Hello, I tried to get an overview of how the permissions of a piece of code are calculated. I enhanced the common equation for the grant set of an assembly to take the permissions of the application domain in account. I'm also providing some pseudo code to illustrate what a stackwalk does. It should be a logical view of what is happening while walking over the stack.
Did I overlook something? I'm looking forward to your comments or suggestions.
************************************** ************************************** Naming conventions for the permission sets: MAX: permissions maximum allowed by the policy MIN: permissions the assembly requires for its operation OPT: permissions the assembly would like to have, but are not necessary REF: permissions that should not be granted to the assembly DOM: permissions granted to the application domain GRANT: granted permission set (result)
Equation (in case of an unmodified stackwalk): GRANT = ((MAX INTERSECT (MIN U OPT)) - REF) INTERSECT DOM
**************************************
Pseudo code for illustration of the stackwalk:
FUNCTION walk: (stack, permissionset) -> (stack, permissionset)
DEFINITION walk (stack, demandset) ==
grant = (MAX INTERSECT (MIN U OPT)) - REF
permset = applyModifications(demandset)
IF permset SUBSETOF grant
IF permset SUBSETOF DOM
walk(POP(stack), permset)
ELSE
throw(SecurityException "Denied by AppDomain")
FI
ELSE
throw(SecurityException "Denied by Assembly or Policy")
FI
The function "applyModifications" applies the stackwalk modifications to the demanded permissionset. If a denied permission is demanded for example the stackwalk is stopped immediatly and exception is thrown. Assertions remove permissions from the demand set. ************************************** **************************************
Thank you in advance!
Regards, Philipp Henkel
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