Testing for Weak password policy (OTG-AUTHN-007)

This article is part of the new OWASP Testing Guide v4.

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Summary

The most prevalent and most easily administered authentication mechanism is a static password. The password represents the keys to the kingdom, but is often subverted by users in the name of usability. In each of the recent high profile hacks that have revealed user credentials, it is lamented that most common passwords are still: 123456, password and qwerty.

Test objectives

Determine the resistance of the application against brute force password guessing using available password dictionaries by evaluating the length, complexity, reuse and aging requirements of passwords.

How to Test

1. What characters are permitted and forbidden for use within a password? Is the user required to use characters from different character sets such as lower and uppercase letters, digits and special symbols?
2. How often can a user change their password? How quickly can a user change their password after a previous change? Users may bypass password history requirements by changing their password 5 times in a row so that after the last password change they have configured their initial password again.
3. When must a user change their password? After 90 days? After account lockout due to excessive log on attempts?
4. How often can a user reuse a password? Does the application maintain a history of the user's previous used 8 passwords?
5. How different must the next password be from the last password?
6. Is the user prevented from using his username or other account information (such as first or last name) in the password?

References

• Brute Force Attacks
• Password length & complexity

Remediation

To mitigate the risk of easily guessed passwords facilitating unauthorized access there are two solutions: introduce additional authentication controls (i.e. two-factor authentication) or introduce a strong password policy. The simplest and cheapest of these is the introduction of a strong password policy that ensures password length, complexity, reuse and aging.