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feature/helm-chart-multi-user-basic-support
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4 Commits

Author SHA1 Message Date
Chris Coutinho babd60e08b feat: Implement ADR-004 Hybrid Flow with comprehensive integration tests 
Implement the ADR-004 Hybrid Flow OAuth pattern where the MCP server
intercepts the OAuth callback to obtain master refresh tokens while
maintaining PKCE security for clients.

## Implementation

### OAuth Routes (ADR-004 Hybrid Flow)
- Add `/oauth/authorize` endpoint: Intercepts client OAuth initiation
- Add `/oauth/callback` endpoint: Receives IdP callback, stores master token
- Add `/oauth/token` endpoint: Exchanges MCP code for client access token
- Implement PKCE code challenge/verifier validation
- Store OAuth sessions with state/challenge correlation

### MCP Server Integration
- Update `setup_oauth_config()` to return client_id and client_secret
- Initialize OAuth context in Starlette lifespan for login routes
- Add OAuth session storage to RefreshTokenStorage
- Configure authlib dependency for OAuth flow management

### Integration Tests
- Create `test_adr004_hybrid_flow.py` with Playwright automation
- Add `adr004_hybrid_flow_mcp_client` session-scoped fixture
- Test MCP session establishment with hybrid flow token
- Test tool execution using stored refresh tokens (on-behalf-of pattern)
- Test persistent access across multiple operations
- All tests passing: ✅ 3 passed in 8.82s

### Documentation
- Update ADR-004 with comprehensive Testing section
- Add integration test commands and coverage details
- Document test implementation and verification steps
- Create TESTING_INSTRUCTIONS.md for manual and automated testing
- Include manual test scripts for reference/debugging

## What This Enables

✅ PKCE code challenge/verifier flow
✅ MCP server intercepts OAuth callback and stores master refresh token
✅ Client receives MCP access token (not master token)
✅ MCP session establishment with hybrid flow token
✅ Tool execution using stored refresh tokens (on-behalf-of pattern)
✅ Multiple operations without re-authentication
✅ Proper token isolation (client never sees master token)

## Testing

Run ADR-004 integration tests:
```bash
uv run pytest tests/server/oauth/test_adr004_hybrid_flow.py --browser firefox -v
```

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
 2025-11-03 02:18:30 +01:00
Chris Coutinho 34df5f5b9a feat: Implement dual-tier token exchange (Standard V2 + Legacy V1 impersonation) 
This commit implements and documents both RFC 8693 token exchange tiers
from ADR-002, enabling both production-ready delegation and advanced
impersonation capabilities.

- Enable Keycloak preview features (`--features=preview`) to support
  both Standard V2 and Legacy V1 token exchange modes

- Update Tier 1 status from "NOT IMPLEMENTED" to "IMPLEMENTED (Legacy V1)"
- Add detailed empirical testing results showing:
  - Standard V2 rejects `requested_subject` parameter
  - Legacy V1 accepts parameter but requires impersonation permissions
  - Complete configuration steps for enabling impersonation
- Add comparison table showing when to use each tier
- Add "When to Use" guidance for both tiers
- Document that Tier 2 (Delegation) is the recommended default

- Update docstring to document both Tier 1 and Tier 2 support
- Add tier-specific logging (shows which tier is being used)
- Document permission requirements for Tier 1 impersonation

**tests/integration/auth/test_token_exchange_standard_v2.py**:
- Test delegation without impersonation (Tier 2)
- Verify sub claim remains unchanged (service account identity)
- Verify no special permissions required
- Test exchanged tokens work with Nextcloud APIs
- All tests PASS ✅

**tests/integration/auth/test_token_exchange_legacy_v1.py**:
- Test impersonation with `requested_subject` (Tier 1)
- Verify sub claim changes to target user
- Auto-skip if impersonation permissions not configured
- Document permission requirements in test docstrings
- Test exchanged tokens work with Nextcloud APIs

**tests/manual/test_impersonation.py**:
- Comprehensive impersonation validation script
- Tests both Standard V2 and Legacy V1 behavior
- Decodes JWT tokens to verify sub claim changes
- Validates tokens against Nextcloud APIs

**tests/manual/configure_impersonation.py**:
- Automated permission configuration helper
- Documents manual Keycloak CLI configuration steps

Both token exchange tiers are now fully implemented and tested:

- **Tier 2 (Delegation)** - ✅ RECOMMENDED
  - Standard V2 (production-ready)
  - No special permissions required
  - Service account identity preserved

- **Tier 1 (Impersonation)** - ✅ Advanced use only
  - Legacy V1 (--features=preview required)
  - Requires manual permission grant via Keycloak CLI
  - Subject claim changes to target user

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
 2025-11-02 22:03:22 +01:00
Chris Coutinho e26c5128b7 docs: Reject service account tokens as OAuth authentication pattern 
Service account tokens (client_credentials grant) violate OAuth "act on-behalf-of"
principles and have been moved to ADR-002's "Will Not Implement" section.

## Problem Discovery

Testing revealed that service account tokens create Nextcloud user accounts
(e.g., `service-account-nextcloud-mcp-server`) due to user_oidc's bearer
provisioning feature. This violates core OAuth principles:

- ❌ Creates stateful server identity in Nextcloud
- ❌ All actions attributed to service account, not real user
- ❌ Breaks audit trail and user attribution
- ❌ Service account becomes "admin by another name"

## Changes

### Documentation (ADR-002)
- Moved service account (old Tier 1) to "Will Not Implement" section
- Added "OAuth Act On-Behalf-Of Principle" section
- Renumbered tiers:
  - Tier 1: Impersonation (NOT IMPLEMENTED)
  - Tier 2: Delegation via token exchange (IMPLEMENTED)
- Updated status to reflect rejection of service accounts

### Code Warnings
- Added comprehensive warning to KeycloakOAuthClient.get_service_account_token()
- Clarified VALID use: only as subject_token for RFC 8693 token exchange
- Clarified INVALID use: direct API access with service account token

### Supporting Documentation
- CLAUDE.md: Removed outdated "Tier 1" references, added rejection note
- oauth-impersonation-findings.md: Added prominent update banner
- audience-validation-setup.md: Updated tier numbers, added rejection note
- tests/manual/test_token_exchange.py: Added warning comment

## Valid Patterns (ADR-002)

✅ Foreground operations: User's access token from MCP request
✅ Background operations: Token exchange (impersonation/delegation)
✅ Offline access: Refresh tokens with user consent
❌ Service accounts: Creates independent server identity (REJECTED)

## Alternative

If service account pattern is truly needed, use BasicAuth mode instead of
OAuth mode. OAuth mode MUST maintain "act on-behalf-of" semantics.

Related: c12df98 (revert of service account test)

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Co-Authored-By: Claude <noreply@anthropic.com>
 2025-11-02 22:03:22 +01:00
Chris Coutinho e331544cee feat: Implement RFC 8693 token exchange for Keycloak (ADR-002 Tier 2) 
Implements OAuth 2.0 Token Exchange (RFC 8693) enabling the MCP server to
exchange service account tokens for user-scoped tokens. This provides an
alternative to refresh tokens for background operations.

**Core Implementation:**
- Added `get_service_account_token()` method to KeycloakOAuthClient for
  client_credentials grant
- Added `exchange_token_for_user()` method implementing RFC 8693 token exchange
- Fixed Fernet encryption key handling in RefreshTokenStorage (was incorrectly
  base64 decoding already-encoded keys)
- Updated OAuth configuration to support offline_access scope and refresh token
  storage infrastructure

**Keycloak Configuration:**
- Enabled `serviceAccountsEnabled` in realm-export.json
- Added `token.exchange.grant.enabled` attribute
- Added `client.token.exchange.standard.enabled` attribute (required for
  Keycloak 26.2+ Standard Token Exchange V2)
- Fresh Keycloak imports now correctly enable token exchange

**Docker Compose:**
- Added TOKEN_ENCRYPTION_KEY and ENABLE_OFFLINE_ACCESS environment variables
- Created oauth-tokens volume for refresh token storage
- Configured both mcp-oauth and mcp-keycloak services

**Testing & Documentation:**
- Added tests/manual/test_token_exchange.py - Validates complete RFC 8693 flow
- Added tests/manual/test_nextcloud_impersonate.py - Documents session-based
  impersonation limitations
- Added docs/oauth-impersonation-findings.md - Comprehensive investigation
  findings and resolution documentation

**Verified Working:**
✅ Service account token acquisition (client_credentials grant)
✅ RFC 8693 token exchange for internal-to-internal tokens
✅ Exchanged tokens validate with Nextcloud APIs
✅ Keycloak 26.4.2 Standard Token Exchange V2 support

**Known Limitations:**
- User impersonation (requested_subject) requires Keycloak Legacy V1 with
  preview features
- Cross-client token exchange limited to same realm
- Refresh token storage infrastructure ready but unused (MCP protocol limitation)

Dependencies: aiosqlite>=0.20.0

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Co-Authored-By: Claude <noreply@anthropic.com>
 2025-11-02 22:03:19 +01:00