extract, compression method=store
┌[siunam♥earth]-(~/ctf/Cyber-Apocalypse-2023/Web/SpyBug)-[2023.03.19|22:25:46(HKT)]
└> unzip web_spybug.zip              
Archive:  web_spybug.zip
   creating: web_spybug/
  inflating: web_spybug/Dockerfile   
  inflating: web_spybug/build-docker.sh  
   creating: web_spybug/challenge/
   creating: web_spybug/challenge/control-panel/
  inflating: web_spybug/challenge/control-panel/example.env  
   creating: web_spybug/challenge/control-panel/middleware/
  inflating: web_spybug/challenge/control-panel/middleware/authagent.js  
  inflating: web_spybug/challenge/control-panel/middleware/authuser.js  
  inflating: web_spybug/challenge/control-panel/index.js  
   creating: web_spybug/challenge/control-panel/utils/
  inflating: web_spybug/challenge/control-panel/utils/database.js  
  inflating: web_spybug/challenge/control-panel/utils/adminbot.js  
   creating: web_spybug/challenge/control-panel/models/
  inflating: web_spybug/challenge/control-panel/models/user.js  
  inflating: web_spybug/challenge/control-panel/models/recordings.js  
  inflating: web_spybug/challenge/control-panel/models/index.js  
  inflating: web_spybug/challenge/control-panel/models/agent.js  
  inflating: web_spybug/challenge/control-panel/package-lock.json  
  inflating: web_spybug/challenge/control-panel/package.json  
   creating: web_spybug/challenge/control-panel/static/
   creating: web_spybug/challenge/control-panel/static/css/
  inflating: web_spybug/challenge/control-panel/static/css/bootstrap.min.css  
  inflating: web_spybug/challenge/control-panel/static/css/custom.css  
  inflating: web_spybug/challenge/control-panel/static/css/bootstrap.min.css.map  
  inflating: web_spybug/challenge/control-panel/static/css/line-awesome.min.css  
   creating: web_spybug/challenge/control-panel/static/js/
  inflating: web_spybug/challenge/control-panel/static/js/bootstrap.min.js  
   creating: web_spybug/challenge/control-panel/static/img/
 extracting: web_spybug/challenge/control-panel/static/img/icon.png  
   creating: web_spybug/challenge/control-panel/static/fonts/
  inflating: web_spybug/challenge/control-panel/static/fonts/la-regular-400.woff  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.ttf  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.eot  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-regular-400.svg  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.woff2  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.woff  
  inflating: web_spybug/challenge/control-panel/static/fonts/Orbitron-Regular.ttf  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.eot  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.ttf  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.woff  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-brands-400.svg  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.woff2  
  inflating: web_spybug/challenge/control-panel/static/fonts/OFL.txt  
 extracting: web_spybug/challenge/control-panel/static/fonts/la-regular-400.woff2  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-regular-400.eot  
  inflating: web_spybug/challenge/control-panel/static/fonts/Orbitron-VariableFont_wght.ttf  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-solid-900.svg  
  inflating: web_spybug/challenge/control-panel/static/fonts/la-regular-400.ttf  
   creating: web_spybug/challenge/control-panel/views/
  inflating: web_spybug/challenge/control-panel/views/login.pug  
  inflating: web_spybug/challenge/control-panel/views/head.pug  
  inflating: web_spybug/challenge/control-panel/views/panel.pug  
   creating: web_spybug/challenge/control-panel/routes/
  inflating: web_spybug/challenge/control-panel/routes/generic.js  
  inflating: web_spybug/challenge/control-panel/routes/agents.js  
  inflating: web_spybug/challenge/control-panel/routes/panel.js  
   creating: web_spybug/challenge/agent/
  inflating: web_spybug/challenge/agent/spybug-agent.go  
  inflating: web_spybug/challenge/agent/go.mod  
  inflating: web_spybug/challenge/agent/go.sum  
  inflating: web_spybug/challenge/agent/rec.wav  
  inflating: web_spybug/challenge/.prettierignore  
  inflating: web_spybug/challenge/.gitignore  
   creating: web_spybug/conf/
  inflating: web_spybug/conf/supervisord.conf

In /views/*.pug, we see that this web application is using a JavaScript template engine called "Pug".

In /views/panel.pug, the username variable is directly concatenated:

body
	div.container.login.mt-5.mb-5
		div.row
			div.col-md-10
				h1
					i.las.la-satellite-dish
					|  Spybug v1
			div.col-md-2.float-right
				a.btn.login-btn.mt-3(href="/panel/logout") Log-out
		hr 
		h2 #{"Welcome back " + username}
		[...]

Maybe it's vulnerable to SSTI (Server-Side Template Injection)?

Let's move on.

In /utils/adminbot.js, we can see that there's an admin bot running a Chromium browser via puppeteer.

Config:

require("dotenv").config();

const puppeteer = require("puppeteer");

const browserOptions = {
  headless: true,
  executablePath: "/usr/bin/chromium-browser",
  args: [
    "--no-sandbox",
    "--disable-background-networking",
    "--disable-default-apps",
    "--disable-extensions",
    "--disable-gpu",
    "--disable-sync",
    "--disable-translate",
    "--hide-scrollbars",
    "--metrics-recording-only",
    "--mute-audio",
    "--no-first-run",
    "--safebrowsing-disable-auto-update",
    "--js-flags=--noexpose_wasm,--jitless",
  ],
};

This adminbot.js has an async function called visitPanel:

exports.visitPanel = async () => {
  try {
    const browser = await puppeteer.launch(browserOptions);
    let context = await browser.createIncognitoBrowserContext();
    let page = await context.newPage();

    await page.goto("http://0.0.0.0:" + process.env.API_PORT, {
      waitUntil: "networkidle2",
      timeout: 5000,
    });

    await page.type("#username", "admin");
    await page.type("#password", process.env.ADMIN_SECRET);
    await page.click("#loginButton");

    await page.waitForTimeout(5000);
    await browser.close();
  } catch (e) {
    console.log(e);
  }
};

It'll launch an incognito browser, then go to http://0.0.0.0:<API_PORT>.

After that, the bot will type it's username admin, password, and click "Login" button.

Finally, the browser will be closed after 5 seconds.

Armed with above information, this challenge is about client-side, and maybe we need to somehow steal admin's password?

In /routes/panel.js, we see routes (endpoints) in this web application.

First off, the /panel route:

router.get("/panel", authUser, async (req, res) => {
  res.render("panel", {
    username:
      req.session.username === "admin"
        ? process.env.FLAG
        : req.session.username,
    agents: await getAgents(),
    recordings: await getRecordings(),
  });
});

When we send a GET request to /panel and we're logged in, it checks the session's username is admin or not.

If we're admin, it'll parse the flag and username to template panel.pug, and renders it.

With that said, our goal in this challenge is to login as admin.

Route /panel/login:

router.post("/panel/login", async (req, res) => {
  let username = req.body.username;
  let password = req.body.password;

  if (!(username && password)) return res.sendStatus(400);
  if (!(await checkUserLogin(username, password)))
    return res.redirect("/panel/login");

  req.session.loggedin = true;
  req.session.username = username;

  res.redirect("/panel");
});

Function checkUserLogin in /utils/database.js:

exports.checkUserLogin = async (username, password) => {
  const results = await db.User.findOne({
    where: {
      username: username,
    },
  });

  if (!results) return false;

  if (!bcrypt.compareSync(password, results.password)) return false;

  return true;
};

When we send a POST request to /panel/login with parameter username and password, it'll check those are valid or not.

If it's valid, create a new session for our user.

Hmm… It seems like we can't do NoSQL injection to bypass the authentication in here…

In /routes/agents.js, we see there are 4 routes.

Route /agents/register:

router.get("/agents/register", async (req, res) => {
  res.status(200).json(await registerAgent());
});

Function registerAgent() in /utils/database.js:

exports.registerAgent = async () => {
  const agentId = uuidv4();
  const agentToken = uuidv4();

  const options = {
    identifier: agentId,
    token: agentToken,
  };

  await db.Agent.create(options);

  return options;
};

When we send a GET request to /agents/register, it'll call function registerAgent() from /utils/database.js to create a new agent, and response us a JSON data.

Route /agents/check/:identifier/:token:

router.get("/agents/check/:identifier/:token", authAgent, (req, res) => {
  res.sendStatus(200);
});

It first checks we're an agent or not from /middleware/authagent.js:

const { checkAgentLogin } = require("../utils/database");

module.exports = async (req, res, next) => {
  const { identifier, token } = req.params;

  if (!(identifier && token)) return res.sendStatus(400);

  if (!(await checkAgentLogin(identifier, token))) return res.sendStatus(401);

  next();
};

Function checkAgentLogin() from /utils/database:

exports.checkAgentLogin = async (agentId, agentToken) => {
  const results = await db.Agent.findOne({
    where: {
      [Op.and]: [{ identifier: agentId }, { token: agentToken }],
    },
  });

  if (!results) return false;

  return true;
};

Route /agents/details/:identifier/:token:

router.post(
  "/agents/details/:identifier/:token",
  authAgent,
  async (req, res) => {
    const { hostname, platform, arch } = req.body;
    if (!hostname || !platform || !arch) return res.sendStatus(400);
    await updateAgentDetails(req.params.identifier, hostname, platform, arch);
    res.sendStatus(200);
  }
);

Function updateAgentDetails() from /utils/database:

exports.updateAgentDetails = async (agentId, hostname, platform, arch) => {
  await db.Agent.update(
    {
      hostname: hostname,
      platform: platform,
      arch: arch,
    },
    {
      where: {
        identifier: agentId,
      },
    }
  );
};

When we send a POST request to /agents/details/:identifier/:token with parameter hostname, platform, arch, it'll update our agent details.

Route /agents/upload/:identifier/:token:

router.post(
  "/agents/upload/:identifier/:token",
  authAgent,
  multerUpload.single("recording"),
  async (req, res) => {
    if (!req.file) return res.sendStatus(400);

    const filepath = path.join("./uploads/", req.file.filename);
    const buffer = fs.readFileSync(filepath).toString("hex");

    if (!buffer.match(/52494646[a-z0-9]{8}57415645/g)) {
      fs.unlinkSync(filepath);
      return res.sendStatus(400);
    }

    await createRecording(req.params.identifier, req.file.filename);
    res.send(req.file.filename);
  }
);

multerUpload:

const storage = multer.diskStorage({
  filename: (req, file, cb) => {
    cb(null, uuidv4());
  },
  destination: (req, file, cb) => {
    cb(null, "./uploads");
  },
});

const multerUpload = multer({
  storage: storage,
  fileFilter: (req, file, cb) => {
    if (
      file.mimetype === "audio/wave" &&
      path.extname(file.originalname) === ".wav"
    ) {
      cb(null, true);
    } else {
      return cb(null, false);
    }
  },
});

Function createRecording() in /utils/database.js:

exports.createRecording = async (agentId, filepath) => {
  await db.Recording.create({
    agentId: agentId,
    filepath: "/uploads/" + filepath,
  });
};

When we send a POST request to /agents/upload/:identifier/:token, it requires to upload a WAV audio file.

Then, it checks the file contains the WAV file signatures:

If the file contains it, create a new recording, and put it to /uploads/<filepath>.

Hmm… What can we do with that…

After some local testing, I found that we can inject HTML code in the /panel via updating agent's details.

First, register a new agent:

┌[siunam♥earth]-(~/ctf/Cyber-Apocalypse-2023/Web/SpyBug/web_spybug/challenge/control-panel)-[2023.03.22|14:19:29(HKT)]
└> curl http://localhost:1337/agents/register 
{"identifier":"7983500a-13af-4cab-a99c-7f93496fcf29","token":"23ccc082-9355-406c-a083-2746a9a583f9"}

Then, use those identifier and token to update the hostname, platform and arch in /agents/details/:identifier/:token:

┌[siunam♥earth]-(~/ctf/Cyber-Apocalypse-2023/Web/SpyBug/web_spybug/challenge/control-panel)-[2023.03.22|14:40:45(HKT)]
└> curl http://localhost:1337/agents/details/7983500a-13af-4cab-a99c-7f93496fcf29/23ccc082-9355-406c-a083-2746a9a583f9 --data "hostname=host&platform=plat&arch=<h1>Header1</h1>" 
OK

After that, I added console.log() in /utils/adminbot.js, so that I can see the admin's password:

[...]
DNUIK9jqISWeLSzh93IKaSFbishkYUYn
2023-03-22 06:43:27,763 INFO reaped unknown pid 964 (terminated by SIGKILL)
2023-03-22 06:43:27,763 INFO reaped unknown pid 947 (terminated by SIGKILL)
2023-03-22 06:43:27,763 INFO reaped unknown pid 948 (terminated by SIGKILL)
2023-03-22 06:43:27,763 INFO reaped unknown pid 926 (terminated by SIGKILL)
2023-03-22 06:43:27,764 INFO reaped unknown pid 927 (terminated by SIGKILL)
[...]

/panel:

Hmm… I wonder if can we exploit stored XSS…

However, in /index.js, we see the CSP (Content Security Policy):

res.setHeader("Content-Security-Policy", "script-src 'self'; frame-ancestors 'none'; object-src 'none'; base-uri 'none';");

That being said, if we can upload our own evil JavaScript, we can execute any JavaScript code in /panel, which we'll then try to steal the flag/admin's password.

So, the exploitation process is:

In route /agents/upload/:identifier/:token, we can upload a WAV audio file:

const multerUpload = multer({
  storage: storage,
  fileFilter: (req, file, cb) => {
    if (
      file.mimetype === "audio/wave" &&
      path.extname(file.originalname) === ".wav"
    ) {
      cb(null, true);
    } else {
      return cb(null, false);
    }
  },
});
[...]
router.post(
  "/agents/upload/:identifier/:token",
  authAgent,
  multerUpload.single("recording"),
  async (req, res) => {
    if (!req.file) return res.sendStatus(400);

    const filepath = path.join("./uploads/", req.file.filename);
    console.log(filepath);
    const buffer = fs.readFileSync(filepath).toString("hex");

    if (!buffer.match(/52494646[a-z0-9]{8}57415645/g)) {
      fs.unlinkSync(filepath);
      return res.sendStatus(400);
    }

    await createRecording(req.params.identifier, req.file.filename);
    res.send(req.file.filename);
  }
);

The multerUpload.single("recording") means the field is recording.

Also, it checks MIME type is audio/wave and the extension is .wav.

Hmm… I wonder if we can upload a file to arbitrary path via path travsal…

┌[siunam♥earth]-(~/ctf/Cyber-Apocalypse-2023/Web/SpyBug)-[2023.03.23|20:33:47(HKT)]
└> curl http://localhost:1337/agents/upload/7e7c1171-d6a9-4a51-a80f-eb71bc39870f/447ab5f5-d794-4c58-be62-ab7acd6b5513 -F "recording=@rec.wav" -H "Content-Type: audio/wave"
Bad Request

However, I couldn't upload it…

Also, the challenge provided a Go lang source code spybug-agent.go, I tried to compile and run it on my VM, but it outputs an error, and says couldn't find my sound card…