private static bool FrameDescSetHelper(FrameSecurityDescriptor secDesc,
PermissionSet demandSet,
out PermissionSet alteredDemandSet)
{
PermissionSet permSet;
// In the common case we are not going to alter the demand set, so just to
// be safe we'll set it to null up front.
// There's some oddness in here to deal with exceptions. The general idea behind
// this is that we need some way of dealing with custom permissions that may not
// handle all possible scenarios of Union(), Intersect(), and IsSubsetOf() properly
// (they don't support it, throw null reference exceptions, etc.).
alteredDemandSet = null;
// An empty demand always succeeds.
if (demandSet == null || demandSet.IsEmpty())
{
return(StackHalt);
}
// In the case of permit only, we define an exception to be failure of the check
// and therefore we throw a security exception.
try
{
permSet = secDesc.GetPermitOnly();
if (permSet != null)
{
if (!demandSet.IsSubsetOf(permSet))
{
throw new SecurityException(Environment.GetResourceString("Security_GenericNoType"));
}
}
}
catch (Exception)
{
throw new SecurityException(Environment.GetResourceString("Security_GenericNoType"));
}
// In the case of denial, we define an exception to be failure of the check
// and therefore we throw a security exception.
try
{
permSet = secDesc.GetDenials();
#if _DEBUG
if (debug)
{
DEBUG_OUT("Checking Denials");
DEBUG_OUT("denials set =\n" + permSet.ToXml().ToString());
DEBUG_OUT("demandSet =\n" + demandSet.ToXml().ToString());
}
#endif
if (permSet != null)
{
PermissionSet intersection = demandSet.Intersect(permSet);
if (intersection != null && !intersection.IsEmpty())
{
throw new SecurityException(Environment.GetResourceString("Security_GenericNoType"));
}
}
}
catch (Exception)
{
throw new SecurityException(Environment.GetResourceString("Security_GenericNoType"));
}
// The assert case is more complex. Since asserts have the ability to "bleed through"
// (where part of a demand is handled by an assertion, but the rest is passed on to
// continue the stackwalk), we need to be more careful in handling the "failure" case.
// Therefore, if an exception is thrown in performing any operation, we make sure to keep
// that permission in the demand set thereby continuing the demand for that permission
// walking down the stack.
if (secDesc.GetAssertAllPossible())
{
return(StackHalt);
}
permSet = secDesc.GetAssertions();
if (permSet != null)
{
// If this frame asserts a superset of the demand set we're done
try
{
if (demandSet.IsSubsetOf(permSet))
{
return(StackHalt);
}
}
catch (Exception)
{
}
// Determine whether any of the demand set asserted. We do this by
// copying the demand set and removing anything in it that is asserted.
if (!permSet.IsUnrestricted())
{
PermissionSetEnumerator enumerator = (PermissionSetEnumerator)demandSet.GetEnumerator();
while (enumerator.MoveNext())
{
IPermission perm
= (IPermission)enumerator.Current;
int i = enumerator.GetCurrentIndex();
if (perm != null)
{
bool unrestricted = perm is System.Security.Permissions.IUnrestrictedPermission;
IPermission assertPerm
= (IPermission)permSet.GetPermission(i, unrestricted);
bool removeFromAlteredDemand = false;
try
{
removeFromAlteredDemand = perm.IsSubsetOf(assertPerm);
}
catch (Exception)
{
}
if (removeFromAlteredDemand)
{
if (alteredDemandSet == null)
{
alteredDemandSet = demandSet.Copy();
}
alteredDemandSet.RemovePermission(i, unrestricted);
}
}
}
}
}
return(StackContinue);
}
