mitigations.md

Mitigation Strategies Analysis for grpc/grpc-go

Mitigation Strategy: Implement Mutual TLS (mTLS) for Strong Authentication

• Description:
  1. Generate Certificates: Generate X.509 certificates for both the gRPC server and clients. These certificates should be signed by a trusted Certificate Authority (CA), or use self-signed certificates for testing/internal environments.
  2. Configure Server TLS in grpc-go: Configure the grpc-go server to use TLS and require client certificates. This involves using credentials.NewTLS with a tls.Config that loads the server certificate and private key, and sets ClientAuth to tls.RequireAndVerifyClientCert for client authentication. Pass these credentials to grpc.NewServer using grpc.Creds.
  3. Configure Client TLS in grpc-go: Configure grpc-go clients to use TLS and provide their client certificate and private key when connecting to the server. Clients also need to trust the server's certificate (or the CA that signed it) using credentials.NewTLS and a tls.Config in grpc.Dial with grpc.WithTransportCredentials.
  4. Enforce TLS for All grpc-go Connections: Ensure that all gRPC connections, especially in production, are established using mTLS. Disable or restrict non-TLS connections by only configuring TLS credentials in grpc.NewServer and grpc.Dial.
  5. Certificate Rotation and Management: Implement a process for regular certificate rotation and secure management of private keys, ensuring these are correctly updated in the tls.Config used by grpc-go.
• Threats Mitigated:
  • Man-in-the-Middle (MitM) Attacks - Severity: High: mTLS encrypts communication and verifies the identity of both client and server, preventing eavesdropping and tampering by attackers positioned between them.
  • Unauthorized Access - Severity: High: mTLS ensures that only clients with valid certificates (and thus, presumably authorized) can connect to the gRPC server.
  • Spoofing/Impersonation - Severity: High: Server and client certificate verification prevents attackers from impersonating legitimate servers or clients.
• Impact:
  • Man-in-the-Middle (MitM) Attacks: High Reduction
  • Unauthorized Access: High Reduction
  • Spoofing/Impersonation: High Reduction
• Currently Implemented: Partially - mTLS is implemented for inter-service communication within the backend using grpc-go, but not consistently enforced for all client types (e.g., external clients).
• Missing Implementation: Extend mTLS enforcement to all client types using grpc-go configurations. Improve certificate management processes and automate certificate rotation within the grpc-go TLS setup.

Mitigation Strategy: Leverage gRPC Interceptors for Authorization

• Description:
  1. Design Authorization Policy: Define a clear authorization policy based on roles, permissions, or attributes. Determine which RPC methods require authorization and what level of access is needed.
  2. Implement Authorization Interceptors in grpc-go: Create gRPC interceptors (both unary and stream) in grpc-go that execute authorization checks before invoking the actual RPC handler. Use grpc.UnaryServerInterceptor and grpc.StreamServerInterceptor and register them when creating the grpc.Server using grpc.UnaryInterceptor and grpc.StreamInterceptor.
  3. Extract Authentication Context from grpc-go Context: Within the interceptor, extract authentication information from the grpc-go context (e.g., from mTLS certificates, JWT tokens in metadata accessed via metadata.FromIncomingContext).
  4. Perform Authorization Checks: Based on the extracted authentication context and the defined authorization policy, implement logic within the interceptor to determine if the request should be authorized. This might involve checking user roles, permissions, or attributes against the requested resource and action.
  5. Return Unauthorized Error using grpc-go Status: If authorization fails, the interceptor should return a gRPC error response using status.Error with the codes.PermissionDenied error code, preventing the RPC handler from being executed.
• Threats Mitigated:
  • Unauthorized Access - Severity: High: Interceptors enforce access control, preventing unauthorized users or services from accessing sensitive RPC methods or data.
  • Privilege Escalation - Severity: High: By implementing fine-grained authorization, interceptors can prevent users from gaining access to resources or operations beyond their intended privileges.
  • Data Breaches - Severity: High: Restricting access to sensitive data through authorization reduces the risk of data breaches caused by unauthorized access.
• Impact:
  • Unauthorized Access: High Reduction
  • Privilege Escalation: High Reduction
  • Data Breaches: High Reduction
• Currently Implemented: Partially - Basic authorization checks are implemented in some services directly within handlers, but grpc-go interceptors are not consistently used for centralized authorization.
• Missing Implementation: Migrate authorization logic to grpc-go interceptors for centralized and consistent enforcement. Implement a robust and flexible authorization framework (e.g., RBAC or ABAC) within grpc-go interceptors. Register these interceptors when creating the grpc.Server.

Mitigation Strategy: Denial of Service (DoS) Prevention using grpc-go Configuration

• Description:
  1. Implement Rate Limiting Interceptor in grpc-go: Create a rate limiting interceptor in grpc-go (as described in previous response) and register it with the grpc.Server.
  2. Set MaxRecvMsgSize and MaxSendMsgSize: Configure grpc-go server options MaxRecvMsgSize and MaxSendMsgSize when creating the grpc.Server using grpc.MaxRecvMsgSize and grpc.MaxSendMsgSize. Set reasonable limits on message sizes to prevent processing of excessively large messages.
  3. Set MaxConcurrentStreams: Configure grpc-go server option MaxConcurrentStreams using grpc.MaxConcurrentStreams to limit the maximum number of concurrent streams per connection, preventing stream exhaustion attacks.
  4. Configure Connection Timeouts: Utilize grpc-go's keepalive parameters (KeepaliveParams, KeepaliveEnforcementPolicy) and connection age limits (MaxConnectionIdle, MaxConnectionAge) using grpc.KeepaliveParams, grpc.KeepaliveEnforcementPolicy, grpc.MaxConnectionIdle, and grpc.MaxConnectionAge when creating the grpc.Server. Fine-tune these settings to detect and close dead or idle connections efficiently, freeing up resources.
  5. Implement Request Timeouts in Handlers: Within your grpc-go handlers, use context deadlines and timeouts (context.WithTimeout, context.WithDeadline) to prevent long-running or stalled requests from consuming server resources indefinitely.
• Threats Mitigated:
  • Denial of Service (DoS) Attacks - Severity: High: Rate limiting and resource limits prevent malicious or abusive clients from overwhelming the server with excessive requests or resource consumption.
  • Resource Exhaustion - Severity: Medium: grpc-go configuration options help protect server resources by preventing excessive consumption due to sudden traffic spikes, large messages, or misbehaving clients.
• Impact:
  • Denial of Service (DoS) Attacks: High Reduction
  • Resource Exhaustion: Medium Reduction
• Currently Implemented: Partially - MaxRecvMsgSize and MaxSendMsgSize are configured in some services using grpc-go options. Connection timeouts and keepalive are using default grpc-go settings. Rate limiting is not implemented at grpc-go level.
• Missing Implementation: Implement grpc-go interceptor-based rate limiting. Review and fine-tune MaxConcurrentStreams, keepalive, and connection timeout settings in grpc-go server configurations. Consistently apply context timeouts in all gRPC handlers.

Mitigation Strategy: Disable gRPC Reflection in Production

• Description:
  1. Omit Reflection Registration in grpc-go Server: When creating the grpc.Server in your grpc-go application for production deployments, simply do not register the reflection service. This means not calling reflection.Register(server) after creating the grpc.Server instance.
  2. Conditional Registration for Development: In development or testing environments, conditionally register the reflection service (e.g., based on environment variables or build flags) by calling reflection.Register(server). Ensure this registration is removed or disabled for production builds.
• Threats Mitigated:
  • Information Disclosure - Severity: Medium: gRPC reflection exposes the service's protobuf schema, which can be used for reconnaissance. Disabling it in grpc-go prevents this exposure in production.
  • Attack Surface Expansion - Severity: Low: Disabling reflection in grpc-go reduces the attack surface by removing an unnecessary endpoint in production.
• Impact:
  • Information Disclosure: Medium Reduction
  • Attack Surface Expansion: Low Reduction
• Currently Implemented: Yes - gRPC reflection is disabled in production deployments by conditionally omitting the reflection.Register(server) call in grpc-go server setup.
• Missing Implementation: N/A - Reflection is already disabled in production grpc-go configurations. Ensure this practice is consistently followed in all services.

Mitigation Strategy: Secure Interceptor Implementation in grpc-go

• Description:
  1. Secure Coding Practices in Interceptors: When developing grpc-go interceptors, follow secure coding practices. Avoid logging sensitive information within interceptors unless absolutely necessary and ensure logs are securely stored. Handle errors gracefully within interceptors and avoid exposing internal error details to clients.
  2. Principle of Least Privilege for Interceptor Logic: Ensure that the logic within your grpc-go interceptors adheres to the principle of least privilege. Interceptors should only perform the necessary actions for their intended purpose (e.g., authorization, logging, rate limiting) and should not have broader permissions or access than required.
  3. Thorough Testing of Interceptors: Thoroughly test your grpc-go interceptors, including security testing. Test for various scenarios, including valid and invalid inputs, authorization failures, rate limiting behavior, and error handling.
  4. Regularly Audit Interceptor Code: Periodically review and audit the code of your grpc-go interceptors to identify and address any potential security flaws or vulnerabilities that may have been introduced during development or maintenance.
• Threats Mitigated:
  • Vulnerabilities Introduced by Interceptors - Severity: Medium to High: Poorly implemented interceptors in grpc-go can introduce new vulnerabilities, such as information leaks through logging, denial of service due to inefficient interceptor logic, or security bypasses due to flawed authorization checks.
  • Information Disclosure - Severity: Medium: Interceptors might unintentionally log or expose sensitive information if not carefully coded.
• Impact:
  • Vulnerabilities Introduced by Interceptors: Medium to High Reduction (depends on the nature of vulnerabilities)
  • Information Disclosure: Medium Reduction
• Currently Implemented: Partially - Secure coding practices are generally followed, but specific security audits of grpc-go interceptor implementations are not regularly conducted.
• Missing Implementation: Implement regular security code reviews and audits specifically focused on grpc-go interceptor implementations. Establish guidelines and best practices for secure grpc-go interceptor development.