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/module.h>
   7 #include <linux/ima.h>
   8
   9 extern struct boot_params boot_params;
  10
  11 static enum efi_secureboot_mode get_sb_mode(void)
  12 {
  13         efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
  14         efi_status_t status;
  15         unsigned long size;
  16         u8 secboot, setupmode;
  17
  18         size = sizeof(secboot);
  19
  20         if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) {
  21                 pr_info("ima: secureboot mode unknown, no efi\n");
  22                 return efi_secureboot_mode_unknown;
  23         }
  24
  25         /* Get variable contents into buffer */
  26         status = efi.get_variable(L"SecureBoot", &efi_variable_guid,
  27                                   NULL, &size, &secboot);
  28         if (status == EFI_NOT_FOUND) {
  29                 pr_info("ima: secureboot mode disabled\n");
  30                 return efi_secureboot_mode_disabled;
  31         }
  32
  33         if (status != EFI_SUCCESS) {
  34                 pr_info("ima: secureboot mode unknown\n");
  35                 return efi_secureboot_mode_unknown;
  36         }
  37
  38         size = sizeof(setupmode);
  39         status = efi.get_variable(L"SetupMode", &efi_variable_guid,
  40                                   NULL, &size, &setupmode);
  41
  42         if (status != EFI_SUCCESS)      /* ignore unknown SetupMode */
  43                 setupmode = 0;
  44
  45         if (secboot == 0 || setupmode == 1) {
  46                 pr_info("ima: secureboot mode disabled\n");
  47                 return efi_secureboot_mode_disabled;
  48         }
  49
  50         pr_info("ima: secureboot mode enabled\n");
  51         return efi_secureboot_mode_enabled;
  52 }
  53
  54 bool arch_ima_get_secureboot(void)
  55 {
  56         static enum efi_secureboot_mode sb_mode;
  57         static bool initialized;
  58
  59         if (!initialized && efi_enabled(EFI_BOOT)) {
  60                 sb_mode = boot_params.secure_boot;
  61
  62                 if (sb_mode == efi_secureboot_mode_unset)
  63                         sb_mode = get_sb_mode();
  64                 initialized = true;
  65         }
  66
  67         if (sb_mode == efi_secureboot_mode_enabled)
  68                 return true;
  69         else
  70                 return false;
  71 }
  72
  73 /* secureboot arch rules */
  74 static const char * const sb_arch_rules[] = {
  75 #if !IS_ENABLED(CONFIG_KEXEC_SIG)
  76         "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig",
  77 #endif /* CONFIG_KEXEC_SIG */
  78         "measure func=KEXEC_KERNEL_CHECK",
  79 #if !IS_ENABLED(CONFIG_MODULE_SIG)
  80         "appraise func=MODULE_CHECK appraise_type=imasig",
  81 #endif
  82         "measure func=MODULE_CHECK",
  83         NULL
  84 };
  85
  86 const char * const *arch_get_ima_policy(void)
  87 {
  88         if (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot()) {
  89                 if (IS_ENABLED(CONFIG_MODULE_SIG))
  90                         set_module_sig_enforced();
  91                 return sb_arch_rules;
  92         }
  93         return NULL;
  94 }