3 files changed, 66 insertions, 3 deletions
diff --git a/phpBB/phpbb/passwords/driver/base.php b/phpBB/phpbb/passwords/driver/base.php
index fd07a61bf4..0997b5b700 100644
--- a/phpBB/phpbb/passwords/driver/base.php
+++ b/phpBB/phpbb/passwords/driver/base.php
@@ -13,7 +13,7 @@
 
 namespace phpbb\passwords\driver;
 
-abstract class base implements driver_interface
+abstract class base implements rehashable_driver_interface
 {
 	/** @var \phpbb\config\config */
 	protected $config;
@@ -21,7 +21,7 @@ abstract class base implements driver_interface
 	/** @var \phpbb\passwords\driver\helper */
 	protected $helper;
 
-	/** @var driver name */
+	/** @var string Driver name */
 	protected $name;
 
 	/**
@@ -53,6 +53,14 @@ abstract class base implements driver_interface
 	}
 
 	/**
+	 * {@inheritdoc}
+	 */
+	public function needs_rehash($hash)
+	{
+		return false;
+	}
+
+	/**
 	* {@inheritdoc}
 	*/
 	public function get_settings_only($hash, $full = false)
diff --git a/phpBB/phpbb/passwords/driver/bcrypt.php b/phpBB/phpbb/passwords/driver/bcrypt.php
index eab1c3d569..eb1aeeeb76 100644
--- a/phpBB/phpbb/passwords/driver/bcrypt.php
+++ b/phpBB/phpbb/passwords/driver/bcrypt.php
@@ -17,6 +17,24 @@ class bcrypt extends base
 {
 	const PREFIX = '$2a$';
 
+	/** @var int Hashing cost factor */
+	protected $cost_factor;
+
+	/**
+	 * Constructor of passwords driver object
+	 *
+	 * @param \phpbb\config\config $config phpBB config
+	 * @param \phpbb\passwords\driver\helper $helper Password driver helper
+	 * @param int $cost_factor Hashing cost factor (optional)
+	 */
+	public function __construct(\phpbb\config\config $config, helper $helper, $cost_factor = 10)
+	{
+		parent::__construct($config, $helper);
+
+		// Don't allow cost factor to be below default setting
+		$this->cost_factor = max(10, $cost_factor);
+	}
+
 	/**
 	* {@inheritdoc}
 	*/
@@ -26,6 +44,18 @@ class bcrypt extends base
 	}
 
 	/**
+	 * {@inheritdoc}
+	 */
+	public function needs_rehash($hash)
+	{
+		preg_match('/^' . preg_quote($this->get_prefix()) . '([0-9]+)\$/', $hash, $matches);
+
+		list(, $cost_factor) = $matches;
+
+		return empty($cost_factor) || $this->cost_factor !== intval($cost_factor);
+	}
+
+	/**
 	* {@inheritdoc}
 	*/
 	public function hash($password, $salt = '')
@@ -46,7 +76,7 @@ class bcrypt extends base
 
 		if ($salt == '')
 		{
-			$salt = $prefix . '10$' . $this->get_random_salt();
+			$salt = $prefix . $this->cost_factor . '$' . $this->get_random_salt();
 		}
 
 		$hash = crypt($password, $salt);
diff --git a/phpBB/phpbb/passwords/driver/rehashable_driver_interface.php b/phpBB/phpbb/passwords/driver/rehashable_driver_interface.php
new file mode 100644
index 0000000000..ca30748502
--- /dev/null
+++ b/phpBB/phpbb/passwords/driver/rehashable_driver_interface.php
@@ -0,0 +1,25 @@
+<?php
+/**
+*
+* This file is part of the phpBB Forum Software package.
+*
+* @copyright (c) phpBB Limited <https://www.phpbb.com>
+* @license GNU General Public License, version 2 (GPL-2.0)
+*
+* For full copyright and license information, please see
+* the docs/CREDITS.txt file.
+*
+*/
+
+namespace phpbb\passwords\driver;
+
+interface rehashable_driver_interface extends driver_interface
+{
+	/**
+	 * Check if password needs to be rehashed
+	 *
+	 * @param string $hash Hash to check for rehash
+	 * @return bool True if password needs to be rehashed, false if not
+	 */
+	public function needs_rehash($hash);
+}