Commit f046fff8 authored by Ilias Apalodimas's avatar Ilias Apalodimas Committed by Ard Biesheuvel
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efi/libstub: measure loaded initrd info into the TPM 



In an effort to ensure the initrd observed and used by the OS is
the same one that was meant to be loaded, which is difficult to
guarantee otherwise, let's measure the initrd if the EFI stub and
specifically the newly introduced LOAD_FILE2 protocol was used.

Modify the initrd loading sequence so that the contents of the initrd
are measured into PCR9.  Note that the patch is currently using
EV_EVENT_TAG to create the eventlog entry instead of EV_IPL.  According
to the TCP PC Client specification this is used for PCRs defined for OS
and application usage.

Co-developed-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarIlias Apalodimas <ilias.apalodimas@linaro.org>
Link: https://lore.kernel.org/r/20211119114745.1560453-5-ilias.apalodimas@linaro.org
[ardb: add braces to initializer of tagged_event_data]
Link: https://github.com/ClangBuiltLinux/linux/issues/1547


Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
parent 20287d56

drivers/firmware/efi/libstub/efi-stub-helper.c

+58 −14
Original line number Diff line number Diff line
@@ -625,6 +625,47 @@ efi_status_t efi_load_initrd_cmdline(efi_loaded_image_t *image, 
				    load_addr, load_size);

}



static const struct {

	efi_tcg2_event_t	event_data;

	efi_tcg2_tagged_event_t tagged_event;

	u8			tagged_event_data[];

} initrd_tcg2_event = {

	{

		sizeof(initrd_tcg2_event) + sizeof("Linux initrd"),

		{

			sizeof(initrd_tcg2_event.event_data.event_header),

			EFI_TCG2_EVENT_HEADER_VERSION,

			9,

			EV_EVENT_TAG,

		},

	},

	{

		INITRD_EVENT_TAG_ID,

		sizeof("Linux initrd"),

	},

	{ "Linux initrd" },

};



static void efi_measure_initrd(unsigned long load_addr, unsigned long load_size)

{

	efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;

	efi_tcg2_protocol_t *tcg2 = NULL;

	efi_status_t status;



	efi_bs_call(locate_protocol, &tcg2_guid, NULL, (void **)&tcg2);

	if (tcg2) {

		status = efi_call_proto(tcg2, hash_log_extend_event,

					0, load_addr, load_size,

					&initrd_tcg2_event.event_data);

		if (status != EFI_SUCCESS)

			efi_warn("Failed to measure initrd data: 0x%lx\n",

				 status);

		else

			efi_info("Measured initrd data into PCR %d\n",

				 initrd_tcg2_event.event_data.event_header.pcr_index);

	}

}



/**

 * efi_load_initrd() - Load initial RAM disk

 * @image:	EFI loaded image protocol
@@ -645,12 +686,13 @@ efi_status_t efi_load_initrd(efi_loaded_image_t *image, 


	if (efi_noinitrd) {

		*load_addr = *load_size = 0;

		return EFI_SUCCESS;

	}



		status = EFI_SUCCESS;

	} else {

		status = efi_load_initrd_dev_path(load_addr, load_size, hard_limit);

		if (status == EFI_SUCCESS) {

			efi_info("Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID device path\n");

			if (*load_size > 0)

				efi_measure_initrd(*load_addr, *load_size);

		} else if (status == EFI_NOT_FOUND) {

			status = efi_load_initrd_cmdline(image, load_addr, load_size,

							 soft_limit, hard_limit);
@@ -661,6 +703,8 @@ efi_status_t efi_load_initrd(efi_loaded_image_t *image, 
			efi_err("Failed to load initrd: 0x%lx\n", status);

			*load_addr = *load_size = 0;

		}

	}



	return status;

}