Add accessSecretStorage helper with common flow setup

This moves the details of dialogs that may be needed when accessing secret
storage to centralised helper. In addition, this clears the secret storage key
cache so that keys are only live for a single operation.

src/CrossSigningManager.js

@@ -19,13 +19,14 @@ import sdk from './index';
 import MatrixClientPeg from './MatrixClientPeg';
 import { deriveKey } from 'matrix-js-sdk/lib/crypto/key_passphrase';
 import { decodeRecoveryKey } from 'matrix-js-sdk/lib/crypto/recoverykey';
+import { _t } from './languageHandler';
 
 // This stores the secret storage private keys in memory for the JS SDK. This is
 // only meant to act as a cache to avoid prompting the user multiple times
-// during the same session. It is considered unsafe to persist this to normal
-// web storage. For platforms with a secure enclave, we will store this key
-// there.
-const secretStorageKeys = {};
+// during the same single operation. Use `accessSecretStorage` below to scope a
+// single secret storage operation, as it will clear the cached keys once the
+// operation ends.
+let secretStorageKeys = {};
 
 export const getSecretStorageKey = async ({ keys: keyInfos }) => {
     const keyInfoEntries = Object.entries(keyInfos);
@@ -73,3 +74,71 @@ export const getSecretStorageKey = async ({ keys: keyInfos }) => {
 
     return [name, key];
 };
+
+export const crossSigningCallbacks = {
+    getSecretStorageKey,
+};
+
+/**
+ * This helper should be used whenever you need to access secret storage. It
+ * ensures that secret storage (and also cross-signing since they each depend on
+ * each other in a cycle of sorts) have been bootstrapped before running the
+ * provided function.
+ *
+ * Bootstrapping secret storage may take one of these paths:
+ * 1. Create secret storage from a passphrase and store cross-signing keys
+ *    in secret storage.
+ * 2. Access existing secret storage by requesting passphrase and accessing
+ *    cross-signing keys as needed.
+ * 3. All keys are loaded and there's nothing to do.
+ *
+ * Additionally, the secret storage keys are cached during the scope of this function
+ * to ensure the user is prompted only once for their secret storage
+ * passphrase. The cache is then
+ *
+ * @param {Function} [func] An operation to perform once secret storage has been
+ * bootstrapped. Optional.
+ */
+export async function accessSecretStorage(func = async () => { }) {
+    const cli = MatrixClientPeg.get();
+
+    try {
+        if (!cli.hasSecretStorageKey()) {
+            // This dialog calls bootstrap itself after guiding the user through
+            // passphrase creation.
+            const { finished } = Modal.createTrackedDialogAsync('Create Secret Storage dialog', '',
+                import("./async-components/views/dialogs/secretstorage/CreateSecretStorageDialog"),
+                null, null, /* priority = */ false, /* static = */ true,
+            );
+            const [confirmed] = await finished;
+            if (!confirmed) {
+                throw new Error("Secret storage creation canceled");
+            }
+        } else {
+            const InteractiveAuthDialog = sdk.getComponent("dialogs.InteractiveAuthDialog");
+            await cli.bootstrapSecretStorage({
+                authUploadDeviceSigningKeys: async (makeRequest) => {
+                    const { finished } = Modal.createTrackedDialog(
+                        'Cross-signing keys dialog', '', InteractiveAuthDialog,
+                        {
+                            title: _t("Send cross-signing keys to homeserver"),
+                            matrixClient: MatrixClientPeg.get(),
+                            makeRequest,
+                        },
+                    );
+                    const [confirmed] = await finished;
+                    if (!confirmed) {
+                        throw new Error("Cross-signing key upload auth canceled");
+                    }
+                },
+            });
+        }
+
+        // `return await` needed here to ensure `finally` block runs after the
+        // inner operation completes.
+        return await func();
+    } finally {
+        // Clear secret storage key cache now that work is complete
+        secretStorageKeys = {};
+    }
+}

src/MatrixClientPeg.js

@@ -31,7 +31,7 @@ import {verificationMethods} from 'matrix-js-sdk/lib/crypto';
 import MatrixClientBackedSettingsHandler from "./settings/handlers/MatrixClientBackedSettingsHandler";
 import * as StorageManager from './utils/StorageManager';
 import IdentityAuthClient from './IdentityAuthClient';
-import * as CrossSigningManager from './CrossSigningManager';
+import { crossSigningCallbacks } from './CrossSigningManager';
 
 interface MatrixClientCreds {
     homeserverUrl: string,
@@ -224,7 +224,7 @@ class MatrixClientPeg {
 
         opts.cryptoCallbacks = {};
         if (SettingsStore.isFeatureEnabled("feature_cross_signing")) {
-            Object.assign(opts.cryptoCallbacks, CrossSigningManager);
+            Object.assign(opts.cryptoCallbacks, crossSigningCallbacks);
         }
 
         this.matrixClient = createMatrixClient(opts);

src/components/views/settings/CrossSigningPanel.js

@@ -19,7 +19,7 @@ import React from 'react';
 import MatrixClientPeg from '../../../MatrixClientPeg';
 import { _t } from '../../../languageHandler';
 import sdk from '../../../index';
-import Modal from '../../../Modal';
+import { accessSecretStorage } from '../../../CrossSigningManager';
 
 export default class CrossSigningPanel extends React.PureComponent {
     constructor(props) {
@@ -78,38 +78,8 @@ export default class CrossSigningPanel extends React.PureComponent {
      */
     _bootstrapSecureSecretStorage = async () => {
         this.setState({ error: null });
-        const cli = MatrixClientPeg.get();
         try {
-            if (!cli.hasSecretStorageKey()) {
-                // This dialog calls bootstrap itself after guiding the user through
-                // passphrase creation.
-                const { finished } = Modal.createTrackedDialogAsync('Create Secret Storage dialog', '',
-                    import("../../../async-components/views/dialogs/secretstorage/CreateSecretStorageDialog"),
-                    null, null, /* priority = */ false, /* static = */ true,
-                );
-                const [confirmed] = await finished;
-                if (!confirmed) {
-                    throw new Error("Secret storage creation canceled");
-                }
-            } else {
-                const InteractiveAuthDialog = sdk.getComponent("dialogs.InteractiveAuthDialog");
-                await cli.bootstrapSecretStorage({
-                    authUploadDeviceSigningKeys: async (makeRequest) => {
-                        const { finished } = Modal.createTrackedDialog(
-                            'Cross-signing keys dialog', '', InteractiveAuthDialog,
-                            {
-                                title: _t("Send cross-signing keys to homeserver"),
-                                matrixClient: MatrixClientPeg.get(),
-                                makeRequest,
-                            },
-                        );
-                        const [confirmed] = await finished;
-                        if (!confirmed) {
-                            throw new Error("Cross-signing key upload auth canceled");
-                        }
-                    },
-                });
-            }
+            await accessSecretStorage();
         } catch (e) {
             this.setState({ error: e });
             console.error("Error bootstrapping secret storage", e);

src/i18n/strings/en_EN.json

@@ -57,6 +57,7 @@
     "Server may be unavailable, overloaded, or you hit a bug.": "Server may be unavailable, overloaded, or you hit a bug.",
     "The server does not support the room version specified.": "The server does not support the room version specified.",
     "Failure to create room": "Failure to create room",
+    "Send cross-signing keys to homeserver": "Send cross-signing keys to homeserver",
     "Send anyway": "Send anyway",
     "Send": "Send",
     "Sun": "Sun",
@@ -495,7 +496,6 @@
     "New Password": "New Password",
     "Confirm password": "Confirm password",
     "Change Password": "Change Password",
-    "Send cross-signing keys to homeserver": "Send cross-signing keys to homeserver",
     "Cross-signing public keys:": "Cross-signing public keys:",
     "on device": "on device",
     "not found": "not found",