docs(guard): relabel integrity sidecars as integrity-not-authenticity (#19)#41
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…#19) The .integrity sidecars for pins.json and guard-policy.yaml are UNKEYED SHA-256 checksums stored beside the file with the same 0o600 perms. They provide INTEGRITY (tamper-evidence vs accidental corruption / cross-machine copies / a different OS-user account), NOT AUTHENTICITY vs a same-user/postinstall attacker: any process that can write the file can also recompute and rewrite the sidecar to match, so there is no attacker/writer asymmetry. The prior comments in pins.ts/policy.ts and the 2026-05-17 Decisions Log row implied these stop a malicious npm postinstall / same-user process. They do not. A keyed scheme (HMAC/signature) needs a secret the writable store lacks — the same constraint as the secret store (issue #15) — so the honest fix is relabel-only: docs + comments, no behavior change. docs/GUARD.md and docs/POLICY.md already stated this correctly; this reconciles the code comments and the Decisions Log. - pins.ts / policy.ts: clarify integrity-not-authenticity at sidecar header + fileSha sites; cite #19. - CLAUDE.md: reconcile the 2026-05-17 sidecar row + add a 2026-06-02 Decisions Log row recording the relabel decision. - pins.test.ts: add tests pinning the honest wording (fail on pre-fix source). Closes #19 Co-Authored-By: Claude Opus 4.8 <[email protected]>
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What
The
.integritysidecars forpins.jsonandguard-policy.yamlare unkeyed SHA-256 checksums stored next to the file with the same0o600permissions. This PR relabels them honestly as providing integrity (tamper-evidence), not authenticity against a same-user/postinstall attacker — and reconciles the contradictory Decisions Log row.Docs/comments only — no behavior change. The checksum-compare-and-throw logic is unchanged and correct as tamper-evidence.
Files touched (in scope):
src/guard/pins.ts— clarify integrity-not-authenticity at the sidecar header +fileShasite; cite [security][MEDIUM] Integrity sidecars are unkeyed SHA-256 — no protection vs same-user/postinstall tampering #19.src/guard/policy.ts— same relabel at the F4 sidecar comment +fileShasite.CLAUDE.md— reconcile the self-contradictory 2026-05-17 sidecar row and add a 2026-06-02 Decisions Log row recording the relabel decision.src/guard/__tests__/pins.test.ts— add tests pinning the honest wording.Why
The sidecars are unkeyed, so any process that can write the file can also recompute and rewrite the sidecar to match — there is no attacker/writer asymmetry. The prior code comments and the 2026-05-17 Decisions Log row claimed protection against a malicious npm
postinstall/ same-user process ("Sidecar protects against same-machine tampering (postinstall scripts, malware)"), which is false and self-contradictory (postinstall scripts are same-user).A keyed scheme (HMAC/signature) needs a secret the writable store lacks — the same constraint as the secret store (issue #15) — so the honest fix is relabel-only.
docs/GUARD.mdanddocs/POLICY.mdalready stated this correctly; this reconciles the code comments and the Decisions Log to match.Satisfies the issue's acceptance criteria: docs no longer claim protection against malicious same-user processes, and the decision is recorded in
CLAUDE.md.Test plan
pnpm lint(tsc) passespnpm test— 1115 passed (added 2 wording-contract tests)pnpm buildsucceeds#19reference are present and the prior overclaiming phrasing is gone.Closes #19
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