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Message-ID: <CAMj1kXEvNoFkSPL-tBUGxow7-FdsaRZ-0p7mVytJfZJzscUkjg@mail.gmail.com>
Date: Sat, 3 Feb 2024 17:59:22 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc: linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: [PATCH v1] efi/libstub: Add Confidential Computing (CC)
measurement support
(cc Ilias)
On Sat, 3 Feb 2024 at 08:58, Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com> wrote:
>
> If the virtual firmware implements TPM support, TCG2 protocol will be
> used for kernel measurements and event logging support. But in CC
> environment, not all platforms support or enable the TPM feature. UEFI
> specification [1] exposes protocol and interfaces used for kernel
> measurements in CC platforms without TPM support.
>
> Currently, the efi-stub only supports the kernel related measurements
> for the platform that supports TCG2 protocol. So, extend it add
> CC measurement protocol (EFI_CC_MEASUREMENT_PROTOCOL) and event logging
> support. Event logging format in the CC environment is the same as
> TCG2.
>
> More details about the EFI CC measurements and logging can be found
> in [1].
>
> Link: https://uefi.org/specs/UEFI/2.10/38_Confidential_Computing.html#efi-cc-measurement-protocol [1]
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> ---
> .../firmware/efi/libstub/efi-stub-helper.c | 113 +++++++++++++-----
> drivers/firmware/efi/libstub/efistub.h | 73 +++++++++++
> include/linux/efi.h | 1 +
> 3 files changed, 159 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
> index bfa30625f5d0..e323b768048f 100644
> --- a/drivers/firmware/efi/libstub/efi-stub-helper.c
> +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
> @@ -219,50 +219,107 @@ static const struct {
> },
> };
>
> +static efi_status_t tcg2_efi_measure(efi_tcg2_protocol_t *tcg2,
> + unsigned long load_addr,
> + unsigned long load_size,
> + enum efistub_event event)
> +{
> + struct efi_measured_event {
> + efi_tcg2_event_t event_data;
> + efi_tcg2_tagged_event_t tagged_event;
> + u8 tagged_event_data[];
> + } *evt;
> + int size = sizeof(*evt) + events[event].event_data_len;
> + efi_status_t status;
> +
> + status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, size,
> + (void **)&evt);
> + if (status != EFI_SUCCESS)
> + return status;
> +
> + evt->event_data = (struct efi_tcg2_event){
> + .event_size = size,
> + .event_header.header_size = sizeof(evt->event_data.event_header),
> + .event_header.header_version = EFI_TCG2_EVENT_HEADER_VERSION,
> + .event_header.pcr_index = events[event].pcr_index,
> + .event_header.event_type = EV_EVENT_TAG,
> + };
> +
> + evt->tagged_event = (struct efi_tcg2_tagged_event){
> + .tagged_event_id = events[event].event_id,
> + .tagged_event_data_size = events[event].event_data_len,
> + };
> +
> + memcpy(evt->tagged_event_data, events[event].event_data,
> + events[event].event_data_len);
> +
> + status = efi_call_proto(tcg2, hash_log_extend_event, 0,
> + load_addr, load_size, &evt->event_data);
> + efi_bs_call(free_pool, evt);
> +
> + return status;
> +}
> +
> +static efi_status_t cc_efi_measure(efi_cc_protocol_t *cc,
> + unsigned long load_addr,
> + unsigned long load_size,
> + enum efistub_event event)
> +{
> + efi_cc_mr_index_t mr;
> + efi_cc_event_t *evt;
> + efi_status_t status;
> + size_t size;
> +
> + status = efi_call_proto(cc, map_pcr_to_mr_index, events[event].pcr_index, &mr);
> + if (status != EFI_SUCCESS) {
> + efi_err("CC_MEASURE: PCR to MR mapping failed\n");
> + return status;
> + }
> +
> + size = sizeof(*evt) + events[event].event_data_len;
> + status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, size, (void **)&evt);
> + if (status != EFI_SUCCESS) {
> + efi_err("CC_MEASURE: Allocating event struct failed\n");
> + return status;
> + }
> +
> + evt->event_size = size;
> + evt->event_header.header_size = sizeof(evt->event_header);
> + evt->event_header.header_version = EFI_CC_EVENT_HEADER_VERSION;
> + evt->event_header.mr_index = mr;
> + evt->event_header.event_type = EV_EVENT_TAG;
> + memcpy(evt->event_data, events[event].event_data, events[event].event_data_len);
> +
Why does this look entirely different from the TCG2 version? What
happened to the tagged event?
> + status = efi_call_proto(cc, hash_log_extend_event, 0, load_addr, load_size, evt);
> + efi_bs_call(free_pool, evt);
> +
> + return status;
> +}
> static efi_status_t efi_measure_tagged_event(unsigned long load_addr,
> unsigned long load_size,
> enum efistub_event event)
> {
> efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
> + efi_guid_t cc_guid = EFI_CC_MEASUREMENT_PROTOCOL_GUID;
> + efi_cc_protocol_t *cc = NULL;
> efi_tcg2_protocol_t *tcg2 = NULL;
> efi_status_t status;
>
> efi_bs_call(locate_protocol, &tcg2_guid, NULL, (void **)&tcg2);
> if (tcg2) {
> - struct efi_measured_event {
> - efi_tcg2_event_t event_data;
> - efi_tcg2_tagged_event_t tagged_event;
> - u8 tagged_event_data[];
> - } *evt;
> - int size = sizeof(*evt) + events[event].event_data_len;
> -
> - status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, size,
> - (void **)&evt);
> + status = tcg2_efi_measure(tcg2, load_addr, load_size, event);
> if (status != EFI_SUCCESS)
> goto fail;
>
> - evt->event_data = (struct efi_tcg2_event){
> - .event_size = size,
> - .event_header.header_size = sizeof(evt->event_data.event_header),
> - .event_header.header_version = EFI_TCG2_EVENT_HEADER_VERSION,
> - .event_header.pcr_index = events[event].pcr_index,
> - .event_header.event_type = EV_EVENT_TAG,
> - };
> -
> - evt->tagged_event = (struct efi_tcg2_tagged_event){
> - .tagged_event_id = events[event].event_id,
> - .tagged_event_data_size = events[event].event_data_len,
> - };
> -
> - memcpy(evt->tagged_event_data, events[event].event_data,
> - events[event].event_data_len);
> -
> - status = efi_call_proto(tcg2, hash_log_extend_event, 0,
> - load_addr, load_size, &evt->event_data);
> - efi_bs_call(free_pool, evt);
> + return EFI_SUCCESS;
> + }
>
> + efi_bs_call(locate_protocol, &cc_guid, NULL, (void **)&cc);
> + if (cc) {
> + status = cc_efi_measure(cc, load_addr, load_size, event);
> if (status != EFI_SUCCESS)
> goto fail;
> +
> return EFI_SUCCESS;
> }
>
> diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
> index 212687c30d79..dbdeb2ad7a93 100644
> --- a/drivers/firmware/efi/libstub/efistub.h
> +++ b/drivers/firmware/efi/libstub/efistub.h
> @@ -882,6 +882,79 @@ union efi_tcg2_protocol {
> } mixed_mode;
> };
>
> +typedef struct {
> + u8 major;
> + u8 minor;
> +} efi_cc_version_t;
> +
> +typedef struct {
> + u8 type;
> + u8 sub_type;
> +} efi_cc_type_t;
> +
> +/* EFI CC type/subtype defines */
> +#define EFI_CC_TYPE_NONE 0
> +#define EFI_CC_TYPE_AMD_SEV 1
> +#define EFI_CC_TYPE_INTEL_TDX 2
> +
> +typedef u32 efi_cc_mr_index_t;
> +
> +typedef struct {
> + u32 event_size;
> + struct {
> + u32 header_size;
> + u16 header_version;
> + u32 mr_index;
> + u32 event_type;
> + } __packed event_header;
> + u8 event_data[0];
> +} __packed efi_cc_event_t;
> +
> +typedef u32 efi_cc_event_log_bitmap_t;
> +typedef u32 efi_cc_event_log_format_t;
> +typedef u32 efi_cc_event_algorithm_bitmap_t;
> +
> +typedef struct {
> + u8 size;
> + efi_cc_version_t structure_version;
> + efi_cc_version_t protocol_version;
> + efi_cc_event_algorithm_bitmap_t hash_algorithm_bitmap;
> + efi_cc_event_log_bitmap_t supported_event_logs;
> + efi_cc_type_t cc_type;
> +} efi_cc_boot_service_cap_t;
> +
> +#define EFI_CC_EVENT_HEADER_VERSION 1
> +
> +#define EFI_CC_BOOT_HASH_ALG_SHA384 0x00000004
> +
> +typedef union efi_cc_protocol efi_cc_protocol_t;
> +
> +union efi_cc_protocol {
> + struct {
> + efi_status_t (__efiapi *get_capability)(efi_cc_protocol_t *,
> + efi_cc_boot_service_cap_t *);
> + efi_status_t (__efiapi *get_event_log)(efi_cc_protocol_t *,
> + efi_cc_event_log_format_t,
> + efi_physical_addr_t *,
> + efi_physical_addr_t *,
> + efi_bool_t *);
> + efi_status_t (__efiapi *hash_log_extend_event)(efi_cc_protocol_t *,
> + u64,
> + efi_physical_addr_t,
> + u64,
> + const efi_cc_event_t *);
> + efi_status_t (__efiapi *map_pcr_to_mr_index)(efi_cc_protocol_t *,
> + u32,
> + efi_cc_mr_index_t *);
> + };
> + struct {
> + u32 get_capability;
> + u32 get_event_log;
> + u32 hash_log_extend_event;
> + u32 map_pcr_to_mr_index;
> + } mixed_mode;
> +};
> +
> struct riscv_efi_boot_protocol {
> u64 revision;
>
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index c74f47711f0b..2f57fec2e629 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -400,6 +400,7 @@ void efi_native_runtime_setup(void);
> #define EFI_CERT_X509_GUID EFI_GUID(0xa5c059a1, 0x94e4, 0x4aa7, 0x87, 0xb5, 0xab, 0x15, 0x5c, 0x2b, 0xf0, 0x72)
> #define EFI_CERT_X509_SHA256_GUID EFI_GUID(0x3bd2a492, 0x96c0, 0x4079, 0xb4, 0x20, 0xfc, 0xf9, 0x8e, 0xf1, 0x03, 0xed)
> #define EFI_CC_BLOB_GUID EFI_GUID(0x067b1f5f, 0xcf26, 0x44c5, 0x85, 0x54, 0x93, 0xd7, 0x77, 0x91, 0x2d, 0x42)
> +#define EFI_CC_MEASUREMENT_PROTOCOL_GUID EFI_GUID(0x96751a3d, 0x72f4, 0x41a6, 0xa7, 0x94, 0xed, 0x5d, 0x0e, 0x67, 0xae, 0x6b)
>
> /*
> * This GUID is used to pass to the kernel proper the struct screen_info
> --
> 2.25.1
>
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