Hi,

I have a question concerning the usage of the FileIOPermissionAttribute. I
have an assembly (essentially a loader) which reads files, does stuff with
the contents and writes records to an SQL database. The paths to the files
on which it operates are passed as parameters on a method within the assembly.

I'd like to be a diligent programmer and tie-down the security requirements
for the assembly. From the point of view of file IO, the requirements are as
follows:
1. Be able to read the contents of any file passed to the assembly method.
2. Not be able to write to any file, anywhere.

I cannot see how to achieve this with the FileIOPermissionAttribute. All of
the examples that I can find show IO permission being granted or denied to
explicit, hard-coded files or paths, eg:
[FileIOPermission(SecurityAction.Assert, Read="c:\\")]

This sort of thing doesn't strike me as being very useful for an attribute
at the assembly, class or method level. It requires the path or file-name to
be hard-coded, akin to having hard-coded paths and names in normal code.

If I want to specify read-access to any local file or deny write access to
any local file, I seem to need to know the layout of the drives of the target
machine at compile time. Obviously I don't know this. E.g. does a
particular target machine have a local C drive, or local C & D drives, or has
the owner been particularly strange and re-arranged the drive mappings so
that the local drives are C and H etc.

So my question is this: Is there a more general means available to allow
the programmer to specify the file IO requirements via the
FileIOPermissionAttribute when the layout of the target file-system is not
know at compile time?

Regards

[quoted text, click to view]

At the method level, you can use imperative rather than declarative
permission forms, and the former support runtime specification of the path.
e.g.:

new FileIOPermission(FileIOPermissionAccess.Read, path).Assert();


[quoted text, click to view]

At the assembly level, only declarative permissions are possible. In .NET
2.0, FileIOPermissionAttribute is equipped with AllFiles and AllLocalFiles
properties. However, in 1.x, you're pretty much stuck making a
RequestOptional for unrestricted read permissions, which will at least allow
administrators to restrict your assembly's permissions as they desire
without preventing it from loading.