PCI DSS Compliance for ChatGPT Apps with Payment Processing

The Payment Card Industry Data Security Standard (PCI DSS) represents the gold standard for protecting cardholder data in digital applications. For ChatGPT apps that process payments, achieving PCI DSS compliance isn't optional—it's a legal and operational imperative that protects both your business and your customers.

Understanding PCI DSS 4.0 Requirements

PCI DSS 4.0, released in March 2022 and mandatory as of March 2026, establishes 12 key requirements organized into six control objectives:

  1. Build and Maintain a Secure Network (Requirements 1-2)
  2. Protect Cardholder Data (Requirements 3-4)
  3. Maintain a Vulnerability Management Program (Requirements 5-6)
  4. Implement Strong Access Control Measures (Requirements 7-9)
  5. Regularly Monitor and Test Networks (Requirements 10-11)
  6. Maintain an Information Security Policy (Requirement 12)

The standard applies to any organization that stores, processes, or transmits cardholder data. Violations carry severe penalties: the Payment Card Industry Security Standards Council can impose fines up to $500,000 per incident, and your merchant account can be terminated.

SAQ Levels: Choosing Your Compliance Path

The Self-Assessment Questionnaire (SAQ) level determines your compliance burden:

  • SAQ A (22 questions): Merchants who fully outsource payment processing to PCI DSS validated third parties (like Stripe Checkout)
  • SAQ A-EP (181 questions): E-commerce merchants with payment pages hosted on merchant website but outsourcing processing
  • SAQ D (329 questions): Merchants storing, processing, or transmitting cardholder data on their systems

For most ChatGPT apps, SAQ A is the optimal approach—redirect users to Stripe-hosted payment pages and never touch cardholder data. This article shows you how to architect your ChatGPT payment integration for SAQ-A compliance while maintaining security best practices across all 12 PCI DSS requirements.


Tokenization Strategy: Never Store Card Data

The cardinal rule of PCI DSS compliance: never store, process, or transmit cardholder data in your ChatGPT app. Tokenization replaces sensitive card data with non-sensitive tokens that can be safely stored and transmitted.

The Tokenization Flow

  1. Client-side tokenization: User enters card details in a Stripe-provided UI component (Payment Element)
  2. Stripe generates token: Card data is sent directly to Stripe's servers via TLS 1.3
  3. Your app receives token: Stripe returns a PaymentMethod ID (e.g., pm_1234567890abcdef)
  4. Process payment: Your backend uses the token to create charges—never sees the actual card number

This architecture ensures your ChatGPT app never enters PCI DSS scope for cardholder data storage.

Stripe Payment Elements Integration

Stripe's Payment Element provides a pre-built, PCI-compliant card input form that handles tokenization automatically:

// frontend/payment-form.ts
import { loadStripe, Stripe, StripeElements } from '@stripe/stripe-js';

/**
 * PCI DSS Compliant Payment Form Component
 * Uses Stripe Payment Elements for client-side tokenization
 *
 * Requirements Met:
 * - REQ 3.2: No storage of sensitive authentication data post-authorization
 * - REQ 4.2: Never send unprotected PANs by end-user messaging technologies
 */
export class PaymentFormManager {
  private stripe: Stripe | null = null;
  private elements: StripeElements | null = null;
  private paymentElement: any = null;

  constructor(private publishableKey: string) {}

  /**
   * Initialize Stripe.js with publishable key
   * Publishable keys are safe to expose client-side
   */
  async initialize(): Promise<void> {
    this.stripe = await loadStripe(this.publishableKey);

    if (!this.stripe) {
      throw new Error('Failed to load Stripe.js');
    }

    // Create elements instance with appearance customization
    this.elements = this.stripe.elements({
      appearance: {
        theme: 'stripe',
        variables: {
          colorPrimary: '#0A0E27',
          colorBackground: '#ffffff',
          colorText: '#30313d',
          colorDanger: '#df1b41',
          fontFamily: 'Inter, system-ui, sans-serif',
          borderRadius: '4px',
        },
      },
      // Client secret from backend payment intent
      clientSecret: await this.fetchClientSecret(),
    });

    // Mount Payment Element to DOM
    this.paymentElement = this.elements.create('payment');
    this.paymentElement.mount('#payment-element');
  }

  /**
   * Fetch PaymentIntent client secret from backend
   * Backend creates PaymentIntent, frontend completes it
   */
  private async fetchClientSecret(): Promise<string> {
    const response = await fetch('/api/payments/create-intent', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${this.getAccessToken()}`,
      },
      body: JSON.stringify({
        amount: 14900, // $149.00 in cents
        currency: 'usd',
        metadata: {
          userId: this.getUserId(),
          plan: 'professional',
        },
      }),
    });

    if (!response.ok) {
      throw new Error('Failed to create payment intent');
    }

    const { clientSecret } = await response.json();
    return clientSecret;
  }

  /**
   * Confirm payment with tokenized card data
   * Card data never passes through your servers
   */
  async confirmPayment(): Promise<{ success: boolean; error?: string }> {
    if (!this.stripe || !this.elements) {
      throw new Error('Stripe not initialized');
    }

    const { error } = await this.stripe.confirmPayment({
      elements: this.elements,
      confirmParams: {
        return_url: `${window.location.origin}/payment-success`,
      },
    });

    if (error) {
      // Payment failed - show error to user
      return {
        success: false,
        error: error.message,
      };
    }

    // Payment succeeded - user will be redirected to return_url
    return { success: true };
  }

  /**
   * Get authenticated user access token
   * PCI DSS Req 7.1: Limit access to system components
   */
  private getAccessToken(): string {
    // Retrieve from secure session storage
    return sessionStorage.getItem('accessToken') || '';
  }

  /**
   * Get authenticated user ID
   * PCI DSS Req 8.1: Assign unique ID to each user
   */
  private getUserId(): string {
    return sessionStorage.getItem('userId') || '';
  }
}

// Usage in ChatGPT widget
const paymentForm = new PaymentFormManager('pk_live_...');
await paymentForm.initialize();

// When user clicks "Pay Now"
const result = await paymentForm.confirmPayment();
if (result.success) {
  console.log('Payment processing...');
} else {
  console.error('Payment failed:', result.error);
}

This implementation ensures your ChatGPT app never handles raw card data—Stripe Payment Elements tokenizes the card on the client side, and your backend only receives non-sensitive tokens.

For detailed integration steps, see our guide on Stripe Payment Integration for ChatGPT Apps.


Network Security: Protecting Payment Infrastructure

PCI DSS Requirements 1 and 2 mandate robust network security controls to isolate payment systems from untrusted networks.

Firewall Configuration Requirements

Requirement 1.2.1: Install and maintain firewall configurations to protect cardholder data environment (CDE):

// infrastructure/firewall-rules.ts
/**
 * Google Cloud Firewall Rules for PCI DSS Compliance
 *
 * Requirements Met:
 * - REQ 1.2.1: Restrict inbound/outbound traffic to that necessary for CDE
 * - REQ 1.3.1: Implement DMZ to limit inbound traffic to protocols necessary
 */

export const pciFirewallRules = {
  // Rule 1: Deny all inbound traffic by default
  default_deny_ingress: {
    priority: 65534,
    direction: 'INGRESS',
    action: 'deny',
    sourceRanges: ['0.0.0.0/0'],
    description: 'PCI DSS 1.2.1: Default deny all inbound',
  },

  // Rule 2: Allow only HTTPS (443) for payment endpoints
  allow_payment_https: {
    priority: 1000,
    direction: 'INGRESS',
    action: 'allow',
    sourceRanges: ['0.0.0.0/0'],
    targetTags: ['payment-gateway'],
    allowed: [
      {
        IPProtocol: 'tcp',
        ports: ['443'], // HTTPS only
      },
    ],
    description: 'PCI DSS 1.3.1: Allow HTTPS for payment processing',
  },

  // Rule 3: Restrict Stripe webhook IPs
  allow_stripe_webhooks: {
    priority: 1001,
    direction: 'INGRESS',
    action: 'allow',
    sourceRanges: [
      '3.18.12.63/32',
      '3.130.192.231/32',
      '13.235.14.237/32',
      '13.235.122.149/32',
      // ... all Stripe webhook IPs
    ],
    targetTags: ['webhook-handler'],
    allowed: [
      {
        IPProtocol: 'tcp',
        ports: ['443'],
      },
    ],
    description: 'PCI DSS 1.3.4: Allow only Stripe webhook IPs',
  },

  // Rule 4: Block all database direct access
  deny_database_public: {
    priority: 900,
    direction: 'INGRESS',
    action: 'deny',
    sourceRanges: ['0.0.0.0/0'],
    targetTags: ['database'],
    denied: [
      {
        IPProtocol: 'tcp',
        ports: ['5432', '3306', '27017'], // PostgreSQL, MySQL, MongoDB
      },
    ],
    description: 'PCI DSS 1.3.2: No direct database access from internet',
  },

  // Rule 5: Allow internal VPC traffic only
  allow_internal_vpc: {
    priority: 1002,
    direction: 'INGRESS',
    action: 'allow',
    sourceRanges: ['10.0.0.0/8'], // Internal VPC CIDR
    targetTags: ['payment-gateway', 'database', 'backend'],
    allowed: [
      {
        IPProtocol: 'tcp',
        ports: ['1-65535'],
      },
    ],
    description: 'PCI DSS 1.2.1: Allow internal VPC communication',
  },
};

Network Segmentation

Isolate payment processing systems from other application components:

  • Payment Gateway Subnet: 10.0.1.0/24 (isolated, restricted egress)
  • Application Subnet: 10.0.2.0/24 (public-facing, no cardholder data)
  • Database Subnet: 10.0.3.0/24 (private, no internet access)

TLS 1.3 Encryption in Transit

Requirement 4.1: Use strong cryptography for transmission of cardholder data across open, public networks:

// backend/payment-gateway.ts
import express from 'express';
import helmet from 'helmet';

const app = express();

// PCI DSS Req 4.1: Strong TLS configuration
app.use(helmet({
  hsts: {
    maxAge: 31536000, // 1 year
    includeSubDomains: true,
    preload: true,
  },
  frameguard: {
    action: 'deny', // Prevent clickjacking
  },
}));

// Enforce TLS 1.3 minimum (disable TLS 1.2 after June 2026)
const tlsOptions = {
  minVersion: 'TLSv1.3',
  ciphers: [
    'TLS_AES_128_GCM_SHA256',
    'TLS_AES_256_GCM_SHA384',
    'TLS_CHACHA20_POLY1305_SHA256',
  ].join(':'),
};

For complete encryption strategies, see Data Encryption for ChatGPT Apps.


Access Controls: Restricting Payment Data Access

PCI DSS Requirements 7-9 mandate strict access controls to ensure only authorized personnel can access payment systems.

Principle of Least Privilege

Requirement 7.1.2: Assign access based on job classification and function:

// backend/middleware/payment-access-control.ts
import { Request, Response, NextFunction } from 'express';
import { auth } from 'firebase-admin';

/**
 * PCI DSS Access Control Middleware
 *
 * Requirements Met:
 * - REQ 7.1.1: Limit access to system components to authorized users
 * - REQ 7.1.2: Assign access based on job function
 * - REQ 8.1.1: Assign unique ID to each user with access
 */

enum PaymentRole {
  PAYMENT_ADMIN = 'payment_admin',     // Full access to payment systems
  PAYMENT_VIEWER = 'payment_viewer',   // Read-only access to transactions
  CUSTOMER = 'customer',               // Can only view own transactions
  SUPPORT = 'support',                 // Can view transactions, no refunds
}

export class PaymentAccessControl {
  /**
   * Verify user has required role for payment operation
   */
  static requireRole(...allowedRoles: PaymentRole[]) {
    return async (req: Request, res: Response, next: NextFunction) => {
      try {
        // Extract and verify Firebase Auth token
        const authHeader = req.headers.authorization;
        if (!authHeader?.startsWith('Bearer ')) {
          return res.status(401).json({
            error: 'Unauthorized',
            message: 'Missing or invalid authorization header',
          });
        }

        const idToken = authHeader.split('Bearer ')[1];
        const decodedToken = await auth().verifyIdToken(idToken);

        // PCI DSS Req 8.1.1: Verify unique user ID
        const userId = decodedToken.uid;
        if (!userId) {
          return res.status(401).json({
            error: 'Unauthorized',
            message: 'Invalid user ID',
          });
        }

        // Retrieve user custom claims (roles assigned via Admin SDK)
        const userRecord = await auth().getUser(userId);
        const userRole = userRecord.customClaims?.paymentRole as PaymentRole;

        // Check if user has required role
        if (!allowedRoles.includes(userRole)) {
          // PCI DSS Req 10.2.5: Log unauthorized access attempts
          await this.logAccessAttempt({
            userId,
            email: decodedToken.email || 'unknown',
            attemptedRole: allowedRoles,
            actualRole: userRole,
            endpoint: req.path,
            timestamp: new Date(),
            result: 'DENIED',
          });

          return res.status(403).json({
            error: 'Forbidden',
            message: 'Insufficient permissions for this operation',
          });
        }

        // PCI DSS Req 10.2.2: Log all access to payment data
        await this.logAccessAttempt({
          userId,
          email: decodedToken.email || 'unknown',
          role: userRole,
          endpoint: req.path,
          timestamp: new Date(),
          result: 'GRANTED',
        });

        // Attach user info to request for downstream handlers
        req.user = {
          uid: userId,
          email: decodedToken.email,
          role: userRole,
        };

        next();
      } catch (error) {
        console.error('Access control error:', error);
        return res.status(401).json({
          error: 'Unauthorized',
          message: 'Token verification failed',
        });
      }
    };
  }

  /**
   * Log access attempts for PCI DSS compliance
   * REQ 10.2: Implement automated audit trails
   */
  private static async logAccessAttempt(event: any): Promise<void> {
    // Write to secure audit log (Google Cloud Logging)
    const { Logging } = require('@google-cloud/logging');
    const logging = new Logging();
    const log = logging.log('pci-access-audit');

    const metadata = {
      resource: { type: 'cloud_function' },
      severity: event.result === 'DENIED' ? 'WARNING' : 'INFO',
    };

    const entry = log.entry(metadata, event);
    await log.write(entry);
  }
}

// Usage in payment routes
import { Router } from 'express';
const router = Router();

// Only payment admins can issue refunds
router.post(
  '/refund',
  PaymentAccessControl.requireRole(PaymentRole.PAYMENT_ADMIN),
  async (req, res) => {
    // Refund logic here
  }
);

// Support and admins can view all transactions
router.get(
  '/transactions',
  PaymentAccessControl.requireRole(
    PaymentRole.PAYMENT_ADMIN,
    PaymentRole.PAYMENT_VIEWER,
    PaymentRole.SUPPORT
  ),
  async (req, res) => {
    // Fetch transactions
  }
);

// Customers can only view their own transactions
router.get(
  '/my-transactions',
  PaymentAccessControl.requireRole(PaymentRole.CUSTOMER),
  async (req, res) => {
    const userId = req.user.uid;
    // Fetch only transactions for this userId
  }
);

Multi-Factor Authentication

Requirement 8.3.1: Require MFA for all administrative access to payment systems:

// Enable MFA enforcement in Firebase Auth
import { auth } from 'firebase-admin';

async function enforcePaymentAdminMFA(userId: string): Promise<void> {
  const userRecord = await auth().getUser(userId);

  // Check if user has payment admin role
  if (userRecord.customClaims?.paymentRole === 'payment_admin') {
    // Require MFA enrollment
    if (!userRecord.multiFactor?.enrolledFactors?.length) {
      throw new Error('Payment admins must enroll in multi-factor authentication');
    }
  }
}

For comprehensive access control patterns, see Security Auditing and Logging.


Monitoring and Testing: Continuous Security Validation

PCI DSS Requirements 10 and 11 mandate continuous monitoring and regular security testing.

Security Event Logging

Requirement 10.2: Log all access to cardholder data and system components:

// backend/middleware/pci-audit-logger.ts
import { Logging } from '@google-cloud/logging';

/**
 * PCI DSS Compliant Audit Logger
 *
 * Requirements Met:
 * - REQ 10.2.1: Log all individual user accesses to cardholder data
 * - REQ 10.2.2: Log all actions by privileged users
 * - REQ 10.2.4: Log invalid logical access attempts
 * - REQ 10.2.5: Log use of identification and authentication mechanisms
 * - REQ 10.3: Record required audit trail entries for each event
 */

export enum AuditEventType {
  PAYMENT_CREATED = 'payment.created',
  PAYMENT_SUCCEEDED = 'payment.succeeded',
  PAYMENT_FAILED = 'payment.failed',
  REFUND_ISSUED = 'refund.issued',
  ACCESS_GRANTED = 'access.granted',
  ACCESS_DENIED = 'access.denied',
  CONFIG_CHANGED = 'config.changed',
  USER_LOGIN = 'user.login',
  USER_LOGOUT = 'user.logout',
}

interface AuditEvent {
  type: AuditEventType;
  userId: string;
  email?: string;
  timestamp: Date;
  result: 'SUCCESS' | 'FAILURE';
  metadata?: Record<string, any>;
}

export class PCIAuditLogger {
  private logging: Logging;
  private log: any;

  constructor() {
    this.logging = new Logging();
    this.log = this.logging.log('pci-audit-trail');
  }

  /**
   * Log audit event with required PCI DSS fields
   * REQ 10.3: Record at minimum: user ID, event type, date/time,
   * success/failure, origination, affected resource
   */
  async logEvent(event: AuditEvent): Promise<void> {
    const entry = this.log.entry(
      {
        resource: { type: 'cloud_function' },
        severity: event.result === 'FAILURE' ? 'ERROR' : 'INFO',
      },
      {
        // REQ 10.3.1: User identification
        userId: event.userId,
        email: event.email,

        // REQ 10.3.2: Type of event
        eventType: event.type,

        // REQ 10.3.3: Date and time
        timestamp: event.timestamp.toISOString(),

        // REQ 10.3.4: Success or failure indication
        result: event.result,

        // REQ 10.3.5: Origination of event
        source: 'payment-gateway',

        // REQ 10.3.6: Identity or name of affected data/resource
        resource: event.metadata?.resourceId || 'unknown',

        // Additional context
        metadata: event.metadata,
      }
    );

    await this.log.write(entry);
  }

  /**
   * Log payment creation attempt
   */
  async logPaymentCreated(
    userId: string,
    amount: number,
    currency: string,
    paymentIntentId: string
  ): Promise<void> {
    await this.logEvent({
      type: AuditEventType.PAYMENT_CREATED,
      userId,
      timestamp: new Date(),
      result: 'SUCCESS',
      metadata: {
        amount,
        currency,
        resourceId: paymentIntentId,
      },
    });
  }

  /**
   * Log failed access attempt (security incident)
   */
  async logAccessDenied(
    userId: string,
    email: string,
    endpoint: string,
    reason: string
  ): Promise<void> {
    await this.logEvent({
      type: AuditEventType.ACCESS_DENIED,
      userId,
      email,
      timestamp: new Date(),
      result: 'FAILURE',
      metadata: {
        endpoint,
        reason,
        severity: 'HIGH', // Flag for security team review
      },
    });
  }
}

Quarterly Vulnerability Scanning

Requirement 11.3.1: Perform external vulnerability scans at least quarterly using PCI SSC Approved Scanning Vendor (ASV):

Recommended ASVs:

  • Qualys
  • Rapid7
  • Tenable.io

Annual Penetration Testing

Requirement 11.4: Perform penetration testing at least annually and after significant changes:

For penetration testing methodologies, see Penetration Testing for ChatGPT Apps.


SAQ-A Compliance: The Optimal Path for ChatGPT Apps

Self-Assessment Questionnaire A (SAQ-A) is the simplest PCI DSS compliance path, consisting of only 22 questions instead of the 329 required for SAQ-D.

Qualifying for SAQ-A

Your ChatGPT app qualifies for SAQ-A if:

  1. All cardholder data is outsourced to PCI DSS validated third-party service providers (Stripe)
  2. Payment pages are hosted by Stripe (Stripe Checkout or Payment Element)
  3. Your servers do not store, process, or transmit cardholder data
  4. Each payment page element comes only from Stripe (no iframe embedding of third-party content)

Stripe Checkout Redirect Flow

The cleanest SAQ-A implementation uses Stripe Checkout with server-side session creation:

// backend/routes/payment-saq-a.ts
import Stripe from 'stripe';
import { Router, Request, Response } from 'express';
import { PaymentAccessControl, PaymentRole } from '../middleware/payment-access-control';

/**
 * SAQ-A Compliant Payment Integration
 *
 * Architecture:
 * 1. Backend creates Stripe Checkout Session (server-side)
 * 2. Frontend redirects user to Stripe-hosted payment page
 * 3. User enters card data directly on Stripe's servers
 * 4. Stripe processes payment and redirects back to success/cancel URL
 * 5. Webhook confirms payment (no cardholder data touches your servers)
 *
 * This flow ensures SAQ-A qualification by completely outsourcing
 * cardholder data handling to Stripe.
 */

const stripe = new Stripe(process.env.STRIPE_SECRET_KEY || '', {
  apiVersion: '2024-11-20.acacia',
});

const router = Router();

/**
 * Create Stripe Checkout Session
 * REQ 3.2: Do not store sensitive authentication data after authorization
 */
router.post(
  '/create-checkout-session',
  PaymentAccessControl.requireRole(PaymentRole.CUSTOMER),
  async (req: Request, res: Response) => {
    try {
      const { priceId, userId, email } = req.body;

      // Validate inputs
      if (!priceId || !userId) {
        return res.status(400).json({
          error: 'Bad Request',
          message: 'Missing required fields: priceId, userId',
        });
      }

      // Create Stripe Checkout Session
      const session = await stripe.checkout.sessions.create({
        mode: 'subscription',
        customer_email: email,
        line_items: [
          {
            price: priceId, // e.g., price_1ProfessionalPlan
            quantity: 1,
          },
        ],
        success_url: `${process.env.FRONTEND_URL}/payment-success?session_id={CHECKOUT_SESSION_ID}`,
        cancel_url: `${process.env.FRONTEND_URL}/payment-cancel`,
        metadata: {
          userId,
          plan: 'professional',
        },
        // Enable customer portal for subscription management
        subscription_data: {
          metadata: {
            userId,
          },
        },
      });

      // Return session URL for redirect
      // Frontend redirects to this URL - user enters card data on Stripe's page
      res.json({
        sessionUrl: session.url,
        sessionId: session.id,
      });
    } catch (error) {
      console.error('Checkout session creation error:', error);
      res.status(500).json({
        error: 'Internal Server Error',
        message: 'Failed to create checkout session',
      });
    }
  }
);

/**
 * Stripe Webhook Handler (payment confirmation)
 * REQ 6.3.2: Review custom code prior to release
 */
router.post('/webhook', async (req: Request, res: Response) => {
  const sig = req.headers['stripe-signature'] as string;
  const webhookSecret = process.env.STRIPE_WEBHOOK_SECRET || '';

  try {
    // Verify webhook signature (prevent replay attacks)
    const event = stripe.webhooks.constructEvent(
      req.body,
      sig,
      webhookSecret
    );

    // Handle checkout.session.completed event
    if (event.type === 'checkout.session.completed') {
      const session = event.data.object as Stripe.Checkout.Session;

      // Update user subscription in Firestore
      const userId = session.metadata?.userId;
      if (userId) {
        await updateUserSubscription(userId, {
          stripeCustomerId: session.customer as string,
          subscriptionId: session.subscription as string,
          plan: session.metadata?.plan || 'professional',
          status: 'active',
        });
      }
    }

    res.json({ received: true });
  } catch (error) {
    console.error('Webhook error:', error);
    res.status(400).json({ error: 'Webhook signature verification failed' });
  }
});

// Helper function to update Firestore subscription
async function updateUserSubscription(
  userId: string,
  subscriptionData: any
): Promise<void> {
  const { getFirestore } = require('firebase-admin/firestore');
  const db = getFirestore();

  await db.collection('subscriptions').doc(userId).set({
    ...subscriptionData,
    createdAt: new Date(),
    updatedAt: new Date(),
  });
}

export default router;

SAQ-A Documentation Requirements

To maintain SAQ-A compliance, document:

  1. Network diagram showing payment flow (user → Stripe Checkout → your webhook)
  2. PCI DSS Attestation of Compliance (signed annually)
  3. Stripe PCI DSS compliance certificate (validates Stripe is Level 1 PCI DSS compliant)
  4. Firewall rules restricting access to webhook endpoints
  5. Access control policies for administrative users

For comprehensive compliance frameworks, see SOC 2 Certification for ChatGPT Apps.


Webhook Signature Verification: Preventing Replay Attacks

Stripe webhooks must be validated to prevent attackers from forging payment events:

// backend/middleware/webhook-signature-verifier.ts
import Stripe from 'stripe';
import { Request, Response, NextFunction } from 'express';

/**
 * Verify Stripe webhook signatures
 * PCI DSS Req 6.5.3: Protect against injection flaws
 */
export function verifyWebhookSignature(
  req: Request,
  res: Response,
  next: NextFunction
): void {
  const stripe = new Stripe(process.env.STRIPE_SECRET_KEY || '', {
    apiVersion: '2024-11-20.acacia',
  });

  const sig = req.headers['stripe-signature'] as string;
  const webhookSecret = process.env.STRIPE_WEBHOOK_SECRET || '';

  try {
    // Verify signature using raw request body
    const event = stripe.webhooks.constructEvent(
      req.body,
      sig,
      webhookSecret
    );

    // Attach verified event to request
    req.stripeEvent = event;
    next();
  } catch (error) {
    console.error('Webhook signature verification failed:', error);
    res.status(400).json({
      error: 'Webhook Error',
      message: 'Invalid signature',
    });
  }
}

Payment Session Manager: Secure State Handling

Manage payment sessions securely with automatic expiration:

// backend/services/payment-session-manager.ts
import { getFirestore, Timestamp } from 'firebase-admin/firestore';

/**
 * Payment Session Manager
 *
 * Requirements Met:
 * - REQ 3.1: Keep cardholder data storage to a minimum
 * - REQ 3.4: Render PAN unreadable (we don't store it at all)
 * - REQ 8.2.4: Change user passwords/passphrases at least every 90 days
 */

interface PaymentSession {
  userId: string;
  sessionId: string;
  amount: number;
  currency: string;
  status: 'pending' | 'completed' | 'expired' | 'failed';
  createdAt: Timestamp;
  expiresAt: Timestamp;
}

export class PaymentSessionManager {
  private db = getFirestore();
  private readonly SESSION_TTL_HOURS = 24;

  /**
   * Create new payment session with automatic expiration
   */
  async createSession(
    userId: string,
    amount: number,
    currency: string = 'usd'
  ): Promise<string> {
    const now = Timestamp.now();
    const expiresAt = Timestamp.fromMillis(
      now.toMillis() + this.SESSION_TTL_HOURS * 60 * 60 * 1000
    );

    const sessionRef = this.db.collection('payment_sessions').doc();
    const sessionData: PaymentSession = {
      userId,
      sessionId: sessionRef.id,
      amount,
      currency,
      status: 'pending',
      createdAt: now,
      expiresAt,
    };

    await sessionRef.set(sessionData);
    return sessionRef.id;
  }

  /**
   * Validate session exists and is not expired
   */
  async validateSession(sessionId: string): Promise<boolean> {
    const sessionDoc = await this.db
      .collection('payment_sessions')
      .doc(sessionId)
      .get();

    if (!sessionDoc.exists) {
      return false;
    }

    const session = sessionDoc.data() as PaymentSession;
    const now = Timestamp.now();

    // Check expiration
    if (session.expiresAt.toMillis() < now.toMillis()) {
      await this.expireSession(sessionId);
      return false;
    }

    return session.status === 'pending';
  }

  /**
   * Mark session as completed
   */
  async completeSession(sessionId: string): Promise<void> {
    await this.db.collection('payment_sessions').doc(sessionId).update({
      status: 'completed',
      completedAt: Timestamp.now(),
    });
  }

  /**
   * Expire old session
   */
  private async expireSession(sessionId: string): Promise<void> {
    await this.db.collection('payment_sessions').doc(sessionId).update({
      status: 'expired',
      expiredAt: Timestamp.now(),
    });
  }

  /**
   * Cleanup expired sessions (run daily via Cloud Scheduler)
   */
  async cleanupExpiredSessions(): Promise<number> {
    const now = Timestamp.now();
    const expiredSessions = await this.db
      .collection('payment_sessions')
      .where('expiresAt', '<', now)
      .where('status', '==', 'pending')
      .get();

    const batch = this.db.batch();
    expiredSessions.docs.forEach((doc) => {
      batch.update(doc.ref, {
        status: 'expired',
        expiredAt: now,
      });
    });

    await batch.commit();
    return expiredSessions.size;
  }
}

Conclusion: Building Payment Security into Your ChatGPT Apps

PCI DSS compliance isn't a checkbox exercise—it's a fundamental architecture decision that protects your business, your customers, and your reputation. By following the SAQ-A compliance path with Stripe Checkout, you can process payments securely while minimizing your compliance burden from 329 questions to just 22.

The key principles:

  1. Never touch cardholder data: Use Stripe Payment Elements for client-side tokenization
  2. Network segmentation: Isolate payment systems with firewall rules and VPC architecture
  3. Strict access controls: Implement role-based access with MFA for administrators
  4. Comprehensive logging: Audit all access to payment systems for compliance and incident response
  5. Continuous validation: Quarterly vulnerability scans and annual penetration testing

For ChatGPT apps processing payments, this approach balances security, compliance, and developer experience—ensuring you can accept payments confidently while meeting all 12 PCI DSS requirements.

Ready to build PCI DSS compliant payment processing into your ChatGPT app? Start your free trial with MakeAIHQ and deploy payment-enabled ChatGPT apps with enterprise-grade security—no coding required. Our platform handles the compliance heavy lifting so you can focus on building exceptional customer experiences.

For real-world implementation, explore our E-commerce Product Recommendations ChatGPT App template, which demonstrates PCI-compliant payment integration for product sales.


Related Resources

  • ChatGPT App Security Best Practices - Comprehensive security guide
  • Stripe Payment Integration for ChatGPT Apps - Step-by-step integration
  • Data Encryption for ChatGPT Apps - Encryption strategies
  • Security Auditing and Logging - Audit trail implementation
  • Penetration Testing for ChatGPT Apps - Security testing methodologies
  • SOC 2 Certification for ChatGPT Apps - Compliance framework
  • E-commerce Product Recommendations ChatGPT App - Payment integration example

About MakeAIHQ: MakeAIHQ is the no-code platform for building production-ready ChatGPT apps with enterprise security and compliance built in. From PCI DSS payment processing to SOC 2 certification, we handle the complex security requirements so you can focus on building exceptional AI experiences for your customers.