Csharp/CSharp Tutorial/File Directory Stream/File Permission

Declarative Permission demo

<source lang="csharp">using System; using System.IO; using System.Security; using System.Security.Permissions; using System.Collections.Generic; using System.Text;

   class Program
   {
       [FileIOPermission(SecurityAction.Demand, AllLocalFiles=FileIOPermissionAccess.Write)]
       static void Main(string[] args)
       {
           FileStream fs = new FileStream("myfile.txt", FileMode.Create);
           fs.WriteByte(65);
           fs.Close();
       }
   }</source>

Demanding permissions

<source lang="csharp">using System; using System.IO; using System.Security.Permissions; [FileIOPermissionAttribute(SecurityAction.Demand,All=@"c:\\temp")] class MainClass {

 public static void Main() 
 {
   FileStream fsOut = File.Create(@"c:\\temp\\test.txt");
   StreamWriter sw = new StreamWriter(fsOut);
   sw.WriteLine("str");
   sw.Flush();
   sw.Close();
 }

}</source>

Permission sets

<source lang="csharp">using System; using System.Collections.Generic; using System.IO; using System.IO.IsolatedStorage; using System.Net; using System.Net.Sockets; using System.Reflection; using System.Security; using System.Security.AccessControl; using System.Security.Policy; using System.Security.Permissions; using System.Security.Principal; using System.Text; public class MainClass {

   public static void Main()
   {
       NamedPermissionSet ps = new NamedPermissionSet("SamplePermissionSet", PermissionState.None);
       ps.AddPermission(new FileIOPermission(FileIOPermissionAccess.AllAccess, @"C:\test\"));
       ps.AddPermission(new ReflectionPermission(PermissionState.Unrestricted));
       ps.AddPermission(new SecurityPermission(SecurityPermissionFlag.Execution));
       Console.WriteLine(ps.ToXml().ToString());
   }

}</source>

<PermissionSet class="System.Security.NamedPermissionSet"
version="1"
Name="SamplePermissionSet">
<IPermission class="System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture
=neutral, PublicKeyToken=b77a5c561934e089"
version="1"
Read="C:\test\"
Write="C:\test\"
Append="C:\test\"
PathDiscovery="C:\test\"/>
<IPermission class="System.Security.Permissions.ReflectionPermission, mscorlib, Version=2.0.0.0, Cul
ture=neutral, PublicKeyToken=b77a5c561934e089"
version="1"
Unrestricted="true"/>
<IPermission class="System.Security.Permissions.SecurityPermission, mscorlib, Version=2.0.0.0, Cultu
re=neutral, PublicKeyToken=b77a5c561934e089"
version="1"
Flags="Execution"/>
</PermissionSet>

Refusing permissions

<source lang="csharp">using System; using System.IO; using System.Security.Permissions; [assembly:FileIOPermissionAttribute(SecurityAction.RequestRefuse,Unrestricted=true)] class MainClass {

 public static void Main() 
 {
   FileStream fsOut = File.Create(@"c:\\temp\\test.txt");
   StreamWriter sw = new StreamWriter(fsOut);
   sw.WriteLine("str");
   sw.Flush();
   sw.Close();
 }

}</source>

Unhandled Exception: System.Security.SecurityException: Request for the permission of type "System.S
ecurity.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77
a5c561934e089" failed.
   at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boole
an isPermSet)
   at System.Security.CodeAccessPermission.Demand()
   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean
 useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, St
ring msgPath, Boolean bFromProxy)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int
32 bufferSize, FileOptions options)
   at MainClass.Main()
The action that failed was:
Demand
The type of the first permission that failed was:
System.Security.Permissions.FileIOPermission
The first permission that failed was:
<IPermission class="System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture
=neutral, PublicKeyToken=b77a5c561934e089"
version="1"
Read="c:\temp\test.txt"
Write="c:\temp\test.txt"/>
The demand was for:
<IPermission class="System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture
=neutral, PublicKeyToken=b77a5c561934e089"
version="1"
Read="c:\temp\test.txt"
Write="c:\temp\test.txt"/>
The granted set of the failing assembly was:
<PermissionSet class="System.Security.PermissionSet"
version="1"
Unrestricted="true"/>
The refused set of the failing assembly was:
<PermissionSet class="System.Security.PermissionSet"
version="1">
<IPermission class="System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture
=neutral, PublicKeyToken=b77a5c561934e089"
version="1"
Unrestricted="true"/>
</PermissionSet>
The assembly or AppDomain that failed was:
main, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null
The method that caused the failure was:
Void Main()
The Zone of the assembly that failed was:
MyComputer
The Url of the assembly that failed was:
file:///C:/Java_Dev/WEB/dev/CSharp/main.exe

Requesting a permission set

<source lang="csharp">using System; using System.IO; using System.Security.Permissions; [assembly:PermissionSetAttribute(SecurityAction.RequestMinimum,Name="FullTrust")] class MainClass {

 public static void Main() 
 {
   FileStream fsOut = File.Create(@"c:\\temp\\test.txt");
   StreamWriter sw = new StreamWriter(fsOut);
   sw.WriteLine("str");
   sw.Flush();
   sw.Close();
 }

}</source>

Requesting minimum permissions

<source lang="csharp">using System; using System.IO; using System.Security.Permissions; [assembly:FileIOPermissionAttribute(SecurityAction.RequestMinimum,All=@"c:\\temp")] class MainClass {

 public static void Main() 
 {
       FileStream fsOut = File.Create(@"c:\\temp\\test.txt");
       StreamWriter sw = new StreamWriter(fsOut);
       sw.WriteLine("str");
       sw.Flush();
       sw.Close();
 }

}</source>

Requesting optional permissions

<source lang="csharp">using System; using System.IO; using System.Security.Permissions; [assembly:FileIOPermissionAttribute(SecurityAction.RequestOptional,All=@"c:\\temp")] class MainClass {

 public static void Main() 
 {
   FileStream fsOut = File.Create(@"c:\\temp\\test.txt");
   StreamWriter sw = new StreamWriter(fsOut);
   sw.WriteLine("str");
   sw.Flush();
   sw.Close();
 }

}</source>