External storage share status not visible for other users

[ghost]

Steps to reproduce

1. Mount an external SMB / CIFS folder (via Admin -> External storage):
   
2. set availability of said folder to group a,
3. create a subfolder on the external folder via Files app (Web UI),
4. share the subfolder as User A (member of group a, LDAP backend) (Details -> Sharing -> Share link),
5. login as User B (LDAP backend),
6. browse to the subfolder.

Expected behaviour

User B sees that the subfolder is shared.

Actual behaviour

User B does not see the share status of the subfolder.
Neither the folder icon nor the details of said folder are indicating the share status.

Server configuration

Operating system: Linux files.starface.de 4.4.0-78-generic #99-Ubuntu SMP Thu Apr 27 15:29:09 UTC 2017 x86_64

Web server: Apache (apache2handler)

Database: pgsql PostgreSQL 9.5.7 on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609, 64-bit

PHP version: 7.0.18-0ubuntu0.16.04.1
Modules loaded: Core, date, libxml, openssl, pcre, zlib, filter, hash, Reflection, SPL, session, standard, apache2handler, PDO, xml, apcu, bz2, calendar, ctype, curl, dom, mbstring, fileinfo, ftp, gd, gettext, gmp, iconv, igbinary, imagick, intl, json, ldap, exif, mcrypt, pdo_pgsql, pgsql, Phar, posix, readline, redis, shmop, SimpleXML, smbclient, sockets, sysvmsg, sysvsem, sysvshm, tokenizer, wddx, xmlreader, xmlwriter, xsl, zip, libsmbclient, Zend OPcache

Nextcloud version: 12.0.0 - 12.0.0.29

Updated from an older Nextcloud/ownCloud or fresh install:

Where did you install Nextcloud from:

Signing status:

Signing status

[]

List of activated apps:

App list

Enabled:
 - activity: 2.5.2
 - admin_audit: 1.2.0
 - bruteforcesettings: 1.0.2
 - calendar: 1.5.3
 - comments: 1.2.0
 - dav: 1.3.0
 - drawio: 0.8.8
 - external: 2.0.3
 - federatedfilesharing: 1.2.0
 - federation: 1.2.0
 - files: 1.7.2
 - files_accesscontrol: 1.2.4
 - files_automatedtagging: 1.2.2
 - files_downloadactivity: 1.1.1
 - files_external: 1.3.0
 - files_pdfviewer: 1.1.1
 - files_retention: 1.1.2
 - files_sharing: 1.4.0
 - files_texteditor: 2.4.1
 - files_trashbin: 1.2.0
 - files_versions: 1.5.0
 - files_videoplayer: 1.1.0
 - firstrunwizard: 2.1
 - gallery: 17.0.0
 - issuetemplate: 0.2.1
 - keeweb: 0.4.0
 - logreader: 2.0.0
 - lookup_server_connector: 1.0.0
 - news: 11.0.5
 - nextcloud_announcements: 1.1
 - notifications: 2.0.0
 - oauth2: 1.0.5
 - password_policy: 1.2.2
 - provisioning_api: 1.2.0
 - serverinfo: 1.2.0
 - sharebymail: 1.2.0
 - survey_client: 1.0.0
 - systemtags: 1.2.0
 - theming: 1.3.0
 - twofactor_backupcodes: 1.1.1
 - twofactor_totp: 1.3.0
 - updatenotification: 1.2.0
 - user_external: 0.4
 - user_ldap: 1.2.1
 - user_saml: 1.3.2
 - workflowengine: 1.2.0

Disabled:
 - encryption

The content of config/config.php:

Config report

{
    "instanceid": "ochx4a4zgar0",
    "passwordsalt": "***REMOVED SENSITIVE VALUE***",
    "secret": "***REMOVED SENSITIVE VALUE***",
    "trusted_domains": [
        "files.starface.de"
    ],
    "datadirectory": "\/var\/www\/data",
    "overwrite.cli.url": "https:\/\/files.starface.de",
    "dbtype": "pgsql",
    "version": "12.0.0.29",
    "dbname": "nextcloud",
    "dbhost": "\/var\/run\/postgresql",
    "dbtableprefix": "oc_",
    "dbuser": "***REMOVED SENSITIVE VALUE***",
    "dbpassword": "***REMOVED SENSITIVE VALUE***",
    "logtimezone": "UTC",
    "installed": true,
    "mail_smtpmode": "smtp",
    "ldapIgnoreNamingRules": false,
    "mail_from_address": "nextcloud",
    "mail_domain": "starface.de",
    "mail_smtpauthtype": "LOGIN",
    "mail_smtpauth": 1,
    "mail_smtphost": "mail.starface.de",
    "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
    "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
    "memcache.local": "\\OC\\Memcache\\APCu",
    "memcache.locking": "\\OC\\Memcache\\Redis",
    "filelocking.enabled": "true",
    "redis": {
        "host": "\/var\/run\/redis\/redis.sock",
        "port": 0,
        "timeout": 0
    },
    "appstore.experimental.enabled": true,
    "maintenance": false,
    "loglevel": 1,
    "ldapProviderFactory": "\\OCA\\User_LDAP\\LDAPProviderFactory",
    "trashbin_retention_obligation": "auto, 14",
    "versions_retention_obligation": "auto, 30",
    "updater.release.channel": "stable",
    "trusted_proxies": [
        "172.17.60.25"
    ]
}

Are you using external storage, if yes which one: Array
(
[10] => \OCA\Files_External\Lib\Storage\SMB
[11] => \OCA\Files_External\Lib\Storage\SMB
)

Are you using encryption: no

Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/...

LDAP configuration (delete this part if not used)

LDAP config

```
With access to your command line run e.g.:
sudo -u www-data php occ ldap:show-config
from within your Nextcloud installation folder

Without access to your command line download the data/owncloud.db to your local
computer or access your SQL server remotely and run the select query:
SELECT * FROM `oc_appconfig` WHERE `appid` = 'user_ldap';


Eventually replace sensitive data as the name/IP-address of your LDAP server or groups.
```

### Client configuration **Browser:** Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/58.0.3029.110 Chrome/58.0.3029.110 Safari/537.36

Operating system:

Logs

Web server error log

Web server error log

``` Insert your webserver log here ```

Nextcloud log (data/nextcloud.log)

Nextcloud log

``` Insert your Nextcloud log here ```

Browser log

Browser log

``` Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log
c) ...
```

[MorrisJobke]

@nextcloud/sharing @icewind1991 @rullzer I guess this is the intended behaviour, right?

[schiessle]

yes, only the owner and the user who created the share sees it. You could argue in this case that the whole group (or all the users configured in the external storage settings) is the owner. But neither our filecache nor our share table can handle something like "group ownership".