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sec-design.md

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Okay, let's create a design document for the StackExchange.Redis project.

BUSINESS POSTURE

Business Priorities and Goals:

  • Provide a high-performance, robust, and reliable Redis client for .NET applications.
  • Enable efficient interaction with Redis servers for caching, session management, pub/sub messaging, and other Redis-based features.
  • Offer a user-friendly API that simplifies Redis usage for developers.
  • Maintain compatibility with various Redis server versions and configurations.
  • Ensure high availability and fault tolerance in Redis interactions.
  • Support synchronous and asynchronous operations for flexibility.
  • Provide comprehensive documentation and support to users.

Most Important Business Risks:

  • Data Breaches: Unauthorized access to sensitive data stored in Redis instances.
  • Service Disruptions: Outages or performance degradation of Redis-dependent applications due to client issues.
  • Data Loss: Loss of cached or persisted data due to client misconfiguration or errors.
  • Compatibility Issues: Inability to connect to or interact with specific Redis server versions or configurations.
  • Security Vulnerabilities: Exploitable weaknesses in the client library that could compromise Redis servers or applications.
  • Supply Chain Attacks: Malicious code introduced into the client library through compromised dependencies or build processes.

SECURITY POSTURE

Existing Security Controls:

  • security control: TLS/SSL Support: The library supports encrypted connections to Redis servers using TLS/SSL, protecting data in transit. (Described in documentation and implemented in the connection management logic).
  • security control: Authentication: Supports Redis authentication mechanisms (passwords, ACLs) to control access to Redis instances. (Described in documentation and implemented in the connection establishment process).
  • security control: Connection Pooling: Manages a pool of connections to Redis servers, reducing the overhead of establishing new connections and improving performance. (Implemented in the connection management logic).
  • security control: Asynchronous Operations: Provides asynchronous methods for most operations, preventing blocking calls and improving application responsiveness. (Implemented throughout the library).
  • security control: Command Flags: Allows developers to specify command flags to control behavior, such as CommandFlags.NoRedirect to prevent automatic redirection to different Redis nodes. (Implemented in the command execution logic).
  • security control: Open Source: The library is open source, allowing for community review and contributions, which can help identify and address security vulnerabilities. (Available on GitHub).
  • security control: Regular Updates: The library is actively maintained, with regular updates and bug fixes, including security patches. (Available on NuGet).

Accepted Risks:

  • accepted risk: Limited Input Validation: The library primarily focuses on providing a low-level interface to Redis. While it performs some basic checks, it relies on developers to validate data sent to Redis.
  • accepted risk: Dependency on Third-Party Libraries: The library may depend on other third-party libraries, which could introduce their own security vulnerabilities.

Recommended Security Controls:

  • security control: Implement robust input sanitization and validation mechanisms within the library to mitigate the risk of command injection attacks.
  • security control: Integrate with security scanning tools (SAST, DAST, SCA) in the CI/CD pipeline to identify and address vulnerabilities early in the development lifecycle.
  • security control: Provide clear guidance and best practices for secure usage of the library, including recommendations for data encryption, access control, and input validation.
  • security control: Implement a mechanism for reporting security vulnerabilities and a process for timely patching and disclosure.
  • security control: Consider adding support for more advanced security features, such as client-side field-level encryption.

Security Requirements:

  • Authentication:

    • Support Redis password authentication.
    • Support Redis ACLs (Access Control Lists).
    • Support TLS/SSL for secure connections.
    • Provide options for configuring connection timeouts and retries.

  • Authorization:

    • Leverage Redis's built-in authorization mechanisms (ACLs).
    • Provide guidance on configuring appropriate permissions for different users and applications.

  • Input Validation:

    • Sanitize user inputs to prevent command injection vulnerabilities.
    • Validate data types and formats to ensure they are compatible with Redis commands.

  • Cryptography:

    • Support TLS/SSL for encrypting data in transit.
    • Provide options for configuring cipher suites and TLS versions.
    • Consider supporting client-side encryption for sensitive data stored in Redis.

DESIGN

C4 CONTEXT

graph LR
    User["User Application (.NET)"] -- Uses --> SE.Redis["StackExchange.Redis Client"]
    SE.Redis -- Connects to --> RedisServer["Redis Server"]
    RedisServer -- Stores data in --> RedisDB[(Redis Database)]
    RedisServer -- Replicates to --> RedisReplica["Redis Replica (Optional)"]
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Context Diagram Element List:

  • Element:

    • Name: User Application (.NET)
    • Type: Software System
    • Description: A .NET application that utilizes the StackExchange.Redis client library to interact with Redis.
    • Responsibilities: Initiates requests to Redis, processes responses, handles data serialization/deserialization.
    • Security controls: Implements application-level security controls, such as input validation, authentication, and authorization.

  • Element:

    • Name: StackExchange.Redis Client
    • Type: Library
    • Description: The .NET client library for interacting with Redis.
    • Responsibilities: Provides an API for connecting to Redis, sending commands, receiving responses, managing connections, and handling errors.
    • Security controls: Supports TLS/SSL, authentication, connection pooling.

  • Element:

    • Name: Redis Server
    • Type: Software System
    • Description: The Redis server instance.
    • Responsibilities: Stores data, processes commands, manages replication, and handles client connections.
    • Security controls: Implements Redis security features, such as password authentication, ACLs, and TLS/SSL.

  • Element:

    • Name: Redis Database
    • Type: Database
    • Description: The in-memory data store within the Redis server.
    • Responsibilities: Stores data in various data structures (strings, lists, sets, hashes, etc.).
    • Security controls: Data is protected by Redis server security controls.

  • Element:

    • Name: Redis Replica (Optional)
    • Type: Software System
    • Description: A replica of the Redis server for high availability and read scaling.
    • Responsibilities: Replicates data from the primary Redis server, handles read requests.
    • Security controls: Inherits security controls from the primary Redis server.

C4 CONTAINER

graph LR
    UserApp["User Application (.NET)"] -- Uses --> SE.Redis["StackExchange.Redis"]
    SE.Redis -- Connects to --> ConnectionMultiplexer["ConnectionMultiplexer"]
    ConnectionMultiplexer -- Manages --> ConnectionPool["Connection Pool"]
    ConnectionPool -- Creates --> RedisConnection["Redis Connection"]
    RedisConnection -- Sends/Receives --> RedisServer["Redis Server"]
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Container Diagram Element List:

  • Element:

    • Name: User Application (.NET)
    • Type: Software System
    • Description: A .NET application that utilizes the StackExchange.Redis client library.
    • Responsibilities: Initiates requests to Redis, processes responses, handles data serialization/deserialization.
    • Security controls: Implements application-level security controls.

  • Element:

    • Name: StackExchange.Redis
    • Type: Library
    • Description: The .NET client library for interacting with Redis.
    • Responsibilities: Provides an API for connecting to Redis, sending commands, receiving responses.
    • Security controls: Supports TLS/SSL, authentication.

  • Element:

    • Name: ConnectionMultiplexer
    • Type: Class
    • Description: The core class in StackExchange.Redis that manages connections to Redis servers.
    • Responsibilities: Handles connection pooling, multiplexing requests, and managing failover.
    • Security controls: Implements TLS/SSL negotiation, authentication handling.

  • Element:

    • Name: Connection Pool
    • Type: Component
    • Description: A pool of connections to Redis servers managed by the ConnectionMultiplexer.
    • Responsibilities: Maintains a set of active connections, reuses connections to reduce overhead.
    • Security controls: Connections within the pool inherit security settings from the ConnectionMultiplexer.

  • Element:

    • Name: Redis Connection
    • Type: Class
    • Description: Represents a single connection to a Redis server.
    • Responsibilities: Sends commands to Redis, receives responses, handles network communication.
    • Security controls: Uses TLS/SSL if configured, performs authentication.

  • Element:

    • Name: Redis Server
    • Type: Software System
    • Description: The Redis server instance.
    • Responsibilities: Stores data, processes commands, manages replication, and handles client connections.
    • Security controls: Implements Redis security features.

DEPLOYMENT

Possible Deployment Solutions:

  1. Standalone Redis Server: A single Redis server instance running on a dedicated machine or virtual machine.
  2. Redis Sentinel: A distributed system that monitors Redis instances and automatically performs failover if the primary server goes down.
  3. Redis Cluster: A distributed system that shards data across multiple Redis nodes, providing high availability and scalability.
  4. Cloud-Based Redis Services: Managed Redis services offered by cloud providers like AWS (ElastiCache), Azure (Cache for Redis), and GCP (Memorystore).

Chosen Deployment Solution (Example: Redis Sentinel):

graph LR
    Client["Client Application"] -- Connects to --> Sentinel1["Redis Sentinel 1"]
    Client -- Connects to --> Sentinel2["Redis Sentinel 2"]
    Client -- Connects to --> Sentinel3["Redis Sentinel 3"]
    Sentinel1 -- Monitors --> RedisMaster["Redis Master"]
    Sentinel1 -- Monitors --> RedisSlave1["Redis Slave 1"]
    Sentinel1 -- Monitors --> RedisSlave2["Redis Slave 2"]
    Sentinel2 -- Monitors --> RedisMaster
    Sentinel2 -- Monitors --> RedisSlave1
    Sentinel2 -- Monitors --> RedisSlave2
    Sentinel3 -- Monitors --> RedisMaster
    Sentinel3 -- Monitors --> RedisSlave1
    Sentinel3 -- Monitors --> RedisSlave2
    RedisMaster -- Replicates to --> RedisSlave1
    RedisMaster -- Replicates to --> RedisSlave2
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Deployment Diagram Element List:

  • Element:

    • Name: Client Application
    • Type: Software System
    • Description: The application using StackExchange.Redis to connect to Redis.
    • Responsibilities: Initiates connections, sends commands, processes responses.
    • Security controls: Application-level security controls.

  • Element:

    • Name: Redis Sentinel 1, 2, 3
    • Type: Software System
    • Description: Redis Sentinel instances that monitor the Redis master and slaves.
    • Responsibilities: Monitors Redis instances, performs automatic failover, provides service discovery.
    • Security controls: Can be configured with TLS/SSL and authentication.

  • Element:

    • Name: Redis Master
    • Type: Software System
    • Description: The primary Redis server instance.
    • Responsibilities: Handles read and write requests, replicates data to slaves.
    • Security controls: Redis server security features (password, ACLs, TLS/SSL).

  • Element:

    • Name: Redis Slave 1, 2
    • Type: Software System
    • Description: Redis slave instances that replicate data from the master.
    • Responsibilities: Replicates data, handles read requests (if configured).
    • Security controls: Inherits security controls from the master.

BUILD

The StackExchange.Redis project uses a standard .NET build process.

Build Process Diagram:

graph LR
    Developer["Developer"] -- Commits code to --> GitHub["GitHub Repository"]
    GitHub -- Triggers --> BuildServer["Build Server (e.g., AppVeyor)"]
    BuildServer -- Fetches code --> BuildServer
    BuildServer -- Runs --> DotnetBuild["dotnet build"]
    DotnetBuild -- Performs --> Compilation["Compilation"]
    DotnetBuild -- Performs --> Testing["Unit & Integration Testing"]
    DotnetBuild -- Performs --> SAST["SAST (Static Analysis)"]
    DotnetBuild -- Performs --> SCAScan["SCA (Software Composition Analysis)"]
    DotnetBuild -- Produces --> NuGetPackages["NuGet Packages"]
    NuGetPackages -- Published to --> NuGetOrg["NuGet.org"]
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Build Process Description:

  1. Developers commit code changes to the GitHub repository.
  2. A build server (e.g., AppVeyor, GitHub Actions) is triggered by the commit.
  3. The build server fetches the latest code from the repository.
  4. The dotnet build command is executed.
  5. Compilation: The .NET compiler compiles the code into assemblies.
  6. Testing: Unit and integration tests are executed to verify the functionality of the code.
  7. SAST (Static Analysis): A static analysis tool (e.g., SonarQube) is run to identify potential security vulnerabilities and code quality issues.
  8. SCA (Software Composition Analysis): A SCA tool is run to identify vulnerabilities in third-party dependencies.
  9. NuGet Packages: The build process creates NuGet packages containing the compiled assemblies and other necessary files.
  10. NuGet Packages are published to NuGet.org.

Security Controls in Build Process:

  • security control: SAST (Static Application Security Testing): Static analysis tools are used to scan the code for potential security vulnerabilities.
  • security control: SCA (Software Composition Analysis): Scans are performed to identify known vulnerabilities in third-party dependencies.
  • security control: Automated Build: The build process is automated, ensuring consistency and reducing the risk of manual errors.
  • security control: Code Reviews: Code changes are reviewed by other developers before being merged into the main branch.
  • security control: Signed NuGet Packages: NuGet packages can be digitally signed to ensure their integrity and authenticity.

RISK ASSESSMENT

Critical Business Processes:

  • Caching: Storing frequently accessed data in Redis to improve application performance and reduce database load.
  • Session Management: Storing user session data in Redis to maintain state across multiple web servers.
  • Pub/Sub Messaging: Using Redis as a message broker for real-time communication between different parts of an application or between different applications.
  • Real-time Analytics: Using Redis data structures to store and process real-time data for analytics and reporting.
  • Distributed Locking: Using Redis to implement distributed locks to coordinate access to shared resources.

Data Sensitivity:

  • Session Data: May contain sensitive user information, such as authentication tokens, user IDs, and personal preferences. (Sensitivity: High)
  • Cached Data: May contain sensitive business data, such as product catalogs, pricing information, or customer data. (Sensitivity: Variable, depending on the data being cached)
  • Pub/Sub Messages: May contain sensitive data being exchanged between different parts of an application. (Sensitivity: Variable, depending on the message content)
  • Analytics Data: May contain sensitive information about user behavior or business operations. (Sensitivity: Variable, depending on the data being analyzed)

QUESTIONS & ASSUMPTIONS

Questions:

  • What specific Redis deployment architecture(s) are most commonly used by users of StackExchange.Redis? (This will help prioritize security considerations for different deployment scenarios.)
  • What are the most common use cases for StackExchange.Redis? (This will help focus on the security requirements for those specific use cases.)
  • Are there any specific compliance requirements (e.g., PCI DSS, HIPAA) that users of StackExchange.Redis need to adhere to?
  • What level of security expertise can be assumed for the average user of StackExchange.Redis? (This will influence the level of detail and guidance provided in security documentation.)
  • What is the current process for handling security vulnerabilities reported in StackExchange.Redis?

Assumptions:

  • BUSINESS POSTURE: Users of StackExchange.Redis prioritize performance and reliability, but also require a reasonable level of security.
  • SECURITY POSTURE: Users are responsible for securing their Redis servers and the data stored within them. StackExchange.Redis provides the necessary tools (TLS/SSL, authentication) to enable secure communication, but it is the user's responsibility to configure and use them correctly.
  • DESIGN: The primary deployment model is a managed Redis service or a Redis Sentinel setup for high availability. Users are familiar with basic Redis concepts and security best practices. The build process is secure and includes static analysis and dependency scanning.