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Threat Model Analysis for pallets/click

Threat: Unexpected Input Type Bypass (Leading to Code Injection)

  • Description: An attacker crafts malicious input that bypasses Click's type conversion (e.g., a string that looks like a number but contains hidden characters, or exploiting edge cases in custom click.ParamType implementations). The attacker specifically targets scenarios where this bypassed input is then used unsafely in a code execution context (e.g., eval, exec, shell command construction, SQL query building).
    • Impact: The attacker achieves arbitrary code execution within the application, potentially leading to complete system compromise.
    • Affected Click Component: click.ParamType, custom type converters, built-in types (if misused or if edge cases exist, and the result is used in a vulnerable way).
    • Risk Severity: High (if leading to RCE, otherwise could be lower).
    • Mitigation Strategies:
      • Implement robust custom validators within Click (click.ParamType) that go beyond basic type checking. Validate length, character sets, and expected patterns.
      • Perform secondary input validation after Click's parsing, treating all input as potentially malicious. Sanitize and escape input appropriately specifically for the code execution context it will be used in (e.g., shell escaping, SQL escaping).
      • Avoid using Click's parsed input directly in any code execution context. If unavoidable, use parameterized queries (for SQL) or safer alternatives to eval/exec.
      • Use a "whitelist" approach to validation.

Threat: Default Value Manipulation (Leading to Code Execution)

  • Description: An attacker modifies a configuration file, environment variable, or other source used to provide default values for Click options. The attacker sets a malicious default value that, when used by the application without further validation, results in code execution (e.g., the default value is used directly in a shell command).
    • Impact: The application executes arbitrary code provided by the attacker, potentially leading to complete system compromise.
    • Affected Click Component: click.option (specifically the default parameter), external configuration sources, and any code that uses the default value unsafely.
    • Risk Severity: High to Critical (depending on the context of the code execution).
    • Mitigation Strategies:
      • Hardcode default values within the application code whenever possible.
      • If defaults must come from external sources, treat them as untrusted input. Validate and sanitize them rigorously before using them in any code execution context.
      • Use a secure configuration file format and protect the configuration file from unauthorized modification.
      • Implement access controls to limit who can modify the configuration source.
      • Avoid using default values directly in security-sensitive operations like shell command construction.

Threat: Terminal Injection via click.echo

  • Description: An attacker provides input that, when displayed using click.echo, contains terminal escape sequences. The attacker crafts these sequences to manipulate the terminal, potentially executing commands or exfiltrating data.
    • Impact: The attacker gains control of the user's terminal, potentially executing arbitrary commands, stealing data displayed on the terminal, or disrupting the user's session.
    • Affected Click Component: click.echo.
    • Risk Severity: High.
    • Mitigation Strategies:
      • Sanitize all output passed to click.echo. Remove or escape any characters that could be interpreted as terminal escape sequences.
      • Use a dedicated library for terminal output that provides built-in sanitization and protection against terminal injection.
      • Avoid displaying raw, untrusted data directly with click.echo.

Threat: Unsafe Use of click.prompt Input (Leading to Code Injection)

  • Description: An attacker provides malicious input to a click.prompt call. This input is then used without proper validation or sanitization directly in a code execution context (e.g., constructing a shell command, building an SQL query, using eval or exec).
    • Impact: The attacker achieves code injection, leading to arbitrary command execution and potential system compromise.
    • Affected Click Component: click.prompt, and any code that uses the result of click.prompt in a vulnerable way.
    • Risk Severity: High to Critical (depending on the specific code execution context).
    • Mitigation Strategies:
      • Treat all input from click.prompt as untrusted.
      • Implement rigorous input validation and sanitization before using the input in any code execution context.
      • Use appropriate escaping techniques based on the context (e.g., shell escaping, SQL escaping). Use parameterized queries for SQL.
      • Avoid using user-provided input directly in eval, exec, or shell command construction.

Threat: Path Traversal via click.open_file

  • Description: An attacker provides a crafted file path to click.open_file (or a Click option that uses it internally) that includes ".." sequences or other path manipulation techniques. The attacker aims to access files outside the intended directory.
    • Impact: The attacker can read, write, or delete files outside the application's intended scope, potentially leading to information disclosure, data corruption, denial of service, or even code execution (if the attacker can overwrite executable files).
    • Affected Click Component: click.open_file, options that accept file paths.
    • Risk Severity: High.
    • Mitigation Strategies:
      • Validate all file paths received from untrusted input. Ensure they are within the expected directory and do not contain ".." or other path traversal sequences.
      • Use a whitelist of allowed file paths or directories, if feasible.
      • Use absolute paths instead of relative paths.
      • Consider using a chroot jail or other sandboxing techniques to restrict the application's file system access.

Threat: Callback Injection

  • Description: An attacker manages to inject malicious code into a callback function used by Click. This is most likely if callbacks are dynamically loaded or constructed from untrusted sources.
    • Impact: Arbitrary code execution with the privileges of the application. This could lead to complete system compromise.
    • Affected Click Component: Callback functions used with click.option, click.argument, click.command, etc.
    • Risk Severity: Critical.
    • Mitigation Strategies:
      • Avoid dynamically generating or loading callback functions from untrusted sources. Hardcode callback functions whenever possible.
      • If dynamic loading is absolutely necessary, use a strict whitelist of allowed functions and ensure the source is trusted and tamper-proof.
      • Implement code signing and verification for dynamically loaded code.