[iOS] DDFileLogger causes crash when logging from background app

[belenko]

DDFileLogger causes application to crash under following conditions:

• Application is running in background
• Device is passcode protected
• Device has been locked for at least 10 seconds (data protection keys are purged from memory after 10 seconds)
• com.apple.developer.default-data-protection entitlement is set to NSFileProtectionComplete (which is default for me -- I haven't specified this value explicitly)

Crash log will show exception being raised in [DDFileLogger logMessage:] as a result of [NSConcreteFileHandle writeData:]. The reason is DDFileLogger tries to write to a file that is encrypted by Data Protection and is not accessible because device is locked.

Workaround is to override default attributes when creating log file, i.e. set attributes to @{NSFileProtectionKey : NSFileProtectionNone} when calling [NSFileManager createFileAtPath:contents:attributes:] in [DDLogFileManagerDefault createNewLogFile].

This has security implications. If application is not supposed to be relaunched by iOS while device is locked (majority of apps are of this kind, I suppose) then NSFileProtectionCompleteUnlessOpen or NSFileProtectionCompleteUntilFirstUserAuthentication should be used instead of NSFileProtectionNone.

[bpoplauschi]

@belenko and @albertodebortoli any updates on this? Does the commit https://github.com/EFEdcuationFirstMobile/CocoaLumberjack/commit/b84dc47c324e587cfdd4c4b99edd103f9021133a fix this issue?

[belenko]

That commit resolves the problem, yes, but it is more of a workaround than a proper fix. Setting log protection class to NSFileProtectionNone has security implications and thus I am not sure that commit should be merged.

[rivera-ernesto]

Fixed by #183.