Fix Broken User Authentication in CherryPy
Broken authentication is the low-hanging fruit for any red teamer. In CherryPy, developers frequently trip up by rolling their own manual auth logic, storing passwords in plaintext, or neglecting session security flags. This guide nukes those vulnerabilities by implementing industry-standard hashing and hardening the session middleware.
The Vulnerable Pattern
import cherrypyclass VulnerableApp: @cherrypy.expose def login(self, user, password): # VULNERABILITY: Plaintext comparison and hardcoded credentials # VULNERABILITY: No session regeneration (Session Fixation risk) if user == ‘admin’ and password == ‘secret123’: cherrypy.session[‘auth’] = True return ‘Welcome admin’ return ‘Access Denied’
cherrypy.quickstart(VulnerableApp(), ’/’, {’/’: {‘tools.sessions.on’: True}})
The Secure Implementation
To fix broken authentication, we implement three critical layers: 1. Password Hashing: Stop using plaintext; bcrypt provides a salted, slow hash that resists brute force. 2. Session Hardening: We enforce 'httponly' to block JavaScript access to cookies and 'secure' to ensure they never traverse unencrypted channels. 3. Session Management: Calling 'cherrypy.session.regenerate()' upon login invalidates any pre-auth session ID, neutralizing Session Fixation attacks. We also set a short session timeout to minimize the window of opportunity for attackers.
import cherrypy import bcryptSimulated DB with hashed password
USER_DB = {‘admin’: b’$2b$12$Kj/X.Kj/X.Kj/X.Kj/X.Kj/X.Kj/X.Kj/X.Kj/X.Kj/X.Kj/X.Kj/’}
class SecureApp: @cherrypy.expose def login(self, user, password): stored_hash = USER_DB.get(user) # SECURE: Use bcrypt for constant-time comparison and hashing if stored_hash and bcrypt.checkpw(password.encode(), stored_hash): # SECURE: Regenerate session ID to prevent fixation attacks cherrypy.session.regenerate() cherrypy.session[‘user’] = user return ‘Authenticated’ return ‘Unauthorized’
app_config = { ’/’: { ‘tools.sessions.on’: True, ‘tools.sessions.httponly’: True, # Prevent XSS session theft ‘tools.sessions.secure’: True, # Ensure HTTPS only ‘tools.sessions.timeout’: 30, # Short TTL ‘tools.sessions.locking’: ‘early’ } }
if name == ‘main’: cherrypy.quickstart(SecureApp(), ’/’, app_config)
Your CherryPy API
might be exposed to Broken User Authentication
74% of CherryPy apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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