matrix-js-sdk/src/crypto/EncryptionSetup.js

import { logger } from "../logger";
import { MatrixEvent } from "../models/event";
import { EventEmitter } from "events";
import { createCryptoStoreCacheCallbacks } from "./CrossSigning";
import { IndexedDBCryptoStore } from './store/indexeddb-crypto-store';
import {
    PREFIX_UNSTABLE,
} from "../http-api";

/**
 * Builds an EncryptionSetupOperation by calling any of the add.. methods.
 * Once done, `buildOperation()` can be called which allows to apply to operation.
 *
 * This is used as a helper by Crypto to keep track of all the network requests
 * and other side-effects of bootstrapping, so it can be applied in one go (and retried in the future)
 * Also keeps track of all the private keys created during bootstrapping, so we don't need to prompt for them
 * more than once.
 */
export class EncryptionSetupBuilder {
    /**
     * @param {Object.<String, MatrixEvent>} accountData pre-existing account data, will only be read, not written.
     * @param {CryptoCallbacks} delegateCryptoCallbacks crypto callbacks to delegate to if the key isn't in cache yet
     */
    constructor(accountData, delegateCryptoCallbacks) {
        this.accountDataClientAdapter = new AccountDataClientAdapter(accountData);
        this.crossSigningCallbacks = new CrossSigningCallbacks();
        this.ssssCryptoCallbacks = new SSSSCryptoCallbacks(delegateCryptoCallbacks);

        this._crossSigningKeys = null;
        this._keySignatures = null;
        this._keyBackupInfo = null;
    }

    /**
     * Adds new cross-signing public keys
     *
     * @param {function} authUpload Function called to await an interactive auth
     * flow when uploading device signing keys.
     * Args:
     *     {function} A function that makes the request requiring auth. Receives
     *     the auth data as an object. Can be called multiple times, first with
     *     an empty authDict, to obtain the flows.
     * @param {Object} keys the new keys
     */
    addCrossSigningKeys(authUpload, keys) {
        this._crossSigningKeys = { authUpload, keys };
    }

    /**
     * Adds the key backup info to be updated on the server
     *
     * Used either to create a new key backup, or add signatures
     * from the new MSK.
     *
     * @param {Object} keyBackupInfo as received from/sent to the server
     */
    addSessionBackup(keyBackupInfo) {
        this._keyBackupInfo = keyBackupInfo;
    }

    /**
     * Adds the session backup private key to be updated in the local cache
     *
     * Used after fixing the format of the key
     *
     * @param {Uint8Array} privateKey
     */
    addSessionBackupPrivateKeyToCache(privateKey) {
        this._sessionBackupPrivateKey = privateKey;
    }

    /**
     * Add signatures from a given user and device/x-sign key
     * Used to sign the new cross-signing key with the device key
     *
     * @param {String} userId
     * @param {String} deviceId
     * @param {String} signature
     */
    addKeySignature(userId, deviceId, signature) {
        if (!this._keySignatures) {
            this._keySignatures = {};
        }
        const userSignatures = this._keySignatures[userId] || {};
        this._keySignatures[userId] = userSignatures;
        userSignatures[deviceId] = signature;
    }

    /**
     * @param {String} type
     * @param {Object} content
     * @return {Promise}
     */
    setAccountData(type, content) {
        return this.accountDataClientAdapter.setAccountData(type, content);
    }

    /**
     * builds the operation containing all the parts that have been added to the builder
     * @return {EncryptionSetupOperation}
     */
    buildOperation() {
        const accountData = this.accountDataClientAdapter._values;
        return new EncryptionSetupOperation(
            accountData,
            this._crossSigningKeys,
            this._keyBackupInfo,
            this._keySignatures,
        );
    }

    /**
     * Stores the created keys locally.
     *
     * This does not yet store the operation in a way that it can be restored,
     * but that is the idea in the future.
     *
     * @param  {Crypto} crypto
     * @return {Promise}
     */
    async persist(crypto) {
        // store private keys in cache
        if (this._crossSigningKeys) {
            const cacheCallbacks = createCryptoStoreCacheCallbacks(
                crypto._cryptoStore, crypto._olmDevice);
            for (const type of ["master", "self_signing", "user_signing"]) {
                logger.log(`Cache ${type} cross-signing private key locally`);
                const privateKey = this.crossSigningCallbacks.privateKeys.get(type);
                await cacheCallbacks.storeCrossSigningKeyCache(type, privateKey);
            }
            // store own cross-sign pubkeys as trusted
            await crypto._cryptoStore.doTxn(
                'readwrite', [IndexedDBCryptoStore.STORE_ACCOUNT],
                (txn) => {
                    crypto._cryptoStore.storeCrossSigningKeys(
                        txn, this._crossSigningKeys.keys);
                },
            );
        }
        // store session backup key in cache
        if (this._sessionBackupPrivateKey) {
            await crypto.storeSessionBackupPrivateKey(this._sessionBackupPrivateKey);
        }
    }
}

/**
 * Can be created from EncryptionSetupBuilder, or
 * (in a follow-up PR, not implemented yet) restored from storage, to retry.
 *
 * It does not have knowledge of any private keys, unlike the builder.
 */
export class EncryptionSetupOperation {
    /**
     * @param  {Map<String, Object>} accountData
     * @param  {Object} crossSigningKeys
     * @param  {Object} keyBackupInfo
     * @param  {Object} keySignatures
     */
    constructor(accountData, crossSigningKeys, keyBackupInfo, keySignatures) {
        this._accountData = accountData;
        this._crossSigningKeys = crossSigningKeys;
        this._keyBackupInfo = keyBackupInfo;
        this._keySignatures = keySignatures;
    }

    /**
     * Runs the (remaining part of, in the future) operation by sending requests to the server.
     * @param  {Crypto} crypto
     */
    async apply(crypto) {
        const baseApis = crypto._baseApis;
        // upload cross-signing keys
        if (this._crossSigningKeys) {
            const keys = {};
            for (const [name, key] of Object.entries(this._crossSigningKeys.keys)) {
                keys[name + "_key"] = key;
            }

            // We must only call `uploadDeviceSigningKeys` from inside this auth
            // helper to ensure we properly handle auth errors.
            await this._crossSigningKeys.authUpload(authDict => {
                return baseApis.uploadDeviceSigningKeys(authDict, keys);
            });

            // pass the new keys to the main instance of our own CrossSigningInfo.
            crypto.crossSigningInfo.setKeys(this._crossSigningKeys.keys);
        }
        // set account data
        if (this._accountData) {
            for (const [type, content] of this._accountData) {
                await baseApis.setAccountData(type, content);
            }
        }
        // upload first cross-signing signatures with the new key
        // (e.g. signing our own device)
        if (this._keySignatures) {
            await baseApis.uploadKeySignatures(this._keySignatures);
        }
        // need to create/update key backup info
        if (this._keyBackupInfo) {
            if (this._keyBackupInfo.version) {
                // session backup signature
                // The backup is trusted because the user provided the private key.
                // Sign the backup with the cross signing key so the key backup can
                // be trusted via cross-signing.
                await baseApis.http.authedRequest(
                    undefined, "PUT", "/room_keys/version/" + this._keyBackupInfo.version,
                    undefined, {
                        algorithm: this._keyBackupInfo.algorithm,
                        auth_data: this._keyBackupInfo.auth_data,
                    },
                    { prefix: PREFIX_UNSTABLE },
                );
            } else {
                // add new key backup
                await baseApis.http.authedRequest(
                    undefined, "POST", "/room_keys/version",
                    undefined, this._keyBackupInfo,
                    { prefix: PREFIX_UNSTABLE },
                );
            }
        }
    }
}

/**
 * Catches account data set by SecretStorage during bootstrapping by
 * implementing the methods related to account data in MatrixClient
 */
class AccountDataClientAdapter extends EventEmitter {
    /**
     * @param  {Object.<String, MatrixEvent>} accountData existing account data
     */
    constructor(accountData) {
        super();
        this._existingValues = accountData;
        this._values = new Map();
    }

    /**
     * @param  {String} type
     * @return {Promise<Object>} the content of the account data
     */
    getAccountDataFromServer(type) {
        return Promise.resolve(this.getAccountData(type));
    }

    /**
     * @param  {String} type
     * @return {Object} the content of the account data
     */
    getAccountData(type) {
        const modifiedValue = this._values.get(type);
        if (modifiedValue) {
            return modifiedValue;
        }
        const existingValue = this._existingValues[type];
        if (existingValue) {
            return existingValue.getContent();
        }
        return null;
    }

    /**
     * @param {String} type
     * @param {Object} content
     * @return {Promise}
     */
    setAccountData(type, content) {
        const lastEvent = this._values.get(type);
        this._values.set(type, content);
        // ensure accountData is emitted on the next tick,
        // as SecretStorage listens for it while calling this method
        // and it seems to rely on this.
        return Promise.resolve().then(() => {
            const event = new MatrixEvent({ type, content });
            this.emit("accountData", event, lastEvent);
        });
    }
}

/**
 * Catches the private cross-signing keys set during bootstrapping
 * by both cache callbacks (see createCryptoStoreCacheCallbacks) as non-cache callbacks.
 * See CrossSigningInfo constructor
 */
class CrossSigningCallbacks {
    constructor() {
        this.privateKeys = new Map();
    }

    // cache callbacks
    getCrossSigningKeyCache(type, expectedPublicKey) {
        return this.getCrossSigningKey(type, expectedPublicKey);
    }

    storeCrossSigningKeyCache(type, key) {
        this.privateKeys.set(type, key);
        return Promise.resolve();
    }

    // non-cache callbacks
    getCrossSigningKey(type, _expectedPubkey) {
        return Promise.resolve(this.privateKeys.get(type));
    }

    saveCrossSigningKeys(privateKeys) {
        for (const [type, privateKey] of Object.entries(privateKeys)) {
            this.privateKeys.set(type, privateKey);
        }
    }
}

/**
 * Catches the 4S private key set during bootstrapping by implementing
 * the SecretStorage crypto callbacks
 */
class SSSSCryptoCallbacks {
    constructor(delegateCryptoCallbacks) {
        this._privateKeys = new Map();
        this._delegateCryptoCallbacks = delegateCryptoCallbacks;
    }

    async getSecretStorageKey({ keys }, name) {
        for (const keyId of Object.keys(keys)) {
            const privateKey = this._privateKeys.get(keyId);
            if (privateKey) {
                return [keyId, privateKey];
            }
        }
        // if we don't have the key cached yet, ask
        // for it to the general crypto callbacks and cache it
        if (this._delegateCryptoCallbacks) {
            const result = await this._delegateCryptoCallbacks.
                getSecretStorageKey({ keys }, name);
            if (result) {
                const [keyId, privateKey] = result;
                this._privateKeys.set(keyId, privateKey);
            }
            return result;
        }
    }

    addPrivateKey(keyId, keyInfo, privKey) {
        this._privateKeys.set(keyId, privKey);
        // Also pass along to application to cache if it wishes
        if (
            this._delegateCryptoCallbacks &&
            this._delegateCryptoCallbacks.cacheSecretStorageKey
        ) {
            this._delegateCryptoCallbacks.cacheSecretStorageKey(keyId, keyInfo, privKey);
        }
    }
}