Solaris Naming Administration Guide

Chapter 11 Administering Passwords

This chapter describes how to use the passwd command from the point of view of an ordinary user (NIS+ principal) and how an NIS+ administrator manages the password system.


Note -

Some NIS+ security tasks can be performed more easily with Solstice AdminSuiteTM tools if you have them available.


Using Passwords

When logging in to a machine, users must enter both a user name (also known as a login ID) and a password. Although login IDs are publicly known, passwords must be kept secret by their owners.

Logging In

Logging in to a system is a two-step process:

  1. Type your login ID at the Login: prompt.

  2. Type your password at the Password: prompt.

    (To maintain password secrecy, your password is not displayed on your screen when you type it.)

    If your login is successful you will see your system's message of the day (if any) and then your command-line prompt, windowing system, or normal application.

The Login incorrect Message

The Login incorrect message indicates that:

The password expired Message

If you receive a Your password has expired message it means that your password has reached its age limit and expired. In other words, the password has been in use for too long and you must choose a new password at this time. (See "Choosing a Password", for criteria that a new password must meet.)

In this case, choosing a new password is a three-step process:

  1. Type your old password at the Enter login password (or similar) prompt.

    Your keystrokes are not shown on your screen.

  2. Type your new password at the Enter new password prompt.

    Your keystrokes are not shown on your screen.

  3. Type your new password again at the Re-enter new password prompt.

    Your keystrokes are not shown on your screen.

The will expire Message

If you receive a Your password will expire in N days message (where N is a number of days), or a Your password will expire within 24 hours message, it means that your password will reach its age limit and expire in that number of days (or hours).

In essence, this message is telling you to change your password now. (See "Changing Your Password".)

The Permission denied Message

After entering your login ID and password, you may get a Permission denied message and be returned to the login: prompt. This means that your login attempt has failed because an administrator has either locked your password, or terminated your account, or your password privileges have expired. In these situations you cannot log in until an administrator unlocks your password or reactivates your account or privileges. Consult your system administrator.

Changing Your Password

To maintain security, you should change your password regularly. (See "Choosing a Password" for password requirements and criteria.)


Note -

The passwd command now performs all functions previously performed by nispasswd. For operations specific to an NIS+ name space, use passwd -r nisplus.


Changing your password is a four-step process:

  1. Run the passwd command at a system prompt.

  2. Type your old password at the Enter login password (or similar) prompt.

    Your keystrokes are not shown on your screen.

    • If you receive a Sorry: less than N days since the last change message, it means that your old password has not been in use long enough and you will not be allowed to change it at this time. You are returned to your system prompt. Consult your system administrator to find out the minimum number of days a password must be in use before it can be changed.

    • If you receive a You may not change this password message, it means that your network administrator has blocked any change.

  3. Type your new password at the Enter new password prompt.

    Your keystrokes are not shown on your screen.

    At this point the system checks to make sure that your new password meets the requirements:

    • If it does meet the requirements, you are asked to enter it again.

    • If your new password does not meet the system requirements, a message is displayed informing you of the problem. You must then enter a new password that does meet the requirements.

    See "Password Requirements" for the requirements a password must meet.

  4. Type your new password again at the Re-enter new password prompt.

    Your keystrokes are not shown on your screen.

    If your second entry of the new password is not identical to your first entry, you are prompted to repeat the process.


    Note -

    When changing root's password, you must always run chkey -p immediately after changing the password. (See "Changing Root Keys From Root" and "Changing Root Keys From Another Machine" for information on using chkey -p to change root's keys.) Failure to run chkey -p after changing root's password will result in root being unable to properly log in.


Password Change Failures

Some systems limit either the number of failed attempts you can make in changing your password or the total amount of time you can take to make a successful change. (These limits are implemented to prevent someone else from changing your password by guessing your current password.)

If you (or someone posing as you) fails to successfully log in or change your password within the specified number of tries or time limit, you will get a Too many failures - try later or Too many tries: try again later message. You will not be allowed to make any more attempts until a certain amount of time has passed. (That amount of time is set by your administrator.)

Choosing a Password

Many breaches of computer security involve guessing another user's password. While the passwd command enforces some criteria for making sure the password is hard to guess, a clever person can sometimes figure out a password just by knowing something about the user. Thus, a good password is one that is easy for you to remember but hard for someone else to guess. A bad password is one that is so hard for you to remember that you have to write it down (which you are not supposed to do), or that is easy for someone who knows about you to guess.

Password Requirements

A password must meet the following requirements:

Bad Choices for Passwords

Bad choices for passwords include:

Good Choices for Passwords

Good choices for passwords include:

Administering Passwords

This section describes how to administer passwords in an NIS+ namespace. This section assumes that you have an adequate understanding of the NIS+ security system in general, and in particular of the role that login passwords play in that system (see Chapter 6, Security Overview, for this information).


Note -

The passwd command now performs all functions previously performed by nispasswd. For operations specific to an NIS+ namespace, use passwd -r nisplus.


nsswitch.conf File Requirements

In order to properly implement the passwd command and password aging on your network, the passwd entry of the nsswitch.conf file on every machine must be correct. This entry determines where the passwd command will go for password information and where it will update password information.

Only five passwd configurations are permitted:


Caution - Caution -

All of the nsswitch.conf files on all of your network's workstations must use one of the passwd configurations shown above. If you configure the passwd entry in any other way, users may not be able to log in.


The nispasswd Command

All functions previously performed by the nispasswd command are now performed by the passwd command. When issuing commands from the command line, you should use passwd, not nispasswd.

(The nispasswd command is still retained with all of its functionality for the purpose of backward compatibility.)

The yppasswd Command

All functions previously performed by the yppasswd command are now performed by the passwd command. When issuing commands from the command line, you should use passwd, not yppasswd.

(The yppasswd is still retained with all of its functionality for the purpose of backward compatibility.)

The passwd Command

The passwd command performs various operations regarding passwords. The passwd command replaces the nispasswd command. You should use the passwd command for all activities which used to be performed with the nispasswd command. (See the passwd command man page for a complete description of all passwd flags, options, and arguments.)

The passwd command allows users to perform the following operations:

Administrators can use the passwd command to perform the following operations:

passwd and the nsswitch.conf File

The name service switch determines where the passwd command (and other commands) obtains and stores password information. If the passwd entry of the applicable nsswitch.conf file points to:

The passwd -r Option

When you run the passwd command with the -r nisplus, -r nis, or -r files arguments, those options override the nsswitch.conf file setting. You will be warned that this is the case. If you continue, the -r option will cause the passwd command to ignore the nsswitch.conf file sequence and update the information in the password information storage location pointed to by the -r flag.

For example, if the passwd entry in the applicable nsswitch.conf file reads:


 passwd: files nisplus

files is the first (primary) source, and passwd run without the -r option will get its password information from the /etc/passwd file. If you run the command with the -r nisplus option, passwd will get its information from the appropriate NIS+ passwd table and make its changes to that table, not to the /etc/passwd file.

The -r option should only be used when you cannot use the nsswitch.conf file because the search sequence is wrong. For example, when you need to update password information that is stored in two places, you can use the order specified in the nsswitch.conf file for the first one, but for the second one you have to force the use of the secondary or tertiary source.

The message:


Your specified repository is not defined in the nsswitch file!

indicates that your change will be made to the password information in the repository specified by the -r option, but that change will not affect anyone until the nsswitch.conf file is changed to point to that repository. For example, suppose the nsswitch.conf file reads passwd: files nis and you use the -r nisplus option to establish password-aging limits in an NIS+ passwd table. Those password-aging rules will sit in that table unused because the nsswitch.conf file is directing everyone to other places for their password information.

The passwd Command and "NIS+ Environment"

In this chapter, the phrase NIS+ environment refers to situations where the passwd entry of the applicable nsswitch.conf file is set to nisplus, or the passwd command is run with the -r nisplus argument.

The passwd Command and Credentials

When run in an NIS+ environment (see above), the passwd command is designed to function with or without credentials. Users without credentials are limited to changing their own password. Other password operations can only be performed by users who have credentials (are authenticated) and who have the necessary access rights (are authorized).

The passwd Command and Permissions

In this discussion of authorization and permissions, it is assumed that everyone referred to has the proper credentials.

By default, in a normal NIS+ environment the owner of the passwd table can change password information at any time and without constraints. In other words, the owner of the passwd table is normally granted full read, modify, create, and destroy authorization (permission) for that table. An owner can also:


Note -

Regardless of what permissions they have, everyone in the world, and nobody classes are forced to comply with password-aging constraints. In other words, they cannot change a password for themselves or anyone else unless that password has aged past its minimum. Nor can members of the group, world, and nobody classes avoid having to change their own passwords when the age limit has been reached. However, age constraints do not apply to the owner of the passwd table.


To use the passwd command in an NIS+ environment, you must have the required authorization (access rights) for the operation:

Table 11-1 Access Rights for passwd Command

This Operation 

Requires These Rights 

To This Object 

Displaying information 

read 

passwd table entry 

Changing Information 

modify 

passwd table entry 

Adding New Information 

modify 

passwd table 

The passwd Command and Keys

If you use passwd in an NIS+ environment to change a principal's password, it tries to update the principal's private (secret) key in the cred table.

The passwd Command and Other Domains

To operate on the passwd table of another domain, use:


passwd [options] -D domainname

The nistbladm Command

The nistbladm command allows you to create, change, and display information about any NIS+ table, including the passwd table.


Caution - Caution -

To perform password operations using the nistbladm command you must apply nistbladm to the shadow column of the passwd table. Applying nistbladm to the shadow column is complex and tricky. Therefore, you should not use the nistbladm command for any operation that can more easily be performed by the passwd command or by using the AdminTool or Solstice AdminSuite tools.


You should use the passwd command or Solstice AdminSuite tools to perform the following operations:

It is possible to use the nistbladm command to:

nistbladm and Shadow Column Fields

You use the nistbladm command to set password parameters by specifying the values of the different fields in the shadow column. These fields are entered in the format:

Graphic

Where:


Caution - Caution -

When using nistbladm on the shadow column of the password table, all of the numeric fields must contain appropriate values. You cannot leave a field blank, or enter a zero, as a no change placeholder.


For example, to specify that the user amy last changed her password on day 9246 (May 1, 1995), cannot change her password until it has been in use for 7 days, must change her password after 30 days, will be warned to change her password after the 25th day, must not remain inactive more than 15 days, and has an account that will expire on day number 9255, you would type:

nistbladm And the Number of Days

Most password aging parameters are expressed in number of days. The following principles and rules apply:

Values are entered in both the Lastchange snd the Expire fields as a number of days since January 1, 1970. For example:

Table 11-2 Number of Days Since 1/1/70

Date 

Day Number 

January 1, 1970 

January 2, 1970 

January 2, 1971 

365 

January 1, 1997 

9863 

Related Commands

The passwd and nistbladm commands provide capabilities that are similar to those offered by other commands. Table 11-3 summarizes their differences.

Table 11-3 Related Commands

Command 

Description 

yppasswd

Is now linked to the passwd command. Using yppasswd simply invokes the passwd command.

nispasswd

Is now linked to the passwd command. Using nispasswd simply invokes the passwd command.

niscat

Can be used to display the contents of the passwd table. 

Displaying Password Information

You can use the passwd command to display password information about all users in a domain or about one particular user:

For your password information


passwd -s

For all users in current domain


passwd -s -a

For a particular user


passwd -s username

Only the entries and columns for which you have read permission will be displayed. Entries are displayed with the following format:

Table 11-4 NIS+ Password Display Format

Field 

Description 

For Further Information 

username

The user's login name. 

status

The user's password status. PS indicates the account has a password. LK indicates the password is locked. NP indicates the account has no password. 

See "Locking a Password".

mm/dd/yy

The date, based on Greenwich mean time, that the user's password was last changed. 

min

The minimum number of days since the last change that must pass before the password can be changed again. 

See "Setting Minimum Password Life".

max

The maximum number of days the password can be used without having to change it. 

See "Setting a Password Age Limit".

warn

The number of days' notice that users are given before their passwords have to be changed. 

See "Establishing a Warning Period".

expire

A date on which users loose the ability to log in to their accounts. 

See "Password Privilege Expiration".

inactive

A limit on the number of days that an account can go without being logged in to. Once that limit is passed without a log in users can no longer access their accounts. 

See "Specifying Maximum Number of Inactive Days".

To display entries from a passwd table in another domain, use the -D option:

For all users in another domain


passwd -s -a -D domainname

For a particular user


passwd -s -D domainname username

Changing Passwords

New passwords must meet the criteria described in "Password Requirements".

Changing Your Own Password

To change your password, type


station1% passwd

You will be prompted for your old password and then the new password and then the new password a second time to confirm it.

Changing Someone Else's Password

To change someone else' password, use:

To change another user's password in the same domain


passwd username

To change another user's password in a different domain


passwd -D domainname username

When using the passwd command in an NIS+ environment (see "The passwd Command and "NIS+ Environment"") to change someone else's password you must have modify rights to that user's entry in the passwd table (this usually means that you are a member of the group for the passwd table and the group has modify rights). You do not have to enter either the user's old password or your password. You will be prompted to enter the new password twice to make sure that they match. If they do not match, you will be prompted to enter them again.

Changing Root's Password

When changing root's password, you must always run chkey -p immediately after changing the password with the passwd command. Failure to run chkey -p after changing root's password will result in root being unable to properly log in.

To change a root password, follow these steps:

  1. Log in as root.

  2. Change root's password using passwd.

    Do not use nispasswd.

  3. Run chkey -p.

    You must use the -p option.

Locking a Password

When operating in an NIS+ environment (see "The passwd Command and "NIS+ Environment""), an administrator (a group member) with modify rights to a user's entry in the passwd table can use the passwd command to lock a password. An account with a locked password cannot be used. When a password is locked, the user will receive a Login incorrect message after each login attempt.

Keep in mind that locked passwords have no effect on users who are already logged in. A locked password only prevents users from performing those operations that require giving a password such as login, rlogin, ftp, or telnet.

Note also that if a user with a locked password is already logged in, and that user uses the passwd command to change passwords, the lock is broken.

You can use this feature to:

To lock a password, use:


passwd -l username

Unlocking a Password

To unlock a user's password, you simply change it. You can "change" it back to the exact same password that it was when it was locked. Or you can change it to something new.

For example, to unlock jody's password, you would enter:


station1% passwd jody

Managing Password Aging

Password aging is a mechanism you can use to force users to periodically change their passwords.

Password aging allows you to:

Keep in mind that users who are already logged in when the various maximums or dates are reached are not affected by the above features. They can continue to work as normal.

Password aging limitations and activities are only activated when a user logs in or performs one of the following operations:

These password aging parameters are applied on user-by-user basis. You can have different password aging requirements for different users. (You can also set general default password aging parameters as described in "Managing Password Aging".)

Forcing Users to Change Passwords

There are two ways to force a user to change passwords the next time the user logs in:

Force change keeping password aging rules in effect


passwd -f username

Force change and turn off password aging rules


passwd -x 0 username

Setting a Password Age Limit

The -max argument to the passwd command sets an age limit for the current password. In other words, it specifies the number of days that a password remains valid. After that number of days, a new password must be chosen by the user. Once the maximum number of days have passed, the next time the user tries to login with the old password a Your password has been expired for too long message is displayed and the user is forced to choose a new password in order to finish logging in to the system.

The max argument uses the following format:


passwd -x max username

Where:

For example, to force the user schweik to change passwords every 45 days, you would type the command:


station1% passwd -x 45 schweik

Setting Minimum Password Life

The min argument to the passwd command specifies the number of days that must pass before a user can change passwords. If a user tries to change passwords before the minimum number of days has passed, a Sorry less than N days since the last change message is displayed.

The min argument uses the following format:


passwd -x max -n min username

Where:

For example, to force the user eponine to change passwords every 45 days, and prevent him from changing it for the first 7 days you would type the command:


station1% passwd -x 45 -n 7 eponine

The following rules apply to the min argument:

Establishing a Warning Period

The warn argument to the passwd command specifies the number of days before a password reaches its age limit that users will start to seeing a Your password will expire in N days message (where N is the number of days) when they log in.

For example, if a user's password has a maximum life of 30 days (set with the -max argument) and the warn value is set to 7 days, when the user logs in on the 24th day (one day past the warn value) the warning message Your password will expire in 7 days is displayed. When the user logs in on the 25th day the warning message Your password will expire in 6 days is displayed.

Keep in mind that the warning message is not sent by Email or displayed in a user's console window. It is displayed only when the user logs in. If the user does not log in during this period, no warning message is given.

Keep in mind that the warn value is relative to the max value. In other words, it is figured backwards from the deadline set by the max value. Thus, if the warn value is set to 14 days, the Your password will expire in N days message will begin to be displayed two weeks before the password reaches its age limit and must be changed.

Because the warn value is figured relative to the max value, it only works if a max value is in place. If there is no max value, warn values are meaningless and are ignored by the system.

The warn argument uses the following format:


passwd -x max -w warn username

Where:

For example, to force the user nilovna to change passwords every 45 days, and display a warning message 5 days before the password reaches its age limit you would type the command:


station1% passwd -x 45 -w 5 nilovna

The following rules apply to the warn argument:


Note -

You can also use Solstice AdminSuiteTM to set a warn value for a user's password.


Turning Off Password Aging

There are two ways to turn off password aging for a given user:

Turn off aging while allowing user to retain current password


passwd -x -1 username

Force user to change password at next login, and then turn off aging


passwd -x 0 username

This sets the max value to either zero or -1 (see "Setting a Password Age Limit" for more information on this value).

For example, to force the user mendez to change passwords the next time he logs in and then turn off password aging you would type the command:


station% passwd -x 0 mendez

Note -

You can also use Solstice AdminSuiteTM to set this parameter for a user's password.


You can also use the nistbladm command to set this value. For example, to turn off password aging for the user otsu and allow her to continue using her current password, you would type:


station1% nistbladm -m `shadow=0:0:-1:0:0:0:0' [name=otsu],passwd.org_dir

For additional information on using the nistbladm command, see "The nistbladm Command".

Password Privilege Expiration

You can set a specific date on which a user's password privileges expires. When a user's password privilege expires, that user can no longer have a valid password at all. In effect, this locks the user out of the system after the given date because after that date the user can no longer log in.

For example, if you specify an expire date of December 31, 1997, for a user named pete, on January 1, 1998 he will not be able to log in under that user ID regardless of what password he uses. After each login attempt he will receive a Login incorrect message.

Password Aging Versus Expiration

Expiration of a user's password privilege is not the same as password aging.

Setting an Expiration Date

Password privilege expiration dates only take effect when the user logs in. If a user is already logged in, the expiration date has no affect until the user logs out or tries to use rlogin or telnet to connect to another machine at which time the user will not be able to log in again. Thus, if you are going to implement password privilege expiration dates, you should require your users to log out at the end of each day's work session.


Note -

If you have Solstice AdminSuiteTM tools available, do not use nistbladm to set an expiration date. Use Solstice AdminSuiteTM tools because they are easier to use and provide less chance for error.


To set an expiration date with the nistbladm command:


nistbladm -m `shadow=n:n:n:n:n:n6:n' [name=login],passwd.org_dir

Where:

For example, to specify an expiration date for the user pete of December 31, 1995 you would type:


station1% nistbladm -m `shadow=n:n:n:n:n:9493:n' [name=pete],passwd.org_dir

Caution - Caution -

All of the fields must be filled in with valid values.


Turning Off Password Privilege Expiration

To turn off or deactivate password privilege expiration, you must use the nistbladm command to place a -1 in this field. For example, to turn off privilege expiration for the user huck, you would type:


station1% nistbladm -m `shadow=n:n:n:n:n:-1:n' [name=huck],passwd.org_dir

Or you can use the nistbladm command reset the expiration date to some day in the future by entering a new number of days in the n6 field.

Specifying Maximum Number of Inactive Days

You can set a maximum number of days that a user can go without logging in on a given machine. Once that number of days passes without the user logging in, that machine will no longer allow that user to log in. In this situation, the user will receive a Login incorrect message after each login attempt.

This feature is tracked on a machine-by-machine basis, not a network-wide basis. That is, in an NIS+ environment, you specify the number of days a user can go without logging in by placing an entry for that user in the passwd table of the user's home domain. That number applies for that user on all machines on the network.

For example, suppose you specify a maximum inactivity period of 10 days for the user sam. On January 1, sam logs in to both machine-A and machine-B, and then logs off both machines. Four days later on January 4, sam logs in on machine-B and then logs out. Nine days after that on January 13, sam can still log in to machine-B because only 9 days have elapsed since the last time he logged in on that machine, but he can no longer log in to machine-A because thirteen days have passed since his last log in on that machine.

Keep in mind that an inactivity maximum cannot apply to a machine the user has never logged in to. No matter what inactivity maximum has been specified or how long it has been since the user has logged in to some other machine, the user can always log in to a machine that the user has never logged in to before.


Caution - Caution -

Do not set inactivity maximums unless your users are instructed to log out at the end of each workday. The inactivity feature only relates to logins; it does not check for any other type of system use. If a user logs in and then leaves the system up and running at the end of each day, that user will soon pass the inactivity maximum because there has been no login for many days. When that user finally does reboot or log out, he or she won't be able to log in.



Note -

If you have Solstice AdminSuiteTM tools available, do not use nistbladm to set an inactivity maximum. Use Solstice AdminSuite tools because they are easier to use and provide less chance for error.


To set a login inactivity maximum, you must use the nistbladm command in the format:


nistbladm -m `shadow=n:n:n:n:n5:n:n' [name=login],passwd.org_dir

Where:

For example, to specify that the user sam must log in at least once every seven days, you would type:


station1% nistbladm -m `shadow=n:n:n:n:n:7:n:n' [name=sam],passwd.org_dir

To clear an inactivity maximum and allow a user who has been prevented from logging in to log in again, use nistbladm to set the inactivity value to -1.

Specifying Password Criteria and Defaults

The following subsections describe various password-related defaults and general criteria that you can specify.

The /etc/defaults/passwd File

The /etc/defaults/passwd file is used to set four general password defaults for users whose nsswitch.conf file points to files. The defaults set by the /etc/defaults/passwd file apply only to those users whose operative password information is taken from /etc files; they do not apply to anyone using either NIS maps or NIS+ tables. An /etc/defaults/passwd file on an NIS+ server only affects local users who happen to be obtaining their password information from those local files. An /etc/defaults/passwd file on an NIS+ server has no effect on the NIS+ environment or users whose nsswitch.conf file points to either nis or nisplus.

The four general password defaults governed by the /etc/defaults/passwd file are:

The following principles apply to defaults set with an /etc/defaults/passwd file:

By default, /etc/defaults/passwd files already contain the entries:


MAXWEEKS=
MINWEEKS=
PASSLENGTH=

To implement an entry, simply type the appropriate number after the equal sign. Entries that do not have a number after the equal sign are inactive and have no affect on any user. Thus, to set a MAXWEEKS default of 4, you would change the /etc/defaults/passwd file to read:


MAXWEEKS=4
MINWEEKS=
PASSLENGTH=

Maximum weeks

You can use the MAXWEEKS default in the /etc/defaults/passwd file to set the maximum number of weeks that a user's password is valid. To set a default maximum time period, type the appropriate number of weeks after the equal sign in the MAXWEEKS= line:


MAXWEEKS=N

Where N is a number of weeks. For example, MAXWEEKS=9.

Minimum Weeks

You can use the MINWEEKS default in the /etc/defaults/passwd file to set the minimum nuber of weeks that must pass before a user can change passwords. To set a default minimum time period, type the appropriate number of weeks after the equal sign on the MINWEEKS= line:


MINWEEKS=N

Where N is a number of weeks. For example, MINWEEKS=2.

Warning Weeks

You can add a WARNWEEKS default to the /etc/defaults/passwd file set the number of weeks prior to a password becoming invalid due to aging that user is warned. for example, if you have set the MAXWEEKS default to 9, and you want users to be warned two weeks before their passwords become invalid, you would set the MAXWEEKS default to 7.

There is no point in setting the WARNWEEKS default unless you also set a MAXWEEKS default.

Remember that WARNWEEKS are counted forward from the date of the user's last password change, not backwards from the MAXWEEKS expiration date. Thus, WARNWEEKS must always be less than MAXWEEKS and cannot be equal to or greater than MAXWEEKS .

A WARNWEEKS default will not work unless there is also a MAXWEEKS default.

To set the warning time period, type the appropriate number of weeks after the equal sign on the WARNWEEKS= line.


WARNWEEKS=N

Where N is the number of weeks. For example, WARNWEEKS=1.

Minimum Password Length

By default, the passwd command assumes a minimum length of six characters. You can use the PASSLENGTH default in the /etc/defaults/passwd files to change that by setting the minimum number of characters that a user's password must contain to some other number.

To set the minimum number of characters to something other than six, type the appropriate number of characters after the equal sign in the PASSLENGTH= line:


PASSLENGTH=N

Where N is the number of characters. For example, PASSLENGTH=7.

Password Failure Limits

You can specify a number-of-tries limit or an amount-of-time limit (or both) for a user's attempt to change passwords. These limits are specified by adding arguments when starting the rpc.nispasswdd daemon.

Limiting the number of attempts or setting a time frame provides a limited (but not foolproof) defense against unauthorized persons attempting to change a valid password to one that they discover through trial and error.

Maximum Number of Tries

To set the maximum number of times a user can try to change a password without succeeding, use the -a number argument with rpc.nispasswdd, where number is the number of allowed tries. (You must have superuser privileges on the NIS+ master server to run rpc.nispasswdd.)

For example, to limit users to no more than four attempts (the default is 3), you would type:


station1# rpc.nispasswdd -a 4

In this case, if a user's fourth attempt at logging in is unsuccessful, the message Too many failures - try later is displayed. No further attempts are permitted for that user ID until a specified period of time has passed.

Maximum Login Time Period

To set the maximum amount a time a user can take to successfully change a password, use the -c minutes argument with rpc.nispasswdd, where minutes is the number of minutes a user has to log in. (You must have superuser privileges on the NIS+ master server to run rpc.nispasswdd.)

For example, to specify that users must successfully log in within 2 minutes, you would type:


station1# rpc.nispasswdd -c 2

In this case, if a user is unable to successfully change a password within 2 minutes, the message is displayed at the end of the two-minute period. No further attempts are permitted for that user ID until a specified period of time has passed.