269 lines
8.2 KiB
TypeScript
269 lines
8.2 KiB
TypeScript
import crypto from 'node:crypto';
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export interface VapidKeys {
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publicKey: string; // base64url uncompressed P-256 (65 bytes)
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privateKey: string; // base64url scalar D (32 bytes) or PEM
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subject: string;
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}
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export interface PushSubscriptionKeys {
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p256dh: string; // base64url
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auth: string; // base64url
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}
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export interface PushSubscriptionTarget {
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endpoint: string;
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keys: PushSubscriptionKeys;
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}
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export interface WebPushSendResult {
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statusCode: number;
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successful: boolean;
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shouldRemoveSubscription: boolean; // 404 Not Found or 410 Gone
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error?: string | undefined;
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}
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export interface WebPushOptions {
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fetchFn?: typeof fetch | undefined;
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ttl?: number | undefined;
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urgency?: ('very-low' | 'low' | 'normal' | 'high') | undefined;
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}
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let cachedEphemeralKeys: VapidKeys | null = null;
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/**
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* Generate a fresh ECDSA P-256 key pair suitable for WebPush VAPID.
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*/
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export function generateVapidKeys(subject = 'mailto:admin@krona.local'): VapidKeys {
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const { publicKey, privateKey } = crypto.generateKeyPairSync('ec', {
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namedCurve: 'prime256v1',
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});
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const pubJwk = publicKey.export({ format: 'jwk' });
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const privJwk = privateKey.export({ format: 'jwk' });
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if (!pubJwk.x || !pubJwk.y || !privJwk.d) {
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throw new Error('Failed to generate EC P-256 key pair');
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}
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const rawPub = Buffer.concat([
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Buffer.from([0x04]),
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Buffer.from(pubJwk.x, 'base64url'),
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Buffer.from(pubJwk.y, 'base64url'),
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]);
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return {
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publicKey: rawPub.toString('base64url'),
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privateKey: privJwk.d,
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subject,
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};
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}
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/**
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* Load VAPID keys from config or environment, or fallback to an in-memory ephemeral key pair.
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*/
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export function resolveVapidKeys(config: {
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VAPID_PUBLIC_KEY?: string | undefined;
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VAPID_PRIVATE_KEY?: string | undefined;
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VAPID_SUBJECT?: string | undefined;
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}): VapidKeys {
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const subject = config.VAPID_SUBJECT || 'mailto:admin@krona.local';
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if (config.VAPID_PUBLIC_KEY && config.VAPID_PRIVATE_KEY) {
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return {
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publicKey: config.VAPID_PUBLIC_KEY,
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privateKey: config.VAPID_PRIVATE_KEY,
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subject,
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};
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}
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if (Boolean(config.VAPID_PUBLIC_KEY) !== Boolean(config.VAPID_PRIVATE_KEY)) {
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throw new Error('VAPID_PUBLIC_KEY and VAPID_PRIVATE_KEY must be configured together');
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}
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// Safe ephemeral fallback in memory for dev/test
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if (!cachedEphemeralKeys) {
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cachedEphemeralKeys = generateVapidKeys(subject);
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}
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return cachedEphemeralKeys;
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}
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/**
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* Convert VAPID private key string to a KeyObject.
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*/
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function createVapidPrivateKeyObject(vapidKeys: VapidKeys): crypto.KeyObject {
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const priv = vapidKeys.privateKey.trim();
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if (priv.startsWith('-----BEGIN')) {
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return crypto.createPrivateKey({ key: priv, format: 'pem' });
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}
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// Raw 32-byte base64url scalar D
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const pubBuf = Buffer.from(vapidKeys.publicKey, 'base64url');
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if (pubBuf.length !== 65 || pubBuf[0] !== 0x04) {
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throw new Error('Invalid VAPID public key length or format');
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}
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const x = pubBuf.subarray(1, 33).toString('base64url');
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const y = pubBuf.subarray(33, 65).toString('base64url');
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return crypto.createPrivateKey({
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key: {
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kty: 'EC',
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crv: 'P-256',
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x,
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y,
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d: vapidKeys.privateKey,
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},
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format: 'jwk',
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});
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}
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/**
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* Create a VAPID Authorization header (RFC 8292).
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*/
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export function createVapidAuthorizationHeader(
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endpoint: string,
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vapidKeys: VapidKeys,
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expirationSeconds = 12 * 3600,
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): string {
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const url = new URL(endpoint);
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const audience = `${url.protocol}//${url.host}`;
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const now = Math.floor(Date.now() / 1000);
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const exp = now + expirationSeconds;
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const header = { typ: 'JWT', alg: 'ES256' };
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const payload = { aud: audience, exp, sub: vapidKeys.subject };
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const headerB64 = Buffer.from(JSON.stringify(header)).toString('base64url');
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const payloadB64 = Buffer.from(JSON.stringify(payload)).toString('base64url');
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const signingInput = `${headerB64}.${payloadB64}`;
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const privateKey = createVapidPrivateKeyObject(vapidKeys);
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const signature = crypto.sign('SHA256', Buffer.from(signingInput, 'utf8'), {
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key: privateKey,
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dsaEncoding: 'ieee-p1363',
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});
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const jwt = `${signingInput}.${signature.toString('base64url')}`;
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return `vapid t=${jwt}, k=${vapidKeys.publicKey}`;
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}
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/**
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* Encrypt a payload using AES-128-GCM content encoding (RFC 8291 / RFC 8188).
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*/
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export function encryptPushPayload(
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payload: string | Buffer,
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keys: PushSubscriptionKeys,
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): Buffer {
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const plaintext = Buffer.isBuffer(payload) ? payload : Buffer.from(payload, 'utf8');
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const recipientP256dh = Buffer.from(keys.p256dh, 'base64url');
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const recipientAuth = Buffer.from(keys.auth, 'base64url');
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if (recipientP256dh.length !== 65 || recipientP256dh[0] !== 0x04) {
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throw new Error('Invalid recipient p256dh key: expected 65-byte uncompressed point');
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}
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if (recipientAuth.length !== 16) {
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throw new Error('Invalid recipient auth secret: expected 16 bytes');
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}
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// 1. Generate ephemeral sender key pair
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const sender = crypto.createECDH('prime256v1');
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sender.generateKeys();
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const senderPublicKey = sender.getPublicKey(); // 65 bytes
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const sharedSecret = sender.computeSecret(recipientP256dh);
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// 2. Derive PRK via HKDF-Extract & Expand (RFC 8291 Section 3.2)
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const keyInfo = Buffer.concat([
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Buffer.from('WebPush: info\0', 'utf8'),
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recipientP256dh,
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senderPublicKey,
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]);
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const prk = Buffer.from(
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crypto.hkdfSync('sha256', sharedSecret, recipientAuth, keyInfo, 32),
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);
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// 3. Generate 16-byte random salt
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const salt = crypto.randomBytes(16);
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// 4. Derive CEK and NONCE (RFC 8291 Section 3.3)
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const cekInfo = Buffer.from('Content-Encoding: aes128gcm\0', 'utf8');
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const cek = Buffer.from(crypto.hkdfSync('sha256', prk, salt, cekInfo, 16));
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const nonceInfo = Buffer.from('Content-Encoding: nonce\0', 'utf8');
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const nonce = Buffer.from(crypto.hkdfSync('sha256', prk, salt, nonceInfo, 12));
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// 5. Append padding delimiter (0x02 for the final/only record in RFC 8188)
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const record = Buffer.concat([plaintext, Buffer.from([0x02])]);
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// 6. Encrypt with AES-128-GCM
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const cipher = crypto.createCipheriv('aes-128-gcm', cek, nonce);
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const ciphertext = Buffer.concat([cipher.update(record), cipher.final()]);
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const tag = cipher.getAuthTag();
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// 7. Build RFC 8188 header:
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// salt (16) + rs (4, uint32 BE = 4096) + idlen (1, uint8 = 65) + keyid (65, senderPublicKey)
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const rs = 4096;
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const rsBuf = Buffer.alloc(4);
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rsBuf.writeUInt32BE(rs, 0);
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const header = Buffer.concat([
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salt,
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rsBuf,
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Buffer.from([senderPublicKey.length]),
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senderPublicKey,
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]);
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return Buffer.concat([header, ciphertext, tag]);
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}
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/**
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* Send an encrypted WebPush notification over HTTPS.
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*/
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export async function sendWebPush(
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target: PushSubscriptionTarget,
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payload: string,
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vapidKeys: VapidKeys,
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options?: WebPushOptions,
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): Promise<WebPushSendResult> {
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if (!target.endpoint.startsWith('https://')) {
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throw new Error('Subscription endpoint must use HTTPS');
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}
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const encryptedBody = encryptPushPayload(payload, target.keys);
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const authHeader = createVapidAuthorizationHeader(target.endpoint, vapidKeys);
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const fetchImpl = options?.fetchFn ?? fetch;
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try {
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const response = await fetchImpl(target.endpoint, {
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method: 'POST',
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headers: {
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'Authorization': authHeader,
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'Content-Type': 'application/octet-stream',
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'Content-Encoding': 'aes128gcm',
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'TTL': String(options?.ttl ?? 86400),
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'Urgency': options?.urgency ?? 'normal',
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},
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body: new Uint8Array(encryptedBody),
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});
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const statusCode = response.status;
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if (statusCode >= 200 && statusCode < 300) {
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return { statusCode, successful: true, shouldRemoveSubscription: false };
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}
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const shouldRemoveSubscription = statusCode === 404 || statusCode === 410;
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const bodyText = await response.text().catch(() => '');
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return {
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statusCode,
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successful: false,
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shouldRemoveSubscription,
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error: `Push service rejected notification: HTTP ${statusCode}${bodyText ? ` (${bodyText.slice(0, 200)})` : ''}`,
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};
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} catch (err) {
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const errorMsg = err instanceof Error ? err.message : String(err);
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return {
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statusCode: 0,
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successful: false,
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shouldRemoveSubscription: false,
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error: `Network error delivering push: ${errorMsg}`,
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};
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}
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}
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