efi: Add an EFI signature blob parser

char * __init efi_md_typeattr_format(char *buf, size_t size,

				     const efi_memory_desc_t *md);

typedef void (*efi_element_handler_t)(const char *source,

				      const void *element_data,

				      size_t element_size);

extern int __init parse_efi_signature_list(

	const char *source,

	const void *data, size_t size,

	efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *));

/**

 * efi_range_is_wc - check the WC bit on an address range

 * @start: starting kvirt address

integrity-$(CONFIG_INTEGRITY_AUDIT) += integrity_audit.o

integrity-$(CONFIG_INTEGRITY_SIGNATURE) += digsig.o

integrity-$(CONFIG_INTEGRITY_ASYMMETRIC_KEYS) += digsig_asymmetric.o

integrity-$(CONFIG_INTEGRITY_PLATFORM_KEYRING) += platform_certs/platform_keyring.o

integrity-$(CONFIG_INTEGRITY_PLATFORM_KEYRING) += platform_certs/platform_keyring.o \

						  platform_certs/efi_parser.o

subdir-$(CONFIG_IMA)			+= ima

obj-$(CONFIG_IMA)			+= ima/

// SPDX-License-Identifier: GPL-2.0+

/* EFI signature/key/certificate list parser

 *

 * Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved.

 * Written by David Howells (dhowells@redhat.com)

 */

#define pr_fmt(fmt) "EFI: "fmt

#include <linux/module.h>

#include <linux/printk.h>

#include <linux/err.h>

#include <linux/efi.h>

/**

 * parse_efi_signature_list - Parse an EFI signature list for certificates

 * @source: The source of the key

 * @data: The data blob to parse

 * @size: The size of the data blob

 * @get_handler_for_guid: Get the handler func for the sig type (or NULL)

 *

 * Parse an EFI signature list looking for elements of interest.  A list is

 * made up of a series of sublists, where all the elements in a sublist are of

 * the same type, but sublists can be of different types.

 *

 * For each sublist encountered, the @get_handler_for_guid function is called

 * with the type specifier GUID and returns either a pointer to a function to

 * handle elements of that type or NULL if the type is not of interest.

 *

 * If the sublist is of interest, each element is passed to the handler

 * function in turn.

 *

 * Error EBADMSG is returned if the list doesn't parse correctly and 0 is

 * returned if the list was parsed correctly.  No error can be returned from

 * the @get_handler_for_guid function or the element handler function it

 * returns.

 */

int __init parse_efi_signature_list(

	const char *source,

	const void *data, size_t size,

	efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *))

{

	efi_element_handler_t handler;

	unsigned int offs = 0;

	pr_devel("-->%s(,%zu)\n", __func__, size);

	while (size > 0) {

		const efi_signature_data_t *elem;

		efi_signature_list_t list;

		size_t lsize, esize, hsize, elsize;

		if (size < sizeof(list))

			return -EBADMSG;

		memcpy(&list, data, sizeof(list));

		pr_devel("LIST[%04x] guid=%pUl ls=%x hs=%x ss=%x\n",

			 offs,

			 list.signature_type.b, list.signature_list_size,

			 list.signature_header_size, list.signature_size);

		lsize = list.signature_list_size;

		hsize = list.signature_header_size;

		esize = list.signature_size;

		elsize = lsize - sizeof(list) - hsize;

		if (lsize > size) {

			pr_devel("<--%s() = -EBADMSG [overrun @%x]\n",

				 __func__, offs);

			return -EBADMSG;

		}

		if (lsize < sizeof(list) ||

		    lsize - sizeof(list) < hsize ||

		    esize < sizeof(*elem) ||

		    elsize < esize ||

		    elsize % esize != 0) {

			pr_devel("- bad size combo @%x\n", offs);

			return -EBADMSG;

		}

		handler = get_handler_for_guid(&list.signature_type);

		if (!handler) {

			data += lsize;

			size -= lsize;

			offs += lsize;

			continue;

		}

		data += sizeof(list) + hsize;

		size -= sizeof(list) + hsize;

		offs += sizeof(list) + hsize;

		for (; elsize > 0; elsize -= esize) {

			elem = data;

			pr_devel("ELEM[%04x]\n", offs);

			handler(source,

				&elem->signature_data,

				esize - sizeof(*elem));

			data += esize;

			size -= esize;

			offs += esize;

		}

	}

	return 0;

}