sec-design.md

BUSINESS POSTURE

• Business Priorities and Goals:

• Priority is to improve application performance by reducing image loading times.

• Goal is to provide a fast and efficient image caching service.

• Goal is to reduce bandwidth costs associated with serving images directly from origin servers.

• Goal is to improve user experience by serving images quickly and reliably.

• Business Risks:

• Risk of service unavailability impacting application performance and user experience.

• Risk of serving stale or incorrect images leading to data integrity issues.

• Risk of increased operational costs if the caching system is not efficient or scalable.

• Risk of security vulnerabilities in the caching system leading to data breaches or service disruptions.

SECURITY POSTURE

• Existing Security Controls:

• security control: Code reviews are likely performed as part of the development process. (Location: GitHub repository workflow)

• security control: Basic unit and integration tests are likely in place. (Location: GitHub repository workflow)

• security control: Project is likely deployed in a cloud environment. (Location: Assumption based on modern software development practices)

• Accepted Risks:

• accepted risk: Potential for minor service disruptions during deployment updates.

• accepted risk: Reliance on cloud provider's security for infrastructure.

• Recommended Security Controls:

• security control: Implement automated security scanning (SAST/DAST) in the CI/CD pipeline.

• security control: Implement input validation for image URLs and cache keys.

• security control: Implement access control to the cache management interface.

• security control: Use HTTPS for all communication to and from the cache.

• security control: Implement monitoring and logging for security events.

• Security Requirements:

• Authentication:

• Requirement: Implement authentication for accessing the cache management interface.

• Requirement: Consider API key or token-based authentication for programmatic access.

• Authorization:

• Requirement: Implement role-based access control (RBAC) for the cache management interface to restrict access to sensitive operations.

• Requirement: Ensure that only authorized services or users can invalidate cache entries.

• Input Validation:

• Requirement: Validate image URLs to prevent injection attacks and ensure they are valid image resources.

• Requirement: Validate cache keys to prevent manipulation and ensure proper cache retrieval.

• Requirement: Sanitize and validate any user-provided data used in cache operations.

• Cryptography:

• Requirement: Use HTTPS for all communication between clients and the cache service to protect data in transit.

• Requirement: Consider encryption at rest for cached images if they contain sensitive data.

DESIGN

• C4 CONTEXT

flowchart LR
    subgraph "Application Users"
        A[Users]
    end
    subgraph "Origin Image Servers"
        B[Image Origin 1]
        C[Image Origin 2]
        ...
        D[Image Origin N]
    end
    E("Fast Image Cache System")

    A --> E
    E --> B
    E --> C
    E --> D

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• C4 CONTEXT Elements:

• Element:

• Name: Users

• Type: Person

• Description: End-users of the application who access images.

• Responsibilities: Requesting images through the application.

• Security controls: User authentication and authorization are handled by the application, not directly by the cache.

• Element:

• Name: Image Origin 1, Image Origin 2, ..., Image Origin N

• Type: External System

• Description: External servers that host the original images.

• Responsibilities: Providing original images when requested by the cache.

• Security controls: Security of origin servers is managed independently. Fast Image Cache system should only access publicly available images or use appropriate authentication if required by origin servers.

• Element:

• Name: Fast Image Cache System

• Type: System

• Description: System responsible for caching images to improve application performance.

• Responsibilities: Caching images fetched from origin servers, serving cached images to users, managing cache invalidation.

• Security controls: Input validation, access control for management interface, HTTPS for communication, monitoring and logging.

• C4 CONTAINER

flowchart LR
    subgraph "Fast Image Cache System"
        A["Web Server"
        \nTechnology: Nginx/Apache]
        B["Cache Storage"
        \nTechnology: Redis/Memcached/Disk]
        C["Management Interface"
        \nTechnology: Web UI/CLI"]
    end
    D[Users]
    E[Image Origin]

    D --> A
    A --> B
    A --> E
    C --> A
    C --> B

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• C4 CONTAINER Elements:

• Element:

• Name: Web Server

• Type: Container

• Description: Handles incoming image requests from users, checks the cache, and serves cached images or fetches from origin servers.

• Responsibilities: Receiving image requests, cache lookup, image retrieval from origin, serving images, cache invalidation requests.

• Security controls: Input validation for image URLs, HTTPS termination, rate limiting, logging of access attempts.

• Element:

• Name: Cache Storage

• Type: Container

• Description: Stores cached images and metadata for efficient retrieval.

• Responsibilities: Storing and retrieving images based on cache keys, managing cache eviction policies.

• Security controls: Access control to the cache storage, potential encryption at rest, monitoring of storage usage.

• Element:

• Name: Management Interface

• Type: Container

• Description: Provides an interface for administrators to manage the cache, such as invalidating entries, monitoring cache statistics, and configuring settings.

• Responsibilities: Cache management operations, monitoring, configuration.

• Security controls: Authentication and authorization for access, audit logging of management actions, secure communication (HTTPS).

• DEPLOYMENT

flowchart LR
    subgraph "Cloud Environment (e.g., AWS)"
        subgraph "Load Balancer"
            A[Load Balancer]
        end
        subgraph "Web Server Instances"
            B1[Web Server Instance 1]
            B2[Web Server Instance 2]
            ...
            Bn[Web Server Instance N]
        end
        subgraph "Cache Storage Cluster"
            C1[Cache Node 1]
            C2[Cache Node 2]
            ...
            Cm[Cache Node M]
        end
        subgraph "Management Instance"
            D[Management Instance]
        end
    end
    E[Users]
    F[Image Origin]

    E --> A
    A --> B1
    A --> B2
    A --> Bn
    B1 --> C1
    B1 --> C2
    B1 --> Cm
    B2 --> C1
    B2 --> C2
    B2 --> Cm
    Bn --> C1
    Bn --> C2
    Bn --> Cm
    D --> B1
    D --> C1
    F --> B1

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• DEPLOYMENT Elements:

• Element:

• Name: Load Balancer

• Type: Infrastructure

• Description: Distributes incoming traffic across multiple web server instances for high availability and scalability.

• Responsibilities: Traffic distribution, health checks for web server instances.

• Security controls: DDoS protection, TLS termination, access control lists.

• Element:

• Name: Web Server Instance 1, Web Server Instance 2, ..., Web Server Instance N

• Type: Infrastructure (Virtual Machine/Container)

• Description: Instances of the web server container running the image caching logic.

• Responsibilities: Handling image requests, interacting with cache storage and origin servers.

• Security controls: Security hardening of the operating system and runtime environment, network firewalls, intrusion detection systems.

• Element:

• Name: Cache Node 1, Cache Node 2, ..., Cache Node M

• Type: Infrastructure (Virtual Machine/Container/Managed Service)

• Description: Nodes in the cache storage cluster providing distributed and scalable caching.

• Responsibilities: Storing and retrieving cached images, data replication and persistence.

• Security controls: Access control to the cache cluster, data encryption at rest and in transit within the cluster, monitoring of cluster health.

• Element:

• Name: Management Instance

• Type: Infrastructure (Virtual Machine/Container)

• Description: Instance hosting the management interface for the cache system.

• Responsibilities: Providing access to the management interface.

• Security controls: Security hardening, network firewalls, access control, HTTPS only access.

• BUILD

flowchart LR
    A[Developer] --> B{Code Changes};
    B --> C[Version Control (e.g., GitHub)];
    C --> D[CI/CD Pipeline (e.g., GitHub Actions)];
    D --> E{Build Process
    \n- Compilation
    \n- Linting
    \n- SAST Scanning
    \n- Unit Tests
    \n- Integration Tests};
    E --> F[Build Artifacts
    \n(e.g., Container Image, Binaries)];
    F --> G[Artifact Repository
    \n(e.g., Container Registry, Package Repository)];

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• BUILD Elements:
• Element:
• Name: Developer
• Type: Person
• Description: Software developer writing and modifying the code.
• Responsibilities: Writing secure code, performing local testing.
• Security controls: Secure coding practices training, code review participation.
• Element:
• Name: Version Control (e.g., GitHub)
• Type: Tool
• Description: System for managing and tracking changes to the codebase.
• Responsibilities: Source code management, access control to codebase, audit logging of changes.
• Security controls: Access control (authentication and authorization), branch protection, audit logs.
• Element:
• Name: CI/CD Pipeline (e.g., GitHub Actions)
• Type: Tool
• Description: Automated system for building, testing, and deploying the application.
• Responsibilities: Automating build process, running security scans, deploying artifacts.
• Security controls: Secure pipeline configuration, secret management, access control to pipeline definitions and execution.
• Element:
• Name: Build Process
• Type: Process
• Description: Steps involved in transforming source code into deployable artifacts. Includes compilation, linting, security scanning, and testing.
• Responsibilities: Creating secure and functional build artifacts.
• Security controls: SAST scanning, dependency scanning, linting, unit and integration tests, secure build environment.
• Element:
• Name: Build Artifacts (e.g., Container Image, Binaries)
• Type: Artifact
• Description: Deployable packages created by the build process.
• Responsibilities: Being deployable and containing the application code and dependencies.
• Security controls: Artifact signing, vulnerability scanning of artifacts.
• Element:
• Name: Artifact Repository (e.g., Container Registry, Package Repository)
• Type: Tool
• Description: System for storing and managing build artifacts.
• Responsibilities: Securely storing and distributing build artifacts.
• Security controls: Access control, vulnerability scanning, audit logging, secure storage.

RISK ASSESSMENT

• Critical Business Processes:

• Serving images to application users quickly and reliably.

• Maintaining cache availability and integrity.

• Efficiently managing cache storage and resources.

• Data to Protect and Sensitivity:

• Cached images: Sensitivity depends on the application using the cache. Assuming publicly available images, sensitivity is low in terms of confidentiality, but high in terms of availability and integrity (serving correct images).

• Cache metadata: Low sensitivity.

• Logs and monitoring data: Low to medium sensitivity, depending on the information logged.

QUESTIONS & ASSUMPTIONS

• Questions:

• What is the expected scale of image requests and cache size?

• What are the performance requirements (latency, throughput)?

• What type of images will be cached (public, private, sensitive)?

• Are there any specific compliance requirements (e.g., GDPR, HIPAA)?

• What is the budget for security controls and infrastructure?

• What is the expected lifespan of the project?

• Assumptions:

• BUSINESS POSTURE:

• The primary business goal is to improve application performance.

• The application serves publicly accessible images.

• Cost-effectiveness is a consideration.

• SECURITY POSTURE:

• Basic security controls like code reviews and testing are in place.

• The system will be deployed in a cloud environment.

• Security is important but should be balanced with performance and cost.

• DESIGN:

• A standard web server (Nginx/Apache) will be used.

• A distributed cache storage (Redis/Memcached/Disk) will be used.

• Deployment will be in a typical cloud environment with load balancers and auto-scaling.

• CI/CD pipeline will be used for build and deployment automation.