label-based security enforcement for web applications

This paper presents SELinks, a programming language focused on building secure multi-tier web applications. SE-Links provides a uniform programming model, in the style of LINQ and Ruby on Rails, with language syntax for accessing objects residing either in the database or at the server. Object-level security policies are expressed as fullycustomizable, first-class labels which may themselves be subject to security policies. Access to labeled data is mediated via trusted, user-provided policy enforcement functions. SELinks has two novel features that ensure security policies are enforced correctly and efficiently. First, SELinks implements a type system called Fable that allows a protected object’s type to refer to its protecting label. The type system can check that labeled data is never accessed directly by the program without first consulting the appropriate policy enforcement function. Second, SELinks compiles policy enforcement code to database-resident user-defined functions that can be called directly during query processing. Database-side checking avoids transferring data to the server needlessly, while still allowing policies to be expressed in a customizable and portable manner. Our experience with two sizable web applications, a model health-care database and a secure wiki with fine-grained security policies, indicates that cross-tier policy enforcement in SELinks is flexible, relatively easy to use, and, when compared to a single-tier approach, improves throughput by nearly an order of magnitude. SELinks is freely available

Tuning an SQL-Based PDM System in a Worldwide Client/Server Environment

The management of product-related data in a uniform and consistent way is a big challenge for many manufacturing enterprises, especially the large ones like DaimlerChrysler. So-called Product Data Management systems (PDMS) are a promising way to achieve this goal. For various reasons PDMS often sit on-top of a relational DBMS using it (more or less) as a simple record manager. User interactions with the PDMS are translated into series of SQL queries. This does not cause too much harm when DBMS and PDMS are located in the same local-area network with high bandwidth and little latency times. The picture may change dramatically, however, if the users are working in geographically distributed environments. Response times may rise by orders of magnitude, e. g. from 1-2 minutes in the local context to 30 minutes and even more in the ”intercontinental” context. The paper shows how a more sophisticated utilization of the (advanced) SQL features coming along with SQL:1999 can help to cut down response times significantly. 1. Introduction – Th

Workflow-Management für Produktentwicklungsprozesse

Workflow-Management-Systeme unterstützen die elektronische Abwicklung von Arbeitsprozessen, sogenannten Workflows. Heutige Systeme erzwingen meist die starre Ausführung vormodellierter Workflows, was ihre praktische Tauglichkeit auf Anwendungsgebiete mit starren Prozessen beschränkt. In vielen Anwendungsbereichen sind Arbeitsprozesse jedoch meist nur semi-strukturiert. Dieses Merkmal ist aufgrund kreativer Teilaufgaben auch typisch für alle Produktentwicklungsprozesse, für die in dieser Arbeit adäquate Modellierungs- und Ausführungskonzepte vorgestellt werden. Diese Konzepte wurden im WEP-Workflow-Management-Systems (WEP = Workflow Management for Engineering Processes) zur Demonstration der Machbarkeit und des praktischen Nutzens prototypisch implementiert