Secure Coding

OWASP Secure Coding Practices

Input Validation

• Validate All Input: Validate all input from untrusted sources (user input, APIs, files)
• Whitelist Approach: Use whitelisting (allow-list) instead of blacklisting
• Validate Type, Length, Format: Validate data type, length, and format
• Sanitize Output: Encode output to prevent injection attacks
• Canonicalize Input: Canonicalize input before validation to prevent bypasses

Output Encoding

• Context-Specific Encoding: Use encoding appropriate for the context (HTML, JavaScript, URL, CSS)
• Encode User-Generated Content: Encode all user-generated content before output
• Use Framework Encoding: Use framework-provided encoding functions
• Avoid Manual Encoding: Avoid manual encoding as it's error-prone

Authentication

• Strong Passwords: Enforce strong password policies (length, complexity, rotation)
• Secure Password Storage: Use strong, slow hashing algorithms (bcrypt, Argon2, scrypt)
• Multi-Factor Authentication: Implement MFA for sensitive operations
• Secure Session Management: Use secure, HTTP-only, SameSite cookies
• Session Expiration: Implement appropriate session timeout
• Secure Password Reset: Implement secure password reset mechanisms

Authorization

• Principle of Least Privilege: Grant minimum necessary permissions
• Role-Based Access Control: Implement RBAC for authorization
• Attribute-Based Access Control: Consider ABAC for complex authorization
• Deny by Default: Deny access by default, explicitly allow
• Check Authorization on Every Request: Verify authorization on every request
• Avoid IDOR: Prevent Insecure Direct Object References

Cryptography

• Use Standard Algorithms: Use well-vetted, standard cryptographic algorithms
• Avoid Rolling Your Own Crypto: Never implement custom cryptography
• Use Secure Key Management: Properly generate, store, and rotate keys
• Use Authenticated Encryption: Use authenticated encryption (AEAD) when possible
• Avoid Deprecated Algorithms: Avoid MD5, SHA1, RC4, DES, etc.
• Use TLS: Use TLS for all network communications

Error Handling

• Generic Error Messages: Use generic error messages for users
• Detailed Logging: Log detailed error information server-side
• Don't Leak Information: Avoid leaking sensitive information in errors
• Handle Exceptions: Properly handle exceptions to prevent information disclosure
• Custom Error Pages: Use custom error pages to prevent information leakage

Language-Specific Security Considerations

JavaScript/TypeScript

• XSS Prevention: Use frameworks with built-in XSS protection (React, Vue, Angular)
• Content Security Policy: Implement CSP to mitigate XSS
• Avoid eval(): Avoid using eval() and similar dynamic code execution
• Validate JSON: Validate JSON input before parsing
• Use Strict Mode: Use strict mode to catch common errors
• Sanitize HTML: Use DOMPurify or similar libraries for HTML sanitization

Python

• SQL Injection: Use parameterized queries or ORM
• Command Injection: Avoid shell=True in subprocess calls
• Pickle Security: Avoid unpickling untrusted data
• Template Injection: Use secure template engines (Jinja2 auto-escaping)
• YAML Loading: Use yaml.safe_load() instead of yaml.load()
• Input Validation: Validate input using libraries like pydantic

Java

• SQL Injection: Use PreparedStatement or JPA
• XSS Prevention: Use OWASP ESAPI or framework-provided encoding
• Deserialization: Avoid deserializing untrusted data
• XML Security: Disable XML external entities (XXE)
• Path Traversal: Validate file paths to prevent directory traversal
• Secure Random: Use SecureRandom for cryptographic random numbers

Go

• SQL Injection: Use prepared statements with sql package
• Path Traversal: Use filepath.Join() and validate paths
• Command Injection: Avoid shell commands, use exec package
• Template Injection: Use html/template with auto-escaping
• Error Handling: Always handle errors explicitly
• Input Validation: Validate input before use

C/C++

• Buffer Overflows: Use safe string functions (strncpy_s, snprintf)
• Memory Safety: Use memory-safe alternatives when possible
• Integer Overflow: Check for integer overflow before arithmetic
• Format String Vulnerabilities: Avoid user-controlled format strings
• Use Safe Libraries: Use safe string and memory libraries
• Static Analysis: Use static analysis tools to catch issues

PHP

• SQL Injection: Use PDO with prepared statements
• XSS Prevention: Use htmlspecialchars() or framework escaping
• File Upload: Validate and sanitize uploaded files
• Include Files: Avoid user-controlled include files
• Type Juggling: Be aware of PHP's type juggling
• Configuration: Use secure configuration settings

Input Validation and Output Encoding

Input Validation Techniques

• Type Validation: Validate data type (integer, string, date, etc.)
• Length Validation: Validate minimum and maximum length
• Format Validation: Validate format (email, phone, URL, etc.)
• Range Validation: Validate numeric ranges
• Pattern Validation: Use regex patterns for complex validation
• Business Rule Validation: Validate against business rules

Output Encoding Contexts

• HTML Context: Encode for HTML entities (<, >, &, ", ')
• JavaScript Context: Encode for JavaScript strings
• URL Context: Encode for URL parameters
• CSS Context: Encode for CSS values
• Attribute Context: Encode for HTML attributes

Encoding Libraries

• JavaScript: DOMPurify, encodeURI(), encodeURIComponent()
• Python: html.escape(), urllib.parse.quote()
• Java: OWASP ESAPI, Apache Commons Text
• Go: html.EscapeString(), url.QueryEscape()
• PHP: htmlspecialchars(), urlencode()

Authentication and Authorization Patterns

Authentication Patterns

• Multi-Factor Authentication: Require multiple factors for authentication
• Password Hashing: Use bcrypt, Argon2, or scrypt for password hashing
• Password Policies: Enforce strong password policies
• Account Lockout: Implement account lockout after failed attempts
• Password Reset: Implement secure password reset flows
• Session Management: Use secure session management practices

Authorization Patterns

• Role-Based Access Control (RBAC): Assign permissions to roles, roles to users
• Attribute-Based Access Control (ABAC): Use attributes for fine-grained access control
• Access Control Lists (ACL): Define access rights for resources
• Capability-Based Security: Use capabilities for access control
• Policy-Based Access Control: Use policies for access decisions
• Hybrid Approaches: Combine multiple authorization patterns

Session Management

• Secure Cookies: Use secure, HTTP-only, SameSite cookies
• Session Expiration: Implement appropriate session timeout
• Session Fixation: Generate new session ID after authentication
• Session Storage: Store session data securely
• Logout: Implement proper logout functionality
• Concurrent Sessions: Limit concurrent sessions if needed

Cryptography Best Practices

Encryption

• Use Standard Algorithms: Use AES-256, ChaCha20-Poly1305, or similar
• Use Authenticated Encryption: Prefer AEAD modes (GCM, CCM, ChaCha20-Poly1305)
• Key Management: Use proper key management (HSM, KMS, key rotation)
• IV/Nonce: Use unique IV/nonce for each encryption
• Key Derivation: Use PBKDF2, Argon2, or scrypt for key derivation
• Avoid ECB Mode: Never use ECB mode for encryption

Hashing

• Use Strong Hashes: Use SHA-256 or stronger for general hashing
• Password Hashing: Use bcrypt, Argon2, or scrypt for passwords
• Salt: Use unique salt for each password hash
• Slow Hashing: Use computationally expensive hashing for passwords
• Avoid MD5/SHA1: Avoid MD5 and SHA1 for security purposes

Key Management

• Key Generation: Use cryptographically secure random number generators
• Key Storage: Store keys securely (HSM, KMS, encrypted at rest)
• Key Rotation: Rotate keys regularly
• Key Separation: Use different keys for different purposes
• Key Destruction: Securely destroy keys when no longer needed
• Key Escrow: Consider key escrow for recovery if needed

TLS/SSL

• Use TLS 1.3: Prefer TLS 1.3 when available
• Strong Ciphers: Use strong cipher suites
• Certificate Validation: Always validate certificates
• HSTS: Implement HTTP Strict Transport Security
• Perfect Forward Secrecy: Use cipher suites with PFS
• Disable Weak Protocols: Disable SSLv2, SSLv3, TLS 1.0, TLS 1.1

Secure API Design

API Security Best Practices

• Authentication: Implement strong authentication (OAuth 2.0, JWT, API keys)
• Authorization: Implement proper authorization for all endpoints
• Rate Limiting: Implement rate limiting to prevent abuse
• Input Validation: Validate all input to API endpoints
• Output Encoding: Encode output appropriately
• Error Handling: Use generic error messages, log details server-side
• HTTPS: Always use HTTPS for API communication
• API Versioning: Use versioning to manage breaking changes
• Documentation: Document security considerations
• Monitoring: Monitor API usage for anomalies

REST API Security

• Stateless: Keep APIs stateless
• Resource-Based Design: Design around resources
• HTTP Methods: Use HTTP methods correctly (GET, POST, PUT, DELETE)
• Status Codes: Use appropriate HTTP status codes
• Pagination: Implement pagination for large datasets
• Filtering/Sorting: Allow filtering and sorting
• CORS: Configure CORS appropriately
• CSRF: Implement CSRF protection for state-changing operations

GraphQL Security

• Query Depth Limiting: Limit query depth to prevent DoS
• Query Complexity Limiting: Limit query complexity
• Rate Limiting: Implement rate limiting
• Authentication: Implement authentication at the resolver level
• Authorization: Implement authorization at the resolver level
• Introspection: Disable introspection in production
• Field-Level Authorization: Implement field-level authorization

Common Security Anti-Patterns

Code Anti-Patterns

• Hardcoded Secrets: Never hardcode passwords, API keys, or tokens
• SQL String Concatenation: Never concatenate SQL strings
• Shell Command Concatenation: Never concatenate shell commands
• eval() Usage: Avoid using eval() or similar functions
• Trust Client-Side Validation: Never trust client-side validation
• Ignore Error Messages: Don't ignore error messages
• Roll Your Own Crypto: Never implement custom cryptography

Configuration Anti-Patterns

• Default Credentials: Never use default credentials in production
• Debug Mode: Never enable debug mode in production
• Verbose Error Messages: Don't expose detailed errors to users
• Insecure Defaults: Don't use insecure default configurations
• Unnecessary Services: Don't run unnecessary services
• Open Ports: Don't expose unnecessary ports

Architecture Anti-Patterns

• Security Through Obscurity: Never rely on obscurity for security
• Single Layer of Defense: Never rely on a single security control
• Trust Boundaries: Don't trust components across trust boundaries
• Assume Safe Input: Never assume input is safe
• Ignore Logging: Don't ignore security logging
• Skip Testing: Never skip security testing

Development Anti-Patterns

• Skip Code Review: Never skip security code reviews
• Ignore Dependencies: Don't ignore dependency vulnerabilities
• Rush Deployment: Don't rush deployments without testing
• Disable Security Controls: Never disable security controls for convenience
• Ignore Alerts: Don't ignore security alerts
• Assume It's Secure: Never assume something is secure without verification