noise-js.ts

1/**2 * Noise NK initiator for browser-to-browser sync.3 * Pattern: Noise_NK_25519_ChaChaPoly_BLAKE2s4 *5 * The protocol state machine lives in the canonical Rust `snow` core and is6 * compiled to WASM here and JNI on Android. This file keeps the stable7 * TypeScript orchestration API plus the post-handshake proof helpers.8 */910import { sharedKey } from "@stablelib/x25519";11import { BLAKE2s } from "@stablelib/blake2s";12import { SHA256 } from "@stablelib/sha256";13import { HMAC } from "@stablelib/hmac";14import {15  rustNoiseKkInitiator,16  rustNoiseKkResponder,17  rustNoiseNkInitiator,18  rustNoiseNkResponder,19} from "./noise-core";2021const PROTOCOL_NAME = "Noise_NK_25519_ChaChaPoly_BLAKE2s";2223// libhydrogen's contributory-behaviour blocklist: the nine small-order X2551924// u-coordinates. Mirrors X25519_SMALL_ORDER_PUBKEYS in crypto-core (PB-26-014)25// so the TS-side DH boundaries fail before the DH, not just the WASM core.26const X25519_SMALL_ORDER_PUBKEYS = new Set([27  "00".repeat(32),28  "01" + "00".repeat(31),29  "e0eb7a7c3b41b8ae1656e3faf19fc46ada098deb9c32b1fd866205165f49b880",30  "5f9c95bca3508c24b1d0b1559c83ef5b04445cc4581c8e86d8224eddd09f11d7",31  "ec" + "ff".repeat(30) + "7f",32  "ed" + "ff".repeat(30) + "7f",33  "ee" + "ff".repeat(30) + "7f",34  "cdeb7a7c3b41b8ae1656e3faf19fc46ada098deb9c32b1fd866205165f49b880",35  "4c9c95bca3508c24b1d0b1559c83ef5b04445cc4581c8e86d8224eddd09f11d7",36]);3738export function isSmallOrderPubkey(publicKey: Uint8Array): boolean {39  return publicKey.length === 32 && X25519_SMALL_ORDER_PUBKEYS.has(bytesToHex(publicKey));40}4142function initProtocolHash(protocolName: string): Uint8Array {43  const nameBytes = new TextEncoder().encode(protocolName);44  if (nameBytes.length <= 32) {45    const h = new Uint8Array(32);46    h.set(nameBytes);47    return h;48  }49  // PCH-01-002: the named pattern hash is BLAKE2s; the protocol-name init hash50  // MUST use it too (Noise spec §5.2), not SHA-256.51  return new BLAKE2s(32).update(nameBytes).digest();52}5354export function initHash(): Uint8Array {55  return initProtocolHash(PROTOCOL_NAME);56}5758export function hkdf2(ck: Uint8Array, ikm: Uint8Array): [Uint8Array, Uint8Array] {59  // PCH-01-002: HKDF must run over the named hash (BLAKE2s), not SHA-256.60  // @stablelib's HKDF reuses one HMAC across blocks and BLAKE2s's restoreState()61  // never clears its `finished` flag, so `new HKDF(BLAKE2s, …)` throws. Run62  // standard HKDF-Expand (RFC 5869, empty info) with a FRESH HMAC-BLAKE2s per63  // block — byte-identical to BouncyCastle `HKDFBytesGenerator(Blake2sDigest)`64  // on peach-android. NOTE: the HMAC-SHA256 post-handshake auth proof is a65  // SEPARATE construction, intentionally unchanged (so the SHA256 import stays).66  const prk = new HMAC(BLAKE2s, ck).update(ikm).digest(); // Extract (salt=ck)67  const k1 = new HMAC(BLAKE2s, prk).update(Uint8Array.of(1)).digest();68  const k2 = new HMAC(BLAKE2s, prk).update(k1).update(Uint8Array.of(2)).digest();69  return [k1, k2];70}7172export interface NoiseNKSession {73  encrypt(plaintext: Uint8Array): Uint8Array;74  decrypt(ciphertext: Uint8Array): Uint8Array;75  readonly handshakeHash: Uint8Array;76  rekeyOutgoing(): void;77  rekeyIncoming(): void;78  close(): void;79}8081/**82 * Standard Noise KK initiator for reconnects.83 *84 * Pre-messages: -> s, <- s85 * Message 1:    -> e, es, ss86 * Message 2:    <- e, ee, se87 *88 * Both static keys are local inputs. There is no negotiation and no fallback89 * to NK: a mismatch hard-fails this handshake.90 */91export async function noiseKKInitiator(92  ourStaticPrivateKey: Uint8Array,93  ourStaticPublicKey: Uint8Array,94  responderStaticPublicKey: Uint8Array,95  send: (msg: Uint8Array) => Promise<void>,96  receive: () => Promise<Uint8Array>,97): Promise<NoiseNKSession> {98  if (isSmallOrderPubkey(responderStaticPublicKey)) {99    throw new Error("noise: small-order X25519 responder static key");100  }101  return rustNoiseKkInitiator(102    ourStaticPrivateKey,103    ourStaticPublicKey,104    responderStaticPublicKey,105    send,106    receive,107  );108}109110/**111 * Standard Noise KK responder. The expected initiator key must come from the112 * local paired-device registry before this function is called.113 */114export async function noiseKKResponder(115  ourStaticPrivateKey: Uint8Array,116  ourStaticPublicKey: Uint8Array,117  expectedInitiatorStaticPublicKey: Uint8Array,118  send: (msg: Uint8Array) => Promise<void>,119  receive: () => Promise<Uint8Array>,120): Promise<NoiseNKSession> {121  if (isSmallOrderPubkey(expectedInitiatorStaticPublicKey)) {122    throw new Error("noise: small-order X25519 initiator static key");123  }124  return rustNoiseKkResponder(125    ourStaticPrivateKey,126    ourStaticPublicKey,127    expectedInitiatorStaticPublicKey,128    send,129    receive,130  );131}132133/**134 * Run the initiator side of the Noise NK handshake. The caller provides135 * `send` / `receive` for the two transport-side handshake messages and gets136 * back a session object that encrypts/decrypts subsequent transport frames.137 */138export async function noiseNKInitiator(139  responderStaticPublicKey: Uint8Array,140  send: (msg: Uint8Array) => Promise<void>,141  receive: () => Promise<Uint8Array>,142): Promise<NoiseNKSession> {143  if (isSmallOrderPubkey(responderStaticPublicKey)) {144    throw new Error("noise: small-order X25519 responder static key");145  }146  return rustNoiseNkInitiator(147    responderStaticPublicKey,148    send,149    receive,150  );151}152153/**154 * Compute the post-handshake auth proof.155 *156 * proof = HMAC-SHA256(157 *   key   = X25519(local_priv, remote_pub),  // 32-byte DH shared158 *   data  = "peach-sync-v1-initiator-auth"159 *        || initiator_public160 *        || responder_public161 *        || nonce_32162 * )163 *164 * Both sides pass the same DH peer key (their PEER's public key) and the same165 * initiator_public/responder_public ordering so the MAC matches. This helper166 * targets the initiator-side: `local_priv` is the initiator's private key,167 * `remote_pub` is the responder's public key.168 */169const AUTH_DOMAIN = new TextEncoder().encode("peach-sync-v1-initiator-auth");170171export function computeAuthProof(172  initiatorPrivate: Uint8Array,173  initiatorPublic: Uint8Array,174  responderPublic: Uint8Array,175  nonce: Uint8Array,176  handshakeHash: Uint8Array,177): Uint8Array {178  if (nonce.length !== 32) throw new Error("auth nonce must be 32 bytes");179  if (handshakeHash.length !== 32) throw new Error("handshake hash must be 32 bytes");180  if (isSmallOrderPubkey(responderPublic)) {181    throw new Error("small-order X25519 responder public key");182  }183184  const dh = sharedKey(initiatorPrivate, responderPublic, true);185  const mac = new HMAC(SHA256, dh);186  // PCH-01-003b: bind the proof to THIS Noise session so it cannot be replayed187  // onto a different handshake. handshakeHash is prepended; both sides hold the188  // identical value and feed it in the same position.189  mac.update(handshakeHash);190  mac.update(AUTH_DOMAIN);191  mac.update(initiatorPublic);192  mac.update(responderPublic);193  mac.update(nonce);194  return mac.digest();195}196197interface AuthChallengeFrame {198  type: "CHALLENGE";199  nonce_hex: string;200  responder_public_key_hex: string;201}202203interface AuthProofFrame {204  type: "PROOF";205  initiator_public_key_hex: string;206  proof_hex: string;207}208209function bytesToHex(bytes: Uint8Array): string {210  return Array.from(bytes, (b) => b.toString(16).padStart(2, "0")).join("");211}212213function hexToBytes(hex: string): Uint8Array {214  if (hex.length % 2 !== 0) throw new Error("invalid hex");215  const bytes = new Uint8Array(hex.length / 2);216  for (let i = 0; i < hex.length; i += 2) {217    bytes[i / 2] = parseInt(hex.slice(i, i + 2), 16);218  }219  return bytes;220}221222/**223 * Drive the initiator side of the post-handshake challenge/proof round. The224 * responder sends a `Challenge` JSON frame; we compute the HMAC and reply225 * with a `Proof` frame. Both frames are encrypted via the post-handshake226 * Noise transport (caller owns the `sendEncrypted` / `receiveEncrypted` pair).227 */228/**229 * Run the responder side of the Noise NK handshake. Symmetric with230 * `noiseNKInitiator` — the caller provides `send` / `receive` for the two231 * handshake messages and gets back a session for transport-phase frames.232 *233 * The Rust core runs the same state machine as the browser initiator and the234 * Android JNI adapter.235 */236export async function noiseNKResponder(237  ourStaticPrivateKey: Uint8Array,238  ourStaticPublicKey: Uint8Array,239  send: (msg: Uint8Array) => Promise<void>,240  receive: () => Promise<Uint8Array>,241): Promise<NoiseNKSession> {242  return rustNoiseNkResponder(243    ourStaticPrivateKey,244    ourStaticPublicKey,245    send,246    receive,247  );248}249250/**251 * Constant-time 32-byte equality. The MAC comparison in `verifyAuthProof`252 * goes through this so a same-LAN attacker can't time the HMAC compare.253 */254function constantTimeEq(a: Uint8Array, b: Uint8Array): boolean {255  if (a.length !== b.length) return false;256  let diff = 0;257  for (let i = 0; i < a.length; i++) diff |= a[i]! ^ b[i]!;258  return diff === 0;259}260261/**262 * Drive the responder side of the post-handshake challenge/proof round. We263 * generate a random 32-byte nonce, send `Challenge`, receive `Proof`, and264 * verify. Returns the initiator's authenticated public key on success.265 *266 * The MAC key is X25519(our_priv, initiator_pub) and the data is the same267 * domain-separated transcript both sides feed into HMAC-SHA256.268 */269export async function performResponderAuth(270  session: NoiseNKSession,271  ourPrivateKey: Uint8Array,272  ourPublicKey: Uint8Array,273  sendEncryptedJson: (data: Uint8Array) => Promise<void>,274  receiveEncryptedJson: () => Promise<Uint8Array>,275): Promise<{ initiatorPublicKey: Uint8Array }> {276  // PCH-01-003b: bind the verifier's recomputed MAC to this Noise session.277278  const nonce = new Uint8Array(32);279  crypto.getRandomValues(nonce);280281  const challenge: AuthChallengeFrame = {282    type: "CHALLENGE",283    nonce_hex: bytesToHex(nonce),284    responder_public_key_hex: bytesToHex(ourPublicKey),285  };286  await sendEncryptedJson(new TextEncoder().encode(JSON.stringify(challenge)));287288  const proofBytes = await receiveEncryptedJson();289  const proofFrame = JSON.parse(new TextDecoder().decode(proofBytes)) as AuthProofFrame;290  if (proofFrame.type !== "PROOF") {291    throw new Error("expected PROOF frame");292  }293294  const initiatorPublicKey = hexToBytes(proofFrame.initiator_public_key_hex);295  const claimedProof = hexToBytes(proofFrame.proof_hex);296  if (initiatorPublicKey.length !== 32) {297    throw new Error("initiator public key must be 32 bytes");298  }299  if (claimedProof.length !== 32) {300    throw new Error("proof must be 32 bytes");301  }302  if (isSmallOrderPubkey(initiatorPublicKey)) {303    throw new Error("small-order X25519 initiator public key");304  }305306  // mac_for(our_priv, initiator_pub_for_dh, initiator_pub, our_pub, nonce)307  const dh = sharedKey(ourPrivateKey, initiatorPublicKey, true);308  const mac = new HMAC(SHA256, dh);309  // PCH-01-003b: must mirror computeAuthProof — handshakeHash first, then the310  // existing domain/keys/nonce transcript. Same value, same position on both ends.311  mac.update(session.handshakeHash);312  mac.update(AUTH_DOMAIN);313  mac.update(initiatorPublicKey);314  mac.update(ourPublicKey);315  mac.update(nonce);316  const expected = mac.digest();317318  if (!constantTimeEq(expected, claimedProof)) {319    throw new Error("auth proof did not verify");320  }321  return { initiatorPublicKey };322}323324export async function performInitiatorAuth(325  session: NoiseNKSession,326  ourPrivateKey: Uint8Array,327  ourPublicKey: Uint8Array,328  responderPublicKey: Uint8Array,329  sendEncryptedJson: (data: Uint8Array) => Promise<void>,330  receiveEncryptedJson: () => Promise<Uint8Array>,331): Promise<void> {332  // PCH-01-003b: the Noise handshake hash is now mixed into the proof, binding333  // it to this exact session (was previously bound via the DH key only).334335  const challengeBytes = await receiveEncryptedJson();336  const challenge = JSON.parse(new TextDecoder().decode(challengeBytes)) as AuthChallengeFrame;337  if (challenge.type !== "CHALLENGE") {338    throw new Error("expected CHALLENGE frame");339  }340  const nonce = hexToBytes(challenge.nonce_hex);341  const responderKeyFromChallenge = hexToBytes(challenge.responder_public_key_hex);342  // Defence against an off-key challenge: the responder's claimed key MUST be343  // the one we Noise-NK-handshook against, otherwise an active MITM that344  // managed to substitute a different key is rerouting the auth round.345  if (346    responderKeyFromChallenge.length !== responderPublicKey.length ||347    !responderKeyFromChallenge.every((b, i) => b === responderPublicKey[i])348  ) {349    throw new Error("responder key in challenge does not match Noise handshake");350  }351352  const proof = computeAuthProof(353    ourPrivateKey,354    ourPublicKey,355    responderPublicKey,356    nonce,357    session.handshakeHash,358  );359  const proofFrame: AuthProofFrame = {360    type: "PROOF",361    initiator_public_key_hex: bytesToHex(ourPublicKey),362    proof_hex: bytesToHex(proof),363  };364  await sendEncryptedJson(new TextEncoder().encode(JSON.stringify(proofFrame)));365}366367export { bytesToHex, hexToBytes };