Skip to content

Latest commit

 

History

History
49 lines (42 loc) · 5.86 KB

attack-surface.md

File metadata and controls

49 lines (42 loc) · 5.86 KB

Attack Surface Analysis for wasmerio/wasmer

Attack Surface: 1. Sandbox Escape (Wasmer Runtime Vulnerability)

  • Description: A vulnerability in the Wasmer runtime itself that allows a compromised Wasm module to break out of the sandbox and gain access to the host system. This is a failure of Wasmer's core security mechanism.
  • Wasmer Contribution: This is a direct vulnerability within Wasmer's core functionality – its ability to isolate the Wasm module. The bug could be in the JIT compiler, memory management, WASI implementation, or other core components.
  • Example: A bug in Wasmer's handling of WASI fd_write allows a specially crafted Wasm module to write to arbitrary file descriptors, including those belonging to the host process, leading to code execution. Or, a flaw in the JIT compiler allows generation of native code that bypasses memory protection.
  • Impact:
    • Complete system compromise. The attacker gains the privileges of the process running Wasmer.
    • Arbitrary code execution on the host.
    • Data theft and manipulation on the host.
  • Risk Severity: Critical.
  • Mitigation Strategies:
    • Keep Wasmer Updated: The most crucial mitigation is to keep Wasmer updated to the latest version. Security patches are regularly released to address vulnerabilities. This is a continuous process.
    • Security Audits (Wasmer): Be aware of the results of security audits performed on the Wasmer project.
    • Minimize WASI Capabilities: Grant the Wasm module only the absolute minimum necessary WASI capabilities. This reduces the attack surface available to a compromised module, even if a Wasmer vulnerability exists. This is a defense-in-depth measure.
    • Run Wasmer with Least Privilege: Run the host application that uses Wasmer with the lowest possible privileges on the operating system. This limits the damage an attacker can do after a successful sandbox escape.
    • Additional Sandboxing: Consider running the entire Wasmer-using application within a container (e.g., Docker) or a virtual machine for an additional layer of isolation. This provides containment even if Wasmer's sandbox is breached.

Attack Surface: 2. Overly Permissive WASI Capabilities (Misconfiguration within Wasmer)

  • Description: While technically a configuration issue, it directly impacts Wasmer's security enforcement. Granting excessive WASI capabilities to a Wasm module allows it to interact with the host system in ways that are not strictly necessary, increasing the impact of any vulnerability (either in the Wasm module or in Wasmer itself).
  • Wasmer Contribution: Wasmer is responsible for enforcing the WASI capabilities. A misconfiguration means Wasmer is not enforcing the intended restrictions, making it a Wasmer-related issue.
  • Example: A Wasm module is granted the ability to open arbitrary network connections, even though it only needs to read a local configuration file. A vulnerability in the module (or a Wasmer vulnerability) could then be used to exfiltrate data or connect to malicious servers.
  • Impact:
    • Significantly increases the risk and impact of other vulnerabilities. Makes sandbox escapes easier and more damaging.
    • Facilitates data breaches, system corruption, or denial of service.
  • Risk Severity: High (Potentially Critical, as it amplifies other risks).
  • Mitigation Strategies:
    • Principle of Least Privilege: Grant only the minimum necessary WASI capabilities to the Wasm module. Carefully review and justify each capability. This is the primary mitigation.
    • Configuration Review: Regularly review the Wasmer configuration (how WASI capabilities are granted) to ensure they are not overly permissive. Automate this review if possible.
    • Documentation: Clearly document the required WASI capabilities for each Wasm module and the rationale behind them.
    • Auditing: Audit the configuration and usage of WASI capabilities to detect any deviations from the principle of least privilege.

Attack Surface: 3. Denial of Service (Resource Exhaustion due to Wasmer Bugs)

  • Description: A bug within Wasmer that allows a wasm module to consume excessive resources. This is different from a malicious module intentionally exhausting resources; this is about Wasmer failing to enforce limits correctly.
  • Wasmer Contribution: Wasmer is responsible for enforcing resource limits (memory, CPU, etc.). A bug in this enforcement mechanism is a direct Wasmer vulnerability.
  • Example: A bug in Wasmer's memory limit enforcement allows a Wasm module to allocate significantly more memory than configured, leading to the host process being killed by the operating system's OOM killer. Or, a bug in the execution timeout mechanism allows a Wasm module to run indefinitely, despite a configured timeout.
  • Impact:
    • Denial of service for the host application.
    • Potential instability of the host system.
  • Risk Severity: High
  • Mitigation Strategies:
    • Keep Wasmer Updated: As with all Wasmer vulnerabilities, keeping Wasmer updated is crucial.
    • Test Resource Limits: Thoroughly test the configured resource limits to ensure they are being enforced correctly by Wasmer. This includes testing edge cases and potential bypasses.
    • Monitoring: Monitor the resource usage of Wasmer itself (not just the Wasm modules) to detect any anomalies that might indicate a bug in resource limit enforcement.
    • Report Bugs: If you discover a bug in Wasmer's resource limit enforcement, report it to the Wasmer developers.