python-cryptographic-failures.mdc

---
description: Detect and prevent cryptographic failures in Python applications as defined in OWASP Top 10:2021-A02
globs: *.py
alwaysApply: false
---
# Python Cryptographic Failures Security Standards (OWASP A02:2021)

This rule enforces security best practices to prevent cryptographic failures in Python applications, as defined in OWASP Top 10:2021-A02.

<rule>
name: python_cryptographic_failures
description: Detect and prevent cryptographic failures in Python applications as defined in OWASP Top 10:2021-A02
filters:
  - type: file_extension
    pattern: "\\.(py)$"
  - type: file_path
    pattern: ".*"

actions:
  - type: enforce
    conditions:
      # Pattern 1: Weak or insecure cryptographic algorithms
      - pattern: "import\\s+(md5|sha1)|hashlib\\.(md5|sha1)\\(|Crypto\\.Hash\\.(MD5|SHA1)|cryptography\\.hazmat\\.primitives\\.hashes\\.(MD5|SHA1)"
        message: "Using weak hashing algorithms (MD5/SHA1). Use SHA-256 or stronger algorithms from the hashlib or cryptography packages."
        
      # Pattern 2: Hardcoded secrets/credentials
      - pattern: "(password|secret|key|token|auth)\\s*=\\s*['\"][^'\"]+['\"]"
        message: "Potential hardcoded credentials detected. Store secrets in environment variables or a secure vault."
        
      # Pattern 3: Insecure random number generation
      - pattern: "random\\.(random|randint|choice|sample)|import random"
        message: "Using Python's standard random module for security purposes. Use secrets module or cryptography.hazmat.primitives.asymmetric for cryptographic operations."
        
      # Pattern 4: Weak SSL/TLS configuration
      - pattern: "ssl\\.PROTOCOL_(SSLv2|SSLv3|TLSv1|TLSv1_1)|SSLContext\\(\\s*ssl\\.PROTOCOL_(SSLv2|SSLv3|TLSv1|TLSv1_1)\\)"
        message: "Using deprecated/insecure SSL/TLS protocol versions. Use TLS 1.2+ (ssl.PROTOCOL_TLS_CLIENT with minimum version set)."
        
      # Pattern 5: Missing certificate validation
      - pattern: "verify\\s*=\\s*False|check_hostname\\s*=\\s*False|CERT_NONE"
        message: "SSL certificate validation is disabled. Always validate certificates in production environments."
        
      # Pattern 6: Insecure cipher usage
      - pattern: "DES|RC4|Blowfish|ECB"
        message: "Using insecure encryption cipher or mode. Use AES with GCM or CBC mode with proper padding."
        
      # Pattern 7: Insufficient key length
      - pattern: "RSA\\([^,]+,\\s*[0-9]+\\s*\\)|key_size\\s*=\\s*([0-9]|10[0-9][0-9]|11[0-9][0-9]|12[0-4][0-9])"
        message: "Using insufficient key length for asymmetric encryption. RSA keys should be at least 2048 bits, preferably 4096 bits."
        
      # Pattern 8: Insecure password hashing
      - pattern: "\\.encode\\(['\"]utf-?8['\"]\\)\\.(digest|hexdigest)\\(\\)|hashlib\\.[a-zA-Z0-9]+\\([^)]*\\)\\.(digest|hexdigest)\\(\\)"
        message: "Using plain hashing for passwords. Use dedicated password hashing functions like bcrypt, Argon2, or PBKDF2."
        
      # Pattern 9: Missing salt in password hashing
      - pattern: "pbkdf2_hmac\\([^,]+,[^,]+,[^,]+,\\s*[0-9]+\\s*\\)"
        message: "Ensure you're using a proper random salt with password hashing functions."
        
      # Pattern 10: Insecure cookie settings
      - pattern: "set_cookie\\([^)]*secure\\s*=\\s*False|set_cookie\\([^)]*httponly\\s*=\\s*False"
        message: "Cookies with sensitive data should have secure and httponly flags enabled."

  - type: suggest
    message: |
      **Python Cryptography Best Practices:**
      
      1. **Secure Password Storage:**
         - Use dedicated password hashing algorithms:
           ```python
           import bcrypt
           hashed = bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt(rounds=12))
           ```
         - Or use Argon2 (preferred) or PBKDF2 with sufficient iterations:
           ```python
           from argon2 import PasswordHasher
           ph = PasswordHasher()
           hash = ph.hash(password)
           ```
      
      2. **Secure Random Number Generation:**
         - Use the `secrets` module for cryptographic operations:
           ```python
           import secrets
           token = secrets.token_hex(32)  # 256 bits of randomness
           ```
         - For cryptographic keys, use proper key generation functions:
           ```python
           from cryptography.hazmat.primitives.asymmetric import rsa
           private_key = rsa.generate_private_key(public_exponent=65537, key_size=4096)
           ```
      
      3. **Secure Communications:**
         - Use TLS 1.2+ for all communications:
           ```python
           import ssl
           context = ssl.create_default_context()
           context.minimum_version = ssl.TLSVersion.TLSv1_2
           ```
         - Always validate certificates:
           ```python
           import requests
           response = requests.get('https://example.com', verify=True)
           ```
      
      4. **Proper Key Management:**
         - Never hardcode secrets in source code
         - Use environment variables or secure vaults:
           ```python
           import os
           api_key = os.environ.get('API_KEY')
           ```
         - Consider using dedicated key management services
      
      5. **Secure Encryption:**
         - Use high-level libraries like `cryptography`:
           ```python
           from cryptography.fernet import Fernet
           key = Fernet.generate_key()
           f = Fernet(key)
           encrypted = f.encrypt(data)
           ```
         - For lower-level needs, use authenticated encryption (AES-GCM):
           ```python
           from cryptography.hazmat.primitives.ciphers.aead import AESGCM
           key = AESGCM.generate_key(bit_length=256)
           aesgcm = AESGCM(key)
           nonce = os.urandom(12)
           encrypted = aesgcm.encrypt(nonce, data, associated_data)
           ```
      
      6. **Secure Cookie Handling:**
         - Set secure and httponly flags:
           ```python
           # Flask example
           response.set_cookie('session', session_id, httponly=True, secure=True, samesite='Lax')
           ```
         - Use signed cookies or tokens:
           ```python
           # Django example - uses signed cookies by default
           request.session['user_id'] = user.id
           ```
      
      7. **Input Validation:**
         - Validate all cryptographic inputs
         - Use constant-time comparison for secrets:
           ```python
           import hmac
           def constant_time_compare(a, b):
               return hmac.compare_digest(a, b)
           ```

  - type: validate
    conditions:
      # Check 1: Proper password hashing
      - pattern: "bcrypt\\.hashpw|argon2|PasswordHasher|pbkdf2_hmac\\([^,]+,[^,]+,[^,]+,\\s*[0-9]{4,}\\s*\\)"
        message: "Using secure password hashing algorithm."
      
      # Check 2: Secure random generation
      - pattern: "secrets\\.|urandom|cryptography\\.hazmat\\.primitives\\.asymmetric"
        message: "Using cryptographically secure random number generation."
      
      # Check 3: Strong TLS configuration
      - pattern: "ssl\\.PROTOCOL_TLS|minimum_version\\s*=\\s*ssl\\.TLSVersion\\.TLSv1_2|create_default_context"
        message: "Using secure TLS configuration."
      
      # Check 4: Proper certificate validation
      - pattern: "verify\\s*=\\s*True|check_hostname\\s*=\\s*True|CERT_REQUIRED"
        message: "Properly validating SSL certificates."

metadata:
  priority: high
  version: 1.0
  tags:
    - security
    - python
    - cryptography
    - encryption
    - owasp
    - language:python
    - framework:django
    - framework:flask
    - framework:fastapi
    - category:security
    - subcategory:cryptography
    - standard:owasp-top10
    - risk:a02-cryptographic-failures
  references:
    - "https://owasp.org/Top10/A02_2021-Cryptographic_Failures/"
    - "https://cheatsheetseries.owasp.org/cheatsheets/Cryptographic_Storage_Cheat_Sheet.html"
    - "https://docs.python.org/3/library/secrets.html"
    - "https://cryptography.io/en/latest/"
    - "https://pypi.org/project/bcrypt/"
    - "https://pypi.org/project/argon2-cffi/"
</rule>