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feat(canary): API-trashing defense — 4-layer fingerprint validation

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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.
This commit is contained in:
anti
2026-04-29 17:41:04 -04:00
parent f86dc79990
commit b26dd8f529
12 changed files with 370 additions and 36 deletions
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10
decnet/canary/fingerprint_payload.js
View File

@@ -3,11 +3,12 @@
// canary worker. Ported from canary-self-test.html with the rendering UI
// stripped out.
//
// Two placeholders are substituted by the Python builder BEFORE
// Three placeholders are substituted by the Python builder BEFORE
// javascript-obfuscator runs:
//
// {{BEACON_URL}} → full URL to /c/<callback_token> (no trailing slash)
// {{MINT_UUID}} → per-mint UUID, baked into the string-array post-obf
// {{MINT_NONCE}} → 16-hex HMAC nonce; the worker rejects ?d=/?o= without it
//
// Beacon strategy (MVP): a bare GET pixel for "I was opened" reliability,
// then a fingerprint payload sent as a base64-URL query param on a second
@@ -17,6 +18,7 @@
(async function () {
var BEACON_URL = "{{BEACON_URL}}";
var MINT_UUID = "{{MINT_UUID}}";
var MINT_NONCE = "{{MINT_NONCE}}";
var fp = { mint: MINT_UUID };
function fire(url) {
@@ -27,7 +29,7 @@
}
// 1) bare-open beacon — fires regardless of whether the rest succeeds
fire(BEACON_URL + "?o=1");
fire(BEACON_URL + "?o=1&k=" + MINT_NONCE);
function sha256(str) {
var buf = new TextEncoder().encode(str);
@@ -276,13 +278,13 @@
// chunk if URL would exceed safe limit (~6KB)
var MAX = 6000;
if (b64.length <= MAX) {
fire(BEACON_URL + "?d=" + b64);
fire(BEACON_URL + "?d=" + b64 + "&k=" + MINT_NONCE);
} else {
var sid = (Math.random() * 1e9 | 0).toString(36);
var total = Math.ceil(b64.length / MAX);
for (var ci = 0; ci < total; ci++) {
var part = b64.substr(ci * MAX, MAX);
fire(BEACON_URL + "?s=" + sid + "&i=" + ci + "&n=" + total + "&d=" + part);
fire(BEACON_URL + "?s=" + sid + "&i=" + ci + "&n=" + total + "&d=" + part + "&k=" + MINT_NONCE);
}
}
} catch (e) { /* swallow */ }