A2A: refuse to serve when no transport credential is configured - #28
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`A2ADemoServer.rpc` guarded its auth check with
if self.bearer_tokens or self.api_keys:
so a server constructed without either served every caller anonymously.
That is the shape auth.py's own docstring names as the thing to avoid: it
reads like a check and behaves like an open door in exactly the state a
fresh checkout is in. `POST /a2a` is mounted in main.py, and message/send
creates and runs a task, so this is not a missing feature -- it hands any
caller the agent's time and budget.
The existing test proves the gate works once tokens exist; nothing covered
it with none.
Unconfigured now answers 503 and names the variable it wants. Serving
anonymously is still possible through an explicit allow_anonymous, so a
caller that wants an open transport has to say so; the adapter fixture
that relied on the old behaviour now does.
Membership also moves to hmac.compare_digest: `presented in accepted`
compares secrets in non-constant time, where the rest of the repo does not.
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The A2A transport check was skipped entirely when no credential happened to be set — so it served every caller anonymously.
What breaks
This is the shape
auth.py's own docstring names as the thing to avoid: "reads like a check and behaves like an open door whenever the variable is unset, which is exactly the state a fresh checkout is in."POST /a2ais mounted inmain.py, andmessage/sendcreates and runs a task. An unconfigured transport is not a missing feature — it hands any caller the agent's time and budget.How to see it break
Start S16 without
S16_A2A_BEARER_TOKENSorS16_A2A_API_KEYS, then post any JSON-RPC call to/a2a. It returns a result, not a 401. I hit this on a running instance.Why it survived
test_jsonrpc_transport_requires_bearer_or_api_keyconstructs the server with tokens. It proves the gate works once armed; nothing covered it disarmed.The fix
auth.py's precedent.allow_anonymous=Truekeeps an open transport available, but only when asked for. The adapter fixture that relied on the old behaviour now says so — which is the point: every open construction becomes visible.hmac.compare_digestreplacespresented in accepted; membership over a set compares secrets in non-constant time, where the rest of the repo does not.Test
test_jsonrpc_transport_refuses_to_serve_with_no_credential_configured— fails before, passes after. Covers both the refusal and the explicit opt-out.