Protection Mechanism of User Process Credentials Using ARM Confidential Computing Architecture

Abstract

A privilege escalation attack exploits operating system (OS) vulnerabilities. In this attack, attackers who infiltrate a computer as normal users exploit vulnerabilities in the OS to obtain higher privileges, enabling them to view confidential information and disable the antivirus software. The complete elimination of OS vulnerabilities remains extremely difficult; therefore, the development of effective countermeasures against exploit-based attacks is a critical research priority. Countermeasures against privilege escalation attacks have been proposed to protect user process credentials within the kernel or in the secure area of ARM TrustZone. However, if a vulnerability in any function other than the security mechanism exists, it can be exploited, and the security mechanism can be disabled. This study proposes a privilege protection mechanism using ARM confidential computing architecture (CCA) (PrivCCA) to render the OS resistant to tampering with user process credentials. PrivCCA protects against privilege escalation attacks by replicating user process credentials in the isolated environment of ARM CCA. This study focuses on system call invocations made by multiple user processes and privilege escalation attacks that exploit kernel vulnerabilities. When a user process is created, the credentials are replicated in the isolated ARM CCA environment. By evaluating PrivCCA, this study confirmed that privilege escalation attacks could be detected, and credentials could be restored. Additionally, performance degradation of 58.79% in process creation, 60.25% in the sequential execution of shell scripts, and 41.61% in parallel execution was observed. This performance degradation is believed to be caused by the load from network communication with the isolated environment. PrivCCA achieves protection in an environment independent of security mechanisms.