[Bug]: Federation share to ldap user only with GUID

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Share Folder from "local-user@local.nextcloud.com" to "ldap-user-UPN@remote.nextcloud.com" as federation.
-> "ldap-user-UPN@remote.nextcloud.com" not get federation reqest.

Share Folder from "local-user@local.nextcloud.com" to "B73209BA-82C2-4VA8-ES01-526472099293@remote.nextcloud.com"
-> "ldap-user-UPN@remote.nextcloud.com" (LDAP GUID "B73209BA-82C2-4VA8-ES01-526472099293") get the federation reqest.

Steps to reproduce

.

Expected behavior

Share Folder from "local-user@local.nextcloud.com" to "ldap-user-UPN@remote.nextcloud.com" as federation sould work without LDAP GUID.

Installation method

Community Docker image

Nextcloud Server version

27

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.2

Web server

Nginx

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

Fresh Nextcloud Server install

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

system
{
    "system": {
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "apps_paths": [
            {
                "path": "\/nextcloud\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "\/apps2",
                "url": "\/apps2",
                "writable": true
            }
        ],
        "enable_previews": false,
        "allow_local_remote_servers": true,
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "logtimezone": "Europe\/Berlin",
        "logdateformat": "Y-m-d H:i:s",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "remote.nextcloud.tld"
        ],
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "memcache.local": "\\OC\\Memcache\\APCu",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 6379
        },
        "filesystem_check_changes": 1,
        "default_phone_region": "de",
        "overwrite.cli.url": "https:\/\/remote.nextcloud.tld",
        "dbtype": "mysql",
        "version": "27.1.4.1",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "loglevel": 0,
        "maintenance": false,
        "mail_smtpmode": "smtp",
        "mail_smtpauthtype": "PLAIN",
        "mail_smtpport": "587",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpsecure": "tls",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauth": 1,
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "app_install_overwrite": [
            "spreed",
            "twofactor_yubikey",
            "twofactor_nextcloud_notification",
            "groupfolders",
            "bookmarks",
            "whiteboard",
            "bruteforcesettings",
            "files_downloadactivity",
            "onlyoffice",
            "twofactor_totp",
            "extract",
            "mail",
            "twofactor_u2f",
            "files_markdown",
            "files_antivirus",
            "richdocumentscode",
            "theming_customcss",
            "richdocuments"
        ],
        "theme": "",
        "updater.release.channel": "stable"
    }
}

List of activated Apps

Enabled:
  - activity: 2.19.0
  - admin_audit: 1.17.0
  - bruteforcesettings: 2.7.0
  - circles: 27.0.1
  - cloud_federation_api: 1.10.0
  - dashboard: 7.7.0
  - dav: 1.27.0
  - deck: 1.11.1
  - federatedfilesharing: 1.17.0
  - federation: 1.17.0
  - files: 1.22.0
  - files_antivirus: 5.4.0
  - files_downloadactivity: 1.16.0
  - files_external: 1.19.0
  - files_markdown: 2.4.1
  - files_pdfviewer: 2.8.0
  - files_reminders: 1.0.0
  - files_rightclick: 1.6.0
  - files_sharing: 1.19.0
  - files_trashbin: 1.17.0
  - files_versions: 1.20.0
  - impersonate: 1.14.0
  - logreader: 2.12.0
  - lookup_server_connector: 1.15.0
  - notes: 4.8.1
  - notifications: 2.15.0
  - oauth2: 1.15.1
  - password_policy: 1.17.0
  - photos: 2.3.0
  - privacy: 1.11.0
  - provisioning_api: 1.17.0
  - related_resources: 1.2.0
  - richdocuments: 8.2.3
  - serverinfo: 1.17.0
  - settings: 1.9.0
  - spreed: 17.1.3
  - survey_client: 1.15.0
  - suspicious_login: 5.0.0
  - text: 3.8.0
  - theming: 2.2.0
  - theming_customcss: 1.15.0
  - twofactor_backupcodes: 1.16.0
  - twofactor_totp: 9.0.0
  - updatenotification: 1.17.0
  - user_status: 1.7.0
  - viewer: 2.1.0
  - weather_status: 1.7.0
  - workflow_pdf_converter: 1.12.0
  - workflowengine: 2.9.0
Disabled:
  - comments: 1.17.0 (installed 1.11.0)
  - contactsinteraction: 1.8.0 (installed 1.2.0)
  - encryption: 2.15.0 (installed 2.0.0)
  - firstrunwizard: 2.16.0 (installed 2.10.0)
  - integration_collaboard: 1.0.4 (installed 1.0.4)
  - nextcloud_announcements: 1.16.0 (installed 1.10.0)
  - recommendations: 1.6.0 (installed 0.4.0)
  - sharebymail: 1.17.0 (installed 1.9.0)
  - support: 1.10.0 (installed 1.3.0)
  - systemtags: 1.17.0 (installed 1.11.0)
  - user_ldap: 1.17.0

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

.

Additional info

.

Start by inspecting the federatedfilesharing, federation, and user_ldap app entry points, then reproduce the share using the LDAP UPN and the LDAP GUID. Trace how the recipient is resolved during federation sharing. Done means the federation request reaches the LDAP user when the UPN is used, with a regression test covering both identifiers.