attack-surface.md

Attack Surface Analysis for nuget/nuget.client

Attack Surface: Compromised or Malicious Package Sources

• Description: Attackers compromise a configured NuGet package source or create a malicious one to distribute harmful packages.
• NuGet.Client Contribution: nuget.client directly relies on configured package sources. It is designed to download and install packages from these sources, trusting their content based on configuration.
• Example: An attacker compromises a company's private NuGet feed. They upload a malicious package with a name similar to a legitimate internal library. Developers using nuget.client to resolve dependencies might unknowingly download and install this malicious package from the compromised source.
• Impact: Code execution on developer machines and build servers, supply chain compromise, data breaches, denial of service, potentially widespread impact across projects using the compromised source.
• Risk Severity: Critical
• Mitigation Strategies:
  • Mandatory HTTPS for all package sources: Enforce the use of HTTPS for all configured package sources within nuget.config or through organizational policies to prevent man-in-the-middle attacks.
  • Strong Package Source Authentication: Implement and enforce strong authentication mechanisms (like API keys, Azure Active Directory, or other secure methods) for accessing private package sources.
  • Package Signature Verification Enforcement: Enable and strictly enforce NuGet package signature verification. Configure nuget.config to require signed packages and reject unsigned ones to ensure package integrity and origin.
  • Regular Auditing of Package Sources: Periodically review and verify the legitimacy and security posture of all configured package sources. Remove or disable any untrusted or unnecessary sources.

Attack Surface: Package Content Vulnerabilities (Malicious Code Execution)

• Description: NuGet packages can contain executable code (install scripts, build tasks, or code within libraries) that can be malicious.
• NuGet.Client Contribution: nuget.client is responsible for downloading, extracting, and in some cases, executing code within NuGet packages during installation and build processes. It directly facilitates the execution of package content.
• Example: A malicious NuGet package contains an install script that, when executed by nuget.client during package installation, downloads and runs malware on the developer's machine or build server. Alternatively, a seemingly benign library package could contain malicious code that executes when the application uses the library.
• Impact: Full system compromise, remote code execution, data exfiltration, supply chain attacks, potentially affecting all systems where the malicious package is installed.
• Risk Severity: Critical
• Mitigation Strategies:
  • Strict Package Signature Verification: Enforce package signature verification to ensure packages originate from trusted publishers. While not foolproof, it adds a layer of trust.
  • Automated Dependency Scanning: Implement automated tools to scan NuGet package dependencies for known vulnerabilities before and after installation. Integrate these scans into CI/CD pipelines.
  • Code Review and Security Audits of Dependencies: Prioritize code review and security audits for dependencies, especially those from less trusted or public sources. Focus on understanding what the package does and if it requests unusual permissions.
  • Principle of Least Privilege for Build Processes: Run nuget.client and build processes with the minimum necessary privileges to limit the potential damage from malicious code execution.
  • Sandboxing or Containerization for Builds: Utilize sandboxed environments or containerization for build processes to isolate them from the host system and limit the impact of malicious package code.

Attack Surface: NuGet.Client Library Vulnerabilities

• Description: Security vulnerabilities or bugs within the nuget.client library itself can be exploited.
• NuGet.Client Contribution: Applications directly use the nuget.client library. Vulnerabilities in nuget.client directly expose the application and the systems running it to potential attacks.
• Example: A buffer overflow vulnerability exists in nuget.client's package parsing logic. An attacker crafts a specially malformed NuGet package. When nuget.client attempts to process this package (e.g., during package restore or installation), the vulnerability is triggered, leading to denial of service or potentially remote code execution on the system running nuget.client.
• Impact: Denial of service, information disclosure, remote code execution, potentially affecting development machines, build servers, or even production environments if nuget.client is used in deployment processes.
• Risk Severity: High to Critical (depending on the nature and exploitability of the vulnerability).
• Mitigation Strategies:
  • Keep NuGet.Client Up-to-Date: Maintain nuget.client at the latest stable version. Regularly update to benefit from security patches and bug fixes released by the NuGet team.
  • Monitor Security Advisories: Subscribe to security advisories and vulnerability databases related to NuGet and .NET to stay informed about any reported vulnerabilities in nuget.client.
  • Security Testing and Vulnerability Assessments: Include nuget.client and its usage patterns in security testing and vulnerability assessments of applications. Perform static and dynamic analysis to identify potential vulnerabilities.

Attack Surface: Insecure Configuration Settings Leading to Package Manipulation

• Description: Misconfiguring nuget.client with insecure settings weakens security and can enable package manipulation attacks.
• NuGet.Client Contribution: nuget.client's behavior and security posture are directly determined by its configuration. Insecure configurations directly reduce its effectiveness in preventing attacks.
• Example: Disabling package signature verification in nuget.config for convenience during development. This removes a critical security control, allowing the installation of unsigned and potentially malicious packages without warning. Or, using HTTP package sources without HTTPS, making communication vulnerable to interception and manipulation.
• Impact: Increased risk of malicious package injection, man-in-the-middle attacks, reduced assurance of package integrity, potentially leading to code execution and supply chain compromise.
• Risk Severity: High
• Mitigation Strategies:
  • Enforce Package Signature Verification: Ensure package signature verification is enabled and enforced in nuget.config across all development and build environments. Do not disable it for convenience.
  • Mandatory HTTPS for Package Sources: Strictly configure all package sources to use HTTPS. Prohibit the use of HTTP sources to prevent insecure communication.
  • Centralized and Secure Configuration Management: Manage nuget.config and related settings centrally and securely. Use configuration management tools to enforce secure settings across the organization.
  • Regular Configuration Reviews: Periodically review nuget.config and other NuGet-related configurations to identify and rectify any insecure settings or deviations from security best practices.