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fix: remove Hybrid Flow, make Progressive Consent default (ADR-004)

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Eliminates scope escalation security vulnerability by removing Hybrid Flow
and making Progressive Consent the only OAuth mode.

Changes:
- Delete oauth_callback() and oauth_token() (Hybrid Flow only, ~314 lines)
- Fix scope flows: Flow 1 requests resource scopes, Flow 2 requests identity+offline
- Remove ENABLE_PROGRESSIVE_CONSENT flag (always enabled in OAuth mode)
- Update documentation to reflect Progressive Consent as default
- Delete test_adr004_hybrid_flow.py test file
- Remove unused variables (ruff lint fixes)

Security improvements:
- No scope escalation: client gets exactly what it requests
- Clear separation: MCP session tokens vs Nextcloud offline tokens
- OAuth2 compliant: follows best practices for scope handling

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

Co-Authored-By: Claude <noreply@anthropic.com>
This commit is contained in:
Chris Coutinho
2025-11-04 00:26:07 +01:00
parent d14f2f666d
commit 15113dbb03
8 changed files with 125 additions and 940 deletions
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CLAUDE.md
+20 -16
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@@ -165,32 +165,36 @@ docker compose exec db mariadb -u root -ppassword nextcloud -e \
3. MCP tools use context pattern: `get_client(ctx)` → `NextcloudClient`
4. All operations are async using httpx
### Progressive Consent Mode (ADR-004)
### Progressive Consent Architecture (ADR-004)
**Status**: Opt-in feature (disabled by default)
**Enable**: Set `ENABLE_PROGRESSIVE_CONSENT=true`
**Default**: Hybrid Flow (backward compatible, single OAuth flow)
**Status**: Always enabled in OAuth mode (default)
**What is Progressive Consent?**
- Dual OAuth flow architecture that separates client authentication (Flow 1) from resource provisioning (Flow 2)
- Flow 1: MCP client authenticates directly to IdP (aud: "mcp-server")
- Flow 2: User explicitly provisions Nextcloud access via separate login (not during MCP session)
- Provides clear separation between session tokens and background job tokens
- Flow 1: MCP client authenticates directly to IdP with resource scopes (notes:*, calendar:*, etc.)
- Token audience: "mcp-server"
- Client receives resource-scoped token for MCP session
- Flow 2: Server explicitly provisions Nextcloud access via separate login
- Server requests: openid, profile, email, offline_access
- Token audience: "nextcloud"
- Server receives refresh token for offline access
- Client never sees this token
- Provides clear separation between session tokens and offline access tokens
**When to use:**
**When to use OAuth mode:**
- Multi-user deployments
- Background jobs requiring offline access
- Enhanced security with separate authorization contexts
- Explicit user control over resource access
**When NOT to use:**
- Simple single-user deployments (use BasicAuth)
- Standard OAuth without background jobs (use default Hybrid Flow)
**When to use BasicAuth instead:**
- Simple single-user deployments
- Local development and testing
**Key difference from Hybrid Flow:**
- Hybrid Flow: Server intercepts OAuth callback, stores refresh token automatically
- Progressive Consent: User explicitly authorizes via `provision_nextcloud_access` tool
**Key features:**
- No scope escalation - client gets exactly what it requests
- User explicitly authorizes via `provision_nextcloud_access` tool
- Clear security boundaries between MCP session and Nextcloud access
## MCP Response Patterns (CRITICAL)