From 8f73052885892bc0dbc01e297f79d7cf4925e491 Mon Sep 17 00:00:00 2001
From: Javier Martinez Canillas <javierm@redhat.com>
Date: Mon, 28 Sep 2020 20:08:33 +0200
Subject: efi: Use grub_is_lockdown() instead of hardcoding a disabled modules
 list

Now the GRUB can check if it has been locked down and this can be used to
prevent executing commands that can be utilized to circumvent the UEFI
Secure Boot mechanisms. So, instead of hardcoding a list of modules that
have to be disabled, prevent the usage of commands that can be dangerous.

This not only allows the commands to be disabled on other platforms, but
also properly separate the concerns. Since the shim_lock verifier logic
should be only about preventing to run untrusted binaries and not about
defining these kind of policies.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 docs/grub.texi                  | 15 +++++++-----
 grub-core/commands/i386/wrmsr.c |  5 ++--
 grub-core/commands/iorw.c       | 19 +++++++--------
 grub-core/commands/memrw.c      | 19 +++++++--------
 4 files changed, 32 insertions(+), 67 deletions(-)

diff --git a/grub-core/commands/i386/wrmsr.c b/grub-core/commands/i386/wrmsr.c
index 9c5e510eb..56a29c29f 100644
--- a/grub-core/commands/i386/wrmsr.c
+++ b/grub-core/commands/i386/wrmsr.c
@@ -24,6 +24,7 @@
 #include <grub/env.h>
 #include <grub/command.h>
 #include <grub/extcmd.h>
+#include <grub/lockdown.h>
 #include <grub/i18n.h>
 #include <grub/i386/cpuid.h>
 #include <grub/i386/wrmsr.h>
@@ -83,8 +84,8 @@ grub_cmd_msr_write (grub_command_t cmd __attribute__ ((unused)), int argc, char
 
 GRUB_MOD_INIT(wrmsr)
 {
-  cmd_write = grub_register_command ("wrmsr", grub_cmd_msr_write, N_("ADDR VALUE"),
-				     N_("Write a value to a CPU model specific register."));
+  cmd_write = grub_register_command_lockdown ("wrmsr", grub_cmd_msr_write, N_("ADDR VALUE"),
+                                              N_("Write a value to a CPU model specific register."));
 }
 
 GRUB_MOD_FINI(wrmsr)
diff --git a/grub-core/commands/iorw.c b/grub-core/commands/iorw.c
index a0c164e54..584baec8f 100644
--- a/grub-core/commands/iorw.c
+++ b/grub-core/commands/iorw.c
@@ -23,6 +23,7 @@
 #include <grub/cpu/io.h>
 #include <grub/i18n.h>
 #include <grub/efi/sb.h>
+#include <grub/lockdown.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -131,17 +132,17 @@ GRUB_MOD_INIT(memrw)
 			  N_("PORT"), N_("Read 32-bit value from PORT."),
 			  options);
   cmd_write_byte =
-    grub_register_command ("outb", grub_cmd_write,
-			   N_("PORT VALUE [MASK]"),
-			   N_("Write 8-bit VALUE to PORT."));
+    grub_register_command_lockdown ("outb", grub_cmd_write,
+                                    N_("PORT VALUE [MASK]"),
+                                    N_("Write 8-bit VALUE to PORT."));
   cmd_write_word =
-    grub_register_command ("outw", grub_cmd_write,
-			   N_("PORT VALUE [MASK]"),
-			   N_("Write 16-bit VALUE to PORT."));
+    grub_register_command_lockdown ("outw", grub_cmd_write,
+                                    N_("PORT VALUE [MASK]"),
+                                    N_("Write 16-bit VALUE to PORT."));
   cmd_write_dword =
-    grub_register_command ("outl", grub_cmd_write,
-			   N_("ADDR VALUE [MASK]"),
-			   N_("Write 32-bit VALUE to PORT."));
+    grub_register_command_lockdown ("outl", grub_cmd_write,
+                                    N_("ADDR VALUE [MASK]"),
+                                    N_("Write 32-bit VALUE to PORT."));
 }
 
 GRUB_MOD_FINI(memrw)
diff --git a/grub-core/commands/memrw.c b/grub-core/commands/memrw.c
index 98769eadb..d401a6db0 100644
--- a/grub-core/commands/memrw.c
+++ b/grub-core/commands/memrw.c
@@ -22,6 +22,7 @@
 #include <grub/env.h>
 #include <grub/i18n.h>
 #include <grub/efi/sb.h>
+#include <grub/lockdown.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -133,17 +134,17 @@ GRUB_MOD_INIT(memrw)
 			  N_("ADDR"), N_("Read 32-bit value from ADDR."),
 			  options);
   cmd_write_byte =
-    grub_register_command ("write_byte", grub_cmd_write,
-			   N_("ADDR VALUE [MASK]"),
-			   N_("Write 8-bit VALUE to ADDR."));
+    grub_register_command_lockdown ("write_byte", grub_cmd_write,
+                                    N_("ADDR VALUE [MASK]"),
+                                    N_("Write 8-bit VALUE to ADDR."));
   cmd_write_word =
-    grub_register_command ("write_word", grub_cmd_write,
-			   N_("ADDR VALUE [MASK]"),
-			   N_("Write 16-bit VALUE to ADDR."));
+    grub_register_command_lockdown ("write_word", grub_cmd_write,
+                                    N_("ADDR VALUE [MASK]"),
+                                    N_("Write 16-bit VALUE to ADDR."));
   cmd_write_dword =
-    grub_register_command ("write_dword", grub_cmd_write,
-			   N_("ADDR VALUE [MASK]"),
-			   N_("Write 32-bit VALUE to ADDR."));
+    grub_register_command_lockdown ("write_dword", grub_cmd_write,
+                                    N_("ADDR VALUE [MASK]"),
+                                    N_("Write 32-bit VALUE to ADDR."));
 }
 
 GRUB_MOD_FINI(memrw)
-- 
2.23.0

