iOS Parse Facebook Login error 308 FBSDKLoginBadChallengeString
A simple solution work for me. Just enable Keychain Sharing in Capabilities
I only saw this error when I logged out, then logged back in.
My login and logout code were located in different files, as the relevant UI for login and logout are entirely different, and I had instantiated two separate FBSDKLoginManager instances. Consolidating to only one instance solved the problem for me.
I've followed the workaround from totvos and its working for me as well when using FBSDKLoginKit 4.7.1 & FBSDKCoreKit 4.8:
Workaround...get the app built and copied to the phone, and then start the app from the device (not the debugger). Then, attach the debugger to the running process. This seems to get around whatever timing issue is breaking this, and the various keychain operations appear to work correctly while debugging.
Reference: https://forums.developer.apple.com/thread/4743#85335
Update:
This workaround didn't work all the time, so I ended up using @coco's answer above: https://stackoverflow.com/a/31480026/877225