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Add TDX guest attestation infrastructure and driver

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Merge tag 'x86_tdx_for_6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 tdx updates from Dave Hansen:
 "This includes a single chunk of new functionality for TDX guests which
  allows them to talk to the trusted TDX module software and obtain an
  attestation report.

  This report can then be used to prove the trustworthiness of the guest
  to a third party and get access to things like storage encryption
  keys"

* tag 'x86_tdx_for_6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  selftests/tdx: Test TDX attestation GetReport support
  virt: Add TDX guest driver
  x86/tdx: Add a wrapper to get TDREPORT0 from the TDX Module
This commit is contained in:
Linus Torvalds 2022-12-12 14:27:49 -08:00
commit a89ef2aa55
15 changed files with 469 additions and 0 deletions
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52
Documentation/virt/coco/tdx-guest.rst Normal file
View file

@ -0,0 +1,52 @@
.. SPDX-License-Identifier: GPL-2.0
===================================================================
TDX Guest API Documentation
===================================================================
1. General description
======================
The TDX guest driver exposes IOCTL interfaces via the /dev/tdx-guest misc
device to allow userspace to get certain TDX guest-specific details.
2. API description
==================
In this section, for each supported IOCTL, the following information is
provided along with a generic description.
:Input parameters: Parameters passed to the IOCTL and related details.
:Output: Details about output data and return value (with details about
the non common error values).
2.1 TDX_CMD_GET_REPORT0
-----------------------
:Input parameters: struct tdx_report_req
:Output: Upon successful execution, TDREPORT data is copied to
tdx_report_req.tdreport and return 0. Return -EINVAL for invalid
operands, -EIO on TDCALL failure or standard error number on other
common failures.
The TDX_CMD_GET_REPORT0 IOCTL can be used by the attestation software to get
the TDREPORT0 (a.k.a. TDREPORT subtype 0) from the TDX module using
TDCALL[TDG.MR.REPORT].
A subtype index is added at the end of this IOCTL CMD to uniquely identify the
subtype-specific TDREPORT request. Although the subtype option is mentioned in
the TDX Module v1.0 specification, section titled "TDG.MR.REPORT", it is not
currently used, and it expects this value to be 0. So to keep the IOCTL
implementation simple, the subtype option was not included as part of the input
ABI. However, in the future, if the TDX Module supports more than one subtype,
a new IOCTL CMD will be created to handle it. To keep the IOCTL naming
consistent, a subtype index is added as part of the IOCTL CMD.
Reference
---------
TDX reference material is collected here:
https://www.intel.com/content/www/us/en/developer/articles/technical/intel-trust-domain-extensions.html
The driver is based on TDX module specification v1.0 and TDX GHCI specification v1.0.

1
Documentation/virt/index.rst
View file

@ -14,6 +14,7 @@ Linux Virtualization Support
ne_overview
acrn/index
coco/sev-guest
coco/tdx-guest
hyperv/index
.. only:: html and subproject

43
Documentation/x86/tdx.rst
View file

@ -210,6 +210,49 @@ converted to shared on boot.
For coherent DMA allocation, the DMA buffer gets converted on the
allocation. Check force_dma_unencrypted() for details.
Attestation
===========
Attestation is used to verify the TDX guest trustworthiness to other
entities before provisioning secrets to the guest. For example, a key
server may want to use attestation to verify that the guest is the
desired one before releasing the encryption keys to mount the encrypted
rootfs or a secondary drive.
The TDX module records the state of the TDX guest in various stages of
the guest boot process using the build time measurement register (MRTD)
and runtime measurement registers (RTMR). Measurements related to the
guest initial configuration and firmware image are recorded in the MRTD
register. Measurements related to initial state, kernel image, firmware
image, command line options, initrd, ACPI tables, etc are recorded in
RTMR registers. For more details, as an example, please refer to TDX
Virtual Firmware design specification, section titled "TD Measurement".
At TDX guest runtime, the attestation process is used to attest to these
measurements.
The attestation process consists of two steps: TDREPORT generation and
Quote generation.
TDX guest uses TDCALL[TDG.MR.REPORT] to get the TDREPORT (TDREPORT_STRUCT)
from the TDX module. TDREPORT is a fixed-size data structure generated by
the TDX module which contains guest-specific information (such as build
and boot measurements), platform security version, and the MAC to protect
the integrity of the TDREPORT. A user-provided 64-Byte REPORTDATA is used
as input and included in the TDREPORT. Typically it can be some nonce
provided by attestation service so the TDREPORT can be verified uniquely.
More details about the TDREPORT can be found in Intel TDX Module
specification, section titled "TDG.MR.REPORT Leaf".
After getting the TDREPORT, the second step of the attestation process
is to send it to the Quoting Enclave (QE) to generate the Quote. TDREPORT
by design can only be verified on the local platform as the MAC key is
bound to the platform. To support remote verification of the TDREPORT,
TDX leverages Intel SGX Quoting Enclave to verify the TDREPORT locally
and convert it to a remotely verifiable Quote. Method of sending TDREPORT
to QE is implementation specific. Attestation software can choose
whatever communication channel available (i.e. vsock or TCP/IP) to
send the TDREPORT to QE and receive the Quote.
References
==========

40
arch/x86/coco/tdx/tdx.c
View file

@ -5,6 +5,8 @@
#define pr_fmt(fmt) "tdx: " fmt
#include <linux/cpufeature.h>
#include <linux/export.h>
#include <linux/io.h>
#include <asm/coco.h>
#include <asm/tdx.h>
#include <asm/vmx.h>
@ -15,6 +17,7 @@
/* TDX module Call Leaf IDs */
#define TDX_GET_INFO 1
#define TDX_GET_VEINFO 3
#define TDX_GET_REPORT 4
#define TDX_ACCEPT_PAGE 6
/* TDX hypercall Leaf IDs */
@ -36,6 +39,12 @@
#define ATTR_SEPT_VE_DISABLE BIT(28)
/* TDX Module call error codes */
#define TDCALL_RETURN_CODE(a) ((a) >> 32)
#define TDCALL_INVALID_OPERAND 0xc0000100
#define TDREPORT_SUBTYPE_0 0
/*
* Wrapper for standard use of __tdx_hypercall with no output aside from
* return code.
@ -100,6 +109,37 @@ static inline void tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
}
/**
* tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
* subtype 0) using TDG.MR.REPORT TDCALL.
* @reportdata: Address of the input buffer which contains user-defined
* REPORTDATA to be included into TDREPORT.
* @tdreport: Address of the output buffer to store TDREPORT.
*
* Refer to section titled "TDG.MR.REPORT leaf" in the TDX Module
* v1.0 specification for more information on TDG.MR.REPORT TDCALL.
* It is used in the TDX guest driver module to get the TDREPORT0.
*
* Return 0 on success, -EINVAL for invalid operands, or -EIO on
* other TDCALL failures.
*/
int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
{
u64 ret;
ret = __tdx_module_call(TDX_GET_REPORT, virt_to_phys(tdreport),
virt_to_phys(reportdata), TDREPORT_SUBTYPE_0,
0, NULL);
if (ret) {
if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
return -EINVAL;
return -EIO;
}
return 0;
}
EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
static void tdx_parse_tdinfo(u64 *cc_mask)
{
struct tdx_module_output out;

2
arch/x86/include/asm/tdx.h
View file

@ -67,6 +67,8 @@ void tdx_safe_halt(void);
bool tdx_early_handle_ve(struct pt_regs *regs);
int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport);
#else
static inline void tdx_early_init(void) { };

2
drivers/virt/Kconfig
View file

@ -52,4 +52,6 @@ source "drivers/virt/coco/efi_secret/Kconfig"
source "drivers/virt/coco/sev-guest/Kconfig"
source "drivers/virt/coco/tdx-guest/Kconfig"
endif

1
drivers/virt/Makefile
View file

@ -11,3 +11,4 @@ obj-$(CONFIG_NITRO_ENCLAVES) += nitro_enclaves/
obj-$(CONFIG_ACRN_HSM) += acrn/
obj-$(CONFIG_EFI_SECRET) += coco/efi_secret/
obj-$(CONFIG_SEV_GUEST) += coco/sev-guest/
obj-$(CONFIG_INTEL_TDX_GUEST) += coco/tdx-guest/

10
drivers/virt/coco/tdx-guest/Kconfig Normal file
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@ -0,0 +1,10 @@
config TDX_GUEST_DRIVER
tristate "TDX Guest driver"
depends on INTEL_TDX_GUEST
help
The driver provides userspace interface to communicate with
the TDX module to request the TDX guest details like attestation
report.
To compile this driver as module, choose M here. The module will
be called tdx-guest.

2
drivers/virt/coco/tdx-guest/Makefile Normal file
View file

@ -0,0 +1,2 @@
# SPDX-License-Identifier: GPL-2.0
obj-$(CONFIG_TDX_GUEST_DRIVER) += tdx-guest.o

102
drivers/virt/coco/tdx-guest/tdx-guest.c Normal file
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@ -0,0 +1,102 @@
// SPDX-License-Identifier: GPL-2.0
/*
* TDX guest user interface driver
*
* Copyright (C) 2022 Intel Corporation
*/
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/string.h>
#include <linux/uaccess.h>
#include <uapi/linux/tdx-guest.h>
#include <asm/cpu_device_id.h>
#include <asm/tdx.h>
static long tdx_get_report0(struct tdx_report_req __user *req)
{
u8 *reportdata, *tdreport;
long ret;
reportdata = kmalloc(TDX_REPORTDATA_LEN, GFP_KERNEL);
if (!reportdata)
return -ENOMEM;
tdreport = kzalloc(TDX_REPORT_LEN, GFP_KERNEL);
if (!tdreport) {
ret = -ENOMEM;
goto out;
}
if (copy_from_user(reportdata, req->reportdata, TDX_REPORTDATA_LEN)) {
ret = -EFAULT;
goto out;
}
/* Generate TDREPORT0 using "TDG.MR.REPORT" TDCALL */
ret = tdx_mcall_get_report0(reportdata, tdreport);
if (ret)
goto out;
if (copy_to_user(req->tdreport, tdreport, TDX_REPORT_LEN))
ret = -EFAULT;
out:
kfree(reportdata);
kfree(tdreport);
return ret;
}
static long tdx_guest_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
switch (cmd) {
case TDX_CMD_GET_REPORT0:
return tdx_get_report0((struct tdx_report_req __user *)arg);
default:
return -ENOTTY;
}
}
static const struct file_operations tdx_guest_fops = {
.owner = THIS_MODULE,
.unlocked_ioctl = tdx_guest_ioctl,
.llseek = no_llseek,
};
static struct miscdevice tdx_misc_dev = {
.name = KBUILD_MODNAME,
.minor = MISC_DYNAMIC_MINOR,
.fops = &tdx_guest_fops,
};
static const struct x86_cpu_id tdx_guest_ids[] = {
X86_MATCH_FEATURE(X86_FEATURE_TDX_GUEST, NULL),
{}
};
MODULE_DEVICE_TABLE(x86cpu, tdx_guest_ids);
static int __init tdx_guest_init(void)
{
if (!x86_match_cpu(tdx_guest_ids))
return -ENODEV;
return misc_register(&tdx_misc_dev);
}
module_init(tdx_guest_init);
static void __exit tdx_guest_exit(void)
{
misc_deregister(&tdx_misc_dev);
}
module_exit(tdx_guest_exit);
MODULE_AUTHOR("Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>");
MODULE_DESCRIPTION("TDX Guest Driver");
MODULE_LICENSE("GPL");

42
include/uapi/linux/tdx-guest.h Normal file
View file

@ -0,0 +1,42 @@
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
/*
* Userspace interface for TDX guest driver
*
* Copyright (C) 2022 Intel Corporation
*/
#ifndef _UAPI_LINUX_TDX_GUEST_H_
#define _UAPI_LINUX_TDX_GUEST_H_
#include <linux/ioctl.h>
#include <linux/types.h>
/* Length of the REPORTDATA used in TDG.MR.REPORT TDCALL */
#define TDX_REPORTDATA_LEN 64
/* Length of TDREPORT used in TDG.MR.REPORT TDCALL */
#define TDX_REPORT_LEN 1024
/**
* struct tdx_report_req - Request struct for TDX_CMD_GET_REPORT0 IOCTL.
*
* @reportdata: User buffer with REPORTDATA to be included into TDREPORT.
* Typically it can be some nonce provided by attestation
* service, so the generated TDREPORT can be uniquely verified.
* @tdreport: User buffer to store TDREPORT output from TDCALL[TDG.MR.REPORT].
*/
struct tdx_report_req {
__u8 reportdata[TDX_REPORTDATA_LEN];
__u8 tdreport[TDX_REPORT_LEN];
};
/*
* TDX_CMD_GET_REPORT0 - Get TDREPORT0 (a.k.a. TDREPORT subtype 0) using
* TDCALL[TDG.MR.REPORT]
*
* Return 0 on success, -EIO on TDCALL execution failure, and
* standard errno on other general error cases.
*/
#define TDX_CMD_GET_REPORT0 _IOWR('T', 1, struct tdx_report_req)
#endif /* _UAPI_LINUX_TDX_GUEST_H_ */

1
tools/testing/selftests/Makefile
View file

@ -74,6 +74,7 @@ TARGETS += sync
TARGETS += syscall_user_dispatch
TARGETS += sysctl
TARGETS += tc-testing
TARGETS += tdx
TARGETS += timens
ifneq (1, $(quicktest))
TARGETS += timers

7
tools/testing/selftests/tdx/Makefile Normal file
View file

@ -0,0 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
CFLAGS += -O3 -Wl,-no-as-needed -Wall -static
TEST_GEN_PROGS := tdx_guest_test
include ../lib.mk

1
tools/testing/selftests/tdx/config Normal file
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@ -0,0 +1 @@
CONFIG_TDX_GUEST_DRIVER=y

163
tools/testing/selftests/tdx/tdx_guest_test.c Normal file
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@ -0,0 +1,163 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Test TDX guest features
*
* Copyright (C) 2022 Intel Corporation.
*
* Author: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
*/
#include <sys/ioctl.h>
#include <errno.h>
#include <fcntl.h>
#include "../kselftest_harness.h"
#include "../../../../include/uapi/linux/tdx-guest.h"
#define TDX_GUEST_DEVNAME "/dev/tdx_guest"
#define HEX_DUMP_SIZE 8
#define DEBUG 0
/**
* struct tdreport_type - Type header of TDREPORT_STRUCT.
* @type: Type of the TDREPORT (0 - SGX, 81 - TDX, rest are reserved)
* @sub_type: Subtype of the TDREPORT (Default value is 0).
* @version: TDREPORT version (Default value is 0).
* @reserved: Added for future extension.
*
* More details can be found in TDX v1.0 module specification, sec
* titled "REPORTTYPE".
*/
struct tdreport_type {
__u8 type;
__u8 sub_type;
__u8 version;
__u8 reserved;
};
/**
* struct reportmac - TDX guest report data, MAC and TEE hashes.
* @type: TDREPORT type header.
* @reserved1: Reserved for future extension.
* @cpu_svn: CPU security version.
* @tee_tcb_info_hash: SHA384 hash of TEE TCB INFO.
* @tee_td_info_hash: SHA384 hash of TDINFO_STRUCT.
* @reportdata: User defined unique data passed in TDG.MR.REPORT request.
* @reserved2: Reserved for future extension.
* @mac: CPU MAC ID.
*
* It is MAC-protected and contains hashes of the remainder of the
* report structure along with user provided report data. More details can
* be found in TDX v1.0 Module specification, sec titled "REPORTMACSTRUCT"
*/
struct reportmac {
struct tdreport_type type;
__u8 reserved1[12];
__u8 cpu_svn[16];
__u8 tee_tcb_info_hash[48];
__u8 tee_td_info_hash[48];
__u8 reportdata[64];
__u8 reserved2[32];
__u8 mac[32];
};
/**
* struct td_info - TDX guest measurements and configuration.
* @attr: TDX Guest attributes (like debug, spet_disable, etc).
* @xfam: Extended features allowed mask.
* @mrtd: Build time measurement register.
* @mrconfigid: Software-defined ID for non-owner-defined configuration
* of the guest - e.g., run-time or OS configuration.
* @mrowner: Software-defined ID for the guest owner.
* @mrownerconfig: Software-defined ID for owner-defined configuration of
* the guest - e.g., specific to the workload.
* @rtmr: Run time measurement registers.
* @reserved: Added for future extension.
*
* It contains the measurements and initial configuration of the TDX guest
* that was locked at initialization and a set of measurement registers
* that are run-time extendable. More details can be found in TDX v1.0
* Module specification, sec titled "TDINFO_STRUCT".
*/
struct td_info {
__u8 attr[8];
__u64 xfam;
__u64 mrtd[6];
__u64 mrconfigid[6];
__u64 mrowner[6];
__u64 mrownerconfig[6];
__u64 rtmr[24];
__u64 reserved[14];
};
/*
* struct tdreport - Output of TDCALL[TDG.MR.REPORT].
* @reportmac: Mac protected header of size 256 bytes.
* @tee_tcb_info: Additional attestable elements in the TCB are not
* reflected in the reportmac.
* @reserved: Added for future extension.
* @tdinfo: Measurements and configuration data of size 512 bytes.
*
* More details can be found in TDX v1.0 Module specification, sec
* titled "TDREPORT_STRUCT".
*/
struct tdreport {
struct reportmac reportmac;
__u8 tee_tcb_info[239];
__u8 reserved[17];
struct td_info tdinfo;
};
static void print_array_hex(const char *title, const char *prefix_str,
const void *buf, int len)
{
int i, j, line_len, rowsize = HEX_DUMP_SIZE;
const __u8 *ptr = buf;
printf("\t\t%s", title);
for (j = 0; j < len; j += rowsize) {
line_len = rowsize < (len - j) ? rowsize : (len - j);
printf("%s%.8x:", prefix_str, j);
for (i = 0; i < line_len; i++)
printf(" %.2x", ptr[j + i]);
printf("\n");
}
printf("\n");
}
TEST(verify_report)
{
struct tdx_report_req req;
struct tdreport *tdreport;
int devfd, i;
devfd = open(TDX_GUEST_DEVNAME, O_RDWR | O_SYNC);
ASSERT_LT(0, devfd);
/* Generate sample report data */
for (i = 0; i < TDX_REPORTDATA_LEN; i++)
req.reportdata[i] = i;
/* Get TDREPORT */
ASSERT_EQ(0, ioctl(devfd, TDX_CMD_GET_REPORT0, &req));
if (DEBUG) {
print_array_hex("\n\t\tTDX report data\n", "",
req.reportdata, sizeof(req.reportdata));
print_array_hex("\n\t\tTDX tdreport data\n", "",
req.tdreport, sizeof(req.tdreport));
}
/* Make sure TDREPORT data includes the REPORTDATA passed */
tdreport = (struct tdreport *)req.tdreport;
ASSERT_EQ(0, memcmp(&tdreport->reportmac.reportdata[0],
req.reportdata, sizeof(req.reportdata)));
ASSERT_EQ(0, close(devfd));
}
TEST_HARNESS_MAIN