[PATCH v12 2/3] selftests: tdx: Test TDX attestation GetReport support

Kuppuswamy Sathyanarayanan
2022-09-08T00:28:08Z

Attestation is used to verify the trustworthiness of a TDX guest.
During the guest bring-up, Intel TDX module measures and records
the initial contents and configuration of the guest, and at runtime,
guest software uses runtime measurement registers (RMTRs) to measure
and record details related to kernel image, command line params, ACPI
tables, initrd, etc. At TDX guest runtime, Intel SGX attestation
infrastructure is re-used to attest to these measurement data.

First step in the TDX attestation process is to get the TDREPORT data.
It is a fixed size data structure generated by the TDX module which
includes the above mentioned measurements data, a MAC to protect the
integerity of the TDREPORT, and a 64-Byte of user specified data passed
during TDREPORT request which can uniquely identify the TDREPORT.

Intel's TDX guest driver exposes TDX_CMD_GET_REPORT IOCTL interface to
get the TDREPORT from the user space.

Add a kernel selftest module to test this ABI and verify the validity
of generated TDREPORT.

Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---

Changes since v11:
* Renamed devname with TDX_GUEST_DEVNAME.

Changes since v10:
* Replaced TD/TD Guest usage with guest or TDX guest.
* Reworded the subject line.

Changes since v9:
* Copied arch/x86/include/uapi/asm/tdx.h to tools/arch/x86/include to
decouple header dependency between kernel source and tools dir.
* Fixed Makefile to adapt to above change.
* Fixed commit log and comments.
* Added __packed to hardware structs.

Changes since v8:
* Please refer to https://lore.kernel.org/all/ \
20220728034420.648314-1-sathyanarayanan.kuppuswamy@linux.intel.com/

tools/arch/x86/include/uapi/asm/tdx.h | 54 ++++++
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/tdx/Makefile | 11 ++
tools/testing/selftests/tdx/config | 1 +
tools/testing/selftests/tdx/tdx_attest_test.c | 155 ++++++++++++++++++
5 files changed, 222 insertions(+)
create mode 100644 tools/arch/x86/include/uapi/asm/tdx.h
create mode 100644 tools/testing/selftests/tdx/Makefile
create mode 100644 tools/testing/selftests/tdx/config
create mode 100644 tools/testing/selftests/tdx/tdx_attest_test.c

diff --git a/tools/arch/x86/include/uapi/asm/tdx.h b/tools/arch/x86/include/uapi/asm/tdx.h
new file mode 100644
index 000000000000..29d8e38f226a
--- /dev/null
+++ b/tools/arch/x86/include/uapi/asm/tdx.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_ASM_X86_TDX_H
+#define _UAPI_ASM_X86_TDX_H
+
+#include <linux/types.h>
+#include <linux/ioctl.h>
+
+#define TDX_GUEST_DEVICE "tdx-guest"
+
+/* 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: Get TDREPORT using REPORTDATA as input.
+ *
+ * @reportdata : User-defined 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 : TDREPORT output from TDCALL[TDG.MR.REPORT].
+ * @rpd_len : Length of the REPORTDATA (fixed as 64 bytes by
+ * the TDX Module specification, but parameter is
+ * added to handle future extension).
+ * @tdr_len : Length of the TDREPORT (fixed as 1024 bytes by
+ * the TDX Module specification, but a parameter
+ * is added to accommodate future extension).
+ * @subtype : Subtype of TDREPORT (fixed as 0 by TDX Module
+ * specification, but added a parameter to handle
+ * future extension).
+ *
+ * Used in TDX_CMD_GET_REPORT IOCTL request.
+ */
+struct tdx_report_req {
+ __u64 reportdata;
+ __u64 tdreport;
+ __u32 rpd_len;
+ __u32 tdr_len;
+ __u8 subtype;
+ __u8 reserved[7];
+};
+
+/*
+ * TDX_CMD_GET_REPORT - Get TDREPORT 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_REPORT _IOWR('T', 0x01, __u64)
+
+#endif /* _UAPI_ASM_X86_TDX_H */
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 10b34bb03bc1..22bdb3d848f5 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -70,6 +70,7 @@ TARGETS += sync
TARGETS += syscall_user_dispatch
TARGETS += sysctl
TARGETS += tc-testing
+TARGETS += tdx
TARGETS += timens
ifneq (1, $(quicktest))
TARGETS += timers
diff --git a/tools/testing/selftests/tdx/Makefile b/tools/testing/selftests/tdx/Makefile
new file mode 100644
index 000000000000..014795420184
--- /dev/null
+++ b/tools/testing/selftests/tdx/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+
+top_srcdir = ../../../..
+
+LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/x86/include
+
+CFLAGS += -O3 -Wl,-no-as-needed -Wall -static -I$(LINUX_TOOL_ARCH_INCLUDE)
+
+TEST_GEN_PROGS := tdx_attest_test
+
+include ../lib.mk
diff --git a/tools/testing/selftests/tdx/config b/tools/testing/selftests/tdx/config
new file mode 100644
index 000000000000..1340073a4abf
--- /dev/null
+++ b/tools/testing/selftests/tdx/config
@@ -0,0 +1 @@
+CONFIG_INTEL_TDX_GUEST=y
diff --git a/tools/testing/selftests/tdx/tdx_attest_test.c b/tools/testing/selftests/tdx/tdx_attest_test.c
new file mode 100644
index 000000000000..b7974050e3cf
--- /dev/null
+++ b/tools/testing/selftests/tdx/tdx_attest_test.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test TDX attestation
+ *
+ * Copyright (C) 2022 Intel Corporation. All rights reserved.
+ *
+ * Author: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <uapi/asm/tdx.h>
+
+#include "../kselftest_harness.h"
+
+#define TDX_GUEST_DEVNAME "/dev/"TDX_GUEST_DEVICE
+#define HEX_DUMP_SIZE 8
+#define __packed __attribute__((packed))
+
+/*
+ * Trusted Execution Environment (TEE) report (TDREPORT_STRUCT) type,
+ * sub type and version. More details can be found in TDX v1.0 Module
+ * specification, sec titled "REPORTTYPE".
+ */
+struct tdreport_type {
+ /* 0 - SGX, 81 -TDX, rest are reserved */
+ __u8 type;
+ /* Default value is 0 */
+ __u8 sub_type;
+ /* Default value is 0 */
+ __u8 version;
+ __u8 reserved;
+} __packed;
+
+/*
+ * struct reportmac - First field in the TRDREPORT_STRUCT. It is common
+ * to Intel’s TEE's e.g., SGX and TDX. It is MAC-protected and contains
+ * hashes of the remainder of the report structure which includes the
+ * TEE’s measurements, and where applicable, the measurements of additional
+ * TCB elements not reflected in CPUSVN – e.g., a SEAM’s measurements.
+ * More details can be found in TDX v1.0 Module specification, sec titled
+ * "REPORTMACSTRUCT"
+ */
+struct reportmac {
+ struct tdreport_type type;
+ __u8 reserved1[12];
+ /* CPU security version */
+ __u8 cpu_svn[16];
+ /* SHA384 hash of TEE TCB INFO */
+ __u8 tee_tcb_info_hash[48];
+ /* SHA384 hash of TDINFO_STRUCT */
+ __u8 tee_td_info_hash[48];
+ /* User defined unique data passed in TDG.MR.REPORT request */
+ __u8 reportdata[64];
+ __u8 reserved2[32];
+ __u8 mac[32];
+} __packed;
+
+/*
+ * struct td_info - 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. These values are copied from
+ * the TDCS by the TDG.MR.REPORT function. More details can be found in
+ * TDX v1.0 Module specification, sec titled "TDINFO_STRUCT".
+ */
+struct td_info {
+ /* TDX Guest attributes (like debug, spet_disable, etc) */
+ __u8 attr[8];
+ __u64 xfam;
+ /* Measurement registers */
+ __u64 mrtd[6];
+ __u64 mrconfigid[6];
+ __u64 mrowner[6];
+ __u64 mrownerconfig[6];
+ /* Runtime measurement registers */
+ __u64 rtmr[24];
+ __u64 reserved[14];
+} __packed;
+
+struct tdreport {
+ /* Common to TDX/SGX of size 256 bytes */
+ struct reportmac reportmac;
+ __u8 tee_tcb_info[239];
+ __u8 reserved[17];
+ /* Measurements and configuration data of size 512 byes */
+ struct td_info tdinfo;
+} __packed;
+
+#ifdef DEBUG
+static void print_array_hex(const char *title, const char *prefix_str,
+ const void *buf, int len)
+{
+ const __u8 *ptr = buf;
+ int i, rowsize = HEX_DUMP_SIZE;
+
+ if (!len || !buf)
+ return;
+
+ printf("\t\t%s", title);
+
+ for (i = 0; i < len; i++) {
+ if (!(i % rowsize))
+ printf("\n%s%.8x:", prefix_str, i);
+ printf(" %.2x", ptr[i]);
+ }
+
+ printf("\n");
+}
+#endif
+
+TEST(verify_report)
+{
+ __u8 reportdata[TDX_REPORTDATA_LEN];
+ struct tdreport tdreport;
+ struct tdx_report_req req;
+ 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++)
+ reportdata[i] = i;
+
+ /* Initialize IOCTL request */
+ req.subtype = 0;
+ req.reportdata = (__u64)reportdata;
+ req.rpd_len = TDX_REPORTDATA_LEN;
+ req.tdreport = (__u64)&tdreport;
+ req.tdr_len = sizeof(tdreport);
+
+ /* Get TDREPORT */
+ ASSERT_EQ(0, ioctl(devfd, TDX_CMD_GET_REPORT, &req));
+
+#ifdef DEBUG
+ print_array_hex("\n\t\tTDX report data\n", "",
+ reportdata, sizeof(reportdata));
+
+ print_array_hex("\n\t\tTDX tdreport data\n", "",
+ &tdreport, sizeof(tdreport));
+#endif
+
+ /* Make sure TDREPORT data includes the REPORTDATA passed */
+ ASSERT_EQ(0, memcmp(&tdreport.reportmac.reportdata[0],
+ reportdata, sizeof(reportdata)));
+
+ ASSERT_EQ(0, close(devfd));
+}
+
+TEST_HARNESS_MAIN
--
2.34.1