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Attack Tree Analysis for bytecodealliance/wasmtime

Objective: Escalate Privileges or Exfiltrate Data from Host via Wasmtime

Attack Tree Visualization

Goal: Escalate Privileges or Exfiltrate Data from Host via Wasmtime

├── 1. Exploit Wasmtime Runtime Vulnerabilities │ ├── 1.1 Memory Corruption in Wasmtime │ │ ├── 1.1.1 Buffer Overflow/Underflow in Wasmtime's JIT Compiler [CRITICAL] │ │ │ ├── 1.1.1.1 Craft Malicious WASM to Trigger Overflow During Compilation │ │ │ └── 1.1.1.2 Exploit Overflow to Overwrite Function Pointers/Return Addresses │ │ └── 1.1.2 Use-After-Free in Wasmtime's Garbage Collector or Memory Management [CRITICAL] │ │ │ ├── 1.1.2.1 Craft Malicious WASM to Trigger Premature Deallocation │ │ │ └── 1.1.2.2 Exploit UAF to Control Freed Memory, Redirect Execution │ └── 1.2 Logic Errors in Wasmtime │ └── 1.2.1 Incorrect Implementation of WASI [CRITICAL] │ ├── 1.2.1.1 Exploit Flaws in WASI API Implementation (e.g., File System Access, Networking) │ └── 1.2.1.2 Bypass WASI Restrictions to Access Unauthorized Resources ├── 2. Exploit Misconfiguration of Wasmtime [HIGH-RISK] │ ├── 2.1 Overly Permissive WASI Capabilities [HIGH-RISK] [CRITICAL] │ │ ├── 2.1.1 Granting Unnecessary File System Access [HIGH-RISK] │ │ │ └── 2.1.1.1 WASM Module Reads/Writes Sensitive Host Files [HIGH-RISK] │ │ ├── 2.1.2 Granting Unnecessary Network Access [HIGH-RISK] │ │ │ └── 2.1.2.1 WASM Module Connects to Unauthorized Networks/Hosts [HIGH-RISK] │ │ └── 2.1.3 Granting Unnecessary Environment Variable Access │ │ └── 2.1.3.1 WASM Module Reads Sensitive Environment Variables │ ├── 2.2 Disabled or Weakened Security Features [HIGH-RISK] │ │ ├── 2.2.1 Disabling Fuel Consumption Limits [HIGH-RISK] │ │ │ └── 2.2.1.1 WASM Module Enters Infinite Loop, Causing Denial of Service (DoS) [HIGH-RISK] │ │ ├── 2.2.2 Disabling Memory Limits [HIGH-RISK] │ │ │ └── 2.2.2.1 WASM Module Allocates Excessive Memory, Causing Host System Instability [HIGH-RISK] │ │ └── 2.2.3 Disabling Stack Overflow Protection │ │ └── 2.2.3.1 WASM Module triggers stack overflow, potentially leading to code execution └── 3. Supply Chain Attacks ├── 3.1 Compromised Wasmtime Build [CRITICAL] │ ├── 3.1.1 Malicious Code Injected During Build Process │ │ └── 3.1.1.1 Backdoored Wasmtime Binary Executes Arbitrary Code on Host │ └── 3.1.2 Compromised Dependencies of Wasmtime │ └── 3.1.2.1 Vulnerability in a Wasmtime Dependency Exploited to Compromise Wasmtime └── 3.2 Compromised WASM module [HIGH-RISK] ├── 3.2.1 Malicious code injected into WASM module [HIGH-RISK] └── 3.2.2 WASM module exploit vulnerabilities in Wasmtime (points back to 1)

Attack Tree Path: 1. Exploit Wasmtime Runtime Vulnerabilities

  • 1.1 Memory Corruption in Wasmtime [CRITICAL]

    • 1.1.1 Buffer Overflow/Underflow in Wasmtime's JIT Compiler:

      • Description: The attacker crafts a malicious WASM module that, when compiled by Wasmtime's JIT compiler (Cranelift), triggers a buffer overflow or underflow. This could occur due to errors in the compiler's code generation or memory management.
      • Attack Steps:
        1. Craft Malicious WASM (1.1.1.1): The attacker carefully constructs WASM code with specific instructions and data that, when processed by the JIT compiler, cause it to write data outside the bounds of an allocated buffer.
        2. Exploit Overflow (1.1.1.2): The attacker leverages the buffer overflow to overwrite critical data structures in memory, such as function pointers or return addresses. This allows them to redirect the control flow of the Wasmtime process to arbitrary code of their choosing.
      • Mitigation: Rigorous fuzzing of the JIT compiler, code audits, and potentially formal verification.

    • 1.1.2 Use-After-Free in Wasmtime's Garbage Collector or Memory Management:

      • Description: The attacker crafts a WASM module that triggers a use-after-free vulnerability in Wasmtime's memory management. This occurs when Wasmtime attempts to use a memory region that has already been freed.
      • Attack Steps:
        1. Craft Malicious WASM (1.1.2.1): The attacker creates WASM code that manipulates object lifetimes or memory allocation in a way that causes Wasmtime to prematurely deallocate a memory region.
        2. Exploit UAF (1.1.2.2): The attacker then triggers a situation where Wasmtime attempts to access the freed memory. If the attacker can control the contents of the freed memory (e.g., through heap spraying), they can redirect execution to arbitrary code.
      • Mitigation: Robust memory management practices, fuzzing, and code audits.

  • 1.2 Logic Errors in Wasmtime

    • 1.2.1 Incorrect Implementation of WASI [CRITICAL]:
      • Description: Vulnerabilities in Wasmtime's implementation of the WebAssembly System Interface (WASI) could allow WASM modules to bypass security restrictions and access unauthorized resources on the host system.
      • Attack Steps:
        1. Exploit Flaws in WASI API (1.2.1.1): The attacker identifies a flaw in how Wasmtime implements a specific WASI API function (e.g., a file system access function, a networking function). This flaw might involve incorrect permission checks, improper handling of symbolic links, or other logic errors.
        2. Bypass WASI Restrictions (1.2.1.2): The attacker crafts a WASM module that calls the vulnerable WASI function with specially crafted arguments to exploit the flaw and gain access to resources that should be restricted.
      • Mitigation: Thorough code reviews of the WASI implementation, fuzzing of WASI API functions, and strict adherence to the WASI specification.

Attack Tree Path: 2. Exploit Misconfiguration of Wasmtime [HIGH-RISK]

  • 2.1 Overly Permissive WASI Capabilities [HIGH-RISK] [CRITICAL]

    • Description: The application using Wasmtime grants the WASM module more WASI capabilities than it needs, allowing the module to access sensitive resources on the host system.
    • Attack Vectors:
      • 2.1.1 Granting Unnecessary File System Access:
        • Attack Step (2.1.1.1): A malicious WASM module, granted read/write access to sensitive directories or files, reads confidential data or modifies critical system files.
      • 2.1.2 Granting Unnecessary Network Access:
        • Attack Step (2.1.2.1): A malicious WASM module, granted network access, connects to external servers controlled by the attacker, exfiltrates data, or receives commands.
      • 2.1.3 Granting Unnecessary Environment Variable Access:
        • Attack Step (2.1.3.1): A malicious WASM module reads sensitive environment variables containing API keys, passwords, or other confidential information.
    • Mitigation: Strictly adhere to the principle of least privilege. Grant only the minimum necessary WASI capabilities. Use pre-opened directories and fine-grained permissions. Regularly audit WASI configurations.

  • 2.2 Disabled or Weakened Security Features [HIGH-RISK]

    • Description: Essential security features of Wasmtime, such as fuel consumption limits or memory limits, are disabled or set to overly permissive values.
    • Attack Vectors:
      • 2.2.1 Disabling Fuel Consumption Limits:
        • Attack Step (2.2.1.1): A malicious WASM module enters an infinite loop, consuming all available CPU resources and causing a denial-of-service (DoS) condition.
      • 2.2.2 Disabling Memory Limits:
        • Attack Step (2.2.2.1): A malicious WASM module allocates an excessive amount of memory, leading to host system instability or a DoS condition.
      • 2.2.3 Disabling Stack Overflow Protection:
        • Attack Step (2.2.3.1): A malicious WASM module, with stack overflow protection disabled, triggers a stack overflow. While less likely to lead directly to code execution than heap-based vulnerabilities, it can still cause crashes and potentially be used in conjunction with other vulnerabilities.
    • Mitigation: Always enable fuel consumption limits, memory limits, and stack overflow protection. Set these limits to appropriate values based on the expected behavior of the WASM modules.

Attack Tree Path: 3. Supply Chain Attacks

  • 3.1 Compromised Wasmtime Build [CRITICAL]

    • Description: The Wasmtime binary itself is compromised, either during the build process or through a compromised distribution channel.
    • Attack Steps:
      • 3.1.1 Malicious Code Injected During Build Process:
        • Attack Step (3.1.1.1): An attacker gains access to the Wasmtime build infrastructure and injects malicious code into the build process. The resulting Wasmtime binary contains a backdoor that allows the attacker to execute arbitrary code on any system running the compromised binary.
      • 3.1.2 Compromised Dependencies of Wasmtime:
        • Attack Step (3.1.2.1): A vulnerability in one of Wasmtime's dependencies is exploited to compromise Wasmtime itself. This could involve a dependency that is used during the build process or a runtime dependency.
    • Mitigation: Secure build environment, reproducible builds, code signing, dependency management (auditing and updating).

  • 3.2 Compromised WASM module [HIGH-RISK]

    • Description: The WASM module loaded into Wasmtime is malicious, either intentionally designed to be harmful or compromised after its creation.
    • Attack Steps:
      • 3.2.1 Malicious code injected into WASM module:
        • The WASM module contains code specifically designed to exploit vulnerabilities in Wasmtime (referring back to section 1) or to misuse granted WASI capabilities (referring back to section 2).
      • 3.2.2 WASM module exploit vulnerabilities in Wasmtime (points back to 1):
        • This is not a separate attack step but rather a reminder that a compromised WASM module is often the vehicle for exploiting vulnerabilities in Wasmtime itself.
    • Mitigation: WASM module provenance (trusted sources), code signing, static analysis, and sandboxing.