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attack-surface.md

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Attack Surface Analysis for briannesbitt/carbon

Attack Surface: Critical: Unvalidated Input

  • Description: Carbon's parsing functions (like parse(), createFromFormat()) can be vulnerable to injection attacks if user-supplied input is not properly validated. If an attacker can control the format string or the input string, they could potentially inject malicious code.
  • How Carbon Contributes: Carbon's flexibility in parsing various date and time formats, while powerful, can be dangerous if not used with extreme caution. The createFromFormat() function, if used with a user-supplied format string, is particularly risky.
  • Example: An attacker could inject format specifiers that cause unexpected behavior, potentially leading to denial of service or even arbitrary code execution if the parsed date is used in a vulnerable context (e.g., in an eval() call or similar).
  • Impact: Remote Code Execution (RCE), Denial of Service (DoS), Information Disclosure.
  • Mitigation:
    • Strictly validate and sanitize all user-supplied input before passing it to Carbon functions. Use whitelisting (allow only known-good formats) rather than blacklisting (trying to filter out bad formats).
    • Avoid using user-supplied format strings with createFromFormat(). If you must, use a very strict whitelist of allowed formats. Prefer parse() with a fixed, trusted format string whenever possible.
    • Use a well-defined and restricted set of allowed date/time formats. Avoid overly permissive formats that could be abused.
    • Consider using a dedicated date/time validation library before passing data to Carbon. This adds an extra layer of defense.

Attack Surface: High: Timezone Manipulation

  • Description: Incorrect handling of timezones can lead to logic errors, data corruption, and potential security vulnerabilities. If the application relies on accurate timezone calculations for security-critical operations (e.g., access control, session management), incorrect timezone handling can be exploited.
  • How Carbon Contributes: While Carbon provides timezone support, it relies on the underlying system's timezone database and PHP's timezone handling. Misconfiguration or outdated timezone data can lead to incorrect results.
  • Example: An attacker might try to manipulate the timezone to bypass time-based restrictions, such as bypassing rate limiting or accessing resources outside of allowed time windows. They might also try to cause data inconsistencies by exploiting differences in timezone handling.
  • Impact: Bypass of security controls, data corruption, denial of service (in some cases).
  • Mitigation:
    • Always explicitly set the default timezone. Use date_default_timezone_set() or a similar mechanism to ensure a consistent timezone across the application.
    • Use UTC for internal storage and calculations whenever possible. Convert to local timezones only for display purposes.
    • Validate and sanitize user-supplied timezone information. Use a whitelist of allowed timezones.
    • Regularly update the system's timezone database (tzdata).
    • Be aware of daylight saving time (DST) transitions and handle them correctly.

Attack Surface: High: Locale-Dependent Parsing Issues

  • Description: Different locales have different date/time formats. If the application doesn't handle locales correctly, it can lead to parsing errors or unexpected behavior.
  • How Carbon Contributes: Carbon's parsing functions can be influenced by the system's locale settings. If the application doesn't explicitly set the locale, it might use a default locale that doesn't match the expected input format.
  • Example: An attacker might provide a date string that is valid in one locale but invalid in the server's default locale, leading to parsing errors or incorrect date interpretation.
  • Impact: Data corruption, denial of service, potential bypass of validation checks.
  • Mitigation:
    • Explicitly set the locale for date/time parsing. Use setlocale() or Carbon's locale-aware methods (e.g., parse('...', 'fr_FR')) to ensure consistent parsing behavior.
    • Validate user-supplied locale information. If users can specify a locale, ensure it's a valid and supported locale.
    • Consider using a standardized date/time format (e.g., ISO 8601) for internal storage and exchange.

Attack Surface: High: Integer Overflow/Underflow (Less Likely, but Possible)

  • Description: While less common with modern PHP versions, extremely large or small timestamp values could potentially lead to integer overflow or underflow issues in some calculations.
  • How Carbon Contributes: Carbon deals with timestamps, which are often represented as integers.
  • Example: An attacker might try to provide a timestamp that, when manipulated, causes an integer overflow or underflow, leading to unexpected behavior.
  • Impact: Unpredictable behavior, potential denial of service.
  • Mitigation:
    • Use 64-bit systems. 64-bit systems have a much larger range for integers, making overflow/underflow less likely.
    • Validate input ranges. Ensure that date/time values are within reasonable bounds.
    • Use appropriate data types. Ensure that variables used to store timestamps are large enough to handle the expected range of values.

Attack Surface: High: Regular Expression Denial of Service (ReDoS) (Low Probability, but worth mentioning)

  • Description: Although Carbon itself doesn't heavily rely on regular expressions for parsing, it's possible that some internal functions or underlying PHP date/time functions might use regular expressions that are vulnerable to ReDoS attacks.
  • How Carbon Contributes: Indirectly, through its reliance on underlying PHP functions.
  • Example: An attacker could craft a specially designed date string that triggers a catastrophic backtracking scenario in a regular expression used for parsing.
  • Impact: Denial of service.
  • Mitigation:
    • Keep PHP updated: PHP updates often include security fixes, including those related to regular expression handling.
    • Avoid custom regular expressions for date/time parsing if possible. Rely on Carbon's built-in parsing functions, which are generally more robust.
    • If you must use custom regular expressions, carefully analyze them for potential ReDoS vulnerabilities. Use tools like regex101.com to test and analyze your regular expressions.