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2 Hardware Platform Security Overview

NIST platform security: roots of trust, firmware and secure enclaves IR 8320
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Hardware Platform Security Overview

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The data center threat landscape has evolved in recent years to encompass more advanced attack surfaces with more persistent attack mechanisms. With increased attention being applied to high- level software security, attackers are pushing lower in the platform stack, forcing security administrators to address a variety of attacks that threaten the platform firmware and hardware. These threats can result in:

• Unauthorized access to and potential extraction of sensitive platform or user data, including direct physical access to dual in-line memory modules (DIMMs)

• Modification of platform firmware, such as that belonging to the Unified Extensible Firmware Interface (UEFI)/Basic Input/Output System (BIOS), Board Management Controller (BMC), Manageability Engine (ME), Peripheral Component Interconnect Express (PCIe) device, and various accelerator cards

• Supply chain interception through the physical replacement of firmware or hardware with malicious versions

• Access to data or execution of code outside of regulated geopolitical or other boundaries

• Circumvention of software and/or firmware-based security mechanisms

For example, LoJax, discovered in August 2018, manifests itself in UEFI malware, allowing it to continuously persist in the firmware layer despite operating system (OS) reinstallations, and thus remain invisible to standard kernel-based virus scans [1] . These attacks can be devastating to cloud environments because they often require server-by-server rebuilds or replacements, which can take weeks. Although still rare, these attacks are increasing as attackers become more sophisticated.

Workloads subject to specific regulations or containing sensitive data present additional security challenges for multi-tenant clouds. While virtualization and containers significantly benefit efficiency, adaptability, and scalability, these technologies consolidate workloads onto fewer physical platforms and introduce the dynamic migration of workloads and data across platforms. Consequently, cloud adoption results in a loss of customer visibility and control over the platforms that host virtualized workloads and data, and introduces the usage of third-party infrastructure administrators. Cloud providers and cloud adopters follow a shared responsibility model, where each party has responsibility for different aspects of the overall implementation. Cloud providers can expose information related to infrastructure security and platform capability in order to provide their tenants with security assurances. Furthermore, cloud providers often have data centers that span multiple geopolitical boundaries, subjecting workload owners to complicated legal and regulatory compliance requirements from multiple countries. Hybrid cloud architectures, in particular, utilize multiple infrastructure providers, each with its own infrastructure configurations and management.

Without physical control over or use of confidential computing features or visibility into platform configurations, conventional security best practices and regulatory requirements become difficult or impossible to implement. With regulatory structures like the General Data Protection Regulation (GDPR) introducing high-stakes fines for noncompliance, having visibility and control over where data may be accessed is more important than ever before. Top concerns among security professionals include the protection of workloads from general security risks, the loss or exposure of data in the event of a data breach, and regulatory compliance.

Existing mitigations of threats against cloud servers are often rooted in firmware or software, making them vulnerable to the same attack strategies. For example, if the firmware can be successfully exploited, the firmware-based security controls can most likely be circumvented in the same fashion. Hardware-enabled security techniques can help mitigate these threats by establishing and maintaining platform trust —an assurance in the integrity of the underlying platform configuration, including hardware, firmware, and software. By providing this assurance, security administrators can gain a level of visibility and control over where access to sensitive workloads and data is permitted. Platform security technologies that establish platform trust can provide notification or even self-correction of detected integrity failures. Platform configurations can automatically be reverted back to a trusted state and give the platform resilience against attack.

To achieve the necessary security controls, an RoT can be leveraged as a starting point that is implicitly trusted. Hardware-based controls can provide a foundation for establishing platform integrity assurances. Combining these functions with a means of producing verifiable evidence that these integrity controls are in place and have been executed successfully is the basis of creating a trusted platform. Minimizing the footprint of this RoT translates to reducing the number of modules or technologies that must be implicitly trusted. This substantially reduces the attack surface.

Platforms that secure their underlying firmware and configuration provide the opportunity for trust to be extended higher in the software stack. Verified platform firmware can, in turn, verify the OS boot loader, which can then verify other software components all the way up to the OS itself and the hypervisor or container runtime layers. The transitive trust described here is consistent with the concept of the chain of trust (CoT) —a method where each software module in a system boot process is required to measure the next module before transitioning control.

Rooting platform integrity and trust in hardware security controls can strengthen and complement the extension of the CoT into the dynamic software category. There, the CoT can be extended even further to include data and workload protection. Hardware-based protections through CoT technology mechanisms can form a layered security strategy to protect data and workloads as they move to multi-tenant environments in a cloud data center or edge computing facility.

In addition, there are other hardware platform security technologies that can protect data at rest, in transit, and in use by providing hardware-accelerated disk encryption or encryption-based memory isolation. Many of these capabilities can help mitigate threats from speculative execution and side-channel attacks. By using hardware to perform these tasks, the attack surface is mitigated, preventing direct access or modification of the required firmware. Isolating these encryption mechanisms to dedicated hardware can allow performance to be addressed and enhanced separately from other system processes as well. An example of hardware-based isolation is discussed later in the document.