Threat Model Analysis for etcd-io/etcd

Threat: Unauthorized Data Access via Client API

Threat: Unauthorized Data Access via Client API
- Description: An attacker gains unauthorized access to the etcd client API (typically port 2379) and issues read requests (e.g., get, range) to retrieve sensitive data. This leverages weaknesses within etcd's authentication or authorization mechanisms or exploits vulnerabilities in the API handling.
- Impact: Exposure of sensitive configuration data, service discovery information, secrets, leading to further compromise.
- Affected etcd Component: etcdserver/api/v3rpc (gRPC server handling client requests), auth module (if authentication is bypassed or flawed).
- Risk Severity: Critical
- Mitigation Strategies:
  - Enable TLS with Mutual Authentication (mTLS): Enforce client certificate verification within etcd.
  - Implement RBAC: Use etcd's RBAC to restrict client access to only necessary keys/prefixes. Regularly audit RBAC rules.
  - Audit Logging: Enable and regularly review etcd's audit logs for unauthorized access.

Threat: Data Modification/Deletion via Client API
- Description: An attacker gains unauthorized access to the etcd client API and issues write requests (e.g., put, delete, txn) to modify or delete data. This exploits vulnerabilities in etcd's authorization, input validation, or transaction handling.
- Impact: Disruption of application functionality, service outages, data loss, potential for complete system compromise.
- Affected etcd Component: etcdserver/api/v3rpc (gRPC server), auth module, mvcc (Multi-Version Concurrency Control) module.
- Risk Severity: Critical
- Mitigation Strategies:
  - Strong Authentication and Authorization (RBAC): Use mTLS and granular RBAC within etcd to strictly control write access.
  - Input Validation (within etcd client libraries): While primarily a client-side concern, etcd client libraries should perform basic validation to prevent obviously malformed requests.
  - Transaction Limits: Use etcd's transaction features correctly; avoid overly large or complex transactions that could be exploited.

Threat: Denial of Service via Excessive Key-Value Operations
- Description: An attacker floods the etcd cluster with read/write requests, exceeding etcd's capacity and causing it to become unresponsive. This targets vulnerabilities in etcd's request handling, resource management, or the Raft consensus algorithm.
- Impact: Denial of service for all applications relying on etcd.
- Affected etcd Component: etcdserver/api/v3rpc (gRPC server), mvcc module, raft module.
- Risk Severity: High
- Mitigation Strategies:
  - Rate Limiting (within etcd): Utilize etcd's built-in rate limiting features to protect against request floods.
  - Connection Limits (within etcd): Configure etcd to limit the number of concurrent connections.
  - Resource Limits (within etcd): Configure appropriate resource limits (CPU, memory) for the etcd process itself.
  - Request Timeouts (within etcd): Ensure etcd has appropriate timeouts configured to prevent slow clients from consuming resources.

Threat: Denial of Service via Lease Exhaustion
- Description: An attacker creates many leases with short TTLs, exhausting etcd's lease ID space and preventing legitimate clients from creating leases. This targets the lease module specifically.
- Impact: Disruption of services relying on leases (leader election, ephemeral data).
- Affected etcd Component: lease module.
- Risk Severity: High
- Mitigation Strategies:
  - Limit Maximum Lease TTL (within etcd): Configure a reasonable maximum TTL within etcd to prevent abuse.
  - Monitor Lease Usage (and alert on anomalies): Track lease creation rates and alert on suspicious activity.
  - Rate Limiting (on lease creation, within etcd): Implement rate limiting specifically for lease creation requests within etcd.

Threat: Compromise of etcd Peer Communication
- Description: An attacker intercepts/modifies communication between etcd cluster members, exploiting vulnerabilities in the Raft communication protocol or its implementation. This could involve injecting false data or disrupting quorum.
- Impact: Loss of data consistency, split-brain, cluster instability, data corruption/loss.
- Affected etcd Component: etcdserver/api/rafthttp (Raft communication), raft module.
- Risk Severity: High
- Mitigation Strategies:
  - Enable TLS for Peer Communication (within etcd): Configure etcd to use TLS for all inter-member communication. Use strong cipher suites.

Threat: Exploitation of etcd Vulnerabilities
- Description: An attacker exploits a known or zero-day vulnerability in the etcd software itself (e.g., buffer overflow, code injection) to gain unauthorized access, execute code, or cause a DoS.
- Impact: Varies; could range from data exposure to complete cluster compromise.
- Affected etcd Component: Potentially any component, depending on the vulnerability.
- Risk Severity: Critical (for exploitable vulnerabilities)
- Mitigation Strategies:
  - Keep etcd Up-to-Date: Regularly update etcd to the latest stable release. This is the primary defense.
  - Monitor Security Advisories: Stay informed about new etcd vulnerabilities.
  - Vulnerability Scanning (of the etcd binary): Use tools to scan the etcd binary for known vulnerabilities.

Threat: Improper Cluster Membership Changes Leading to Split Brain
- Description: An operator incorrectly adds or removes nodes, violating quorum or causing partitions, leading to a "split-brain" where multiple inconsistent clusters form. This is a direct operational error interacting with etcd's core functionality.
- Impact: Data inconsistency, data loss, cluster unavailability.
- Affected etcd Component: raft module, etcdserver/api/membership.
- Risk Severity: High
- Mitigation Strategies:
  - Strictly Adhere to etcd Documentation: Follow official procedures for membership changes.
  - Use etcdctl for Membership Changes: Use the etcdctl commands; avoid manual configuration edits.
  - Monitor Cluster Health: Closely monitor health during and after changes.