How to use obfuscation for ClickOnce?

Question

If one will release a ClickOnce version, how can it be obfuscated by Dotfuscator?

Answer 1

You can use the commercial version of Dotfuscator to automatically obfuscate a ClickOnce application by adding the deployment manifest ("foo.application") as an input to your Dotfuscator project. Dotfuscator will allow you to add any necessary exclusions to the assemblies contained in the ClickOnce application and will create updated deployment and application manifests containing the obfuscated assemblies.

The free version of Dotfuscator included in Visual Studio (including Visual Studio 2010) does not have the feature to automatically obfuscate ClickOnce applications. In order to get a functioning obfuscated ClickOnce application you will need to recreate or update the ClickOnce manifests since obfuscation changes the signatures of the assemblies.

You can use mage.exe or mageui.exe (included in the Windows/.NET SDK) to update the ClickOnce manifests. If you are going to use mage.exe you need to be aware that you cannot use the "Use .deploy file extension" option in your ClickOnce options as it does not recognize it.

Assuming your ClickOnce application is named "Foo" and is at version 1.0.0.0 the process you will want to follow is:

1. Publish your ClickOnce application to a directory on disk
2. Run Dotfuscator CE and add the assemblies you want to be obfuscated from the bin directory of your project
3. Obfuscate the assemblies. The obfuscated assemblies will be put into a subdirectory named "Dotfuscated" by default.
4. Resign your obfuscated assemblies with sn.exe (only if you initially strong named them)
5. Copy the obfuscated assemblies over top of the ones in the ClickOnce publish\Application Files\Foo_1_0_0_0 directory

6. Update the application manifest and resign it:

   mage.exe -Update "Application Files\Foo_1_0_0_0\Foo.exe.manifest" -CertFile "c:\Foo\foo.pfx" -Password password

7. Update the deployment manifest and resign it:

   mage.exe -Update Foo.application -AppManifest "Application Files\Foo_1_0_0_0\Foo.exe.manifest" -CertFile "c:\Foo\foo.pfx" -Password password

You now have a valid application and deployment manifest using obfuscated assemblies. You can also use the MageUI.exe tool to accomplish the same tasks (and it knows how to handle assemblies with the .deploy extension) but it is not as easy to automate.