Date: Sat, 30 May 1998 02:15:42 +0200 (CEST) From: Andrzej Bialecki <abial@nask.pl> To: freebsd-hackers@FreeBSD.ORG Subject: Signed executables, safe delete etc. Message-ID: <Pine.NEB.3.95.980530015011.17272D-100000@korin.warman.org.pl>
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Hi hackers,
Recently I was thinking about various security-related issues, and came up
with this idea (I'm sure nothing new at all).
What I imagine is e.g. to have kernel and/or init(8) check it's own binary
file against a checksum of some kind (preferably MD5 or SHA) stored
somewhere. If the checksumming fails (i.e. the kernel or init have been
tampered with) it refuses to go on. This checking could go even earlier,
that is in the bootblocks (I know - there is not single byte left
there...), which could require user to enter a password in order to load
the kernel (possibly decrypting previously encrypted part of freebsd
partition).
As for the signed binaries: this could be also a good way to ensure of the
creator, owner etc of the binary, even with his email address and PGP
key... :-) (ok, maybe I'v gone too far).
I'm sure there are many difficult issues to resolve in this idea (such
as: how to manage the keys).
You can wonder what all this is for: it helps to ensure that no element of
the system has been changed without you knowing it. It could be performed
during startup of the system, and/or just before executing each binary (as
far as I understand it, ELF allows to put pretty arbitrary sections into
the binary). Moreover, this helps to ensure that the system won't boot
without proper authorization, and even if someone steals it, it could
refuse to give in (this would require encrypting the disk contents, of
course - that's why I said about bootblocks...).
The second idea is to add new flag and functionality to FFS: purge on
delete. If this flag is set, kernel would wipe out the contents of the
file which is being deleted, using special patterns (3-7 times). This
would ensure that if you delete the sensitive data, they are really
deleted and unrecoverable.
So, my question is: is this something worth pursuing? Has anyone seen
something similar? etc, etc...
Andrzej Bialecki
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abial@nask.pl | if(halt_per_mth > 0) { fetch("http://www.freebsd.org") }
Research & Academic | "Be open-minded, but don't let your brains to fall out."
Network in Poland | All of the above (and more) is just my personal opinion.
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