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sec-design.md

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Okay, let's create a design document for the Alibaba Sentinel project.

BUSINESS POSTURE

Sentinel is a flow control and service resilience component designed for distributed systems. It aims to ensure service stability and availability, particularly in microservice architectures. The core business priorities are:

  • Reliability: Ensuring services remain available and responsive even under high load or partial failures.
  • Performance: Minimizing the impact of flow control and resilience mechanisms on overall system performance.
  • Maintainability: Providing a framework that is easy to integrate, configure, and monitor.
  • Scalability: Handling increasing traffic and complexity as the system grows.
  • Observability: Providing insights into system behavior and performance metrics.

Business Risks:

  • Service Outages: The primary risk is that a service becomes unavailable or unresponsive, leading to cascading failures and impacting end-users.
  • Performance Degradation: Poorly configured flow control or resilience rules could inadvertently degrade performance under normal conditions.
  • Complexity Overhead: Adding Sentinel could introduce unnecessary complexity if not implemented and managed correctly.
  • Integration Challenges: Difficulties integrating Sentinel with existing systems and frameworks could hinder adoption and effectiveness.
  • False Positives/Negatives: Incorrectly configured rules could lead to either blocking legitimate traffic (false positive) or failing to protect against actual overload (false negative).

SECURITY POSTURE

Existing Security Controls (based on the GitHub repository and common practices):

  • security control: Dependency Management: The project uses Maven for dependency management, which allows for tracking and updating dependencies. (pom.xml)
  • security control: Code Quality Tools: The project appears to use FindBugs/SpotBugs for static analysis, as indicated by the Maven configuration. (pom.xml)
  • security control: Testing: The project includes unit and integration tests, which help ensure the correctness and stability of the code. (sentinel-core/src/test, etc.)
  • security control: Documentation: The project provides documentation on how to use and configure Sentinel, which is crucial for secure and correct implementation. (README.md, wiki)

Accepted Risks:

  • accepted risk: Limited Built-in Authentication/Authorization: Sentinel itself primarily focuses on flow control and resilience, not on authentication or authorization of end-user requests. It relies on the surrounding application and infrastructure to handle these aspects.
  • accepted risk: Configuration Complexity: Incorrect configuration of Sentinel rules can lead to security and availability issues. This risk is mitigated by documentation and best practices, but user error remains a possibility.
  • accepted risk: Supply Chain Vulnerabilities: While dependency management is used, there's always a risk of vulnerabilities in third-party libraries. This is a common risk in software development.
  • accepted risk: Denial of Service (DoS) against Sentinel Dashboard: While Sentinel protects services, the dashboard itself could be a target for DoS attacks.

Recommended Security Controls:

  • security control: Integrate with existing Authentication/Authorization mechanisms: Ensure that Sentinel integrates seamlessly with the application's existing security framework for user authentication and authorization.
  • security control: Secure Configuration Management: Implement secure practices for storing and managing Sentinel configurations, potentially using a centralized configuration service with access controls.
  • security control: Regular Security Audits and Penetration Testing: Conduct periodic security assessments to identify and address potential vulnerabilities.
  • security control: Enhanced Input Validation: While Sentinel primarily deals with traffic flow, validating input parameters to its API and dashboard is crucial to prevent injection attacks.
  • security control: Monitor Sentinel's own resource usage: Implement monitoring to detect if Sentinel itself is becoming a bottleneck or a target of resource exhaustion attacks.
  • security control: Implement SLSA framework to improve supply chain security.

Security Requirements:

  • Authentication: Sentinel's dashboard and API should require authentication to prevent unauthorized access and configuration changes.
  • Authorization: Access to Sentinel's features (e.g., modifying rules) should be controlled based on roles and permissions.
  • Input Validation: All inputs to Sentinel's API and dashboard should be validated to prevent injection attacks and ensure data integrity.
  • Cryptography: If sensitive data is transmitted or stored (e.g., API keys), appropriate encryption mechanisms should be used.
  • Audit Logging: Sentinel should log all significant events, including configuration changes, rule violations, and security-related events.

DESIGN

C4 CONTEXT

graph LR
    User(("User")) --> Application
    Application --> Sentinel
    Application --> OtherServices
    Sentinel --> Dashboard
    OtherServices(("Other Services"))

    classDef element fill:#f9f,stroke:#333,stroke-width:2px
    class User,Application,Sentinel,OtherServices,Dashboard element
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Element Descriptions:

  • Element:

    • Name: User
    • Type: Person
    • Description: Represents an end-user interacting with the application.
    • Responsibilities: Accessing application features.
    • Security controls: Authentication and authorization are typically handled by the Application.

  • Element:

    • Name: Application
    • Type: Software System
    • Description: The application that is being protected by Sentinel.
    • Responsibilities: Providing core business functionality.
    • Security controls: Authentication, authorization, input validation, data protection.

  • Element:

    • Name: Sentinel
    • Type: Software System
    • Description: The Sentinel flow control and resilience component.
    • Responsibilities: Enforcing flow control rules, circuit breaking, and other resilience mechanisms.
    • Security controls: Input validation for API calls, secure configuration management.

  • Element:

    • Name: Other Services
    • Type: Software System
    • Description: Other services that the Application interacts with.
    • Responsibilities: Providing supporting functionality.
    • Security controls: Depend on the specific services.

  • Element:

    • Name: Dashboard
    • Type: Software System
    • Description: The Sentinel dashboard for monitoring and configuration.
    • Responsibilities: Providing a user interface for managing Sentinel.
    • Security controls: Authentication, authorization, input validation.

C4 CONTAINER

graph LR
    User(("User")) --> ApplicationAPI
    ApplicationAPI --> SentinelCore
    ApplicationAPI --> OtherServiceClients
    OtherServiceClients --> OtherServices
    SentinelCore --> SentinelDashboardAPI
    SentinelDashboardAPI --> DashboardUI
    OtherServices(("Other Services"))
    DashboardUI(("Dashboard UI"))

    classDef element fill:#f9f,stroke:#333,stroke-width:2px
    class User,ApplicationAPI,SentinelCore,OtherServiceClients,OtherServices,SentinelDashboardAPI,DashboardUI element
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Element Descriptions:

  • Element:

    • Name: User
    • Type: Person
    • Description: Represents an end-user interacting with the application.
    • Responsibilities: Accessing application features.
    • Security controls: Authentication and authorization are typically handled by the Application API.

  • Element:

    • Name: Application API
    • Type: API
    • Description: The main entry point for the application.
    • Responsibilities: Handling user requests, interacting with Sentinel and other services.
    • Security controls: Authentication, authorization, input validation, rate limiting.

  • Element:

    • Name: Sentinel Core
    • Type: Library/Component
    • Description: The core Sentinel library embedded within the application.
    • Responsibilities: Enforcing flow control rules, circuit breaking.
    • Security controls: Input validation for API calls.

  • Element:

    • Name: Other Service Clients
    • Type: Library/Component
    • Description: Clients for interacting with other services.
    • Responsibilities: Communicating with other services.
    • Security controls: Secure communication protocols (e.g., TLS).

  • Element:

    • Name: Other Services
    • Type: Software System
    • Description: Other services that the Application interacts with.
    • Responsibilities: Providing supporting functionality.
    • Security controls: Depend on the specific services.

  • Element:

    • Name: Sentinel Dashboard API
    • Type: API
    • Description: API for the Sentinel dashboard.
    • Responsibilities: Providing data and configuration options to the dashboard UI.
    • Security controls: Authentication, authorization, input validation.

  • Element:

    • Name: Dashboard UI
    • Type: Web Application
    • Description: User interface for the Sentinel dashboard.
    • Responsibilities: Displaying monitoring data, allowing configuration changes.
    • Security controls: Authentication, authorization, input validation, XSS protection.

DEPLOYMENT

Possible Deployment Solutions:

  1. Embedded within Application: Sentinel Core is typically embedded directly within the application as a library. The dashboard can be deployed as a separate application.
  2. Sidecar: Sentinel could be deployed as a sidecar container alongside the application container. This is less common but possible.
  3. Dedicated Service: Sentinel could be deployed as a standalone service, with applications communicating with it remotely. This is also less common.

Chosen Solution (Most Common): Embedded within Application

graph LR
    AppServer(("Application Server")) --> AppContainer
    AppContainer(("Application Container")) --> SentinelCoreLib
    SentinelCoreLib(("Sentinel Core Library"))
    DashboardServer(("Dashboard Server")) --> DashboardContainer
    DashboardContainer(("Dashboard Container")) --> DashboardApp
    DashboardApp(("Dashboard Application"))

    classDef element fill:#f9f,stroke:#333,stroke-width:2px
    class AppServer,AppContainer,SentinelCoreLib,DashboardServer,DashboardContainer,DashboardApp element
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Element Descriptions:

  • Element: * Name: AppServer * Type: Server * Description: Server hosting application. * Responsibilities: Run application container. * Security controls: OS hardening, firewall.

  • Element: * Name: AppContainer * Type: Container * Description: Container running application code. * Responsibilities: Execute application logic. * Security controls: Container image security, resource limits.

  • Element: * Name: SentinelCoreLib * Type: Library * Description: Sentinel core library embedded in application. * Responsibilities: Flow control, resilience. * Security controls: Input validation.

  • Element: * Name: DashboardServer * Type: Server * Description: Server hosting Sentinel dashboard. * Responsibilities: Run dashboard container. * Security controls: OS hardening, firewall.

  • Element: * Name: DashboardContainer * Type: Container * Description: Container running Sentinel dashboard. * Responsibilities: Serve dashboard UI. * Security controls: Container image security, resource limits.

  • Element: * Name: DashboardApp * Type: Web Application * Description: Sentinel dashboard application. * Responsibilities: Provide UI for monitoring and configuration. * Security controls: Authentication, authorization, input validation.

BUILD

The Sentinel project uses Maven for build automation. The build process includes:

  1. Developer: Writes code and commits to the repository.
  2. Build Server (e.g., GitHub Actions, Jenkins): Triggered by commits, pulls the code.
  3. Maven Build: Executes Maven commands (mvn clean install).
    • Compilation: Compiles the Java code.
    • Testing: Runs unit and integration tests.
    • Static Analysis: Executes FindBugs/SpotBugs for static code analysis.
    • Packaging: Creates JAR files.
  4. Artifact Repository: The resulting JAR files are published to a Maven repository (e.g., Maven Central).
graph LR
    Developer(("Developer")) --> Commit
    Commit --> BuildServer
    BuildServer(("Build Server")) --> MavenBuild
    MavenBuild(("Maven Build")) --> Compilation
    Compilation --> Testing
    Testing --> StaticAnalysis
    StaticAnalysis --> Packaging
    Packaging(("Packaging")) --> ArtifactRepository
    ArtifactRepository(("Artifact Repository"))

    classDef element fill:#f9f,stroke:#333,stroke-width:2px
    class Developer,Commit,BuildServer,MavenBuild,Compilation,Testing,StaticAnalysis,Packaging,ArtifactRepository element
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Security Controls in Build Process:

  • security control: Dependency Management (Maven): Tracks and manages dependencies, allowing for vulnerability scanning.
  • security control: Static Analysis (FindBugs/SpotBugs): Detects potential code quality and security issues.
  • security control: Automated Testing: Ensures code correctness and helps prevent regressions.
  • security control: Build Automation (Maven, GitHub Actions/Jenkins): Provides a consistent and repeatable build process.
  • security control: Artifact Repository: Securely stores build artifacts.

RISK ASSESSMENT

Critical Business Processes:

  • Service Availability: Ensuring that services remain available and responsive to user requests.
  • Service Resilience: Maintaining service functionality even in the face of partial failures or high load.
  • Data Consistency: Protecting the consistency and integrity of data processed by the services.

Data Sensitivity:

  • Sentinel itself does not directly handle sensitive user data. However, the configuration data for Sentinel (rules, thresholds) is sensitive because it controls the availability and behavior of the protected services. Incorrect or malicious configuration could lead to service disruption.
  • The monitoring data collected by Sentinel (metrics, logs) may indirectly reveal information about application usage patterns, which could be considered sensitive in some contexts.

QUESTIONS & ASSUMPTIONS

Questions:

  • What specific authentication and authorization mechanisms are used by the applications that will be protected by Sentinel?
  • What is the expected deployment environment (e.g., Kubernetes, cloud provider)?
  • Are there any specific compliance requirements (e.g., PCI DSS, HIPAA) that need to be considered?
  • What is the process for managing and updating Sentinel configurations in production?
  • What are the existing monitoring and alerting systems in place?
  • What level of access will Sentinel have to other services or resources?
  • Are there any specific performance requirements or SLAs for the protected services?

Assumptions:

  • BUSINESS POSTURE: The organization prioritizes service availability and resilience.
  • SECURITY POSTURE: The organization has a basic security awareness and follows some secure development practices. Existing security controls are in place at the application and infrastructure levels to handle authentication, authorization, and data protection.
  • DESIGN: Sentinel will be primarily used in a microservices environment. The Sentinel Core library will be embedded within the application. The Sentinel Dashboard will be deployed separately. The build process will use Maven and a CI/CD system.