Comparing BCrypt hash between PHP and NodeJS

Question

For an app I'm working on, nodejs needs to verify hashes created by PHP and vice-versa.

The problem is, the hashes generated in PHP (via Laravel's Hash class, which just uses PHP's password_hash function) return false when tested in node.js.

The following node.js script:

var bcrypt = require('bcrypt');

var password = 'password';

var phpGeneratedHash  = '$2y$10$jOTwkwLVn6OeA/843CyIHu67ib4RixMa/N/pTJVhOjTddvrG8ge5.';
var nodeGeneratedHash = '$2a$10$ZiBH5JtTDtXqDajO6f4EbeBIXGwtcGg2MGwr90xTH9ki34SV6rZhO';

console.log(
  bcrypt.compareSync(password, phpGeneratedHash)  ? 'PHP passed' : 'PHP failed',
  bcrypt.compareSync(password, nodeGeneratedHash) ? 'nodejs passed' : 'nodejs failed'
);

outputs: 'PHP failed nodejs passed', whereas the following PHP script:

<?php

$password = 'password';

$phpGeneratedHash  = '$2y$10$jOTwkwLVn6OeA/843CyIHu67ib4RixMa/N/pTJVhOjTddvrG8ge5.';
$nodeGeneratedHash = '$2a$10$ZiBH5JtTDtXqDajO6f4EbeBIXGwtcGg2MGwr90xTH9ki34SV6rZhO';

print password_verify($password, $phpGeneratedHash)  ? 'PHP passed' : 'PHP failed';
print password_verify($password, $nodeGeneratedHash) ? 'nodejs passed' : 'nodejs failed';

outputs 'PHP passed nodejs passed'.

I've run the tests in Ubuntu 14.04.1 using PHP 5.5.18, node.js v0.10.32 and the npm bcrypt module.

Answer 1

This fails because the types of bcrypt hashes being generated from php and node are different. Laravel generates the $2y$ while node generates the $2a$. But the good news is the only difference between 2a and 2y are their prefixes.

So what you can do is make one of the prefix similar to the other. Like:

$phpGeneratedHash  = '$2y$10$jOTwkwLVn6OeA/843CyIHu67ib4RixMa/N/pTJVhOjTddvrG8ge5.';
$nodeGeneratedHash = '$2a$10$ZiBH5JtTDtXqDajO6f4EbeBIXGwtcGg2MGwr90xTH9ki34SV6rZhO';

To something like:

$phpGeneratedHash  = '$2y$10$jOTwkwLVn6OeA/843CyIHu67ib4RixMa/N/pTJVhOjTddvrG8ge5.';
$nodeGeneratedHash = '$2y$10$ZiBH5JtTDtXqDajO6f4EbeBIXGwtcGg2MGwr90xTH9ki34SV6rZhO';

Notice that I replaced the $2a$ of the node hash to $2y$. You can simply do this with:

PHP

$finalNodeGeneratedHash = str_replace("$2a$", "$2y$", $nodeGeneratedHash);

Node

finalNodeGeneratedHash = nodeGeneratedHash.replace('$2a$', '$2y$');

Then compare phpGeneratedHash to finalNodeGeneratedHash.

Note: It is recommended that if you're comparing in PHP, change the prefix of the NodeJS generated hash to $2y$ and if you're comparing in NodeJS; change the prefix of the PHP generated hash to $2a$.