  AMD SEV is a hardware feature designed for the secure encryption of virtual
machines. SEV aims to protect virtual machine memory not only from other
malicious guests and physical attackers, but also from a possibly malicious
hypervisor. This relieves cloud and virtual server customers from fully
trusting their server providers and the hypervisors they are using. We present
the design and implementation of SEVered, an attack from a malicious hypervisor
capable of extracting the full contents of main memory in plaintext from
SEV-encrypted virtual machines. SEVered neither requires physical access nor
colluding virtual machines, but only relies on a remote communication service,
such as a web server, running in the targeted virtual machine. We verify the
effectiveness of SEVered on a recent AMD SEV-enabled server platform running
different services, such as web or SSH servers, in encrypted virtual machines.
With these examples, we demonstrate that SEVered reliably and efficiently
extracts all memory contents even in scenarios where the targeted virtual
machine is under high load.
