looks_like_ept used jwt.get_unverified_header, which validates the WHOLE token
and therefore rejects anything with a malformed signature segment. Routing
consequently depended on signature well-formedness: an EPT-shaped token with a
bad signature fell through to the HUMAN path, where it was refused for the wrong
reason and — with require_verified_jwt off (dev) — could have been read as a
human identity via its `sub` claim.
Now the header segment is decoded directly, so routing depends only on what the
token CLAIMS to be; whether it is authentic remains verify_ept's job.
Also routes alg:none to the EPT verifier regardless of typ, since a `none`
token is never valid for any caller. Both forged shapes now return 401
ept_invalid — the honest code — instead of 503 "feature not ready".
Found by noticing a forged EPT returned 503 where the verifier should have
answered 401, rather than accepting "it was refused, close enough".
80 tests green.
Co-Authored-By: Claude (Fable 5) <noreply@anthropic.com>
REOPENS the agent path — but only because possession is now actually proven.
EPT verification (api/app/ept.py): ES256 against Eternitas's published key set
at /.well-known/eternitas-keys. algorithms=["ES256"] makes alg:none and
algorithm confusion unrepresentable rather than merely unlikely; issuer and exp
are enforced by the library; an unknown kid is refused.
Order is deliberate: signature FIRST, trust lookup second. These EPTs live ~365
days and carry rev/tru baked in at issuance, so a year-old "rev: false" proves
nothing — revocation and band still come from a live lookup on every request.
Found while building it: real EPTs put the passport in the "sub" claim. The old
code read "passport"/"sub_passport", which no genuine EPT carries — so real
agents were never recognised and ONLY forged tokens ever authenticated. The
bypass was not just a hole, it was the only thing that worked.
Throttle (api/app/throttle.py): BAND_MULTIPLIER and rate_*_per_day were defined
and read by nothing. Now enforced on repo.create and grant.create, counted
against agent_actions (one source of truth, not a private counter that drifts
from the audit log). Fails CLOSED — a limiter that fails open protects you until
the moment something is wrong. Untrusted band is 403 read-only, not 429, because
"slow down" would be a lie.
Tests: 14 behavioral, signing real ES256 tokens with a locally-generated key so
they exercise the crypto path with no network dependency — genuine tokens
accepted, and alg:none / foreign key / tampered payload / expired / wrong issuer
/ unknown kid / missing claims all refused. 74 green.
Co-Authored-By: Claude (Fable 5) <noreply@anthropic.com>
