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Security Code Review

Purpose

Systematically review code for security vulnerabilities, identify potential attack vectors, and ensure implementation follows secure coding practices to protect against common exploits.

When to Use

• Reviewing code before deployment
• Analyzing security-sensitive features (authentication, payments, data handling)
• Conducting security audits
• Investigating potential security incidents
• Validating third-party integrations

Key Capabilities

1. OWASP Top 10 Detection - Identify common web application vulnerabilities
2. Secure Coding Validation - Verify adherence to security best practices
3. Authentication/Authorization Review - Validate access control implementations

Approach

1. Identify Security-Critical Areas

   • Authentication and session management
   • Authorization and access control
   • Input validation and sanitization
   • Data encryption and storage
   • External API interactions

2. Check for Common Vulnerabilities

   • Injection flaws (SQL, command, LDAP)
   • Broken authentication
   • Sensitive data exposure
   • XML external entities (XXE)
   • Broken access control
   • Security misconfiguration
   • Cross-site scripting (XSS)
   • Insecure deserialization
   • Using components with known vulnerabilities
   • Insufficient logging and monitoring

3. Validate Security Controls

   • Input validation on all user inputs
   • Output encoding to prevent XSS
   • Parameterized queries to prevent SQL injection
   • Proper session management
   • Secure password storage (bcrypt, argon2)
   • HTTPS enforcement
   • CSRF protection
   • Rate limiting on sensitive endpoints

4. Review Cryptographic Implementations

   • Use of strong algorithms (AES-256, RSA-2048+)
   • Proper key management
   • Secure random number generation
   • Certificate validation

5. Check Configuration Security

   • No hardcoded credentials
   • Secrets in environment variables or vaults
   • Secure headers (CSP, HSTS, X-Frame-Options)
   • Minimal exposed services
   • Proper error handling (no stack traces to users)

Example

Context : Reviewing authentication endpoint

Code Under Review :

@app.route('/login', methods=['POST'])
def login():
    username = request.form['username']
    password = request.form['password']
    
    user = db.execute(
        f"SELECT * FROM users WHERE username='{username}' AND password='{password}'"
    ).fetchone()
    
    if user:
        session['user_id'] = user['id']
        return redirect('/dashboard')
    return "Invalid credentials"

Security Issues Identified :

1. SQL Injection (Critical) : String concatenation in query
2. Plaintext Passwords (Critical) : No password hashing
3. Missing CSRF Protection (High) : No token validation
4. Information Disclosure (Medium) : Generic error message is good, but could add rate limiting
5. No Account Lockout (Medium) : Vulnerable to brute force
6. Session Fixation Risk (Medium) : Should regenerate session ID after login

Secure Implementation :

from werkzeug.security import check_password_hash
from flask import session, request, redirect
from flask_wtf.csrf import CSRFProtect
import secrets

@app.route('/login', methods=['POST'])
@limiter.limit("5 per minute")  # Rate limiting
def login():
    # CSRF protection (via flask_wtf)
    if not validate_csrf(request.form.get('csrf_token')):
        return "Invalid request", 403
    
    username = request.form.get('username', '').strip()
    password = request.form.get('password', '')
    
    # Input validation
    if not username or not password:
        return "Invalid credentials", 401
    
    # Parameterized query prevents SQL injection
    user = db.execute(
        "SELECT id, password_hash, failed_attempts, locked_until "
        "FROM users WHERE username = ?",
        (username,)
    ).fetchone()
    
    # Check account lockout
    if user and user['locked_until'] and user['locked_until'] > datetime.now():
        return "Account temporarily locked", 429
    
    # Check password with timing-safe comparison
    if user and check_password_hash(user['password_hash'], password):
        # Reset failed attempts
        db.execute("UPDATE users SET failed_attempts = 0 WHERE id = ?", (user['id'],))
        
        # Regenerate session to prevent fixation
        session.clear()
        session['user_id'] = user['id']
        session['csrf_token'] = secrets.token_hex(32)
        
        # Log successful login
        log_security_event('login_success', user_id=user['id'], ip=request.remote_addr)
        
        return redirect('/dashboard')
    
    # Track failed attempts
    if user:
        attempts = user['failed_attempts'] + 1
        if attempts >= 5:
            locked_until = datetime.now() + timedelta(minutes=15)
            db.execute(
                "UPDATE users SET failed_attempts = ?, locked_until = ? WHERE id = ?",
                (attempts, locked_until, user['id'])
            )
        else:
            db.execute("UPDATE users SET failed_attempts = ? WHERE id = ?", (attempts, user['id']))
    
    # Log failed attempt
    log_security_event('login_failure', username=username, ip=request.remote_addr)
    
    return "Invalid credentials", 401

Expected Result : Secure authentication with:

• SQL injection prevention
• Secure password handling
• CSRF protection
• Rate limiting
• Account lockout
• Session security
• Audit logging

Best Practices

• ✅ Use parameterized queries or ORMs to prevent injection
• ✅ Hash passwords with bcrypt/argon2, never store plaintext
• ✅ Validate and sanitize all user inputs
• ✅ Use HTTPS for all communications
• ✅ Implement proper session management
• ✅ Apply principle of least privilege
• ✅ Keep dependencies updated and scan for vulnerabilities
• ✅ Log security events for monitoring
• ✅ Use security headers (CSP, HSTS, X-Frame-Options)
• ✅ Implement rate limiting on sensitive endpoints
• ✅ Store secrets in environment variables or vaults
• ❌ Avoid: Trusting user input without validation
• ❌ Avoid: Rolling your own cryptography
• ❌ Avoid: Exposing detailed error messages to users
• ❌ Avoid: Hardcoding credentials or API keys
• ❌ Avoid: Using deprecated or weak cryptographic algorithms

Weekly Installs

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Repository

dasien/retrowarden

GitHub Stars

4

First Seen

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Security Audits

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