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Deep Security Analysis of Eclipse Mosquitto

1. Objective, Scope, and Methodology

Objective: The objective of this deep analysis is to perform a thorough security assessment of the Eclipse Mosquitto MQTT broker, focusing on its key components, identifying potential vulnerabilities, and providing actionable mitigation strategies. The analysis will consider the broker's architecture, data flow, security controls, and deployment context. The key components to be analyzed include:

  • Listener: Network connection handling and TLS/SSL.
  • Authentication Plugin System: Credential verification and integration with external providers.
  • Core Broker Logic: Message routing, ACL enforcement, and input validation.
  • Persistence Layer: Data storage security (if enabled).
  • Bridge Connector: Security of connections to other brokers.
  • Build Process: Security of the build pipeline.

Scope: This analysis covers the Eclipse Mosquitto MQTT broker itself, its configuration, and its interaction with clients and other brokers in a Kubernetes-based deployment. It does not cover the security of client applications or IoT devices connecting to the broker, except to the extent that the broker's configuration impacts their security. It also does not cover the security of the underlying Kubernetes infrastructure, although recommendations will touch upon integration points.

Methodology:

  1. Architecture and Data Flow Review: Analyze the provided C4 diagrams and descriptions, combined with information from the Mosquitto documentation and source code (where necessary), to understand the broker's architecture, data flow, and component interactions.
  2. Threat Modeling: Identify potential threats to each component based on its function, exposure, and interactions. This will leverage the STRIDE model (Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, Elevation of Privilege).
  3. Vulnerability Analysis: Assess the likelihood and impact of identified threats, considering existing security controls and accepted risks.
  4. Mitigation Strategy Recommendation: Propose specific, actionable mitigation strategies to address identified vulnerabilities and strengthen the overall security posture of the Mosquitto deployment. These will be tailored to the Kubernetes deployment context.

2. Security Implications of Key Components

This section breaks down the security implications of each key component, applying the STRIDE threat model.

2.1 Listener

  • Responsibilities: Accepting connections, TLS/SSL negotiation, parsing MQTT packets.
  • Threats:
    • Spoofing: An attacker could attempt to impersonate a legitimate client or the broker itself.
    • Tampering: An attacker could modify MQTT packets in transit.
    • Information Disclosure: An attacker could eavesdrop on unencrypted communication or exploit vulnerabilities in the TLS/SSL implementation (e.g., weak ciphers, outdated protocols).
    • Denial of Service: An attacker could flood the listener with connection requests or malformed packets, preventing legitimate clients from connecting.
    • Elevation of Privilege: Vulnerabilities in the packet parsing logic could allow an attacker to execute arbitrary code.

2.2 Authentication Plugin System

  • Responsibilities: Verifying client credentials, interacting with external authentication providers.
  • Threats:
    • Spoofing: An attacker could provide false credentials or impersonate an authentication provider.
    • Tampering: An attacker could modify authentication requests or responses.
    • Information Disclosure: An attacker could gain access to stored credentials or intercept communication with external providers.
    • Repudiation: Lack of sufficient audit logging could make it difficult to trace authentication failures or successes.
    • Elevation of Privilege: Vulnerabilities in a plugin could allow an attacker to bypass authentication or gain unauthorized access.

2.3 Core Broker Logic

  • Responsibilities: Managing subscriptions, routing messages, enforcing ACLs, handling QoS levels.
  • Threats:
    • Spoofing: An attacker could impersonate a client to publish or subscribe to unauthorized topics.
    • Tampering: An attacker could modify messages in transit or inject malicious messages.
    • Information Disclosure: An attacker could gain access to messages intended for other clients due to ACL misconfiguration or vulnerabilities.
    • Denial of Service: An attacker could send a large number of messages or subscriptions, overwhelming the broker. Exploiting QoS levels (especially QoS 2) could lead to resource exhaustion.
    • Elevation of Privilege: Vulnerabilities in the message handling or ACL enforcement logic could allow an attacker to gain unauthorized access. Topic wildcard abuse could lead to unintended access.

2.4 Persistence Layer

  • Responsibilities: Storing and retrieving messages, managing persistent sessions.
  • Threats:
    • Information Disclosure: An attacker could gain access to stored messages if the persistence layer is not properly secured.
    • Tampering: An attacker could modify or delete stored messages.
    • Denial of Service: An attacker could fill the storage, preventing new messages from being stored.

2.5 Bridge Connector

  • Responsibilities: Establishing and maintaining bridge connections, forwarding messages between brokers.
  • Threats:
    • Spoofing: An attacker could impersonate a legitimate broker.
    • Tampering: An attacker could modify messages in transit between brokers.
    • Information Disclosure: An attacker could eavesdrop on unencrypted communication between brokers.
    • Denial of Service: An attacker could disrupt the bridge connection, preventing communication between brokers.

2.6 Build Process

  • Responsibilities: Compiling code, running tests, creating and publishing Docker images.
  • Threats:
    • Tampering: An attacker could inject malicious code into the source code repository or compromise the build pipeline to produce a malicious Docker image.
    • Information Disclosure: Sensitive information (e.g., API keys, credentials) could be leaked if stored insecurely in the build environment.
    • Elevation of Privilege: An attacker who gains control of the build pipeline could potentially gain access to other systems.

3. Vulnerability Analysis

This section analyzes the likelihood and impact of the threats identified above, considering existing controls and accepted risks.

| Component | Threat | Likelihood | Impact | Existing Controls