security/integrity/platform_certs/efi_parser.c

   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.b, 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 }