CTF Flag Validator

Aimed at learners and organizers, this tool validates flags, computes scores, and tracks challenge data for CTF exercises and prep.

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About This Tool

The tool provides a structured model for CTF challenges and a deterministic evaluation method. It accepts a set of challenges with id, name, points, and a flag_pattern that defines valid submissions. When user_attempts are provided, each submission is checked against its corresponding flag_pattern using regex matching. Correct matches award the assigned points, while repeated correct submissions do not accrue additional points. The result is a per-challenge verdict and a total score for the run. This approach ensures repeatable scoring across sessions and events. Benefits include rapid feedback for learners, clear auditing for instructors, and scalable scoring for large teams. Use cases cover classroom practice, online training, and tournament preparation, where consistent evaluation and challenge catalog management are essential. Unique differentiators include strict pattern-based validation, explicit non-credit for duplicates, and a clean separation between challenge metadata and evaluation logic, enabling easy imports/exports and reproducible runs.

How to Use

  1. Provide challenges with id, name, points, and flag_pattern (regex).
  2. Provide user_attempts with challenge_id and submitted_flag for each challenge.
  3. Run the calculation to obtain per-challenge results and total_score.
  4. Review outputs to identify solved vs unsolved challenges and to adjust strategy or difficulty.
  5. Optional: export results for records or import a new catalog for a different event.
How to use online tool buuctf

Frequently Asked Questions

Find Quick Answers

What happens if a submitted flag matches multiple challenges?
Each submission is evaluated against its associated challenge via its flag_pattern. If a submitted flag could match more than one pattern, only the match with the corresponding challenge will be considered; cross-challenge matches do not grant duplicate points.
Can I reuse a solved flag to earn more points later?
No. Points are awarded once per challenge per run. Re-submitting a previously solved flag yields zero additional points to prevent inflation of scores.
What if a challenge uses a complex scoring rule?
The tool supports per-challenge fixed points. If you need dynamic scoring (e.g., partial points), model that behavior in the challenge’s points field and document it in the metadata; the core engine maintains a consistent per-run calculation.
Is historical data preserved across runs?
Historical runs are not required by default. You can enable data persistence to keep per-run results, enabling trend analysis and performance tracking over time.

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