The dogfood principle now runs in BOTH directions. Agents already
verified signatures through the proven dalek path; now the provider
SIGNS with it too, and proves to itself that the signing code is in its
own log before every signature:
- dogfood binary gains a `sign` mode (seed over stdin, never argv;
ed25519_dalek::SigningKey from the same pinned merkleized workspace).
Honesty ledger unchanged: the library's VERIFY path is
certificate-covered; its signing path is declared trusted base - but
it is the ATTESTED artifact, not an un-attested third implementation.
- sign_payload_ed25519_detailed: signing dispatch mirroring the verify
dispatch; the backend that actually signed is recorded in every
attestation signature block and STH.
- THE SELF-REFERENTIAL CHECK: before signing any tree head, the
provider runs the SAME Merkle inclusion verification an agent runs -
against the very tree it is about to sign - for the newest leaf
attesting the signing library itself, and embeds the result in the
signature block:
signing_provenance:
signing_backend: verified-dalek-serial
signing_library_component: dalek-ed25519-verified
signing_library_source_commit: aa0f6ab...
self_inclusion: verified
signing_library_leaf_index: 4
signing_library_certificates_proven: 16/16
A root signature that names the leaf vouching for the code that
produced it. First-append chicken-and-egg is handled honestly
(self_inclusion: library_not_in_log).
- Evidence refreshed: all four receipts re-issued under dogfood-signed
STHs; the full agent verify loop re-run green.
50/50 tests (new signing roundtrip test, skip-safe where unbuilt).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
A transparency log without split-view defense is just a signature with
extra steps: the provider could serve one tree to the agent and another
to the world, or roll the log back, and standalone receipt verification
would never notice. The primitives (RFC 9162 consistency proofs) were
already implemented and correct; this closes the loop on the AGENT side.
- src/pacta/sthstore.py: a local STH pin store. Unknown log -> pin
(trust-on-first-use, recorded as such). Same tree size -> the root
must match the pin byte-for-byte; a mismatch is named EQUIVOCATION
and is a hard rejection. Larger tree -> a consistency proof FROM THE
PINNED SIZE is required and verified before the pin advances
(receipts already embed a from-previous anchor; the anchor's root is
itself checked against the pin so a lying anchor cannot bridge a
split view). Smaller tree -> LOG ROLLBACK, hard rejection.
- Freshness policy: --max-sth-age-seconds rejects stale (or
future-dated) tree heads - an old-but-valid STH can hide later
entries.
- Wired into receipt-verify, claims, and agent (--sth-store,
--consistency-proof, --max-sth-age-seconds); evidence records the
pin action; any accountability failure fails the receipt closed.
- Provider: log-consistency --from-size N (serve proofs for pinning
agents whose pin is older than the receipt's embedded anchor) and
log-audit (monitor self-check: recompute the tree, verify the stored
STH and per-entry leaf hashes).
Live drill in this commit's validation: pin-on-first-use -> matched ->
grown-with-proof advance -> a real forged same-size split view REJECTED
with the equivocation diagnostic -> freshness rejection -> clean
self-audit. tests/test_sthstore.py covers pin/match/equivocation,
growth-without-proof, lying consistency anchors, rollback, freshness.
45/45 tests green.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
