The security of systems such as operating systems, hypervisors, and web browsers depend critically on reference monitors to correctly enforce their desired security policy in the presence of adversaries. Recent progress in developing reference monitors with small code size and narrow interfaces has made automated formal verification of reference monitors a more tractable goal. However, a significant remaining factor for the complexity of automated verification is the size of the data structures (e.g., access control matrices) over which the programs operate. This paper develops a parametric verification technique that scales even when reference monitors and adversaries operate over unbounded, but finite data structures. Specifically, we develop a parametric guarded command language for modeling reference monitors and adversaries. We also present a parametric temporal specification logic for expressing security policies that the monitor is expected to enforce. The central technical results of the paper are a set of small model theorems. These theorems state that in order to verify that a policy is enforced by a reference monitor with an arbitrarily large data structure, it is sufficient to model check the monitor with just one entry in its data structure. We apply our methodology to verify the designs of two hypervisors, SecVisor and the sHype mandatory-access-control extension to Xen. Our approach is able to prove that sHype and a variant of the original SecVisor design correctly enforces the expected security properties in the presence of powerful adversaries.

We explore the extent to which newly available CPU-based security technology can reduce the Trusted Computing Base (TCB) for security-sensitive applications. We find that although this new technology represents a step in the right direction, significant performance issues remain. We offer several suggestions that leverage existing processor technology, retain security, and improve performance. Implementing these recommendations will finally allow application developers to focus exclusively on the security of their own code, enabling it to execute in isolation from the numerous vulnerabilities in the underlying layers of legacy code.

We propose SecVisor, a tiny hypervisor that ensures code integrity for commodity OS kernels. In particular, SecVisor ensures that only user-approved code can execute in kernel mode over the entire system lifetime. This protects the kernel against code injection attacks, such as kernel rootkits. SecVisor can achieve this propertyeven against an attacker who controls everything but the CPU, the memory controller, and system memory chips. Further, SecVisor can even defend against attackers with knowledge of zero-day kernel exploits.

We propose an architecture that allows code to execute in complete isolation from other software while trusting only a tiny software base that is orders of magnitude smaller than even minimalist virtual machine monitors. Our technique also enables more meaningful attestation than previous proposals, since only measurements of the security-sensitive portions of an application need to be included. We achieve these guarantees by leveraging hardware support provided by commodity processors from AMD and Intel that are shipping today.

We propose a primitive, called Pioneer, as a first step towards verifiable code execution on untrusted legacy hosts. Pioneer does not require any hardware support such as secure co-processors or CPU-architecture extensions. We implement Pioneer on an Intel Pentium IV Xeon processor. Pioneer can be used as a basic building block to build security systems. We demonstrate this by building a kernel rootkit detector.

We expect a future where we are surrounded by embedded devices, ranging from Java-enabled cell phones to sensor networks and smart appliances. An adversary can compromise our privacy and safety by maliciously modifying the memory contents of these embedded devices. In this paper, we propose a softWare-based attestation technique (SWATT) to verify the memory contents of embedded devices and establish the absence of malicious changes to the memory contents. SWATT does not need physical access to the device's memory, yet provides memory content attestation similar to TCG or NGSCB without requiring secure hardware. SWATT can detect any change in memory contents with high probability, thus detecting viruses, unexpected configuration settings, and Trojan Horses. To circumvent SWATT, we expect that an attacker needs to change the hardware to hide memory content changes. We present an implementation of SWATT in off-the-shelf sensor network devices, which enables us to verify the contents of the program memory even while the sensor node is running.