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_char16_t efi_SecureBoot_name[] = L"SecureBoot";
  14         efi_char16_t efi_SetupMode_name[] = L"SecureBoot";
  15         efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
  16         efi_status_t status;
  17         unsigned long size;
  18         u8 secboot, setupmode;
  19
  20         size = sizeof(secboot);
  21
  22         if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
  23                 pr_info("ima: secureboot mode unknown, no efi\n");
  24                 return efi_secureboot_mode_unknown;
  25         }
  26
  27         /* Get variable contents into buffer */
  28         status = efi.get_variable(efi_SecureBoot_name, &efi_variable_guid,
  29                                   NULL, &size, &secboot);
  30         if (status == EFI_NOT_FOUND) {
  31                 pr_info("ima: secureboot mode disabled\n");
  32                 return efi_secureboot_mode_disabled;
  33         }
  34
  35         if (status != EFI_SUCCESS) {
  36                 pr_info("ima: secureboot mode unknown\n");
  37                 return efi_secureboot_mode_unknown;
  38         }
  39
  40         size = sizeof(setupmode);
  41         status = efi.get_variable(efi_SetupMode_name, &efi_variable_guid,
  42                                   NULL, &size, &setupmode);
  43
  44         if (status != EFI_SUCCESS)      /* ignore unknown SetupMode */
  45                 setupmode = 0;
  46
  47         if (secboot == 0 || setupmode == 1) {
  48                 pr_info("ima: secureboot mode disabled\n");
  49                 return efi_secureboot_mode_disabled;
  50         }
  51
  52         pr_info("ima: secureboot mode enabled\n");
  53         return efi_secureboot_mode_enabled;
  54 }
  55
  56 bool arch_ima_get_secureboot(void)
  57 {
  58         static enum efi_secureboot_mode sb_mode;
  59         static bool initialized;
  60
  61         if (!initialized && efi_enabled(EFI_BOOT)) {
  62                 sb_mode = boot_params.secure_boot;
  63
  64                 if (sb_mode == efi_secureboot_mode_unset)
  65                         sb_mode = get_sb_mode();
  66                 initialized = true;
  67         }
  68
  69         if (sb_mode == efi_secureboot_mode_enabled)
  70                 return true;
  71         else
  72                 return false;
  73 }
  74
  75 /* secureboot arch rules */
  76 static const char * const sb_arch_rules[] = {
  77 #if !IS_ENABLED(CONFIG_KEXEC_SIG)
  78         "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig",
  79 #endif /* CONFIG_KEXEC_SIG */
  80         "measure func=KEXEC_KERNEL_CHECK",
  81 #if !IS_ENABLED(CONFIG_MODULE_SIG)
  82         "appraise func=MODULE_CHECK appraise_type=imasig",
  83 #endif
  84         "measure func=MODULE_CHECK",
  85         NULL
  86 };
  87
  88 const char * const *arch_get_ima_policy(void)
  89 {
  90         if (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot()) {
  91                 if (IS_ENABLED(CONFIG_MODULE_SIG))
  92                         set_module_sig_enforced();
  93                 return sb_arch_rules;
  94         }
  95         return NULL;
  96 }