summaryrefslogtreecommitdiffstats
path: root/Documentation/security/tpm/xen-tpmfront.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/security/tpm/xen-tpmfront.rst')
-rw-r--r--Documentation/security/tpm/xen-tpmfront.rst124
1 files changed, 124 insertions, 0 deletions
diff --git a/Documentation/security/tpm/xen-tpmfront.rst b/Documentation/security/tpm/xen-tpmfront.rst
new file mode 100644
index 000000000..31c67522f
--- /dev/null
+++ b/Documentation/security/tpm/xen-tpmfront.rst
@@ -0,0 +1,124 @@
+=============================
+Virtual TPM interface for Xen
+=============================
+
+Authors: Matthew Fioravante (JHUAPL), Daniel De Graaf (NSA)
+
+This document describes the virtual Trusted Platform Module (vTPM) subsystem for
+Xen. The reader is assumed to have familiarity with building and installing Xen,
+Linux, and a basic understanding of the TPM and vTPM concepts.
+
+Introduction
+------------
+
+The goal of this work is to provide a TPM functionality to a virtual guest
+operating system (in Xen terms, a DomU). This allows programs to interact with
+a TPM in a virtual system the same way they interact with a TPM on the physical
+system. Each guest gets its own unique, emulated, software TPM. However, each
+of the vTPM's secrets (Keys, NVRAM, etc) are managed by a vTPM Manager domain,
+which seals the secrets to the Physical TPM. If the process of creating each of
+these domains (manager, vTPM, and guest) is trusted, the vTPM subsystem extends
+the chain of trust rooted in the hardware TPM to virtual machines in Xen. Each
+major component of vTPM is implemented as a separate domain, providing secure
+separation guaranteed by the hypervisor. The vTPM domains are implemented in
+mini-os to reduce memory and processor overhead.
+
+This mini-os vTPM subsystem was built on top of the previous vTPM work done by
+IBM and Intel corporation.
+
+
+Design Overview
+---------------
+
+The architecture of vTPM is described below::
+
+ +------------------+
+ | Linux DomU | ...
+ | | ^ |
+ | v | |
+ | xen-tpmfront |
+ +------------------+
+ | ^
+ v |
+ +------------------+
+ | mini-os/tpmback |
+ | | ^ |
+ | v | |
+ | vtpm-stubdom | ...
+ | | ^ |
+ | v | |
+ | mini-os/tpmfront |
+ +------------------+
+ | ^
+ v |
+ +------------------+
+ | mini-os/tpmback |
+ | | ^ |
+ | v | |
+ | vtpmmgr-stubdom |
+ | | ^ |
+ | v | |
+ | mini-os/tpm_tis |
+ +------------------+
+ | ^
+ v |
+ +------------------+
+ | Hardware TPM |
+ +------------------+
+
+* Linux DomU:
+ The Linux based guest that wants to use a vTPM. There may be
+ more than one of these.
+
+* xen-tpmfront.ko:
+ Linux kernel virtual TPM frontend driver. This driver
+ provides vTPM access to a Linux-based DomU.
+
+* mini-os/tpmback:
+ Mini-os TPM backend driver. The Linux frontend driver
+ connects to this backend driver to facilitate communications
+ between the Linux DomU and its vTPM. This driver is also
+ used by vtpmmgr-stubdom to communicate with vtpm-stubdom.
+
+* vtpm-stubdom:
+ A mini-os stub domain that implements a vTPM. There is a
+ one to one mapping between running vtpm-stubdom instances and
+ logical vtpms on the system. The vTPM Platform Configuration
+ Registers (PCRs) are normally all initialized to zero.
+
+* mini-os/tpmfront:
+ Mini-os TPM frontend driver. The vTPM mini-os domain
+ vtpm-stubdom uses this driver to communicate with
+ vtpmmgr-stubdom. This driver is also used in mini-os
+ domains such as pv-grub that talk to the vTPM domain.
+
+* vtpmmgr-stubdom:
+ A mini-os domain that implements the vTPM manager. There is
+ only one vTPM manager and it should be running during the
+ entire lifetime of the machine. This domain regulates
+ access to the physical TPM on the system and secures the
+ persistent state of each vTPM.
+
+* mini-os/tpm_tis:
+ Mini-os TPM version 1.2 TPM Interface Specification (TIS)
+ driver. This driver used by vtpmmgr-stubdom to talk directly to
+ the hardware TPM. Communication is facilitated by mapping
+ hardware memory pages into vtpmmgr-stubdom.
+
+* Hardware TPM:
+ The physical TPM that is soldered onto the motherboard.
+
+
+Integration With Xen
+--------------------
+
+Support for the vTPM driver was added in Xen using the libxl toolstack in Xen
+4.3. See the Xen documentation (docs/misc/vtpm.txt) for details on setting up
+the vTPM and vTPM Manager stub domains. Once the stub domains are running, a
+vTPM device is set up in the same manner as a disk or network device in the
+domain's configuration file.
+
+In order to use features such as IMA that require a TPM to be loaded prior to
+the initrd, the xen-tpmfront driver must be compiled in to the kernel. If not
+using such features, the driver can be compiled as a module and will be loaded
+as usual.