Help me to undersand ???

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serge calderara - 25 Apr 2006 10:17 GMT

Dear all,

I am practiciing security in .NET, partriculary CAS.
For that I have a simple example that I try to run on my system. This
example is issue from MS-Press books lab and is as follow :

==========================
<Assembly: PrintingPermission(SecurityAction.RequestMinimum)>
<Assembly: FileIOPermission(SecurityAction.RequestOptional, Read:="C:\")>
<Assembly: FileIOPermission(SecurityAction.RequestRefuse,
Read:="C:\Windows\")>

Module Module1

Sub Main()
Console.WriteLine("Rad boot.ini file line")
Dim sr As StreamReader = New StreamReader("c:\boot.ini")
Console.WriteLine("line red : " & sr.ReadLine)
Console.ReadLine()
End Sub

=========================

When executing this code, I get following error :

"An unhandled exception of type 'System.Security.Policy.PolicyException'
occurred in Unknown Module.
Additional information: Required permissions cannot be acquired."

I have reset all my CAS setting to default, to be sure that I did not make
someting wrong.

What can I check to make it work ?

thnaks for help
regard
Serge

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Nicole Calinoiu - 25 Apr 2006 15:32 GMT

Are you trying to run it from within VStudio? If so, you'll need
unrestricted UIPermission as well.

> Dear all,
>
[quoted text clipped - 33 lines]
> regard
> Serge

Reply to this Message

serge calderara - 26 Apr 2006 08:04 GMT

hi,

Yes I am running it within visual studio.
I have default settings under CAS, it means that I get Unrestricted already
no ?

could you clarify one point for me that I reaaly do not catch.
First of all when you apply security for a file/folder with with Windows
explorer, you select the folder or file then add users or group permission
for that folder or file.

Then for assemblies, how does it really work. Does the .NET framework by
default run the assemblie inside all level ( Enterprise, Machine, users) with
default access and then you only start to fine tune security in your code as
imperative or declarative way ?

Or are you able to select within CAS tool, your assembly name then similar
as a folder specify the level in which you want to run your assembly and
finally security rules ?

thnaks for your info
regards
serge

> Are you trying to run it from within VStudio? If so, you'll need
> unrestricted UIPermission as well.
[quoted text clipped - 36 lines]
> > regard
> > Serge

Reply to this Message

Nicole Calinoiu - 26 Apr 2006 14:44 GMT

> hi,
>
> Yes I am running it within visual studio.
> I have default settings under CAS, it means that I get Unrestricted
> already
> no ?

Your assembly may be granted unrestricted permissions under CAS policy, but
using even one RequestOptional is effectively equivalent to rejecting all
permissions that you do not explicitly request via either a RequestMinimum
or RequestOptional. In order to gain back UIPermission, you would need to
request it. e.g.:

<Assembly: UIPermission(SecurityAction.RequestMinimum, Unrestricted:=True)>

> could you clarify one point for me that I reaaly do not catch.
> First of all when you apply security for a file/folder with with Windows
[quoted text clipped - 7 lines]
> as
> imperative or declarative way ?

No. For starters, when the terms "imperative" and "declarative" are used
for CAS, they almost always refer to demanding permissions, not setting
them. While the assembly-level permissions you are applying are, strictly
speaking, an application of a declarative syntax, they are not used for
demanding permissions.

In addition, assembly-level permission attributes can only be used to
decrease, not increase, the permission grant for an assembly. They are not
used so much for "fine tuning" as they are for either documenting required
permissions or deliberately restricting what an assembly is allowed to do.

> Or are you able to select within CAS tool, your assembly name then similar
> as a folder specify the level in which you want to run your assembly and
> finally security rules ?

You can grant permissions at the assembly level via CAS policy if you so
desire. However, that's just one of many possible adjustments one might
wish to make to the policy.

Reply to this Message

serge calderara - 27 Apr 2006 06:31 GMT

Thnaks nicole.

I am actually prpearing my MCSD and i select as next exam .Net security. For
that I get the MS -Express book which is quite well explain as long as you
have catch the idea. Sounds a bit clear for me now

have you ever rrun in that book ? do you thonk it would be enought ?
Of cours a lot of more info on MSDN too that I found

regards
serge

> > hi,
> >
[quoted text clipped - 41 lines]
> desire. However, that's just one of many possible adjustments one might
> wish to make to the policy.

Reply to this Message

Nicole Calinoiu - 27 Apr 2006 14:34 GMT

I am unfamiliar with the book, so I can't comment on its contents.

> Thnaks nicole.
>
[quoted text clipped - 69 lines]
>> desire. However, that's just one of many possible adjustments one might
>> wish to make to the policy.

Reply to this Message

serge calderara - 27 Apr 2006 14:44 GMT

how deep are you involev with security in your daily work ?
Do you work in a company or as a consultant in security ?

> I am unfamiliar with the book, so I can't comment on its contents.
>
[quoted text clipped - 71 lines]
> >> desire. However, that's just one of many possible adjustments one might
> >> wish to make to the policy.

Reply to this Message

Nicole Calinoiu - 27 Apr 2006 14:56 GMT

I work at a developer and architect at a software company, not as a security
consultant. Security is not the main focus of my job, but it is an
important consideration in my work.

> how deep are you involev with security in your daily work ?
> Do you work in a company or as a consultant in security ?
[quoted text clipped - 86 lines]
>> >> might
>> >> wish to make to the policy.

Reply to this Message

Help me to undersand ???

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