| From e4c62c12635a371e43bd17e8d33a936668264491 Mon Sep 17 00:00:00 2001 |
| From: Dave Howells <dhowells@redhat.com> |
| Date: Fri, 5 May 2017 08:21:58 +0100 |
| Subject: [PATCH 2/4] efi: Add an EFI signature blob parser |
| |
| Add a function to parse an EFI signature blob 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 function pointed to by the |
| get_handler_for_guid argument 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. |
| |
| Signed-off-by: David Howells <dhowells@redhat.com> |
| |
| certs/Kconfig | 8 ++++ |
| certs/Makefile | 1 + |
| certs/efi_parser.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| include/linux/efi.h | 9 +++++ |
| 4 files changed, 130 insertions(+) |
| create mode 100644 certs/efi_parser.c |
| |
| diff --git a/certs/Kconfig b/certs/Kconfig |
| index 6ce51ed..630ae09 100644 |
| |
| |
| @@ -82,4 +82,12 @@ config SYSTEM_BLACKLIST_HASH_LIST |
| wrapper to incorporate the list into the kernel. Each <hash> should |
| be a string of hex digits. |
| |
| +config EFI_SIGNATURE_LIST_PARSER |
| + bool "EFI signature list parser" |
| + depends on EFI |
| + select X509_CERTIFICATE_PARSER |
| + help |
| + This option provides support for parsing EFI signature lists for |
| + X.509 certificates and turning them into keys. |
| + |
| endmenu |
| diff --git a/certs/Makefile b/certs/Makefile |
| index 4119bb3..738151a 100644 |
| |
| |
| @@ -9,6 +9,7 @@ obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_hashes.o |
| else |
| obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_nohashes.o |
| endif |
| +obj-$(CONFIG_EFI_SIGNATURE_LIST_PARSER) += efi_parser.o |
| |
| ifeq ($(CONFIG_SYSTEM_TRUSTED_KEYRING),y) |
| |
| diff --git a/certs/efi_parser.c b/certs/efi_parser.c |
| new file mode 100644 |
| index 0000000..4e396f9 |
| |
| |
| @@ -0,0 +1,112 @@ |
| +/* EFI signature/key/certificate list parser |
| + * |
| + * Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved. |
| + * Written by David Howells (dhowells@redhat.com) |
| + * |
| + * This program is free software; you can redistribute it and/or |
| + * modify it under the terms of the GNU General Public Licence |
| + * as published by the Free Software Foundation; either version |
| + * 2 of the Licence, or (at your option) any later version. |
| + */ |
| + |
| +#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 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; |
| +} |
| diff --git a/include/linux/efi.h b/include/linux/efi.h |
| index 3259ad6..08024c6 100644 |
| |
| |
| @@ -1055,6 +1055,15 @@ extern int efi_memattr_apply_permissions(struct mm_struct *mm, |
| 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 |
| -- |
| 2.9.3 |
| |