noise-js.ts

1/**2 * Noise NK initiator for Android / Capacitor.3 * Pattern: Noise_NK_25519_ChaChaPoly_BLAKE2s4 *5 * The native Rust host runs `snow` to drive the same pattern; this JS6 * implementation produces wire-identical bytes so a Capacitor WebView client7 * can connect to the desktop host over WebSocket.8 *9 * MUST stay in lockstep with the native side. The cross-check test in10 * `noise-js.test.ts` pins exact byte outputs against fixed inputs so a11 * regression on either side fails CI before any device pair gets wedged.12 */1314import { generateKeyPair, sharedKey } from "@stablelib/x25519";15import { ChaCha20Poly1305 } from "@stablelib/chacha20poly1305";16import { BLAKE2s } from "@stablelib/blake2s";17import { HKDF } from "@stablelib/hkdf";18import { SHA256 } from "@stablelib/sha256";19import { HMAC } from "@stablelib/hmac";2021const PROTOCOL_NAME = "Noise_NK_25519_ChaChaPoly_BLAKE2s";2223function initHash(): Uint8Array {24  const nameBytes = new TextEncoder().encode(PROTOCOL_NAME);25  if (nameBytes.length <= 32) {26    const h = new Uint8Array(32);27    h.set(nameBytes);28    return h;29  }30  const sha = new SHA256();31  sha.update(nameBytes);32  return sha.digest();33}3435function mixHash(h: Uint8Array, data: Uint8Array): Uint8Array {36  const blake = new BLAKE2s(32);37  blake.update(h);38  blake.update(data);39  return blake.digest();40}4142function hkdf2(ck: Uint8Array, ikm: Uint8Array): [Uint8Array, Uint8Array] {43  const out = new HKDF(SHA256, ikm, ck).expand(64);44  return [out.slice(0, 32), out.slice(32, 64)];45}4647export interface NoiseNKSession {48  encrypt(plaintext: Uint8Array): Uint8Array;49  decrypt(ciphertext: Uint8Array): Uint8Array;50  handshakeHash: Uint8Array;51}5253/**54 * Run the initiator side of the Noise NK handshake. The caller provides55 * `send` / `receive` for the two transport-side handshake messages and gets56 * back a session object that encrypts/decrypts subsequent transport frames.57 */58export async function noiseNKInitiator(59  responderStaticPublicKey: Uint8Array,60  send: (msg: Uint8Array) => Promise<void>,61  receive: () => Promise<Uint8Array>,62): Promise<NoiseNKSession> {63  let h: Uint8Array = initHash();64  let ck: Uint8Array = h.slice();6566  // NK pre-message: mix responder static public key.67  h = mixHash(h, responderStaticPublicKey);6869  const ephemeral = generateKeyPair();7071  // --- Message 1: e, es ---72  h = mixHash(h, ephemeral.publicKey);73  const es = sharedKey(ephemeral.secretKey, responderStaticPublicKey);74  const [ck1, k1] = hkdf2(ck, es);75  ck = ck1;7677  const cipher1 = new ChaCha20Poly1305(k1);78  const nonce1 = new Uint8Array(12);79  const encrypted1 = cipher1.seal(nonce1, new Uint8Array(0), h);80  h = mixHash(h, encrypted1);8182  const msg1 = new Uint8Array(32 + encrypted1.length);83  msg1.set(ephemeral.publicKey, 0);84  msg1.set(encrypted1, 32);85  await send(msg1);8687  // --- Message 2: e, ee ---88  const msg2 = await receive();89  if (msg2.length < 48) throw new Error("Noise NK: msg2 too short");9091  const remoteEphemeralPublic = msg2.slice(0, 32);92  const encrypted2 = msg2.slice(32);9394  h = mixHash(h, remoteEphemeralPublic);95  const ee = sharedKey(ephemeral.secretKey, remoteEphemeralPublic);96  const [ck2, k2] = hkdf2(ck, ee);97  ck = ck2;9899  const cipher2 = new ChaCha20Poly1305(k2);100  const nonce2 = new Uint8Array(12);101  const decrypted2 = cipher2.open(nonce2, encrypted2, h);102  if (!decrypted2) {103    throw new Error("Noise NK: msg2 auth failed — wrong responder key or MITM");104  }105  h = mixHash(h, encrypted2);106107  // --- Transport phase ---108  const [sendKey, recvKey] = hkdf2(ck, new Uint8Array(0));109  const handshakeHash = h.slice();110111  let sendNonce = 0n;112  let recvNonce = 0n;113114  function nonceBytes(n: bigint): Uint8Array {115    const buf = new Uint8Array(12);116    new DataView(buf.buffer).setBigUint64(4, n, true);117    return buf;118  }119120  const sendCipher = new ChaCha20Poly1305(sendKey);121  const recvCipher = new ChaCha20Poly1305(recvKey);122123  return {124    encrypt(plaintext) {125      return sendCipher.seal(nonceBytes(sendNonce++), plaintext, new Uint8Array(0));126    },127    decrypt(ciphertext) {128      const result = recvCipher.open(nonceBytes(recvNonce++), ciphertext, new Uint8Array(0));129      if (!result) throw new Error("Noise NK: decryption failed");130      return result;131    },132    handshakeHash,133  };134}135136/**137 * Compute the auth proof byte-for-byte identically to the native host.138 * See `native/peach-sync-host/src/auth.rs::proof_for`.139 *140 * proof = HMAC-SHA256(141 *   key   = X25519(local_priv, remote_pub),  // 32-byte DH shared142 *   data  = "peach-sync-v1-initiator-auth"143 *        || initiator_public144 *        || responder_public145 *        || nonce_32146 * )147 *148 * The initiator and responder both pass the same DH peer key (their PEER's149 * public key) and the same initiator_public/responder_public ordering so the150 * MAC matches. `mac_for` in auth.rs implements both directions; this helper151 * targets the initiator-side: `local_priv` is the initiator's private key,152 * `remote_pub` is the responder's public key.153 */154const AUTH_DOMAIN = new TextEncoder().encode("peach-sync-v1-initiator-auth");155156export function computeAuthProof(157  initiatorPrivate: Uint8Array,158  initiatorPublic: Uint8Array,159  responderPublic: Uint8Array,160  nonce: Uint8Array,161): Uint8Array {162  if (nonce.length !== 32) throw new Error("auth nonce must be 32 bytes");163164  const dh = sharedKey(initiatorPrivate, responderPublic);165  const mac = new HMAC(SHA256, dh);166  mac.update(AUTH_DOMAIN);167  mac.update(initiatorPublic);168  mac.update(responderPublic);169  mac.update(nonce);170  return mac.digest();171}172173interface AuthChallengeFrame {174  type: "CHALLENGE";175  nonce_hex: string;176  responder_public_key_hex: string;177}178179interface AuthProofFrame {180  type: "PROOF";181  initiator_public_key_hex: string;182  proof_hex: string;183}184185function bytesToHex(bytes: Uint8Array): string {186  return Array.from(bytes, (b) => b.toString(16).padStart(2, "0")).join("");187}188189function hexToBytes(hex: string): Uint8Array {190  if (hex.length % 2 !== 0) throw new Error("invalid hex");191  const bytes = new Uint8Array(hex.length / 2);192  for (let i = 0; i < hex.length; i += 2) {193    bytes[i / 2] = parseInt(hex.slice(i, i + 2), 16);194  }195  return bytes;196}197198/**199 * Drive the initiator side of the post-handshake challenge/proof round. The200 * responder sends a `Challenge` JSON frame; we compute the HMAC and reply201 * with a `Proof` frame. Both frames are encrypted via the post-handshake202 * Noise transport (caller owns the `sendEncrypted` / `receiveEncrypted` pair).203 */204/**205 * Run the responder side of the Noise NK handshake. Symmetric with206 * `noiseNKInitiator` — the caller provides `send` / `receive` for the two207 * handshake messages and gets back a session for transport-phase frames.208 *209 * Wire-identical with the Rust `snow` responder so an Android-as-host210 * pairing session can be driven by the desktop initiator and vice versa.211 */212export async function noiseNKResponder(213  ourStaticPrivateKey: Uint8Array,214  ourStaticPublicKey: Uint8Array,215  send: (msg: Uint8Array) => Promise<void>,216  receive: () => Promise<Uint8Array>,217): Promise<NoiseNKSession> {218  let h: Uint8Array = initHash();219  let ck: Uint8Array = h.slice();220221  // NK pre-message: mix our (responder) static public key. The initiator222  // pre-mixed the same key on its side; both transcripts must match.223  h = mixHash(h, ourStaticPublicKey);224225  // --- Message 1: e, es ---226  const msg1 = await receive();227  if (msg1.length < 48) throw new Error("Noise NK: msg1 too short");228  const remoteEphemeralPublic = msg1.slice(0, 32);229  const encrypted1 = msg1.slice(32);230231  h = mixHash(h, remoteEphemeralPublic);232  const es = sharedKey(ourStaticPrivateKey, remoteEphemeralPublic);233  const [ck1, k1] = hkdf2(ck, es);234  ck = ck1;235236  const cipher1 = new ChaCha20Poly1305(k1);237  const nonce1 = new Uint8Array(12);238  const decrypted1 = cipher1.open(nonce1, encrypted1, h);239  if (!decrypted1) {240    throw new Error("Noise NK: msg1 auth failed — wrong static key or MITM");241  }242  h = mixHash(h, encrypted1);243244  // --- Message 2: e, ee ---245  const ephemeral = generateKeyPair();246  h = mixHash(h, ephemeral.publicKey);247  const ee = sharedKey(ephemeral.secretKey, remoteEphemeralPublic);248  const [ck2, k2] = hkdf2(ck, ee);249  ck = ck2;250251  const cipher2 = new ChaCha20Poly1305(k2);252  const nonce2 = new Uint8Array(12);253  const encrypted2 = cipher2.seal(nonce2, new Uint8Array(0), h);254  h = mixHash(h, encrypted2);255256  const msg2 = new Uint8Array(32 + encrypted2.length);257  msg2.set(ephemeral.publicKey, 0);258  msg2.set(encrypted2, 32);259  await send(msg2);260261  // --- Transport phase ---262  // hkdf2 returns (k1, k2); the initiator uses k1 to send and k2 to receive,263  // so the responder swaps: k1 → recv, k2 → send.264  const [initiatorSendKey, responderSendKey] = hkdf2(ck, new Uint8Array(0));265  const handshakeHash = h.slice();266267  let sendNonce = 0n;268  let recvNonce = 0n;269270  function nonceBytes(n: bigint): Uint8Array {271    const buf = new Uint8Array(12);272    new DataView(buf.buffer).setBigUint64(4, n, true);273    return buf;274  }275276  const sendCipher = new ChaCha20Poly1305(responderSendKey);277  const recvCipher = new ChaCha20Poly1305(initiatorSendKey);278279  return {280    encrypt(plaintext) {281      return sendCipher.seal(nonceBytes(sendNonce++), plaintext, new Uint8Array(0));282    },283    decrypt(ciphertext) {284      const result = recvCipher.open(nonceBytes(recvNonce++), ciphertext, new Uint8Array(0));285      if (!result) throw new Error("Noise NK: decryption failed");286      return result;287    },288    handshakeHash,289  };290}291292/**293 * Constant-time 32-byte equality. The MAC comparison in `verifyAuthProof`294 * goes through this so a same-LAN attacker can't time the HMAC compare.295 */296function constantTimeEq(a: Uint8Array, b: Uint8Array): boolean {297  if (a.length !== b.length) return false;298  let diff = 0;299  for (let i = 0; i < a.length; i++) diff |= a[i]! ^ b[i]!;300  return diff === 0;301}302303/**304 * Drive the responder side of the post-handshake challenge/proof round. We305 * generate a random 32-byte nonce, send `Challenge`, receive `Proof`, and306 * verify. Returns the initiator's authenticated public key on success.307 *308 * Mirrors `auth.rs::verify_proof`: the MAC key is X25519(our_priv,309 * initiator_pub) and the data is the same domain-separated transcript both310 * sides feed into HMAC-SHA256.311 */312export async function performResponderAuth(313  session: NoiseNKSession,314  ourPrivateKey: Uint8Array,315  ourPublicKey: Uint8Array,316  sendEncryptedJson: (data: Uint8Array) => Promise<void>,317  receiveEncryptedJson: () => Promise<Uint8Array>,318): Promise<{ initiatorPublicKey: Uint8Array }> {319  void session;320321  const nonce = new Uint8Array(32);322  crypto.getRandomValues(nonce);323324  const challenge: AuthChallengeFrame = {325    type: "CHALLENGE",326    nonce_hex: bytesToHex(nonce),327    responder_public_key_hex: bytesToHex(ourPublicKey),328  };329  await sendEncryptedJson(new TextEncoder().encode(JSON.stringify(challenge)));330331  const proofBytes = await receiveEncryptedJson();332  const proofFrame = JSON.parse(new TextDecoder().decode(proofBytes)) as AuthProofFrame;333  if (proofFrame.type !== "PROOF") {334    throw new Error("expected PROOF frame");335  }336337  const initiatorPublicKey = hexToBytes(proofFrame.initiator_public_key_hex);338  const claimedProof = hexToBytes(proofFrame.proof_hex);339  if (initiatorPublicKey.length !== 32) {340    throw new Error("initiator public key must be 32 bytes");341  }342  if (claimedProof.length !== 32) {343    throw new Error("proof must be 32 bytes");344  }345346  // mac_for(our_priv, initiator_pub_for_dh, initiator_pub, our_pub, nonce)347  const dh = sharedKey(ourPrivateKey, initiatorPublicKey);348  const mac = new HMAC(SHA256, dh);349  mac.update(AUTH_DOMAIN);350  mac.update(initiatorPublicKey);351  mac.update(ourPublicKey);352  mac.update(nonce);353  const expected = mac.digest();354355  if (!constantTimeEq(expected, claimedProof)) {356    throw new Error("auth proof did not verify");357  }358  return { initiatorPublicKey };359}360361export async function performInitiatorAuth(362  session: NoiseNKSession,363  ourPrivateKey: Uint8Array,364  ourPublicKey: Uint8Array,365  responderPublicKey: Uint8Array,366  sendEncryptedJson: (data: Uint8Array) => Promise<void>,367  receiveEncryptedJson: () => Promise<Uint8Array>,368): Promise<void> {369  void session; // hash bound into MAC via the DH key only — kept for future fields370371  const challengeBytes = await receiveEncryptedJson();372  const challenge = JSON.parse(new TextDecoder().decode(challengeBytes)) as AuthChallengeFrame;373  if (challenge.type !== "CHALLENGE") {374    throw new Error("expected CHALLENGE frame");375  }376  const nonce = hexToBytes(challenge.nonce_hex);377  const responderKeyFromChallenge = hexToBytes(challenge.responder_public_key_hex);378  // Defence against an off-key challenge: the responder's claimed key MUST be379  // the one we Noise-NK-handshook against, otherwise an active MITM that380  // managed to substitute a different key is rerouting the auth round.381  if (382    responderKeyFromChallenge.length !== responderPublicKey.length ||383    !responderKeyFromChallenge.every((b, i) => b === responderPublicKey[i])384  ) {385    throw new Error("responder key in challenge does not match Noise handshake");386  }387388  const proof = computeAuthProof(ourPrivateKey, ourPublicKey, responderPublicKey, nonce);389  const proofFrame: AuthProofFrame = {390    type: "PROOF",391    initiator_public_key_hex: bytesToHex(ourPublicKey),392    proof_hex: bytesToHex(proof),393  };394  await sendEncryptedJson(new TextEncoder().encode(JSON.stringify(proofFrame)));395}396397export { bytesToHex, hexToBytes };