Broken Authentication and Session Management

OWASP Top 10 2013 - A2



What is Broken authentication and session management?

These types of weaknesses can allow an attacker to either capture or bypass the authentication methods that are used by a web application.

  • User authentication credentials are not protected when stored.
  • Predictable login credentials.
  • Session IDs are exposed in the URL (e.g., URL rewriting).
  • Session IDs are vulnerable to session fixation attacks.
  • Session value does not timeout or does not get invalidated after logout.
  • Session IDs are not rotated after successful login.
  • Passwords, session IDs, and other credentials are sent over unencrypted connections.

The goal of an attack is to take over one or more accounts and for the attacker to get the same privileges as the attacked user.


Broken authentication and session management examples

Example #1: URL rewriting

A travel reservations application supports URL rewriting, putting session IDs in the URL.

        http://example.com/sale/saleitems;jsessionid=2P0OC2JSNDLPSKHCJUN2JV?dest=Hawaii

Risk

  • An authenticated user of the site wants to let their friends know about the sale. The user e-mails the link above without realizing they are also giving away their session ID. When the friends use the link they use the user’s session and credit card.

Example #2: Application’s timeout is not set properly

The user utilizes a public computer to access a site. Instead of selecting “logout” the user simply closes the browser tab and walks away. An attacker uses the same browser an hour later, and that browser is still authenticated.

Example #3: Passwords are not properly hashed and salted

An insider or external attacker gains access to the system’s password database. User passwords are not properly hashed and salted, exposing every user’s password.

Risk

  • Stored username and password values should be salted and hashed, in addition to being encrypted.

Example #4: Predictable login credentials

Username and Password values that are easy to guess or that are used frequently can be guessed by attackers to obtain unauthorized access.

Risk

  • Force users to use a strong password policy.


How to prevent Broken Authentication and Session Management

Session management

  • Credentials should be protected: User authentication credentials should be protected when stored using hashing or encryption.
  • Do not expose session ID in the URL: Session IDs should not be exposed in the URL (e.g., URL rewriting).
  • Session IDs should timeout: User sessions or authentication tokens should be properly invalidated during logout.
  • Recreate session IDs: Session IDs should be recreated after successful login.
  • Do not send credentials over unencrypted connections: Passwords, session IDs, and other credentials should not be sent over unencrypted connections.

Broken authentication

  • Password length: Minimum password length should be at least eight (8) characters long. Combining this length with complexity makes a password difficult to guess using a brute force attack.
  • Password complexity: Passwords should be a combination of alphanumeric characters. Alphanumeric characters consist of letters, numbers, punctuation marks, mathematical and other conventional symbols.
  • Username/Password Enumeration: Authentication failure responses should not indicate which part of the authentication data was incorrect. For example, instead of "Invalid username" or "Invalid password", just use "Invalid username and/or password" for both. Error responses must be truly identical in both display and source code.
  • Protection against brute force login: Enforce account disabling after an established number of invalid login attempts (e.g., five attempts is common). The account must be disabled for a period of time sufficient to discourage brute force guessing of credentials, but not so long as to allow for a denial-of-service attack to be performed.

How Hdiv protects against A2 risk

Risk Covered

  • Hdiv detects the use of hardcoded keys and passwords within the code, too long session timeouts, session and URL rewriting, weak passwords, if HttpOnly flag is being used to session handling header, plus others; and protects applications against brute force login attacks and does not allow access to unauthorized resources thanks to its information flow control.
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