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sec-design.md

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Okay, let's create a design document for the Sarama project, a Go library for Apache Kafka.

BUSINESS POSTURE

Sarama is a pure Go library for working with Apache Kafka, a distributed, fault-tolerant, high-throughput, real-time messaging system. It's an open-source project maintained by Shopify. Given its nature as a foundational library, the primary business goals and priorities are:

  • Reliability: The library must be stable and dependable, as it forms the basis for applications that rely on Kafka. Any instability directly impacts downstream applications.
  • Performance: Kafka is often used in high-throughput scenarios. The library must be performant to avoid becoming a bottleneck.
  • Maintainability: As an open-source project, maintainability is crucial. The codebase should be easy to understand, modify, and extend. This includes good documentation and a clear structure.
  • Compatibility: Kafka evolves, and the library must maintain compatibility with different Kafka versions.
  • Completeness: The library should provide a comprehensive API covering all major Kafka features.
  • Community Support: Foster a community around the library to encourage contributions and provide support.

Business risks that need to be addressed, based on these priorities:

  • Data Loss/Corruption: Bugs in the library could lead to message loss or corruption, which is a critical risk for any messaging system.
  • Performance Degradation: Inefficient code or poor handling of concurrency could lead to performance bottlenecks, impacting applications using the library.
  • Security Vulnerabilities: Vulnerabilities in the library could be exploited to compromise Kafka clusters or the applications interacting with them. This includes unauthorized access, data breaches, or denial-of-service attacks.
  • Incompatibility: Failure to keep up with Kafka API changes or broker version updates could render the library unusable.
  • Lack of Adoption: If the library is difficult to use, poorly documented, or perceived as unreliable, it may not gain widespread adoption, limiting its impact and community support.

SECURITY POSTURE

Existing security controls (based on the GitHub repository and common practices):

  • security control: Code Reviews: Shopify likely has internal code review processes before merging changes. (Inferred from Shopify's general engineering practices).
  • security control: Static Analysis: Go's built-in tooling (e.g., go vet, go lint) and likely additional static analysis tools are used to identify potential bugs and security issues. (Inferred from standard Go development practices).
  • security control: Testing: The repository contains a comprehensive suite of unit and integration tests. (Visible in the repository).
  • security control: Dependency Management: Go modules are used to manage dependencies, allowing for version pinning and vulnerability scanning. (Visible in go.mod and go.sum).
  • security control: Issue Tracking: Security vulnerabilities can be reported and tracked via GitHub Issues. (Standard GitHub functionality).
  • security control: Documentation: The project includes documentation on how to configure security features like TLS and SASL. (Visible in the repository).

Accepted risks:

  • accepted risk: Reliance on Third-Party Libraries: The library depends on external libraries (e.g., for compression). Vulnerabilities in these libraries could impact Sarama. This is mitigated by dependency management and regular updates.
  • accepted risk: Complexity of Kafka Security: Kafka's security model (especially with SASL and ACLs) can be complex. Misconfiguration by users of the Sarama library is a risk, though the library aims to provide a user-friendly API.
  • accepted risk: Evolving Threat Landscape: New vulnerabilities in Kafka or related technologies may emerge, requiring ongoing updates and security patches to Sarama.

Recommended security controls (high priority):

  • security control: Fuzz Testing: Implement fuzz testing to proactively discover edge cases and potential vulnerabilities that might be missed by traditional testing.
  • security control: Regular Security Audits: Conduct periodic security audits, both internal and potentially external, to identify potential vulnerabilities.
  • security control: Supply Chain Security: Implement measures to verify the integrity of dependencies and prevent supply chain attacks (e.g., using tools like cosign or in-toto).
  • security control: Security Policy: Create and publish a SECURITY.md file outlining the vulnerability reporting process and security policies.

Security Requirements:

  • Authentication:

    • The library must support secure connections to Kafka brokers using TLS.
    • The library must support SASL authentication mechanisms (e.g., PLAIN, SCRAM, GSSAPI, OAUTHBEARER).
    • Configuration options for authentication should be clearly documented and easy to use.

  • Authorization:

    • The library should not handle authorization directly; authorization is managed by Kafka brokers using ACLs. The library's role is to correctly authenticate the client.

  • Input Validation:

    • The library must validate user-provided inputs (e.g., topic names, configuration parameters) to prevent injection attacks or unexpected behavior.
    • Error handling should be robust and provide informative error messages without leaking sensitive information.

  • Cryptography:

    • The library must use strong cryptographic algorithms for TLS and SASL.
    • Key management should be handled securely, relying on the underlying operating system or external key management systems where appropriate.
    • The library should not implement its own cryptographic primitives but rely on well-vetted libraries (like Go's standard library).

DESIGN

C4 CONTEXT

graph LR
    subgraph Kafka Cluster
        Broker1["Kafka Broker"]
        Broker2["Kafka Broker"]
        Broker3["Kafka Broker"]
    end

    UserApp["User Application"] -- Uses --> Sarama["Sarama (Kafka Client Library)"]
    Sarama -- Connects to --> Kafka

    AdminTool["Kafka Admin Tool"] -- Manages --> Kafka
    MonitoringSystem["Monitoring System"] -- Monitors --> Kafka

    Kafka -- Stores Data In --> Zookeeper["ZooKeeper"]

    classDef external fill:#ddd,stroke:#000
    class UserApp,AdminTool,MonitoringSystem,Zookeeper external
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C4 CONTEXT Element List:

    1. Name: User Application
    • Type: External System
    • Description: An application that uses the Sarama library to produce or consume messages from a Kafka cluster.
    • Responsibilities: Sending and receiving data, processing messages, handling business logic.
    • Security controls: Authentication to Kafka (via Sarama), authorization (managed by Kafka ACLs), input validation, data encryption (if applicable).
    1. Name: Sarama (Kafka Client Library)
    • Type: System
    • Description: The Go library for interacting with Apache Kafka. This is the system being designed.
    • Responsibilities: Providing an API for producing and consuming messages, handling Kafka protocol details, managing connections, supporting security features (TLS, SASL).
    • Security controls: TLS, SASL authentication, input validation.
    1. Name: Kafka Cluster
    • Type: External System
    • Description: A cluster of Kafka brokers that store and manage messages.
    • Responsibilities: Receiving messages from producers, storing messages, delivering messages to consumers, managing replication and fault tolerance.
    • Security controls: Network security, authentication (TLS, SASL), authorization (ACLs), data encryption (if configured).
    1. Name: Kafka Admin Tool
    • Type: External System
    • Description: Tools used to manage and administer the Kafka cluster (e.g., creating topics, managing ACLs).
    • Responsibilities: Cluster management, configuration, monitoring.
    • Security controls: Authentication to Kafka, authorization (managed by Kafka ACLs).
    1. Name: Monitoring System
    • Type: External System
    • Description: Systems used to monitor the health and performance of the Kafka cluster.
    • Responsibilities: Collecting metrics, generating alerts, providing dashboards.
    • Security controls: Authentication to Kafka (if required for monitoring).
    1. Name: ZooKeeper
    • Type: External System
    • Description: A distributed coordination service used by Kafka for cluster management.
    • Responsibilities: Maintaining cluster metadata, managing broker membership, coordinating leader elections.
    • Security controls: Network security, authentication (if configured), authorization (if configured).

C4 CONTAINER

graph LR
    subgraph Sarama
        Producer["Producer API"]
        Consumer["Consumer API"]
        Admin["Admin API"]
        Config["Configuration"]
        Network["Network Client"]
        Protocol["Protocol Handling"]
        Compression["Compression/Decompression"]

        UserApp["User Application"] -- Uses --> Producer
        UserApp -- Uses --> Consumer
        UserApp -- Uses --> Admin

        Producer -- Uses --> Config
        Consumer -- Uses --> Config
        Admin -- Uses --> Config

        Producer -- Uses --> Protocol
        Consumer -- Uses --> Protocol
        Admin -- Uses --> Protocol

        Protocol -- Uses --> Network
        Protocol -- Uses --> Compression

        Network -- Connects to --> Kafka["Kafka Broker"]
    end

    classDef external fill:#ddd,stroke:#000
    class UserApp,Kafka external
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C4 CONTAINER Element List:

    1. Name: Producer API
    • Type: Container
    • Description: Provides an interface for applications to send messages to Kafka topics.
    • Responsibilities: Handling message encoding, partitioning, and sending to the appropriate brokers.
    • Security controls: TLS, SASL authentication (passed through from configuration).
    1. Name: Consumer API
    • Type: Container
    • Description: Provides an interface for applications to consume messages from Kafka topics.
    • Responsibilities: Managing consumer groups, fetching messages from brokers, handling offsets, and rebalancing.
    • Security controls: TLS, SASL authentication (passed through from configuration).
    1. Name: Admin API
    • Type: Container
    • Description: Provides an interface for administrative tasks, such as creating topics, deleting topics, and managing consumer groups.
    • Responsibilities: Sending administrative requests to Kafka brokers.
    • Security controls: TLS, SASL authentication (passed through from configuration).
    1. Name: Configuration
    • Type: Container
    • Description: Handles configuration settings for the library, including connection parameters, security settings, and client behavior.
    • Responsibilities: Parsing configuration options, validating inputs, providing default values.
    • Security controls: Input validation, secure handling of sensitive configuration values (e.g., passwords).
    1. Name: Network Client
    • Type: Container
    • Description: Manages the underlying network connections to Kafka brokers.
    • Responsibilities: Establishing connections, handling reconnections, managing timeouts, and sending/receiving data.
    • Security controls: TLS encryption.
    1. Name: Protocol Handling
    • Type: Container
    • Description: Implements the Kafka protocol for encoding and decoding messages and requests.
    • Responsibilities: Serializing and deserializing data according to the Kafka protocol specification.
    • Security controls: Input validation (to prevent malformed messages from causing issues).
    1. Name: Compression/Decompression
    • Type: Container
    • Description: Handles message compression and decompression (e.g., using Gzip, Snappy, LZ4, Zstd).
    • Responsibilities: Compressing messages before sending, decompressing messages after receiving.
    • Security controls: Using well-vetted compression libraries.

DEPLOYMENT

Possible deployment solutions:

  1. As a Go library, Sarama is not "deployed" in the traditional sense of a standalone application. It's included as a dependency in other Go applications.
  2. The Go applications that use Sarama can be deployed in various ways:
    • Bare metal servers
    • Virtual machines (e.g., AWS EC2, Google Compute Engine, Azure VMs)
    • Containers (e.g., Docker, Kubernetes)
    • Serverless functions (e.g., AWS Lambda, Google Cloud Functions, Azure Functions)

Chosen deployment solution (Containers using Kubernetes):

graph LR
    subgraph Kubernetes Cluster
        subgraph Node 1
            Pod1["Pod (User App + Sarama)"]
        end
        subgraph Node 2
            Pod2["Pod (User App + Sarama)"]
        end
        subgraph Node 3
            Pod3["Pod (User App + Sarama)"]
        end
    end

    Pod1 -- Connects to --> Kafka["Kafka Cluster"]
    Pod2 -- Connects to --> Kafka
    Pod3 -- Connects to --> Kafka

    classDef external fill:#ddd,stroke:#000
    class Kafka external
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DEPLOYMENT Element List:

    1. Name: Kubernetes Cluster
    • Type: Infrastructure Node
    • Description: A cluster of machines managed by Kubernetes.
    • Responsibilities: Orchestrating containers, managing resources, providing networking and storage.
    • Security controls: Network policies, RBAC (Role-Based Access Control), pod security policies, secrets management.
    1. Name: Node (1, 2, 3)
    • Type: Infrastructure Node
    • Description: A worker machine within the Kubernetes cluster.
    • Responsibilities: Running pods, providing resources (CPU, memory, storage).
    • Security controls: OS hardening, network security, container runtime security.
    1. Name: Pod (User App + Sarama)
    • Type: Container Instance
    • Description: A Kubernetes pod containing a container running the user application that includes the Sarama library.
    • Responsibilities: Running the application logic, producing/consuming messages from Kafka.
    • Security controls: Container image security (scanning for vulnerabilities), least privilege principle, network policies.
    1. Name: Kafka Cluster
    • Type: External System
    • Description: The Kafka cluster (external to the Kubernetes cluster).
    • Responsibilities: See C4 Context description.
    • Security controls: See C4 Context description.

BUILD

The build process for Sarama, being a Go library, is integrated into the Go toolchain.

graph LR
    Developer["Developer"] -- Writes Code --> LocalMachine["Local Machine"]
    LocalMachine -- Runs Tests --> LocalMachine
    LocalMachine -- Pushes Code --> GitHub["GitHub Repository"]
    GitHub -- Triggers --> GitHubActions["GitHub Actions (CI)"]
    GitHubActions -- Runs Tests --> GitHubActions
    GitHubActions -- Builds --> GitHubActions
    GitHubActions -- Lints --> GitHubActions
    GitHubActions -- Static Analysis --> GitHubActions
    GitHubActions -- (if tagged) Publishes --> GoProxy["Go Proxy"]

    classDef external fill:#ddd,stroke:#000
    class GoProxy external
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Build Process Description:

  1. Developer writes code and runs tests locally.
  2. Code is pushed to the GitHub repository.
  3. GitHub Actions (or a similar CI system) is triggered.
  4. The CI pipeline performs the following steps:
    • Runs unit and integration tests.
    • Builds the library.
    • Runs linters (e.g., go vet, go lint).
    • Performs static analysis (potentially using additional tools).
    • If the commit is tagged (indicating a release), the library is published to the Go Proxy (proxy.golang.org).

Security Controls in Build Process:

  • security control: Automated Testing: Unit and integration tests are run automatically on every commit.
  • security control: Static Analysis: Linters and static analysis tools are used to identify potential bugs and security issues.
  • security control: Dependency Management: Go modules ensure consistent and reproducible builds, and allow for vulnerability scanning of dependencies.
  • security control: CI/CD Pipeline: The build process is automated, reducing the risk of manual errors and ensuring consistency.
  • security control: Code Review: (Inferred) Code reviews are likely required before merging changes to the main branch.

RISK ASSESSMENT

Critical Business Processes:

  • Real-time data ingestion and processing: Many applications rely on Kafka for real-time data pipelines. Sarama's reliability is critical for these processes.
  • Event-driven architectures: Kafka is often used as the backbone for event-driven systems. Sarama's stability and performance are essential for these architectures to function correctly.
  • Data streaming and analytics: Kafka is used for streaming data to analytics platforms. Sarama's ability to handle high throughput is crucial for these use cases.

Data Sensitivity:

The data sensitivity depends entirely on the content of the messages being passed through Kafka by applications using Sarama. Sarama itself does not inherently handle sensitive data, but it transports it. Therefore:

  • Data Sensitivity: Varies greatly depending on the application. Can range from non-sensitive (e.g., public sensor data) to highly sensitive (e.g., financial transactions, PII).
  • Data to Protect: The messages being transmitted through Kafka.
  • Protection Goals:
    • Confidentiality: Ensure that messages are not intercepted or read by unauthorized parties (achieved through TLS).
    • Integrity: Ensure that messages are not tampered with during transit (achieved through TLS and proper message handling).
    • Availability: Ensure that messages can be reliably produced and consumed (achieved through robust library design and proper error handling).

QUESTIONS & ASSUMPTIONS

Questions:

  • What specific Kafka versions are officially supported by Sarama?
  • What are the performance benchmarks and targets for Sarama?
  • Are there any specific security certifications or compliance requirements that Sarama aims to meet (e.g., SOC 2, ISO 27001)?
  • What is the process for handling security vulnerability reports? Is there a dedicated security contact?
  • Are there plans to integrate with specific key management systems (e.g., HashiCorp Vault)?

Assumptions:

  • BUSINESS POSTURE: Assumed that Shopify prioritizes the reliability, performance, and security of Sarama due to its use in their own infrastructure.
  • SECURITY POSTURE: Assumed that Shopify has internal security practices and code review processes that are not publicly documented in the repository. Assumed that regular dependency updates are performed.
  • DESIGN: Assumed that the C4 diagrams accurately represent the high-level architecture of Sarama and its interactions with other systems. Assumed that the deployment scenario using Kubernetes is a common use case. Assumed that GitHub Actions is the primary CI/CD system used.