Re: [PATCH v16 3/3] selftests: tdx: Test TDX attestation GetReport support

[Wander Lairson Costa]

On Thu, Oct 27, 2022 at 05:28:20PM -0700, Kuppuswamy Sathyanarayanan wrote:
> Attestation is used to verify the trustworthiness of a TDX guest.
> During the guest bring-up, the 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 guest runtime, the attestation process is used
> to attest to these measurements.
> 
> The 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 ID to
> protect the integrity 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
> enable guest userspace to get the TDREPORT.
> 
> Add a kernel self test module to test this ABI and verify the validity
> of the generated TDREPORT.
> 
> Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
> Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> Acked-by: Kai Huang <kai.huang@xxxxxxxxx>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> ---
> 
> Changes since v15:
>  * None
> 
> Changes since v14:
>  * Fixed format issue in struct comments.
>  * Rebased on top of v6.1-rc1
> 
> Changes since v13:
>  * Removed __packed from TDREPORT structs.
>  * Since the guest driver is moved to drivers/virt/coco, removed
>    tools/arch/x86/include header folder usage.
>  * Fixed struct comments to match kernel-doc format.
>  * Fixed commit log as per review comments.
>  * Fixed some format issues in the code.
> 
> Changes since v12:
>  * Changed #ifdef DEBUG usage with if (DEBUG).
>  * Initialized reserved entries values to zero.
> 
> 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@xxxxxxxxxxxxxxx/
> 
>  tools/testing/selftests/Makefile             |   1 +
>  tools/testing/selftests/tdx/Makefile         |   7 +
>  tools/testing/selftests/tdx/config           |   1 +
>  tools/testing/selftests/tdx/tdx_guest_test.c | 175 +++++++++++++++++++
>  4 files changed, 184 insertions(+)
>  create mode 100644 tools/testing/selftests/tdx/Makefile
>  create mode 100644 tools/testing/selftests/tdx/config
>  create mode 100644 tools/testing/selftests/tdx/tdx_guest_test.c
> 
> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index 0464b2c6c1e4..f60e14d16bfd 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -73,6 +73,7 @@ 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..8dd43517cd55
> --- /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_guest_test
> +
> +include ../lib.mk
> diff --git a/tools/testing/selftests/tdx/config b/tools/testing/selftests/tdx/config
> new file mode 100644
> index 000000000000..aa1edc829ab6
> --- /dev/null
> +++ b/tools/testing/selftests/tdx/config
> @@ -0,0 +1 @@
> +CONFIG_TDX_GUEST_DRIVER=y
> diff --git a/tools/testing/selftests/tdx/tdx_guest_test.c b/tools/testing/selftests/tdx/tdx_guest_test.c
> new file mode 100644
> index 000000000000..a5c243f73adc
> --- /dev/null
> +++ b/tools/testing/selftests/tdx/tdx_guest_test.c
> @@ -0,0 +1,175 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Test TDX guest features
> + *
> + * Copyright (C) 2022 Intel Corporation.
> + *
> + * Author: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> + */
> +
> +#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;
> +
> +	if (!len || !buf)

If len is not zero and buf is null, this would be bug. It is better to
let the code crash or assert buf isn't null after testing len.