semgrep-rule-creator

To write Semgrep rules for security vulnerabilities, use a test-first approach by creating vulnerable and safe test cases with ruleid and ok annotations before authoring the YAML configuration to ensure reliable correctness guarantees.

Use Semgrep taint mode for data-flow vulnerabilities involving sources, sinks, and sanitizers. Use pattern matching for syntactic checks to detect specific bug patterns. Taint mode is preferred for tracking untrusted data propagation across your codebase.

Test Semgrep rules by generating a test file with required ok and ruleid annotations, then running semgrep --test. Iterate between AST understanding and rule adjustments using Semgrep validation until all tests pass to minimize false positives and false negatives.

Your Semgrep pattern may not match because it differs from how Semgrep actually parses the target language. Use Semgrep AST inspection to align patterns with the parsed syntax, and validate with semgrep --test to ensure rule correctness.

The correct structure for a Semgrep rule enforces a per-rule directory layout containing exactly one YAML rule file and one test file. This production-grade output structure ensures strict testing and validated semantics for your security rules.

Yes, you must review WebFetch-backed Semgrep documentation before implementation. This ensures your rules comply with strict testing standards, avoid generic patterns, and correctly utilize taint mode or pattern matching features.