buildroot/boot/grub2/0002-grub-mkconfig-Restore-umask-for-the-grub.cfg.patch

From 4c1ad500e73d46c83dec369da85db39ae2fe62dd Mon Sep 17 00:00:00 2001
From: Michael Chang <mchang@suse.com>
Date: Fri, 3 Dec 2021 16:13:28 +0800
Subject: [PATCH] grub-mkconfig: Restore umask for the grub.cfg

The commit ab2e53c8a (grub-mkconfig: Honor a symlink when generating
configuration by grub-mkconfig) has inadvertently discarded umask for
creating grub.cfg in the process of running grub-mkconfig. The resulting
wrong permission (0644) would allow unprivileged users to read GRUB
configuration file content. This presents a low confidentiality risk
as grub.cfg may contain non-secured plain-text passwords.

This patch restores the missing umask and sets the creation file mode
to 0600 preventing unprivileged access.

Fixes: CVE-2021-3981

Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Upstream: https://git.savannah.gnu.org/gitweb/?p=grub.git;a=commit;h=0adec29674561034771c13e446069b41ef41e4d4
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
---
 util/grub-mkconfig.in | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/util/grub-mkconfig.in b/util/grub-mkconfig.in
index f8cbb8d7a..84f356ea4 100644
--- a/util/grub-mkconfig.in
+++ b/util/grub-mkconfig.in
@@ -300,7 +300,10 @@ and /etc/grub.d/* files or please file a bug report with
     exit 1
   else
     # none of the children aborted with error, install the new grub.cfg
+    oldumask=$(umask)
+    umask 077
     cat ${grub_cfg}.new > ${grub_cfg}
+    umask $oldumask
     rm -f ${grub_cfg}.new
   fi
 fi
-- 
2.41.0