🚀 go-pugleaf

In article <1992Aug17.175123.3793@hpcvusn.cv.hp.com> mark@hpcvlx.cv.hp.com writes:
>It is true that properly implemented MAC would prevent the use of my
>example.  That does not in any way prevent this from being an example
>of a covert channel, it's simply a covert channel that can be eliminated
>by MAC.  MAC does not define a covert channel.  What defines a covert
>channel is how the data is being transmitted.  It is either overt or
>covert.  An overt channel is a channel that transmits data in a known
>manner as intended by the system administrators.  A covert channel is
>anything else.

Given the example you provided, putting something in the mail headers
is not an example of a covert channel.  A mail system which permits the
user to place data anywhere in the mail message (including your
hypothetically concealed header data) must be assumed to be used.  Your
example would make concealing data in nursery rhymes that the system
administrator doesn't understand a "covert channel".

The definition which I have always used for "covert channel" is the one
straight out of the Orange Book - "covert channel - A communications
channel that allows a process to transfer information in a manner that
violates the system's security policy."  If you are permitted to change
the mail headers, doing so cannot violate the system's security policy.
-- 
John F. Haugh II                   | Life's Little Instruction Book:
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