AppBastion: Protection from Untrusted Apps and OSes on ARM

ARM-based (mobile) devices are more popular than ever. They are used to access, process, and store confidential information and participate in sensitive authentication protocols, making them extremely attractive targets. Many attacks focus on compromising the primary operating system – for example, by convincing the user to download OS rootkits concealed within seemingly innocent apps. To partially mitigate the impact, device manufacturers responded by offering hardware-rooted trusted environments (TEEs). Yet, making use of TEEs (e.g., by securely porting existing apps) is not easy. Only a small number of security-critical applications make use of TEEs, leaving all others to run on a potentially vulnerable OS, under the control of users that all too often fall prey to cleverly disguised malware. AppBastion is a general-purpose platform that leverages the now ubiquitous ARM TrustZone TEE to secure application data from untrusted OSes. AppBastion enables applications to maintain confidential data in memory regions protected even from a compromised OS. Only approved, signed applications can access their associated protected memory regions. Data never leaves protected regions unencrypted and applications can communicate or declassify protected data only through explicit AppBastion channels. AppBastion ensures that application confidential data cannot be accessed, spoofed, or leaked by the OS.