Gemini CLI Security Skill

Overview

This skill adapts the Gemini CLI Security Extension's analysis methodology for the agent-studio framework. The original extension uses two MCP server patterns — a security analysis server and an OSV-Scanner integration — to provide dual-vector coverage. This skill implements equivalent analysis using native Claude Code tools (WebFetch for OSV.dev API, Grep/Bash for static analysis patterns).

Source repository: https://github.com/gemini-cli-extensions/security

License: Apache 2.0 Performance: 90% precision, 93% recall (OpenSSF CVE benchmark, TypeScript/JavaScript)

When to Use

• Before merging pull requests to detect introduced vulnerabilities

• During security reviews of new code changes

• For dependency auditing against known CVE databases

• For LLM-integrated applications requiring prompt injection defense review

• As part of CI/CD pipeline security gates

Iron Law

NO PRODUCTION CODE WITHOUT SECURITY ANALYSIS FOR AUTH/SECRETS/EXTERNAL-INPUT HANDLERS

All code paths handling authentication, hardcoded values, external input, or AI model outputs MUST be analyzed before production deployment.

Vulnerability Coverage

Category 1: Secrets Management

Pattern Detection Method

Hardcoded API keys Grep for key patterns + entropy analysis

Hardcoded passwords Credential keyword detection

Private keys in source PEM block / base64 key detection

Encryption keys Symmetric key constant patterns

Category 2: Injection Attacks

Attack Type Examples

SQL injection String concatenation in queries

XSS Unescaped user content in HTML/JS output

Command injection Shell exec with user-controlled args

SSRF User-controlled URLs in server requests

Template injection Unsanitized user input in template engines

Category 3: Authentication Flaws

Flaw Detection

Session bypass Missing auth middleware

Weak tokens Predictable token generation

Insecure password reset Token-less or email-only resets

Missing MFA enforcement Auth flows without 2FA checks

Category 4: Data Handling

Issue Detection

Weak cryptography MD5/SHA1 for secrets; DES/RC4 usage

Sensitive data in logs PII/credential patterns in log statements

PII violations Unencrypted PII storage or transmission

Insecure deserialization Unsafe pickle/eval/deserialize calls

Category 5: LLM Safety (Novel)

Risk Detection

Prompt injection User content injected into LLM prompts without sanitization

Unsafe output handling LLM output used in exec/eval/shell without validation

Insecure tool integration Tool calls with unchecked LLM-provided parameters

Usage

Invocation

// From an agent Skill({ skill: 'gemini-cli-security' });

// With arguments via Bash integration Skill({ skill: 'gemini-cli-security', args: 'src/ --scan-deps' });

Workflow Execution

Analyze code in a directory

node .claude/skills/gemini-cli-security/scripts/main.cjs --target src/

Scan dependencies for CVEs

node .claude/skills/gemini-cli-security/scripts/main.cjs --scan-deps

JSON output for CI integration

node .claude/skills/gemini-cli-security/scripts/main.cjs --target . --json

Scoped analysis with natural language

node .claude/skills/gemini-cli-security/scripts/main.cjs --target src/auth/ --scope "focus on token handling and session management"

Output Format

Default output (markdown report):

Security Analysis Report

CRITICAL

• [AUTH-001] Hardcoded API key found in src/config.ts:42 Pattern: const API_KEY = "sk-..." Remediation: Move to environment variable

HIGH

• [INJ-002] SQL injection risk in src/db/users.ts:87 Pattern: String concatenation in query builder Remediation: Use parameterized queries

Dependencies

• lodash@4.17.15 → CVE-2021-23337 (HIGH) - Prototype pollution Fix: Upgrade to lodash@4.17.21+

JSON output (--json flag):

{ "findings": [ { "id": "AUTH-001", "severity": "CRITICAL", "category": "secrets", "file": "src/config.ts", "line": 42, "description": "Hardcoded API key", "remediation": "Move to environment variable" } ], "dependencies": [ { "package": "lodash", "version": "4.17.15", "cve": "CVE-2021-23337", "severity": "HIGH", "fix": "4.17.21" } ], "summary": { "critical": 1, "high": 2, "medium": 3, "low": 0, "precision": 0.9, "recall": 0.93 } }

OSV.dev Dependency Scanning

The skill integrates with the OSV.dev API (no authentication required) to check dependencies:

// OSV.dev batch query endpoint WebFetch({ url: 'https://api.osv.dev/v1/querybatch', prompt: 'Extract vulnerability IDs, severity, and affected versions for these packages', });

Supported ecosystems: npm, PyPI, RubyGems, Maven, Go, Cargo, NuGet, Packagist

GitHub Actions Integration

The original extension supports PR analysis via GitHub Actions. This skill includes an equivalent workflow template:

.github/workflows/security.yml

name: Security Analysis on: [pull_request] jobs: security: runs-on: ubuntu-latest steps: - uses: actions/checkout@v4 - name: Run security analysis run: node .claude/skills/gemini-cli-security/scripts/main.cjs --target . --json

Implementation Notes

Why native tools over MCP servers: The original extension uses two MCP servers (security analysis server + OSV-Scanner binary). This skill uses native Claude Code tools instead:

• WebFetch replaces OSV-Scanner for dependency CVE lookups (OSV.dev has a public REST API)

• Grep/Bash replace the security analysis server for pattern-based detection

• This approach works immediately without binary installation or session restart

Deviation from source: The original uses Gemini AI for code analysis; this skill uses the pattern-based detection methodology documented in the extension's benchmarking. The AI analysis component can be provided by the invoking agent (security-architect) rather than an embedded AI call.

Assigned Agents

Agent Role

security-architect

Primary: comprehensive security audits

developer

Supporting: pre-commit security checks

code-reviewer

Supporting: PR review security layer

Memory Protocol (MANDATORY)

Before starting: Read .claude/context/memory/learnings.md

After completing:

• New vulnerability pattern found -> .claude/context/memory/learnings.md

• Issue with scanning -> .claude/context/memory/issues.md

• Decision about scope -> .claude/context/memory/decisions.md

ASSUME INTERRUPTION: If it's not in memory, it didn't happen.