Commands communications
In an example, a hypervisor measuring the state of a protected virtual machine using a Trusted Platform Module (TPM) filter. Using the TPM filter, the system ensures an untrusted operating system attempting to access the TPM is secure, without having to trust the security of the operating system or the operating system's built in hypervisor.
1 . A non-transitory computer-readable medium having instructions that, when executed by a processor of a computing device, cause the computing device to:
intercept, from an operating system of the computing device, a command that attempts to interact with a trusted platform module (TPM) of the computing device;
identify, from among a plurality of platform configuration registers in the TPM, a particular PCR that the command targets; and
block in response to determining that the particular PCR is assigned to a protected virtual application that executes within a virtual machine, the command from interacting with the TPM.
2 . The non-transitory computer-readable medium of claim 1 , wherein the instructions, when executed by the processor, cause the computing device to:
create a set of pate table mappings to protect memory-mapped I/O (MMIO) registers associated with input/output interfaces of the TPM.
3 . The non-transitory computer readable medium of claim 2 , wherein the instructions, when executed by the processor, cause the computing device to:
protect the set of memory-mapped I/O (MMIO) registers.
4 . The non-transitory computer-readable medium of claim 1 , wherein the instructions, when executed by the processor, cause the computing device to:
store, in the particular PCR upon determining that the particular PCR is assigned to the protected virtual application, a digest comprising identifying information of the virtual machine and a random number associated with the virtual machine.
5 . The non-transitory computer-readable medium of claim 4 , wherein the random number provides sequence for future logging events of the virtual machine.
6 . The non-transitory computer-readable medium of claim 4 , wherein the virtual machine decides to reveal the random number to an authorized remote party.
7 . The non-transitory computer-readable medium of claim 4 , wherein the digest is recorded in a Boot Log.
8 . The non-transitory computer-readable medium of claim 4 , wherein the digest is recorded in a Hypervisor Log.
9 . The non-transitory computer-readable medium of claim 1 , wherein the instructions, when executed by the processor, cause the computing device to:
redirect, upon intercepting the command, the command to physical memory residing outside the trusted platform module.
10 . The non-transitory computer-readable medium of claim 1 , wherein the instructions, when executed by the processor, cause the computing device to:
allow, in response to determining that the particular PCR is not assigned to the protected virtual application, the command to interact with the trusted platform module.
11 . The non-transitory computer-readable medium of claim 1 , wherein the trusted platform module is a hardware-based security module that provides cryptographic functions and storage of integrity measurements.
12 . The non-transitory computer-readable medium of claim 1 , wherein the computing device redirects, upon blocking the command, the command to a shadow page in memory separate from the TPM.
13 . The non-transitory computer-readable medium of claim 1 , wherein identifying the particular PCR comprises determining that the command includes a TPM2_PCR_Extend or TPM2_PCR_Event command targeting the particular PCR.
14 . The non-transitory computer-readable medium of claim 1 , wherein the computing device comprises a hypervisor.
15 . The non-transitory computer-readable medium of claim 14 , wherein the hypervisor is to intercept the command when directed to the particular PCR.
16 . The non-transitory computer-readable medium of claim 14 , wherein the hypervisor is to block the command from reaching the particular PCR.
17 . The non-transitory computer-readable medium of claim 16 , wherein the hypervisor is to block the command in response to determining that the particular PCR is one of a subset of the platform configuration registers (PCRs) designated as protected.
18 . The non-transitory computer-readable medium of claim 14 , wherein the hypervisor is to associate the particular PCR with the protected virtual application.
19 . The non-transitory computer-readable medium of claim 14 , wherein the hypervisor is to identify the particular PCR.
20 . The non-transitory computer-readable medium of claim 14 , wherein the hypervisor is to assign the particular PCR to the protected virtual application.
21 . The non-transitory computer-readable medium of claim 14 , wherein the hypervisor is to manage execution of the virtual machine.