Refresh checkpoint with upload pick tokens

CHECKPOINT-encryption.md

@@ -1,4 +1,4 @@
-# Checkpoint — Renderer IPC method allowlist (2026-08-21)
+# Checkpoint — Upload pick tokens (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.
@@ -6,35 +6,45 @@ verified green at the moment this file was written.
 ## Where things are
 
 - Project: `/home/avi/Projects/0_Nostr`
-- Git repo: `master` @ `4bde395` ("Restrict renderer IPC to an explicit method allowlist").
+- Git repo: `master` @ `6e627a3` ("Replace upload file paths with single-use pick tokens").
+  Before it: `4bde395` ("Restrict renderer IPC to an explicit method allowlist"), then
+  `dafed33` (checkpoint refresh), on top of contact-aware feed (`a1445d1`) etc.
 - Working tree is **clean** apart from this checkpoint update, which is committed right after.
-- Underneath sit the contact-aware feed (`a1445d1`), feed aggregation (`37a9d94`) and the
-  NIP-46 signer work, all committed.
 
-## What was completed: security hardening item #1 (IPC allowlist)
+## What was completed: security hardening items #1 and #2
 
-First fix from the 2026-08-21 security audit. The Electron main process now enforces an
-explicit allowlist of renderer-callable methods, so a compromised web page inside the app
-can no longer invent arbitrary backend calls (e.g. unknown/future methods or typos that
-might alias onto sensitive ones).
+Fixes from the 2026-08-21 security audit.
 
-- **Electron** (`frontend/electron/main.ts`):
-  - New `RENDERER_METHODS` set: the three native methods (`pick_image`, `link_preview`,
-    `upload_image`) plus every Rust-backend method actually used by `frontend/src/lib/api.ts`
-    (init/get_state, profiles, publish, feed, relays, settings, vault password/unlock,
-    reveal_secret_key, signer control/approve).
-  - `isAllowedMethod()` gate at the top of the `backend:request` handler; anything not in
-    the list returns `{status:'error', code:'unknown_method'}` and is logged to stderr —
-    it never reaches the backend process.
-  - No behaviour change for the real UI: `window.backend.request` is only ever called from
-    `api.ts`, whose full surface is covered by the allowlist (confirmed by grep + tests).
-- Remaining audit items (not yet done): token-based upload path validation (#2), CSP
-  `'unsafe-inline'` removal + window-open deny (#3), legacy-vault permissions (#4),
-  permission race windows (#5), key zeroization (#6).
+**#1 IPC method allowlist (`4bde395`, `main.ts` only):**
+- `RENDERER_METHODS` set in the Electron main process: the three native methods
+  (`pick_image`, `link_preview`, `upload_image`) plus every Rust-backend method used by
+  `frontend/src/lib/api.ts`.
+- `isAllowedMethod()` gate at the top of the `backend:request` handler; unknown methods get
+  `{status:'error', code:'unknown_method'}`, are logged, and never reach the backend.
+- No behaviour change for the real UI (only `api.ts` calls `window.backend.request`).
+
+**#2 Upload pick tokens (`6e627a3`):**
+The renderer used to send raw filesystem paths back to main for upload, so a compromised
+page could read+publish arbitrary local files to nostr.build. Now:
+- `pickImage()` (`main.ts`) mints a random 32-hex-char token per picked file via
+  `crypto.randomBytes`; tokens map to the file record in `pickedTokens` (main-process memory
+  only). The renderer receives `{token, name, mime}` — it never sees any path.
+- `upload_image` accepts only a valid `token`; the token is consumed (deleted) before the
+  upload starts, so each pick authorises exactly one upload. Unknown/used/expired tokens
+  return `{status:'error', code:'unknown_token', message:'That image selection has expired.
+  Please attach it again.'}` — the user just re-picks the image.
+- Renderer updates: `PickedImage.path` → `PickedImage.token` (`types.ts`), `api.uploadImage(token)`
+  (`api.ts`), context type + callback (`AppProvider.tsx`), `ComposeScreen.onAttach` uses
+  `image.token`.
+- Fake backend mirrors the contract: `upload_image` without a non-empty `token` throws an
+  `unknown_token` error, so tests exercise the same protocol rule.
 
 ## Commits
 
-- `4bde395` "Restrict renderer IPC to an explicit method allowlist" — `main.ts` only (+49 lines).
+- `6e627a3` "Replace upload file paths with single-use pick tokens" — main.ts, api.ts,
+  types.ts, AppProvider.tsx, ComposeScreen.tsx, fakeBackend.ts (+62/−27).
+- `4bde395` "Restrict renderer IPC to an explicit method allowlist" — main.ts (+49 lines).
+- `dafed33` "Refresh checkpoint with IPC allowlist hardening".
 
 ## How it was verified (all green)
 
@@ -47,31 +57,34 @@ npm run typecheck     # clean (frontend/)
 npm run lint          # clean (pre-existing module-type warning only)
 npm run format:check  # clean
 npm test              # 78 passed (14 files)
-npm run electron:build # compiles the Electron main process with the new gate
+npm run electron:build # compiles the Electron main process
 npm run build         # rebuilds the React bundle (dist/)
 ```
 
+Manual protocol checks worth doing once:
+- DevTools console: `window.backend.request('not_a_method')` → `unknown_method` envelope (#1).
+- DevTools console: `window.backend.request('upload_image', {path:'/etc/passwd'})` →
+  `unknown_token` error; no file is read (#2). Real attachment flow works unchanged.
+
 ## How to resume
 
 1. Open the repo: `cd /home/avi/Projects/0_Nostr`
-2. State is committed: `git status` should be clean; `git log --oneline -3` shows `4bde395`
+2. State is committed: `git status` should be clean; `git log --oneline -4` shows `6e627a3`
    on top.
 3. Launch as usual: `cd frontend && npm start` (backend already built in `target/release/`).
-4. To see the gate working: from the DevTools console run
-   `window.backend.request('not_a_method')` → resolves to a `unknown_method` error envelope;
-   normal screens keep working unchanged.
-5. Re-run verification with the commands above.
+4. Re-run verification with the commands above.
 
 ## Outstanding / next steps (if you continue)
 
-Security-audit follow-ups in priority order:
+Remaining audit items in priority order:
 
-1. **Upload path tokens** — `upload_image` currently reads any renderer-supplied file path;
-   issue random tokens per picked file and accept only those (`main.ts`).
-2. **CSP** — drop `'unsafe-inline'` from `script-src` in `frontend/index.html`; add
-   `setWindowOpenHandler` deny + `shell.openExternal` for external links in `main.ts`.
-3. **Legacy vault perms** — repo-root `profiles_vault.json` is group-readable (0664);
-   chmod 600 / delete after confirming migration; also auto-tighten during migration in
-   `src/vault.rs`.
-4. **Write-race fixes** — create files with mode 0600 at creation time in `vault.rs`.
-5. **Zeroize** — wipe decrypted key material via the `zeroize` crate.
+1. **CSP** — drop `'unsafe-inline'` from `script-src` in `frontend/index.html`; add
+   `setWindowOpenHandler(() => ({action:'deny'}))` + route external links through
+   `shell.openExternal` in `main.ts`.
+2. **Legacy vault perms** — repo-root `profiles_vault.json` is group-readable (0664);
+   chmod 600 / delete after confirming migration; auto-tighten during migration in `src/vault.rs`.
+3. **Write-race fixes** — create files with mode 0600 at creation time in `vault.rs`
+   (`write_restricted`, `backup_file`).
+4. **Zeroize** — wipe decrypted key material via the `zeroize` crate.
+5. Smaller: link-preview SSRF guard (block loopback/private IPs), signer pending-cap,
+   NIP-46 secret echo check, backend request timeout.