Seeking alternative to AppDomain.CreateDomain(string, evidence) due to obsolete CAS policy

I am working through the Microsoft .Net Framework--Application Development Foundation Training Kit book Chapter 8 Lesson 2: Configuring Application Domains

ShowWinIni being the assembly name for the program I want to execute

object[] hostEvidence = { new Zone(SecurityZone.MyComputer) };
Evidence e = new Evidence(hostEvidence, null);

// Create an AppDomain.
AppDomain d = AppDomain.CreateDomain("New Domain", e);

// Run the assembly
d.ExecuteAssemblyByName("ShowWinIni");

When I execute:

AppDomain d = AppDomain.CreateDomain("New Domain", e);

I get the following message: "This method implicitly uses CAS policy, which has been obsoleted by the .NET Framework. In order to enable CAS policy for compatibility reasons, please use the NetFx40_LegacySecurityPolicy configuration switch. Please see http://go.microsoft.com/fwlink/?LinkID=155570 for more information."

I 开发者_运维技巧can execute the assembly fine when I create an AppDomain without an Evidence object.

Of course, I visited http://go.microsoft.com/fwlink/?LinkID=155570 but I am still confused as to how to create an application domain with specified privileges.

The next most helpful site I found was http://msdn.microsoft.com/en-us/library/bb763046.aspx but my StrongName object computes to NULL.

StrongName fullTrustAssembly =
     typeof(Program).Assembly.Evidence.GetHostEvidence<StrongName>();

Program being the name of the class implementing all this code.

Thanks in advance for your advice and tips!

I found a way to make the original code example work without having to enable NetFX40_LegacySecurityPolicy.

EvidenceBase[] hostEvidence = { new Zone(SecurityZone.MyComputer) };
Evidence e = new Evidence(hostEvidence, null);

AppDomain d = AppDomain.CreateDomain("New Domain", e);

d.ExecuteAssemblyByName("ShowWinIni");

This will not work if you change the SecurityZone to Internet, it will try to use the obsoleted CAS security policy resulting in a NotSupportedException. What I want is a SecurityException... meaning that the assembly I want to execute does not have the permissions it needs.

To execute an assembly in an AppDomain with restricted permissions, you need to use sandboxing. The best example of sandboxing I found is here: http://www.simple-talk.com/dotnet/.net-framework/whats-new-in-code-access-security-in-.net-framework-4.0---part-i/

I think that page also explains the changes made to CAS in 4.0 very well!

Many sources, including MSDN, had me convinced I needed to provide a StrongName array when calling:

AppDomain.CreateDomain( string friendlyName,
                        Evidence securityInfo,
                        AppDomainSetup info,
                        PermissionSet grantSet,
                        params StrongName[] fullTrustAssemblies);

As stated in my original post, I was (and still am) having trouble getting a StrongName object instead of null. Turns out I didn't even need it!

This is my completed example for sandboxing:

Evidence ev = new Evidence();
ev.AddHostEvidence(new Zone(SecurityZone.Internet));
PermissionSet internetPS = SecurityManager.GetStandardSandbox(ev);

AppDomainSetup adSetup = new AppDomainSetup();
adSetup.ApplicationBase = Path.GetFullPath(pathToUntrusted);

AppDomain newDomain = AppDomain.CreateDomain("Sandbox Domain", null, adSetup, internetPS);

newDomain.ExecuteAssemblyByName(untrustedAssembly);

pathToUntrusted = a string representation of the file path to my assembly

untrustedAssembly = a string representation of the assembly name

After seeking help from colleagues, I got this working.

Apparently the book's exercise was designed to use in .Net's 3.5 framework, while I am using 4.0. After modifying both my project and the ShowWinIni project properties to use the 3.5 framework, everything worked... but I still wanted to make this work with the 4.0 framework.

To address the following message: "This method implicitly uses CAS policy, which has been obsoleted by the .NET Framework. In order to enable CAS policy for compatibility reasons, please use the NetFx40_LegacySecurityPolicy configuration switch. Please see http://go.microsoft.com/fwlink/?LinkID=155570 for more information."

I created an app.config file and added the following to it:

<configuration>
   <runtime>
      <NetFx40_LegacySecurityPolicy enabled="true"/>
   </runtime>
</configuration>

You can read more about NetFx40_LegacySecurityPolicy at http://msdn.microsoft.com/en-us/library/dd409253.aspx

This ended up making my program an untrusted application, throwing a Security Exception when I tried to debug. To make my application trusty again, I enabled ClickOnce security settings and marked "This is a full trust application" in my project's properties.

At this point, I could debug my program but a Security Exception was now being thrown when I executed this statement:

d.ExecuteAssemblyByName("ShowWinIni");

This statement worked fine before I started trying to include an Evidence object when I created my AppDomain object. Well it turns out there's another method... AppDomain.ExecuteAssemblyByName(string, evidence), you can read about at http://msdn.microsoft.com/en-us/library/5kd4z003.aspx. So I replaced the above code snippet with the following:

d.ExecuteAssemblyByName("ShowWinIni", e);

'e' being my Evidence object created in my original question.

Now I do NOT think this is the best solution. Ideally, I would rather not force my program to use NetFx40_LegacySecurityPolicy and I believe real world apps should not rely on obsoleted methods. I thought this solution was worth posting should anyone be working through the same book as me.