[ticket/13203] Add method for byte by byte comparison to drivers helper

PHPBB3-13203

phpBB/phpbb/passwords/driver/helper.php

@@ -142,4 +142,24 @@ class helper
 		}
 		return $random;
 	}
+
+	/**
+	 * Compare two strings byte by byte
+	 *
+	 * @param string $string_a The first string
+	 * @param string $string_b The second string
+	 *
+	 * @return bool True if strings are the same, false if not
+	 */
+	public function string_compare($string_a, $string_b)
+	{
+		$difference = strlen($string_a) != strlen($string_b);
+
+		for ($i = 0; $i < strlen($string_a) && $i < strlen($string_b); $i++)
+		{
+			$difference |= $string_a[$i] != $string_b[$i];
+		}
+
+		return $difference === 0;
+	}
 }

tests/passwords/manager_test.php

@@ -326,4 +326,22 @@ class phpbb_passwords_manager_test extends \phpbb_test_case
 		$this->assertFalse($this->manager->hash(str_repeat('a', 1024 * 1024 * 16)));
 		$this->assertLessThanOrEqual(5, time() - $start_time);
 	}
+
+	public function data_test_string_compare()
+	{
+		return array(
+			array('foo', 'bar', false),
+			array(1, '1', false),
+			array('one', 'one', true),
+			array('foobar', 'foobaf', false),
+		);
+	}
+
+	/**
+	 * @dataProvider data_test_string_compare
+	 */
+	public function test_string_compare($a, $b, $expected)
+	{
+		$this->assertSame($expected, $this->driver_helper->string_compare($a, $b));
+	}
 }