Configuring password control

Password control refers to a set of functions provided by the local authentication server to control user login passwords, super passwords, and user login status based on predefined policies. The rest of this section describes password control functions in detail.

• Minimum password length

  By setting a minimum password length, you can enforce users to use passwords long enough for system security. If a user specifies a shorter password, the system rejects the setting and prompts the user to re-specify a password.

• Minimum password update interval

  This function allows you to set the minimum interval at which users can change their passwords. If a non-manage level user logs in to change the password but the time elapsed since the last change is less than this interval, the system denies the request. For example, if you set this interval to 48 hours, a non-manage level user cannot change the password twice within 48 hours. This prevents users from changing their passwords frequently.

  This function is not effective on users of the manage level. For information about user levels, see Fundamentals Configuration Guide.

  This function is not effective on a user who is prompted to change the password at the first login or a user whose password has just been aged out.

• Password aging

  Password aging imposes a lifecycle on a user password. After the password aging time expires, the user needs to change the password.

  If a user enters an expired password when logging in, the system displays an error message. The user is prompted to provide a new password and to confirm it by entering it again. The new password must be a valid one and the user must enter exactly the same password when confirming it.

• Early notice on pending password expiration

  When a user logs in, the system checks whether the password will expire in a time equal to or less than the specified period. If so, the system notifies the user of the expiration time and provides a choice for the user to change the password. If the user provides a new password that is qualified, the system records the new password and the time. If the user chooses to leave the password or the user fails to change it, the system allows the user to log in using the current password.

  Telnet, SSH, and terminal users (log in to the device through the console interface) can change their passwords by themselves. FTP users, on the contrary, can only have their passwords changed by the administrator.

• Login with an expired password

  You can allow a user to log in a certain number of times within a specific period of time after the password expires. For example, if you set the maximum number of logins with an expired password to three and the time period to 15 days, a user can log in three times within 15 days after the password expires.

• Password history

  With this feature enabled, the system maintains certain entries of passwords that a user has used. When a user changes the password, the system checks the new password against the history passwords and the current password. The new password must be different from the used ones by at least four characters and the four characters must not be the same. Otherwise, the user will fail to change the password and the system displays an error message.

  You can set the maximum number of history password records for the system to maintain for each user. When the number of history password records exceeds your setting, the latest record overwrites the earliest one.

• Login attempt limit

  Limiting the number of consecutive failed login attempts can effectively prevent password guessing.

  If an FTP or VTY user fails authentication due to a password error, the system adds the user to a password control blacklist. If a user fails to provide the correct password after the specified number of consecutive attempts, the system takes action as configured:

  • Prohibiting the user from logging in until the user is removed from the password control blacklist manually.

  • Allowing the user to try continuously and removing the user from the password control blacklist when the user logs in to the system successfully or the blacklist entry times out (the blacklist entry aging time is one minute).

  • Prohibiting the user from logging in within a configurable period of time, and allowing the user to log in again after the period of time elapses or the user is removed from the password control blacklist.

  A password control blacklist can contain up to 1024 entries.

  A login attempt using a wrong username will undoubtedly fail but the username will not be added into the password control blacklist.

  Users accessing the system through the console interface are not blacklisted. This is because the system is unable to obtain the IP addresses of these users and these users are privileged and therefore relatively secure to the system.

• Password composition checking

  A password can be a combination of characters from the following four types:

  • Uppercase letters A to Z

  • Lowercase letters a to z

  • Digits 0 to 9

  • 32 special characters. For information about special characters, see the password command in Security Command Reference.

  Depending on the system security requirements, you can set the minimum number of character types a password must contain and the minimum length of characters that are from each type.

  There are four password combination levels: 1, 2, 3, and 4, each representing the number of character types that a password must at least contain. Level 1 means that a password must contain characters of one type, level 2 at least two types, and so on.

  When a user sets or changes the password, the system checks if the password satisfies the composition requirement. If not, the system displays an error message.

• Password complexity checking

  A less complicated password such as a password containing the username or repeated characters is more likely to be cracked. For higher security, you can configure a password complexity checking policy to make sure that all user passwords are relatively complicated. With such a policy configured, when a user configures a password, the system checks the complexity of the password. If the password is not qualified, the system refuses the password and displays a password configuration failure message.

  You can impose the following password complexity requirements:

  • A password cannot contain the username or the reverse of the username. For example, if the username is abc, a password such as abc982 or 2cba is not qualified.

  • No character of the password is repeated three or more times consecutively. For example, password a111 is not qualified.

• Password display in the form of a string of asterisks (*)

  For the sake of security, the password a user enters is displayed in the form of a string of asterisks (*).

• Authentication timeout management

  Authentication timeout management is only for Telnet and Terminal users.

  The authentication period is from when the server obtains the username to when the server finishes authenticating the user's password. If a user fails to log in within the configured period of time, the system tears down the connection.

• Maximum account idle time

  You can set the maximum account idle time so that accounts staying idle for this period of time become invalid. For example, if you set the maximum account idle time to 60 days and the user of the account test has not logged in successfully within 60 days after the last successful login, the account becomes invalid and the user is unable to log in again.

• Logging

  The system logs all successful password changing events and the events of adding users to the password control blacklist.