Telegram Bot 6.0 Validating data received via the Web App node implementation

verifyTelegramWebAppData.tsx

const TELEGRAM_BOT_TOKEN = '110201543:AAHdqTcvCH1vGWJxfSeofSAs0K5PALDsaw'; // https://core.telegram.org/bots#creating-a-new-bot


export const verifyTelegramWebAppData = async (telegramInitData: string): boolean => {
  // The data is a query string, which is composed of a series of field-value pairs.
  const encoded = decodeURIComponent(telegramInitData); 
  
  
  // HMAC-SHA-256 signature of the bot's token with the constant string WebAppData used as a key.
  const secret = crypto
    .createHmac('sha256', 'WebAppData')
    .update(TELEGRAM_BOT_TOKEN);

  // Data-check-string is a chain of all received fields'.
  const arr = encoded.split('&');
  const hashIndex = arr.findIndex(str => str.startsWith('hash='));
  const hash = arr.splice(hashIndex)[0].split('=')[1];
  // sorted alphabetically
  arr.sort((a, b) => a.localeCompare(b));
  // in the format key=<value> with a line feed character ('\n', 0x0A) used as separator
  // e.g., 'auth_date=<auth_date>\nquery_id=<query_id>\nuser=<user>
  const dataCheckString = arr.join('\n');
  
  // The hexadecimal representation of the HMAC-SHA-256 signature of the data-check-string with the secret key
  const _hash = crypto
    .createHmac('sha256', secret.digest())
    .update(dataCheckString)
    .digest('hex');
  
  // if hash are equal the data may be used on your server.
  // Complex data types are represented as JSON-serialized objects.
  return _hash === hash;
};

@Fuchsoria thank you so much!

Thank you!

Example suggested by @TopYar wrapped in middleware for Nestjs/Fastify with nodejs native crypto

declarations.d.ts

declare module 'http' {
  interface IncomingHttpHeaders {
    'tg-init-data'?: string
  }
}

check-init-data.middleware

import {Injectable, Logger, NestMiddleware, UnauthorizedException} from '@nestjs/common';
import {FastifyRequest, FastifyReply} from 'fastify';
import * as crypto from 'crypto';

const {
  env: {
    TELEGRAM_BOT_TOKEN
  }
} = process;

@Injectable()
export class CheckInitDataMiddleware implements NestMiddleware {
  private readonly logger: Logger = new Logger(CheckInitDataMiddleware.name);

  use(req: FastifyRequest['raw'], res: FastifyReply['raw'], next: () => void) {
    this.logger.log(`Checking webapp init data`);

    const {headers: {['tg-init-data']: tgInitData}} = req;
    const initData = new URLSearchParams(tgInitData);
    const hashFromClient = initData.get('hash');
    const dataToCheck: string[] = [];

    initData.sort();
    initData.forEach((v, k) => k !== 'hash' && dataToCheck.push(`${k}=${v}`));

    const secret = crypto
      .createHmac('sha256', 'WebAppData')
      .update(TELEGRAM_BOT_TOKEN);

    const signature = crypto
      .createHmac('sha256', secret.digest())
      .update(dataToCheck.join('\n'));

    const referenceHash = signature.digest('hex');

    if (hashFromClient === referenceHash) {
      return next();
    }
    throw new UnauthorizedException('Invalid init data');
  }
}

I love you! 💘

Note that it seems to doesn't work when the user in telegram has a special character in its firstname or lastname.
Try it on your own :

• In telegram add '&' in your firstname or lastname
• try to connect on your webapp (with this auth mechanism)

You'll see that the hash generated by this method is different from the one generated by telegram

Fixed the problem with '&' not working correctly:

const verifyInitData = (telegramInitData: string): boolean => {
    const urlParams = new URLSearchParams(telegramInitData);

    const hash = urlParams.get('hash');
    urlParams.delete('hash');
    urlParams.sort();

    let dataCheckString = '';
    for (const [key, value] of urlParams.entries()) {
        dataCheckString += `${key}=${value}\n`;
    }
    dataCheckString = dataCheckString.slice(0, -1);

    const secret = crypto.createHmac('sha256', 'WebAppData').update(process.env.API_TOKEN ?? '');
    const calculatedHash = crypto.createHmac('sha256', secret.digest()).update(dataCheckString).digest('hex');

    return calculatedHash === hash;
}

@motsgar Thanks! <3

Fixed the problem with '&' not working correctly:

const verifyInitData = (telegramInitData: string): boolean => {
    const urlParams = new URLSearchParams(telegramInitData);

    const hash = urlParams.get('hash');
    urlParams.delete('hash');
    urlParams.sort();

    let dataCheckString = '';
    for (const [key, value] of urlParams.entries()) {
        dataCheckString += `${key}=${value}\n`;
    }
    dataCheckString = dataCheckString.slice(0, -1);

    const secret = crypto.createHmac('sha256', 'WebAppData').update(process.env.API_TOKEN ?? '');
    const calculatedHash = crypto.createHmac('sha256', secret.digest()).update(dataCheckString).digest('hex');

    return calculatedHash === hash;
}

thanks. it's works

Here's a variant for initDataUnsafe, which will create the right string for validation from the object and check the hash

const verifyDataIntegrity = (initDataUnsafe, hash) => {
        const dataCheckString = Object.entries(initDataUnsafe).sort().map(([k, v]) => {
            if (typeof v === "object" && v !== null) {
                v = JSON.stringify(v);
            }
            
            return `${k}=${v}`;
        }).join("\n");

        const secret = crypto.createHmac("sha256", "WebAppData").update(process.env.API_TOKEN ?? "");
        const calculatedHash = crypto.createHmac("sha256", secret.digest()).update(dataCheckString).digest("hex");
        
        return calculatedHash === hash;
};

Example of use

const { hash, ...rest } = window.Telegram.WebApp.initDataUnsafe;
console.log(verifyDataIntegrity(rest, hash));

Here is an example with ruby

def validate(init_data)
      parsed_data = CGI.parse(init_data)

      # Extract the hash from the parsed data
      return false unless parsed_data['hash']
      received_hash = parsed_data.delete('hash').first

      # Create the data_check_string
      data_check_string = parsed_data.keys.sort.map do |key|
        "#{key}=#{parsed_data[key].first}"
      end.join("\n")

      # Compute the secret_key
      secret_key = OpenSSL::HMAC.digest(
        'SHA256',
        'WebAppData',
        bot_token # your bot token
      )

      # Compute the HMAC-SHA-256 of the data_check_string with the secret key
      check_hash = OpenSSL::HMAC.hexdigest(
        'SHA256',
        secret_key,
        data_check_string
      )

      # Compare the computed hash with the received hash
      check_hash == received_hash
end

Thank you man it works!

NestJS people

import { Injectable, NestMiddleware } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';
import crypto from 'crypto';
import TelegramBot from 'node-telegram-bot-api';

function verifyInitData(telegramInitData: string, botToken: string): { isVerified: boolean, urlParams: URLSearchParams } {
  const urlParams: URLSearchParams = new URLSearchParams(telegramInitData);

  const hash = urlParams.get('hash');
  urlParams.delete('hash');
  urlParams.sort();

  let dataCheckString = '';
  for (const [key, value] of urlParams.entries()) {
    dataCheckString += `${key}=${value}\n`;
  }
  dataCheckString = dataCheckString.slice(0, -1);

  const secret = crypto.createHmac('sha256', 'WebAppData').update(botToken);
  const calculatedHash = crypto.createHmac('sha256', secret.digest()).update(dataCheckString).digest('hex');

  const isVerified = calculatedHash === hash;

  return { isVerified, urlParams };
}

@Injectable()
export class ValidateTelegramDataMiddleware implements NestMiddleware {
  use(req: Request & { user: any }, res: Response, next: NextFunction) {
    const telegramInitData = ((req.headers.initdata ?? req.query.initData ?? req.query.initdata) as string);
    const botToken = process.env.TELEGRAM_TOKEN;

    if (!telegramInitData || !botToken) {
      return res.status(400).send('Invalid request');
    }

    const { urlParams, isVerified } = verifyInitData(telegramInitData, botToken);

    if (!isVerified) {
      return res.status(403).send('Unauthorized request');
    }

    const user: TelegramBot.User = typeof urlParams.get('user') === 'string' ? JSON.parse(urlParams.get('user')) : urlParams.get('user');

    req.user = user;

    next();
  }
}

Python impl here ))

import hmac

BOT_TOKEN = 'my-bot-token'

def hmac_256(key: str | bytes, value: str | bytes, as_hex: bool = False) -> str | bytes:
    """Makes HMAX digest of key, value as bytes or a hex string"""
    if isinstance(key, str):
        key = key.encode()
    if isinstance(value, str):
        value = value.encode()
    if as_hex: return hmac.new(key, value, 'sha256').hexdigest()
    return hmac.digest(key, value, 'sha256')

def hmac_validate(digest1: str | bytes, digest2: str | bytes) -> bool:
    """Validates a pair of HMAC hashes - must use this instead of simple == for security reasons!"""
    if type(digest1) != type(digest2): return False
    return hmac.compare_digest(digest1, digest2)

def validate_web_app(initdata: str) -> bool:
    # see https://core.telegram.org/bots/webapps#validating-data-received-via-the-mini-app
    their_hash = None
    vals = sorted(initdata.split('&'))
    for val in vals:
        if val.startswith('hash='):
            their_hash = val.split('=')[1].strip() or None
            vals.remove(val)
            break
    if not their_hash: return False
    initdata = '\n'.join(vals)
    secret_key = hmac_256('WebAppData', BOT_TOKEN)
    my_hash = hmac_256(secret_key, initdata, True)
    return hmac_validate(my_hash, their_hash)

@S0mbre Thanks!!

Thx

Python implementation
For anyone who have tried @S0mbre's solution - but NOT WORK

import hmac
import hashlib
from urllib.parse import parse_qs

TELEGRAM_BOT_TOKEN = ""

def verify_telegram_web_app_data(telegram_init_data):
    # Get hash_value from the query string
    init_data = parse_qs(telegram_init_data)
    hash_value = init_data.get('hash', [None])[0]
    data_to_check = []

    # Sort key-value pair by alphabet
    sorted_items = sorted((key, val[0]) for key, val in init_data.items() if key != 'hash')
    data_to_check = [f"{key}={value}" for key, value in sorted_items]

    # HMAC Caculation
    secret = hmac.new(b"WebAppData", TELEGRAM_BOT_TOKEN.encode(), hashlib.sha256).digest()
    _hash = hmac.new(secret, "\n".join(data_to_check).encode(), hashlib.sha256).hexdigest()
    
    return _hash == hash_value

@TheBlackHacker thanks, that one works great!

You can use the init-data-py library for Python.
Install init-data-py library:

pip install init-data-py

This library allows you to validate, parse, create, and sign Telegram Mini App data. below is an example of how to validate the data:

from init_data_py import InitData

bot_token = "" # Bot token from which the mini app is launched
query_string = "" # window.Telrgram.WebApp.initData

init_data = InitData.parse(query_string)

init_data.validate(bot_token, lifetime=60)

Thanks man