drivers/tpm: add xen tpmfront interface
This is a complete rewrite of the Xen TPM frontend driver, taking advantage of a simplified frontend/backend interface and adding support for cancellation and timeouts. The backend for this driver is provided by a vTPM stub domain using the interface in Xen 4.3. Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov> Acked-by: Matthew Fioravante <matthew.fioravante@jhuapl.edu> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Acked-by: Peter Huewe <peterhuewe@gmx.de> Reviewed-by: Peter Huewe <peterhuewe@gmx.de> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Daniel De Graaf
Konrad Rzeszutek Wilk
parent
6efa20e49b
commit
e2683957fb
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@ -0,0 +1,113 @@
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Virtual TPM interface for Xen
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Authors: Matthew Fioravante (JHUAPL), Daniel De Graaf (NSA)
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This document describes the virtual Trusted Platform Module (vTPM) subsystem for
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Xen. The reader is assumed to have familiarity with building and installing Xen,
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Linux, and a basic understanding of the TPM and vTPM concepts.
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INTRODUCTION
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The goal of this work is to provide a TPM functionality to a virtual guest
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operating system (in Xen terms, a DomU). This allows programs to interact with
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a TPM in a virtual system the same way they interact with a TPM on the physical
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system. Each guest gets its own unique, emulated, software TPM. However, each
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of the vTPM's secrets (Keys, NVRAM, etc) are managed by a vTPM Manager domain,
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which seals the secrets to the Physical TPM. If the process of creating each of
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these domains (manager, vTPM, and guest) is trusted, the vTPM subsystem extends
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the chain of trust rooted in the hardware TPM to virtual machines in Xen. Each
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major component of vTPM is implemented as a separate domain, providing secure
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separation guaranteed by the hypervisor. The vTPM domains are implemented in
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mini-os to reduce memory and processor overhead.
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This mini-os vTPM subsystem was built on top of the previous vTPM work done by
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IBM and Intel corporation.
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DESIGN OVERVIEW
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---------------
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The architecture of vTPM is described below:
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+------------------+
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| Linux DomU | ...
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| | ^ |
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| v | |
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| xen-tpmfront |
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+------------------+
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| ^
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v |
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+------------------+
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| mini-os/tpmback |
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| | ^ |
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| v | |
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| vtpm-stubdom | ...
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| | ^ |
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| v | |
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| mini-os/tpmfront |
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+------------------+
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| ^
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v |
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+------------------+
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| mini-os/tpmback |
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| | ^ |
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| v | |
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| vtpmmgr-stubdom |
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| | ^ |
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| v | |
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| mini-os/tpm_tis |
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+------------------+
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| ^
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v |
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+------------------+
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| Hardware TPM |
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+------------------+
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* Linux DomU: The Linux based guest that wants to use a vTPM. There may be
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more than one of these.
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* xen-tpmfront.ko: Linux kernel virtual TPM frontend driver. This driver
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provides vTPM access to a Linux-based DomU.
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* mini-os/tpmback: Mini-os TPM backend driver. The Linux frontend driver
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connects to this backend driver to facilitate communications
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between the Linux DomU and its vTPM. This driver is also
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used by vtpmmgr-stubdom to communicate with vtpm-stubdom.
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* vtpm-stubdom: A mini-os stub domain that implements a vTPM. There is a
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one to one mapping between running vtpm-stubdom instances and
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logical vtpms on the system. The vTPM Platform Configuration
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Registers (PCRs) are normally all initialized to zero.
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* mini-os/tpmfront: Mini-os TPM frontend driver. The vTPM mini-os domain
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vtpm-stubdom uses this driver to communicate with
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vtpmmgr-stubdom. This driver is also used in mini-os
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domains such as pv-grub that talk to the vTPM domain.
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* vtpmmgr-stubdom: A mini-os domain that implements the vTPM manager. There is
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only one vTPM manager and it should be running during the
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entire lifetime of the machine. This domain regulates
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access to the physical TPM on the system and secures the
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persistent state of each vTPM.
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* mini-os/tpm_tis: Mini-os TPM version 1.2 TPM Interface Specification (TIS)
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driver. This driver used by vtpmmgr-stubdom to talk directly to
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the hardware TPM. Communication is facilitated by mapping
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hardware memory pages into vtpmmgr-stubdom.
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* Hardware TPM: The physical TPM that is soldered onto the motherboard.
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INTEGRATION WITH XEN
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--------------------
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Support for the vTPM driver was added in Xen using the libxl toolstack in Xen
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4.3. See the Xen documentation (docs/misc/vtpm.txt) for details on setting up
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the vTPM and vTPM Manager stub domains. Once the stub domains are running, a
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vTPM device is set up in the same manner as a disk or network device in the
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domain's configuration file.
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In order to use features such as IMA that require a TPM to be loaded prior to
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the initrd, the xen-tpmfront driver must be compiled in to the kernel. If not
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using such features, the driver can be compiled as a module and will be loaded
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as usual.
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@ -91,4 +91,15 @@ config TCG_ST33_I2C
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To compile this driver as a module, choose M here; the module will be
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called tpm_stm_st33_i2c.
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config TCG_XEN
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tristate "XEN TPM Interface"
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depends on TCG_TPM && XEN
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---help---
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If you want to make TPM support available to a Xen user domain,
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say Yes and it will be accessible from within Linux. See
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the manpages for xl, xl.conf, and docs/misc/vtpm.txt in
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the Xen source repository for more details.
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To compile this driver as a module, choose M here; the module
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will be called xen-tpmfront.
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endif # TCG_TPM
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@ -18,3 +18,4 @@ obj-$(CONFIG_TCG_ATMEL) += tpm_atmel.o
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obj-$(CONFIG_TCG_INFINEON) += tpm_infineon.o
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obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
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obj-$(CONFIG_TCG_ST33_I2C) += tpm_i2c_stm_st33.o
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obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
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@ -0,0 +1,473 @@
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/*
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* Implementation of the Xen vTPM device frontend
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*
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* Author: Daniel De Graaf <dgdegra@tycho.nsa.gov>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2,
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* as published by the Free Software Foundation.
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*/
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#include <linux/errno.h>
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#include <linux/err.h>
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#include <linux/interrupt.h>
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#include <xen/events.h>
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#include <xen/interface/io/tpmif.h>
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#include <xen/grant_table.h>
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#include <xen/xenbus.h>
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#include <xen/page.h>
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#include "tpm.h"
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struct tpm_private {
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struct tpm_chip *chip;
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struct xenbus_device *dev;
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struct vtpm_shared_page *shr;
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unsigned int evtchn;
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int ring_ref;
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domid_t backend_id;
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};
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enum status_bits {
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VTPM_STATUS_RUNNING = 0x1,
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VTPM_STATUS_IDLE = 0x2,
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VTPM_STATUS_RESULT = 0x4,
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VTPM_STATUS_CANCELED = 0x8,
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};
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static u8 vtpm_status(struct tpm_chip *chip)
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{
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struct tpm_private *priv = TPM_VPRIV(chip);
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switch (priv->shr->state) {
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case VTPM_STATE_IDLE:
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return VTPM_STATUS_IDLE | VTPM_STATUS_CANCELED;
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case VTPM_STATE_FINISH:
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return VTPM_STATUS_IDLE | VTPM_STATUS_RESULT;
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case VTPM_STATE_SUBMIT:
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case VTPM_STATE_CANCEL: /* cancel requested, not yet canceled */
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return VTPM_STATUS_RUNNING;
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default:
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return 0;
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}
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}
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static bool vtpm_req_canceled(struct tpm_chip *chip, u8 status)
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{
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return status & VTPM_STATUS_CANCELED;
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}
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static void vtpm_cancel(struct tpm_chip *chip)
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{
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struct tpm_private *priv = TPM_VPRIV(chip);
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priv->shr->state = VTPM_STATE_CANCEL;
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wmb();
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notify_remote_via_evtchn(priv->evtchn);
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}
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static unsigned int shr_data_offset(struct vtpm_shared_page *shr)
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{
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return sizeof(*shr) + sizeof(u32) * shr->nr_extra_pages;
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}
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static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
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{
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struct tpm_private *priv = TPM_VPRIV(chip);
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struct vtpm_shared_page *shr = priv->shr;
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unsigned int offset = shr_data_offset(shr);
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u32 ordinal;
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unsigned long duration;
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if (offset > PAGE_SIZE)
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return -EINVAL;
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if (offset + count > PAGE_SIZE)
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return -EINVAL;
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/* Wait for completion of any existing command or cancellation */
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if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, chip->vendor.timeout_c,
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&chip->vendor.read_queue, true) < 0) {
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vtpm_cancel(chip);
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return -ETIME;
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}
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memcpy(offset + (u8 *)shr, buf, count);
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shr->length = count;
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barrier();
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shr->state = VTPM_STATE_SUBMIT;
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wmb();
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notify_remote_via_evtchn(priv->evtchn);
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ordinal = be32_to_cpu(((struct tpm_input_header*)buf)->ordinal);
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duration = tpm_calc_ordinal_duration(chip, ordinal);
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if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, duration,
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&chip->vendor.read_queue, true) < 0) {
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/* got a signal or timeout, try to cancel */
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vtpm_cancel(chip);
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return -ETIME;
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}
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return count;
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}
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static int vtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
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{
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struct tpm_private *priv = TPM_VPRIV(chip);
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struct vtpm_shared_page *shr = priv->shr;
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unsigned int offset = shr_data_offset(shr);
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size_t length = shr->length;
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if (shr->state == VTPM_STATE_IDLE)
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return -ECANCELED;
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/* In theory the wait at the end of _send makes this one unnecessary */
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if (wait_for_tpm_stat(chip, VTPM_STATUS_RESULT, chip->vendor.timeout_c,
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&chip->vendor.read_queue, true) < 0) {
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vtpm_cancel(chip);
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return -ETIME;
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}
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if (offset > PAGE_SIZE)
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return -EIO;
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if (offset + length > PAGE_SIZE)
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length = PAGE_SIZE - offset;
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if (length > count)
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length = count;
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memcpy(buf, offset + (u8 *)shr, length);
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return length;
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}
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ssize_t tpm_show_locality(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct tpm_chip *chip = dev_get_drvdata(dev);
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struct tpm_private *priv = TPM_VPRIV(chip);
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u8 locality = priv->shr->locality;
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return sprintf(buf, "%d\n", locality);
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}
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ssize_t tpm_store_locality(struct device *dev, struct device_attribute *attr,
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const char *buf, size_t len)
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{
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struct tpm_chip *chip = dev_get_drvdata(dev);
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struct tpm_private *priv = TPM_VPRIV(chip);
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u8 val;
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int rv = kstrtou8(buf, 0, &val);
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if (rv)
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return rv;
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priv->shr->locality = val;
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return len;
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}
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static const struct file_operations vtpm_ops = {
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.owner = THIS_MODULE,
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.llseek = no_llseek,
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.open = tpm_open,
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.read = tpm_read,
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.write = tpm_write,
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.release = tpm_release,
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};
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static DEVICE_ATTR(pubek, S_IRUGO, tpm_show_pubek, NULL);
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static DEVICE_ATTR(pcrs, S_IRUGO, tpm_show_pcrs, NULL);
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static DEVICE_ATTR(enabled, S_IRUGO, tpm_show_enabled, NULL);
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static DEVICE_ATTR(active, S_IRUGO, tpm_show_active, NULL);
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static DEVICE_ATTR(owned, S_IRUGO, tpm_show_owned, NULL);
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static DEVICE_ATTR(temp_deactivated, S_IRUGO, tpm_show_temp_deactivated,
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NULL);
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static DEVICE_ATTR(caps, S_IRUGO, tpm_show_caps, NULL);
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static DEVICE_ATTR(cancel, S_IWUSR | S_IWGRP, NULL, tpm_store_cancel);
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static DEVICE_ATTR(durations, S_IRUGO, tpm_show_durations, NULL);
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static DEVICE_ATTR(timeouts, S_IRUGO, tpm_show_timeouts, NULL);
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static DEVICE_ATTR(locality, S_IRUGO | S_IWUSR, tpm_show_locality,
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tpm_store_locality);
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static struct attribute *vtpm_attrs[] = {
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&dev_attr_pubek.attr,
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&dev_attr_pcrs.attr,
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&dev_attr_enabled.attr,
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&dev_attr_active.attr,
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&dev_attr_owned.attr,
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&dev_attr_temp_deactivated.attr,
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&dev_attr_caps.attr,
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&dev_attr_cancel.attr,
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&dev_attr_durations.attr,
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&dev_attr_timeouts.attr,
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&dev_attr_locality.attr,
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NULL,
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};
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static struct attribute_group vtpm_attr_grp = {
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.attrs = vtpm_attrs,
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};
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#define TPM_LONG_TIMEOUT (10 * 60 * HZ)
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static const struct tpm_vendor_specific tpm_vtpm = {
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.status = vtpm_status,
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.recv = vtpm_recv,
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.send = vtpm_send,
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.cancel = vtpm_cancel,
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.req_complete_mask = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
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.req_complete_val = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
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.req_canceled = vtpm_req_canceled,
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.attr_group = &vtpm_attr_grp,
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.miscdev = {
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.fops = &vtpm_ops,
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},
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.duration = {
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TPM_LONG_TIMEOUT,
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TPM_LONG_TIMEOUT,
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TPM_LONG_TIMEOUT,
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},
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};
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static irqreturn_t tpmif_interrupt(int dummy, void *dev_id)
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{
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struct tpm_private *priv = dev_id;
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switch (priv->shr->state) {
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case VTPM_STATE_IDLE:
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case VTPM_STATE_FINISH:
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wake_up_interruptible(&priv->chip->vendor.read_queue);
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break;
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case VTPM_STATE_SUBMIT:
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case VTPM_STATE_CANCEL:
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default:
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break;
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}
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return IRQ_HANDLED;
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}
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static int setup_chip(struct device *dev, struct tpm_private *priv)
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{
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struct tpm_chip *chip;
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chip = tpm_register_hardware(dev, &tpm_vtpm);
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if (!chip)
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return -ENODEV;
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init_waitqueue_head(&chip->vendor.read_queue);
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priv->chip = chip;
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TPM_VPRIV(chip) = priv;
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return 0;
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}
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/* caller must clean up in case of errors */
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static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv)
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{
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struct xenbus_transaction xbt;
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const char *message = NULL;
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int rv;
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priv->shr = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
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if (!priv->shr) {
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xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
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return -ENOMEM;
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}
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rv = xenbus_grant_ring(dev, virt_to_mfn(priv->shr));
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if (rv < 0)
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return rv;
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priv->ring_ref = rv;
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rv = xenbus_alloc_evtchn(dev, &priv->evtchn);
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if (rv)
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return rv;
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rv = bind_evtchn_to_irqhandler(priv->evtchn, tpmif_interrupt, 0,
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"tpmif", priv);
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if (rv <= 0) {
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xenbus_dev_fatal(dev, rv, "allocating TPM irq");
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return rv;
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}
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priv->chip->vendor.irq = rv;
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again:
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rv = xenbus_transaction_start(&xbt);
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if (rv) {
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xenbus_dev_fatal(dev, rv, "starting transaction");
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return rv;
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}
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rv = xenbus_printf(xbt, dev->nodename,
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"ring-ref", "%u", priv->ring_ref);
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if (rv) {
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message = "writing ring-ref";
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goto abort_transaction;
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}
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rv = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
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priv->evtchn);
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if (rv) {
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message = "writing event-channel";
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||||
goto abort_transaction;
|
||||
}
|
||||
|
||||
rv = xenbus_printf(xbt, dev->nodename, "feature-protocol-v2", "1");
|
||||
if (rv) {
|
||||
message = "writing feature-protocol-v2";
|
||||
goto abort_transaction;
|
||||
}
|
||||
|
||||
rv = xenbus_transaction_end(xbt, 0);
|
||||
if (rv == -EAGAIN)
|
||||
goto again;
|
||||
if (rv) {
|
||||
xenbus_dev_fatal(dev, rv, "completing transaction");
|
||||
return rv;
|
||||
}
|
||||
|
||||
xenbus_switch_state(dev, XenbusStateInitialised);
|
||||
|
||||
return 0;
|
||||
|
||||
abort_transaction:
|
||||
xenbus_transaction_end(xbt, 1);
|
||||
if (message)
|
||||
xenbus_dev_error(dev, rv, "%s", message);
|
||||
|
||||
return rv;
|
||||
}
|
||||
|
||||
static void ring_free(struct tpm_private *priv)
|
||||
{
|
||||
if (!priv)
|
||||
return;
|
||||
|
||||
if (priv->ring_ref)
|
||||
gnttab_end_foreign_access(priv->ring_ref, 0,
|
||||
(unsigned long)priv->shr);
|
||||
else
|
||||
free_page((unsigned long)priv->shr);
|
||||
|
||||
if (priv->chip && priv->chip->vendor.irq)
|
||||
unbind_from_irqhandler(priv->chip->vendor.irq, priv);
|
||||
|
||||
kfree(priv);
|
||||
}
|
||||
|
||||
static int tpmfront_probe(struct xenbus_device *dev,
|
||||
const struct xenbus_device_id *id)
|
||||
{
|
||||
struct tpm_private *priv;
|
||||
int rv;
|
||||
|
||||
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
|
||||
if (!priv) {
|
||||
xenbus_dev_fatal(dev, -ENOMEM, "allocating priv structure");
|
||||
return -ENOMEM;
|
||||
}
|
||||
|
||||
rv = setup_chip(&dev->dev, priv);
|
||||
if (rv) {
|
||||
kfree(priv);
|
||||
return rv;
|
||||
}
|
||||
|
||||
rv = setup_ring(dev, priv);
|
||||
if (rv) {
|
||||
tpm_remove_hardware(&dev->dev);
|
||||
ring_free(priv);
|
||||
return rv;
|
||||
}
|
||||
|
||||
tpm_get_timeouts(priv->chip);
|
||||
|
||||
dev_set_drvdata(&dev->dev, priv->chip);
|
||||
|
||||
return rv;
|
||||
}
|
||||
|
||||
static int tpmfront_remove(struct xenbus_device *dev)
|
||||
{
|
||||
struct tpm_chip *chip = dev_get_drvdata(&dev->dev);
|
||||
struct tpm_private *priv = TPM_VPRIV(chip);
|
||||
tpm_remove_hardware(&dev->dev);
|
||||
ring_free(priv);
|
||||
TPM_VPRIV(chip) = NULL;
|
||||
return 0;
|
||||
}
|
||||
|
||||
static int tpmfront_resume(struct xenbus_device *dev)
|
||||
{
|
||||
/* A suspend/resume/migrate will interrupt a vTPM anyway */
|
||||
tpmfront_remove(dev);
|
||||
return tpmfront_probe(dev, NULL);
|
||||
}
|
||||
|
||||
static void backend_changed(struct xenbus_device *dev,
|
||||
enum xenbus_state backend_state)
|
||||
{
|
||||
int val;
|
||||
|
||||
switch (backend_state) {
|
||||
case XenbusStateInitialised:
|
||||
case XenbusStateConnected:
|
||||
if (dev->state == XenbusStateConnected)
|
||||
break;
|
||||
|
||||
if (xenbus_scanf(XBT_NIL, dev->otherend,
|
||||
"feature-protocol-v2", "%d", &val) < 0)
|
||||
val = 0;
|
||||
if (!val) {
|
||||
xenbus_dev_fatal(dev, -EINVAL,
|
||||
"vTPM protocol 2 required");
|
||||
return;
|
||||
}
|
||||
xenbus_switch_state(dev, XenbusStateConnected);
|
||||
break;
|
||||
|
||||
case XenbusStateClosing:
|
||||
case XenbusStateClosed:
|
||||
device_unregister(&dev->dev);
|
||||
xenbus_frontend_closed(dev);
|
||||
break;
|
||||
default:
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
static const struct xenbus_device_id tpmfront_ids[] = {
|
||||
{ "vtpm" },
|
||||
{ "" }
|
||||
};
|
||||
MODULE_ALIAS("xen:vtpm");
|
||||
|
||||
static DEFINE_XENBUS_DRIVER(tpmfront, ,
|
||||
.probe = tpmfront_probe,
|
||||
.remove = tpmfront_remove,
|
||||
.resume = tpmfront_resume,
|
||||
.otherend_changed = backend_changed,
|
||||
);
|
||||
|
||||
static int __init xen_tpmfront_init(void)
|
||||
{
|
||||
if (!xen_domain())
|
||||
return -ENODEV;
|
||||
|
||||
return xenbus_register_frontend(&tpmfront_driver);
|
||||
}
|
||||
module_init(xen_tpmfront_init);
|
||||
|
||||
static void __exit xen_tpmfront_exit(void)
|
||||
{
|
||||
xenbus_unregister_driver(&tpmfront_driver);
|
||||
}
|
||||
module_exit(xen_tpmfront_exit);
|
||||
|
||||
MODULE_AUTHOR("Daniel De Graaf <dgdegra@tycho.nsa.gov>");
|
||||
MODULE_DESCRIPTION("Xen vTPM Driver");
|
||||
MODULE_LICENSE("GPL");
|
||||
|
|
@ -0,0 +1,52 @@
|
|||
/******************************************************************************
|
||||
* tpmif.h
|
||||
*
|
||||
* TPM I/O interface for Xen guest OSes, v2
|
||||
*
|
||||
* This file is in the public domain.
|
||||
*
|
||||
*/
|
||||
|
||||
#ifndef __XEN_PUBLIC_IO_TPMIF_H__
|
||||
#define __XEN_PUBLIC_IO_TPMIF_H__
|
||||
|
||||
/*
|
||||
* Xenbus state machine
|
||||
*
|
||||
* Device open:
|
||||
* 1. Both ends start in XenbusStateInitialising
|
||||
* 2. Backend transitions to InitWait (frontend does not wait on this step)
|
||||
* 3. Frontend populates ring-ref, event-channel, feature-protocol-v2
|
||||
* 4. Frontend transitions to Initialised
|
||||
* 5. Backend maps grant and event channel, verifies feature-protocol-v2
|
||||
* 6. Backend transitions to Connected
|
||||
* 7. Frontend verifies feature-protocol-v2, transitions to Connected
|
||||
*
|
||||
* Device close:
|
||||
* 1. State is changed to XenbusStateClosing
|
||||
* 2. Frontend transitions to Closed
|
||||
* 3. Backend unmaps grant and event, changes state to InitWait
|
||||
*/
|
||||
|
||||
enum vtpm_shared_page_state {
|
||||
VTPM_STATE_IDLE, /* no contents / vTPM idle / cancel complete */
|
||||
VTPM_STATE_SUBMIT, /* request ready / vTPM working */
|
||||
VTPM_STATE_FINISH, /* response ready / vTPM idle */
|
||||
VTPM_STATE_CANCEL, /* cancel requested / vTPM working */
|
||||
};
|
||||
/* The backend should only change state to IDLE or FINISH, while the
|
||||
* frontend should only change to SUBMIT or CANCEL. */
|
||||
|
||||
|
||||
struct vtpm_shared_page {
|
||||
uint32_t length; /* request/response length in bytes */
|
||||
|
||||
uint8_t state; /* enum vtpm_shared_page_state */
|
||||
uint8_t locality; /* for the current request */
|
||||
uint8_t pad;
|
||||
|
||||
uint8_t nr_extra_pages; /* extra pages for long packets; may be zero */
|
||||
uint32_t extra_pages[0]; /* grant IDs; length in nr_extra_pages */
|
||||
};
|
||||
|
||||
#endif
|
||||
Loading…
Reference in New Issue