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APCKeychainStore.stringForKey randomly returning empty values  #119

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APCKeychainStore.stringForKey randomly returning empty values #119

Description

@brendenwest
brendenwest
opened on Jul 28, 2015

I'm seeing unpredictable behavior with APCKeychain, where APCKeychainStore.stringForKey incorrectly returns an empty value about 1/3 of the time. Where APCKeychainStore incorrectly returns empty values, I can force-close the app and see the correct values returned on subsequent queries.

I'm getting and setting keychain values via Swift, like this:

var email : String {
    get {
        if let value = APCKeychainStore.stringForKey(kEmailPropertyName) {
            return value
        }
        return ""
    }
    set {
        APCKeychainStore.setString(newValue, forKey: kEmailPropertyName)
    }
}

var password : String {
    get {
        if let value = APCKeychainStore.stringForKey(kPasswordPropertyName) {
            return value
        }
        return ""
    }
    set {
        APCKeychainStore.setString(newValue, forKey: kPasswordPropertyName)
    }
}

Activity

  1. rsanchezsaez commented on Jul 29, 2015

    @rsanchezsaez
    rsanchezsaez
    on Jul 29, 2015

    Could this be related to the infamous -34018 (errSecMissingEntitlement) keychain bug?

  2. brendenwest commented on Jul 29, 2015

    @brendenwest
    brendenwest
    on Jul 29, 2015
    Author

    I get no errors on compile or at run time.

    Also, I haven't enabled the Keychain sharing entitlement, since I don't expect to share the keychain data with other apps.

  3. rsanchezsaez commented on Jul 29, 2015

    @rsanchezsaez
    rsanchezsaez
    on Jul 29, 2015

    Are you sure you don't see any keychain-related message logged onto the console at runtime when you get nil from the stringForKey() method? (AppCore should be compiled in Debug for you to see them)

    The bug I was mentioning would manifest by APCKeychainStore running this code path, which would print a debug log message on the console and return nil.

    There's more info about this issue here. It has been a longstanding keychain issue on iOS, and unfortunately it's quite random.

  4. brendenwest commented on Jul 29, 2015

    @brendenwest
    brendenwest
    on Jul 29, 2015
    Author

    I see this error when I haven't yet set a passcode:

    APC_DEBUG in +[APCKeychainStore dataForKey:service:accessGroup:] at APCKeychainStore.m:105 => SecItemCopyMatching query failed with error code: 4294941996i

    But an error is expected there. I haven't recently repro'd the issue of unexpected missing values.

  5. Erin-Mounts
    added a commit that references this issue on Jun 8, 2016

    Merge pull request ResearchKit#119 from dephillipsmichael/feature/gra…

    f58ea53
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