familysync/.planning/phases/20-admin-member-editor-form-declutter/20-SECURITY.md

phase, slug, status, threats_open, asvs_level, created

phase	slug	status	threats_open	asvs_level	created
20	admin-member-editor-form-declutter	verified	0	1	2026-06-18

Phase 20 — Security

Per-phase security contract: threat register, accepted risks, and audit trail. Result: SECURED — 10/10 threats CLOSED. register_authored_at_plan_time: true (verify-only; no new-threat scan).

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Trust Boundaries

Boundary	Description	Data Crossing
client → /api/admin	Untrusted admin-session input crosses into the admin surface; guarded by router-wide requireAdmin (admin.ts:48). No NEW boundary added by this phase.	Member profile fields, isAdmin toggle, app-password credential
PWA → /api/admin	Client fetch (updateMemberProfile, saveCredential) calls into the admin surface; server-side requireAdmin + last-admin guard are the real boundaries. Client toggle state is non-authoritative.	Same as above; password fields are write-only

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Threat Register

Threat ID	Category	Component	Disposition	Mitigation	Status
T-20-01	Elevation of Privilege	PATCH /members/:id isAdmin toggle	mitigate	Router-wide requireAdmin first statement (admin.ts:48); PATCH adds no second/weaker guard (:234); 403 test (admin.test.ts:1180-1190)	closed
T-20-02	Denial of Service (self-lockout)	last-admin demotion	mitigate	Last-admin 409 guard, count+update in txn with FOR UPDATE (admin.ts:271-293); 409 test (:1128-1150), self-demote-with-2nd-admin 200 test (:1153-1177)	closed
T-20-03	Tampering	malformed :id / wrong-type body	mitigate	parsePositiveIntParam rejects bad ids → 400 (admin.ts:88-93,235); updateMemberSchema + noEchoHook reject wrong types → 400 (:225-234,76); test F (:1193-1216)	closed
T-20-04	Information Disclosure	error echo on invalid input	mitigate	noEchoHook returns only { error: 'Invalid request' } (admin.ts:76-80); request body never logged (:241,297-300)	closed
T-20-05	Spoofing (stale session)	updateMemberProfile fetch	mitigate	SessionExpiredError on 401/opaqueredirect reuses existing re-auth flow (client.ts:261); redirect:'manual' + credentials:'include' (:254-258)	closed
T-20-06	Elevation of Privilege (client trust)	last-admin sentinel	accept	Server 409 authoritative (admin.ts:271-293); client only surfaces 'last-admin' sentinel (client.ts:262). See Accepted Risks Log.	closed
T-20-07	Information Disclosure	password / app-password fields	mitigate	Fields write-only: type=password + autoComplete="new-password", blank init (MemberEditorSheet.tsx:188-205,639-882); no console.* logging (0 grep matches)	closed
T-20-08	Tampering	CalDAV credential	mitigate	App-password save routes through saveCredential → server-side CalDAV validation before store (MemberEditorSheet.tsx:338, admin.ts:373-393); invalid → failure copy, nothing stored (:355)	closed
T-20-09	Elevation of Privilege (UI bypass)	admin toggle	mitigate	Toggle cosmetic role=switch (MemberEditorSheet.tsx:546); reverts + inline error on last-admin (:288-295); real enforcement is server 409 (T-20-02)	closed
T-20-SC	Tampering (supply chain)	npm installs	mitigate	No new packages; lucide-react@1.17.0 already in package.json:30; imports AdminPage.tsx:28, MemberEditorSheet.tsx:25-27	closed

Status: open · closed Disposition: mitigate (implementation required) · accept (documented risk) · transfer (third-party)

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Accepted Risks Log

Risk ID	Threat Ref	Rationale	Accepted By	Date
AR-20-01	T-20-06	Client-side last-admin toggle state is non-authoritative by design. The demotion guard is enforced server-side (409, admin.ts:271-293); the client only surfaces the rejection via the 'last-admin' sentinel (client.ts:262) and reverts the toggle (MemberEditorSheet.tsx:294). A tampered client that ignores the sentinel still cannot bypass the guard — the server rejects regardless. Matches existing pattern: "isAdmin drives nav visibility; the real boundary is server-side." Residual risk: none beyond the already-mitigated server boundary at ASVS L1.	Lucas Berger (per Plan 20-02 threat model)	2026-06-18

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Security Audit Trail

Audit Date	Threats Total	Closed	Open	Run By
2026-06-18	10	10	0	gsd-security-auditor

Notable hardening beyond plan: the last-admin guard wraps count+update in a transaction with a FOR UPDATE locking read (admin.ts:249-286) to defeat a concurrent double-demotion race — strengthens T-20-02 past the plan minimum.

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Sign-Off

• All threats have a disposition (mitigate / accept / transfer)
• Accepted risks documented in Accepted Risks Log
• threats_open: 0 confirmed
• status: verified set in frontmatter

Approval: verified 2026-06-18