Following last week's disclosure of new iOS malware called XcodeGhost, which arose from malicious versions of Xcode hosted on third-party servers, Apple has outlined instructions for developers to ensure the version of Xcode they are using is valid.
When downloading Xcode from the Mac App Store, or Apple's website so long as Gatekeeper is enabled, OS X automatically checks the app's code signature and validates it against Apple's code. If you must obtain Xcode elsewhere, follow these steps:
To verify the identity of your copy of Xcode run the following command in Terminal on a system with Gatekeeper enabled:
spctl --assess --verbose /Applications/Xcode.appwhere /Applications/ is the directory where Xcode is installed. This tool performs the same checks that Gatekeeper uses to validate the code signatures of applications. The tool can take up to several minutes to complete the assessment for Xcode.
The tool should return the following result for a version of Xcode downloaded from the Mac App Store:
/Applications/Xcode.app: accepted
source=Mac App Storeand for a version downloaded from the Apple Developer web site, the result should read either
/Applications/Xcode.app: accepted
source=Appleor
/Applications/Xcode.app: accepted
source=Apple SystemAny result other than ‘accepted’ or any source other than ‘Mac App Store’, ‘Apple System’ or ‘Apple’ indicates that the application signature is not valid for Xcode. You should download a clean copy of Xcode and recompile your apps before submitting them for review.
Apple issued a statement in response to XcodeGhost over the weekend, noting that it has removed all infected apps it is aware of from the App Store and is working with developers to ensure they are using a legitimate version of Xcode.
"We’ve removed the apps from the App Store that we know have been created with this counterfeit software. We are working with the developers to make sure they’re using the proper version of Xcode to rebuild their apps."
XcodeGhost affected dozens, and possibly hundreds, of App Store apps. iPhone, iPad and iPod touch users should read what you need to know about XcodeGhost to learn more about the malware and how to keep yourself protected.
