attack-tree.md

Attack Tree Analysis for pallets/click

Objective: Execute Arbitrary Code or Cause Click-Specific DoS

Attack Tree Visualization

Goal: Execute Arbitrary Code or Cause Click-Specific DoS ├── 1. Manipulate Command/Option Parsing (Primary Attack Vector) │ ├── 1.1.2 Type Juggling (Exploit Python's dynamic typing) [HIGH-RISK] │ │ └── 1.1.2.1 Pass string where integer/float is expected, hoping for unsafe evaluation or type conversion. [CRITICAL] │ ├── 1.3 Argument Injection [HIGH-RISK] │ │ └── 1.3.1.1 Use shell metacharacters (e.g., ;, |, $()) if Click doesn't properly escape them before passing to system calls. [CRITICAL] │ ├── 1.4 Bypass Validation Logic │ │ ├── 1.4.1 Exploit weaknesses in custom click.ParamType implementations. [HIGH-RISK] │ │ │ └── 1.4.1.1 If the application uses a custom type, find flaws in its convert() method. [CRITICAL] │ └── 1.5 Exploit Environment Variable Handling [HIGH-RISK] │ └── 1.5.1.1 Set unexpected or malicious values for environment variables used by Click or the application. [CRITICAL] └── 3. Exploit Vulnerabilities in Click's Dependencies [HIGH-RISK] └── 3.1 Dependency Confusion └── 3.1.1 If a malicious package with the same name as a Click dependency is published to a public repository, it could be installed instead. [CRITICAL]

Attack Tree Path: 1.1.2 Type Juggling (Exploit Python's dynamic typing) [HIGH-RISK]

• 1.1.2.1 Pass string where integer/float is expected, hoping for unsafe evaluation or type conversion. [CRITICAL]
  • Description: The attacker provides a string value to a Click command or option that expects a numerical type (integer or float). The vulnerability lies in how the application subsequently uses this string value. If the application uses functions like eval(), exec(), or performs unsafe string formatting or concatenation that incorporates this user-provided string without proper sanitization, it can lead to arbitrary code execution.
  • Likelihood: Medium
  • Impact: High (Potential for arbitrary code execution)
  • Effort: Low
  • Skill Level: Intermediate
  • Detection Difficulty: Medium to Hard (Requires code analysis and runtime monitoring to detect unsafe string handling)
  • Mitigation:
    • Use Click's built-in type validation (click.INT, click.FLOAT, etc.).
    • Never use eval() or exec() with user-supplied input.
    • If string formatting is necessary, use parameterized queries or template engines that handle escaping automatically.
    • Sanitize and validate all string inputs, even if they are initially expected to be numbers.

Attack Tree Path: 1.3 Argument Injection [HIGH-RISK]

• 1.3.1.1 Use shell metacharacters (e.g., ;, |, $()) if Click doesn't properly escape them before passing to system calls. [CRITICAL]
  • Description: The attacker injects shell metacharacters into arguments or options passed to the Click application. If the application then uses these arguments to construct shell commands without proper escaping, the attacker can execute arbitrary commands on the system. This is a classic command injection vulnerability.
  • Likelihood: Medium (Higher if the application interacts with the shell)
  • Impact: Very High (Potential for full system compromise)
  • Effort: Low
  • Skill Level: Intermediate
  • Detection Difficulty: Medium to Hard (Requires careful monitoring of system calls and input validation)
  • Mitigation:
    • Avoid using shell commands if possible. Use Python libraries to perform the desired operations directly.
    • If shell commands are absolutely necessary, use shlex.quote() to properly escape all user-supplied input before incorporating it into the command string.
    • Use subprocess with a list of arguments, rather than a single string, to avoid shell interpretation. (e.g., subprocess.run(["ls", "-l", user_input]) is safer than subprocess.run("ls -l " + user_input))
    • Implement strict input validation to reject any input containing shell metacharacters.

Attack Tree Path: 1.4 Bypass Validation Logic [HIGH-RISK]

• 1.4.1 Exploit weaknesses in custom click.ParamType implementations. [CRITICAL]
  • Description: The application uses a custom click.ParamType subclass to define a new input type. The attacker finds a flaw in the convert() method of this custom type, allowing them to bypass validation and provide malicious input.
  • Likelihood: Medium (Depends on the quality of the custom implementation)
  • Impact: Medium to High (Depends on what the custom type is used for)
  • Effort: Medium (Requires understanding the custom code)
  • Skill Level: Intermediate to Advanced
  • Detection Difficulty: Medium to Hard (Requires code review and potentially dynamic analysis)
  • Mitigation:
    • Thoroughly review and audit the convert() method of any custom click.ParamType subclasses.
    • Perform extensive fuzz testing on the custom type to identify unexpected behavior.
    • Follow secure coding practices when implementing the convert() method. Handle all possible error conditions and invalid input gracefully.
    • Consider using existing, well-tested validation libraries instead of creating custom types whenever possible.

Attack Tree Path: 1.5 Exploit Environment Variable Handling [HIGH-RISK]

• 1.5.1.1 Set unexpected or malicious values for environment variables used by Click or the application. [CRITICAL]
  • Description: The application uses environment variables for configuration. The attacker gains the ability to modify these environment variables (e.g., through a compromised process or a misconfigured system). They set the environment variables to unexpected or malicious values, causing the application to behave in an insecure way.
  • Likelihood: Medium
  • Impact: Low to High (Depends on what the environment variables control)
  • Effort: Low (If the attacker has access to the environment)
  • Skill Level: Novice to Intermediate
  • Detection Difficulty: Medium (Requires monitoring environment variable changes)
  • Mitigation:
    • Validate and sanitize all environment variables before using them. Do not assume they are safe.
    • Use a whitelist approach: only accept specific, expected values for environment variables.
    • Run the application with the minimum necessary privileges (principle of least privilege).
    • Consider using a dedicated configuration file instead of relying solely on environment variables.

Attack Tree Path: 3. Exploit Vulnerabilities in Click's Dependencies [HIGH-RISK]

• 3.1 Dependency Confusion
  • 3.1.1 If a malicious package with the same name as a Click dependency is published to a public repository, it could be installed instead. [CRITICAL]
    • Description: An attacker publishes a malicious package to a public package repository (like PyPI) with the same name as a legitimate dependency of Click (or a transitive dependency). If the application's dependency resolution process is misconfigured, it might install the malicious package instead of the legitimate one.
    • Likelihood: Low
    • Impact: Very High (Potential for arbitrary code execution)
    • Effort: Medium to High
    • Skill Level: Advanced
    • Detection Difficulty: Hard (Requires monitoring package installations and comparing checksums)
    • Mitigation:
      • Dependency Pinning: Pin all dependencies, including transitive dependencies, to specific versions in requirements.txt or Pipfile. Use a lock file (Pipfile.lock or requirements.txt generated with pip freeze).
      • Private Package Repository: Use a private package repository (like JFrog Artifactory or AWS CodeArtifact) to host trusted packages and control the source of dependencies.
      • Package Verification: Verify the integrity of downloaded packages using checksums or digital signatures.
      • Vulnerability Scanning: Regularly scan dependencies for known vulnerabilities using tools like pip-audit, safety, or Snyk.