0bc9ae395b
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> Signed-off-by: Nayna Jain <nayna@linux.ibm.com> Acked-by: Serge Hallyn <serge@hallyn.com> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
109 lines
2.9 KiB
C
109 lines
2.9 KiB
C
// 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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