Architecture

openDesk is designed as a Kubernetes deployment.

It consists of a set of Helm charts orchestrated by Helmfile.

openDesk includes the functional applications, like file management, chat, and email. Other services such as databases and object storage are included for evaluation purposes only. In production, you must provide these services yourself.

Overview

The following diagram shows a high-level overview of openDesk.

flowchart TD
    A(User) -->|Log In| B[Keycloak]
    subgraph Nubus
        B -->C[Portal]
        B -->|User Directory| OpenLDAP
    end
    C -->|Manage Files| NC[fa:fa-file Nextcloud]
    C -->|Chat & Call| EL[fa:fa-comments Element]
    C -->|Send/Receive E-Mails| OXE[fa:fa-envelope OX App Suite]
    C -->|Manage Appointments| OXC[fa:fa-calendar OX App Suite]
    NC -->|Edit Office Documents| CO[fa:fa-file-word Collabora Online]
    NC -->|Edit diagram.net Documents| CP[fa:fa-chart-diagram CryptPad]
    C -->|Manage Tasks| OP[fa:fa-diagram-project OpenProject]
    C -->|Store Knowledge| XW[fa:fa-book XWiki]
    C -->|Meet People| JI[fa:fa-video Jitsi]

Source

flowchart TD
    A(User) -->|Log In| B[Keycloak]
    subgraph Nubus
        B -->C[Portal]
        B -->|User Directory| OpenLDAP
    end
    C -->|Manage Files| NC[fa:fa-file Nextcloud]
    C -->|Chat & Call| EL[fa:fa-comments Element]
    C -->|Send/Receive E-Mails| OXE[fa:fa-envelope OX App Suite]
    C -->|Manage Appointments| OXC[fa:fa-calendar OX App Suite]
    NC -->|Edit Office Documents| CO[fa:fa-file-word Collabora Online]
    NC -->|Edit diagram.net Documents| CP[fa:fa-chart-diagram CryptPad]
    C -->|Manage Tasks| OP[fa:fa-diagram-project OpenProject]
    C -->|Store Knowledge| XW[fa:fa-book XWiki]
    C -->|Meet People| JI[fa:fa-video Jitsi]

openDesk includes a portal that allows navigation to the respective application. The portal is part of the Identity and Access Management (IAM) application shipped with openDesk: Nubus. Nubus includes OpenLDAP for storing users, groups, and permissions, and Keycloak for single sign-on with LDAP user federation configured to the aforementioned OpenLDAP.

When the user is authenticated by Keycloak, the portal shows the applications the user is permitted to access.

The user can now access applications and use the corresponding functionality without the need to authenticate to applications again. This is implemented using the OpenID Connect (OIDC) protocol.

Nubus (IAM)

Nubus is a specialized IAM platform developed by Univention GmbH to centralize and simplify identity management in IT environments. It is typically used in contexts where user authentication, role-based access control, and integration with multiple systems are essential.

In openDesk, Nubus serves the following purposes:

1. Identity Provider (IdP)

   Nubus acts as the central IdP in a federated authentication system, issuing and managing authentication tokens for applications.

2. Access Control Layer

   As a gateway, Nubus ensures that only authorized users can access specific systems, services, or APIs, enforcing RBAC policies.

3. Integration Hub

   Links applications by synchronizing identity and access data across them, ensuring consistency.

4. User Provisioning

   Automates the process of creating, updating, and deactivating user accounts across integrated systems based on organizational workflows.

5. IAM Administration

   The user, group and permission information which is stored in Nubus' OpenLDAP service is managed by IAM Admin(s) using a stripped down version of the UMC (Univention Management Console).

6. Frontend Integration Authentication

   A specialized component - the Intercom Service - acts according to the Backend-for-Frontend pattern when it comes to certain integration use cases requiring the frontend of one application to call the API of another service that also has the need for user authentication. See Component integration for more details.

7. Portal

   Nubus provides a Portal component for users to access the connected applications, that also includes a self service e.g. for password reset.

For additional information, refer to the Nubus for Kubernetes Architecture Manual.

Authentication

openDesk uses the OpenID Connect (OIDC) protocol for authentication and authorization.

Identity data flows

An overview of

• components that consume the LDAP service.
  • The components access the LDAP using a component-specific LDAP search account.
• components using Univention Keycloak as an identity provider (IdP).
  • The components should use OAuth2 / OIDC flows if not otherwise denoted.
  • All components have a client configured in Keycloak.

Some components trust others to handle authentication for them.

flowchart TD
 K[IdP]-->L[LDAP]
 N[Nextcloud]-->L
 O[OpenProject] --> L
 A[OX AppSuite]-->L
 D[OX Dovecot]-->L
 P[Portal/Admin]-->L
 X[XWiki]-->L
 A-->K
 N-->K
 D-->K
 O-->K
 X-->K
 P-->|SAML|K
 E[Element]-->K
 J[Jitsi]-->K
 I[IntercomService]-->K
 C[Collabora]-->N
 R[CryptPad]-->N
 F[Postfix]-->D

Source

flowchart TD
 K[IdP]-->L[LDAP]
 N[Nextcloud]-->L
 O[OpenProject] --> L
 A[OX AppSuite]-->L
 D[OX Dovecot]-->L
 P[Portal/Admin]-->L
 X[XWiki]-->L
 A-->K
 N-->K
 D-->K
 O-->K
 X-->K
 P-->|SAML|K
 E[Element]-->K
 J[Jitsi]-->K
 I[IntercomService]-->K
 C[Collabora]-->N
 R[CryptPad]-->N
 F[Postfix]-->D

OpenID Connect (OIDC)

OIDC is an identity layer on top of the OAuth 2.0 protocol, allowing clients (Relying Party (RP)) to verify the identity of end-users based on the authentication performed by an authorization server (OpenID Provider (OP)). In openDesk, Keycloak serves as the OIDC provider, managing user authentication and issuing tokens for secure access to applications.

The following sequence diagram shows an OIDC flow of a user logging into openDesk's project management application. In openDesk, applications such as OpenProject take the role of the OIDC Relying Party, whereas Keycloak acts as the OIDC provider and OpenLDAP as the IdP.

sequenceDiagram
    autonumber
    participant Browser as Browser
    participant OpenProject as OpenProject
OIDC Relying Party
    participant Keycloak as Keycloak
OIDC Provider
    participant LDAP as OpenLDAP
IdP
    Browser->>OpenProject: GET https://projects.domain.tld
    OpenProject-->>Browser: Redirect to OIDC provider authentication form (with request)
    Browser->>Keycloak: Authenticate with username/password, optionally 2FA
    Keycloak->>LDAP: Retrieve/update user information
    LDAP->>Keycloak: Return user info
    Keycloak-->>Browser: 302 Redirect https://projects.domain.tld/callback?[...]
    Browser->>OpenProject: GET https://projects.domain.tld/callback?[...]
    OpenProject->>Keycloak: POST https://id.domain.tld/oauth/token
    Keycloak-->>OpenProject: Return JSON with token, signature
    OpenProject->>OpenProject: Verify token signature valid, signed by Provider
    OpenProject-->>Browser: 302 Redirect https://projects.domain.tld
    Note over Browser: User is authenticated

Source

sequenceDiagram
    autonumber
    participant Browser as Browser
    participant OpenProject as OpenProject<br/>OIDC Relying Party
    participant Keycloak as Keycloak<br>OIDC Provider
    participant LDAP as OpenLDAP<br>IdP
    Browser->>OpenProject: GET https://projects.domain.tld
    OpenProject-->>Browser: Redirect to OIDC provider authentication form (with request)
    Browser->>Keycloak: Authenticate with username/password, optionally 2FA
    Keycloak->>LDAP: Retrieve/update user information
    LDAP->>Keycloak: Return user info
    Keycloak-->>Browser: 302 Redirect https://projects.domain.tld/callback?[...]
    Browser->>OpenProject: GET https://projects.domain.tld/callback?[...]
    OpenProject->>Keycloak: POST https://id.domain.tld/oauth/token
    Keycloak-->>OpenProject: Return JSON with token, signature
    OpenProject->>OpenProject: Verify token signature valid, signed by Provider
    OpenProject-->>Browser: 302 Redirect https://projects.domain.tld
    Note over Browser: User is authenticated

Note:
Nubus' Portal and UMC still use SAML 2.0 to authenticate users. However, Nubus will switch to OIDC in an upcoming release, eliminating the use of SAML in openDesk altogether.

Keycloak

Keycloak is an open-source identity and access management solution for web based applications and services. It provides features such as single sign-on, multi-factor authentication, user federation, and centralized user management.

In openDesk, Keycloak serves as the OIDC provider, handling user authentication and issuing tokens for secure access to applications.

For more information, see the Keycloak Documentation.

Keycloak Extensions

Part of Nubus are the Keycloak Extensions used for

• Login brute force protection: Blocking authentication requests upon too much failed attempts from a device or IP. The available CAPTCHA option is deactivated in openDesk.
• New device notification: Sending the use an email after successful login from a new device.

To address these use cases the Keycloak Extensions act as a proxy to Keycloak.

OpenLDAP

OpenLDAP is an open-source implementation of the Lightweight Directory Access Protocol (LDAP) that provides a central repository for user and group information. In openDesk, OpenLDAP is used as the user directory to store user and group data and manage access control policies across the applications.

Authorization

LDAP Group Synchronization

LDAP group synchronization ensures that user group memberships are consistent across the applications in openDesk that make use of the IAM group information. Nubus uses OpenLDAP to store and manage user groups, which are synchronized with integrated applications to enforce access control policies.

Beside Keycloak LDAP groups are available to the following applications, none of the application supports nested groups. It means that users must be direct members of a group, as members of sub groups are ignored.

• Files / Nextcloud: Reads all groups that are enabled for Nextcloud twice a day based on the setting background_sync_interval in the user_ldap app.
• Knowledge Management / XWiki: Reads all groups that are enabled for XWiki use, this is done nightly based the jobs LDAP Group Import Job and Mapped groups daily updater that admin users can access in /bin/view/Scheduler.
• Project Management / OpenProject: Reads all groups that are enabled for OpenProject hourly.
• Webmail / OX AppSuite: Requires a webmail user to be part of a group before the group is actively provisioned to OX AppSuite.

Provisioning

Part of the already mentioned Nubus IAM is a provisioning service.

Beside the Nubus internal user of the provisioning service the OX AppSuite is currently the only openDesk application that is getting data actively provisioned in contrast to scenarios where applications fetch the required information from the LDAP.

OX Connector

As the OX AppSuite is using an application specific format to get e.g. users provisioned, there is also a specific connector component that links to provisioning service to the OX AppSuite, it is called the OX Connector.

The OX SOAP API is used by the OX Connector to synchronize information about the follow OX AppSuite objects:

• Contexts
• Functional Mailboxes
• Groups
• (Managed) Resources
• Users

To find out more, see Roles & Permissions.

SCIM

System for Cross-domain Identity Management (SCIM) is an open standard for automating the exchange of user identity information between identity domains or IT systems. SCIM is designed to make user provisioning and management easier by providing a standardized way to manage user identities in cloud-based applications and services.

In openDesk, SCIM will be used in the future to automate the process of creating, updating, and deactivating user accounts across the applications. This ensures that user data is consistent and up-to-date across all applications, reducing the administrative overhead and potential for errors.

Note:
SCIM support is planned in openDesk for 2025.

Component integration

Important, especially from the end user perspective are the functional integrations between the different openDesk applications.

flowchart TD
 OX-AppSuite_Frontend-->|Silent Login, Filepicker, Central Navigation|Intercom_Service
 Element-->|Silent Login, Central Navigation|Intercom_Service
 Intercom_Service-->|Silent Login, Token Exchange|IdP
 Intercom_Service-->|Filepicker|Nextcloud
 Intercom_Service-->|Central Navigations|Portal
 Intercom_Service-->|Newsfeed|XWiki
 OX-AppSuite_Backend-->|Filepicker|Nextcloud
 OX-AppSuite_Backend-->|Videoconferences|Element
 Nextcloud-->|Central Navigation|Portal
 OpenProject-->|Central Navigation|Portal
 OpenProject-->|File Store|Nextcloud
 XWiki-->|Central Navigation|Portal
 Nextcloud-->|Central Contacts|OX-AppSuite_Backend
 OX-AppSuite_Frontend-->|Filepicker|OX-AppSuite_Backend
 Portal-->|Newsfeed|Intercom_Service

Source

flowchart TD
 OX-AppSuite_Frontend-->|Silent Login, Filepicker, Central Navigation|Intercom_Service
 Element-->|Silent Login, Central Navigation|Intercom_Service
 Intercom_Service-->|Silent Login, Token Exchange|IdP
 Intercom_Service-->|Filepicker|Nextcloud
 Intercom_Service-->|Central Navigations|Portal
 Intercom_Service-->|Newsfeed|XWiki
 OX-AppSuite_Backend-->|Filepicker|Nextcloud
 OX-AppSuite_Backend-->|Videoconferences|Element
 Nextcloud-->|Central Navigation|Portal
 OpenProject-->|Central Navigation|Portal
 OpenProject-->|File Store|Nextcloud
 XWiki-->|Central Navigation|Portal
 Nextcloud-->|Central Contacts|OX-AppSuite_Backend
 OX-AppSuite_Frontend-->|Filepicker|OX-AppSuite_Backend
 Portal-->|Newsfeed|Intercom_Service

Details can be found in the upstream documentation that is linked in the respective sections.

Intercom Service / Silent Login

The Intercom Service is deployed in the context of Nubus. Its role is to enable cross-application integration based on the user's browser interaction as handling authentication when the frontend of an application has to call the API from another application is often a challenge.

To establish a session with the Intercom Service, applications can use the silent login feature within an iframe.

Currently, only OX AppSuite and Element are using the frontend-based integration.

Links

• Intercom Service upstream documentation.

Central Contacts

OX App Suite is managing contacts in openDesk. Therefore, Nextcloud's PHP backend is using the OX AppSuite's middleware Contacts API to

• create a new contact in the user's contacts folder when a file is shared with an unknown email address.
• retrieve contacts from the user's contacts folder to support search-as-you-type when starting to share a file.

Links:

• Currently used OX Contacts API (deprecated).
• New OX Addressbooks API the Central Contacts integration will switch to.

Central Navigation

Central navigation is based on an API endpoint in the Nubus portal that returns a JSON containing the portal's contents for a given user. The response from the API endpoint is used in the openDesk applications to render the central navigation.

The API can be called by

• frontend services through the Intercom Service's /navigation.json endpoint or
• backend services directly at the portal’s /univention/portal/navigation.json endpoint.

The central navigation expects the API caller to present a shared secret for authentication and the username for whom the portal contents should be returned for.

A curl based request returning the navigation contents looks like this:

curl 'https://portal./univention/portal/navigation.json?base=https%3A//portal.&language=de-DE' -u ":"

Filepicker

The Nextcloud Filepicker is integrated into the OX AppSuite, supporting the following use cases against the respective openDesk instance's Nextcloud:

• Attach files from Nextcloud to emails.
• Create and add links to Nextcloud files into emails.
• Save attachments from emails into Nextcloud.
• Attach files from Nextcloud to calendar entries.

The Filepicker uses frontend and backend-based integration:

• For frontend-based integration, the OX AppSuite frontend uses the Intercom Service.
• Backend-based integration is coming from OX AppSuite middleware. The middleware communicates directly with Nextcloud when adding a file to an email or storing a file into Nextcloud to avoid passing these files through the user's browser.

Links

• OX AppSuite Nextcloud Integration upstream documentation.

Newsfeed

The portal renders a newsfeed based on entries of a predefined openDesk blog in XWiki. It accesses the required XWiki service through the Intercom Service's /wiki endpoint, in combination with the previously described silent login.

Links:

• XWiki Blog feature

(OpenProject) File Store

While OpenProject allows you to attach files to work packages directly, it is often preferred that the files are stored within Nextcloud or to link an existing file from your openDesk Nextcloud to a work package.

Therefore, openDesk pre-configures the trust between the openDesk instance’s OpenProject and Nextcloud during the openproject-boostrap deployment step. As a prerequisite for that, openDesk’s Nextcloud contains the integration_openproject app.

The file store must still be enabled per project in OpenProject’s project admin section.

Links:

• OpenProject’s documentation on Nextcloud integration
• OpenProject Integration Nextcloud app

Applications vs. Services

openDesk consists of a variety of open-source projects, please find an overview below:

Name	Description	Type
Certificates	TLS certificates	Service
ClamAV (Distributed)	Antivirus engine	Service
ClamAV (Simple)	Antivirus engine	Service
Collabora	Weboffice	Application
CryptPad	diagrams.net editor	Application
dkimpy-milter	DKIM milter for Postfix	Service
Element	Secure communications platform	Application
Jitsi	Videoconferencing	Application
MariaDB	Database	Service
Memcached	Cache Database	Service
MinIO	Object Storage	Service
Nextcloud	File share	Application
Nubus (UMS)	Identity Management & Portal	Application
OpenProject	Project management	Application
OX Appsuite & Dovecot	Groupware with IMAP mail backend	Application
Postfix	MTA	Service
PostgreSQL	Database	Service
Redis	Cache Database	Service
XWiki	Knowledge Management	Application

The end user focussed components are called applications and provide the functional scope of openDesk, please find separate paragraphs on each of the applications below.

Other components are of type “Service”, these are used for development and evaluation purposes only, they need to be replaced in production deployments.

For the APIs / Protocols supported by the applications, please read the apis.md.

Collabora (Office)

Collabora is a powerful online document editing suite.

In openDesk, Collabora is used for editing Office documents such as rich texts, spreadsheets and presentations.

CryptPad Online (Diagrams)

CryptPad is a collaborative editor framework supporting end-to-end encryption..

In openDesk, CryptPad is for editing diagrams.net documents.

Element/Synapse (Chat & Call)

Element Web is the web frontend for Synapse, the reference implementation of the sovereign and secure Matrix protocol.

In openDesk, Element is used for chat and direct audio & video calling.

Jitsi (Video Conferencing)

Jitsi is an open-source video conferencing solution that allows users to hold secure video meetings.

In openDesk, Jitsi is used for video conferencing and online meetings. It integrates with other applications to provide seamless communication capabilities.

Nextcloud (Files)

Nextcloud is a file storage and sync platform with powerful collaboration capabilities with desktop, mobile and web interfaces.

Nubus (Identity and Access Management / Portal)

Nubus is a unified Identity & Access Management, providing you with full control and digital sovereignty over your IAM processes and data.

In openDesk Nubus is providing the management for user, groups and other IAM stored objects, as well as the portal, the Identity provider for Single Sign-On and federation scenarios and the

OpenProject (Project management)

OpenProject is a project management tool that supports agile project management, team collaboration, issue tracking, and more.

OX App Suite (Groupware) with OX Dovecot (Mail backend)

OX App Suite is a groupware application using OX Dovecot as its backend mail store.

In openDesk, OX App Suite is used for email, calendar, address book and personal task management.

XWiki (Knowledge management)

XWiki is an open-source wiki platform for knowledge management and collaboration.

Application specific user accounts

While the IAM managed users centrally, some applications come with local accounts for administrative purposes.

Application	Account name	Purpose	Password
Collabora	collabora-internal-admin	To access the Collabora admin dashboard	secrets.collabora.adminPassword
Element	uvs	The account for the “User Verification Service”. It is used by Jitsi integrated into Element.	secrets.matrixUserVerificationService.password
	meeting-bot	Used by the Nordeck Meeting-Bot to manage meeting rooms in Synapse.	secrets.matrixNeoDateFixBot.password
Nextcloud	nextcloud	Bootstrap the Nextcloud fileshare for OpenProject with opendesk-openproject-bootstrap job1.	secrets.nextcloud.adminPassword
OX App Suite	admin	OX-Connector to provision context, users, groups etc.	secrets.oxAppsuite.adminPassword
OpenProject	set in secrets.openproject.apiAdminUsername	Bootstrap the Nextcloud fileshare for OpenProject with opendesk-openproject-bootstrap job1.	secrets.openproject.apiAdminPassword
XWiki	superadmin	Only available with debug.enabled: true, can be used for interactive login using /bin/view/Main/?oidc.skipped=true.	secrets.xwiki.superadminpassword

Footnotes

Footnotes

1. We are working on a new approach to provision the OpenProject filestore, therefore the accounts are planned to be deactivated/removed with openDesk 1.2. ↩ ↩²