sec-design.md

Okay, let's create a design document for etcd based on the provided GitHub repository.

BUSINESS POSTURE

etcd is a distributed key-value store designed to provide a reliable way to store data across a cluster of machines. It's a critical component for many distributed systems, particularly those built on Kubernetes.

Priorities and Goals:

• Provide a highly available and consistent data store for configuration management, service discovery, and distributed synchronization.
• Ensure data durability and fault tolerance.
• Offer a simple, well-defined API for interacting with the store.
• Maintain strong consistency guarantees (linearizability).
• Support a watch mechanism for real-time updates.
• Be performant under various workloads.

Business Risks:

• Data Loss or Corruption: As a critical data store, any loss or corruption of data within etcd can have cascading effects on the systems that rely on it, potentially leading to widespread outages or incorrect behavior.
• Availability Outages: Downtime of the etcd cluster can render dependent systems unable to function correctly, especially in dynamic environments where configuration changes and service discovery are frequent.
• Security Breaches: Unauthorized access to etcd could expose sensitive configuration data, secrets, or allow malicious actors to manipulate the state of the distributed system.
• Performance Bottlenecks: Slow performance of etcd can impact the responsiveness and scalability of the entire system relying on it.
• Inconsistency Issues: Violations of consistency guarantees can lead to unpredictable behavior in distributed systems, making debugging and recovery extremely difficult.
• Operational Complexity: Difficulty in managing, monitoring, and operating the etcd cluster can increase operational overhead and the risk of human error.

SECURITY POSTURE

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

• security control: TLS Encryption: etcd supports TLS for both client-to-server and peer-to-peer communication, encrypting data in transit. Implemented via configuration options and command-line flags.
• security control: Authentication: etcd supports client certificate authentication, preventing unauthorized access to the cluster. Implemented via configuration options and command-line flags.
• security control: Role-Based Access Control (RBAC): etcd provides RBAC to limit the operations that authenticated users can perform. Implemented via etcd's authentication and authorization mechanisms. Described in the security documentation.
• security control: Auditing: etcd can be configured to log all requests, providing an audit trail for security analysis. Implemented via configuration options.
• security control: Regular Security Audits and Penetration Testing: The etcd project undergoes periodic security audits and penetration testing. Described in security reports and community discussions.
• security control: Dependency Management: The project uses Go modules, which helps manage dependencies and their vulnerabilities. Described in go.mod and go.sum files.
• security control: Static Analysis: The project likely uses static analysis tools to identify potential security vulnerabilities in the codebase. Inferred from best practices and CI/CD pipelines.
• security control: Fuzz Testing: etcd uses fuzz testing to find potential bugs and vulnerabilities. Described in the fuzzing documentation.

Accepted Risks:

• accepted risk: Complexity of Secure Configuration: Properly configuring etcd for secure operation (TLS, authentication, RBAC) can be complex, and misconfigurations can lead to security vulnerabilities.
• accepted risk: Operational Overhead: Managing a secure etcd cluster requires ongoing monitoring, maintenance, and security updates.
• accepted risk: Potential for Zero-Day Exploits: Like any software, etcd is susceptible to zero-day vulnerabilities that may be exploited before patches are available.

Recommended Security Controls:

• Network Segmentation: Isolate the etcd cluster on a dedicated network segment to limit exposure to other systems.
• Regular Vulnerability Scanning: Implement automated vulnerability scanning of the etcd cluster and its dependencies.
• Intrusion Detection System (IDS): Deploy an IDS to monitor network traffic to and from the etcd cluster for suspicious activity.
• Secrets Management: Integrate etcd with a secrets management solution (e.g., HashiCorp Vault) to securely store and manage sensitive configuration data.

Security Requirements:

• Authentication:
  • All clients and peers must authenticate using strong authentication mechanisms (e.g., client certificates).
  • Support for multiple authentication providers (e.g., static users, external identity providers).
• Authorization:
  • Implement fine-grained RBAC to control access to specific keys and operations.
  • Regularly review and update access control policies.
• Input Validation:
  • Validate all client inputs to prevent injection attacks or unexpected behavior.
  • Enforce key naming conventions and data size limits.
• Cryptography:
  • Use strong cryptographic algorithms and protocols (e.g., TLS 1.3 or higher).
  • Regularly rotate cryptographic keys.
  • Protect private keys using secure storage mechanisms (e.g., HSMs).
• Auditing:
  • Log all successful and failed requests, including user, operation, and data accessed.
  • Securely store and protect audit logs.

DESIGN

C4 CONTEXT

graph LR
    subgraph etcd Cluster
        etcd[etcd]
    end
    User[Users/Operators] --> etcd
    Kubernetes[Kubernetes API Server] --> etcd
    OtherApps[Other Applications] --> etcd
    Monitoring[Monitoring Systems] --> etcd

Loading

Element Descriptions:

• Element:

  • Name: etcd
  • Type: Distributed key-value store
  • Description: The core etcd system, providing a consistent and highly available data store.
  • Responsibilities: Storing data, managing cluster membership, handling client requests, ensuring data consistency and durability.
  • Security controls: TLS encryption, authentication, RBAC, auditing.

• Element:

  • Name: Users/Operators
  • Type: Human users or automated systems
  • Description: Individuals or systems that directly interact with etcd using command-line tools (etcdctl) or client libraries.
  • Responsibilities: Managing etcd configuration, performing administrative tasks, reading and writing data.
  • Security controls: Authentication, RBAC.

• Element:

  • Name: Kubernetes API Server
  • Type: Software System
  • Description: The central control plane component of Kubernetes, which uses etcd as its primary data store.
  • Responsibilities: Managing Kubernetes resources, scheduling workloads, interacting with etcd to store and retrieve cluster state.
  • Security controls: Authentication, RBAC (within Kubernetes), TLS communication with etcd.

• Element:

  • Name: Other Applications
  • Type: Software Systems
  • Description: Other applications that use etcd for service discovery, configuration management, or distributed coordination.
  • Responsibilities: Reading and writing data to etcd, watching for changes.
  • Security controls: Authentication, RBAC, TLS communication with etcd.

• Element:

  • Name: Monitoring Systems
  • Type: Software System
  • Description: Systems that monitor the health and performance of the etcd cluster.
  • Responsibilities: Collecting metrics, generating alerts, providing dashboards.
  • Security controls: Authentication, TLS communication with etcd.

C4 CONTAINER

graph LR
    subgraph etcd Cluster
        ClientAPI[Client API]
        Raft[Raft Consensus Module]
        Storage[Storage Engine]
        WAL[Write-Ahead Log]
        Snapshot[Snapshot]
    end
    User[Users/Operators] --> ClientAPI
    Kubernetes[Kubernetes API Server] --> ClientAPI
    OtherApps[Other Applications] --> ClientAPI
    Monitoring[Monitoring Systems] --> ClientAPI
    ClientAPI --> Raft
    Raft --> Storage
    Raft --> WAL
    Storage --> WAL
    Storage --> Snapshot

Loading

Element Descriptions:

• Element:

  • Name: Client API
  • Type: API
  • Description: The interface through which clients interact with etcd. Provides gRPC endpoints for key-value operations, watch, lease, and maintenance operations.
  • Responsibilities: Handling client requests, validating inputs, forwarding requests to the Raft module.
  • Security controls: TLS encryption, authentication, RBAC, input validation.

• Element:

  • Name: Raft Consensus Module
  • Type: Algorithm Implementation
  • Description: Implements the Raft consensus algorithm to ensure data consistency and fault tolerance across the cluster.
  • Responsibilities: Managing leader election, log replication, and state machine updates.
  • Security controls: Secure communication between Raft peers (TLS).

• Element:

  • Name: Storage Engine
  • Type: Database
  • Description: The underlying storage engine that persists data to disk. etcd uses a bbolt based backend.
  • Responsibilities: Storing data, providing read and write access, managing transactions.
  • Security controls: Data encryption at rest (if configured).

• Element:

  • Name: WAL (Write-Ahead Log)
  • Type: Log File
  • Description: A persistent log of all changes made to the etcd cluster. Used for recovery and data durability.
  • Responsibilities: Recording all operations before they are applied to the storage engine.
  • Security controls: File system permissions, data integrity checks.

• Element:

  • Name: Snapshot
  • Type: Data Snapshot
  • Description: A point-in-time snapshot of the etcd data. Used for faster recovery and reducing the size of the WAL.
  • Responsibilities: Storing a consistent view of the data at a specific point in time.
  • Security controls: File system permissions, data integrity checks.

DEPLOYMENT

Possible Deployment Solutions:

1. Static: Manually configure each etcd member with static IP addresses and cluster information.
2. etcd Discovery: Use a separate etcd cluster (or a single instance) for bootstrapping the main etcd cluster.
3. DNS Discovery: Use DNS SRV records to allow etcd members to discover each other.
4. Kubernetes: Deploy etcd as a StatefulSet within a Kubernetes cluster.

Chosen Solution (Kubernetes):

graph LR
    subgraph Kubernetes Cluster
        subgraph etcd StatefulSet
            etcdPod1[etcd Pod 1]
            etcdPod2[etcd Pod 2]
            etcdPod3[etcd Pod 3]
        end
        PersistentVolumeClaim1[PersistentVolumeClaim 1]
        PersistentVolumeClaim2[PersistentVolumeClaim 2]
        PersistentVolumeClaim3[PersistentVolumeClaim 3]
        StorageClass[StorageClass]
        etcdPod1 --> PersistentVolumeClaim1
        etcdPod2 --> PersistentVolumeClaim2
        etcdPod3 --> PersistentVolumeClaim3
        PersistentVolumeClaim1 --> StorageClass
        PersistentVolumeClaim2 --> StorageClass
        PersistentVolumeClaim3 --> StorageClass
    end
    Client[Client] --> etcdPod1
    Client --> etcdPod2
    Client --> etcdPod3

Loading

Element Descriptions:

• Element:

  • Name: etcd Pod 1, etcd Pod 2, etcd Pod 3
  • Type: Kubernetes Pod
  • Description: Instances of the etcd container running within Kubernetes.
  • Responsibilities: Running the etcd server process, handling client requests, participating in the Raft consensus.
  • Security controls: Kubernetes network policies, pod security policies, container image security scanning.

• Element:

  • Name: PersistentVolumeClaim 1, PersistentVolumeClaim 2, PersistentVolumeClaim 3
  • Type: Kubernetes PersistentVolumeClaim
  • Description: Requests for persistent storage to store etcd data.
  • Responsibilities: Providing persistent storage to the etcd pods.
  • Security controls: Storage encryption (if supported by the storage provider), access controls on the storage provider.

• Element:

  • Name: StorageClass
  • Type: Kubernetes StorageClass
  • Description: Defines the type of storage to be used for the PersistentVolumeClaims.
  • Responsibilities: Provisioning persistent volumes based on the defined storage class.
  • Security controls: Depends on the specific storage provider and its configuration.

• Element:

  • Name: Client
  • Type: External System or User
  • Description: Represents any client connecting to the etcd cluster.
  • Responsibilities: Interacting with the etcd cluster.
  • Security controls: Authentication, authorization, TLS encryption.

BUILD

The etcd build process leverages Go modules, Makefiles, and CI/CD pipelines (likely GitHub Actions, though not explicitly stated in the provided link, it's a common practice).

graph LR
    Developer[Developer] --> GitHub[GitHub Repository]
    GitHub --> BuildServer[Build Server (e.g., GitHub Actions)]
    BuildServer --> Linting[Linting (e.g., gofmt, go vet)]
    BuildServer --> UnitTests[Unit Tests]
    BuildServer --> IntegrationTests[Integration Tests]
    BuildServer --> FuzzTests[Fuzz Tests]
    BuildServer --> SAST[Static Analysis (SAST)]
    BuildServer --> BuildArtifacts[Build Artifacts (etcd binaries)]
    BuildArtifacts --> Release[Release (e.g., GitHub Releases)]

Loading

Security Controls in Build Process:

• Dependency Management: Go modules (go.mod, go.sum) ensure consistent and verifiable dependencies, reducing the risk of supply chain attacks.
• Linting: Tools like gofmt and go vet enforce code style and identify potential errors, improving code quality and reducing vulnerabilities.
• Unit Tests: Extensive unit tests verify the correctness of individual components.
• Integration Tests: Integration tests ensure that different parts of the system work together correctly.
• Fuzz Tests: Fuzzing helps discover edge cases and potential vulnerabilities by providing random inputs to the system.
• Static Analysis (SAST): Static analysis tools scan the codebase for potential security vulnerabilities.
• Build Automation: CI/CD pipelines automate the build process, ensuring consistency and repeatability.
• Signed Releases: etcd releases are likely signed with a GPG key, allowing users to verify the authenticity of the binaries. (Common practice, but needs confirmation from the repository).

RISK ASSESSMENT

Critical Business Processes:

• Configuration Management: Storing and retrieving configuration data for distributed systems.
• Service Discovery: Enabling services to find and communicate with each other.
• Distributed Coordination: Providing primitives for distributed consensus and locking.
• Kubernetes Cluster State Management: Storing the entire state of a Kubernetes cluster.

Data Sensitivity:

• Configuration Data: Can range from non-sensitive to highly sensitive, depending on the specific application. May include API keys, database credentials, and other secrets.
• Service Discovery Information: May reveal the internal network topology and services running within an organization.
• Kubernetes Cluster State: Contains all information about the Kubernetes cluster, including deployments, secrets, configurations, and more. This is highly sensitive data.

Data Sensitivity Levels:

• Configuration Data: Variable (Non-sensitive to Highly Sensitive)
• Service Discovery Information: Moderately Sensitive
• Kubernetes Cluster State: Highly Sensitive

QUESTIONS & ASSUMPTIONS

Questions:

• What specific static analysis tools are used in the CI/CD pipeline?
• Are there any specific compliance requirements (e.g., PCI DSS, HIPAA) that need to be considered?
• What is the process for handling security vulnerabilities and releasing patches?
• Are there any plans to integrate with external secrets management solutions?
• What is the key rotation policy for TLS certificates and other cryptographic keys?
• Is there a documented incident response plan for security breaches?
• Are there regular backups of etcd data, and are these backups tested?
• What is the exact mechanism for signing releases?

Assumptions:

• BUSINESS POSTURE: The primary business goal is to provide a reliable and secure distributed key-value store.
• SECURITY POSTURE: The etcd project follows security best practices, including regular audits and penetration testing.
• DESIGN: The deployment model will be within a Kubernetes cluster using a StatefulSet. The build process uses GitHub Actions.
• The etcd project has a process for handling security vulnerabilities.
• Regular backups of etcd data are performed.