security: v2.0 — AES-GCM crypto, SSRF guards, rate limits, hardening

Breaking wire-format change: dual-read (V1+V2) / single-write (V2) so
existing user secrets, stored messages, and inter-tenant key keep
working. Old clients and relays lose cross-version chat until both
sides are upgraded.

Relay
- Switch clientEncrypt/masterEncrypt to AES-256-GCM with HKDF-derived
  per-ciphertext salts; keep CBC-V1 fallback on decrypt only.
- On-bootstrap migration re-envelopes tenant secret_encrypted and the
  inter-tenant key to GCM-V2 (idempotent).
- CORS: stop reflecting arbitrary Origin; allow own origin + optional
  RELAY_CORS_ORIGINS env allowlist; drop Access-Control-Allow-Credentials.
- Generic error messages replace "no such user: <name>" enumeration.
- Exception messages no longer echoed back; logged server-side.
- Collab-lock max hold capped at 10min so a member can't grief-refresh
  forever.
- Attachment filenames validated against hex.<ext> pattern.
- Passwords min length 10; /api/account/password rate-limited.

App / Electron client
- Shared hyprcrdRelayEncrypt/Decrypt helpers (GCM-V2 write, V1 read).
- Chat + collab-buckets plugins delegate to the shared helpers.
- Poll + push + attachments migrated to the dual-format path.
- /api/relay/settings GET returns has_key boolean; secret never echoed.
- Setup endpoint now CSRF-checked.
- SSRF: CURLOPT_PROTOCOLS restricted to HTTP(S) everywhere; bookmarks
  favicon fetch also blocks private/loopback/link-local.
- Login / password-change rate limiter moved to DB-backed IP keying.
- Passwords min length 10 throughout.
- Zip import enforces per-file (25MB) and total (500MB) caps, extension
  allowlist, no-overwrite.
- Verbose relay-push debug gated behind APP_DEBUG env.

Version bumped to 2.0.0 (protocol-breaking).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

public/plugins/collab-buckets/backend.php

@@ -110,32 +110,24 @@
     ");
 })();
 
-/** Encrypt a JSON payload with the local relay_key using the same envelope
- * format the rest of hyprcrd uses (HYPRCRD-RELAY-V1). */
+/** Encrypt a JSON payload with the local relay_key using the shared
+ * dual-format envelope (GCM-V2 writes, V1 read-only fallback lives in
+ * hyprcrdRelayDecrypt). */
 function collabEncryptPayload(array $fields): ?string {
     $key = collabRelaySettings()['key'] ?? '';
     if ($key === '') return null;
-    $encKey = substr(hash('sha256', $key), 0, 32);
     $plain = json_encode($fields);
-    $iv = random_bytes(16);
-    $cipher = openssl_encrypt($plain, 'aes-256-cbc', $encKey, OPENSSL_RAW_DATA, $iv);
-    if ($cipher === false) return null;
-    return "HYPRCRD-RELAY-V1\n" . base64_encode($iv . $cipher);
+    if ($plain === false) return null;
+    return hyprcrdRelayEncrypt($plain, $key);
 }
 
 /** Decrypt the inverse. Returns an associative array, or null on failure. */
 function collabDecryptPayload(string $envelope): ?array {
-    if (!str_starts_with($envelope, 'HYPRCRD-RELAY-V1')) return null;
-    $b64 = trim(substr($envelope, strlen('HYPRCRD-RELAY-V1') + 1));
-    $raw = base64_decode($b64);
-    if (!$raw || strlen($raw) < 17) return null;
+    if (!str_starts_with($envelope, HYPRCRD_RELAY_GCM_MAGIC) && !str_starts_with($envelope, HYPRCRD_RELAY_CBC_MAGIC)) return null;
     $key = collabRelaySettings()['key'] ?? '';
     if ($key === '') return null;
-    $encKey = substr(hash('sha256', $key), 0, 32);
-    $iv = substr($raw, 0, 16);
-    $cipher = substr($raw, 16);
-    $plain = openssl_decrypt($cipher, 'aes-256-cbc', $encKey, OPENSSL_RAW_DATA, $iv);
-    if ($plain === false) return null;
+    $plain = hyprcrdRelayDecrypt($envelope, $key);
+    if ($plain === '') return null;
     $data = json_decode($plain, true);
     return is_array($data) ? $data : null;
 }