[PATCH 2/2] efi_loader: add PE/COFF image measurement
Heinrich Schuchardt
xypron.glpk at gmx.de
Wed Apr 21 12:57:29 CEST 2021
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 at 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, ®s, &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;
>
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