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Testing for Default or Guessable User Account (OWASP-AT-003)

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OWASP Testing Guide v3 Table of Contents

This article is part of the OWASP Testing Guide v3. The entire OWASP Testing Guide v3 can be downloaded here.

OWASP at the moment is working at the OWASP Testing Guide v4: you can browse the Guide here

Brief Summary

Today's web applications typically run on popular open source or commercial software that is installed on servers and requires configuration or customization by the server administrator. In addition, most of today's hardware appliances, i.e., network routers and database servers, offer web-based configuration or administrative interfaces.

Often these applications are not properly configured and the default credentials provided for initial authentication and configuration are never updated. In addition, it is typical to find generic accounts, left over from testing or administration, that use common usernames and passwords and are left enabled in the application and its infrastructure.

These default username and password combinations are widely known by penetration testers and malicious attackers, who can use them to gain access to various types of custom, open source, or commercial applications.
In addition, weak password policy enforcements seen in many applications allow users to sign up using easy to guess usernames and passwords, and may also not allow password changes to be undertaken.

Description of the Issue

The root cause of this problem can be identified as:

  • Inexperienced IT personnel, who are unaware of the importance of changing default passwords on installed infrastructure components.
  • Programmers who leave backdoors to easily access and test their application and later forget to remove them.
  • Application administrators and users that choose an easy username and password for themselves
  • Applications with built-in, non-removable default accounts with a pre-set username and password.
  • Applications which leak information as to the validity of usernames during either authentication attempts, password resets, or account signup.

An additional problem stems from the use of blank passwords, which are simply the result of a lack of security awareness or a desire to simplify administration.

Black Box testing and example

In Blackbox testing the tester knows nothing about the application, its underlying infrastructure, and any username or password policies. In reality this is often not the case, and some information about the application is known. If this is the case, simply skip the steps that refer to obtaining information you already have.

When testing a known application interface, for example a Cisco router web interface or a Weblogic administrator portal, check that the known usernames and passwords for these devices do not result in successful authentication. Common credentials for many systems can be found using a search engine or by using one of the sites listed in the Further Reading section.

When facing applications to which we do not have a list of default and common user accounts, or when common accounts do not work, we can perform manual testing.

Note that the application being tested may have an account lockout, and multiple password guess attempts with a known username may cause the account to be locked. If it is possible to lock the administrator account, it may be troublesome for the system administrator to reset it.

Many applications have verbose error messages that inform the site users as to the validity of entered usernames. This information will be helpful when testing for default or guessable user accounts. Such functionality can be found, for example, on the login page, password reset and forgotten password page, and sign up page. More information on this can be seen in the section Testing for user enumeration.

  • Try the following usernames - "admin", "administrator", "root", "system", "guest", "operator", or "super". These are popular among system administrators and are often used. Additionally you could try "qa", "test", "test1", "testing" and similar names. Attempt any combination of the above in both the username and the password fields. If the application is vulnerable to username enumeration, and you successfully manage to identify any of the above usernames, attempt passwords in a similar manner. In addition try an empty password or one of the following "password", "pass123", "password123", "admin", or "guest" with the above accounts or any other enumerated accounts. Further permutations of the above can also be attempted. If these passwords fail, it may be worth using a common username and password list and attempting multiple requests against the application. This can, of course, be scripted to save time.
  • Application administrative users are often named after the application or organization. This means if you are testing an application named "Obscurity", try using obscurity/obscurity or any other similar combination as the username and password.
  • When performing a test for a customer, attempt using names of contacts you have received as usernames with any common passwords.
  • Viewing the User Registration page may help determine the expected format and length of the application usernames and passwords. If a user registration page does not exist, determine if the organization uses a standard naming convention for user names such as their email address or the name before the "@" in the email.
  • Attempt using all the above usernames with blank passwords.
  • Review the page source and javascript either through a proxy or by viewing the source. Look for any references to users and passwords in the source. For example "If username='admin' then starturl=/admin.asp else /index.asp" (for a successful login vs a failed login). Also, if you have a valid account, then login and view every request and response for a valid login vs an invalid login, such as additional hidden parameters, interesting GET request (login=yes), etc.
  • Look for account names and passwords written in comments in the source code. Also look in backup directories, etc for source code that may contain comments of interest.
  • Try to extrapolate from the application how usernames are generated. For example, can a user create their own username or does the system create an account for the user based on some personal information or a predictable sequence? If the application does create its own accounts in a predictable sequence, such as user7811, try fuzzing all possible accounts recursively. If you can identify a different response from the application when using a valid username and a wrong password, then you can try a brute force attack on the valid username (or quickly try any of the identified common passwords above or in the reference section).
  • If the application creates its own passwords for new users, whether or not the username is created by the application or by the user, then try to determine if the password is predictable. Try to create many new accounts in quick succession to compare and determine if the passwords are predictable. If predictable, then try to correlate these with the usernames, or any enumerated accounts, and use them as a basis for a brute force attack.

Result Expected:
Successful authentication to the application or system being tested.

Gray Box testing and example

The following steps rely on an entirely Gray Box approach. If only some of the information is available to you, refer to black box testing to fill the gaps.

  • Talk to the IT personnel to determine passwords they use for administrative access and how administration of the application is undertaken.
  • Examine the password policy for the application, checking whether username and passwords are complex, difficult to guess, and not related to the application name, person name, or administrative names ("system").
  • Examine the user database for default names, application names, and easily guessed names as described in the Black Box testing section. Check for empty password fields.
  • Examine the code for hard coded usernames and passwords.
  • Check for configuration files that contain usernames and passwords.

Result Expected:
Successful authentication to the application or system being tested.