threat-modeling.md

Threat Model Analysis for fmtlib/fmt

Threat: Format String Injection

• Description: An attacker provides a malicious format string as input, which is then processed by fmt::format or similar functions. The attacker aims to manipulate the formatting process to read sensitive data, cause a denial of service, or trigger unexpected behavior. They might achieve this by injecting format specifiers like %p (to read memory addresses), %n (to write to memory - less relevant in fmt), or by crafting complex format strings that exploit parsing vulnerabilities.
  • Impact:
    • Information Disclosure: Reading sensitive data from memory or application state.
    • Denial of Service (DoS): Causing resource exhaustion or application crashes.
    • Unexpected Application Behavior: Triggering errors or logic flaws leading to unpredictable outcomes.
  • Affected fmt component: fmt::format, fmt::runtime, format string parsing logic.
  • Risk severity: High
  • Mitigation strategies:
    • Avoid user-controlled format strings: Hardcode format strings whenever possible.
    • Input validation and sanitization: If user input influences formatting, strictly validate and sanitize the input, whitelisting allowed format specifiers.
    • Minimize fmt::runtime usage: Use fmt::runtime with extreme caution and treat dynamic format strings as untrusted input.
    • Regularly update fmtlib: Ensure you are using the latest version with security patches.

Threat: Bugs and Vulnerabilities in fmtlib Code

• Description: fmtlib itself, like any software, may contain undiscovered bugs or security vulnerabilities in its code. An attacker could potentially exploit these vulnerabilities to cause various impacts, depending on the nature of the bug. This could range from memory safety issues to logic errors, potentially leading to more severe consequences in critical vulnerabilities.
  • Impact:
    • Wide range of impacts depending on the vulnerability: crashes, memory corruption, information disclosure, potentially remote code execution in severe cases (though less likely in a formatting library, but still possible depending on the nature of the bug).
  • Affected fmt component: Core fmtlib library code, any module or function within the library.
  • Risk severity: High (can escalate to critical depending on the specific vulnerability).
  • Mitigation strategies:
    • Regularly update fmtlib: Staying up-to-date is crucial to receive bug fixes and security patches.
    • Monitor security advisories: Subscribe to security advisories and vulnerability databases related to fmtlib and its dependencies.
    • Static analysis and fuzzing: Use static analysis and fuzzing tools to proactively identify potential vulnerabilities in the application's usage of fmtlib and in fmtlib itself if possible.
    • Code review: Conduct regular code reviews to identify potential security issues in the application's integration with fmtlib.