attack-surface.md

Attack Surface Analysis for yarnpkg/berry

Attack Surface: Plug'n'Play (PnP) .pnp.cjs File Compromise

• Description: The .pnp.cjs file, central to Yarn Berry's Plug'n'Play module resolution, dictates how modules are loaded. If compromised, it can lead to arbitrary code execution during module loading.
• Berry Contribution: Yarn Berry's core PnP functionality relies entirely on the integrity of this file. Its compromise directly enables malicious code execution within the application's process during module resolution, a mechanism unique to PnP.
• Example: An attacker gains write access to the project repository and injects malicious JavaScript code into the .pnp.cjs file. When the application starts or modules are loaded, this injected code executes within the Node.js process, potentially hijacking the application's functionality.
• Impact: Critical - Arbitrary code execution on the server or developer machine, potentially leading to complete application takeover, data breaches, and system compromise.
• Risk Severity: Critical
• Mitigation Strategies:
  • File Integrity Monitoring: Implement systems to detect and alert on unauthorized modifications to the .pnp.cjs file.
  • Strict Access Controls: Restrict write access to the project repository and the .pnp.cjs file to only authorized personnel and automated processes.
  • Secure Build Pipelines: Harden CI/CD pipelines to prevent malicious injection during the build process that could alter .pnp.cjs.
  • Code Review: Include .pnp.cjs in code reviews to identify any unexpected or malicious changes.

Attack Surface: Malicious PnP Custom Resolver or Fetcher

• Description: Yarn Berry's extensibility allows custom resolvers and fetchers for dependency resolution and package downloads. A malicious or compromised custom resolver/fetcher can redirect downloads to malicious sources or execute arbitrary code during the resolution process.
• Berry Contribution: Yarn Berry's plugin system and resolver/fetcher architecture enable this extensibility, making it possible to replace or augment the standard package resolution process. This feature, if misused, becomes a direct attack vector.
• Example: A developer installs a plugin or configures a custom resolver from an untrusted source. This malicious resolver is designed to intercept requests for a common library and serve a compromised version containing malware. During dependency installation, the malicious library is downloaded and integrated into the project, leading to potential runtime compromise.
• Impact: High - Supply chain attack, potentially leading to arbitrary code execution within the application, data theft, or the introduction of backdoors through compromised dependencies.
• Risk Severity: High
• Mitigation Strategies:
  • Vet Custom Resolvers/Fetchers: Thoroughly examine the code and origin of any custom resolvers or fetchers before use. Only utilize resolvers/fetchers from highly trusted and reputable sources.
  • Code Review of Custom Logic: If developing custom resolvers/fetchers, rigorously code review them for security vulnerabilities and adhere to secure coding practices.
  • Principle of Least Privilege: Limit the permissions granted to custom resolvers and fetchers to only what is strictly necessary for their intended function.
  • Dependency Source Verification: Implement mechanisms to verify the integrity and authenticity of downloaded packages, even when using custom resolvers/fetchers, if technically feasible.

Attack Surface: Malicious Plugin Installation and Exploitation

• Description: Yarn Berry's plugin architecture allows extending its functionality. Installing untrusted or malicious plugins grants them broad access to Yarn's internal APIs and the project environment, potentially leading to arbitrary code execution, data exfiltration, or modification of project files.
• Berry Contribution: Yarn Berry's plugin system is a core feature designed for extensibility. This very design, however, introduces a significant attack surface if malicious plugins are installed, as plugins can deeply integrate with Yarn's operations.
• Example: A developer installs a seemingly benign Yarn plugin from an untrusted source. This plugin contains malicious code that exfiltrates sensitive environment variables, project files, or executes arbitrary commands on the developer's machine or build server during Yarn operations, compromising the development environment or build process.
• Impact: High - Arbitrary code execution, data breach, compromise of the Yarn installation itself, potentially affecting all projects managed by that Yarn instance and related development environments.
• Risk Severity: High
• Mitigation Strategies:
  • Minimize Plugin Usage: Reduce the number of installed plugins to the absolute minimum necessary for project needs. Avoid installing plugins unless there is a clear and compelling requirement.
  • Trusted Plugin Sources: Only install plugins from highly trusted and reputable sources, such as the official Yarn plugin registry or verified developers/organizations with established security reputations.
  • Plugin Vetting and Code Review: Thoroughly vet plugins before installation, carefully reviewing their code, permissions requests, and intended functionality. Understand the full scope of capabilities the plugin requests and the actions it performs.
  • Plugin Security Scanners: Utilize plugin security scanners, if available, to proactively identify potential vulnerabilities or malicious code within plugins before installation.
  • Principle of Least Privilege for Plugins: Where technically possible and if plugin architecture allows, limit the permissions and access granted to plugins to the minimum necessary for their operation.

Attack Surface: yarn.lock File Manipulation and Supply Chain Attacks

• Description: While yarn.lock ensures reproducible builds, compromising this file can lead to the installation of malicious or vulnerable dependency versions, undermining the lockfile's intended security benefit.
• Berry Contribution: yarn.lock is a central component of Yarn Berry's deterministic dependency resolution and security model. Its integrity is paramount for preventing supply chain attacks by ensuring consistent and verified dependency installations.
• Example: An attacker compromises a developer's machine or a CI/CD pipeline and maliciously modifies the yarn.lock file. They replace a legitimate dependency version with a known vulnerable or backdoored version. When other developers or the automated build system subsequently install dependencies using yarn install, they unknowingly install the compromised dependency, introducing vulnerabilities into the application.
• Impact: High - Supply chain attack, leading to the installation of vulnerable or malicious packages across development and production environments, potentially resulting in arbitrary code execution and widespread application compromise.
• Risk Severity: High
• Mitigation Strategies:
  • File Integrity Monitoring for yarn.lock: Implement robust file integrity monitoring systems to immediately detect and alert on any unauthorized changes to the yarn.lock file.
  • Version Control for yarn.lock: Treat yarn.lock as a critical security file and strictly manage it under version control. Carefully track all changes and rigorously review them before committing.
  • Secure Dependency Resolution Process: Ensure the entire dependency resolution process is secured and protected from man-in-the-middle attacks. Enforce the use of HTTPS for all package registry communication to prevent tampering during download.
  • Integrity Checks and Checksums: Enable and strictly enforce integrity checks (checksums) for all downloaded packages as specified within the yarn.lock file. Verify package integrity during every installation process to ensure downloaded packages match expected hashes.
  • Dependency Scanning of Locked Dependencies: Regularly and automatically scan the dependencies listed in yarn.lock for known vulnerabilities using automated security scanning tools. Integrate these scans into CI/CD pipelines to proactively identify and address vulnerabilities in locked dependencies.