Undocumented Permission Surprises
I'm trying to tighten our permission demands, so that we only demand the
permissions that we absolutely need. Looking at the documentation for StandardPrinterController, no
mention of permissions is made in the requirements. Being the suspicious
type I fired up Reflector and
made quite the set of discoveries.
All of the OnStartXXX() and OnEndXXX() methods call
Check.Security():
private void CheckSecurity(PrintDocument document)
{
if (document.PrinterSettings.PrintDialogDisplayed)
{
IntSecurity.SafePrinting.Demand();
}
else if (document.PrinterSettings.IsDefaultPrinter)
{
IntSecurity.DefaultPrinting.Demand();
}
else
{
IntSecurity.AllPrinting.Demand();
}
}
I think this is testing how the document was created (PrintDialogDisplayed
isn't documented either). My guess is, if the user created this
PrintDocument via the standard Print dialog then only safe printing is
required. Otherwise stronger demands are made.
The next surpise all the methods demand Unmanaged Code Permission. The
final indignity both the OnStartXXX() methods demand AllPrinting permission.
The moral of this story, MS hasn't done a very good job of documenting the
security requirements of many of the classes in the BCL. When you have a
sneaking suspicion that an operation requires a permission that isn't
documented, you might just be right. Fire up reflector and take a closer
look.