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attack-surface.md

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Attack Surface Analysis for nuget/nuget.client

Attack Surface: Malicious Package Source

  • Description: An attacker compromises or manipulates the configured NuGet package sources, causing NuGet.Client to download packages from a malicious repository.
    • NuGet.Client Contribution: NuGet.Client is the direct component responsible for fetching packages from the configured sources. Its handling of source URLs and the fetching process are the core vulnerability points.
    • Example: An attacker modifies environment variables used by NuGet.Client to point to a malicious NuGet feed. NuGet.Client then unknowingly downloads and installs compromised packages.
    • Impact: Complete system compromise. Malicious code within a downloaded package can execute with the application's privileges.
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Strict Source Control: Use only trusted, official, or internally controlled and vetted private feeds. Do not allow arbitrary or user-controlled sources.
      • Source Verification: Implement a mechanism (e.g., a whitelist, checksum verification, or signed configuration) to ensure that only approved sources are used by NuGet.Client.
      • HTTPS Enforcement: Mandate HTTPS for all package sources and enforce strict certificate validation within NuGet.Client's configuration. Disable any HTTP fallback.
      • Secure Configuration: Protect NuGet.Config and any environment variables or in-code configurations used by NuGet.Client using OS-level security or secure configuration stores.
      • Least Privilege: Run any process using NuGet.Client with the absolute minimum necessary privileges.

Attack Surface: Package Typosquatting/Brandjacking

  • Description: An attacker publishes a malicious package to a legitimate repository, and NuGet.Client downloads and installs it because a developer makes a mistake or is tricked.
    • NuGet.Client Contribution: NuGet.Client performs the download and installation based on the provided package name. It does not inherently differentiate between a legitimate package and a malicious one with a similar name. The act of downloading is the direct contribution.
    • Example: A developer intends to install AWSSDK.Core but accidentally types AWSSDK.C0re (a malicious package). NuGet.Client downloads and installs the malicious package from nuget.org.
    • Impact: System compromise, as the malicious package's code executes within the application's context.
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Package Signature Verification: Enable and strictly enforce package signature verification within NuGet.Client. Configure it to trust only packages signed by specific, known authors or organizations.
      • Careful Package Selection: Developers must meticulously review package names, descriptions, author information, and download counts before instructing NuGet.Client to install them.
      • Internal Package Naming Conventions: Use very clear and distinct naming conventions for internal packages to minimize the risk of typos and confusion with public packages.

Attack Surface: Dependency Confusion

  • Description: An attacker publishes a malicious package to a public repository with the same name as a private package, and NuGet.Client downloads the malicious public version.
    • NuGet.Client Contribution: NuGet.Client's package resolution logic is directly responsible for choosing which package to download. If misconfigured or if naming conventions are poor, it will make the wrong choice.
    • Example: An organization has an internal package named InternalUtils. An attacker publishes a malicious InternalUtils to nuget.org. If the build configuration prioritizes nuget.org, NuGet.Client will download the attacker's package.
    • Impact: System compromise, as the malicious package's code is executed.
    • Risk Severity: High
    • Mitigation Strategies:
      • Scoped Packages: Use scoped package names (e.g., @mycompany/InternalUtils) for all private packages to guarantee no naming collisions with public packages. This is the most robust solution.
      • Explicit Source Mapping: Configure NuGet.Client (via NuGet.Config or programmatically) to explicitly map package names to specific sources. This prevents NuGet.Client from searching other sources for a given package name. This is crucial.
      • Private Feeds: Use private NuGet feeds for all internal packages, and ensure that these feeds are properly secured and always prioritized in NuGet.Client's configuration.