Adds per-mint nonce gating, structural shape validation, mint UUID
consistency checks, and a per-(token, IP) rate limiter to the canary
worker so attackers who extract a canary from a decky filesystem cannot
poison fingerprint forensics by replaying or forging ?d= submissions.
Changes:
base.py
fingerprint_nonce: Optional[str] added to CanaryArtifact so generators
can surface the nonce to the cultivator without coupling the generator
directly to DB code.
obfuscator.py
nonce_for(callback_token, mint_uuid): HMAC-SHA256 keyed on
DECNET_CANARY_FINGERPRINT_SECRET, truncated to 16 hex chars.
FingerprintSecretMissing raised at mint time if env var is unset.
render_fingerprint_js() now accepts nonce= and substitutes MINT_NONCE.
fingerprint_payload.js
New MINT_NONCE placeholder. Appended as &k= on all beacon URLs (bare-open,
single-shot, chunked). Using &k= avoids colliding with &n= (chunk total).
fingerprint_html.py / fingerprint_svg.py
Derive nonce via nonce_for() and pass to render_fingerprint_js(). Set
artifact.fingerprint_nonce so the cultivator can persist it.
cultivator.py
Passes fingerprint_nonce into create_canary_token() when present on the
artifact; NULL for all non-fingerprint generators.
canary.py (model)
fingerprint_nonce: Optional[str] = Field(default=None, max_length=16)
added to CanaryToken. None for non-fingerprint tokens.
worker.py
_extract_fingerprint now returns (meta_dict, parsed_fp) tuple.
_record_hit accepts parsed_fp + raw_nonce and runs 4 layers after
token lookup: nonce match, shape check, mint UUID consistency, rate limit.
Each failure sets _fp_invalid_* flag and drops structured _fp.
Trigger row always lands regardless.
tests/canary/conftest.py
Session-scoped autouse fixture sets DECNET_CANARY_FINGERPRINT_SECRET so
fingerprint generator and worker tests work offline.
tests
5 new worker HTTP tests and 2 new generator tests covering each
validation layer.
The fingerprint payload beacons fingerprint data as base64url JSON in
GET query params: ?o=1 for the bare-open beacon, ?d=<blob> for a
single-shot dump, or ?s/i/n/d=<chunk> for chunked dumps. Until now
those params were buried inside request_path; consumers had to parse
the URL themselves.
Worker now extracts them in _extract_fingerprint and merges into
raw_headers under reserved _fp* keys:
* _fp_open — bare-open marker
* _fp — decoded fingerprint dict (single-shot path)
* _fp_sid/idx/total/chunk — chunked metadata + raw base64 (reassembly
is a downstream concern, not the worker's job)
* _fp_decode_error / _fp_oversize — failure markers for trash dumps
Per-chunk size capped at 8KB so an attacker spamming /c/<known_slug>
can't inflate trigger rows indefinitely. Decode failures degrade
gracefully — the trigger row still records the hit, just with a
_fp_decode_error flag instead of structured fingerprint data.
Tests cover the single-shot decode, bare-open flag, chunked metadata,
malformed input, and oversize drop paths.
