Use room key encryption for private chat

apps/api/src/chat/routes.ts

@@ -1,19 +1,26 @@
 import { Router } from "express";
 import { z } from "zod";
 import { requireAuth } from "../auth/middleware.js";
-import { addMessage, addReaction, listChat } from "./store.js";
+import { addMessage, addReaction, listChat, upsertKeyWrap } from "./store.js";
 
 export const chatRouter = Router();
 
 const MessageBody = z.object({
-  content: z.string().trim().min(1).max(2000),
+  content: z.string().trim().min(1).max(12000),
   replyToId: z.string().max(128).optional(),
   replyToPubkey: z.string().max(128).optional(),
 });
 
 const ReactionBody = z.object({
   messageId: z.string().min(1).max(128),
-  content: z.string().trim().min(1).max(32),
+  content: z.string().trim().min(1).max(12000),
+});
+
+const KeyWrapBody = z.object({
+  wraps: z.array(z.object({
+    recipientPubkey: z.string().regex(/^[0-9a-f]{64}$/),
+    ciphertext: z.string().trim().min(1).max(12000),
+  })).min(1).max(10),
 });
 
 chatRouter.use(requireAuth);
@@ -42,3 +49,15 @@ chatRouter.post("/reactions", (req, res) => {
   });
   res.status(201).json(reaction);
 });
+
+chatRouter.post("/key-wraps", (req, res) => {
+  const body = KeyWrapBody.parse(req.body);
+  const wraps = body.wraps.map((wrap) =>
+    upsertKeyWrap({
+      recipientPubkey: wrap.recipientPubkey,
+      senderPubkey: req.session!.pubkey,
+      ciphertext: wrap.ciphertext,
+    }),
+  );
+  res.status(201).json({ wraps });
+});

apps/api/src/chat/store.ts

@@ -15,14 +15,26 @@ export type StoredChatReaction = {
   createdAt: number;
 };
 
+export type StoredChatKeyWrap = {
+  recipientPubkey: string;
+  senderPubkey: string;
+  ciphertext: string;
+  updatedAt: number;
+};
+
 const MAX_MESSAGES = 500;
 const MAX_REACTIONS = 2000;
 
 const messages: StoredChatMessage[] = [];
 const reactions: StoredChatReaction[] = [];
+const keyWraps: StoredChatKeyWrap[] = [];
 
-export function listChat(): { messages: StoredChatMessage[]; reactions: StoredChatReaction[] } {
-  return { messages: [...messages], reactions: [...reactions] };
+export function listChat(): {
+  messages: StoredChatMessage[];
+  reactions: StoredChatReaction[];
+  keyWraps: StoredChatKeyWrap[];
+} {
+  return { messages: [...messages], reactions: [...reactions], keyWraps: [...keyWraps] };
 }
 
 export function addMessage(input: {
@@ -60,3 +72,26 @@ export function addReaction(input: {
   if (reactions.length > MAX_REACTIONS) reactions.splice(0, reactions.length - MAX_REACTIONS);
   return reaction;
 }
+
+export function upsertKeyWrap(input: {
+  recipientPubkey: string;
+  senderPubkey: string;
+  ciphertext: string;
+}): StoredChatKeyWrap {
+  const updatedAt = Math.floor(Date.now() / 1000);
+  const existing = keyWraps.find((wrap) => wrap.recipientPubkey === input.recipientPubkey);
+  if (existing) {
+    existing.senderPubkey = input.senderPubkey;
+    existing.ciphertext = input.ciphertext;
+    existing.updatedAt = updatedAt;
+    return existing;
+  }
+  const wrap: StoredChatKeyWrap = {
+    recipientPubkey: input.recipientPubkey,
+    senderPubkey: input.senderPubkey,
+    ciphertext: input.ciphertext,
+    updatedAt,
+  };
+  keyWraps.push(wrap);
+  return wrap;
+}