Path: utzoo!attcan!uunet!portal!cup.portal.com!David_W_Tamkin
From: David_W_Tamkin@cup.portal.com
Newsgroups: comp.sys.cbm
Subject: Protecting Sectors from Validation
Message-ID: <10761@cup.portal.com>
Date: 2 Nov 88 01:28:18 GMT
Organization: The Portal System (TM)
Lines: 18

If you have allocated sectors on a disk outside a file (typically the boot
sector[s] of a disk intended to be used with a 128), validating the disk
frees them again and leaves them vulnerable to overwriting.

In the 1581 format one can protect them by partitioning them off.

If one points a dummy file to a boot sector, its first two bytes provide an
invalid link ($43, $42) and make the validation abort in midstream, making
things even worse.

I had the idea that perhaps relative files were validated by reading the
list of blocks named in the side sectors as a more efficient way than going
through all the links in the chain of data sectors.  If one tampered with the
side sector[s] to name the boot sectors instead, perhaps that would protect
the boot sector[s] from being de-allocated during validation.

Well, it didn't work.  In validating a relative file, the 1571 goes down the
chain of side sectors and the chain of data sectors.  So did my MSD-2.