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Attack Surface Analysis for briannesbitt/carbon

Attack Surface: Denial of Service (DoS) via Complex Input Strings

  • Description: An attacker crafts and submits intentionally complex or ambiguous date/time strings that, when processed by Carbon's parsing functions (like Carbon::parse() or Carbon::createFromFormat()), consume excessive server resources (CPU, memory) leading to application slowdown or unavailability. This is due to the inherent complexity of parsing a wide range of date/time formats, which can become computationally expensive with maliciously crafted inputs.
    • Carbon Contribution: Carbon's design to handle flexible date/time parsing, while a feature, becomes a point of vulnerability when faced with adversarial inputs designed to exploit parsing complexity. The library's parsing logic is directly responsible for processing these strings and incurring the resource cost.
    • Example: An attacker targets an application endpoint that uses Carbon::parse($_GET['date']) without input validation. They send numerous requests with extremely long, nested, or ambiguous date strings (e.g., strings with repeated timezones, unusual separators, or excessive length) specifically crafted to maximize Carbon's parsing time.
    • Impact: Application performance degrades significantly, potentially leading to unresponsiveness or complete service outage. Critical application functions relying on date/time processing become unavailable. Server resources can be exhausted, impacting other applications on the same server.
    • Risk Severity: High
    • Mitigation Strategies:
      • Strict Input Validation: Implement robust input validation before passing date/time strings to Carbon. Define and enforce expected date/time formats using regular expressions or whitelists. Reject any input that deviates from the expected format or exceeds reasonable length limits.
      • Parsing Timeouts (Application Level): Implement application-level timeouts for date/time parsing operations. If Carbon's parsing takes longer than a defined threshold, interrupt the operation and return an error. This prevents indefinite resource consumption.
      • Rate Limiting: Apply rate limiting to endpoints that process user-provided date/time inputs to restrict the number of requests from a single IP address or user within a given timeframe, mitigating the impact of bulk DoS attempts.
      • Resource Monitoring and Alerting: Continuously monitor server resource utilization (CPU, memory) and set up alerts to detect unusual spikes that might indicate a DoS attack targeting date/time parsing.