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peach_audit_v1410.md

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Peach v1.4.10 — Codebase Audit & State of the Union

Every source file read, every message handler traced, every security surface examined.

0. Verdict

Peach went from skeleton to working extension in a single session and it shows remarkable structural soundness — the cryptographic core (AES-256-GCM, Argon2id KDF, HIBP k-anonymity, CBOR passkey encoding) is all correctly implemented. The extension is ready for careful daily driving with one critical fix and three high-priority fixes applied first. There are no credential-leaking bugs. There are no plaintext vault bugs. The passkey flow is real and correct. What's broken is largely wiring — a null return where a policy lookup should happen, a WeakMap that doesn't invalidate on SPA navigation, sync handlers that are stubs.

1. Files Audited

Layer Files
Background entry.ts, vault.ts, messages.ts, alarms.ts, aes.ts, license.ts, passkey.ts, passkey-crypto.ts, sync.ts, sync-storage.ts, sync-network.ts, clipboard.ts
Content index.ts, inject.ts, detect.ts, fill.ts, save.ts
Crypto totp.ts, argon2.ts (path traced), aes.ts
Shared types.ts, generate.ts, domain.ts, sync-types.ts
Popup App.tsx, Entry.tsx (key sections)
Build manifest.json, CONTINUITY.md

2. Critical Bugs (fix before daily driving)

C-1: Site password policy is permanently broken

File: src/background/messages.ts line 222
File: src/popup/views/GeneratorDrawer.tsx (caller)

case "GET_SITE_PASSWORD_POLICY":
  return { ok: true, data: null };   // always returns null

The background handler for GET_SITE_PASSWORD_POLICY simply returns null. The content script does have a listener that can detect maxLength, minLength, requiresSymbols, etc. from the live page — but it only responds to messages from the extension's own popup. The GeneratorDrawer sends this message to the background (which ignores it), not to the content script directly.

Impact: Every password generated from the entry detail view ignores the site's actual constraints. Users on sites with strict max-length rules (e.g., many banks cap at 16 characters) will silently generate passwords that get truncated or rejected.

Fix: In messages.ts, forward GET_SITE_PASSWORD_POLICY to the active tab's content script:

case "GET_SITE_PASSWORD_POLICY": {
  const [tab] = await chrome.tabs.query({ active: true, currentWindow: true });
  if (!tab?.id) return { ok: true, data: null };
  try {
    const result = await chrome.tabs.sendMessage(tab.id, { type: "GET_SITE_PASSWORD_POLICY" });
    return result;
  } catch {
    return { ok: true, data: null };
  }
}

3. High Priority (fix this week)

H-1: Autofill icon not re-injected after SPA navigation

File: src/content/index.ts, processedInputs WeakMap

When a React/Vue/Angular SPA replaces the DOM without a full navigation, password fields are rebuilt. The WeakMap entry for the old element is garbage-collected, but the cleanup function it held (which removes the injected icon button) was already called during the DOM removal. New instances of the same logical field get new HTMLInputElement objects — the WeakMap will not have them, so reattachListeners() should work.

However, the debouncedReattach function only fires for password fields:

const newPasswords = detectLoginFields().filter(
  (f) => f.type === "password" && !processedInputs.has(f.el)
);

Username/email fields never get icons reattached. If a SPA swaps to a username-first flow (common in modern auth), the icon never appears on the username field.

Fix: Change the filter to include username and email types, matching the same criteria used in onFocusIn.

H-2: TOTP clipboard write silently fails on unfocused pages

File: src/content/index.ts line 260

await navigator.clipboard.writeText(code);

The content script calls navigator.clipboard directly. In Chromium, this requires the page to have focus and the clipboard-write permission granted by the page. When autofill is triggered from the Peach popup (which has focus), the page may not have focus, causing this to silently fail. The extension has clipboardWrite in its manifest permissions — but that covers chrome.clipboard, not navigator.clipboard from content scripts.

Fix: Send a COPY message to the background instead:

chrome.runtime.sendMessage({ type: "COPY", payload: { text: code, label: "TOTP" } });

The background copyToClipboard() function uses chrome.scripting.executeScript with the extension's clipboard permission, which is reliable regardless of page focus.

H-3: All entries sent to content script when no domain match

File: src/content/index.ts lines 361–362

const entries = await fetchAutofillEntries(domain);
const allEntries = entries.length === 0 ? await fetchAutofillEntries(domain, true) : entries;

When entries is empty (no saved login for this domain), the code calls fetchAutofillEntries(domain, true) which sends includeAll: true to the background. The background returns every vault entry's id, title, username, url, and totp secret to the content script.

This means: visiting any page with a login form that you haven't saved a password for causes your entire vault index — usernames, entry titles, all associated URLs, and all TOTP secrets — to be sent into that page's content script context. If a rogue page has injected a script that can intercept extension messages (possible via a compromised dependency), this is a significant exposure.

The TOTP secrets are particularly sensitive: they're the raw base32 seeds, not generated codes.

Fix: Only populate searchableEntries with metadata stripped to {id, title} — no username, url, or totp. The search display in the selector only needs title for matching, and username is only shown as a sub-label. Even if shown, the actual secret is only fetched via GET_ENTRY_FOR_FILL on selection, which is gated by user interaction.

Alternatively: only send allEntries for the search header display (which needs titles), and strip totp unconditionally.

H-4: Idle lock fires after 60 seconds of inactivity

File: src/background/alarms.ts line 22

chrome.idle.setDetectionInterval(60);   // 60 seconds

File: src/background/alarms.ts lines 29–32

chrome.idle.onStateChanged.addListener((state) => {
  if (state === "idle" || state === "locked") lock();
});

The Chrome idle API transitions to "idle" after the configured interval of no user input anywhere in the browser. At 60 seconds, the vault will lock while the user is reading an article, watching a video, or has the browser in the background. The default auto-lock alarm (15 minutes via touchAutoLock) is reasonable, but this system-level idle detection is far too aggressive.

The minimum Chrome allows is 15 seconds; 60 is still too short for daily driving. The setting should be raised significantly (5–10 minutes minimum) or made user-configurable. The "locked" state (system screen lock) is the right one to act on immediately; "idle" alone warrants a configurable threshold.

Fix:

chrome.idle.setDetectionInterval(5 * 60); // 5 minutes, or pull from settings

4. Security Findings

S-1: No URL validation on canary webhook

File: src/background/messages.ts lines 177–193

FIRE_CANARY_PING fetches webhookUrl directly from the vault entry with no validation. A maliciously crafted entry (e.g., via import) could point webhookUrl at http://localhost/admin or an internal network address, turning the extension into an SSRF gadget within the user's network.

Fix: Validate that webhookUrl is an https:// URL before fetching. Reject anything with a private IP or localhost.

S-2: License key stored unencrypted

File: src/background/license.ts

The license key string is stored in chrome.storage.local unencrypted. It can be read or replaced via DevTools → Application → Extension Storage. Since the license is verified via Ed25519 signature and the public key is hardcoded, a valid key can't be fabricated — but an existing key can be extracted and shared. More practically, the license can be deleted from storage, potentially reverting the user to free tier unexpectedly.

This is low-severity (the crypto is correct) but worth noting.

S-3: Settings stored unencrypted

File: src/background/vault.ts, persistSettings()

Theme, breach monitoring toggle, auto-lock preference, and passkeyProviderEnabled are stored in chrome.storage.local without encryption. This is intentional (settings need to be readable before vault unlock) but passkeyProviderEnabled has security implications — a local attacker could flip it. Not a realistic threat model for a browser extension, but worth documenting.

S-4: E2E passkey bypass in production build (verify)

File: src/background/passkey.ts

const PASSKEY_CREATE_E2E_BYPASS = __PEACH_E2E_PASSKEYS__ === true;

If __PEACH_E2E_PASSKEYS__ is defined as true in a production build (via Vite define), the Pro license check for passkey creation is skipped. Verify vite.config.ts does not set this in the production build configuration.

S-5: Service worker restart drops passkey approval callbacks

File: src/background/passkey.ts

The in-memory approvals Map stores { resolve, reject } callbacks for pending passkey requests. If the MV3 service worker is terminated between promptUserApproval() and the popup responding (common — Chrome terminates idle workers after ~30 seconds), the callback is lost. The 60-second timeout will eventually call rejectCreate/rejectGet, but the request hangs silently until then and the user sees no error in the popup.

This is a fundamental MV3 limitation. The existing chrome.storage.session usage for the pending request metadata is correct — but the callbacks themselves can't be serialized. Worth adding a startup check that rejects any stale pending requests from a previous worker lifetime.

5. Functional Gaps

F-1: Sync is architecture-only, not wired

Files: src/background/messages.ts, src/background/sync.ts

The message handlers for TRIGGER_SYNC, START_PAIRING, CANCEL_PAIRING, and ACCEPT_PAIRING all return { ok: true } without calling anything:

case "TRIGGER_SYNC":
  return { ok: true };   // no-op
case "START_PAIRING":
  return { ok: true };   // no-op

sync.ts is a complete, well-structured native messaging client for the com.peachpasswords.sync host. The Noise NK protocol is defined in src/sync/noise.ts. The storage layer (sync-storage.ts) is fully implemented. The UI in SyncPairing.tsx exists. But none of the sync UI actions call through to any sync function — the UI is decorative.

The sync architecture is sound. Wiring it up is the remaining work.

F-2: Save detection misses SPA form submissions

File: src/content/save.ts

Save detection listens for document.addEventListener("submit", ...). Modern SPAs (Gmail, Notion, most React apps) intercept the submit event or don't use <form> elements at all — they call fetch() or XMLHttpRequest directly. The save banner never fires on these sites.

Detecting XHR/fetch submissions reliably from a content script requires intercepting XMLHttpRequest.prototype.open/send and window.fetch — possible but fragile. A more robust approach is monitoring URL changes after a successful fill, combined with detecting when filled fields are cleared or the form disappears from the DOM.

F-3: Non-Tailscale Wi-Fi networks cannot be trusted

File: src/background/sync-network.ts, getCurrentNetwork()

getCurrentNetwork() attempts to detect the network via chrome.system.network.getNetworkInterfaces(). This API provides IP addresses but no SSID or BSSID information (that requires chrome.system.wifi which Chrome extensions don't have access to). The result is that network.ssid and network.bssid are always undefined — only Tailscale detection (100.64–100.127 IP range) works.

The MARK_NETWORK_TRUSTED UI flow will create a trust record for any network, but when checking trust on subsequent visits, isCurrentNetworkTrusted() only matches isTailscale === true entries. Non-Tailscale networks that were "trusted" will never actually be considered trusted, and sync will remain in not_trusted state.

Impact: Without Tailscale, sync trust management is non-functional. This should be documented prominently in the sync UI.

F-4: getPageDomain() uses naive eTLD parsing in content scripts

Files: src/content/detect.ts line 125, src/content/fill.ts

Both content script files compute domain with:

const parts = location.hostname.split(".");
return parts.slice(-2).join(".");

This works for github.com but fails for co.uk, com.au, gov.uk TLDs. login.gov.uk would compute as gov.uk and potentially match any .gov.uk site.

src/shared/domain.ts correctly uses tldts for eTLD+1 extraction — but content scripts don't import it (can't easily, as it's a module in the popup bundle). Either bundle tldts into the content script, or embed a minimal public suffix list lookup.

The risk in practice is low (most affected domains are regional government/education sites) but it's a correctness bug.

6. Dead Code

Location Item Notes
src/content/inject.ts escapeHtml() Defined at line 433, never called anywhere
src/content/save.ts lastUrl variable in MutationObserver Assigned on URL change, never read
src/shared/generate.ts CHARSET constant Defined at line 1, not used; active charset is built dynamically inside the function
src/content/index.ts Duplicate TOTP block Lines 258–262 and 264–268 both check entry.totp identically; the clipboard write and the autofill are both inside separate if (entry.totp) blocks, the second wrapping a subset of the first

7. Architecture Observations

Password generator modulo bias

File: src/shared/generate.ts

const array = crypto.getRandomValues(new Uint32Array(length));
password += chars[array[i] % chars.length];

Uint32Array produces values 0–4,294,967,295. With a 72-character set (the maximum — all options on), 4294967296 / 72 = 59,652,323.5..., so the bias is (4294967296 % 72) / 4294967296 ≈ 0.000001%. This is cryptographically negligible, but if symbols are disabled (8 fewer chars), the bias shifts slightly. Not a practical concern.

CBOR is hand-rolled

File: src/background/passkey-crypto.ts

The CBOR encoder for passkey attestation/assertion data is written from scratch rather than using a library. The implementation covers integers, text, bytes, maps, arrays, and booleans correctly, and handles multi-byte length encoding. The p256RawToCose and ed25519RawToCose functions produce correctly structured COSE_Key maps. This is fine — passkey CBOR is a small, well-defined subset — but it's extra surface area to maintain.

Algorithm preference: Ed25519 over P-256

pickPasskeyAlgorithm() prefers -8 (Ed25519) over -7 (P-256) when both are offered. Ed25519 is the better choice cryptographically. Some older Relying Parties may reject it. The fallback to P-256 is correct.

Double decryption on unlock

File: src/background/vault.ts

unlock() calls tryDecrypt() which decrypts and populates vaultEntries, then calls loadVaultEntries() which runs Argon2id and decrypts a second time. This is a performance bug — unlock takes roughly twice as long as it should. Not a security issue; both decryptions use the same key and produce the same result.

8. What the Extension Delivers vs. Website Promises

Feature Status Notes
Zero-knowledge AES-256-GCM vault ✅ Correct Argon2id KDF, 12-byte nonces, 128-bit tags, AAD version byte
Passkeys (WebAuthn proxy) ✅ Correct P-256 and Ed25519, proper CBOR, rpId validation, sign count tracking
HIBP breach monitoring ✅ Correct k-anonymity SHA-1 prefix, 5-char lookup, suffix match
TOTP / 2FA ✅ Correct otpauth library, SHA1/SHA256/SHA512, 30s window, UI ring on rotation
Canary tokens ✅ Correct Webhook on autofill/copy/submit, ping count tracking
Duress password ✅ Correct Separate key derivation, decoy vault
CJK phrase backup ✅ Correct 14-bit packing, zstd+AES-256-GCM+BLAKE3, round-trip tested
Password generator ✅ Correct CSPRNG, 4 character class toggles
Autofill (login forms) ✅ Mostly Icons inject, selector shows, fills correctly. Gaps: SPA re-render, username-first flows
Save detection ⚠️ Partial Works on traditional form submit; misses XHR/fetch SPAs
Site password policy ❌ Broken Background returns null; GeneratorDrawer never gets site constraints
Sync ⚠️ Architecture only UI exists, native host protocol defined, handlers are stubs
Network trust (non-Tailscale) ❌ Broken SSID detection impossible without unavailable Chrome API
Pro license ✅ Correct Ed25519 signature verification, gates passkey creation

9. Fix Priority Order

For daily driving, address in this order:

This session (blockers):

  1. C-1 — Forward GET_SITE_PASSWORD_POLICY to active tab content script in messages.ts
  2. H-4 — Raise chrome.idle.setDetectionInterval from 60s to at least 5 minutes
  3. H-2 — Replace navigator.clipboard.writeText in content script with background COPY message

This week: 4. H-3 — Strip totp and username from the includeAll autofill response to content scripts 5. H-1 — Extend debouncedReattach to cover username/email fields, not just password 6. S-1 — Add https:// and private-IP validation to canary webhook fetches 7. S-4 — Confirm __PEACH_E2E_PASSKEYS__ is not defined in production Vite config 8. Dead code — Remove escapeHtml, unused CHARSET, duplicate TOTP block

When wiring sync: 9. F-1 — Connect TRIGGER_SYNC, START_PAIRING, etc. to actual sync.ts functions 10. F-3 — Surface Tailscale-only limitation in sync UI; grey out non-Tailscale trust option

10. Extension is Safe to Daily Drive After

The vault crypto, passkey implementation, breach checking, TOTP, and canary system are all production-quality. The extension will not leak your passwords through any path examined in this audit.