RTTI and Application Security
Are there any security implications of using RTTI in applications that process untrusted data?
Using RTTI (Run-Time Type Information) in applications that process untrusted data can indeed have security implications.
While RTTI itself doesn't directly introduce vulnerabilities, its misuse or the information it exposes could potentially be exploited by malicious actors. Let's explore some of these security considerations:
1. Information Disclosure
RTTI can potentially expose internal details about your application's structure:
#include <iostream>
#include <typeinfo>
class SecretClass {
// Contains sensitive information
};
void ProcessUserInput(const std::string& input) {
// Unsafe: Exposes class name to user
std::cout << "Processing with: "
<< typeid(SecretClass).name() << "\n";
}An attacker could use this information to gain insights into your application's internal structure, potentially aiding in further attacks.
2. Type Confusion Attacks
Incorrect use of RTTI, especially with user-controlled data, could lead to type confusion:
#include <string>
#include <typeinfo>
class Base {
public:
virtual ~Base() = default;
};
class Derived : public Base {};
void ProcessObject(Base* obj, const std::string& type) {
// Unsafe comparison
if (typeid(*obj).name() == type) {
Derived* derived = dynamic_cast<Derived*>(obj);
// Use derived...
}
}An attacker could potentially manipulate the type string to cause unexpected behavior.
3. Performance Degradation
While not directly a security issue, excessive use of RTTI could lead to performance problems, potentially making your application more vulnerable to denial-of-service attacks:
#include <vector>
#include <memory>
#include <typeinfo>
class Base {};
class Derived : public Base {};
void ProcessLargeDataSet(
const std::vector<std::unique_ptr<Base>>& data) {
for (const auto& item : data) {
// Costly if called frequently
if (typeid(*item) == typeid(Derived)) {
// Process item
}
}
}4. RTTI Bypass
In some cases, attackers might try to bypass RTTI checks:
#include <typeinfo>
class Base {};
class Secure : public Base {
public:
void AccessSecureData() {
//...
}
};
void ProcessUserData(Base* data) {
if (typeid(*data) == typeid(Secure)) {
static_cast<Secure*>(data)->AccessSecureData();
}
}An attacker might try to craft an object that passes the RTTI check but doesn't behave like a Secure object.
Best Practices
To mitigate these risks, avoid exposing type information to users:
void SafeProcessUserInput(const std::string& input) {
// Process input without revealing type information
}Use strong typing and avoid type casts with user-controlled data:
class Base {
public:
virtual ~Base() = default;
};
class A : public Base {};
class B : public Base {};
enum class AllowedTypes { TypeA, TypeB };
void SafeProcessObject(Base* obj, AllowedTypes type) {
switch (type) {
case AllowedTypes::TypeA:
if (auto* derivedA = dynamic_cast<A*>(obj)) {
// Process DerivedA
}
break;
case AllowedTypes::TypeB:
if (auto* derivedB = dynamic_cast<B*>(obj)) {
// Process DerivedB
}
break;
}
}Consider alternatives to RTTI where possible:
class Base {
public:
virtual ~Base() = default;
virtual void Process() = 0;
};
class Derived : public Base {
public:
void Process() override {
// Derived-specific processing
}
};
void SafeProcessObject(Base* obj) {
// Polymorphic call, no RTTI needed
obj->Process();
}If you must use RTTI with untrusted data, sanitize and validate all inputs:
bool IsValidTypeName(const std::string& name) {
// Check against a whitelist of allowed type names
return true;
}
void SafeProcessObject(
Base* obj, const std::string& type
) {
if (IsValidTypeName(type)
&& typeid(*obj).name() == type) {
// Process object
}
}Be cautious with serialization and deserialization involving RTTI:
class SafeSerializer {
public:
template <typename T>
static std::string Serialize(const T& obj) {
// Implement safe serialization
}
template <typename T>
static std::unique_ptr<T> Deserialize(
const std::string& data
) {
// Implement safe deserialization with
// strict type checking
}
};In conclusion, while RTTI itself isn't inherently insecure, its use in applications processing untrusted data requires careful consideration.
Always validate inputs, avoid exposing internal type information, and consider alternatives to RTTI where possible to maintain the security of your application.
Run Time Type Information (RTTI) and typeid()
Learn to identify and react to object types at runtime using RTTI, dynamic casting and the typeid() operator