hashing.md

Hashing

• Introduction
• Configuration
• Basic Usage
  • Hashing Passwords
  • Verifying That a Password Matches a Hash
  • Determining if a Password Needs to be Rehashed
• Hash Algorithm Verification

Introduction

The Laravel Hash facade provides secure Bcrypt and Argon2 hashing for storing user passwords. If you are using one of the Laravel application starter kits, Bcrypt will be used for registration and authentication by default.

Bcrypt is a great choice for hashing passwords because its "work factor" is adjustable, which means that the time it takes to generate a hash can be increased as hardware power increases. When hashing passwords, slow is good. The longer an algorithm takes to hash a password, the longer it takes malicious users to generate "rainbow tables" of all possible string hash values that may be used in brute force attacks against applications.

Configuration

By default, Laravel uses the bcrypt hashing driver when hashing data. However, several other hashing drivers are supported, including argon and argon2id.

You may specify your application's hashing driver using the HASH_DRIVER environment variable. But, if you want to customize all of Laravel's hashing driver options, you should publish the complete hashing configuration file using the config:publish Artisan command:

php artisan config:publish hashing

Basic Usage

Hashing Passwords

You may hash a password by calling the make method on the Hash facade:

<?php

namespace App\Http\Controllers;

use Illuminate\Http\RedirectResponse;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Hash;

class PasswordController extends Controller
{
    /**
     * Update the password for the user.
     */
    public function update(Request $request): RedirectResponse
    {
        // Validate the new password length...

        $request->user()->fill([
            'password' => Hash::make($request->newPassword)
        ])->save();

        return redirect('/profile');
    }
}

Adjusting The Bcrypt Work Factor

If you are using the Bcrypt algorithm, the make method allows you to manage the work factor of the algorithm using the rounds option; however, the default work factor managed by Laravel is acceptable for most applications:

$hashed = Hash::make('password', [
    'rounds' => 12,
]);

Adjusting The Argon2 Work Factor

If you are using the Argon2 algorithm, the make method allows you to manage the work factor of the algorithm using the memory, time, and threads options; however, the default values managed by Laravel are acceptable for most applications:

$hashed = Hash::make('password', [
    'memory' => 1024,
    'time' => 2,
    'threads' => 2,
]);

Note

For more information on these options, please refer to the official PHP documentation regarding Argon hashing.

Verifying That a Password Matches a Hash

The check method provided by the Hash facade allows you to verify that a given plain-text string corresponds to a given hash:

if (Hash::check('plain-text', $hashedPassword)) {
    // The passwords match...
}

Determining if a Password Needs to be Rehashed

The needsRehash method provided by the Hash facade allows you to determine if the work factor used by the hasher has changed since the password was hashed. Some applications choose to perform this check during the application's authentication process:

if (Hash::needsRehash($hashed)) {
    $hashed = Hash::make('plain-text');
}

Hash Algorithm Verification

To prevent hash algorithm manipulation, Laravel's Hash::check method will first verify the given hash was generated using the application's selected hashing algorithm. If the algorithms are different, a RuntimeException exception will be thrown.

This is the expected behavior for most applications, where the hashing algorithm is not expected to change and different algorithms can be an indication of a malicious attack. However, if you need to support multiple hashing algorithms within your application, such as when migrating from one algorithm to another, you can disable hash algorithm verification by setting the HASH_VERIFY environment variable to false:

HASH_VERIFY=false