From 7e3bac9f015f6730e9e4be635269bd0f8cfe80e6 Mon Sep 17 00:00:00 2001
From: Gary Lin <[email protected]>
Date: Thu, 3 Aug 2023 15:52:52 +0800
Subject: [PATCH 163/272] 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.

Signed-off-by: Gary Lin <[email protected]>
---
 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 84da399b8..184efe425 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);
 }
-- 
2.41.0