From d3a98a523f9526a25ab6803899ad1f177e902d32 Mon Sep 17 00:00:00 2001
From: Pavel Djundik <xPaw@users.noreply.github.com>
Date: Thu, 11 Jul 2019 23:10:03 +0300
Subject: [PATCH] Verify reverse DNS when looking up hostnames for webirc

Fixes #3293
---
 src/server.js | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/server.js b/src/server.js
index c0cfbbdf..9b62a7ff 100644
--- a/src/server.js
+++ b/src/server.js
@@ -744,11 +744,23 @@ function performAuthentication(data) {
 }
 
 function reverseDnsLookup(ip, callback) {
-	dns.reverse(ip, (err, hostnames) => {
-		if (!err && hostnames.length) {
-			return callback(hostnames[0]);
+	dns.reverse(ip, (reverseErr, hostnames) => {
+		if (reverseErr || hostnames.length < 1) {
+			return callback(ip);
 		}
 
-		callback(ip);
+		dns.resolve(hostnames[0], net.isIP(ip) === 6 ? "AAAA" : "A", (resolveErr, resolvedIps) => {
+			if (resolveErr || resolvedIps.length < 1) {
+				return callback(ip);
+			}
+
+			for (const resolvedIp of resolvedIps) {
+				if (ip === resolvedIp) {
+					return callback(hostnames[0]);
+				}
+			}
+
+			return callback(ip);
+		});
 	});
 }