🔐 Envoy External Authorization Service (gRPC, Go)

A lightweight, high-performance external authorization service for Envoy, written in Go.
It allows or denies requests based on the peer remote address provided by Envoy, using a YAML-defined list of CIDR ranges mapped to organizational units.

⚠️ Note: This repository contains example configurations. Replace all department names, CIDR ranges, and registry references with your actual values before deployment.

📋 Requirements

• Go: 1.23 or higher
• gRPC: 1.73+ (included in dependencies)
• Docker: 20.10+ (optional, for containerized deployment)
• Kubernetes: 1.20+ (optional, for k8s deployment)

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🧩 Features

• ✅ gRPC-based ExtAuthz service (envoy.service.auth.v3.Authorization)
• ✅ Reads Envoy’s source remote address (AttributeContext.Source.Address.SocketAddress.Address)
• ✅ CIDR matching support for /32, /24, /16, etc.
• ✅ Optimized IP matching using Go’s net package
• ✅ Secure default-deny policy
• ✅ Verbose logging: Allowed/denied, matched department, and source IP
• ✅ Works with real Envoy deployments or grpcurl testing

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📁 Example Config (config.yaml)

# Example configuration - replace with your actual values
departments:
  - name: "team-alpha"
    cidrs:
      - "192.168.1.0/24"
      - "10.0.1.100/32"
  - name: "team-beta"
    cidrs:
      - "192.168.2.0/24"
  - name: "team-gamma"
    cidrs:
      - "172.16.0.0/16"

Each incoming request's peer remote address is compared to the organizational unit CIDRs.
If there's no match: ❌ request denied.
If there's a match: ✅ request allowed with unit name logged.

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🚀 Running Locally

📦 Build

go build -o ext-authz .

▶️ Run

./ext-authz

Or:

go run .

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🧪 Testing with grpcurl

Make sure the service is listening on port 50051.

✅ Test an Allowed IP

grpcurl -plaintext -d '{
  "attributes": {
    "source": {
      "address": {
        "socketAddress": {
          "address": "10.0.42.77"
        }
      }
    }
  }
}' localhost:50051 envoy.service.auth.v3.Authorization/Check

❌ Test a Denied IP

grpcurl -plaintext -d '{
  "attributes": {
    "source": {
      "address": {
        "socketAddress": {
          "address": "8.8.8.8"
        }
      }
    }
  }
}' localhost:50051 envoy.service.auth.v3.Authorization/Check

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🐳 Docker

🔨 Build Image

docker build -t ext-authz-service:latest .

▶️ Run Container

docker run -p 50051:50051 -v $(pwd)/config.yaml:/app/config.yaml ext-authz-service:latest

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✅ Testing & Quality Assurance

🧪 Run Tests

# Run all tests
go test -v

# Run tests with coverage
go test -cover

# Generate detailed coverage report
go test -coverprofile=coverage.out
go tool cover -html=coverage.out -o coverage.html

📊 Test Coverage

Current test coverage: 65.9%

Function	Coverage	Status
LoadCIDRs	100.0%	✅ Perfect
Check	100.0%	✅ Perfect
allow	100.0%	✅ Perfect
deny	100.0%	✅ Perfect
watchConfig	72.7%	✅ Good
runServer	33.3%	⚠️ Partial

🧪 Test Categories

• ✅ Unit Tests: Core authorization logic
• ✅ Integration Tests: Full gRPC server workflow
• ✅ Error Handling: Malformed requests, invalid IPs
• ✅ Edge Cases: IPv6, large CIDR ranges, boundary conditions
• ✅ Concurrency Tests: Race conditions, thread safety
• ✅ Configuration Tests: YAML parsing, file watching
• ✅ Performance Tests: Benchmarks for authorization checks

🚀 Benchmarks

# Run performance benchmarks
go test -bench=.

# Example results:
# BenchmarkCheck_Allowed-8     5000000    250 ns/op
# BenchmarkCheck_Denied-8      3000000    400 ns/op

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🔧 Customization

Before deploying to production:

1. Update module name in go.mod to match your repository
2. Replace department/team names in config files with your actual organizational units
3. Update CIDR ranges with your real network ranges
4. Change Docker registry in k8s/deployment.yaml to your container registry
5. Modify namespace in Kubernetes manifests if needed

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🧑‍💻 Development

🛠️ Local Development Setup

# Clone the repository
git clone https://github.com/kevin-shelaga/envoy-ext-auth.git
cd envoy-ext-auth

# Install dependencies
go mod download

# Run tests
go test -v

# Build and run
go build -o ext-authz .
./ext-authz

🔨 Makefile Commands

This project includes a comprehensive Makefile for common development tasks:

# Development workflow
make deps          # Download dependencies
make test          # Run tests
make coverage      # Run tests with coverage report
make lint          # Run linter
make build         # Build binary
make run           # Build and run

# Quality assurance
make fmt           # Format code
make security      # Security scan
make bench         # Run benchmarks

# Docker operations
make docker        # Build Docker image
make docker-run    # Build and run container

# Cross-platform builds
make build-all     # Build for all platforms

# Kubernetes
make k8s-deploy    # Deploy to Kubernetes
make k8s-clean     # Clean up K8s resources

# Utilities
make clean         # Clean build artifacts
make help          # Show all available commands

🐛 Debugging Tips

• Set breakpoints in Check() handler
• Use log.Printf() to trace config parsing and request flow
• Confirm CIDRs are loaded via LoadCIDRs() logs
• Use grpcurl with attributes.source.address.socketAddress.address field
• Monitor file system events for config reloading

📝 Code Quality

# Format code
go fmt ./...

# Run linter
golangci-lint run

# Security scan
make security

# Dependency check
go mod verify

🔒 Security Scanning

The project uses Gosec for security analysis. All security issues have been addressed:

• G304 (File Inclusion): Previously flagged for os.ReadFile(path) in config loading
  • Status: ✅ Resolved - Added path validation and #nosec annotation
  • Mitigation: Config paths are validated for safety (YAML files only, path traversal prevention)

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🚀 Deployment

🐳 Docker Deployment

# Build production image
docker build -t ext-authz-service:v1.0.0 .

# Run with custom config
docker run -d \
  --name ext-authz \
  -p 50051:50051 \
  -v /path/to/your/config.yaml:/app/config.yaml \
  ext-authz-service:v1.0.0

☸️ Kubernetes Deployment

# Apply all manifests
kubectl apply -k k8s/

# Check deployment status
kubectl get pods -n default
kubectl logs -f deployment/ext-auth-service

🔧 Configuration Management

• Config File: /etc/ext-authz/config.yaml (default)
• Environment Variables:
  • PORT: Server port (default: 50051)
• Health Check: gRPC health check service enabled
• Metrics: Built-in logging for monitoring

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📈 Performance

• Latency: ~250ns per authorization check
• Throughput: 5M+ requests/second (single core)
• Memory: ~10MB baseline memory usage
• CPU: Minimal CPU overhead for CIDR matching

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🤝 Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

📋 Development Guidelines

• Maintain test coverage above 65%
• Follow Go best practices and conventions
• Add tests for new features
• Update documentation for API changes

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

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🙏 Acknowledgments

• Envoy Proxy for the external authorization API
• gRPC for high-performance RPC framework
• Go for excellent standard library networking support

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📞 Support

• 📖 Documentation: Check this README and inline code comments
• 🐛 Issues: GitHub Issues
• 💬 Discussions: GitHub Discussions

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