Re: [PATCH v9 2/6] selftests: tdx: Test GetReport TDX attestation feature

[Kai Huang]

On Wed, 2022-07-27 at 20:44 -0700, Kuppuswamy Sathyanarayanan wrote:
> In TDX guest, attestation is used to verify the trustworthiness of a
> TD. During the TD bring-up, Intel TDX module measures and records the
> initial contents and configuration of TD, and at runtime, TD software
> uses runtime measurement registers (RMTRs) to measure and record
> details related to kernel image, command line params, ACPI tables,
> initrd, etc. At TD 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 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@xxxxxxxxx>
> Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> ---
>  tools/testing/selftests/Makefile              |   1 +
>  tools/testing/selftests/tdx/Makefile          |   7 +
>  tools/testing/selftests/tdx/tdx_attest_test.c | 160 ++++++++++++++++++
>  3 files changed, 168 insertions(+)
>  create mode 100644 tools/testing/selftests/tdx/Makefile
>  create mode 100644 tools/testing/selftests/tdx/tdx_attest_test.c
> 
> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index de11992dc577..807a839d69c4 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -69,6 +69,7 @@ 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..281db209f9d6
> --- /dev/null
> +++ b/tools/testing/selftests/tdx/Makefile
> @@ -0,0 +1,7 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +CFLAGS += -O3 -Wl,-no-as-needed -Wall -static
> +
> +TEST_GEN_PROGS := tdx_attest_test
> +
> +include ../lib.mk
> 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..7155cc751eaa
> --- /dev/null
> +++ b/tools/testing/selftests/tdx/tdx_attest_test.c
> @@ -0,0 +1,160 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Test TDX attestation feature
> + *
> + * Copyright (C) 2022 Intel Corporation. All rights reserved.
> + *
> + * Author: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> + */
> +
> +
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/ioctl.h>
> +#include <sys/time.h>
> +#include <sys/types.h>
> +#include <time.h>
> +#include <unistd.h>
> +
> +#include "../kselftest_harness.h"
> +#include "../../../../arch/x86/include/uapi/asm/tdx.h"
> +
> +#define devname         "/dev/tdx-guest"
> +#define HEX_DUMP_SIZE	8
> +
> +/*
> + * struct td_info - It contains the measurements and initial configuration of
> + * the TD 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.
> + */
> +struct td_info {
> +	/* TD 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];
> +};
> +
> +/*
> + * Trusted Execution Environment (TEE) report (TDREPORT_STRUCT) type,
> + * sub type and version..
> + */
> +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;
> +};
> +
> +/*
> + * struct reportmac - First field in the TEE report structure
> + * (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.
> + */
> +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];
> +};
> +
> +struct tee_tcb_info {
> +	__u8 data[239];
> +};
> +
> +struct tdreport_data {
> +	struct reportmac _reportmac;
> +	struct tee_tcb_info _tcb_info;
> +	__u8 reserved[17];
> +	struct td_info _tdinfo;
> +};

I think 'struct tdreport' is enough.  The _data postfix only causes it to be
more confusing.

Btw, as it appears you only verified reportdata below, is it worth to have all
those data structures (and they are used by hardware but not __packed)?  Perhaps
a macro to define REPORTDATA offset in TDREPORT is good enough?  Or maybe I am
missing something.

> +
> +#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_data *tdr_data;
> +	__u8 tdreport[TDX_REPORT_LEN];
> +	struct tdx_report_req req;
> +	int devfd, i;
> +
> +	devfd = open(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     = TDX_REPORT_LEN;
> +
> +	/* Get TDREPORT */
> +	ASSERT_EQ(0, ioctl(devfd, TDX_CMD_GET_REPORT, &req));
> +
> +	tdr_data = (struct tdreport_data *)tdreport;
> +
> +#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(&tdr_data->_reportmac.reportdata[0], reportdata,
> +				sizeof(reportdata)));
> +
> +	ASSERT_EQ(0, close(devfd));
> +}
> +
> +TEST_HARNESS_MAIN