feat(security): #504 MVP — --emit-attest sidecar + perry verify --attest

[proggeramlug]

Closes #504 (MVP — see follow-up matrix; full reproducible builds + CI publication tracked separately).

Summary

perry compile --emit-attest main.ts -o myapp now writes myapp.attest.json next to the executable. The sidecar holds SHA-256 of the post-strip binary plus provenance metadata (perry version, git commit, build timestamp) so users who download the binary can verify it matches the publisher's build:

perry verify --attest myapp

The verifier recomputes SHA-256 of the binary on disk and compares against the sidecar. Mismatch fails with a verbose diagnostic reproducing both hashes — exactly the signal a swapped/tampered binary would produce.

Manifest shape

{
  "version": 1,
  "sha256": "abcd1234...",
  "size": 1048576,
  "perry_version": "0.5.999",
  "commit_sha": "0a1b2c3...",
  "built_at_unix": 1715990400,
  "binary_filename": "myapp"
}

version: 1 reserves room for future top-level keys (CI signature blob, sigstore bundle, reproducible-builds flags log) without breaking existing parsers.

Cross-platform

Hooks into the platform-agnostic compile_command driver after strip / codesign / other post-link rewrites — same code path for every target (LLVM / WASM / ArkTS / HarmonyOS / Glance / SwiftUI / JS). The captured hash matches the file users will actually download regardless of which backend produced it.

Plumbing (mirrors --fast-math / --emit-sandbox)

• CompileArgs gains pub emit_attest: bool (#[arg(long)]).
• CompilationContext gains pub emit_attest: bool (default false).
• Precedence ladder (last wins): perry.emitAttest in package.json → PERRY_EMIT_ATTEST=1 env → --emit-attest CLI.
• New module commands::attest:
  • AttestationManifest with #[derive(Serialize, Deserialize)].
  • sha256_hex(path) — streaming hash (doesn't OOM on big binaries).
  • discover_commit_sha(project_root) — shells out to git; empty string when not a git checkout (best-effort).
  • build_attestation / write_attestation / verify_against_sidecar.

New CLI: perry verify --attest <binary>

The existing perry verify does remote runtime-verification via verify.perryts.com. The new --attest flag short-circuits to local-attest mode — no tokio runtime, no network, no beta-consent prompt. Prints either ✓ attestation matches + provenance OR the mismatch diagnostic with exit 1.

Test coverage

6 unit tests in commands::attest::tests:

• sha256_hex_matches_known_vector — pins SHA-256 of "hello\n".
• build_and_write_roundtrip — manifest fields + on-disk JSON shape.
• verify_passes_when_hash_matches — golden path.
• verify_fails_when_binary_tampered — pins security: reproducible builds + binary attestation #504 cite in mismatch diagnostic.
• verify_fails_when_sidecar_missing — pins actionable "produced by --emit-attest" guidance.
• manifest_is_pretty_printed_json — readable git diff invariant.

End-to-end smoke

perry compile --emit-attest main.ts -o out
# Wrote executable: out
# Wrote attestation: out.attest.json
# Binary size: 1.0MB

perry verify --attest out
# ✓ attestation matches: /path/to/out + provenance

echo extra >> out
perry verify --attest out
# Error: attestation MISMATCH ... (exit 1)

Implementation note

First attempt hooked the emission next to the Wrote executable: print, which fires BEFORE strip. The smoke test caught this immediately when verify detected a 1.3 MB → 1.0 MB size shift between the linker output and the final on-disk binary. Final placement is between the strip pass and the Binary size: print — a comment in the source documents the placement for the next reader.

What's NOT covered (MVP)

• Deterministic builds — same source on two machines doesn't yet produce a bit-identical binary. The attestation proves "this binary came from THIS specific build run", not "this is the only binary that could come from this source". Full determinism (stable LLVM pass ordering, fixed timestamps, hash-stable iteration) is the next security: reproducible builds + binary attestation #504 milestone.
• CI attestation publication — sigstore / GitHub native attestations / signed bundles. The MVP ships the local primitive; CI publication layers on top.
• Verifying against a published attestation — currently the sidecar must travel with the binary. A future perry verify --attest-url <url> would fetch from a published source.

Notes

No Cargo.toml version bump, no CLAUDE.md touch, no CHANGELOG.md entry — maintainer folds those in at merge time.