diff options
| -rw-r--r-- | Documentation/tpm/xen-tpmfront.txt | 113 | ||||
| -rw-r--r-- | drivers/char/tpm/Kconfig | 11 | ||||
| -rw-r--r-- | drivers/char/tpm/Makefile | 1 | ||||
| -rw-r--r-- | drivers/char/tpm/xen-tpmfront.c | 473 | ||||
| -rw-r--r-- | include/xen/interface/io/tpmif.h | 52 |
5 files changed, 650 insertions, 0 deletions
diff --git a/Documentation/tpm/xen-tpmfront.txt b/Documentation/tpm/xen-tpmfront.txt new file mode 100644 index 0000000..69346de --- /dev/null +++ b/Documentation/tpm/xen-tpmfront.txt @@ -0,0 +1,113 @@ +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. diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig index dbfd564..205ed35 100644 --- a/drivers/char/tpm/Kconfig +++ b/drivers/char/tpm/Kconfig @@ -91,4 +91,15 @@ config TCG_ST33_I2C To compile this driver as a module, choose M here; the module will be called tpm_stm_st33_i2c. +config TCG_XEN + tristate "XEN TPM Interface" + depends on TCG_TPM && XEN + ---help--- + If you want to make TPM support available to a Xen user domain, + say Yes and it will be accessible from within Linux. See + the manpages for xl, xl.conf, and docs/misc/vtpm.txt in + the Xen source repository for more details. + To compile this driver as a module, choose M here; the module + will be called xen-tpmfront. + endif # TCG_TPM diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile index a3736c9..eb41ff9 100644 --- a/drivers/char/tpm/Makefile +++ b/drivers/char/tpm/Makefile @@ -18,3 +18,4 @@ obj-$(CONFIG_TCG_ATMEL) += tpm_atmel.o obj-$(CONFIG_TCG_INFINEON) += tpm_infineon.o obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o obj-$(CONFIG_TCG_ST33_I2C) += tpm_i2c_stm_st33.o +obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c new file mode 100644 index 0000000..7a7929b --- /dev/null +++ b/drivers/char/tpm/xen-tpmfront.c @@ -0,0 +1,473 @@ +/* + * Implementation of the Xen vTPM device frontend + * + * Author: Daniel De Graaf <dgdegra@tycho.nsa.gov> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2, + * as published by the Free Software Foundation. + */ +#include <linux/errno.h> +#include <linux/err.h> +#include <linux/interrupt.h> +#include <xen/events.h> +#include <xen/interface/io/tpmif.h> +#include <xen/grant_table.h> +#include <xen/xenbus.h> +#include <xen/page.h> +#include "tpm.h" + +struct tpm_private { + struct tpm_chip *chip; + struct xenbus_device *dev; + + struct vtpm_shared_page *shr; + + unsigned int evtchn; + int ring_ref; + domid_t backend_id; +}; + +enum status_bits { + VTPM_STATUS_RUNNING = 0x1, + VTPM_STATUS_IDLE = 0x2, + VTPM_STATUS_RESULT = 0x4, + VTPM_STATUS_CANCELED = 0x8, +}; + +static u8 vtpm_status(struct tpm_chip *chip) +{ + struct tpm_private *priv = TPM_VPRIV(chip); + switch (priv->shr->state) { + case VTPM_STATE_IDLE: + return VTPM_STATUS_IDLE | VTPM_STATUS_CANCELED; + case VTPM_STATE_FINISH: + return VTPM_STATUS_IDLE | VTPM_STATUS_RESULT; + case VTPM_STATE_SUBMIT: + case VTPM_STATE_CANCEL: /* cancel requested, not yet canceled */ + return VTPM_STATUS_RUNNING; + default: + return 0; + } +} + +static bool vtpm_req_canceled(struct tpm_chip *chip, u8 status) +{ + return status & VTPM_STATUS_CANCELED; +} + +static void vtpm_cancel(struct tpm_chip *chip) +{ + struct tpm_private *priv = TPM_VPRIV(chip); + priv->shr->state = VTPM_STATE_CANCEL; + wmb(); + notify_remote_via_evtchn(priv->evtchn); +} + +static unsigned int shr_data_offset(struct vtpm_shared_page *shr) +{ + return sizeof(*shr) + sizeof(u32) * shr->nr_extra_pages; +} + +static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count) +{ + struct tpm_private *priv = TPM_VPRIV(chip); + struct vtpm_shared_page *shr = priv->shr; + unsigned int offset = shr_data_offset(shr); + + u32 ordinal; + unsigned long duration; + + if (offset > PAGE_SIZE) + return -EINVAL; + + if (offset + count > PAGE_SIZE) + return -EINVAL; + + /* Wait for completion of any existing command or cancellation */ + if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, chip->vendor.timeout_c, + &chip->vendor.read_queue, true) < 0) { + vtpm_cancel(chip); + return -ETIME; + } + + memcpy(offset + (u8 *)shr, buf, count); + shr->length = count; + barrier(); + shr->state = VTPM_STATE_SUBMIT; + wmb(); + notify_remote_via_evtchn(priv->evtchn); + + ordinal = be32_to_cpu(((struct tpm_input_header*)buf)->ordinal); + duration = tpm_calc_ordinal_duration(chip, ordinal); + + if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, duration, + &chip->vendor.read_queue, true) < 0) { + /* got a signal or timeout, try to cancel */ + vtpm_cancel(chip); + return -ETIME; + } + + return count; +} + +static int vtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count) +{ + struct tpm_private *priv = TPM_VPRIV(chip); + struct vtpm_shared_page *shr = priv->shr; + unsigned int offset = shr_data_offset(shr); + size_t length = shr->length; + + if (shr->state == VTPM_STATE_IDLE) + return -ECANCELED; + + /* In theory the wait at the end of _send makes this one unnecessary */ + if (wait_for_tpm_stat(chip, VTPM_STATUS_RESULT, chip->vendor.timeout_c, + &chip->vendor.read_queue, true) < 0) { + vtpm_cancel(chip); + return -ETIME; + } + + if (offset > PAGE_SIZE) + return -EIO; + + if (offset + length > PAGE_SIZE) + length = PAGE_SIZE - offset; + + if (length > count) + length = count; + + memcpy(buf, offset + (u8 *)shr, length); + + return length; +} + +ssize_t tpm_show_locality(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct tpm_chip *chip = dev_get_drvdata(dev); + struct tpm_private *priv = TPM_VPRIV(chip); + u8 locality = priv->shr->locality; + + return sprintf(buf, "%d\n", locality); +} + +ssize_t tpm_store_locality(struct device *dev, struct device_attribute *attr, + const char *buf, size_t len) +{ + struct tpm_chip *chip = dev_get_drvdata(dev); + struct tpm_private *priv = TPM_VPRIV(chip); + u8 val; + + int rv = kstrtou8(buf, 0, &val); + if (rv) + return rv; + + priv->shr->locality = val; + + return len; +} + +static const struct file_operations vtpm_ops = { + .owner = THIS_MODULE, + .llseek = no_llseek, + .open = tpm_open, + .read = tpm_read, + .write = tpm_write, + .release = tpm_release, +}; + +static DEVICE_ATTR(pubek, S_IRUGO, tpm_show_pubek, NULL); +static DEVICE_ATTR(pcrs, S_IRUGO, tpm_show_pcrs, NULL); +static DEVICE_ATTR(enabled, S_IRUGO, tpm_show_enabled, NULL); +static DEVICE_ATTR(active, S_IRUGO, tpm_show_active, NULL); +static DEVICE_ATTR(owned, S_IRUGO, tpm_show_owned, NULL); +static DEVICE_ATTR(temp_deactivated, S_IRUGO, tpm_show_temp_deactivated, + NULL); +static DEVICE_ATTR(caps, S_IRUGO, tpm_show_caps, NULL); +static DEVICE_ATTR(cancel, S_IWUSR | S_IWGRP, NULL, tpm_store_cancel); +static DEVICE_ATTR(durations, S_IRUGO, tpm_show_durations, NULL); +static DEVICE_ATTR(timeouts, S_IRUGO, tpm_show_timeouts, NULL); +static DEVICE_ATTR(locality, S_IRUGO | S_IWUSR, tpm_show_locality, + tpm_store_locality); + +static struct attribute *vtpm_attrs[] = { + &dev_attr_pubek.attr, + &dev_attr_pcrs.attr, + &dev_attr_enabled.attr, + &dev_attr_active.attr, + &dev_attr_owned.attr, + &dev_attr_temp_deactivated.attr, + &dev_attr_caps.attr, + &dev_attr_cancel.attr, + &dev_attr_durations.attr, + &dev_attr_timeouts.attr, + &dev_attr_locality.attr, + NULL, +}; + +static struct attribute_group vtpm_attr_grp = { + .attrs = vtpm_attrs, +}; + +#define TPM_LONG_TIMEOUT (10 * 60 * HZ) + +static const struct tpm_vendor_specific tpm_vtpm = { + .status = vtpm_status, + .recv = vtpm_recv, + .send = vtpm_send, + .cancel = vtpm_cancel, + .req_complete_mask = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT, + .req_complete_val = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT, + .req_canceled = vtpm_req_canceled, + .attr_group = &vtpm_attr_grp, + .miscdev = { + .fops = &vtpm_ops, + }, + .duration = { + TPM_LONG_TIMEOUT, + TPM_LONG_TIMEOUT, + TPM_LONG_TIMEOUT, + }, +}; + +static irqreturn_t tpmif_interrupt(int dummy, void *dev_id) +{ + struct tpm_private *priv = dev_id; + + switch (priv->shr->state) { + case VTPM_STATE_IDLE: + case VTPM_STATE_FINISH: + wake_up_interruptible(&priv->chip->vendor.read_queue); + break; + case VTPM_STATE_SUBMIT: + case VTPM_STATE_CANCEL: + default: + break; + } + return IRQ_HANDLED; +} + +static int setup_chip(struct device *dev, struct tpm_private *priv) +{ + struct tpm_chip *chip; + + chip = tpm_register_hardware(dev, &tpm_vtpm); + if (!chip) + return -ENODEV; + + init_waitqueue_head(&chip->vendor.read_queue); + + priv->chip = chip; + TPM_VPRIV(chip) = priv; + + return 0; +} + +/* caller must clean up in case of errors */ +static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv) +{ + struct xenbus_transaction xbt; + const char *message = NULL; + int rv; + + priv->shr = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO); + if (!priv->shr) { + xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring"); + return -ENOMEM; + } + + rv = xenbus_grant_ring(dev, virt_to_mfn(priv->shr)); + if (rv < 0) + return rv; + + priv->ring_ref = rv; + + rv = xenbus_alloc_evtchn(dev, &priv->evtchn); + if (rv) + return rv; + + rv = bind_evtchn_to_irqhandler(priv->evtchn, tpmif_interrupt, 0, + "tpmif", priv); + if (rv <= 0) { + xenbus_dev_fatal(dev, rv, "allocating TPM irq"); + return rv; + } + priv->chip->vendor.irq = rv; + + again: + rv = xenbus_transaction_start(&xbt); + if (rv) { + xenbus_dev_fatal(dev, rv, "starting transaction"); + return rv; + } + + rv = xenbus_printf(xbt, dev->nodename, + "ring-ref", "%u", priv->ring_ref); + if (rv) { + message = "writing ring-ref"; + goto abort_transaction; + } + + rv = xenbus_printf(xbt, dev->nodename, "event-channel", "%u", + priv->evtchn); + if (rv) { + message = "writing event-channel"; + 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"); diff --git a/include/xen/interface/io/tpmif.h b/include/xen/interface/io/tpmif.h new file mode 100644 index 0000000..28e7dcd --- /dev/null +++ b/include/xen/interface/io/tpmif.h @@ -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 |
