Wire up RFC 8693 token exchange throughout the MCP server to support
stateless per-request token conversion for external IdP scenarios.
Changes:
Authentication Flow:
- Add exchange_token_for_audience() for pure RFC 8693 exchange
- Update context_helper to use stateless token exchange
- Remove fallback to standard OAuth on exchange failure
- Make storage initialization lazy (only for delegation, not MCP tools)
Application Configuration:
- Add ENABLE_TOKEN_EXCHANGE environment variable support
- Skip provisioning tools when token exchange enabled
- Pass mcp_client_id to token broker for proper validation
- Update docker-compose.yml with token exchange config
Token Exchange Service:
- Add TOKEN_EXCHANGE_GRANT constant
- Implement exchange_token_for_audience() method
- Support both "mcp-server" and client_id audiences
- Lazy storage initialization for delegation scenarios
- Enhanced error handling and logging
Progressive Token Verifier:
- Add mcp_client_id parameter for external IdP validation
- Accept both "mcp-server" and configured client_id
- Support external IdP token verification
Key Behavior Changes:
- When ENABLE_TOKEN_EXCHANGE=true: Each MCP tool call triggers
stateless token exchange (client token → Nextcloud token)
- When ENABLE_TOKEN_EXCHANGE=false: Uses pass-through mode
(validates Flow 1 token and passes to Nextcloud)
- No provisioning tools registered in exchange mode
- No refresh tokens needed for request-time operations
This completes the token exchange implementation. The MCP server now
supports both pass-through (default) and exchange (opt-in) modes for
federated authentication architectures.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
Implements Progressive Consent architecture with dual OAuth flows:
- Flow 1: Direct client authentication (aud: "mcp-server")
- Flow 2: Resource provisioning with refresh tokens
Components added:
- Client registry with validation (client_registry.py)
- Progressive token verifier (progressive_token_verifier.py)
- Token broker service integration
- Provisioning decorator for MCP tools
- OAuth provisioning tools (provision_nextcloud_access, etc.)
Configuration:
- Progressive Consent enabled by default (ENABLE_PROGRESSIVE_CONSENT=true)
- Client validation with pre-registered clients
- Audience separation framework
KNOWN ISSUE - Token Exchange Pattern Incorrect:
The current implementation does NOT properly implement token exchange.
MCP session tokens should be EXCHANGED for delegated Nextcloud tokens
during tool calls, not stored/reused. Critical corrections needed:
1. Session tokens: Flow 1 token → exchange → ephemeral Nextcloud token
- Generated on-demand per tool call
- Short-lived, not stored
- Scopes limited to tool requirements
2. Background tokens: Flow 2 refresh token → background Nextcloud token
- Only for offline/background jobs
- Potentially different scopes than session tokens
- Must NOT be used for MCP session tool calls
The token exchange mechanism needs to be implemented to properly
separate session-time delegation from background job authorization.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
Chris Coutinho