1 // SPDX-License-Identifier: GPL-2.0+
2 /* EFI signature/key/certificate list parser
3  *
4  * Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  */
7 
8 #define pr_fmt(fmt) "EFI: "fmt
9 #include <linux/module.h>
10 #include <linux/printk.h>
11 #include <linux/err.h>
12 #include <linux/efi.h>
13 
14 /**
15  * parse_efi_signature_list - Parse an EFI signature list for certificates
16  * @source: The source of the key
17  * @data: The data blob to parse
18  * @size: The size of the data blob
19  * @get_handler_for_guid: Get the handler func for the sig type (or NULL)
20  *
21  * Parse an EFI signature list looking for elements of interest.  A list is
22  * made up of a series of sublists, where all the elements in a sublist are of
23  * the same type, but sublists can be of different types.
24  *
25  * For each sublist encountered, the @get_handler_for_guid function is called
26  * with the type specifier GUID and returns either a pointer to a function to
27  * handle elements of that type or NULL if the type is not of interest.
28  *
29  * If the sublist is of interest, each element is passed to the handler
30  * function in turn.
31  *
32  * Error EBADMSG is returned if the list doesn't parse correctly and 0 is
33  * returned if the list was parsed correctly.  No error can be returned from
34  * the @get_handler_for_guid function or the element handler function it
35  * returns.
36  */
37 int __init parse_efi_signature_list(
38 	const char *source,
39 	const void *data, size_t size,
40 	efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *))
41 {
42 	efi_element_handler_t handler;
43 	unsigned int offs = 0;
44 
45 	pr_devel("-->%s(,%zu)\n", __func__, size);
46 
47 	while (size > 0) {
48 		const efi_signature_data_t *elem;
49 		efi_signature_list_t list;
50 		size_t lsize, esize, hsize, elsize;
51 
52 		if (size < sizeof(list))
53 			return -EBADMSG;
54 
55 		memcpy(&list, data, sizeof(list));
56 		pr_devel("LIST[%04x] guid=%pUl ls=%x hs=%x ss=%x\n",
57 			 offs,
58 			 &list.signature_type, list.signature_list_size,
59 			 list.signature_header_size, list.signature_size);
60 
61 		lsize = list.signature_list_size;
62 		hsize = list.signature_header_size;
63 		esize = list.signature_size;
64 		elsize = lsize - sizeof(list) - hsize;
65 
66 		if (lsize > size) {
67 			pr_devel("<--%s() = -EBADMSG [overrun @%x]\n",
68 				 __func__, offs);
69 			return -EBADMSG;
70 		}
71 
72 		if (lsize < sizeof(list) ||
73 		    lsize - sizeof(list) < hsize ||
74 		    esize < sizeof(*elem) ||
75 		    elsize < esize ||
76 		    elsize % esize != 0) {
77 			pr_devel("- bad size combo @%x\n", offs);
78 			return -EBADMSG;
79 		}
80 
81 		handler = get_handler_for_guid(&list.signature_type);
82 		if (!handler) {
83 			data += lsize;
84 			size -= lsize;
85 			offs += lsize;
86 			continue;
87 		}
88 
89 		data += sizeof(list) + hsize;
90 		size -= sizeof(list) + hsize;
91 		offs += sizeof(list) + hsize;
92 
93 		for (; elsize > 0; elsize -= esize) {
94 			elem = data;
95 
96 			pr_devel("ELEM[%04x]\n", offs);
97 			handler(source,
98 				&elem->signature_data,
99 				esize - sizeof(*elem));
100 
101 			data += esize;
102 			size -= esize;
103 			offs += esize;
104 		}
105 	}
106 
107 	return 0;
108 }
109