grub2/0003-cryptodisk-wipe-out-the-cached-keys-from-protectors.patch

From 370e435b6ada53314888f04dcd8f096fc11cfadb Mon Sep 17 00:00:00 2001
From: Gary Lin <glin@suse.com>
Date: Thu, 3 Aug 2023 15:52:52 +0800
Subject: [PATCH 3/4] cryptodisk: wipe out the cached keys from protectors

An attacker may insert a malicious disk with the same crypto UUID and
trick grub2 to mount the fake root. Even though the key from the key
protector fails to unlock the fake root, it's not wiped out cleanly so
the attacker could dump the memory to retrieve the secret key. To defend
such attack, wipe out the cached key when we don't need it.

Cc: Fabian Vogt <fvogt@suse.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
---
 grub-core/disk/cryptodisk.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
index f9842f776..aa0d43562 100644
--- a/grub-core/disk/cryptodisk.c
+++ b/grub-core/disk/cryptodisk.c
@@ -1355,7 +1355,11 @@ grub_cryptodisk_clear_key_cache (struct grub_cryptomount_args *cargs)
     return;
 
   for (i = 0; cargs->protectors[i]; i++)
-    grub_free (cargs->key_cache[i].key);
+    {
+      if (cargs->key_cache[i].key)
+	grub_memset (cargs->key_cache[i].key, 0, cargs->key_cache[i].key_len);
+      grub_free (cargs->key_cache[i].key);
+    }
 
   grub_free (cargs->key_cache);
 }
-- 
2.35.3