Formally Verifying the Correctness and Safety of OpenTitan Boot Code using CBMC
Translated title
Formel Verifikation af Korrektheden og Sikkerheden af OpenTitan Boot Code ved brug af CBMC
Term
4. term
Education
Publication year
2021
Submitted on
2021-06-16
Pages
124
Abstract
The correctness and safety of heavily relied upon software is crucial. OpenTitan is an open-source silicon root-of-trust project. Based on an extensive analysis of the OpenTitan project, we, together with SV106f21, developed C code that corresponds to the initial boot stage of OpenTitan. CBMC is a bounded model checker for ANSI-C verification. We verify numerous safety properties for the developed boot code using CBMC. In addition, we propose an overview of the CBMC architecture and theory as well as a structured approach to verify C code using CBMC. We use CBMC nondeterminism to create a C model of the boot code's hardware environment. In total, we verified that the developed boot code adheres to all 11 security properties, with most of them being derived from security goals from our previous work. We also further investigate the safety of the boot code by modeling various hardware attacks and verify for their implication. We discover that the current implementation is vulnerable to attacks on flash, ROM, and the OpenTitan Big Number Accelerator, with the consequence of either executing malicious code or crashing.
Documents