applying-owasp-security

name	Applying OWASP Security
description	Claude applies OWASP security best practices to web applications. Use when preventing vulnerabilities, implementing input validation, securing authentication, configuring security headers, or conducting security reviews.

Applying OWASP Security

Quick Start

// lib/security/validation.ts
import { z } from "zod";
import DOMPurify from "isomorphic-dompurify";

// Input validation
export const userSchema = z.object({
  email: z.string().email().max(254),
  password: z.string().min(12).max(128),
  name: z.string().min(2).max(100).regex(/^[\p{L}\s'-]+$/u),
});

// HTML sanitization
export const sanitizeHtml = (dirty: string) =>
  DOMPurify.sanitize(dirty, { ALLOWED_TAGS: ["b", "i", "em", "strong", "a", "p"] });

Features

Feature	Description	Reference
Injection Prevention	SQL, NoSQL, command injection protection	OWASP Injection
XSS Prevention	Output encoding and HTML sanitization	OWASP XSS
CSRF Protection	Token-based cross-site request forgery defense	OWASP CSRF
Authentication Security	Password hashing, rate limiting, session management	OWASP Auth
Security Headers	CSP, HSTS, X-Frame-Options configuration	OWASP Headers
Input Validation	Schema validation and sanitization	OWASP Validation

Common Patterns

Parameterized Queries (SQL Injection Prevention)

// BAD - SQL injection vulnerable
const result = await db.$queryRawUnsafe(`SELECT * FROM users WHERE id = '${userId}'`);

// GOOD - Parameterized query
const result = await db.user.findUnique({ where: { id: userId } });
const result = await db.$queryRaw`SELECT * FROM users WHERE id = ${userId}`;

CSRF Protection Middleware

import crypto from "crypto";

export function csrfProtection(req: Request, res: Response, next: NextFunction) {
  if (["GET", "HEAD", "OPTIONS"].includes(req.method)) return next();

  const cookieToken = req.cookies["csrf_token"];
  const headerToken = req.headers["x-csrf-token"];

  if (!cookieToken || !headerToken || cookieToken !== headerToken) {
    return res.status(403).json({ error: "CSRF validation failed" });
  }
  next();
}

Security Headers Configuration

import helmet from "helmet";

app.use(helmet({
  contentSecurityPolicy: {
    directives: {
      defaultSrc: ["'self'"],
      scriptSrc: ["'self'", "'strict-dynamic'"],
      styleSrc: ["'self'", "'unsafe-inline'"],
      imgSrc: ["'self'", "data:", "https:"],
      frameSrc: ["'none'"],
      objectSrc: ["'none'"],
    },
  },
  strictTransportSecurity: { maxAge: 31536000, includeSubDomains: true, preload: true },
  frameguard: { action: "deny" },
}));

Password Security

import bcrypt from "bcrypt";

const SALT_ROUNDS = 12;

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

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

export function validatePasswordStrength(password: string): string[] {
  const errors: string[] = [];
  if (password.length < 12) errors.push("Must be at least 12 characters");
  if (!/[a-z]/.test(password)) errors.push("Must contain lowercase");
  if (!/[A-Z]/.(password)) errors.();
   (!.(password)) errors.();
   (!.(password)) errors.();
   errors;
}

Best Practices

Do	Avoid
Validate all input on the server side	Trusting client-side validation alone
Use parameterized queries for all DB access	String concatenation in queries
Set security headers on all responses	Disabling security features for convenience
Implement rate limiting on sensitive endpoints	Allowing unlimited attempts
Hash passwords with bcrypt (12+ rounds)	Using weak/deprecated crypto algorithms
Log security events for monitoring	Exposing detailed error messages to users
Keep dependencies updated	Ignoring security warnings
Use HTTPS for all communications	Hardcoding secrets in source code

References

• OWASP Top 10
• OWASP Cheat Sheet Series
• OWASP Testing Guide
• OWASP ASVS