Application from unidentified developer if I change app's icon before packaging it

[Spillou]

Hello !

For some reasons, I would like to change the default icon of FileMaker Pro. I install the app, change the icon in the information tab and package it using Composer.

But when I deploy it on some test computers with a Jamf policy, I have different message errors like "The app is damaged and cannot be opened", sometimes with a message telling me to drop it in the trash. If I right click on the app or it's dock icon then click "Open", it will open.

I would like to be able to avoid this message,  allowing the app to open using command line or Apple Script to bypass that security, or another way to customize the FileMaker Pro's icon without having this message.

I found that it could be possible to make appear again the ability to choose to open apps from any source, but I would like to avoid that option for security purpose. I want to keep it as "Open from Apple and identified developers".

Thank you !

[AJPinto · Accepted solution]

You can't break an application up, screw with it, and hope that its signature and notarization would not be revoked. Once you mess with the App, it is no longer published by an identified developer. This is basically everything working as intended, and there is no way to suppress these warnings without turning off gatekeeper. 

[Shyamsundar]

I would not recommend modifying the Package which is signed and Notarized, you can try moving the original package to composer and use it to convert it to source and try to replace the icon from the composer and try to repackage it. 

[rqomsiya]

Why not just make an alias with your own custom icon pointing to FMP? 

[sdagley]

@Spillou You might want to take a look at https://github.com/mklement0/fileicon which will allow you to script changing of the FileMaker icon after you've installed it on a machine.

[Spillou]

@rqomsiya Unluckily, it doesn't work. The shortcut's icon reverts back to the original one of FMP.
@sdagley I'll take a look at your solution, but I may think that it will end with the same problem as the one I have. Filels and folders are OK, but applications, it will be problematic with the signature of the app.
@Shyamsundar The original FMP app is in a .dmg and just needs to be drag and dropped in the applications folder.

The way I found for that is to package the app to deploy it with Jamf, with my custom icon in a temporary folder. I then launch FileMaker Pro, quit it, then move that icon in the /Content/Resources inside FileMaker Pro.app, with the name of the original icon. Of course, I make a backup of the original one. I could script all that stuff and it works great !

Thank you everyone for your answers !