[Bug]: Previews and Download not available for Link Shares of Remote Shares

[kesselb]

Bug description

While testing the backports for #51389, I noticed that although link shares can be opened, previews are not displayed, and the download button is missing. This behavior seems unusual, but I'm not familiar with the topic, so it might be the expected outcome. 🤷

Steps to Reproduce:

1. Set up Alice on Instance A and Bob on Instance B.
2. Alice uploads a folder containing pizza pictures to Instance A.
3. Alice shares the pizza folder with Bob on Instance B, granting "View only" or "Can edit" permissions.
4. Bob can open the share, view the pizza pictures, and sees the download option.
5. Bob creates a public link share for the folder.
6. When opening the link, the list of images is displayed, but previews are not shown, and it's not possible to open or download the images.

Additionally, I observed that the "hide download" option for the link share is enabled and cannot be unchecked because checkInheritedAttributes overwrites it. Reverting #50642 did not help.

Instance A (share initiator)

Instance B (share receiver)

Instance B (public link share)

Expected behavior:

I'm unsure 🙈

[ignaciovidalfranco]

I can confirm this. The behaviour that I expect from this feature is to be able to view a picture in the browser through the publicly shared link, but hide any download options (even though I know a tech savvy user could still download them).

When I share a folder with the "hide download" checkbox active, I can only list filenames. If I click on them, I am getting 403 errors in the nginx logs. They stop coming as soon as I uncheck the "hide download" checkbox.

GET /public.php/dav/files/REDACTED/filename.jpg HTTP/2.0" 403 20 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:136.0) Gecko/20100101 Firefox/136.0"
GET /apps/files_sharing/publicpreview/REDACTED?file=%2Ffilename.jpg&x=32&y=32&mimeFallback=true&v=afe644&a=0 HTTP/2.0" 403 20 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:136.0) Gecko/20100101 Firefox

[gdnmhr]

This does not only apply to link shares, but also to local reshares on Server B, see #51245 for reference.

[boneycursor]

I think this is the same bug I came here to report:

• Make a folder
• Put a video in it
• Make a public link to the folder
• Video cannot be previewed

Workarounds:

• Put the folder inside folder and make a link to the parent folder
  or
• Make a link directly to the video

It would be great to see a fix a for this, I'm already getting confused phonecalls.