# VPN Access Server Development Plan

## 1. Objectives

The goal of this project is to extend an OpenVPN-based VPN access server with the following custom features:

- **MAC Address Validation**: Ensure that only devices with authorized MAC addresses can connect.
- **Session Time Management**: Enforce per-user session duration policies.

## 2. System Architecture

### Components

- **OpenVPN Server**: Handles client VPN connections and enforces authentication hooks.
- **Python Access Control Scripts**: Custom scripts invoked by OpenVPN hooks (via `client-connect` and `client-disconnect`).
- **MySQL Database**: Centralized storage for user, MAC, and session management.
- **Syslog / Logging**: Logs authentication attempts, MAC rejections, and session usage.

### Architecture Flow

1. OpenVPN receives a connection attempt.
2. OpenVPN calls the Python script (`client-connect`) with client environment variables.
3. Python script queries **MySQL database** to validate:
   - User is active.
   - MAC address is allowed for the user.
   - Session time limit not exceeded.
4. If validation fails → OpenVPN rejects the session.
5. On disconnect, Python script (`client-disconnect`) updates session time in the database.

## 3. Database Schema

### `employees` table
| Column          | Type         | Notes                                              |
|-----------------|--------------|----------------------------------------------------|
| id              | INT (PK)     | Primary key                                        |
| username        | VARCHAR(255) | Unique, not null, indexed                          |
| employee_name   | VARCHAR(255) | Employee/VPN name (not null)                       |
| employee_email  | VARCHAR(255) | Unique email, indexed                              |
| is_active       | BOOLEAN      | Default TRUE, indexed                              |
| session_limit   | INT          | Max allowed session (secs)                         |
| created_at      | DATETIME     | Default CURRENT_TIMESTAMP                          |
| updated_at      | DATETIME     | Auto-updated on change                             |

**Constraints**: `UNIQUE (username)`, `UNIQUE (employee_email)`  
**Indexes**: `idx_username`, `idx_email`, `idx_active`  

---

### `mac_addresses` table
| Column        | Type         | Notes                                              |
|---------------|--------------|----------------------------------------------------|
| id            | INT (PK)     | Primary key                                        |
| employee_id   | INT (FK)     | References `employees.id` (ON DELETE CASCADE)       |
| mac           | VARCHAR(17)  | Allowed MAC address (unique per employee)           |
| created_at    | DATETIME     | Default CURRENT_TIMESTAMP                          |
| updated_at    | DATETIME     | Auto-updated on change                             |

**Constraints**: `UNIQUE (employee_id, mac)`  
**Indexes**: `idx_mac`  

---

### `sessions` table
| Column        | Type         | Notes                                              |
|---------------|--------------|----------------------------------------------------|
| id            | INT (PK)     | Primary key                                        |
| employee_id   | INT (FK)     | References `employees.id` (ON DELETE CASCADE)       |
| start_time    | DATETIME     | Connection start (not null), indexed               |
| end_time      | DATETIME     | Connection end, indexed                            |
| duration      | INT          | Session length in seconds                          |
| created_at    | DATETIME     | Default CURRENT_TIMESTAMP                          |
| updated_at    | DATETIME     | Auto-updated on change                             |

**Indexes**: `idx_user_id`, `idx_start_time`, `idx_end_time`  


## 4. Python Script Design

### `client-connect.py`
- Input: OpenVPN environment vars (`common_name`, `ifconfig_pool_remote_ip`, `trusted_ip`, etc.).
- Workflow:
  1. Extract username and MAC from environment.
  2. Query database:
     - Check if user is active.
     - Check if MAC is in allowed list.
     - Check total session duration for today vs. `session_limit`.
  3. If pass → allow connection, insert row into `sessions` with `start_time`.
  4. If fail → exit with error code (OpenVPN rejects).

### `client-disconnect.py`
- Input: OpenVPN environment vars.
- Workflow:
  1. Lookup current session by user and start time.
  2. Update `end_time` and `duration` in `sessions`.
  3. Commit changes to DB.

## 5. Development Plan

### Phase 1: Environment Setup
- Configure OpenVPN server with `client-connect` and `client-disconnect` hooks.
- Setup Python virtual environment under `/etc/openvpn/access`.
- Setup **MySQL database** schema.

### Phase 2: Database Integration
- Write Python database utility module for MySQL connection pooling.
- Test CRUD operations on `users`, `mac_addresses`, and `sessions`.

### Phase 3: Client Validation Logic
- Implement `client-connect.py` logic for user/MAC/session validation.
- Implement `client-disconnect.py` for session tracking.

### Phase 4: Testing
- Unit test Python scripts with mock environment variables.
- Integration test with OpenVPN clients.

### Phase 5: Deployment
- Deploy Python scripts into `/etc/openvpn/access`.
- Secure DB credentials with `.env` or config file.
- Harden OpenVPN server config.

## 6. Security Considerations
- Use parameterized SQL queries to prevent injection.
- Secure DB access with strong user/password, TLS if available.
- Log all failed validation attempts.
- Apply principle of least privilege for DB accounts.
# VPN Access Server Development Plan

## 1. Objectives
- Validate client MAC addresses during VPN authentication.
- Manage session time (e.g., max duration, timeout) per user.
- Store and manage data in MySQL.
- Provide an extensible Python-based server-side solution for OpenVPN integration.

---

## 2. System Architecture

### Components
1. **OpenVPN Server**  
   - Uses TUN mode.  
   - Forwards traffic to the NAS subnet (`172.16.14.0/24`) via the Ubuntu VPN gateway.  
   - Executes external Python scripts for authentication and session management.  

2. **VPN Access Server (Python)**  
   - Python service located under `/etc/openvpn/access/`.  
   - Handles MAC validation and session management logic.  
   - Directly interacts with **MySQL** for data persistence (no extra management tool needed).  

3. **MySQL Database**  
   - Stores user credentials, MAC addresses, and session details.  
   - Provides logs for auditing.  

---

---
#### Recommended Project Structure
```
vpn-access-server/
│
├── access/                     # Core Python scripts (linked to OpenVPN)
│   ├── __init__.py
│   ├── auth.py                 # User authentication & MAC validation
│   ├── session.py              # Session tracking and enforcement
│   ├── db.py                   # MySQL connection and queries
│   ├── utils.py                # Shared utilities
│   └── config.py               # Config loader (DB creds, constants)
│
├── tests/                      # Unit & integration tests
│   ├── test_auth.py
│   ├── test_session.py
│   └── test_db.py
│
├── scripts/                    # Helper scripts (migration, DB setup)
│   ├── init_db.py
│   └── seed_data.py
│
├── requirements.txt            # Python dependencies
├── README.md                   # Documentation
```

This structure follows a **modular layered architecture** (separating auth, session, db, utils).  
It is clean, scalable, and easy to maintain.  

---