fix: Pass the mountpoint target user to storages without owner

[juliushaertl]

Storages that do not have a dedicated owner (e.g. groupfolders, external
storages) currently always assume the current session user as the owner.
This leads to several issues when there is no user session but a node is
obtained through a user folder.

In order to have the correct user available we need to pass the user
that is used to setup a mountpoint along to the storage layer as we
generally assume that an owner is available for those.

Steps to see the issue:

Text

• Setup a local global external storage
• As a user with access to it
  • Have text enabled
  • Create a share link with edit permissions
  • Access the share link in a private browser window
  • Try to save the file which fails because file hooks like the version backend or files metadata extractors try to operate with the storage owner

[come-nc]

Is it not possible to set the user in the session?
I’m not sure I understand how this works not having a session, apart from public share.

Other places like https://github.com/nextcloud/server/blob/master/apps/dav/lib/SystemTag/SystemTagsRelationsCollection.php#L56 (Just know this one because I had a conflict about this line in another PR) expects to have a user in session, won’t that cause troubles?

[juliushaertl]

Yeah, when debugging further I noticed that setting the session user temporarily would be more sensible for the onlyoffice bug. I came up with #44295 for that. For public share links we though still need this as the node does not hold information about the share (or share owner) which is used to construct the user folder

server/lib/private/Share20/Share.php

Line 188 in e7a7b4a

$userFolder = $this->rootFolder->getUserFolder($this->sharedBy);

but is lost afterwards before this PR.

[come-nc]

Should something like https://github.com/nextcloud/server/blob/master/apps/dav/lib/Storage/PublicOwnerWrapper.php be used for public links?

[juliushaertl]

That's a great hint, wasn't aware of that wrapper, let me see if that can be adopted

[juliushaertl]

Is it not possible to set the user in the session?
I’m not sure I understand how this works not having a session, apart from public share.

Collabora requests don't have a session itself. Using the current session user might lead to wrong assumptions further down, the mountpoint target user is the more correct one. The larger problem is that the storage API doesn't really cover the use case of having a storage that has "shared" ownership, but at least the mount owner is more correct then just always assuming the logged in user. The nodes API is flexible so that a user folder for a different user can be requested where the current session user would actually be incorrect.

Should something like https://github.com/nextcloud/server/blob/master/apps/dav/lib/Storage/PublicOwnerWrapper.php be used for public links?

I checked this but think setting the owner on the storage itself seems cleaner to me as it is passed along when building the storage class instance.

[come-nc]

Suggested change

	* @param string|null $user
	* @param string|null $user Owner user id

[nickvergessen]

@juliushaertl Please document in https://docs.nextcloud.com/server/latest/developer_manual/app_publishing_maintenance/app_upgrade_guide/upgrade_to_30.html#id1

(all changes in lib/public/)

[juliushaertl]

/backport to stable29

[juliushaertl]

/backport to stable28

[juliushaertl]

/backport to stable28

[backportbot]

The backport to stable28 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable28
git pull origin stable28

# Create the new backport branch
git checkout -b backport/44294/stable28

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 4910e7e2

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/44294/stable28

Error: Failed to create pull request: Validation Failed: {"resource":"PullRequest","code":"custom","message":"A pull request already exists for nextcloud:backport/44294/stable28."}

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.