totp.ts · Source

totp.tsapps/api/src/modules/org/totp.tsraw ← org3,019 B← Back to the app
1/**
2 * TASK-0133 — TOTP (RFC 6238) for the org `require2FA` policy.
3 *
4 * Pure `node:crypto` (no dependency — rule 17): HMAC-SHA1, 30 s step, 6
5 * digits (the industry default; the shared `otpauth` URI is built in
6 * `two-factor.service.ts`). The SEED is a 20-byte random value, stored
7 * AES-256-GCM encrypted on `User.twoFactorSecret` (base64 envelope, same
8 * scheme as SSO/webhook secrets) — `null` = not enrolled.
9 *
10 * Verification accepts a ±1 step window (60 s clock drift tolerance).
11 */
12import { createHmac, randomBytes, timingSafeEqual } from "node:crypto";
13 
14const BASE32_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
15const STEP_SECONDS = 30;
16const DIGITS = 6;
17 
18export function base32Encode(buffer: Buffer): string {
19  let bits = 0;
20  let value = 0;
21  let out = "";
22  for (const byte of buffer) {
23    value = (value << 8) | byte;
24    bits += 8;
25    while (bits >= 5) {
26      out += BASE32_ALPHABET[(value >>> (bits - 5)) & 31];
27      bits -= 5;
28    }
29  }
30  if (bits > 0) out += BASE32_ALPHABET[(value << (5 - bits)) & 31];
31  return out;
32}
33 
34export function base32Decode(input: string): Buffer {
35  const clean = input.toUpperCase().replace(/=+$/g, "").replace(/\s/g, "");
36  let bits = 0;
37  let value = 0;
38  const out: number[] = [];
39  for (const ch of clean) {
40    const idx = BASE32_ALPHABET.indexOf(ch);
41    if (idx === -1) throw new Error("invalid base32 character");
42    value = (value << 5) | idx;
43    bits += 5;
44    if (bits >= 8) {
45      out.push((value >>> (bits - 8)) & 0xff);
46      bits -= 8;
47    }
48  }
49  return Buffer.from(out);
50}
51 
52function hotp(secret: Buffer, counter: bigint): string {
53  const buf = Buffer.alloc(8);
54  buf.writeBigUInt64BE(counter);
55  const hmac = createHmac("sha1", secret).update(buf).digest();
56  const offset = hmac[hmac.length - 1] & 0x0f;
57  const code =
58    ((hmac[offset] & 0x7f) << 24) |
59    (hmac[offset + 1] << 16) |
60    (hmac[offset + 2] << 8) |
61    hmac[offset + 3];
62  return (code % 10 ** DIGITS).toString().padStart(DIGITS, "0");
63}
64 
65/** The code for `nowMs` (default: wall clock). */
66export function totpAt(secret: Buffer, nowMs: number = Date.now()): string {
67  return hotp(secret, BigInt(Math.floor(nowMs / 1000 / STEP_SECONDS)));
68}
69 
70/** Verify a 6-digit code against the seed (±1 step window, constant-time). */
71export function totpVerify(secret: Buffer, code: string, nowMs: number = Date.now()): boolean {
72  const cleaned = code.replace(/\s+/g, "");
73  if (!/^\d{6}$/.test(cleaned)) return false;
74  const step = Math.floor(nowMs / 1000 / STEP_SECONDS);
75  for (const offset of [0, -1, 1]) {
76    const expected = hotp(secret, BigInt(step + offset));
77    if (
78      cleaned.length === expected.length &&
79      timingSafeEqual(Buffer.from(cleaned), Buffer.from(expected))
80    ) {
81      return true;
82    }
83  }
84  return false;
85}
86 
87/** Fresh 20-byte seed + its base32 string (revealed once at enrollment). */
88export function generateTotpSeed(): { seed: Buffer; secret: string } {
89  const seed = randomBytes(20);
90  return { seed, secret: base32Encode(seed) };
91}
92