Hardware-based approach to guarantee trusted system boot in embedded systems

Abstract

In recent years, computer systems spread in our daily lives have been experiencing an increasing wave of attacks that disrupt their normal operation or leak sensitive data. Some of them, so-called I/O attacks, are performed by malicious peripherals that perform read or write accesses to DRAM memory through unauthorized DMA (Direct Memory Access) requests during the system boot. During this period the system is particularly vulnerable, which allows hackers to make use of peripherals to perform malicious accesses to DRAM memory. As consequence, it degrades system security. In this context, this paper presents a hardware-based secure-system boot sniffer (SBS) Watchdog to prevent I/O attacks during system boot. The SBS Watchdog is tightly connected to the PCIe communication bus to prevent peripherals from accessing DRAM memory during the BIOS execution and operating system loading, i.e., during the system boot. Compared to existing approaches, the proposed technique is fully transparent to the user, can be applied to any operating system, induces no performance degradation since the SBS Watchdog is turned-off after system boot, and cannot be unintentionally disabled by users during system configuration procedure. The proposed technique was implemented in a commercial FPGA. Practical experiments have demonstrated the high effectiveness of the proposed technique to prevent I/O attacks during system boot.