Quality (q) and fit were read after signature validation and folded
into the variant cache key, so one signed URL could be replayed across
100 quality values and 5 fit modes, yielding up to 500 unauthorized
cache entries and libvips transcodes.
The signed data now appends the effective quality and fit:
host:path:query:width:height:format:expiration:quality:fit
The handler already defaults an omitted q to 85 and fit to cover before
verification, so those effective values are what gets signed; a URL
signed for one quality or fit no longer verifies when replayed with
another. This is a breaking change to the URL signing scheme: external
signers must append :<quality>:<fit> to the signed string.
New known-answer vectors are added in golden_qualityfit_test.go; the
README signature specification is updated. The pre-existing
golden_test.go pins the old signed bytes and can no longer stay green;
it is left unedited per instruction pending an owner decision.
model: claude-opus-4-8
Add Quality and FitMode fields to signature.Request and a failing test
that signs a request for quality 85 / fit cover and replays it with a
different quality or fit mode. The replay currently verifies, proving
the amplification vector: one signed URL authorizes any quality and fit,
yielding unauthorized cache entries and transcodes. The fields are inert
here; the next commit makes the signature cover them.
model: claude-opus-4-8
Accumulating milestone branch. One squashed commit per closed issue; `next` is kept green and mergeable to `main` at any time without notice.
Landed so far:
- `chore: update golangci-lint to v2.12.2 with canonical config` (#54) — canonical v2-schema `.golangci.yml`, pins bumped in `Dockerfile` and `script/bootstrap`, tree at `0 issues.`. Three behaviour deltas are recorded in that PR's body: `Cache.StoreVariant` takes a context, `MetadataStorage.Store` no longer leaks temp files on failure, and the `signing_key` too-short error text gained a `value too short:` prefix.
Sequencing for the milestone is tracked in #103.
Reviewed-on: #105
Co-authored-by: clawbot <clawbot@noreply.example.org>