CalDav not working with Let's Encrypt certificate or Synology DSM anymore?

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CalDav not working with Let's Encrypt certificate or Synology DSM anymore?

For quite a while I have been using a CalDAV calendar hosted on my private Synology NAS. A few days ago (beginning of August?) accessing this calendar by my iPhone (iOS 15.6) stopped working, whereas accessing it by Thunderbird still works. This means: DSM calendar itself is still working fine.

I've already deleted the calendar account on my phone and tried to recreate it, but iOS says it can not connect by using SSL (but Thunderbird does!). Of course I do not want to use the calendar without SSL.

It's just a guess, but does iOS calendar does not support Let's encrypt certificates anymore?? However Safari can connect to the calendar just fine, without certificate warning or similar. It does not make sense to me that one iOS app should accept the LE certificate and the other should not. Calendar account setup does also not show me the certificate to allow me to accept it, nor a meaningful information why it refuses to connect...

Thanks in advance!

Frank

Posted on Aug 5, 2022 6:23 AM

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Answer 1

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Starfish4711 Author

Level 1

4 points

Aug 7, 2022 8:16 AM in response to Starfish4711

Seem's I got it!

It has nothing to do with certificates: when I deleted the account to recreate it, beforehand I've noted all settings of the old account, including the URL. But the URL shown by iOS is not correct, it is incomplete. For DSM Calendar the URL has to contain additional data, but this data seems to be truncated after saving the account successfully. Therefor I tried to recreate the account with the incomplete URL all the time. Now when I looked up the URL within DSM Calendar, I realized the additional data and using this longer URL I was able to recreate the account on my iPhone.

It does not explain why the account stopped working some days ago, but at least it is working now again. :-)

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Answer 2

Aug 5, 2022 6:35 AM in response to Starfish4711

Is this your corporate iPhone? Then please contact the system administrator of your corporate
If it is your personal device, in that case, do you have any profile installed by your corporate/organisation/enterprise/School Management?
1. Erase the profile added by you If you have installed a profile on your own --> Install or remove configuration profiles on iPhone - Apple ...
2. Or please contact the system administrator of the organisation who provided the profile to you
If you want to turn on SSL trust for that certificate, go to Settings > General > About > Certificate Trust Settings. Under "Enable full trust for root certificates," turn on trust for the certificate. Apple recommends deploying certificates via Apple Configurator or Mobile Device Management (MDM). --> Trust manually installed certificate profiles in iOS and iPadOS ...

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Answer 3

Starfish4711 Author

Level 1

4 points

Aug 6, 2022 1:49 AM in response to SravanKrA

1.: no, it's no corporate iphone in means of MDM or similar

2.: there is no profile for accessing my Synology Calendar. There are profiles for VPN connection or internal CAs, but these profiles have been there before I had added my Synology Calendar some month ago and have not changed in between.

3.: At "Settings > General > About > Certificate Trust Settings" there are only 2 certificates and these do not belong to my Synology Calendar. I could try to download the Let's Encrypt CA certificate and add it here (how without MDM?), but this CA certificate should be known by iOS already, otherwise Safari would not allow me to browse websites which are encrypted with LE certificates.

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CalDav not working with Let's Encrypt certificate or Synology DSM anymore?

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