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Mitigation Strategies Analysis for urfave/cli

Mitigation Strategy: Strict Input Validation and Sanitization (CLI-Focused)

Description:

  1. Identify All urfave/cli Input Points: List all flags and arguments defined using urfave/cli (e.g., StringFlag, IntFlag, StringSliceFlag, etc.).
  2. Define Expected Input Formats: For each flag and argument, define the precise expected format. Use regular expressions, whitelists, and length/value constraints. Go beyond urfave/cli's basic type checking.
  3. Implement Validation After urfave/cli Parsing: Within the Action function of each urfave/cli command (or in a function called by the Action), add code to validate each flag and argument value against its defined format. Use Go's regexp package and standard library functions.
  4. Reject Invalid Input: If validation fails, immediately return an error from the Action function (using fmt.Errorf or a custom error type). urfave/cli will then typically display the error message and usage information.
  5. Sanitize (if necessary, and with extreme caution): If the validated input must be used in a context requiring escaping (e.g., shell commands), use context-aware escaping after validation. Prefer avoiding shell commands entirely.
  6. Test CLI Input: Create unit tests that specifically test the urfave/cli commands with various valid and invalid inputs, including edge cases. Use the cli.App.Run function in your tests to simulate command execution.

Threats Mitigated:

  • Command Injection (via CLI flags/arguments): (Severity: Critical) - Prevents attackers from injecting malicious code through CLI input.
  • Denial of Service (DoS) via Resource Exhaustion (partial, CLI-specific): (Severity: High) - Reduces DoS risk by limiting input size and values passed through the CLI.
  • Information Disclosure (partial, CLI-specific): (Severity: Medium) - Helps prevent disclosure by ensuring CLI input conforms to expectations.

Impact:

  • Command Injection: Risk significantly reduced (near elimination for CLI-based injection if implemented correctly).
  • DoS: Risk partially reduced (limits CLI-based DoS attacks).
  • Information Disclosure: Risk partially reduced (prevents some CLI-based information disclosure).

Currently Implemented:

  • cmd/server/start.go - Basic type checking using urfave/cli's IntFlag and StringFlag.
  • cmd/user/create.go - Regular expression validation for username format (within the Action function).

Missing Implementation:

  • cmd/data/import.go - No validation on the --file flag (a StringFlag). Needs regular expression validation and potentially path sanitization within the Action function.
  • cmd/server/config.go - No length limits on string flags. Needs length restrictions added to the flag definitions and checked within the Action function.
  • No consistent validation strategy across all commands. Needs a unified approach.

Mitigation Strategy: Custom Error Handling (CLI-Specific)

Description:

  1. Identify urfave/cli Error Points: Focus on the Action functions of your urfave/cli commands, as these are the primary points where errors will be returned to the user.
  2. Create Custom Error Types (Optional): Consider defining custom error types for CLI-specific errors.
  3. Log Detailed Errors (Internally): Log detailed error information (including stack traces, if appropriate) to an internal log file before returning the error from the Action function.
  4. Present Generic User Messages (via urfave/cli): Return only generic, non-revealing error messages from the Action function. urfave/cli will display these messages to the user. Avoid exposing internal details.
  5. Override Default urfave/cli Error Handlers: Use App.ExitErrHandler (for global error handling) or Command.OnUsageError (for command-specific usage errors) to customize how urfave/cli handles and displays errors. This allows you to control the formatting and content of error messages.
  6. Test Error Output: Create unit tests that specifically test the error output of your urfave/cli commands, ensuring that appropriate (generic) error messages are displayed to the user.

Threats Mitigated:

  • Information Disclosure (via CLI error messages): (Severity: Medium) - Prevents attackers from gaining information through overly verbose CLI error messages.

Impact:

  • Information Disclosure: Risk significantly reduced (prevents information disclosure via CLI error messages).

Currently Implemented:

  • cmd/server/start.go - Uses a custom error handler (within the Action function) to log detailed errors and return a generic message.

Missing Implementation:

  • cmd/data/import.go - Directly returns errors from os/exec to the user (via the Action function), potentially revealing system information. Needs custom error handling within the Action.
  • App.ExitErrHandler and Command.OnUsageError are not used consistently. Needs a project-wide strategy for customizing urfave/cli's error handling.

Mitigation Strategy: Input Size and Rate Limiting (CLI-Focused)

Description:

  1. Identify Resource-Intensive urfave/cli Commands: Determine which CLI commands consume significant resources.
  2. Implement Input Size Limits (within Action functions): For string flags and arguments defined by urfave/cli, enforce maximum length limits within the Action function, after parsing. For numeric flags, enforce maximum and minimum values.
  3. Rate Limiting (Less Common for CLIs, but consider): If the CLI is exposed in a way that allows for repeated, automated invocations (e.g., via SSH), consider implementing rate limiting. This is less common for typical CLI usage but important in specific scenarios.
  4. Timeout Handling (within Action functions): Set timeouts for any operations within the Action functions that involve external resources or long-running calculations. Use Go's context package.
  5. Test Resource Limits: Create tests that specifically try to trigger resource exhaustion and rate limiting (if implemented) by providing large inputs or making rapid calls to the CLI.

Threats Mitigated:

  • Denial of Service (DoS) via Resource Exhaustion (CLI-specific): (Severity: High) - Reduces DoS risk by limiting resource consumption triggered by CLI input.

Impact:

  • DoS: Risk significantly reduced (limits CLI-based DoS attacks).

Currently Implemented:

  • cmd/server/start.go - Has timeouts for network connections (within the Action function).

Missing Implementation:

  • No input size limits on most urfave/cli flags. Needs length and value restrictions added to flag definitions and checked within the Action functions.
  • No rate limiting implemented. Needs to be considered if the CLI is exposed in a way that allows for abuse.

Mitigation Strategy: Flag Combination Validation

Description:

  1. Identify Potentially Dangerous Flag Combinations: Analyze your urfave/cli commands and identify any combinations of flags that could lead to unexpected behavior, security vulnerabilities, or data corruption.
  2. Implement Validation Logic (within Action functions): After urfave/cli parses the flags, add code within the Action function to check for invalid or dangerous flag combinations.
  3. Reject Invalid Combinations: If an invalid combination is detected, return an error from the Action function, preventing further processing.
  4. Test Flag Combinations: Create unit tests that specifically test various combinations of flags, including both valid and invalid combinations.

Threats Mitigated:

  • Information Disclosure (via unexpected flag combinations): (Severity: Medium) - Prevents attackers from discovering sensitive information by exploiting unusual flag combinations.
  • Logic Errors/Unexpected Behavior: (Severity: Variable) - Prevents unexpected application behavior caused by invalid flag combinations.

Impact:

  • Information Disclosure: Risk reduced (prevents some forms of information disclosure).
  • Logic Errors: Risk reduced (prevents unexpected behavior).

Currently Implemented:

  • None.

Missing Implementation:

  • Needs analysis of all commands to identify potentially dangerous flag combinations. Validation logic needs to be added to the Action functions of relevant commands. Example: If a command has a --dry-run flag and a --force flag, ensure that --force is ignored or an error is returned when --dry-run is also specified.

Mitigation Strategy: Review and Customize Default Help Text

Description:

  1. Generate Help Text: Use urfave/cli's built-in help generation (usually by running the application with no arguments or with --help).
  2. Review for Sensitive Information: Carefully review the generated help text for each command. Look for any information that could be considered sensitive, such as internal file paths, default credentials (even if they are placeholders), or details about the application's architecture.
  3. Customize Help Text: Use urfave/cli's options to customize the help text. This includes:
    • App.Name, App.Usage, App.Description
    • Command.Name, Command.Usage, Command.Description, Command.UsageText, Command.HelpName
    • Flag.Name, Flag.Usage, Flag.EnvVars (be careful with environment variables in help text)
  4. Remove Unnecessary Information: Remove any information that is not essential for users to understand how to use the command.
  5. Test Help Text Generation: After customizing, regenerate the help text and review it again to ensure the changes are correct.

Threats Mitigated:

  • Information Disclosure (via help text): (Severity: Low to Medium) - Reduces the risk of inadvertently disclosing sensitive information through the CLI's help output.

Impact:

  • Information Disclosure: Risk reduced (prevents some forms of information disclosure).

Currently Implemented:

  • Basic usage of urfave/cli's default help generation.

Missing Implementation:

  • Needs a thorough review of the generated help text for all commands.
  • Needs customization to remove any potentially sensitive information and improve clarity.