The presence of large numbers of security vulnerabilities in popular feature-rich commodity operating systems has inspired a long line of work on excluding these operating systems from the trusted computing base of applications, while retaining many of their benefits. Legacy applications continue to run on the untrusted operating system, while a small hyper visor or trusted hardware prevents the operating system from accessing the applications' memory. In this paper, we introduce controlled-channel attacks, a new type of side-channel attack that allows an untrusted operating system to extract large amounts of sensitive information from protected applications on systems like Overshadow, Ink Tag or Haven. We implement the attacks on Haven and Ink Tag and demonstrate their power by extracting complete text documents and outlines of JPEG images from widely deployed application libraries. Given these attacks, it is unclear if Over shadow's vision of protecting unmodified legacy applications from legacy operating systems running on off-the-shelf hardware is still tenable.

/pdf/controlled-channel-attacks-deterministic-side-channels-for-26lzcntreu.pdf

Controlled-Channel Attacks: Deterministic Side Channels for Untrusted Operating Systems

Today’s cloud computing infrastructure requires substantial trust. Cloud users rely on both the provider’s staff and its globally distributed software/hardware platform not to expose any of their private data.We introduce the notion of shielded execution, which protects the confidentiality and integrity of a program and its data from the platform on which it runs (i.e., the cloud operator’s OS, VM, and firmware). Our prototype, Haven, is the first system to achieve shielded execution of unmodified legacy applications, including SQL Server and Apache, on a commodity OS (Windows) and commodity hardware. Haven leverages the hardware protection of Intel SGX to defend against privileged code and physical attacks such as memory probes, and also addresses the dual challenges of executing unmodified legacy binaries and protecting them from a malicious host. This work motivated recent changes in the SGX specification.

Shielding Applications from an Untrusted Cloud with Haven

We present unikernels, a new approach to deploying cloud services via applications written in high-level source code. Unikernels are single-purpose appliances that are compile-time specialised into standalone kernels, and sealed against modification when deployed to a cloud platform. In return they offer significant reduction in image sizes, improved efficiency and security, and should reduce operational costs. Our Mirage prototype compiles OCaml code into unikernels that run on commodity clouds and offer an order of magnitude reduction in code size without significant performance penalty. The architecture combines static type-safety with a single address-space layout that can be made immutable via a hypervisor extension. Mirage contributes a suite of type-safe protocol libraries, and our results demonstrate that the hypervisor is a platform that overcomes the hardware compatibility issues that have made past library operating systems impractical to deploy in the real-world.

/pdf/unikernels-library-operating-systems-for-the-cloud-2g23pju8w2.pdf

Unikernels: library operating systems for the cloud

Today's cloud computing infrastructure requires substantial trust. Cloud users rely on both the provider's staff and its globally-distributed software/hardware platform not to expose any of their private data.We introduce the notion of shielded execution, which protects the confidentiality and integrity of a program and its data from the platform on which it runs (i.e., the cloud operator's OS, VM and firmware). Our prototype, Haven, is the first system to achieve shielded execution of unmodified legacy applications, including SQL Server and Apache, on a commodity OS (Windows) and commodity hardware. Haven leverages the hardware protection of Intel SGX to defend against privileged code and physical attacks such as memory probes, but also addresses the dual challenges of executing unmodified legacy binaries and protecting them from a malicious host. This work motivated recent changes in the SGX specification.

https://www.usenix.org/system/files/conference/osdi14/osdi14-paper-baumann.pdf

Shielding applications from an untrusted cloud with Haven

Trusted execution environments (TEEs) see rising use in devices from embedded sensors to cloud servers and encompass a range of cost, power constraints, and security threat model choices. On the other hand, each of the current vendor-specific TEEs makes a fixed set of trade-offs with little room for customization. We present Keystone---the first open-source framework for building customized TEEs. Keystone uses simple abstractions provided by the hardware such as memory isolation and a programmable layer underneath untrusted components (e.g., OS). We build reusable TEE core primitives from these abstractions while allowing platform-specific modifications and flexible feature choices. We showcase how Keystone-based TEEs run on unmodified RISC-V hardware and demonstrate the strengths of our design in terms of security, TCB size, execution of a range of benchmarks, applications, kernels, and deployment models.

https://dl.acm.org/doi/pdf/10.1145/3342195.3387532

Keystone: an open framework for architecting trusted execution environments

This paper revisits an old approach to operating system construc-tion, the library OS, in a new context. The idea of the library OS is that the personality of the OS on which an application depends runs in the address space of the application. A small, fixed set of abstractions connects the library OS to the host OS kernel, offering the promise of better system security and more rapid independent evolution of OS components.We describe a working prototype of a Windows 7 library OS that runs the latest releases of major applications such as Microsoft Excel, PowerPoint, and Internet Explorer. We demonstrate that desktop sharing across independent, securely isolated, library OS instances can be achieved through the pragmatic reuse of net-working protocols. Each instance has significantly lower overhead than a full VM bundled with an application: a typical application adds just 16MB of working set and 64MB of disk footprint. We contribute a new ABI below the library OS that enables application mobility. We also show that our library OS can address many of the current uses of hardware virtual machines at a fraction of the overheads. This paper describes the first working prototype of a full commercial OS redesigned as a library OS capable of running significant applications. Our experience shows that the long-promised benefits of the library OS approach better protection of system integrity and rapid system evolution are readily obtainable.

/pdf/rethinking-the-library-os-from-the-top-down-1fetscopoy.pdf

Rethinking the library OS from the top down

A library operating system is employed in conjunction with an application in a virtual environment to facilitate dynamic application migration. An application executing in a virtual environment with a library operating system on a first machine can be suspended, and application state can be captured. Subsequently, the state can be restored and execution resumed on the first machine or a second machine.

Dynamic application migration

Library OS (LibOS) architectures implement the OS personality as a user-mode library, giving each application the flexibility to choose its LibOS. This approach is appealing for many reasons, not least the ability to extend or customise the LibOS. Recent work with Drawbridge [29] showed that an existing commodity OS (Windows 7) could be refactored to produce a LibOS while retaining application compatibility.This paper presents Bascule, an architecture for LibOS extensions based on Drawbridge. Rather than relying on the application developer to customise a LibOS, Bascule allows OS-independent extensions to be attached at runtime. Extensions interpose on a narrow binary interface of primitive OS abstractions, such as files and virtual memory. Thus, they are independent of both guest and host OS, and composable at runtime. Since an extension runs in the same process as an application and its LibOS, it is safe and efficient.Bascule demonstrates extension reuse across diverse guest LibOSes (Windows and Linux) and host OSes (Windows and Barrelfish). Current extensions include file system translation, checkpointing, and architecture adaptation.

/pdf/composing-os-extensions-safely-and-efficiently-with-bascule-wdr3jnx8a2.pdf

Composing OS extensions safely and efficiently with Bascule

Architecture that facilitates seamless migration of server-hosted code to the client machine and back. Migration is of a running instance of a process by communicating only a small amount of state data, which makes this feasible over current network connection speeds. The web browsing experience for applications is retained. The migration capabilities are facilitated by an operating construction, referred to as the library OS (operating system) system in a context of state and execution migration between server and client. An application binary interface is provided that resides below the library OS to provide the state and execution mobility.

Migration of cloud applications between a local computing device and cloud

The described implementations relate to virtual computing techniques. One implementation provides a technique that can include receiving a request to execute an application. The application can include first application instructions from a guest instruction set architecture. The technique can also include loading an emulator and a guest operating system into an execution context with the application. The emulator can translate the first application instructions into second application instructions from a host instruction set architecture. The technique can also include running the application by executing the second application instructions.

Reuben R. Olinsky

Papers

Rethinking the library OS from the top down

Dynamic application migration

Composing OS extensions safely and efficiently with Bascule

Migration of cloud applications between a local computing device and cloud

Instruction set emulation for guest operating systems