arch/x86/kernel/ima_arch.c

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * Copyright (C) 2018 IBM Corporation
   4  */
   5 #include <linux/efi.h>
   6 #include <linux/ima.h>
   7
   8 extern struct boot_params boot_params;
   9
  10 static enum efi_secureboot_mode get_sb_mode(void)
  11 {
  12         efi_char16_t efi_SecureBoot_name[] = L"SecureBoot";
  13         efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
  14         efi_status_t status;
  15         unsigned long size;
  16         u8 secboot;
  17
  18         size = sizeof(secboot);
  19
  20         /* Get variable contents into buffer */
  21         status = efi.get_variable(efi_SecureBoot_name, &efi_variable_guid,
  22                                   NULL, &size, &secboot);
  23         if (status == EFI_NOT_FOUND) {
  24                 pr_info("ima: secureboot mode disabled\n");
  25                 return efi_secureboot_mode_disabled;
  26         }
  27
  28         if (status != EFI_SUCCESS) {
  29                 pr_info("ima: secureboot mode unknown\n");
  30                 return efi_secureboot_mode_unknown;
  31         }
  32
  33         if (secboot == 0) {
  34                 pr_info("ima: secureboot mode disabled\n");
  35                 return efi_secureboot_mode_disabled;
  36         }
  37
  38         pr_info("ima: secureboot mode enabled\n");
  39         return efi_secureboot_mode_enabled;
  40 }
  41
  42 bool arch_ima_get_secureboot(void)
  43 {
  44         static enum efi_secureboot_mode sb_mode;
  45         static bool initialized;
  46
  47         if (!initialized && efi_enabled(EFI_BOOT)) {
  48                 sb_mode = boot_params.secure_boot;
  49
  50                 if (sb_mode == efi_secureboot_mode_unset)
  51                         sb_mode = get_sb_mode();
  52                 initialized = true;
  53         }
  54
  55         if (sb_mode == efi_secureboot_mode_enabled)
  56                 return true;
  57         else
  58                 return false;
  59 }
  60
  61 /* secureboot arch rules */
  62 static const char * const sb_arch_rules[] = {
  63 #if !IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG)
  64         "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig",
  65 #endif /* CONFIG_KEXEC_VERIFY_SIG */
  66         "measure func=KEXEC_KERNEL_CHECK",
  67         NULL
  68 };
  69
  70 const char * const *arch_get_ima_policy(void)
  71 {
  72         if (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot())
  73                 return sb_arch_rules;
  74         return NULL;
  75 }