Security Best Practices for Serverless Applications on AWS Lambda
Building secure serverless applications is paramount. This module explores key security best practices for AWS Lambda, focusing on minimizing attack surfaces, managing permissions effectively, and protecting sensitive data.
Principle of Least Privilege
The cornerstone of serverless security is the principle of least privilege. This means granting your Lambda functions only the permissions they absolutely need to perform their intended tasks. Over-privileged functions are a significant security risk, as a compromise of one function could lead to broader system access.
Grant only necessary permissions to Lambda functions.
AWS Identity and Access Management (IAM) roles are used to define permissions for Lambda functions. Create granular IAM policies that specify the exact AWS services and actions a function can access.
When creating an IAM role for your Lambda function, avoid using broad permissions like * for actions or resources. Instead, define specific actions (e.g., s3:GetObject, dynamodb:PutItem) and resource ARNs (Amazon Resource Names) that the function needs to interact with. Regularly review and audit these permissions to ensure they remain appropriate.
The principle of least privilege.
Securing Function Code and Dependencies
Your Lambda function's code and its dependencies are potential entry points for attackers. It's crucial to maintain a secure development lifecycle.
Vulnerable dependencies are a common attack vector. Regularly scan your project's dependencies for known vulnerabilities using tools like npm audit, yarn audit, or AWS Inspector.
Keep your runtime environments and SDKs up-to-date. AWS regularly releases patches for managed runtimes. For custom runtimes or container images, ensure you are building from secure base images and applying security updates promptly.
Input Validation and Sanitization
Never trust input from external sources, including API Gateway requests, S3 events, or messages from SQS/SNS. Malicious input can lead to injection attacks (e.g., SQL injection, command injection) or unexpected behavior.
Implement robust input validation at the entry point of your serverless application (e.g., API Gateway). This involves checking data types, formats, lengths, and ranges. Sanitize input by removing or encoding potentially harmful characters before processing. For example, when accepting user input for a database query, use parameterized queries or an Object-Relational Mapper (ORM) to prevent SQL injection.
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To prevent injection attacks and unexpected behavior from untrusted external data.
Managing Secrets and Sensitive Data
Avoid hardcoding sensitive information like API keys, database credentials, or encryption keys directly into your Lambda function code or environment variables. This is a major security vulnerability.
Store secrets securely outside your Lambda function.
AWS Secrets Manager and AWS Systems Manager Parameter Store (SecureString type) are designed for securely storing and retrieving secrets. Your Lambda function can then fetch these secrets at runtime using the AWS SDK.
When using Secrets Manager, you can configure automatic rotation of secrets, further enhancing security. Parameter Store offers a more straightforward way to store configuration data, including sensitive strings encrypted with AWS KMS. Ensure the IAM role for your Lambda function has the necessary permissions to access these services.
Logging and Monitoring
Comprehensive logging and vigilant monitoring are essential for detecting and responding to security incidents. AWS CloudWatch Logs and CloudWatch Alarms are key services for this.
| Aspect | CloudWatch Logs | CloudWatch Alarms |
|---|---|---|
| Purpose | Record function execution details, errors, and custom logs. | Notify when specific metrics exceed predefined thresholds. |
| Security Relevance | Provides audit trails, helps identify suspicious activity, and aids in post-incident analysis. | Alerts on anomalies like sudden spikes in errors, unusual invocation patterns, or unauthorized access attempts. |
| Configuration | Enabled by default; configure log retention policies. | Define metrics (e.g., ErrorCount, Throttles) and thresholds. |
API Gateway Security
If your Lambda functions are exposed via API Gateway, securing the API endpoint is critical. This includes authentication, authorization, and rate limiting.
Secure your API Gateway endpoints.
Utilize API Gateway features like AWS IAM authorization, Amazon Cognito User Pools for user authentication, or custom authorizers (Lambda functions) to control access to your APIs.
Implement throttling and usage plans to prevent abuse and denial-of-service attacks. Consider using AWS WAF (Web Application Firewall) with API Gateway to protect against common web exploits like cross-site scripting (XSS) and SQL injection.
Data Encryption
Protect sensitive data both in transit and at rest. AWS Lambda integrates with AWS KMS (Key Management Service) for encryption.
Ensure that any data stored in services like S3 or DynamoDB is encrypted at rest using AWS KMS. For data in transit, always use HTTPS for API Gateway endpoints and ensure secure connections when your Lambda function communicates with other AWS services or external APIs.
AWS Secrets Manager and AWS Systems Manager Parameter Store (SecureString).
Learning Resources
The official AWS documentation detailing comprehensive security best practices for developing and deploying Lambda functions.
Learn about fundamental IAM best practices, including the principle of least privilege, which is crucial for securing Lambda functions.
A blog post from AWS Security that dives into practical steps for securing serverless applications, covering authentication, authorization, and input validation.
A detailed video explaining various security considerations for AWS Lambda, including IAM, VPC, and code security.
Official AWS documentation for Secrets Manager, a service for managing secrets securely and rotating them automatically.
Learn about Parameter Store for securely storing configuration data and secrets, including the SecureString parameter type.
Documentation on how to integrate AWS WAF with API Gateway to protect your APIs from common web exploits.
An OWASP resource explaining the importance of input validation and common vulnerabilities related to improper validation.
A practical guide from Serverless.com covering essential security measures for AWS Lambda functions, including dependency scanning and IAM.
Understand the Lambda Runtime API, which is relevant for custom runtimes and ensuring your execution environment is secure and up-to-date.