Refresh checkpoint: all audit findings closed

CHECKPOINT-encryption.md

@@ -1,4 +1,4 @@
-# Checkpoint — Key material zeroization (2026-08-21)
+# Checkpoint — All audit items closed (2026-08-21)
 
 A stopping point you can return to if this session is closed. Everything below was
 verified green at the moment this file was written.
@@ -6,14 +6,15 @@ verified green at the moment this file was written.
 ## Where things are
 
 - Project: `/home/avi/Projects/0_Nostr`
-- Git repo: `master` @ `130d7e2` ("Zeroize transient secret key material in memory").
-  Before it: `4461307` (owner-only writes), `4bd7660` (legacy vault perms), `4d4dfde`
-  (CSP + navigation guards), `6e627a3` (upload pick tokens), `4bde395` (IPC allowlist).
+- Git repo: `master` @ `f7db29e` ("Add SSRF guard, signer queue cap, secret echo, request
+  timeout"). Before it: `130d7e2` (zeroization), `4461307` (owner-only writes), `4bd7660`
+  (legacy vault perms), `4d4dfde` (CSP + navigation guards), `6e627a3` (upload tokens),
+  `4bde395` (IPC allowlist).
 - Working tree is **clean** apart from this checkpoint update, which is committed right after.
 
-## What was completed: security hardening items #1–#6
+## What was completed: the full 2026-08-21 security audit remediation
 
-Fixes from the 2026-08-21 security audit.
+All ten findings from the 2026-08-21 security audit are fixed.
 
 **#1 IPC method allowlist (`4bde395`, `main.ts` only):**
 - `RENDERER_METHODS` set in the Electron main process: the three native methods
@@ -93,8 +94,25 @@ Decrypted secrets and derived keys no longer linger in unscrubbed heap memory:
   `std::mem::take` without extra copies (plaintext-at-rest is that feature's purpose).
 - Callers in `publish.rs`, `uploads.rs`, `signer.rs` needed no changes (deref coercion).
 
+**Smaller items (`f7db29e`, main.ts + signer.rs):**
+- **SSRF guard**: `fetchLinkPreview` resolves the URL's host and refuses loopback/private/
+  link-local targets — literal IPs, DNS answers, and localhost/.local names all checked
+  (`ipv4IsPrivate`/`ipv6IsPrivate`/`resolvesToPrivateAddress`). Crafted note links can no
+  longer make the app probe localhost or the LAN.
+- **Signer queue cap** (`MAX_PENDING_APPROVALS = 20`): a relay flooding `sign_event`
+  requests cannot grow the approval queue unboundedly or bury a genuine prompt; overflow
+  requests get the standard "no decision" error.
+- **NIP-46 secret echo**: when the nostrconnect:// link carried a secret, the client's
+  `connect` request must echo it back or it is refused ("did not include the expected
+  secret"), proving the link arrived unmodified.
+- **Backend request timeout**: `backendRequest` reaps any round-trip after 120s (generous
+  enough for multi-relay publishes), deleting its pending entry so a hung backend cannot
+  leak promises.
+
 ## Commits
 
+- `f7db29e` "Add SSRF guard, signer queue cap, secret echo, request timeout" — main.ts +
+  signer.rs (+204/−3).
 - `130d7e2` "Zeroize transient secret key material in memory" — Cargo.toml, crypto.rs,
   profiles.rs, app.rs (+77/−23).
 - `4461307` "Create vault files owner-only from the first byte" — src/vault.rs (+48/−2).
@@ -137,13 +155,21 @@ Manual protocol checks worth doing once:
 
 ## Outstanding / next steps (if you continue)
 
-Remaining smaller hardening items from the audit:
+Nothing outstanding from the audit — all ten findings are closed:
 
-1. Link-preview SSRF guard — block loopback/private IPs in `fetchLinkPreview` (`main.ts`).
-2. Signer pending-cap — bound the approval queue (e.g. max 10) against relay spam.
-3. NIP-46 secret echo check — verify the client echoes the handshake `secret`.
-4. Backend request timeout — `backendRequest` in `main.ts` has no timeout; hung backend
-   leaks pending promises.
+| # | Finding | Fix commit |
+|---|---------|-----------|
+| 1 | Unrestricted renderer→backend IPC | `4bde395` |
+| 2 | Arbitrary file upload paths | `6e627a3` |
+| 3 | CSP `unsafe-inline`, no nav guards | `4d4dfde` |
+| 4 | Legacy vault world-readable | `4bd7660` |
+| 5 | Permission race windows on write | `4461307` |
+| 6 | Key material not zeroized | `130d7e2` |
+| 7 | Link-preview SSRF | `f7db29e` |
+| 8 | Signer queue flooding | `f7db29e` |
+| 9 | NIP-46 secret not verified | `f7db29e` |
+| 10 | No backend request timeout | `f7db29e` |
 
-All six primary findings are closed (#1 IPC allowlist, #2 upload tokens, #3 CSP +
-navigation, #4 legacy vault perms, #5 write-race windows, #6 zeroization).
+Possible future work (not audit items): DNS-rebinding TOCTOU in the SSRF guard, OS keyring
+integration for the vault password, an automated dependency-audit CI job (`cargo audit`,
+`npm audit`).