Code Access Security Part - 2 (.Net FrameWork Tools Series)
Please read the Part - 1 before you read this article.
Before we start with our sample app we need to view the security configuration files on the machine. You will find them under
Enterprise Level Security configuration file is :- enterprise.config
Machine Level Security configuration file is :- security.config
You will find the user security configuration file in
<drive>:\Documents and Settings\<userprofile>\Application
Data\Microsoft\CLR Security Config\v1.1.4322\security.config
Let us now create our sample app.In this we will create .Windows Forms application which will try and read and write to the local disk.
1) Go to VS.NET create a new Win App.
2) On the Form Place one text box And one button Make the multiline property of the text box true.
3) In the click event of the button write the followinf piece of code which writes to a file wat ever is written in the text box.
StreamWriter sWriter = new StreamWriter("C://MyTextFile.txt");
4) If you run this from your machine you will be able to create the file and write the textbox contents in it.
Well Currently this code is executing on the local machine cause in the local mahinc policy MyComputer Zone has Full trust permission set.
Check it out by typing caspol -m -lg
Suppose if we were to run this same app from a local network share then the Intranet code access group does not have the permission to write to the local hard disk.
5) Place the exe on a network share and execut it. It should give you a Security Permission Exception.
6) Modify your code to catch the exception and give a user friendly message. Run the file again from the network share.
Suppose that we wanted this application to run from the network share. For that we will need to change the Intranet Permission set.
caspol.exe -chggroup 1.2 FulTrust.
Note : Please be extremely careful to chagne the permission sets as this can coz a lot viruses and other spy wares to come in. Change the permission sets only if you have not made any custom changes to your PC. After changing the permission set use caspol.exe.
Thus in this way we can prevent malicious code to access our resources.
Lets now explore the other options of caspol.exe
Turning the Security On/Off
It is possible to turn the .Net Security Off if so for any reason. By default it is On.
caspol.exe -security off
To reset the security to .Net default security use
To create a new code group
caspol.exe -addgroup 1.3 -site www. <name of the site>
To create a code group under intranet with fulltrust to a particular share on the network
caspol.exe -addgroup 1.2 -url <A href="file://<machinename>/<foldername>/">file:
To remove a code group give the codegroup number (as shown in the list groups) with -remgroup option
caspol.exe -remgroup 1.3.2
To change the code group's permission( we just sw above when we changed the permission for our intranet code group)
caspol.exe -chggroup 1.2 FullTrust
You can add code group for a particular strong name E.g. If you have an application MyApp.exe and you want any version of this application have FullTrust you can achieve that by using the a similar command
caspol.exe -addgroup l -strong -file \bin\debug\MyApp.exe - noname -noversion FullTrust
This command will create a new strong Name code group. You can view it by giving caspol -lg command.
You will see that are already 2 strong name code groups installed by default. They belong to Microsoft and ECMA.
Namratha Shah a.k.a. Nasha is from orginally from Bombay, India but currently residing NJ, USA. She has to her credit, a Bachelor’s Degree in Microbiology and Biotechnology and a Master's in Computer and Software Applications (1999-2001) from Somaiya College Bombay. She started her career with C and C++ and then moved on to Microsoft Technologies. She has over 7.5 years experience in software architecture, design and development. She is a Certified Scrum Master and a member of the CORE .NET Architecture team. She has been Awarded with Microsoft’s Prestigious Most Valuable Professional (MVP) twice consecutively in years 2005 and 2006 in Visual C#.NET for her outstanding contributions to the .NET community.