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Changing vBulletin 4 its password hashing to use BCrypt
by Dave 03 Oct 2014
Rating: (3 votes - 3.67 average)
This article has also been published at http://blog.technidev.com/changing-vbulletin-4-its-password-hashing-to-use-bcrypt/, my personal blog about security, exploits, development, etc.

Introduction
By default, vBulletin uses a very basic and easy to crack password hashing:
PHP Code:
md5(md5($password) . $salt) 
With the GPU's of these days, it may be a matter of minutes to crack a password using a dictionary attack/rainbow tables.

Fortunately, it's very easy to change the password hashing. I will change the password hashing of vBulletin to use BCrypt, a much better algorithm. The password hashing will look like this at the end of this guide:
PHP Code:
password_hash(md5(md5($password) . $salt), PASSWORD_BCRYPT, array('salt' => $salt)) 

Requirements for this guide:
- Access to the FTP or permission to edit .php files on the server.
- PHP version of 5.5+ (we make use of the http://php.net/manual/en/function.password-hash.php function)
- You must update all of the passwords in the current database.
- vBulletin 4.2.2 (this modification has been made on 4.2.2)
- Database access in the form of SSH/PHPMyAdmin or any other database manager tool

Create a backup of the files we are going to edit first so you can always restore it in case it goes wrong!

Step 1: modify password column type

First things first, we have to modify the type of the password column in the user table.
You can either do this in PHPMyAdmin by changing it to char(60) or by executing the following query:
PHP Code:
ALTER TABLE user MODIFY password char(60); 

Step 2: edit /includes/functions_login.php

Now let's modify the verify_authentication function in the /includes/functions_login.php file.
Look for:
PHP Code:
        if (
            $vbulletin->userinfo['password'] != iif($password AND !$md5password, md5(md5($password) . $vbulletin->userinfo['salt']), '') AND
            $vbulletin->userinfo['password'] != iif($md5password, md5($md5password . $vbulletin->userinfo['salt']), '') AND
            $vbulletin->userinfo['password'] != iif($md5password_utf, md5($md5password_utf . $vbulletin->userinfo['salt']), '')
        ) 
And replace it with:
PHP Code:
        $hash1 = password_hash(md5(md5($password) . $vbulletin->userinfo['salt']), PASSWORD_BCRYPT, array('salt' => $vbulletin->userinfo['salt']));
        $hash2 = password_hash(md5($md5password . $vbulletin->userinfo['salt']), PASSWORD_BCRYPT, array('salt' => $vbulletin->userinfo['salt']));
        $hash3 = password_hash(md5($md5password_utf . $vbulletin->userinfo['salt']), PASSWORD_BCRYPT, array('salt' => $vbulletin->userinfo['salt']));

        if (
            $vbulletin->userinfo['password'] != iif($password AND !$md5password, $hash1, '') AND
            $vbulletin->userinfo['password'] != iif($md5password, $hash2, '') AND
            $vbulletin->userinfo['password'] != iif($md5password_utf, $hash3, '')
        ) 
This function will, as the function name describes, very the authentication.

Step 3: edit /includes/class_dm_user.php

This file contains the verify_password and hash_password function which must be changed as well.
Look for the hash_password function:
PHP Code:
    function hash_password($password, $salt)
    {
        // if the password is not already an md5, md5 it now
        if ($password == '')
        {
        }
        else if (!$this->verify_md5($password))
        {
            $password = md5($password);
        }

        // hash the md5'd password with the salt
        return md5($password . $salt);
    } 
And replace it with:
PHP Code:
    function hash_password($password, $salt)
    {
        // if the password is not already an md5, md5 it now
        if ($password == '')
        {
        }
        else if (!$this->verify_md5($password))
        {
            $password = md5($password);
        }

        // hash the md5'd password with the salt
        return password_hash(md5($password . $salt), PASSWORD_BCRYPT, array('salt' => $salt));
    } 
Now look for the verify_password function:
PHP Code:
    function verify_password(&$password)
    {
        //regenerate the salt when the password is changed.  No reason not to and its
        //an easy way to increase the size when the user changes their password (doing
        //it this way avoids having to reset all of the passwords)
        $this->user['salt'] = $salt = $this->fetch_user_salt();

        // generate the password
        $password = $this->hash_password($password, $salt);

        if (!defined('ALLOW_SAME_USERNAME_PASSWORD'))
        {
            // check if password is same as username; if so, set an error and return false
            if ($password == md5(md5($this->fetch_field('username')) . $salt))
            {
                $this->error('sameusernamepass');
                return false;
            }
        }

        $this->set('passworddate', 'FROM_UNIXTIME(' . TIMENOW . ')', false);

        return true;
    } 
And replace it with:
PHP Code:
    function verify_password(&$password)
    {
        //regenerate the salt when the password is changed.  No reason not to and its
        //an easy way to increase the size when the user changes their password (doing
        //it this way avoids having to reset all of the passwords)
        $this->user['salt'] = $salt = $this->fetch_user_salt();

        // generate the password
        $password = $this->hash_password($password, $salt);

        if (!defined('ALLOW_SAME_USERNAME_PASSWORD'))
        {
            // check if password is same as username; if so, set an error and return false
            if ($password == password_hash(md5(md5($this->fetch_field('username')) . $salt), PASSWORD_BCRYPT, array('salt' => $salt)))
            {
                $this->error('sameusernamepass');
                return false;
            }
        }

        $this->set('passworddate', 'FROM_UNIXTIME(' . TIMENOW . ')', false);

        return true;
    } 
We have to modify this function since there's a check to see if the password matches the current username, which is not allowed by default.

Step 4: update all passwords in the user table

The only downside of this is that we have to update all passwords in the database.
But no worries, no one will have to change or update their password to make this work since we use the old password hashing in BCrypt.

Please make a backup of your database or user table before doing this so you can restore it in case it does not work as intended!

Create a file in the root of your forum and name it something like update_passwords.php. Contents of the file:
PHP Code:
require("./global.php");
$query = $db->query_read("SELECT userid, password, salt FROM user WHERE password NOT LIKE '$%' ORDER BY userid ASC");

echo 'We have ' . $db->num_rows($query) . ' password(s) to update..<br><br>';

while($row = $db->fetch_array($query)){
    $db->query_write("UPDATE user SET password = '" . password_hash($row['password'], PASSWORD_BCRYPT, array('salt' => $row['salt'])) . "' WHERE userid = '" . $row['userid'] . "'");
}

echo 'Updated all passwords, re-run this script to be sure!'; 
This will update all of the current password hashes to use BCrypt.
In case the script timed out, just run it again or change the script execution timeout.

Step 5: verifying functionality

Now try to login onto your forum and see if that works, in case you get an incorrect username/password error, it means you did something wrong in this guide.
In case it works, try to update your password and relog to see if that part works as well.

I tested the login, registration, remember me checkbox and changing password function on a local test forum which seemed to work fine.

Support will be provided http://technidev.com/changing-vbulletin-4-its-password-hashing-to-use-bcrypt/ (comment box). I'll answer the most basic questions here at vbulletin.org.

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