vulnerabilities-workflow-1.md

Combined Vulnerability List

This document consolidates vulnerabilities identified across multiple analyses into a unified list, eliminating duplicates and providing a comprehensive view of security concerns.

• Vulnerability Name: Arbitrary File Read via Unvalidated Mount Point Configuration in sysfs

  • Description: The library’s core initializer for its filesystem abstraction (implemented in NewFS) takes a mount point string (e.g. the expected “/sys” directory) without internal validation, canonicalization, or enforcement of an allowed set of mount points. Although the design document assumes that callers supply a trusted constant (such as “/sys”), in practice the mount point is provided by external configuration or environment variables. An attacker who can influence this configuration (for example, by altering startup parameters, misconfigurations in container orchestration setups, or other configuration injection attacks) may replace the expected sysfs mount point with a path under attacker control. When the rest of the sysfs package uses its internal FS’s Path() function to build file references (e.g. for “class/net”, “devices/system/cpu/vulnerabilities”, etc.), the attacker-controlled mount point allows arbitrary files to be read—instead of the intended kernel‐provided interface files.

  • Impact:

    • Information Disclosure: An attacker may force the application to read and expose contents from arbitrary locations on the host filesystem.
    • Leakage of Sensitive Data: This can reveal system internals, configuration files, credentials, or any other sensitive information that resides in the substituted directory.
    • Further Exploitation: When exposed via metrics endpoints or logs, this information may allow the attacker to further compromise the system or lateral move to other assets.

  • Vulnerability Rank: High

  • Currently Implemented Mitigations:

    • The FS initializers (in both the sysfs package and the underlying internal/fs package) do check that the given mount point exists and is a directory.
    • The design assumes that the caller uses a constant within a trusted environment (for example, “/sys”).

  • Missing Mitigations:

    • Input Sanitization/Canonicalization: There is no internal canonicalization (using, for example, filepath.Clean or filepath.Abs) to verify that the supplied mount point exactly matches an expected value.
    • Whitelist Enforcement: There is no enforcement to limit the mount point only to a set of allowed paths (e.g. “/sys”, “/proc”, etc.).
    • Hard Configuration Boundaries: The library delegates the “safety” of the mount point entirely to the caller rather than enforcing strict limits in its own API.

  • Preconditions:

    • The attacker (or misconfigured deployment in a hostile environment) must be able to influence the mount point value passed to NewFS—for example, through a configurable environment variable or command‑line argument.
    • The application must run with sufficient privileges (or in a configuration where the attacker can change the configuration) so that the altered mount point is honored.
    • The downstream code later invokes filesystem functions (through FS.Path and related routines) to open and read files based on the attacker‑controlled mount point.

  • Source Code Analysis:

    • In /code/sysfs/fs.go, the function

      func NewFS(mountPoint string) (FS, error) {
          fs, err := fs.NewFS(mountPoint)
          if err != nil {
              return FS{}, err
          }
          return FS{fs}, nil
      }

      simply passes the caller‑supplied mount point to the internal FS initializer.
    • In /code/internal/fs/fs.go, the implementation of NewFS(mountPoint string) only checks that the file (mount point) exists and that it is a directory:

      info, err := os.Stat(mountPoint)
      if err != nil {
          return "", fmt.Errorf("could not read %q: %w", mountPoint, err)
      }
      if !info.IsDir() {
          return "", fmt.Errorf("mount point %q is not a directory", mountPoint)
      }

      No further checks (such as canonicalization or comparing against an allowed list) are performed.
    • Consequently, if an attacker is able to supply an alternate directory (for example, by setting the mount point to /tmp/malicious), subsequent calls like

      fs.sys.Path("class/net")

      will translate to /tmp/malicious/class/net. This means that if the attacker populates /tmp/malicious with files named identically to the expected sysfs entries, the application will parse and expose that data.

  • Security Test Case:

    1. Setup:
       • Deploy the application (e.g. a metrics exporter) that uses the sysfs package to read system metrics.
       • Ensure that the mount point used by the library is configurable (for example, via an environment variable or a configuration file).
    2. Injection:
       • Create a directory (for example, /tmp/malicious) and place files with names that mimic sysfs entries (such as class/net, devices/system/cpu/vulnerabilities, etc.).
       • Populate these files with attacker‑controlled (and easily recognizable) content.
    3. Trigger:
       • Change the configuration so that the application calls NewFS("/tmp/malicious") instead of the default /sys.
       • Start (or restart) the application so that it initializes its filesystem handle using the malicious directory.
    4. Observation:
       • Trigger the metric collection routines (for example, by scraping metrics from the application’s HTTP endpoint).
       • Verify that at least one metric’s output corresponds to content from your fabricated files (for example, showing the attacker‑controlled content rather than real system data).
    5. Confirmation:
       • Revert the configuration back to /sys and confirm that the output now reflects genuine system data.
       • The difference in output confirms that without built‑in mount point validation, the application reads files from an arbitrary location, thereby confirming the vulnerability.