Gitlab CI Validator

GitLab CI/CD Validator

Validates, lints, tests, and secures GitLab CI/CD pipeline configurations (.gitlab-ci.yml files) across three layers: syntax/schema validation, best practices analysis, and security scanning.

Core Validation Workflow

1. Syntax Validation (Required first)

bash scripts/validate_gitlab_ci.sh --syntax-only .gitlab-ci.yml

Checks: YAML structure, GitLab CI schema compliance, job definitions, stage references, dependency graphs (needs/dependencies/extends), include configurations (component, project, remote, local, template), circular dependency detection, and GitLab limits (500 jobs max, 255-char job names, 50 max needs, 100 max components).

Action: Fix all syntax errors before proceeding.

2. Best Practices Review (Recommended)

bash scripts/validate_gitlab_ci.sh --best-practices .gitlab-ci.yml

Checks: Cache usage for dependency installation, artifact expiration settings, DAG optimization with needs, parallel execution opportunities, Docker image version pinning, deprecated only/except → rules migration, missing timeouts and retries, resource group usage.

Action: Review suggestions and apply relevant optimizations.

3. Security Audit (Required)

bash scripts/validate_gitlab_ci.sh --security-only .gitlab-ci.yml

Checks: Hardcoded secrets and credentials, component security (version pinning, trusted sources), remote include integrity, insecure script patterns (curl | bash, eval), SSL/TLS verification bypasses, dangerous file permissions (chmod 777), overly broad artifact paths, variable masking, path traversal in local includes.

Action: Fix all critical and high-severity issues immediately.

4. Local Pipeline Testing (Optional)

# Install gitlab-ci-local first (requires Docker and Node.js)
bash scripts/install_tools.sh

# Test pipeline locally
gitlab-ci-local

# Or via the validator script
bash scripts/validate_gitlab_ci.sh --test-only .gitlab-ci.yml

Simulates local pipeline execution to test job ordering, dependencies, and environment setup. Requires Docker and gitlab-ci-local.

5. Complete Validation

# Full validation (all three layers)
bash scripts/validate_gitlab_ci.sh .gitlab-ci.yml

# Strict mode (fail on warnings)
bash scripts/validate_gitlab_ci.sh .gitlab-ci.yml --strict

Usage

Validation Options

bash scripts/validate_gitlab_ci.sh .gitlab-ci.yml --syntax-only
bash scripts/validate_gitlab_ci.sh .gitlab-ci.yml --best-practices
bash scripts/validate_gitlab_ci.sh .gitlab-ci.yml --security-only
bash scripts/validate_gitlab_ci.sh .gitlab-ci.yml --no-best-practices
bash scripts/validate_gitlab_ci.sh .gitlab-ci.yml --no-security
bash scripts/validate_gitlab_ci.sh .gitlab-ci.yml --strict

Individual Validators

python3 scripts/validate_syntax.py .gitlab-ci.yml
python3 scripts/check_best_practices.py .gitlab-ci.yml
python3 scripts/check_security.py .gitlab-ci.yml

Output Example

════════════════════════════════════════════════════════════════════════════════
  Validation Summary
════════════════════════════════════════════════════════════════════════════════

Syntax Validation:      PASSED
Best Practices:         WARNINGS
Security Scan:          PASSED

✓ All validation checks passed

CI/CD Integration

stages:
  - validate

validate_pipeline:
  stage: validate
  script:
    - pip3 install PyYAML
    - bash .claude/skills/gitlab-ci-validator/scripts/validate_gitlab_ci.sh .gitlab-ci.yml --strict

Adding Custom Validation Rules

Add custom rules directly to the relevant script:

# In check_best_practices.py
def _check_custom_rule(self):
    """Check for custom organization rule"""
    for job_name, job in self.config.items():
        if not self._is_job(job_name):
            continue
        if 'tags' not in job:
            self.issues.append(BestPracticeIssue(
                'warning',
                self._get_line(job_name),
                f"Job '{job_name}' should specify runner tags",
                'custom-missing-tags',
                "Add 'tags' to select appropriate runners"
            ))

• Syntax rules: scripts/validate_syntax.py
• Best practice rules: scripts/check_best_practices.py
• Security rules: scripts/check_security.py

Requirements

• Python 3.7+
• PyYAML: pip3 install PyYAML
• Bash: For the orchestrator script

Anti-Patterns

NEVER skip syntax validation before running gitlab-ci-local

• WHY: Local execution without pre-validation produces obscure runtime errors; resolve schema and syntax errors first to get actionable output.
• BAD: Run gitlab-ci-local on an untested config and debug runtime failures.
• GOOD: Run bash scripts/validate_gitlab_ci.sh --syntax-only .gitlab-ci.yml first; proceed to local testing only after syntax passes.

NEVER ignore only/except deprecation warnings

• WHY: Pipelines using deprecated keywords will break when GitLab removes them; treat these as errors, not warnings.
• BAD: Leave only: [main] after the validator flags it as deprecated.
• GOOD: Migrate to rules: syntax during the same fix session.

NEVER validate the pipeline file without also checking all referenced include: targets

• WHY: A valid base file with an invalid include template causes mysterious pipeline failures at queue time.
• BAD: Validate only .gitlab-ci.yml and skip templates/*.yml includes.
• GOOD: Validate all local include files as well; the validator checks include:local paths automatically.

NEVER run --strict as the first validation step on an unfamiliar pipeline

• WHY: Strict mode fails on warnings and produces noise that obscures real errors; establish a baseline first.
• BAD: Run --strict on an inherited pipeline and skip the output because it has 50 warnings.
• GOOD: Run without --strict first; fix errors and critical warnings, then enable strict mode as a CI gate.

References

• docs/gitlab-ci-reference.md — Complete GitLab CI/CD YAML syntax reference
• docs/best-practices.md — Detailed best practices guide
• docs/common-issues.md — Common issues and solutions
• docs/RULES.md — Full validation rules catalog (syntax, best practice, security)
• examples/basic-pipeline.gitlab-ci.yml — Simple three-stage pipeline
• examples/docker-build.gitlab-ci.yml — Docker build and push workflow
• examples/multi-stage.gitlab-ci.yml — Multi-stage pipeline with DAG
• examples/complex-workflow.gitlab-ci.yml — Advanced workflow with all features
• examples/component-pipeline.gitlab-ci.yml — GitLab 17.0+ pipeline using CI/CD components

# Test with examples
bash scripts/validate_gitlab_ci.sh examples/basic-pipeline.gitlab-ci.yml
bash scripts/validate_gitlab_ci.sh examples/component-pipeline.gitlab-ci.yml

Fetching Latest Documentation

When encountering custom GitLab features or version-specific requirements, this skill can:

1. Use Context7 MCP to fetch version-aware GitLab documentation
2. Use WebSearch to find latest GitLab CI/CD documentation
3. Use WebFetch to retrieve specific pages from docs.gitlab.com

Note: This skill validates GitLab CI/CD configurations but does not execute pipelines. Use GitLab's CI Lint tool or gitlab-ci-local for testing actual pipeline execution.