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mcvsphere/OAUTH-ARCHITECTURE.md
Ryan Malloy ab83c70c31 docs: update OAuth/RBAC architecture documentation 
Rewrites the architecture doc from design proposal to implementation
reference. Documents the complete RBAC system including:

- 5 permission levels (READ_ONLY → FULL_ADMIN)
- 5 OAuth groups with permission mappings
- RBACMiddleware implementation details
- Audit log format with user identity
- Configuration environment variables
- OIDC provider setup (Authentik example)
- Troubleshooting guide for common issues

Updates implementation checklist to reflect completed status.
2025-12-27 08:22:02 -07:00

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# OAuth & RBAC Architecture for mcvsphere
## Overview
mcvsphere supports multi-user OAuth 2.1 authentication with Role-Based Access Control (RBAC). This enables:
1. **Single Sign-On** via any OIDC provider (Authentik, Keycloak, Auth0, etc.)
2. **User Identity** for audit logging - know WHO made each request
3. **Group-Based Permissions** - control what users can do based on OAuth groups
4. **Audit Trail** - every tool invocation logged with user identity and timing
---
## Architecture
```
┌─────────────────────────────────────────────────────────────────┐
│ MCP Client (Claude Code) │
└────────────────────────────┬────────────────────────────────────┘
│
│ 1. OAuth 2.1 + PKCE flow
│ (browser opens for login)
│
┌────────────────────────────▼────────────────────────────────────┐
│ OIDC Provider │
│ (Authentik, Keycloak, Auth0, etc.) │
│ │
│ - Issues JWT access tokens │
│ - Validates user credentials │
│ - Includes groups claim in token │
└────────────────────────────┬────────────────────────────────────┘
│
│ 2. JWT Bearer token
│ Authorization: Bearer <jwt>
│
┌────────────────────────────▼────────────────────────────────────┐
│ mcvsphere │
│ (FastMCP + pyvmomi) │
│ │
│ ┌─────────────────────────────────────────────────────────┐ │
│ │ OIDCProxy (FastMCP) │ │
│ │ - Validates JWT signature via JWKS endpoint │ │
│ │ - Extracts user identity (preferred_username, email) │ │
│ │ - Extracts groups from token claims │ │
│ └─────────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌─────────────────────────────────────────────────────────┐ │
│ │ RBACMiddleware │ │
│ │ - Intercepts ALL tool calls via on_call_tool() │ │
│ │ - Maps OAuth groups → Permission levels │ │
│ │ - Denies access if user lacks required permission │ │
│ │ - Logs audit events with user identity │ │
│ └─────────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌─────────────────────────────────────────────────────────┐ │
│ │ VMware Tools (94) │ │
│ │ - Execute vCenter/ESXi operations via pyvmomi │ │
│ │ - Single service account connection to vCenter │ │
│ └─────────────────────────────────────────────────────────┘ │
└────────────────────────────┬────────────────────────────────────┘
│
│ 3. pyvmomi (service account)
│
┌────────────────────────────▼────────────────────────────────────┐
│ vCenter / ESXi │
│ - Receives API calls as service account │
│ - mcvsphere audit logs show real user identity │
└─────────────────────────────────────────────────────────────────┘
```
---
## RBAC Permission Model
### Permission Levels
mcvsphere defines 5 permission levels, from least to most privileged:
| Level | Description | Example Tools |
|-------|-------------|---------------|
| `READ_ONLY` | View-only operations | `list_vms`, `get_vm_info`, `vm_screenshot` |
| `POWER_OPS` | Power and snapshot operations | `power_on`, `create_snapshot`, `reboot_guest` |
| `VM_LIFECYCLE` | Create/delete/modify VMs | `create_vm`, `clone_vm`, `add_disk`, `deploy_ovf` |
| `HOST_ADMIN` | ESXi host operations | `reboot_host`, `enter_maintenance_mode` |
| `FULL_ADMIN` | Everything including guest OS ops | `run_command_in_guest`, `restart_service` |
### OAuth Groups → Permissions
Users are granted permissions based on their OAuth group memberships:
| OAuth Group | Permissions Granted |
|-------------|---------------------|
| `vsphere-readers` | READ_ONLY |
| `vsphere-operators` | READ_ONLY, POWER_OPS |
| `vsphere-admins` | READ_ONLY, POWER_OPS, VM_LIFECYCLE |
| `vsphere-host-admins` | READ_ONLY, POWER_OPS, VM_LIFECYCLE, HOST_ADMIN |
| `vsphere-super-admins` | ALL (full access) |
**Security Note:** Users with NO recognized groups are denied ALL access. There is no default permission.
### Tool → Permission Mapping
All 94 tools are mapped to permission levels in `src/mcvsphere/permissions.py`:
```python
# READ_ONLY - 32 tools
"list_vms", "get_vm_info", "list_snapshots", "get_vm_stats", ...
# POWER_OPS - 14 tools
"power_on", "power_off", "create_snapshot", "revert_to_snapshot", ...
# VM_LIFECYCLE - 33 tools
"create_vm", "clone_vm", "delete_vm", "add_disk", "deploy_ovf", ...
# HOST_ADMIN - 6 tools
"enter_maintenance_mode", "reboot_host", "shutdown_host", ...
# FULL_ADMIN - 11 tools
"run_command_in_guest", "write_guest_file", "restart_service", ...
```
---
## Implementation Details
### Key Files
| File | Purpose |
|------|---------|
| `src/mcvsphere/auth.py` | OIDCProxy configuration |
| `src/mcvsphere/permissions.py` | Permission levels and tool mappings |
| `src/mcvsphere/middleware.py` | RBACMiddleware implementation |
| `src/mcvsphere/audit.py` | Audit logging with user context |
| `src/mcvsphere/server.py` | Server setup with OAuth + RBAC |
### RBACMiddleware Flow
```python
class RBACMiddleware(Middleware):
"""Intercepts all tool calls to enforce permissions."""
async def on_call_tool(self, context, call_next):
# 1. Extract user from OAuth token
claims = self._extract_user_from_context(context.fastmcp_context)
username = claims.get("preferred_username", "unknown")
groups = claims.get("groups", [])
# 2. Check permission
tool_name = context.message.name
if not check_permission(tool_name, groups):
required = get_required_permission(tool_name)
audit_permission_denied(tool_name, {...}, required.value)
raise PermissionDeniedError(username, tool_name, required)
# 3. Execute tool with timing
start = time.perf_counter()
result = await call_next(context)
duration_ms = (time.perf_counter() - start) * 1000
# 4. Audit log
audit_log(tool_name, {...}, result="success", duration_ms=duration_ms)
return result
```
### Audit Log Format
```json
{
"timestamp": "2025-12-27T08:15:32.123456+00:00",
"user": "ryan@example.com",
"groups": ["vsphere-admins", "vsphere-operators"],
"tool": "power_on",
"args": {"vm_name": "web-server"},
"duration_ms": 1234.56,
"result": "success"
}
```
Permission denied events:
```json
{
"timestamp": "2025-12-27T08:15:32.123456+00:00",
"user": "guest@example.com",
"groups": ["vsphere-readers"],
"tool": "delete_vm",
"args": {"vm_name": "web-server"},
"required_permission": "vm_lifecycle",
"event": "PERMISSION_DENIED"
}
```
---
## Configuration
### Environment Variables
```bash
# ═══════════════════════════════════════════════════════════════
# OAuth Configuration
# ═══════════════════════════════════════════════════════════════
OAUTH_ENABLED=true
OAUTH_ISSUER_URL=https://auth.example.com/application/o/mcvsphere/
OAUTH_CLIENT_ID=<from-oidc-provider>
OAUTH_CLIENT_SECRET=<from-oidc-provider>
OAUTH_BASE_URL=https://mcp.example.com # Public URL for callbacks
OAUTH_SCOPES='["openid", "profile", "email", "groups"]'
# ═══════════════════════════════════════════════════════════════
# Transport (must be HTTP for OAuth)
# ═══════════════════════════════════════════════════════════════
MCP_TRANSPORT=streamable-http
MCP_HOST=0.0.0.0
MCP_PORT=8080
# ═══════════════════════════════════════════════════════════════
# vCenter Connection (service account)
# ═══════════════════════════════════════════════════════════════
VCENTER_HOST=vcenter.example.com
VCENTER_USER=svc-mcvsphere@vsphere.local
VCENTER_PASSWORD=<service-account-password>
VCENTER_INSECURE=false
# ═══════════════════════════════════════════════════════════════
# Optional
# ═══════════════════════════════════════════════════════════════
LOG_LEVEL=INFO
```
### Server Startup Banner
When OAuth is enabled, the server shows:
```
mcvsphere v0.2.1
────────────────────────────────────────
Starting HTTP transport on 0.0.0.0:8080
OAuth: ENABLED via https://auth.example.com/application/o/mcvsphere/
RBAC: ENABLED - permissions enforced via groups
────────────────────────────────────────
```
---
## OIDC Provider Setup
### Authentik (Recommended)
1. **Create OAuth2/OIDC Provider:**
- Name: `mcvsphere`
- Client Type: **Confidential**
- Redirect URIs:
- `http://localhost:*/callback` (for local dev)
- `https://mcp.example.com/auth/callback`
- Signing Key: Select RS256 certificate
2. **Create Application:**
- Name: `mcvsphere`
- Slug: `mcvsphere`
- Provider: Select provider from step 1
3. **Create Groups:**
- `vsphere-readers`
- `vsphere-operators`
- `vsphere-admins`
- `vsphere-host-admins`
- `vsphere-super-admins`
4. **Add Scope Mapping for Groups:**
- Ensure `groups` claim is included in tokens
- Authentik includes this by default
5. **Note Credentials:**
- Copy Client ID and Client Secret
- Discovery URL: `https://auth.example.com/application/o/mcvsphere/.well-known/openid-configuration`
### Other Providers
The same pattern works with Keycloak, Auth0, Okta, etc. Key requirements:
- OIDC Discovery endpoint (`.well-known/openid-configuration`)
- JWT access tokens (not opaque)
- `groups` claim in tokens with group names
---
## OAuth Flow
```
1. Client connects to mcvsphere
→ POST /mcp (no auth)
→ Server returns 401 + OAuth metadata URL
2. Client initiates OAuth flow
→ Opens browser to OIDC provider
→ User logs in
→ Provider redirects with authorization code
3. Client exchanges code for tokens
→ POST to provider token endpoint
→ Receives JWT access token
4. Client reconnects with token
→ POST /mcp with Authorization: Bearer <jwt>
→ Server validates JWT via JWKS
→ Server extracts user + groups
→ RBACMiddleware checks permissions
→ User can invoke allowed tools
5. Tool invocation
→ Client: "power on web-server"
→ Middleware: Validate user has POWER_OPS
→ Tool: Execute pyvmomi call
→ Audit: Log with user identity
→ Client: Receive response
```
---
## Implementation Status
### Completed
- [x] OIDCProxy configuration (`auth.py`)
- [x] Permission levels and tool mappings (`permissions.py`)
- [x] RBACMiddleware with FastMCP integration (`middleware.py`)
- [x] Audit logging with user context (`audit.py`)
- [x] Server integration with OAuth + RBAC (`server.py`)
- [x] Startup banner showing OAuth/RBAC status
- [x] Security fix: deny-by-default for no groups
- [x] Authentik setup with 5 vsphere-* groups
### Future Enhancements
- [ ] Per-user vCenter credential mapping (Vault integration)
- [ ] Rate limiting per user
- [ ] Session management and token refresh
- [ ] Admin tools for permission management
- [ ] Prometheus metrics for RBAC decisions
---
## Security Considerations
1. **Default Deny**: Users without recognized groups get NO access
2. **Token Validation**: JWTs validated via OIDC provider's JWKS endpoint
3. **Audit Trail**: All operations logged with user identity
4. **Secrets**: Client secrets should be stored securely (env vars, Docker secrets, Vault)
5. **HTTPS**: Production deployments should use TLS (via Caddy, nginx, etc.)
6. **Service Account**: Use minimal vCenter permissions for the service account
---
## Troubleshooting
### "401 Unauthorized" on all requests
- Check `OAUTH_ISSUER_URL` points to valid OIDC discovery endpoint
- Verify client ID and secret match provider configuration
- Ensure token hasn't expired
### "Permission denied" errors
- Check user's group memberships in OIDC provider
- Verify groups claim is included in JWT (decode at jwt.io)
- Confirm group names match exactly (e.g., `vsphere-admins` not `vsphere_admins`)
### Token validation fails
- Ensure OIDC provider issues JWTs (not opaque tokens)
- Check signing key is configured in provider
- Verify `OAUTH_BASE_URL` matches redirect URI in provider
### Audit logs not showing user
- Check `groups` scope is requested
- Verify token contains `preferred_username` or `email` claim
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