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// 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;
}
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