diff options
Diffstat (limited to 'Documentation/security/tpm')
| -rw-r--r-- | Documentation/security/tpm/index.rst | 3 | ||||
| -rw-r--r-- | Documentation/security/tpm/tpm_event_log.rst | 55 | ||||
| -rw-r--r-- | Documentation/security/tpm/tpm_ftpm_tee.rst | 27 | ||||
| -rw-r--r-- | Documentation/security/tpm/xen-tpmfront.rst (renamed from Documentation/security/tpm/xen-tpmfront.txt) | 105 |
4 files changed, 143 insertions, 47 deletions
diff --git a/Documentation/security/tpm/index.rst b/Documentation/security/tpm/index.rst index af77a7bbb070..fc40e9f23c85 100644 --- a/Documentation/security/tpm/index.rst +++ b/Documentation/security/tpm/index.rst @@ -4,4 +4,7 @@ Trusted Platform Module documentation .. toctree:: + tpm_event_log tpm_vtpm_proxy + xen-tpmfront + tpm_ftpm_tee diff --git a/Documentation/security/tpm/tpm_event_log.rst b/Documentation/security/tpm/tpm_event_log.rst new file mode 100644 index 000000000000..f00f7a1d5e92 --- /dev/null +++ b/Documentation/security/tpm/tpm_event_log.rst @@ -0,0 +1,55 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +TPM Event Log +============= + +This document briefly describes what TPM log is and how it is handed +over from the preboot firmware to the operating system. + +Introduction +============ + +The preboot firmware maintains an event log that gets new entries every +time something gets hashed by it to any of the PCR registers. The events +are segregated by their type and contain the value of the hashed PCR +register. Typically, the preboot firmware will hash the components to +who execution is to be handed over or actions relevant to the boot +process. + +The main application for this is remote attestation and the reason why +it is useful is nicely put in the very first section of [1]: + +"Attestation is used to provide information about the platform’s state +to a challenger. However, PCR contents are difficult to interpret; +therefore, attestation is typically more useful when the PCR contents +are accompanied by a measurement log. While not trusted on their own, +the measurement log contains a richer set of information than do the PCR +contents. The PCR contents are used to provide the validation of the +measurement log." + +UEFI event log +============== + +UEFI provided event log has a few somewhat weird quirks. + +Before calling ExitBootServices() Linux EFI stub copies the event log to +a custom configuration table defined by the stub itself. Unfortunately, +the events generated by ExitBootServices() don't end up in the table. + +The firmware provides so called final events configuration table to sort +out this issue. Events gets mirrored to this table after the first time +EFI_TCG2_PROTOCOL.GetEventLog() gets called. + +This introduces another problem: nothing guarantees that it is not called +before the Linux EFI stub gets to run. Thus, it needs to calculate and save the +final events table size while the stub is still running to the custom +configuration table so that the TPM driver can later on skip these events when +concatenating two halves of the event log from the custom configuration table +and the final events table. + +References +========== + +- [1] https://trustedcomputinggroup.org/resource/pc-client-specific-platform-firmware-profile-specification/ +- [2] The final concatenation is done in drivers/char/tpm/eventlog/efi.c diff --git a/Documentation/security/tpm/tpm_ftpm_tee.rst b/Documentation/security/tpm/tpm_ftpm_tee.rst new file mode 100644 index 000000000000..8c2bae16e3d9 --- /dev/null +++ b/Documentation/security/tpm/tpm_ftpm_tee.rst @@ -0,0 +1,27 @@ +============================================= +Firmware TPM Driver +============================================= + +This document describes the firmware Trusted Platform Module (fTPM) +device driver. + +Introduction +============ + +This driver is a shim for firmware implemented in ARM's TrustZone +environment. The driver allows programs to interact with the TPM in the same +way they would interact with a hardware TPM. + +Design +====== + +The driver acts as a thin layer that passes commands to and from a TPM +implemented in firmware. The driver itself doesn't contain much logic and is +used more like a dumb pipe between firmware and kernel/userspace. + +The firmware itself is based on the following paper: +https://www.microsoft.com/en-us/research/wp-content/uploads/2017/06/ftpm1.pdf + +When the driver is loaded it will expose ``/dev/tpmX`` character devices to +userspace which will enable userspace to communicate with the firmware TPM +through this device. diff --git a/Documentation/security/tpm/xen-tpmfront.txt b/Documentation/security/tpm/xen-tpmfront.rst index 69346de87ff3..00d5b1db227d 100644 --- a/Documentation/security/tpm/xen-tpmfront.txt +++ b/Documentation/security/tpm/xen-tpmfront.rst @@ -1,4 +1,6 @@ +============================= Virtual TPM interface for Xen +============================= Authors: Matthew Fioravante (JHUAPL), Daniel De Graaf (NSA) @@ -6,7 +8,8 @@ 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 +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 @@ -24,81 +27,89 @@ This mini-os vTPM subsystem was built on top of the previous vTPM work done by IBM and Intel corporation. -DESIGN OVERVIEW +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 +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 +* 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 +* 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 +* 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 +* 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 +* 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) +* 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. +* Hardware TPM: + The physical TPM that is soldered onto the motherboard. -INTEGRATION WITH XEN +Integration With Xen -------------------- Support for the vTPM driver was added in Xen using the libxl toolstack in Xen |