OAuth 2.0 authentication server for Model Context Protocol (MCP) integration with OpenMetadata, enabling secure access to metadata through Claude Desktop and other MCP clients.
Overview
This module implements a complete OAuth 2.0 Authorization Code Flow with PKCE for MCP clients, enabling user authentication via OpenMetadata's existing SSO providers (Google, Okta, Azure AD, Auth0, AWS Cognito, Custom OIDC, LDAP, SAML) or Basic Auth. The implementation provides secure, standards-compliant access to OpenMetadata's metadata management capabilities through MCP tools.
Important: This is user SSO authentication for MCP clients, not connector-based OAuth for data sources. Users authenticate with their OpenMetadata credentials (SSO or username/password), and MCP tools execute with that user's permissions.
Features
OAuth 2.0 Implementation
- Authorization Code Flow with PKCE - RFC 7636 compliant, preventing authorization code interception attacks
- Refresh Token Rotation - Automatic token refresh with rotation for enhanced security
- Token Encryption - Fernet symmetric encryption for tokens at rest
- CSRF Protection - State parameter validation across the OAuth flow
- Session Fixation Prevention - Session regeneration after successful authentication
Authentication Methods
- SSO Integration - OAuth 2.0 integration with Google, Okta, Azure AD, Auth0, AWS Cognito, Custom OIDC, LDAP, and SAML providers via pac4j
- Basic Auth - Username/password authentication with OpenMetadata credentials
- User Impersonation - Support for impersonated user contexts in MCP tools
- Auto-Detection - Automatically selects SSO or Basic Auth based on OpenMetadata configuration
Security Features
- PKCE Validation - SHA-256 code challenge/verifier validation
- Token Expiry Management - Configurable access token (1 hour) and refresh token (7 days) lifetimes
- Rate Limiting - Registration (10/hour per IP) and token (30/minute per IP) endpoint protection
- Thread-Safe Concurrent Processing - ThreadLocal storage for request isolation
- Audit Logging - OAuth operations logged via SLF4J (oauth_audit_log table available for future use)
Database-Driven Configuration
- Runtime Configuration - Update MCP settings without server restart via REST API
- Cluster Synchronization - Database polling (10-second interval) ensures all cluster instances have consistent configuration
- Configuration Change Listeners - Dynamic CORS origin updates when configuration changes
- Persistent Storage - Configuration changes persist across server restarts (database-first, YAML fallback)
- HTTP Timeout Configuration - Configurable connection and read timeouts for SSO provider metadata fetching
MCP Integration
- Claude Desktop Support - First-class integration with Claude Desktop MCP client
- OAuth Discovery Endpoints - Standard .well-known endpoints for client configuration
- Dynamic Client Registration - RFC 7591 compliant client registration
- JWKS Support - Public key endpoint for JWT validation
Architecture
Core Components
UserSSOOAuthProvider
- Main OAuth provider implementing authorization code flow
- Handles both Google SSO and Basic Auth flows
- Token generation, validation, and refresh logic
- PKCE challenge/verifier validation with timing-safe comparison
OAuthHttpStatelessServerTransportProvider
- HTTP transport layer for OAuth endpoints
- Routes authorization, token, and discovery requests
- Servlet-based stateless request handling
- Provider-aware OAuth scope configuration
SecurityConfigurationManager
- Singleton manager for runtime security configuration (authentication, authorization, MCP settings)
- Database-first configuration loading with YAML fallback
- Configuration change listener pattern for reactive updates
- Cluster-aware polling mechanism (10-second interval) to detect changes across instances
- Rollback mechanism for failed configuration updates
- Thread-safe synchronized getters for consistent configuration reads
OAuth Repositories
- OAuthClientRepository - Client management and validation
- OAuthAuthorizationCodeRepository - Authorization code CRUD operations
- OAuthAccessTokenRepository - Access token lifecycle management
- OAuthRefreshTokenRepository - Refresh token rotation and cleanup
- McpPendingAuthRequestRepository - Database-backed OAuth state persistence
- OAuthAuditLogRepository - Comprehensive audit trail
Database Schema
Five core OAuth tables with audit logging:
- oauth_clients - Dynamically registered MCP clients via RFC 7591
- oauth_authorization_codes - Short-lived codes (10 min TTL) with PKCE challenge
- oauth_access_tokens - JWT access tokens (1 hour TTL) with encryption
- oauth_refresh_tokens - Refresh tokens (7 days TTL) with automatic rotation
- mcp_pending_auth_requests - OAuth state parameters for cross-domain redirects (10 min TTL)
- oauth_audit_log - Comprehensive audit trail of all OAuth operations
Cleanup Job: OAuthTokenCleanupJob runs every 10 minutes to purge expired tokens and pending requests.
OAuth Flow
Authorization Code Flow with PKCE
┌─────────────┐ ┌──────────────┐
│ Claude │ │ OpenMetadata │
│ Desktop │ │ MCP │
│ (MCP Client)│ │ Server │
└──────┬──────┘ └──────┬───────┘
│ │
│ 1. Generate PKCE code_verifier (random 43-128 chars) │
│ Calculate code_challenge = BASE64URL(SHA256(verifier)) │
│ │
│ 2. GET /api/v1/mcp/authorize │
│ ?client_id={registered_client_id} │
│ &redirect_uri=http://127.0.0.1:XXXXX/callback │
│ &code_challenge={challenge} │
│ &code_challenge_method=S256 │
│ &state={client_state} │
│─────────────────────────────────────────────────────────────────>│
│ │
│ 3. Store OAuth state in database: │
│ - client_id, redirect_uri │
│ - code_challenge, method │
│ - state, scopes, TTL (10 min) │
│ Generate authRequestId │
│ │
│ 4. 302 Redirect to Auth Page │
│ /api/v1/mcp/authorize?state=mcp:{authRequestId} │
│<─────────────────────────────────────────────────────────────────│
│ │
│ 5. User authenticates via: │
│ ┌──────────────────────────────────────┐ │
│ │ Option A: SSO Provider │ │
│ │ - Redirect to SSO provider: │ │
│ │ • Google OAuth │ │
│ │ • Okta │ │
│ │ • Azure AD │ │
│ │ • Auth0 │ │
│ │ • AWS Cognito │ │
│ │ • Custom OIDC │ │
│ │ • LDAP │ │
│ │ • SAML │ │
│ │ - User grants consent │ │
│ │ - SSO callback with ID token (pac4j)│ │
│ └──────────────────────────────────────┘ │
│ OR │
│ ┌─────────────────────────────┐ │
│ │ Option B: Basic Auth │ │
│ │ - Username/password form │ │
│ │ - Validate with │ │
│ │ OpenMetadata │ │
│ └─────────────────────────────┘ │
│ │
│ 6. Lookup OAuth state from DB using │
│ authRequestId from state parameter │
│ Generate authorization code │
│ Store code + code_challenge in DB │
│ │
│ 7. 302 Redirect with authorization code │
│ {redirect_uri}?code={auth_code}&state={client_state} │
│<─────────────────────────────────────────────────────────────────│
│ │
│ 8. POST /api/v1/mcp/token │
│ grant_type=authorization_code │
│ code={auth_code} │
│ code_verifier={verifier} │
│ client_id={registered_client_id} │
│ redirect_uri=http://127.0.0.1:XXXXX/callback │
│─────────────────────────────────────────────────────────────────>│
│ │
│ 9. PKCE Validation: │
│ Lookup code_challenge from DB │
│ Verify: BASE64URL(SHA256(verifier)) │
│ == code_challenge │
│ Delete authorization code (single-use)│
│ │
│ 10. 200 OK │
│ { │
│ "access_token": "eyJhbGc...", // JWT, 1 hour TTL │
│ "refresh_token": "fernet_encrypted", // 7 days TTL │
│ "token_type": "Bearer", │
│ "expires_in": 3600 │
│ } │
│<─────────────────────────────────────────────────────────────────│
│ │
│ 11. Use MCP Tools │
│ Authorization: Bearer eyJhbGc... │
│─────────────────────────────────────────────────────────────────>│
│ MCP Tool Execution (lineage, search, discovery, etc.) │
│<─────────────────────────────────────────────────────────────────│
│ │
│ 12. Token Expiry - Refresh Flow │
│ POST /api/v1/mcp/token │
│ grant_type=refresh_token │
│ refresh_token={encrypted_token} │
│─────────────────────────────────────────────────────────────────>│
│ │
│ 13. Refresh Token Rotation: │
│ - Decrypt and validate refresh token │
│ - Delete old refresh token │
│ - Generate new access + refresh tokens│
│ │
│ 14. 200 OK │
│ { │
│ "access_token": "eyJhbGc...", // New JWT │
│ "refresh_token": "new_encrypted", // New rotated token │
│ "token_type": "Bearer", │
│ "expires_in": 3600 │
│ } │
│<─────────────────────────────────────────────────────────────────│
│ │
Key Security Mechanisms
PKCE (Proof Key for Code Exchange)
- Client generates random code_verifier (43-128 characters)
- Calculates code_challenge = BASE64URL(SHA256(code_verifier))
- Server stores code_challenge with authorization code
- Client proves possession by sending code_verifier on token exchange
- Server validates: BASE64URL(SHA256(code_verifier)) == stored code_challenge
- Prevents authorization code interception attacks
Database-Backed State Persistence
- OAuth state parameters stored in database, not HTTP sessions
- Survives cross-domain redirects (e.g., Google OAuth callback)
- Each request gets unique authRequestId embedded in state parameter
- 10-minute TTL prevents stale state attacks
- Single-use: deleted after successful callback
Token Security
- Access tokens: JWT signed with RSA-256, validated via JWKS endpoint
- Refresh tokens: Fernet symmetric encryption at rest
- Authorization codes: Single-use, 10-minute expiry, tied to PKCE challenge
- Refresh token rotation: Old token invalidated when new one issued
Configuration
MCP Configuration (Database-Driven)
MCP-specific settings are managed via REST API with database persistence:
curl -H "Authorization: Bearer $TOKEN" \
http://localhost:8585/api/v1/system/mcp/config
curl -X PUT -H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{
"baseUrl": "https://metadata.example.com",
"allowedOrigins": ["https://app.example.com"],
"connectTimeout": 30000,
"readTimeout": 60000,
"enabled": true
}' \
http://localhost:8585/api/v1/system/mcp/config
Configuration Properties:
baseUrl - OAuth issuer URL (used for metadata endpoints)allowedOrigins - CORS whitelist for OAuth endpoints (use specific origins, not *)connectTimeout - HTTP connection timeout for SSO provider metadata (milliseconds)readTimeout - HTTP read timeout for SSO provider metadata (milliseconds)enabled - Enable/disable MCP server
Key Features:
- Changes take effect immediately across all cluster instances (10-second polling interval)
- Configuration persists across server restarts (database-first, YAML fallback)
- CORS origins update dynamically without restart via listener pattern
OAuth Server Configuration
The OAuth server is configured in openmetadata.yaml:
- JWT Configuration - RSA key pair for token signing, JWKS endpoint URL
- Token Expiry - Access token (1 hour) and refresh token (7 days) lifetimes
- Rate Limiting - Registration (10/hour per IP) and token endpoint (30/minute per IP) rate limits
- SSO Provider - Google, Okta, Azure AD, etc. OAuth client ID and secret for SSO integration
- Callback URLs - Allowed redirect URIs for OAuth clients
Client Registration
MCP clients use Dynamic Client Registration (RFC 7591) via POST /api/v1/mcp/register:
- client_name - Human-readable client name
- redirect_uris - Allowed callback URLs for OAuth redirects
- scopes - Requested OAuth scopes (openid, profile, email, offline_access)
- grant_types - Supported grant types (authorization_code, refresh_token)
The registration endpoint returns a client_id and optional client_secret for the OAuth flow.
All MCP tools authenticate using the Bearer token from the OAuth flow:
- GetLineageTool - Retrieve entity lineage with authorization checks
- SearchTool - Search metadata with user permissions
- DiscoveryTool - Discover entities with access control
Permission Model: Tool permissions are enforced by OpenMetadata's Authorizer using the user's identity from the JWT. This ensures MCP users have the same access as they would in the OpenMetadata UI - respecting all policies, roles, and ownership rules. OAuth authenticates the user; the Authorizer enforces what they can access.
The transport provider extracts and validates the JWT on every request, setting up the security context for downstream MCP tool execution.
Recent Improvements
Security and Reliability Fixes
Thread Safety and Concurrency
- Fixed race conditions in configuration reads with synchronized getters
- Implemented ThreadLocal cleanup in outer finally block to prevent memory leaks
- Added rollback mechanism for failed configuration updates
HTTP Client Configuration
- Replaced JVM-wide system properties with pac4j-specific HTTP timeouts
- Configurable connection and read timeouts for SSO provider metadata fetching
- Prevents timeout changes from affecting other HTTP clients
Session Security
- Added null check after session regeneration to handle invalidate/recreate fallback
- Synchronized pac4j client callback URL modification to prevent race conditions
- Improved CSRF protection with proper session handling
Configuration Management
- Database-first loading ensures configuration persists across restarts
- Cluster polling (10-second interval) for consistent configuration across instances
- Configuration change listeners for dynamic CORS updates without restart
- URL validation for MCP configuration API (prevents invalid protocols, partial wildcards)
Input Validation
- Validates baseUrl protocol (HTTP/HTTPS only)
- Rejects partial wildcard origins (e.g.,
https://*.example.com)
- Accepts exact wildcard (
*) for development environments
Unit Tests
SecurityConfigurationManagerTest (9 tests)
- Singleton pattern verification
- Listener registration and removal
- Thread-safe configuration access (10 threads × 100 iterations)
- Synchronized getters preventing race conditions (50 concurrent threads)
- Rollback mechanism validation
- Configuration getter behavior
MCPConfigurationIntegrationTest (9 tests, on hold)
- Database-first loading verification
- Configuration update via API
- Configuration persistence across cache reload
- Configuration change detection with polling
- Input validation (invalid protocols, wildcard origins)
- Listener notification on configuration reload
- Multiple sequential updates
Testing
OAuth Flow Testing
15 comprehensive integration tests in UserSSOOAuthProviderIntegrationTest:
- Authorization endpoint validation (client_id, redirect_uri, PKCE parameters)
- Token exchange with PKCE verification
- Refresh token rotation
- Invalid PKCE challenge/verifier rejection
- Expired authorization code handling
- Invalid client_id and redirect_uri validation
- Missing parameter error handling
Security Testing
- PKCE challenge/verifier validation across multiple test cases
- Token expiry and refresh flow validation
- Authorization code single-use enforcement
- CSRF state parameter validation
- Rate limiting behavior validation
SSO Integration Testing
Tests SSO provider integration using pac4j with mock identity providers (Google, Okta, Azure AD, etc.). The UserSSOOAuthProvider auto-detects the configured SSO provider from OpenMetadata's authentication configuration.
Deployment
Database Migrations
Schema migrations in bootstrap/sql/migrations/native/1.12.0/:
- mysql/schemaChanges.sql - OAuth tables creation (oauth_clients, oauth_authorization_codes, oauth_access_tokens, oauth_refresh_tokens, mcp_pending_auth_requests, oauth_audit_log)
- postgres/schemaChanges.sql - OAuth tables creation (PostgreSQL equivalent)
Server Initialization
OAuth components initialized in McpServer:
- JwtFilter and authorizer setup
- OAuth repositories instantiation
- UserSSOOAuthProvider initialization with SSO config
- OAuthHttpStatelessServerTransportProvider registration at /mcp/*
- SSO callback servlet and Basic Auth login servlet registration
- OAuthTokenCleanupJob scheduled (10-minute intervals)
Environment Variables
SSO Provider Configuration (varies by provider):
- OIDC_CLIENT_ID - OAuth client ID for SSO provider (Google, Okta, Azure, etc.)
- OIDC_CLIENT_SECRET - OAuth client secret for SSO provider
- OIDC_TYPE - SSO provider type (google, okta, azure, auth0, aws-cognito, custom-oidc)
- OIDC_DISCOVERY_URI - OIDC discovery endpoint URL
JWT Token Configuration:
- JWT_ISSUER - JWT issuer claim for token validation
- JWT_KEY_ID - RSA key pair ID for token signing
MCP Configuration (optional, can be set via API):
- MCP_BASE_URL - OAuth issuer base URL
- MCP_ALLOWED_ORIGINS - Comma-separated CORS origins
Security Considerations
- Public Client Security - PKCE mandatory for all authorization code flows
- Redirect URI Validation - HTTP redirect URIs restricted to loopback addresses per RFC 8252; HTTPS URIs validated against registered client URIs
- Token Storage - Refresh tokens encrypted at rest using Fernet
- Session Management - Stateless design with database-backed state persistence
- Audit Trail - All OAuth operations logged for compliance and forensics
- Rate Limiting - Registration (10/hour per IP) and token (30/minute per IP) endpoint rate limiting
- CORS Security - Deny-all CORS when MCP configuration is unavailable (no permissive localhost fallback)
- Single-Use Codes - Authorization codes deleted after exchange
- Token Rotation - Refresh tokens rotated on every refresh to limit exposure
- Timing-Safe Comparisons - CSRF and PKCE validation use MessageDigest.isEqual() to prevent timing attacks
- Provider-Aware Scopes - OAuth scopes automatically adjusted based on SSO provider (Google, Okta, Azure, etc.)
- JWK Caching - 6-hour TTL with cache-miss retry for responsive key rotation handling
License
Apache License 2.0