Python, Flask for REST Tx

Chapters:

Install Flask on Redhat (repo available)

sudo dnf install python3-flask

🚀 Run Flask App (No pip needed)

Save the app.py somewhere (e.g., /home/tux/transferdepot/app.py)
Run it directly:

python3 /home/tux/transferdepot/app.py

Or set FLASK_APP and use the built-in CLI:

export FLASK_APP=app.py
flask run --host=0.0.0.0 --port=8080

📍 Flask RPM Notes on RHEL 8

Package: python3-flask
Installed location: /usr/lib/python3.6/site-packages/flask/
Installed with all dependencies (Werkzeug, Jinja2, etc.)
Managed by dnf, not pip = easy maintenance in air-gapped setup

Define two Routes

| Route                  | Method | Description                                                      |
| ---------------------- | ------ | ---------------------------------------------------------------- |
| `/upload`              | POST   | Accepts file upload (requires `Authorization: Bearer SECRET123`) |
| `/download/<filename>` | GET    | Downloads a file from the upload folder                          |

This is our basic app.py - before customization with two routes: upload, download

from flask import Flask, request, send_from_directory
import os

app = Flask(__name__)
UPLOAD_FOLDER = '/opt/transferdepot/uploads'
os.makedirs(UPLOAD_FOLDER, exist_ok=True)

@app.route('/upload', methods=['POST'])
def upload():
    token = request.headers.get('Authorization')
    if token != 'Bearer SECRET123':
        return 'Unauthorized', 401
    file = request.files['file']
    filepath = os.path.join(UPLOAD_FOLDER, file.filename)
    file.save(filepath)
    return 'File uploaded successfully', 200

@app.route('/download/<filename>', methods=['GET'])
def download(filename):
    return send_from_directory(UPLOAD_FOLDER, filename)

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8080)

How to Run

python3 /home/tux/transferdepot/app.py

Or use Flask CLI:

export FLASK_APP=/home/tux/transferdepot/app.py
flask run --host=0.0.0.0 --port=8080

First customization:

Add Zones

/opt/transferdepot/
├── logs/
└── zones/
    ├── MSE/
    ├── MP/
    ├── TTCS/
    └── RS2/

Assumption: Each directory is used for both uploads and downloads within that zone — file goes in, file gets picked up later from the same spot.

(Optional) - Add /wormhole Endpoint

A fun (and secure) route for transferring files between zones in a special manner (perhaps a "faster" or "VIP" route). This could be a unique endpoint for certain high-priority transfers.

Updated `app.py` with Zone-Based Logic

from flask import Flask, request, send_from_directory, abort
import os

app = Flask(__name__)
UPLOAD_ROOT = '/opt/transferdepot/uploads'
ZONES = ['MSE', 'MP', 'TTCS', 'RS2']

# Make sure zone folders exist
for zone in ZONES:
    os.makedirs(os.path.join(UPLOAD_ROOT, zone), exist_ok=True)

@app.route('/upload/<zone>', methods=['POST'])
def upload(zone):
    if zone not in ZONES:
        return 'Invalid zone', 400

    token = request.headers.get('Authorization')
    if token != f'Bearer {zone}123':
        return 'Unauthorized', 401

    if 'file' not in request.files:
        return 'No file part', 400

    file = request.files['file']
    save_path = os.path.join(UPLOAD_ROOT, zone, file.filename)
    file.save(save_path)
    return 'File uploaded to zone successfully', 200

@app.route('/download/<zone>/<filename>', methods=['GET'])
def download(zone, filename):
    if zone not in ZONES:
        abort(404)
    return send_from_directory(os.path.join(UPLOAD_ROOT, zone), filename)

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8080)

🚀 The upload and download were eventually removed because I couldn't figure out what they were used for. It didn't work. We can put them back in for a good reason, but not because they used to be there.

Tests

Test Upload (from same machine or Frodo)

curl -X POST http://localhost:8080/upload/MSE/dropoff \
  -H "Authorization: Bearer MSE123" \
  -F "file=@myfile.txt"

Test Download

curl -O http://localhost:8080/download/MSE/pickup/b0b.txt

Result:

secret.txt should download to current directory
activity.jsonl gets a log entry

Current State

TransferDepot app (app.py) is built and ready. ✅
- Basic routes for upload and download are in place. ✅
- Zone-based directories (dropoff, pickup) are being created on the fly. ✅
- Logging is active, storing each file transfer in activity.jsonl. ✅
- Authentication via bearer tokens (Bearer <zone>123).

Next Steps -- TBD -- after demo and approval --

Here are a few things we can add with ease:

1. More Robust Security (Optional)

Stronger token handling: Instead of using hardcoded Bearer <zone>123, we could introduce a more flexible method of handling authentication — perhaps with a shared secrets file or token generation system.
IP whitelisting: Ensure that only trusted machines/servers can interact with the TransferDepot.

2. Add `/status` Endpoint (Optional)

Show the current status of the TransferDepot, such as:
- Total number of files uploaded.
- Size of current transfer directories.
- Last 10 logs (for quick checks).
- Zone status (available dropoff/pickup spaces).

3. Advanced Logging (Optional)

Currently, the app logs transfers to a single activity.jsonl. We can:
- Expand logging to log failed attempts, errors, etc.
- Set up file rotation to prevent activity.jsonl from growing too large.
- Store logs separately per zone, if you want more detailed analysis per zone.

4. Add /wormhole Endpoint (Optional)

A fun (and secure) route for transferring files between zones in a special manner (perhaps a "faster" or "VIP" route). This could be a unique endpoint for certain high-priority transfers.

5. Systemd Integration

Turn the app into a systemd service so it starts automatically when the machine boots up. This would ensure TransferDepot runs persistently without needing manual python3 app.py every time.

Example systemd service file:

[Unit]
Description=TransferDepot Service
After=network.target

[Service]
User=tux
WorkingDirectory=/home/tux/transferdepot
ExecStart=/usr/bin/python3 /home/tux/transferdepot/app.py
Restart=always

[Install]
WantedBy=multi-user.target

6. Testing and Monitoring (Optional)

Use curl to run tests across zones and check the logs.
Monitor performance, especially as file sizes increase, to see if you hit any memory or performance issues with large uploads.

Flask App