wip: adds datatrans proof of concept
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Livio Bieri
Christian Cueni
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296ae32c9a
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# Datatrans - Proof of Concept
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## Links
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- https://admin.sandbox.datatrans.com
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- https://api-reference.datatrans.ch/#section/Idempotency
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- https://docs.datatrans.ch/docs/redirect-lightbox#section-initializing-transactions
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## Code
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Simple example of the payment flow with Datatrans:
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```python
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from flask import Flask, request, render_template_string, jsonify, abort
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import uuid
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import hmac
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import hashlib
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import requests
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import os
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app = Flask(__name__)
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if "HMAC_KEY" not in os.environ:
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exit("Please set the HMAC_KEY environment variable.")
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if "BASIC_AUTH" not in os.environ:
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exit("Please set the BASIC_AUTH environment variable.")
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# https://admin.sandbox.datatrans.com/MerchSecurAdmin.jsp
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HMAC_KEY = os.environ["HMAC_KEY"]
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BASIC_AUTH = os.environ["BASIC_AUTH"]
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API_ENDPOINT = "https://api.sandbox.datatrans.com/v1/transactions"
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LIGHTBOX_PAGE = """
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<html>
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<head>
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<script src="https://pay.sandbox.datatrans.com/upp/payment/js/datatrans-2.0.0.js"></script>
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</head>
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<body>
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<button id="payButton">Pay Now</button>
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<script>
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var payButton = document.getElementById('payButton');
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payButton.onclick = function() {
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Datatrans.startPayment({
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transactionId: "{{ transaction_id }}",
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opened: function() { console.log('payment-form opened'); },
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loaded: function() { console.log('payment-form loaded'); },
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closed: function() { console.log('payment-page closed'); },
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error: function(errorData) { console.log('error', errorData); }
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});
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};
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</script>
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</body>
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</html>
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"""
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SUCCESS_PAGE = "<html><body><h1>Payment Success</h1></body></html>"
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ERROR_PAGE = "<html><body><h1>Payment Error</h1></body></html>"
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CANCEL_PAGE = "<html><body><h1>Payment Cancelled</h1></body></html>"
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# TODO: There is now way to test this locally, so we need to use ngrok (?)
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BASE_URL = "https://89d3-2a02-21b4-9679-d800-ac5f-489-e9f6-694e.ngrok-free.app"
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@app.route("/success", methods=["GET"])
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def success():
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return render_template_string(SUCCESS_PAGE)
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@app.route("/error", methods=["GET"])
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def error():
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return render_template_string(ERROR_PAGE)
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@app.route("/cancel", methods=["GET"])
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def cancel():
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return render_template_string(CANCEL_PAGE)
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@app.route("/init_transaction", methods=["GET"])
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def init_transaction():
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# TODO
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# for debugging, it might be handy to know the
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# user who initiated the transaction
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refno = uuid.uuid4().hex
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# TODO
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# The language of user
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language = "en"
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# Transaction payload
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payload = {
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"currency": "CHF",
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"refno": refno,
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"amount": 10_00, # 10 CHF
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"autoSettle": True,
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"language": language,
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"redirect": {
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"successUrl": f"{BASE_URL}/success",
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"errorUrl": f"{BASE_URL}/error",
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"cancelUrl": f"{BASE_URL}/cancel",
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},
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"webhook": {
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"url": f"{BASE_URL}/webhook",
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},
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}
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# Headers
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headers = {
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"Authorization": f"Basic {BASIC_AUTH}",
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"Content-Type": "application/json",
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}
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# 1. USING LIGHTBOX
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response = requests.post(API_ENDPOINT, json=payload, headers=headers)
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if response.ok:
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transaction_id = response.json().get("transactionId")
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return render_template_string(LIGHTBOX_PAGE, transaction_id=transaction_id)
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else:
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return (
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jsonify(
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{"error": "Failed to initiate transaction", "details": response.text}
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),
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response.status_code,
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)
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# 2. USING REDIRECT
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# # Send POST request to Datatrans API
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# response = requests.post(url, json=payload, headers=headers)
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# if response.ok:
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# transaction_id = response.json().get('transactionId')
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# payment_url = f'https://pay.sandbox.datatrans.com/v1/start/{transaction_id}'
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# return redirect(payment_url)
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# else:
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# # Return error message
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# return jsonify({"error": "Failed to initiate transaction", "details": response.text}), response.status_code
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@app.route("/webhook", methods=["POST"])
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def webhook():
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"""
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Checks the Datatrans-Signature header of the incoming request and validates the signature:
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https://api-reference.datatrans.ch/#section/Webhook/Webhook-signing
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"""
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hmac_key = HMAC_KEY
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def calculate_signature(key: str, timestamp: str, payload: str) -> str:
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key_bytes = bytes.fromhex(key)
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signing_data = f"{timestamp}{payload}".encode("utf-8")
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hmac_obj = hmac.new(key_bytes, signing_data, hashlib.sha256)
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return hmac_obj.hexdigest()
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# Header format:
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# Datatrans-Signature: t={{timestamp}},s0={{signature}}
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datatrans_signature = request.headers.get("Datatrans-Signature", "")
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try:
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parts = datatrans_signature.split(",")
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timestamp = parts[0].split("=")[1]
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received_signature = parts[1].split("=")[1]
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calculated_signature = calculate_signature(
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hmac_key, timestamp, request.data.decode("utf-8")
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)
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if calculated_signature == received_signature:
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return "Signature validated.", 200
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else:
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abort(400, "Invalid signature.")
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except (IndexError, ValueError):
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abort(400, "Invalid Datatrans-Signature header.")
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if __name__ == "__main__":
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app.run(debug=True, host="0.0.0.0", port=5500)
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```
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