cryptodisk: Wipe out the cached keys from protectors

An attacker may insert a malicious disk with the same crypto UUID and
trick GRUB 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>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>

diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
index 4219f1fb68b1d4573b142779cf7f4ca3138693b5..5fc41979eb9b0449eccf33d57f4c4ac64762c048 100644 (file)
--- a/grub-core/disk/cryptodisk.c
+++ b/grub-core/disk/cryptodisk.c
@@ -1405,7 +1405,11 @@ 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);
 }