Implement keep: self-hosted E2E encrypted secrets sync

Server: Express + better-sqlite3 (WAL), multi-recipient key-wrapping
per IMPLEMENTATION.md's design — vaults/recipients/vault_grants/
access_log. Two auth paths: ADMIN_PASSWORD header for recipient
management and revoke (pure metadata operations), signed-request
auth (Ed25519 signature over method+path+timestamp+body-hash) for
push/pull/grant, mirroring the spirit of this project family's other
signed-handshake patterns without naming them.

CLI: identity init/show/set-id, push/pull/grant/log, admin recipient
add/list/remove and revoke. Grant is a client-side crypto operation
(the granter unwraps the vault's current key locally and reseals it
for the new recipient) rather than a server-side operation, since the
server never holds an unwrapped key to grant with.

Verified end-to-end with two independent local identities against a
live server and separately against the built Docker image: register,
push, pull (granted and ungranted), grant without re-pushing, admin
revoke, a subsequent rotation confirming the revoked recipient stays
excluded, and rejection of missing/malformed signed-request auth.

Two real bugs caught during verification, not just written up:
- libsodium-wrappers' published ESM build does a relative import only
  resolvable under bundler-style resolution — broken under plain Node
  ESM. Fixed via createRequire to force the CJS build.
- Express's req.path inside a sub-router is relative to the mount
  point, which would have silently mismatched a client signing the
  full request path. Fixed by verifying against req.originalUrl.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/server/adminRoutes.ts

@@ -0,0 +1,47 @@
+import { Router } from 'express';
+import { randomBytes } from 'node:crypto';
+import { listRecipients, createRecipient, deleteRecipient, deleteGrant, getAccessLog, logAccess } from './db.js';
+import { requireAdminAuth } from './auth.js';
+
+export const router = Router();
+
+router.use(requireAdminAuth);
+
+function newRecipientId(label: string): string {
+  const slug = label.toLowerCase().replace(/[^a-z0-9]+/g, '-').replace(/^-+|-+$/g, '').slice(0, 24);
+  const suffix = randomBytes(3).toString('hex');
+  return slug ? `${slug}-${suffix}` : suffix;
+}
+
+router.get('/recipients', (_req, res) => {
+  res.json(listRecipients().map(r => ({ recipientId: r.recipient_id, label: r.label, publicKey: r.public_key, createdAt: r.created_at })));
+});
+
+router.post('/recipients', (req, res) => {
+  const body = req.body as { label?: string; publicKey?: string };
+  if (!body.label || !body.publicKey) {
+    res.status(400).json({ error: 'label and publicKey are required' });
+    return;
+  }
+  const recipientId = newRecipientId(body.label);
+  createRecipient(recipientId, body.label, body.publicKey);
+  res.json({ recipientId });
+});
+
+router.delete('/recipients/:id', (req, res) => {
+  deleteRecipient(req.params.id);
+  res.json({ ok: true });
+});
+
+// Revocation is pure metadata deletion — no crypto material is touched,
+// which is exactly why admin alone (no vault access of their own
+// required) can perform it, unlike `grant`.
+router.delete('/vaults/:key/grants/:recipientId', (req, res) => {
+  deleteGrant(req.params.key, req.params.recipientId);
+  logAccess(req.params.key, req.params.recipientId, 'revoke');
+  res.json({ ok: true });
+});
+
+router.get('/vaults/:key/log', (req, res) => {
+  res.json(getAccessLog(req.params.key));
+});

src/server/auth.ts

@@ -0,0 +1,77 @@
+// Signed-request authentication for recipient-facing endpoints
+// (push/pull/grant/log) — distinct from the ADMIN_PASSWORD header used by
+// admin-only routes (recipient add/remove, revoke). A recipient proves
+// their identity by signing a canonical string derived from the request
+// itself; no session, no cookie, stateless like every other password/
+// signature check in this project family.
+import type { Request, Response, NextFunction } from 'express';
+import { getRecipient } from './db.js';
+import { Identity, signingString } from '../shared/crypto.js';
+import { config } from './config.js';
+
+export interface AuthedRequest extends Request {
+  recipientId?: string;
+  rawBody?: Buffer;
+}
+
+export async function requireRecipientAuth(req: AuthedRequest, res: Response, next: NextFunction): Promise<void> {
+  const recipientId = req.get('X-Recipient-Id');
+  const signature = req.get('X-Signature');
+  const timestampHeader = req.get('X-Timestamp');
+
+  if (!recipientId || !signature || !timestampHeader) {
+    res.status(401).json({ error: 'missing auth headers' });
+    return;
+  }
+
+  const timestamp = Number(timestampHeader);
+  if (!Number.isFinite(timestamp) || Math.abs(Date.now() / 1000 - timestamp) > config.requestMaxSkewSeconds) {
+    res.status(401).json({ error: 'timestamp out of range' });
+    return;
+  }
+
+  const recipient = getRecipient(recipientId);
+  if (!recipient) {
+    res.status(401).json({ error: 'unknown recipient' });
+    return;
+  }
+
+  // req.path is relative to whichever router mounted this middleware
+  // (e.g. "/vaults/x/pull" inside a router mounted at "/api"), which would
+  // silently disagree with a client that signs the full request path.
+  // req.originalUrl is always the full path as actually requested,
+  // regardless of router nesting — strip the query string, since the
+  // client doesn't sign one.
+  const fullPath = req.originalUrl.split('?')[0];
+  const body = req.rawBody ?? Buffer.alloc(0);
+  const expected = signingString(req.method, fullPath, timestamp, body);
+
+  let sigBytes: Uint8Array;
+  try {
+    sigBytes = Buffer.from(signature, 'hex');
+  } catch {
+    res.status(401).json({ error: 'bad signature encoding' });
+    return;
+  }
+
+  const ok = Identity.verify(recipient.public_key, Buffer.from(expected, 'utf8'), sigBytes);
+  if (!ok) {
+    res.status(401).json({ error: 'signature verification failed' });
+    return;
+  }
+
+  req.recipientId = recipientId;
+  next();
+}
+
+export function requireAdminAuth(req: Request, res: Response, next: NextFunction): void {
+  if (!config.adminPassword) {
+    res.status(503).json({ error: 'admin disabled — ADMIN_PASSWORD not set' });
+    return;
+  }
+  if (req.get('X-Admin-Password') !== config.adminPassword) {
+    res.status(401).json({ error: 'bad password' });
+    return;
+  }
+  next();
+}

src/server/config.ts

@@ -0,0 +1,12 @@
+import path from 'node:path';
+
+export const config = {
+  port: parseInt(process.env.PORT ?? '3050', 10),
+  dataDir: process.env.DATA_DIR ?? path.resolve('data'),
+  // Gates recipient management + revoke. Unset disables admin routes
+  // entirely (503) rather than refusing to start — push/pull/grant for
+  // already-registered recipients keep working regardless.
+  adminPassword: process.env.ADMIN_PASSWORD || null,
+  // Replay-protection window for signed requests.
+  requestMaxSkewSeconds: parseInt(process.env.REQUEST_MAX_SKEW_SECONDS ?? '300', 10),
+};

src/server/db.ts

@@ -0,0 +1,159 @@
+import Database from 'better-sqlite3';
+import fs from 'node:fs';
+import path from 'node:path';
+import { config } from './config.js';
+
+fs.mkdirSync(config.dataDir, { recursive: true });
+
+export const db = new Database(path.join(config.dataDir, 'keep.db'));
+db.pragma('journal_mode = WAL');
+
+db.exec(`
+  CREATE TABLE IF NOT EXISTS vaults (
+    vault_key    TEXT PRIMARY KEY,
+    ciphertext   BLOB NOT NULL,
+    nonce        BLOB NOT NULL,
+    updated_at   INTEGER NOT NULL,
+    updated_by   TEXT NOT NULL
+  );
+
+  CREATE TABLE IF NOT EXISTS recipients (
+    recipient_id TEXT PRIMARY KEY,
+    label        TEXT NOT NULL,
+    public_key   TEXT NOT NULL,
+    created_at   INTEGER NOT NULL
+  );
+
+  -- Deleting a row IS the revocation for that (vault, recipient) pair.
+  CREATE TABLE IF NOT EXISTS vault_grants (
+    vault_key    TEXT NOT NULL,
+    recipient_id TEXT NOT NULL,
+    wrapped_key  TEXT NOT NULL,  -- base64 crypto_box_seal(vault_symmetric_key, recipient_pubkey)
+    granted_at   INTEGER NOT NULL,
+    PRIMARY KEY (vault_key, recipient_id)
+  );
+
+  CREATE TABLE IF NOT EXISTS access_log (
+    id           INTEGER PRIMARY KEY AUTOINCREMENT,
+    vault_key    TEXT NOT NULL,
+    recipient_id TEXT NOT NULL,
+    action       TEXT NOT NULL,
+    accessed_at  INTEGER NOT NULL
+  );
+`);
+
+export interface VaultRow {
+  vault_key: string;
+  ciphertext: Buffer;
+  nonce: Buffer;
+  updated_at: number;
+  updated_by: string;
+}
+
+export interface RecipientRow {
+  recipient_id: string;
+  label: string;
+  public_key: string;
+  created_at: number;
+}
+
+export interface GrantRow {
+  vault_key: string;
+  recipient_id: string;
+  wrapped_key: string;
+  granted_at: number;
+}
+
+export function getVault(vaultKey: string): VaultRow | undefined {
+  return db.prepare(`SELECT * FROM vaults WHERE vault_key = ?`).get(vaultKey) as VaultRow | undefined;
+}
+
+export function upsertVault(vaultKey: string, ciphertext: Buffer, nonce: Buffer, updatedBy: string): void {
+  db.prepare(
+    `INSERT INTO vaults (vault_key, ciphertext, nonce, updated_at, updated_by)
+     VALUES (?, ?, ?, ?, ?)
+     ON CONFLICT(vault_key) DO UPDATE SET
+       ciphertext = excluded.ciphertext, nonce = excluded.nonce,
+       updated_at = excluded.updated_at, updated_by = excluded.updated_by`,
+  ).run(vaultKey, ciphertext, nonce, Math.floor(Date.now() / 1000), updatedBy);
+}
+
+export function getRecipient(recipientId: string): RecipientRow | undefined {
+  return db.prepare(`SELECT * FROM recipients WHERE recipient_id = ?`).get(recipientId) as RecipientRow | undefined;
+}
+
+export function listRecipients(): RecipientRow[] {
+  return db.prepare(`SELECT * FROM recipients ORDER BY created_at ASC`).all() as RecipientRow[];
+}
+
+export function createRecipient(recipientId: string, label: string, publicKey: string): void {
+  db.prepare(
+    `INSERT INTO recipients (recipient_id, label, public_key, created_at) VALUES (?, ?, ?, ?)`,
+  ).run(recipientId, label, publicKey, Math.floor(Date.now() / 1000));
+}
+
+export function deleteRecipient(recipientId: string): void {
+  const tx = db.transaction(() => {
+    db.prepare(`DELETE FROM recipients WHERE recipient_id = ?`).run(recipientId);
+    db.prepare(`DELETE FROM vault_grants WHERE recipient_id = ?`).run(recipientId);
+  });
+  tx();
+}
+
+export function hasGrant(vaultKey: string, recipientId: string): boolean {
+  const row = db.prepare(
+    `SELECT 1 FROM vault_grants WHERE vault_key = ? AND recipient_id = ?`,
+  ).get(vaultKey, recipientId);
+  return row != null;
+}
+
+export function getGrant(vaultKey: string, recipientId: string): GrantRow | undefined {
+  return db.prepare(
+    `SELECT * FROM vault_grants WHERE vault_key = ? AND recipient_id = ?`,
+  ).get(vaultKey, recipientId) as GrantRow | undefined;
+}
+
+export function listGrantsForVault(vaultKey: string): GrantRow[] {
+  return db.prepare(`SELECT * FROM vault_grants WHERE vault_key = ?`).all(vaultKey) as GrantRow[];
+}
+
+export function setGrant(vaultKey: string, recipientId: string, wrappedKeyB64: string): void {
+  db.prepare(
+    `INSERT INTO vault_grants (vault_key, recipient_id, wrapped_key, granted_at)
+     VALUES (?, ?, ?, ?)
+     ON CONFLICT(vault_key, recipient_id) DO UPDATE SET wrapped_key = excluded.wrapped_key, granted_at = excluded.granted_at`,
+  ).run(vaultKey, recipientId, wrappedKeyB64, Math.floor(Date.now() / 1000));
+}
+
+// Used by `push` (rotation): replaces every wrapped-key row for a vault
+// in one transaction, so a concurrent grant/revoke can't interleave with
+// a partial rewrap and leave the vault in a mixed old/new-key state.
+export function replaceAllGrantsForVault(vaultKey: string, wrappedByRecipientId: Map<string, string>): void {
+  const tx = db.transaction(() => {
+    db.prepare(`DELETE FROM vault_grants WHERE vault_key = ?`).run(vaultKey);
+    const insert = db.prepare(
+      `INSERT INTO vault_grants (vault_key, recipient_id, wrapped_key, granted_at) VALUES (?, ?, ?, ?)`,
+    );
+    const now = Math.floor(Date.now() / 1000);
+    for (const [recipientId, wrappedKeyB64] of wrappedByRecipientId) {
+      insert.run(vaultKey, recipientId, wrappedKeyB64, now);
+    }
+  });
+  tx();
+}
+
+export function deleteGrant(vaultKey: string, recipientId: string): void {
+  db.prepare(`DELETE FROM vault_grants WHERE vault_key = ? AND recipient_id = ?`).run(vaultKey, recipientId);
+}
+
+export function logAccess(vaultKey: string, recipientId: string, action: 'pull' | 'push' | 'grant' | 'revoke'): void {
+  db.prepare(
+    `INSERT INTO access_log (vault_key, recipient_id, action, accessed_at) VALUES (?, ?, ?, ?)`,
+  ).run(vaultKey, recipientId, action, Math.floor(Date.now() / 1000));
+}
+
+export function getAccessLog(vaultKey: string, limit = 50): { recipient_id: string; action: string; accessed_at: number }[] {
+  return db.prepare(
+    `SELECT recipient_id, action, accessed_at FROM access_log WHERE vault_key = ? ORDER BY accessed_at DESC LIMIT ?`,
+  ).all(vaultKey, limit) as { recipient_id: string; action: string; accessed_at: number }[];
+}

src/server/index.ts

@@ -0,0 +1,34 @@
+import express from 'express';
+import { config } from './config.js';
+import { router as apiRouter } from './routes.js';
+import { router as adminRouter } from './adminRoutes.js';
+import type { AuthedRequest } from './auth.js';
+
+const app = express();
+
+// Capture the raw body bytes alongside the parsed JSON — signature
+// verification needs to hash exactly what was sent, not a re-serialized
+// version of the parsed object (which could differ in key order/spacing
+// and produce a different hash than what the client signed).
+app.use(express.json({
+  verify: (req, _res, buf) => {
+    (req as AuthedRequest).rawBody = Buffer.from(buf);
+  },
+}));
+
+// Must be registered before apiRouter — that router applies
+// requireRecipientAuth to every path under /api via router.use(), which
+// would otherwise swallow this unauthenticated health check too, since
+// Express matches route registration order and app.use('/api', ...)
+// matches /api/health as a prefix.
+app.get('/api/health', (_req, res) => res.json({ ok: true }));
+
+app.use('/api/admin', adminRouter);
+app.use('/api', apiRouter);
+
+app.listen(config.port, () => {
+  console.log(`[keep] listening on :${config.port}`);
+  if (!config.adminPassword) {
+    console.log('[keep] ADMIN_PASSWORD not set — /api/admin is disabled');
+  }
+});

src/server/routes.ts

@@ -0,0 +1,135 @@
+import { Router } from 'express';
+import {
+  getVault,
+  upsertVault,
+  hasGrant,
+  getGrant,
+  listGrantsForVault,
+  setGrant,
+  replaceAllGrantsForVault,
+  logAccess,
+  getAccessLog,
+  listRecipients,
+} from './db.js';
+import { requireRecipientAuth, type AuthedRequest } from './auth.js';
+
+export const router = Router();
+
+router.use(requireRecipientAuth);
+
+// Recipient public keys aren't secret — knowing one doesn't grant access
+// to anything — so this is recipient-authenticated (proves you're a
+// registered identity) rather than admin-gated. Needed so a recipient can
+// look up who else exists before granting them access to a vault.
+router.get('/recipients', (_req, res) => {
+  res.json(listRecipients().map(r => ({ recipientId: r.recipient_id, label: r.label, publicKey: r.public_key })));
+});
+
+// Existence isn't secret — lets `keep push` distinguish "vault doesn't
+// exist yet, fine to self-bootstrap" from "vault exists but I have no
+// grant," which a bare 403 on /recipients can't tell apart.
+router.get('/vaults/:key/exists', (req, res) => {
+  res.json({ exists: getVault(req.params.key) != null });
+});
+
+// Only current grantees of a vault can see who else has access to it —
+// needed by `keep push` to know who to re-wrap the rotated key for.
+router.get('/vaults/:key/recipients', (req: AuthedRequest, res) => {
+  const vaultKey = req.params.key;
+  if (!hasGrant(vaultKey, req.recipientId!)) {
+    res.status(403).json({ error: 'no access to this vault' });
+    return;
+  }
+  const grants = listGrantsForVault(vaultKey);
+  const byId = new Map(listRecipients().map(r => [r.recipient_id, r]));
+  res.json(grants.map(g => {
+    const r = byId.get(g.recipient_id);
+    return { recipientId: g.recipient_id, label: r?.label ?? null, publicKey: r?.public_key ?? null };
+  }));
+});
+
+router.get('/vaults/:key/pull', (req: AuthedRequest, res) => {
+  const vaultKey = req.params.key;
+  const recipientId = req.recipientId!;
+  const grant = getGrant(vaultKey, recipientId);
+  const vault = getVault(vaultKey);
+
+  if (!grant || !vault) {
+    logAccess(vaultKey, recipientId, 'pull'); // logged even on failure — a spike of failed pulls from an unexpected identity is exactly the signal this exists to surface
+    res.status(404).json({ error: 'no vault or no access' });
+    return;
+  }
+
+  logAccess(vaultKey, recipientId, 'pull');
+  res.json({
+    ciphertext: vault.ciphertext.toString('base64'),
+    nonce: vault.nonce.toString('base64'),
+    wrappedKey: grant.wrapped_key,
+    updatedAt: vault.updated_at,
+    updatedBy: vault.updated_by,
+  });
+});
+
+// Rotation: replaces the vault's ciphertext AND every recipient's wrapped
+// key in one call — the client has already generated a fresh symmetric
+// key and re-wrapped it for every currently-granted recipient (fetched
+// via GET /vaults/:key/recipients first). Existing vaults require the
+// pusher to already be a grantee (read implies write, v1 decision from
+// IMPLEMENTATION.md); a brand-new vault key may be created by any
+// registered recipient, who becomes its first grantee.
+router.post('/vaults/:key/push', (req: AuthedRequest, res) => {
+  const vaultKey = req.params.key;
+  const recipientId = req.recipientId!;
+  const existing = getVault(vaultKey);
+
+  if (existing && !hasGrant(vaultKey, recipientId)) {
+    res.status(403).json({ error: 'no access to this vault' });
+    return;
+  }
+
+  const body = req.body as { ciphertext?: string; nonce?: string; wrappedKeys?: Record<string, string> };
+  if (!body.ciphertext || !body.nonce || !body.wrappedKeys || Object.keys(body.wrappedKeys).length === 0) {
+    res.status(400).json({ error: 'ciphertext, nonce, and at least one wrapped key are required' });
+    return;
+  }
+
+  upsertVault(vaultKey, Buffer.from(body.ciphertext, 'base64'), Buffer.from(body.nonce, 'base64'), recipientId);
+  replaceAllGrantsForVault(vaultKey, new Map(Object.entries(body.wrappedKeys)));
+
+  logAccess(vaultKey, recipientId, 'push');
+  res.json({ ok: true });
+});
+
+// Adds ONE new recipient to an existing vault using the CURRENT
+// (unrotated) symmetric key — the granter must already hold a grant
+// (meaning they can unwrap the current key locally) and supplies a fresh
+// seal of that same key for the new recipient's public key. Does not
+// touch the ciphertext or any other recipient's wrapped key.
+router.post('/vaults/:key/grant', (req: AuthedRequest, res) => {
+  const vaultKey = req.params.key;
+  const granterId = req.recipientId!;
+
+  if (!hasGrant(vaultKey, granterId)) {
+    res.status(403).json({ error: 'no access to this vault' });
+    return;
+  }
+
+  const body = req.body as { recipientId?: string; wrappedKey?: string };
+  if (!body.recipientId || !body.wrappedKey) {
+    res.status(400).json({ error: 'recipientId and wrappedKey are required' });
+    return;
+  }
+
+  setGrant(vaultKey, body.recipientId, body.wrappedKey);
+  logAccess(vaultKey, granterId, 'grant');
+  res.json({ ok: true });
+});
+
+router.get('/vaults/:key/log', (req: AuthedRequest, res) => {
+  const vaultKey = req.params.key;
+  if (!hasGrant(vaultKey, req.recipientId!)) {
+    res.status(403).json({ error: 'no access to this vault' });
+    return;
+  }
+  res.json(getAccessLog(vaultKey));
+});