Agent skill
auth-module-builder
Implements secure authentication patterns including login/registration, session management, JWT tokens, password hashing, cookie settings, and CSRF protection. Provides auth routes, middleware, security configurations, and threat model documentation. Use when building "authentication", "login system", "JWT auth", or "session management".
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/security/auth-module-builder-patricio0312rev-skillset-5d9112ae
SKILL.md
Auth Module Builder
Implement secure, production-ready authentication systems.
Core Components
Routes: POST /login, /register, /logout, /refresh, /forgot-password Middleware: authenticate, requireAuth, optionalAuth Security: bcrypt hashing, JWT signing, secure cookies, CSRF tokens Session: Redis/DB storage, expiration, refresh tokens Threats: Document common attacks and mitigations
JWT Pattern
// Generate tokens
const accessToken = jwt.sign(
{ userId: user.id, email: user.email },
process.env.JWT_SECRET,
{ expiresIn: "15m" }
);
const refreshToken = jwt.sign(
{ userId: user.id, type: "refresh" },
process.env.JWT_REFRESH_SECRET,
{ expiresIn: "7d" }
);
// Verify middleware
export const authenticate = async (req, res, next) => {
const token = req.headers.authorization?.split(" ")[1];
if (!token) return res.status(401).json({ error: "No token" });
try {
const decoded = jwt.verify(token, process.env.JWT_SECRET);
req.user = await User.findById(decoded.userId);
next();
} catch (err) {
res.status(401).json({ error: "Invalid token" });
}
};
Session Pattern
// Express session with Redis
app.use(
session({
store: new RedisStore({ client: redisClient }),
secret: process.env.SESSION_SECRET,
resave: false,
saveUninitialized: false,
cookie: {
secure: process.env.NODE_ENV === "production",
httpOnly: true,
maxAge: 1000 * 60 * 60 * 24 * 7, // 7 days
sameSite: "lax",
},
})
);
Password Security
import bcrypt from "bcrypt";
// Hash password
const hashedPassword = await bcrypt.hash(password, 10);
// Verify password
const isValid = await bcrypt.compare(password, user.hashedPassword);
Security Checklist
- Passwords hashed with bcrypt (cost ≥10)
- JWT secrets from environment, rotated regularly
- HTTPS only in production
- httpOnly, secure cookies
- CSRF protection enabled
- Rate limiting on auth routes
- Account lockout after failed attempts
- Password reset tokens expire
- Email verification for new accounts
Threat Model
Brute Force: Rate limit + account lockout Token Theft: Short expiry, httpOnly cookies, HTTPS only CSRF: SameSite cookies + CSRF tokens Session Fixation: Regenerate session ID on login XSS: Sanitize inputs, CSP headers
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