AI Sec Watch: A Security Intelligence Platform for AI Systems

Luu, T.J.

Implement custom authentication for tools integration using request Lambda interceptor in AgentCore Gateway

infonews

security

Source: AWS Security BlogAugust 18, 2026

Summary

AWS Bedrock AgentCore Gateway supports modern authentication methods like OAuth 2.0 and IAM, but some enterprises need legacy Basic Auth (a simple username-password encoding method). A request Lambda interceptor (custom code that runs when an AI agent calls a tool) can retrieve credentials from AWS Secrets Manager and add a Basic Auth header to requests, keeping credentials hidden from the AI model to reduce risk from prompt injection (tricking an AI by hiding instructions in its input).

Solution / Mitigation

Use a request Lambda interceptor in AgentCore Gateway to: (1) re-validate the inbound JWT (a token issued by an identity provider) as a defense-in-depth measure; (2) retrieve the system service account credential from Secrets Manager; (3) construct a compliant Basic Auth header using the system credential and add it to the outbound request. For the service account credential lifecycle, manually seed the credential once (a system administrator creates the service account in Active Directory and stores the initial credential in Secrets Manager), then trigger an immediate rotation to retire the human-known password. After seeding, use Secrets Manager's built-in automation to periodically generate new passwords and update both Secrets Manager and Active Directory simultaneously. Additionally, implement compensating controls such as ensuring all communication with the downstream tool API uses TLS encryption and conducting two-person review of Lambda code changes.