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integrate session backup with room encryption and megolm decryption

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This commit is contained in:
Bruno Windels 2020-09-17 14:20:15 +02:00
parent 3941af93d2
commit 17fc249fa8
2 changed files with 110 additions and 30 deletions
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47
src/matrix/e2ee/RoomEncryption.js
View file

@ -37,6 +37,13 @@ export class RoomEncryption {
this._eventIdsByMissingSession = new Map();
this._senderDeviceCache = new Map();
this._storage = storage;
this._sessionBackup = null;
}
setSessionBackup(sessionBackup) {
this._sessionBackup = sessionBackup;
// TODO: query session backup for all missing sessions so far
// can we query multiple? no, only for sessionId, all for room, or all
}
notifyTimelineClosed() {
@ -125,13 +132,53 @@ export class RoomEncryption {
const sessionId = event.content?.["session_id"];
const key = `${senderKey}|${sessionId}`;
let eventIds = this._eventIdsByMissingSession.get(key);
// new missing session
if (!eventIds) {
this._requestMissingSessionFromBackup(sessionId).catch(err => {
console.error(`Could not get session ${sessionId} from backup`, err);
});
eventIds = new Set();
this._eventIdsByMissingSession.set(key, eventIds);
}
eventIds.add(event.event_id);
}
async _requestMissingSessionFromBackup(sessionId) {
if (!this._sessionBackup) {
// somehow prompt for passphrase here
return;
}
const session = await this._sessionBackup.getSession(this._room.id, sessionId);
if (session?.algorithm === MEGOLM_ALGORITHM) {
const txn = await this._storage.readWriteTxn([this._storage.storeNames.inboundGroupSessions]);
let roomKey;
try {
roomKey = await this._megolmDecryption.addRoomKeyFromBackup(
this._room.id, sessionId, session, txn);
} catch (err) {
txn.abort();
throw err;
}
await txn.complete();
if (roomKey) {
// this will call into applyRoomKeys below
await this._room.notifyRoomKeys([roomKey]);
}
} else if (session?.algorithm) {
console.info(`Backed-up session of unknown algorithm: ${session.algorithm}`);
}
}
/**
* @type {RoomKeyDescription}
* @property {RoomKeyDescription} senderKey the curve25519 key of the sender
* @property {RoomKeyDescription} sessionId
*
*
* @param {Array<RoomKeyDescription>} roomKeys
* @return {Array<string>} the event ids that should be retried to decrypt
*/
applyRoomKeys(roomKeys) {
// retry decryption with the new sessions
const retryEventIds = [];

93
src/matrix/e2ee/megolm/Decryption.js
View file

@ -138,40 +138,73 @@ export class Decryption {
return;
}
const session = new this._olm.InboundGroupSession();
try {
session.create(sessionKey);
let incomingSessionIsBetter = true;
const existingSessionEntry = await txn.inboundGroupSessions.get(roomId, senderKey, sessionId);
if (existingSessionEntry) {
const existingSession = new this._olm.InboundGroupSession();
try {
existingSession.unpickle(this._pickleKey, existingSessionEntry.session);
incomingSessionIsBetter = session.first_known_index() < existingSession.first_known_index();
} finally {
existingSession.free();
}
}
if (incomingSessionIsBetter) {
const sessionEntry = {
roomId,
senderKey,
sessionId,
session: session.pickle(this._pickleKey),
claimedKeys: {ed25519: claimedEd25519Key},
};
txn.inboundGroupSessions.set(sessionEntry);
newSessions.push(sessionEntry);
}
} finally {
session.free();
const sessionEntry = await this._writeInboundSession(
roomId, senderKey, claimedEd25519Key, sessionId, sessionKey, txn);
if (sessionEntry) {
newSessions.push(sessionEntry);
}
}
// this will be passed to the Room in notifyRoomKeys
return newSessions;
}
/*
sessionInfo is a response from key backup and has the following keys:
algorithm
forwarding_curve25519_key_chain
sender_claimed_keys
sender_key
session_key
*/
async addRoomKeyFromBackup(roomId, sessionId, sessionInfo, txn) {
const sessionKey = sessionInfo["session_key"];
const senderKey = sessionInfo["sender_key"];
const claimedEd25519Key = sessionInfo["sender_claimed_keys"]?.["ed25519"];
if (
typeof roomId !== "string" ||
typeof sessionId !== "string" ||
typeof senderKey !== "string" ||
typeof sessionKey !== "string" ||
typeof claimedEd25519Key !== "string"
) {
return;
}
return await this._writeInboundSession(
roomId, senderKey, claimedEd25519Key, sessionId, sessionKey, txn);
}
async _writeInboundSession(roomId, senderKey, claimedEd25519Key, sessionId, sessionKey, txn) {
const session = new this._olm.InboundGroupSession();
try {
session.create(sessionKey);
let incomingSessionIsBetter = true;
const existingSessionEntry = await txn.inboundGroupSessions.get(roomId, senderKey, sessionId);
if (existingSessionEntry) {
const existingSession = new this._olm.InboundGroupSession();
try {
existingSession.unpickle(this._pickleKey, existingSessionEntry.session);
incomingSessionIsBetter = session.first_known_index() < existingSession.first_known_index();
} finally {
existingSession.free();
}
}
if (incomingSessionIsBetter) {
const sessionEntry = {
roomId,
senderKey,
sessionId,
session: session.pickle(this._pickleKey),
claimedKeys: {ed25519: claimedEd25519Key},
};
txn.inboundGroupSessions.set(sessionEntry);
return sessionEntry;
}
} finally {
session.free();
}
}
}