fix: add API key auth gate on all mutating routes via before_request

[Joshua-Medvinsky]

Summary

The Flask application exposes all endpoints — including message handling (/a2a POST), streaming, task creation/cancellation, and the AgentFlow management API — with no authentication. Any unauthenticated HTTP client can invoke agent logic, create/cancel tasks, spawn subprocesses, and read all agent outputs. The server defaults to binding on 0.0.0.0:5000.

Fix

Add a before_request hook that checks A2A_API_KEY env var on all mutating routes (POST, PUT, DELETE, PATCH). If the key is set, requests must include it as a Bearer token in the Authorization header. If the key is not set, the server operates in open-access dev mode (backwards compatible).

Test Plan

• With A2A_API_KEY set, unauthenticated POST returns 401
• With A2A_API_KEY set, authenticated POST with correct Bearer token succeeds
• Without A2A_API_KEY, all routes work as before (dev mode)
• GET routes remain unauthenticated (agent card discovery)

Security Note

Severity: High. Fail-open auth on all mutating endpoints allows unauthenticated task execution, agent hijacking, and subprocess spawning.

[failsafesecurity]

Hi maintainers — friendly follow-up on this security hardening PR. It has been open for a while with no reviewer feedback, so I wanted to resurface it.

Happy to rebase, adjust the approach, add tests, or split the change differently if that would make review easier. Thanks!

[failsafesecurity]

Hi — this security PR has been open for 40 days without maintainer response. Per our responsible disclosure policy, I'll be closing this PR shortly. I may resubmit via a bounty platform if appropriate. Thanks for your time.

[failsafesecurity]

Closing per responsible disclosure policy: 35+ days open with no maintainer response. May resubmit via bounty platform.

[failsafesecurity]

This security fix has been open for 30+ days. Per our responsible disclosure timeline, we'd like to move toward resolution. We can: (1) rebase and adjust the patch, (2) reach out via security@ email, or (3) resubmit via a bounty platform. Please let us know your preference.