Yes, it is possible but it will usually require that you re-sign the .app bundle after making the change.

Note that modifying the .ipa file is not necessary in normal use. This article is provided purely for informational purposes.

Example: removing a file from a .ipa archive

For this example assume that the name of the Xamarin.iOS project is iPhoneApp1 and the generated session id is cc530d20d6b19da63f6f1c6f67a0a254

1. Build the .ipa file as normal from Visual Studio.

2. Switch over to the Mac build host.

3. Find the build in the ~/Library/Caches/Xamarin/mtbs/builds folder. You can paste this path into Finder > Go > Go to Folder to browse the folder in Finder. Look for the folder that matches the project name. Within that folder, look for the folder that matches the generated session id of the build. This will most likely be the subfolder that has the most recent modification time.

4. Open a new Terminal.app window.

5. Type cd into the Terminal.app window, and then drag & drop the generated session id folder into the Terminal.app window:

   

6. Type the return key to change directory into the generated session id folder.

7. Unzip the .ipa file into a temporary old/ folder using the following command. Adjust the Ad-Hoc and iPhoneApp1 names as needed for your particular project.

   ditto -xk bin/iPhone/Ad-Hoc/iPhoneApp1-1.0.ipa old/

8. Keep the Terminal.app window open.

9. Delete the desired files from the .ipa. You can either move them to the Trash using Finder, or delete them on the command line using Terminal.app. To view the contents of the Payload/iPhone file in Finder, Control-click the file and select Show Package Contents.

10. Using the same general approach as in step 3, find the log file under ~/Library/Logs/Xamarin/MonoTouchVS/ that has both the project name and the generated session id in the name:

    

11. Open the build log from step 10, for example by double-clicking it.

12. Find the line that includes tool /usr/bin/codesign execution started with arguments: -v --force --sign.

13. Type /usr/bin/codesign into the Terminal.app window from step 8.

14. Copy all of the arguments starting with -v from the line in step 12, and paste them into the Terminal.app window.

15. Change the last argument to be the .app bundle located within the old/Payload/ folder, and then run the command.

    /usr/bin/codesign -v --force --sign SOMELONGSTRING in/iPhone/Ad-Hoc/iPhoneApp1.app/ResourceRules.plist --entitlements obj/iPhone/Ad-Hoc/Entitlements.xcent old/Payload/iPhoneApp1.app

16. Change into the old/ directory in Terminal:

    cd old

17. Zip up the contents of the directory into a new .ipa file using the zip command. You can change the "$HOME/Desktop/iPhoneApp1-1.0.ipa" argument to output the .ipa file wherever you'd like:

    zip -yr "$HOME/Desktop/iPhoneApp1-1.0.ipa" *

Common error messages

If you see Invalid Signature. A sealed resource is missing or invalid., that generally means that something was changed within the .app bundle, and that the .app bundle was not correctly re-signed afterwards. Also note that if you wish to create an .ipa with a distribution profile, you must build the original .ipa with a distribution profile. Otherwise the Entitlements.xcent will be incorrect.

To give a concrete example of how this error can arise, if you run the following codesign --verify command in the Terminal window after step 9, you will see the error along with the precise cause of the error:

$ codesign -dvvv --no-strict --verify old/Payload/iPhoneApp1.app
old/Payload/iPhoneApp1.app: a sealed resource is missing or invalid
file missing: /Users/macuser/Library/Caches/Xamarin/mtbs/builds/iPhoneApp1/cc530d20d6b19da63f6f1c6f67a0a254/old/Payload/iPhoneApp1.app/MyFile.png

And the App Store verification process will report a similar error message:

ERROR ITMS-90035: "Invalid Signature. A sealed resource is missing or invalid. The binary at path [iPhoneApp1.app/iPhoneApp1] contains an invalid signature. Make sure you have signed your application with a distribution certificate, not an ad hoc certificate or a development certificate. Verify that the code signing settings in Xcode are correct at the target level (which override any values at the project level). Additionally, make sure the bundle you are uploading was built using a Release target in Xcode, not a Simulator target. If you are certain your code signing settings are correct, choose "Clean All" in Xcode, delete the "build" directory in the Finder, and rebuild your release target. For more information, please consult https://developer.apple.com/library/ios/documentation/Security/Conceptual/CodeSigningGuide/Introduction/Introduction.html"