Leopard and Skype problems
I’ve been having problems with Skype under Leopard. Basically, it won’t launch. I would re-install it and then it would run fine. But after that first launch and I try to re-launch it again, the problem is back and I can’t launch Skype.
After searching through the web, there seems to be an explanation. Now whether Leopard or Skype is the culprit is not subject to debate.
From this forum post, it appears that Leopard’s firewall remembers the structure of an application and creates a digital signature based on this. Change the structure and the digital signature changes. If the digital signature changes, then the application cannot run.
OS X 10.5 now digitally signs all applications. The first time you run the app OS X will confirm that you want to run the app downloaded from the internet and will apply a digital signature to the app.
If the digital signature of the app changes (by even one byte) the app will no longer run as it no longer matches the signature originally approved. OS X will prevent it from running. If Skype is making ANY change inside the /Applications/Skype.app bundle when it runs it would cause this issue.
Ars Technica has more details. Go to the section on “Code Signing.”
Code signing also means an end to the practice of applications modifying themselves (e.g., saving custom theme files inside the application bundle itself rather than in
~/Library/Application Support/MyAppor another user-specific location). This practice has always been discouraged by Apple, and now there’s another reason avoid it.
Well, at least the problem has been identified. If you ask me, programmers should adhere to the strategy of Apple. If the application does modify itself, then how can one validate if it is a legitimate modification or that of a virus or malware?
So is the problem caused by Apple’s firewall or is it because the application is poorly programmed?
November 10 2007 10:45 am | OS and Software
