From 80f7489df006e43980cacb3550245213706c802a Mon Sep 17 00:00:00 2001
From: Sergey Bugaev <bugaevc@serenityos.org>
Date: Sun, 14 Feb 2021 15:17:27 +0300
Subject: [PATCH] LookupServer: Fix serializing name data in DNS answers

When serializing a RR of type PTR, we should use the DNS name serialization
format, not a raw string.
---
 Userland/Services/LookupServer/DNSName.cpp   |  7 +++++++
 Userland/Services/LookupServer/DNSName.h     |  1 +
 Userland/Services/LookupServer/DNSPacket.cpp | 10 ++++++++--
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/Userland/Services/LookupServer/DNSName.cpp b/Userland/Services/LookupServer/DNSName.cpp
index d3e8bf732a..edf8cb9fa7 100644
--- a/Userland/Services/LookupServer/DNSName.cpp
+++ b/Userland/Services/LookupServer/DNSName.cpp
@@ -70,6 +70,13 @@ DNSName DNSName::parse(const u8* data, size_t& offset, size_t max_offset, size_t
     }
 }
 
+size_t DNSName::serialized_size() const
+{
+    if (m_name.is_empty())
+        return 1;
+    return m_name.length() + 2;
+}
+
 OutputStream& operator<<(OutputStream& stream, const DNSName& name)
 {
     auto parts = name.as_string().split_view('.');
diff --git a/Userland/Services/LookupServer/DNSName.h b/Userland/Services/LookupServer/DNSName.h
index dc0fe7b5c2..08ad651648 100644
--- a/Userland/Services/LookupServer/DNSName.h
+++ b/Userland/Services/LookupServer/DNSName.h
@@ -38,6 +38,7 @@ public:
 
     static DNSName parse(const u8* data, size_t& offset, size_t max_offset, size_t recursion_level = 0);
 
+    size_t serialized_size() const;
     const String& as_string() const { return m_name; }
 
 private:
diff --git a/Userland/Services/LookupServer/DNSPacket.cpp b/Userland/Services/LookupServer/DNSPacket.cpp
index b2658aa944..4723553f45 100644
--- a/Userland/Services/LookupServer/DNSPacket.cpp
+++ b/Userland/Services/LookupServer/DNSPacket.cpp
@@ -92,8 +92,14 @@ ByteBuffer DNSPacket::to_byte_buffer() const
         stream << htons(answer.type());
         stream << htons(answer.class_code());
         stream << htonl(answer.ttl());
-        stream << htons(answer.record_data().length());
-        stream << answer.record_data().bytes();
+        if (answer.type() == T_PTR) {
+            DNSName name { answer.record_data() };
+            stream << htons(name.serialized_size());
+            stream << name;
+        } else {
+            stream << htons(answer.record_data().length());
+            stream << answer.record_data().bytes();
+        }
     }
 
     return stream.copy_into_contiguous_buffer();