Telegram website login widget, signature check sample using Node.js

check_telegram_signature.js

// Copied by https://gist.github.com/dotcypress/8fd12d6e886cd74bba8f1aa8dbd346aa,
// thanks for improving code style

const { createHash, createHmac } = require('crypto');
const TOKEN = "ABC:12345...";

// I prefer get the secret's hash once but check the gist linked
// on line 1 if you prefer passing the bot token as a param
const secret = createHash('sha256')
  .update(TOKEN)
  .digest()

function checkSignature ({ hash, ...data }) {
  const checkString = Object.keys(data)
    .sort()
    .filter((k) => data[k])
    .map(k => (`${k}=${data[k]}`))
    .join('\n');
  const hmac = createHmac('sha256', secret)
    .update(checkString)
    .digest('hex');
  return hmac === hash;
}

// Sample usage
const payload = {
  id: '424242424242',
  first_name: 'John',
  last_name: 'Doe',
  username: 'username',
  photo_url: 'https://t.me/i/userpic/320/username.jpg',
  auth_date: '1519400000',
  hash: '87e5a7e644d0ee362334d92bc8ecc981ca11ffc11eca809505'
}
checkSignature(payload)

For some reason I've found this fails for some users, but works fine for others.

Essentially the hash from telegram is not coming out to be the same as the one output from hmac. However it does work for most users... so odd any ideas why?

I'm not sure. Is it possible that you are receiving requests that are not from Telegram? Did you make any change to my code?

Did you actually use this token const TOKEN = "ABC:12345..."; to create the hash in payload?
The example as it is doesn't work for me. It works as soon as I use real data, i.e. a live response from Telegram and my own bot token.
I think people merely copy/pasting and expecting this to work is what leads to confusion.

Replace payload.hash with fdd4901b22ee5ea34d77caeac88b5ecba818226ab9c7c7775c8ff675d7e4cb92 and this example works.

I think the gist you copied this from always used some made-up value for the hash, to begin with. Even the length doesn't add up.

@ImTheDeveloper I had the same issue and found out that when users do not specify their last_name the hash does not match. To fix the error, I've filtered out empty data for checkString:

const checkString = Object.keys(data)
    .sort()
    .filter((k) => data[k])
    .map(k => (`${k}=${data[k]}`))
    .join('\n');

Perfect!

…

On 17 Nov 2022, 02:35 +0000, Liubov Pitko ***@***.***>, wrote: @lub0v commented on this gist. @ImTheDeveloper I had the same issue and found out that when users do not specify their last_name the hash does not match. To fix the error, I've filtered out empty data for checkString: const checkString = Object.keys(data) .sort() .filter((k) => data[k]) .map(k => (`${k}=${data[k]}`)) .join('\n'); — Reply to this email directly, view it on GitHub or unsubscribe. You are receiving this email because you were mentioned. Triage notifications on the go with GitHub Mobile for iOS or Android.

Thanks @lub0v, I updated the gist with your suggestion :)

Updated version

const secret = crypto.createHash('sha256')
      .update(botToken?.trim())
      .digest();

const checkString = Object.keys(data)
    .sort()
    .filter((k) => data[k])
    .filter((k) => ![ 'hash' ].includes(k))
    .map(k => (`${k}=${data[k]}`))
    .join('\n');

const hmac = crypto.createHmac('sha256', secret)
    .update(checkString)
    .digest('hex');

return hmac === data.hash;

Hi for me it did nit work without WebAppData

  const originalHash = Buffer.from(data.hash, 'hex');
    delete data.hash;
    const checkString = Object.keys(data)
      .sort()
      .map((key) => `${key}=${data[key]}`)
      .join('\n'); 
 
    const hmacKey = crypto
      .createHmac('sha256', 'WebAppData')
      .update(Buffer.from(botToken, 'utf8'))
      .digest();
    const hmac = crypto.createHmac('sha256', hmacKey);
    hmac.update(checkString);
    const computedHash = hmac.digest();
    return crypto.timingSafeEqual(computedHash, originalHash);

IT WORKS, THANKS!