[feature/passwords] Add method for obtaining the hash settings only

This is needed for combined hashing of passwords.

PHPBB3-11610

phpBB/includes/crypto/driver/bcrypt.php

@@ -87,4 +87,22 @@ class phpbb_crypto_driver_bcrypt extends phpbb_crypto_driver_base
 	{
 		return $this->helper->hash_encode64($this->helper->get_random_salt(22), 22);
 	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function get_settings_only($hash, $full = false)
+	{
+		if ($full)
+		{
+			$pos = stripos($hash, '$', 1) + 1;
+			$length = 22 + (strripos($hash, '$') + 1 - $pos);
+		}
+		else
+		{
+			$pos = strripos($hash, '$') + 1;
+			$length = 22;
+		}
+		return substr($hash, $pos, $length);
+	}
 }

phpBB/includes/crypto/driver/interface.php

@@ -50,7 +50,19 @@ interface phpbb_crypto_driver_interface
 	/**
 	* Check the password against the supplied hash
 	*
+	* @param string		$password The password to check
+	* @param string		$hash The password hash to check against
 	* @return bool		True if password is correct, else false
 	*/
 	public function check($password, $hash);
+
+	/**
+	* Get only the settings of the specified hash
+	*
+	* @param string		$hash Password hash
+	* @param bool		$full Return full settings or only settings
+	*			related to the salt
+	* @return string	String containing the hash settings
+	*/
+	public function get_settings_only($hash, $full = false);
 }

phpBB/includes/crypto/driver/salted_md5.php

@@ -141,4 +141,12 @@ class phpbb_crypto_driver_salted_md5 extends phpbb_crypto_driver_base
 			'full'	=> substr($hash, 0, 12),
 		);
 	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function get_settings_only($hash, $full = false)
+	{
+		return substr($hash, 3, 9);
+	}
 }