v13: E2E encrypted DMs via ECDH + AES-256-GCM (Web Crypto API)
Server: - /keys POST: register ECDH public key (JWK) for a username - /keys GET: list users with registered keys - /keys/<user> GET: get user's public key - /dm POST: relay encrypted DM blob to recipient - SSE streams now register for DM delivery via name param - Server never sees plaintext - only ciphertext passes through Web UI: - Auto-generates ECDH P-256 key pair on load (no setup needed) - /dm @username message - sends E2E encrypted DM - /users - list users with registered keys - DMs shown with lock icon, pink color, direction arrows - Decryption happens entirely in browser - Key re-registered on name change - Derived AES keys cached per peer Protocol: - ECDH key exchange: each client exports JWK public key - Shared secret derived via ECDH P-256 - Messages encrypted with AES-256-GCM + random 12-byte nonce - Ciphertext + nonce sent as base64 through server Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Siavash Sameni
225
chat.py
225
chat.py
@@ -25,7 +25,7 @@ import html
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import urllib.parse
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PORT = 9999
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VERSION = "12"
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VERSION = "13"
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TUNNEL_TARGETS = {
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"parspack": ("185.208.174.152", 22),
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"mequ": ("188.213.68.133", 2022),
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@@ -36,6 +36,11 @@ MAX_TOTAL_STORAGE = 50 * 1024 * 1024 # 50 MB total
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# ── Server ──────────────────────────────────────────────────────────────
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# E2E encryption: public key registry (username -> JWK public key JSON string)
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user_keys: dict[str, str] = {}
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# DM routing: username -> list of (group, queue) for SSE, or (group, writer) for TCP
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dm_targets: dict[str, list] = {}
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uploaded_files: dict[str, bytes] = {} # file_id -> raw bytes (insertion order)
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total_file_bytes = 0
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@@ -129,6 +134,7 @@ CHAT_HTML = r"""<!DOCTYPE html>
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.msg a.auto-link { color: #67c7eb; }
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.ts { color: #666; }
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.sys { color: #5e9ca0; font-style: italic; }
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.dm-hint { color: #555; font-size: 0.8em; display: block; margin-top: 2px; }
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.file-link { display: inline-block; background: #0f3460; border: 1px solid #444;
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padding: 6px 12px; border-radius: 4px; margin: 2px 0; color: #67c7eb;
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text-decoration: none; }
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@@ -194,7 +200,7 @@ CHAT_HTML = r"""<!DOCTYPE html>
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<div id="header">
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<input id="name" placeholder="Name" value="" autocomplete="off">
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<span id="group-tag"></span>
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<span id="header-info">Shift+Enter newline · /setpass <pw> · /clearpass</span>
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<span id="header-info">/dm @user msg · /users · /setpass · /color</span>
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</div>
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<div id="messages"></div>
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<div id="bottom">
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@@ -305,6 +311,21 @@ function send() {
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localStorage.setItem('chat-name', name);
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if (!text) return;
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// Local commands
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const dmMatch = text.match(/^\/dm\s+@?(\S+)\s+([\s\S]+)/);
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if (dmMatch) {
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encryptAndSendDM(dmMatch[1], dmMatch[2]);
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$input.value = '';
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$input.style.height = 'auto';
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return;
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}
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if (text === '/users' || text === '/online') {
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fetch('/keys').then(r => r.json()).then(users => {
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addMsg({ts:Date.now()/1000, user:'***', text:'Users with keys: ' + users.join(', ')});
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});
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$input.value = '';
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$input.style.height = 'auto';
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return;
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}
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if (text === '/colors' || text === '/color') {
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reshuffleColors();
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$input.value = '';
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@@ -406,7 +427,11 @@ window.addEventListener('focus', function() {
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let sessionPass = sessionStorage.getItem('pw-' + GROUP) || '';
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function startSSE() {
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const url = BASE + '/events' + (sessionPass ? '?password=' + encodeURIComponent(sessionPass) : '');
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const myName = $name.value.trim() || 'anon';
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const params = new URLSearchParams();
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if (sessionPass) params.set('password', sessionPass);
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params.set('name', myName);
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const url = BASE + '/events?' + params.toString();
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const es = new EventSource(url);
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es.onmessage = function(e) {
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// Check for auth error
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@@ -416,7 +441,11 @@ function startSSE() {
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showPasswordPrompt();
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return;
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}
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addMsg(data);
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if (data.dm && data.encrypted) {
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handleEncryptedDM(data);
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} else {
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addMsg(data);
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}
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notify(data);
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};
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es.onerror = function() {
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@@ -439,6 +468,110 @@ document.getElementById('pw-input').onkeydown = function(e) {
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if (e.key === 'Enter') document.getElementById('pw-btn').click();
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};
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// ── E2E Encrypted DMs (ECDH + AES-256-GCM via Web Crypto) ──
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let myKeyPair = null;
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let myPubJwk = null;
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const derivedKeys = {}; // cache: username -> CryptoKey (AES)
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async function initCrypto() {
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myKeyPair = await crypto.subtle.generateKey(
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{ name: 'ECDH', namedCurve: 'P-256' }, true, ['deriveBits']
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);
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myPubJwk = await crypto.subtle.exportKey('jwk', myKeyPair.publicKey);
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// Register our public key with the server
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const myName = $name.value.trim() || 'anon';
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fetch('/keys', {
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method: 'POST',
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headers: {'Content-Type': 'application/x-www-form-urlencoded'},
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body: 'name=' + encodeURIComponent(myName) + '&key=' + encodeURIComponent(JSON.stringify(myPubJwk))
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});
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}
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// Re-register key when name changes
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$name.addEventListener('change', function() {
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localStorage.setItem('chat-name', this.value);
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if (myPubJwk) {
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fetch('/keys', {
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method: 'POST',
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headers: {'Content-Type': 'application/x-www-form-urlencoded'},
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body: 'name=' + encodeURIComponent(this.value.trim()) + '&key=' + encodeURIComponent(JSON.stringify(myPubJwk))
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});
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}
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});
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async function deriveAESKey(theirPubJwk) {
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const theirPub = await crypto.subtle.importKey(
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'jwk', theirPubJwk, { name: 'ECDH', namedCurve: 'P-256' }, false, []
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);
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const bits = await crypto.subtle.deriveBits(
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{ name: 'ECDH', public: theirPub }, myKeyPair.privateKey, 256
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);
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return crypto.subtle.importKey('raw', bits, 'AES-GCM', false, ['encrypt', 'decrypt']);
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}
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async function getAESKey(username) {
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if (derivedKeys[username]) return derivedKeys[username];
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const resp = await fetch('/keys/' + encodeURIComponent(username));
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if (!resp.ok) return null;
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const jwk = JSON.parse(await resp.text());
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const key = await deriveAESKey(jwk);
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derivedKeys[username] = key;
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return key;
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}
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async function encryptAndSendDM(recipient, plaintext) {
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const aesKey = await getAESKey(recipient);
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if (!aesKey) {
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addMsg({ts: Date.now()/1000, user: '***', text: 'User "' + recipient + '" has no key registered. They must be online.'});
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return;
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}
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const nonce = crypto.getRandomValues(new Uint8Array(12));
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const enc = await crypto.subtle.encrypt(
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{ name: 'AES-GCM', iv: nonce }, aesKey, new TextEncoder().encode(plaintext)
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);
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const myName = $name.value.trim() || 'anon';
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fetch('/dm', {
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method: 'POST',
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headers: {'Content-Type': 'application/x-www-form-urlencoded'},
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body: 'from=' + encodeURIComponent(myName)
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+ '&to=' + encodeURIComponent(recipient)
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+ '&encrypted=' + encodeURIComponent(btoa(String.fromCharCode(...new Uint8Array(enc))))
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+ '&nonce=' + encodeURIComponent(btoa(String.fromCharCode(...nonce)))
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});
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}
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async function handleEncryptedDM(data) {
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const myName = $name.value.trim();
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// Only decrypt if we are sender or recipient
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if (data.to !== myName && data.user !== myName) return;
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const otherUser = data.user === myName ? data.to : data.user;
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try {
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const aesKey = await getAESKey(otherUser);
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if (!aesKey) throw new Error('no key');
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const ciphertext = Uint8Array.from(atob(data.encrypted), c => c.charCodeAt(0));
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const nonce = Uint8Array.from(atob(data.nonce), c => c.charCodeAt(0));
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const plain = await crypto.subtle.decrypt({ name: 'AES-GCM', iv: nonce }, aesKey, ciphertext);
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const text = new TextDecoder().decode(plain);
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const d = document.createElement('div');
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d.className = 'msg';
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const t = new Date(data.ts * 1000).toLocaleTimeString([], {hour:'2-digit',minute:'2-digit'});
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const arrow = data.user === myName ? '→ ' + esc(data.to) : '← ' + esc(data.user);
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d.innerHTML = '<span class="ts">' + t + '</span> <span style="color:#ff6b9d">🔒 DM ' + arrow + '</span>: ' + renderMd(text);
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$msg.appendChild(d);
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$msg.scrollTop = $msg.scrollHeight;
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} catch(e) {
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const d = document.createElement('div');
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d.className = 'msg';
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const t = new Date(data.ts * 1000).toLocaleTimeString([], {hour:'2-digit',minute:'2-digit'});
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d.innerHTML = '<span class="ts">' + t + '</span> <span style="color:#ff6b9d">🔒 DM from ' + esc(data.user) + '</span>: <em>[cannot decrypt]</em>';
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$msg.appendChild(d);
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$msg.scrollTop = $msg.scrollHeight;
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}
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}
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initCrypto();
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// Check password requirement and start
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if (HAS_PASSWORD && !sessionPass) {
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showPasswordPrompt();
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@@ -783,6 +916,10 @@ async def handle_http(reader, writer, first_line):
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q: asyncio.Queue = asyncio.Queue()
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grp.sse_queues.append(q)
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# Register for DM delivery
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dm_name = qs.get("name", [""])[0]
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if dm_name:
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dm_targets.setdefault(dm_name, []).append(q)
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try:
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while True:
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msg = await q.get()
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@@ -793,6 +930,13 @@ async def handle_http(reader, writer, first_line):
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finally:
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if q in grp.sse_queues:
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grp.sse_queues.remove(q)
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if dm_name and dm_name in dm_targets:
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try:
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dm_targets[dm_name].remove(q)
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except ValueError:
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pass
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if not dm_targets[dm_name]:
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del dm_targets[dm_name]
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writer.close()
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return
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@@ -845,6 +989,79 @@ async def handle_http(reader, writer, first_line):
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writer.close()
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return
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# ── E2E encrypted DM routes ──
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# POST /keys — register public key: body = name=...&key=<JWK JSON>
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if method == "POST" and path == "/keys":
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params = urllib.parse.parse_qs(body.decode())
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name = params.get("name", [""])[0]
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key = params.get("key", [""])[0]
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if name and key:
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user_keys[name] = key
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writer.write(b"HTTP/1.1 204 No Content\r\n\r\n")
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await writer.drain()
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writer.close()
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return
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# GET /keys/<username> — get public key
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if method == "GET" and path.startswith("/keys/"):
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username = urllib.parse.unquote(path[6:])
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key = user_keys.get(username)
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if key:
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resp = key.encode()
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writer.write(b"HTTP/1.1 200 OK\r\n")
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writer.write(b"Content-Type: application/json\r\n")
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writer.write(f"Content-Length: {len(resp)}\r\n".encode())
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writer.write(b"\r\n")
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writer.write(resp)
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else:
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writer.write(b"HTTP/1.1 404 Not Found\r\nContent-Length: 0\r\n\r\n")
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await writer.drain()
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writer.close()
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return
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# GET /keys — list all registered usernames
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if method == "GET" and path == "/keys":
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resp = json.dumps(list(user_keys.keys())).encode()
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writer.write(b"HTTP/1.1 200 OK\r\n")
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writer.write(b"Content-Type: application/json\r\n")
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writer.write(f"Content-Length: {len(resp)}\r\n".encode())
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writer.write(b"\r\n")
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writer.write(resp)
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await writer.drain()
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writer.close()
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return
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# POST /dm — relay an encrypted DM: body = from=...&to=...&encrypted=...&nonce=...
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if method == "POST" and path == "/dm":
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params = urllib.parse.parse_qs(body.decode())
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sender = params.get("from", [""])[0]
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recipient = params.get("to", [""])[0]
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encrypted = params.get("encrypted", [""])[0]
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nonce = params.get("nonce", [""])[0]
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if sender and recipient and encrypted:
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dm_msg = {
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"ts": time.time(), "user": sender, "dm": True,
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"to": recipient, "encrypted": encrypted, "nonce": nonce
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}
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# Deliver to all SSE queues registered for this recipient
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for q in dm_targets.get(recipient, []):
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try:
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q.put_nowait(dm_msg)
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except Exception:
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pass
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# Also deliver to sender so they see their own DM
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if sender != recipient:
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for q in dm_targets.get(sender, []):
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try:
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q.put_nowait(dm_msg)
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except Exception:
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pass
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writer.write(b"HTTP/1.1 204 No Content\r\n\r\n")
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await writer.drain()
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writer.close()
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return
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# GET /files/<id>/<filename> — download uploaded file
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if method == "GET" and path.startswith("/files/"):
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parts = path.split("/")
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