[IronPython] Safe execution of python scripts on my .net application

Dino Viehland dinov at microsoft.com
Tue Dec 1 16:18:22 PST 2009


I think you need to add an Assert into FileFactory.createFile/deleteFile.

See also: http://blogs.msdn.com/shawnfa/archive/2004/08/23/219155.aspx and http://msdn.microsoft.com/en-us/library/system.security.codeaccesspermission.assert.aspx

W/o the assert I think the stack walk will continue and find the lower trust caller higher on the stack, but w/ it the stack walk should stop.

From: users-bounces at lists.ironpython.com [mailto:users-bounces at lists.ironpython.com] On Behalf Of Nicolás Buttarelli
Sent: Tuesday, December 01, 2009 10:49 AM
To: Discussion of IronPython
Subject: Re: [IronPython] Safe execution of python scripts on my .net application

Hi all, I'm bringing again some problem that I though that it was solved for me.

I have to run some python code that comes from a web service, so I want to execute it in a sandbox with restricted permissions. I also want to execute some .NET code from these scripts and I want to have all the permissions (create files, access to the database, etc) for them. I have tried several options and I can't get it working. I have follow the last options that Dino told me but they didn't work either. I will try to explain all the options that I have managed, please let me know if something is not clear enough.

[1] I am creating my AppDomain in the following way.

AppDomainSetup anAppDomainSetup = new AppDomainSetup();
anAppDomainSetup.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory;
anAppDomainSetup.ApplicationName = "Testing";
Evidence evidence = new Evidence();
evidence.AddHost(new Zone(SecurityZone.Internet));
return AppDomain.CreateDomain("Test Domain", evidence, anAppDomainSetup);

[2] Another option is to create it using AppDomain.CreateDomain(aName, aEvidence, anAppDomainSetup, aPermissionSet, aStrongNameArray), but I have already told here, when you try to create the engine using Python.CreateEngine(appDomain), it throws an Serialization exception of the Microsoft.Scripting.

[3] I have also added the StrongName of the assembly to de Evidence using:

evidence.AddHost(CreateStrongName(Assembly.GetAssembly(typeof(TestingAssembly.FileFactory))));

but it doesn't work.

[4] I have subclassified my class FileFactory with MarshalByRefObject class, then I have created another appDomain with all the permissions. Then I create an instance of this class FileFactory using:

FileFactory aFileFactory = (FileFactory)appDomain.CreateInstanceAndUnwrap("TestingAssembly", "TestingAssembly.FileFactory")

and finally, I have set o the scope the variable aFileFactory

scope.SetVariable("aFileFactory", aFileFactory);

but when I try to create or delete a file previously created, it doesn't work.

[5] I had to add the attribute to the assembly to allow Partially Trusted Callers

[assembly: AllowPartiallyTrustedCallers]

and the code is executed, but the AppDomain where the script is execute applies its security policy without taking into account the AppDomain where the object have been instantiated.

[6] Here is an example of a test that probably will clarify what I am trying to do.

AppDomain appDomain = TestSupportMethods.CreateFullTrustSandboxedAppDomain();
FileFactory aFileFactory = (FileFactory)appDomain.CreateInstanceAndUnwrap("TestingAssembly", TestingAssembly.FileFactory");

// Here the file is created and then deleted, so it means that the FullTrustSandboxed allows to create files.
aFileFactory.createFile();
aFileFactory.deleteFile();
string pythonCode = @"aFileFactory.createFile()";
ScriptEngine engine = Python.CreateEngine(TestSupportMethods.CreateSafeSandboxedAppDomainWithEvidence());
ScriptSource source = engine.CreateScriptSourceFromString(pythonCode);
ScriptScope scope = engine.CreateScope();
scope.SetVariable("aFileFactory", aFileFactory);
source.Execute(scope);

It throws...

System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed..

Well, sorry about the size of the email.

Please let me know if you have new ideas, I will do my best to test them.

Regards,
Nicolas


On Mon, Nov 9, 2009 at 7:44 PM, Dino Viehland <dinov at microsoft.com<mailto:dinov at microsoft.com>> wrote:
Couple of options spring to mind:

1.       Setup evidence such that your assembly is given full trust.  I believe you had the start of this in your other code where you were adding some strong name evidence.  You should be able to search the web for normal .NET partial trust scenarios for getting this right.

2.       Setup your object model so that it is a MarshalByRefObject which lives in another app domain.  You can then expose the remote object to the partial trust app domain via SetVariable.

As far as including the DLL - you can call LoadAssembly on the ScriptRuntime and give it your assembly.  Then the user can import all of the types from your DLL as they need them.  That won't work w/ #2 though.  Alternately you can implement IAttributesCollection (or use a dynamic object in 2.6 although IAC is still supported) and create a scope w/ that as the backing storage.  Then you'll be able to lazily resolve the members rather than eagerly populating them - although you still need some code to lazily resolve them.

From: users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com> [mailto:users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com>] On Behalf Of Nicolás Buttarelli
Sent: Monday, November 09, 2009 7:49 AM

To: Discussion of IronPython
Subject: Re: [IronPython] Safe execution of python scripts on my .net application

Hi all again, I am still working with the same problem.

Now I am creating the appDomain in this way by recommendation of Dino:

        public static AppDomain CreateSandboxAppDomain()
        {
            AppDomainSetup anAppDomainSetup = new AppDomainSetup();
            anAppDomainSetup.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory;
            anAppDomainSetup.ApplicationName = "Testing";
            Evidence evidence = new Evidence();
            evidence.AddHost(new Zone(SecurityZone.Internet));

            AppDomain aSandboxedDomain = AppDomain.CreateDomain("Test Domain",
                                                                evidence,
                                                                anAppDomainSetup);

            return aSandboxedDomain;
        }

Now it is working but I have security restrictions over some .dll that I want to have full trusted permissions. I am trying to do this:

string aPythonScript =
@"aDocument = CDLDocument()
aFigure = TextBlock(1, 'type 1')
anotherFigure = TextBlock(2, 'type 2')
aDocument.AddFigure(aFigure)
aDocument.AddFigure(anotherFigure)
aList = aDocument.Figures
";

ScriptSource source = engine.CreateScriptSourceFromString(aPythonScript);
ScriptScope scope = engine.CreateScope();

scope.SetVariable("CDLDocument", typeof(CDLDocument));
scope.SetVariable("TextBlock", typeof(TextBlock));
source.Execute(scope);

This is throwing the  System.Security.SecurityException.

1. How can I give full trusted to a specific dll in an AppDomain?

2. How can I include a .dll to the scope instead of do a SetVariable for each type which I have to manage from the python script?

Thanks!
Nicolás

2009/11/6 Nicolás Buttarelli <nbuttarelli at gmail.com<mailto:nbuttarelli at gmail.com>>
Hi,
On Fri, Nov 6, 2009 at 1:07 AM, Dino Viehland <dinov at microsoft.com<mailto:dinov at microsoft.com>> wrote:
So you've run this as a standalone program and it's failing?  In the standalone app are all of the IronPython and DLR DLLs present (IronPython.dll, IronPython.modules.dll, Microsoft.Scripting.Core.dll, Microsoft.Scripting.dll, Microsoft.Dynamic.dll and Micrsoft.Scripting.Extensionattribute.dll)?
Yes I have all this dlls present.

A slightly modified version of this, dropping the strong name, works just fine for me:

using System;
using Microsoft.Scripting;
using Microsoft.Scripting.Hosting;
using IronPython.Hosting;
using System.Security;
using System.Security.Permissions;

class Test {
    public static void Main(string[] args) {

        PermissionSet aRestrictedPermissionSet = new PermissionSet(PermissionState.None);
        aRestrictedPermissionSet.AddPermission(new SecurityPermission(SecurityPermissionFlag.Execution));

        AppDomainSetup domaininfo = new AppDomainSetup();
        domaininfo.ApplicationBase = System.Environment.CurrentDirectory;

        AppDomain aSandboxedDomain = AppDomain.CreateDomain("Sandboxed Domain",
                  AppDomain.CurrentDomain.Evidence,
                  domaininfo,
                  aRestrictedPermissionSet);

        ScriptEngine engine = Python.CreateEngine(aSandboxedDomain);
        ScriptSource source = engine.CreateScriptSourceFromString("2+2");
        ScriptScope scope = engine.CreateScope();
        Console.WriteLine(source.Execute(scope));

    }
}

Great, I will try this after university. Thanks!
Compile with:

csc test.cs /r:Microsoft.Scripting.Core.dll /r:Microsoft.Scripting.dll /r:IronPython.dll

And run and it prints 4.  Does that not work for you?

We also have a different way we do this in our test suite which also works:

            AppDomainSetup info = new AppDomainSetup();
            info.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory;
            info.ApplicationName = "Test";
            Evidence evidence = new Evidence();
            evidence.AddHost(new Zone(SecurityZone.Internet));
            AppDomain newDomain = AppDomain.CreateDomain("test", evidence, info);

            // create runtime in partial trust...
            ScriptRuntime runtime = Python.CreateRuntime(newDomain);

            // get the Python engine...
            ScriptEngine engine = runtime.GetEngine("py");

This make sense too, I will try it. Thanks again.


From: users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com> [mailto:users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com>] On Behalf Of Nicolás Buttarelli
Sent: Thursday, November 05, 2009 11:18 AM

To: Discussion of IronPython
Subject: Re: [IronPython] Safe execution of python scripts on my .net application

Again, thanks everyone for your help.

But.. I bring bad news. This is still not working and it doesn't depend on the Test environment.

I create another proyect, a Form project, with one button which executes the following code:

 // Creating the permission set to grant other assemblies
PermissionSet aRestrictedPermissionSet = new PermissionSet(PermissionState.None);
aRestrictedPermissionSet.AddPermission(new SecurityPermission(SecurityPermissionFlag.Execution));

AppDomainSetup domaininfo = new AppDomainSetup();
domaininfo.ApplicationBase = System.Environment.CurrentDirectory;

List<StrongName> strongNameList = new List<StrongName>();
strongNameList.Add(CreateStrongName(Assembly.GetExecutingAssembly()));

AppDomain aSandboxedDomain = AppDomain.CreateDomain("Sandboxed Domain",
                                                                                          AppDomain.CurrentDomain.Evidence,
                                                                                          domaininfo,
                                                                                          aRestrictedPermissionSet,
                                                                                          strongNameList.ToArray<StrongName>());

ScriptEngine engine = Python.CreateEngine(aSandboxedDomain);
ScriptSource source = engine.CreateScriptSourceFromString(pythonScript);
ScriptScope scope = engine.CreateScope();
source.Execute(scope);

It throws this error:
Type is not resolved for member 'Microsoft.Scripting.Hosting.ScriptRuntimeSetup,Microsoft.Scripting, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.

I used the fuslogvw application to see if the Microsoft.Scripting is loaded, an it is.

What seems strange for me is that anyone has tried this before. I hope to find some more help here.

Regards,
Nicolas


On Wed, Nov 4, 2009 at 7:36 PM, Shri Borde <Shri.Borde at microsoft.com<mailto:Shri.Borde at microsoft.com>> wrote:
http://www.dev102.com/2008/03/22/3-ways-to-run-nunit-from-visual-studio/ has some info about test projects and appbase problems.

You can also use fuslogvw (http://msdn.microsoft.com/en-us/library/e74a18c4(VS.71).aspx)<http://msdn.microsoft.com/en-us/library/e74a18c4%28VS.71%29.aspx%29> to see why Microsoft.Scripting.dll is failing to load.

From: users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com> [mailto:users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com>] On Behalf Of Dino Viehland
Sent: Tuesday, November 03, 2009 1:52 PM

To: Discussion of IronPython
Subject: Re: [IronPython] Safe execution of python scripts on my .net application

Test projects are weird and somehow you don't end up inheriting the application base.  This seems to work though:

            AppDomainSetup setup = new AppDomainSetup();
            setup.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory;
            AppDomain aSandboxedDomain = AppDomain.CreateDomain("Sandboxed Domain", null, setup);
            ScriptEngine engine = Python.CreateEngine(aSandboxedDomain);
            ScriptSource source = engine.CreateScriptSourceFromString("2+2");
            ScriptScope scope = engine.CreateScope();
            Console.WriteLine(source.Execute(scope));

From: users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com> [mailto:users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com>] On Behalf Of Nicolás Buttarelli
Sent: Tuesday, November 03, 2009 1:30 PM
To: Discussion of IronPython
Subject: Re: [IronPython] Safe execution of python scripts on my .net application

I have create a new "Test Project" and an Unit Test class in order to test the following code inside:

AppDomain aSandboxedDomain = AppDomain.CreateDomain("Sandboxed Domain");
ScriptEngine engine = Python.CreateEngine(aSandboxedDomain);
ScriptSource source = engine.CreateScriptSourceFromString(pythonScript);
ScriptScope scope = engine.CreateScope();
source.Execute(scope);


I have add the references:

- IronPython
- Microsoft.Scripting
- Microsoft.ScriptingCore

But it still not working and throwing the same System.Runtime.Serialization.SerializationException: Type is not resolved for member 'Microsoft.Scripting.Hosting.ScriptRuntimeSetup,Microsoft.Scripting.

Any ideas?


2009/11/3 Nicolás Buttarelli <nbuttarelli at gmail.com<mailto:nbuttarelli at gmail.com>>
Thanks Shri, I will try.

In addition, I found this open issue: http://dlr.codeplex.com/WorkItem/View.aspx?WorkItemId=2816. I think that it is related.

On Tue, Nov 3, 2009 at 9:29 PM, Shri Borde <Shri.Borde at microsoft.com<mailto:Shri.Borde at microsoft.com>> wrote:
I think this happens if the new appdomain cannot load the required assembly. By default, the new appdomain should inherit its BaseDirectory property from the creating domain and should be able to load Microsoft.Scripting.dll. Is your exe and all the dlls in the same folder? If not, can you try to put all assemblies in the same folder (or in the GAC) to see if it works? If that works, you can then figure out how to configure the new appdomain such that it can load Microsoft.Scripting.dll. There may be some setting in AppDomainSetup, or you could hook the AssemblyResolve event...

From: users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com> [mailto:users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com>] On Behalf Of Nicolás Buttarelli
Sent: Tuesday, November 03, 2009 12:08 PM

To: Discussion of IronPython
Subject: Re: [IronPython] Safe execution of python scripts on my .net application

Hi again, thanks for your clear response.

I was trying to do what you proposed but it is not working. I am receiving an exception:

Test method CadworX3WCFRestTest.IronPython.SafeScriptExecutionTest.writingAFileTest threw exception:  System.Runtime.Serialization.SerializationException: Type is not resolved for member 'Microsoft.Scripting.Hosting.ScriptRuntimeSetup,Microsoft.Scripting, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'..
I tried to find a solution but I couldn't. This is the minimal code that I am running to get this exception (I have removed all the security stuff but apparently that does not resolve the problem):

AppDomain aSandboxedDomain = AppDomain.CreateDomain("Sandboxed Domain");

ScriptEngine engine = Python.CreateEngine(aSandboxedDomain);
ScriptSource source = engine.CreateScriptSourceFromString(pythonScript);
SriptScope scope = engine.CreateScope();
source.Execute(scope);

The exception is thronged in this line:
ScriptEngine engine = Python.CreateEngine(aSandboxedDomain);


Do you have any idea which could be the problem?

Thanks again,
Nicolas

On Mon, Nov 2, 2009 at 10:25 PM, Dino Viehland <dinov at microsoft.com<mailto:dinov at microsoft.com>> wrote:
Assuming the app domain is setup properly then there's no way for the Python code to elevate permissions (modulo CLR security bugs which are few and far between).  This is because IronPython its self is 100% security transparent and does not affect any security decisions or assert any form of trust - so it's all up to the CLR to limit permissions.  So for example while you can access the file object, or import ctypes, or call various other Python APIs which would require trust you'll get a security exception from the CLR when you don't have permissions to do something.

For more complex scenarios you might also have an object model which you expose to the application and inject in via its scope.  Once you've done that you'll want to make sure that the object model is also secure.


From: users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com> [mailto:users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com>] On Behalf Of Nicolás Buttarelli
Sent: Monday, November 02, 2009 1:20 PM
To: Discussion of IronPython
Subject: Re: [IronPython] Safe execution of python scripts on my .net application

Thanks for your response.

But what happens with the python code? Does not exist a way to write some scripts that can do some damage to my app, the server, the database, etc?

Thanks again,
Nicolas

On Mon, Nov 2, 2009 at 9:41 PM, Dino Viehland <dinov at microsoft.com<mailto:dinov at microsoft.com>> wrote:
After creating your app domain you can do:

ScriptEngine engine = Python.CreateEngine(someAppDomain);

And then the rest of your code should work as it's written.


From: users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com> [mailto:users-bounces at lists.ironpython.com<mailto:users-bounces at lists.ironpython.com>] On Behalf Of Nicolás Buttarelli
Sent: Monday, November 02, 2009 12:39 PM
To: users at lists.ironpython.com<mailto:users at lists.ironpython.com>
Subject: [IronPython] Safe execution of python scripts on my .net application

Sorry, I don't know if my previous message have arrived. So, here it is:


Hello all,

I am starting with python and I would like to add to my web application some web services. This services will allow the different clients of my application to execute some python scripts.

I would like to know if someone did this before and how can I do this in a secure way. I mean, how can I do to restrict the environment where the scripts will be executed.

In .net I can do this using the AppDoman and setting the permission set.

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


Is there a way to do the same with my python scripts?

I am running them using this:

ScriptEngine engine = Python.CreateEngine();
ScriptSource source = engine.CreateScriptSourceFromString(scriptAsString);
ScriptScope scope = engine.CreateScope();
source.Execute(scope);

Thanks in advance.
Nicolas

_______________________________________________
Users mailing list
Users at lists.ironpython.com<mailto:Users at lists.ironpython.com>
http://lists.ironpython.com/listinfo.cgi/users-ironpython.com


_______________________________________________
Users mailing list
Users at lists.ironpython.com<mailto:Users at lists.ironpython.com>
http://lists.ironpython.com/listinfo.cgi/users-ironpython.com


_______________________________________________
Users mailing list
Users at lists.ironpython.com<mailto:Users at lists.ironpython.com>
http://lists.ironpython.com/listinfo.cgi/users-ironpython.com



_______________________________________________
Users mailing list
Users at lists.ironpython.com<mailto:Users at lists.ironpython.com>
http://lists.ironpython.com/listinfo.cgi/users-ironpython.com


_______________________________________________
Users mailing list
Users at lists.ironpython.com<mailto:Users at lists.ironpython.com>
http://lists.ironpython.com/listinfo.cgi/users-ironpython.com



_______________________________________________
Users mailing list
Users at lists.ironpython.com<mailto:Users at lists.ironpython.com>
http://lists.ironpython.com/listinfo.cgi/users-ironpython.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ironpython.com/pipermail/users-ironpython.com/attachments/20091202/5d7e0af0/attachment-0001.htm>


More information about the Users mailing list