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sec-design.md

File metadata and controls

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BUSINESS POSTURE

  • Business Priorities and Goals:

    • Provide a secure and reliable platform for file storage, sharing, and collaboration.
    • Enable users to maintain control over their data and ensure data privacy.
    • Offer a comprehensive suite of productivity applications beyond file storage, such as calendar, contacts, and office suite integration.
    • Support a wide range of deployment options, from personal use to large enterprise deployments.
    • Foster an open and extensible platform through its open-source nature and app ecosystem.
    • Build a strong community and ecosystem around the platform.

  • Business Risks:

    • Data breaches and data loss due to security vulnerabilities in the platform or its extensions.
    • Reputational damage and loss of user trust due to security incidents.
    • Compliance violations with data privacy regulations (e.g., GDPR, CCPA) if data is not handled securely.
    • Service disruptions and downtime impacting user productivity and data accessibility.
    • Difficulty in attracting and retaining users if the platform is perceived as insecure or unreliable.
    • Competition from other file storage and collaboration platforms, both open-source and proprietary.
    • Risks associated with maintaining a large and complex open-source project, including community management and contribution quality.

SECURITY POSTURE

  • Existing Security Controls:

    • security control: Regular security audits and penetration testing (location: Nextcloud security advisories and blog posts).
    • security control: Secure coding practices and code reviews (location: Development guidelines and community contributions).
    • security control: Input validation and output encoding to prevent common web vulnerabilities (location: Codebase and security documentation).
    • security control: Protection against Cross-Site Scripting (XSS) attacks (location: Codebase and security documentation).
    • security control: Protection against Cross-Site Request Forgery (CSRF) attacks (location: Codebase and security documentation).
    • security control: Strong password hashing and secure session management (location: Codebase and security documentation).
    • security control: Encryption of data at rest and in transit (location: Server-side encryption and HTTPS configuration documentation).
    • security control: Two-Factor Authentication (2FA) support (location: User documentation and authentication settings).
    • security control: Brute-force protection and rate limiting (location: Security hardening documentation and server configuration).
    • security control: App store review process with security checks for community apps (location: App store guidelines and processes).
    • security control: Security vulnerability reporting and disclosure program (location: Nextcloud security policy and website).
    • security control: Regular security updates and patches (location: Release notes and update channels).

  • Accepted Risks:

    • accepted risk: Potential vulnerabilities in third-party apps available in the app store, despite review processes.
    • accepted risk: Security misconfigurations by users during deployment and setup.
    • accepted risk: Social engineering attacks targeting users to gain access to accounts or data.
    • accepted risk: Zero-day vulnerabilities that may exist before patches are available.
    • accepted risk: Complexity of the platform may lead to overlooked security issues.

  • Recommended Security Controls:

    • security control: Implement automated security scanning (SAST/DAST) in the development pipeline.
    • security control: Enhance security monitoring and logging capabilities for incident detection and response.
    • security control: Improve security awareness training for users and administrators.
    • security control: Formalize and document the Secure Software Development Lifecycle (SSDLC) process.
    • security control: Implement dependency scanning and management to address vulnerabilities in third-party libraries.
    • security control: Introduce security champions within development teams to promote security best practices.
    • security control: Conduct regular threat modeling exercises for new features and components.

  • Security Requirements:

    • Authentication:

      • Requirement: Secure authentication mechanisms to verify user identity.
      • Requirement: Support for strong passwords and password policies.
      • Requirement: Multi-factor authentication (MFA) options.
      • Requirement: Protection against brute-force attacks on authentication endpoints.
      • Requirement: Secure session management to prevent session hijacking.

    • Authorization:

      • Requirement: Role-based access control (RBAC) to manage user permissions.
      • Requirement: Fine-grained access control to files and folders based on user roles and groups.
      • Requirement: Secure sharing mechanisms with configurable permissions and expiration dates.
      • Requirement: Audit logging of authorization decisions and access attempts.

    • Input Validation:

      • Requirement: Comprehensive input validation for all user-supplied data to prevent injection attacks.
      • Requirement: Validation on both client-side and server-side to ensure data integrity.
      • Requirement: Use of parameterized queries or ORM frameworks to prevent SQL injection.
      • Requirement: Encoding of output data to prevent cross-site scripting (XSS) vulnerabilities.

    • Cryptography:

      • Requirement: Encryption of data at rest using strong encryption algorithms.
      • Requirement: Encryption of data in transit using TLS/HTTPS.
      • Requirement: Secure key management practices for encryption keys.
      • Requirement: Use of cryptographic libraries and APIs securely to avoid common pitfalls.
      • Requirement: Hashing of sensitive data like passwords using strong hashing algorithms.

DESIGN

C4 CONTEXT

flowchart LR
    subgraph "Nextcloud Environment"
        A["Nextcloud Server"]
    end
    B["Users"]:::person -- "Access files, collaborate, use applications" --> A
    C["Web Browsers"]:::browser -- "Access Nextcloud Web Interface" --> A
    D["Mobile Apps"]:::mobile -- "Access Nextcloud via Mobile Apps" --> A
    E["Desktop Clients"]:::desktop -- "Sync files, access Nextcloud" --> A
    F["LDAP/AD"]:::database -- "User Authentication and Directory Services" --> A
    G["SMTP Server"]:::email -- "Send Email Notifications" --> A
    H["Database Server"]:::database -- "Store Application Data and Metadata" --> A
    I["Object Storage/File Storage"]:::database -- "Store User Files" --> A
    J["External Services"]:::external -- "Integrate with external services (e.g., Collabora Online, OnlyOffice)" --> A

    classDef person fill:#aaf,stroke:#333,stroke-width:2px
    classDef browser fill:#ccf,stroke:#333,stroke-width:2px
    classDef mobile fill:#fcc,stroke:#333,stroke-width:2px
    classDef desktop fill:#cfc,stroke:#333,stroke-width:2px
    classDef database fill:#eee,stroke:#333,stroke-width:2px
    classDef email fill:#eee,stroke:#333,stroke-width:2px
    classDef external fill:#eee,stroke:#333,stroke-width:2px
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  • Context Diagram Elements:
      • Name: Users
      • Type: Person
      • Description: Individuals who use Nextcloud to store, share, and collaborate on files, and utilize various applications offered by the platform.
      • Responsibilities: Access and manage their files, collaborate with other users, utilize Nextcloud applications for productivity.
      • Security controls: Strong passwords, multi-factor authentication, account security settings.
      • Name: Web Browsers
      • Type: Browser
      • Description: Web browsers used by users to access the Nextcloud web interface.
      • Responsibilities: Render the Nextcloud web application, interact with the Nextcloud server via HTTP/HTTPS.
      • Security controls: Browser security features, HTTPS connection to Nextcloud server.
      • Name: Mobile Apps
      • Type: Mobile Application
      • Description: Nextcloud mobile applications for iOS and Android platforms, providing access to files and other features on mobile devices.
      • Responsibilities: Provide mobile access to Nextcloud features, sync files, capture media, and interact with the Nextcloud server via APIs.
      • Security controls: App security features, secure storage of credentials, HTTPS communication.
      • Name: Desktop Clients
      • Type: Desktop Application
      • Description: Nextcloud desktop clients for Windows, macOS, and Linux, enabling file synchronization between desktops and the Nextcloud server.
      • Responsibilities: Synchronize files between local file systems and the Nextcloud server, provide desktop notifications, and interact with the Nextcloud server via APIs.
      • Security controls: Secure storage of credentials, encrypted file synchronization, HTTPS communication.
      • Name: LDAP/AD
      • Type: Database
      • Description: Lightweight Directory Access Protocol (LDAP) or Active Directory (AD) server used for user authentication and directory services in enterprise environments.
      • Responsibilities: Authenticate users, provide user and group information to Nextcloud for authorization.
      • Security controls: Secure LDAP/AD configuration, access controls to directory information, secure communication protocols.
      • Name: SMTP Server
      • Type: Email Server
      • Description: Simple Mail Transfer Protocol (SMTP) server used by Nextcloud to send email notifications to users.
      • Responsibilities: Relay email notifications for file sharing, activity updates, and other events.
      • Security controls: Secure SMTP configuration, authentication for sending emails, TLS encryption for email transmission.
      • Name: Database Server
      • Type: Database
      • Description: Database server (e.g., MySQL, PostgreSQL, MariaDB, SQLite) used by Nextcloud to store application data, metadata, user profiles, and configuration information.
      • Responsibilities: Persist application data, provide data access to the Nextcloud server.
      • Security controls: Database access controls, encryption at rest, regular backups, database hardening.
      • Name: Object Storage/File Storage
      • Type: Database
      • Description: Storage system used to store user files. This can be local file system, network storage (NAS), or object storage services (e.g., AWS S3, OpenStack Swift).
      • Responsibilities: Store user files securely and reliably, provide file access to the Nextcloud server.
      • Security controls: Storage access controls, encryption at rest, data redundancy and backups, physical security of storage infrastructure.
      • Name: External Services
      • Type: External System
      • Description: External services and applications that integrate with Nextcloud to provide additional functionalities, such as online office suites (Collabora Online, OnlyOffice), video conferencing, and other integrations.
      • Responsibilities: Extend Nextcloud functionality, provide specialized services, interact with Nextcloud server via APIs and protocols.
      • Security controls: Secure API integrations, authentication and authorization mechanisms for external service access, data exchange security.
      • Name: Nextcloud Server
      • Type: Software System
      • Description: The core Nextcloud server application, providing file storage, sharing, collaboration, and application platform functionalities.
      • Responsibilities: Manage user accounts, authenticate users, authorize access, handle file storage and sharing, run applications, provide APIs for clients and integrations, manage security controls.
      • Security controls: Authentication, authorization, input validation, cryptography, session management, access controls, security updates, logging and monitoring.

C4 CONTAINER

flowchart LR
    subgraph "Nextcloud Server"
        A["Web Server"]:::container -- "Handles HTTP requests, reverse proxy, TLS termination"
        B["PHP Application"]:::container -- "Core Nextcloud application logic, API endpoints, business logic"
        C["Database"]:::container -- "Stores application data and metadata"
        D["File Storage"]:::container -- "Stores user files"
        E["Background Jobs Processor"]:::container -- "Handles asynchronous tasks, cron jobs, background processing"
        F["App Store"]:::container -- "Manages and distributes Nextcloud Apps"
    end
    G["Web Browser"]:::container -- "User interface for Nextcloud" --> A
    H["Mobile App"]:::container -- "Mobile client for Nextcloud" --> B
    I["Desktop Client"]:::container -- "Desktop sync client" --> B
    J["LDAP/AD Server"]:::container -- "User directory and authentication" --> B
    K["SMTP Server"]:::container -- "Email notifications" --> B
    L["External Services"]:::container -- "Third-party integrations" --> B

    A -- "PHP-FPM/FastCGI" --> B
    B -- "SQL" --> C
    B -- "File System/Object Storage APIs" --> D
    B -- "Message Queue (e.g., Redis, RabbitMQ)" --> E
    B -- "HTTP APIs" --> F

    classDef container fill:#cce,stroke:#333,stroke-width:2px
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  • Container Diagram Elements:
      • Name: Web Server
      • Type: Container
      • Description: Web server (e.g., Apache, Nginx) responsible for handling HTTP/HTTPS requests, serving static content, acting as a reverse proxy, and managing TLS termination.
      • Responsibilities: Handle incoming web requests, route requests to the PHP application, serve static files, manage TLS encryption, implement web server security configurations.
      • Security controls: TLS configuration, web server hardening, access controls, rate limiting, web application firewall (WAF).
      • Name: PHP Application
      • Type: Container
      • Description: The core Nextcloud application written in PHP, containing the application logic, API endpoints, business logic, and handling user requests.
      • Responsibilities: Implement Nextcloud features, manage user authentication and authorization, handle file operations, interact with the database and file storage, process user requests, generate web pages and API responses.
      • Security controls: Input validation, output encoding, secure session management, authorization checks, secure coding practices, vulnerability scanning.
      • Name: Database
      • Type: Container
      • Description: Database system (e.g., MySQL, PostgreSQL, MariaDB, SQLite) used to store application data, metadata, user profiles, and configuration.
      • Responsibilities: Persist application data, provide data access to the PHP application, ensure data integrity and availability.
      • Security controls: Database access controls, encryption at rest, regular backups, database hardening, monitoring and auditing.
      • Name: File Storage
      • Type: Container
      • Description: Storage system for user files, which can be a local file system, network storage, or object storage service.
      • Responsibilities: Store user files securely and reliably, provide file access to the PHP application.
      • Security controls: Storage access controls, encryption at rest, data redundancy and backups, physical security of storage infrastructure.
      • Name: Background Jobs Processor
      • Type: Container
      • Description: Component responsible for processing asynchronous tasks, scheduled jobs (cron jobs), and background operations, such as file scanning, notifications, and maintenance tasks.
      • Responsibilities: Execute background tasks, manage job queues, improve application responsiveness by offloading tasks from the main request processing.
      • Security controls: Secure job scheduling, access controls to job processing, monitoring of background job execution.
      • Name: App Store
      • Type: Container
      • Description: Component for managing and distributing Nextcloud applications (apps), allowing users to extend Nextcloud functionality.
      • Responsibilities: Provide a platform for discovering and installing Nextcloud apps, manage app updates, enforce app security policies.
      • Security controls: App review process, security scanning of apps, access controls to app installation, sandboxing of apps (if applicable).
      • Name: Web Browser
      • Type: Container
      • Description: User's web browser accessing the Nextcloud web interface.
      • Responsibilities: Render the Nextcloud web application, interact with the Web Server.
      • Security controls: Browser security features, HTTPS connection.
      • Name: Mobile App
      • Type: Container
      • Description: Nextcloud mobile application.
      • Responsibilities: Mobile client functionality, interacts with PHP Application via APIs.
      • Security controls: App security features, secure API communication.
      • Name: Desktop Client
      • Type: Container
      • Description: Nextcloud desktop synchronization client.
      • Responsibilities: Desktop sync functionality, interacts with PHP Application via APIs.
      • Security controls: Client security features, secure API communication.
      • Name: LDAP/AD Server
      • Type: Container
      • Description: LDAP or Active Directory server.
      • Responsibilities: User directory and authentication services for PHP Application.
      • Security controls: Secure LDAP/AD configuration.
      • Name: SMTP Server
      • Type: Container
      • Description: SMTP server for email notifications.
      • Responsibilities: Email delivery for PHP Application.
      • Security controls: Secure SMTP configuration.
      • Name: External Services
      • Type: Container
      • Description: External services integrated with Nextcloud.
      • Responsibilities: Extend Nextcloud functionality, interacts with PHP Application via APIs.
      • Security controls: Secure API integrations.

DEPLOYMENT

  • Deployment Options:

    • On-premises deployment on physical servers or virtual machines.
    • Deployment in private cloud environments.
    • Deployment in public cloud environments (e.g., AWS, Azure, GCP).
    • Containerized deployment using Docker and Kubernetes.
    • Deployment using pre-packaged appliances or cloud images.

  • Detailed Deployment (Example: Docker Containerized Deployment on Kubernetes):

flowchart LR
    subgraph "Kubernetes Cluster"
        subgraph "Nodes"
            subgraph "Node 1"
                A["Pod: nextcloud-web"]:::pod -- "Web Server, PHP Application"
            end
            subgraph "Node 2"
                B["Pod: nextcloud-db"]:::pod -- "Database Server"
                C["Pod: nextcloud-redis"]:::pod -- "Redis (for caching/background jobs)"
            end
            subgraph "Node 3"
                D["Pod: nextcloud-background"]:::pod -- "Background Jobs Processor"
                E["Persistent Volume Claim"]:::pvc -- "Persistent Storage for Files and Database"
            end
        end
        F["Load Balancer"]:::lb -- "External Access Point"
        F -- "HTTP/HTTPS" --> A
        A -- "TCP" --> B
        A -- "TCP" --> C
        A -- "TCP" --> D
        A -- "Persistent Volume" --> E
        B -- "Persistent Volume" --> E
        D -- "Persistent Volume" --> E
    end
    G["User"]:::user -- "Access Nextcloud" --> F

    classDef pod fill:#cef,stroke:#333,stroke-width:2px
    classDef pvc fill:#fec,stroke:#333,stroke-width:2px
    classDef lb fill:#cfa,stroke:#333,stroke-width:2px
    classDef user fill:#aaf,stroke:#333,stroke-width:2px
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  • Deployment Diagram Elements:
      • Name: Kubernetes Cluster
      • Type: Infrastructure
      • Description: Kubernetes cluster providing container orchestration and management.
      • Responsibilities: Manage container deployment, scaling, and networking, provide high availability and resilience.
      • Security controls: Kubernetes RBAC, network policies, pod security policies, security audits, container image scanning.
      • Name: Nodes (Node 1, Node 2, Node 3)
      • Type: Infrastructure
      • Description: Worker nodes in the Kubernetes cluster, providing compute resources for running containers.
      • Responsibilities: Execute containers, provide compute and storage resources.
      • Security controls: Operating system hardening, security updates, access controls, monitoring.
      • Name: Pod: nextcloud-web
      • Type: Container
      • Description: Kubernetes pod containing containers for the Web Server and PHP Application.
      • Responsibilities: Serve web requests, run the Nextcloud application logic.
      • Security controls: Container security context, resource limits, network policies.
      • Name: Pod: nextcloud-db
      • Type: Container
      • Description: Kubernetes pod containing the Database Server container.
      • Responsibilities: Store application data.
      • Security controls: Container security context, resource limits, network policies, database access controls.
      • Name: Pod: nextcloud-redis
      • Type: Container
      • Description: Kubernetes pod containing Redis for caching and background job queuing.
      • Responsibilities: Caching, message queuing for background jobs.
      • Security controls: Container security context, resource limits, network policies, Redis access controls.
      • Name: Pod: nextcloud-background
      • Type: Container
      • Description: Kubernetes pod containing the Background Jobs Processor container.
      • Responsibilities: Process background tasks.
      • Security controls: Container security context, resource limits, network policies.
      • Name: Persistent Volume Claim
      • Type: Storage
      • Description: Kubernetes Persistent Volume Claim for persistent storage of files and database data.
      • Responsibilities: Provide persistent storage for application data and files across pod restarts and deployments.
      • Security controls: Storage access controls, encryption at rest (depending on underlying storage provider), backups.
      • Name: Load Balancer
      • Type: Network Device
      • Description: Load balancer providing external access to the Nextcloud service.
      • Responsibilities: Distribute traffic to the web pods, provide a single entry point for users.
      • Security controls: TLS termination, DDoS protection, access controls, security monitoring.
      • Name: User
      • Type: Person
      • Description: End user accessing Nextcloud.
      • Responsibilities: Use Nextcloud services.
      • Security controls: User authentication, strong passwords, MFA.

BUILD

flowchart LR
    A["Developer"] -- "Code Changes, Commit, Push" --> B["Version Control System (GitHub)"]
    B -- "Webhook Trigger" --> C["CI/CD System (GitHub Actions)"]
    subgraph "CI/CD System (GitHub Actions)"
        D["Checkout Code"]
        E["Dependency Management"]
        F["Static Analysis Security Testing (SAST)"]
        G["Unit Tests"]
        H["Build Artifacts (Docker Images, Packages)"]
        I["Container Scanning"]
        J["Publish Artifacts (Container Registry, Package Repository)"]
    end
    C --> D
    D --> E
    E --> F
    F --> G
    G --> H
    H --> I
    I --> J
    J -- "Deployment Trigger" --> K["Deployment Environment"]

    style A fill:#aaf,stroke:#333,stroke-width:2px
    style K fill:#eee,stroke:#333,stroke-width:2px
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  • Build Process Description:

    • Developer writes code, commits changes, and pushes them to the Version Control System (e.g., GitHub).
    • A webhook in the Version Control System triggers the CI/CD system (e.g., GitHub Actions) upon code changes.
    • The CI/CD pipeline starts automatically:
      • Checkout Code: The latest code changes are checked out from the repository.
      • Dependency Management: Project dependencies are resolved and managed securely.
      • Static Analysis Security Testing (SAST): SAST tools scan the codebase for potential security vulnerabilities.
      • Unit Tests: Automated unit tests are executed to ensure code quality and functionality.
      • Build Artifacts: Build artifacts are created, such as Docker images, packages, or compiled code.
      • Container Scanning: Container images are scanned for vulnerabilities using container scanning tools.
      • Publish Artifacts: Build artifacts are published to artifact repositories, such as container registries (e.g., Docker Hub, GitHub Container Registry) or package repositories.
    • Upon successful build and publish, a deployment trigger can be initiated to deploy the new artifacts to the Deployment Environment.

  • Build Process Security Controls:

    • security control: Secure Version Control System (GitHub) with access controls and audit logging.
    • security control: Automated CI/CD pipeline to ensure consistent and repeatable builds.
    • security control: Static Analysis Security Testing (SAST) to identify code vulnerabilities early in the development cycle.
    • security control: Dependency scanning to detect vulnerabilities in third-party libraries and dependencies.
    • security control: Container scanning to identify vulnerabilities in container images before deployment.
    • security control: Secure artifact repositories with access controls and vulnerability scanning.
    • security control: Code signing and artifact verification to ensure integrity and authenticity of build artifacts.
    • security control: Principle of least privilege for CI/CD system access and credentials.
    • security control: Audit logging of CI/CD pipeline activities.

RISK ASSESSMENT

  • Critical Business Processes:

    • Secure Storage and Retrieval of User Data: Ensuring data integrity, confidentiality, and availability.
    • User Authentication and Authorization: Verifying user identity and controlling access to resources.
    • File Sharing and Collaboration: Enabling secure and controlled sharing of files between users.
    • Application Functionality: Ensuring the availability and reliability of core Nextcloud applications and features.
    • Data Privacy and Compliance: Protecting user data in accordance with privacy regulations.

  • Data Sensitivity:

    • User Files: Highly sensitive. Can contain personal information, confidential documents, intellectual property, and other sensitive data. Confidentiality, integrity, and availability are critical.
    • User Credentials (Passwords, API Keys): Highly sensitive. Confidentiality and integrity are paramount.
    • User Personal Information (Profiles, Contact Details): Sensitive. Confidentiality and integrity are important for privacy and compliance.
    • Application Configuration and Metadata: Moderately sensitive. Integrity and availability are important for system operation.
    • Audit Logs: Moderately sensitive. Integrity and availability are important for security monitoring and incident response.

QUESTIONS & ASSUMPTIONS

  • Questions:

    • What is the target deployment environment (on-premises, cloud, hybrid)?
    • What are the specific compliance requirements (GDPR, HIPAA, etc.)?
    • What is the organization's risk appetite and security maturity level?
    • Are there specific performance or scalability requirements?
    • What is the process for managing and updating third-party apps in the Nextcloud ecosystem?
    • What are the incident response procedures in case of a security breach?
    • What is the budget and timeline for implementing security enhancements?

  • Assumptions:

    • BUSINESS POSTURE:

      • Security and data privacy are high priorities for Nextcloud users and the project.
      • The project aims to provide a secure and reliable platform for a wide range of users and organizations.
      • Open-source nature and community collaboration are important aspects of the project.

    • SECURITY POSTURE:

      • Basic security controls are already in place, but there is room for improvement in areas like automated security testing, security monitoring, and formalizing SSDLC.
      • Third-party apps pose a potential security risk.
      • User security awareness and secure configuration are important factors in overall security.

    • DESIGN:

      • A containerized deployment on Kubernetes is a relevant and modern deployment option.
      • The build process includes standard security checks like SAST and container scanning.
      • The design is modular and scalable, allowing for future growth and feature additions.