RAT profile QR code is regenerated every time the screen is opened

[Ein-Tim]

Avoid duplicates

• [X] Bug is not mentioned in the FAQ
• [X] Bug affects both Android and iOS, for specific issues / questions that apply only to one operating system, please raise them in the respective repositories:
  • Android repository
  • iOS repository
• [X] Bug is not already reported in another issue

Technical details

• Device name: iPhone 6s / Huawei P Smart 2019
• iOS/Android version: 15.2 / 10
• App version: 2.15.1

Describe the bug

The QR code on the RAT profile screen is regenerated every time the screen is opened.

Here are two videos:

https://user-images.githubusercontent.com/67682506/147862890-3a2dbbd0-0054-4906-bfa3-282560581321.mov

https://user-images.githubusercontent.com/67682506/147862888-1415d3d7-cbfb-4f3b-9fac-305fbfbbe835.mp4

Steps to reproduce the issue

1. Open the Corona-Warn-App
2. Click on the "Manage Your Tests" box
3. (Scroll down &) click on "Rapid Test Profile"
4. Generate a new profile if one isn't already generated
5. Take a look at the lower left part of the QR code
6. Close the view
7. Open the view again
8. Take another look at the lower left part of the QR code
9. Notice that the QR code has changed

Expected behaviour

The QR code should only change if the data stored in the QR code has changed.

Additional context

It seems like the REV field in the v-card changes every time, however, If I understand the documentation on https://datatracker.ietf.org/doc/html/rfc6350#section-6.7.4 correctly, this field should only change if the rest of the data (e.g. BDAY) changes.

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Internal Tracking ID: EXPOSUREAPP-11133

[MikeMcC399]

@Ein-Tim As far as the Android app is concerned, it seems that this is "works-as-designed".

See https://github.com/corona-warn-app/cwa-app-android/blob/main/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/coronatest/antigen/profile/VCard.kt#L34

val rev = now.toString(revDateFormatter) // Time the vCard was updated

where it uses the current time to build that field in the QR code.

[MikeMcC399]

Just for comparison, when Microsoft Outlook creates a VCARD .vcf file from a contact it also uses the current time for the REV: field, not the "Modified" date/time-stamp.

[Jo-Achim]

But... somehow I have a bad feeling when data (in this case a QR code) that is supposed to provide one specific information changes!? (Without changing the basic 'in fact' information.)

[larswmh]

Hi @Ein-Tim, thanks for your report. We have created an internal ticket and will raise this topic internally. Internal Tracking ID: EXPOSUREAPP-11133

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Corona-Warn-App Open Source Team

[MikeMcC399]

The real test whether this is a bug, is if it causes a problem when reading the Rapid Test Profile at a testing center. If the test center software does not use the REV field or does not care about its actual value, then it could be omitted from the vCard QR code produced by CWA.

According to the standard, which @Ein-Tim quoted (https://datatracker.ietf.org/doc/html/rfc6350), the field is optional. (See the definition of REV in section 6.7.4 which specifies a cardinality of *1 for this field. and the definition of Property cardinalities in section 3.3 where *1 is equated to "Exactly one instance per vCard MAY be present".)

[dsarkar]

No problems have been reported, It currently works as designed/intended.

[Ein-Tim]

Okay, closing.