From 0adec29674561034771c13e446069b41ef41e4d4 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>

---

 util/grub-mkconfig.in | 3 +++

 1 file changed, 3 insertions(+)

diff --git a/util/grub-mkconfig.in b/util/grub-mkconfig.in

index c3ea7612e..62335d027 100644

--- a/util/grub-mkconfig.in

+++ b/util/grub-mkconfig.in

@@ -301,7 +301,10 @@ 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

-- 

2.33.0