feat: migrate to UnifiedPush

app/api/push/jmap/[id]/route.ts

@@ -1,7 +1,7 @@
 import { NextRequest, NextResponse } from 'next/server';
 import { logger } from '@/lib/logger';
 import { subscriptionStore } from '@/lib/push/store';
-import { sendExpoPush } from '@/lib/push/expo';
+import { sendUnifiedPush } from '@/lib/push/unified-push';
 import { isValidSubscriptionId } from '@/lib/push/validation';
 import type { JmapPushBody } from '@/lib/push/types';
 
@@ -75,7 +75,7 @@ export async function POST(
     }
 
     if (body['@type'] === 'StateChange') {
-      const ok = await sendExpoPush(record, body);
+      const ok = await sendUnifiedPush(record, body);
       record.lastPushAt = Date.now();
       await subscriptionStore.put(id, record);
       return NextResponse.json({ ok });

app/api/push/register/route.ts

@@ -2,41 +2,57 @@ import { NextRequest, NextResponse } from 'next/server';
 import { logger } from '@/lib/logger';
 import { subscriptionStore } from '@/lib/push/store';
 import {
-  isValidExpoPushToken,
+  isValidAuthSecret,
+  isValidP256dh,
+  isValidPushEndpoint,
   isValidSubscriptionId,
 } from '@/lib/push/validation';
 import type { SubscriptionRecord } from '@/lib/push/types';
 
 /**
  * POST /api/push/register
- * Body: { subscriptionId, expoPushToken, accountLabel? }
+ * Body: { subscriptionId, endpoint, p256dh, auth, accountLabel? }
  *
- * Called by the mobile app once it has created a JMAP PushSubscription and
- * received the subscriptionId it plans to use. We hold only the device's
- * Expo push token + that id — no user credentials pass through the relay.
+ * Called by the mobile app once its UnifiedPush distributor has produced a
+ * push endpoint. We hold only the Web Push keys needed to encrypt payloads
+ * per RFC 8291 — no user credentials pass through the relay.
  */
 export async function POST(request: NextRequest) {
   try {
     const body = (await request.json().catch(() => null)) as {
       subscriptionId?: unknown;
-      expoPushToken?: unknown;
+      endpoint?: unknown;
+      p256dh?: unknown;
+      auth?: unknown;
       accountLabel?: unknown;
     } | null;
     if (!body) return NextResponse.json({ error: 'Invalid JSON' }, { status: 400 });
 
-    const { subscriptionId, expoPushToken, accountLabel } = body;
+    const { subscriptionId, endpoint, p256dh, auth, accountLabel } = body;
     if (!isValidSubscriptionId(subscriptionId)) {
       return NextResponse.json({ error: 'Invalid subscriptionId' }, { status: 400 });
     }
-    if (!isValidExpoPushToken(expoPushToken)) {
-      return NextResponse.json({ error: 'Invalid expoPushToken' }, { status: 400 });
+    if (!isValidPushEndpoint(endpoint)) {
+      return NextResponse.json({ error: 'Invalid endpoint' }, { status: 400 });
+    }
+    if (!isValidP256dh(p256dh)) {
+      return NextResponse.json({ error: 'Invalid p256dh' }, { status: 400 });
+    }
+    if (!isValidAuthSecret(auth)) {
+      return NextResponse.json({ error: 'Invalid auth' }, { status: 400 });
     }
 
+    // Preserve verificationCode if a previous record exists — the JMAP server
+    // may have already POSTed PushVerification before the app re-registers.
+    const existing = await subscriptionStore.get(subscriptionId);
+
     const record: SubscriptionRecord = {
-      expoPushToken,
-      verificationCode: null,
-      createdAt: Date.now(),
-      lastPushAt: null,
+      endpoint,
+      p256dh,
+      auth,
+      verificationCode: existing?.verificationCode ?? null,
+      createdAt: existing?.createdAt ?? Date.now(),
+      lastPushAt: existing?.lastPushAt ?? null,
       accountLabel:
         typeof accountLabel === 'string' ? accountLabel.slice(0, 120) : undefined,
     };

app/api/push/vapid/route.ts

@@ -0,0 +1,22 @@
+import { NextResponse } from 'next/server';
+import { logger } from '@/lib/logger';
+import { getVapidKeys } from '@/lib/push/vapid';
+
+/**
+ * GET /api/push/vapid
+ *
+ * Returns the relay's VAPID public key. The mobile app passes this to the
+ * UnifiedPush distributor so the distributor can lock the endpoint to pushes
+ * signed by us. Generated on first call; persisted under `data/push/vapid.json`.
+ */
+export async function GET() {
+  try {
+    const keys = await getVapidKeys();
+    return NextResponse.json({ publicKey: keys.publicKey });
+  } catch (error) {
+    logger.error('push: vapid key fetch failed', {
+      error: error instanceof Error ? error.message : 'Unknown error',
+    });
+    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
+  }
+}

lib/push/base64url.ts

@@ -0,0 +1,14 @@
+export function b64uEncode(buf: Buffer | Uint8Array): string {
+  const b = Buffer.isBuffer(buf) ? buf : Buffer.from(buf);
+  return b
+    .toString('base64')
+    .replace(/\+/g, '-')
+    .replace(/\//g, '_')
+    .replace(/=+$/, '');
+}
+
+export function b64uDecode(value: string): Buffer {
+  const padded = value.replace(/-/g, '+').replace(/_/g, '/');
+  const padLen = (4 - (padded.length % 4)) % 4;
+  return Buffer.from(padded + '='.repeat(padLen), 'base64');
+}

lib/push/expo.ts

@@ -1,61 +0,0 @@
-import { logger } from '@/lib/logger';
-import type { StateChange, SubscriptionRecord } from './types';
-
-// Expo's push API. Swap via env when self-hosting.
-function getExpoPushUrl(): string {
-  return process.env.EXPO_PUSH_URL ?? 'https://exp.host/--/api/v2/push/send';
-}
-
-export async function sendExpoPush(
-  record: SubscriptionRecord,
-  change: StateChange,
-): Promise<boolean> {
-  // Summarize the JMAP StateChange into a hint the user can see on lock
-  // screen. The app wakes on receipt, re-fetches via JMAP with its own creds,
-  // and can replace the notification via `presentNotificationAsync` if
-  // subject/sender should be shown.
-  const types = new Set<string>();
-  for (const perAccount of Object.values(change.changed)) {
-    for (const type of Object.keys(perAccount)) types.add(type);
-  }
-  const hasEmail = types.has('Email') || types.has('EmailDelivery');
-
-  const message = {
-    to: record.expoPushToken,
-    title: hasEmail ? 'New mail' : 'Mailbox updated',
-    body: record.accountLabel ?? '',
-    sound: 'default',
-    priority: 'high' as const,
-    channelId: 'mail',
-    data: {
-      kind: 'jmap-state-change',
-      changed: change.changed,
-    },
-    _contentAvailable: true,
-  };
-
-  try {
-    const res = await fetch(getExpoPushUrl(), {
-      method: 'POST',
-      headers: {
-        'content-type': 'application/json',
-        accept: 'application/json',
-        'accept-encoding': 'gzip, deflate',
-      },
-      body: JSON.stringify(message),
-    });
-    if (!res.ok) {
-      logger.warn('push: expo delivery failed', {
-        status: res.status,
-        body: await res.text().catch(() => ''),
-      });
-      return false;
-    }
-    return true;
-  } catch (error) {
-    logger.warn('push: expo delivery error', {
-      error: error instanceof Error ? error.message : 'Unknown error',
-    });
-    return false;
-  }
-}

lib/push/types.ts

@@ -2,7 +2,13 @@
 // so both server code and admin UIs can import without pulling `node:fs`.
 
 export interface SubscriptionRecord {
-  expoPushToken: string;
+  // UnifiedPush / Web Push endpoint the distributor gave the app. The relay
+  // POSTs RFC 8291 aes128gcm-encrypted bodies here.
+  endpoint: string;
+  // P-256 public key (UA), uncompressed 65-byte point, base64url without padding.
+  p256dh: string;
+  // Auth secret, 16 bytes, base64url without padding.
+  auth: string;
   verificationCode: string | null;
   createdAt: number;
   lastPushAt: number | null;

lib/push/unified-push.ts

@@ -0,0 +1,57 @@
+import { logger } from '@/lib/logger';
+import type { StateChange, SubscriptionRecord } from './types';
+import { sendWebPush } from './web-push';
+import { getVapidKeys } from './vapid';
+
+interface UnifiedPushPayload {
+  kind: 'jmap-state-change';
+  title: string;
+  body: string;
+  changed: Record<string, Record<string, string>>;
+}
+
+function buildPayload(record: SubscriptionRecord, change: StateChange): UnifiedPushPayload {
+  const types = new Set<string>();
+  for (const perAccount of Object.values(change.changed)) {
+    for (const type of Object.keys(perAccount)) types.add(type);
+  }
+  const hasEmail = types.has('Email') || types.has('EmailDelivery');
+  return {
+    kind: 'jmap-state-change',
+    title: hasEmail ? 'New mail' : 'Mailbox updated',
+    body: record.accountLabel ?? '',
+    changed: change.changed,
+  };
+}
+
+export async function sendUnifiedPush(
+  record: SubscriptionRecord,
+  change: StateChange,
+): Promise<boolean> {
+  try {
+    const vapid = await getVapidKeys();
+    const payload = Buffer.from(JSON.stringify(buildPayload(record, change)), 'utf-8');
+    const result = await sendWebPush({
+      endpoint: record.endpoint,
+      p256dh: record.p256dh,
+      auth: record.auth,
+      payload,
+      vapid,
+      ttlSeconds: 60,
+      urgency: 'high',
+    });
+    if (!result.ok) {
+      logger.warn('push: unified-push delivery failed', {
+        status: result.status,
+        body: result.body,
+      });
+      return false;
+    }
+    return true;
+  } catch (error) {
+    logger.warn('push: unified-push delivery error', {
+      error: error instanceof Error ? error.message : 'Unknown error',
+    });
+    return false;
+  }
+}

lib/push/validation.ts

@@ -2,11 +2,30 @@ export function isValidSubscriptionId(id: unknown): id is string {
   return typeof id === 'string' && /^[A-Za-z0-9_-]{8,128}$/.test(id);
 }
 
-export function isValidExpoPushToken(token: unknown): token is string {
-  if (typeof token !== 'string') return false;
-  // Expo managed tokens, or raw FCM/APNs tokens for bare workflows.
-  return (
-    /^ExponentPushToken\[[A-Za-z0-9_-]+\]$/.test(token) ||
-    /^[A-Za-z0-9:_-]{40,250}$/.test(token)
-  );
+export function isValidPushEndpoint(url: unknown): url is string {
+  if (typeof url !== 'string' || url.length > 2048) return false;
+  try {
+    const parsed = new URL(url);
+    return parsed.protocol === 'https:' || parsed.protocol === 'http:';
+  } catch {
+    return false;
+  }
+}
+
+export function isBase64Url(value: unknown, minBytes: number, maxBytes: number): value is string {
+  if (typeof value !== 'string') return false;
+  if (!/^[A-Za-z0-9_-]+$/.test(value)) return false;
+  // base64url decoded length: floor(n * 3 / 4) where n is input length (no padding).
+  const decodedLen = Math.floor((value.length * 3) / 4);
+  return decodedLen >= minBytes && decodedLen <= maxBytes;
+}
+
+export function isValidP256dh(value: unknown): value is string {
+  // Uncompressed P-256 point is 65 bytes (0x04 || X || Y). base64url no padding.
+  return isBase64Url(value, 64, 66);
+}
+
+export function isValidAuthSecret(value: unknown): value is string {
+  // RFC 8291 requires 16 bytes.
+  return isBase64Url(value, 16, 16);
 }

lib/push/vapid.ts

@@ -0,0 +1,90 @@
+import crypto from 'node:crypto';
+import { readFile, writeFile, mkdir } from 'node:fs/promises';
+import { existsSync } from 'node:fs';
+import path from 'node:path';
+import { b64uDecode, b64uEncode } from './base64url';
+
+interface StoredVapid {
+  publicKey: string;
+  privateKeyPem: string;
+  subject: string;
+}
+
+export interface VapidKeys {
+  publicKey: string;
+  publicKeyBuf: Buffer;
+  privateKeyPem: string;
+  subject: string;
+}
+
+function getVapidPath(): string {
+  const dir = process.env.PUSH_DATA_DIR || path.join(process.cwd(), 'data', 'push');
+  return path.join(dir, 'vapid.json');
+}
+
+function getSubject(): string {
+  return process.env.VAPID_SUBJECT?.trim() || 'mailto:admin@localhost';
+}
+
+// P-256 SPKI DER wraps a 26-byte algorithm identifier followed by a BIT STRING
+// containing the uncompressed point (0x04 || X || Y). Strip the header to get
+// the raw 65-byte public key that VAPID requires.
+function extractUncompressedPoint(spkiDer: Buffer): Buffer {
+  if (spkiDer.length < 65) throw new Error('SPKI DER too short for P-256');
+  return spkiDer.subarray(spkiDer.length - 65);
+}
+
+let cached: VapidKeys | null = null;
+let loading: Promise<VapidKeys> | null = null;
+
+async function loadOrCreate(): Promise<VapidKeys> {
+  const file = getVapidPath();
+  try {
+    const raw = await readFile(file, 'utf-8');
+    const parsed = JSON.parse(raw) as StoredVapid;
+    return {
+      publicKey: parsed.publicKey,
+      publicKeyBuf: b64uDecode(parsed.publicKey),
+      privateKeyPem: parsed.privateKeyPem,
+      subject: parsed.subject,
+    };
+  } catch (error) {
+    if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error;
+  }
+
+  const { publicKey, privateKey } = crypto.generateKeyPairSync('ec', {
+    namedCurve: 'prime256v1',
+  });
+  const spki = publicKey.export({ format: 'der', type: 'spki' });
+  const uncompressed = extractUncompressedPoint(spki);
+  const privateKeyPem = privateKey.export({ format: 'pem', type: 'pkcs8' }) as string;
+  const stored: StoredVapid = {
+    publicKey: b64uEncode(uncompressed),
+    privateKeyPem,
+    subject: getSubject(),
+  };
+
+  const dir = path.dirname(file);
+  if (!existsSync(dir)) await mkdir(dir, { recursive: true });
+  const tmp = file + '.tmp';
+  await writeFile(tmp, JSON.stringify(stored, null, 2), 'utf-8');
+  await import('node:fs/promises').then((fs) => fs.rename(tmp, file));
+
+  return {
+    publicKey: stored.publicKey,
+    publicKeyBuf: uncompressed,
+    privateKeyPem: stored.privateKeyPem,
+    subject: stored.subject,
+  };
+}
+
+export async function getVapidKeys(): Promise<VapidKeys> {
+  if (cached) return cached;
+  if (!loading) {
+    loading = loadOrCreate().then((keys) => {
+      cached = keys;
+      return keys;
+    });
+  }
+  return loading;
+}

lib/push/web-push.ts

@@ -0,0 +1,149 @@
+import crypto from 'node:crypto';
+import { b64uDecode, b64uEncode } from './base64url';
+import type { VapidKeys } from './vapid';
+
+// RFC 5869 HKDF-Extract + HKDF-Expand using SHA-256.
+function hkdf(salt: Buffer, ikm: Buffer, info: Buffer, length: number): Buffer {
+  const prk = crypto.createHmac('sha256', salt).update(ikm).digest();
+  const out = Buffer.alloc(length);
+  let previous = Buffer.alloc(0);
+  let offset = 0;
+  let counter = 1;
+  while (offset < length) {
+    const hmac = crypto.createHmac('sha256', prk);
+    hmac.update(previous);
+    hmac.update(info);
+    hmac.update(Buffer.from([counter]));
+    previous = hmac.digest();
+    const copyLen = Math.min(previous.length, length - offset);
+    previous.subarray(0, copyLen).copy(out, offset);
+    offset += copyLen;
+    counter++;
+  }
+  return out;
+}
+
+// RFC 8291 aes128gcm Web Push content encoding (single record).
+export function encryptAes128gcm(params: {
+  p256dh: Buffer;
+  auth: Buffer;
+  payload: Buffer;
+}): Buffer {
+  const ecdh = crypto.createECDH('prime256v1');
+  const serverPublic = ecdh.generateKeys();
+  const sharedSecret = ecdh.computeSecret(params.p256dh);
+  const salt = crypto.randomBytes(16);
+
+  // RFC 8291 §3.3: PRK_key = HMAC-SHA-256(auth_secret, IKM)
+  //                IKM = ECDH shared secret
+  //                info = "WebPush: info\0" || ua_public || as_public
+  const keyInfo = Buffer.concat([
+    Buffer.from('WebPush: info\0', 'utf-8'),
+    params.p256dh,
+    serverPublic,
+  ]);
+  const prkKey = hkdf(params.auth, sharedSecret, keyInfo, 32);
+
+  // RFC 8188 §2.2: derive CEK and nonce from PRK_key with salt.
+  const cek = hkdf(salt, prkKey, Buffer.from('Content-Encoding: aes128gcm\0', 'utf-8'), 16);
+  const nonce = hkdf(salt, prkKey, Buffer.from('Content-Encoding: nonce\0', 'utf-8'), 12);
+
+  // Single-record padding: plaintext || 0x02 (end-of-last-record delimiter).
+  const padded = Buffer.concat([params.payload, Buffer.from([0x02])]);
+
+  const cipher = crypto.createCipheriv('aes-128-gcm', cek, nonce);
+  const ciphertext = Buffer.concat([cipher.update(padded), cipher.final()]);
+  const tag = cipher.getAuthTag();
+
+  // Per RFC 8188 §2.1: salt (16) || rs (4 BE) || idlen (1) || keyid || ciphertext+tag.
+  const rsBuf = Buffer.alloc(4);
+  rsBuf.writeUInt32BE(4096, 0);
+  const idlenBuf = Buffer.from([serverPublic.length]);
+
+  return Buffer.concat([salt, rsBuf, idlenBuf, serverPublic, ciphertext, tag]);
+}
+
+// ECDSA DER → raw r||s (64 bytes) for ES256 signature encoding used by JWT.
+function derEs256ToRaw(der: Buffer): Buffer {
+  if (der[0] !== 0x30) throw new Error('Invalid DER signature');
+  let offset = 2;
+  if (der[1] & 0x80) offset += der[1] & 0x7f;
+  if (der[offset] !== 0x02) throw new Error('Invalid DER r marker');
+  const rLen = der[offset + 1];
+  let r = der.subarray(offset + 2, offset + 2 + rLen);
+  offset += 2 + rLen;
+  if (der[offset] !== 0x02) throw new Error('Invalid DER s marker');
+  const sLen = der[offset + 1];
+  let s = der.subarray(offset + 2, offset + 2 + sLen);
+  const pad = (buf: Buffer) => {
+    if (buf.length === 32) return buf;
+    if (buf.length === 33 && buf[0] === 0x00) return buf.subarray(1);
+    if (buf.length > 32) throw new Error('ECDSA component > 32 bytes');
+    const out = Buffer.alloc(32);
+    buf.copy(out, 32 - buf.length);
+    return out;
+  };
+  return Buffer.concat([pad(r), pad(s)]);
+}
+
+function buildVapidJwt(endpoint: string, vapid: VapidKeys): string {
+  const audience = new URL(endpoint).origin;
+  const header = b64uEncode(Buffer.from(JSON.stringify({ typ: 'JWT', alg: 'ES256' })));
+  const claims = b64uEncode(
+    Buffer.from(
+      JSON.stringify({
+        aud: audience,
+        exp: Math.floor(Date.now() / 1000) + 12 * 3600,
+        sub: vapid.subject,
+      }),
+    ),
+  );
+  const signingInput = `${header}.${claims}`;
+  const der = crypto.createSign('SHA256').update(signingInput).sign(vapid.privateKeyPem);
+  return `${signingInput}.${b64uEncode(derEs256ToRaw(der))}`;
+}
+
+export interface WebPushResult {
+  ok: boolean;
+  status: number;
+  body?: string;
+}
+
+export async function sendWebPush(params: {
+  endpoint: string;
+  p256dh: string;
+  auth: string;
+  payload: Buffer;
+  vapid: VapidKeys;
+  ttlSeconds?: number;
+  urgency?: 'very-low' | 'low' | 'normal' | 'high';
+  topic?: string;
+}): Promise<WebPushResult> {
+  const body = encryptAes128gcm({
+    p256dh: b64uDecode(params.p256dh),
+    auth: b64uDecode(params.auth),
+    payload: params.payload,
+  });
+  const jwt = buildVapidJwt(params.endpoint, params.vapid);
+  const headers: Record<string, string> = {
+    'content-type': 'application/octet-stream',
+    'content-encoding': 'aes128gcm',
+    'content-length': String(body.length),
+    ttl: String(params.ttlSeconds ?? 60),
+    urgency: params.urgency ?? 'high',
+    authorization: `vapid t=${jwt}, k=${params.vapid.publicKey}`,
+  };
+  if (params.topic) headers.topic = params.topic;
+
+  const res = await fetch(params.endpoint, {
+    method: 'POST',
+    headers,
+    body: new Uint8Array(body),
+  });
+  const ok = res.status >= 200 && res.status < 300;
+  return {
+    ok,
+    status: res.status,
+    body: ok ? undefined : await res.text().catch(() => undefined),
+  };
+}