secure-code-guardian

Jeffallan/claude-skillsSecurityAudit passedSnapshot d9162c9e2aa1

Summary

Use when implementing authentication/authorization, securing user input, or preventing OWASP Top 10 vulnerabilities — including custom security implementations such as hashing passwords with bcrypt/argon2, sanitizing SQL queries with parameterized statements, configuring CORS/CSP headers, validating input with Zod, and setting up JWT tokens. Invoke for authentication, authorization, input validation, encryption, OWASP Top 10 prevention, secure session management, and security hardening. For pre-built OAuth/SSO integrations or standalone security audits, consider a more specialized skill.

SKILL.md

Secure Code Guardian

Core Workflow

Threat model — Identify attack surface and threats
Design — Plan security controls
Implement — Write secure code with defense in depth; see code examples below
Validate — Test security controls with explicit checkpoints (see below)
Document — Record security decisions

Validation Checkpoints

After each implementation step, verify:

Authentication: Test brute-force protection (lockout/rate limit triggers), session fixation resistance, token expiration, and invalid-credential error messages (must not leak user existence).
Authorization: Verify horizontal and vertical privilege escalation paths are blocked; test with tokens belonging to different roles/users.
Input handling: Confirm SQL injection payloads (' OR 1=1--) are rejected; confirm XSS payloads (<script>alert(1)</script>) are escaped or rejected.
Headers/CORS: Validate with a security scanner (e.g., curl -I, Mozilla Observatory) that security headers are present and CORS origin allowlist is correct.

Reference Guide

Load detailed guidance based on context:

Topic	Reference	Load When

import bcrypt from 'bcrypt';

const SALT_ROUNDS = 12; // minimum 10; 12 balances security and performance

export async function hashPassword(plaintext: string): Promise<string> {
  return bcrypt.hash(plaintext, SALT_ROUNDS);
}

export async function verifyPassword(plaintext: string, hash: string): Promise<boolean> {
  return bcrypt.compare(plaintext, hash);
}

// NEVER: `SELECT * FROM users WHERE email = '${email}'`
// ALWAYS: use positional parameters
import { Pool } from 'pg';
const pool = new Pool();

export async function getUserByEmail(email: string) {
  const { rows } = await pool.query(
    'SELECT id, email, role FROM users WHERE email = $1',
    [email]  // value passed separately — never interpolated
  );
  return rows[0] ?? null;
}

import { z } from 'zod';

const LoginSchema = z.object({
  email: z.string().email().max(254),
  password: z.string().min(8).max(128),
});

export function validateLoginInput(raw: unknown) {
  const result = LoginSchema.safeParse(raw);
  if (!result.success) {
    // Return generic error — never echo raw input back
    throw new Error('Invalid credentials format');
  }
  return result.data;
}

import jwt from 'jsonwebtoken';

const JWT_SECRET = process.env.JWT_SECRET!; // never hardcode

export function verifyToken(token: string): jwt.JwtPayload {
  // Throws if expired, tampered, or wrong algorithm
  const payload = jwt.verify(token, JWT_SECRET, {
    algorithms: ['HS256'],   // explicitly allowlist algorithm
    issuer: 'your-app',
    audience: 'your-app',
  });
  if (typeof payload === 'string') throw new Error('Invalid token payload');
  return payload;
}

import express from 'express';
import rateLimit from 'express-rate-limit';
import helmet from 'helmet';

const app = express();
app.use(helmet()); // sets CSP, HSTS, X-Frame-Options, etc.
app.use(express.json({ limit: '10kb' })); // limit payload size

const authLimiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 10,                   // 10 attempts per window per IP
  standardHeaders: true,
  legacyHeaders: false,
});

app.post('/api/login', authLimiter, async (req, res) => {
  // 1. Validate input
  const { email, password } = validateLoginInput(req.body);

  // 2. Authenticate — parameterized query, constant-time compare
  const user = await getUserByEmail(email);
  if (!user || !(await verifyPassword(password, user.passwordHash))) {
    // Generic message — do not reveal whether email exists
    return res.status(401).json({ error: 'Invalid credentials' });
  }

  // 3. Authorize — issue scoped, short-lived token
  const token = jwt.sign(
    { sub: user.id, role: user.role },
    JWT_SECRET,
    { algorithm: 'HS256', expiresIn: '15m', issuer: 'your-app', audience: 'your-app' }
  );

  // 4. Secure response — token in httpOnly cookie, not body
  res.cookie('token', token, { httpOnly: true, secure: true, sameSite: 'strict' });
  return res.json({ message: 'Authenticated' });
});

secure-code-guardian

Summary

SKILL.md

Secure Code Guardian

Core Workflow

Validation Checkpoints

Reference Guide

Constraints

MUST DO

MUST NOT DO

Code Examples

Password Hashing (bcrypt)

Parameterized SQL Query (Node.js / pg)

Input Validation with Zod

JWT Validation

Securing an Endpoint — Full Flow

Output Templates

Knowledge Reference

Related skills