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Attack Tree Analysis for jamesnk/newtonsoft.json

Objective: Compromise Application via Exploiting Newtonsoft.Json Vulnerabilities

Attack Tree Visualization

Compromise Application
├─── [HIGH RISK PATH] (OR)─ Exploit Deserialization Vulnerabilities
│   ├─── [HIGH RISK PATH] (OR)─ Abuse TypeNameHandling Settings
│   │   ├───(AND)─ **Critical Node: Identify Deserialization Endpoint**
│   │   ├───(AND)─ **Critical Node: Determine TypeNameHandling Configuration**
│   │   ├───(AND)─ **Critical Node: Craft Malicious JSON Payload with TypeNameHandling**
│   │   │   ├─── [HIGH RISK PATH] (OR)─ Remote Code Execution (RCE) via Gadget Chains
│   │   └─── [HIGH RISK PATH] (OR)─ Bypass TypeNameHandling Restrictions (if any)
│   │       ├───(AND)─ **Critical Node: Identify Implemented TypeNameHandling Restrictions**
│   │       ├───(AND)─ **Critical Node: Find Bypass for Restrictions**
│   │       │   ├─── [HIGH RISK PATH] (OR)─ Exploiting Weak Whitelists
│   │       │   ├─── [HIGH RISK PATH] (OR)─ Type Confusion Attacks
│   │       │   ├─── [HIGH RISK PATH] (OR)─ Exploiting Logic Errors in Custom Deserialization

Attack Tree Path: Exploit Deserialization Vulnerabilities

  • Attack Vector: This is the overarching high-risk category. It encompasses exploiting weaknesses in how Newtonsoft.Json deserializes data, potentially leading to code execution, denial of service, or other security breaches.
  • Mitigation Focus: Prioritize secure deserialization practices, input validation, and minimizing the attack surface related to JSON processing.

Attack Tree Path: Abuse TypeNameHandling Settings

  • Attack Vector: This path focuses on the most critical vulnerability: insecure use of TypeNameHandling. When TypeNameHandling is enabled with settings like Auto, Objects, All, or Arrays, it allows an attacker to control the types being deserialized. This can be leveraged to instantiate arbitrary .NET types, leading to Remote Code Execution (RCE).
  • Mitigation Focus: Completely disable TypeNameHandling if possible. If absolutely necessary, use TypeNameHandling.None by default and implement strict allow lists for specific scenarios. Thoroughly review code for insecure TypeNameHandling configurations.

Attack Tree Path: Identify Deserialization Endpoint

  • Attack Vector: Attackers must first identify endpoints in the application that accept JSON data and use Newtonsoft.Json for deserialization. This is a prerequisite for exploiting any deserialization vulnerability.
  • Attack Steps:
    • Analyze application routes and APIs.
    • Review code for usage of JsonConvert.DeserializeObject, JsonConvert.PopulateObject, or JsonSerializerSettings.
    • Examine documentation or API specifications.
  • Mitigation Focus: Minimize the number of exposed JSON deserialization endpoints. Implement strict authentication and authorization on these endpoints.

Attack Tree Path: Determine TypeNameHandling Configuration

  • Attack Vector: Once a deserialization endpoint is found, attackers need to determine if and how TypeNameHandling is configured. This information is crucial for crafting a successful exploit.
  • Attack Steps:
    • Analyze application code and configuration files (e.g., web.config, appsettings.json).
    • Debug the running application to inspect JsonSerializerSettings.
    • Attempt to trigger errors that might reveal configuration details.
  • Mitigation Focus: Securely manage configuration and prevent unauthorized access to configuration files. Avoid exposing configuration details in error messages.

Attack Tree Path: Craft Malicious JSON Payload with TypeNameHandling

  • Attack Vector: Based on the TypeNameHandling configuration, attackers craft a malicious JSON payload that exploits deserialization vulnerabilities. This typically involves using the $type property to specify a malicious .NET type.
  • Attack Steps:
    • Utilize known .NET gadget chains (e.g., using tools like ysoserial.net).
    • Embed gadget chains within the $type property in the JSON payload.
    • Target vulnerable types based on the TypeNameHandling setting.
  • Mitigation Focus: Disable insecure TypeNameHandling. Implement input validation and sanitization even if TypeNameHandling is used (though disabling is the strongest mitigation).

Attack Tree Path: Remote Code Execution (RCE) via Gadget Chains

  • Attack Vector: This is the most severe outcome of TypeNameHandling abuse. Attackers use known .NET gadget chains within the malicious JSON payload to execute arbitrary code on the server.
  • Attack Steps:
    • Leverage pre-built gadget chains or develop custom chains.
    • Embed the chosen gadget chain within the $type property.
    • Send the malicious JSON to the vulnerable endpoint.
  • Mitigation Focus: Prevent TypeNameHandling abuse. Regularly update Newtonsoft.Json and .NET framework to patch known vulnerabilities. Implement robust security monitoring to detect suspicious activity.

Attack Tree Path: Bypass TypeNameHandling Restrictions (if any)

  • Attack Vector: If the application attempts to mitigate TypeNameHandling risks by implementing whitelists, blacklists, or custom deserialization logic, attackers will try to bypass these restrictions.
  • Mitigation Focus: Avoid relying solely on whitelists or blacklists for TypeNameHandling mitigation as they are often bypassable. Focus on disabling TypeNameHandling entirely. If restrictions are used, ensure they are rigorously tested and regularly reviewed for bypasses.

Attack Tree Path: Identify Implemented TypeNameHandling Restrictions

  • Attack Vector: To bypass restrictions, attackers must first understand what restrictions are in place. This involves analyzing code for custom deserialization logic, binders, or type filters.
  • Attack Steps:
    • Code review to identify custom deserialization logic.
    • Reverse engineering to understand implemented filters or binders.
    • Testing with various payloads to probe for restrictions.
  • Mitigation Focus: Minimize the complexity of custom deserialization logic. Securely manage and protect any custom security measures.

Attack Tree Path: Find Bypass for Restrictions

  • Attack Vector: Once restrictions are understood, attackers research and attempt to find bypasses. This often involves exploiting weaknesses in the restriction logic itself or using type confusion techniques.
  • Attack Steps:
    • Research known bypasses for common restriction patterns.
    • Experiment with type confusion attacks.
    • Analyze custom logic for vulnerabilities or loopholes.
  • Mitigation Focus: Assume that any restrictions can be bypassed. Focus on defense-in-depth and layered security.

Attack Tree Path: Exploiting Weak Whitelists

  • Attack Vector: Whitelists intended to limit allowed types for deserialization can be weak if they are too broad or include types that can still be exploited indirectly.
  • Attack Steps:
    • Analyze the whitelist for overly permissive entries.
    • Identify types within the whitelist that can be used as part of gadget chains or for other exploits.
  • Mitigation Focus: If whitelists are used, make them as narrow and specific as possible. Regularly review and update whitelists.

Attack Tree Path: Type Confusion Attacks

  • Attack Vector: Type confusion attacks aim to confuse the deserializer by providing unexpected types or structures that bypass intended restrictions.
  • Attack Steps:
    • Experiment with different JSON structures and type hints.
    • Attempt to exploit differences in how the deserializer handles various types.
    • Look for edge cases or unexpected behaviors in the deserialization process.
  • Mitigation Focus: Implement robust input validation and schema validation to enforce expected data types and structures.

Attack Tree Path: Exploiting Logic Errors in Custom Deserialization

  • Attack Vector: If custom deserialization logic is implemented, it may contain logic errors or vulnerabilities that can be exploited to bypass security measures or achieve unintended behavior.
  • Attack Steps:
    • Analyze custom deserialization code for logic flaws.
    • Identify potential injection points or vulnerabilities in custom logic.
    • Craft payloads that exploit these logic errors.
  • Mitigation Focus: Thoroughly review and test custom deserialization logic. Follow secure coding practices and minimize the complexity of custom code.