security-patterns

Security Patterns

When to Load

• Trigger: Auth flows, encryption, secrets management, CORS configuration, input validation, rate limiting
• Skip: No security surface involved in the current task

Security Implementation Workflow

Copy this checklist and track progress:

Security Implementation Progress:
- [ ] Step 1: Choose authentication strategy
- [ ] Step 2: Implement authorization model
- [ ] Step 3: Set up password hashing
- [ ] Step 4: Configure secrets management
- [ ] Step 5: Enable encryption (transit + rest)
- [ ] Step 6: Configure CORS
- [ ] Step 7: Add rate limiting
- [ ] Step 8: Validate against anti-patterns checklist

Authentication Patterns

JWT (JSON Web Tokens)

import jwt from "jsonwebtoken";

function generateTokens(user: User) {
  const accessToken = jwt.sign(
    { sub: user.id, role: user.role },
    process.env.JWT_SECRET!,
    { expiresIn: "15m", algorithm: "HS256" },
  );
  const refreshToken = jwt.sign(
    { sub: user.id, tokenVersion: user.tokenVersion },
    process.env.JWT_REFRESH_SECRET!,
    { expiresIn: "7d" },
  );
  return { accessToken, refreshToken };
}

// WRONG: localStorage (XSS vulnerable) | CORRECT: httpOnly cookie for refresh, memory for access
res.cookie("refreshToken", refreshToken, {
  httpOnly: true,
  secure: true,
  sameSite: "strict",
  maxAge: 7 * 24 * 60 * 60 * 1000,
  path: "/api/auth/refresh",
});

JWT Verification Middleware

function authenticate(req: Request, res: Response, next: NextFunction) {
  const header = req.headers.authorization;
  if (!header?.startsWith("Bearer ")) {
    return res.status(401).json({ error: "Missing token" });
  }

  try {
    const token = header.slice(7);
    const payload = jwt.verify(token, process.env.JWT_SECRET!) as JwtPayload;
    req.user = { id: payload.sub, role: payload.role };
    next();
  } catch (err) {
    if (err instanceof jwt.TokenExpiredError) {
      return res.status(401).json({ error: "Token expired" });
    }
    return res.status(401).json({ error: "Invalid token" });
  }
}