From e7b05beb7d90b4ea53ef13da86ff8b8ccde1193b Mon Sep 17 00:00:00 2001
From: sfan5 <sfan5@live.de>
Date: Thu, 19 Aug 2021 20:14:22 +0200
Subject: [PATCH] Validate staticdata and object property length limits
 (#11511)

Some games provide users with enough freedom to create items
with metadata longer than 64KB, preventing this from causing
issues is on them but we'll still do the minimum not to abort
the server if this happens.
---
 src/object_properties.cpp       | 34 ++++++++++++++++++++++++++++++++-
 src/object_properties.h         |  2 ++
 src/script/lua_api/l_object.cpp |  2 ++
 src/staticobject.cpp            | 24 +++++++++++++++++++++++
 4 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/src/object_properties.cpp b/src/object_properties.cpp
index 2eebc27d6..db06f8930 100644
--- a/src/object_properties.cpp
+++ b/src/object_properties.cpp
@@ -83,6 +83,39 @@ std::string ObjectProperties::dump()
 	return os.str();
 }
 
+bool ObjectProperties::validate()
+{
+	const char *func = "ObjectProperties::validate(): ";
+	bool ret = true;
+
+	// cf. where serializeString16 is used below
+	for (u32 i = 0; i < textures.size(); i++) {
+		if (textures[i].size() > U16_MAX) {
+			warningstream << func << "texture " << (i+1) << " has excessive length, "
+				"clearing it." << std::endl;
+			textures[i].clear();
+			ret = false;
+		}
+	}
+	if (nametag.length() > U16_MAX) {
+		warningstream << func << "nametag has excessive length, clearing it." << std::endl;
+		nametag.clear();
+		ret = false;
+	}
+	if (infotext.length() > U16_MAX) {
+		warningstream << func << "infotext has excessive length, clearing it." << std::endl;
+		infotext.clear();
+		ret = false;
+	}
+	if (wield_item.length() > U16_MAX) {
+		warningstream << func << "wield_item has excessive length, clearing it." << std::endl;
+		wield_item.clear();
+		ret = false;
+	}
+
+	return ret;
+}
+
 void ObjectProperties::serialize(std::ostream &os) const
 {
 	writeU8(os, 4); // PROTOCOL_VERSION >= 37
@@ -105,7 +138,6 @@ void ObjectProperties::serialize(std::ostream &os) const
 	writeU8(os, is_visible);
 	writeU8(os, makes_footstep_sound);
 	writeF32(os, automatic_rotate);
-	// Added in protocol version 14
 	os << serializeString16(mesh);
 	writeU16(os, colors.size());
 	for (video::SColor color : colors) {
diff --git a/src/object_properties.h b/src/object_properties.h
index db28eebfd..79866a22c 100644
--- a/src/object_properties.h
+++ b/src/object_properties.h
@@ -68,6 +68,8 @@ struct ObjectProperties
 
 	ObjectProperties();
 	std::string dump();
+	// check limits of some important properties (strings) that'd cause exceptions later on
+	bool validate();
 	void serialize(std::ostream &os) const;
 	void deSerialize(std::istream &is);
 };
diff --git a/src/script/lua_api/l_object.cpp b/src/script/lua_api/l_object.cpp
index 8e308cd9e..c404cb63c 100644
--- a/src/script/lua_api/l_object.cpp
+++ b/src/script/lua_api/l_object.cpp
@@ -685,6 +685,7 @@ int ObjectRef::l_set_properties(lua_State *L)
 		return 0;
 
 	read_object_properties(L, 2, sao, prop, getServer(L)->idef());
+	prop->validate();
 	sao->notifyObjectPropertiesModified();
 	return 0;
 }
@@ -752,6 +753,7 @@ int ObjectRef::l_set_nametag_attributes(lua_State *L)
 	std::string nametag = getstringfield_default(L, 2, "text", "");
 	prop->nametag = nametag;
 
+	prop->validate();
 	sao->notifyObjectPropertiesModified();
 	lua_pushboolean(L, true);
 	return 1;
diff --git a/src/staticobject.cpp b/src/staticobject.cpp
index 86e455b9f..1160ec68f 100644
--- a/src/staticobject.cpp
+++ b/src/staticobject.cpp
@@ -37,6 +37,7 @@ void StaticObject::serialize(std::ostream &os)
 	// data
 	os<<serializeString16(data);
 }
+
 void StaticObject::deSerialize(std::istream &is, u8 version)
 {
 	// type
@@ -49,6 +50,29 @@ void StaticObject::deSerialize(std::istream &is, u8 version)
 
 void StaticObjectList::serialize(std::ostream &os)
 {
+	// Check for problems first
+	auto problematic = [] (StaticObject &obj) -> bool {
+		if (obj.data.size() > U16_MAX) {
+			errorstream << "StaticObjectList::serialize(): "
+				"object has excessive static data (" << obj.data.size() <<
+				"), deleting it." << std::endl;
+			return true;
+		}
+		return false;
+	};
+	for (auto it = m_stored.begin(); it != m_stored.end(); ) {
+		if (problematic(*it))
+			it = m_stored.erase(it);
+		else
+			it++;
+	}
+	for (auto it = m_active.begin(); it != m_active.end(); ) {
+		if (problematic(it->second))
+			it = m_active.erase(it);
+		else
+			it++;
+	}
+
 	// version
 	u8 version = 0;
 	writeU8(os, version);