Production AI agents necessitate secure access to external services. Amazon Bedrock AgentCore Identity, now available as a standalone service, provides a robust mechanism to secure how your AI agents access these services, irrespective of whether they run on compute platforms like Amazon ECS, Amazon EKS, AWS Lambda, or on-premises environments.
While a previous post covered AgentCore Identity's credential management for AI agents, deploying agents in compute environments such as ECS introduces specific challenges: establishing an application-owned Session Binding endpoint and managing the lifecycle of workload access tokens.
This article details an implementation of the Authorization Code Grant (3-legged OAuth) on Amazon ECS, incorporating secure session binding and scoped tokens. This working implementation offers several key advantages:
- Secure session binding that effectively prevents CSRF (Cross-Site Request Forgery) and browser-swapping attacks.
- Auth tokens are scoped to each user session, strictly adhering to least-privilege principles.
- A clear separation of concerns between the agent workload and the session binding service.
Authentication and Authorization with OAuth 2.0 and OIDC
This solution leverages OAuth 2.0 (RFC 6749) for authorization and OpenID Connect (OIDC) for user authentication. OIDC verifies "who" the user is, while OAuth 2.0 dictates "what" actions they are authorized to perform.
The focus here is on the Authorization Code Grant, suitable for user-delegated access scenarios. In this flow, the user authenticates with an identity provider and explicitly grants consent. Subsequently, the application exchanges the obtained authorization code for an access token. Amazon Bedrock AgentCore Identity then securely stores this scoped access token within its token vault. This process ensures that each token is bound to a specific user identity with explicit consent, thereby maintaining an auditable chain from initial user authentication through to the agent's actions.
The Authorization Code Grant is particularly well-suited for agentic workloads acting on behalf of users because it mandates user consent prior to agent action, incorporates session binding to verify the consistency between the user initiating the request and granting consent, and provides scoped delegation, limiting the agent to only the permissions explicitly approved by the user.
Distinguishing Callback URL from Session Binding URL
Within the context of the Authorization Code Grant flow, two URLs are often confused:
- Callback URL: Automatically generated when creating an OAuth client in AgentCore Identity. It points directly to AgentCore Identity and must be registered with the Authorization Server as the redirect target where the authorization code is sent after successful user authentication.
- Session Binding URL: This URL points to a customer-managed service responsible for completing the session binding between the authenticated user and the OAuth flow. This endpoint is implemented and hosted by the customer.