use random pickle key on all platforms, and store access token encrypted in IDB

src/BasePlatform.ts

@@ -18,6 +18,7 @@ limitations under the License.
 */
 
 import {MatrixClient} from "matrix-js-sdk/src/client";
+import {encodeUnpaddedBase64} from "matrix-js-sdk/src/crypto/olmlib";
 import dis from './dispatcher/dispatcher';
 import BaseEventIndexManager from './indexing/BaseEventIndexManager';
 import {ActionPayload} from "./dispatcher/payloads";
@@ -25,6 +26,7 @@ import {CheckUpdatesPayload} from "./dispatcher/payloads/CheckUpdatesPayload";
 import {Action} from "./dispatcher/actions";
 import {hideToast as hideUpdateToast} from "./toasts/UpdateToast";
 import {MatrixClientPeg} from "./MatrixClientPeg";
+import {idbLoad, idbSave, idbDelete} from "./IndexedDB";
 
 export const SSO_HOMESERVER_URL_KEY = "mx_sso_hs_url";
 export const SSO_ID_SERVER_URL_KEY = "mx_sso_is_url";
@@ -273,7 +275,40 @@ export default abstract class BasePlatform {
      *     pickle key has been stored.
      */
     async getPickleKey(userId: string, deviceId: string): Promise<string | null> {
-        return null;
+        if (!window.crypto || !window.crypto.subtle) {
+            return null;
+        }
+        let data;
+        try {
+            data = await idbLoad("pickleKey", [userId, deviceId]);
+        } catch (e) {}
+        if (!data) {
+            return null;
+        }
+        if (!data.encrypted || !data.iv || !data.cryptoKey) {
+            console.error("Badly formatted pickle key");
+            return null;
+        }
+
+        const additionalData = new Uint8Array(userId.length + deviceId.length + 1);
+        for (let i = 0; i < userId.length; i++) {
+            additionalData[i] = userId.charCodeAt(i);
+        }
+        additionalData[userId.length] = 124; // "|"
+        for (let i = 0; i < deviceId.length; i++) {
+            additionalData[userId.length + 1 + i] = deviceId.charCodeAt(i);
+        }
+
+        try {
+            const key = await crypto.subtle.decrypt(
+                {name: "AES-GCM", iv: data.iv, additionalData}, data.cryptoKey,
+                data.encrypted,
+            );
+            return encodeUnpaddedBase64(key);
+        } catch (e) {
+            console.error("Error decrypting pickle key");
+            return null;
+        }
     }
 
     /**
@@ -284,7 +319,33 @@ export default abstract class BasePlatform {
      *     support storing pickle keys.
      */
     async createPickleKey(userId: string, deviceId: string): Promise<string | null> {
-        return null;
+        if (!window.crypto || !window.crypto.subtle) {
+            return null;
+        }
+        const crypto = window.crypto;
+        const randomArray = new Uint8Array(32);
+        crypto.getRandomValues(randomArray);
+        const cryptoKey = await crypto.subtle.generateKey(
+            {name: "AES-GCM", length: 256}, false, ["encrypt", "decrypt"],
+        );
+        const iv = new Uint8Array(32);
+        crypto.getRandomValues(iv);
+
+        const additionalData = new Uint8Array(userId.length + deviceId.length + 1);
+        for (let i = 0; i < userId.length; i++) {
+            additionalData[i] = userId.charCodeAt(i);
+        }
+        additionalData[userId.length] = 124; // "|"
+        for (let i = 0; i < deviceId.length; i++) {
+            additionalData[userId.length + 1 + i] = deviceId.charCodeAt(i);
+        }
+
+        const encrypted = await crypto.subtle.encrypt(
+            {name: "AES-GCM", iv, additionalData}, cryptoKey, randomArray,
+        );
+
+        await idbSave("pickleKey", [userId, deviceId], {encrypted, iv, cryptoKey});
+        return encodeUnpaddedBase64(randomArray);
     }
 
     /**
@@ -293,5 +354,8 @@ export default abstract class BasePlatform {
      * @param {string} userId the device ID that the pickle key is for.
      */
     async destroyPickleKey(userId: string, deviceId: string): Promise<void> {
+        try {
+            await idbDelete("pickleKey", [userId, deviceId]);
+        } catch (e) {}
     }
 }