Payment Authentication

import os
import requests

def authenticate_payment(payment, cardholder):
    res = requests.post(
        "https://api.facesign.ai/sessions",
        headers={
            "Authorization": f"Bearer {os.environ['FACESIGN_API_KEY']}",
            "Content-Type": "application/json",
        },
        json={
            "clientReferenceId": f"pay-{payment['order_id']}",
            "metadata": {
                "orderId": payment["order_id"],
                "amount": payment["amount"],
                "currency": payment["currency"],
                "merchantName": payment["merchant_name"],
                "cardLast4": payment["card_last4"],
                "riskReason": payment["risk_reason"],
            },
            "providedData": {
                "email": cardholder["email"],
            },
            "flow": [
                {"id": "start", "type": "start", "outcome": "greeting"},
                {
                    "id": "greeting",
                    "type": "conversation",
                    "prompt": (
                        "Say: Hi! I need to verify a payment on your card "
                        "before we can complete the purchase. It only takes a "
                        "few seconds — I'll take a quick look, then read the "
                        "payment details back to you."
                    ),
                    "outcomes": [
                        {"id": "next", "targetNodeId": "liveness", "condition": ""}
                    ],
                },
                {
                    "id": "liveness",
                    "type": "liveness_detection",
                    "outcomes": {
                        "livenessDetected": "confirm_payment",
                        "deepfakeDetected": "closing",
                        "noFace": "closing",
                    },
                },
                {
                    "id": "confirm_payment",
                    "type": "conversation",
                    "prompt": (
                        f"Say: I need to verify a payment on your card ending in "
                        f"{payment['card_last4']}. You're authorizing a charge of "
                        f"{payment['amount']} {payment['currency']} to "
                        f"{payment['merchant_name']}. Can you confirm this purchase "
                        f"is yours?"
                    ),
                    "outcomes": [
                        {
                            "id": "confirmed",
                            "targetNodeId": "email_otp",
                            "condition": "The user explicitly confirmed the payment is theirs",
                        },
                        {
                            "id": "denied",
                            "targetNodeId": "closing",
                            "condition": "The user denied the payment, did not recognize it, or disputed any of the details",
                        },
                        {
                            "id": "stall",
                            "targetNodeId": "closing",
                            "condition": "Conversation reached 4 exchanges with no clear answer",
                        },
                    ],
                },
                {
                    "id": "email_otp",
                    "type": "two_factor_email",
                    "otpLength": 6,
                    "expirySeconds": 300,
                    "outcomes": {
                        "verified": "closing",
                        "delivery_failed": "closing",
                        "failed_unverified": "closing",
                        "cancelled": "closing",
                    },
                },
                {
                    "id": "closing",
                    "type": "conversation",
                    "prompt": (
                        "Thank the user for completing the verification and "
                        "tell them the session is now complete. Keep it to one sentence."
                    ),
                    "doesNotRequireReply": True,
                    "outcomes": [
                        {"id": "done", "targetNodeId": "end", "condition": ""}
                    ],
                },
                {"id": "end", "type": "end"},
            ],
            "videoAIAnalysisEnabled": True,
        },
    )

    data = res.json()
    session = data["session"]
    client_secret = data["clientSecret"]

    # Hold the payment until verification completes
    db.payments.update(
        payment["order_id"],
        status="pending_authentication",
        facesign_session_id=session["id"],
    )

    return client_secret["url"]

import hmac, hashlib, json, os
from flask import Flask, request, jsonify, abort
import requests

app = Flask(__name__)


def verify_facesign_signature(raw_body: bytes, signature_header: str, secret: str) -> bool:
    """HMAC-SHA256 of ``{timestamp}.{raw_body}`` must match ``v1`` in the header."""
    if not signature_header:
        return False
    try:
        parts = dict(p.split("=", 1) for p in signature_header.split(","))
    except ValueError:
        return False
    if "t" not in parts or "v1" not in parts:
        return False
    expected = hmac.new(
        secret.encode("utf-8"),
        f"{parts['t']}.".encode("utf-8") + raw_body,
        hashlib.sha256,
    ).hexdigest()
    return hmac.compare_digest(parts["v1"], expected)


@app.route("/webhooks/facesign", methods=["POST"])
def handle_webhook():
    # Read the raw body before parsing — signature is computed over the
    # exact bytes we received.
    raw_body = request.get_data()
    signature = request.headers.get("X-FaceSign-Signature")

    if not verify_facesign_signature(
        raw_body, signature, os.environ["FACESIGN_WEBHOOK_SECRET"]
    ):
        abort(401, description="Invalid signature")

    event = json.loads(raw_body)

    if event["type"] != "session.status":
        return jsonify({"received": True}), 200

    # Fetch the full session. GET /sessions/:id returns
    # {"session": ..., "clientSecret": ...} — unpack the inner session.
    session_res = requests.get(
        f"https://api.facesign.ai/sessions/{event['sessionId']}",
        headers={
            "Authorization": f"Bearer {os.environ['FACESIGN_API_KEY']}",
        },
    )
    session = session_res.json()["session"]

    payment = db.payments.find_by(
        facesign_session_id=event["sessionId"]
    )

    if not payment:
        return jsonify({"received": True}), 200

    # Check all verification steps
    node_reports = (session.get("report") or {}).get("nodeReports") or []
    liveness_report = next(
        (r for r in node_reports if r["nodeId"] == "liveness"), None
    )
    otp_report = next(
        (r for r in node_reports if r["nodeId"] == "email_otp"), None
    )

    liveness_pass = (
        liveness_report
        and liveness_report.get("outcome") == "livenessDetected"
    )
    otp_pass = otp_report and otp_report.get("outcome") == "verified"
    session_complete = session["status"] == "complete"

    if session_complete and liveness_pass and otp_pass:
        # Authorize the payment
        db.payments.update(
            payment["order_id"],
            status="authenticated",
        )
        payment_processor.authorize(
            payment["order_id"],
            authentication_method="facesign",
            session_id=session["id"],
        )
    else:
        # Decline the payment
        db.payments.update(
            payment["order_id"],
            status="authentication_failed",
            failure_reason="liveness_failed" if not liveness_pass else "otp_failed",
        )
        payment_processor.decline(
            payment["order_id"],
            reason="step_up_authentication_failed",
        )

    return jsonify({"received": True}), 200