MCP Gateway

A flexible and extensible proxy gateway for MCP (Model Context Protocol) servers, providing enterprise-grade middleware capabilities including authentication, authorization, rate limiting, and observability.

🚀 Features

🔐 Authentication & Authorization

• Multiple Auth Providers: Okta OAuth2/JWT
• Role-Based Permissions: Fine-grained tool access control
• attribute-to-Role Mapping: Flexible user permission assignment
• JWT Token Verification: Secure token validation

📊 Enterprise Ready

• Multiple Storage Backends: Memory (dev), PostgreSQL
• RESTful Admin API: Dynamic configuration management
• Prometheus Metrics: Built-in observability
• Structured Logging: JSON and text output formats
• Health Endpoints: Container orchestration support

⚙️ Flexible Configuration

• YAML Configuration: Environment variable substitution
• CLI Flags: Override any configuration option
• Hot Configuration: Runtime proxy/role management via API

🏗️ Architecture

┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   AI Client     │───▶│  MCP Gateway    │───▶│   MCP Server    │
│ (Claude, etc.)  │    │                 │    │  (n8n, etc.)    │
└─────────────────┘    │  ┌───────────┐  │    └─────────────────┘
                       │  │           │  │
                       │  │Okta Auth  │  │    ┌─────────────────┐
                       │  │  Roles    │  │───▶│ Another Server  │
                       │  │ Metrics   │  │    └─────────────────┘
                       │  └───────────┘  │
                       └─────────────────┘

🚀 Quick Start

Using Go (Development)

# Clone and run without authentication
git clone https://github.com/matthisholleville/mcp-gateway.git
cd mcp-gateway

# Run without authentication
go run main.go serve \
  --log-format=text \
  --log-level=debug 

Using Docker

# Pull the latest image
docker pull ghcr.io/matthisholleville/mcp-gateway:latest

# Run with environment variables
docker run -p 8082:8082 \
  ghcr.io/matthisholleville/mcp-gateway:latest serve

Using Docker Compose (with PostgreSQL)

# Start PostgreSQL
docker-compose up -d postgres

# Run migrations
go run main.go migrate up \
  --backend-engine=postgres \
  --backend-uri='postgresql://mcp-gateway:changeme@localhost:5439/mcp-gateway?sslmode=disable'

# Start server with PostgreSQL backend
go run main.go serve \
  --log-format=text \
  --log-level=debug \
  --backend-engine=postgres \
  --backend-uri='postgresql://mcp-gateway:changeme@localhost:5439/mcp-gateway?sslmode=disable' \
  --backend-encryption-key=0123456789abcdeffedcba9876543210cafebabefacefeeddeadbeef00112233

Using Helm

helm repo add mcp-gateway https://matthisholleville.github.io/mcp-gateway
helm install mcp-gateway mcp-gateway/mcp-gateway

⚙️ Configuration

Configuration Sources (Priority Order)

1. CLI Flags (highest priority)
2. Environment Variables (MCP_GATEWAY_*)
3. YAML Configuration File (config/config.yaml)
4. Default Values (lowest priority)

YAML Configuration Example

# config/config.yaml
server:
  url: "http://localhost:8082"

# Authentication
authProvider:
  enabled: true
  name: "okta"
  okta:
    issuer: "https://custom-xxx.okta.com/oauth2/default"
    orgUrl: "https://custom-xxx.okta.com"
    clientId: "xxx"
    privateKey: "-----BEGIN PRIVATE KEY-----xxx-----END PRIVATE KEY-----"
    privateKeyId: "xxx"

oauth:
  enabled: true
  provider: "okta"
  authorizationServers:
    - "https://custom-xxx.okta.com/oauth2/default"
  bearerMethodsSupported: ["Bearer"]
  scopesSupported: ["openid", "email", "profile"]

# Storage backend
backendConfig:
  engine: "memory"  # "postgres" coming soon
  # uri: "postgres://user:pass@localhost/mcp_gateway"

# Proxy configuration
proxy:
  cacheTTL: 300s
  heartbeat:
    enabled: true
    intervalSeconds: 10s

Environment Variables

All configuration options can be set via environment variables with MCP_GATEWAY_ prefix:

export MCP_GATEWAY_AUTH_PROVIDER_ENABLED=true
export MCP_GATEWAY_OAUTH_ENABLED=true

🔐 Authentication Providers

Okta OAuth2

go run main.go serve \
  --auth-provider-name=okta \
  --okta-issuer=https://your-domain.okta.com/oauth2/default \
  --okta-org-url=https://your-domain.okta.com \
  --okta-client-id=your-client-id
  --okta-private-key="-----BEGIN RSA PRIVATE KEY-----\n..."
  --okta-private-key-id="akXpH7Ha5VKCe2kNT3eCPn_YRaJ0..."

📦 Storage Backends

Memory Backend (Development)

• Usage: Development and testing
• Persistence: None (data lost on restart)
• Configuration: --backend-engine=memory

PostgreSQL Backend

• Usage: Production environments
• Persistence: Full durability
• Configuration: --backend-engine=postgres --backend-uri=postgres://...

🛠️ Admin API

You can update the admin API Key with --http-admin-api-key flag

The gateway provides RESTful APIs for runtime configuration management:

Proxy Management

Swagger is available at http://localhost:8082/swagger/index.html

# List all proxies
curl -H "X-API-Key: your-api-key" http://localhost:8082/v1/admin/proxies

# Add/Update proxy
curl -X PUT -H "X-API-Key: your-api-key" \
  -H "Content-Type: application/json" \
  -d '{"name":"n8n","type":"streamable-http","connection":{"url":"http://n8n:5678"}}' \
  http://localhost:8082/v1/admin/proxies/n8n

Role Management

• objectType can be * or tools
• objectName is the tool name if objectType is tools. Can be * or your object name
• proxy is the proxy name. Can be * or your proxy name

# Create role
curl -X PUT -H "X-API-Key: your-api-key" \
  -H "Content-Type: application/json" \
  -d '{"name":"admin","permissions":[{"objectType":"*","proxy":"*","objectName":"*"}]}' \
  http://localhost:8082/v1/admin/roles

Attribute-to-Role Mapping

• attributeKey is the key in your JWT attributes
• attributeValue is the attribute value
• roles is the list of roles. You must create the roles before creating the attribute-to-role mapping

# Map user attributes to roles
curl -X PUT -H "X-API-Key: your-api-key" \
  -H "Content-Type: application/json" \
  -d '{"attributeKey":"groups","attributeValue":"admins","roles":["admin"]}' \
  http://localhost:8082/v1/admin/attribute-to-roles

📊 API Endpoints

🛠️ Development

Prerequisites

• Go 1.24.3+
• Docker (optional)
• Make

Commands

# Install dependencies
make deps

# Run in development
make dev

# Build binary
make build

# Run tests
make test

# Generate coverage
make test-cover

# Build Docker image
make docker-build

Configuration Paths

The gateway searches for config.yaml in:

• /etc/mcp-gateway/
• $HOME/.mcp-gateway/
• ./config/

📝 CLI Reference

Common Flags

--log-format              # text, json
--log-level               # debug, info, warn, error
--log-timestamp-format    # Format for logging timestamps
--auth-provider-enabled   # Enable authentication
--auth-provider-name      # okta
--oauth-enabled           # Enable OAuth2
--backend-engine          # memory, postgres
--http-addr               # Server address (default: :8082)
--http-admin-api-key      # Admin API key for MCP Gateway configuration

Proxy Flags

--proxy-cache-ttl         # TTL for the proxy cache
--proxy-heartbeat-interval # Interval for the proxy heartbeat

Backend Flags

--backend-uri                    # URI for the auth backend
--backend-username               # The username to use for the auth backend. It will override the username in the URI if provided.
--backend-password               # The password to use for the auth backend. It will override the password in the URI if provided.
--backend-max-open-conns         # Maximum number of open database connections
--backend-max-idle-conns         # Maximum number of idle connections in pool
--backend-conn-max-idle-time     # Maximum time a connection may be idle
--backend-conn-max-lifetime      # Maximum time a connection may be reused

OAuth Flags

--oauth-authorization-servers           # OAuth authorization servers
--oauth-resource                        # OAuth resource (e.g. http://localhost:8082)
--oauth-bearer-methods-supported        # Bearer methods supported for OAuth
--oauth-scopes-supported                # OAuth scopes supported (e.g. openid,email,profile)

Okta Flags

--okta-issuer           # Okta authorization server
--okta-org-url          # Okta organization URL
--okta-client-id        # Okta client ID
--okta-private-key      # Private key for client auth
--okta-private-key-id   # Private key ID

🤝 Contributing

We welcome contributions! Please see CONTRIBUTING.md for guidelines.

📄 License

Licensed under the Apache License 2.0 - see LICENSE for details.

Made with ❤️ by Matthis Holleville