arXiv subjects

Mark Kuhne

Publications and source records attributed to Mark Kuhne.

6 recordsLinked to original sources

arXiv2024

Dorami: Privilege Separating Security Monitor on RISC-V TEEs

TEE implementations on RISC-V offer an enclave abstraction by introducing a trusted component called the security monitor (SM). The SM performs critical tasks such as isolating enclaves from each other as well as from the OS by using privileged ISA instructions that enforce the physical memory protection. However, the SM executes at the highest privilege layer on the platform (machine-mode) along side firmware that is not only large in size but also includes third-party vendor code specific to the platform. In this paper, we present Dorami - a privilege separation approach that isolates the SM from the firmware thus reducing the attack surface on TEEs. Dorami re-purposes existing ISA features to enforce its isolation and achieves its goals without large overheads.

cs.CR↗

arXiv2024

Devlore: Device Interrupt Protection for Confidential VMs

Modern confidential computing executes sensitive computation in an abstraction called confidential VMs and protects from the hypervisor, host OS, and other co-resident VMs. It has been shown that an attacker can inject malicious interrupts to break the confidentiality and integrity of confidential VMs. We present Devlore, a device interrupt isolation mechanism that protects confidential VMs from interrupt manipulation attacks. Our design employs a delegate-but-check strategy by offloading interrupt management to the hypervisor, but adds correctness checks in the trusted software. We prototype our design on Arm Confidential Computing Architecture (CCA). We evaluate it on Arm FVP to demonstrate four diverse devices attached to confidential VMs and report costs on a Rock5b board. Our case studies show the feasibility of real-world use cases and that Devlore incurs minimal overheads of 0.06% for typical integrated GPU applications.

cs.CR↗

arXiv2024

Aster: Fixing the Android TEE Ecosystem with Arm CCA

The Android ecosystem relies on either TrustZone (e.g., OP-TEE, QTEE, Trusty) or trusted hypervisors (pKVM, Gunyah) to isolate security-sensitive services from malicious apps and Android bugs. TrustZone allows any secure world code to access the normal world that runs Android. Similarly, a trusted hypervisor has full access to Android running in one VM and security services in other VMs. In this paper, we motivate the need for mutual isolation, wherein Android, hypervisors, and the secure world are isolated from each other. Then, we propose a sandboxed service abstraction, such that a sandboxed execution cannot access any other sandbox, Android, hypervisor, or secure world memory. We present Aster which achieves these goals while ensuring that sandboxed execution can still communicate with Android to get inputs and provide outputs securely. Our main insight is to leverage the hardware isolation offered by Arm Confidential Computing Architecture (CCA). However, since CCA does not satisfy our sandboxing and mutual isolation requirements, Aster repurposes its hardware enforcement to meet its goals while addressing challenges such as secure interfaces, virtio, and protection against interrupts. We implement Aster to demonstrate its feasibility and assess its compatibility. We take three case studies, including one currently deployed on Android phones and insufficiently secured using a trusted hypervisor, to demonstrate that they can be protected by Aster.

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arXiv2024

Heckler: Breaking Confidential VMs with Malicious Interrupts

Hardware-based Trusted execution environments (TEEs) offer an isolation granularity of virtual machine abstraction. They provide confidential VMs (CVMs) that host security-sensitive code and data. AMD SEV-SNP and Intel TDX enable CVMs and are now available on popular cloud platforms. The untrusted hypervisor in these settings is in control of several resource management and configuration tasks, including interrupts. We present Heckler, a new attack wherein the hypervisor injects malicious non-timer interrupts to break the confidentiality and integrity of CVMs. Our insight is to use the interrupt handlers that have global effects, such that we can manipulate a CVM's register states to change the data and control flow. With AMD SEV-SNP and Intel TDX, we demonstrate Heckler on OpenSSH and sudo to bypass authentication. On AMD SEV-SNP we break execution integrity of C, Java, and Julia applications that perform statistical and text analysis. We explain the gaps in current defenses and outline guidelines for future defenses.

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arXiv2023

ACAI: Protecting Accelerator Execution with Arm Confidential Computing Architecture

Trusted execution environments in several existing and upcoming CPUs demonstrate the success of confidential computing, with the caveat that tenants cannot securely use accelerators such as GPUs and FPGAs. In this paper, we reconsider the Arm Confidential Computing Architecture (CCA) design, an upcoming TEE feature in Armv9-A, to address this gap. We observe that CCA offers the right abstraction and mechanisms to allow confidential VMs to use accelerators as a first-class abstraction. We build ACAI, a CCA-based solution, with a principled approach of extending CCA security invariants to device-side access to address several critical security gaps. Our experimental results on GPU and FPGA demonstrate the feasibility of ACAI while maintaining security guarantees.

cs.CR↗

arXiv2023

It's TEEtime: A New Architecture Bringing Sovereignty to Smartphones

Modern smartphones are complex systems in which control over phone resources is exercised by phone manufacturers, OS vendors, and users. These stakeholders have diverse and often competing interests. Barring some exceptions, users entrust their security and privacy to OS vendors (Android and iOS) and need to accept their constraints. Manufacturers protect their firmware and peripherals from the OS by executing in the highest privilege and leveraging dedicated CPUs and TEEs. OS vendors need to trust the highest privileged code deployed by manufacturers. This division of control over the phone is not ideal for OS vendors and is even more disadvantageous for the users. Users are generally limited in what applications they can install on their devices, in the privacy model and trust assumptions of the existing applications, and in the functionalities that applications can have. We propose TEEtime, a new smartphone architecture based on trusted execution allowing to balance the control different stakeholders exert over phones. More leveled control over the phone means that no stakeholder is more privileged than the others. In particular, TEEtime makes users sovereign over their phones: It enables them to install sensitive applications in isolated domains with protected access to selected peripherals alongside an OS. TEEtime achieves this while maintaining compatibility with the existing smartphone ecosystem and without relying on virtualization; it only assumes trust in a phone's firmware. TEEtime is the first TEE architecture that allows isolated execution domains to gain protected and direct access to peripherals. TEEtime is based on Armv8-A and achieves peripheral isolation using a novel mechanism based on memory and interrupt controller protection. We demonstrate the feasibility of our design by implementing a prototype of TEEtime, and by running exemplary sensitive applications.

cs.CR↗