Nextcloud CardDAV Error - "Image can't be decoded"

[stefanpinter]

hi!
davx5 is having a very hard time synchronizing/initial downloading contacts from Nextcloud... it always tells me "Image can't be decoded" but it is downloading some contacts very slowly...
what can I do?

[rfc2822]

Hi,

There's an invalid image in your vCard. Can you fix it on the server side? In the next DAVx⁵ version, these errors will be ignored again (like in previous versions). Where did you get DAVx⁵ from (which version)?

But the root cause is that there's an invalid image in the vCard.

[stefanpinter]

ah, thanks! I don't see images in nextcloud, but yes, when i click on "Delete Image" it syncs the affected user until the next "invalid image"
hopefully the next version is online soon :)

[rfc2822]

We'll push it very soon. Do you have the Google Play version?

[stefanpinter]

yes Google Play version
I now deleted all "images" and it is syncing properly now though :)

[rfc2822]

Unfortunately, Google is holding back our update because they told us to shorten the app name in the store, which has to be verified first. But it will be there soon. Glad to hear that the workaround works.

[justjulian]

@rfc2822 Thanks for the details. I'm facing the same error message. The line in the vcard is similar to:

PHOTO;VALUE=URI:https://example.com/store/avatars/d0c94ecb-8485-4cb8
 -ab3d-e46a2defdc39.jpg?1647875700

This is auto-generated by https://github.com/monicahq/monica (image consisting of two letters based on first name and last name).
I'm no expert on vcard syntax. Does this look invalid to you?

[devvv4ever]

Version 4.2.0.2 should fix this!

[rfc2822]

Yes, but 4.2.0.2 (already released) will just ignore the problem (like in earlier versions) but the image remains invalid and thus unsynced.

Depends on what the .jpg URL contains… probably something invalid?

[justjulian]

The URL returns a valid JPG, however, only for valid credentials (same credentials as for the DAV endpoint). I guess only public images are supported here?

[rfc2822]

No, DAVx⁵ sends authentication (for instance, this is used by iCloud). However I can't say why it fails in your case without verbose logs. You can enable verbose logs in DAVx⁵ and then see everything that is sent/received.

[justjulian]

Thanks for the very quick replies, really appreciate it! I went through the logs, quite detailed, really well to read!

The URL is correctly processed and authorization header is being set. However, then a 302 redirect from https://example.com/store/avatars/8fb8ad17-9f7a-4455-acb3-21b0ab248a2b.jpg?1647875700 to https://example.com is received. It looks like the passed credentials only work for the DAV endpoint but not for the images.
This seems to be the related issue in my case: monicahq/monica#5861

Of course, DAVx⁵ can't do anything at that point because DAVx⁵ would need another set of credentials for the images.