vcl-ut #25 P5d: Tier-2 C-ABI Ed25519 attestation fallback (RESOLVED) — closes the workstream

[hyperpolymath]

P5d — Tier-2 C-ABI Ed25519 attestation fallback (RESOLVED) — closes vcl-ut#25

The Tier-2 fallback of the canonical two-tier boundary model
(VERIFICATION-STANCE.adoc). For consumers that cannot run the Tier-1
recompute wasm32 module: a C ABI cannot carry a re-checkable proof,
so the honest ceiling is trusted-certifier attestation — now
reached. This was the last NAMED-OWED item under #25.

New crate src/interface/attest (vcltotal-attest)

Standalone workspace; crypto contained here, never touches the
zero-dep #![forbid(unsafe_code)] core.

• mint: decode → run the conformance-pinned
  vcltotal_parse::certified_level → sign iff 0..=10. Token =
  Ed25519 over DOMAIN ‖ sha256(stmt_wire) ‖ sha256(schema_wire) ‖ level. Fail-closed: decode failure / Reject ⇒ no token.
• verify: recompute the bound message, Ed25519-verify vs the
  certifier pubkey. Unforgeable + bound — tampered
  query/schema/level/sig or wrong key all reject. Does not re-run
  the decider (Tier-2 trusts the certifier; weaker than Tier-1,
  labelled so).
• vclut_rs_verify C-ABI — the previously declared-but-unlinked
  backend. One audited, documented host/guest unsafe block; all
  logic in the forbid-unsafe parse crate + audited ed25519-dalek.
• Crypto: ed25519-dalek (de-facto standard, audited — your
  decision) + sha2, minimal features, Cargo.lock pinned.
• 9 tests: roundtrip; 5 tamper variants
  (query/schema/level/sig/key); fail-closed garbage; C-ABI
  roundtrip+fail-closed; C-ABI small-out/null. clippy -D warnings +
  fmt clean.

Zig linkage

build.zig cargo-builds libvcltotal_attest.a and links it (+gcc_s
for std's _Unwind_* under panic=abort) into every artefact incl.
the test runner. lib.zig: extern vclut_rs_verify + new
vclut_verify_wire export (fail-closed wrapper). New end-to-end Zig
test: garbage wire ⇒ -1 across the Zig↔Rust boundary, out
untouched. zig build test 4/4 (real backend linked, not a stub).

Authoritative flip

VERIFICATION-STANCE.adoc: Tier-2/P5d OWED→RESOLVED across the
canonical two-tier model, headline, NAMED-OWED, consumer guidance,
roadmap, provenance, closing — both tiers now RESOLVED. ADR-0002
status → both tiers RESOLVED. New
src/interface/attest/ATTESTATION-FORMAT.adoc (normative wire spec) +
README; CHANGELOG/PROOF-NEEDS currency. The only remaining items are
the precisely-scoped disclosed limits (NaN payload; find/elemBy
cross-module Refl non-reduction; L9/L10 predicate depth;
additive↔ceil sliver; Idris→wire encode — needed by neither tier) —
not gaps.

Verified locally

Corpus idris2 --build exit 0 (12 modules, escape-scan OK,
unchanged); parse 6/6, recompute-wasm 3/3, attest 9/9 (all
clippy -D warnings + fmt clean); zig build test 4/4 end-to-end.

Closes the workstream

Both the Tier-1 recompute-PCC path and the Tier-2 attestation fallback
are RESOLVED; every limitation disclosed, not faked. vcl-ut#25 is
complete.

Refs #25.

🤖 Generated with Claude Code

[github-actions]

🔍 Hypatia Security Scan

Findings: 25 issues detected

Severity	Count
🔴 Critical	6
🟠 High	9
🟡 Medium	10

⚠️ Action Required: Critical security issues found!

View findings

[
  {
    "reason": "Issue in quality.yml",
    "type": "missing_workflow",
    "file": "quality.yml",
    "action": "create",
    "rule_module": "workflow_audit",
    "severity": "high"
  },
  {
    "reason": "Issue in security-policy.yml",
    "type": "missing_workflow",
    "file": "security-policy.yml",
    "action": "create",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Action hyperpolymath/standards/.github/workflows/governance-reusable.yml@main needs attention",
    "type": "unpinned_action",
    "file": "governance.yml",
    "action": "pin_sha",
    "rule_module": "workflow_audit",
    "severity": "high"
  },
  {
    "reason": "Action actions/upload-artifact@v4 needs attention",
    "type": "unpinned_action",
    "file": "release.yml",
    "action": "pin_sha",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Action actions/download-artifact@v4 needs attention",
    "type": "unpinned_action",
    "file": "release.yml",
    "action": "pin_sha",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "codeql.yml lists `language: javascript-typescript` but the repo has no source files in any CodeQL-scannable language. The analyze job will exit 'no source files' on every run. Switch the matrix to `actions` (which scans workflow files — every repo has those).",
    "type": "codeql_language_matrix_mismatch",
    "file": "codeql.yml",
    "action": "switch_codeql_matrix_to_actions",
    "rule_module": "workflow_audit",
    "severity": "high"
  },
  {
    "reason": "assert_smaller bypasses termination checker (1 occurrences, CWE-704)",
    "type": "assert_smaller",
    "file": "/home/runner/work/vcl-ut/vcl-ut/src/core/Checker.idr",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "high"
  },
  {
    "reason": "believe_me undermines formal verification (2 occurrences, CWE-704)",
    "type": "believe_me",
    "file": "/home/runner/work/vcl-ut/vcl-ut/src/core/Decide.idr",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "critical"
  },
  {
    "reason": "believe_me undermines formal verification (3 occurrences, CWE-704)",
    "type": "believe_me",
    "file": "/home/runner/work/vcl-ut/vcl-ut/src/core/Composition.idr",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "critical"
  },
  {
    "reason": "assert_total bypasses totality checker (1 occurrences, CWE-704)",
    "type": "assert_total",
    "file": "/home/runner/work/vcl-ut/vcl-ut/src/core/Composition.idr",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "high"
  }
]

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