Protecting Instruction Set Randomization from Code Reuse Attacks

Instruction Set Randomization (ISR) prevents code injection by randomizing the instruction encoding used by programs, thus preventing an attacker from preparing a payload that can be injected in a victim. In this paper we show that code-reuse attacks can be used to circumvent existing ISR techniques and we demonstrate these attacks on an ARMv7 CPU that has been extended with ISR support. To counter this treat, we propose a new ISR that does not have the same vulnerabilities as the existing solutions, imposes moderate decryption cost, does not require additional memory per instruction, and affords efficient random access to the encrypted code. These properties enable efficient hardware implementation of our solution. In order to evaluate our proposal, we implement the new ISR in a hardware simulator and we compare its overhead with respect to existing ISR.