Provided by: openafs-kpasswd_1.6.15-1ubuntu1.1_amd64 
NAME
kas_setfields - Sets fields in an Authentication Database entry
SYNOPSIS
kas setfields -name <name of user>
[-flags <hex flag value or flag name expression>]
[-expiration <date of account expiration>]
[-lifetime <maximum ticket lifetime>]
[-pwexpires <number days password is valid ([0..254])>]
[-reuse <permit password reuse (yes/no)>]
[-attempts <maximum successive failed login tries ([0..254])>]
[-locktime <failure penalty [hh:mm or minutes]>]
[-admin_username <admin principal to use for authentication>]
[-password_for_admin <admin password>] [-cell <cell name>]
[-servers <explicit list of authentication servers>+]
[-noauth] [-help]
kas setf -na <name of user>
[-f <hex flag value or flag name expression>]
[-e <date of account expiration>]
[-li <maximum ticket lifetime>]
[-pw <number days password is valid ([0..254])>]
[-r <permit password reuse (yes/no)>]
[-at <maximum successive failed login tries ([0..254])>]
[-lo <failure penalty [hh:mm or minutes]>]
[-ad <admin principal to use for authentication>]
[-pa <admin password>] [-c <cell name>]
[-s <explicit list of authentication servers>+] [-no] [-h]
kas sf -na <name of user>
[-f <hex flag value or flag name expression>]
[-e <date of account expiration>]
[-li <maximum ticket lifetime>]
[-pw <number days password is valid ([0..254])>]
[-r <permit password reuse (yes/no)>]
[-at <maximum successive failed login tries ([0..254])>]
[-lo <failure penalty [hh:mm or minutes]>]
[-ad <admin principal to use for authentication>]
[-pa <admin password>] [-c <cell name>]
[-s <explicit list of authentication servers>+] [-no] [-h]
DESCRIPTION
The kas setfields command changes the Authentication Database entry for the user named by the -name
argument in the manner specified by the various optional arguments, which can occur singly or in
combination:
• To set the flags that determine whether the user has administrative privileges to the Authentication
Server, can obtain a ticket, can change his or her password, and so on, include the -flags argument.
• To set when the Authentication Database entry expires, include the -expiration argument.
• To set the maximum ticket lifetime associated with the entry, include the -lifetime argument. klog(1)
explains how this value interacts with others to determine the actual lifetime of a token.
• To set when the user's password expires, include the -pwexpires argument.
• To set whether the user can reuse any of the previous twenty passwords when creating a new one,
include the -reuse argument.
• To set the maximum number of times the user can provide an incorrect password before the
Authentication Server refuses to accept any more attempts (locks the issuer out), include the
-attempts argument. After the sixth failed authentication attempt, the Authentication Server logs a
message in the UNIX system log file (the syslog file or equivalent, for which the standard location
varies depending on the operating system).
• To set how long the Authentication Server refuses to process authentication attempts for a locked-out
user, set the -locktime argument.
The kas examine command displays the settings made with this command.
CAUTIONS
The password lifetime set with the -pwexpires argument begins at the time the user's password was last
changed, rather than when this command is issued. It can therefore be retroactive. If, for example, a
user changed her password 100 days ago and the password lifetime is set to 100 days or less, the password
effectively expires immediately. To avoid retroactive expiration, instruct the user to change the
password just before setting a password lifetime.
Administrators whose authentication accounts have the "ADMIN" flag enjoy complete access to the sensitive
information in the Authentication Database. To prevent access by unauthorized users, use the -attempts
argument to impose a fairly strict limit on the number of times that a user obtaining administrative
tokens can provide an incorrect password. Note, however, that there must be more than one account in the
cell with the "ADMIN" flag. The kas unlock command requires the "ADMIN" privilege, so it is important
that the locked-out administrator (or a colleague) can access another "ADMIN"-privileged account to
unlock the current account.
In certain circumstances, the mechanism used to enforce the number of failed authentication attempts can
cause a lockout even though the number of failed attempts is less than the limit set by the -attempts
argument. Client-side authentication programs such as klog and an AFS-modified login utility normally
choose an Authentication Server at random for each authentication attempt, and in case of a failure are
likely to choose a different Authentication Server for the next attempt. The Authentication Servers
running on the various database server machines do not communicate with each other about how many times a
user has failed to provide the correct password to them. Instead, each Authentication Server maintains
its own separate copy of the auxiliary database file kaserverauxdb (located in the /var/lib/openafs/local
directory by default), which records the number of consecutive authentication failures for each user
account and the time of the most recent failure. This implementation means that on average each
Authentication Server knows about only a fraction of the total number of failed attempts. The only way to
avoid allowing more than the number of attempts set by the -attempts argument is to have each
Authentication Server allow only some fraction of the total. More specifically, if the limit on failed
attempts is f, and the number of Authentication Servers is S, then each Authentication Server can only
permit a number of attempts equal to f divided by S (the Ubik synchronization site for the Authentication
Server tracks any remainder, f mod S).
Normally, this implementation does not reduce the number of allowed attempts to less than the configured
limit (f). If one Authentication Server refuses an attempt, the client contacts another instance of the
server, continuing until either it successfully authenticates or has contacted all of the servers.
However, if one or more of the Authentication Server processes is unavailable, the limit is effectively
reduced by a percentage equal to the quantity U divided by S, where U is the number of unavailable
servers and S is the number normally available.
To avoid the undesirable consequences of setting a limit on failed authentication attempts, note the
following recommendations:
• Do not set the -attempts argument (the limit on failed authentication attempts) too low. A limit of
nine failed attempts is recommended for regular user accounts, to allow three failed attempts per
Authentication Server in a cell with three database server machines.
• Set fairly short lockout times when including the -locktime argument. Although guessing passwords is
a common method of attack, it is not a very sophisticated one. Setting a lockout time can help
discourage attackers, but excessively long times are likely to be more of a burden to authorized
users than to potential attackers. A lockout time of 25 minutes is recommended for regular user
accounts.
• Do not assign an infinite lockout time on an account (by setting the -locktime argument to 0 [zero])
unless there is a highly compelling reason. Such accounts almost inevitably become locked at some
point, because each Authentication Server never resets the account's failure counter in its copy of
the kaauxdb file (in contrast, when the lockout time is not infinite, the counter resets after the
specified amount of time has passed since the last failed attempt to that Authentication Server).
Furthermore, the only way to unlock an account with an infinite lockout time is for an administrator
to issue the kas unlock command. It is especially dangerous to set an infinite lockout time on an
administrative account; if all administrative accounts become locked, the only way to unlock them is
to shut down all instances of the Authentication Server and remove the kaauxdb file on each.
OPTIONS
-name <name of user>
Names the Authentication Database account for which to change settings.
-flags <hex flag or flag name expression>
Sets one or more of four toggling flags, adding them to any flags currently set. Either specify one
or more of the following strings, or specify a hexadecimal number that combines the indicated values.
To return all four flags to their defaults, provide a value of 0 (zero). To set more than one flag at
once using the strings, connect them with plus signs (example: "NOTGS+ADMIN+CPW"). To remove all the
current flag settings before setting new ones, precede the list with an equal sign (example:
"=NOTGS+ADMIN+CPW").
ADMIN
The user is allowed to issue privileged kas commands (hexadecimal equivalent is 0x004, default is
"NOADMIN").
NOTGS
The Authentication Server's Ticket Granting Service (TGS) refuses to issue tickets to the user
(hexadecimal equivalent is 0x008, default is "TGS").
NOSEAL
The Ticket Granting Service cannot use the contents of this entry's key field as an encryption
key (hexadecimal equivalent is 0x020, default is "SEAL").
NOCPW
The user cannot change his or her own password or key (hexadecimal equivalent is 0x040, default
is "CPW").
-expiration <date of account expiration>
Determines when the entry itself expires. When a user entry expires, the user becomes unable to log
in; when a server entry such as "afs" expires, all server processes that use the associated key
become inaccessible. Provide one of the three acceptable values:
never
The account never expires (the default).
mm/dd/yyyy
Sets the expiration date to 12:00 a.m. on the indicated date (month/day/year). Examples:
"01/23/1999", "10/07/2000".
"mm/dd/yyyy hh:MM"
Sets the expiration date to the indicated time (hours:minutes) on the indicated date
(month/day/year). Specify the time in 24-hour format (for example, "20:30" is 8:30 p.m.) Date
format is the same as for a date alone. Surround the entire instance with quotes because it
contains a space. Examples: "01/23/1999 22:30", "10/07/2000 3:45".
Acceptable values for the year range from 1970 (1 January 1970 is time 0 in the standard UNIX date
representation) through 2037 (2037 is the maximum because the UNIX representation cannot accommodate
dates later than a value in February 2038).
-lifetime <maximum ticket lifetime>
Specifies the maximum lifetime that the Authentication Server's Ticket Granting Service (TGS) can
assign to a ticket. If the account belongs to a user, this value is the maximum lifetime of a token
issued to the user. If the account corresponds to a server such as "afs", this value is the maximum
lifetime of a ticket that the TGS issues to clients for presentation to the server during mutual
authentication.
Specify an integer that represents a number of seconds (3600 equals one hour), or include a colon in
the number to indicate a number of hours and minutes ("10:00" equals 10 hours). If this argument is
omitted, the default setting is 100:00 hours (360000 seconds).
-pwexpires <number of days password is valid>
Sets the number of days after the user's password was last changed that it remains valid. Provide an
integer from the range 1 through 254 to specify the number of days until expiration, or the value 0
to indicate that the password never expires (the default).
When the password expires, the user is unable to authenticate, but has 30 days after the expiration
date in which to use the kpasswd command to change the password (after that, only an administrator
can change it by using the kas setpassword command). Note that the clock starts at the time the
password was last changed, not when the kas setfields command is issued. To avoid retroactive
expiration, have the user change the password just before issuing a command that includes this
argument.
-reuse (yes | no)
Specifies whether or not the user can reuse any of his or her last 20 passwords. The acceptable
values are "yes" to allow reuse of old passwords (the default) and "no" to prohibit reuse of a
password that is similar to one of the previous 20 passwords.
-attempts <maximum successive failed login tries>
Sets the number of consecutive times the user can provide an incorrect password during authentication
(using the klog command or a login utility that grants AFS tokens). When the user exceeds the limit,
the Authentication Server rejects further attempts (locks the user out) for the amount of time
specified by the -locktime argument. Provide an integer from the range 1 through 254 to specify the
number of failures allowed, or 0 to indicate that there is no limit on authentication attempts (the
default value).
-locktime <failure penalty>
Specifies how long the Authentication Server refuses authentication attempts from a user who has
exceeded the failure limit set by the -attempts argument.
Specify a number of hours and minutes (hh:mm) or minutes only (mm), from the range 01 (one minute)
through "36:00" (36 hours). The kas command interpreter automatically reduces any larger value to
"36:00" and also rounds up any non-zero value to the next higher multiple of 8.5 minutes. A value of
0 (zero) sets an infinite lockout time; an administrator must issue the kas unlock command to unlock
the account.
-admin_username <admin principal>
Specifies the user identity under which to authenticate with the Authentication Server for execution
of the command. For more details, see kas(8).
-password_for_admin <admin password>
Specifies the password of the command's issuer. If it is omitted (as recommended), the kas command
interpreter prompts for it and does not echo it visibly. For more details, see kas(8).
-cell <cell name>
Names the cell in which to run the command. For more details, see kas(8).
-servers <authentication servers>+
Names each machine running an Authentication Server with which to establish a connection. For more
details, see kas(8).
-noauth
Assigns the unprivileged identity "anonymous" to the issuer. For more details, see kas(8).
-help
Prints the online help for this command. All other valid options are ignored.
EXAMPLES
In the following example, an administrator using the "admin" account grants administrative privilege to
the user "smith", and sets the Authentication Database entry to expire at midnight on 31 December 2000.
% kas setfields -name smith -flags ADMIN -expiration 12/31/2000
Password for admin:
In the following example, an administrator using the "admin" account sets the user "pat"'s password to
expire in 60 days from when it last changed, and prohibits reuse of passwords.
% kas setfields -name pat -pwexpires 60 -reuse no
Password for admin:
PRIVILEGE REQUIRED
The issuer must have the "ADMIN" flag set on his or her Authentication Database entry.
SEE ALSO
kaserverauxdb(5), kas(8), kas_examine(8), kas_setpassword(8), kas_unlock(8), klog(1), kpasswd(1)
COPYRIGHT
IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved.
This documentation is covered by the IBM Public License Version 1.0. It was converted from HTML to POD
by software written by Chas Williams and Russ Allbery, based on work by Alf Wachsmann and Elizabeth
Cassell.