File sharing and Security

File Sharing

Nextcloud users can share files with their Nextcloud groups and other users on the same Nextcloud server, with Nextcloud users on other Nextcloud servers, and create public shares for people who are not Nextcloud users. You have control of a number of user permissions on file shares.

Configure your sharing policy on your Admin page in the Sharing section.

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  • Check Allow apps to use the Share API to enable users to share files. If this is not checked, no users can create file shares.

  • Check Set default expiration date for shares to set a default expiration date on local user and group shares.

  • Check Enforce expiration date to always enforce the configured expiration date on local user and group shares.

    Note

    Users will not be able to set the expiration date further in the future than the enforced expiration date, although they will be able to set a more recent date. Also note that users will be able to update the expiration date again at a later point. The expiration date is based on the current date and not on the share creation date. The user will be able to extend the expiration date again whenever a previous expiration date is close to be reached.

  • Check Allow users to share via link to enable creating public shares for people who are not Nextcloud users via hyperlink.

  • Check Allow public uploads to allow anyone to upload files to public shares.

  • Check Always ask for a password to proactively ask a user to set a password for a share link.

  • Check Enforce password protection to force users to set a password on all public share links. This does not apply to local user and group shares.

  • Check Set default expiration date for link shares to set a default expiration date on public shares.

  • Check Enforce expiration date to always enforce the configured expiration date on public shares.

    Note

    Users will not be able to set the expiration date further in the future than the enforced expiration date, although they will be able to set a more recent date. Also note that users will be able to update the expiration date again at a later point. The expiration date is based on the current date and not on the share creation date. The user will be able to extend the expiration date again whenever a previous expiration date is close to be reached.

  • Check Allow resharing to enable users to re-share files shared with them.

  • Check Allow sharing with groups to enable users to share with groups.

  • Check Restrict users to only share with users in their groups to confine sharing within group memberships.

    Note

    This setting does not apply to the Federated Cloud sharing feature. If Federated Cloud Sharing is enabled, users can still share items with any users on any instances (including the one they are on) via a remote share.

  • Check Exclude groups from sharing to prevent members of specific groups from creating any file shares in those groups. When you check this, you’ll get a dropdown list of all your groups to choose from. Members of excluded groups can still receive shares, but not create any.

  • Check Allow username autocompletion in share dialog to enable auto-completion of Nextcloud usernames.

  • Check Restrict username autocompletion to users within the same groups to limit username autocompletion to users from within the same groups as the share owner.

  • Check Show disclaimer text on the public link upload page to set and show a disclaimer text on public links with hidden file lists.

With Default share permissions you are able to set the default permissions for user-shares (Create, Change, Delete and Reshare) without forcing them.

Note

Nextcloud does not preserve the mtime (modification time) of directories, though it does update the mtimes on files. See the Wrong folder date when syncing for a discussion of this.

Note

There are more sharing options on config.php level available: Configuration Parameters

Distinguish between max expiration date and default expiration date

The expiration date which can be set and enforced in the settings above are the hard limit and the default value at the same time. Sometimes admins want to have a moderate default expire date, for example 7 days but make sure that the user can’t extend it to more than 14 days.

In order to do so, set an enforced expiration date in the settings as described above and set the default value to something below the maximal possible expiration date with the following OCC commands:

occ config:app:set --value <DAYS> core internal_defaultExpDays
occ config:app:set --value <DAYS> core link_defaultExpDays

Get a notification before a share expires

Users can get a notification before a share expires. In order to do so a cronjob need to be configured which calls the following OCC command once a day:

occ sharing:expiration-notification

A notification will be send for all shares which expire within the next 24 hours.

Transferring files to another user

You may transfer files from one user to another with occ. This is useful when you have to remove a user. Be sure to transfer the files before you delete the user! This transfers all files from user1 to user2, and the shares and metadata info associated with those files (shares, tags, comments, etc). Trashbin contents are not transferred:

occ files:transfer-ownership user1 user2

(See Using the occ command for a complete occ reference.)

Users may also transfer files or folders selectively by themselves. See user documentation for details.

Creating persistent file Shares

When a user is deleted, their files are also deleted. As you can imagine, this is a problem if they created file shares that need to be preserved, because these disappear as well. In Nextcloud files are tied to their owners, so whatever happens to the file owner also happens to the files.

One solution is to create persistent shares for your users. You can retain ownership of them, or you could create a special user for the purpose of establishing permanent file shares. Simply create a shared folder in the usual way, and share it with the users or groups who need to use it. Set the appropriate permissions on it, and then no matter which users come and go, the file shares will remain. Because all files added to the share or edited in it, automatically become owned by the owner of the share regardless of who adds or edits them.

 

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