From 0038d1ea109265d5e5aada14d197a2cea9adf4e8 Mon Sep 17 00:00:00 2001
From: Wiebe Cazemier <wiebe@halfgaar.net>
Date: Mon, 21 Dec 2020 15:34:11 +0100
Subject: [PATCH] Check publish paths

---
 mqttpacket.cpp |  9 ++++++++-
 utils.cpp      | 14 ++++++++++++++
 utils.h        |  2 ++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/mqttpacket.cpp b/mqttpacket.cpp
index 277fd57..4d574ef 100644
--- a/mqttpacket.cpp
+++ b/mqttpacket.cpp
@@ -4,6 +4,8 @@
 #include <list>
 #include <cassert>
 
+#include "utils.h"
+
 RemainingLength::RemainingLength()
 {
     memset(bytes, 0, 4);
@@ -254,9 +256,14 @@ void MqttPacket::handlePublish(std::shared_ptr<SubscriptionStore> &subscriptionS
     if (qos == 3)
         throw ProtocolError("QoS 3 is a protocol violation.");
 
-    // TODO: validate UTF8.
     std::string topic(readBytes(variable_header_length), variable_header_length);
 
+    if (!isValidUtf8(topic) || !isValidPublishPath(topic))
+    {
+        std::cerr << "Client " << sender->repr() << " sent topic with wildcards or invalid UTF8. Ignoring.";
+        return;
+    }
+
     if (qos)
     {
         throw ProtocolError("Qos not implemented.");
diff --git a/utils.cpp b/utils.cpp
index 46076bb..dec6f8a 100644
--- a/utils.cpp
+++ b/utils.cpp
@@ -111,3 +111,17 @@ bool strContains(const std::string &s, const std::string &needle)
 {
     return s.find(needle) != std::string::npos;
 }
+
+bool isValidPublishPath(const std::string &s)
+{
+    if (s.empty())
+        return false;
+
+    for (const char c : s)
+    {
+        if (c == '#' || c == '+')
+            return false;
+    }
+
+    return true;
+}
diff --git a/utils.h b/utils.h
index 66b14e0..4a5a8c5 100644
--- a/utils.h
+++ b/utils.h
@@ -27,4 +27,6 @@ bool isValidUtf8(const std::string &s);
 
 bool strContains(const std::string &s, const std::string &needle);
 
+bool isValidPublishPath(const std::string &s);
+
 #endif // UTILS_H
--
libgit2 0.21.4