// SPDX-License-Identifier: GPL-2.0+
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/* EFI signature/key/certificate list parser
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*
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* Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#define pr_fmt(fmt) "EFI: "fmt
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#include <linux/module.h>
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#include <linux/printk.h>
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#include <linux/err.h>
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#include <linux/efi.h>
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/**
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* parse_efi_signature_list - Parse an EFI signature list for certificates
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* @source: The source of the key
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* @data: The data blob to parse
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* @size: The size of the data blob
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* @get_handler_for_guid: Get the handler func for the sig type (or NULL)
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*
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* Parse an EFI signature list looking for elements of interest. A list is
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* made up of a series of sublists, where all the elements in a sublist are of
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* the same type, but sublists can be of different types.
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*
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* For each sublist encountered, the @get_handler_for_guid function is called
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* with the type specifier GUID and returns either a pointer to a function to
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* handle elements of that type or NULL if the type is not of interest.
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*
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* If the sublist is of interest, each element is passed to the handler
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* function in turn.
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*
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* Error EBADMSG is returned if the list doesn't parse correctly and 0 is
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* returned if the list was parsed correctly. No error can be returned from
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* the @get_handler_for_guid function or the element handler function it
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* returns.
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*/
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int __init parse_efi_signature_list(
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const char *source,
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const void *data, size_t size,
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efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *))
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{
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efi_element_handler_t handler;
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unsigned int offs = 0;
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pr_devel("-->%s(,%zu)\n", __func__, size);
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while (size > 0) {
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const efi_signature_data_t *elem;
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efi_signature_list_t list;
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size_t lsize, esize, hsize, elsize;
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if (size < sizeof(list))
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return -EBADMSG;
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memcpy(&list, data, sizeof(list));
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pr_devel("LIST[%04x] guid=%pUl ls=%x hs=%x ss=%x\n",
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offs,
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list.signature_type.b, list.signature_list_size,
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list.signature_header_size, list.signature_size);
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lsize = list.signature_list_size;
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hsize = list.signature_header_size;
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esize = list.signature_size;
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elsize = lsize - sizeof(list) - hsize;
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if (lsize > size) {
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pr_devel("<--%s() = -EBADMSG [overrun @%x]\n",
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__func__, offs);
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return -EBADMSG;
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}
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if (lsize < sizeof(list) ||
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lsize - sizeof(list) < hsize ||
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esize < sizeof(*elem) ||
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elsize < esize ||
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elsize % esize != 0) {
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pr_devel("- bad size combo @%x\n", offs);
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return -EBADMSG;
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}
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handler = get_handler_for_guid(&list.signature_type);
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if (!handler) {
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data += lsize;
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size -= lsize;
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offs += lsize;
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continue;
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}
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data += sizeof(list) + hsize;
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size -= sizeof(list) + hsize;
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offs += sizeof(list) + hsize;
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for (; elsize > 0; elsize -= esize) {
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elem = data;
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pr_devel("ELEM[%04x]\n", offs);
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handler(source,
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&elem->signature_data,
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esize - sizeof(*elem));
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data += esize;
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size -= esize;
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offs += esize;
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}
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}
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return 0;
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}
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