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Pu, Calton

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Author: Singaravelu, Lenin ×

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    Enforcing Configurable Trust in Client-side Software Stacks by Splitting Information Flow
    (Georgia Institute of Technology, 2007) Singaravelu, Lenin ; Kauer, Bernhard ; Boettcher, Alexander ; Härtig, Hermann ; Pu, Calton ; Jung, Gueyoung ; Weinhold, Carsten
    Current client-server applications such as online banking employ the same client-side software stack to handle information with differing security and functionality requirements, thereby increasing the size and complexity of software that needs to be trusted. While the high complexity of existing software is a significant hindrance to testing and analysis, existing software and interfaces are too widely used to be entirely abandoned. We present a proxy-based approach called FlowGuard to address the problem of large and complex client-side software stacks. FlowGuard’s proxy employs mappings from sensitiveness of information to trustworthiness of software stacks to demultiplex incoming messages amongst multiple client-side software stacks. One of these stacks is a fully-functional legacy software stack and another is a small and simple stack designed to handle sensitive information. In contrast to previous approaches, FlowGuard not only reduces the complexity of software handling sensitive information but also minimizes modifications to legacy software stacks. By allowing users and service providers to define the mappings, FlowGuard also provides flexibility in determining functionality-security tradeoffs. We demonstrate the feasibility of our approach by implementing a FlowGuard, called BLAC, for https-based applications. BLAC relies on text patterns to identify sensitive information in HTTP responses and redirects such responses to a small and simple TrustedViewer, with an unmodified legacy software stack handling the rest of the responses. We developed a prototype implementation that works with a prominent bank’s online banking site. Our evaluation shows that BLAC reduces size and complexity of software that needs to be trusted by an order of magnitude, with a manageable overhead of few tens of milliseconds per HTTP response.
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    A Secure Middleware Architecture for Web Services
    (Georgia Institute of Technology, 2007) Singaravelu, Lenin ; Wei, Jinpeng ; Pu, Calton
    Current web service platforms (WSPs) often perform all web services related processing, including security-sensitive information handling, in the same protection domain. Consequently, the entire WSP may have access to security-sensitive information such as credit card numbers, forcing us to trust a large and complex piece of software. To address this problem, we propose ISO-WSP, a new middleware architecture that decomposes current WSPs into two parts executing in separate protection domains: (1) a small trusted T-WSP to handle security-sensitive data, and (2) a large, legacy untrusted U-WSP that provides the normal WSP functionality, but uses the T-WSP for security-sensitive data handling. By restricting security-sensitive data access to T-WSP, ISO-WSP reduces the software complexity of trusted code, thereby improving the testability of ISO-WSP. To achieve end-to-end security, the application code is also decomposed into two parts, isolating a small trusted part from the remaining untrusted code. The trusted part encapsulates all accesses to security-sensitive data through a Secure Functional Interface (SFI). To ease the migration of legacy applications to ISO-WSP, we developed tools to translate direct manipulations of security-sensitive data by the untrusted part into SFI invocations. Using a prototype implementation based on the Apache Axis2 WSP, we show that ISO-WSP reduces software complexity of trusted components by a factor of five, while incurring a modest performance overhead of few milliseconds per request. We also show that existing applications can be migrated to run on ISO-WSP with minimal effort: a few tens of lines of new and modified code.