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attack-surface.md

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Attack Surface Analysis for bytecodealliance/wasmtime

Attack Surface: JIT Compiler Vulnerabilities

  • Description: Bugs in Wasmtime's Just-In-Time (JIT) compiler leading to memory corruption or arbitrary code execution when compiling WebAssembly.
  • Wasmtime Contribution: Wasmtime's JIT compiler is a core component for performance, and its vulnerabilities directly expose the application.
  • Example: A malicious Wasm module triggers a JIT compiler bug during compilation, allowing it to overwrite Wasmtime's memory and execute arbitrary code on the host.
  • Impact: Sandbox escape, arbitrary code execution on the host system.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Regularly update Wasmtime to the latest version.
    • Consider using the interpreter mode if security is paramount and performance is less critical.

Attack Surface: Wasm Validation Bypass

  • Description: Flaws in Wasmtime's validation process that allow execution of malformed or malicious Wasm modules intended to be rejected.
  • Wasmtime Contribution: Wasmtime's validation is crucial for security; bypasses directly undermine its sandbox guarantees.
  • Example: A crafted Wasm module with invalid bytecode bypasses Wasmtime's validation due to a bug. This allows the module to perform unsafe memory operations or escape the sandbox during execution.
  • Impact: Sandbox escape, memory corruption, arbitrary code execution.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Regularly update Wasmtime to benefit from validation bug fixes.
    • Report any suspected validation bypasses to the Wasmtime project.

Attack Surface: Outdated Wasmtime Version

  • Description: Using an outdated version of Wasmtime containing known, unpatched security vulnerabilities.
  • Wasmtime Contribution: Direct dependency on Wasmtime means using an old version directly inherits its vulnerabilities.
  • Example: A publicly disclosed vulnerability exists in Wasmtime version X. An application using version X remains vulnerable, allowing attackers to exploit the flaw via malicious Wasm.
  • Impact: Exposure to known vulnerabilities, potentially leading to sandbox escape or arbitrary code execution.
  • Risk Severity: High to Critical (depending on the specific vulnerability)
  • Mitigation Strategies:
    • Maintain a process for regularly updating Wasmtime.
    • Monitor Wasmtime security advisories and release notes.

Attack Surface: Resource Exhaustion via Wasm Modules

  • Description: Wasm modules consuming excessive resources (CPU, memory) within Wasmtime, leading to denial of service of the host application.
  • Wasmtime Contribution: Wasmtime executes Wasm and needs to provide resource management; insufficient limits expose the host to resource exhaustion.
  • Example: A Wasm module is designed to allocate excessive memory or enter an infinite loop. Wasmtime, without proper configuration, allows this, causing the host application to become unresponsive.
  • Impact: Denial of service for the host application.
  • Risk Severity: High
  • Mitigation Strategies:
    • Configure Wasmtime with resource limits (memory, execution time).
    • Monitor resource usage of Wasm modules and implement termination mechanisms for abusive modules.

Attack Surface: Data Type Mismatches in Host Function Interface (HFI)

  • Description: Incorrect handling of data types during calls between Wasm modules and host functions by Wasmtime's interface, leading to memory safety issues.
  • Wasmtime Contribution: Wasmtime manages the Host Function Interface and data marshaling; errors in this layer can introduce vulnerabilities.
  • Example: Wasmtime incorrectly handles data type conversion when passing arguments to a host function. This leads to the host function misinterpreting data as a pointer when it's not, causing a crash or exploitable memory access.
  • Impact: Crashes, memory corruption, potential for exploitation.
  • Risk Severity: High
  • Mitigation Strategies:
    • Use Wasmtime's HFI API correctly and ensure proper type handling in host functions.
    • Thoroughly test data interactions between Wasm and host functions.

Attack Surface: Insufficient Sandboxing Configuration

  • Description: Incorrect or weak configuration of Wasmtime's sandboxing features, resulting in a less secure execution environment for Wasm modules.
  • Wasmtime Contribution: Wasmtime provides sandboxing features, but their effectiveness depends on correct configuration by the user.
  • Example: Wasmtime is configured with overly permissive settings, disabling key sandboxing features. This allows a malicious Wasm module to access host resources or capabilities it should not have access to.
  • Impact: Weakened sandbox, potential for sandbox escape and unauthorized access to host resources.
  • Risk Severity: High
  • Mitigation Strategies:
    • Carefully review and configure Wasmtime's sandboxing options to enforce strong isolation.
    • Follow security best practices for Wasmtime configuration and deployment.

Attack Surface: Malicious Code Injection into Wasmtime Project

  • Description: Compromise of the Wasmtime project itself, leading to malicious code being injected into the Wasmtime codebase.
  • Wasmtime Contribution: Direct dependency on Wasmtime means any compromise in the project directly impacts users.
  • Example: Attackers compromise Wasmtime's build infrastructure and inject malicious code into a release. Applications using this compromised Wasmtime version become vulnerable.
  • Impact: Widespread compromise of applications using Wasmtime, arbitrary code execution.
  • Risk Severity: Critical (though low probability for reputable projects)
  • Mitigation Strategies:
    • Use official Wasmtime releases from trusted sources.
    • Verify checksums of downloaded Wasmtime binaries.
    • Rely on the security practices of the Bytecode Alliance and the open-source community.

Attack Surface: Compromised Wasmtime Dependencies

  • Description: Vulnerabilities or malicious code introduced through third-party dependencies used by the Wasmtime project.
  • Wasmtime Contribution: Wasmtime relies on external dependencies; vulnerabilities in these can indirectly affect Wasmtime's security.
  • Example: A vulnerability is discovered in a dependency used by Wasmtime. This vulnerability is then exploitable through Wasmtime, even if Wasmtime's core code is secure.
  • Impact: Indirect vulnerabilities in Wasmtime, potentially leading to sandbox escape or arbitrary code execution.
  • Risk Severity: High
  • Mitigation Strategies:
    • Monitor Wasmtime's dependencies for known vulnerabilities.
    • Use dependency scanning tools to identify vulnerable dependencies.
    • Keep Wasmtime updated to benefit from dependency updates and security fixes.