stacklok / toolhive / 30376052943

70%

Build Type

push

github

Committed by web-flow

Commit Message

Reject malformed prior act claims at token exchange (#6114)

* Reject malformed prior act claims at token exchange

RFC 8693 §4.1 requires the act claim to be a JSON object, but the token
exchange handler copied a subject token's prior act into the newly minted
token without checking its shape. The depth gate did not catch it either:
actChainDepth returned 0 for any non-map, making "absent" and "malformed"
indistinguishable, so a subject token carrying act: "some-agent" produced
a minted token asserting a delegation chain we ourselves would flag as
non-conformant on the consuming side.

Reuse the shared audit-side parser adopted in #6107 rather than teaching
the bespoke walker about shapes: it reports the depth and the conformance
verdict in one pass, so the two cannot disagree. The exchange is now
rejected with invalid_grant, consistent with the adjacent depth, consent,
and expiry gates.

The new gate is monotonically stricter than the old one: a well-formed
chain yields len(Chain) == min(depth, cap), so the depth boundary is
unchanged and nothing previously rejected is newly accepted.

Closes #6093

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* Pin the iss_not_string rejection reason

The gate rejects on every reason ParseDelegationChain reports and surfaces
the reason in the client-visible hint, but only three of the four were
covered. Add the non-string iss case so the fourth reason and its hint are
pinned too.

The hop keeps a valid sub: the parser reports the first violation it finds
and checks iss before sub, so a hop with both non-string would report only
iss_not_string and leave this branch unpinned.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Coverage Stats

19 of 19 new or added lines in 1 file covered. (100.0%)

4 existing lines in 2 files now uncovered.

81804 of 117058 relevant lines covered (69.88%)

97.88 hits per line