From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Jan Hlavac <jhlavac@redhat.com>

Date: Fri, 20 Nov 2020 23:51:47 +0100

Subject: [PATCH] grub-install: disable support for EFI platforms

For each platform, GRUB is shipped as a kernel image and a set of

modules. These files are then used by the grub-install utility to

install GRUB on a specific device. However, in order to support UEFI

Secure Boot, the resulting EFI binary must be signed by a recognized

private key. For this reason, for EFI platforms, most distributions also

ship prebuilt EFI binaries signed by a distribution-specific private

key. In this case, however, the grub-install utility should not be used

because it would overwrite the signed EFI binary.

The current fix is suboptimal because it preserves all EFI-related code.

A better solution could be to modularize the code and provide a

build-time option.

Resolves: rhbz#1737444

Signed-off-by: Jan Hlavac <jhlavac@redhat.com>

---

 util/grub-install.c | 35 ++++++++++++++++-------------------

 docs/grub.texi      |  7 +++++++

 util/grub-install.8 |  4 +++-

 3 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/util/grub-install.c b/util/grub-install.c

index 3bf0e063a..65bb2f99e 100644

--- a/util/grub-install.c

+++ b/util/grub-install.c

@@ -888,6 +888,22 @@ main (int argc, char *argv[])

   platform = grub_install_get_target (grub_install_source_directory);

+  switch (platform)

+    {

+    case GRUB_INSTALL_PLATFORM_ARM_EFI:

+    case GRUB_INSTALL_PLATFORM_ARM64_EFI:

+    case GRUB_INSTALL_PLATFORM_I386_EFI:

+    case GRUB_INSTALL_PLATFORM_IA64_EFI:

+    case GRUB_INSTALL_PLATFORM_X86_64_EFI:

+      is_efi = 1;

+      grub_util_error (_("this utility cannot be used for EFI platforms"

+                         " because it does not support UEFI Secure Boot"));

+      break;

+    default:

+      is_efi = 0;

+      break;

+    }

+

   {

     char *platname = grub_install_get_platform_name (platform);

     fprintf (stderr, _("Installing for %s platform.\n"), platname);

@@ -994,26 +1010,7 @@ main (int argc, char *argv[])

   grub_hostfs_init ();

   grub_host_init ();

-  switch (platform)

-    {

-    case GRUB_INSTALL_PLATFORM_I386_EFI:

-    case GRUB_INSTALL_PLATFORM_X86_64_EFI:

-    case GRUB_INSTALL_PLATFORM_ARM_EFI:

-    case GRUB_INSTALL_PLATFORM_ARM64_EFI:

-    case GRUB_INSTALL_PLATFORM_IA64_EFI:

-      is_efi = 1;

-      break;

-    default:

-      is_efi = 0;

-      break;

-

-      /* pacify warning.  */

-    case GRUB_INSTALL_PLATFORM_MAX:

-      break;

-    }

-

   /* Find the EFI System Partition.  */

-

   if (is_efi)

     {

       grub_fs_t fs;

diff --git a/docs/grub.texi b/docs/grub.texi

index c54bee316..fa11cc0af 100644

--- a/docs/grub.texi

+++ b/docs/grub.texi

@@ -6185,6 +6185,13 @@ grub2-install @var{install_device}

 The device name @var{install_device} is an OS device name or a GRUB

 device name.

+In order to support UEFI Secure Boot, the resulting GRUB EFI binary must

+be signed by a recognized private key. For this reason, for EFI

+platforms, most distributions also ship prebuilt GRUB EFI binaries

+signed by a distribution-specific private key. In this case, however,

+@command{grub2-install} should not be used because it would overwrite

+the signed EFI binary.

+

 @command{grub2-install} accepts the following options:

 @table @option

diff --git a/util/grub-install.8 b/util/grub-install.8

index 76272a39d..02371930f 100644

--- a/util/grub-install.8

+++ b/util/grub-install.8

@@ -1,4 +1,4 @@

-.TH GRUB-INSTALL 1 "Wed Feb 26 2014"

+.TH GRUB-INSTALL 1 "Fri Nov 20 2020"

 .SH NAME

 \fBgrub-install\fR \(em Install GRUB on a device.

@@ -31,6 +31,8 @@

 .SH DESCRIPTION

 \fBgrub-install\fR installs GRUB onto a device.  This includes copying GRUB images into the target directory (generally \fI/boot/grub\fR), and on some platforms may also include installing GRUB onto a boot sector.

+In order to support UEFI Secure Boot, the resulting GRUB EFI binary must be signed by a recognized private key. For this reason, for EFI platforms, most distributions also ship prebuilt GRUB EFI binaries signed by a distribution-specific private key. In this case, however, the \fBgrub-install\fR utility should not be used because it would overwrite the signed EFI binary.

+

 .SH OPTIONS

 .TP

 \fB--modules\fR=\fIMODULES\fR\!