Re: [PATCH 2/2] efi_loader: add PE/COFF image measurement

On 4/15/21 3:30 PM, Masahisa Kojima wrote:

"TCG PC Client Platform Firmware Profile Specification" requires to measure every attempt to load and execute a OS Loader(a UEFI application) into PCR[4]. This commit adds the PE/COFF image measurement, extends PCR, and appends measurement into Event Log.

Signed-off-by: Masahisa Kojima masahisa.kojima@linaro.org

include/efi_loader.h | 4 + include/efi_tcg2.h | 10 ++ include/tpm-v2.h | 1 + lib/efi_loader/efi_image_loader.c | 7 ++ lib/efi_loader/efi_tcg2.c | 187 ++++++++++++++++++++++++++++-- 5 files changed, 199 insertions(+), 10 deletions(-)

diff --git a/include/efi_loader.h b/include/efi_loader.h index de1a496a97..b02bc93c8e 100644 --- a/include/efi_loader.h +++ b/include/efi_loader.h @@ -426,6 +426,10 @@ efi_status_t efi_disk_register(void); efi_status_t efi_rng_register(void); /* Called by efi_init_obj_list() to install EFI_TCG2_PROTOCOL */ efi_status_t efi_tcg2_register(void); +/* measure the pe-coff image, extend PCR and add Event Log */ +efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,

• 		   struct efi_loaded_image_obj *handle,
  

• 		   struct efi_loaded_image *loaded_image_info);
  

  /* Create handles and protocols for the partitions of a block device */ int efi_disk_create_partitions(efi_handle_t parent, struct blk_desc *desc, const char *if_typename, int diskid,

diff --git a/include/efi_tcg2.h b/include/efi_tcg2.h index 40e241ce31..f8d46c5fd2 100644 --- a/include/efi_tcg2.h +++ b/include/efi_tcg2.h @@ -9,6 +9,8 @@ #if !defined _EFI_TCG2_PROTOCOL_H_ #define _EFI_TCG2_PROTOCOL_H_

+#include <efi.h>

This include is already included in efi_api.h.

+#include <efi_api.h> #include <tpm-v2.h>

#define EFI_TCG2_PROTOCOL_GUID \ @@ -53,6 +55,14 @@ struct efi_tcg2_event { u8 event[]; } __packed;

+struct uefi_image_load_event {

• efi_physical_addr_t image_location_in_memory;
• u64 image_length_in_memory;
• u64 image_link_time_address;
• u64 length_of_device_path;
• struct efi_device_path device_path[];

A device path is not an array of struct efi_device_path. But the first element is of this type. So ok.

+} __packed;

Why should this be __packed? You don't use arrays of this structure and it is naturally packed.

• struct efi_tcg2_boot_service_capability { u8 size; struct efi_tcg2_version structure_version;

diff --git a/include/tpm-v2.h b/include/tpm-v2.h index df67a196cf..ab9c04dc0a 100644 --- a/include/tpm-v2.h +++ b/include/tpm-v2.h @@ -61,6 +61,7 @@ struct udevice; #define EV_S_CRTM_VERSION ((u32)0x00000008) #define EV_CPU_MICROCODE ((u32)0x00000009) #define EV_TABLE_OF_DEVICES ((u32)0x0000000B)

Please, add a comment here that the following values are defined in the "TCG EFI Platform Specification".

+#define EV_EFI_BOOT_SERVICES_APPLICATION ((u32)0x80000003)

Please, add all EV_EFI_* constants.

/* TPMS_TAGGED_PROPERTY Structure */ struct tpms_tagged_property { diff --git a/lib/efi_loader/efi_image_loader.c b/lib/efi_loader/efi_image_loader.c index 2c35cb5651..b032ec5dd8 100644 --- a/lib/efi_loader/efi_image_loader.c +++ b/lib/efi_loader/efi_image_loader.c @@ -829,6 +829,13 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, goto err; }

+#if CONFIG_IS_ENABLED(EFI_TCG2_PROTOCOL)

• /* Measure an PE/COFF image */
• if (tcg2_measure_pe_image(efi, efi_size, handle,

• 		  loaded_image_info))
  

• log_err("PE image measurement failed\n");
  

+#endif

• /* Copy PE headers */ memcpy(efi_reloc, efi, sizeof(*dos)

diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c index ed86a220fb..9fab07605f 100644 --- a/lib/efi_loader/efi_tcg2.c +++ b/lib/efi_loader/efi_tcg2.c @@ -13,8 +13,10 @@ #include <efi_loader.h> #include <efi_tcg2.h> #include <log.h> +#include <malloc.h> #include <version.h> #include <tpm-v2.h> +#include <u-boot/rsa.h> #include <u-boot/sha1.h> #include <u-boot/sha256.h> #include <u-boot/sha512.h> @@ -709,6 +711,172 @@ out: return EFI_EXIT(ret); }

+static efi_status_t tcg2_hash_pe_image(void *efi, u64 efi_size,

• 		       struct tpml_digest_values *digest_list)
  

+{

• IMAGE_NT_HEADERS32 *nt;
• WIN_CERTIFICATE *wincerts = NULL;
• size_t wincerts_len;
• struct efi_image_regions *regs = NULL;
• void *new_efi = NULL;
• size_t new_efi_size;
• u8 hash[TPM2_SHA512_DIGEST_SIZE];
• efi_status_t ret;
• u32 active;
• int i;
• ret = efi_check_pe(efi, efi_size, (void **)&nt);

Why are you calling this function? It is already called in efi_load_pe().

• if (ret != EFI_SUCCESS) {

• log_err("Not a valid PE-COFF file\n");
  

• return EFI_INVALID_PARAMETER;
  

• }
• /*

• * Size must be 8-byte aligned and the trailing bytes must be
  

• * zero'ed. Otherwise hash value may be incorrect.
  

• */
  

• if (!IS_ALIGNED(efi_size, 8)) {

• new_efi_size = ALIGN(efi_size, 8);
  

• new_efi = calloc(new_efi_size, 1);
  

• if (!new_efi)
  

• 	return EFI_OUT_OF_RESOURCES;
  

• memcpy(new_efi, efi, efi_size);
  

• efi = new_efi;
  

• efi_size = new_efi_size;
  

• }
• if (!efi_image_parse(efi, efi_size, &regs, &wincerts,

• 	     &wincerts_len)) {
  

• log_err("Parsing PE executable image failed\n");
  

• ret = EFI_INVALID_PARAMETER;
  

• goto out;
  

• }

Please, don't duplicate code from efi_image_authenticate(). Extract a common function instead.

• ret = __get_active_pcr_banks(&active);
• if (ret != EFI_SUCCESS) {

• ret = EFI_DEVICE_ERROR;
  

• goto out;
  

• }
• digest_list->count = 0;
• for (i = 0; i < MAX_HASH_COUNT; i++) {

• u16 hash_alg = hash_algo_list[i].hash_alg;
  

• if (!(active & alg_to_mask(hash_alg)))
  

• 	continue;
  

• switch (hash_alg) {
  

• case TPM2_ALG_SHA1:
  

SHA1 is known to be unsafe. Why would we support it?

• 	hash_calculate("sha1", regs->reg, regs->num, hash);
  

• 	digest_list->count++;
  

Why do you repeat this line in every case of the switch statement? Please, put it below.

• 	break;
  

• case TPM2_ALG_SHA256:
  

• 	hash_calculate("sha256", regs->reg, regs->num, hash);
  

• 	digest_list->count++;
  

• 	break;
  

• case TPM2_ALG_SHA384:
  

• 	hash_calculate("sha384", regs->reg, regs->num, hash);
  

• 	digest_list->count++;
  

• 	break;
  

• case TPM2_ALG_SHA512:
  

• 	hash_calculate("sha512", regs->reg, regs->num, hash);
  

• 	digest_list->count++;
  

• 	break;
  

• default:
  

• 	EFI_PRINT("Unsupported algorithm %x\n", hash_alg);
  

• 	return EFI_INVALID_PARAMETER;
  

• }
  

• digest_list->digests[i].hash_alg = hash_alg;
  

• memcpy(&digest_list->digests[i].digest, hash, (u32)alg_to_len(hash_alg));
  

• }

+out:

• free(new_efi);
• free(regs);
• return ret;

+}

+efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,

• 		   struct efi_loaded_image_obj *handle,
  

• 		   struct efi_loaded_image *loaded_image)
  

+{

• struct tpml_digest_values digest_list;
• efi_status_t ret;
• struct udevice *dev;
• u32 pcr_index, event_type, event_size;
• struct uefi_image_load_event *image_load_event;
• u8 *event;

The variable event is not needed. You can use image_load_event directly.

• struct efi_device_path *device_path;
• u32 device_path_length;
• IMAGE_DOS_HEADER *dos;
• IMAGE_NT_HEADERS32 *nt;
• ret = platform_get_tpm2_device(&dev);
• if (ret != EFI_SUCCESS)

• return ret;
  

• if (handle->image_type == IMAGE_SUBSYSTEM_EFI_APPLICATION) {

We should measure drivers too. Cf. EV_EFI_BOOT_SERVICES_DRIVER, EV_EFI_RUNTIME_SERVICES_DRIVER.

• pcr_index = 4;
  

• event_type = EV_EFI_BOOT_SERVICES_APPLICATION;
  

• } else {

• return EFI_UNSUPPORTED;
  

• }
• ret = tcg2_hash_pe_image(efi, efi_size, &digest_list);
• if (ret != EFI_SUCCESS)

• return ret;
  

• ret = tcg2_pcr_extend(dev, pcr_index, &digest_list);
• if (ret != EFI_SUCCESS)

• return ret;
  

• loaded_image->system_table->boottime->handle_protocol(&handle->header,

• 			&efi_guid_loaded_image_device_path,
  

• 			(void **)&device_path);
  

You would have to use EFI_CALL() here.

Please, use efi_search_protocol() instead of all this indirection.

Best regards

Heinrich

• device_path_length = efi_dp_size(device_path);
• if (device_path_length > 0) {

• /* add end node size */
  

• device_path_length += sizeof(struct efi_device_path);
  

• }
• event_size = sizeof(struct uefi_image_load_event) + device_path_length;
• event = malloc(event_size);
• if (!event)

• return EFI_OUT_OF_RESOURCES;
  

• image_load_event = (struct uefi_image_load_event *)event;
• image_load_event->image_location_in_memory = (efi_physical_addr_t)efi;
• image_load_event->image_length_in_memory = efi_size;
• image_load_event->length_of_device_path = device_path_length;
• dos = (IMAGE_DOS_HEADER *)efi;
• nt = (IMAGE_NT_HEADERS32 *)(efi + dos->e_lfanew);
• if (nt->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR64_MAGIC) {

• IMAGE_NT_HEADERS64 *nt64 = (IMAGE_NT_HEADERS64 *)nt;
  

• image_load_event->image_link_time_address =
  

• 		nt64->OptionalHeader.ImageBase;
  

• } else if (nt->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR32_MAGIC) {

• image_load_event->image_link_time_address =
  

• 		nt->OptionalHeader.ImageBase;
  

• } else {

• ret = EFI_INVALID_PARAMETER;
  

• goto out;
  

• }
• if (device_path_length > 0) {

• memcpy(image_load_event->device_path, device_path,
  

•        device_path_length);
  

• }
• ret = tcg2_agile_log_append(pcr_index, event_type, &digest_list,

• 		    event_size, event);
  

+out:

• free(event);
• return ret;

+}

• /**
  • efi_tcg2_hash_log_extend_event() - extend and optionally log events

@@ -761,24 +929,23 @@ efi_tcg2_hash_log_extend_event(struct efi_tcg2_protocol *this, u64 flags, /* * if PE_COFF_IMAGE is set we need to make sure the image is not * corrupted, verify it and hash the PE/COFF image in accordance with

• * the  procedure  specified  in  "Calculating  the  PE  Image  Hash"
  

• * section  of the "Windows Authenticode Portable Executable Signature
  

• * the procedure specified in "Calculating the PE Image Hash"
  

• * section of the "Windows Authenticode Portable Executable Signature
  

  • Format"

• * Not supported for now
  

  */ if (flags & PE_COFF_IMAGE) {

• ret = EFI_UNSUPPORTED;
  

• goto out;
  

• ret = tcg2_hash_pe_image((void *)data_to_hash, data_to_hash_len,
  

• 			 &digest_list);
  

• } else {

• ret = tcg2_create_digest((u8 *)data_to_hash, data_to_hash_len,
  

• 			 &digest_list);
  

  }

• if (ret != EFI_SUCCESS)

• goto out;
  
  

  pcr_index = efi_tcg_event->header.pcr_index; event_type = efi_tcg_event->header.event_type;

• ret = tcg2_create_digest((u8 *)data_to_hash, data_to_hash_len,

• 		 &digest_list);
  

• if (ret != EFI_SUCCESS)

• goto out;
  

• ret = tcg2_pcr_extend(dev, pcr_index, &digest_list); if (ret != EFI_SUCCESS) goto out;