first draft of olm encryption
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Bruno Windels
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src/matrix/e2ee/olm/Encryption.js
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src/matrix/e2ee/olm/Encryption.js
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/*
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Copyright 2020 The Matrix.org Foundation C.I.C.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import {groupByWithCreator} from "../../../utils/groupBy.js";
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import {verifyEd25519Signature, OLM_ALGORITHM} from "./common.js";
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import {createSessionEntry} from "./Session.js";
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function findFirstSessionId(sessionIds) {
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return sessionIds.reduce((first, sessionId) => {
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if (!first || sessionId < first) {
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return sessionId;
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} else {
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return first;
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}
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}, null);
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}
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const OTK_ALGORITHM = "signed_curve25519";
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export class Encryption {
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constructor({account, olm, olmUtil, userId, storage, now, pickleKey}) {
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this._account = account;
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this._olm = olm;
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this._olmUtil = olmUtil;
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this._userId = userId;
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this._storage = storage;
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this._now = now;
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this._pickleKey = pickleKey;
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}
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async encrypt(type, content, devices, hsApi) {
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const txn = this._storage.readTxn([this._storage.storeNames.olmSessions]);
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const sessionIdsForDevice = await Promise.all(devices.map(async device => {
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return await txn.olmSessions.getSessionIds(device.curve25519Key);
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}));
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const devicesWithoutSession = devices.filter((_, i) => {
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const sessionIds = sessionIdsForDevice[i];
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return !(sessionIds?.length);
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});
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const timestamp = this._now();
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let encryptionTuples = [];
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if (devicesWithoutSession.length) {
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const newEncryptionTuples = await this._claimOneTimeKeys(hsApi, devicesWithoutSession);
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try {
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for (const tuple of newEncryptionTuples) {
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const {device, oneTimeKey} = tuple;
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tuple.session = this._account.createOutboundOlmSession(device.curve25519Key, oneTimeKey);
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}
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this._storeSessions(newEncryptionTuples, timestamp);
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} catch (err) {
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for (const tuple of newEncryptionTuples) {
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tuple.dispose();
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}
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}
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encryptionTuples = encryptionTuples.concat(newEncryptionTuples);
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}
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const existingEncryptionTuples = devices.map((device, i) => {
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const sessionIds = sessionIdsForDevice[i];
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if (sessionIds?.length > 0) {
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const sessionId = findFirstSessionId(sessionIds);
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return EncryptionTuple.fromSessionId(device, sessionId);
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}
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}).filter(tuple => !!tuple);
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// TODO: if we read and write in two different txns,
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// is there a chance we overwrite a session modified by the decryption during sync?
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// I think so. We'll have to have a lock while sending ...
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await this._loadSessions(existingEncryptionTuples);
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encryptionTuples = encryptionTuples.concat(existingEncryptionTuples);
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const ciphertext = this._buildCipherText(type, content, encryptionTuples);
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await this._storeSessions(encryptionTuples, timestamp);
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return {
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type: "m.room.encrypted",
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content: {
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algorithm: OLM_ALGORITHM,
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sender_key: this._account.identityKeys.curve25519,
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ciphertext
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}
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};
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}
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_buildPlainTextMessageForDevice(type, content, device) {
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return {
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keys: {
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"ed25519": this._account.identityKeys.ed25519
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},
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recipient_keys: {
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"ed25519": device.ed25519Key
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},
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recipient: device.userId,
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sender: this._userId,
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content,
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type
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}
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}
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_buildCipherText(type, content, encryptionTuples) {
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const ciphertext = {};
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for (const {device, session} of encryptionTuples) {
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if (session) {
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const message = session.encrypt(this._buildPlainTextMessageForDevice(type, content, device));
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ciphertext[device.curve25519Key] = message;
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}
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}
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return ciphertext;
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}
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async _claimOneTimeKeys(hsApi, deviceIdentities) {
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// create a Map<userId, Map<deviceId, deviceIdentity>>
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const devicesByUser = groupByWithCreator(deviceIdentities,
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device => device.userId,
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() => new Map(),
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(deviceMap, device) => deviceMap.set(device.deviceId, device)
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);
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const oneTimeKeys = Array.from(devicesByUser.entries()).reduce((usersObj, [userId, deviceMap]) => {
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usersObj[userId] = Array.from(deviceMap.values()).reduce((devicesObj, device) => {
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devicesObj[device.deviceId] = OTK_ALGORITHM;
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return devicesObj;
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}, {});
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return usersObj;
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}, {});
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const claimResponse = await hsApi.claimKeys({
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timeout: 10000,
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one_time_keys: oneTimeKeys
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}).response();
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// TODO: log claimResponse.failures
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const userKeyMap = claimResponse?.["one_time_keys"];
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return this._verifyAndCreateOTKTuples(userKeyMap, devicesByUser);
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}
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_verifyAndCreateOTKTuples(userKeyMap, devicesByUser) {
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const verifiedEncryptionTuples = [];
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for (const [userId, userSection] of Object.entries(userKeyMap)) {
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for (const [deviceId, deviceSection] of Object.entries(userSection)) {
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const [firstPropName, keySection] = Object.entries(deviceSection)[0];
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const [keyAlgorithm] = firstPropName.split(":");
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if (keyAlgorithm === OTK_ALGORITHM) {
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const device = devicesByUser.get(userId)?.get(deviceId);
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if (device) {
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const isValidSignature = verifyEd25519Signature(
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this._olmUtil, userId, deviceId, device.ed25519Key, keySection);
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if (isValidSignature) {
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verifiedEncryptionTuples.push(EncryptionTuple.fromOTK(device, keySection.key));
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}
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}
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}
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}
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}
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return verifiedEncryptionTuples;
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}
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async _loadSessions(encryptionTuples) {
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const txn = this._storage.readTxn([this._storage.storeNames.olmSessions]);
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await Promise.all(encryptionTuples.map(async encryptionTuple => {
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const sessionEntry = await txn.olmSessions.get(
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encryptionTuple.device.curve25519Key, encryptionTuple.sessionId);
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if (sessionEntry) {
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const olmSession = new this._olm.Session();
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encryptionTuple.session =
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}
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}));
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}
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async _storeSessions(encryptionTuples, timestamp) {
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const txn = this._storage.readWriteTxn([this._storage.storeNames.olmSessions]);
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try {
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for (const tuple of encryptionTuples) {
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const sessionEntry = createSessionEntry(
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tuple.session, tuple.device.curve25519Key, timestamp, this._pickleKey);
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txn.olmSessions.set(sessionEntry);
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}
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} catch (err) {
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txn.abort();
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throw err;
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}
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await txn.complete();
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}
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}
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// just a container needed to encrypt a message for a recipient device
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// it is constructed with either a oneTimeKey
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// (and later converted to a session) in case of a new session
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// or an existing session
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class EncryptionTuple {
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constructor(device, oneTimeKey, sessionId) {
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this.device = device;
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this.oneTimeKey = oneTimeKey;
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this.sessionId = sessionId;
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// an olmSession, should probably be called olmSession
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this.session = null;
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}
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static fromOTK(device, oneTimeKey) {
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return new EncryptionTuple(device, oneTimeKey, null);
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}
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static fromSessionId(device, sessionId) {
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return new EncryptionTuple(device, null, sessionId);
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}
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dispose() {
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if (this.session) {
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this.session.free();
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}
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}
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}
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