mitigations.md

Mitigation Strategies Analysis for pallets/click

Mitigation Strategy: Sanitize User Input from Click Options and Arguments

Description:

1. Explicitly define input types using click's parameter types (click.INT, click.FLOAT, click.Path, click.Choice, etc.) in @click.option and @click.argument decorators. This provides initial type validation at the click level.
2. Utilize click.Choice for options that accept a limited set of valid values. This restricts user input to predefined choices directly within click's parsing.
3. Implement custom validation logic within your Click command functions. After click parses the input, add Python code to further validate the data based on your application's specific requirements and security policies. This goes beyond basic type checking and allows for business rule validation.
4. For string inputs received via click options or arguments, apply sanitization techniques such as regular expressions or allowlists within your command functions to restrict characters and patterns. This is crucial for preventing injection attacks originating from user-provided command-line input.
   • Threats Mitigated:
     • Command Injection (High Severity) - Through unsanitized input passed via click parameters.
     • Path Traversal (High Severity) - If file paths are accepted through click.Path without further validation.
     • Cross-Site Scripting (XSS) if outputting to web (Medium Severity) - If click output is used in web context and input is not sanitized.
     • Data Integrity Issues (Medium Severity) - Invalid input from command-line arguments leading to application errors.
   • Impact:
     • Command Injection: High reduction in risk. Directly sanitizing click input is key to preventing this.
     • Path Traversal: High reduction in risk. Validating click.Path input confines file access.
     • XSS: Medium reduction in risk. Sanitization of click output helps mitigate XSS if output is web-bound.
     • Data Integrity Issues: High reduction in risk. click type validation and custom checks ensure data validity.
   • Currently Implemented: Partially implemented. click parameter types are used in some areas, and click.Choice might be used for specific options, but consistent custom validation and sanitization within command functions are lacking.
     • Location: cli.py - parameter definitions use some types and click.Choice in places, but validation logic in command functions is inconsistent.
   • Missing Implementation: Systematically implement custom validation functions and sanitization for all relevant click options and arguments, especially those handling strings and file paths, within the command functions in cli.py and related modules.

Mitigation Strategy: Path Traversal Prevention using click.Path Features

Description:

1. Leverage click.Path with resolve_path=True and path_type=Path for all file path parameters. resolve_path=True within click.Path resolves symbolic links and normalizes paths, while path_type=Path ensures you work with pathlib.Path objects directly from click.
2. Utilize click.Path's exists, file_okay, dir_okay, readable, writable, executable parameters to enforce basic file system checks directly within click parameter definition. This validates file existence and permissions at the click parsing stage.
3. Combine click.Path with manual path confinement checks. After click processing, use pathlib.Path.resolve().is_relative_to(base_directory) to verify that the resolved path from click.Path is within an expected base directory. This adds an extra layer of security beyond click's built-in checks.
   • Threats Mitigated:
     • Path Traversal (High Severity) - By misusing or bypassing click.Path's intended file path handling.
     • Unauthorized File Access (High Severity) - Gaining access to files outside the intended scope through click.Path parameters.
   • Impact:
     • Path Traversal: High reduction in risk. Properly using click.Path features and confinement checks is very effective.
     • Unauthorized File Access: Medium to High reduction in risk. Depends on the strictness of base directory definition and usage of click.Path parameters.
   • Currently Implemented: Partially implemented. click.Path is used, but resolve_path=True, path_type=Path, and is_relative_to checks are not consistently applied. Built-in click.Path checks (exists, etc.) might be underutilized.
     • Location: cli.py - some file path parameters use click.Path, but not always with recommended settings and confinement checks are missing.
   • Missing Implementation: Enforce resolve_path=True, path_type=Path for all click.Path parameters. Consistently use built-in click.Path checks where applicable. Implement is_relative_to checks in command functions handling file paths from click.Path in cli.py and related modules.

Mitigation Strategy: Secure Prompting with click.prompt

Description:

1. Always use hide_input=True in click.prompt when prompting for sensitive information like passwords or API keys. This prevents the input from being echoed on the terminal, reducing the risk of shoulder surfing.
2. Apply input validation and sanitization to the input obtained from click.prompt just as you would for click.option and click.argument. Validate the format, length, and content of the prompted input within your command function.
3. Consider using click.password_prompt() as a more specialized alternative to click.prompt(hide_input=True) for password input. click.password_prompt() is designed specifically for password prompting and may offer additional security considerations.
   • Threats Mitigated:
     • Information Disclosure (Low Severity) - Passwords echoed on screen during click.prompt.
     • Input Validation Issues (Medium Severity) - Invalid or malicious input provided through click.prompt.
   • Impact:
     • Information Disclosure: Low reduction in risk (primarily cosmetic for password echoing). hide_input=True effectively addresses this.
     • Input Validation Issues: Medium to High reduction in risk. Validating click.prompt input ensures data integrity.
   • Currently Implemented: Partially implemented. hide_input=True might be used for password prompts, but consistent input validation for data from click.prompt is not guaranteed. click.password_prompt() might not be used.
     • Location: Command functions using click.prompt in cli.py.
   • Missing Implementation: Ensure hide_input=True is consistently used for sensitive prompts. Implement input validation and sanitization for all data obtained from click.prompt. Evaluate and potentially switch to click.password_prompt() for password inputs.

Mitigation Strategy: Review Click Command Structure for Unintended Functionality and Authorization

Description:

1. Carefully design your Click command structure (commands, subcommands, options, arguments) to reflect intended functionality and access control. Ensure that the command hierarchy logically represents the application's features and user roles.
2. Implement authorization checks within your Click command functions. Based on user roles or permissions, verify if the current user is authorized to execute the requested command and access the specified resources (e.g., files, data) indicated by click parameters.
3. Test various combinations of Click commands, subcommands, options, and arguments to identify any unintended execution paths or authorization bypasses. Focus on testing edge cases and unexpected input combinations to uncover potential logical flaws in your command structure.
   • Threats Mitigated:
     • Authorization Bypass (Medium to High Severity) - Exploiting unintended command combinations in click to bypass access controls.
     • Logical Vulnerabilities (Medium Severity) - Flaws in click command structure leading to unexpected or insecure behavior.
   • Impact:
     • Authorization Bypass: Medium to High reduction in risk. Well-designed click structure and authorization checks are crucial.
     • Logical Vulnerabilities: Medium reduction in risk. Reduces the likelihood of logical flaws in command execution flow.
   • Currently Implemented: Partially implemented. Command structure is designed, but explicit authorization checks within command functions and dedicated security review of command combinations are likely missing.
     • Location: cli.py - command and subcommand definitions and logic. Authorization logic might be present but not consistently applied or reviewed in the context of click command structure.
   • Missing Implementation: Implement robust authorization checks within relevant command functions in cli.py. Conduct a security review specifically focused on the click command structure and potential authorization bypasses through command combinations.

Mitigation Strategy: Secure Handling of Shell Completion Scripts Generated by Click

Description:

1. Review the shell completion scripts generated by click (using your_cli --bash-completion, etc.). Examine the scripts for any potential security vulnerabilities, such as unintended command execution or information leaks within the completion logic.
2. If distributing shell completion scripts, ensure they are served over secure channels (HTTPS) and integrity is verified (e.g., using checksums). Prevent modification of completion scripts during distribution.
3. Consider the security implications of enabling shell completion, especially in shared or less trusted environments. In highly sensitive environments, disabling shell completion might be a more secure default.
4. Regenerate and review shell completion scripts after any changes to the Click application's command structure. Ensure that updates to the CLI do not introduce new vulnerabilities in the completion scripts.
   • Threats Mitigated:
     • Information Disclosure (Low Severity) - Shell completion scripts potentially revealing internal paths or command structures.
     • Minor Security Risks (Low Severity) - In rare cases, poorly designed completion scripts could introduce minor vulnerabilities.
   • Impact:
     • Information Disclosure: Low reduction in risk. Reviewing completion scripts minimizes information leakage.
     • Minor Security Risks: Low reduction in risk. Mitigates potential minor security issues in completion script logic.
   • Currently Implemented: Not implemented. Shell completion scripts are generated by click, but they are not actively reviewed for security implications, and distribution/handling is not secured.
     • Location: Shell completion script generation process (user-initiated). Distribution and usage are outside the application's direct control but need consideration.
   • Missing Implementation: Implement a process to review generated shell completion scripts for security vulnerabilities. Define secure distribution and handling procedures for completion scripts if they are offered to users. Evaluate the necessity of enabling shell completion based on the application's security context.