threat-modeling.md

Threat Model Analysis for spf13/cobra

Threat: Command Structure Injection via Unvalidated Flag Values

• Threat: Command Structure Injection via Unvalidated Flag Values

  • Description: An attacker provides crafted input to a command's flags. This input is not treated as a simple value but is used in a way that alters the intended program logic or accesses resources inappropriately. The attacker manipulates the application's internal logic through Cobra's flag parsing, not by injecting shell commands. For example, a flag intended for a filename might be used to inject a path traversal sequence (../../), or a numeric ID flag might be used to inject a large number to cause a denial of service.
  • Impact:
    • Unauthorized file access (read or write).
    • Modification of application state.
    • Triggering of unintended application functions.
    • Denial of service (DoS) through resource exhaustion.
  • Cobra Component Affected:
    • Flags() and related methods (e.g., StringVar, IntVar, StringSliceVar, etc.) used to define command flags.
    • Run and RunE functions where flag values are used without proper validation.
    • PersistentFlags() if misused in subcommands (where a parent command's persistent flag influences a subcommand's behavior).
  • Risk Severity: High to Critical (depending on how flag values are used).
  • Mitigation Strategies:
    • Strict Input Validation: Implement rigorous validation for all flag values. Use allow-lists (whitelists) whenever possible. Validate data types, lengths, allowed characters, and formats (e.g., using regular expressions).
    • Type-Specific Validation: Use Cobra's type-specific flag functions (e.g., IntVar, Float64Var) to enforce basic type checking.
    • Custom Validation Functions: Use Cobra's RegisterFlagCompletionFunc (with caution, see separate threat) and custom validation logic within PreRun or RunE to perform more complex validation checks.
    • Contextual Validation: Validate flag values in the context of their intended use. For example, if a flag represents a file path, ensure it's a valid and safe path within the application's allowed scope.
    • Avoid Direct Use in Sensitive Operations: Do not directly use unvalidated flag values in security-sensitive operations like file system access, database queries, or system calls. Sanitize and escape the input appropriately.

Threat: Misuse of PreRun and PostRun Hooks

• Threat: Misuse of PreRun and PostRun Hooks

  • Description: The application uses PreRun or PostRun hooks to perform actions based on flag values or other user input. If this input is not validated within the hooks, an attacker could manipulate these hooks to perform unauthorized actions. This is a direct vulnerability because it involves the misuse of a specific Cobra feature.
  • Impact:
    • Similar to command structure injection, but localized to the PreRun or PostRun context.
    • Unauthorized file access, modification of application state, or triggering of unintended functions.
  • Cobra Component Affected:
    • PreRun, PreRunE, PostRun, and PostRunE fields of the cobra.Command struct.
  • Risk Severity: High.
  • Mitigation Strategies:
    • Input Validation within Hooks: Thoroughly validate all input used within PreRun and PostRun hooks, just as you would within the main Run function. This is the most critical mitigation.
    • Avoid Security-Sensitive Operations: Minimize the use of PreRun and PostRun for security-sensitive operations. If necessary, ensure these operations are performed with appropriate safeguards.
    • Consider Alternatives: If possible, refactor the code to perform the necessary actions within the main Run function, where input validation is already expected and more naturally enforced.

Threat: Denial of Service (DoS) via Unbounded Flag Input (Specifically StringSliceVar and unbounded Args)

• Threat: Denial of Service (DoS) via Unbounded Flag Input (Specifically StringSliceVar and unbounded Args)

  • Description: An attacker provides excessively large input to a StringSliceVar flag, or a very large number of arguments to a command that accepts a variable number of arguments without proper limits. This causes the application to allocate excessive memory, leading to a denial of service. This is directly related to Cobra because it involves the misuse of specific flag types and argument handling.
  • Impact:
    • Application crash due to out-of-memory errors.
    • System instability due to excessive memory consumption.
    • Denial of service for other users or processes.
  • Cobra Component Affected:
    • Flags().StringSliceVar() when used without length/count limits.
    • Commands that accept a variable number of arguments (using Args in the cobra.Command struct) without validation (e.g., missing cobra.MaximumNArgs).
  • Risk Severity: High
  • Mitigation Strategies:
    • Slice Size Limits: For StringSliceVar, implement custom validation (e.g., in PreRunE) to check the length of the slice and enforce a reasonable maximum.
    • Argument Count Limits: If a command accepts a variable number of arguments, always set a reasonable maximum limit using cobra.Command.Args (e.g., cobra.MaximumNArgs(10)). This is a direct and effective mitigation.
    • Input Length Limits (for individual strings): Even within a slice, limit the length of individual strings accepted.
    • Resource Monitoring: Monitor application resource usage (memory, CPU) and implement alerts or automatic termination if limits are exceeded.