semgrep-rule-variant-creator
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- Unspecified (assume cross-platform)
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- Read-only
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- 26 variants
Profile is derived at build time from SKILL.md and install vectors. Subject to drift from author intent.
Heads up: 未限定 allowed-tools，默认拥有全部工具权限。
---
name: semgrep-rule-variant-creator
description: Creates language variants of existing Semgrep rules. Use when porting a Semgrep rule to specifie…
category: engineering
runtime: no special runtime
---
# semgrep-rule-variant-creator output preview
## PART A: Task fit
- Use case: Creates language variants of existing Semgrep rules. Use when porting a Semgrep rule to specified target languages. Takes an existing rule and target languages as input, produces independent rule+test directories for each language..
- Inputs: target material, constraints, expected output, and acceptance criteria.
- Evidence boundary: follow “When to Use / When NOT to Use / Input Specification” and do not present inference as author intent.
## PART B: Execution result
- **01** The card summarizes the use case; runtime output centers on “Creates language variants of existing Semgrep rules. Use when porting a Semgrep rule to specified target languages. Takes an existing rule and target languages as input, produces independent rule+test directories for each language.”.
- **02** When the source has headings, the agent prioritizes “When to Use / When NOT to Use / Input Specification” so the result follows the author’s structure.
- **03** Typical output includes task judgment, concrete steps, required commands or file edits, validation, and follow-up options.
- **04** Risk context follows the fingerprint: read files, write/modify files; mostly runs locally; usually needs no extra API key.
## Running Rules
- read files, write/modify files; mostly runs locally; usually needs no extra API key.
- Validate with a small sample before expanding scope.
- Return the result, validation criteria, and next iteration options.The source does not require a stable slash command. After installation, invoke the skill by name and describe the task.
Name target files or source material, expected output, forbidden changes, and whether network or shell access is allowed. Permission fingerprint: read files, write/modify files.
Start with a small task and check whether the result follows “When to Use / When NOT to Use / Input Specification”. Inspect diffs, logs, previews, or tests before expanding scope.
Confirm the final output includes a concrete result, evidence, and next action. If it stays generic, tighten inputs, boundaries, and acceptance criteria.
---
name: semgrep-rule-variant-creator
description: Creates language variants of existing Semgrep rules. Use when porting a Semgrep rule to specifie…
category: engineering
source: trailofbits/skills
---
# semgrep-rule-variant-creator
## When to use
- Creates language variants of existing Semgrep rules. Use when porting a Semgrep rule to specified target languages. Ta…
- Use it when the task has clear inputs, repeatable steps, and validation criteria.
## What to provide
- Target material, scope, expected result, and forbidden changes.
- Whether network, commands, file writes, or external services are allowed.
## Execution rules
- Organize steps around “When to Use / When NOT to Use / Input Specification” and keep inference separate from source facts.
- read files, write/modify files; mostly runs locally; usually needs no extra API key.
- Validate with a small sample before expanding the task.
## Output requirements
- Return the deliverable, key evidence, validation method, and next action.
- Mark missing information as unknown; do not invent commands, platforms, or dependencies.The author source anchors workflow facts; repository files anchor sources and commands; Fluxly only adds fit, limitations, and quality judgment.
skill "semgrep-rule-variant-creator" {
input -> user goal + target files + boundaries + acceptance criteria
context -> When to Use / When NOT to Use / Input Specification
rules -> SKILL.md triggers / order / output contract
runtime -> no special runtime | read files, write/modify files | mostly runs locally
guardrails -> usually needs no extra API key + small-sample validation + diff/log review
output -> copyable result + checklist + next iteration
}Semgrep Rule Variant Creator
Port existing Semgrep rules to new target languages with proper applicability analysis and test-driven validation.
When to Use
Ideal scenarios:
- Porting an existing Semgrep rule to one or more target languages
- Creating language-specific variants of a universal vulnerability pattern
- Expanding rule coverage across a polyglot codebase
- Translating rules between languages with equivalent constructs
When NOT to Use
Do NOT use this skill for:
- Creating a new Semgrep rule from scratch (use
semgrep-rule-creatorinstead) - Running existing rules against code
- Languages where the vulnerability pattern fundamentally doesn't apply
- Minor syntax variations within the same language
Input Specification
This skill requires:
- Existing Semgrep rule - YAML file path or YAML rule content
- Target languages - One or more languages to port to (e.g., "Golang and Java")
Output Specification
For each applicable target language, produces:
<original-rule-id>-<language>/
├── <original-rule-id>-<language>.yaml # Ported Semgrep rule
└── <original-rule-id>-<language>.<ext> # Test file with annotationsExample output for porting sql-injection to Go and Java:
sql-injection-golang/
├── sql-injection-golang.yaml
└── sql-injection-golang.go
sql-injection-java/
├── sql-injection-java.yaml
└── sql-injection-java.javaRationalizations to Reject
When porting Semgrep rules, reject these common shortcuts:
| Rationalization | Why It Fails | Correct Approach |
|---|---|---|
| "Pattern structure is identical" | Different ASTs across languages | Always dump AST for target language |
| "Same vulnerability, same detection" | Data flow differs between languages | Analyze target language idioms |
| "Rule doesn't need tests since original worked" | Language edge cases differ | Write NEW test cases for target |
| "Skip applicability - it obviously applies" | Some patterns are language-specific | Complete applicability analysis first |
| "I'll create all variants then test" | Errors compound, hard to debug | Complete full cycle per language |
| "Library equivalent is close enough" | Surface similarity hides differences | Verify API semantics match |
| "Just translate the syntax 1:1" | Languages have different idioms | Research target language patterns |
Strictness Level
This workflow is strict - do not skip steps:
- Applicability analysis is mandatory: Don't assume patterns translate
- Each language is independent: Complete full cycle before moving to next
- Test-first for each variant: Never write a rule without test cases
- 100% test pass required: "Most tests pass" is not acceptable
Overview
This skill guides the creation of language-specific variants of existing Semgrep rules. Each target language goes through an independent 4-phase cycle:
FOR EACH target language:
Phase 1: Applicability Analysis → Verdict
Phase 2: Test Creation (Test-First)
Phase 3: Rule Creation
Phase 4: Validation
(Complete full cycle before moving to next language)Foundational Knowledge
The semgrep-rule-creator skill is the authoritative reference for Semgrep rule creation fundamentals. While this skill focuses on porting existing rules to new languages, the core principles of writing quality rules remain the same.
Consult semgrep-rule-creator for guidance on:
- When to use taint mode vs pattern matching - Choosing the right approach for the vulnerability type
- Test-first methodology - Why tests come before rules and how to write effective test cases
- Anti-patterns to avoid - Common mistakes like overly broad or overly specific patterns
- Iterating until tests pass - The validation loop and debugging techniques
- Rule optimization - Removing redundant patterns after tests pass
When porting a rule, you're applying these same principles in a new language context. If uncertain about rule structure or approach, refer to semgrep-rule-creator first.
Four-Phase Workflow
Phase 1: Applicability Analysis
Before porting, determine if the pattern applies to the target language.
Analysis criteria:
- Does the vulnerability class exist in the target language?
- Does an equivalent construct exist (function, pattern, library)?
- Are the semantics similar enough for meaningful detection?
Verdict options:
APPLICABLE→ Proceed with variant creationAPPLICABLE_WITH_ADAPTATION→ Proceed but significant changes neededNOT_APPLICABLE→ Skip this language, document why
See applicability-analysis.md for detailed guidance.
Phase 2: Test Creation (Test-First)
Always write tests before the rule.
Create test file with target language idioms:
- Minimum 2 vulnerable cases (
ruleid:) - Minimum 2 safe cases (
ok:) - Include language-specific edge cases
// ruleid: sql-injection-golang
db.Query("SELECT * FROM users WHERE id = " + userInput)
// ok: sql-injection-golang
db.Query("SELECT * FROM users WHERE id = ?", userInput)Phase 3: Rule Creation
- Analyze AST:
semgrep --dump-ast -l <lang> test-file - Translate patterns to target language syntax
- Update metadata: language key, message, rule ID
- Adapt for idioms: Handle language-specific constructs
See language-syntax-guide.md for translation guidance.
Phase 4: Validation
# Validate YAML
semgrep --validate --config rule.yaml
# Run tests
semgrep --test --config rule.yaml test-fileCheckpoint: Output MUST show All tests passed.
For taint rule debugging:
semgrep --dataflow-traces -f rule.yaml test-fileSee workflow.md for detailed workflow and troubleshooting.
Quick Reference
| Task | Command |
|---|---|
| Run tests | semgrep --test --config rule.yaml test-file |
| Validate YAML | semgrep --validate --config rule.yaml |
| Dump AST | semgrep --dump-ast -l <lang> <file> |
| Debug taint flow | semgrep --dataflow-traces -f rule.yaml file |
Key Differences from Rule Creation
| Aspect | semgrep-rule-creator | This skill |
|---|---|---|
| Input | Bug pattern description | Existing rule + target languages |
| Output | Single rule+test | Multiple rule+test directories |
| Workflow | Single creation cycle | Independent cycle per language |
| Phase 1 | Problem analysis | Applicability analysis per language |
| Library research | Always relevant | Optional (when original uses libraries) |
Documentation
REQUIRED: Before porting rules, read relevant Semgrep documentation:
- Rule Syntax - YAML structure and operators
- Pattern Syntax - Pattern matching and metavariables
- Pattern Examples - Per-language pattern references
- Testing Rules - Testing annotations
- Trail of Bits Testing Handbook - Advanced patterns
Next Steps
- For applicability analysis guidance, see applicability-analysis.md
- For language translation guidance, see language-syntax-guide.md
- For detailed workflow and examples, see workflow.md
Decide Fit First
Design Intent
How To Use It
Boundaries And Review