Nextcloud Apps page: no screenshots (403 from usercontent.apps.nextcloud.com)

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I have searched the forum for similar issues

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This category is for issues regarding specific apps, NOT general issues with YunoHost.

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What app is this about, and its version

Nextcloud 33.0.4~ynh1, now upgraded to 35.0.1~ynh1

What YunoHost version are you running

12.1.41.2 (Debian 12 bookworm)

What type of hardware are you using

Old laptop or computer

Describe your issue

After restoring a full backup on the new machine, the Apps page in Nextcloud shows no screenshots. Most apps show a gear icon, and a few show a black “Preview not available / Image not recognized” box. App names, descriptions and the Download and enable buttons all work.

image

Does anyone know what could be wrong/what the solution is?

Share relevant logs or error messages

I asked Claude for help diagnosing the issue and this is a summary of that after reading through logs:

  • In browser dev tools, the failing image requests go to usercontent.apps.nextcloud.com and return 403 Forbidden. This happens in every browser, including private windows. Nothing reaches my nginx access log.
  • The long path in the request decodes (base64) to another usercontent.apps.nextcloud.com/<base64> address, and only inside that is the real GitHub raw image. So the screenshot address is wrapped by the proxy twice.
  • The app store’s own JSON already contains addresses of the form usercontent.apps.nextcloud.com/<base64>. Counting the first 16 characters after the slash: aHR0cHM6Ly9yYXcu (a single-wrapped https://raw) appears about 1000 times, both in the cached apps.json and in a fresh download from apps.nextcloud.com/api/v1/platform/33.0.4/apps.json. The double-wrapped form (aHR0cHM6Ly91c2Vy) appears in neither.
  • In Nextcloud 33.0.4, apps/settings/lib/Controller/AppSettingsController.php builds the address like this, with no check for whether it is already proxied: 534: 'screenshot' => isset($app['screenshots'][0]['url']) ? 'https://usercontent.apps.nextcloud.com/' . base64_encode($app['screenshots'][0]['url']) : '',
    Network is fine. From the server, curl -I to raw.githubusercontent.com and apps.nextcloud.com both return HTTP/2 200, and PHP as the app user can download from GitHub. Nextcloud’s config has no has_internet_connection, appstoreurl or proxy overrides.
  • occ status is healthy and nextcloud.log shows no errors about images or the app store.

Please let me know if I need to upload any specific logs.

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I didn’t find it before I made my post, but there is a bug report about this here - [Bug]: App Store does not show preview screenshots · Issue #65055 · nextcloud/server · GitHub

The solution in this issue worked for me to get images working again.

What I did:

In apps/appstore/lib/Controller/ApiController.php replaced line 309 with return $this->proxify($url); and line 481 with 'screenshot' => isset($app['screenshots'][0]['url']) ? $this->proxify($app['screenshots'][0]['url']) : '', then added before the very last closing bracket in this file:

private function proxify(string $url): string {
    $prefix = 'https://usercontent.apps.nextcloud.com/';
    return str_starts_with($url, $prefix) ? $url : $prefix . base64_encode($url);
}

Verified syntax was ok with php -l apps/appstore/lib/Controller/ApiController.php

Then I reloaded php with sudo systemctl reload php8.4-fpm php8.5-fpm and the images on the app page are working again.