Don't allow upgrade from untrusted key backup.

If we trust the key backup at upgrade time then we can sign it so
key backup will work automatically when cross-signing is trusted.
If we don't sign it at this point we'll end up with cross-signing
and key backup set up but key backup untrusted by the cross-signing
key which is a bit of a broken situation.

With https://github.com/matrix-org/matrix-js-sdk/pull/1144 fixes
https://github.com/vector-im/riot-web/issues/11747

src/async-components/views/dialogs/secretstorage/CreateSecretStorageDialog.js

@@ -24,14 +24,15 @@ import { _t } from '../../../../languageHandler';
 import Modal from '../../../../Modal';
 
 const PHASE_LOADING = 0;
-const PHASE_MIGRATE = 1;
+const PHASE_RESTORE_KEY_BACKUP = 1;
-const PHASE_PASSPHRASE = 2;
+const PHASE_MIGRATE = 2;
-const PHASE_PASSPHRASE_CONFIRM = 3;
+const PHASE_PASSPHRASE = 3;
-const PHASE_SHOWKEY = 4;
+const PHASE_PASSPHRASE_CONFIRM = 4;
-const PHASE_KEEPITSAFE = 5;
+const PHASE_SHOWKEY = 5;
-const PHASE_STORING = 6;
+const PHASE_KEEPITSAFE = 6;
-const PHASE_DONE = 7;
+const PHASE_STORING = 7;
-const PHASE_OPTOUT_CONFIRM = 8;
+const PHASE_DONE = 8;
+const PHASE_OPTOUT_CONFIRM = 9;
 
 const PASSWORD_MIN_SCORE = 4; // So secure, many characters, much complex, wow, etc, etc.
 const PASSPHRASE_FEEDBACK_DELAY = 500; // How long after keystroke to offer passphrase feedback, ms.
@@ -67,6 +68,8 @@ export default class CreateSecretStorageDialog extends React.PureComponent {
             downloaded: false,
             zxcvbnResult: null,
             setPassPhrase: false,
+            backupInfo: null,
+            backupSigStatus: null,
         };
 
         this._fetchBackupInfo();
@@ -80,10 +83,16 @@ export default class CreateSecretStorageDialog extends React.PureComponent {
 
     async _fetchBackupInfo() {
         const backupInfo = await MatrixClientPeg.get().getKeyBackupVersion();
+        const backupSigStatus = await MatrixClientPeg.get().isKeyBackupTrusted(backupInfo);
+
+        const phase = backupInfo ?
+            (backupSigStatus.usable ? PHASE_MIGRATE : PHASE_RESTORE_KEY_BACKUP) :
+            PHASE_PASSPHRASE;
 
         this.setState({
-            phase: backupInfo ? PHASE_MIGRATE: PHASE_PASSPHRASE,
+            phase,
             backupInfo,
+            backupSigStatus,
         });
     }
 
@@ -268,6 +277,22 @@ export default class CreateSecretStorageDialog extends React.PureComponent {
         return this.state.zxcvbnResult && this.state.zxcvbnResult.score >= PASSWORD_MIN_SCORE;
     }
 
+    _renderPhaseRestoreKeyBackup() {
+        const DialogButtons = sdk.getComponent('views.elements.DialogButtons');
+        return <div>
+            <p>{_t(
+                "Key Backup is enabled on your account but has not been set " +
+                "up from this sign-in. To set up secret storage, " +
+                "restore your key backup.",
+            )}</p>
+            <DialogButtons primaryButton={_t('Cancel')}
+                onPrimaryButtonClick={this._onCancel}
+                hasCancel={false}
+            >
+            </DialogButtons>
+        </div>;
+    }
+
     _renderPhaseMigrate() {
         // TODO: This is a temporary screen so people who have the labs flag turned on and
         // click the button are aware they're making a change to their account.
@@ -277,7 +302,7 @@ export default class CreateSecretStorageDialog extends React.PureComponent {
         const DialogButtons = sdk.getComponent('views.elements.DialogButtons');
         return <div>
             <p>{_t(
-                "Secret Storage will be set up using your existing key backup details." +
+                "Secret Storage will be set up using your existing key backup details. " +
                 "Your secret storage passphrase and recovery key will be the same as " +
                 " they were for your key backup",
             )}</p>
@@ -527,6 +552,8 @@ export default class CreateSecretStorageDialog extends React.PureComponent {
 
     _titleForPhase(phase) {
         switch (phase) {
+            case PHASE_RESTORE_KEY_BACKUP:
+                return _t('Restore Your Key Backup');
             case PHASE_MIGRATE:
                 return _t('Migrate from Key Backup');
             case PHASE_PASSPHRASE:
@@ -569,6 +596,9 @@ export default class CreateSecretStorageDialog extends React.PureComponent {
                 case PHASE_LOADING:
                     content = this._renderBusyPhase();
                     break;
+                case PHASE_RESTORE_KEY_BACKUP:
+                    content = this._renderPhaseRestoreKeyBackup();
+                    break;
                 case PHASE_MIGRATE:
                     content = this._renderPhaseMigrate();
                     break;

src/i18n/strings/en_EN.json

@@ -1933,7 +1933,8 @@
     "The export file will be protected with a passphrase. You should enter the passphrase here, to decrypt the file.": "The export file will be protected with a passphrase. You should enter the passphrase here, to decrypt the file.",
     "File to import": "File to import",
     "Import": "Import",
-    "Secret Storage will be set up using your existing key backup details.Your secret storage passphrase and recovery key will be the same as  they were for your key backup": "Secret Storage will be set up using your existing key backup details.Your secret storage passphrase and recovery key will be the same as  they were for your key backup",
+    "Key Backup is enabled on your account but has not been set up from this sign-in. To set up secret storage, restore your key backup.": "Key Backup is enabled on your account but has not been set up from this sign-in. To set up secret storage, restore your key backup.",
+    "Secret Storage will be set up using your existing key backup details. Your secret storage passphrase and recovery key will be the same as  they were for your key backup": "Secret Storage will be set up using your existing key backup details. Your secret storage passphrase and recovery key will be the same as  they were for your key backup",
     "Great! This passphrase looks strong enough.": "Great! This passphrase looks strong enough.",
     "<b>Warning</b>: You should only set up secret storage from a trusted computer.": "<b>Warning</b>: You should only set up secret storage from a trusted computer.",
     "We'll use secret storage to optionally store an encrypted copy of your cross-signing identity for verifying other devices and message keys on our server. Protect your access to encrypted messages with a passphrase to keep it secure.": "We'll use secret storage to optionally store an encrypted copy of your cross-signing identity for verifying other devices and message keys on our server. Protect your access to encrypted messages with a passphrase to keep it secure.",
@@ -1960,6 +1961,7 @@
     "Your access to encrypted messages is now protected.": "Your access to encrypted messages is now protected.",
     "Without setting up secret storage, you won't be able to restore your access to encrypted messages or your cross-signing identity for verifying other devices if you log out or use another device.": "Without setting up secret storage, you won't be able to restore your access to encrypted messages or your cross-signing identity for verifying other devices if you log out or use another device.",
     "Set up secret storage": "Set up secret storage",
+    "Restore Your Key Backup": "Restore Your Key Backup",
     "Migrate from Key Backup": "Migrate from Key Backup",
     "Secure your encrypted messages with a passphrase": "Secure your encrypted messages with a passphrase",
     "Confirm your passphrase": "Confirm your passphrase",