???: Move code around
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@ -1,6 +1,8 @@
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library omemo_dart;
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export 'src/bundle.dart';
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export 'src/double_ratchet.dart';
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export 'src/errors.dart';
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export 'src/helpers.dart';
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export 'src/key.dart';
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export 'src/x3dh.dart';
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@ -1,281 +1,196 @@
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import 'dart:convert';
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import 'package:cryptography/cryptography.dart';
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import 'package:meta/meta.dart';
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import 'package:omemo_dart/protobuf/schema.pb.dart';
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import 'package:omemo_dart/src/bundle.dart';
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import 'package:omemo_dart/src/double_ratchet/crypto.dart';
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import 'package:omemo_dart/src/double_ratchet/kdf.dart';
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import 'package:omemo_dart/src/helpers.dart';
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import 'package:omemo_dart/src/key.dart';
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import 'package:omemo_dart/src/x3dh.dart';
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class OmemoRatchetStepResult {
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/// Amount of messages we may skip per session
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const maxSkip = 1000;
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const OmemoRatchetStepResult(this.header, this.cipherText);
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final List<int> header;
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final List<int> cipherText;
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class RatchetStep {
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const RatchetStep(this.header, this.ciphertext);
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final OMEMOMessage header;
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final List<int> ciphertext;
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}
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class OmemoEncryptionResult {
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@immutable
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class SkippedKey {
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const OmemoEncryptionResult(this.cipherText, this.keys);
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/// The encrypted plaintext
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final List<int> cipherText;
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/// Mapping between Device id and the key to decrypt cipherText;
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final Map<String, List<int>> keys;
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const SkippedKey(this.dh, this.n);
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final OmemoPublicKey dh;
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final int n;
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@override
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bool operator ==(Object other) {
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return other is SkippedKey && other.dh == dh && other.n == n;
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}
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@override
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int get hashCode => dh.hashCode ^ n.hashCode;
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}
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/// The session state of one party
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class AliceOmemoSession {
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class OmemoDoubleRatchet {
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AliceOmemoSession(
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this.dhs,
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this.dhr,
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this.ek,
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this.rk,
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this.cks,
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this.ckr,
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this.ns,
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this.nr,
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this.pn,
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// this.skippedMessages,
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this.ad,
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OmemoDoubleRatchet(
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this.dhs, // DHs
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this.dhr, // DHr
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this.rk, // RK
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this.cks, // CKs
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this.ckr, // CKr
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this.ns, // Ns
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this.nr, // Nr
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this.pn, // Pn
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this.sessionAd,
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);
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/// The Diffie-Hellman sending key pair
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final OmemoKeyPair dhs;
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/// Sending DH keypair
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OmemoKeyPair dhs;
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/// The Diffie-Hellman receiving key pair
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final OmemoPublicKey dhr;
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/// Receiving Public key
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OmemoPublicKey? dhr;
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/// The EK used by X3DH
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final OmemoKeyPair ek;
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/// The Root Key
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/// 32 byte Root Key
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List<int> rk;
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/// Sending Chain Key
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List<int> cks;
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/// Receiving Chain Key
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/// Sending and receiving Chain Keys
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List<int>? cks;
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List<int>? ckr;
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/// Message number for sending
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/// Sending and receiving message numbers
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int ns;
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/// Message number for receiving
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int nr;
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/// Number of messages in the previous sending chain
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/// Previous sending chain number
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int pn;
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/// The associated data from the X3DH
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final List<int> ad;
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// TODO(PapaTutuWawa): Track skipped over message keys
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final List<int> sessionAd;
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static Future<AliceOmemoSession> newSession(OmemoBundle bundle, OmemoKeyPair ik) async {
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// TODO(PapaTutuWawa): Error handling
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final x3dhResult = await x3dhFromBundle(bundle, ik);
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final Map<SkippedKey, List<int>> mkSkipped = {};
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/// This is performed by the initiating entity
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static Future<OmemoDoubleRatchet> initiateNewSession(OmemoPublicKey spk, List<int> sk, List<int> ad) async {
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final dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
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final dhr = bundle.ik;
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final ek = x3dhResult.ek;
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final sk = x3dhResult.sk;
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final kdfRkResult = await kdfRk(sk, await dh(dhs, dhr, 2));
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return AliceOmemoSession(
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final dhr = spk;
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final rk = await kdfRk(sk, await dh(dhs, dhr, 0));
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final cks = rk;
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return OmemoDoubleRatchet(
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dhs,
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dhr,
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ek,
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kdfRkResult.rk,
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kdfRkResult.ck,
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rk,
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cks,
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null,
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0,
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0,
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0,
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x3dhResult.ad,
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ad,
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);
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}
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/// The associated_data parameter is implicit as it belongs to the session
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Future<List<int>> _encrypt(List<int> mk, List<int> plaintext, List<int> associatedData) async {
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final algorithm = Hkdf(
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hmac: Hmac(Sha256()),
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outputLength: 80,
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/// This is performed by the accepting entity
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static Future<OmemoDoubleRatchet> acceptNewSession(OmemoKeyPair spk, List<int> sk, List<int> ad) async {
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final dhs = spk;
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return OmemoDoubleRatchet(
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dhs,
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null,
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sk,
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null,
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null,
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0,
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0,
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0,
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ad,
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);
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final hkdfResult = await algorithm.deriveKey(
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secretKey: SecretKey(mk),
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nonce: List<int>.filled(32, 0x00),
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info: utf8.encode(encryptHkdfInfoString),
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);
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final bytes = await hkdfResult.extractBytes();
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final encKey = bytes.sublist(0, 32);
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final authKey = bytes.sublist(32, 64);
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final iv = bytes.sublist(64, 82);
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// TODO(PapaTutuWawa): Remove once done
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assert(encKey.length == 32);
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assert(authKey.length == 32);
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assert(iv.length == 16);
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// 32 = 256 / 8
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final encodedPlaintext = pkcs7padding(plaintext, 32);
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final aesAlgorithm = AesCbc.with256bits(
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macAlgorithm: Hmac.sha256(),
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);
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final secretBox = await aesAlgorithm.encrypt(
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encodedPlaintext,
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secretKey: SecretKey(encKey),
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nonce: iv,
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);
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final ad_ = associatedData.sublist(0, ad.length);
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final message = OMEMOMessage.fromBuffer(associatedData.sublist(ad.length))
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..ciphertext = secretBox.cipherText;
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final messageBytes = message.writeToBuffer();
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final input = concat([ad_, messageBytes]);
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final authBytes = (await Hmac.sha256().calculateMac(
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input,
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secretKey: SecretKey(authKey),
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)).bytes.sublist(0, 16);
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final authenticatedMessage = OMEMOAuthenticatedMessage()
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..mac = authBytes
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..message = messageBytes;
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return authenticatedMessage.writeToBuffer();
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}
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Future<List<int>> ratchetStep(List<int> plaintext) async {
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final kdfResult = await kdfCk(cks);
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final message = OMEMOMessage()
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..dhPub = await dhs.pk.getBytes()
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..pn = pn
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..n = ns;
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final header = message.writeToBuffer();
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cks = kdfResult.ck;
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ns++;
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return _encrypt(
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kdfResult.mk,
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plaintext,
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concat([ad, header]),
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);
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}
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}
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Future<OmemoEncryptionResult> encryptForSessions(List<AliceOmemoSession> sessions, String plaintext) async {
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// TODO(PapaTutuWawa): Generate random data
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final key = List<int>.filled(32, 0x0);
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final algorithm = Hkdf(
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hmac: Hmac(Sha256()),
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outputLength: 80,
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);
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final result = await algorithm.deriveKey(
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secretKey: SecretKey(key),
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nonce: List<int>.filled(32, 0x0),
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info: utf8.encode(encryptionHkdfInfoString),
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);
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final bytes = await result.extractBytes();
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final encKey = bytes.sublist(0, 32);
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final authKey = bytes.sublist(32, 64);
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final iv = bytes.sublist(64, 80);
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final encodedPlaintext = pkcs7padding(utf8.encode(plaintext), 32);
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final aesAlgorithm = AesCbc.with256bits(
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macAlgorithm: Hmac.sha256(),
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);
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final secretBox = await aesAlgorithm.encrypt(
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encodedPlaintext,
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secretKey: SecretKey(encKey),
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nonce: iv,
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);
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final hmac = (await Hmac.sha256().calculateMac(
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secretBox.cipherText,
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secretKey: SecretKey(authKey),
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)).bytes.sublist(0, 16);
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final keyData = concat([encKey, hmac]);
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final keyMap = <String, List<int>>{};
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for (final session in sessions) {
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final ratchetKey = await session.ratchetStep(keyData);
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}
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return OmemoEncryptionResult(
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secretBox.cipherText,
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keyMap,
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);
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}
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/// Result of the KDF_RK function from the Double Ratchet spec.
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class KdfRkResult {
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const KdfRkResult(this.rk, this.ck);
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/// 32 byte Root Key
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final List<int> rk;
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/// 32 byte Chain Key
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final List<int> ck;
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}
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/// Result of the KDF_CK function from the Double Ratchet spec.
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class KdfCkResult {
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const KdfCkResult(this.ck, this.mk);
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/// 32 byte Chain Key
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final List<int> ck;
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/// 32 byte Message Key
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final List<int> mk;
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}
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/// Amount of messages we may skip per session
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const maxSkip = 1000;
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/// Info string for KDF_RK
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const kdfRkInfoString = 'OMEMO Root Chain';
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/// Info string for ENCRYPT
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const encryptHkdfInfoString = 'OMEMO Message Key Material';
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/// Info string for encrypting a message
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const encryptionHkdfInfoString = 'OMEMO Payload';
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/// Flags for KDF_CK
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const kdfCkNextMessageKey = 0x01;
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const kdfCkNextChainKey = 0x02;
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Future<KdfRkResult> kdfRk(List<int> rk, List<int> dhOut) async {
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final algorithm = Hkdf(
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hmac: Hmac(Sha256()),
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outputLength: 32,
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);
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final result = await algorithm.deriveKey(
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secretKey: SecretKey(dhOut),
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nonce: rk,
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info: utf8.encode(kdfRkInfoString),
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);
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// TODO(PapaTutuWawa): Does the rk in the tuple (rk, ck) refer to the input rk?
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return KdfRkResult(rk, await result.extractBytes());
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}
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Future<KdfCkResult> kdfCk(List<int> ck) async {
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final hkdf = Hkdf(hmac: Hmac(Sha256()), outputLength: 32);
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final newCk = await hkdf.deriveKey(
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secretKey: SecretKey(ck),
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nonce: [kdfCkNextChainKey],
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);
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final mk = await hkdf.deriveKey(
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secretKey: SecretKey(ck),
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nonce: [kdfCkNextMessageKey],
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);
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return KdfCkResult(
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await newCk.extractBytes(),
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await mk.extractBytes(),
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);
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Future<RatchetStep> ratchetEncrypt(List<int> plaintext) async {
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final newCks = await kdfCk(cks!, kdfCkNextChainKey);
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final mk = await kdfCk(cks!, kdfCkNextMessageKey);
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cks = newCks;
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final header = OMEMOMessage()
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..n = ns
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..pn = pn
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..dhPub = await dhs.pk.getBytes();
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ns++;
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return RatchetStep(
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header,
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await encrypt(mk, plaintext, concat([sessionAd, header.writeToBuffer()]), sessionAd),
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);
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}
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Future<List<int>?> trySkippedMessageKeys(OMEMOMessage header, List<int> ciphertext) async {
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final key = SkippedKey(
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// TODO(PapaTutuWawa): Is this correct
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OmemoPublicKey.fromBytes(header.dhPub, KeyPairType.ed25519),
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header.n,
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);
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if (mkSkipped.containsKey(key)) {
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final mk = mkSkipped[key]!;
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mkSkipped.remove(key);
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return decrypt(mk, ciphertext, concat([sessionAd, header.writeToBuffer()]), sessionAd);
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}
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return null;
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}
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Future<void> skipMessageKeys(int until) async {
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if (nr + maxSkip < until) {
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// TODO(PapaTutuWawa): Custom exception
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throw Exception();
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}
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if (ckr != null) {
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while (nr < until) {
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final newCkr = await kdfCk(ckr!, kdfCkNextChainKey);
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final mk = await kdfCk(ckr!, kdfCkNextMessageKey);
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ckr = newCkr;
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mkSkipped[SkippedKey(dhr!, nr)] = mk;
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nr++;
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}
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}
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}
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Future<void> dhRatchet(OMEMOMessage header) async {
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pn = header.n;
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ns = 0;
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nr = 0;
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dhr = OmemoPublicKey.fromBytes(header.dhPub, KeyPairType.ed25519);
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final newRk = await kdfRk(rk, await dh(dhs, dhr!, 2));
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rk = newRk;
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ckr = newRk;
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dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
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final newNewRk = await kdfRk(rk, await dh(dhs, dhr!, 2));
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rk = newNewRk;
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cks = newNewRk;
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}
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Future<List<int>> ratchetDecrypt(OMEMOMessage header, List<int> ciphertext) async {
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// Check if we skipped too many messages
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final plaintext = await trySkippedMessageKeys(header, ciphertext);
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if (plaintext != null) {
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return plaintext;
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}
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if (header.dhPub != await dhr?.getBytes()) {
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await skipMessageKeys(header.pn);
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await dhRatchet(header);
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}
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await skipMessageKeys(header.n);
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final newCkr = await kdfCk(ckr!, kdfCkNextChainKey);
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final mk = await kdfCk(ckr!, kdfCkNextMessageKey);
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ckr = newCkr;
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nr++;
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return decrypt(mk, ciphertext, concat([sessionAd, header.writeToBuffer()]), sessionAd);
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}
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}
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109
lib/src/double_ratchet/crypto.dart
Normal file
109
lib/src/double_ratchet/crypto.dart
Normal file
@ -0,0 +1,109 @@
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import 'dart:convert';
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import 'package:cryptography/cryptography.dart';
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import 'package:omemo_dart/protobuf/schema.pb.dart';
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import 'package:omemo_dart/src/helpers.dart';
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/// Info string for ENCRYPT
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const encryptHkdfInfoString = 'OMEMO Message Key Material';
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/// cryptography _really_ wants to check the MAC output from AES-256-CBC. Since
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/// we don't have it, we need the MAC check to always "pass".
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class NoMacSecretBox extends SecretBox {
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NoMacSecretBox(super.cipherText, { required super.nonce }) : super(mac: Mac.empty);
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@override
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Future<void> checkMac({
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required MacAlgorithm macAlgorithm,
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required SecretKey secretKey,
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required List<int> aad,
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}) async {}
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}
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/// Signals ENCRYPT function as specified by OMEMO 0.8.0.
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/// Encrypt [plaintext] using the message key [mk], given associated_data [associatedData]
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/// and the AD output from the X3DH [sessionAd].
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Future<List<int>> encrypt(List<int> mk, List<int> plaintext, List<int> associatedData, List<int> sessionAd) async {
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final hkdf = Hkdf(
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hmac: Hmac(Sha256()),
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outputLength: 80,
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);
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final hkdfResult = await hkdf.deriveKey(
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secretKey: SecretKey(mk),
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nonce: List<int>.filled(32, 0x0),
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info: utf8.encode(encryptHkdfInfoString),
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);
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final hkdfBytes = await hkdfResult.extractBytes();
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// Split hkdfBytes into encryption, authentication key and IV
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final encryptionKey = hkdfBytes.sublist(0, 32);
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final authenticationKey = hkdfBytes.sublist(32, 64);
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final iv = hkdfBytes.sublist(64, 80);
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||||
|
||||
final aesResult = await AesCbc.with256bits(
|
||||
macAlgorithm: MacAlgorithm.empty,
|
||||
).encrypt(
|
||||
plaintext,
|
||||
secretKey: SecretKey(encryptionKey),
|
||||
nonce: iv,
|
||||
);
|
||||
|
||||
final header = OMEMOMessage.fromBuffer(associatedData.sublist(sessionAd.length))
|
||||
..ciphertext = aesResult.cipherText;
|
||||
final headerBytes = header.writeToBuffer();
|
||||
final hmacInput = concat([sessionAd, headerBytes]);
|
||||
final hmacResult = (await Hmac.sha256().calculateMac(
|
||||
hmacInput,
|
||||
secretKey: SecretKey(authenticationKey),
|
||||
)).bytes.sublist(0, 16);
|
||||
|
||||
final message = OMEMOAuthenticatedMessage()
|
||||
..mac = hmacResult
|
||||
..message = headerBytes;
|
||||
return message.writeToBuffer();
|
||||
}
|
||||
|
||||
/// Signals DECRYPT function as specified by OMEMO 0.8.0.
|
||||
/// Decrypt [ciphertext] with the message key [mk], given the associated_data [associatedData]
|
||||
/// and the AD output from the X3DH.
|
||||
Future<List<int>> decrypt(List<int> mk, List<int> ciphertext, List<int> associatedData, List<int> sessionAd) async {
|
||||
// Generate the keys and iv from mk
|
||||
final hkdf = Hkdf(
|
||||
hmac: Hmac(Sha256()),
|
||||
outputLength: 80,
|
||||
);
|
||||
final hkdfResult = await hkdf.deriveKey(
|
||||
secretKey: SecretKey(mk),
|
||||
nonce: List<int>.filled(32, 0x0),
|
||||
info: utf8.encode(encryptHkdfInfoString),
|
||||
);
|
||||
final hkdfBytes = await hkdfResult.extractBytes();
|
||||
|
||||
// Split hkdfBytes into encryption, authentication key and IV
|
||||
final encryptionKey = hkdfBytes.sublist(0, 32);
|
||||
final authenticationKey = hkdfBytes.sublist(32, 64);
|
||||
final iv = hkdfBytes.sublist(64, 80);
|
||||
|
||||
// Assumption ciphertext is a OMEMOAuthenticatedMessage
|
||||
final message = OMEMOAuthenticatedMessage.fromBuffer(ciphertext);
|
||||
final header = OMEMOMessage.fromBuffer(message.message);
|
||||
|
||||
final hmacInput = concat([sessionAd, header.writeToBuffer()]);
|
||||
final hmacResult = (await Hmac.sha256().calculateMac(
|
||||
hmacInput,
|
||||
secretKey: SecretKey(authenticationKey),
|
||||
)).bytes.sublist(0, 16);
|
||||
|
||||
// TODO(PapaTutuWawa): Check the HMAC result
|
||||
|
||||
final plaintext = await AesCbc.with256bits(
|
||||
macAlgorithm: MacAlgorithm.empty,
|
||||
).decrypt(
|
||||
NoMacSecretBox(
|
||||
header.ciphertext,
|
||||
nonce: iv,
|
||||
),
|
||||
secretKey: SecretKey(encryptionKey),
|
||||
);
|
||||
|
||||
return plaintext;
|
||||
}
|
||||
35
lib/src/double_ratchet/kdf.dart
Normal file
35
lib/src/double_ratchet/kdf.dart
Normal file
@ -0,0 +1,35 @@
|
||||
import 'dart:convert';
|
||||
import 'package:cryptography/cryptography.dart';
|
||||
|
||||
/// Info string for KDF_RK
|
||||
const kdfRkInfoString = 'OMEMO Root Chain';
|
||||
|
||||
/// Flags for KDF_CK
|
||||
const kdfCkNextMessageKey = 0x01;
|
||||
const kdfCkNextChainKey = 0x02;
|
||||
|
||||
/// Signals KDF_CK function as specified by OMEMO 0.8.0.
|
||||
Future<List<int>> kdfCk(List<int> ck, int constant) async {
|
||||
final hkdf = Hkdf(hmac: Hmac(Sha256()), outputLength: 32);
|
||||
final result = await hkdf.deriveKey(
|
||||
secretKey: SecretKey(ck),
|
||||
nonce: [constant],
|
||||
);
|
||||
|
||||
return result.extractBytes();
|
||||
}
|
||||
|
||||
/// Signals KDF_RK function as specified by OMEMO 0.8.0.
|
||||
Future<List<int>> kdfRk(List<int> rk, List<int> dhOut) async {
|
||||
final algorithm = Hkdf(
|
||||
hmac: Hmac(Sha256()),
|
||||
outputLength: 32,
|
||||
);
|
||||
final result = await algorithm.deriveKey(
|
||||
secretKey: SecretKey(dhOut),
|
||||
nonce: rk,
|
||||
info: utf8.encode(kdfRkInfoString),
|
||||
);
|
||||
|
||||
return result.extractBytes();
|
||||
}
|
||||
@ -59,6 +59,9 @@ Future<List<int>> dh(OmemoKeyPair kp, OmemoPublicKey pk, int identityKey) async
|
||||
ckp = await kp.toCurve25519();
|
||||
} else if (identityKey == 2) {
|
||||
cpk = await pk.toCurve25519();
|
||||
} else if (identityKey == 3) {
|
||||
ckp = await kp.toCurve25519();
|
||||
cpk = await pk.toCurve25519();
|
||||
}
|
||||
|
||||
final shared = await Cryptography.instance.x25519().sharedSecretKey(
|
||||
|
||||
109
test/double_ratchet_test.dart
Normal file
109
test/double_ratchet_test.dart
Normal file
@ -0,0 +1,109 @@
|
||||
import 'dart:convert';
|
||||
import 'package:cryptography/cryptography.dart';
|
||||
import 'package:omemo_dart/omemo_dart.dart';
|
||||
import 'package:omemo_dart/protobuf/schema.pb.dart';
|
||||
import 'package:omemo_dart/src/double_ratchet/crypto.dart';
|
||||
import 'package:test/test.dart';
|
||||
|
||||
void main() {
|
||||
test('Test encrypting and decrypting', () async {
|
||||
final sessionAd = List<int>.filled(32, 0x0);
|
||||
final mk = List<int>.filled(32, 0x1);
|
||||
final plaintext = utf8.encode('Hallo');
|
||||
final header = OMEMOMessage()
|
||||
..n = 0
|
||||
..pn = 0
|
||||
..dhPub = List<int>.empty();
|
||||
final asd = concat([sessionAd, header.writeToBuffer()]);
|
||||
|
||||
final ciphertext = await encrypt(
|
||||
mk,
|
||||
plaintext,
|
||||
asd,
|
||||
sessionAd,
|
||||
);
|
||||
|
||||
final decrypted = await decrypt(
|
||||
mk,
|
||||
ciphertext,
|
||||
asd,
|
||||
sessionAd,
|
||||
);
|
||||
|
||||
expect(decrypted, plaintext);
|
||||
});
|
||||
|
||||
/*
|
||||
test('Test the Double Ratchet', () async {
|
||||
// Generate keys
|
||||
final ikAlice = await OmemoKeyPair.generateNewPair(KeyPairType.ed25519);
|
||||
final ikBob = await OmemoKeyPair.generateNewPair(KeyPairType.ed25519);
|
||||
final spkBob = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
|
||||
final opkBob = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
|
||||
final bundleBob = OmemoBundle(
|
||||
'1',
|
||||
await spkBob.pk.asBase64(),
|
||||
'3',
|
||||
base64Encode(
|
||||
await sig(ikBob, await spkBob.pk.getBytes()),
|
||||
),
|
||||
//'Q5in+/L4kJixEX692h6mJkPMyp4I3SlQ84L0E7ipPzqfPHOMiraUlqG2vG/O8wvFjLsKYZpPBraga9IvwhqVDA==',
|
||||
await ikBob.pk.asBase64(),
|
||||
{
|
||||
'2': await opkBob.pk.asBase64(),
|
||||
},
|
||||
);
|
||||
|
||||
// Alice does X3DH
|
||||
final resultAlice = await x3dhFromBundle(bundleBob, ikAlice);
|
||||
|
||||
// Alice sends the inital message to Bob
|
||||
// ...
|
||||
|
||||
// Bob does X3DH
|
||||
final resultBob = await x3dhFromInitialMessage(
|
||||
X3DHMessage(
|
||||
ikAlice.pk,
|
||||
resultAlice.ek.pk,
|
||||
'2',
|
||||
),
|
||||
spkBob,
|
||||
opkBob,
|
||||
ikBob,
|
||||
);
|
||||
|
||||
print('X3DH key exchange done');
|
||||
|
||||
// Alice and Bob now share sk as a common secret and ad
|
||||
final alicesRatchet = await OmemoDoubleRatchet.initiateNewSession(
|
||||
spkBob.pk,
|
||||
resultAlice.sk,
|
||||
resultAlice.ad,
|
||||
);
|
||||
final bobsRatchet = await OmemoDoubleRatchet.acceptNewSession(
|
||||
spkBob,
|
||||
resultBob.sk,
|
||||
resultBob.ad,
|
||||
);
|
||||
|
||||
expect(alicesRatchet.sessionAd, bobsRatchet.sessionAd);
|
||||
//expect(await alicesRatchet.dhr.getBytes(), await ikBob.pk.getBytes());
|
||||
|
||||
// Alice encrypts a message
|
||||
final aliceRatchetResult = await alicesRatchet.ratchetEncrypt(utf8.encode('Hello Bob'));
|
||||
print('Alice sent the message');
|
||||
|
||||
// Alice sends it to Bob
|
||||
// ...
|
||||
|
||||
// Bob tries to decrypt it
|
||||
final bobRatchetResult = await bobsRatchet.ratchetDecrypt(
|
||||
aliceRatchetResult.header,
|
||||
aliceRatchetResult.ciphertext,
|
||||
);
|
||||
print('Bob decrypted the message');
|
||||
|
||||
expect(utf8.encode('Hello Bob'), bobRatchetResult);
|
||||
});
|
||||
*/
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user