Testing for Vulnerable Remember Password (OTG-AUTHN-005)

Summary
Browsers will sometimes ask a user if they wish to remember the password that they just entered. The browser will then store the password, and automatically enter it whenever the same authentication portal is visited. This is a convenience for the user.

Description of the Issue
Whilst a convenience for the user, having the browser storing passwords is also a convenience for an attacker. If an attacker can gain access to the victim's browser (e.g. through a Cross Site Scripting attack, or through a shared computer), then they can retrieve the stored passwords. It is not uncommon for browsers to store these passwords in a fully retrievable manner, but even if the browser were to store the passwords encrypted and only retrievable through the use of a master password, an attacker could retrieve the password by visiting the target authentication portal web site, entering the victim's username, and letting the browser to enter the password.

Black Box testing and example

 * Enter a username and password in the target authentication portal and determine whether the browser asks the user whether they want the password remembered.
 * View the authentication portal's HTML source code and look for the autocomplete="off" attribute in the password form field. The code for this will usually be along the following lines:
 * Also look for passwords being stored in a cookie. Examine the cookies stored by the application. Verify that the credentials are not stored in cleartext, but are hashed. Examine the hashing mechanism: if it is a common, well-known algorithm, check for its strength; in homegrown hash functions, attempt several usernames to check whether the hash function is easily guessable. Additionally, verify that the credentials are only sent during the login phase, and not sent together with every request to the application.
 * Also look for other areas where a password may be entered, e.g. a Change Password form.
 * Also consider other sensitive form fields (e.g. an answer to a secret question, used for Forgotten Password forms).

Remediation
Any fields that contain sensitive information and passwords should be flagged in the HTML with AUTOCOMPLETE=”off”. Moreover no credentials have to be stored, in cleartext, into cookies.