Fast-fail when trying to create a DM with a non-friend user

node/src/client.js

@@ -1212,8 +1212,9 @@ export default class PeerClient {
 	 */
 	createDirectChat = async (req) => {
 		const userClient = this.#getUser(req.mxid)
-		const channelList = userClient.talkClient.channelList.normal
+		await this.#requireInFriendsList(userClient.serviceClient, req.user_id)
 
+		const channelList = userClient.talkClient.channelList.normal
 		const createChannel =
 			!req.user_id.equals(userClient.userId)
 			? channelList.createChannel.bind(channelList, {
@@ -1237,6 +1238,22 @@ export default class PeerClient {
 		return res
 	}
 
+	/**
+	 * @param {ServiceApiClient} serviceClient
+	 * @param {Long} id
+	 */
+	async #requireInFriendsList(serviceClient, id) {
+		let listRes = await serviceClient.requestFriendList()
+		if (!listRes.success) {
+			this.error("Failed to check friends list")
+			throw listRes
+		}
+		const isFriend = -1 != listRes.result.friends.findIndex(friend => id.equals(friend.userId))
+		if (!isFriend) {
+			throw new ProtocolError("This user is not in your friends list")
+		}
+	}
+
 	/**
 	 * @param {object} req
 	 * @param {string} req.mxid