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Use when implementing authentication/authorization, securing user input, or preventing OWASP Top 10 vulnerabilities — including custom security implementations such as hashing passwords with bcrypt/ar
The skill file stays in the publisher's repository.
Paste the copied command in a terminal. It installs this SKILL.md into that agent.
npx skills add Jeffallan/claude-skills --skill secure-code-guardian -a cursor -y
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.
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.
After each implementation step, verify:
' OR 1=1--) are rejected; confirm XSS payloads (<script>alert(1)</script>) are escaped or rejected.curl -I, Mozilla Observatory) that security headers are present and CORS origin allowlist is correct.Load detailed guidance based on context:
| Topic | Reference | Load When |
|---|---|---|
| OWASP | references/owasp-prevention.md | OWASP Top 10 patterns |
| Authentication | references/authentication.md | Password hashing, JWT |
| Input Validation | references/input-validation.md | Zod, SQL injection |
| XSS/CSRF | references/xss-csrf.md | XSS prevention, CSRF |
| Headers | references/security-headers.md | Helmet, rate limiting |
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' });
});
When implementing security features, provide:
OWASP Top 10, bcrypt/argon2, JWT, OAuth 2.0, OIDC, CSP, CORS, rate limiting, input validation, output encoding, encryption (AES, RSA), TLS, security headers
Maintained by @jeffallan, Principal Consultant at Synergetic Solutions