Merge pull request #564 from vector-im/bwindels/dehydrated-device

Device dehydration support

src/domain/AccountSetupViewModel.js

@@ -0,0 +1,136 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import {ViewModel} from "./ViewModel.js";
+import {KeyType} from "../matrix/ssss/index.js";
+import {Status} from "./session/settings/SessionBackupViewModel.js";
+
+export class AccountSetupViewModel extends ViewModel {
+    constructor(accountSetup) {
+        super();
+        this._accountSetup = accountSetup;
+        this._dehydratedDevice = undefined;
+        this._decryptDehydratedDeviceViewModel = undefined;
+        if (this._accountSetup.encryptedDehydratedDevice) {
+            this._decryptDehydratedDeviceViewModel = new DecryptDehydratedDeviceViewModel(this, dehydratedDevice => {
+                this._dehydratedDevice = dehydratedDevice;
+                this._decryptDehydratedDeviceViewModel = undefined;
+                this.emitChange("deviceDecrypted");
+            });
+        }
+    }
+
+    get decryptDehydratedDeviceViewModel() {
+        return this._decryptDehydratedDeviceViewModel;
+    }
+
+    get deviceDecrypted() {
+        return !!this._dehydratedDevice;
+    }
+
+    get dehydratedDeviceId() {
+        return this._accountSetup.encryptedDehydratedDevice.deviceId;
+    }
+
+    finish() {
+        this._accountSetup.finish(this._dehydratedDevice);
+    }
+}
+
+// this vm adopts the same shape as SessionBackupViewModel so the same view can be reused.
+class DecryptDehydratedDeviceViewModel extends ViewModel {
+    constructor(accountSetupViewModel, decryptedCallback) {
+        super();
+        this._accountSetupViewModel = accountSetupViewModel;
+        this._isBusy = false;
+        this._status = Status.SetupKey;
+        this._error = undefined;
+        this._decryptedCallback = decryptedCallback;
+    }
+
+    get decryptAction() {
+        return this.i18n`Restore`;
+    }
+
+    get purpose() {
+        return this.i18n`claim your dehydrated device`;
+    }
+
+    get offerDehydratedDeviceSetup() {
+        return false;
+    }
+
+    get dehydratedDeviceId() {
+        return this._accountSetupViewModel._dehydratedDevice?.deviceId;
+    }
+    
+    get isBusy() {
+        return this._isBusy;
+    }
+
+    get backupVersion() { return 0; }
+
+    get status() {
+        return this._status;
+    }
+
+    get error() {
+        return this._error?.message;
+    }
+
+    showPhraseSetup() {
+        if (this._status === Status.SetupKey) {
+            this._status = Status.SetupPhrase;
+            this.emitChange("status");
+        }
+    }
+
+    showKeySetup() {
+        if (this._status === Status.SetupPhrase) {
+            this._status = Status.SetupKey;
+            this.emitChange("status");
+        }
+    }
+
+    async _enterCredentials(keyType, credential) {
+        if (credential) {
+            try {
+                this._isBusy = true;
+                this.emitChange("isBusy");
+                const {encryptedDehydratedDevice} = this._accountSetupViewModel._accountSetup;
+                const dehydratedDevice = await encryptedDehydratedDevice.decrypt(keyType, credential);
+                this._decryptedCallback(dehydratedDevice);
+            } catch (err) {
+                console.error(err);
+                this._error = err;
+                this.emitChange("error");
+            } finally {
+                this._isBusy = false;
+                this.emitChange("");
+            }
+        }
+    }
+
+    enterSecurityPhrase(passphrase) {
+        this._enterCredentials(KeyType.Passphrase, passphrase);
+    }
+
+    enterSecurityKey(securityKey) {
+        this._enterCredentials(KeyType.RecoveryKey, securityKey);
+    }
+
+    disable() {}
+}

src/domain/SessionLoadViewModel.js

@@ -14,6 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import {AccountSetupViewModel} from "./AccountSetupViewModel.js";
 import {LoadStatus} from "../matrix/SessionContainer.js";
 import {SyncStatus} from "../matrix/Sync.js";
 import {ViewModel} from "./ViewModel.js";
@@ -29,6 +30,8 @@ export class SessionLoadViewModel extends ViewModel {
         this._loading = false;
         this._error = null;
         this.backUrl = this.urlCreator.urlForSegment("session", true);
+        this._accountSetupViewModel = undefined;
+
     }
 
     async start() {
@@ -39,6 +42,11 @@ export class SessionLoadViewModel extends ViewModel {
             this._loading = true;
             this.emitChange("loading");
             this._waitHandle = this._sessionContainer.loadStatus.waitFor(s => {
+                if (s === LoadStatus.AccountSetup) {
+                    this._accountSetupViewModel = new AccountSetupViewModel(this._sessionContainer.accountSetup);
+                } else {
+                    this._accountSetupViewModel = undefined;
+                }
                 this.emitChange("loadLabel");
                 // wait for initial sync, but not catchup sync
                 const isCatchupSync = s === LoadStatus.FirstSync &&
@@ -97,6 +105,10 @@ export class SessionLoadViewModel extends ViewModel {
 
     // to show a spinner or not
     get loading() {
+        const sc = this._sessionContainer;
+        if (sc && sc.loadStatus.get() === LoadStatus.AccountSetup) {
+            return false;
+        }
         return this._loading;
     }
 
@@ -110,6 +122,10 @@ export class SessionLoadViewModel extends ViewModel {
         // Statuses related to login are handled by respective login view models
         if (sc) {
             switch (sc.loadStatus.get()) {
+                case LoadStatus.QueryAccount:
+                    return `Querying account encryption setup…`;
+                case LoadStatus.AccountSetup:
+                    return ""; // we'll show a header ing AccountSetupView
                 case LoadStatus.SessionSetup:
                     return `Setting up your encryption keys…`;
                 case LoadStatus.Loading:
@@ -136,4 +152,13 @@ export class SessionLoadViewModel extends ViewModel {
         const logExport = await this.logger.export();
         this.platform.saveFileAs(logExport.asBlob(), `hydrogen-logs-${this.platform.clock.now()}.json`);
     }
+
+    async logout() {
+        await this._sessionContainer.logout();
+        this.navigation.push("session", true);
+    }
+
+    get accountSetupViewModel() {
+        return this._accountSetupViewModel;
+    }
 }

src/domain/login/LoginViewModel.js

@@ -107,7 +107,7 @@ export class LoginViewModel extends ViewModel {
 
     async attemptLogin(loginMethod) {
         this._setBusy(true);
-        this._sessionContainer.startWithLogin(loginMethod);
+        this._sessionContainer.startWithLogin(loginMethod, {inspectAccountSetup: true});
         const loadStatus = this._sessionContainer.loadStatus;
         const handle = loadStatus.waitFor(status => status !== LoadStatus.Login);
         await handle.promise;

src/domain/session/room/timeline/tiles/GapTile.js

@@ -54,12 +54,10 @@ export class GapTile extends SimpleTile {
     }
 
     updatePreviousSibling(prev) {
-        console.log("GapTile.updatePreviousSibling", prev);
         super.updatePreviousSibling(prev);
         const isAtTop = !prev;
         if (this._isAtTop !== isAtTop) {
             this._isAtTop = isAtTop;
-            console.log("isAtTop", this._isAtTop);
             this.emitChange("isAtTop");
         }
     }

src/domain/session/settings/SessionBackupViewModel.js

@@ -15,18 +15,60 @@ limitations under the License.
 */
 
 import {ViewModel} from "../../ViewModel.js";
+import {KeyType} from "../../../matrix/ssss/index.js";
+import {createEnum} from "../../../utils/enum.js";
+
+export const Status = createEnum("Enabled", "SetupKey", "SetupPhrase", "Pending"); 
 
 export class SessionBackupViewModel extends ViewModel {
     constructor(options) {
         super(options);
         this._session = options.session;
-        this._showKeySetup = true;
         this._error = null;
         this._isBusy = false;
+        this._dehydratedDeviceId = undefined;
+        this._status = undefined;
+        this._reevaluateStatus();
         this.track(this._session.hasSecretStorageKey.subscribe(() => {
-            this.emitChange("status");
+            if (this._reevaluateStatus()) {
+                this.emitChange("status");
+            }
         }));
     }
+
+    _reevaluateStatus() {
+        if (this._isBusy) {
+            return false;
+        }
+        let status;
+        const hasSecretStorageKey = this._session.hasSecretStorageKey.get();
+        if (hasSecretStorageKey === true) {
+            status = this._session.sessionBackup ? Status.Enabled : Status.SetupKey;
+        } else if (hasSecretStorageKey === false) {
+            status = Status.SetupKey;
+        } else {
+            status = Status.Pending;
+        }
+        const changed = status !== this._status;
+        this._status = status;
+        return changed;
+    }
+
+    get decryptAction() {
+        return this.i18n`Set up`;
+    }
+
+    get purpose() {
+        return this.i18n`set up session backup`;
+    }
+
+    offerDehydratedDeviceSetup() {
+        return true;
+    }
+
+    get dehydratedDeviceId() {
+        return this._dehydratedDeviceId;
+    }
     
     get isBusy() {
         return this._isBusy;
@@ -37,15 +79,7 @@ export class SessionBackupViewModel extends ViewModel {
     }
 
     get status() {
-        if (this._session.sessionBackup) {
+        return this._status;
-            return "enabled";
-        } else {
-            if (this._session.hasSecretStorageKey.get() === false) {
-                return this._showKeySetup ? "setupKey" : "setupPhrase";
-            } else {
-                return "pending";
-            }
-        }
     }
 
     get error() {
@@ -53,46 +87,61 @@ export class SessionBackupViewModel extends ViewModel {
     }
 
     showPhraseSetup() {
-        this._showKeySetup = false;
+        if (this._status === Status.SetupKey) {
-        this.emitChange("status");
+            this._status = Status.SetupPhrase;
+            this.emitChange("status");
+        }
     }
 
     showKeySetup() {
-        this._showKeySetup = true;
+        if (this._status === Status.SetupPhrase) {
-        this.emitChange("status");
+            this._status = Status.SetupKey;
+            this.emitChange("status");
+        }
     }
 
-    async enterSecurityPhrase(passphrase) {
+    async _enterCredentials(keyType, credential, setupDehydratedDevice) {
-        if (passphrase) {
+        if (credential) {
             try {
                 this._isBusy = true;
                 this.emitChange("isBusy");
-                await this._session.enableSecretStorage("phrase", passphrase);
+                const key = await this._session.enableSecretStorage(keyType, credential);
+                if (setupDehydratedDevice) {
+                    this._dehydratedDeviceId = await this._session.setupDehydratedDevice(key);
+                }
             } catch (err) {
                 console.error(err);
                 this._error = err;
                 this.emitChange("error");
             } finally {
                 this._isBusy = false;
+                this._reevaluateStatus();
                 this.emitChange("");
             }
         }
     }
 
-    async enterSecurityKey(securityKey) {
+    enterSecurityPhrase(passphrase, setupDehydratedDevice) {
-        if (securityKey) {
+        this._enterCredentials(KeyType.Passphrase, passphrase, setupDehydratedDevice);
-            try {
+    }
-                this._isBusy = true;
+
-                this.emitChange("isBusy");
+    enterSecurityKey(securityKey, setupDehydratedDevice) {
-                await this._session.enableSecretStorage("key", securityKey);
+        this._enterCredentials(KeyType.RecoveryKey, securityKey, setupDehydratedDevice);
-            } catch (err) {
+    }
-                console.error(err);
+
-                this._error = err;
+    async disable() {
-                this.emitChange("error");
+        try {
-            } finally {
+            this._isBusy = true;
-                this._isBusy = false;
+            this.emitChange("isBusy");
-                this.emitChange("");
+            await this._session.disableSecretStorage();
-            }
+        } catch (err) {
+            console.error(err);
+            this._error = err;
+            this.emitChange("error");
+        } finally {
+            this._isBusy = false;
+            this._reevaluateStatus();
+            this.emitChange("");
         }
     }
 }

src/domain/session/settings/SettingsViewModel.js

@@ -57,16 +57,11 @@ export class SettingsViewModel extends ViewModel {
         return this._sessionContainer.session;
     }
 
-    logout() {
+    async logout() {
-        return this.logger.run("logout", async log => {
+        this._isLoggingOut = true;
-            this._isLoggingOut = true;
+        await this._sessionContainer.logout();
-            this.emitChange("isLoggingOut");
+        this.emitChange("isLoggingOut");
-            try {
+        this.navigation.push("session", true);
-                await this._session.logout(log);
-            } catch (err) {}
-            await this._sessionContainer.deleteSession(log);
-            this.navigation.push("session", true);
-        });
     }
 
     get isLoggingOut() { return this._isLoggingOut; }

src/logging/ConsoleLogger.js

@@ -21,7 +21,6 @@ export class ConsoleLogger extends BaseLogger {
     }
 }
 
-
 const excludedKeysFromTable = ["l", "id"];
 function filterValues(values) {
     if (!values) {
@@ -79,7 +78,7 @@ function itemCaption(item) {
     } else if (item._values.l && item.error) {
         return `${item._values.l} failed`;
     } else if (typeof item._values.ref !== "undefined") {
-        return `ref ${item._values.ref}`
+        return `ref ${item._values.ref}`;
     } else {
         return item._values.l || item._values.type;
     }

src/matrix/Session.js

@@ -24,6 +24,7 @@ import { ObservableMap } from "../observable/index.js";
 import {User} from "./User.js";
 import {DeviceMessageHandler} from "./DeviceMessageHandler.js";
 import {Account as E2EEAccount} from "./e2ee/Account.js";
+import {uploadAccountAsDehydratedDevice} from "./e2ee/Dehydration.js";
 import {Decryption as OlmDecryption} from "./e2ee/olm/Decryption.js";
 import {Encryption as OlmEncryption} from "./e2ee/olm/Encryption.js";
 import {Decryption as MegOlmDecryption} from "./e2ee/megolm/Decryption";
@@ -39,6 +40,8 @@ import {
     keyFromCredential as ssssKeyFromCredential,
     readKey as ssssReadKey,
     writeKey as ssssWriteKey,
+    removeKey as ssssRemoveKey,
+    keyFromDehydratedDeviceKey as createSSSSKeyFromDehydratedDeviceKey
 } from "./ssss/index.js";
 import {SecretStorage} from "./ssss/SecretStorage.js";
 import {ObservableValue, RetainedObservableValue} from "../observable/ObservableValue";
@@ -106,9 +109,9 @@ export class Session {
         return this._sessionInfo.userId;
     }
 
+    /** @internal call SessionContainer.logout instead */
     async logout(log = undefined) {
-        const response = await this._hsApi.logout({log}).response();
+        await this._hsApi.logout({log}).response();
-        console.log("logout", response);
     }
 
     // called once this._e2eeAccount is assigned
@@ -203,6 +206,12 @@ export class Session {
             this._storage.storeNames.accountData,
         ]);
         await this._createSessionBackup(key, readTxn);
+        await this._writeSSSSKey(key);
+        this._hasSecretStorageKey.set(true);
+        return key;
+    }
+
+    async _writeSSSSKey(key) {
         // only after having read a secret, write the key
         // as we only find out if it was good if the MAC verification succeeds
         const writeTxn = await this._storage.readWriteTxn([
@@ -215,7 +224,29 @@ export class Session {
             throw err;
         }
         await writeTxn.complete();
-        this._hasSecretStorageKey.set(true);
+    }
+
+    async disableSecretStorage() {
+        const writeTxn = await this._storage.readWriteTxn([
+            this._storage.storeNames.session,
+        ]);
+        try {
+            ssssRemoveKey(writeTxn);
+        } catch (err) {
+            writeTxn.abort();
+            throw err;
+        }
+        await writeTxn.complete();
+        if (this._sessionBackup) {
+            for (const room of this._rooms.values()) {
+                if (room.isEncrypted) {
+                    room.enableSessionBackup(undefined);
+                }
+            }
+            this._sessionBackup?.dispose();
+            this._sessionBackup = undefined;
+        }
+        this._hasSecretStorageKey.set(false);
     }
 
     async _createSessionBackup(ssssKey, txn) {
@@ -248,23 +279,76 @@ export class Session {
     async createIdentity(log) {
         if (this._olm) {
             if (!this._e2eeAccount) {
-                this._e2eeAccount = await E2EEAccount.create({
+                this._e2eeAccount = await this._createNewAccount(this._sessionInfo.deviceId, this._storage);
-                    hsApi: this._hsApi,
-                    olm: this._olm,
-                    pickleKey: PICKLE_KEY,
-                    userId: this._sessionInfo.userId,
-                    deviceId: this._sessionInfo.deviceId,
-                    olmWorker: this._olmWorker,
-                    storage: this._storage,
-                });
                 log.set("keys", this._e2eeAccount.identityKeys);
                 this._setupEncryption();
             }
             await this._e2eeAccount.generateOTKsIfNeeded(this._storage, log);
-            await log.wrap("uploadKeys", log => this._e2eeAccount.uploadKeys(this._storage, log));
+            await log.wrap("uploadKeys", log => this._e2eeAccount.uploadKeys(this._storage, false, log));
         }
     }
 
+    /** @internal */
+    async dehydrateIdentity(dehydratedDevice, log) {
+        log.set("deviceId", dehydratedDevice.deviceId);
+        if (!this._olm) {
+            log.set("no_olm", true);
+            return false;
+        }
+        if (dehydratedDevice.deviceId !== this.deviceId) {
+            log.set("wrong_device", true);
+            return false;
+        }
+        if (this._e2eeAccount) {
+            log.set("account_already_setup", true);
+            return false;
+        }
+        if (!await dehydratedDevice.claim(this._hsApi, log)) {
+            log.set("already_claimed", true);
+            return false;
+        }
+        this._e2eeAccount = await E2EEAccount.adoptDehydratedDevice({
+            dehydratedDevice,
+            hsApi: this._hsApi,
+            olm: this._olm,
+            pickleKey: PICKLE_KEY,
+            userId: this._sessionInfo.userId,
+            olmWorker: this._olmWorker,
+            deviceId: this.deviceId,
+            storage: this._storage,
+        });
+        log.set("keys", this._e2eeAccount.identityKeys);
+        this._setupEncryption();
+        return true;
+    }
+
+    _createNewAccount(deviceId, storage = undefined) {
+        // storage is optional and if omitted the account won't be persisted (useful for dehydrating devices)
+        return E2EEAccount.create({
+            hsApi: this._hsApi,
+            olm: this._olm,
+            pickleKey: PICKLE_KEY,
+            userId: this._sessionInfo.userId,
+            olmWorker: this._olmWorker,
+            deviceId,
+            storage,
+        });
+    }
+
+    setupDehydratedDevice(key, log = null) {
+        return this._platform.logger.wrapOrRun(log, "setupDehydratedDevice", async log => {
+            const dehydrationAccount = await this._createNewAccount("temp-device-id");
+            try {
+                const deviceId = await uploadAccountAsDehydratedDevice(
+                    dehydrationAccount, this._hsApi, key, "Dehydrated device", log);
+                log.set("deviceId", deviceId);
+                return deviceId;
+            } finally {
+                dehydrationAccount.dispose();
+            }
+        });
+    }
+
     /** @internal */
     async load(log) {
         const txn = await this._storage.readTxn([
@@ -321,11 +405,17 @@ export class Session {
 
     dispose() {
         this._olmWorker?.dispose();
+        this._olmWorker = undefined;
         this._sessionBackup?.dispose();
-        this._megolmDecryption.dispose();
+        this._sessionBackup = undefined;
+        this._megolmDecryption?.dispose();
+        this._megolmDecryption = undefined;
+        this._e2eeAccount?.dispose();
+        this._e2eeAccount = undefined;
         for (const room of this._rooms.values()) {
             room.dispose();
         }
+        this._rooms = undefined;
     }
 
     /**
@@ -334,7 +424,7 @@ export class Session {
      *                                      and useful to store so we can later tell what capabilities
      *                                      our homeserver has.
      */
-    async start(lastVersionResponse, log) {
+    async start(lastVersionResponse, dehydratedDevice, log) {
         if (lastVersionResponse) {
             // store /versions response
             const txn = await this._storage.readWriteTxn([
@@ -346,6 +436,15 @@ export class Session {
         }
         // enable session backup, this requests the latest backup version
         if (!this._sessionBackup) {
+            if (dehydratedDevice) {
+                await log.wrap("SSSSKeyFromDehydratedDeviceKey", async log => {
+                    const ssssKey = await createSSSSKeyFromDehydratedDeviceKey(dehydratedDevice.key, this._storage, this._platform);
+                    if (ssssKey) {
+                        log.set("success", true);
+                        await this._writeSSSSKey(ssssKey);
+                    }
+                })
+            }
             const txn = await this._storage.readTxn([
                 this._storage.storeNames.session,
                 this._storage.storeNames.accountData,
@@ -517,7 +616,7 @@ export class Session {
         if (!isCatchupSync) {
             const needsToUploadOTKs = await this._e2eeAccount.generateOTKsIfNeeded(this._storage, log);
             if (needsToUploadOTKs) {
-                await log.wrap("uploadKeys", log => this._e2eeAccount.uploadKeys(this._storage, log));
+                await log.wrap("uploadKeys", log => this._e2eeAccount.uploadKeys(this._storage, false, log));
             }
         }
     }

src/matrix/SessionContainer.js

@@ -29,14 +29,17 @@ import {Session} from "./Session.js";
 import {PasswordLoginMethod} from "./login/PasswordLoginMethod.js";
 import {TokenLoginMethod} from "./login/TokenLoginMethod.js";
 import {SSOLoginHelper} from "./login/SSOLoginHelper.js";
+import {getDehydratedDevice} from "./e2ee/Dehydration.js";
 
 export const LoadStatus = createEnum(
     "NotLoading",
     "Login",
     "LoginFailed",
+    "QueryAccount", // check for dehydrated device after login
+    "AccountSetup", // asked to restore from dehydrated device if present, call sc.accountSetup.finish() to progress to the next stage
     "Loading",
     "SessionSetup", // upload e2ee keys, ...
-    "Migrating",    //not used atm, but would fit here
+    "Migrating",    // not used atm, but would fit here
     "FirstSync",
     "Error",
     "Ready",
@@ -63,6 +66,7 @@ export class SessionContainer {
         this._requestScheduler = null;
         this._olmPromise = olmPromise;
         this._workerPromise = workerPromise;
+        this._accountSetup = undefined;
     }
 
     createNewSessionId() {
@@ -85,7 +89,7 @@ export class SessionContainer {
                 if (!sessionInfo) {
                     throw new Error("Invalid session id: " + sessionId);
                 }
-                await this._loadSessionInfo(sessionInfo, false, log);
+                await this._loadSessionInfo(sessionInfo, null, log);
                 log.set("status", this._status.get());
             } catch (err) {
                 log.catch(err);
@@ -127,7 +131,7 @@ export class SessionContainer {
         });
     }
 
-    async startWithLogin(loginMethod) {
+    async startWithLogin(loginMethod, {inspectAccountSetup} = {}) {
         const currentStatus = this._status.get();
         if (currentStatus !== LoadStatus.LoginFailed &&
             currentStatus !== LoadStatus.NotLoading &&
@@ -154,7 +158,6 @@ export class SessionContainer {
                     lastUsed: clock.now()
                 };
                 log.set("id", sessionId);
-                await this._platform.sessionInfoStorage.add(sessionInfo);            
             } catch (err) {
                 this._error = err;
                 if (err.name === "HomeServerError") {
@@ -173,21 +176,31 @@ export class SessionContainer {
                 }
                 return;
             }
+            let dehydratedDevice;
+            if (inspectAccountSetup) {
+                dehydratedDevice = await this._inspectAccountAfterLogin(sessionInfo, log);
+                if (dehydratedDevice) {
+                    sessionInfo.deviceId = dehydratedDevice.deviceId;
+                }
+            }
+            await this._platform.sessionInfoStorage.add(sessionInfo);            
             // loading the session can only lead to
             // LoadStatus.Error in case of an error,
             // so separate try/catch
             try {
-                await this._loadSessionInfo(sessionInfo, true, log);
+                await this._loadSessionInfo(sessionInfo, dehydratedDevice, log);
                 log.set("status", this._status.get());
             } catch (err) {
                 log.catch(err);
+                // free olm Account that might be contained
+                dehydratedDevice?.dispose();
                 this._error = err;
                 this._status.set(LoadStatus.Error);
             }
         });
     }
 
-    async _loadSessionInfo(sessionInfo, isNewLogin, log) {
+    async _loadSessionInfo(sessionInfo, dehydratedDevice, log) {
         log.set("appVersion", this._platform.version);
         const clock = this._platform.clock;
         this._sessionStartedByReconnector = false;
@@ -233,7 +246,9 @@ export class SessionContainer {
             platform: this._platform,
         });
         await this._session.load(log);
-        if (!this._session.hasIdentity) {
+        if (dehydratedDevice) {
+            await log.wrap("dehydrateIdentity", log => this._session.dehydrateIdentity(dehydratedDevice, log));
+        } else if (!this._session.hasIdentity) {
             this._status.set(LoadStatus.SessionSetup);
             await log.wrap("createIdentity", log => this._session.createIdentity(log));
         }
@@ -247,7 +262,9 @@ export class SessionContainer {
                     this._requestScheduler.start();
                     this._sync.start();
                     this._sessionStartedByReconnector = true;
-                    await log.wrap("session start", log => this._session.start(this._reconnector.lastVersionsResponse, log));
+                    const d = dehydratedDevice;
+                    dehydratedDevice = undefined;
+                    await log.wrap("session start", log => this._session.start(this._reconnector.lastVersionsResponse, d, log));
                 });
             }
         });
@@ -266,8 +283,10 @@ export class SessionContainer {
             if (this._isDisposed) {
                 return;
             }
+            const d = dehydratedDevice;
+            dehydratedDevice = undefined;
             // log as ref as we don't want to await it
-            await log.wrap("session start", log => this._session.start(lastVersionsResponse, log));
+            await log.wrap("session start", log => this._session.start(lastVersionsResponse, d, log));
         }
     }
 
@@ -300,6 +319,32 @@ export class SessionContainer {
         }
     }
 
+    _inspectAccountAfterLogin(sessionInfo, log) {
+        return log.wrap("inspectAccount", async log => {
+            this._status.set(LoadStatus.QueryAccount);
+            const hsApi = new HomeServerApi({
+                homeserver: sessionInfo.homeServer,
+                accessToken: sessionInfo.accessToken,
+                request: this._platform.request,
+            });
+            const olm = await this._olmPromise;
+            const encryptedDehydratedDevice = await getDehydratedDevice(hsApi, olm, this._platform, log);
+            if (encryptedDehydratedDevice) {
+                let resolveStageFinish;
+                const promiseStageFinish = new Promise(r => resolveStageFinish = r);
+                this._accountSetup = new AccountSetup(encryptedDehydratedDevice, resolveStageFinish);
+                this._status.set(LoadStatus.AccountSetup);
+                await promiseStageFinish;
+                const dehydratedDevice = this._accountSetup?._dehydratedDevice;
+                this._accountSetup = null;
+                return dehydratedDevice;
+            }
+        });
+    }
+
+    get accountSetup() {
+        return this._accountSetup;
+    }
 
     get loadStatus() {
         return this._status;
@@ -331,6 +376,15 @@ export class SessionContainer {
         return !this._reconnector;
     }
 
+    logout() {
+        return this._platform.logger.run("logout", async log => {
+            try {
+                await this._session?.logout(log);
+            } catch (err) {}
+            await this.deleteSession(log);
+        });
+    }
+
     dispose() {
         if (this._reconnectSubscription) {
             this._reconnectSubscription();
@@ -339,12 +393,15 @@ export class SessionContainer {
         this._reconnector = null;
         if (this._requestScheduler) {
             this._requestScheduler.stop();
+            this._requestScheduler = null;
         }
         if (this._sync) {
             this._sync.stop();
+            this._sync = null;
         }
         if (this._session) {
             this._session.dispose();
+            this._session = null;
         }
         if (this._waitForFirstSyncHandle) {
             this._waitForFirstSyncHandle.dispose();
@@ -378,3 +435,20 @@ export class SessionContainer {
         this._loginFailure = null;
     }
 }
+
+class AccountSetup {
+    constructor(encryptedDehydratedDevice, finishStage) {
+        this._encryptedDehydratedDevice = encryptedDehydratedDevice;
+        this._dehydratedDevice = undefined;
+        this._finishStage = finishStage;
+    }
+
+    get encryptedDehydratedDevice() {
+        return this._encryptedDehydratedDevice;
+    }
+
+    finish(dehydratedDevice) {
+        this._dehydratedDevice = dehydratedDevice;
+        this._finishStage();
+    }
+}

src/matrix/e2ee/Account.js

@@ -22,6 +22,24 @@ const ACCOUNT_SESSION_KEY = SESSION_E2EE_KEY_PREFIX + "olmAccount";
 const DEVICE_KEY_FLAG_SESSION_KEY = SESSION_E2EE_KEY_PREFIX + "areDeviceKeysUploaded";
 const SERVER_OTK_COUNT_SESSION_KEY = SESSION_E2EE_KEY_PREFIX + "serverOTKCount";
 
+async function initiallyStoreAccount(account, pickleKey, areDeviceKeysUploaded, serverOTKCount, storage) {
+    const pickledAccount = account.pickle(pickleKey);
+    const txn = await storage.readWriteTxn([
+        storage.storeNames.session
+    ]);
+    try {
+        // add will throw if the key already exists
+        // we would not want to overwrite olmAccount here
+        txn.session.add(ACCOUNT_SESSION_KEY, pickledAccount);
+        txn.session.add(DEVICE_KEY_FLAG_SESSION_KEY, areDeviceKeysUploaded);
+        txn.session.add(SERVER_OTK_COUNT_SESSION_KEY, serverOTKCount);
+    } catch (err) {
+        txn.abort();
+        throw err;
+    }
+    await txn.complete();
+}
+
 export class Account {
     static async load({olm, pickleKey, hsApi, userId, deviceId, olmWorker, txn}) {
         const pickledAccount = await txn.session.get(ACCOUNT_SESSION_KEY);
@@ -35,6 +53,21 @@ export class Account {
         }
     }
 
+    static async adoptDehydratedDevice({olm, dehydratedDevice, pickleKey, hsApi, userId, olmWorker, storage}) {
+        const account = dehydratedDevice.adoptUnpickledOlmAccount();
+        const oneTimeKeys = JSON.parse(account.one_time_keys());
+        // only one algorithm supported by olm atm, so hardcode its name
+        const oneTimeKeysEntries = Object.entries(oneTimeKeys.curve25519);
+        const serverOTKCount = oneTimeKeysEntries.length;
+        const areDeviceKeysUploaded = true;
+        await initiallyStoreAccount(account, pickleKey, areDeviceKeysUploaded, serverOTKCount, storage);
+        return new Account({
+            pickleKey, hsApi, account, userId,
+            deviceId: dehydratedDevice.deviceId,
+            areDeviceKeysUploaded, serverOTKCount, olm, olmWorker
+        });
+    }
+
     static async create({olm, pickleKey, hsApi, userId, deviceId, olmWorker, storage}) {
         const account = new olm.Account();
         if (olmWorker) {
@@ -43,24 +76,13 @@ export class Account {
             account.create();
             account.generate_one_time_keys(account.max_number_of_one_time_keys());
         }
-        const pickledAccount = account.pickle(pickleKey);
         const areDeviceKeysUploaded = false;
-        const txn = await storage.readWriteTxn([
+        const serverOTKCount = 0;
-            storage.storeNames.session
+        if (storage) {
-        ]);
+            await initiallyStoreAccount(account, pickleKey, areDeviceKeysUploaded, serverOTKCount, storage);
-        try {
-            // add will throw if the key already exists
-            // we would not want to overwrite olmAccount here
-            txn.session.add(ACCOUNT_SESSION_KEY, pickledAccount);
-            txn.session.add(DEVICE_KEY_FLAG_SESSION_KEY, areDeviceKeysUploaded);
-            txn.session.add(SERVER_OTK_COUNT_SESSION_KEY, 0);
-        } catch (err) {
-            txn.abort();
-            throw err;
         }
-        await txn.complete();
         return new Account({pickleKey, hsApi, account, userId,
-            deviceId, areDeviceKeysUploaded, serverOTKCount: 0, olm, olmWorker});
+            deviceId, areDeviceKeysUploaded, serverOTKCount, olm, olmWorker});
     }
 
     constructor({pickleKey, hsApi, account, userId, deviceId, areDeviceKeysUploaded, serverOTKCount, olm, olmWorker}) {
@@ -80,7 +102,11 @@ export class Account {
         return this._identityKeys;
     }
 
-    async uploadKeys(storage, log) {
+    setDeviceId(deviceId) {
+        this._deviceId = deviceId;
+    }
+
+    async uploadKeys(storage, isDehydratedDevice, log) {
         const oneTimeKeys = JSON.parse(this._account.one_time_keys());
         // only one algorithm supported by olm atm, so hardcode its name
         const oneTimeKeysEntries = Object.entries(oneTimeKeys.curve25519);
@@ -95,7 +121,8 @@ export class Account {
                 log.set("otks", true);
                 payload.one_time_keys = this._oneTimeKeysPayload(oneTimeKeysEntries);
             }
-            const response = await this._hsApi.uploadKeys(payload, {log}).response();
+            const dehydratedDeviceId = isDehydratedDevice ? this._deviceId : undefined;
+            const response = await this._hsApi.uploadKeys(dehydratedDeviceId, payload, {log}).response();
             this._serverOTKCount = response?.one_time_key_counts?.signed_curve25519;
             log.set("serverOTKCount", this._serverOTKCount);
             // TODO: should we not modify this in the txn like we do elsewhere?
@@ -105,12 +132,12 @@ export class Account {
             await this._updateSessionStorage(storage, sessionStore => {
                 if (oneTimeKeysEntries.length) {
                     this._account.mark_keys_as_published();
-                    sessionStore.set(ACCOUNT_SESSION_KEY, this._account.pickle(this._pickleKey));
+                    sessionStore?.set(ACCOUNT_SESSION_KEY, this._account.pickle(this._pickleKey));
-                    sessionStore.set(SERVER_OTK_COUNT_SESSION_KEY, this._serverOTKCount);
+                    sessionStore?.set(SERVER_OTK_COUNT_SESSION_KEY, this._serverOTKCount);
                 }
                 if (!this._areDeviceKeysUploaded) {
                     this._areDeviceKeysUploaded = true;
-                    sessionStore.set(DEVICE_KEY_FLAG_SESSION_KEY, this._areDeviceKeysUploaded);
+                    sessionStore?.set(DEVICE_KEY_FLAG_SESSION_KEY, this._areDeviceKeysUploaded);
                 }
             });
         }
@@ -246,16 +273,20 @@ export class Account {
     }
 
     async _updateSessionStorage(storage, callback) {
-        const txn = await storage.readWriteTxn([
+        if (storage) {
-            storage.storeNames.session
+            const txn = await storage.readWriteTxn([
-        ]);
+                storage.storeNames.session
-        try {
+            ]);
-            await callback(txn.session);
+            try {
-        } catch (err) {
+                await callback(txn.session);
-            txn.abort();
+            } catch (err) {
-            throw err;
+                txn.abort();
+                throw err;
+            }
+            await txn.complete();
+        } else {
+            await callback(undefined);
         }
-        await txn.complete();
     }
 
     signObject(obj) {
@@ -273,4 +304,13 @@ export class Account {
             obj.unsigned = unsigned;
         }
     }
+
+    pickleWithKey(key) {
+        return this._account.pickle(key);
+    }
+
+    dispose() {
+        this._account.free();
+        this._account = undefined;
+    }
 }

src/matrix/e2ee/Dehydration.js

@@ -0,0 +1,115 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+const DEHYDRATION_LIBOLM_PICKLE_ALGORITHM = "org.matrix.msc2697.v1.olm.libolm_pickle"; 
+import {KeyDescription} from "../ssss/common.js";
+import {keyFromCredentialAndDescription} from "../ssss/index.js";
+
+export async function getDehydratedDevice(hsApi, olm, platform, log) {
+    try {
+        const response = await hsApi.getDehydratedDevice({log}).response();
+        if (response.device_data.algorithm === DEHYDRATION_LIBOLM_PICKLE_ALGORITHM) {
+            return new EncryptedDehydratedDevice(response, olm, platform);
+        }
+    } catch (err) {
+        if (err.name !== "HomeServerError") {
+            log.error = err;
+        }
+        return undefined;
+    }
+}
+
+export async function uploadAccountAsDehydratedDevice(account, hsApi, key, deviceDisplayName, log) {
+    const response = await hsApi.createDehydratedDevice({
+        device_data: {
+            algorithm: DEHYDRATION_LIBOLM_PICKLE_ALGORITHM,
+            account: account.pickleWithKey(key.binaryKey),
+            passphrase: key.description?.passphraseParams || {},
+        },
+        initial_device_display_name: deviceDisplayName
+    }).response();
+    const deviceId = response.device_id;
+    account.setDeviceId(deviceId);
+    await account.uploadKeys(undefined, true, log);
+    return deviceId;
+}
+
+class EncryptedDehydratedDevice {
+    constructor(dehydratedDevice, olm, platform) {
+        this._dehydratedDevice = dehydratedDevice;
+        this._olm = olm;
+        this._platform = platform;
+    }
+
+    async decrypt(keyType, credential) {
+        const keyDescription = new KeyDescription("dehydrated_device", this._dehydratedDevice.device_data.passphrase);
+        const key = await keyFromCredentialAndDescription(keyType, credential, keyDescription, this._platform, this._olm);
+        const account = new this._olm.Account();
+        try {
+            const pickledAccount = this._dehydratedDevice.device_data.account;
+            account.unpickle(key.binaryKey.slice(), pickledAccount);
+            return new DehydratedDevice(this._dehydratedDevice, account, key);
+        } catch (err) {
+            account.free();
+            if (err.message === "OLM.BAD_ACCOUNT_KEY") {
+                return undefined;
+            } else {
+                throw err;
+            }
+        }
+    }
+
+    get deviceId() {
+        return this._dehydratedDevice.device_id;
+    }
+}
+
+class DehydratedDevice {
+    constructor(dehydratedDevice, account, key) {
+        this._dehydratedDevice = dehydratedDevice;
+        this._account = account;
+        this._key = key;
+    }
+
+    async claim(hsApi, log) {
+        try {
+            const response = await hsApi.claimDehydratedDevice(this.deviceId, {log}).response();
+            return response.success;
+        } catch (err) {
+            return false;
+        }
+    }
+
+    // make it clear that ownership is transfered upon calling this
+    adoptUnpickledOlmAccount() {
+        const account = this._account;
+        this._account = undefined;
+        return account;
+    }
+
+    get deviceId() {
+        return this._dehydratedDevice.device_id;
+    }
+
+    get key() {
+        return this._key;
+    }
+
+    dispose() {
+        this._account?.free();
+        this._account = undefined;
+    }
+}

src/matrix/e2ee/RoomEncryption.js

@@ -49,7 +49,7 @@ export class RoomEncryption {
     }
 
     enableSessionBackup(sessionBackup) {
-        if (this._sessionBackup) {
+        if (this._sessionBackup && !!sessionBackup) {
             return;
         }
         this._sessionBackup = sessionBackup;

src/matrix/e2ee/megolm/decryption/KeyLoader.ts

@@ -212,6 +212,7 @@ class KeyOperation {
 
     dispose() {
         this.session.free();
+        this.session = undefined as any;
     }
 
     /** returns whether the key for this operation has been checked at some point against storage

src/matrix/net/HomeServerApi.js

@@ -18,6 +18,9 @@ limitations under the License.
 import {encodeQueryParams, encodeBody} from "./common.js";
 import {HomeServerRequest} from "./HomeServerRequest.js";
 
+const CS_R0_PREFIX = "/_matrix/client/r0";
+const DEHYDRATION_PREFIX = "/_matrix/client/unstable/org.matrix.msc2697.v2";
+
 export class HomeServerApi {
     constructor({homeserver, accessToken, request, reconnector}) {
         // store these both in a closure somehow so it's harder to get at in case of XSS?
@@ -28,8 +31,8 @@ export class HomeServerApi {
         this._reconnector = reconnector;
     }
 
-    _url(csPath) {
+    _url(csPath, prefix = CS_R0_PREFIX) {
-        return `${this._homeserver}/_matrix/client/r0${csPath}`;
+        return this._homeserver + prefix + csPath;
     }
 
     _baseRequest(method, url, queryParams, body, options, accessToken) {
@@ -92,15 +95,15 @@ export class HomeServerApi {
     }
 
     _post(csPath, queryParams, body, options) {
-        return this._authedRequest("POST", this._url(csPath), queryParams, body, options);
+        return this._authedRequest("POST", this._url(csPath, options?.prefix || CS_R0_PREFIX), queryParams, body, options);
     }
 
     _put(csPath, queryParams, body, options) {
-        return this._authedRequest("PUT", this._url(csPath), queryParams, body, options);
+        return this._authedRequest("PUT", this._url(csPath, options?.prefix || CS_R0_PREFIX), queryParams, body, options);
     }
 
     _get(csPath, queryParams, body, options) {
-        return this._authedRequest("GET", this._url(csPath), queryParams, body, options);
+        return this._authedRequest("GET", this._url(csPath, options?.prefix || CS_R0_PREFIX), queryParams, body, options);
     }
 
     sync(since, filter, timeout, options = null) {
@@ -170,8 +173,12 @@ export class HomeServerApi {
         return this._unauthedRequest("GET", `${this._homeserver}/_matrix/client/versions`, null, null, options);
     }
 
-    uploadKeys(payload, options = null) {
+    uploadKeys(dehydratedDeviceId, payload, options = null) {
-        return this._post("/keys/upload", null, payload, options);
+        let path = "/keys/upload";
+        if (dehydratedDeviceId) {
+            path = path + `/${encodeURIComponent(dehydratedDeviceId)}`;
+        }
+        return this._post(path, null, payload, options);
     }
 
     queryKeys(queryRequest, options = null) {
@@ -229,6 +236,21 @@ export class HomeServerApi {
     logout(options = null) {
         return this._post(`/logout`, null, null, options);
     }
+
+    getDehydratedDevice(options = {}) {
+        options.prefix = DEHYDRATION_PREFIX;
+        return this._get(`/dehydrated_device`, null, null, options);
+    }
+
+    createDehydratedDevice(payload, options = {}) {
+        options.prefix = DEHYDRATION_PREFIX;
+        return this._put(`/dehydrated_device`, null, payload, options);
+    }
+
+    claimDehydratedDevice(deviceId, options = {}) {
+        options.prefix = DEHYDRATION_PREFIX;
+        return this._post(`/dehydrated_device/claim`, null, {device_id: deviceId}, options);
+    }
 }
 
 import {Request as MockRequest} from "../../mocks/Request.js";

src/matrix/room/BaseRoom.js

@@ -463,7 +463,7 @@ export class BaseRoom extends EventEmitter {
     enableSessionBackup(sessionBackup) {
         this._roomEncryption?.enableSessionBackup(sessionBackup);
         // TODO: do we really want to do this every time you open the app?
-        if (this._timeline) {
+        if (this._timeline && sessionBackup) {
             this._platform.logger.run("enableSessionBackup", log => {
                 return this._roomEncryption.restoreMissingSessionsFromBackup(this._timeline.remoteEntries, log);
             });

src/matrix/ssss/common.js

@@ -15,9 +15,9 @@ limitations under the License.
 */
 
 export class KeyDescription {
-    constructor(id, keyAccountData) {
+    constructor(id, keyDescription) {
         this._id = id;
-        this._keyAccountData = keyAccountData;
+        this._keyDescription = keyDescription;
     }
 
     get id() {
@@ -25,11 +25,30 @@ export class KeyDescription {
     }
 
     get passphraseParams() {
-        return this._keyAccountData?.content?.passphrase;
+        return this._keyDescription?.passphrase;
     }
 
     get algorithm() {
-        return this._keyAccountData?.content?.algorithm;
+        return this._keyDescription?.algorithm;
+    }
+
+    async isCompatible(key, platform) {
+        if (this.algorithm === "m.secret_storage.v1.aes-hmac-sha2") {
+            const kd = this._keyDescription;
+            if (kd.mac) {
+                const otherMac = await calculateKeyMac(key.binaryKey, kd.iv, platform);
+                return kd.mac === otherMac;
+            } else if (kd.passphrase) {
+                const kdOther = key.description._keyDescription;
+                if (!kdOther.passphrase) {
+                    return false;
+                }
+                return kd.passphrase.algorithm === kdOther.passphrase.algorithm && 
+                    kd.passphrase.iterations === kdOther.passphrase.iterations && 
+                    kd.passphrase.salt === kdOther.passphrase.salt;
+            }
+        }
+        return false;
     }
 }
 
@@ -39,6 +58,14 @@ export class Key {
         this._binaryKey = binaryKey;
     }
 
+    withDescription(description) {
+        return new Key(description, this._binaryKey);
+    }
+
+    get description() {
+        return this._keyDescription;
+    }
+
     get id() {
         return this._keyDescription.id;
     }
@@ -51,3 +78,24 @@ export class Key {
         return this._keyDescription.algorithm;
     }
 }
+
+async function calculateKeyMac(key, ivStr, platform) {
+    const {crypto, encoding} = platform;
+    const {utf8, base64} = encoding;
+    const {derive, aes, hmac} = crypto;
+
+    const iv = base64.decode(ivStr);
+
+    // salt for HKDF, with 8 bytes of zeros
+    const zerosalt = new Uint8Array(8);
+    const ZERO_STR = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
+    
+    const info = utf8.encode("");
+    const keybits = await derive.hkdf(key, zerosalt, info, "SHA-256", 512);
+    const aesKey = keybits.slice(0, 32);
+    const hmacKey = keybits.slice(32);
+    const ciphertext = await aes.encryptCTR({key: aesKey, iv, data: utf8.encode(ZERO_STR)});
+    const mac = await hmac.compute(hmacKey, ciphertext, "SHA-256");
+
+    return base64.encode(mac);
+}

src/matrix/ssss/index.js

@@ -18,9 +18,12 @@ import {KeyDescription, Key} from "./common.js";
 import {keyFromPassphrase} from "./passphrase.js";
 import {keyFromRecoveryKey} from "./recoveryKey.js";
 import {SESSION_E2EE_KEY_PREFIX} from "../e2ee/common.js";
+import {createEnum} from "../../utils/enum.js";
 
 const SSSS_KEY = `${SESSION_E2EE_KEY_PREFIX}ssssKey`;
 
+export const KeyType = createEnum("RecoveryKey", "Passphrase");
+
 async function readDefaultKeyDescription(storage) {
     const txn = await storage.readTxn([
         storage.storeNames.accountData
@@ -34,7 +37,7 @@ async function readDefaultKeyDescription(storage) {
     if (!keyAccountData) {
         return;
     }
-    return new KeyDescription(id, keyAccountData);
+    return new KeyDescription(id, keyAccountData.content);
 }
 
 export async function writeKey(key, txn) {
@@ -47,7 +50,14 @@ export async function readKey(txn) {
         return;
     }
     const keyAccountData = await txn.accountData.get(`m.secret_storage.key.${keyData.id}`);
-    return new Key(new KeyDescription(keyData.id, keyAccountData), keyData.binaryKey);
+    if (keyAccountData) {
+        return new Key(new KeyDescription(keyData.id, keyAccountData.content), keyData.binaryKey);
+    }
+}
+
+
+export async function removeKey(txn) {
+    await txn.session.remove(SSSS_KEY);
 }
 
 export async function keyFromCredential(type, credential, storage, platform, olm) {
@@ -55,13 +65,24 @@ export async function keyFromCredential(type, credential, storage, platform, olm
     if (!keyDescription) {
         throw new Error("Could not find a default secret storage key in account data");
     }
+    return await keyFromCredentialAndDescription(type, credential, keyDescription, platform, olm);
+}
+
+export async function keyFromCredentialAndDescription(type, credential, keyDescription, platform, olm) {
     let key;
-    if (type === "phrase") {
+    if (type === KeyType.Passphrase) {
         key = await keyFromPassphrase(keyDescription, credential, platform);
-    } else if (type === "key") {
+    } else if (type === KeyType.RecoveryKey) {
         key = keyFromRecoveryKey(keyDescription, credential, olm, platform);
     } else {
         throw new Error(`Invalid type: ${type}`);
     }
     return key;
 }
+
+export async function keyFromDehydratedDeviceKey(key, storage, platform) {
+    const keyDescription = await readDefaultKeyDescription(storage);
+    if (await keyDescription.isCompatible(key, platform)) {
+        return key.withDescription(keyDescription);
+    }
+}

src/platform/web/ui/css/login.css

@@ -54,15 +54,12 @@ limitations under the License.
     padding: 0 0.4em 0.4em;
 }
 
-.SessionLoadStatusView, .LoginView_query-spinner {
+.SessionLoadStatusView > .status, .LoginView_query-spinner {
     display: flex;
+    gap: 12px;
 }
 
-.SessionLoadStatusView> :not(:first-child), .LoginView_query-spinner> :not(:first-child) {
+.SessionLoadStatusView > .status p, .LoginView_query-spinner p {
-    margin-left: 12px;
-}
-
-.SessionLoadStatusView p, .LoginView_query-spinner p {
     flex: 1;
     margin: 0;
 }

src/platform/web/ui/css/themes/element/theme.css

@@ -629,6 +629,19 @@ a {
 
 .Settings .row .label {
     flex: 0 0 200px;
+    align-self: flex-start;
+}
+
+.Settings .row .content p {
+    margin: 8px 0;
+}
+
+.Settings .row .content p:first-child {
+    margin-top: 0;
+}
+
+.Settings .row .content p:last-child {
+    margin-bottom: 0;
 }
 
 .error {

src/platform/web/ui/login/AccountSetupView.js

@@ -0,0 +1,41 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import {TemplateView} from "../general/TemplateView";
+import {SessionBackupSettingsView} from "../session/settings/SessionBackupSettingsView.js";
+
+export class AccountSetupView extends TemplateView {
+    render(t, vm) {
+        return t.div({className: "Settings" /* hack for now to get the layout right*/}, [
+            t.h3(vm.i18n`Restore your encrypted history?`),
+            t.ifView(vm => vm.decryptDehydratedDeviceViewModel, vm => new SessionBackupSettingsView(vm.decryptDehydratedDeviceViewModel)),
+            t.map(vm => vm.deviceDecrypted, (decrypted, t) => {
+                if (decrypted) {
+                    return t.p(vm.i18n`That worked out, you're good to go!`);
+                } else {
+                    return t.p(vm.i18n`This will claim the dehydrated device ${vm.dehydratedDeviceId}, and will set up a new one.`);
+                }
+            }),
+            t.div({ className: "button-row" }, [
+                t.button({
+                    className: "button-action primary",
+                    onClick: () => { vm.finish(); },
+                    type: "button",
+                }, vm => vm.deviceDecrypted ? vm.i18n`Continue` : vm.i18n`Continue without restoring`),
+            ]),
+        ]);
+    }
+}

src/platform/web/ui/login/SessionLoadStatusView.js

@@ -16,6 +16,7 @@ limitations under the License.
 
 import {TemplateView} from "../general/TemplateView";
 import {spinner} from "../common.js";
+import {AccountSetupView} from "./AccountSetupView.js";
 
 /** a view used both in the login view and the loading screen
 to show the current state of loading the session.
@@ -27,9 +28,19 @@ export class SessionLoadStatusView extends TemplateView {
                 onClick: () => vm.exportLogs()
             }, vm.i18n`Export logs`);
         });
+        const logoutButtonIfFailed = t.if(vm => vm.hasError, (t, vm) => {
+            return t.button({
+                onClick: () => vm.logout()
+            }, vm.i18n`Log out`);
+        });
         return t.div({className: "SessionLoadStatusView"}, [
-            spinner(t, {hiddenWithLayout: vm => !vm.loading}),
+            t.p({className: "status"}, [
-            t.p([vm => vm.loadLabel, exportLogsButtonIfFailed])
+                spinner(t, {hidden: vm => !vm.loading}),
+                t.p(vm => vm.loadLabel),
+                exportLogsButtonIfFailed,
+                logoutButtonIfFailed
+            ]),
+            t.ifView(vm => vm.accountSetupViewModel, vm => new AccountSetupView(vm.accountSetupViewModel)),
         ]);
     }
 }

src/platform/web/ui/login/SessionPickerView.js

@@ -19,30 +19,6 @@ import {TemplateView} from "../general/TemplateView";
 import {hydrogenGithubLink} from "./common.js";
 import {SessionLoadStatusView} from "./SessionLoadStatusView.js";
 
-function selectFileAsText(mimeType) {
-    const input = document.createElement("input");
-    input.setAttribute("type", "file");
-    if (mimeType) {
-        input.setAttribute("accept", mimeType);
-    }
-    const promise = new Promise((resolve, reject) => {
-        const checkFile = () => {
-            input.removeEventListener("change", checkFile, true);
-            const file = input.files[0];
-            if (file) {
-                resolve(file.text());
-            } else {
-                reject(new Error("No file selected"));
-            }
-        }
-        input.addEventListener("change", checkFile, true);
-    });
-    input.click();
-    return promise;
-}
-
-
-
 class SessionPickerItemView extends TemplateView {
     _onDeleteClick() {
         if (confirm("Are you sure?")) {
@@ -81,10 +57,6 @@ export class SessionPickerView extends TemplateView {
                 t.h1(["Continue as …"]),
                 t.view(sessionList),
                 t.div({className: "button-row"}, [
-                    t.button({
-                        className: "button-action secondary",
-                        onClick: async () => vm.import(await selectFileAsText("application/json"))
-                    }, vm.i18n`Import a session`),
                     t.a({
                         className: "button-action primary",
                         href: vm.cancelUrl

src/platform/web/ui/session/settings/SessionBackupSettingsView.js

@@ -21,25 +21,31 @@ export class SessionBackupSettingsView extends TemplateView {
     render(t, vm) {
         return t.mapView(vm => vm.status, status => {
             switch (status) {
-                case "enabled": return new TemplateView(vm, renderEnabled)
+                case "Enabled": return new TemplateView(vm, renderEnabled)
-                case "setupKey": return new TemplateView(vm, renderEnableFromKey)
+                case "SetupKey": return new TemplateView(vm, renderEnableFromKey)
-                case "setupPhrase": return new TemplateView(vm, renderEnableFromPhrase)
+                case "SetupPhrase": return new TemplateView(vm, renderEnableFromPhrase)
-                case "pending": return new StaticView(vm, t => t.p(vm.i18n`Waiting to go online…`))
+                case "Pending": return new StaticView(vm, t => t.p(vm.i18n`Waiting to go online…`))
             }
         });
     }
 }
 
 function renderEnabled(t, vm) {
-    return t.p(vm.i18n`Session backup is enabled, using backup version ${vm.backupVersion}.`);
+    const items = [
+        t.p([vm.i18n`Session backup is enabled, using backup version ${vm.backupVersion}. `, t.button({onClick: () => vm.disable()}, vm.i18n`Disable`)])
+    ];
+    if (vm.dehydratedDeviceId) {
+        items.push(t.p(vm.i18n`A dehydrated device id was set up with id ${vm.dehydratedDeviceId} which you can use during your next login with your secret storage key.`));
+    }
+    return t.div(items);
 }
 
 function renderEnableFromKey(t, vm) {
     const useASecurityPhrase = t.button({className: "link", onClick: () => vm.showPhraseSetup()}, vm.i18n`use a security phrase`);
     return t.div([
-        t.p(vm.i18n`Enter your secret storage security key below to set up session backup, which will enable you to decrypt messages received before you logged into this session. The security key is a code of 12 groups of 4 characters separated by a space that Element created for you when setting up security.`),
+        t.p(vm.i18n`Enter your secret storage security key below to ${vm.purpose}, which will enable you to decrypt messages received before you logged into this session. The security key is a code of 12 groups of 4 characters separated by a space that Element created for you when setting up security.`),
         renderError(t),
-        renderEnableFieldRow(t, vm, vm.i18n`Security key`, key => vm.enterSecurityKey(key)),
+        renderEnableFieldRow(t, vm, vm.i18n`Security key`, (key, setupDehydratedDevice) => vm.enterSecurityKey(key, setupDehydratedDevice)),
         t.p([vm.i18n`Alternatively, you can `, useASecurityPhrase, vm.i18n` if you have one.`]),
     ]);
 }
@@ -47,22 +53,34 @@ function renderEnableFromKey(t, vm) {
 function renderEnableFromPhrase(t, vm) {
     const useASecurityKey = t.button({className: "link", onClick: () => vm.showKeySetup()}, vm.i18n`use your security key`);
     return t.div([
-        t.p(vm.i18n`Enter your secret storage security phrase below to set up session backup, which will enable you to decrypt messages received before you logged into this session. The security phrase is a freeform secret phrase you optionally chose when setting up security in Element. It is different from your password to login, unless you chose to set them to the same value.`),
+        t.p(vm.i18n`Enter your secret storage security phrase below to ${vm.purpose}, which will enable you to decrypt messages received before you logged into this session. The security phrase is a freeform secret phrase you optionally chose when setting up security in Element. It is different from your password to login, unless you chose to set them to the same value.`),
         renderError(t),
-        renderEnableFieldRow(t, vm, vm.i18n`Security phrase`, phrase => vm.enterSecurityPhrase(phrase)),
+        renderEnableFieldRow(t, vm, vm.i18n`Security phrase`, (phrase, setupDehydratedDevice) => vm.enterSecurityPhrase(phrase, setupDehydratedDevice)),
         t.p([vm.i18n`You can also `, useASecurityKey, vm.i18n`.`]),
     ]);
 }
 
 function renderEnableFieldRow(t, vm, label, callback) {
-    const eventHandler = () => callback(input.value);
+    let setupDehydrationCheck;
-    const input = t.input({type: "password", disabled: vm => vm.isBusy, placeholder: label, onChange: eventHandler});
+    const eventHandler = () => callback(input.value, setupDehydrationCheck?.checked || false);
+    const input = t.input({type: "password", disabled: vm => vm.isBusy, placeholder: label});
+    const children = [
+        t.p([
+            input,
+            t.button({disabled: vm => vm.isBusy, onClick: eventHandler}, vm.decryptAction),
+        ]),
+    ];
+    if (vm.offerDehydratedDeviceSetup) {
+        setupDehydrationCheck = t.input({type: "checkbox", id:"enable-dehydrated-device"});
+        const moreInfo = t.a({href: "https://github.com/uhoreg/matrix-doc/blob/dehydration/proposals/2697-device-dehydration.md", target: "_blank", rel: "noopener"}, "more info");
+        children.push(t.p([
+            setupDehydrationCheck,
+            t.label({for: setupDehydrationCheck.id}, [vm.i18n`Back up my device as well (`, moreInfo, ")"])
+        ]));
+    }
     return t.div({className: `row`}, [
         t.div({className: "label"}, label),
-        t.div({className: "content"}, [
+        t.div({className: "content"}, children),
-            input,
-            t.button({disabled: vm => vm.isBusy, onClick: eventHandler}, vm.i18n`Set up`),
-        ]),
     ]);
 }
 

src/platform/web/ui/session/settings/SettingsView.js

@@ -48,7 +48,7 @@ export class SettingsView extends TemplateView {
                     }
                 },
                 disabled: vm => vm.isLoggingOut
-            }, vm.i18n`Log out`))
+            }, vm.i18n`Log out`)),
         );
         settingNodes.push(
             t.h3("Session Backup"),
@@ -91,7 +91,7 @@ export class SettingsView extends TemplateView {
                     }),
                     t.map(vm => vm.pushNotifications.serverError, (err, t) => {
                         if (err) {
-                            return t.p("Couln't not check on server: " + err.message);
+                            return t.p("Couldn't not check on server: " + err.message);
                         }
                     })
                 ]);