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Attack Tree Analysis for serde-rs/serde

Objective: Achieve RCE or DoS via Serde Exploitation

Attack Tree Visualization

Goal: Achieve RCE or DoS via Serde Exploitation
├── 1. Achieve Remote Code Execution (RCE)
│   ├── 1.1 Exploit Deserialization of Untrusted Data [HIGH RISK]
│   │   ├── 1.1.1  Find/Use Existing Deserialization Gadget Chain
│   │   │   ├── 1.1.1.1  Identify vulnerable dependency with known gadget chain usable with Serde. [CRITICAL NODE]
│   │   │   │   └── 1.1.1.1.1 Craft malicious payload using the identified gadget chain and format.
│   │   │   ├── 1.1.1.2  Discover new gadget chain in application's custom Deserialize implementations.
│   │   │   │   └── 1.1.1.2.1  Analyze custom Deserialize implementations for code paths leading to unsafe operations. [CRITICAL NODE]
│   │   │   │   └── 1.1.1.2.2  Craft malicious payload triggering the discovered gadget chain.
│   │   ├── 1.1.2  Exploit Format-Specific Vulnerabilities [HIGH RISK]
│   │   │   ├── 1.1.2.1  Bincode:  Exploit potential integer overflows or underflows (if size limits are not enforced). [HIGH RISK] [CRITICAL NODE]
│   │   │   │   └── 1.1.2.1.1 Craft a Bincode payload with manipulated size fields.
│   │   │   ├── 1.1.2.3 YAML (via `serde_yaml`): Exploit known YAML vulnerabilities. [HIGH RISK] [CRITICAL NODE]
│   │   │   │   └── 1.1.2.3.1 Craft a YAML payload with recursive references or custom constructors.
├── 2. Achieve Denial of Service (DoS)
│   ├── 2.1  Resource Exhaustion [HIGH RISK]
│   │   ├── 2.1.1  "Billion Laughs" Attack (XML, YAML) [HIGH RISK] [CRITICAL NODE]
│   │   │   └── 2.1.1.1  Craft a payload with deeply nested, recursive data structures.
│   │   ├── 2.1.2  Large Allocation Attack [HIGH RISK] [CRITICAL NODE]
│   │   │   └── 2.1.2.1  Craft a payload that tricks Serde into allocating a very large amount of memory.
│   │   │   └── 2.1.2.2 Bincode: Exploit integer overflows to cause large allocations.
│   ├── 2.2  Panic-Induced DoS
│   │   └── 2.2.2 Exploit unwrap() or expect() calls in custom Deserialize implementations. [CRITICAL NODE]
    └── 2.3 Deserialization loop
        └── 2.3.1 Send cyclic data structures. [CRITICAL NODE]

Attack Tree Path: 1. Achieve Remote Code Execution (RCE)

  • 1.1 Exploit Deserialization of Untrusted Data [HIGH RISK]

    • Description: This is the core vulnerability. Deserializing data from untrusted sources without proper validation opens the door to various attacks, including RCE.

    • Mitigation:

      • Never deserialize untrusted data without strict validation.
      • Use a schema validation library.
      • Enforce strict size limits.
      • Prefer safer serialization formats (like JSON with size limits) over inherently riskier ones (like Bincode) for untrusted input.
      • Consider sandboxing the deserialization process.

    • 1.1.1 Find/Use Existing Deserialization Gadget Chain

      • 1.1.1.1 Identify vulnerable dependency with known gadget chain usable with Serde. [CRITICAL NODE]

        • Description: Attackers search for known vulnerabilities in the application's dependencies (including Serde itself and format crates) that can be used to construct a "gadget chain" – a sequence of operations that ultimately leads to RCE.
        • Mitigation:
          • Keep all dependencies updated.
          • Use a dependency vulnerability scanner (e.g., cargo audit).
          • Minimize the number of dependencies.

      • 1.1.1.1.1 Craft malicious payload using the identified gadget chain and format.

        • Description: Once a gadget chain is found, the attacker crafts a malicious payload in the appropriate format (e.g., JSON, Bincode, YAML) that triggers the chain during deserialization.
        • Mitigation: Same as 1.1.1.1

      • 1.1.1.2 Discover new gadget chain in application's custom Deserialize implementations.

        • 1.1.1.2.1 Analyze custom Deserialize implementations for code paths leading to unsafe operations. [CRITICAL NODE]
          • Description: Attackers carefully examine any custom Deserialize implementations in the application's code, looking for potential vulnerabilities that could be chained together to achieve RCE. This often involves looking for unsafe blocks, calls to std::process::Command, file system access, or other potentially dangerous operations.
          • Mitigation:
            • Avoid unsafe code in Deserialize implementations if at all possible.
            • Thoroughly review and test all custom Deserialize implementations.
            • Use fuzzing to test these implementations.
            • Follow secure coding practices for Rust.
        • 1.1.1.2.2 Craft malicious payload triggering the discovered gadget chain.
          • Description: After identifying a potential gadget chain, the attacker crafts a malicious payload to trigger it.
          • Mitigation: Same as 1.1.1.2.1

    • 1.1.2 Exploit Format-Specific Vulnerabilities [HIGH RISK]

      • 1.1.2.1 Bincode: Exploit potential integer overflows or underflows (if size limits are not enforced). [HIGH RISK] [CRITICAL NODE]

        • Description: Bincode's encoding format can be vulnerable to integer overflows or underflows if the application doesn't enforce size limits during deserialization. An attacker can craft a payload with manipulated size fields, causing Bincode to allocate an incorrect amount of memory, leading to memory corruption and potentially RCE.
        • Mitigation:
          • Always use bincode::options().with_limit() to set explicit size limits when deserializing Bincode data, especially from untrusted sources.
          • Consider using a different serialization format for untrusted input.

      • 1.1.2.1.1 Craft a Bincode payload with manipulated size fields.

        • Description: The attacker creates a Bincode payload with carefully crafted size values designed to trigger an integer overflow or underflow.
        • Mitigation: Same as 1.1.2.1

      • 1.1.2.3 YAML (via serde_yaml): Exploit known YAML vulnerabilities. [HIGH RISK] [CRITICAL NODE]

        • Description: YAML is a complex format with a history of security vulnerabilities. Attackers can exploit features like custom constructors, tags, and recursive references to achieve RCE or DoS.
        • Mitigation:
          • Avoid using YAML for untrusted input if possible.
          • If you must use YAML, use a safe subset of the language.
          • Disable custom constructors and tags.
          • Use a YAML parser that is specifically designed for security (if available).
          • Enforce strict size and recursion limits.

      • 1.1.2.3.1 Craft a YAML payload with recursive references or custom constructors.

        • Description: The attacker creates a YAML payload that uses features like recursive references or custom constructors to trigger vulnerabilities in the YAML parser.
        • Mitigation: Same as 1.1.2.3

Attack Tree Path: 2. Achieve Denial of Service (DoS)

  • 2.1 Resource Exhaustion [HIGH RISK]

    • 2.1.1 "Billion Laughs" Attack (XML, YAML) [HIGH RISK] [CRITICAL NODE]

      • Description: This attack uses nested entity references in XML or YAML to cause exponential expansion of the data during parsing, consuming all available memory and leading to a DoS.
      • Mitigation:
        • Use a parser that limits entity expansion (most modern XML and YAML parsers have this feature).
        • Set strict limits on the depth of nested structures.
        • Avoid using XML or YAML for untrusted input if possible.

    • 2.1.1.1 Craft a payload with deeply nested, recursive data structures.

      • Description: The attacker creates a payload with deeply nested, recursive structures designed to consume excessive memory.
      • Mitigation: Same as 2.1.1

    • 2.1.2 Large Allocation Attack [HIGH RISK] [CRITICAL NODE]

      • Description: The attacker crafts a payload that tricks Serde into allocating a very large amount of memory (e.g., a huge array or string), exhausting available memory and causing a DoS.
      • Mitigation:
        • Enforce strict size limits on all deserialized data.
        • Validate the size of arrays, strings, and other data structures before deserialization.

    • 2.1.2.1 Craft a payload that tricks Serde into allocating a very large amount of memory.

      • Description: The attacker creates a payload with large size values for arrays, strings, or other data structures.
      • Mitigation: Same as 2.1.2

    • 2.1.2.2 Bincode: Exploit integer overflows to cause large allocations.

      • Description: Similar to the RCE scenario, integer overflows in Bincode can be used to cause large, unintended memory allocations, leading to DoS.
      • Mitigation: Same as 1.1.2.1 (use bincode::options().with_limit()).

  • 2.2 Panic-Induced DoS

    • 2.2.2 Exploit unwrap() or expect() calls in custom Deserialize implementations. [CRITICAL NODE]
      • Description: If a custom Deserialize implementation uses unwrap() or expect() on potentially invalid data, an attacker can craft input that causes a panic, crashing the application.
      • Mitigation:
        • Avoid using unwrap() and expect() in Deserialize implementations.
        • Use proper error handling (e.g., Result and the ? operator) to gracefully handle potential errors.
        • Validate input thoroughly before attempting to deserialize it.

  • 2.3 Deserialization loop

    • 2.3.1 Send cyclic data structures. [CRITICAL NODE]
      • Description: If the application doesn't handle cyclic data structures correctly, an attacker can send a payload containing cycles, causing an infinite loop during deserialization and leading to resource exhaustion or a stack overflow.
      • Mitigation:
        • If your application does not require cyclic data structures, configure Serde or the underlying format parser to reject them.
        • Implement cycle detection if cyclic data structures are necessary.