Jailbreaking the AMD Secure Processor: Enabling Live Analysis of SEV-SNP's Undocumented Security Boundaries

AMD's Secure Encrypted Virtualization with Secure Nested Paging (SEV-SNP) protects virtual machines using its hardware root of trust, the AMD Secure Processor (ASP). However, its security relies on complex, opaque firmware features, such as a dynamic hot-patching mechanism, that create attack surfaces shielded from independent scrutiny. To overcome this "black-box" challenge, we present ASPBreaker, the first practical, fully deterministic jailbreak of the ASP, achieved by exploiting a novel combination of memory aliasing and time-of-check-to-time-of-use (TOCTOU) vulnerability.

Using this jailbreak as a tool for live analysis, we demonstrate how achieving arbitrary code execution on a vulnerable firmware version can be used to subvert the security of a subsequent, fully-patched one. Our analysis revealed critical flaws, enabling two practical attacks against the latest firmware: one that allows an adversary to decrypt the memory of a virtual machine and another that bypasses existing mitigations to forge attestation reports. Our findings, which were responsibly disclosed, demonstrate a fundamental break in the forward-security model of SEV-SNP and highlight the critical need for independent auditing of opaque firmware boundaries.