feat(compute-gateway): mount read-path masking PDP (policy veto + field masking + sealed decision) - #1157
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feat(compute-gateway): mount read-path masking PDP (policy veto + field masking + sealed decision)#1157mdheller wants to merge 3 commits into
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…ld masking + sealed decision)
Mounts the masking moat on the one governed door. For read-effect kinds
(graph-query / graph-stats), engine.execute now passes dispatched outputs through
a field-level masking policy BETWEEN dispatch and seal, so the Ed25519 receipt
attests exactly what the caller received and the masking decision rides the same
attestation (the verifiable-evidence property WKC-style dynamic masking lacks).
compute_gateway/masking.py (new)
- OFF by default: no GATEWAY_MASKING_POLICY → exact passthrough (zero behaviour
change on the live gateway). Fail-closed WHEN configured.
- forbidden identity-mixture veto (e.g. no_health_adtech) → withholds records,
returns only the deny decision.
- field masking schemes (compact read subset of tokenization-profile.v1):
hmac_pseudonym (domain-scoped, deterministic), one_way_hash, redact, suppress,
generalize; unknown scheme fails closed to redact.
- emits identity-prime.masking-decision.v1 as a ComputeOutput → sealed + attested.
engine.py
- import masking; one guarded call between dispatch (raw) and seal, scoped to
masking.READ_KINDS. ~8 lines, no change to receipts.seal / signing.
tests/test_masking.py (6 tests): off-by-default passthrough, field masking + sealed
decision shape, forbidden-mixture deny/withhold, deterministic pseudonym, unknown
scheme fail-closed, invalid-policy disables-off. Existing engine-seal + gateway
suites unaffected (26 pass).
Canonical desensitisation primitives remain in the exodus reference engine
(exodus_tokenize / exodus_mask); Chameleon algebraic re-keying + NIST FF1 + HSM keys
swap in behind _transform with no PDP or caller change.
…ution
Follow-up to the masking mount: policy is no longer a single global env value.
GATEWAY_MASKING_POLICIES is a table {selector: policy} resolved by project, then
entitlement, then a "*"/"default" fallback — so different tenants/entitlements carry
different masking rules through the one gateway. Legacy single GATEWAY_MASKING_POLICY
remains the global fallback. Still off-by-default and fail-closed.
Tests: per-tenant selection, entitlement selector, legacy-global fallback (9 total).
…ant leak) Adversarial self-review before merge found a real defect in the masking mount: the compute memo keys reads by (project,kind,backend,spec) and serves any matching caller. Masking makes read results depend on actor/entitlement (per-tenant policy + forbidden-mixture veto), so a memoized masked read could be served to a DIFFERENT tenant — a cross-tenant data leak (under-masking) or wrong-policy masking. Fix: read_memo_spec() folds actor+entitlement into the memo spec for maskable read kinds, so masked reads are never shared across callers via the cache. Non-read kinds keep cross-caller memoization. Test asserts read keys differ by caller, match within a caller, and non-read keys are caller-independent. Full suite: 232 pass.
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Mounts the masking moat (P1 #5→serving) on
compute-gateway, the estate's one governed door — the smallest real increment from the A/B/C strategy read.What
For read-effect kinds (
graph-query/graph-stats),engine.executepasses the dispatched outputs through a field-level masking policy between dispatch and seal, so the existing Ed25519 receipt (receipts.seal/signing.attest) attests exactly what the caller received, and the masking decision itself is emitted as a sealed output — the verifiable-evidence property WKC-style dynamic masking does not produce.compute_gateway/masking.py(new): off by default (noGATEWAY_MASKING_POLICY→ exact passthrough, zero behaviour change on a live gateway); fail-closed when configured. Forbidden identity-mixture veto (no_health_adtech) withholds records; field schemes = compact read subset oftokenization-profile.v1(hmac_pseudonym,one_way_hash,redact,suppress,generalize); unknown scheme → redact. Emitsidentity-prime.masking-decision.v1.engine.py: import + one guarded call scoped toREAD_KINDS. No change toreceipts.seal/signing.Tests
tests/test_masking.py— 6 tests, all green. Existingtest_engine_seal+test_gateway(26) unaffected.Scope
Serving mount only. Canonical primitives stay in the exodus reference engine; Chameleon algebraic re-keying / NIST FF1 / HSM-held keys swap in behind
_transformwith no PDP or caller change. Policy wiring to per-tenant entitlement is the next increment.🤖 Generated with Claude Code