fix(imap-socket-hang): When allocating IMAP connection, check if socket is still alive ZMS-196 (#772)

* when allocating IMAP connection, check if socket is still alive

* imap notifier add optional chaining + fallback

Author: NickOvt

lib/imap-notifier.js

@@ -393,19 +393,29 @@ class ImapNotifier extends EventEmitter {
         }
 
         let rlkey = 'lim:' + data.service;
-        this.counters.limitedcounter(rlkey, data.user, 1, data.limit || 15, (err, res) => {
-            if (err) {
-                return callback(err);
-            }
+        const { closed: socketClosed, connecting, destroyed } = data.session?.socket || {};
 
-            if (!res.success) {
-                return callback(null, false);
-            }
+        if (!socketClosed && !connecting && !destroyed) {
+            // socket alive, not closed
+            this.counters.limitedcounter(rlkey, data.user, 1, data.limit || 15, (err, res) => {
+                if (err) {
+                    return callback(err);
+                }
 
-            this.connectionSessions.set(data.session, { service: data.service, user: data.user });
+                if (!res.success) {
+                    return callback(null, false);
+                }
 
-            return callback(null, true);
-        });
+                this.connectionSessions.set(data.session, { service: data.service, user: data.user });
+
+                return callback(null, true);
+            });
+        } else {
+            // socket dead/closed/undefined
+            const err = new Error('[ALERT] Socket closed unexpectedly before authentication completed.');
+            err.response = 'NO';
+            return callback(err, false);
+        }
     }
 
     releaseConnection(data, callback) {