[Bug]: vCard version 3.0 generated from uploaded vCard 4.0 is invalid

⚠️ 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

If a vCard version 4.0 is uploaded to Nextcloud (NC), NC creates a vCard 3.0 from it, which is invalid. The TEL property is not transformed correctly. The resulting erroneous vCard 3.0:

BEGIN:VCARD
VERSION:3.0
PRODID:-//Sabre//Sabre VObject 4.5.4//EN
UID:yllwtc17w1zf0ln772rjv4xcdtcc7kpech32
FN:test v4-2
N:v4-2;test;;;
REV:20240820T123443Z
TEL;TYPE=cell;VALUE=URI:tel:+491234567890
END:VCARD

Because of the invalid TEL property, if you sync the resulting vCard 3.0 to an android phone, the phone number (i.e., TEL) is not shown or available there.

I have noticed this because NC contacts shows the number as tel:+491234567890, including the tel, and thus the URI in the contacts web app becomes tel:tel:+491234567890.

Also, here is the output of vcard, a Python vCard version 3.0 validator:

$ vcard --verbose ../vcard3nc.vcf
Invalid parameter name (See RFC 2426 section 4 for param-name syntax): VALUE
File: ../vcard3nc.vcf
File line: 8
vCard line: 7
Property: TEL
Property line: TEL;TYPE=cell;VALUE=URI:tel:+49133742069

vCard specifications v3.0 & v4.0.

Steps to reproduce

1. Create a vCard version 4.0. I'm using khard for this.
   Example of a resulting vCard:

BEGIN:VCARD
VERSION:4.0
UID:yllwtc17w1zf0ln772rjv4xcdtcc7kpech32
FN:test v4-2
N:v4-2;test;;;
REV:20240820T123443Z
TEL;TYPE=cell;VALUE=uri:tel:+491234567890
END:VCARD

2. Upload this vCard to Nextcloud. I'm using vdirsyncer for it.
3. Download version 3.0 of this vCard, which was created by Nextcloud: curl -ku '<USERNAMER>:<PASSWORD>' https://<NC-DOMAIN>/remote.php/dav/addressbooks/users/<USERNAME>/<ADDRESSBOOK>/<UID>.vcf -H 'Depth: 0' -H 'Content-Type: text/vcard; charset=utf-8;' -H 'Accept: text/vcard; version=3.0'

Expected behavior

A valid vCard version 3.0 should be generated from the vCard 4.0. The TEL property should be transformed such that it conforms to the vCard version 3.0 spec.

Installation method

Community NextcloudPi appliance

Nextcloud Server version

28.0.8

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.2

Web server

Apache (supported)

Database engine version

MariaDB

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

Well, I did a major upgrade in the past.

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": {
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": {
            "0": "localhost",
            "1": "nextcloudpi.local",
            "2": "nextcloudpi",
            "3": "nextcloudpi.lan",
            "20": "picloud",
            "21": "picloud.home.arpa",
            "22": "192.168.10.5"
        },
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "28.0.8.1",
        "overwrite.cli.url": "https:\/\/picloud\/",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "memcache.local": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 0,
            "timeout": 0,
            "password": "***REMOVED SENSITIVE VALUE***"
        },
        "tempdirectory": "\/var\/www\/nextcloud-data\/data\/tmp",
        "mail_smtpmode": "sendmail",
        "mail_smtpauthtype": "LOGIN",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "preview_max_x": "2048",
        "preview_max_y": "2048",
        "jpeg_quality": "60",
        "overwriteprotocol": "https",
        "data-fingerprint": "f1f8769978c71c0cd5016428782b7ccb",
        "maintenance": false,
        "maintenance_window_start": 3,
        "theme": "",
        "loglevel": 2,
        "htaccess.RewriteBase": "\/",
        "default_phone_region": "DE",
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "logfile": "\/var\/www\/nextcloud-data\/data\/nextcloud.log",
        "app_install_overwrite": [
            "news",
            "files_rightclick"
        ]
    }
}

List of activated Apps

Enabled:
  - calendar: 4.7.15
  - cloud_federation_api: 1.11.0
  - contacts: 5.5.3
  - cookbook: 0.11.1
  - dav: 1.29.2
  - federatedfilesharing: 1.18.0
  - files: 2.0.0
  - files_reminders: 1.1.0
  - files_versions: 1.21.0
  - logreader: 2.13.0
  - lookup_server_connector: 1.16.0
  - news: 24.0.0
  - notes: 4.10.1
  - notifications: 2.16.0
  - notify_push: 0.7.0
  - oauth2: 1.16.3
  - photos: 2.4.0
  - provisioning_api: 1.18.0
  - related_resources: 1.3.0
  - serverinfo: 1.18.0
  - settings: 1.10.1
  - tasks: 0.16.1
  - text: 3.9.2
  - theming: 2.3.0
  - twofactor_backupcodes: 1.17.0
  - unroundedcorners: 1.1.3
  - viewer: 2.2.0
  - workflowengine: 2.10.0
Disabled:
  - activity: 2.20.0 (installed 2.8.2)
  - admin_audit: 1.18.0
  - bruteforcesettings: 2.8.0
  - circles: 28.0.0 (installed 25.0.0)
  - comments: 1.18.0 (installed 1.6.0)
  - contactsinteraction: 1.9.0 (installed 1.1.0)
  - dashboard: 7.8.0 (installed 7.0.0)
  - encryption: 2.16.0 (installed 2.7.0)
  - federation: 1.18.0 (installed 1.5.0)
  - files_external: 1.20.0
  - files_pdfviewer: 2.9.0 (installed 1.5.0)
  - files_rightclick: 0.15.1 (installed 0.15.1)
  - files_sharing: 1.20.0 (installed 1.8.0)
  - files_trashbin: 1.18.0 (installed 1.15.0)
  - firstrunwizard: 2.17.0 (installed 2.4.0)
  - nextcloud_announcements: 1.17.0 (installed 1.5.0)
  - nextcloudpi: 0.0.2 (installed 0.0.1)
  - password_policy: 1.18.0 (installed 1.5.0)
  - previewgenerator: 99.99.99
  - privacy: 1.12.0 (installed 1.0.0)
  - recommendations: 2.0.0 (installed 0.4.0)
  - sharebymail: 1.18.0 (installed 1.6.0)
  - support: 1.11.1 (installed 1.0.0)
  - survey_client: 1.16.0 (installed 1.3.0)
  - suspicious_login: 6.0.0
  - systemtags: 1.18.0 (installed 1.5.0)
  - twofactor_totp: 10.0.0-beta.2
  - updatenotification: 1.18.0 (installed 1.11.0)
  - user_ldap: 1.19.0
  - user_status: 1.8.1 (installed 1.0.0)
  - weather_status: 1.8.0 (installed 1.0.0)

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

{"reqId":"ZsR_3xlX3J4_eWOANZ2sPQAAAA4","level":0,"time":"2024-08-20T11:37:03+00:00","remoteAddr":"fd01::8888:aac:d27b:96fc","user":"<USERNAME>","app":"dav","method":"PUT","url":"/remote.php/dav/addressbooks/users/<USERNAME>/contacts/3dbjzjxxtw30lw9d1x8xj0vahea0j9nlh2a6.vcf","message":"Activity generated for a new card in addressbook 3","userAgent":"vdirsyncer/0.19.2","version":"28.0.8.1","data":{"app":"dav"}}

Additional info

No response

Start by reproducing the conversion through the remote.php/dav/addressbooks endpoint using the provided vCard 4.0 input and version 3.0 request, then trace the DAV vCard conversion and Sabre VObject handling. Done means the downloaded vCard validates as version 3.0 and its TEL value no longer includes the invalid VALUE parameter or duplicated tel scheme.