Cwa-app-ios: Number of active days is wrong if time is set to a past date

[Ein-Tim]

Avoid duplicates

• [x] Bug is not mentioned in the FAQ
• [x] Bug is not already reported in another issue

Technical details

• Device name: iPhone 6s
• iOS Version: iOS 14.4 Public Beta RC 1 / iOS 14.3
• App Version: 1.10.1

Describe the bug

If you set the system time of your iPhone back (f.e. a month - but one day is also enough), CWA will show an unrealistic high number of active days.

Steps to reproduce the issue

1. Close CWA completetly
2. Open the iOS-Settings: General -> Date & Time -> Set Automatically OFF -> Change to any date in the past
3. Open CWA
4. See unexpected long number of days

Expected behaviour

The quote "Exposure logging was active for 0 of the past 14 days." should be shown
or
(how it is done if the user's time is in the future) the "Exposure check failed" card and this pop up should be shown.

Additional context

@MikeMcC399 could you maybe check the behavior under Android?

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Internal Tracking ID: EXPOSUREAPP-4755

[MikeMcC399]

@Ein-Tim
This is similar to https://github.com/corona-warn-app/cwa-app-android/issues/1786 where a negative number was being displayed as a large positive number.

4.294.967.268 = 0xFFFF FFE4 or -28 in DWORD

I couldn't reproduce it with CWA Android 1.10.1.

For Android there is a related PR https://github.com/corona-warn-app/cwa-app-android/pull/2019 related to "time travel" however it hasn't been merged into a released version yet.

[Ein-Tim]

Okay thanks @MikeMcC399.

I know about the Android Issue, and since this was a bug in Googles ENS, I fear that this is the same bug but for Apples ENF.

I will leave this Issue here since you could not reproduce it and according to @dsarkar in https://github.com/corona-warn-app/cwa-app-android/issues/1786 this should be fixed in version 1.8.

[dsarkar]

@Ein-Tim I can reproduce this on iOS 14.3.

[dsarkar]

Any updates will be reported here.
Internal Tracking ID: EXPOSUREAPP-4755

[dsarkar]

@MikeMcC399 Thanks for your comments, which have been added to the ticket as additional remarks.

[Ein-Tim]

I actually can't reproduce this anymore on CWA 1.11 and iOS 14.4.
What about you @dsarkar?

I've uninstalled the App and downloaded version 1.11 from the App Store. I did the onboarding and afterwards I set the time back (1 month back). Everything looked correct, "Risiko-Ermittlung war für 0 der letzten 14 Tage aktiv".

So the problem with the large number seems to be solved, still I think the behavior for a shifted back time should be the same as for a time in the future.

[dsarkar]

@Ein-Tim

• CWA 1.11 / iOS 14.4 / iPhone6s / Wifi on / SIM card and Vodafone network

• I set the date to 1.12.2020 and I get a warning, see screenshot.

• Same behavior for future date 28.02.2021
• So, looks good now!

[Ein-Tim]

Yes, looks definitely better than before.
I have different behaviors, either the screen that you have is shown or the quote "Exposure logging was active for 0 of the past 14 days."

will close this now

[dsarkar]

@Ein-Tim Thanks!