基于AWS的机器对机器REST API认证授权方案咨询

Hey there! Let's break down whether the Cognito + API Gateway + Lambda stack makes sense for your backend-to-backend API use case, and tweak it to fit that Stripe-style secret key paradigm you're aiming for.

Cognito is built primarily for end-user authentication—think login flows for mobile apps, web UIs, or user-specific token generation. For your scenario (backend services calling your API directly, no UI involved), it’s often overkill unless you have a specific need to tie API access to individual users that your customers manage.

If your model is "each customer gets a static secret key to call your API" (just like Stripe’s secret API key), you can skip Cognito entirely and use simpler AWS features that align better with this pattern.

For backend-to-backend secret key auth, this stack will serve you better:

• API Gateway: Leverage its built-in features to secure endpoints:
  • API Keys + Usage Plans: Create a unique API key for each customer, then tie it to a Usage Plan to enforce rate limits, request quotas, and even tiered access (perfect for paid tiers). API Gateway automatically validates the key on every incoming request—no extra Lambda code needed for basic validation.
  • AWS Signature Version 4 (SigV4): If your customers are also using AWS, they can sign requests with their own IAM credentials. You’d create an IAM policy that grants access to your API, and API Gateway validates the SigV4 signature. This is more secure than static keys since it uses temporary, rotating credentials.
• Lambda: Your core API logic stays right here—no changes needed from your initial plan.
• AWS Secrets Manager: Store your customers’ secret keys securely (instead of hardcoding them) and set up automatic rotation if you want to enforce regular key updates. You can also let customers store their own credentials here if using SigV4.

Maybe you have a requirement that makes Cognito necessary—like if your customers need to generate temporary tokens for their own end-users to call your API, or you want to centralize identity management across multiple services. Here’s how to adapt it:

• Use the Cognito Client Credentials Flow: Create a Cognito App Client for each customer (or a single client that all customers use), then have their backend services request an access token by sending their client ID and client secret to Cognito’s token endpoint.
• Configure API Gateway to validate the Cognito access token using either a built-in Cognito authorizer or a custom Lambda authorizer.
• Note: This adds an extra step (token generation and renewal) compared to static API keys, which might not match the "grab the secret key and go" experience Stripe offers.

• Billing & Usage Tracking: API Gateway’s Usage Plans integrate with CloudWatch, so you can track per-customer request counts to bill accordingly. You can also sync this data to a billing platform using Lambda to automate invoicing.
• Security Best Practices: Static API keys are simple but require careful management. Use Secrets Manager to store them, and encourage customers to rotate keys regularly. If using SigV4, ensure customers follow IAM least-privilege principles.
• Monitoring & Alerting: Set up CloudWatch alerts for high error rates, unexpected traffic spikes, or quota breaches to proactively address issues for your paid customers.

内容的提问来源于stack exchange，提问作者vanvasquez