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Mattermost Server Project Design Document for Threat Modeling

Version: 1.1 Date: 2023-10-27 Author: AI Software Architect

1. Introduction

This document provides an enhanced and more detailed design overview of the Mattermost server project, based on the open-source repository https://github.com/mattermost/mattermost-server. Building upon version 1.0, this document offers a deeper dive into the system architecture, component functionalities, data flow, and security considerations. It is designed to be a robust foundation for comprehensive threat modeling activities, focusing on the server-side architecture and its interactions with clients and external services.

2. Project Overview

Mattermost is a leading open-source, self-hosted collaboration platform, providing a secure and flexible alternative to proprietary messaging solutions. Key features include:

  • Channels: Flexible organization of communication into public, private, and direct message channels.
  • Messaging: Real-time text, voice, and video messaging capabilities, including rich formatting and emoji support.
  • File Sharing & Management: Secure and integrated file sharing with preview and search functionalities.
  • Advanced Search: Powerful full-text search across messages, files, and users.
  • Extensibility & Integrations: Rich ecosystem of integrations via webhooks, slash commands, REST APIs, and a plugin framework.
  • Multi-Platform Clients: Consistent user experience across web, desktop, and mobile applications (iOS and Android).
  • Customization & Branding: Extensive customization options for branding, themes, and feature sets.
  • Compliance & Auditing: Features for data retention policies, audit logs, and compliance requirements.

Target Users:

Mattermost is designed for organizations prioritizing data security, control, and customization in their communication platform. It serves diverse teams, from small businesses to large enterprises, across various industries, especially those with stringent security and compliance needs.

3. System Architecture

The Mattermost server architecture is designed for high availability, scalability, and security. The following diagram illustrates the system components and their interactions, emphasizing data flow and key interfaces.

graph LR
    subgraph "User Clients"
        "Web Client" --> "Load Balancer"
        "Desktop Client" --> "Load Balancer"
        "Mobile Client" --> "Load Balancer"
    end

    "Load Balancer" --> "Proxy/Web Server (Nginx/Apache)"
    "Proxy/Web Server (Nginx/Apache)" --> "Mattermost Server(s)"
    "Mattermost Server(s)" --> "Database (PostgreSQL/MySQL)"
    "Mattermost Server(s)" --> "File Storage (Local/S3/etc)"
    "Mattermost Server(s)" --> "Push Notification Service (APNS/FCM)"
    "Mattermost Server(s)" --> "Email Service (SMTP)"

    subgraph "External Integrations"
        "Webhooks" --> "Mattermost Server(s)"
        "Slash Commands" --> "Mattermost Server(s)"
        "REST API Clients" --> "Mattermost Server(s)"
        "Plugins" --> "Mattermost Server(s)"
    end
Loading

Note: This diagram highlights the core components. Internal communication within "Mattermost Server(s)" is not explicitly shown for simplicity but involves various modules communicating via internal APIs and message queues.

4. Component Description

This section provides a detailed description of each component, including functionalities, technologies, and key interactions.

  • User Clients (Web Client, Desktop Client, Mobile Client):

    • Function: User interface layer providing access to Mattermost features. Handles user input, displays information, and interacts with the server API.
    • Technologies:
      • Web Client: React, Redux, JavaScript, HTML5, CSS3. Communicates via REST API over WebSocket for real-time updates.
      • Desktop Client: Electron framework embedding the Web Client. Provides native OS integration and notifications.
      • Mobile Client: React Native, leveraging native UI components for iOS and Android. Utilizes push notifications and background synchronization.
    • Interaction: Clients authenticate with the server via session-based or token-based authentication. They communicate with the Mattermost Server primarily through RESTful APIs over HTTPS for actions like sending messages, creating channels, and managing user settings. WebSockets are used for real-time event streaming (e.g., new messages, user status updates).

  • Load Balancer:

    • Function: Distributes incoming client traffic across multiple Mattermost Server instances to ensure high availability and scalability. Manages session persistence and health checks.
    • Technologies: Nginx, HAProxy, AWS ELB, Azure Load Balancer, GCP Load Balancer. Supports various load balancing algorithms (Round Robin, Least Connections, IP Hash).
    • Interaction: Receives HTTPS requests from clients and forwards them to healthy Mattermost Server instances based on configured rules. May handle TLS termination and HTTP header manipulation.

  • Proxy/Web Server (Nginx/Apache):

    • Function: Acts as a reverse proxy, providing essential security and performance enhancements. Handles TLS termination, static content serving, request routing, and security headers.
    • Technologies: Nginx (recommended for performance and security), Apache HTTP Server.
    • Interaction:
      • TLS Termination: Decrypts HTTPS traffic, securing communication between clients and the server infrastructure.
      • Static Content Serving: Efficiently serves static assets for the Web Client (JavaScript, CSS, images).
      • Request Routing: Routes API requests to Mattermost Server instances.
      • Security Headers: Adds security-related HTTP headers (e.g., HSTS, X-Frame-Options, X-Content-Type-Options) to enhance client-side security.
      • Rate Limiting & DDoS Protection: Can be configured to implement basic rate limiting and protection against denial-of-service attacks.

  • Mattermost Server(s):

    • Function: The core application server, implementing the business logic of Mattermost. Manages user authentication, authorization, channel and team management, message processing, plugin execution, and API endpoints.
    • Technologies: Go programming language, leveraging Go's concurrency and performance capabilities. Utilizes various Go libraries for web frameworks, database interaction, and networking.
    • Modules (Conceptual):
      • API Layer: Exposes RESTful API endpoints for client and external integrations.
      • Channel Service: Manages channels, channel memberships, and channel settings.
      • Post Service: Handles message creation, storage, retrieval, and updates.
      • User Service: Manages user accounts, profiles, authentication, and authorization.
      • Team Service: Manages teams, team memberships, and team settings.
      • Plugin Framework: Provides an extensible platform for plugins to add custom features and integrations.
      • Notification Service: Manages push notifications and email notifications.
      • Search Service: Indexes and provides search functionality for messages and files.
    • Interaction:
      • Receives requests from the Proxy/Web Server.
      • Interacts with the Database for persistent data storage and retrieval using database drivers (e.g., pq for PostgreSQL, go-sql-driver/mysql for MySQL).
      • Interacts with File Storage via SDKs or APIs for object storage services (e.g., AWS SDK for Go for S3).
      • Communicates with Push Notification Services (APNS, FCM) using their respective APIs.
      • Sends emails via SMTP using Go's net/smtp package or external libraries.
      • Handles Webhook and Slash Command requests, and processes REST API calls from external clients.
      • Internal communication between modules might use gRPC or in-memory channels for performance and efficiency.

  • Database (PostgreSQL/MySQL):

    • Function: Persistent storage for all application data, including users, channels, messages, posts, configurations, sessions, and audit logs.
    • Technologies: PostgreSQL (recommended for advanced features and robustness), MySQL (supported).
    • Data Categories:
      • User Data: User accounts, profiles, roles, permissions.
      • Channel Data: Channel metadata, channel members, channel settings.
      • Post Data: Message content, timestamps, user IDs, channel IDs.
      • Configuration Data: System settings, plugin configurations, feature flags.
      • Session Data: User session tokens, session expiry.
      • Audit Logs: Security-related events, admin actions, access logs.
    • Interaction: Mattermost Server performs CRUD (Create, Read, Update, Delete) operations on the database to manage application state and data persistence. Database connections are typically pooled for performance.

  • File Storage (Local/S3/etc):

    • Function: Stores file attachments uploaded by users. Supports various storage backends for scalability, durability, and cost optimization.
    • Technologies:
      • Local File System (for development or small-scale deployments).
      • Amazon S3 (Scalable cloud object storage).
      • MinIO (Open-source S3-compatible object storage).
      • Google Cloud Storage, Azure Blob Storage, other S3-compatible storage providers.
    • Access Control: File access is typically controlled by the Mattermost Server. Clients usually receive pre-signed URLs or temporary access tokens to download files directly from the storage backend, enhancing security and offloading traffic from the server.
    • Interaction: Mattermost Server uploads files to and retrieves files from the configured storage backend. It generates URLs for clients to access files.

  • Push Notification Service (APNS/FCM):

    • Function: Enables real-time push notifications to mobile and desktop clients for new messages and events, improving user engagement and responsiveness.
    • Technologies:
      • Apple Push Notification service (APNS) for iOS and macOS clients.
      • Firebase Cloud Messaging (FCM) for Android and potentially web clients.
    • Security: Communication with APNS and FCM is secured using API keys and certificates managed by Mattermost. Device tokens are securely stored and used for targeted notifications.
    • Interaction: Mattermost Server sends notification payloads (message content, channel information, etc.) along with device tokens to APNS and FCM. These services then deliver notifications to the respective client applications.

  • Email Service (SMTP):

    • Function: Sends emails for user account management (registration, password reset, email verification) and optional email notifications for mentions or channel activity.
    • Technologies: SMTP server (e.g., SendGrid, Mailgun, Postfix, Exchange). Supports TLS/STARTTLS for secure email transmission.
    • Security: SMTP connections should be encrypted using TLS. Credentials for the SMTP server should be securely stored and managed.
    • Interaction: Mattermost Server uses SMTP protocol to send emails through a configured email service provider or SMTP server.

  • External Integrations (Webhooks, Slash Commands, REST API Clients, Plugins):

    • Function: Extends Mattermost functionality and integrates with external applications and services.
      • Webhooks: Allow external services to send messages and data to Mattermost channels in real-time.
      • Slash Commands: Enable users to trigger actions in external services directly from Mattermost using commands.
      • REST API Clients: Provide programmatic access to Mattermost features for external applications to automate tasks, retrieve data, and integrate workflows.
      • Plugins: Extend server and client functionality with custom features, integrations, and modifications. Plugins can access Mattermost APIs and events.
    • Technologies: HTTP/HTTPS for communication, JSON for data exchange, REST API standards, plugin frameworks (Go for server-side, React/JavaScript for client-side).
    • Security:
      • Webhook Security: Webhook URLs should be treated as secrets. Consider signature verification for incoming webhooks.
      • Slash Command Security: Command permissions and input validation are crucial.
      • REST API Security: API authentication (personal access tokens, OAuth 2.0), authorization, and rate limiting are essential.
      • Plugin Security: Plugin sandboxing, code reviews, and security audits are important to prevent malicious plugins.
    • Interaction: External integrations communicate with the Mattermost Server via HTTP/HTTPS requests to specific API endpoints or through the plugin framework.

5. Data Flow Diagram

This diagram provides a more detailed view of data flow, highlighting specific data types and interactions between components for common user actions.

graph LR
    subgraph "User"
        "User Client"
    end
    subgraph "Mattermost System"
        "Load Balancer" --> "Proxy/Web Server"
        "Proxy/Web Server" --> "Mattermost Server"
        "Mattermost Server" --> "Database"
        "Mattermost Server" --> "File Storage"
        "Mattermost Server" --> "Push Notification Service"
        "Mattermost Server" --> "Email Service"
        "Mattermost Server" <-- "External Integration"
    end
    subgraph "External Services"
        "Push Notification Service" --> "User Client"
        "Email Service" --> "User"
    end

    "User Client" -- "HTTPS (API Request)" --> "Load Balancer"
    "Load Balancer" --> "Proxy/Web Server"
    "Proxy/Web Server" -- "HTTPS (API Request)" --> "Mattermost Server"
    "Mattermost Server" -- "SQL Queries" --> "Database"
    "Mattermost Server" -- "S3 API (File Operations)" --> "File Storage"
    "Mattermost Server" -- "APNS/FCM API" --> "Push Notification Service"
    "Mattermost Server" -- "SMTP" --> "Email Service"
    "Mattermost Server" <-- "HTTPS (Webhook/API)" -- "External Integration"
    "Push Notification Service" -- "Push Notification" --> "User Client"
    "Email Service" -- "Email" --> "User"
    "User Client" -- "WebSocket (Real-time Events)" --> "Proxy/Web Server"
    "Proxy/Web Server" -- "WebSocket (Real-time Events)" --> "Mattermost Server"
    "Mattermost Server" -- "WebSocket (Real-time Events)" --> "Proxy/Web Server"
    "Proxy/Web Server" -- "WebSocket (Real-time Events)" --> "User Client"


    style "Mattermost Server" fill:#ccf,stroke:#333,stroke-width:2px
    style "Database" fill:#eee,stroke:#333,stroke-width:2px
    style "File Storage" fill:#eee,stroke:#333,stroke-width:2px
Loading

Corrected Data Flow Diagram (without style attributes as requested):

graph LR
    subgraph "User"
        "User Client"
    end
    subgraph "Mattermost System"
        "Load Balancer" --> "Proxy/Web Server"
        "Proxy/Web Server" --> "Mattermost Server"
        "Mattermost Server" --> "Database"
        "Mattermost Server" --> "File Storage"
        "Mattermost Server" --> "Push Notification Service"
        "Mattermost Server" --> "Email Service"
        "Mattermost Server" <-- "External Integration"
    end
    subgraph "External Services"
        "Push Notification Service" --> "User Client"
        "Email Service" --> "User"
    end

    "User Client" -- "HTTPS (API Request)" --> "Load Balancer"
    "Load Balancer" --> "Proxy/Web Server"
    "Proxy/Web Server" -- "HTTPS (API Request)" --> "Mattermost Server"
    "Mattermost Server" -- "SQL Queries" --> "Database"
    "Mattermost Server" -- "S3 API (File Operations)" --> "File Storage"
    "Mattermost Server" -- "APNS/FCM API" --> "Push Notification Service"
    "Mattermost Server" -- "SMTP" --> "Email Service"
    "Mattermost Server" <-- "HTTPS (Webhook/API)" -- "External Integration"
    "Push Notification Service" -- "Push Notification" --> "User Client"
    "Email Service" -- "Email" --> "User"
    "User Client" -- "WebSocket (Real-time Events)" --> "Proxy/Web Server"
    "Proxy/Web Server" -- "WebSocket (Real-time Events)" --> "Mattermost Server"
    "Mattermost Server" -- "WebSocket (Real-time Events)" --> "Proxy/Web Server"
    "Proxy/Web Server" -- "WebSocket (Real-time Events)" --> "User Client"
Loading

Data Flow Description (Example: Sending a Message):

  1. User Action: User types a message in the "User Client" and clicks "Send".
  2. API Request: "User Client" sends an HTTPS POST request to the /api/v4/posts endpoint on the "Load Balancer" (or directly to "Proxy/Web Server" if no Load Balancer).
  3. Request Routing & Proxy: "Load Balancer" and "Proxy/Web Server" route the request to an available "Mattermost Server" instance.
  4. Authentication & Authorization: "Mattermost Server" authenticates the user session and authorizes the user to post in the target channel.
  5. Message Processing: "Mattermost Server" processes the message content, performs input validation, and stores the message in the "Database".
  6. Real-time Notification: "Mattermost Server" sends real-time event notifications via WebSockets to connected "User Clients" in the channel, informing them of the new message.
  7. Push Notification (Optional): If configured and if recipient users are offline or in background, "Mattermost Server" sends push notification requests to "Push Notification Service" (APNS/FCM) to notify mobile and desktop clients.
  8. Response: "Mattermost Server" sends an HTTPS response back to the "Proxy/Web Server", "Load Balancer", and finally to the "User Client", confirming successful message delivery.

6. Security Considerations

This section expands on initial security considerations, categorized for clarity and providing more specific examples for threat modeling.

6.1. Confidentiality: Protecting sensitive data from unauthorized access.

  • Data Encryption in Transit:
    • HTTPS/TLS: Enforce HTTPS for all client-server communication and server-server communication where applicable (e.g., between Proxy/Web Server and Mattermost Server).
    • TLS for SMTP: Use STARTTLS or TLS for secure email transmission.
    • WebSocket Encryption: Ensure WebSockets are also encrypted (WSS).
  • Data Encryption at Rest:
    • Database Encryption: Implement database encryption at rest (e.g., Transparent Data Encryption for PostgreSQL/MySQL) to protect stored data.
    • File Storage Encryption: Utilize server-side encryption or client-side encryption for files stored in "File Storage" (e.g., AWS S3 encryption).
  • Access Control & Least Privilege:
    • Role-Based Access Control (RBAC): Implement RBAC to control access to channels, teams, system settings, and administrative functions based on user roles.
    • Channel Permissions: Granular channel permissions (public, private, direct message) to restrict access to conversations.
    • System Admin Roles: Differentiate system administrator roles with varying levels of privileges.

6.2. Integrity: Maintaining the accuracy and completeness of data.

  • Input Validation:
    • Server-Side Validation: Implement robust server-side input validation for all API endpoints to prevent injection attacks (SQL injection, XSS, command injection) and data corruption.
    • Client-Side Validation: Implement client-side validation for user input to provide immediate feedback and reduce unnecessary server requests (but server-side validation is primary).
  • Output Encoding:
    • Context-Aware Output Encoding: Apply context-aware output encoding (e.g., HTML escaping, JavaScript escaping, URL encoding) to prevent Cross-Site Scripting (XSS) vulnerabilities.
  • Data Integrity Checks:
    • Database Constraints: Utilize database constraints (e.g., foreign keys, unique constraints, not-null constraints) to enforce data integrity.
    • Data Validation Rules: Implement application-level data validation rules to ensure data consistency and correctness.

6.3. Availability: Ensuring reliable access to the system and its data.

  • High Availability Architecture:
    • Load Balancing: Use "Load Balancer" to distribute traffic and prevent single points of failure.
    • Redundant Mattermost Servers: Deploy multiple "Mattermost Server" instances for redundancy.
    • Database Replication: Implement database replication (e.g., master-slave or multi-master) for database availability.
    • File Storage Redundancy: Utilize redundant file storage solutions (e.g., S3 with replication) for data durability and availability.
  • DDoS Protection:
    • Rate Limiting: Implement rate limiting at the "Proxy/Web Server" and "Mattermost Server" levels to prevent abuse and denial-of-service attacks.
    • Web Application Firewall (WAF): Consider using a WAF to protect against common web attacks and DDoS attempts.
  • Monitoring and Alerting:
    • System Monitoring: Implement comprehensive monitoring of all components (server, database, storage, network) to detect and respond to failures promptly.
    • Alerting System: Configure alerts for critical system events and performance degradation.

6.4. Authentication and Authorization: Verifying user identity and controlling access.

  • Authentication Mechanisms:
    • Username/Password Authentication: Standard username/password login with secure password hashing (e.g., bcrypt).
    • Multi-Factor Authentication (MFA): Support MFA (e.g., TOTP, WebAuthn) for enhanced security.
    • Single Sign-On (SSO): Integrate with SSO providers (e.g., SAML, OAuth 2.0, OpenID Connect, Active Directory/LDAP) for centralized authentication.
  • Session Management:
    • Secure Session Cookies: Use HTTP-only and secure cookies for session management to prevent session hijacking.
    • Session Timeout: Implement appropriate session timeout and idle timeout settings.
    • Session Revocation: Provide mechanisms for users and administrators to revoke active sessions.
  • API Authentication:
    • Personal Access Tokens: Support personal access tokens for API clients.
    • OAuth 2.0: Consider OAuth 2.0 for delegated authorization for third-party applications.

6.5. Auditing and Logging: Tracking system events and security-related activities.

  • Security Auditing:
    • Audit Logs: Log security-relevant events, such as login attempts, permission changes, administrative actions, and data access.
    • Access Logs: Log access to API endpoints and resources.
  • Logging Configuration:
    • Centralized Logging: Centralize logs for easier analysis and security monitoring.
    • Log Retention: Define appropriate log retention policies for compliance and incident investigation.
  • Security Monitoring:
    • Security Information and Event Management (SIEM): Integrate with SIEM systems for real-time security monitoring and threat detection.

6.6. Plugin and Integration Security: Securing the extensibility points of Mattermost.

  • Plugin Sandboxing: Implement plugin sandboxing to limit the capabilities of plugins and prevent malicious code execution.
  • Plugin Permissions: Define a permission model for plugins to control access to Mattermost APIs and resources.
  • Plugin Security Audits: Conduct security reviews and audits of plugins, especially those from untrusted sources.
  • Webhook Verification: Implement webhook signature verification to ensure the authenticity and integrity of incoming webhook requests.
  • Slash Command Security: Validate slash command inputs and permissions to prevent abuse.
  • API Rate Limiting: Apply rate limiting to REST APIs to prevent abuse and denial-of-service attacks from integrations.

7. Deployment Model Security Considerations

Security considerations vary depending on the deployment model.

  • On-Premises Deployment:
    • Full Security Responsibility: The organization is responsible for securing all layers of the infrastructure, including physical security, network security, server security, and application security.
    • Network Security: Secure network segmentation, firewalls, intrusion detection/prevention systems (IDS/IPS) are crucial.
    • Physical Security: Physical access control to data centers and server rooms is essential.
    • Operating System Security: Hardening operating systems, patching vulnerabilities, and secure configuration are critical.
  • Cloud (IaaS/PaaS) Deployment:
    • Shared Responsibility Model: Security is a shared responsibility between the cloud provider and the organization. The cloud provider is responsible for the security of the cloud infrastructure, while the organization is responsible for securing what they put in the cloud (VMs, containers, applications, data).
    • Cloud Security Configurations: Securely configure cloud services (e.g., AWS EC2, Azure VMs, GCP Compute Engine, S3, Azure Blob Storage) and follow cloud security best practices.
    • Identity and Access Management (IAM): Utilize cloud IAM services to manage access to cloud resources and enforce least privilege.
    • Network Security Groups (NSGs): Configure NSGs or security groups to control network traffic to and from cloud resources.
    • Data Residency and Compliance: Consider data residency requirements and compliance regulations when choosing cloud regions and services.
  • Containerized (Docker/Kubernetes) Deployment:
    • Container Security: Secure container images, vulnerability scanning of images, and container runtime security are important.
    • Kubernetes Security: Secure Kubernetes cluster configuration, RBAC for Kubernetes API access, network policies to isolate containers, and security audits of Kubernetes components.
    • Image Registry Security: Secure access to container image registries and scan images for vulnerabilities.
    • Orchestration Security: Secure communication between Kubernetes components and secure access to the Kubernetes API server.

8. Conclusion

This enhanced design document provides a more detailed and structured foundation for threat modeling the Mattermost server project. It expands on the system architecture, component functionalities, data flow, and security considerations, offering a comprehensive view of the system's attack surface. By leveraging this document, security professionals can conduct thorough threat modeling exercises using methodologies like STRIDE or PASTA to identify potential vulnerabilities and develop effective mitigation strategies. This proactive approach to security will contribute to building a more secure and resilient Mattermost platform. The next step is to utilize this document in a structured threat modeling workshop to identify, analyze, and prioritize potential threats and define specific security requirements and controls.