Software vulnerabilities have had a devastating effect on the Internet. Worms such as CodeRed and Slammer can compromise hundreds of thousands of hosts within hours or even minutes, and cause millions of dollars of damage [26, 43]. To successfully combat these fast automatic Internet attacks, we need fast automatic attack detection and filtering mechanisms. In this paper we propose dynamic taint analysis for automatic detection of overwrite attacks, which include most types of exploits. This approach does not need source code or special compilation for the monitored program, and hence works on commodity software. To demonstrate this idea, we have implemented TaintCheck, a mechanism that can perform dynamic taint analysis by performing binary rewriting at run time. We show that TaintCheck reliably detects most types of exploits. We found that TaintCheck produced no false positives for any of the many different programs that we tested. Further, we describe how TaintCheck could improve automatic signature generation in

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Dynamic Taint Analysis for Automatic Detection, Analysis, and Signature Generation of Exploits on Commodity Software

We provide an extensive overview of existing research in the field of software refactoring. This research is compared and discussed based on a number of different criteria: the refactoring activities that are supported, the specific techniques and formalisms that are used for supporting these activities, the types of software artifacts that are being refactored, the important issues that need to be taken into account when building refactoring tool support, and the effect of refactoring on the software process. A running example is used to explain and illustrate the main concepts.

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A survey of software refactoring

Over the past 20 years, organic transistors have developed from a laboratory curiosity to a commercially viable technology. This critical review provides a short summary of several important aspects of organic transistors, including materials, microstructure, carrier transport, manufacturing, electrical properties, and performance limitations (200 references).

Organic thin-film transistors.

Current software attacks often build on exploits that subvert machine-code execution. The enforcement of a basic safety property, Control-Flow Integrity (CFI), can prevent such attacks from arbitrarily controlling program behavior. CFI enforcement is simple, and its guarantees can be established formally even with respect to powerful adversaries. Moreover, CFI enforcement is practical: it is compatible with existing software and can be done efficiently using software rewriting in commodity systems. Finally, CFI provides a useful foundation for enforcing further security policies, as we demonstrate with efficient software implementations of a protected shadow call stack and of access control for memory regions.

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Control-flow integrity

We explore a novel paradigm for data management in which a third party service provider hosts "database as a service", providing its customers with seamless mechanisms to create, store, and access their databases at the host site. Such a model alleviates the need for organizations to purchase expensive hardware and software, deal with software upgrades, and hire professionals for administrative and maintenance tasks which are taken over by the service provider. We have developed and deployed a database service on the Internet, called NetDB2, which is in constant use. In a sense, a data management model supported by NetDB2 provides an effective mechanism for organizations to purchase data management as a service, thereby freeing them to concentrate on their core businesses. Among the primary challenges introduced by "database as a service" are the additional overhead of remote access to data, an infrastructure to guarantee data privacy, and user interface design for such a service. These issues are investigated. We identify data privacy as a particularly vital problem and propose alternative solutions based on data encryption. The paper is meant as a challenge for the database community to explore a rich set of research issues that arise in developing such a service.

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Providing database as a service

The usual way of installing a new version of a software system is to shut down the running program and then install the new version. This necessitates a sometimes unacceptable delay during which service is denied to the users of the software. An online software replacement system replaces parts of the software while it is in execution, thus eliminating the shutdown. While a number of implementations of online version change systems have been described in the literature, little investigation has been done on its theoretical aspects. We describe a formal framework for studying online software version change. We give a general definition of validity of an online change, show that it is in general undecidable and then develop sufficient conditions for ensuring validity for a procedural language.

A formal framework for on-line software version change

An analysis of the difference in behavior of top and bottom contact organic thin film transistors using device simulation

The usual way of installing a new version of a piece of software is to shut down the running program and then install the new version. This necessitates a sometimes unacceptable delay during which service is denied to the users of the software. An on-line software replacement system replaces parts of the software while it is in execution, thus eliminating the shutdown. In this paper, we describe a system for on-line software version change for software written in the C language. When the change is initiated by the user, the system instantiates a new process with the new version of the software, transfers state from the old process to the new one at an appropriate time, and transfers the control to the new process. The user sees a minimal delay in this switchover.

On line software version change using state transfer between processes

Buffer overflow exploits make use of the treatment of strings in C as character arrays rather than as first-class objects. Manipulation of arrays as pointers and primitive pointer arithmetic make it possible for a program to access memory locations which it is not supposed to access. There have been many efforts in the past to overcome this vulnerability by performing array bounds checking in C. Most of these solutions are either inadequate, inefficient or incompatible with legacy code. In this paper, we present an efficient and transparent runtime approach for protection against all known forms of buffer overflow attacks. Our solution consists of two tools: TIED (Type Information Extractor and Depositor) and LibsafePlus. TIED extracts size information of all global and automatic buffers defined in the program from the debugging information produced by the compiler and inserts it back in the program binary as a data structure available at runtime. LibsafePlus is a dynamic library which provides wrapper functions for unsafe C library functions such as strcpy. These wrapper functions check the source and target buffer sizes using the information made available by TIED and perform the requested operation only when it is safe to do so. For dynamically allocated buffers, the sizes and starting addresses are recorded at runtime. With our simple design we are able to protect most applications with a performance overhead of less than 10%.

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TIED, LibsafePlus: tools for runtime buffer overflow protection

CERTIFICATE Certiied that the work contained in the thesis entitled \On-line Software Version Change", by \Deepak Gupta", has been carried out under our supervision and that this work has not been submitted elsewhere for a degree. ii Synopsis On-line software version change has emerged in the recent years as a technique for installing software changes in systems in which the shutdown necessitated by the conventional method of installing a new version of a running program can not be tolerated. In the present thesis, we present a formal framework for modelling changes to running programs and use it to study the validity of an on-line change. We also discuss some implementation issues and describe a prototype implementation. Our framework for on-line changes is based on the notion of processes and process states. An on-line change is deened as a sequence of actions involving stopping a running process, changing its code, mapping its state and then continuing it. The overall behavior of a process that has undergone an on-line change is likely to be diierent from any behavior that can be exhibited by either of the two program versions. It is, therefore, important to deene what constitutes an \acceptable" behavior of such a process. We capture this notion in our deenition of the validity of an on-line change. We deene an on-line change to be valid if some time after the change, the process reaches a reachable state of the new program version. Thus, validity ensures that following a change, the process starts behaving like the new version of the program after a \transition period". We rst consider validity of on-line changes to programs written in sequential procedure based languages. For this purpose, a very simple model in which procedures and functions are not allowed is rst considered. State is modelled as a mapping from variable names to values. For this model, we show that it is undecidable to nd whether or not a given on-line change is valid. This result has important consequences. It means that computable necessary and suucient conditions for validity of change can not be obtained. Undecidability in this simple model also iii implies undecidability in other more realistic models. We then develop a set of suucient conditions which ensure validity and show how they can be checked using data-ow analysis. We then extend the model to include functions and procedures and consider a function (or procedure) as …

Deepak Gupta

Papers

A formal framework for on-line software version change

An analysis of the difference in behavior of top and bottom contact organic thin film transistors using device simulation

On line software version change using state transfer between processes

TIED, LibsafePlus: tools for runtime buffer overflow protection

On Line Software Version Change