feat(chat): add stateless ciphertext relay

2026-08-19 23:52:15 +00:00 · 2026-07-15 07:02:08 +02:00
parent 8fee98834c
commit f2eee6dc41
8 changed files with 219 additions and 3 deletions
@@ -0,0 +1,43 @@
+import { describe, expect, it } from 'vitest';
+import { Buffer } from 'node:buffer';
+import {
+    CHAT_CIPHERTEXT_MAX_BYTES,
+    createChatEnvelope,
+    normalizeChatCiphertext
+} from './chat.js';
+
+const encoded = (length) => Buffer.alloc(length, 7).toString('base64url');
+
+describe('encrypted chat relay envelopes', () => {
+    it('accepts canonical base64url within the encrypted message bounds', () => {
+        expect(normalizeChatCiphertext(encoded(29))).toBe(encoded(29));
+        expect(normalizeChatCiphertext(encoded(CHAT_CIPHERTEXT_MAX_BYTES))).toBe(encoded(CHAT_CIPHERTEXT_MAX_BYTES));
+    });
+
+    it('rejects malformed, padded, too-small, and oversized payloads', () => {
+        expect(normalizeChatCiphertext('<script>')).toBeNull();
+        expect(normalizeChatCiphertext(`${encoded(29)}=`)).toBeNull();
+        expect(normalizeChatCiphertext(encoded(28))).toBeNull();
+        expect(normalizeChatCiphertext(encoded(CHAT_CIPHERTEXT_MAX_BYTES + 1))).toBeNull();
+        expect(normalizeChatCiphertext('A')).toBeNull();
+    });
+
+    it('stamps authoritative metadata and keeps only ciphertext from the sender', () => {
+        const ciphertext = encoded(64);
+        const envelope = createChatEnvelope({
+            ciphertext,
+            id: 'spoofed',
+            senderId: 'mallory',
+            timestamp: 1,
+            text: 'plaintext must not survive'
+        }, 'alice', () => 1234, () => 'server-id');
+
+        expect(envelope).toEqual({
+            id: 'server-id',
+            senderId: 'alice',
+            timestamp: 1234,
+            ciphertext
+        });
+        expect(JSON.stringify(envelope)).not.toContain('plaintext');
+    });
+});