Assert the permission of accessing the file system. in VS .NET

Making QR in VS .NET Assert the permission of accessing the file system.

Assert the permission of accessing the file system.
QR Code Generation In Visual Studio .NET
Using Barcode creation for .NET Control to generate, create QR image in .NET applications.
www.OnBarcode.com
Scanning Quick Response Code In .NET Framework
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Dim filePerm As New FileIOPermission(PermissionState.Unrestricted)
Making Barcode In .NET
Using Barcode drawer for .NET Control to generate, create bar code image in .NET framework applications.
www.OnBarcode.com
Recognizing Barcode In VS .NET
Using Barcode recognizer for .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
filePerm.Assert()
Printing Quick Response Code In Visual C#
Using Barcode creator for VS .NET Control to generate, create QR Code ISO/IEC18004 image in .NET framework applications.
www.OnBarcode.com
QR Code Maker In .NET Framework
Using Barcode printer for ASP.NET Control to generate, create QR image in ASP.NET applications.
www.OnBarcode.com
Access the file system here.
QR Code ISO/IEC18004 Printer In VB.NET
Using Barcode generator for .NET framework Control to generate, create QR Code JIS X 0510 image in .NET applications.
www.OnBarcode.com
USS Code 39 Printer In VS .NET
Using Barcode printer for .NET framework Control to generate, create Code-39 image in Visual Studio .NET applications.
www.OnBarcode.com
Dim sr As New StreamReader( c:\myapp\vars.ini )
Generating UCC - 12 In .NET
Using Barcode creation for VS .NET Control to generate, create Universal Product Code version A image in VS .NET applications.
www.OnBarcode.com
Encoding Bar Code In VS .NET
Using Barcode generator for .NET Control to generate, create bar code image in VS .NET applications.
www.OnBarcode.com
33:
Bar Code Generation In Visual Studio .NET
Using Barcode maker for .NET framework Control to generate, create barcode image in Visual Studio .NET applications.
www.OnBarcode.com
USPS Intelligent Mail Generator In .NET
Using Barcode generator for .NET Control to generate, create 4-State Customer Barcode image in Visual Studio .NET applications.
www.OnBarcode.com
Security
Decode Code 128 Code Set C In VS .NET
Using Barcode reader for VS .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Code 39 Full ASCII Drawer In VB.NET
Using Barcode drawer for VS .NET Control to generate, create USS Code 39 image in .NET applications.
www.OnBarcode.com
As for the PermitOnly and Deny methods, there can be only one active Assert in the current procedure at any given time. You must use the CodeAccessPermission.RevertAssert shared method before you can assert a different permission inside the same procedure. By default, only assemblies in the My_Computer_Zone and LocalIntranet_Zone code groups can call the Assert method because the permission set associated with these zones includes a SecurityPermission object with the Assertion flag enabled. As you might expect, an assembly can only assert a permission object that the assembly owns for example, an assembly from the local intranet can assert the permission for printing to the default printer and displaying UI elements, but it can t assert the right to enumerate types and methods via reflection. If your assembly calls unmanaged code via either PInvoke or COM Interop, you should assert an appropriate SecurityPermission object, as follows:
Recognize Data Matrix 2d Barcode In None
Using Barcode recognizer for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
Painting Code 3 Of 9 In C#
Using Barcode creation for VS .NET Control to generate, create Code 39 Full ASCII image in .NET framework applications.
www.OnBarcode.com
Dim secPerm As New SecurityPermission(SecurityPermissionFlags.UnmanagedCode)
Drawing Code 128B In Java
Using Barcode creator for Java Control to generate, create Code 128 image in Java applications.
www.OnBarcode.com
EAN13 Recognizer In C#.NET
Using Barcode reader for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
secPerm.Assert()
Scan QR Code JIS X 0510 In Visual C#.NET
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Generate QR Code JIS X 0510 In None
Using Barcode printer for Microsoft Excel Control to generate, create Quick Response Code image in Microsoft Excel applications.
www.OnBarcode.com
Access unmanaged code here.
If you fail to do this assertion, your assembly can t be used by untrusted code. In addi tion, if your assembly has a strong name, it must be marked with the AllowPartial lyTrustedCallers attribute, otherwise untrusted code won t be able to even load it. (See the Partially Trusted Assemblies section earlier in this chapter.) It s crucial that you use the Assert method judiciously. By asserting a permission you are claiming that callers can t trick your assembly into doing anything dangerous. Let s suppose you need to provide users with the ability to read and write files only in the C:\MyApp directory. You might be tempted to use the following approach:
Public Sub DeleteFile(ByVal filename As String) Ensure that filename begins with C:\MyApp\. If Not filename.ToLower().StartsWith( c:\myapp\ ) Then Throw New ArgumentException( Path not allowed ) End If Assert the right to access the file system. Dim filePerm As New FileIOPermission(PermissionState.Unrestricted) filePerm.Assert() Delete the file. File.Delete(filename) End Sub
Alas, a smart (and wicked) caller can delete a system file by providing a string argu ment that passes your validation test:
DeleteFile( C:\MyApp\..\Windows\Soap Bubbles.bmp )
Of course, you might suffer from problems far more serious than just losing your favor ite wallpaper. Here s a better approach, which is also more concise:
Part VII:
Advanced Topics
Public Sub DeleteFile(ByVal filename As String) Assert the right to access the C:\MyApp. Dim filePerm As New FileIOPermission(FileIOPermissionAccess.AllAccess, C:\MyApp ) filePerm.Assert() Delete the file. File.Delete(filename) End Sub
The Demand and Assert methods are often used together on the same permission object to improve the performance of your code. Let s say you are authoring a library that repeatedly accesses the file system from inside a method. Each time your assembly accesses a file, the .NET runtime must check the permission objects associated with your assembly, your caller, the caller of your caller, and so on. The greater the number of callers that are above your assembly in the stack, the longer this operation takes. You can reduce this overhead by demanding and then asserting a specific permission object:
Dim filePerm As New FileIOPermission(PermissionState.Unrestricted)
Ensure that all callers in the stack have this permission.
filePerm.Demand()
Tell the .NET runtime that you have checked.
filePerm.Assert()
File operations from now on fire a *partial* stack walk.
By demanding and then asserting a permission object, you are telling the .NET runtime, I checked that my callers have this permission, so you don t have to recheck them each time this resource is accessed.
The PermissionSet Class
The PermitOnly, Deny, and Demand methods can grant, deny, or demand one permis sion at a time. In real-world applications, however, an assembly typically accesses mul tiple resources for example, the registry, the file system, and the user interface. To work with such compound permission, you need to define a custom permission set:
Sub TestPermissionSet() Define three permission objects. Dim filePerm As New FileIOPermission(FileIOPermissionAccess.AllAccess, c:\myapp ) Dim regPerm As New RegistryPermission(PermissionState.Unrestricted) Dim uiPerm As New UIPermission(PermissionState.Unrestricted) Combine them in a permission set. Dim ps As New PermissionSet(PermissionState.None) ps.AddPermission(filePerm) ps.AddPermission(regPerm) ps.AddPermission(uiPerm) Permit only those actions, until the end of the procedure. ps.PermitOnly() The permission set is discarded when the procedure returns. End Sub
33:
Copyright © OnBarcode.com . All rights reserved.