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;
};

@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)