Transforming transactions: Streamlining PCI compliance using AWS serverless architecture

Compliance with the Payment Card Industry Data Security Standard (PCI DSS) is critical for organizations that handle cardholder data. Achieving and maintaining PCI DSS compliance can be a complex and challenging endeavor. Serverless technology has transformed application development, offering agility, performance, cost, and security.

In this blog post, we examine the benefits of using AWS serverless services and highlight how you can use them to help align with your PCI DSS compliance responsibilities. You can remove additional undifferentiated compliance heavy lifting by building modern applications with abstracted AWS services. We review an example payment application and workflow that uses AWS serverless services and showcases the potential reduction in effort and responsibility that a serverless architecture could provide to help align with your compliance requirements. We present the review through the lens of a merchant that has an ecommerce website and include key topics such as access control, data encryption, monitoring, and auditing—all within the context of the example payment application. We don’t discuss additional service provider requirements from the PCI DSS in this post.

This example will help you navigate the intricate landscape of PCI DSS compliance. This can help you focus on building robust and secure payment solutions without getting lost in the complexities of compliance. This can also help reduce your compliance burden and empower you to develop your own secure, scalable applications. Join us in this journey as we explore how AWS serverless services can help you meet your PCI DSS compliance objectives.

PCI DSS v4.0 and serverless

In April 2022, the Payment Card Industry Security Standards Council (PCI SSC) updated the security payment standard to “address emerging threats and technologies and enable innovative methods to combat new threats.” Two of the high-level goals of these updates are enhancing validation methods and procedures and promoting security as a continuous process. Adopting serverless architectures can help meet some of the new and updated requirements in version 4.0, such as enhanced software and encryption inventories. If a customer has access to change a configuration, it’s the customer’s responsibility to verify that the configuration meets PCI DSS requirements. There are more than 20 PCI DSS requirements applicable to Amazon Elastic Compute Cloud (Amazon EC2). To fulfill these requirements, customer organizations must implement controls such as file integrity monitoring, operating system level access management, system logging, and asset inventories. Using AWS abstracted services in this scenario can remove undifferentiated heavy lifting from your environment. With abstracted AWS services, because there is no operating system to manage, AWS becomes responsible for maintaining consistent time settings for an abstracted service to meet Requirement 10.6. This will also shift your compliance focus more towards your application code and data.

This makes more of your PCI DSS responsibility addressable through the AWS PCI DSS Attestation of Compliance (AOC) and Responsibility Summary. This attestation package is available to AWS customers through AWS Artifact.

Reduction in compliance burden

You can use three common architectural patterns within AWS to design payment applications and meet PCI DSS requirements: infrastructure, containerized, and abstracted. We look into EC2 instance-based architecture (infrastructure or containerized patterns) and modernized architectures using serverless services (abstracted patterns). While both approaches can help align with PCI DSS requirements, there are notable differences in how they handle certain elements. EC2 instances provide more control and flexibility over the underlying infrastructure and operating system, assisting you in customizing security measures based on your organization’s operational and security requirements. However, this also means that you bear more responsibility for configuring and maintaining security controls applicable to the operating systems, such as network security controls, patching, file integrity monitoring, and vulnerability scanning.

On the other hand, serverless architectures similar to the preceding example can reduce much of the infrastructure management requirements. This can relieve you, the application owner or cloud service consumer, of the burden of configuring and securing those underlying virtual servers. This can streamline meeting certain PCI requirements, such as file integrity monitoring, patch management, and vulnerability management, because AWS handles these responsibilities.

Using serverless architecture on AWS can significantly reduce the PCI compliance burden. Approximately 43 percent of the overall PCI compliance requirements, encompassing both technical and non-technical tests, are addressed by the AWS PCI DSS Attestation of Compliance.

The following table provides an analysis of each PCI DSS requirement against the serverless architecture in Figure 1, which shows a sample payment application workflow. You must evaluate your own use and secure configuration of AWS workload and architectures for a successful audit.

Note: The preceding table is based on the example reference architecture that follows. The actual extent of PCI DSS requirements reduction can vary significantly depending on your cardholder data environment (CDE) scope, implementation, and configurations.

Sample payment application and workflow

This example serverless payment application and workflow in Figure 1 consists of several interconnected steps, each using different AWS services. The steps are listed in the following text and include brief descriptions. They cover two use cases within this example application — consumers making a payment and a business analyst generating a report.

The example outlines a basic serverless payment application workflow using AWS serverless services. However, it’s important to note that the actual implementation and behavior of the workflow may vary based on specific configurations, dependencies, and external factors. The example serves as a general guide and may require adjustments to suit the unique requirements of your application or infrastructure.

Several factors, including but not limited to, AWS service configurations, network settings, security policies, and third-party integrations, can influence the behavior of the system. Before deploying a similar solution in a production environment, we recommend thoroughly reviewing and adapting the example to align with your specific use case and requirements.

Keep in mind that AWS services and features may evolve over time, and new updates or changes may impact the behavior of the components described in this example. Regularly consult the AWS documentation and ensure that your configurations adhere to best practices and compliance standards.

This example is intended to provide a starting point and should be considered as a reference rather than an exhaustive solution. Always conduct thorough testing and validation in your specific environment to ensure the desired functionality and security.

Figure 1: Serverless payment architecture and workflow

• Use case 1: Consumers make a payment
  1. Consumers visit the e-commerce payment page to make a payment.
  2. The request is routed to the payment application’s domain using Amazon Route 53, which acts as a DNS service.
  3. The payment page is protected by AWS WAF to inspect the initial incoming request for any malicious patterns, web-based attacks (such as cross-site scripting (XSS) attacks), and unwanted bots.
  4. An HTTPS GET request (over TLS) is sent to the public target IP. Amazon CloudFront, a content delivery network (CDN), acts as a front-end proxy and caches and fetches static content from an Amazon Simple Storage Service (Amazon S3) bucket.
  5. AWS WAF inspects the incoming request for any malicious patterns, if the request is blocked, the request doesn’t return static content from the S3 bucket.
  6. User authentication and authorization are handled by Amazon Cognito, providing a secure login and scalable customer identity and access management system (CIAM)
  7. AWS WAF processes the request to protect against web exploits, then Amazon API Gateway forwards it to the payment application API endpoint.
  8. API Gateway launches AWS Lambda functions to handle payment requests. AWS Step Functions state machine oversees the entire process, directing the running of multiple Lambda functions to communicate with the payment processor, initiate the payment transaction, and process the response.
  9. The cardholder data (CHD) is temporarily cached in Amazon DynamoDB for troubleshooting and retry attempts in the event of transaction failures.
  10. A Lambda function validates the transaction details and performs necessary checks against the data stored in DynamoDB. A web notification is sent to the consumer for any invalid data.
  11. A Lambda function calculates the transaction fees.
  12. A Lambda function authenticates the transaction and initiates the payment transaction with the third-party payment provider.
  13. A Lambda function is initiated when a payment transaction with the third-party payment provider is completed. It receives the transaction status from the provider and performs multiple actions.
  14. Consumers receive real-time notifications through a web browser and email. The notifications are initiated by a step function, such as order confirmations or payment receipts, and can be integrated with external payment processors through an Amazon Simple Notification Service (Amazon SNS) Amazon Simple Email Service (Amazon SES) web hook.
  15. A separate Lambda function clears the DynamoDB cache.
  16. The Lambda function makes entries into the Amazon Simple Queue Service (Amazon SQS) dead-letter queue for failed transactions to retry at a later time.
• Use case 2: An admin or analyst generates the report for non-PCI data
  17. An admin accesses the web-based reporting dashboard using their browser to generate a report.
  18. The request is routed to AWS WAF to verify the source that initiated the request.
  19. An HTTPS GET request (over TLS) is sent to the public target IP. CloudFront fetches static content from an S3 bucket.
  20. AWS WAF inspects incoming requests for any malicious patterns, if the request is blocked, the request doesn’t return static content from the S3 bucket. The validated traffic is sent to Amazon S3 to retrieve the reporting page.
  21. The backend requests of the reporting page pass through AWS WAF again to provide protection against common web exploits before being forwarded to the reporting API endpoint through API Gateway.
  22. API Gateway launches a Lambda function for report generation. The Lambda function retrieves data from DynamoDB storage for the reporting mechanism.
  23. The AWS Security Token Service (AWS STS) issues temporary credentials to the Lambda service in the non-PCI serverless account, allowing it to launch the Lambda function in the PCI serverless account. The Lambda function retrieves non-PCI data and writes it into DynamoDB.
  24. The Lambda function fetches the non-PCI data based on the report criteria from the DynamoDB table from the same account.

Additional AWS security and governance services that would be implemented throughout the architecture are shown in Figure 1, Label-25. For example, Amazon CloudWatch monitors and alerts on all the Lambda functions within the environment.

Label-26 demonstrates frameworks that can be used to build the serverless applications.

Scoping and requirements

Now that we’ve established the reference architecture and workflow, lets delve into how it aligns with PCI DSS scope and requirements.

PCI scoping

Serverless services are inherently segmented by AWS, but they can be used within the context of an AWS account hierarchy to provide various levels of isolation as described in the reference architecture example.

Segregating PCI data and non-PCI data into separate AWS accounts can help in de-scoping non-PCI environments and reducing the complexity and audit requirements for components that don’t handle cardholder data.

PCI serverless production account

• This AWS account is dedicated to handling PCI data and applications that directly process, transmit, or store cardholder data.
• Services such as Amazon Cognito, DynamoDB, API Gateway, CloudFront, Amazon SNS, Amazon SES, Amazon SQS, and Step Functions are provisioned in this account to support the PCI data workflow.
• Security controls, logging, monitoring, and access controls in this account are specifically designed to meet PCI DSS requirements.

Non-PCI serverless production account

• This separate AWS account is used to host applications that don’t handle PCI data.
• Since this account doesn’t handle cardholder data, the scope of PCI DSS compliance is reduced, simplifying the compliance process.

Note: You can use AWS Organizations to centrally manage multiple AWS accounts.

AWS IAM Identity Center (successor to AWS Single Sign-On) is used to manage user access to each account and is integrated with your existing identify provider. This helps to ensure you’re meeting PCI requirements on identity, access control of card holder data, and environment.

Now, let’s look at the PCI DSS requirements that this architectural pattern can help address.

Requirement 1: Install and maintain network security controls

• Network security controls are limited to AWS Identity and Access Management (IAM) and application permissions because there is no customer controlled or defined network. VPC-centric requirements aren’t applicable because there is no VPC. The configuration settings for serverless services can be covered under Requirement 6 to for secure configuration standards. This supports compliance with Requirements 1.2 and 1.3.

Requirement 2: Apply secure configurations to all system components

• AWS services are single function by default and exist with only the necessary functionality enabled for the functioning of that service. This supports compliance with much of Requirement 2.2.
• Access to AWS services is considered non-console and only accessible through HTTPS through the service API. This supports compliance with Requirement 2.2.7.
• The wireless requirements under Requirement 2.3 are not applicable, because wireless environments don’t exist in AWS environments.

Requirement 3: Protect stored account data

• AWS is responsible for destruction of account data configured for deletion based on DynamoDB Time to Live (TTL) values. This supports compliance with Requirement 3.2.
• DynamoDB and Amazon S3 offer secure storage of account data, encryption by default in transit and at rest, and integration with AWS Key Management Service (AWS KMS). This supports compliance with Requirements 3.5 and 4.2.
• AWS is responsible for the generation, distribution, storage, rotation, destruction, and overall protection of encryption keys within AWS KMS. This supports compliance with Requirements 3.6 and 3.7.
• Manual cleartext cryptographic keys aren’t available in this solution, Requirement 3.7.6 is not applicable.

Requirement 4: Protect cardholder data with strong cryptography during transmission over open, public networks

• AWS Certificate Manager (ACM) integrates with API Gateway and enables the use of trusted certificates and HTTPS (TLS) for secure communication between clients and the API. This supports compliance with Requirement 4.2.
• Requirement 4.2.1.2 is not applicable because there are no wireless technologies in use in this solution. Customers are responsible for ensuring strong cryptography exists for authentication and transmission over other wireless networks they manage outside of AWS.
• Requirement 4.2.2 is not applicable because no end-user technologies exist in this solution. Customers are responsible for ensuring the use of strong cryptography if primary account numbers (PAN) are sent through end-user messaging technologies in other environments.

Requirement 5: Protect a ll systems and networks from malicious software

• There are no customer-managed compute resources in this example payment environment, Requirements 5.2 and 5.3 are the responsibility of AWS.

Requirement 6: Develop and maintain secure systems and software

• Amazon Inspector now supports Lambda functions, adding continual, automated vulnerability assessments for serverless compute. This supports compliance with Requirement 6.2.
• Amazon Inspector helps identify vulnerabilities and security weaknesses in the payment application’s code, dependencies, and configuration. This supports compliance with Requirement 6.3.
• AWS WAF is designed to protect applications from common attacks, such as SQL injections, cross-site scripting, and other web exploits. AWS WAF can filter and block malicious traffic before it reaches the application. This supports compliance with Requirement 6.4.2.

Requirement 7: Restrict access to system components and cardholder data by business need to know

• IAM and Amazon Cognito allow for fine-grained role- and job-based permissions and access control. Customers can use these capabilities to configure access following the principles of least privilege and need-to-know. IAM and Cognito support the use of strong identification, authentication, authorization, and multi-factor authentication (MFA). This supports compliance with much of Requirement 7.

Requirement 8: Identify users and authenticate access to system components

• IAM and Amazon Cognito also support compliance with much of Requirement 8.
• Some of the controls in this requirement are usually met by the identity provider for internal access to the cardholder data environment (CDE).

Requirement 9: Restrict physical access to cardholder data

• AWS is responsible for the destruction of data in DynamoDB based on the customer configuration of content TTL values for Requirement 9.4.7. Customers are responsible for ensuring their database instance is configured for appropriate removal of data by enabling TTL on DDB attributes.
• Requirement 9 is otherwise not applicable for this serverless example environment because there are no physical media, electronic media not already addressed under Requirement 3.2, or hard-copy materials with cardholder data. AWS is responsible for the physical infrastructure under the Shared Responsibility Model.

Requirement 10: Log and monitor all access to system components and cardholder data

• AWS CloudTrail provides detailed logs of API activity for auditing and monitoring purposes. This supports compliance with Requirement 10.2 and contains all of the events and data elements listed.
• CloudWatch can be used for monitoring and alerting on system events and performance metrics. This supports compliance with Requirement 10.4.
• AWS Security Hub provides a comprehensive view of security alerts and compliance status, consolidating findings from various security services, which helps in ongoing security monitoring and testing. Customers must enable PCI DSS security standard, which supports compliance with Requirement 10.4.2.
• AWS is responsible for maintaining accurate system time for AWS services. In this example, there are no compute resources for which customers can configure time. Requirement 10.6 is addressable through the AWS Attestation of Compliance and Responsibility Summary available in AWS Artifact.

Requirement 11: Regularly test security systems and processes

• Testing for rogue wireless activity within the AWS-based CDE is the responsibility of AWS. AWS is responsible for the management of the physical infrastructure under Requirement 11.2. Customers are still responsible for wireless testing for their environments outside of AWS, such as where administrative workstations exist.
• AWS is responsible for internal vulnerability testing of AWS services, and supports compliance with Requirement 11.3.1.
• Amazon GuardDuty, a threat detection service that continuously monitors for malicious activity and unauthorized access, providing continuous security monitoring. This supports the IDS requirements under Requirement 11.5.1, and covers the entire AWS-based CDE.
• AWS Config allows customers to catalog, monitor and manage configuration changes for their AWS resources. This supports compliance with Requirement 11.5.2.
• Customers can use AWS Config to monitor the configuration of the S3 bucket hosting the static website. This supports compliance with Requirement 11.6.1.

Requirement 12: Support information security with organizational policies and programs

• Customers can download the AWS AOC and Responsibility Summary package from Artifact to support Requirement 12.8.5 and the identification of which PCI DSS requirements are managed by the third-party service provider (TSPS) and which by the customer.

Conclusion

Using AWS serverless services when developing your payment application can significantly help reduce the number of PCI DSS requirements you need to meet by yourself. By offloading infrastructure management to AWS and using serverless services such as Lambda, API Gateway, DynamoDB, Amazon S3, and others, you can benefit from built-in security features and help align with your PCI DSS compliance requirements.

Contact us to help design an architecture that works for your organization. AWS Security Assurance Services is a Payment Card Industry-Qualified Security Assessor company (PCI-QSAC) and HITRUST External Assessor firm. We are a team of industry-certified assessors who help you to achieve, maintain, and automate compliance in the cloud by tying together applicable audit standards to AWS service-specific features and functionality. We help you build on frameworks such as PCI DSS, HITRUST CSF, NIST, SOC 2, HIPAA, ISO 27001, GDPR, and CCPA.

More information on how to build applications using AWS serverless technologies can be found at Serverless on AWS.

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