Commodity operating systems entrusted with securing sensitive data are remarkably large and complex, and consequently, frequently prone to compromise. To address this limitation, we introduce a virtual-machine-based system called Overshadow that protects the privacy and integrity of application data, even in the event of a total OS compromise. Overshadow presents an application with a normal view of its resources, but the OS with an encrypted view. This allows the operating system to carry out the complex task of managing an application’s resources, without allowing it to read or modify them. Thus, Overshadow offers a last line of defense for application data. Overshadow builds on multi-shadowing, a novel mechanism that presents different views of “physical ” memory, depending on the context performing the access. This primitive offers an additional dimension of protection beyond the hierarchical protection domains implemented by traditional operating systems and processor architectures. We present the design and implementation of Overshadow and show how its new protection semantics can be integrated with existing systems. Our design has been fully implemented and used to protect a wide range of unmodified legacy applications running on an unmodified Linux operating system. We evaluate the performance of our implementation, demonstrating that this approach is practical.

Even as modern computing systems allow the manipulation and distribution of massive amounts of information, users of these systems are unable to manage the confidentiality of their data in a practical fashion. Conventional access control security mechanisms cannot prevent the illegitimate use of privileged data once access is granted. For example, information provided by a user during an online purchase may be covertly delivered to malicious third parties by an untrustworthy web browser. Existing information-flow security mechanisms do provide this assurance, but only for programmer-specified policies enforced during program development as a static analysis on special-purpose type-safe languages. Not only are these techniques not applicable to many commonly used programs, but they leave the user with no defense against malicious programmers or altered binaries. In this paper, we propose RIFLE, a runtime informationflow security system designed from the user’s perspective. By addressing information-flow security using architectural support, RIFLE gives users a practical way to enforce their own information-flow security policy on all programs. We prove that, contrary to statements in the literature, runtime systems like RIFLE are no less secure than existing language-based techniques. Using a model of the architectural framework and a binary translator, we demonstrate RIFLE’s correctness and illustrate that the performance cost is reasonable. 1.

The future of digital systems is complexity, and complexity is the worst enemy of security.-- Bruce Schneier [40]. The large size and high complexity of securitysensitive applications and systems software is a primary cause for their poor testability and high vulnerability. One approach to alleviate this problem is to extract the security-sensitive parts of application and systems software, thereby reducing the size and complexity of software that needs to be trusted. At the system software level, we use the Nizza architecture which relies on a kernelized trusted computing base (TCB) and on the reuse of legacy code using trusted wrappers to minimize the size of the TCB. At the application level, we extract the security-sensitive portions of an already existing application into an AppCore. The AppCore is executed as a trusted process in the Nizza architecture while the rest of the application executes on a virtualized, untrusted legacy operating system. In three case studies of real-world applications (ecommerce transaction client, VPN gateway and digital signatures in an e-mail client), we achieved a considerable reduction in code size and complexity. In contrast to the few hundred thousand lines of current application software code running on millions of lines of systems software code, we have AppCores with tens of thousands of lines of code running on a hundred thousand lines of systems software code. We also show the performance penalty of AppCores to be modest (a few percent) compared to current software.

Buffer overflow vulnerabilities are currently the most prevalent security vulnerability; they are responsible for over half of the CERT advisories issued in the last three years. Since many attacks exploit buffer overflow vulnerabilities, techniques that prevent buffer overflow attacks would greatly increase the difficulty of writing a new worm. This paper examines both software and hardware solutions for protecting code pointers from buffer overflow attacks. We first evaluate the performance overhead of the existing Point-Guard software solution for protecting code pointers, and show that it can be applied using binary modification to protect return pointers on the stack. These software techniques guard against write attacks, but not read attacks, where an attacker is attempting to gain information about the pointer protection mechanism in order to later mount a write buffer attack. To address this, we examine encryption hardware to provide security for code pointers from read and write attacks. In addition, we show that pure software solutions can degrade program performance, and the light-weight encryption hardware techniques we examine can be used to provide protection with little performance overhead. 1.

This paper presents the design and an evaluation of Mondrix, a version of the Linux kernel with Mondriaan Memory Protection (MMP). MMP is a combination of hardware and software that provides efficient fine-grained memory protection between multiple protection domains sharing a linear address space. Mondrix uses MMP to enforce isolation between kernel modules which helps detect bugs, limits their damage, and improves kernel robustness and maintainability. During development, MMP exposed two kernel bugs in common, heavily-tested code, and during fault injection experiments, it prevented three of five file system corruptions. The Mondrix implementation demonstrates how MMP can bring memory isolation to modules that already exist in a large software application. It shows the benefit of isolation for robustness and error detection and prevention, while validating previous claims that the protection abstractions MMP offers are a good fit for software. This paper describes the design of the memory supervisor, the kernel module which implements permissions policy. We present an evaluation of Mondrix using full-system simulation of large kernel-intensive workloads. Experiments with several benchmarks where MMP was used extensively indicate the additional space taken by the MMP data structures reduce the kernel’s free memory by less than 10%, and the kernel’s runtime increases less than 15 % relative to an unmodified kernel.

Encrypting data in unprotected memory has gained much interest lately for digital rights protection and security reasons. Counter Mode is a well-known encryption scheme. It is a symmetric-key encryption scheme based on any block cipher, e.g. AES. The scheme’s encryption algorithm uses a block cipher, a secret key and a counter (or a sequence number) to generate an encryption pad which is XORed with the data stored in memory. Like other memory encryption schemes, this method suffers from the inherent latency of decrypting encrypted data when loading them into the onchip cache. One solution that parallelizes data fetching and encryption pad generation requires the sequence numbers of evicted cache lines to be cached on-chip. On-chip sequence number caching can be successful in reducing the latency at the cost of a large area overhead.

A large fraction of email spam, distributed denial-ofservice (DDoS) attacks, and click-fraud on web advertisements are caused by traffic sent from compromised machines that form botnets. This paper posits that by identifying human-generated traffic as such, one can service it with improved reliability or higher priority, mitigating the effects of botnet attacks. The key challenge is to identify human-generated traffic in the absence of strong unique identities. We develop NAB (“Not-A-Bot”), a system to approximately identify and certify human-generated activity. NAB uses a small trusted software component called an attester, which runs on the client machine with an untrusted OS and applications. The attester tags each request with an attestation if the request is made within a small amount of time of legitimate keyboard or mouse activity. The remote entity serving the request sends the request and attestation to a verifier, which checks the attestation and implements an application-specific policy for attested requests. Our implementation of the attester is within the Xen hypervisor. By analyzing traces of keyboard and mouse activity from 328 users at Intel, together with adversarial traces of spam, DDoS, and click-fraud activity, we estimate that NAB reduces the amount of spam that currently passes through a tuned spam filter by more than 92%, while not flagging any legitimate email as spam. NAB delivers similar benefits to legitimate requests under DDoS and click-fraud attacks. 1

Tamper-proof coprocessors for secure computing are poised to become a standard hardware feature on future computers. Such hardware provides the primitives necessary to support trustworthy computing applications, that is, applications that can provide strong guarantees about their run time behavior. Current operating systems, however, lack the architecture and abstractions required to support trustworthy computing. Traditional operating systems, whether monolithic or based on a microkernel architecture, rely on a large trusted computing base (TCB) that is error-prone, expensive to audit, and inherently difficult to trust. Current abstractions they provide do not support the newly emerging secure coprocessing hardware. The construction of trustworthy applications, whose run time properties can be queried, inspected and assured, remains ad hoc in the absence of general-purpose system abstractions for trusted computing.

Multi-tenant cloud, which usually leases resources in the form of virtual machines, has been commercially available for years. Unfortunately, with the adoption of commodity virtualized infrastructures, software stacks in typical multi-tenant clouds are non-trivially large and complex, and thus are prone to compromise or abuse from adversaries including the cloud operators, which may lead to leakage of security-sensitive data. In this paper, we propose a transparent, backward-compatible approach that protects the privacy and integrity of customers ’ virtual machines on commodity virtualized infrastructures, even facing a total compromise of the virtual machine monitor (VMM) and the management VM. The key of our approach is the separation of the resource management from security protection in the virtualization layer. A tiny security monitor is introduced underneath the commodity VMM using nested virtualization and provides protection to the hosted VMs. As a result, our approach allows virtualization software (e.g., VMM, management VM and tools) to handle complex tasks of managing leased VMs for the cloud, without breaking security of users ’ data inside the VMs. We have implemented a prototype by leveraging commercially-available hardware support for virtualization. The prototype system, called CloudVisor, comprises only 5.5K LOCs and supports the Xen VMM with multiple Linux and Windows as the guest OSes. Performance evaluation shows that CloudVisor incurs moderate slowdown for I/O intensive applications and very small slowdown for other applications.

The Trusted Computing Group (TCG) has issued several specifications to enhance the architecture of common computing platforms by means of new functionalities, amongst others the (binary) attestation to verify the integrity of a (remote) computing platform/application. However, as pointed out recently, the binary attestation has some shortcomings, in particular when used for applications: First, it reveals information about the configuration of a platform (hardware and software) or application. This can be misused to discriminate certain configurations (e.g., operating systems) and the corresponding vendors, or be exploited to mount attacks. Second, it requires the verifier to know all possible “trusted ” configurations of all platforms as well as managing updates and patches that change the configuration. Third, it does not necessarily imply that the platform complies with desired (security) properties. A recent proposal to overcome these problems is to transform the binary attestation into property-based attestation, which requires to only attest whether a platform or an application fulfills the desired (security) requirements without revealing the specific software or/and hardware configuration. Based on previous works, we propose a concrete efficient model for the main functionalities provided by TCG-compliant platforms. We prove the security of this protocol under the strong RSA assumption and the discrete logarithm assumption in the random oracle model. Our scheme allows blind verification and revocation of mappings between properties and configurations.