What Is Deserialization and How Does It Impact Security?
Deserialization is the process of converting a data structure or object state stored in a format like JSON, XML, or a binary format into a usable object in memory. This technique is commonly used in applications for data transmission or saving objects to files.
Deserialization is essential in programming environments where objects need to be transferred, saved, or shared between different parts of an application or different applications. However, it can introduce security vulnerabilities if not handled carefully.
Attackers can exploit deserialization processes to execute malicious code, leading to data breaches or unauthorized access to system resources. Awareness and proper handling of the data being deserialized are crucial for maintaining application security.
This is part of a series of articles about data security
Serialization vs. Deserialization: What Is the Difference?
Serialization and deserialization are complementary processes involved in the conversion of objects into a format that can be easily stored, transmitted, and reconstructed.
Serialization is the process of converting an object’s state into a format that can be stored or transmitted. The formats commonly used for serialization include JSON, XML, and binary. This process is crucial for saving objects to files, sending objects over a network, or storing them in databases. The goal is to preserve the object’s state (including its data and structure) in a way that can be easily reconstructed later.
Deserialization is the reverse process. It involves converting the stored or transmitted data back into an object. This is necessary when data received from a file, database, or network needs to be utilized as an object within the application. Deserialization reconstructs the object’s state from the serialized format, enabling the application to use the object as needed.
Together, they facilitate the secure and efficient transfer of objects between different systems or components of a system, ensuring that the integrity and structure of the objects are maintained throughout the process.
The Deserialization Process
Deserialization is a critical process in many software applications, allowing them to reconstruct objects from a series of bytes or a structured text format like JSON or XML.
This process typically involves several steps to ensure that the serialized data is accurately converted back into an object with its original state and behavior:
- Reading the serialized data: The first step involves reading the data from its source, which could be a file, a database, or a network stream. This data represents the object’s state but in a non-executable format such as JSON, XML, or a binary format.
- Parsing the data: Next, the serialized data is parsed according to its format. For example, if the data is in JSON format, a JSON parser will be used to interpret the data structure. This step translates the structured text or binary data into a format that the deserialization mechanism can understand.
- Object creation: The application creates a new instance of the object that was serialized. This step doesn’t yet populate the object with data; it only creates a “shell” that will soon contain the original object’s state.
- Restoring state: This step involves restoring the serialized object’s state. It involves mapping the parsed data to the corresponding attributes or fields of the new object instance. For complex objects, this may also involve recursively deserializing nested objects.
- Object finalization: Once the object’s state has been fully restored, any finalization steps required by the object or the programming environment are performed. This could involve running initialization code, resolving dependencies, or performing sanity checks to ensure the object is in a valid state.
What Is the Impact of Insecure Deserialization?
Insecure deserialization occurs when untrusted data is used to abuse the logic of an application, leading to various kinds of attacks such as remote code execution, replay attacks, injection attacks, and privilege escalation. The impact of insecure deserialization can be severe, affecting the security and functionality of an application:
- Remote Code Execution (RCE): Attackers can craft malicious data that, when deserialized, executes arbitrary code on the server. This gives attackers control over the server, allowing them to steal sensitive information, manipulate server functions, or deploy malware.
- Replay Attacks: Attackers can capture serialized objects and replay them to perform unauthorized operations. For example, an attacker might replay serialized authentication tokens to gain unauthorized access to user accounts.
- Injection Attacks: Similar to SQL injection, deserialization vulnerabilities can be exploited to inject malicious code or data into an application. This can result in data breaches, data corruption, or unauthorized data manipulation.
- Privilege Escalation: Attackers can exploit deserialization vulnerabilities to escalate their privileges within the application. By deserializing crafted objects, they can bypass normal authentication and authorization processes, gaining access to restricted areas of the application.
- Denial of Service (DoS): Deserializing large or complex objects crafted by an attacker can consume excessive system resources, slowing down the application or crashing it entirely.
Deserialization Attack Vectors
Attackers can use various methods to exploit deserialization vulnerabilities.
Malicious Object Creation
In a malicious object creation attack, an attacker crafts serialized data that, when deserialized, results in the creation of an object that can execute arbitrary code or disrupt application functionality. This can lead to unauthorized actions being performed under the guise of the application’s trusted execution environment.
Data Tampering
Data tampering involves altering serialized data before it’s deserialized by the target application. This can lead to unauthorized changes in application state, data leaks, or execution of unintended actions. Ensuring data integrity between serialization and deserialization points is crucial for preventing these attacks.
Injection Attacks
Injection attacks involve embedding malicious instructions or code within serialized data. When deserialized, the embedded content is executed, potentially compromising the application. These attacks exploit vulnerabilities in the deserialization process to execute code, manipulate application logic, or access unauthorized data.
5 Ways to Protect Applications Against Deserialization Vulnerabilities
Here are some important measures for preventing deserialization attacks.
1. Avoid Deserialization of Data from Untrusted Sources
This requires strict control over the data sources, ensuring that any serialized data the application processes come from secure, authenticated sources. Adopting a principle of least privilege for data access and operation execution further secures applications against unauthorized deserialization attacks.
By limiting the data and operations that can be accessed or executed through deserialized objects, applications can minimize the potential impact of a successful attack.
2. Implement Input Validation
Input validation involves scrutinizing serialized data before it is deserialized to ensure it conforms to expected formats, types, and values. It can prevent various deserialization attacks by rejecting data that contains unexpected or malicious content.
Validators should be configured to explicitly check for and allow only legitimate data structures, and any deviation from these should be treated as a potential attack. This prevents attackers from exploiting the deserialization process to execute arbitrary code or disrupt application functionality.
3. Use Safe Serialization Libraries
It’s important to use serialization libraries that are designed with security in mind. These libraries include built-in mechanisms to prevent common deserialization attacks, such as restricting or monitoring the types of objects that can be deserialized.
It’s also important to configure these libraries properly. Many serialization libraries offer settings that can enhance security, such as enabling strict type checks or disabling the deserialization of certain dangerous classes.
4. Use Runtime Application Self-Protection (RASP)
Runtime Application Self-Protection (RASP) technology integrates with applications to provide continuous security monitoring and protection at runtime. RASP solutions can detect and block deserialization attacks in real time by analyzing the application’s behavior and the data it processes.
By leveraging RASP, applications can prevent unauthorized or malicious activities resulting from deserialization vulnerabilities.
5. Use a Web Application Firewall (WAF)
A Web Application Firewall (WAF) provides an external layer of security that monitors and controls incoming and outgoing web traffic based on predetermined security rules. WAFs are able to recognize and block attempts to exploit deserialization vulnerabilities. By scrutinizing data packets for known attack patterns or anomalies, they prevent malicious data from reaching the application.
It’s important to implement a WAF as part of a comprehensive security strategy, especially in applications exposed to the Internet. Regular updates and rule tuning are necessary to ensure that the WAF remains effective given changes to the application and new deserialization attack techniques.
Related content: Read our guide to data protection
Deserialization Protection with Imperva
Imperva provides a Web Application Firewall, which prevents attacks with world-class analysis of web traffic to your applications, and Runtime Application Self-Protection (RASP) which provides real-time attack detection and prevention from your application runtime environment, both of which can help mitigate deserialization vulnerabilities.
In addition, Imperva provides the following application security capabilities:
API Security – Automated API protection ensures your API endpoints are protected as they are published, shielding your applications from exploitation.
Advanced Bot Protection – Prevent business logic attacks from all access points – websites, mobile apps and APIs. Gain seamless visibility and control over bot traffic to stop online fraud through account takeover or competitive price scraping.
DDoS Protection – Block attack traffic at the edge to ensure business continuity with guaranteed uptime and no performance impact. Secure your on premises or cloud-based assets – whether you’re hosted in AWS, Microsoft Azure, or Google Public Cloud.
Attack Analytics – Ensures complete visibility with machine learning and domain expertise across the application security stack to reveal patterns in the noise and detect application attacks, enabling you to isolate and prevent attack campaigns.
Client-Side Protection – Gain visibility and control over third-party JavaScript code to reduce the risk of supply chain fraud, prevent data breaches, and client-side attacks.
