From 8f702928bc1216718f934d376354cd5e6e400e08 Mon Sep 17 00:00:00 2001
From: Franck Royer <franck@royer.one>
Date: Thu, 23 Sep 2021 15:42:15 +1000
Subject: [PATCH] Add encryption for chat groups

---
 packages/status-communities/package.json         |  1 +
 packages/status-communities/src/chat.ts          | 16 +++++++++++++---
 packages/status-communities/src/encryption.ts    |  9 +++++++++
 .../status-communities/src/messenger.spec.ts     |  4 ++--
 packages/status-communities/src/messenger.ts     | 13 ++++++++-----
 yarn.lock                                        |  3 ++-
 6 files changed, 35 insertions(+), 11 deletions(-)
 create mode 100644 packages/status-communities/src/encryption.ts

diff --git a/packages/status-communities/package.json b/packages/status-communities/package.json
index cf5a4389..09a82cd4 100644
--- a/packages/status-communities/package.json
+++ b/packages/status-communities/package.json
@@ -44,6 +44,7 @@
   },
   "dependencies": {
     "buffer": "^6.0.3",
+    "ecies-geth": "^1.5.3",
     "js-sha3": "^0.8.0",
     "js-waku": "^0.12.0",
     "protobufjs": "^6.11.2",
diff --git a/packages/status-communities/src/chat.ts b/packages/status-communities/src/chat.ts
index 2de593a1..20abeb14 100644
--- a/packages/status-communities/src/chat.ts
+++ b/packages/status-communities/src/chat.ts
@@ -1,13 +1,23 @@
 import { ChatMessage } from "./chat_message";
 import { chatIdToContentTopic } from "./contentTopic";
+import { createSymKeyFromPassword } from "./encryption";
 
+/**
+ * Represent a chat room. Only public chats are currently supported.
+ */
 export class Chat {
   private lastClockValue?: number;
   private lastMessage?: ChatMessage;
-  public id: string;
 
-  constructor(id: string) {
-    this.id = id;
+  private constructor(public id: string, public symKey: Uint8Array) {}
+
+  /**
+   * Create a public chat room.
+   */
+  public static async create(id: string) {
+    const symKey = await createSymKeyFromPassword(id);
+
+    return new Chat(id, symKey);
   }
 
   public get contentTopic(): string {
diff --git a/packages/status-communities/src/encryption.ts b/packages/status-communities/src/encryption.ts
new file mode 100644
index 00000000..4aa297b2
--- /dev/null
+++ b/packages/status-communities/src/encryption.ts
@@ -0,0 +1,9 @@
+import { kdf } from "ecies-geth";
+
+const AESKeyLength = 32; // bytes
+
+export async function createSymKeyFromPassword(
+  password: string
+): Promise<Uint8Array> {
+  return kdf(Buffer.from(password, "utf-8"), AESKeyLength);
+}
diff --git a/packages/status-communities/src/messenger.spec.ts b/packages/status-communities/src/messenger.spec.ts
index e6441f7f..dd074b8f 100644
--- a/packages/status-communities/src/messenger.spec.ts
+++ b/packages/status-communities/src/messenger.spec.ts
@@ -47,8 +47,8 @@ describe("Messenger", () => {
   it("Sends & Receive message in public chat", async function () {
     this.timeout(10_000);
 
-    messengerAlice.joinChat(testChatId);
-    messengerBob.joinChat(testChatId);
+    await messengerAlice.joinChat(testChatId);
+    await messengerBob.joinChat(testChatId);
 
     const text = "This is a message.";
 
diff --git a/packages/status-communities/src/messenger.ts b/packages/status-communities/src/messenger.ts
index 0436a96d..05cfbb89 100644
--- a/packages/status-communities/src/messenger.ts
+++ b/packages/status-communities/src/messenger.ts
@@ -39,10 +39,12 @@ export class Messenger {
    *
    * Use `addListener` to get messages received on this chat.
    */
-  public joinChat(chatId: string) {
+  public async joinChat(chatId: string) {
     if (this.chatsById.has(chatId)) throw "Chat already joined";
 
-    const chat = new Chat(chatId);
+    const chat = await Chat.create(chatId);
+
+    this.waku.relay.addDecryptionKey(chat.symKey);
 
     this.waku.relay.addObserver(
       (wakuMessage: WakuMessage) => {
@@ -72,7 +74,7 @@ export class Messenger {
    */
   public async sendMessage(text: string, chatId: string): Promise<void> {
     const chat = this.chatsById.get(chatId);
-    if (!chat) throw `Chat not joined: ${chatId}`;
+    if (!chat) throw `Failed to send message, chat not joined: ${chatId}`;
 
     const chatMessage = chat.createMessage(text);
 
@@ -82,10 +84,11 @@ export class Messenger {
       this.identity
     );
 
-    // TODO: Use version 1 with signature
+    // TODO: Add signature
     const wakuMessage = await WakuMessage.fromBytes(
       appMetadataMessage.encode(),
-      chat.contentTopic
+      chat.contentTopic,
+      { symKey: chat.symKey }
     );
 
     await this.waku.relay.send(wakuMessage);
diff --git a/yarn.lock b/yarn.lock
index c5160f68..7a787ad0 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1734,7 +1734,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"ecies-geth@npm:^1.5.2":
+"ecies-geth@npm:^1.5.2, ecies-geth@npm:^1.5.3":
   version: 1.5.3
   resolution: "ecies-geth@npm:1.5.3"
   dependencies:
@@ -5635,6 +5635,7 @@ fsevents@~2.3.2:
     "@typescript-eslint/parser": ^4.31.1
     buffer: ^6.0.3
     chai: ^4.3.4
+    ecies-geth: ^1.5.3
     eslint: ^7.32.0
     eslint-config-prettier: ^8.3.0
     eslint-import-resolver-node: ^0.3.6