[ticket/14733] Support increasing hashing cost factor

PHPBB3-14733

phpBB/phpbb/passwords/driver/base.php

@@ -52,6 +52,14 @@ abstract class base implements driver_interface
 		return false;
 	}
 
+	/**
+	 * {@inheritdoc}
+	 */
+	public function needs_rehash($hash)
+	{
+		return false;
+	}
+
 	/**
 	* {@inheritdoc}
 	*/

phpBB/phpbb/passwords/driver/bcrypt.php

@@ -17,6 +17,23 @@ 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
+	 */
+	public function __construct(\phpbb\config\config $config, helper $helper, $cost_factor)
+	{
+		parent::__construct($config, $helper);
+
+		// Don't allow cost factor to be below default setting
+		$this->cost_factor = max(10, $cost_factor);
+	}
+
 	/**
 	* {@inheritdoc}
 	*/
@@ -25,6 +42,18 @@ class bcrypt extends base
 		return self::PREFIX;
 	}
 
+	/**
+	 * {@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}
 	*/
@@ -46,7 +75,7 @@ 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);

phpBB/phpbb/passwords/driver/driver_interface.php

@@ -29,6 +29,14 @@ interface driver_interface
 	*/
 	public function is_legacy();
 
+	/**
+	 * 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);
+
 	/**
 	* Returns the hash prefix
 	*

phpBB/phpbb/passwords/manager.php

@@ -297,7 +297,7 @@ class manager
 		}
 		else
 		{
-			$this->convert_flag = false;
+			$this->convert_flag = $stored_hash_type->needs_rehash($hash);
 		}
 
 		// Check all legacy hash types if prefix is $CP$