Casey Schaufler wrote:
<snip>
Smack provides mandatory access controls based on the label attached
to a task and the label attached to the object it is attempting to
access. Smack labels are deliberately short (1-7 characters) text
strings. Single character labels using special characters are reserved
for system use. The only operation applied to Smack labels is equality
comparison. No wildcards or expressions, regular or otherwise, are
used.

A file always gets the Smack label of the task that created it.

Smack defines and uses these labels:

    "*" - pronounced "star"
    "_" - pronounced "floor"
    "^" - pronounced "hat"
    "?" - pronounced "huh"

The access rules enforced by Smack are, in order:

1. Any access requested by a task labeled "*" is denied.
2. A read or execute access requested by a task labeled "^"
   is permitted.
3. A read or execute access requested on an object labeled "_"
   is permitted.
4. Any access requested on an object labeled "*" is permitted.
5. Any access requested by a task on an object with the same
   label is permitted.
6. Any access requested that is explicitly defined in the loaded
   rule set is permitted.
7. Any other access is denied.

Rules may be explicitly defined by writing subject,object,access
triples to /smack/load.

Smack rule sets can be easily defined that describe Bell&LaPadula
sensitivity, Biba integrity, and a variety of interesting
configurations. Smack rule sets can be modified on the fly to
accomodate changes in the operating environment or even the time
of day.


How exactly can you describe a blp policy with this module? How do you define dominance relationships between levels and over categories without a very complex policy?

My main concern is that I don't see any real security goals or use cases that this can address, can you provide some use cases that make this a viable security mechanism?


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